Airmen experience St. Elmo’s fire while flying a KC-10 aircraft into a thundercloud from an undisclosed location, March 22, 2017. St. Elmo’s fire occurs when the electric field around the aircraft ionizes air molecules, producing sparks. Credit: Senior Airman Brian Kelly

On the ground, windy conditions strengthen these electrical flashes, but new experiments tell a different story for flying objects.

At the height of a thunderstorm, the tips of cell towers, telephone poles, and other tall, electrically conductive structures can spontaneously emit a flash of blue light. This electric glow, known as a corona discharge, is produced when the air surrounding a conductive object is briefly ionized by an electrically charged environment.

For centuries, sailors observed corona discharges at the tips of ship masts during storms at sea. They coined the phenomenon St. Elmo’s fire, after the patron saint of sailors.

Scientists have found that a corona discharge can strengthen in windy conditions, glowing more brightly as the wind further electrifies the air. This wind-induced intensification has been observed mostly in electrically grounded structures, such as trees and towers. Now aerospace engineers at MIT have found that wind has an opposite effect on ungrounded objects, such as airplanes and some wind turbine blades.

In some of the last experiments performed in MIT’s Wright Brothers Wind Tunnel before it was dismantled in 2019, the researchers exposed an electrically ungrounded model of an airplane wing to increasingly strong wind gusts. They found that the stronger the wind, the weaker the corona discharge, and the dimmer the glow that was produced.

The team’s results appear in the Journal of Geophysical Research: Atmospheres. The study’s lead author is Carmen Guerra-Garcia, an assistant professor of aeronautics and astronautics at MIT. Her co-authors at MIT are Ngoc Cuong Nguyen, a senior research scientist; Theodore Mouratidis, a graduate student; and Manuel Martinez-Sanchez, a post-tenure professor of aeronautics and astronautics.

Carmen Guerra-Garcia, an assistant professor of aeronautics and astronautics at MIT, is the lead author of a new study analyzing the effect of wind on underground corona discharges. Credit: Lillie Paquette, MIT School of Engineering

Electric friction

Within a storm cloud, friction can build up to produce extra electrons, creating an electric field that can reach all the way to the ground. If that field is strong enough, it can break apart surrounding air molecules, turning neutral air into a charged gas, or plasma. This process most often occurs around sharp, conductive objects such as cell towers and wing tips, as these pointed structures tend to concentrate the electric field in a way that electrons are pulled from surrounding air molecules toward the pointed structures, leaving behind a veil of positively charged plasma immediately around the sharp object.

Once a plasma has formed, the molecules within it can begin to glow via the process of corona discharge, where excess electrons in the electric field ping-pong against the molecules, knocking them into excited states. In order to come down from those excited states, the molecules emit a photon of energy, at a wavelength that, for oxygen and nitrogen, corresponds to the characteristic blueish glow of St. Elmo’s fire.

In previous laboratory experiments, scientists found that this glow, and the energy of a corona discharge, can strengthen in the presence of wind. A strong gust can essentially blow away the positively charged ions, that were locally shielding the electric field and reducing its effect — making it easier for electrons to trigger a stronger, brighter glow.

These experiments were mostly carried out with electrically grounded structures, and the MIT team wondered whether wind would have the same strengthening effect on a corona discharge that was produced around a sharp, ungrounded object, such as an airplane wing.

To test this idea, they fabricated a simple wing structure out of wood and wrapped the wing in foil to make it electrically conductive. Rather than try to produce an ambient electric field similar to what would be generated in a thunderstorm, the team studied an alternative configuration in which the corona discharge was  generated in a metal wire running parallel to the length of the wing, and connecting a small high-voltage power source between wire and wing. They fastened the wing to a pedestal made from an insulating material that, because of its nonconductive nature, essentially made the wing itself electrically suspended, or ungrounded.

The team placed the entire setup in MIT’s Wright Brothers Wind Tunnel, and subjected it to increasingly higher velocities of wind, up to 50 meters per second, as they also varied the amount of voltage that they applied to the wire. During these tests, they measured the amount of electrical charge building up in the wing, the current of the corona and also used an ultraviolet-sensitive camera to observe the brightness of the corona discharge on the wire.

