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En la actualidad la Resonancia Paramagnética Electrónica (RPE) de la alanina (CH3CH(NH2)COOH) irradiada, es la base del sistema dosimétrico Alanina/RPE que se utiliza para controlar procesos de irradiación a nivel industrial y a nivel terapéutico. En este sistema dosimétrico generalmente se mide la intensidad de la línea central . del patrón de polvos de RPE de los radicales libres de alanina (el CH3 e HCOOH y posiblemente otras especies), inducidos previamente por radiaci6n ionizante, para luego relacionar esta intensidad con la dosis absorbida. El origen del patrón de polvos de RPE de la alanina irradiada, base de este sistema dosimétrico hasta ahora, sin embargo, no ha sido perfectamente interpretado. En este trabajo se analizan su estructura y su origeri. Como antecedentes se puede mencionar que, en general, se acepta que algunas de las señales de resonancia que aparecen en el espectro de RPE son debidas a . la especie de radical libre CH3 e HR (R = CO2). en donde el griJpo amino NH2 de la alanina CH3CH(NH2)R es eliminado por el efecto de la radiación (Miyagawa and Gordy, 1960, 1962 ; Morton et al., 1961 ). Por otra parte, también existen evidencias experimentales de que se pueden inducir especies secundarias de radicales libres (Brustad et al., 1964; Samskog et al., 1980 ; Kuroda et al., 1982 ; Matsuki et al., 1982 ; Cabral Prieto et al., 1994 ; Pilbrow et al., 1996; Vitaly et al., 1996) y/o defectos cristalin,:,s (Kuroda et al., 1982 ; Hófer et al., 1989 ; Nakagawa et al., 1993 ; Brustolon et al., 1994) al irradiar alanina con radiación ionizante. Un rasgo espectral adicional del patrón de polvos de RPE de l0s radicales libres de alanina son las denominadas líneas satélite, debidas a transiciones de baja probabilidad (prohibidas por la regla de selección de espin, .1m1 = ± 1) , que aparecen en el espectro (Miyagawa and Gordy, 1960 ; Hófer et al., 1989 ; Arber et al., 1991 ; Barnard et al., 1996; presente trabajo). Si bien e'5taf, líneas satélite ya fueron identificadas, a partir de su medición surge una señalización mas sistemática de ellas. La asignación de estas líneas como satélite aún, sin embargo, presenta controversias. A partir del. estudio de esas líneas satélite en este trabajo, se muestran evidencias adicionales sobre la generación de al menos cuatro especies secundarias de radicales libres al irradiar, a temperatura ambiente, muestras de alanina policristalina. Esto último, como resultado del análisis numérico de convolución y deconvolución que se realiza a los espectrcs de RPE que se observan después de tratar a los radicales de alanina con luz UV y calor. Por otra parte, cuando se analiza el efecto que tiene el sili cón (rr.aterial aglutinante que se utiliza para producir el dosímetro de alanina del LFAM c1el ININ1) sobre la generación de los radicales libres al irradiar alanina, se obtienen evidencias de que este material aglutinante (el silicón) inhibe la formación de al menos (i) una especie secundaria de radicales libres y/o (ii) de defectos cristalinos. Como parte de este trabajo y en el contexto de los datos experimentales sobre el efecto del aglutinante (silicón), el efecto de otros aglutinantes (como parafina y otros polímeros, etc.) podrá también estudiarse para ampliar el estudio de la naturaleza de los radicales libres que se inducen al irradiar muestras de ala 1ina aglutinada. Dado que la técnica de deconvolución, para aumentar la resolL:ción espectral, es una herramienta básica de este trabajo, se reporta la comp::lración entre dos métodos numéricos de deconvolución (uno aproximado y otro no aproximado), mostrando la utilidad de dichas técnicas de análisis para los casos en donde existe una gran superposición de señales espectrales. Adicionalmente a esta comparación, entre métodos de deconvolución (Cabral Prieto et al., 1991, 1993, 1994 ; Hedberg y Ehrnberg, 1968), la técnica de deconvolución es mejorada al poder eliminar señales de alta frecuencia que pueden aparecer en los espectros deconvolucionados ; esto es, como resultado del proceso numérico de deconvolución.

