755 research outputs found

    Self-Reliant and Deferred Privacy Stances: A Natural Quasi-Experiment of iOS Users’ Acceptance of Privacy Offerings

    Get PDF
    We often assume that technology users are concerned about their privacy and will readily take steps to protect it. But while there is clear evidence that users harbor serious privacy concerns, it is increasingly unclear whether users actually accept offers to improve their privacy. This study brings to light two strategies—a self-reliant privacy stance and a deferred privacy stance—that many users take to cope with their increasing loss of control over privacy. We argue that the two privacy stances help users envision positive future outcomes regarding their privacy but can paradoxically cause users to hesitate in accepting new privacy offerings from technology firms. We conduct a natural quasi- experiment studying how iPhone users under some mixture of the two privacy stances respond to a major privacy offering from Apple, in the form of an iOS update to that helps users control the tracking behavior of mobile apps like Facebook. We find that users taking a deferred privacy stance are less likely to accept the privacy offering than users with less staunch privacy stances. This hesitance on part of technology users is an underexamined challenge to privacy measures. By modeling privacy stances, information systems researchers can gain a more nuanced understanding of how people deal with the complex mix of threats to their privacy and the offers to manage their privacy. And by understanding privacy stances, firms might better calibrate their messaging to users holding out from technology offerings that genuinely seek to address privacy or security threats

    Binary frequency of planet-host stars at wide separations: A new brown dwarf companion to a planet-host star

    Full text link
    The aim of the project is to improve our knowledge on the multiplicity of planet-host stars at wide physical separations. We cross-matched approximately 6200 square degree area of the Southern sky imaged by the Visible Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) with the Two Micron All Sky Survey (2MASS) to look for wide common proper motion companions to known planet-host stars. We complemented our astrometric search with photometric criteria. We confirmed spectroscopically the co-moving nature of seven sources out of 16 companion candidates and discarded eight, while the remaining one stays as a candidate. Among these new wide companions to planet-host stars, we discovered a T4.5 dwarf companion at 6.3 arcmin (~9000 au) from HIP70849, a K7V star which hosts a 9 Jupiter mass planet with an eccentric orbit. We also report two new stellar M dwarf companions to one G and one metal-rich K star. We infer stellar and substellar binary frequencies for our complete sample of 37 targets of 5.4+/-3.8% and 2.7+/-2.7% (1 sigma confidence level), respectively, for projected physical separations larger than ~60-160 au assuming the range of distances of planet-host stars (24-75 pc). These values are comparable to the frequencies of non planet-host stars. We find that the period-eccentricity trend holds with a lack of multiple systems with planets at large eccentricities (e > 0.2) for periods less than 40 days. However, the lack of planets more massive than 2.5 Jupiter masses and short periods (<40 days) orbiting single stars is not so obvious due to recent discoveries by ground-based transit surveys and space missions.Comment: Accepted for publication in A&A, 13 pages, 5 figures, 3 tables, optical spectra will be available at CDS Strasbour

    Electric dipole rovibrational transitions in HD molecule

    Full text link
    The rovibrational electric dipole transitions in the ground electronic state of the HD molecule are studied. A simple, yet rigorous formula is derived for the transition rates in terms of the electric dipole moment function D(R)D(R), which is calculated in a wide range of RR. Our numerical results for transition rates are in moderate agreement with experiments and previous calculations, but are at least an order of magnitude more accurate.Comment: 7 pages, 1 figur

    Measurement of AC Loss and Magnetic Field during Ramps in the LHC Model Dipoles

    Get PDF
    We describe the systems for AC loss and magnetic field measurements developed for the LHC superconducting magnets. AC loss measurements are performed using an electric method, while field measurements are performed using either fixed pick-ups or rotating coils. We present results obtained on 1-m long model dipoles, and compare the results of the different methods in terms of average inter-strand resistance and low order field harmonics

    Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association

    Get PDF
    We present the discovery of a companion near the deuterium burning mass limit located at a very wide distance, at an angular separation of 4.6+/-0.1 arcsec (projected distance of ~ 670 AU) from UScoCTIO108, a brown dwarf of the very young Upper Scorpius association. Optical and near-infrared photometry and spectroscopy confirm the cool nature of both objects, with spectral types of M7 and M9.5, respectively, and that they are bona fide members of the association, showing low gravity and features of youth. Their masses, estimated from the comparison of their bolometric luminosities and theoretical models for the age range of the association, are 60+/-20 and 14^{+2}_{-8} MJup, respectively. The existence of this object around a brown dwarf at this wide orbit suggests that the companion is unlikely to have formed in a disk based on current planet formation models. Because this system is rather weakly bound, they did not probably form through dynamical ejection of stellar embryos.Comment: 10 pages, including 4 figures and 2 table

    Optical Linear Polarization of Late M- and L-Type Dwarfs

    Full text link
    (Abridged). We report on the linear polarimetric observations in the Johnson I filter of 44 M6-L7.5 ultracool dwarfs (2800-1400 K). Eleven (10 L and 1 M) dwarfs appear to have significant linear polarization (P = 0.2-2.5%). We have compared the M- and L-dwarf populations finding evidence for a larger frequency of high I-band polarization in the coolest objects, supporting the presence of significant amounts of dust in L-dwarfs. The probable polarizing mechanism is related to the presence of heterogeneous dust clouds nonuniformly distributed across the visible photospheres and the asymmetric shape of the objects. In some young ultracool dwarfs, surrounding dusty disks may also yield polarization. For polarimetric detections, a trend for slightly larger polarization from L0 to L6.5 may be present in our data, suggesting changes in the distribution of the grain properties, vertical height of the clouds, metallicity, age, and rotation speed. One of our targets is the peculiar brown dwarf (BD) 2MASS J2244+20 (L6.5), which shows the largest I-band polarization degree. Its origin may lie in a surrounding dusty disk or rather large photospheric dust grains. The M7 young BD CFHT-BD-Tau 4 and the L3.5 field dwarf 2MASS J0036+18 were also observed in the Johnson R filter. Our data support the presence of a circum(sub)stellar disk around the young accreting BD. Our data also support a grain growth in the submicron regime in the visible photosphere of J0036+18 (1900 K). The polarimetric data do not obviously correlate with activity or projected rotational velocity. Three polarized early- to mid-L dwarfs display I-band light curves with amplitudes below 10 mmag.Comment: Accepted for publication in ApJ (March 2005), 35 pages, 5 figure

