The effect of weld residual stresses and their re-distribution with crack growth during fatigue under constant amplitude loading

In this work the evolution of the residual stresses in a MIG-welded 2024-T3 aluminium alloy M(T) specimen during in situ fatigue crack growth at constant load amplitude has been measured with neutron diffraction. The plastic relaxation and plasticity-induced residual stresses associated with the fatigue loading were found to be small compared with the stresses arising due to elastic re-distribution of the initial residual stress field. The elastic re-distribution was modelled with a finite element simulation and a good correlation between the experimentally-determined and the modelled stresses was found. A significant mean stress effect on the fatigue crack growth rate was seen and this was also accurately predicted using the measured initial residual stresses

A Reanalysis of the Carbon Abundance in the Translucent Cloud toward HD 24534

We have reanalyzed the Goddard High Resolution Spectrograph data set presented by Snow et al. which contains the interstellar intersystem C II] 2325A line through the translucent cloud toward HD 24534 (X Persei). In contrast to the results of Snow et al., we clearly detect the C II] feature at the 3-sigma confidence level and measure a C^+ column density of 2.7 +/- 0.8 x 10^17 cm^-2. Accounting for the C I column density along the line of sight, we find 10^6 C/H = 106 +/- 38 in the interstellar gas toward this star. This gas-phase carbon-to-hydrogen ratio suggests that slightly more carbon depletion may be occurring in translucent as compared to diffuse clouds. The average diffuse-cloud C/H, however, is within the 1-sigma uncertainty of the measurement toward HD 24534. We therefore cannot rule out the possibility that the two cloud types have comparable gas-phase C/H, and therefore comparable depletions of carbon.Comment: 9 pages, 3 figures, to appear in the Astrophysical Journal Letter

Numerical study of strength mismatch in cross-weld tensile testing

The strength mismatch effect on the deformation behaviour of defect-free cross-weld tensile specimens, where there is a variation in strength along the length of the specimen, was investigated through 2D finite element analysis. A simple bi-material model, which is generally used in current engineering assessments (e.g. R6 “Assessment of the integrity of structures containing defects”) to examine the strength mismatch effect on the deformation and fracture behaviour of a weld which actually includes a heat-affected-zone, could lead to non- conservative or overly conservative predictions. In fusion welded components, one would generally observe that there is a heat-affected zone where the material properties are different from the weld and base material, and there is a continuous gradient of properties between the two. The material properties in HAZ are generally assigned discretely; however, in our multi-material model these properties are successfully assigned continuously by embedding subroutines into finite element model. This multi-material approach was used to examine the effect of strength mismatch on the local and global deformation behavior of fusion welds. It has been found that the bi-material modeling, by ignoring the HAZ, and multi-material discrete HAZ modeling of the cross-weld specimens leads to unrealistically biaxial stresses at the interfaces where there is an abrupt variation of the material properties. However, multi- material continuous HAZ modeling eliminates unrealistic stress biaxiality and enables to examine the local deformation more accurately. It was also found that the global stress-strain behaviour obtained using the bi- material and multi-material modeling is different

The zinc finger transcription factor PLAGL2 enhances stem cell fate and activates expression of ASCL2 in intestinal epithelial cells

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Power Coupling Alternatives for the NEP Thermionic Power System

Three output power coupling methods which can eliminate the high temperature insulator from the Nuclear Electric Propulsion (NEP) power system are described and estimates of their effects on the NEP system masses and cooling requirements are presented. Nominal 400 kWe power systems using push-pull and flux reset inductive output coupling are shown to have specific masses of 22.2 kg/kWe and 18.8 kg/kWe, respectively. Series connected heat pipe systems, which use the heat pipe-to-heat pipe resistance to isolate converters on adjacent heat pipes, are shown to have specific masses 0.5 to 1.4 kg/kWe lower than the NEP baseline system. Increasing the number and temperature of the heat pipes in the system without changing the electric output reduces the calculated system specific mass only slightly, whereas increasing the output power significantly reduces the specific mass. Estimates of cooling requirements indicate that 11-45 sq m of power conditioning radiator are needed. A possible location for the power conditioning radiator may be in the present location of the kapton sputter shield

Should Species Distribution Models Account for Spatial Autocorrelation? A Test of Model Projections Across Eight Millennia of Climate Change

Aim: The distributions of many organisms are spatially autocorrelated, but it is unclear whether including spatial terms in species distribution models (SDMs) improves projections of species distributions under climate change. We provide one of the first comparative evaluations of the ability of a purely spatial SDM, a purely non-spatial SDM and a SDM that combines spatial and environmental information to project species distributions across eight millennia of climate change. Location: Eastern North America. Methods: To distinguish between the importance of climatic versus spatial explanatory variables we fit three Bayesian SDMs to modern occurrence data for Fagus and Tsuga, two tree genera whose distributions can be reliably inferred from fossil pollen: a spatially varying intercept model, a non-spatial model with climatic variables and a spatially varying intercept plus climate model. Using palaeoclimate data with a high temporal resolution, we hindcasted the SDMs in 1000-year time steps for 8000 years, and compared model projections with palynological data for the same periods. Results: For both genera, spatial SDMs provided better fits to the calibration data, more accurate predictions of a hold-out validation dataset of modern trees and higher variance in current predictions and hindcasted projections than non-spatial SDMs. Performance of non-spatial and spatial SDMs according to the area under the receiver operating curve varied by genus. For both genera, false negative rates between non-spatial and spatial models were similar, but spatial models had lower false positive rates than non-spatial models. Main conclusions: The inclusion of computationally demanding spatial random effects in SDMs may be warranted when ecological or evolutionary processes prevent taxa from shifting their distributions or when the cost of false positives is high.Organismic and Evolutionary Biolog