Purpose This case report deals with helium cold plasma as an alternative therapy for healing diabetic foot infections. Methods A surgical cleaning of neuropathic ulceration was performed before each one of three diary 0.025 Ls−1 helium plasma needle treatments with a duration in time of 180 s over the entire wound area. The distance between the output reactor and the wound surface varied between 3 and 5 mm, meanwhile the plasma dose was keept at 0.42 W/cm2. Results An 83-year-old female patient with diabetes mellitus type 2, diagnosed 25 years ago, presented with a chronic ulcer on the left foot was treated with cold plasma. It was applied as circular movements of approximately 10 mm displacement, covering an area of around 10 mm2 and continuing this procedure until completely covering the wound, trying to provide a uniform treatment over the entire surface of the wound. Conclusion The wound presented ischemia, and according to the classification DEPA had a score of 10, which implied a poor healing prognosis and even had the risk of amputation of the foot. After application of the plasma-based treatment the healing of the chronic wound was promoted due a higher proliferation of endothelial cells that are the promoters of angiogenesis.

In this work we used the Pulsed Plasma in Liquid technique to synthesize zero-valent iron nanostructures. We used a DC Power Source to produce such plasma on water and methanol. The obtained particles were characterized by TEM to determine their shape and size and Mossbauer Spectroscopy to investigate the chemical state of the iron present. We found that 80% of the particles produced in water are composed of metallic iron and when methanol is used 97% of the particles are metallic iron. Once the Fe colloid was formed, orange skin was impregnated with these nanostructures for the removal of in water solution. The Cr(VI) removal experiments were done in a batch system in the presence of the composites at an inicial concentration of 50 ppm of Cr(VI). When using the iron nanostructures supported on the orange peel, the percentage of removal is 100% in the case of nanostructures formed in water and 96% when obtained in methanol.

The degradation of methyl orange (MO) in presence of a natural zeolite from San Luis Potosi, Mexico, previously homo-ionized with Na cations (HNaZ) and impregnated with iron boride nanoparticles (HNaZ-Fe) is presented. Iron boride nanoparticles (FeB-NPs) synthesized by chemical reduction, as well as HNaZ and HNaZ-Fe materials were characterized by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX), Mossbauer and UV–vis spectroscopies. SEM and TEM measurements showed characteristic spherical shapes associated with FeB-NPs with mean diameter of 120 nm and located on the zeolite’s surface. Whereas the homo-ionized zeolitic material, HNaZ, did not present any type of interactions with MO, the HNaZ-Fe material, with a mass ratio 1:0.06 of HNaZ:Fe, respectively, mostly degraded this dye. The kinetic study showed that the degradation process of MO followed the second order kinetic reaction with a degradation rate constant of 0.0012 g/(mg h) and an 80% dye degradation was always obtained for all used concentrations of MO, which ranged from 50 up to 500 mg/L. The degradation of MO was confirmed by the presence of sulfanilic acid, as detected by UV–vis spectroscopy through the band at 248 nm.

The degradation of methyl orange (MO) dye, in the presence of pure iron nanoparticles (Fe-NPs) and supporting them in natural zeolite-type clinoptilolite (Fe-Z), were studied. The degradation tests consisted of analyzing the dependence of pH, initial concentration of MO, contact time between systems Fe-NPs ↔ MO and Fe-Z ↔ MO, and temperature, respectively. The highest degradation percentages of MO ranging from 80 to 100% occurred at pH values between 3 and 10; below 3 and above 10, relatively low degradation percentages were measured. Whereas nearly 100% of MO degradation was obtained with pure Fe-NPs for all studied MO concentrations and from 30 °C to 50 °C, for the composite Fe-Z, the degradation of MO was both MO concentration and temperature dependent with the highest degradation percentages at 50 °C. Besides, while using pure Fe-NPs the degradation of 100% of MO was reached at a contact time of 6 h at temperatures between 20 °C and 50 °C. However, when using the composite Fe-Z, the degradation percentages of MO were from 80% to 90% which was reached in 17 h, for temperatures between 15 °C and 50 °C. The resulting kinetic degradation data of MO from pure and supported Fe-NPs was analyzed by considering several empirical models, from which the temperature dependent rate constants were obtained, with best values of ~0.2 h−1at 15 °C and ~1.86 h−1at 50 °C and establishing endothermic-degradation processes. By using these rate constants and the Arrhenius relation, an activation energy (Ea) for the degradation process was determined, being for the Fe-NPs ↔ MO system slightly higher than for the Fe-Z↔ MO system.

