65 research outputs found
Locating Planetesimal Belts in the Multiple-planet Systems HD 128311, HD 202206, HD 82943, and HR 8799
In addition to the Sun, six other stars are known to harbor multiple planets and debris disks: HD 69830, HD 38529, HD 128311, HD 202206, HD 82943, and HR 8799. In this paper, we set constraints on the location of the dust-producing planetesimals around the latter four systems. We use a radiative transfer model to analyze the spectral energy distributions of the dust disks (including two new Spitzer IRS spectra presented in this paper), and a dynamical model to assess the long-term stability of the planetesimals' orbits. As members of a small group of stars that show evidence of harboring a multiple planets and planetesimals, their study can help us learn about the diversity of planetary systems
Spandex: Secure password tracking for android
Abstract This paper presents SpanDex, a set of extensions to Android's Dalvik virtual machine that ensures apps do not leak users' passwords. The primary technical challenge addressed by SpanDex is precise, sound, and efficient handling of implicit information flows (e.g., information transferred by a program's control flow). SpanDex handles implicit flows by borrowing techniques from symbolic execution to precisely quantify the amount of information a process' control flow reveals about a secret. To apply these techniques at runtime without sacrificing performance, SpanDex runs untrusted code in a data-flow sensitive sandbox, which limits the mix of operations that an app can perform on sensitive data. Experiments with a SpanDex prototype using 50 popular Android apps and an analysis of a large list of leaked passwords predicts that for 90% of users, an attacker would need over 80 login attempts to guess their password. Today the same attacker would need only one attempt for all users
A Spitzer IRS Study of Debris Disks Around Planet-Host Stars
Since giant planets scatter planetesimals within a few tidal radii of their
orbits, the locations of existing planetesimal belts indicate regions where
giant planet formation failed in bygone protostellar disks. Infrared
observations of circumstellar dust produced by colliding planetesimals are
therefore powerful probes of the formation histories of known planets. Here we
present new Spitzer IRS spectrophotometry of 111 Solar-type stars, including
105 planet hosts. Our observations reveal 11 debris disks, including two
previously undetected debris disks orbiting HD 108874 and HD 130322. Combining
our 32 micron spectrophotometry with previously published MIPS photometry, we
find that the majority of debris disks around planet hosts have temperatures in
the range 60 < T < 100 K. Assuming a dust temperature T = 70 K, which is
representative of the nine debris disks detected by both IRS and MIPS, we find
that debris rings surrounding Sunlike stars orbit between 15 and 240 AU,
depending on the mean particle size. Our observations imply that the planets
detected by radial-velocity searches formed within 240 AU of their parent
stars. If any of the debris disks studied here have mostly large, blackbody
emitting grains, their companion giant planets must have formed in a narrow
region between the ice line and 15 AU.Comment: Accepted for publication in the Astronomical Journal. 14 pages,
including five figures and two table
High-Performance Work Systems and Organizational Performance in Emerging Economies: Evidence from MNEs in Turkey
This study examines the association between the usage of high-performance work systems (HPWS) by subsidiaries of multinational enterprises (MNEs) in Turkey and employee and subsidiary level outcomes. The study is based on a survey of 148 MNE subsidiaries operating in Turkey. The results show that the usage of HPWS has a significant positive impact on employee effectiveness. However, their impact on employee skills and development, and organizational financial performance are far less clear. Our findings highlight the extent to which HWPS need to be adapted to take account of context-specific institutional realities. © 2014 Springer-Verlag Berlin Heidelberg
The Vahland School
© 1979 Geoffrey LawlerFrom cover: Humanities Research Report, 5th YearThe City of Bendigo owes a great deal of its early heritage to the great number of German immigrants who came to the Sandhurst area during the gold rush years and settled there. More than any other Victorian centre, Bendigo benefited from this particular country and especially so in its architecture. It was this aspect that first aroused my interest in Bendigonian architecture and it led me to the most prominent architect in Bendigo between the years 1850-1900, Wilhelm Karl Vahland.
Further investigation led me to find that there was a strong German group working with Vahland and the study could be expanded to include his partners Getzschmann and his son H.E. Vahland and a principal employee William Nicolai. These four German architects between them, accounted for the majority of significant buildings in Bendigo and the various partnerships with Vahland were, by far, the longest running practice in Bendigo. This is evidenced in the chart included. (From Introduction
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Harry Kesten (1931-2019), a personal and scientific tribute
The mathematical achievements of Harry Kesten since the mid-1950s have
revolutionized probability theory as a subject in its own right and in its
associations with aspects of algebra, analysis, geometry, and statistical
physics. Through his personality and scientific ability, he has framed the
modern subject to a degree exceeded by no other. The impact of his work and
personality is summarised in this memoir
Transport Of Fine Sediment And Sediment–Associated Contaminants Within An Urban Gravel-Bed River, River Tame, UK
Transport Of Fine Sediment And Sediment–Associated Contaminants Within An Urban Gravel-Bed River, River Tame, UK
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