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Two theoretical physicists at the University of California, Davis have a new candidate for dark matter, and a possible way to detect it. They presented their work June 6 at the Planck 2019 conference in Granada, Spain and it has been submitted for publication.

Dark matter is thought to make up just over a quarter of our universe, with most of the rest being even-more mysterious dark energy. It cannot be seen directly, but dark matter's presence can be detected because its gravity determines the shape of distant galaxies and other objects.

Many physicists believe that dark matter is made up of some particle yet to be discovered. For some time, the favorite candidate has been the Weakly Interacting Massive Particle or WIMP. But despite years of effort, WIMPs have so far not shown up in experiments designed to detect them.

"We still don't know what dark matter is," said John Terning, professor of physics at UC Davis and coauthor on the paper. "The primary candidate for a long time was the WIMP, but it looks like that's almost completely ruled out."

An alternative to the WIMP model of dark matter calls for a form of "dark electromagnetism" including "dark photons" and other particles. Dark photons would have some weak coupling with "regular" photons.

In their new paper, Terning and postdoctoral researcher Christopher Verhaaren add a twist to this idea: a dark magnetic "monopole" that would interact with the dark photon.

In the macroscopic world, magnets always have two poles, north and south. A monopole is a particle that acts like one end of a magnet. Monopoles are predicted by quantum theory, but have never been observed in an experiment. The scientists suggest that dark monopoles would interact with dark photons and dark electrons in the same way that theory predicts electrons and photons interact with monopoles.

A new way to detect dark matter

And that implies a way to detect these dark particles. The physicist Paul Dirac predicted that an electron moving in a circle near a monopole would pick up a change of phase in its wave function. Because electrons exist as both particles and waves in quantum theory, the same electron could pass on either side of the monopole and as a result be slightly out of phase on the other side.

This interference pattern, called the Aharonov-Bohm effect, means that an electron passing around a magnetic field is influenced by it, even if it does not pass through the field itself.

Terning and Verhaaren argue that you could detect a dark monopole because of the way it shifts the phase of electrons as they pass by.

"This is a new type of dark matter but it comes with a new way to look for it as well," Terning said.

Electron beams are relatively easy to come by: electron microscopes were used to demonstrate the Aharonov-Bohm effect in the 1960s, and electron beam technology has improved with time, Terning noted.

Theoretically, dark matter particles are streaming through us all the time. To be detectable in Terning and Verhaaren's model, the monopoles would have to be excited by the Sun. Then they would take about a month to reach Earth, traveling at about a thousandth of the speed of light.

On the other hand, the predicted phase shift is extremely small -- smaller than that needed to detect gravity waves, for example. However, Terning noted that when the LIGO gravity wave experiment was first proposed, the technology to make it work did not exist --instead, technology caught up over time.

HOUSTON - (June 10, 2019) - New Rice University research has found that people selling stuff on classified ad websites prefer dealing with buyers from affluent neighborhoods.

"Disentangling the Effects of Race and Place in Economic Transactions: Findings from an Online Field Experiment" will appear in an upcoming edition of City and Community.

Max Besbris, an assistant professor of sociology at Rice and the study's lead author, tested whether transactions conducted through online resale websites were affected by the addresses where prospective buyers live. He also studied the role played by race and ethnicity.

"For several decades, social scientists have investigated how the geographic organization of inequality affects social and economic outcomes of those living in disadvantaged places," Besbris said. "We were interested in seeing if this inequality extended to the online resale marketplace."

So Besbris conducted an original field experiment in the market for secondhand goods. Researchers answered advertisements for used cellphones in ways that signaled the prospective buyer's race and ethnicity, as well as whether the buyer lived in an advantaged or disadvantaged neighborhood.

As Besbris hypothesized, inquiries that included the name of a disadvantaged neighborhood received 12% fewer responses than those that referenced an advantaged neighborhood. In addition, those that received responses after claiming they were from disadvantaged neighborhoods were 25% more likely to have a seller suggest an alternate meeting place to complete the transaction.

Sellers were also less likely to respond to inquiries that claimed to be from neighborhoods with a high percentage of black residents than to inquiries from neighborhoods with a high percentage of Latinos. And inquiries that didn't include an address received a nearly identical number of responses as those that indicated they came from a disadvantaged neighborhood.

"This evidence of discrimination or preference based on neighborhood of residence is a crucial contribution to our understanding of how place can shape life outcomes," Besbris said. "What it reveals is that where you live affects all aspects of your life -- even mundane interactions with others."

Besbris and his colleagues conducted the study over 18 months, responding to 2,321 advertisements for used iPhones in 16 U.S. cities. He hopes the research will add to understanding of the wide-ranging effects of segregation and broaden the scope of anti-discrimination policies to include where people live.

Researchers have developed a new technique that uses microneedle patches to collect DNA from plant tissues in one minute, rather than the hours needed for conventional techniques. DNA extraction is the first step in identifying plant diseases, and the new method holds promise for the development of on-site plant disease detection tools.

"When farmers detect a possible plant disease in the field, such as potato late blight, they want to know what it is right away; rapid detection can be important for addressing plant diseases that spread quickly," says Qingshan Wei, an assistant professor of chemical and biomolecular engineering at North Carolina State University and co-corresponding author of a paper on the work.

"One of the obstacles to rapid detection is the amount of time it takes to extract DNA from a plant sample, and our technique provides a fast, simple solution to that problem," Wei says.

"Some plant diseases have similar leaf symptoms, such as late blight caused by the famed Irish famine pathogen Phytophthora infestans, and Phytophthora blight caused by a sister species P. nicotianae," says Jean Ristaino, William Neal Reynolds Distinguished Professor of Plant Pathology at NC State and co-corresponding author of the paper. "The gold standard for disease identification is a molecular assay. Our new technique is important because you can't run an amplification or genotyping assay on strains of P. infestans, or any other plant disease, until you've extracted DNA from the sample."

Typically, DNA is extracted from a plant sample using a method called CTAB extraction, which has to be done in a lab, requires a lot of equipment, and takes at least 3 to 4 hours. CTAB extraction is a multi-step process involving everything from tissue grinding to organic solvents and centrifuges.

By contrast, the new DNA extraction technique involves only a microneedle patch and an aqueous buffer solution. The patch is about the size of a postage stamp and is made of an inexpensive polymer. The surface on one side of the patch is made up of hundreds of needles that are only 0.8 millimeters long.

A farmer or researcher can apply the microneedle patch to a plant they suspect is diseased, hold the patch in place for a few seconds, then peel it off. The patch is then rinsed with the buffer solution, washing genetic material off of the microneedles and into a sterile container. The entire process takes about a minute.

