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July

July

July is the seventh month of the year in the Gregorian Calendar and one of seven Gregorian months with the length of 31 days. July begins (astrologically) with the sun in the sign of Cancer and ends in the sign of Leo. Astronomically speaking, the sun begins in the constellation of Gemini and ends in the constellation of Cancer. July was renamed for Julius Caesar; previously, it was called Quintilis in Latin, since it was the fifth month in the Roman calendar which started in March. It also was named because it was the month that Caesar was born. Because of its origin, until the 18th century this month's name was pronounced the same way as the name "Julie". In old Japanese calendar, the month is called fumi zuki (文月). In the pagan wheel of the year July ends at or near to Lughnasadh in the northern hemisphere and Imbolc in the southern hemisphere. Imbolc

Other names

- In the Irish Calendar the month is called Iúil and is the third and last month of the Summer season.
- In Finnish, the month is called heinäkuu, meaning "month of hay".

Trivia

- July begins on the same day of the week as April every year and also January in leap years.
- July's flower is the water lily.
- July's birthstone is the ruby.

Seventh

In music, see the intervals:

seventh, musical group

- Major seventh
- minor seventh
- diminished seventh The note of a chord forming any of the above intervals with the chord's root. The leading tone or subtonic, and the chord built on the leading tone, is often called simply the seventh as it is the seventh scale degree. wiktionary:seventh

Month

:In Egyptian mythology, Month is an alternate spelling for Menthu. A month is that from one date to the next months date with the same number. so Emma's wrong. The month is a unit of time, used with calendars, which is approximately as long as some natural period related to the motion of the Moon (moon gives month in the same way that wide gives width and broad gives breadth). The traditional concept arose with the cycle of moon phases; such months are synodic months and last ~29.53 days. From excavated tally sticks, researchers have deduced that people counted days in relation to the Moon's phases as early as the Paleolithic age. Synodic months are still the basis of many calendars.

Astronomical background

The motion of the Moon in its orbit is very complicated and its period is not constant. Moreover, many cultures (most notably those using the ancient Hebrew (Jewish) calendar and the Islamic calendar) start a month with the first appearance of the thin crescent of the new moon after sunset over the western horizon. The date and time of this actual observation depends on the exact geographical longitude as well as latitude, atmospheric conditions, the visual acuity of the observers, etc. Therefore the beginning and lengths of months in these calendars can not be accurately predicted. Most Jews currently follow a precalculated calendar, but the Karaites rely on actual moon observations.

Sidereal month

The actual period of the Moon's orbit as measured in a fixed frame of reference is known as a sidereal month, because it is the time it takes the Moon to return to the same position on the celestial sphere among the fixed stars (Latin: sidus): 27.321 661 days (27d 7h 43min 11.5sec) or about 27 ⅓ days. This type of "month" has appeared among cultures in the Middle East, India, and China in the following way: they divided the sky in 27 or 28 lunar mansions, characterized by asterisms (apparent groups of stars), one for each day that the Moon follows its track among the stars.

Tropical month

It is customary to specify positions of celestial bodies with respect to the vernal equinox. Because of precession, this point moves back slowly along the ecliptic. Therefore it takes the Moon less time to return to an ecliptic longitude of zero than to the same point amidst the fixed stars: 27.321 582 days (27d 7h 43min 4.7sec). This slightly shorter period is known as tropical month; cf. the analogous tropical year of the Sun.

Anomalistic month

Like all orbits, the Moon's orbit is an ellipse rather than a circle. However, the orientation (as well as the shape) of this orbit is not fixed. In particular, the position of the extreme points (the line of the apsides: perigee and apogee), makes a full circle in about nine years. It takes the Moon longer to return to the same apsis because it moved ahead during one revolution. This longer period is called the anomalistic month, and has an average length of 27.554 551 days (27d 13h 18min 33.2sec), or about 27 ¹/₂ days. The apparent diameter of the Moon varies with this period, and therefore this type of month has some relevance for the prediction of eclipses (see saros), whose extent, duration, and appearance (whether total or annular) depend on the exact apparent diameter of the Moon. The apparent diameter of the full moon varies with the full moon cycle which is the beat period of the synodic and anomalistic month, and also the period after which the apsides point to the Sun again.

Draconic month

The orbit of the Moon lies in a plane that is tilted with respect to the plane of the ecliptic: it has an inclination of about five degrees. The line of intersection of these planes defines two points on the celestial sphere: the ascending and descending nodes. The plane of the Moon's orbit precesses over a full circle in about 18.6 years, so the nodes move backwards over the ecliptic with the same period. Hence the time it takes the Moon to return to the same node is again shorter than a sidereal month: this is called the draconic, nodical, or draconitic month. It lasts 27.212 220 days (27d 5h 5min 35.8sec), or about 27 ⅕ days. It is important for predicting eclipses: these take place when the Sun, Earth and Moon are on a line. Now (as seen from the Earth) the Sun moves along the ecliptic, while the Moon moves along its own orbit that is inclined on the ecliptic. The three bodies are only on a line when the Moon is on the ecliptic, i. e. when it is at one of the nodes. The "draconic/draconitic" month refers to the mythological dragon that lives in the nodes and regularly eats the Sun or Moon during an eclipse.

Synodic month

The cause of moon phases is that from the Earth we see the part of the Moon that is illuminated by the Sun from different angles as the Moon traverses its orbit. So the appearance depends on the position of the Moon with respect to the Sun (as seen from the Earth). Because the Earth orbits the Sun, it takes the Moon extra time (after completing a sidereal month, i. e. a full circle) to catch up and return to the same position with respect to the Sun. This longer period is called the synodic month (from Greek syn hodô or σὺν ὁδῴ, with the way, i. e. the Moon travelling with the Sun). Because of the perturbations of the orbits of the Earth and Moon, the actual time between lunations may range from about 29.27 to about 29.83 days. The long-term average duration is 29.530 588 days (29d 12h 44min 2.8sec), or about 29 ½ days.

Month lengths

Here is a list of the average length of the various astronomical lunar months . These are not constant, so a first-order (linear) approximation of the secular change is provided: Valid for the epoch J2000.0 (1 Jan. 2000 12:00 TT): Note: time expressed in Ephemeris Time (more precisely Terrestrial Time) with days of 86400 SI seconds. y is years since the epoch (2000), expressed in Julian years of 365.25 days. Note that for calendrical calculations, one would probably use days measured in the time scale of Universal Time, which follows the somewhat unpredictable rotation of the Earth, and progressively accumulates a difference with ephemeris time called ΔT.

Calendrical consequences

:For more details on this topic, see lunar calendar and lunisolar calendar. At the simplest level, all lunar calendars are based on the approximation that 2 lunations last 59 days: 30 day full month followed by a 29 day hollow month — but this is only marginally accurate and quickly needs correction by using larger cycles, or the equivalent of leap days. Second, the synodic month does not fit easily into the year, which makes constructing accurate, rule-based lunisolar calendars difficult. The most common solution to this problem is the Metonic cycle, which takes advantage of the fact that 235 lunations are approximately 19 tropical years (which add up to not quite 6940 days). However, a Metonic calendar (such as the Hebrew calendar) will drift against the seasons by about 1 day every 200 years. The problems of creating reliable lunar calendars may explain why solar calendars, having months which no longer relate to the phase of the moon, and being based only on the more predictable motion of the sun against the sky, have generally replaced lunar calendars for civil use in most societies.

Months in various calendars

Julian and Gregorian calendars

The Gregorian calendar, like the Julian calendar before it, has twelve months: #January, 31 days #February, 28 days, 29 in leap years, or 30 on certain occasions in related calenders #March, 31 days #April, 30 days #May, 31 days #June, 30 days #July, 31 days #August, 31 days #September, 30 days #October, 31 days #November, 30 days #December, 31 days For the rationale behind the unusual day lengths, see February and August. One of Wikipedia's sister projects, Wiktionary, provides translations of each of the Gregorian/Julian calendar months into a dozen or more languages. Month-by-month links are provided here: January, February, March, April, May, June, July, August, September, October, November, December. Months existing in the Roman calendar in the past include:
- Mercedonius, an occasional month after February to realign the calendar.
- Quintilis, renamed to July in honor of Julius Caesar.
- Sextilis, renamed to August in honor of Caesar Augustus. The famous mnemonic Thirty days hath September is the most common way of teaching the lengths of the months.

