Synthesis and characterization of an acrylate polymer containing chlorine-1,3-dioxalane groups in side chains

Poly[2-（4-chlorophenyl）-1,3-dioxolan-4-yl]methyl acrylate,poly（CPhDMA）,was synthesized with radical polymerization process using 2,2′-azobisisobutyronitrile as radical initiator in 1,4-dioxane at 60℃.The structure of poly（CPhDMA） was confirmed by means of UV-Vis,FT-IR,¹H-NMR,and ¹³C-NMR spectral techniques.The molecular weight distribution values of the polymer were determined with gel permeation chromatography（GPC）.The number-average molecular weight（M_n）,weight-average molecular weight（M_W） and polydispersity index（PDI） values of poly（CPhDMA） were determined to be 10300,21600 and 2.097,respectively.The thermal degradation kinetics of the polymer was investigated by using TG/DTG-DTA and DSC analyses at different heating rates in dynamic nitrogen atmosphere.The apparent activation energy values obtained by Flynn-Wall-Ozawa and Friedman methods were found to be 91.68 and 85.23 kJ mol^-1,respectively,for thermal decomposition of poly（CPhDMA）.Also,the thermal degradation activation energy value of poly（CPhDMA） was calculated by using the Kissinger method based on the DTG,DTA and DSC data.Then the mechanism function of it was determined by master plots method.Finally,electrical and optical properties of poly（CPhDMA） were determined by four-point probe and UV-Vis techniques,respectively.     

Facilitated Transfer of Alkali and Alkaline‐Earth Metal Ions by a Calix[4]arene Derivative Across Water/1,2‐Dichloroethane Microinterface: Amperometric Detection of Ca2+

The host–guest complexation reactions between 5,11,17,23‐tetra‐tert‐butyl‐25,27‐diethoxycarbonylmethoxy‐26,28‐dimethoxy calix[4]arene (BDDC4) and alkali and alkaline‐earth metal ions were investigated by facilitated ion transfer processes across water/1,2‐dichloroethane microinterface by using steady‐state cyclic voltammetry and differential pulse voltammetry. The obtained facilitated transfers for Li⁺, Na⁺, K⁺, Rb⁺ and Ca²⁺ were evaluated under the different experimental conditions, at the excess concentrations of metal ions with respect to BDDC4 and vice versa. The association constants having 1 : 1 stoichiometry for Li⁺, Na⁺, K⁺ and Rb⁺ in 1,2‐DCE were determined. Also, we demonstrated that BDDC4 can play an important role for the development of highly selective chemical sensor for Ca²⁺ among alkaline‐metal ions in the concentration range of 0.1–1.0 mM in aqueous solution.     

MoS<Subscript>2</Subscript>-Ti composite films having (002) orientation and low Ti content

MoS₂ is a solid lubricant exhibiting the properties like graphite as structure. The selection and control of deposition parameters should be attached importance very much since it exposes the properties desired from tribological and mechanical directions. Its usage is limited at atmospheric conditions because it is very sensitive to humidity. Therefore, both mechanical strength and resistant to oxidation can be provided by adding a suitable selected interleaving metal into MoS₂ matrix and by using suitable deposition parameters. In this work, MoS₂-Ti, composite films were grown on AISI 52100 steel by PMS (pulsed magnetron sputtering), and evaluated mechanically, structurally and tribologically. The produced film exhibited a low friction coefficient, low wear rate and significantly high wear life. This development was attributed to (002) basal plane orientation which is chemically inert, and low %Ti content and the use of pulsed-dc which is offers a stable deposition process, and also the accordance between the hardness values of substrate and film.     

Spectrofluorimetric Determination of Aliskiren in Tablets and Spiked Human Plasma through Derivatization with Dansyl Chloride

A simple and sensitive method has been developed and validated for the determination of aliskiren (ALS) in its dosage forms and spiked plasma. The method was based on the reaction of the drug with dansyl chloride in the presence of bicarbonate solution of pH 10.5 to give a highly fluorescent derivative which was measured at 501 nm with excitition at 378 nm in dichloromethane. Different experimental parameters affecting the development of the method and stability were carefully studied and optimized. The calibration curves were linear over the concentration ranges of 100–700 and 50–150 ng/mL for standard solution and plasma, respectively. The limits of detection were 27.52 ng/mL in standard solution, 4.91 ng/mL in plasma. The developed method was successfully applied to the analysis the drug in the commercial tablets and spiked plasma samples. The mean recovery of ALS from tablets and plasma was 100.10 and 97.81%, respectively. A proposal of the reaction pathway was presented.     

