Rapid method for analysis of sphingomyelin by microwave derivatisation for gas chromatography–mass spectrometry

Esterification and transesterification of lipids using boron trifluoride in methanol is widely used in lipid chemistry to study fatty acid (FA) profiles of various lipids by GC–MS. Transesterification of the FAs in sphingolipids is a difficult and time‐consuming task. A rapid and convenient method for preparation of FAMEs from sphingomyelin (SM) using microwaves (MWs) was developed for GC–MS analysis. Experiments with three levels of power were performed and the yields were compared at regular time intervals. The maximum yields for all power levels were the same, but the time to reach these yields varied with the power. It was found that at a power of 70 W the maximum yield was reached after 27 min having a stable time window of 8 min for this yield. Practical applications: The technique presented here enables a rapid and easy method for preparing FAMEs from SM by the use of a MW reactor. The reaction time has been reduced from several hours down to only 27 min, with excellent yields.     

Simultaneous quantification of etoposide and etoposide phosphate in human plasma by capillary electrophoresis using laser-induced native fluorescence detection

A method using capillary electrophoresis with UV laser-induced native fluorescence detection was developed as a sensitive and selective assay for the simultaneous determination of etoposide and etoposide phosphate in human plasma. Laser-induced native fluorescence detection with a frequency-doubled argon ion laser at an excitation wavelength of 257 nm was used for the simultaneous assay of etoposide and etoposide phosphate in plasma to improve the sensitivity compared to that obtained with UV absorption. The detection system consists of an imaging spectrograph and an intensified CCD camera which views an illuminated 1.5-mm section of the capillary. This setup is able to record the whole emission spectra of the analytes to achieve additional wavelength-resolved electropherograms. In the concentration range of 200 microg/L-50 mg/L in plasma for etoposide and 100 microg/L-20 mg/L for etoposide phosphate, coefficients of correlation were better than 0.998. Within-day variation determined with three different concentrations showed accuracies ranging from 91.0 to 109.3% for etoposide and from 91.2 to 109.9% for etoposide phosphate (n = 6) with a precision of about 8%. Day-to-day variation presented accuracies ranging from 91.8 to 107.9% for etoposide and from 94.4 to 109.3% for etoposide phosphate with a relative standard deviation less than 6% (n = 5). To our knowledge, this is the first method for the simultaneous quantification of etoposide and etoposide phosphate in plasma samples.     

Der Asynchronmotor mit drei und sechs Wicklungssträngen am stromeinprägenden Wechselrichter

Übersicht Für Drehzahlstellantriebe größerer Leistung bietet der Käligläufermotor mit 6 Wicklungsphasen und Versorgung durch zwei Stromumrichter deutliche Vorteile gegen-fiber dem 3-Phasenmotor mit 6-pulsiger oder auch 12-pulsiger Umrichterspeisung. Es werden die Größen untersucht und verglichen, die für die Wechselwirkung zwischen Motor und Umrichter charakteristisch sind:Die Induktivitäten und Phasenkopplungen, das Ersatzschahbild, die Pendelmomente und die Wirbelstromverluste.

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The current-source inverter-supplied induction motor with three and six phases

Contents For speed control drives of greater power ratings the induction motor with 6 phases supplied by two current source inverters is superior to the 3-phases motor supplied by an inverter working in 6- or 12-pulse mode. All quantities characteristic for interactions between motor and inverter are analysed.The inductances and phase couplings, the electrical equivalent circuit, the torque harmonics and the eddy current losses.

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Verwendete Symbole d _L Leiterdurchmesser - f, f ₁ Speisefrequenz - k() Kopplungsfaktor zweier um den Winkel versetzter Stränge - Widerstandserhöhung der in Nuten liegenden Leiter - Widerstandserhöhung der gesamten Wicklung - l _i ideelle Eisenlänge - l _s mittlere Länge der Stirnverbindungen - L _h Hauptinduktivität - L _K Kurzschlußinduktivität - L ₁,L ₂ Ständer- bzw. Läuferstreuinduktivität - L _N Nutstreuinduktivität - L _oS Stirnstreuinduktivität - L _oW Induktivität der doppelt verketteten Streuung - m Strangzahl - m _el Luftspaltmoment (als Zeitfunktion) - M _N Nennmoment - n Drehzahl - n Ordnungszahl für (räumliche) Oberwellen des Luftspaltfeldes - N Nutzahl - p Polpaarzahl - q Zahl der Ständernuten je Pol und Strang - s Sehnung in Nutteilungen - t _smin minimale Schonzeit der Thyristoren - V Magnetisierungsdurchflutung eines Pols - Windungszahl eines Stranges - _Sp Windungszahl einer Spule - W _S Spulenweite - Operatorimpedanz - Phasenverschiebung zwischen den Strömen der Ober- und Unterschicht - _res magnetisch wirksamer Luftspalt - ... Beiwert des magnetischen Leitwerts - Ordnungszahl der (zeitlichen) Oberschwingungen der Ströme und des Drehmoments - reduzierte Leiterhöhe nach [10] - _(n ) Wicklungsfaktor fürn-te Oberwelle des Luftspaltfelds - _K für die Kommutierung wirksamer totaler Streufaktor - _p Polteilung - (), () Hilfsfunktionen, siehe Gleichungen (54), (57) - Polfluß - verketteter Fluß - , Winkel, siehe Bild 9 - , ₁ Speisefrequenz - ₂ Läuferkreisfrequenz - ₀ Eigenkreisfrequenz des Kommutierungskreises Indizierung u ₁,i ₁,U ₁,... Ständergrößen - u ₂,i ₂,U ₂,... Läufergrößen - L _..a Stranginduktivität - L _..b Koppelinduktivität zweier um 30° versetzter Stränge - L _..c Sternpunktinduktivität - I _..(), Î_..(), M_..(),... Anteil der -ten Oberschwingung - Anteil dern-ten Oberwelle     

