Detection Limits of Organic Compounds Achievable with Intense, Short-Pulse Lasers

Many organic molecules have strong absorption bands which can be accessed by ultraviolet short pulse lasers to produce efficient ionization. This resonant multiphoton ionization scheme has already been exploited as an ionization source in time-of-flight mass spectrometers used for environmental trace analysis. In the present work we quantify the ultimate potential of this technique by measuring absolute ion yields produced from the interaction of 267 nm femtosecond laser pulses with the organic molecules indole and toluene, and gases Xe, N2 and O2. Using multiphoton ionization cross sections extracted from these results, we show that the laser pulse parameters required for real-time detection of aromatic molecules at concentrations of one part per trillion in air and a limit of detection of a few attomoles are achievable with presently available commercial laser systems. The potential applications for the analysis of human breath, blood and tissue samples are discussed.

Temporal Narrowing of Neutrons Produced by High-Intensity Short-Pulse Lasers

The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a similar to 3 ns duration neutron pulse with 10(4) n/MeV/sr/shot at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. This neutron pulse compares favorably to the duration of conventional accelerator sources and should scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.

HES6 drives a critical AR transcriptional programme to induce castration-resistant prostate cancer through activation of an E2F1-mediated cell cycle network

<p>Castrate-resistant prostate cancer (CRPC) is poorly characterized and heterogeneous and while the androgen receptor (AR) is of singular importance, other factors such as c-Myc and the E2F family also play a role in later stage disease. HES6 is a transcription co-factor associated with stem cell characteristics in neural tissue. Here we show that HES6 is up-regulated in aggressive human prostate cancer and drives castration-resistant tumour growth in the absence of ligand binding by enhancing the transcriptional activity of the AR, which is preferentially directed to a regulatory network enriched for transcription factors such as E2F1. In the clinical setting, we have uncovered a HES6-associated signature that predicts poor outcome in prostate cancer, which can be pharmacologically targeted by inhibition of PLK1 with restoration of sensitivity to castration. We have therefore shown for the first time the critical role of HES6 in the development of CRPC and identified its potential in patient-specific therapeutic strategies.</p>

Generation of overdense and high-energy electron-positron-pair plasmas by irradiation of a thin foil with two ultraintense lasers

A scheme for enhanced quantum electrodynamics (QED) production of electron-positron-pair plasmas is proposed that uses two ultraintense lasers irradiating a thin solid foil from opposite sides. In the scheme, under a proper matching condition, in addition to the skin-depth emission of gamma-ray photons and Breit-Wheeler creation of pairs on each side of the foil, a large number of high-energy electrons and photons from one side can propagate through it and interact with the laser on the other side, leading to much enhanced gamma-ray emission and pair production. More importantly, the created pairs can be collected later and confined to the center by opposite laser radiation pressures when the foil becomes transparent, resulting in the formation of unprecedentedly overdense and high-energy pair plasmas. Two-dimensional QED particle-in-cell simulations show that electron-positron-pair plasmas with overcritical density 10(22) cm(-3) and a high energy of 100s of MeV are obtained with 10 PW lasers at intensities 10(23) W/cm(2), which are of key significance for laboratory astrophysics studies.

The generation and amplification of intergalactic magnetic fields in analogue laboratory experiments with high power lasers

The advent of high-power laser facilities has, in the past two decades, opened a new field of research where astrophysical environments can be scaled down to laboratory dimensions, while preserving the essential physics. This is due to the invariance of the equations of magneto-hydrodynamics to a class of similarity transformations. Here we review the relevant scaling relations and their application in laboratory astrophysics experiments with a focus on the generation and amplification of magnetic fields in cosmic environment. The standard model for the origin of magnetic fields is a multi stage process whereby a vanishing magnetic seed is first generated by a rotational electric field and is then amplified by turbulent dynamo action to the characteristic values observed in astronomical bodies. We thus discuss the relevant seed generation mechanisms in cosmic environment including resistive mechanism, collision-less and fluid instabilities, as well as novel laboratory experiments using high power laser systems aimed at investigating the amplification of magnetic energy by magneto-hydrodynamic (MHD) turbulence. Future directions, including efforts to model in the laboratory the process of diffusive shock acceleration are also discussed, with an emphasis on the potential of laboratory experiments to further our understanding of plasma physics on cosmic scales.

