Science in Society: News Items

A Tall, Cool Drink of..Sewage? (News Item)

Science in Society — 2008-08-13T05:00:00Z

In response to the increasing demand (and shortage) of water, Orange County recently opened a new groundwater replenishment system that will funnel treated wastewater into the general supply. While the idea of drinking what essentially used to be sewage is alarming, the "recycled" water is filtered to the point that it is cleaner than rain. After these treatments, it is channeled into a lake water reservoir where it remains for at least six months, filtering again naturally through sand and gravel.

Scientists and the general population differ in their opinion about using treated wastewater for drinking. Some see it as a smart solution to a growing problem, especially in our increasingly eco-conscious society. Others are worried about risks to the public health, or are just plain squeamish about the water's origins. When thinking about the general "ick" factor, though, consider this-- following treatment at the plant, the "recycled" water tested more pure than a popular brand of bottled water.

A Dead Zone in the Gulf of Mexico (News Item)

Science in Society — 2008-08-04T22:14:18Z

Imagine an area the size of Massachusetts in the Gulf of Mexico that is completely devoid of marine life. This so-called "dead zone" develops each spring, driven by fertilizer runoff from the Mississippi river basin that empties into the Gulf. Given that ~50% of the nation's farmland empties into the Mississippi, it's easy to see that we're talking about a LOT of fertilizer.

Fertilizer contains high concentrations of nitrogen, an element that is normally "limiting" in a marine environment. Adding additional nitrogen to the water leads to explosive growth of algae. When the algae die, their decomposition uses up large amounts of oxygen. This depletes the water of dissolved oxygen, on which organisms like fish and shellfish depend. They must either move to different waters, or perish.

There is also the issue of harmful algal blooms, in which the algae produce neurotoxins that kill fish, dolphins, and other marine life. If the toxins build up in fish or shellfish, then other organisms such as birds and even humans may get sick.

The obvious solution is to drastically reduce fertilizer usage, but this is unlikely to happen anytime soon. Other tricks are being explored for "capturing" phosphorus and nitrogen, including building wastewater treatment plants that use algae to remove these elements (e.g. growing algae in a controlled environment). The algae would then be used as biomass to produce biofuels. But could this be done on a large enough scale?

Exploring Realities of Offshore Drilling (News Item)

Science in Society — 2008-07-25T19:05:24Z

Last Friday's NPR-Science Friday podcast features an interview with Boston University researcher and energy expert Robert Kaufman, exploring the economic realities of offshore oil drilling. President Bush recently reversed a longstanding ban on offshore drilling in an effort to increase oil supply and lower prices. For much of the US coastline, with the exception of several Gulf states, offshore drilling is off-limits.

Some interesting tidbits from the interview: Kaufman estimates that offshore drilling would only increase US oil production by 1-4% over the next decade, insufficient to make a dent in gas prices. In fact, he says opening up all protected lands for oil drilling would only be a drop in the bucket compared to our total energy needs.

Kaufman further speculates that one of the reasons that the oil lobby is pushing for access to the protected Arctic National Wildlife Refuge is to increase the economic "lifespan" of their expensive Trans Alaska Pipeline, which has essentially been paid for by all the oil it has already transported. So the push is not to increase oil supply, but rather to increase profit margin.

When one considers the environmental risks that come with drilling in protected Alaskan wilderness or offshore, it seems we really need to focus on conservation and renewable energy sources, not finding more oil.

Gore Urges Change to Dodge an Energy Crisis (News Item)

Science in Society — 2008-07-18T05:00:00Z

In a speech yesterday, 2007 Nobel Laureate and former Vice President Al Gore called for a national effort to convert our electricity production from oil-based sources to renewable sources like wind, solar, and biofuels.

"Today I challenge our nation to commit to producing 100 percent of our electricity from renewable energy and truly clean carbon-free sources within 10 years. This goal is achievable, affordable and transformative. It represents a challenge to all Americans – in every walk of life: to our political leaders, entrepreneurs, innovators, engineers, and to every citizen."

Can it be done? Monetarily, he claims that it will cost between $1.5 and $3 trillion - an amount that he says the United States will need to invest in new power plants anyway, just to meet the burgeoning demand for electricity. Scientifically, he points out that enough sunlight falls on the earth every hour which, if harnessed, could meet our energy needs for a year. The trick, of course, is harnessing the energy in an economically viable way.

