The Golod property for powers of ideals and Koszul ideals

Let S be a regular local ring or a polynomial ring over a field and I be an ideal of S. Motivated by a recent result of Herzog and Huneke, we study the natural question of whether $I^m$ is a Golod ideal for all $m\ge 2$. We observe that the Golod property of an ideal can be detected through the vanishing of certain maps induced in homology. This observation leads us to generalize some known results from the graded case to local rings and obtain new classes of Golod ideals.     

Quantitation of atorvastatin in human plasma using directly suspended acceptor droplet in liquid-liquid-liquid microextraction and high-performance liquid chromatography-ultraviolet detection

A simple and sensitive methodology based on liquid-liquid-liquid microextraction (LLLME) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) has been successfully developed for the determination of atorvastatin (AT) in human plasma. AT was first extracted from 4.5 mL acidic aqueous sample (diluted plasma, donor phase, pH 1) at temperature 45 °C through 400 μL 1-octanol for 4.5 min, while being agitated by a stirring bar at 1250 rpm. Then, a 5.5 μL free suspended basic aqueous droplet (acceptor phase, pH 10) was delivered to the top-center position of the organic membrane. The mixture was stirred at 650 rpm for 7.5 min and the analyte was back-extracted into the droplet. Finally, the acceptor phase was taken into a microsyringe and injected directly into the HPLC. An enrichment factor of 187 along with substantial sample clean up was obtained under the optimized conditions. The calibration curve showed linearity in the range of 1-500 ng mL⁻¹ with regression coefficient corresponding to 0.996. Limits of detection (S/N = 3) and quantification (S/N = 10) were 0.4 and 1 ng mL⁻¹, respectively. A reasonable relative recovery (91%) and satisfactory intra-assay (4.4-7.0%, n = 6) and inter-assay (4.9-7.7%, n = 8) precision illustrated good performance of the analytical procedure. This technique was eventually applied for the determination of AT in human plasma after oral administration of 40 mg single dose of drug. The protocol proved to be highly cost-effective and reliable for the screening purpose.     

The interactive effect of agitation condition and titania particle size in hydrothermal synthesis of titanate nanostructures

The nucleation and growth mechanisms of hydrothermal synthesized nanotitanates are proposed based on the interaction effect between agitation condition and pristine titania particle size. TEM examination and N₂ adsorption measurements revealed distinct morphology and textural properties depending on TiO₂ particle size in constant agitation condition. Regarding to the supersaturation degree, heterogeneous nucleation dominates for nanotubes formation from large particle size of raw material. On the other hand, homogeneous nucleation determines nanospheres formation from small particle size of raw material. The nanotubes have an outer diameter ranging from 8 to 10 nm and inner diameter of 2 to 3 nm. The nanospheres have diameters ranging from 50 to 100 nm.     

Preconcentration and determination of ceftazidime in real samples using dispersive liquid–liquid microextraction and high‐performance liquid chromatography with the aid of experimental design

A rapid and simple method for the extraction and preconcentration of ceftazidime in aqueous samples has been developed using dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography analysis. The extraction parameters, such as the volume of extraction solvent and disperser solvent, salt effect, sample volume, centrifuge rate, centrifuge time, extraction time, and temperature in the dispersive liquid–liquid microextraction process, were studied and optimized with the experimental design methods. Firstly, for the preliminary screening of the parameters the taguchi design was used and then, the fractional factorial design was used for significant factors optimization. At the optimum conditions, the calibration curves for ceftazidime indicated good linearity over the range of 0.001–10 μg/mL with correlation coefficients higher than the 0.98, and the limits of detection were 0.13 and 0.17 ng/mL, for water and urine samples, respectively. The proposed method successfully employed to determine ceftazidime in water and urine samples and good agreement between the experimental data and predictive values has been achieved.     

Multilayer film of thiourea and gold nanoparticles as an effective platform for immobilization of activated non-labeled-DNA and construction of an ultrasensitive electrochemical DNA biosensor

In this work, self assembly of thiourea and gold nano-particle multilayer built up on a thiourea modified gold nanoparticles Au electrode, has been used as a platform for immobilization of activated ss-DNA. Two NH₂ group of thiourea on a multilayer surface can interact with an activated phosphate group of non-labeled ss-DNA. Activated non-labeled ss-DNA was prepared using N-(3 dimethylaminopropyl)-N-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxy-succinimide (NHS). The whole DNA biosensor fabrication process was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods with the use of ferricyanide as an electrochemical redox indicator. Methylene Blue (MB) was used as the electrochemical indicator for monitoring the hybridization reaction after hybridized with the target ssDNA and the reduction current of MB intercalation decreased with increasing the concentration of target DNA, ranging from 7.9 × 10^–13 to 1.2 × 10^–8 M with a very low detection limit of 3.8 × 10^–13 M (S/N = 3).     

