Expression of the Mitochondrial Genome in HeLa Cells. XV. Effect of Inhibition of Mitochondrial Protein Synthesis on Mitochondrial Formation

The effect of selective inhibition of mitochondrial protein synthesis by chloramphenicol at 40 or 200 µg/ml on the formation of mitochondria in HeLa cells was investigated. HeLa cells, under the conditions used in the present work, grow at a decreasing rate for at least four cell generations in the presence of 40 µg/ml chloramphenicol, and for two generations in the presence of 200 µg/ml chloramphenicol. The progressive cell growth inhibition which begins after 2 days of exposure of the cells to 40 µg/ml chloramphenicol is immediately or gradually reversible, upon removal of the drug, for periods up to at least 8 days of treatment, though there is a progressive loss of cloning efficiency. In cells which have been treated for 6–7 days with 40 or 200 µg/ml of chloramphenicol, mitochondrial protein synthesis occurs at a normal or near-normal rate 1 h after removal of the drug. Mitochondria increase normally in number and show a normal size and amount of cristae in the presence of either concentration of drug. However, in 4–5% of the mitochondrial profiles the cristae appear to be arranged in unusual, circular, looped or whorled configuration

Temporary work agencies and equilibrium unemployment. CES Germany & Europe Working Paper no. 02.6, 2002

A striking feature of OECD labor markets in the 1990s has been the very rapid increase of temporary agency work. We augment the equilibrium unemployment model as developed by Pissarides and Mortensen with temporary work agencies in order to focus on their role as matching intermediaries and to examine the aggregate impact on employment. Our model implies that the improvement in the matching efficiency of agencies led to the emergence and growth of temporary agency work. We also show that temporary agency work does not necessarily crowd out other jobs. In this paper we extend an equilibrium unemployment model, as in Diamond (1981), Mortensen (1982), and Pissarides (1990) with temporary agency work in order to focus on its role as a matching intermediary and its aggregate impact on employment

Spitzer Warm Mission Workshop Introduction

The Spitzer Warm Mission Workshop was held June 4–5, 2007, to explore the science drivers for the warm Spitzer mission and help the Spitzer Science Center develop a new science operations philosophy. We must continue to maximize the science return with the reduced resources available, both using (a) the shortest two IRAC channels, and (b) archival research with the rich Spitzer archive. This paper summarizes the overview slides presented to the workshop participant

Benchmarking European labour market performance with efficiency frontier techniques

The issue addressed in this paper is how to obtain a composite measure of several indicators using benchmarking principles. While the exposition is only in two dimensions, and thus can be presented graphically, this is sufficient to capture the essence of the methodology and provide the basis for a critical examination of the assumptions. The data used is labour market statistics for the Member States of the European Union. The proposed approach comes from a technique originally used in production theory, namely efficiency frontiers. Here, however, we benchmark not efficiency but performance. There are two main problems. First, related to composite measures, how does one compare (weigh) indicators that are not obviously comparable? Second, related to benchmarking, how does one benchmark countries that may differ considerably as regards the mix of the various indicators. Both these issues concern weights and require that the weighting system should be parsimonious as regards assumptions and flexible, in that not all countries should necessarily be awarded the same weights. -- In der Analyse wird gezeigt, wie ein Gesamtindikator aus Einzelindikatoren konzipiert werden kann, die auf der Basis von Benchmarking-Kriterien entwickelt worden sind. Obwohl sich der Ansatz auf (nur) zwei Parameter beschränkt - und er so graphisch darstellbar wird - ist dies ausreichend, um den Kern des methodischen Ansatzes erfassen und kritisch überprüfen zu können. Die verwendeten Daten sind Arbeitsmarktstatistiken der EU-Mitgliedstaaten. Der vorgeschlagene Ansatz wurde ursprünglich in der Produktionstheorie verwendet, insbesondere zur Ermittlung der vordersten Effizienzgrenze (frontier). In der vorliegenden Analyse wird allerdings nicht die Effizienz, sondern die Leistung (performance) gemessen. Es stellen sich hauptsächlich zwei Probleme. Das erste Problem hängt mit dem Charakter von Gesamtindikatoren zusammen: Wie sollen Indikatoren gewichtet und verglichen werden, die nicht auf den ersten Blick vergleichbar sind? Das zweite Problem bezieht sich auf das Benchmarking: Wie können sehr unterschiedliche Länder durch einen Mix sehr unterschiedlicher Indikatoren vergleichend gemessen werden? Beide Aspekte beziehen sich auf Gewichtungsprobleme und erfordern, in den Gewichtungsprozeß möglichst wenige (normative) Annahmen einfließen zu lassen und das Gewichtungssystem so flexibel zu konzipieren, daß nicht allen Ländern automatisch das gleiche Gewicht zugemessen wird.

