PAETE.ORG FORUMS
Paetenians Home on the Net

HOME | ABOUT PAETE | USAP PAETE MUNISIPYO  | MEMBERS ONLY  | PICTORIAL PAETE | SINING PAETE  | LINKS  |

FORUM GUIDELINES
please read before posting

USAP PAETE Forum Index USAP PAETE
Discussion Forums for the people of Paete, Laguna, Philippines
 
 FAQFAQ   SearchSearch    UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

(Math) (Chem) Symmetry: It's True: No Two Snowflakes Alike

 
Post new topic   Reply to topic   printer-friendly view    USAP PAETE Forum Index -> Science Lessons Forum
View previous topic :: View next topic  
Author Message
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Sat Jan 14, 2006 9:13 am    Post subject: (Math) (Chem) Symmetry: It's True: No Two Snowflakes Alike Reply with quote






Symmetry is everywhere. Things repeat. some can be divided into equal or identical parts. Crystals are among the materials that exhibit or demonstrate a great deal of symmetry. This lesson takes us through a world of symmetry. It is an important mathematical skill - to recognize patterns. Recognizing the parts make us understand the whole. The news article talks about snowflakes - but children in the Philippines can look at table salt crystals instead.

A website that I strongly recommend to help you understand symmetry is the following:

http://www.linkslearning.org/K....._Symmetry/

The above is a real good introduction to symmetry.


Photos Show It's True: No Two Snowflakes Alike
By Sara Goudarzi
Special to LiveScience
posted: 13 January 2006
12:17 pm ET

Through rain and sleet and dead of night and all that, your letters next winter can be delivered bearing snowflakes artfully photographed by a physicist who weathers those same storms to study nature's crystal magic.

Starting in October, the U.S. Postal Service will issue a set of four stamps featuring pictures of snowflakes taken by Kenneth Libbrecht, a professor of physics at the California Institute of Technology.

For years, Libbrecht has been studying the physics of snowflakes, looking at the different patterns of crystal growth and snowflake formation.

Snowflakes generally take one of seven basic forms. For example, stellar, or starlike, snowflakes usually grow six primary branches that support arms, which often develop thin plates of ice at the ends. Bitter-cold conditions create crystals with more facets. The most symmetrical snowflakes occur during light snowfalls when there is cold weather and little wind. If the air is warmer, crystals tend to stick together to form less symmetrical snowflakes, or they can take on a needlelike shape. In higher humidity, snowflakes may branch more, making them dendritic, or plantlike, in appearance.

The Holiday Snowflakes stamps are photographs of two basic snowflake patterns by physicist Kenneth Libbrecht. They are stellar dendrites, which form branching treelike arms, and sectored plates, which as their name suggests, form platelike arms.

Falling from thousands of feet, these intricate ice crystals commonly begin as a piece of dust tumbling through the clouds. Gathering water molecules, they blossom into crystal forms in endlessly different patterns because of the constantly changing conditions of the atmosphere.

"I'm trying to understand the dynamics of how crystals grow, all the way down to the molecular level," Libbrecht said. "This is a very complicated problem, and I've been looking at ice as a particularly interesting case study."

Snowflakes are nothing more than ice, but the forms a single flake can take are dizzyingly complex. A single crystal of ice is known as a snow crystal. And one or more snow crystals stuck together make a snowflake.

There is, as you've heard, endless possibilities for how they stick together.

Searching for better snowflakes

When Libbrecht started making snowflakes in the laboratory, he took microscopic photographs in order to be able to study the basic physics of each flake. In 2001, he started capturing images of natural snowflakes.

Location is important.

"Fairbanks sometimes offers some unusual crystal types, because it's so cold," Libbrecht said. "Warmer climates, for example, in New York State and the vicinity, tend to produce less spectacular crystals."

"I visit the frozen North and wait for snow to fall," Libbrecht said in a recent email interview. "I'm in northern Ontario right now."

Since ice is mostly clear, the flakes have to be lit properly to reveal their beauty.

"I use different types of colored lights shining through the crystals, so the ice structures act like complex lenses to refract the light in different ways. The better the lighting, the more interesting is the final photograph." He has to work quickly, using a paintbrush to place a flake into his portable studio for the shoot. When flakes have fallen, they stop growing and within minutes they typically lose their sharp edges and become less interesting.

