Hamiltonian map approach to 1D Anderson model

A one-dimensional diagonal tight binding electronic system is analyzed with the Hamiltonian map approach to study analytically the inverse localization length of an infinite sample. Both the uncorrelated and the dichotomic correlated random potential sequences are considered in the evaluations of the inverse localization length. Analytical expressions for the invariant measure or the angle density distribution are the main motivation of this work in order to derive analytical results. The well-known uncorrelated weak disorder result of the inverse localization length is derived with a clear procedure. In addition, an analytical expression for high disorder is obtained near the band edge. It is found that the inverse localization length goes to 1 in this limit. Following the procedure used in the uncorrelated situation, an analytical expression for the inverse localization length is also obtained for the dichotomic correlated sequence in the small disorder situation.     

Properties of a Non-Aromatic Epoxy Polymer-Based Monolithic Capillary Column for μ-HPLC

We report the chromatographic properties of a new type of epoxy polymer-based monolithic capillary column, the Tetrad-C column. The column was prepared by a completely new method—reaction of a tetra-functional epoxy monomer, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (trade name Tetrad-C), with a diamine, 4-[(4-aminocyclohexyl)methyl)cyclohexane (BACM). This polymer monolith has no aromatic functional groups reducing chromatographic performance. The columns were carefully observed by scanning electron microscopy and evaluated chromatographically by use of a μ-HPLC system. It was found that morphological control of the epoxy polymer-based monolith was possible simply by changing the polymerization conditions, i.e., the polymerization temperature and/or the relative amounts of porogenic solvent and BACM. Another advantage was that volumetric shrinkage of the tetra-functional epoxy-based monolith during the polymerization reaction was much less than for the tri-functional epoxy-based monolithic (TEPIC) column reported in our previous paper. A Tetrad-C column 200 mm long afforded up to 10,000 plates for alkylbenzenes in reversed-phase-mode. This column can also work in HILIC mode, although the hydrophobicity of the column was greater than that of the TEPIC column. Heat treatment (160 °C for 2 h; to eliminate residual, unreacted, functional groups) had a negligible effect on column performance, indicating the columns were thermally stable.     

Quantitative analysis of ezetimibe in human plasma by gas chromatography‐mass spectrometry

A new, specific and sensitive GC‐MS method with electron impact ionization technique was developed for quantitative analysis of ezetimibe (EZE) in human plasma. Prior to GC analysis, EZE was derivatized with N‐methyl‐N‐trimethylsilyl‐trifluoroacetamide (MSTFA), which is a trimethyl silylating reagent. The derivatization reaction was optimized and parameters such as catalyst, derivatization time, temperature, solvent and the volume of silylating reagent were investigated. Trimethylsilyl ether derivative of EZE was determined in selected ion monitoring (SIM, mass‐to‐charge ratio (m/z): 326) mode. The method was validated with respect to LOD and LOQ, precision, accuracy, linearity, specificity, stability, and recovery. The LOQ and LOD were found as 15 and 10 ng/mL, respectively. The linearity of the method ranged from 15 to 250 ng/mL. The correlation coefficient of the calibration curve was 0.9977 ± 0.0004 (± S.E.M.). The intra‐ and inter‐day precisions (RSD) were less than 6% and accuracies (bias) for intra‐ and inter‐day accuracy were found between –4.04 and 9.71% at four different concentration levels (15, 40, 100, 250 ng/mL). The proposed method was successfully applied to real human plasma samples for determination of total EZE.     

MHD mixed convection of a viscous dissipating fluid about a permeable vertical flat plate

The problem of steady laminar magnetohydrodynamic (MHD) mixed convection heat transfer about a vertical plate is studied numerically, taking into account the effects of Ohmic heating and viscous dissipation. A uniform magnetic field is applied perpendicular to the plate. The resulting governing equations are transformed into the non-similar boundary layer equations and solved using the Keller box method. Both the aiding-buoyancy mode and the opposing-buoyancy mode of the mixed convection are examined. The velocity and temperature profiles as well as the local skin friction and local heat transfer parameters are determined for different values of the governing parameters, mainly the magnetic parameter, the Richardson number, the Eckert number and the suction/injection parameter, f_w. For some specific values of the governing parameters, the results agree very well with those available in the literature. Generally, it is determined that the local skin friction coefficient and the local heat transfer coefficient increase owing to suction of fluid, increasing the Richardson number, Ri (i.e. the mixed convection parameter) or decreasing the Eckert number. This trend reverses for blowing of fluid and decreasing the Richardson number or decreasing the Eckert number. It is disclosed that the value of Ri determines the effect of the magnetic parameter on the momentum and heat transfer.     

Fully automated liquid chromatography-mass spectrometry determination of 17beta-estradiol in river water

Surface modified molecularly imprinted polymers (SM-MIPs) for 17beta-estradiol (E2), utilizing 6-ketoecradiol as a pseudo template were prepared. MIPs for E2 were synthesized using 4-vinyl pyridine and ethylene dimethacrylate as a functional monomer and cross-linking agent, respectively. MIPs selectively retained E2 and provided excellent chromatographic resolution from interfering compounds inherent in river water sample matrices. Therefore, freshly prepared MIPs were applied to quantitative mass spectrometric (negative electrospray ionization mode) detection of low levels of E2 in river water sample. In order to pre-concentrate the target compound for HPLC analysis, column switching was coupled with a pretreatment column packed with the MIPs. The repeatability of actual determinations of river water sample, in which background E2 was not detected, spiked with 50 ng/L of E2 was 2.2% RSD with a detection limit and qualification limit of 1.8 and 5.4 ng/L, respectively. Surface modification of MIP particlefs packed in the pretreatment column provided selective affinity and on-line concentration of low levels of E2 while simultaneously eliminating sample matrix interference, resulting in a significant increase in sensitivity and reproducibility for liquid chromatography-mass spectrometry analysis of E2 in river water sample.     

