105 research outputs found
Differences between the activity size distributions of the different natural radionuclide aerosols in outdoor air
No full textThe results of the activity size distribution of the short-lived ((218)po, Bi-214/Po-214) and long-lived (Pb-210, Po-210)radon decay product aerosols. the thoron decay product aerosols (Pb-212, Po-212) and Be-7 of the outdoor atmosphere are presented. The results were obtained from measurements averaged over an extended period (4 weeks) and were carried out with a low-pressure On-Line Alpha Cascade Impactor (OLACI). The size distributions of the radionuclides were obtained from the same measurement run with the OLACI, so that the size classification technique and the atmospheric and weather conditions for all radionuclides were identical. This measurement technique made it possible to measure the correct differences between the size distributions of the different natural radionuclides in the environmental air. The differences between the activity size distributions of the long- and short-lived radionuclides could be explained by coagulation with aerosol particles of the atmosphere as for instance Pb-210 was shown. (C) 2004 Elsevier Ltd. All rights reserved
Characterisation of an electronic radon gas personal dosemeter
No full textThe monitoring of radon exposure at workplaces is of great importance. Up to now passive measurement systems have been used for the registration of radon gas. Recently an electronic radon gas personal dosemeter came onto the market as an active measurement system for the registration of radon exposure (DOSEman; Sarad GmbH, Dresden, Germany). In this personal monitor. the radon gas diffuses through a membrane into a measurement chamber. A silicon detector system records spectroscopically the alpha decays of the radon gas and of the short-lived progeny Po-218 and Po-214 gathered onto the detector by an electrical field. In this work the calibration was tested and a proficiency test of this equipment was made. The diffusion behaviour of the radon gas into the measurement chamber. susceptibility to thoron, efficiency, influence of humidity, accuracy and the detection limit were checked
Characterisation of an electronic radon gas personal dosemeter
No full textThe monitoring of radon exposure at workplaces is of great importance. Up to now passive measurement systems have been used for the registration of radon gas. Recently an electronic radon gas personal dosemeter came onto the market as an active measurement system for the registration of radon exposure (DOSEman; Sarad GmbH, Dresden, Germany). In this personal monitor. the radon gas diffuses through a membrane into a measurement chamber. A silicon detector system records spectroscopically the alpha decays of the radon gas and of the short-lived progeny Po-218 and Po-214 gathered onto the detector by an electrical field. In this work the calibration was tested and a proficiency test of this equipment was made. The diffusion behaviour of the radon gas into the measurement chamber. susceptibility to thoron, efficiency, influence of humidity, accuracy and the detection limit were checked
Fraction of the positive Po-218 and Pb-214 clusters in indoor air
No full textThe fraction of the positively charged unattached radon decay products, Po-218 and Pb-214 in indoor air was determined by model calculations. The results of the calculations were confirmed by measurements in a test chamber (volume: 8 m(3)). The fraction of both radionuclides depends on the attachment parameter (S-1) and the neutralisation rate (v) in room air. The total removal parameter S-1 = lambda(1) + v + q(f) + X =lambda(1) C-1/C-0 considers the attachment rate to aerosol particles (X), plate-out rate to room surfaces (q(f)) and the ventilation rate (v) (A,: decay constant of Po-218). The S-1-value of room can be determined by measurement of the concentration of the unattached Po-218 clusters (C-1(f)) and radon (CO). The neutralisation rate (v) in environmental air depends mainly on the ion production rate. The influence of the relative humidity in the range 30-95% (temperature: 20 degrees C) is negligible. In addition, equal neutralisation rates for Po-218 and Pb-214 could be derived. In room air with ion production rates between 5 and 500 nC kg(-1) h(-1) mainly generated by the alpha emitters of radon, thoron and their short-lived decay products, the fractions for positive Po-218 clusters vary between 55 and 17% and for Pb-214 clusters between 53 and 14%. For a typical average concentration of radon (50 Bq m(-3)) and thoron (10 Bq m(-3)) in homes, 48% of Po-218 clusters and 45% of Pb-214 clusters are positively charged
Estimating the Inf-Sup Constant in Reduced Basis Methods for Time-Harmonic Maxwell's Equations
No full textInfluence of the temperature and the ionisation potential on the hyperfine interaction of Cd-111 ions in gaseous radioactive indium-halides
