32,991 research outputs found
A novel cost effective and high-throughput isolation and identification method for marine microalgae
Background: Marine microalgae are of major ecologic and emerging economic importance. Biotechnological screening schemes of microalgae for specific traits and laboratory experiments to advance our knowledge on algal biology and evolution strongly benefit from culture collections reflecting a maximum of the natural inter- and intraspecific diversity. However, standard procedures for strain isolation and identification, namely DNA extraction, purification, amplification, sequencing and taxonomic identification still include considerable constraints increasing the time required to establish new cultures. Results: In this study, we report a cost effective and high-throughput isolation and identification method for marine microalgae. The throughput was increased by applying strain isolation on plates and taxonomic identification by direct PCR (dPCR) of phylogenetic marker genes in combination with a novel sequencing electropherogram based screening method to assess the taxonomic diversity and identity of the isolated cultures. For validation of the effectiveness of this approach, we isolated and identified a range of unialgal cultures from natural phytoplankton communities sampled in the Arctic Ocean. These cultures include the isolate of a novel marine Chlorophyceae strain among several different diatoms. Conclusions: We provide an efficient and effective approach leading from natural phytoplankton communities to isolated and taxonomically identified algal strains in only a few weeks. Validated with sensitive Arctic phytoplankton, this approach overcomes the constraints of standard molecular characterisation and establishment of unialgal cultures
The Dilemma of Delegating Search: Budgeting in Public Employment Services
The poor performance often attributed to many public employment services may be explained in part by a delegation problem between the central office and local job centers. In markets characterized by frictions, job centers function as match-makers, linking job seekers with relevant vacancies. Because their search intensity in contacting employers and collecting data is not verifiable by the central authority, a typical moral hazard problem can arise. To overcome the delegation problem and provide high-powered incentives for high levels of search effort on the part of job centers, we propose output-related schemes that assign greater staff capacity to agencies achieving high strike rates.matching unemployment, public employment service, delegation problem, moral hazard, search theory
The Dilemma of Delegating Search: Budgeting in Public Employment Service
The Recent German research has suggested that extending the number of caseworkers may have a very positive effect on PES performance. The present paper accepts this key insight but argues that there are other factors that may independently drive outcomes and in particular local agentsâ discretion. That is, it focuses on the delegation problem between the central office and the local job center âmatchmakers.â Because their (search) effort in contacting employers and collecting data is not verifiable by the central authority, a typical moral hazard problem can arise. To overcome the delegation problem and provide highâpowered incentives for increased levels of search effort on the part of job centers, we propose outputârelated schemes that assign greater staff capacity to agencies achieving high strike rates.matching unemployment, public employment service, active labor market policy, moral hazard, search theory
Asset Prices in Taylor Rules: Specification, Estimation, and Policy Implications for the ECB
This paper estimates standard and extended Taylor rules for core countries in the euro area, namely France, Germany and Italy, as well as for the ECB. Forward, backward and forecast-based rules are estimated for a variety of samples since the late 1970s. We are particularly interested in the impact of adding asset prices to the standard Taylor rule specification. Since forward-looking Taylor rules are usually estimated via GMM we perform extensive tests for over-identifying restrictions and instrument relevance, a practice generally eschewed in previous work. We find that asset prices can be highly relevant as instruments rather than as separate arguments in policy rules. Backwardlooking Taylor rules, however, cannot be rejected outright. Forecast-based rules perform best using the root mean squared error metric but produce coefficients implying that central banks may be too aggressive at fighting inflation. Encompassing tests are therefore required to select the ?best? policy rule and these suggest that policy rules need to have a mix of forward and forecast-based elements. Furthermore too aggressive reactions to stock prices in particular would have led to an implausible monetary policy. Hence, asset prices appear at best to serve as indicators of the direction of interest rates and not as a variable that the ECB directly reacts to. --reaction function,asset prices
Did the Bundesbank React to Stock Price Movements?
