The New White Flight

White charter school enclaves—defined as charter schools located in school districts that are thirty percent or less white, but that enroll a student body that is fifty percent or greater white— are emerging across the country. The emergence of white charter school enclaves is the result of a sobering and ugly truth: when given a choice, white parents as a collective tend to choose racially segregated, predominately white schools. Empirical research supports this claim. Empirical research also demonstrates that white parents as a collective will make that choice even when presented with the option of a more racially diverse school that is of good academic quality. Despite the connection between collective white parental choice and school segregation, greater choice continues to be injected into the school assignment process. School choice assignment policies, particularly charter schools, are proliferating at a substantial rate. As a result, parental choice rather than systemic design is creating new patterns of racial segregation and inequality in public schools. Yet the Supreme Court’s school desegregation jurisprudence insulates racial segregation in schools ostensibly caused by parental choice rather than systemic design from regulation. Consequently, the new patterns of racial segregation in public schools caused by collective white parental choice largely escapes regulation by courts. This article argues that the time has come to reconsider the legal and normative viability of regulating racial segregation in public schools caused by collective white parental choice. The article makes two important contributions to the legal literature on school desegregation. First, using white charter school enclaves as an example, it documents the ways in which school choice policies are being used to allow whites as a collective to satisfy their preference for segregated predominately white schools. Second, the article sets forth both constitutional and normative arguments for regulating the private choices that result in stark racial segregation patterns in public schools

INITIAL LENGTH SCALE ESTIMATE FOR WAVEGUIDES WITH SOME RANDOM SINGULAR POTENTIALS

Abstract. In this work we consider three examples of random singular perturbations in multi-dimensional models of waveguides. These perturbations are described by a large potential supported on a set of a small measure, by a compactly supported fast oscillating potential, and by a delta-potential. In all cases we prove initial length scale estimate

Parameters of mini straw grader

The purpose study is to substantiate the parameters of a mini straw shredder. The diagram rotor of a cone-shaped shredder is given. The basic laws of theoretical mechanics and mathematical analysis were used in theoretical studies to substantiate the parameters mini shredder. Single-and multifactorial experiments were carried out when determining the optimal parameters mini shredder. In theoretical studies, analytical links were obtained to determine the length of the mini straw grader knife, the slope angle, its base, and the force required to cut the straw. According to the results of studies, the degree of grinding salmon and energy consumption depended mainly on the length blade, the mass balancing truck, and the slope angle blade. It is established that to ensure the required fullness of grinding with minimal energy consumption, the length knife should be within 87.66-88.38 mm, the weight of the balancing weight should be 0.0368-0.0536 kg, and the angle of inclination of the knife 2848º

Emergence of Spacetime

Starting from a background Zero Point Field (or Dark Energy) we show how an array of oscillators at the Planck scale leads to the formation of elementary particles and spacetime and also to a cosmology consistent with latest observations.Comment: Latex, 39 page

СРАВНИТЕЛЬНАЯ ХАРАКТЕРИСТИКА АНЕСТЕЗИОЛОГИЧЕСКОГО ОБЕСПЕЧЕНИЯ И ВИДОВ ОПЕРАТИВНОГО ВМЕШАТЕЛЬСТВА У ПАЦИЕНТОВ С АТЕРОСКЛЕРОТИЧЕСКИМ ПОРАЖЕНИЕМ БРАХИОЦЕФАЛЬНЫХ АРТЕРИЙ

