g-natural symmetries on tangent bundles

The study of symmetries is a well known research topic in differential geometry with relevant physical interpretations. Given a Riemannian manifold $(M,g)$, we consider pseudo-Riemannian g-natural metrics G on its tangent bundle $TM$ and characterize conformal, homothetic and Killing vector fields of $(TM,G)$ obtained from natural lifts of vector fields of M.     

Catalytically induced electrokinetics for motors and micropumps

We have explored the role of electrokinetics in the spontaneous motion of platinum-gold nanorods suspended in hydrogen peroxide (H2O2) solutions that may arise from the bimetallic electrochemical decomposition of H2O2. The electrochemical decomposition pathway was confirmed by measuring the steady-state short-circuit current between platinum and gold interdigitated microelectrodes (IMEs) in the presence of H2O2. The resulting ion flux from platinum to gold implies an electric field in the surrounding solution that can be estimated from Ohm's Law. This catalytically generated electric field could in principle bring about electrokinetic effects that scale with the Helmholtz-Smoluchowski equation. Accordingly, we observed a linear relationship between bimetallic rod speed and the resistivity of the bulk solution. Previous observations relating a decrease in speed to an increase in ethanol concentration can be explained in terms of a decrease in current density caused by the presence of ethanol. Furthermore, we found that the catalytically generated electric field in the solution near a Pt/Au IME in the presence of H2O2 is capable of inducing electroosmotic fluid flow that can be switched on and off externally. We demonstrate that the velocity of the fluid flow in the plane of the IME is a function of the electric field, whether catalytically generated or applied from an external current source. Our findings indicate that the motion of PtAu nanorods in H2O2 is primarily due to a catalytically induced electrokinetic phenomenon and that other mechanisms, such as those related to interfacial tension gradients, play at best a minor role.     

Organocatalysis in synthesis: L-proline as an enantioselective catalyst in the synthesis of pyrans and thiopyrans

The multicomponent reaction (MCR) of aromatic aldehydes 1 and malononitrile (2) with active methylenes 5a-h in the presence of L-proline produced pyrans and thiopyrans 6a-h stereospecifically and in good yields. Moreover a novel MCR of ethyl propiolate (8) with 1 and 2 in the presence of L-proline to afford (R)-polysubstituted pyran is also reported. X-ray structures, e.e. and optical activity of the synthesized compounds indicated that L-proline as a catalyst is responsible for the observed enantioselectivity in the studied reactions.     

Exploration of structural,optical, and photoluminescent properties of (1-x)NiCo2O4/xPbS nanocomposites for optoelectronic applications

The (1-x)NiCo₂O₄/xPbS (0≤ x≤ 0.2) nanocomposite samples are synthesized using the hydrothermal and thermolysis procedures. The different phases developed in the obtained nanocomposite samples are accurately determined using the x-ray diffraction technique equipped with a line-detector. The percentage of the formed phases (NiCo₂O₄ (NCO), PbS, PbSO₄), structural and microstructure parameters are determined using Rietveld quantitative phase analysis. The transmission electron microscope (TEM) images and Rietveld analysis reveal almost isotropic particle size in the nano range with a very narrow size distribution. The obtained phase percentage of PbS and PbSO₄ are smaller than nominated values (x) suggesting dissolving of some Pb and S ions into NCO which is then confirmed by the analysis of Fourier-transform infrared (FTIR) spectra of nanocomposite samples. The absorption spectra are modified upon doping NCO with PbS. The optical band gaps of the nanocomposites increase as the amount of PbS augments. The effect of alloying on extinction coefficient, refractive index, dielectric constant, optical conductivity, the intensity, and emitted color from the photoluminescence of the nanocomposite samples are also studied. The refractive index value of NCO and NCO-PbS nanocomposite samples exhibit normal dispersions. The photoluminescent measurements reveal that the NCO-PbS nanocomposites can emit a violet color. The improvement in the values of the nonlinear optical (NLO) parameters of pristine NCO at high frequencies or the nanocomposite samples at low frequencies, are made them used in NLO photonic devices.     

Thermosensitive dendrimer formulation for drug delivery at physiologically relevant temperatures

A simple and versatile dendrimer based platform to deliver therapeutic agents at temperatures within the physiological range, is reported. Lipoic acid conjugated at the periphery of the thermosensitive dendrimer formulations undergoes slow and sustained release at 37-42 °C, and rescues the cells from oxidative stress and a pro-inflammatory endotoxic agent.     

Digitally enhanced thin layer chromatography for simultaneous determination of norfloxacin and tinidazole with the aid of Taguchi orthogonal array and desirability function approach: Greenness assessment by analytical Eco‐Scale

In this study, an eco‐friendly fast simple method was developed for simultaneous determination of norfloxacin and tinidazole based on thin‐layer chromatography and image‐processing analysis. The binary mixture was separated using reversed phase ‐ thin layer chromatography plates and 30% trifluoroacetic acid only as mobile phase. Mobile phase composition was optimized using Taguchi orthogonal array and Derringer's desirability function. The plates were viewed under UV lamp and photographed by iPhone camera followed by image processing with Fiji software using integrated density as the measured response. As decreasing illumination increases the sensitivity of the method, this method was applied on two different ranges for each drug. The first one was 0.6–6.0 and 0.9–9.0 µg/spot for norfloxacin and tinidazole, respectively measured on the original image with normal illumination. The second one was measured after decreasing the illumination of the captured images at 0.06–0.60 and 0.09–0.90 µg/spot for norfloxacin and tinidazole, respectively. The proposed method was successfully applied for the determination of both drugs in tablets dosage form without interference from the commonly encountered excipients. Analytical Eco‐Scale was used to evaluate the greenness profile of the proposed method and it was found to be excellent green analytical method.     

