Magnetic field effects in few-level quantum dots: theory, and application to experiment

We examine several effects of an applied magnetic field on Anderson-type models for both single- and two-level quantum dots, and make direct comparison between numerical renormalization group (NRG) calculations and recent conductance measurements. On the theoretical side the focus is on magnetization, single-particle dynamics and zero-bias conductance, with emphasis on the universality arising in strongly correlated regimes; including a method to obtain the scaling behavior of field-induced Kondo resonance shifts over a very wide field range. NRG is also used to interpret recent experiments on spin-1/2 and spin-1 quantum dots in a magnetic field, which we argue do not wholly probe universal regimes of behavior; and the calculations are shown to yield good qualitative agreement with essentially all features seen in experiment. The results capture in particular the observed field-dependence of the Kondo conductance peak in a spin-1/2 dot, with quantitative deviations from experiment occurring at fields in excess of $\sim$ 5 T, indicating the eventual inadequacy of using the equilibrium single-particle spectrum to calculate the conductance at finite bias.Comment: 15 pages, 12 figures. Version as published in PR

Correlated electron physics in multilevel quantum dots: phase transitions, transport, and experiment

We study correlated two-level quantum dots, coupled in effective 1-channel fashion to metallic leads; with electron interactions including on-level and inter-level Coulomb repulsions, as well as the inter-orbital Hund's rule exchange favoring the spin-1 state in the relevant sector of the free dot. For arbitrary dot occupancy, the underlying phases, quantum phase transitions (QPTs), thermodynamics, single-particle dynamics and electronic transport properties are considered; and direct comparison is made to conductance experiments on lateral quantum dots. Two distinct phases arise generically, one characterised by a normal Fermi liquid fixed point (FP), the other by an underscreened (USC) spin-1 FP. Associated QPTs, which occur in general in a mixed valent regime of non-integral dot charge, are found to consist of continuous lines of Kosterlitz-Thouless transitions, separated by first order level-crossing transitions at high symmetry points. A `Friedel-Luttinger sum rule' is derived and, together with a deduced generalization of Luttinger's theorem to the USC phase (a singular Fermi liquid), is used to obtain a general result for the T=0 zero-bias conductance, expressed solely in terms of the dot occupancy and applicable to both phases. Relatedly, dynamical signatures of the QPT show two broad classes of behavior, corresponding to the collapse of either a Kondo resonance, or antiresonance, as the transition is approached from the Fermi liquid phase; the latter behavior being apparent in experimental differential conductance maps. The problem is studied using the numerical renormalization group method, combined with analytical arguments.Comment: 22 pages, 18 figures, submitted for publicatio

Excess Body Weight and Gait Influence Energy Cost of Walking in Older Adults

Purpose: To study how excess body weight influences the energy cost of walking (Cw) and determine if overweight and obese older adults self-select stride frequency to minimize Cw. Methods: Using body mass index (BMI) men and women between the ages of 65–80 yr were separated into normal weight (NW, BMI ≤ 24.9 kg m−2, n = 13) and overweight-obese groups (OWOB, BMI ≥25.0 kg m−2, n = 13). Subjects walked at 0.83 m s−1 on an instrumented treadmill that recorded gait parameters, and completed three, six-minute walking trials; at preferred stride frequency (PSF), at +10% PSF, and at −10% PSF. Cw was determined by indirect calorimetry. Repeated measures analysis of variance was used to compare groups, and associations were tested with Pearson correlations, α = 0.05. Results: OWOB had 62% greater absolute Cw (301 ± 108 vs. 186 ± 104 J m−1, P \u3c 0.001) and 20% greater relative Cwkg (3.48 ± 0.95 vs. 2.91 ± 0.94 J kg−1 m−1, P = 0.046) than NW. Although PSF was not different between OWOB and NW (P = 0.626), Cw was 8% greater in OWOB at +10% PSF (P \u3c 0.001). At PSF OWOB spent less time in single-limb support (33.1 ± 1.5 vs. 34.9 ± 1.6 %GC, P = 0.021) and more time in double-limb support (17.5 ± 1.6 vs. 15.4 ± 1.4 %GC, P = 0.026) than NW. In OWOB, at PSF, Cw was correlated to impulse (r = −0.57, P = 0.027) and stride frequency (r = 0.51, P = 0.046). Conclusions: Excess body weight is associated with greater Cw in older adults, possibly contributing to reduced mobility in overweight and obese older persons

The Z-Wave Routing Protocol and Its Security Implications

Z-Wave is a proprietary technology used to integrate sensors and actuators over RF and perform smart home and office automation services. Lacking implementation details, consumers are under-informed on the security aptitude of their installed distributed sensing and actuating systems. While the Physical (PHY) and Medium Access Control (MAC) layers of the protocol have been made public, details regarding the network layer are not available for analysis. Using a real-world Z-Wave network, the frame forwarding and topology management aspects of the Z-Wave routing protocol are reverse engineered. A security analysis is also performed on the network under study to identify source and data integrity vulnerabilities of the routing protocol. It is discovered that the topology and routes may be modified by an outsider through the exploitation of the blind trust inherent to the routing nodes of the network. A Black Hole attack is conducted on a real-world Z-Wave network to demonstrate a well-known routing attack that exploits the exposed vulnerabilities. As a result of the discoveries, several recommendations are made to enhance the security of the routing protocol

Refractive error and visual impairment in school children in Northern Ireland

To describe the prevalence of refractive error (myopia and hyperopia) and visual impairment in a representative sample of white school children

