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排序方式: 共有632条查询结果,搜索用时 15 毫秒
131.
M. Atilla Tasdelen Baris Kiskan Yusuf Yagci 《Macromolecular rapid communications》2006,27(18):1539-1544
Summary: Free radical polymerization of methyl methacrylate (MMA) is initiated upon irradiation at λ > 350 nm in CH2Cl2 that contains benzoxazine (P‐a) and one of the following photosensitizers: benzophenone (BP), thioxanthone (TX), 2‐chlorothioxanthone (CTX), 2‐isopropyl thioxanthone (ITX), and camphorquinone (CQ). The postulated mechanism is based on the intermolecular reaction of the excited photosensitizer with the tertiary amino moiety of the ground state P‐a and a subsequent hydrogen abstraction reaction. The resulting aminoalkyl radicals initiate the polymerization. The incorporation of P‐a groups into polymers is demonstrated by spectroscopic methods. The possibility of deep curing using the described photoinitiating system followed by the thermal ring opening of the incorporated P‐a groups is also demonstrated.
132.
Cagatay Altinkok Baris Kiskan Yusuf Yagci 《Journal of polymer science. Part A, Polymer chemistry》2011,49(11):2445-2450
The preparation of soluble and processable polybenzoxazine precursors capable of forming high performance networks is an important field of research with a broad spectrum of application. This study demonstrates an approach that utilizes aromatic sulfonediamine, bisphenol‐A, and formaldehyde in Mannich‐type polycondesation to prepare polybenzoxazine precursor. The structure of the oligomeric precursor (Mn = 2600) was confirmed by FTIR and 1H NMR spectral analysis. The precursor contained both sulfone and benzoxazine ring structures in the backbone. It was shown that small amount of ring‐opened phenolic groups were also present. Thermally activated self‐curing behavior of precursor in the absence of catalyst was studied by differential scanning calorimetry. Thermal properties of the cured polymers were also investigated by thermo gravimetric analysis. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
133.
S. M. Yusuf 《Pramana》2004,63(1):133-141
We have investigated magnetic correlations in various CMR manganites on macroscopic, mesoscopic and microscopic length scales
by carrying out DC magnetization, neutron depolarization, and neutron diffraction measurements. We present here the effect
of substituting Mn with Fe and La with Dy in the ferromagnetic La0.7−xCaxMnO3 (x ∼ 0.3–0.33) compounds. Neutron diffraction has been used in order to characterize the long-range magnetic order and its gradual
suppression by the substitution. Neutron depolarization study has been carried out in order to bridge the gap in our understanding
regarding the nature of magnetic correlation obtained from the macroscopic and microscopic measurements. In particular, our
study on La0.67Ca0.33Mn0.9Fe0.1O3 has established the fact that a true double exchange mediated spin-glass is insulating. In another study of La-site ionic
size effect and its disorder in (La1−x
Dy
x
)0.7Ca0.3MnO3, we have investigated the evolution of the length scale of magnetic ordering with a possible microscopic explanation and
the results have been compared with that for the light rare earth substituted compounds. 相似文献
134.
Paola Falsini Roberto Pini Renzo Salimbeni Matteo Vannini A.F.M.Yusuf Haider Roberto Buffa 《Optics Communications》1985,53(6):421-424
A simple combination of a lens-based unstable resonator and an inverted telescope coupling geometry working in a XeCl laser pumped H2 Raman cell are presented. Raman spectrum optimization is achieved by varying the pump beam numerical aperture. 70% pump depletion and energy conversion efficiencies as high as 66% and 7.8% have been obtained for S1, S2 and S3 respectively. 相似文献
135.
Dr. Abuzar Khan Dr. Asma M. Elsharif Dr. Aasif Helal Prof. Zain H. Yamani Dr. Abbas Saeed Hakeem Dr. Mohd Yusuf Khan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(43):11132-11140
Mixed-matrix membranes (MMMs) with combination of two distinct dimensional nanofillers (such as 1D-3D, 2D-3D, or 3D-3D, etc.) have drawn special attention for gas separation applications due to their concerted effects on gas permeation and mechanical properties. An amine-functionalized 1D multiwalled carbon nanotube (NH2-MWCNT) with exceptional mechanical strength and rapid gas transport was crosslinked with an amine-functionalized 3D metal-organic framework (UiO-66-NH2) with high CO2 affinity in a Schiff base reaction. The resultant crosslinked mixed-dimensional nanostructure was used as a nanofiller in a polysulfone (PSf) polymer matrix to explore the underlying synergy between 1D and 3D nanostructures on the gas separation performance of MMMs. Cross-sectional scanning electron microscopy and mapping revealed the homogenous dispersion of UiO-66@MWCNT in the polymer matrix. The MMM containing 5.0 wt. % UiO-66@MWCNT demonstrated a superior permeability 8.3 Barrer as compared to the 4.2 Barrer of pure PSf membrane for CO2. Moreover, the selectivity (CO2/CH4) of this MMM was enhanced to 39.5 from the 28.0 observed for pure PSf under similar conditions of pressure and temperature. 相似文献
136.
