A brain tumor (brain tumour in the UK) is any intracranial tumor created by abnormal and uncontrolled cell division, normally either in the brain itself (neurons, glial cells (astrocytes, oligodendrocytes, ependymal cells), lymphatic tissue, blood vessels), in the cranial nerves (myelin-producing Schwann cells), in the brain envelopes (meninges), skull, pituitary and pineal gland, or spread from cancers primarily located in other organs (metastatic tumors). Primary (true) brain tumors are commonly located in the posterior cranial fossa in children and in the anterior two-thirds of the cerebral hemispheres in adults, although they can affect any part of the brain. In the United States in the year 2005, it was estimated that there were 43,800 new cases of brain tumors (Central Brain Tumor Registry of the United States, Primary Brain Tumors in the United States, Statistical Report, 2005 - 2006), which accounted for 1.4 percent of all cancers, 2.4 percent of all cancer deaths, and 20–25 percent of pediatric cancers.Ultimately, it is estimated that there are 13,000 deaths per year in the United States alone as a result of brain tumors.
Thursday, October 30, 2008
Brain tumor
A brain tumor (brain tumour in the UK) is any intracranial tumor created by abnormal and uncontrolled cell division, normally either in the brain itself (neurons, glial cells (astrocytes, oligodendrocytes, ependymal cells), lymphatic tissue, blood vessels), in the cranial nerves (myelin-producing Schwann cells), in the brain envelopes (meninges), skull, pituitary and pineal gland, or spread from cancers primarily located in other organs (metastatic tumors). Primary (true) brain tumors are commonly located in the posterior cranial fossa in children and in the anterior two-thirds of the cerebral hemispheres in adults, although they can affect any part of the brain. In the United States in the year 2005, it was estimated that there were 43,800 new cases of brain tumors (Central Brain Tumor Registry of the United States, Primary Brain Tumors in the United States, Statistical Report, 2005 - 2006), which accounted for 1.4 percent of all cancers, 2.4 percent of all cancer deaths, and 20–25 percent of pediatric cancers.Ultimately, it is estimated that there are 13,000 deaths per year in the United States alone as a result of brain tumors.
Tuesday, October 21, 2008
Wheat

Modern body armor may combine a ballistic vest with other items of protective clothing, such as a helmet. Vests intended for police and military use may also include ballistic shoulder, and side protection armor components.
Wheat (Triticum spp.) is a worldwide cultivated grass from the Levant area of the Middle East. Globally, after maize, wheat is the second most produced food among the cereal crops; rice ranks third. Wheat grain is a staple food used to make flour for leavened, flat and steamed breads; cookies, cakes, pasta, juice, noodles and couscous;and for fermentation to make beer, alcohol, vodka or biofuel.Wheat is planted to a limited extent as a forage crop for livestock, and the straw can be used as fodder for livestock or as a construction material for roofing thatch.
Although wheat supplies much of the world's dietary protein and food supply, as many as one in every 100 to 200 people has Coeliac disease, a condition which results from an immune system response to a protein found in wheat: gluten (based on figures for the United States).
Wheat (Triticum spp.) is a worldwide cultivated grass from the Levant area of the Middle East. Globally, after maize, wheat is the second most produced food among the cereal crops; rice ranks third. Wheat grain is a staple food used to make flour for leavened, flat and steamed breads; cookies, cakes, pasta, juice, noodles and couscous;and for fermentation to make beer, alcohol, vodka or biofuel.Wheat is planted to a limited extent as a forage crop for livestock, and the straw can be used as fodder for livestock or as a construction material for roofing thatch.
Although wheat supplies much of the world's dietary protein and food supply, as many as one in every 100 to 200 people has Coeliac disease, a condition which results from an immune system response to a protein found in wheat: gluten (based on figures for the United States).
Monday, October 13, 2008
3G
3G is the third generation of mobile phone standards and technology, superseding 2.5G. It is based on the International Telecommunication Union (ITU) family of standards under the IMT-2000.
3G networks enable network operators to offer users a wider range of more advanced services while achieving greater network capacity through improved spectral efficiency. Services include wide-area wireless voice telephony, video calls, and broadband wireless data, all in a mobile environment. Additional features also include HSPA data transmission capabilities able to deliver speeds up to 14.4Mbit/s on the downlink and 5.8Mbit/s on the uplink.
Unlike IEEE 802.11 (common names Wi-Fi or WLAN) networks, 3G networks are wide area cellular telephone networks which evolved to incorporate high-speed internet access and video telephony. IEEE 802.11 networks are short range, high-bandwidth networks primarily developed for data.
Monday, September 29, 2008
High-speed Bluetooth
On March 28, 2006, the Bluetooth Special Interest Group announced its selection of the WiMedia Alliance Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) version of UWB for integration with current Bluetooth wireless technology.