Snow science

The pictures have helped Libbrecht describe a growth instability in snowflakes that other researchers had missed. By applying high voltage to a growing snow crystal in the lab, Libbrecht is able to analyze unique growth mechanisms, especially on very small scales.

"These instabilities are new and important for understanding how crystals grow, but they're hard to explain," Libbrecht told LiveScience.

Nonetheless, the knowledge can be applied in making semiconductors, solid materials whose electrical conductivity operates many electronic gadgets. Semiconductors are made in part by condensing certain substances into solid forms.

The Holiday Snowflakes stamps will feature multi-branched stellar dendrites, with six symmetrical main branches and many randomly placed side branches and sectored plates. These represent but one of seven primary types of snowflake patterns.

As you'd expect, no two of the stamps are alike. But what about out in the field? Are they really all different?

"The answer is basically yes, because there is such an incredibly large number of possible ways to make a complex snowflake," Libbrecht said. "In many cases, there are very clear differences between snow crystals, but of course there are many similar crystals as well. In the lab we often produce very simple, hexagonal crystals, and these all look very similar."

*************************************************************

Questions to explore further this topic:

Image Gallery of Snowflakes

http://www.livescience.com/php.....mp;index=0

Images and Animations of Snowflakes

http://ww2.lafayette.edu/%7Ereiterc/mvp/sfn/

What are snowflakes?

http://www.its.caltech.edu/~at.....primer.htm
http://www.macatawa.org/~oias/snowflak.htm
http://www.units.muohio.edu/dr.....snow.shtml

How do snowflakes form?

http://www.pa.msu.edu/~sciencet/ask_st/100897.html
http://chemistry.about.com/lib.....21001a.htm

What shapes snowflakes?

http://www.usatoday.com/weather/wsnocrys.htm

Why do we have snow?

http://www.usatoday.com/weathe.....risnow.htm

Photos and images of snow

http://wintercenter.homestead.com/photoindex.html

A poem about snowflakes (Longfellow)

http://www.naic.edu/~gibson/poems/longfellow1.html

What are crystals?

http://www.chemistry.co.nz/crystals_defined.htm
http://www.cis.yale.edu/ynhti/.....agner.html
http://www.unmuseum.org/crystals.htm
http://www.xray.ncsu.edu/student_faq_xtal.html

How do crystals form?

http://www.chemistry.co.nz/crystals_forming.htm
http://www.sdnhm.org/kids/mine.....ystal.html
http://www.nationalgeographic......yfun1.html
http://www.creativekidsathome......stals.html

Images of Crystals

http://www.crystalminers.com/

An introduction to symmetry

http://www.linkslearning.org/K....._Symmetry/
http://www.mathdance.org/symme.....roups.html

An introduction to patterns

http://www.linkslearning.org/K.....index.html

What are tangrams?

http://www.linkslearning.org/K.....index.html

Crystal Structure at the Atomic Level

http://bouman.chem.georgetown......lect28.htm
http://bouman.chem.georgetown......lect29.htm
http://bouman.chem.georgetown......lect30.htm

Symmetry in Chemistry

http://csi.chemie.tu-darmstadt.....index.html

GAMES

http://www.popularfront.com/snowdays/
http://snowflakes.lookandfeel.com/
http://w3.tvi.edu/~cgulick/snowflakes.htm
http://www.montessoriworld.org.....wflak.html
http://www.northcanton.sparcc......ntrate.htm


Last edited by adedios on Sat Jan 27, 2007 4:11 pm; edited 4 times in total
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Sat Nov 25, 2006 7:45 am    Post subject: Snow Crystals Reply with quote

Snow Crystals

This Web site, created by Caltech physicist Kenneth G. Libbrecht, is all about snow crystals and snowflakes.

http://www.snowcrystals.com/
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Wed Dec 13, 2006 1:51 pm    Post subject: Yes, Virginia, some snowflakes can look the same! Reply with quote

American Chemical Society
13 December 2006


Yes, Virginia, some snowflakes can look the same!


Snowflakes are one of the most recognizable and endearing symbols of winter. Their intricate shapes have been the inspiration for Christmas ornaments, jewelry and U.S. postage stamps. They are the subject of song, school projects and even scientific investigation, including a possible impact on global warming.

Jon Nelson, a researcher with Ritsumeikan University in Japan, has studied snowflakes for 15 years, and has some interesting insights into their delicate structures.

