Mastodon Scientific Frontline

Wednesday, September 28, 2022

Novel Carrier Doping in p-type Semiconductors Enhances Photovoltaic Device Performance by Increasing Hole Concentration


The carrier concentration and conductivity in p-type monovalent copper semiconductors can be significantly enhanced by adding alkali metal impurities, as shown recently by Tokyo Tech researchers. Doping with isovalent and larger-sized alkali metal ions effectively increased the free charge carrier concentration and the mechanism was unraveled by their theoretical calculations. Their carrier doping technology enables high carrier concentration and high mobility p-type thin films to be prepared from the solution process, with photovoltaic device applications.

Perovskite solar cells have been the subject of much research as the next generation of photovoltaic devices. However, many challenges remain to be overcome for the practical application. One of them concerns the hole transport layer (p-type semiconductor) in photovoltaic cells that carries holes generated by light to the electrode. In conventional p-type organic transport semiconductors, hole dopants are chemically reactive and degrade the photovoltaic device. Inorganic p-type semiconductors, which are chemically stable, are promising alternatives, but fabrication of conventional inorganic p-type semiconductors requires high temperature treatment. In this regard, the p-type inorganic semiconductors that can be fabricated at low temperatures and have excellent hole transport ability have been desired.

Inorganic p-type copper iodide (CuI) semiconductor is a leading candidate for such hole transport materials in photovoltaic device applications. In this material, native defects give rise to charge imbalance and free charge carriers. However, the overall number of defects is generally too low for satisfactory device performance.

Ural Scientists Propose to Create Citric Acid Using Microorganisms

More than 60% of citric acid is used annually in industry: metallurgy, oil production, medicine and related fields.
Photo credit: Alina Spiridonova

New scientific development will help to create Russia's own production of citric acid, which is currently fully imported. The new method is more technologically advanced and environmentally friendly, as it involves more rational use of microscopic mushrooms for biosynthesis of acid from waste sugar production or products of deep processing of grain. It also avoids large amounts of waste, wastewater and gas emissions. Aleksey Byuler from the UrFU Research Laboratory "Mathematical Modeling in Physiology and Medicine Based on Supercomputers" talked about it on the air of the radio "Komsomolskaya Pravda".

In Russia, the traditional method of citric acid extraction from beet molasses using calcium citrate was used for citric acid production. This led to the formation of significant amounts of waste production: 1 kg of the obtained product had 2 kg of gypsum waste. Such gypsum is not applicable to construction purposes, and its processing requires a lot of energy, so all the gypsum was usually sent to waste, which created a serious impact on the environment. For this reason, the only Russian plant producing citric acid was shut down several years ago. A new linear method using membrane (ultrafiltration) and electrodialysis technologies proposed by the scientists will make it possible to synthesize and isolate citric acid without harming the environment.

Tuesday, September 27, 2022

A Different Kind of Chaos

The experimental setup used by the Weld Lab.
Photo Credit: Tony Mastres

Physicists at UC Santa Barbara and the University of Maryland, and also at the University of Washington have found an answer to the longstanding physics question: How do interparticle interactions affect dynamical localization?

“It’s a really old question inherited from condensed matter physics,” said David Weld, an experimental physicist at UCSB with specialties in ultracold atomic physics and quantum simulation. The question falls into the category of ‘many-body’ physics, which interrogates the physical properties of a quantum system with multiple interacting parts. While many-body problems have been a matter of research and debate for decades, the complexity of these systems, with quantum behaviors such as superposition and entanglement, lead to multitudes of possibilities, making it impossible to solve through calculation alone. “Many aspects of the problem are beyond the reach of modern computers,” Weld added.

Fortunately, this problem was not beyond the reach of an experiment that involves ultracold lithium atoms and lasers. So, what emerges when you introduce interaction in a disordered, chaotic quantum system?

A “weird quantum state,” according to Weld. “It’s a state which is anomalous, with properties which in some sense lie between the classical prediction and the non-interacting quantum prediction.”

The physicists’ results are published in the journal Nature Physics.

Trees get overheated in a warmer rainforest

Maria Wittemann has been conducting field studies in Rwanda with colleagues from the University of Rwanda.
Photo credit: Myriam Mujawamariya

The ability of rainforests to store carbon can decrease in pace with climate change. This is due to photosynthesis rates in the leaves of rainforest species falling at higher temperatures and the trees’ natural cooling systems failing during droughts. Increased heat threatens especially the species that store most carbon. This has been shown in a new thesis from the University of Gothenburg.

