Kaluza-Klein Towers in the Early Universe: Phase Transitions, Relic Abundances, and Applications to Axion Cosmology

We study the early-universe cosmology of a Kaluza-Klein (KK) tower of scalar fields in the presence of a mass-generating phase transition, focusing on the time-development of the total tower energy density (or relic abundance) as well as its distribution across the different KK modes. We find that both of these features are extremely sensitive to the details of the phase transition and can behave in a variety of ways significant for late-time cosmology. In particular, we find that the interplay between the temporal properties of the phase transition and the mixing it generates are responsible for both enhancements and suppressions in the late-time abundances, sometimes by many orders of magnitude. We map out the complete model parameter space and determine where traditional analytical approximations are valid and where they fail. In the latter cases we also provide new analytical approximations which successfully model our results. Finally, we apply this machinery to the example of an axion-like field in the bulk, mapping these phenomena over an enlarged axion parameter space that extends beyond those accessible to standard treatments. An important by-product of our analysis is the development of an alternate "UV-based" effective truncation of KK theories which has a number of interesting theoretical properties that distinguish it from the more traditional "IR-based" truncation typically used in the extra-dimension literature.Comment: 30 pages, LaTeX, 18 figures. Replaced to match published versio

Graduate Student Impairment: The Impact on Counselor Training Programs

This article focuses on the issue of student impairment in graduate level counselor training programs and the factors that affect it, including: A definition of graduate student impairment; the prevalence of student impairment in counselor training programs; an explanation of the legal consequences when addressing student impairment; organizational issues in universities dealing with this issue; and, the impact of graduate student impairment on the counseling professions

High-fidelity simulation increases obstetric self-assurance and skills in undergraduate medical students

Objective: Teaching intrapartum care is one of the most challenging tasks in undergraduate medical education. High-fidelity obstetric simulators might support students' learning experience. The specific educational impact of these simulators compared with traditional methods of model-based obstetric teaching has not yet been determined. Study design: We randomly assigned 46 undergraduate medical students to be taught using either a high-fidelity simulator or a scale wood-and-leather phantom. Their self-assessments were evaluated using a validated questionnaire. We assessed obstetric skills and asked students to solve obstetric paper cases. Main outcome measures: Assessment of fidelity-specific teaching impact on procedural knowledge, motivation, and interest in obstetrics as well as obstetric skills using high- and low-fidelity training models. Results: High-fidelity simulation specifically improved students' feeling that they understood both the physiology of parturition and the obstetric procedures. Students in the simulation group also felt better prepared for obstetric house jobs and performed better in obstetric skills evaluations. However, the two groups made equivalent obstetric decisions. Conclusion: This study provides first data on the impact of high-fidelity simulation in an undergraduate setting

Deciphering the Archaeological Record: Cosmological Imprints of Non-Minimal Dark Sectors

Many proposals for physics beyond the Standard Model give rise to a dark sector containing many degrees of freedom. In this work, we explore the cosmological implications of the non-trivial dynamics which may arise within such dark sectors, focusing on decay processes which take place entirely among the dark constituents. First, we demonstrate that such decays can leave dramatic imprints on the resulting dark-matter phase-space distribution. In particular, this distribution need not be thermal -- it can even be multi-modal, exhibiting a non-trivial pattern of peaks and troughs as a function of momentum. We then proceed to show how these features can induce modifications to the matter power spectrum. Finally, we assess the extent to which one can approach the archaeological "inverse" problem of deciphering the properties of an underlying dark sector from the matter power spectrum. Indeed, one of the main results of this paper is a remarkably simple conjectured analytic expression which permits the reconstruction of many of the important features of the dark-matter phase-space distribution directly from the matter power spectrum. Our results therefore provide an interesting toolbox of methods for learning about, and potentially constraining, the features of non-minimal dark sectors and their dynamics in the early universe.Comment: 55 pages, LaTeX, 21 figures, 4 table

A Quantitative Analysis of Simultaneous Supply and Demand Disruptions on a Multi-Echelon Supply Chain

Modern supply chains have grown to be far more complex than their predecessors, as global trade and accessibility have opened avenues of trade that were previously impossible. As such, the inherent risk of internal and/or external disruptions impacting the performance of a supply chain has also grown due to the interconnectivity of industries throughout the world. Because of the widespread severity of the COVID-19 pandemic, companies have shifted their perspective to viewing disruption risk protection as a necessity. As companies begin to invest further resources in their supply chains, it is important for them to understand how different disruptions and potential mitigation strategies could impact the performance of their supply chains. In response to this need, this research aimed to uncover how different supply and demand disruption features impact the performance of a multi-echelon supply chain. To accomplish this goal, a discrete-event simulation model was developed in ARENA and a full factorial designed experiment was conducted to understand how different disruption characteristics affect the key performance metrics of a multi-echelon supply chain. Historical supply chain data was obtained for a four-echelon supply chain owned by a single company that operated under the guaranteed service model (GSM) inventory policy. Finally, analysis of variance (ANOVA) was used to derive insights from the results of the designed experiment. This research revealed several key insights about supply chain behavior during simultaneous supply and demand disruptions. For example, it was found that the severity of a demand disruption (i.e., the level of demand spike) had considerable impact on the performance of the supply chain during the disruption period. In addition, disruptions which occurred further upstream in the supply chain were more likely to experience performance decreases in the post-disruption period compared to other disruptions. It was also found that additional inventory could be expected to accumulate at a disrupted node which, in turn, resulted in inventory reductions immediately upstream of the disrupted node

