Potential facile separation strategy for mixtures of 3- and 4-methylpyridine by employing N,N′-bis(9-phenyl-9-xanthenyl)ethylenediamine as an alternative host compound

In the present work, a plausible host candidate is provided for the separation of 3-methylpyridine (3MP) from 4-methylpyridine (4MP), isomers that are extremely difficult to separate by conventional means. Host compound N,N′-bis(9-phenyl-9-xanthenyl)ethylenediamine (H2), when recrystallized from an equimolar mixture of 3MP and 4MP, contained 91.6% 3MP, a significantly improved outcome compared with the alternate host compound N,N′-bis(9-phenyl-9-thioxanthenyl)ethylenediamine (H1) which only enclathrated 70% of this isomer in the same experimental conditions. Single crystal diffraction and thermoanalytical experiments were conducted in order to investigate this preference for 3MP by considering both host?guest interactions and relative complex stabilities. Many of the guest components in 3(H2)·5(3MP)·0.268(O) experienced at least one other short contact measuring less than the sum of the van der Waals radii of the involved atoms, an observation that may explain the selectivity of H2 for this guest since this was not the case in complexes containing PYR and 4MP. Results from the thermal analyses were less informative.

     

Precision measurements of the nucleon strange form factors at Q2 approximately 0.1 GeV2

We report new measurements of the parity-violating asymmetry A(PV) in elastic scattering of 3 GeV electrons off hydrogen and 4He targets with approximately 6.0 degrees . The 4He result is A(PV)=(+6.40+/-0.23(stat)+/-0.12(syst))x10(-6). The hydrogen result is A(PV)=(-1.58+/-0.12(stat)+/-0.04(syst))x10(-6). These results significantly improve constraints on the electric and magnetic strange form factors G(E)(s) and G(M)(s). We extract G(E)(s)=0.002+/-0.014+/-0.007 at =0.077 GeV2, and G(E)(s)+0.09G(M)(s)=0.007+/-0.011+/-0.006 at =0.109 GeV2, providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions.     

Determination of coumarin, vanillin, and ethyl vanillin in vanilla extract products: liquid chromatography mass spectrometry method development and validation studies

A LC-MS method was developed for the determination of coumarin, vanillin, and ethyl vanillin in vanilla products. Samples were analyzed using LC-electrospray ionization (ESI)-MS in the positive ionization mode. Limits of detection for the method ranged from 0.051 to 0.073 microg mL(-1). Using the optimized method, 24 vanilla products were analyzed. All samples tested negative for coumarin. Concentrations ranged from 0.38 to 8.59 mg mL(-1) (x =3.73) for vanillin and 0.33 to 2.27 mg mL(-1) (x =1.03) for ethyl vanillin. The measured concentrations are compared to values calculated using UV monitoring and to results reported in a similar survey in 1988. Analytical results, method precision, and accuracy data are presented.     

Comparative evaluation of extraction procedures and method validation for determination of carbohydrates in cereals and dairy products by capillary electrophoresis

This work describes the development and application of two optimized electrolytes: 15 mmol/L sorbate, 0.2 mmol/L CTAB, and 35 mmol/L sodium hydroxide for the determination of fructose, glucose, maltose, maltotriose, and sucrose in cereals and 15 mmol/L sorbate, 0.3 mmol/L CTAB, and 55 mmol/L sodium hydroxide for the determination of fructose, glucose, galactose, lactose, and sucrose in dairy products. Both methods were validated with respect to linearity, limits of detection (using both signal-to-noise ratio and the Eurachem approach), recovery tests, and intra- and inter-day precision exhibiting adequate performance. Additionally, statistically similar results were obtained in a comparative study of extraction procedures for carbohydrates using the AOAC protocol, ultrasound extraction, magnetic stirring, and sample dissolution.     

