Summary
The challenge‐hindrance model of stress proposes that stressors can be divided into two distinct groups: those that challenge employees and those that hinder employees. This critical review ...seeks to explain the history of the model and its basic tenets, while succinctly summarizing the findings of existing studies based on the model. A thorough search of the stress literature uncovered 32 studies that specifically examined the relationship between challenge and hindrance stressors and important personal/organizational variables. Results were reviewed and analyzed, specifically by describing past meta‐analyses on the model, looking at the overall pattern of results from primary studies, and meta‐analyzing the relationships presented in those papers. This synthesis suggests that although there are some differential relationships of challenge and hindrance stressors with organizational variables (e.g., performance and engagement), the relationships to other key variables, such as counterproductive work behaviors, psychological strains, and physical health, are consistently negative for both challenge and hindrance stressors. Thus, we propose that stress research move away from the current challenge‐hindrance model in favor of other established models and/or a more appraisal‐based approach.
The biogenesis of iron–sulfur (Fe/S) proteins in eukaryotes is a multistage, multicompartment process that is essential for a broad range of cellular functions, including genome maintenance, protein ...translation, energy conversion, and the antiviral response. Genetic and cell biological studies over almost 2 decades have revealed some 30 proteins involved in the synthesis of cellular 2Fe-2S and 4Fe-4S clusters and their incorporation into numerous apoproteins. Mechanistic aspects of Fe/S protein biogenesis continue to be elucidated by biochemical and ultrastructural investigations. Here, we review recent developments in the pursuit of constructing a comprehensive model of Fe/S protein assembly in the mitochondrion.
Timing is critical to most forms of learning, behavior, and sensory-motor processing. Converging evidence supports the notion that, precisely because of its importance across a wide range of brain ...functions, timing relies on intrinsic and general properties of neurons and neural circuits; that is, the brain uses its natural cellular and network dynamics to solve a diversity of temporal computations. Many circuits have been shown to encode elapsed time in dynamically changing patterns of neural activity—so-called population clocks. But temporal processing encompasses a wide range of different computations, and just as there are different circuits and mechanisms underlying computations about space, there are a multitude of circuits and mechanisms underlying the ability to tell time and generate temporal patterns.
Temporal processing is among the most fundamental computations the brain performs. Paton and Buonomano review recent experimental and theoretical advances in the field and conclude that timing relies in part on the natural dynamics of neurons and neural circuits.
Kratom is a plant with partial opioid agonist effects, and its use has become popular to ameliorate symptoms of opioid withdrawal. However, use has been linked to thousands of poisonings, although ...most have involved use of other drugs. Little is known regarding prevalence and correlates of use in the general U.S. population.
Data were examined from the 2019 National Survey on Drug Use and Health, a nationally representative probability sample of non-institutionalized individuals aged ≥12 years in the U.S. (N=56,136). Prevalence and correlates of past-year kratom use were estimated. Data were analyzed in 2020.
An estimated 0.7% (95% CI=0.6, 0.8) of individuals in the U.S. have used kratom in the past year. Past-year proxy diagnosis of prescription opioid use disorder was associated with increased odds for kratom use (AOR=3.20, 95% CI=1.38, 7.41), with 10.4% (95% CI=6.7, 15.9) of those with use disorder reporting use. Opioid misuse not accompanied with use disorder was not associated with kratom use. Those reporting past-year cannabis use both with (AOR=4.33, 95% CI=2.61, 7.19) and without (AOR=4.57, 95% CI=3.29, 6.35) use disorder and those reporting past-year cocaine use (AOR=1.69, 95% CI=1.06, 2.69) and prescription stimulant misuse (AOR=2.10, 95% CI=1.44, 3.05) not accompanied with use disorder were at higher odds for kratom use.
Kratom use is particularly prevalent among those with prescription opioid use disorder, but it is also prevalent among people who use other drugs. Research is needed to determine reasons for use and potential dangers associated with adding kratom to drug repertoires.
Conspectus Triarylamine molecules and triarylamine-based covalent polymers have been extensively investigated for more than 60 years in academics and industry because of their intriguing electronic ...and optical characteristics. However, despite the profusion of studies made on these derivatives, only very recently have the first examples of supramolecular polymers based on the triarylamine motif been described in the literature. Specifically, our research group has shown that, by adding supplementary hydrogen bonding moieties such as amide functions in their periphery, it becomes possible to tightly pack triarylamine molecules in columnar supramolecular stacks presenting a collinear arrangement of their central nitrogen atoms. These supramolecular polymers can self-assemble into various soft hierarchical structures such as helical fibers, nanorods, nanospheres, and nanoribbons in the sol and in the gel states, into liquid-crystalline mesophases, and into highly organized supramolecular frameworks and single crystals thereof. Interestingly, the associated supramolecular polymerization mechanism involves a nucleation step of high activation energy, which requires the flattening of the triarylamine core. Because of this singularity and although dependent on the precise chemical nature of the building blocks, it has been demonstrated that their supramolecular polymerization can be triggered by original tools, such as light irradiation or electrochemistry, and that it can display autocatalytic growth behaviors, remarkably strong amplifications of chirality, and complex and competing thermodynamic and kinetic self-assembly pathways. Further, from a functional point of view, it has been highlighted that a partial oxidation of the triarylamine molecules results in an enhanced through-space delocalization of the charge carriers along the π–π stacked supramolecular polymers, a feature that confers to these nanowires exceptional transport properties. Upon increasing the charge carrier concentration, the electronic nature of these soft materials can be switched from semiconducting to metallic behavior, and the presence of highly delocalized unpaired electrons in supramolecular polaronic band structures has been further exploited to implement plasmonic properties within subwavelength organic interconnects and microscopic optical waveguides. Finally, by making use of the unusual dynamics and functions of triarylamine-based nanostructures, it becomes possible to precisely address their self-construction within confined environments or within nano- and micrometer scale devices. This has been demonstrated for instance between nanoparticles and between electrodes, inside inorganic nanopores, and inside phospholipid bilayers, as well as at the liquid–liquid interface. Such a meeting point between bottom-up and top-down technologies is of high interest to envision further developments and applications for this entirely new class of supramolecular polymers, which combine a unique relationship between their structures, their dynamics, and their subsequent emerging functional properties.
