56 research outputs found

    High-Momentum Response of Liquid 3He

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    A final-state-effects formalism suitable to analyze the high-momentum response of Fermi liquids is presented and used to study the dynamic structure function of liquid 3He. The theory, developed as a natural extension of the Gersch-Rodriguez formalism, incorporates the Fermi statistics explicitly through a new additive term which depends on the semidiagonal two-body density matrix. The use of a realistic momentum distribution, calculated using the diffusion Monte Carlo method, and the inclusion of this additive correction allows for good agreement with available deep-inelastic neutron scattering data

    Quantifying 210Po/210Pb disequilibrium in seawater: A comparison of two precipitation methods with differing results

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    The disequilibrium between lead-210 (210Pb) and polonium-210 (210Po) is increasingly used in oceanography to quantify particulate organic carbon (POC) export from the upper ocean. This proxy is based on the deficits of 210Po typically observed in the upper water column due to the preferential removal of 210Po relative to 210Pb by sinking particles. Yet, a number of studies have reported unexpected large 210Po deficits in the deep ocean indicating scavenging of 210Po despite its radioactive mean life of ∼ 200 days. Two precipitation methods, Fe(OH)3 and Co-APDC, are typically used to concentrate Pb and Po from seawater samples, and deep 210Po deficits raise the question whether this feature is biogeochemically consistent or there is a methodological issue. Here, we present a compilation of 210Pb and 210Po studies that suggests that 210Po deficits at depths \u3e 300 m are more often observed in studies where Fe(OH)3 is used to precipitate Pb and Po from seawater, than in those using Co-APDC (in 68 versus 33% of the profiles analyzed for each method, respectively). In order to test whether 210Po/210Pb disequilibrium can be partly related to a methodological artifact, we directly compared the total activities of 210Pb and 210Po in four duplicate ocean depth-profiles determined by using Fe(OH)3 and Co-APDC on unfiltered seawater samples. While both methods produced the same 210Pb activities, results from the Co-APDC method showed equilibrium between 210Pb and 210Po below 100 m, whereas the Fe(OH)3 method resulted in activities of 210Po significantly lower than 210Pb throughout the entire water column. These results show that 210Po deficits in deep waters, but also in the upper ocean, may be greater when calculated using a commonly used Fe(OH)3 protocol. This finding has potential implications for the use of the 210Po/210Pb pair as a tracer of particle export in the oceans because 210Po (and thus POC) fluxes calculated using Fe(OH)3 on unfiltered seawater samples may be overestimated. Recommendations for future research are provided based on the possible reasons for the discrepancy in 210Po activities between both analytical methods

    Considerations for COVID-19 management in reception centers for refugees, asylum seekers, and migrants, Spain 2020

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    Shortly after the declaration of the COVID-19 pandemic, governments around the world were urged to leave no population behind. Following a COVID-19 risk evaluation in a refugee and asylum seekers reception center, in September 2020, we considered the priorities of managing COVID-19 in these settings. We encourage actions on four fronts to reduce the COVID-19 associated burden amongst these vulnerable populations based on our interviews, observations and recommendations: (i) decongestion, (ii) facilitated testing, (iii) screening for symptoms and (iv) targeted public health and risk communication.S

    Quantifying 210Po/210Pb Disequilibrium in Seawater: A Comparison of Two Precipitation Methods With Differing Results

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    The disequilibrium between lead-210 (210Pb) and polonium-210 (210Po) is increasingly used in oceanography to quantify particulate organic carbon (POC) export from the upper ocean. This proxy is based on the deficits of 210Po typically observed in the upper water column due to the preferential removal of 210Po relative to 210Pb by sinking particles. Yet, a number of studies have reported unexpected large 210Po deficits in the deep ocean indicating scavenging of 210Po despite its radioactive mean life of ∼ 200 days. Two precipitation methods, Fe(OH)3 and Co-APDC, are typically used to concentrate Pb and Po from seawater samples, and deep 210Po deficits raise the question whether this feature is biogeochemically consistent or there is a methodological issue. Here, we present a compilation of 210Pb and 210Po studies that suggests that 210Po deficits at depths >300 m are more often observed in studies where Fe(OH)3 is used to precipitate Pb and Po from seawater, than in those using Co-APDC (in 68 versus 33% of the profiles analyzed for each method, respectively). In order to test whether 210Po/210Pb disequilibrium can be partly related to a methodological artifact, we directly compared the total activities of 210Pb and 210Po in four duplicate ocean depth-profiles determined by using Fe(OH)3 and Co-APDC on unfiltered seawater samples. While both methods produced the same 210Pb activities, results from the Co-APDC method showed equilibrium between 210Pb and 210Po below 100 m, whereas the Fe(OH)3 method resulted in activities of 210Po significantly lower than 210Pb throughout the entire water column. These results show that 210Po deficits in deep waters, but also in the upper ocean, may be greater when calculated using a commonly used Fe(OH)3 protocol. This finding has potential implications for the use of the 210Po/210Pb pair as a tracer of particle export in the oceans because 210Po (and thus POC) fluxes calculated using Fe(OH)3 on unfiltered seawater samples may be overestimated. Recommendations for future research are provided based on the possible reasons for the discrepancy in 210Po activities between both analytical methods

    Introduction to the French GEOTRACES North Atlantic Transect (GA01): GEOVIDE cruise

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    The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French-led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this special issue (https://www.biogeosciences.net/special_issue900.html), results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among 18 articles. Here, the scientific context, project objectives, and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue

