TAnko SCIEnce
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BELIEVE IT OR NOT
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AEROGEL(THE INSULATOR)
Despite their name, aerogels are solid, rigid, and dry materials that do not resemble a gel in their physical properties: The name comes from the fact that they are made from gels. Pressing softly on an aerogel typically does not leave even a minor mark; pressing more firmly will leave a permanent depression. Pressing extremely firmly will cause a catastrophic breakdown in the sparse structure, causing it to shatter like glass – a property known as friability; although more modern variations do not suffer from this. Despite the fact that it is prone to shattering, it is very strong structurally. Its impressive load bearing abilities are due to the dendritic microstructure, in which sphericalparticles of average size (2–5 nm) are fused together into clusters. These clusters form a three-dimensional highly porous structure of almost fractal chains, with pores just under 100 nm. The average size and density of the pores can be controlled during the manufacturing process.
Aerogel is a material that is 98.2% air. The lack of solid material allows aerogel to be almost weightless. The reason for the difference in the composition is the structure of the aerogel. Aerogel has a porous solid network that contains air pockets, with the air pockets taking up majority of space within the material.[8]
Aerogels are good thermal insulators because they almost nullify two of the three methods of heat transfer (convection, conduction, andradiation). They are good conductive insulators because they are composed almost entirely from a gas, and gases are very poor heat conductors. Silica aerogel is especially good because silica is also a poor conductor of heat (a metallic aerogel, on the other hand, would be less effective). They are good convective inhibitors because air cannot circulate through the lattice. Aerogels are poor radiative insulators because infrared radiation (which transfers heat) passes through silica aerogel.
Owing to its hygroscopic nature, aerogel feels dry and acts as a strong desiccant. People handling aerogel for extended periods should wear gloves to prevent the appearance of dry brittle spots on their skin.
The slight color it does have is due to Rayleigh scattering of the shorter wavelengths of visible light by the nano-sized dendritic structure. This causes it to appear smoky blue against dark backgrounds and yellowish against bright backgrounds.
Aerogel is an open porous network. The difference between an open porous network and a closed porous network is that an open porous network allows gases to enter and leave the substance without any limitation, while a closed porous network traps the gases within the material. [9]
Aerogels by themselves are hydrophilic, but chemical treatment can make them hydrophobic. If they absorb moisture they usually suffer a structural change, such as contraction, and deteriorate, but degradation can be prevented by making them hydrophobic. Aerogels with hydrophobic interiors are less susceptible to degradation than aerogels with only an outer hydrophobic layer, even if a crack penetrates the surface. Hydrophobic treatment facilitates processing because it allows the use of a water jet cutter.
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PC Cards (PCMCIA) were the first commercial memory card formats (type I cards) to come out , but are now mainly used in industrial applications and to connect I/O devices such as modems. Since 1994, a number of memory card formats smaller than the PC Card arrived, the first one was CompactFlash later SmartMedia and Miniature Card. The desire for smaller cards for cell-phones, PDAs, and compact digital cameras drove a trend that left the previous generation of "compact" cards looking big. In digital cameras SmartMedia and CompactFlash had been very successful[neutrality is disputed]. In 2001, SM alone captured 50% of the digital camera market and CF had captured the professional digital camera market. By 2005 however, SD/MMC had nearly taken over SmartMedia's spot, though not to the same level and with stiff competition coming from Memory Stick variants, as well as CompactFlash. In industrial and embedded fields, even the venerable PC card (PCMCIA) memory cards still manage to maintain a niche, while in mobile phones and PDAs, the memory card market was highly fragmented until 2010 when micro-SD came to dominate new high-end phones and tablet computers.
Since 2010, new products of Sony (previously only using Memory Stick) and Olympus (previously only using XD-Card) have been offered with an additional SD-Card slot.[1]Effectively the format war has turned in SD-Card's favor.
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WOMEN sPEAKS.....
Do Women Talk More than Men?
About a year ago, Louann Brizendine, founder and director of the University of California, San Francisco's Women's Mood and Hormone Clinic, published The Female Brain. One of the most cited gems within its pages was a claim that women are chatterboxes, speaking an average of 20,000 words per day, nearly three times the mere 7,000 spoken by men.
Seemed to make sense, given the rep of women as purveyors of gossip, not to mention creatures incapable of keeping their traps shut. Right? Wrong.
A new study published today in Science reports men and woman actually use roughly the same number of words daily.
James Pennebaker, chair of the University of Texas at Austin's psychology department, says he was skeptical of the lopsided stats when he saw them quoted in an interview with Brizendine in The New York Times Magazine. "I read that and I knew it couldn't be true simply because we've run too many studies," he says, "it just didn't make sense." In fact, he had been collecting data over the past decade with colleagues at the University of Arizona in Tucson that specifically showed that the sexes are about equal when it comes to a war of words.
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THE SLOw.. CHANGING MAN
The plica semilunaris is a small fold of bulbar conjunctiva on the medial canthus of the eye. It functions during movement of the eye, to help maintain tear drainage via the lacrimal lake, and to permit greater rotation of the globe, for without the plica the conjunctiva would attach directly to the eyeball, restricting movement.[1] It is the vestigial remnant of the nictitating membrane (the "third eyelid") which is drawn across the eye for protection, and is present in other animals such as birds, reptiles, and fish, but is rare in mammals, mainly found in monotremes and marsupials.[2] Its associated muscles are also vestigial.[3] It is loose, thus eye movements are not restricted by it. Only one species of primate, the Calabar Angwantibo, is known to have a functioning nictitating membrane.
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