Scientists observe the ion “glow” of corona discharge in an electrically ungrounded object (left) compared to a grounded object (right). Credit: Courtesy of the researchers

In the end, they found that the strength of the corona discharge and its resulting brightness decreased as the wind increased — a surprising and opposite effect from what scientists have seen for wind acting on grounded structures.

Pulled against the wind

The team developed numerical simulations to try and explain the effect, and found that, for ungrounded structures, the process is largely similar to what happens with grounded objects — but with something extra.

In both cases, the wind is blowing away the positive ions generated by the corona, leaving behind a stronger field in the surrounding air. For ungrounded structures, however, because they are electrically isolated, they become more negatively charged. This results in a weakening of  the positive corona discharge. The amount of negative charge that the wing retains is set by the competing effects of positive ions blown by the wind and those attracted and pulled back as a result of the negative excursion. This secondary effect, the researchers found, acts to weaken the local electric field, as well as the corona discharge’s electric glow.

“The corona discharge is the first stage of lightning in general,” Guerra-Garcia says. “How corona discharge behaves is important and kind of sets the stage for what could happen next in terms of electrification.”

In flight, aircraft such as planes and helicopters inherently produce wind, and a glow corona system like the one tested in the wind tunnel could actually be used to control the electrical charge of the vehicle. Connecting to some prior work by the team, she and her colleagues previously showed that if a plane could be negatively charged, in a controlled fashion, the plane’s risk of being struck by lightning could be reduced. The new results show that charging of an aircraft in flight to negative values can be achieved using a controlled positive corona discharge.

‘’The exciting thing about this study is that, while trying to demonstrate that the electrical charge of an aircraft can be controlled using a corona discharge, we actually discovered that classical theories of corona discharge in wind do not apply for airborne platforms, that are electrically isolated from their environment,” Guerra-Garcia says. “Electrical breakdown occurring in aircraft really presents some unique features that do not allow the direct extrapolation from ground studies.”

Reference: “Corona Discharge in Wind for Electrically Isolated Electrodes” by C. Guerra‐Garcia, N. C. Nguyen, T. Mouratidis and M. Martinez‐Sanchez, 28 July 2020, JGR Atmospheres.
DOI: 10.1029/2020JD032908

This research was funded, in part, by The Boeing Company, through the Strategic Universities for Boeing Research and Technology Program.

In the USA, where the curve of infections has not yet flattened since the beginning of the pandemic, 158,000 people have died from Covid-19 already. And despite the choice by all US states to gradually ease lockdown from late May onwards to save the economy, 14 million Americans have lost their job, while the economic output in the second quarter of 2020 dropped by 9.5%. To help entrepreneurs decide on how they can safely reopen their business, mathematicians and statisticians here develop a model for the spread of infections within companies and the economic payoff of safety measures. Their findings are published today in Frontiers in Applied Mathematics and Statistics.

“Our aim was to provide a quantitative yet simple modeling tool for business executives to plan for reopening their workplace,” says lead author Prof Hongyu Miao, Director of the Center for Biostatistics Collaboration and Data Services at the University of Texas Health Science Center in Houston, Texas.

The authors show mathematically that, under a wide range of parameters, reopening your business will only be feasible if at least these safety measures are adopted: wearing goggles, gloves, and masks (when employees aren’t alone); frequent hand washing; routine sanitation of the workfloor; social distancing; monitoring body temperature; and quarantine of exposed and sick employees. These measures won’t only control the spread of Covid-19 within the company, but also increase your net profit under the assumptions of the model.

“We show that a business entity may stand a good opportunity to generate positive net profit after reopening only if necessary protection measures are strictly implemented,” warns Miao. “It is also very important to monitor the number of infections through virus testing and contact tracing, especially at the early stage of reopening.”

