November 28, 2007, 10:09 PM CT

Growth of CT scan use significant public health problem

Computed Tomography (CT) scans are an increasingly used X-ray-based tool for providing a three-dimensional view of a particular organ or tissue. The value of Computerized axial tomography scanning to diagnose injury, cancer and other health problems is undisputed. But are these scans being used too frequently, in some cases unnecessarily" What are the health consequences of having too a number of Computerized axial tomography scans over the course of a persons life".

In a Nov. 29, 2007 article in The New England Journal (NEJM), David J. Brenner, Ph.D., and Eric J. Hall, Ph.D., from the Center for Radiological Research at Columbia University Medical Center, argue that the potential carcinogenic effects from using Computerized axial tomography scans may be underestimated or overlooked. This is of particular concern, because perhaps one-third of all Computerized axial tomography scans performed in the United States may not be medically necessary, the radiation scientists say.

It is estimated that more than 62 million Computerized axial tomography scans per year are currently given in the United States, in comparison to three million 1980. Because Computerized axial tomography scans result in a far larger radiation exposure compared with conventional plain-film X-ray, this has resulted in a marked increase in the average personal radiation exposure in the United States, which has about doubled since 1980, largely because of the increased CT usage......... Posted by: Sean      Read more         Source

November 27, 2007, 10:46 PM CT

Climate change and life in the Southern Ocean

Bremerhaven, November 27, 2007. A ten-week expedition to the Lazarev Sea and the eastern part of the Weddell Sea opens this year's Antarctic research season of the German research vessel Polarstern. On the evening of November 28, just some two hours after an official ceremony at the Berlin Museum of Natural History honouring Polarstern's 25th anniversary of service, the research vessel will begin its 24th scientific voyage to the Southern Ocean from Cape Town. The 53 researchers from eight nations aboard Polarstern will focus much of their work on climate-related research as part of the International Polar Year. In addition, Polarstern will also supply the German Neumayer Station during the first leg of the trip, and accompany the freighter 'Naja Arctica' which will deliver construction materials for the new research station Neumayer III to the Antarctic. On February 4, 2008, Polarstern is expected to return to Cape Town.

"Our research projects will improve the understanding of physical and biological processes linked to the Antarctic Circumpolar Current and the Weddell Gyre, both of which play a key role for the earth's climate", explains chief scientist Prof Dr Ulrich Bathmann of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association, referring to the central goal of the expedition. Plankton algae from these two marine currents south of the Atlantic Ocean are absorbing significant amounts of the climate gas carbon dioxide through their growth during the summer. By sinking to the Antarctic deep sea, these algae are subsequently transferring the carbon dioxide to the seafloor, where, in some cases below 4000 meter water depth, they provide food for bottom dwelling organisms. "The efficiency of this biological pump is controlled, for example, by nutrients, by physical dynamics in the ocean surface layer, and by the species of algae involved", says Bathmann. "We have to investigate these complex interactions further, in order to optimise scientific climate predictions"......... Posted by: Tyler      Read more         Source

November 27, 2007, 10:44 PM CT

Where does stored nuclear waste go?

Millions of gallons of hazardous waste resulting from the nations nuclear weapons program lie in a remote location in southeastern Washington state called Hanford. Beneath this desert landscape about two million curies of radioactivity and hundreds of thousands of tons of chemicals are captured within the stratified vadose zone below which gives rise to complex subsurface flow paths. These paths create uncertainties about where the contaminants go and what happens to them. With the mighty Columbia River bordering much of the site, where these nuclear wastes migrate, their composition and how fast they are traveling are of vital importance to both people and the environment.

The recent issue of Vadose Zone Journal features a series of papers addressing the mysteries within the vadose zone beneath Hanford. The series outlines scientific work funded by the Department of Energy and carried out by researchers at Pacific Northwest National Laboratory and contributing associates with other national laboratories, universities and contractors.

The detailed series outlines how scientists have investigated Hanfords vadose zone to better understand the migration of these contaminants, ultimately reducing or stemming their flow toward the Columbia River, thereby protecting the river and the people living downstream. By studying the geologic, biologic, geochemical and hydrologic conditions at the Hanford site, the scientists seek to understand and manipulate the factors that control contaminants fate and transport......... Posted by: Tyler      Read more         Source

November 27, 2007, 10:21 PM CT

Nanowires may be practical oscillators

Nanowires grown at the National Institute of Standards and Technology (NIST) have a mechanical quality factor at least 10 times higher than reported values for other nanoscale devices such as carbon nanotubes, and comparable to that of commercial quartz crystals. Because a high Q factor indicates a capacity for stable vibrations, the nanowires might be used as oscillators in nano-electromechanical systems for future nano-sensors and communications devices.

