Earth

According to the Intergovernmental Panel on Climate Change (IPCC), addressing carbon emissions from our food sector is absolutely essential to combatting climate change. While land and agriculture took center stage in the panel's most recent report, missing was how the oceans at large could help in that fight.

Seaweed, perceived by some as little more than marine debris on the beach, could be a new player in the effort to mitigate climate change. So say researchers at UC Santa Barbara, who investigated the carbon offsetting potential of seaweed aquaculture.

"It's not a silver bullet, nor an industry that exists yet," said Halley Froehlich, an assistant professor in the Department of Environmental Studies and in the Department of Ecology, Evolution and Marine Biology. "But it has huge potential." Froehlich is lead author of a first-ever global assessment of seaweed aquaculture's carbon sequestration scaling potential, which appears in Current Biology.

According to Froehlich and co-authors Jamie Afferbach, Melanie Frazier and Benjamin Halpern from the National Center for Ecological Analysis and Synthesis, who synthesized diverse datasets from scientific literature, seaweed aquaculture could indeed be a powerful new way to sequester carbon. The process would involve cultivating seaweed and harvesting it for the purpose of sinking the algae in the deeper ocean, where the carbon stored in its tissues would remain 'buried.'

"We really wanted to know if it could be beneficial, but also be realistic about its potential," Froehlich said of the research, which they bounded with constraints including nutrients, temperature and geographic suitability, as well as assessed production growth and cost. The researchers also investigated the mitigation potential on various scales with a focus on the food sector -- a major source of greenhouse gases and considerable hurdle to fight climate change.

There is substantial suitable area -- roughly 48 million square kilometers -- in which seaweed could be farmed, and a relatively small proportion (0.001%) would be enough to render the entire global aquaculture industry carbon neutral, according to the study.

However, the benefits don't scale proportionally against the much higher greenhouse gas-emitting global agricultural sector, in part due to cost and growth constraints, Froehlich said. Farming seaweed alone won't balance emissions from global food production, she added, but could be a useful new tool in a suite that includes other carbon reduction and offset measures such as cleaner sources of energy, reforestation and protection of carbon sinks.

Greenhouse gas-mitigating seaweed farming could have the most potential when it comes to achieving local and regional carbon neutrality goals, the study found. California is particularly well-primed to reap the mitigating benefits of seaweed aquaculture, given the state's strong climate action policy and its long, nutrient-rich coast. An area of only 3.8% of the West Coast Exclusive Economic Zone (a marine zone that extends no more than 200 miles from the coast) would be enough to offset the carbon produced by the state's agriculture sector.

Relative to the rest of the world, U.S. seaweed aquaculture is still somewhat in its infancy.

"The vast majority of seaweed aquaculture occurs in Southeast Asia," Froehlich said. While no measurable seaweed farming was occurring in the United States in 2016 -- the most recent time period of the study -- small seaweed farms are starting to emerge in the U.S., though primarily for food and other commercial purposes, and not for carbon sequestration.

The U.S., meanwhile, is the world's second-biggest emitter of greenhouse gases, Froehlich pointed out, underscoring the need for solutions such as seaweed farming to mitigate the millions of tons of carbon dioxide equivalents the country emits per year. Fortunately, seaweed farming has other appealing and beneficial environmental effects, she noted.

"We like to call it 'charismatic carbon' because it has additional benefits," Froehlich said, "such as potentially providing habitat for fish and other marine life, reducing ocean acidification and oxygen depletion, and taking up excess nutrients in local areas."

Seaweed cultivation's beneficial climate effects far outweigh the fact that it can't completely offset the country's food production greenhouse gas emissions. In fact, according to co-author Halpern, there is not -- and never will be -- a single tool for dealing with climate change.

"The problem has become too big for simple solutions," he said. "We need all hands on deck." While solutions to climate change will not be easy, he added, the more strategies, the better.

"The huge advantage is that if we can actually deploy many different strategies -- from seaweed farming to renewable energy to energy efficiency and others -- the solution is more resilient," Halpern said.

To make it a real option in the United States, policy would need to enable and accelerate seaweed cultivation for carbon sequestration, farmers would need to respond by dramatically scaling up production and the carbon market would need to expand to offer higher prices.

In the meantime, research will continue to investigate seaweed cultivation's potential for mitigating climate change.

"My colleagues and I are now assessing other paths seaweed can take to find the 'best bang for your buck' on carbon mitigation," Froehlich said. Given that farmed seaweed is also subject to climate change effects, a better understanding of how it could be affected would greatly inform how it could be cultivated and managed in the long term.

Mathematical modeling suggests that the diversity of interactions between species in an ecological community plays a greater role in maintaining community functioning than previously thought. Vincent Miele of the CNRS in Lyon, France, and colleagues present these findings in PLOS Computational Biology.

Ecologists have long been interested in how species diversity--the number of species found in a given community--affects the functioning of that community. Communities are also diverse in the types of ecological interactions that occur between species, but research on these communities rarely considers these complex interaction networks.

To better understand the significance of interaction diversity, Miele and colleagues employed a mathematical model of an ecological community that incorporates a variety of interaction types, including competition between predators and competition for space between species that are immobile. They used the model to investigate how the abundance and intensity of multiple interactions affects communities.

The analysis showed that when the entire bundle of ecological interactions are considered simultaneously--incorporating feeding, inter-species facilitation, and competitive interactions--their diversity affects the community's diversity of species and overall function. Interaction diversity also strengthens the relationship between species diversity and community functioning compared to situations where only feeding interactions are taken into account.

