Agglomeration effects on labour demand

"How do agglomeration effects influence the demand for labour? To answer this question, approaches on labour demand are linked with an analysis of the classic 'urbanization effect'. We use models for static and for dynamic labour demand to find out, whether agglomerations develop faster or slower than other regions. Estimations of the static model show the influence of different degrees of regional concentration at the employment level. The model of dynamic labour demand is used to estimate the effect of different regional types on the growth rate of labour demand. The empirical results (received with the linked employer-employee database of the IAB) on long-run or static labour demand indicate substantial agglomeration effects, since c. p. employment is higher in densely populated areas. In the dynamic model, however, labour demand in core cities grows slower than the average. This is not a contradiction. Labour demand is especially high in large cities, but the other areas are slowly reducing the gap." (Author's abstract, IAB-Doku) ((en))Arbeitskräftenachfrage, Region, regionaler Arbeitsmarkt, regionale Disparität, Ballungsraum, Stadt, Stadtregion, ländlicher Raum, Peripherie, Siedlungsdichte, Beschäftigungseffekte, Dienstleistungsbereich, Suburbanisierung, Nachfrageentwicklung, regionale Faktoren, Beschäftigungsentwicklung, Arbeitsmarktregion, IAB-Linked-Employer-Employee-Datensatz

Agglomeration effects on labour demand

"How do agglomeration effects influence the demand for labour? To answer this question, approaches on labour demand are linked with an analysis of the classic 'urbanization effect'. We use models for static and for dynamic labour demand to find out, whether agglomerations develop faster or slower than other regions. Estimations of the static model show the influence of different degrees of regional concentration at the employment level. The model of dynamic labour demand is used to estimate the effect of different regional types on the growth rate of labour demand. The empirical results (received with the linked employer-employee database of the IAB) on long-run or static labour demand indicate substantial agglomeration effects, since c. p. employment is higher in densely populated areas. In the dynamic model, however, labour demand in core cities grows slower than the average. This is not a contradiction. Labour demand is especially high in large cities, but the other areas are slowly reducing the gap." (author's abstract)Wie beeinflussen Agglomerationseffekte die Arbeitsnachfrage? Um diese Frage zu beantworten, werden Nachfrage-Ansätze mit einer Analyse des klassischen Urbanisations-Effekts verknüpft. Modelle der statischen und dynamischen Arbeitsnachfrage werden eingesetzt, um herauszufinden, ob sich Agglomerationen schneller oder langsamer als andere Regionen entwickeln. Schätzungen auf der Basis des statischen Modells belegen den Einfluss regionaler Konzentration auf der Ebene der Beschäftigung. Dynamische Modelle werden eingesetzt, um die Auswirkungen unterschiedlicher Arten von Regionen auf die Wachstumsquote der Arbeitsnachfrage abzuschätzen. Die Ergebnisse der empirischen Untersuchung, die sich auf den Linked-Employer-Employee-Datensatz des IAB stützen, ergeben für die langfristige oder statische Nachfrage bedeutende Agglomerationseffekte, da das Beschäftigungsniveau in dicht besiedelten Gebieten höher ist. Dem dynamischen Modell zufolge wächst die Arbeitsnachfrage in den Kernstädten hingegen unterdurchschnittlich langsam. Dies wird jedoch nicht als Widerspruch betrachtet. Die Nachfrage nach Arbeit ist vor allem in den großen Städten hoch, aber die anderen Regionen holen langsam auf. Der Dienstleistungsbereich entwickelt sich in allen Arten von Regionen besser als in den Kernstädten; hier wird der Trend zur Suburbanisierung sichtbar. (IAB

Temperature Dependence of Fast and Slow Gating Relaxations of ClC-0 Chloride Channels

