Flow of a non‐linear (density‐gradient‐dependent) viscous fluid with heat generation,viscous dissipation and radiation

In this paper, we study the flow of a compressible (density‐gradient‐dependent) non‐linear fluid down an inclined plane, subject to radiation boundary condition. The convective heat transfer is also considered where a source term, similar to the Arrhenius type reaction, is included. The non‐dimensional forms of the equations are solved numerically and the competing effects of conduction, dissipation, heat generation and radiation are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and Characterization of pH‐Sensitive Positive‐charge Silica Nanoparticles for Oral Anionic Drug Delivery

The objective of this study is to utilize the pH sensitivity of modified mesoporous silica nanoparticles (MSN) for oral drug delivery. In the first time, a pH‐sensitive ionic liquid was synthesized through the quaternization of 3‐aminopropyltrimethoxysilane (3‐ATMS) with sodium monochloroacetate (SMCA). Then, silica nanoparticle was modified by this pH‐sensitive ionic liquid and converted to a pH‐sensitive positive‐charge silica nanoparticle (PCSN). The nanoparticle was characterized by FTIR and SEM. Naproxen as anionic drug molecules was entrapped in this pH‐sensitive positive‐charge silica nanoparticles (PCSN) and the in vitro release profiles were established separately in both (SGF, pH 1) and (SIF, pH 7.4).     

One Pot Synthesis of Some New Spiro[3H-Indol-3,5′(4′H)-[1,2,4] Oxadiazol]-2-Ones and Bis[Spiro[3H-Indol-3,5′(4′H)-[1,2,4] Oxadiazol]-2-Ones]

A facile preparation of the title compound by 1,3-dipolar cycloaddition reaction of benzonitrile oxides with isatin imines or isatin diimines, in excellent yield, are reported.     

A New Solvated Phosphoric Triamide, [(C6H4(3-CH3)NH)3P(O)] · (C2H5OH): A Database Analysis of N Atom Geometry in Compounds with an [N]3P(O) Fragment

Abstract

In the crystal structure of the title compound C₂₁H₂₄N₃OP · C₂H₅OH, there are three crystallographically independent phosphoric triamide molecules and three ethanol molecules. The environments of the nitrogen atoms are practically planar. The phosphorus atoms display a distorted tetrahedral environment; the maximum and minimum values of angles are observed for one O?P?N and one N?P?N angles, respectively. In this structure, the phosphoramide and ethanol molecules are linked by some different intermolecular O?H···O and N?H···O hydrogen bonds to form chains. The title solvated compound has been further characterized by IR and ³¹P{¹H}, ¹H and ¹³C NMR spectroscopy. The geometry of the nitrogen atoms in this compound is analyzed and compared with those of analogous structures deposited in the Cambridge Structural Database (CSD; Allen, Acta Cryst. 2002, B58, 380-388).     

A novel amido–pyrophosphate MnII chelate complex with the synthetic ligand O{P(O)[NHC(CH3)3]2}2 (L): [Mn(L)2{OC(H)N(CH3)2}2]Cl2·2H2O

The title complex, trans‐bis(dimethylformamide‐κO)bis{N,N′‐N′′,N′′′‐tetra‐tert‐butyl[oxybis(phosphonic diamide‐κO)]}manganese(II) dichloride dihydrate, [Mn(C₁₆H₄₀N₄O₃P₂)₂(C₃H₇NO)₂]Cl₂·2H₂O, is the first example of a bis‐chelate amido–pyrophosphate (pyrophosphoramide) complex containing an O[P(O)(NH)₂]₂ fragment. Its asymmetric unit contains half of the complex dication, one chloride anion and one water molecule. The Mn^II atom, located on an inversion centre, is octahedrally coordinated, with a slight elongation towards the monodentate dimethylformamide ligand. Structural features of the title complex, such as the P=O bond lengths and the planarity of the chelate ring, are compared with those of previously reported complexes with six‐membered chelates involving the fragments C(O)NHP(O), (X)NP(O) [X = C(O), C(S), S(O)₂ and P(O)] and O[P(O)(N)₂]₂. This analysis shows that the six‐membered chelate rings are less puckered in pyrophosphoramide complexes containing a P(O)OP(O) skeleton, such as the title compound. The extended structure of the title complex involves a linear aggregate mediated by N—H...O and N—H...Cl hydrogen bonds, in which the chloride anion is an acceptor in two additional O—H...Cl hydrogen bonds.     

Conformational flexibility in amidophosphoesters: a CSD analysis completed with two new crystal structures of (C6H5O)2P(O)X [X = NHC7H13 and N(CH2C6H5)2]

The crystal structures of diphenyl (cycloheptylamido)phosphate, C₁₉H₂₄NO₃P or (C₆H₅O)₂P(O)(NHC₇H₁₃), ( I ), and diphenyl (dibenzylamido)phosphate, C₂₆H₂₄NO₃P or (C₆H₅O)₂P(O)[N(CH₂C₆H₅)₂], ( II ), are reported. The NHC₇H₁₃ group in ( I ) provides two significant hydrogen‐donor sites in N—H…O and C—H…O hydrogen bonds, needed for a one‐dimensional hydrogen‐bond pattern along [100] in the crystal, while ( II ), with a (C₆H₅CH₂)₂N moiety, lacks these hydrogen bonds, but its three‐dimensional supramolecular structure is mediated by C—H…π interactions. The conformational behaviour of the phenyl rings in ( I ), ( II ) and analogous structures from the Cambridge Structural Database (CSD) were studied in terms of flexibility, volume of the other group attached to phosphorus and packing forces. From this study, synclinal (±sc), anticlinal (±ac) and antiperiplanar (±ap) conformations were found to occur. In the structure of ( II ), there is an intramolecular C_ortho—H…O interaction that imposes a +sc conformation for the phenyl ring involved. For the structures from the CSD, the +sc and ±ap conformations appear to be mainly imposed by similar C_ortho—H…O intramolecular interactions. The large contribution of the C…H/H…C contacts (32.3%) in the two‐dimensional fingerprint plots of ( II ) is a result of the C—H…π interactions. The differential scanning calorimetry (DSC) analyses exhibit peak temperatures (T_m) at 109 and 81 °C for ( I ) and ( II ), respectively, which agree with the strengths of the intermolecular contacts and the melting points.     

A Simple and Sensitive Analytical Method for Determination of Naltrexone Level in Plasma by GC–MS

A gas chromatography-mass spectrometry method for determination of naltrexone in plasma is presented. The method is based on pre-column derivatization of analyte to trimethylsilyl derivative of naltrexone. The analyte and internal standard were extracted from plasma by liquid–liquid extraction. Validation of the method has been studied in the concentration range 1–50 ng mL⁻¹.

     

Effect of temperature on the intrinsic viscosity of poly(ethylene glycol) in water/dimethyl sulfoxide solutions

In this work, the intrinsic viscosities of poly(ethylene glycol) with molar mass of 20 kg mol^− 1 were measured in water/dimethyl sulfoxide solutions from (298.15 to 318.15) K. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The expansion factor were decreased by increasing temperature; therefore the chain of PEG shrinks and the end-to-end distance become smaller by increasing temperature. Perhaps the interactions of segment-segment are favored toward segment-solvent by increasing temperature; therefore the hydrodynamic volumes of the polymer coils become smaller by increasing temperature. The thermodynamic parameters (entropy of dilution parameter, the heat of dilution parameter, theta temperature and polymer-solvent interaction parameter) were derived by the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that the interactions of segment-segment were increased by increasing temperature.