Employment consequences of restrictive permanent contracts: Evidence from Spanish labor market reforms

Temporary employment contracts allowing unrestricted dismissals were introduced in Spain in 1984 and quickly came to account for most new jobs. As a result, temporary employment increased from around 10% in the mid-eighties to more than 30% in the early nineties. In 1997, however, the Spanish government attempted to reduce the incidence of temporary employment by reducing payroll taxes and dismissal costs for permanent contracts. In this paper, we use individual data from the Spanish Labor Force Survey to estimate the effects of reduced payroll taxes and dismissal costs on the distribution of employment and worker flows. We exploit the fact that recent reforms apply only to certain demographic groups to set up a natural experiment research design that can be used to study the effects of contract regulations. Our results show that the reduction of payroll taxes and dismissal costs increased the employment of young workers on permanent contracts, although the effects for young women are not always significant. Results for older workers show insignificant effects. The results suggest a moderately elastic response of permanent employment to non-wage labor costs for young men. We also find positive effects on the transitions from unemployment and temporary employment into permanent employment for young and older workers, although the effects for older workers are not always significant. On the other hand, transitions from permanent employment to non-employment increased only for older men, suggesting that the reform had little effect on dismissals.Temporary employment, dismissal costs, payroll taxes, European unemployment

X-ray monitoring of classical novae in the central region of M31. III. Autumn and winter 2009/10, 2010/11 and 2011/12

[Abridged] Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy M31. We performed a dedicated monitoring of the M31 central region, aimed to detect SSS counterparts of CNe, with XMM-Newton and Chandra between Nov and Mar of the years 2009/10, 2010/11 and 2011/12. In total we detected 24 novae in X-rays. Seven of these sources were known from previous observations, including the M31 nova with the longest SSS phase, M31N~1996-08b, which was found to fade below our X-ray detection limit 13.8 yr after outburst. Of the new discoveries several novae exhibit significant variability in their short-term X-ray light curves with one object showing a suspected period of about 1.3 h. We studied the SSS state of the most recent outburst of a recurrent nova which had previously shown the shortest time ever observed between two outbursts (about 5 yr). The total number of M31 novae with X-ray counterpart was increased to 79 and we subjected this extended catalogue to detailed statistical studies. Four previously indicated correlations between optical and X-ray parameters could be confirmed and improved. We found indications that the multi-dimensional parameter space of nova properties might be dominated by a single physical parameter. We discuss evidence for a different X-ray behaviour of novae in the M31 bulge and disk. Exploration of the multi-wavelength parameter space of optical and X-ray measurements is shown to be a powerful tool for examining properties of extragalactic nova populations. While there are hints that the different stellar populations of M31 (bulge vs disk) produce dissimilar nova outbursts, there is also growing evidence that the overall behaviour of an average nova might be understood in surprisingly simple terms.Comment: 39 pages (half of them for 9 tables), 14 figures, accepted for publication in A&A; updated after language editing stag

Evidence for nonlinear diffusive shock acceleration of cosmic-rays in the 2006 outburst of the recurrent nova RS Ophiuchi

Spectroscopic observations of the 2006 outburst of the recurrent nova RS Ophiuchi at both infrared (IR) and X-ray wavelengths have shown that the blast wave has decelerated at a higher rate than predicted by the standard test-particle adiabatic shock-wave model. Here we show that the observed evolution of the nova remnant can be explained by the diffusive shock acceleration of particles at the blast wave and the subsequent escape of the highest energy ions from the shock region. Nonlinear particle acceleration can also account for the difference of shock velocities deduced from the IR and X-ray data. The maximum energy that accelerated electrons and protons can have achieved in few days after outburst is found to be as high as a few TeV. Using the semi-analytic model of nonlinear diffusive shock acceleration developed by Berezhko & Ellison, we show that the postshock temperature of the shocked gas measured with RXTE/PCA and Swift/XRT imply a relatively moderate acceleration efficiency.Comment: Accepted for publication in ApJ

Parabolic curves for diffeomorphisms in C2

We give a simple proof of the existence of parabolic curves for diffeomorphisms in (C 2 , 0) tangent to the identity with isolated fixed point

