SALT LAKE CITY – More than 150 years after a small Eurasian tree named tamarisk or saltcedar started taking over river banks throughout the U.S. Southwest, saltcedar leaf beetles were unleashed to defoliate the exotic invader.

Now, University of Utah scientists say their new study shows it is feasible to use satellite data to monitor the extent of the beetle’s attack on tamarisk, and whether use of the beetles may backfire with unintended environmental consequences.

“We don’t have any idea of the long-term impacts of using the beetles; their release may have unexpected repercussions,” says Philip Dennison, an assistant professor of geography and first author of the study scheduled for online publication later this month in the journal Remote Sensing of Environment.

“The impact of this defoliation is largely unknown,” says study co-author Kevin Hultine, a research assistant professor of biology at the University of Utah. “The net impact of controlling tamarisk could be positive or negative.”

“We would like on-the-ground scientists and managers to understand and think about the long-term impact – what are these riparian [riverbank] areas going to look like 15 years from now, and how can we can maintain ecosystems” as well as water flows for farms, cities and river recreation, Hultine says.

Dennison and Hultine conducted the study with Jim Ehleringer, a distinguished professor of biology at the University of Utah; physical scientist Pamela Nagler, of the U.S. Geological Survey in Tucson, Ariz.; and Edward Glenn, a University of Arizona environmental scientist.

A Shady Invader from Eurasia

Anyone who has rafted Southwestern rivers like the Green and Colorado knows about the shady thickets of tamarisk that line the riverbanks. The trees can grow up to 30 feet tall. There are about 10 species of tamarisk.

This 2007 infrared image from the ASTER instrument on NASA’s Terra satellite shows the effects of saltcedar leaf beetles that were released to defoliate tamarisk. An alfalfa field along the Colorado River remains vegetated and thus is bright red. But the wet “bottom” area along the Dolores River (lower right) appears much darker than in the 2006 image because the beetles have eaten tamarisk leaves. Remaining areas of bright red within the “bottom” area are due to willow and cottonwood trees. University of Utah researchers propose using satellites to monitor tamarisk defoliation by beetles in remote areas of the Southwest.

Credit: Phil Dennison, University of Utah, from NASA data.

The U.S. Animal and Plant Health Inspection Service (APHIS) says saltcedar or tamarisk is “a highly invasive, exotic weed” in the form of “a large shrub or small tree that was introduced to North America from Asia in the early 1800s. The plant has been used for windbreaks, ornamentals, and erosion control. By 1850, saltcedar had infested river systems and drainages in the Southwest, often displacing native vegetation.”

“By 1938, infestations were found from Florida to California and as far north as Idaho,” according to APHIS. “Saltcedar continues to spread rapidly and currently infests water drainages and areas throughout the United States.”

Tamarisk dominates riverbank habitats, limiting camping areas for river runners, reducing diversity and providing poor habitat for some species of wildlife. Tamarisk also raises the risk of fires that destroy cottonwoods and other native plants but not tamarisk, which re-sprouts from roots. And tamarisk forms a dense canopy, also helping wipe out competing plants. Finally, tamarisk has a bad rap as a water-sucking wastrel that dries springs, lowers water tables and reduces stream flows, even impairing boating.

Dennison and Hultine say recent research indicates tamarisk’s thirst is overstated.

“Some of the earliest research on tamarisk water use suggested tamarisk uses dramatically more water than other tree species,” Hultine says. “So a lot of estimates on water loss over entire river reaches are based on information that now has been discredited in the scientific literature.”

Hultine believes that unless aggressive programs to restore defoliated areas are implemented, tamarisk will be replaced by other invaders – Russian knapweed, Russian olive and pepperweed – that may use more water than tamarisk. Eradicating tamarisk with beetles also may reduce bird habitat, he adds.

Monitoring the Attack of the Tamarisk-Munching Beetles

The saltcedar leaf beetle, Diorhabda elongata, was brought to the U.S. from Kazakhstan. After an environmental assessment, APHIS approved them for tamarisk control.

Dennison says thousands of the beetles first were released in Utah during summer 2004, then again in summer 2005 and 2006 at locations along the Colorado River near Moab. Widespread defoliation of tamarisk in the area was noted during summer 2007.

