The D-region of the ionosphere

The D-region of the ionosphere, traditionally defined as the region of ionization below 100 km, is a link between the non-ionized stratosphere below and the dense plasma above. In it, minor neutral constituents play a dominant role and chemical reactions, both neutral and ionic, are dominant. It plays a very important role in the propagation of radiowaves at all frequencies below 30 MHz, and is particularly important in effecting communication over areas of the earth, such as polar regions, that are inaccessible to synchronous satellite links.     

Attitudes on Barriers and Benefits of Distance Education among Mississippi Delta Allied Health Community College Faculty,Staff, and Students

Online distance education creates increased opportunities for continuing education and advanced training for allied health professionals living in underserved and geographically isolated areas. The purpose of this article was to explore attitudes on barriers and benefits of distance education technology among underrepresented minority allied health students. It also addressed potential issues to geographic isolation that may contribute to the shortage of adequately trained health professionals in the Mississippi Delta. Community college students, faculty, and staff of Mississippi Delta allied health programs were interviewed about their experience, barriers and benefits to participation, and self efficacy with distance education. Four focus groups meetings with 34 participants were conducted to understand perceptions of community college students and professionals about distance education. Exposure to and experience with online and distance learning format, frequent Internet usage, and plans to matriculate to a four-year university are significant factors when examining attitudes on barriers and benefits. Faculty and staff perceive that community college students would be more confident during discussions in an online environment; that an online class will reduce out-of-pocket educational expenses; and online learning will save time by making all course materials accessible from one webpage. Attitudes on benefits to distance education should be evaluated to assess whether distance education programs meet the needs of the students in underserved areas.     

Theory-based Change and Change-based Theory: Going Deeper, Going Broader

This article examines the questions of sustaining and extending theory-based educational change reforms, which are designed by laboratories outside of schools and whose motivating theoretical base assumes change in elemental aspects of classroom practice. This article defines sustainability of theory-based reform as more than maintaining current implementation, rather as deepening reforms in ways that allow for flexible response to changes in student, curricular, and school contexts. It draws upon five years of research in schools and classrooms engaged in one of three theory-based reforms to discuss five essential factors affecting sustainability: resources, reformers' learning, knowledge of the first principles of the reform and the support of a community of practice, the principal, and the district. This article then turns to ``scaling up.' Rather than merely replicating structures, extending theory-based reform to new sites requires building compatibility between the normative base of the reform with that in the classrooms, schools and districts in which they are growing as well as the capacity of the classroom, school, and district to see it through. This article suggests three main factors that reform founders must focus upon to scale up their reforms – attention to site selection, a proactive stance toward district contexts, and planned transfer of authority. The article concludes that issues of invention, implementation, sustainability, and scale occur simultaneously when going deeper and broader with theory-based change.     

Acquisition of computer literacy skills through self-organizing systems of learning among children in Bhutan and India

This article describes a study under the Reaching the Unreached component of the Chiphen Rigpel project between the governments of Bhutan and India. This initiative is an attempt to provide computer literacy to children of Bhutan through setting up “hole in the wall” (HiWEL) Playground Learning Station(s) (PLSs). The study described here involves 14 sites (the experimental group), where PLSs are installed, and another 8 sites (the control group) without PLSs, but having similar demographic and socioeconomic profiling as the experimental group. This article compares the acquisition of computer literacy of school-going children in India with those in Bhutan. Results indicate that Bhutanese children have acquired computer literacy on their own and that their level of computer skills acquisition is similar to that of Indian children when the scores are normalized. This study was done over a one-year period, with results reported for eight months. In addition to verifying the earlier Indian results, this article hints at the fact that, irrespective of ethnicity, culture, and country, an identical—and possibly universal—self-organized learning mechanism seems to work with children vis-à-vis the Internet.     

Optimization of total harmonic current distortion and torque pulsation reduction in high-power induction motors using genetic algorithms

This paper presents a powerful application of genetic algorithm （GA） for the minimization of the total harmonic current distortion （THCD） in high-power induction motors fed by voltage source inverters, based on an approximate harmonic model. That is, having defined a desired fundamental output voltage, optimal pulse patterns （switching angles） are determined to produce the fundamental output voltage while minimizing the THCD. The complete results for the two cases of three and five switching instants in the first quarter period of pulse width modulation （PWM） waveform are presented. Presence of harmonics in the stator excitation leads to a pulsing-torque component. Considering the fact that if the pulsing-torques are at low frequencies, they can cause troublesome speed fluctuations, shaft fatigue, and unsatisfactory performance in the feedback control system, the 5th, 7th, 1 lth, and 13th current harmonics （in the case of five switching angles） are constrained at some pre-specified values, to mitigate the detrimental effects of low-frequency harmonics. At the same time, the THCD is optimized while the required fundamental output voltage is maintained.     

