Western Washington University

Couplings exist between power-electronic converters' positive and negative impedances. While such couplings have been considered in many works for stability analysis of grid-forming converters, many other studies have accurately predicted the converter-grid stability with couplings ignored. This paper provides a detailed comparative analysis of the sequence impedance coupling in droop control-based converter (DBC) and virtual synchronous machine (VSM). The impacts of droop gains, virtual inertia, and voltage controllers are mainly outlined. It is shown that the VSM has notably less impedance coupling than the typical DBC, basically due to its virtual exciter's integrator. Additionally, this paper introduces the VSM's impedance coupling saturation phenomenon. The improper design of the VSM's voltage exciter leads to impedance coupling as high as that of the typical DBC, regardless of the virtual inertia. Based on the analysis and the impedance-coupling saturation phenomenon, a simple yet effective control-design-based mechanism is proposed to weaken the impedance coupling in VSM and in a modified DBC with an integrator in its voltage loop. The proposed impedance weakening method eases the converter-grid interactions and stability analysis by deploying the normal Nyquist stability criterion. Detailed time-domain and real-time simulations are carried out under different grid strengths to justify the theoretical analysis.

Marine diatoms are pervasive in many planktonic and benthic environments and represent an important food source for a wide range of species. Some diatoms produce polyunsaturated aldehydes (PUAs) as defensive toxins. PUA exposure is known to reduce the fecundity of invertebrate grazers like copepods and echinoderm larvae, but little is known about the effects of PUAs on vertebrates. Many fish species are likely to come into close contact with diatoms. Many may deposit eggs on diatom-coated substrates, consume diatoms as larvae, and/or feed heavily on zooplankters that may be gut-loaded with diatoms. The purpose of this study was to test whether dissolved diatom PUAs affect the early life stages of a model fish, Danio rerio (zebrafish). To test this, zebrafish embryos and larvae were exposed to proportionally increasing mixtures of the dissolved diatom PUAs 2E,4E-decadienal, 2E,4E-octadienal and 2E,4E-heptadienal. Under PUA exposure, three metrics of fitness were assessed: embryo heart rate, larval size at hatch, and pre-feeding mortality rate. Zebrafish embryos exposed at 24 h post fertilization (hpf) experienced decreased average heart rate after 2 days of PUA exposure. Embryos 24 hpf exposed to PUA mixtures for 6 days showed a reduction in size in comparison to embryos from controls. Embryos exposed to PUAs from 2 hpf until death showed lower survivorship compared to larvae in controls. The results of this study suggest that larval fish that are sympatric with PUA producing diatoms during their embryonic and larval stages may be susceptible to detrimental effects from PUA exposure.

This paper presents the development and application of the equity and climate impacts optimization in community energy (ECOCE) model, a mixed integer linear tool designed to optimize equity-driven investment in community solar projects (CSPs). By providing insight on a variety of impacts of CSP investments, including electricity bill savings, solar production, and greenhouse gas emissions reduction, the model assists policymakers in understanding the possible trade-offs in benefits and impacts of CSP investments. Using a detailed case study of a one-time $100 million investment in CSPs in Washington State, the model evaluates potential scenarios under various funding distributions to determine the optimal allocation of state funds. The study highlights considerations of geographical equity and participation, trade-offs between maximizing greenhouse gas reductions and minimizing energy burden, and the potential to use the model in different regional contexts. The findings suggest that targeted investments can provide significant electricity bill savings ($6.5–8.5 million annually) for low-income communities while contributing to state decarbonization goals (4–42 kTons of avoided emissions annually) in Washington State, though political and practical considerations may influence the feasibility of these optimized allocations. The ECOCE model provides a robust framework for decision-makers aiming to balance a variety of political, equity, and climate change mitigation considerations in the transition to renewable energy.

We investigate effects of culturally situated differences in cognition on Japanese and US firms’ responses to performance feedback through R&D investments. Performance feedback research has mostly assumed a universal nature of decision makers’ cognition and responses. We posit firms from Japan should have a more holistic cognitive orientation than US firms, making them less responsive to problemistic and slack search mechanisms of performance feedback when making R&D investments. These expectations are largely supported in the context of 37 Japanese and 19 US automotive firms (546 firm-year-observations) from 2003 to 2019. We find further support using data on 106 global automotive firms (902 firm-year-observations), from 14 holistic or analytic oriented countries. This study establishes the culturally situated cognitive-orientation theoretical construct as a moderator of problemistic and slack search. Additionally, managers could adopt decision-making processes reflecting both holistic and analytic cognitive orientations while responding to performance feedback, to avoid biases.

