Dynamic detection of electron spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance

A distinguishing feature of spin accumulation in ferromagnet-semiconductor devices is precession of the non-equilibrium spin population of the semiconductor in a magnetic field. This is the basis for detection techniques such as the Hanle effect, but these approaches become less effective as the spin lifetime in the semiconductor decreases. For this reason, no electrical Hanle measurement has been demonstrated in GaAs at room temperature. We show here that by forcing the magnetization in the ferromagnet (the spin injector and detector) to precess at the ferromagnetic resonance frequency, an electrically generated spin accumulation can be detected from 30 to 300 K. At low temperatures, the distinct Larmor precession of the spin accumulation in the semiconductor can be detected by ferromagnetic resonance in an oblique field. We verify the effectiveness of this new spin detection technique by comparing the injection bias and temperature dependence of the measured spin signal to the results obtained using traditional methods. We further show that this new approach enables a measurement of short spin lifetimes (< 100 psec), a regime that is not accessible in semiconductors using traditional Hanle techniques.Comment: 4 figure

Myonuclear Domain Flexibility Challenges Rigid Assumptions on Satellite Cell Contribution to Skeletal Muscle Fiber Hypertrophy

Satellite cell-mediated myonuclear accretion is thought to be required for skeletal muscle fiber hypertrophy, and even drive hypertrophy by preceding growth. Recent studies in humans and rodents provide evidence that challenge this axiom. Specifically, Type 2 muscle fibers reliably demonstrate a substantial capacity to hypertrophy in the absence of myonuclear accretion, challenging the notion of a tightly regulated myonuclear domain (i.e., area that each myonucleus transcriptionally governs). In fact, a “myonuclear domain ceiling”, or upper limit of transcriptional output per nucleus to support hypertrophy, has yet to be identified. Satellite cells respond to muscle damage, and also play an important role in extracellular matrix remodeling during loading-induced hypertrophy. We postulate that robust satellite cell activation and proliferation in response to mechanical loading is largely for these purposes. Future work will aim to elucidate the mechanisms by which Type 2 fibers can hypertrophy without additional myonuclei, the extent to which Type 1 fibers can grow without myonuclear accretion, and whether a true myonuclear domain ceiling exists

Translocation as a strategy to rehabilitate the queen conch (Strombus gigas) population in the Florida Keys

Queen conch (Strombus gigas) stocks in the Florida Keys once supported commercial and recreational fisheries, but overharvesting has decimated this once abundant snail. Despite a ban on harvesting this species since 1985, the local conch population has not recovered. In addition, previous work has reported that conch located in nearshore Keys waters are incapable of spawning because of poor gonadal condition, although reproduction does occur offshore. Queen conch in other areas undergo ontogenetic migrations from shallow, nearshore sites to offshore habitats, but conch in the Florida Keys are prevented from doing so by Hawk Channel. The present study was initiated to determine the potential of translocating nonspawning nearshore conch to offshore sites in order to augment the spawning stock. We translocated adult conch from two nearshore sites to two offshore sites. Histological examinations at the initiation of this study confirmed that nearshore conch were incapable of reproduction, whereas offshore conch had normal gonads and thus were able to reproduce. The gonads of nearshore females were in worse condition than those of nearshore males. However, the gonadal condition of the translocated nearshore conch improved, and these animals began spawning after three months offshore. This finding suggests that some component of the nearshore environment (e.g., pollutants, temperature extremes, poor food or habitat quality) disrupts reproduction in conch, but that removal of nearshore animals to suitable offshore habitat can restore reproductive viability. These results indicate that translocations are preferable to releasing hatchery-reared juveniles because they are more cost-effective, result in a more rapid increase in reproductive output, and maintain the genetic integrity of the wild stock. Therefore, translocating nearshore conch to offshore spawning aggregations may be the key to expediting the recovery of queen conch stocks in the Florida Keys

Myonuclear Transcriptional Dynamics in Response to Exercise Following Satellite Cell Depletion

Skeletal muscle is composed of post-mitotic myofibers that form a syncytium containing hundreds of myonuclei. Using a progressive exercise training model in the mouse and single nucleus RNA-sequencing (snRNA-seq) for high-resolution characterization of myonuclear transcription, we show myonuclear functional specialization in muscle. After 4 weeks of exercise training, snRNA-seq reveals that resident muscle stem cells, or satellite cells, are activated with acute exercise but demonstrate limited lineage progression while contributing to muscle adaptation. In the absence of satellite cells, a portion of nuclei demonstrates divergent transcriptional dynamics associated with mixed-fate identities compared with satellite cell replete muscles. These data provide a compendium of information about how satellite cells influence myonuclear transcription in response to exercise

Meta-analysis of outcomes of patients with COVID-19 infection with versus without gastrointestinal symptoms.

