Patient flow modeling and simulation to study HAI incidence in an Emergency Department.

Healthcare-associated infections (HAIs), or nosocomial infections, refer to patients getting new infections while getting treatment for an existing condition in a healthcare facility. HAI poses a significant challenge in healthcare delivery that results in higher rates of mortality and morbidity as well as a longer duration of hospital stay. While the real cause of HAI in a hospital varies widely and in most cases untraceable, it is popularly believed that patient flow in a hospital-which hospital units patients visit and where they spend the most time since their admission into the hospital-can trace back to HAI incidence in the hospital. Based on this observation, we, in this paper, model and simulate patient flow in an emergency department of a hospital and then utilize the developed model to study HAI incidence therein. We obtain (a) a flowchart of patient movement (admission to discharge) and (b) anonymous patient data from University Health Medical Center for a duration of 11 months (Aug 2022-June 2023). Based on these data, we develop and validate the patient flow model. Our model captures patient movement in different areas of a typical emergency department, such as triage, waiting room, and minor procedure rooms. We employ the discrete-event simulation (DES) technique to model patient flow and associated HAI infections using the simulation software, Anylogic. Our simulation results show that the rates of HAI incidence are proportional to both the specific areas patients occupy and the duration of their stay. By utilizing our model, hospital administrators and infection control teams can implement targeted strategies to reduce the incidence of HAI and enhance patient safety, ultimately leading to improved healthcare outcomes and more efficient resource allocation.

Impact of working from home on activity-travel behavior during the COVID-19 Pandemic: An aggregate structural analysis.

The ongoing COVID-19 pandemic has created significant public health concerns that led the public and private sectors to impose stay-at-home and work-from-home policies. Although working from home has been a conventional albeit infrequent behavior, the prevalence of this option was significantly and rapidly accelerated during the pandemic. This study explored the impacts of working from home on activity-travel behavior during the pandemic. Both work and non-work activity participation declined during the pandemic but to what extent was this due to working from home? How did working from home affect other measures of travel such as person-miles traveled? We approached these questions by developing a Structural Regression model and using cross-sectional data for the early phase of the pandemic when the infection curve was flattened and activity-travel behavior became relatively stable following the drastic changes observed during the pandemic's initial shock. Combining U.S. county-level data from the Maryland Transportation Institute and Google Mobility Reports, we concluded that the proportion of people working from home directly depended on pandemic severity and associated public health policies as well as on a range of socio-economic characteristics. Working from home contributed to a reduction in workplace visits. It also reduced non-work activities but only via a reduction in non-work activities linked to work. Finally, a higher working from home proportion in a county corresponded to a reduction in average person-miles traveled. A higher degree of state government responses to containment and closure policies contributed to an increase in working from home, and decreases in workplace and non-workplace visits and person-miles traveled in a county. The results of this study provide important insights into changes in activity-travel behavior associated with working from home as a response strategy to major disruptions such as those imposed by a pandemic.

2D Electron Crystallography of Membrane Protein Single-, Double-, and Multi-Layered Ordered Arrays.

The electron cryo-microscopy (cryo-EM) approach of 2D electron crystallography allows for structure determination of two-dimensional (2D) crystals of soluble and membrane proteins, employing identical principles and methods once 2D crystals are obtained. Two-dimensional crystallization trials of membrane proteins can result in multiple outcomes of ordered arrays, which may be suited for either 2D electron crystallography, helical analysis, or MicroED.The membrane protein 2D crystals used for 2D electron crystallography are either single- or double-layered ordered proteoliposome vesicles or sheet-like membranes. We have developed a cryo-EM grid preparation approach, which allows for the analysis of stacked 2D crystals that are neither suitable for MicroED nor for directly applying 2D electron crystallography. This new grid preparation approach, the peel-blot, uses the capillary force generated by submicron filter paper and mechanical means for the separation of stacked 2D crystals into single-layered 2D crystals, for which standard 2D electron crystallography can then be employed. The preparation of 2D crystals, the peel-blot grid preparation, and the structure determination by 2D electron crystallography are described here.

Complementary Mutations in the N and L Proteins for Restoration of Viral RNA Synthesis.

During viral RNA synthesis by the viral RNA-dependent RNA polymerase (vRdRp) of vesicular stomatitis virus, the sequestered RNA genome must be released from the nucleocapsid in order to serve as the template. Unveiling the sequestered RNA by interactions of vRdRp proteins, the large subunit (L) and the phosphoprotein (P), with the nucleocapsid protein (N) must not disrupt the nucleocapsid assembly. We noticed that a flexible structural motif composed of an α-helix and a loop in the N protein may act as the access gate to the sequestered RNA. This suggests that local conformational changes in this structural motif may be induced by interactions with the polymerase to unveil the sequestered RNA, without disrupting the nucleocapsid assembly. Mutations of several residues in this structural motif-Glu169, Phe171, and Leu174-to Ala resulted in loss of viral RNA synthesis in a minigenome assay. After implementing these mutations in the viral genome, mutant viruses were recovered by reverse genetics and serial passages. Sequencing the genomes of the mutant viruses revealed that compensatory mutations in L, P, and N were required to restore the viral viability. Corresponding mutations were introduced in L, P, and N, and their complementarity to the N mutations was confirmed by the minigenome assay. Introduction of the corresponding mutations is also sufficient to rescue the mutant viruses. These results suggested that the interplay of the N structural motif with the L protein may play a role in accessing the nucleotide template without disrupting the overall structure of the nucleocapsid.IMPORTANCE During viral RNA synthesis of a negative-strand RNA virus, the viral RNA-dependent RNA polymerase (vRdRp) must gain access to the sequestered RNA in the nucleocapsid to use it as the template, but at the same time may not disrupt the nucleocapsid assembly. Our structural and mutagenesis studies showed that a flexible structural motif acts as a potential access gate to the sequestered RNA and plays an essential role in viral RNA synthesis. Interactions of this structural motif within the vRdRp may be required for unveiling the sequestered RNA. This mechanism of action allows the sequestered RNA to be released locally without disrupting the overall structure of the nucleocapsid. Since this flexible structural motif is present in the N proteins of many NSVs, release of the sequestered RNA genome by local conformational changes in the N protein may be a general mechanism in NSV viral RNA synthesis.

Inducing two-dimensional crystallization of membrane proteins by dialysis for electron crystallography.

Electron crystallography is an electron cryo-microscopy (cryo-EM) method that is particularly suitable for structure-function studies of small membrane proteins, which are crystallized in two-dimensional (2D) arrays for subsequent cryo-EM data collection and image processing. This approach allows for structural analysis of membrane proteins in a close-to-native, phospholipid bilayer environment. The process of growing 2D crystals from purified membrane proteins by dialysis detergent removal is described in this chapter. A short section covers screening for and identifying 2D crystals by transmission electron microscopy, and in the last section, optimization of the purification to obtain crystals of higher quality is discussed.