Because long stretches of rivers in the Colorado River Basin are remote, Dennison and colleagues decided to test the feasibility of using satellite images to detect tamarisk leaf loss due to the spread of the saltcedar leaf beetles.

This 2006 infrared image of the confluence of the Colorado and Dolores rivers in Utah was taken by the ASTER instrument on NASA’s Terra satellite. The Colorado flows from north to south and the Dolores enters the image from the east. Vegetation appears bright red, including an alfalfa field along the Colorado and a wet “bottom” area along the Dolores that has extensive tamarisk, an invasive tree from Eurasia.

Credit: Phil Dennison, University of Utah, from NASA data.

They mapped 56 accessible areas already defoliated by tamarisk, and studied if the defoliation could be detected using two instruments on Terra, one of the National Aeronautics and Space Administration’s Earth-observing satellites.

Both instruments make images using red and near-infrared light. Plant pigments absorb red from sunlight and reflect near-infrared. In near-infrared images, tamarisk-covered areas appear red. Defoliated areas appear brown or black because there are no leaves to absorb red light and reflect near-infrared light. The two instruments are:

• ASTER, the Advanced Spaceborne Thermal Emission and Reflection Radiometer, obtains relatively high-resolution images, with each pixel covering an area about 50 feet long by 50 feet wide. It can detect big changes like tamarisk defoliation on an even smaller scale. It only obtains one to three images of a given area every summer.
• MODIS, the Moderate Resolution Imaging Spectroradiometer, which can detect less detail – a pixel measures about 820 feet by 820 feet. But it can see where large swaths of tamarisk have been defoliated, Dennison says. MODIS makes daily images.

Dennison says the infrequent, higher-resolution ASTER images allow researchers to map defoliated areas, while the frequent, lower-resolution MODIS images help them detect changes in vegetation over time.

The area studied included four sites along the Colorado River northeast of Moab, and a fifth site along the tributary Dolores River at the Entrada Field Station operated by the University of Utah for education and research. The five sites covered 589 acres, and within them, researchers mapped 56 polygon-shaped areas totaling 57 acres where tamarisk had been defoliated by the beetles.

ASTER measured what is known as NVDI – the normalized difference vegetation index, which is the difference between red light absorbed by plants and near-infrared light reflected by them. The index is high when plants are present, low when they are absent.

Those satellite measurements showed minor changes in vegetation at the test sites from 2005 to 2006, but a large change between 2006 and 2007 – indicating extensive defoliation of tamarisk, even though the defoliated plants regrow within about six weeks.

The satellite’s MODIS instrument used another vegetation index that also revealed widespread tamarisk defoliation at the five sites in July 2007.

While some tamarisk has died in Nevada where the beetles first were established, “we don’t understand whether repeated defoliation eventually will kill most of the trees, or will they reach some point where they’ll just have less leaf area over the entire year,” Hultine says.

The researchers also used the satellite to estimate “evapotranspiration” – the evaporation of water from soil and the transpiration or use of water by plants – to learn more about how defoliation of tamarisk affects water use. For comparison, Hultine measured sap flow through trees, which reflects how much water is used by the trees.

Satellite estimates of tamarisk water use declined modestly as the plants were defoliated, Dennison says. The findings also were consistent with earlier research indicating tamarisk is less of a water hog than previously thought.

Dennison says he and his colleagues did the study to test the feasibility of using satellites to monitor tamarisk defoliation on an ongoing basis. That, he says, could be done by federal agencies such as the Bureau of Land Management, Bureau of Reclamation and U.S. Geological Survey.

Source: University of Utah

If plants could speak they will boast about being part of remedies such as the common aspirin to a leukaemia drug derived from the rosy periwinkle. Over a quarter of western medicines contain plant toxins some deriving from tropical forest species. Forest plants have been the source of the most effective drugs in the history of pharmacology but only two per cent have been screened for their pharmaceutical potential.

The Social Life of Plants, a one day event, as part of the Economic and Social Research Council’s Festival of Social Science (6th to 15th March), will reveal the links between humans and plants. Hands-on activities like basket weaving, growing your own herb garden, exhibitions and films will give members of the public the chance to rediscover the fundamentals of a plant life. Anthropologists and Ethnobotanists will explore how plants affect the lives of individuals around the world, in medicine, food, materials and rituals.

