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Contract managers change contracts to respond to unforeseen events and to improve the likelihood of securing critical supplies. This study employs data from the General Service Administration's SAM.gov Data Bank on over 8,000 contracts to examine the prevalence, reasons for, and timing of contract modifications and terminations in federal purchasing of personal protective equipment (PPE) in the first year of the COVID-19 public health crisis. Results show that modifications that transform transactional contracts to more collaborative designs were utilized for some of the highest-risk contracts and were associated with increased obligations, indicating that collaborative designs led to more purchasing of PPE. Competitive selection increased the likelihood of termination, the rate at which terminations occurred, and deobligations, indicating that the approach increased the costs of administration without improving the likelihood of securing supplies. A substantial portion of modifications and terminations occurred within the first forty days of delivery, revealing how contract management capacity was needed in the early stages of critical supply acquisition. [ABSTRACT FROM AUTHOR]

The majority of genetic variants associated with common human diseases map to enhancers, non-coding elements that shape cell-type-specific transcriptional programs and responses to extracellular cues. Systematic mapping of functional enhancers and their biological contexts is required to understand the mechanisms by which variation in non-coding genetic sequences contributes to disease. Functional enhancers can be mapped by genomic sequence disruption, but this approach is limited to the subset of enhancers that are necessary in the particular cellular context being studied. We hypothesized that recruitment of a strong transcriptional activator to an enhancer would be sufficient to drive target gene expression, even if that enhancer was not currently active in the assayed cells. Here we describe a discovery platform that can identify stimulus-responsive enhancers for a target gene independent of stimulus exposure. We used tiled CRISPR activation (CRISPRa) to synthetically recruit a transcriptional activator to sites across large genomic regions (more than 100 kilobases) surrounding two key autoimmunity risk loci, CD69 and IL2RA. We identified several CRISPRa-responsive elements with chromatin features of stimulus-responsive enhancers, including an IL2RA enhancer that harbours an autoimmunity risk variant. Using engineered mouse models, we found that sequence perturbation of the disease-associated Il2ra enhancer did not entirely block Il2ra expression, but rather delayed the timing of gene activation in response to specific extracellular signals. Enhancer deletion skewed polarization of naive T cells towards a pro-inflammatory T helper (TH17) cell state and away from a regulatory T cell state. This integrated approach identifies functional enhancers and reveals how non-coding variation associated with human immune dysfunction alters context-specific gene programs.

T-cell genome engineering holds great promise for cell-based therapies for cancer, HIV, primary immune deficiencies, and autoimmune diseases, but genetic manipulation of human T cells has been challenging. Improved tools are needed to efficiently "knock out" genes and "knock in" targeted genome modifications to modulate T-cell function and correct disease-associated mutations. CRISPR/Cas9 technology is facilitating genome engineering in many cell types, but in human T cells its efficiency has been limited and it has not yet proven useful for targeted nucleotide replacements. Here we report efficient genome engineering in human CD4(+) T cells using Cas9:single-guide RNA ribonucleoproteins (Cas9 RNPs). Cas9 RNPs allowed ablation of CXCR4, a coreceptor for HIV entry. Cas9 RNP electroporation caused up to ∼40% of cells to lose high-level cell-surface expression of CXCR4, and edited cells could be enriched by sorting based on low CXCR4 expression. Importantly, Cas9 RNPs paired with homology-directed repair template oligonucleotides generated a high frequency of targeted genome modifications in primary T cells. Targeted nucleotide replacement was achieved in CXCR4 and PD-1 (PDCD1), a regulator of T-cell exhaustion that is a validated target for tumor immunotherapy. Deep sequencing of a target site confirmed that Cas9 RNPs generated knock-in genome modifications with up to ∼20% efficiency, which accounted for up to approximately one-third of total editing events. These results establish Cas9 RNP technology for diverse experimental and therapeutic genome engineering applications in primary human T cells.

