Hexbyte Glen Cove Image: Hubble revisits the Veil Nebula thumbnail

Hexbyte Glen Cove Image: Hubble revisits the Veil Nebula

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Credit: ESA/Hubble & NASA, Z. Levay

This image taken by the NASA/ESA Hubble Space Telescope revisits the Veil Nebula, which was featured in a previous Hubble image release. In this image, new processing techniques have been applied, bringing out fine details of the nebula’s delicate threads and filaments of ionized gas.

To create this colorful image, observations were taken by Hubble’s Wide Field Camera 3 instrument using five different filters. The new post-processing methods have further enhanced details of emissions from doubly ionized oxygen (seen here in blues), ionized hydrogen, and ionized nitrogen (seen here in reds).

The Veil Nebula lies around 2,100 light-years from Earth in the constellation of Cygnus (the Swan), making it a relatively close neighbor in astronomical terms. Only a small portion of the was captured in this image.

The Veil Nebula is the visible portion of the nearby Cygnus Loop, a supernova remnant formed roughly 10,000 years ago by the death of a massive star. That star—which was 20 times the mass of the Sun—lived fast and died young, ending its life in a cataclysmic release of energy. Despite this stellar violence, the shockwaves and debris from the supernova sculpted the Veil Nebula’s delicate tracery of ionized gas—creating a scene of surprising astronomical beauty.

The Veil Nebula is also featured in Hubble’s Caldwell Catalog, a collection of astronomical objects that have been imaged by Hubble and are visible to amateur astronomers in the night sky.



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Image: Hubble revisits the Veil Nebula (2021, April 2)
retrieved 3 April 2021
from https://phys.org/news/2021-04-image-hubble-revisits-veil-nebula.html

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Hexbyte Glen Cove Serving size, satisfaction influence food waste on campus thumbnail

Hexbyte Glen Cove Serving size, satisfaction influence food waste on campus

Hexbyte Glen Cove

Credit: Unsplash/CC0 Public Domain

Understanding what drives food choices can help high-volume food service operations like universities reduce waste, according to a new study.

Researchers have concluded that in places like university cafeterias is driven by how much people put on their plates, how familiar they are with what’s on the menu and how much they like—or don’t like—what they’re served.

Food waste has been studied often in households, but not so often in institutional settings like university dining commons. What drives food choices in these “all-you-care-to-eat” facilities is different because diners don’t perceive personal financial penalty if they leave food on their plates.

Published in the journal Foods, “Food Choice and Waste in University Dining Commons—A Menus of Change University Research Collaborative Study” was conducted by a team of experts from Rice University; the University of California, Davis; Stanford University; Lebanon Valley College; the University of California, Santa Barbara; and the University of California, Berkeley.

Co-author Eleanor Putnam-Farr, assistant marketing professor at Rice’s Jones Graduate School of Business, is available to discuss the findings and potential impact with .

The researchers conducted student surveys during the 2019 spring and fall semesters to study foods types, diner confidence and satisfaction. They used photos taken by diners themselves before and after eating to measure how much food was taken and how much of it went to waste. “Diners were intercepted at their dining halls and asked if they wanted to participate in a study about and satisfaction, but the objective of investigating food waste behavior was not disclosed,” the authors wrote.

The study found the amount of food wasted didn’t significantly differ among types of food. Instead, researchers discovered waste was related to the amount of food diners put on their plates, how satisfied they were with their meals and how often they went to the dining commons. If students were satisfied with their food, they tended waste less of it. And diners who visited the commons most often—making them more familiar with the menus and more confident in their choices—tended to waste less.

Mixed dishes, like sandwiches or stir-fry, took up a greater percentage of the surface area on surveyed plates than animal proteins or grains and starches. Those three types of food took up a greater area of the plates than fruits, vegetables or plant proteins. The amount of food wasted, however, did not significantly differ among the various food categories.

The mixed dishes and animal proteins that took up greater portions of the tended to be pre-plated by the commons staff or have a suggested serving size. The study’s results showed that greater amounts of food taken by diners correlated with the item being pre-plated or served by others.

