Efficient water‐soluble drag reducing star polymers with improved mechanical stability

We describe here the first example of the synthesis of 4‐arm star poly(acrylic acid) for use as a water‐soluble drag reducing agent, by applying Cu(0)‐mediated polymerization technique. High molecular weight 4‐arm star poly(tert‐butyl acrylate) (M_n = 3.0–9.0 × 10⁵ g mol^?1) was first synthesized using 4,4′‐oxybis(3,3‐bis(2‐bromopropionate)butane as an initiator and a simple Cu(0)/TREN catalyst system. Then, 4‐arm star poly(tert‐butyl acrylate) were subjected to hydrolysis using trifluoroacetic acid resulting in water‐soluble 4‐arm star poly(acrylic acid). Drag reduction test rig analysis showed 4‐arm star poly(acrylic acid) to be effective as a drag reducing agent with drag reduction of 24.3%. Moreover, 4‐arm star poly(acrylic acid) exhibited superior mechanical stability when compared with a linear poly(acrylic acid) and commercially available drag reducing polymers; Praestol and poly(ethylene oxide). The linear poly(acrylic acid), Praestol, and poly(ethylene oxide) all showed a large decrease in drag reduction of 8–12% when cycled 30 times through the drag reduction test rig while, in contrast, 4‐arm star poly(acrylic acid) demonstrated much higher mechanical stability. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 335–344     

Reactions of 4-alkylidene (arylidene)-1-phenylpyrazolidine-3,5-dione

Reactions of 4-alkylidene(arylidene)-1-phenylpyrazolidine-3,5-dione with oxidizing (chromium trioxide/acetic acid) as well as with reducing (sodium borohydride/methanol) agents were carried out. Phenylhydrazine reacted with 4-arylidene-1-phenylpyrazolidine-3,5-diones via fission of exo C=C bond to give 1-phenylpyrazolidine-3,5-dione and the corresponding aryl hydrazones. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1335–1341, September, 2007.     

Determination of methylmalonic acid in urine by HPLC with intramolecular excimer-forming fluorescence derivatization

We developed and validated an HPLC method with intramolecular excimer-forming fluorescence derivatization to determine methylmalonic acid, a unique biochemical marker for methylmalonic aciduria. Methylmalonic acid in urine and an internal standard were derivatized with pyrenebutyric hydrazide and separated on a C8 column. The derivatives were detected by monitoring the fluorescence at 475 nm (excitation wavelength 345 nm). At a signal-to-noise ratio of 3, the detection limit was 0.33 pmol on the column and the calibration curve was linear up to 1 mmol[sol ]L in urine. In a retrospective study on a relatively large number of known methylmalonic aciduria cases (n = 48), the method enabled us to differentiate methylmalonic aciduria cases from healthy controls (n = 52), regardless of age of patients at sampling or years of specimen storage. No interference was observed from isomeric or other dicarboxylic acids, or other urine constituents. As described, the method can be used retrospectively or prospectively for the diagnosis of methylmalonic aciduria and can be easily adopted by laboratories with no access to gas chromatography-mass spectrometry.     

Ensemble of a subset of <Emphasis Type="Italic">k</Emphasis>NN classifiers

Combining multiple classifiers, known as ensemble methods, can give substantial improvement in prediction performance of learning algorithms especially in the presence of non-informative features in the data sets. We propose an ensemble of subset of kNN classifiers, ESkNN, for classification task in two steps. Firstly, we choose classifiers based upon their individual performance using the out-of-sample accuracy. The selected classifiers are then combined sequentially starting from the best model and assessed for collective performance on a validation data set. We use bench mark data sets with their original and some added non-informative features for the evaluation of our method. The results are compared with usual kNN, bagged kNN, random kNN, multiple feature subset method, random forest and support vector machines. Our experimental comparisons on benchmark classification problems and simulated data sets reveal that the proposed ensemble gives better classification performance than the usual kNN and its ensembles, and performs comparable to random forest and support vector machines.     

Further investigations on the thermophysical properties of gamma-irradiated urania-doped orthoferrites

(Y_1.85?U_0.15) FeO₃ orthoferrite was carefully prepared using the solid-state high temperature ceramic and sintering technique. On this orthoferrite, numerous measurements have been undertaken before and after 1.24 Mrad γ-absorbed dose, namely X-ray diffraction (XRD), DC-electrical conductivity versus temperature, UV/Vis. absorption, IR absorption, Mössbauer effect (ME) and EPR. In the present work the results obtained were explained, interpreted and discussed in details on the basis of lattice structure of the new perovskite investigated and the interaction of γ-radiation with the orthoferrite lattice.     

