C35 Hopanoid Side Chain Biosynthesis: Reduction of Ribosylhopane into Bacteriohopanetetrol by a Cell‐Free System Derived from Methylobacterium organophilum

The major bacterial triterpenoids of the hopane series each consist of a C₃₀ triterpene hopane moiety and an additional nonterpene C₅ side chain derived from D ‐ribose and linked through its C‐5 carbon atom to the hopane side chain. Bacteriohopanetetrol and aminobacteriohopanetriol are the most common representatives of this natural product series, adenosylhopane and ribosylhopane being putative precursors. Deuterium‐labelled ribosylhopane was obtained by hemisynthesis and converted into deuterium‐labelled bacteriohopanetetrol in the presence of NADPH, thus giving evidence of this as yet unknown precursor‐to‐product relationship in the bacterial hopanoid metabolic pathway.     

Calibration of flow rate in cone calorimeter tests

The cone calorimeter is one of the major fire tests. The measurement method is based on the evaluation of mass flow and oxygen concentration of fire effluents to calculate heat release rate. Different studies highlighted that the governing parameter for uncertainty at important values of heat release rate was the characteristic constant of an orifice plate used to measure mass flow (C‐factor). This parameter is usually determined each testing day by oxygen consumption calorimetry with a reference methane burner. This publication presents a calibration method for volumetric flow rate without using orifice plate and then an extension to C‐factor determination without methane burner and calorimetry. The uncertainty calculation applied to a real example highlights the fact that the method is suitable to respect tolerance of standardized test conditions for both parameters. Copyright © 2013 John Wiley & Sons, Ltd.     

Volume Control in Hemodialysis Patients

Cardiovascular disease is the main cause of the high mortality of dialysis patients and is largely due to poor control of blood pressure. Establishing and maintaining normal extracellular volume (ECV) is required to achieve normotension. The dry weight concept links ECV and blood pressure by a simple clinical relationship. Dry weight is the ideal postdialysis weight that allows a constantly normal blood pressure to be maintained without using antihypertensive medications. Maintenance of normal ECV requires control of salt intake to reduce interdialytic weight gain ( i.e., saline overload) combined with the diffusive and convective removal of salt and water from the body during dialysis sessions. Several problems are to be faced when using the dry weight method. Clinical evaluation must take into account the following confounding factors: weight varies with nutrition, clinical symptoms are unspecific and sometimes discordant, and there is a lag time between ECV and blood pressure changes. On the other hand, achievement of dry weight is hampered by dialysis times that are too short (and weight gains that are too high), by antihypertensive medications, and by poor heart conditions. A longer session time allows for a slower, easier, and more comfortable ultrafiltration.     

Electrochemical polymerization of 1,2-ethanedithiol as a new way to synthesize polyethylenedisulfide

Preliminary studies of the electrochemical oxidation of 1,2-ethanedithiol in acetonitrile at platinum electrode surfaces are presented. A permanent modification of the electrode surfaces was observed after the anodic oxidation of 1,2-ethanedithiol. This modification is due to the formation of an organic polymer coating strongly tied to the electrode surfaces. This electrochemical polymerization process was studied by coupling electrochemistry and in situ electrochemical quartz crystal microbalance experiments, while ex situ X-ray photoelectron spectroscopy, Raman spectroscopy and Infrared spectroscopy were used to determine the structure of the polymer film. These spectroscopic techniques allowed us to identify the polymer films obtained by oxidation of 1,2-ethanedithiol as polyethylenedisulfide films.     

Effect of chronic administration of Ginkgo biloba extract or Ginkgolide on the hypothalamic-pituitary-adrenal axis in the rat

The hypersecretion of glucocorticoids during exposure to various stressors may induce or worsen pathological states in predisposed subjects. Therefore it is of interest to evaluate drugs able to reduce glucocorticoid secretion. It has recently been shown that chronic administration of a Ginkgo biloba extract (EGb 761) inhibits stress-induced corticosterone hypersecretion through a reduction in the number of adrenal peripheral benzodiazepine receptors. The present study was designed to analyze the effect of EGb 761 and one of its components, Ginkgolide B on the biosynthesis and secretion of CRH and AVP, the hypothalamic neurohormones that regulate the pituitary-adrenal axis. Chronic administration of EGb 761 (50 or 100 mg/kg p.o. daily for 14 days) reduced basal corticosterone secretion and the subsequent increase in CRH and AVP gene expression. Under the same conditions, surgically-induced increase in CRH secretion was attenuated while the activation of CRH gene expression, ACTH and corticosterone secretion following insulin-induced hypoglycemia remained unchanged. Chronic i.p. injection of Ginkgolide B reduced basal corticosterone secretion without alteration in the subsequent CRH and AVP increase. However, the stimulation of CRH gene expression by insulin-induced hypoglycemia was attenuated by Ginkgolide B. These data confirm that the administration of EGb 761 and Ginkgolide B reduces corticosterone secretion. In addition, these substances act also at the hypothalamic level and are able to reduce CRH expression and secretion. However the latter effect appears to be complex and may depend upon both the nature of stress and substance (Ginkgolide B or other compounds of EGb 761).     

Measurement of noise (cross-) power spectra for frequency-domainsystem identification purposes: large-sample results

Several frequency-domain estimators of parametric transfer function models assume that the (cross-) power spectra of the disturbing noise sources are known. This paper presents a time-efficient method to measure these noise (cross-) power spectra and studies its influence on the asymptotic properties of the estimated model parameters     

Noncontact critical dimension metrology sensor for chrome photomasks featuring a low-temperature co-fired ceramic technology

This paper describes a noncontact capacitive-sensor metrology sensor developed to measure minimum feature sizes, also called critical dimensions, patterned on photomasks that are used in semiconductor device manufacture. Additionally, this paper describes the test structures printed on photomasks that facilitate linewidth metrology with the new sensor. The metrology sensor is fabricated using a low temperature co-fired ceramic technology and its principle is based on noncontact microcapacitance measurements of features on chrome-on-glass reticles.     

Separation and characterization of phenolic compounds in argan fruit pulp using liquid chromatography–negative electrospray ionization tandem mass spectroscopy

Liquid chromatography (LC) coupled to negative electrospray ionization (ESI) tandem mass spectrometry (MS/MS) was used for the sensitive identification of phenolic compounds in argan fruit pulp. Sixteen compounds were identified, mainly flavonoid glycosides and flavonoid aglycons.