An avalanche-and-surge robust ultrawide-bandgap heterojunction for power electronics.

Avalanche and surge robustness involve fundamental carrier dynamics under high electric field and current density. They are also prerequisites of any power device to survive common overvoltage and overcurrent stresses in power electronics applications such as electric vehicles, electricity grids, and renewable energy processing. Despite tremendous efforts to develop the next-generation power devices using emerging ultra-wide bandgap semiconductors, the lack of effective bipolar doping has been a daunting obstacle for achieving the necessary robustness in these devices. Here we report avalanche and surge robustness in a heterojunction formed between the ultra-wide bandgap n-type gallium oxide and the wide-bandgap p-type nickel oxide. Under 1500 V reverse bias, impact ionization initiates in gallium oxide, and the staggered band alignment favors efficient hole removal, enabling a high avalanche current over 50 A. Under forward bias, bipolar conductivity modulation enables the junction to survive over 50 A surge current. Moreover, the asymmetric carrier lifetime makes the high-level carrier injection dominant in nickel oxide, enabling a fast reverse recovery within 15 ns. This heterojunction breaks the fundamental trade-off between robustness and switching speed in conventional homojunctions and removes a key hurdle to advance ultra-wide bandgap semiconductor devices for power industrial applications.

The Effects of Aspirin With Combined Compound Danshen Dropping Pills on Hemorheology and Blood Lipids in Middle-Aged and Elderly Patients With CHD: A Systematic Review and Meta-Analysis.

Background: Coronary heart disease (CHD) is one of the most common diseases in clinical cardiovascular practice, mainly afflicting the middle-aged and elderly. It will greatly affect elderly quality of life, and even affect their psychological and physical health. At present, CHD is treated with western drugs alone, but this can produce drug dependency. In recent years, Traditional Chinese Medicine (TCM) combine western drugs has been used as a complementary and alternative therapy, and its effectiveness and safety have been proven, attracting the attention of numerous researchers. Objective: Our study aimed to compare the efficacy of Aspirin with Combined Compound Danshen Dropping Pills had a superior effect on the treatment of Hemorheology and Blood Lipids in Middle-aged and Elderly Patients with CHD. Determine the effectiveness and safety of Aspirin with Combined Compound Danshen Dropping Pills in the treatment of CHD, and obtain high quality clinical evidence. Methods: Based on the PRISMA Statement, inclusion and exclusion criteria were formulated. Randomized controlled trials (RCTs) on the Effects of Aspirin with Combined Compound Danshen Dropping Pills on Hemorheology and Blood Lipids in Middle-aged and Elderly Patients with CHD were found following a search of 4 mainstream medical databases. RCTs found to meet the study's requirement were included; data information was then extracted, and the quality assessed using the Cochrane bias risk assessment tool. Through RevMan software, Meta analysis was carried out for overall TC, TG, HDL-C, LDL-C hematocrit, high shear viscosity, low shear viscosity, plasma viscosity, PAGM, and TXB2 effective rate. The relative risk (RR) and 95% confidence interval (95% CI) were calculated; heterogeneity was tested and its source found; publication bias was assessed through the Egger and Begg tests, and by means of funnel plots. Result: 22 RCTs were found, involving 1,987 cases. The results of the Meta analysis showed that, compared to drug therapy alone, Aspirin with Combined Compound Danshen Dropping Pills had a superior effect on the treatment of Hemorheology and Blood Lipids in Middle-aged and Elderly Patients with CHD. The meta analysis results show the effects on TC [MD = -0.91, 95% CI (-1.09, -0.73)], on TG [MD = -0.94, 95% CI (-1.22, -0.66)], on HDL-C [MD = 0.40, 95% CI (0.27, 0.53)], on LDL-C [MD = -0.99, 95% CI (-1.24, -0.74)], on hematocrit [MD = -2.69, 95% CI (-3.73, -1.65)], on high shear blood viscosity [MD = -1.11, 95% CI (-2.18, -0.05)], on low shear viscosity [MD = -0.79, 95% CI (-0.89, -0.68)], on plasma viscosity [MD = -0.26, 95% CI (-0.52, 0.01)], on PAMG [MD = -10.75, 95% CI (-16.84, -4.67)], and on TXB2 [MD = -11.84, 95% CI (-14.75, -8.92)]. The source of heterogeneity might be related to the state of patient, efficacy of drugs in the control group and difference in judgment criteria for efficacy. The Egger test and Begg test showed that publication bias did not occur in our study. Conclusions: The combination of compound dropping pill DSP with aspirin has some therapeutic effect on blood lipids and hemorheology in patients with CHD, ince some of the RCTs featured a very small sample size, the reliability and validity of our study's conclusion may have been affected as well; therefore, the explanation should be treated with some caution. In the future, a large number of higher-quality RCTs are still needed to confirm the results of our study.

