999 research outputs found
Community Colleges and COVID-19: An Exploration of Challenges and Inequities
COVID-19 drastically changed many aspects of life in the U.S. and most certainly changed standard operating procedures in higher education. Moving all classes completely online created numerous challenges not only for students, but also for faculty. For students, these challenges included issues related to physical and mental health, job loss, and caregiving, as well as access to internet and even access to a home computer. Faculty also faced challenges. For example, many colleges and universities rely on adjunct faculty who are compensated on a course-by-course basis. Although most institutions provided faculty development sessions to make a smooth transition to online teaching, adjunct faculty were not necessarily invited to participate and, when they were, they were not compensated for time spent in these sessions or the additional work incurred to transition and teach in the online environment. This essay explores how community college students and faculty in the basic course responded to the COVID-19 crisis. Specifically, we discuss issues of employment, family responsibilities, and the digital divide as they reveal systemic inequities in the college setting, as well as in society
Potential Anti-cancer and Anti-bacterial Activities of Philippine Echinoderm Extracts
In high-throughput search for bioactive compounds under resource-limited settings from Philippine echinoderms, the aqueous, methanol, chloroform and hexane extracts of seven Philippine echinoderms namely Holothuria nobilis (sea cucumber), Bohadscia marmorata (sea cucumber), Stichopus chloronatus (sea cucumber), Holothuria axiologa (sea cucumber), Linckia laevigata (starfish), Oreaster nodusus (starfish) and Ophiocoma ochoenleinii (brittle star) were screened for antitumor and antibacterial activity. Antitumor activity was determined using brine shrimp lethality assay while antibacterial assay was performed using turbidimetric method. Both assays utilized 96-well microtiter plates to facilitate speed and ease in screening. The chloroform extract of H. nobilis gave a positive result on antitumor activity while almost all sample extracts showed antibacterial activity against E. coli
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Predicting responses to climate change using a joint species, spatially dependent physiologically guided abundance model
Predicting the effects of warming temperatures on the abundance and distribution of organisms under future climate scenarios often requires extrapolating species-environment correlations to climatic conditions not currently experienced by a species, which can result in unrealistic predictions. For poikilotherms, incorporating species' thermal physiology to inform extrapolations under novel thermal conditions can result in more realistic predictions. Furthermore, models that incorporate species and spatial dependencies may improve predictions by capturing correlations present in ecological data that are not accounted for by predictor variables. Here, we present a joint species, spatially dependent physiologically guided abundance (jsPGA) model for predicting multispecies responses to climate warming. The jsPGA model uses a basis function approach to capture both species and spatial dependencies. We apply the jsPGA model to predict the response of eight fish species to projected climate warming in thousands of lakes in Minnesota, USA. By the end of the century, the cold-adapted species was predicted to have high probabilities of extirpation across its current range-with 10% of lakes currently inhabited by this species having an extirpation probability >0.90. The remaining species had varying levels of predicted changes in abundance, reflecting differences in their thermal physiology. Though the model did not identify many strong species dependencies, the variation in estimated spatial dependence across species suggested that accounting for both dependencies was important for predicting the abundance of these fishes. The jsPGA model provides a new tool for predicting changes in the abundance, distribution, and extirpation probability of poikilotherms under novel thermal conditions
Direct simulation of ion beam induced stressing and amorphization of silicon
Using molecular dynamics (MD) simulation, we investigate the mechanical
response of silicon to high dose ion-irradiation. We employ a realistic and
efficient model to directly simulate ion beam induced amorphization. Structural
properties of the amorphized sample are compared with experimental data and
results of other simulation studies. We find the behavior of the irradiated
material is related to the rate at which it can relax. Depending upon the
ability to deform, we observe either the generation of a high compressive
stress and subsequent expansion of the material, or generation of tensile
stress and densification. We note that statistical material properties, such as
radial distribution functions are not sufficient to differentiate between
different densities of amorphous samples. For any reasonable deformation rate,
we observe an expansion of the target upon amorphization in agreement with
experimental observations. This is in contrast to simulations of quenching
which usually result in denser structures relative to crystalline Si. We
conclude that although there is substantial agreement between experimental
measurements and most simulation results, the amorphous structures being
investigated may have fundamental differences; the difference in density can be
attributed to local defects within the amorphous network. Finally we show that
annealing simulations of our amorphized samples can lead to a reduction of high
energy local defects without a large scale rearrangement of the amorphous
network. This supports the proposal that defects in amorphous silicon are
analogous to those in crystalline silicon.Comment: 13 pages, 12 figure
mu-Opioid inhibition of Ca2+ currents and secretion in isolated terminals of the neurohypophysis occurs via ryanodine-sensitive Ca2+ stores
mu-Opioid agonists have no effect on calcium currents (I(Ca)) in neurohypophysial terminals when recorded using the classic whole-cell patch-clamp configuration. However, mu-opioid receptor (MOR)-mediated inhibition of I(Ca) is reliably demonstrated using the perforated-patch configuration. This suggests that the MOR-signaling pathway is sensitive to intraterminal dialysis and is therefore mediated by a readily diffusible second messenger. Using the perforated patch-clamp technique and ratio-calcium-imaging methods, we describe a diffusible second messenger pathway stimulated by the MOR that inhibits voltage-gated calcium channels in isolated terminals from the rat neurohypophysis (NH). Our results show a rise in basal intracellular calcium ([Ca(2+)]i) in response to application of [D-Ala(2)-N-Me-Phe(4),Gly5-ol]-Enkephalin (DAMGO), a MOR agonist, that is blocked by D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), a MOR antagonist. Buffering DAMGO-induced changes in [Ca(2+)]i with BAPTA-AM completely blocked the inhibition of both I(Ca) and high-K(+)-induced rises in [Ca(2+)]i due to MOR activation, but had no effect on kappa-opioid receptor (KOR)-mediated inhibition. Given the presence of ryanodine-sensitive stores in isolated terminals, we tested 8-bromo-cyclic adenosine diphosphate ribose (8Br-cADPr), a competitive inhibitor of cyclic ADP-ribose (cADPr) signaling that partially relieves DAMGO inhibition of I(Ca) and completely relieves MOR-mediated inhibition of high-K(+)-induced and DAMGO-induced rises in [Ca(2+)]i. Furthermore, antagonist concentrations of ryanodine completely blocked MOR-induced increases in [Ca(2+)]i and inhibition of I(Ca) and high-K(+)-induced rises in [Ca(2+)]i while not affecting KOR-mediated inhibition. Antagonist concentrations of ryanodine also blocked MOR-mediated inhibition of electrically-evoked increases in capacitance. These results strongly suggest that a key diffusible second messenger mediating the MOR-signaling pathway in NH terminals is [Ca(2+)]i released by cADPr from ryanodine-sensitive stores
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