Weld pool dynamics and the formation of ripples in 3D gas metal arc welding

© 2008, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 InternationalThis article studies the transient weld pool dynamics under the periodical impingement of filler droplets that carry mass, momentum, thermal energy, and species in a moving 3D gas metal arc welding. The complicated transport phenomena in the weld pool are caused by the combined effect of droplet impingement, gravity, electromagnetic force, plasma arc force, and surface tension force (Marangoni effect). The weld pool shape and the distributions of temperature, velocity, and species in the weld pool are calculated as a function of time. The phenomena of ‘‘open and close-up” for a crater in the weld pool and the corresponding weld pool dynamics are analyzed. The commonly observed ripples at the surface of a solidified weld bead are, for the first time, predicted by the present model. Detailed mechanisms leading to the formation of ripples are discussed.http://dx.doi.org/10.1016/j.ijheatmasstransfer.2007.07.04

Computational methods for studying parent-of-origin effects via reciprocal mouse crosses

Imprinted genes have been linked with diseases ranging from cancer, to metabolic syndromes, to psychiatric illness. With regard to psychiatric illness in particular, numerous lines of evidence, both from human and mouse studies, suggest imprinted genes affect behavior along with brain development and function. Nonetheless, the effect of imprinted genes on most complex traits is not well characterized. Moreover, the architecture of environment-by-imprinting effects is even less well-understood. The lack of characterization is likely due to the general difficulty of observing ``parent-of-origin effects'' (POEs), which typically arise in mammals from maternal effects--or from imprinting. To study POE/environment-by-POE, we can employ a relatively neglected but maximally powerful POE-detection system: the reciprocal cross (RX). Towards this end, we develop and apply computational methods for designing and analyzing RX experiments. Here, these techniques are applied in the context of RXs of inbred lines of mice, with a focus on behavior--but these techniques could be similarly employed in any model organism subject to POE, and on any complex trait. The first set of methods focuses on the analysis of expression and behavioral data from RXs of a single pair of classical inbred mouse strains, with offspring exposed in utero to various diets. In this analysis, we detected dozens of POE/diet-by-POE on gene expression, a handful of similar effects on behavior, and a possible connection between POE on expression and behavior. Motivated by these results, we engaged in a similar but larger study, the CC-POE, in which we RXd multiple pairs of inbred lines drawn from the Collaborative Cross (CC)--a panel of multiparental recombinant inbred mouse strains. To aid in the CC-POE design, we developed a novel method for selecting an optimal set of reciprocal crosses: the Reciprocal Cross Explorer. Finally, with the goal of analyzing CC-POE data, we develop a resource for variant imputation in the CC: the Inbred Strain Variant Database (available online at https://isvdb.unc.edu ). Taken together, methods developed in this dissertation represent progress towards a new way of studying POEs via RXs.Doctor of Philosoph

Numerical Analysis of the Effects of Selected Geometrical Parameters and Fluid Properties on MHD Natural Convection Flow in an Inclined Elliptic Porous Enclosure with Localized Heating

Magnetohydrodynamic (MHD) natural convection flow and associated heat convection in an oriented elliptic enclosure has been investigated with numerical simulations. A magnetic field was applied to the cylindrical wall of the configuration, the top and bottom walls of the enclosure were circumferentially cooled and heated, respectively, while the extreme ends along the cross-section of the elliptic duct were considered adiabatic. The full governing equations in terms of continuity, momentum, and energy transport were transformed into nondimensional form and solved numerically using finite difference method adopting Gauss–Seidel iteration technique. The selected geometrical parameters and flow properties considered for the study were eccentricity (0, 0.2, 0.4, 0.6, and 0.8), angle of inclination (0°, 30°, 60°, and 90°), Hartmann number (0, 25, and 50), Grashof number (104, 105, and 106), and Darcy number (10−3, 10−4, and 10−5). The Prandtl number was held constant at 0.7. Numerical results were presented by velocity distributions as well as heat transfer characteristics in terms of local and average Nusselt numbers (i.e., rate of heat transfer). The optimum heat transfer rate was attained at e value of 0.8. Also, the heat transfer rate increased significantly between the angles of inclination 58° and 90°. In addition, Hartmann number increased with decreased heat transfer rate and flow circulation. A strong flow circulation (in terms of velocity distribution) was observed with increased Grashof and Darcy numbers. The combination of the geometric and fluid properties thereforHeat Trans Asian Res, 00(0): 1–33, 2016; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21211e can be used to regulate the circulation and heat transfer characteristics of the flow in the enclosure. C⃝ 2016 Wiley Periodicals, Inc

