Radiation resistance

Strain engineering based on either a global approach using high-mobility substrates or the implementation of so-called processing-induced stressors has become common practice for 90 nm and below CMOS technologies. Although the main goal is to improve the performance by increasing the drive current, other electrical parameters such as the threshold voltage, the multiplication current, the low frequency noise and the gate oxide quality in general may be influenced. This paper reviews the impact of different global and local strain engineering techniques on the gate stack quality and its reliability, including hot carrier performance, negative bias temperature instabilities, time dependent dielectric breakdown and radiation hardness. Recent insights will be discussed and the influence of different strain engineering approaches illustrated.

Cancer stem cells (CSCs) refer to a subset of tumor cells with the potential to self-renew and differentiate into different cancer subtypes, including leukemias and solid tumors. Dysregulated gene expression and alteration of critical signaling pathways have been observed in CSCs, compared to low-tumorigenic bulk tumor cells. CSCs are thought to be responsible for tumor onset, self-renewal/maintenance, recurrence, distant metastasis, angiogenesis, and drug/radiation resistance. In recent years, CSCs have attracted a great deal of attention due to the remarkable potential for the development of specific therapies targeting CSCs and the identification of key molecules that play a critical role in controlling the unique features of CSC-enriched populations. During the last several years, a tremendous amount of work has been done on developing new drugs and therapeutic products, such as small molecule inhibitors, antibodies, and
small interfering RNAs (siRNAs). These CSC-targeting agents selectively inhibit key components of various intrinsic signaling
pathways or specific cell surface markers of CSCs. Many novel therapeutic agents and new molecular targeting compounds have been tested, some of which are currently under investigation in preclinical and clinical trials. In this review
article, we provide an overview of the current status of the CSC hypothesis and discuss the various critical signaling pathways and specific cell surface markers involved in the development and maintenance of CSC populations. In addition, we also review various patents and CSC-targeting therapeutic strategies that may eventually lead to eradication of both bulk tumor cells and CSCs.

The conversion efficiency of InGaP/(In)GaAs/Ge -based multijunction solar cells has been improved up to 29-30% (AM0) and 31-32% (AM1Á5G) by technologies, such as double-hetero wide band-gap tunnel junctions, combination with Ge bottom cell with the InGaP first hetero-growth layer, and precise lattice-matching to Ge substrate by adding 1% indium to the conventional GaAs lattice-match structure. Employing a 1Á95 eV AlInGaP top cell should improve efficiency further. For space use, radiation resistance has been improved by technologies such as introducing of an electric field in the base layer of the lowest-resistance middle cell, and EOL current matching of sub-cells to the highest-resistance top cell. A grid structure and cell size have been designed for concentrator applications in order to reduce the energy loss due to series resistance, and 38% (AM1Á5G, 100-500 suns) efficiency has been demonstrated. Furthermore, thin-film structure which is InGaP/GaAs dual junction cell on metal film has been newly developed. The thin-film cell demonstrated high flexibility, lightweight, high efficiency of over 25% (AM0) and high radiation resistance.

This paper introduces a modified enhanced transmission-line theory to account for higher-order modes while using a standard transmission line equation solver or equivalently a Baum, Liu and Tesche (BLT) equation solver. The complex per-unit-length parameters as defined by Nitsch et al. are first cast into an appropriate per-unit-length resistance, inductance, capacitance and conductance (RLCG) form. Besides, these per-unit-length parameters are modified to account for radiation losses with reasonable approximations. This modification is introduced by an additional per-unit-length resistance. The reason and explanations for this parameter are provided. Results obtained with this new formalism are comparable to those obtained using an electromagnetic full-wave solver, thus extending the capability of conventional transmission line solvers.

Electron microscopic studies of polymers are limited due to beam damage. Two concerns are the damage mechanism in a particular material, and the maximum dose for a material before damage effects are observed. From the knowledge of the dose required for damage to the ...