Modeling of dielectrophoretic transport of myoglobin molecules in microchannels

Myoglobin is one of the premature identifying cardiac markers, whose concentration increases from 90 pg∕ml or less to over 250 ng∕ml in the blood serum of human beings after minor heart attack. Separation, detection, and quantification of myoglobin play a vital role in revealing the cardiac arrest in advance, which is the challenging part of ongoing research. In the present work, one of the electrokinetic approaches, i.e., dielectrophoresis (DEP), is chosen to separate the myoglobin. A mathematical model is developed for simulating dielectrophoretic behavior of a myoglobin molecule in a microchannel to provide a theoretical basis for the above application. This model is based on the introduction of a dielectrophoretic force and a dielectric myoglobin model. A dielectric myoglobin model is developed by approximating the shape of the myoglobin molecule as sphere, oblate, and prolate spheroids. A generalized theoretical expression for the dielectrophoretic force acting on respective shapes of the molecule is derived. The microchannel considered for analysis has an array of parallel rectangular electrodes at the bottom surface. The potential and electric field distributions are calculated using Green’s theorem method and finite element method. These results also compared to the Fourier series method, closed form solutions by Morgan et al. [J. Phys. D: Appl. Phys. 34, 1553 (2001)] and Chang et al. [J. Phys. D: Appl. Phys. 36, 3073 (2003)]. It is observed that both Green’s theorem based analytical solution and finite element based numerical solution for proposed model are closely matched for electric field and square electric field gradients. The crossover frequency is obtained as 40 MHz for given properties of myoglobin and for all approximated shapes of myoglobin molecule. The effect of conductivity of medium and myoglobin on the crossover frequency is also demonstrated. Further, the effect of hydration layer on the crossover frequency of myoglobin molecules is also presented. Both positive and negative DEP effects on myoglobin molecules are obtained by switching the frequency of applied electric field. The effect of different shapes of myoglobin on DEP force is studied and no significant effect on DEP force is observed. Finally, repulsion of myoglobin molecules from the electrode plane at 1 KHz frequency and 10 V applied voltage is observed. These results provide the ability of applying DEP force for manipulating nanosized biomolecules such as myoglobin.     

The Remarkable Roles of the Receptor for Advanced Glycation End Products (RAGE) and Its Soluble Isoforms in COVID-19: The Importance of RAGE Pathway in the Lung Injuries

The respiratory symptoms of acute respiratory distress syndrome (ARDS) in the coronavirus disease 2019 (COVID-19) patients is associated with accumulation of pre-inflammatory molecules such as advanced glycation end-products (AGES), calprotectin, high mobility group box family-1 (HMGB1), cytokines, angiotensin converting enzyme 2 (ACE2), and other molecules in the alveolar space of lungs and plasma. The receptor for advanced glycation end products (RAGEs), which is mediated by the mitogen-activated protein kinase (MAPK), plays a critical role in the severity of chronic inflammatory diseases such as diabetes mellitus (DM) and ARDS. The RAGE gene is most expressed in the alveolar epithelial cells (AECs) of the pulmonary system. Several clinical trials are now being conducted to determine the possible association between the levels of soluble isoforms of RAGE (sRAGE and esRAGE) and the severity of the disease in patients with ARDS and acute lung injury (ALI). In the current article, we reviewed the most recent studies on the RAGE/ligands axis and sRAGE/esRAGE levels in acute respiratory illness, with a focus on COVID-19–associated ARDS (CARDS) patients. According to the research conducted so far, sRAGE/esRAGE measurements in patients with CARDS can be used as a powerful chemical indicator among other biomarkers for assessment of early pulmonary involvement. Furthermore, inhibiting RAGE/MAPK and Angiotensin II receptor type 1 (ATR1) in CARDS patients can be a powerful strategy for diminishing cytokine storm and severe respiratory symptoms.     

Explicit design formulae for digital tan filters with low-pass,high-pass,band-pass,and band- stop characteristics

Explicit expressions of transfer functions for digital tan filters with low-pass, high-pass, band-pass, and band-stop characteristics approximating given design specifications are advanced. The higher order transfer function satisfying the design specification is expressed as the product of first-order and second-order filter sections of identical forms but with different coefficient values. All coefficients of these low-order filter sections are expressed in explicit forms related simply to the specification values. Thus, the result developed can be easily applied for the cascade or time-sharing realization. The low-order filter section developed here can be implemented with the fewest multipliers.The design formulae for Butterworth, Chebyshev, inverse Chebyshev and elliptic approximations are included. The transfer functions for all these filters are expressed in the same form of low-order filter section with different coefficient values.     

Student support services in open schooling: a case study of students' needs and satisfaction in India

This paper identifies the key factors that contribute to the Open School in India students' satisfaction, considering student support elements at pre‐entry, start up, learning, evaluation and certification and after certification phases. The study adapted Rekkedal and Eriksen's importance‐satisfaction model to recognise areas that are important to students as well as their degree of satisfaction with each attribute. It is found that the student group considered is generally satisfied with the support elements that they perceive to be important and there is a strong positive linear relationship (r =0.83) between importance and satisfaction. However, according to the group, priority needs to be given to personal contact programmes in the study centres, online tutorials and feedback on assignments, which are three prime support elements in the learning phase.     

Assessement of Blood Lead and Cadmium Levels in Occupationally Exposed Workers of Jodhpur,Rajasthan

In spite of the established knowledge regarding their toxicities, occupational exposure to heavy metals like lead and cadmium still continues because of their wide distribution in environment. Due to lack of awareness, most of the workers usually eat, smoke, drink at their workplace which may aggravate the metal exposure. The present study was planned to assess the blood levels of lead and cadmium in occupationally exposed workers of Jodhpur (India). A total of 110 individuals working in different industrial set ups (furniture, metal handicraft, welders) of Jodhpur district (exposed group), aged between 20 and 60 years and 97 apparently healthy people (controls) with no history of occupational heavy metal exposure aged between 25 and 60 were recruited. Details of personal habits and demographics were recorded by means of self-developed questionnaire. 5 ml of whole blood was drawn from every individual. Metal levels were measured by graphite furnace atomic absorption spectrophotometer. Statistical analysis was done using GraphPad Prism Software. Results showed that Blood Lead Level and Blood Cadmium Level (CdB) were significantly higher in the exposed group as compared to the non-exposed group. Significant age and gender-based differences were found in terms of blood cadmium levels but no such difference was observed in case of blood lead. The study also revealed that higher blood levels of these metals in workers are influenced by their occupational practices, lack of protection against workplace environment pollutants, thus increasing their susceptibility to metal toxicity.