Production of Sc medical radioisotopes with proton and deuteron beams.

Proton and deuteron beams (15.3 and 6.8 MeV, respectively) extracted from the PETtrace medical cyclotron at the Radiopharmaceuticals Production and Research Centre in the University of Warsaw, Heavy Ion Laboratory, 28 MeV protons from the C30 cyclotron at the National Centre for Nuclear Research, Swierk, near Warsaw and 33 MeV protons from the ARRONAX accelerator, Nantes were used to produce and investigate the medically interesting Sc radioisotopes. Both natural and isotopically enriched CaCO3 and TiO2 targets were used (42Ca, 43Ca, 44Ca, 48Ca, 48Ti). The production efficiency and isotopic purity were determined and are reported here for the highest commercially available enrichments of the target material. The Thick Target Yield, Activities at the End of Bombardment (EOB) and the relative activities of produced impurities at EOB are reported for 43Sc, 44gSc, 44mSc and 47Sc produced with particle energies below 33 MeV.

EPR investigation of UV light effect on calcium carbonate powders with different grain sizes.

This study is based on investigation of calcium carbonate powders with different grain sizes exposed to UV light. Calcium carbonate is widely used in many branches of industry, e.g. as a filler for polymer materials; therefore, knowing its properties, among them also its reaction to UV light, is essential. Samples of powdered calcium carbonate with average grain sizes of 69 and 300 nm and 2.1, 6, 16, 25 µm were used in this investigation. Measurements were performed at room temperature using EPR X-band spectrometer, and they have shown the additional signals induced by the light from Hg lamp. The effect of annealing of the micro-grain samples was also studied. The spectra of four micro-grain samples after irradiation are similar, but there are differences between them and the other two powders, which could be related to the different sizes of their grains. Further studies based on these preliminary results may prove useful in research of photodegradation of CaCO3-filled materials, as well as helpful in increasing the accuracy of dating of archaeological and geological objects.

Photo-activated ionic gelation of alginate hydrogel: real-time rheological monitoring of the two-step crosslinking mechanism.

We examine the gelation of alginate undergoing ionic crosslinking upon ultraviolet (UV) irradiation using in situ dynamic rheology. Hydrogels are formed by combining alginate with calcium carbonate (CaCO3) particles and a photoacid generator (PAG). The PAG is photolyzed upon UV irradiation, resulting in the release of free calcium ions for ionic crosslinking. The viscous and elastic moduli during gelation are monitored as a function of the UV irradiation intensity, exposure time, alginate concentration, and the ratio between alginate and calcium carbonate. Gel time decreases as irradiation intensity increases because a larger concentration of PAG is photolyzed. Interestingly, dark curing, the continuing growth of microstructure in the absence of UV light, is observed. In some instances, the sample transitions from a solution to a gel during the dark curing phase. Additionally, when exposed to constant UV irradiation after the dark curing phase, samples reach the same plateau modulus as samples exposed to constant UV without dark curing, implying that dark curing does not affect the gelation mechanism. We believe the presence of dark curing is the result of the acidic environment persisting within the sample, allowing CaCO3 to dissociate, thereby releasing free Ca(2+) ions capable of binding with the available appropriate ionic blocks of the polymer chains. The growth of microstructure is then detected if the activation barrier has been crossed to release sufficient calcium ions. In this regard, we calculate a value of 30 J that represents the activation energy required to initiate gelation.

TEM preparation methods and influence of radiation damage on the beam sensitive CaCO3 shell of Emiliania huxleyi.

The ultrastructure of biologically formed calcium carbonate crystals like the shell of Emiliania huxleyi depends on the environmental conditions such as pH value, temperature and salinity. Therefore, they can be used as indicator for climate changes. However, for this a detailed understanding of their crystal structure and chemical composition is required. High resolution methods like transmission electron microscopy can provide those information on the nanoscale, given that sufficiently thin samples can be prepared. In our study, we developed sample preparation techniques for cross-section and plan-view investigations and studied the sample stability under electron bombardment. In addition to the biological material (Emiliania huxleyi) we also prepared mineralogical samples (Iceland spar) for comparison. High resolution transmission electron microscopy imaging, electron diffraction and electron energy-loss spectroscopy studies revealed that all prepared samples are relatively stable under electron bombardment at an acceleration voltage of 300 kV when using a parallel illumination. Above an accumulated dose of ∼10(5) e/nm2 the material--independent whether its origin is biological or geological--transformed to poly-crystalline calcium oxide.