As well as bringing people and plants together, the many entertaining and informative films on show will look at the fascinating and often overlooked facts on plants. One such film, Seeds of Plenty, Seeds of Sorrow, will show the more problematic side of the green revolution and the damage it has done to the social structure and ecologies of developing countries.

Practitioners and researchers of the event hope that the social life of plants will be an inspiration for people of all ages and create a sense of excitement about plants and their place in our lives. We tend to forget the use plants in our everyday life, from our daily hot drink, the colour of the jumper we wear, ingredients in our food to the medicine we take.

2009 is a big year for botany with the 200th anniversary of Charles Darwin’s birth. Darwin’s observations so many years ago contributed to the groundbreaking understanding of plant biodiversity. This event also compliments, the Royal Anthropological Institute’s educational outreach programme, where 14-19 year old, deal with above issues as part of the national curriculum.

Source: Economic & Social Research Council

J.K. Rowling may not have realized just how close Harry Potter’s invisibility cloak was to becoming a reality when she introduced it in the first book of her best-selling fictional series in 1998. Scientists, however, have made huge strides in the past few years in the rapidly developing field of cloaking. Ranked the number five breakthrough of the year by Science magazine in 2006, cloaking involves making an object invisible or undetectable to electromagnetic waves.

A paper published in the March 2009 issue of SIAM Review, “Cloaking Devices, Electromagnetic Wormholes, and Transformation Optics,” presents an overview of the theoretical developments in cloaking from a mathematical perspective. One method involves light waves bending around a region or object and emerging on the other side as if the waves had passed through empty space, creating an “invisible” region which is cloaked. For this to happen, however, the object or region has to be concealed using a cloaking device, which must be undetectable to electromagnetic waves. Manmade devices called metamaterials use structures having cellular architectures designed to create combinations of material parameters not available in nature.

Mathematics is essential in designing the parameters needed to create metamaterials and to show that the material ensures invisibility. The mathematics comes primarily from the field of partial differential equations, in particular from the study of equations for electromagnetic waves described by the Scottish mathematician and physicist James Maxwell in the 1860s.

One of the “wrinkles” in the mathematical model of cloaking is that the transformations that define the required material parameters have singularities, that is, points at which the transformations fail to exist or fail to have properties such as smoothness or boundness that are required to demonstrate cloaking. However, the singularities are removable; that is, the transformations can be redefined over the singularities to obtain the desired results. The authors of the paper describe this as “blowing up a point.” They also show that if there are singularities along a line segment, it is possible to “blow up a line segment” to generate a “wormhole.” (This is a design for an optical device inspired by, but distinct from the notion of a wormhole appearing in the field of gravitational physics.) The cloaking version of a wormhole allows for an invisible tunnel between two points in space through which electromagnetic waves can be transmitted.

Some possible applications for cloaking via electromagnetic wormholes include the creation of invisible fiber optic cables, for example for security devices, and scopes for MRI-assisted medical procedures for which metal tools would otherwise interfere with the magnetic resonance images. The invisible optical fibers could even make three-dimensional television screens possible in the distant future. The effectiveness and implementation of cloaking devices in practice, however, are dependent on future developments in the design, investigation, and production of metamaterials. The “muggle” world will have to wait on further scientific research before Harry Potter’s invisibility cloak can become a reality.

Source: Society for Industrial and Applied Mathematics

The water levels in the Dead Sea – the deepest point on Earth – are dropping at an alarming rate with serious environmental consequences, according to Shahrazad Abu Ghazleh and colleagues from the University of Technology in Darmstadt, Germany. The projected Dead Sea-Red Sea or Mediterranean-Dead Sea Channels therefore need a significant carrying capacity to re-fill the Dead Sea to its former level, in order to sustainably generate electricity and produce freshwater by desalinization. The study (1), published online this week in Springer’s journal, Naturwissenschaften, also shows that the drop in water levels is not the result of climate change; rather it is due to ever-increasing human water consumption in the area.