The authors recommend future research on the topic uses their multicampus approach—which enabled them to study food choice among a large and diverse group—to better understand what causes and find out if it can be reduced by interventions such as posting signs that encourage healthier choices.



More information:
Tiffany Wiriyaphanich et al. Food Choice and Waste in University Dining Commons—A Menus of Change University Research Collaborative Study, Foods (2021). DOI: 10.3390/foods10030577

Citation:
Serving size, satisfaction influence food waste on campus (2021, April 2)
retrieved 3 April 2021
from https://phys.org/news/2021-04-size-satisfaction-food-campus.html

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Hexbyte Glen Cove From stardust to pale blue dot: Carbon's interstellar journey to Earth thumbnail

Hexbyte Glen Cove From stardust to pale blue dot: Carbon’s interstellar journey to Earth

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Credit: Unsplash/CC0 Public Domain

We are made of stardust, the saying goes, and a pair of studies including University of Michigan research finds that may be more true than we previously thought.

The first study, led by U-M researcher Jie (Jackie) Li and published in Science Advances, finds that most of the on Earth was likely delivered from the interstellar medium, the material that exists in space between stars in a galaxy. This likely happened well after the , the cloud of dust and gas that circled our young sun and contained the building blocks of the planets, formed and warmed up.

Carbon was also likely sequestered into solids within one million years of the sun’s birth—which means that carbon, the backbone of life on , survived an interstellar journey to our planet.

Previously, researchers thought carbon in the Earth came from molecules that were initially present in nebular gas, which then accreted into a when the gases were cool enough for the molecules to precipitate. Li and her team, which includes U-M astronomer Edwin Bergin, Geoffrey Blake of the California Institute of Technology, Fred Ciesla of the University of Chicago and Marc Hirschmann of the University of Minnesota, point out in this study that the gas molecules that carry carbon wouldn’t be available to build the Earth because once carbon vaporizes, it does not condense back into a solid.

“The condensation model has been widely used for decades. It assumes that during the formation of the sun, all of the planet’s elements got vaporized, and as the disk cooled, some of these gases condensed and supplied chemical ingredients to solid bodies. But that doesn’t work for carbon,” said Li, a professor in the U-M Department of Earth and Environmental Sciences.

Much of carbon was delivered to the disk in the form of organic molecules. However, when carbon is vaporized, it produces much more volatile species that require very low temperatures to form solids. More importantly, carbon does not condense back again into an organic form. Because of this, Li and her team inferred most of Earth’s carbon was likely inherited directly from the , avoiding vaporization entirely.

To better understand how Earth acquired its carbon, Li estimated the maximum amount of carbon Earth could contain. To do this, she compared how quickly a seismic wave travels through the core to the known sound velocities of the core. This told the researchers that carbon likely makes up less than half a percent of Earth’s mass. Understanding the upper bounds of how much carbon the Earth might contain tells the researchers information about when the carbon might have been delivered here.

“We asked a different question: We asked how much carbon could you stuff in the Earth’s core and still be consistent with all the constraints,” Bergin said, professor and chair of the U-M Department of Astronomy. “There’s uncertainty here. Let’s embrace the uncertainty to ask what are the true upper bounds for how much carbon is very deep in the Earth, and that will tell us the true landscape we’re within.”

A planet’s carbon must exist in the right proportion to support life as we know it. Too much carbon, and the Earth’s atmosphere would be like Venus, trapping heat from the sun and maintaining a temperature of about 880 degrees Fahrenheit. Too little carbon, and Earth would resemble Mars: an inhospitable place unable to support water-based life, with temperatures around minus 60.

In a second study by the same group of authors, but led by Hirschmann of the University of Minnesota, the researchers looked at how carbon is processed when the small precursors of planets, known as planetesimals, retain carbon during their early formation. By examining the metallic cores of these bodies, now preserved as iron meteorites, they found that during this key step of planetary origin, much of the carbon must be lost as the planetesimals melt, form cores and lose gas. This upends previous thinking, Hirschmann says.

