Deformation Behavior of an Extruded 7075 Aluminum Alloy at Elevated Temperatures.

Hot compression tests were conducted to explore the deformation behavior of an extruded 7075 aluminum alloy bar at elevated temperatures. Specimens with 0°, 45°, and 90° angles along the extrusion direction were prepared. The compression temperatures were 300 and 400 °C, and the strain rates ranged from 0.001 to 0.1 s-1. The corresponding microstructures were characterized via OM and TEM, and the macroscopic texture was tested using XRD. The results indicated that the strength of the 7075 alloy decreases with higher compression temperatures and is in a proportional relationship with respect to the strain rate. During high-temperature compression, it is easier to stimulate atomic diffusion in the matrix, which can improve thermal activation abilities and facilitate dynamic recovery and dynamic recrystallization. In addition, the coarsening of precipitates also contributed to dynamic softening. When compressed at 300 °C, the stress levels of the 0° specimens ranked first, and those for the 45° specimens were the lowest. When compressed at 400 °C, the flow stresses of the specimens along three directions were comparable. The anisotropic mechanical behavior can be explained by the fiber grains and brass {011} <211> texture component. However, higher temperature deformation leads to recrystallization, which can weaken the anisotropy of mechanical properties.

Deformation Behavior and Processing Maps of 7075 Aluminum Alloy under Large-Strain Thermal Compression.

The investigation of thermal deformation behavior plays a significant role in guaranteeing the overall performance of alloy materials. In this manuscript, a series of isothermal compression tests at different temperatures (300, 350, 400, and 450 °C) and strain rates (0.001, 0.01, 0.1, and 1 s-1) were conducted to study the thermal deformation behavior of 7075 aluminum alloy. Subsequently, processing maps at a strain from 0.4 to 1.39 were established according to the stress-strain data obtained from various deformation parameters. The microstructural evolution of the target alloy was observed with an optical microscope and transmission electron microscope. The results reveal the unstable regions are located at (360-450 °C, 0.04-1 s-1) and (300-315 °C, 0.01-0.22 s-1). Precipitation particles, pinned dislocations, and highly dislocated areas can be observed in the microstructure of the alloy in the unstable regions. This is a potential crack and defect formation point. The identified optimum processing parameters are located at (375-450 °C, 0.001-0.03 s-1), with a maximum dissipation efficiency of 0.6.

High-Temperature Tensile Mechanical Properties and Microstructure of Rolled 6082-T6 Aluminum Alloy Sheets.

The tensile properties of rolled 6082-T6 aluminum alloy were tested at a high temperature, and the influences of tensile temperature on its flow stress and anisotropy were studied. The microstructure evolution was characterized using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was concluded that the tensile strength of the studied alloy decreases with increasing temperature. In higher-temperature deformation, the dislocation density decreases alongside the coarsening of precipitates, leading to a decrease in deformation resistance, and increase in the number of dimples and deepening of their sizes, exhibiting good plasticity. The alloy displays anisotropic mechanical properties at 200 °C due to the elongated grains and the orientation of the α-phase. The anisotropy becomes weaker with increasing temperature. There is no evident anisotropy at 400 °C, as the slip systems are activated more easily and the grains begin to recrystallize.

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To investigate the effects of Spartina alterniflora invasion on mangrove wetland ecosystem, the benthic crustacean and fish samples were collected using cage nets in Zhangjiang Estuary Mangrove Wetland, Fujian Pro-vince in August 2020, January and April 2021. The five sampling sites included two mangroves (Avicennia marina and Kandelia obovata) sites, two S. alterniflora sites, and one mudflat site. The abundance, biomass, index of relative importance (IRI), Shannon diversity index (H), Pielou evenness index (J), and Margalef richness index (D) were used to quantify the dominant species and species diversity of benthic crustaceans and fishes. The functional groups and niche of dominant species were also analyzed. A total of 37 species, from 2 phyla, 2 classes, 8 orders, and 17 families, were identified across the three seasons. Most of them were warm-water and euryhaline species, mainly carnivorous and omnivorous functional groups. The results of two-way analysis of variance and NMDS showed that the community diversity index of benthic crustacean and fish did not change significantly after the invasion of S. alterniflora compared with mudflat. Functional groups had changed significantly, with the species number of plankton functional groups, carnivorous and phytophagous functional groups being increased. Compared with mangrove sites, the number of species of benthic crustacean and fish in S. alterniflora sites was significantly increased. The spatio-temporal niche breadth of dominant species ranged from 0 to 1.4186, with Liza carinata (1.4186), Bostrychus sinensis (1.0168), Metapenaeus ensis (0.9469) and Exopalaemon carinicauda (0.8922) as the top four species.

Microstructure, Texture and Mechanical Properties of AZ31 Magnesium Alloy Fabricated by High Strain Rate Biaxial Forging.

