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The carbon fiber (T300-6K) with a three-dimensional four-way braiding structure was selected as the reinforcement, and the 3D-Cf/6061Al composites at different braiding angles (10°, 20° and 30°) were prepared by the pressure infiltration method, and the effects of different braiding angles on the mechanical properties of the composites were discussed. It is found that the pressure infiltration avoids the weak bonding force between the carbon fiber and the aluminum matrix to a certain extent, so that a better infiltration effect can be obtained. The bending performance of the composites become worse with the increase of braiding angle. With the increase of braiding angle, the strain force of the composites also increases, and the greater the elongation is, the better the toughness is. When the braiding angle was larger, the transverse component force of the fiber was larger, the unevenness of the fiber fracture surface increases, the pulling phenomenon was obvious.

Objective To explore the effects of dexmedetomidine (Dex) on systemic inflammatory response induced by renal ischemia reperfusion (rIRI) and the possible mechanism. Methods Fifteen C57BL/6J mice were randomly divided into 3 groups, that is, sham operation group (laparotomy without renal pedicle occlusion), rIRI group (bilateral renal pedicles was clamped for 60 min with a microvascular clamp), and rIRI+Dex group (intraperitoneal injection of 25 μg/ml Dex in 15 min prior to bilateral renal ischemia). In 24 h after surgery or reperfusion, the blood samples were harvested and analyzed for counts of neutrophils, monocytes and lymphocytes by blood analyzer and for the serum levels of inflammatory cytokines (TNF-α, IL-1β and IL-10) by ELISA. Western blotting was used to detect iNOS and Arg 1 in the harvested peritoneal macrophages for the polarization. Results Compared with the mice in the sham group, the counts of neutrophils, monocytes and lymphocytes were significantly elevated (P < 0.01), the serum levels of TNF-α and IL-1β were increased (P < 0.01), and the expression of M1 marker iNOS was enhanced while that of M2 marker Arg 1 was decreased (P < 0.01). Dex pretreatment resulted in no significant changes in the counts of neutrophils, monocytes and lymphocytes (P>0.05), reduced serum levels of TNF-α and IL-1β (P < 0.01) and increased level of IL-10 (P < 0.01), and decreased expression of iNOS (P < 0.01) as well as increase of Arg 1 (P < 0.05) when compared with the indicators in the rIRI group. Conclusion Dex inhibits the systemic inflammatory response induced by rIRI, which may be associated with modulation of macrophage polarization.

Objective To observe the changes of cardiopulmonary function in elderly patients undergoing unilateral knee arthroplasty, and to explore the effects of ischemic preconditioning and ulinastatin infusion on them. Methods A total of 45 elderly patients undergoing knee arthroplasty under epidural combined subarachnoid anesthesia in our hospital from November 2012 to May 2018 were prospectively recruited in this study. They were randomly divided into control group (Group C, n=15, routine anesthesia management), limb ischemic preconditioning group (Group IP, n=15, the tourniquet pressurized to 480 mmHg followed by being opened 5 min later, 3 cycles before surgery) and ulinastati infusion group [Group U, n=15, venous infusion of 200 kU ulinastatin within 20 min after anesthesia, then continuously pumping at 20 U/(kg·min) until the end of surgery]. Iliac (femoral) arterial blood samples were collected at 5 min before (T0) and 1 (T1), 6 (T2) and 24 h (T3) after tourniquets were relaxed. Myocardial enzymes detection (CK, CKMB, LDH), blood gas analysis [respiratory index (RI), lactic acid (cLac)], inflammatory cytokines (TNF-α, IL-1, IL-6), malondialdehyde (MDA) and xanthine oxidase (XOD) measurement were carried out respectively. Results In Group C, CK were significantly increased at T2 and T3 (P < 0.05), RI remarkably rose at T1 and T2 (P < 0.05), cLac and OXD also elevated notably at T2 (P < 0.05) when compared with the levels at T0. These markers were significantly reduced in Group IP at T2 (P < 0.05) and tended to decline in Group U at the above time points (P>0.05). There were no obvious differences in the levels of CKMB, LDH, TNF-α, IL-1, IL-6 and MDA in intra- or inter-groups (P>0.05). Conclusion For the elderly patients undergoing knee arthroplasty, no significant changes are seen in cardiac function, but their pulmonary function may be impaired at different degrees due to oxidative stress instead of systemic inflammatory reaction. Lower limb ischemic preconditioning can improve pulmonary function by inhibiting oxidative stress.

