脉冲等离子体辐射微波机理的初步研究

 在分析了等离子体辐射微波的电流波形和喇叭天线接收到的微波信号波形的基础上,对脉冲等离子体辐射微波的机理进行了理论分析：阴阳极间存在TEM和TM两种模式的波;流经等离子体的电流产生的磁场使等离子体中的波成为慢波;高频场的激励因素有两个,一是作加速运动的电子,二是阳极斑点溅射时阳极电位突降;同一时刻具有不同速度的电子将能量转换给相应相速的波是其产生超宽带辐射的原因。     

轻介质传输中辐射热传导近似成立的判别因子

 从辐射输运方程出发,通过递推的方法,推导并得到了包含高级修正的辐射能流表达式。利用这个表达式,分析了辐射在轻介质中传输时,辐射热传导近似的成立条件。热传导近似的成立条件总是要求温度空间变化尺度与自由程之比远大于某个值,该值即判别因子,它表征热传导近似条件满足的苛刻程度,其值越大,热传导近似就越难满足。讨论得出：当同时考虑轫致和散射过程时,这一判别因子的值在3~60之间。并进一步分析了密度的空间变化以及1维球坐标下的半径对判别因子的影响。     

Role of Divalent Metals in Polymer Degradation

The role of divalent metals in the degradation of the physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of metals (Cu, Mg, etc.) of different concentrations (0–30ppm) to natural rubber latex and irradiated with various radiation doses (0–20kGy). The radiation doses were optimized (12kGy), and the adverse effect of metal ions was studied against a reference film prepared with no metal ions. Tensile strength, tear strength, and cross-linking density of the irradiated rubber films decreased with increasing metal ion concentrations and decreasing radiation doses. The mechanical properties of the films were reduced by 10–15% for 30ppm metal ions and at the optimum dose. In contrast, elongation at break, permanent set, and swelling ratio of the films increased at the same conditions. The relative effect of metal ions can be explained by the classical electron concept, reported in this article.     

Development and application of chip calorimeter as an X-ray detector

Radiotherapy for cancer patients requires accurate measurement of the absorbed dose of radiation in a treatment planning step. Various types of radiation detectors are currently utilized for dose measurement. Among them, calorimeters are known to be the most precise detector for measuring absorbed dose, but their on-site application is limited by the large size of the equipment. We developed a miniaturized chip calorimeter for application as a radiation detector. The calorimetric radiation detector was built using micro/nano fabrication techniques, and consists of an SU-8 photoresist absorber and high-sensitivity vanadium oxide (VO_x) thermistors. The thermistors had a temperature resolution of 135 μK, and the calorimeter showed a thermal conductance of 11 μW/K. The detector was irradiated with various X-ray dose rates from a linear accelerator, and the absorbed dose to SU-8 was measured. The detector responses showed high linearity with dose rates, demonstrating the feasibility of the radiation detector for practical uses.     

Relativistic Lagrangians for the Lorentz–Dirac equation

We present two types of relativistic Lagrangians for the Lorentz–Dirac equation written in terms of an arbitrary world-line parameter. One of the Lagrangians contains an exponential damping function of the proper time and explicitly depends on the world-line parameter. Another Lagrangian includes additional cross-terms consisting of auxiliary dynamical variables and does not depend explicitly on the world-line parameter. We demonstrate that both the Lagrangians actually yield the Lorentz–Dirac equation with a source-like term.     

Differential mobility spectrometry (DMS) reveals the elevation of urinary acetylcarnitine in non‐human primates (NHPs) exposed to radiation

Acetylcarnitine has been identified as one of several urinary biomarkers indicative of radiation exposure in adult rhesus macaque monkeys (non‐human primates, NHPs). Previous work has demonstrated an up‐regulated dose‐response profile in a balanced male/female NHP cohort. 1 As a contribution toward the development of metabolomics‐based radiation biodosimetry in human populations and other applications of acetylcarnitine screening, we have developed a quantitative, high‐throughput method for the analysis of acetylcarnitine. We employed the Sciex SelexIon DMS‐MS/MS QTRAP 5500 platform coupled to flow injection analysis (FIA), thereby allowing for fast analysis times of less than 0.5 minutes per injection with no chromatographic separation. Ethyl acetate is used as a DMS modifier to reduce matrix chemical background. We have measured NHP urinary acetylcarnitine from the male cohorts that were exposed to the following radiation levels: control, 2, 4, 6, 7, and 10 Gy. Biological variability, along with calibration accuracy of the FIA‐DMS‐MS/MS method, indicates LOQ of 20 μM, with observed biological levels on the order of 600 μM and control levels near 10 μM. There is an apparent onset of intensified response in the transition from 6 to 10 Gy. The results demonstrate that FIA‐DMS‐MS/MS is a rapid, quantitative technique that can be utilized for the analysis of urinary biomarker levels for radiation biodosimetry.     