Aharonov–Casher effect for spin-1 particles in a non-commutative space

In this work, the Aharonov–Casher (AC) phase is calculated for spin-1 particles in a non-commutative space. The AC phase has previously been calculated from the Dirac equation in a non-commutative space using a gauge-like technique. In the spin-1 case, we use the Kemmer equation to calculate the phase in a similar manner. It is shown that the holonomy receives non-trivial kinematical corrections. By comparing the new result with the already known spin-1/2 case, one may conjecture a generalized formula for the corrections to holonomy for higher spins. PACS 02.40.Gh; 03.65.Pm     

A novel magnetic poly(aniline-naphthylamine)-based nanocomposite for micro solid phase extraction of rhodamine B

A novel Fe₃O₄–poly(aniline-naphthylamine)-based nanocomposite was synthesized by chemical oxidative polymerization process as a magnetic sorbent for micro solid phase extraction. The scanning electron microscopy images of the synthesized nanocomposite revealed that the copolymer posses a porous structure with diameters less than 50 nm. The extraction efficiency of this sorbent was examined by isolation of rhodamine B, a mutagenic and carcinogenic dye, from aquatic media in dispersion mode. Among different synthesized polymers, Fe₃O₄/poly(aniline-naphthylamine) nanocomposite showed a prominent efficiency. Parameters including the desorption solvent, amount of sorbent, desorption time, sample pH, ionic strength, extraction time and stirring rate were optimized. Under the optimum condition, a linear spiked calibration curve in the range of 0.35–5.00 μg L⁻¹ with R² = 0.9991 was obtained. The limits of detection (3S_b) and limits of quantification (10S_b) of the method were 0.10 μg L⁻¹ and 0.35 μg L⁻¹ (n = 3), respectively. The relative standard deviation for water sample with 0.5 μg L⁻¹ of RhB was 4.2% (n = 5) and the absolute recovery was 92%. The method was applied for the determination of rhodamine B in dishwashing foam, dishwashing liquid, shampoo, pencil, matches tips and eye shadows samples and the relative recovery percentage were in the range of 94–99%.     

Comparative DFT study to determine if α-oxoaldehydes are precursors for pentosidine formation

We report a comprehensive density functional theory (DFT) study of the mechanism of pentosidine formation. This work is a continuation of our earlier studies in which we proposed pathways for formation of glucosepane (J. Mol. Model. 2011, pp 1-15, DOI 10.1007/s00894-011-1161-x), GODIC (glyoxal-derived imidazolium cross-link), and MODIC (methyl glyoxal-derived imidazolium cross-link; J. Phys. Chem. 2011, 115, pp 13542-13555). Here we show that formation of pentosidine via reaction of α-oxoaldehydes with lysine and arginine in aqueous solution is possible thermodynamically and kinetically, in good agreement with the available experimental evidence. Five pathways, A-E, were characterized, as in our previous GODIC and MODIC work. In pathways A and B, a Schiff base is first formed from lysine and methyl glyoxal (MGO), and this is followed by addition of arginine and glyoxal (GO). By contrast, in pathways C, D, and E, addition of arginine to MGO occurs first, resulting in the formation of imidazolone, which then reacts with lysine and GO to give pentosidine. Our calculations show that the reaction process is highly exergonic and that the three pathways A, C, and E are competitive. These results serve to underline the potentially important role that α-oxoaldehydes play as precursors in pentosidine formation in the complex field of glycation.     

Highly Selective and Sensitive Aggregation-Induced Emission of Fluorescein-Coated Metal Oxide Nanoparticles

We report the synthesis, characterization, and photophysical properties of novel metal oxide nanoparticles (NPs) coated with specially designed fluorescein substituents which are capped with electron-withdrawing groups. The fluorescein-coated nanoparticles were synthesized in excellent yields, and their structures were confirmed using various advanced spectroscopic, instrumental, and surface analysis techniques, revealing the formation of the target functionalized nanoparticles (FNPs) which show superior chemical and thermal stabilities. In addition, the photophysical properties of the FNPs were examined using UV-visible absorption and fluorescence spectroscopy. These latter techniques disclosed aggregation-induced emission (AIE) properties for most of the target FNPs, namely those which are soluble in common organic solvents at selective concentration ranges of water fractions in the solvent mixture.     

Study of Phenolic Compounds Removal from Aqueous Solution by Polymeric Sorbent

This study describes preparation of polymeric sorbent and its use in removal of some phenolic compounds from aqueous solution. The polymer [poly(ethylene glycol dimethacrylate ‐ co‐methacrylic acid)] is stable both thermally and chemically. High temperature (200°C) and strong acidic or alkaline solutions (4 M HCl or NaOH) are not effective on the adsorption characteristics of polymer. Removal process of phenols is pH‐dependent and from the obtained results pH = 7.0 was selected as an optimum pH. Different parameters affecting sorption process were tested, and it was found that the kinetic of sorption is fast; therefore, column experiment at higher flow rates or batch experiment can be used. Methanol was selected as a washing solvent in column experiments. Capacity of sorbent for the studied compounds was tested and the following order was obtained: p‐chlorophenol > p‐aminophenol > phenol.