These findings suggest that removing species from the community has a greater impact on functioning if different kinds of interactions are considered. This also suggests that existing models that ignore the variety of interaction types underestimate the consequences of species losses.

"Our study shows that considering the variety of interaction types matters for understanding how nature functions and predicting how it will respond to global changes," says Sonia Kéfi, corresponding author of the study. "This is especially relevant in a time when many species are considered to be threatened with extinction."

Next, the researchers plan to investigate whether some species play different roles regarding their position in the complex species interplay when considering the variety of interaction types.

DALLAS (SMU) - Humans started making an impact on the global ecosystem through intensive farming much earlier than previously estimated, according to a new study published in the journal Science.

Evidence of the earliest domesticated plants and animals dates back to around 10,000 years ago. But findings from a team of more than 250 archeologists, including two from SMU (Southern Methodist University), show that by 3,000 years ago our ancestors had dramatically changed the world to grow food.

"Our study shows in detail the progression from the origins of agriculture to its spread around the world," said SMU anthropologist Mark D. McCoy. "It turns out that earth science models are probably too conservative, and intensive reshaping of the environment for food production was common by thousands of years before the onset of the kind of industrial scale farming we see today.

"That is important because over the time periods discussed, humans became the major force shaping ecosystems around the world," McCoy said.

The new global assessment by the ArchaeoGLOBE Project also shows that scientists have previously underestimated the impact of early human land use.

Led by archeologist Lucas Stephens, a researcher affiliated with the Max Planck Institute for the Science of Human History, ArchaeoGLOBE used a crowdsourcing approach, inviting experts in ancient land use to contribute to a questionnaire on 146 regions (covering all continents except Antarctica) at ten historical time intervals to assess and integrate archaeological knowledge at a global scale. The result was a complete, though uneven, meta-analysis of global land use over time.

Significantly, the study also reveals that hunting and gathering was more varied and complex than originally thought, helping archeologists to recognize that foragers "may have initiated dramatic and sometimes irreversible environmental change." Intensive forms of agriculture reported around the world included activities like clearing land, creating fields that were fixed on the landscape, raising large herds of animals, and putting increasing amounts of effort into growing food.

SMU anthropologist and ArchaeoGLOBE team member K. Ann Horsburgh notes the rise in agriculture and livestock is primarily due to growing populations needing to be fed.

"Food production such as agriculture and pastoralism, when compared with foraging in the same environment, is linked to a faster population growth and can sustain higher population densities," said Horsburgh.

Horsburgh, Assistant Professor of Anthropology, and McCoy, Associate Professor of Anthropology, provided information on land use in Africa and the remote islands of the Pacific, respectively. McCoy also brought his expertise in geospatial technology to study how people in the past inhabited and shaped the world around them, while Horsburgh brought her knowledge of ancient DNA to retrace the spread of domesticated animals.

The map could provide new light on how the spread of farming and herding were linked to major migrations in human prehistory.

"This is first time that regional expertise on ancient land use has been synthesized on this scale," Horsburgh said. "That matters because we know that although the shift from foraging to farming tends to be a 'one-way' transition, it did not progress the same way around the world. The details of how it did progress has shaped everything from our diets to the languages we speak today."

Horsburgh went on to say, "What remains the topic of intense study is how much of the transition is food producers spreading and displacing foragers, and how much is it foragers adopting or marrying into food producing groups, or some other scenario. Most of this was done in the absence of written records, so it is up to anthropology to sort things out.

"The natural next step for this revised model of the spread of different types, and intensities, of land use is to compare them with human genetics and linguistics and integrate these findings into the big story of humanity," said Horsburgh.

Scientists have created miniature brains from stem cells that developed functional neural networks. Despite being a million times smaller than human brains, these lab-grown brains are the first observed to produce brain waves that resemble those of preterm babies. The study, published August 29 in the journal Cell Stem Cell, could help scientists better understand human brain development.

"The level of neural activity we are seeing is unprecedented in vitro," says Alysson Muotri, a biologist at the University of California, San Diego. "We are one step closer to have a model that can actually generate these early stages of a sophisticated neural network."

The pea-sized brains, called cerebral organoids, are derived from human pluripotent stem cells. By putting them in culture that mimics the environment of brain development, the stem cells differentiate into different types of brain cells and self-organize into a 3D structure resembling the developing human brain.

Scientists have successfully grown organoids with cellular structures similar to those of human brains. However, none of the previous models developed human-like functional neural networks. Networks appear when neurons are mature and become interconnected, and they are essential for most brain activities.

"You can use brain organoids for several things, including understand normal human neurodevelopment, disease modeling, brain evolution, drug screening, and even to inform artificial intelligence," Muotri says.

Muotri and colleagues designed a better procedure to grow stem cells, including optimizing the culture medium formula. These adjustments allowed their organoids to become more mature than previous models. The team grew hundreds of organoids for 10 months and used multi-electrode arrays to monitor their neural activities.

The team began to detect bursts of brain waves from organoids at about two months. The signals were sparse and had the same frequency, a pattern seen in very immature human brains. As the organoids continued to grow, they produced brain waves at different frequencies, and the signals appeared more regularly. This suggests the organoids have further developed their neural networks.

"This is a result of having more functional synapses, and you are forming more connections between the neurons," Muotri says. The interactions between neurons contribute to signals at various frequencies, he says.

To compare the brain wave patterns of organoids with those of human brains early in development, the team trained a machine learning algorithm with brain waves recorded from 39 premature babies between six and nine-and-a-half months old. The algorithm was able to predict how many weeks the organoids have developed in culture, which suggests these organoids and human brain share a similar growth trajectory.

