EFFECTS OF PHASE-LAGS AND VARIABLE THERMAL CONDUCTIVITY IN A THERMOVISCOELASTIC SOLID WITH A CYLINDRICAL CAVITY

( Ashraf M. Zenkour ) 호남수학회 2016 호남수학학술지 Vol.38 No.3

This paper investigates the effect of dual-phase-lags on a thermoviscoelastic orthotropic solid with a cylindrical cavity. The cylindrical cavity is subjected to a thermal shock varying heat and its material is taken to be of Kelvin-Voigt type. The phase-lag thermoelastic model, Lord and Shulman`s model and the coupled thermoelasticity model are employed to study the thermomechanical coupling, thermal and mechanical relaxation (viscous) effects. Numerical solutions for temperature, displacement and thermal stresses are obtained by using the method of Laplace transforms. Numerical results are plotted to illustrate the effect phase-lags, viscoelasticity, and the variability thermal conductivity parameter on the studied fields. The variations of all field quantities in the context of dual-phase-lags and coupled thermoelasticity models follow similar trends while the Lord and Shulman`s model may be different. The influence of viscosity parameter and variability of thermal conductivity is very pronounced on temperature and thermal stresses of the thermoviscoelastic solids.

Snapshot of phase transition in thermoresponsive hydrogel PNIPAM: Role in drug delivery and tissue engineering

Ashraf, S.,Park, H. K.,Park, H.,Lee, S. H. THE POLYMER SOCIETY OF KOREA 2016 Macromolecular Research Vol.24 No.4

<P>Hydrogels are physically and chemically cross-linked, 3D, porous, hydrated molecular structures that mimic the native tissue microenvironment. Hydrogels fabricated with environmentally sensitive polymers can possess additional properties such as thermoresponsiveness. This property originates from its phase transition from gel to solution and vice versa with temperature variation. Phase transition mechanisms also depend on the interaction between the polymers and surrounding environment. Their thermoresponsiveness makes hydrogels attractive for drug delivery, gene therapy, cell culture, and tissue engineering approaches. The resemblance to living tissue of such thermoresponsive hydrogels produced by crosslinking of natural polymers opens up many biomedical application opportunities for human use. The most intensively studied natural thermoresponsive polymer is poly(N-isopropyl-acrylamide) (PNIPAM). This review focuses on the phase transition mechanism in thermoresponsive PNIPAM, the factors affecting the behavior of the gel, its specific properties, and, in particular, the role of PNIPAM's phase transition in drug delivery, cell culture, and tissue engineering.</P>

Zwitterionic surface coating of quantum dots reduces protein adsorption and cellular uptake

Ashraf, S.,Park, J.,Bichelberger, M.,Kantner, K.,Hartmann, R.,Maffre, P.,Said, A.,Feliu, N.,Lee, J.,Lee, D. Royal Society of Chemistry 2016 Nanoscale Vol.8 No.41

<P>We have studied the effect of the zwitterionic surface coating of quantum dots (QDs) on their interaction with a serum supplemented cell medium and their internalization by human cervical carcinoma (HeLa) cells. Zwitterionic QDs showed negligible adsorption of human serum albumin (HSA) selected as a model serum protein, in contrast to similar but negatively charged QDs. The incorporation of zwitterionic QDs by HeLa cells was found to be lower than for negatively charged QDs and for positively charged QDs, for which the uptake yield was largest. Our results suggest that the suppression of protein adsorption, here accomplished by zwitterionic QD surfaces, offers a strategy that allows for reducing the cellular uptake of nanoparticles.</P>

Purification and Characterization of a New L-Methioninase from Solid Cultures of Aspergillus flavipes

Ashraf S. A. El-Sayed 한국미생물학회 2011 The journal of microbiology Vol.49 No.1

L-Methioninase was purified to electrophoretic homogeneity from cultures of Aspergillus flavipes using anionexchange and gel filtration chromatography by 12.1 fold compared to the crude enzyme preparation. The purified enzyme had a molecular mass of 47 kDa under denaturing conditions and an isoelectric point of 5.8 with no structural glycosyl residues. The enzyme had optimum activity at pH 7.8 and pH stability from 6.8-8.0 at 35°C. The enzyme appeared to be catalytically stable below 40°C. The enzyme activity was strongly inhibited by DL-propargylglycine, hydroxylamine, PMSF, 2-mercaptoethanol, Hg^(2+), Cu^(2+), and Fe^(2+), with slight inhibition by Triton X-100. A. flavipes L-methioninase has a higher catalytic affinity towards L-methionine (Km, 6.5 mM and Kcat, 14.1 S^(-1)) followed by a relative demethiolating activity to L-homocysteine (Km, 12 mM and Kcat, 9.3 S^(-1)). The enzyme has two absorption maxima at 280 and 420 nm,typical of other PLP-enzymes. Apo-L-methioninase has the ability to reconstitute its structural catalytic state completely upon addition of 0.15 mM PLP. L-Methioninase has neither an appreciable effect on liver function, platelet aggregation, nor hemolysis of human blood. The purified L-methioninase from solid cultures of A. flavipes displayed unique biochemical and catalytic properties over the currently applied Pseudomonad enzyme.

