Carbon coated Co-SiC nanocomposite with high-performance microwave absorption.

A carbon coated Co-SiC nanocomposite was fabricated via in situ pyrolysis of methane on a hierarchical Co3O4-SiC nanostructure, which was obtained by hydrothermal synthesis. By the reduction of methane, the Co3O4 was in situ converted to cobalt nanoparticles, and coated by carbon or filled in the CNTs. The as-prepared composite exhibits excellent microwave absorption performance in the frequency range of 2-18 GHz. When the match thickness is 1.8 mm, the composite has a reflection loss value below -10 dB in the range 12.2 to 18 GHz, which nearly covers the whole Ku-band (12-18 GHz). When the thickness is 2.6 mm, the reflection loss value below -10 dB distributes at 8.2-11.5 GHz, covering most of the X-band (8-12 GHz). Moreover, by further tuning the match thickness, the composite can selectively absorb some certain frequency bands of microwaves.

Reyanning Mixture on Asymptomatic or Mild SARS-CoV-2 Infection in Children and Adolescents: A Randomized Controlled Trial.

OBJECTIVE: To assess the effect and safety of Reyanning Mixture (RYN) in treating asymptomatic or mild severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children and adolescents. METHODS: This is a prospective, open-label, randomized controlled trial. Patients aged 1-17 years and diagnosed with asymptomatic or mild coronavirus disease-2019 (COVID-19) were assigned to an intervention group (RYN plus standard care) and a control group (standard care) according to a randomization list. The primary outcomes were SARS-CoV-2 negative conversion time. Secondary outcomes included negative conversion rate on days 3 and 7, hospital length of stay, symptom relief rate, new-onset symptoms of asymptomatic infected patients, and progressive disease rate. The cycle threshold (Ct) values of ORF1ab or N genes were also tested. RESULTS: A total of 214 patients in the intervention group and 217 in the control group were analyzed. The SARS-CoV-2 negative conversion time was significantly shortened in the intervention group [5 days (interquartile range (IQR): 5-6) vs. 7 days (IQR: 6-7), P<0.01]. By days 3 and 7, the negative conversion rates were significantly higher in the intervention group (day 3: 32.7% vs. 21.2%, P=0.007; day 7: 75.2% vs. 60.8%, P=0.001). Ct values significantly increase on day 2 [ORF1ab gene: 35.62 (IQR: 29.17-45.00) vs. 34.22 (IQR: 28.41-39.41), P=0.03; N gene: 34.97 (IQR: 28.50-45.00) vs. 33.51 (IQR: 27.70-38.25), P=0.024] and day 3 [ORF1ab gene: 38.00 (IQR: 32.72-45.00) vs. 35.81 (IQR: 29.96-45.00), P=0.003; N gene: 37.16 (IQR: 32.01-45.00) vs. 35.26 (IQR: 29.09-45.00), P=0.01]. No significant difference was found in hospital length of stay between the two groups (P>0.05). Symptoms of cough were significantly improved (82.2% vs. 70.0%, P=0.02) and wheezing was significantly reduced (0.7% vs. 12.9%, P<0.01) in the intervention group compared with the control group. During the trial, no disease progression or serious adverse events were reported. CONCLUSION: Adding RYN to standard care may be a safe and effective treatment for children with asymptomatic and mild SARS-CoV-2 infection. (Registration No. ChiCTR2200060292).

Synergistic Effect of Segregated Pd and Au Nanoparticles on Semiconducting SiC for Efficient Photocatalytic Hydrogenation of Nitroarenes.

Efficient catalytic hydrogenation of nitroarenes to anilines with molecular hydrogen at room temperature is still a challenge. In this study, this transformation was achieved by using a photocatalyst of SiC-supported segregated Pd and Au nanoparticles. Under visible-light irradiation, the nitrobenzene hydrogenation reached a turnover frequency as high as 1715 h-1 at 25 °C and 0.1 MPa of H2 pressure. This exceptional catalytic activity is attributed to a synergistic effect of Pd and Au nanoparticles on the semiconducting SiC, which is different from the known electronic or ensemble effects in Pd-Au catalysts. This kind of synergism originates from the plasmonic electron injection of Au and the Mott-Schottky contact at the interface between Pd and SiC. This three-component system changes the electronic structures of the SiC surface and produces more active sites to accommodate the active hydrogen that spills over from the surface of Pd. These active hydrogen species have weaker interactions with the SiC surface and thus are more mobile than on an inert support, resulting in an ease in reacting with the N═O bonds in nitrobenzene absorbed on SiC to produce aniline.

