1,716 research outputs found
Ground-based imaging remote sensing of ice clouds : uncertainties caused by sensor, method and atmosphere
Ground-based imaging remote sensing of ice clouds : uncertainties caused by sensor, method and atmosphere
In this study a method is introduced for the retrieval of optical thickness and effective particle size of ice clouds over a wide range of optical thickness from ground-based transmitted radiance measurements. Low optical thickness of cirrus clouds and their complex microphysics present a challenge for cloud remote sensing. In transmittance, the relationship between optical depth and radiance is ambiguous. To resolve this ambiguity the retrieval utilizes the spectral slope of radiance between 485 and 560âŻnm in addition to the commonly employed combination of a visible and a short-wave infrared wavelength.
An extensive test of retrieval sensitivity was conducted using synthetic test spectra in which all parameters introducing uncertainty into the retrieval were varied systematically: ice crystal habit and aerosol properties, instrument noise, calibration uncertainty and the interpolation in the lookup table required by the retrieval process. The most important source of errors identified are uncertainties due to habit assumption: Averaged over all test spectra, systematic biases in the effective radius retrieval of several micrometre can arise. The statistical uncertainties of any individual retrieval can easily exceed 10âŻÂ”m. Optical thickness biases are mostly below 1, while statistical uncertainties are in the range of 1 to 2.5.
For demonstration and comparison to satellite data the retrieval is applied to observations by the Munich hyperspectral imager specMACS (spectrometer of the Munich Aerosol and Cloud Scanner) at the Schneefernerhaus observatory (2650âŻmâŻa.s.l.) during the ACRIDICON-Zugspitze campaign in September and October 2012. Results are compared to MODIS and SEVIRI satellite-based cirrus retrievals (ACRIDICON â Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems; MODIS â Moderate Resolution Imaging Spectroradiometer; SEVIRI â Spinning Enhanced Visible and Infrared Imager). Considering the identified uncertainties for our ground-based approach and for the satellite retrievals, the comparison shows good agreement within the range of natural variability of the cloud situation in the direct surrounding
Moduli spaces of toric manifolds
We construct a distance on the moduli space of symplectic toric manifolds of
dimension four. Then we study some basic topological properties of this space,
in particular, path-connectedness, compactness, and completeness. The
construction of the distance is related to the Duistermaat-Heckman measure and
the Hausdorff metric. While the moduli space, its topology and metric, may be
constructed in any dimension, the tools we use in the proofs are
four-dimensional, and hence so is our main result.Comment: To appear in Geometriae Dedicata, minor changes to previous version,
19 pages, 6 figure
Studies of aging and HV break down problems during development and operation of MSGC and GEM detectors for the Inner Tracking System of HERA-B
The results of five years of development of the inner tracking system of the
HERA-B experiment and first experience from the data taking period of the year
2000 are reported. The system contains 184 chambers, covering a sensitive area
of about 20 * 20 cm2 each. The detector is based on microstrip gas counters
(MSGCs) with diamond like coated (DLC) glass wafers and gas electron
multipliers (GEMs). The main problems in the development phase were gas
discharges in intense hadron beams and aging in a high radiation dose
environment. The observation of gas discharges which damage the electrode
structure of the MSGC led to the addition of the GEM as a first amplification
step. Spurious sparking at the GEM cannot be avoided completely. It does not
affect the GEM itself but can produce secondary damage of the MSGC if the
electric field between the GEM and the MSGC is above a threshold depending on
operation conditions. We observed that aging does not only depend on the dose
but also on the spot size of the irradiated area. Ar-DME mixtures had to be
abandoned whereas a mixture of 70% Ar and 30% CO2 showed no serious aging
effects up to about 40 mC/cm deposited charge on the anodes. X-ray measurements
indicate that the DLC of the MSGC is deteriorated by the gas amplification
process. As a consequence, long term gain variations are expected. The Inner
Tracker has successfully participated in the data taking at HERA-B during
summer 2000.Comment: 29 pages, 22 figure
Production cross sections from 82Se fragmentation as indications of shell effects in neutron-rich isotopes close to the drip-line
Production cross sections for neutron-rich nuclei from the fragmentation of a
82Se beam at 139 MeV/u were measured. The longitudinal momentum distributions
of 126 neutron-rich isotopes of elements 11 <= Z <= 32 were scanned using an
experimental approach of varying the target thickness. Production cross
sections with beryllium and tungsten targets were determined for a large number
of nuclei including several isotopes first observed in this work. These are the
most neutron-rich nuclides of the elements 22 <= Z <= 25 (64Ti, 67V, 69Cr,
72Mn). One event was registered consistent with 70Cr, and another one with
75Fe. The production cross sections are correlated with Qg systematics to
reveal trends in the data. The results presented here confirm our previous
result from a similar measurement using a 76Ge beam, and can be explained with
a shell model that predicts a subshell closure at N = 34 around Z = 20. This is
demonstrated by systematic trends and calculations with the Abrasion-Ablation
model that are sensitive to separation energies.Comment: 13 pages, 11 figures, accepted to Phys.Rev.
