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71.
Rosa Pereira Tommy Julianto Peh-Kim Ang Sharon Sheue-Nee Ling Carlos Mauricio Barbosa Kah-Hay Yuen Abu Bakar Abdul Majeed 《Chromatographia》2010,71(5-6):373-381
A sensitive and rapid routine LC method was validated for measuring cefotaxime incorporated in three different pH-sensitive nanoparticles. The drug was chromatographed on a C18 reversed-phase column; the mobile phase used was 0.05 M aqueous ammonium acetate, acetonitrile and tetrahydrofuran (87:11:2, v/v) adjusted to pH 5.5 with acetic acid. The flow rate was 1 mL min?1 and cefotaxime was quantified at 254 nm, with a sensitivity range of 0.005 AUFS. The validated method was specific, linear (R 2 ≥ 0.999), precise and accurate in a concentration range of 0.2–50.0 μg mL?1. The method was rapid, selective and suitable for evaluation of cefotaxime in pH-sensitive Eudragit nanoparticles. 相似文献
72.
M.A. Abid H. Abu HassanZ. Hassan S.S. NgS.K. Mohd. Bakhori N.H. Abd. Raof 《Physica B: Condensed Matter》2011,406(8):1379-1384
Raman and Fourier transform infrared (FTIR) spectroscopies have been utilized to measure long-wavelength optical lattice vibrations of high-quality quaternary AlxInyGa1−x−yN thin films at room temperature. The AlxInyGa1−x−yN films were grown on c-plane (0 0 0 1) sapphire substrates with AlN as buffer layers using plasma assisted molecular beam epitaxy (PA-MBE) technique with aluminum (Al) mole fraction x ranging from 0.0 to 0.2 and constant indium (In) mole fraction y=0.1. Pseudo unit cell (PUC) model was applied to investigate the phonons frequency, mode number, static dielectric constant, and high frequency dielectric constant of the AlxInyGa1−x−yN mixed crystals. The theoretical results were compared with the experimental results obtained from the quaternary samples by using Raman and FTIR spectroscopies. The experimental results indicated that the AlxInyGa1−x−yN alloy had two-mode behavior, which includes A1(LO), E1(TO), and E2(H). Thus, these results are in agreement with the theoretical results of PUC model, which also revealed a two-mode behavior for the quaternary nitride. We also obtained new values of E1(TO) and E2(H) for the quaternary nitride samples that have not yet been reported in the literature. 相似文献
73.
A.SH. Hussein Z. Hassan S.M. Thahab Abu Hassan M.A. Abid C.W. Chin 《Physica B: Condensed Matter》2011,406(6-7):1267-1271
We have studied the structural properties of undoped and Si-doped AlxGa1?xN/GaN/AlN on Si (1 1 1) substrate prepared by plasma-assisted molecular beam epitaxy (PA-MBE) using high-resolution X-ray diffraction (HR-XRD) and atomic force microscopy (AFM). In comparison with undoped AlGaN, the roughness and dislocation density on the surface of the AlGaN layer decrease with Si doping. Full width half maximum (FWHM) of the undoped and Si-doped samples were equal to 0.69° and 0.52°, respectively. This indicates that the Si doping improves the crystalline quality of the AlxGa1?xN layer compared with the undoped one. Raman scattering measurement reveals that the optical phonon modes of A1(LO) and E2(H) of the AlGaN show a one-mode and two-modes behavior, respectively. The Fourier-transform infrared reflectance (FTIR) investigation confirms the one-mode (two-mode) behavior of the LO (TO) phonon in our samples. This is in good agreement with Raman measurement. Finally, the barrier height (ΦB) of undoped and Si-doped AlxGa1?xN samples was found to be 0.86 and 0.74 eV, respectively. 相似文献
74.
Iqbal Mahmud A.J.F. Samed Md. Anamul Haque Md. Abu Bin Hasan Susan 《Journal of Saudi Chemical Society》2011,15(3):203-208
Cyclic voltammetric behavior of anthraquinone in aqueous medium has been studied in presence of a non-ionic surfactant, Triton X-100 (TX-100) using sodium salt of anthraquinone-2-sulphonic acid (AQS) as the electro-active species. When cathodic potential is applied, the anthraquinone (AQ) group of AQS is reduced to its dianion. In the reverse scan, the oxidation of AQ2− gives AQ. The electrochemical behavior shows a profound influence from the dissolved state of TX-100 in aqueous media. Spectrophotometric results indicate interaction between AQ and TX-100. A CEC (chemical–electrochemical–chemical) mechanism with the electrochemical reaction coupled with preceding interaction of AQS with TX-100 and following protonation reaction of reduced AQ has been proposed. 相似文献
75.