However, it's not likely these organoids have mental activities, such as consciousness, Muotri says. "The organoid is still a very rudimentary model--we don't have other brain parts and structures. So these brain waves might not have anything to do with activities in real brains."

"It might be that in the future, we will get something that is really close to the signals in the human brains that control behaviors, thoughts, or memory," Muotri says. "But I don't think we have any evidence right now to say we have any of those."

Looking forward, the team aims to further improve the organoids and use them to understand diseases associated with neural network malfunctioning, such as autism, epilepsy, and schizophrenia.

"As a scientist, I want to get closer and closer to the human brain," Muotri says. "I want to do that because I see the good in it. I can help people with neurological conditions by giving them better treatments and better quality of life. But it's up to us to decide where the limit is. It might be that the technology is not ready yet, or we don't know how to control the technology. This is the same kind of discussion around CRISPR in babies, and that's why we have ethics committees to represent all parts of the society."

Brain organoids -- also called mini-brains -- are 3D cellular models that represent aspects of the human brain in the laboratory. Brain organoids help researchers track human development, unravel the molecular events that lead to disease and test new treatments. They aren't prefect replicas, of course. Brain organoids do not replicate cognitive function, but researchers can check how an organoid's physical structure or gene expression changes over time or as a result of a virus or drug.

University of California San Diego researchers have now taken brain organoids one step further, achieving an unprecedented level of neural network activity -- electrical impulses that can be recorded by multi-electrode arrays. Using data from babies born up to three-and-a-half months premature, the team developed an algorithm to predict their age based upon EEG patterns. The algorithm then read lab-grown brain organoids the same way, and assigned them an age.

The electrical impulse pattern for nine-month-old brain organoids revealed similar features to those of a premature infant who had reached full-term (40 weeks gestation).

These new optimized brain organoids, described in the August 29, 2019 issue of Cell Stem Cell, may make it possible for researchers to study mental illnesses that aren't caused by or result in overt physiological changes, but instead involve disturbances in brain cell network activity, such as autism or epilepsy. For many of these conditions, there are no relevant laboratory or animal models.

"We couldn't believe it at first -- we thought our electrodes were malfunctioning," said co-senior author Alysson R. Muotri, PhD, professor of pediatrics and cellular and molecular medicine at UC San Diego School of Medicine. "Because the data were so striking, I think many people were kind of skeptical about it, and understandably so." Muotri led the study with Bradley Voytek, PhD, associate professor of cognitive science in the UC San Diego Division of Social Sciences.

Brain organoid construction begins with a perhaps surprising source: an adult skin sample. In the lab, researchers convert the skin cells into induced pluripotent stem cells (iPSCs). Like most stem cells, with the right cocktail of molecular factors, iPSCs can be directed to specialize into any cell type. In this case, they become brain cells -- different types of neurons and glia, for example.

At UC San Diego, brain organoids have been used to produce the first direct experimental proof that the Brazilian Zika virus can cause severe birth defects and to repurpose existing HIV drugs for a rare, inherited neurological disorder. Muotri and team also recently sent their brain organoids to the International Space Station to test microgravity's effect on brain development -- and maybe prospects for human life beyond Earth.

In the latest study, Muotri and colleagues optimized every step of brain organoid construction. For example, they started from single cells, rather than the clumps of cells used in most protocols. They also tweaked the precise timing and concentration of factors added to prompt brain cell organization. There wasn't a single secret ingredient or innovation, he said, but rather several improvements over time.

The optimization paid off in terms of cellular diversity and cellular network activity. For example, the team detected a particular primate-specific neuron, called a cortical GABAergic neuron, that had never before been generated in a lab dish. According to Muotri, these cells are important players in the sophistication of neural networks.

To measure cellular network activity, the researchers grew their newly optimized brain organoids on multi-electrode arrays. The electrodes capture and record electrical impulses, which appear as patterns of waves and spikes in an EEG read-out. With the new protocol, the brain organoids went from producing 3,000 spikes per minute to 300,000 spikes per minute.

In humans, oscillations change with age, as brain cell connectivity develops. Newborn baby brains tend to have periods of rest (no waves) between spikes of electrical activity. Those quiet periods get shorter and shorter as the brain develops. In time, brain activity becomes constant, though levels vary. These brain oscillation patterns often correlate with human cognition and disease states.

Muotri and team compared their brain organoid electrical patterns to a publicly available dataset of 567 EEG recordings from 39 babies born prematurely, between 24 and 38 weeks gestation, and for several weeks after birth. From their initial days to nine months, the brain organoids produced similar levels of electric activity, following a similar pattern: less quiet time, more frequent electrical impulses.

Muotri said he is often asked about the ethical implications of this work, with questions like: "Are we getting too close to re-creating the human brain?" These brain organoids dramatically differ from human brains in many ways, he explained. For example, they are several times smaller than an adult human brain. They do not have hemispheres or blood vessels. And they are not surrounded by protective skulls or connected to other tissues.

"They are far from being functionally equivalent to a full cortex, even in a baby," said Muotri, who is also director of the UC San Diego Stem Cell Program and a member of the Sanford Consortium for Regenerative Medicine. "In fact, we don't yet have a way to even measure consciousness or sentience."

Muotri's brain organoids can live for years in the lab, but their activity plateaus at nine months. He said a number of reasons might apply, including the lack of blood vessels or the need for additional neurons to continue maturing.