Introduction. Atherosclerotic lesions of the branches of the aortic arch in 60% of cases is the cause of the development of ischemic stroke. As a radical means of preventing neurological disorders, carotid endarterectomy is used, since there is currently no effective drug treatment.Material and methods. This article presents a comparative characteristic of anesthesiological support and types of surgical intervention in 710 patients with atherosclerotic lesions of brachiocephalic arteries in the period from January 2010 to December 2017 in Department of Vascular Surgery at the Clinic of the Bashkir State Medical University. To perform this comparative characteristic, the patients were divided into 2 groups, depending on the time interval. Group 1 — patients operated from 2010 to 2013 (291 patients). Group 2 — patients operated from 2014 to 2017 (491 patients). In Group 1, operations were predominantly performed under regional anesthesia and classical carotid endarterectomy predominated over an eversion. In Group 2, operations were performed under general anesthesia, and here the overthe-top carotid endarterectomy predominated over the classical one. Patients were comparable in age, sex and risk of anesthesia and surgical intervention according to the ASA classification. The overall incidence of ischemic postoperative complications was 4.22%.Results. According to our data, the application of the eversion method of carotid endarterectomy under general anesthesia reduces the relative risk of neurological complications by 1.648 times (as in the 2nd group the technique of eversion carotid endarterectomy under general anesthesia was used). The use of general anesthesia with carotid endarterectomy allows to provide adequate gas exchange, manageability by hemodynamic parameters, absence of emotional reactions from the patient.Conclusion. Thus, at the present moment, our experience in treating patients with atherosclerotic lesions of the brachiocephalic arteries is approaching the optimal one, allowing us to achieve good results of carotid endarterectomy. Введение. Атеросклеротическое поражение ветвей дуги аорты в 60% случаев является причиной развития ишемического инсульта. Как радикальное средство профилактики неврологических нарушений применяется операция каротидная эндартерэктомия, поскольку эффективного медикаментозного лечения в настоящее время не существует.Материалы и методы. В данной статье представлена сравнительная характеристика анестезиологического обеспечения и видов оперативного вмешательства у 710 пациентов с атеросклеротическим поражением брахиоцефальных артерий в период с января 2010 г. по декабрь 2017 г. в отделении сосудистой хирургии Клиники Башкирского государственного медицинского университета. Для проведения данной сравнительной характеристики больные были разделены на две группы в зависимости от временного интервала: 1-я группа — пациенты, прооперированные с 2010 по 2013 г. (291 пациент); 2-я группа — пациенты, прооперированные с 2014 по 2017 г. (491 пациент). Пациенты были сопоставимы по возрасту, полу и риску анестезиологического и оперативного вмешательства согласно классификации ASA. В 1-й группе операции преимущественно выполнялись под регионарной анестезией и доминировала классическая каротидная эндартерэктомия над эверсионной. Во 2-й группе операции выполнялись под общей анестезией, и здесь доминировала эверсионная каротидная эндартерэктомия над классической. Общая частота ишемических послеоперационных осложнений составила 4,22%.Результаты. По нашим данным, применение эверсионной методики каротидной эндартерэктомии под общей анестезией с применением церебральной оксиметрии снижает относительный риск неврологических осложнений в 1,648 раза (так как во 2-й группе в основном применялась методика эверсионной каротидной эндартерэктомии под общей анестезией). Применение общей анестезии при КЭАЭ позволяет обеспечить адекватный газообмен, управляемость гемодинамическими показателями, отсутствие эмоциональных реакций со стороны пациента.Заключение. Таким образом, на настоящий момент наш опыт лечения пациентов с атеросклеротическим поражением брахиоцефальных артерий приближается к оптимальному, позволяет достичь хороших результатов проведения каротидной эндартерэктомии.

Left Ventricular Function after Revascularization in Patients with Chronical Coronary Syndromes

Background: The purpose of this study was to determine the dynamics of morpho-functional and myocardial deformation characteristics of the left ventricle after revascularization in patients with chronic coronary syndromes (CCS). Methods and Results: The study included 136 CCS patients of both sexes with stable anginal symptoms [(i) clinical scenario] and asymptomatic coronary artery disease (CAD) at screening [(vi) clinical scenario]. Diagnosis of CCS was performed according to the 2019 ESC Guidelines for the diagnosis and management of chronic coronary syndromes. All patients underwent the following examinations: assessment of traditional risk factors, physical examination, general clinical and laboratory blood tests, 12-lead ECG, transthoracic echocardiography, two-dimensional speckle tracking echocardiography (STE), and coronary angiography (CAG). The SYNTAX score was calculated retrospectively according to the SYNTAX score algorithm. A total of 100 patients with CCS were enrolled in the main group (MG) and underwent revascularization by PCI with intracoronary stenting using drug-eluting stents. Among the main-group patients, one-vessel, two-vessel, and three-vessel CAD were detected in 36(26.5%), 34(25%), and 30(22.0%) cases, respectively. The comparison group (CG) included 36 CCS patients with hemodynamically non-significant coronary lesions (<50% stenosis). LVEF values were within the normal range in all groups, with the highest value in the CG, followed by the one-, two- and three-vessel lesion groups. LVEF obtained by the area-length method and modified biplane Simpson's method did not differ. The assessment of the contractile function of the LV myocardium was also obtained by assessing the global longitudinal strain (GLS) and global longitudinal strain rate (GLSR). The comparative analysis of the LV myocardial deformation properties in the studied groups showed that less negative GLS and GLSR were found in the three-vessel CAD, followed by the two-vessel and one-vessel CAD groups, and CG. CG demonstrated more negative GLS and GLSR than all MG subgroups. We analyzed the effect of revascularization on the GLS and found no statistically significant differences before and 48 hours after revascularization in all studied MG subgroups and CG. Thirty days after revascularization, GLS significantly showed more negative values in all MG subgroups: -18.12±0.63 versus -17.9±0.4 in one-vessel CAD, -16.13±0.71 versus -15.9±0.4 in two-vessel CAD and -13.91±1.25 versus -13.1±1.1 in three-vessel CAD. In CG with medical treatment only, GLS did not change statistically significantly but had more negative values than in the studied MG subgroups. Analysis of changes in LVEF after revascularization in the MG of patients with one-, two- and three-vessel CAD and in the CG after medical treatment did not reveal statistically significant dynamics. Conclusion: the results indicate the absence of statistically significant changes in myocardial deformation indicators and morpho-functional parameters of the left ventricle in CCS patients 48 hours after revascularization. Thirty days after revascularization, GLS significantly improves, while LVEF remains unchanged. GLS is superior to LVEF in visualizing improvement in LV function after revascularization in patients with CCS

