Exact Analysis Research Articles

EPMA and PIXE Analyses of High Grade Metamorphic Rocks

Background/Objectives: The demand for exact quantification analyses in complex ore assemblages is increasing rapidly as mineral processing studies become more sophisticated. In response to this need, an Electron Micro Probe Analysis and Proton Induced X-ray Emission complementary based analytical tool procedure for the chemical characterization of minerals was employed to study the metamorphic rocks. Methods : In this work, we compare the quantitative analysis of high-grade metamorphic rocks by proton induced X-ray emission (PIXE) with that of the previous analyses by electron probe microanalysis (EPMA). During this investigation, the PIXE analytical method on a nuclear microprobe was added to the previously well-known EPMA for the chemical quantification of high-grade metamorphic rocks from the Charnockite Hill, Visakhapatnam, A.P., India. For the evolution and geochemical characterization of the metamorphic rocks, the above two methods are compared and discussions are made with respect to certain elements. Findings: Particle-induced X-ray emission is well-matched except for certain elements for the chemical characterization of metamorphic rocks belonging to earth material samples. This comparison with EPMA demonstrates the elemental quantification characteristics for such analyses. Not only is an exploratory study of proton induced X-ray emission benefit presented, but also a synopsis of comparison with electron probe microanalysis aimed at a responsible reply to metamorphic rock analytical questions. Novelty: The complementary technique, especially EPMA, is required to fill the elemental gaps that are not determined in the case of matrix complex charnockite compositional analysis by PIXE with 3MeV and a Si (Li) detector. Keywords: Electron and Proton Microprobes; Complementary Techniques; Metamorphic Rocks; Elemental Analysis

Suitability of milk lactate dehydrogenase and serum albumin for pathogen-specific mastitis detection in automatic milking systems

In response to intramammary infection (IMI), blood-derived leukocytes are transferred into milk, which can be measured as an increase of somatic cell count (SCC). Additionally, pathogen-dependent IgG increases in milk following infection. The IgG transfer into milk is associated with the opening of the blood-milk barrier, which is much more pronounced during gram-negative than gram-positive IMI. Thus, milk IgG concentration may help to predict the pathogen type causing IMI. Likewise, lactate dehydrogenase (LDH) and serum albumin (SA) cross the blood-milk barrier with IgG if its integrity is reduced. Because exact IgG analysis is complicated and difficult to automate, LDH activity and SA concentration aid as markers to predict the IgG transfer into milk in automatic milking systems (AMS). This study was conducted to test the hypothesis that LDH and SA in milk correlate with the IgG transfer, and in combination with SCC these factors allow the differentiation between gram-positive and gram-negative IMI or even more precisely the infection-causing pathogen. Further, the expression of these parameters in foremilk before (BME) and after (AME) milk ejection was tested. In the AMS, quarter milk samples (n = 686) from 48 Holstein-Friesian cows were collected manually BME and AME, followed by an aseptic sample for bacteriological culture. Mixed models were used to (1) predict the concentration of IgG transmitted from blood into milk based on LDH and SA; (2) use principal component analysis to evaluate joint patterns of SCC (cells/mL), IgG (mg/mL), LDH (U/L), and SA (mg/mL) and use the principal component scores to compare gram-positive, gram-negative, and control IMI types and BME versus AME samples; and (3) predict gram-positive and gram-negative IMI by inclusion of combined SCC-LDH and SCC-SA as predictors in the model. Overall, the SA and LDH had similar ability to predict IgG transmission from blood into milk. Comparing the areas under the curve (AUC) of the receiver operator characteristic curves, the SCC-LDH versus SCC-SA had lower gram-positive (AUC = 0.984 vs. 0.986) but similar gram-negative (AUC = 0.995 vs. 0.998) IMI prediction ability. The SCC, IgG, LDH, and SA were greater in gram-negative than in gram-positive IMI (BME and AME) in early lactation. All measured factors had higher values in milk samples taken BME than AME. In conclusion, LDH and SA could be used as replacement markers to indicate the presence of IgGtransfer from blood into milk; in combination with SCC, both SA and LDH are suitable for differentiating IMI type, and BME is better for mastitis detection in AMS.