Hypnotic control of anticipatory emesis in patients receiving cancer chemotherapy.

Nausea and vomiting in anticipation of chemotherapy often develop in patients undergoing cancer treatment. In this study, deep muscle relaxation hypnosis controlled these conditioned reactions in 6 female patients (aged 24–56 yrs). Anticipatory emesis recurred when hypnosis was not used. During subsequent sessions in which hypnosis was reinstated, anticipatory emesis was again controlled. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deuterium storage in FeTi. Measurement of desorption isotherms and structural studies by means of neutron diffraction

Activation of pure stoichiometric FeTi turned out to be difficult and deactivation processes due to gas impurities limit the hydrogen storage capability. Isotherms of deuterium desorption are reported for the temperature range T = (25÷70)°C. At room temperature the crystal structures of FeTiD_x (x = 0÷1.74) and FeTiH_0.78D_0.22 were investigated by means of neutron diffraction at D₂-pressures up to 84 bar. Deuterium absorption in FeTi yields ternary deuterides and is associated with symmetry reduction corresponding to considerable distortions of the CsCl-type metal structure. In FeTiD deuterium occupies octahedral sites with two iron and four titanium atoms as nearest neighbour coordination (space group P222₁ or $\text{P}\text{2}\text{c}$). Hydrogenation does not change essentially the order parameter of FeTi.     

P.C.M. counter-coder principle for segmented a law

A p.c.m. counter-coder for the segmented A law is described. The suggested compression technique takes advantage of the exponential voltage decay in an RC circuit and the linear decay in a circuit composed of a capacitor and a current sink. The necessary number of counter steps per sample is 38 for an 8-digit code.     

Use of electrochemical noise to detect stress corrosion crack initiation in simulated BWR environments

The objective of this research was to investigate the use of electrochemical noise (EN) for detecting stress corrosion crack (SCC) initiation in boiling water reactor (BWR) environments. Initial experiments examined the response of sensitized AISI Type 304 stainless steel (SS) in slow strain-rate tensile (SSRT) tests in oxygenated, 288°C/10.4 MPa water, a laboratory simulation of the normal BWR environment. This combination of specimen condition and geometry assured abundant nucleation of intergranular cracks, with controllable propagation and arrest via changes in either loading or environment. In the latter case, addition of gaseous hydrogen was used to simulate BWR hydrogen water chemistry (HWC) and lower the specimen potential into a non-cracking region. The SSRT tests provided an ideal platform for optimizing the electrochemical cell configuration, while establishing the nature of electrochemical potential and current noise (EPN and ECN) responses to crack initiation, propagation and arrest. The standard deviation of electrochemical potential, a measure of EPN amplitude, proved to be the best indicator of SCC initiation, but the degree of correlation depended upon both the periodicity of the calculation and the electrode configuration. Further development work is expected to lead to a useful, in-plant sensor for real-time detection of SCC activity.     

Slow strain rate stress corrosion testing at elevated temperatures and high pressures

Slow strain rate stress corrosion cracking experiments have been performed on single phase and duplex phase 304 stainless steels at 290°C. Environmental variables included chloride concentrations (0–1000 ppm), oxygen concentration (0–2 ppm) and potential (?_corr to + 500 mV vs Ag/AgCl). These experiments have shown that s.c.c. resistance is relatively unaffected by Cl^? if O₂ concentrations approach zero. However, at 2 ppm O₂ concentration, there is a large decrease in resistance with increasing Cl^? concentrations. Anodic polarization of the steels during straining in solutions containing 100 ppm Cl^? and 0 ppm O₂ showed a threshold potential for s.c.c. at ～ 500 mV more noble than the corrosion potential (? 650 ± 60 mV vs Ag/AgCl at temperature).     

All-fiber spectral compression of picosecond pulses at telecommunication wavelength enhanced by amplitude shaping

We demonstrate efficient spectral compression of picosecond pulses in an all-fiber configuration at telecommunication wavelengths. A spectral compression by a factor of 12 is achieved. Performing temporal shaping with a parabolic pulse significantly improves the spectral compression with much lower substructures and an enhanced Strehl ratio.