Sponge-like porous polyvinyl alcohol/chitosan-based hydrogel with integrated cushioning, pH-indicating and antibacterial functions.

Developing a packaging material with integrated cushioning, intelligent and active functions is highly desired but remains challenging in the food industry. Here we show that a sponge-like porous hydrogel with pH-indicating and antibacterial additives can meet this requirement. We use polyvinyl alcohol and chitosan as the primary polymers to construct a hydrogel with hierarchical structures through a freeze-casting method in combination with salting-out treatment. The synergy of aggregated polymer chains and the sponge-like porous structure makes the hydrogel resilient and efficient in energy absorption. It also enables rapid movement of molecules/particles and fast reaction due to the large specific surface area of the pore structures and the large amount of free water in it, leading to a sensitive pH-indicating function. The hydrogel shows an obvious color variation within a wide pH range in 3 min. The silver nanoparticles are fixed in the dense polymer networks, enabling a lasting release of silver ions. The porous structure makes the silver ion reach the protected item in a short time, achieving an antibacterial effect against S. aureus and E. coli with little cytotoxicity. This work paves the way for fabricating multifunctional hydrogels for diverse advanced packaging systems.

Defect- and Interface-Induced Dielectric Loss in ZnFe2O4/ZnO/C Electromagnetic Wave Absorber.

Controlling defects and interfaces in composite absorbers can effectively regulate electromagnetic (EM) parameters and enhance the electromagnetic wave (EMW) absorption ability, but the mechanism still needs to be further elucidated. In this study, ZnFe2O4/ZnO/C composite was synthesized via the hydrothermal method followed by post-annealing in different atmospheres. Defects and interfaces were characterized by Raman, PL spectroscopy, XPS and TEM, and their relationship with dielectric loss and EMW absorption performance was discussed in detail. Results show that the N2-annealed ZnFe2O4/ZnO/C composite with abundant defects and interfaces as well as an optimized composition exhibits excellent EMW dissipation ability, with a RLmin value of -17.4 dB and an fe of 3.85 GHz at a thickness of 2.28 mm. The excellent EMW absorption performance originates from suitable impedance matching, significant conduction loss and strong dielectric loss (interfacial polarization, diploe polarization and defect polarization) dominated by lattice defects and interfaces. This study provides a view into the relationship between defects, interfaces, EM parameters and EMW absorption ability, and also suggests an effective way to promote EMW dissipation ability of the absorbers by controlling defects and interfaces.

Virus removal during sewage treatment by anaerobic membrane bioreactor (AnMBR): The role of membrane fouling.

Anaerobic membrane bioreactor (AnMBR) is a low-energy and promising solution for sewage treatment. During the treatment, the fouled membrane of AnMBR is recognized as an important barrier against pathogenic viruses. Here, the role of membrane fouling of an AnMBR at room temperature in the virus removal was investigated using MS2 bacteriophage as a virus surrogate. Results revealed that the virus removal efficiency of AnMBR was in the range of 0.2 to 3.6 logs, gradually increasing with the course of AnMBR operation. Virus removal efficiency was found to be significantly correlated with transmembrane pressure (R2=0.92, p<0.01), especially in the rapid fouling stage, indicating that membrane fouling was the key factor in the virus removal. The proportion of virus decreased from 52.03% to 15.04% in the membrane foulants when membrane fouling was aggravating rapidly, yet increased from 0.74% to 21.52% in the mixed liquor. Meanwhile, the permeate flux dramatically dropped. These imply that the primary rejection mechanism of virus by membrane in the slow fouling stage is the virus adsorption onto membrane, while the sieving effect is the main reason in the rapid fouling stage. Ex-situ virus rejection test unveiled that the cake layer was the main contributor to the overall virus rejection, while the greatest resistance-specific virus rejection was provided by the organic pore blocking. This paper provides operation strategies to balance enhanced virus removal and high permeate flux by regulating the membrane fouling process.

Partial-nitritation of low-strength anaerobic effluent: A moderate-high dissolved oxygen concentration facilitates ammonia-oxidizing bacteria disinhibition and nitrite-oxidizing bacteria suppression.