Electron-impact excitation of Ar+: an improved determination of Ar impurity influx in tokamaks

Electron-impact scattering data for argon and its ions continue to be of interest in studies of magnetically confined plasmas. In an earlier paper, Griffin et al (1997 J. Phys. B: At. Mol. Opt. Phys. 30 3543) employed the results of 28-term and 40-term R-matrix calculations of electron-impact excitation in Ar+ to carry out a collisional-radiative modelling study of the impurity influx of argon in tokamaks. We have now completed a 452-term R-matrix with pseudo-states (RMPS) calculation of electron-impact excitation for Ar+ in order to provide more accurate excitation data; using these improved data, we have repeated the modelling studies presented in the earlier paper. We compare our excitation data, as well as the results of the collisional radiative calculations, with those arising from the 40-term R-matrix calculation and find significant differences.

Electron-impact excitation of Ar 2+

Context: Emission from Ar III is seen in planetary nebulae, in H II regions, and from laboratory plasmas. The analysis of such spectra requires accurate electron impact excitation data. Aims: The aim of this work is to improve the electron impact excitation data available for Ar2+, for application in studies of planetary nebulae and laboratory plasma spectra. The effects of the new data on diagnostic line ratios are also studied. Methods: Electron-impact excitation collision strengths have been calculated using the R-Matrix Intermediate-Coupling Frame-Transformation method and the R-Matrix Breit-Pauli method. Excitation cross sections are calculated between all levels of the configurations 3s^23p^4, 3s3p^5, 3p^6, 3p^53d, and 3s^23p^3nl (3d ��� nl ��� 5s). Maxwellian effective collision strengths are generated from the collision strength data. Results: Good agreement is found in the collision strengths calculated using the two R-Matrix methods. The collision strengths are compared with literature values for transitions within the 3s^23p4 configuration. The new data has a small effect on Te values obtained from the I(��7135 ��+ ��7751 ��)/ I(��5192 ��) line ratio, and a larger effect on the Ne values obtained from the I(��7135 ��)/I(��9 ��m) line ratio. The final effective collision strength data is archived online.

Valence-shell photoionization of chlorinelike Ar+ ions

Absolute cross-section measurements for valence-shell photoionization of Ar + ions are reported for photon energies ranging from 27.4 eV to 60.0 eV. The data, taken by merging beams of ions and synchrotron radiation at a photon energy resolution of 10 meV, indicate that the primary ion beam was a statistically weighted mixture of the 2P o3/2 ground state and the 2P o1/2 metastable state of Ar +. Photoionization of this Cell-like ion is characterized by multiple Rydberg series of autoionizing resonances superimposed on a direct photoionization continuum. Observed resonance lineshapes indicate interference between indirect and direct photoionization channels. Resonance features are spectroscopically assigned and their energies and quantum defects are tabulated. The measurements are satisfactorily reproduced by theoretical calculations based on an intermediate coupling semi-relativistic Breit-Pauli approximation.

