dx+ey= f---------------2

multiply equation 1 by d and equation 2 by a , to give:

adx + bdy = cd-------3

adx + aey = af--------4

Subtract equation 4 from equation 3

bdy - aey = cd-af

simplifying, we have

y(bd-ae) = cd-af

dividing both sides by bd-ae

y(bd-ae)/bd-ae = cd-af/bd-ae

y= cd-af/bd-ae

Derivation for x

ax + by = c-----------1

dx +ey = f------------2

Multiply equation1 by e and equation 2 by b, to give

aex + bey = ce-------------------3

bdx +bey = bf-------------------4

subtract equation 4 from equation 3

aex - bdx = ce- bf

Simplify the L.H.S, we have

x(ae-bd) = ce-bf

dividing both sides by ae - bd

x = ce-bf/ae-bd

Using Samuel's equation to solve simultaneous equation

2x + 3y =5-----------1

3x + 4y =7-----------2

solve for x, using x = ce-bf/ae-bd

Note, a =2, b =3, c=5, d=3, e=4, f=7

x = 5(4) - 3(7)/2(4) - 3(3)

=20 - 21/8 - 9

=-1/-1

=1

Assignment: Solve for Y using Samuel's Formula

What is acne?

Acne (acne vulgaris, common acne) is a disease of the hair follicles of the face, chest, and back that affects almost all males and females during puberty; the only exception being teenage members of a few primitive isolated tribes living in Neolithic societies. It is not caused by bacteria, although bacteria play a role in its development. It is not unusual for some women to develop acne in their mid- to late-20s.
Acne appears on the skin as...

• congested pores ("comedones"), also known as blackheads or whiteheads,
• tender red bumps also known as pimples or zits,
• pustules, and occasionally as
• cysts (deep pimples, boils).

You can do a lot to treat your acne using products available at a drugstore or cosmetic counter that do not require a prescription. However, for tougher cases of acne, you should consult a physician for treatment options.

What causes acne?

No one factor causes acne. Acne happens when sebaceous (oil) glands attached to the hair follicles are stimulated at the time of puberty by elevated levels of male hormones. Sebum (oil) is a natural substance which lubricates and protects the skin. Associated with increased oil production is a change in the manner in which the skin cells mature so that they are predisposed to clog the follicular openings or pores. The clogged hair follicle gradually enlarges, producing a bump. As the follicle enlarges, the wall may rupture, allowing irritating substances and normal skin bacteria access into the deeper layers of the skin, ultimately producing inflammation.
Inflammation near the skin's surface produces a pustule; deeper inflammation results in a papule (pimple); deeper still and it's a cyst. If the oil breaks though to the surface, the result is a "whitehead." If the oil accumulates melanin pigment or becomes oxidized, the oil changes from white to black, and the result is a "blackhead." Blackheads are therefore not dirt and do not reflect poor hygiene.
Here are some factors that don't usually play a role in acne:

• Heredity: With the exception of very severe acne, most people do not have the problem exactly as their parents did. Almost everyone has some acne at some point in their life.
• Food: Parents often tell teens to avoid pizza, chocolate, greasy and fried foods, and junk food. While these foods may not be good for overall health, they don't cause acne or make it worse. Although some recent studies have implicated milk and pure chocolate in aggravating acne, these findings are very far from established.
• Dirt: As mentioned above, "blackheads" are oxidized oil, not dirt. Sweat does not cause acne, therefore, it is not necessary to shower instantly after exercise for fear that sweat will clog pores. On the other hand, excessive washing can dry and irritate the skin.
• Stress: Some people get so upset by their pimples that they pick at them and make them last longer. Stress, however, does not play much of a direct role in causing acne.

In occasional patients, the following may be contributing factors:

• Pressure: In some patients, pressure from helmets, chin straps, collars, suspenders, and the like can aggravate acne.
• Drugs: Some medications may cause or worsen acne, such as those containing iodides, bromides, or oral or injected steroids (either the medically prescribed prednisone [Deltasone, Orasone, Prednicen-M, Liquid Pred] or the steroids that bodybuilders or athletes take). Other drugs that can cause or aggravate acne are anticonvulsant medications and lithium (Eskalith, Lithobid), which is used to treat bipolar disorder. Most cases of acne, however, are not drug related.
• Occupations: In some jobs, exposure to industrial products like cutting oils may produce acne.
• Cosmetics: Some cosmetics and skin-care products are pore clogging ("comedogenic"). Of the many available brands of skin-care products, it is important to read the list of ingredients and choose those which have water listed first or second if you are concerned about acne. These "water-based" products are usually safe.