This systematic review analyzed whether the presence or absence of gastrointestinal symptoms in patients with SARS-COV-2 infection is associated with adverse outcomes. Searching the Cochrane Center Register of Controlled Trials, we included any studies looking at patients with COVID-19 with gastrointestinal symptoms (nausea, vomiting, diarrhea, abdominal pain) compared to those with COVID-19 but without gastrointestinal manifestations as a control group. The final search yielded 186 articles, all of which were individually screened. Seven studies were identified but three were excluded: one due to lack of a control group without gastrointestinal symptoms, one reported as viral RNA in the stool, and one with only non-critically ill patients. Results of the meta-analysis showed a pooled odds ratio for mortality among those with COVID-19 and gastrointestinal symptoms of 0.91 (confidence interval 0.49-1.68) with heterogeneity of 0% and a pooled odds ratio for acute respiratory distress syndrome of 2.94 (confidence interval 1.17-7.40) with heterogeneity of 0%. In conclusion, gastrointestinal symptoms with COVID-19 are associated with a higher risk of acute respiratory distress syndrome, but do not increase the risk for mortality

An Embryonic Stem Cell-Based System for Rapid Analysis of Transcriptional Enhancers

With the growing use of genome-wide screens for cis-regulatory elements, there is a pressing need for platforms that enable fast and cost-effective experimental validation of identified hits in relevant developmental and tissue contexts. Here, we describe a murine embryonic stem cell (ESC)-based system that facilitates rapid analysis of putative transcriptional enhancers. Candidate enhancers are targeted with high efficiency to a defined genomic locus via recombinase-mediated cassette exchange. Targeted ESCs are subsequently differentiated in vitro into desired cell types, where enhancer activity is monitored by reporter gene expression. As a proof of principle, we analyzed a previously characterized, Sonic hedgehog (Shh)-dependent, V3 interneuron progenitor (pV3)-specific enhancer for the Nkx2.2 gene, and observed highly specific enhancer activity. Given the broad potential of ESCs to generate a spectrum of cell types, this system can serve as an effective platform for the characterization of gene regulatory networks controlling cell fate specification and cell function.Molecular and Cellular BiologyStem Cell and Regenerative BiologyOther Research Uni

Fusion and Beyond: Satellite Cell Contributions to Loading-Induced Skeletal Muscle Adaptation

Satellite cells support adult skeletal muscle fiber adaptations to loading in numerous ways. The fusion of satellite cells, driven by cell-autonomous and/or extrinsic factors, contributes new myonuclei to muscle fibers, associates with load-induced hypertrophy, and may support focal membrane damage repair and long-term myonuclear transcriptional output. Recent studies have also revealed that satellite cells communicate within their niche to mediate muscle remodeling in response to resistance exercise, regulating the activity of numerous cell types through various mechanisms such as secretory signaling and cell–cell contact. Muscular adaptation to resistance and endurance activity can be initiated and sustained for a period of time in the absence of satellite cells, but satellite cell participation is ultimately required to achieve full adaptive potential, be it growth, function, or proprioceptive coordination. While significant progress has been made in understanding the roles of satellite cells in adult muscle over the last few decades, many conclusions have been extrapolated from regeneration studies. This review highlights our current understanding of satellite cell behavior and contributions to adaptation outside of regeneration in adult muscle, as well as the roles of satellite cells beyond fusion and myonuclear accretion, which are gaining broader recognition

Time-Series Classification of High-Temporal Resolution AVHRR NDVI Imagery of Mexico

Time-series data from wide-field sensors, acquired for the period of a growing season or longer, capitalize on phenological changes in vegetation and make it possible to identify vegetated land cover types in greater detail. Our objective was to examine the utility of time-series data to rapidly update maps of vegetation condition and land cover change in Mexico as an input to biodiversity modeling. We downloaded AVHRR NDVI 10-day composites from the USGS EROS Data Center for 1992-1993 and adjusted for cloud contamination by further aggregating the data. In the first phase of our analysis, we selected training sites for various land cover types using a land cover map created by the Mexican National Institute of Statistics, Geography, and Informatics (INEGI) as a guide. Since there is a high degree of spectral variability within many of the vegetated land cover types, we subjected the spectral response patterns to cluster analysis. We then used the statistics of the clusters as training data in a supervised classification. We also compared unsupervised and univariate decision tree approaches, but these provided unsatisfactory results. Best results were achieved with a 19-class map of land use/land cover employing a supervised approach

Global rural temperature trends

Using rural/urban land surface classifications derived from maps and satellite observed nighttime surface lights, global mean land surface air temperature time series were created using data from all weather observing stations in a global temperature data base and from rural stations only. The global rural temperature time series and trends are very similar to those derived from the full data set. Therefore, the well-known global temperature time series from in situ stations is not significantly impacted by urban warming

Global rural temperature trends

Using rural/urban land surface classifications derived from maps and satellite observed nighttime surface lights, global mean land surface air temperature time series were created using data from all weather observing stations in a global temperature data base and from rural stations only. The global rural temperature time series and trends are very similar to those derived from the full data set. Therefore, the well-known global temperature time series from in situ stations is not significantly impacted by urban warming