Corrosion resistance and blood compatibility of lanthanum ion implanted pure iron by MEVVA

Pure iron is a potential material applying for coronary artery stents based on its biocorrodible and nontoxic properties. However, the degradation characteristics of pure iron in vivo could reduce the mechanical stability of iron stents prematurely. The purpose of this work was to implant the lanthanum ion into pure iron specimens by metal vapor vacuum arc (MEVVA) source at an extracted voltage of 40 kV to improve its corrosion resistance and biocompatibility. The implanted fluence was up to 5 × 10¹⁷ ions/cm². The X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical state and depth profiles of La, Fe and O elements. The results showed lanthanum existed in the +3 oxidation state in the surface layer, most of the oxygen combined with lanthanum and form a layer of oxides. The lanthanum ion implantation layer could effectively hold back iron ions into the immersed solution and obviously improved the corrosion resistance of pure iron in simulated body fluids (SBF) solution by the electrochemical measurements and static immersion tests. The systematic evaluation of blood compatibility, including in vitro platelets adhesion, prothrombin time (PT), thrombin time (TT), indicated that the number of platelets adhesion, activation, aggregation and pseudopodium on the surface of the La-implanted samples were remarkably decreased compared with pure iron and 316L stainless steel, the PT and TT were almost the same as the original plasma. It was obviously showed that lanthanum ion implantation could effectively improve the corrosion resistance and blood compatibility of pure iron.     

First-principles calculations for electronic and optical properties of the zinc-blende structured BeS compound under pressure

The electronic and the optical properties of the cubic zinc-blende (ZB) BeS under high pressure have been investigated by using \it ab initio plane-wave pseudopotential density functional theory method in the generalised gradient approximation (GGA) for exchange-correlation interaction. The electronic band structure and the pressure dependence of the total and partial densities of state under pressure are successfully described. Our calculations show that the ZB BeS has large and indirect band gaps associated with (Γ → X) transitions in ambient conditions. The results obtained are consistent with the experimental data available and other calculations. The optical properties, including dielectric function, energy-loss function, complex refractive index, reflection and absorption spectra, are investigated and analysed at different external pressures. The results suggest that the optical absorption appears mostly in the ultra-violet region and the curve of refractive index shift toward high energies (blue shift) with pressure increasing.     

M-ary information processing via an optimal nonlinear detector

This paper presents a novel approach of M-ary baseband pulse amplitude modulated signal processing via a parameter-optimized nonlinear dynamic system.This nonlinear system usually shows the phenomenon of stochastic resonance by adding noise.To thoroughly discuss the signal processing performance of the nonlinear system,we tune the system parameters to obtain a nonlinear detector with optimal performance.For characterizing the output of the nonlinear system,the derivation of the probability of detection error is given by the system response speed and the probability density function of the nonlinear system output.By varying the noise intensity with fixed system parameters,the phenomenon of stochastic resonance is shown and by tuning the system parameters with fixed noise,the probability of detection error is minimized and the nonlinear system is optimized.The detection performance of the two cases is compared with the theoretical probability of detection error,which is validated by numerical simulation.     

Differential conductance in normal-metal/insulator/metal/d-wave superconductor junction carrying a supercurrent

This paper applies the Bogoliubov--de Gennes equation and the Blonder--Tinkham--Klapwijk approach to study the oscillatory behaviour of differential conductance in a normal metal/insulator/metal/d-wave superconductor junction carrying a supercurrent I_s. We find that (i) a three-humped structure appears at a nearly critical supercurrent I_s and z ≈ 0.5 for the normal metal/insulator/metal/d_x² + y²-wave superconductor junction; (ii) the zero-bias conductance peak splits into two peaks with sufficiently large applied current for the normal metal/insulator/metal/d_xy-wave superconductor junction; (iii) the conductance spectrum exhibits oscillating behaviour with the bias voltage and the peaks of the resonances are suppressed by increasing supercurrent I_s.     

Formation energies and swelling of uranium dioxide by point defects

Hybrid density functional theory is used to study the stability and behavior of rare gases in uranium dioxide. Three insertion sites are considered: the octahedral interstitial position and the oxygen and uranium substitution sites. The optimized lattice constant, the volume variation induced by gaseous atom incorporation, and the defect formation energy are studied for each rare gas. Both lattice constants and formation energies increase with increase in radii of the rare gases. The octahedral interstitial position is the most favorable occupation site. The formation energy is found to be negative only for He at an interstitial site.     