Shaikh A. Ali N. Y. Abu‐Thabit Hasan A. Al‐Muallem 《Journal of polymer science. Part A, Polymer chemistry》2010,48(24):5693-5703
The zwitterionic monomer, ethyl 3‐(N,N‐diallylammonio)propanephosphonate, was cyclopolymerized in aqueous solutions using t‐butylhydroperoxide or ammonium persulfate as initiators to afford a polyphosphonobetaine (PPB). The protonation of P(?O)OEtO– and deprotonation of ? NH+ groups in PPB by HCl and NaOH, gave the corresponding cationic polyphosphononic acid (CPP) and anionic polyphosphonate (APP). The presence of two pH‐responsive functionalities in APP has led to establish the equilibria: APP ? PPB ? CPP, the position of which very much dictates the viscosity behavior of its aqueous solution. The PPB demonstrated “antipolyelectrolyte” viscosity behavior; however, in contrast to many polycarbo‐ and polysulfo‐betaines, it was found to be soluble in salt‐free water as well as in salt‐added solutions. Basicity constant (K1) of the amine group in APP, as determined by potentiometric technique, were found to be “apparent,” and as such followed the modified Henderson‐Hasselbalch equation. The study demonstrated a correlation between the basicity constants and viscosity values. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
76.
Kietics of oxidation of phenylhydrazine and p-bromophenylhydrazine by hexacyanoferrate(III) in acidic medium have been studied. The reactions follow similar kinetics, being first order with respect to both hydrazine and exacyanoferrate(III) and inverse first order with respect to the hydrogen ion. Addition of hexacyanoferrate(II) has no retarding effect on the rate of oxidation. The effects of varying ionic strength, dielectric constant, and temperature on the reaction rates have been investigated. A plausible mechanism has been proposed to account for the experimental results. Benzene and bromobenzene have been identified as the oxidation products. 相似文献
77.
78.
C. F. Mok F. Muhamad N. A. Abu Osman Ramesh Singh 《International Journal of Polymer Analysis and Characterization》2017,22(4):294-304
Poly(vinyl alcohol)-α-chitin composite films reinforced by oil palm empty fruit bunch fiber-derived nanocellulose were prepared by casting technique. Fourier transform infrared spectroscopy analysis revealed partial miscibility between chitin and poly(vinyl alcohol) through hydrogen bonding, as supported by differential scanning calorimetry and field emission scanning electron microscopy. Tensile strength of the poly(vinyl alcohol)/chitin films increased with α-chitin content varied from 10 to 30?wt%, which was from 29.06 to 39.27?MPa. With the addition of 1?wt% nanocellulose, a maximum improvement of 57.64 and 50.66% in terms of tensile strength and Young’s modulus was achieved, respectively. 相似文献
79.
The poor aqueous solubility and the physicochemical instability of many marketed drugs and new chemical entities is one of the most challenging issues in pharmaceutical research and development. Polymeric micelles (PMs) are produced by the self-assembly of polymeric amphiphiles and they represent one of the most extensively investigated nanotechnology platforms for encapsulation, delivery and targeting of hydrophobic drugs. However, a main challenge is preventing their disassembly under extreme dilution in the body fluids, which leads to uncontrolled release of the encapsulated cargo. In this work, we developed an amphiphilic nanomaterial that resembles the core-corona architecture of a PM with superior stability in the body fluids. Specifically, we utilized carboxylated nanodiamonds (cNDs) as particulate anchors to covalently link amphiphilic diblock copolymers consisting of poly(epsilon-caprolactone) (PCL) and poly(ethylene glycol) monomethyl ether (PEG) as hydrophobic and hydrophilic components, respectively. We confirmed a successful core-corona nanostructure using various characterization techniques. In addition, TEM revealed the presence of a thin polymeric layer. Then, the cell compatibility was evaluated in Caco2 cell monolayers, an in vitro model of the intestinal epithelium. Finally, the encapsulation of the hydrophobic anti-helmintic drug nitazoxanide was studied. Cargoes as high as 17.5% w/w were achieved and the sustained release of the cargo according to the Korsmeyer-Peppas model demonstrated in vitro. Overall, preliminary results highlight the potential of this novel approach to extend the applicability of PMs in drug delivery. 相似文献
80.
In this study, two-dimensional transient dynamic response of orthotropic plane layered media is investigated. The plane multilayered
media consist of N different generally orthotropic, homogeneous and linearly elastic layers with different ply angles. In the generally orthotropic
layer, representing a ply reinforced by unidirectional fibers with an arbitrary orientation angle, the principal material
directions do not coincide with body coordinate axes. The solution is obtained by employing a numerical technique which combines
the use of Fourier transform with the method of characteristics. The numerical results are displayed in curves denoting the
variations of stress and displacement components with time at different locations. These curves clearly reveal, in wave profiles,
the scattering effects caused by the reflections and refractions of waves at the boundaries and at the interfaces of the layers,
and also the effects of anisotropy caused by fiber orientation angle. The curves properly predict the sharp variations in
the response at the neighborhood of the wave fronts, which shows the power of the numerical technique employed in the study.
By suitably adjusting the elastic constants, the results for multilayered media with transversely isotropic layers, or layers
with cubic symmetry, or isotropic layers can easily be obtained from the general formulation. Furthermore, solutions for some
special cases, including Lamb’s problem for an elastic half-space, are obtained and compared with the available solutions
in the literature and very good agreement is found.
Preliminary version presented at the Second International Congress on Mechatronics (MECH2K3), Graz, Austria, July 14-17, 2003. 相似文献