Regional Labor Market Disparities

Regionale Arbeitsmärkte unterscheiden sich erheblich hinsichtlich wesentlicher Kennzahlen wie der Arbeitslosenquote, des Lohnniveaus oder der Beschäftigungsentwicklung. Wegen ihrer Persistenz sind diese Unterschiede von hoher Relevanz für die Politik. Die wirtschaftswissenschaftliche Literatur liefert bereits theoretische Modelle für die Analyse regionaler Arbeitsmärkte. In der Regel sind diese Modelle aber nicht dazu geeignet, regionale Arbeitsmarktunterschiede endogen zu erklären. Das bedeutet, dass sich die Unterschiede regionaler Arbeitsmärkte in der Regel nicht aus den Modellzusammenhängen selbst ergeben, sondern „von außen“ eingebracht werden müssen. Die empirische Literatur liefert Hinweise, dass die Unterschiede zwischen regionalen Arbeitsmärkten auf die Höhe der regionalen Arbeitsnachfrage zurückzuführen sind. Die Arbeitsnachfrage wiederum leitet sich aus den Gütermärkten ab: Es hängt von der Entwicklung der regionalen Gütermärkte ab, wie viele Arbeitskräfte benötigt werden. Daraus folgt, dass die Ursachen für Unterschiede regionaler Arbeitsmärkte in den Unterschieden zwischen den regionalen Gütermärkten zu suchen sind. Letztere werden durch die Literatur zur Neuen Ökonomischen Geographie (NÖG) untersucht. Die Literatur zur NÖG erklärt Unterschiede regionaler Gütermärkte, indem sie zentripetale und zentrifugale Kräfte gegenüberstellt. Zentripetale Kräfte sind solche, welche hin zur Agglomeration ökonomischer Aktivität wirken. Im Zentrum dieser Diskussion steht vor allem das Marktpotenzial: Unternehmen siedeln sich bevorzugt an solchen Standorten an, welche nahe an großen Märkten liegen. Erwerbspersonen wiederum bevorzugen solche Regionen, welche ihnen entsprechende Erwerbsaussichten bieten. Beides zusammen bildet einen sich selbst verstärkenden Prozess, der zur Agglomeration ökonomischer Aktivität führt. Dem stehen jedoch zentrifugale Kräfte gegenüber, welche eine gleichmäßigere Verteilung ökonomischer Aktivität bewirken. Diese entstehen beispielsweise durch immobile Produktionsfaktoren oder Ballungskosten wie etwa Umweltverschmutzung, Staus oder hohe Mietpreise. Sind die zentripetalen Kräfte hinreichend stark, so bilden sich Zentren heraus, in denen sich die ökonomische Aktivität konzentriert, während die Peripherie ausdünnt. In welchem Ausmaß dies geschieht, hängt von dem Verhältnis beider Kräfte ab. Üblicherweise konzentriert sich die Literatur zur NÖG auf Unterschiede zwischen regionalen Gütermärkten und geht von der Annahme perfekter Arbeitsmärkte ohne Arbeitslosigkeit aus. Die Entstehung und Persistenz regionaler Arbeitsmarktunterschiede kann die NÖG daher üblicherweise nicht erklären. An dieser Stelle setzt die Dissertation an. Sie erweitert die NÖG um Friktionen auf dem Arbeitsmarkt, um die Entstehung und Persistenz regionaler Arbeitsmarktunterschiede zu erklären. Sie greift dazu auf eine empirische Regelmäßigkeit zurück: Zahlreiche Studien belegen einen negativen Zusammenhang zwischen Lohn und Arbeitslosigkeit. In Regionen, in denen die Arbeitslosigkeit hoch ist, ist das Lohnniveau gering und umgekehrt. Dieser Zusammenhang wird als Lohnkurve bezeichnet. Auf regionaler Ebene lässt sich die Lohnkurve mithilfe der Effizienzlohntheorie erklären, die als theoretische Grundlage in der Dissertation Anwendung findet. Konzentriert sich nun die ökonomische Aktivität aufgrund der zentripetalen Kräfte in einer Region, so ist in diesem Zentrum die Arbeitsnachfrage höher. Damit befindet sich das Zentrum auf einer günstigen Position der Lohnkurve mit geringer Arbeitslosigkeit und hohem Lohnniveau. Umgekehrt findet sich die Peripherie auf einer ungünstigen Position mit hoher Arbeitslosigkeit und geringem Lohnniveau wieder. Allerdings kann sich die Lohnkurve in Abhängigkeit des Agglomerationsgrades verschieben. Das komplexe Zusammenspiel der endogenen Agglomeration mit den Arbeitsmarktfriktionen kann dann unterschiedliche Muster regionaler Arbeitsmarktdisparitäten hervorrufen. Die Dissertation zeigt auf, wie im Zusammenspiel der NÖG mit Effizienzlöhnen regionale Arbeitsmarktdisparitäten hervorgerufen werden. Es werden theoretische Modelle formuliert, die diese Interaktionen erklären und welche die bestehende Literatur durch spezifische Beiträge erweitern. Darüber hinaus werden die zentralen Argumente der Theorie einem empirischen Test unterworfen. Es kann gezeigt werden, dass das zentrale Argument – der positive Effekt des Marktpotentials auf die Arbeitsnachfrage – relevant ist. Außerdem werden Politikimplikationen abgeleitet und der weitere Forschungsbedarf aufgezeigt.

