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Background Neurodevelopmental disorders (NDDs) are heterogeneous, debilitating conditions that include motor and cognitive disability and social deficits. The genetic factors underlying the complex phenotype of NDDs remain to be elucidated. Accumulating evidence suggest that the Elongator complex plays a role in NDDs, given that patient-derived mutations in its ELP2, ELP3, ELP4 and ELP6 subunits have been associated with these disorders. Pathogenic variants in its largest subunit ELP1 have been previously found in familial dysautonomia and medulloblastoma, with no link to NDDs affecting primarily the central nervous system. Methods Clinical investigation included patient history and physical, neurological and magnetic resonance imaging (MRI) examination. A novel homozygous likely pathogenic ELP1 variant was identified by whole-genome sequencing. Functional studies included in silico analysis of the mutated ELP1 in the context of the holo-complex, production and purification of the ELP1 harbouring the identified mutation and in vitro analyses using microscale thermophoresis for tRNA binding assay and acetyl-CoA hydrolysis assay. Patient fibroblasts were harvested for tRNA modification analysis using HPLC coupled to mass spectrometry. Results We report a novel missense mutation in the ELP1 identified in two siblings with intellectual disability and global developmental delay. We show that the mutation perturbs the ability of ELP123 to bind tRNAs and compromises the function of the Elongator in vitro and in human cells. Conclusion Our study expands the mutational spectrum of ELP1 and its association with different neurodevelopmental conditions and provides a specific target for genetic counselling.

Nowadays, according to the observational evidences the curvature parameter of the universe is neglected and spatially flat FLRW model is on the top of interest for cosmologists. However, due to some discrepancies between $\Lambda$-CDM model anticipations and observations, one may think out the curvature parameter as the solution even though it may be very small. So, in this article we investigate the eras in which the curvature influence was or is more significant. In addition, a geometrical interpretation of Hubble parameter is dedicated. We find that the Hubble parameter is more appropriate to be defined as the mean curvature of the spatial section of the universe because the concept of the scale factor in a non-homogeneous universe is not precisely clear., Comment: 11 pages, version published in Gravit. Cosmol

Histone lysine demethylases (KDMs) are enzymes that remove the methylation marks on lysines in nucleosomes' histone tails. These changes in methylation marks regulate gene transcription during both development and malignant transformation. Depending on which lysine residue is targeted, the effect of a given KDM on gene transcription can be either activating or repressing, and KDMs can regulate the expression of both oncogenes and tumour suppressors. Thus, the functions of KDMs can be regarded as both oncogenic and tumour suppressive, contingent on cell context and the enzyme isoform. Finally, KDMs also demethylate nonhistone proteins and have a variety of demethylase-independent functions. These epigenetic and other mechanisms that KDMs control make them important regulators of malignant tumours. Here, we present an overview of eight KDM subfamilies, their most-studied lysine targets and selected recent data on their roles in cancer stem cells, tumour aggressiveness and drug tolerance.

Dual-specificity tyrosine phosphorylation-related kinase 1A (DYRK1A) is a dual-specificity protein kinase that catalyses phosphorylation and autophosphorylation. Higher DYRK1A expression correlates with cancer, in particular glioblastoma present within the brain. We report here the synthesis and biological evaluation of new heterocyclic diphenolic derivatives designed as novel DYRK1A inhibitors. The generation of these heterocycles such as benzimidazole, imidazole, naphthyridine, pyrazole-pyridines, bipyridine, and triazolopyrazines was made based on the structural modification of the lead DANDY and tested for their ability to inhibit DYRK1A. None of these derivatives showed significant DYRK1A inhibition but provide valuable knowledge around the importance of the 7-azaindole moiety. These data will be of use for developing further structure-activity relationship studies to improve the selective inhibition of DYRK1A.

