Picosecond metrology of laser-driven proton bursts

Tracking primary radiation-induced processes in matter requires ultrafast sources and high precision timing. While compact laser-driven ion accelerators are seeding the development of novel high instantaneous flux applications, combining the ultrashort ion and laser pulse durations with their inherent synchronicity to trace the real-time evolution of initial damage events has yet to be realized. Here we report on the absolute measurement of proton bursts as short as 3.5±0.7 ps from laser solid target interactions for this purpose. Our results verify that laser-driven ion acceleration can deliver interaction times over a factor of hundred shorter than those of state-of-the-art accelerators optimized for high instantaneous flux. Furthermore, these observations draw ion interaction physics into the field of ultrafast science, opening the opportunity for quantitative comparison with both numerical modelling and the adjacent fields of ultrafast electron and photon interactions in matter.

The influence of water motion on the growth rate of the kelp Laminaria digitata

The shallow water kelp Laminaria digitata, abundant in coastal zones of the North Atlantic, is exposed to a range of hydrodynamic environments that makes it ideal for assessing the role of water motion on their growth rate. Here we quantify the growth of L. digitata, as a factor of blade and stipe elongation, at sites adjacent to Strangford Lough, Northern Ireland under different hydrodynamic conditions over a one year period. A modelling approach was used to numerically determine both the temporal and spatial variability of the hydrodynamic environment. Ambient seawater nutrient concentrations, temperature and irradiance were measured as well as the internal nutrient status of the L. digitata populations. Kelp populations growing in the greatest and lowest water motion showed the lowest growth rates. Differences observed in growth rate could not be attributed to seawater nutrient availability, temperature or light. The internal nutrient status also suggested no influence on the observed differences in growth rate. Therefore if there are minimal differences in light, temperature and nutrients between sites, then populations of L. digitata exposed to different water motions are likely to exhibit different growth rates. It is suggested that the growth rate differences observed were a function of water motion with the possibility that, in response to the hydrodynamic forces experienced by the algal cells, L. digitata kelps in the high energy environments were putting more energy into strengthening cell walls rather than blade elongation

Electron-impact ionization of Al

Perturbative distorted-wave and non-perturbative close-coupling methods are used to calculate electron-impact ionization cross sections for the ground state of the neutral Al atom. Configuration-average distorted-wave calculations are made for both direct ionization and excitation-autoionization contributions. The total perturbative results are found to be almost a factor of 2 higher than experiment over a wide energy range. On the other hand, the R-matrix with pseudo-states results for total ionization are found to be in good agreement with experiment. Comparison of time-dependent close-coupling calculations for the direct ionization with the R-matrix with pseudo-state calculations for total ionization reveals that both the direct ionization and excitation-autoionization contributions are strongly affected by correlation effects.

Evaluation of an improved atomic data basis for carbon in UEDGE emission modeling for L-mode plasmas in DIII-D

New scaled carbon atomic electron-impact excitation data is utilized to evaluate comparisons between experimental measurements and fluid emission modeling of detached plasmas at DIII-D. The C I and C II modeled emission lines for 909.8 and 514.7 nm were overestimated by a factor of 10-20 than observed experimentally for the inner leg, while the outer leg was within a factor of 2. Due to higher modeled emissions, a previous study using the UEDGE code predicted that a higher amount of carbon was required to achieve a detached outboard divertor plasma in L-mode at DIII-D. The line emission predicted by using the new scaled carbon data yields closer results when compared against experiment. We also compare modeling and measurements of Dα emission from neutral deuterium against predictions from newly calculated R-Matrix with pseudostates data available at the ADAS database. © 2013 Published by Elsevier B.V.

Electron-impact ionization of argon using the R-matrix with a pseudo-states method

Electron-impact ionization cross sections for argon are calculated using both non-perturbative R-matrix with pseudo-states (RMPS) and perturbative distorted-wave methods. At twice the ionization potential, the 3p(61)S ground-term cross section from a distorted-wave calculation is found to be a factor of 4 above crossed-beams experimental measurements, while with the inclusion of term-dependent continuum effects in the distorted-wave method, the perturbative cross section still remains almost a factor of 2 above experiment. In the case of ionization from the metastable 3p(5)4s(3)P term, the distorted-wave ionization cross section is also higher than the experimental cross section. On the other hand, the ground-term cross section determined from a nonperturbative RMPS calculation that includes 27 LS spectroscopic terms and another 282 LS pseudo-state terms to represent the high Rydberg states, and the target continuum is found to be in excellent agreement with experimental measurements, while the RMPS result is below the experimental cross section for ionization from the metastable term. We conclude that both continuum term dependence and interchannel coupling effects, which are included in the RMPS method, are important for ionization from the ground term, and interchannel coupling is also significant for ionization from the metastable term

