Influence of Topological Edge States on the Properties of Al/Bi2Se3/Al Hybrid Josephson Devices

In superconductor-topological insulator-superconductor hybrid junctions, the barrier edge states are expected to be protected against backscattering, to generate unconventional proximity effects, and, possibly, to signal the presence of Majorana fermions. The standards of proximity modes for these types of structures have to be settled for a neat identification of possible new entities. Through a systematic and complete set of measurements of the Josephson properties we find evidence of ballistic transport in coplanar Al-Bi2Se3-Al junctions that we attribute to a coherent transport through the topological edge state. The shunting effect of the bulk only influences the normal transport. This behavior, which can be considered to some extent universal, is fairly independent of the specific features of superconducting electrodes. A comparative study of Shubnikov - de Haas oscillations and Scanning Tunneling Spectroscopy gave an experimental signature compatible with a two dimensional electron transport channel with a Dirac dispersion relation. A reduction of the size of the Bi2Se3 flakes to the nanoscale is an unavoidable step to drive Josephson junctions in the proper regime to detect possible distinctive features of Majorana fermions.Comment: 11 pages, 14 figure

Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water

Background While previous research has suggested that there is an association between fluoride ingestion and the incidence of hypothyroidism, few population level studies have been undertaken. In England, approximately 10% of the population live in areas with community fluoridation schemes and hypothyroidism prevalence can be assessed from general practice data. This observational study examines the association between levels of fluoride in water supplies with practice level hypothyroidism prevalence. Methods We used a cross-sectional study design using secondary data to develop binary logistic regression models of predictive factors for hypothyroidism prevalence at practice level using 2012 data on fluoride levels in drinking water, 2012/2013 Quality and Outcomes Framework (QOF) diagnosed hypothyroidism prevalence data, 2013 General Practitioner registered patient numbers and 2012 practice level Index of Multiple Deprivation scores. Findings We found that higher levels of fluoride in drinking water provide a useful contribution for predicting prevalence of hypothyroidism. We found that practices located in the West Midlands (a wholly fluoridated area) are nearly twice as likely to report high hypothyroidism prevalence in comparison to Greater Manchester (non-fluoridated area). Interpretation In many areas of the world, hypothyroidism is a major health concern and in addition to other factors—such as iodine deficiency—fluoride exposure should be considered as a contributing factor. The findings of the study raise particular concerns about the validity of community fluoridation as a safe public health measure

Increased circulating ANG II and TNF-α represents important risk factors in obese Saudi adults with hypertension irrespective of diabetic status and BMI

Central adiposity is a significant determinant of obesity-related hypertension risk, which may arise due to the pathogenic inflammatory nature of the abdominal fat depot. However, the influence of pro-inflammatory adipokines on blood pressure in the obese hypertensive phenotype has not been well established in Saudi subjects. As such, our study investigated whether inflammatory factors may represent useful biomarkers to delineate hypertension risk in a Saudi cohort with and without hypertension and/or diabetes mellitus type 2 (DMT2). Subjects were subdivided into four groups: healthy lean controls (age: 47.9±5.1 yr; BMI: 22.9±2.1 Kg/m2), non-hypertensive obese (age: 46.1±5.0 yr; BMI: 33.7±4.2 Kg/m2), hypertensive obese (age: 48.6±6.1 yr; BMI: 36.5±7.7 Kg/m2) and hypertensive obese with DMT2 (age: 50.8±6.0 yr; BMI: 35.3±6.7 Kg/m2). Anthropometric data were collected from all subjects and fasting blood samples were utilized for biochemical analysis. Serum angiotensin II (ANG II) levels were elevated in hypertensive obese (p<0.05) and hypertensive obese with DMT2 (p<0.001) compared with normotensive controls. Systolic blood pressure was positively associated with BMI (p<0.001), glucose (p<0.001), insulin (p<0.05), HOMA-IR (p<0.001), leptin (p<0.01), TNF-α (p<0.001) and ANG II (p<0.05). Associations between ANG II and TNF-α with systolic blood pressure remained significant after controlling for BMI. Additionally CRP (p<0.05), leptin (p<0.001) and leptin/adiponectin ratio (p<0.001) were also significantly associated with the hypertension phenotype. In conclusion our data suggests that circulating pro-inflammatory adipokines, particularly ANG II and, TNF-α, represent important factors associated with a hypertension phenotype and may directly contribute to predicting and exacerbating hypertension risk

