Tungsten (W) film is increasingly utilized in various microheater applications due to its numerous advantages. These advantages include a high melting point, positive constant temperature coefficient ...of resistance (TCR), good mechanical stability, and compatibility with semiconductor processes. In this paper, deposition parameters for enhancing the properties of W film were investigated, and an optimized microheater was fabricated. It was found that the deposition temperature and pressure can modify the TCR to be negative or positive and the crystalline phase of W films to be alpha phases or mixed with beta phases. A W film deposited under 650 °C with a pressure of 1 pa has a positive TCR and pure alpha phase crystalline structure. We applied this optimized W film as a microheater in an RF phase-change switch (RFPCS), and the maximum voltage of the optimized W microheater increased by at least 48% in this work. By optimizing the microheater, the phase-change switch can be successfully actuated in both on and off states, demonstrated by the Raman results of the phase-change material. A voltage pulse of 20 V/200 ns was enough to turn the switch off with MΩ, and 11 V/3 μs could turn the switch on with 138 Ω. The optimized microheater and device can cycle 500 times without failure. The insertion loss and isolation of the device at 20 GHz was 1.0 dB and 22 dB.
Slicing fully mechanized caving mining is a standard high-efficiency mining method for ultrathick coal seams. However, the effectiveness of gas control has accentuated the difficulty in fully ...mechanized top coal caving of low-permeability ultrathick coal seams. This study focused on mining the No. 9-15 coal in Liuhuanggou Coal Mine, Xinjiang Province, China. To this aim, the results of theoretical analyses and field tests were combined to explore a comprehensive gas control method for fully mechanized caving of low-permeability ultrathick coal seams. The No. (9-15)06 panel was a top-slicing panel of the No. 9-15 coal with a mining height of 9 m. Gas analysis results revealed that gas emissions in the No. (9-15)06 panel are mainly sourced from the coal wall, caving top coal, goaf, and neighboring coal seams. Based on gas source separation, a comprehensive gas control method was proposed. The proposed method was based on the combination of gas predrainage alongside the coal seam, high-position drilling on the top, preburial of pipes in the goaf, and pressure-balancing ventilation. The permeability and gas predrainage were enhanced by hydraulic fracturing in low-permeability coal seams. According to the characterizations of coal seam and crustal stress distribution, the arrangement of the boreholes and backward-segmented fracturing technology were designed. From the field results, the coal seam presented a remarkable prefracturing under hydraulic fracturing. Besides, the mean gas predrainage from the boreholes was enhanced by four times compared to the prehydraulic fracturing state. Finally, using the proposed comprehensive control method based on the gas sources, field tests were performed in the No. (9-15)06 panel. The measured results demonstrated that gas concentration in the return airflow is fluctuated within a range of 0.05% to 0.35%. The proposed gas control method can provide an insightful reference for other similar projects.
In this article, nanostructured superhydrophobic polymeric surfaces were fabricated by a simple (one-step) reproductive method of anodic aluminum oxide (AAO) template extrusion. By tuning the ...diameter of the AAO template and the pressure to extrude, high-density polyethylene (HDPE) nanofiber surfaces with different nanometer roughness were prepared, and various sliding angles (SAs) of drops on these surfaces were measured. The results of the impact of drops on the nanostructured HDPE surfaces indicated that SAs were very important for the dynamic wettability of superhydrophobic surfaces. The one-step AAO template extrusion method has the advantage of tailoring the SA values on polymeric surfaces. Therefore, we believe it to be a promising industrial basis for manufacturing functional materials in the fields of agriculture, electronics, and optics.