High strain rate biaxial forging (HSRBF) was performed on AZ31 magnesium alloy to an accumulated strain of ΣΔε = 1.32, the related microstructure, texture and mechanical properties were investigated. It was found that the microstructure evolution can be divided into two steps during HSRBF. In the early forging processes, the refinement of the grain is obvious, the size of ~10 µm can be achieved; this can be attributed to the unique mechanisms including the formation of high density twins ({101(-)2} extension twin and {101(-)1}-{101(-)2} secondary twin) and subsequently twining induced DRX (dynamic recrystallization). The thermal activated temperature increases with the increase of accumulated strain and results in the grain growth. Rolling texture is the main texture in the high strain rate biaxial forged (HSRBFed) alloys, the intensity of which decreases with the accumulated strain. Moreover, the basal pole rotates towards the direction of forging direction (FD) after each forging pass, and a basal texture with basal pole inclining at 15-20° from the rolling direction (RD) is formed in the full recrystallized HSRBFed alloys. The grain refinement and tiled texture are attributed to the excellent strength and ductility of HSRMBFed alloys with full recrystallized structure. As the accumulated strain is ΣΔε = 0.88, the HSRMBFed alloy displays an outstanding combination of mechanical properties, the ultimate tensile strength (UTS) is 331.2 MPa and the elongation is 25.1%.

Direct electron-beam patterning of transferrable plasmonic gold nanoparticles using a HAuCl4/PVP composite resist.

Reliable fabrication of gold nanoparticles with desirable size, geometry and spatial arrangement is essential for plasmonic applications. A common fabrication flow usually involves electron-beam lithography and a vacuum-evaporation-based lift-off process or etching. In this work, we evaluate an alternative approach to directly fabricate a plasmonic gold nanoparticle array without involving the vacuum evaporation process by using a chloroauric acid/poly(vinyl pyrrolidone) (HAuCl4/PVP) hybrid as a functional electron-beam resist. Systematic experiments were conducted to investigate the patterning behaviors in the fabrication process. With the optimized fabrication parameters, we show that the HAuCl4/PVP composite resist has a high patterning resolution and pure gold nanoparticles with tens of nanometers can be obtained after an annealing-based pyrolysis process. More particularly, compared to the patterned plasmonic gold nanoparticles obtained by conventional methods, the gold nanoparticles fabricated by our method can be transferred to soft substrates due to the absence of an adhesion layer, enabling various potential applications in flexible and stretchable optics. As an example, we demonstrated that the transferred gold nanoparticle array can be conformably assembled onto a flat gold surface to form a particle-on-film structure for surface-enhanced Raman scattering (SERS) applications.

Efficacy observation on application of negative pressure therapy in the treatment of superficial partial-thickness scald wound in children / 中华烧伤杂志

<p><b>OBJECTIVE</b>To observe the effect of negative pressure therapy in the treatment of superficial partial-thickness scald in children.</p><p><b>METHODS</b>Three hundred and seven children with superficial partial-thickness scald hospitalized from August 2009 to May 2012 were divided into negative pressure therapy group (NPT, n = 145) and control group (C, n = 162) according to the random number table. Patients in group NPT were treated with negative pressure from within post injury day (PID) 3 to PID 9 (with -16 kPa pressure), while traditional occlusive dressing method was used in group C. Changes in body temperature, wound healing condition, frequency of dressing change were compared between group NPT and group C. Bacterial culture results of wounds were compared before and after treatment in group NPT. Volume of drained transudate per one percent of wound area was recorded in group NPT on PID 1 to PID 3. Data were processed with t test or chi-square test.</p><p><b>RESULTS</b>The incidence of high fever was significantly lower in group NPT (26.9%, 39/145) than in group C (63.6%, 103/162, χ(2) = 41.419, P < 0.01). On PID 9, complete wound epithelization was observed in 138 patients in group NPT, and in 7 patients there were a few residual wounds which healed after dressing change for 2 days. The wound healing time of patients in group NPT [(9.2 ± 0.6) d] was obviously shorter than that in group C [(10.1 ± 1.6) d, t = 6.895, P < 0.01]. The frequency of dressing change among patients in group NPT [(2.05 ± 0.22) times] was significantly decreased as compared with that in group C [(4.82 ± 0.81) times, t = 39.878, P < 0.01]. Bacteria were found in wound secretion of seventeen patients in group NPT before treatment, while no bacterium was discovered in all patients after treatment. Volumes of drainage fluid in group NPT were proportional to wound areas, which were respectively (9.8 ± 3.2), (6.2 ± 2.1), (4.1 ± 1.6) mL per one percent of wound area on PID 1, 2, and 3.</p><p><b>CONCLUSIONS</b>NPT can decrease times of dressing change, and alleviate infection and inflammatory response by drainage of transudate, which promotes wound healing at last. NPT is proved to be a safe and effective approach for treatment of children with superficial partial-thickness scald.</p>

