Effect of viscous dissipation on the mixed convection heat transfer from an exponentially stretching surface

The mixed convection flow and heat transfer from an exponentially stretching vertical surface in a quiescent fluid is analyzed using similarity solution technique. Wall temperature and stretching velocity are assumed to have specific exponential function forms. The influence of buoyancy along with viscous dissipation on the convective transport in the boundary layer region is analyzed in both aiding and opposing flow situations. The flow is governed by the mixed convection parameter Gr/Re². The velocity and temperature inside the boundary layer are observed to be influenced by the parameters like Prandtl number Pr, Gebhart number Gb. Significant changes are observed in non-dimensional skin friction and heat transfer coefficients due to viscous dissipation in the medium. The flow and temperature distributions inside the boundary layer are analyzed and the results for non-dimensional skin friction and heat transfer coefficients are discussed through computer generated plots.     

Structure,optical and magnetic properties of LaFeO3 nanoparticles prepared by polymerized complex method

This work reports the study the structure, optical and magnetic properties of LaFeO₃ nanoparticles synthesized by the polymerized complex method. The LaFeO₃ nanoparticles were successfully obtained from calcination of the precursor at different temperatures from 750 to 1,050 °C in air for 2 h. The calcined LaFeO₃ nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Visible spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge spectroscopy (XANES) and vibrating sample magnetometry. The XRD and TEM results showed that all LaFeO₃ samples had a single phase nature with the orthorhombic structure. The estimated crystallite sizes were in the range of 44.5 ± 2.4–74.1 ± 4.9 nm. UV–Vis spectra showed strong UV and Vis absorption with small band gap energy. The valence states of Fe ions were in the Fe³⁺ and Fe⁴⁺ state, as confirmed by XPS and XANES results. The weak ferromagnetic behavior with specific saturation magnetization of 0.1 emu/g at 10 kOe was obtained for the small particle of 44.5 ± 2.4 nm. The uncompensated spins at the surface was proposed as playing a part in the magnetic properties of small sized LaFeO₃.     

A rapid method for detection of cell adhesion molecules (CAMs) on human umbilical vein endothelial cells (HUVECs)

Detection of cell surface proteins is widely used as molecular markers for initiation, progression and severity of many diseases. In particular, detection of cell adhesion molecules (CAMs) on endothelial cells is important as it indicates the extent of inflammation associated with several diseases including arthritis, asthma, tumor metastasis, etc. Here, we report, a rapid method for detection of CAMs on endothelial cells by covalently immobilizing TNF-α induced cells on a photoactivated polystyrene microtiter plate at 50 °C in 45 min followed by performing enzyme-linked immunosorbent assay (ELISA) technique at elevated temperature. Our method reduced the time of cell-ELISA to 3 h with results akin to conventional cell-ELISA carried out in 38 h. The method thus described herein could be potentially useful in clinical and research laboratories for rapid detection of cell surface proteins including CAMs on intact cell samples.     

Measurement of high-power microwave pulse under intense electromagnetic noise

KALI-1000 pulse power system has been used to generate single pulse nanosecond duration high-power microwaves (HPM) from a virtual cathode oscillator (VIRCATOR) device. HPM power measurements were carried out using a transmitting-receiving system in the presence of intense high frequency (a few MHz) electromagnetic noise. Initially, the diode detector output signal could not be recorded due to the high noise level persisting in the ambiance. It was found that the HPM pulse can be successfully detected using wide band antenna, RF cable and diode detector set-up in the presence of significant electromagnetic noise. Estimated microwave peak power was ∼59.8 dBm (∼1 kW) at 7 m distance from the VIRCATOR window. Peak amplitude of the HPM signal varies on shot-to-shot basis. Duration of the HPM pulse (FWHM) also varies from 52 ns to 94 ns for different shots.     

Practical method to estimate the standard deviation in absorption coefficients measured with THz time-domain spectroscopy

A model of standard deviation in the intensity spectrum of electric field observed with the terahertz time-domain spectroscopy (THz-TDS) is proposed to estimate the random error in the transmittance and absorption coefficients from a single or a few measurements of a sample. The proposed standard deviation which is derived on the basis of the statistical standard deviation and noise floor of intensity spectrum of reference fits well to the standard deviation of transmittance as well as absorption coefficient computed statistically. This study contributes the simple and computationally efficient method to demonstrate the accuracy in optical constants like imaginary part of refractive index and absorption coefficients measured using the THz-TDS.     