A PDF transcript of his speech can be found here.

Developing new approaches for solar energy is a major focus of researchers at Northwestern and Argonne National Labs, through the ANSER project. Read a summary of the project.

The Migration History of Humans: DNA Study Traces Human Origins Across the Continents (News Item)

Science in Society — 2008-07-10T19:17:32Z

Modern genetics is revealing an ever-clearer picture of mankind's ancestral migration out of Africa tens of thousands of years ago. This Scientific American article summarizes the science and the interesting conclusions of contemporary human evolutionary studies.

In addition to providing important details about our origins, these studies are changing our concepts of race. According to Pasteur Institute genetics researcher Lluis Quintana-Murci, “There is no race ... What we see [from the standpoint of genetics] is geographical gradients. There are no sharp differences between Europeans and Asians. From Ireland to Japan, there is no sharp boundary where something has changed completely.”

NCI Grant Launches Clinical Trials For Colon Cancer Screening (News Item)

Science in Society — 2008-07-10T05:00:00Z

Northwestern researcher Vadim Backman was recently funded by the National Cancer Institute to continue his work on technology that may lead to a less expensive and less invasive test to detect colon cancer.

Backman's group has developed a molecular flashlight, of sorts. Using light from a xenon bulb, they have devised a method to detect miniscule changes in a cell's structure that are diagnostic for cancer. The technique is able to detect these changes before they can be seen with a microscope. As is true for all cancers, early detection is a key factor in survival rate.

Backman, professor of biomedical engineering at McCormick, is also working on a screening method for pancreatic cancer. This project was featured in a recent SiS Research Digest article, found here.

The Environmental Impact of Corn-Based Plastics (News Item)

Science in Society — 2008-07-03T05:11:53Z

This Scientific American article explores the purported benefits of corn-based plastics (also known as polylactic acid, or PLA) over the more conventional petroleum-based plastic. The results may surprise you.

Although PLA is technically renewable, saves oil, and is less polluting to manufacture, its biodegradability is far from perfect. It's also a headache for recyclers because PLA "contaminates" the conventional plastic recycling process. The two must be separated, leading to higher costs for recycled plastic and lower overall demand.

Some experts have also suggested that the marketing of PLA as "green" plastic has led to rampant overpackaging and a proliferation of single-serving plastic containers.

A related 2006 Smithsonian Magazine article can be found here.

New ‘Photo Op’ For Ovaries May Solve Some Mysteries Of Infertility (News Item)

Science in Society — 2008-06-24T05:00:00Z

Northwestern University researchers led by Teresa Woodruff, director of the Center for Reproductive Research at the University's Feinberg School of Medicine, are approaching women's infertility from a new direction.

Woodruff and her team are looking at ovaries themselves, and how eggs are selected for ovulation, rather than the more traditional methods of studying genes and hormones. Frank Miller, professor of radiology at Feinberg, and his colleagues are developing a new way to image ovaries, allowing researchers to closely study an organ that, being small and deep, has previously been difficult to examine.

Woodruff's research was recently funded by a $6.5 million grant from the National Institutes of Health.

Inside the Solar-Hydrogen House: No More Power Bills–Ever (News Item)

Science in Society — 2008-06-23T18:18:25Z

Scientific American has a feature story on a New Jersey resident that has not paid a gas or electric utility bill in two years - because his house is powered by solar-generated hydrogen. Part of the hydrogen he generates also goes to fuel his car.

The cost of this sunlight-capturing energy system? Approximately $500,000. But he thinks a similar system could be built today for only $90,000.

Is ADHD an Advantage for Nomadic Tribesmen in Kenya? (News Item)

Science in Society — 2008-06-16T05:00:00Z

A new study from Northwestern University's Weinberg College of Arts and Sciences suggests that the version of a gene associated with ADHD may actually prove beneficial for certain populations.

The study looked at the body mass index (BMI) and height of males from a tribe called Ariaal in northern Kenya. Some members of this tribe continue to live their traditional nomadic lifestyle, while others have recently settled and started to grow crops.

It turns out that those who are living the nomadic lifestyle with the genetic variant associated with ADHD fared much better than the settled tribesmen who also had the variant. According to Dan Eisenberg, lead author on the study, this suggests that it's "possible that, in a nomadic setting, a boy with this allele might be able to more effectively defend livestock against raiders or locate food and water sources, but that the same tendencies might not be as beneficial in settled pursuits such as focusing in school, farming or selling goods.”