NaBH3CN and other systems as substitutes of tin and silicon hydrides in the light or heat-initiated reduction of halosugars: a tunable access to either 2-deoxy sugars or 1,5-anhydro-itols

UV light-promoted reduction of acetobromoglucose by NaBH₃CN in t-BuOH afforded 1,3,4,6-tetra-O-acetyl-2-deoxy-α-d-arabino-hexopyranose in high yield and purity, via a Surzur–Tanner rearrangement, while, with 10 mol % thiophenol added, acetylated 1,5-anhydro-d-glucitol was cleanly obtained. Such tin-free and mild reductions, presumed to proceed via radical pathways, were more efficient with NaBH₃CN compared to NaBH₄ or NaBD₄, and do not occur with acetochloroglucose. Similar reductions to 1,3,4,6-tetra-O-acetyl-2-deoxy-α-d-arabino-hexopyranose were achieved upon heating to 80 °C t-BuOH or CH₃CN solutions of NaBH₃CN and AIBN, but with a lower selectivity due to competing ionic reactions. With other pyranosyl bromides, reductions by NaBH₃CN could be tuned similarly (d-galacto), but some (d-manno, 5-thio-d-xylo) gave mainly or exclusively 1,5-anhydro-itols. Other conditions, or reagents promoting SET process, afforded also reduced products, but with lower rates or selectivities. Primary iodides were reduced readily with NaBH₃CN under UV light.     

New traceability chains in the photometric and radiometric measurements at the National Metrology Institute of Turkey

Optical Standards Laboratory of the National Metrology Institute of Turkey (UME) performs photometric, radiometric and fiber optics measurements related to SI-based units. The new traceability chains in the photometric and radiometric measurements are established in 2004, where top of the chains is based on primary-level optical power measurements with a cryogenic radiometer facility.     

An adaptive resource reservation for vehicular mobile networks

This paper presents the time‐based bandwidth reservation (TBR) algorithm, suitable for handoff management in cellular systems. TBR is based on real‐time measurements of mobile stations (position, velocity and acceleration). The scheme consists in sending reservation requests to the neighboring cells based on an extrapolation of the user's motion. The originality of our approach lies in dynamically adjusting the amount of time for which bandwidth has to be allocated and reserved in a cell. In addition, we propose an optimal channel requests arrangement (CRA) algorithm in order to improve the performance of TBR in terms of resource utilization. Finally, we propose VTBR, an adapted and extended version of TBR for better support of vehicular network specificities where service degradation or forced call termination may occur owing to frequent handoffs. Detailed simulation results for TBR and VTBR schemes and a comparison with the guard channel scheme are presented. The results show that TBR and VTBR can efficiently improve the flow dropping probability. Copyright © 2008 John Wiley & Sons, Ltd.     

4-Nitrophenyl sulfenyl chloride as a new precursor for the formation of aromatic SAMs on gold surfaces

4-Nitrophenyl sulfenyl chloride was used as a new precursor for the formation of densely packed aromatic SAMs on gold. The adsorption involves the reductive dissociation of the S-Cl bond. A well-ordered row structure corresponding to a √3 × 4 phase with a molecular area of 27.8 ?(2) is obtained.     

Physical structure of standing-up aromatic SAMs revealed by scanning tunneling microscopy

Long-range-ordered aromatic SAMs are formed on Au(111) using 4-nitrophenyl sulfenyl chloride as a precursor. Although the main structure is a √3 × √3 with a molecular density similar to that usually found for aliphatic SAMs, particular spots presenting specific shapes are also observed by STM. These include hexagons, partial hexagons, parallelograms, and zigzags resulting from specific arrangements of adsorbed molecules. These molecular arrangements are reversible as they form and dissociate or "vanish" in various areas on the surface. STM shows that these particular structures provide some order to their surrounding because areas void of these structures look less ordered. More interestingly, STM shows submolecular details of the molecules involved in forming these structures, hence providing direct experimental evidence for the ability of the STM to provide physical structure information of standing up SAMs. This is indeed a heavily debated question, and this work reports the first experimental example where submolecular physical structure is revealed by STM for standing-up SAMs.