No full textThe hyperfine interaction (HFI) of Cd-111 in different indium-halides was studied by perturbed angular correlation (PAC). The Cd-111 ion arises from a In-111 by electron capture decay (EC) and joined Auger cascade. Coulomb fragmentation of the indium-halide molecule produces the free excited Cd-111 ion. The nucleus decays via a gamma-gamma -cascade which is perturbed by the HFI. Collisions of the Cd-111 ion with indium-halide molecules can strongly change the perturbation. The perturbation was measured by the attenuation coefficient G(22)(infinity) and G(22)(t). The molecular densities varied between 10(14) and 10(20) cm(-3). The present article shows the temperature dependence of the indium(III)-halides and a fit for an empirical basic approach. The investigation of the InBr shows the independence of the attenuation coefficient from the temperature by indium(I)-halides in contrast to the dependence of the indium(III)-halides
Cellular Dialogues: Cell-Cell Communication through Diffusible Molecules Yields Dynamic Spatial Patterns
No full textCells form spatial patterns by coordinating their gene expressions. How a group of mesoscopic numbers (hundreds to thousands) of cells, without pre-existing morphogen gradients and spatial organization, self-organizes spatial patterns remains poorly understood. Of particular importance are dynamic spatial patterns such as spiral waves that perpetually move and transmit information. We developed an open-source software for simulating a field of cells that communicate by secreting any number of molecules. With this software and a theory, we identified all possible “cellular dialogues”—ways of communicating with two diffusing molecules—that yield diverse dynamic spatial patterns. These patterns emerge despite widely varying responses of cells to the molecules, gene-expression noise, spatial arrangements, and cell movements. A three-stage, “order-fluctuate-settle” process forms dynamic spatial patterns: cells form long-lived whirlpools of wavelets that, following erratic dynamics, settle into a dynamic spatial pattern. Our work helps in identifying gene-regulatory networks that underlie dynamic pattern formations. Dang et al. developed a software and a theoretical framework to discover and classify all moving spatial patterns (e.g., waves) that cells can form by secreting two diffusible molecules that control their gene expressions. They identified all gene regulations that the molecules can have for forming moving patterns, which self-organize through a three-stage, “order-fluctuate-settle” dynamic.OLD BN/Hyun Youk La
Understanding Placement into Preparatory-Level Courses and the Effects on Academic Success
No full textPlacement into preparatory courses presents a significant challenge related to access and equity in higher education; it connects to conversations around college readiness, particularly in geographical areas that have been underserved, or which have larger minority populations and underprepared students. At the same time, the research points to relationships between enrollment in preparatory coursework in higher education and lower rates of retention and college persistence; students who take these courses are more likely to drop out from the institution. These courses often carry no academic or transferable credit to be applied towards a college degree, yet the student has still accrued the same amount of debt as any other student who has taken credit-bearing courses. Therefore, these issues peripherally relate to matters surrounding college affordability and student debt. As a secondary analysis of Mid-Atlantic University data, this project investigated how preparatory coursework impacts college persistence and retention. It used the existing literature on placement into preparatory courses and any relationship to retention, with a focus on any noted disparities or inequities by student characteristics. Specifically, this study explored whether taking preparatory courses impacts some student groups differently than others in relation to retention and persistence. The data set was analyzed using quantitative, statistical methods. Findings include that students who take preparatory courses are more likely to be from minority backgrounds, are first-generation, are from homes where English is not the native language spoken and are from lower socio-economic status. There are also differential outcomes amongst those who take preparatory courses dependent upon student characteristics. Finally, preparatory students’ responses on a New Student Questionnaire trend towards lower levels of academic and social integration. The implications of the results were focused on offering practitioners a unique look at the student data about the impact of pre-college course placement, which can be used to better support students placed into preparatory courses to increase the retention rates and improve academic outcomes of this vulnerable population.Policy, Organizational and Leadership Studie
Coelioxys (Xerocoelioxys) immaculatus Cockerell 1912
No full textCoelioxys (Xerocoelioxys) immaculatus Cockerell 1912 (New state record) County records: Livingston, Oceana. Notes. This cleptoparasite of Megachile, including M. addenda Cresson in New Jersey (Cane et al. 1996), has been collected once in Michigan and in adjacent areas of Indiana (Grundel et al. 2011; Jean 2010). Material examined. Oceana Co.: Hart, 19 Jun. 1939, C.W. Sabrosky (1 ♀ MSUC).Published as part of Gibbs, Jason, Ascher, John S., Rightmyer, Molly G. & Isaacs, Rufus, 2017, The bees of Michigan (Hymenoptera: Apoidea: Anthophila), with notes on distribution, taxonomy, pollination, and natural history, pp. 1-160 in Zootaxa 4352 (1) on page 105, DOI: 10.11646/zootaxa.4352.1.1, http://zenodo.org/record/106385
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