Purpose To compare the clinical outcomes of arthroscopic anterior cruciate ligament (ACL) reconstruction with hamstring tendon autograft versus irradiated allograft. Methods All irradiated hamstring ...tendon allografts (gracilis and semitendinosus), which were sterilized with 2.5 Mrad of irradiation before distribution, were obtained from a single certified tissue bank. A total of 78 patients undergoing arthroscopic ACL reconstruction were prospectively randomized consecutively into 1 of 2 groups: autograft and irradiated allograft. The same surgical technique was used in all operations, which were performed by the same senior surgeon. Before surgery and at a mean of 42.2 months of follow-up, patients were evaluated by the same observer according to objective and subjective clinical evaluations. Results Of the patients, 67 (36 in autograft group and 31 in irradiated allograft group) were available for full evaluation. When the irradiated allograft group was compared with the autograft group at the final follow-up by the Lachman test, anterior drawer test, pivot-shift test, and KT-2000 arthrometer (MEDmetric, San Diego, CA) assessment, statistically significant differences were found ( P = .00011, P = .00016, P = .008, and P = .00021, respectively). Most importantly, 86.1% of patients in the autograft group and only 32.3% in the irradiated allograft group had a side-to-side difference of less than 3 mm according to KT-2000 assessment. The rate of laxity (side-to-side difference >5 mm) with irradiated allograft (32.3%) was higher than that with autograft (8.3%). The anterior and rotational stabilities decreased significantly in the irradiated allograft group. According to the overall International Knee Documentation Committee rating, functional and subjective evaluations, and activity level testing, no statistically significant differences were found between the 2 groups. However, patients in the irradiated allograft group had a shorter operative time and a longer duration of postoperative fever. When the patients had a fever, the laboratory examination findings of all patients were almost normal (white blood cell count, normal; erythrocyte sedimentation rate, 8 to 20 mm/h; and C-reactive protein level, 4 to 11 mg/L). Conclusions The clinical outcome of ACL reconstruction with hamstring tendon autograft was satisfactory, whereas the difference in instrumented laxity between the 2 groups was significant and the difference in functional test results was not significant. Level of Evidence Level II, prospective comparative study.
Engineering atomic-scale native point defects has become an attractive strategy to improve the performance of thermoelectric materials. Here, we theoretically predict that Ag-Mg antisite defects as ...shallow acceptors can be more stable than other intrinsic defects under Mg-poor‒Ag/Sb-rich conditions. Under more Mg-rich conditions, Ag vacancy dominates the intrinsic defects. The p-type conduction behavior of experimentally synthesized α-MgAgSb mainly comes from Ag vacancies and Ag antisites (Ag on Mg sites), which act as shallow acceptors. Ag-Mg antisite defects significantly increase the thermoelectric performance of α-MgAgSb by increasing the number of band valleys near the Fermi level. For Li-doped α-MgAgSb, under more Mg-rich conditions, Li will substitute on Ag sites rather than on Mg sites and may achieve high thermoelectric performance. A secondary valence band is revealed in α-MgAgSb with 14 conducting carrier pockets.
Zinc tungstate (ZnWO4) is an outstanding photocatalyst for water splitting and organic contaminant degradation under visible light irradiation. Surface termination stabilities are significant for ...understanding the photochemical oxidation and reactions on the ZnWO4 surface. Based on density functional theory, we calculated the thermodynamic stability of possible surface terminations for ZnWO4(100). The surface stability phase diagrams show that the Zn2O4-Zn8W6O28, W2O4-Zn8W10O36, and Zn2-Zn8W6O24 terminations of ZnWO4(100) can be stabilized under certain thermodynamic equilibrium conditions. The electronic structures for these three possible stability surface terminations are calculated based on the Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional to give dependable theoretical band gap values. It is found that the surface states of W2O4-Zn8W10O36 termination are in the band gap, which shows a delocalized performance. The calculated absorption coefficients of W2O4-Zn8W10O36 termination show stronger absorption than bulk ZnWO4 in the visible-light region. The band edge calculation shows that the valence band maximum and conduction band minimum of the W2O4-Zn8W10O36 termination can fulfill the hydrogen evolution reaction and oxygen evolution reaction requirements at the same time. Furthermore, work functions are extraordinarily distinct for various surface terminations. This result suggests that the ZnWO4-based direct Z-scheme heterostructure can be controlled by obtaining the thermodynamically preferred surface termination under suitable conditions. Our results can predict ZnWO4(100) surface structures and properties under the entire range of accessible environmental conditions.
Mechanisms mediating the protective effects of molecular hydrogen (H
) are not well understood. This study explored the possibility that H
exerts its anti-inflammatory effect by modulating energy ...metabolic pathway switch. Activities of glycolytic and mitochondrial oxidative phosphorylation systems were assessed in asthmatic patients and in mouse model of allergic airway inflammation. The effects of hydrogen treatment on airway inflammation and on changes in activities of these two pathways were evaluated. Monocytes from asthmatic patients and lungs from ovalbumin-sensitized and challenged mice had increased lactate production and glycolytic enzyme activities (enhanced glycolysis), accompanied by decreased ATP production and mitochondrial respiratory chain complex I and III activities (suppressed mitochondrial oxidative phosphorylation), indicating an energy metabolic pathway switch. Treatment of ovalbumin-sensitized and challenged mice with hydrogen reversed the energy metabolic pathway switch, and mitigated airway inflammation. Hydrogen abrogated ovalbumin sensitization and challenge-induced upregulation of glycolytic enzymes and hypoxia-inducible factor-1α, and downregulation of mitochondrial respiratory chain complexes and peroxisome proliferator activated receptor-γ coactivator-1α. Hydrogen abrogated ovalbumin sensitization and challenge-induced sirtuins 1, 3, 5 and 6 downregulation. Our data demonstrates that allergic airway inflammation is associated with an energy metabolic pathway switch from oxidative phosphorylation to aerobic glycolysis. Hydrogen inhibits airway inflammation by reversing this switch. Hydrogen regulates energy metabolic reprogramming by acting at multiple levels in the energy metabolism regulation pathways.