“Most models have the carbon and other life-essential materials such as water and nitrogen going from the nebula into primitive rocky bodies, and these are then delivered to growing planets such as Earth or Mars,” said Hirschmann, professor of earth and environmental sciences. “But this skips a key step, in which the planetesimals lose much of their carbon before they accrete to the planets.”

Hirschmann’s study was recently published in Proceedings of the National Academy of Sciences.

“The planet needs carbon to regulate its climate and allow life to exist, but it’s a very delicate thing,” Bergin said. “You don’t want to have too little, but you don’t want to have too much.”

Bergin says the two studies both describe two different aspects of carbon loss—and suggest that carbon loss appears to be a central aspect in constructing the Earth as a habitable planet.

“Answering whether or not Earth-like planets exist elsewhere can only be achieved by working at the intersection of disciplines like astronomy and geochemistry,” said Ciesla, a U. of C. professor of geophysical sciences. “While approaches and the specific questions that researchers work to answer differ across the fields, building a coherent story requires identifying topics of mutual interest and finding ways to bridge the intellectual gaps between them. Doing so is challenging, but the effort is both stimulating and rewarding.”

Blake, a co-author on both studies and a Caltech professor of cosmochemistry and planetary science, and of chemistry, says this kind of interdisciplinary work is critical.

“Over the history of our galaxy alone, rocky like the Earth or a bit larger have been assembled hundreds of millions of times around stars like the Sun,” he said. “Can we extend this work to examine carbon loss in planetary systems more broadly? Such research will take a diverse community of scholars.”



More information:
“Earth’s carbon deficit caused by early loss through irreversible sublimation” Science Advances (2021). advances.sciencemag.org/lookup … .1126/sciadv.abd3632

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Hexbyte Glen Cove 2D materials combine, becoming polarized and giving rise to photovoltaic effect thumbnail

Hexbyte Glen Cove 2D materials combine, becoming polarized and giving rise to photovoltaic effect

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Tungsten selenide (WSe2) and black phosphorus (BP) do not exhibit polarized electronic behavior until combined such that their structures overlap. Credit: ©2021 Ideue et al.

For the first time, researchers have discovered a way to obtain polarity and photovoltaic behavior from certain nonphotovoltaic, atomically flat (2D) materials. The key lies in the special way in which the materials are arranged. The resulting effect is different from, and potentially superior to, the photovoltaic effect commonly found in solar cells.

Solar power is considered a key technology in the move away from fossil fuels. Researchers continually innovate more efficient means to generate solar energy. And many of these innovations come from the world of research. Research Associate Toshiya Ideue from the University of Tokyo’s Department of Applied Physics and his team are interested in the photovoltaic properties of 2D materials and their interfaces where these materials meet.

“Quite often, interfaces of multiple 2D materials exhibit different properties to the individual crystals alone,” said Ideue. “We have discovered that two specific materials which ordinarily exhibit no do so when stacked in a very particular way.”

The two materials are tungsten selenide (WSe2) and black phosphorus (BP), both of which have different crystal structures. Originally, both materials are nonpolar (do not have a preferred direction of conduction) and do not generate a photocurrent under light. However, Ideue and his team found that by stacking sheets of WSe2 and BP together in the right way, the sample exhibited polarization, and when a light was cast on the material, it generated a current. The effect takes place even if the area of illumination is far from the electrodes at either end of the sample; this is different from how the ordinary effect works.

Under laser illumination, the layered material generates a current. Credit: ©2021 Ideue et al.

Key to this behavior is the way the WSe2 and BP are aligned. The crystalline structure of BP has reflective, or mirror, symmetry in one plane, whereas WSe2 has three lines of mirror symmetry. When the symmetry lines of the materials align, the sample gains polarity. This kind of layer stacking is delicate work, but it also reveals to researchers new properties and functions that could not be predicted just by looking at the ordinary form of the materials.

