Tuesday, March 23, 2010


Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham (Arabic: ابو علي، الحسن بن الحسن بن الهيثم, Persian: ابن هیثم, Latinized: Alhacen or (deprecated) Alhazen) (965 in Basra - c. 1039 in Cairo) was an Arab or Persian scientist and polymath. He made significant contributions to the principles of optics, as well as to physics, anatomy, astronomy, engineering, mathematics, medicine, ophthalmology, philosophy, psychology, visual perception, and to science in general with his early application of the scientific method. He is sometimes called al-Basri (Arabic: البصري), after his birthplace in the city of Basra. He was also nicknamed Ptolemaeus Secundus ("Ptolemy the Second") or simply "The Physicist" in medieval Europe.
Ibn al-Haytham is regarded as the "father of modern optics" for his influential Book of Optics which proved the intromission theory of vision and refined it into essentially its modern form. He is also recognized so for his experiments on optics, including experiments on lenses, mirrors, refraction, reflection, and the dispersion of light into its constituent colours. He studied binocular vision and the Moon illusion, described the finite speed of light, and argued that it is made of particles travelling in straight lines. Due to his formulation of a modern quantitative and empirical approach to physics and science, he is considered the pioneer of the modern scientific method and the originator of the experimental nature of physics and science. Author Bradley Steffens describes him as the "first scientist". He is also considered by A. I. Sabra to be the founder of experimental psychology for his approach to visual perception and optical illusions, and a pioneer of the philosophical field of phenomenology or the study of consciousness from a first-person perspective. His Book of Optics has been ranked with Isaac Newton's Philosophiae Naturalis Principia Mathematica as one of the most influential books in the history of physics, for starting a revolution in optics and visual perception.
Ibn al-Haytham's achievements include many advances in physics and mathematics. He gave the first clear description and correct analysis of the camera obscura. He enunciated Fermat's principle of least time and the concept of inertia (Newton's first law of motion), and developed the concept of momentum. He described the attraction between masses and was aware of the magnitude of acceleration due to gravity at-a-distance. He stated that the heavenly bodies were accountable to the laws of physics and also presented a critique and reform of Ptolemaic astronomy. He was the first to state Wilson's theorem in number theory, and he formulated the Lambert quadrilateral and a concept similar to Playfair's axiom now used in non-Euclidean geometry. Moreover, he formulated and solved Alhazen's problem geometrically using early ideas related to infinitesimal calculus and mathematical induction.

Ibn al-Haythem made significant improvements in optics, physical science, and the scientific method which influenced the development of science for over five hundred years after his death. Ibn al-Haytham's work on optics is credited with contributing a new emphasis on experiment. His influence on physical sciences in general, and on optics in particular, has been held in high esteem and, in fact, ushered in a new era in optical research, both in theory and practice. The scientific method is considered to be so fundamental to modern science that some—especially philosophers of science and practising scientists—consider earlier inquiries into nature to be pre-scientific.
Richard Powers nominated Ibn al-Haytham's scientific method and scientific skepticism as the most influential idea of the second millennium. Recipient of the Nobel Prize in Physics Abdus Salam considered Ibn-al-Haytham "one of the greatest physicists of all time." George Sarton, the father of the history of science, wrote that "Ibn Haytham's writings reveal his fine development of the experimental faculty" and considered him "not only the greatest Muslim physicist, but by all means the greatest of mediaeval times." Robert S. Elliot considers Ibn al-Haytham to be "one of the ablest students of optics of all times." The author Bradley Steffens considers him to be the "first scientist", and Professor Jim Al-Khalili also considers him the "world's first true scientist". The Biographical Dictionary of Scientists wrote that Ibn al-Haytham was "probably the greatest scientist of the Middle Ages" and that "his work remained unsurpassed for nearly 600 years until the time of Johannes Kepler." At a scientific conference in February 2007 as a part of the Hockney-Falco thesis, Charles M. Falco argued that Ibn al-Haytham's work on optics may have influenced the use of optical aids by Renaissance artists. Falco said that his and David Hockney's examples of Renaissance art "demonstrate a continuum in the use of optics by artists from circa 1430, arguably initiated as a result of Ibn al-Haytham's influence, until today." The Latin translation of his main work, Kitab al-Manazir (Book of Optics), exerted a great influence on Western science: for example, on the work of Roger Bacon, who cites him by name, and on Johannes Kepler. It brought about a great progress in experimental methods. His research in catoptrics (the study of optical systems using mirrors) centred on spherical and parabolic mirrors and spherical aberration. He made the observation that the ratio between the angle of incidence and refraction does not remain constant, and investigated the magnifying power of a lens. His work on catoptrics also contains the problem known as "Alhazen's problem". Meanwhile in the Islamic world, Ibn al-Haytham's work influenced Averroes' writings on optics, and his legacy was further advanced through the 'reforming' of his Optics by Persian scientist Kamal al-Din al-Farisi (d. ca. 1320) in the latter's Kitab Tanqih al-Manazir (The Revision of [Ibn al-Haytham's] Optics). The correct explanations of the rainbow phenomenon given by al-Fārisī and Theodoric of Freiberg in the 14th century depended on Ibn al-Haytham's Book of Optics. The work of Ibn al-Haytham and al-Fārisī was also further advanced in the Ottoman Empire by polymath Taqi al-Din in his Book of the Light of the Pupil of Vision and the Light of the Truth of the Sights (1574). He wrote as many as 200 books, although only 55 have survived, and many of those have not yet been translated from Arabic. Even some of his treatises on optics survived only through Latin translation. During the Middle Ages his books on cosmology were translated into Latin, Hebrew and other languages. The crater Alhazen on the Moon is named in his honour, as was the asteroid "59239 Alhazen".