U.S. Experts Bemoan Nation's Loss of Stature in the World of Science (News Item)

Science in Society — 2008-06-06T14:53:31Z

Scientists attending the opening of the first World Science Festival in New York City had harsh words for US politicians and the low priority they have given science in recent years. Critics chided the government's stagnant federal funding for research, and the views of some officials that intelligent design is a scientific alternative to evolution.

Somewhat surprisingly, even the 2008 presidential candidates seem reluctant to tackle the tough scientific issues facing our country. The Science Debate 2008 initiative, supported by the National Academy of Sciences, the American Association for the Advancement of Science, and hundreds of universities (including Northwestern), has invited the Clinton, McCain, and Obama camps to an organized debate on issues of science and technology. Thus far, none of the candidates have agreed to participate.

Mars Lander Transmits Photos of Arctic Terrain (News Item)

Science in Society — 2008-05-28T05:00:00Z

A 422-million-mile, 10-month journey to Mars ended Sunday with the successful arrival of the Phoenix lander on the Martian surface.

The mission, to the northerly arctic region of Mars, is designed to gather chemical data from soil and water that will allow researchers to better understand the geologic history of water on Mars. This data will also provide clues as to whether biological life ever existed on this now cold planet.

A full description of the Phoenix mission can be found on NASA's website, complete with pictures, mission updates, and a very cool video summarizing the mission.

Scientists See Supernova in Action (News Item)

Science in Society — 2008-05-23T15:12:40Z

In what several scientists have termed “winning the astronomy lottery,” Princeton researchers were able for the first time to witness a supernova, or the explosive death of a star, as it happened.

Supernovae happen when the hydrogen fuel powering the star’s nuclear reactor “furnace” runs out. During a star’s lifetime, hydrogen is converted to helium, then to oxygen and carbon, then finally to iron. As this process nears its end, the star’s core becomes so heavy that it collapses on itself and explodes. The explosion sends the matter of the star - carbon, oxygen, iron, nitrogen, and other elements - hurtling into space. It is theorized that many elements on Earth, including those that make up our bodies, originated from supernovae.

As is true with many scientific discoveries, good fortune played a key part in the observation. Researchers were observing the remnants of an old supernova in the galaxy NGC2770 using an X-ray telescope when the new supernova occurred. The initial x-ray blast of a supernova is the earliest event in the explosion, and had never before been captured.

Even in the cosmos, it pays to be looking in the right place at the right time!

Bush Signs Anti-Discrimination Bill (News Item)

Science in Society — 2008-05-23T15:04:26Z

On Wednesday, President Bush signed the Genetic Information Nondiscrimination Act (GINA), a bill designed to prevent employers and health insurance companies from discriminating against individuals based on their genetic makeup, into law.

As reported in an earlier news story, this legislation was under consideration in Congress for more than a decade. It’s good to see that it’s finally here!

Some Athletes’ Genes Help Outwit Doping Test (News Item)

Science in Society — 2008-05-06T19:08:19Z

With the summer Olympics just around the corner, a report in this month's Journal of Clinical Endocrinology and Metabolism is unusually timely. The report suggests that some illicit testosterone users have evaded detection because of their genes.

Researchers found that nearly two-thirds of Asian men and approximately 10% of Caucasian men lack the gene that converts testosterone into a form that can be detected in urine. Thus, these individuals can take extra testosterone without the fear of being caught via routine screening methods. Dr. Don Catlin, the chief executive of Anti-Doping Research, called it "...a license to cheat."

While there are more sensitive methods available to catch offenders, they are more expensive and time consuming. It remains to be seen whether this news will lead to genetic tests being required for elite-level athletes, or whether a different test can be developed.

It will be interesting to see how the International Olympic Committee responds to this news - and Major League Baseball, for that matter.

What Darwin Saw Out Back (News Item)

Science in Society — 2008-04-28T01:41:47Z

Charles Darwin is widely recognized as the father of evolutionary theory. In recognition of his 200th birthday and the 150th anniversary of his seminal book, “The Origin of Species,” the New York Botanical Garden has launched a stunning exhibition of his life and scientific work.