An accurate radiation degradation model, based on measured radiation damages to devices and physical principles on radiation-induced defects in Si, has been established to improve the radiation-resistance of the Czochralski (CZ)grown and floating-zone (FZ)-grown single-crystal Si space solar cells. We have successfully carried out the optimization of radiation-resistant Si space solar cells by taking into account the effective base carrier concentration dependence of the most important analytical parameters, damage coefficient KL KL KL for the minority-carrier diffusion length and carrier removal rate RC RC RC for majority-carrier. The model can be used to adequately predict the radiation degradation of the Si solar cells irradiated with a complete spectrum of electrons fluence. It has been established that the radiation-resistance of the silicon solar cell is very dependent on effective carrier concentration under high fluence range and irradiation tolerance can be improved further by varying the base carrier concentration upon irradiation.

In this work, several "anti-rads" (highly conjugated aromatic compounds) were added to a commercial silicone sealant films as external radiation protective agents. This work introduces the use of protective agents against gamma radiation effects in silicone sealants. The "anti-rad" materials inhibit crosslinking that results upon exposure to gamma radiation.

Laser-produced plasmas (LPP) are laboratory-scale, table-top and high-brightness sources of partially coherent radiation that can be tuned between the extreme ultraviolet and the hard X-rays. A few LPP emission wavelengths find important applications in bio-photonics. As an example, LPP emitting in the so called “water window” (spectral range λ= 4.4 nm – 2.3 nm) allowed the world first X-ray scanning microscopy and contact microscopy, the latter being able to perform in vivo molecules imaging with 50-nm spatial resolution.

The safety of irradiated pork packed in 25% C02:75% N2 and stored at abuse temperature (10 or 15OC) was assessed by inoculation studies involving Salmonella typhimuriurn, Listeria monocyiogenes, Escherichia coli, Yersinia enterocolitica and Clostridium perfringens. Irradiation to a dose of 1.75 kGy reduced pathogen numbers to below the detection limit of lo2 cells g-'. When higher inoculum levels were used (lo6 cells g-') irradiation at 1.75 kGy reduced pathogen numbers by 1 -> 5 loglo cycles depending on strain. Clostridium perfringens was the most resistant, and Y. enterocolitica the most sensitive of the pathogens studied.

Matrix glass composition for a possible immobilization of radioactive waste is selected. Borosilicate glass is low-alkali and relatively low-melting. It has a sufficiently high initial chemical resistance. To improve radiation chemical resistance was used such additives: oxides of cerium, iron, and manganese. After irradiation by quantum's (Co 60 ) with high-dose exposure, samples were tested for chemical resistance against water action. Experiments demonstrated the effectiveness of such additives.

Low tissue oxygen concentration has been shown to be important in the response of human tumors to radiation therapy, chemotherapy and other treatment modalities. Hypoxia is also known to be a prognostic indicator, as hypoxic human tumors are more biologically aggressive and are more likely to recur locally and metastasize. Herein, we discuss and summarize the various methods under investigation to directly or indirectly measure tissue oxygen in vivo. Secondly, we consider the advantages and disadvantages of each of these techniques. These considerations are made in light of our specific hypotheses that hypoxia should be measured as a continuum, not a binary measurement and that moderate, not severe hypoxia is of great biological consequence. q

