Intense slow beams of bosonic potassium isotopes

We report on an experimental realization of a two-dimensional magneto-optical trap (2D-MOT) that allows the generation of cold atomic beams of 39K and 41K bosonic potassium isotopes. The high measured fluxes up to 1.0x10^11 atoms/s and low atomic velocities around 33 m/s are well suited for a fast and reliable 3D-MOT loading, a basilar feature for new generation experiments on Bose-Einstein condensation of dilute atomic samples. We also present a simple multilevel theoretical model for the calculation of the light-induced force acting on an atom moving in a MOT. The model gives a good agreement between predicted and measured flux and velocity values for our 2D-MOT.Comment: Updated references, 1 figure added, 10 pages, 9 figure

Collisional properties of sympathetically cooled 39^{39}K

We report the experimental evidence of the sympathetic cooling of $^{39}$K with $^{87}$Rb down to 1 $\mu$K, obtained in a novel tight confining magnetic trap. This allowed us to perform the first direct measurement of the elastic cross section of $^{39}$K below 50 $\mu$K. The result obtained for the triplet scattering length, $a_T = -51(7)$ Bohr radii, agrees with previous results derived from photoassociation spectra and from Feshbach spectroscopy of $^{40}$K.Comment: 7 pages, 4 figures, submitted to Phys. Rev.

Risk-Informed design process of the IRIS reactor

Westinghouse is currently conducting the pre-application licensing of the International Reactor Innovative and Secure (IRIS). The design philosophy of the IRIS has been based on the concept of Safety-by-DesignTM and within this framework the PSA is being used as an integral part of the design process. The basis for the PSA contribution to the design phase of the reactor is the close iteration between the PSA team and the design and safety analysis team. In this process the design team is not only involved in the initial phase of providing system information to the PSA team, allowing in this way the identification of the high risk scenarios, but it is also receiving feedback from the PSA team that suggests design modification aimed at reaching risk-related goals. During the first iteration of this process, the design modifications proposed by the PSA team allowed reducing the initial estimate of Core Damage Frequency (CDF) due to internal events from 2E-6/ry to 2E-8/ry. Since the IRIS design is still in a development phase, a number of assumptions have to be confirmed when the design is finalized. Among key assumptions are the success criteria for both the accident sequences analyzed and the systems involved in the mitigation strategies. The PSA team developed the initial accident sequence event trees according to the information from the preliminary analysis and feasibility studies. A recent coupling between the RELAP and GOTHIC codes made possible the actual simulation of all LOCA sequences identified in the first draft of the Event Trees. Working in close coordination, the PSA and the safety analysis teams developed a matrix case of sequences not only with the purpose of testing the assumed success criteria, but also with the perspective of identifying alternative sequences developed mainly by relaxing the extremely conservative assumptions previously made. The results of these simulations, bounded themselves with conservative assumptions on the Core Damage definition, suggested two new versions of the LOCA Event Tree with two possible configurations of the Automatic Depressurization System. The new CDF has been evaluated for both configurations and the design team has been provided with an additional and risk-related perspective that will help choosing the design alternative to be implemented

Adapting to Crisis

This article draws on our experiences of carrying out PhD research on migration during the COVID-19 pandemic. We are all involved with the University College London Migration Research Unit (MRU), and our PhD research explores the lived experiences of migrants and people affected by migration. This is the first of two articles in this issue of Migration and Society addressing the implications of COVID-19 on migration research from the perspective of postgraduate researchers. In this article, we firstly reflect on how “crises,” including the COVID-19 pandemic, inevitably shape contexts of migration research. We then share how COVID-19 has shaped our relationship to “the field” and our formal research institutions. Finally, we share how we have adapted our methodologies in response to COVID-19 and, considering the complex ethical and practical challenges posed by this context, reflect on what it means to make methodological “adaptations” in times of overlapping crises

O conceito de conflitos ambientais na revista de direito ambiental no ano de 2010

Em continuidade à pesquisa sobre conflitos ambientais, realizada no ano de 2010, busca-se verificar a visão de articulistas de uma revista especializada em direito ambiental dos conflitos atuais, categorizando seus conceitos e perspectivas. No presente estudo, ainda em andamento, foram selecionados 08 artigos publicados no ano de 2010 na Revista de Direito Ambiental da Editora Revista dos Tribunais, referência na área, detentora de avaliação B2 no sistema Qualis, pertencente ao acervo da Biblioteca Central do UniFOA. Está sendo realizado, a partir da leitura dos referidos artigos, a identificação do que consiste, em cada caso, na perspectiva do autor, o conflito ambiental. Estão sendo avaliados a conceituação de conflito, identificando o bem ambiental violado, os atores envolvidos e seus papéis. O objetivo foi o de identificar os conflitos ambientais abordados nos artigos publicados, categorizar conceitos de conflitos ambientais, relacionar os argumentos utilizados e estabelecer uma relação entre os conflitos e os fundamentos utilizados para a sua solução

Evaluation of the Uro-Quick system for antibiotic susceptibility tests of strains collected from intensive care units

During the period January–June 2004, 525 pathogens isolated from intensive care units were examined with the new rapid Uro-Quick method for antibiotic susceptibility tests. The results were compared with those obtained by the reference NCCLS methods (disk diffusion or dilution). Antibiotic (in appropriate concentration) was introduced in a vial containing 2 ml of Mueller-Hin ton broth, then 0.5 ml of 5×10 or 106 cells/ml of the strain culture were added. After 3–6 h of incubation, depending on the microorganism studied, the instrument printed the results: no growth and a growth curve similar to that of the untreated control are representative of a susceptible and resistant strain respectively. The following drugs were tested: ciprofloxacin, ampicillin, aztreonam, co-clavulanate, piperacillin/tazobactam, ceftazidime, cefotaxime, cefuroxime, ceftriaxone, imipenem, amikacin, gentamicin, trimethoprim-sulfamethoxazole, clindamycin, erythromycin, linezolid, penicillin, tetracycline, vancomycin, oxacillin. Gram-negative strains tested were 252 and Gram-positive 273: agreement between the two methods ranged from 85.6% (piperacillin/tazobactam) to 98.5% (ciprofloxact) in Gram-negative pathogens, from 90 to 100% in Gram-positive, with the exception of erythromycin (84.2%) against enterococci. On the basis of the present findings the Uro-Quick system appears to be very useful for the rapid detection of antibiotic susceptibility in pathogens collected from intensive care units

One-Dimensional Discrete Stark Hamiltonian and Resonance Scattering by Impurities

A one-dimensional discrete Stark Hamiltonian with a continuous electric field is constructed by extension theory methods. In absence of the impurities the model is proved to be exactly solvable, the spectrum is shown to be simple, continuous, filling the real axis; the eigenfunctions, the resolvent and the spectral measure are constructed explicitly. For this (unperturbed) system the resonance spectrum is shown to be empty. The model considering impurity in a single node is also constructed using the operator extension theory methods. The spectral analysis is performed and the dispersion equation for the resolvent singularities is obtained. The resonance spectrum is shown to contain infinite discrete set of resonances. One-to-one correspondence of the constructed Hamiltonian to some Lee-Friedrichs model is established.Comment: 20 pages, Latex, no figure