Not smoking is associated with lower risk of hypertension: results of the Olivetti Heart Study.

Few epidemiological investigations evaluated the role of smoking cessation on blood pressure (BP), and the results are not univocal. Therefore, the aim of this study was to assess the effect of smoking cessation on the risk to develop hypertension (HPT) and on BP values. METHODS: This longitudinal study, with a follow-up period of 8 years, included the participants of the Olivetti Heart Study. Participants were 430 untreated normotensive non-diabetic men with normal renal function, examined twice in 1994-95 and in 2002-04. The sample included current smokers (S, n = 212), former smokers (ES, n = 145) and never smokers (NS, n = 73) at baseline. RESULTS: Basal body mass index (BMI), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were significantly higher in ES than in S (ES vs. S; BMI: 27.0 ± 2.5 vs. 26.1 ± 2.9 kg/m(2); P < 0.01; SBP/DBP: 121.2 ± 9.3/80.0 ± 5.8 vs. 19.1 ± 9.9/77.4 ± 6.7 mm Hg; P < 0.05; M ± SD). After 8 years of follow-up, BP changes (Δ) were significantly lower in ES than in S (ΔSBP/DBP: 12.6 ± 13.4/7.9 ± 8.1 vs. 16.0 ± 14.9/10.3 ± 10.1 mm Hg; P < 0.05; M ± SD), also after adjustment for potential confounders. Moreover, at the last examination, the overall HPT prevalence was 33%, with lower values in ES than in S (25 vs. 38%, P = 0.01). After accounting for age, BP and BMI at baseline, and changes in smoking habit over the 8-year period, ES still had significant lower risk of HPT than S (odds ratio 0.30, 95% confidence interval 0.15-0.58; P < 0.01). CONCLUSIONS: In this sample of healthy men, smoking cessation was associated with lower BP increment and minor HPT risk, independently of potential confounders

Microwave studies of the fractional Josephson effect in HgTe-based Josephson junctions

The rise of topological phases of matter is strongly connected to their potential to host Majorana bound states, a powerful ingredient in the search for a robust, topologically protected, quantum information processing. In order to produce such states, a method of choice is to induce superconductivity in topological insulators. The engineering of the interplay between superconductivity and the electronic properties of a topological insulator is a challenging task and it is consequently very important to understand the physics of simple superconducting devices such as Josephson junctions, in which new topological properties are expected to emerge. In this article, we review recent experiments investigating topological superconductivity in topological insulators, using microwave excitation and detection techniques. More precisely, we have fabricated and studied topological Josephson junctions made of HgTe weak links in contact with two Al or Nb contacts. In such devices, we have observed two signatures of the fractional Josephson effect, which is expected to emerge from topologically-protected gapless Andreev bound states. We first recall the theoretical background on topological Josephson junctions, then move to the experimental observations. Then, we assess the topological origin of the observed features and conclude with an outlook towards more advanced microwave spectroscopy experiments, currently under development.Comment: Lectures given at the San Sebastian Topological Matter School 2017, published in "Topological Matter. Springer Series in Solid-State Sciences, vol 190. Springer

A computationally efficient reduced order model to generate multi-parameter fluid-thermal databases