Amazing a child was born with six limbs(legs) in Pakistan unbelievable.

Lesson 1: Let's get started

In this first lesson, you will get a brief presentation of the tools you need to make a website.

What is needed?

Most likely you already have everything you need.
You have a "browser". A browser is the program that makes it possible to browse and open websites. Right now you are looking at this page in your browser.
It is not important which browser you use. The most common is Microsoft Internet Explorer. But there are others such as Opera and Mozilla Firefox and they can all be used.
You might have heard about, or even used, programs such as Microsoft FrontPage, Macromedia Dreamweaver or even Microsoft Word, which can - or claim that they can - create websites for you. Forget these programs for now! They are not of any help to you when learning how to code your own website.
Instead, you need a simple text editor. If you are using Windows you can use Notepad, which is usually found in the start menu under Programs in Accessories:

If you are not using Windows, you can use a similar simple text editor. For example, Pico (Linux) or TextEdit (Mac).
Notepad is a very basic text editing program which is excellent for coding because it does not interfere with what you are typing. It gives you complete control. The problem with many of the programs that claim they can create websites is that they have a lot of standard functions, which you can choose from. The downside is that, everything needs to fit into these standard functions. Thus, this type of programs often cannot create a website exactly as you want it. Or - even more annoyingly - they make changes to your hand-written code. With Notepad or other simple text editors, you only have yourself to thank for your successes and errors.
A browser and Notepad (or a similar simple text editor) are all you need to go through this tutorial and make your own websites.

Do I need to be online?

You do not need to be connected to the Internet - neither while reading this tutorial, nor while making your websites.
If you want to avoid being online while reading this tutorial, you can either print it out or simply disconnect from the Internet while reading on screen. You can make the website on your computer's hard disk and upload it to the Internet when it is finished.

What's next?

Go to the next lesson and read about HTML before the fun really starts in Lesson 3.

Titration

A titration is a method of analysis that will allow you to determine the precise endpoint of a reaction and therefore the precise quantity of reactant in the titration flask. A buret is used to deliver the second reactant to the flask and an indicator or pH Meter is used to detect the endpoint of the reaction.

Doing a Titration

Begin by preparing your buret, as described on the buret page. Your buret should be conditioned and filled with titrant solution. You should check for air bubbles and leaks, before proceding with the titration.

Take an initial volume reading and record it in your notebook. Before beginning a titration, you should always calculate the expected endpoint volume.

Prepare the solution to be analyzed by placing it in a clean Erlenmeyer flask or beaker. If your sample is a solid, make sure it is completely dissoloved. Put a magnetic stirrer in the flask and add indicator.

Use the buret to deliver a stream of titrant to within a couple of mL of your expected endpoint. You will see the indicator change color when the titrant hits the solution in the flask, but the color change disappears upon stirring.

Approach the endpoint more slowly and watch the color of your flask carefully. Use a wash bottle to rinse the sides of the flask and the tip of the buret, to be sure all titrant is mixed in the flask.

As you approach the endpoint, you may need to add a partial drop of titrant. You can do this with a rapid spin of a teflon stopcock or by partially opening the stopcock and rinsing the partial drop into the flask with a wash bottle. Ask your TA to demonstrate these techniques for you, in the lab.

Make sure you know what the endpoint should look like. For phenolphthalein, the endpoint is the first permanent pale pink. The pale pink fades in 10 to 20 minutes.

If you think you might have reached the endpoint, you can record the volume reading and add another partial drop. Sometimes it is easier to tell when you have gone past the endpoint.


When you have reached the endpoint, read the final volume in the buret and record it in your notebook.


Subtract the initial volume to determine the amount of titrant delivered. Use this, the concentration of the titrant, and the stoichiometry of the titration reaction to calculate the number of moles of reactant in your analyte solution.

Titration with a pH meter follows the same procedure as a titration with an indicator, except that the endpoint is detected by a rapid change in pH, rather than the color change of an indicator.

Arrange the sample, stirrer, buret, and pH meter electrode so that you can read the pH and operate the buret with ease.