Is it true that no two snowflakes are alike?

The old adage that ‘no two snowflakes are alike' may ring true for larger snowflakes, but it might not hold true for smaller, simpler crystals that fall before they've had a chance to fully develop. Regardless, snow crystals have tremendous diversity, partly due to their very high sensitivity to tiny temperature changes as they fall through the clouds.

How do snowflakes form?

A snowflake starts as a dust grain floating in a cloud. Water vapor in the air sticks to the dust grain and the resulting droplet turns directly into ice. And that's where the science kicks in.

First, the tiny ice crystal becomes hexagonal (six-sided). This shape originates from the chemistry of the water molecule, which consists of two hydrogen atoms bonded to an oxygen atom. Because of the angle of the water molecule and its hydrogen-bonding, the water molecules in a snowflake chemically bond to each other to form the six-sided flake. The flake eventually sprouts six tiny branches. Each of these branches grows to form side branches in a direction and shape that are influenced by the clustering of water molecules on the ice crystal surfaces.

CLICK HERE TO VIEW ILLUSTRATION ABOUT HOW SNOWFLAKES ARE FORMED: http://acswebcontent.acs.org/j.....poster.pdf

Why are scientists interested in the study of snowflakes?

The study of snowflakes, which are really ice crystals, has recently become important due to the possible influences that these crystals have on global climate change. Researchers now believe that ice crystals play a crucial role in ozone depletion, possibly by acting as a catalyst to break down ozone. Ice crystals in the atmosphere also play a key role in building up electric charges in clouds and are therefore believed to influence the production of lightning, although the mechanism is unclear.


###
Jon Nelson has written several research papers on snowflakes, including one in the American Chemical Society journal, "Crystal Growth & Design." That paper, published in 2005, helped explain several previously unanswered phenomena about snowflakes.

The American Chemical Society – the world's largest scientific society – is a nonprofit organization chartered by the U.S. Congress and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

EDITOR'S NOTE: The American Chemical Society's "WonderNet" Web site has a step-by-step hands-on activity for children to make their own snowflakes. http://www.chemistry.org/porta.....splay.html"DOC=wondernet%5Cactivities%5Ccrystals%5Csnowflakes.html
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Thu Jan 18, 2007 12:43 pm    Post subject: MU Scientists Discover Way to Order Polar Molecules in Cryst Reply with quote

Jan 16 2007
Contact: Katherine Kostiuk
Sr. Information Specialist

MU Scientists Discover Way to Order Polar Molecules in Crystals
The discovery has implications for future of telecommunications and computing



COLUMBIA, Mo. - Researchers at the University of Missouri-Columbia have found a way to organize molecules in a crystal so that the poles align in the same direction. In preliminary tests, the scientists also have discovered that aligned crystals hold potential to change the frequency of light, making them important to the future of telecommunications and computing.

"Making crystals parallel is difficult to do, but we've found a way to do it and are getting better at it," said Rainer Glaser, professor of chemistry in MU's College of Arts and Science. "Our preliminary testing indicates that there is a synergism we didn't expect. As a chemist, I was expecting the potential of a parallel crystal to be the sum of all its molecules, but in our collaborative work, we've found that there is even greater potential for these crystals than I anticipated."

Glaser has collaborated with Yongqiang Sui, a doctoral student in chemistry, and Ping Yu, MU assistant professor of physics, in this interdisciplinary effort. As a physicist, Yu has been able to look at the crystals in new ways and consider different applications for them. He has found that when an infrared laser is focused at a parallel crystal, the frequency of light changes. This finding, still in the preliminary stages, could have the potential to lead to technology that would create faster and more efficient microchips.

"If you have a laptop computer sitting on your knees, you'll feel heat from it, but with this technology, the computer would not get hot," Sui said. "Large computing facilities spend millions of dollars in energy bills every year to keep their computers cool. Technology using crystals would not only reduce those costs, but also create faster computers. We hope that our discoveries might play a role in the development of this technology."

Glaser said the team's next step is to test different types of crystals to determine what has the best potential.

