2,780 research outputs found
An integrated analysis of micro- and macro-habitat features as a tool to detect weather-driven constraints: a case study with cavity nesters
The effects of climate change on animal populations may be shaped by habitat characteristics at both micro- and macro-habitat level, however, empirical studies integrating these two scales of observation are lacking. As analyses of the effects of climate change commonly rely on data from a much larger scale than the microhabitat level organisms are affected at, this mismatch risks hampering progress in developing understanding of the details of the ecological and evolutionary responses of organisms and, ultimately, effective actions to preserve their populations. Cavity nesters, often with a conservation status of concern, are an ideal model because the cavity is a microenvironment potentially different from the macroenvironment but nonetheless inevitably interacting with it. The lesser kestrel (Falco naumanni) is a cavity nester which was until recently classified by as Vulnerable species. Since 2004, for nine years, we collected detailed biotic and abiotic data at both micro- and macro-scales of observation in a kestrel population breeding in the Gela Plain (Italy), a Mediterranean area where high temperatures may reach lethal values for the nest content. We show that macroclimatic features needed to be integrated with both abiotic and biotic factors recorded at a microscale before reliably predicting nest temperatures. Among the nest types used by lesser kestrels, we detected a preferential occupation of the cooler nest types, roof tiles, by early breeders whereas, paradoxically, late breeders nesting with hotter temperatures occupied the overheated nest holes. Not consistent with such a suggested nest selection, the coolest nest type did not host a higher reproductive success than the overheated nests. We discussed our findings in the light of cavity temperatures and nest types deployed within conservation actions assessed by integrating selected factors at different observation scales
Reduced-rank spatio-temporal modeling of air pollution concentrations in the Multi-Ethnic Study of Atherosclerosis and Air Pollution
There is growing evidence in the epidemiologic literature of the relationship
between air pollution and adverse health outcomes. Prediction of individual air
pollution exposure in the Environmental Protection Agency (EPA) funded
Multi-Ethnic Study of Atheroscelerosis and Air Pollution (MESA Air) study
relies on a flexible spatio-temporal prediction model that integrates land-use
regression with kriging to account for spatial dependence in pollutant
concentrations. Temporal variability is captured using temporal trends
estimated via modified singular value decomposition and temporally varying
spatial residuals. This model utilizes monitoring data from existing regulatory
networks and supplementary MESA Air monitoring data to predict concentrations
for individual cohort members. In general, spatio-temporal models are limited
in their efficacy for large data sets due to computational intractability. We
develop reduced-rank versions of the MESA Air spatio-temporal model. To do so,
we apply low-rank kriging to account for spatial variation in the mean process
and discuss the limitations of this approach. As an alternative, we represent
spatial variation using thin plate regression splines. We compare the
performance of the outlined models using EPA and MESA Air monitoring data for
predicting concentrations of oxides of nitrogen (NO)-a pollutant of primary
interest in MESA Air-in the Los Angeles metropolitan area via cross-validated
. Our findings suggest that use of reduced-rank models can improve
computational efficiency in certain cases. Low-rank kriging and thin plate
regression splines were competitive across the formulations considered,
although TPRS appeared to be more robust in some settings.Comment: Published in at http://dx.doi.org/10.1214/14-AOAS786 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Performance of the CMS Pixel Detector at an upgraded LHC
The CMS experiment will include a pixel detector for pattern recognition and
vertexing. It will consist of three barrel layers and two endcaps on each side,
providing three space-points up to a pseudoraditity of 2.1. Taking into account
the expected limitations of its performance in the LHC environment an 8-9 layer
pixel detector for an upgraded LHC is discussed.Comment: Contribution to the 10th European Symposium on Semiconductor
Detectors, June 12 - 16, 2005 in Wildbad Kreuth, Germany. 6 pages, 4 figures,
1 table. Referee's comments implemente
The Semi-Chiral Quotient, Hyperkahler Manifolds and T-duality
We study the construction of generalized Kahler manifolds, described purely
in terms of N=(2,2) semichiral superfields, by a quotient using the semichiral
vector multiplet. Despite the presence of a b-field in these models, we show
that the quotient of a hyperkahler manifold is hyperkahler, as in the usual
hyperkahler quotient. Thus, quotient manifolds with torsion cannot be
constructed by this method. Nonetheless, this method does give a new
description of hyperkahler manifolds in terms of two-dimensional N=(2,2) gauged
non-linear sigma models involving semichiral superfields and the semichiral
vector multiplet. We give two examples: Eguchi-Hanson and Taub-NUT. By
T-duality, this gives new gauged linear sigma models describing the T-dual of
Eguchi-Hanson and NS5-branes. We also clarify some aspects of T-duality
relating these models to N=(4,4) models for chiral/twisted-chiral fields and
comment briefly on more general quotients that can give rise to torsion and
give an example.Comment: 31 page
Design and Tests of the Silicon Sensors for the ZEUS Micro Vertex Detector
To fully exploit the HERA-II upgrade,the ZEUS experiment has installed a
Micro Vertex Detector (MVD) using n-type, single-sided, silicon micro-strip
sensors with capacitive charge division. The sensors have a readout pitch of
120 micrometers, with five intermediate strips (20 micrometer strip pitch). The
designs of the silicon sensors and of the test structures used to verify the
technological parameters, are presented. Results on the electrical measurements
are discussed. A total of 1123 sensors with three different geometries have
been produced by Hamamatsu Photonics K.K. Irradiation tests with reactor
neutrons and Co-60 photons have been performed for a small sample of sensors.
