691 research outputs found
Optimization and quality control of suspended particulate matter concentration measurement using turbidity measurements
The dry weight concentration of suspended particulate material, [SPM] (units: mg L?1), is measured by passing a known volume of seawater through a preweighed filter and reweighing the filter after drying. This is apparently a simple procedure, but accuracy and precision of [SPM] measurements vary widely depending on the measurement protocol and experience and skills of the person filtering. We show that measurements of turbidity, T (units: FNU), which are low cost, simple, and fast, can be used to optimally set the filtration volume, to detect problems with the mixing of the sample during subsampling, and to quality control [SPM]. A relationship between T and ?optimal filtration volume?, Vopt, is established where Vopt is the volume at which enough matter is retained by the filter for precise measurement, but not so much that the filter clogs. This relationship is based on an assessment of procedural uncertainties in the [SPM] measurement protocol, including salt retention, filter preparation, weighing, and handling, and on a value for minimum relative precision for replicates. The effect of filtration volume on the precision of [SPM] measurement is investigated by filtering volumes of seawater ranging between one fifth and twice Vopt. It is shown that filtrations at Vopt maximize precision and cost effectiveness of [SPM]. Finally, the 90% prediction bounds of the T versus [SPM] regression allow the quality control of [SPM] determinations. In conclusion it is recommended that existing [SPM] gravimetric measurements be refined to include measurement of turbidity to improve their precision and quality control
Ionic Strength Effect Alters the Heterogeneous Ozone Oxidation of Methoxyphenols in Going from Cloud Droplets to Aerosol Deliquescent Particles
Coordinated and tailored work rehabilitation: a randomized controlled trial with economic evaluation undertaken with workers on sick leave due to musculoskeletal disorders
Introduction In Denmark, the magnitude and impact of work disability on the individual worker and society has prompted the development of a new "coordinated and tailored work rehabilitation" (CTWR) approach. The aim of this study was to compare the effects of CTWR with conventional case management (CCM) on return-to-work of workers on sick leave due to musculoskeletal disorders (MSDs). Methods The study was a randomized controlled trial with economic evaluation undertaken with workers on sick leave for 4-12 weeks due to MSDs. CTWR consists of a work disability screening by an interdisciplinary team followed by the collaborative development of a RTW plan. The primary outcome variable was registered cumulative sickness absence hours during 12 months follow-up. Secondary outcomes were work status as well as pain intensity and functional disability, measured at baseline, 3 and 12 months follow-up. The economic evaluation (intervention costs, productivity loss, and health care utilization costs) was based on administrative data derived from national registries. Results For the time intervals 0-6 months, 6-12 months, and the entire follow-up period, the number of sickness absence hours was significantly lower in the CTWR group as compared to the control group. The total costs saved in CTWR participants compared to controls were estimated at US 10,666 per person at 12 months follow-up. Conclusions Workers on sick leave for 4-12 weeks due to MSD who underwent "CTWR" by an interdisciplinary team had fewer sickness absence hours than controls. The economic evaluation showed that-in terms of productivity loss-CTWR seems to be cost saving for the society
Ionic Strength Effect on Photochemistry of Fluorene and Dimethylsulfoxide at the Air-Sea Interface: Alternative Formation Pathway of Organic Sulfur Compounds in a Marine Atmosphere
Self-organization of actin filament orientation in the dendritic-nucleation/array-treadmilling model
Author Posting. © The Author(s), 2006. This is the author's version of the work. It is posted here by permission of National Academy of Sciences of the USA for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences 104 (2007): 7086-7091, doi:10.1073/pnas.0701943104.The dendritic-nucleation/array-treadmilling model provides a conceptual framework for
the generation of the actin network driving motile cells. We have incorporated it into a 2-D,
stochastic computer model to study lamellipodia via the self-organization of filament
orientation patterns. Essential dendritic-nucleation sub-models were incorporated,
including discretized actin monomer diffusion, Monte-Carlo filament kinetics, and flexible
filament and plasma membrane mechanics. Model parameters were estimated from the
literature and simulation, providing values for the extent of the leading edge
branching/capping-protective zone (5.4 nm) and the auto-catalytic branch rate (0.43 /s).
For a given set of parameters the system evolved to a steady state filament count and
velocity, at which total branching and capping rates were equal only for specific
orientations; net capping eliminated others. The standard parameter set evoked a sharp
preference for the ±35 deg. filaments seen in lamellipodial electron micrographs, requiring
~ 12 generations of successive branching to adapt to a 15 deg. change in protrusion
direction. This pattern was robust with respect to membrane surface and bending energies
and to actin concentrations, but required protection from capping at the leading edge and
branching angles greater than 60 deg. A +70/0/-70 deg. pattern was formed with flexible
filaments ~ 100 nm or longer and with velocities less than ~ 20% of free polymerization
rates
Iron and Nickel spectral opacity calculations in conditions relevant for pulsating stellar envelopes and experiments
Seismology of stars is strongly developing. To address this question we have
formed an international collaboration OPAC to perform specific experimental
measurements, compare opacity calculations and improve the opacity calculations
in the stellar codes [1]. We consider the following opacity codes: SCO,
CASSANDRA, STA, OPAS, LEDCOP, OP, SCO-RCG. Their comparison has shown large
differences for Fe and Ni in equivalent conditions of envelopes of type II
supernova precursors, temperatures between 15 and 40 eV and densities of a few
mg/cm3 [2, 3, 4]. LEDCOP, OPAS, SCO-RCG structure codes and STA give similar
results and differ from OP ones for the lower temperatures and for spectral
interval values [3]. In this work we discuss the role of Configuration
Interaction (CI) and the influence of the number of used configurations. We
present and include in the opacity code comparisons new HULLAC-v9 calculations
[5, 6] that include full CI. To illustrate the importance of this effect we
compare different CI approximations (modes) available in HULLAC-v9 [7]. These
results are compared to previous predictions and to experimental data.
Differences with OP results are discussed.Comment: 4 pages, 3 figures, conference Inertial Fusion Sciences and
Applications, Bordeaux, 12th to 16th September 2011; EPJ web of Conferences
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