The nanoparticles technology has received considerable attention for its potential applications in groundwater treatment for the removal of various pollutants as Cadmium. In this work, iron boride nanoparticles were synthesized in pure form and in presence of homo-ionized zeolite clinoptilolite, as support material. These materials were used for removing Cd (II) from aqueous solutions containing 10, 50, 100, 150, 200, 250, 300 and 400 mg/L. The characterization of these materials was made by using X-ray Diffraction, Scanning Electron Microscopy and Mossbauer Spectroscopy. Pure iron boride particles show a broad X-ray diffraction peak centered at 45∘ (2𝜃), inferring the presence of nanocrystals of Fe2B as identified from Mossbauer Spectroscopy. The size of these Fe2B particles was within the range of 50 and 120 nm. The maximum sorption capacities for Cd (II) of iron boride particles and supported iron boride particles in homo-ionized zeolitic material were nearly 100 %. For homo-ionized zeolite and homo-ionized zeolite plus sodium borohydride was ≥ 95 %.

Spent radioactive sources are considered a type of radioactive waste which must be stored properly. These sources are usually conditioned in concrete that functions as shield and physical barrier to prevent the potential migration of radionuclides, and must have suitable properties: mechanical, thermal or irradiation resistance. Concretes used in the conditioning of spent radioactive source in Mexico were tested, preparing concrete test specimens with Portland cement CPC 30RS EXTRA CEMEX and aggregates, and subjected to compression strength, γ-ray-irradiation and thermal resistance assays and subsequently analyzed by Mossbauer and Raman Spectroscopies as well as by Scanning Electron Microscopy, in order to correlate the radiation and temperature effects on the compressive strengths, the oxidation states of iron and the structural features of the concrete. Iron was found in the concrete in Fe 2+ and Fe 3+ in the tetrahedral (T) and two octahedral positions (O1, O2). Radiolysis of water causes the dehydratation (200-600 kGy) and rehydratation (1000-10000 kGy) of calcium silicate hydrates (C-S-H) and ferric hydrate phases in concretes and structural distortion around the iron sites in concretes. The compressive strength of concretes are not significantly affected by γ-radiation or heat.

The synthesis by co-precipitation and characterization by X-ray diffraction, Raman and Mossbauer spectroscopies of Mg-Fe-hydrotalcite compounds, and their sorption capacities for Cr(VI) in aqueous media were carried out. The average sorption capacity of Cr(VI) for the non-thermal treated samples was of 6.2 mg/g. The ferrihydrite was omnipresent in all prepared hydrotalcite samples. A brief discussion is made on the role of both the hydrotalcite and ferrihydrite for removing such amount of Cr(VI).

Nanometric magnetite (nm-Fe3O4) particles were prepared by the reverse co-precipitation synthesis method, obtaining particle sizes that ranged from 4 to 8.5 nm. In their synthesis, the concentration of iron salts of ferric nitrate, Fe(NO3)3⋅9H2O, and ferrous sulfate, FeSO4⋅7H2O, were varied relative to the chemical reaction volume and by using different surfactants such as oleic acid (OA) and hexadecyltrimethylammonium bromide (CTAB). The nm-Fe3O4 particles were characterized by transmission electron microscopy (TEM), Mossbauer spectroscopy (MS), magnetic and X-ray diffraction (XRD) measurements. Typical asymmetrical and/or broad lines shapes appeared in all Mossbauer spectra of the as prepared samples suggesting strong magnetic inter-particle interactions, reducing these interactions to some extent by gentle mechanical grinding. For the smallest particles, maghemite instead of magnetite was the main preparation product as low temperature Mossbauer and magnetic measurements indicated. For the intermediate and largest particles a mixture of magnetite and maghemite phases were produced as the saturation magnetization values of MS ∼ 60 emu/g indicated; these values were measured for most samples, independently of the coating surfactant concentration, and according to the ZFC-FC curves the blocking temperatures were 225K and 275K for the smallest and largest magnetite nanoparticles, respectively. The synthesis method was highly reproducible.