To detect the endpoint accurately, record pH vs. volume of titrant added and plot the titration curve as you titrate.

 

What is the history of HIV, and when was HIV discovered?

The history of the human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) dates back to 1981, when homosexual men with symptoms of a disease that now are considered typical of AIDS were first described in Los Angeles and New York. The men had an unusual type of lung infection (pneumonia) called Pneumocystis carinii (now known as Pneumocystis jiroveci) pneumonia (PCP) and rare skin tumors called Kaposi's sarcomas. The patients were noted to have a severe reduction in a type of cell in the blood (CD4 cells) that is an important part of the immune system. These cells, often referred to as T cells, help the body fight infections. Shortly thereafter, this disease was recognized throughout the United States, Western Europe, and Africa. In 1983, researchers in the United States and France described the virus that causes AIDS, now known as HIV, belonging to the group of viruses called retroviruses. While HIV infection is required to develop AIDS, the actual definition of AIDS is the development of a low CD4 cell count (<200 cells/mm³) or any one of a long list of complications of HIV infection ranging from a variety of so-called "opportunistic infections," cancers, neurologic symptoms, and wasting syndromes.

What tests are used in the diagnosis of HIV?

In 1985, a blood test became available that measures antibodies to HIV that are the body's immune response to the HIV. The test used most commonly for diagnosing infection with HIV is referred to as an ELISA. If the ELISA finds HIV antibodies, the results must be confirmed, typically by a test called a Western blot. HIV antibody tests remain the best method for diagnosing HIV infection. Recently, tests have become available to look for these same antibodies in saliva, some providing results within one to 20 minutes of testing. Antibodies to HIV typically develop within several weeks of infection. During this interval, patients have virus in their body but will test negative by the standard antibody test, the so called "window period." In this setting, the diagnosis can be made if a test is used that actually detects the presence of virus in the blood rather than the antibodies, such as tests for HIV RNA or p24 antigen. Recently, a new test has been approved that measures both HIV antibodies and p24 antigen, shrinking the duration of the window period from infection to diagnosis. There also are many testing centers around the country that are routinely screening blood samples that are HIV-antibody negative for HIV RNA.
Although the tests for detecting HIV infection continue to improve, they still require that people volunteer for testing. It is estimated that approximately 20% of those infected with HIV in the United States are unaware of their infection because they have never been tested. In order to decrease the number that are unaware of their HIV infection status, in 2006, the Centers for Disease Control and Prevention recommended that all people between the ages of 13 and 64 years be provided HIV testing whenever they encounter the health-care system for any reason. In addition, resources are available to facilitate people finding local HIV testing centers

Dinosaur Feather Color Determined

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Angiosperms

Photo courtesy PDPhoto.org

Angiosperms, also called flowering plants, are the most numerous of all the divisions in the Plant Kingdom. They are vital to all life on earth as they provide oxygen, shelter, clothing, food, and medicine for other living organisms. With the exception of extreme habitats, angiosperms populate every land biome and aquatic community.
Angiosperms are characterized by two basic systems: a root system and a shoot system. The flower, a component of the shoot system, is responsible for seed development and reproduction. Flowers that contain both male and female reproductive structures (stamens and carpels) are called perfect flowers. Flowers that are missing either stamens or carpels are called imperfect flowers. A complete flower contains not only stamens and carpels, but sepals and petals as well.

Petroleum (L. petroleum, from Greek: petra (rock) + Latin: oleum (oil)^[1]) or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. A fossil fuel, it is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and undergo intense heat and pressure. Petroleum is recovered mostly through oil drilling. This latter stage comes after the studies of structural geology (at the reservoir scale), sedimentary basin analysis, reservoir characterization (mainly in terms of porosity and permeable structures).^[2][3] It is refined and separated, most easily by boiling point, into a large number of consumer products, from petrol and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals.^[4] Petroleum is used in manufacturing a wide variety of materials,^[5] and it is estimated that the world consumes about 88 million barrels each day. The use of fossil fuels such as petroleum can have a negative impact on Earth's biosphere, releasing pollutants and greenhouse gases into the air and damaging ecosystems through events such as oil spills.