We think the most interesting thing about these wires is the very high quality factor observed for such a small object, says NIST researcher and co-author Kris Bertness, who grew the nanowires.

NIST has developed a unique way of growing hexagonal gallium nitride (GaN) nanowires featuring low defect density and high luminescence intensity. In a new paper*, scientists at NIST and the University of Colorado at Boulder report high Q factors in wires that are 30 to 500 nanometers in diameter and 5 to 20 micrometers long, vibrating between 400,000 and 2.8 million times per second. (For comparison, the quartz crystals used in watches commonly vibrate about 32,000 times a second.) The nanowires vibrated when placed on a piezoelectric device stimulated by an electrical signal. The nanowires also oscillated when excited directly by an electron beam, apparently due to the GaN materials intrinsic piezoelectric ability to covert voltage to mechanical force......... Posted by: Kevin      Read more         Source

November 27, 2007, 10:10 PM CT

Thermoelectric materials are one key to energy savings

Breathing new life into an old idea, MIT Institute Professor Mildred S. Dresselhaus and co-workers are in the process of developing innovative materials for controlling temperatures that could lead to substantial energy savings by allowing more efficient car engines, photovoltaic cells and electronic devices.

Novel thermoelectric materials have already resulted in a new consumer product: a simple, efficient way of cooling car seats in hot climates. The devices, similar to the more-familiar car seat heaters, provide comfort directly to the individual rather than cooling the entire car, saving on air-conditioning and energy costs.

The research is based on the principle of thermoelectric cooling and heating, which was first discovered in the early 19th century and was advanced into some practical applications in the 1960s by MIT professor (and former president) Paul Gray, among others.

Dresselhaus and his colleagues are now applying nanotechnology and other cutting-edge technologies to the field. She'll describe her work toward better thermoelectric materials in an invited talk on Monday, Nov. 26 at the annual meeting of the Materials Research Society in Boston.

Thermoelectric devices are based on the fact that when certain materials are heated, they generate a significant electrical voltage. On the other hand, when a voltage is applied to them, they become hotter on one side, and colder on the other. The process works with a variety of materials, and particularly well with semiconductors -- the materials from which computer chips are made. But it always had one big drawback: it is very inefficient......... Posted by: Kevin      Read more         Source

November 26, 2007, 9:47 PM CT

Single main migration across Bering Strait

Did a relatively small number of people from Siberia who trekked across a Bering Strait land bridge some 12,000 years ago give rise to the native peoples of North and South America?.

Or did the ancestors of todays native peoples come from other parts of Asia or Polynesia, arriving multiple times at several places on the two continents, by sea as well as by land, in successive migrations that began as early as 30,000 years ago?.

The questions featured on magazine covers and TV specials have agitated anthropologists, archaeologists and others for decades.

University of Michigan scientists, working with an international team of geneticists and anthropologists, have produced new genetic evidence thats likely to hearten proponents of the land bridge theory. The study, published online in PLoS Genetics, is one of the most comprehensive analyses so far among efforts to use genetic data to shed light on the topic.

The scientists examined genetic variation at 678 key locations or markers in the DNA of present-day members of 29 Native American populations across North, Central and South America. They also analyzed data from two Siberian groups. The analysis shows:

o genetic diversity, as well as genetic similarity to the Siberian groups, decreases the farther a native population is from the Bering Strait adding to existing archaeological and genetic evidence that the ancestors of native North and South Americans came by the northwest route......... Posted by: William      Read more         Source

November 21, 2007, 5:09 AM CT

Digging biblical history, or the end of the world

Some come to dig the Tel Aviv University-directed archeological site at Tel Megiddo because they are enchanted by ancient stories of King Solomon. Others come because they believe in a New Testament prophecy that the mound of dirt will be the location of a future Judgment Day apocalyptic battle. Hence the second, rather more chilling name for the site: "Armageddon".

Tel Megiddo has been the subject of many decisive battles in ancient times (among the Egyptian, Hebrew and Assyrian peoples) and today it holds a venerated place in archaeology, explains site co-director and world-renowned archeologist Prof. Israel Finkelstein.

Says Prof. Finkelstein, from the Department of Archaeology and Ancient Near Eastern Cultures at Tel Aviv University, "Megiddo is one of the most interesting sites in the world for the excavation of biblical remains. Now volunteers and students from around the world can participate in the dig which lets them uncover 3,000 years worth of history -- from the late 4th millennium B.C.E. to the middle of the first millennium C.E."

