28,365 research outputs found
M2M modelling of the Galactic disc via PRIMAL: Fitting to Gaia Error Added Data
We have adapted our made-to-measure (M2M) algorithm PRIMAL to use mock Milky
Way like data constructed from an N-body barred galaxy with a boxy bulge in a
known dark matter potential. We use M0 giant stars as tracers, with the
expected error of the ESA space astrometry mission Gaia. We demonstrate the
process of constructing mock Gaia data from an N-body model, including the
conversion of a galactocentric Cartesian coordinate N-body model into
equatorial coordinates and how to add error to it for a single stellar type. We
then describe the modifications made to PRIMAL to work with observational
error. This paper demonstrates that PRIMAL can recover the radial profiles of
the surface density, radial velocity dispersion, vertical velocity dispersion
and mean rotational velocity of the target disc, along with the pattern speed
of the bar, to a reasonable degree of accuracy despite the lack of accurate
target data. We also construct mock data which take into account dust
extinction and show that PRIMAL recovers the structure and kinematics of the
disc reasonably well. In other words, the expected accuracy of the Gaia data is
good enough for PRIMAL to recover these global properties of the disc, at least
in a simplified condition, as used in this paper.Comment: 16 pages, 10 figures, submitted to MNRAS 17th Dec 2013, accepted 30th
June 201
Managing multiple morbidity in mid-life: a qualitative study of attitudes to drug use
OBJECTIVE: To examine attitudes towards drug use among middle aged respondents with high levels of chronic morbidity. DESIGN: Qualitative study with detailed interviews. SETTING: West of Scotland. PARTICIPANTS: 23 men and women aged about 50 years with four or more chronic illnesses. MAIN OUTCOME MEASURE: Participants' feelings about long term use of drugs to manage chronic multiple morbidity. RESULTS: Drugs occupied a central place in the way people managed their comorbidities. Respondents expressed an aversion to taking drugs, despite acknowledging that they depended on drugs to live as "normal" a life as possible. Respondents expressed ambivalence to their drugs in various ways. Firstly, they adopted both regular and more flexible regimens and might adhere to a regular regimen in treating one condition (such as hypertension) while adopting a flexible regimen in relation to others, in response to their experience of symptoms or varying demands of their daily life. Secondly, they expressed reluctance to take drugs, but an inability to be free of them. Thirdly, drugs both facilitated performance of social roles and served as evidence of an inability to perform such roles. CONCLUSIONS: Insight into the considerable tension experienced by people managing complex drug regimens to manage multiple chronic illness may help medical carers to support self care practices among patients and to optimise concordance in their use of prescribed drugs
Open Access Policy: Numbers, Analysis, Effectiveness
The PASTEUR4OA project analyses what makes an Open Access (OA) policy
effective. The total number of institutional or funder OA policies worldwide is
now 663 (March 2015), over half of them mandatory. ROARMAP, the policy
registry, has been rebuilt to record more policy detail and provide more
extensive search functionality. Deposit rates were measured for articles in
institutions' repositories and compared to the total number of WoS-indexed
articles published from those institutions. Average deposit rate was over four
times as high for institutions with a mandatory policy. Six positive
correlations were found between deposit rates and (1) Must-Deposit; (2)
Cannot-Waive-Deposit; (3) Deposit-Linked-to-Research-Evaluation; (4)
Cannot-Waive-Rights-Retention; (5) Must-Make-Deposit-OA (after allowable
embargo) and (6) Can-Waive-OA. For deposit latency, there is a positive
correlation between earlier deposit and (7) Must-Deposit-Immediately as well as
with (4) Cannot-Waive-Rights-Retention and with mandate age. There are not yet
enough OA policies to test whether still further policy conditions would
contribute to mandate effectiveness but the present findings already suggest
that it would be useful for current and future OA policies to adopt the seven
positive conditions so as to accelerate and maximise the growth of OA.Comment: 49 pages, 21 figures, 15 tables. Pasteur4OA Work Package 3 report:
Open Access policies 201
A Semantic Hierarchy for Erasure Policies
We consider the problem of logical data erasure, contrasting with physical
erasure in the same way that end-to-end information flow control contrasts with
access control. We present a semantic hierarchy for erasure policies, using a
possibilistic knowledge-based semantics to define policy satisfaction such that
there is an intuitively clear upper bound on what information an erasure policy
permits to be retained. Our hierarchy allows a rich class of erasure policies
to be expressed, taking account of the power of the attacker, how much
information may be retained, and under what conditions it may be retained.
While our main aim is to specify erasure policies, the semantic framework
allows quite general information-flow policies to be formulated for a variety
of semantic notions of secrecy.Comment: 18 pages, ICISS 201
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Termination-insensitive noninterference leaks more than just a bit
Current tools for analysing information flow in programs build upon ideas going back to Denning's work from the 70's. These systems enforce an imperfect notion of information flow which has become known as termination-insensitive noninterference. Under this version of noninterference, information leaks are permitted if they are transmitted purely by the program's termination behaviour (i.e., whether it terminates or not). This imperfection is the price to pay for having a security condition which is relatively liberal (e.g. allowing while-loops whose termination may depend on the value of a secret) and easy to check. But what is the price exactly? We argue that, in the presence of output, the price is higher than the “one bit” often claimed informally in the literature, and effectively such programs can leak all of their secrets. In this paper we develop a definition of termination-insensitive noninterference suitable for reasoning about programs with outputs. We show that the definition generalises “batch-job” style definitions from the literature and that it is indeed satisfied by a Denning-style program analysis with output. Although more than a bit of information can be leaked by programs satisfying this condition, we show that the best an attacker can do is a brute-force attack, which means that the attacker cannot reliably (in a technical sense) learn the secret in polynomial time in the size of the secret. If we further assume that secrets are uniformly distributed, we show that the advantage the attacker gains when guessing the secret after observing a polynomial amount of output is negligible in the size of the secret
Using Simple Neural Networks to Correct Errors in Optical Data Transmission.
We have demonstrated the applicability of
neural-network-based systems to the problem
of reducing the effects of signal distortion,
and shown that such a system has the potential
to reduce the bit-error-rate in the digitized
version of the analogue electrical signal
derived from an optical data stream by a
substantial margin over existing techniques
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