Use of hyperpolarized [1-C]pyruvate and [2-C]pyruvate to probe the effects of the anticancer agent dichloroacetate on mitochondrial metabolism in vivo in the normal rat

Development of hyperpolarized technology utilizing dynamic nuclear polarization has enabled the measurement of ¹³C metabolism in vivo at very high signal-to-noise ratio (SNR). In vivo mitochondrial metabolism can, in principle, be monitored with pyruvate, which is catalyzed to acetyl-CoA via pyruvate dehydrogenase (PDH). The purpose of this work was to determine whether the compound sodium dichloroacetate (DCA) could aid the study of mitochondrial metabolism with hyperpolarized pyruvate. DCA stimulates PDH by inhibiting its inhibitor, pyruvate dehydrogenase kinase. In this work, hyperpolarized [1-¹³C]pyruvate and [2-¹³C]pyruvate were used to probe mitochondrial metabolism in normal rats. Increased conversion to bicarbonate (+ 181±69%, P=.025) was measured when [1-¹³C]pyruvate was injected after DCA administration, and increased glutamate (+ 74±23%, P=.004), acetoacetate (+ 504±281%, P=.009) and acetylcarnitine (+ 377±157%, P=.003) were detected when [2-¹³C]pyruvate was used.     

An improved automatic time-of-flight picker for medical ultrasound tomography

Objective and motivationTime-of-flight (TOF) tomography used by a clinical ultrasound tomography device can efficiently and reliably produce sound-speed images of the breast for cancer diagnosis. Accurate picking of TOFs of transmitted ultrasound signals is extremely important to ensure high-resolution and high-quality ultrasound sound-speed tomograms. Since manually picking is time-consuming for large datasets, we developed an improved automatic TOF picker based on the Akaike information criterion (AIC), as described in this paper.MethodsWe make use of an approach termed multi-model inference (model averaging), based on the calculated AIC values, to improve the accuracy of TOF picks. By using multi-model inference, our picking method incorporates all the information near the TOF of ultrasound signals. Median filtering and reciprocal pair comparison are also incorporated in our AIC picker to effectively remove outliers.ResultsWe validate our AIC picker using synthetic ultrasound waveforms, and demonstrate that our automatic TOF picker can accurately pick TOFs in the presence of random noise with absolute amplitudes up to 80% of the maximum absolute signal amplitude. We apply the new method to 1160 in vivo breast ultrasound waveforms, and compare the picked TOFs with manual picks and amplitude threshold picks. The mean value and standard deviation between our TOF picker and manual picking are 0.4 μs and 0.29 μs, while for amplitude threshold picker the values are 1.02 μs and 0.9 μs, respectively. Tomograms for in vivo breast data with high signal-to-noise ratio (SNR) (∼25 dB) and low SNR (∼18 dB) clearly demonstrate that our AIC picker is much less sensitive to the SNRs of the data, compared to the amplitude threshold picker.Discussion and conclusionsThe picking routine developed here is aimed at determining reliable quantitative values, necessary for adding diagnostic information to our clinical ultrasound tomography device - CURE. It has been successfully adopted into CURE, and allows us to generate such values reliably. We demonstrate that in vivo sound-speed tomograms with our TOF picks significantly improve the reconstruction accuracy and reduce image artifacts.     

The structure and optical characters of the ZnO film grown on GaAs/Al2O3 substrate

In this paper ZnO films are grown on GaAs/Al₂O₃ substrates at different temperature by metal-organic chemical vapor deposition (MOCVD). The GaAs/Al₂O₃ substrates are formed by depositing GaAs layer (∼35 nm) on the Al₂O₃ substrate. The results of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) demonstrate that most of the Ga and As atoms form Ga-As bond and the GaAs layer does not present any orientation. The characters of the ZnO films grown on GaAs/Al₂O₃ substrates are investigated by XRD, photoluminescence (PL), atomic force microscopy (AFM) and Raman scattering. Compared with ZnO film grown on Al₂O₃ substrate, ZnO film prepared by our fabrication scheme has good crystal and optical quality. Meanwhile its grain size becomes bigger according to the AFM image. Raman analysis indicates that the intrinsic defects and the in-plane tensile stress are obviously reduced in ZnO/GaAs/Al₂O₃ samples.     

Effect of the thermal and hydrothermal treatment on textural properties of Zr-MCM-41 mesoporous molecular sieve

Zr-containing mesoporous molecular sieves were synthesized by hydrothermal method using cetyltrimethyl ammonium bromide as a template and sodium silicate and zirconium sulfate as raw materials. The structure and morphology of the synthesized samples were characterized via various physicochemical methods, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, solid state nuclear magnetic resonance (²⁹Si MAS-NMR) techniques, thermal gravimetric-differential scanning calorimeter (TG-DSC) and N₂ physical adsorption, respectively. The effect of the different initial ZrO₂:SiO₂ molar ratio, the different thermal treatment temperature and the different hydrothermal treatment time on textural property was investigated. The experimental results reveal that the as synthesized samples possess a typical mesoporous structure of MCM-41. On the other hand, the specific surface area and pore volume of the synthesized Zr-MCM-41 mesoporous molecular sieve decrease with the increase of the amount of zirconium incorporated in the starting material, the rise of thermal treatment temperature and the prolonging of hydrothermal treatment time, the mesoporous ordering becomes poor. Also, when the molar ratio of ZrO₂:SiO₂ in the starting material is 0.1, the mesoporous structure of the Zr-MCM-41 mesoporous molecular sieve still retains after calcination at 750 °C for 3 h or hydrothermal treatment at 100 °C for 6 d, and have specific surface areas of 423.9 and 563.9 m²/g, respectively.