Islamic calendar

There are also twelve months in the Islamic calendar. They are named as follows: # Muharram ul Haram (or shortened to Muharram) محرّم # Safar صفر # Rabi`-ul-Awwal (Rabi' I) ربيع الأول # Rabi`-ul-Akhir (or Rabi` al-THaany) (Rabi' II) ربيع الآخر أو ربيع الثاني # Jumaada-ul-Awwal (Jumaada I) جمادى الأول # Jumaada-ul-Akhir (or Jumaada al-THaany) (Jumaada II) جمادى الآخر أو جمادى الثاني # Rajab رجب # Sha'aban شعبان # Ramadhan رمضان # Shawwal شوّال # Dhul Qadah ذو القعدة (or Thw al-Qi`dah) # Dhul Hijja ذو الحجة (or Thw al-Hijjah) For details, please see Islamic calendar.

Hebrew Calendar

The Hebrew calendar has 12 or 13 months. # Nisan, 30 days # Iyyar, 29 days # Sivan, 30 days # Tammuz, 29 days # Av, 30 days # Elul, 29 days # Tishri, 30 days # Heshvan, 29/30 days # Kislev, 29/30 days # Tevet, 29 days # Shevat, 30 days # Adar 1, 30 days, intercalary month # Adar 2, 29 days Adar 1 is only added in leap years. In ordinary years, Adar 2 is simply called Adar.

Hindu Calendar

The Hindu Calendar has various systems of naming the months. The months in the lunar calendar are: # Chaitra # Vaishaakha # Jyaishtha # Aashaadha # Shraavana # Bhaadrapada # Aashvayuja # Kaartika # Maargashiirsha # Pausha # Maagha # Phaalguna These are also the names used in the Indian national calendar for the newly redefined months. The names in the solar calendar are just the names of the zodiac sign in which the sun travels. They are # Mesha # Vrishabha # Mithuna # Kataka # Simha # Kanyaa # Tulaa # Vrishcika # Dhanus # Makara # Kumbha # Miina

Iranian/Persian calendar

The Iranian / Persian calendar, currently used in Iran and Afghanistan, also has 12 months. The Persian names are included in the parentheses. # Farvardin (فروردین)‎, 31 days # Ordibehesht (اردیبهشت)‎, 31 days # Khordad (خرداد)‎, 31 days # Tir (تیر)‎, 31 days # Mordad (مرداد)‎, 31 days # Shahrivar (شهریور)‎, 31 days # Mehr (مهر)‎, 30 days # Aban (آبان)‎, 30 days # Azar (آذر)‎, 30 days # Dey (دی)‎, 30 days # Bahman (بهمن)‎, 30 days # Esfand (اسفند)‎, 29 days, 30 in leap years

Icelandic/Old Norse calendar

The old icelandic calendar is not in official use anymore, but some holidays and annual feasts are still calculated according to it in Iceland. It has 12 months, broken down into two groups of six.
- Skammdegi (e. Short days) # Gormánuður (14. October - 13. November, e. slaughter month or Gór's month) # Ýlir (14. November - 13. December, e. Yule month) # Mörsugur (14. December - 12. January, e. fat sucking month) # Þorri (13. January - 11. February, e. frozen snow month) # Góa (12. February - 13. march, e. Góa's month, see Nór) # Einmánuður (14. march - 13. April, e. lone or single month)
- Náttleysi (e. Nightless days) # Harpa (14. April - 13. may, Harpa is a female name, probably a forgotten goddess) # Skerpla (14. may - 12. June, another forgotten goddess) # Sólmánuður (13. June - 12. July, e. sun month) # Heyannir (13. July - 14. August, e. hay business month) # Tvímánuður (15. August - 14. September, e. two or second month) # Haustmánuður (15. September - 13. October, e. autumn month)

Notes

# Derived from ELP2000-85: M. Chapront-Touzé, J. Chapront (1991): Lunar tables and programs from 4000 B. C. to A. D. 8000. Willmann-Bell, Richmond VA; ISBN 0-943396-33-6

Cancer

Cancer is a class of diseases characterized by uncontrolled cell division and the ability of these cells to invade other tissues, either by direct growth into adjacent tissue (invasion) or by migration of cells to distant sites (metastasis). This unregulated growth is caused by damage to DNA, resulting in mutations to vital genes that control cell division, among other functions. One or more of these mutations, which can be inherited or acquired, can lead to uncontrolled cell division and tumor formation. Tumor ("swelling" in Latin) refers to any abnormal mass of tissue, but may be either malignant (cancerous) or benign (noncancerous). Only malignant tumors are capable of invading other tissues or metastasizing. Cancer can cause many different symptoms, depending on the site and character of the malignancy and whether there is metastasis. A definitive diagnosis usually requires the microscopic examination of tissue obtained by biopsy. Once diagnosed, cancer is usually treated with surgery, chemotherapy and/or radiation. If untreated, most cancers eventually cause death; cancer is one of the leading causes of death in developed countries. Most cancers can be treated and many cured, especially if treatment begins early. Many forms of cancer are associated with environmental factors, which may be avoidable. Cigarette smoking leads to more cancers than any other environmental factor.

Diagnosing cancer

Most cancers are initially recognized either because signs or symptoms appear or through screening. Neither of these lead to a definitive diagnosis, which usually requires a biopsy. Some cancers are discovered accidentally during medical evaluation of an unrelated problem.

Signs and symptoms

Roughly, cancer symptoms can be divided into three groups:
- Local symptoms: unusual lumps or swelling (tumor), hemorrhage (bleeding), pain and/or ulceration. Compression of surrounding tissues may cause symptoms such as jaundice.
- Symptoms of metastasis (spreading): enlarged lymph nodes, cough and hemoptysis, hepatomegaly (enlarged liver), bone pain, fracture of affected bones and neurological symptoms. Although advanced cancer may cause pain, it is often not the first symptom.
- Systemic symptoms: weight loss, poor appetite and cachexia (wasting), excessive sweating (night sweats), anemia and specific paraneoplastic phenomena, i.e. specific conditions that are due to an active cancer, such as thrombosis or hormonal changes. Every single item in the above list can be caused by a variety of conditions (a list of which is referred to as the differential diagnosis). Cancer may be a common or uncommon cause of each item.

Biopsy

A cancer may be suspected for a variety of reasons, but the definitive diagnosis of most malignancies must be confirmed by microscopic examination of the cancerous cells by a pathologist. The procedure of obtaining cells and/or pieces of tissue, and their examination, is referred to as a biopsy. The tissue diagnosis indicates the type of cell that is proliferating, its severity (degree of dysplasia), and its extent and size. Cytogenetics and immunohistochemistry may provide information about future behavior of the cancer (prognosis) and best treatment. All cancers can be cured if entirely removed, and sometimes this can be accomplished by the biopsy procedure. When the whole mass of abnormal tissue (the "lesion") is removed, the borders of the sample are examined closely to see if all malignant tissue has truly been excised. If the cancer has spread to other sites in the body (metastasis), complete surgical excision is impossible. The nature of the biopsy depends on the organ that is sampled. Many biopsies (such as those of the skin, breast or liver) can happen on an outpatient basis. Biopsies of other organs are performed under anesthesia and require surgery.