The EXIT Strategy: an Approach for Identifying Bacterial Proteins Exported during Host Infection

ABSTRACT Exported proteins of bacterial pathogens function both in essential physiological processes and in virulence. Past efforts to identify exported proteins were limited by the use of bacteria growing under laboratory ( in vitro ) conditions. Thus, exported proteins that are exported only or preferentially in the context of infection may be overlooked. To solve this problem, we developed a genome-wide method, named EXIT ( ex ported i n vivo t echnology), to identify proteins that are exported by bacteria during infection and applied it to Mycobacterium tuberculosis during murine infection. Our studies validate the power of EXIT to identify proteins exported during infection on an unprecedented scale (593 proteins) and to reveal in vivo induced exported proteins (i.e., proteins exported significantly more during in vivo infection than in vitro ). Our EXIT data also provide an unmatched resource for mapping the topology of M. tuberculosis membrane proteins. As a new approach for identifying exported proteins, EXIT has potential applicability to other pathogens and experimental conditions. IMPORTANCE There is long-standing interest in identifying exported proteins of bacteria as they play critical roles in physiology and virulence and are commonly immunogenic antigens and targets of antibiotics. While significant effort has been made to identify the bacterial proteins that are exported beyond the cytoplasm to the membrane, cell wall, or host environment, current methods to identify exported proteins are limited by their use of bacteria growing under laboratory ( in vitro ) conditions. Because in vitro conditions do not mimic the complexity of the host environment, critical exported proteins that are preferentially exported in the context of infection may be overlooked. We developed a novel method to identify proteins that are exported by bacteria during host infection and applied it to identify Mycobacterium tuberculosis proteins exported in a mouse model of tuberculosis

High resolution in-vivo electrode localization using microfocal X-rays.

Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Statement of responsibility "by Daniel Oreper" taken from abstract, p. 1. Leaf 109 blank.Includes bibliographical references (leaf 108).Neuroscientists lack the ability to perform in-vivo electrode localization with high accuracy, especially in deep brain structures. The design, implementation and testing of a microfocal x-ray stereo system that offers an efficient, accurate, and relatively low-cost solution this localization problem is presented. The results indicate the ability to localize a targets to within -50 microns, in a brain-tissue-based frame. This accuracy is approximately twice as good as than the existing gold standard in electrophysiology (microlesions), and, unlike the microlesion method, the stereo microfocal x-ray method has important advantages. In particular, while only tens of neuronal recording sites can be reliably reconstructed with the microlesion method, microfocal x-ray method can be repeatedly performed to accurately estimate an essentially unlimited number of serial penetrations, and the localization results are available in nearly real time without animal sacrifice.M.Eng.and S.B

Performance of point-of-care severity scores to predict prognosis in patients admitted through the emergency department with COVID-19.