Both tumour suppressive and oncogenic functions have been reported for dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A). Herein, we performed a detailed investigation to delineate the role of DYRK1A in glioblastoma. Our phosphoproteomic and mechanistic studies show that DYRK1A induces degradation of cyclin B by phosphorylating CDC23, which is necessary for the function of the anaphase-promoting complex, a ubiquitin ligase that degrades mitotic proteins. DYRK1A inhibition leads to the accumulation of cyclin B and activation of CDK1. Importantly, we established that the phenotypic response of glioblastoma cells to DYRK1A inhibition depends on both retinoblastoma (RB) expression and the degree of residual DYRK1A activity. Moderate DYRK1A inhibition leads to moderate cyclin B accumulation, CDK1 activation and increased proliferation in RB-deficient cells. In RB-proficient cells, cyclin B/CDK1 activation in response to DYRK1A inhibition is neutralized by the RB pathway, resulting in an unchanged proliferation rate. In contrast, complete DYRK1A inhibition with high doses of inhibitors results in massive cyclin B accumulation, saturation of CDK1 activity and cell cycle arrest, regardless of RB status. These findings provide new insights into the complexity of context-dependent DYRK1A signalling in cancer cells.

Within the closed universe, we obtain the amplitude and frequency of gravitational waves in the terms of discrete wave numbers, wave propagation time, and cosmological constant using the deviation equation in the first-order perturbed metric. We demonstrate that the cosmological constant effect on GWs is only seen in the early universe. Also, by considering the time evolution of a gravitational wave in a closed spacetime, we investigate its effect on a circle of nearby massless particles, which will be compared with this case in the flat spacetime. Expanding the universe has effective damping on GWs; thus, we suggest it can be used as a tool to characterize the large-scale curvature of the universe, Comment: 22 pages, 11 figures

MerTK has been identified as a promising target for therapeutic intervention in glioblastoma. Genetic studies documented a range of oncogenic processes that MerTK targeting could influence, however robust pharmacological validation has been missing. The aim of this study was to assess therapeutic potential of MerTK inhibitors in glioblastoma therapy. Unlike previous studies, our work provides several lines of evidence that MerTK activity is dispensable for glioblastoma growth. We observed heterogeneous responses to MerTK inhibitors that could not be correlated to MerTK inhibition or MerTK expression in cells. The more selective MerTK inhibitors UNC2250 and UNC2580A lack the anti-proliferative potency of less-selective inhibitors exemplified by UNC2025. Functional assays in MerTK-high and MerTK-deficient cells further demonstrate that the anti-cancer efficacy of UNC2025 is MerTK-independent. However, despite its efficacy in vitro, UNC2025 failed to attenuate glioblastoma growth in vivo. Gene expression analysis from cohorts of glioblastoma patients identified that MerTK expression correlates negatively with proliferation and positively with quiescence genes, suggesting that MerTK regulates dormancy rather than proliferation in glioblastoma. In summary, this study demonstrates the importance of orthogonal inhibitors and disease-relevant models in target validation studies and raises a possibility that MerTK inhibitors could be used to target dormant glioblastoma cells.

We write down Boltzmann equation for massive particles in a spatially curved FRW universe and solve the approximate line-of-sight solution for evolution of matter density, including the effects of spatial curvature to the first order of approximation. It is shown that memory of early time gravitational potential is affected by presence of spatial curvature. Then we revisit Boltzmann equation for photons in the general FRW background. Using it, we show that how the frequency of oscillations and damping factor (known as Silk damping) changed in presence of spatial curvature. At last, using this modified damping factor in hydrodynamic regime of cosmological perturbations, we find our analytic solution which shows the effects of spatial curvature on growing mode of matter density., Comment: 20 pages, no figure , accepted for publication in JCAP