Temporary work agencies and equilibrium unemployment

During the 1990s, temporary agency work has increased rapidly in most OECD countries. We augment the equilibrium unemployment model developed by Pissarides and Mortensen with temporary work agencies. Our model implies that technological improvements for placements and de-regulation of the sector caused the emergence and growth of temporary agency work. Simulations of a calibrated version of the model show that `temp' work does not necessarily crowd out other, regular jobs. -- Während der neunziger Jahre stieg der Anteil der Zeitarbeit gemessen an der Gesamtbeschäftigung in fast allen OECD Ländern stark an. Wir erweitern das von Pissarides und Mortensen entwickelte Arbeitsmarktmodell mit Zeitarbeit. Auf der Grundlage unseres Modells lässt sich zeigen, dass technologische Veränderungen in der Informations- und Kommunikationstechnologie und die Deregulierung der Zeitarbeit Aufkommen und Wachstum des Zeitarbeitssektors verursachten. Simulationen des kalibrierten Modells legen nahe, dass Zeitarbeit nicht notwendigerweise Normalarbeitsverhältnisse verdrängt.

Temporary Work in Turbulent Times: The Swedish Experience

Sweden has experienced a substantial increase in temporary work over the 1990s, with most of the rise occurring during a severe macroeconomic recession with mass unemployment. By the early 1990s, workers on fixed-term contracts accounted for 10 percent of the number of employees; by the end of the decade they accounted for 16 percent. The paper presents the Swedish institutional setting, documents basic stylised facts about fixed-term contracts, and discusses the causes of their increased prevalence. Our analysis reveals that open-ended and temporary employment exhibit strikingly different cyclical behaviour with temporary employment being more volatile. A recession is associated with an initial decline in temporary employment followed by a sharp rise from the trough to the end of the recession. We argue that the severe recession of the 1990s is a major factor behind the rise in temporary work in Sweden. Adverse macroeconomic conditions make firms more prone to offer fixed-term contracts and workers more willing to accept them.Temporary jobs; Labour market dynamics; Unemployment

The evolution of Omega(HI) and the epoch of formation of damped Lyman-alpha absorbers

We present a study of the evolution of the column density distribution, f(N,z), and total neutral hydrogen mass in high-column density quasar absorbers using candidates from a recent high-redshift survey for damped Lyman-alpha (DLA) and Lyman limit system (LLS) absorbers. The observed number of LLS (N(HI)> 1.6 * 10^{17} atom/cm^2) is used to constrain f(N,z) below the classical DLA Wolfe et al. (1986) definition of 2 * 10^{20} atom/cm^2. The joint LLS-DLA analysis shows unambiguously that f(N,z) deviates significantly from a single power law and that a Gamma-law distribution of the form f(N,z)=(f_*/N_*)(N/N_*)^{-Beta} exp(-N/N_*) provides a better description of the observations. These results are used to determine the amount of neutral gas contained in DLAs and in systems with lower column density. Whilst in the redshift range 2 to 3.5, ~90% of the neutral HI mass is in DLAs, we find that at z>3.5 this fraction drops to only 55% and that the remaining 'missing' mass fraction of the neutral gas lies in sub-DLAs with N(HI) 10^{19} - 2 * 10^{20} atom/cm^2. The characteristic column density, N_*, changes from 1.6 * 10^{21} atom/cm^2 at z3.5, supporting a picture where at z>3.5, we are directly observing the formation of high column density neutral hydrogen DLA systems from lower column density units. Moreover since current metallicity studies of DLA systems focus on the higher column density systems they may be giving a biased or incomplete view of global galactic chemical evolution at z>3. After correcting the observed mass in HI for the ``missing'' neutral gas the comoving mass density now shows no evidence for a decrease above z=2. (abridged)Comment: Replaced to match version published in MNRAS. One figure and appendix added, analysis and conclusions unchange