While prior research has long identified the centrality of critical supply acquisition to the government's response to a crisis, there is less understanding of how to secure critical supplies that depend on global supply chains. The acquisition of personal protective equipment (PPE) in the immediate aftermath of the coronavirus disease 2019 outbreak (COVID-19) proved challenging not only due to threats of contractor deception but also due to disruptions in contractor supply chains. This research analyzes primary interview data with contracting officials involved in purchasing PPE in the early stages of the COVID-19 crisis. The results indicate the ways that contractor relationships were perceived useful in anticipating risks surrounding a contractor's behavior (behavioral uncertainties), but insufficient in anticipating disruptions that can result from a contractor's supply chains (environmental uncertainties). Contractor relations were perceived to help in predicting industry disruptions, but such relations were likely to be formed alongside transactional and short-term contract designs—and likely to require comparison with other data sources. The results indicate that improving the reliability of critical supply acquisition for future crises is likely to depend on developing expertise in supply chain analysis, especially as the U.S. government increasingly relies on global supply chains in critical supply acquisition. [ABSTRACT FROM AUTHOR]

Co-inhibitory immune receptors can contribute to T cell dysfunction in patients with cancer.sup.1,2. Blocking antibodies against cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death 1 (PD-1) partially reverse this effect and are becoming standard of care in an increasing number of malignancies.sup.3. However, many of the other axes by which tumours become inhospitable to T cells are not fully understood. Here we report that V-domain immunoglobulin suppressor of T cell activation (VISTA) engages and suppresses T cells selectively at acidic pH such as that found in tumour microenvironments. Multiple histidine residues along the rim of the VISTA extracellular domain mediate binding to the adhesion and co-inhibitory receptor P-selectin glycoprotein ligand-1 (PSGL-1). Antibodies engineered to selectively bind and block this interaction in acidic environments were sufficient to reverse VISTA-mediated immune suppression in vivo. These findings identify a mechanism by which VISTA may engender resistance to anti-tumour immune responses, as well as an unexpectedly determinative role for pH in immune co-receptor engagement. V-domain immunoglobulin suppressor of T cell activation (VISTA) selectively engages P-selectin glycoprotein ligand-1 (PSGL-1) and suppresses T cells at acidic pH similar to those in tumour microenvironments, thereby mediating resistance to anti-tumour immune responses., Author(s): Robert J. Johnston [sup.1] , Linhui Julie Su [sup.2] , Jason Pinckney [sup.3] , David Critton [sup.4] , Eric Boyer [sup.1] , Arathi Krishnakumar [sup.5] , Martin Corbett [sup.6] [...]

The problem of estimating signal parameters using an array of sensors is studied. The closed-form expressions of the probability density function and of the variance of the estimates in the one source scenario and a closed-form expression of this estimator variance in the two sources scenario is brought out.

The nonasymptotic behavior of the maximum likelihood method in the context of lacunar array processing is investigated. The computer simulations confirm the validity of the theoretical investigations.

The purpose of this work is the estimation of Doppler echoes spectral moments. In case of strong overlapping, Fourier-like techniques provide poor results because of the lack of resolution. We propose the use of stochastic maximum-likelihood (SML) and subspace-based methods (WPSF algorithm) for a joint estimation of spectral moments. The statistical performances (theoretical and empirical by Monte Carlo simulations) of estimators are compared with the Cramer-Rao lower bound. The results of tests performed on very high frequency (VHF) times series obtained during Thunderstorm, Arecibo, PR during September and October 1998 validate the model and algorithms and confirm the interest of both approaches. Index Terms--Maximum likelihood, performance analysis, spectral moment estimation, weighted subspace fitting.

Do male and female executives approach leadership in similar ways? What do their approaches reveal about their potentials for addressing contemporary leadership challenges and promoting leadership ascension? While considerable research has been conducted on the ways that gender influences leadership styles, the issue has received limited attention in the nonprofit sector. This research provides a unique perspective on the ways that male and female executives align their leadership approaches with gendered constructs of leadership outlined in the agentic-communal framework. The results indicate that while male and female leaders adhered to many aspects of the gendered domains of the framework, there were some notable exceptions. Female executives were generally more likely to adopt interpersonal approaches to leadership, and while common aspects of executive leadership reflected masculine constructs of leadership traits, male and female executives displayed more variance in their approaches to leadership skills and behaviors. [ABSTRACT FROM AUTHOR]