Exercise sheet 3

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Exercise sheet 3 pdf

Exercises and solutions in PDF

Incongruence between test statistics and P values in medical papers

Given an observed test statistic and its degrees of freedom, one may compute the observed P value with most statistical packages. It is unknown to what extent test statistics and P values are congruent in published medical papers. Methods: We checked the congruence of statistical results reported in all the papers of volumes 409–412 of Nature (2001) and a random sample of 63 results from volumes 322–323 of BMJ (2001). We also tested whether the frequencies of the last digit of a sample of 610 test statistics deviated from a uniform distribution (i.e., equally probable digits).Results: 11.6% (21 of 181) and 11.1% (7 of 63) of the statistical results published in Nature and BMJ respectively during 2001 were incongruent, probably mostly due to rounding, transcription, or type-setting errors. At least one such error appeared in 38% and 25% of the papers of Nature and BMJ, respectively. In 12% of the cases, the significance level might change one or more orders of magnitude. The frequencies of the last digit of statistics deviated from the uniform distribution and suggested digit preference in rounding and reporting.Conclusions: this incongruence of test statistics and P values is another example that statistical practice is generally poor, even in the most renowned scientific journals, and that quality of papers should be more controlled and valued

Measuring root traits in barley (Hordeum vulgare ssp vulgare and ssp spontaneum) seedlings using gel chambers, soil sacs and X-ray microtomography

Root characteristics of seedlings of five different barley genotypes were analysed in 2D using gel chambers, and in 3D using soil sacs that were destructively harvested and pots of soil that were assessed non-invasively using X-ray microtomography. After 5 days, Chime produced the greatest number of root axes (similar to 6) and Mehola significantly less (similar to 4) in all growing methods. Total root length was longest in GSH01915 and shortest in Mehola for all methods, but both total length and average root diameter were significantly larger for plants grown in gel chambers than those grown in soil. The ranking of particular growth traits (root number, root angular spread) of plants grown in gel plates, soil sacs and X-ray pots was similar, but plants grown in the gel chambers had a different order of ranking for root length to the soil-grown plants. Analysis of angles in soil-grown plants showed that Tadmore had the most even spread of individual roots and Chime had a propensity for non-uniform distribution and root clumping. The roots of Mehola were less well spread than the barley cultivars supporting the suggestion that wild and landrace barleys tend to have a narrower angular spread than modern cultivars. The three dimensional analysis of root systems carried out in this study provides insights into the limitations of screening methods for root traits and useful data for modelling root architecture.

Does reactive surface area depend on grain size? Results from pH 3, 25 circle C far-from-equilibrium flow-through dissolution experiments on anorthite and biotite