Fifty‐six million years ago a massive flux of exogenic carbon was rapidly released into Earth's oceans and atmosphere during the Paleocene‐Eocene Thermal Maximum (PETM). The warming associated with this release persisted for ∼200 kyr. It had severe impacts on ocean environments, global ecosystems, and the hydrologic cycle. Yet, regional patterns of response within continental settings are not well constrained. Here we describe the first recognition of the PETM in the Greater Green River Basin of western Wyoming, USA. We present new sedimentologic, chemostratigraphic, and paleontologic data from the Chappo Member of the Wasatch Formation in the Sevier fold‐and‐thrust belt. The Chappo Member contains lithofacies indicative of debris flows, ephemeral and incisional stream channels, and well‐drained overbank deposits, which, along with the geographic position of the study area, indicate a distal alluvial fan setting. Using pedogenic carbonates, we find a negative carbon isotope excursion (CIE) of ∼3.8‰ associated with the first appearance of Celtis endocarps stratigraphically above beds containing late Paleocene mammals. The CIE magnitude here is considerably smaller, compared to records from the Bighorn Basin, which we interpret to represent drier, better‐drained conditions. High baseline carbon isotope values suggest dry conditions in the study area, which likely resulted from well‐drained sediments associated with the distal alluvial fan. Low amounts of precipitation, as suggested by previous climate models, may have contributed to dryness. We also find sedimentologic evidence consistent with an enhanced hydrologic cycle during the PETM, as seen in other basins in the region.

We present a new proof of the compactness of bilinear paraproducts with CMO symbols. By drawing an analogy to compact linear operators, we first explore further properties of compact bilinear operators on Banach spaces and present examples. We then prove compactness of bilinear paraproducts with CMO symbols by combining one of the properties of compact bilinear operators thus obtained with vanishing Carleson measure estimates and interpolation of bilinear compactness.

Variational flooding is an enhanced sampling method for obtaining kinetic rates from molecular dynamics simulations. This method is inspired by the idea of conformational flooding that employs a boost potential acting along a chosen reaction coordinate to accelerate rare events. In this work, we show how the empirical distribution of crossing times from variational flooding simulations can be modeled with analytical Kramers’ time-dependent rate (KTR) theory. An optimized bias potential that fills metastable free energy basins is constructed from the variationally enhanced sampling (VES) method. This VES-derived flooding potential is then augmented by a switching function that determines the fill level of the boost. Having a prescribed time-dependent fill rate of the flooding potential gives an analytical expression for the distribution of crossing times from KTR theory that is used to extract unbiased rates. In the case of a static boost potential, the distribution of barrier crossing times follows an expected exponential distribution, and unbiased rates are extracted from a series of boosted simulations at discrete fill levels. Introducing a time-dependent boost that increases the fill level gradually over the simulation time leads to a simplified procedure for fitting the biased distribution of crossing times to analytical theory. We demonstrate the approach for the paradigmatic cases of alanine dipeptide in vacuum, the asymmetric SN2 reaction, and the folding of chignolin in explicit solvent.

Peer review serves to evaluate the scientific validity and quality of research by other researchers within the same field. Psychology, like many other disciplines, uses peer review to determine whether researchers’ work is published, where it is published, and in what form. However, the peer review system is imperfect, often perpetuating harm, exclusion, and inequities. We believe these problems hinder psychology from becoming a truly representative and valid science. In this paper, we uncover the historical roots of the peer review system in psychology and describe how these roots persist today. Then, using personality psychology as an exemplar, we leverage a social justice lens to: (1) document key contemporary problems in the peer review system; (2) identify global challenges in peer review; and (3) provide recommendations and guiding questions that might help the field become more equitable, diverse, just, and inclusive. To do so, we draw upon three sources of information: our personal experiences, qualitative and quantitative data from 104 self-identifying personality psychologists, and the prior literature. Ultimately, the goal of this work is to give voice to those who have been harmed in peer review, and to inform how we might reimagine peer review in personality psychology and beyond.