Screening

Cancer screening is an attempt to detect unsuspected cancers in the population. Screening tests suitable for large numbers of healthy people must be relatively affordable, safe, noninvasive procedures with acceptably low rates of false positive results. If signs of cancer are detected, more definitive and invasive followup tests are performed to confirm the diagnosis. Screening for cancer can lead to earlier diagnosis. Early diagnosis may lead to extended life. A number of different screening tests have been developed. Breast cancer screening can be done by breast self-examination. Screening by regular mammograms detects tumors even earlier than self-examination, and many countries use it to systematically screen all middle-aged women. Colorectal cancer can be detected through fecal occult blood testing and colonoscopy, which reduces both colon cancer incidence and mortality, presumably through the detection and removal of premalignant polyps. Similarly, cervical cytology testing (using the Pap smear) leads to the identification and excision of precancerous lesions. Over time, such testing has been followed by a dramatic reduction of cervical cancer incidence and mortality. Testicular self-examination is recommended for men beginning at the age of 15 years to detect testicular cancer. Prostate cancer can be screened for by a digital rectal exam along with prostate specific antigen (PSA) blood testing. Screening for cancer is controversial in cases when it is not yet known if the test actually saves lives. The controversy arises when it is not clear if the benefits of screening outweigh the risks of follow-up diagnostic tests and cancer treatments. For example: when screening for prostate cancer, the PSA test may detect small cancers that would never become life threatening, but once detected will lead to treatment. This situation, called overdiagnosis, puts men at risk for complications from unnecessary treatment such as surgery or radiation. Followup procedures used to diagnose prostate cancer (prostate biopsy) may cause side effects, including bleeding and infection. Prostate cancer treatment may cause incontinence (inability to control urine flow) and erectile dysfunction (erections inadequate for intercourse). Similarly, for breast cancer, there have recently been criticisms that breast screening programs in some countries cause more problems than they solve. This is because screening of women in the general population will result in a large number of women with false positive results which require extensive follow-up investigations to exclude cancer, leading to having a high number-to-treat (or number-to-screen) to prevent or catch a single case of breast cancer early. Cervical cancer screening via the Pap smear has the best cost-benefit profile of all the forms of cancer screening from a public health perspective as, being a cancer, it has clear risk factors (sexual contact), and the natural progression of cervical cancer is that it normally spreads slowly over a number of years therefore giving more time for the screening program to catch it early. Moreover, the test itself is easy to perform and relatively cheap. For these reasons, it is important that the benefits and risks of diagnostic procedures and treatment be taken into account when considering whether to undertake cancer screening. Use of medical imaging to search for cancer in people without clear symptoms is similarly marred with problems. There is a significant risk of detection of what has been recently called an incidentaloma - a benign lesion that may be interpreted as a malignancy and be subjected to potentially dangerous investigations.

Types of cancer

Cancer cells within a tumor are the descendants of a single cell, even after it has metastasized. Hence, a cancer can be classified by the type of cell in which it originates and by the location of the cell. Carcinomas originate in epithelial cells (e.g. the digestive tract or glands). Hematological malignancies, such as leukemia and lymphoma, arise from cells of hematopoeitic origin, such as blood and bone marrow. Sarcoma arises from connective tissue, bone or muscle. Malignant tumors usually end in suffix "-carcinoma" for epithelial cancers, and "-sarcomas" for connective tissue tumors. Otherwise, benign tumors of both origins are denoted as "-omas." For instance, benign tumor of fat cells are known as "lipoma," while its malignant form is known as "liposarcoma."

Adult cancers

In the USA and other developed countries, cancer is presently responsible for about 25% of all deaths. On a yearly basis, 0.5% of the population is diagnosed with cancer. For adult males in the United States, the most common cancers are prostate cancer (33% of all cancer cases), lung cancer (13%), colorectal cancer (10%), bladder cancer (7%) and cutaneous melanoma (5%). As a cause of death lung cancer is the most common (31%) cause, followed by prostate cancer (10%), colorectal cancer (10%), pancreatic cancer (5%) and leukemia (4%). For adult females in the United States, breast cancer is the most common cancer (32% of all cancer cases) followed by lung cancer (12%), colorectal cancer (11%), endometrial cancer (6%, uterus) and non-Hodgkin's lymphoma (4%). By cause of death, lung cancer is again the most common (27% of all cancer deaths), followed by breast cancer (15%), colorectal cancer (10%), ovarian cancer (6%) and pancreatic cancer (6%). These statistics vary substantially in other countries. Other cancers not mentioned:
- Epithelial tumors: skin cancer (this is in fact the most common cancer but often not classified as such in health statistics), cervical cancer, anal carcinoma, esophageal cancer, hepatocellular carcinoma (in the liver), laryngeal cancer, renal cell carcinoma (in the kidneys), stomach cancer, many testicular cancers, and thyroid cancer.
- Hematological malignancies (blood and bone marrow): leukemia, lymphoma, multiple myeloma.
- Sarcomas: osteosarcoma (in bone), chondrosarcoma (arising from cartilage), rhabdomyosarcoma (in muscle)
- Miscellaneous origin: brain tumors, gastrointestinal stromal tumors (GIST), mesothelioma (in the pleura or pericardium), thymoma and teratomas, melanoma

Childhood cancers

Cancer can also occur in young children and adolescents. Here, the aberrant genetic processes that fail to safeguard against the clonal proliferation of cells with unregulated growth potential occur early in life and can progress quickly. The age of peak incidence of cancer in children occurs during the first year of life. Leukemia (usually ALL) is the most common infant malignancy (30%), followed by the central nervous system cancers and neuroblastoma. The remainder consists of Wilms' tumor, lymphomas, rhabdomyosarcoma (arising from muscle), retinoblastoma, osteosarcoma and Ewing's sarcoma. Female infants and male infants have essentially the same overall cancer incidence rates, but white infants have substantially higher cancer rates than black infants for most cancer types. Relative survival for infants is very good for neuroblastoma, Wilms' tumor and retinoblastoma, and fairly good (80%) for leukemia, but not for most other types of cancer.

Causes and pathophysiology

Origins of cancer

Cell division (proliferation) is a physiological process that occurs in almost all tissues and under many circumstances. Normally the balance between proliferation and cell death is tightly regulated to ensure the integrity of organs and tissues. Mutations in DNA that lead to cancer disrupt these orderly processes. The uncontrolled and often rapid proliferation of cells can lead to either a benign tumor or a malignant tumor (cancer). Benign tumors do not spread to other parts of the body or invade other tissues, and they are rarely a threat to life unless they extrinsically compress vital structures. Malignant tumors can invade other organs, spread to distant locations (metastasize) and become life-threatening.

