Physics of Proximity Josephson Sensor

We study the proximity Josephson sensor (PJS) in both bolometric and calorimetric operation and optimize it for different temperature ranges between 25 mK and a few Kelvin. We investigate how the radiation power is absorbed in the sensor and find that the irradiated sensor is typically in a weak nonequilibrium state. We show in detail how the proximity of the superconductors affects the device response: for example via changes in electron-phonon coupling and out-of-equilibrium noise. In addition, we estimate the applicability of graphene as the absorber material.Comment: 13 pages, 11 figures, submitted to Journal of Applied Physics, v2: Addition of a new section discussing the radiation coupling to the device, several minor change

Theory of temperature fluctuation statistics in superconductor-normal metal tunnel structures

We describe the statistics of temperature fluctuations in a SINIS structure, where a normal metal island (N) is coupled by tunnel junctions (I) to two superconducting leads (S). We specify conditions under which this structure exhibits manifestly non-Gaussian fluctuations of temperature. We consider both the Gaussian and non-Gaussian regimes of these fluctuations, and the current fluctuations that are caused by the fluctuating temperature. We also describe a measurement setup that could be used to observe the temperature fluctuations.Comment: 10 pages, 9 figures, final versio

Development of high-speed directly-modulated DFB and DBR lasers with surface gratings

The conventional distributed feedback and distributed Bragg reflector edge-emitting lasers employ buried gratings, which require two or more epitaxial growth steps. By using lateral corrugations of the ridge-waveguide as surface gratings the epitaxial overgrowth is avoided, reducing the fabrication complexity, increasing the yield and reducing the fabrication cost. The surface gratings are applicable to different materials, including Al-containing ones and can be easily integrated in complex device structures and photonic circuits. Single-contact and multiple contact edge-emitting lasers with laterally-corrugated ridge waveguide gratings have been developed both on GaAs and InP substrates with the aim to exploit the photon-photon resonance in order to extend their direct modulation bandwidth. The paper reports on the characteristics of such surface-grating-based lasers emitting both at 1.3 and 1.55 μm and presents the photon-photon resonance extended small-signal modulation bandwidth (> 20 GHz) achieved with a 1.6 mm long single-contact device under direct modulation. Similarly structured devices, with shorter cavity lengths are expected to exceed 40 GHz smallsignal modulation bandwidth under direct modulatio

Negotiation of entitlement in proposal sequences

Meetings are complex institutional events at which participants recurrently negotiate institutional roles, which are oriented to, renegotiated, and sometimes challenged. With a view to gaining further understanding of the ongoing negotiation of roles at meetings, this article examines one specific recurring feature of meetings: the act of proposing future action. Based on microanalysis of video recordings of two-party strategy meetings, the study shows that participants orient to at least two aspects when making proposals: 1) the acceptance or rejection of the proposal; and 2) questions of entitlement: who is entitled to launch a proposal, and who is entitled to accept or reject it? The study argues that there is a close interrelation between questions of entitlement, aligning and affiliating moves, and the negotiation of institutional roles. The multimodal analysis also reveals the use of various embodied practices by participants for the local negotiation of entitlement and institutional roles

Ambient aromatic hydrocarbon measurements at Welgegund, South Africa

Aromatic hydrocarbons are associated with direct adverse human health effects and can have negative impacts on ecosystems due to their toxicity, as well as indirect negative effects through the formation of tropospheric ozone and secondary organic aerosol, which affect human health, crop production and regional climate. Measurements of aromatic hydrocarbons were conducted at the Welgegund measurement station (South Africa), which is considered to be a regionally representative background site. However, the site is occasionally impacted by plumes from major anthropogenic source regions in the interior of South Africa, which include the western Bushveld Igneous Complex (e.g. platinum, base metal and ferrochrome smelters), the eastern Bushveld Igneous Complex (platinum and ferrochrome smelters), the Johannesburg–Pretoria metropolitan conurbation (> 10 million people), the Vaal Triangle (e.g. petrochemical and pyrometallurgical industries), the Mpumalanga Highveld (e.g. coal-fired power plants and petrochemical industry) and also a region of anticyclonic recirculation of air mass over the interior of South Africa. The aromatic hydrocarbon measurements were conducted with an automated sampler on Tenax-TA and Carbopack-B adsorbent tubes with heated inlet for 1 year. Samples were collected twice a week for 2 h during daytime and 2 h during night-time. A thermal desorption unit, connected to a gas chromatograph and a mass selective detector was used for sample preparation and analysis. Results indicated that the monthly median (mean) total aromatic hydrocarbon concentrations ranged between 0.01 (0.011) and 3.1 (3.2) ppb. Benzene levels did not exceed the local air quality standard limit, i.e. annual mean of 1.6 ppb. Toluene was the most abundant compound, with an annual median (mean) concentration of 0.63 (0.89) ppb. No statistically significant differences in the concentrations measured during daytime and night-time were found, and no distinct seasonal patterns were observed. Air mass back trajectory analysis indicated that the lack of seasonal cycles could be attributed to patterns determining the origin of the air masses sampled. Aromatic hydrocarbon concentrations were in general significantly higher in air masses that passed over anthropogenically impacted regions. Inter-compound correlations and ratios gave some indications of the possible sources of the different aromatic hydrocarbons in the source regions defined in the paper. The highest contribution of aromatic hydrocarbon concentrations to ozone formation potential was also observed in plumes passing over anthropogenically impacted regions

