Finanzierungssituation der sächsischen Handwerksunternehmen

Das Handwerk ist mit seinen vielen kleinen und mittelgroßen Betrieben ein Kernstück der regionalen Wirtschaft; die Finanzierung der Handwerksbetriebe aufgrund von unternehmens- und branchenspezifischen Besonderheiten jedoch oft schwierig. Eine aktuelle Untersuchung der Niederlassung Dresden des IFO INSTITUTS gibt Einblicke in die Finanzierungssituation der sächsischen Handwerksbetriebe. Die Ergebnisse der Untersuchung zeigen, dass die klassische Kreditfinanzierung einerseits nach wie vor von herausragender Bedeutung für die Handwerksbetriebe ist. Andererseits wird deutlich, dass verschiedene Entwicklungen in den Handwerksunternehmen den Zugang zu dieser Finanzierungsform in Zukunft erschweren können. Der vorliegende Artikel stellt diese Entwicklung und deren Auswirkungen auf die Finanzierungssituation der Handwerksbetriebe dar und diskutiert geeignete Lösungsansätze.Handwerk; Klein- und Mittelunternehmen; Regionale Wirtschaftskraft; Betriebsvermögen; Kapitalstruktur; Kredit; Sachsen

Quantum analog of channeled electron trajectories in periodic magnetic and electric fields

We calculate the quantum states corresponding to the drifting and channeled classical orbits in a two-dimensional electron gas (2DEG) with strong magnetic and electric modulations along one spatial direction, $x$. The channeled states carry high, concentrated currents along the $y$ axis, and are confined in an effective potential well. The quantum and the classical states are compared.Comment: 8 pages with 4 included ps figures, contribution to "SemiMag 13" Nijmegen, August 1998, to appear in Physica

Function of novel enzymes of the microbial heme biosynthesis

Der Biosyntheseweg von Häm galt lange Zeit als hochkonserviert zwischen allen Reichen des Lebens. Jedoch zeigten Genomsequenzanalysen verschiedener Organismen, welche Häm bilden, dass bisher bekannte Gene der Häm-Biosynthese fehlten. Hierbei handelte es sich vor allem um Gene, welche für die Protoporphyrinogen IX Oxidase (PPO) und Coproporphyrinogen III Oxidase (CPO) codieren. Einer dieser Organismen mit ungewöhnlicher Häm-Biosynthese ist Leishmania spp.. Es weist einen verkürzten Biosyntheseweg auf, welcher nur aus den letzten drei Genen des Syntheseweges (CPO, PPO und FC) besteht. In der vorliegenden Arbeit konnte die Aktivität der PPO, welche zum HemG-Typ zählt experimentell nachgewiesen werden. Dies gelang zum einen in vivo über Komplementationsstudien mit einer delta hemG E. coli Mutante und zum anderen in vitro mit gereinigtem L. major HemG Protein. Des Weiteren konnte die Kopplung der PPO an die Atmungskette von E. coli aufgezeigt werden. Zudem wurde FMN als Kofaktor identifiziert. Basierend auf einem Strukturmodell sowie in vivo und in vitro Experimenten konnte für die Aminosäurereste Y134, Y137 und R142 eine Beteiligung an der Katalyse der durch die PPO katalysierten Reaktion gezeigt werden. Dabei war der Effekt für Y137 am stärksten ausgeprägt. Dies stellt die erste Charakterisierung einer PPO des HemG-Types in Eukaryoten dar. Zusätzlich hierzu wurde auch die potentielle CPO YtpQ aus B. subtilis untersucht. Es gelang YtpQ rekombinant zu produzieren und die CPO Aktivität erstmals zu beweisen. Zudem gelang es, das in dieser 2-stufigen Reaktion gebildete Intermediat Haderoporphyrinogen in seiner oxidierten Form Haderoporpyrin nachzuweisen. Ein möglicher Metallkofaktor, wie das vermutete Kobalt, konnte nicht identifiziert werden. Zusammengefasst, konnten in dieser Arbeit zwei neuartige Enzymtypen der Häm-Biosynthese erstmals identifiziert und charakterisiert werden.The heme biosynthesis pathway was thought to be highly conserved throughout all domains of life. However, recent genome analysis of heme synthesizing bacteria showed a lack of known heme biosynthesis genes especially for the protoporphyrinogen IX oxidase (PPO) and coproporphyrinogen III oxidase (CPO). One of these organisms with an uncommon heme biosynthesis is Leishmania spp.. This organism has a shorten biosynthesis pathway consisting only of the last three enzymes (CPO, PPO, ferrochelatase (FC)). In the present study the activity of the HemG-type PPO could be experimentally demonstrated. Therefore, in vivo complementation studies with a delta hemG E. coli mutant as well as in vitro activity assays with purified L. major HemG were performed. Furthermore, the coupling of the PPO with the respiratory chain of E. coli could be shown. In addition, flavin mononucleotide was elucidated as Cofactor of the L. major PPO. Based on a protein structure model as well as in vivo and in vitro experiments the amino acid residues Y134, Y137, and R142 could be revealed as being involved in the PPO catalyzing reaction. Hereby, the effect for Y137 was the strongest. Thus, this study represents the first of a eukaryotic HemG-type PPO. Additionally, the potential CPO YtpQ of B. subtilis was analyzed. YtpQ was recombinantly produced and its CPO activity could be shown for the first time. Also, the intermediate of the 2-ary CPO reaction haderoporphyrinogen in its oxidized form haderoporphyrin were detected. A possible metal cofactor, like the assumed cobalt was not identified. Summarized, in this study two new enzyme types of the heme biosynthesis were identified and characterized for the first time