Video multicast cooperative communication in 5G systems with radio frequency energy harvesting

Ashraf, Mateen,Jang, Ju Wook,Han, Jong-Ki,Lee, Kyung-Geun Elsevier 2018 Journal of Computer Communications Vol.118 No.-

<P><B>Abstract</B></P> <P>In this paper, the performance of radio frequency energy harvesting cooperative multicast communication is analyzed in terms of outage probability. The multicast communication between base station (BS) and multiple destinations is assisted by one energy harvesting relay chosen from multiple energy harvesting relays. The relays harvest energy from the BS transmissions to be able to transmit for cooperation. We propose two power splitting approaches at the relays for energy harvesting. The first approach splits the received signal at the relays into two portions and send them to decoding/energy harvesting circuitry, simultaneously. In the second approach, the received signal during any receiving time is either sent to the information decoding circuitry or energy harvesting circuitry depending on the strength of the received signal. Analytical expressions of outage probability for these two power splitting approaches are derived. The derived expressions are validated by comparing them with the simulation results. Further, the outage probability of our proposed energy harvesting cooperative multicast system is almost equal to the non-energy harvesting cooperative multicast system.</P>

Smart Energy Efficient Device-to-Multidevice Cooperative Clustering for Multicasting Content

Ashraf, Mateen,Yeo, Woon-Young,Woo, Miae,Lee, Kyung-Geun Taylor & Francis 2016 INTERNATIONAL JOURNAL OF DISTRIBUTED SENSOR NETWOR Vol.2016 No.-

ON SEMIDERIVATIONS IN 3-PRIME NEAR-RINGS

Ashraf, Mohammad,Boua, Abdelkarim Korean Mathematical Society 2016 대한수학회논문집 Vol.31 No.3

In the present paper, we expand the domain of work on the concept of semiderivations in 3-prime near-rings through the study of structure and commutativity of near-rings admitting semiderivations satisfying certain differential identities. Moreover, several examples have been provided at places which show that the assumptions in the hypotheses of various theorems are not altogether superfluous.

Nine months versus 12 months of adjuvant trastuzumab for patients with HER2-positive breast cancer

Ashraf Mahmoud El-Enbaby,Nadia Ahmed Abd El Moneim,Gehan Abd El atti Khedr,Yasmine Mohamed Nagy Elwany 대한종양외과학회 2018 Korean Journal of Clinical Oncology Vol.14 No.2

Purpose: This study aimed to compare the results of treatment with adjuvant trastuzumab for 9 months versus 12 months in human epider�mal growth factor 2 (HER2)-positive breast cancer patients. The primary endpoint was disease-free survival. Secondary endpoints included cardiac safety, tolerability, and overall survival. Methods: The study included 60 non-metastatic HER2-positive breast cancer patients. All study patients underwent surgery, received adju�vant chemotherapy, radiotherapy and hormonal therapy if indicated. Thirty patients were randomized in each group. Group I patients received adjuvant trastuzumab for 12 months, while group II patients received adjuvant trastuzumab for 9 months. Patients were assessed by clinical examination and Echocardiography during treatment. Results: After median follow-up of 12 months, 90% of the patients in group I were disease free and 83.3% of patients in group II were dis�ease free (P=0.402). All studied population in both groups I and II were alive at the end of the 1-year follow-up period after the completion of adjuvant trastuzumab treatment thus overall survival is 100%. Conclusion: Trastuzumab is tolerable and its side effects are reversible. Nine months of adjuvant trastuzumab treatment is more cost effec�tive than the standard 12 months.

Physicochemical analysis of structural alteration and advanced glycation end products generation during glycation of H2A histone by 3-deoxyglucosone : GLYCATING POTENTIAL OF 3-DG WITH H2A HISTONE PROTEIN

Ashraf, Jalaluddin M.,Ahmad, Saheem,Rabbani, Gulam,Jan, Arif Tasleem,Lee, Eun Ju,Khan, Rizwan Hasan,Choi, Inho Wiley (John WileySons) 2014 IUBMB life Vol.66 No.10

<P>Advanced glycation end-products comprise a complex and heterogeneous group of compounds that have been implicated in diabetes-related complications. The importance of the Maillard reaction is depicted by the formation of reactive intermediate products known as α-oxoaldehydes, such as 3-deoxyglucosone (3-DG). This product has been found to be involved in accelerated vascular damage in diabetes. In the present study, calf thymus histone H2A was reacted with 3-DG, and the generation of advanced glycation end products was investigated by determining the degree of side chain modifications (lysine and arginine residues), Amadori products, carbonyl content, N(ε) -carboxymethyl lysine, and pentosidine using various physicochemical techniques. Moreover, fluorescence, absorbance as well as structural characteristics of glycated-H2A were comprehensively investigated. Overall, this study demonstrates structural perturbation, formation of different intermediates, and AGEs that are believed to hamper the normal functioning of H2A histone, compromising the integrity of chromatin structures and function in secondary complications of diabetes.</P>

The effect of two temperatures on a FG nanobeam induced by a sinusoidal pulse heating

Ashraf M. Zenkour,Ahmed E. Abouelregal 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.2

The present investigation is concerned with the effect of two temperatures on functionally graded (FG) nanobeams subjected to sinusoidal pulse heating sources. Material properties of the nanobeam are assumed to be graded in the thickness direction according to a novel exponential distribution law in terms of the volume fractions of the metal and ceramic constituents. The upper surface of the FG nanobeam is fully ceramic whereas the lower surface is fully metal. The generalized two-temperature nonlocal theoryof thermoelasticity in the context of Lord and Shulman's (LS) model is used to solve this problem. The governing equations are solved in the Laplace transformation domain. The inversion of the Laplace transformation is computed numerically using a method based on Fourier series expansion technique. Somecomparisons have been shown to estimate the effects of the nonlocal parameter, the temperature discrepancy and the pulse width of the sinusoidal pulse. Additional results across the thickness of the nanobeam are presented graphically.