Dispersion of graphite nanoplates in polypropylene by melt mixing: the effects of hydrodynamic stresses and residence time

This work combines experimental and numerical (computational fluid dynamics) data to better understand the kinetics of the dispersion of graphite nanoplates in a polypropylene melt, using a mixing device that consists of a series of stacked rings with an equal outer diameter and alternating larger and smaller inner diameters, thereby creating a series of converging/diverging flows. Numerical simulation of the flow assuming both inelastic and viscoelastic responses predicted the velocity, streamlines, flow type and shear and normal stress fields for the mixer. Experimental and computed data were combined to determine the trade-off between the local degree of dispersion of the PP/GnP nanocomposite, measured as area ratio, and the absolute average value of the hydrodynamic stresses multiplied by the local cumulative residence time. A strong quasi-linear relationship between the evolution of dispersion measured experimentally and the computational data was obtained. Theory was used to interpret experimental data, and the results obtained confirmed the hypotheses previously put forward by various authors that the dispersion of solid agglomerates requires not only sufficiently high hydrodynamic stresses, but also that these act during sufficient time. Based on these considerations, it was estimated that the cohesive strength of the GnP agglomerates is in the range of 5-50 kPa.This research was funded by FCT (Portuguese Foundation for Science and Technology) through scholarship SFRH/BPD/100353/2014 and projects UIDB/00013/2020 and UIDP/00013/2020. This work was also funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT under the projects UID-B/05256/2020 and UID-P/05256/2020

Direct observation of Levy flight of holes in bulk n-InP

We study the photoluminescence spectra excited at an edge side of n-InP slabs and observed from the broadside. In a moderately doped sample the intensity drops off as a power-law function of the distance from the excitation - up to several millimeters - with no change in the spectral shape.The hole distribution is described by a stationary Levy-flight process over more than two orders of magnitude in both the distance and hole concentration. For heavily-doped samples, the power law is truncated by free-carrier absorption. Our experiments are near-perfectly described by the Biberman-Holstein transport equation with parameters found from independent optical experiments.Comment: 4 pages, 3 figure

Validation of a questionnaire for young women to assess knowledge, attitudes and behaviors towards cervical screening and vaccination against HPV in Italy

Background: Despite knowledge about HPV may be an important determinant for vaccine acceptance and uptake, only few studies have assessed HPV-related knowledge in young females. The aim of this study was to assess the reliability and validity of the questionnaire, in Italian women ≥18 years old, as a tool to examine knowledge, attitudes and behaviors towards screening and vaccination against HPV and reliable source of information. Methods: The questionnaire was administered to 30 girls in anonymous, voluntary and self -administered form with close-ended type of questions, except for the socio-demographic characteristics. It was composed in 3 sections for a total of 69 items. Participation in the study was entirely voluntary and anonymous. Descriptive analyses were performed using frequencies, percentages, and frequency table for categorical variables. Reliability analysis was tested and content validity was evaluated using Cronbach's alpha to check internal consistency and avoid misinterpretation of the results. The study was conducted in 4 Italian cities: Ferrara, Rome, Cassino and Palermo, to represent the different Italian geographical areas and knowledge, attitudes and behaviors towards screening and vaccination against HPV and reliable source of information. Data were collected in October 2010. Statistical analysis was performed with the statistical software for Windows SPSS, version 19.0. Results: The highest value of Cronbach's alpha resulted on 24 items (alpha= 0,774); the addition of other items, one at a time, decreased the value. Cronbach's alpha on all the 3 sections together resulted in a value of 0, 059. Young women generally knew that HPV can cause cervical cancer (93.3%) and genital warts (16.7%) and 76.7% of them recognized Pap-test as a screening tool. The main sources of information about HPV vaccination are represented by magazines / books (33.3%), TV (26.7%), and gynecologists (23.3%). Conclusions: This pilot study demonstrated that a short version of the questionnaire has very good reliability properties in the study and this needs to be taken into account for future studies

Нелинейно-инерционная модель диода с учетом зависимости времени жизни неравновесных носителей заряда от прямого тока для повышения качества моделирования РЭА

