Netzreduktion zur Berechnung von Schaltvorgängen in großen Hochspannungsnetzen

Übersicht Das transiente Verhalten von Hochspannungsnetzen wird bei Schaltvorgängen im wesentlichen durch die ersten Pole und Nullstellen der Übertragungsfunktionen geprägt. Unter Verwendung eines Verfahrens von Cauer wird diese Eigenschaft in der vorliegenden Arbeit bei einer systematischen n-Tor-Synthese berücksichtigt. Auf diese Weise gelangt man zu reduzierten Ersatzschaltbildern, die es gestatten, den numerischen Aufwand zur Berechnung der transienten Vorgänge zu senken.

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Newwork reduction method for calculation of switching transients in h.v. power systems

Contents The switching transients in h.v. power systems are mainly influenced by the first lying poles and zeros of the transfer functions. Considering this property a systematic n-port-synthesis is given by using a method of Cauer. The resultant equivalent network can be reduced and thereby the computer time is diminished demanded for the calculation of switching transients.

     

Meeting filial responsibilities in brothers-only sibling groups

OBJECTIVES: This research examined how sons in brothers-only sibling groups meet the needs of their elderly parents. METHODS: 49 pairs of brothers without sisters whose parents were 74 years of age or older participated in open-ended interviews to explain how their parents' needs were met. Inductive analysis of interviews identified elements of these brothers' approaches. RESULTS: Brothers were in routine contact with and performed "masculine" services for their parents. Brothers acted independently and expected to be asked rather than volunteering help to their parents, except during times of crisis and transition. They defined their parents as self-sufficient, even when their parents' situations were precarious, and acted to reestablish their parents' independence when it was threatened. They viewed their parents' use of informal networks and formal services as appropriate. Brothers' wives provided "gender-appropriate" services. Wives' levels of involvement appeared to be a function of the quality of their relationships with their parents-in-law. Wives who helped were part of a support network. DISCUSSION: Brothers' goals of maintaining or reestablishing independence for their parents matches most parents' wishes to be independent and not to burden their children. The brothers' goal of self-sufficiency for their parents precluded their wives being the sole providers of support to their parents.     

Chronic Activation of AMPK Induces Mitochondrial Biogenesis through Differential Phosphorylation and Abundance of Mitochondrial Proteins in Dictyostelium discoideum

Mitochondrial biogenesis is a highly controlled process that depends on diverse signalling pathways responding to cellular and environmental signals. AMP-activated protein kinase (AMPK) is a critical metabolic enzyme that acts at a central control point in cellular energy homeostasis. Numerous studies have revealed the crucial roles of AMPK in the regulation of mitochondrial biogenesis; however, molecular mechanisms underlying this process are still largely unknown. Previously, we have shown that, in cellular slime mould Dictyostelium discoideum, the overexpression of the catalytic α subunit of AMPK led to enhanced mitochondrial biogenesis, which was accompanied by reduced cell growth and aberrant development. Here, we applied mass spectrometry-based proteomics of Dictyostelium mitochondria to determine the impact of chronically active AMPKα on the phosphorylation state and abundance of mitochondrial proteins and to identify potential protein targets leading to the biogenesis of mitochondria. Our results demonstrate that enhanced mitochondrial biogenesis is associated with variations in the phosphorylation levels and abundance of proteins related to energy metabolism, protein synthesis, transport, inner membrane biogenesis, and cellular signalling. The observed changes are accompanied by elevated mitochondrial respiratory activity in the AMPK overexpression strain. Our work is the first study reporting on the global phosphoproteome profiling of D. discoideum mitochondria and its changes as a response to constitutively active AMPK. We also propose an interplay between the AMPK and mTORC1 signalling pathways in controlling the cellular growth and biogenesis of mitochondria in Dictyostelium as a model organism.     

Central and peripheral administration of kisspeptin activates gonadotropin but not somatotropin secretion in prepubertal gilts

It is well established that kisspeptin signaling is necessary for the onset of puberty in laboratory animals. However, the role that kisspeptin may have in regulating puberty in large domestic animals is unknown. We tested the hypothesis that either central or peripheral infusion of kisspeptin would stimulate gonadotropin and GH secretion in prepubertal gilts. In experiment 1, prepubertal gilts were fitted with i.c.v. cannula and indwelling jugular catheters. Animals were randomly assigned to receive 0, 10, or 100 microg kisspeptin in saline. In experiment 2, prepubertal gilts, fitted with indwelling jugular catheters, randomly received 0, 1, 2.5, or 5 mg kisspeptin in saline intravenously. Serial blood samples were collected every 15 min for 3 h before and 5 h after infusions, and serum concentrations of LH, FSH, and GH were determined. Mean concentrations of LH and FSH remained at basal levels for control animals but were increased (P<0.001) for animals receiving i.c.v. infusion of kisspeptin. Area under the LH and FSH curves following i.c.v. infusion of kisspeptin increased (P<0.001) in a dose-dependent manner. Concentrations of GH were unaffected by i.c.v. treatment. Peripheral administration of kisspeptin increased (P<0.05) serum concentrations of LH but not FSH or GH. Thus, kisspeptin can activate gonadotropic but not somatotropic hormone secretion in prepubertal gilts. The present data support the concept that kisspeptin plays a role in the mechanism involved in initiating puberty in swine.     