The survival of Escherichia coli bacteria and mouse glioma cells were studied under different temperatures using direct heating in water, ultrasound, and magnetic fluid hyperthermia. The survival of these microorganisms depended on whether the heating mode was continuous or discontinuous, surviving more in the former than in the discontinuous heating mode. Whereas Escherichia coli bacteria did not survive at temperatures ≥50∘C, the mouse glioma cells did not survive at temperatures ≥48∘C. The survival of both these microorganisms was independent of the presence or absence of the magnetic nanoparticles of magnetite, suggesting that these, having mean particle sizes of 9.5, 8.5 and 5, did not show any apparent cytotoxicity effect. Present results also showed that the inductive heating system which used a radiofrequency of 13.56 MHz, providing a maximum magnetic field strength of 160 A/m, the electric rather than magnetic heating predominated.

Heat induced surface changes on A533B stainless steel were followed by XRD and CXMS techniques. Whereas the XRD patterns of the studied A533B samples were characteristic of α-Fe phase only, the surface Mossbauer spectrum showed a broad sextet, being fitted with two magnetic patterns whose hyperfine magnetic fields were 33 and 31 T associated with a pure and perturbed α-Fe phase, respectively and a broad singlet with an isomer shift δ A533B = −0.115(4) mms $^{-1}/\alpha $ -Fe, characteristic of the γ-Fe phase. This singlet, probably, arising from the samples’ surface only was further analyzed by using a singlet and a quadrupole doublet. From hyperfine distribution and discrete value calculations of their corresponding hyperfine parameters, the quadrupole interaction was the most affected by thermal treatments ranging from 300° to 700 °C showing a slight decrease at 600 °C. The average values of the hyperfine parameters were δ 1 = − 0.110(6) mms $^{-1}/\alpha $ -Fe for the singlet, and δ 2 = −0.081 (6) mms $^{-1}/\alpha $ -Fe and Δ2 = 0.143(7) mm/s) for the quadrupole doublet, respectively. In spite of the temperature dependence of the quadrupole splitting on the doublet, which was higher than that of the isomer shifts of both patterns, only a single defect type was suggested, being associated with monovacancias near the 57Fe sites.

Dehydrated polycrystalline powder of LTA-type zeolite and its pellets, prepared from 7.86 × 10 −2 to 1.5728 GPa, were studied by XRD, SEM, BET and PALS. Crystal size, texture and changes in the inter-particle pellet volume were observed from XRD and SEM results, respectively, as the pellet pressure increased. Positron lifetime spectra of these zeolite samples consisted of four lifetime components ( τ i , I i ; i = 1, 2, 3, 4), remaining practically constant each lifetime ( τ i ) as the pellet pressure was varied, but their intensities were pressure dependent. The decreasing tendency of the inter-particle pellet volume can be followed by the mean lifetime τ 124 + τ 1 * I 1 + τ 2 * I 2 + τ 4 * I 4 , where the third lifetime component was practically pellet pressure independent. The third and fourth lifetime components ( τ 3 , I 3 ; τ 4 , I 4 ) can be assigned to o -Ps annihilating in the dehydrated β and α cages of the zeolite, respectively, as inferred from the correlation between the calculated specific internal surface area of the zeolite and that obtained from PALS data, registered either form the 50 or 800 ns instrumental windows.

