Mode Confinement in Photonic Quasi-Crystal Point-Defect Cavities for Particle Accelerators

In this Letter, we present a study of the confinement properties of point-defect resonators in finite-size photonic-bandgap structures composed of aperiodic arrangements of dielectric rods, with special emphasis on their use for the design of cavities for particle accelerators. Specifically, for representative geometries, we study the properties of the fundamental mode (as a function of the filling fraction, structure size, and losses) via 2-D and 3-D full-wave numerical simulations, as well as microwave measurements at room temperature. Results indicate that, for reduced-size structures, aperiodic geometries exhibit superior confinement properties by comparison with periodic ones.Comment: 4 pages, 4 figures, accepted for publication in Applied Physics Letter

Raising awareness on gender issues: A path through physics, outreach and diversity.

When and where it is convenient to start working on raising awareness on gender issues? Our answer is that high school is definitely a good start, mainly if we think that outreach activities can have a role in the transition to an environment for learning, teaching and researching in physics that is equally attractive and supportive to all genders, at each stage of their education and career path. As researchers of INFN and CNR we promoted a school competition devoted to consider the role of women in science and particularly in Physics. Outreach activities can have the role of raising awareness, knowledge through an active involvement of students for changing the culture and removing stereotypes. In these years we organized 3 contests, with 226 videos, more than 100 high schools and a thousand of students involved. The idea was to try to understand the thinking and knowledge of young people on present and past gender issues connected to women and science, to know how they imagine the society of the future, to understand if they are unaware "carriers" of stereotypes and prejudices and if the cultural change can start from/with them. The students have been asked to produce a video on subjects regarding these questions. The article describes the contests, the evaluation process, the results of first analysis. The work started inside the EU-funded GENERA project, to which both research groups belong, and continues inside the GENERA Network. The collaboration among physicists and sociologists has been, and still is, fundamental in these years

GENOVATE conference digital story with Maria Rosaria Masullo

Ye

Biochemical and functional characterization of superoxide dismutase from the psychrophilic eubacterium Pseudoalteromonas haloplanktis

Superoxide dismutase (SOD) is a metal-enzyme, catalyzing the dismutation of superoxide anion in molecular oxygen and hydrogen peroxide. It is involved in the cellular defence mechanism against the reactive and toxic products of oxygen metabolism. SODs have been classified into two main families, according to their different structural folding and metal content: the Cu/Zn family and that containing Fe or Mn in the active site. SODs isolated from extremophilic organisms are suitable models to study the structure-function relationships and the molecular and evolutive mechanisms for the adaptation of proteins to extreme environments. We have previously isolated a SOD from the hyperthermophilic archaeon Sulfolobus solfataricus (SsSOD). Its is a Fe-SOD endowed with a remarkable heat stability, its t1/2 being 2 hours at 100°C. Structural ands functional studies on the recombinant SsSOD and the analysis of some mutant and modified forms have explained several aspects about the mechanisms adopted by the enzyme to function at high temperatures. Therefore, it could be interesting to carry out similar studies also in a psychrophilic organism. In this communication we report the purification and the preliminary biochemical characterization of SOD from the psychrophilic eubacterium Pseudoalteromonas haloplanktis, isolated from Antarctic marine sediments and adapted to grow at low temperatures. SOD from P. haloplanktis (PhSOD) was purified to homogeneity from cells grown at 4°C by two chromatographic steps on a DEAE-Sepharose and HTP. The relative molecular mass of the purified enzyme, estimated by SDS-PAGE is 22,000. As SsSOD, also PhSOD shows a homotetrameric structure, as determined by gel filtration. PhSOD has a unusual thermal stability for a psychrophilic enzyme, as evaluated by its half-life of 10 min at 52°C. Similar results were obtained by UV-melting curves. The heat stability seems to be a feature possessed by a number of SODs; for instance, rat mitochondrial Mn-SOD has a a melting temperature of 87°C. Enzymatic assays showed that PhSOD has a specific activity of 6500 U/mg, The enzyme is inactivated by hydrogen peroxide and it is inhibited by sodium azide, whereas PMSF, a specific SsSOD inactivator, has no effect. According to this preliminary characterization PhSOD could be classified as a Fe-SOD. Future research plan includes the determination of the metal content and the cloning of the gene encoding PhSOD from a genomic DNA library. To this aim, a molecular probe will be designed on the basis of the amino acid sequence of some tryptic fragments of the purified protein

Superoxide dismutase from the psychrophilic Antarctic eubacterium Pseudoalteromonas haloplanktis

The antioxidant function of Fe- and Mn-containing superoxide dismutases (SOD) observed under constraints from extreme rather than mild cellular conditions could reflect an adaptive evolution to oxygen tolerance in the structural organisation of this class of enzymes. For instance, the mitochondrial human Mn-SOD and the hyperthermophilic archaeal Fe-SOD from Sulfolobus solfataricus (SsSOD) share a similar structural organisation. Further studies on members of this ubiquitous enzyme isolated from differently adapted micro–organisms could give useful information on possible adaptive mechanisms in the structure-function relationships of this SOD family. For this reason, this enzyme has been purified and characterised from Pseudoalteromonas haloplanktis, a psychrophilic eubacterium isolated from marine Antarctic sediments. Two chromatographic steps on DEAE-Sepharose and HTP allowed to purify SOD from P. haloplanktis (PhSOD) to homogeneity. The relative molecular weight of the purified enzyme estimated by SDS-PAGE is about 20,000. As SsSOD, also PhSOD shows a homotetrameric structure, as determined by gel filtration. PhSOD has an unusual thermal stability for a psycrophilic enzyme, as evaluated by its half-life of 10 min at 52°C. Similar results were obtained by UV-melting curves. Enzymatic assays showed that PhSOD has a specific activity of 6500 U/mg. The enzyme is inactivated by hydrogen peroxide and it is inhibited by sodium azide, whereas PMSF, a specific inactivator of the archaeal SsSOD, has no effect. Future research plan includes the determination of the metal content and the cloning of the gene encoding PhSOD. To this aim, a molecular probe has been designed on the basis of the amino acid sequence of some fragments of the purified protein

Optical cavity alignment and mirror damage in the LELA FEL experiment

Abstract The alignment of the LELA optical cavity, 17.5 m long, is described. The procedure to attain a close alignment of the undulator radiation axis and the cavity axis using an external laser is reported. Measurements of Q from stored light spectra are presented. Mirror degradation at increasing integrated electron currents is considered