Narrow Results

The paper presents results of studying temperature dependences of the specific volume resistance of nonirradiated and irradiated $\gamma$-rays with a different dose of $\mathrm{\text{LDPE}}+x$ vol.%TlInSe₂ composites in the temperature range 300–380 K. The technique for modifying the structure of composites with semiconductor filler was carried out on a ${}^{60}$Co-type MPX $\gamma$-25 M isotope $\gamma$-emitter at a temperature of 300 K in vacuum ampoules at doses of $0$–$10^6$ Gy. The electrical properties of the composites were studied before and after irradiation with $\gamma$-rays. Samples were prepared by mechanically mixing the filler ${\mathrm{\text{TlInSe}}}_2$ powder with a low density polyethylene powder until obtaining a uniform mixture. The mixture is kept for 5 min at the melting temperature of the polymer under a pressure of 5 MPa. At the same temperature, by pressing a homogeneous mixture, the pressure rises to 15 MPa, at this pressure the sample is held for another 5 min, and then quickly cooled in water. The specific volume resistivity of the composites was measured using a DC bridge of the P-4053 type with additional measuring electrodes. Samples before testing are aged for 24 h at a temperature of $20\pm 2^{\circ }$C and a relative humidity of $65\pm 5$%. It was revealed that with an increase in the volume content ${\mathrm{\text{TlInSe}}}_2$, the specific volume of resistivity of composites decreases. Under the action of $\gamma$-radiation and a change in the filler content, the magnitude and nature of ${\rho }_V(T)$ dependence changes, and this allows to manage the physical parameters of studied composites by varying the filler content and $\gamma$-radiation dose.

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CHINA — A Major Nanobiology Research Project is Initiated at CAS

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JAPAN — Radiation Exposure in utero and in Young Children Increases Adult Cancer Risk

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NEW ZEALAND — New Diabetes Treatment Now Available in New Zealand

NEW ZEALAND — Trans-Tasman Scientists Study Livestock Methane

PHILIPPINES — Philippines Bioethanol Capacity to Expand

SINGAPORE — Asia's First Research Center for Palliative Care Opens in Singapore

SINGAPORE — Millipore Corporation (MIL) Announces New Facility in Singapore

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SINGAPORE — NTUC Childcare Issues Health Alert Following Hong Kong Flu Outbreak

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A C-arm fluoroscopy is a useful instrument for finding out the position of a needle in a minimally invasive surgery, but its use means that the surgeon and patient are exposed to radiation while the surgeon places the C-arm into the previous position and orientation as well as he/she regularly uses it to take X-ray images. In this paper, a two-bar link system and moving mechanism added on a C-arm are proposed to reduce the dose of the exposure. The two-bar link system consists of two bar links and three absolute encoders. It measures the relative position and angle between the C-arm and the surgical table in real time and stores the measurements in the system. The moving platform of C-arm is proposed to have two switchable casters for both passive freewheeling and active motor driving. Passive freewheeling allows the C-arm to be freely moved by human force and active motor driving returns the C-arm to its original position automatically. A simple experiment is performed to verify the feasibility of C-arm repositioning using a two-bar link system.

Potential biological effects initiated by exposure to ionizing radiation are described in some detail, including the characteristics of radiation sources, radiation fields, dosimetry, and fundamental radiation protection quantities and units. Special attention is paid to exposure pathways and the risk assessment of radiation exposure to the human body in terms of relevant health risks reflecting biological effects resulting from external and internal radiation exposure. Some particulars are presented to illustrate the nature and severity of stochastic and deterministic effects caused by the exposure. The chapter then presents an overview of pertinent radiation protection requirements and monitoring methods for the evaluation of exposure of persons in regular and emergency situations, as well as the assessment of environmental radioactive contamination inflicted by releases of radioactivity from facilities where radioactive materials are used or stored, taking into account their possible damage or destruction resulting from accidents and potential terrorist attacks, sabotage, or other malevolent actions. In all these cases, discharges of radioactive substances from various sources, including those used in medicine, industry, and research facilities, should be considered to obtain reliable information about specific radiation routes. Radioactive materials, in the form of solid particulates, aerosols, and gases, disperse in several ways known as exposure pathways. It is essential that the description of both exposure pathways and their characteristics be expressed in officially recommended and generally accepted quantities and units. In general, the final part of an exposure pathway refers to how a person can come into contact with hazardous substances, including materials containing radionuclides.

Radionuclides are present in the environment or result from human activities, such as the use of radiation or nuclear technologies. The presence of radionuclides in foods can pose certain health risks, and their toxicity depends on several factors, including the intake of radionuclides, the type of radionuclide, its concentration, and the specific characteristics of the food. Under typical situations, the contributions of internal exposure to the human body from food or water, where only trace concentrations of usually natural radionuclides are present, are minor in most cases. Slightly different situations may occur when food, due to radionuclides from man-made sources used in various applications in industry and medicine or radioactivity induced during radiation sterilization of food, shows an increased level compared with the natural background concentrations. But even here, there is no reason to consider the impact on living organisms to be serious since the increase in exposure levels is only a fraction of exposure due to the natural background.

On the other hand, however, the concentration may be higher in some cases when the food is produced from plants or animals that are heavily contaminated. Specific aspects of radioactivity or, in general, ionizing radiation (hereinafter, simply, radiation), which can be detected even at particularly small levels thanks to the availability of very sensitive instrumentation, have to be stressed here. Radiation monitors are able to measure even extremely insignificant changes within the fluctuation level of natural radiation. When the instrument shows some results close to the background level or even up to several times this level, there is no need to be concerned since the impact of such exposure on a person is almost negligible in comparison with other, much more dangerous situations we face daily in our typical living or working environment caused by many other, much more hazardous agents. The chapter will present an overview of the health risks attributed to the toxicity resulting from exposure to foods contaminated by radionuclides of various origins.