Tu Delft Researchers Designed Hybrid Energy System For Martian Habitats (Planetary Science / Engineering)

Roland Schmehl and student team designed a hybrid wind-solar energy system to power the construction and subsequent use of a subsurface Mars habitat. Their study recently appeared in Arxiv.

Several space agencies are aiming to send the humans to Mars with the goal to establish a habitat. One of the main problems to overcome is how humans will generate energy for a possible colony on Mars. We all know that generating renewable energy on mars is technologically challenging. Firstly, because compared to Earth, key energy resources such as solar and wind are weak as a result of very low atmospheric pressure and low solar irradiation. Secondly, because of the harsh environmental conditions, the required high degree of automation and the exceptional effort and costs to transport material to the planet. Like on Earth, it is crucial to combine complementary resources for an effective renewable energy solution. So, to fulfill all these requirements, Roland Schmehl and student team designed an energy system for a Mars habitat.

“Our students worked for 10 weeks fulltime on this so-called “Design Synthesis Exercise” which is the Bachelor end project at the Faculty of Aerospace Engineering of TU Delft and presented the result of a design synthesis exercise, a 10 kW microgrid solution, based on a pumping kite power system and photovoltaic solar modules to power the construction as well as the subsequent use of a Mars habitat”

— told Dr. Schmehl, Associate Professor at the Faculty of Aerospace Engineering of TU Delft, working on the emerging technology Airborne Wind Energy.

Their energy system consists of five main components: the power management system, the energy storage system, the central control system and the two energy generation subsystems.

The primary generation subsystem is based on wind energy, using a flying kite to convert the kinetic energy of Martian wind into a resultant aerodynamic force and corresponding tether force, which is further converted by the ground-based reeling mechanism and connected generator into shaft power and electrical power, respectively. The subsystem is equipped with its own control unit and super-capacitor, to balance the energy production and consumption phases of the pumping cycles.

Figure 1: Architecture and interfacing of the entire renewable energy system. Schematic from Corte Vargas et al (2020). © R. Schmehl et al.

While, the secondary generation subsystem uses solar PV technology, with a dual axis-system support system. The subsystem is equipped with dust protection and tilting mechanisms to minimize losses and ensure the best incidence angle of the radiation.

In order to store wind and solar energy, they also designed an energy storage system to which excess energy is charged during harvesting times. The energy storage system includes short-term storage, using lithium-sulfur batteries to cover the nights, and long-term storage, using CO2 compressed into underground cavities, to cover months with lower resource availability.

“Carbon dioxide makes up roughly 95% of the Martian atmosphere and the analysis showed that its use for compressed air energy storage (CAES) was meeting the long-term energy storage requirements of the mission.”

— told Dr. Schmehl.

In addition, the power management system connects the energy harvesting systems and the storage solutions, ensuring reliable electric delivery to the habitat. It makes use of a DC microgrid with underground power cables, to protect against the harsh Martian conditions. Moreover, the central control system manages the communication of all system components, ensuring the proper functioning of all components.

“The combination of all these subsystems results in a design that can reliably produce and distribute enough energy for the Mars habitat, at a total base cost of €8.95 million, excluding transportation. This proves that renewable energy is a feasible option for a Mars mission and that further investigation needs to be done to finalize the design.”

— told Dr. Schmehl

Finally, it has been recommended that, environmental conditions on Mars must be determined accurately and further research must be conducted in order to obtain a more practical expenditure prognosis for the kite and remaining subsystems.

Featured image: Kite power system of TU Delft in operation and simulated pumping cycle (Fechner, 2016). © R. Schmehl et al.


Reference: Lora Ouroumova, Daan Witte, Bart Klootwijk, Esmée Terwindt, Francesca van Marion, Dmitrij Mordasov, Fernando Corte Vargas, Siri Heidweiller, Márton Géczi, Marcel Kempers, Roland Schmehl, “Combined Airborne Wind and Photovoltaic Energy System for Martian Habitats”, Arxiv, pp. 1-14, 2021. https://arxiv.org/abs/2104.09506


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Materials Scientists Discover Faster, More Efficient Way to Manufacture Multifunctional Vascular Materials (Material Science)

Beckman researchers use frontal polymerization to manufacture environmentally-adaptive multifunctional materials in a matter of minutes instead of days.

Developing self-healing materials is nothing new for Nancy Sottos, Swanlund Endowed Chair, head of the Department of Materials Science and Engineering, and lead of the Autonomous Materials Systems Group.

Drawing inspiration from biological circulatory systems — such as blood vessels or the leaves on a tree — University of Illinois researchers have worked on developing vascularized structural composites for more than a decade, creating materials that are lightweight and able to self-heal and self-cool.