Introduction La mastopathie diabetique(MD), ou lobulite lymphocytaire sclerosante est une pathologie rare, qui s’observe principalement chez des femmes jeunes presentant un diabete de type 1 ancien et complique. A travers une observation d’une patiente presentant une MD, nous rappelons les aspects cliniques, radiologiques et evolutifs de cette affection. Observation Il s’agissait d’une jeune patiente âgee de 33 ans suivie pour un diabete type 1 depuis l’âge de 16 ans sous insulinotherapie. Elle est au stade de complications chroniques a type de retinopathie diabetique. Au cours de son rendez-vous de controle a la consultation externe, elle rapportait la presence de deux masses au niveau des seins evoluant depuis 10 mois. L’examen clinique a montre deux masses siegeant au niveau des quadrants superieurs des 2 seins. L’echographie mammaire couplee a la mammographie ont montre des plages hypoechogenes attenuantes des quadrants superieurs des deux seins. Les 2 seins ont ete classes ACR4 a droite comme a gauche. Une microbiopsie mammaire a ete realisee concluant a une dystrophie fibreuse des seins droit et gauche. Conclusion La mastopathie diabetique est une affection pseudo-tumorale benigne qui merite d’etre connue par les cliniciens, radiologues et anatomopathologistes. La physiopathologie n’est pas clairement etablie mais le role de l’hyperglycemie chronique est probable. L’infiltration lymphocytaire suggere le role de l’autoimmunite. Connaitre cette affection benigne permettrait de rassurer les patientes et d’eviter toute chirurgie abusive.

The goal of this paper is studying the integro-differential equation of gravitational waves (GWs) in matter-dominated era while the presence of free streaming neutrinos is taken into account via stress tensor with high accuracy. Our focus is on GWs that enter the horizon in the matter dominated era and transmitted to the Λ − dominated era. The results show that the squared amplitude is reduced by ∼ 3% (61%) in the matter dominated era and this reduction is less after transition for the flat (closed) background. Finally, we compared with the radiation-dominated era for both flat and closed background as well. A stable global topological effect has been inferred from comparison of results for two cases.

[Image: see text] Sensitivity to microtubule-targeting agents (MTAs) varies among cancers and predicting the response of individual cancer patients to MTAs remains challenging. As microtubules possess vast molecular heterogeneity generated by tubulin isotypes and their post-translational modifications, we questioned whether this heterogeneity can impact MTA sensitivity. We investigated microtubule heterogeneity in 15 glioblastoma cell lines and measured sensitivity of orthogonal MTAs using a per-division growth rate inhibition method that corrects for the confounding effects of variable cell proliferation rates. We found that the tubulin profile is unique for each glioblastoma cell line and that the total α- and β-tubulin levels impact on MTA sensitivity. The baseline levels of α- and β-tubulin were up to 20% lower in cells that were not effectively killed by MTAs. We report that lower α/β-tubulin expression is associated with lack of cell differentiation and increased expression of stemness markers. The dedifferentiated stem-like cells with low α/β-tubulin levels survive MTAs treatment via reversible nonmutational dormancy. Our findings provide novel insights into the relationships between microtubules and MTAs and lay a foundation for better understanding of the sensitivity of cancer cells to MTAs.

In the field of kinase inhibitors for applications in cancer research, tubulin is emerging as a targeted cellular protein that can significantly contribute to their activities. However, investigation of kinase inhibitors beyond the kinome is an area often neglected. Herein, we describe the results of pharmacological studies using drugs targeting kinases, tubulin or both. A key finding is that if cells are treated with a kinase inhibitor unintentionally targeting tubulin, their characteristic shape will diminish within a short timeframe. These changes in cell morphology are not seen when cells are treated with bona fide kinase inhibitors that do not directly target tubulin. Thus, early changes in cell morphology upon treatments are a strong indication that the inhibitor is directly targeting tubulin. Recognizing tubulin as a target of kinase inhibitors will build confidence in the future mechanistic studies using kinase inhibitors.

We consider a mimetic set up in which the mimetic scalar is coupled to a vector field. It is shown that such a field with a time-like component does not contribute to the background equations and yet produces healthy isocurvature perturbations with respect to ghost and gradient instabilities in spite of the absence of any propagating curvature perturbations at the level of the quadratic action. We then consider a vector field with space-like components which leads to an anisotropic Bianchi universe and show that the ghost and gradient instabilities are absent in the limit of high momenta and that the propagating curvature perturbations have healthy UV behavior., 12 pages, 4 figures, to appear in PRD

