Electronic excitations and the tunneling spectra of metallic nanograins

Tunneling-induced electronic excitations in a metallic nanograin are classified in terms of {\em generations}: subspaces of excitations containing a specific number of electron-hole pairs. This yields a hierarchy of populated excited states of the nanograin that strongly depends on (a) the available electronic energy levels; and (b) the ratio between the electronic relaxation rate within the nano-grain and the bottleneck rate for tunneling transitions. To study the response of the electronic energy level structure of the nanograin to the excitations, and its signature in the tunneling spectrum, we propose a microscopic mean-field theory. Two main features emerge when considering an Al nanograin coated with Al oxide: (i) The electronic energy response fluctuates strongly in the presence of disorder, from level to level and excitation to excitation. Such fluctuations produce a dramatic sample dependence of the tunneling spectra. On the other hand, for excitations that are energetically accessible at low applied bias voltages, the magnitude of the response, reflected in the renormalization of the single-electron energy levels, is smaller than the average spacing between energy levels. (ii) If the tunneling and electronic relaxation time scales are such as to admit a significant non-equilibrium population of the excited nanoparticle states, it should be possible to realize much higher spectral densities of resonances than have been observed to date in such devices. These resonances arise from tunneling into ground-state and excited electronic energy levels, as well as from charge fluctuations present during tunneling.Comment: Submitted to the Physical Review

Effects of morphology on phonons of nanoscopic silver grains

The morphology of nanoscopic Ag grains significantly affects the phonons. Atomistic simulations show that realistic nanograin models display complex vibrational properties. (1) Single-crystalline grains. Nearly-pure torsional and radial phonons appear at low frequencies. For low-energy, faceted models, the breathing mode and acoustic gap (lowest frequency) are about 10% lower than predicted by elasticity theory (ET) for a continuum sphere of the same volume. The sharp edges and the atomic lattice split the ET-acoustic-gap quintet into a doublet and triplet. The surface protrusions associated with nearly spherical, high-energy models produce a smaller acoustic gap and a higher vibrational density of states (DOS) at frequencies \nu<2 THz. (2) Twined icosahedra. In contrast to the single-crystal case, the inherent strain produce a larger acoustic gap, while the core atoms yield a DOS tail extending beyond the highest frequency of single-crystalline grains. (3) Mark's decahedra, in contrast to (1) and (2), do not have a breathing mode; although twined and strained, do not exhibit a high-frequency tail in the DOS. (4) Irregular nanograins. Grain boundaries and surface disorder yield non-degenerate phonon frequencies, and significantly smaller acoustic gap. Only these nanograins exhibit a low-frequency \nu^2 DOS in the interval 1-2 THz.Comment: Version published in Phys. Rev.

Hops (\u3cem\u3eHumulus lupulus\u3c/em\u3e L.) Bitter Acids: Modulation of Rumen Fermentation and Potential as an Alternative Growth Promoter

Antibiotics can improve ruminant growth and efficiency by altering rumen fermentation via selective inhibition of microorganisms. However, antibiotic use is increasingly restricted due to concerns about the spread of antibiotic-resistance. Plant-based antimicrobials are alternatives to antibiotics in animal production. The hops plant (Humulus lupulus L.) produces a range of bioactive secondary metabolites, including antimicrobial prenylated phloroglucinols, which are commonly called alpha- and beta-acids. These latter compounds can be considered phyto-ionophores, phytochemicals with a similar antimicrobial mechanism of action to ionophore antibiotics (e.g., monensin, lasalocid). Like ionophores, the hop beta-acids inhibit rumen bacteria possessing a classical Gram-positive cell envelope. This selective inhibition causes several effects on rumen fermentation that are beneficial to finishing cattle, such as decreased proteolysis, ammonia production, acetate: propionate ratio, and methane production. This article reviews the effects of hops and hop secondary metabolites on rumen fermentation, including the physiological mechanisms on specific rumen microorganisms, and consequences for the ruminant host and ruminant production. Further, we propose that hop beta-acids are useful model natural products for ruminants because of (1) the ionophore-like mechanism of action and spectrum of activity and (2) the literature available on the plant due to its use in brewing. The purpose of this review is to collect and reexamine experiments that evaluated bitter acids from the hops plant (Humulus lupulus L.) as modifiers of rumen microbiology. These experiments were largely performed and reported over the last decade. However, historical work is drawn upon for context and for the origins of hypotheses. The thesis of the review is that the effects of bitter acids on rumen bacteria are similar to the effects of ionophore antibiotics, which have been used in ruminant nutrition for many years. This similarity and the vast body of current and historical literature on the hops plant make it an ideal model among rumen-active plant secondary metabolites. We have encountered a number of natural products researchers interested in microbiological uses of the bitter acids, but unfamiliar with rumen microbiology and its role in ruminant nutrition. Likewise, there are many ruminant scientists who are unfamiliar with the plant and its biochemistry. Both of these groups are the intended audience. Therefore, the review includes introductions to rumen microbiology and the hops plant

Fishing and bottom water temperature as drivers of change in maximum shell length in Atlantic surfclams (Spisula solidissima)

Maximum shell length of Atlantic surfclams (Spisula solidissima) on the Middle Atlantic Bight (MAB) continental shelf, obtained from federal fishery survey data from 1982-present, has decreased by 15-20 mm. Two potential causes of this decreasing trend, fishery removal of large animals and stress due to warming bottom temperatures, were investigated using an individual-based model for post-settlement surfclams and a fifty-year hindcast of bottom water temperatures on the MAB. Simulations showed that fishing and/or warming bottom water temperature can cause decreases in maximum surfclam shell length (body size) equivalent to those observed in the fished stock. Independently, either localized fishing rates of 20% or sustained bottom temperatures that are 2 degrees C warmer than average conditions generate the observed decrease in maximum shell length. However, these independent conditions represent extremes and are not sustained in the MAB. The combined effects of fishing and warmer temperatures can generate simulated length decreases that are similar to observed decreases. Interannual variability in bottom water temperatures can also generate fluctuations in simulated shell length of up to 20 mm over a period of 10-15 years. If the change in maximum size is not genotypic, simulations also suggest that shell size composition of surfclam populations can recover if conditions change; however, that recovery could take a decade to become evident

Effect of nanostructured ceria as support for the iron catalysed hydrogenation of CO2 into hydrocarbons.