UWB integration will create a version of Bluetooth wireless technology with a high-speed/high-data-rate option. This new version of Bluetooth technology will meet the high-speed demands of synchronizing and transferring large amounts of data, as well as enabling high-quality video and audio applications for portable devices, multi-media projectors and television sets, and wireless VOIP.
At the same time, Bluetooth technology will continue catering to the needs of very low power applications such as mouse, keyboards, and mono headsets, enabling devices to select the most appropriate physical radio for the application requirements, thereby offering the best of both worlds.
Tuesday, September 23, 2008
Default gateway
A gateway is a node (a router) on a computer network that serves as an access point to another network.
A Default Gateway (Def.GW) is the node on the computer network that is chosen when the IP address does not belong to any other entities in the Routing Table.
In homes, the gateway is usually the ISP-provided device that connects the user to the Internet, such as a DSL or cable modem.
In enterprises, however, the gateway is the node that routes the traffic from a workstation to another network segment. The default gateway is commonly used to be the node connecting the internal networks and the outside network (Internet). In such a situation, the gateway node could act as a proxy server and a firewall. The gateway is also associated with both a router, which uses headers and forwarding tables to determine where packets are sent, and a switch, which provides the actual path for the packet in and out of the gateway
Tuesday, September 16, 2008
Touch
Touch, also called tactition, mechanoreception or somatic sensation, is the sense of pressure perception, generally in the skin. There are a variety of nerve endings that respond to variations in pressure (e.g., firm, brushing, and sustained). The inability to feel anything or almost anything is called anesthesia. Paresthesia is a sensation of tingling, pricking, or numbness of a person's skin with no apparent long term physical effect.
Monday, September 08, 2008
Neolithic
"Neolithic" means "New Stone Age." This was a period of primitive technological and social development, toward the end of the "Stone Age." Beginning in the 10th millennium BCE (12,000 BP), the Neolithic period saw the development of early villages, agriculture, animal domestication, tools and the onset of the earliest recorded incidents of warfare.The Neolithic term is commonly used in the Old World, as its application to cultures in the Americas and Oceania that did not fully develop metal-working technology raises problems.
Tuesday, September 02, 2008
Personal Space as it Relates to Body Language
Generally, if you are closer than arm’s reach, then you are in someone’s personal space. To create more space in crowded areas such as elevators and bars, people often tense up and use their arms as protection. They will hold them close to their body – often crossed – and will also avoid eye contact. People guard their intimate space passionately, wherever it is, and do not appreciate others invading it. Respecting people’s intimate space involves not invading it with objects like bags or jackets, or with body parts unless they are welcomed. Intimate space is closer then 50 centimetres (18 inches), social is at around 50 centimetres (18 inches) - 1.5 metres (5 feet) and casual (for strangers) is at 1.5 - 3 metres (5-10 feet). These distances differ from culture to culture; in China for example, they are smaller.
Monday, August 25, 2008
Multitasking
Multitasking refers to the running of multiple independent computer programs on the same computer, giving the appearance that it is performing the tasks at the same time. Since most computers can do at most one or two things at one time, this is generally done via time sharing, which means that each program uses a share of the computer's time to execute.
An operating system kernel contains a piece of software called a scheduler which determines how much time each program will spend executing, and in which order execution control should be passed to programs. Control is passed to a process by the kernel, which allows the program access to the CPU and memory. At a later time control is returned to the kernel through some mechanism, so that another program may be allowed to use the CPU. This so-called passing of control between the kernel and applications is called a context switch.
An early model which governed the allocation of time to programs was called cooperative multitasking. In this model, when control is passed to a program by the kernel, it may execute for as long as it wants before explicitly returning control to the kernel. This means that a malfunctioning program may prevent any other programs from using the CPU.
The philosophy governing preemptive multitasking is that of ensuring that all programs are given regular time on the CPU. This implies that all programs must be limited in how much time they are allowed to spend on the CPU without being interrupted. To accomplish this, modern operating system kernels make use of a timed interrupt. A protected mode timer is set by the kernel which triggers a return to supervisor mode after the specified time has elapsed. (See above sections on Interrupts and Dual Mode Operation.)
On many single user operating systems cooperative multitasking is perfectly adequate, as home computers generally run a small number of well tested programs. Windows NT was the first version of Microsoft Windows which enforced preemptive multitasking, but it didn't reach the home user market until Windows XP, (since Windows NT was targeted at professionals.)
Tuesday, August 19, 2008
Community Ecology Data and methods
There are two methods of data collection: direct and indirect. Direct data come from vital statistics registries that track all births and deaths as well as certain changes in legal status such as marriage, divorce, and migration (registration of place of residence). In developed countries with good registration systems (such as the United States and much of Europe), registry statistics are the best method for estimating the number of births and deaths.