Guiding center picture of magnetoresistance oscillations in rectangular superlattices

We calculate the magneto-resistivities of a two-dimensional electron gas subjected to a lateral superlattice (LSL) of rectangular symmetry within the guiding-center picture, which approximates the classical electron motion as a rapid cyclotron motion around a slowly drifting guiding center. We explicitly evaluate the velocity auto-correlation function along the trajectories of the guiding centers, which are equipotentials of a magnetic-field dependent effective LSL potential. The existence of closed equipotentials may lead to a suppression of the commensurability oscillations, if the mean free path and the LSL modulation potential are large enough. We present numerical and analytical results for this suppression, which allow, in contrast to previous quantum arguments, a classical explanation of similar suppression effects observed experimentally on square-symmetric LSL. Furthermore, for rectangular LSLs of lower symmetry they lead us to predict a strongly anisotropic resistance tensor, with high- and low-resistance directions which can be interchanged by tuning the externally applied magnetic field.Comment: 12 pages, 9 figure

Histone deacetylases in replicative senescence: evidence for a senescence-specific form of HDAC-2

AbstractTo analyze mechanisms of senescence-associated gene expression, we have investigated histone deacetylases (HDACs) in human fibroblasts undergoing replicative senescence. We found that the overall acetylation pattern of histones does not vary detectably with replicative senescence. By Northern blot and Western blot, we found a significant decrease in the abundance of HDAC-1 in senescent cells. Biochemical analysis of deacetylase activities in extracts from old and young cells revealed a striking difference. While by anion exchange chromatography we found a single peak of activity in extracts from young cells, which coincided with the elution of both HDAC-1 and HDAC-2, in senescent cells a second peak of activity was found. This second peak of activity is associated with HDAC-2 but does not contain HDAC-1. These results suggest that HDAC-2 is present in at least two distinct forms, one of which is specific for senescent cells. Further biochemical characterization of the enzyme activity revealed that addition of nicotinamide adenine dinucleotide (NAD) did not detectably influence the activity of any fraction, suggesting that NAD is not an essential co-factor for the analyzed HDACs from diploid human fibroblasts

Origin of positive magnetoresistance in small-amplitude unidirectional lateral superlattices

We report quantitative analysis of positive magnetoresistance (PMR) for unidirectional-lateral-superlattice samples with relatively small periods (a=92-184 nm) and modulation amplitudes (V_0=0.015-0.25 meV). By comparing observed PMR's with ones calculated using experimentally obtained mobilities, quantum mobilities, and V_0's, it is shown that contribution from streaming orbits (SO) accounts for only small fraction of the total PMR. For small V_0, the limiting magnetic field B_e of SO can be identified as an inflection point of the magnetoresistance trace. The major part of PMR is ascribed to drift velocity arising from incompleted cyclotron orbits obstructed by scatterings.Comment: 12 pages, 9 figures, REVTe

The Elasticity of Factor Substitution Between Capital and Labor in the U.S. Economy: A Meta-Regression Analysis

The elasticity of factor substitution between capital and labor is a crucial parameter in many economic fields. However, despite extensive research, there is no agreement on its value. Utilizing 738 estimates from 41 studies published between 1961 and 2016, this paper provides the first meta-regression analysis of capital-labor substitution elasticities for the U.S. economy. We show that heterogeneity in reported estimates is driven by the choice of estimation equations, the modeling of technological dynamics, and data characteristics. Based on the underlying meta-regression sample and a "best practice" specification, we estimate a long-run elasticity in the range of 0.6 to 0.7. For all estimated elasticities the hypothesis of a Cobb-Douglas production function is rejected