The exhibit features a full-scale replica of Darwin's house and garden. His simple "at-home" experiments with plants provided him with key insights that contributed to his overall theory of evolution.

The New York Times article linked below includes a very informative slideshow, showcasing the exhibit. For those of you living in New York or planning to visit, “Darwin’s Garden: An Evolutionary Adventure,” runs through June 15.

Tests Confirm T. Rex Kinship With Birds (News Item)

Science in Society — 2008-04-28T01:39:26Z

By analyzing proteins extracted from dinosaur bones, researchers have concluded with high certainty that birds are the modern-day living descendants of dinosaurs.

The work, published in Science, supports a wealth of previous work examining the similarities of dinosaur and bird skeletons. Interestingly, several fossils from meat-eating dinosaurs were unearthed in the mid to late 1990's that contained evidence of feather-like plumage. Though the "feather theory" was not universally accepted at the time, the current findings from Tyrannosaurus rex bones definitely support the bird-dinosaur linkage.

Senate Passes Genetic Nondiscrimination Bill (News Item)

Science in Society — 2008-04-25T05:00:00Z

After more than a decade of legislative wrangling, the Genetic Information Nondiscrimination Act (GINA) is well on its way to enactment. The Senate passed the bill yesterday by a vote of 95-0, and the House of Representatives is expected to vote on the bill soon. The President has already stated he will sign it.

Passage of this bill is viewed as critical to realizing the promise of genetic medicine. The spectre of losing one's job or health insurance because of a genetic test result has led to many at-risk individuals choosing not to take potentially lifesaving tests.

GINA is also important for the future of genetics research. A 2007 poll from the Genetics and Public Policy Center at Johns Hopkins revealed widespread concern among potential participants in genetic research studies that insurers or employers might be able to gain access to their genetic information. A copy of the poll can be found here.

Scientists Seek New Ways to Produce Biofuel (News Item)

Science in Society — 2008-04-14T03:11:55Z

In this NPR podcast by Science Friday's Ira Flatow, researchers describe several new ideas in the quest to efficiently produce fuel from foodstuffs.

One one example, Mariam Sticklen (Michigan State University) describes a technique to use a gene from a microbe that lives in a cow's stomach to convert fiber into fermentable sugar. Her approach is to insert the gene into a corn plant, only producing the enzyme in the leaves and corn stalk – not in the pollen, root, or ear of corn itself. This way, humans and animals can eat the corn, while the stalk and leaves (containing the enzyme) are ready to be used for energy production.

Promising New Nanotechnology for Spinal Cord Injury (News Item)

Science in Society — 2008-04-13T05:00:00Z

The laboratory of Dr. John Kessler, professor and chair of neurology at Northwestern, has published a promising new approach for treating spinal cord injury. The technique utilizes a nanotechnology-inspired gel, developed by collaborator Dr. Sam Stupp, professor of materials science and director of Northwestern's Institute for BioNanotechnology in Medicine.

The gel, injected as a liquid into the injury site, self-assembles into a scaffolding that reduces scarring at the injury site, facilitating re-growth of damaged neurons. Initial experiments in rodents showed promising results, as detailed recently in the Journal of Neuroscience.

If you are interested in learning more about the research that led to this finding, it is profiled in Terra Incognita: Mapping Stem Cell Research, a feature-length documentary film about Dr. Kessler's laboratory (view film trailer).

Study Ties Genetic Variations to Schizophrenia (News Item)

Science in Society — 2008-04-02T05:00:00Z

Researchers have used a new approach to identify genes that lead to elevated risk for schizophrenia, which affects approximately 1% of the population.

The new method, known as a genome-wide association (GWA) study, compares the genomes of people with a particular disease to those without the disease. By identifying key differences between the two, one can generate hot leads as to which genes might be involved. The trick is identifying which genes are truly related, and which are not – a difficult task, to be sure.

This approach has become important for identifying the many genes thought to contribute small increases in risk for diseases like diabetes, heart disease, and schizophrenia. Previously, these genes were difficult to track and identify using classic, family-based genetic discovery techniques.

At Northwestern, researchers in the NUgene project were recently funded by the National Institutes of Health to use the GWA approach to look for genes involved in diabetes and asthma.

