稻壳灰负载FeCl2·2H2O:一个温和高效的多相催化剂用于Friedlnder杂成环反应合成多取代喹啉（英文）

Rice husk ash was used as a new, green, and cheap adsorbent for FeCl3. Characterization of the obtained reagent showed that rice husk ash supported FeCl2·2H2O was formed. This reagent is efficient at catalyzing the synthesis of multisubstituted quinolines by the Friedl鋘der heteroannulation of o‐aminoaryl ketones with ketones or β‐diketones under mild reaction conditions. This methodology allows for the synthesis of a broad range of substituted quinolines in high yields and with excellent regioselectivity in the absence of a solvent.     

Direct measurements of C3F7I dissociation rate constants using a shock tube ARAS technique

This work presents the first direct experimental study on the thermal unimolecular decomposition of n-C₃F₇I. Experiments were performed behind incident and reflected shock waves using the atomic resonance absorption spectroscopy (ARAS) technique on a resonant line of atomic iodine at 183.04 nm. The reaction C₃F₇I + Ar → C₃F₇ + I + Ar (1) was studied at specific temperature (800–1200 K) and pressure (0.6–8.3 bar) ranges. Under experimental conditions, the obtained values of the rate constant at temperatures below 950 K are close to the high-pressure limit; however, considering theoretical calculations, the influence of pressure on the rate constant at elevated temperatures remains noticeable. The resulting value of the experimental rate constant of reaction 1 is presented in the following Arrhenius form: Experimental data were found to correlate with the results of the Rice–Ramsperger–Kassel–Marcus –master equation analysis based on quantum-chemical calculations. The following low- and high-pressure limiting rate coefficients were obtained over the temperature range T = 300–3000 K: with the center broadening factor F_c = 0.119.     

Analytical evaluation of enzyme-linked immunosorbent assay for neonicotinoid dinotefuran for potential application to quick and simple screening method in rice samples

The analytical performance of a kit-based enzyme-linked immunosorbent assay (ELISA) for the determination of a neonicotinoid insecticide dinotefuran residue in rice samples is addressed. The sensitivity (I₅₀ value) was 5.4 ng/mL, with the limit of detection, 0.6 ng/mL and the dynamic range from 1.0 to 30 ng/mL. The ELISA showed substantially high specificity toward dinotefuran besides clothianidin (184%). For rice samples, dinotefuran was extracted with methanol and the extracts were directly determined with the ELISA because of no significant matrix interference. Good recoveries were observed and ranged from 92.5% to 113.2% with coefficients of variation below 10%. The results obtained with the ELISA correlated well with those by the HPLC method for rice samples (r > 0.98). These findings strongly indicate that the evaluated and validated ELISA has a potential utility in a quick, simple, and reliable residue analysis, especially a screening method before shipment contributing to food safety.     

Three-phase free-water flash calculations using a new Modified Rachford–Rice equation

A novel Modified Rachford–Rice equation is developed for three-phase equilibrium calculations in hydrocarbon–water systems, based on the free-water assumption, i.e., the water-rich liquid phase consists of pure water only. In the inner loop of the flash algorithm, the three-phase problem (consisting in a system of two non-linear equations) is replaced by a pseudo-two-phase problem (consisting in a non-linear equation). Unlike previous formulations, the new Modified Rachford–Rice function is guaranteed to monotonically decrease between two adjacent asymptotes. The negative flash concept is used, and a search window is proposed for the vapor fraction. The new free-water flash method proved to be robust, and excellent agreement between full three-phase flash and pseudo-two-phase free-water flash was obtained for various test problems. The proposed method is very useful in compositional reservoir simulation of certain oil recovery methods and in process simulation.     