Molecular biology

metastasize Carcinogenesis (meaning literally, the creation of cancer) is the process of derangement of the rate of cell division due to damage to DNA. Cancer is, ultimately, a disease of genes. Carcinogenesis usually requires multiple mutations in many genes, thus mutations in single gene is simply not enough. A cell divides without any regulatory manner when its normal program of proliferation is disrupted, and often times these disruptions are about promotion of mitogenic signals and suppression of anti-mitogenic signals. These two processes involve oncogenes, and tumor suppressor genes, respectively. Proto-oncogenes, broadly defined, are genes whose gene products promote cellular growth. These products can be hormones, mitogens, cell surface receptors, members of intracellular signaling pathways, and transcription factors. Often mutations in these proto-oncogenes cause them to become overactive, thus signalling the cells to divide and undergo uncontrolled growth. Tumor suppressor genes typically encode for anti-proliferation signals and proteins that suppresses mitosis. Generally tumor suppressors are transcription factors that are activated by cellular stress or DNA damage. Their main function is to arrest the progression of cell cycle before any DNA damage is repared. Otherwise, these genetic lesions, which may contribute to further genomic instability, may be passed on to daughter cells. Canonical tumor suppressors include p53, which is a transcription factor activated by many cellular stress including hypoxia and UV damage. In general, mutations in both types of genes are required for cancer to occur. For example, a mutation limited to one oncogene would be suppressed by normal mitosis control (the Knudson or 1-2-hit hypothesis) and tumor suppressor genes. A mutation to only one tumor suppressor gene would not cause cancer either, due to the presence of many "backup" genes that duplicate its functions. It is only when enough proto-oncogenes have mutated into oncogenes, and enough tumor suppressor genes deactivated or damaged, that the signals for cell growth overwhelm the signals to regulate it, that cell growth quickly spirals out of control. On a genetic side note, mutations in proto-oncogenes are dominant, or gain of function mutations, while mutations in tumor suppressors are recessive, or loss of function mutations. Each cell has two copies of a same gene (one inherited from each parent), and under most cases gain of function mutation in one copy of a particular proto-oncogene is enough to make that gene a true oncogene, while usually loss of function mutation need to happen in both copies of a tumor suppressor gene to render that gene completely non-functional. However, cases exist in which one loss of function copy of a tumor suppressor gene can render (or poison) the other copy non-functional, and this is called dominant negative effect. This is observed in many p53 mutations. Tumor suppressors are indicated in many families with hereditary cancers. Members within these families have increased incidence and decreased latency of multiple tumors. The mode of inheritance of mutant tumor suppressors is that affected member inherits a defective copy from one parent, and a normal copy from another. Because mutations in tumor suppressers act in a recessive manner (note, however, there are exceptions), the loss of the normal copy creates the cancer phenotype. For instance, individuals who are heterozygous for p53 mutations are often victims of Li-Fraumeni Syndrome, and those who are heterozygous for Rb mutations develop retinoblastoma. Similarly, mutations in APC are linked to adenopolyposis colon cancer (thousands of polyps in colon while young), while mutations in BRCA lead to early onset of breast cancer (often bilateral). Cancer is ultimately due to accumulation of genetic insults, which are fundamentally mutations in the DNA. Substances that cause these mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens. Particular substances have been linked to specific types of cancer. Tobacco smoking is associated with lung cancer. Breathing asbestos fibers is associated with mesothelioma. Prolonged exposure to radiation, particularly ultraviolet radiation from the sun, leads to melanoma and other skin malignancies. Even though most carcinogens are mutagens, some carcinogens are not. For instance estrogen is required for proliferation in a subset of breast tumor (estrogen-dependent breast cancer), even though estrogen does not induce DNA damage. These mitogens promote cancers through their stimulatory effect on the rate of cell mitosis. Faster rates of mitosis increasingly leave less time for DNA repair, therefore increasingly the likelihood of a genetic mistake being passed onto daughter cells, which in turn accumulates multiple mutations that may lead to carcinogenesis or progression of the disease. Furthermore, many cancers are viral in origin; this is especially true in animals such as birds, but less so in humans. The mode of virally-induce tumors can be divided into two, acutely or slowly- transforming. In acutely transforming viruses, the viral particles carry a gene that encodes for a overactive oncogene called viral-oncogene (or v-onc), and the infected cell is transformed as soon as v-onc is expressed. In contrast, in slowly-transforming viruses, virus genome is inserted (viral genome insertion is obligatory part of retroviruses) near a proto-oncogene in the host genome and the viral promoter or other transcription regulatory elements in turn cause overexpression of that proto-oncogene, which in turn induces uncontrolled cellular proliferation. Because viral genome insertion is not specific to proto-oncogenes and the chance of insertion near that proto-onc is low, slowly-transforming viruses have very long tumor latency compared to acutely-transforming virus, which already carries the v-onc. Most cases the etiology of cancer is unknown. However, with the help of molecular biological and gross karyotyping techniques, it is possible to characterize the mutations and chromosomal aberrations of tumor cells, and rapid progress is being made in prognosis based on the type and spectrum of mutations in some cases. For example, up to half of all tumors have a defective p53 gene, a tumor suppressor gene also known as "the guardian of the genome". This mutation is associated with poor prognosis, since those tumor cells are less likely to go into apoptosis (programmed cell death) when cells are challenged by chemotherapeutics and radiation. Malignant tumors cells have distinct properties (examples):
- evading apoptosis (down-regulation of death ligands in tumor cells)
- unlimited growth potential (immortalitization) (loss of regulatory region of receptor)
- self-sufficiency of growth factors (see above)
- insensitivity to anti-growth factors (see above)
- increased cell division rate (loss of Rb, which induces mitosis arrest)
- altered ability to differentiate (expression of embryonic markers)
- no ability for contact inhibition (down-regulation of E-cadherin, a celllular adhesion molecule)
- ability to invade neighbouring tissues (expression of metalloproteinases, which break down extracellular matrix)
- ability to build metastases at distant sites
- ability to promote blood vessel growth (angiogenesis) (expression of VEGF)

Morphology

angiogenesis Cancer tissue has a distinctive appearance under the microscope. Among the distinguishing traits are a large number of dividing cells, variation in nuclear size and shape, variation in cell size and shape, loss of specialized cell features, loss of normal tissue organization, and a poorly defined tumor boundary. Immunohistochemistry and other molecular methods may characterise specific markers on tumor cells, which may aid in diagnosis and prognosis. Biopsy and microscopical examination can also distinguish between malignancy and hyperplasia, which refers to tissue growth based on an excessive rate of cell division, leading to a larger than usual number of cells but with a normal orderly arrangement of cells within the tissue. This process is considered reversible. Hyperplasia can be a normal tissue response to an irritating stimulus, for example callus. Dysplasia is an abnormal type of excessive cell proliferation characterized by loss of normal tissue arrangement and cell structure. Often such cells revert back to normal behavior, but occasionally, they gradually become malignant. The most severe cases of dysplasia are referred to as "carcinoma in situ." In Latin, the term "in situ" means "in place", so carcinoma in situ refers to an uncontrolled growth of cells that remains in the original location and shows no propensity to invade other tissues. Nevertheless, carcinoma in situ may develop into an invasive malignancy and is usually removed surgically, if possible.

Heredity

Most forms of cancer are "sporadic", and have no basis in heredity. There are, however, a number of recognised syndromes of cancer with a hereditary component. Examples are:
- certain inherited mutations in the genes BRCA1 and BRCA2 are associated with an elevated risk of breast cancer and ovarian cancer
- tumors of various endocrine organs in multiple endocrine neoplasia (MEN types 1, 2a, 2b)
- Li-Fraumeni syndrome (various tumors such as osteosarcoma, breast cancer, soft-tissue sarcoma, brain tumors) due to mutations of p53
- Turcot syndrome (brain tumors and colonic polyposis)
- Familial adenomatous polyposis an inherited mutation of the APC gene that leads to early onset of colon carcinoma.
- Retinoblastoma in young children is an inherited cancer

Environment and diet

colon carcinoma The most consistent finding, over decades of research, is the strong association between tobacco use and cancers of many sites. Hundreds of epidemiological studies have confirmed this association. Further support comes from the fact that lung cancer death rates in the United States have mirrored smoking patterns, with increases in smoking followed by dramatic increases in lung cancer death rates and, more recently, decreases in smoking followed by decreases in lung cancer death rates in men. Up to half of all cancer cases can be attributed to smoking, diet, and environmental pollution.

Treatment of cancer

Cancer can be treated by surgery, chemotherapy, radiation therapy, immunotherapy or other methods. The choice of therapy depends upon the location and grade of the tumor and the stage of the disease, as well as the general state of the patient (performance status). A number of experimental cancer treatments are also under development. Complete removal of the cancer without damage to the rest of the body is the goal of treatment. Sometimes this can be accomplished by surgery, but the propensity of cancers to invade adjacent tissue or to spread to distant sites by microscopic metastasis often limits its effectiveness. The effectiveness of chemotherapy is often limited by toxicity to other tissues in the body. Radiation can also cause damage to normal tissue. Because "cancer" refers to a class of diseases, it is unlikely that there will ever be a single "cure for cancer" any more than there will be a single treatment for all infectious diseases.

Surgery

If the tumor is localized, surgery is often the preferred treatment. Example procedures include mastectomy for breast cancer and prostatectomy for prostate cancer. The goal of the surgery can be either the removal of only the tumor, or the entire organ. Since a single cancer cell can grow into a sizable tumor, removing only the tumor leads to a greater chance of recurrence. A margin of healthy tissue is often resected to make sure all cancerous tissue is removed. In addition to removal of the primary tumor, surgery is often necessary for staging, e.g. determining the extent of the disease and whether there has been metastasis to regional lymph nodes. Staging determines the prognosis and the need for adjuvant therapy. Occasionally, surgery is necessary to control symptoms, such as spinal cord compression or bowel obstruction. This is referred to as palliative treatment.

