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1.
Nurs Clin North Am ; 56(1): 1-21, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33549278

RESUMO

The Food and Drug Administration (FDA) classifies herbal preparations as food supplements. New herbal supplements and products are not governed by the strict FDA drug approval process and there is no premarket approval required. The FDA prohibits manufacturers and distributors from marketing adulterated or misbranded products but does not rigorously define safe practices. Scientific evidence related to herbal supplements is limited. Herbal supplements have been associated with adverse reactions and herbal-drug interactions. Information and precautions for 20 common herbal supplements, including St. John's wort, ginseng, echinacea, and ginkgo, are reviewed. Resources for consumers and health care professionals are highlighted.


Assuntos
Suplementos Nutricionais/efeitos adversos , Suplementos Nutricionais/estatística & dados numéricos , Fitoterapia/efeitos adversos , Fitoterapia/estatística & dados numéricos , Preparações de Plantas/efeitos adversos , Preparações de Plantas/uso terapêutico , Ginkgo biloba/efeitos adversos , Humanos , Hypericum/efeitos adversos , Kava/efeitos adversos , Panax/efeitos adversos , Zumbido/terapia , Estados Unidos , United States Food and Drug Administration
2.
J Stroke Cerebrovasc Dis ; : 105657, 2021 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-33579545

RESUMO

Studying the neuropathologic autopsy findings in subjects with chronic kidney disease (CKD) or chronic renal failure (CRF) is difficult for several reasons: etiology of the CKD may be heterogeneous, affected patients may have one or more major co-morbidities that themselves can cause significant neurologic disease, and agonal events may result in significant findings that were of minimal significance earlier in a patient's life. We studied the constellation of neuropathologic abnormalities in 40 autopsy brains originating from subjects of ages 34-95 years (no children in the study). The most common pathologic change was that of ischemic infarcts (cystic, lacunar and/or microinfarcts), which were seen in over half of subjects. These were associated with both large artery atherosclerosis and arteriolosclerosis (A/S), the latter finding being present in 29/40 subjects. Charcot-Bouchard microaneurysms were present in the brains of three subjects, in one case associated with severe amyloid angiopathy. Microvascular calcinosis (medial sclerosis in the case of arterioles) was seen in the basal ganglia (n=8) and/or endplate region of the hippocampus (n=7) and occasional ischemic infarcts in one brain showed severe calcification. Sequelae of cerebrovascular disease (especially A/S or microvascular disease) are a common neuropathologic substrate for neurologic disability and brain lesions in this complex group of patients. Regulation of calcium metabolism within brain microvessel walls may be worthy of further research in both human brain specimens and animal models.

3.
Sci Adv ; 7(7)2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33579704

RESUMO

Storing carbon in forests is a leading land-based strategy to curb anthropogenic climate change, but its planetary cooling effect is opposed by warming from low albedo. Using detailed geospatial data from Earth-observing satellites and the national forest inventory, we quantify the net climate effect of losing forest across the conterminous United States. We find that forest loss in the intermountain and Rocky Mountain West causes net planetary cooling but losses east of the Mississippi River and in Pacific Coast states tend toward net warming. Actual U.S. forest conversions from 1986 to 2000 cause net cooling for a decade but then transition to a large net warming over a century. Avoiding these forest conversions could have yielded a 100-year average annual global cooling of 0.00088°C. This would offset 17% of the 100-year climate warming effect from a single year of U.S. fossil fuel emissions, underscoring the scale of the mitigation challenge.

4.
PLoS One ; 16(2): e0247139, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33596273

RESUMO

BACKGROUND: A significant proportion of the worldwide population is at risk of social isolation and loneliness as a result of the COVID-19 pandemic. We aimed to identify effective interventions to reduce social isolation and loneliness that are compatible with COVID-19 shielding and social distancing measures. METHODS AND FINDINGS: In this rapid systematic review, we searched six electronic databases (Medline, Embase, Web of Science, PsycINFO, Cochrane Database of Systematic Reviews and SCOPUS) from inception to April 2020 for systematic reviews appraising interventions for loneliness and/or social isolation. Primary studies from those reviews were eligible if they included: 1) participants in a non-hospital setting; 2) interventions to reduce social isolation and/or loneliness that would be feasible during COVID-19 shielding measures; 3) a relevant control group; and 4) quantitative measures of social isolation, social support or loneliness. At least two authors independently screened studies, extracted data, and assessed risk of bias using the Downs and Black checklist. Study registration: PROSPERO CRD42020178654. We identified 45 RCTs and 13 non-randomised controlled trials; none were conducted during the COVID-19 pandemic. The nature, type, and potential effectiveness of interventions varied greatly. Effective interventions for loneliness include psychological therapies such as mindfulness, lessons on friendship, robotic pets, and social facilitation software. Few interventions improved social isolation. Overall, 37 of 58 studies were of "Fair" quality, as measured by the Downs & Black checklist. The main study limitations identified were the inclusion of studies of variable quality; the applicability of our findings to the entire population; and the current poor understanding of the types of loneliness and isolation experienced by different groups affected by the COVID-19 pandemic. CONCLUSIONS: Many effective interventions involved cognitive or educational components, or facilitated communication between peers. These interventions may require minor modifications to align with COVID-19 shielding/social distancing measures. Future high-quality randomised controlled trials conducted under shielding/social distancing constraints are urgently needed.