    F.J. Clemens and Some Aspects of Neo-Scholasticism in the Education of F. Brentano

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    Among the few publications which consider the Scholastic roots of Brentano’s thinking, an article by Dieter Münch stands out. In it, he claims that the Aristotelian studies of Brentano and his whole philosophical project are inspired by the German Neo-Scholastic movement. Münch presents the Neo-Scholastic tendency as an ultra-conservative and reactionary program against modernity. Now, such a description makes almost inexplicable the fact that Brentano, who was educated in this context, could have developed a wholly personal and independent philosophy. To approach this framework objectively, I propose to pay attention to F.J. Clemens, a Neo-Scholastic who influenced Brentano’s way of thinking. It is true that Clemens puts faith above reason and affirms that any conclusion obtained through the power of reason must be discarded when it contradicts faith. However, this is not an ultramontane innovation but simply the traditional theological point of view. He also argues that St. Thomas should be followed as a guide to orient oneself in the process of rational inquiry. Nevertheless, he doesn’t want to understand philosophy as a repetition of Aquinas’ claims; on the contrary, he rather proposes an intelligent use of tradition, which allows us to delve deeper into philosophical truth. For this very reason, he does not discard modernity or condemn it altogether. This perspective is also reflected in the early writings of Brentano, where he showed discontinuity from the Neo-Scholastic school of thought

    Effectiveness of influenza vaccine against laboratory-confirmed influenza, in the late 2011-2012 season in Spain, among population targeted for vaccination

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    Background: In Spain, the influenza vaccine effectiveness (VE) was estimated in the last three seasons using the observational study cycEVA conducted in the frame of the existing Spanish Influenza Sentinel Surveillance System. The objective of the study was to estimate influenza vaccine effectiveness (VE) against medically attended, laboratory-confirmed influenza-like illness (ILI) among the target groups for vaccination in Spain in the 2011-2012 season. We also studied influenza VE in the early (weeks 52/2011-7/2012) and late (weeks 8-14/2012) phases of the epidemic and according to time since vaccination. Methods: Medically attended patients with ILI were systematically swabbed to collect information on exposure, laboratory outcome and confounding factors. Patients belonging to target groups for vaccination and who were swabbed 4 months, respectively, since vaccination. A decrease in VE with time since vaccination was only observed in individuals aged ≥ 65 years. Regarding the phase of the season, decreasing point estimates were only observed in the early phase, whereas very low or null estimates were obtained in the late phase for the shortest time interval. Conclusions: The 2011-2012 influenza vaccine showed a low-to-moderate protective effect against medically attended, laboratory-confirmed influenza in the target groups for vaccination, in a late season and with a limited match between the vaccine and circulating strains. The suggested decrease in influenza VE with time since vaccination was mostly observed in the elderly population. The decreasing protective effect of the vaccine in the late part of the season could be related to waning vaccine protection because no viral changes were identified throughout the season

    Interim 2017/18 influenza seasonal vaccine effectiveness: Combined results from five European studies

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    Between September 2017 and February 2018, influenza A(H1N1)pdm09, A(H3N2) and B viruses (mainly B/Yamagata, not included in 2017/18 trivalent vaccines) co-circulated in Europe. Interim results from five European studies indicate that, in all age groups, 2017/18 influenza vaccine effectiveness was 25 to 52% against any influenza, 55 to 68% against influenza A(H1N1)pdm09, -42 to 7% against influenza A(H3N2) and 36 to 54% against influenza B. 2017/18 influenza vaccine should be promoted where influenza still circulates

    Optimisation and characterisation of durable microelectrodes for electroanalysis in molten salt

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    This work presents microfabricated microelectrodes, capable of quantitative analysis in molten salt (MS). MSs are an electrolytic medium of growing interest, especially in the area of nuclear reprocessing. However, designing sensors for a MS-based nuclear reprocessing system is a challenge, owing to the usually corrosive nature and high operating temperatures (typically 450 - 500◦C) of MS. Microelectrodes are well placed as sensors, with numerous advantages over macro-scale electrodes. As a consequence, there have been previous attempts to utilise microelectrodes inMS. However, these have not been successful and all have suffered disadvantages inherent in traditional microelectrode manufacturing. The microelectrodes presented in this work were produced using standard microfabrication techniques and characterised in MS. An analysis of failure mechanisms guided a systematic study of material combinations. This resulted in a sensor, which is capable of delivering quantifiable electrochemistry in MS. However, the lifetime and yield of the sensor were determined to only be 46% and 1.4 hours respectively. Further investigation of the microelectrode failure mechanisms guided several layout changes to the microelectrode design. By reducing critical area, where defects or pinholes could form, these resulted in improvements in performance. This increased the yield to 65%, while the average lifetime increased up to 45 hours. Test structures were designed to investigate the causes of the continued microelectrode failures and identified shorting between the electrode metal and silicon substrate. This suggests the existence of defects in the underlying insulator are the cause of the 35% of microelectrodes which never functioned. Separate test structures suggested the lifetimes of the microelectrodes could also be improved by removing the need for a metal adhesion layer. Tantalum has been suggested as a replacement electrode metal and a proof of concept study demonstrated the feasibility of employing thin film tantalum as an electrode metal in LKE. Using this technology as a platform, several proof-of-concept microelectrode designs are also presented: liquid microelectrodes, microelectrode arrays, and a nanoelectrode. These are targeted at specific sensing applications, and provide an expanded spectrum of measurements in MS
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