Analysis of gene expression in the bovine corpus luteum through generation and characterisation of 960 ESTs

To gain new insights into gene identity and gene expression in the bovine corpus luteum (CL) a directionally cloned CL cDNA library was constructed, screened with a total CL cDNA probe and clones representing abundant and rare mRNA transcripts isolated. The 5Vterminal DNA sequence of 960 cDNA clones, composed of 192 abundant and 768 rare mRNA transcripts was determined and clustered into 351 non-redundant expressed sequence tag (EST) groups. Bioinformatic analysis revealed that 309 (88%) of the ESTs showed significant homology to existing sequences in the protein and nucleotide public databases. Several previously unidentified bovine genes encoding proteins associated with key aspects of CL function including extracellular matrix remodelling, lipid metabolism/steroid biosynthesis and apoptosis, were identified. Forty-two (12%) of the ESTs showed homology with human or with other uncharacterised ESTs, some of these were abundantly expressed and may therefore play an important role in primary CL function. Tissue-specificity and temporal CL gene expression of selected clones previously unidentified in bovine CL tissue was also examined. The most interesting finds indicated that mRNA encoding squalene epoxidase was constitutively expressed in CL tissue throughout the oestrous cycle and 7-fold down-regulated ( P < 0.05)in late luteal tissue, concomitant with the disappearance of systemic progesterone, suggesting that de novo cholesterol biosynthesis plays an important role in steroidogenesis. The mRNA encoding the growth factor, insulin-like growth factor-binding protein-related protein 1 (IGFBP-rP1), remained constant during the oestrous cycle and was 1.8-fold up-regulated ( P < 0.05) in late luteal tissue implying a role in CL regression

Spread of community-acquired meticillin-resistant Staphylococcus aureus skin and soft-tissue infection within a family: implications for antibiotic therapy and prevention.

Outbreaks or clusters of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) within families have been reported. We describe a family cluster of CA-MRSA skin and soft-tissue infection where CA-MRSA was suspected because of recurrent infections which failed to respond to flucloxacillin. While the prevalence of CA-MRSA is low worldwide, CA-MRSA should be considered in certain circumstances depending on clinical presentation and risk assessment. Surveillance cultures of family contacts of patients with MRSA should be considered to help establish the prevalence of CA-MRSA and to inform the optimal choice of empiric antibiotic treatment

Advanced Hybrid Spacesuit Concept Featuring Integrated Open Loop and Closed Loop Ventilation Systems

A document discusses the design and prototype of an advanced spacesuit concept that integrates the capability to function seamlessly with multiple ventilation system approaches. Traditionally, spacesuits are designed to operate both dependently and independently of a host vehicle environment control and life support system (ECLSS). Spacesuits that operate independent of vehicle-provided ECLSS services must do so with equipment selfcontained within or on the spacesuit. Suits that are dependent on vehicle-provided consumables must remain physically connected to and integrated with the vehicle to operate properly. This innovation is the design and prototype of a hybrid spacesuit approach that configures the spacesuit to seamlessly interface and integrate with either type of vehicular systems, while still maintaining the ability to function completely independent of the vehicle. An existing Advanced Crew Escape Suit (ACES) was utilized as the platform from which to develop the innovation. The ACES was retrofitted with selected components and one-off items to achieve the objective. The ventilation system concept was developed and prototyped/retrofitted to an existing ACES. Components were selected to provide suit connectors, hoses/umbilicals, internal breathing system ducting/ conduits, etc. The concept utilizes a lowpressure- drop, high-flow ventilation system that serves as a conduit from the vehicle supply into the suit, up through a neck seal, into the breathing helmet cavity, back down through the neck seal, out of the suit, and returned to the vehicle. The concept also utilizes a modified demand-based breathing system configured to function seamlessly with the low-pressure-drop closed-loop ventilation system

Effects of acute intermittent hypoxia on corticospinal excitability within the primary motor cortex

Purpose Acute intermittent hypoxia (AIH) is a safe and non-invasive treatment approach that uses brief, repetitive periods of breathing reduced oxygen air alternated with normoxia. While AIH is known to affect spinal circuit excitability, the effects of AIH on cortical excitability remain largely unknown. We investigated the effects of AIH on cortical excitability within the primary motor cortex. Methods Eleven healthy, right-handed participants completed two testing sessions: (1) AIH (comprising 3 min in hypoxia [fraction of inspired oxygen ~ 10%] and 2 min in normoxia repeated over five cycles) and (2) normoxia (NOR) (equivalent duration to AIH). Single- and paired-pulse transcranial magnetic stimulations were delivered to the primary motor cortex, before and 0, 25, and 50 min after AIH and normoxia. Results The mean nadir in arterial oxygen saturation was lower (p  0.05). There was no association between arterial oxygen saturation and changes in corticospinal excitability after AIH (r = 0.05, p = 0.87). Conclusion Overall, AIH did not modify either corticospinal excitability or excitability of intracortical facilitatory and inhibitory circuits within the primary motor cortex. Future research should explore whether a more severe or individualised AIH dose would induce consistent, measurable changes in corticospinal excitability