A study of positive energy condition in Bianchi V spacetimes via Noether symmetries

In this paper we use Noether symmetries of the geodesic Lagrangian in Bianchi V spacetimes to study various cosmological solutions of Einstein's field equations. Our first result is the identification of the subalgebras of Noether symmetries of the equations of motions in such spacetimes with dimension 4, 5, 6, 7, 9 or 10 of the maximal algebra of Lie point symmetries of dimension 13. Secondly we give physical interpretation of new cosmological solutions which satisfy positive energy condition and yield critical bounds on the expansion coefficient $\alpha$, in which the underlying non-flat spacetimes carry interesting physical properties. Specifically the energy density behaves in one of the following ways. (i) It is positive and constant for all time. (ii) It varies with time and attains a global maximum after some time and then asymptotically converges to zero. (iii) It increases for all time and attains a maximum value at the asymptotic limit $t\rightarrow \infty$. In particular a non-flat spacetime is obtained that mimics the expansion in a flat FRW universe dominated by vacuum energy such that the expansion factor has the same form in both. However, the energy density is dynamical in the former.Comment: Some typos are corrected. Some considerations into f(R) gravity is also carried out in the light of obtained results. Accepted for publication in EPJ

Hapniku elektrokeemiline redutseerumine Pt katalüsaatoritel

Väitekirja elektrooniline versioon ei sisalda publikatsiooneSelle töö eesmärk oli parendada süsinikule seondatud plaatinakatalüsaatorite aktiivsust ja eluiga hapniku elektrokeemilisel redutseerumisel madalatemperatuursetes kütuseelementides. Töös kasutati erinevaid meetodeid Pt nanoosakeste valmistamiseks: magnetrontolmustamist, elektrokeemilist sadestamist, keemilist sünteesi ja fotokeemilist sünteesi. Pinnaanalüüsiks kasutati skaneerivat ja läbistuselektronmikroskoopiat, röntgenfotoelektronspektroskoopiat, röntgendifraktsioonanalüüsi, tsüklilist voltamperomeetriat ja adsorbeerunud CO elektrokeemilist oksüdeerimist. Hapniku elektroredutseerumise kineetikat uuriti põhjalikult pöörleva ketaselektroodi meetodil. Töö esimeses osas sadestati plaatina nanoosakesed süsinikul põhinevatele materjalidele nagu mitmeseinalised süsiniknanotorud ja grafeeni nanoliistakud ja uuriti nende elektrokatalüütilist aktiivsust nii aluselises kui ka happelises lahuses. Töö teises osas keskenduti Pt nanoosakestele, mis olid seondatud metallioksiidide (TiO2 või SnO2) ja süsinikmaterjalide komposiitidele eesmärgiga parandada katalüsaatori stabiilsust ja aktiivsust hapniku redutseerumisel. Põhjaliku testimise tulemused näitasid, et metallioksiidid tõstavad märgatavalt elektrokatalüütilist aktiivsust ja pikaaegset stabiilsust tugeva metall-katalüsaatorikandja vastastiktoime tõttu. Kõik selles töös uuritud materjalid näitasid märkimisväärset aktiivsust hapniku redutseerumisel ja paremat stabiilsust võrreldes kommertsiaalse 20% Pt/C katalüsaatoriga.The aim of this study is to improve the electrocatalytic activity and lifetime of the platinum catalyst supported on carbon-based materials for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. Various methods were employed for the deposition of platinum nanoparticles on the support such as magnetron sputtering, electrochemical deposition, chemical synthesis and photo-deposition. Surface characterisation of the prepared electrocatalysts was performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) analysis, cyclic voltammetry and CO stripping experiments. The kinetics of the ORR has been thoroughly studied employing the rotating disk electrode (RDE) method. In the first part of the PhD studies, platinum nanoparticles were deposited on carbon-based support materials such as multi-walled carbon nanotubes and modified graphene nanosheets, the electrochemical measurements were carried out in both alkaline and acidic solutions. The second part of the research was devoted to investigate the activity and durability of platinum nanoparticles supported on metal oxide-carbon composites. Electrochemical results revealed that incorporating metal oxide (TiO2 or SnO2) into the carbon-based support materials increases the electrocatalytic activity and durability of the catalysts by the strong metal-support interaction. All the different types of electrocatalysts prepared and investigated in this work showed remarkable ORR activity and better long-term durability than that of the commercially available 20 wt.% Pt/C catalyst.https://www.ester.ee/record=b524279