Dielectronic recombination of W20 + (4d104f8): Addressing the half-open f shell

A recent measurement of the dielectronic recombination (DR) of W20+ [Schippers et al., Phys.Rev.A 83, 012711 (2011)] found an exceptionally large contribution from near-threshold resonances (1 eV). This still affected the Maxwellian rate coefficient at much higher temperatures. The experimental result was found to be higher by a factor of 4 or more than that currently in use in the 100- to 300-eV range, which is of relevance for modeling magnetic fusion plasmas. We have carried out DR calculations with AUTOSTRUCTURE which include all significant single-electron promotions. Our intermediate-coupling (IC) results are more than a factor of 4 larger than our LS-coupling ones at 1 eV but still lie a factor of 3 below experiment here. If we assume complete (chaotic)mixing of near-threshold autoionizing states, then our results come into agreement (to within 20%)with experiment below 2 eV. Our total IC Maxwellian rate coefficients are 50%–30% smaller than those based on experiment over 100–300 eV.

Electron-impact excitation of Xe 26+ and its resultant spectral signature

We have carried out a 129 close-coupling level Dirac-Coulomb R-matrix calculation for the electron-impact excitation of Ni-like Xe. We have utilized this data to generate the spectral signature of Xe26+ in terms of feature photon-emissivity coefficients (F-PεCs). We have compared these F-PεCs with those generated using semi-relativistic plane-wave Born excitation data, which forms the heavy species baseline for the Atomic Data and Analysis Structure (ADAS), We find that the Born-based F-PεCs give a reasonable qualitative description of the spectral signature but that, quantitatively, the R-matrix-based F-PεCs differ by up to a factor of 2. The spectral signature of heavy species is key to diagnosing hot plasmas such as will be found in the International Thermonuclear Experimental Reactor.

Effective collision strengths for fine-structure forbidden transitions among the 3s 23p 3 levels of Ar IV

The multichannel R-matrix method is used to compute electron impact excitation collision strengths in Ar IV for all fine-structure transitions among the ⁴S°, ²D° and ²P° levels in the 3s ²3p ³ ground configuration. Included in the expansion of the total wavefunction are the lowest 13 LS target eigenstates of Ar iv formed from the 3s ²3p ³, 3s3p ⁴ and 3s ²3p ²3d configurations. The effective collision strengths, obtained by averaging the electron collision strengths over a Maxwellian distribution of electron velocities, are presented for all 10 fine-structure transitions over a wide range of electron temperatures of astrophysical interest (T _e = 2000-100 000 K). Comparisons are made with an earlier 7-state close-coupling calculation by Zeippen, Butler & Le Bourlot, and significant differences are found to occur for many of the forbidden transitions considered, in particular those involving the ⁴S° ground state, where discrepancies of up to a factor of 3 are found in the low-temperature region. © 1997 RAS.

M Dwarf Flare Continuum Variations on One-second Timescales: Calibrating and Modeling of ULTRACAM Flare Color Indices

We present a large data set of high-cadence dMe flare light curves obtained with custom continuum filters on the triple-beam, high-speed camera system ULTRACAM. The measurements provide constraints for models of the near-ultraviolet (NUV) and optical continuum spectral evolution on timescales of ≈1 s. We provide a robust interpretation of the flare emission in the ULTRACAM filters using simultaneously obtained low-resolution spectra during two moderate-sized flares in the dM4.5e star YZ CMi. By avoiding the spectral complexity within the broadband Johnson filters, the ULTRACAM filters are shown to characterize bona fide continuum emission in the NUV, blue, and red wavelength regimes. The NUV/blue flux ratio in flares is equivalent to a Balmer jump ratio, and the blue/red flux ratio provides an estimate for the color temperature of the optical continuum emission. We present a new “color-color” relationship for these continuum flux ratios at the peaks of the flares. Using the RADYN and RH codes, we interpret the ULTRACAM filter emission using the dominant emission processes from a radiative-hydrodynamic flare model with a high nonthermal electron beam flux, which explains a hot, T ≈ 104 K, color temperature at blue-to-red optical wavelengths and a small Balmer jump ratio as observed in moderate-sized and large flares alike. We also discuss the high time resolution, high signal-to-noise continuum color variations observed in YZ CMi during a giant flare, which increased the NUV flux from this star by over a factor of 100. Based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium, based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofsica de Canarias, and observations, and based on observations made with the ESO Telescopes at the La Silla Paranal Observatory under programme ID 085.D-0501(A).