Integrating anaerobic treatment with partial nitritation (PN)/anammox is a promising technology to achieve energy-efficient wastewater treatment, while partial nitritation of the mainstream anaerobic effluent (Aneff) was rarely reported. A PN reactor fed with low-strength Aneff was employed in this study to investigate the performance and technology bottleneck of this process. When operated at low dissolved oxygen (DO) concentration (0.30-0.43 mg/L), gene coding hydroxylamine oxidation (hao) was severely suppressed by bio-refractory organics, which results in a decreased ammonia-oxidizing bacteria activity and nitrite accumulation rate. The ammonium conversion and nitrite accumulation were recovered by increasing the DO concentration to a moderate-high level (1.10 ± 0.20 mg/L) and achieved long-term stable operation. At this condition, hao showed a dramatic increase while gene encoding nitrite oxidoreductase was appropriately suppressed; the effluent NO2-/NH4+ ratio reached 1.17, and a low NO3-/NOx- ratio of 0.38 was achieved simultaneously. The findings in this study revealed the adverse effects of Aneff on PN and supported a practical operating strategy for efficient PN of Aneff.

Biomechanical evaluation of tendon connection with novel suture techniques.

PURPOSE: Achilles tendon rupture is a severe injury with poor curative effect due to its anatomical characteristic and mechanical peculiarity. Internal fixation of limited loop (IFLL) with steel-wire has been applied on patients with tendon rupture to fix the broken ends before physical rehabilitation. The purpose of this study is to investigate the biomechanical property and radiological characteristic of such suture technique for the repairment of tendon rupture. METHODS: Tendons of pigs' hint feet were separated for the biomechanical study. Suture surgery was performed according to the protocol of IFLL. Biomechanical Testing Machine was adopted to conduct the biomechanical tensile load examination. The maximal load, elastic modulus and tendon stiffness of the stitched tendons with or without reinforcement were examined. RESULTS: The maximum tensile load of the stitched tendons using IFLL reached 1/4 of the uninjured tendon's maximum tensile load, indicating that such suture technique is capable of providing enough tension for the ruptured tendon. Surprisingly, tendons fixed with titanium wire showed the highest load tension, which was comparable to the undamaged tendon. Therefore, we found the biomechanical basis of using IFLL in effectively connecting the rupture ends of tendons. CONCLUSIONS: In conclusion, we provide biomechanical evidence for the use of IFLL in treatment of Achilles tendon rupture, by providing enough strength for the ankle function. Such suture technique could help the patients with better rehabilitation and reduced in-hospital stay after Achilles tendon injury.

The effect of pressure on the crystallization of rapidly supercooled zirconium melts.

Molecular dynamics simulations have been performed to explore the effect of pressure (P) on the crystallization of zirconium (Zr) under rapid cooling. The structural evolutions have been analysed in terms of the system energy, the pair distribution function and the largest standard cluster analysis. It was found that at the cooling rate of 1.0 × 1011 K s-1, which can crystallize Zr melts into hcp crystals via the bcc intermediate state under zero pressure, the critical pressure (Pc) for vitrification is about 28.75 GPa, and the larger the pressure, the higher the glass transition temperature Tg. At P < Pc the Ostwald's step rule is applied to Zr melts. Crystallization of rapidly super-cooled Zr melts under pressure always begins with the bcc phase and ends in the hcp crystal; the higher the pressure, the lower the onset temperature (Tc) of crystallization. Unlike the single-intermediate-state crystallization (SisC) under zero pressure, multiple-intermediate-state crystallization (MisC) is usually observed under pressure. Structural analysis reveals that if nucleation is essentially completed at the end of the first crystalline (bcc-dominated) stage, MisC will occur; otherwise, SisC occurs. The origin of such an observation is also discussed from the effect of pressure upon the thermodynamics and kinetics factors. These findings are useful for comprehensively understanding the solidification of metals under pressure.

Structural evolutions and hereditary characteristics of icosahedral nano-clusters formed in Mg70Zn30 alloys during rapid solidification processes.