Simulated and experimental broadened Mossbauer spectra are analyzed using several distribution functions. The resolution Hesse and Rubartsch data are reproduced in order to analyze the origin of the oscillations appearing in the recovered distribution function. The lined triangular distribution is used and some of its properties are described. The no implicit nth-nomial distribution function P(x) = (aCos (πx) + bSin (πx)) n is introduced, complementing the Window and Hesse and Rubartasch no implicit distribution functions. This new no implicit distribution function gives similar results of those of Window’s method. In addition, the Window method has also been modified by inserting a smoothing factor λC. For 0 1, the opposite is obtained. The Levenberg-Marquardt algorithm is used to solve the involved Fredholm integral equation rather than the typical second order regularized algorithm. From the extracted hyperfine field distribution functions of the Mossbauer spectra of the amorphous and crystallized Fe70Cr2Si5B16 magnetic alloy the short range atomic order for the amorphous state of this alloy can be inferred.

Amorphous alloy ribbons of Fe77Cr2B16Si5 were exposed to cold plasmas of N2 and Ar–N2 at temperatures lower than Tx = 808 K. The conversion X-ray Mossbauer spectra of the plasma-exposed ribbons consist of a singlet and a broadened magnetic sextet. The singlet with isomer shift \(\updelta = -0.11\) mm/s can be assigned to \(\upgamma \)-Fe austenite phase. Minor bulk magnetic changes in the alloy were measured as a consequence of these treatments; e.g. the relative intensities A23 of the transmission Mossbauer spectra of the untreated and treated samples, were 3.22 and 3.56, respectively, the Bhf values changed from 22.9 T (untreated sample) to 22.4 T (plasma treated samples). Unexpectedly, the \(\upgamma \)-Fe phase can also be produced by simply heating the alloy ribbons under N2 flux at temperatures as low as 423 K. Mossbauer data of the crystallized samples are also reported, and a qualitative assessment on the mechanical properties of the Fe77Cr2B16Si5 alloy associated with the plasma and/or temperature surface induced \(\upgamma \)-Fe phase is given.

Chromium is important from the environmental point of view since its behavior and toxicity properties depend on its oxidation states. The Cr(VI) concentration in wells of Buenavista, Guanajuato, Mexico, is higher than the permissible level of it for drinking water, 0.05mg/L. The objective of this research was to determine the elution of chromium with deionized water from contaminated soil samples and to determine the oxidation state of Fe, which is an element that can limit the mobility of chromium. These results will be considered in a pump and treat remediation scheme for this site. Chromium contaminated soil samples were obtained from an industrial area of Leon, Guanajuato, Mexico. O, Na, Mg, K, Al, Si, Ca, Cr and Fe were found in the chemical analysis by EDS of the contaminated samples. In the soluble species only O, Na, S, Ca and Cr were found. The oxidation state of iron was determined by Mossbauer spectroscopy (MS) in the soil contaminated with chromium, in the soil washed with deionizer water and also in the soluble samples. CaCrO 4 was found in the soluble fraction, as a single crystalline phase by XRD. MS indicated that at least two iron species were present, one insoluble and the other sparingly soluble.

The pick-off annihilation lifetimes of o -Ps, τpo, in dehydrated Co2+ and Mn2+ exchanged zeolites LTA, in dehydrated Co2+ exchanged zeolite 13X, and in dehydrated Na+ zeolites LTA and 13X, are estimated. Although τpo can be estimated from the lifetime spectra of the cation exchanged zeolites LTA and 13X, this lifetime can not be estimated from those spectra of Na+ zeolite LTA unambiguously. The estimated pick-off lifetimes due to the annihilation of o -Ps in the internal walls of the zeolites are systematically lower than the average lifetime of p -Ps and o -Ps in vacuum τa = 0.5 ns. Since the pick-off process of o -Ps occurs particularly on the internal cavity walls of dehydrated zeolites, the replacement of \overline {\tau_a} by τpo within the classical model of Tao-Eldrup to calculate cavity radius should provide more realistic cavity radii of these porous materials than when using \overline {\tau_a}. This suggestion is supported by previous and present results. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)