The Serpens South embedded cluster, which is located in the constricted part of a long, filamentary, infrared dark cloud, is believed to be in a very early stage of cluster formation. We present ...results of near-infrared (JHKs) polarization observations of the filamentary cloud. Our polarization measurements of near-infrared point sources indicate a well-ordered global magnetic field that is perpendicular to the main filament, implying that the magnetic field is likely to have controlled the formation of the main filament. On the other hand, the sub-filaments, which converge on the central part of the cluster, tend to run along the magnetic field. The global magnetic field appears to be curved in the southern part of the main filament. Such morphology is consistent with the idea that the global magnetic field is distorted by gravitational contraction along the main filament toward the northern part, which contains larger mass. Applying the Chandrasekhar-Fermi method, the magnetic field strength is roughly estimated to be a few X100 Delta *mG, suggesting that the filamentary cloud is close to magnetically critical.
The effect of annealing temperature on MnAl alloy powder synthesized by electrodeposition method was investigated. Single L10-MnAl (τ-phase) with nearly stoichiometric composition was obtained by ...electrodeposition method. In annealed at 400°C sample coercivity of 12.3 kOe was observed. And by annealing at 450–550°C, metamagnetic behavior was observed. In these samples, the main phase was τ-phase although weak peaks of low-temperature Al-rich γ2 phase appeared. The order parameter S of the τ-phase exhibited a peak value with variation of the annealing temperature. The peak value was 0.90 at an annealing temperature of 500°C, where the metamagnetic behavior was most clearly observed. This indicates that the nearly perfectly ordered τ-phase shows metamagnetism and the Mn atoms occupying the Al sites play an important role in the metamagnetism of the τ-phase.
Abstract
There has been significant concern about increases in the exposure dose in living areas due to the accumulation of radiocesium discharged from contaminated mountainous forests in Fukushima. ...In this study, we investigated the history of radiocesium deposition on several floodplains in Fukushima following the nuclear power plant accident. Radiocesium concentrations in river suspended particles and the air dose rates on the floodplains were observed continuously. The annual sediment accumulation on the floodplains was 5.5–200 kg m−2, and the observed radiocesium concentration decreased with the decrease in the radiocesium concentration of suspended particles. The air dose rates on the floodplains were gradually decreasing with time. In 2015, with heavy flood discharge, a sediment accumulation of 180–200 kg m−2 and a sharp decrease in the air dose rate were observed at the Takase River, which does not have a reservoir. Conversely, the sediment accumulation at the Ukedo River was significantly reduced due to deposition in an upstream reservoir.
The high-resolution electron back-scatter diffraction technique was employed to study the grain structure evolution during friction-stir welding of AZ31 magnesium alloy. The material flow was found ...to be a very complex process associated mainly with basal slip. The grain structure development was demonstrated to be dictated by the texture evolution but also to involve
{
1
0
1
¯
2
}
twinning, geometrical effects of strain and limited discontinuous recrystallization.
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Friction stir welding (FSW) was applied to 3
mm-thick Ti–6Al–4V plates under different rotational speeds. Defect-free welds were successfully produced at rotational speeds of 400 and 500
rpm. The ...base material (BM) had a deformed α/β lamellar microstructure. FSW produced a full lamellar structure with refined prior β grains in the SZ, while the HAZ contained a bimodal microstructure consisting of the equiaxed primary α and α/β lamellar structure within the prior β structure. An increase in rotational speed increased the sizes of α colonies and prior β grains. The SZ exhibited higher hardness than the BM, with the lowest hardness found in the HAZ. Results of the transverse tensile test showed that all welds fractured in the HAZ and that they exhibited lower strength and elongation than the BM. The tensile test for only the SZ showed it to be characterized by higher strength and elongation than the BM.
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Data from the human motor cortex suggest that, depending on polarity, direct current (DC) brain polarization can depress or activate cortical neurons. Activating effects on the frontal lobe might be ...beneficial for patients with frontal lobe disorders. This phase 1 study tested the safety of frontal DC, including its effects on frontal and other brain functions.
The authors applied 20 minutes of anodal, cathodal, or sham DC to the left prefrontal cortex in three groups of right-handed subjects and looked for effects on global measures of processing and psychomotor speed, emotion, and verbal fluency, a measure of local cortical function. In one experiment (n = 30), the authors tested before and after 1 mA DC and monitored EEG in 9 subjects. In two other experiments using 1 mA (n = 43) and 2 mA (n = 30), the authors tested before and then starting 5 minutes after the onset of DC.