The census is the other common direct method of collecting demographic data. A census is usually conducted by a national government and attempts to enumerate every person in a country. However, in contrast to vital statistics data, which are typically collected continuously and summarized on an annual basis, censuses typically occur only every 10 years or so, and thus are not usually the best source of data on births and deaths. Analyses are conducted after a census to estimate how much over or undercounting took place. Censuses do more than just count people. They typically collect information about families or households, as well as about such individual characteristics as age, sex, marital status, literacy/education, employment status and occupation, and geographical location. They may also collect data on migration (or place of birth or of previous residence), language, religion, nationality (or ethnicity or race), and citizenship. In countries in which the vital registration system may be incomplete, the censuses are also used as a direct source of information about fertility and mortality; for example the censuses of the People's Republic of China gather information on births and deaths that occurred in the 18 months immediately preceding the census.
Indirect methods of data collections are required in countries where full data are not available, such as is the case in much of the developing world. One of these techniques is the sister method, where survey researchers ask women how many of their sisters have died or had children and at what age. With these surveys, researchers can then indirectly estimate birth or death rates for the entire population. Other indirect methods include asking people about siblings, parents, and children.
Monday, August 11, 2008
Reverse proxy server
A reverse proxy is a proxy server that is installed in the neighborhood of one or more web servers. All traffic coming from the Internet and with a destination of one of the web servers goes through the proxy server. There are several reasons for installing reverse proxy servers:
- Encryption / SSL acceleration: when secure web sites are created, the SSL encryption is often not done by the web server itself, but by a reverse proxy that is equipped with SSL acceleration hardware. See Secure Sockets Layer.
- Load balancing: the reverse proxy can distribute the load to several web servers, each web server serving its own application area. In such a case, the reverse proxy may need to rewrite the URLs in each web page (translation from externally known URLs to the internal locations).
- Serve/cache static content: A reverse proxy can offload the web servers by caching static content like pictures and other static graphical content.
- Compression: the proxy server can optimize and compress the content to speed up the load time.
- Spoon feeding: reduces resource usage caused by slow clients on the web servers by caching the content the web server sent and slowly "spoon feeds" it to the client. This especially benefits dynamically generated pages.
- Security: the proxy server is an additional layer of defense and can protect against some OS and WebServer specific attacks. However, it does not provide any protection to attacks against the web application or service itself, which is generally considered the larger threat.
- Extranet Publishing: a reverse proxy server facing the Internet can be used to communicate to a firewalled server internal to an organization, providing extranet access to some functions while keeping the servers behind the firewalls. If used in this way, security measures should be considered to protect the rest of your infrastructure in case this server is compromised, as it's web application is exposed to attack from the Internet.
Monday, August 04, 2008
Reproduction in plants
In flowering plants,the anther produces male gametophytes, the sperm is produced in pollen grains, which attach to the stigma on top of a carpel, in which the female gametophytes (inside ovules) are located. After the pollen tube grows through the carpel's style, the sex cell nuclei from the pollen grain migrate into the ovule to fertilize the egg cell and endosperm nuclei within the female gametophyte in a process termed double fertilization. The resulting zygote develops into an embryo, while the triploid endosperm (one sperm cell plus two female cells) and female tissues of the ovule give rise to the surrounding tissues in the developing seed. The ovary, which produced the female gametophyte(s), then grows into a fruit, which surrounds the seed(s). Plants may either self-pollinate or cross-pollinate. Nonflowering plants like ferns, moss and liverworts use other means of sexual reproduction.
Ferns typically produce large diploid sporophytes with rhizomes, roots and leaves; and on fertile leaves called sporangium, spores are produced. The spores are released and germinate to produce short, thin gametophytes that are typically heart shaped, small and green in color. The gametophytes or thallus, produce both motile sperm in the antheridia and egg cells in separate archegonia. After rains or when dew deposits a film of water, the motile sperm are splashed away from the antheridia, which are normally produce on the top side of the thallus, and swim in the film of water to the antheridia where they fertilize the egg. To promote out crossing or cross fertilization the sperm are released before the eggs are receptive of the sperm, making it more likely that the sperm will fertilize the eggs of diffrent thallus. A zygote is formed after fertilization, which grows into a new sporophytic plant. The condition of having separate sporephyte and gametophyte plants is call alternation of generations. Other plants with similar reproductive means include the Psilotum, Lycopodium, Selaginella and Equisetum.
