Electro-electrodialysis of HI–I2–H2O mixture using radiation-grafted polymer electrolyte membranes

In the thermochemical water-splitting iodine–sulfur process for hydrogen production, new polymer electrolyte membranes were applied in an electro-membrane process (electro-electrodialysis, EED) to increase the HI molality of HIx solution (HI + I₂ + H₂O mixture) to be over quasi-azeotropic. Radiation grafting of a styrene monomer into a poly(ethylene-co-tetrafluoroethylene) base film and subsequent sulfonation provided electrolyte membranes that had ion exchange capacities (IECs) of 1.1–1.6 mmol/g. With the EED of the HIx solutions using [HI] = [I₂] = 10 mol/kg at 40 °C the transport number of protons, ratio of permeated quantities of water to the protons, and current efficiency all appeared to depend on the IEC of the resulting membranes. When compared to Nafion, the self-made membranes exhibited lower electric cell resistance, and thereby decreasing up to 32% of the overall energy required in the concentration operation.     

Cloud and aerosol contributions to variation in shortwave surface irradiance over East Asia in July during 2001 and 2007

It is important to clarify the contributions of clouds and aerosols to the variation of surface shortwave irradiance (S) for climatological studies. This study examined the contributions of clouds and aerosols to the variation in S over East Asia (75-135°E, 20-55°N) in July during 2001 and 2007 using the index of potential radiative forcing (PRF) to characterize the temporal and geographical variations. After confirming the validity of PRF for multiyear analyses, we performed several temporal analyses of clouds and aerosols over the whole research domain. Changes in the geographical distribution, contribution histograms, and averaged values were studied. In agreement with previous studies that treated single-year cases, we confirmed that the magnitudes of the temporal changes in S variations due to clouds and aerosols were highly variable geographically. As for domain-averaged S variations, we did not observe defined trends for the research period. It was also found that the temporal variation between one parameter and its S variation was negatively correlated, from the point analyses at two locations. Based on these results, we concluded that PRF is a promising tool for research into long-term S variations. This kind of information will be quite valuable as basic data for use in climate modeling.     

Evidence of formation of tetravacancies in uniformly oxygen irradiated n-type silicon

High purity n-type silicon single crystal with resistivity in the order of 4000 Ω cm has been irradiated with high-energy oxygen ions at room temperature up to a fluence of 5E15 ions/cm². The energy of the beam was varied from 3 to 140 MeV using a rotating degrader to achieve a depthwise near-uniform implantation profile. Radiation induced defects and their dynamics have been studied using positron annihilation spectroscopy along with isochronal annealing up to 700 °C in steps of 50 °C for 30 min. After annealing the sample at 200 °C for 30 min, formation of silicon tetravacancies has been noticed. The formation of the tetravacancies was found to be due to agglomeration of divacancies present in the irradiated sample. An experimentally obtained positron lifetime value of 338±10 ps has been reported for silicon tetravacancies, which has a very close agreement with the value obtained from recent theoretical calculations. The tetravacancies were found to dissociate into trivacancy clusters upon further annealing. The trivacancies thus obtained were observed to agglomerate beyond 400 °C to form larger defect clusters. Finally, all the defects were found to anneal out after annealing the sample at 650 °C.     

基于同步辐射加速器的康普顿背散射γ光源性质及其应用研究

本文介绍了利用康普顿背散射 (BCS)产生γ射线的原理 ,并以SSRF储存环电子运行参数为例 ,给出了利用BCS方法产生MeV量级γ射线束的计算结果 ,预期该光子束具有高强度、高极化度、单色性、方向性好等优点。同时对国际上已运行和拟建的高能和低能γ束线站的装置和性能作了简要介绍 ,并分别探讨了高能和低能准单色极化γ射线在核物理和核天体物理研究中广泛的应用前景。文中对基于正对以及离轴几何条件下 ,采用直线加速器加速的电子同短脉冲强激光发生Compton/Thomson散射的激光同步辐射源作了初步探讨 ,这一方法为我们构建超短脉冲的高亮度、准单色、可调谐的X γ射线源开辟了一条新途径。     

Differentiation between intra-axial metastatic tumor progression and radiation injury following fractionated radiation therapy or stereotactic radiosurgery using MR spectroscopy, perfusion MR imaging or volume progression modeling

Objective

To determine the accuracy of magnetic resonance spectroscopy (MRS), perfusion MR imaging (MRP), or volume modeling in distinguishing tumor progression from radiation injury following radiotherapy for brain metastasis.

Methods

Twenty-six patients with 33 intra-axial metastatic lesions who underwent MRS (n=41) with or without MRP (n=32) after cranial irradiation were retrospectively studied. The final diagnosis was based on histopathology (n=4) or magnetic resonance imaging (MRI) follow-up with clinical correlation (n=29). Cho/Cr (choline/creatinine), Cho/NAA (choline/N-acetylaspartate), Cho/nCho (choline/contralateral normal brain choline) ratios were retrospectively calculated for the multi-voxel MRS. Relative cerebral blood volume (rCBV), relative peak height (rPH) and percentage of signal-intensity recovery (PSR) were also retrospectively derived for the MRPs. Tumor volumes were determined using manual segmentation method and analyzed using different volume progression modeling. Different ratios or models were tested and plotted on the receiver operating characteristic curve (ROC), with their performances quantified as area under the ROC curve (AUC). MRI follow-up time was calculated from the date of initial radiotherapy until the last MRI or the last MRI before surgical diagnosis.