Wednesday, March 17, 2010

George Town, Penang

George Town World Heritage Site
THE World Heritage Committee meeting in Quebec City added George Town to UNESCO’s World Heritage List on the morning of 7 July 2008. George Town's built heritage comprises architectural traditions adapted to local conditions from both East and West. Its historic core has the largest concentration of pre-World War II architecture in Southeast Asia. Over the last 222 years, a unique way of life based upon East-West exchanges has developed here. The influences of Asia and Europe have endowed the city with a specific multicultural heritage.
George Town is one of three great historic settlements along the Straits of Malacca. The other settlements are Malacca, also a World Heritage Site, and Singapore. The island of Penang, in north-west Malaysia, was the first of these three British colonies to be established, and George Town is its capital.

In 1786, Captain Francis Light established an English East India Company (EIC) trading post here. However, Light was not the first settler and his role as “founder” is much contested, for Penang was, until then, part of the ancient Kedah Sultanate.

Achenese traders had already settled along the Pinang River when Francis Light arrived. Chinese tombstones in Tanjong Tokong allegedly predate Light’s arrival. In those days, however, Penang Island was very sparsely populated. After Francis Light arrived, George Town soon attracted migrants from all over Asia and Europe, contributing to a rapidly burgeoning multicultural identity.

In 1805, the British government designated the colony as an Indian Presidency, under the administration of Bengal, and a multiethnic Committee of Assessors was established to set rates and help manage the city. This was the precursor to the George Town Municipal Council, and the first in Malaysia.

In its early days, George Town attracted traders from India and Indonesia because it was a major port for textiles and pepper within the region, and later nutmeg. These commodities were of great importance financially. But the big money was in the China trade that passed through the Malacca Straits. It was based almost entirely upon tea, but included silk and ceramics.

In the opposite direction, ships carried opium and silver, and sundry other items that were of interest to the Chinese. However, Penang never became the main port for the China trade, because its role was soon usurped by Singapore (est 1819), which was fast developing under the administration of Stamford Raffles, who had the ear of the British Government.

In 1826, George Town became the capital of the British Straits Settlements comprising Penang, Malacca and Singapore. But by 1832, Singapore had taken over George Town’s administrative role. With declining trade and disease threatening its pepper and nutmeg plantations, the city’s future was bleak.

This decline was stemmed 10 years later by the discovery of tin in the neighbouring Malay States. Migrants from south-eastern China soon arrived, adding to the city’s cosmopolitan character. The Triads, fighting men affiliated with Chinese clans and dialect groups, accompanied them.

In 1857, competition amongst the Chinese over the monopoly for opium and tin trading exploded into open warfare. The Penang Riots resulted in the end of indirect rule. Up till then, the British had ruled through local headmen called “Kapitans”. In their place, the British established an inspectorate of police that enforced British laws throughout the colony.

By 1869, the year the Suez Canal opened, George Town had developed into the region’s chief entrepot port. Wealth from trade, tin mining and commercial agriculture resulted in the largest conglomeration of pre-World War II architecture in Southeast Asia.