Synthesis of novel phthalazine derivatives as pharmacological activities

Phthalazine derivatives attached to amino acid derivatives were synthesized with high yields. The reaction of phthalazine derivatives with different phthalyl and tosylamino acids such as glycine, alanine, phenylalanine, valine, serine, and threonine in the presence of N,N-dicyclo hexylcarbodiimide (DCC) as a dehydrating agent reagent yielded high yields of the afforded compounds. Phthalylamino acids derivatives were obtained by deprotection of phthalazine derivatives, with the latter heating with hydrazine hydrate. The chemical structures of all phthalazine derivatives were affirmed by elemental analysis and spectral data (IR, MS, ¹HNMR, and ¹³C NMR). Screening out and estimation of the synthesized derivatives for their cytotoxic and antioxidant activity were done, and most of them showed powerful activity in comparison with standard drugs.     

Bidentate dicarboxylate capping groups and photosensitizers control the size of IrO2 nanoparticle catalysts for water oxidation

Dicarboxylic acid ligands (malonate, succinate, and butylmalonate) stabilize 2 nm diameter IrO2 particles synthesized by hydrolysis of aqueous IrCl(6)2- solutions. Analogous monodentate (acetate) and tridentate (citrate) carboxylate ligands, as well as phosphonate and diphosphonate ligands, are less effective as stabilizers and lead to different degrees of nanoparticle aggregation, as evidenced by transmission electron microscopy. Succinate-stabilized 2 nm IrO2 particles are good catalysts for water photo-oxidation in persulfate/sensitizer solutions. Ruthenium tris(2,2'-bipyridyl) sensitizers containing malonate and succinate groups in the 4,4'-positions are also good stabilizers of 2 nm diameter IrO2 colloids. The excited-state emission of these bound succinate-terminated sensitizer molecules is efficiently quenched on a time scale of approximately 30 ns, most likely by electron transfer to Ir(IV). In 1 M persulfate solutions in pH 5.8 Na2SiF6/NaHCO3 buffer solutions, the excited-state of the bound sensitizer is quenched oxidatively on the time scale of approximately 9 ns. Electron transfer from Ir(IV) to Ru(III) occurs with a first-order rate constant of 8x10(2) s(-1), and oxygen is evolved. The turnover number for oxygen evolution under these conditions was approximately 150. The sensitizer-IrO2 diad is thus a functional catalyst for photo-oxidation of water, and may be a useful building block for overall visible light water splitting systems.     

Acoustic Propulsion of Nanorod Motors Inside Living Cells

The ultrasonic propulsion of rod‐shaped nanomotors inside living HeLa cells is demonstrated. These nanomotors (gold rods about 300 nm in diameter and about 3 μm long) attach strongly to the external surface of the cells, and are readily internalized by incubation with the cells for periods longer than 24 h. Once inside the cells, the nanorod motors can be activated by resonant ultrasound operating at 4 MHz, and show axial propulsion as well as spinning. The intracellular propulsion does not involve chemical fuels or high‐power ultrasound and the HeLa cells remain viable. Ultrasonic propulsion of nanomotors may thus provide a new tool for probing the response of living cells to internal mechanical excitation, for controllably manipulating intracellular organelles, and for biomedical applications.     

Multiobjective optimization strategy based on desirability functions used for the microemulsion liquid chromatographic separation and quantification of norfloxacin and tinidazole in plasma and formulations

The aim of the present study was to optimize a microemulsion liquid chromatography method for the simultaneous determination of norfloxacin and tinidazole binary mixture using a chemometric protocol. Optimization experiments were conducted through a process of screening and optimization. A 2^7‐4 fractional factorial design was used as screening design. While the location of optimum conditions was established by applying Derringer's desirability function. The optimal mobile phase composition was predicted to be: 3.5% w/v SDS, 10.03% v/v 1‐propanol, 0.5% v/v 1‐octanol, and 0.3% triethylamine in 0.02 M phosphoric acid at pH 6.5. The mobile phase was delivered isocratically at a flow rate of 1 mL/min with UV detection at 290 nm. Tinidazole and norfloxacin were eluted with retention times of 1.8 and 5.8 min, respectively. The calibration plots displayed good linear relationships in the concentration ranges of 0.5–50 and 0.75–75 μg/mL for norfloxacin and tinidazole, respectively. The method was successfully applied for determination of both drugs in pharmaceutical dosage forms and real human plasma. Where the accuracy was proved by the low values of % error and high values of recovery, also the relative standard deviation for the results did not exceed 1.5%, proving the precision of the method.