Magnetic microwires as macrospins in a long-range dipole-dipole interaction

The long-range dipole-dipole interaction in an array of ferromagnetic microwires is studied through magnetic hysteresis measurements and Monte Carlo simulation. The experimental study has been performed on glass-coated amorphous Fe77.5Si7.5B15 microwire with diameter of 5 mu m and lengths from 5 to 60 mm. Hysteresis loops performed at room temperature for an array of N microwires (N = 2, 3, 3, and 5) exhibit jumps and plateaux on the demagnetization, each step correspondent to the magnetization reversal of an individual wire. A model has been constructed taking into account the fact that the magnetization reversal is nucleated at the ends of each wire, under the influence of a dipolar field due to all other wires. Measurements for two wires allowed us to conclude that the dipolar field (or constant coupling) is independent of distance, at least for an array of a few wires. With the exception of three wires, where frustration seems to be present, the predicted reversal fields of our model are in good agreement with measurements. Ln order to study the role played by the number of wires on the demagnetization process, we calculate hysteresis loops for a large number of wires through the Monte Carlo method.61138976898

Presence of pathogenic Escherichia coli is correlated with bacterial community diversity and composition on pre-harvest cattle hides

Citation: Chopyk, J., Moore, R. M., DiSpirito, Z., Stromberg, Z. R., Lewis, G. L., Renter, D. G., . . . Wommack, K. E. (2016). Presence of pathogenic Escherichia coli is correlated with bacterial community diversity and composition on pre-harvest cattle hides. Microbiome, 4, 11. doi:10.1186/s40168-016-0155-4Background: Since 1982, specific serotypes of Shiga toxin-producing Escherichia coli (STEC) have been recognized as significant foodborne pathogens acquired from contaminated beef and, more recently, other food products. Cattle are the major reservoir hosts of these organisms, and while there have been advancements in food safety practices and industry standards, STEC still remains prevalent within beef cattle operations with cattle hides implicated as major sources of carcass contamination. To investigate whether the composition of hide-specific microbial communities are associated with STEC prevalence, 16S ribosomal RNA (rRNA) bacterial community profiles were obtained from hide and fecal samples collected from a large commercial feedlot over a 3-month period. These community data were examined amidst an extensive collection of prevalence data on a subgroup of STEC that cause illness in humans, referred to as enterohemorrhagic E. coli (EHEC). Fecal 16S rRNA gene OTUs (operational taxonomic units) were subtracted from the OTUs found within each hide 16S rRNA amplicon library to identify hide-specific bacterial populations. Results: Comparative analysis of alpha diversity revealed a significant correlation between low bacterial diversity and samples positive for the presence of E. coli O157:H7 and/or the non-O157 groups: O26, O111, O103, O121, O45, and O145. This trend occurred regardless of diversity metric or fecal OTU presence. The number of EHEC serogroups present in the samples had a compounding effect on the inverse relationship between pathogen presence and bacterial diversity. Beta diversity data showed differences in bacterial community composition between samples containing O157 and non-O157 populations, with certain OTUs demonstrating significant changes in relative abundance. Conclusions: The cumulative prevalence of the targeted EHEC serogroups was correlated with low bacterial community diversity on pre-harvest cattle hides. Understanding the relationship between indigenous hide bacterial communities and populations may provide strategies to limit EHEC in cattle and provide biomarkers for EHEC risk assessment

Observation of Quantum Asymmetry in an Aharonov-Bohm Ring

We have investigated the Aharonov-Bohm effect in a one-dimensional GaAs/GaAlAs ring at low magnetic fields. The oscillatory magnetoconductance of these systems are for the first time systematically studied as a function of density. We observe phase-shifts of $\pi$ in the magnetoconductance oscillations, and halving of the fundamental $h/e$ period, as the density is varied. Theoretically we find agreement with the experiment, by introducing an asymmetry between the two arms of the ring.Comment: 4 pages RevTex including 3 figures, submitted to Phys. Rev.

