Long-range correlation energy calculated from coupled atomic response functions

An accurate determination of the electron correlation energy is essential for describing the structure, stability, and function in a wide variety of systems, ranging from gas-phase molecular assemblies to condensed matter and organic/inorganic interfaces. Even small errors in the correlation energy can have a large impact on the description of chemical and physical properties in the systems of interest. In this context, the development of efficient approaches for the accurate calculation of the long-range correlation energy (and hence dispersion) is the main challenge. In the last years a number of methods have been developed to augment density functional approximations via dispersion energy corrections, but most of these approaches ignore the intrinsic many-body nature of correlation effects, leading to inconsistent and sometimes even qualitatively incorrect predictions. Here we build upon the recent many-body dispersion (MBD) framework, which is intimately linked to the random-phase approximation for the correlation energy. We separate the correlation energy into short-range contributions that are modeled by semi-local functionals and long-range contributions that are calculated by mapping the complex all-electron problem onto a set of atomic response functions coupled in the dipole approximation. We propose an effective range-separation of the coupling between the atomic response functions that extends the already broad applicability of the MBD method to non-metallic materials with highly anisotropic responses, such as layered nanostructures. Application to a variety of high-quality benchmark datasets illustrates the accuracy and applicability of the improved MBD approach, which offers the prospect of first-principles modeling of large structurally complex systems with an accurate description of the long-range correlation energy.Comment: 15 pages, 3 figure

An Experimental Thrust Measurement Study on the Nozzle Asymmetry of Turbulent Pulsed Jets

The resurgence of pulsejet engines has renewed the interest of the flow characteristics responsible for the high levels of thrust augmentation that are necessary for Vertical/Short Take-Off and Landing (V/STOL) aircraft. It is well known that pulsation of the engine plays an important role on the thrust performance, but many of the characteristics that are primarily responsible for these enhancements are not well understood. This study is carried out to elucidate the effect of nozzle exit Mach number and the nozzle exit geometry on the characteristics of a high Reynolds number (~105), turbulent free pulsed jet. Direct thrust measurements are conducted using a pulsed jet as the driving source with different nozzle geometries (circular, diamond, elliptic, and rectangular) over a range of exit Mach numbers (Mj) from 0.10 to 0.30. The data show that for a given geometry, the jet strongly depends on the pulsing frequency. Further increase in pulsation will decrease thrust and eventually perform similar to an equivalent steady jet

Means to an End: A Qualitative Interview Study on Medical Students and Debt

Today, 43.4 million Americans owe 1.7 trillion dollars in student loan debt (Hanson, 2022). The American Association of Medical Colleges (2021) reported that 73% of medical students graduate with educational debt, of which the average medical student borrowed $203,062 in student loans. The problem addressed through this study is that as the narrative about student loan debt grows, the hegemonic understanding of debt revolves around the undergraduate student\u27s experience and their eminent struggles regarding repayment of student loans and employment. However, limited research exists on how medical students understand and experience debt. Several researchers have discussed the lack of understanding about medical students and debt. For instance, Kahn et al. (2006) suggested that medical students make major life choices based on several complex factors, but further research is needed. Rohlfing et al. (2014) discussed the necessity of a study specifically looking at the impact of the cost of attendance on medical student debt and major life choices. Young et al. (2016) echoed for further research on understanding the complex ways and multiple dimensions in which in medical students and residents understand debt. This qualitative study aimed to expand on how medical students experience and make meaning of debt. Two semi-structured interviews were conducted with 10 medical students during their final year of medical school. The following question guided this study: How do graduating medical students at Florida International University experience and understand debt? Three super-ordinate themes and 10 sub-themes were developed from participants’ interview transcripts utilizing an interpretative phenomenological analysis. The super-ordinate themes are: a) Debt (Re)Articulated, b) Emotions and Approaches to Debt, and c) The Temporality of Debt. The study’s key findings revealed that participants’ articulations vary from the commonsensical understandings of debt as financial to non-financial obligations to family, institution, and God. Participants felt burdened and frustrated by the cost of obtaining a medical degree while also accepting their student loan debt as an investment that can be managed and paid off in the future. Participants expressed the influence of their student loan debt in their daily decisions and the expected influence it will have in delaying major life decisions and the foreclosing of opportunities in the future. The implications of this study call for reform in federal loan and medical education policies and action by medical colleges to reduce the debt burden placed on medical students

Equalization and detection for digital communication over nonlinear bandlimited satellite communication channels

