• Energy Research
• Closed Access close
• DE close
• CH close
• UA close
• University of Göttingen close

Acetic acid bacteria such as Gluconobacter oxydans are used in several biotechnological processes due to their ability to perform rapid incomplete regio- and stereo-selective oxidations of a great variety of carbohydrates, alcohols, and related compounds by their membrane-bound dehydrogenases. In order to understand the growth physiology of industrial strains such as G. oxydans ATCC 621H that has high substrate oxidation rates but poor growth yields, we compared its genome sequence to the genome sequence of strain DSM 3504 that reaches an almost three times higher optical density. Although the genome sequences are very similar, DSM 3504 has additional copies of genes that are absent from ATCC 621H. Most importantly, strain DSM 3504 contains an additional type II NADH dehydrogenase (ndh) gene and an additional triosephosphate isomerase (tpi) gene. We deleted these additional paralogs from DSM 3504, overexpressed NADH dehydrogenase in ATCC 621H, and monitored biomass and the concentration of the representative cell components as well as O2 and CO2 transfer rates in growth experiments on mannitol. The data revealed a clear competition of membrane-bound dehydrogenases and NADH dehydrogenase for channeling electrons in the electron transport chain of Gluconobacter and an important role of the additional NADH dehydrogenase for increased growth yields. The less active the NADH dehydrogenase is, the more active is the membrane-bound polyol dehydrogenase. These results were confirmed by introducing additional ndh genes via plasmid pAJ78 in strain ATCC 621H, which leads to a marked increase of the growth rate.

The exact mechanism of brain atrophy in patients with chronic alcoholism remains unknown. There is growing evidence that chronic alcoholism is associated with oxidative stress and with a derangement in sulphur amino acid metabolism (e.g. ethanol-induced hyperhomocysteinemia). Furthermore, it has been reported that homocysteine induces neuronal cell death by stimulating N-methyl-D-aspartate receptors as well as by producing free radicals. To further evaluate this latter hypothesis we analysed serum levels of both homocysteine and markers of oxidative stress (malondialdehyde) in alcoholic patients who underwent withdrawal from alcohol. Homocysteine and malondialdehyde were quantified by high performance liquid chromatography (HPLC) in serum samples of 35 patients (active drinkers). There was a significant correlation (P<0. 01) between blood alcohol concentration and elevated homocysteine (Spearman's r=0.71) and malondialdehyde (r=0.90) levels on admission. In addition, homocysteine and malondialdehyde levels were found to be significant decreased after 3 days of withdrawal treatment (Wilcoxon test: homocysteine, Z=-5.127; malondialdehyde, Z=-3.120; P<0.01). We postulate that excitatory neurotransmitters and mechanisms of oxidative stress in patients with chronic alcoholism may partly mediate excitotoxic neuronal damage and hereby cause brain shrinkage.

Although the literature on emission inequality is abundant, this study differentiates itself by focusing on emission inequality at the household-level. We further separate measures on emission inequality based on household characteristics as well as decompose it into sources of emission. The results show that as per capita expenditure increases, within group emission inequality tends to decline until the middle-income group but then further increase in expenditure worsens emission inequality. We also find that expenditure inequality is the predominant driver of emission inequality although recent increases in expenditure inequality have not lead to a commensurate increase in emission inequality. The decomposition of inequality based on emission sources suggests that energy-transportation predominantly contributes of the overall emission inequality; reducing the emission intensity of these sources would serve to lower emission inequality substantially.

Liver carbohydrate metabolism and blood flow are regulated by hepatic nerves and hormones such as glucagon, insulin or catecholamines. Acute and chronic application of alcohol are known to depress the function of central and peripheral nerves. The extent of inhibition of the autonomic nervous system is not well characterized; thus, the possible impairment of hepatic nerve function by acute and chronic application of ethanol was investigated.Rat livers were perfused simultaneously via both the portal vein and hepatic artery. Hepatic nerves were stimulated electrically for 2 min (20 Hz, 20 V, 2 ms). As a control, noradrenaline (1 microM) was infused into the portal vein for 2 minutes.During acute application of ethanol in portal concentrations of 50, 150 and 300 mM, which elevated basal glucose release, stimulation of hepatic nerves as well as portal noradrenaline infusion caused the same increase in glucose output and decrease in portal and arterial flow as in controls. Following chronic application of ethanol by feeding rats the Lieber-DeCarli liquid diet containing 5% (v/v) ethanol for 4 and 6 weeks, only nerve stimulation caused a significantly reduced enhancement of glucose output (50%, p < 0.025), whereas portal noradrenaline was as effective as in controls. Noradrenaline overflow was significantly reduced following nerve stimulation.The decrease in nerve stimulation-dependent glucose output and noradrenaline overflow in chronically ethanol fed rats indicates an impaired function of hepatic nerves.