5.
Nat Methods ; 18(2): 156-164, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33542514

RESUMO

This paper describes outcomes of the 2019 Cryo-EM Model Challenge. The goals were to (1) assess the quality of models that can be produced from cryogenic electron microscopy (cryo-EM) maps using current modeling software, (2) evaluate reproducibility of modeling results from different software developers and users and (3) compare performance of current metrics used for model evaluation, particularly Fit-to-Map metrics, with focus on near-atomic resolution. Our findings demonstrate the relatively high accuracy and reproducibility of cryo-EM models derived by 13 participating teams from four benchmark maps, including three forming a resolution series (1.8 to 3.1 Å). The results permit specific recommendations to be made about validating near-atomic cryo-EM structures both in the context of individual experiments and structure data archives such as the Protein Data Bank. We recommend the adoption of multiple scoring parameters to provide full and objective annotation and assessment of the model, reflective of the observed cryo-EM map density.

6.
Blood Adv ; 5(3): 674-686, 2021 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-33560379

RESUMO

The exocyst is an octameric complex comprising 8 distinct protein subunits, exocyst complex components (EXOC) 1 to 8. It has an established role in tethering secretory vesicles to the plasma membrane, but its relevance to platelet granule secretion and function remains to be determined. Here, EXOC3 conditional knockout (KO) mice in the megakaryocyte/platelet lineage were generated to assess exocyst function in platelets. Significant defects in platelet aggregation, integrin activation, α-granule (P-selectin and platelet factor 4), dense granule, and lysosomal granule secretion were detected in EXOC3 KO platelets after treatment with a glycoprotein VI (GPVI)-selective agonist, collagen-related peptide (CRP). Except for P-selectin exposure, these defects were completely recovered by maximal CRP concentrations. GPVI surface levels were also significantly decreased by 14.5% in KO platelets, whereas defects in proximal GPVI signaling responses, Syk and LAT phosphorylation, and calcium mobilization were also detected, implying an indirect mechanism for these recoverable defects due to decreased surface GPVI. Paradoxically, dense granule secretion, integrin activation, and changes in surface expression of integrin αIIb (CD41) were significantly increased in KO platelets after protease-activated receptor 4 activation, but calcium responses were unaltered. Elevated integrin activation responses were completely suppressed with a P2Y12 receptor antagonist, suggesting enhanced dense granule secretion of adenosine 5'-diphosphate as a critical mediator of these responses. Finally, arterial thrombosis was significantly accelerated in KO mice, which also displayed improved hemostasis determined by reduced tail bleeding times. These findings reveal a regulatory role for the exocyst in controlling critical aspects of platelet function pertinent to thrombosis and hemostasis.