A study detailing the discovery of how to achieve polar order will be published in the January 2007 issue of the journal Accounts of Chemical Research, which also will feature a cover graphic illustrating the potential of these crystals to alter light frequency. Glaser, Yu and Sui and co-investigators Nathan Knotts, Linghui Li, Meera Chandrasekhar, Christopher Martin and Charles L. Barnes presented a paper on this topic earlier this year at the international conference "Dalton Discussion 9: Functional Molecular Assemblies," and this paper has been published in a special issue of the journal "Dalton Transaction."
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Sun Jan 28, 2007 6:59 am    Post subject: Knitting Network Reply with quote

Week of Jan. 27, 2007; Vol. 171, No. 4

Knitting Network
Ivars Peterson

More than 5,000 mathematicians come annually to the Joint Mathematics Meetings (JMM). This year's edition was held in New Orleans earlier this month. For those particularly interested in mathematical crafting, one highlight was a Saturday evening devoted to knitting, crocheting, beading, needlework, paper folding, and more.

Organized by sarah-marie belcastro of Smith College and Carolyn A. Yackel of Mercer University, the event brought together a wide variety of people, both experts and beginners.

In the realm of counted cross stitch, Mary D. Shepherd of Northwest Missouri State University displayed her painstakingly woven symmetry patterns. For the type of cloth and technique that she uses, the fabric is a grid of squares, and one cross stitch covers one square of the fabric. The only possible subdivision of this square is with a stitch that "covers" half a square on the diagonal, Shepherd says.

These features constrain the number of symmetry patterns that you can weave. Of 17 possible wallpaper patterns, for example, only 12 can be done in counted cross stitch.

For the full article:

http://sciencenews.org/article.....thtrek.asp
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Sat Feb 24, 2007 8:25 am    Post subject: Ancient Islamic Penrose Tiles Reply with quote

Week of Feb. 24, 2007; Vol. 171, No. 8

Ancient Islamic Penrose Tiles
Julie J. Rehmeyer

When Peter J. Lu traveled to Uzbekistan, he had no idea of the mathematical journey that he was about to embark on as well.

The Harvard graduate student in physics was fascinated by the beautiful and intricate geometric "girih" patterns on the 800-year-old buildings there, and he wanted to know how ancient artisans had created them. He discovered more than just a clever construction method. He also found an entirely unexpected level of mathematical sophistication in the designs, pointing at mathematical ideas that weren't formally developed until hundreds of years later.

Lu's determination to find out took him on a journey through hundreds of photographs of Islamic architecture in the libraries at Harvard—and now it's landed him an article in Science.

For the full article:

http://sciencenews.org/article.....thtrek.asp
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Mon Mar 19, 2007 7:42 am    Post subject: Mathematicians Map E8 Reply with quote

Mathematicians Map E8
American Institute of Mathematics
18 March 2007

Mathematicians have mapped the inner workings of one of the most complicated structures ever studied: the object known as the exceptional Lie group E8. This achievement is significant both as an advance in basic knowledge and because of the many connections between E8 and other areas, including string theory and geometry. The magnitude of the calculation is staggering: the answer, if written out in tiny print, would cover an area the size of Manhattan. Mathematicians are known for their solitary work style, but the assault on E8 is part of a large project bringing together 18 mathematicians from the U.S. and Europe for an intensive four-year collaboration.
"This is exciting," said Peter Sarnak, Eugene Higgins Professor of Mathematics at Princeton University (not affiliated with the project). "Understanding and classifying the representations of Lie Groups has been critical to understanding phenomena in many different areas of mathematics and science including algebra, geometry, number theory, Physics and Chemistry. This project will be valuable for future mathematicians and scientists."

Bigger than the Human Genome
The magnitude of the E8 calculation invites comparison with the Human Genome Project. The human genome, which contains all the genetic information of a cell, is less than a gigabyte in size. The result of the E8 calculation, which contains all the information about E8 and its representations, is 60 gigabytes in size. That is enough space to store 45 days of continuous music in MP3 format. While many scientific projects involve processing large amounts of data, the E8 calculation is very different: the size of the input is comparatively small, but the answer itself is enormous, and very dense.
Like the Human Genome Project, these results are just the beginning. According to project leader Jeffrey Adams, "This is basic research which will have many implications, most of which we don't understand yet. Just as the human genome does not instantly give you a new miracle drug, our results are a basic tool which people will use to advance research in other areas." This could have unforeseen implications in mathematics and physics which do not appear for years.

