In this paper, the double-pulse laser-induced breakdown spectroscopy (DP-LIBS) technique was used to analyze the heavy metal samples collected in the atmosphere using an air sampler. The enhancement ...characteristics of the plasma spectra were studied by using different laser wavelength combinations with 1064, 532, and 355 nm Nd:YAG lasers. The plasma spectrum of the sample was greatly enhanced when the combined laser wavelengths were 355 and 1064 nm. On this basis, the optimal inter-pulse delay time is obtained to get the maximum plasma spectrum. The relationship of the signal to background ratio, electron temperature, and electron density of the plasma spectrum with inter-pulse delay and acquisition delay is also discussed. Finally, the optimal pulse delay and acquisition time were obtained. DP-LIBS technology can effectively improve the detection effect of heavy metals in the atmosphere, which is a very promising tool in the field of environmental monitoring.
We propose a compact nanotube-mode-locked all-fiber laser that can simultaneously generate picosecond and femtosecond solitons at different wavelengths. The pulse durations of picosecond and ...femtosecond solitons are measured to be ∼10.6 ps and ∼466 fs, respectively. Numerical results agree well with the experimental observations and clearly reveal that the dynamic evolutions of the picosecond and femtosecond solitons are qualitatively distinct in the intracavity. Our study presents a simple, stable, low-cost, and dual-scale ultrafast-pulsed laser source suitable for practical applications in optical communications.
An experimental investigation into noise reduction of supersonic jets through nozzle trailing-edge modifications was conducted, whereby far-field acoustic measurements were captured for two different ...stepped nozzles under two distinct under-expanded conditions. When compared to a baseline nozzle, results show that stepped nozzles lead to significant noise reductions at certain polar and azimuthal angles. In particular, a maximum noise reduction of 6 dB is observed for the longest stepped nozzle at a nozzle-pressure-ratio of 4 and 0° azimuthal angle. Spectral analysis shows that the noise reduction is mainly due to reduction in broadband shock associated noise and elimination of jet screech phenomenon. Abrupt changes in nozzle lip lengths of the stepped nozzles appear to disrupt acoustic feedback loop, thus resulting in screech cessation. Qualitative schlieren imaging and quantitative schlieren measurements were subsequently performed to correlate the shock structures and density gradient fields with the resulting noise components. Unlike those produced by the baseline nozzle, shock structures generated by the stepped nozzles are highly irregular and the jet plumes undergo discernible deflections. Lastly, the reduction in broadband shock associated noise is related to the lower shock strengths, as demonstrated by the density gradient profiles.
Despite improvements in the emergency treatment of myocardial infarction (MI), early mortality and morbidity remain high. The antiplatelet agent clopidogrel adds to the benefit of aspirin in acute ...coronary syndromes without ST-segment elevation, but its effects in patients with ST-elevation MI were unclear.
45 852 patients admitted to 1250 hospitals within 24 h of suspected acute MI onset were randomly allocated clopidogrel 75 mg daily (n=22 961) or matching placebo (n=22 891) in addition to aspirin 162 mg daily. 93% had ST-segment elevation or bundle branch block, and 7% had ST-segment depression. Treatment was to continue until discharge or up to 4 weeks in hospital (mean 15 days in survivors) and 93% of patients completed it. The two prespecified co-primary outcomes were: (1) the composite of death, reinfarction, or stroke; and (2) death from any cause during the scheduled treatment period. Comparisons were by intention to treat, and used the log-rank method. This trial is registered with
ClinicalTrials.gov, number NCT00222573.
Allocation to clopidogrel produced a highly significant 9% (95% CI 3–14) proportional reduction in death, reinfarction, or stroke (2121 9·2% clopidogrel
vs 2310 10·1% placebo; p=0·002), corresponding to nine (SE 3) fewer events per 1000 patients treated for about 2 weeks. There was also a significant 7% (1–13) proportional reduction in any death (1726 7·5%
vs 1845 8·1%; p=0·03). These effects on death, reinfarction, and stroke seemed consistent across a wide range of patients and independent of other treatments being used. Considering all fatal, transfused, or cerebral bleeds together, no significant excess risk was noted with clopidogrel, either overall (134 0·58%
vs 125 0·55%; p=0·59), or in patients aged older than 70 years or in those given fibrinolytic therapy.