Ferns typically produce large diploid sporophytes with rhizomes, roots and leaves; and on fertile leaves called sporangium, spores are produced. The spores are released and germinate to produce short, thin gametophytes that are typically heart shaped, small and green in color. The gametophytes or thallus, produce both motile sperm in the antheridia and egg cells in separate archegonia. After rains or when dew deposits a film of water, the motile sperm are splashed away from the antheridia, which are normally produce on the top side of the thallus, and swim in the film of water to the antheridia where they fertilize the egg. To promote out crossing or cross fertilization the sperm are released before the eggs are receptive of the sperm, making it more likely that the sperm will fertilize the eggs of diffrent thallus. A zygote is formed after fertilization, which grows into a new sporophytic plant. The condition of having separate sporephyte and gametophyte plants is call alternation of generations. Other plants with similar reproductive means include the Psilotum, Lycopodium, Selaginella and Equisetum.
Monday, July 28, 2008
Prediction for a stable cultural and social future
Cultural evolution follows punctuated equilibrium which Gould and Eldredge developed for biological evolution. Bloomfield has written that human societies follow punctuated equilibrium which would mean first, a stable society, a transition resulting in a subsequent stable society with greater complexity. Using these guidelines, mankind has had a stable animal society, a transition to a stable tribal society, another transition to a stable peasant society and is currently in a transitional industrial society.
The status of a human society rests on the productivity of food production. Deevey reported on the growth of the number of humans. Deevey also reported on the productivity of food production, noting that productivity changes very little for stable societies, but increases during transitions. When productivity and especially food productivity can no longer be increased, Bloomfield has proposed that man will have achieved a stable automated society. Space is also assumed to allow for the continued growth of the human population, as well as provide a solution to the current pollution problem by providing limitless energy from solar satellite power stations.
The status of a human society rests on the productivity of food production. Deevey reported on the growth of the number of humans. Deevey also reported on the productivity of food production, noting that productivity changes very little for stable societies, but increases during transitions. When productivity and especially food productivity can no longer be increased, Bloomfield has proposed that man will have achieved a stable automated society. Space is also assumed to allow for the continued growth of the human population, as well as provide a solution to the current pollution problem by providing limitless energy from solar satellite power stations.
Monday, July 21, 2008
Bronze Age
The term Bronze Age refers to a period in human cultural development when the most advanced metalworking (at least in systematic and widespread use) included techniques for smelting copper and tin from naturally-occurring outcroppings of copper and tin ores, creating a bronze alloy by melting those metals together, and cast them into bronze artifacts. These naturally-occurring ores typically included arsenic as a common impurity. Copper/tin ores are rare, as reflected in the fact that there were no tin bronzes in western Asia before 3,000 B.C. The Bronze Age forms part of the three-age system for prehistoric societies. In this system, it follows the Neolithic in some areas of the world. On the other hand, in many parts of sub-Saharan Africa, the Neolithic is directly followed by the Iron Age.[citation needed] In some parts of the world, a Copper Age follows the Neolithic and precedes the Bronze Age.
Tuesday, July 15, 2008
Phenotype
A phenotype is any observable characteristic of an organism, such as its morphology, development, biochemical or physiological properties, or behavior. Phenotypes result from the expression of an organism's genes as well as the influence of environmental factors and possible interactions between the two. The genotype of an organism are the inherited instructions it carries with in its genetic code. Not all organisms with the same genotype look or act the same way, because appearance and behavior are modified by environmental and developmental conditions. Also in the same way, not all organisms that look alike necessarily have the same genotype. This genotype-phenotype distinction was proposed by Wilhelm Johannsen in 1911 to make clear the difference between an organism's heredity and what that heredity produces. The distinction is similar to that proposed by August Weismann, who distinguished between germ plasm (heredity) and somatic cells (the body). A more modern version is Francis Crick's Central dogma of molecular biology.
Despite its seemingly straightforward definition, the concept of the phenotype has some hidden subtleties. First, most of the molecules and structures coded by the genetic material are not visible in the appearance of an organism, yet they are observable (for example by Western blotting) and are thus part of the phenotype. Human blood groups are an example. So, by extension, the term phenotype must include characteristics that can be made visible by some technical procedure. Another extension adds behaviour to the phenotype since behaviours are also affected by both genotypic and environmental factors.
Second, the phenotype is not simply a product of the genotype, but is influenced by the environment to a greater or lesser extent (see also phenotypic plasticity). And, further, if the genotype is defined narrowly, then it must be remembered that not all heredity is carried by the nucleus. For example, mitochondria transmit their own DNA directly, not via the nucleus, though they divide in unison with the nucleus.
The phenotype is composed of traits or characteristics . Some phenotypes are controlled entirely by the individual's genes. Others are controlled by genes but are significantly affected by extragenetic or environmental factors. Almost all humans inherit the capacity to speak and understand language, but which language they learn is entirely an environmental matter.