In this article we investigate dependency of the adiabatic and entropy spectral indices of the cosmological perturbations on the geometry and topology of the background universe. Our discussion includes the post-inflationary universe i.e. radiation-dust mixture era. For this purpose, we first extract an explicit equation describing evolution of the comoving curvature perturbation in the FLRW universe with arbitrary spatial sectional curvature. We may percept when $K\neq 0$, curvature scale would be as significant as the perturbations scales to recognize the behavior of the spectral indices. We also focus on the entropy perturbation in order to extract behavior of the isocurvature spectral index in terms of the curvature index and time. Our analysis shows that spectra of curvature and entropy perturbations in sub-horizon scales could be function of topology. Moreover, an accurate analysis makes clear that time-average of isocurvature index in case $K=0$ is about zero,so that imprint of entropy perturbation in time duration may be negligible. We also consider evolution of the cosmological indices for super-curvature modes in the case $K=-1$. In the most results dependency to curvature, initial conditions and scale modes are thoroughly vivid., Comment: 9 pages,12 figures

The scalar mode polarization of the cosmic microwave background is derived in a spatially closed universe from the Boltzmann equation using the line of sight integral method. The EE and TE multipole coefficients have been extracted analytically by considering some tolerable approximations such as considering the evolution of perturbation hydrodynamically and sudden transition from opacity to transparency at the time of last scattering. As the major advantage of analytic expressions, EE and TE multipole coefficients explicitly show the dependencies on baryon density, matter density, curvature, primordial spectral index, primordial power spectrum amplitude, Optical depth, recombination width and recombination time. Using a realistic set of cosmological parameters taken from a fit to data from Planck, the closed universe EE and TE power spectrums in the scalar mode are compared with numerical results from the CAMB code and also latest observational data. The analytic results agree with the numerical ones on the big and moderate scales. The peak positions are in good agreement with the numerical result on these scales while the peak heights agree with that to within 20% due to the approximations have been considered for these derivations. Also, several interesting properties of CMB polarization are revealed by the analytic spectra., Comment: 14 pages, 12 figures. arXiv admin note: substantial text overlap with arXiv:1709.06549

Protein kinases are one of the most studied drug targets in current pharmacological research, as evidenced by the vast number of kinase-targeting agents enrolled in active clinical trials. Dual-specificity Tyrosine phosphorylation-Regulated Kinase 1A (DYRK1A) has been much less studied compared to many other kinases. DYRK1A primary function occurs during early development, where this protein regulates cellular processes related to proliferation and differentiation of neuronal progenitor cells. Although most extensively characterised for its role in brain development, DYRK1A is over-expressed in a variety of diseases including a number of human malignancies, such as haematological and brain cancers. Here we review the accumulating molecular studies that support our understanding of how DYRK1A signalling could underlie these pathological functions. The relevance of DYRK1A in a number of diseases is also substantiated with intensive drug discovery efforts to develop potent and selective inhibitors of DYRK1A. Several classes of DYRK1A inhibitors have recently been disclosed and some molecules are promising leads to develop DYRK1A inhibitors as drugs for DYRK1A-dependent diseases.

Recently, some departures from the Λ CDM model have been reported by WMAP and Planck satellites such as suppression of the lowest CMB multipoles, and the hemispherical asymmetry in CMB anisotropy plan. It motivates us to consider models with nonzero curvature index and study the imprints of curvature and topology on the observed anomalies. So in this article we study the positively curved inflationary paradigm. For this purpose, first, we derive the power spectra of comoving curvature perturbation and primordial gravitational waves in the FLRW universes with K = + 1 and maximally symmetry spatial sections according to the slowly rolling inflationary scenario. Our study includes two spherical and elliptical models with S 3 and R P 3 as the spatial topology respectively. It can be shown that the curvature spectral index in this model automatically has a small negative running parameter which is compatible with observational measurements. We also investigate the relative amplitude of the scalar and tensor perturbations. It will be clear that the tensor–scalar ratio for both models are equal and depends on the wavelength of the perturbations severely. Furthermore, the discrepancy between BICEP2 results and slow-rolling inflationary model in spatially flat background may be reduced although it does not seem statistically significant.