There are practical concerns, though, with how this type of research finding might be used by doctors and their patients. Should genetic tests be ordered for conditions where the risk factors are small, or where treatment options may not exist? For many diseases, more informative risk factors are evident just by looking at one’s health record and family history. For example, risk factors for diabetes, including weight, lifestyle, and family history (the simplest genetic test), are straightforward to interpret and quite informative.

So while this news is exciting to researchers because it represents a start for unraveling the genetic contributions to schizophrenia, this is not likely to be information that will directly benefit a patient quite yet.

Stuff of Life (but Not Life Itself) Is Detected on a Distant Planet (News Item)

Science in Society — 2008-03-24T05:00:00Z

Researchers at NASA's Jet Propulsion Laboratory recently reported the detection of water and methane, a simple organic molecule, a distant planet outside of our solar system. This finding is exciting to scientists because it confirms that organic molecules and water - two potential building blocks of life - can be identified on distant planets.

The planet, known in astronomy circles as HD189733b, orbits a star slightly smaller than our Sun. It is located a long ways from earth - 369 trillion miles (63 light years), to be exact. It's surface temperature is ~ 1,700 degrees Fahrenheit, far too hot to support life as we know it. Therefore, the detection of methane and water on HD189733b is more proof of principle, rather than a hot lead for life.

Data were collected using the Hubble Space Telescope. Researchers measured light originating from the planet's star that had passed through the planetary atmosphere. The properties of light passing through a planetary atmosphere are are altered slightly by the the types of molecules found therein. A full description of the method can be found in an NPR interview with NASA scientist Mark Swain.

The ability to conduct these types of measurements opens the door to similar studies of other planets whose surface temperature might be more like our own.

The Jet Propulsion Laboratory website has nice collection of audio and video features, including a clip on the search for life on other planets.

Brain Enhancement is Wrong, Right? (News Item)

Science in Society — 2008-03-14T14:55:26Z

An article in the New York Times this week explores the much-covered topic of performance enhancing drugs. This time, however, the users are not athletes, and the goal isn't more home runs.

Instead, as reported in the journal Nature, prescription drugs such as Adderall, used to treat attention deficit disorder, and Provigil, used to treat narcolepsy, are being taken by college students and faculty alike to increase academic performance through enhanced concentration and wakefulness.

Opinions on the ethical issues surrounding "brain-boosting" differ, especially between those who use the drugs and the experts who speculate on the long term consequences. Some urge that widespread use will eventually raise "normal" standards, creating an unfair advantage for those with access to the drugs over those who do not. Others suggest that making people who are already driven and productive even more productive could be seen as a positive thing, assuming- and this is a big assumption- that no one, including the user, is harmed in the process.

Kissing the Earth Goodbye in About 7.59 Billion Years (News Item)

Science in Society — 2008-03-13T02:27:49Z

The earth has approximately seven and a half billion years left to live, according to mathematical models made by researchers at University of Guanajuato in Mexico and the University of Sussex in England.

The earth’s demise is being driven by an aging sun, which is actually becoming larger, brighter, and warmer with age. In fact, life on earth may end well before the 7.5 billion year estimate, when the earth will be engulfed by the sun. Researchers speculate that one billion years from now, the temperature of earth will have risen to the point where the oceans boil off, effectively ending life on earth.

Although this news sounds rather bleak, it’s worth noting that estimates of the earliest, single-celled life forms on earth are in the 3 billion-year-old range. We definitely have some time to explore other solar systems….

Fragile Ecosystems, Mathematically Speaking (News Item)

Science in Society — 2008-03-07T16:06:57Z

In all fields of science, researchers rely on mathematical models to make predictions about future events (will an asteroid hit earth?), predict how a system might react if perturbed, (does an excess of carbon dioxide in the atmosphere lead to global warming?), and even to investigate why a process works the way it does (how do neurons in our brain communicate with each other?).

In a recent issue of the journal Nature, University of Wisconsin researchers report that they have developed a mathematical model to examine the behavior of a complex lake ecosystem involving fish, insects, and hard-shelled algae known as diatoms. The model was developed using data from an Iceland lake whose fish population declined rapidly in over the last 25 years. The model suggests that the lake's insect population is extremely sensitive to changes in the ecosystem, and that the observed crash in fish population may have been caused by human activity.