Analysis of Production systems with Variable Transfer Batch Size

In this paper, we propose a new queueing networks decomposition method for the analysis of production systems with variable transfer batch sizes. In many production and manufacturing systems, jobs arrive in batches and they are moved between stations also in batches. Batching decisions have a considerable impact on costs and lead times. Most of the literature assumes that the batch size remains constant throughout the process. However, in many real-life situations, different transfer batch sizes are used between stations due to practicality or different setup times. We consider queueing network models that incorporate this feature. Since exact analysis is possible for only a limited class of queuing networks, the decomposition methodology is used to obtain approximate results.

Heat Transfer of Casson Fluid over a Vertical Plate with Arbitrary Shear Stress and Exponential Heating

The basic objective of this work is to study the heat transfer of Casson fluid of non-Newtonian nature. The fluid is considered over a vertical plate such that the plate exhibits arbitrary wall shear stress at the boundary. Heat transfers due to exponential plate heating and natural convection are due to buoyancy force. Magnetohydrodynamic (MHD) analysis in the occurrence of a uniform magnetic field is also considered. The medium over the plate is porous and hence Darcy’s law is applied. The governing equations are established for the velocity and temperature fields by the usual Boussinesq approximation. The problem is first written in dimensionless form using some useful non-dimensional quantities and then solved. The exact analysis is performed and hence solutions via integral transform are established. The analysis of various pertinent parameters on temperature distribution and velocity field are reported graphically. It is found that pours medium permeability parameter retards the fluid motion whereas, velocity decreases with increasing magnetic parameter. Velocity and temperature decrease with increasing Prandtl number whereas the Grashof number enhances the fluid motion. Further, it is concluded from this study that the results obtained here are more general and in a limiting sense several other solutions can be recovered. The Newtonian fluid results can be easily established by taking the Casson parameter infinitely large i.e., when .

Multi-queue system with finite shared buffer under batch Poisson and/or interrupted batch Poisson arrivals: a computational analysis

This paper studies a model of a multi-queue system with a finite common buffer shared by queues with batch arrivals. The study is performed for a few buffer-sharing policies. For batch Poisson arrivals with an arbitrary batch size distribution, the analysis benefits from the fact that the stationary state distribution has a product form. For the special case of geometrically distributed batches, closed form solutions for normalisation constant are obtained. They lead to efficient computational procedures. For bursty interrupted batch Poisson arrivals, it is shown that an exact numerical analytic analysis is only possible for very small models. For real-life sized systems, an approximation method has been developed.

Exact Three-Dimensional Stability Analysis of Plate Using an Direct Variational Energy Method

In this paper, direct variational calculus was put into practical use to analyses the three dimensional (3D) stability of rectangular thick plate which was simply supported at all the four edges (SSSS) under uniformly distributed compressive load. In the analysis, both trigonometric and polynomial displacement functions were used. This was done by formulating the equation of total potential energy for a thick plate using the 3D constitutive relations, from then on, the equation of compatibility was obtained to determine the relationship between the rotations and deflection. In the same way, governing equation was obtained through minimization of the total potential energy functional with respect to deflection. The solution of the governing equation is the function for deflection. Functions for rotations were obtained from deflection function using the solution of compatibility equations. These functions, deflection and rotations were substituted back into the energy functional, from where, through minimizations with respect to displacement coefficients, formulas for analysis were obtained. In the result, the critical buckling loads from the present study are higher than those of refined plate theories with 7.70%, signifying the coarseness of the refined plate theories. This amount of difference cannot be overlooked. However, it is shown that, all the recorded average percentage differences between trigonometric and polynomial approaches used in this work and those of 3D exact elasticity theory is lower than 1.0%, confirming the exactness of the present theory. Thus, the exact 3D plate theory obtained, provides a good solution for the stability analysis of plate and, can be recommended for analysis of any type of rectangular plates under the same loading and boundary condition. Doi: 10.28991/CEJ-2022-08-01-05 Full Text: PDF