Laboratory determined mineral weathering rates need to be normalised to allow their extrapolation to natural systems. The principle normalisation terms used in the literature are mass, and geometric- and BET specific surface area (SSA). The purpose of this study was to determine how dissolution rates normalised to these terms vary with grain size. Different size fractions of anorthite and biotite ranging from 180-150 to 20-10 mu m were dissolved in pH 3, HCl at 25 degrees C in flow through reactors under far from equilibrium conditions. Steady state dissolution rates after 5376 h (anorthite) and 4992 h (biotite) were calculated from Si concentrations and were normalised to initial- and final- mass and geometric-, geometric edge- (biotite), and BET SSA. For anorthite, rates normalised to initial- and final-BET SSA ranged from 0.33 to 2.77 X 10(-10) mol(feldspar) m(-2) s(-1), rates normalised to initial- and final-geometric SSA ranged from 5.74 to 8.88 X 10(-10) mol(feldspar) m(-2) s(-1) and rates normalised to initial- and final-mass ranged from 0.11 to 1.65 mol(feldspar) g(-1) s(-1). For biotite, rates normalised to initial- and final-BET SSA ranged from 1.02 to 2.03 X 10(-12) mol(biotite) m(-2) s(-1), rates normalised to initial- and final-geometric SSA ranged from 3.26 to 16.21 X 10(-12) mol(biotite) m(-2) s(-1), rates normalised to initial- and final-geometric edge SSA ranged from 59.46 to 111.32 x 10(-12) mol(biotite) m(-2) s(-1) and rates normalised to initial- and final-mass ranged from 0.81 to 6.93 X 10(-12) mol(biotite) g(-1) s(-1). For all normalising terms rates varied significantly (p <= 0.05) with grain size. The normalising terms which gave least variation in dissolution rate between grain sizes for anorthite were initial BET SSA and initial- and final-geometric SSA. This is consistent with: (1) dissolution being dominated by the slower dissolving but area dominant non-etched surfaces of the grains and, (2) the walls of etch pits and other dissolution features being relatively unreactive. These steady state normalised dissolution rates are likely to be constant with time. Normalisation to final BET SSA did not give constant ratios across grain size due to a non-uniform distribution of dissolution features. After dissolution coarser grains had a greater density of dissolution features with BET-measurable but unreactive wall surface area than the finer grains. The normalising term which gave the least variation in dissolution rates between grain sizes for biotite was initial BET SSA. Initial- and final-geometric edge SSA and final BET SSA gave the next least varied rates. The basal surfaces dissolved sufficiently rapidly to influence bulk dissolution rate and prevent geometric edge SSA normalised dissolution rates showing the least variation. Simple modelling indicated that biotite grain edges dissolved 71-132 times faster than basal surfaces. In this experiment, initial BET SSA best integrated the different areas and reactivities of the edge and basal surfaces of biotite. Steady state dissolution rates are likely to vary with time as dissolution alters the ratio of edge to basal surface area. Therefore they would be more properly termed pseudo-steady state rates, only appearing constant because the time period over which they were measured (1512 h) was less than the time period over wich they would change significantly. (c) 2006 Elsevier Inc. All rights reserved.

Rate-limiting steps in the development of atherosclerosis: the response-to-influx theory

A large number of processes are involved in the pathogenesis of atherosclerosis but it is unclear which of them play a rate-limiting role. One way of resolving this problem is to investigate the highly non-uniform distribution of disease within the arterial system; critical steps in lesion development should be revealed by identifying arterial properties that differ between susceptible and protected sites. Although the localisation of atherosclerotic lesions has been investigated intensively over much of the 20th century, this review argues that the factor determining the distribution of human disease has only recently been identified. Recognition that the distribution changes with age has, for the first time, allowed it to be explained by variation in transport properties of the arterial wall; hitherto, this view could only be applied to experimental atherosclerosis in animals. The newly discovered transport variations which appear to play a critical role in the development of adult disease have underlying mechanisms that differ from those elucidated for the transport variations relevant to experimental atherosclerosis: they depend on endogenous NO synthesis and on blood flow. Manipulation of transport properties might have therapeutic potential. Copyright (C) 2004 S. Karger AG, Basel.

Evidence that GABA rho subunits contribute to functional ionotropic GABA receptors in mouse cerebellar Purkinje cells