BACKGROUND: Identifying COVID-19 patients at the highest risk of poor outcomes is critical in emergency department (ED) presentation. Sepsis risk stratification scores can be calculated quickly for COVID-19 patients but have not been evaluated in a large cohort. OBJECTIVE: To determine whether well-known risk scores can predict poor outcomes among hospitalized COVID-19 patients. DESIGNS, SETTINGS, AND PARTICIPANTS: A retrospective cohort study of adults presenting with COVID-19 to 156 Hospital Corporation of America (HCA) Healthcare EDs, March 2, 2020, to February 11, 2021. INTERVENTION: Quick Sequential Organ Failure Assessment (qSOFA), Shock Index, National Early Warning System-2 (NEWS2), and quick COVID-19 Severity Index (qCSI) at presentation. MAIN OUTCOME AND MEASURES: The primary outcome was in-hospital mortality. Secondary outcomes included intensive care unit (ICU) admission, mechanical ventilation, and vasopressors receipt. Patients scored positive with qSOFA ≥ 2, Shock Index > 0.7, NEWS2 ≥ 5, and qCSI ≥ 4. Test characteristics and area under the receiver operating characteristics curves (AUROCs) were calculated. RESULTS: We identified 90,376 patients with community-acquired COVID-19 (mean age 64.3 years, 46.8% female). 17.2% of patients died in-hospital, 28.6% went to the ICU, 13.7% received mechanical ventilation, and 13.6% received vasopressors. There were 3.8% qSOFA-positive, 45.1% Shock Index-positive, 49.8% NEWS2-positive, and 37.6% qCSI-positive at ED-triage. NEWS2 exhibited the highest AUROC for in-hospital mortality (0.593, confidence interval [CI]: 0.588-0.597), ICU admission (0.602, CI: 0.599-0.606), mechanical ventilation (0.614, CI: 0.610-0.619), and vasopressor receipt (0.600, CI: 0.595-0.604). CONCLUSIONS: Sepsis severity scores at presentation have low discriminative power to predict outcomes in COVID-19 patients and are not reliable for clinical use. Severity scores should be developed using features that accurately predict poor outcomes among COVID-19 patients to develop more effective risk-based triage

Going From an Academic Medical Center to a Community Hospital: Patient Experiences with TransfersGoing from an academic medical center to a community hospital: Patient experiences with transfers

Academic medical centers (AMCs) often operate at or near full capacity, which leads to delays in care while smaller community hospitals may have excess capacity. To address this issue and to match patient needs to care acuity, patients may be transferred from an AMC emergency department for direct admission to a community hospital. We aimed to explore the experiences and perspectives of patients who were transferred. We randomly selected patients transferred between February 2019 and February 2020. We conducted structured thirty-minute interviews containing fixed response and open-ended questions focusing on the transfer rationale and experience, care quality, and patient financial outcomes. We used descriptive statistics to summarize questions with fixed responses and thematic analysis for open-ended questions. We interviewed a total of 40 patients. While most (88%) understood the rationale for transfer, many (60%) did not feel they had agency in the decision despite the voluntary nature of the program. Patients generally had a positive experience with the transfer (65%) and valued the expedited admission. However, some highlighted issues with transfer-related billing and the mismatch between the expectations of presenting to an academic hospital and the reality of being admitted to a community one. We conclude that patients are amenable to transfers for an expedited admission and understand the rationale for such transfers. However, participants should receive a clear explanation of benefits to them, guidance that the program is voluntary, and protection from financial risk Experience Framework This article is associated with the Patient, Family & Community Engagement lens of The Beryl Institute Experience Framework (https://www.theberylinstitute.org/ExperienceFramework). Access other PXJ articles related to this lens. Access other resources related to this lens

Convection in Arc Weld Pools Electromagnetic and surface tension forces are shown to dominate flow behavior, in some cases producing double circulation loops in the weld pool

ABSTRACT. A mathematical model has been developed to account for convection and temperature distributions in stationary arc weld pools driven by buoyancy, electromagnetic and surface tension forces. It is shown that the electromagnetic and surface tension forces dominate the flow behavior. In some cases, these forces produce double circulation loops, which are indirectly confirmed by experimental measurements of segregation in the weld pool. It is also shown that the surface tension driven flows are very effective in dissipating the incident energy flux on the pool surface which, in turn, reduces the vaporization from the weld pool

Analysis of Clinical Criteria for Discharge Among Patients Hospitalized for COVID-19: Development and Validation of a Risk Prediction Model.