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

<p>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 &amp; 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.</p>

Impacte da qualidade do ar urbana na sa��de p��blica: o caso da cidade do Porto

O benzeno foi o primeiro poluente atmosf��rico carcinog��nico a ser regulamentado a n��vel europeu. V��rios trabalhos t��m sido publicados demonstrando a rela����o deste poluente com diversos tipos de neoplasias nomeadamente decorrentes de exposi����es a n��vel ocupacional. Por��m, o estudo deste poluente para concentra����es atmosf��ricas em ambientes exteriores ainda �� pouco conhecido e est�� em clara evolu����o. Neste sentido, este trabalho pretende ser um contributo para o conhecimento da rela����o entre o benzeno atmosf��rico e a incid��ncia de patologias que afectam os tecidos linf��ticos e ��rg��os hematopoi��ticos nomeadamente linfomas de Hodgkin, linfomas de n��o-Hodgkin e leucemias na popula����o residente na ��rea Metropolitana do Porto. Dado a quase aus��ncia de dados de monitoriza����o das concentra����es de benzeno atmosf��rico actualmente em Portugal, estas foram estimadas com base na defini����o de uma rela����o entre o benzeno e o mon��xido de carbono. O conhecimento das concentra����es em todo o dom��nio de estudo baseou-se na an��lise dos dados da Rede Autom��tica de Monitoriza����o da Qualidade do Ar por��m, de modo a aumentar o detalhe espacial e temporal recorreu-se �� modela����o atmosf��rica aplicando o modelo TAPM. Para perceber a evolu����o temporal das concentra����es, a modela����o foi efectuada para os anos de 1991, 2001 e 2006 com base no ano meteorol��gico de 2006 e emiss��es para os respectivos anos ao n��vel da freguesia. O modelo foi previamente validado de acordo com uma metodologia proposta para este tipo de modelos. Contudo, mais do que perceber qual a varia����o da qualidade do ar a n��vel exterior, �� importante conhecer o impacte de fontes interiores e o seu efeito na popula����o. Assim, desenvolveu-se um modelo de exposi����o e dose que permitem conhecer os valores m��dios populacionais. A modela����o da exposi����o populacional �� efectuada com base nos perfis de actividade-tempo, nos movimentos pendulares inter-concelhos e nas concentra����es de benzeno em ambientes exteriores e interiores. Na modela����o da dose �� ainda poss��vel varia����es por sexo e idade. Por outro lado, para o estudo das patologias em an��lise efectuou-se uma an��lise epidemiol��gica espacial nomeadamente no que respeita �� elabora����o de mapas de incid��ncia padronizados pela idade, e estudo da associa����o com a exposi����o ao benzeno atmosf��rico. Os resultados indicam associa����o entre o benzeno e as doen��as em estudo. Esta evid��ncia �� mais not��ria quando a an��lise �� realizada junto ��s principais fontes de emiss��o deste poluente, vias de tr��fego e postos de abastecimento de combust��vel. Por��m, a aus��ncia de informa����o limita o estudo n��o permitindo o controlo de potenciais vari��veis de confundimento como a exposi����o ao fumo do tabaco. A metodologia permite efectuar uma gest��o integrada da qualidade do ar exterior e interior, funcionando como uma ferramenta do apoio �� decis��o para elabora����o de planos de preven����o de longo prazo de potenciais efeitos na sa��de das popula����es nomeadamente para outro tipo de patologias.