Normally, the water levels of closed lakes such as the Dead Sea reflect climatic conditions – they are the result of the balance between water running into the lake from the tributary area and direct precipita-tion, minus water evaporation. In the case of the Dead Sea, the change in water level is due to intensive human water consumption from the Jordan and Yarmouk Rivers for irrigation, as well as the use of Dead Sea water for the potash industry by both Israel and Jordan. Over the last 30 years, this water consumption has caused an accelerated decrease in water level (0.7 m/a), volume (0.47 km³/a) and surface area (4 km² /a), according to this study.

Abu Ghazleh and colleagues developed a model of the surface area and water volume of the Dead Sea and found that the lake has lost 14 km3 of water in the last 30 years. The receding water has left leveled sections on the lake’s sides – erosional terraces – which the authors recorded precisely for the first time using Differential Global Positioning System (DGPS) field surveys. They were able to date the terraces to specific years.

The authors point out that this rapid drop in the level of the Dead Sea has a number of detrimental con-sequences, including higher pumping costs for the factories using the Dead Sea to extract potash, salt and magnesium; an accelerated outflow of fresh water from surrounding underground water aquifers; receding shorelines making it difficult for tourists to access the water for medicinal purposes; and the creation of a treacherous landscape of sinkholes and mud as a result of the dissolution of buried salt which causes severe damage to roads and civil engineering structures.

To address the mounting stress on water resources in the Dead Sea basin and the environmental ha-zards caused by its lowering, the authors suggest that the diversion of Jordan water to the Mediterra-nean coast could be replaced by desalinization of seawater, causing the recession of the Dead Sea to be considerably slowed, and buying time to consider the long-term alternatives such as the Red Sea-Dead Sea Channel or the Mediterranean-Dead Sea Channel.

The authors conclude that either of these channels will require a carrying capacity of more than 0.9 km3 per year to slowly fill the lake back to its levels of 30 years ago and to ensure its long-term sustai-nability for energy production and desalinization to fresh water. Such a channel will also maintain tour-ism and potash industry on both sides of the Dead Sea.

Source: Springer

CAMBRIDGE, Mass.–MIT engineers are using carbon nanotubes only billionths of a meter thick to stitch together aerospace materials in work that could make airplane skins and other products some 10 times stronger at a nominal increase in cost.

Moreover, advanced composites reinforced with nanotubes are also more than one million times more electrically conductive than their counterparts without nanotubes, meaning aircraft built with such materials would have greater protection against damage from lightning, said Brian L. Wardle, the Charles Stark Draper Assistant Professor in the Department of Aeronautics and Astronautics.

Wardle is lead author of a theoretical paper on the new nanotube-reinforced composites that will appear in the Journal of Composite Materials (http://jcm.sagepub.com/). He also described the work as keynote speaker at a Society of Plastics Engineers conference this week.

The advanced materials currently used for many aerospace applications are composed of layers, or plies, of carbon fibers that in turn are held together with a polymer glue. But that glue can crack and otherwise result in the carbon-fiber plies coming apart. As a result, engineers have explored a variety of ways to reinforce the interface between the layers by stitching, braiding, weaving or pinning them together.

All of these processes, however, are problematic because the relatively large stitches or pins penetrate and damage the carbon-fiber plies themselves. “And those fiber plies are what make composites so strong,” Wardle said.

So Wardle wondered whether it would make sense to reinforce the plies in advanced composites with nanotubes aligned perpendicular to the carbon-fiber plies. Using computer models of how such a material would fracture, “we convinced ourselves that reinforcing with nanotubes should work far better than all other approaches,” Wardle said. His team went on to develop processing techniques for creating the nanotubes and for incorporating them into existing aerospace composites, work that was published last year in two separate journals.

How does nanostitching work? The polymer glue between two carbon-fiber layers is heated, becoming more liquid-like. Billions of nanotubes positioned perpendicular to each carbon-fiber layer are then sucked up into the glue on both sides of each layer. Because the nanotubes are 1000 times smaller than the carbon fibers, they don’t detrimentally affect the much larger carbon fibers, but instead fill the spaces around them, stitching the layers together.

“So we’re putting the strongest fibers known to humankind [the nanotubes] in the place where the composite is weakest, and where they’re needed most,” Wardle said. He noted that these dramatic improvements can be achieved with nanotubes comprising less than one percent of the mass of the overall composite. In addition, he said, the nanotubes should add only a few percent to the cost of the composite, “while providing substantial improvements in bulk multifunctional properties.”