The chloride channel from the Torpedo electric organ, ClC-0, is the best studied member of a large gene-family (Jentsch, T.J. 1996. Curr. Opin. Neurobiol. 6:303–310.). We investigate the temperature dependence of both the voltage- and chloride-dependent fast gate and of the slow gate of the “double-barreled” ClC-0 expressed in Xenopus oocytes. Kinetics of the fast gate exhibit only a moderate temperature dependence with a Q10 of 2.2. Steady-state popen of the fast gate is relatively independent of temperature. The slow gate, in contrast, is highly temperature sensitive. Deactivation kinetics at positive voltages are associated with a Q10 of ∼40. Steady-state open probability of the slow gate (popenslow(V)) can be described by a Boltzmann distribution with an apparent gating valence of ≈2 and a variable “offset” at positive voltages. We note a positive correlation of this offset (i.e., the fraction of channels that are not closed by the slow gate) with the amount of expression. This offset is also highly temperature sensitive, being drastically decreased at high temperatures. Paradoxically, the maximum degree of activation of the slow gate also decreases at higher temperatures. The strong temperature dependence of the slow gate was also observed at the single channel level in inside-out patches. The results imply that within a Markovian-type description at least two open and two closed states are needed to describe slow gating. The strong temperature dependence of the slow gate explains the phenotype of several ClC-0 point-mutants described recently by Ludewig et al. (Ludewig, U., T.J. Jentsch, and M. Pusch. 1996. J. Physiol. (Lond.). In press). The large Q10 of slow gating kinetics points to a complex rearrangement. This, together with the correlation of the fraction of noninactivating channels with the amount of expression and the fact that the slow gate closes both protochannels simultaneously suggests that the slow gate is coupled to subunit interaction of the multimeric ClC-0 channel

H+-Independent Glutamine Transport in Plant Root Tips

BACKGROUND: Glutamine is one of the primary amino acids in nitrogen assimilation and often the most abundant amino acid in plant roots. To monitor this important metabolite, a novel genetically encoded fluorescent FRET-reporter was constructed and expressed in Arabidopsis thaliana. As a candidate for the glutamine fluxes, the root tip localized, putative amino acid transporter CAT8 was analyzed and heterologously expressed in yeast and oocytes. PRINCIPAL FINDINGS: Rapid and reversible in vivo fluorescence changes were observed in reporter-expressing root tips upon exposure and removal of glutamine. FRET changes were detected at acid and neutral pH and in the presence of a protonophore, suggesting that part of the glutamine fluxes were independent of the pH. The putative amino acid transporter CAT8 transported glutamine, had a half maximal activity at approximately 100 microM and the transport was independent of external pH. CAT8 localized not only to the plasma membrane, but additionally to the tonoplast, when tagged with GFP. Ultrastructural analysis confirmed this dual localization and additionally identified CAT8 in membranes of autophagosomes. Loss-of function of CAT8 did not affect growth in various conditions, but over-expressor plants had increased sensitivity to a structural substrate analog, the glutamine synthetase inhibitor L-methionine sulfoximine. CONCLUSIONS: The combined data suggest that proton-independent glutamine facilitators exist in root tips

Chasing the busy-beaver : notes and observations on a competition to find the 5-state busy beaver

This is a report on the results of a competition which was initiated on the occasion of the 6th GI-conference on Theoretical Computer Science, which took place at the University of Dortmund from January 5th to 7th, 1983. It was asked for the best solution of the 5-state Busy-Beaver-Game. At first we make some historical remarks, introduce the formalism, and list some results. Then the two best solutions are described. Next we make some remarks on the behaviour of good beavers and on the strange behaviour of some Turing machines. Zoological names were given to the latter machines. The amusing results are written down in the last chapter. In the appendix you can find a lot of examples

Different Transport Mechanisms in Plant and Human AMT/Rh-type Ammonium Transporters

The conserved family of AMT/Rh proteins facilitates ammonium transport across animal, plant, and microbial membranes. A bacterial homologue, AmtB, forms a channel-like structure and appears to function as an NH3 gas channel. To evaluate the function of eukaryotic homologues, the human RhCG glycoprotein and the tomato plant ammonium transporter LeAMT1;2 were expressed and compared in Xenopus oocytes and yeast. RhCG mediated the electroneutral transport of methylammonium (MeA), which saturated with Km = 3.8 mM at pHo 7.5. Uptake was strongly favored by increasing the pHo and was inhibited by ammonium. Ammonium induced rapid cytosolic alkalinization in RhCG-expressing oocytes. Additionally, RhCG expression was associated with an alkali-cation conductance, which was not significantly permeable to NH4+ and was apparently uncoupled from the ammonium transport. In contrast, expression of the homologous LeAMT1;2 induced pHo-independent MeA+ uptake and specific NH4+ and MeA+ currents that were distinct from endogenous currents. The different mechanisms of transport, including the RhCG-associated alkali-cation conductance, were verified by heterologous expression in appropriate yeast strains. Thus, homologous AMT/Rh-type proteins function in a distinct manner; while LeAMT1;2 carries specifically NH4+, or cotransports NH3/H+, RhCG mediates electroneutral NH3 transport