Uzbekistan’s development experiment: An assessment of Karimov’s peculiar economic legacy

Uzbekistan’s unique post-independence experiment with development was led by Islam Karimov until his sudden death in September 2016. Despite defying international advice on structural reforms, under Karimov’s rule, Uzbekistan achieved an average annual growth rate of 5% in the period 1996–2016, which was particularly impressive (over 8%) in 2004–2016. Karimov also left behind strong macroeconomic fundamentals for his successor. Since taking over the presidency in December 2016, Shavkat Mirziyoyev has introduced wide-ranging reforms, creating an impression of a de facto start to transition in Uzbekistan. This study analyses Karimov’s economic legacy and assesses whether it has enabled or hindered the developmental targets set by his successor

Homogeneously derived transit timings for 17 exoplanets and reassessed TTV trends for WASP-12 and WASP-4

We homogeneously analyse ∼3.2 × 105 photometric measurements for ∼1100 transit lightcurves belonging to 17 exoplanet hosts. The photometric data cover 16 years 2004–2019 and include amateur and professional observations. Old archival lightcurves were reprocessed using up-to-date exoplanetary parameters and empirically debiased limb-darkening models. We also derive self-consistent transit and radial-velocity fits for 13 targets. We confirm the nonlinear TTV trend in the WASP-12 data at a high significance, and with a consistent magnitude. However, Doppler data reveal hints of a radial acceleration about ( − 7.5 ± 2.2) m/s/yr, indicating the presence of unseen distant companions, and suggesting that roughly 10 per cent of the observed TTV was induced via the light-travel (or Roemer) effect. For WASP-4, a similar TTV trend suspected after the recent TESS observations appears controversial and model-dependent. It is not supported by our homogeneus TTV sample, including 10 ground-based EXPANSION lightcurves obtained in 2018 simultaneously with TESS. Even if the TTV trend itself does exist in WASP-4, its magnitude and tidal nature are uncertain. Doppler data cannot entirely rule out the Roemer effect induced by possible distant companions

Electronic properties and phase transitions in low-dimensional semiconductors

We present the first review of the current state of the literature on electronic properties and phase transitions in TlX and TlMX2 (M = Ga, In; X = Se, S, Te) compounds. These chalcogenides belong to a family of the low-dimensional semiconductors possessing chain or layered structure. They are of significant interest because of their highly anisotropic properties, semi- and photoconductivity, non-linear effects in their I-V characteristics (including a region of negative differential resistance), switching and memory effects, second harmonic optical generation, relaxor behavior and potential applications for optoelectronic devices. We review the crystal structure of TlX and TlMX2 compounds, their transport properties under ambient conditions, experimental and theoretical studies of the electronic structure, transport properties and semiconductor-metal phase transitions under high pressure, and sequences of temperature-induced structural phase transitions with intermediate incommensurate states. Electronic nature of the ferroelectric phase transitions in the above-mentioned compounds, as well as relaxor behavior, nanodomains and possible occurrence of quantum dots in doped and irradiated crystals is discussed.Comment: 70 pages, 38 figure