The results on neutron irradiation (with a fluence of 1 x 10^{13} 1 MeV
equivalent neutrons / cm^2) are well described by empirical formulae for bulk
damage. The Co-60 photons (with doses up to 2.9 kGy) show the presence of
generation currents in the SiO_2-Si interface, a large shift of the flatband
voltage and a decrease of the hole mobility.Comment: 33 pages, 25 figures, 3 tables, accepted for publication in NIM
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Electronic hand hygiene monitoring: accuracy, impact on the Hawthorne effect and efficiency
Objectives:
To evaluate a type five electronic monitoring system (EMS) for hand hygiene (HH) adherence with respect to accuracy and ability to avoid the Hawthorne effect.
Design:
HH events were observed manually and electronically. The agreement between the two observation methods was evaluated. Continuous electronic measurement was made throughout the study.
Setting:
An acute 31-bed medical ward in a National Health Service trust in London, United Kingdom.
Participants:
Staff working or attached to the ward.
Intervention:
A newly developed type five EMS that can measure disinfectant dispenser usage as well as continuous movements of health workers throughout the ward with arm-length precision and analyse HH adherence was installed at the ward.
Results:
A total of 294 HH events were observed in five sessions by an observer previously unknown to the ward. There was concordance between HH adherence assessed by manual observer and the EMS on 84% (79.1%â89.9%) of the occasions. During the five observation sessions, the observed HH adherence increased from 24% to 76% while the EMS measurements immediately before the arrival of the observer remained constant for all sessions.
Conclusion:
The 84% agreement between the EMS and the manual observation suggest a high level of precision for the evaluated system. The Hawthorne effect (higher rate of HH performance) was clearly seen in the increase by a factor of three in the manually observed adherence from session to session as the health workers became more aware of them being observed. The EMS was able to avoid the Hawthorne effect when the observer was not present
Near-Field Scanning Microwave Microscopy in the Single Photon Regime
The microwave properties of nano-scale structures are important in a wide
variety of applications in quantum technology. Here we describe a low-power
cryogenic near-field scanning microwave microscope (NSMM) which maintains
nano-scale dielectric contrast down to the single microwave photon regime, up
to times lower power than in typical NSMMs. We discuss the remaining
challenges towards developing nano-scale NSMM for quantum coherent interaction
with two-level systems as an enabling tool for the development of quantum
technologies in the microwave regime
Relating harmonic and projective descriptions of N=2 nonlinear sigma models
Recent papers have established the relationship between projective superspace
and a complexified version of harmonic superspace. We extend this construction
to the case of general nonlinear sigma models in both frameworks. Using an
analogy with Hamiltonian mechanics, we demonstrate how the Hamiltonian
structure of the harmonic action and the symplectic structure of the projective
action naturally arise from a single unifying action on a complexified version
of harmonic superspace. This links the harmonic and projective descriptions of
hyperkahler target spaces. For the two examples of Taub-NUT and Eguchi-Hanson,
we show how to derive the projective superspace solutions from the harmonic
superspace solutions.Comment: 25 pages; v3: typo fixed in eq (1.36
Topological A-Type Models with Flux
We study deformations of the A-model in the presence of fluxes, by which we
mean rank-three tensors with antisymmetrized upper/lower indices, using the
AKSZ construction. Generically these are topological membrane models, and we
show that the fluxes are related to deformations of the Courant bracket which
generalize the twist by a closed 3-from , in the sense that satisfying the
AKSZ master equation implies the integrability conditions for an almost
generalized complex structure with respect to the deformed Courant bracket. In
addition, the master equation imposes conditions on the fluxes that generalize
. The membrane model can be defined on a large class of - and -structure manifolds, including geometries inspired by
supersymmetric -models with additional supersymmetries due to almost
complex (but not necessarily complex) structures in the target space.
Furthermore, we show that the model can be defined on three particular
half-flat manifolds related to the Iwasawa manifold.
When only -flux is turned on it is possible to obtain a topological string
model, which we do for the case of a Calabi-Yau with a closed 3-form turned on.
The simplest deformation from the A-model is due to the
component of a non-trivial -field. The model is generically no longer
evaluated on holomorphic maps and defines new topological invariants.
Deformations due to -flux can be more radical, completely preventing
auxiliary fields from being integrated out.Comment: 30 pages. v2: Improved Version. References added. v3: Minor changes,
published in JHE
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