Supercurrent-induced temperature gradient across a nonequilibrium SNS Josephson junction

Using tunneling spectroscopy, we have measured the local electron energy distribution function in the normal part of a superconductor-normal metal-superconductor (SNS) Josephson junction containing an extra lead to a normal reservoir. In the presence of simultaneous supercurrent and injected quasiparticle current, the distribution function exhibits a sharp feature at very low energy. The feature is odd in energy, and odd under reversal of either the supercurrent or the quasiparticle current direction. The feature represents an effective temperature gradient across the SNS Josephson junction that is controllable by the supercurrent.Comment: 4 pages, 4 figures, corrected typos, added plot to figure

Moreenin geotekniset ominaisuudet Suomessa

Tiivistelmä. Tässä pro gradu -työssä on tutkittu Suomen moreenien geoteknisiä ominaisuuksia. Työssä on tutkittu näytteitä ympäri Suomea, niin että ne edustavat kattavasti Suomen moreeneja. Tutkittuja näytteitä oli 11 kappaletta ja ne oli kerätty kuudelta eri paikkakunnalta. Erityisinä mielenkiinnon kohteina tutkielmassa oli moreenien kapillaarisuusominaisuudet sekä moreenien käyttökelpoisuus patorakenteiden eristävänä kerroksena tai vastaavana geoeristeenä sekä muissa rakennuskohteissa rakennusmateriaalina. Kapillaarisuuden suhteen mielenkiintona on se, että aiheuttaako moreenissa tapahtuva kapillaarinen nousu metalli- ja muiden ionien rikastumista moreenipatjan tai muun tyyppisen maaperän pintaosiin. Kerätyistä näytteistä tutkittiin niiden rakeisuus, tiivistyvyys, vedenjohtavuus, ominaispinta-ala, kapillaarisuus, ja niiden konsistenssirajat. Tutkimusmenetelminä käytettiin kullekin ominaisuudelle yleisesti Suomessa käytössä olevia tutkimusmenetelmiä. Tutkielman perusteella tutkittavat näytteet edustavat lajitepitoisuudeltaan pääsääntöisesti sangen hienorakeisia hiekkamoreeneja. Kaikissa näytteissä oli saviainesta vähintään 5 %. Niiden tiivistyvyysarvot ovat moreeneille tyypilliset. Vedenläpäisevyydeltään näytteet olivat huonosti vettä läpäiseviä. Näytteiden vedenläpäisevyys vaihteli 92 %-tiiviydessä 1,82×10⁻⁷ m/s:ta 5,32×10⁻¹⁰ m/s:n. Näytteiden kapillaarisuuden arvot olivat suuret. Noin puolelle näytteistä kapillaarisuutta ei saanut tarkasti mitattua, koska kapillaarimetrillä ei saatu tarpeeksi korkeita arvoja. Näytteiden ominaispinta-alat olivat moreeneiksi varsin pieniä. Keski-Lapin rapakalliomoreeneilla sekä Pyhäsalmityyppistä moreenia edustaneella hiekkaisella silttimoreenilla oli muihin tutkielman näytteisiin verrattuna suuremmat ominaispinta-alan arvot. Tutkielman näytteet eivät olleet Pyhäsalmityyppistä moreenia lukuun ottamatta plastisia. Tutkielman perusteella moreenien käyttöä vaikeuttaa niiden routivuus, joten tämän perusteella niitä ei voi sellaisenaan käyttää kohteissa, jotka vaativat routimatonta materiaalia. Vedenläpäisevyyden puolesta silttimoreeni kelpaavat mahdollisesti patorakenteisiin eristäväksi kerrokseksi. Kapillaarisuuden tutkimustulosten perusteella on mahdollista, että metallit nousevat mineralisaatiosta sitä peittävässä moreenikerroksessa. Näin ollen se on moreenien puolesta mahdollinen malminetsinnän väline

Supercurrent and Andreev bound state dynamics in superconducting quantum point contacts under microwave irradiation

We present here an extensive theoretical analysis of the supercurrent of a superconducting point contact of arbitrary transparency in the presence of a microwave field. Our study is mainly based on two different approaches: a two-level model that describes the dynamics of the Andreev bound states in these systems and a fully microscopic method based on the Keldysh-Green function technique. This combination provides both a deep insight into the physics of irradiated Josephson junctions and quantitative predictions for arbitrary range of parameters. The main predictions of our analysis are: (i) for weak fields and low temperatures, the microwaves can induce transitions between the Andreev states leading to a large suppression of the supercurrent at certain values of the phase, (ii) at strong fields, the current-phase relation is strongly distorted and the corresponding critical current does not follow a simple Bessel-function-like behavior, and (iii) at finite temperature, the microwave field can enhance the critical current by means of transitions connecting the continuum of states outside the gap region and the Andreev states inside the gap. Our study is of relevance for a large variety of superconducting weak links as well as for the proposals of using the Andreev bound states of a point contact for quantum computing applications.Comment: 16 pages, 11 figures, submitted to Phys. Rev.