Chemotherapy

Chemotherapy is the treatment of cancer with drugs ("anticancer drugs") that can destroy cancer cells. It interferes with cell division in various possible ways, e.g. with the duplication of DNA or the separation of newly formed chromosomes. Most forms of chemotherapy target all rapidly dividing cells and are not specific for cancer cells. Hence, chemotherapy has the potential to harm healthy tissue, especially those tissues that have a high replacement rate (e.g. intestinal lining). These cells usually repair themselves after chemotherapy. Because some drugs work better together than alone, two or more drugs are often given at the same time. This is called "combination chemotherapy"; most chemotherapy regimens are given in a combination. A novel technique involves taking samples of the patient's tissue before chemotherapy. These tissues samples are screened to ensure they do not contain cancerous cells. The samples are expanded using tissue engineering techniques, and are then re-implanted following high dose chemotherapy in order to recolonise the damaged and somewhat destroyed tissue. A variation upon this method uses allogenic samples (samples donated by a different donor) instead of the patient's own tissue.

Immunotherapy

Immunotherapy is the use of immune mechanisms against tumors. These are used in various forms of cancer, such as breast cancer (trastuzumab/Herceptin®) but also in leukemia (gemtuzumab ozogamicin/Mylotarg®). The agents are monoclonal antibodies directed against proteins that are characteristic to the cells of the cancer in question, or cytokines that modulate the immune system's response.

Radiation therapy

Radiation therapy (also called radiotherapy, X-ray therapy, or irradiation) is the use of ionizing radiation to kill cancer cells and shrink tumors. Radiation therapy can be administered externally via external beam radiotherapy (EBRT) or internally via brachytherapy. The effects of radiation therapy are localised and confined to the region being treated. Radiation therapy injures or destroys cells in the area being treated (the "target tissue") by damaging their genetic material, making it impossible for these cells to continue to grow and divide. In addition, they cut off the blood supply to the cancer cells causing them to die in a process called necrosis. Although radiation damages both cancer cells and normal cells, most normal cells can recover from the effects of radiation and function properly. The goal of radiation therapy is to damage as many cancer cells as possible, while limiting harm to nearby healthy tissue. Hence, it is given in many fractions, allowing healthy tissue to recover between fractions. Radiation therapy may be used to treat almost every type of solid tumor, including cancers of the brain, breast, cervix, larynx, lung, pancreas, prostate, skin, stomach, uterus, or soft tissue sarcomas. Radiation is also used to treat leukemia and lymphoma. Radiation dose to each site depends on a number of factors, including the radiosensitivty of each cancer type and whether there are tissues and organs nearby that may be damaged by radiation. Thus, as with every form of treatment, radiation therapy is not without its side effects. These side effects include temporary (reversible) or permanent side effects (irreversible damage).

Hormonal suppression

The growth of nearly all tissues, including cancers, can be accelerated or inhibited by providing or blocking certain hormones. This allows an additional method of treatment for many cancers. Common examples of hormone-sensitive tumors include certain types of breast, prostate, and thyroid cancers. Removing or blocking estrogen, testosterone, or TSH, respectively, is often an important additional treatment.

Symptom control

Although the control of the symptoms of cancer is not typically thought of as a treatment directed at the cancer, it is an important determinant of the quality of life of cancer patients, and plays an important role in the decision whether the patient is able to undergo other treatments. Although all practicing doctors have the therapeutic skills to control pain, nausea, vomiting, diarrhea, hemorrhage and other common problems in cancer patients, the multidisciplinary specialty of palliative care has arisen specifically in response to the symptom control needs of this group of patients. Analgesia (painkillers, frequently opioids such as morphine) and antiemetics (drugs to suppress nausea and vomiting) are very commonly used in patients with cancer-related symptoms.

Treatment trials

Clinical trials, also called research studies, test new treatments in people with cancer. The goal of this research is to find better ways to treat cancer and help cancer patients. Clinical trials test many types of treatment such as new drugs, new approaches to surgery or radiation therapy, new combinations of treatments, or new methods such as gene therapy. A clinical trial is one of the final stages of a long and careful cancer research process. The search for new treatments begins in the laboratory, where scientists first develop and test new ideas. If an approach seems promising, the next step may be testing a treatment in animals to see how it affects cancer in a living being and whether it has harmful effects. Of course, treatments that work well in the lab or in animals do not always work well in people. Studies are done with cancer patients to find out whether promising treatments are safe and effective. Patients who take part may be helped personally by the treatment(s) they receive. They get up-to-date care from cancer experts, and they receive either a new treatment being tested or the best available standard treatment for their cancer. Of course, there is no guarantee that a new treatment being tested or a standard treatment will produce good results. New treatments also may have unknown risks, but if a new treatment proves effective or more effective than standard treatment, study patients who receive it may be among the first to benefit.

Complementary and alternative medicine

Complementary and alternative medicine (CAM) treatments are the diverse group of medical and health care systems, practices, and products that are not presently considered to be effective by the standards of conventional medicine. Some non-conventional treatment methods are used to "complement" conventional treatment, to provide comfort or lift the spirits of the patient, while others are offered as alternatives to be used instead of conventional treatments in hope of curing the cancer. Common complementary measures include prayer or psychological approaches such as "imaging" to aid in pain relief, or improve mood. Many people feel these approaches benefit them, but most have not been scientifically proven and therefore face skepticism. Other complementary approaches include traditional medicine like Traditional Chinese Medicine. A wide range of alternative treatments have been offered for cancer over the last century. The appeal of alternative cures arises from the daunting risks, costs, or potential side effects of many conventional treatments, or in the limited prospect for cure. Proponents of these therapies are unable or unwilling to demonstrate effectiveness by conventional criteria. Alternative treatments have included special diets or dietary supplements (e.g., the "grape diet" or megavitamin therapy), electrical devices (e.g., "zappers"), specially formulated compounds (e.g., laetrile), unconventional use of conventional drugs (e.g., insulin), purges or enemas, or physical manipulations of the body. Some of these treatments meet all the criteria for fraud. Collectively they are referred to by skeptics as cancer quackery. An extensive, explanatory catalog of these treatments is available at Quackwatch [http://www.quackwatch.org/00AboutQuackwatch/altseek.html]. Almost all physicians recommend against using these modalities as sole treatment for potentially fatal conditions such as cancer.

Epidemiology

In some Western countries, such as the USA and the UK, cancer is overtaking cardiovascular disease as the leading cause of death. In many Third World countries cancer incidence (insofar as this can be measured) appears much lower, most likely because of the higher death rates due to infectious disease or injury. With the increased control over malaria and tuberculosis in some Third World countries, incidence of cancer is expected to rise; this is termed the iceberg phenomenon in epidemiological terminology. Cancer epidemiology closely mirrors risk factor spread in various countries. Hepatocellular carcinoma (liver cancer) is rare in the West but is the main cancer in China and neighboring countries, most likely due to the endemic presence of hepatitis B and aflatoxin in that population. Similarly, with tobacco smoking becoming more common in various Third World countries, lung cancer incidence has increased in a parallel fashion.

Prevention

Cancer prevention is defined as active measures to decrease the incidence of cancer. This can be accomplished by avoiding carcinogens or altering their metabolism, pursuing a lifestyle or diet that modifies cancer-causing factors and/or medical intervention (chemoprevention, treatment of premalignant lesions). Much of the promise for cancer prevention comes from observational epidemiologic studies that show associations between modifiable life style factors or environmental exposures and specific cancers. Evidence is now emerging from randomized controlled trials designed to test whether interventions suggested by the epidemiologic studies, as well as leads based on laboratory research, actually result in reduced cancer incidence and mortality. Examples of modifiable cancer risk include alcohol consumption (associated with increased risk of oral, esophageal, breast, and other cancers), physical inactivity (associated with increased risk of colon, breast, and possibly other cancers), and being overweight (associated with colon, breast, endometrial, and possibly other cancers). Based on epidemiologic evidence, it is now thought that avoiding excessive alcohol consumption, being physically active, and maintaining recommended body weight may all contribute to reductions in risk of certain cancers; however, compared with tobacco exposure, the magnitude of effect is modest or small and the strength of evidence is often weaker. Other lifestyle and environmental factors known to affect cancer risk (either beneficially or detrimentally) include certain sexual and reproductive practices, the use of exogenous hormones, exposure to ionizing radiation and ultraviolet radiation, certain occupational and chemical exposures, and infectious agents.

