On the Order of Growth of Solutions to Complex Non-homogeneous Linear Differential Equations

Habib, Habib,Belaidi, Benharrat Department of Mathematics 2016 Kyungpook mathematical journal Vol.56 No.3

In this paper, we study the order of growth of solutions to the non-homogeneous linear differential equation $$f^{(k)}+A_{k-1}e^{az}f^{(k-1)}+{\cdots}+A_1e^{az}f^{\prime}+A_0e^{az}f=F_1e^{az}+F_2e^{bz}$$, where $A_j(z)$ (${\not\equiv}0$) ($j=0,1,{\cdots},k-1$), $F_j(z)$ (${\not\equiv}0$) (j = 1, 2) are entire functions and a, b are complex numbers such that $ab(a-b){\neq}0$.

An improved method for the derivation of high quality iPSCs in the absence of c-Myc

Habib, O.,Habib, G.,Choi, H.W.,Hong, K.S.,Tae Do, J.,Moon, S.H.,Chung, H.M. Academic Press 2013 Experimental cell research Vol.319 No.20

Induced pluripotent stem cells (iPSCs) hold tremendous potential for the development of new regenerative medicine therapies and the study of molecular mechanisms of pluripotency and development. However, reactivation of c-Myc, which results in tumor formation in chimeric mice, is a major roadblock in the translation of iPSCs into therapies. Although ectopic expression of c-Myc is not absolutely required for somatic reprogramming, in the absence of c-Myc, the overall efficiency of reprogramming is drastically reduced and the reprogramming time is increased. Subtle, abnormal epigenetic modifications in iPSCs derived in the absence of c-Myc have also been documented. Therefore, we developed a reprogramming method without c-Myc to generate high-quality iPSCs, a prerequisite to harnessing the full potential of iPSCs. In this study, we determined that serum replacement (SR)-based culture conditions dramatically increased the transcription factor-mediated reprogramming of mouse embryonic fibroblast cells (MEFs). The process was shortened to approximately 8 days when Oct4/Sox2/Klf4 (3F)-transduced MEFs were first cultured for 3 days under low serum conditions (LS protocol). The 3F-derived iPSCs that were generated by this method resembled mouse ES cells (mESCs) in morphology, gene expression, and in vitro differentiation. Finally, we observed that 3F-derived iPSC colonies were able to reach definite pluripotency in terms of molecular signatures when the catalytic function of c-Myc was tolerated. The 3F induction of pluripotency described here should facilitate the use of iPSCs and may also facilitate the mechanistic dissection of somatic reprogramming.

Effect of uncertainty parameters on graphene sheets Young’s modulus prediction

Habib Sahlaoui,Mohamed Guedri,Habib Sidhom 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.9

Software based on molecular structural mechanics approach (MSMA) and using finite element method (FEM) has been developed to predict the Young’s modulus of graphene sheets. Obtained results have been compared to results available in the literature and good agreement has been shown when the same values of uncertainty parameters are used. A sensibility of the models to their uncertainty parameters has been investigated using a stochastic finite element method (SFEM). The different values of the used uncertainty parameters,such as molecular mechanics force field constants r k and kθ , thickness (t) of a graphene sheet and length ( B L ) of a carboncarbon bonds, have been collected from the literature. Strong sensibilities of 91% to the thickness and of 21% to the stretching force ( r k )have been shown. The results justify the great difference between Young’s modulus predicted values of the graphene sheets and their large disagreement with experimental results.

Ground-State Conditions Promote Robust Prdm14 Reactivation and Maintain an Active Dlk1-Dio3 Region during Reprogramming

habib omer,Gizem Habib,문성환,홍기성,도정태,Youngsok Choi,장성운,정형민 한국분자세포생물학회 2014 Molecules and cells Vol.37 No.1

Induced pluripotent stem cells (iPSCs) are capable of unlimited self-renewal and can give rise to all three germ layers, thereby providing a new platform with which to study mammalian development and epigenetic reprogramming. However, iPSC generation may result in subtle epigenetic variations, such as the aberrant methylation of the Dlk1-Dio3 locus, among the clones, and this heterogeneity constitutes a major drawback to harnessing the full potential of iPSCs. Vitamin C has recently emerged as a safeguard to ensure the normal imprinting of the Dlk1-Dio3 locus during reprogramming. Here, we show that vitamin C exerts its effect in a manner that is independent of the reprogramming kinetics. Moreover, we demonstrate that reprogramming cells under 2i conditions leads to the early upregulation of Prdm14, which in turn results in a highly homogeneous population of authentic pluripotent colonies and prevents the abnormal silencing of the Dlk1-Dio3 locus.