UVA and UVB decrease the expression of CD44 and hyaluronate in mouse epidermis, which is counteracted by topical retinoids

The transmembrane glycoprotein CD44 is currently thought to be the main cell surface receptor for the glycosaminoglycan hyaluronate. We previously showed that (1) CD44 regulate keratinocyte proliferation; (2) topical retinoids dramatically increase the expression of CD44, hyaluronate and hyaluronate synthase (HAS)s in mouse epidermis; (3) topical retinaldehyde restores the epidermal thickness and CD44 expression which are correlated with clinical improvement in lichen sclerosus et atrophicus lesions; and (4) retinaldehyde-induced proliferative response of keratinocytes is a CD44-dependent phenomenon and requires the presence of HB-EGF, erbB1 and matrix metalloproteinases. In this study, we analyzed the effect of UV irradiation on the levels of epidermal hyaluronate and CD44 in mice, as well as its potential prevention by topical retinoids. UVA (10 J/cm(2)) or UVB (1 J/cm(2)) irradiation significantly decreased the expression of CD44 and hyaluronate in the epidermis of hairless mice after 2 h. Expression of both epidermal CD44 and hyaluronate was reconstituted within 24 h. Topical application of retinaldehyde for 3 days prior to UVA or UVB irradiation prevented the decrease of CD44 and hyaluronate expression. Topical retinol and retinoic acid also increased the basal levels of epidermal CD44 and hyaluronate, although their preventive effect on UV-induced decrease of these molecules was less pronounced as compared to topical retinaldehyde. These data confirm the relationships between retinoid and CD44 pathways, although the primary target(s) of UV leading to CD44 and hyaluronate degradation remain to be elucidated.     

Acoustic beam splitting in a sonic crystal around a directional band gap

Beam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size,which facilitates circumvention of a directional band gap.Experiments reveal that two distinct beams emerge at crystal output,in agreement with the numerical results obtained through the finite-element method.Beam splitting occurs at sufficiently-small source sizes comparable to lattice periodicity determined by the spatial gap width in reciprocal space.Split beams propagate in equal amplitude,whereas beam splitting is destructed for oblique incidence above a critical incidence angle.     

Numerical study of turbulent flow and heat transfer of Al2O3–water mixture in a square duct with uniform heat flux

Turbulent flow and convective heat transfer of a nanofluid made of Al₂O₃ (1–4 vol.%) and water through a square duct is numerically studied. Single-phase model, volumetric concentration, temperature-dependent physical properties, uniform wall heat flux boundary condition and Renormalization Group Theory k-ε turbulent model are used in the computational analysis. A comparison of the results with the previous experimental and numerical data revealed 8.3 and 10.2 % mean deviations, respectively. Numerical results illustrated that Nu number is directly proportional with Re number and volumetric concentration. For a given Re number, increasing the volumetric concentration of nanoparticles does not have significant effect on the dimensionless velocity contours. At a constant dimensionless temperature, increasing the particle volume concentration increases the size of the temperature profile. Maximum value of dimensionless temperature increases with increasing x/D_h value for a given Re number and volumetric concentration.     

An alternative approach on the calculation of cohesive energy density and isothermal compressibility of alkali metal halides

In the present paper, new and useful theoretical methods for the estimation of cohesive energy density (Ced) and isothermal compressibility (k_T) of alkali metal halides are described. The mentioned theoretical methods include the use of Kaya molecular hardness equation published by us in recent years. Cohesive energy density and isothermal compressibility of alkali metal halides were calculated in the framework of mentioned theoretical methods and the results obtained were compared with both experimental data and the results of previous theoretical methods proposed to calculate the aforementioned quantities, namely cohesive energy density and isothermal compressibility. It is important to note that the results obtained in the study are in good agreement with the available experimental data and with the results of previous theoretical methods. Additionally, we also investigated the correlation with lattice energy of cohesive energy density and isothermal compressibility for alkali halides.     

Investigation of directional solidified Al–Ti alloy

Al–1 wt% Ti alloy was directionally solidified upwards under argon atmosphere under the two conditions; with different temperature gradients (G = 2.20–5.82 K/mm) at a constant growth rate (V = 8.30 μm/s) and with different growth rates (V = 8.30–498.60 μm/s) at a constant temperature gradient (G = 5.82 K/mm) in a Bridgman furnace. The dependence of characteristic microstructure parameters such as primary dendrite arm spacing (λ₁), secondary dendrite arm spacing (λ₂), dendrite tip radius (R) and mushy zone depth (d) on the velocity of crystal growth and the temperature gradient were determined by using a linear regression analysis. A detailed analysis of microstructure development with models of dendritic solidification and with previous similar experimental works on dendritic growth for binary alloys were also made.