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231.
Self-scaled barrier functions on self-scaled cones were axiomatically introduced by Nesterov and Todd in 1994 as a tool for
the construction of primal—dual long-step interior point algorithms. This paper provides firm foundations for these objects
by exhibiting their symmetry properties, their close ties with the symmetry groups of their domains of definition, and subsequently
their decomposition into irreducible parts and their algebraic classification theory. In the first part we recall the characterization
of the family of self-scaled cones as the set of symmetric cones and develop a primal—dual symmetric viewpoint on self-scaled
barriers, results that were first discovered by the second author. We then show in a short, simple proof that any pointed,
convex cone decomposes into a direct sum of irreducible components in a unique way, a result which can also be of independent
interest. We then proceed to showing that any self-scaled barrier function decomposes, in an essentially unique way, into
a direct sum of self-scaled barriers defined on the irreducible components of the underlying symmetric cone. Finally, we present
a complete algebraic classification of self-scaled barrier functions using the correspondence between symmetric cones and
Euclidean—Jordan algebras.
December 5, 1999. Final version received: September 6, 2001. 相似文献
232.
M. Emin Günay Osman Dayan Ayta Gürhan Gke Muhittin Aygün Bekir etinkaya Orhan Büyükgüngr 《Polyhedron》2008,27(18):3607-3610
Treatment of N,N′-bis(mesityl)pyridine-2,6-carboxyimidoyl dichloride, 1, in toluene solution with [Pt(PPh3)4] at 100 °C afforded a novel platinacyclic compound, 3, in 63% yield, instead of the expected compound 2. The molecular and crystal structures of the title compound, 3, have been determined by the single crystal X-ray diffraction technique. The coordination geometries around the Pt atoms are distorted square-planar. In the crystal structure, the molecules are linked by a pair of C–H···N hydrogen bonds into a centrosymmetric dimer with an ring, centred at (1/2,1/2,1/2). 相似文献
233.
Talal F. Al-Azemi Hicham H. Dib Nouria A. Al-Awadi Osman M.E. El-Dusouqui 《Tetrahedron》2008,64(18):4126-4134
Compounds containing both carbonate and ester functionalities were synthesized and then subjected to online-GC gas-phase pyrolysis. The carbonate groups were cleaved selectively in all elimination reactions. The end products of the reaction were found to be affected by the nature of the substrate. The presence of hydrogen and carbonyl substituents on the carbon β to the carbonate group resulted in further product decomposition through a concerted six-membered transition state. Results from flash vacuum pyrolysis (FVP) and analysis of the GC data indicate that the cleavage of the carbonate group is fast, and that the slower secondary decomposition reactions are independent of the presence of the carbonate group. Spectroscopic analyses of the products are reported. 相似文献
234.
Micellar properties of dodecylpyridinium chloride (DPC) were investigated by means of electrical conductometry with emphasis
on the influences of cosolvent-water content and temperature. Ethanol was used as a cosolvent. Conductivity measurements gave
information about critical micelle concentration and micellar ionization degree of the water-ethanol micellar solutions at
different temperatures. In all solvent mixtures, it was observed that the critical micelle concentration of DPC and the degree
of the counterion dissociation increase with an increasing concentration of ethanol and increasing temperature. Micellar and
thermodynamics data were obtained from the temperature dependence of critical micelle concentrations in various aqueous mixtures
of ethanol. In order to explain the effect of the cosolvent, the differences in the Gibbs energies of micellization of DPC
between water and binary cosolvent were determined. The standard free energy (ΔG°mic) of micellization was found to be negative as the concentration of the solvent increases, but it is roughly independent of
temperature. Although the enthalpic contribution was found to be larger than the entropic one, in particular at lower temperatures,
an entropy-enthalpy compensation effect was observed for all systems. Also, enthalpy (ΔH°mic) and entropy (ΔS°mic) of micellization are strongly temperature dependent and decrease with increasing temperature and cosolvent content.
The text was submitted by the authors in English. 相似文献
235.
