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 $ab(a-b){\neq}0$.

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.

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.

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.

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.

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.

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

Effect of Cyclic Pre-straining on the Dynamic Behavior of Very Dense Sand

Habib Shahnazari,Ali Akbar Heshmati,Hossein Sarbaz 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.1

Earthquakes, including the main shock, fore-shocks and after-shocks, are among the most devastating natural disasters. Mostbuilding structures that are damaged due to a main shock then experience more damage when they are subjected to aftershocks. Anystrong shock may decrease the strength of a steel or concrete structure. However, depending on its magnitude, a foreshock may eitherincrease or decrease the shear strength of an earth-fill structure. A loose granular specimen usually gains some shear strength whensubjected to pre-loading. This behavior is mainly due to an increase in relative density and experience of shear history. For a verydense granular material, it is unclear whether fore-shocks and main shocks increase or decrease its shear strength. However, theanswer to this uncertainty is vital when evaluating the safety factor of a well-compacted granular earth-fill dam after an earthquake. The objective of this study is to study the effects of cyclic pre-straining on the dynamic behavior of saturated and very dense sandspecimens. The major findings from the laboratory study are the following: (a) under small pre-strain, the microstructure remainsessentially unchanged, but an increase in density leads to an increase in the soil strength; and (b) under large pre-strain, themicrostructure is completely altered to a new form. In this case, if the loading amplitude is identical to the one in the previous prestrain,the soil strength increases; however, if the loading amplitude is less than the previous pre-strain, the strength decreases in thenext stage. Such a decrease occurs even though the relative density increases.

Evaluation of energy release rate of composites laminated with finite element method

Habib Achache,Benali Boutabout,Abdelouahab Benzerdjeb,Djamel Ouinas 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.1

Control of the mechanical behavior of composite materials and structures under monotonic and dynamic loads for cracks and damage is a vast and complex area of research. The modeling of the different physical phenomena and behavior characteristics of a composite material during deformation play an important role in the structural design. Our study aims to analyze numerically the energy release rate parameter G of a composite laminated plate (glass or boron / epoxy) cross-ply [+α, −α] in the presence of a crack between two circular notches under the effect of several parameters such as fiber orientation α, the crack orientation β, the orientation γ of the two considered circular notches and the effect of mechanical properties. Our results show clearly that both notches orientation has more effect on G than the cracks and fibers orientations.

The Effect of Shape and Stiffness of Originally Different Marine Soil Grains on Their Contractive and Dilative Behavior

Habib Shahnazari,Hossein Salehzadeh,Reza Rezvani,Yasser Dehnavi 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.4

Laboratory research was conducted to compare the monotonic behavior of two different marine calcareous sands - Hormuz Island(HI) and Bushehr Port (BP) - with siliceous sand named Firoozkuh sand (F). A series of undrained isotropically consolidated triaxialtests was performed on reconstituted specimens of these sands. In this experimental investigation, their contractive and dilativebehaviors were evaluated. The effect of some important parameters, such as relative density and confining pressure on the behaviorof these specimens was studied. To analyze the effect of shape and stiffness (resistance to particle breakage) on the contractive andthe dilative responses of these soils, the influence of axial strain on the crushability of the calcareous soils was assessed. Thereafter,the undrained behavior of the soils was analyzed, using two parameters, which represented a normalized variation of excess porewater pressure in two phases of monotonic triaxial tests. The contractive and dilative behavior of the two different calcareous sandswas compared to the siliceous sand. The results showed that particle shape played a key role in the behavior of soils in contractivephase. However, the shearing response of the used carbonate soils was more affected by particle crushing in dilation.