Sensitive liquid chromatographic-tandem mass spectrometric method for the determination of fluoxetine and its primary active metabolite norfluoxetine in human plasma

A sensitive method for the simultaneous determination of fluoxetine and its major active metabolite norfluoxetine in plasma was developed, using high-performance liquid chromatographic separation with tandem mass spectrometric detection. The samples were extracted from alkalised plasma with hexane-isoamyl alcohol (98:2, v/v) followed by back-extraction into formic acid (2%). Chromatography was performed on a Phenomenex Luna C18 (2) 5 microm, 150x2 mm column with a mobile phase consisting of acetonitrile-0.02% formic acid (340:660, v/v) at a flow-rate of 0.35 ml/min. Detection was achieved by a Perkin-Elmer Sciex API 2000 mass spectrometer (LC-MS-MS) set at unit resolution in the multiple reaction monitoring mode. TurbolonSpray ionisation was used for ion production. The mean recoveries for fluoxetine and norfluoxetine were 98 and 97%, respectively, with a lower limit of quantification set at 0.15 ng/ml for the analyte and its metabolite. This assay method makes use of the increased sensitivity and selectivity of mass spectrometric (MS-MS) detection to allow for a more rapid (extraction and chromatography) and sensitive method for the simultaneous determination of fluoxetine and norfluoxetine in human plasma than has previously been described.     

Beam-target double-spin asymmetry A{LT} in charged pion production from deep inelastic scattering on a transversely polarized {3}He target at 1.4<Q{2}<2.7 GeV{2}

We report the first measurement of the double-spin asymmetry A{LT} for charged pion electroproduction in semi-inclusive deep-inelastic electron scattering on a transversely polarized {3}He target. The kinematics focused on the valence quark region, 0.16相似文献   

Mechanical stimulation of epithelial cells using polypyrrole microactuators

The importance of mechanotransduction for physiological systems is becoming increasingly recognized. The effect of mechanical stimulation is well studied in organs and tissues, for instance by using flexible tissue culture substrates that can be stretched by external means. However, on the cellular and subcellular level, dedicated technology to apply appropriate mechanical stimuli is limited. Here we report an organic electronic microactuator chip for mechanical stimulation of single cells. These chips are manufactured on silicon wafers using traditional microfabrication and photolithography techniques. The active unit of the chip consists of the electroactive polymer polypyrrole that expands upon the application of a low potential. The fact that polypyrrole can be activated in physiological electrolytes makes it well suited as the active material in a microactuator chip for biomedical applications. Renal epithelial cells, which are responsive to mechanical stimuli and relevant from a physiological perspective, are cultured on top of the microactuator chip. The cells exhibit good adhesion and spread along the surface of the chip. After culturing, individual cells are mechanically stimulated by electrical addressing of the microactuator chip and the response to this stimulation is monitored as an increase in intracellular Ca(2+). This Ca(2+) response is caused by an autocrine ATP signalling pathway associated with mechanical stimulation of the cells. In conclusion, the present work demonstrates a microactuator chip based on an organic conjugated polymer, for mechanical stimulation of biological systems at the cellular and sub-cellular level.     

Precise extraction of the induced polarization in the 4He(e,e'p)3H reaction

We measured with unprecedented precision the induced polarization P(y) in (4)He(e,e'p)(3)H at Q(2)=0.8 and 1.3 (GeV/c)(2). The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are overestimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin-independent charge-exchange term in the latter calculation.     

Search for a new gauge boson in electron-nucleus fixed-target scattering by the APEX experiment

We present a search at the Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling α' to electrons. Such a particle A' can be produced in electron-nucleus fixed-target scattering and then decay to an e + e- pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175-250 MeV, found no evidence for an A'→ e+ e- reaction, and set an upper limit of α'/α ~/= 10(-6). Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.     

Isometries between non-commutative symmetric spaces associated with semi-finite von Neumann algebras

Positivity - We show that positive surjective isometries between symmetric spaces associated with semi-finite von Neumann algebras are projection disjointness preserving if they are finiteness...