Dataset of electrophysiological patch-clamp recordings of the effect of the compounds deltamethrin, ATx-II and ÎČ4-peptide on human cardiac Nav1.5 sodium channel gating properties.
This article describes the effect of the pyrethroid insecticide deltamethrin on the cardiac voltage-gated sodium channel Nav1.5. Two concentrations of deltamethrin were used and the effects were compared with those of the sea anemone toxin ATx-II and ÎČ4-peptide, which is the C-terminus of the Nav channel ÎČ-subunit. Activation, fast inactivation, deactivation, persistent currents and resurgent currents of Nav1.5 channels were assessed in the presence of these compounds. The data display not only the effect of separately applied compounds on Nav1.5 channels but also investigates how combinations of these substances affect Nav1.5 channel gating properties. The dataset presented in this article is related to the research article "Mechanism underlying hooked resurgent-like tail currents induced by an insecticide in human cardiac Nav1.5âł (Sarah Thull, Cristian Neacsu, Andrias O. O'Reilly, Stefanie Bothe, Ralf Hausmann, Tobias Huth, Jannis Meents, Angelika Lampert, doi: 10.1016/j.taap.2020.11501), that investigates the effect of the pyrethroid insecticide deltamethrin on Nav channel gating properties and explains the mechanism underlying hooked, resurgent-like tail currents induced by deltamethrin in Nav1.5 channels
Liquid 4He near the superfluid transition in the presence of a heat current and gravity
The effects of a heat current and gravity in liquid 4He near the superfluid
transition are investigated for temperatures above and below T_lambda. We
present a renormalization-group calculation based on model F for the Green's
function in a self-consistent approximation which in quantum many-particle
theory is known as the Hartree approximation. The approach can handle a zero
average order parameter above and below T_lambda and includes effects of
vortices. We calculate the thermal conductivity and the specific heat for all
temperatures T and heat currents Q in the critical regime. Furthermore, we
calculate the temperature profile. Below T_lambda we find a second correlation
length which describes the dephasing of the order parameter field due to
vortices. We find dissipation and mutual friction of the superfluid-normal
fluid counterflow and calculate the Gorter-Mellink coefficient A. We compare
our theoretical results with recent experiments.Comment: 26 pages, 9 figure
Production cross sections of neutron rich isotopes from a 82Se beam
Production cross sections for neutron-rich nuclei from the fragmentation of a
82Se beam at 139 MeV/u were measured. The longitudinal momentum distributions
of 122 neutron-rich isotopes of elements were determined by
varying the target thickness. Production cross sections with beryllium and
tungsten targets were determined for a large number of nuclei including several
isotopes first observed in this work. These are the most neutron-rich nuclides
of the elements (64Ti, 67V, 69Cr, 72Mn). One event was
registered consistent with 70Cr, and another one with 75Fe. A one-body Qg
systematics is used to describe the production cross sections based on thermal
evaporation from excited prefragments. The current results confirm those of our
previous experiment with a 76Ge beam: enhanced production cross sections for
neutron-rich fragments near Z=20.Comment: Talk given at the 11th International Conference on Nucleus-Nucleus
Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear
in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS
A robust, scanning quantum system for nanoscale sensing and imaging
Controllable atomic-scale quantum systems hold great potential as sensitive
tools for nanoscale imaging and metrology. Possible applications range from
nanoscale electric and magnetic field sensing to single photon microscopy,
quantum information processing, and bioimaging. At the heart of such schemes is
the ability to scan and accurately position a robust sensor within a few
nanometers of a sample of interest, while preserving the sensor's quantum
coherence and readout fidelity. These combined requirements remain a challenge
for all existing approaches that rely on direct grafting of individual solid
state quantum systems or single molecules onto scanning-probe tips. Here, we
demonstrate the fabrication and room temperature operation of a robust and
isolated atomic-scale quantum sensor for scanning probe microscopy.
Specifically, we employ a high-purity, single-crystalline diamond nanopillar
probe containing a single Nitrogen-Vacancy (NV) color center. We illustrate the
versatility and performance of our scanning NV sensor by conducting
quantitative nanoscale magnetic field imaging and near-field single-photon
fluorescence quenching microscopy. In both cases, we obtain imaging resolution
in the range of 20 nm and sensitivity unprecedented in scanning quantum probe
microscopy
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