Despite its seemingly straightforward definition, the concept of the phenotype has some hidden subtleties. First, most of the molecules and structures coded by the genetic material are not visible in the appearance of an organism, yet they are observable (for example by Western blotting) and are thus part of the phenotype. Human blood groups are an example. So, by extension, the term phenotype must include characteristics that can be made visible by some technical procedure. Another extension adds behaviour to the phenotype since behaviours are also affected by both genotypic and environmental factors.
Second, the phenotype is not simply a product of the genotype, but is influenced by the environment to a greater or lesser extent (see also phenotypic plasticity). And, further, if the genotype is defined narrowly, then it must be remembered that not all heredity is carried by the nucleus. For example, mitochondria transmit their own DNA directly, not via the nucleus, though they divide in unison with the nucleus.
The phenotype is composed of traits or characteristics . Some phenotypes are controlled entirely by the individual's genes. Others are controlled by genes but are significantly affected by extragenetic or environmental factors. Almost all humans inherit the capacity to speak and understand language, but which language they learn is entirely an environmental matter.
Sunday, July 06, 2008
Duel
As practised from the 11th to 20th centuries in Western societies, a duel is an engagement in combat between two individuals, with matched weapons in accordance with their combat doctrines. In the modern application the term is applied to air combat between fighter pilots.
The Romanticism depiction of medieval duels was based on either a pretext of defence of honor, usually accompanied by a trusted representative (who might themselves fight), often in contravention of the duelling conventions, or as a matter of challenge of the champion which developed out of the desire of one party (the challenger) to redress a perceived insult to his or his sovereign's honor. The goal of the honourable duel was often not so much to kill the opponent as to gain "satisfaction", that is, to restore one's honor by demonstrating a willingness to risk one's life for it.
Duels may be distinguished from trials by combat, in that duels were not used to determine guilt or innocence, nor were they official procedures. Indeed, from early 19th century duels were often illegal in Europe, though in most societies where duelling was socially accepted, participants in a fair duel were not prosecuted, or if they were, were not convicted. Only gentlemen were considered to have honor, and therefore only they were qualified to duel. If a gentleman was insulted by a person of lower class, he would not duel him, but would beat him with a cane, riding crop, a whip or have his servants do so.[citation needed] Duelling is now illegal in all but a few countries around the world.[citation needed]
The Romanticism depiction of medieval duels was based on either a pretext of defence of honor, usually accompanied by a trusted representative (who might themselves fight), often in contravention of the duelling conventions, or as a matter of challenge of the champion which developed out of the desire of one party (the challenger) to redress a perceived insult to his or his sovereign's honor. The goal of the honourable duel was often not so much to kill the opponent as to gain "satisfaction", that is, to restore one's honor by demonstrating a willingness to risk one's life for it.
Duels may be distinguished from trials by combat, in that duels were not used to determine guilt or innocence, nor were they official procedures. Indeed, from early 19th century duels were often illegal in Europe, though in most societies where duelling was socially accepted, participants in a fair duel were not prosecuted, or if they were, were not convicted. Only gentlemen were considered to have honor, and therefore only they were qualified to duel. If a gentleman was insulted by a person of lower class, he would not duel him, but would beat him with a cane, riding crop, a whip or have his servants do so.[citation needed] Duelling is now illegal in all but a few countries around the world.[citation needed]
Sunday, June 29, 2008
Albinism Treatment of the symptoms
Albinism is a condition that cannot be "cured" per se, but small things can be done to improve the quality of life for those affected. Most importantly to improve vision, protect the eyes from bright lights, and avoid skin damage from sunlight. The extent and success rate of these measures depend on the type of albinism and severity of the symptoms; in particular, people with ocular albinism are likely to have normally-pigmented skin, and thus do not need to take special precautions against skin damage.
Surgical treatment
For the most part, treatment of the eye conditions consists of visual rehabilitation.[citation needed] Surgery is possible on the ocular muscles to decrease nystagmus, strabismus and common refractive errors like astigmatism. Strabismus surgery may improve the appearance of the eyes.[citation needed] Nystagmus-damping surgery can also be performed, to reduce the "shaking" of the eyes back and forth.The effectiveness of all these procedures varies greatly and depends on individual circumstances. More importantly, since surgery will not restore a normal RPE or foveae, surgery will not provide fine binocular vision.[citation needed] In the case of esotropia (the "crossed eyes" form of strabismus), surgery may help vision by expanding the visual field Vision aids.
Glasses and other vision aids, large-print materials and closed captioning, as well as bright but angled reading lights, can help individuals with albinism, even though their vision cannot be corrected completely. Some albinistic people do well using bifocals (with a strong reading lens), prescription reading glasses, and/or hand-held devices such as magnifiers or monoculars.
Contact lenses may be colored to block light transmission through the iris. Some use bioptics, glasses which have small telescopes mounted on, in, or behind their regular lenses, so that they can look through either the regular lens or the telescope. Newer designs of bioptics use smaller light-weight lenses. Some US states allow the use of bioptic telescopes for driving motor vehiclesAlthough still disputed among the experts,[who?] many ophthalmologists recommend the use of glasses from early childhood onward to allow the eyes the best development possible.
