Triplet superconductivity and proximity effect induced by Bloch and N\'{e}el domain walls

Noncollinear magnetic interfaces introduced in superconductor (SC)/ferromagnet/SC heterostructures allow for spin-flipping processes and are able to generate equal-spin spin-triplet pairing correlations within the ferromagnetic region. This leads to the occurrence of the so-called long-range proximity effect. Particular examples of noncollinear magnetic interfaces include Bloch and N\'{e}el domain walls. Here, we present results for heterostructures containing Bloch and N\'{e}el domain walls based on self-consistent solutions of the spin-dependent Bogoliubov$-$de Gennes equations in the clean limit. In particular, we investigate the thickness dependence of Bloch and N\'{e}el domain walls on induced spin-triplet pairing correlations and compare with other experimental and theoretical results, including conical magnetic layers as noncollinear magnetic interfaces. It is shown that both, Bloch and N\'{e}el domain walls lead to the generation of unequal-spin spin-triplet pairing correlations of similar strength as for conical magnetic layers. However, for the particular heterostructure geometries investigated, only Bloch domain walls lead to the generation of equal-spin spin-triplet pairing correlations. They are stronger than those generated by an equivalent thickness of conical magnetic layers. In order for N\'{e}el domain walls to induce equal-spin spin-triplet pairing correlations, they have to be oriented such that the noncollinearity appears within the plane parallel to the interface region.Comment: 11 pages, 4 figure

Proximity effect in superconductor/conical magnet/ferromagnet heterostructures

At the interface between a superconductor and a ferromagnetic metal spin-singlet Cooper pairs can penetrate into the ferromagnetic part of the heterostructure with an oscillating and decaying spin-singlet Cooper pair density. However, if the interface allows for a spin-mixing effect, equal-spin spin-triplet Cooper pairs can be generated that can penetrate much further into the ferromagnetic part of the heterostructure, known as the long-range proximity effect. Here, we present results of spin-mixing based on self-consistent solutions of the microscopic Bogoliubov-de Gennes equations incorporating a tight-binding model. In particular, we include a conical magnet into our model heterostructure to generate the spin-triplet Cooper pairs and analyse the influence of conical and ferromagnetic layer thickness on the unequal-spin and equal-spin spin-triplet pairing correlations. It will be show that, in agreement with experimental observations, a minimum thickness of the conical magnet is necessary to generate a sufficient amount of equal-spin spin-triplet Cooper pairs allowing for the long-range proximity effect.Comment: 14 pages, 7 figures, 1 tabl

Spin-flipping with Holmium: Case study of proximity effect in superconductor/ferromagnet/superconductor heterostructures

Superconductor/ferromagnet/superconductor heterostructures exhibit a so-called long-range proximity effect provided some layers of conical magnet Holmium are included in the respective interface regions. The Ho layers lead to a spin-flip process at the interface generating equal-spin spin-triplet pairing correlations in the ferromagnet. These equal-spin spin-triplet pairing correlations penetrate much further into the heterostructure compared to the spin-singlet and unequal-spin spin-triplet correlations which occur in the absence of Ho. Here we present calculations of this effect based on the spin-dependent microscopic Bogoliubov-de Gennes equations solved within a tight-binding model in the clean limit. The influence of the ferromagnet and conical magnet layer thickness on the induced equal-spin spin-triplet pairing correlations is obtained and compared to available experimental data. It is shown that, in agreement with experiment, a critical minimum thickness of conical magnet layers has to be present in order to observe a sizeable amount of equal-spin spin-triplet pairing correlations.Comment: 8 pages, 6 figure

Proximity effect in superconductor/conical magnet heterostructures

The presence of a spin-flip potential at the interface between a superconductor and a ferromagnetic metal allows for the generation of equal-spin spin-triplet Cooper pairs. These Cooper pairs are compatible with the exchange interaction within the ferromagnetic region and hence allow for the long-range proximity effect through a ferromagnet or half-metal. One suitable spin-flip potential is provided by incorporating the conical magnet Holmium (Ho) into the interface. The conical magnetic structure is characterised by an opening angle $\alpha$ with respect to the crystal $c$-axis and a turning (or pitch) angle $\beta$ measuring the rotation of magnetisation with respect to the adjacent layers. Here, we present results showing the influence of conical magnet interface layers with varying $\alpha$ and $\beta$ on the efficiency of the generation of equal-spin spin-triplet pairing. The results are obtained by self-consistent solutions of the microscopic Bogoliubov$-$de Gennes equations in the clean limit within a tight-binding model of the heterostructure. In particular, the dependence of unequal-spin and equal-spin spin-triplet pairing correlations on the conical magnetic angles $\alpha$ and $\beta$ are discussed in detail.Comment: 12 pages, 6 figure

