Independent Orbiter Assessment (IOA): Analysis of the orbital maneuvering system

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The independent analysis results for the Orbital Maneuvering System (OMS) hardware are documented. The OMS provides the thrust to perform orbit insertion, orbit circularization, orbit transfer, rendezvous, and deorbit. The OMS is housed in two independent pods located one on each side of the tail and consists of the following subsystems: Helium Pressurization; Propellant Storage and Distribution; Orbital Maneuvering Engine; and Electrical Power Distribution and Control. The IOA analysis process utilized available OMS hardware drawings and schematics for defining hardware assemblies, components, and hardware items. Each level of hardware was evaluted and analyzed for possible failure modes and effects. Criticality was asigned based upon the severity of the effect for each failure mode

Engineering pyruvate decarboxylase-mediated ethanol production in the thermophilic host Geobacillus thermoglucosidasius

This study reports the expression, purification, and kinetic characterization of a pyruvate decarboxylase (PDC) from Gluconobacter oxydans . Kinetic analyses showed the enzyme to have high affinity for pyruvate (120 μM at pH 5), high catalytic efficiency (4.75×105 M−1 s−1 at pH 5), a pHopt of approximately 4.5 and an in vitro temperature optimum at approximately 55 °C. Due to in vitro thermostablity (approximately 40 % enzyme activity retained after 30 min at 65 °C), this PDC was considered to be a suitable candidate for heterologous expression in the thermophile Geobacillus thermoglucosidasius for ethanol production. Initial studies using a variety of methods failed to detect activity at any growth temperature (45–55 °C). However, the application of codon harmonization (i.e., mimicry of the heterogeneous host’s transcription and translational rhythm) yielded a protein that was fully functional in the thermophilic strain at 45 °C (as determined by enzyme activity, Western blot, mRNA detection, and ethanol productivity). Here, we describe the first successful expression of PDC in a true thermophile. Yields as high as 0.35±0.04 g/g ethanol per gram of glucose consumed were detected, highly competitive to those reported in ethanologenic thermophilic mutants. Although activities could not be detected at temperatures approaching the growth optimum for the strain, this study highlights the possibility that previously unsuccessful expression of pdcs in Geobacillus spp. may be the result of ineffective transcription/translation coupling.Web of Scienc

Acetic Acid Bacteria: Physiology and Carbon Sources Oxidation

Acetic acid bacteria (AAB) are obligately aerobic bacteria within the family Acetobacteraceae, widespread in sugary, acidic and alcoholic niches. They are known for their ability to partially oxidise a variety of carbohydrates and to release the corresponding metabolites (aldehydes, ketones and organic acids) into the media. Since a long time they are used to perform specific oxidation reactions through processes called “oxidative fermentations”, especially in vinegar production. In the last decades physiology of AAB have been widely studied because of their role in food production, where they act as beneficial or spoiling organisms, and in biotechnological industry, where their oxidation machinery is exploited to produce a number of compounds such as l-ascorbic acid, dihydroxyacetone, gluconic acid and cellulose. The present review aims to provide an overview of AAB physiology focusing carbon sources oxidation and main products of their metabolism

Interactive effects of DAOA (G72) and catechol-O-methyltransferase on neurophysiology in prefrontal cortex

Background: Accumulating evidence indicates that genetic polymorphisms of D-amino acid oxidase activator (DAOA) (M24; rs1421292; T-allele) and catechol-O-methyltransferase (COMT) (Val(158)Met; rs4680) likely enhance susceptibility to schizophrenia. Previously, clinical association between DAOA M24 (T-allele) and a functionally inefficient 3-marker COMT haplotype (that included COMT Val(158)Met) uncovered epistatic effects on risk for schizophrenia. Therefore, we projected that healthy control subjects with risk genotypes for both DAOA M24 (T/T) and COMTVal(158)Met (Val/Val) would produce prefrontal inefficiency, a critical physiological marker of the dorsolateral prefrontal cortex (DLPFC) in schizophrenic patients influenced by both familial and heritable factors

Taking Advantage of Hg−C Bonds: Synthesis of the First Homoleptic Bis-β-diketiminate Complex Bound through the γ-Carbons

The most common β-diketiminate ligand, [{N(2,6-iPr2C6H3)C(Me)}2CH]− (BDI), was used to synthesize a new mercury complex in which two BDI ligands are bound to the metal through the γ-carbons in the solid state. In solution, one of the BDI ligands switches to an N,N′-binding mode; this complex is in equilibrium with the homoleptic species. The thermodynamic parameters, ΔH° (−2.52 kcal mol−1), ΔS° (−9.24 cal mol−1 K−1), and ΔG°298 (0.23 kcal mol−1), were measured using variable-temperature 1H NMR spectroscopy