Kinetics of oxidation of ethanol by acid bromate

The kinetics of oxidation of ethanol by bromate ion in hydrochloric acid medium has been investigated. The reaction involves the formation of the intermediate bromate ester which is facilitated by the methyl group in ethanol but the electron attracting character (F>Cl>Br) of the halogens attached to the -carbon of the alcohol makes the esterification more difficult.

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. , , , (F>Cl>Br), - , .

     

Solvent effect profiles of absorbance and fluorescence spectra of some indole based chalcones

The photophysical properties of a series of 3-(1′H-Indol-3′-yl)-1-phenylprop-2-en-1-one and its derivatives (indole chalcones) were studied in different solvents. Solvent effects on the absorption and fluorescence spectra were quantified using Reichardt’s and bulk solvent polarity parameters and were complemented by the results of the Kamlet-Taft treatment. The observed excited state dipole moment was found to be larger than the ground state dipole moment of these chalcones. The correlation of the solvatochromic Stokes-shifts with the microscopic solvent polarity parameter (E_T^N E_T^N ) was found to be superior to that obtained using bulk solvent polarity functions.     

Cyano‐Bridged ‘Oximato’ Complexes: Synthesis,Structure, and Catalase‐Like Activities

The reaction of the ‘oximato’‐ligand precursor A (Fig. 1) and metal salts with KCN gave two mononuclear complexes [ML(CN)(H₂O)_n](ClO₄) ( 1 and 2 ; L={N‐(hydroxy‐κO)‐α‐oxo‐N′‐[(pyridin‐2‐yl‐κN)methyl[1,1′‐biphenyl]‐4‐ethanimidamidato‐κN′}; M=Co^II ( 1 ), Cu^II ( 2 ); n=2 for Co^II, n=0 for Cu^II; Figs. 2 and 3). The new cyano‐bridged pentanuclear ‘oximato’ complexes [{ML(H₂O)_n(NC)}₄M¹(H₂O)_x](ClO₄)₂ ( 3 – 6 ) and trinuclear complexes [{ML(H₂O)_n(NC)}₂M¹L](ClO₄) ( 7 – 10 ) ([M¹=Mn^II, Cu^II; x=2 for Mn^II, x=0 for Cu^II] were synthesized from mononuclear complexes and characterized by elemental analyses, magnetic susceptibility, molar conductance, and IR and thermal analysis. The four [ML(CN)(H₂O)_n]⁺ moieties are connected by a metal(II) ion in the pentanuclear complexe 3 – 6 , each one involving four cyano bridging ligands (Fig. 4). The central metal ion displays a square‐planar or octahedral geometry, with the cyano bridging ligands forming the equatorial plane. The axial positions are occupied by two aqua ligands in the case of the central Mn‐atom. The two [ML(CN)(H₂O)_n]⁺ moieties and an ‘oximato’ ligand are connected by a metal(II) ion in the trinuclear complexes 7 – 10 , each one involving two cyano bridging ligands (Fig. 5). The central metal ions display a distorted square‐pyramidal geometry, with two cyano bridging ligands and the donor atoms of the tridentate ‘oximato’ ligand. Moreover catalytic activities of the complexes for the disproportionation of hydrogen peroxide (H₂O₂) were also investigated in the presence of 1H‐imidazole. The synthesized homopolynuclear Cu^II complexes 6 and 10 displayed eficiency in disproportion reactions of H₂O₂ producing H₂O and dioxygen thus showing catalase‐like activity.     

Novel glucose derived non-ionic gemini surfactants as reverse micellar systems for encapsulation of d- and l-enantiomers of some aromatic α-amino acids in n-hexane

Novel glucose-based non-ionic gemini amphiphiles comprising two sugar head groups, two hydrophobic tails having chain length of C₁₂, C₁₄, and C₁₈ and a –CH₂–Ar–CH₂– spacer have been synthesized. The head groups of the geminis consist of glucose entities (with reducing function blocked in cyclic acetal group) connected through C-6 to tertiary amines. These amphiphiles were explored as reverse micellar systems, for the encapsulation of d- and l-enantiomers of ultraviolet-absorbing aromatic α-amino acids histidine (H), phenylalanine (F), tyrosine (Y) and tryptophan (W) in n-hexane, without any added water. Reverse micellar studies revealed that aromatic α-amino acids were encapsulated in the sequence H?>?F?>?Y?>?W. In most cases, specifically for F, d-enantiomer was found better encapsulated than l-enantiomer in the reverse micellar probes of the gemini surfactants.