Scrupulous recognition of biologically important acids by fluorescent “turn off-on” mechanism of thaicalix reduced silver nanoparticles

Water dispersible silver nanoparticles(AgNps) were prepared using thiacalix[4]arene tetrahydrazide(TCTH) as a reducing and stabilizing agent.TCTH-AgNps were characterized by surface plasmon resonance(SPR),transmission electron microscopy(TEM) and energy dispersive X-ray(EDX).Relatively uniform 20 nm spherical particles of TCTH-AgNps were efficiently formed over a pH range of 5-9 and from 10-40 ℃.The interaction behavior of TCTH-AgNps with different amino acids was investigated using spectrophotometry and spectrofluorimetry.Among the amino acids tested,only tryptophan and histidine showed fluorescence quenching and fluorescence enhancement,respectively.The linear detection range by Stern-Volmer plot was 5 nmol/L to 0.48 μmol/L for tryptophan and 4 nmol/L to 0.54 μmol/L for histidine.TCTH-AgNps were able to effectively reduce the levels of gram-positive bacteria,gram-negative bacteria,and fungi.These properties argue for the potential use of TCTH-AgNps as detectors of histidine and tryptophan and as antibiotics.     

A validated HPTLC method for quantification of cordifolioside A, 20-β-hydroxyecdysone and columbin with HPTLC–ESI–MS/MS characterization in stems of Tinospora cordifolia

JPC – Journal of Planar Chromatography – Modern TLC - The objective of the present work was to develop a simple, specific, and fast high-performance thin-layer chromatographic (HPTLC)...     

Extension of the angular spectrum method to calculate pressure from a spherically curved acoustic source

The angular spectrum method is an accurate and computationally efficient method for modeling acoustic wave propagation. The use of the typical 2D fast Fourier transform algorithm makes this a fast technique but it requires that the source pressure (or velocity) be specified on a plane. Here the angular spectrum method is extended to calculate pressure from a spherical transducer-as used extensively in applications such as magnetic resonance-guided focused ultrasound surgery-to a plane. The approach, called the Ring-Bessel technique, decomposes the curved source into circular rings of increasing radii, each ring a different distance from the intermediate plane, and calculates the angular spectrum of each ring using a Fourier series. Each angular spectrum is then propagated to the intermediate plane where all the propagated angular spectra are summed to obtain the pressure on the plane; subsequent plane-to-plane propagation can be achieved using the traditional angular spectrum method. Since the Ring-Bessel calculations are carried out in the frequency domain, it reduces calculation times by a factor of approximately 24 compared to the Rayleigh-Sommerfeld method and about 82 compared to the Field II technique, while maintaining accuracies of better than 96% as judged by those methods for cases of both solid and phased-array transducers.     

Magnetic properties of the mixed spinel NiAlxCrxFe2-2xO4

The crystal structure and magnetic properties of the Al and Cr cosubstituted disordered spinel series NiAl_xCr_xFe_2-2xO₄ are investigated by means of Xray diffraction, magnetization, a.c. susceptibility and Mössbauer effect measurements. The lattice constants are determined and the applicability of Vegard's law has been tested. The variation of the saturation magnetic moment per formula unit measured at 77 K and 300 K with Al–Cr content is satisfactorily explained on the basis of Neel's collinear spin ordering model for =0.1–0.5. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe³⁺ at tetrahedral (A) and octahedral (B) sites for 0.5. Mössbauer results confirm a collinear ferrimagnetic structure for =0.1–0.5. The Curie temperature obtained from a.c. susceptibility decreases nearly linear with increase of Al–Cr concentration from =0.1 to 0.5.     

Metal-Ylide Complex-Initiated Radical Copolymerization of Methylmethacrylate and Styrene

Abstract

Phenacyl dimethylsulfonium ylide complex of mercuric chloride (PDSY-HgCl₂)-initiated radical copolymerization of styrene with methylmethacrylate (MMA) at 85 ± 0.1°C using dioxane as an inert solvent yields random copolymers as evidenced by NMR spectroscopy. The kinetic equation for the present system was R_p α [PDSY-HgCl₂]^0.5 [Sty]^1.0 [MMA]^1.0. The values of energy of activation (ΔE) and k² _p/k₁ were 48.0 kJ mol^?1 and 8.6 × 10^?4 L mol^?1 s^?1, respectively. The mechanism of the reaction has also been proposed for the present system. The properties of copolymer were studied in the form of film. The film was highly absorptive for nitric acid but less absorptive for acetic acid. The film was water impermeable.     