Treatment strategies for mass burn casualties / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Mass burn casualties are always a great challenge to a medical team because a large number of seriously injured patients were sent in within a short time. Usually a high mortality is impending. Experiences gained from successful treatment of the victims may be useful in guiding the care of mass casualties in an armed conflict.</p><p><b>METHODS</b>Thirty-five burn victims in a single batch, being transferred nonstop by air and highway from a distant province, were admitted 48 hours post-injury. All patients were male with a mean age of (22.4 +/- 8.7) years. The burn extent ranged from 4% to 75% ((13.6 +/- 12.9)%) total body surface area. Among them, thirty-two patients were complicated by moderate and severe inhalation injury, and tracheostomy had been performed in 15 patients. Decompression incisions of burn eschar on extremities were done in 17 cases before transportation. All the thirty-five patients arrived at the destination smoothly via 4-hour airlift and road transportation. Among them, twenty-five patients were in critical condition.</p><p><b>RESULTS</b>These thirty-five patients were evacuated 6 hours from the scene of the injury, and they were transferred to a local hospital for primary emergency care. The patients were in very poor condition when admitted to our hospital because of the severe injury with delayed and inadequate treatment. Examination of these patients at admission showed that one patient was suffering from sepsis and multiple organ dysfunction syndrome. Dysfunction of the heart, lung, liver, kidney, and coagulation were all found in the patients. Forty-eight operations were performed in the 23 patients during one month together with comprehensive treatment, and the function of various organs was ameliorated after appropriate treatment. All the 35 patients survived.</p><p><b>CONCLUSIONS</b>A well-organized team consisting of several cooperative groups with specified duties is very important. As a whole, the treatment protocol should be individualized, basing on the extent of the injury and the care that the patient had received at the spot. During airlift, the stretchers should be arranged perpendicular to the longitudinal axis of the cabin. The treatment protocol in our hospital consisted mainly of prompt effective relief of all life-threatening complications, followed by early closure of burn wounds, appropriate use of anti-infection therapy, emphasis on nutritional support, correction of metabolic disorders, alleviation of immunosuppression, correction of coagulopathy, and effective support and protection of organ function.</p>

Characteristics of and strategies for patients with severe burn-blast combined injury / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Severe burn-blast combined injury is a great challenge to medical teams for its high mortality. The aim of this study was to elucidate the clinical characteristics of the injury and to present our clinical experiences on the treatment of such cases.</p><p><b>METHODS</b>Five patients with severe burn-blast combined injuries were admitted to our hospital 77 hours post-injury on June 7, 2005. The burn extent ranged from 80% to 97% (89.6% +/- 7.2%) of TBSA (full-thickness burns 75% - 92% (83.4% +/- 7.3%)). All the patients were diagnosed as having blast injury and moderate or severe inhalation injury. Functions of the heart, liver, kidney, lung, pancreas and coagulation were observed. Autopsy samples of the heart, liver, and lungs were taken from the deceased. Comprehensive measures were taken during the treatment, including protection of organ dys function, use of antibiotics, early anticoagulant treatment, early closure of burn wounds, etc. All the data were analyzed statistically with t test.</p><p><b>RESULTS</b>One patient died of septic shock 23 hours after admission (four days after injury), the others survived. Dysfunction of the heart, liver, lungs, pancreas, and coagulation were found in all the patients on admission, and the functions were ameliorated after appropriate treatments.</p><p><b>CONCLUSIONS</b>Burn-blast combined injury may cause multiple organ dysfunctions, especially coagulopathy. Proper judgment of patients' condition, energetic anticoagulant treatment, early closure of burn wounds, rational use of antibiotics, nutritional support, intensive insulin treatment, timely and effective support and protection of organ function are the most important contributory factors in successful treatment of burn-blast combined injuries.</p>

Expression of human beta-defensin 3 in COS-7 cell / 中国医学科学杂志(英文版)

<p><b>OBJECTIVE</b>To establish a cell line for stable expression of human beta-defensin 3 (hBD3).</p><p><b>METHODS</b>Full length cDNA of hBD3 was isolated from previously constructed pGEM-hBD3 and then inserted into pcDNA3. The recombinant vector identified carrying hBD3 with right direction was introduced into COS-7 cells by Lipofectamine. Cell clones survived in G418-rich medium and with stable expression of hBD3 in both mRNA and protein levels were identified by RT-PCR and Western blot respectively. Genomic integration of the hBD3 gene with the COS-7 cells was confirmed by Southern dot blot and primary analysis. The antimicrobial activity of the secreted hBD3 was also evaluated.</p><p><b>RESULTS</b>COS-7 cells transfected with pcDNA3-hBD3 expressed hBD3 stably in mRNA and protein level. Southern dot blot analysis showed successful integration of the hBD3 gene into the genome of COS-7 cell and the hBD-3 protein secreted into the culture medium showed antimicrobial activity.</p><p><b>CONCLUSION</b>We successfully established a hBD3-expressing cell line.</p>