Comparison between exact and approximate methods for geometrically nonlinear analysis prescribed in design standards for steel and reinforced concrete structures

abstract: Current practices in structural engineering demand ever-increasing knowledge and expertise concerning stability of structures from professionals in this field. This paper implements standardized procedures for geometrically nonlinear analysis of steel and reinforced concrete structures, with the objective of comparing methodologies with one another and with a geometrically exact finite element analysis performed with Ansys 14.0. The following methods are presented in this research: Load Amplification Method, from NBR 8800:2008; the γ z coefficient method, from NBR 6118:2014; the P-Delta iterative method and the α c r coefficient method, prescribed in EN 1993-1-1:2005. A bibliographic review focused on standardized approximate methods and models for consideration of material and geometric nonlinearities is presented. Numerical examples are included, from which information is gathered to ensure a valid comparison between methodologies. In summary, the presented methods show a good correlation of results when applied within their respective recommended applicability limits, of which, Eurocode 3 seems to present the major applicability range. The treated approximate methods show to be more suitable for regular framed structures subjected to regular load distributions.

Gender trends of authors presenting at a regional vascular surgery meeting.

We hypothesized a potential gender disparity within a regional society like the Southern Association of Vascular Surgery (SAVS) when compared with vascular surgery demographics in the region. To assess this, we analyzed meeting and membership participation at the SAVS compared with regional data from the Society of Vascular Surgery as well as board certification in vascular surgery published by the American Board of Surgery (ABS). The published programs from the SAVS Annual Meeting from 2012 to 2019 were analyzed for membership, presenter gender, type, topic, discussant gender, moderator gender, postgraduate course presenter gender, and manuscript publication demographics. The ABS was petitioned and yearly Vascular Surgery diplomate (ABS-VS) gender from member states of the SAVS was examined for the same period. Fisher's exact Student's t-test and analysis of covariance were used. There were 257 total presentations (184 podium, 71.6%; 73 poster, 28.4%). A total of 61.4% (n= 43) of presentations by females were podium presentations, compared with 75.4% (n= 141) by males (P= .03). Females were less likely to be published when compared with their male counterparts (41.8% vs 58.7%, P= .02). The percentage of female gendered presenters statistically increased over the time period examined compared with a decrease in male presenters (R2= 0.61, m= 1.27 vs R2= 0.08, m=-0.35, P= .02). Female presenters had a female discussant 10.5% of the time compared with male presenters who had a male discussant 95.1% of the time (P< .0001). Females comprised 3.8%± 1.1% of SAVS yearly membership compared with 12.0%± 4.6% ABS-VS diplomates among SAVS member states (P< .0001). SAVS female membership significantly lagged behind the increase in ABS-VS female diplomate rate (P= .001). Only 39.1% of SAVS members were cross-listed in Society of Vascular Surgery membership rolls, with a total of 464 potential SAVS members, 11.2% or 52 of whom are female. We found that female presenters at the SAVS Annual Meeting were less likely to be podium presenters, interface with other female discussants, and publish manuscripts when compared with their male counterparts. Statistically, female members were underrepresented within the SAVS membership rolls when compared with known boarded female vascular surgeons among southern member states. This gender gap highlights a unique opportunity to enhance and potentially increase mentorship opportunities for female trainees who are presenting and/or attending this regional vascular surgery meeting.

Aligning Student-Faculty Mentorship Expectations and Needs to Promote Professional Identity Formation in Undergraduate Medical Education.