This paper demonstrates the key role of the property-structure relationship of the support on iron/ceria catalysts on the hydrocarbon selectivity and olefin-to-paraffin ratio for the direct hydrogenation of carbon dioxide into hydrocarbons. The effect is directly related to the reducibility of the different nanostructured ceria supports and their interaction with the iron particles. Herein, we demonstrate that the iron-based catalysts can be modified not only by the addition of promoters, commonly reported in the literature, but also by careful control of the morphology of the ceria support.The authors thanks the UK Engineering and Physical Science Research Council (EPSRC, grant numbers: EP/L020432/2 and EP/G03768X/1).This is the final version of the article. It first appeared from the Royal Society of Chemistry via http://dx.doi.org/10.1039/C5CP07788

Red wine consumption and cardiovascular health

Wine is a popular alcoholic beverage that has been consumed for hundreds of years. Benefits from moderate alcohol consumption have been widely supported by the scientific literature and, in this line, red wine intake has been related to a lesser risk for coronary heart disease (CHD). Experimental studies and meta-analyses have mainly attributed this outcome to the presence in red wine of a great variety of polyphenolic compounds such as resveratrol, catechin, epicatechin, quercetin, and anthocyanin. Resveratrol is considered the most effective wine compound with respect to the prevention of CHD because of its antioxidant properties. The mechanisms responsible for its putative cardioprotective effects would include changes in lipid profiles, reduction of insulin resistance, and decrease in oxidative stress of low-density lipoprotein cholesterol (LDL-C). The aim of this review is to summarize the accumulated evidence correlating moderate red wine consumption with prevention of CHD by focusing on the different mechanisms underlying this relationship. Furthermore, the chemistry of wine as well as chemical factors that influence the composition of the bioactive components of red wine are also discussed

Time-walk and jitter correction in SNSPDs at high count rates

Superconducting nanowire single-photon detectors (SNSPDs) are a leading detector type for time correlated single photon counting, especially in the near-infrared. When operated at high count rates, SNSPDs exhibit increased timing jitter caused by internal device properties and features of the RF amplification chain. Variations in RF pulse height and shape lead to variations in the latency of timing measurements. To compensate for this, we demonstrate a calibration method that correlates delays in detection events with the time elapsed between pulses. The increase in jitter at high rates can be largely canceled in software by applying corrections derived from the calibration process. We demonstrate our method with a single-pixel tungsten silicide SNSPD and show it decreases high count rate jitter. The technique is especially effective at removing a long tail that appears in the instrument response function at high count rates. At a count rate of 11.4 MCounts/s we reduce the full width at one percent maximum level (FW1%M) by 45%. The method therefore enables certain quantum communication protocols that are rate-limited by the (FW1%M) metric to operate almost twice as fast. \c{opyright} 2022. All rights reserved.Comment: 5 pages, 3 figure

Sistema informático para la identificación de mascotas en la Provincia de Salta, Argentina

Actualmente en la ciudad de Salta no existe un sistema de identificación confiable para las mascotas. Además hay desconocimiento por parte de los propietarios, sobre tenencia responsable de animales y su bienestar. Es por eso que se puso en marcha este proyecto de investigación y desarrollo tecnológico veterinario, para proporcionar los medios necesarios para la identificación correcta de caninos y felinos domésticos, en conjunto con la difusión de la tenencia responsable de mascotas. El proyecto se basa en el estudio y desarrollo de un prototipo de sistema de identificación electrónica de mascotas, mediante la incorporación de un microchip subcutáneo vinculando los datos del canino y/o felino con los del propietario. Toda esta información se registrará en un sistema informático de gestión (SIG), desarrollado por la Facultad de Ingeniería. El centro operativo de procesamiento de los datos obtenidos estará a cargo de la Facultad de Veterinaria, que será la encargada de realizar evaluación, análisis estadísticos y epidemiológicos de la población canina y felina de la ciudad de Salta. Otro recurso en desarrollo será una aplicación de celulares (APP) de acceso público, que registrará datos de los propietarios y de sus mascotas, los cuales serán descargados en el sistema informático configurado en la Facultad de Ciencias Agrarias y Veterinarias. Los propietarios tendrán acceso a conocer el estado sanitario de su mascota, obtener información relacionada a la tenencia responsable, saber las patologías más frecuentes de la región, conocer el padrón de médicos veterinarios de la zona y -entre otras opciones- localizar a sus mascotas en caso de extravío

Ethical sensitivity in teaching and teacher education

Peer reviewe

Is self-assessment in religious education unique?

This paper addresses the question: is self-assessment in religious education unique? It first presents an overview of some challenges for assessment from subject differences, and then reviews the generic literature on self-assessment. It builds on earlier empirical research on self-assessment in religious education, carried out in an English state secondary school (Fancourt 2010); this was used to propose a variant of self-assessment which is tailored to the demands of religious education – reflexive self-assessment. Its implications for more general understandings of the relationship between subject pedagogy and self-assessment are discussed, especially the recognition of values not only in religious education but in other subjects too, reinforcing the need to develop subject-specific variants of self-assessment that reflect the breadth of learning outcomes