Results

Median MRI follow-up was 16 months (range: 2-33). Thirty percent of lesions (n=10) were determined to be radiation injury; 70% (n=23) were determined to be tumor progression. For the MRS, Cho/nCho had the best performance (AUC of 0.612), and Cho/nCho >1.2 had 33% sensitivity and 100% specificity in predicting tumor progression. For the MRP, rCBV had the best performance (AUC of 0.802), and rCBV >2 had 56% sensitivity and 100% specificity. The best volume model was percent increase (AUC of 0.891); 65% tumor volume increase had 100% sensitivity and 80% specificity.

Conclusion

Cho/nCho of MRS, rCBV of MRP, and percent increase of MRI volume modeling provide the best discrimination of intra-axial metastatic tumor progression from radiation injury for their respective modalities. Cho/nCho and rCBV appear to have high specificities but low sensitivities. In contrast, percent volume increase of 65% can be a highly sensitive and moderately specific predictor for tumor progression after radiotherapy. Future incorporation of 65% volume increase as a pretest selection criterion may compensate for the low sensitivities of MRS and MRP.     

Solving the radiation diffusion and energy balance equations using pseudo-transient continuation

We develop a scheme for the system coupling the radiation diffusion and matter energy balance equations. The method is based on fully implicit, first-order, backward Euler differencing; Picard-Newton iterations solve the nonlinear system. We show that iterating on the radiation energy density and the emission source is more robust. Since the Picard-Newton scheme may not converge for all initial conditions and time steps, pseudo-transient continuation (Ψtc) is introduced. The combined Ψtc-Picard-Newton scheme is analyzed. We derive conditions on the Ψtc parameter that guarantee physically meaningful iterates, e.g., positive energies. Successive Ψtc iterates are bounded and the radiation energy density and emission source tend to equilibrate. The scheme is incorporated into a multiply dimensioned, massively parallel, Eulerian, radiation-hydrodynamic computer program with automatic mesh refinement (AMR). Three examples are presented that exemplify the scheme's performance. (1) The Pomraning test problem that models radiation flow into cold matter. (2) A similar, but more realistic problem simulating the propagation of an ionization front into tenuous hydrogen gas with a Saha model for the equation-of-state. (3) A 2D axisymmetric (R,Z) simulation with real materials featuring jetting, radiatively driven, interacting shocks.     

Measurements and inverse calculations of spectral radiation intensities of a turbulent ethylene/air jet flame

Fast (6250 Hz) line-of-sight measurements of infrared spectral radiation intensities (I_λ) from a luminous flame and a new deconvolution technique for the estimate of local scalar properties using inverse radiation calculations are reported. Time series data of I_λ for one diametric and nine chord-like radiation paths in a representative horizontal plane were measured. Statistical properties of I_λ, including mean, root mean square (rms), probability density function, autocorrelation coefficient, and power spectral density, were obtained from the time series data. The measured statistical properties of I_λ at two representative wavelengths, which are dominated by carbon dioxide (CO₂) and soot radiation, respectively, are reported. The autocorrelation coefficient data show large negative loops with repeatable zero crossings at 20 ms and minimum values as low as −0.2 at 30–40 ms. Radial distributions of mean and rms CO₂ mole fractions and temperatures were estimated using inverse calculations of mean I_λ at two different wavelengths dominated by CO₂ radiation in conjunction with the relationship of these quantities to mixture fractions. Soot volume fraction distributions were also estimated using inverse calculations of mean I_λ at a wavelength dominated by continuum soot radiation. The estimated local mixture fraction distributions were in reasonably good agreement with sampling data from similar flames. The calculated mean I_λ from 1.4 to 4.8 μm other than those used in the inverse calculations matched the experimental data well. The present method provides non-intrusive measurements of major gas species and temperature statistics in turbulent soot containing flames not accessible to other optical diagnostics.     

Development of an X-ray detector using surface plasmon resonance

A new X-ray detector using surface plasmon resonance (SPR) is proposed. The detector consists of a prism coated with a thin metal film and semiconductor film. Optical laser pulse induces SPR condition on the metal surface, and synchronized X-ray pulse which is absorbed into the semiconductor film can be detected by measuring the change of the resonance condition of the surface plasmon. The expected time and spatial resolution of this detector is better than that of conventional X-ray detectors by combining this SPR measurement with ultra-short laser pulse as the probe beam. Our preliminary investigation using Au and ZnSe coated prism implies this scheme works well as the detector for the ultra-short X-ray pulse.     

1 MeV电子辐照对短波Hg1-xCdxTe光伏探测器的影响

 研究了1 MeV电子辐照对短波Hg_1-xCd_xTe光伏探测器的影响。通过测试电子辐照前后光伏探测器的响应光谱、信号、噪声、暗电流等性能参数，分析了电子辐照对Hg_xCdxTe光伏器件的影响机制。实验结果发现：电子辐照后器件响应光谱在短波处有变窄的趋势，但响应峰值波长和截止波长基本无变化；随着辐照剂量的增加，通过p-n结的暗电流有所增加，光伏器件的探测率有减小的趋势。