The Echo of Job Displacement

This paper examines whether the loss of a job increases the likelihood of future difficulties on the labour market. We study displacement resulting from all plant closures (with ten or more employees) in Sweden in 1987 and follow their labor market outcome up to 1999. The control group is extracted from a random sample of non-displaced employees by matching on propensity scores. We find a rapid and almost total initial recovery of those displaced in 1987 compared to the control group up to 1990, both with respect to employment and unemployment measures. However, with the advent of the deep recession in 1990, the two groups again diverge. There is some relative recovery in the mid to late 1990s. However, by the end of the 1990s, the echo of the job loss 13 years earlier had still not subsided. We attribute the long-term effects as being either due to recurrent loss of match-specific capital or statutory seniority lay-offs rules.Plant closure, displaced workers, unemployment scarring, linked employeremployee data, propensity score matching.

Temporary Work in Turbulent Times: The Swedish Experience

Sweden has experienced a substantial increase in temporary work over the 1990s, with most of the rise occurring during a severe macroeconomic recession with mass unemployment. By the early 1990s, workers on fixed-term contracts accounted for 10 percent of the number of employees; by the end of the decade they accounted for 16 percent. The paper presents the Swedish institutional setting, documents basic stylised facts about fixed-term contracts, and discusses the causes of their increased prevalence. Our analysis reveals that open-ended and temporary employment exhibit strikingly different cyclical behaviour with temporary employment being more volatile. A recession is associated with an initial decline in temporary employment followed by a sharp rise from the trough to the end of the recession. We argue that the severe recession of the 1990s is a major factor behind the rise in temporary work in Sweden. Adverse macroeconomic conditions make firms more prone to offer fixed-term contracts and workers more willing to accept them.temporary jobs, labour market dynamics, unemployment

Evolution of Neutral Gas at High Redshift -- Implications for the Epoch of Galaxy Formation

Though observationally rare, damped Lya absorption systems dominate the mass density of neutral gas in the Universe. Eleven high redshift damped Lya systems covering 2.84 QSO Survey, extending these absorption system surveys to the highest redshifts currently possible. Combining our new data set with previous surveys we find that the cosmological mass density in neutral gas, omega_g, does not rise as steeply prior to z~2 as indicated by previous studies. There is evidence in the observed omega_g for a flattening at z~2 and a possible turnover at z~3. When combined with the decline at z>3.5 in number density per unit redshift of damped systems with column densities log N(HI)>21 atoms cm^-2, these results point to an epoch at z>3 prior to which the highest column density damped systems are still forming. We find that over the redshift range 2<z<4 the total mass in neutral gas is marginally comparable with the total visible mass in stars in present day galaxies. However, if one considers the total mass visible in stellar disks alone, ie excluding galactic bulges, the two values are comparable. We are observing a mass of neutral gas comparable to the mass of visible disk stars. Lanzetta, Wolfe & Turnshek (1995) found that omega_g(z~3.5) was twice omega_g(z~2), implying a much larger amount of star formation must have taken place between z=3.5 and z=2 than is indicated by metallicity studies. This created a `cosmic G-dwarf problem'. The more gradual evolution of omega_g we find alleviates this. These results have profound implications for theories of galaxy formation.Comment: To appear in MNRAS. Latex file (4 pages of text) plus 3 separate postscript figure files. Requires mn.sty. Postscript version with figures embedded is available at http://www.ociw.edu/~lisa/publications.htm