Source: Massachusetts Institute of Technology

Super-thin films of carbon with exotic properties, now taking the scientific world by storm, may soon mean a new era of brighter, faster, and smaller computers, smart phones, and other consumer electronics. Brighter digital displays that flex like a sheet of paper. Faster computer chips. Smaller computers. That’s the word from an article scheduled for the March 2 issue of Chemical & Engineering News, ACS’ weekly newsmagazine.

In the magazine’s cover story, C&EN Senior Editor Mitch Jacoby notes that these so-called graphene sheets —50,000 times thinner than the width a single human hair — were first isolated by researchers just a few years ago. The nano-size sheets perform better than life-size carbon, with higher strength and the ability to conduct electricity faster. These properties make them attractive for developing new and improved electronic devices, the article notes.

Scientists in academia and industry have stepped up their efforts to improve the performance and manufacture of graphene sheets. At least one company plans to produce the sheets on an industrial scale in ton quantities. Scientists had predicted the existence of these unusual carbon sheets just a few years ago but had not produced actual thin-films until recently. “Graphene is one of the hottest topics in materials science these days,” says one authority in the C&EN article.

Source: American Chemical Society

Scientists in Germany are reporting development of a new, more effective method to determine whether milk marketed as “organic” is genuine or just ordinary milk mislabeled to hoodwink consumers. Their report appears in the current edition of ACS’ Journal of Agricultural and Food Chemistry, a bi-weekly publication.

In the study, Joachim Molkentin and colleagues point out that organic milk has soared in popularity in many countries. Sales in Germany, for instance, rose by almost one-third between 2006 and 2007. Consequently, crooks may take advantage of the situation by marketing increasing quantities of fake organic milk. That situation created a need for better tests to detect the fraud.

To address the issue, the scientists developed a test based on an analysis of milk fat for the ratio of stable isotopes of carbon. They used it to identify milk samples from cows raised on feed containing a higher ration of maize. Such a feeding regimen is typical of conventional milk production. Organically raised cows are fed less maize but more pasture feed. In addition, the team identified a significant difference in the alpha-linolenic acid content of milk fat between organic and conventional milk samples. Organic milk typically has a higher alpha-linolenic acid content than conventional milk. -MB

Source: Federal Research Institute of Nutrition and Food, American Chemical Society.

Two food additives with previously unrecognized estrogen-like effects in two food additives Chemical Research in Toxicology

Scientists in Italy are reporting development and successful use of a fast new method to identify food additives that act as so-called “xenoestrogens” — substances with estrogen-like effects that are stirring international health concerns. They used the method in a large-scale screening of additives that discovered two additives with previously unrecognized xenoestrogen effects. Their report appears in the current edition of ACS’ Chemical Research in Toxicology, a monthly journal.

In the study, Pietro Cozzini and colleagues cite increasing concern about identifying these substances and about the possible health effects. Synthetic chemicals that mimic natural estrogens (called “xenoestrogens,” literally, “foreign estrogens”) have been linked to a range of human health effects. They range from reduced sperm counts in men to an increased risk of breast cancer in women.

The scientists used the new method to search a food additive database of 1,500 substances, and verified that the method could identify xenoestrogens. In the course of that work, they identified two previous unrecognized xenoestrogens. One was propyl gallate, a preservative used to prevent fats and oils from spoiling. The other was 4-hexylresorcinol, used to prevent discoloration in shrimp and other shellfish. “Some caution should be issued for the use of propyl gallate and 4-hexylresocrinol as food additives,” they recommend in the study. -MB

Source: University of Parma, Parma, Italy, American Chemical Society.

Credit: ESO/L. Calçada

“With lots of methane in the atmosphere, it becomes clear why Pluto’s atmosphere is so warm,” says Emmanuel Lellouch, lead author of the paper reporting the results.

Pluto, which is about a fifth the size of Earth, is composed primarily of rock and ice. As it is about 40 times further from the Sun than the Earth on average, it is a very cold world with a surface temperature of about minus 220 degrees Celsius!

