We report a detailed study of the strain hardening behavior of a Fe–16Mn–10Al–0.86C–5Ni (weight percent) high specific strength (i.e. yield strength-to-mass density ratio) steel (HSSS) during ...uniaxial tensile deformation. The dual-phase (γ-austenite and B2 intermetallic compound) HSSS possesses high yield strength of 1.2–1.4 GPa and uniform elongation of 18–34%. The tensile deformation of the HSSS exhibits an initial yield-peak, followed by a transient characterized by an up-turn of the strain hardening rate. Using synchrotron based high-energy in situ X-ray diffraction, the evolution of lattice strains in both the γ and B2 phases was monitored, which has disclosed an explicit elasto-plastic transition through load transfer and strain partitioning between the two phases followed by co-deformation. The unloading-reloading tests revealed the Bauschinger effect: during unloading yield in γ occurs even when the applied load is still in tension. The extraordinary strain hardening rate can be attributed to the high back stresses that arise from the strain incompatibility caused by the microstructural heterogeneity in the HSSS.
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With the aim of gathering temporal trends on bacterial epidemiology and resistance from multiple laboratories in China, the CHINET surveillance system was organized in 2005. Antimicrobial ...susceptibility testing was carried out according to a unified protocol using the Kirby-Bauer method or automated systems. Results were analyzed according to Clinical and Laboratory Standards Institute (CLSI) 2014 definitions. Between 2005 and 2014, the number of bacterial isolates ranged between 22 774 and 84 572 annually. Rates of extended-spectrum β-lactamase production among Escherichia coli isolates were stable, between 51.7 and 55.8%. Resistance of E. coli and Klebsiella pneumoniae to amikacin, ciprofloxacin, piperacillin/tazobactam and cefoperazone/sulbactam decreased with time. Carbapenem resistance among K. pneumoniae isolates increased from 2.4 to 13.4%. Resistance of Pseudomonas aeruginosa strains against all of antimicrobial agents tested including imipenem and meropenem decreased with time. On the contrary, resistance of Acinetobacter baumannii strains to carbapenems increased from 31 to 66.7%. A marked decrease of methicillin resistance from 69% in 2005 to 44.6% in 2014 was observed for Staphylococcus aureus. Carbapenem resistance rates in K. pneumoniae and A. baumannii in China are high. Our results indicate the importance of bacterial surveillance studies.
Abstract How pulsars radiate is a long-standing problem. Detailed polarization measurements of individual pulses shed light on currently unknown emission processes. Recently, based on supersensitive ...observations, dwarf pulses have been recognized as weak narrow pulses often appearing during the nulling state. In this study, we report the detection of dwarf pulses from 10 pulsars, PSRs B0525+21, B1237+25, J1538+2345, J1824−0127, J1851−0053, B1901+10, J1939+10, B1944+17, B2000+40, and J2112+4058, based on observations conducted with the Five-hundred-meter Aperture Spherical radio Telescope. Dwarf pulses of five pulsars are clearly discernible in the two-dimensional distribution of pulse intensity and pulse width. For the other five pulsars, PSRs J1538+2345, J1824−0127, J1939+10, B2000+40, and J2112+4058, only a few dwarf pulses are detected from pulse stacks. The dwarf pulses can emerge in both cone and core emission components for PSR B1237+25, and the polarization angles of these dwarf pulses are mostly in the orthogonal polarization mode of normal pulses for PSR B1944+17. In general, pulsars with detected dwarf pulses tend to be located within the “death valley” region of the distribution of pulsar periods and period derivatives.