According to Hermann Nicolai, Director of the Albert Einstein Institute in Bonn, Germany (not affiliated with the project), "This is an impressive achievement. While mathematicians have known for a long time about the beauty and the uniqueness of E8, we physicists have come to appreciate its exceptional role only more recently --- yet, in our attempts to unify gravity with the other fundamental forces into a consistent theory of quantum gravity, we now encounter it at almost every corner! Thus, understanding the inner workings of E8 is not only a great advance for pure mathematics, but may also help physicists in their quest for a unified theory."


How big is the answer?

The E8 Calculation
The team that produced the E8 calculation began work four years ago. They meet together at the American Institute of Mathematics every summer, and in smaller groups throughout the year. Their work requires a mix of theoretical mathematics and intricate computer programming. According to team member David Vogan from MIT, "The literature on this subject is very dense and very difficult to understand. Even after we understood the underlying mathematics it still took more than two years to implement it on a computer." And then there came the problem of finding a computer large enough to do the calculation.
For another year, the team worked to make the calculation more efficient, so that it might fit on existing supercomputers, but it remained just beyond the capacity of the hardware available to them. The team was contemplating the prospect of waiting for a larger computer when Noam Elkies of Harvard pointed out an ingenious way to perform several small versions of the calculation, each producing an incomplete version of the answer. These incomplete answers could be assembled to give the final solution. The cost was having to run the calculation four times, plus the time to combine the answers. In the end the calculation took about 77 hours on the supercomputer Sage.

Beautiful Symmetry
At the most basic level, the E8 calculation is an investigation of symmetry. Mathematicians invented the Lie groups to capture the essence of symmetry: underlying any symmetrical object, such as a sphere, is a Lie group.
Lie groups come in families. The classical groups A1, A2, A3, ... B1, B2, B3, ... C1, C2, C3, ... and D1, D2, D3, ... rise like gentle rolling hills towards the horizon. Jutting out of this mathematical landscape are the jagged peaks of the exceptional groups G2, F4, E6, E7 and, towering above them all, E8. E8 is an extraordinarily complicated group: it is the symmetries of a particular 57-dimensional object, and E8 itself is 248-dimensional!

To describe the new result requires one more level of abstraction. The ways that E8 manifests itself as a symmetry group are called representations. The goal is to describe all the possible representations of E8. These representations are extremely complicated, but mathematicians describe them in terms of basic building blocks. The new result is a complete list of these building blocks for the representations of E8, and a precise description of the relations between them, all encoded in a matrix with 205,263,363,600 entries.

The Atlas of Lie Groups Project
The E8 calculation is part of an ambitious project known as the Atlas of Lie Groups and Representations. The goal of the Atlas project is to determine the unitary representations of all the Lie groups. This is one of the great unsolved problems of mathematics, dating from the early 20th century. The success of the E8 calculation leaves little doubt that the Atlas team will complete their task.

The Atlas team consists of about 20 researchers from the United States and Europe. The core group consists of Jeffrey Adams (University of Maryland), Dan Barbasch (Cornell), John Stembridge (University of Michigan), Peter Trapa (University of Utah) , Marc van Leeuwen (Poitiers), David Vogan (MIT), and (until his death in 2006) Fokko du Cloux (Lyon).

David Vogan is giving a talk on the E8 computation at MIT on Monday, March 19, at 2 PM in Building 1, Room 190. The talk is open to the public.

The Atlas project is funded by the National Science Foundation through the American Institute of Mathematics.

What is E8?

http://aimath.org/E8/e8.html
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Sat Apr 21, 2007 6:53 am    Post subject: Forms of Symmetry Reply with quote

Week of April 21, 2007; Vol. 171, No. 16

Forms of Symmetry
Julie J. Rehmeyer

Symmetry attracts us. Studies comparing people's reactions to different faces have shown, for example, that they find highly symmetrical faces more attractive than less symmetrical faces. The symmetry of faces is simple and bilateral, but other three-dimensional objects can be symmetric in complex ways, leading to different kinds of beauty.

Bathsheba Grossman, a sculptor in Santa Cruz, California, mines subtle forms of symmetry for inspiration. Her results are swirling and proportional. They may be simple or complex, but they always come together into a precise, intriguingly symmetrical pattern.