In a wide range of patients with acute MI, adding clopidogrel 75 mg daily to aspirin and other standard treatments (such as fibrinolytic therapy) safely reduces mortality and major vascular events in hospital, and should be considered routinely.
Micro Reactors with power below 10 MW can offer many benefits for ocean or space exploration with their favorable characteristics, such as low specific mass, long-lasting life, highly flexible power ...supply and strong environment adaptability. The heat pipe cooled micro molten salt reactor (micro-MSR) which is an innovative concept combining molten salt reactor and heat pipe technology, is proposed in this work and furthermore, a 50 kWth version of micro-MSR is designed. The main neutronic characteristics, including the neutron spectrum, reactivity control with control drums inserted in the radial reflector, temperature reactivity coefficient (TRC), neutron flux, power deposition, and neutron balance are provided and discussed, respectively. The diameter and height of the designed core are about 0.69 m and 0.96 m, respectively, and the total mass of the core is merely about 1.3 tons, which is desirable for application in space, ocean and remote, off-grid locations. Meanwhile, an analysis of reactivity worth and interference effects of control drums are performed, which indicates that the reactivity control can be achieved by using the control drums. The results of TRC that governs the inherent safety of the micro-MSR demonstrate the feasibility of a self-actuated shutdown mechanism owing to a sufficiently negative TRC of about −13.91 pcm/K. A design of radiation shield mainly for effective protection of the electronic components is provided and it is found that a 47 cm thickness of shield can limit the neutron and gamma dose to the permissible range. Additionally, the performance of the heat pipes (HPs) in the core is evaluated, and the results indicate that the heat transfer capacity of the HP is great enough to ensure the cooling of the fuel salt in the core.
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•A micro-MSR adopting heat pipe technology is designed.•The micro-MSR can ensure inherent safety by its strong negative temperature reactivity coefficient.•The micro-MSR can be applied in space, ocean and remote & off-grid locations.
The chronic performance of implantable neural electrodes is hindered by inflammatory brain tissue responses, including microglia activation, glial scarring, and neuronal loss. Melatonin (MT) has ...shown remarkable neuroprotective and neurorestorative effects in treating central nervous system (CNS) injuries and degeneration by inhibiting caspase-1, -3, and -9 activation and mitochondrial cytochrome c release, as well as reducing oxidative stress and neuroinflammation. This study examined the effect of MT administration on the quality and longevity of neural recording from an implanted microelectrode in the visual cortex of mice for 16 weeks. MT (30 mg/kg) was administered via daily intraperitoneal injection for acute (3 days before and 14 days post-implantation) and chronic (3 days before and 16 weeks post-implantation) exposures. During the first 4 weeks, both MT groups showed significantly higher single-unit (SU) yield, signal-to-noise ratio (SNR), and amplitude compared to the vehicle control group. However, after 4 weeks of implantation, the SU yield of the acute treatment group dropped to the same level as the control group, while the chronic treatment group maintained significantly higher SU yield compared to both acute (week 5–16) and control (week 0–16) mice. Histological studies revealed a significant increase in neuronal viability and decrease in neuronal apoptosis around the implanted electrode at week 16 in the chronic group in comparison to control and acute subjects, which is correlated with reduced oxidative stress and increased number of pro-regeneration arginase-1 positive microglia cells. These results demonstrate the potent effect of MT treatment in maintaining a high-quality electrode-tissue interface and suggest that MT promotes neuroprotection possibly through its anti-apoptotic, anti-inflammatory, and anti-oxidative properties.
Flow behaviour of a hydrofoil with leading-edge tubercles was experimentally studied using particle image velocimetry technique at a Reynolds number of Re=1.4×104. Four angles-of-attack of α=0°, 10°, ...15° and 20° were considered. Proper orthogonal decomposition (POD) technique was used to analyse the instantaneous velocity fields and derive information on the variation of corresponding coefficients and flow energy content. Results show that tubercles can alter the vortical behaviour and lead to increased flow unsteadiness. At lower angles-of-attack, the flow behaviour for the baseline hydrofoil is dominated by wake vortex-shedding, which represents a significant percentage of flow energy content. In contrast, separated shear layer and flow reattachment become the dominant flow behaviour for the hydrofoil with tubercles. Higher order POD modes 4 and 5 are associated with coherent vortex convection in the shear layer, which is similar to that of the baseline hydrofoil at higher angles-of-attack. At α=15°, POD modes 2 and 3 along the tubercle trough and peak show coherent vortex-shedding in the flow separation region. However, unstable flow separations are observed along the Mid-plane between the peaks and troughs, as a result of the separated shear layers associated with POD modes 1 and 2.