BackgroundDuring professional identity formation, medical students integrate their newly developing professional identities with their longstanding personal identities. Longitudinal mentorship has been shown to aid students in this process. Lack of clear relationship expectations among students and faculty is a barrier to effective longitudinal mentorship relationships.MethodsA cross-sectional, survey-based study collected information about experiences from both students (mentees) and faculty (mentors). Surveys focused on collecting participants’ attitudes and expectations regarding ideal and actual mentorship experiences. Descriptive statistics and Fisher's exact test analyses were used to compare the responses within and between students and faculty.ResultsA total of 234 faculty and 181 medical students completed the survey. There were 187 faculty respondents (79.9%) who had previously mentored students. Faculty who had versus had not previously mentored students differed significantly in their responses on the importance of mentors discussing aspects of their personal lives (71.1% vs. 54.3%, respectively, p = 0.0491), a quality valued by the majority of student respondents. As students progressed through medical school, they expressed increasing needs for personal mentorship and conversations regarding work/life integration and wellness (M1: 12.2%, M2: 18.8%, M3: 29.3%, M4: 51.7%). A minority of students (27% of M3 and 14.8% of M4 students) reported meeting faculty mentors through their clinical year experiences.ConclusionsFaculty mentoring experience may improve student-faculty value alignment, which may in turn help to address student-identified needs pertaining to personal development and professional identity formation in medical school. By contrasting student-identified mentorship expectations with those of faculty at various stages of mentorship experience, this study lays the groundwork for the formation of more effective longitudinal mentorship programs.

Analysis of LCL Filter Topologies for DC-DC Isolated Cuk Converter at CCM Operation

In this study, the application and analysis of LCL filter topologies including an LCL, an LCL with damping, and an LCL trap filter used by a DC-DC isolated Ćuk converter operated at CCM are presented. The converter is designed for 50 W with 42 kHz switching frequency using a SiC MOSFET as a power switch. Although LCL filter topologies are commonly used with an inverter, their use in DC-DC converters has not been studied in detail. The main contribution of the paper is the application, design, and analysis of an LCL trap filter, which is not presented for a DC-DC converter in the literature, as an input filter of a DC-DC isolated Ćuk converter. For exact analysis of the effect of the filter, as a second main contribution of the paper, a state-space average mathematical model, small signal analysis of an isolated Ćuk converter for CCM operation, which was not presented before in the literature, is derived and its transfer function is obtained. In this paper, the practical design and transfer functions of LCL-based filter topologies are also presented. In order to analyze the effect of filter topologies by using linear methods including root locus and Bode graphs, the transfer function of the converter is cascaded with the transfer function of each filter separately, which is the third contribution of the paper because such analysis has not been presented in the literature. Furthermore, each cascaded transfer function and the transfer function of the converter are validated by step responses. All LCL filters, with an LC filter for comparison, are employed in the experimental setup. Owing to the applications, control characteristics and input current ripples are measured. In addition, the efficiencies of each different structure are determined. As a result of the analysis and measurements, the LCL trap filter gives better results in terms of efficiency (86%) and input current ripple (0.96 A peak). Moreover, the LCL with damping filter gives poorer control characteristics, but the maximum gain of the controller avoiding the instability of LCL with damping is 0.0855, which is higher than that of the others. Furthermore, it is shown that each LCL filter topology provides a 45% lower total inductor value compared to the LC filter.

A marginal analysis framework to incorporate the externality effect of ordering perishables

The exact analysis of optimal ordering policies for periodic-review perishable inventory systems is challenging because of their high-dimensional state space arising from multiple interrelated ordering decisions over many periods and age distributions of on-hand products. We develop a new marginal analysis framework to approximate this complex multiple-decision model into a single-decision model with an externality term, which internalizes the long-term impact of ordering decisions. Our externality-based approximation utilizes a constant base-stock policy; it is fast and easy to apply. Numerical experiments show that our approach provides state-dependent ordering amounts almost identical to the optimal dynamic programming-based policy.