7.
J Manuf Syst ; 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-33551537

RESUMO

The COVID-19 pandemic has disrupted the supply chain for personal protective equipment (PPE) for medical professionals, including N95-type respiratory protective masks. To address this shortage, many have looked to the agility and accessibility of additive manufacturing (AM) systems to provide a democratized, decentralized solution to producing respirators with equivalent protection for last-resort measures. However, there are concerns about the viability and safety in deploying this localized download, print, and wear strategy due to a lack of commensurate quality assurance processes. Many open-source respirator designs for AM indicate that they do not provide N95-equivalent protection (filtering 95% of SARS-CoV-2 particles) because they have either not passed aerosol generation tests or not been tested. Few studies have quantified particle transmission through respirator designs outside of the filter medium. This is concerning because several polymer-based AM processes produce porous parts, and inherent process variation between printers and materials also threaten the integrity of tolerances and seals within the printed respirator assembly. No study has isolated these failure mechanisms specifically for respirators. The goal of this paper is to measure particle transmission through printed respirators of different designs, materials, and AM processes. The authors compare the performance of printed respirators to N95 respirators and cloth masks. Respirators in this study printed using desktop- and industrial-scale fused filament fabrication processes and industrial-scale powder bed fusion processes were not sufficiently reliable for widespread distribution and local production of N95-type respiratory protection. Even while assuming a perfect seal between the respirator and the user's face, although a few respirators provided >90% efficiency at the 100-300 nm particle range, almost all printed respirators provided <60% filtration efficiency. Post-processing procedures including cleaning, sealing surfaces, and reinforcing the filter cap seal generally improved performance, but the printed respirators showed similar performance to various cloth masks. The authors further explore the process-driven aspects leading to low filtration efficiency. Although the design/printer/material combination dictates the AM respirator performance, the identified failure modes originate from system-level constraints and are therefore generalizable across multiple AM processes. Quantifying the limitations of AM in producing N95-type respiratory protective masks advances understanding of AM systems toward the development of better part and machine designs to meet the needs of reliable, functional, end-use parts.

8.
PLoS Negl Trop Dis ; 15(2): e0009071, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33529215

RESUMO

African sleeping sickness is caused by Trypanosoma brucei, a parasite transmitted by the bite of a tsetse fly. Trypanosome infection induces a severe transcriptional downregulation of tsetse genes encoding for salivary proteins, which reduces its anti-hemostatic and anti-clotting properties. To better understand trypanosome transmission and the possible role of glycans in insect bloodfeeding, we characterized the N-glycome of tsetse saliva glycoproteins. Tsetse salivary N-glycans were enzymatically released, tagged with either 2-aminobenzamide (2-AB) or procainamide, and analyzed by HILIC-UHPLC-FLR coupled online with positive-ion ESI-LC-MS/MS. We found that the N-glycan profiles of T. brucei-infected and naïve tsetse salivary glycoproteins are almost identical, consisting mainly (>50%) of highly processed Man3GlcNAc2 in addition to several other paucimannose, high mannose, and few hybrid-type N-glycans. In overlay assays, these sugars were differentially recognized by the mannose receptor and DC-SIGN C-type lectins. We also show that salivary glycoproteins bind strongly to the surface of transmissible metacyclic trypanosomes. We suggest that although the repertoire of tsetse salivary N-glycans does not change during a trypanosome infection, the interactions with mannosylated glycoproteins may influence parasite transmission into the vertebrate host.

9.
Tissue Eng Part A ; 2021 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-33528293

RESUMO

International regulatory agencies such as the Food and Drug Administration have mandated that the scientific community develop humanized microphysiological systems (MPS) as an in vitro alternative to animal models in the near future. While the breast cancer research community has long appreciated the importance of three-dimensional (3D) growth dynamics in their experimental models, there are remaining obstacles preventing a full conversion to humanized MPS for drug discovery and pathophysiological studies. This perspective evaluates the current status of human tissue-derived cells and scaffolds as building blocks for an "idealized" breast cancer MPS based on bioengineering design principles. It considers the utility of adipose tissue as a potential source of endothelial, lymphohematopoietic, and stromal cells for the support of breast cancer epithelial cells. The relative merits of potential MPS scaffolds derived from adipose tissue, blood components, and synthetic biomaterials is evaluated relative to the current "gold standard" material, Matrigel, a murine chondrosarcoma-derived basement membrane-enriched hydrogel. The advantages and limitations of a humanized breast cancer MPS are discussed in the context of in-process and destructive read-out assays.

10.
Health Justice ; 9(1): 3, 2021 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-33528702

RESUMO

BACKGROUND: Universal school-based prevention programs for alcohol, tobacco, and other drug use are typically designed for all students within a particular school setting. However, it is unclear whether such broad-based programs are effective for youth at risk for substance use and violence in juvenile justice settings. METHOD: The present study tested the feasibility, appropriateness, and efficacy of a preventive intervention to reduce risk factors for substance use and delinquency among youth in juvenile justice diversionary settings by promoting positive youth development and building personal strengths and prosocial relationships. Participants in the study (N = 288) were predominantly male (69%) and in the 9th grade (14 years old) or higher (91%), received the preventive intervention, and completed confidential questionnaires at the pre-test and post-test. RESULTS: The majority of youth who participated in the intervention rated the program topics (77.9%) and activities (72%) as appropriate for their age, would recommend it to their peers (73.6%), and would use the skills learned in the future (85.4%). Comparison of post-test adjusted means revealed that the prevention program had a significant positive impact on key knowledge, attitudes, and skills including goal-setting, stress-management, and communication skills. CONCLUSIONS: The findings indicate that an evidence-based prevention approach adapted for youth diversionary settings can be effectively implemented and well-received by participating youth, and can produce positive changes in psychosocial skills and protective factors known to prevent multiple risk behaviors among youth. Future efforts to implement substance use prevention in community juvenile justice settings may benefit from highlighting a positive youth development, skills-based approach.