The explanation goes like this: lake dredging led to subtle changes in the diatoms' ecosystem that in turn resulted in profound changes in the lake's food chain. Dredging changed the algae's distribution in the lake, which led to fewer algae for insects to eat, which lead to fewer insects for the fish to eat. In a normal ecosystem, the population of insects normally rises and falls over a regular, predictable interval. But in this instance, the interval is irregular. This may explain why the fish population collapsed.

Most importantly, this research reinforces the sensitivity of natural ecosystems to seemingly small natural and/or man-made changes.

U.S. Study Shows Why Winter is "Flu Season" (News Item)

Science in Society — 2008-03-07T15:50:18Z

Researchers have long wondered why the flu virus seems to be more prevalent and spread more quickly during the winter season. The answer may, in part, lie in the molecular components from which the virus is built.

Viruses consist of a small amount of genetic material, inside of an outer membrane-like coat of protein and lipid (fat). During the life cycle of a virus, it first binds to a host cell and inserts its genetic material into the cell. Viral genes hijack the cell’s machinery to make copies of itself. This process destroys the cell. Newly formed viruses spread within the body and ultimately between individuals.

Researchers at the National Institute of Child Health and Human Development examined the properties of the virus's outer, protective coat with respect to temperature. They discovered that the outer coat becomes more protective at lower temperatures – a result of the lipid components of the outer coat becoming more gel-like as the temperature decreases.

These types of basic insights into how viruses protect themselves will further the development of more effective anti-viral medications.

More Expensive Placebos Bring More Relief (News Item)

Science in Society — 2008-03-06T06:00:00Z

Following up on a news item we reported in February (My Cortex Made Me Buy It), a recent medical study adds credence to the misplaced notion that expensive = effective.

Researchers asked study participants to rate the effectiveness of two pills allegedly designed to provide pain relief. The subjects were told that one pill cost $2.50, while the other pill cost $0.10. Each subject was given a small electrical shock and asked to rate the effectiveness of each pill. In truth, both pills were placebos (sugar pills).

For both pills, subjects perceived significant pain relief (a placebo effect). But with the $2.50 pill, perceived pain relief was 24 percentage points higher than for the $0.10 pill.

Let's hope this doesn't give pharma companies justification to raise prices...

Genetic Mutations Offer Insights on Human Diversity (News Item)

Science in Society — 2008-02-27T03:23:36Z

Recent studies of human genetic variation have provided some interesting perspectives on our evolutionary history and the degree to which people from distant lands are closely related, genetically speaking.

In one study, researchers measured genetic variation at more than half a million sites within the genome's three billion DNA letters. They did this for approximately 1,000 individuals representing 51 regions across the globe. Consistent with evolutionary theory, they found that African populations had the highest genetic diversity, with European populations having lower diversity.

Such studies provide unique insights into evolutionary migrations, allowing researchers to better understand how human populations moved out of Africa less than 100,000 years ago. Population-based genetic studies are also important in health care, providing a baseline that allows researchers to figure out how DNA variation may lead to higher disease risk.

A National Public Radio interview with Stanford researcher Dr. Richard Meyers can be found here.

Insurance Fears Lead Many to Shun DNA Tests (News Item)

Science in Society — 2008-02-27T03:22:46Z

This New York Times article nicely summarizes the complex issues facing patients considering a genetic test. On one hand, genetic tests can help improve an individual's health care prospects. On the other hand, there is considerable fear that the results from a genetic test could be used in a discriminatory way - resulting in the loss of health insurance, or even one's job.

While there have been few documented cases of actual discrimination by health care insurers or employers, the spectre of discrimination leads many to pay out of pocket for genetic tests and use fake identities to learn of their test results.

Illinois has a state law prohibiting discrimination on the basis of a genetic test, but similar legislation is currently lacking at the national level. A bill to outlaw genetic discrimination, the Genetic Information Non-Discrimination Act (GINA), passed the U.S. House of Representatives in April of 2007 by a vote of 420-3, but has not yet made it to the Senate floor. A legislative summary of the bill can be found here.

Biofuel, Partly From Nuts, Is Tested on an Airline Flight (News Item)

Science in Society — 2008-02-26T22:12:03Z

Virgin Atlantic Airways is the first airline to use biofuel on a commercial flight. The fuel, derived from babassu nuts and coconut oil, formed 25% of the jet fuel. The remainder was kerosene, the typical fuel for jet engines.