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
137.
Arca Anil Omer Faruk Sadak Bartu Karakurt Dr. Yusuf Kocak Dr. Igor Lyubinetsky Prof. Dr. Emrah Ozensoy 《Chemphyschem》2023,24(13):e202200787
Understanding the activation of CO2 on the surface of the heterogeneous catalysts comprised of metal/metal oxide interfaces is of critical importance since it is not only a prerequisite for converting CO2 to value-added chemicals but also often, a rate-limiting step. In this context, our current work focuses on the interaction of CO2 with heterogeneous bi-component model catalysts consisting of small MnOx clusters supported on the Pd(111) single crystal surface. These metal oxide-on-metal ‘reverse’ model catalyst architectures were investigated via temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) techniques under ultra-high vacuum (UHV) conditions. Enhancement of CO2 activation was observed upon decreasing the size of MnOx nanoclusters by lowering the preparation temperature of the catalyst down to 85 K. Neither pristine Pd(111) single crystal surface nor thick (multilayer) MnOx overlayers on Pd(111) were not capable of activating CO2, while CO2 activation was detected at sub-monolayer (∼0.7 ML) MnOx coverages on Pd(111), in correlation with the interfacial character of the active sites, involving both MnOx and adjacent Pd atoms. 相似文献
138.
Adewale S. Oladipo Olusegun A. Ajayi Akeem A. Oladipo Solmaz L. Azarmi Yusuf Nurudeen Abdulazeez Y. Atta Shola S. Ogunyemi 《Comptes Rendus Chimie》2018,21(7):684-695
A magnetically recyclable eggshell-based catalyst (MKEC) was synthesized to circumvent saponification during the conversion of neem, Jatropha, and waste cooking oils (free fatty acid, 2.3–6.6%) to biodiesel. The characterization results indicated that MKEC had a mesoporous structure with the pore width of 3.24 nm, a specific surface area of 128 m2/g, and a pore volume of 0.045 cm3/g. The results confirmed that the MKEC is more tolerant to fatty acid poisoning than calcined eggshell. The effects of process parameters for maximum fatty acid methyl ester (FAME) content were evaluated by central composite design (CCD) and artificial neural network (ANN). The experimental FAME content of 94.5% was achieved for neem oil with a standard deviation (SD) of 0.68, which was in reasonable agreement with predicted values (CCD, 96.9%; ANN, 95.9%; SD, 0.73). The reusability studies showed that the mesoporous catalyst can be reused efficiently for five cycles without much deterioration in its activity. 相似文献
139.
Davut Avcı Sümeyye Altürk Fatih Sönmez Ömer Tamer Adil Başoğlu Yusuf Atalay Belma Zengin Kurt Necmi Dege 《Tetrahedron》2018,74(50):7198-7208
Novel complexes of 6?methylpyridine?2?carboxylic acid and thiocyanate {[Cu(NCS)(6-mpa)2], (1); [Cd(NCS)(6-mpa)]n, (2); [Cr(NCS)(6-mpa)2·H2O], (3)} were synthesized, and their structures were characterized by XRD analysis, FT–IR and UV–Vis spectroscopic techniques. The inhibitory activities of the synthesized complexes (1–3) on α-glucosidase were determined by using genistein reference compound. Furthermore, the optimized geometry and vibrational harmonic frequencies for the complexes 1–3 were obtained by DFT/HSEh1PBE/6–311G(d,p)/LanL2DZ level. Electronic spectral properties were examined by using TD-DFT/HSEh1PBE/6–311G(d,p)/LanL2DZ level with CPCM model. Additionally, major contributions to the electronic transitions were determined via Swizard program. The refractive index, linear optical and non?nonlinear optical parameters of the complexes 1–3 were investigated at HSEh1PBE/6–311G(d,p) level. The docking studies of the complexes 1–3 to the binding site of the target protein (the template structure S. cerevisiae isomaltase are fulfilled. Lastly, natural bond orbital analysis was used to investigate inter- and intra-molecular bonding and interaction among bonds. 相似文献
140.
Turan Nevin Buldurun Kenan Alan Yusuf Savci Ahmet Çolak Naki Mantarcı Asim 《Research on Chemical Intermediates》2019,45(6):3525-3540
Research on Chemical Intermediates - In this study, the complex combinations of Ru(II), Co(II) and Ni(II) with Schiff base obtained through the condensation of (E)-methyl... 相似文献