"It is exciting to see the new application of microneedle patch technology in agriculture and plant science," says Zhen Gu, a professor of bioengineering at the University of California, Los Angeles and co-corresponding author of the paper, who developed several microneedle-based drug delivery systems for human health.

"In experimental testing, we found that the microneedle technique does result in slightly higher levels of impurities in the sample, as compared to CTAB," Wei says. "However, the microneedle technique's purity levels were comparable to other, validated laboratory methods of DNA extraction. Most importantly, we found that the slight difference in purity levels between the microneedle and CTAB samples did not interfere with the ability to accurately test the samples by a PCR or LAMP assay."

"The fact that microneedles extract a smaller sampling volume seems not to be an issue," says Rajesh Paul, a Ph.D. student at NC State and first author of the paper. "The microneedle technique successfully extracted pathogen DNA from all field-collected infected tomato leaves in a recent blind test."

"DNA extraction has been a significant hurdle to the development of on-site testing tools," Wei says. "We are now moving forward with the goal of creating an integrated, low-cost, field-portable device that can perform every step of the process from taking the sample to identifying the pathogen and reporting the results of an assay."

The paper, "Extraction of Plant DNA by Microneedle Patch for Rapid Detection of Plant Diseases," is published in the journal ACS Nano. The paper was co-authored by Amanda Saville, lab manager in Ristaino's lab; Jeana Hansel, a graduate student at NC State; Carmin Ball and Alyssa Williams, undergraduates at NC State; Yanqi Ye, a former graduate student in the Joint Biomedical Engineering Department at NC State and the University of North Carolina, Chapel Hill; Xinyuan Chang, an undergraduate at Tianjin University who worked as a visiting researcher at NC State; and Guojun Chen, postdoctoral researcher at UCLA.

Alcohol consumption during pregnancy has been linked to poor growth of the placenta, causing conditions such as fetal growth restriction and low birth weight. Although most women cease drinking once they know they are pregnant, the effect of alcohol during the initial stages of pregnancy, even as early as around the time of conception, is less well understood. Now, Dr Jacinta Kalisch-Smith together with Professor Karen Moritz at the University of Queensland in Australia have investigated the impact of alcohol consumption on the placenta early in pregnancy. They show that the growth of the placentas of rats that consumed alcohol around the time of conception was reduced significantly, providing new evidence for how pregnancy-related conditions develop. This research has just been published in the scientific journal Development at http://dev.biologists.org.

"We wanted to know whether early alcohol exposure could affect the development of the early embryo and the placenta. Using a rat model, we assessed the ability of the embryo to implant into the uterus, and, later, how well blood vessels formed in the placenta," explained Kalisch-Smith.

Using this approach, the scientists were able to study changes that happen throughout the rat's pregnancy and found that even early exposure to alcohol (between 4 days before and 4 days after fertilisation) restricted the growth and function of the placenta.

"We found early alcohol exposure reduced blood vessel formation in the placenta, and this led to fewer nutrients being delivered to the embryo," said Kalisch-Smith.

Strikingly, the placentas of female embryos were particularly susceptible, with up to a 17% reduction in size and a 32% drop in blood vessel formation, limiting the ability of the placenta to transport nutrients.

"This has implications for human health by helping to explain, in part, why babies exposed to alcohol in the womb are often born small," said Kalisch-Smith. "It is important to understand the causes of low birth weight, because it has been shown to be an independent risk factor for diseases later in adulthood, such as type 2 diabetes, hypertension and obesity."

These observations provide an important basis for future research into pregnancy-associated conditions like fetal growth restriction. Kalisch-Smith added, "The next part of this project is to see whether nutrient supplementation can reduce or even prevent the adverse effects of alcohol exposure."

Millennials - young adults in their 20s and 30s - earn less money without a college degree and are more likely to die prematurely from suicide or drug overdose than previous generations, according to a new report from the Stanford Center on Poverty and Inequality.

The report also found that millennials also have a wider set of identities from which they can choose: Unlike older generations, millennials are frequently embracing multiracial and unconventional gender identities. However, this doesn't mean they are any more accepting of people different from them compared with previous generations. The report found that millennials believe common racial and gender stereotypes to be true just as much as people from the Baby Boomer cohort, who were born from 1946 to 1964, and Generation X, born between 1965 and 1980.

The report, issued on June 6, brought together some of the country's leading experts on poverty and inequality and offers a comprehensive assessment of data on education, health, employment and income, occupational segregation, debt and poverty rates, economic mobility, racial and gender identities, social connections, housing and incarceration trends.

"Millennials are the first generation to experience in a full-throttled way the social and economic problems of our time," said David Grusky, professor of sociology and director of the Stanford Center on Poverty and Inequality.

As millennials tried to enter the job market during the Great Recession of the late 2000s, they also had to deal with decades-long economic issues, such as rising inequality and declining economic mobility. This made it an especially difficult period, he said.

"We can think of them as canaries in the coalmine who reveal just how toxic those problems are. By assembling a report that provides a comprehensive understanding of their situation, we can go beyond the usual patchwork policy and begin to address underlying problems," Grusky said.

Millennial education

Contrary to some popular assumptions, when college-educated millennials entered the labor market, they earned just as much as Baby Boomers and Gen Xers when they were their age.

But millennials with only a high school diploma or less are earning much less than their counterparts from previous generations, according to the report's analyses of education, written by Stanford sociologist Florencia Torche and doctoral sociology student Amy Johnson.

For example, the median earnings for 25-year-old millennial men with a bachelor's or higher degree were about $50,000 per year, which is slightly higher than for previous generations after adjusting for inflation. The median earnings for 25-year-old millennial men who have high school degrees or less were $29,000 per year, which is about $2,600 dollars less than Gen Xers and nearly $10,000 less than Baby Boomers received at the same age, according to Torche and Johnson's analysis of U.S. Census data from 1975 to 2018.

"It's not that going to college amounts to striking gold for most people," Grusky said. "The big news is that if you don't go to college you're likely to do worse than ever. What makes college attractive is mainly that it offers some protection from that fate."

Millennial health

Mortality rates among young adults have also increased substantially, according to the report's analyses of health, written by Stanford economist Mark Duggan and economics undergraduate Jackie Li.

Between 2008 and 2016, mortality rates among those between 25 and 34 years old increased by more than 20 percent. These deaths were mainly driven by a rise in suicides and drug overdoses, Duggan and Li found. The mortality rate among non-Hispanic whites, aged 20 through 34, saw the highest jump - 27 percent - in comparison to a 9 percent increase for blacks and a 6 percent increase for the Hispanic population, according to their analyses of data from the Centers for Disease Control and Prevention.