Abstract
Discovery of pulsars is one of the main goals for large radio telescopes. The Five-hundred-meter Aperture Spherical radio Telescope (FAST), that incorporates an L-band 19-beam receiver with ...a system temperature of about 20 K, is the most sensitive radio telescope utilized for discovering pulsars. We designed the
snapshot
observation mode for a FAST key science project, the Galactic Plane Pulsar Snapshot (GPPS) survey, in which every four nearby pointings can observe
a cover
of a sky patch of 0.1575 square degrees through beam-switching of the L-band 19-beam receiver. The integration time for each pointing is 300 seconds so that the GPPS observations for a cover can be made in 21 minutes. The goal of the GPPS survey is to discover pulsars within the Galactic latitude of ± 10° from the Galactic plane, and the highest priority is given to the inner Galaxy within ± 5°. Up to now, the GPPS survey has discovered 201 pulsars, including currently the faintest pulsars which cannot be detected by other telescopes, pulsars with extremely high dispersion measures (DMs) which challenge the currently widely used models for the Galactic electron density distribution, pulsars coincident with supernova remnants, 40 millisecond pulsars, 16 binary pulsars, some nulling and mode-changing pulsars and rotating radio transients (RRATs). The follow-up observations for confirmation of new pulsars have polarization-signals recorded for polarization profiles of the pulsars. Re-detection of previously known pulsars in the survey data also leads to significant improvements in parameters for 64 pulsars. The GPPS survey discoveries are published and will be updated at
http://zmtt.bao.ac.cn/GPPS/
.
To investigate the feasibility and safety of a fluoroscopy-assisted interventional technique for removal of bullet-shaped self-expanding covered metallic stents from bronchopleural fistulas (BPFs).
...Clinical data for 49 consecutive patients who underwent removal of bullet-shaped self-expanding covered metal stents from October 2010 to November 2019 were analysed retrospectively. Fifty-one stents were removed in all, including 29 large Y-shaped bullet stents, 10 small Y-shaped bullet stents, and 12 branched bullet-shaped stents. The average duration for which tracheal stents were in place was 99.4±8.5 days.
Fifty-one stents were removed successfully, of which 49 were directly removed on the first attempt. The time required for stent removal ranged from 7–60 minutes (median time, 22 minutes). In eight cases, the stent was removed by the conventional method (i.e., grasping the upper tip of the stent to collapse and adduct the proximal end), and in 43 by the eversion method (i.e., grasping the distal end of the stent to invert and peel out).
Interventional radiology is a simple, safe, and effective method to extract self-expanding covered metallic bullet-shaped stents, with no need for general anaesthesia and tracheal intubation. It has a short operation time, is well tolerated by patients, and is worthy of clinical application.
•We invented a technology for fluoroscopy-guided airway stent removal.•We applied this technique to remove 51 airway stents.•All stents were removed successfully, with no serious complications.•The technique is feasible and safe for fluoroscopy-guided airway stent removal.
Aims
The gut microbiota is believed to play important roles in the health of pregnant mammals, including their nutrient metabolism, immune programming and metabolic regulation. However, until ...recently, the shifts in gut microbiota composition and faecal and blood metabolic activity during different stages of pregnancy had not been investigated.
Methods and Results
We investigated the shifts in backfat thickness, plasma and faecal metabolites and gut microbiota on days 30, 60, 90 and 110 of pregnancy and on day 21 after parturition (weaning) in sows. The backfat thickness of sows did not significantly differ among the different stages of pregnancy. The plasma concentrations of lipid metabolites, including triacylglycerol (TG), total cholesterol, high‐density lipoprotein‐cholesterol, low‐density lipoprotein‐cholesterol and calcium were reduced (P < 0·05) during pregnancy. In addition, the concentration of these metabolites, except TG, reached their maximum at the time of weaning. We also found that Tenericutes, Fibrobacteres and Cyanobacteria varied significantly according to the stages of pregnancy in sows (P < 0·05). Most of the genera, such as Clostridiales, Desulfovibrio, Mogibacteriaceae and Prevotella, increased (P < 0·05) with the progression of pregnancy and decreased (P < 0·05) at weaning. The alpha diversity values (i.e., Shannon diversity and observed species) of sow gut microbiota increased (P < 0·05) from pregnancy to weaning. Pregnancy stages also significantly influenced (P < 0·05) the community structure (beta diversity) of gut microbiota. The progression of pregnancy was associated with changes in lipid metabolism and several carbohydrate‐degradation bacteria (i.e., Prevotella, Succinivibrio, Bacteroides and Parabacteroides).
Conclusions
Although causal links between the measured parameters remain hypothetical, these findings suggest that the increased diversity and concentration of beneficial gut microbes are associated with the metabolism of pregnant sows.
Significance and Impact of the Study
Manipulation of the sow gut microbiota composition may potentially influence metabolism and health during pregnancy.