But now, a team of Beckman researchers led by Sottos and Mayank Garg, postdoctoral research associate and lead author of the newly published Nature Communications paper, “Rapid Synchronized Fabrication of Vascularized Thermosets and Composites,” have shortened a two-day manufacturing process to approximately two minutes by harnessing frontal polymerization of readily available resins.

“For the past several years we’ve been looking for ways to make vascular networks in high-performance materials,” Sottos said. “This is a real breakthrough for making vascular networks in structural materials in a way that saves a lot of time and saves a lot of energy.”

Fig4_FP-VaSC_nolabels_NComm
Synchronized manufacturing of a bioinspired structure with a hierarchical vascular network. © Beckman Institute

Garg said the simplest way to understand their work is to picture the composition of a leaf with its internal channels and structural networks. Now, imagine that the leaf is made from a tough structural material; inside, fluid flows through different spouts and channels of its interconnected vasculature. In the case of the researchers’ composites, the liquid is capable of a variety of functions, such as cooling or heating in response to extreme environments.

“We want to create these life-like structures, but we also want them to maintain their performance over substantially longer times compared to existing infrastructure by adopting an approach biology uses ubiquitously,” Garg said. “Trees have networks for transporting nutrients and water from the ground against gravity and transporting synthesized food from the leaf to the rest of the tree. The fluids flow in both directions to regulate temperature, grow new material, and repair existing material over the entire lifecycle of the tree. We try to replicate these dynamic functions in a non-biological system.”

However, creating these complex materials has historically been a long, daunting process for the Autonomous Materials Systems Group. In previous research on self-healing materials, researchers needed a hot oven, vacuum, and at least a day to create the composites. The lengthy manufacturing cycle involved curing the host material and subsequently burning or vaporizing a sacrificial template to leave behind hollow, vascular networks. Sottos said the latter process can take 24 hours. The more complicated the vascular network, the more difficult and time-consuming it is to remove.

To create the host materials, scientists opt for frontal polymerization, a reaction-thermal diffusion system that uses the generation and diffusion of heat to promote two different chemical reactions concurrently. The heat is created internally during solidification of the host and surplus heat deconstructs an embedded template in tandem to manufacture the vascular material. This means the researchers are able to shorten the process by combining two steps into one, creating the vascular networks as well as the polymerized host material without an oven. Additionally, the new process enables researchers to have more control in the creation of the networks, meaning the materials could have increased complexity and function in the future.

“With this research, we’ve figured out how to put in vascular networks by using frontal polymerization to drive the vascularization,” Sottos said. “It gets done in minutes now instead of days — and we don’t have to put it in an oven.”

Self-healing materials can be beneficial wherever strong materials are essential to maintain function under sustained damage — such as the construction of a skyscraper. But in the case of the researchers, the most likely applications are for planes, spaceships, and even the International Space Station. Sottos explained materials produced in this manner could be commercially manufactured in five to 10 years, though the researchers note that all required materials and processing equipment are currently commercially available.

Beckman Institute Director Jeff Moore, a Stanley O. Ikenberry Endowed Chair of chemistry, as well as Bliss Professor of aerospace engineering and Executive Associate Dean of The Grainger College of Engineering Philippe Geubelle were also involved in the project.

From a computational standpoint, Geubelle explained that he was able to capture the frontal polymerization and endothermic phase change taking place in the sacrificial templates.

“We performed adaptive, transient, nonlinear finite element analyses to study this competition and determine the conditions under which this simultaneous frontal polymerization and vascularization of the gel can be achieved,” he said. “This technology will lead to a more energy efficient and substantially faster way to create composites with complex microvascular networks.”

Mayank Garg © Beckman Institute

Thanks to the team’s interdisciplinary discovery, dynamic multifunctional materials are now easier to manufacture than ever before.

“This research is a combination of experimental work as well as computational work,” Garg said. “It requires synchronized communication among team members from various disciplines — chemistry, engineering, and materials science — to overhaul traditional non-sustainable manufacturing strategies.”

“There’s nothing better than to see ideas bubble up from students and postdocs in the AMS group resulting from interactions and joint group meetings,” Moore added. “The Moore Group has studied chain unzipping depolymerization reactions for years. I was delighted when I learned that the AMS team recognized how the thermal energy produced in a heat-evolving polymerization reaction could be synced to chain unzipping depolymerization in another material for the purpose of fabricating channels. The first time I saw Mayank’s results, I thought to myself, ‘I wish I’d have thought of that idea.’

Featured image: Nancy Sottos © Beckman Institute


Editor’s note: The paper “Rapid Synchronized Fabrication of Vascularized Thermosets and Composites,” can be found at https://doi.org/10.1038/s41467-021-23054-7.


