254 research outputs found
Improvement of nonlinear dynamic models containing neural networks based on domain partitioning
Investigation of Horizontal Velocity Fields in Stirred Vessels with Helical Coils by PIV
Horizontal velocity flow fields were measured by particle image velocimetry for a stirred vessel with baffles and two helical coils for enlargement of heat transfer area. The investigation was carried out in a cylindrical vessel with flat base and two different stirrers (radial-flow Rushton turbine and axial-flow propeller stirrer). Combined velocity plots for flow fields at different locations are presented. It was found that helical coils change the flow pattern significantly. Measurements for the axial-flow Rushton turbine showed a strong deflection by the coils, leading to a mainly tangential flow pattern. Behind baffles large areas of unused heat transfer area were found. First results for the axial-flow propeller reveal an extensive absence of fluid movement in the horizontal plane. Improved design considerations for enhanced heat transfer by more compatible equipment compilation are proposed
Magnetic domain structure of epitaxial Ni-Mn-Ga films
For the magnetic shape memory effect, knowledge about the interaction between
martensitic and magnetic domain structure is essential. In the case of Ni-Mn-Ga
bulk material and foils, a staircase-like magnetic domain structure with
90{\deg}- and 180{\deg}-domain walls is known for modulated martensite. In the
present paper we show that the magnetic domain pattern of thin epitaxial films
is fundamentally different. Here we analyze epitaxial Ni-Mn-Ga films by atomic
and magnetic force microscopy to investigate the correlation between the
twinned martensitic variants and the magnetic stripe domains. The observed
band-like domains with partially perpendicular outof-plane magnetization run
perpendicular to the microstructure domains defined by twinning variants. These
features can be explained by the finite film thickness, resulting in an
equilibrium twinning period much smaller than the domain period. This does not
allow the formation of a staircase domain patter. Instead the energies of the
magnetic and martensitic microstructures are minimized independently by
aligning both patterns perpendicularly to each other. By analyzing a thickness
series we can show that the observed magnetic domain pattern can be
quantitatively described by an adapted band domain model of Kittel.Comment: 12 pages, 4 figure
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Micromagnetic investigation of domain and domain wall evolution through the spin-reorientation transition of an epitaxial NdCo5 film
The domain pattern and the domain wall microstructure throughout the spin-reorientation transition of an epitaxial NdCo5 thin film are investigated by micromagnetic simulations. The temperature-dependent anisotropy constants K1 and K2, which define the anisotropy energy term in the model, are chosen to reflect the easy axis—easy cone—easy plane spin-reorientation transition observed in epitaxial NdCo5 thin films. Starting at the high-temperature easy c-axis regime, the anisotropy constants are changed systematically corresponding to a lowering of the temperature of the system. The character of the domain walls and their profiles are analysed. The calculated domain configurations are compared to the experimentally observed temperature-dependent domain structure of an in-plane textured NdCo5 thin film
Structural genomics of human proteins – target selection and generation of a public catalogue of expression clones
BACKGROUND: The availability of suitable recombinant protein is still a major bottleneck in protein structure analysis. The Protein Structure Factory, part of the international structural genomics initiative, targets human proteins for structure determination. It has implemented high throughput procedures for all steps from cloning to structure calculation. This article describes the selection of human target proteins for structure analysis, our high throughput cloning strategy, and the expression of human proteins in Escherichia coli host cells. RESULTS AND CONCLUSION: Protein expression and sequence data of 1414 E. coli expression clones representing 537 different proteins are presented. 139 human proteins (18%) could be expressed and purified in soluble form and with the expected size. All E. coli expression clones are publicly available to facilitate further functional characterisation of this set of human proteins
Development of Dietary-Based Toxicity Reference Values to Assess the Risk of Chlorophacinone to Non-Target Raptorial Birds
Regulatory changes in the use of some second-generation anticoagulant rodenticides in parts of North America may result in expanded use of first-generation anticoagulant rodenticides (FGARs). Recent toxicological studies with captive raptors have demonstrated that these species are considerably more sensitive to the FGAR diphacinone than traditional avian wildlife test species (mallard, bobwhite). We have now examined the toxicity of the FGAR chlorophacinone (CPN) to American kestrels fed rat tissue mechanically amended with CPN, or rat tissue containing biologically-incorporated CPN, for 7 days. Nominal CPN concentrations in these diets were 0.15, 0.75, and 1.5 μg/g food wet weight, and actual CPN concentration in diets were analytically verified as being close to target values. Food intake was consistent among groups, body weight fluctuated by less than 6%, exposure and adverse effects were generally dose-dependent, and there were no dramatic differences in toxicity between mechanically-amended and biologically-incorporated CPN diets. Using benchmark dose statistical methods, toxicity reference values at which clotting times were prolonged in 50% of the kestrels was estimated to be about 80 μg CPN consumed/kg body weight-day for prothrombin time and 40 μg CPN/kg body weight-day for Russell’s viper venom time. Based upon carcass CPN residues reported in rodents from field baiting studies, empirical measures of food consumption in kestrels, and dietary-based toxicity reference values derived from the 7-day exposure scenario, some free-ranging raptors consuming CPN-exposed prey might exhibit coagulopathy and hemorrhage. These sublethal responses associated with exposure to environmentally realistic concentrations of CPN could compromise survival of exposed birds
Toxicity reference values for chlorophacinone and their application for assessing anticoagulant rodenticide risk to raptors
Despite widespread use and benefit, there are
growing concerns regarding hazards of second-generation
anticoagulant rodenticides to non-target wildlife which
may result in expanded use of first-generation compounds,
including chlorophacinone (CPN). The toxicity of CPN
over a 7-day exposure period was investigated in American
kestrels (Falco sparverius) fed either rat tissue mechanically-
amended with CPN, tissue from rats fed Rozol bait
(biologically-incorporated CPN), or control diets (tissue
from untreated rats or commercial bird of prey diet)
ad libitum. Nominal CPN concentrations in the formulated
diets were 0.15, 0.75 and 1.5 µg/g food wet weight, and
measured concentrations averaged 94 % of target values.
Kestrel food consumption was similar among groups and
body weight varied by less than 6 %. Overt signs of
intoxication, liver CPN residues, and changes in prothrombin
time (PT), Russell’s viper venom time (RVVT)
and hematocrit, were generally dose-dependent. Histological
evidence of hemorrhage was present at all CPN dose levels, and most frequently observed in pectoral muscle and heart. There were no apparent differences in toxicity
between mechanically-amended and biologically-incorporated
CPN diet formulations. Dietary-based toxicity reference
values at which clotting times were prolonged in
50 % of the kestrels were 79.2 µg CPN consumed/kg body
weight-day for PT and 39.1 µg/kg body weight-day for
RVVT. Based upon daily food consumption of kestrels and
previously reported CPN concentrations found in small
mammals following field baiting trials, these toxicity reference
values might be exceeded by free-ranging raptors
consuming such exposed prey. Tissue-based toxicity reference
values for coagulopathy in 50 % of exposed birds
were 0.107 µg CPN/g liver wet weight for PT and
0.076 µg/g liver for RVVT, and are below the range of
residue levels reported in raptor mortality incidents
attributed to CPN exposure. Sublethal responses associated
with exposure to environmentally realistic concentrations
of CPN could compromise survival of free-ranging raptors,
and should be considered in weighing the costs and benefits
of anticoagulant rodenticide use in pest control and eradication
programs
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