Ampumataulukoiden laatimisen automatisointi

Artikkelissa esitellään ulkoballistiikassa tapahtunutta matematiikan ja fysiikan sovellutusalueen hyödyntämistä ja sen kehittymistä eri aikakausina. Artikkelissa kuvataan muun muassa normaaliratamenetelmän käyttöön ja kehittämiseen liittyneitä tekijöitä. "Tarkoituksena on ollut muodostaa normaalirataverkko, josta voitaisiin saada interpoloimalla minkä tahansa koeammunnan tulosten käsittelyssä tarvittavat normaaliradat." Artikkelin loppuosassa käsitellään tietojenkäsittelyn nopean kehityksen mukanaan tuomia mahdollisuuksia ratalaskun kehittämisessä. "Tätä esitystä kirjoitettaessa on ampumataulukoiden laatimisen automaatio saavuttanut tietyn tavoitteen; ampumataulukoiden laatimiseen tarvittavat rutiinilaskelmat on saatu siirretyksi tietokoneelle." Kirjoittajat toteavat lopuksi, että "Kaikki mahdollisuudet tietokonetekniikan soveltamiselle ballistiikassa eivät suinkaan ole vielä loppuun käytetyt.

Interlayer Heat Transfer in Bilayer Carrier Systems

We study theoretically how energy and heat are transferred between the two-dimensional layers of bilayer carrier systems due to near-field interlayer carrier interaction. We derive general expressions for the interlayer heat transfer and thermal conductance. Approximation formulas and detailed calculations for semiconductor and graphene based bilayers are presented. Our calculations for GaAs, Si and graphene bilayers show that the interlayer heat transfer can exceed the electron-phonon heat transfer below (system dependent) finite crossover temperature. We show that disorder strongly enhances the interlayer heat transport and pushes the threshold towards higher temperatures.Comment: 8 pages, 4 figures. Changes adopted during the review process: title changed, introduction and abstract rearranged, section headings added, Figure 1 enhanced, more details and a new figure on graphene adde

Ambient sesquiterpene concentration and its link to air ion measurements

International audienceAmbient air ion size distributions have been measured continuously at the Finnish boreal forest site in Hyytiälä since spring 2003. In general, these measurements show a maximum of air ions below 1.0 nm in diameter. But this physical characterization does not provide any information about the ion's chemical composition, which is one key question regarding the explanation of nucleation events observed. In this study we propose a link of the observed maximum of negative air ions between 0.56 and 0.75 nm to the so-called stabilised Criegee biradical, formed in the reaction of biogenic sesquiterpenes with ozone and predominantly destroyed by its reaction with ambient water vapour. Calculations of the electron and proton affinities of 120 kJ mol?1 (1.24 eV) and of 960 kJ mol?1 support this link. Other possible candidates such as sulphuric acid derived clusters are unable to explain the observations made. By using this approach, we are able to calculate the ambient concentration of sesquiterpenes at the air ion instrument inlet with a high time resolution on the daily and seasonal scale. The estimated concentration is found to reveal the same seasonal pattern as emission measurements conducted at shoot level. As expected for biogenic VOCs, the concentration is obtained highest during summer (maximum values of about 100 pptv) and smallest during winter (minimum less than 1 pptv). Because of the sesquiterpenes high reactivity and its low ambient concentrations, this approach can be a first step in understanding their emission and their impact on atmospheric chemistry in more detail. The findings presented are highly relevant for emission budgets too, since boreal forests are extended over large areas of the globe