By the turn of the 20th century, George Town had become a regional education and intellectual centre through its English schools and lively modern press. It became a haven for religious reformers, revolutionaries and proto-nationalists. It was also a modern city with electric tram-cars and a funicular railway linking the city to the Penang Hills. As with so many major ports in the 1930s, George Town was a centre not just for trade and finance, but also for recreation, with its Great World Parks, jazz bands and cabarets.

In 1941, this cosmopolitan society was shattered by the bombing raids of the Japanese Imperial Air Force and nearly extinguished by the brutal three and a half year occupation that followed. Rebuilding went on in earnest after the war ended in 1945, but George Town’s role as an imperial port city was played out as the post-war British Empire was quickly dismantled, to be replaced by the looser affiliations of the Commonwealth.

On 1 January 1957, George Town was granted city status by HRH Queen Elizabeth II. It was now settling into its new role as the second city in the new Malaysian Federation. In the 1960s, as entrepot trade declined further, George Town also declined. A decade later, with a shift away from trade, manufacturing and mass tourism took over, creating new townships. Manufacturing concentrated in the south-west, with tourism to the north.

Friday, March 12, 2010


Chikungunya (in the Makonde language "that which bends up") virus (CHIKV) is an insect-borne virus, of the genus Alphavirus, that is transmitted to humans by virus-carrying Aedes mosquitoes. There have been recent outbreaks of CHIKV associated with severe illness. CHIKV causes an illness with symptoms similar to dengue fever. CHIKV manifests itself with an acute febrile phase of the illness lasting only two to five days, followed by a prolonged arthralgic disease that affects the joints of the extremities. The pain associated with CHIKV infection of the joints persists for weeks or months, or in some cases years.

Signs and symptoms
The incubation period of Chikungunya disease is from two to four days. Symptoms of the disease include a fever up to 40 °C (104 °F), a petechial or maculopapular rash of the trunk and occasionally the limbs, and arthralgia or arthritis affecting multiple joints. Other nonspecific symptoms can include headache, conjunctival Injection, and slight photophobia. Typically, the fever lasts for two days and then ends abruptly. However, other symptoms—namely joint pain, intense headache, insomnia and an extreme degree of prostration—last for a variable period; usually for about 5 to 7 days. Patients have complained of joint pains for much longer time periods depending on their age.

Chikungunya virus is indigenous to tropical Africa and Asia, where it is transmitted to humans by the bite of infected mosquitoes, usually of the genus Aedes. Chikungunya virus belongs to alpha-virus under Togaviridae family. It is an "Arbovirus" (Ar-arthropod, bo-borne). CHIK fever epidemics are sustained by human-mosquito-human transmission. The word "chikungunya" is thought to derive from description in local dialect of the contorted posture of patients afflicted with the severe joint pain associated with this disease. The main virus reservoirs are monkeys, but other species can also be affected, including humans.

There are no specific treatments for Chikungunya. There is no vaccine currently available. A Phase II vaccine trial, sponsored by the US Government and published in the American Journal of Tropical Medicine and Hygiene in 2000, used a live, attenuated virus, developing viral resistance in 98% of those tested after 28 days and 85% still showed resistance after one year.
A serological test for Chikungunya is available from the University of Malaya in Kuala Lumpur, Malaysia.
Chloroquine is gaining ground as a possible treatment for the symptoms associated with Chikungunya, and as an anti-inflammatory agent to combat the arthritis associated with Chikungunya virus. A University of Malaya study found that for arthritis-like symptoms that are not relieved by aspirin and non-steroidal anti-inflammatory drugs (NSAID), chloroquine phosphate (250 mg/day) has given promising results. Research by an Italian scientist, Andrea Savarino, and his colleagues together with a French government press release in March 2006 have added more credence to the claim that chloroquine might be effective in treating chikungunya. Unpublished studies in cell culture and monkeys show no effect of chloroquine treatment on reduction of chikungunya disease. The fact sheet on Chikungunya advises against using aspirin, ibuprofen, naproxen and other NSAIDs that are recommended for arthritic pain and fever.

