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Atomistic insights into the binding of SARS-CoV-2 spike receptor binding domain with the human ACE2 receptor: The importance of residue 493
No full textSARS-CoV-2 is a coronavirus that has created a global pandemic. The virus contains a spike protein which has been shown to bind to the ACE2 receptor on the surface of human cells. Vaccines have been developed that recognize elements of the SARS-CoV-2 spike protein and they have been successful in preventing infection. Recently, the Omicron variant of the SARS-CoV-2 virus was reported and quickly became a variant of concern due to its transmissibility. This variant contained an unusually large number (32) of point mutations, of which 15 of those mutations are in the receptor binding domain of the spike protein. While several computational and experimental investigations comparing the binding of the Omicron and wild type RBD to the human ACE2 receptor have been conducted, many of these report contradictory findings. In order to assess the differential binding ability, we conducted 2 μs of classical molecular dynamics (cMD) simulation to estimate the binding affinities and behaviors. Based upon MM-GBSA binding affinity, per-residue energy decomposition analysis, center of mass distance measurements, ensemble clustering, pairwise residue decomposition and hydrogen bonding analysis, our results suggest that a single point mutation is responsible for the enhanced binding of the Omicron mutant relative to the WT. While the 15-point mutations in the receptor binding domain contribute positively and negatively to the affinity of the spike protein for the human ACE2 receptor, it is the point mutation Q493R that confers enhanced binding while the Q493K mutation results in similar binding. The MM-GBSA binding estimations over a 2 μs trajectory, suggest that the wild type binds to ACE2 with a value of −29.69 kcal/mol while the Q493K and Q493R Omicron mutants bind with energy values of −26.67 and −34.56 kcal/mol, respectively. These values are significantly different, given the error estimates associated with the MM-GBSA method. In general, while some mutations increase binding, more mutations diminish binding, leading to an overall similar picture of binding for Q493K and enhanced binding for Q493R
Floral Nectar is Sugar Water
No full textFor this article, let’s turn our attention to the chemical and nutritional qualities of floral nectar. Unfortunately, I know of no detailed scientific literature on composition of floral nectar in the genus Eutrochium, but the general principles addressed here are certainly as pertinent to Joe Pye Weeds as they are for any other nectar-producing plants
Engaging with “Fringe” Beliefs: Why, When, and How
No full textI argue that in many cases, there are good reasons to engage with people who hold fringe beliefs such as debunked conspiracy theories. I (1) discuss reasons for engaging with fringe beliefs; (2) discuss the conditions that need to be met for engagement to be worthwhile; (3) consider the question of how to engage with such beliefs, and defend what Jeremy Fantl has called “closed-minded engagement” and (4) address worries that such closed-minded engagement involves problematic deception or manipulation. Thinking about how we engage with irrational emotions offers a way of responding to these concerns. Reflection on engagement with fringe beliefs has wider implications for two distinct philosophical discussions. First, it can help illuminate the nature of beliefs, lending support to the view that not all states which are deeply resistant to evidence thereby fail to be beliefs. Second, an implication of the view I put forth is that it need not constitute a lack of respect to adopt what Peter Strawson called “the objective stance” in relationships
Closed-form analytical solution for the transfer matrix based on Pendry-MacKinnon discrete Maxwell\u27s equations
No full textPendry and MacKinnon meaningful discretization of Maxwell\u27s equations was put forward specifically as part of a finite-element numerical algorithm. By contrast with a numerical approach, in the same spirit evoked by the relationships between the difference and the differential equations, we provide an analytical solution for the transfer matrix elements generated by this discretization of Maxwell\u27s equations. The method, valid for all modes and any non-magnetic pattern with frequency-dependent permittivities, is exemplified for a bilaminar structure. The results from hundreds of path-operators simplify to a small number of propagation channels, which transfer the electromagnetic field between input and output. A specific bilaminar device is design-optimized and used to generate a topological map from permittivities to the number of modes and very high Q-factor resonances
Photonics roadmap for ultra-high-temperature thermophotovoltaics
No full textThe ability to control thermal emission is crucial for the thermal regulation of devices, barrier coatings, and thermophotovoltaic (TPV) systems. However, only a limited number of naturally occurring materials are stable at high temperatures (\u3e1,800C), and their emission spectra are set a priori by their intrinsic optical properties. Optical structures involving nanoscale textures can result in tunable emission spectra, albeit stable only at much lower temperatures. Here, we present an alternative approach that enables temperatures beyond 1,800 C through a bilayer stack achieved by combining the optical and thermal properties of 2,809 coating/substrate pairs. By varying the film thickness, we tailor the emission spectrum to create high-temperature, stable emitters. We illustrate this effect in combination with the most common TPV systems (GaSb, Ge, InGaAs, and InGaAsSb), showing power conversion efficiencies approaching 50% and power outputs as high as 10.2 W cm2. These concepts can be expanded to other high-temperature photonic applications for the spectral control of thermal emission