Optometrists or ophthalmologists who are experienced in working with low vision patients can recommend various optical aids. Some low-vision clinics provide these aids on trial loan, with instruction in their use.
Sun protection
It is vital that people with albinism use sunscreen when exposed to sunlight to prevent premature skin aging or skin cancer. This poses a problem for those who cannot afford sunscreen, especially in regions with high exposure to sunlight, as in Africa.
Use of sunglasses and hats with wide brims can make the glare outside bearable. Other things that can help people with albinism are avoiding sudden changes of the lighting situation (switching the light on in complete darkness), using dimmable switches and adding tint to car windows or blinds to normal windows. Lights should be yellowish rather than blue[citation needed] and not point towards the usual position of a person with albinism
Surgical treatment
For the most part, treatment of the eye conditions consists of visual rehabilitation.[citation needed] Surgery is possible on the ocular muscles to decrease nystagmus, strabismus and common refractive errors like astigmatism. Strabismus surgery may improve the appearance of the eyes.[citation needed] Nystagmus-damping surgery can also be performed, to reduce the "shaking" of the eyes back and forth.The effectiveness of all these procedures varies greatly and depends on individual circumstances. More importantly, since surgery will not restore a normal RPE or foveae, surgery will not provide fine binocular vision.[citation needed] In the case of esotropia (the "crossed eyes" form of strabismus), surgery may help vision by expanding the visual field Vision aids.
Glasses and other vision aids, large-print materials and closed captioning, as well as bright but angled reading lights, can help individuals with albinism, even though their vision cannot be corrected completely. Some albinistic people do well using bifocals (with a strong reading lens), prescription reading glasses, and/or hand-held devices such as magnifiers or monoculars.
Contact lenses may be colored to block light transmission through the iris. Some use bioptics, glasses which have small telescopes mounted on, in, or behind their regular lenses, so that they can look through either the regular lens or the telescope. Newer designs of bioptics use smaller light-weight lenses. Some US states allow the use of bioptic telescopes for driving motor vehiclesAlthough still disputed among the experts,[who?] many ophthalmologists recommend the use of glasses from early childhood onward to allow the eyes the best development possible.
Optometrists or ophthalmologists who are experienced in working with low vision patients can recommend various optical aids. Some low-vision clinics provide these aids on trial loan, with instruction in their use.
Sun protection
It is vital that people with albinism use sunscreen when exposed to sunlight to prevent premature skin aging or skin cancer. This poses a problem for those who cannot afford sunscreen, especially in regions with high exposure to sunlight, as in Africa.
Use of sunglasses and hats with wide brims can make the glare outside bearable. Other things that can help people with albinism are avoiding sudden changes of the lighting situation (switching the light on in complete darkness), using dimmable switches and adding tint to car windows or blinds to normal windows. Lights should be yellowish rather than blue[citation needed] and not point towards the usual position of a person with albinism
Sunday, June 22, 2008
Sporophyte
All land plants, and some algae, have life cycles in which a haploid gametophyte generation alternates with a diploid sporophyte, the generation of a plant or alga that has a double set of chromosomes. A multicellular sporophyte generation or phase is present in the life cycle of all land plants and in some green algae. For common flowering plants (Angiosperms), the sporophyte generation comprises almost their whole life cycle (i.e. whole green plant, roots etc), except phases of small reproductive structures (pollen and ovule).
The sporophyte produces spores (hence the name), by meiosis. These meiospores develop into a gametophyte. Both the spores and the resulting gametophyte are haploid, meaning they only have one set of homologous chromosomes. The mature gametophyte produces male or female gametes (or both) by mitosis. The fusion of male and female gametes produces a diploid zygote which develops into a new sporophyte. This cycle is known as alternation of generations or alternation of phases.
n the normal course of events, the zygote and sporophyte will have a full double set of chromosomes again. An exception is when a diploid and haploid gamete fuse, resulting in a triploid sporophyte, which will usually be sterile, as dividing three sets of chromosomes into two halves causes complications.
Bryophytes (mosses, liverworts and hornworts) have a dominant gametophyte stage on which the adult sporophyte is dependent on the gametophyte for nutrition. The embryo of the sporophyte develops from the zygote within the female sex organ or archegonium, and in its early development is therefore nurtured by the gametophyte. Because this embryo-nurturing feature of the life cycle is common to all land plants they are known collectively as the Embryophytes.
