Ultrastrong and Stiff Carbon Nanotube/Aluminum-Copper Nanocomposite via Enhancing Friction between Carbon Nanotubes.

Researchers have been aiming to replace copper with carbon nanotube/copper nanocomposites, which are lighter and exhibit better electrical, mechanical, and thermal properties. However, the strength is far below pure carbon nanotube assembly and even much lower than some copper-based alloys. This disadvantage hinders the extensive application of carbon nanotube/copper nanocomposites. In this study, the carbon nanotube/aluminum-copper nanocomposites with ultra-strength and stiffness were prepared. The strength and elasticity modulus of composite reached as high as 6.6 and 500 GPa, respectively, while a high conductivity of 1.8 × 107 S/m was maintained. This can be attributed to the diffusion of Cu and Al atoms into the carbon nanotube fiber, which enhances friction between the carbon nanotubes by "pinning" and "bridging". This structure provides us with novel insights into the design of carbon nanotubes/metal nanocomposites with ultrahigh strength and conductivity.

Large Elasto-Optic Effect in Epitaxial PbTiO(3) Films.

First-principles calculations are performed to investigate the elasto-optic properties of four different structural phases in (001) epitaxial PbTiO(3) films under tensile strain: a tetragonal (T) phase and an orthorhombic (O) phase, which are the ground states for small and large strain, respectively, and two low-symmetry, monoclinic phases of Cm and Pm symmetries that have low total energy in the intermediate strain range. It is found that the refractive indices of the T and O phases respond differently to epitaxial strain, evidenced by a change of sign of their effective elasto-optic coefficients, and as a result of presently discovered correlations between refractive index, axial ratio, and magnitude of the ferroelectric polarization. The difference in refractive indices between T and O and the existence of such correlations naturally lead to large elasto-optic coefficients in the Cm and Pm states in the intermediate strain range, because Cm structurally bridges the T and O phases (via polarization rotation and a rapid change of its axial ratio) and Pm adopts a similar axial ratio and polarization magnitude to Cm. The present results therefore broaden the palette of functionalities of ferroelectric materials, and suggest new routes to generate systems with unprecedentedly large elasto-optic conversion.

Development of a new animal model of liver cirrhosis in swine.

This study aimed to develop a new experimental model of liver cirrhosis in swine by using carbon tetrachloride (CCl(4)) and ethanol. Liver cirrhosis was induced by intraperitoneal injection of CCl(4) twice a week for 9 weeks. Maize flour was the only food provided and the animals drunk a 5% alcohol-water mixture. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, bilirubin and portal venous pressure (PVP) levels were determined throughout CCl(4) treatment. The animals were sacrificed under general anesthesia at week 9 and liver samples were collected for histological analysis. 83.3% of the swine had liver cirrhosis and 33.3% had died. There was no change of body weight during the course of the experiment (p > 0.05). The AST and ALT levels increased significantly in the early stage of the study but had a trend to decrease during the late phase. The level of bilirubin increased greatly and albumin decreased during the whole experiment (p < 0.05). PVP levels decreased in the early stage in CCl(4)-treated swine, but increased significantly at the late phase. In conclusion, this study was successful in producing liver cirrhosis and offers an ideal experimental model for observing surgical therapeutic efficacy.

Size-dependent thermodynamic properties of metallic nanowires.

Analytical models for size-dependent melting temperature Tm(D), melting enthalpy DeltaHm(D), and surface energy gammasv(D) of metallic nanowires have been proposed in terms of the unified nanothermodynamical model where D denotes the diameter of nanowire. As D decreases, Tm(D), DeltaHm(D), and gammasv(D) functions are found to decrease almost with the same size-dependent trend. Due to the inclusion of the effect of dimensionality, the developed model can be applied to other low-dimensional systems. It is found that the ratio of depression of these thermodynamic parameters for spherical nanoparticle, nanowire, and thin film is 3:2:1 when D is large enough (>20h with h being the atomic diameter). The validity of the model is verified by the data of experiments, molecular dynamics simulations, and other theoretical models.

Giant electric-field-induced strain in lead-free piezoelectric materials.

First-principles calculations are performed to investigate the structures, electrical, and magnetic properties of compressive BiFeO3 films under electric-field and pressure perpendicular to the films. A reversible electric-field-induced strain up 10% is achieved in the compressive BiFeO3 films. The giant strain originates from rhombohedral-tetragonal (R-T) phase transition under electric-filed, and is recoverable from tetragonal-rhombohedral (T-R) phase transition by compressive stress. Additionally, the weak ferromagnetism in BiFeO3 films is largely changed in R-T phase transition under electric-filed and T-R phase transition under pressure - reminiscent of magnetoelectric effect and magnetoelastic effect. These results suggest exciting device opportunities arising from the giant filed-induced strain, large magnetoelectric effect and magnetoelastic effect.

Diagnosis and treatment of congenital choledochal cyst: 20 years' experience in China.