Malignant pleural mesothelioma is an asbestos-related multi-resistant tumour with increasing incidence worldwide. Well-characterized snap-frozen normal parietal, visceral pleura and mesothelioma samples were analysed with Affymetrix Human Genome U133 Plus 2.0 GeneChip oligoarray of 38 500 genes. We discovered a close relation between gene profile and resistance towards topoisomerase poisons, alkylating agents, antitubulines, antifolates, platinum compounds and radiation therapy. Target genes of chemo-(e.g. TOP2A, BIRC5/Survivin and proteasome) and radiotherapy (e.g. BRCA2, FANCA, FANCD2, CCNB1 and RAD50) were significantly overexpressed. The Fanconi anemia/BRCA2 pathway, responsible for homologous recombination DNA repair appears as a key pathway in both chemo-and radio-resistance of mesothelioma. Leukocyte trans-endothelial migration gene down-regulation could partly explain resistance against immunological therapies. Gene expression features found in other resistant cancer types related to DNA repair and replication are shared by mesothelioma and could represent general features of tumour resistance. Targeted suppression of some of those key genes and pathways combined with chemotherapy or radiation could improve the outcome of mesothelioma therapy. We propose CHEK1, RAD21, FANCD2 and RAN as new co-targets for mesothelioma treatment. The pro-angiogenic AGGF1 mRNA and protein was highly overexpressed in all tumours and may serve as a target for anti-angiogenic treatment. Overexpression of NQO1 may render mesothelioma sensitive to the novel compound beta-Lapachone.

The radiation impedance of a capacitive micromachined ultrasonic transducer (cMUT) with a circular membrane is calculated analytically using its velocity profile for the frequencies up to its parallel resonance frequency for both the immersion and the airborne applications. The results are verified by finite element simulations. The work is extended to calculate the radiation impedance of an array of cMUT cells positioned in a hexagonal pattern. A higher radiation resistance improves the bandwidth as well as the efficiency of the cMUT. The radiation resistance is determined to be a strong function of the cell spacing. It is shown that a center-to-center cell spacing of 1.25 wavelengths maximizes the radiation resistance, if the membranes are not too thin. It is also found that excitation of nonsymmetric modes may reduce the radiation resistance in immersion applications.

Glioblastoma multiforme (GBM) is a highly invasive primary brain tumour that has poor prognosis despite aggressive treatment. A hallmark of these tumours is diffuse invasion into the surrounding brain, necessitating a multi-modal treatment approach, including surgery, radiation and chemotherapy. We have previously demonstrated the ability of our model to predict radiographic response immediately following radiation therapy in individual GBM patients using a simplified geometry of the brain and theoretical radiation dose. Using only two pre-treatment magnetic resonance imaging scans, we calculate net rates of proliferation and invasion as well as radiation sensitivity for a patient's disease. Here, we present the application of our clinically targeted modelling approach to a single glioblastoma patient as a demonstration of our method. We apply our model in the full three-dimensional architecture of the brain to quantify the effects of regional resistance to radiation owing to hy...

The effect of combining low-dose irradiation (1.75 kGy) with modified atmosphere packaging (MAP) on the microbiological and sensory quality of pork chops stored at refrigeration temperatures was studied. The microflora of irradiated MAP pork was almost exclusively composed of lactic acid bacteria, predominantly Lactobacillus spp. Modified atmospheres containing either 25 or 50% CO2, balance N2, resulted in the best microbial control in irradiated pork held at 4°C, compared to an unirradiated MAP control, and these atmospheres were subsequently used in sensory studies. The atmosphere containing 25% CO2 75% N2 maintained the uncooked colour and odour of irradiated pork chops more effectively than 50% CO2 50% N2. Therefore packaging in a modified atmosphere containing 25% CO2, balance N2, followed by irradiation to a dose of 1.75 kGy is recommended to improve the microbiological and sensory quality of pork chops.

The safety of irradiated pork packed in 25% CO2:75% N2 and stored at abuse temperature (10 or 15°C) was assessed by inoculation studies involving Salmonella typhimurium, Listeria monocytogenes, Escherichia coli, Yersinia enterocolitica and Clostridium perfringens. Irradiation to a dose of 1.75 kGy reduced pathogen numbers to below the detection limit of 102 cells g-1. When higher inoculum levels were used (106 cells g-1) irradiation at 1.75 kGy reduced pathogen numbers by 1 –>5 log10 cycles depending on strain. Clostridium perfringens was the most resistant, and Y. enterocolitica the most sensitive of the pathogens studied.In all cases when high numbers (106 to 107g-1) of spoilage and/or pathogenic bacteria were present initially on the pork the meat appeared spoiled, and although irradiation reduced the number of microorganisms, the meat was still unacceptable from a sensory viewpoint after treatment.It was concluded that the microbiological safety of irradiated, modified atmosp...