“The biggest challenge for us will be to find a good combination of 2D materials with higher electric-generation efficiency and also to study the effect of changing the angles of the stacks,” said Ideue. “But it’s so rewarding to discover never-before-seen emergent properties of materials. Hopefully, one day this research could improve solar panels. We would like to explore more unprecedented properties and functionalities in nanomaterials.”

The study is published in Science.



More information:
A van der Waals interface that creates in-plane polarization and a spontaneous photovoltaic effect. Science, science.sciencemag.org/cgi/doi … 1126/science.aaz9146

Citation:
2D materials combine, becoming polarized and giving rise to photovoltaic effect (2021, April 1)
retrieved 1 April 2021
from https://phys.org/news/2021-04-2d-materials-combine-polarized-photovoltaic.html

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part may be reproduced without the written permission. The content is provided for information purposes only.

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Hexbyte Glen Cove Increasing applied pesticide toxicity threatens bees and marine life thumbnail

Hexbyte Glen Cove Increasing applied pesticide toxicity threatens bees and marine life

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In this July 16, 2014, file photo, a bee works on a honeycomb at an apiary in central California. A study published in the journal Science on Thursday, April 1, 2021 finds that farmers in the U.S. are using smaller amounts of better targeted pesticides, but these are harming pollinators, aquatic insects and some plants far more than decades ago. (AP Photo/Marcio Jose Sanchez, File)

American farmers are using smaller amounts of better targeted pesticides, but these are harming pollinators, aquatic insects and some plants far more than decades ago, a new study finds.

Toxicity levels have more than doubled since 2005 for important species, including honeybees, mayflies and buttercup flowers, as the country switched to a new generation of pesticides. But dangerous chemical levels in birds and mammals have plummeted at the same time, according to a paper in Thursday’s journal Science.

“The bottom line is that these pesticides, once believed to be relatively benign and so short-lived that they would not damage ecosystems, are anything but,” said Dr. Lynn Goldman, a former U.S. Environmental Protection Agency assistant administrator for toxic substances who wasn’t part of the study and is now dean of George Washington University’s school of public health

German scientists examined 381 pesticides used in the United States between 1992 and 2016, combining EPA data that calculates toxic dosage effects for eight types of animals and plants with U.S. Geological Survey data on how much of the chemicals were used year by year for dozens of agricultural crops. The scientists calculated a new measurement they call total applied toxicity for the eight groupings of species and trends over time.

“Very often politicians, media, scientists just talk about amounts. They always argue ‘OK, the amount pesticides we use is reduced so things are getting better’ and this is not necessarily true,” said lead author Ralf Schulz, a professor of environmental sciences at the University of Kolenz-Landau. “It’s sometimes true, but not always,”

In this Aug. 4, 2009 file photo, a crop duster sprays a field in Alabama. A study published in the journal Science on Thursday, April 1, 2021 finds that farmers in the U.S. are using smaller amounts of better targeted pesticides, but these are harming pollinators, aquatic insects and some plants far more than decades ago. (AP Photo/Dave Martin, File)

Industry keeps developing new pesticides and “very often these new compounds are more toxic,” Schulz said. They include neonicotinoids, which have been connected to one of the many causes of dwindling honeybee numbers.

The newer pesticides are aimed more toward animals without backbones to spare birds and mammals, but this means insects such as pollinators get poisoned, Schulz said.

The same goes for some land plants and for aquatic invertebrates including dragonflies and mayflies, which birds and mammals eat, he said, adding that future studies should look at the harm higher up the food chain.

Chris Novak, president of the pesticide industry group CropLife America, said in an email that “it is critical to note that the study found great reductions in acute toxicity have been achieved for humans and mammals over the past few decades.”

Novak noted pesticides go through extensive studies and “only one in 10,000 discoveries make the 11-year journey from the lab to the market.”

It’s not surprising that newer generations of pesticides generally are more harmful to insects, which are undergoing a massive decline for many reasons, said University of Connecticut entomologist David Wagner, who wasn’t part of the study. But Wagner said this newest research doesn’t provide data needed to show “that pesticides are the major driver of insect declines.”



