2,185 research outputs found
Precision metering of microliter volumes of biological fluids in micro-gravity
Concepts were demonstrated and investigated for transferring accurately known and reproducible microliter volumes of biological fluids from sample container onto dry chemistry slides in microgravity environment. Specific liquid transfer tip designs were compared. Information was obtained for design of a liquid sample handling system to enable clinical chemical analysis in microgravity. Disposable pipet tips and pipet devices that were designed to transfer microliter volumes of biological fluid from a (test tube) sample container in 1-G environment were used during microgravity periods of parabolic trajectories of the KC-135 aircraft. The transfer process was recorded using charge coupled device camera and video cassette equipment. Metering behavior of water, a synthetic aqueous protein solution, and anticoagulated human blood was compared. Transfer of these liquids to 2 substrate materials representative of rapidly wettable and slowly wettable dry chemistry slide surface was compared
Global evaluation of particulate organic carbon flux parameterizations and implications for atmospheric pCO\u3csub\u3e2\u3c/sub\u3e
The shunt of photosynthetically derived particulate organic carbon (POC) from the euphotic zone and deep remineralization comprises the basic mechanism of the âbiological carbon pump.â POC raining through the âtwilight zoneâ (euphotic depth to 1 km) and âmidnight zoneâ (1 km to 4 km) is remineralized back to inorganic form through respiration. Accurately modeling POC flux is critical for understanding the âbiological pumpâ and its impacts on airâsea CO2 exchange and, ultimately, longâterm ocean carbon sequestration. Yet commonly used parameterizations have not been tested quantitatively against global data sets using identical modeling frameworks. Here we use a single oneâdimensional physicalâbiogeochemical modeling framework to assess three common POC flux parameterizations in capturing POC flux observations from moored sediment traps and thoriumâ234 depletion. The exponential decay, Martin curve, and ballast model are compared to data from 11 biogeochemical provinces distributed across the globe. In each province, the model captures satelliteâbased estimates of surface primary production within uncertainties. Goodness of fit is measured by how well the simulation captures the observations, quantified by bias and the rootâmeanâsquare error and displayed using âtarget diagrams.â Comparisons are presented separately for the twilight zone and midnight zone. We find that the ballast hypothesis shows no improvement over a globally or regionally parameterized Martin curve. For all provinces taken together, Martin\u27s b that best fits the data is [0.70, 0.98]; this finding reduces by at least a factor of 3 previous estimates of potential impacts on atmospheric pCO2 of uncertainty in POC export to a more modest range [â16 ppm, +12 ppm]
Maximum Likelihood Estimation for Single Particle, Passive Microrheology Data with Drift
Volume limitations and low yield thresholds of biological fluids have led to
widespread use of passive microparticle rheology. The mean-squared-displacement
(MSD) statistics of bead position time series (bead paths) are either applied
directly to determine the creep compliance [Xu et al (1998)] or transformed to
determine dynamic storage and loss moduli [Mason & Weitz (1995)]. A prevalent
hurdle arises when there is a non-diffusive experimental drift in the data.
Commensurate with the magnitude of drift relative to diffusive mobility,
quantified by a P\'eclet number, the MSD statistics are distorted, and thus the
path data must be "corrected" for drift. The standard approach is to estimate
and subtract the drift from particle paths, and then calculate MSD statistics.