Tierschutzgerechte Schlachtung Afrikanischer Welse: Untersuchungen zur Erprobung von geeigneten Betäubungsverfahren für die Schlachtung Afrikanischer Welse (Clarias gariepinus)

Der Afrikanische Wels (Clarias gariepinus) ist ein robuster Warmwasserfisch, der sich gut für die Aufzucht in Warmwasserkreislaufanlagen eignet. Seine Vermarktung ist erschwert, weil dieser Fisch mit den nach Tierschutzschlachtverordnung zulässigen Betäubungsverfahren nicht erfolgreich betäubt werden kann. Es waren deshalb sowohl die tierschutzrechtlich zulässigen als auch andere potenziell geeignete Betäubungsverfahren zu untersuchen, zu kombinieren und zu modifizieren. Mit der Eiswasserbehandlung wird die Wahrnehmungs- und Empfindungslosigkeit nicht ausreichend schnell erreicht. Für kleine Schlachtzahlen bzw. als Alternative zur Betäubung per Kopfschlag erscheint die untersuchte Methode der Elektrobetäubung per Kopfdurchströmung durchaus geeignet. Zur Validierung der Kombination von Vorkühlung, Elektrobetäubung und Eiswasserbehandlung sind weitere Untersuchungen erforderlich

Function of the anion transporter AtCLC-d in the trans-Golgi network

Anion transporting proteins of the CLC type are involved in anion homeostasis in a variety of organisms. CLCs from Arabidopsis have been shown to participate in nitrate accumulation and storage. In this study, the physiological role of the functional chloride transporter AtCLC-d from Arabidopsis was investigated. AtCLC-d is weakly expressed in various tissues, including the root. When transiently expressed as a GFP fusion in protoplasts, it co-localized with the VHA-a1 subunit of the proton-transporting V-type ATPase in the trans-Golgi network (TGN). Stable expression in plants showed that it co-localized with the endocytic tracer dye FM4-64 in a brefeldin A-sensitive compartment. Immunogold electron microscopy confirmed the localization of AtCLC-d to the TGN. Disruption of the AtCLC-d gene by a T-DNA insertion did not affect the nitrate and chloride contents. The overall morphology of these clcd-1 plants was similar to that of the wild-type, but root growth on synthetic medium was impaired. Moreover, the sensitivity of hypocotyl elongation to treatment with concanamycin A, a blocker of the V-ATPase, was stronger in the clcd-1 mutant. These phenotypes could be complemented by overexpression of AtCLC-d in the mutant background. The results suggest that the luminal pH in the trans-Golgi network is adjusted by AtCLC-d-mediated transport of a counter anion such as Cl− or NO3−

Ion transport versus gas conduction: function of AMT/Rh-type proteins.

Although lipid membranes exhibit some permeability to the weak base NH3, organisms have developed specialized proteins that increase and regulate the NH3 fluxes across cellular membranes. In humans, the Rh glycoproteins, such as the erythrocyte-specific RhAG and the liver and kidney homologs RhBG and RhCG, are involved in the passage of NH3. Rh glycoproteins have distant relatives, called ammonium transporters (AMTs), in archae and bacteria. The crystal structures of AMTs show that the proteins are homo-trimers and that the center of each monomer forms a pore. AMT/Rh proteins have also been identified in plants. In contrast to the human Rh glycoproteins, these AMTs specifically transport NH4+ or co-transport NH3/H+. Hence, they can transport against NH3 gradients. The molecular determinants for the different transport mechanisms within proteins of the same family are currently unclear. The functional differences between AMT/Rh transporters are likely to be an evolutionary adaptation to different ammonium and nitrogen requirements in bacteria, plants and animals