Inhibition Effects of Dilute-Acid Prehydrolysate of Corn Stover on Enzymatic Hydrolysis of Solka Floc

Dilute-acid pretreatment liquor (PL) produced at NREL through a continuous screw-driven reactor was analyzed for sugars and other potential inhibitory components. Their inhibitory effects on enzymatic hydrolysis of Solka Floc were investigated. When the PL was mixed into the enzymatic hydrolysis reactor at 1:1 volume ratio, the glucan and xylan digestibility decreased by 63% and 90%, respectively. The tolerance level of the enzyme for each inhibitor was determined. Of the identified degradation components, acetic acid was found to be the strongest inhibitor for cellulase activity, as it decreased the glucan yield by 10% at 1 g/L. Among the sugars, cellobiose and glucose were found to be strong inhibitors to glucan hydrolysis, whereas xylose is a strong inhibitor to xylan hydrolysis. Xylo-oligomers inhibit xylan digestibility more strongly than the glucan digestibility. Inhibition by the PL was higher than that of the simulated mixture of the identifiable components. This indicates that some of the unidentified degradation components, originated mostly from lignin, are potent inhibitors to the cellulase enzyme. When the PL was added to a simultaneous saccharification and co-fermentation using Escherichia coli KO11, the bioprocess was severely inhibited showing no ethanol formation or cell growth.     

间苯二酚保护的抗菌Pd纳米粒子催化C-C偶联反应活性(英文)

合成了新型四甲氧基间苯二酚-四酰肼(TMRTH),并作为还原剂和封端剂用于合成水分散性稳定的Pd纳米粒子(PdNPs).采用紫外-可见光谱、透射电镜、能量散射谱和粉末X射线衍射对所得TMRTH-PdNPs样品进行了表征.结果表明,所制纳米粒子具有多分散性,粒径为5±2 nm,并在Suzuki-Miyuara交叉偶联反应中可重复使用5次,具有较高的催化效率.该纳米催化剂在反应时间、催化剂用量和可重复使用性能等方面优于常规Pd催化剂.另外,TMRTH-PdNPs样品对革兰(氏)阳性菌具有较好的抗菌活性,因而有望用于一些生物领域.     

Phenacyl dimethyl sulphonium ylide-mercuric chloride complex initiated radical polymerization of methylmethacrylate

Summary The metal-ylide-initiated radical polymerization of methylmethacrylate (MMA) at 85±0.1°C using dioxan as inert solvent was investigated by dilatometry. Kinetic parameters, average rate of polymerization (R _p ) and reaction orders with respect to initiator and monomer have been determined and are 0.33±0.1 and 1.33, respectively. Polymerization was inhibited by hydroquinone and non-polar solvents, but is favoured by polar solvent. The activation energy (E) and k _p ² /k_t values were 64.0 kJ mol^–1 and 3.3×10^–2 l mol^–1 s^–1 respectively. A suitable mechanism consistent with the observed kinetic data is proposed.     

Magnetic properties of the mixed spinel Co1+xSnxFe2−2xO4

The structural and magnetic properties of the mixed spinel Co_1+xSn_xFe_2?2xO₄ system for 0.1≤x≤0.5 have been studied by means of X‐ray diffraction, magnetization, a.c. susceptibility and Mössbauer effect measurements. X‐ray intensity calculations indicate that Sn⁴⁺ ions occupy only octahedral (B) sites replacing Fe³⁺ ions and the added Co²⁺ ions substitute for A‐site Fe³⁺ ions. The lattice constants are determined and the applicability of Vegard's law has been tested. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe³⁺ at tetrahedral (A) and octahedral (B) sites for x≤0.4. The Mössbauer intensity data show that Sn possesses a preference for the B‐site of the spinel. As expected, the hyperfine field and Curie temperature determined from a.c. susceptibility decreases with increasing Sn content. The variation of the saturation magnetic moment per formula unit measured at 77 and 300 K with Sn content is satisfactorily explained on the basis of Néel's collinear spin ordering model for x=0.1–0.4.