For the full article:

http://sciencenews.org/article.....thtrek.asp
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Sat Aug 18, 2007 2:02 pm    Post subject: Alien Pizza, Anyone? Reply with quote

Week of Aug. 18, 2007; Vol. 172, No. 7 , p. 107

Alien Pizza, Anyone?
Biochemistry may have taken a different turn on other worlds
Davide Castelvecchi

Everything was ready for the celebratory feast. Weeks earlier, the alien fleet had entered Earth's orbit and made radio contact, and now the visitors would receive their official welcome. Dozens of heads of state would greet humanity's guests during an official dinner at the White House.

For the full article:

http://sciencenews.org/articles/20070818/bob9.asp
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Sun Dec 16, 2007 8:47 am    Post subject: Determination of Enantiomeric Purity by 2H NMR Spectroscopy Reply with quote

Determination of Enantiomeric Purity by 2H NMR Spectroscopy
Mengping Zhu, Georgetown University
15 December 2007

Researchers at University of Leeds in United Kingdom reported a reliable method for determining enantiomeric purity by using 2H NMR spectroscopy.

Along with the increasing importance of asymmetric synthesis, developing more convenient, reliable methods for determination of enantiomeric purity are gaining growing interest. New methods based on NMR technique would be of paramount significance due to its near-ubiquitous availability. 13C isotopic labeling method was proven to be very efficient; however, requirement of prochiral carbon substituents limits its application. Luckily, 2H isotopic labeling, which is much more easily accessible, can take place of 13C for analysis of enantiomeric purity.

The 2H nucleus is NMR active with spin +1, and analysis can be performed on standard spectrometers by utilizing the deuterium lock channel as the observation channel, which could make this method available to most workers.

Deuteration on the methylene unit next to the chiral site is the first step of this strategy. If the target is an enantiomerically pure compound, 2H NMR could afford us a single signal; On the other hand, racemic mixture would show a second peak due to the enantiomeric counterpart. Quantitatively, those two signals have 1:1 ratio, which is consistent with racemic mixture. Ee values can be determined by calculating the integration of two peaks.

In order to assess the accuracy, comparison of HPLC vs 2H NMR for determination of enantiopurity of a series of sample ranging 0-90% ee was carried out. The results were pleasing. A good agreement between ee values measured by both techniques was found within a difference ±5%.

This method offers the potential to monitor reaction progress in situ and complements the existing methods for nonchromatographic determination of enantiomeric purity. In addition, used in conjunction with linked autosamplers, this would facilitate automated parallel screening programmes and the accumulation of real-time kinetic data.

Questions to explore further this topic:

What is 2H NMR?
http://chem.ch.huji.ac.il/nmr/.....ow1/h.html

What is enantiomeric purity?
http://en.wikipedia.org/wiki/Enantiopurity

What is asymmetric synthesis?
http://en.wikipedia.org/wiki/Asymmetric_synthesis

What is a lock channel?
http://www.umich.edu/~chemnmr/....._nmr_2.pdf

What is a racemic mixture?
http://en.wikipedia.org/wiki/Racemic

What is HPLC?
http://en.wikipedia.org/wiki/HPLC

What is ee?
http://en.wikipedia.org/wiki/Enantiomeric_excess

What is an autosampler?
http://www.labhut.com/products.....ht300l.php
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Thu Dec 20, 2007 9:34 pm    Post subject: Results promising for computational quantum chemical methods Reply with quote

Virginia Tech
20 December 2007

Results promising for computational quantum chemical methods for drug development
Blacksburg, Va. – New research, led by a Virginia Tech chemist, may someday help natural-products chemists decrease by years the amount of time it takes for the development of certain types of medicinal drugs. The research by T. Daniel Crawford, associate professor of chemistry, involves computations of optical rotation angles on chiral—non-superimposable—molecules. The research titled, The Current State of ‘Ab Initio’ Calculations of Optical Rotation and Electronic Circular Dichcoism Spectra, appeared recently as the cover article in The Journal of Physical Chemistry A.

Many chiral molecules are important for medical treatment for illnesses ranging from acid-reflux to cancer. The term “chiral” means that two mirror images of a molecule cannot be superimposed onto each other. In other words, some are “left-handed” and some are “right-handed.”