Dr. Chunwei Dong Dr. Ren-Wu Huang Dr. Arunachalam Sagadevan Dr. Peng Yuan Dr. Luis Gutiérrez-Arzaluz Dr. Atanu Ghosh Saidkhodzha Nematulloev Badriah Alamer Prof. Dr. Omar F. Mohammed Prof. Dr. Irshad Hussain Prof. Dr. Magnus Rueping Prof. Dr. Osman M. Bakr 《Angewandte Chemie (International ed. in English)》2023,62(37):e202307140
Elucidating single-atom effects on the fundamental properties of nanoparticles is challenging because single-atom modifications are typically accompanied by appreciable changes to the overall particle's structure. Herein, we report the synthesis of a [Cu58H20PET36(PPh3)4]2+ ( Cu58 ; PET: phenylethanethiolate; PPh3: triphenylphosphine) nanocluster—an atomically precise nanoparticle—that can be transformed into the surface-defective analog [Cu57H20PET36(PPh3)4]+ ( Cu57 ). Both nanoclusters are virtually identical, with five concentric metal shells, save for one missing surface copper atom in Cu57 . Remarkably, the loss of this single surface atom drastically alters the reactivity of the nanocluster. In contrast to Cu58 , Cu57 shows promising activity for click chemistry, particularly photoinduced [3+2] azide-alkyne cycloaddition (AAC), which is attributed to the active catalytic site in Cu57 after the removal of one surface copper atom. Our study not only presents a unique system for uncovering the effect of a single-surface atom modification on nanoparticle properties but also showcases single-atom surface modification as a powerful means for designing nanoparticle catalysts. 相似文献
236.
H. I. Abdel‐Gawad M. Tantawy M. S. Osman 《Mathematical Methods in the Applied Sciences》2016,39(2):168-176
E. Sanchez‐Palencia In this paper, we investigate the dynamic of DNA described via DNA double‐stranded model with transverse and longitudinal motions. This model admits solitary, soliton, periodic, or chirped wave solution. It is justified that the most admissible physical solution is the soliton or chirped wave solution. The stability analysis of all these solutions is performed by using the Sturm–Liouville problem and the topological invariance. We found that soliton and chirped waves are unstable so that the unbounded amplitude may occur. In the view of these models, damage of DNA membrane or bases may occur under small disturbance. Also, the suggested models will be indispensable when inhomogeneity or medium dissipation is taken into account. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
237.
Orhan Altan Osman Serindağ Koray Sayın Duran Karakaş 《Phosphorus, sulfur, and silicon and the related elements》2016,191(7):993-999
Novel phosphine oxides, (((3-methylpyridin-2-yl)amino)methyl)diphenylphosphine oxide (1) and diphenyl((pyrazin-2-ylamino)methyl)phosphine oxide (2), were synthesized and characterized. Phosphines ligands (3 and 4) were obtained by the reduction of 1 and 2 with AlH3, monitored by 31P NMR spectroscopy. Pd(II) complexes of 3 and 4 were synthesized and characterized (5 and 6). The catalytic activity of 5 and 6 was tested on the reaction of styrene with both activated and deactivated aryl bromides in air. The results of the catalytic experiments were discussed through DFT calculations. 相似文献
238.
The interactions of cationic surfactants with anionic dyes were studied by conductometric method. Benzyltrimethylammonium chloride (BTMACl), benzyltriethylammonium chloride (BTEACl) and benzyltributylammonium chloride (BTBACl) were used as cationic surfactants and indigo carmine (IC) and amaranth (Amr) were chosen as anionic dyes. The specific conductance of dye–surfactant mixtures was measured at 25, 35 and 45 °C. A decrease in measured specific conductance values of dye–surfactant mixture was caused by the formation of non-conducting or less-conducting dye–surfactant complex. The equilibrium constants, K1, the standard free energy changes, ΔG1°, the standard enthalpy changes, ΔH1° and the standard entropy changes, ΔS1° for the first association step of dye–surfactant complex formation were calculated by a theoretical model. The results showed that the equilibrium constants and the negative standard free energy change values for all systems decreased as temperature increased. Also these values decreased for all systems studied with increasing alkyl chains of surfactants due to the steric effect. When the equilibrium constant values, K1, for the first association step of IC–surfactant and Amr–surfactant systems with the same surfactant were compared, the values of K1 for IC–surfactant system were higher than that of Amr–surfactant system. 相似文献
239.