New Perspectives on Stability of Decoupled Double Synchronous Reference Frame PLL

Modeling and interpretation of synchronization stability of energy conversion systems with the unbalanced grid is a very practical, complicated, and less explored topic. This article demonstrates an inherent instability phenomenon in the synchronous reference frame phase locked-loop (SRF-PLL). The need for the small-signal model improvement and Floquet-stability-theory-based analysis is thereby demonstrated. Furthermore, decoupled double synchronous reference frame (DDSRF) PLL, which is a benchmark tool for unbalanced grid synchronization, is investigated for its behavior upon small disturbances. A precise sixth-order small-signal linear time-periodic model of DDSRF-PLL is obtained considering parameters of the input signal as well as of PLL. Floquet-theory-based stability and modal analysis are carried out to gain insights into dynamic properties of DDSRF-PLL. Impacts of distortions in grid voltage such as unbalance, harmonics, jumps in amplitude, phase, and frequency are analyzed for both performance and stability. This article is useful for the design and exact analysis of unbalanced grid interfaced converter systems and system interaction studies.

Cable structures: An exact geometric analysis using catenary curve and considering the material nonlinearity and temperature effect

Structures formed by cables constitute structural systems of great practical application in engineering, such as suspension bridges, cable-stayed bridges, cable cars, transmission lines in which case they are used as supporting elements that conduct electricity, overcoming the spans between the towers or in stays for the so-called cable-stayed towers, among other applications. Cable structures have a highly non-linear behavior both from a geometric point of view, arising from their initial equilibrium configuration, and from a material point of view, since the constitutive laws of the cables present an elastoplastic behavior. The objective of this work is to present a geometrically exact formulation for static analysis of cable structures considering the catenary configuration. For this, both geometric and material nonlinearities are included in the development of the the catenary cable element formulation. The effect of temperature variation is also considered. A rigorous updated Lagrangian description combined with the corotational approach is employed to obtain the consistent tangent stiffness matrix of the exact cable element. The proposed methodology was implemented in the software program called Advanced Structural Analysis System (ASTRAS), which is an academic software based on the Finite Element Method (FEM). Finally, numerical examples are analyzed using the present procedure and the obtained results are compared with those found in the literature and given by commercial softwares in order to demonstrate the consistency and precision of the formulation.

Design Procedure Based on Maximum Efficiency for Wireless Power Transfer Battery Chargers with Lightweight Vehicle Assembly

This paper analyzes two different design procedures for a series-parallel compensated WPT battery charger, based on different definitions of the operating resonant frequency in the condition of maximum link efficiency. The behaviour of the voltage gain magnitude and the input impedance angle of the resulting WPT links is studied for different loads and coupling coefficients. The design algorithms are supported by analytical formulas derived from an exact circuit analysis of the WPT link, avoiding approximations as far as possible. To support the theoretical approach a case study is proposed, in which both design procedures are implemented considering specifications in line with the actual automotive standards. To conclude, a characterization of the efficiency in both cases is derived.

Cardiotoxicity among Patients Using Pertuzumab, Trastuzumab and Taxane with HER2-Positive Early-Stage Breast Cancer: A Single-Centre Experience

Aim: In this study, we aimed to investigate the incidence rate, risk factors, and mortality rates in patients with early-stage breast cancer using anti-HER2 (Human epidermal growth factor receptor-2) treatment.&#x0D; Patients and Methods: A total of 106 patients diagnosed with human epidermal growth factor 2 (HER2)-positive early-stage breast cancer and receiving anti-HER2 treatment at King Abdulaziz Medical City (KAMC) from 2015 to 2019 were included in the analysis to assess the incidence of cardiotoxicity was collected as a retrospective study. Univariate and multivariate analyses as well as multiple exact logistic regression analysis were conducted to understand the relationships between the left ventricular ejection fraction (LVEF) and treatment combinations and comorbidities&#x0D; Results: The LVEF measurements using an echocardiography method at the baseline (before any treatment) and during the anti-HER2 therapy were assessed. The results suggest that the higher the drug combination, the higher the odds ratio for the declined ejection fraction (EF) patient group. Further, patients treated with the pertuzumab and trastuzumab combination were four times more likely to have a decline in their EF than those who did not use the pertuzumab and trastuzumab drug combination (OR 4.28, 95% CI [1.68–10.91]).&#x0D; Conclusion: This study demonstrated that the drug combination considered here is associated with reduced LVEF and, similarly, comorbidities were also related to EF. However, a larger study in a global patient population will confirm the present observations.

