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Tuesday, December 17, 2013

Molecules Formed by Covalent Bonds

For example, the oxygen molecule consists of two atoms of oxygen. In the case of oxygen, the bond that holds the two atoms together is known as a covalent bond, and here is how it works.

The oxygen atom has 8 each of protons, neutrons, and electrons. The protons and neutrons are found in the center of the atom, known as the nucleus, and the electrons surround the nucleus in layers, or shells. The oxygen atom has 2 electrons in its first shell, and 6 in its second and outer shell. However, in chemistry, there exists the octet rule, which states that atoms generally strive to have 8 electrons in their outer shell. The oxygen therefore is 2 electrons away from a complete outer shell. When it binds with another oxygen atom, they can share two pairs of electrons and so each will have 8. When atoms share electrons like that, they form a molecule through a covalent bond.

Molecules Formed by Ionic Bonds

Molecules can also be formed through other kinds of chemical bonds, for example, an ionic bond. An example this is sodium chloride, or table salt. In an ionic bond, one atom has a much greater ability to attract electrons than the other atom. In this case, the chlorine, which is only 1 electron short of a complete outer shell, will steal that electron from the sodium, which has only 1 outermost electron. This turns the sodium into a positively charged ion, and the chlorine into a negatively charged ion, and the two atoms end up being held together by an electrostatic charge.

Meaning of a Mole

Now what is a mole? A mole is simply a counting number, much like a dozen. When we say "dozen", we mean 12; well, when we say "a mole" we mean 6.022 x 10 to the 23. Moles make it easier to quantify chemical substances. The periodic table lists the weights of all the elements in grams per mole.

Examples of Finding Molar Mass

For example, oxygen has molar mass of 16, which means 6.022 x 10 to the 23 atoms of oxygen weigh 16 grams. Hydrogen has a molar mass of 1. To find out the molar mass of a molecule, such as water, we need to add up the molar masses of the atoms it is composed of. Since water has two atoms of hydrogen and 1 atom of oxygen, its molar mass is 18 grams per mole.

On This Day in Science History -- December 17 -- Carbon 14 Dating

December 17th is Willard Libby's birthday. Libby was the American physical chemist who developed the carbon-14 dating technique. This method is used to determine the age of 'once living' objects up to approximately 50,000 years.

Carbon 14 is an isotope of carbon that is created naturally in the atmosphere by cosmic rays which in turn is breathed by living things or absorbed by plants. Over a lifetime of breathing, plants and animals maintain a natural ratio of carbon-14 to carbon-12. When the living thing dies, it stops absorbing the carbon-14 from the air.
                                                              147N + 10n → 146C + 11H
Carbon-14 decays into nitrogen by beta decay over time, but the process takes a long time. The half life of carbon-14 is 5,720 years, meaning after 5,720 years, the organism will have half the carbon-14 levels it did when it was alive. If you measure the amount of carbon-14 in a once living object, you can determine the approximate age of the organism.

Find out what else occurred on this day in science history.

Can we turn unwanted carbon dioxide into electricity?

Researchers are developing a new kind of geothermal power plant that will lock away unwanted carbon dioxide (CO2) underground -- and use it as a tool to boost electric power generation by at least 10 times compared to existing geothermal energy approaches.
The technology to implement this design already exists in different industries, so the researchers are optimistic that their new approach could expand the use of geothermal energy in the U.S. far beyond the handful of states that can take advantage of it now.
At the American Geophysical Union meeting on Friday, Dec. 13, the research team debuted an expanded version of the design, along with a computer animated movie that merges advances in science with design and cognitive learning techniques to explain the role that energy technologies can have in addressing Climate-Change'>climate change.