Detectability of gamma-ray emission from classical novae with Swift/BAT

Classical novae are expected to emit gamma rays during their explosions. The most important contribution to the early gamma-ray emission comes from the annihilation with electrons of the positrons generated by the decay of 13N and 18F. The photons are expected to be down-scattered to a few tens of keV, and the emission is predicted to occur some days before the visual discovery and to last ~2 days. Despite a number of attempts, no positive detections of such emission have been made, due to lack of sensitivity and of sky coverage. Because of its huge field of view, good sensitivity, and well-adapted energy band, Swift/BAT offers a new opportunity for such searches. BAT data can be retrospectively used to search for prompt gamma-ray emission from the direction of novae after their optical discovery. We have estimated the expected success rate for the detection with BAT of gamma rays from classical novae using a Monte Carlo approach. Searches were performed for emission from novae occurring since the launch of Swift. Using the actual observing program during the first 2.3 years of BAT operations as an example, and sensitivity achieved, we estimate the expected rate of detection of classical novae with BAT as ~0.2-0.5/yr, implying that several should be seen within a 10 yr mission. The search for emission in the directions of the 24 classical novae discovered since the Swift launch yielded no positive results, but none of these was known to be close enough for this to be a surprise. Detections of a recurrent nova (RS Oph) and a nearby dwarf nova (V455 And) demonstrate the efficacy of the technique. The absence of detections is consistent with the expectations from the Monte Carlo simulations, but the long-term prospects are encouraging given an anticipated Swift operating lifetime of ~10 years.Comment: 10 pages, 6 figures. Accepted for publication in A&

A remarkable recurrent nova in M 31: The predicted 2014 outburst in X-rays with Swift

The M 31 nova M31N 2008-12a was recently found to be a recurrent nova (RN) with a recurrence time of about 1 year. This is by far the fastest recurrence time scale of any known RNe. Our optical monitoring programme detected the predicted 2014 outburst of M31N 2008-12a in early October. We immediately initiated an X-ray/UV monitoring campaign with Swift to study the multiwavelength evolution of the outburst. We monitored M31N 2008-12a with daily Swift observations for 20 days after discovery, covering the entire supersoft X-ray source (SSS) phase. We detected SSS emission around day six after outburst. The SSS state lasted for approximately two weeks until about day 19. M31N 2008-12a was a bright X-ray source with a high blackbody temperature. The X-ray properties of this outburst were very similar to the 2013 eruption. Combined X-ray spectra show a fast rise and decline of the effective blackbody temperature. The short-term X-ray light curve showed strong, aperiodic variability which decreased significantly after about day 14. Overall, the X-ray properties of M31N 2008-12a are consistent with the average population properties of M 31 novae. The optical and X-ray light curves can be scaled uniformly to show similar time scales as those of the Galactic RNe U Sco or RS Oph. The SSS evolution time scales and effective temperatures are consistent with a high-mass WD. We predict the next outburst of M31N 2008-12a to occur in autumn 2015.Comment: 13 pages, 7 figures, 3 tables; accepted for publication in A&

Recent discoveries of supersoft X-ray sources in M 31

Classical novae (CNe) have recently been reported to represent the major class of supersoft X-ray sources (SSSs) in the central area of our neighbouring galaxy M 31. This paper presents a review of results from recent X-ray observations of M 31 with XMM-Newton and Chandra. We carried out a dedicated optical and X-ray monitoring program of CNe and SSSs in the central area of M 31. We discovered the first SSSs in M 31 globular clusters (GCs) and their connection to the very first discovered CN in a M 31 GC. This result may have an impact on the CN rate in GCs. Furthermore, in our optical and X-ray monitoring data we discovered the CN M31N 2007-11a, which shows a very short SSS phase of 29 - 52 days. Short SSS states (durations < 100 days) of CNe indicate massive white dwarfs (WDs) that are candidate progenitors of supernovae type Ia. In the case of M31N 2007-11a, the optical and X-ray light curves suggest a binary containing a WD with M_WD > 1.0 M_sun. Finally, we present the discovery of the SSS counterpart of the CN M31N 2006-04a. The X-ray light curve of M31N 2006-04a shows short-time variability, which might indicate an orbital period of about 2 hours.Comment: 4 pages, 1 figure; Proc. of workshop "Supersoft X-ray Sources - New Developments", ESAC, May 2009; accepted for publication in Astronomische Nachrichte

Reconsidering the generation time hypothesis based on nuclear ribosomal ITS sequence comparisons in annual and perennial angiosperms