These findings are in juxtaposition with the fact that more millennials were covered by health insurance. Duggan and Li found that because of the Affordable Care Act, the share of adults in their 20s without health insurance fell by more than half from 2009 to 2017.

Duggan and Li also showed that the racial gap in health insurance coverage has grown smaller through the expansion of health insurance under the ACA.

Millennial identities

The report shows that millennials were more likely to identify as multiracial and to adopt unconventional gender identities.

But millennials embrace racial and gender stereotypes in a similar way to previous generations. According to the report, one-fifth of millennials still adopt traditional views of gender roles, nearly the same as the rates among Gen Xers and Baby Boomers, according to analysis of data from the General Social Survey between 1994 and 2016 and previous research from Stanford scholars.

Millennials are also equally likely as Gen Xers to believe that blacks are lazier than whites, according to analyses by sociologist Aliya Saperstein and sociology doctoral student Sasha Shen Johfre.

"When it comes to their identities, millennials are a truly innovative generation that is forging new options," Grusky said. "But when it comes to their attitudes about race and gender, they're just not as special."

Compassion for young adults

Among other findings, the report shows that the racial gap in homeownership among young adults was larger for millennials than for any generation in the past century.

In 2010, young white adults between 20 and 29 years old were 2.7 times more likely to own a home than their black counterparts, according to an analysis of U.S. Census data from 1940 to 2017. Even if you reach back to the Silent Generation, which includes those born between 1928 and 1945, the racial gap in homeownership among those young adults was smaller than it is now.

According to Grusky, these and other results make it clear that millennials are facing big challenges, many of which stem from the "endemic racial, gender and economic problems" of our time. He hopes that the report can inform future policies.

"If you understand the economic and social context within which millennials are growing up," Grusky says, "it's natural to feel real empathy and hard, by contrast, to understand the anger that's often directed toward them."

At Earlham Institute (EI), artificial intelligence based techniques such as machine learning is moving from being merely an exciting premise to having real-life applications, where it's needed most: improving efficiency and precision on the farm.

Researchers in the Zhou Group at EI, in cooperation with Ely-based G's Growers, have developed a machine learning platform, AirSurf-Lettuce, which works with computer vision and ultra-scale images taken from the air to help categorise lettuce crops in fields.

The advanced software includes measuring quantity, size and pinpointing location to help farmers harvest with precision and getting the crop to market in the most efficient possible way. Importantly, this technology can be applied to other crops, widening the scope for positive impact across the food chain.

Lettuce is big business, especially in East Anglia, with 122,000 tonnes produced in the UK each year. Up to 30% of yield can be lost due to inefficiencies in the growing process as well as harvest strategies, which, if made up, could provide a significant economic boost.

It's very important that farmers and growers understand precisely when crops will become harvest-ready, so that they can set in motion the planning of logistics, trading and marketing their produce further along the chain.

Traditionally, however, measuring crops in fields has been very time-consuming and labour intensive, as well as prone to error; therefore novel AI solutions based on aerial images can provide a much more robust and effective method.

Another barrier to efficiency is the fact that inclement weather conditions, which have been increasing in recent years, can throw off harvesting times quite significantly, as crops take different lengths of time to mature.

The AirSurf technology - developed by members of the Zhou Group, including first authors of the paper on the project, Alan Bauer and Aaron Bostrom - uses 'deep learning' (a deep structured machine learning technique) combined with sophisticated, ultra-wide-scale imaging analysis to measure iceberg lettuce in a high-throughput mode. This is able to identify the precise quantity and location of lettuce plants, with the additional advantage of recognising crop quality, i.e. small, medium or large lettuce heads.

Combining this system with GPS allows farmers to precisely track size distribution of lettuce in fields, which can only help in increasing the precision and effectiveness of farming practice, including harvest time.

First author, Alan Bauer at EI, said: " This cross-disciplinary collaboration integrates computer vision and machine learning with the lettuce growing business to demonstrate how we can improve crop yields using machine learning."

Group Leader at EI, Dr Ji Zhou, said: "My lab is keen to seek every possible approach to translate our public funded research in algorithm design, machine learning, computer vision, and crop phenomics to techniques and tools that can be used by academic and industrial partners to address challenging problems in crop research and crop production.

"Utilising our research work supported by BBSRC and other public and industry jointly funded projects, we have partnered with G's, leading vegetable growers in the UK, to equip our Agri-Food sector with smart and precise crop surveillance and analytical methods, for which we are confident that better crop management decisions and enhanced crop marketability could be achieved through our joint efforts".

Industry partner at G's Growers, Innovation Manager Jacob Kirwan, added: "Farming at a large scale means that precision is essential when ensuring that we are producing crops in an environmentally and economically sustainable way. Using technology like AirSurf means that growers are able to understand the variability in their fields and crops at a much higher level of detail that was previously possible.

"The decisions that can then be taken from this information, such as varying applications of inputs and irrigation; changing harvest strategies and planning the optimum time to sell crop, will all contribute towards increasing on farm yields and improving farm productivity."

TROY, N.Y. --Machine learning has the potential to vastly advance medical imaging, particularly computerized tomography (CT) scanning, by reducing radiation exposure and improving image quality.

Those new research findings were just published in Nature Machine Intelligence by engineers at Rensselaer Polytechnic Institute and radiologists at Massachusetts General Hospital and Harvard Medical School.

According to the research team, the results published in this high-impact journal make a strong case for harnessing the power of artificial intelligence to improve low-dose CT scans.

"Radiation dose has been a significant issue for patients undergoing CT scans. Our machine learning technique is superior, or, at the very least, comparable, to the iterative techniques used in this study for enabling low-radiation dose CT," said Ge Wang, an endowed chair professor of biomedical engineering at Rensselaer, and a corresponding author on this paper. "It's a high-level conclusion that carries a powerful message. It's time for machine learning to rapidly take off and, hopefully, take over."

Low-dose CT imaging techniques have been a significant focus over the past several years in an effort to alleviate concerns about patient exposure to X-ray radiation associated with widely used CT scans. However, decreasing radiation can decrease image quality.

To solve that, engineers worldwide have designed iterative reconstruction techniques to help sift through and remove interferences from CT images. The problem, Wang said, is that those algorithms sometimes remove useful information or falsely alter the image.

The team set out to address this persistent challenge using a machine learning framework. Specifically, they developed a dedicated deep neural network and compared their best results to the best of what three major commercial CT scanners could produce with iterative reconstruction techniques.

This work was performed in close collaboration with Dr. Mannudeep Kalra, a professor of radiology at Massachusetts General Hospital and Harvard Medical School, who was also a corresponding author on the paper.