11.
Artigo em Inglês | MEDLINE | ID: mdl-33446513

RESUMO

Telomere biology disorders, largely characterized by telomere lengths below the first centile for age, are caused by variants in genes associated with telomere replication, structure, or function. One of these genes, ACD, which encodes the shelterin protein TPP1, is associated with both autosomal dominantly and autosomal recessively inherited telomere biology disorders. TPP1 recruits telomerase to telomeres and stimulates telomerase processivity. Several studies probing the effect of various synthetic or patient-derived variants have mapped specific residues and regions of TPP1 that are important for interaction with TERT, the catalytic component of telomerase. However, these studies have come to differing conclusions regarding ACD haploinsufficiency. Here, we report a proband with compound heterozygous novel variants in ACD (NM_001082486.1)-c.505_507delGAG, p.(Glu169del); and c.619delG, p.(Asp207Thrfs*22)-and a second proband with a heterozygous chromosomal deletion encompassing ACD: arr[hg19] 16q22.1(67,628,846-67,813,408)x1. Clinical data, including symptoms and telomere length within the pedigrees, suggested that loss of one ACD allele was insufficient to induce telomere shortening or confer clinical features. Further analyses of lymphoblastoid cell lines showed decreased nascent ACD RNA and steady-state mRNA, but normal TPP1 protein levels, in cells containing heterozygous ACD c.619delG, p.(Asp207Thrfs*22), or the ACD-encompassing chromosomal deletion compared to controls. Based on our results, we conclude that cells are able to compensate for loss of one ACD allele by activating a mechanism to maintain TPP1 protein levels, thus maintaining normal telomere length.

12.
Phys Med Biol ; 2021 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-33472189

RESUMO

Simultaneous acquisition of cone beam CT (CBCT) projections using both the kV and MV imagers of an image guided radiotherapy (IGRT) system reduces set-up scan times -- a benefit to lung cancer radiation oncology patients -- but increases noise in the 3D reconstruction. In this article, we present a kV-MV scan time reduction technique that uses two noise-reducing measures to achieve superior performance. The first is a high DQE multi-layer MV imager prototype. The second is a beam hardening correction algorithm which combines poly-energetic modeling with edge-preserving, regularized smoothing of the projections. Performance was tested in real acquisitions of the Catphan 604 and a thorax phantom. Percent noise was quantified from voxel values in a soft tissue volume of interest (VOI) while edge blur was quantified from a VOI straddling a boundary between air and soft material. Comparisons in noise/resolution performance trade-off were made between our proposed approach, a dose-equivalent kV-only scan, and a kV-MV reconstruction technique previously published by Yin et al. (2005 Med. Phys. (32) 9). The proposed technique demonstrated lower noise as a function of spatial resolution than the baseline kV-MV method, notably a 50% noise reduction at typical edge blur levels. Our proposed method also exhibited fainter non-uniformity artifacts and in some cases superior contrast. Overall, we find that the combination of a multi-layer MV imager, acquiring at a LINAC source energy of 2.5 MV, and a denoised beam hardening correction algorithm enables noise, resolution, and dose performance comparable to standard kV-imager only set-up CBCT, but with nearly half the gantry rotation time.

