19,916 research outputs found
The effect of cave illumination on bats
Artificial light at night has large impacts on nocturnal wildlife such as bats, yet its effect varies with wavelength of light, context, and across species involved. Here, we studied in two experiments how wild bats of cave-roosting species (Rhinolophus mehelyi, R. euryale, Myotis capaccinii and Miniopterus schreibersii) respond to LED lights of different colours. In dual choice experiments, we measured the acoustic activity of bats in response to neutral-white, red or amber LED at a cave entrance and in a flight room – mimicking a cave interior. In the flight room, M. capaccinii and M. schreibersii preferred red to white light, but showed no preference for red over amber, or amber over white light. In the cave entrance experiment, all light colours reduced the activity of all emerging species, yet red LED had the least negative effect. Rhinolophus species reacted most strongly, matching their refusal to fly at all under any light treatment in the flight room. We conclude that the placement and light colour of LED light should be considered carefully in lighting concepts for caves both in the interior and at the entrance. In a cave interior, red LED light could be chosen – if needed at all – for careful temporary illumination of areas, yet areas important for bats should be avoided based on the precautionary principle. At cave entrances, the high sensitivity of most bat species, particularly of Rhinolophus spp., towards light sources almost irrespective of colour, calls for utmost caution when illuminating cave entrances
Properties of optically selected BL Lac candidates from the SDSS
\textbf{Context.} Deep optical surveys open the avenue for find large numbers
of BL Lac objects that are hard to identify because they lack the unique
properties classifying them as such. While radio or X-ray surveys typically
reveal dozens of sources, recent compilations based on optical criteria alone
have increased the number of BL Lac candidates considerably. However, these
compilations are subject to biases and may contain a substantial number of
contaminating sources. \textbf{Aims.} In this paper we extend our analysis of
182 optically selected BL Lac object candidates from the SDSS with respect to
an earlier study. The main goal is to determine the number of bona fide BL Lac
objects in this sample. \textbf{Methods.} We examine their variability
characteristics, determine their broad-band radio-UV SEDs, and search for the
presence of a host galaxy. In addition we present new optical spectra for 27
targets with improved S/N with respect to the SDSS spectra. \textbf{Results.}
At least 59% of our targets have shown variability between SDSS DR2 and our
observations by more than 0.1-0.27 mag de- pending on the telescope used. A
host galaxy was detected in 36% of our targets. The host galaxy type and
luminosities are consistent with earlier studies of BL Lac host galaxies.
Simple fits to broad-band SEDS for 104 targets of our sample derived
synchrotron peak frequencies between with a peak at
. Our new optical spectra do not reveal any new
redshift for any of our objects. Thus the sample contains a large number of
bona fide BL Lac objects and seems to contain a substantial fraction of
intermediate-frequency peaked BL Lacs.Comment: Accepted for publication in A\&
Sources of Income Variation in Colombia: Personal and Regional Effects
A sample of 860,000 individuals from the 1973 Colombia Census Population is used to study income determinants and income inequality. Men and women are analyzed separately, as are employees and employer. Within these groups, education, age, region, and rural/urban differences in income are distinguished using a variety of procedures including simple cross tabulations and decompositions of the log variance of income by analysis of variance and by regression techniques. By standard statistical conventions, the four way classification by educational attainment is much the most important determinant of the logarithm of monthly income, while the seven age categories are generally somewhat more significant than the six regions. The fourteen parameters used to model these main effects account for a third of the log variance in income of employees and a quarter of that of employers. Each year of schooling is on the average associated with about 20 percent more income for male employees and employers. The restricted specification of a conventional earnings function increases the standard error of estimate by only .1 percent. Within education and age classes relative dispersions of incomes across regions are larger for the less educated, and for the very young and old.Fields224_Sources_of_income_variation.pdf: 432 downloads, before Oct. 1, 2020
Regional Inequality and Other Sources of Income Variation in Colombia
[Excerpt] Regional inequality is of interest for a variety of reasons: planning development policies aimed at alleviating poverty and reducing personal inequality, gauging the degree of a country\u27s labor market integration, understanding patterns of population movement in general and labor force migration in particular, predicting future urbanization, and characterizing the poor. Policymakers often aim development programs at particular target groups such as those living in certain regions of a country. In this paper we analyze the determinants of incomes and income inequality in one less developed country, Colombia, examining both personal and regional aspects. The results help clarify the potential of a development strategy emphasizing the poorest regions of the country.