Some species of trees are able to handle rising heat in the tropics by sucking up large quantities of water to their leaves and transpiring through wide-opened pores in their leaves. These are mainly fast-growing trees that establish themselves early as a rainforest grows up. The same cannot be said for the trees that make up the canopy of rainforests in old growth forests. They grow slower, but get bigger and taller, and their leaves do not have the same ability to cool themselves via transpiration.

Water powers the ‘air conditioning’

“The tropics have not experienced Ice Ages and have thus had a relatively stable climate historically as well as seasonally. With climate change, it has started to get warmer and then we have seen that some species of trees are showing increased mortality rates, but we have not really known why before,” says Maria Wittemann, who wrote the thesis.

Neurodegenerative disease can progress in newly identified patterns


Neurodegenerative diseases — like amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease), Alzheimer’s, and Parkinson’s — are complicated, chronic ailments that can present with a variety of symptoms, worsen at different rates, and have many underlying genetic and environmental causes, some of which are unknown. ALS, in particular, affects voluntary muscle movement and is always fatal, but while most people survive for only a few years after diagnosis, others live with the disease for decades. Manifestations of ALS can also vary significantly; often slower disease development correlates with onset in the limbs and affecting fine motor skills, while the more serious, bulbar ALS impacts swallowing, speaking, breathing, and mobility. Therefore, understanding the progression of diseases like ALS is critical to enrollment in clinical trials, analysis of potential interventions, and discovery of root causes.

However, assessing disease evolution is far from straightforward. Current clinical studies typically assume that health declines on a downward linear trajectory on a symptom rating scale, and use these linear models to evaluate whether drugs are slowing disease progression. However, data indicate that ALS often follows nonlinear trajectories, with periods where symptoms are stable alternating with periods when they are rapidly changing. Since data can be sparse, and health assessments often rely on subjective rating metrics measured at uneven time intervals, comparisons across patient populations are difficult. These heterogenous data and progression, in turn, complicate analyses of invention effectiveness and potentially mask disease origin.

Archaeologists uncover ancient mosaics on the shore of the Sea of Galilee

JGU students recording the outlines of the mosaic – with a tall waterside plant with blossoms and small green leaves on three stems in the exposed portion and the stern and rudder of a boat on the lower left
Credit: Hans-Peter Kuhnen

With the help of geomagnetic surface surveys and subsequent hands-on digging, an excavation team from Johannes Gutenberg University Mainz (JGU) has revealed new insights into the area in which the caliph's palace of Khirbat al-Minya was built on the shores of the Sea of Galilee. According to these findings, there had already been a settlement occupied by Christian or Jewish inhabitants in the immediate vicinity long before the palace was built.

"This time we have really hit the jackpot with our excavations," said site director and archaeologist Professor Hans-Peter Kuhnen with regard to the outcome of the most recent undertakings in the area around the early Islamic caliph's palace Khirbat al-Minya in Israel. The team of archaeologists from Mainz made this major discovery using geomagnetic methods and by digging test pits on the basis of the findings. They discovered that in the early 8th century the caliph had commissioned the building of his palace, with its incorporated mosque and a 15-meter-high gateway tower, not – as hitherto suspected – on greenfield land on the unoccupied shore of the Sea of Galilee, but adjacent to and respectfully co-existing with a prior settlement. The research project was initially conceived as a means of training students in archeological field work. It was undertaken with the support of the Israel Antiquities Authority and financed by the Fritz Thyssen Foundation, the Axel Springer Foundation, the Santander Foundation, and the German Academic Exchange Service (DAAD). The team was accommodated in the Tabgha Pilgerhaus guesthouse run by the German Association of the Holy Land (DVHL), which has owned the site of the excavations on the northwest shore of the Sea of Galilee since 1895.

Study shows how turtles fared decade after oil spill

Dr. Josh Otten, who graduated in May from UToledo with a Ph.D. in biology, holds a turtle while downloading data to his computer on the Kalamazoo River. Otten is lead author of a new study that confirmed turtles rehabilitated in the aftermath of an oil spill disaster 12 years ago on the river had high long-term survival rates.
Source: University of Toledo

Twelve years after an oil spill coated nearly 35 miles of the Kalamazoo River, new research at The University of Toledo confirms that turtles rehabilitated in the aftermath of the disaster had high long-term survival rates.

Turtles were the most commonly captured oiled animals following a ruptured Enbridge pipeline near Marshall, Mich., in July 2010 that spilled 843,000 gallons of oil into a tributary creek of the river, one of the largest inland oil spills in U.S. history.