Behavior of fluids in the vicinity of the critical point

Fluid behavior in vicinity of critical poin

Regional Knowledge and the Emergence of an Industry: Laser Systems Production in West Germany, 1975-2005

We analyze the emergence and spatial evolution of the German laser systems industry. Regional knowledge in the related field of laser sources, as well as the presence of universities with physics or engineering departments, is conducive to the emergence of laser systems suppliers. The regional presence of source producers is also positively related to entry into laser systems. One important mechanism behind regional entry is the diversification of upstream laser source producers into the downstream systems market. Entry into the materials processing submarket appears to be unrelated to academic knowledge in the region, but the presence of laser source producers and the regional stock of laser knowledge are still highly predictive in this submarket.Innovation, regional knowledge, laser technology, emerging industries, diversification

What If Unemployment Insurance Coverage Were Extended to Agricultural Workers.

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Influence de la température sur l'accumulation par la voie directe du 60Co chez un poisson dulçaquicole

L'influence du facteur thermique sur la contamination de la carpe par le 60Co a été étudiée pour 4 températures : 8 °C, 15 °C, 20 °C et 25 °C. Pour chaque expérience, un lot homogène de 10 individus, d'une masse initiale d'environ 2,3 g et nourris ad libitum, est introduit dans 5 litres d'eau, renouvelée tous les 3 à 4 jours et contaminée à raison de 1,2.105 Bq.l-1.Entre deux renouvellements, la concentration du 60Co dans l'eau décroît sensiblement et l'état ionique du radionucléide, introduit à 100 % sous forme cationique, évolue vers des formes anioniques et neutres. Ces deux faits sont liés au métabolisme des poissons dont la croissance pondérale est corrélée à la température, la distribution de la nourriture étant adaptée aux besoins des individus.Globalement, la quantité totale de radiocobalt fixée par les carpes apparaît très fortement liée au facteur thermique mais, selon le niveau des températures, des situations différentes se dégagent pour des mêmes écarts. Il n'y a pas proportionnalité comptéte entre élévation de température et accumulation du 60Co mais une augmentation discontinue témoignant de l'existence de paliers, dont le plus important se situe à 20 °C.Le facteur de concentration du 60Co est, par contre, peu influencé par le facteur thermique pour les écarts inférieurs à 10 °C ou quand la température maximale est inférieure à 20 °C. L'incidence de la température devient sensible quand les écarts dépassent 10 °C et notamment lorsque sont atteintes des valeurs correspondant à l'optimum thermique des carpes. A l'équilibre, le facteur de concentration moyen du 60Co est de 3,6 à 8 °C, 4,4 à 15 °C, 5,1 à 20 °C et 6 à 25 °C.The problems of simultaneous thermal and radionuclide pollutions have led to a number of laboratory and field studies of the temperature effects on the radioactive contamination of aquatic organisms. AMIARD and KHALANSKI (1981) concluded from their bibliographic study that a temperature rise generally has a positive effect on biological accumulation of radionuclides in freshwater organisms. Due to insufficient data, however, this conclusion does not appear to be substantiated for 60Co uptake by fish. An experimental study was therefore undertaken to assess the effect of temperature on 60Co uptake by Caprinus carpio.The importance of 60Co results from the fact that, apart from tritium, radioactive cobalt isotopes represent the major components of liquid wastes discharged from pressurized water reactors, which are widely operated in France (BARDIN et al., 1982; PICAT et al., 1986). The common carp (Caprinus carpio L.) was selected as the subject of this experimentation because of its wide geographic distribution and the frequency with which it is found in field samples, making it a suitable biological indicator (D'AUBENTON and SPILLMANN, 1978; FOULQUIER and PALLY, 1982; FOULQUIER et al., 1985).The effect of temperature on 60Co contamination of the carp was investigated by conducting the same experiment at four temperatures (8 °C, 15 °C, 20 °C and 25 °C) determined by ecological and physiological criteria. In each experiment, young carps with a mean weight of 2.3 g were placed in a tank containing 5 liters of water contaminated with 1.2 x 105 Bq.l-1 of 60Co. The water was renewed at intervals of 3 - 4 days. Modifications in the ionic form of the radio-active cobalt dissolved in the water were monitored by percolating filtered water samples through ion exchange resin columns. The carps were fed to satiation with an industrial food containing 12 % minerals, 8 % fats and 58 % proteins (dry weight) together with vitamins and trace elements including 0.2 mg.kg-1 of cobalt. Radioactivity levels in the fish were measured, after mild anesthesia, with a single-channel amplitude selector equipped with a thallium-activated flat sodium iodine probe.Between