44,200 research outputs found
Rotating bio-reactor cell culture apparatus
A bioreactor system is described in which a tubular housing contains an internal circularly disposed set of blade members and a central tubular filter all mounted for rotation about a common horizontal axis and each having independent rotational support and rotational drive mechanisms. The housing, blade members and filter preferably are driven at a constant slow speed for placing a fluid culture medium with discrete microbeads and cell cultures in a discrete spatial suspension in the housing. Replacement fluid medium is symmetrically input and fluid medium is symmetrically output from the housing where the input and the output are part of a loop providing a constant or intermittent flow of fluid medium in a closed loop
Method for culturing mammalian cells in a perfused bioreactor
A bio-reactor system wherein a tubular housing contains an internal circularly disposed set of blade members and a central tubular filter all mounted for rotation about a common horizontal axis and each having independent rotational support and rotational drive mechanisms. The housing, blade members and filter preferably are driven at a constant slow speed for placing a fluid culture medium with discrete microbeads and cell cultures in a discrete spatial suspension in the housing. Replacement fluid medium is symmetrically input and fluid medium is symmetrically output from the housing where the input and the output are part of a loop providing a constant or intermittent flow of fluid medium in a closed loop
Experimental measurement of the orbital paths of particles sedimenting within a rotating viscous fluid as influenced by gravity
Measurements were taken of the path of a simulated typical tissue segment or 'particle' within a rotating fluid as a function of gravitational strength, fluid rotation rate, particle sedimentation rate, and particle initial position. Parameters were examined within the useful range for tissue culture in the NASA rotating wall culture vessels. The particle moves along a nearly circular path through the fluid (as observed from the rotating reference frame of the fluid) at the same speed as its linear terminal sedimentation speed for the external gravitational field. This gravitationally induced motion causes an increasing deviation of the particle from its original position within the fluid for a decreased rotational rate, for a more rapidly sedimenting particle, and for an increased gravitational strength. Under low gravity conditions (less than 0.1 G), the particle's motion through the fluid and its deviation from its original position become negligible. Under unit gravity conditions, large distortions (greater than 0.25 inch) occur even for particles of slow sedimentation rate (less than 1.0 cm/sec). The particle's motion is nearly independent of the particle's initial position. Comparison with mathematically predicted particle paths show that a significant error in the mathematically predicted path occurs for large particle deviations. This results from a geometric approximation and numerically accumulating error in the mathematical technique
Saber: window-based hybrid stream processing for heterogeneous architectures
Modern servers have become heterogeneous, often combining multicore CPUs with many-core GPGPUs. Such heterogeneous architectures have the potential to improve the performance of data-intensive stream processing applications, but they are not supported by current relational stream processing engines. For an engine to exploit a heterogeneous architecture, it must execute streaming SQL queries with sufficient data-parallelism to fully utilise all available heterogeneous processors, and decide how to use each in the most effective way. It must do this while respecting the semantics of streaming SQL queries, in particular with regard to window handling. We describe SABER, a hybrid high-performance relational stream processing engine for CPUs and GPGPUs. SABER executes windowbased streaming SQL queries in a data-parallel fashion using all available CPU and GPGPU cores. Instead of statically assigning query operators to heterogeneous processors, SABER employs a new adaptive heterogeneous lookahead scheduling strategy, which increases the share of queries executing on the processor that yields the highest performance. To hide data movement costs, SABER pipelines the transfer of stream data between different memory types and the CPU/GPGPU. Our experimental comparison against state-ofthe-art engines shows that SABER increases processing throughput while maintaining low latency for a wide range of streaming SQL queries with small and large windows sizes
Test of the gravitational redshift with stable clocks in eccentric orbits: application to Galileo satellites 5 and 6
The Einstein Equivalence Principle (EEP) is one of the foundations of the
theory of General Relativity and several alternative theories of gravitation
predict violations of the EEP. Experimental constraints on this fundamental
principle of nature are therefore of paramount importance. The EEP can be split
in three sub-principles: the Universality of Free Fall (UFF), the Local Lorentz
Invariance (LLI) and the Local Position Invariance (LPI). In this paper we