The researchers were looking to determine how the performance of their deep learning approach compared to the selected representative iterative algorithms currently being used clinically.

Several radiologists from Massachusetts General Hospital and Harvard Medical School assessed all of the CT images. The deep learning algorithms developed by the Rensselaer team performed as well as, or better than, those current iterative techniques in an overwhelming majority of cases, Wang said.

Researchers found that their deep learning method is also much quicker, and allows the radiologists to fine-tune the images according to clinical requirements, Dr. Kalra said.

These positive results were realized without access to the original, or raw, data from all the CT scanners. Wang pointed out that if original CT data is made available, a more specialized deep learning algorithm should perform even better.

"This has radiologists in the loop," Wang said. "In other words, this means that we can integrate machine intelligence and human intelligence together in the deep learning framework, facilitating clinical translation."

He said that these results confirm that deep learning could help produce safer, more accurate CT images while also running more rapidly than iterative algorithms.

"We are excited to show the community that machine learning methods are potentially better than the traditional methods," Wang said. "It sends the scientific community a strong signal. We should go for machine learning."

This research by Wang's team is among the significant advancements consistently being made by faculty in the Biomedical Imaging Center within the Center for Biotechnology and Interdisciplinary Studies (CBIS) at Rensselaer.

"Professor Wang's work is an excellent example of how advances in artificial intelligence, and machine and deep learning can improve biomedical tools and practices by addressing hard problems--in this case helping to provide high-quality CT images using a lower radiation dose. Transformative developments from these collaborative teams will lead to more precise and personalized medicine," said Deepak Vashishth, director of CBIS.

Mount Sinai was part of the largest clinical trial for asthma self-management support in older patients, which resulted in improved control and quality of life, and fewer emergency department visits.

Topic: Asthma affects 7 percent of Americans older than 65 and causes more symptoms and hospitalizations in this age group than in younger patients with asthma. While experts have called for interventions specifically targeting this population, few relevant studies have been reported. Mount Sinai and other institutions tested the effect of a comprehensive, patient-tailored asthma self-management support intervention for older adults on clinical and self-management outcomes.

What: This is the largest study ever conducted for an intervention to improve outcomes in older adults with asthma. It is also the first study to screen patients for barriers to control of their asthma, including social determinants of health, and target only the identified barriers for intervention. The intervention resulted in improved asthma control and quality of life, and led to fewer emergency department visits. Additionally, very few studies involve systematic evaluation of social determinants of health with actions linked to the data that are collected.

Corresponding Author: Alex D. Federman, MD, MPH, Professor of Medicine (General Internal Medicine), Icahn School of Medicine at Mount Sinai

Results: In this randomized trial that included 391 adults, intervention patients had significantly better asthma control, quality of life, medication adherence, and inhaler technique than control patients. The proportion of intervention patients with an emergency department visit for asthma was 6 percent vs. 12 percent, a significant difference.

Why the Research Is Interesting: Older adults receiving a patient-tailored self-management support intervention for asthma, whether in the home or clinic, achieved meaningful improvements in asthma control and quality of life, self-management behaviors, and reductions in ED visits compared to patients in usual care. By specifically targeting social determinants of health and other drivers of health-related behaviors, the intervention is a promising model of self-management support and disease control for older adults with asthma, and possibly other chronic diseases.

Who: Division of General Internal Medicine, Icahn School of Medicine at Mount Sinai, New York; Division of General Internal Medicine, Feinberg School of Medicine, Northwestern University, Chicago; Department of Psychology, The Graduate Center, City University of New York; City Health Works, New York; Institute for Family Medicine, New York; Little Sisters of the Assumption Family Health Service, New York; Department of Psychology, Hunter College, City of New York.

When: Three-arm randomized clinical trial conducted between February 2014 and December 2017 at primary care practices and personal residences in New York City.

Paper Title: 'Effect of a self-management support intervention on asthma outcomes in older adults: The SAMBA Study randomized clinical trial.'

Said Mount Sinai's Dr. Federman of the research:

"Health systems, insurers, and policymakers are increasingly recognizing the powerful influence of social factors on health and outcomes of health like hospitalizations and health care spending. Despite gaining more attention, few studies have tested ways of providing health care that address these social determinants of health. This newly developed approach is helping people with complex health problems, in this case older adults with asthma. By screening patients for barriers to controlling their asthma and addressing the barriers that were identified, the new program helped these older adults take their medications regularly, improve their control of asthma, and reduce their visits to emergency departments by more than 50 percent."

ANN ARBOR--If astronomers want to learn about how supermassive black holes form, they have to start small--really small, astronomically speaking.

In fact, a team including University of Michigan astronomer Elena Gallo has discovered that a black hole at the center of a nearby dwarf galaxy, called NGC 4395, is about 40 times smaller than previously thought. Their findings are published in the journal Nature Astronomy.

Currently, astronomers believe that supermassive black holes sit at the center of every galaxy as massive as or larger than the Milky Way. But they're curious about black holes in smaller galaxies such as NGC 4395 as well. Knowing the mass of the black hole at the center of NGC 4395--and being able to measure it accurately--can help astronomers apply these techniques to other black holes.

"The question remains open for small or dwarf galaxies: Do these galaxies have black holes, and if they do, do they scale the same way as supermassive black holes?" Gallo said. "Answering these questions might help us understand the very mechanism through which these monster black holes were assembled when the universe was in its infancy."

To determine the mass of NGC's black hole, Gallo and her fellow researchers employed reverberation mapping. This technique measures mass by monitoring radiation thrown off by what's called an accretion disk around the black hole. An accretion disk is a mass of matter collected by the gravitational pull of black holes.

As radiation travels outward from this accretion disk, it passes through another cloud of material farther out from the black hole that's more diffuse than the accretion disk. This area is called the broad-line region.

When the radiation hits gas in the broad-line region, it causes atoms in it to undergo a transition. This means that the radiation bumps an electron out of the shell of an atom of hydrogen, for example, causing the atom to occupy a more energetic level of the atom. After the radiation passes, the atom settles back into its previous state. Astronomers can image this transition, which looks like a flash of brightness.

By measuring how long it takes for the accretion disk radiation to hit the broad-line region and cause these flashes, the astronomers can estimate how far the broad-line region is from the black hole. Using this information, they can then calculate the black hole's mass.

"The distance is thought to depend on the black hole mass," Gallo said. "The larger the black hole, the larger the distance and the longer you expect for light to be emitted from the accretion disk to hit the broad-line region."