Diet and cancer

The consensus on diet and cancer is that obesity increases the risk of developing cancer. Particular dietary practices often explain differences in cancer incidence in different countries (e.g. gastric cancer is more common in Japan, while colon cancer is more common in the United States). Studies have shown that immigrants develop the risk of their new country, suggesting a link between diet and cancer rather than a genetic basis. Despite frequent reports of particular substances (including foods) having a beneficial or detrimental effect on cancer risk, few of these have an established link to cancer. These reports are often based on studies in cultured cell media or animals. Public health recommendations cannot be made on the basis of these studies until they have been validated in an observational (or occasionally a prospective interventional) trial in humans. The case of beta-carotene provides an example of the necessity of randomized clinical trials. Epidemiologists studying both diet and serum levels observed that high levels of beta-carotene, a precursor to vitamin A, were associated with a protective effect, reducing the risk of cancer. This effect was particularly strong in lung cancer. This hypothesis led to a series of large randomized trials conducted in both Finland and the United States (CARET study) during the 1980s and 1990s. This study provided about 80,000 smokers or former smokers with daily supplements of beta-carotene or placebos. Contrary to expectation, these tests found no benefit of beta-carotene supplementation in reducing lung cancer incidence and mortality. In fact, the risk of lung cancer was slightly, but significantly, increased in smokers, leading to an early termination of the study.

Other chemoprevention agents

Daily use of tamoxifen, a selective estrogen receptor modulator, for up to 5 years, has been demonstrated to reduce the risk of developing breast cancer in high-risk women by about 50%. Cis-retinoic acid also has been shown to reduce risk of second primary tumors among patients with primary head and neck cancer. Finasteride, a 5-alpha reductase inhibitor, has been shown to lower the risk of prostate cancer. Other examples of drugs that show promise for chemoprevention include COX-2 inhibitors (which inhibit a cyclooxygenase enzyme involved in the synthesis of proinflammatory prostaglandins).

Cancer vaccines

Considerable research effort is now devoted to the development of vaccines (to prevent infection by oncogenic infectious agents, as well as to mount an immune response against cancer-specific epitopes) and to potential venues for gene therapy for individuals with genetic mutations or polymorphisms that put them at high risk of cancer. No cancer vaccines are presently in use, and most of the research is still in its initial stages. As of October 2005, researchers found that an experimental vaccine for HPV types 16 and 18 was 100% successful at preventing infection with these types of HPV and, thus, are able to prevent the majority of cervical cancer cases. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&list_uids=15541448&dopt=Abstract]

Genetic testing

Genetic testing for high-risk individuals, with enhanced surveillance, chemoprevention, or risk-reducing surgery for those who test positive, is already available for certain cancer-related genetic mutations.

Coping with cancer

Many local organizations offer a variety of practical and support services to people with cancer. Support can take the form of support groups, counseling, advice, financial assistance, transportation to and from treatment, or information about cancer. Neighborhood organizations, local health care providers, or area hospitals are a good place to start looking. While some people are reluctant to seek counseling, studies show that having someone to talk to reduces stress and helps people both mentally and physically. Counseling can also provide emotional support to cancer patients and help them better understand their illness. Different types of counseling include individual, group, family, self-help (sometimes called peer counseling), bereavement, patient-to-patient, and sexuality. Many governmental and charitable organizations have been established to help patients cope with cancer. These organizations often are involved in cancer prevention, cancer treatment, and cancer research. Examples include: American Cancer Society, BC Cancer Agency, Macmillan Cancer Relief , the Terry Fox Foundation, Cancer Research UK, Canadian Cancer Society, International Agency for Research on Cancer and the National Cancer Institute (US).

Social impact

Once refered to as "the C-word," cancer has a reputation for being a deadly disease. While this certainly applies to certain particular types, the truths behind the historical connotations of cancer are increasingly being overturned by advances in medical care. Some types of cancer have a prognosis that is substantially better than nonmalignant diseases such as heart failure and stroke. Progressive and disseminated malignant disease has a substantial impact on a cancer patient's quality of life, and many cancer treatments (such as chemotherapy) may have severe side-effects. In the advanced stages of cancer, many patients need extensive care, affecting family members and friends. Palliative care solutions may include permanent or "respite" hospice nursing.

Cancer research

Cancer research is the intense scientific effort to understand disease processes and discover possible therapies. While understanding of cancer has increased exponentially since the last decades of the 20th century, radically new therapies are only discovered and introduced gradually. Targeted therapy in the late 1990s was considered a major breakthrough. This constitutes the use of agents specific for the deregulated proteins of cancer cells. Small molecules (such as the tyrosine kinase inhibitors imatinib and gefitinib) and monoclonal antibodies have proven to be a major step in oncological treatment.

References

- Jemal A, Murray T, Ward E, Samuels A, Tiwari RC, Ghafoor A, Feuer EJ, Thun MJ. Cancer statistics, 2005. CA Cancer J Clin 2005;55:10-30. [http://caonline.amcancersoc.org/cgi/content/full/55/1/10 Fulltext]. PMID 15661684.
- [http://news.bbc.co.uk/1/hi/health/1015657.stm Cancer: Number one killer] (9 November, 2000). BBC News online. Retrieved 2005-01-29.
- [http://cis.nci.nih.gov/fact/4_13.htm Questions and Answers About Beta Carotene Chemoprevention Trials]
- Bilal A, Treating Cancer with Stem Cells, Medical Engineer, 25 July 2005 [http://www.medicalengineer.co.uk/Treating+Cancer+with+Stem+Cells.php Fulltext]

External links

Professional and research

- [http://www.who.int/cancer/en/ The World Health Organisation's cancer site] A review of worldwide strategies for the prevention and treatment of cancer.
- [http://www.cancer.org/docroot/STT/content/STT_1x_Cancer_Facts__Figures_2005.asp Cancer Facts & Figures 2005] - 2005 United States Cancer Statistics
- [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=cmed.TOC&depth=2 Cancer Medicine, 6th Edition] Textbook
- [http://www.nccn.org National Comprehensive Cancer Network] - has free guidelines for professionals and many pages of quality information for patients with all types of cancers
- [http://www.cancer.gov US National Cancer Institute] Government organization for research and treatment
- [http://www.eortc.be EORTC] European Organization for Research and Treatment of Cancer. A European non-profit organization that sets up and executes clinical trials.

Support and advocacy

- [http://www.americancancersociety.org American Cancer Society] Patient advocate group
- [http://www.aacr.org American Association for Cancer Research] Largest scientific organization in the world
- [http://www.nlm.nih.gov/medlineplus/cancer.html Cancer] from MedlinePlus - provides links to news, general sites, diagnosis, treatment and alternative therapies, clinical trials, research, related issues, organizations, other MedlinePlus [http://www.nlm.nih.gov/medlineplus/cancers.html Cancers Topics] and [http://www.nlm.nih.gov/medlineplus/cancerlivingwithcancer.html Living with Cancer], and more. Also, links to pre-formulated searches of the MEDLINE/PubMed database for recent research articles.
- [http://info.cancerresearchuk.org Cancer Research UK - Cancer Resources] - In-depth, up-to-date information for people with a professional or general interest in cancer and health.
- [http://www.cancerhelp.org.uk Cancer Research UK - Cancer Help] - Free information service about cancer and cancer care for people with cancer and their families.
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- ko:암 ms:Penyakit Barah ja:悪性腫瘍 simple:Cancer th:มะเร็ง

Leo

Leo (20px, Latin for lion) is a constellation of the zodiac. Leo lies between dim Cancer to the west and Virgo to the east.

Notable features

This constellation contains many bright stars, such as Regulus (α Leonis), the lion's heart; Denebola (β Leonis); and γ¹ Leonis (Algieba). Many other fainter stars have been named as well, such as δ Leo (Zosma), θ Leo (Chort), κ Leo (Al Minliar al Asad ), λ Leo (Alterf), and (ο Leo (Subra). Regulus, η Leonis, and γ Leonis, together with the fainter stars ζ Leo (Adhafera), μ Leo (Ras Elased Borealis), and ε Leo (Ras Elased Australis), make up the asterism known as the Sickle. These stars represent the head and the mane of the lion. A former asterism representing the tuft of the lion's tail has since become its own constellation, Coma Berenices. The star Wolf 359, one of the nearest stars to Earth's solar system (7.7 light-years), is in Leo. Gliese 436, a faint star in Leo about 33 light years away from the Sun, is orbited by one of the smallest extrasolar planets ever found. [http://www.theglobeandmail.com/servlet/story/RTGAM.20040831.wplanet20831a/BNStory/specialScienceandHealth/]

Notable deep sky objects

Leo contains many bright galaxies of which the twins M65, M66 and M95, M96 are the most famous.

