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排序方式: 共有174条查询结果,搜索用时 512 毫秒
91.
S. A. Nouh Yasmine E. Radwan Dalia Elfiky M. M. Abutalib Radiyah A. Bahareth S. S. Fouad 《辐射效应与固体损伤》2013,168(11-12):975-987
The effects of 28 GeV 56Fe and 13.72 GeV 28Si ion irradiation on the structural properties of two types of Bayfol, namely DPF 5023 and CR 1–4 polycarbonates, have been investigated. It is worth mentioning that this report is almost the first one dealing with the topic of material changes in such a high energy range. Samples from each type of Bayfol were classified into two groups. The first group has been exposed to Fe ion fluences at levels between 2000 and 8000 ion/cm2. The second group has been exposed to Si ions with similar fluences. The total energy deposited is between 27.44 and 224 E12 eV. The modifications induced in Bayfol samples due to ion irradiation have been studied using X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy. The results indicate that the Fe ion irradiation causes crosslinking in Bayfol DPF 5023, reflected as a decrease in the ordering character. Also, the tendency of Bayfol CR 1–4 to crosslinking due to Fe ion irradiation is lower than that of Bayfol DPF 5023. On the other hand, the Si ion irradiation causes mainly chain scission at the carbonate site of both types of Bayfol associated with the formation of hydroxyl group. 相似文献
92.
93.
Patrícia da Silva Malheiros Voltaire Sant’Anna Yasmine Miguel Serafini Micheletto Nadya Pesce da Silveira Adriano Brandelli 《Journal of nanoparticle research》2011,13(8):3545-3552
Antimicrobial peptide P34, a substance showing antibacterial activity against pathogenic and food spoilage bacteria, was encapsulated
in liposomes prepared from partially purified soybean phosphatidylcholine, and their physicochemical characteristics were
evaluated. The antimicrobial activity was estimated by agar diffusion assay using Listeria monocytogenes ATCC 7644 as indicator strain. A concentration of 3,200 AU/mL of P34 was encapsulated in nanovesicles and stocked at 4 °C.
No significant difference (p > 0.05) in the biological activity of free and encapsulated P34 was observed through 24 days. Size and PDI of liposomes,
investigated by light scattering analysis, were on average 150 nm and 0.22 respectively. Zeta potential was −27.42 mV. There
was no significant change (p > 0.05) in the physicochemical properties of liposomes during the time of evaluation. The liposomes presented closed spherical
morphology as visualized by transmission electron microscopy (TEM). The mode of action of liposome-encapsulated P34 under
L. monocytogenes cells was investigated by TEM. Liposomes appeared to adhere but not fuse with the bacterial cell wall, suggesting that the
antimicrobial is released from nanovesicles to act against the microorganism. The effect of free and encapsulated P34 was
tested against L. monocytogenes, showing that free bacteriocin inhibited the pathogen more quickly than the encapsulated P34. Liposomes prepared with low-cost
lipid showed high encapsulation efficiency for a new antimicrobial peptide and were stable during storage. The mode of action
against the pathogen L. monocytogenes was characterized. 相似文献
94.
Sanim Rahman Dr. Vered Wineman-Fisher Dr. Péter R. Nagy Dr. Yasmine Al-Hamdani Prof. Alexandre Tkatchenko Prof. Sameer Varma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(42):11005-11014
Lysine methylation can modify noncovalent interactions by altering lysine's hydrophobicity as well as its electronic structure. Although the ramifications of the former are documented, the effects of the latter remain largely unknown. Understanding the electronic structure is important for determining how biological methylation modulates protein−protein binding, and the impact of artificial methylation experiments in which methylated lysines are used as spectroscopic probes and protein crystallization facilitators. The benchmarked first-principles calculations undertaken here reveal that methyl-induced polarization weakens the electrostatic attraction of amines with protein functional groups – salt bridges, hydrogen bonds and cation-π interactions weaken by as much as 10.3, 7.9 and 3.5 kT, respectively. Multipole analysis shows that weakened electrostatics is due to the altered inductive effects, which overcome increased attraction from methyl-enhanced polarizability and dispersion. Due to their fundamental nature, these effects are expected to be present in many cases. A survey of methylated lysines in protein structures reveals several cases in which methyl-induced polarization is the primary driver of altered noncovalent interactions; in these cases, destabilizations are found to be in the 0.6–4.7 kT range. The clearest case of where methyl-induced polarization plays a dominant role in regulating biological function is that of the PHD1-PHD2 domain, which recognizes lysine-methylated states on histones. These results broaden our understanding of how methylation modulates noncovalent interactions. 相似文献
95.
Yasmine Abtahi 《Research in Mathematics Education》2018,20(1):1-13
In this article, I use the Vygotskian concept of the Zone of Proximal Development (ZPD) to examine the learning experience of two grade seven pupils as they attempted to solve an addition of fractions problem using fraction strips. The aim is to highlight how tools can facilitate the enactment of a ZPD, within which the tool provides the guidance. Viewing the ZPD as a zone that allows for the emergence of various forms of guided talk and actions, I present a detailed analysis of a short video-recording of the pupils’ participation in a tool-mediated problem-solving activity. I show how their knowing of the concept of fractions and their perceptions of the affordances of the fraction strips marked what they said and did. I conclude by suggesting that the ZPD emerges through participation and interaction, not only between individuals but also between individuals and tools. 相似文献
96.