Over 130,000 juveniles are detained in the United States each year with 70,000 in detention on any given day, yet little is known about whether such a penalty deters future crime or interrupts social ...and human capital formation in a way that increases the likelihood of later criminal behavior. This article uses the incarceration tendency of randomly assigned judges as an instrumental variable to estimate causal effects of juvenile incarceration on high school completion and adult recidivism. Estimates based on over 35,000 juvenile offenders over a 10-year period from a large urban county in the United States suggest that juvenile incarceration results in substantially lower high school completion rates and higher adult incarceration rates, including for violent crimes. In an attempt to understand the large effects, we found that incarceration for this population could be very disruptive, greatly reducing the likelihood of ever returning to school and, for those who do return, significantly increasing the likelihood of being classified as having an emotional or behavioral disorder.
The sensory pathways of animals are well adapted to processing a special class of signals, namely stimuli from the animal's environment. An important fact about natural stimuli is that they are ...typically very redundant and hence the sampled representation of these signals formed by the array of sensory cells is inefficient. One could argue for some animals and pathways, as we do in this review, that efficiency of information representation in the nervous system has several evolutionary advantages. Consequently, one might expect that much of the processing in the early levels of these sensory pathways could be dedicated towards recoding incoming signals into a more efficient form. In this review, we explore the principle of efficiency of information representation as a design principle for sensory processing. We give a preliminary discussion on how this principle could be applied in general to predict neural processing and then discuss concretely some neural systems where it recently has been shown to be successful. In particular, we examine the fly's LMC coding strategy and the mammalian retinal coding in the spatial, temporal and chromatic domains.
Plant cell walls are dynamic structures that are synthesized by plants to provide durable coverings for the delicate cells they encase. They are made of polysaccharides, proteins, and other ...biomolecules and have evolved to withstand large amounts of physical force and to resist external attack by herbivores and pathogens but can in many cases expand, contract, and undergo controlled degradation and reconstruction to facilitate developmental transitions and regulate plant physiology and reproduction. Recent advances in genetics, microscopy, biochemistry, structural biology, and physical characterization methods have revealed a diverse set of mechanisms by which plant cells dynamically monitor and regulate the composition and architecture of their cell walls, but much remains to be discovered about how the nanoscale assembly of these remarkable structures underpins the majestic forms and vital ecological functions achieved by plants.
IMPORTANCE: Data on the use of antiretroviral drugs, including new drugs and formulations, for the treatment and prevention of HIV infection continue to guide optimal practices. OBJECTIVE: To ...evaluate new data and incorporate them into current recommendations for initiating HIV therapy, monitoring individuals starting on therapy, changing regimens, preventing HIV infection for those at risk, and special considerations for older people with HIV. EVIDENCE REVIEW: New evidence was collected since the previous International Antiviral (formerly AIDS) Society–USA recommendations in 2018, including data published or presented at peer-reviewed scientific conferences through August 22, 2020. A volunteer panel of 15 experts in HIV research and patient care considered these data and updated previous recommendations. FINDINGS: From 5316 citations about antiretroviral drugs identified, 549 were included to form the evidence basis for these recommendations. Antiretroviral therapy is recommended as soon as possible for all individuals with HIV who have detectable viremia. Most patients can start with a 3-drug regimen or now a 2-drug regimen, which includes an integrase strand transfer inhibitor. Effective options are available for patients who may be pregnant, those who have specific clinical conditions, such as kidney, liver, or cardiovascular disease, those who have opportunistic diseases, or those who have health care access issues. Recommended for the first time, a long-acting antiretroviral regimen injected once every 4 weeks for treatment or every 8 weeks pending approval by regulatory bodies and availability. For individuals at risk for HIV, preexposure prophylaxis with an oral regimen is recommended or, pending approval by regulatory bodies and availability, with a long-acting injection given every 8 weeks. Monitoring before and during therapy for effectiveness and safety is recommended. Switching therapy for virological failure is relatively rare at this time, and the recommendations for switching therapies for convenience and for other reasons are included. With the survival benefits provided by therapy, recommendations are made for older individuals with HIV. The current coronavirus disease 2019 pandemic poses particular challenges for HIV research, care, and efforts to end the HIV epidemic. CONCLUSION AND RELEVANCE: Advances in HIV prevention and management with antiretroviral drugs continue to improve clinical care and outcomes among individuals at risk for and with HIV.
Cell walls define the shape of plant cells, controlling the extent and orientation of cell elongation, and hence organ growth. The main load-bearing component of plant cell walls is cellulose, and ...how plants regulate its biosynthesis during development and in response to various environmental perturbations is a central question in plant biology. Cellulose is synthesized by cellulose synthase (CESA) complexes (CSCs) that are assembled in the Golgi apparatus and then delivered to the plasma membrane (PM), where they actively synthesize cellulose. CSCs travel along cortical microtubule paths that define the orientation of synthesis of the cellulose microfibrils. CSCs recycle between the PM and various intracellular compartments, and this trafficking plays an important role in determining the level of cellulose synthesized. In this review, we summarize recent findings in CESA complex organization, CESA posttranslational modifications and trafficking, and other components that interact with CESAs. We also discuss cell wall integrity maintenance, with a focus on how this impacts cellulose biosynthesis.
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