propose to use stable clocks in eccentric orbits to perform a test of the
gravitational redshift, a consequence of the LPI. The best test to date was
performed with the Gravity Probe A (GP-A) experiment in 1976 with an
uncertainty of . Our proposal considers the opportunity of
using Galileo satellites 5 and 6 to improve on the GP-A test uncertainty. We
show that considering realistic noise and systematic effects, and thanks to a
highly eccentric orbit, it is possible to improve on the GP-A limit to an
uncertainty around after one year of integration of
Galileo 5 and 6 data.Comment: 13 pages, 5 figures, accepted in Classical and Quantum Gravity as a
Fast Track Communicatio
Relaxation dynamics of a protein solution investigated by dielectric spectroscopy
In the present work, we provide a dielectric study on two differently
concentrated aqueous lysozyme solutions in the frequency range from 1 MHz to 40
GHz and for temperatures from 275 to 330 K. We analyze the three dispersion
regions, commonly found in protein solutions, usually termed beta-, gamma-, and
delta-relaxation. The beta-relaxation, occurring in the frequency range around
10 MHz and the gamma-relaxation around 20 GHz (at room temperature) can be
attributed to the rotation of the polar protein molecules in their aqueous
medium and the reorientational motion of the free water molecules,
respectively. The nature of the delta-relaxation, which often is ascribed to
the motion of bound water molecules, is not yet fully understood. Here we
provide data on the temperature dependence of the relaxation times and
relaxation strengths of all three detected processes and on the dc conductivity
arising from ionic charge transport. The temperature dependences of the beta-
and gamma-relaxations are closely correlated. We found a significant
temperature dependence of the dipole moment of the protein, indicating
conformational changes. Moreover we find a breakdown of the
Debye-Stokes-Einstein relation in this protein solution, i.e., the dc
conductivity is not completely governed by the mobility of the solvent
molecules. Instead it seems that the dc conductivity is closely connected to
the hydration shell dynamics.Comment: 11 pages, 7 figure
Role of spatial coherence in polarization tomography
We analyze an experimental setup in which a quasi-monochromatic spatially
coherent beam of light is used to probe a paraxial optical scatterer. We
discuss the effect of the spatial coherence of the probe beam on the Mueller
matrix representing the scatterer. We show that according to the degree of
spatial coherence of the beam, the \emph{same} scattering system can be
represented by \emph{different} Mueller matrices. This result should serve as a
warning for experimentalists.Comment: 3 pages, 1 figur
Survival of Fecal Contamination Indicator Organisms in Soil
Soils amended with human or animal waste may result in pathogen contamination of ground and surface water. Because temperature has been shown to affect pathogen survival, two laboratory studies were conducted to evaluate the impact of extremes in temperature on bacterial and viral pathogen indicator die-off in soil. A Captina silt loam was amended with broiler litter (0.1 g/g dry soil), septic tank effluent, or Escherichia coli (ATCC 13706) culture (both at 0.04 and 0.1 mL/g dry soil in the two respective studies), incubated at 5 and 35°C, and analyzed over time to determine the number of fecal coliform, E. coli, and coliphage remaining. Pathogen indicator die-off rate constants (k) for all indicator- temperature-treatment combinations were determined by first-order kinetics. For all three pathogen indicators, die-off was significantly more rapid at 35°C than at 5°C. In both studies, fecal coliform die-off rates were not different from E. coli die-off rates across each temperature-treatment combination. Levels of these bacterial indicators appeared in a ratio of 1:0.94 with 95% confidence intervals at 0.89 and 0.99 in the E. coli- and litter-amended soils. Die-off of the viral indicator was significantly slower than the die-off of the bacterial indicators at 5°C in litter-amended soil. Die-off of the bacterial indicator, E. coli, in soil amended with E. coli culture was not significantly different than die-off in soil amended with broiler litter at 5 or 35°C in the two studies. Because the higher incubation temperature increased die-off rates for all three indicators, it is expected that the potential for contamination of ground and surface water decreases with increasing temperature
High aspect reactor vessel and method of use
An improved bio-reactor vessel and system useful for carrying out mammalian cell growth in suspension in a culture media are presented. The main goal of the invention is to grow and maintain cells under a homogeneous distribution under acceptable biochemical environment of gas partial pressures and nutrient levels without introducing direct agitation mechanisms or associated disruptive mechanical forces. The culture chamber rotates to maintain an even distribution of cells in suspension and minimizes the length of a gas diffusion path. The culture chamber design is presented and discussed
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