    High spatial resolution and high contrast optical speckle imaging with FASTCAM at the ORM

    Full text link
    In this paper, we present an original observational approach, which combines, for the first time, traditional speckle imaging with image post-processing to obtain in the optical domain diffraction-limited images with high contrast (1e-5) within 0.5 to 2 arcseconds around a bright star. The post-processing step is based on wavelet filtering an has analogy with edge enhancement and high-pass filtering. Our I-band on-sky results with the 2.5-m Nordic Telescope (NOT) and the lucky imaging instrument FASTCAM show that we are able to detect L-type brown dwarf companions around a solar-type star with a contrast DI~12 at 2" and with no use of any coronographic capability, which greatly simplifies the instrumental and hardware approach. This object has been detected from the ground in J and H bands so far only with AO-assisted 8-10 m class telescopes (Gemini, Keck), although more recently detected with small-class telescopes in the K band. Discussing the advantage and disadvantage of the optical regime for the detection of faint intrinsic fluxes close to bright stars, we develop some perspectives for other fields, including the study of dense cores in globular clusters. To the best of our knowledge this is the first time that high contrast considerations are included in optical speckle imaging approach.Comment: Proceedings of SPIE conference - Ground-based and Airborne Instrumentation for Astronomy III (Conference 7735), San Diego 201

    Cortisol, Heart Rate, and Perceived Exertion Responses to Different Resistance Training Protocols with and Without Blood Flow Restriction

    Get PDF
    ABSTRACT PURPOSE: The purpose of this study was to examine the effects of different resistance exercise protocols on cortisol, heart rate, and perceived exertion. METHODS: Eight males and eight females (age = 21.8 ± 2.6) performed three randomly assigned exercise protocols on three separate occasions: low-intensity resistance training (RT) exercises with blood flow restriction (BFR) at 20% of one repetition maximum (1-RM) (BFR20), moderate-intensity RT exercises with BFR at 40% of 1-RM (BFR40), and traditional high-intensity RT exercises at 80% of 1-RM (HI80). Participants completed 2-3 circuits of four sets in the leg press and leg extension machines. Total volume of resistance training (RT) exercises performed was about 25% for the BFR20 session and 50% for the BFR40 session compared to the volume of RT exercises for the HI80 session. Heart rate (HR) and rating of perceived exertion (RPE) were monitored throughout each session. Saliva samples were collected before and immediately after each exercise session. Samples were stored at -80 ℃ and later analyzed with ELISA for salivary cortisol concentrations. RESULTS: No significant differences in cortisol concentrations were noted between conditions, but significant increases in cortisol concentrations were seen from pre- to post-exercise exercise (pCONCLUSION: The cortisol findings may indicate that all three exercise protocols resulted in similar levels of stimuli to the hypothalamic-pituitary-adrenal axis. It should be highlighted that the BFR20 session with lowest training volume and intensity resulted in similar objective (i.e., HR) but significantly lower subjective level of exertion (i.e., RPE) compared to the HI80 session with highest training volume and intensity. The cortisol, HR, and RPE responses to various RT sessions indicate that the findings of the present study may have some clinical and/or practical applications

    The use of Polystyrene from Ballpen Barrels and Wood Ash as Additives in Making Lightweight Bricks.

    Get PDF
    This study aimed to determine the ability of polystyrene in ballpen barrels of making a brick to be more compacted than the ordinary clay bricks. Polystyrene is a synthetic aromatic hydrocarbon polymer made from the monomer styrene that also makes a brick denser. The Wood ash from burned wood are usually used by the gardeners as a good source of potash. Wood ash has an ability of making the bricks lighter than the usual clay bricks. Additional wood ash is better than coal ash, because coal ash has a dangerous chemicals that may harm human. The goal of this study is to lessen the ballpen barrels and wood ash that are not disposed properly and make this in a creative way. Five test was conducted to determine the potential of polystyrene and wood ash namely water absorption test, drop test, efflorescence test, compressive test and heat resistance test. Based from the data gathered, it concluded that polystyrene from ballpen barrel and wood ash with the ratio of 50% Cement, 25% Wood Ash, 25% Ballpen Barrels is effective additives in production of lightweigh

    A Methane Isolated Planetary Mass Object in Orion

    Full text link
    We report on the discovery of a free-floating methane dwarf toward the direction of the young star cluster sigma Orionis. Based on the object's far-red optical and near-infrared photometry and spectroscopy, we conclude that it is a possible member of this association. We have named it as S Ori J053810.1-023626 (S Ori 70 is the abridged name). If it is a true member of sigma Orionis, the comparison of the photometric and spectroscopic properties of S Ori 70 with state-of-the-art evolutionary models yields a mass of 3 (+5/-1) Jupiter mass for ages between 1 Myr and 8 Myr. The presence of such a low-mass object in our small search area (55.4 sq. arcmin) would indicate a rising substellar initial mass function in the sigma Orionis cluster even for planetary masses.Comment: Accepted for publication in the ApJ. Twelve pages, figures and tables include
    • 

    corecore