The Schizosaccharomycespombe radl gene consists of three exons and the cDNA sequence is partially homologous to the Ustilago maydis RECl cDNA (Nucleotide SUMMARY We show that the radl gene of Schizosaccharomyces pombe is comprised of three exons and encodes a protein of 37 kDa. A cDNA clone containing these three exons complements the sensitivity of the radl-1 mutant to ultraviolet and y-radiation and to hydroxyurea. The newly identified ORF of the radl gene was found to exhibit partial homology to the RECl gene of Ustilago maydis. These two genes share putative functional similarities in their respective organisms.

Dispersoid strengthening is particularly important for ferritic based structural components used in nuclear applications due to their superior radiation resistance and creep strength at high temperatures. Within nuclear technologies yttrium particles dispersed throughout the matrix are the most promising ferritic steels to achieve these improved materials properties by acting as obstacles to dislocation motion. Due to radiation damage in these alloys considerable production of helium bubbles can be observed. Their amalgamation into large structures can be detrimental to the material's lifetime and it is therefore important to understand how their interaction with other defects can be controlled and what effect their presence has. Increased computational power now allows the direct study of such dislocation-obstacle interactions using 3D Discrete Dislocation Dynamics simulations at the mesoscale. In this work the effect of helium bubbles in irradiated dispersion strengthened ferritic steels and the response of the critical resolved shear stress is studied and found to increase with the density of helium bubbles.

In the silicon-on-insulator four-gate transistors (G 4 -FETs), the conducting channel can be surrounded by depletion regions induced by independent vertical metal-oxidesemiconductor gates and lateral JFET gates. This unique conduction mechanism named depletion-all-around (DAA) enables majority carriers to flow in the volume of the silicon film far from the silicon/oxide interfaces. Especially when the interfaces are driven to inversion, the control of the lateral JFET gates on the conduction is maximized, while the sensitivity of the volume channel to the oxide and interface defects is minimized. This leads to excellent analog performance, low noise, and reduced sensitivity to ionizing radiation. The G 4 -FET properties in DAA mode are presented from multiple perspectives: experimental results, 3-D device simulations, and analytical modeling.

An accurate radiation degradation model, based on measured radiation damages to devices and physical principles on radiation-induced defects in Si, has been established to improve the radiation-resistance of the Czochralski (CZ)grown and floating-zone (FZ)-grown single-crystal Si space solar cells. We have successfully carried out the optimization of radiation-resistant Si space solar cells by taking into account the effective base carrier concentration dependence of the most important analytical parameters, damage coefficient KL KL KL for the minority-carrier diffusion length and carrier removal rate RC RC RC for majority-carrier. The model can be used to adequately predict the radiation degradation of the Si solar cells irradiated with a complete spectrum of electrons fluence. It has been established that the radiation-resistance of the silicon solar cell is very dependent on effective carrier concentration under high fluence range and irradiation tolerance can be improved further by varying the base carrier concentration upon irradiation.

This paper describes various reliability concerns of the newly developed INGRID detector. This radiation detector is fabricated by waferscale CMOS post-processing; fresh detectors show excellent performance. Since the microsystems will be used unpackaged they are susceptible to all kinds of environmental conditions. The device passed tests of micro-ESD, radiation hardness, dielectric strength; but humidity tests show one weakness of SU-8 as a structural material. Already after 1 day of exposure to a humid condition the structural integrity, as measured by a shear stress test, is dramatically lowered. Dry storage of these devices is therefore a necessity. KMPR photoresist shows promising results as an alternative structural material.

