4He adsorbed in cylindrical silica nanopores: Effect of size on the single-atom mean kinetic energy

This paper reports a study of the short-time dynamics of helium confined in silica nanopores (xerogel powder), with average pore diameters of 24 and 160 Å. The longitudinal momentum distribution of helium adsorbed in xerogels has been determined via deep inelastic neutron scattering (DINS) measurements performed on the VESUVIO spectrometer at the ISIS spallation source. DINS measurements, in the attosecond time scale, (i.e., 10−16–10−15 s), were performed at a temperature of T=2.5 K and saturated vapor pressure conditions, with 95% pore volume filling. The average wave-vector transfer q was about 130 Å−1. For confined helium, significant changes in the values of the single-particle mean kinetic energies ⟨EK⟩ are found in the bulk phase. These are 32.6±8.7 K for the 24 Å and 24.4±5.3 K for the 160 Å pore diameters, remarkably higher than ⟨EK⟩=16.2±0.4 K, the value of normal liquid 4He at T=2.5 K and saturated vapor pressure conditions. The results are interpreted in terms of a model where 4He atoms are arranged in concentric annuli along the cylindrical pore axis, with ⟨EK⟩ mainly dependent on the ratio between the atomic “effective” diameter and the pore diameter. The number of solid layers close to pore surface is found to be strongly pore-size dependent with one single solid layer for 24 Å diameter pore and three solid layers for 160 Å diameter pore

Direct Measurement of Competing Quantum Effects on the Kinetic Energy of Heavy Water upon Melting

Even at room temperature, quantum mechanics plays a major role in determining the quantitative behaviour of light nuclei, changing significantly the values of physical properties such as the heat capacity. However, other observables appear to be only weakly affected by nuclear quantum effects (NQEs): for instance, the melting temperatures of light and heavy water differ by less than 4 K. Recent theoretical work has attributed this to a competition between intra and inter molecular NQEs, which can be separated by computing the anisotropy of the quantum kinetic energy tensor. The principal values of this tensor change in opposite directions when ice melts, leading to a very small net quantum mechanical effect on the melting point. This paper presents the first direct experimental observation of this phenomenon, achieved by measuring the deuterium momentum distributions n(p) in heavy water and ice using Deep Inelastic Neutron Scattering (DINS), and resolving their anisotropy. Results from the experiments, supplemented by a theoretical analysis, show that the anisotropy of the quantum kinetic energy tensor can also be captured for heavier atoms such as oxygen

Hydrogen mean force and anharmonicity in polycrystalline and amorphous ice

The hydrogen mean force from experimental neutron Compton profiles is derived using deep inelastic neutron scattering on amorphous and polycrystalline ice. The formalism of mean force is extended to probe its sensitivity to anharmonicity in the hydrogen-nucleus effective potential. The shape of the mean force for amorphous and polycrystalline ice is primarily determined by the anisotropy of the underlying quasi-harmonic effective potential. The data from amorphous ice show an additional curvature reflecting the more pronounced anharmonicity of the effective potential with respect to that of ice Ih.Comment: 12 pages, 7 figures, original researc

Compact accelerator-driven neutron sources

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The correction of Inelastic Neutron Scattering data of organic samples using the Average Functional Group Approximation

The use of the Average Functional Group Approximation for self-shielding corrections at inelastic neutron spectrometers is discussed. By taking triptindane as a case study, we use the above-mentioned approximation to simulate a synthetic dynamic structure factor as measured on an indirect-geometry spectrometer, as well as the related total scattering cross section as a function of incident neutron energy and sample temperature, and the transmission spectra depending on the sample thickness. These quantities, obtained in a consistent way from the Average Functional Group Approximation, are used to calculate the energy-dependent self-shielding correction affecting the sample under investigation. The impact on the intensities of low-energy vibrational modes is discussed, showing that at typical experimental conditions the sample-dependent attenuation factor is about 15% higher compared to the correction at higher energies

Time-resolved prompt-gamma activation analysis at spallation neutron sources and applications to cultural heritage, security, and radiation protection

Abstract The present and future developments of time-resolved prompt-gamma activation analysis (T-PGAA) at pulsed neutron sources is discussed in the framework of the successful history of neutron-activation techniques. A brief description of the state of the art and the most important user facilities using standard prompt-gamma activation analysis (PGAA) is provided. Then, we discuss the challenges and the opportunities for T-PGAA at pulsed neutron sources, and the potential impact for applications to cultural heritage, radiation protection, and security. We notice some inversions of trend needed for the further development of T-PGAA with epithermal and fast neutrons, such as the possibility to use fast and high-efficiency γ-ray scintillators with lower energy resolution (compared to usual high-purity germanium detectors) when the signal from neutron capture resonance is selected. We also suggest how detection systems often used in other fields, such as medical physics, can be of interest and inspiration also in the case of neutron-based investigations. Finally, we present new data of T-PGAA measurements on VESUVIO using neutron energies up to the keV using the scintillators available on the instrument, for samples of gold (of interest in cultural heritage), cadmium (for environmental safety), and tantalum (a material used in biomedical implants)