About the model

Miao and colleagues first developed — and (approximately) solved numerically — five differential equations for the numbers of susceptible, infectious, quarantined, deceased, and recovered employees within a company. These assumed that all workers who can work from home do so, and that workers self-quarantine as soon as they present symptoms, or if they have been in close contact with a known carrier. They further assumed that infected employees who aren’t detected — because they are asymptomatic or only mildly symptomatic cases, in the early stages of the disease, or apparently recovered but still infectious — can continue to infect their susceptible coworkers as “silent spreaders,” and that sick and quarantined workers receive their full pay.

In addition, the authors modeled the net profit, based on the average salary and productivity of US workers, the cost of PPE and other safety measures, and the reduction in productivity expected from a limit on working hours and the need for distancing. They estimated values for key parameters from the literature, for example the effectiveness of PPE in preventing transmission, the expected pricetag of these measures, and the dynamics of infection.

Four scenarios compared

The authors then took a large, well-known Texan company as a hypothetical example. Under the least safe scenario, where no safety measures are taken, the prevalence of Covid-19 within the company steadily rises to become 30-fold higher than in the general US population, indicating that reopening won’t be feasible. Under the safest scenario, where all possible safety measures are adopted, its prevalence falls to 104-fold lower than in the population, resulting in a higher and more stable net profit. Results are similar under the second-safest scenario, where only the most expensive measures are omitted — non-contact sensors for real-time fever detection, reducing working hours by 30% to limit exposure, and UV purification or High-Efficiency Particulate Air (HEPA) filters that prevent viral transmission in aerosols. Finally, under the third-safest scenario, where employees further drop the use of PPE, the workplace again quickly becomes a “hot spot” of infection, resulting in a lower net profit.

Reference: 11 August 2020, Frontiers in Applied Mathematics and Statistics.

DOI: 10.3389/fams.2020.00035

This artist’s rendition shows how a Mars lidar could be deployed on a landed mission to Mars. Credit: NASA

Insights and technology gleaned from creating a carbon-measuring instrument for Earth climate studies is being leveraged to build another that would remotely profile, for the first time, water vapor up to nine miles above the Martian surface, along with wind speeds and minute particles suspended in the planet’s atmosphere.

Scientists Jim Abshire and Scott Guzewich, both at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have won NASA technology-development funding to build and demonstrate a small prototype atmospheric lidar for a future lander on Mars, and possibly Titan, Saturn’s largest moon and the only to have a dense atmosphere.

Selected for further development by the agency’s Planetary Instrument Concepts for the Advancement of Solar System Observations (PICASSO) program, the concept traces its heritage to other similar-type instruments originally conceived through Goddard’s Internal Research and Development (IRAD) program. Another IRAD-supported technology, a Raman mass spectrometer, also received PICASSO funding.

Understanding the Boundary Layer

Abshire and Guzewich are particularly interested in obtaining measurements of Mars’s boundary layer, an atmospheric section that begins at the surface and can extend as high as nine miles above, depending on the time of day. Because this layer is difficult to measure from orbit, the team wants to deploy the lidar on a lander or rover that would directly gather around-the-clock data from the surface up — data that could reveal how conditions change over time and altitude. 

This layer is important because it controls the transfer of heat, momentum, dust, and water and can reveal greater insights about the planet’s modern climate, including the stability of its ice caps, how wind shapes the landscape, and how dust is lifted and transported. Furthermore, scientists can use this data to validate and improve general circulation models, Guzewich said.

“From a human spaceflight perspective, this layer is also critical for operations,” Abshire said. “This is the environment in which landed missions will operate.”

This is a closeup of the lidar instrument, which would remotely profile, for the first time, water vapor up to nine miles above the Martian surface, along with wind speeds and minute particles suspended in the planet’s atmosphere. Credit: NASA

NASA has landed atmospheric lidars before, successfully measuring winds as well as aerosols, including dust and ice, but this particular instrument would provide the missing element — direct measurements of water vapor in vertical columns above the surface.

“We’re motivated by science questions,” Guzewich said. “We want to measure water vapor and winds at the same time. The whole point is understanding water and how it’s being moved around through the atmosphere. We know where the water is, we just don’t know how it moves.”