A novel method of using artificial neural networks (ANNS) for the calculation of the radiation resistance of a coax-fed rectangular microstrip antenna is presented in this Letter. The network is trained with the results of three different antennas and tested for the fourth antenna. The tested results are in very good agreement. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 51–53, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10370

Dispersoid strengthening is particularly important for ferritic based structural components used in nuclear applications due to their superior radiation resistance and creep strength at high temperatures. Within nuclear technologies yttrium particles dispersed throughout the matrix are the most promising ferritic steels to achieve these improved materials properties by acting as obstacles to dislocation motion. Due to radiation damage in these alloys considerable production of helium bubbles can be observed. Their amalgamation into large structures can be detrimental to the material's lifetime and it is therefore important to understand how their interaction with other defects can be controlled and what effect their presence has. Increased computational power now allows the direct study of such dislocation-obstacle interactions using 3D Discrete Dislocation Dynamics simulations at the mesoscale. In this work the effect of helium bubbles in irradiated dispersion strengthened ferritic steels and the response of the critical resolved shear stress is studied and found to increase with the density of helium bubbles.

Cell lines derived from human prostate cancer are regarded as relatively resistant to both radiation-induced clonogenic death and apoptosis. Here we attempted to modulate the response of LNCaP prostate cancer cells to radiation therapy (XRT) by pretreatment with 12-O-tetradecanoylphorbol acetate (TPA), a known apoptogenic agent in LNCaP cells. Using plateau-phase cultures, we investigated the response of these cells to XRT, TPA, and a combination of XRT and TPA. LNCaP irradiation did not result in ceramide generation or apoptosis. However, pretreatment with TPA enabled XRT to generate ceramide via activation of the enzyme ceramide synthase and signal apoptosis. Apoptosis was abrogated by the competitive inhibitor of ceramide synthase, fumonisin B1. Furthermore, when transplanted orthotopically into the prostate of nude mice, LNCaP cells produced tumors that recapitulated the responses of LNCaP cells in vitro. XRT or TPA failed to signal apoptosis in LNCaP tumors, whereas a combinati...

Radiation hardness is tested for 4H-SiC n-p-n bipolar junction transistors designed for 1200-V breakdown voltage by implanting MeV protons and carbon ions at different doses and energies. The current gain is found to be a very sensitive parameter, and a fluence as low as 1 × 10 7 cm −2 of 10 MeV 12 C can be clearly detected in the forward-output characteristics, I C (V CE ). At this low dose, no influence of ion radiation is seen in the open-collector characteristics, I B (V EB ), or the reverse bias leakage and breakdown properties. Moreover, by annealing the implanted devices at 420 • C for 30 min, a complete recovery of the electrical characteristics is accomplished.

RLIP76 is a stress-responsive membrane protein implicated in the regulation of multiple cellular signaling pathways. It represents the predominant glutathione-conjugate (GS-E) transporter in cells. We have shown that RLIP76 plays a crucial role in defending cancer cells from radiation and chemotherapeutic toxin-mediated apoptosis, and that its inhibition by antibodies or depletion by siRNA or antisense causes apoptosis in a number of cancer cell types. We demonstrated for the first time that the striking anti-neoplastic effects with no evident toxicity in terms of either weight loss or metabolic effects are also demonstrable for the antibody, antisense and siRNA in a renal cell xenografts model of Caki-2 cells (Singhal et al., Cancer Res., 2009, 69: 4244). Present studies were performed to determine if RLIP76 targeting is more broadly applicable in other kidney cancer cell lines, to compare the signaling effects of RLIP76 antisense with kinase inhibitors used in treatment of renal cell carcinoma, and to determine whether kinase inhibitors were substrates for transport by RLIP76. Results of these studies show that sorafenib as well as sunitinib are substrates for transport by RLIP76 thus are competitive inhibitors of GS-E transport. Furthermore, kinase inhibition in the ERK as well as PI3K pathways by RLIP76 depletion is more profound and consistent and is more widely apparent in a number of renal carcinoma cell lines. These studies offer strong support for our overall hypothesis that RLIP76 is an overarching anti-apoptosis mechanism that, if inhibited, can be more broadly effective in the treatment of renal cell carcinoma.

