Search results for "sampling"
showing 10 items of 788 documents
Crystallization of hard spheres revisited. I. Extracting kinetics and free energy landscape from forward flux sampling
2018
We investigate the kinetics and the free energy landscape of the crystallization of hard spheres from a supersaturated metastable liquid though direct simulations and forward flux sampling. In this first paper, we describe and test two different ways to reconstruct the free energy barriers from the sampled steady state probability distribution of cluster sizes without sampling the equilibrium distribution. The first method is based on mean first passage times, and the second method is based on splitting probabilities. We verify both methods for a single particle moving in a double-well potential. For the nucleation of hard spheres, these methods allow us to probe a wide range of supersatura…
Reconstruction of time-dependent coefficients: a check of approximation schemes for non-Markovian convolutionless dissipative generators
2010
We propose a procedure to fully reconstruct the time-dependent coefficients of convolutionless non-Markovian dissipative generators via a finite number of experimental measurements. By combining a tomography based approach with a proper data sampling, our proposal allows to relate the time-dependent coefficients governing the dissipative evolution of a quantum system to experimentally accessible quantities. The proposed scheme not only provides a way to retrieve full information about potentially unknown dissipative coefficients but also, most valuably, can be employed as a reliable consistency test for the approximations involved in the theoretical derivation of a given non-Markovian convo…
High redshift galaxies in the ALHAMBRA survey
2015
Context. Most observational results on the high redshift restframe UV-bright galaxies are based on samples pinpointed using the so called dropout technique or Ly-alpha selection. However, the availability of multifilter data allows now replacing the dropout selections by direct methods based on photometric redshifts. In this paper we present the methodology to select and study the population of high redshift galaxies in the ALHAMBRA survey data. Aims. Our aim is to develop a less biased methodology than the traditional dropout technique to study the high redshift galaxies in ALHAMBRA and other multifilter data. Thanks to the wide area ALHAMBRA covers, we especially aim at contributing in th…
(Table 1) Stable oxygen and carbon isotopic ratios of tree rings, and tree ring width of white spruce (Picea glauca), Ennadai Lake
2012
Stable isotope ratios from tree rings and peatland mosses have become important proxies of past climate variations. We here compare recent stable carbon and oxygen isotope ratios in cellulose of tree rings from white spruce (Picea glauca), growing near the arctic tree line; and cellulose of Sphagnum fuscum stems, growing in a hummock of a subarctic peatland, in west-central Canada. Results show that carbon isotopes in S. fuscum correlate significantly with July temperatures over the past ~20 yr. The oxygen isotopes correlate with both summer temperature and precipitation. Analyses of the tree-ring isotopes revealed summer temperatures to be the main controlling factor for carbon isotope var…
Selektive Blutentnahme aus dem Sinus petrosus inferior: Vergleich von CRF- und TRH-Stimulation
1993
In 10 patients with hypophyseal Cushing microadenomas, selective bilateral sampling from the inferior petrosal sinuses was performed and the effect of stimulation by iv TRH and CRF was compared. On the side of the microadenoma. ACTH concentration rose from 650 +/- 242 pg/ml to 2712 +/- 843 pg/ml following injection of CRF and 2025 +/- 242 pg/ml after TRH. Contralateral values were 165 +/- 79 pg/ml, 490 +/- 200 pg/ml and 165 +/- 72 pg/ml respectively. Prolactin concentration on the side of the adenoma was 98 +/- 49 ng/ml before stimulation, 236 +/- 62 ng/ml after CRF and 747 +/- 168 ng/ml after TRH. Contralateral concentration was 22 +/- 10 ng/ml, 64 +/- 19 ng/ml respectively. Sampling local…
From Sample to Section
1998
A sound analysis of microstructures relies on correct sampling and on the right choice of the direction in which thin sections are cut from samples. This chapter discusses the steps of sample collection; choice of sectioning plane, and problems involved in the interpretation of three-dimensional structures from two-dimensional sections.
Total Variation Based Image Restoration
2004
For the purpose of image restoration the process of image formation can be modeled in a first approximation by the formula [207] $$ {u_d} = Q\{ II(k*u) + n\} , $$ (1.1) where u represents the photonic flux k is the point spread function of the optical-captor joint apparatus П is a sampling operator, i.e., a Dirac comb supported by the centers of the matrix of digital sensors, n represents a random perturbation due to photonic or electronic noise, and Qis a uniform quantization operator mapping ℝ to a discrete interval of values, typically [0, 255].
Passive Sampling of Atmospheric Organic Contaminants
2012
The state of the art of passive sampling monitoring studies of atmospheric contaminants is reviewed in this chapter. The following passive samplers were considered: badge-type diffusive samplers; diffusive tubes; semi-permeable membrane devices; Radiello samplers; solid-phase microextraction fibers; polyurethane foam disks; XAD-2 passive air samplers; stir-bar samplers; polymer-coated glass surfaces; versatile, easy and rapid atmospheric monitor; and vegetation. A summary of the passive samplers used, sampling times, sampling rates, and analyte concentrations found is provided for different organic compounds, such as: carbonyl compounds, volatile compounds, polycyclic aromatic hydrocarbons,…
Air Pollution Research Based on Spider Web and Parallel Continuous Particulate Monitoring—A Comparison Study Coupled with Identification of Sources
2021
Air pollution is monitored mainly in urban or industrial areas, even if it is known that in rural ones, low emission can significantly worsen air quality. Hence, cheap and easily accessible methods of monitoring are needed. Recently, spider webs biomonitoring is getting popular, however, there is no information about its comparison with active methods. In this study, PTEs accumulated on spider webs were compared with results from continuous particulate monitor (CPM). Generally, higher potentially toxic elements concentrations were noted in spider web, with exception in the case of Zn. Zn may be present rather in smaller fractions, hence it needs more time for accumulation on spider web whil…
The Olt River pollution monitoring, using spatial analysis, analityc hierarchy process and technique for order preference by similarity methods
2016
Abstract Environmental pollution is one of the most serious problems of the contemporary world. Chemical industry is one of the major sources of environmental pollutants. Human knowledge and experience is currently focused on the use of assessment methods and techniques before and during the onset of such activities. For instance, it is common to consider the integration of multiple constraining factors and also, taking into account their high complexity and the application of one of the various techniques of Multi-Criteria Decision Making. The purpose of this study is to determine the location of the least and most polluted areas from several sampling points on the Olt River, in Romania. I…