The CONNIE detector prototype is operating at a distance of 30 m from the core of a 3.8 GW sub(th) nuclear reactor with the goal of establishing Charge-Coupled Devices (CCD) as a new technology for ...the detection of coherent elastic neutrino-nucleus scattering. We report on the results of the engineering run with an active mass of 4 g of silicon. The CCD array is described, and the performance observed during the first year is discussed. A compact passive shield was deployed around the detector, producing an order of magnitude reduction in the background rate. The remaining background observed during the run was stable, and dominated by internal contamination in the detector packaging materials. The in-situ calibration of the detector using X-ray lines from fluorescence demonstrates good stability of the readout system. The event rates with the reactor ON and OFF are compared, and no excess is observed coming from nuclear fission at the power plant. The upper limit for the neutrino event rate is set two orders of magnitude above the expectations for the standard model. The results demonstrate the cryogenic CCD-based detector can be remotely operated at the reactor site with stable noise below 2 e super(-) RMS and stable background rates. The success of the engineering test provides a clear path for the upgraded 100 g detector to be deployed during 2016.
The CONNIE Experiment (Coherent Neutrino Nucleus Interaction Experiment) is currently collecting reactor neutrino data to search for the undiscovered standard model process of coherent ...neutrino-nucleus scattering (CNNS). The detector is composed of a silicon target of thick, fully-depleted, low-noise CCD detectors. Results from data collected in 2015 indicate backgrounds are controlled, and allow an estimate of sensitivity to be presented for a larger scale detector. A 2016 upgrade, adding additional target mass, and reducing readout noise, has been performed, increasing the total yield of signal events by a factor of 30, and already yielding science-quality data. Low-energy nuclear calibrations have been performed, enabling calibration down to the device energy threshold. An estimate of the sensitivity expected for measuring the coherent neutrino process is presented. Future prospects with improved detector energy thresholds are estimated.
Low-energy neutrinos are clean messengers from supernovae explosions and probably carry unique insights into the process of stellar evolution. We estimate the expected number of events considering ...coherent elastic scattering of neutrinos off silicon nuclei, as would happen in Charge Coupled Devices (CCD) detectors. The number of expected events, integrated over a window of about 18 s, is ∼4 if we assume 10 kg of silicon and a supernovae 1 kpc away. For a distance similar to the red supergiant Betelgeuse, the number of expected events increases to ∼ 30–120, depending on the supernovae model. We argue that silicon detectors can be effective for supernovae neutrinos, and might possibly distinguish between models for certain target masses and distances.
Abstract This article presents the results of our study on the public perception of science during the COVID-19 pandemic in Brazil, carried out at the Centro de Estudos SoU_Ciência, from Universidade ...Federal de São Paulo (UNIFESP). To answer the question: “Has the COVID-19 pandemic changed the perception of Brazilian society about science, scientists, and universities?”, quantitative and qualitative studies were conducted between August 2021 and July 2022. In national quantitative public opinion surveys, we collected exclusive data from a historical series of polls on the subject in Brazil, and in focus groups, we deepened studies on the perception and political position of different social segments. Amid the growth of scientific denialism; political and social setbacks; and the dismantling of public policies, specifically scientific and technological, resulting from the impeachment of 2016 and the election of Bolsonaro in 2018, research indicates, apparently contrary to an obscurantist political tendency, a significant expansion of public interest in science during the pandemic in the country. This paper analyzes the emergence of a “pro-science wave” in public opinion in Brazil, the factors that led to its emergence during the pandemic, and its current prospects.