Provided by Beckman Institute

Introducing Weizmann Fast Astronomical Survey Telescope (W-FAST) (Astronomy)

Eran Ofek and colleagues in their recent paper presented an overview, performance metrics, science objectives, and some first results of the Weizmann Fast Astronomical Survey Telescope (W-FAST). Their study recently appeared in Arxiv.

The Weizmann Fast Astronomical Survey Telescope is a 55-cm Schmidt telescopes. The telescope is located at the Wise Observatory near Mizpe-Ramon in the Negev desert in Israel and is expected to be relocated to a new site in Neot-Smadar, Israel, during 2021.

The Telescopes were designed and built in the Weizmann Institute. The telescope design provides a 23 deg² corrected field of view on a 9×9 cm in the focal plane.

It is equipped with a fast readout sCMOS-camera, having a 7 deg² field of view and is capable of taking 100 images per second with low read noise.

In addition, it is equipped with a single filter at any given time. There are two available filters that can be manually exchanged. The F505W from Asahi, has a tophat transmission curve between 400 to 610 nm. This filter was chosen to maximize throughput at the blue side of the visible spectrum (where the Fresnel scale is smaller). A second filter, F600W, covers the range 500–700 nm.

Fig 1: Transmission curves for the F505W and F600W filters © Eran Ofek et al.

What are its goals?

W-FAST is built to explore the periodic and variable sources, as well as short duration transients.

One of the science goals of W-FAST is to use occultations of background stars to detect Solar System objects that are too faint to detect in reflected light. For these purposes, W-FAST produces lightcurves and raw-data cutouts for a few thousand of the brightest stars in the field at a cadence of 10–25 Hz, as well as full-frame coadded images with a cadence of 4–10 seconds. The coadded images provide measurements of dimmer, lower-time-scale objects. The first objects they expect to detect using this method are Kuiper Belt Objects, which are estimated to be detectable at a rate of ≈ 1 per month. Another class of objects are Oort cloud objects for which the detection rates are uncertain.

W-FAST will have the advantage of high-cadence, continuous coverage when searching for short-time periodic signals. Even low amplitude periodic variations could be detected when added coherently on a long enough time-span. Thus, it can also be used to detect or follow-up Mdwarf flares, close binaries, variability of accreting compact objects, FRB optical counterparts, Near Earth Objects (NEOs) etc.

First results

1) Search for fast transients

During 2020 July and August E. Ofek and colleagues conducted a blind search for sub-second transients using a custom pipeline running that search for transients in the 25 Hz, full-frame imaging data. They have detected a high rate (30–40 events per day per deg²) of short-duration glints (on the order of 0.2 s), with magnitude in the 9–11 range, coming from geosynchronous satellites. These glints would be an important foreground to any searches for astrophysical transients.

2) Cataclysmic Variables: DQ Her

DQ Her is an intermediate polar, with a white dwarf rotating on a shorter period than the orbital period. The orbital period is 4.65 hr while the rotation period of the white dwarf is 71s, and the B-band magnitude of the system is around 14.5. E. Ofek and colleagues obtained an hour of observations at 2020 May 26, of a field centered on DQ Herculis. They used slow-mode (native 3s exposure times) to observe this target. They showed the resulting lightcurves for DQ Her and a few other stars of similar magnitudes in Figure below. The lightcurves of the other stars, shown in fig. for comparison, have a relative RMS of about 2-3%. The lower plot, for DQ Her, shows variability of 6%, with obvious structure, but no apparent periodic signal. When plotting the power spectrum they saw a clear peak at a period of 71.4s. This is consistent with the white dwarf rotation period. The power at lower frequencies is due to systematic red-noise and shot-noise from the object itself.

Fig 2: Lightcurves of DQ Herculis and three other stars in the field, with similar magnitudes, for comparison. Data was taken at cadence of about 3s. The lower, purple plot is for DQ Her. The relative RMS of the other stars is around 2-3%, while the DQ Her lightcurve shows variability of 6%. The apparent variations are not periodic, but a 71s period is buried under the noise © Ofek et al.

3) Targeted KBO occultation

In this, they observed an occultation by a known KBO, 38628 Huya, which is a ≈ 400 km object in the Kuiper belt and set a lower bound (of at least 364 km) on the diameter of Huya.

Findings

They showed that, the system can reach a photometric precision of better than 1% for bright stars (Bp < 10) and 2% for faint stars (Bp < 13) when summing data from multiple exposures at ∼minute time-scales. They also found that, with a large sample of stars in each field, self-calibration could help reduce some of the systematics involved with co-adding images over longer time-scales, reaching down to few milli-mag precision.