Objective To explore the correlation of intraoperative hypotension and other risk factors with perioperative death in elderly patients. Methods We reviewed the clinical data of 26 758 patients aged 65 years or above who underwent surgery in our hospital between January, 2007 and August, 2017, and selected 156 patients with perioperative death (observation group) and 312 surviving patients (control group, selected randomly from the total surviving patients) for this study. The intraoperative blood pressure and surgical data of the enrolled patients were collected using the Maddie Ston anesthesia information system. Univariate and multivariate logistic regression analyses were performed to identify the risk factors for perioperative mortality in the elderly patients. Results The Results of univariate logistic regression analysis suggested a mean arterial blood pressure (MAP) ≤65 mmHg with a systolic blood pressure (SBP) ≤120 mmHg, age, ASA classification, cardiac function classification, general anesthesia, preoperative complications, surgical types, intraoperative use of vasoactive drugs, and intraoperative blood transfusion were all significantly correlated with perioperative mortality in the elderly patients (P < 0.05). Multivariate logistic regression analysis revealed that intraoperative hypotension (a MAP between 61 and 65 mmHg) was a high-risk factor for perioperative death in these patients, and the perioperative mortality rate could be increased when the cumulative hypotention time approached 8% of the total operative time. The other high-risk factors associated with perioperative mortality in the elderly patients included age, ASA classification, pre-existing coronary heart disease or malignant neoplasms, craniocerebral surgery and intraoperative blood transfusion (OR > 1). Conclusion Prolonged intraoperative hypotension (with a MAP below 65 mmHg) is correlated with an increased risk of perioperative death in elderly patients. Age, ASA classification, coronary heart disease or malignant tumor, craniocerebral surgery and intraoperative blood transfusion are all high-risk factors for perioperative death in elderly patients.

Fiber-reinforced composites were widely used in aerospace, automotive, and wind energy industries, due to their lightweight, high specific strength and stiffness, design flexibility, and durability. This study prepared hybrid fiber preforms using a three-dimensional braided technique. These preforms made of carbon fiber (CF) and aramid fiber (AF) were reinforced into resin-based (ER) composites by a vacuum infusion process (VIP). Our study focused on evaluating the mechanical properties of these composites under different blend arrangements and ratios, with four blend arrangements including layer-by-layer, half-by-half, bundle-by-bundle, and block-by-block. The results showed that the bending strain of the composites with a 3:1 aramid fiber/carbon fiber yarn ratio (3AF1CF) increased by 105.56% compared to that of CF/ER, and the addition of AF improved the toughness of the composite. The tensile strength and modulus of the composites with a 3:1 carbon fiber/aramid fiber yarn ratio (1AF3CF) were improved by 31.17% and 109.68%, respectively, compared to those of AF/ER, and the bending strength and modulus increased by 106.12% and 115.32%, respectively, and increasing the CF ratio thus significantly improved the mechanical properties of the composites. In addition, in four hybrid arrangements with the same AF/CF ratio, the aramid fiber/carbon fiber yarn ratio of 2:2 (2AF2CF-4) possessed the best mechanical properties, with tensile strength and of 608.36 MPa and 13.8 GPa, and bending strength and modulus of 417.203 MPa and 22.9 GPa, respectively. [ABSTRACT FROM AUTHOR]

In order to further improve the oxidation resistance of SiC-coated C/C composites used in extreme environments, TaSi2 coatings were deposited on the surfaces of SiC-coated C/C composites by supersonic air plasma spraying (SAPS) with different spraying power parameters, under other fixed parameter (gas flow, power feed rate, spraying distance and nozzle diameter) conditions. The micro-structures and phase characteristics of the TaSi2 coatings prepared with the four kinds of spraying powers (40 kW, 45 kW, 50 kW and 55 kW) were analyzed. Also, the inter-facial bonding strengths and fracture modes between the four TaSi2 coatings and the SiC coating were studied. The results showed that with an increase in the spraying power, the morphologies of the TaSi2 coatings appeared from loose to dense to loose. When the spraying power was 50 kW, the deposition rate reached a maximum of 39.8%. The TaSi2 coating presented an excellent micro-structure without obvious pores and microcracks, and its inter-facial bonding strength was 15.3 ± 2.3 N. Meanwhile, the fracture surface of the sample exhibited a brittle characteristic. [ABSTRACT FROM AUTHOR]

Conductive hydrogels are viewed as the most promising materials for flexible devices. However, their applications in aquatic environments are severely limited by their inevitable swelling behavior. Herein, we report a MXene-based polyampholyte anti-swelling hydrogel possessing high stretchability (1391%), good conductivity, admirable self-healing ability (healing efficiency reached 66% after healing for 1 h), and fast photoresponsive behavior. Besides, the hydrogel-based sensor displayed a wide sensing range (2–400%) and could realize underwater monitoring and communication. More importantly, an underwater warning system was assembled, which can offer efficient real-time underwater positioning and urban waterlogging pre-warning. This work provides a new strategy for developing anti-swelling hydrogel sensors and expands their potential applications in marine exploitation and urban construction. [ABSTRACT FROM AUTHOR]