Thermoluminescence study of X-ray and UV irradiated natural calcite and analysis of its trap and recombination level.

Thermoluminescence (TL) of natural light-orange color calcite (CaCO3) mineral in micro-grain powder form was studied at room temperature X-ray and UV irradiation under various irradiation times. TL was recorded in linear heating rate (2 K/s) from room temperature (300 K) to 523 K. Trapping parameters such as activation energy, order of kinetics, frequency factor have been evaluated by Computerized Glow Curve Deconvolution technique. Three electron trap centers had been estimated at depth 0.70, 1.30 and 1.49 eV from the conduction band. Investigation of emission spectra recorded at various temperatures showed single recombination center at depth 2.74 eV from the conduction band. Due to thermally assisted tunneling of electron and subsequent center-to-center recombination, a distinct peak of lower activation energy (0.60 eV) was observed at relatively higher temperature (~360 K) for X-ray irradiated sample. In UV excitation, there was an indication of photo-transfer phenomenon, where low TL intensity might have been observed; but due to simultaneous excitation of electrons from valence band to the trap level, TL intensity was found to increase with UV irradiation time. The results obtained within temperature range 300-523 K were explained by considering a band diagram.

Acoustic streaming enhances the Multicyclic CO2 capture of natural limestone at Ca-looping conditions.

The Ca-Looping (CaL) process, based on the multicyclic carbonation/calcination of CaO at high temperatures, is a viable technology to achieve high CO2 capture efficiencies in both precombustion and postcombustion applications. In this paper we show an experimental study on the multicyclic CO2 capture of a natural limestone in a fixed bed at CaL conditions as affected by the application of a high-intensity acoustic field. Our results indicate that sound promotes the efficiency of CO2 sorption in the fast carbonation phase by enhancing the gas-solids mass transfer. The fundamentals of the physical mechanism responsible for this effect (acoustic streaming) as well as the technical feasibility of the proposed technique allows envisaging that sonoprocessing will be beneficial to enhance multicyclic CO2 capture in large-scale applications.

Atomic modifications by synchrotron radiation at the calcite-ethanol interface.

This article reports on studies of the chemical alterations induced by synchrotron radiation at the calcite-ethanol interface, a simple model system for interfaces between minerals and more complex organic molecules containing OH groups. A combination of X-ray reflectivity and X-ray photoelectron spectroscopy of natural calcite, cleaved in distilled ethanol to obtain new clean interfaces, indicated that, during a 5 h period, the two top atomic layers of calcite, CaCO(3), transform into calcium oxide, CaO, by releasing CO(2). Also, the occupation of the first ordered layer of ethanol attached to calcite by hydrogen bonds almost doubles. Comparison between radiated and non-radiated areas of the same samples demonstrate that these effects are induced only by radiation and not caused by aging. These observations contribute to establishing a time limit for synchrotron experiments involving fluid-mineral interfaces where the polar OH group, as present in ethanol, plays a key role in their molecular structure and bonding. Also, the chemical evolution observed in the interface provides new insight into the behavior of some complex organic molecules involved in biomineralization processes.

The analysis of thermoluminescent glow peaks of natural calcite after beta irradiation.

In this study, the thermoluminescence properties of natural calcite samples were examined in detail. The glow curve of the sample irradiated with beta radiation shows two main peaks, P1 (at 115 °C) and P4 (at 254 °C). The additive dose, variable heating rate, computer glow curve deconvolution, peak shape and three point methods have been used to evaluate the trapping parameters, namely the order of kinetics (b), activation energy (E) and the frequency factor (s) associated with the dosimetric thermoluminescent glow peaks (P1 and P4) of natural calcite after different dose levels with beta irradiation.