STABILIZED NUMERICAL METHODS FOR THE TWO KINDS OF PROBLEMS OF INCOMPRESSIBLE FLUID FLOWS

A mixed finite element method (MFEM) stabilized for the two kinds of problems related to the incompressible fluid flow is demonstrated. In the first kind, the Newtonian fluid flow is illustrated with the MFEM and considered discontinuous scheme. Initially, the model equations are considered nonlinear and un-stabilize. The model equations are solved for linear terms with the special technique first and then the model equation with the extra added term is utilized later to stabilize the model equations. A steady-state viscoelastic Oseen fluid flow model with Oldroyd-B type formulations was demonstrated in the second kind of problem with SUPG method. The nonlinear problems are linearized through the Oseen scheme. Numerical results for both the model equations are given and compared. The SUPG method is found more suitable and active

A proposal for establishment of a maritime university in Bangladesh

The main aim of the study is to formulate a process to establish an integrated centre for higher maritime studies and research in Bangladesh. An assessment is made to verify the need for such specialised higher education and research at postgraduate and at doctoral level for the maritime and shipping personnel. It also highlights the need and appropriation for in-service continued education and research. The geographical location, historical background of the emergence of this new country in 1971 and the rehabilitation programme thereafter (in shipping sector) is described. Its diplomatic and political relation with other regional countries is discussed briefly. A brief look is taken to review the existing maritime education, the requirement of post-sea and shipping trade related higher education and research and unification of two seafaring streams, i.e. marine engineering and navigation. The roles and responsibilities of shipping managers, maritime administrators and maritime lecturers are examined. The local, regional and global impact of this university and scope to perform as a regional university is acknowledged. Most importantly the establishment process (physical and academic) is described and the government education policy and the legal procedure in establishing such institution is reviewed. Finally it has been concluded that there is a clear need for an integrated centre for maritime studies and research in Bangladesh and that may be fulfilled by establishing the proposed Bangabandhu Maritime University

Molecular Genetic Analysis of Autosomal Recessive Primary Microcephaly in Pakistani Kindreds