History of the name

Early Hindu astronomers knew it as Asleha and as Sinha, the Tamil Simham but later, influenced by Greece and Rome, as Leya or Leyaya, from the word Leo, as the Romans commonly called it. Ovid wrote it as Herculeus Leo and Violentus Leo. Bacchi Sidus (Star of Bacchus) was another of its titles, the god always being identified with this animal, and its shape the one often adopted by him in his numerous transformations, while a lion's skin was his frequent dress. But Manilius had it Jovis et Junonis Sidus (Star of Jove and Juno), as being under the guardianship of these deities, perhaps appropriately considering its regal character, especially that of its lucida. The Persians called it Ser or Shir; the Turks, Artan; the Syrians, Aryo; the Jews, Arye; and the Babylonians, Aru - all meaning a lion. In Euphratean astronomy it was additionally known as Gisbar-namru-sa-pan, variously translated, but by Bertin, as the Shining Disc which precedes Bel, "Bel" being our Ursa Major, or in some way intimately connected therewith.

History of the symbol

Ursa Major The adoption of this animal's form for the zodiac sign has been attributed to the fact that when the Sun was among its stars in midsummer the lions of the desert left their accustomed haunts for the banks of the Nile, where they could find relief from the heat in the waters of the inundation. Pliny wrote that the Egyptians worshipped the stars of Leo because the rise of their great river was coincident with the Sun's entrance among them. For the same reason the Sphinx is said to have been sculptured with Leo's body and the head of the adjacent Virgo, although Egyptologists maintain that this head represented one of the early kings, or the god Harmachis. Distinct reference is made to Leo in an inscription of the walls of the Ramesseum at Thebes, which, like the Nile temples generally, was adorned with the animal's bristles, while on the planisphere of Dendera its figure is shown standing on an outstretched serpent. The Egyptian stellar Lion, however, comprised only a part of ours, and in the earliest records some of its stars were shown as a knife, as they now are as a sickle. Kircher gave its title there as Πιμεντεκεων, Cubitus Nili. The astrological symbol 20px has been supposed to portray the animal's mane, but it also might be the animal's tail. Gaius Julius Hyginus's writing published in 1488 and Albumasar's in 1489 showing this latter member of extraordinary length, twisting between the hind legs and over the back, Hygnus's manuscript properly locating the star Denebola in the end. But the International Dictionary says that this symbol is a corruption of the initial letter of Λεων (Leon). Lajard's Cultes de Mithra mentions the hieroglyph of Leo as among the symbols of Mithraic worship, but how their Lion agreed, if at all, with ours is not known.

Mythology

In Greek mythology, it was identified as the Nemean Lion (and may have been a source of the tale) which was killed by Herakles during one of his twelve labours, and subsequently put into the sky.

Astrology

The Western astrological sign Leo of the tropical zodiac (July 24 - August 23) differs from the astronomical constellation and the Hindu astrological sign of the sidereal zodiac (August 10 - September 15). In some cosmologies, Leo is associated with the classical element Fire, and thus called a Fire Sign (with Aries and Sagittarius). Leo is also one of the Fixed signs (along with Taurus, Scorpio, and Aquarius). It is the domicile of the Sun. The Egyptian pharaoh Necepsos, and his philosopher Petosiris, taught that at the creation of the world the Sun rose here near Denebola, and hence Leo was Domicilium Solis, the emblem of fire and heat, and the "House of the Sun". Each astrological sign is assigned a part of the body, viewed as the seat of its power. Leo rules the heart and spine.

Alchemy

In the symbolism of alchemy, Leo denoted the absorption or assimilation of one substance by another.

Stars

:Stars with proper names: :
- Regulus or Cor Leonis or Kalb [Kabelaced, Al Kalb al Asad] or Rex (32/α Leo) 1.36 :
- : < rēgulus The prince :
- : < cor leōnis The heart of the lion :
- : < القلب الأسد al-qalb[u] al-´asad The heart of the lion :
- (94/β Leo) 2.14 Denebola [Deneb Alased, Deneb Aleet] :
- : < الذنب الأسد að-ðanab[u] al-asad The tail of the lion :
- (41/γ¹ Leo) 2.01 Algieba [Al Gieba, Algeiba] :
- : < الجبهة al-jabha[h] The forehead :
- : (or perhaps Arabicized Latin juba The mane) :
- (68/δ Leo) 2.56 Zosma [Zozma, Zozca, Zosca, Zubra] or Duhr [Dhur] :
- (17/ε Leo) 2.97 Ras Elased [Ras Elased Australis] or Algenubi :
- : < رأس الأسد الجنوبي ra´s al-´asad aj-janūbiyy Southern lion head :
- (36/ζ Leo) 3.43 Adhafera [Aldhafera, Aldhafara] :
- : < الضفيرة ađ̧-đ̧afīra[h] The braid/curl (of the mane) :
- (70/θ Leo) 3.33 Chertan [Chort] or Coxa :
- : < ? al-xarat The rib (two small ribs?) :
- : < cōxa The hip :
- (78/ι Leo) 4.00 Tsze Tseang :
- : < 次將 (Mandarin cìjiàŋ) The vice-general :
- (1/κ Leo) 4.47 Al Minliar al Asad :
- (4/λ Leo) 4.32 Alterf or Al Terf :
- : < الطرف aţ-ţarf The eye, the glance (of the lion) :
- (24/μ Leo) 3.88 Rasalas [Ras Elased Borealis, Ras al Asad al Shamaliyy] or Alshemali :
- : < رأس الأسد الشمالي ra´s al-´asad aš-šamāliyy The northern lion head :
- (14/ο Leo) – double 3.52, 3.7 Subra :Stars with Bayer designations: :: 41/γ² Leo 3.80; 30/η Leo 3.48; 27/ν Leo 5.26; 5/ξ Leo 4.99; 29/π Leo 4.68; 47/ρ Leo 3.84; 77/σ Leo 4.05; 84/τ Leo 4.95; 91/υ Leo 4.30; 63/χ Leo 4.62; 74/φ Leo 4.45; 16/ψ Leo 5.36; 2/ω Leo 5.40 :Stars with Flamsteed designations: :: 3 Leo 5.72; 7 Leo 6.32; 8 Leo 5.73; 9 Leo 6.61; 10 Leo 5.00; 11 Leo 6.63; 13 Leo 6.26; 18 Leo 5.67; 19 Leo 6.44; 20 Leo 6.10; 23 Leo 6.45; 34 Leo 6.43; 35 Leo 5.95; 37 Leo 5.42; 39 Leo 5.81; 40 Leo 4.78; 42 Leo 6.16; 43 Leo 6.06; 44 Leo 5.61; 45 Leo 6.01; 46 Leo 5.43; 48 Leo 5.07; 49 Leo 5.67; 54 Leo – double 4.30, 6.30; 55 Leo 5.91; 56 Leo 5.91; 64 Leo 6.48; 67 Leo 5.70; 71 Leo 7.31; 72 Leo 4.56; 75 Leo 5.18; 76 Leo 5.90; 79 Leo 5.39; 80 Leo 6.35; 81 Leo 5.58; 83 Leo – double 6.49, 7.57; comp. B has a planet; 85 Leo 5.74; 86 Leo 5.54; 88 Leo 6.27; 89 Leo 5.76; 90 Leo 5.95; 92 Leo 5.26; 93 Leo 4.50 :Other notable stars: :
- Wolf 359 13.45 – flare star; 3rd closest star :
- GJ 436 10.68 – nearby; has a planet :
- HD 88133 8.06 – has a planet

References

- Star Names: Their Lore and Meaning, by Richard Allen Hinckley, Dover. ISBN 0486210790
- Dictionary of Symbols, by Carl G. Liungman, W. W. Norton & Company. ISBN 0393312364

External links

- [http://www.allthesky.com/constellations/leo/ The Deep Photographic Guide to the Constellations: Leo] Category:Astrological signs
- ko:사자자리 ja:しし座 th:กลุ่มดาวสิงโต

Gemini

:For information on the US space program named Gemini see Project Gemini. :In mythology, the Gemini are Castor and Polydeuces. :For the awards for Canadian television, see Gemini Award. Gemini (18px, and Latin for twins) is one of the constellations of the zodiac. It is part of the winter sky, lying between Taurus to the west and the dim Cancer to the east, with Auriga and the near-invisible Lynx to the north and Monoceros and Canis Minor to the south. The Gemini program is named for it.