successive water renewals, the 60Co concentration diminished (Table 1) and the ionic form of the radionuclide remaining in solution was significantly modified. The 60Co was introduced in chloride form and was initially found exclusively as a cation; anionic or neutral forms appeared and became dominant after a few days (Figure 1). These two phenomena are probably related to the fish metabolism which is temperature dependent. Thus, food was distributed according to the individual requirements, and an exponential correlation was observed between the temperature and the weight gain in the carps (Table 1). The appearance of anionic and neutral forms may be attributed to excessive amounts of organic matter due to the presence of the fish and food (FUKAI and MURRAY, 1973; KILLEY et al., 1984). This evolution also results from a significant increase in ions such as HCO3-, Cl-, SO4--, PO4-- and NH4+ (FRITSCH and BAUDIN, 1984) which may combine with Co++ ions to form neutral molecules and anionic complexes (TRISHAN et al., 1981). Radioactive decay in the mater is also temperature-dependent : the amount of fecal matter, which strongly adsorbs radioactive cobalt, is proportional to the metabolic intensity in the fish.The overall 60Co uptake by the carps (Table 2) appears to be strongly related to the temperature, but the effect of a given temperature rise varied with the initial temperature (Table 4). The 60Co uptake was not fully proportional to the temperature rise, but was observed to increase in stepwise fashion indicating the existence of various thresholds. The most significant of these was noted at 20 °C, which is the lower limit of the optimum temperature range for carps.The 60Co concentration in th fish (Table 3) was influenced to a much lower extent by the temperature than the total uptake. Small temperature variations (5 - 7 °C) had little or no effect on the concentration factor; this was also true for larger variations, from 8 °C to 20 °C (Table 4). Temperature effects were only significant between 8 °C and 25 °C, and between 15 °C and 25 °C.The 60Co concentration variation in time was similar for all four temperatures, with two successive phases (Figure 2). It can be expressed mathematically by an exponential model based on the existence of several compartments in living organisms characterized by the influx and efflux rates for the element under consideration (GOLSTEIN and ELWOOD, 1971; AOYAMA and INOUE, 1973; PENTREATH, 1975; GONTIER, 1983). The maximum value and the time required to reach equilibrium were determined by extrapolation from the equations for the concentration factor variations. The results were 3.6 and 510 days at 8 °C, 4.4 and 220 days at 15 °C, 5.1 and 125 days at 20 °C, and 6 and 110 days at 25 °C. These values indicate that a temperature rise diminishes the time required to reach equilibrium and slightly increases the concentration factor by an amount that is statistically significant only for major temperature differences (Table 4).Detailed investigations of various freshwater species, notably Caprinus carpio, have demonstrated the decisive effect of temperature on metabolic activity in these animals (LEVESQUE, 1980). The results presented here indicate that the 60Co uptake rate in the carp is not proportional to the temperature rise as is generally the case for physiological processes. From a radiation protection standpoint, this observation suggests that the temperature is not an essential factor in 60Co contamination of freshwater fish

Personal neoantigen cancer vaccines: The momentum builds

Neoantigen-based cancer vaccines designed to target the unique immunogenic mutations arising in each patient’s tumor are breathing new life into a struggling approach. Data continue to demonstrate the importance of neoantigens in immune control of cancer. Despite manufacturing complexity, outstanding questions and desired further improvements, neoantigen vaccines are currently undergoing clinical evaluation

Multi-Modal Human-Machine Communication for Instructing Robot Grasping Tasks

A major challenge for the realization of intelligent robots is to supply them with cognitive abilities in order to allow ordinary users to program them easily and intuitively. One way of such programming is teaching work tasks by interactive demonstration. To make this effective and convenient for the user, the machine must be capable to establish a common focus of attention and be able to use and integrate spoken instructions, visual perceptions, and non-verbal clues like gestural commands. We report progress in building a hybrid architecture that combines statistical methods, neural networks, and finite state machines into an integrated system for instructing grasping tasks by man-machine interaction. The system combines the GRAVIS-robot for visual attention and gestural instruction with an intelligent interface for speech recognition and linguistic interpretation, and an modality fusion module to allow multi-modal task-oriented man-machine communication with respect to dextrous robot manipulation of objects.Comment: 7 pages, 8 figure