A reduced order model (ROM) is proposed to generate multi-parameter databases of some fluid-thermal problems, using a combination of proper orthogonal decomposition, a gradient-like method, and a continuation method. The resulting ROM greatly reduces the CPU time required by slower methods based on genetic algorithm formulations. As a byproduct, the number of required snapshots is also reduced, which yields an additional improvement of the computational efficiency. The work presented in this article aims to facilitate the use of ROMs in industrial environments, in which time is a very important asset. The methodology is illustrated with the non-isothermal flow past a backward-facing step in the laminar regime, which is a representative problem, related to the engineering design of micro-heat sinks

The building up of the disk galaxy M33 and the evolution of the metallicity gradient

The evolution of radial gradients of metallicity in disk galaxies and its relation with the disk formation are not well understood. Theoretical models of galactic chemical evolution make contrasting predictions about the time evolution of metallicity gradients. To test chemical evolution models and trace the star formation and accretion history of low luminosity disk galaxies we focus on the Local Group galaxy M33. We analyze O/H and S/H abundances in planetary nebulae, H{\sc ii} regions, and young stars, together with known [Fe/H] abundances in the old stellar population of M33. With a theoretical model, we follow the time evolution of gas (diffuse and condensed in clouds), stars, and chemical abundances in the disk of M33, assuming that the galaxy is accreting gas from an external reservoir. Our model is able to reproduce the available observational constraints on the distribution of gas and stars in M33 and to predict the time evolution of several chemical abundances. In particular, we find that a model characterized by a continuous infall of gas on the disk, at a rate of $\dot M_{\rm inf}\approx 1$ $M_\odot$ yr$^{-1}$, almost constant with time, can also account for the relatively high rate of star formation and for the shallow chemical gradients. Supported by a large sample of high resolution observations for this nearby galaxy, we conclude that the metallicity in the disk of M33 has increased with time at all radii, with a continuous flattening of the gradient over the last $\sim 8$ Gyr.Comment: 16 pages, 11 figures, A&A accepte

Past and present distribution, densities and movements of blue whales <i>Balaenoptera musculus</i> in the Southern Hemisphere and northern Indian Ocean

1Blue whale locations in the Southern Hemisphere and northern Indian Ocean were obtained from catches (303 239), sightings (4383 records of =8058 whales), strandings (103), Discovery marks (2191) and recoveries (95), and acoustic recordings.2Sighting surveys included 7 480 450 km of effort plus 14 676 days with unmeasured effort. Groups usually consisted of solitary whales (65.2%) or pairs (24.6%); larger feeding aggregations of unassociated individuals were only rarely observed. Sighting rates (groups per 1000 km from many platform types) varied by four orders of magnitude and were lowest in the waters of Brazil, South Africa, the eastern tropical Pacific, Antarctica and South Georgia; higher in the Subantarctic and Peru; and highest around Indonesia, Sri Lanka, Chile, southern Australia and south of Madagascar.3Blue whales avoid the oligotrophic central gyres of the Indian, Pacific and Atlantic Oceans, but are more common where phytoplankton densities are high, and where there are dynamic oceanographic processes like upwelling and frontal meandering.4Compared with historical catches, the Antarctic (‘true’) subspecies is exceedingly rare and usually concentrated closer to the summer pack ice. In summer they are found throughout the Antarctic; in winter they migrate to southern Africa (although recent sightings there are rare) and to other northerly locations (based on acoustics), although some overwinter in the Antarctic.5Pygmy blue whales are found around the Indian Ocean and from southern Australia to New Zealand. At least four groupings are evident: northern Indian Ocean, from Madagascar to the Subantarctic, Indonesia to western and southern Australia, and from New Zealand northwards to the equator. Sighting rates are typically much higher than for Antarctic blue whales.6South-east Pacific blue whales have a discrete distribution and high sighting rates compared with the Antarctic. Further work is needed to clarify their subspecific status given their distinctive genetics, acoustics and length frequencies.7Antarctic blue whales numbered 1700 (95% Bayesian interval 860–2900) in 1996 (less than 1% of original levels), but are increasing at 7.3% per annum (95% Bayesian interval 1.4–11.6%). The status of other populations in the Southern Hemisphere and northern Indian Ocean is unknown because few abundance estimates are available, but higher recent sighting rates suggest that they are less depleted than Antarctic blue whales.</li