Photoremovable protecting groups added to bioactive molecules provide spatial and temporal control of the biological effects. We present synthesis and characterization of the first photoactivatable small-molecule tubulin inhibitor. By blocking the pharmacophoric OH group on compound 1 with photoremovable 4,5-dimethoxy-2-nitrobenzyl moiety we developed the photocaged prodrug 2 that had no effect in biological assays. Short UV light exposure of the derivative 2 or UV-irradiation of cells treated with 2 resulted in fast and potent inhibition of tubulin polymerization, attenuation of cell viability, and apoptotic cell death, implicating release of the parent active compound. This study validates for the first time the photoactivatable prodrug concept in the field of small molecule tubulin inhibitors. The caged derivative 2 represents a novel tool in antitubulin approaches.

The DYRK family contains kinases that are up-regulated in malignancy and control several cancer hallmarks. To assess the anticancer potential of inhibitors targeting DYRK kinases, we developed a series of novel DYRK inhibitors based on the 7-azaindole scaffold. All compounds were tested for their ability to inhibit DYRK1A, DYRK1B, DYRK2, and the structurally related CLK1. The library was screened for anticancer efficacy in established and stem cell-like glioblastoma cell lines. The most potent inhibitors (IC50 ≤ 50 nM) significantly decreased viability, clonogenic survival, migration, and invasion of glioblastoma cells. Target engagement was confirmed with genetic knockdown and the cellular thermal shift assay. We demonstrate that DYRK1A’s thermal stability in cells is increased upon compound treatment, confirming binding in cells. In summary, we present synthesis, structure–activity relationship, and efficacy in glioblastoma-relevant models for a library of novel 7-azaindoles.

The scalar mode temperature fluctuations of the cosmic microwave background has been derived in a spatially closed universe from two different methods. First, by following the photon trajectory after the last scattering and then from the Boltzmann equation in a closed background and the line of sight integral method. An analytic expression for the temperature multipole coefficient has been extracted at the hydrodynamical limit, where we have considered some tolerable approximations. By considering a realistic set of cosmological parameters taken from a fit to data from Planck, the TT power spectrum in the scalar mode for the closed universe has been compared with numerical one by using the CAMB code and also latest observational data. The analytic result agrees with the numerical one on almost all scales. The peak positions are in very good agreement with numerical result while the peak heights agree with that to within 10% due to the approximations have been considered for this derivation., Comment: 15 pages, 8 figures

Simple classifiers have the advantage of more generalization capability with the side effect of less power. It would be a good idea if we could build a classifier which is as simple as possible while giving it the ability of classifying complex patterns. In this paper, a hybrid classifier called “constrained classifier” is presented that classifies most of the input patterns using a simple, for example, a linear classifier. It performs the classification in four steps. In the “Dividing” step, the input patterns are divided into linearly separable and nonlinearly separable groups. The patterns belonging to the first group are classified using a simple classifier while the second group patterns (named “constraints”) are modeled in the “Modeling” step. The results of previous steps are merged together in the “Combining” step. The “Evaluation” step tests and fine tunes the membership of patterns into two groups. The experimental results of comparison of the new classifier with famous classifiers such as “support vector machine”, k-NN, and “Classification and Regression Trees” are very encouraging.

Intracystic papillary carcinoma is a rare malignant tumor of the breast. It occurs communally in postmenopausal women. Clinically it can be asymptomatic or manifested by a breast mass or a nipple discharge. On imaging intracystic papillary carcinoma has usually benign features. Pathologic diagnosis can be difficult at classical histological examination and identification of myoepithelial cells layer by immunohistochemical study can be useful. In the majority of cases of pure intracystic papillary carcinoma, conservative management is possible. Adjuvant therapy is still controversial and prognosis is excellent. We report three cases of intracystic papillary carcinoma diagnosed on immunohistochemical examination and managed with conservative surgery.

We have investigated the vacuum maximally symmetric solutions of recently proposed density-metric unimodular gravity theory,the results are widely different from inflationary senario.The exponential dependence on time in deSitter space is substiuted by a power law. Open space-times with non-zero cosmological constant are excluded in this theory, Comment: 15 pages, no figures,stability section omitted

We present our derivations for Kerr–de Sitter metric in a proper comoving coordinate system. It asymptotically approaches to the de Sitter metric in Robertson–Walker form. This has been done by considering the stationary axially-symmetric space–time in which motion of particle is integrable. That is the Hamilton–Jacobi and Klein–Gordon equations are separable. In this form it is asymptotically consistent with comoving frame.