Factors Associated With Hospitalization Among Breast Cancer Patients With COVID-19: A Diverse Multi-Center Los Angeles Cohort Study

BackgroundThe SARS-CoV-2 virus has infected and killed millions of people worldwide. Breast cancer is the most prevalent cancer in women and few studies have investigated the outcomes of patients with a history of breast cancer and COVID-19. We report the clinical outcomes of patients with invasive breast cancer who tested positive for SARS-CoV-2, including hospitalization and death, and evaluate demographic and cancer-related factors associated with these outcomes. PatientsPatients with a history of invasive breast cancer and positive SARS-CoV-2 test from January 1 to December 31, 2020 at two large, academic Los Angeles health systems were included. MethodsRetrospective chart review of the electronic medical record was performed. Data for demographic and cancer-related factors were manually abstracted. Relationships between outcomes and clinical variables were evaluated using Fisher's exact test and linear regression analysis. ResultsAmong a total of 132 patients, 40 (30.3%) were hospitalized, while 11 (8.3%) required intensive care support, and 8 patients (6.1%) died. Older age and presence of one or more additional comorbidities were associated with hospitalization and death (P = .010, P = .003, P = .034, P < .001). Hispanic/Latinx ethnicity was associated with hospitalization (P = .047). Cancer treatment was not associated with hospitalization or death. ConclusionIn our diverse, multi-center, breast cancer cohort, Hispanic/Latinx ethnicity, older age and presence of other comorbidities were associated with worse outcomes from COVID-19. Breast cancer treatment, including surgery, radiation, systemic therapy, and endocrine therapy, was not associated with hospitalization in our cohort. Further studies are needed to explore the relationship between breast cancer and COVID-19 outcomes.

Universal ratio in random matrix theory and chaotic-to-integrable transition in type-I and type-II hybrid Sachdev-Ye-Kitaev models

We investigate chaotic to integrable transition in two types of hybrid SYK models, which contain both $q=4$ SYK with interaction $J$ and $q=2$ SYK with an interaction $K$ in type-I or ${(q=2)}^{2}$ SYK with an interaction $\sqrt{K}$ in type-II. These models include hybrid Majorana fermion, complex fermion, and bosonic SYK. For the Majorana fermion case, we discuss both $N$ even and $N$ odd case. We make exact symmetry analysis on the possible symmetry class of both types of hybrid SYK in the 10-fold way by random matrix theory (RMT) and also work out the degeneracy of each energy levels. We introduce a new universal ratio, which is the ratio of the next-nearest-neighbor (NNN) energy level spacing to characterize the RMT. We perform exact diagonalization to evaluate both the known NN ratio and the new NNN ratio, then use both ratios to study chaotic to integrable transitions (CIT) in both types of hybrid SYK models. Some preliminary results on possible quantum analog of Kolmogorov-Arnold-Moser (KAM) theorem and its dual version in the quantum chaotic side are given. We explore some intrinsic connections between the two complementary approaches to quantum chaos: the RMT and the Lyapunov exponent by the $1/N$ expansion in the large $N$ limit at a suitable temperature range. We stress the crucial differences between the quantum phase transition (QPT) characterized by renormalization groups at $N=\ensuremath{\infty}$, $1/N$ expansions at a finite $N$, and the CIT characterized by the RMT at a finite $N$: the former focus on the ground state and its low-energy excitations (edge states in the Fock space), the latter on excited states (bulk states in the Fock space). We also discuss eigenstate thermalization hypothesis (ETH)'s power on a quantum chaotic bulk state and its inability to encode the edge states. Comments on some previously related works are given. Some future perspectives, especially the failure of the Zamoloddchikov's c-theorem in 1d CFT RG flow are outlined.