The better brain organoids can replicate the human brain in the lab, Muotri said, the less researchers will need to rely on animal models and fetal tissue to better understand and treat human disease.

"Our work doesn't yet replace the need for human fetal brain tissue for research, but it's very attractive as a potential alternative," he said.

CINCINNATI - One of the most common brain cancers in children, Sonic Hedgehog (SHH) medulloblastoma, also is one of the more survivable for most kids. Unfortunately, for a subset of patients the cancer resists treatment and relapses with a vengeance to then turn deadly.

Researchers at Cincinnati Children's Hospital Medical Center used a powerful new computer-assisted technology called single-cell transcriptomics that measures thousands of individual cells simultaneously to map cell types and molecular cascades that drive the growth of SHH-medulloblastoma. In a study published Aug. 29 by the journal Cancer Cell, the scientists report they discovered new treatment strategies for the disease that may help patients fight a recurrent cancer.

Scientists used direct genetic manipulation to block genetic and molecular cascades they discovered in SHH-medulloblastoma tumors. The genetic-molecular block stopped the cancer growth and prevented relapse in tumor-forming laboratory mice, according Q. Richard Lu, PhD, a senior study investigator and scientific director of the Brain Tumor Center at Cincinnati Children's.

"Medulloblastoma is driven by a diverse group of cell types and molecular pathways that haven't been understood very well," said Lu. "But after identifying the molecular triggers and potential cells of origin for tumor initiation and recurrence, we determined from further testing that there are existing small molecule inhibitors that can target the oncogenic cascade pathways that cause SHH tumor initiation and recurrence."

Cells of Origin Revealed

The researchers developed their new data by subjecting SHH-medulloblastoma tumors in lab animals at various stages of tumor growth to single-cell transcriptomic analysis. The technique generated an extensive dataset that identifies the complete set of transcribed DNA sequences in every single cancer cell. The scan revealed that immature oligodendrocyte progenitor cells in the brain--which can assume stem-cell-like qualities--grow out of control to form medulloblastoma tumors and the molecular cascade that fuels recurring brain cancer.

Although additional preclinical research is need before clinical testing can be proposed for patients, the current study points to several molecular targets that respond to combined treatment with existing drugs, according to study co-lead author Xuelian He, MD, PhD, a former member of the Lu laboratory and now at Boston Children's Hospital. Combination therapies allow lower drug doses and improved drug tolerability for patients while achieving a certain level of therapeutic efficacy.

One treatment target proposed by the study is the HIPPO-YAP/TAZ molecular pathway, which can be targeted with an FDA-approved drug already in use for cancer treatment. The pathway is normally responsible for helping control programs that turn cell growth on and off to ensure the body's tissues and organs are accurately shaped and sized. In SHH-medulloblastoma the pathway becomes overactive. This prompts cells to expand rapidly and grow out of control near the lower central rear of the brain, which mainly controls balance and coordination.

The other potential target is the MYCN/AURORA kinase molecular pathway, which is important in regulating accurate cell structure. In SHH-medulloblastoma, the pathway is overactive and disrupts the formation of cells that otherwise would be structured and function normally. Instead, the cells transform into cancer cells.

Prodrug Potential

Lu said his research collaborators are also working together on a prodrug that will target another molecular cascade related to OLIG2, a protein and transcription factor that is an important regulator in the development of oligodendrocyte cells and motor neurons in the central nervous system. A prodrug is a compound designed as an inactive biological compound that doesn't turn on and metabolize into a specific, active drug until it reaches the appropriate part of the body.

Molecular testing shows that OLIG2is often elevated in the early stage and treatment-resistant SHH-medulloblastomas. When OLIG2 is overexpressed its energies turn towards forming cancer cells.

Because the preclinical findings in the current study were obtained with human cell cultures and mouse laboratory models, the data will have to be rigorously tested and verified by additional research before clinical testing can be proposed, according to the authors.

A new species of prehistoric murine -- the group of mammals that includes mice, rats, and their relatives -- has been identified from fossils discovered in Lebanon. The findings, presented in Scientific Reports, represent the first known physical evidence that the initial dispersal of mice from Asia to Africa took place through the Levant.

Murinae, the largest subfamily of mammals, are thought to have originated 16 million years ago in southern Asia. Yet, the possible routes and timing of the first murine dispersal have remained unclear.

Raquel López-Antoñanzas and colleagues analysed fossil teeth excavated in Lebanon in 2013 and 2018 and identified them as belonging to a previously undiscovered species, which they named Progonomys manolo. They find that P. manolo is morphologically comparable to the oldest populations of Progonomys, which lived around 10.5-11 million years ago. This suggests that P. manolo is one of the earliest representatives of Progonomys. The genus Progonomys was the first mouse to spread out of southern Asia, where mice are believed to have originated.

Given the proximity of Lebanon to the African continent, P. manolo is likely to have given rise to later populations of Progonomys that settled in Africa the authors suggest.

Dental analysis of various species of Progonomys also revealed that their teeth changed throughout the course of evolution. Later species had broader molars, which suggests a transition from an omnivorous, generalist diet to a more specialist, herbivorous one. This is related to the transition from a warm and moist middle Miocene to an increasingly drier one in the Late Miocene.

The findings, which constitute the first record of the genus Progonomys in the Arabian Peninsula, enhance the importance of the 'Levantine Corridor' as a crossroad between Eurasia and Africa and provide additional detail on the oldest intercontinental dispersal of the Murinae.