Prof. Finkelstein, who belongs to the Sonia and Marco Nadler Institute of Archaeology at Tel Aviv University, has been co-directing the site with Prof. David Ussishkin, also of Tel Aviv University, since 1994......... Posted by: William      Read more         Source

November 21, 2007, 4:57 AM CT

Secrets in rare cartography

Whales were the economic drivers of the 1850s. So important was this resource that the founder of the U.S. Oceanographic Office, Matthew Fontaine Maury, created a map showing the worldwide distribution of sperm and right whales in 1851.

Whale oil then was like petroleum is today, says Christopher Baruth. This is a graphic device that showed where the whales were located by type and season.

Baruth is curator of the American Geographical Society (AGS) Library, where a copy of the whale map is one of thousands of rare cartographical materials and geographical photographs.

Quietly housed at the University of Wisconsin-Milwaukee (UWM) since 1978, the AGS Library contains more than a million items, half of which are maps and charts, some dating to 15th century, and some that arent available anywhere else, even at the Library of Congress.

The value of the items in the AGS collections is compounded by their connection to the society. AGS is the oldest national geographical society in the United States, founded in 1851 in New York City.

Explorer-members, such as Charles Lindbergh, Robert Peary and Theodore Roosevelt, are among those who donated items linked to their exploits to the society over the years. Materials in the collection have been consulted not only by scholars, but also by the U.S. government during and at the end of both world wars. Today, it attracts scholars from as far away as Uzbekistan......... Posted by: Kevin      Read more         Source

November 21, 2007, 4:50 AM CT

Surface Orbital "Roughness" in Manganites

Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have shown that in a class of materials called manganites, the electronic behavior at the surface is considerably different from that found in the bulk. Their findings, which were published online in the November 18, 2007, issue of Nature Materials, could have implications for the next generation of electronic devices, which will involve increasingly smaller components.

As devices shrink, the proportion of surface area grows compared to the material's volume. Therefore, it's important to understand the characteristics of a material's surface in order to predict how those materials behave and how electrons will travel across an interface, said Brookhaven physicist John Hill.

Hill and his fellow scientists were especially interested in how the outer electrons of atoms in a so-called manganite material are arranged. Manganites - consisting of a rare-earth element such as lanthanum combined with manganese and oxygen - show a huge change in electrical resistance when a magnetic field is applied. Taking advantage of this "colossal magnetoresistance effect" could be the key to developing advanced magnetic memory devices, magnetic field sensors, or transistors.

The research team, which also includes researchers from KEK (Japan), CNRS (France), Ames Laboratory, and Argonne National Laboratory, used x-ray scattering at Brookhaven's National Synchrotron Light Source and Argonne's Advanced Photon Source to study the orbital order - the arrangement of electrons in the outermost shell - of the material at the surface and in its bulk......... Posted by: Kevin      Read more         Source

November 19, 2007, 8:43 PM CT

The Earliest Chocolate Drink Of The New World

The earliest known use of cacao--the source of our modern day chocolate--has been pushed back more than 500 years, to somewhere between 1400 and 1100 B.C.E., thanks to new chemical analyses of residues extracted from pottery excavated at an archaeological site at Puerto Escondido in Honduras. The new evidence also indicates that, long before the flavor of the cacao seed (or bean) became popular, it was the sweet pulp of the chocolate fruit, used in making a fermented (5% alcohol) beverage, which first drew attention to the plant in the Americas.

That cacao's popularity on the world stage began with its role in an alcoholic beverage does not surprise archaeochemist Dr. Patrick McGovern, Senior Research Scientist, Museum Applied Science Center for Archaeology (MASCA) at the University of Pennsylvania Museum of Archaeology and Anthropology and one of five authors of the scientific research article on the discovery ("Chemical and archaeological evidence for the earliest cacao beverages," by John S. Henderson, Rosemary A. Joyce, Gretchen R. Hall, W. Jeffrey Hurst, and Patrick E. McGovern) would be published on-line in Early Edition the week of Nov. 12 http://www.pnas.org/ and in the November 27, 2007 print issue of PNAS USA (pp. 18937-18940, Issue 48, Volume 104).

"This development probably provided the impetus to domesticate the chocolate tree and only later, to prepare a beverage based on the more bitter beans," suggested Dr. McGovern. "An alcoholic beverage from the pulp, carrying on this ancient tradition, continues to be made in parts of Latin America"......... Posted by: William      Read more         Source