Mesoscopic Stern-Gerlach device to polarize spin currents

Spin preparation and spin detection are fundamental problems in spintronics and in several solid state proposals for quantum information processing. Here we propose the mesoscopic equivalent of an optical polarizing beam splitter (PBS). This interferometric device uses non-dispersive phases (Aharonov-Bohm and Rashba) in order to separate spin up and spin down carriers into distinct outputs and thus it is analogous to a Stern-Gerlach apparatus. It can be used both as a spin preparation device and as a spin measuring device by converting spin into charge (orbital) degrees of freedom. An important feature of the proposed spin polarizer is that no ferromagnetic contacts are used.Comment: Updated to the published versio

Channel Interference in a Quasi Ballistic Aharonov-Bohm Experiment

New experiments are presented on the transmission of electron waves through a 2DEG (2 dimensional electron gas) ring with a gate on top of one of the branches. Magnetoconductance oscillations are observed, and the phase of the Aharanov-Bohm signal alternates between 0 and pi as the gate voltage is scanned. A Fourier transform of the data reveals a dominant period in the voltage which corresponds to the energy spacing between successive transverse modes.A theoretical model including random phase shifts between successive modes reproduces the essential features of the experiment.Comment: 4 pages, 6 Postscript figures, TEX, submitted to Physical Review Letter

Revisiting the role of swine on the risk of Japanese Encephalitis Virus (JEV) transmission in the United States: a rapid systematic review of the literature

Japanese Encephalitis (JE) is an emerging, zoonotic disease transmitted primarily by Culex species mosquitoes (particularly Culex tritaeniorhynchus) carrying the flavivirus Japanese encephalitis virus (JEV). Japanese encephalitis virus maintains its life cycle between mosquitoes and vertebrate hosts, primarily pigs and wading birds (Le Flohic et al., 2013). In humans, JEV infection causes inflammation of the brain (encephalitis) that can cause fever, headache, respiratory distress, gastrointestinal pain, confusion, seizures, and, in some cases, death (Fischer et al., 2012; Hills et al., 2014). The global incidence of JE is uncertain. Effectivity and quality of JE surveillance in endemic countries vary (Jayatilleke et al. 2020), as does availability of diagnostic testing throughout the world. In 2006, the WHO published a position paper on JE vaccines reporting an annual estimation of at least 50,000 new JE cases among those living in countries considered endemic. Campbell et al. (2011) updated prior estimations and predicted a global incidence of JE cases to be nearly 67,900 per year. Most recently, Quan et al. (2020) reported a global estimation of JE incidence of approximately 100,000 per year. Among all clinical cases, children under the age of 10 comprise the majority affected (WHO, 2006). Whereas less than 1% of the cases are accompanied by symptoms, 30% of the symptomatic cases are fatal (Campbell et al., 2011). Furthermore, JE is an untreatable and incurable disease that, once introduced in a community, can lead to devastating economic and health impacts. The United States (US) is considered a susceptible region with great potential for JEV introduction. The availability of competent vectors, susceptible maintenance hosts (avian), intensive travel and trade activities to and from JEV-affected countries, areas with similar climatic and environmental conditions to countries where the virus is epidemic, and large populations of susceptible, amplifying hosts (domestic and feral pigs), makes the US the perfect next-stop in the JEV travel itinerary. In fact, the US is the world’s third-largest producer and consumer of pork and pork products (USDA - ERS). The size of the swine industry in the US can not only be positively correlated with the ability of this virus to invade and establish itself, but also to the impact that an incursion would cause to the economy and the populations’ health. As pigs are considered the main amplifying host of JEV, an extensive review of the literature and identification of knowledge gaps may guide researchers, stakeholders, and policy makers on effort prioritization, development of precautionary intervention measures (to prevent JEV introduction), and evaluation of disease control measures (in case of JEV incursion). Although current conditions have not been favorable for JEV to establish in the US, increases in international trade and globalization, as well as changes in climate and land use, and reductions in pesticide use, can contribute to its rapid and wide geographical spread (Oliveira et al., 2018). A good understanding of the role of swine as an amplifying host for this virus is critical to public health authorities when planning and executing interventions to control the spread of JEV. Therefore, our objectives are 1) to investigate the role of swine on the risk of JEV transmission in the US as an effort for preparedness in the case of an introduction, and 2) to identify knowledge gaps that may serve as a guide to future research efforts

Friedel phases and phases of transmission amplitudes in quantum scattering systems