Thinning is a widely-used management practice to reduce tree competition and improve wood production and quality in forest plantations. Thinning affects the soil ecosystem by changing the microclimate and plant growth, as well as litter inputs above and belowground, with all the resulting consequences for microbial communities and functions. Although many case studies have been carried out, a comprehensive understanding of the thinning effects on soil properties and microbial communities and functions in plantations remains to be explored. In this study, a meta-analysis was performed on 533 paired observations based on 90 peer-reviewed articles to evaluate the general responses of soil (mainly 0-20 cm depth) physicochemical properties, microbial biomass and community structure, and enzyme activities to thinning. Results showed that thinning increased soil temperature (13 %), moisture (8.0 %), electric conductivity (13 %), and the contents of total nitrogen (TN, 4.1 %), dissolved organic carbon (DOC, 9.7 %), nitrate N (NO3--N, 27 %) and available phosphorous (22 %). For microbial properties, thinning decreased the fungi to bacteria ratio (F:B, -28 %) and the gram-positive bacteria to gram-negative bacteria ratio (G+:G-, -12 %), while increased microbial biomass C (7.1 %), microbial respiration (13 %), and nutrient-cycle related enzyme activities, including phenol oxidase (14 %), cellobiohydrolase (21 %), urease (10 %), and acid phosphatase (9 %). In particular, moderate thinning (30-60 % intensity) has higher conservation benefits for soil C and nutrients than light and heavy intensity, thus being recommended as the optimal thinning activity. This meta-analysis suggests that thinning consistently altered soil properties, shifted microbial community compositions from K- to-r strategist dominance, and stimulated microbial activities. These results are essential for optimizing plantation thinning management and provide evidence for applying the macro-ecology theory to ecosystem disturbance in soil microbial ecology.

AbstractEs wird eine Autoklavenanlage für Korrosions‐und Oxidationsuntersuchungen mit Hochdruckwasser bzw. Wasserdampf beschrieben. Die Auslegungsdaten des Autoklaven sind 250 bar bei 500 °C. Der Autoklav besitzt 4 Schleusen, über die während des Betriebes ein Probenwechsel ohne größeren Einfluß auf die Betriebsbedingungen möglich ist. Das korrodierende Medium kann kontinuierlich mit einer max. Rate von 2,5 l/h ausgetauscht werden. Neben der Druck‐ und Temperaturkontrolle ist eine Überwachung der Wasserqualität vorgesehen.

Abstract This review paper summarizes recent advances and challenges in the assessment of rock behavior and performance in deep low-permeability and high-temperature geothermal reservoirs. Geothermal energy systems for electricity production target deep rock between ca. 2 km and 5 km depth to obtain sufficiently elevated temperatures. Rock permeability enhancement faces many challenges, and therefore the development of Enhanced Geothermal Systems (EGS) still represents a pioneering effort. The potential and advantage of EGS above conventional geothermal reservoirs is its independence of the location that supplies sufficient heat and fluid. Several issues prevent the successful application of EGS technology. First, the effects of non-uniform in-situ stresses and loading history on rock fracturing are not well understood. Second, the role of rock anisotropy, heterogeneity and thermal effects on rock properties in the design of hydraulic fracturing operations is not clear. Third, the reduction of induced seismicity effects raises safety and public acceptance issues. This manuscript formulates outlines for future research directions. Specifically, the recommendations focus on the development of tools for better understanding and mitigating problems, which occur during stimulation of deep geothermal reservoirs.

AbstractReview: use of manganese complexes in substitution and annulation reactions of arenes nvolving directed C‐H activation; 167 refs.