The new power plant design resembles a cross between a typical geothermal power plant and the Large Hadron Collider: It features a series of concentric rings of horizontal wells deep underground. Inside those rings, CO2, nitrogen and water circulate separately to draw heat from below ground up to the surface, where the heat can be used to turn turbines and generate electricity.
The design contrasts with conventional geothermal plants, explained study co-author Jeffrey Bielicki, assistant professor of energy policy in the Department of Civil, Environmental and Geodetic Engineering and the John Glenn School of Public Affairs at The Ohio State University.
"Typical geothermal power plants tap into hot water that is deep under ground, pull the heat off the hot water, use that heat to generate electricity, and then return the cooler water back to the deep subsurface. Here the water is partly replaced with CO2 or another fluid -- or a combination of fluids," he said.
CO2 extracts heat more efficiently than water, he added.
This approach -- using concentric rings that circulate multiple fluids -- builds upon the idea to use CO2 originally developed by Martin Saar and others at the University of Minnesota, and can be at least twice as efficient as conventional geothermal approaches, according to computer simulations.
"When we began to develop the idea to use CO2 to produce geothermal energy, we wanted to find a way to make CO2 storage cost-effective while expanding the use of geothermal energy," said Jimmy Randolph, postdoctoral researcher in the Department of Earth Sciences at the University of Minnesota.
"We hope that we can expand the reach of geothermal energy in the United States to include most states west of the Mississippi River," Bielicki said.
The current research team includes Ohio State, the University of Minnesota and Lawrence Livermore National Laboratory, where geoscientist Tom Buscheck came up with the idea to add nitrogen to the mix.
He and his colleagues believe that the resulting multifluid design will enable geothermal power plants to store energy away -- perhaps hundreds of gigawatt hours -- for days or even months, so that it is available when the electricity grid needs it. The underground geothermal formation could store hot, pressurized CO2 and nitrogen, and release the heat to the surface power plant when electricity demand is greatest. The plant could also suspend heat extraction from the subsurface during times of low power demand, or when there is already a surplus of renewable power on the grid.
"What makes this concept transformational is that we can deliver renewable energy to customers when it is needed, rather than when the wind happens to be blowing, or when spring thaw causes the greatest runoff," Buscheck said.
In computer simulations, a 10-mile-wide system of concentric rings of horizontal wells situated about three miles below ground produced as much as half a gigawatt of electrical power -- an amount comparable to a medium-sized coal-fired power plant -- and more than 10 times bigger than the 38 megawatts produced by the average geothermal plant in the United States.
The simulations also revealed that a plant of this design might sequester as much as 15 million tons of CO2 per year, which is roughly equivalent to the amount produced by three medium-sized coal-fired power plants in that time.
Bielicki noted the possibility of expanding the use of geothermal energy around the country. Right now, most geothermal power plants are in California and Nevada, where very hot water is relatively close to the surface. But the new design is so much more efficient at both storing energy and extracting heat that even smaller-scale "hotspots" throughout the western U.S. could generate power.
The eastern U.S. is mostly devoid of even small hotspots, so geothermal power would still be limited to a few particularly active areas such as West Virginia, he said.
Another caveat: The geothermal plant would probably have to be connected to a large CO2 source, such as a coal-fired power plant that is scrubbing the CO2 from its own emissions. That connection would likely be made by pipeline.
Buscheck added, however, that the study showed that this design could work effectively with or without CO2, and said a pilot plant based on this design could initially be powered solely by nitrogen injection to prove the economic viability of using CO2. The research team is currently working on more detailed computer model simulations and economic analyses for specific geologic settings in the U.S.
The project is unusual in part because, as they were refining their ideas, the engineers joined with Shannon Gilley, then a master of fine arts student at the Minneapolis College of Art and Design. Bielicki worked with Gilley for more than a year to create the computer animated video titled "Geothermal Energy: Enhancing our Future." Part of Gilley's task was to communicate the more complex details of Climate-Change'>climate change, CO2 storage and geothermal energy to the general public.
"We built this concept of public outreach into our efforts not just to communicate our work, but also to explore new ways for scientists, engineers, economists and artists to work together," Bielicki said.
Co-authors on the presentation also included Mingjie Chen, Yue Hao and Yunwei Sun, all of Lawrence Livermore National Laboratory. Work at the University of Minnesota and Ohio State has been funded by the National Science Foundation, while work at Lawrence Livermore National Laboratory has been funded by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy.
Heat Mining Co. LLC, a startup company spun off from the University of Minnesota, expects to have an operational project, based on an earlier form of the approach, in 2016.