We illustrate the relation between the scattering phase appearing in the Friedel sum rule and the phase of the transmission amplitude for quantum scatterers connected to two one-dimensional leads. Transmission zero points cause abrupt phase changes $\pm\pi$ of the phase of the transmission amplitude. In contrast the Friedel phase is a continuous function of energy. We investigate these scattering phases for simple scattering problems and illustrate the behavior of these models by following the path of the transmission amplitude in the complex plane as a function of energy. We verify the Friedel sum rule for these models by direct calculation of the scattering phases and by direct calculation of the density of states.Comment: 12 pages, 12 figure

MARTA: A high-energy cosmic-ray detector concept with high-accuracy muon measurement

A new concept for the direct measurement of muons in air showers is presented. The concept is based on resistive plate chambers (RPCs), which can directly measure muons with very good space and time resolution. The muon detector is shielded by placing it under another detector able to absorb and measure the electromagnetic component of the showers such as a water-Cherenkov detector, commonly used in air shower arrays. The combination of the two detectors in a single, compact detector unit provides a unique measurement that opens rich possibilities in the study of air showers.Comment: 11 page

Practical Application of Sample Size Determination Models for Assessment of Mortality Outcomes in Swine Field Trials

Mortality within livestock production has a substantial impact on economic sustain­ability of enterprises. The livestock industry has a unique opportunity to maximize animal welfare and production efficiency by minimizing morbidity and mortality. To do so, investigators must appropriately balance the utilization of limited resources with the quantity necessary for robust research. The objective of the study was to illustrate the use of readily implementable statistical models to determine sample size neces­sary to detect statistically significant differences between groups with varying levels of mortality. To this end, a series of examples were created where the unit to which a treatment is independently applied (experimental unit, EU) is either half of a 1,200 pig barn (group-level) or an individual pen (pen-level, 25 pigs per pen, 48 total pens) within a 1,200 pig barn. These examples and corresponding models can be readily adapted and implemented using SAS software to meet individual needs. Model inputs include the number of pigs, barns, and pens when appropriate, and model output is the calculated statistical power. When the EU is half-barn and mortality is measured on a group-level, 7 barns would be necessary to detect a 1 percentage unit difference in mortality (2% vs. 1% for two groups, respectively). As the observed difference in mortality between groups increases, the number of barns needed to detect the respec­tive difference decreases and vice versa. When the EU is the individual pen containing 25 pigs, and mortality is measured on the pen level, a total of 240 pens or 5 barns would be necessary to detect the same 1 percentage unit reduction in mortality from 2% to 1%. Comparing the results derived from group or pen-level mortality, a relatively close number of pigs is necessary to detect differences. For example, if comparing group mortalities of 3% vs. 4%, the number of barns necessary for group-level mortality is 11 and for pen-level mortality is 9. The models currently proposed incorporate appropriate design structure features for a series of different study designs and assume that observed mortality follows a binomial distribution. Performing proper sample size calculations prior to initiation of research trials is critical to determine the necessary sample size to reasonably expect to see statistical differences. It is very important to recognize that proper use of this information requires background knowledge regarding statistical analysis including understanding of EU, observational unit, and design features such as blocking, subsampling, and other design features. When these assumptions change based on the experiment being planned, appropriate modifications must be made to the models. It is always recommended to engage a statistician in the early stages of experimental design to ensure all facets of the proposed experiment are appropriately accounted for and to reduce the risk of making inaccurate production decisions. Lastly, it is not recommended that these models be used in a manner that assumes one size fits all. Rather, we provide the information as a foundation from which the reader can use appropriate content expertise and statistical principles to assist with designing experi­ments

Neutrinos Angra experiment: commissioning and first operational measurements

The Neutrinos Angra Experiment has completed a major step by finishing the comissioning of the detector and the data acquisition system at the experimental site located in the Angra dos Reis nuclear power plant. The experiment consists of a water-based detector and associated electronics, both designed with the goal of detecting the electron antineutrinos produced by the nuclear reactor. The detection is possible due to the Inverse Beta Decay, where the final products in the water are photons in the UV-to-visible range of the spectrum. The assembled detector comprises three active volumes filled with water: (i) a cubic target detector for electron antineutrinos, covered by 32 8-inches PMTs, (ii) a lateral layer surrounding the target (veto) equipped with 4 PMTs and (iii) a third volume covering the top of both, also equipped with 4~PMTs. In the present document the main features of the detector assembly as well as the integration of the readout electronics on-site are reported. Finally, some operational characteristics are shown based on straightforward analysis of the first measurements performed during the last months with the fully working detector