Polydactyly or polydactylism (from Ancient Greek πολύς (polus) "many" + δάκτυλος (daktulos) "finger"), also known as hyperdactyly, is a congenital physical anomaly in humans, dogs, and cats having supernumerary fingers or toes.^[1]
The extra digit is usually a small piece of soft tissue that can be removed. Occasionally it contains bone without joints; rarely it may be a complete, functioning digit. The extra digit is most common on the ulnar (little finger) side of the hand, less common on the radial (thumb) side, and very rarely within the middle three digits. These are respectively known as postaxial (little finger), preaxial (thumb), and central (ring, middle, index fingers) polydactyly. The extra digit is most commonly an abnormal fork in an existing digit, or it may rarely originate at the wrist as a normal digit does.^[2]. The world record holder for highest number of digits is Akshat Saxena from Uttar Pradesh, India. He was born in 2010 with 7 digits on each hand and 10 digits on each foot, for a total of 34 digits.^[3]

 Genetics

Polydactyly can occur by itself, or more commonly, as one feature of a syndrome of congenital anomalies. When it occurs by itself, it is associated with autosomal dominant mutations in single genes, i.e. it is not a multifactorial trait.^[4] But mutation in a variety of genes can give rise to polydactyly. Typically the mutated gene is involved in developmental patterning, and a syndrome of congenital anomalies results, of which polydactyly is one feature or two.
Types include:

OMIM	Type	Locus
174200	Postaxial A1	GLI3 at 7p13
602085	Postaxial A2	13q21-q32
607324	Postaxial A3	19p13.2-p13.1
608562	Postaxial A4	7q22
174400	Preaxial I	?
174500	Preaxial II	SHH at 7q36
174600	Preaxial III	?
174700	Preaxial IV	GLI3 at 7p13

Syndromes including polydactyly include Acrocallosal syndrome, Basal cell nevus syndrome, Bardet-Biedl syndrome, Biemond syndrome, Ectrodactyly-ectodermal dysplasias-cleft lip/palate syndrome, Ellis van Creveld syndrome, Meckel Gruber syndrome, McKusick-Kaufman syndrome, Mirror hand deformity, Mohr syndrome, Oral-facial-digital syndrome, Pallister-Hall syndrome, Rubinstein-Taybi syndrome, Short rib polydactyly, and VATER association.^[5] It can also occur with a triphalangeal thumb.

Epidemiology

The condition has an incidence of 1 in every 500 live births.^[6] Postaxial hand polydactyly is a common isolated disorder in African black and African American children, and autosomal dominant transmission is suspected. Postaxial polydactyly is more frequent in blacks than in whites and is more frequent in male children.^[7] In contrast, postaxial polydactyly seen in white children is usually syndromic and associated with an autosomal recessive transmission. One study by Finley et al. combined data from Jefferson County, Alabama, United States and Uppsala County, Sweden. This study showed incidence of all types of polydactyly to be 2.3 per 1000 in white males, 0.6 per 1000 in white females, 13.5 per 1000 in black males, and 11.1 per 1000 in black females.^[8]

 Society and culture

 People with polydactyly

• Gemma Arterton, an actress who has starred in Prince of Persia and Quantum of Solace, was born with an extra finger on each hand. The vestigial digits were removed when she was a child.^[9][10]
• Anne Boleyn, former Queen of England, was rumoured to have six fingers on one hand.
• Antonio Alfonseca, professional baseball player.
• Hampton Hawes, jazz pianist, was born with six fingers on each hand (surgically removed shortly after birth).^[11]
• Kamani Hubbard, a boy born with a rare case of polydactyly with both 12 fully functioning fingers and 12 toes.^[12]
• Varalakshmi V, a girl from Bangalore with eight fingers in each hand and about four to five extra toes in each foot.^[13]
• Hrithik Roshan, a Bollywood actor born with a supernumerary thumb on his right hand.^[14]
• Garfield Sobers, West Indian cricketer, had an extra finger on each hand which he removed himself during childhood "with the aid of catgut and a sharp knife".^[15]
• Yoandri "24" Hernandez Garrido, Cuba with six fingers on each hand and six toes on each foot [1].

The photos of his hands and feet look like they were photoshopped to add an extra digit , but they weren't. Devender Harne was born with twelve fingers and thirteen toes. That seems like it would be pretty useful. It certainly helps him type faster. It may also earn him a place in the Guinness Book of World Records. (via J-Walk)