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131.
Mohammad Shahidul Islam Abdullah Saleh Alammari Assem Barakat Saeed Alshahrani Matti Haukka Abdullah Mohammed Al-Majid 《Molecules (Basel, Switzerland)》2021,26(23)
Five new C2-symmetric chiral ligands of 2,5-bis(imidazolinyl)thiophene (L1–L3) and 2,5-bis(oxazolinyl)thiophene (L4 and L5) were synthesized from thiophene-2,5-dicarboxylic acid (1) with enantiopure amino alcohols (4a–c) in excellent optical purity and chemical yield. The utility of these new chiral ligands for Friedel–Crafts asymmetric alkylation was explored. Subsequently, the optimized tridentate ligand L5 and Cu(OTf)2 catalyst (15 mol%) in toluene for 48 h promoted Friedel–Crafts asymmetric alkylation in moderate to good yields (up to 76%) and with good enantioselectivity (up to 81% ee). The bis(oxazolinyl)thiophene ligands were more potent than bis(imidazolinyl)thiophene analogues for the asymmetric induction of the Friedel–Crafts asymmetric alkylation. 相似文献
132.
Priti Tagde Pooja Tagde Fahadul Islam Sandeep Tagde Muddaser Shah Zareen Delawar Hussain Md. Habibur Rahman Agnieszka Najda Ibtesam S. Alanazi Mousa O. Germoush Hanan R. H. Mohamed Mardi M. Algandaby Mohammed Z. Nasrullah Natalia Kot Mohamed M. Abdel-Daim 《Molecules (Basel, Switzerland)》2021,26(23)
Curcumin is the primary polyphenol in turmeric’s curcuminoid class. It has a wide range of therapeutic applications, such as anti-inflammatory, antioxidant, antidiabetic, hepatoprotective, antibacterial, and anticancer effects against various cancers, but has poor solubility and low bioavailability. Objective: To improve curcumin’s bioavailability, plasma concentration, and cellular permeability processes. The nanocurcumin approach over curcumin has been proven appropriate for encapsulating or loading curcumin (nanocurcumin) to increase its therapeutic potential. Conclusion: Though incorporating curcumin into nanocurcumin form may be a viable method for overcoming its intrinsic limitations, and there are reasonable concerns regarding its toxicological safety once it enters biological pathways. This review article mainly highlights the therapeutic benefits of nanocurcumin over curcumin. 相似文献
133.
Stability of Bragg grating solitons in a semilinear dual-core system with cubic–quintic nonlinearity
The existence and stability of quiescent Bragg grating solitons in a dual-core fiber, where one core contains a Bragg grating with cubic–quintic nonlinearity, and the other is a linear are studied. The model admits two disjoint bandgaps when the relative group velocity in the linear core, c, is zero: one in the upper half and the other in the lower half of the system’s linear spectrum. In the general case (i.e., \(c\ne 0\)), a central gap (which is a genuine gap) is formed, while the lower and upper gaps overlap with one branch of continuous spectrum, and therefore, they are not genuine bandgaps. For quiescent solitons, exact analytical solutions are found in implicit form for \(c=0\). For nonzero c, soliton solutions are obtained numerically. The system supports two disjoint families (referred to as Type 1 and Type 2) of zero-velocity soliton solutions, separated by a border. Both Type 1 and Type 2 soliton solutions exist throughout the upper and lower gaps but not in the central gap. The stability of both soliton families is investigated by means of systematic numerical simulations. It is found that Type 2 solitons are always unstable and are destroyed upon propagation. On the other hand, unstable Type 1 solitons may either decay into radiation or radiate some energy and evolve into a moving Type 1 soliton. Also, in the case of Type 1 solitons, we have identified stable regions in the plane of quintic nonlinearity and frequency. The influence of coupling coefficient and the relative group velocity in the linear core on the stability of solitons are analyzed. 相似文献
134.
A catalyst-free green methodology for the synthesis of pharmacologically important spirooxindole derivatives has been developed by a three-component domino reaction between isatin, various amino compounds, and 1,3-dicarbonyl or 3-phenylisoxazolone compounds in ethyl l-lactate medium at room temperature. This new efficient synthetic method facilitated the formation of a wide range of biologically significant spirooxindole derivatives (including 17 new spirooxindoles) under very mild conditions. The cytotoxic activity of one of the isoxazole-fused spirooxindoles was evaluated in MDA-MB 468 breast cancer cell line. It was found that cell survivability decreases with increasing concentration of the selected compound in MDA-MB 468 breast cancer cells. 相似文献
135.
An Alternative Method for Solving Lagrange's First-Order Partial Differential Equation with Linear Function Coefficients
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Syed Md Himayetul Islam & J. Das 《偏微分方程(英文版)》2015,28(3):208-224
An alternative method of solving Lagrange's first-order partial differential equation of the form $$(a_1x+b_1y+c_1z)p+(a_2x+b_2y+c_2z)q=a_3x+b_3y+c_3z,$$ where p=∂z/∂x, q=∂z/∂y and a_i, b_i, c_i (i=1,2,3) are all real numbers has been presented here. 相似文献
136.