Organic luminophores with high emission efficiency in solution as well as solid‐state have received increasing attention due to their promising applications in biosensors, biological imaging, and optoelectronic devices. Herein, four triphenylamine (TPA)‐substituted boron ketoimine molecules (TPA‐BKI a‐d) are designed and synthesized by combining a donor‐acceptor (D‐A) electronic system and highly twisted block. The asymmetry of molecular and the planarity of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) sides in the excited state endow TPA‐BKI a‐d with rigidified conformations, allowing bright emission in dilute solution. Additionally, their highly twisted structures avoid close contact between molecules and detrimental exciton interactions, leading to efficient emission in the solid state. Meanwhile, the emission colors are modulated by the incorporation of different substituents through the amino‐yne click reaction. Furthermore, because of the protonation and deprotonation of the amino substituents, TPA‐BKI‐d exhibits reversible alterations of optical properties in both solution and solid states. [ABSTRACT FROM AUTHOR]

The spatially controllable shape-shifting behaviors of a planar two-dimensional (2D) film to three-dimensional (3D) shapes upon external stimuli are of paramount significance for the development of smart materials. Herein, the present work focuses on fabricating plain film whose shape can be remotely and spatially transformed into various 3D configurations via the formation of a laser-induced temperature gradient; when subjected to laser irradiation, the prestretched hybrid films exhibit out-of-plane bending behavior owing to anisotropic chain relaxation and strain energy release. On this basis, various sophisticated shape transformations can be achieved by site-specific irradiations of laser with a controllable magnitude. Meanwhile, shape morphing involving reversible bending transformations can also be realized by employing the laser on the corresponding opposite side of the hybrid films. Remarkably, under a 160 mW/cm2 simulated sunlight illumination, the transformation of flat 2D film into 3D chiral actuators is driven by material anisotropy and geometrical heterogeneity of a bilayer strip design, and it yields right and left-handed helix, the morphologies of the helix shape can be precisely tailored by the strip angles and strain values. [ABSTRACT FROM AUTHOR]

In the process of using adhesive method for variable cross-section 3D weaving, the introduction of adhesive at the yarn increasing point greatly increases the friction and wear between carbon fibers, which can lead to a decrease in the overall performance of the prefabricated component. In response to the above issues, a self-made experimental fixture was developed to test the friction and wear performance between carbon fibers in bonding process. The effects of friction angle, preloaded tension, and friction frequency on the friction properties between carbon fiber bundles were investigated. Solidworks is used to model bonded carbon fiber bundles with a friction angle of 90°, and ABAQUS is used to simulate the friction of the bonded carbon fiber bundle. The experimental results show that stress concentration occurs in the center of the friction area, and the wear degree at the center is more obvious, and the number of fiber breaks at the center was more than that of the side. Friction angle has great influence on friction coefficient, while pre-tensioning and friction frequency had a negligible effect. Based on the above results, when performing variable cross-section 3D weaving, it is recommended to increase the spacing between adjacent carriers and shorten the distance between the weaving chassis and the prefabricated parts. Additionally, it is advised to reduce the pre-added tension on the carrier device and increase the knitting frequency as much as possible within the scope of working conditions. The study results are of great significance for developing 3D weaving devices in terms of theoretical and engineering guidance. [ABSTRACT FROM AUTHOR]

Carbon foam composites, reinforced by micro-nano multiscale phases, were prepared with CNTs modified phenolic resin as the carbon source, magnesium borate whiskers (Mg2B2O5w) and ZrO2 nano-particles as the reinforcement, and hollow microspheres as dispersed phase, respectively. The effects of micro-nano multi-scale phases on the microstructure, mechanical properties, electromagnetic shielding and thermal oxidation properties of the carbon foams were investigated. The results demonstrated that Mg2B2O5w and ZrO2 nano particles contributed a lot to the performance of carbon foam composites synergistically. With the increase of Mg2B2O5w doping, the mechanical properties of the composites first increased and then decreased. The compressive strength reached the maximum (15.4 MPa) with the doping amount of 6 %, which was 111% higher than that of pure carbon foam. Its electromagnetic shielding performance also improved with the increase of Mg2B2O5w doping. The total electromagnetic shielding of 8% CPF was up to 51 dB at 9 GHz, which was 62% higher than that of pure carbon foam. 6% CPF showed the best high-temperature oxidation resistance. Its mass loss reduced from 25% to 15% during isothermal oxidation, at 600 °C for 20 min. The high-temperature oxida¬tion resistance improved by 40 %, compared to that of pure carbon foam. [ABSTRACT FROM AUTHOR]