18,951 research outputs found

    The WFCAM Multi-wavelength Variable Star Catalog

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    Stellar variability in the near-infrared (NIR) remains largely unexplored. The exploitation of public science archives with data-mining methods offers a perspective for the time-domain exploration of the NIR sky. We perform a comprehensive search for stellar variability using the optical-NIR multi-band photometric data in the public Calibration Database of the WFCAM Science Archive (WSA), with the aim of contributing to the general census of variable stars, and to extend the current scarce inventory of accurate NIR light curves for a number of variable star classes. We introduce new variability indices designed for multi-band data with correlated sampling, and apply them for pre-selecting variable star candidates, i.e., light curves that are dominated by correlated variations, from noise-dominated ones. Pre-selection criteria are established by robust numerical tests for evaluating the response of variability indices to colored noise characteristic to the data. We find 275 periodic variable stars and an additional 44 objects with suspected variability with uncertain periods or apparently aperiodic variation. Only 44 of these objects had been previously known, including 11 RR~Lyrae stars in the outskirts of the globular cluster M3 (NGC~5272). We provide a preliminary classification of the new variable stars that have well-measured light curves, but the variability types of a large number of objects remain ambiguous. We classify most of the new variables as contact binary stars, but we also find several pulsating stars, among which 34 are probably new field RR~Lyrae and 3 are likely Cepheids. We also identify 32 highly reddened variable objects close to previously known dark nebulae, suggesting that these are embedded young stellar objects. We publish our results and all light-curve data as the WFCAM Variable Star Catalog.Comment: 21 pages, 11 figure

    Detecting and developing new business opportunities in society 5.0 contexts: A sociotechnical approach

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    Rapid technological evolution has become a great challenge for businesses and societies due to the openness provided by new digital technologies, platforms, and infrastructure and to the impacts of these innovations on how people work and live. The concept of a super-smart society (i.e., Society 5.0) comprises a fresh way to apply these innovations, in which human beings contribute to adapting technologies to daily activities in their society and making Society 5.0 ideas applicable to different areas of each individual’s life. Digital transformation and technological innovation are basic components of this paradigm. This study sought to develop a decision-support model that can help companies structure and prioritize new business opportunities within Society 5.0 contexts. The analysis system relies on a constructivist approach that promotes debates between specialists and combinations of methodologies such as cognitive mapping and interpretive structural modeling. The results highlight the most important areas in which new business opportunities can arise, thereby demonstrating that the proposed model is a valuable tool for incorporating a future orientation into business technological innovation initiatives.info:eu-repo/semantics/publishedVersio

    Light scattering by a medium with a spatially modulated optical conductivity: the case of graphene

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    We describe light scattering from a graphene sheet having a modulated optical conductivity. We show that such modulation enables the excitation of surface plasmon-polaritons by an electromagnetic wave impinging at normal incidence. The resulting surface plasmon-polaritons are responsible for a substantial increase of electromagnetic radiation absorption by the graphene sheet. The origin of the modulation can be due either to a periodic strain field or to adatoms (or absorbed molecules) with a modulated adsorption profile.Comment: http://iopscience.iop.org/0953-8984/24/24/24530

    Editorial

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    Magnetized Accretion-Ejection Structures: 2.5D MHD simulations of continuous Ideal Jet launching from resistive accretion disks

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    We present numerical magnetohydrodynamic (MHD) simulations of a magnetized accretion disk launching trans-Alfvenic jets. These simulations, performed in a 2.5 dimensional time-dependent polytropic resistive MHD framework, model a resistive accretion disk threaded by an initial vertical magnetic field. The resistivity is only important inside the disk, and is prescribed as eta = alpha_m V_AH exp(-2Z^2/H^2), where V_A stands for Alfven speed, H is the disk scale height and the coefficient alpha_m is smaller than unity. By performing the simulations over several tens of dynamical disk timescales, we show that the launching of a collimated outflow occurs self-consistently and the ejection of matter is continuous and quasi-stationary. These are the first ever simulations of resistive accretion disks launching non-transient ideal MHD jets. Roughly 15% of accreted mass is persistently ejected. This outflow is safely characterized as a jet since the flow becomes super-fastmagnetosonic, well-collimated and reaches a quasi-stationary state. We present a complete illustration and explanation of the `accretion-ejection' mechanism that leads to jet formation from a magnetized accretion disk. In particular, the magnetic torque inside the disk brakes the matter azimuthally and allows for accretion, while it is responsible for an effective magneto-centrifugal acceleration in the jet. As such, the magnetic field channels the disk angular momentum and powers the jet acceleration and collimation. The jet originates from the inner disk region where equipartition between thermal and magnetic forces is achieved. A hollow, super-fastmagnetosonic shell of dense material is the natural outcome of the inwards advection of a primordial field.Comment: ApJ (in press), 32 pages, Higher quality version available at http://www-laog.obs.ujf-grenoble.fr/~fcass

    Critical temperature of a fully anisotropic three-dimensional Ising model

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    The critical temperature of a three-dimensional Ising model on a simple cubic lattice with different coupling strengths along all three spatial directions is calculated via the transfer matrix method and a finite size scaling for L x L oo clusters (L=2 and 3). The results obtained are compared with available calculations. An exact analytical solution is found for the 2 x 2 oo Ising chain with fully anisotropic interactions (arbitrary J_x, J_y and J_z).Comment: 17 pages in tex using preprint.sty for IOP journals, no figure

    How daily negative affect and emotional exhaustion correlates with work engagement and presenteeism-constrained productivity

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    Exploring productivity loss due to presenteeism and how it can have an influence on employees’ productivity has been an important concern for human resource managers. Using the conservation of resources theory and the job demands-resources model, this study investigated how work engagement could mediate the relationship between both emotional exhaustion and negative affect and productivity loss due to presenteeism in a country experiencing an economic downturn. A total of 42 employees from a health care institution completed a 10-day diary survey (420 diary tasks). Multilevel linear modeling results, including power analyses, showed that negative affect and emotional exhaustion predicted productivity loss due to presenteeism positively, whereas work engagement predicted productivity loss negatively. Furthermore, we found that at a day-level, work engagement mediated the effects of emotional exhaustion and negative affect on productivity loss due to presenteeism. This study highlights the importance of promoting work engagement to reduce the effects of negative affect and emotional exhaustion on productivity loss due to presenteeism through intervention.info:eu-repo/semantics/acceptedVersio
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