Cosmogenic activation of materials

The production of radioactive isotopes in materials due to exposure to cosmic rays can become an hazard for experiments demanding ultra-low background conditions. Generation of long-lived products by cosmic nucleons at sea level has been studied for detector materials like germanium and tellurium and for other materials commonly used like copper; the main results will be summarized, considering both measurements and calculations. The isotope production cross sections and the cosmic ray spectrum are the two main ingredients when calculating this cosmogenic activation; the different alternatives for implementing them will be discussed. But cosmogenic activation can take place also deep underground due to cosmic muons, being relevant in this case the short-lived products. Studies carried out to evaluate the underground activation mainly for liquid scintillator materials will be commented too

Genotypic and phenotypic characterization of a Salmonella Typhimurium strain resistant to pulsed electric fields

Pulsed Electric Fields (PEF) technology is regarded as one of the most interesting alternatives to current food preservation methods, due to its capability to inactivate vegetative microorganisms while leaving the product's organoleptic and nutritional properties mostly unchanged. However, many aspects regarding the mechanisms of bacterial inactivation by PEF are still not fully understood. The aim of this study was to obtain further insight into the mechanisms responsible for the increased resistance to PEF of a Salmonella Typhimurium SL1344 variant (SL1344-RS, Sagarzazu et al., 2013), and to quantify the impact that the acquisition of PEF resistance has on other aspects of S. enterica physiology, such as growth fitness, biofilm formation ability, virulence and antibiotic resistance. WGS, RNAseq and qRT-PCR assays indicated that the increased PEF resistance of the SL1344-RS variant is due to a higher RpoS activity caused by a mutation in the hnr gene. This increased RpoS activity also results in higher resistance to multiple stresses (acidic, osmotic, oxidative, ethanol and UV-C, but not to heat and HHP), decreased growth rate in M9-Gluconate (but not in TSB-YE or LB-DPY), increased ability to adhere to Caco-2 cells (but no significant change in invasiveness) and enhanced antibiotic resistance (to six out of eight agents). This study significantly contributes to the understanding of the mechanisms of the development of stress resistance in Salmonellae and underscores the crucial role played by RpoS in this process. Further studies are needed to determine whether this PEF-resistant variant would represent a higher, equal or lower associated hazard than the parental strain

Background reduction and sensitivity for germanium double beta decay experiments

Germanium detectors have very good capabilities for the investigation of rare phenomena like the neutrinoless double beta decay. Rejection of the background entangling the expected signal is one primary goal in this kind of experiments. Here, the attainable background reduction in the energy region where the neutrinoless double beta decay signal of 76Ge is expected to appear has been evaluated for experiments using germanium detectors, taking into consideration different strategies like the granularity of the detector system, the segmentation of each individual germanium detector and the application of Pulse Shape Analysis techniques to discriminate signal from background events. Detection efficiency to the signal is affected by background rejection techniques, and therefore it has been estimated for each of the background rejection scenarios considered. Finally, conditions regarding crystal mass, radiopurity, exposure to cosmic rays, shielding and rejection capabilities are discussed with the aim to achieve a background level of 10-3 c keV-1 kg-1 y-1 in the region of interest, which would allow to explore neutrino effective masses around 40 meV.Comment: 13 pages, 19 figures. Accepted by Astroparticle Physic

Protective effect of glutathione on Escherichia coli cells upon lethal heat stress

Heat treatments are widely used by the food industry to obtain safe and stable products, therefore a deeper knowledge of its mode of action on microorganisms would allow a better profit of this technology. Heat shows a multitarget mechanism of action on bacteria, affecting various cellular structures, and causing unbalances in several homeostatic parameters. The aim of this work was to study the effect of glutathione on bacterial survival against heat treatments, in order to acquire knowledge about the mode of action of heat on bacterial cells. Cells were treated in presence or absence of added glutathione and the level of inactivation, soluble protein concentration, enzymatic activities, intracellular ROS level and membrane damages were studied. Results showed that glutathione protected microorganisms against heat inactivation. Moreover, glutathione in the treatment medium preserved intracellular enzyme activity, membrane structure and reduced ROS detection. Besides, glutathione decreased sublethal injury in E. coli. Data presented in this work add new knowledge about bacterial inactivation and survival by heat