Bacterial sortases are a family of cysteine transpeptidases in Gram‐positive bacteria of which sortase A (SrtA) enzymes are responsible for ligating proteins to the peptidoglycan layer of the cell surface. Engineered versions of sortases are also used in sortase‐mediated ligation (SML) strategies for a variety of protein engineering applications. Although a versatile tool, substrate recognition by Staphylococcus aureus SrtA (saSrtA), the most commonly utilized enzyme in SML, is stringent and relies on an LPXTG pentapeptide motif. Previous structural studies revealed that the requirement of a glycine in the binding motif may be due to potential steric hindrance of amino acids possessing a β‐carbon by W194, a tryptophan located in the β7‐β8 loop of the enzyme. Here, we measured the effect of seven single point mutants of W194 (A, D, F, G, N, S, Y) saSrtA using a FRET‐based activity assay. We found that while the LPXTG motif remains a requirement for initial proteolytic cleavage, the nucleophile specificity of our variants is altered. In particular, W194A and W194S saSrtA recognize a D‐Ala nucleophile and are able to perform ligation reactions. Notably, an LPXT(D‐Ala) peptide was not cleaved by either mutant enzyme. We hypothesize that these variants may potentially be utilized to develop an irreversible sortase‐mediated reaction. Taken together, this experiment reveals new insight into sortase specificity and possible future SML strategies.

This chapter adds perspectives to the growing body of literature on pláticas, a methodology to dialogue and theorize about ourselves, our teaching, research, and contexts. Following hooks (1994), who stated that liberation is facilitated by finding spaces to express ourselves freely, use our voices creatively, and engage in dialogue both verbally and aesthetically that (re)interprets imposed and oppressive truths, the authors show how pláticas challenged understanding of place and offered a transformative space for healing by forming new boundaries across home and professional lives. Reflecting on intimate situations while teaching on Zoom from home during the COVID-19 pandemic, the authors found ways to challenge “being put in one’s place” (as mothers/daughters and/or faculty) and began to reimagine their identities.

The Himalaya orogen evolved since the Eocene as the Tethyan‐, Greater‐, Lesser‐ and Sub‐Himalaya thrust sheets were uplifted and exhumed in sequence. Reconstructing the provenance of sediment in Himalayan River systems can inform on stages in the tectonic history of the orogen. Here, we analyze the oxygen, carbon and “clumped” isotope compositions of carbonate minerals from Himalayan bedrock, Ganga River sediments and Bengal Fan turbidite deposits. We demonstrate that river sediments consist of a mixture of Himalayan‐derived and authigenic calcite precipitated in the river system. The relative abundance and clumped isotope apparent temperatures of detrital calcite in turbidite deposits decreased between the Late Miocene and Pliocene, while chemical weathering intensity did not increase during this interval. Considered together, these results reflect the establishment of the Lesser Himalaya as an important carbonate sediment source for Himalayan rivers, driven by the uplift and exhumation of this thrust sheet.

Seasonal snow in the extratropical Andes is a primary water source for major rivers supplying water for drinking, agriculture, and hydroelectric power in Central Chile. Here, we used estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) to analyze changes in snow cover extent over the period 2001–2022 in a total of 18 watersheds spanning approximately 1,100 km across the Chilean Andes (27–36°S). We found that the annual snow cover extent is receding in the watersheds analyzed at an average pace of approximately 19% per decade. These alarming trends have impacted meltwater runoff, resulting in historically low river streamflows during the dry season. We examined streamflow records dating back to the early 1980s for 10 major rivers within our study area. Further comparisons with large-scale climate modes suggest that the detected decreasing trends in snow cover extent are likely driven by the poleward migration of the westerly winds associated with a positive trend in the Southern Annular Mode (SAM).

Lay Description What is already known about this topic Social media has been proved to be a valid and helpful resource for teachers' professional learning purposes. Most previous work heavily relied on qualitative methods and self‐report data, focusing on how social‐media‐based professional learning promotes teachers' connections and how participants perceive these tools. There is a lack in quantitative analysis to investigate the large informal professional learning networks using authentic data. What this paper adds This study examined massive informal professional learning networks on Twitter, using a data set of more than 400,000 tweets. Through the lens of community commitment, we provided a comprehensive and in‐depth overview of the structure and development of massive informal online professional networks. This study examined the commitment dynamics from multiple perspectives: network level, community level, and individual level. This study utilized social network analysis and data mining techniques to identify meaningful structures, participants' commitment dynamics, and behavioural patterns at the network, community and individual levels. Implications for practice and/or policy Methodologically, the usage of longitudinal data enabled a temporal perspective to our analysis. Our finding that around 30% of the participants remain committed to the learning network without intervention could be used as a benchmark in assessing informal online learning networks. We identified a natural cluster pattern that participants tend to form communities with peers who behave similarly, providing reference for developers and moderators of informal online learning.