Supercompliant and Soft (CH_{3}NH_{3})_{3}Bi_{2}I_{9} Crystal with Ultralow Thermal Conductivity.

In this Letter, we show the phonon dispersion of (CH_{3}NH_{3})_{3}Bi_{2}I_{9} single crystals at 300 K measured by inelastic x-ray scattering. The frequencies of acoustic phonons are among the lowest of crystals. Nanoindentation measurements verified that these crystals are very compliant and considerably soft. The frequency overlap between acoustic and optical phonons results in strong acoustic-optical scattering. All these features lead to an ultralow thermal conductivity. The fundamental knowledge obtained from this study will accelerate the design of novel hybrid materials for energy applications.

Experimental Phonon Dispersion and Lifetimes of Tetragonal CH3NH3PbI3 Perovskite Crystals.

Hybrid organic-inorganic perovskites were reported to have ultralow thermal conductivity in recent studies. In this Letter, we report the first experimental phonon dispersion and lifetimes of tetragonal CH3NH3PbI3 single crystals at both 200 and 300 K by high-energy resolution inelastic X-ray scattering, which enables a thorough understanding of the underlying mechanisms for the ultralow thermal conductivity. Notably, we observed unusual and significant phonon dips along the [100] and [110] directions at both temperatures. The ultralow thermal conductivity can be attributed to small group velocities due to ultrasoft acoustic modes and short phonon lifetimes originating from the strong acoustic-optical coupling. We further provided the structural origins for these peculiar phonon features. Moreover, our results and interpretation are consistent with the reported temperature-dependent trend for thermal conductivity of CH3NH3PbI3. Our work offers critical guidelines for accelerating the design and discovery of novel hybrid materials for energy applications including photovoltaics and thermoelectrics.

Thermal Switching of Thermoresponsive Polymer Aqueous Solutions.

Thermal switches are of great importance to thermal management in a wide variety of applications. However, traditional thermal switches suffer from being large and having slow transition rates. To overcome these limitations, we took advantage of abrupt second-order phase transitions in thermoresponsive polymer aqueous solutions to enable fast thermal switching. While thermoresponsive polymers have been widely studied for biomedical applications, their thermal switching capability has not been studied. In this work, we used poly(N-isopropylacrylamide) (PNIPAM) as a model system to demonstrate abrupt thermal conductivity changes of thermoresponsive polymer aqueous solutions across their transition temperatures by using a powerful approach, the transient thermal grating technique, which has high sensitivity. We observed a thermal switching ratio up to 1.15 in dilute PNIPAM aqueous solutions (up to 0.025 g/mL) across the transition. This work may provide new opportunities to engineer thermal switches using second-order phase transitions of thermoresponsive polymer aqueous solutions or abrupt higher-order phase transitions in general.

A near infrared colorimetric and fluorometric probe for organophosphorus nerve agent mimics by intramolecular amidation.

A near infrared probe for sensitive colorimetric and fluorimetric detection of nerve agent mimics, DCP and DCNP, was reported based on the activation of a carboxylic acid group by the mimics to conduct an intramolecular amidation reaction in the heptamethine chromophore, where its absorption or excitation maximum wavelength could be greatly red-shifted by attenuating the electron-donating ability of the amine group in the bridgehead site of heptamethine cyanine.