Determination of oxolinic acid in cow's milk and human urine by means of a single-use phosphorimetric sensor

A single-use phosphorimetric drop plane sensor for the determination of oxolinic acid (OXA) is proposed. The sensor was formed by a 30x16 mm(2) rectangular strip of Mylar type polyester as solid support that contained a circular sensing zone, 6 mm in diameter and 20 mum in thickness, formed by PVC plasticized with tributylphosphate adhered to its surface. When the strip was introduced for 1 hour into a sample solution, the analyte was retained in the sensing zone, making it possible to directly measure the phosphorescence intensity emitted by the OXA in the solid phase, at lambda(exc)=330 nm and lambda(em)=449 nm. The variables that affect the construction of the sensor have been studied, along with the experimental variables that influence the fixation of the analyte in the sensor. The method's detection limit was 0.01 mg l(-1) with an applicable concentration range from 0.04 to 1.50 mg l(-1) and a repeatability of 2.6% at the concentration range of 0.8 mg l(-1). The method was applied to samples of human urine and cows' milk, with recovery percentages ranging between 97.6 and 108.7%.     

Synthesis of Hexahydro-<Emphasis Type="Italic">1H</Emphasis>-pyrido[3,2-<Emphasis Type="Italic">c</Emphasis>]azepines as Hypotensive Agents of Expected Calcium-Channel Blocking Activity

Summary. Michael addition reaction of 3-(4-fluorophenylamino)-2-cyclohexenone and its 5,5-dimethyl derivative to the acrylonitrile derivatives afforded the novel hexahydroquinolines. The target hexahydro-1H-pyrido[3,2-c]azepine derivatives were obtained via ring enlargement of the corresponding hexahydroquinolines under Schmedt conditions. Some novel pyrido[3,2-c]azepines showed hypotensive activity in vivo on normotensive anaesthetized male adult albino rats and their effects on the ventricular contraction and auricular rate of isolated rabbit hearts using Langendorff’s method and nefidipine as a reference drug were studied. Compounds 29 and 36 which bear some structural similarities to nefidipine exhibited the highest hypotensive activity and negative inotropic as well as chronotropic activities.     

Exploiting pH mismatch in preparative high-performance liquid chromatographic recovery of ertapenem from mother liquor streams

Preparative chromatography was successfully employed to recover ertapenem from mother liquor streams. The recovery process involved concentration of mother liquor stream by evaporation, purification by reversed-phase preparative high-performance liquid chromatography (HPLC), and removal of chromatographic solvents in the recovered fractions by evaporation. HPLC feed was prepared by stripping off the organic solvents from the mother liquor using a wiped-film evaporator. Purification was first carried out on a 25 cm x 0.46 cm analytical column packed with 10-microm Kromasil C8 particles and then scaled up to a 25 cm x 5 cm preparative column. Gram-level recovery of ertapenem with high purity was achieved by exploiting a novel approach based on pH mismatch between the feed and the eluent. Purified ertapenem streams from preparative HPLC runs were combined, evaporated and recycled into the crystallizer for ertapenem isolation.     

Nonlinear surface wave instability for electrified Kelvin fluids

A weakly nonlinear approach is utilized here to discuss surface wave instability for two superposed electrified fluids of Kelvin type. The influence of a vertical electric field is discussed. The linear form for equations of motion is solved in the light of nonlinear boundary conditions. The method of multiple scales is used for the purpose of nonlinear perturbation. The surface wave response is governed by the well-known nonlinear Ginzburg-Landau equation rather than the transcendental dispersion relation in the linear scope. Although linear stability conditions are not available for arbitrary viscosity, the nonlinear analysis allowed deriving necessary and sufficient stability conditions. Moreover, at the marginal state, the nonlinear scope for stability is discussed through its dependence on the wavetrain frequency, in which short-wave disturbance is assumed to relax the linear transcendental terms. Besides the linear stability constraint, the nonlinear scope gives an additional constraint on the wavetrain frequency. Nonlinear stability criteria are derived and are performed in view of a nondimensional form. Furthermore, the nonlinear analysis is repeated for an arbitrary wave disturbance. A suitable choice for dimensionless form made it possible to relax transcendental terms included in stability conditions. Numerical calculations at the marginal state show that both the vertical electric field and the stratified fluid density play a dual role in the stability criteria. This dual role is the opposite to the dual role that the stratified viscosity plays in the stability profile. For the marginal state representation, numerical examination shows that elasticity plays a dual role in the stability criteria in a manner similar to that of the viscosity behavior.     

Euphroside,A New Iridoid Glucoside from Euphrasia salisburgensis HOPPE

Five iridoid glucosides have been isolated from the whole plant of Euphrasia salisburgensis. The structure of the new compound, named euphroside, and the identity of the others have been established by chemical transformations and spectral data.