Redistribution of o-Ps in Porous Vycor Glass. Crystallization of Silica at High Temperatures

The positron annihilation lifetime spectroscopy was applied to study the porous Vycor glass annealed at the temperatures between 950 and 1050 K. With increased temperature the spectra show significant decrease in o-Ps lifetime and intensity in the pores, while the rise of intensity in the small intermolecular voids is observed. Similar changes are observed as a function of annealing time at fixed temperature depending on the time and temperature of thermal treatment. They can originate from partial crystallization of the silica in the material under study

Redistribution of o-Ps in Porous Vycor Glass. Crystallization of Silica at High Temperatures

The positron annihilation lifetime spectroscopy was applied to study the porous Vycor glass annealed at the temperatures between 950 and 1050 K. With increased temperature the spectra show significant decrease in o-Ps lifetime and intensity in the pores, while the rise of intensity in the small intermolecular voids is observed. Similar changes are observed as a function of annealing time at fixed temperature depending on the time and temperature of thermal treatment. They can originate from partial crystallization of the silica in the material under study

Porosity structure in photon active glasses

Two kinds of photon active glasses were investigated using positron annihilation lifetime spectroscopy (PALS). Both kinds of glasses were prepared using a sol-gel technique, doped by complex of ruthenium tris bipyridyl chloride. Glasses differed from the initial matrix: the first one was prepared using silicon oxide while the second one - zircon oxide. The ortho-positronium (o-Ps) lifetime and intensities were determined from lifetime spectra. Different porosity structure concluded from PALS measurements was found in both cases. In the silica based glasses small free volumes (angstrom size) and pores (from 1 to 10 nm) existed in the material. On the contrary, in zirconia based glasses small intermolecular voids were produced in the structure only, independently of the way of material preparation

Analiza obrazu MRI u chorych z guzem ośrodkowego układu nerwowego : próba opracowania algorytmu postępowania

Magnetic resonance imaging study is currently the reference method for the detection and diagnosis of the central nervous system tumors. A large number of tumors, especially high-grade, has a higher water content in the cells, which results in prolongation of MRI T1 and T2 what appearance as increased signal intensity in in T2-weighted images and the reduction in T1-weighted images. MRI can be performed with administration of contrast agent, which shortens T1 and increases signal on T1-weighted sequences. This allows to identify areas of increased angiogenesis), which is the exponent of the cancer malignancy degree and its biological activity. Obtained MRI images are analyzed and evaluated by a radiologist and a clinician. Most of the time it is the "by the eye" analysis, which is based on the MRI image evaluation by the generally accepted radiological standards. However, this method is relatively inaccurate. which in turn can bring to the wrong diagnosis of the disease and implementation or even lack of implementation of appropriate treatment. More and more researches are conducted in this area, but developed methods are usually very complicated and difficult to carry out by the "layman" which is the clinician. That is why the attempt is made, to develop a simple and clear algorithm for MRI image analysis in patients with the central nervous system tumors, allowing for quick and objective evaluation of magnetic resonance imaging study.Badanie metodą rezonansu magnetycznego jest aktualnie metodą referencyjną przy wykrywaniu i diagnozowaniu nowotworów centralnego układu nerwowego. Duża część nowotworów, zwłaszcza o wysokim stopniu złośliwości, charakteryzuje się większą zawartością wody w komórkach, co w badaniu MRI skutkuje wydłużeniem T1 i T2, uwidocznionym jako nasilenie sygnału w obrazach T2-zależnych oraz jego obniżeniem w obrazach T1-zależnych. MRI można przeprowadzić z podaniem środka kontrastowego, co powoduje skrócenie czasu T1 i podniesieni

Gas Pressure Induced Porosity of CYTOP Polymer. A Positron Study

The pore formation in CYTOP polymer under high pressure of argon or nitrogen gases was investigated by positron annihilation spectroscopy. In the range 0-70 MPa, formation of large open pores was observed. After reduction of pressure to normal one, the free volumes inside the polymer structure remained enlarged. The structure of CYTOP can be restored by applying the temperature over 470 K at normal pressure

Testing the Extended Tao-Eldrup Model. Silica Gels Produced with Polymer Template

The temperature dependence of o-Ps lifetime in the pores calculated from extended Tao-Eldrup model was compared to the experimental data, collected for a set of silica gels synthesized using the polymer template technique. For the sample with average pore radii 2.0 nm rather good agreement between the model and experiment was found. For the sample with narrow pores (near 1.0 nm) the lifetime spectrum was complex. Except the range of highest temperatures the lifetimes are far from model calculations

Transplantable Melanomas in Hamsters and Gerbils as Models for Human Melanoma. Sensitization in Melanoma Radiotherapy—From Animal Models to Clinical Trials

The focus of the present review is to investigate the role of melanin in the radioprotection of melanoma and attempts to sensitize tumors to radiation by inhibiting melanogenesis. Early studies showed radical scavenging, oxygen consumption and adsorption as mechanisms of melanin radioprotection. Experimental models of melanoma in hamsters and in gerbils are described as well as their use in biochemical and radiobiological studies, including a spontaneously metastasizing ocular model. Some results from in vitro studies on the inhibition of melanogenesis are presented as well as radio-chelation therapy in experimental and clinical settings. In contrast to cutaneous melanoma, uveal melanoma is very successfully treated with radiation, both using photon and proton beams. We point out that the presence or lack of melanin pigmentation should be considered, when choosing therapeutic options, and that both the experimental and clinical data suggest that melanin could be a target for radiosensitizing melanoma cells to increase efficacy of radiotherapy against melanoma