“Most drugs have this handedness property,” Crawford said, “and for many of these drugs, even though both hands can cause a reaction, it is a situation where one hand does a good thing and one does a bad thing.” He used thalidomide as an example. A mixture of both hands of the drug was used in the late 1950s and early 1960s to treat morning sickness in pregnant women. Later studies revealed that, while one of the two hands acted as the desired sedative, the other hand was found to cause significant birth defects. Thalidomide was never approved by the FDA in the United States and was eventually taken off the market in Europe.

For chemists, therefore, it is often vital to determine which hand of a molecule they are using. In other words, when you have a sample of a chiral molecule, how do you distinguish between the left and right hand"

This is where a technique called polarimetry comes in to play. By shooting plane-polarized light through a sample of one hand, the chiral molecule in question will rotate to a characteristic angle either clockwise or counterclockwise, and the two hands of a chiral molecule produce opposite rotations.

“So if we figure out the direction and rotation of the light or each hand, we have a frame of reference for determining whether we have the left or right hand of a molecule,” Crawford said.

The problem with this method is that synthesizing the two hands of chiral molecules is often extremely time consuming. “It can take anywhere from weeks to years,” Crawford said.

Crawford’s research applies the theory of quantum mechanics to devise computational methods in order to eliminate having to create a synthetic molecule. “The hope is that this will allow us to calculate things like optical rotation very accurately,” he said. “So when an organic chemist has a molecule and doesn’t know if it is left- or right-handed, we can calculate that directly on the computer.”

Crawford said the ultimate goal in his research is to be able to provide organic chemists with computational tools to determine the handedness of a particular molecule they are working with. He said that such tools could speed up the drug development process by years.
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Thu Jan 03, 2008 2:49 pm    Post subject: Diamond's Structural Secrets Revealed Reply with quote

Diamond's Structural Secrets Revealed
By Andrea Thompson, LiveScience Staff Writer

posted: 03 January 2008 01:38 pm ET

Sure, diamonds are shiny and sparkly, but their beauty may ultimately come from their unique crystal structure, one mathematician says.

Toshikazu Sunada, of Japan's Meiji University, conducted a mathematical analysis of the crystal structure of diamond and found that it has certain special properties, especially in its symmetry.

For the full article:

http://www.livescience.com/str.....cture.html
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Fri Jan 04, 2008 2:28 pm    Post subject: Strange-behaving crystals could have impact on research, tec Reply with quote

Kansas State University
3 January 2008

Strange-behaving crystals could have impact on research, technology

Says K-State chemist and co-author of article in Jan. 4 issue of Science
MANHATTAN, KAN. -- All of us break the rules from time to time -- even crystals.

"There are all sorts of rules about what crystals can do during phase transitions," said Mark D. Hollingsworth, associate professor of chemistry at Kansas State University. "For a long time, scientists have assumed that the norm applied for all sorts of substances.

But aperiodic materials -- those that lack a regularly repeating structure -- don't necessarily work like this, Hollingsworth said.

These aperiodic, rule-bending crystals are the focus of an article co-authored by Hollingsworth that appears in the Jan. 4 issue of the journal Science. Building on results from Hollingsworth's collaborator, French researcher Bertrand Toudic, Hollingsworth, Toudic and their co-authors looked at how these aperiodic crystals behave differently from "normal" periodic crystals. These differences could have implications not only for research but also for technology that relies on crystals, from computer displays to hard drives, Hollingsworth said.

For the research featured in the Science article, Hollingsworth and colleagues looked at crystals that form a host-guest structure. In this case, urea molecules formed tunnels around nonadecane molecules, making a honeycomb-like structure that takes the form of a double-helix -- the shape of DNA. In periodic host-guest crystals, Hollingsworth said the host molecules forming the tunnels and the guest molecules inside form a regularly repeating structure. But not so with the rule-breaking aperiodic crystals.

"Sometimes the host and guest fit nicely, sometimes they don't," Hollingsworth said. "This can have a huge effect on all sorts of properties. During crystal growth, for example, periodic and aperiodic host-guest crystals can behave very differently."

In aperiodic crystals, in which the host and guest structures don't match, the guest molecules protrude from the ends of the crystals, making the surface rough. This means it's easier to attach new molecules to the end of the crystal. Such crystals, including the ones featured in the Science article, are shaped like long needles.

But it really gets weird when the crystals undergo transitions from one phase to another.

"Bertrand and I have been talking about this for years, trying to find out what's going on in this system," Hollingsworth said. "The idea of studying these systems is to better understand how phase transitions work in aperiodic materials."

