Analysis and experimental investigation into a finite time current observer based adaptive backstepping control of buck converters

In this paper, the issue of output voltage regulation in buck type dc-dc converters is addressed using a current sensorless control technique. The proposed strategy integrates a finite time current observer with an adaptive backstepping control scheme to yield a cost-effective and robust control mechanism. The overall controller stability in the sense of Lyapunov is proved. Applicability of the proposed control is verified experimentally on a buck converter in the laboratory. The control scheme is implemented on dSPACE DS1103 platform based on DSP TM320F240 processor. To examine the efficacy of the proposed method, the buck converter is subjected to a wide change in input voltage, load resistance and reference voltage. For comparison purpose, a conventional adaptive backstepping control scheme is evaluated under identical conditions of experimental study to examine the merit of the proposed control. The results obtained reveal that the proposed control is prompt in rejecting perturbations and achieves a smooth, reliable and satisfactory output voltage regulation with faithful and time bound estimation of inductor current. Thereby, this investigation demonstrates the validity of the proposed control in maintaining a stringent output voltage regulation in buck converters.     

Probing the mechanical properties of brain cancer cells using a microfluidic cell squeezer device

Despite being invasive within surrounding brain tissues and the central nervous system, little is known about the mechanical properties of brain tumor cells in comparison with benign cells. Here, we present the first measurements of the peak pressure drop due to the passage of benign and cancerous brain cells through confined microchannels in a “microfluidic cell squeezer” device, as well as the elongation, speed, and entry time of the cells in confined channels. We find that cancerous and benign brain cells cannot be differentiated based on speeds or elongation. We have found that the entry time into a narrow constriction is a more sensitive indicator of the differences between malignant and healthy glial cells than pressure drops. Importantly, we also find that brain tumor cells take a longer time to squeeze through a constriction and migrate more slowly than benign cells in two dimensional wound healing assays. Based on these observations, we arrive at the surprising conclusion that the prevailing notion of extraneural cancer cells being more mechanically compliant than benign cells may not apply to brain cancer cells.     

Hematological Parameters and RBC TBARS Level of Q 10 Supplemented Tribal Sickle Cell Patients: A Hospital Based Study

The study has been undertaken as number of sickle cell patients in Chhattisgarh tribal population is 23.7 %. The Co enzyme Q10 is a strong antioxidant and energy producing compound. The patients were divided into three groups group A homozygous (SS), group B heterozygous (AS) and group C controls for TBARS study. The age group is 10–55 years and 200 mg of CoQ10 was given to A and B groups. The hematological parameters, C reactive protein as well as RBC TBARS level were performed by usual and standard techniques. The results were obtained as 25.37 % increased RBC level in group A and 23.24 % in group B. The increased hemoglobin level was observed as 16.73 % in group A and 10.7 % in group B. In case of WBC it was observed increased 24.38 % in group A and 12.0 % in group B. C-reactive protein was observed 7.8 times decreased in group A and 1.54 times in group B. The RBC TBARS level was also found decreased 48 % in group A and 51 % in group B as compared to group C. During the supplementation of coenzyme Q10 the pain caused by vaso-occlusive events has reduced. This significant increase in hematological parameters as well as decreased C-reactive protein and TBARS level suggest that the Q10 should be included in the diet of sickle cell patients.     

Glial cells: The other cells of the nervous system

Neuroscientists have believed for a long time that glial cells are supportive elements of the nervous system and have little role in neuronal function. Despite outnumbering neurons tenfold in the Central Nervous System (CNS), and contributing to more than half the brain volume, not much attention was paid to these cells. Recently, glial cells have been found to be far more active participants in CNS function. A set of glial cells, the oligodendrocytes, has attracted attention as their precursors have been found to be extremely plastic. Though these precursor cells are initially committed to form oligodendrocytes alone, they can also be induced to form astrocytes and neurons. Such examples of transdetermination are opening up new lines of research with immense clinical implications. In this part of the series we review some aspects of oligodendrocyte structure and function.     

Gender and Education for All: Progress and problems in achieving gender equity

The paper explores the effects of rapid increases in gender parity in primary schooling in Bangladesh and Malawi on gender inequities in schools and communities. Based on an analysis of comparative case studies of marginalized communities, we argue that educational initiatives focused on achieving gender parity provide limited evidence that girls’ educational experiences modeled significantly different gender norms than in communities, or that by being educated, girls experienced a transformation of the inequitable gender relations they faced in society. The data illustrate persistent gender discrimination related to educational attainment and learning, and gender-based violence in schools. These patterns of gendered discrimination and violence largely mirrored those that girls and boys experienced in their homes and communities, raising important questions about the transformational capacity of current gender parity and schooling models.     

Intensity of parasitic infestation in silver carp, Hypophthalmichthys molitrix

Silver carp, Hypopthalmichthys molitrix is one of the most economically valuable fish species in Bangladesh. However, its production is often hindered by parasite-induced mortality. The present study reports the intensity of parasitic infestation in 216 specimens of H. molitrix collected from different fish markets in Rajshahi City, Bangladesh. Nine different parasite species (Trichodina pediculatus, Dactylogyrus vastator, Ichthyophthirius multifilis, Gyrodactylus elegans, Lernaea sp., Apiosoma sp., Myxobolus rohitae, Camallanus ophiocephali, and Pallisentis ophiocephali) were recovered from the gill, skin, stomach, and intestine of host fish. The highest level of infection was observed for host skin, while lower levels were observed for host gill, stomach, and intestine. The results also revealed that the intensity of parasite infection in different organs of H. molitrix varied with the season. In particular, the highest levels of infection were recorded during the winter period (November-February), when fish are most susceptible to parasites. The findings of the study will help in the management and conservation of H. molitrix.     

Policy versus ground reality: secondary English language assessment system in Bangladesh

Any policy reform in education is highly effective when it is planned and implemented ‘holistically’ and yet, it is the most challenging way forward. Many countries in Asia have reformed their English language policies and syllabi in the last two decades due to the increasing value of the language worldwide. Motivated by a ‘communicative approach’ to English language teaching, Bangladesh was one of the countries that launched such a reform in the 1990s. However, this reform has been criticised for imposing the changes on teachers without preparing them sufficiently. More importantly, there is limited evidence as to how much the secondary English language assessment system is aligned with the changes introduced in the curriculum. In order to explore this gap, a medium-scale study was conducted in 38 secondary schools in Bangladesh, following a mixed methods approach. The findings highlighted a ‘mismatch’ between the intended English language learning outcomes and current assessment practices, including the resulting challenges faced by the teachers. This paper argues that language education reform is likely to fail if the assessment system is not aligned with the curriculum.     

Dargah libraries in India: a comparative study

This paper relates to the difficulty in retrieving precise information from big repositories of magazine articles in full text, and proposes an Extended Markup Language (XML) vocabulary for improving retrieval rates. The hypothesis tested was as follows: Magazine articles marked up with an XML vocabulary, indexed only by selected parts, give more precise search results than the same search using full text index.

The study was exploratory with the following characteristics: 29 magazine articles were tested for results, 8 scholars were interviewed for defining 23 search strategies and evaluating results. The data showed that precision improved from 40.72% with full text search to 62.84% using XML markup and searching only in specific labels.

Revision of the vocabulary and more testing has to be done by the library and information science community in order to obtain a valid vocabulary and provide more research results. Cultural characteristics and politics of librarians and information managers’ community are as important as technical issues in order to consider any technical proposal to be implemented successfully to achieve interoperability.