Барботажные химические эффекты: их виды, механизмы возникновения и геохимические проявления

Експериментально досліджено зміни значень pH і Eh у воді і водних розчинах NaCl при 20 ºС під час пропускання чистих газів (N2, O2, повітря без CO2) в різних режимах барботажу. Результати проаналізовано з врахуванням сучасних уявлень про структуру рідкої води і її поверхні (інтерфейсу). Як правило, барботажний процес складається із двох етапів: I – перші 10 хвилин із швидким збільшенням значення рН і зменшенням значення Eh внаслідок вимивання розчинених CO2 і O2; II – до 2–3 годин, коли значення Eh продовжує повільно зменшуватись, а значення pH може як зростати (лужний БХЕ) так і зменшуватись (кислотний БХЕ), що вказує на кислотний характер поверхні газ/вода і утворених при барботажі аерозолів. Спеціальні досліди на магнітній мішалці показали, що помітні зміни pH і Eh починаються лише після переходу перемішування із ламінарного режиму в турбулентний, що приводить до значного підвищення структурної температури води і відповідного зменшення розчинності кисню та величини Eh. Це і є основна причина змін на першому етапі барботажу, який можна назвати турбулентним БХЕ. Окремо потрібно виділити диференціацію йонів під час барботажу у змішаних розчинах солей. Для пояснення явища йонного БХЕ запропонована і обґрунтовано гіпотезу нейтральних йонних пар, яка задовільно пояснює генезис і властивості морських аерозолів.The changes of pH and Eh in water and aqueous NaCl – solutions at 20 °C during the transmission of pure gases (N2, O2, air, CO22) in different modes of barbotage are experimentally investigated. The results are analyzed taking into account modern notions of the structure of liquid water and its surface (interface). Generally, the barbotage process consists of two stages: I – the first 10 minutes with the rapid increasing in pH and decreasing in Eh due to leaching of dissolved CO2 and O2; II – up to 2-3 hours when Eh continues to decrease slowly, but pH can increase (alkaline BCE) or decrease (acid BCE), indicating the acidic nature of gas/water surface and aerosols produced during barbotage. Special experiments on the magnetic stirrer showed that noticeable changes in pH and Eh begin only after the transition from laminar regime of mixing to turbulent, which leads to a significant increasing of the structural temperature of water and a corresponding reduction in the solubility of oxygen and Eh values. This is the main reason for the changes at the first step of barbotage, which can be called as the turbulent BCE. We must highlight the differentiation of ions during barbotage in mixed salt solutions. To explain this phenomenon of ion BCE, the hypothesis of neutral ion pairs has been proposed and substantiated, which satisfactorily explains the genesis and properties of marine aerosols.Экспериментально исследованы изменения значений pH и Eh в воде и водных растворах NaCl при 20 ºС во время пропускания чистых газов (N2, O2, воздуха без CO2) в различных режимах барботажа. Результаты проанализированы с учетом современных представлений о структуре жидкой воды и ее поверхности (интерфейса). Как правило, барботажный процесс состоит из двух этапов: I – первые 10 минут с быстрым увеличением значений рН и уменьшением Eh, вследствие вымывания растворенных CO2 и O2; II – до 2-3 часов, когда Eh продолжают медленно уменьшаться, а pH может как расти (щелочной БХЕ) так и уменьшаться (кислотный БХЕ), что указывает на кислотный характер поверхности раздела фаз газ/вода и аэрозолей, образованных при барботаже. Специальные опыты на магнитной мешалке показали, что заметные изменения значений pH и Eh начинаются только после перехода перемешивания из ламинарного режима в турбулентный, что приводит к значительному повышению структурной температуры воды и соответствует уменьшению растворимости кислорода и величины Eh. Это и есть основная причина изменений на первом этапе барботажа, который можно назвать турбулентным БХЕ. Отдельно нужно выделить дифференциацию ионов при барботаже в смешанных растворах солей. Для объяснения этого явления ионного БХЕ предложена и обоснована гипотеза нейтральных ионных пар, которая удовлетворительно объясняет генезис и свойства морских аэрозолей

Development of a lightweight cryogenic insulating system Final report, 30 Jun. 1964 - 31 May 1966

Lightweight external panel insulation systems for thermal protection of cryogenic launch vehicle propellant tank