Cellular compatibility of a gamma-irradiated modified siloxane-poly(lactic acid)-calcium carbonate hybrid membrane for guided bone regeneration.

A bi-layered silicon-releasable membrane consisting of a siloxane-poly(lactic acid) (PLA)-vaterite hybrid material (Si-PVH) microfiber mesh and a PLA microfiber mesh has been developed by an electrospinning method for guided bone regeneration (GBR) application. The bi-layered membrane was modified to a three-laminar structure by sandwiching an additional PLA microfiber mesh between the Si-PVH and PLA microfiber meshes (Si-PVH/PLA membrane). In this study, the influence of gamma irradiation, used for sterilization, on biological properties of the Si-PVH/PLA membrane was evaluated with osteoblasts and fibroblasts. After gamma irradiation, while the average molecular weight of the Si-PVH/PLA membrane decreased, the Si-PVH/PLA membrane promoted cell proliferation and differentiation (alkaline phosphatase activity and calcification) of osteoblasts, compared with the poly(lactide-co-glycolide) membrane. These results suggest that the gamma-irradiated Si-PVH/PLA membrane is biocompatible with both fibroblasts and osteoblasts, and may have an application for GBR.

Ultrasonic reactivation of phosphonate poisoned calcite during crystal growth.

The effect of ultrasonic irradiation (42,150 Hz, 17 W dm(-3)/7.1 W cm(-2)) on the growth of calcite in the presence of the inhibitor nitrilotris(methylene phosphonic acid) (NTMP) was investigated at constant composition conditions. In seeded growth experiments, it was found that the inhibiting effect of NTMP on crystal growth could be seriously mitigated under influence of ultrasonic irradiation. An approximately twofold increase in volumetric growth rate was achieved during ultrasonic irradiation, and recovery of the growth rate following inhibition was strongly enhanced compared to growth experiments without ultrasonic irradiation. The results could be explained in part by the physical effect of ultrasound that causes breakage and attrition of poisoned crystals, which resulted in an increase in fresh surface area. Mass spectroscopy analysis of sonicated NTMP solutions revealed that there is also a chemical effect of ultrasound that plays an important role. Several breakdown products were identified, which showed that ultrasound caused the progressive loss of phosphonate groups from NTMP, probably by means of physicochemically generated free radicals and/or pyrolysis in the hot bubble-bulk interface.

Radioactivity and dose assessment of marble samples from Igbeti mines, Nigeria.

The concentration and distribution of natural radionuclides in marble around Igbeti marble mines, Nigeria, were measured to evaluate the environmental radioactivity and health effects which the marble samples may posses. The concentration of radionuclides was determined using gamma-ray spectrometry with NaI (Tl) detector. The measured values of the activities of (226)Ra, (232)Th and (40)K in the marble samples were found to lie in the ranges 2.0-2.7, 0.3-1.2 and 5.7-7.3 Bq kg(-1), respectively. The samples were also found to have radium equivalent activity in the range 3.4-4.6 Bq kg(-1), external hazard indices of 0.009-0.012 and internal hazard indices of 0.014-0.019. The estimated representative (I(gammar)) hazard index is 0.028. The measurements show that marble samples from Igbeti mine have low level of natural radioactivity and therefore the use of these types of marble in construction of dwellings is safe for inhabitants.

Damage creation in swift heavy ion-irradiated calcite single crystals: Raman and infrared study.

Raman and Infrared studies were carried out on pristine and 100 MeV Ag(8+) ion irradiated calcite single crystals in the fluence range 1 x 10(11) to 1 x 10(13)ions/cm(2). Raman and Infrared modes were assigned according to factor theory analysis. It is observed that the intensities of the Raman and infrared bands decrease with increase of ion fluence. The decrease of these bands is attributed to breakage of carbonate ions and other details are discussed.

The laser-induced discoloration of stonework; a comparative study on its origins and remedies.