Germination and outgrowth are critical steps for returning Bacillus subtilis spores to life. However, oxidative stress due to full hydration of the spore core during germination and activation of metabolism in spore outgrowth may generate oxidative DNA damage that in many species is processed by apurinic/apyrimidinic (AP) endonucleases. B. subtilis spores possess two AP endonucleases, Nfo and ExoA; the outgrowth of spores lacking both of these enzymes was slowed, and the spores had an elevated mutation frequency, suggesting that these enzymes repair DNA lesions induced by oxidative stress during spore germination and outgrowth. Addition of H 2 O 2 also slowed the outgrowth of nfo exoA spores and increased the mutation frequency, and nfo and exoA mutations slowed the outgrowth of spores deficient in either RecA, nucleotide excision repair (NER), or the DNA-protective ␣/␤-type small acid-soluble spore proteins (SASP). These results suggest that ␣/␤-type SASP protect DNA of germinating spores against damage that can be repaired by Nfo and ExoA, which is generated either spontaneously or promoted by addition of H 2 O 2 . The contribution of RecA and Nfo/ExoA was similar to but greater than that of NER in repair of DNA damage generated during spore germination and outgrowth. However, nfo and exoA mutations increased the spontaneous mutation frequencies of outgrown spores lacking uvrA or recA to about the same extent, suggesting that DNA lesions generated during spore germination and outgrowth are processed by Nfo/ExoA in combination with NER and/or RecA. These results suggest that Nfo/ExoA, RecA, the NER system, and ␣/␤-type SASP all contribute to the repair of and/or protection against oxidative damage of DNA in germinating and outgrowing spores.

RLIP76 is a stress-responsive membrane protein implicated in the regulation of multiple cellular signaling pathways. It represents the predominant glutathione-conjugate (GS-E) transporter in cells. We have shown that RLIP76 plays a crucial role in defending cancer cells from radiation and chemotherapeutic toxin-mediated apoptosis, and that its inhibition by antibodies or depletion by siRNA or antisense causes apoptosis in a number of cancer cell types. We demonstrated for the first time that the striking anti-neoplastic effects with no evident toxicity in terms of either weight loss or metabolic effects are also demonstrable for the antibody, antisense and siRNA in a renal cell xenografts model of Caki-2 cells (Singhal et al., Cancer Res., 2009, 69: 4244). Present studies were performed to determine if RLIP76 targeting is more broadly applicable in other kidney cancer cell lines, to compare the signaling effects of RLIP76 antisense with kinase inhibitors used in treatment of renal cell carcinoma, and to determine whether kinase inhibitors were substrates for transport by RLIP76. Results of these studies show that sorafenib as well as sunitinib are substrates for transport by RLIP76 thus are competitive inhibitors of GS-E transport. Furthermore, kinase inhibition in the ERK as well as PI3K pathways by RLIP76 depletion is more profound and consistent and is more widely apparent in a number of renal carcinoma cell lines. These studies offer strong support for our overall hypothesis that RLIP76 is an overarching anti-apoptosis mechanism that, if inhibited, can be more broadly effective in the treatment of renal cell carcinoma.