In this paper, we investigate the relationship between stock returns and short-term interest rates. Identification of the stock return-interest rate relation is solved by using a new technique that relies on the heteroskedasticity of shocks to stock market returns. We suggest some improvements to the identification technique and its justification, as well as providing some new findings. In particular, we ask whether the Bundesbank, prior to the European Central Bank taking responsibility for monetary policy in 1999, reacted systematically to stock price movements. In contrast to the results for the US, our empirical findings for the 1985 - 1998 period show a positive, but statistically insignificant, parameter for the relationship between German stock returns and short-term interest rates at the daily frequency. The same result is found at the monthly frequency. Nevertheless, the confidence bands are wide enough that we cannot entirely exclude the possibility of a reaction at lower frequencies. The results are extremely robust to alternative methods used to identify changes in heteroskedasticity. The evidence is, therefore, inconsistent with the hypothesis of a systematic reaction of the Bundesbank to every wiggle in German stock prices. Both the historical and institutional evidence are supportive of this conclusion. -- In diesem Diskussionspapier untersuchen wir den Zusammenhang zwischen AktienkursverĂ€nderungen und VerĂ€nderungen der kurzfristigen ZinssĂ€tze. Die ökonometrische Identifikation dieses Zusammenhangs erfolgt mit Hilfe eines neuen Verfahrens, das die Heteroskedastie von AktienkursverĂ€nderungen ausnutzt. Wir schlagen einige Verbesserungen und Rechtfertigungen zu diesem Verfahren vor und liefern neue empirische Befunde. Im Vordergrund der Betrachtungen steht die Frage, ob die Bundesbank vor der Ăbernahme der geldpolitischen Entscheidungen durch die EuropĂ€ische Zentralbank im Jahre 1999 systematisch auf VerĂ€nderungen der Aktienkurse reagiert hat. Im Unterschied zu den verfĂŒgbaren Ergebnissen fĂŒr die Vereinigten Staaten von Amerika, finden wir auf Basis von Tagesdaten zwar einen positiven, aber statistisch nicht signifikanten Parameter fĂŒr die Reaktion des kurzfristigen Zinssatzes auf Ănderungen des Aktienkurses. Auf der Grundlage von Monatsdaten ist der Parameter ebenfalls positiv und statistisch insignifikant. Die Konfidenzintervalle sind aber sehr breit, so dass eine Reaktion auf der niedrigeren Frequenz nicht völlig ausgeschlossen werden kann. Die empirischen Resultate sind sehr robust gegenĂŒber unterschiedlichen Modellspezifikationen. Die empirische Evidenz widerspricht somit der These einer systematischen Reaktion der Bundesbank auf jede Bewegung am Aktienmarkt, was durch die historischen und institutionellen Gegebenheiten gestĂŒtzt wird.
Local Compressibility Measurements of Correlated States in Suspended Bilayer Graphene
Bilayer graphene has attracted considerable interest due to the important
role played by many-body effects, particularly at low energies. Here we report
local compressibility measurements of a suspended graphene bilayer. We find
that the energy gaps at filling factors v = 4 do not vanish at low fields, but
instead merge into an incompressible region near the charge neutrality point at
zero electric and magnetic field. These results indicate the existence of a
zero-field ordered state and are consistent with the formation of either an
anomalous quantum Hall state or a nematic phase with broken rotational
symmetry. At higher fields, we measure the intrinsic energy gaps of
broken-symmetry states at v = 0, 1 and 2, and find that they scale linearly
with magnetic field, yet another manifestation of the strong Coulomb
interactions in bilayer graphene.Comment: 9 pages, including 4 figures and supplementary material
Phase coherence in the inelastic cotunneling regime
Two quantum dots with tunable mutual tunnel coupling have been embedded in a
two-terminal Aharonov-Bohm geometry. Aharonov-Bohm oscillations are
investigated in the cotunneling regime. Visibilities of more than 0.8 are
measured indicating that phase-coherent processes are involved in the elastic
and inelastic cotunneling. An oscillation-phase change of pi is detected as a
function of bias voltage at the inelastic cotunneling onset.Comment: 4 pages, 4 figure
TEXES Observations of Pure Rotational H_2 Emission from AB Aurigae
We present observations of pure rotational molecular hydrogen emission from the Herbig Ae star, AB Aur. Our observations were made using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility and the Gemini North Observatory. We searched for H_2 emission in the S(1), S(2), and S(4) lines at high spectral resolution and detected all three. By fitting a simple model for the emission in the three transitions, we derive T = 670 ± 40 K and M = 0.52 ± 0.15 M_â for the emitting gas. On the basis of the 8.5 km s^(-1) FWHM of the S(2) line, assuming the emission comes from the circumstellar disk, and with an inclination estimate of the AB Aur system taken from the literature, we place the location for the emission near 18 AU. Comparison of our derived temperature to a disk structure model suggests that UV and X-ray heating are important in heating the disk atmosphere
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