For understanding the phenomena associated with the discoloration observed in some cases of infrared laser cleaned stonework surfaces, a comparative study of three different types and morphologies of pollution encrustation and stone substrates was undertaken. Fragments originating from monuments with historic and/or artistic value, bearing homogeneous thin soiling on Pentelic marble (Athens, Greece), thick encrustation on Hontoria limestone (Burgos, Spain) and compact thin crust on gypsum decorations (Athens, Greece), have been studied on the basis of their composition and origin, together with the conditions that may induce yellowing effects upon their laser cleaning with IR wavelengths. While irradiation in the UV (i.e. at 355 nm) could not effectively remove the encrustations studied, irradiation at 1,064 nm was found efficient to remove all the studied pollution accumulations. Discoloration towards yellow was evident in all cases and at different levels, including the samples with intentional patination layer. To the limit of Raman detection no chemical alterations were detected on the irradiated areas while the presence of yellow polar compounds in all the pollution crusts studied supports the argument that the discoloration of the stone surfaces upon their IR irradiation may be due to the uncovering of existing yellow layers as result of the migration of these compounds inwards to the original stone surface. To correct and/or prevent such undesired coloration the use of IR and UV radiation both in sequential and synchronous mode was considered, with positive results.

The photochemical stability of carbonates on Mars.

Carbonates, predominately MgCO3, have been spectroscopically identified at a level of 2-5% in martian dust. However, in spite of this observation, and a large number of climate studies that suggest 1 to several bars of CO2 should be sequestered in carbonate rocks, no outcrop-scale exposures of carbonate have been detected anywhere on Mars to date. To address one hypothesis for this long-standing puzzle, the effect of ultraviolet (UV) light on the stability of calcium carbonate in a simulated martian atmosphere was experimentally investigated. Using 13C-labeled calcite, we found no experimental evidence of the UV photodecomposition of calcium carbonate in a simulated martian atmosphere. Extrapolating the lower limit of detection of our experimental system to an upper limit of carbonate decomposition on Mars yields a quantum efficiency of 3.5 x 10(-8) molecules/photon over the wavelength interval of 190-390 nm and a maximum UV photodecomposition rate of 1.2 x 10(-13) kg m(-2) s(-1) from a calcite surface. The maximum loss of bulk calcite due to this process would be 2.5 nm year(-1) (Mars year). However, calcite is expected to be thermodynamically stable on the surface of Mars, and potential UV photodecomposition reaction mechanisms indicate that, though calcium carbonate may decompose under vacuum, it would be stable in a CO2 atmosphere. Given the expected stability of carbonate on Mars and our inability to detect carbonate decomposition, we conclude that it is unlikely that the apparent absence of extensive carbonate deposits on the martian surface is due to UV photodecomposition in the current environment.

Analysis of induced radionuclides in low-activation concrete (limestone concrete) using the 12 GeV proton synchrotron accelerator facility at KEK.

22Na is one of the long-lived radionuclides induced in shielding concrete of a beam-line tunnel of a high-energy particle accelerator facility and poses a problem of radiation wastes at the decommissioning of the facility. In order to estimate the 22Na concentration induced in shielding concrete, chemical reagents such as NaHCO3, MgO, Al203, SiO2 and CaCO3 were irradiated at several locations in the beam-line tunnel of the 12 GeV proton synchrotron accelerator at KEK, and the 22Na concentrations induced in those chemical reagents were measured. Low-activation concrete made up of limestone aggregates was also irradiated by secondary particles in the beam-line tunnel and the long-lived radionuclide, such as 22Na, concentrations induced in the concrete were measured. It was confirmed that 22Na concentrations induced in Mg, Al, Si and Ca were lower than that in Na, and that 22Na concentrations induced in the low-activation concrete was lower than those induced in ordinary concrete made up of sandstone aggregates.