Using data from the MDM Observatory, the astronomers calculated that it took about 83 minutes, give or take 14 minutes, for radiation to reach the broad-line region from the accretion disk. To calculate the black hole mass, they also had to measure the intrinsic speed of the broad-line region, which is the speed at which the region cloud is moving under the influence of the black hole gravity. To do this, they took a high-quality spectrum with the GMOS spectrometer on GEMINI North telescope.

By knowing this number, the speed of the broad-line region, the speed of light and what's called the gravitational constant, or a measure of gravitational force, the astronomers were able to determine that the black hole's mass was about 10,000 times the mass of our sun--about 40 times lighter than previously thought. This is also the smallest black hole found via reverberation mapping.

"This regime of dwarf galaxies is largely unexplored when it comes to the properties of their nuclear black holes," Gallo said. "We don't even know if every galaxy has a black hole. This adds a new member to the family of black holes we have information about."

This information also could help astronomers understand how much larger black holes shape the galaxies they occupy. A field called black hole feedback explores how black holes affect the properties of their host galaxies at much larger scales than their gravitational pull should reach.

"There's no reason why stars that live at orders of magnitude larger than the area where black hole gravity dominates should even know that there's a black hole in their galaxy, but somehow they do," Gallo said. "Black holes somehow shape the galaxy they live in on very large scales, and because we don't know much about smaller galaxies with their smaller black holes, we don't know whether that's true all the way down. With this measurement, we can add more information to this relationship."

This result came out of a partnership between U-M Astronomy and the Department of Physics and Astronomy at Seoul National University. Observations were made at the GEMINI North observatory in Hawaii and the MDM Observatory in Arizona. GEMINI is operated by a partnership between the United States, Canada, Chile, Brazil, Argentina and Korea.

For many people, climate change feels like a distant threat -- something that happens far away, or far off in the future. Scientists and climate communicators often think that if everyone saw the devastating impacts of climate change, we'd all be more likely to accept it as real, and that accepting climate science is essential to taking action against it. A recent study, published in Regional Environmental Change, challenges the latter part of this assumption.

The study examined decision-making in three places affected by melting glaciers. For these communities in the Italian Alps, the Peruvian Andes, and the U.S.'s North Cascades, glacier retreat is a visible fact -- "and the causes of glacier retreat are almost exclusively warming," explains lead author Ben Orlove, an anthropologist and co-director of the Center for Research on Environmental Decisions at Columbia University's Earth Institute.

Orlove and his colleagues wondered whether the people who live in the three locales notice these changes, whether they understand them to be the result of climate change, and whether this climate connection motivates them to take action.

They found that people in these villages are indeed aware of climate change and are even taking action to adapt to it. But the villagers don't often talk about climate change as a motivation for adapting. Instead, they're more likely to look closer to home for reasons to respond to the changing environment, focusing on how the responses can benefit their communities. The study suggests one potential way to reframe the conversation around climate adaptation and make it more appealing.

Exploring different frames of mind

Orlove's team looked at the frames of thinking that mountain-dwellers use to understand the changes happening around them. Mental "frames" help us sort new information and reconcile it with our previous knowledge and beliefs. For example, says Orlove, "If a hydropower plant in the Italian Alps doesn't get enough water to generate electricity, what kinds of associations do the villagers make when they think or talk about these changes?"

The team examined how mountain-dwellers utilized two frames when talking about glacial retreat. The first was a climate change frame that focuses on global changes and the need for global solutions. The second was a community frame emphasizing action at a local level and recognizing positive opportunities for local advancement, in addition to the negative challenges of environmental change.

By analyzing peoples' speech patterns during in-depth interviews, focus groups, and in records of community meetings, the researchers investigated how often people in the mountain communities used these two frames when talking about the impacts of climate change.

Different regions, different challenges, similar framing

The study found that villages in all three research sites are undertaking actions that could be described as adaptations to climate change. However, the communities themselves don't always think of their actions that way. The authors present three cast studies.

Tourism in the North Cascades

Glaciers, rivers, lakes, and snowpack draw tourists to the slopes of Mount Baker in Washington State, providing the major source of income for the towns of Concrete and Glacier. But those natural resources are at risk as the planet's temperature climbs.

Orlove's team argues that these communities in the North Cascades are adapting to glacial retreat by finding ways to expand other forms of tourism. One example is through festivals that celebrate historical heritage and wildlife, and help to bring the community together.

However, Concrete and Glacier residents rarely used words associated with the climate change frame when describing the changes or the local response. Instead, they use a community frame, emphasizing the importance of bolstering tourism and supporting livelihoods and the next generation.

"These kids who get out of high school, there's not much for them to do except go out of town and find a job in [the nearby town of] Mount Vernon or Seattle," said one interviewee. "Some of them of course go to college, but probably the majority of them don't. So there's no real way to make a livelihood up here. We're dependent on tourism."

Hydropower in the Italian Alps

As glaciers in the Italian Alps shrink, river levels are declining, reducing the ability of hydropower plants to generate electricity. To keep up with demand, the villages of Trafoi, Stilfs, and Sulden have installed biomass generators that burn wood chips to generate electricity, and the extra heat gets piped into homes.

The researchers found that although residents sometimes describe the wood chips as a renewable resource -- a term from the climate change frame -- they're more often to rely on the community frame. Many villagers mentioned liking the wood heat for its coziness, and emphasized that that the wood chips are a local resource that supports local independence. Others mentioned the next generation, noting that the wood chip industry provides local jobs and that the pipes have provided conduits to install fiber optic cables; both of these encourage younger people to stay in their communities rather than seeking a future elsewhere.

Water in the Peruvian Andes

The village of Copa in the Peruvian Andes is also watching its water supply fall. Meanwhile, its need for water has only increased, as warmer temperatures and irregular rainfall make crop irrigation more important.

To adapt to these changes, Copa has upgraded its water infrastructure to reduce water leakage. It is using concrete to line the canals that carry water from the river, and building pipe systems to bring water into homes instead of hauling buckets from the canal. As with the previous examples, these developments are most often seen through a community frame, with a focus on how the modern water system earns recognition for the village. "They speak with pride of the village square," says Orlove, "with piped water giving it a more urban look."

By the numbers

Using both human judgment and computer keyword analysis, Orlove and his team analyzed how often people in these communities referred to environmental changes, whether they attributed these changes to climate change, and whether they described their activities as adaptive responses to the ongoing changes.

They found that the villagers frequently talk about climate change impacts. In interviews, focus groups, and community meetings, changes in ice, water, socioeconomic changes, weather, and agriculture come up in about 13 percent of conversation turns (defined as the words that one person speaks without interruption). "In other words," the paper notes, "they do not find climate change hard to see."