To find out what's going on in the phase transitions, the researchers observed the crystals at different temperatures above the phase transition, when the guest molecules are moving rapidly inside their tunnel-like hosts, and also at extremely cold temperatures as molecules are becoming frozen in place. To probe the crystals, the researchers scattered neutrons from them and measured different types of reflections. One class of reflections, called satellite reflections, measures the interaction between the guest and host molecules.

The researchers were surprised by what happened when the crystal was cooled to about -190 degrees Fahrenheit. The satellite reflections showed a change in the interaction between the host and guest structures but no noticeable changes in either the host or guest structures themselves.

"Previously, we thought these materials had homogenous phase transitions and that the normal rules concerning symmetry breaking applied to them," Hollingsworth said. "I don't think anyone would have predicted what happens in this phase transition."

Because these aperiodic materials don't play by the same rules, Hollingsworth said the impact on research is that scientists need to figure out what rules these aperiodic crystals are playing by in phase transitions. In addition to affecting research, these different rules also could have impacts on technology, he said. Crystals like the ones featured in the Science article are ferroelastic. That means that the molecules within the crystals reorient when the crystals are squeezed. The researchers can do this with a small anvil and observe the rotations of large domains in the crystals by viewing the crystal under a microscope. Closely related ferroelectric materials are important to technology because the domains within these materials can be reoriented with electric fields to allow or prohibit polarized light to pass through. This makes them useful in electronic displays.

"The question is whether these phases that we have observed will have unusual properties that are useful," he said.

As research on aperiodic crystals continues, Hollingsworth said that researchers expect this same unusual phase transition behavior in materials other than the urea-nonadecane crystals used in this study.
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Mon Jan 14, 2008 2:05 pm    Post subject: Solving the mystery of the metallic sheen of fish Reply with quote

Solving the mystery of the metallic sheen of fish
14 January 2008
Crystal Growth & Design

The bright, metallic sheen of fish skin — source of endless fascination for fishermen and aquarium owners — is due to a sophisticated system of crystals that enhance light reflection and may help fish hide from predators in the wild, scientists in Israel are reporting. Their study is scheduled for the current issue of ACS’ Crystal Growth & Design, a bi-monthly journal.

In the new study, Lia Addadi and colleagues note that researchers have known for years that guanine crystals in the skin underneath the scales of fish reflect light to produce a mirror-like sheen. This silvery reflectance acts as a form of camouflage that helps protect fish from predators as fish swim near the water’s surface. However, the exact shape of these guanine crystals and how they work remained a mystery.

The researchers extracted guanine crystals from the skin of the Japanese Koi fish and analyzed the crystals using X-ray diffraction and an electron microscope. They compared the results to guanine crystals made in the laboratory. The researchers found that the biogenic crystals develop in an unexpected direction that differs from the lab-made crystals and that their unique shape improves light reflectivity. The arrangement represents a “strategy evolved by fish to produce more efficient photonic crystals,” the article states. - MTS

ARTICLE #3 FOR IMMEDIATE RELEASE “Biogenic Guanine Crystals from the Skin of Fish May Be Designed to Enhance Light Reflectance”

DOWNLOAD PDF http://pubs.acs.org/cgi-bin/sa.....704753.pdf

DOWNLOAD HTML http://pubs.acs.org/cgi-bin/sa.....04753.html
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Mon May 05, 2008 1:07 pm    Post subject: Insights into symmetry Reply with quote

Insights into symmetry
By Julie Rehmeyer
May 4th, 2008
Abel Prize awarded for advances in group theory

Symmetrical snowflakeSnowflakes show nearly perfect six-fold rotational symmetry.Kenneth Libbrecht, www.snowflakes.comThe 2008 Abel Prize was awarded to John Griggs Thompson of the University of Florida and Jacques Tits of the Collège de France for their contributions to group theory, the mathematical field that analyzes symmetry. The Abel Prize is widely considered mathematics’ equivalent of the Nobel Prize.

For the full article:

http://sciencenews.org/view/ge.....o_symmetry
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic   printer-friendly view    USAP PAETE Forum Index -> Science Lessons Forum All times are GMT - 5 Hours
Page 1 of 1

 
Jump to:  
You can post new topics in this forum
You can reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group