Design and numerical analysis of a photonic crystal fiber (PCF)-based flattened dispersion THz waveguide

Optical Review - We present the modeling of a porous core dispersion flatten photonic crystal fiber (PCF) for the fruitful transmission of THz signals. The model comprises only rectangular holes in...     

Hydrotropic Behavior of Sodium Salicylate in Presence of Additives

It is well known that, like surfactants aggregating at a certain concentration (called critical micelle concentration, CMC), hydrotropes also have minimum hydrotrope concentration (MHC). However, unlike surfactant CMC, this MHC value is usually very high, thereby reducing their application. In this paper we report the results of conductivity and viscosity measurements with a well known hydrotrope sodium salicylate (NaSal) solutions in presence and absence of additives (propanol, PrOH; butanol, BuOH; pentanol, PeOH and tetrabutylammonium bromide, Bu₄NBr). We have found that MHC value of NaSal decreases in presence of additives. Alcohols increase the hydrophobic interactions and decrease the MHC while Bu₄NBr, in addition to ameliorating the hydrophobic interactions, reduces the charge on head groups and MHC decreases more steeply in its presence. Increased solubility of riboflavin in NaSal containing the above additives corroborates the results.     

Multispectroscopic Studies on the Interaction of a Platinum(II) Complex Containing l-Histidine and 1,10-Phenanthroline Ligands with Bovine Serum Albumin

The mechanism of the interaction between bovine serum albumin (BSA) and [Pt(phen) (histidine)]⁺ complex was studied employing ultraviolet (UV) absorption, circular dichroism (CD), FT-IR, differential pulse voltammetry (DPV), and fluorescence spectral methods. Fluorescence data showed that the intrinsic fluorescence of BSA was strongly quenched by Pt(II) complex in terms of an untypical static quenching process. The corresponding number of binding sites (n) and binding constant (K _b) of BSA and complex at 283, 298, and 310 K were calculated to be 0.61?×?10⁶, 19?×?10⁶, and 42?×?10⁶ M^?1, respectively. The results showed that the increasing temperature improves the stability of the complex–BSA system, which results in a higher binding constant and the number of binding sites of the complex–BSA system. The positive ΔH and positive ΔS indicated that hydrophobic forces might play a major role in the binding between complex and BSA. Based on Forster’s theory of non-radiation energy transfer, the binding distance (r) between the donor (BSA) and acceptor (Pt(II) complex) was evaluated. The results of CD, UV–vis, DPV, and FT-IR spectroscopy showed that the binding of Pt(II) complex to BSA induced conformational changes in BSA     

Prediction of optimal conditions for verbal-communication quality in eating establishments

This paper discusses the prediction of verbal-communication quality in eating establishments (EEs). EEs contain talkers and listeners who require high speech intelligibility at their tables, and high speech privacy between tables. Using catt-Acoustic, verbal-communication quality--quantified by speech transmission index (STI)--in models of three existing EEs was predicted. Talker voice-output levels were predicted using an existing empirical model accounting for the Lombard effect. With these, catt-Acoustic predicted impulse responses, speech levels and noise levels at primary and secondary listener positions, and the corresponding STIs. The untreated EEs were first modeled for various talker and listener positions, and occupancies. Then various treated configurations, involving reduced volume, increased absorption and barriers were studied to determine the effectiveness of the treatments. The results suggest that placing barriers around tables can be an effective way to achieve good verbal-communication quality. Increasing the absorption of the room surfaces or decreasing the ceiling height to control reverberation may not be effective. However, increasing the surface absorption and putting barriers around tables may achieve optimal speech conditions in EEs. Subdividing large EEs into smaller ones can also be effective.     

Diagnosis of Toxoplasmosis Using a Synthetic Glycosylphosphatidylinositol Glycan

Around 2 billion people worldwide are infected with the apicomplexan parasite Toxoplasma gondii which induces a variety of medical conditions. For example, primary infection during pregnancy can result in fetal death or mental retardation of the child. Diagnosis of acute infections in pregnant women is challenging but crucially important as the drugs used to treat T. gondii infections are potentially harmful to the unborn child. Better, faster, more reliable, and cheaper means of diagnosis by using defined antigens for accurate serological tests are highly desirable. Synthetic pathogen‐specific glycosylphosphatidylinositol (GPI) glycan antigens are diagnostic markers and have been used to distinguish between toxoplasmosis disease states using human sera.     

Application of modified multiwalled carbon nanotubes for palladium preconcentration and determination in water and soil samples by flame atomic absorption spectrometry

A new solid-phase extraction method for determination of palladium by atomic absorption spectrometry is described. Multiwalled carbon nanotube (MWCNT) modified with 1-butyl 3-methyl imidazolium hexafluorophosphate (MWCNT-[BMIM]PF₆) and supported on sawdust was used as an adsorbent for preconcentration of palladium. Palladium ions are retained on (MWCNT-[BMIM]PF₆) adsorbent as [PdI₄]^2? and eluted from the column with a thiosulfate–ammonia mixture. The optimum conditions for the adsorption were evaluated by changing various parameters such as pH, sample volume, concentration and volume of eluent, iodide concentration and interfering ions to achieve highest sensitivity and selectivity. The calibration graph was linear in the range of 2–120 ng mL^?1 of palladium in the initial solution and the limit of detection based on 3S_b was 0.41 ng mL^?1. The method was applied to the determination of palladium in water, wastewater and soil samples.     

Simple optical determination of silver ion in aqueous solutions using benzo crown-ether modified gold nanoparticles

We describe a method for the modification of gold nanoparticles (Au-NPs) with benzo-15-crown-5 that led to the development of a colorimetric assay for Ag(I) ion. The brown color of a solution of the modified Au-NPs turns to purple on addition of Ag(I) ion. The ratio of the UV–vis absorption at 600 nm and 525 nm is proportional to the concentration of Ag(I) ions in the range from 20 to 950 nM, and the detection limit is 12.5 nM. Other metal ions do not interfere if present in up to millimolar concentrations. The method enables a rapid determination of Ag(I) in lake and drinking water and is amenable to bare-eye readout.

Determination of caffeine in black tea leaves by Fourier transform infrared spectrometry using multiple linear regression

A simple and fast analytical procedure was developed for the determination of caffeine in black tea leaves. The method is based on multiple linear regression treatment of Fourier transform infrared spectrometric data obtained in the wave number range 1800–1300 cm⁻¹ after extraction of caffeine in CHCl₃ from tea samples, wetted with an aqueous solution of NH₃ (0.1 M). The procedure requires no complex sample preparation. It provided a limit of detection of 0.035 mg/ml, a sampling frequency of 6 h⁻¹ and a coefficient of variation of 0.8% for five independent measurements of a tea sample with 3.68% w/w caffeine content. This procedure provides a drastic reduction in the consuming organic solvent for each sample compare to that of the reference chromatographic determination. The accuracy of technique is evaluated by comparing the obtained results with those of a reference HPLC technique. An average value of 3.60±0.07% w/w was obtained by HPLC for a powdered tea sample which is compromising when is compared to 3.68±0.03% (w/w) obtained by this FTIR technique.