A new issue of the scholarly, open-access and peer-reviewed journal PhytoKeys focuses on the Chinese biodiversity hotspots and their substantial role in understanding the country's unique flora. The special issue embarks on a treasure hunt into China's biodiversity hotspots, including the descriptions of 23 species previously unknown to science and new insights into the ecological diversity of ferns based on their DNA sequences.

In China, biodiversity-rich landscapes vary from the dry Northwest region, through the surrounded by massive mountain ranges of the Qinghai-Tibet Plateau, to the tropical and subtropical southern China. The combination of remote and hard to reach mountain areas and diverse microclimates promises high levels of endemism.

"With extended collaboration among Chinese scientists and coordination of networks on plant conservation and taxonomy across China, we synthesize a special issue entitled "Revealing the plant diversity in China's biodiversity hotspots", to present the latest findings by Chinese botanists, and to update knowledge of the flora for China and adjacent countries", explained De-Zhu Li, professor of botany at Kunming Institute of Botany (KIB), Chinese Academy of Sciences (CAS), in the editorial.

Among the newly described species, four new members of the African violet family were found from a subtropical forest in Yunnan province in southern China, discovered by researchers from Xishuangbanna Tropical Botanical Garden, CAS and their collaborators. Half of them were found only from a sole population and require further botanical examinations to deploy the conservation priorities, remark the scientists.

In another paper, scientists Yun-Feng Huang and Li-Na Dong and Wei-Bin Xu, representatives of Guangxi Institute of Botany, revealed the discovery of a new species from the primrose family. Found nowhere outside the limestone areas in Liucheng county (Guangxi, China), this rare plant species is currently facing serious threats of extinction because of the fragility and sensitivity of its habitat to the environmental changes associated with the rapid economic development of China.

Another team from the Guizhou University of Traditional Chinese Medicine and KIB describes a new representative of the parachute flowers. Ceropegia jinshaensis, characterized by the shape and size of its leaves and flowers.

"More conservation efforts are needed in this region to counteract the increasing anthropogenic disturbance and destruction", state the leading authors from KIB, who discovered a new species of orchid in the Eastern Himalaya biodiversity hotspot.

The special issue features the description of additional two orchid species, discovered in Motuo, located at the Himalayan border between China, Myanmar and India. The region is well known for its vertical vegetation system, varying from tropical forest to permanent glaciers. Ji-Dong Ya and Cheng Liu from the KIB and Xiao-Hua Jin from the Institute of Botany, CAS underline that the difficult access to the area allows the thriving and diversification of plants.

Imperfections of crystal structure, especially edge dislocations of an elongated nature, deeply modify basic properties of the entire material and, in consequence, drastically limit its applications. Using silicon carbide as an example, physicists from Cracow and Warsaw have shown that even such computationally demanding defects can be successfully examined with atomic accuracy by means of a cleverly constructed, small in size, model.

Mathematics loves perfection. Unfortunately, perfection does not love physical reality. Theoreticians modelling crystals have long tried to include defects in real crystalline structures and predict their impact on the physical properties of materials. The models, based on the results of various experiments, have described changes in the basic properties of a material without explaining the real causes and effects of the occurring phenomena.

A new model of silicon carbide (SiC), built by physicists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow, has allowed them to demonstrate that now it is possible to study crystals ab initio with such complex defects as edge dislocations and to explain their characteristics by processes occurring on an atomic scale. This spectacular result, recently presented at the Multiscale Phenomena in Molecular Matter 2019 conference in Cracow, was achieved by the IFJ PAN physicists in cooperation with the Institute of Fundamental Technological Research of the Polish Academy of Sciences and the Institute of High Pressure Physics of the Polish Academy of Sciences, both located in Warsaw.

"We tried to find the mechanisms responsible at the atomic level for lowering the breakdown voltage in silicon carbide crystals. Our ab initio calculations lead to a qualitative understanding of the problem and contribute to explaining the details of this phenomenon", says Dr. Jan Lazewski, professor at the IFJ PAN.

Ab initio calculations have now a long history related to Nobel Prize for Walter Kohn and John Pople in 1998 (however to linear crystal defect simulations they have only recently been introduced). This term is used to describe calculations carried out using quantum mechanics equations, supported only by knowledge about the structure of the atom and the symmetry of crystals. There is no direct information from experiments in such models, which means that they can also be used to analyse materials that have never been studied or even synthesized before. Because of relatively substantial complication of the issue, so far ab initio calculations worked, at most, in the case of point defects, related to vacancies (missing atoms or holes in the crystal structure) as well as admixtures introduced into the crystal.

It was not without reason that the Cracow researchers used silicon carbide. The properties of this semiconductor are so interesting that in the past it was even considered a successor to silicon. Its band gap (the barrier the charge has to overcome to get from the valence band to the conduction band and conduct current) is almost three times greater than in silicon, the permissible conduction current density - twice as great, the ability to dissipate heat - more than three times greater, and the cutoff frequency of crystal operation as many as six times greater. In addition, silicon carbide systems can operate at temperatures up to 650 degrees Celsius, while silicon systems already begin to have problems at 120 degrees Celsius. SiC also has a high melting point, it is hard, resistant to acid and radiation. Its disadvantages include above all the price: whilst two-inch silicon wafers cost only a few dollars, the value of similar silicon carbide wafers runs into thousands. Low quality silicon carbide crystals are a popular abrasive material, also used in bulletproof vests and in the brake discs of the world's most expensive cars, such as Lamborghini or Bugatti. High quality crystals are used to produce mirrors for telescopes and in high voltage devices with high resistance to temperature.