To investigate the structural evolution and hereditary mechanism of icosahedral nano-clusters formed during rapid solidification, a molecular dynamics (MD) simulation study has been performed for a system consisting of 107 atoms of liquid Mg70Zn30 alloy. Adopting Honeycutt-Anderson (HA) bond-type index method and cluster type index method (CTIM-3) to analyse the microstructures in the system it is found that for all the nano-clusters including 2~8 icosahedral clusters in the system, there are 62 kinds of geometrical structures, and those can be classified, by the configurations of the central atoms of basic clusters they contained, into four types: chain-like, triangle-tailed, quadrilateral-tailed and pyramidal-tailed. The evolution of icosahedral nano-clusters can be conducted by perfect heredity and replacement heredity, and the perfect heredity emerges when temperature is slightly less than Tm then increase rapidly and far exceeds the replacement heredity at Tg; while for the replacement heredity, there are three major modes: replaced by triangle (3-atoms), quadrangle (4-atoms) and pentagonal pyramid (6-atoms), rather than by single atom step by step during rapid solidification processes.

Crystallization characteristics in supercooled liquid zinc during isothermal relaxation: A molecular dynamics simulation study.

The crystallization characteristics in supercooled liquid Zn during isothermal relaxation were investigated using molecular dynamics simulations by adopting the cluster-type index method (CTIM) and the tracing method. Results showed that the crystallization process undergo three different stages. The size of the critical nucleus was found to be approximately 90-150 atoms in this system; the growth of nuclei proceeded via the successive formation of hcp and fcc structures with a layered distribution; and finally, the system evolved into a much larger crystal with a distinct layered distribution of hcp and fcc structures with an 8R stacking sequence of ABCBACAB by adjusting all of the atoms in the larger clusters according to a certain rule.

A versatile chemical conversion synthesis of Cu2S nanotubes and the photovoltaic activities for dye-sensitized solar cell.

A versatile, low-temperature, and low-cost chemical conversion synthesis has been developed to prepare copper sulfide (Cu2S) nanotubes. The successful chemical conversion from ZnS nanotubes to Cu2S ones profits by the large difference in solubility between ZnS and Cu2S. The morphology, structure, and composition of the yielded products have been examined by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction measurements. We have further successfully employed the obtained Cu2S nanotubes as counter electrodes in dye-sensitized solar cells. The light-to-electricity conversion results show that the Cu2S nanostructures exhibit high photovoltaic conversion efficiency due to the increased surface area and the good electrocatalytical activity of Cu2S. The present chemical route provides a simple way to synthesize Cu2S nanotubes with a high surface area for nanodevice applications.

Application of internal fixation of steel-wire limited loop in early Achilles tendon rupture.

OBJECTIVE: To explore the clinical effect and safety of internal fixation of steel-wire limited loop in early Achilles tendon rupture. METHODS: Seventy-six patients respectively with early transected and avulsed types of Achilles tendon rupture were selected and treated with internal fixation of steel-wire limited loop. The patients began to take exercise for their lower limbs through continous passive motion as early as possible after surgical repair, and the loops were removed after 3-5 months. Six months later, the condition of complications including Achilles tendon re-rupture, wound fistula, wound infection and skin necrosis, cutaneous sensation in sural nerve dominance region, time back to preinjury work or learning as well as time to physical activities were observed. One year later, the therapeutic effect was evaluated, and the maximum circumferences of bilateral legs and ruptured plane circumferences of Achilles tendon were measured. RESULTS: The wound of all patients healed well, no complications like Achilles tendon re-rupture, wound fistula, wound infection and skin necrosis occured, and the cutaneous sensation in sural nerve dominance region was normal. The mean time back to preinjury work or learning as well as to pysical activities of all patients were respectively 10 and 22 weeks. Seventy out of 76 patients (92.1%) achieved an excellent effect, and 6 (7.9%) good effect. The excellent and good rate came up to 100%. The maximum circumference in the affected leg decreased to 2 mm averagely compared with the offside, while the ruptured plane circumferences of Achilles tendon in the affected side increased to 2.2 mm compared with the offside. CONCLUSIONS: For early Achilles tendon rupture, internal fixation of steel-wire limited loop can recover the ankle function better, return to the preinjury state in the shortest time, and has few complications.