Formation mechanism of Si3N4 nanowires via carbothermal reduction of carbonaceous silica xerogels.

Si3N4 nanowires prepared from the carbothermal reduction of carbonaceous silica xerogels with metal salt additives usually contain a small amount of nanotubes. This paper is devoted to the investigation of the formation mechanism of the Si3N4 nanowires. As-prepared samples heated at 1300 degrees C for different reaction times (1, 5, 10, and 30 h) were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results showed that all the samples mainly consisted of nanowires, while their crystalline phases changed with the heating time. Nitrogen-doped silicon oxide nanowires were first produced via the vapor-liquid-solid process and then underwent a stepwise surface nitrogenization to silicon nitride. The suggested mechanism can easily explain the existence of nanotubes in the Si3N4 nanowires.

[Vacuum sealing drainage combined with free skin graft in repairing cutaneous deficiency of traumatic shank amputation stump].

OBJECTIVE: To observe clinical efficacy in treating cutaneous deficiency of traumatic shank amputation stump with full-thickness skin graft combined with vacuum sealing drainage. METHODS: From September 2009 to December 2012, 15 patients with cutaneous deficiency of traumatic shank amputation stump were treated with full-thickness skin graft combined with vacuum sealing drainage. Among patients, there were 11 males and 4 females with an average age of 41.5 (ranged from 25 to 62) years old. Ten cases were caused by traffic accident and 5 cases were caused by heavy object, 9 cases on left and 6 cases on right. Six patients with smashed wound were treated with debridement and amputation, combined with vacuum aspiration in-emergency; 9 patients caused by infection and necrosis were treated with debridement and amputation, combined with vacuum aspiration, and full-thickness skin graft were performed at stage II. The skin defect area of residual limbs ranged from 40 cm x 20 cm to 25 cm x 15 cm. RESULTS: All patients were followed up from 3 months to 1 year. Full-thickness skin graft of residual limbs were survived,and obtained satisfactory walking function with prosthetic. Residual skin increased thicken, wearproof without rupture and pain. CONCLUSION: Full-thickness skin graft combined with vacuum sealing drainage in treating cutaneous deficiency of traumatic shank amputation stump could reserve the length of residual limbs, increase survival rate of skin graft with less scar of survival skin, get good wearability and it is conducive to prosthetic wear. It is a simple and easy treatment method.

In situ grafted carbon on sawtooth-like SiC supported Ni for high-performance supercapacitor electrodes.

A novel C-Ni-SiC composite using sawtooth-like SiC as support and carbon as modified material was prepared by hydrothermal synthesis and thermochemical pyrolysis. As a supercapacitor electrode, it exhibits very high specific capacitance (1780 F g(-1)) and excellent cycling performance (>96% for 2500 cycles).

[Treatment of carpal tunnel syndrome with mini-incision decompression].

OBJECTIVE: To introduce the method of the transverse carpal ligament (TCL) transection through palmar mini-incision for carpal tunnel syndrome (CTS) and evaluate its efficacy and safety. METHODS: From January 2006 to September 2007, 15 patients (18 hands) with CTS were treated with palmar longitudinal mini-incision decompression. There were 2 males and 13 females, with an average age of 48 years (ranged 34 to 69) and an average course of 18 months (ranged 8 to 26). The main clinical symptom including the radial numbness or pain of the 3 and a half fingers, wrist pain and radiation to the forearm, the night awake history of numbness, thenar muscle atrophy, positive Tinel sign and Phalen sign. Median nerve electrophysiology showed that sensory nerve conduction velocity (SCV) slowed down and sensory nerve action potential (SNAP) decreased or missed, short abductor muscle of thumb had spontaneous potential in severe cases. Clinical effect were evaluated according to the Global symptom score (GSS) scoring in aspect of pain, numbness, paraesthesia, weakness and nocturnal awakening. RESULTS: Postoperative wound smoothly healed in all patients and no complications occurred. All patients were followed up from 20 to 28 months with an average of 24 months. Symptoms of 1 patient had not incomplete relief, other patient's symptoms disappeared and muscle force of abductor pollicis brevis reinforced. Postoperative GSS scoring obviously improved than preoperative (P < 0.05). CONCLUSION: Treatment of carpal tunnel syndrome through palmar mini-incision decompression has advantages such as higher safe, shorter operative time, less invasive, smaller scar, which can cut off carpi transversum ligament and thoroughly decompress median nerve under direct sight, it is a safe and effective operative approach.