Chikungunya virus is an alphavirus closely related to the O'nyong'nyong virus, the Ross River virus in Australia, and the viruses that cause eastern equine encephalitis and western equine encephalitis.
Chikungunya is generally spread through bites from Aedes aegypti mosquitoes, but recent research by the Pasteur Institute in Paris has suggested that Chikungunya virus strains in the 2005-2006 Reunion Island outbreak incurred a mutation that facilitated transmission by Aedes albopictus (Tiger mosquito). Concurrent studies by arbovirologists at the University of Texas Medical Branch in Galveston, Texas, confirmed definitively that enhanced chikungunya virus infection of Aedes albopictus was caused by a point mutation in one of the viral envelope genes (E1). Enhanced transmission of chikungunya virus by Aedes albopictus could mean an increased risk for chikungunya outbreaks in other areas where the Asian tiger mosquito is present. A recent epidemic in Italy was likely perpetuated by Aedes albopictus.
In Africa, chikungunya is spread via a sylvatic cycle in which the virus largely resides in other primates in between human outbreaks.
On 28 May 2009 in Changwat Trang of Thailand where the virus is endemic, the provincial hospital decided to deliver by Caesarean section a male baby from his Chikungunya-infected mother—Khwanruethai Sutmueang, 28, a Trang native—in order to prevent mother-foetus virus transmission. However, after delivering the baby, the physicians discovered that the baby was infected with Chikungunya virus, and put him into intensive care because the infection had left the baby unable to breathe by himself or to drink milk. The physicians presumed that Chikungunya virus might be able to be transmitted from a mother to her foetus; however, there is no laboratory confirmation for this presumption.

Sunday, March 7, 2010

Geomagnetic storm

A geomagnetic storm is a temporary disturbance of the Earth's magnetosphere caused by a disturbance in space weather. Associated with solar coronal mass ejections (CME), coronal holes, or solar flares, a geomagnetic storm is caused by a solar wind shock wave which typically strikes the Earth's magnetic field 24 to 36 hours after the event. This only happens if the shock wave travels in a direction toward Earth. The solar wind pressure on the magnetosphere will increase or decrease depending on the Sun's activity. These solar wind pressure changes modify the electric currents in the ionosphere. Magnetic storms usually last 24 to 48 hours, but some may last for many days. In 1989, an electromagnetic storm disrupted power throughout most of Quebec—it caused auroras as far south as Texas.

Radiation hazards to humans
Intense solar flares release very-high-energy particles that can cause radiation poisoning to humans (and mammals in general) in the same way as low-energy radiation from nuclear blasts.
Earth's atmosphere and magnetosphere allow adequate protection at ground level, but astronauts in space are subject to potentially lethal doses of radiation. The penetration of high-energy particles into living cells can cause chromosome damage, cancer, and a host of other health problems. Large doses can be fatal immediately.
Solar protons with energies greater than 30 MeV are particularly hazardous. In October 1989, the Sun produced enough energetic particles that an astronaut wearing only a space suit and caught out in the brunt of the storm, would probably have died; the expected dose would be about 7000 rem. Note that Astronauts who had time to gain safety in a shelter beneath moon soil would have absorbed only slight amounts of radiation.
The cosmonauts on the Mir station were subjected to daily doses of about twice the yearly dose on the ground, and during the solar storm at the end of 1989 they absorbed their full-year radiation dose limit in just a few hours.
Solar proton events can also produce elevated radiation aboard aircraft flying at high altitudes. Although these risks are small, monitoring of solar proton events by satellite instrumentation allows the occasional exposure to be monitored and evaluated, and eventually the flight paths and altitudes adjusted in order to lower the absorbed dose of the flight crews.

Disrupted systems - Communications
Many communication systems use the ionosphere to reflect radio signals over long distances. Ionospheric storms can affect radio communication at all latitudes. Some radio frequencies are absorbed and others are reflected, leading to rapidly fluctuating signals and unexpected propagation paths. TV and commercial radio stations are little affected by solar activity, but ground-to-air, ship-to-shore, shortwave broadcast, and amateur radio (mostly the bands below 30 MHz) are frequently disrupted. Radio operators using HF bands rely upon solar and geomagnetic alerts to keep their communication circuits up and running.
Some military detection or early warning systems are also affected by solar activity. The over-the-horizon radar bounces signals off the ionosphere to monitor the launch of aircraft and missiles from long distances. During geomagnetic storms, this system can be severely hampered by radio clutter. Some submarine detection systems use the magnetic signatures of submarines as one input to their locating schemes. Geomagnetic storms can mask and distort these signals.
The Federal Aviation Administration routinely receives alerts of solar radio bursts so that they can recognize communication problems and forego unnecessary maintenance. When an aircraft and a ground station are aligned with the Sun, jamming of air-control radio frequencies can occur. This can also happen when an Earth station, a satellite, and the Sun are in alignment.
The telegraph lines in the past were affected by geomagnetic storms as well. The telegraphs used a long wire for the data line, stretching for many miles, using ground as the return wire and being fed with DC power from a battery; this made them (together with the power lines mentioned below) susceptible to being influenced by the fluctuations caused by the ring current. The voltage/current induced by the geomagnetic storm could have led to diminishing of the signal, when subtracted from the battery polarity, or to overly strong and spurious signals when added to it; some operators in such cases even learned to disconnect the battery and rely on the induced current as their power source. In extreme cases the induced current was so high the coils at the receiving side burst in flames, or the operators received electric shocks. Geomagnetic storms affect also long-haul telephone lines, including undersea cables unless they are fiber optic.
Damage to communications satellites can disrupt non-terrestrial telephone, television, radio, and Internet links.