Updated information and services can be found at: These include: REFERENCES http://jb.asm.org/content/190/6/2031#ref-list-1 at: This article cites 34 articles, 17 of which can be accessed free CONTENT ALERTS more» articles cite this article), Receive: RSS Feeds, eTOCs, free email alerts (when new http://journals.asm.org/site/misc/reprints.xhtml Information about commercial reprint orders:

The radiation impedance of a capacitive micromachined ultrasonic transducer (cMUT) with a circular membrane is calculated analytically using its velocity profile for the frequencies up to its parallel resonance frequency for both the immersion and the airborne applications. The results are verified by finite element simulations. The work is extended to calculate the radiation impedance of an array of cMUT cells positioned in a hexagonal pattern. A higher radiation resistance improves the bandwidth as well as the efficiency of the cMUT. The radiation resistance is determined to be a strong function of the cell spacing. It is shown that a center-to-center cell spacing of 1.25 wavelengths maximizes the radiation resistance, if the membranes are not too thin. It is also found that excitation of nonsymmetric modes may reduce the radiation resistance in immersion applications.

A new theoretical model is presented in which the radiation-induced zero-resistance states and resistivity oscillations are analyzed. The basis of our model is an exact solution for the harmonic oscillator wave function in the presence of radiation and a perturbation treatment for elastic scattering due to randomly distributed charged impurities. Following this model most experimental results are reproduced: zero-resistance states, resistivity oscillations and the dependence of resistivity with temperature, where a physical model of interaction with acoustic phonon is presented, and an activation energy is calculated.

Radiation hardness is tested for 4H-SiC n-p-n bipo- lar junction transistors designed for 1200-V breakdown voltage by implanting MeV protons and carbon ions at different doses and energies. The current gain is found to be a very sensitive parameter, and a fluence as low as 1 × 107 cm−2 of 10 MeV 12C can be clearly detected in the forward-output characteristics, IC (VCE). At this low dose, no influence of ion radiation is seen in the open-collector characteristics, IB (VEB), or the reverse bias leakage and breakdown properties. Moreover, by annealing the implanted devices at 420 ◦C for 30 min, a complete recovery of the electrical characteristics is accomplished.

The goal of this study was to develop an assay that makes possible the assessment of the glioma cell response to single-fraction high-dose Gamma Knife surgery. In this assay, the isolation of radioresistant cell subpopulations facilitates mechanistic studies of radioresistance. Methods. A tissue-equivalent paraffin phantom with an aperture capable of holding an Opticell cell culture cassette was developed for treatment with the Leksell Gamma Knife model C. A second apparatus, which the authors also created, uses the manufacturer-supplied polystyrene phantom, thereby allowing this assay to be performed in the Leksell Gamma Knife Perfexion. After treatment, the cells were morphologically assessed to determine their response to radiation treatment. Two specific parameters were used to determine radiosensitivity: 1) the diameter of the clearing zone, defined as the central region of cell death; and 2) the number of surviving colonies within this central high-dose clearing zone. Results. Radioresistance was compared in 2 different cell lines from glioblastomas. The first cell line, ME, was established from a primary tumor before its treatment, and the second cell line, DIV, was established from a tumor that recurred after treatment with chemotherapy and fractionated radiotherapy. The ME cell line had the most robust response to radiosurgery, as characterized by a consistently larger clearing zone (28.33 ± 1.1 mm). In contrast, the clearing zone produced when the DIV cell line was used was 24.0 ± 1 mm, indicating an approximate response difference of 5 Gy. The mean number of surviving colonies within the clearing zone for the ME cell line was 1.33 ± 1 compared with that for the DIV cell line, which was 66.67 ± 2. Conclusions. The authors developed a biological dosimeter to model the response of cells from glioblastomas to single-fraction high-dose radiation. This system also allows the identification and isolation of radioresistant cells.

The radiation resistances of electrically small antennas are precisely measured on the basis of the Wheeler cap method, reducing drift error, which is due to thermal fluctuation of components of a network analyser, by using a double-stub tuner. For the first time in antenna measurements, quantitative consideration of the reduction or the drift error for the network analyser is conductcd. Also, time fluctuation of the drift error is characterised with a vector diagram to find an effective method for the drift error reduction. As a result, the ineasuremcnt precision of the antenna with a very large input reactance (niore than 18OQ in its absolute value) is considerably improved using the stub tuner.