Osman Yusuf Raisuddin Ali Abdullah H. Alomrani Aws Alshamsan Abdullah K. Alshememry Abdulaziz M. Almalik Afsaneh Lavasanifar Ziyad Binkhathlan 《Molecules (Basel, Switzerland)》2021,26(9)
The objective of this study was to synthesize and characterize a set of biodegradable block copolymers based on TPGS-block-poly(ε-caprolactone) (TPGS-b-PCL) and to assess their self-assembled structures as a nanodelivery system for paclitaxel (PAX). The conjugation of PCL to TPGS was hypothesized to increase the stability and the drug solubilization characteristics of TPGS micelles. TPGS-b-PCL copolymer with various PCL/TPGS ratios were synthesized via ring opening bulk polymerization of ε-caprolactone using TPGS, with different molecular weights of PEG (1–5 kDa), as initiators and stannous octoate as a catalyst. The synthesized copolymers were characterized using 1H NMR, GPC, FTIR, XRD, and DSC. Assembly of block copolymers was achieved via the cosolvent evaporation method. The self-assembled structures were characterized for their size, polydispersity, and CMC using dynamic light scattering (DLS) technique. The results from the spectroscopic and thermal analyses confirmed the successful synthesis of the copolymers. Only copolymers that consisted of TPGS with PEG molecular weights ≥ 2000 Da were able to self-assemble and form nanocarriers of ≤200 nm in diameter. Moreover, TPGS2000-b-PCL4000, TPGS3500-b-PCL7000, and TPGS5000-b-PCL15000 micelles enhanced the aqueous solubility of PAX from 0.3 µg/mL up to 88.4 ug/mL in TPGS5000-b-PCL15000. Of the abovementioned micellar formulations, TPGS5000-b-PCL15000 showed the slowest in vitro release of PAX. Specifically, the PAX-loaded TPGS5000-b-PCL15000 micellar formulation showed less than 10% drug release within the first 12 h, and around 36% cumulative drug release within 72 h compared to 61% and 100% PAX release, respectively, from the commercially available formulation (Ebetaxel®) at the same time points. Our results point to a great potential for TPGS-b-PCL micelles to efficiently solubilize and control the release of PAX. 相似文献
240.
Nur Hilwani Ismail Khairul Osman Aini Farzana Zulkefli Mohd Helmy Mokhtar Siti Fatimah Ibrahim 《Molecules (Basel, Switzerland)》2021,26(11)
Gelam honey (GH) is a prized natural product synthesized from the nectar of flowers from Gelam trees (Melaleuca sp.). Gelam is an evergreen tree species that grows in tropical regions such as Malaysia. GH is a multifloral honey with proven antioxidant and anti-inflammatory properties. However, the beneficial effect of GH on female reproductive tissue has yet to be substantiated. Herein, we investigated the effects of GH administration on the uterine and vaginal epithelial thickness of sexually mature Sprague–Dawley rats. Epithelia thickness could be an indicator of an atrophy manifesting as a symptom of a cardio syndrome. Rats were given oral doses of GH in four groups for 14 days; the lowest dose was 0.2 g GH/kg body weight (bw) rat/day and the highest dose was 8 g GH/kg bw rat/day. The physicochemical characteristics of GH were assessed through hydroxymethylfurfural and moisture content determination and sugar identification. GH attenuated the atrophy of the uterine and vaginal epithelia and increased the thickness of the endometrial stroma and endometrial surface endothelial layer. However, the dissonance observed in the effect of GH administration on the vaginal epithelium requires further investigation. Nevertheless, GH may have a strong potential in attenuating uterine and vaginal atrophies. 相似文献