Posthypoxic behavioral impairment and mortality of Drosophila melanogaster are associated with high temperatures, enhanced predeath activity and oxidative stress

Habib Pardes,Jung Jennifer,Wilms Gina Maria,Kokott-Vuong Alma,Habib Shahin,Schulz Jörg B.,Voigt Aaron 생화학분자생물학회 2021 Experimental and molecular medicine Vol.53 No.-

Hypoxia is an underlying pathophysiological condition of a variety of devastating diseases, including acute ischemic stroke (AIS). We are faced with limited therapeutic options for AIS patients, and even after successful restoration of cerebral blood flow, the poststroke mortality is still high. More basic research is needed to explain mortality after reperfusion and to develop adjunct neuroprotective therapies. Drosophila melanogaster (D.m.) is a suitable model to analyze hypoxia; however, little is known about the impacts of hypoxia and especially of the subsequent reperfusion injury on the behavior and survival of D.m . To address this knowledge gap, we subjected two wild-type D.m . strains (Canton-S and Oregon-R) to severe hypoxia (<0.3% O 2 ) under standardized environmental conditions in a well-constructed hypoxia chamber. During posthypoxic reperfusion (21% O 2 ), we assessed fly activity (evoked and spontaneous) and analyzed molecular characteristics (oxidative stress marker abundance, reactive oxygen species (ROS) production, and metabolic activity) at various timepoints during reperfusion. First, we established standard conditions to induce hypoxia in D.m . to guarantee stable and reproducible experiments. Exposure to severe hypoxia under defined conditions impaired the climbing ability and reduced the overall activity of both D.m . strains. Furthermore, a majority of the flies died during the early reperfusion phase (up to 24 h). Interestingly, the flies that died early exhibited elevated activity before death compared to that of the flies that survived the entire reperfusion period. Additionally, we detected increases in ROS and stress marker (Catalase, Superoxide Dismutase and Heat Shock Protein 70) levels as well as reductions in metabolic activity in the reperfusion phase. Finally, we found that changes in environmental conditions impacted the mortality rate. In particular, decreasing the temperature during hypoxia or the reperfusion phase displayed a protective effect. In conclusion, our data suggest that reperfusion-dependent death might be associated with elevated temperatures, predeath activity, and oxidative stress.

Ground-State Conditions Promote Robust Prdm14 Reactivation and Maintain an Active Dlk1-Dio3 Region during Reprogramming

Habib, Omer,Habib, Gizem,Moon, Sung-Hwan,Hong, Ki-Sung,Do, Jeong Tae,Choi, Youngsok,Chang, Sung Woon,Chung, Hyung-Min Korean Society for Molecular and Cellular Biology 2014 Molecules and cells Vol.37 No.1

Induced pluripotent stem cells (iPSCs) are capable of unlimited self-renewal and can give rise to all three germ layers, thereby providing a new platform with which to study mammalian development and epigenetic reprogramming. However, iPSC generation may result in subtle epigenetic variations, such as the aberrant methylation of the Dlk1-Dio3 locus, among the clones, and this heterogeneity constitutes a major drawback to harnessing the full potential of iPSCs. Vitamin C has recently emerged as a safeguard to ensure the normal imprinting of the Dlk1-Dio3 locus during reprogramming. Here, we show that vitamin C exerts its effect in a manner that is independent of the reprogramming kinetics. Moreover, we demonstrate that reprogramming cells under 2i conditions leads to the early upregulation of Prdm14, which in turn results in a highly homogeneous population of authentic pluripotent colonies and prevents the abnormal silencing of the Dlk1-Dio3 locus.