•Dominant flow structures for unmodified hydrofoil at zero angle-of-attack are associated with wake vortex-shedding.•Coherent vortex-shedding occurs along the Trough- and Peak-planes of the modified hydrofoil at 15° angle-of-attack.•In contrast, flow separation size varies temporally along Mid-plane of the modified hydrofoil at post-stall conditions.•Spanwise flows due to counter-rotating vortex pairs play an important role in the unstable flow behaviour.
A retrospective study was designed to evaluate the diagnostic value of transvaginal four-dimensional hysterosalpingo-contrast sonography (TVS 4D-HyCoSy) combined with recanalization versus ...laparoscopy for patients with tubal infertility.
A total of 195 patients undergoing TVS 4D-HyCoSy were analyzed retrospectively. Of these, 72 patients underwent laparoscopy, which was the gold standard. The endpoints were coincidence rate (defined as a parameter consistent with results arising from TVS 4D-HyCoSy and laparoscopic examination using dye), sensitivity, specificity, positive predictive value, negative predictive value, and Youden index for TVS 4D-HyCoSy.
A total of 385 fallopian tubes were assessed by TVS 4D-HyCoSy, of which 147 (38.2%) were tubal patency, 178 (46.2%) as partial tubal obstruction, and 60 (15.6%) as complete tubal obstruction. Of 195 patients, 72 patients with 144 fallopian tubes underwent laparoscopy and a total coincidence rate of 90.97% compared with TVS 4D-HyCoSy. The sensitivity, specificity, positive predictive value, negative predictive value, and Youden index for 4D-HyCoSy versus laparoscopy were 97.7%, 86.7%, 98.4%, 81.3%, and 0.84, respectively.
TVS 4D-HyCoSy represents a highly useful method for diagnosing tubal patency. However, further large-scale studies are warranted to investigate our findings in patients with tubal infertility.
Thermomechanical relaxation events and different water states in cottonseed protein bioplastics are presented whilst investigating the effects of aldehyde cross-linking agents. Thermomechanical ...relaxation of cottonseed protein bioplastics associated with protein denaturation, moisture absorption and broad glass transitions (T sub(g)) were observed from DSC and DMA measurements. It was shown that variation of the aldehyde influences the storage modulus at very low temperature (below T sub(g)). From measurements of the water fusion point, enthalpy, vaporisation, and weight loss, three water states in the water-absorbed bioplastics are suggested; namely strongly-bound-to-polymer, weakly-bound-to-polymer and bulk-like water. The water content and unreacted cross-linking agents are influential factors in controlling formation of the different water states, whilst the selection of different aldehydes was found to be negligible. These results could be valuable for adjusting the thermomechanical relaxations of protein based bioplastics, and tailoring their properties in wet environments.
A new experiment station was installed on beamline 4B7A at Beijing Synchrotron Radiation Facility (BSRF), making it possible to record X-ray absorption fine structure (XAFS) spectrum in three modes ...over an energy range from 1750eV to 6000eV. A 13-element Si(Li) array detector and a single-element SDD detector were used to acquire data in partial fluorescence yield (PFY) mode. Two low-pressure noble gas ion chambers were adopted for measuring XAFS in transmission mode. In total electron yield (TEY) mode the current of sample is recorded. Solid, wet and liquid samples were suitable for this experimental station. Some representative results obtained from this station were shown and discussed.
•A new experiment station was installed on beamline 4B7A at BSRF.•This experiment station has three modes for recording X-ray XAFS spectrum.•The energy region covers the K-edge of elements Si, P, S, Cl, K, Ca and Ti.•Solid, wet and liquid samples can be measured in this experiment station.
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