However, people linked these alterations to climate change in only 4 percent of the conversation turns, and they describe their actions as adaptive responses in only 5 percent of conversation turns. Overall, people were five times more likely to refer to the community frame than the climate change frame (4.83 percent versus 0.93 percent).

Reframing the conversation

In each of the case studies, communities see the effects of climate change and take steps to address the impacts. Yet they do all of this without making much use of climate change terminology. While the villagers believe in climate change and do occasionally bring it up in conversation, the community is more relevant for them.

To Orlove and his colleagues, this challenges the notion that people need to 'believe' in climate change in order to take action against it. Furthermore, the authors write, "it could be argued that the community frame is more effective than the climate change frame because it emphasizes 'co-benefits' of adaptation" -- such as protecting local resources from outsiders, retaining control over energy production, and increasing one's connection to their community.

The findings emphasize that climate change communication should be more of a dialogue than a one-way conversation, and that scientists can learn a great deal from the communities they work with.

"It's not that the only solutions are found in these locally organized communities," says Orlove, "but people have not often looked for resources there, and when you do, you'll see that there is social capital. People value their town, and they know each other and interact. They care about their environments and about their communities. We can recognize that as a resource that shouldn't be overlooked at a time when climate needs far exceed available funds."

This ability of people to engage with their neighbors and to craft solutions they care about could be helpful outside of mountain villages as well, says Orlove. "If we see self-organizing here, can we see self-organizing in other places, like in New York?"

Could a small ringlike structure made of plastic and copper amplify the already powerful imaging capabilities of a magnetic resonance imaging (MRI) machine? Xin Zhang, Stephan Anderson, and their team at the Boston University Photonics Center can clearly picture such a feat. With their combined expertise in engineering, materials science, and medical imaging, Zhang and Anderson, along with Guangwu Duan and Xiaoguang Zhao, designed a new magnetic metamaterial, reported in Communications Physics, that can improve MRI quality and cut scan time in half.

Zhang and Anderson say that their magnetic metamaterial could be used as an additive technology to increase the imaging power of lower-strength MRI machines, increasing the number of patients seen by clinics and decreasing associated costs, without any of the risks that come with using higher-strength magnetic fields. They even envision the metamaterial being used with ultra-low field MRI, which uses magnetic fields that are thousands of times lower than the standard machines currently in use. This would open the door for MRI technology to become widely available around the world.

"This [magnetic metamaterial] creates a clearer image that may be produced at more than double the speed" of a current MRI scan, says Anderson, a School of Medicine professor of radiology and vice chairman of research in Boston Medical Center's radiology department.

MRI uses magnetic fields and radio waves to create images of organs and tissues in the human body, helping doctors diagnose potential problems or diseases. Doctors use MRI to identify abnormalities or diseases in vital organs, as well as many other types of body tissue, including the spinal cord and joints. "[MRI] is one of the most complex systems invented by human beings," says Zhang, a College of Engineering professor of mechanical engineering, electrical and computer engineering, biomedical engineering, materials science and engineering, and a professor at the Photonics Center.

Depending on what part of the body is being analyzed and how many images are required, an MRI scan can take up to an hour or more. Patients can face long wait times when scheduling an examination and, for the healthcare system, operating the machines is time-consuming and costly. Strengthening MRI from 1.5 T (the symbol for tesla, the measurement for magnetic field strength) to 7.0 T can definitely "turn up the volume" of images, as Anderson and Zhang describe. But although higher-power MRIs can be done using stronger magnetic fields, they come with a host of safety risks and even higher costs to medical clinics. The magnetic field of an MRI machine is so strong that chairs and objects from across the room can be sucked toward the machine--posing dangers to operators and patients alike.

The magnetic metamaterial designed by the Boston University researchers is made up of an array of units called helical resonators--three-centimeter-tall structures created from 3-D-printed plastic and coils of thin copper wire--materials that aren't too fancy on their own. But put together, helical resonators can be grouped in a flexible array, pliable enough to cover a person's kneecap, abdomen, head, or any part of the body in need of imaging. When the array is placed near the body, the resonators interact with the magnetic field of the machine, boosting the signal-to-noise ratio (SNR) of the MRI, "turning up the volume of the image" as Anderson says.

"A lot of people are surprised by its simplicity," says Zhang. "It's not some magic material. The 'magical' part is the design and the idea."

To test the magnetic array, the team scanned chicken legs, tomatoes, and grapes using a 1.5 T machine. They found that the magnetic metamaterial yielded a 4.2 fold increase in the SNR, a radical improvement, which could mean that lower magnetic fields could be used to take clearer images than currently possible.

Now, Zhang and Anderson hope to partner with industry collaborators so that their magnetic metamaterial can be smoothly adapted for real-world clinical applications.

"If you are able to deliver something that can increase SNR by a significant margin, we can start to think about possibilities that didn't exist before," says Anderson, such as the possibility of having MRI near battlefields or in other remote locations. "Being able to simplify this advanced technology is very appealing," he says.

A team of researchers from the NYU Silver School of Social Work has found that bureaucratic barriers rather than personal intransigence lead many street homeless people in New York City to refuse outreach workers' offers of shelter.

The qualitative study of 43 people living unsheltered in Manhattan was led by Silver School Professor Deborah Padgett with the assistance of PhD student Lynden Bond, MSW student Anna Nathanson (a May '19 graduate of the school), and research assistant Christina Wusinich of the non-profit homeless advocacy organization Human.nyc. For the past three years, Padgett has been working closely with Human.nyc, which was founded by alumni from NYU's Stern School of Business.

For six months beginning in September 2017, members of Padgett's team randomly sampled and interviewed 33 men and 10 women living on the streets in Manhattan neighborhoods with high concentrations of street homelessness. Interviewers asked participants about barriers they faced in obtaining housing and accessing services, their interactions with outreach workers, and any experiences with the New York City shelter system.

When New York City announced expanded homeless outreach efforts in January 2018, Mayor Bill de Blasio said, "It can take dozens or more contacts to convince homeless New Yorkers to come in off the streets and into permanent housing." In fact, Padgett said, "Our research indicates that if people were really being offered permanent housing, they would take it without hesitation. The allure of living on the streets is a myth."

Dr. Padgett, who is the co-lead of the Grand Challenges for Social Work's End Homelessness Challenge, noted that the process of gaining access to permanent housing is lengthy and confusing. As illustrated on the Human.nyc website, eligibility is dependent on being seen bedded down in the same location multiple times by outreach teams and living on the streets for at least nine months. Gathering all the required documentation, such as a birth certificate, can be time-consuming and costly, delaying a move forward in the housing process. Once a person is deemed eligible, the search for transitional or permanent housing can take months or years due to a scarcity of available units in a market where supply is exceeded by demand.