All subjects tolerated DC well. There were no significant effects on performance with 1 mA DC. At 2 mA, verbal fluency improved significantly with anodal and decreased mildly with cathodal DC. There were no clinically significant effects on the other measures.
Limited exposure to direct current polarization of the prefrontal cortex is safe and can enhance verbal fluency selectively in healthy subjects. As such, it deserves consideration as a procedure to improve frontal lobe function in patients.
A dissimilar friction stir weld of Al alloy 1050 and Mg alloy AZ31 was produced. The weld had a large volume of intermetallic compound Al
12Mg
17 and significantly higher hardness in the weld center. ...The present study suggests that constitutional liquation resulted in the intermetallic compound Al
12Mg
17 in the weld center.
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We evaluated electrical velocimetry, a noninvasive method for continuous cardiac output measurement, in very-low and low birth weight infants and the influence of patent ductus arteriosus (PDA) and ...ventilators on this method.
This prospective study compared 81 pairs of simultaneous cardiac output measurements by electrical velocimetry and transthoracic echocardiography in 28 patients. Data were compared by correlation, Bland-Altman analysis and two-way analysis of variance.
The two methods exhibited a high correlation (r=0.859, P<0.0001). The bias (mean difference of the methods) and percent error (100 × 1.96 × s.d./mean cardiac output) were -6 ml min(-1) and 29.2%, respectively. PDA significantly affected the bias (P=0.0004), but ventilators did not (P=0.14). Hemodynamically significant PDA had a larger bias (-36 ml min(-1)) and higher percent error (38.6%).
Although influenced by PDA, electrical velocimetry was generally interchangeable with transthoracic echocardiography even using ventilators.
SUMMARY
Many recent studies have tried to determine the influence of geometry of faults in earthquake mechanics. However, it still remains largely unknown, and it is explored mainly with numerical ...models. In this paper, we will try to understand how exactly does the geometry come into play in the mechanics of an earthquake from analytical perspective. We suggest a new interpretation of the effect of geometry on the stress on a fault, where the curvatures of the fault that multiply the slip play a major role. Starting from the representation theorem, which links the displacement in a medium to the slip distribution on its boundary, and assuming a 3-D, homogeneous, infinite medium, a regularized boundary-element equation can be obtained. Using this equation, it is possible to separate the influence of geometry, as expressed by the curvatures and torsions of the field lines of slip on the fault surface, which multiply the slip, from the effect of the gradient of slip. This allows us to shed new light on the mechanical effects of geometrical complexities on the fault surface, with the key parameters being the curvatures and torsions of the slip field lines. We have used this new approach to show that, in 2-D static in-plane problems, the shear traction along the fault is mainly controlled by the gradient of slip along the fault, while the normal traction is mainly controlled by the slip that multiplies the curvature along the fault. Finally, we applied this new approach to re-interpret the effect of roughness (why there is a need for a minimum lengthscale in linear elasticity, how to study mechanically the difference of roughness measurements with the direction of slip, scaling of slip distribution versus geometry), bends and kinks (what is the difference between the two, are they sometimes equivalent), as well as to explain further the false paradox between smooth-and-abrupt-bends. This unified framework allows us to improve greatly our understanding of the effect of fault geometry on the mechanics of earthquakes.
Material flow during friction stir spot welding Yang, Q.; Mironov, S.; Sato, Y.S. ...
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
06/2010, Volume:
527, Issue:
16
Journal Article
Peer reviewed
Material flow during friction stir spot welding (FSSW) is investigated using tracer material technique. Three distinct regions are developed in a weld after the rotating shoulder comes in close ...contact with the upper sheet. They are called flow transition zone, stir zone, and torsion zone which are evolved due to the combination of rotational, horizontal and vertical motions of the plasticized material. An incorporation of the upper and lower sheet materials takes place in the flow transition zone, and the intermingled materials flowing from the flow transition zone contribute primarily to the formation of the stir zone. A new model of material flow during FSSW is developed on the basis of experimental observations. It is believed that the intrinsic driving force for the downward motion of the plasticized material is originated from the material release from the rotating pin through an outward-spinning motion.
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