It has been known since the 1980s that Pluto also has a tenuous atmosphere [1], which consists of a thin envelope of mostly nitrogen, with traces of methane and probably carbon monoxide. As Pluto moves away from the Sun, during its 248 year-long orbit, its atmosphere gradually freezes and falls to the ground. In periods when it is closer to the Sun — as it is now — the temperature of Pluto’s solid surface increases, causing the ice to sublimate into gas.

Until recently, only the upper parts of the atmosphere of Pluto could be studied. By observing stellar occultations (ESO 21/02), a phenomenon that occurs when a Solar System body blocks the light from a background star, astronomers were able to demonstrate that Pluto’s upper atmosphere was some 50 degrees warmer than the surface, or minus 170 degrees Celsius. These observations couldn’t shed any light on the atmospheric temperature and pressure near Pluto’s surface. But unique, new observations made with the CRyogenic InfraRed Echelle Spectrograph (CRIRES), attached to ESO’s Very Large Telescope, have now revealed that the atmosphere as a whole, not just the upper atmosphere, has a mean temperature of minus 180 degrees Celsius, and so it is indeed “much hotter” than the surface.

In contrast to the Earth’s atmosphere [2], most, if not all, of Pluto’s atmosphere is thus undergoing a temperature inversion: the temperature is higher, the higher in the atmosphere you look. The change is about 3 to 15 degrees per kilometre. On Earth, under normal circumstances, the temperature decreases through the atmosphere by about 6 degrees per kilometre.

“It is fascinating to think that with CRIRES we are able to precisely measure traces of a gas in an atmosphere 100 000 times more tenuous than the Earth’s, on an object five times smaller than our planet and located at the edge of the Solar System,” says co-author Hans-Ulrich Käufl. “The combination of CRIRES and the VLT is almost like having an advanced atmospheric research satellite orbiting Pluto.”

The reason why Pluto’s surface is so cold is linked to the existence of Pluto’s atmosphere, and is due to the sublimation of the surface ice; much like sweat cools the body as it evaporates from the surface of the skin, this sublimation has a cooling effect on the surface of Pluto. In this respect, Pluto shares some properties with comets, whose coma and tails arise from sublimating ice as they approach the Sun.

The CRIRES observations also indicate that methane is the second most common gas in Pluto’s atmosphere, representing half a percent of the molecules. “We were able to show that these quantities of methane play a crucial role in the heating processes in the atmosphere and can explain the elevated atmospheric temperature,” says Lellouch.

Two different models can explain the properties of Pluto’s atmosphere. In the first, the astronomers assume that Pluto’s surface is covered with a thin layer of methane, which will inhibit the sublimation of the nitrogen frost. The second scenario invokes the existence of pure methane patches on the surface.

“Discriminating between the two will require further study of Pluto as it moves away from the Sun,” says Lellouch. “And of course, NASA’s New Horizons space probe will also provide us with more clues when it reaches the dwarf planet in 2015.”

Source: ESO

The anthropology world is all abuzz with a discovery in Africa that’s knocking scientists off their feet.

It’s the finding of 1.5 million-year-old fossilized human footprints in Kenya at Rutgers University’s Koobi Fora Field School.

Researchers say the ancient footprints show that some of the earliest humans walked just like we do today and also had anatomically modern feet.

The area around the human footprints was also littered with a range of animal prints, all discovered within two 1.5 million-year-old sedimentary layers near Ileret in northern Kenya.

Three footprint trails were found in the upper sediment layer. Two of them had two prints each, while the other had seven prints and numerous isolated prints. Perfectly preserved 15 feet below were one trail of two prints and a single isolated smaller print, possibly that of a child.

The discovery is detailed in this month’s issue of the journal Science.

What makes these footprints decidely human? Researchers say the big toe is parallel to the other toes, whereas in apes, it is separated for better grasping in the trees. What’s more, the footprints show a human-like arch and short toes, typically associated with walking upright. Other clues found to be within the range of modern humans were the size, spacing and depth of the impressions which provided estimates of weight, stride and gait.

The authors say the size of the footprints and their modern anatomical characteristics point to the hominid Homo ergaster, the name by which early Homo erectus is more generally known. This was the first hominid to have had the same body proportions (longer legs and shorter arms) as modern Homo sapiens. Other H. ergaster or H. erectus remains have been found in Tanzania, Ethiopia, Kenya and South Africa, at dates consistent with the Ileret footprints.