13.
Biochemistry ; 60(3): 219-230, 2021 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-33416314

RESUMO

The acyl carrier protein (ACP) is an indispensable component of both fatty acid and polyketide synthases and is primarily responsible for delivering acyl intermediates to enzymatic partners. At present, increasing numbers of multidomain ACPs have been discovered with roles in molecular recognition of trans-acting enzymatic partners as well as increasing metabolic flux. Further structural information is required to provide insight into their function, yet to date, the only high-resolution structure of this class to be determined is that of the doublet ACP (two continuous ACP domains) from mupirocin synthase. Here we report the solution nuclear magnetic resonance (NMR) structure of the doublet ACP domains from PigH (PigH ACP1-ACP2), which is an enzyme that catalyzes the formation of the bipyrrolic intermediate of prodigiosin, a potent anticancer compound with a variety of biological activities. The PigH ACP1-ACP2 structure shows each ACP domain consists of three conserved helices connected by a linker that is partially restricted by interactions with the ACP1 domain. Analysis of the holo (4'-phosphopantetheine, 4'-PP) form of PigH ACP1-ACP2 by NMR revealed conformational exchange found predominantly in the ACP2 domain reflecting the inherent plasticity of this ACP. Furthermore, ensemble models obtained from SAXS data reveal two distinct conformers, bent and extended, of both apo (unmodified) and holo PigH ACP1-ACP2 mediated by the central linker. The bent conformer appears to be a result of linker-ACP1 interactions detected by NMR and might be important for intradomain communication during the biosynthesis. These results provide new insights into the behavior of the interdomain linker of multiple ACP domains that may modulate protein-protein interactions. This is likely to become an increasingly important consideration for metabolic engineering in prodigiosin and other related biosynthetic pathways.

14.
Neural Comput ; : 1-5, 2021 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-33513323

RESUMO

In this note, I study how the precision of a binary classifier depends on the ratio r of positive to negative cases in the test set, as well as the classifier's true and false-positive rates. This relationship allows prediction of how the precision-recall curve will change with r, which seems not to be well known. It also allows prediction of how Fß and the precision gain and recall gain measures of Flach and Kull (2015) vary with r.

15.
Pract Radiat Oncol ; 2021 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-33476841

RESUMO

PURPOSE: Patients with locally advanced non-small cell lung cancer (LA-NSCLC) have a high prevalence of pre-existing coronary heart disease and face excess cardiac risk after thoracic radiation therapy. We sought to assess whether statin therapy is a predictor of overall survival (OS) after thoracic radiation therapy. METHODS AND MATERIALS: We performed a retrospective analysis of 748 patients with LA-NSCLC treated with thoracic radiation therapy, using Kaplan-Meier OS estimates and Cox regression. RESULTS: Statin use among high cardiac risk patients (Framingham risk ≥20% or pre-existing coronary heart disease; n = 496) was 51.2%. After adjustment for baseline cardiac risk and other prognostic factors, statin therapy was associated with a significantly increased risk of all-cause mortality (adjusted hazard ratio, 1.39; 95% confidence interval [CI], 1.00-1.91; P = .048) but not major adverse cardiac events (adjusted hazard ratio, 1.18; 95% CI, 0.52-2.68; P = .69). Among statin-naïve patients, mean heart dose ≥10 Gy versus <10 Gy was associated with a significantly increased risk of all-cause mortality (hazard ratio, 1.32; 95% CI, 1.04-1.68; P = .022), with 2-year OS estimates of 46.9% versus 60.0%, respectively. However, OS did not differ by heart dose among patients on statin therapy (hazard ratio, 1.00; 95% CI, 0.76-1.32; P = 1.00; P-interaction = .031), with 2-year OS estimates of 46.9% versus 50.3%, respectively. CONCLUSIONS: Among patients with LA-NSCLC, only half of statin-eligible high cardiac risk patients were on statin therapy, reflecting the highest cardiac risk level of our cohort. Statin use was an independent predictor of all-cause mortality but not major adverse cardiac events. Elevated mean heart dose (≥10 Gy) was associated with increased risk of all-cause mortality in statin-naïve patients but not among those on statin therapy, identifying a group of patients in which early intervention with statins may mitigate the deleterious effects of high heart radiation therapy dose. This warrants evaluation in prospective trials.

16.
Gastroenterology ; 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33388316

RESUMO

BACKGROUND & AIMS: Patients with inflammatory bowel disease (IBD) demonstrate nutritional selenium deficiencies and are at greater risk of developing colon cancer. Previously, we determined that global reduction of the secreted antioxidant selenium-containing protein, selenoprotein P (SELENOP), substantially increased tumor development in an experimental colitis-associated cancer (CAC) model. We next sought to delineate tissue-specific contributions of SELENOP to intestinal inflammatory carcinogenesis and define clinical context. METHODS: Selenop floxed mice crossed with Cre driver lines to delete Selenop from the liver, myeloid lineages, or intestinal epithelium were placed on an azoxymethane/dextran sodium sulfate experimental CAC protocol. SELENOP loss was assessed in human ulcerative colitis (UC) organoids, and expression was queried in human and adult UC samples. RESULTS: Although large sources of SELENOP, both liver- and myeloid-specific Selenop deletion failed to modify azoxymethane/dextran sodium sulfate-mediated tumorigenesis. Instead, epithelial-specific deletion increased CAC tumorigenesis, likely due to elevated oxidative stress with a resulting increase in genomic instability and augmented tumor initiation. SELENOP was down-regulated in UC colon biopsies and levels were inversely correlated with endoscopic disease severity and tissue S100A8 (calprotectin) gene expression. CONCLUSIONS: Although global selenium status is typically assessed by measuring liver-derived plasma SELENOP levels, our results indicate that the peripheral SELENOP pool is dispensable for CAC. Colonic epithelial SELENOP is the main contributor to local antioxidant capabilities. Thus, colonic SELENOP is the most informative means to assess selenium levels and activity in IBD patients and may serve as a novel biomarker for UC disease severity and identify patients most predisposed to CAC development.