Disrupted systems - Geologic exploration
Earth's magnetic field is used by geologists to determine subterranean rock structures. For the most part, these geodetic surveyors are searching for oil, gas, or mineral deposits. They can accomplish this only when Earth's field is quiet, so that true magnetic signatures can be detected. Other surveyors prefer to work during geomagnetic storms, when the variations to Earth's normal subsurface electric currents help them to see subsurface oil or mineral structures. For these reasons, many surveyors use geomagnetic alerts and predictions to schedule their mapping activities.

Monday, March 1, 2010

Antenna (biology)

Antennae (singular: antenna) in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in many cell types of eukaryotes.
In arthropods, antennae are connected to the front-most segments. In crustaceans, they are biramous and present on the first two segments of the head, with the smaller pair known as antennules. All other arthropod groups, except chelicerates, proturans and arachnids which have none, have a single, uniramous pair of antennae. These antennae are jointed, at least at the base, and generally extend forward from the head. They are sensory organs, although the exact nature of what they sense and how they sense it is not the same in all groups, nor always clear. Functions may variously include sensing touch, air motion, heat, vibration (sound), and especially olfaction (smell) or gustation (taste).

Antenna are the primary olfactory sensors of an insect and are accordingly well-equipped with a wide variety of sensilla (singular : sensillum). Paired, mobile, and segmented, they are located between the eyes on the forehead. Embryologically, they represent the appendages of the second head segment.
All insects have antenna though these may be greatly reduced in the larval forms. Amongst the non-insect classes of Hexapoda, Collembola and Diplura have antenna, but Protura do not.

The three basic segments of the typical insect antenna are the scape (base), the pedicel (stem), and finally the flagellum, which often comprises many units known as flagellomeres.
Muscles are only present in the two first segments, the scape and pedicel. The scape is surrounded by a membranous region of the head. It pivots on a single marginal point called the antennifer, allowing it to move in any direction.
The number of flagellomeres can vary greatly, and is often of diagnostic importance. True flagellomeres have a membranous articulation between them, but in many insects, especially the more primitive groups, the flagellum is entirely or partially composed of a flexible series of small annuli, which are not true flagellomeres.
In many beetles and in the chalcidoid wasps, the apical flagellomeres form a club, and the collective term for the segments between the club and the antennal base is the funicle; for traditional reasons, in beetles it is the segments between the club and the scape, but in wasps, it is the segments between the club and the pedicel.
In the groups with more uniform antennae (for example: Diplopoda), all segments are called antennomeres. Some groups have a simple or variously modified apical or subapical bristle called an arista (this may be especially well-developed in various Diptera).

Olfactory receptors on the antennae bind to odour molecules, including pheromones. The neurons that possess these receptors signal this binding by sending action potentials down their axons to the antennal lobe in the brain. From there, neurons in the antennal lobes connect to mushroom bodies that identify the odour. The sum of the electrical potentials of the antenna to a given odor can be measured using an electroantennogram.
In the case of the Monarch, it has been shown that antennae are necessary for proper time-compensated Sun compass orientation during migration, that antennal clocks exist in monarchs, and that they likely provide the primary timing mechanism for Sun compass orientation.

Crustaceans bear two pairs of antennae. The first pair are uniramous and are often referred to as antennules, while the second pair are biramous, meaning that each antenna is composed of two parts, joined at their base. In most adults, the antenna are sensory organs, but they are used by the nauplius larva for swimming. In some groups of crustaceans, such as the spiny lobsters and slipper lobsters, the second antennae are enlarged, while in others, such as crabs, the antennae are reduced in size.

Cellular antennae
Within the biological and medical disciplines, recent discoveries have noted that primary cilia in many types of cells within eukaryotes serve as cellular antennae. These cilia play important roles in chemosensation, mechanosensation, and thermosensation. The current scientific understanding of primary cilia organelles views them as "sensory cellular antennae that coordinate a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation."
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