Our specific objectives are to measure the relative importance of personal and regional effects on income variation in Colombia and to determine within relatively homogeneous segments of the labor force how place of residence is associated with personal income levels and dispersion. In Section II we explore income differences across a number of dimensions (education, sex, age, type of employment, and region) with particular reference to regional inequality. We then turn, in Section III, to more formal procedures (analysis of variance and regression) for systematically analyzing the relationship between income and age, education, type of employment, and region, and for quantifying these effects. The paper concludes with some implications of the empirical findings
Quantitative assessment of pinning forces and the superconducting gap in NbN thin films from complementary magnetic force microscopy and transport measurements
Epitaxial niobium-nitride thin films with a critical temperature of Tc=16K
and a thickness of 100nm were fabricated on MgO(100) substrates by pulsed laser
deposition. Low-temperature magnetic force microscopy (MFM) images of the
supercurrent vortices were measured after field cooling in a magnetic field of
3mT at various temperatures. Temperature dependence of the penetration depth
has been evaluated by a two-dimensional fitting of the vortex profiles in the
monopole-monopole model. Its subsequent fit to a single s-wave gap function
results in the superconducting gap amplitude Delta(0) = 2.9 meV = 2.1*kB*Tc, in
perfect agreement with previous reports. The pinning force has been
independently estimated from local depinning of individual vortices by lateral
forces exerted by the MFM tip and from transport measurements. A good
quantitative agreement between the two techniques shows that for low fields, B
<< Hc2, MFM is a powerful and reliable technique to probe the local variations
of the pinning landscape. We also demonstrate that the monopole model can be
successfully applied even for thin films with a thickness comparable to the
penetration depth.Comment: 6 pages, 6 figures, 2 table
State education as high-yield investment: human capital theory in European policy discourse
Human Capital Theory has been an increasingly important phenomenon in economic thought over the last 50 years. The central role it affords to education has become even more marked in recent years as the concept of the ‘knowledge economy’ has become a global concern. In this paper, the prevalence of Human Capital Theory within European educational policy discourse is explored. The paper examines a selection of policy documents from a number of disparate European national contexts and considers the extent to which the ideas of Human Capital Theory can be seen to be influential. In the second part of the paper, the implications of Human Capital Theory for education are considered, with a particular focus on the possible ramifications at a time of economic austerity. The paper argues that Human Capital Theory risks offering a diminished view of the person, a diminished view of education, but that with its sole focus on economic goals leaves room for educationists and others to argue for the educational, social, and moral values it ignores, and for the conception of the good life and good society it fails to mention
Monopolelike probes for quantitative magnetic force microscopy: calibration and application
A local magnetization measurement was performed with a Magnetic Force
Microscope (MFM) to determine magnetization in domains of an exchange coupled
[Co/Pt]/Co/Ru multilayer with predominant perpendicular anisotropy. The
quantitative MFM measurements were conducted with an iron filled carbon
nanotube tip, which is shown to behave like a monopole. As a result we
determined an additional in-plane magnetization component of the multilayer,
which is explained by estimating the effective permeability of the sample
within the \mu*-method.Comment: 3 pages, 3 figure
Density matrix reconstruction from displaced photon number distributions
We consider state reconstruction from the measurement statistics of phase
space observables generated by photon number states. The results are obtained
by inverting certain infinite matrices. In particular, we obtain reconstruction
formulas, each of which involves only a single phase space observable.Comment: 19 page
The Effect of 45{\deg} Grain Boundaries and associated Fe particles on Jc and resistivity in Ba(Fe0.9Co0.1)2As2 Thin Films
The anisotropy of the critical current density Jc depends in general on both
the properties of the flux lines (such as line tension, coherence length and
penetration depth) and the properties of the defects (such as density, shape,
orientation etc.). Whereas the Jc anisotropy in microstructurally clean films
can be scaled to an effective magnetic field containing the Ginzburg-Landau
anisotropy term, it is in general not possible (or only in a limited field
range) for samples containing extended defects. Here, the Jc anisotropy of a
Co-doped BaFe2As2 sample with 45{\deg} [001] tilt grain boundaries (GBs), i.e.
grain boundaries created by 45{\deg} in-plane rotated grains, as well as
extended Fe particles is investigated. This microstructure leads to c-axis
correlated pinning, both due to the GBs and the Fe particles and manifests in a
c-axis peak in the Jc anisotropy at low magnetic fields and a deviation from
the anisotropic Ginzburg-Landau scaling at higher fields. Strong pinning at
ellipsoidal extended defects, i.e. the Fe particles, is discussed, and the full
Jc anisotropy is fitted successfully with the vortex path model. The results
are compared to a sample without GBs and Fe particles. 45{\deg} GBs seem to be
good pinning centers rather than detrimental to current flow.Comment: 8 pages, 7 figures, CEC-ICMC 2013 proceeding, accepted for
publication in Advances in Cryogenic Engineering (Materials
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