“In the near future, we intend to conduct a galactic plane survey, to characterize stellar variability on second time-scales and to detect short period binaries. We are also actively searching for astrophysical sub-second transients inside the Earth’s shadow, where flashes. from high-orbit satellites should not be visible.”

— concluded authors of the study

Featured image: The W-FAST dome in Mizpe-Ramon, Israel. © Weizmann Institute of Science


Reference: Guy Nir, Eran O. Ofek, Sagi Ben-Ami, Noam Segev, David Polishook, Ofir Hershko, Oz Diner, Ilan Manulis, Barak Zackay, Avishay Gal-Yam, Ofer Yaron, “The Weizmann Fast Astronomical Survey Telescope (W-FAST): System Overview”, Arxiv, pp. 1-13, 2021. https://arxiv.org/abs/2105.03436


Note for editors of other websites: To reuse this article fully or partially kindly give credit either to our author S. Aman or provide a link of our article

Using Micro-sized Cut Metal Wires, Japanese Team Foundation Forges Path to New Uses For Terahertz Waves (Physics)

Japanese researchers successfully tested reflectionless, highly refractive index metasurface that may eventually be used in practical applications to send, receive, and manipulate light and radio waves in the terahertz waveband (THz). THz is measured in millionths of a meter, known as micrometers. The metasurface, an artificial two-dimensional flat material, was made of micro-sized cut metal wires of silver paste ink placed on both the front and back of a polyimide film. The team, led by Takehito Suzuki, Associate Professor at the Tokyo University of Agriculture and Technology (TUAT) Institute of Engineering, published their findings on April 29, 2021 in Optics Express.

Such flat metasurfaces represent a leap forward in the study of THz optics, because they may be flexible, adaptable to a much wider array of potential uses, and far smaller than the present generation of THz optics which rely upon naturally occurring materials that have fixed indices of refraction in the THz waveband, such as cyclo-olefin polymer, magnesium oxide, and silicon. An index of refraction of a material shows that how slow electromagnetic waves travel in the material compared to a vacuum.

A greater ability to receive, transmit, control, and manipulate electromagnetic waves above 1.0 THz is necessary to unlock their potential, which remains largely untapped, according to Suzuki. “The reflectionless metasurface with a high refractive index above 1.0 THz can offer an accessible platform for terahertz flat optics such as 6G wireless communications and other possible commercial applications,” Suzuki said. “In addition to vastly faster wireless data transfer speeds, a better ability to manipulate THz waves using metasurfaces may greatly advance technology in the areas of wavefront shaping, beam forming, polarization control, and optical vortices – subjects of great interest to the scientific and communication communities.”

Suzuki’s research team set out to support the greater scientific community’s goal of replacing conventional three-dimensional bulky optical components with two-dimensional flat ones, a feat that would free up space and allow the development of smaller, more adaptable scientific and communication instruments, as well as more advanced security cameras.

The team, Harumi Asada, Kota Endo, and Takehito Suzuki, created their experimental metasurface using silver paste ink and a very thin polyimide film. Cut metal wires with a silver paste ink laid onto the film by a super-fine ink-jet printer (SIJ Technology, Inc.) capable of drawing lines in the order of 10 micrometers in width, yielded the result they had hoped for: The metasurface, which was made of 80,036 pairs of cut metal wires with silver paste ink on both the front and back of 6×6 square millimeters (roughly an infant’s thumbnail) plot of a polyimide film, has a high refractive index and low reflection at 3.0 THz.

Suzuki and his collaborating scientists plan to further investigate the potential of flat optics for use in the THz waveband, with the hope of finding scalable, commercially viable materials suitable for a wide array of future uses.

Funding:

Japan Society for the Promotion of Science (Grant-in-Aid for Scientific Research (C) (No.18K04970)), Precursory Research for Embryonic Science and Technology from the Japan Science and Technology Agency (JST) (JPMJPR18I5), Inamori Foundation, Kato Foundation for Promotion of Science, Iketani Science and Technology Foundation, TEPCO Memorial Foundation, GMO Internet Foundation, and The Noguchi Institute.

Featured image: Researchers from Tokyo University of Agriculture and Technology successfully tested reflectionless, highly refractive index metasurfaces that may eventually be used in practical applications to send, receive, and manipulate light and radio waves in the terahertz waveband (THz). © Takehito Suzuki, Tokyo University of Agriculture and Technology


Reference: Asada Harumi, Kota Endo, and Takehito Suzuki, “Reflectionless metasurface with high refractive index in the terahertz waveband,” Opt. Express 29, 14513-14524 (2021) https://doi.org/10.1364/OE.420827


Provided by Tokyo University of Agriculture and Technology

Researchers Develop 3D-Printed Jelly (Material Science)

Hydrogels merge two physical forms of the same seaweed material for strength, flexibility.

 controlled properties can be created by merging micro- and nano-sized networks of the same materials harnessed from seaweed, according to new research from North Carolina State University. The findings could have applications in biomedical materials – think of biological scaffolds for growing cells – and soft robotics.