At the atomic level, silicon carbide crystals are composed of many flat layers arranged one on top of each other. Each layer resembles a honeycomb: it consists of hexagonal cells in which the silicon carbide molecules are located vertically in the corners. Each two adjacent layers can be combined in three ways. The multilayer 'sandwiches' with different layouts create so-called polytypes, of which there exist more than 250 in the case of silicon carbide. The group from IFJ PAN used the 4H-SiC polymorph.

"When modelling such structures, one of the main problems is computational complexity. A model of pure crystal, devoid of admixtures or dislocations, is characterized by high symmetry and can be calculated even in a few minutes. In order to carry out a calculation for a material with dislocation, we need months working on a high power computer", emphasizes Dr. Pawel Jochym, professor at the IFJ PAN.

The problems with edge dislocations result from the scale of their influence on the crystal structure of the material. As an illustration, they can be compared to the problem of disguising a gap in a row of tiles on a floor. The gap can be 'camouflaged' by moving the tiles of adjacent rows, but the defect will always remain visible. Edge dislocations resulting from the lack of whole lengths or regions of atoms/molecules in individual crystal layers act similarly, affecting the positions of atoms and molecules in many adjacent layers. And since the dislocations can extend over long distances, in practice the disturbances caused by them include the entire crystal.

The most interesting phenomena take place in the dislocation core, i.e. in the vicinity of the edge of the damaged layer of the crystal network. In order to eliminate long-range effects caused by a single dislocation, and thus significantly reduce the number of atoms under consideration, a trick was employed: a second dislocation of the opposite effect was introduced. In this way, the impact of the first dislocation over longer distances was compensated for.

The SiC crystal model consisted of about 400 atoms. The simulations showed that in the layers of crystals, along the edge of the core of the defect, 'tunnels' appear in the form of channels with reduced charge density. They lower the potential barrier locally and cause electric charges to 'leak' from the valence band. In addition, in the forbidden gap, which in the insulator guarantees a lack of electrical conductivity, conditions appear which reduce its width and effectiveness in limiting the flow of charge. It was shown that these states originate from atoms located in the dislocation core.

"The situation can be compared to a deep, steep ravine that a squirrel is trying to cross. If the bottom of the ravine is empty, the squirrel will not get to the other side. However, if there are a number of trees at the bottom that are high enough, the squirrel can jump over their tops to the other side of the ravine. In the crystal we modelled, the squirrels are the electrical charges, the valence band is one edge of the ravine, the conduction band is the other, and the trees are the aforementioned states associated with the atoms of the dislocation core," says Prof. Lazewski.

Now that the mechanisms responsible for lowering the threshold of the energy barrier have become known at the atomic level, there is a huge scope for experimentation. The proposed mechanism will have to be verified in order to be able to use it to limit the negative influence of the tested defects. Fortunately, there are already technical possibilities for this.

"The future will verify whether our ideas will be confirmed in their entirety. However, we are confident about the fate of our model and the presented approach to simulating edge dislocations. We already know that the ab initio model has proved its worth in confrontation with certain experimental data", concludes Prof. Jochym.

Over the past 50 years, the water in lakes and watercourses has turned increasingly brown. The so-called browning has a negative impact on both drinking water production and ecosystems. If nothing is done, the water is likely to turn even browner - however, there is hope.

Supported by a new study, researchers from Lund University and the Swedish University of Agricultural Sciences (SLU) are pointing to measures that could be taken with the purpose of mitigating and, in the long term, reversing this development.

Lakes, brooks, streams and rivers are turning brown due to iron and organic matter leaching from the surrounding soil into the water. This is a natural process that is common across the Northern Hemisphere. However, in recent decades, the colour has intensified and more and more lakes and watercourses have turned noticeably brown.

One consequence is that the water treatment plants have been forced to take more measures in the purification process and to use more chemicals to purify water for human consumption. Another consequence is that the lakes' ecosystems are affected. A third is that it is less tempting to go for a swim on a warm summer's day if the lake is brown.

"Browning is a problem; however, the fact that land use is one of the drivers of this phenomenon, suggests it is possible to do something about it. Not least at the local level where forest owners' associations and companies can take measures that may reverse the development", says Emma Kritzberg, Lund University.

Over the past hundred years, the focus on coniferous forests in forestry has contributed to the browning. Spruce has been planted near lakes resulting in much greater accumulation of organic matter than when the same ground was covered with deciduous forest or used as agricultural land.

A return to more deciduous trees and less coniferous forest near lakes is likely to be beneficial, according to Emma Kritzberg and her colleagues Lars-Anders Hansson, Lund University, and Hjalmar Laudon, SLU. Since land use has been underestimated as a factor contributing to browning, more research is needed to address the hypotheses we present as ways to mitigate browning.

They also suggest that waterlogged areas, which are directly connected to lakes and water courses, can be protected and not cultivated in any way, to reduce leakage of organic matter into the surface water.

"Several of these measures are very well in line with the industry's own visions of how forestry should be managed near water", says Hjalmar Laudon.

By analysing the fossilised teeth of some of our most ancient ancestors, a team of scientists led by the universities of Bristol (UK) and Lyon (France) have discovered that the first humans significantly breastfed their infants for longer periods than their contemporary relatives.

The results, published in the journal Science Advances, provide a first insight into the practice of weaning that remain otherwise unseen in the fossil record.

The team sampled minute amounts from nearly 40 fossilised teeth of our South African fossil relatives, early Homo, Paranthropus robustus and Australopithecus africanus.

They measured the proportions of their stable calcium isotopes in the tooth enamel, which are a function of the mother milk intake by infants.