Unsurprisingly, many study participants were left frustrated and uncertain about their future. These barriers are exacerbated by their reasonable aversion to shelters seen as over-crowded and unsafe. "In the process of trying to secure safe, permanent housing there is almost no light at the end of the tunnel and little to be gained by cooperation when the results are so disappointing. In this context, homeless people are not 'service resistant,' they are rational actors all too familiar with un-kept promises," Padgett said.

The researchers found other barriers, including the exclusion of pets from city shelters and a lack of accommodations for homeless people with physical disabilities. "Given the prevalence of disabilities and complex healthcare needs among people living on the street, it is shocking how few options are open to them, leaving them no alternative to a hospital emergency room," said Professor Padgett.

Study participants told the researchers that they survived by using soup kitchens, drop-in centers and panhandling. Their safety was most at risk at night, leading many to seek out the subways or busy areas where they might be left alone. Simple daily tasks such as bathing and using a toilet remained major challenges and theft of their belongings was a constant risk. Passersby could be exceedingly generous or hostile--living outdoors left them vulnerable at all times.

Findings from the NYU Silver study were vividly illustrated by 40 videotaped testimonials Human.nyc gathered from people living unsheltered across the five boroughs. Co-Founder Josh Dean, who earned his BS at NYU Stern in 2016, said, "New York City leaders say their goal is to reduce street homelessness, but the city's own process makes it remarkably difficult for street homeless New Yorkers to secure housing. For those who understandably avoid shelters, the best case scenario is moving into transitional housing after nine months, but even that timeline is rarely met. We believe that we can do better for our fellow New Yorkers."

Human.nyc, recently proposed ways to expedite the street-to-home journey. Their recommendations include streamlining the process to secure case management services, maximizing the usage of faith-based respite sites, designating a number of shelter and transitional housing sites as pet-friendly, and strengthening initiatives to increase permanent affordable and supportive housing.

The organization's recommendations align with Dr. Padgett's advocacy for the evidence-based "Housing First" approach, which rejects prerequisites and moves homeless individuals directly into permanent housing with support services. Dr. Padgett, who co-authored the book Housing First: Ending Homelessness, Changing Systems and Transforming Lives (2016, Oxford University Press) said, "While smaller, less restrictive safe havens are better than large shelters, the lasting solution is Housing First along with the expansion of affordable housing. HF is a policy priority in the U.S. and many other nations; it is humane and also saves money compared to shelters and other alternatives. Diverting a portion of the $2 billion spent annually by the City's Department of Homeless Services to increased investment in rental assistance and support services could end homelessness for thousands of New Yorkers."

For a copy of the report, or to speak with Deborah Padgett and her co-authors, please contact the NYU Press Officer listed with this release.

Pill testing services at music festivals may be most effective in reducing harm for people trying ecstasy for the first time, but less so for prior users.

The new Edith Cowan University (ECU) research also found:

Experienced ecstasy users are no more knowledgeable than novices when it comes to safe dosage amounts and harmful ingredients.

Festival attendees would be willing to pay an average $12 subsidy to fund pill testing services.

The study led by Dr Ross Hollett, from the School of Arts and Humanities, looked at ecstasy-using intentions following different pill test scenarios to determine the factors that predict subsequent risky behaviour.

Over 250 music festival attendees were presented with three hypothetical pill test scenarios and reported their risk intentions, ecstasy use history and sensation seeking.

"The findings from the study suggest that people who attend a festival and might be looking to try ecstasy for the first time are most cautious after a pill test, regardless of the outcome of the test," Dr Hollett said.

"For prior ecstasy users (60 per cent of the sample), they were only more likely to reduce their harm intentions if the ecstasy contained a toxic contaminant, not if the test revealed a high dose or an inconclusive result.

"This finding is important because some of the recent ecstasy-related deaths at festivals in Australia have been linked to high doses of ecstasy," Dr Hollett said.

"Additionally, if the participant was a prior ecstasy user who was also high in sensation seeking, then they were at the greatest risk of harm, even after participating in the pill test," he said.

More education needed

Dr Hollett said introducing counselling and drug education services alongside formal pill testing could further reduce the risk of harm.

"People who had previously used ecstasy were no more knowledgeable than people who had never used ecstasy in terms of sensible doses and harmful contaminants," he said.

Festival attendees in favour of pill testing

Festival attendees surveyed indicated they would be willing to pay $12 on average to support the provision of pill testing services.

"Almost 50 per cent of ecstasy users reported they did not know or trust their supplier.

"These findings suggest that the provision of a pill checking service would greatly improve some people's ability to manage risk," Dr Hollett said.

Trichoplax is one of the simplest animals one can imagine, and looks like a shapeless little blob. Senior author Nicole Dubilier says it reminds her of a potato chip. Trichoplax lives in warm coastal waters around the world, where it grazes on microscopic algae that cover sand and rocks. Although most aquarists may not know it, Trichoplax can also be found in almost any saltwater aquarium with corals.

Trichoplax, together with sponges and jellyfish, belongs to one of the most basal lineages of the animal kingdom. Until the 70ies, it was not even clear if Trichoplax is a proper, fully-grown animal or just the juvenile stage of a jellyfish. Only about a half a millimetre in diameter, these animals lack a mouth, gut and any other organs, and are made up of only six different kinds of cells. Its simplicity makes it a popular model organism for biologists.

Scientists from the Max Planck Institute for Marine Microbiology in Bremen, Germany, the University of Hawaii and North Carolina State University have now discovered that Trichoplax is not as simple as it looks. It lives in a remarkably sophisticated symbiosis with highly unusual bacteria.

Simple is beautiful

The first observation of bacteria in Trichoplax was nearly 50 years ago by the German zoologist Karl Grell. But no one has really taken a closer look since then. An international group of scientists around Harald Gruber-Vodicka, Niko Leisch and Nicole Dubilier from the Max Planck Institute for Marine Microbiology, and Michael Hadfield from the University of Hawaii have now investigated the bacterial tenants of Trichoplax by sequencing their genomes and using high-resolution microscopy to see where they live. "Despite being so simple, Trichoplax harbors two very different and highly unusual bacterial symbionts in its cells," says Gruber-Vodicka. "Both symbionts are very picky - or cell-specific, as we call it. Each symbiont lives in only one type of host cell."