To find out, the lidar would bounce a laser light tuned to 1911 nanometers — a specific wavelength in the near-infrared band ideal for detecting water vapor — into the sky and then analyze the reflected light or signal to learn more about the atmospheric dynamics occurring from the surface to nine miles above the surface. Equipped with a sesame seed-sized, already developed infrared detector, the instrument would be able to sense the returning signal at a single-photon level, providing unprecedented resolution.

IRAD Heritage

“Our approach for profiling atmospheric water vapor and winds using a lidar at 1911 nanometers is new,” Abshire said.

However, he and his colleagues have vast experience developing atmospheric lidar instruments. For Earth science, they built the Co2 Sounder lidar tuned to 1572 nanometers, which is effective for measuring carbon dioxide in the atmosphere. The new lidar also traces its heritage to the Mars Lidar for Global Climate Measurements from Orbit, which Abshire envisioned as an on-orbit instrument to measure wind speeds.

The challenge is producing an instrument that is robust, practical, yet small enough to fit onto a rover. “Our challenge is to show that we can do this. Fortunately, we can rely on the unique capabilities of Goddard, Abshire said. “We have great capabilities in lidar, space lasers, and detectors. There really is no other place that combines all this capability and expertise.”

Raman-Mass Spectrometer

Goddard Principal Investigator Andrej Grubisic also won a three-year PICASSO award to advance RAMS, short for RAman-Mass Spectrometer. Raman spectroscopy and mass spectrometry are two common analytical chemistry techniques for determining sample composition through identification of individual molecules and specific minerals. With his PICASSO award, Grubisic said he and the RAMS team plan to demonstrate a hybrid instrument that would be capable of acquiring micron-level composition maps of organic molecules and mineral phases that exist in samples gathered on comets and asteroids as well as from samples acquired on the icy moons in the outer solar system,

Such measurements would give scientists the necessary information to help them understand the origin of organic material in the solar system, the habitability of other planets, and the potential for life beyond Earth.

A combination of genetic and emotional differences may lead to post-traumatic stress (PTS) in police officers, a new study finds.

Based on biological studies of officers in major cities, the study showed that the most significant PTS predictors are the tendency to startle at sudden sounds, early career displays of mental health symptoms (e.g., anxiety and depression), and certain genetic differences, including some known to influence a person’s immune system.

“If we can identify major risk factors that cause PTS and treat them before they have the chance to develop into full-blown post-traumatic stress disorder, or PTSD, we can improve the quality of life for police officers and perhaps other emergency responders, and better help them deal with the stressors of their work,” says senior study author Charles Marmar, MD, the Lucius N. Littauer Professor of Psychiatry at NYU Grossman School of Medicine.

Publishing online Aug. 10 in the journal Translational Psychiatry, the study authors employed a mathematical computer program developed by scientists at NYU Langone Health and the University of Minnesota. They used a combination of statistical analyses to test which of a large number of features linked by past studies to PTSD were the best at predicting its occurrence in police officers.

Some of this winnowing that determined the best predictors was accomplished using machine learning, mathematical models trained with data to find patterns. These algorithms enabled researchers to track how experiences, situations, and characteristics may have interacted over time to lead to PTS symptoms, and represent the first use of such techniques in PTS research in police officers, the authors say.

“Based on these techniques, our study identified specific causes of PTS, rather than possible links,” says Marmar, also chair of the Department of Psychiatry at NYU Langone.

He adds that the need for better information is urgent. An estimated eight out of every 100 people experience PTS in their lifetimes, according to the National Institute of Mental Health. Police officers are particularly vulnerable, he says, facing an average of three traumatic experiences for every sixth months of service. Common symptoms include nightmares, aggression, and distressing flashbacks of the traumatic event, which can lead to poor sleep, anxiety, depression, and increased risk of suicide.

In the new study, the investigators analyzed data collected on 207 police officers from departments in New York City, San Francisco, Oakland, and San Jose who had PTS. All officers had experienced at least one life-threatening event during their first year on the job.