BACKGROUND: Patients hospitalized with COVID-19 can clinically deteriorate after a period of initial stability, making optimal timing of discharge a clinical and operational challenge. OBJECTIVE: To determine risks for post-discharge readmission and death among patients hospitalized with COVID-19. DESIGN: Multicenter retrospective observational cohort study, 2020-2021, with 30-day follow-up. PARTICIPANTS: Adults admitted for care of COVID-19 respiratory disease between March 2, 2020, and February 11, 2021, to one of 180 US hospitals affiliated with the HCA Healthcare system. MAIN MEASURES: Readmission to or death at an HCA hospital within 30 days of discharge was assessed. The area under the receiver operating characteristic curve (AUC) was calculated using an internal validation set (33% of the HCA cohort), and external validation was performed using similar data from six academic centers associated with a hospital medicine research network (HOMERuN). KEY RESULTS: The final HCA cohort included 62,195 patients (mean age 61.9 years, 51.9% male), of whom 4704 (7.6%) were readmitted or died within 30 days of discharge. Independent risk factors for death or readmission included fever within 72 h of discharge; tachypnea, tachycardia, or lack of improvement in oxygen requirement in the last 24 h; lymphopenia or thrombocytopenia at the time of discharge; being ≤ 7 days since first positive test for SARS-CoV-2; HOSPITAL readmission risk score ≥ 5; and several comorbidities. Inpatient treatment with remdesivir or anticoagulation were associated with lower odds. The models AUC for the internal validation set was 0.73 (95% CI 0.71-0.74) and 0.66 (95% CI 0.64 to 0.67) for the external validation set. CONCLUSIONS: This large retrospective study identified several factors associated with post-discharge readmission or death in models which performed with good discrimination. Patients 7 or fewer days since test positivity and who demonstrate potentially reversible risk factors may benefit from delaying discharge until those risk factors resolve

I CAN DO Surgical ACP (Improving Completion, Accuracy and Dissemination of Surgical Advanced Care Planning): a protocol for a multisite, single-blinded, pragmatic randomised controlled trial to improve ACP completion in older adults in the presurgical setting.

IntroductionApproximately, 20 million older adults undergo major elective surgery annually, yet less than 10% engage in advance care planning (ACP). This is a critical missed opportunity to optimally engage in patient-aligned medical decisions and communications in the perioperative setting. The PREPARE ACP programme (easy-to-read advance directives (ADs) and a patient-directed, online ACP programme) has been shown to increase ACP documentation and patient and clinician empowerment to discuss ACP. Yet, a gap remains in extending PREPAREs use to surgical populations. We hypothesise that by delivering PREPARE in a patient-facing electronic health record (EHR) centric presurgery workflow for older adults, supported by automated patient reminders and outreach from a healthcare navigator (HCN), we can enable patients and/or surgical teams to engage in ACP discussions.Methods and analysisThis is a three-site, single-blinded, pragmatic randomised trial comparing increasing intensity of ACP-focused, patient-facing EHR messaging and HCN support. The outreach occurs prior to a new presurgical clinic visit. We will enrol 6000 patients (2000 each site) aged 65 and older and randomise them equally to the following study arms: (Arm 1(AArm 1) ACP-related cover letter and PREPARE URL information sent via patient portal and postal mail (includes cover letter, AD and PREPARE pamphlet); (Arm 2) Arm 1 plus reminder message via text or MyChart message and (Arm 3) Arm 2 plus HCN outreach and support. The primary outcome is clinically meaningful ACP documentation in the EHR (ie, surrogate designation, documented discussions and ADs) within 6 months of the new surgical visit. The rate of ACP documentation will be compared between treatment groups using generalised estimating equations. Secondary outcomes include a validated four-item ACP engagement survey, administered 2 weeks after the presurgical visit and 6 months later. All analyses will follow the intention-to-treat principle and recent Consolidated Standards of Reporting Trials guidelines.Ethics and disseminationThe study will be conducted according to the Declaration of Helsinki, Protection of Human Volunteers (21 Code of Federal Regulations (CFR) 50), Institutional Review Boards (21 CFR 56) and Obligations of Clinical Investigators (21 CFR 312). The protocol and consent form were reviewed and approved by Advarra, an National Insitutes of Health (NIH)-approved, commercial, centralised Institutional Review Board (IRB). The IRB/Independent Ethics Committee of each participating centre reviewed and approved the protocol and consent and obtained reliance agreements with Advarra prior to study initiation. The study is guided by input from patient and clinical advisory boards and a data safety monitoring board. The results of the study will be disseminated to both academic and community stakeholders, complying with all applicable privacy laws.Trial registration numberClinicalTrials.gov ID: NCT06090552.Protocol numberAdvarra Pro 00070994.University of california, san francisco irb iris number23-38948.Protocol Date: 24 October 2024.Protocol version4