Described in the journal Nature Communications, the findings show that these water-based gels – called homocomposite hydrogels – are both strong and flexible. They are composed of alginates – chemical compounds found in seaweed and algae that are commonly used as thickening agents and in wound dressings.

Merging different-size scale networks of the same alginate together eliminates the fragility that can sometimes occur when differing materials are merged together in a hydrogel, says Orlin Velev, S. Frank and Doris Culberson Distinguished Professor of Chemical and Biomolecular Engineering at NC State and corresponding author of the paper.

“Water-based materials can be soft and brittle,” he said. “But these homocomposite materials – soft fibrillar alginate particles inside a medium of alginate – are really two hydrogels in one: one is a particle hydrogel and one is a molecular hydrogel. Merged together they produce a jelly-like material that is better than the sum of its parts, and whose properties can be tuned precisely for shaping through a 3D printer for on-demand manufacturing.”

“We are reinforcing a hydrogel material with the same material, which is remarkable because it uses just one material to improve the overall mechanical properties,” said Lilian Hsiao, an assistant professor of chemical and molecular engineering at NC State and a co-author of the paper. “Alginates are used in wound dressings, so this material potentially could be used as a strengthened 3D-printed bandage or as a patch for wound healing or drug delivery.”

“These types of materials have the potential to be most useful in medical products, in food products as a thickening agent, or in soft robotics,” said Austin Williams, one of the paper’s first coauthors and a graduate student in Velev’s lab.

Future work will attempt to fine-tune this method of merging of homocomposite materials to advance 3D printing for biomedical applications or biomedical injection materials, Velev said.

“This technique may have uses with other types of gels, like those used in coatings or in consumer products,” Hsiao said.

Former NC State Ph.D. student Sangchul Roh is the paper’s other first coauthor. Coauthor Simeon Stoyanov from Wageningen University participated in the conception of the new material.

The research is funded by the National Science Foundation under grants CMMI-1825476, CBET-1804462 and ECCS-2025064.

Featured image: Researchers develop a 3D-printable jelly that is strong and flexible. Photo courtesy of Orlin Velev, NC State University.


Reference: Austin Williams, Sangchul Roh, Alan Jacob, Lilian Hsiao, and Orlin D. Velev, Simeon Stoyanov, “Printable homocomposite hydrogels with synergistically reinforced molecular-colloidal networks”, May 14, 2021 in Nature Communications DOI: 10.1038/s41467-021-23098-9


Provided by NC state

Researchers Suggest Pathway For Improving Stability of Next-generation Solar Cells (Material Science)

Scientists have uncovered the exact mechanism that causes new solar cells to break down, and suggest a potential solution.

Solar cells harness energy from the Sun and provide an alternative to non-renewable energy sources like fossil fuels. However, they face challenges from costly manufacturing processes and poor efficiency – the amount of sunlight converted to useable energy.

Perovskites are materials developed for next-generation solar cells. Although perovskites are more flexible cheaper to make than traditional silicon-based solar panels and deliver similar efficiency, perovskites contain toxic lead substances. Versions of perovskites using alternatives to lead are therefore being investigated.

Versions using tin instead of lead show promise but degrade quickly. Now, researchers at Imperial and the University of Bath have shown how these perovskites degrade to tin iodide, which, when exposed to moisture and oxygen, forms iodine. This iodine then helps form more tin iodide, causing cyclic degradation.

The team also show how the selection of a crucial layer within the perovskite can mitigate against degradation under ambient conditions and increase stability. They hope this will help researchers design more stable high-performance tin perovskites that show potential as new solar cells.

Lead researcher Professor Saif Haque, from the Department of Chemistry at Imperial, said: “Knowing the mechanism will help us overcome a major stumbling block for this exciting new technology. Our results will also enable the design of tin perovskite materials with improved stability, paving the way for cheaper, more flexible solar harvesting devices.”

Featured image: Proposed cyclic degradation mechanism of a tin iodide perovskite under ambient air exposure. © Lanzetta et al.


Reference: Lanzetta, L., Webb, T., Zibouche, N. et al. Degradation mechanism of hybrid tin-based perovskite solar cells and the critical role of tin (IV) iodide. Nat Commun 12, 2853 (2021). https://doi.org/10.1038/s41467-021-22864-z


Provided by Imperial College London

New Pre-Clinical Model Could Hold the Key to Better HIV Treatments (Medicine)

A team led by researchers at Weill Cornell Medicine and Children’s National Hospital has developed a unique pre-clinical model that enables the study of long-term HIV infection, and the testing of new therapies aimed at curing the disease.

