Search results for "Single"

Effective cloud optical depth for overcast conditions determined with a UV radiometers

2014

Using a sky camera, episodes characterized by overcast low clouds in the Valencia region of Spain have been selected for analysis. One year of cloud optical depth data have been produced by inverting UV erythemal irradiance measured with a UVB-1 radiometer from Yankee Environmental Systems using the LibRadtran radiative transfer model. Measurement uncertainties, aerosol single scattering albedo and cloud properties are, in order of decreasing importance, the most important factors influencing the accuracy of cloud optical depth retrieval when using UV erythemal radiometers. Statistics for cloud optical depth show a highly skewed frequency distribution best described by a gamma distribution …

2017

Abstract. In situ single particle analysis of ice particle residuals (IPRs) and out-of-cloud aerosol particles was conducted by means of laser ablation mass spectrometry during the intensive INUIT-JFJ/CLACE campaign at the high alpine research station Jungfraujoch (3580 m a.s.l.) in January–February 2013. During the 4-week campaign more than 70 000 out-of-cloud aerosol particles and 595 IPRs were analyzed covering a particle size diameter range from 100 nm to 3 µm. The IPRs were sampled during 273 h while the station was covered by mixed-phase clouds at ambient temperatures between −27 and −6 °C. The identification of particle types is based on laboratory studies of different types of biolo…

Incorporation of aerosol effects in a clear-sky semi-empirical model of UVER radiation for Valencia, Spain

2011

The study develops a simple but physically based model for estimating erythemal irradiance [(UV erythemal radiation (UVER)] for cloudless urban regions with substantial aerosol load, such as that of the Valencia environment in Spain. The model estimates direct and diffuse UVER for cloudless aerosol-free conditions using the LibRadtran model with a DISORT algorithm. Aerosol optical thickness for UVER (τaER) is obtained as a residual term by comparing measured direct UVER against modelled direct UVER in the absence of aerosol load. On average, τaER is 18% higher than τ data extrapolated to 305 nm using the CIMEL CE-318. Comparison of measured direct and diffuse UVER with model estimates provi…

Sensitivity of the atmospheric temperature profile to the aerosol absorption in the presence of dust

2014

Abstract Radiative transfer simulations in the shortwave (SW) and longwave (LW) spectral regions have been carried out to investigate the time evolution of the atmospheric heating/cooling rates and their influence on the temperature profiles under different vertical distributions of the aerosol absorption. The case study is based on measurements made at Rome, Italy, on 20 June 2007, when a dust layer was present above the urban boundary layer (BL) and the column aerosol optical depth at 550 nm was about 0.37. Column-integrated aerosol optical depth and single scattering albedo, as well as vertical profiles of aerosol extinction and meteorological variables have been derived from observation…

Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: single particle analysis during the Cloud and…

2010

Abstract. Two different single particle mass spectrometers were operated in parallel at the Swiss High Alpine Research Station Jungfraujoch (JFJ, 3580 m a.s.l.) during the Cloud and Aerosol Characterization Experiment (CLACE 6) in February and March 2007. During mixed phase cloud events ice crystals from 5–20 μm were separated from larger ice aggregates, non-activated, interstitial aerosol particles and supercooled droplets using an Ice-Counterflow Virtual Impactor (Ice-CVI). During one cloud period supercooled droplets were additionally sampled and analyzed by changing the Ice-CVI setup. The small ice particles and droplets were evaporated by injection into dry air inside the Ice-CVI. The …

Size distribution, mass concentration, chemical and mineralogical composition and derived optical parameters of the boundary layer aerosol at Tinfou,…

2009

During the SAMUM 2006 field campaign in southern Morocco, physical and chemical properties of desert aerosols were measured. Mass concentrations ranging from 30 Ã�¼g m-3 for PM2.5 under desert background conditions up to 300,000 Ã�¼g m-3 for total suspended particles (TSP) during moderate dust storms were measured. TSP dust concentrations are correlated with the local wind speed, whereas PM10 and PM2.5 concentrations are determined by advection from distant sources. Size distributions were measured for particles between 20 nm and 500 Ã�¼m diameter (parameterizations are given). Two major regimes of the size spectrum can be distinguished. Smaller than 500 nm particle diameter, the distrib…

A Theoretical Study of the Low-Lying Excited States of trans- and cis-Urocanic Acid

1999

A multiconfigurational second-order perturbation theory (CASPT2) study of the lowest lying states in the gas-phase electronic spectra of trans- and cis-urocanic acid is presented. Geometries of both isomers have been optimized at the MP2/6-31G(d) and π-CASSCF/ANO-L(4s3p1d,2s) levels of theory. The geometries are found to differ considerably between the two levels. The vertical and 0−0 excitation spectra were calculated for each isomer. Both singlet and triplet states are described for each, including the lowest lying ππ* excitations and the nOπ* excitations. Remarkably, in the trans spectrum, it is found that the nOπ* state has a higher vertical excitation energy than the lowest ππ* (5.12 v…

Meaning and magnitude of the reduced density matrix cumulants

2012

Abstract Within the framework of a generalized normal ordering (GNO), invented by Mukherjee [1] , the reduced density matrix cumulants of the (multiconfigurational) reference wave function play a central role, as they arise directly from the contraction rules. The extended Wick theorem allows contractions of an arbitrary number of active annihilators and creators through a cumulant of corresponding rank. Because the cumulant rank truncates naturally only at the number of active spin orbitals, practical applications of the GNO concept seem to rely on a fast convergence of the cumulant series, allowing one to neglect cumulants with high rank. By computing cumulant norms for selected systems (…

Safety and feasibility of atropine added in patients with sub-maximal heart rate during exercise myocardial perfusion SPECT.

2006

Failure to reach 80% of maximal predicted heart rate (HR) during exercise may render a myocardial perfusion single photon emission computed tomography (SPECT) study non-diagnostic for ischemia detection. We sought to investigate the injection of atropine in patients who fail to achieve 80% of age-predicted HR during exercise performed for myocardial perfusion SPECT (MPS), defining its safety and efficacy to raise HR to adequate levels as well as its effect on MPS interpretation.Between January 2002 and December 2004, we studied 3,150 consecutive patients (2,253 men and 897 women, mean age 55 +/- 6 years) who were referred to a single office-based nuclear cardiology laboratory for MPS using …

Evaluation of a new pooling strategy based on leukocyte count for rapid quantification of allele frequencies.

2007

Abstract Background: Allele frequencies of single-nucleotide polymorphisms (SNPs) can be quantified from DNA pools. The conventional preparation of DNA pools requires DNA isolation and quantification for each blood sample. We hypothesized that pooling of whole blood samples according to their leukocyte count, which determines DNA content, would be as reliable as the conventional pooling method but much less tedious to perform. Methods: We collected 100 whole blood samples and measured the leukocyte count. Samples were frozen until further use. After thawing, pools were generated by combining aliquots containing an equal number of leukocytes. In parallel, DNA was extracted from another aliqu…