17.
Biophys J ; 2021 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-33460600

RESUMO

This work builds upon the record-breaking speed and generous immediate release of new experimental three-dimensional structures of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) proteins and complexes, which are crucial to downstream vaccine and drug development. We have surveyed those structures to catch the occasional errors that could be significant for those important uses and for which we were able to provide demonstrably higher-accuracy corrections. This process relied on new validation and correction methods such as CaBLAM and ISOLDE, which are not yet in routine use. We found such important and correctable problems in seven early SARS-CoV-2 structures. Two of the structures were soon superseded by new higher-resolution data, confirming our proposed changes. For the other five, we emailed the depositors a documented and illustrated report and encouraged them to make the model corrections themselves and use the new option at the worldwide Protein Data Bank for depositors to re-version their coordinates without changing the Protein Data Bank code. This quickly and easily makes the better-accuracy coordinates available to anyone who examines or downloads their structure, even before formal publication. The changes have involved sequence misalignments, incorrect RNA conformations near a bound inhibitor, incorrect metal ligands, and cis-trans or peptide flips that prevent good contact at interaction sites. These improvements have propagated into nearly all related structures done afterward. This process constitutes a new form of highly rigorous peer review, which is actually faster and more strict than standard publication review because it has access to coordinates and maps; journal peer review would also be strengthened by such access.

18.
Phys Med Biol ; 2021 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-33503603

RESUMO

We developed and validated a method for optimally combining the sub-images of mega-voltage (MV) multi-layer imager (MLI) devices that are built with heterogeneous layers. Two MLI configurations were modeled within the GATE Monte Carlo package by stacking different layers of a Gd2O2S:Tb (GOS) phosphor and a LKH-5 glass scintillator. Detector response was characterized in terms of the modulation transfer function (MTF), normalized noise power spectrum (NNPS) and detective quantum efficiency (DQE). Spatial frequency-dependent weighting factors were then analytically derived for each layer such that the total DQE of the summed combination image would be maximized across all spatial modes. The final image is obtained as the weighted sum of the sub-images from each layer. Optimal weighting factors that maximize the DQE were found to be the quotient of MTF and NNPS of each layer in the heterogeneous MLI detector. Results validated the improvement of the DQE across the entire frequency domain. For the LKH-5 slab configuration, DQE(0) increases between 2-3%, while the corresponding improvement for the LKH-5 pixelated configuration was around 7%. The performance of the weighting method was quantitatively evaluated with respect to spatial resolution, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of simulated planar images of phantoms at 2.5 and 6 MV. The line pair phantom acquisition exhibit two fold increases in CNR and SNR, however MTF was degraded at spatial frequencies greater than 0.2 lp/mm. For the Las Vegas phantom, the weighting improved the CNR by around 30% depending on the contrast region while the SNR values are higher by a factor of 2.5. These results indicate that the imaging performance of MLI systems can be enhanced using the proposed frequency-dependent weighting scheme. The CNR and SNR of the weighted combined image is improved across all spatial scales independent of the detector combination or photon beam energy.

19.
Am J Public Health ; : e1-e3, 2021 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-33476231

RESUMO

This study tested the effectiveness of a small-group preventive intervention designed to prevent unwanted sexual contact among cadets at the US Air Force Academy. Among cadets in the incoming class of 2021, unwanted sexual contact was cut by nearly half in the intervention group relative to the control group. This study is one of the first rigorously designed trials to demonstrate a significant impact on unwanted sexual contact among students attending a US military service academy.Trial Registration. ClinicalTrials.gov identifier: NCT03839797. (Am J Public Health. Published online ahead of print January 21, 2021: e1-e3. https://doi.org/10.2105/AJPH.2020.306050).

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