The Physical and Clinical Aspects of Radiation Therapy in Skin Cancer and Subcutaneous Tissue Neoplasm

Cancers, malignant melanoma and sarcomas of the skin represent the most common group of malignancies in humans. The main treatment method of almost all skin cancers and subcutaneous tissue tumours is surgery, which consists of complete removal of a neoplastic lesion, with an adequate margin of healthy tissue. Radiotherapy plays an adjuvant role in this process, meaning complementing of the surgical procedure. This study compared four methods of irradiation treatment of cancer located in the skin or in subcutaneous tissues: contact brachytherapy, conventional orthovoltage therapy, electron beam conformal teleradiotherapy and IMRT dynamically shaped photonic beams conformal teleradiotherapy. In order to compare the methods and techniques of surface radiotherapy, following specific objectives were formulated. At the beginning in order to compare the scopes of the absorbed doses at different tissue depths, an analysis of parameters describing particular beams or radiation source has been performed—the curves for the absorbed-dose depth drop-offs. Doses distribution in tissue-like phantoms stimulating homogeneous cuboidal tissue block has been determined. A quality comparison of dose distribution in 2D and 3D treatment planning system for contact brachytherapy application has been made. The dose distribution for electron beam in the system has been determined. Conformal plannings for electron beam treatment, contact brachytherapy applicator treatment and 4 photon beams treatment optimized in IMRT technology have been performed. Dose distribution has been performed for the irradiated female patient within the well chest—the target included the recurrence area in the post-operative scar. The radiation therapy with X-rays has actually been completely eliminated from skin cancer and subcutaneous tissue radiotherapy by the electrons generated in linear accelerators, contact brachytherapy HDR and by high-energy photons used in conformal techniques, ex. IMRT. It is because the residual dose beyond the target is the highest for single X-ray beam. Although in brachytherapy HDR a rapid dose drop-off is observed, 5 cm from its normalization level for the target the residual radiation remains at the level of several percent. So, both X-rays beam radiation and brachytherapy in skin cancer treatment is connected with the administration of the dose with a high gradient in the health tissues. The dose distribution for photon conformal techniques IMRT or for electron radiation looks different. There with the dose normalization at the level of 90% or 85% we deal with the dose layer, the division does not exceed 15% of heterogeneity.

Numerical simulation of radio signal from extended air showers

The burst of radio emission by an extensive air shower provides a promising alternative for detecting ultra-high energy cosmic rays. We have developed an inde- pendent numerical program to simulate these radio signals. Our code is based on a microscopic treatment, with both the geosynchrotron radiation and charge included. Here we give the first presentation of our basic program and its results. When the time-domain signals for different polarizations are computed, we find that the pulses take on a bipolar pattern and the spectrum is suppressed towards the lower frequencies. We investigate how showers at different heights in the atmosphere contribute to the total signal, and examine the signal strength and distribution at sites with different elevations. We also study the signal from showers with different inclination angles and azimuth directions. In all these cases we find the charge excess effect is important.

The application of microwave remote sensing technology in rock mechanics

During the process of rock compression up to failure, the microwave radiation of rocks was observed and studied by remote sensing. The microwave radiometers for wave lengths of 8 mm, 2 cm and 10 cm were used. The experiments show that the luminance temperature of microwave radiation of rocks increases with increasing stress during loading, and that the increase speeds up just before rock failure. This phenomenon can be considered as a new precursor of rock failure. The concept of remote sensing rock mechanics (or remote sensing rock physics) advanced on the experimental basis of infrared remote sensing observation during rock failure has been enriched by these new experimental results. Its contents have been extended from infrared remote sensing to microwave remote sensing, and the prospects of applying remote sensing rock mechanics in the study of earthquake and rock burst prediction have also been broadened.

Galactic center research:manifestations of the central black hole

This review summarizes a few of the frontiers of Galactic center research that are currently the focus of considerable activity and attention. It is aimed at pro- viding a necessarily incomplete sketch of some of the timely work being done on phenomena taking place in, or originating in, the central few parsecs of the Galaxy, with particular attention to topics related to the Galactic black hole （GBH）. We have chosen to expand on the following exciting topics： 1） the characterization and the im- plications for the variability of emission from the GBH, 2） the strong evidence for a powerful X-ray flare in the Galactic center within the past few hundred years, and the likelihood that the GBH is implicated in that event, 3） the prospects for detecting the ＂shadow＂ of the GBH, 4） an overview of the current state of research on the central S-star cluster, and what has been learned from the stellar orbits within that cluster, and 5） the current hypotheses for the origin of the G2 dust cloud that is projected to make a close passage by the GBH in 2013.

Electrical and γ-ray energy spectrum response properties of PbI_2 crystal grown by physical vapor transport

Lead iodide single crystal was grown by physical vapor transport method.Two radiation detectors with different configurations were fabricated from the as-grown crystal.The electrical and y-ray response properties at room temperature of the both detectors were investigated.It is found that the dark resistivity of the detectors are respectively 3×10^（10）Ω·cm for bias electric field parallel to crystal c-axis（E//c） and 2×10~8Ω·cm for perpendicular to crystal c-axis（E⊥c）.The energy spectrum response measurement shows that both detectors were sensitive to ^（241） Am 59.5 keVγ-rays,and achieved a good energy resolution of 16.8%for the E⊥c-axis configuration detector with a full width at half maximum of 9.996 keV.