In this paper, reflectivity of a Distributed Bragg Reflector (DBR) has been computed by considering the effects of changes of wavelength on the changes of the refractive index of the materials of DBR layers. The intrinsic losses of the materials have been included in the computation of the reflectivity of the DBR. It has been found that the effect of change of the wavelength on the refractive index of the DBR materials reduces the Full Width Half Maxima (FWHM) of the stop band significantly which is expected to improve the laser characteristics. If the FWHM is reduced, the thickness of the active layer of a VCSEL can also be reduced which will further reduce the threshold current of the device. It has been found that the intrinsic losses of the materials have a significant effect on the reflectivity of a DBR. It has also been found that peak reflectivity of a 20 pair AlAs/GaAs DBR reduces by 0.2% after including the intrinsic losses (with a value of the intrinsic losses α = 10 cm?1). 相似文献
137.
Dominique Costa Kamal Sharkas Mazharul M. Islam Philippe Marcus 《Surface science》2009,603(16):2484-2493
The reactivity of the (0 0 0 1)-Cr–Cr2O3 surface towards water was studied by means of periodic DFT + U. Several water coverages were studied, from 1.2H2O/nm2 to 14.1H2O/nm2, corresponding to ¼, 1, 2 and 3 water/Cr at the (0 0 0 1)-Cr2O3 surface, respectively. With increasing coverage, water gradually completes the coordination sphere of the surface Cr atoms from 3 (dry surface) to 4 (1.2 and 4.7H2O/nm2), 5 (9.4H2O/nm2) and 6 (14.1H2O/nm2). For all studied coverages, water replaces an O atom from the missing above plane. At coverages 1.2 and 4.7H2O/nm2, the Cr–Os (surface oxygen) acid–base character and bond directionality govern the water adsorption. The adsorption is molecular at the lowest coverage. At 4.7H2O/nm2, molecular and dissociative states are isoenergetic. The activation energy barrier between the two states being as low as 12 kJ/mol, allowing protons exchanges between the OH groups, as evidenced by ab inito molecular dynamics at room temperature. At coverages of 9.4 and 14.1H2O/nm2, 1D- (respectively, 2D-) water networks are formed. The resulting surface terminations are –Cr(OH)2 and –Cr(OH)3– like, respectively. The increased stability of those terminations as compared to the previous ones are due to the stabilization of the adsorbed phase through a H-bond network and to the increase in the Cr coordination number, stabilizing the Cr (t2g) orbitals in the valence band. An atomistic thermodynamic approach allows us to specify the temperature and water pressure domains of prevalence for each surface termination. It is found that the –Cr(OH)3-like, –Cr(OH)2 and anhydrous surfaces may be stabilized depending on (T, P) conditions. Calculated energies of adsorption and OH frequencies are in good agreement with published experimental data and support the full hydroxylation model, where the Cr achieves a 6-fold coordination, at saturation. 相似文献
138.
Goverdhan Mehta Gagliardini Vanessa Kabirul Islam Kailasam Venkatesan 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(1):o90-o93
The cis,syn,cis‐tricyclic [2+2]‐dimer of cyclooctatetraene, C16H16, crystallizes in space group Pca21 with two molecules in the asymmetric unit. An extensive network of weak C—H⋯π(Czdbnd;C) interactions between the two independent molecules, A and B, as well as A⋯A and B⋯B interactions, are observed in the supramolecular assembly. The C—H groups point more towards one C atom than to the centre of the Czdbnd;C bond. Notable among the interactions are bifurcated (cyclobutane)C—H⋯Czdbnd;C contacts that span transannularly the eight‐membered ring. 相似文献
139.
Nazrul Islam Peter M. Campbell Thomas J. V. Higgins Hisashi Hirano Raymond J. Akhurst 《Electrophoresis》2009,30(11):1863-1868
Differential in‐gel electrophoresis showed contrasting effects of the transgenic expression of an α‐amylase inhibitor from beans on the proteomes of two pea cultivars. One cultivar showed minor changes relative to its non‐transgenic parent with only one protein changing by more than about twofold. Changes in the abundance of certain endogenous proteins in the other cultivar were of greater number and magnitude with some endogenous proteins undetected while some new protein spots appeared in the transgenic proteome. The sets of proteins with altered expression were generally different between the two cultivars. Some of the proteins that were differentially expressed were identified by MS. Most were seed storage globulins, which are sited together with the transgenic product. Some of the changes may be due to alterations in expression levels but there were also changes due to post‐translational processing. 相似文献
140.
The thermodynamics of binding of Me-alpha(-GalNAc, Gal-beta-1-3GalNAc-alpha-O-Me (T-antigen-alpha), Gal-beta-1-3GalNAc and Gal-alpha-1-6Glc (mellibiose) to Artocarpus hirsuta lectin was studied using fluorescence spectroscopy. The binding affinities of the saccharides are in the order Gal-beta-1-3GalNAc-alpha-O-Me > Me-alpha-GalNAc > Me-alpha-Gal > Gal-beta-1-3GalNAc > Gal-alpha-1-6Glc. The binding affinities were comparable to those for jacalin. However, binding of the saccharides to the A. hirsuta lectin was not affected as strongly by temperature as observed in jacalin and the trend was found to be reversed. Values for AH and AS were found to be positive in A. hirsuta lectin-disaccharide binding despite similar binding affinities. Thus, with 99% structural and 96% sequence homology, with similar sugar specificity and affinity, the energetics of the disaccharide binding of the two lectins seem to be different. Me-alpha-GalNAc binding to A. hirsuta lectin is enthalpically driven, because the association constant decreases with increasing temperature. However, the binding of the T-antigen disaccharides and mellibiose disaccharides to the lectin is entropically driven. The difference in the molecular associations in the packing and variation of the C-terminal length of the beta chain of the A. hirsuta lectin could be reflected in the different disaccharide binding energetics. 相似文献