Nitrogen deposition poses threat to diversity of Europe's forest vegetation

Unless nitrogen emissions are curbed, the diversity of plant communities in Europe's forests will decrease. Atmospheric nitrogen deposition has already changed the number and richness of forest floor vegetation species in European forests over the last 20-30 years. In particular, the coverage of plant species adapted to nutrient-poor conditions has reduced. However, levels of nitrogen deposition in Finnish forests remain small compared to Southern and Central Europe.
These results will be presented as part of international research published in the journal Global Change Biology. Researchers from the Finnish Environment Institute and the Finnish Forest Research Institute (Metla) participated in this research, which concludes that unless nitrogen emissions are curbed, the diversity of plant communities in Europe's forests will decrease. The work involved the examination of long-term changes in vascular plant communities within a 1 300 monitoring grid covering 28 forested areas in various parts of Europe.
The number and richness of forest floor vegetation species in European forests have changed over the last 20 to 30 years, due to wet and dry deposition of atmospheric nitrogen. In particular, low-nutrient or acidic habitats are sensitive to long-term nitrogen deposition. Among such habitats, coverage of species such as heather and may lily has been reduced in many areas, in which nitrogen deposition has exceeded a certain threshold value i.e. the critical nitrogen load.
The largest changes in vegetation have occurred in Southern and Central European forests. Although deposition has not yet markedly affected species numbers within plant communities, most new species spreading into forests during the monitoring period have been types that favour nitrogen.
Finland still has a small nitrogen load
Four monitoring areas located in Finnish nature reserves were covered by the research. These areas were subject to markedly lower nitrogen deposition (0.6-1.9 kg of nitrogen per hectare per year) compared to areas subject to greater nitrogen deposition in Central Europe (10-20 kg N/ha/year) or Italy (20-30 kg N/ha/year).
Critical nitrogen loads applied in the research are based on the previously published results of long-term field research and experiments. By critical nitrogen loads, we refer to nitrogen deposition known to have harmful effects on the functions of more sensitive organisms in the ecosystem. The critical nitrogen load in boreal forests is estimated to be fairly small (5-8 kg N/ha/y), since northern forest ecosystems are highly sensitive to the effects of excess nitrogen. Such areas in Finland include nutrient-poor and dry pine forests in particular.
Although nitrogen deposition remains small in Northern Europe, even a slight rise in long-term deposition could change the competitive relationship of vascular plants by promoting the dissemination and growth of nitrogen-favouring species.
The effects of nitrogen deposition on Finland's forest vegetation can only be investigated with the assistance of a permanent environmental monitoring network. According to long-term monitoring by the Finnish Forest Research Institute (Metla), tree felling is still the key factor in changes to forest floor vegetation.
This monitoring reveals a reduction in lichens throughout Finland, including in unfelled forests. In Northern Finland, reindeer grazing is the key factor in lichen reduction. Slow-growing lichens in Southern Finland can also suffer due to the rapid growth of and shading by plants benefiting from nitrogen deposition.

FDA issues proposed rule to determine safety and effectiveness of antibacterial soaps

