Hydrophilic Characteristics of Cellulose Treated with Saturated Water Vapor

The reaction of water with cellulose treated with saturated water vapor at various temperatures for various times was studied. Trends in variation of its sorption and hydrophilic characteristics were examined.     

Fenton’s reagent-mediated degradation of residual Kraft black liquor

In this work, the effect of Fento’s reagent on the degradation of residual Kraft black liquor was investigated. The effect of Fenton’s reagent on the black liquor degradation was dependent on the concentration of H₂O₂. At low concentrations (5 and 15 mM) of H₂O₂, Fenton’s reagent caused the degradation of phenolic groups (6.8 and 44.8%, respectively), the reduction of reaction medium pH (18.2%), and the polymerization of black liquor lignin. At a high concentration (60 mM) of H₂O₂, Fenton’s reagent induced an extensive degradation of lignin (95–100%) and discoloration of the black liquor. In the presence of traces of iron, the addition of H₂O₂ alone induced mainly lignin fragmentation. In conclusion, Fenton’s reagent and H₂O₂ alone can degrade residual Kraft black liquor under acidic conditions at room temperature.     

A Femtosecond Pulse Train with a Selectable Carrier–Envelope Offset Phase

Optics and Spectroscopy - A method and a scheme of obtaining a femtosecond pulse train without frequency comb offset and selectable carrier–envelope offset phase are proposed.     

Synthesis of 7,8‐Dihydrothieno[3′,2′:4,5]pyrrolo[1,2‐a]pyrazin‐5(6H)‐ones Using a Modification of Four‐Component Ugi Reaction

We describe an efficient synthesis of novel 7,8‐dihydrothieno [3′,2′:4,5]pyrrolo[1,2‐a]pyrazin‐5(6H)‐one heterocyclic structures. The target compounds were prepared by a novel modification of four‐component Ugi reaction of heterocyclic bifunctional keto acids, isonitriles, and amines. We demonstrate the usefulness and versatility of the developed approach, which is amenable to production of combinatorial libraries.     

Assessment of a Possibility to Differentiate the Tumor Histological Type and Localization in Patients with Lung Cancer by the Composition of Exhaled Air

Journal of Analytical Chemistry - In clinical practice, exhaled air analysis is a promising approach for diagnosing lung cancer due to a possibility of rapid and noninvasive sampling. We analyzed...     

α- and β-phases of the Al-Mn-Si system

Homogeneity regions and crystal structures of ternary α- and β-phases based on Al₉Mn₂Si and Al₉Mn₃Si have been investigated at a temperature of 823 K by scanning electron microscopy, X-ray, and electron probe microanalysis techniques. It is established that the α-phase is formed in the composition region of 7.4–15.9 at % of Si at a manganese isoconcentrate of ～18 at %. When the manganese concentration is 24–26%, the β-phase has a homogeneity region from 3.7 to 18.5 at % of Si and is situated parallel to the Al-Si side. A fragment of the isothermal section for the Al-Mn-Si system in an aluminum-rich alloy region has been constructed.     

Specific features of the detection of hydrogen chloride in air with semiconductor sensors

The donor and acceptor character of the change in the resistance of semiconductor sensors in the presence of hydrogen chloride in air was elucidated. Conditions controlling the character of the sensor signal were revealed. The donor signal of the sensor increases with increasing temperature of the sensor, increasing air humidity, and decreasing concentration of hydrogen chloride. On the contrary, a decrease in the temperature of the sensor, a decrease in humidity, and an increase in the concentration of hydrogen chloride enhance the acceptor signal of the sensor. Air humidity has the decisive effect on the character of the sensor signal. It was demonstrated that semiconductor sensors allow the determination of hydrogen chloride in air at a level of the maximum permissible concentration (MPC) in the sanitary zone (0.2 mg/m³). Original Russian Text ￠ L.A. Obvintseva, E.A. Oksengoit-Gruzman, V.L. Kuchaev, A.K. Avetisov, F.Kh. Chibirova, M.P. Dmitrieva, 2008, published in Zhurnal Analiticheskoi Khimii, 2008, Vol. 63, No. 3, pp. 308–313.     

Synthesis and Acid–Base,Absorption, and Fluorescence Properties of Phthalocyanine Derivatives

Russian Journal of General Chemistry - Tetrakis{5,6-bis(4-tert-butylphenyl)pyrazino[2,3-c]}porphyrazine and tetra(4-tert-butyl)phthalocyanine have been synthesized, and their acid–base...     

An unusual acetylene–allene rearrangement in iodomethylates of cotarnine acetylene derivatives

1. Download : Download high-res image (94KB)
2. Download : Download full-size image

     

Standard enthalpies of the formation of malonic acid and products of its dissociation in an aqueous solution

Enthalpies of the dissolution of malonic acid in aqueous solutions of perchloric acid and sodium perchlorate were measured at ionic strength I = 1.0; 1.5; 2.0; 2.5 mol/l and T = 298.15 K by calorimetry. The standard enthalpies of the formation of malonic acid and the products of its dissociation in a aqueous solution were calculated.