Ordinary mice cannot be infected with HIV, so previous HIV mouse models have used mice that carry human stem cells or CD4 T cells, a type of immune cell that can be infected with HIV. But these models tend to have limited utility because the human cells soon perceive the tissues of their mouse hosts as “foreign,” and attack—making the mice gravely ill.

By contrast, the new mouse model, described in a paper in the Journal of Experimental Medicine on May 14, avoids this problem by using a subset of human CD4 cells that mostly excludes the cells that would attack mouse tissue. The researchers showed that the mice can usefully model the dynamics of long-term HIV infection, including the virus’s response to experimental therapies.

“We expect this to be a valuable and widely used tool for studying the basic science of HIV infection, and for speeding the development of better therapies,” said co-first author Dr. Chase McCann. During the study, Dr. McCann was a Weill Cornell Graduate School student in the laboratory of senior author Dr. Brad Jones, associate professor of immunology in medicine in the Division of Infectious Diseases at Weill Cornell Medicine. Dr. McCann, who was supported at Weill Cornell by a Clinical and Translational Science Center (CTSC) TL1 training award, is now the Cell Therapy Lab Lead in the Center for Cancer and Immunology Research at Children’s National Hospital in Washington, DC. The other co-first authors of the study are Dr. Christiaan van Dorp of Los Alamos National Laboratory and Dr. Ali Danesh, a senior research associate in medicine at Weill Cornell Medicine.

The invention of the new mouse model is part of a wider effort to develop and test cell therapies against HIV infection. Cell therapies, such as those using the patient’s own engineered T cells, are increasingly common in cancer treatment and have achieved some remarkable results. Many researchers hope that a similar strategy can work against HIV and can potentially be curative. But the lack of good mouse models has hampered the development of such therapies.

Drs. Jones and McCann and their colleagues showed in the study that the cell-attacks-host problem found in prior mouse models is chiefly due to so-called “naïve” CD4 cells. These are CD4 cells that have not yet been exposed to targets, and apparently include a population of cells that can attack various mouse proteins. When the researchers excluded naïve CD4 cells and instead used only “memory” CD4 cells, which circulate in the blood as sentinels against infection following exposure to a specific pathogen, the cells survived indefinitely in the mice without causing major damage to their hosts.

The researchers observed that the human CD4 cells also could be infected and killed by HIV, or protected by standard anti-HIV drugs, essentially in the same way that they are in humans. Thus, they showed that the mice, which they termed “participant-derived xenograft” or PDX mice, served as a workable model for long-term HIV infection. This term is akin to the “patient-derived xenograft” PDX models used to study cancer therapies, while recognizing the contributions of people with HIV as active participants in research.

Lastly, the researchers used the new model to study a prospective new T-cell based therapy, very similar to one that is now being tested against cancers. They put memory CD4 T cells from a human donor into the mice to permit HIV infection, and then, after infection was established, treated the mice with another infusion of human T cells, these being CD8-type T cells, also called “killer T cells.”

The killer T cells were from the same human donor and could recognize a vulnerable structure on HIV—so that they attacked the virus wherever they found it within the mice. To boost the killer T cells’ effectiveness, the researchers supercharged them with a T cell-stimulating protein called IL-15.

The treatment powerfully suppressed HIV in the mice. And although, as often seen in human cases, the virus ultimately evolved to escape recognition by the killer T cells, the ease of use of the mouse model allowed the researchers to monitor and study these long-term infection and viral escape dynamics in detail.

“I think that the major impact of this model will be its acceleration of the development of T cell-based therapies that can overcome this problem of viral escape,” Dr. Jones said.

He and his laboratory are continuing to study such therapies using the new mouse model, with engineered T cells from Dr. McCann’s laboratory and others.

Featured image: Scanning electron micrograph of a human T lymphocyte (T cell) from a healthy donor’s immune system. Credit: National Institute of Allergy and Infectious Diseases/NIH


Provided by Weill Cornell Medicine

Our Dreams Weirdness Might Be Why We Have Them, Argues New AI-inspired Theory of Dreaming (Engineering)

The question of why we dream is a divisive topic within the scientific community: it’s hard to prove concretely why dreams occur and the neuroscience field is saturated with hypotheses. Inspired by techniques used to train deep neural networks, Erik Hoel (@erikphoel), a research assistant professor of neuroscience at Tufts University, argues for a new theory of dreams: the overfitted brain hypothesis. The hypothesis, described May 14 in a review in the journal Patterns, suggests that the strangeness of our dreams serves to help our brains better generalize our day-to-day experiences.