Metasurfaces are two-dimensional arrangements of antennas that control the propagation of electromagnetic waves with a subwavelength thickness and resolution. Previously, metasurfaces have been ...mostly used to obtain the function of a single optical element. Here, we demonstrate a plasmonic metasurface that represents the combination of a phase mask generating a double-helix point spread function (DH-PSF) and a metalens for imaging. DH-PSF has been widely studied in three-dimensional (3D) super-resolution imaging, biomedical imaging, and particle tracking, but the current DH-PSFs are inefficient, bulky, and difficult to integrate. The multielement metasurface, which we label as DH-metalens, enables a DH-PSF with transfer efficiency up to 70.3% and an ultrahigh level of optical system integration, three orders of magnitude smaller than those realized by conventional phase elements. Moreover, the demonstrated DH-metalens can work in broadband visible wavelengths and in multiple incident polarization states. Finally, we demonstrate the application of the DH-metalens in 3D imaging of point sources. These results pave ways for realizing integrated DH-PSFs, which have applications in 3D super-resolution microscopy, single particle tracking/imaging, and machine vision.
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► Ratchet-like superhydrophobic surfaces were fabricated. ► One-dimensional anisotropic wettabilities are observed on such ratchet-like surfaces. ► Directional differences of ...wettabilities are tailored by the ratchet-like structures. ► Low retention and ratchet-like structures are keys for the directional wettabilities.
In this article, directional movements of drops on the ratchet-like superhydrophobic surfaces were observed. High-speed CCD images showed the caterpillar-like crawl of a drop on the inclined superhydrophobic surfaces as it rolled along the ridge of ratchet. In contrast, along the opposite direction, the movement of the drop only depended on the end of triple phase contact line while the front of contact line was pinned. The sliding angle (SA) measurements indicated that the ratchet-like superhydrophobic surfaces had directional drop retention traits. Moreover, the reduction of the rise angle
ω
1, the height
d of the ratchet's ridge and the volume
V of the drop can greatly enhance the directional difference of drop retention on the ratchet-like superhydrophobic surfaces. Therefore, it was concluded that the superhydrophobicity and the periodic ratchet-like microstructures were the keys to the directional drop sliding at one-dimensional level. We believe that these findings would be helpful to better understand the ratchet-like effect on the superhydrophobic surfaces and guide some novel engineering applications.
Native defects and nonmetal doping have been shown to be an effective way to optimize the photocatalytic properties of Bi2WO6. However, a detailed understanding of defect physics in Bi2WO6 has been ...lacking. Here, using the Heyd–Scuseria–Ernzerhof hybrid functional defect calculations, we study the formation energies, electronic structures, and optical properties of native defects and nonmetal element (C, N, S, and P) doping into Bi2WO6. We find that the Bi vacancy (Bivac), O vacancy (Ovac), S doping on the O site (SO), and N doping on the O site (NO) defects in the Bi2WO6 can be stable depending on the Fermi level and chemical potentials. By contrast, the substitution of an O atom by a C or P atom (CO, PO) has high formation energy and is unlikely to form. The calculated electronic structures of the Bivac, Ovac, SO, and NO defects indicate that the band-gap reduction of Ovac 2+, Bivac 3–, and SO defects is mainly due to forming shallow impurity levels within the band gap. The calculated absorption coefficients of Ovac 2+, Bivac 3–, and SO show strong absorption in the visible light region, which is in good agreement with the experimental results. Hence, Ovac 2+, Bivac 3–, and SO defects can improve the adsorption capacity of Bi2WO6, which helps enhance its photocatalytic performance. Our results provide insights into how to enhance the photocatalytic activity of Bi2WO6 for energy and environmental applications through the rational design of defect-controlled synthesis conditions.
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