Anonymity and Information Hiding in Multiagent Systems

We provide a framework for reasoning about information-hiding requirements in multiagent systems and for reasoning about anonymity in particular. Our framework employs the modal logic of knowledge within the context of the runs and systems framework, much in the spirit of our earlier work on secrecy [Halpern and O'Neill 2002]. We give several definitions of anonymity with respect to agents, actions, and observers in multiagent systems, and we relate our definitions of anonymity to other definitions of information hiding, such as secrecy. We also give probabilistic definitions of anonymity that are able to quantify an observer s uncertainty about the state of the system. Finally, we relate our definitions of anonymity to other formalizations of anonymity and information hiding, including definitions of anonymity in the process algebra CSP and definitions of information hiding using function views.Comment: Replacement. 36 pages. Full version of CSFW '03 paper, submitted to JCS. Made substantial changes to Section 6; added references throughou

Report of the Integrated Stroke Care Workshop

The Stroke Project has been underway since October 2000. This workshop represented the first mechanism where by issues surrounding the project have been addressed by the multi- disciplinary stroke team and the Darent Valley Hospital Staff. Approximately 35 members of staff attended the workshop, demonstrating the high level of interest and ownership. Currently, the hospital receives an average eight or nine new stroke admissions a week. The turnover is such that patients suffering from stroke account for around 22-23 occupied beds in the acute hospital at any point in time. In the past the Acute Trust had had a lead Stroke Physician responsible for 20 designated stroke beds within a stroke unit. In that system many (but not all) cases of acute stroke admitted under the General Physicians would have been referred to the stroke unit and had their acute care and acute rehabilitation provided on site in that unit. At that time the overall number of beds occupied by cases of stroke was around 28- 29

Visual recovery of desert pavement surfaces following impacts from vehicle and foot traffic in the Ross Sea region of Antarctica

Sites of past human activity were investigated to assess the visual recovery of the desert pavement following impacts from human trampling and vehicle traffic. Visually disturbed and nearby control sites were assessed using comparative photographic records, a field-based Visual Site Assessment, and Desert Pavement Recovery Assessment. Sites included: vehicle and walking tracks at Marble Point and Taylor Valley; a campsite, experimental treading trial site, and vehicle tracks in Wright Valley; and vehicle and walking tracks at Cape Roberts. The time since last disturbance ranged from three months to over 50 years. This investigation also attempted to determine what has the greatest lasting visual impact on soil surfaces in the Ross Sea region: dispersed trafficking or track formation? Walking tracks remained visible in the landscape (due to larger clasts concentrating along track margins) long after the desert pavement surface had recovered. However, randomly dispersed footprints were undetectable within five years. For many sites, allowing widespread trampling will give lower medium-term visible impact than concentrating traffic flow by track formation. For steep slopes and sites where repeated visits occur, use of a single track is recommended. Some 1950s vehicle tracks remain visible in the Antarctic landscape, but where visually obvious impacts were remediated, evidence of former occupation was almost undetectable

Superorbital Period in the High Mass X-ray Binary 2S 0114+650

We report the detection of a superorbital period in the high-mass X-ray binary 2S 0114+650. Analyses of data from the Rossi X-ray Timing Explorer (RXTE) All-Sky Monitor (ASM) from 1996 January 5 to 2004 August 25 reveal a superorbital period of 30.7 +/- 0.1 d, in addition to confirming the previously reported neutron star spin period of 2.7 h and the binary orbital period of 11.6 d. It is unclear if the superorbital period can be ascribed to the precession of a warped accretion disc in the system.Comment: 5 pages, 5 figures, submitted to MNRAS 27th January 2005. Manuscript expanded to include discussion of evolution of periods, and hardness ratio variability. Number of figures increased from 5 to 9. Accepted for publication 19th December 200

A Multicoloured View of 2S 0114+650

We report the results of radio and X-ray observations of the high mass X-ray binary 2S 0114+650, made with the Giant Meterwave Radio Telescope and the Rossi X-ray Timing Explorer respectively. No emission was detected at radio wavelengths. The neutral hydrogen column density was found to vary over the orbital period, while no variability over the the super-orbital period was observed. We discuss the causes of the observed relationships and the implications for the underlying mechanisms.Comment: 4 pages, 2 figures; to appear in proceedings for "The multicoloured landscape of compact objects and their explosive progenitors", Cefalu, Sicily, 2006 June 11-24, AIP, submitte