Grellia - the first known symbiont to live in the endoplasmic reticulum

One symbiont, named Grellia after the zoologist Karl Grell, lives inside the endoplasmic reticulum (ER) of Trichoplax, and is the first symbiont known to permanently live in an animal's ER. The ER plays a central role in protein and membrane production. Proving that Grellia is truly in the ER was challenging. "We reconstructed a detailed three-dimensional model of the ER to show that Grellia lives inside of it, supported by the electron microscopy facility of the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden," Niko Leisch explains. "Other parasitic bacteria imitate the structure of the ER to trick the hosts into thinking they are not harmful. However, our imaging data clearly showed that Grellia lives inside its host's ER." Intriguingly, Grellia, although closely related to parasites, doesn't appear to be harmful for Trichoplax. "Although it has genes that would allow it to steal energy from its host, it does not use them," Leisch continues.

Ruthmannia - seeing microbial dark matter

The second symbiont of Trichoplax, Ruthmannia, belongs to a group of bacteria that were only recently discovered, the Margulisbacteria. "Before our study, Margulisbacteria were part of the so-called microbial dark matter - the vast majority of microbial organisms that biologists find through sequencing, but are unable to culture," explains Harald Gruber-Vodicka. "We have never actually seen them, even though their genetic traces were found in aquatic samples all over the globe." Now Gruber-Vodicka and Leisch took the first images of a Margulisbacteria. "It's the first time we could see a member of this group. For us, observing this microbial dark matter was just as exciting as imaging black holes." This symbiont lives in cells that Trichoplax uses to digest its algal food. "Ruthmannia appears to only eat the fats and other lipids of the algae, and leaves the rest to its host. In return, we think Ruthmannia may provide Trichoplax with vitamins and amino acids." With Trichoplax thriving in the lab cellars of the Max Planck Institute for Marine Microbiology, the authors now have continuous access to this enigmatic group of bacteria.

What's next

"In this study, we focused on the symbiotic partners of a single Trichoplax species," says Nicole Dubilier, Director at the Max Planck Institute for Marine Microbiology. "However, at least 20 more species have been described, and our first results indicate that each host species has its own, very specific set of symbionts. We are excited about taking a closer look at this remarkable diversity and how it evolved. These tiny animals not only look like potato chips, they also pack a crunch when it comes to what's inside them."

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Plant scientists at the Universities of Cambridge and Bordeaux have discovered a gene that they hope can be used to widen a nutrient trafficking bottleneck and potentially increase crop yields.

Plant scientists around the world are working on a number of different strategies to sustainably increase crop yields. Increasing the efficiency of how plants transport sugars, proteins and other organic nutrients between different parts of the plant is one of the approaches that could contribute to this next Green Revolution.

Having an understanding of factors that affect local and long distance transport within a plant could enable plant biotechnologists to breed more productive crops in the future. Ultimately, it might be possible to direct transport of organic nutrients to specific parts of the plant that are harvested (seeds, fruits and storage tubers).

Professor Yrjö Helariutta's research team at the Sainsbury Laboratory Cambridge University (SLCU) and Dr Emmanuelle Bayer's team at the University of Bordeaux/CNRS have brought this goal a step closer by discovering Phloem Unloading Modulator (PLM), a novel gene that affects nutrient trafficking by altering the channels connecting neighbouring plant cells called plasmodesmata. These nanoscale membrane-lined channels traverse the cell wall barrier to link plant cells together and enable the transfer of essential substances (see notes).

The study, published today in Nature Plants, shows that Arabidopsis thaliana mutant plants missing the PLM gene were found to release more substances from the phloem (a specialised tissue for long distance transport) at the tips of their roots. Using a fluorescent protein as a proxy for macromolecules, the scientists could see that the PLM gene was having a clear controlling effect on the amount of phloem unloading. To find out how the gene was doing this, they looked at what was happening at different cell interfaces in the roots of seedling plants.

Lead author, Dr Dawei Yan, from Cambridge's Sainsbury Laboratory, explains: "We found that mutating PLM relieves a trafficking bottleneck, that was previously reducing the outward movement of nutrients from the vascular system to the rapidly growing tissues in the roots.

PLM is specifically acting at the interface between the phloem pole pericycle (PPP) and endodermal cells, an interface important for the radial movement of substances after unloading. Removing PLM gene activity could enable plants to more rapidly and efficiently transport nutrients to where they are needed."

As a result of the increased unloading, the roots in the mutant plants grew faster and longer.

Further molecular and genetic investigations also revealed that PLM is involved in the biosynthesis of sphingolipids, which are a class of lipids associated with plant development and response to environment. While Dr Bayer's team had previously shown that the membranes of plasmodesmata are enriched with sphingolipids, this is the first study to link sphingolipids to plasmodesmata function.

The next step was to determine how PLM was affecting cell-to-cell conductivity. The team looked at whether PLM was influencing plasmodesmata density - it wasn't. The team also confirmed that PLM was not modifying callose accumulation, which was the only well-known regulator of plasmodesmata permeability.

Second author and PhD student in the Helariutta group, Andrea Paterlini, went to France to work with Dr Bayer to take a closer look at whether PLM was instead affecting the plasmodesmata structure. They used electron tomography to create a 3D map of the channels at the nanometre scale.

Paterlini says: "This allowed us to detect fine alterations to the plasmodesmal architecture. We found equal proportions of simple and branched plasmodesmata in both the plm mutant and wild type plants. However, plants without PLM only had Type I plasmodesmata (see notes), rather than the two types normally found.

"Previous models have assumed that the size of the cytoplasmic sleeve (the spacing between endoplasmic reticulum and plasma membranes in plasmodesmata) would positively correlate with transport capacity. The results of our paper challenge this and show that Type I plasmodesmata, those with a very narrow cytoplasmic sleeve, are actually more conductive than Type II plasmodesmata, which have an open cytoplasmic sleeve."

Professor Helariutta says: "The correlation between the gene function (lipid biosynthesis) and the alteration in plasmodesmata ultrastructure is likely to be the result of a defect in the organisation of the tethers that separate the plasma membrane from the endoplasmic reticulum within plasmodesmata: This results in the majority of the plasmodesmata lacking visible cytoplasmic sleeves in the plants with a mutated PLM gene.

"There are still many new questions to be answered for future research, such as, how and why plasmodesmata that lack cytoplasmic sleeves have higher rates of trafficking and how the metabolism of sphingolipids is mechanistically related to the function of PLM.

"However, this research has advanced our understanding of the factors regulating plant nutrient transport. There is an urgent need to develop crops with increased nutrient efficiency, both to reduce the use of fertilisers and to increase the yield of crops. We may eventually be able to use this information about nutrient transport to more efficiently partition nutrients between various organs and direct nutrients from stems and leaves to fruit and storage organs."