This dissertation evaluates receiver-based methods for mitigating the effects due to nonlinear bandlimited signal distortion present in high data rate satellite channels. The effects of the nonlinear bandlimited distortion is illustrated for digitally modulated signals. A lucid development of the low-pass Volterra discrete time model for a nonlinear communication channel is presented. In addition, finite-state machine models are explicitly developed for a nonlinear bandlimited satellite channel. A nonlinear fixed equalizer based on Volterra series has previously been studied for compensation of noiseless signal distortion due to a nonlinear satellite channel. This dissertation studies adaptive Volterra equalizers on a downlink-limited nonlinear bandlimited satellite channel. We employ as figure of merits performance in the mean-square error and probability of error senses. In addition, a receiver consisting of a fractionally-spaced equalizer (FSE) followed by a Volterra equalizer (FSE-Volterra) is found to give improvement beyond that gained by the Volterra equalizer. Significant probability of error performance improvement is found for multilevel modulation schemes. Also, it is found that probability of error improvement is more significant for modulation schemes, constant amplitude and multilevel, which require higher signal to noise ratios (i.e., higher modulation orders) for reliable operation. The maximum likelihood sequence detection (MLSD) receiver for a nonlinear satellite channel, a bank of matched filters followed by a Viterbi detector, serves as a probability of error lower bound for the Volterra and FSE-Volterra equalizers. However, this receiver has not been evaluated for a specific satellite channel. In this work, an MLSD receiver is evaluated for a specific downlink-limited satellite channel. Because of the bank of matched filters, the MLSD receiver may be high in complexity. Consequently, the probability of error performance of a more practical suboptimal MLSD receiver, requiring only a single receive filter, is evaluated

Electronic Rubric Grading: Establishing a Foundation for the Future

Many institutions of higher education measure learning outcomes through performance-based assessments or rubrics, resulting in the exploration of innovative methods to administer these types of assessments (Anglin, Anglin, Schumann & Kaliski, 2008). At Western University of Health Sciences – College of Dental Medicine, performance-based assessments have been transformed into interactive, electronic versions in which faculty graders use their computers or mobile devices to submit scored rubrics complete with feedback for the students. A major advantage of the software, ExamSoft, we utilize is the ability to link learning outcomes to assessments, resulting in generating robust reports that display longitudinal data for individual students and each cohort. A pilot test was launched in December 2014 and lasted through February 2015 in order to gather data and improve processes prior to fully transitioning to electronic rubrics for dental competency exams. The development, implementation, and launching of electronic rubric grading was challenging, yet produced numerous benefits for the dental program. Faculty, staff, and administration can generate more robust reports that measure students’ institutional and program learning outcomes. With this data, longitudinal reports are a means to track and measure student outcomes. The transition to electronic grading has also resulted in a streamlined process, efficient and smoother workflow, decrease in the likelihood of miscalculations due to human error, quicker turnaround for releasing grades and feedback to faculty members and students, and data to support recommended improvements to the curriculum. Our advancement in electronic grading ensures our place at the forefront of dental education, assessment technologies, and higher education

Reliability prediction for structures under cyclic loads and recurring inspections

This work presents a methodology for determining the reliability of fracture control plans for structures subjected to cyclic loads. It considers the variability of the parameters involved in the problem, such as initial flaw and crack growth curve. The probability of detection (POD) curve of the field non-destructive inspection method and the condition/environment are used as important factors for structural confidence. According to classical damage tolerance analysis (DTA), inspection intervals are based on detectable crack size and crack growth rate. However, all variables have uncertainties, which makes the final result totally stochastic. The material properties, flight loads, engineering tools and even the reliability of inspection methods are subject to uncertainties which can affect significantly the final maintenance schedule. The present methodology incorporates all the uncertainties in a simulation process, such as Monte Carlo, and establishes a relationship between the reliability of the overall maintenance program and the proposed inspection interval, forming a “cascade” chart. Due to the scatter, it also defines the confidence level of the “acceptable” risk. As an example, the damage tolerance analysis (DTA) results are presented for the upper cockpit longeron splice bolt of the BAF upgraded F-5EM. In this case, two possibilities of inspection intervals were found: one that can be characterized as remote risk, with a probability of failure (integrity nonsuccess) of 1 in 10 million, per flight hour; and other as extremely improbable, with a probability of nonsuccess of 1 in 1 billion, per flight hour, according to aviation standards. These two results are compared with the classical military airplane damage tolerance requirements

Listening to the Voices of Latinos in Omaha: Their Experiences and Ideas for Improving Access to Health Care

CPACS Urban Research Awards Part of the mission of the College of Public Affairs and Community Service (CPACS) is to conduct research, especially as it relates to concerns of our local and statewide constituencies. CPACS has always had an urban mission, and one way that mission is served is to preform applied research relevant to urban society in general, and the Omaha metropolitan area and other Nebraska urban communities in particular. Beginning in 2014, the CPACS Dean provided funding for the projects with high relevance to current urban issues, with the potential to apply the findings to practice in Nebraska, Iowa, and beyond

Chemical Speciation of constituents in pyrolytic liquid from cassava harvest residues by APPI-Orbitrap MS

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