Refractive and corneal astigmatism in white school children in Northern Ireland

To study the prevalence of and relation between refractive and corneal astigmatism in white school children in Northern Ireland and to describe the association between refractive astigmatism and refractive error

Beyond Plants: The Ultra-Processing of Global Diets Is Harming the Health of People, Places, and Planet

Global food systems are a central issue for personal and planetary health in the Anthropocene. One aspect of major concern is the dramatic global spread of ultra-processed convenience foods in the last 75 years, which is linked with the rising human burden of disease and growing sustainability and environmental health challenges. However, there are also calls to radically transform global food systems, from animal to plant-derived protein sources, which may have unintended consequences. Commercial entities have moved toward this “great plant transition” with vigor. Whether motivated by profit or genuine environmental concern, this effort has facilitated the emergence of novel ultra-processed “plant-based” commercial products devoid of nutrients and fiber, and sometimes inclusive of high sugar, industrial fats, and synthetic additives. These and other ingredients combined into “plant-based” foods are often assumed to be healthy and lower in calorie content. However, the available evidence indicates that many of these products can potentially compromise health at all scales—of people, places, and planet. In this viewpoint, we summarize and reflect on the evidence and discussions presented at the Nova Network planetary health meeting on the “Future of Food”, which had a particular focus on the encroachment of ultra-processed foods into the global food supply, including the plant-sourced animal protein alternatives (and the collective of ingredients therein) that are finding their way into global fast-food chains. We contend that while there has been much uncritical media attention given to the environmental impact of protein and macronutrient sources—meat vs. novel soy/pea protein burgers, etc.—the impact of the heavy industrial processing on both human and environmental health is significant but often overlooked, including effects on cognition and mental health. This calls for a more nuanced discourse that considers these complexities and refocuses priorities and value systems towards mutualistic solutions, with co-benefits for individuals, local communities, and global ecology.publishedVersio

Potential Mercurian Analogues: Aubrite and Enstatite Chondrite Impact Melt Meteorites

The MESSENGER (MErcury Surface Space ENvironment GEochemistry and Ranging Spacecraft) mission provided new data that have helped us better constrain the surficial mineralogy and composition of Mercury. Mercury has an extremely low oxygen fugacity (f O2) (Iron Wustite (IW) -7.3 to IW -2.6), and at these unique conditions, elements, which usually exhibit lithophile behavior on Earth, can exhibit chalcophile or siderophile behavior on Mercury. No samples have been returned from Mercury; therefore, we must study candidate meteorite analogs to better understand the formation conditions of minerals inferred to be present at the Mercurian surface and Mercurian magmatic processes. In this study, we present a comprehensive analysis of a representative suite of eight aubrites and four enstatite chondrite impact melts (ECIM), which both have a similar f O2 to Mercury, and contain exotic sulfides that have been inferred to be present at the Mercurian surface. These characteristics allow us to assess their relevance for understanding the mineralogy and magmatic processes of Mercury. The ECIM were previously classified as aubrites, but we show that they are actually ECIM with a potential EH (high enstatite) parent body origin due to the presence of niningerite, Si-enriched kamacite, and uniform Ni in schreibersite. We propose that, with respect to the aubrites, the ECIM represent an ideal candidate for Mercurian studies due to their mineralogy and modal mineralogy. Compared to the aubrites, the ECIM samples do not contain forsterite or diopside, show a poorer sulfide diversity, contain graphite, and have a higher volume percentage of metal phases. Although the Mercurian surface contains forsterite and diopside, graphite and a similar amount of metal and sulfides as seen in the ECIM are inferred to be present on Mercury. According to the calculated normative Mercurian mineralogy, both candidate meteorites are most analogous to the Caloris Basin and Northern Plains Lower Mg regions

A catch-and-release approach to selective modification of accessible tyrosine residues

The tyrosine side chain is amphiphilic leading to significant variations in the surface exposure of tyrosine residues in the folded structure of a native sequence protein. This variability can be exploited to give residue-selective functionalization of a protein substrate by using a highly reactive diazonium group tethered to an agarose-based resin. This novel catch-and-release approach to protein modification has been demonstrated for proteins with accessible tyrosine residues, which are compared with a control group of proteins in which there are no accessible tyrosine residues. MS analysis of the modified proteins showed that functionalization was highly selective, but reactivity was further attenuated by the electrostatic environment of any individual residue. Automated screening of PDB structures allows identification of potential candidates for selective modification by comparison with the accessibility of the tyrosine residue in a benchmark peptide (GYG)

Physiological Considerations to Support Podium Performance in Para-Athletes

The twenty-first century has seen an increase in para-sport participation and the number of research publications on para-sport and the para-athlete. Unfortunately, the majority of publications are case reports/case series or study single impairment types in isolation. Indeed, an overview of how each International Paralympic Committee classifiable impairment type impact athlete physiology, health, and performance has not been forthcoming in the literature. This can make it challenging for practitioners to appropriately support para-athletes and implement evidence-based research in their daily practice. Moreover, the lack of a cohesive publication that reviews all classifiable impairment types through a physiological lens can make it challenging for researchers new to the field to gain an understanding of unique physiological challenges facing para-athletes and to appreciate the nuances of how various impairment types differentially impact para-athlete physiology. As such, the purpose of this review is to (1) summarize how International Paralympic Committee classifiable impairments alter the normal physiological responses to exercise; (2) provide an overview of “quick win” physiological interventions targeted toward specific para-athlete populations; (3) discuss unique practical considerations for the para-sport practitioner; (4) discuss research gaps and highlight areas for future research and innovation, and (5) provide suggestions for knowledge translation and knowledge sharing strategies to advance the field of para-sport research and its application by para-sport practitioners