Most algae have dominant gametophyte generations, but in some species the gametophytes and sporophytes are morphologically similar (isomorphic). An independent sporophyte is the dominant form in all clubmosses, horsetails, ferns, gymnosperms, and angiosperms (flowering plants) that have survived to the present day. Early land plants had sporophytes that produced identical spores (isosporous or homosporous) but the ancestors of the gymnosperms evolved complex heterosporous life cycles in which the spores producing male and female gametophytes were of different sizes, the female megaspores tending to be larger, and fewer in number, than the male microspores.
During the Devonian period several plant groups independently evolved heterospory and subsequently the habit of endospory, in which single megaspores were retained within the sporangia of the parent sporophyte, instead of being freely liberated into the environment as in ancestral exosporous plants. These endosporic megaspores contained within them a miniature multicellular female gametophyte complete with female sex organs or archegonia containing oocytes which were fertilised by free-swimming sperm produced by windborne miniatuarised male gametophytes in the form of pre-pollen. The resulting zygote developed into the next sporophyte generation while still retained within the pre-ovule, the single large female meiospore or megaspore contained in the modified sporangium or nucellus of the parent sporophyte. The evolution of heterospory and endospory were among the earliest steps in the evolution of seeds of the kind produced by gymnosperms and angiosperms today.
The sporophyte produces spores (hence the name), by meiosis. These meiospores develop into a gametophyte. Both the spores and the resulting gametophyte are haploid, meaning they only have one set of homologous chromosomes. The mature gametophyte produces male or female gametes (or both) by mitosis. The fusion of male and female gametes produces a diploid zygote which develops into a new sporophyte. This cycle is known as alternation of generations or alternation of phases.
n the normal course of events, the zygote and sporophyte will have a full double set of chromosomes again. An exception is when a diploid and haploid gamete fuse, resulting in a triploid sporophyte, which will usually be sterile, as dividing three sets of chromosomes into two halves causes complications.
Bryophytes (mosses, liverworts and hornworts) have a dominant gametophyte stage on which the adult sporophyte is dependent on the gametophyte for nutrition. The embryo of the sporophyte develops from the zygote within the female sex organ or archegonium, and in its early development is therefore nurtured by the gametophyte. Because this embryo-nurturing feature of the life cycle is common to all land plants they are known collectively as the Embryophytes.
Most algae have dominant gametophyte generations, but in some species the gametophytes and sporophytes are morphologically similar (isomorphic). An independent sporophyte is the dominant form in all clubmosses, horsetails, ferns, gymnosperms, and angiosperms (flowering plants) that have survived to the present day. Early land plants had sporophytes that produced identical spores (isosporous or homosporous) but the ancestors of the gymnosperms evolved complex heterosporous life cycles in which the spores producing male and female gametophytes were of different sizes, the female megaspores tending to be larger, and fewer in number, than the male microspores.
During the Devonian period several plant groups independently evolved heterospory and subsequently the habit of endospory, in which single megaspores were retained within the sporangia of the parent sporophyte, instead of being freely liberated into the environment as in ancestral exosporous plants. These endosporic megaspores contained within them a miniature multicellular female gametophyte complete with female sex organs or archegonia containing oocytes which were fertilised by free-swimming sperm produced by windborne miniatuarised male gametophytes in the form of pre-pollen. The resulting zygote developed into the next sporophyte generation while still retained within the pre-ovule, the single large female meiospore or megaspore contained in the modified sporangium or nucellus of the parent sporophyte. The evolution of heterospory and endospory were among the earliest steps in the evolution of seeds of the kind produced by gymnosperms and angiosperms today.
Sunday, June 15, 2008
Field-programmable gate array
A field-programmable gate array is a semiconductor device containing programmable logic components called "logic blocks", and programmable interconnects. Logic blocks can be programmed to perform the function of basic logic gates such as AND, and XOR, or more complex combinational functions such as decoders or mathematical functions. In most FPGAs, the logic blocks also include memory elements, which may be simple flip-flops or more complete blocks of memory.
A hierarchy of programmable interconnects allows logic blocks to be interconnected as needed by the system designer, somewhat like a one-chip programmable breadboard. Logic blocks and interconnects can be programmed by the customer or designer, after the FPGA is manufactured, to implement any logical function—hence the name "field-programmable".
FPGAs are usually slower than their application-specific integrated circuit (ASIC) counterparts, cannot handle as complex a design, and draw more power (for any given semiconductor process). But their advantages include a shorter time to market, ability to re-program in the field to fix bugs, and lower non-recurring engineering costs. Vendors can sell cheaper, less flexible versions of their FPGAs which cannot be modified after the design is committed. The designs are developed on regular FPGAs and then migrated into a fixed version that more resembles an ASIC.
"Complex Programmable Logic Device" (CPLDs) are an alternative for simpler designs. They also retain their programming over powerdowns.