More information:
R. Schulz el al., “Applied pesticide toxicity shifts toward plants and invertebrates, even in GM crops,” Science (2021). science.sciencemag.org/cgi/doi … 1126/science.abe1148

© 2021 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed without permission.

Citation:
Study: US pesticide use falls but harms pollinators more (2021, April 1)
retrieved 1 April 2021
from https://phys.org/news/2021-04-pesticide-toxicity-threatens-bees-marine.html

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Hexbyte Glen Cove Physicists observe new phase in Bose-Einstein condensate of light particles thumbnail

Hexbyte Glen Cove Physicists observe new phase in Bose-Einstein condensate of light particles

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On the right is a microscope objective used to observe and analyze the light emerging from the resonator. Credit: © Gregor Hübl/Uni Bonn

About 10 years ago, researchers at the University of Bonn produced an extreme aggregate photon state, a single “super-photon” made up of many thousands of individual light particles, and presented a completely new light source. The state is called an optical Bose-Einstein condensate and has captivated many physicists ever since, because this exotic world of light particles is home to its very own physical phenomena. Researchers led by Prof. Dr. Martin Weitz, who discovered the super photon, and theoretical physicist Prof. Dr. Johann Kroha now report a new observation: a so-called overdamped phase, a previously unknown phase transition within the optical Bose-Einstein condensate. The study has been published in the journal Science.

The Bose-Einstein is an extreme physical state that usually only occurs at very low temperatures. The particles in this system are no longer distinguishable and are predominantly in the same quantum mechanical state; in other words, they behave like a single giant “superparticle.” The state can therefore be described by a single wave function.

In 2010, researchers led by Martin Weitz succeeded for the first time in creating a Bose-Einstein condensate from particles (photons). Their special system is still in use today: Physicists trap light particles in a resonator made of two curved mirrors spaced just over a micrometer apart that reflect a rapidly reciprocating beam of light. The space is filled with a liquid dye solution, which serves to cool down the photons. The dye molecules “swallow” the photons and then spit them out again, which brings the light particles to the temperature of the dye solution—equivalent to room temperature. The system makes it possible to cool light particles because their natural characteristic is to dissolve when cooled.

Credit: Gregor Hübl/Uni Bonn

Clear separation of two phases

A phase transition is what physicists call the transition between water and ice during freezing. But how does the particular phase transition occur within the system of trapped light particles? The scientists explain it this way: The somewhat translucent mirrors cause photons to be lost and replaced, creating a non-equilibrium that results in the system not assuming a definite temperature and being set into oscillation. This creates a transition between this oscillating phase and a damped phase. Damped means that the amplitude of the vibration decreases.

“The overdamped phase we observed corresponds to a new state of the light field, so to speak,” says lead author Fahri Emre Öztürk, a doctoral student at the Institute for Applied Physics at the University of Bonn. The special characteristic is that the effect of the laser is usually not separated from that of Bose-Einstein condensate by a phase transition, and there is no sharply defined boundary between the two states. This means that physicists can continually move back and forth between effects.

“However, in our experiment, the overdamped state of the optical Bose-Einstein condensate is separated by a phase transition from both the oscillating state and a standard laser,” says study leader Prof. Dr. Martin Weitz. “This shows that there is a Bose-Einstein condensate, which is really a different state than the standard laser. “In other words, we are dealing with two separate phases of the optical Bose-Einstein condensate,” he says.

The researchers plan to use their findings as a basis for further studies to search for new states of the light field in multiple coupled light condensates, which can also occur in the system. “If suitable quantum mechanically entangled states occur in coupled light condensates, this may be interesting for transmitting quantum-encrypted messages between multiple participants,” says Fahri Emre Öztürk.



More information:
“Observation of a non-Hermitian phase transition in an optical quantum gas” Science (2021). science.sciencemag.org/cgi/doi … 1126/science.abe9869

Citation:
Physicists observe new phase in Bose-Einstein condensate of light particles (2021, April 1)
retrieved 1 April 2021
from https://phys.org/news/2021-04-physicists-phase-bose-einstein-condensate-particles.html

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