By reconstructing the age at tooth enamel development, they show that early Homo offspring was breastfed in significant proportions until the age of around three to four years, which likely played a role in the apparition of traits that are specific to human lineage, such as the brain development.

In contrast, infants of Paranthropus robustus, that became extinct around one million years ago and were a more robust species in terms of dental anatomy, as well as infants of Australopithecus africanus, stopped drinking sizeable proportions of mother milk in the course of the first months of life.

These differences in nursing behaviours likely come with major changes in the social structures of groups as well as the time between the birth of one child and the birth of the next.

One of the study's lead authors, Dr Theo Tacail from the University of Bristol's School of Earth Sciences, said: "The practice of weaning - the duration of breastfeeding, age at non-milk food introduction and the age at cessation of suckling - differs among the modern members of the hominid family which includes humans and modern great apes: orangutan, gorillas, chimpanzees and bonobos.

"The development of such behavioural differences likely played major roles in the evolution of the members of human lineage, being associated for instance with size and structure of social groups, brain development or demography.

"However, getting insights into these behavioural changes from fossils that are millions of years old is a challenge and, so far, little evidence allow discussing nursing practices in these fossil species.

"The findings stress the need for further exploration of calcium stables isotopes compositions in the fossil record in order to understand the co-evolution of weaning practices with other traits such as brain size or social behaviours."

WASHINGTON - New research finds Arctic Ocean currents and storms are moving bacteria from ocean algae blooms into the atmosphere where the particles help clouds form. These particles, which are biological in origin, can affect weather patterns throughout the world, according to the new study in the AGU journal Geophysical Research Letters.

Particles suspended in air called aerosols can sometimes accelerate ice crystal formation in clouds, impacting weather climate and weather patterns. Such ice-nucleating particles include dust, smoke, pollen, fungi and bacteria. Previous research had shown marine bacteria were seeding clouds in the Arctic, but how they got from the ocean to the clouds was a mystery.

In the new study, the researchers took samples of water and air in the Bering Strait, and tested the samples for the presence of biological ice nucleating particles. Bacteria normally found near the sea floor was present in the air above the ocean surface, suggesting ocean currents and turmoil help make the bacteria airborne.

Oceanic currents and weather systems brought bacteria feeding off algae blooms to the sea spray above the ocean's surface, helping to seed clouds in the atmosphere, according to the new research.

"These special types of aerosols can actually 'seed' clouds, kind of similar to how a seed would grow a plant. Some of these seeds are really efficient at forming cloud ice crystals," said Jessie Creamean, an atmospheric scientist at Colorado State University in Fort Collins, Colorado, and lead author on the new study.

Understanding how clouds are seeded can help scientists understand Arctic weather patterns.

Pure water droplets in clouds don't freeze until roughly minus 40 degrees Celsius (minus 40 degrees Fahrenheit). They are supercooled below their freezing point but still liquid. Aerosols raise the base freezing temperature in supercooled clouds to minus five degrees Celsius (23 degrees Fahrenheit), by providing a surface for water to crystalize on, and creating clouds mixed with supercooled droplets and ice crystals. Mixed clouds are the most common type of clouds on the planet and the best for producing rain or snow.

"Cloud seeds," like the bacteria found in algae blooms, can create more clouds with varying amounts of ice and water. An increase in clouds can affect how much heat is trapped in the atmosphere, which can influence climate. The clouds' compositions can affect the Arctic's water cycle, changing the amount of rain and snow that is produced. Increasing the number of clouds and changing the composition of Arctic clouds also affects northern weather systems, potentially affecting weather trends worldwide, the authors of the new study said.

Without ice nucleating particles, precipitation from clouds is less likely to happen, Heike Wex, an atmospheric scientist at the Leibniz Institute for Tropospheric Research in Leipzig, Germany, unaffiliated with the new study explained.

From the ocean to the atmosphere

To learn how biological "cloud seeds" travel from ocean depths to the atmosphere, Creamean and her colleagues took samples from 8 meters (26 feet) below the water's surface and air samples roughly 20 meters (66 feet) above the water's surface in the Bering Strait during an algae bloom.

Algae blooms are big increases in photosynthetic plant-like microorganisms that many ocean animals eat, including some kinds of bacteria. The researchers found bacteria known to seed clouds at the bottom of a phytoplankton bloom in the Bering Strait, but not in the surrounding air. The scientists found the same bacteria roughly 250 kilometers (155.3 miles) northwest of the bloom, suggesting a strong current transported the bacteria to a new spot. The bacteria were also in the air above the water. A storm brought the bacteria from the ocean depths to the surface, transporting the bacterial "cloud seeds" into the air in water droplets.

"What existed at the bottom of the ocean was making its way up to the surface waters," Creamean said.

Since the scientists only were able to take samples from 20 meters (66 feet) up, they don't yet know how the ice nucleating particles ascend to cloud elevation, which on average starts at 1.9 kilometers (1.2 miles) above the surface.

The polar regions are experiencing rapid warming from climate change. The Arctic's accelerated warming could cause more algae blooms as well as more bacteria of the type found to seed clouds, in turn further affecting its weather systems, according to the authors.

"This is a piece of the puzzle as to how these clouds form in the Arctic and potentially impact weather patterns all over the world," Creamean said.

A University of Minnesota-led research team recently discovered a new way animals can modify their vision. Crystal-like structures in the photoreceptors of larval mantis shrimp simultaneously reflect and transmit light onto light sensitive cells. This newly described structure resembles how a human-made optical device, known as Fiber Bragg Grating, works. Fiber Bragg Grating is a filter commonly used in sensors that monitor extreme conditions for a variety of industries.