Layer potential techniques in spectral analysis. Part I: Complete asymptotic expansions for eigenvalues of the Laplacian in domains with small inclusions

Ammari, Habib,Kang, Hyeonbae,Lim, Mikyoung,Zribi, Habib American Mathematical Society 2010 Transactions of the American Mathematical Society Vol.362 No.6

Experimental and analytical study in determining the seismic performance of the ELBRF-E and ELBRF-B braced frames

Habib Ghasemi Jouneghani,Abbas Haghollahi 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.5

In this article the seismic demand and performance of two recent braced steel frames named steel moment frames with the elliptic bracing (ELBRFs) are assessed through a laboratory program and numerical analyses of FEM. Here, one of the specimens is without connecting bracket from the corner of the frame to the elliptic brace (ELBRF-E), while the other is with the connecting brackets (ELBRF-B). In both the elliptic braced moment resisting frames (ELBRFs), in addition to not having any opening space problem in the bracing systems when installed in the surrounding frames, they improve structure’s behavior. The experimental test is run on ½ scale single-story single-bay ELBRF specimens under cyclic quasi-static loading and compared with X-bracing and SMRF systems in one story base model. This system is of appropriate stiffness and a high ductility, with an increased response modification factor. Moreover, its energy dissipation is high. In the ELBRF bracing systems, there exists a great interval between relative deformation at the yield point and maximum relative deformation after entering the plastic region. In other words, the distance from the first plastic hinge to the collapse of the structure is fairly large. The experimental outcomes here, are in good agreement with the theoretical predictions.

Theoretical formulation for calculating elastic lateral stiffness in a simple steel frame equipped with elliptic brace

Habib Ghasemi Jouneghani,Nader Fanaie,Abbas Haghollahi 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.3

Elliptic-braced simple resisting frame as a new lateral bracing system installed in the middle bay of frame in building facades has been recently introduced. This system not only creates a problem for opening space from the architectural viewpoint but also improves the structural behavior. Despite the researches on the seismic performance of lateral bracing systems, there are few studies performed on the effect of the stiffness parameters on the elastic story drift and calculation of period in simple braced steel frames. To overcome this shortcoming, in this paper, for the first time, an analytical solution is presented for calculating elastic lateral stiffness in a simple steel frame equipped with elliptic brace subjected to lateral load. In addition, for the first time, in this study, a precise formulation has been developed to evaluate the elastic stiffness variation in a steel frame equipped with a two-dimensional single-story single-span elliptic brace using strain energy and Castigliano’s theorem. Thus, all the effective factors, including axial and shear loads as well as bending moments of elliptic brace could be considered. At the end of the analysis, the lateral stiffness can be calculated by an improved and innovative relation through the energy method based on the geometrical properties of the employed sections and specification of the used material. Also, an equivalent element of an elliptic brace was presented for the ease of modeling and use in linear designs. Application of the proposed relation have been verified through a variety of examples in OpenSees software. Based on the results, the error percentage between the elastic stiffness derived from the developed equations and the numerical analyses of finite element models was very low and negligible.

PROBING GALAXY FORMATION MODELS IN COSMOLOGICAL SIMULATIONS WITH OBSERVATIONS OF GALAXY GROUPS

HABIB. G., KHOSROSHAHI,GOZALIASL, GHASSEM,FINOGUENOV, ALEXIS,RAOUF, MOJTABA,MIRAGHEE, HALIME The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

We use multi-wavelength observations of galaxy groups to probe the formation models for galaxy formation in cosmological simulations, statistically. The observations include Chandra and XMM-Newton X-ray observations, optical photometry and radio observations at 1.4 GHz and 610 MHz. Using a large sample of galaxy groups observed by the XMM-Newton X-ray telescope as part of the XMM-Large Scale Survey, we carried out a statistical study of the redshift evolution of the luminosity gap for a well defined mass-selected group sample and show the relative success of some of the semi-analytic models in reproducing the observed properties of galaxy groups up to redshift z ~ 1.2. The observed trend argues in favour of a stronger evolution of the feedback from active galactic nuclei at z < 1 compared to the models. The slope of the relation between the magnitude of the brightest cluster galaxy and the value of the luminosity gap does not evolve with redshift and is well reproduced by the models. We find that the radio power of giant elliptic galaxies residing in galaxy groups with a large luminosity gap are lower compared to giant ellipticals of the same stellar masses but in typical galaxy groups.