Sensitivity plots for WIMP modulation searches

Prospects of WIMP searches using the annual modulation signature are discussed on statistical grounds, introducing sensitivity plots for the WIMP-nucleon scalar cross section.Comment: 3 pages, 2 figures, talk given at TAUP'99, september 199

Crab-meat-isolated psychrophilic spore forming bacteria inactivation by electron beam ionizing radiation

The present work was performed to evaluate the potential of electron beam ionizing radiation for the inactivation of three psychrophilic spore forming bacteria (Bacillus mycoides, Bacillus weihenstephanensis and Psychrobacillus psychrodurans) isolated from ready-to-eat brown crab (Cancer pagurus). Inactivation curves for the three spores were performed in both types of crab meat, brown and white. Also the effect of pH and water activity (aw) on the lethal efficacy of ionizing radiation, for the three different psychrophilic spore forming bacteria, was evaluated. The effects of pH, aw and their possible interactions were assessed in citrate-phosphate buffers of different pH, ranging between 7 and 4, and aw, ranging from 0.99 and 0.90, while an aw reduction from 0.90 to 0.80 had a minor impact on their resistance. In contrast to aw, the effect of pH showed a greater variability depending on the spore species. While pH did not affect the resistance of B. weihenstephanensis at any aw, B. mycoides showed slightly higher resistance at pH 5.5¿at aw of 0.90 and 0.80. pH showed a significant effect on the resistance of P. psychrodurans. For the two types of crab meat, slightly differences were observed in 6D values. B. weihenstephanensis was the most resistant, requiring 7.3–7.6¿kGy to inactivate 6 Log10-cycles of this spore forming bacterium, while for B. mycoides and P. psychrodurans 6.1–6.3 and 5.4–5.3¿kGy respectively were necessary to reach the same inactivation level in crab meat. An agreement between spore resistance in crab meats and lab media, with similar characteristics in pH and aw, was also observed. The results obtained in this research demonstrated the potential for ionizing radiation to achieve an appropriate inactivation level of spores naturally present in brown crab with the application of doses lower than 10¿kGy

Cuadriceplastia de Judet : una alternativa quirúrgica para las rigideces graves en extensión de la rodilla

Introducción. La contractura en extensión de la rodilla es una complicación de las fracturas femorales con importante afectación de partes blandas. La cuadriceplastia de Judet es una alternativa quirúrgica para aumentar la movilidad. Material y métodos. Presentamos el caso de un paciente con rigidez grave de rodilla en extensión tras una fractura abierta bifocal de fémur estabilizada mediante osteosíntesis que se complicó con una infección y retardo de consolidación que requirió varias cirugías para su estabilización. Se realizó una cuadriceplastia de Judet seguida de una rehabilitación intensiva para conseguir aumentar la flexión de la rodilla. Resultados. En el postoperatorio inmediato conseguía una flexoextensión de 0-100º que se redujo a 95º a los 3 meses y se mantuvo a los 6 meses postoperatorios, con una fuerza muscular de 4 sobre 5 en cuádriceps y psoas. Conclusion. La cuadriceplastia de Judet es una técnica efectiva que permite recuperar la movilidad en caso de rigideces graves en extensión.Introduction. Extension contracture of the knee is a complication of femoral fractures with significant soft tissue injury. The Judet quadricepsplasty is a surgical alternative to increase knee range of motion. Material and methods. We report the case of a patient with severe stiffness of knee following an open bifocal femoral fracture stabilized by osteosynthesis that was complicated by an infection and delayed healing that required several surgeries for stabilization. Judet quadricepsplasty was performed followed by intensive rehabilitation for increasing knee flexion. Results. In the postoperative care flexion and extension of 0-100º was achieved, and reduced to 95º after 3 months and remained the same at 6 months postoperatively, with a muscular strength of 4 out of 5 in quadriceps and psoas. Conclusion. The Judet quadricepsplasty is an effective technique to regain mobility in case of severe extension stiffnes