Modela����o da qualidade do ar e da sa��de humana: da mesoescala �� dose

O actual, e crescente, padr��o de consumo tem repercuss��es no ambiente que, inevitavelmente, se reflectem na sa��de humana. A polui����o atmosf��rica assume-se, na Europa, como um problema ambiental premente, por ter um elevado impacte na sa��de dos cidad��os. Entre estes, h�� grupos particularmente vulner��veis, como os idosos, os doentes cr��nicos e as crian��as. V��rios estudos colocam em evid��ncia a sensibilidade dos doentes asm��ticos, em particular das crian��as, �� polui����o atmosf��rica. No entanto, permanece por esclarecer o facto de a polui����o atmosf��rica poder causar o aumento da preval��ncia desta doen��a, assim como a identifica����o dos principais poluentes atmosf��ricos respons��veis e os n��veis de exposi����o seguros. O objectivo desta tese consiste no estudo da rela����o entre a polui����o atmosf��rica e a sa��de, contribuindo para o conhecimento nesta tem��tica atrav��s do desenvolvimento de uma ferramenta e da sua aplica����o a um caso de estudo concreto. Neste caso de estudo analisou-se a rela����o entre v��rios poluentes atmosf��ricos e o agravamento da sintomatologia em crian��as asm��ticas. Neste ��mbito, foi desenvolvido o modelo doseAr, que possibilita o c��lculo da exposi����o e da dose inalada, ao n��vel individual, de poluentes atmosf��ricos. Os resultados da aplica����o do doseAr permitem a identifica����o dos microambientes onde a contribui����o para a exposi����o e dose inalada de poluentes �� mais relevante. Os microambientes interiores, em particular aqueles onde �� desenvolvida actividade f��sica exigente, s��o identificados como especialmente importantes. A rela����o entre a exposi����o e a dose inalada �� claramente associada ao agravamento da asma nestas crian��as, apesar dos n��veis de polui����o identificados serem baixos, face aos padr��es de qualidade do ar existentes.

Efeitos da embalagem em ar, sob v��cuo e em atmosfera modificada sobre a qualidade de filetes de peixe-porco Balistes capriscus

Disserta����o de mest, Tecnologia de Alimentos, Instituto Superior de Engenharia, Univ. do Algarve, 2013

Desempenho da flota����o por ar dissolvido na remo����o de cianobact��rias de diferentes morfologias

A presen��a de cianobact��rias em reservat��rios utilizados para produ����o de ��gua para consumo humano representa um elevado risco para a sa��de p��blica. Estes organismos contribuem para a redu����o da qualidade da ��gua e t��m a capacidade de produzir cianotoxinas que podem afectar a sa��de humana e animal. Existem casos em todo o mundo de intoxica����o letal de diversos animais por consumo de ��gua de lagos contaminados com cianobact��rias, e mesmo casos de morte de humanos, atribu��das �� exposi����o de cianotoxinas. De modo a fazer face a este crescente problema �� necess��rio desenvolver e implementar tecnologias de tratamento de ��gua nas ETA que permitam fazer face a uma floresc��ncia de cianobact��rias num reservat��rio de ��gua destinado ao abastecimento humano. Neste trabalho avaliou-se a capacidade do processo C/F/DAF na remo����o cianobact��rias de diferentes morfologias, c��lulas e col��nias de M. aeruginosa e filamentos de P. rubescens, em ��guas sint��ticas hidrof��bicas e hidrof��licas, com concentra����o de DOC moderada e moderada/elevada. Assim como da sequ��ncia C/F/DAF���NF na remo����o de c��lulas e de toxinas de cianobact��rias. A remo����o de NOM e o seu efeito na remo����o de cianobact��rias foram tamb��m avaliados. Concluiu-se que o processo C/F/DAF �� eficiente na remo����o de cianobact��rias de diferentes morfologias, com remo����es entre 78 e 100% de MC intra. No entanto, a morfologia que apresentou remo����es mais elevadas foram os filamentos, enquanto as col��nias apresentaram valores mais baixos. Globalmente, verificou-se que o aumento da concentra����o de NOM facilita a remo����o de cianobact��rias, sendo que as ��guas hidrof��bicas apresentaram-se mais f��ceis de tratar por C/F/DAF. Por sua vez, o tratamento C/F/DAF���NF, �� uma op����o eficiente para fazer face a um eventual bloom de cianobact��rias em ETA, uma vez que a remo����o de cianobact��rias (em MC intra e chl_a) foi de 100% e a remo����o de microcistina extracelular de 95%, aproximadamente.

A produ����o de culturas ao ar livre em modo de produ����o biol��gico, no Algarve: um diagn��stico do sector e contas de cultura

Disserta����o de mestrado, Hortofruticultura, Faculdade de Ci��ncias e Tecnologia, Universidade do Algarve, 2014