用近红外透射光谱技术测定精米蛋白质含量研究

应用近红外透射光谱技术．采用3种不同回归统计分析方法建立业米蛋白质含量(PC)定量回归方程。结果表明,用改进的最小二乘法(MPLS)、偏最小二乘法(PLS)和主成分回归法(PCR)进行饺正时．校正标准误差(SEC)、交叉检验标准误差(SECV)分别为0．1258、0．134O(MPLS)．0．1177、0．1175(PLS)．0．1207、0．1275(PCR)校正相关系数(RSQ)和交叉验证相关系数(1-VR)分别为0．9941、0．9931(MPLS)．0．9950、0．9942(PLS)．0．9947、0．9942(PCR)。由此可见,3种回归统计方法在建立业米蛋白质含量回归方程时差异不明显．都具有较好的预测效果。近红外透射光谱法作为一种快速而准确的定量分析手段,在稻米加工企业品质管理、大米品质分析和大米贸易检测上有广阔的应用前景。     

Trace analysis of some organophosphorus pesticides in rice samples using ultrasound‐assisted dispersive liquid–liquid microextraction and high‐performance liquid chromatography

An ultrasound‐assisted dispersive liquid–liquid microextraction based on solidification of a floating organic drop method followed by high‐performance liquid chromatography was developed for the extraction, preconcentration, and determination of trace amounts of organophosphorus pesticides in rice samples. Variables affecting the performance of both steps were thoroughly investigated. Some effective parameters on extraction were studied and optimized. Under the optimum conditions, recoveries for rice sample are in the range of 58.0–66.0%. The calibration graphs are linear in the range of 4–800 μg/kg and, limits of detection and limits of quantification are in the range of 1.5–3 and 4.2–8.5 μg/kg, respectively. The relative standard deviation for 50.0 μg/kg of organophosphorus pesticides in rice sample are in the range of 4.4–5.1% (n = 5). The obtained results show that proposed method is a fast and simple method for the determination of pesticides in cereals.     

Escaping the Tyranny of Carbothermal Reduction: Fumed Silica from Sustainable,Green Sources without First Having to Make SiCl4

Fumed silica is produced in 1000 tons per year quantities by combusting SiCl₄ in H₂/O₂ flames. Given that both SiCl₄ and combustion byproduct HCl are corrosive, toxic and polluting, this route to fumed silica requires extensive safeguards that may be obviated if an alternate route were found. Silica, including rice hull ash (RHA) can be directly depolymerized using hindered diols to generate distillable spirocyclic alkoxysilanes or Si(OEt)₄. We report here the use of liquid‐feed flame spray pyrolysis (LF‐FSP) to combust the aforementioned precursors to produce fumed silica very similar to SiCl₄‐derived products. The resulting powders are amorphous, necked, <50 nm average particle sizes, with specific surface areas (SSAs) of 140–230 m² g^?1. The LF‐FSP approach does not require the containment constraints of the SiCl₄ process and given that the RHA silica source is produced in million ton per year quantities worldwide, the reported approach represents a sustainable, green and potentially lower‐cost alternative.     

Preparation,characterization and application of RHA/TiO2 nanocomposites in the acetylation of alcohols,phenols and amines

In this work, anatase-phase nano-titania was prepared by embedding in rice husk ash, and identified using a variety of techniques. The obtained nanocomposite (RHA/TiO₂) was used as a green and inexpensive catalyst for the promotion of the acetylation of alcohols, phenols and amines with Ac₂O at room temperature under solvent free conditions. The procedure gave the products in excellent yields during all reaction times. Also this catalyst can be reused for several times without loss of its catalytic activity.     

Chemical Constituents from the Hulls of <Emphasis Type="Italic">Oryza sativa</Emphasis> with Cytotoxic Activity

Five new compounds, orizaterpenol (1), orizaterpenoid (2), orizaterpenyl benzoate (3), orizanor-diterpenyl benzoate (4), and orizaditerpenyl benzoate (5), along with nine known compounds, were isolated and identified from the rice hulls of Oryza sativa. Their structures were elucidated with the help of different spectroscopic techniques. Orizaterpenol (1) and the known momilactone A (6) and B (7) were found to have cytotoxic effects against P388 murine leukaemia cells, while the other new and known compounds exhibited weak cytotoxicity.__________Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 146–151, March–April, 2005.