Clinical predictive value of serum angiogenic factor in patients with osteosarcoma.

OBJECTIVE: To explore serum angiogenic factor expression in patients with osteosarcoma and its relationship with metastasis. METHODS: Immunohistochemistry was used to test the expression of CD34 and FVIII-Rag in osteosarcoma tissues of 36 patients (osteosarcoma group) and microvessel density (MVD) was also recorded. In addition, ELISA was used to test the level of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), transforming growth factor-ß1 (TGF-ß1) and endostatin (ES) in the osteosarcoma group and in a control group. RESULTS: VEGF and ES level were significantly higher than in the control group before operation (P<0.01), VEGF, bFGF and TGF-ß1 correlating with the ES level (P<.01). Serum VEGF and ES levels of osteosarcoma patients before surgery were closely related to relapse and metastasis; moreover, serum VEGF increased with MVD (P<0.01). Postoperative VEGF and ES levels were lower than the preoperation values (P<0.01); ES level in relapse group was significantly higher than that of the non-relapse group (P<0.01). CONCLUSION: Preoperative serum VEGF and postoperative ES levels have great predictive value with regard to relapse of osteosarcoma patients.

Atomic mechanism of liquid-glass transition for Ca7Mg3 alloy.

The atomic mechanism of liquid-glass transition for Ca(7)Mg(3) alloy during the rapid quenching processes is studied by the molecular dynamics simulations. The temperature dependences of structural, thermodynamic, and dynamic properties during the liquid-glass transition have been investigated. It is found that onset temperatures where these different properties begin to deviate from the equilibrium liquid are identical and near the melting temperature T(m). The liquid-glass transition temperatures in structure (T(g)(Str)) and dynamics (T(g)(Dyn)) are identical and higher than the calorimetric one (T(g)(Cal)), which are consistent with many experiments and computer simulations. The solid- and liquid-like atoms are defined by the Debye-Waller factor. It reveals that the solid-like atoms hold lower potential and higher degree of local order. On the basis of the evolution of solid-like atoms, the atomic mechanisms in structure, thermodynamics, and dynamics transition are systematically elucidated, which are consistent with the potential energy landscape.

Formation and evolution of metastable bcc phase during solidification of liquid Ag: a molecular dynamics simulation study.

On the basis of the quantum Sutton-Chen potential, the rapid solidification processes of liquid silver have been studied by molecular dynamics simulation for four cooling rates. By means of several analysis methods, the competitions and transitions between microstructures during the cooling processes have been analyzed intensively. It is found that there are two phase transitions in all simulation processes. The first one is from liquid state to metastable (transitional) body-centered cubic (bcc) phase. The initial crystallization temperature T(ic) increases with the decrease of the cooling rate. The second one is from the transitional bcc phase to the final solid phase. This study validates the Ostwald's step rule and provides evidence for the prediction that the metastable bcc phase forms first from liquid. Further analyses reveal that the final solid at 273 K can be a mixture of hexagonal close-packed (hcp) and face-centered cubic (fcc) microstructures with various proportions of the two, and the slower the cooling rate is, the higher proportion the fcc structure occupies.

Formation mechanism of critical nucleus during nucleation process of liquid metal sodium.

To deeply understand the formation mechanism of a critical nucleus during the nucleation process of liquid metal sodium, a system consisting of 10 000 Na atoms has been simulated by using molecular dynamics method. The evolutions of nuclei are traced directly, adopting the cluster-type index method. It is found that the energies of clusters and their geometrical constraints interplay to form the favorable microstructures during the nucleation process. The nucleus can be formed through many different pathways, and the critical size of the nucleus would be different for each pathway. It is also found that the critical nucleus is nonspherical and may include some metastable structures. Furthermore, the size of the cluster and its internal structure both play a crucial role in determining whether it is a critical nucleus, and this is in agreement with the simulations by computing the free energy of the Lennard-Jones system [D. Moroni, P. R. ten Wolde, and P. G. Bolhuis, Phys. Rev. Lett. 94, 235703 (2005)].