“There’s obviously an incredible number of theories of why we dream,” says Hoel. “But I wanted to bring to attention a theory of dreams that takes dreaming itself very seriously–that says the experience of dreams is why you’re dreaming.”

A common problem when it comes to training AI is that it becomes too familiar with the data it’s trained on–it starts to assume that the training set is a perfect representation of anything it might encounter. Data scientists fix this by introducing some chaos into the data; in one such regularization method, called “dropout,” some data is randomly ignored. Imagine if black boxes suddenly appeared on the internal screen of a self-driving car: the car that sees the random black boxes on the screen and focuses on overarching details of its surroundings, rather than the specifics of that particular driving experience, will likely better understand the general experience of driving.

“The original inspiration for deep neural networks was the brain,” Hoel says. And while comparing the brain to technology is not new, he explains that using deep neural networks to describe the overfitted brain hypothesis was a natural connection. “If you look at the techniques that people use in regularization of deep learning, it’s often the case that those techniques bear some striking similarities to dreams,” he says.

With that in mind, his new theory suggests that dreams happen to make our understanding of the world less simplistic and more well-rounded–because our brains, like deep neural networks, also become too familiar with the “training set” of our everyday lives. To counteract the familiarity, he suggests, the brain creates a weirded version of the world in dreams, the mind’s version of dropout. “It is the very strangeness of dreams in their divergence from waking experience that gives them their biological function,” he writes.

Hoel says that there’s already evidence from neuroscience research to support the overfitted brain hypothesis. For example, it’s been shown that the most reliable way to prompt dreams about something that happens in real life is to repetitively perform a novel task while you are awake. He argues that when you over-train on a novel task, the condition of overfitting is triggered, and your brain attempts to then generalize for this task by creating dreams.

But he believes that there’s also research that could be done to determine whether this is really why we dream. He says that well-designed behavioral tests could differentiate between generalization and memorization and the effect of sleep deprivation on both.

Another area he’s interested to explore is on the idea of “artificial dreams.” He came up with overfitted brain hypothesis while thinking about the purpose of works of fiction like film or novels. Now, he hypothesizes that outside stimuli like novels or TV shows might act as dream “substitutions”–and that they could perhaps even be designed to help delay the cognitive effects of sleep deprivation by emphasizing their dream-like nature (for instance, by virtual reality technology).

While you can simply turn off learning in artificial neural networks, Hoel says, you can’t do that with a brain. Brains are always learning new things–and that’s where the overfitted brain hypothesis comes in to help. “Life is boring sometimes,” he says. “Dreams are there to keep you from becoming too fitted to the model of the world.”

Featured image: This illustration represents the overfitted brain hypothesis of dreaming, which claims that the sparse and hallucinatory quality of dreams is not a bug, but a feature, since it helps prevent the brain from overfitting to its biased daily sources of learning © Georgia Turner


Reference: Erik Hoel, “The overfitted brain: Dreams evolved to assist generalization”, Patterns, 2(5), 2021. DOI: https://doi.org/10.1016/j.patter.2021.100244


Provided by Cell Press

Sensors Developed at URI Can Identify Threats at the Molecular Level (Engineering)

Sensors developed at URI can identify explosive materials, particles from a potentially deadly virus and illegal drugs at the part-per-quadrillion level

We are frequently reminded of how vulnerable our health and safety are to threats from nature or those who wish to harm us.

New sensors developed by Professor Otto Gregory, of the College of Engineering at the University of Rhode Island, and chemical engineering doctoral student Peter Ricci, are so powerful that they can detect threats at the molecular level, whether it’s explosive materials, particles from a potentially deadly virus or illegal drugs entering the country.

“This is potentially life-saving technology,” said Gregory. “We have detected things at the part-per-quadrillion level. That’s really single molecule detection.”

Broad-Based Applications

Because Gregory’s sensors are so small and so powerful, there is a wide range of applications.

“The platform is broad-based, so you can apply it to lots of different venues, with lots of different end users,” said Gregory.

While his research is largely funded by the Department of Homeland Security, other government agencies have taken notice of Gregory’s sensors.

The Department of Defense may be interested in using it to monitor wounds in soldiers and to detect roadside improvised explosive devices (IEDs).

If a soldier or first responder suffered an open wound from shrapnel, Gregory’s sensors could help determine if the wound became infected.

“Hydrogen peroxide generated by the human body for wounds is an indication of how good or how bad antibiotics are working to fight the wound,” said Ricci. “Our sensor could be used as a wearable device to sniff out peroxide coming from the wound at the part-per-billion level.”