Ionotropic gamma-amino butyric acid (GABA) receptors composed of heterogeneous molecular subunits are major mediators of inhibitory responses in the adult CNS. Here, we describe a novel ionotropic GABA receptor in mouse cerebellar Purkinje cells (PCs) using agents reported to have increased affinity for rho subunit-containing GABA(C) over other GABA receptors. Exogenous application of the GABA(C)-preferring agonist cis-4-aminocrotonic acid (CACA) evoked whole-cell currents in PCs, whilst equimolar concentrations of GABA evoked larger currents. CACA-evoked currents had a greater sensitivity to the selective GABA(C) antagonist (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) than GABA-evoked currents. Focal application of agonists produced a differential response profile; CACA-evoked currents displayed a much more pronounced attenuation with increasing distance from the PC soma, displayed a slower time-to-peak and exhibited less desensitization than GABA-evoked currents. However, CACA-evoked currents were also completely blocked by bicuculline, a selective agent for GABA(A) receptors. Thus, we describe a population of ionotropic GABA receptors with a mixed GABA(A)/GABA(C) pharmacology. TPMPA reduced inhibitory synaptic transmission at interneurone-Purkinje cell (IN-PC) synapses, causing clear reductions in miniature inhibitory postsynaptic current (mIPSC) amplitude and frequency. Combined application of NO-711 (a selective GABA transporter subtype 1 (GAT-1) antagonist) and SNAP-5114 (a GAT-(2)/3/4 antagonist) induced a tonic GABA conductance in PCs; however, TPMPA had no effect on this current. Immunohistochemical studies suggest that rho subunits are expressed predominantly in PC soma and proximal dendritic compartments with a lower level of expression in more distal dendrites; this selective immunoreactivity contrasted with a more uniform distribution of GABA(A) alpha 1 subunits in PCs. Finally, co-immunoprecipitation studies suggest that rho subunits can form complexes with GABA(A) receptor alpha 1 subunits in the cerebellar cortex. Overall, these data suggest that rho subunits contribute to functional ionotropic receptors that mediate a component of phasic inhibitory GABAergic transmission at IN-PC synapses in the cerebellum.

Production, hidden action, and the payment system

In this paper, we study a model economy that examines the optimal intraday rate. In Freeman’s (1996) paper, he shows that the efficient allocation can be implemented by adopting a policy in which the intraday rate is zero. We modify the production set and show that such a model economy can account for the non-uniform distribution of settlements within a day. In addition, by modifying both the consumption set and the production set, we show that the central bank may be able to implement the planner’s allocation with a positive intraday interest rate.

Coalescence of particles by differential sedimentation

We consider a three dimensional system consisting of a large number of small spherical particles, distributed in a range of sizes and heights (with uniform distribution in the horizontal direction). Particles move vertically at a size-dependent terminal velocity. They are either allowed to merge whenever they cross or there is a size ratio criterion enforced to account for collision efficiency. Such a system may be described, in mean field approximation, by the Smoluchowski kinetic equation with a differential sedimentation kernel. We obtain self-similar steady-state and time-dependent solutions to the kinetic equation, using methods borrowed from weak turbulence theory. Analytical results are compared with direct numerical simulations (DNS) of moving and merging particles, and a good agreement is found.

The population dynamics of disease on short and long time-scales

Observational evidence is scarce concerning the distribution of plant pathogen population sizes or densities as a function of time-scale or spatial scale. For wild pathosystems we can only get indirect evidence from evolutionary patterns and the consequences of biological invasions.We have little or no evidence bearing on extermination of hosts by pathogens, or successful escape of a host from a pathogen. Evidence over the last couple of centuries from crops suggest that the abundance of particular pathogens in the spectrum affecting a given host can vary hugely on decadal timescales. However, this may be an artefact of domestication and intensive cultivation. Host-pathogen dynamics can be formulated mathematically fairly easily–for example as SIR-type differential equation or difference equation models, and this has been the (successful) focus of recent work in crops. “Long-term” is then discussed in terms of the time taken to relax from a perturbation to the asymptotic state. However, both host and pathogen dynamics are driven by environmental factors as well as their mutual interactions, and both host and pathogen co-evolve, and evolve in response to external factors. We have virtually no information about the importance and natural role of higher trophic levels (hyperpathogens) and competitors, but they could also induce long-scale fluctuations in the abundance of pathogens on particular hosts. In wild pathosystems the host distribution cannot be modelled as either a uniform density or even a uniform distribution of fields (which could then be treated as individuals). Patterns of short term density-dependence and the detail of host distribution are therefore critical to long-term dynamics. Host density distributions are not usually scale-free, but are rarely uniform or clearly structured on a single scale. In a (multiply structured) metapopulation with coevolution and external disturbances it could well be the case that the time required to attain equilibrium (if it exists) based on conditions stable over a specified time-scale is longer than that time-scale. Alternatively, local equilibria may be reached fairly rapidly following perturbations but the meta-population equilibrium be attained very slowly. In either case, meta-stability on various time-scales is a more relevant than equilibrium concepts in explaining observed patterns.