Notable features

Gemini includes two bright stars, named after the two twins, who correspond to the Dioscuri in Greek mythology - Castor (α), a pretty telescopic binary (actually sextuple), and Pollux (β), which is brighter and more southwesterly. The other stars are relatively dim - only one, γ Gem (Alhena) is ever seen from a large city - and trace out a rectangle to the southeast. The planet Pluto was discovered in this constellation in 1930, near the star δ Gem (Wasat).

Notable deep sky objects

The brightest deep sky object of Gemini is M35, an open cluster of 5th magnitude, 2 800 light-years from earth. It is northwest of η Geminorum, near the western edge of the constellation.

Mythology

Since this constellation is easily viewable as two parallel stick figures [http://www.coldwater.k12.mi.us/lms/planetarium/myth/Gem.gif], considering faint stars visible to the naked eye, it was associated with the myth of Castor and Polydeuces (also known as the Dioscuri). A myth of these twins heavily concerns cattle theft, and may be connected to early views of the Milky Way, as a herd of dairy cows or cattle, by which they are situated. The orientation of the constellation can vary (since they readily form stick figures whether leaning right or left), though the twins are usually viewed as left leaning. However, when right leaning, one of the twins resides in the Milky Way, and the other outside it, a situation making it appear that one of the twins is stealing the cattle, and the other is observing. In this situation, together with the area of the sky that is deserted (now considered as the new and extremely faint constellations Camelopardalis and Lynx), and the other features of the area in the Zodiac sign of Gemini (i.e. Orion, Auriga, and Canis Major), this may be the origin of the myth of the cattle of Geryon, which forms one of The Twelve Labours of Herakles.

Astrology

The Western astrological sign Gemini of the tropical zodiac (May 21 - June 20) differs from the astronomical constellation and the Hindu astrological sign of the sidereal zodiac (June 20 - July 20). In some cosmologies, Gemini is associated with the classical element Air, and thus called an Air Sign (with Libra and Aquarius). It is also one of the four mutable signs (along with Virgo, Sagittarius, and Pisces). Its polar opposite is Sagittarius. It is the domicile of Mercury. Each astrological sign is assigned a part of the body, viewed as the seat of its power. Gemini rules the hands and arms. The symbol for Gemini is the twins.

Gemini

:Stars with proper names: :
- Castor (66/α Gem) – sextuple 1.98, 2.88 :
- Pollux (78/β Gem) 1.16 :
- (24/γ Gem) 1.93 Alhena or Almeisan :
- : < ? al-han'ah The brand (on the neck of a camel) :
- : < ? al-maisan The shining one :
- (55/δ Gem) 3.50 Wasat [Wesat] :
- : < وسط السما wasaţ as-samā Middle of the sky :
- (27/ε Gem) 3.06 Mebsuta [Melucta, Meboula] :
- : < المبسوطة al-mabsūţa[h] The outstretched (paw of Leo) :
- (43/ζ Gem) 4.01 Mekbuda :
- : < المقبوضة al-maqbūđ̧a[h] The pulled in (paw) :
- (7/η Gem) 3.31 Propus [Praepes] or Tejat Prior :
- : < πρόπους The fore foot :
- (60/ι Gem) (or Propus, see η Gem) 3.78 :
- (13/μ Gem) 2.87 Tejat Posterior or Nuhatai or Calx or Pish Pai :
- (31/ξ Gem) 3.35 Alzirr :
- : < الزر az-zarr/az-zir :
- 1 Gem (or Propus, see η Gem) 4.16 :Stars with Bayer designations: :: 34/θ Gem 3.60; 77/κ Gem 3.57; 54/λ Gem 3.58; 18/ν Gem 4.13; 71/ο Gem 4.89; 80/π Gem 5.14; 62/ρ Gem 4.16; 75/σ Gem 4.23; 46/τ Gem 4.41; 69/υ Gem 4.06; χ Gem 4.94; 83/φ Gem 4.97; 42/ω Gem 5.20; 65/b Gem 5.01; 76/c Gem 5.30; 36/d Gem 5.28; 38/e Gem 4.73; 74/f Gem 5.04; 81/g Gem 4.89; 57/A Gem 5.04 :Stars with Flamsteed designations: :: 2 Gem 6.67; 3 Gem 5.75; 4 Gem 6.88; 5 Gem 5.83; 6/BU Gem 6.51; 8 Gem 6.09; 9 Gem 6.24; 10 Gem 6.58; 11 Gem 6.91; 12 Gem 6.95; 15 Gem 6.54; 15 Gem 9.21; 16 Gem 6.22; 19 Gem 6.38; 20 Gem 6.26; 23 Gem 6.73; 25 Gem 6.45; 26 Gem 5.20; 28 Gem 5.42; 30 Gem 4.49; 32 Gem 6.47; 33 Gem 5.87; 35 Gem 5.68; 37 Gem 5.74 – nearby; 39 Gem 6.20; 40 Gem 6.40; 41 Gem 5.73; 44 Gem 6.00; 45 Gem 5.47; 47 Gem 5.75; 48 Gem 5.85; 49 Gem 7.06; 51 Gem 5.07; 52 Gem 5.84; 53 Gem 5.75; 56 Gem 5.09; 58 Gem 6.17; 59 Gem 5.77; 61 Gem 5.94; 63 Gem 5.20; 64 Gem 5.07; 68 Gem 5.27; 70 Gem 5.58; 79 Gem 6.53; 82 Gem 6.18; 85 Gem 5.38

External links

- [http://www.allthesky.com/constellations/gemini/ The Deep Photographic Guide to the Constellations: Gemini]
- [http://astrology.yahoo.com/astrology/general/dailyoverview/gemini Gemini Links on Yahoo.com]
- [http://www.astrology.com/ssc/gemini.html?ice=ast,scopes,mssc Gemini Links on Astrology.com]
- [http://www.doublesign.com/astro/western/signs.php?signid=gemini Gemini Links on DoubleSign.com] Category:Astrological signs ko:쌍둥이자리 ja:ふたご座 th:กลุ่มดาวคนคู่

July

Other names

Trivia

See also

Seventh

seventh, musical group

Month

Astronomical background

Sidereal month

Tropical month

Anomalistic month

Draconic month

Synodic month

Month lengths

Calendrical consequences

Months in various calendars

Julian and Gregorian calendars

Islamic calendar

Hebrew Calendar

Hindu Calendar

Iranian/Persian calendar

Icelandic/Old Norse calendar

Notes

See also

Cancer

Diagnosing cancer

Signs and symptoms

Biopsy

Screening

Types of cancer

Adult cancers

Childhood cancers

Causes and pathophysiology

Origins of cancer

Molecular biology

Morphology

Heredity

Environment and diet

Treatment of cancer

Surgery

Chemotherapy

Immunotherapy

Radiation therapy

Hormonal suppression

Symptom control

Treatment trials

Complementary and alternative medicine

Epidemiology

Prevention

Diet and cancer

Other chemoprevention agents

Cancer vaccines

Genetic testing

Coping with cancer

Social impact

Cancer research

See also

References

External links

Professional and research

Support and advocacy

Leo

Notable features

Notable deep sky objects

History of the name

History of the symbol

Mythology

Astrology

Alchemy

Stars

References

External links

Gemini

Notable features

Notable deep sky objects

Mythology

Astrology

Gemini

External links

Cancer