DYRK1A is a novel target for epidermal growth factor receptor (EGFR)-dependent glioblastoma and it represents a promising strategy for cancer therapy. DYRK1A inhibition has been found to promote EGFR degradation in glioblastoma cells by triggering endocytosis and lysosomal degradation, thus reducing the self-renewal ability of tumorigenic cells. Using a deconstruction approach of a DYRK1A lead molecule DANDY (1a), a set of novel ring-opened compounds was prepared. Despite showing no activity towards DYRK1A, a reduction in the viability of glioblastoma cells was observed with some of the compounds. This suggests other mechanistic pathways are leading to the apoptosis of glioblastoma cells.

The availability of nitrogen, lysine and 9 essential amino acids was determined in corn before and after baking. Lysine availability was determined by the growth response method on weaning rats using regression analysis of body weight gain or moisture gain against lysine consumed from corn flour and corn bread. The results show a high correlation between lysine consumed and weight gain or moisture gain (r = 0.95) for rats fed the standard diets for 3 weeks. A good correlation was also obtained for corn bread. The results of lysine availability show that baking greatly improves availability by both ways of calculation. The availability of nitrogen and essential amino acids were also investigated by the balance trials with rats. Results show that availability values for nitrogen and all amino acids except threonine increased by baking. Data for food intake, weight gain, food efficiency, PER, NPR and true digestibility revealed that baking had little or no effect on nutritive value of corn tested in this investigation.

Radiation hybrid maps were constructed for river buffalo and cattle Y chromosomes. A total of 41 cattle-derived Y-chromosome molecular markers were selected and tested with 2 previously described 5,000-rad whole-genome radiation hybrid (RH) panels (river buffalo – BBURH5000 and cattle – BTARH5000) for generation of maps. Among the initial 41 selected markers, a subset of 26 markers generated PCR products suitable for scoring with the BBURH5000 panel. Of these, 19 markers (73%) were distributed in 1 linkage group spanning 341.3 cR. Retention frequencies (RF) for individual markers ranged from 17.8% for SMCY to 56.7% for BTY1, with an average RF of 37.6%. From the selected markers, 37 generated reliable scores using the BTARH5000 panel. The newly constructed BTAY RH map contains 28 markers distributed within 1 linkage group. Twenty-four of these markers had been previously mapped on BTAY using a 7,000-rad cattle-hamster WG-RH panel and 4 markers were mapped for the first time (ZFY, SeqRep, RepSeqS4 and BTY1). The length of the BTAY RH map was estimated to be 602.4 cR. Retention frequencies for individual mapped markers ranged from 10% (INRA126) to 63.3% (SeqRep), with an average RF of 35.3%. RH marker positions along the Y chromosome were compared between BBUY and BTAY, which revealed differences in the order of some of the markers. The BBUY pseudoautosomal region (PAR) is delineated by 3 BTAY PAR markers (MAF45, TGLA325 and UMN2008). These markers are telomeric in both species but are not found in the same order. Here we have demonstrated the effective use of bovine Y chromosome markers for the development of the first BBUY RH map. Likewise, these set of markers can be used for comparative assessment of Y chromosomes in other members of the Bovidae family.

The laminar flow of a viscous incompressible electrically conducting fluid in a backward-facing step is investigated under the usual magnetohydrodynamic (MHD) hypothesis. Numerical simulations are performed for Reynolds numbers less then Re = 380 in the range of 0 ≤ N ≤ 0.2, where N is the Stuart number or interaction parameter which is the ratio of electromagnetic force to inertia force. Heat transfer is investigated for Prandtl number ranging from Pr = 0.02 corresponding to liquid metal, to Pr = 7 corresponding to water. It is found through the calculation of the reattachment length that external magnetic field acts to decrease the size of the recirculation zone. Velocity profiles show that, out of the recirculation zone, the basic flow is damped by the magnetic induced force, whereas flow near the walls channel is accelerated. Heat transfer is significantly enhanced by the magnetic field in the case of fluids of high Prandtl numbers.

