297,501 research outputs found
Function-based Intersubject Alignment of Human Cortical Anatomy
Making conclusions about the functional neuroanatomical organization of the human brain requires methods for relating the functional anatomy of an individual's brain to population variability. We have developed a method for aligning the functional neuroanatomy of individual brains based on the patterns of neural activity that are elicited by viewing a movie. Instead of basing alignment on functionally defined areas, whose location is defined as the center of mass or the local maximum response, the alignment is based on patterns of response as they are distributed spatially both within and across cortical areas. The method is implemented in the two-dimensional manifold of an inflated, spherical cortical surface. The method, although developed using movie data, generalizes successfully to data obtained with another cognitive activation paradigmâviewing static images of objects and facesâand improves group statistics in that experiment as measured by a standard general linear model (GLM) analysis
Policy Driven Management for Distributed Systems
Separating management policy from the automated managers which interpret the policy facilitates the dynamic change of behavior of a distributed management system. This permits it to adapt to evolutionary changes in the system being managed and to new application requirements. Changing the behavior of automated managers can be achieved by changing the policy without having to reimplement themâthis permits the reuse of the managers in different environments. It is also useful to have a clear specification of the policy applying to human managers in an enterprise. This paper describes the work on policy which has come out of two related ESPRIT funded projects, SysMan and IDSM. Two classes of policy are elaboratedâauthorization policies define what a manager is permitted to do and obligation policies define what a manager must do. Policies are specified as objects which define a relationship between subjects (managers) and targets (managed objects). Domains are used to group the objects to which a policy applies. Policy objects also have attributes specifying the action to be performed and constraints limiting the applicability of the policy. We show how a number of example policies can be modeled using these objects and briefly mention issues relating to policy hierarchy and conflicts between overlapping policies. © 1994, Plenum Publishing Corporation. All rights reserved.Accepted versio
Constrained simulations of the local universe: I. Mass and motion in the Local Volume
It has been recently claimed that there is no correlation between the
distribution of galaxies and their peculiar velocities within the Local Volume
(LV), namely a sphere of R=7/h Mpc around the Local Group (LG). It has been
then stated that this implies that either locally dark matter is not
distributed in the same way as luminous matter, or peculiar velocities are not
due to fluctuations in mass. To test that statement a set of constrained N-body
cosmological simulations, designed to reproduce the main observed large scale
structure, have been analyzed. The simulations were performed within the
flat-Lambda, open and flat matter only CDM cosmogonies. Two unconstrained
simulations of the flat-Lambda and open CDM models were performed for
comparison. LG-like objects have been selected so as to mimic the real LG
environment. The local gravitational field due to all halos found within each
LV is compared with the exact gravitational field induced by all matter in the
simulation. We conclude that there is no correlation between the exact and the
local gravitational field obtained by pairwise newtonian forces between halos.
Moreover, the local gravitational field is uncorrelated with the peculiar
velocities of halos. The exact gravitational field has a linear correlation
with peculiar velocities but the proportionality constant relating the velocity
with gravitational field falls below the prediction of the linear theory. Upon
considering all matter inside the LVs, the exact and local gravitational
accelerations show a much better correlation, but with a considerable scatter
independent on the cosmological models. The main conclusion is that the lack of
correlation between the local gravitation and the peculiar velocity fields
around LG-like objects is naturally expected in the CDM cosmologies.Comment: 10 pages, 19 figures. Accepted for publication in MNRA
Simulation of a distributed CORBA-based SCP
This paper examines load balancing issues relating to a distributed CORBA-based Service Control Point. Two types of load balancing strategies are explored through simulation studies: (i) a novel ant-based load balancing algorithm, which has been devised specically for this type of system. This algorithm is compared to more traditional algorithms, (ii) a method for optimal distribution of the computational objects composing the service programs. This is based on mathematically minimising the expected communication ows between network nodes and message-level processing costs. The simulation model has been based on the recently adopted OMG IN/CORBA Interworking specication and the TINA Service Session computational object model
A Rigorous Approach to Relate Enterprise and Computational Viewpoints
Multiviewpoint approaches allow stakeholders to design a system from stakeholder-specific viewpoints. By this, a separation of concerns is achieved, which makes designs more manageable. However, to construct a consistent multiviewpoint design, the relations between viewpoints must be defined precisely, so that the consistency of designs from these viewpoints can be verified. The goal of this paper is to make the consistency rules between (a slightly adapted version of) the RM-ODP enterprise and computational viewpoints more precise and to make checking the consistency between these viewpoints practically applicable. To achieve this goal, we apply a generic framework for relating viewpoints that includes reusable consistency rules. We implemented the consistency rules in a tool to show their applicability
Policy based roles for distributed systems security
Distributed systems are increasingly being used in commercial environments necessitating the development of trustworthy and reliable security mechanisms. There is often no clear informal or formal specification of enterprise authorisation policies and no tools to translate policy specifications to access control implementation mechanisms such as capabilities or Access Control Lists. It is thus difficult to analyse the policy to detect conflicts or flaws and it is difficult to verify that the implementation corresponds to the policy specification. We present in this paper a framework for the specification of management policies. We are concerned with two types of policies: obligations which specify what activities a manager or agent must or must not perform on a set of target objects and authorisations which specify what activities a subject (manager or agent) can or can not perform on the set of target objects. Management policies are then grouped into roles reflecting the organisation..
Clinical encounter and the logic of relationality : Reconfiguring bodies and subjectivities in clinical relations
Acknowledgements I would like to thank all the patients and staff for their collaboration in the study and to acknowledge the other members of the team: James NâDow and Sara MacLennan for their helpful guidance. I am grateful to ZoĂ« Skea and Vikki Entwistle for the early discussions of the paper, to Natasha Mauthner and Lorna McKee for their insightful comments to various drafts, and to two anonymous reviewers for their thoughtful suggestions, which helped to clarify its argument. Funding The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was supported by a grant from the Big Lottery Fund. The views expressed here are the authorâs and do not necessarily reflect those of the funding bodies or any other organisation.Peer reviewedPostprin
Pattern Reification as the Basis for Description-Driven Systems
One of the main factors driving object-oriented software development for
information systems is the requirement for systems to be tolerant to change. To
address this issue in designing systems, this paper proposes a pattern-based,
object-oriented, description-driven system (DDS) architecture as an extension
to the standard UML four-layer meta-model. A DDS architecture is proposed in
which aspects of both static and dynamic systems behavior can be captured via
descriptive models and meta-models. The proposed architecture embodies four
main elements - firstly, the adoption of a multi-layered meta-modeling
architecture and reflective meta-level architecture, secondly the
identification of four data modeling relationships that can be made explicit
such that they can be modified dynamically, thirdly the identification of five
design patterns which have emerged from practice and have proved essential in
providing reusable building blocks for data management, and fourthly the
encoding of the structural properties of the five design patterns by means of
one fundamental pattern, the Graph pattern. A practical example of this
philosophy, the CRISTAL project, is used to demonstrate the use of
description-driven data objects to handle system evolution.Comment: 20 pages, 10 figure
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