Introduction. Adequate modeling of semiconductor devices with a p–n-junction in reverse bias represents a relevant research problem. The existing quasistatic and non-quasistatic models fail to provide a satisfactory description for the dependence of nonequilibrium charge carrier lifetime on current density. This leads to significant simulation errors (tens of percent) at pulsed broadband signals. Simulation errors arise, because the existing models regard the lifetime as a constant value.Aim. To propose and investigate an equivalent circuit of a p–n-junction considering the dependence of the lifetime of nonequilibrium charge carriers on direct current, with the possibility of its simple integration into CAD.Materials and methods. The study was carried out on the example of a fast recovery silicon diode BAS16J with a p–n-junction manufactured by Nexperia. A modified diode model is proposed in the form of an equivalent circuit that considers the dependence of the lifetime of nonequilibrium charge carriers on the direct current of the p–njunction at high injection levels.Results. The discrepancy between the experimental and simulated curves did not exceed ±9 % under pulsed diode operation. The extraction of parameters in the proposed model is carried out conventionally, from the current-voltage and capacitance-voltage characteristics of the diode.Conclusion. The proposed non-quasistatic equivalent diode circuit can be used when designing radio electronic devices operated at short-pulse broadband signals. The proposed diode model can be easily implemented in modern CAD systems at the user level.Введение. Адекватное моделирование полупроводниковых приборов с p–n-переходом в обратном смещении представляет проблему. Существующие квазистатические и неквазистатические модели не в состоянии удовлетворительно охарактеризовать зависимость времени жизни неравновесных носителей заряда от плотности тока. Это приводит к большой погрешности (десятки процентов) моделирования на импульсных широкополосных сигналах. Погрешность моделирования объясняется тем, что в существующих моделях время жизни представлено в виде неизменного значения.Цель работы. Предложить и исследовать эквивалентную схему p–n-перехода, учитывающую зависимость времени жизни неравновесных носителей заряда от прямого тока, с возможностью простой интеграции этой схемы в САПР.Материалы и методы. Исследование выполнено на примере кремниевого быстровосстанавливающегося диода BAS16J с p–n-переходом, производства Nexperia. Предложена модифицированная модель диода в виде эквивалентной схемы, учитывающая зависимость времени жизни неравновесных носителей заряда от прямого тока p–n-перехода при высоком уровне инжекции.Результаты. Расхождение между экспериментальной и модельной кривыми не превышает ±9 % при импульсном воздействии на диод. Экстракция параметров в предложенной модели происходит обычными способами из вольт-амперной и вольт-фарадной характеристик диода.Заключение. Рассмотренная неквазистатическая эквивалентная схема диода представляет большой интерес при проектировании радиоэлектронных устройств, работающих с короткоимпульсными широкополосными сигналами. Представленная модель диода в виде эквивалентной схемы позволяет беспрепятственно реализовать ее в современных САПР на пользовательском уровне

Минималистичная система характеристик нелинейных видеоимпульсных устройств и ее измерение