OZÔNIO NO CONTROLE DE MICRO-ORGANISMOS EM RESÍDUOS DE SERVIÇOS DE SAÚDE

Os resíduos dos serviços de saúde estão recebendo merecida atenção nos últimos anos, não pela quantidade gerada, mas pelo risco potencial que representa à saúde e ao meio ambiente. Diferentes métodos são empregados com a finalidade de destruição dos micro-organismos. Nesta linha o ozônio é uma tecnologia que vem sendo utilizada em diversos segmentos, a fim de reduzir ou eliminar diversos micro-organismos, em virtude do seu alto poder de oxidação. O estudo teve como objetivo verificar a eficiência do ozônio no controle in vitro de micro-organismos isolados de Resíduos de Serviço de Saúde. Foi realizada análise microbiológica dos RSS e verificado eficiência do ozônio sobre os micro-organismos.  Foram identificados os seguintes micro-organismos patogênicos: Escherichia coli, Pseudomonas aeruginosa, Candida albicans, Clostridium tetani, Staphylococcus sp, Aspergillus niger, Trichophyton mentagrophytes, Microsporum gypseum e Clostridium sp.. Quando estes micro-organismos foram tratados com agua ozonizada verificou-se eficácia do ozônio no controle in vitro dos mesmos

MWCNT/rGO/natural rubber latex dispersions for innovative, piezo‐resistive and cement‐based composite sensors

The present study is focused on the development and characterization of innovative cementitious-based composite sensors. In particular, multifunctional cement mortars with enhanced piezoresistive properties are realized by exploiting the concept of confinement of Multiwall Carbon Nanotubes (MWCNTs) and reduced Graphene Oxide (rGO) in a three-dimensional percolated network through the use of a natural-rubber latex aqueous dispersion. The manufactured cement-based composites were characterized by means of Inelastic Neutron Scattering to assess the hydration reactions and the interactions between natural rubber and the hydrated-cement phases and by Scanning Electron Microscopy and X-Ray diffraction to evaluate the morphological and mineralogical structure, respectively. Piezo-resistive properties to assess electro-mechanical behavior in strain condition are also measured. The results show that the presence of natural rubber latex allows to obtain a three-dimensional rGO/MWCNTs segregate structure which catalyzes the formation of hydrated phases of the cement and increases the piezo-resistive sensitivity of mortar composites, representing a reliable approach in developing innovative mortar-based piezoresistive strain sensors

O uso de checklist como estratégia para redução de Pneumonia Associada à Ventilação Mecânica em uma Unidade de Terapia Intensiva Adulto

Justificativa e objetivos: Avaliar a efetividade uso do instrumento Fast-Check List desenvolvido por uma equipe interdisciplinar como estratégia de redução de tempo de ventilação mecânica(VM) e Pneumonia Associada à Ventilação Mecânica (PAV) em uma Unidade de Terapia Intensiva – Adulto. Métodos: Estudo quantitativo, longitudinal, observacional, realizado entre os meses de janeiro de 2018 a junho de 2019. Os dados foram analisados pelo teste de T. Resultados: Foram avaliados 759 internamentos entre janeiro de 2018 a junho de 2019, destes 283 utilizaram ventilação mecânica (VM). Os dados mostraram que antes do Fast-CheckList havia uma média de 3,22 de PAV e após a instituição do instrumento, o valor reduziu significativamente para 0,33(p=0,001). Condição igualmente observado para os dias de VM. A média de VM era de 157 dias, e passou para 133 (p=0,037) e a Densidade de PAV (DIPAV) era de 21,62 e passou para 2,82 (p=0,003). Através da análise, dá para inferir uma redução de 4,9% mês a mês dos casos de PAV. Conclusão: O uso de instrumentos como o checklist para redução de pneumonia associada à ventilação mecânica, acompanhado da mudança de cultura e participação ativa de equipes interdisciplinares são de extrema relevância na redução deste tipo de infecção e infecções relacionadas à assistência à saúde

Prevalência e fatores associados à fragilidade em idosos atendidos em um ambulatório de especialidades

Estudo transversal desenvolvido com 374 idosos de um hospital de ensino da região dos Campos Gerais que buscou identificar a prevaleência e fatores associados ã fragilidade em idosos de um ambulatório de especialidades médicas. A coleta de dados compreendeu entrevista, Mini Exame do Estado Mental e Escala Fragilidade de Edmonton. Realizou-se análise bivariada e múltipla por meio de regessão de Poisson com respectivos intervalos de confiança de 95% e nível de significância de p?0,05. A prevalência de fragilidade foi de 40,1%, com associação significativa às variáveis sexo feminino (p=0,002), baixa escolaridade (p=0,020), presença de doença(s) autorreferida(s) (p=0,006), medicamentos (p=0,001), perda de urina (p=0,001), quedas (p=0,001) e à hospitalização (p=0,001). A prevalência de fragilidade identificada foi discretamente inferior à constatada em estudo de um centro de referência e superior a idosos da comunidade, com fatores sociodemográficos e clínicos associados. Requerendo olhar atento dos profissionais da saúde acerca deste perfil