Removal of oxygen from silicon by electron beam melting

Small amounts of multicrystalline silicon were melted in an electron beam furnace in different experimental conditions in order to investigate the oxygen evaporation behavior during the electron beam melting (EBM) process. The oxygen content level before and after EBM was determined by secondary ion mass spectroscopy. The oxygen content was reduced from 6.177 to 1.629 ppmw when silicon was melted completely at 15 kW with removal efficiency up to 73.6 %. After that, it decreased continually to <0.0517 ppmw when the refining time exceeded 600 s with a removal efficiency of more than 99.08 %. During the melting process, the evaporation rate of silicon is 1.10 × 10^?5 kg/s. The loss of silicon could be reduced up to 1.7 % during oxygen removal process to a desirable figure, indicating EBM is an effective method to remove oxygen from silicon and decrease the loss of silicon.     

Rains of solitons in a figure-of-eight passively mode-locked fiber laser

We report experimental observation of rains of solitons in figure-of-eight fiber laser passively mode-locked through nonlinear optical loop mirror. Soliton pulses are created from an extended noisy background and drift until they reach a condensed phase comprising several tens of aggregated solitons. The observation of this dynamics tends to strengthen the idea of the universality of the collective behavior of solitons.     

Investigation of 2-aminoethanethiol as corrosion inhibitor for steel using response surface methodology (RSM)

The inhibition efficiency of 2-aminoethanethiol (2-AEE) has been investigated against steel corrosion in 0.1 M HCl solution. The effect of temperature, pH, and concentration were studied with the help of potentiodynamic measurement, electrochemical impedance spectroscopy, scanning electron microscopy, and atomic absorption spectroscopy techniques. The potential of zero charge (E_pzc) studies showed that the adsorption occurs via ?SH group; the metal surface is positively charged in corrosive test solution. The adsorptive interaction is evaluated, and best correlation was obtained with Langmuir isotherm. 2-AEE was shown to have significant inhibition efficiency against steel corrosion. The response surface methodology was employed to explain the relation between pH, inhibitor concentration, and the efficiency. The regression analysis was realized for development of an equation between independent variables and the output. The success of fitting model was tested with basic statistical arguments, residual and variance analysis, T and F tests, and R ² value. The statistical evaluations showed that the obtained polynomial equation can be successfully used for optimization of applications involving the use of 2-AEE as inhibitor.     

Evaluation of an oral carrier system in rats: bioavailability and gastrointestinal absorption properties of curcumin encapsulated PBCA nanoparticles

A new oral delivery system, polybutylcyanoacrylate nanoparticles (PBCNs), was introduced to improve the oral bioavailability of curcumin (CUR), a poorly soluble drug. The formulation was optimized by orthogonal design and the optimal PBCNs loading CUR exhibited a spherical shape under transmission electron microscopy with a range of 40?C400?nm. Physicochemical state of CUR in PBCN was investigated by X-ray diffraction and the possible structure changes occurring in CUR after conjugating with polybutylcyanoacrylate were studied with FTIR. The results indicated that CUR in PBCN was in a non-crystalline state and CUR was encapsulated in PBCN without chemical reaction. The oral pharmacokinetic study was conducted in rats and the relative bioavailability of CUR encapsulated PBCNs to the crude CUR was more than 800%. The in situ absorption experiment in rat intestine indicated the absorption was first order with passive diffusion mechanism. The absorption results in various segments of intestine showed that the main absorption sites were ileum and colon. It can be concluded that PBCNs as an oral carrier can significantly improve the oral absorption of a poorly soluble drug.     

Time evolution of information entropy for a stochastic system with double singularities driven by quasimonochromatic noise

<正>This paper deals with the time evolution of information entropy for a stochastic system with double singularities driven by quasimonochromatic noise.The dimension of the Fokker-Planck equation is reduced by the linear transformation. The exact expression of the time dependence of information entropy is obtained based on the definition of Shannon’s information entropy.The relationships between the properties of dissipative parameters,system singularity strength parameter,quasimonochromatic noise,and their effects on information entropy are discussed.     

Digitalized Mirror Array and Its Application in Large Telescope： Principle and Case Studies

In this article, we report the principle and conceptual design of a fundamentally different technology in fabricating high precision aberration free optical devices. The tip-tilt of facet in a mirror array is produced by digitally controlled line-tilts of rows and columns. It has not only provided a cost-effective designing methodology in optical physics but also led to a much finer precision of 1 mili arc sec or less. As examples of the application of the proposed digitalised optics, two case studies have been given： a 10 m Schmidt telescope （off-axis） and an 8 m Cassegrain telescope （on-axis）.     

Evidence for spin correlation in t ̅t production

We present a measurement of the ratio of events with correlated t and t ?t spins to the total number of t ?t events. This ratio f is evaluated using a matrix-element-based approach in 729 t ?t candidate events with a single lepton ? (electron or muon) and at least four jets. The analyzed p ?p collisions data correspond to an integrated luminosity of 5.3 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider operating at a center-of-mass energy √s=1.96 TeV. Combining this result with a recent measurement of f in dileptonic final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in t ?t events with a significance of more than 3 standard deviations.     

Dynamical coupling between gradients and transport in fusion plasmas

The dynamical coupling between density gradients and particle transport has been investigated using similar experimental tools in the plasma boundary of different tokamak (JET, ISTTOK) and stellarator (TJ-II) devices, showing that the size of turbulent events is minimum in the proximity of the most probable density gradient. Experimental results were found to be consistent with results from two very different models of plasma turbulence and transport. The present findings, common to several plasma devices, suggest the importance of self-regulation mechanisms between plasma transport and gradients in fusion devices.     

Enhancement of upconversion luminescence of YAlO3:Er3+ by Gd3+ doping

The upconversion luminescences of YAlO3:Er3+ phosphor co-doping with different Gd3+ concentrations are investigated under the excitation of 980- and 532-nm diode lasers. A near ultraviolet upconversion emission at 410 nm is observed in YAlO3 under 532-nm excitation. Moreover, the inactive Gd3+ ions can improve the upconversion intensity efficiently in a certain range of concentration. Under 980-nm excitation, the visible upconversion emissions at 546 and 646 nm are enhanced by about 10 and 8 times at the Gd3+ concentration of 40%, respectively. The upconversion emission at 410 nm under 532-nm excitation is also enhanced by 7 times. The substitution of Gd3+ ions for Y3+ sites changes the local symmetry of Er3+, leading to the improvement of upconversion efficiency.