Impaired peripheral reaching and on-line corrections in patient DF: optic ataxia with visual form agnosia

An influential model of vision suggests the presence of two visual streams within the brain: a dorsal occipito-parietal stream which mediates action and a ventral occipito-temporal stream which mediates perception. One of the cornerstones of this model is DF, a patient with visual form agnosia following bilateral ventral stream lesions. Despite her inability to identify and distinguish visual stimuli, DF can still use visual information to control her hand actions towards these stimuli. These observations have been widely interpreted as demonstrating a double dissociation from optic ataxia, a condition observed after bilateral dorsal stream damage in which patients are unable to act towards objects that they can recognize. In Experiment 1, we investigated how patient DF performed on the classical diagnostic task for optic ataxia, reaching in central and peripheral vision. We replicated recent findings that DF is remarkably inaccurate when reaching to peripheral targets, but not when reaching in free vision. In addition we present new evidence that her peripheral reaching errors follow the optic ataxia pattern increasing with target eccentricity and being biased towards fixation. In Experiments 2 and 3, for the first time we examined DF’s on-line control of reaching using a double-step paradigm in fixation-controlled and free-vision versions of the task. DF was impaired when performing fast on-line corrections on all conditions tested, similarly to optic ataxia patients. Our findings question the long-standing assumption that DF’s dorsal visual stream is functionally intact and that her on-line visuomotor control is spared. In contrast, in addition to visual form agnosia, DF also has visuomotor symptoms of optic ataxia which are most likely explained by bilateral damage to the superior parietal occipital cortex. We thus conclude that patient DF can no longer be considered as an appropriate single-case model for testing the neural basis of perception and action dissociations

Relationship between low Ankle-Brachial Index and rapid renal function decline in patients with atrial fibrillation: A prospective multicentre cohort study

OBJECTIVE: To investigate the relationship between Ankle-Brachial Index (ABI) and renal function progression in patients with atrial fibrillation (AF). DESIGN: Observational prospective multicentre cohort study. SETTING:Atherothrombosis Center of I Clinica Medica of 'Sapienza' University of Rome; Department of Medical and Surgical Sciences of University Magna Græcia of Catanzaro; Atrial Fibrillation Registry for Ankle-Brachial Index Prevalence Assessment-Collaborative Italian Study. PARTICIPANTS: 897 AF patients on treatment with vitamin K antagonists. MAIN OUTCOME MEASURES: The relationship between basal ABI and renal function progression, assessed by the estimated Glomerular Filtration Rate (eGFR) calculated with the CKD-EPI formula at baseline and after 2 years of follow-up. The rapid decline in eGFR, defined as a decline in eGFR >5 mL/min/1.73 m(2)/year, and incident eGFR<60 mL/min/1.73 m(2) were primary and secondary end points, respectively. RESULTS: Mean age was 71.8±9.0 years and 41.8% were women. Low ABI (ie, ≤0.90) was present in 194 (21.6%) patients. Baseline median eGFR was 72.7 mL/min/1.73 m(2), and 28.7% patients had an eGFR60 mL/min/1.73 m(2), 153 (23.9%) had a reduction of the eGFR <60 mL/min/1.73 m(2). ABI ≤0.90 was also an independent predictor for incident eGFR<60 mL/min/1.73 m(2) (HR 1.851, 95% CI 1.205 to 2.845, p=0.005). CONCLUSIONS: In patients with AF, an ABI ≤0.90 is independently associated with a rapid decline in renal function and incident eGFR<60 mL/min/1.73 m(2). ABI measurement may help identify patients with AF at risk of renal function deterioration