[Thumb replantation through bridging ulnar proper digital artery and dorsal carpal branch of radial artery].

OBJECTIVE: To introduce treatment method of replantation of severed thumb trauma with proximal arterial, and to evaluate its efficacy. METHODS: From February 2007 to March 2009,13 patients with severed thumb in serious injury of proximal arterial were treated with vein graft of volar forearm,bridging between dorsal carpal branch of radial artery on nasopharyngeal fossa and distal stump of ulnar proper digital artery. Among them, there were 11 males and 2 females with an average age of 34.5 years ranging from 16 to 50 years. Seven cases were in the left thumb,6 in the right thumb. Eight cases were complete separation, incomplete separation in 5 cases. Ten cases recieved emergency reimplantation, 3 cases with the arterial crisis after conventional replantation were explorated and repaired. RESULTS: Thumb of 13 cases all survived. All patients were followed-up for 8 to 17 months (averaged, 11 months). Replantation thumb obtained satisfactory appearance. According to Chinese Medical Association Society of Hand Surgery Trial criteria, the results were excellent in 9 fingers, good in 3 fingers, 1 poor finger. Two point discrimination of finger pulp was 5 to 8 mm (averaged 6.5 mm). CONCLUSION: By repairing artery of thumb with vein graft of volar forearm, bridging between dorsal carpal branch of radial artery on nasopharyngeal fossa and distal stump of ulnar proper digital artery,complex severed thumb replants on surgery position comfortable,without affecting the blood supply of the hand, expanding the indications for replantation and improving the success rate of replantation.

Cuprous oxide nanoparticles dispersed on reduced graphene oxide as an efficient electrocatalyst for oxygen reduction reaction.

Cuprous oxide (Cu(2)O) nanoparticles dispersed on reduced graphene oxide (RGO) were prepared by reducing copper acetate supported on graphite oxide using diethylene glycol as both solvent and reducing agent. The Cu(2)O/RGO composite exhibits excellent catalytic activity and remarkable tolerance to methanol and CO in the oxygen reduction reaction.

Avoiding Loss of Catalytic Activity of Pd Nanoparticles Partially Embedded in Nanoditches in SiC Nanowires.

Nanoditches from selective etching of periodically twinned SiC nanowires were employed to hinder the migration and coalescence of Pd nanoparticles supported on the nanowires, and thus to improve their catalytic stability for total combustion of methane. The results show that the etched Pd/SiC catalyst can keep the methane conversion of almost 100% while the unetched one has an obvious decline in the catalytic activity from 100 to 82% after ten repeated reaction cycles. The excellent catalytic stability originates from the limitation of the nanoditches to the migration and growth of Pd nanoparticles.

Periodically twinned SiC nanowires.

Twinning has been recognized to be an important microstructural defect in nanoscale materials. Periodically twinned SiC nanowires were largely synthesized by the carbothermal reduction of a carbonaceous silica xerogel prepared from tetraethoxysilane and biphenyl with iron nitrate as an additive. The twinned ß-SiC nanowires, with a hexagonal cross section, a diameter of 50-300 nm and a length of tens to hundreds of micrometers, feature a zigzag arrangement of periodically twinned segments with a rather uniform thickness along the entire growth length. Computer simulation has been used to generate three-dimensional atomic structures of the zigzag columnar twin structure by the stacking of hexagonal discs of {111} planes of SiC. A minimum surface energy and strain energy argument is proposed to explain the formation of periodic twins in the SiC nanowires. The thickness of the periodic twinned segments is found to be linearly proportional to the nanowire diameter, and a constant volume model is proposed to explain the relation.