Introduction. The general system of parameters, including compression points and intersection points of various harmonics, is unsuitable for devices operating under the influence of baseband pulses (for example, before the modulator in the transmitter, after the demodulator in the receiver). Previously, the authors have developed simple models in the form of nonlinear recursive filters, which give a satisfactory error in describing the response of a wide class of baseband pulse circuits. The system of nonlinear functions of such models can be considered as a new system of characteristics of nonlinear-dynamical baseband impulse circuits, for which it is necessary to develop a method that ensures their measurement with an acceptable error. In the general formulation, this problem is rather challenging; therefore, this article considers only a first-order nonlinear recursive filter. However, the obtained result gives satisfactory results for devices without flat top transient overshoot.Aim. To consider a method for measuring the characteristics of nonlinear-dynamical baseband impulse devices without overshoot on the flat top of the transient response.Materials and methods. The considered recursive filter is represented by an equivalent circuit consist of nonlinear resistive and capacitive elements. Therefore, the task is reduced to measuring their current-voltage characteristics (IV) and charge-voltage characteristics (CVC). IV characteristics are measured at the flat tops of the transient characteristics of the device. Having a certain IV, we obtain the opportunity to calculate the current (and then the charge) of the capacitive element. The experimental study was carried out on the example of a three-stage amplifier with an aperiodic transient response.Results. The transient characteristics of the filter are approximated by the model with an accuracy of no worse than 3.2 %.Conclusion. The considered system of functions can be obtained with a definable error that satisfactory for practice, which allows it to be considered as a new system of parameters for nonlinear baseband pulse devices.Введение. Распространенная система параметров, включающая точки компрессии и точки пересечения для различных гармоник, непригодна для устройств, работающих при видеоимпульсных воздействиях (например, до модулятора в передатчике, после демодулятора в приемнике). Ранее авторами разработаны простые модели в виде нелинейных рекурсивных фильтров, дающие удовлетворительную погрешность описания отклика широкого класса видеоимпульсных цепей. Система нелинейных функций таких моделей может рассматриваться как новая система характеристик нелинейно-инерционных видеоимпульсных цепей, для чего необходимо разработать метод, обеспечивающий их измерение с допустимой погрешностью. В общей постановке эта задача весьма сложна, поэтому в настоящей статье рассмотрен лишь нелинейный рекурсивный фильтр первого порядка. Полученные зависимости, тем не менее, дают удовлетворительные результаты для устройств без выброса на плоской вершине переходной характеристики.Цель работы. Рассмотреть способ измерения характеристик нелинейно-инерционных видеоимпульсных устройств без выброса на плоской вершине переходной характеристики.Материалы и методы. Рассмотренный рекурсивный фильтр представлен эквивалентной схемой из нелинейных резистивного и емкостного элементов. Поэтому задача сводится к измерению их вольт-амперной характеристики (ВАХ) и кулон-вольтовой характеристики. ВАХ измеряется на плоских вершинах переходных характеристик устройства. Имея определенную ВАХ, получаем возможность вычислить ток (и далее заряд) емкостного элемента. Экспериментальное исследование выполнено на примере трехкаскадного усилителя с апериодической переходной характеристикой.Результаты. Переходные характеристики фильтра аппроксимированы моделью с точностью не хуже 3.2 %.Заключение. Рассмотренная система функций может быть получена с определяемой и удовлетворительной для практики погрешностью, что позволяет ее рассматривать как новую систему параметров нелинейных видеоимпульсных устройст

PGI12 Organizational and Economic Issues Related to the Introduction of Boceprevir in the Treatment of Patients with Genotype 1 Chronic Hepatitis C in Italy

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БИОХИМИЧЕСКИЕ ИЗМЕНЕНИЯ В ОРГАНИЗМЕ КРУПНОГО РОГАТОГО СКОТА ПРИ ФАСЦИОЛЁЗЕ

Functioning of a number of transamination enzymes and alkaline phosphatase as well as some values of carbohydrate and lipid metabolism on background of protein in cattle blood at fasciolosis are studied. Total blood protein was determined by Loury method, alkaline phosphatase activity – by colorimetric method based on the hydrolysis of n-nitrophenol phosphate. The glutamate transferase activity was estimated by L.J. Olsen method, transaminase activity – by Reitman-Frankel method. Cholesterol levels were measured according to Liebermann–Burchard reaction, the pyruvate content was determined using the diphenylhydrazine method, and lactate – according to reaction withparaoxydiphenyl. The functional status of blood at fasciolosis is marked by the decrease in total protein and pyruvate with the increase of activity of glutamate transferase, alkaline phosphatase, lactate and cholesterol.Изучено функционирование ряда ферментов трансаминирования, щелочной фосфатазы, а также некоторые показатели углеводного и липидного обменов на фоне содержания белка в крови крупного рогатого скота при фасциолезе. В сыворотке крови определяли количество общего белка по Лоури и активность щелочной фосфатазы колориметрическим методом на основе гидролиза n-нитрофенолфосфата. Активность глутаматтрансаминазы определяли по методу Олсона, трансаминаз – по методу Рейтмана и Френкеля, содержание холестерола – по реакции Либермана–Бурхарда, пирувата дифенилгидразиновым и лактата – по реакции с параоксидифенилом. Функциональное состояние крови при фасциолезе характеризуется понижением уровня общего белка и пирувата с одновременным увеличением активности глутаматтрансаминазы, щелочной фосфатазы, лактата и холестерола

Study of the psychophysiological state of students of the medical and preventive faculty of USMU on distance learning

The aim of the study – to assess the psychophysiological state of students of the Faculty of Medicine and Prevention who were on distance learning in connection with the pandemic.Цель исследования – оценить психофизиологическое состояние студентов медико-профилактического факультета, находившихся на дистанционной форме обучения в связи с пандемией