UV albedo of arctic snow in spring

International audienceThe relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67.37° N, 26.63° E, 179 m a.s.l.) during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period and 0.5?0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0°C on the following mornings. Hence, the reversible diurnal change, evident for ~1?2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again

Diurnal variations in the UV albedo of arctic snow

The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67°22'N, 26°39'E, 179 m a.s.l.) during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period, and from 0.5 to 0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0°C on the following mornings. Hence, the reversible diurnal change, evident for ~1–2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again

C-reactive Protein and Temperament: An Instrumental Variable Analysis

BACKGROUND: Temperament is associated with circulating inflammatory biomarkers, such as C-reactive protein (CRP), which has been associated with various health conditions, including depression. This study aims to investigate whether genetic disposition for increased circulating CRP concentration may influence temperament over the life-course. METHODS: Using a longitudinal cohort that began in 1980—the Cardiovascular Risk in Young Finns Study (YFS)—we included 920 participants (59.8% female) aged 3–12 years old at baseline (childhood), and the same participants again at ages 30–39 years old (adulthood) in this study. We used both ordinary least-squares regression (OLS linear regression) and instrumental variable (IV) regression to assess associations between CRP concentration and temperament dimensions (negative emotionality, activity, and sociability). To represent genetically determined risk for increase in circulating CRP concentration, we calculated a weighted genetic risk score (GRS) which reflects risk for increased circulating CRP concentration. RESULTS: In OLS linear regression analyses, we found that increased circulating CRP concentration in childhood was associated with slightly higher scores for sociability in childhood (19% increase, CI ​= ​7–32%) and adulthood (13% increase, CI ​= ​2–27%), and lower activity scores in adulthood (15% decrease, CI ​= ​3–25%). For all IV regressions, there were no apparent associations between GRS and temperament in either childhood or adulthood (all p>0.3). The Durbin-Wu-Hausman test for endogeneity produced p-values (all>0.05) that suggest there is no evidence for disagreement between the OLS and IV estimates. CONCLUSIONS: We found no clear evidence for an association of GRS for elevated CRP with childhood or adulthood emotionality, activity, or sociability, although circulating CRP was associated with some of these traits

Formation of segregation structures in Hafnarhraun pāhoehoe lobe, SW Iceland: a window into crystal–melt separation in basaltic magma

Publisher's version (útgefin grein).To gain insights into crystal–melt separation processes during basalt differentiation, we have studied an 8-m-thick pāhoehoe lava lobe from the Hafnarhraun lava flow field in SW Iceland. The lobe has abundant melt segregations, porous cylindrical and sheet-like structures, generally interpreted as separated residual melts of a lava lobe. We divide these melt segregations into three types based on morphology and composition: vesicle cylinders (VC), type 1 horizontal vesicle sheets (HVS1), and type 2 horizontal vesicle sheets (HVS2). Remarkably, the studied VC are not simple residual melts generated by fractional crystallization, but their composition points to removal of plagioclase from the parental lava. HVS1 resemble VC, but have fractionated more olivine (ol) + plagioclase (plg) ± augite and have lost most, if not all, of their olivine phenocrysts. HVS2 are Fe-rich and evolved, corresponding to residual melts after 50–60% fractional crystallization of the lobe. We suggest that the Hafnarhraun VC formed in a two-stage process. Firstly, VC forming residual melt and vapor detached as rising diapirs from ol+plg+melt+vapor mush near the lava base, and later, these VC diapirs accumulated ol phenocrysts and minor plg microphenocrysts in the lava core. HVS1 represent accumulations of VC to the viscous base of the solidifying upper crust of the lobe, and HVS2 formed as evolved vapor-saturated residual melts seeped into voids within the upper crust. Such vapor-aided differentiation, here documented for the Hafnarhraun lava, may also apply to shallow crustal magma storage zones, contributing to the formation of evolved basalts.The Nordic Volcanological Center funded this work 2015–2017. We thank Robert A. Askew and Leó Kristjánsson for the aid in sampling, Atli Hjartarson and Guðmundur H. Guðfinnsson for the help in sample preparation and microprobe analyses, and Richard J. Brown for the editorial handling. Comments from Kaisa Nikkilä, Scott Rowland, and anonymous reviewer significantly improved the manuscript. Funding information: Open access funding provided by University of Helsinki including Helsinki University Central Hospital.Peer Reviewe

An Optical-Lattice-Based Quantum Simulator For Relativistic Field Theories and Topological Insulators

We present a proposal for a versatile cold-atom-based quantum simulator of relativistic fermionic theories and topological insulators in arbitrary dimensions. The setup consists of a spin-independent optical lattice that traps a collection of hyperfine states of the same alkaline atom, to which the different degrees of freedom of the field theory to be simulated are then mapped. We show that the combination of bi-chromatic optical lattices with Raman transitions can allow the engineering of a spin-dependent tunneling of the atoms between neighboring lattice sites. These assisted-hopping processes can be employed for the quantum simulation of various interesting models, ranging from non-interacting relativistic fermionic theories to topological insulators. We present a toolbox for the realization of different types of relativistic lattice fermions, which can then be exploited to synthesize the majority of phases in the periodic table of topological insulators.Comment: 24 pages, 6 figure

Quality assurance of the Brewer UV measurements in Finland

International audienceThe quality assurance of the two Brewer spectrophotometers of the Finnish Meteorological Institute is discussed in this paper. The complete data processing chain from raw signal to high quality spectra is presented. The quality assurance includes daily maintenance, laboratory characterizations, calculation of long term spectral responsivity, data processing and quality assessment. The cosine correction of the measurements is based on a new method, and included in the data processing software. The results showed that the actual cosine correction factor of the Finnish Brewers can vary between 1.08?1.13 and 1.08?1.12, respectively, depending on the sky radiance distribution and wavelength. The temperature characterization showed a linear temperature dependence between the internal temperature and the photon counts per cycle, and a temperature correction was used for correcting the measurements. The long term spectral responsivity was calculated using time series of several lamps using two slightly different methods. The long term spectral responsivity was scaled to the irradiance scale of the Helsinki University of Technology (HUT) for the whole measurement time periods 1990?2006 and 1995?2006 for Sodankylä and Jokioinen, respectively. Both Brewers have participated in many international spectroradiometer comparisons, and have shown good stability. The differences between the Brewers and the portable reference spectroradiometer QASUME have been within 5% during 2002?2007