The U.S. Food and Drug Administration today issued a proposed rule to require manufacturers of antibacterial hand soaps and body washes to demonstrate that their products are safe for long-term daily use and more effective than plain soap and water in preventing illness and the spread of certain infections. Under the proposal, if companies do not demonstrate such safety and effectiveness, these products would need to be reformulated or relabeled to remain on the market.
Today’s action is part of a larger, ongoing review of antibacterial active ingredients by the FDA to ensure these ingredients are proven to be safe and effective. This proposed rule does not affect hand sanitizers, wipes, or antibacterial products used in health care settings.
Millions of Americans use antibacterial hand soap and body wash products. Although consumers generally view these products as effective tools to help prevent the spread of germs, there is currently no evidence that they are any more effective at preventing illness than washing with plain soap and water. Further, some data suggest that long-term exposure to certain active ingredients used in antibacterial products—for example, triclosan (liquid soaps) and triclocarban (bar soaps)—could pose health risks, such as bacterial resistance or hormonal effects.
“Antibacterial soaps and body washes are used widely and frequently by consumers in everyday home, work, school, and public settings, where the risk of infection is relatively low,” said Janet Woodcock, M.D., director of the FDA’s Center for Drug Evaluation and Research (CDER). “Due to consumers’ extensive exposure to the ingredients in antibacterial soaps, we believe there should be a clearly demonstrated benefit from using antibacterial soap to balance any potential risk.”
The widespread consumer use of antibacterial products, the accumulated scientific information and concerns raised by health care and consumer groups have prompted the FDA to reevaluate what data are needed to classify the active ingredients in consumer antibacterial products as “generally recognized as safe and effective” or GRASE.  Under the proposed rule, manufacturers who want to continue marketing antibacterial products will be required to provide the agency with additional data on the products’ safety and effectiveness, including data from clinical studies to demonstrate that these products are superior to non-antibacterial soaps in preventing human illness or reducing infection.
“While the FDA continues to collect additional information on antibacterial hand soaps and body washes, we encourage consumers to make an educated choice about what products they choose to use,” said Sandra Kweder, M.D., deputy director, Office of New Drugs at CDER. “Washing with plain soap and running water is one of the most important steps consumers can take to avoid getting sick and to prevent spreading germs to others.”
Consumers should continue to be diligent about washing their hands. If soap and water are not available, an alcohol-based hand sanitizer that contains at least 60 percent alcohol should be used.  More information on appropriate hand washing from the CDC may be found here.
Almost all soaps labeled “antibacterial” or “antimicrobial” contain at least one of the antibacterial ingredients addressed in the proposed rule. The most common active ingredients in antibacterial soaps are triclosan and triclocarban. Some soaps labeled “deodorant” may also contain these ingredients.
The proposed rule does not require the antibacterial soap products to be removed from the market at this time. When the proposed rule is finalized, as previously stated, either companies will have provided data to support an antibacterial claim, or if not, they will have to reformulate (remove antibacterial active ingredients) or relabel (remove the antibacterial claim from the product’s labeling) these products in order to continue marketing. The proposed rule is available for public comment for 180 days, with a concurrent one year period for companies to submit new data and information, followed by a 60-day rebuttal comment period.
Source: FDA

Monday, December 16, 2013

‘শপথ এবার প্রতিরোধের’

লাখো কণ্ঠে ‘আমার সোনার বাংলা’

বেয়াল্লিশ বছর আগে যে মুহূর্তে যে স্থানটিতে বাঙালির মুক্তির সনদ লেখা হয়েছিল, মুক্তিযুদ্ধে বিজয়ের সেই ক্ষণে সেই স্বাধীনতার উদ্যানেই লাখো কণ্ঠ গাইল ‘আমার সোনার বাংলা, আমি তোমায় ভালোবাসি’।

রবীন্দ্রনাথ ঠাকুরের এই গানটিই একাত্তরের রণাঙ্গনে বাঙালি জাতিকে প্রেরণা যুগিয়েছিল, যা পরে বাংলাদেশের জাতীয় সংগীত হিসাবে গ্রহণ করা হয়।
সোহরাওয়ার্দী উদ্যানে স্থাপিত ‘বিজয় ২০১৩’র মঞ্চে সোমবার বিকাল ৪টা ৩১মিনিটে এই গানে কণ্ঠ মেলান উপস্থিত জনতা।
এবার সম্মিলিতভাবে এই উত্সব পালন করছে বিজয় ২০১৩ উদযাপন জাতীয় কমিটি, গণজাগরণ মঞ্চ, সেক্টর কমান্ডার্স ফোরাম, মুক্তিযুদ্ধ চেতনা বাস্তবায়ন কমিটি এবং বিজয় ৪:৩১ মঞ্চ।