This essay examines June Jordan’s design writings to elaborate a political theory of redesign in her work. I show that Jordan’s redesign offers political principles for reimagining space at multiple scales and speaks to the question of how more livable, beautiful worlds may be wrought from the material contexts in which we presently live. Against the grain of the dismantling of public goods in the late twentieth century, Jordan re-envisioned public city spaces and housing with dignity and room for human flourishing. Her primary barometer for design was the fullest expression of human aliveness—she insisted that the built environment should “[cherish] as it amplifies the experience of being alive.” Jordan’s visionary pragmatism anticipates what Deva Woodly calls the “radical Black feminist pragmatism” of the twenty-first century’s Movement for Black Lives and speaks to contemporary abolitionist thought and struggles over the future of public goods.

The Mars 2020 Perseverance rover discovered fine‐grained clastic sedimentary rocks in the “Hogwallow Flats” member of the “Shenandoah” formation at Jezero crater, Mars. The Hogwallow Flats member shows evidence of multiple phases of diagenesis including Fe/Mg‐sulfate‐rich (20–30 wt. %) outcrop transitioning downward into red‐purple‐gray mottled outcrop, Fe/Mg clay minerals and oxides, putative concretions, occasional Ca sulfate‐filled fractures, and variable redox state over small (cm) spatial scales. This work uses Mastcam‐Z and SuperCam instrument data to characterize and interpret the sedimentary facies, mineralogy and diagenetic features of the Hogwallow Flats member. The lateral continuity of bedrock similar in tone and morphology to Hogwallow Flats that occurs over several km within the western Jezero sedimentary fan suggests widespread deposition in a lacustrine or alluvial floodplain setting. Following deposition, sediments interacted with multiple fluids of variable redox state and salinity under habitable conditions. Three drilled sample cores were collected from this interval of the Shenandoah formation as part of the Mars Sample Return campaign. These samples have very high potential to preserve organic compounds and biosignatures. Drill cores may partially include dark‐toned mottled outcrop that lies directly below light‐toned, sulfate‐cemented outcrop. This facies may represent some of the least oxidized material observed at this interval of the Shenandoah formation. This work reconstructs the diagenetic history of the Hogwallow Flats member and discusses implications for biosignature preservation in rock samples for possible return to Earth.

In the early twentieth century, one could find kimono-like garments of various kinds in Britain: kimono made originally for Japanese consumers, contemporary robes made in Japan expressly for export, and kimono-inspired clothing made domestically. The present essay probes the merchandising of these new products in Britain, examining both British consumer tendencies and Japanese marketing practices, through analysis of Japanese trade statistics and reports on the international expositions of the day. Ultimately, this paper argues that kimono played a role, both literally and figuratively, in staging increased social justice for British women in the twentieth century, offering at least occasional relief from the debilitating fashions of the period, all of which required a corset, and providing a metaphor for a less restrictive social environment. While other scholars have hinted at such associations, this paper provides evidence, through analysis of contemporaneous journalism and advertising, that the women who wore these garments explicitly made such connections. More than an artistic stimulus of japonisme , the kimono and the fashions it subsequently inspired became symbols of the women’s suffrage movement in early twentieth-century Britain.

The NASA Perseverance rover discovered light-toned float rocks scattered across the surface of Jezero crater that are particularly rich in alumina ( ~ 35 wt% Al2O3) and depleted in other major elements (except silica). These unique float rocks have heterogeneous mineralogy ranging from kaolinite/halloysite-bearing in hydrated samples, to spinel-bearing in dehydrated samples also containing a dehydrated Al-rich phase. Here we describe SuperCam and Mastcam-Z observations of the float rocks, including the first in situ identification of kaolinite or halloysite on another planet, and dehydrated phases including spinel and apparent partially dehydroxylated kaolinite. The presence of spinel in these samples is likely detrital in origin, surviving kaolinitization, pointing to an ultramafic origin. However, the association of low hydration with increased Al2O3 abundances suggests heating-induced dehydration which could have occurred during the lithification or impact excavation of these rocks. Given the orbital context of kaolinite-bearing megabreccia in the Jezero crater rim, we propose an origin for these rocks involving intense aqueous alteration of the parent material, followed by dehydration/lithification potentially through impact processes, and dispersion into Jezero crater through flood or impact-related processes.