Navier‐Stokes Equations in Gas Dynamics: Green's Function, Singularity, and Well‐Posedness

The purpose of the present article is to study weak solutions of viscous conservation laws in physics. We are interested in the well‐posedness theory and the propagation of singularity in the weak solutions for the initial value problem. Our approach is to convert the differential equations into integral equations on the level of weak solutions. This depends on exact analysis of the associated linear equations and their Green's functions. We carry out our approach for the Navier‐Stokes equations in gas dynamics. Local in time as well as time‐asymptotic behaviors of weak solutions, and the continuous dependence of the solutions on their initial data are established. © 2022 Wiley Periodicals LLC.

Malaysian nurses' knowledge and attitudes regarding BRCA genetic testing.

Breast cancer genetic (BRCA) testing for cancer susceptibility is an emerging technology in medicine. This study assessed the knowledge and attitude of nurses regarding BRCA genetic testing in a tertiary teaching hospital in Malaysia. A descriptive cross-sectional study was conducted among 150 nurses using a simple random sampling technique in a tertiary teaching hospital in northeast peninsular Malaysia. Data were collected using a self-administered questionnaire consisting of socio-demographic data, assessing nurses' knowledge and attitude regarding BRCA genetic testing. Fisher exact test analysis was used to determine the association between socio-demographic characteristics with knowledge and attitude level. In addition, the overall knowledge and attitude were analysed using the sum score of each outcome based on Bloom's cut-off point. Of the 150 nurses, 66.7% had high knowledge level about BRCA genetic testing, and 58% were positive towards genetic testing. The participants' mean age was 28.9 years (SD = 6.70). Years of working experience (p = 0.014) significantly influenced knowledge level on BRCA genetic testing, whereas speciality working experience (p <0.001) significantly influenced BRCA genetic testing attitudes. The results show that most nurses have adequate knowledge of BRCA genetic testing. However, their attitude could be termed negative. Therefore, targeted education programs on BRCA genetic testing and risk are needed to improve the knowledge and attitude of nurses and, ultimately, can educate the women and increase health-seeking behaviour among eligible women.

1204. Assessing Perceptions and Efficacy of COVID-19 Case and Contact Investigations – Dallas County, Texas, 2020

BackgroundDuring 2020, a total of 193,318 cases of COVID-19 were reported in Dallas, with daily average case rates exceeding 50 per 100,000 for over 7 weeks. An adaptable survey functionality within a newly implemented COVID-19 surveillance system provided an opportunity to assess case knowledge and attitudes about isolation and contact tracing efforts.MethodsCOVID-19 illnesses were classified using the 2020 CSTE case definitions. Cases were interviewed and records reviewed for exposures and illness characteristics. Supplemental questionnaires assessing knowledge of public health recommendations were given to a convenience sample of 987 cases during the month of December 2020. Fishers exact and chi-square analyses were performed using SAS 9.4.ResultsOf the 987 respondents, 99% reported beginning isolation on or before receipt of test results, and 1% were not in isolation at the time of public health interview. Of cases reporting contacts, 92% had advised household members to quarantine prior to interview, and 91% did not want public health to call their household. Of cases reporting non-household close contacts, 75% had advised these contacts to quarantine prior to interview, and 91.3% did not want the health department to call these persons. Cases ≥ 65 years were less likely to have notified their own close contacts (OR: 0.2; 95% CI=0.1-0.8) of their test results, and more likely to prefer the health department to notify their household contacts of their positive result (OR: 4.1; 95% CI=1.3-12.5). Compared with White cases, Hispanic cases were less likely to be aware that their test was positive at the time of interview (OR: 0.3; 95% CI=0.1-0.7). Non-White cases were less likely to be aware of resources for food, rent and utility assistance prior to interview (OR: 0.25; 95% CI=0.1-0.7). All respondents perceived the public health interview to have been of some value to them, most often to answer their questions about retesting (51%) and duration of isolation (48%).ConclusionThe aversion of a majority of COVID-19 cases for health department notification of their contacts is a significant deterrent to name-based contact tracing approaches. Acknowledgement of this limitation could better focus existing resources on the delivery of expedited notifications and information to contacts by proxy.Disclosures All Authors: No reported disclosures