Autosomal recessive primary microcephaly (MCPH) is a rare genetic disorder in which the afflicted individuals have head circumference more than 3 SDs below the age- and sex-related mean. The reduced head circumference is due to a small but architecturally normal cerebral cortex. MCPH is characterized by a pronounced heterogeneity with seven loci, designated MCPH1-7, have already been identified. The underlying genetic defects were found in the following seven genes, MCPH1, WDR62, CDK5RAP2, CEP152, ASPM, CENPJ, and STIL/SIL. The incidence of this disorder is highest in Pakistan (Woods et al., 2005). Here, I ascertained thirty families with MCPH from various regions of Pakistan. Homozygosity mapping revealed linkage in 19 families to the MCPH5 locus, in 2 to MCPH2, in 2 to MCPH4, in 1 to MCPH1, in 1 to MCPH6, and in 5 families linkage to all known MCPH loci was excluded. Families linked to the MCPH1, MCPH2, MCPH5, and MCPH6 loci were also subjected to direct genomic sequencing of the corresponding genes, i.e. MCPH1, WDR62, ASPM, and CENPJ, respectively. This revealed one, two, and nine novel mutations in MCPH1, WDR62, and ASPM, respectively. Genome-wide linkage analysis in the 5 families previously excluded to be linked to any of the known loci resulted in 5 different new gene loci, MCPH8-MCPH12, situated on different chromosomes. For two of the five new loci, namely MCPH8 on chromosome 7q21-q22 (LOD score 10.47) and MCPH9 on chromosome 4p14-4q12 (LOD score 2.53), the causative genes could be identified. Positional candidate gene sequencing revealed mutations in CDK6 (c.589G>A, p.A197T) at the MCPH8 locus and in CEP135 (c.970delC, p.Gln324Serfs*2) at the MCPH9 locus as the most likely pathogenic variants. These variants were not found in 768 chromosomes from healthy Pakistani controls. These two novel MCPH proteins cyclin-dependent kinase 6 (CDK6) and a centrosomal protein of 135kDa (CEP135) presented as transient or permanent components of the centrosome. Cdk6 and Cep135 showed a high expression level in the developing neuroepithelium of the mouse cerebral cortex of E11.5 and E15.5 embryos. In human cell lines, the localization of CDK6 at the spindle pole was observed. Primary fibroblasts of the patient with the CDK6 mutation failed to grow normally and showed an aberrant nuclear shape as well as centrosome-nucleus distance. CDK6 suppression by shRNA mimicked the defects in cell proliferation, nuclear shape, and microtubule organization. Likewise, overexpression of mutant CDK6 resulted in the production of multiple centrosomes and disorganised microtubules. Primary fibroblasts of the patient with the CEP135 mutation showed multiple and fragmented centrosomes, a disorganised microtubule system, misshapen and fragmented nuclei, and sometimes a complete loss of centrosomes. Altered levels of wild-type and mutant CEP135 protein by overexpression caused disorganization of microtubules, while overexpression of mutant CEP135 showed also multiple centrosomes observed before in the patient’s primary fibroblasts. Based on the data on CDK6, I propose that mutation p.A197T may lead to a reduced cell proliferation and may also affect the correct functioning of the centrosome in microtubule organisation and its positioning near the nucleus. The abnormal centrosome number associated with mutant CEP135 strengthens its role in centriole biogenesis, whereas a disorganisation of the microtubule network points to its role at the centrosome as a microtubule organising center. The data obtained lend further support to the hypothesis that the exquisite control of the cleavage furrow orientation in mammalian neural precursor cell mitosis, controlled in great part by the centrosomes and spindle poles, is critical in the etiology of MCPH (Fish et al., 2006, Thornton and Woods, 2009)

Association of long term sodium valproate monotherapy and vitamin D3 levels in epileptic children

Objective: To determine the association of long term sodium valproate monotherapy and vitamin D3 levels in epileptic children Methods: This cross-sectional study was conducted in the Department of Pediatrics, Children Hospital, Pakistan Institute of Medical Sciences, Islamabad for six months from 15th February 2019 to 14th August 2019. A total of one hundred and thirty (n=130) children and adolescents of either gender between age 3-18 years who had a history of two seizures at least 24 hours apart in their life and were on sodium valproate monotherapy for more than one year were enrolled in this study through non-probability, consecutive sampling. Serum vitamin D3 (25-hydroxy vitamin D) levels were measured in all the patients at the time of enrolment into the study. All the demographic data and laboratory investigations were entered on the predesigned proforma and analyzed through SPSS version 17. Results: Vitamin D3 deficiency was found in 47 (36.2%) children which were significantly higher among patients with older age and longer duration of treatment (P<0.05) while gender and BMI of the patients did not show any significant difference (P>0.05). Conclusion: Significant percentage of epileptic children on sodium valproate monotherapy was found to have vitamin D3 deficiency. Therefore we recommend routine screening of vitamin D3 deficiency in all the epileptic children on long-term sodium valproate therapy followed by vitamin D supplementation in deficient patients. &nbsp

Reforming public education in developing countries: Turning challenges into opportunities

This paper tries to respond to a basic question: “Can public education (or some aspects of it) be reformed?” The authors’ response to this question is, “Yes, public education can be reformed, if contextual possibilities are exploited efficiently.” Although a straight forward and simplistic response to the question, this was felt necessary to counter an unfavourable bias towards public education sector without recognizing the challenges that it faces, and without recognizing the potential of many of the public teachers who continuously strive to change these negative perceptions. This paper recognizes the potential of public sector education and shares a relatively successful example of improving competencies among public teachers to support the response