Using the computer program, the investigators searched for patterns in 148 different characteristics previously thought to be involved in PTS. They mapped out 83 different possible combinations of factors, or pathways, which could have influenced the officers as they developed the condition.

Then, they identified factors which appeared most frequently, and found that every pathway to PTS shared one of five causes. Besides the tendency to startle easily, severe distress following a traumatic experience, and a set of emotional health problems, such as anxiety and depression, played a key role in PTS. Genetic causes included mutations in the HDC gene, which is linked to problems in the immune system and mutations in the MR gene, which is involved in the body’s immediate reaction to threats, known as the fight-or-flight response. If all five factors were eliminated, researchers say, the officers would not be expected to develop PTS.

“Because the factors we identified are causal, they should be actionable as well,” says lead study investigator Glenn Saxe, MD, a professor in NYU Langone’s Department of Child and Adolescent Psychiatry. “Several of the causal factors we identified — the HDC gene, the MR gene, and the startle response — point to well-mapped nerve circuits, which should allow us to find drugs and behavioral therapies that might help. Down the road, we see the possibility of using information collected from patients about causal factors to select the interventions that would provide the most benefit to them.”

Saxe says other future interventions might target factors that may not cause PTS on their own, but frequently contribute to its development. For example, the study found that difficulty adjusting to work contributed to PTS development in 60 percent of the causal pathways. Therefore, a straightforward solution, like giving more support to new police officers who are having difficulty adjusting to police work, may reduce their risk of getting PTS, according to Saxe.

Moving forward, the researchers plan to apply the same algorithm technique in a much larger group of traumatized adults and children, focusing on a more extensive set of characteristics and experiences.

###

Reference: 11 August 2020, Translational Psychiatry.

Funding for the study was provided by National Institute of Mental Health grant R01 MH056350 and Substance Abuse and Mental Health Services Administration grants U79 SM080049 and U79 SM080013.

In addition to Marmar and Saxe, other NYU Langone researchers include Leah J. Morales, BS; and Isaac Galatzer-Levy, PhD. Other study authors are Sisi Ma, PhD; and Constantin Aliferis, MD PhD, at the University of Minnesota in Minneapolis.

Findings suggest that national estimates of opioid overdose burden may be grossly underestimated.

A 7-year comprehensive study of deaths attributed to out of hospital cardiac arrest (OHCA) in San Francisco found that more than one in six of those deaths were actually from occult overdose. These findings suggest that published national overdose mortality estimates may be substantially underestimated. A brief research report is published in Annals of Internal Medicine.

Researchers from the University of California, San Francisco conducted a case-series analysis of the POST SCD (POstmortem SysTematic Investigation of Sudden Cardiac Death) Study, to compare the characteristics of occult overdose OHCA deaths with all other causes of OHCA deaths and to classify primary intoxicants and whether intoxicants were prescribed for each death investigated. After toxicology and autopsy, the researchers found that more than one in six deaths attributed to OHCA were really due to overdose. Most occult overdose OHCA deaths involved multiple drugs, including opioids, and approximately one-half of intoxicants were prescribed by a physician.

These findings have important implications nationally, as San Francisco’s age-adjusted overdose mortality rate is nearly identical to the national median overdose mortality rate. As such, published national mortality estimates based on recognized overdoses may significantly underestimate its true burden because occult overdose deaths masquerading as sudden cardiac deaths are missed without postmortem toxicology analysis. According to the researchers, their findings affirm the need for continued efforts to combat the opioid epidemic and for policymakers to consider naloxone in selected OHCA resuscitations.

Reference: 10 August 2020, Annals of Internal Medicine.
DOI: 10.7326/M20-0977

Pupil size predicts death and hospital readmission in patients with heart failure, according to research published today in ESC Heart Failure, a journal of the European Society of Cardiology (ESC).

“Our results suggest that pupil area is a novel way to identify heart patients at elevated risk of death or hospital readmission,” said study author Dr. Kohei Nozaki of Kitasato University Hospital, Kanagawa, Japan. “This provides an opportunity to intervene and improve outlook.”