Cu
2
Se is a p-type semiconducting compound that possesses excellent thermoelectric properties but degrades at elevated temperatures under large currents, precluding it from applications in ...harvesting waste heat. In this study, we make use of a doping approach to attempt to chemically stabilize Cu
2
Se while maintaining its superior thermoelectric properties. Specifically, we synthesized Cu
2(1−
x
)
Sn
x
Se (
x
= 0, 0.01, 0.02 and 0.05)
via
melting, annealing and spark plasma sintering. We found that the
ZT
was enhanced the most in the
x
= 0.01 sample, averaging approximately a 15% increase over the pure Cu
2
Se throughout a broad temperature range of 473-823 K, and achieving a maximum
ZT
= 1 at
T
= 823 K. The enhancement is due to an increased power factor and a reduced thermal conductivity, which is a result of point defect scattering from Sn atoms in the Cu
2
Se matrix and grain boundary scattering from a micron-size secondary phase of SnSe. We further tested the ability of the Sn dopant to prevent material degradation at elevated temperatures under large currents. Increasing the Sn dopant content does indeed decrease the solid Cu precipitation but not enough to resolve the issue of material degradation. As a result, despite its improved
ZT
, Cu
1.98
Sn
0.01
Se is not yet ready for thermoelectric applications, and requires further effort to stabilize the structure.
Doping Cu
2
Se with Sn enhances the thermoelectric figure of merit and decreases material degradation in thermoelectric power generation conditions.
Abstract
In the current study, based on the disclination quadrupole, the thermodynamic process of the necklace-like TDRX structures with smooth and straight boundaries is theoretically modeled. The ...influence of the applied shear stress and the twin thickness-length ratio on the misorientation angle between TDRX and matrix grain and the volume ratio of TDRX to parent twin band are numerically analyzed and experimentally validated by the electron back-scatter diffraction characterization. The results show that: (1) the misorientation angle increases with increasing applied shear stress; (2) The greater the thickness-length ratio is, the lower the volume ratio of TDRX to parent twin is; (3) The elevation of the applied shear stress can clearly escalate the volume ratio of TDRX to parent twin. Based on the above results, some strategies regulating TDRX are given based on the control of the applied shear stress and twin thickness-length ratio.
To review the removal of Y-shaped airway self-expanding covered metallic stents using the interventional technique under fluoroscopy.
The clinical data of 33 patients who underwent removal of ...Y-shaped airway self-expanding covered metallic stents from March 2011 to August 2019 were analysed retrospectively.
A total of 35 Y-shaped stents were removed. The average indwelling duration of the tracheal stents was 101.7 ± 105.4 days. Four cases were removed via the conventional method (grasping the upper tip of the stent to collapse and adduct the proximal end of the stent), whereas 31 cases were removed using the reversal method (grasping the distal end of the stent to invert and strip out the stent). The duration of stent removal was 24.3 ± 12.4 minutes (median time, 20 minutes).
The interventional radiology technique is a feasible, safe, and effective method for removing Y-shaped airway self-expanding covered metallic stents, and can be considered for use in the clinical setting.
•Technology for removal of Y-shaped airway stents under fluoroscopy was developed.•The technique was applied to 33 patients to remove airway stents.•All the stents were removed successfully, without serious complications.•The technique for fluoroscopic removal of the airway stent is feasible and safe.
A micro-duplex structure consisting of austenite and ferrite was produced by equal channel angular pressing and subsequent intercritical annealing. As compared to coarse-grained (CG) counterpart, the ...strength and ductility of micro-duplex samples are enhanced simultaneously due to smaller grain sizes in both phases and more uniformly distributed austenite in ferrite matrix. The average yield stress and uniform elongation are increased to 540MPa and 0.3 as compared to 403MPa and 0.26 of its CG counterpart respectively. The Hall–Petch coefficients of austenite and ferrite grain boundaries were quantitatively measured as 224.9 and 428.9MPaμm1/2 respectively. In addition, a Hall–Petch type coefficient was used to describe the ability of phase boundary to obstruct dislocation motion, which was measured as 309.7MPaμm1/2. Furthermore, the surface-to-volume ratio of phase boundary in micro-duplex structure was estimated to be 1.17×106m−1, which is increased by an order of magnitude as compared to 1.2×105m−1 of its CG counterpart. Based on the strain gradient theory, a model was proposed to describe the effect of surface-to-volume ratio of phase boundary on strain hardening rate, which shows a good agreement with the experimental results.
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