17 pages, 3 figures, 5 tables.-- PMID: 19113991 [PubMed].[Background] Differences in plant annual/perennial habit are hypothesized to cause a generation time effect on divergence rates. Previous studies that compared rates of divergence for internal transcribed spacer (ITS1 and ITS2) sequences of nuclear ribosomal DNA (nrDNA) in angiosperms have reached contradictory conclusions about whether differences in generation times (or other life history features) are associated with divergence rate heterogeneity. We compared annual/perennial ITS divergence rates using published sequence data, employing sampling criteria to control for possible artifacts that might obscure any actual rate variation caused by annual/perennial differences.[Results] Relative rate tests employing ITS sequences from 16 phylogenetically-independent annual/perennial species pairs rejected rate homogeneity in only a few comparisons, with annuals more frequently exhibiting faster substitution rates. Treating branch length differences categorically (annual faster or perennial faster regardless of magnitude) with a sign test often indicated an excess of annuals with faster substitution rates. Annuals showed an approximately 1.6-fold rate acceleration in nucleotide substitution models for ITS. Relative rates of three nuclear loci and two chloroplast regions for the annual Arabidopsis thaliana compared with two closely related Arabidopsis perennials indicated that divergence was faster for the annual. In contrast, A. thaliana ITS divergence rates were sometimes faster and sometimes slower than the perennial. In simulations, divergence rate differences of at least 3.5-fold were required to reject rate constancy in > 80 % of replicates using a nucleotide substitution model observed for the combination of ITS1 and ITS2. Simulations also showed that categorical treatment of branch length differences detected rate heterogeneity > 80% of the time with a 1.5-fold or greater rate difference.[Conclusion] Although rate homogeneity was not rejected in many comparisons, in cases of significant rate heterogeneity annuals frequently exhibited faster substitution rates. Our results suggest that annual taxa may exhibit a less than 2-fold rate acceleration at ITS. Since the rate difference is small and ITS lacks statistical power to reject rate homogeneity, further studies with greater power will be required to adequately test the hypothesis that annual and perennial plants have heterogeneous substitution rates. Arabidopsis sequence data suggest that relative rate tests based on multiple loci may be able to distinguish a weak acceleration in annual plants. The failure to detect rate heterogeneity with ITS in past studies may be largely a product of low statistical power.This work was supported by a doctoral fellowship to D. F. Soria-Hernanz from the Spanish Ministerio de Educación y Ciencia, graduate support from Georgetown University and the Department of Biology, the Cosmos Foundation, and a National Science Foundation grant to M.B.H. (DEB9983014). Publication charges supported by the Department of Biology, Georgetown University.Peer reviewe

Caracterización fisicoquímica de mieles monoflorales de Euphorbia resinifera

The physicochemical characteristics of Euphorbia resinifera honey were studied. Considering the low water content, the majority of the honeys presented a proper maturity. The values of acidity revealed the absence of inappropriate fermentation, while the low values of hydroxymethylfurfural (0.4–16.48 mg/kg) were suitable for of unprocessed honeys. The average values for electrical conductivity and ashes were 451 µS/cm and 1.6 g/kg, respectively. As for the mineral content, the K was the most abundant element; Ca, Na, Mg, P, S, and Si are all present in differing quantities in the honeys. On the other hand, Principal Components Analysis (PCA) and Stepwise Discriminant Analysis (SDA) were applied to distinguish between three related Euphorbia honey types. PCA showed that the cumulative variance of the two first factors explained approximately 53%. The results of SDA showed that variables with a higher discriminant power were K, C*ab and a*, and 100% of the samples were properly classified in their corresponding class.Los parámetros fisicoquímicos de 29 de mieles monoflorales de Euphorbia resinifera fueron estudiadas. 24 parámetros, incluyendo humedad, pH, acidez (libre, lactónica y total), HMF, cenizas, conductividad eléctrica, monosacáridos (glucosa y fructosa), contenido mineral y parámetros cromáticos fueron analizados. Desde el punto de vista de su calidad las mieles fueron acordes con la legislación Europea en cuanto a contenido en agua, acidez y HMF. Los valores de cenizas y conductividad eléctrica fueron 1,6 g/kg y 451 μS/cm, respectivamente. El contenido en minerales mostró que el K es el elemento más abundante; mientras que Ca, Na, Mg, P, S y Si se presentaron en contenidos intermedios. En cuanto a los valores de los parámetros del color fueron típicos de mieles ámbar claras. Se ha realizado un análisis estadístico multivariante a los datos obtenidos para diferenciar tres especies de mieles de Euphorbia. El análisis discriminante permite diferencia las mieles por su origen botánico siendo el contenido en K, C*ab y la variable cromática a* las variables con mayor poder discriminate, siendo el 100% de las muestras clasificadas correctamente en su grupo