জাতীয় সংগীত পরিবেশনের আগে স্বাধীন বাংলা বেতার কেন্দ্রের শিল্পীরা পরিবেশন করেন একাত্তরে মুক্তিকামী মানুষকে শক্তি যোগানো বিভিন্ন গান। পরে তারাও সমবেত কণ্ঠের জাতীয় সংগীতে অংশ নেন।
১৯৭১ সালের ১৬ ডিসেম্বর বিকাল ৪টা ৩১ মিনিটে পাকিস্তানি বাহিনী এই উদ্যানেই আত্মসমর্পণের দলিলে সই করেছিল, তখন এর নাম ছিল রেসকোর্স ময়দান।মুক্তিযুদ্ধের উপ অধিনায়ক অবসরপ্রাপ্ত এয়ার ভাইস মার্শাল একে খন্দকার বীর উত্তম বলেন, “সেই ক্ষণে জাতীয়ভাবে আমাদের প্রাণের জাতীয় সংগীতকে কোটি কণ্ঠে পরিবেশনাই আজকের অনুষ্ঠানের মূল প্রতিপাদ্য।”

World's largest human flag !

Bangladesh attempts to create the world's largest 'human flag'





This Day in Science History -- December 16 -- Johann Ritter

December 16th is Johann Wilhelm Ritter's birthday. Ritter was a German scientist who invented one of the first dry pile galvanic batteries. Early batteries used electrodes dipped in an acid solution where the energy is produced through oxidation reactions. A dry pile uses just enough moisture to function and did not have the dangers of spilling acid solutions. Ritter's pile used alternating pieces of silver and zinc foil separated by pieces of paper.

Ritter was also responsible for the discovery of the ultraviolet region of the electromagnetic spectrum. While investigating the discoloration of silver salt crystals exposed to sunlight, he discovered there was a part of sunlight beyond the violet range responsible for the discoloration. He initially called this part of the light spectrum 'de-oxidizing rays' because of their chemical reactivity.

Find out more about electrochemical cells, redox reactions and what else occurred on this day in science history.

Introduction to Chemistry

What Is Chemistry?Chemistry is the study of matter and energy and the interactions between them. This is also the definition for physics, by the way. Chemistry and physics are specializations of physical science. Chemistry tends to focus on the properties of substances and the interactions between different types of matter, particularly reactions that involve electrons. Physics tends to focus more on the nuclear part of the atom, as well as the subatomic realm. Really, they are two sides of the same coin.

Why Study Chemistry?
Because understanding chemistry helps you to understand the world around you. Cooking is chemistry. Everything you can touch or taste or smell is a chemical. When you study chemistry, you come to understand a bit about how things work. Chemistry isn't secret knowledge, useless to anyone but a scientist. It's the explanation for everyday things, like why laundry detergent works better in hot water or how baking soda works or why not all pain relievers work equally well on a headache. If you know some chemistry, you can make educated choices about everyday products that you use.

What Fields of Study Use Chemistry?
You could use chemistry in most fields, but it's commonly seen in the sciences and in medicine. Chemists, physicists, biologists, and engineers study chemistry. Doctors, nurses, dentists, pharmacists, physical therapists, and veterinarians all take chemistry courses. Science teachers study chemistry. Fire fighters and people who make fireworks learn about chemistry. So do truck drivers, plumbers, artists, hairdressers, chefs... the list is extensive.
What Do Chemists Do?
Whatever they want. Some chemists wor
k in a lab, in a research environment, asking questions and testing hypotheses with experiments. Other chemists may work on a computer developing theories or models or predicting reactions. Some chemists do field work. Others contribute advice on chemistry for projects. Some chemists write. Some chemists teach. The career options are extensive.

অধ্যায় - ৫ রাসায়নিক বন্ধন

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