Resumo O artigo apresenta resultados de pesquisas sobre percepção pública da ciência na pandemia no Brasil, realizadas no Centro de Estudos SoU_Ciência, sediado na Universidade Federal de São Paulo (Unifesp). Com o intuito de responder à pergunta: “A pandemia da COVID-19 alterou a percepção da sociedade brasileira sobre ciência, cientistas e universidades?”, realizamos estudos quantitativos e qualitativos entre agosto/2021 e julho/2022. Em levantamentos quantitativos nacionais de opinião pública, coletamos dados exclusivos de série histórica de enquetes sobre o tema no Brasil, e em grupos focais, aprofundamos estudos sobre percepção e posicionamento político de diferentes segmentos sociais. Em meio ao quadro de crescimento do negacionismo científico, retrocessos políticos e sociais, desmonte de políticas públicas, especificamente científicas e tecnológicas, decorrentes do impeachment de 2016 e da eleição de Bolsonaro em 2018, as pesquisas indicam, aparentemente contrariando a tendência política obscurantista, uma expressiva ampliação do interesse público pela ciência na pandemia no país. Este trabalho analisa a emergência de uma “onda pró-ciência” na opinião pública no Brasil, os fatores que propiciaram seu surgimento na pandemia e suas perspectivas na atualidade.
Enveloped animal viruses must undergo membrane fusion to deliver their genome into the host cell. We demonstrate that high pressure inactivates two membrane-enveloped viruses, influenza and Sindbis, ...by trapping the particles in a fusion-intermediate state. The pressure-induced conformational changes in Sindbis and influenza viruses were followed using intrinsic and extrinsic fluorescence spectroscopy, circular dichroism, and fusion, plaque, and hemagglutination assays. Influenza virus subjected to pressure exposes hydrophobic domains as determined by tryptophan fluorescence and by the binding of bis-8-anilino-1-naphthalenesulfonate, a well established marker of the fusogenic state in influenza virus. Pressure also produced an increase in the fusion activity at neutral pH as monitored by fluorescence resonance energy transfer using lipid vesicles labeled with fluorescence probes. Sindbis virus also underwent conformational changes induced by pressure similar to those in influenza virus, and the increase in fusion activity was followed by pyrene excimer fluorescence of the metabolically labeled virus particles. Overall we show that pressure elicits subtle changes in the whole structure of the enveloped viruses triggering a conformational change that is similar to the change triggered by low pH. Our data strengthen the hypothesis that the native conformation of fusion proteins is metastable, and a cycle of pressure leads to a final state, the fusion-active state, of smaller volume.
The CONNIE detector prototype is operating at a distance of 30 m from the core of a 3.8 GW\(_{\rm th}\) nuclear reactor with the goal of establishing Charge-Coupled Devices (CCD) as a new technology ...for the detection of coherent elastic neutrino-nucleus scattering. We report on the results of the engineering run with an active mass of 4 g of silicon. The CCD array is described, and the performance observed during the first year is discussed. A compact passive shield was deployed for the detector, producing an order of magnitude reduction in the background rate. The remaining background observed during the run was stable, and dominated by internal contamination in the detector packaging materials. The {\it in-situ} calibration of the detector using X-ray lines from fluorescence demonstrates good stability of the readout system. The event rates with the reactor on and off are compared, and no excess is observed coming from nuclear fission at the power plant. The upper limit for the neutrino event rate is set two orders of magnitude above the expectations for the standard model. The results demonstrate the cryogenic CCD-based detector can be remotely operated at the reactor site with stable noise below 2 e\(^-\) RMS and stable background rates. The success of the engineering test provides a clear path for the upgraded 100 g detector to be deployed during 2016.