Around 26 million people worldwide currently live with heart failure. It is a life-threatening condition in which the heart is unable to pump enough blood to meet the body’s needs. Symptoms include shortness of breath, swollen limbs, and fatigue. Up to 45% of patients admitted to hospital with heart failure die within one year of admission and the majority die within five years of admission.

“Finding better ways to pinpoint which patients are more likely to be readmitted or die is crucial,” said Dr. Nozaki.

One of the causes of worsening heart failure is disturbed function of the body’s autonomic system, which controls heart rate, digestion, respiration, and so on. Autonomic function is typically evaluated by measuring changes in heart rate. However, this method is ineffective in patients with a heart rhythm disorder called atrial fibrillation, which is common in those with heart failure.

Pupil area is another way to assess autonomic function and has been used in patients with Parkinson’s disease and diabetes. This study examined whether pupil area could predict prognosis in patients with heart failure.

The study was conducted in 870 patients hospitalized for acute heart failure in 2012 to 2017. The average age was 67 years and 37% were women. Pupil area was measured in both eyes at least seven days after hospital admission. For the test, patients put on goggles, waited five minutes for their eyes to adapt to the dark, then photos were taken of the eyes. Patients were tested at a standard time (between 09:00 and 12:00) since the autonomic system is affected by time of day.

Patients were divided into the small pupil area group and large pupil area group according to whether their measurement was below or above the median (16.6 mm2). They were then followed-up for all-cause death (the primary endpoint) and readmission due to heart failure (the secondary endpoint). Results of the small and large pupil area groups were compared.

Over a median follow-up of 1.9 years, 131 patients died and 328 were rehospitalized because of heart failure. Compared to the large pupil area group, patients in the small pupil area group had a significantly poorer survival rate and significantly higher rate of readmission for heart failure.

After adjusting for other factors that could affect prognosis such as body mass index (BMI) and kidney function, patients with a small pupil area had a 28% lower risk of all-cause mortality and an 18% reduced risk of readmission due to heart failure compared to patients with a large pupil area.

Large pupil area was consistently linked with favorable survival regardless of age, sex, and the presence of either normal heart rhythm or atrial fibrillation.

Dr. Nozaki said: “Pupil area can be obtained rapidly, easily, and non-invasively. Our study indicates that it could be used in daily clinical practice to predict prognosis in patients with heart failure, including those who also have atrial fibrillation. Patients with a small pupil area (e.g. less than 16.6 mm2) could be prioritized for cardiac rehabilitation with physical activity, which has been reported to improve autonomic function.”

Dr. Nozaki noted that pupil area cannot be used in patients with severe retinopathy or other eye diseases.

References:

“Prognostic value of pupil area for all-cause mortality in patients with heart failure” by Nozaki K, Hamazaki N, Yamamoto S, et al., 10 August 2020, ESC Heart Failure.
DOI: 10.1002/ehf2.12933

“Heart failure: preventing disease and death worldwide” by Piotr Ponikowski, Stefan D. Anker, Khalid F. AlHabib, Martin R. Cowie, Thomas L. Force, Shengshou Hu, Tiny Jaarsma, Henry Krum, Vishal Rastogi, Luis E. Rohde, Umesh C. Samal, Hiroaki Shimokawa, Bambang Budi Siswanto, Karen Sliwa and Gerasimos Filippatos, 30 September 2014, ESC Heart Failure.
DOI: 10.1002/ehf2.12005

This study was supported by a Grant-in-Aid [JSPS KAKENHI Grant Number JP 19K19884] from the Japan Society for the Promotion of Science.

The hybrid remotely-operated vehicle Nereus was used to collect seafloor samples, in addition to remotely operated vehicle Jason II, at Piccard vents at Mid-Cayman Rise. Credit: Jill McDermott

Scientists analyzing hydrothermal fluid from Piccard vents at Mid-Cayman Rise find non-biological processes deplete hydrogen that was thought to be readily available to subseafloor microbial communities; discovery could impact global hydrogen budget.