Paramagnetic defects induced by ion implantation in oxide glasses

Radiation defects induced by ion bombardment of multicomponent oxide glasses of five compositions (phosphates and borosilicates) were investigated by means of electron paramagnetic resonance (EPR). The samples were implanted with N⁺, O⁺, Ar⁺, Mn⁺, Cu⁺ and Pb⁺ ions at energy E=150 keV at three different doses between 3×10¹⁵ and 10¹⁷ ions/cm². The broad anisotropic EPR spectra with principal g-values answering the relationship g_z>g_y>g_x˜g_e (g_e is g-factor of free electron) were observed for the samples of all five compositions. The g-values depend on glass composition. For example, g_z ranges from 2.016 to 2.057. Computer simulation shows that the spectra of many samples are superpositions of two spectra with g-values answering the mentioned relationship. These spectra are attributed to molecular O₂⁻ ions weakly coupled with glass network. In some samples narrow almost symmetric lines with g=2.0025±0.0005 were observed. The possible radiation defects responsible for this signal are discussed.     

Radiation-induced defects in sucrose single crystals, revisited: a combined electron magnetic resonance and density functional theory study

The results are presented of an electron magnetic resonance analysis at 110 K of radiation-induced defects in sucrose single crystals X-irradiated at room temperature, yielding a total of nine (1)H hyperfine coupling tensors assigned to three different radical species. Comparisons are made with results previously reported in the literature. By means of electron paramagnetic resonance and electron nuclear double resonance temperature variation scans, most of the discrepancies between the present 110 K study and a previous 295 K study by Sagstuen and co-workers are shown to originate from the temperature dependence of proton relaxation times and hyperfine coupling constants. Finally, radical models previously suggested in the literature are convincingly refuted by means of quantum chemical density functional theory calculations.     

Soret and Dufour aspect of viscoelastic fluid due to moving cylinder with viscous dissipation and convective boundary conditions

Owing to contribution of thermo-diffusion phenomenon in various engineering and industrial frame works, scientists have presented some exclusive investigations on this topic. In current research, the thermos-diffusion prospective of second grade material accounted by a moving cylinder have been predicted. The applications of Soret and Dufour effects based on the thermos-diffusion phenomenon is evaluated. The magnetic force and viscous dissipation effects are presented for the current flow model. Additionally, the improvement in thermal transport of viscoelastic fluid is suggested with radiative phenomenon. The convective boundary constraints are used to report the thermos-diffusion phenomenon. The system based on dimensionless form is obtained with interaction of new variables. The shooting technique is used for numerical observations by using MATLAB software. The physical impact of phenomenon in view of parameters is graphically attributed. It has been noted that increasing velocity profile is results due to curvature parameter and viscoelastic parameter. The enhancement in thermal profile is noted due to Dufour number and Eckert number.     

Reduction of Platinum(IV) Prodrug Hemoglobin Nanoparticles with Deeply Penetrating Ultrasound Radiation for Tumor-Targeted Therapeutically Enhanced Anticancer Therapy

The development of Pt^IV prodrugs that are reduced into the therapeutically active Pt^II species within the tumor microenvironment has received much research interest. In order to provide spatial and temporal control over the treatment, there is a high demand for the development of compounds that could be selectively activated upon irradiation. Despite recent progress, the majority of Pt^IV complexes are excited with ultraviolet or blue light, limiting the use of such compounds to superficial application. To overcome this limitation, herein, the first example of Pt^IV prodrug nanoparticles that could be reduced with deeply penetrating ultrasound radiation is reported, enabling the treatment of deep-seated or large tumors. The nanoparticles were found to selectively accumulate inside a mouse colon carcinoma tumor upon intravenous injection and were able to eradicate the tumor upon exposure to ultrasound radiation.