This paper reports the numerical determination of the entropy generation due to heat transfer, mass transfer and fluid friction in steady state for laminar double diffusive convection, in an inclined enclosure with heat and mass diffusive walls, by solving numerically the mass, momentum, species conservation and energy balance equations, using a Control Volume Finite-Element Method. The influences of the inclination angle, the thermal Grashof number and the buoyancy ratio on total entropy generation were investigated. The irreversibilities localization due to heat transfer, mass transfer and fluid friction is discussed for three inclination angles at a fixed thermal Grashof number.

The issue of entropy generation in Poiseuille–Benard channel flow is analyzed by solving numerically the mass, momentum and energy equations with the use of the classic Boussinesq incompressible approximation. The numerical scheme is based on Control Volume Finite Element Method with the SIMPLER algorithm for pressure–velocity coupling. Results are obtained for Rayleigh numbers Ra and irreversibility φ ranging from 103 to 5×104 and from 10−4 to 10 respectively. Variations of entropy generation and the Bejan number as a function of Ra and φ are studied. The limit value φl for which entropy generation due to heat transfer is equal to entropy due to fluid friction is evaluated. It has been found that φl is a decreasing function of the Rayleigh number Ra. φl varies from 0.0015 to 0.096 when Ra decrease from 5×104 to 103. Stream lines and entropy generation maps are plotted at six times over one period at Ra =104 and φ=10−3. It has been found that the maximum entropy generation is localized at areas where heat exchanged between the walls and the flow is maximum. No significant entropy production is seen in the main flow.

The structures wakes behind a square cylinder in a laminar channel flow is conducted numerically. The Strouhal number, drag and lift coefficients were studied in a periodic flow for different blockage ratios β=1/4, 1/6 and 1/8 at Reynolds number ranging from 62 to 300. The governing equations are solved by using control volume finite element method (CVFEM) adapted to the staggered grid. The SIMPLER algorithm is used for the velocity-pressure coupling. The critical Reynolds numbers corresponding to the onset of vortex shedding and its change from simple periodic to complex periodic motion are established. A discussion about the effect of the blockage ratio on the Strouhal number, the time-averaged drag coefficient and the amplitude of the lift coefficient is also presented.

A numerical investigation was conducted to analyze the unsteady flow field and heat transfer characteristics in a horizontal channel with a built-in heated square cylinder. Hydrodynamic behavior and heat transfer results are obtained by the solution of the complete Navier–Stokes and energy equations using a control volume finite element method (CVFEM) adapted to the staggered grid. The Computation was made for two channel blockage ratios (β=1/4 and 1/8), different Reynolds and Richardson numbers ranging from 62 to 200 and from 0 to 0.1 respectively at Pr=0.71. The flow is found to be unstable when the Richardson number crosses the critical value of 0.13. The results are presented to show the effects of the blockage ratio, the Reynolds and the Richardson numbers on the flow pattern and the heat transfer from the square cylinder. Heat transfer correlation are obtained through forced and mixed convection.

The entropy generation due to heat transfer and friction has been determined in transient state for laminar natural convection by solving numerically the mass, momentum and energy balance equations, using a control volume finite-element method. The variations of the total entropy generation as function of time for Rayleigh number and irreversibility distribution ratio set at 103⩽Ra⩽105 and 10−4⩽ϕ⩽10−1 were investigated. The evolution of the maximum of entropy generation with the Rayleigh number is studied. The effect of the irreversibility distribution ratio on the maximum entropy generation and the entropy generation in steady state are analyzed. The irreversibility maps for Rayleigh number set at 103⩽Ra⩽105 and irreversibility distribution ratio ϕ=10−4 are plotted.

In this paper, we present a comparison of linear and exponential interpolation functions for control volume finite element method. The exponential interpolation function is expressed in the elemental local coordinate system whereas the classic linear interpolation function is expressed in the global coordinate system. The comparison is achieved in the case of the Green‐Taylor vortex, a flow from which we know the analytical solution. Firstly, the two functions are applied to a triangular element of the domain to compare the results given by each interpolation function to the exact value. Secondly, these two functions are compared when used to solve the discretized equations over the entire domain.