Concentric characterization and classification of complex network nodes: Application to an institutional collaboration network

Differently from theoretical scale-free networks, most real networks present multi-scale behavior, with nodes structured in different types of functional groups and communities. While the majority of approaches for classification of nodes in a complex network has relied on local measurements of the topology/connectivity around each node, valuable information about node functionality can be obtained by concentric (or hierarchical) measurements. This paper extends previous methodologies based on concentric measurements, by studying the possibility of using agglomerative clustering methods, in order to obtain a set of functional groups of nodes, considering particular institutional collaboration network nodes, including various known communities (departments of the University of Sao Paulo). Among the interesting obtained findings, we emphasize the scale-free nature of the network obtained, as well as identification of different patterns of authorship emerging from different areas (e.g. human and exact sciences). Another interesting result concerns the relatively uniform distribution of hubs along concentric levels, contrariwise to the non-uniform pattern found in theoretical scale-free networks such as the BA model. (C) 2008 Elsevier B.V. All rights reserved.

Fault detection in a cold forging process through feature extraction with a neural network

This paper investigates the application of neural networks to the recognition of lubrication defects typical to an industrial cold forging process employed by fastener manufacturers. The accurate recognition of lubrication errors, such as coating not being applied properly or damaged during material handling, is very important to the quality of the final product in fastener manufacture. Lubrication errors lead to increased forging loads and premature tool failure, as well as to increased defect sorting and the re-processing of the coated rod. The lubrication coating provides a barrier between the work material and the die during the drawing operation; moreover it needs be sufficiently robust to remain on the wire during the transfer to the cold forging operation. In the cold forging operation the wire undergoes multi-stage deformation without the application of any additional lubrication. Four types of lubrication errors, typical to production of fasteners, were introduced to a set of sample rods, which were subsequently drawn under laboratory conditions. The drawing force was measured, from which a limited set of features was extracted. The neural network based model learned from these features is able to recognize all types of lubrication errors to a high accuracy. The overall accuracy of the neural network model is around 98% with almost uniform distribution of errors between all four errors and the normal condition.

Potentiostatic control of ionic liquid surface film formation on ZE41 magnesium alloy

The generation of potentially corrosion-resistant films on light metal alloys of magnesium have been investigated. Magnesium alloy, ZE41 [Mg−Zn−Rare Earth (RE)-Zr, nominal composition 4 wt % Zn, 1.7 wt % RE (Ce), 0.6 wt % Zr, remaining balance, Mg], was exposed under potentiostatic control to the ionic liquid trihexyl(tetradecyl)phosphonium diphenylphosphate, denoted [P_6,6,6,14][DPP]. During exposure to this IL, a bias potential, shifted from open circuit, was applied to the ZE41 surface. Electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) were used to monitor the evolution of film formation on the metal surface during exposure. The EIS data indicate that, of the four bias potentials examined, applying a potential of −200 mV versus OCP during the exposure period resulted in surface films of greatest resistance. Both EIS measurements and scanning electron microscopy (SEM) imaging indicate that these surfaces are substantially different to those formed without potential bias. Time of flight-secondary ion mass spectrometry (ToF-SIMS) elemental mapping of the films was utilized to ascertain the distribution of the ionic liquid cationic and anionic species relative to the microstructural surface features of ZE41 and indicated a more uniform distribution compared with the surface following exposure in the absence of a bias potential. Immersion of the treated ZE41 specimens in a chloride contaminated salt solution clearly indicated that the ionic liquid generated surface films offered significant protection against pitting corrosion, although the intermetallics were still insufficiently protected by the IL and hence favored intergranular corrosion processes.

Fabrication of nano-particle reinforced metal matrix composites

Nanoparticle reinforced metal matrix possess much better mechanical properties over microparticle reinforced metal matrix composites as well as corresponding monolithic matrix materials. However, the fabrication methods of nanoparticle reinforced metal matrix composites are complex and expensive. This paper investigates and discusses the mechanisms of all the fabrication process, such as powder metallurgy, liquid metallurgy, compocasting and hybrid methods, available in the literature. This gives an insight on challenges associated with different processes and ways to improve the fabrication processes. It is found that modified traditional fabrication processes are mainly applied for these materials. The main problem is to achieve reasonably uniform distribution of nanoparticle reinforcement in the methods other than mechanical alloying when the volume or weight percent of reinforcement is higher (> 1%).