Chemistry of Toothpaste

Toothpaste is used to clean teeth. It is slightly basic to neutralise the acids in food. A commonly used base is aluminium hydroxide. Fluoride is also added to help prevent tooth decay. This works by increasing the growth rate and size of enamel crystals causing a process called remineralization, where minerals are deposited on cavities caused by plaque. It also makes teeth less prone to decay in future. A polishing agent is another ingredient, added to scrub teeth. Common polishing agents used include dicalcium phosphate, CaHPO4.2H2O, calcium pyrophosphate and insoluble sodium metaphosphate.

There are many more ingredients in toothpaste, added for various reasons. The toothpaste must, of course, be marketable. To sweeten it, saccharin or cyclamate is often added. Titanium dioxide is used to give the white colour.

A liquid such as glycerine, C3H803, is included for plasticity i.e. it keeps the paste together and prevents it from drying out. Sodium salicylate is often used to make an antiseptic for toothpaste and also for mouthwashes.

The last of toothpaste's main ingredients is a binder, which helps the paste keep its shape when on the brush. Many different binders are used including gum tragacanth and seaweed or cellulose derivatives.

Diabetes in pregnancy can hamper infant memory

Diabetes in pregnancy can hamper infant memory

Babies whose mothers had diabetes during pregnancy may be less able to form early memories than children whose mothers had normal pregnancies, a U.S. researcher said on Friday.

The study, presented at the annual meeting of the American Association for the Advancement of Science in San Francisco, suggests that babies deprived of oxygen and iron before birth are not as able to develop early memories.

The need for iron doubles during pregnancy because it is used to make blood cells for the fetus. In pregnant mothers with diabetes, fluctuating glucose levels can result in iron deficiency, which can reduce the blood`s capacity to carry oxygen.

"When oxygen and iron deficiencies occur prenatally, they alter the development of memory," said Tracy DeBoer of the University of California Davis.

DeBoer studied infants of diabetic mothers at 12 months and again at age 3 1/2. Her study suggested that memory deficits that appeared at one year persisted into early childhood.

She did not specify which type of diabetes the mothers had, but type-1, type-2 and gestational diabetes all affect blood sugar levels.

In the older group, the babies were shown a series of nine objects in three levels of difficulty. In the highest level of difficulty, babies whose mothers had been diabetic during pregnancy on average could recall two fewer objects than those whose mothers had a normal pregnancy.

The finding was consistent with the deficits measured in a simpler test of infants at 12 months, she said.

The notion that babies could recall anything at all in the first two years of life is relatively new.

Researchers have long thought that childhood amnesia -- the inability to remember early life -- was because babies could not form memories, but researchers at the meeting said new studies suggested infants could recall things as early as 4 months of age.

Duke University researcher Patricia Bauer told the meeting new studies suggest that infants do form memories by late in the first year that are similar to adults, but "the rate of forgetting is faster than in adults."

Memories from early childhood that survive this process of forgetting tend to be particularly meaningful, she added.

Source:zeenews.com/articles.asp?aid=354759&sid=ENV&ssid=28

New citizenship test in U.S.

New citizenship test in U.S.

27th Feb. 07: India, Britain, Mexico and Vietnam were among the first in the United States to try out a new citizenship test that the Government wants to have ready for 2008.

The new test is designed to make immigrants think more about American concepts instead of memorising lists of facts. And those who volunteered said they did quite well.

`It seemed like a good cause,'' said Sandeep Nayyar (37), of India, who answered correctly all 10 of the civics questions he faced. `If it helps result in a better test, why not?''

The U.S. Citizenship and Immigration Services wants 6,000 people in 10 cities to take the pilot test, which also includes reading and writing portions that are slightly different as well.

To pass the civics section, applicants must answer six of 10 questions correctly in an oral exam.

There are 140 possible questions in all, which will be trimmed to 100 as immigration officials watch how the volunteers do.

Source: The Hindu

Ultra On-Chip Memory Tech by IBM

Ultra On-Chip Memory Tech by IBM




In papers presented at the International Solid State Circuits Conference (ISSCC) today, IBM revealed a first-of-its-kind, on-chip memory technology that features the fastest access times ever recorded in eDRAM (embedded dynamic random access memory).

This new technology, designed using IBM’s Silicon-on-Insulator (SOI) for high-performance at low power, vastly improves microprocessor performance in multi-core designs and speeds the movement of graphics in gaming, networking, and other image intensive, multi-media applications.

The technology is expected to be a key feature of IBM’s 45nm (nanometer) microprocessor roadmap and will become available beginning in 2008.

IBM’s new eDRAM technology, designed in stress-enabled 65nm SOI using deep trench, dramatically improves on-processor memory performance in about one-third the space with one-fifth the standby power of conventional SRAM (static random access memory).

“With this breakthrough solution to the processor/memory gap, IBM is effectively doubling microprocessor performance beyond what classical scaling alone can achieve,” said Dr. Subramanian Iyer, Distinguished Engineer and director of 45 nm technology development at IBM. “As semiconductor components have reached the atomic scale, design innovation at the chip-level has replaced materials science as a key factor in continuing Moore’s Law. Today’s announcement further demonstrates IBM’s leadership in this critical area of microprocessor design innovation.”

"This DRAM now is almost as fast as SRAM. It may not be as fast at the micro level, but when you get down to 45-nm, it will be faster at the system level. It's going to just blow the doors off," John Barth, senior technology staff member and chief of eDRAM architecture for IBM said. "A typical microprocessor takes 14 clock cycles to get data from its cache. Using DRAM slows that down, but only one clock [cycle]. By doubling the amount of memory on the die, we can get double-digit percentage gains at the system level."

IBM innovations in microelectronics and the company's groundbreaking system-on-a-chip designs have transformed the world of semiconductors. IBM breakthroughs include High-k, which enhances the transistor’s function while allowing it to be shrunk beyond today's limits, dual-core and multi-core microprocessors, copper on-chip wiring, silicon-on-insulator and silicon germanium transistors, strained silicon, and eFUSE, a technology that enables computer chips to automatically respond to changing conditions.

The technology could have a big impact on consumer electronics, since IBM supplies chips for all three of the top gaming consoles: PlayStation 3, Nintendo Wii and Xbox 360.
eDRAM Specifications

Among the specifications of IBM’s high-performance eDRAM technology:

cell size: 0.126 mm2
Power supply: 1 V
availability: 98.7%
Tile: 1K RowX16 Col X146 (2Mb)
AC power: 76 mW
standby keep alive Power: 42 mW
Random cycle time: 2ns
Latency: 1.5ns

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