The Second Radio Synchrotron Background Workshop: Conference Summary and Report
No full textWe summarize the second radio synchrotron background workshop, which took place on 2022 June 15–17 in Barolo, Italy. This meeting was convened because available measurements of the diffuse radio zero level continue to suggest that it is several times higher than can be attributed to known Galactic and extragalactic sources and processes, rendering it the least well-understood electromagnetic background at present and a major outstanding question in astrophysics. The workshop agreed on the next priorities for investigations of this phenomenon, which include searching for evidence of the radio Sunyaev–Zel\u27dovich effect, carrying out cross-correlation analyses of radio emission with other tracers, and supporting the completion of the 310 MHz absolutely calibrated sky map project
China on Campus: A Conversation with China Scholars of Asian Heritage
No full textIncreasing tensions between the United States and China, a rise in anti-Asian sentiment, and the risk of government surveillance has dramatically altered the teaching and research contexts for scholars of Chinese politics. In this conversation, Dan Chen (University of Richmond), Rongbin Han (University of Georgia), and John Yasuda (Johns Hopkins University) discuss how questions of identity, politics, and security have affected classroom dynamics and their future research endeavors
Is Graduate School Worth It? Harassment and Graduate-Student Satisfaction in Political Science
No full textThis article investigates the dynamics of discrimination in political science PhD programs with a survey of current political science graduate students in the top 50 departments. The study focuses on mentorship, funding, sexual harassment, racism, homophobia, and labor exploitation: 20% of respondents reported labor exploitation, 19% experienced racial discrimination, 9% reported sexual harassment, and 6% experienced homophobia. Discrimination is uneven across individuals; some groups of graduate students experience widespread discrimination, especially racial discrimination, whereas other groups are largely unaware of these issues. We conducted a survey experiment to gauge the impact of misconduct on formal reporting mechanisms and find that hearing about racial discrimination has a chilling effect on reporting. We find that experiencing discrimination harms how satisfied students are in their program. We find that factors linked to student vulnerability, such as international status and funding, are significantly associated with harassment and that reporting discrimination predicts more discrimination
A Configurational Theory of Generalized Exchange in Stakeholder-Oriented Firms
Get PDFRecent developments in stakeholder theory have refined our understanding of value creation via bilateral reciprocity. Generalized exchange is another important microfoundational mechanism in value creation, but because of the potential for free-riding it is surprising that some stakeholders contribute more resources to a firm’s value-creating nexus than would be expected based on contractual obligations, and even beyond what bilateral reciprocity would predict. This paper aims to identify the minimum conditions that promote generalized exchange in a firm’s value-creating nexus. Because generalized exchange is causally complex—it can occur in multiple contexts and through various combinations of explanatory factors—a configurational theorizing approach is applied. We identify four combinations of attributes that consistently promote generalized exchange and limit free-riding behavior, such that generalized exchange can make a net positive difference in a firm’s nexus: the entrepreneurial logic (high rewards, strong institutional drivers), the conformity logic (powerful sanctions, strong institutional drivers), the influencer logic (powerful sanctions, individual or firm drivers), and the identification logic (high rewards, individual or firm drivers). This work provides an important additional explanation for why stakeholder-oriented firms tend to have higher performance, and can also help managers devise policies for increasing the amount of generalized exchange exhibited among their firm’s stakeholders
Sutra
No full textFEATURED POET
Tomaž Šalamun (1941-2014) published more than 55 books of poetry in Slovenia. Translated into over 25 languages, his poetry received numerous awards, including the Jenko Prize, the Prešeren Prize, the European Prize for Poetry, and the Mladost Prize. In the 1990s, he served for several years as the Cultural Attaché for the Slovenian Embassy in New York, and later held visiting professorships at various universities in the U.S. FEATURED TRANSLATOR
Brian Henry is the author of eleven books of poetry and, most recently, the prose book Things Are Completely Simple: Poetry and Translation. He has translated Tomaž Šalamun’s Woods and Chalices, Aleš Debeljak’s Smugglers, and five books by Aleš Šteger. He co-edited Verse from 1995 to 2018. His work has received numerous honors, including two NEA fellowships, the Alice Fay di Castagnola Award, a Howard Foundation fellowship, a Slovenian Academy of Arts and Sciences grant, and the Best Translated Book Award