Infection mechanism of Diplodia corticola

Diplodia corticola is regarded as the most virulent fungus involved in cork oak decline, being able to infect not only Quercus species (mainly Q. suber and Q. ilex), but also grapevines (Vitis vinifera) and eucalypts (Eucalyptus sp.). This endophytic fungus is also a pathogen whose virulence usually manifests with the onset of plant stress. Considering that the infection normally culminates in host death, there is a growing ecologic and socio-economic concern about D. corticola propagation. The molecular mechanisms of infection are hitherto largely unknown. Accordingly, the aim of this study was to unveil potential virulence effectors implicated in D. corticola infection. This knowledge is fundamental to outline the molecular framework that permits the fungal invasion and proliferation in plant hosts, causing disease. Since the effectors deployed are mostly proteins, we adopted a proteomic approach. We performed in planta pathogenicity tests to select two D. corticola strains with distinct virulence degrees for our studies. Like other filamentous fungi D. corticola secretes protein at low concentrations in vitro in the presence of high levels of polysaccharides, two characteristics that hamper the fungal secretome analysis. Therefore, we first compared several methods of extracellular protein extraction to assess their performance and compatibility with 1D and 2D electrophoretic separation. TCA-Acetone and TCA-phenol protein precipitation were the most efficient methods and the former was adopted for further studies. The proteins were extracted and separated by 2D-PAGE, proteins were digested with trypsin and the resulting peptides were further analysed by MS/MS. Their identification was performed by de novo sequencing and/or MASCOT search. We were able to identify 80 extracellular and 162 intracellular proteins, a milestone for the Botryosphaeriaceae family that contains only one member with the proteome characterized. We also performed an extensive comparative 2D gel analysis to highlight the differentially expressed proteins during the host mimicry. Moreover, we compared the protein profiles of the two strains with different degrees of virulence. In short, we characterized for the first time the secretome and proteome of D. corticola. The obtained results contribute to the elucidation of some aspects of the biology of the fungus. The avirulent strain contains an assortment of proteins that facilitate the adaptation to diverse substrates and the identified proteins suggest that the fungus degrades the host tissues through Fenton reactions. On the other hand, the virulent strain seems to have adapted its secretome to the host characteristics. Furthermore, the results indicate that this strain metabolizes aminobutyric acid, a molecule that might be the triggering factor of the transition from a latent to a pathogenic state. Lastly, the secretome includes potential pathogenicity effectors, such as deuterolysin (peptidase M35) and cerato-platanin, proteins that might play an active role in the phytopathogenic lifestyle of the fungus. Overall, our results suggest that D. corticola has a hemibiotrophic lifestyle, switching from a biotrophic to a necrotrophic interaction after plant physiologic disturbances.This understanding is essential for further development of effective plant protection measures.

The Educational and Employment Aspirations of Adolescents from Areas of High Deprivation in London

Adolescents from areas of high deprivation are often assumed to have low aspirations for the future. However, recent research has suggested otherwise and there have been calls for more substantial investigation into the relationship between poverty and aspiration. This article reports levels and variation in aspiration from 1,214 adolescents (49.5% male; 50.5% female) living in areas of high deprivation across 20 London boroughs. A strength of this study is our large and diverse population of low socio-economic status (SES) adolescents, comprising of white British (22%), black African (21%), black Caribbean (9%), Indian/Pakistani/Bangladeshi/Other Asian (24%), mixed ethnicity (9%), and 15% defining themselves as Other. Our measures indicated a high group level of reported aspiration with notable variations. Females reported higher educational (but not occupational) aspirations than males; white British students reported lower educational and occupational aspirations than other ethnic groups; and black African children reported the highest educational aspirations. Perceived parental support for education had the largest positive association with aspirations. In contrast to previous findings from studies carried out in the United States, aspirations were found to be negatively associated with perceptions of school and school peer environment. These measures explored feelings of safety, happiness and belonging within the school environment and school peer group. We discuss possible explanations for this unexpected finding within our population of adolescents from UK state schools and how it might affect future policy interventions. This study makes an important contribution to the literature on adolescent aspirations because of the unique nature of the data sample and the multiple domains of functioning and aspiration measured.

Characterization of pro- and anti-angiogenic factors in models of diabetic retinopathy

Dissertação de mestrado, Ciências Biomédicas, Departamento de Ciências Biomédicas e Medicina, Universidade do Algarve, 2015

Validation of a method for the analysis of volatile organic compounds in water

Dissertação de mestrado, Qualidade em Análises, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

Interference of mycobacterium tuberculosis with the endocytic/ antigen presentation pathways on macrophages and dendritic cells

Tese de doutoramento, Farmácia (Biologia Celular e Molecular), Universidade de Lisboa, Faculdade de Farmácia, 2014

Identification of the cellular and molecular mechanism by which CD2AP, a regulator of neuronal intracellular transport contributes to the development of Alzheimer’s disease

Tese de mestrado. Biologia (Biologia Molecular e Genética). Universidade de Lisboa, Faculdade de Ciências,2014