The discovery of hydrothermal vents — where volcanoes at the seafloor produce hot fluid exceeding 350 degrees Celsius, or 662 degrees Fahrenheit, fundamentally changed our understanding about Earth and life in the 1970s. Yet, life at and underneath the seafloor is still very much a mystery today.

Gaining a better understanding of these volcanically active areas is important, as the chemistry at seafloor vents impacts ocean chemistry more generally. In addition, the seafloor’s unique environment supports biological and non-biological processes that offer clues as to how life on Earth first began, how it is sustained over time — and the potential for life on other planetary bodies.

According to geochemist Jill McDermott, a professor in the Department of Earth and Environmental Science at Lehigh University, past studies of the chemistry of hydrothermal vent fluids have revealed reductions in certain gas species, such as molecular hydrogen. These depletions were thought to be caused by microbiological communities living in the shallow seafloor, collectively called the subseafloor biosphere.

Too hot to host life, the high temperature Beebe Vents black smokers serve as the source fluids for nearby mixing zones that span the thermal boundary between habitable and uninhabitable below-seafloor environments. All vent fluids were collected with gas-tight, titanium hydrothermal fluid samplers that maintain bottom pressure before shipboard sample retrieval. Credit: Chris German, WHOI/NASA, NSF/ROV Jason/Woods Hole Oceanographic Institution

However, results of a new study by McDermott and colleagues contradict that assumption. The researchers analyzed gas-tight hydrothermal fluid samples from the world’s deepest known vent field, the Piccard hydrothermal field at the Mid-Cayman Rise, which is at a depth of 4970 meters, or about 16,000 feet below sea level. They observed chemical shifts in their samples, including a large loss of molecular hydrogen, that could only be the result of abiotic (non-biological) and thermogenic (thermal breakdown) processes, because the fluid temperatures were beyond the limits that support life — understood to be 122 degrees Celsius, or around 250 degrees Fahrenheit, or lower.

The results were published online today in an article “Abiotic redox reactions in hydrothermal mixing zones: decreased energy availability for the subsurface biosphere” in the Proceedings of the National Academy of Sciences. Additional authors include: Christopher German, Senior Scientist in Geology & Geophysics and Jeffrey Seewald, Senior Scientist in Marine Chemistry & Geochemistry and Sean Sylva, Research Associate III, in Marine Chemistry & Geochemistry from the Woods Hole Oceanographic Institution; and Shuhei Ono, Associate Professor, Massachusetts Institute of Technology.

“Our study finds that these shifts in chemistry are driven by non-biological processes that remove energy before microbial communities gain access to it,” says McDermott. “This could have critical implications for constraining the extent to which global geochemical cycles can sustain a deep biosphere, and for the global hydrogen budget.”

She adds “This also means the subsurface biosphere is likely receiving less energy than anyone had realized previously. The degree to which non-biological hydrogen consumption in the oceanic crust may reduce the impact of life inhabiting the seafloor is a great target for future studies.”

Lead author Jill McDermott performing a chemical analysis called titration to analyze the hydrogen sulfide content of vent fluid samples onboard the R/V Falkor in 2013. Credit: Julie Huber

Using chemical analysis of dissolved gases, inorganic compounds, and organic compounds, the team found that the low-temperature fluid samples originated from mixing between seawater and the nearby Beebe Vents black smokers, so named because the fluid expelled from the vents resembles black smoke from a chimney. In these mixed fluid samples, many chemical species are either high or low in abundance, according to McDermott. The sample with the largest shifts in the amount of gas had a seafloor temperature of 149 degrees Celsius, or 300 degrees Fahrenheit, a temperature that is too hot to host life. Thus, they concluded, the process responsible for the geochemical changes could not directly involve life.

The non-biological reactions they identified as responsible for these chemical shifts include sulfate reduction and the thermal degradation of biomass, and are supported by mass balance considerations, stable isotope measurements, and chemical energetics calculations.