We investigated the mechanisms of anticoagulant activity mediated by sulfated galactans. The anticoagulant activity of sulfated
polysaccharides is achieved mainly through potentiation of plasma ...cofactors, which are the natural inhibitors of coagulation
proteases. Our results indicated the following. 1) Structural requirements for the interaction of sulfated galactans with
coagulation inhibitors and their target proteases are not merely a consequence of their charge density. 2) The structural
basis of this interaction is complex because it involves naturally heterogeneous polysaccharides but depends on the distribution
of sulfate groups and on monosaccharide composition. 3) Sulfated galactans require significantly longer chains than heparin
to achieve anticoagulant activity. 4) Possibly, it is the bulk structure of the sulfated galactan, and not a specific minor
component as in heparin, that determines its interaction with antithrombin. 5) Sulfated galactans of â¼15 to â¼45 kDa bind to
antithrombin but are unable to link the plasma inhibitor and thrombin. This last effect requires a molecular size above 45
kDa. 6) Sulfated galactan and heparin bind to different sites on antithrombin. 7) Sulfated galactans are less effective than
heparin at promoting antithrombin conformational activation. Overall, these observations indicate that a different mechanism
predominates over the conformational activation of antithrombin in ensuring the antithrombin-mediated anticoagulant activity
of the sulfated galactans. Possibly, sulfated galactan connects antithrombin and thrombin, holding the protease in an inactive
form. The conformational activation of antithrombin and the consequent formation of a covalent complex with thrombin appear
to be less important for the anticoagulant activity of sulfated galactan than for heparin. Our results demonstrate that the
paradigm of heparin-antithrombin interaction cannot be extended to other sulfated polysaccharides. Each type of polysaccharide
may form a particular complex with the plasma inhibitor and the target protease.
Enveloped viruses fuse their membranes with cellular membranes to transfer their genomes into cells at the beginning of infection. What is not clear, however, is the role of the envelope (lipid ...bilayer and glycoproteins) in the stability of the viral particle. To address this question, we compared the stability between enveloped and nucleocapsid particles of thealphavirus Mayaro using hydrostatic pressure and urea. The effects were monitored by intrinsic fluorescence, light scattering, and binding of fluorescent dyes, including bis(8-anilinonaphthalene-1-sulfonate) and ethidium bromide. Pressure caused a drastic dissociation of the nucleocapsids as determined by tryptophan fluorescence, light scattering, and gel filtration chromatography. Pressure-induced dissociation of the nucleocapsids was poorly reversible. In contrast, when the envelope was present, pressure effects were much less marked and were highly reversible. Binding of ethidium bromide occurred when nucleocapsids were dissociated under pressure, indicating exposure of the nucleic acid, whereas enveloped particles underwent no changes. Overall, our results demonstrate that removal of the envelope with the glycoproteins leads the particle to a metastable state and, during infection, may serve as the trigger for disassembly and delivery of the genome. The envelope acts as a “Trojan horse,” gaining entry into the host cell to allow release of a metastable nucleocapsid prone to disassembly.
The pressure-induced dissociation of the dimeric DNA binding domain of the E2 protein of human papillomavirus (E2-DBD) is a reversible process with a Kd of 5.6 × 10−8m at pH 5.5. The complete ...exposure of the intersubunit tryptophans to water, together with the concentration dependence of the pressure effect, is indicative of dissociation. Dissociation is accompanied by a decrease in volume of 76 ml/mol, which corresponds to an estimated increase in solvent-exposed area of 2775 Å2. There is a decrease in fluorescence polarization of tryptophan overlapping the red shift of fluorescence emission, supporting the idea that dissociation of E2-DBD occurs in parallel with major changes in the tertiary structure. The dimer binds bis(8-anilinonaphthalene-1-sulfonate), and pressure reduces the binding by about 30%, in contrast with the almost complete loss of dye binding in the urea-unfolded state. These results strongly suggest the persistence of substantial residual structure in the high pressure state. Further unfolding of the high pressure state was produced by low concentrations of urea, as evidenced by the complete loss of bis(8-anilinonaphthalene-1-sulfonate) binding with less than 1m urea. Following pressure dissociation, a partially folded state is also apparent from the distribution of excited state lifetimes of tryptophan. The combined data show that the tryptophans of the protein in the pressure-dissociated state are exposed long enough to undergo solvent relaxation, but the persistence of structure is evident from the observed internal quenching, which is absent in the completely unfolded state. The average rotational relaxation time (derived from polarization and lifetime data) of the pressure-induced monomer is shorter than the urea-denatured state, suggesting that the species obtained under pressure are more compact than that unfolded by urea.
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