"Nature often inspires human design and invention," said Kathryn Feller, Ph.D., the study's lead author and a researcher in the College of Biological Sciences at the University of Minnesota. "In this case, humans invented something before they knew a natural analog existed. The structure discovered in mantis shrimp offers a different way to build a useful optical device."

In an article published today in the journal Current Biology, Feller and colleagues describe the unique filters. "While many animal eyes use either reflectors or colorful filters -- such as cats and birds, respectively -- to tune their vision, this is the first example of a visual structure that simultaneously reflects and filters a band of light in a living creature," said Feller.

Researchers found each reflecting filter is located within the rhabdom -- or photoreceptive unit -- of a larval compound eye and selectively reflects a band of yellow light from a crystalline assembly of small, spherical units within the structure. Feller states that out of the 17 or more mantis shrimp families, the larvae of only one family (Nannosquillidae) possess these reflectors. Scientists hypothesize that the structures may help the mantis shrimp larvae see bioluminescence.

"The big question is what this new larval visual system can tell us about the evolution of adult mantis shrimp color vision, which is the most complex on the planet," said Feller.

When climates change, plants and animals often are forced to colonize new areas - or possibly go extinct. Because the climate is currently changing, biologists are keenly interested in predicting how climate-induced migrations influence organisms over time.

In a study to be published Thursday in the journal Evolution Letters, researchers at the University of Virginia and Washington State University reveal how the colonization of new environments after the last ice age, about 15,000 years ago, fundamentally altered the American bellflower, a wildflower native to Virginia.

"The plant is ideal for study because it expanded its range when the climate last warmed and glaciers retreated," said Laura Galloway, a UVA professor of biology and co-author of the study. "We learned that migration causes evolution that is both beneficial - making it easier for plants to reproduce - and detrimental - reducing the success of that reproduction."

The Washington State researchers sequenced the genomes of American bellflowers from across their current geographic range. They found patterns of genetic mutations that helped them identify a location in what is now eastern Kentucky, in the foothills of the Appalachian Mountains, where the plant likely persisted during the last glaciation. They also showed that the process of expansion to the species' current range in the eastern United States involved repeated periods when populations were small and gradually increasing through colonization.

Galloway and UVA post-doctoral associate Matthew Koski further found that populations with the longest expansion routes - those farthest from their area of origin -evolved the ability to self-fertilize, but also accumulated mutations that can be harmful to the well-being of the species over time.

"These combined changes - self-fertilization and detrimental mutations - provide strong evidence that while colonizing new environments causes plants to adapt to the absence of mates in those environments - and that's why they can now self-fertilize - at the same time, it creates genetic change that reduces overall vigor," Galloway said.

This study is important, she said, because it draws attention to the potential legacies of climate change.

"Biologists think that current climate change means species will either adapt, die or migrate," Galloway said. "While migration is often viewed as a means for species to proliferate in new environments, in this research we find that there also are inherent perils of expansion, such as a shallow gene pool. While migration will lead to individuals that are better able to reproduce in the small populations expected in new habitats, it may also cause genetic change that limits their ability to survive in the long term."

The first documented discovery of "extreme corals" in mangrove lagoons around Australia's Great Barrier Reef is yielding important information about how corals deal with environmental stress, scientists say. Thirty four species of coral were found to be regularly exposed to extreme low pH, low oxygen and highly variable temperature conditions making two mangrove lagoons on the Woody Isles and Howick Island potential "hot-spots" of coral resilience.

Although coral cover was typically low and somewhat patchy in the lagoon waters, DECRA Research Fellow Dr Emma Camp, from the University of Technology Sydney (UTS) said the discovery was important because it "provides novel information on the mechanisms that support coral resilience to stressors such as climate change and pollution."

"This highlights the need to study environments that would usually be considered unfavourable to corals in order to understand how stress tolerance in corals works.

"There is a lot we don't know. For example are these extreme corals already at their limit, can they survive more stress, if we transplant them to more stable environments will they maintain their stress tolerance?," Dr Camp said.

Dr Camp is no stranger to searching for corals in unexpected places. Camp and colleagues were the first to recognise that the corals they found in the murky lagoon waters of New Caledonia could provide answers to help support coral reef survival in the face of unprecedented global coral reef bleaching events.

With the support of Wavelength Reef Charters and funding from Waitt Foundation/National Geographic the research team surveyed 250km of the northern GBR visiting eight lagoons located on five off-shore islands.

Analysis of coral samples showed that a combination of photosynthetic "strategy" (physiological plasticity) and microbial diversity supports coral survival. However with survival comes a trade-off - the corals had reduced calcification rates, meaning they are growing more slowly than their reef counterparts.

Team Leader of the UTS Climate Change Cluster Future Reefs Research Group, Associate Professor David Suggett, said the study outcomes were important "as we look for innovative ways to support coral survival into the future".

"It's likely these mangrove lagoon corals have the best chance to persist into the future given that they are already conditioned to the complex interaction of warmer waters, ocean acidification and deoxygenation predicted for reefs under climate change" he said.

Having just discovered these "tough" examples of one of nature's most extraordinary symbiotic relationships the researchers say there is a need to help coral survival by giving enhanced protection to these special places on the Great Barrier Reef where corals persist into mangrove lagoons.

The researchers say that because these habitats carry previously unrecognised ecosystem service value for corals, spanning from acting as places of refuge to stress preconditioning, "this makes their protection even more important."