Detección de los cálculos de fosfato octocálcico mediante análisis infrarrojo / Detection of octocalcium phosphate stones by infrared spectroscopy

El fosfato octocálcico presente en los cálculos urinarios es difícil de detectar a pesar de emplear la espectroscopia de Infrarrojos, ya que cuando está presente en un cálculo suele hacerlo en escasa proporción frente a otros tipos de fosfatos, lo que enmascara su detección. Por otra parte, sus frecuencias de vibración son del mismo orden que las de los carbonatos de apatita y quedan enmascarados cuando el fosfato octocálcico está presente en pequeña cantidad. Sólamente en aquellas ocasiones en que predomina en la muestra, el espectro infrarrojo revela con nitidez su presencia. En el resto de los casos, se requiere una búsqueda minuciosa (AU)

The present octocalcium phosphate in the urinary stones is difficult to detect spite the infrared spectroscopy, since when it la present in a stone usually it does it in a little proportion as opposed to other types of phosphates, which masks its detection. On the other hand, their vibration frequencies are of the same order that those of carbonates apatite and are masked when the octocalcium phosphate la present in small amount. Just in those occasions in which it predominates in the sample, the infrared spectrum clearly reveals its presence. In the rest of the cases, a meticulous search is required (AU)

Detection of free radicals in gamma-irradiated seasnail hard tissues by electron paramagnetic resonance.

Gamma-irradiated seasnail (from family of Helix lukortium) hard tissues (CaCO3) were investigated by electron paramagnetic resonance (EPR) at room temperature. The radicals produced by gamma-irradiation in seasnail were attributed to orthorhombic C*O2-, freely rotating C*O2-, orthorhombic C*O3-, axial C*O3-, and axial C*O3(3-) free radicals. Unirradiated seasnail hard tissues also feature Mn2+ ions in their EPR spectra. The hyperfine values were determined for the 13C nucleus in the orthorhombic C*O2- and axial C*O3(3-) free radicals and for the manganese impurity ions. The g values of all the free radicals have been measured. The results were compared with the literature data for similar defects.

Multifrequency EPR study of carbonate- and sulfate-derived radicals produced by radiation in shells and corallite.

Shells of two sea mollusks (Venus sp.), pearl oyster (Meleagrina vulgaris) and corallite (white coral) were exposed to ionizing radiation (gamma and X rays) and then examined by EPR spectroscopy in X, Q and W band. The resulting spectra were analyzed and the g values of the EPR lines in the multicomponent spectra were determined. The increased resolution in Q- and W-band spectra allowed us to assign the observed lines to CO(2)(-) ion radicals (isotropic and orthorhombic), SO(2)(-) isotropic, SO(3)(-) (isotropic and axial), and Mn(2+) species. The assignments were confirmed by simulations of the spectra. Practical implications for the use of Q and/or W band in low-dose quantitative EPR measurements for dating and for accidental dose estimation are discussed.

Experimental simulations of the photodecomposition of carbonates and sulphates on Mars.

There is indirect spectroscopic evidence for the presence of sulphates and carbonates on the martian surface, and such minerals are also found in SNC meteorites, which are thought to be of martian origin. But although carbonates are expected to be abundant in the martian regolith, attempts to detect them directly have been unsuccessful. Here we report laboratory studies of the decompostion of calcium carbonate and magnesium sulphate under ultraviolet irradiation, which mimic the conditions under which photodecomposition of surface minerals by solar ultraviolet light might occur on Mars. We find that, even for a low abundance of carbonate minerals in the martian regolith, the rate of CO2 release due to photodecomposition is higher than the rate of CO2 loss from the atmosphere by solar-wind-induced sputtering processes, making this process a potential net source of atmospheric CO2 over time. SO2 is also released from the sulphate, albeit more slowly. The rate of carbonate degradation is high enough to explain the apparent absence of these compounds at the martian surface.

[ESR and HPLC studies of the detection of gamma irradiation of eggs]. / ESR- und HPLC-Untersuchungen zum Nachweis der gamma-Bestrahlung bei Eiern.

Two methods for the identification of irradiated eggs are presented. Electron spin resonance (ESR) detects radiation-specific radicals in the calcite matrix of eggshells. ESR gives unequivocal results for doses clearly below the technologically relevant dose. The stability of the radical in the calcite matrix was tested over a period of 6 weeks. Products that contain no or only low amounts of fat but a high percentage of protein can be identified by HPLC. Only in the chromatograms of irradiated samples is a peak of the amino acid ortho-tyrosine present. This HPLC method may be of great interest especially for the identification of irradiated pasteurized liquid egg white.