AIM: To summarize the experience of diagnosis and treatment of congenital choledochal cyst in the past 20 years (1980-2000). METHODS: The clinical data of 108 patients admitted from 1980 to 2000 were analyzed retrospectively. RESULTS: Abdominal pain,jaundice and abdominal mass were presented in most child cases. Clinical symptoms in adult cases were non-specific, resulting in delayed diagnosis frequently. Fifty-seven patients (52.7%) had coexistent pancreatiobiliary disease. Carcinoma of the biliary duct occurred in 18 patients (16.6%). Ultrasonic examination was undertaken in 94 cases, ERCP performed in 46 cases and CT in 71 cases. All of the cases were correctly diagnosed before operation. Abnormal pancreatobiliary duct junction was found in 39 patients. Before 1985 the diagnosis and classification of congenital choledochal cyst were established by ultrasonography preoperatively and confirmed during operation, the main procedures were internal drainage by cyst enterostomy. After 1985, the diagnosis was established by ERCP and CT, and cystectomy with Roux-en-Y hepaticojejunostomy was the conventional procedures.In 1994, we reported a new and simplified operative procedure in order to reduce the risk of choledochal cyst malignancy. Postoperative complication was mainly retrograde infection of biliary tract, which could be controlled by the administration of antibiotics, there was no perioperative mortality. CONCLUSION: The concept in diagnosis and treatment of congenital choledochal cyst has obviously been changed greatly.CT and ERCP were of great help in the classification of the disease.Currently, cystectomy with Roux-en-Y hepaticojejunostomy is strongly recommended as the choice for patients with type I and type IV cysts. Piggyback orthotopic liver transplantation is indicated in type V cysts (Caroli's disease) with frequently recurrent cholangitis.

Facile synthesis of superparamagnetic Ni-Fe ultrafine nanoalloy nanoparticles with equilibrium ordered phase structure via a sol-gel process.

Ni-Fe nanoalloy nanoparticles with an average grain size of 4 nm in diameter have been prepared by a sol-gel method under a hydrogen atmosphere where ethanol and oleic acid have been used as solvent and surfactant, respectively. X-ray diffraction (XRD) and selected area electron diffraction (SAED) examinations of the nanoparticles show the occurrence of (111), (200), (220) and (311) diffraction peaks and rings, meaning that the nanoparticles have a face-centered-cubic phase structure. Moreover, a superlattice diffraction peak and a diffraction ring/spot can also be observed in XRD and SAED results, indicating the formation of an equilibrium ordered L1(2) phase structure. The as-prepared Ni-Fe nanoalloy particles show typical superparamagnetic behavior at room temperature and the blocking temperature of the nanoparticles is determined to be about 50 K.

Size- and dimensionality-dependent thermodynamic properties of ice nanocrystals.

Although the melting of ice is the most ubiquitous phase transition, (pre)melting and the quasi-liquid layer remain a matter of debate, and little is known about the relationship between the thermodynamic properties of ice nanocrystals and their size and dimensionality. Here, we model analytically the size- and dimensionality-dependent melting temperature, premelting temperature, and melting enthalpy of hydrogen-bonded ice nanocrystals. These three thermodynamic parameters are found to increase with increasing size and dimensionality where the size effect is principle while the dimensionality effect is secondary, and the size dependence of premelting temperature almost follows the same trend as that of melting temperature. The model predictions correspond to the available molecular dynamic simulation and experimental results of ice nanoparticles and nanowires. These agreements enable us to determine theoretically the thickness of the quasi-liquid layer for the first time, which is found to be not constant but slightly increase with increasing size and thus accounts for the occurrence of different reported thicknesses of the quasi-liquid layer.

Individual auditory thalamic reticular neurons have large and cross-modal sources of cortical and thalamic inputs.

In the present study, the sources of thalamic and cortical inputs of thalamic reticular nucleus (TRN) neurons were examined by investigating the responses of the TRN neurons to electrical stimulation of different sites in the thalamus and the cortex of the rat. The recurrent excitation of the corticothalamic system that is triggered by electrical stimulation was eliminated by ablating the auditory cortex and by temporarily inactivating the medial geniculate body (MGB), when studying the sources of thalamic and cortical inputs, respectively. Single TRN neurons responded to electrical stimulation of 50-100 µA of the thalamus over a large area (dorsoventrally 1.2-2.4 mm and mediolaterally 1.0-2.3 mm, n=9). Four of 16 auditory TRN neurons responded to electrical stimulation of the lateral geniculate nucleus. The TRN neurons responded to cortical stimulation over a rostrocaudal distance of 2.6±0.5 mm (range: 1.5-3.5 mm, n=24) of the auditory cortex. Visual or auditory TRN neurons also responded to electrical stimulation in the auditory or visual cortices, respectively. The present study revealed that each TRN neuron received a wide range of inputs from both ascending thalamic and descending cortical projections. The projection could be cross-modal. Having a strong and lasting inhibition on the thalamus, the TRN neurons are likely to be involved in adjusting global states relating to awareness and attention in the thalamocortical system.

[Analysis on poliomyelitis cases in Inner Mongolia in 1990-1993].

Out of 97 AFP cases, 68 were confirmed polio in Inner Mongolia in 1990-1993, in which 44.12% were diagnosed according to laboratory results. In this period, 13 strains of polio virus were isolated and identified from the stool samples of 62 AFP cases. The etiological results suggested that there was no dominant strain of polio virus in the whole region. Serological results showed that the positive rates of IgM antibody against polio virus were 75%, 26% and 0% in 1990, 1991, 1993 respectively which seemed to have a declining trend.

[Discussion on the elimination of measles based on the 45-year-incidence data in Inner Mongolia].

Measles incidence data collected since 1950 in Inner Mongolia is analyzed in this paper. The following characteristics have been noticed after measles vaccine was widely used: (1) the incidence and the mortality of measles kept decreasing, (2) The epidemic still occasionally appeared at low incidence level; (3) the proportion of cases in older children increased; (4) the peak month of the disease occurrence postponed; (5) the differences of incidence among districts depending on the implementation of vaccine and immunization. Since the goal of poliomyolitis eradication is given priority to and should be achieved, measles eradication program should not be overemphasized.