We present an alternative, parametric approach using maximum likelihood
estimation that simultaneously fits drift and diffusive model parameters from
the path data; the MSD statistics (and consequently the compliance and dynamic
moduli) then follow directly from the best-fit model. We illustrate and compare
both methods on simulated path data over a range of P\'eclet numbers, where
exact answers are known. We choose fractional Brownian motion as the numerical
model because it affords tunable, sub-diffusive MSD statistics consistent with
typical 30 second long, experimental observations of microbeads in several
biological fluids. Finally, we apply and compare both methods on data from
human bronchial epithelial cell culture mucus.Comment: 29 pages, 12 figure
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Design and development of a large shear box for testing working platform material
On large construction projects where deep foundations are to be installed, a working platform is placed across the entire site. This is comprised of a layer of aggregate (often crushed construction waste) usually with a particle size ranging from 120 mm downwards. Deep foundations are installed using heavy and tall drilling rigs and the working platform is thus safety critical to reduce the risk of machinery sinking and/or toppling which would lead to accidents and often serious injury to workers. Currently available design guidance is felt to result in conservative designs and there are many benefits to be gained from a greater understanding of the behaviour of working platform material. The design of these platforms is primarily governed by the angle of friction of the platform material. The measurement of friction angle for geomaterials that have large particle sizes is problematic (due to reasons of scale) and is often addressed by scaling down the material's grading curve prior to testing in small to medium size direct shear apparatus. The work presented here details the design of and the rationale for a large scale direct shear apparatus suitable for testing geomaterials with particle size distributions of the type that would be utilised in working platforms
Promising Practices of Dairy, Horse, and Livestock Evaluation Career Development Event Coaches: A Mixed-Methods Study
The present study describes promising practices of successful dairy, horse, and livestock judging coaches. Expert coaches were interviewed regarding previous experience, coaching philosophy, coaching objectives, coaching style, and advice. Twenty-seven promising practices and eight themes were identified from the interviews. A questionnaire was sent to the accessible population of coaches to determine practice usage and relationship to youth performance. Influential and motivating practices were found to be most used by coaches. Youth performance was related to use of competitive and expectancy related promising practices. Findings suggest use of promising practices would facilitate greater coaching success in competition and youth development
Global ocean particulate organic carbon flux merged with satellite parameters
Particulate organic carbon (POC) flux estimated from POC concentration observations from sediment traps and 234 Th are compiled across the global ocean. The compilation includes six time series locations: CARIACO, K2, OSP, BATS, OFP, and HOT. Efficiency of the biological pump of carbon to the deep ocean depends largely on biologically mediated export of carbon from the surface ocean and its remineralization with depth; thus biologically related parameters able to be estimated from satellite observations were merged at the POC observation sites. Satellite parameters include net primary production, percent microplankton, sea surface temperature, photosynthetically active radiation, diffuse attenuation coefficient at 490 nm, euphotic zone depth, and climatological mixed layer depth. Of the observations across the globe, 85% are concentrated in the Northern Hemisphere with 44% of the data record overlapping the satellite record. Time series sites accounted for 36% of the data, while 71% of the data are measured atâ„ 500m with the most common deployment depths between 1000 and 1500m. This data set is valuable for investigations of CO2 drawdown, carbon export, remineralization, and sequestration. The compiled data can be freely accessed at doi.org/10.1594/PANGAEA.855600
Fingerprinting Soft Materials: A Framework for Characterizing Nonlinear Viscoelasticity
We introduce a comprehensive scheme to physically quantify both viscous and
elastic rheological nonlinearities simultaneously, using an imposed large
amplitude oscillatory shear (LAOS) strain. The new framework naturally lends a
physical interpretation to commonly reported Fourier coefficients of the
nonlinear stress response. Additionally, we address the ambiguities inherent in
the standard definitions of viscoelastic moduli when extended into the
nonlinear regime, and define new measures which reveal behavior that is
obscured by conventional techniques.Comment: 10 pages, 3 figures, full-page double-space preprint forma
The Family Name as Socio-Cultural Feature and Genetic Metaphor: From Concepts to Methods
A recent workshop entitled The Family Name as Socio-Cultural Feature and Genetic Metaphor: From Concepts to Methods was held in Paris in December 2010, sponsored by the French National Centre for Scientific Research (CNRS) and by the journal Human Biology. This workshop was intended to foster a debate on questions related to the family names and to compare different multidisciplinary approaches involving geneticists, historians, geographers, sociologists and social anthropologists. This collective paper presents a collection of selected communications
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