This study deals with the performance of projective interior point methods for linear semidefinite program. We propose a modification in the initialization phases of the method in order to reduce the computation time.This purpose is confirmed by numerical experiments showing the efficiency which are presented in the last section of the paper. 相似文献
97.
MOUSSAOUI Abdelkrim KHODJA Brahim 《偏微分方程(英文版)》2009,22(2):111-126
In this paper, we study the existence of nontrivial solutions for the problem
{-△u=f(x,u,v)+h1(x)in Ω
-△v=g(x,u,v)+h2(x)inΩ
u=v=0 onδΩ
where Ω is bounded domain in R^N and h1,h2 ∈ L^2 (Ω). The existence result is obtained by using the Leray-Schauder degree under the following condition on the nonlinearities f and g:
{lim s,|t|→+∞f(x,s,t)/s=lim |s|,t→+∞g(x,s,t)/t=λ+1 uniformly on Ω,
lim -s,|t|→+∞f(x,s,t)/s=lim |s|,-t→+∞g(x,s,t)/t=λ-,uniformly on Ω,
where λ+,λ-∈(0)∪σ(-△),σ(-△)denote the spectrum of -△. The cases (i) where λ+ = λ_ and (ii) where λ+≠λ_ such that the closed interval with endpoints λ+,λ_ contains at most one simple eigenvatue of -△ are considered. 相似文献
{-△u=f(x,u,v)+h1(x)in Ω
-△v=g(x,u,v)+h2(x)inΩ
u=v=0 onδΩ
where Ω is bounded domain in R^N and h1,h2 ∈ L^2 (Ω). The existence result is obtained by using the Leray-Schauder degree under the following condition on the nonlinearities f and g:
{lim s,|t|→+∞f(x,s,t)/s=lim |s|,t→+∞g(x,s,t)/t=λ+1 uniformly on Ω,
lim -s,|t|→+∞f(x,s,t)/s=lim |s|,-t→+∞g(x,s,t)/t=λ-,uniformly on Ω,
where λ+,λ-∈(0)∪σ(-△),σ(-△)denote the spectrum of -△. The cases (i) where λ+ = λ_ and (ii) where λ+≠λ_ such that the closed interval with endpoints λ+,λ_ contains at most one simple eigenvatue of -△ are considered. 相似文献
98.
In this paper, we study the existence of positive smooth solutions for a class of singular (p(x), q(x))-Laplacian systems using sub and supersolution methods. 相似文献
99.
Moulai Sarah Ghezini Rachid Hasnaoui Abdelkrim Bengueddach Abdelkader Weidler Peter G. 《Research on Chemical Intermediates》2019,45(3):1653-1668
Research on Chemical Intermediates - This work deals with the preparation of MAPO-5 zeolite by a hydrothermal method. In order to study the adsorption properties of this zeolite several transition... 相似文献
100.
Katharigatta N. Venugopala Sandeep Chandrashekharappa Christophe Tratrat Pran Kishore Deb Rahul D. Nagdeve Susanta K. Nayak Mohamed A. Morsy Pobitra Borah Fawzi M. Mahomoodally Raghu Prasad Mailavaram Mahesh Attimarad Bandar E. Aldhubiab Nagaraja Sreeharsha Anroop B. Nair Osama I. Alwassil Michelyne Haroun Viresh Mohanlall Pottathil Shinu Rashmi Venugopala Mahmoud Kandeel Belakatte P. Nandeshwarappa Yasmine F. Ibrahim 《Molecules (Basel, Switzerland)》2021,26(12)
The cyclooxygenase-2 (COX-2) enzyme is an important target for drug discovery and development of novel anti-inflammatory agents. Selective COX-2 inhibitors have the advantage of reduced side-effects, which result from COX-1 inhibition that is usually observed with nonselective COX inhibitors. In this study, the design and synthesis of a new series of 7-methoxy indolizines as bioisostere indomethacin analogues (5a–e) were carried out and evaluated for COX-2 enzyme inhibition. All the compounds showed activity in micromolar ranges, and the compound diethyl 3-(4-cyanobenzoyl)-7-methoxyindolizine-1,2-dicarboxylate (5a) emerged as a promising COX-2 inhibitor with an IC50 of 5.84 µM, as compared to indomethacin (IC50 = 6.84 µM). The molecular modeling study of indolizines indicated that hydrophobic interactions were the major contribution to COX-2 inhibition. The title compound diethyl 3-(4-bromobenzoyl)-7-methoxyindolizine-1,2-dicarboxylate (5c) was subjected for single-crystal X-ray studies, Hirshfeld surface analysis, and energy framework calculations. The X-ray diffraction analysis showed that the molecule (5c) crystallizes in the monoclinic crystal system with space group P 21/n with a = 12.0497(6)Å, b = 17.8324(10)Å, c = 19.6052(11)Å, α = 90.000°, β = 100.372(1)°, γ = 90.000°, and V = 4143.8(4)Å3. In addition, with the help of Crystal Explorer software program using the B3LYP/6-31G(d, p) basis set, the theoretical calculation of the interaction and graphical representation of energy value was measured in the form of the energy framework in terms of coulombic, dispersion, and total energy. 相似文献