Dr. Josh Otten, who graduated in May from UToledo with a Ph.D. in biology, holds a turtle while downloading data to his computer on the Kalamazoo River. Otten is lead author of a new study that confirmed turtles rehabilitated in the aftermath of an oil spill disaster 12 years ago on the river had high long-term survival rates.

Immediately following the spill, nearly 8% of recovered northern map turtles died.

One of the first environmental responders on the scene was biologist Dr. Josh Otten, lead author of the new study published in the journal Environmental Pollution who graduated in May from UToledo with a Ph.D. in biology.

Revealing the Genome of the Common Ancestor of All Mammals

An international team has reconstructed the genome organization of the earliest common ancestor of all mammals. The reconstructed ancestral genome could help in understanding the evolution of mammals and in conservation of modern animals. The earliest mammal ancestor likely looked like this fossil animal, Morganucodon, which lived about 200 million years ago.
Image via Wikipedia by user Funkmonk, Creative Commons Attribution-Share Alike 3.0 Unported license.

Every modern mammal, from a platypus to a blue whale, is descended from a common ancestor that lived about 180 million years ago. We don’t know a great deal about this animal, but the organization of its genome has now been computationally reconstructed by an international team of researchers. The work is published in Proceedings of the National Academy of Sciences.

“Our results have important implications for understanding the evolution of mammals and for conservation efforts,” said Harris Lewin, distinguished professor of evolution and ecology at the University of California, Davis, and senior author on the paper.

The researchers drew on high-quality genome sequences from 32 living species representing 23 of the 26 known orders of mammals. They included humans and chimps, wombats and rabbits, manatees, domestic cattle, rhinos, bats and pangolins. The analysis also included the chicken and Chinese alligator genomes as comparison groups. Some of these genomes are being produced as part of the Earth BioGenome Project and other large-scale biodiversity genome sequencing efforts. Lewin chairs the Working Group for the Earth BioGenome Project.

Novel imaging system could mean near-instant biopsy results

Tissue biopsied with a novel imaging system based on 2-photon fluorescence microscopy (TPFM) is showing promising results. The system, described in the journal JAMA Dermatology, was developed by University of Rochester biomedical engineer Michael Giacomelli.
Photo credit: Giacomelli lab

Medicine has advanced dramatically during the last century. But when it comes to getting biopsy results, very little has changed. Consider, for example, what happens when a patient comes in to have a skin lesion biopsied for nonmelanoma skin cancer.

“The surgeon will take a little piece of the skin out,” says Michael Giacomelli, an assistant professor of biomedical engineering and of optics at the University of Rochester. “Someone in pathology will look at it weeks or even a month later under a microscope. And then, depending on what they find, the patient is notified that everything’s fine, don’t worry about it, or we need you to come back for a second appointment so we can treat you.”

Giacomelli is developing a novel imaging system, contained on a portable cart, to shorten this process to two minutes. This would enable a surgeon to immediately determine whether the lesion is cancerous and, if so, to “treat the patient during the same visit instead of stretching it out over the next month and multiple visits.”

The system—using two-photon fluorescence microscopy (TPFM)—demonstrated remarkable accuracy in a pilot study summarized recently in JAMA Dermatology. When tested on 15 biopsies of known nonmelanoma skin cancer, the technology was able to detect basal cell carcinoma with perfect accuracy (100 percent sensitivity and specificity) and squamous cell carcinoma with high accuracy (89 percent sensitivity and 100 percent specificity).

Seawater could have provided phosphorous required for emerging life

Artist Concept of an Early Earth 
Credit: NASA

The problem of how phosphorus became a universal ingredient for life on Earth may have been solved by researchers from the University of Cambridge and the University of Cape Town, who have recreated primordial seawater containing the element in the lab.

Their results, published in the journal Nature Communications, show that seawater might be the missing source of phosphate, meaning that it could have been available on a large enough scale for life without requiring special environmental conditions.

“This could really change how we think about the environments in which life first originated,” said co-author Professor Nick Tosca from Cambridge's Department of Earth Sciences.

The study, which was led by Matthew Brady, a PhD student from Cambridge's Department of Earth Sciences, shows that early seawater could have held one thousand to ten thousand times more phosphate than previously estimated — as long as the water contained a lot of iron.

Phosphate is an essential ingredient in creating life’s building blocks — forming a key component of DNA and RNA — but it is one of the least abundant elements in the cosmos in relation to its biological importance. When in its mineral form, phosphate is also relatively inaccessible — it can be hard to dissolve in water so that life can use it.

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