At Miami Heat basketball games, dogs have been used to sniff traces of COVID-19 coming from the pores in people’s skin. In an article published in the prestigious journal Nature, Gregory stated that his sensors could be used for the same purpose.

“Where dogs are detecting it from the skin, our sensors would detect it from biomarkers in people’s breath,” Ricci said, who is from West Warwick.

The Coast Guard has shown an interest in using the technology to “sniff out” illegal drugs being smuggled into the United State aboard ships.

Shrinking the ‘Digital Dog Nose’

“Anything that can typically be sniffed out by a dog we can do,” said Gregory. “That’s why we’ve called it the Digital Dog Nose.”

The Digital Dog Nose was featured on shows such as CBS This Morning in November 2019, but what was once the size of a toolbox has been reduced to a quarter of the size of a pack of cigarettes.

“By decreasing the thermal mass of the sensor, we’ve decreased the amount of power required to run the sensor,” said Gregory. “We started with a thermal mass on the order of grams. Now the thermal mass of our sensor is on the order of micrograms.”

One of the keys to making a device as small and powerful as Gregory’s is to find the right battery.

“We have partnered with a company that makes very thin, low-mass batteries in Colorado called ITN Energy Systems,” Gregory said. “They make lithium batteries that are no thicker than a piece of paper. The process has been about finding the right partners, which helps us improve our catalysts and improve our sensor platform.”

Passing the Test

In March 2021, the Naval Research Laboratory brought its mobile testing unit to URI’s W. Alton Jones Campus to put Gregory’s explosives sensors and others to the test.

“They set up a field test outside using their vapor test bed,” said Ricci. “They were able to select an explosive molecule and deliver it to the sensor system. Knowing what the level was, they wanted to see how our sensor would respond. One of the tests was at the part-per-quadrillion level.”

Staying a Step Ahead

As bad guys have developed new explosives or new ways to improvise on existing explosives, the good guys have tried to stay a step ahead.

“The Department of Homeland Security has asked us to be flexible enough to anticipate and adapt to emerging threats that may come several years down the road,” said Gregory. “We can tweak our catalysts for a specific molecule that is the current threat. That’s what we do with biomarkers. That’s what we do with drugs. What’s nice about this platform is that it’s flexible.”

Coming a Long Way

The sensors Gregory and Ricci have developed have been tested and improved upon over a long period of time. The professor’s research was originally funded 20 years ago by the Defense Advanced Research Projects Agency (DARPA), a research and development agency of the United States Department of Defense that is responsible for the development of emerging technologies for use by the military.

After two years of DARPA funding, the Army funded the project for a year. The Department of Homeland Security has provided funding ever since.

“At the time, this research was very novel and very different,” said Gregory. “DARPA funds projects that are high risk, high reward. We’ve demonstrated that the gamble they took on our concept back then has paid off.”

Michael Silevitch, the Robert D. Black Distinguished Professor of Engineering at Northeastern University, has collaborated with Gregory on his research for more than 10 years.

“This is breakthrough technology,” said Silevitch. “Otto’s work on chemical detectors has evolved to the point of being ready for use in many applications, including the deployment of his sensors on a drone-based platform to help protect soft targets such as schools, shopping malls or places of worship.”

Taking the New Steps

Now that the sensors are very small and lightweight, they could be attached to drones, leading to many new applications.

“We’ve been talking to drone companies about using our sensors on their drones,” said Gregory. “Drones need very lightweight, portable power supplies and you have to tap into their wireless communication. It’s a much different set of engineering conditions than using a robot arm that the Army is looking to use for roadside IEDs.”

Gregory and Ricci are also working on sensor arrays, to differentiate one explosive, or threat, from another.

“We’ll need an array of sensors to detect a specific explosive in the presence of other explosives or precursors,” said Ricci. “If there’s a plume of three different explosives, we may need to identify one from the others.”

Ready to Use

Now that the sensors have proven to be effective, implementing them in real-world situations is just a matter of funding.

“Our sensor is not an off-the-shelf commercial product yet, but we have a potential partner,” Gregory said. “We just need a customer to step up to the plate and say here’s an order for 1,000 of these, can you deliver them?”

YouTube Video Caption

University of Rhode Island Professor Otto Gregory and URI doctoral student Peter Ricci demonstrate and explain how the sensors developed in the Thin Film Sensors Laboratory at URI can be used on drones to identify security and health threats at the molecular level.

Featured image: URI doctoral student Peter Ricci (left) and Professor Otto Gregory test the Digital Dog Nose sensors platform in Gregory’s Thin Film Sensors Laboratory at URI. The blue devices on the table represent the two latest versions of the Digital Dog Nose. Photo courtesy of Otto Gregory.


Provided by University of Rhode Island