The samples were collected during two research expeditions using two remotely operated vehicles, Jason II and Nereus, both designed for deep-water exploration and to conduct a diverse range of scientific investigations in the world’s oceans.

“This was a really exciting field program that provided a rare opportunity for us to explore the complex interplay between the chemistry of a natural environment and the life that it supports,” said Seewald. “We are now in a much better position to estimate the amount of microbial life that may exist beneath the seafloor.”

Discovered in 2010, the Piccard Hydrothermal Field is located just south of Grand Cayman in the Caribbean. The fluid samples the researchers examined vented at 44 to 149 degrees Celsius (111 to 300 degrees Fahrenheit), providing a rare opportunity for the team to study the transition between life-supporting and non-life-supporting environments.

“The cool (hot) thing about this study is that we were able to find a set of vents that spanned from where it was too hot for life, to where it was just right,” says German. “That particularly cute set of circumstances opened up the possibility to gain new insights into what life might (and might not) be able to do, down beneath the seafloor.”

Shifts in hydrothermal vent fluid temperature and chemical composition are known to serve as an important control on microbial community structure and function in the oceanic crust throughout the world’s oceans.

“This relationship exists because hydrothermal fluids provide energy for specific microbial metabolic reactions,” says McDermott. “However, the reverse question of whether vent fluid chemistry is modified by life itself, or instead by non-living processes, is an important one that is rarely addressed.”

The team’s discovery may serve to open up a new path of exploration toward assessing whether non-biological processes serve as important controls on energy availability, in addition to microbial processes.

Reference: 10 August 2020, Proceedings of the National Academy of Sciences.

Prenatal depression symptoms were associated with weakened white matter tracts in the cingulum (left) and amygdala pathway (right). Credit: Hay et al., JNeurosci 2020

Weakened brain connections may mediate prenatal depression’s influence on child behavior.

Altered brain connectivity may be one way prenatal depression influences child behavior, according to new research in JNeurosci.

Up to one fifth of women experience depression symptoms during pregnancy, with unknown effects on the fetus. Prenatal depression is correlated with behavioral and developmental issues in the child, as well as an increased risk of developing depression at age 18. But how prenatal depression leads to these changes remains unclear.

Hay et al. studied 54 mother/child pairs. Mothers answered a survey about their depression symptoms at several points during their pregnancy. The research team employed diffusion MRI, an imaging technique that reveals the strength of structural connections between brain regions, to examine the children’s white matter.

Greater prenatal depression symptoms were associated with weaker white matter connections between brain regions involved in emotional processing. This change could lead to dysregulated emotional states in the children and may explain why the children of depressed mothers have a higher risk of developing depression themselves. The weakened white matter was associated with increased aggression and hyperactivity in the male children. These findings highlight the need for better prenatal care to recognize and treat prenatal depression in order to support the mother and the child’s development.

Reference:” Amygdala-Prefrontal Structural Connectivity Mediates the Relationship Between Prenatal Depression and Behaviour in Preschool Boys” 10 August 2020, JNeurosci.
DOI:JNEUROSCI.0481-20.2020

The researchers used the IBM Quantum Experience to conduct their experiments. Credit: IBM

Australian and North American physicists display rigorous, scalable diagnostic tool.

Noise is the main obstacle to building large-scale quantum computers. To tame the noise (interference or instability), scientists need to understand how it affects an entire quantum system.

Until now this information was only available for very small devices or subsets of devices.

Work by Dr. Robin Harper and colleagues published today in Nature Physics develops algorithms that will work across large quantum devices.

They demonstrate this by diagnosing the noise in an IBM Quantum Experience device, discovering correlations in the 14-qubit machine not previously detected.

Dr. Harper said: “The results are the first implementation of provably rigorous and scalable diagnostic algorithms capable of being run on current quantum devices and beyond.”

Reference: 10 August 2020, Nature Physics.
DOI: 10.1038/s41567-020-0992-8

Dr. Harper is a postdoctoral researcher at the University of Sydney Nano Institute and part of the Australian Research Council Centre of Excellence for Engineered Quantum System