To configure ("program") an FPGA or CPLD you specify how you want the chip to work with a logic circuit diagram or a source code using a hardware description language (HDL). The HDL form might be easier to work with when handling large structures because it's possible to just specify them numerically rather than having to draw every piece by hand. On the other hand, schematic entry might allow for a more tight specification of what you want.
Going from schematic/HDL source files to actual configuration: The source files are fed to a software suite from the FPGA/CPLD vendor that through different steps will produce a file. This file is then transferred to the FPGA/CPLD via a serial interface (JTAG) interface or to external memory device like an EEPROM.
A hierarchy of programmable interconnects allows logic blocks to be interconnected as needed by the system designer, somewhat like a one-chip programmable breadboard. Logic blocks and interconnects can be programmed by the customer or designer, after the FPGA is manufactured, to implement any logical function—hence the name "field-programmable".
FPGAs are usually slower than their application-specific integrated circuit (ASIC) counterparts, cannot handle as complex a design, and draw more power (for any given semiconductor process). But their advantages include a shorter time to market, ability to re-program in the field to fix bugs, and lower non-recurring engineering costs. Vendors can sell cheaper, less flexible versions of their FPGAs which cannot be modified after the design is committed. The designs are developed on regular FPGAs and then migrated into a fixed version that more resembles an ASIC.
"Complex Programmable Logic Device" (CPLDs) are an alternative for simpler designs. They also retain their programming over powerdowns.
To configure ("program") an FPGA or CPLD you specify how you want the chip to work with a logic circuit diagram or a source code using a hardware description language (HDL). The HDL form might be easier to work with when handling large structures because it's possible to just specify them numerically rather than having to draw every piece by hand. On the other hand, schematic entry might allow for a more tight specification of what you want.
Going from schematic/HDL source files to actual configuration: The source files are fed to a software suite from the FPGA/CPLD vendor that through different steps will produce a file. This file is then transferred to the FPGA/CPLD via a serial interface (JTAG) interface or to external memory device like an EEPROM.
Sunday, June 08, 2008
Ultra Music Festival
Ultra Music Festival is an outdoor electronic music event held annually in Miami, Florida during the Winter Music Conference which occurs annually during the month of March. It is a 2-day event (although it was a 1-day event until 2007) that takes place across 12 different stages featuring over 200 artists, DJs, producers and promoters.
From 2001 to 2005, UMF was held outdoors in Bayfront Park, Miami. The first two UMFs (1999, & 2000) were actually held on South Beach in Miami Beach, however UMF attendance exceeded the possible beach permits and was subsequently moved to the venue of Bayfront Park. The top DJs and artists of the evening perform in the amphitheater designed to hold thousands of attendees. There is a second main stage (called the 'Sound stage') and 10 other specialized music areas scattered throughout the park featuring Drum and Bass, House, Techno, Electro, Breakbeats, Trance, and other various styles of electronic music.
In 2005 the concert was so popular that it sold out. With the festival growing so big, in 2006 the Miami event had been moved to an even bigger venue, Bicentennial Park, next door to its past home. In 2007, with Winter Music Conference in full swing, Ultra Music Festival had its first 2-Day Event held at Bicentennial Park with a record breaking 50,000+ electronic music fans. Ultra Music Festival celebrated its 10th anniversary on Friday, March 28th and Saturday March 29th, 2008, where an announcement was made that the festival had set a new City of Miami record for the number of tickets sold at a single event.
Ultra Music Festival, in association with Ultra Records, produces an event in New York City's Central Park called ULTRA:NY, which also sold out in 2005. The success has brought Ultra:NY back for a second year.
From 2001 to 2005, UMF was held outdoors in Bayfront Park, Miami. The first two UMFs (1999, & 2000) were actually held on South Beach in Miami Beach, however UMF attendance exceeded the possible beach permits and was subsequently moved to the venue of Bayfront Park. The top DJs and artists of the evening perform in the amphitheater designed to hold thousands of attendees. There is a second main stage (called the 'Sound stage') and 10 other specialized music areas scattered throughout the park featuring Drum and Bass, House, Techno, Electro, Breakbeats, Trance, and other various styles of electronic music.
In 2005 the concert was so popular that it sold out. With the festival growing so big, in 2006 the Miami event had been moved to an even bigger venue, Bicentennial Park, next door to its past home. In 2007, with Winter Music Conference in full swing, Ultra Music Festival had its first 2-Day Event held at Bicentennial Park with a record breaking 50,000+ electronic music fans. Ultra Music Festival celebrated its 10th anniversary on Friday, March 28th and Saturday March 29th, 2008, where an announcement was made that the festival had set a new City of Miami record for the number of tickets sold at a single event.
Ultra Music Festival, in association with Ultra Records, produces an event in New York City's Central Park called ULTRA:NY, which also sold out in 2005. The success has brought Ultra:NY back for a second year.
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