Recent trends on the development of photobiological processes and photobioreactors for the improvement of hydrogen production

Hydrogen production through biological routes is promising because they are environmentally friendly. Hydrogen production through biophotolysis or photofermentation is usually a two stage process. In the first stage CO₂ is utilized for biomass production which is followed by hydrogen production in the second stage in anaerobic/sulfur-deprived conditions. In addition, one-stage photobiological hydrogen production process can be achieved using selected cyanobacterial strains. The major challenges confronting the large scale production of biomass/hydrogen are limited not only on the performance of the photobioreactors in which light penetration in dense cultures is a major bottleneck but also on the characteristics of the organisms. Other dependable factors include area/volume (A/V) ratio, mode of agitation, temperature and gas exchange. Photobioreactors of different geometries are reported for biohydrogen production: Tubular, Flat plate, Fermentor type etc. Every reactor has its own advantages and disadvantages. Airlift, helical tubular and flat plate reactors are found most suitable with respect to biomass production. These bioreactors may be employed for hydrogen production with necessary modifications to overcome the existing bottlenecks like gas hold up, oxygen toxicity and poor agitation. This review article attempts to focus on existing photobioreactors with respect to biomass generation and hydrogen production and the steps taken to improve its performance through engineering innovation that definitely help in the future design and construction of photobioreactors.     

Ermittlung von Ersatzschaltbildern eines Transformators aus seiner Impedanzmatrix

Übersicht Ein Transformator mit beliebiger Wicklungszahl wird zunächst durch ein lineares Modell beschrieben. Aus der Impedanzmatrix des Modells kann nit netzwerksynthetischen Methoden eine Ersatzschaltung gewonnen werden. Diese Schaltung ist leicht zu erweitern, so daß Wirbelströme im Kern und nichtlineare Magnetisierungskennlinien Berücksichtigung finden. Die Transformator-Nachbildung ist zur Berechnung von langsam verlaufenden Ausgleichsvorgängen geeignet.

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Transformer equivalent circuit derived from the impedance matrix

Contents A transformer withN windings is first described by a linear model. An equivalent circuit can be derived from the impedance matrix of the model using methods of network synthesis. The circuit is modified to include eddy currents in the core and the nonlinearity of the magnetizing branch. The transformer representation can be used in the calculation of slow transients.

     

Biological enhancement of tetrachloroethene dissolution and associated microbial community changes

A bench-scale study was performed to evaluate the enhancement of tetrachloroethene (PCE) dissolution from a dense nonaqueous phase liquid (DNAPL) source zone due to reductive dechlorination. The study was conducted in a pair of two-dimensional bench-scale aquifer systems using soil and groundwater from Dover Air Force Base, DE. After establishment of PCE source zones in each aquifer system, one was biostimulated (addition of electron donor) while the other was biostimulated and then bioaugmented with the KB1 dechlorinating culture. Biostimulation resulted in the growth of iron-reducing bacteria (Geobacter) in both systems as a result of the high iron content of the Dover soil. After prolonged electron donor addition methanogenesis dominated, but no dechlorination was observed. Following bioaugmentation of one system, dechlorination to ethene was achieved, coincident with growth of introduced Dehalococcoides and other microbes in the vicinity and downgradient of the PCE DNAPL (detected using DGGE and qPCR). Dechlorination was not detected in the nonbioaugmented system over the course of the study, indicating that the native microbial community, although containing a member of the Dehalococcoides group, was not able to dechlorinate PCE. Over 890 days, 65% of the initial emplaced PCE was removed in the bioaugmented, dechlorinating system, in comparison to 39% removal by dissolution from the nondechlorinating system. The maximum total ethenes concentration (3 mM) in the bioaugmented system occurred approximately 100 days after bioaugmentation, indicating that there was at least a 3-fold enhancement of PCE dissolution atthis time. Removal rates decreased substantially beyond this time, particularly during the last 200 days of the study, when the maximum concentrations of total ethenes were only about 0.5 mM. However, PCE removal rates in the dechlorinating system remained more than twice the removal rates of the nondechlorinating system. The reductions in removal rates over time are attributed to both a shrinking DNAPL source area, and reduced flow through the DNAPL source area due to bioclogging and pore blockage from methane gas generation.