A platform for dynamic organization of agents in agent-based systems

In most agent-based systems, different middle agents are employed to increase their flexibility. However, there are still three issues remain unsolved. In centralized architecture with single middle agent, the middle agent itself is a bottleneck and suffers from single point failure; middle agents in distributed architecture lack capability of dynamic organization of agents; The reliability is not strong because of the single point failure and lack of effective architecture. We introduce a platform with ring architectural model to solve all above problems. In the platform, multiple middle agents are dynamically supported for solving the first problem. For solving the second problem, middle agents dynamically manage the registration and cancellation of service provider agents and application teams, each of which includes a set of closely interacting requester agents to complete an independent task. Redundancy middle agent technique is proposed for solving the third problem. All middle agents are of the feature of proliferation and self-cancellation according to the sensory inputs from their environment. For organizing the middle agents effectively, a ring architectural model is proposed. We demonstrate the applicability of the platform by its application and present experimental evidence that the platform is flexible and robust.

Perceived characteristics and pedagogical efficacy of animated conversational agents

We investigated college students' perceptions of a diverse sample of animated conversational agents. We also examined the pedagogical efficacy of those agents. We found that people perceive differences among the agents on several dimensions, such as likeability, and that the agents differ in pedagogical efficacy. However, none of the characteristics that we measured accounted for differences in pedagogical efficacy across the agents. We discuss implications for the field of agent studies with pmiicular emphasis on the creation of pedagogically effective conversational agents and suggest directions for future research.

Incorporating track records of agents into matchmaking in middle agents

Middle agents play a very important role in multiagent systems used in open and dynamic environments. The performance of middle agents relies heavily on the matchmaking algorithms used. The actual performance of provider agents in accomplishing delegated tasks has a significant impact on the matchmaking outcomes of middle agents. With those observations in mind, this paper discusses the incorporation of the track records of agents in accomplishing delegated tasks into the matchmaking process. How to provide initial values for track records in the algorithm are detailed. A prototype is also built to verify the algorithm. Based on the improved algorithm, the matchmaking outcomes are more accurate and reasonable.

Subcellular localisation of proteins in fluorescent microscope images using a random forest

This paper presents a system that employs random forests to formulate a method for subcellular localisation of proteins. A random forest is an ensemble learner that grows classification trees. Each tree produces a classification decision, and an integrated output is calculated. The system classifies the protein-localisation patterns within fluorescent microscope images. 2D images of HeLa cells that include all major classes of subcellular structures, and the associated feature set are used. The performance of the developed system is compared against that of the support vector machine and decision tree approaches. Three experiments are performed to study the influence of the training and test set size on the performance of the examined methods. The calculated classification errors and execution times are presented and discussed. The lowest classification error (2.9%) has been produced by the developed system.

Housing service officers : agents of the state or customer service officers?

Staff employed in the Victorian Office of Housing are invariably required to exercise discretion in their day-to-day work managing housing assets and providing services to public housing tenants. Policies specify processes but they never cover all situations and do not provide guidance on competing objectives. For example, preparing a property for reletting is a process with protocols and budget constraints. However, staff can make procedural variations that compy with policy. These variations, generally learnt from peers on the job, often result in budget over runs, but do result in improved properties for new tenants. Discretion is being exercised in balancing housing asset, budget control and tenant service objectives. A housing officer sums up the enduring tension in balancing objectives in the question and statement:’ Am I an agent of the state or a customer service officer? Because I can’t be both’. Organisationally these tensions are spoken about as ‘management issues’, ‘policy reengineering’ and ‘unrealistic understandings’. Using data from an ethnographic study in the Victorian Office of Housing, the paper addresses the question: ‘What do we know about the way in which front line housing officers manage competing objectives in their daily work and how might this knowledge be usefully used in the development of operational policy?’ The paper will explore the way in which complex administrative rules are used as a device to align staff to the Office of Housing objectives and limit the exercise of discretion by frontline staff. Against the background of this analysis the paper will consider the limitations of rule making and the extent to which other organisational strategies might be important for improvements in service provision in a context of constrained resources and limited resources.

Using mobile agents to recover from node and database compromise in path-based DoS attacks in wireless sensor networks

Wireless sensor networks represent a new generation of real-time embedded systems with significantly different communication constraints from the traditional networked systems. With their development, a new attack called a path-based DoS (PDoS) attack has appeared. In a PDoS attack, an adversary, either inside or outside the network, overwhelms sensor nodes by flooding a multi-hop end-to-end communication path with either replayed packets or injected spurious packets. Detection and recovery from PDoS attacks have not been given much attention in the literature. In this article, we consider wireless sensor networks designed to collect and store data. In a path-based attack, both sensor nodes and the database containing collected data can be compromised. We propose a recovery method using mobile agents which can detect PDoS attacks easily and efficiently and recover the compromised nodes along with the database.

Building capacity for rural health : the role of boundary crossers in coalition maturity for partnerships with external agents

The concept of partnership has entered policy rhetoric and is urged as good practice in a variety of domains including health. Rural communities tend to have fewer resources available for the provision of services such as health than their metropolitan counterparts, and so could be expected to benefit from partnerships with external agencies. Indicators of coalition maturity for working in partnership with external agents in order to build stronger communities are distilled from the group development and partnership research literature and considered in the light of the experiences of the University Department of Rural Health in community engagement. The chapter draws on experiences of two rural community coalitions working to plan and negotiate health service provision. The coalitions were analysed against the indicators. A key indicator of maturity and readiness for working in partnership with external agents is related to the behaviour of ‘boundary crossers’. Boundary crossers are defined as people who move freely between two or more domains and who understand the values, cultures and language, and have the trust, of both. Domains can be within a community or be the community and an external sector. Community health professionals, especially those in senior positions, often act as boundary crossers between the community and broader domains such as regional/state health services or policy, although other community members can fill the role. Other key indicators of coalition maturity for working in partnership with external agents include local leadership that empowers the community, a willingness of community coalitions to take risks and mould opportunities to meet their vision, and a culture of critical reflection and evaluation of past actions.

This chapter analyses the impact of boundary crossing behaviour on community readiness and partnerships with external agents that are intended to build rural community capacity to plan and negotiate health service provision. It is argued that the characteristics and modus operandi of boundary crossers who are members of rural community coalitions affect the level of maturity of the coalitions and community readiness to work with external agents. An understanding of the characteristics and modus operandi of boundary crossers provides valuable insights for external agents in designing their approach to partnerships that build rural community capacity for health.

The effect of flicker from fluorescent lights on mate choice in captive birds

The visual systems of birds are hypothesized to have higher temporal resolution than those of humans, suggesting that they may be able to perceive the flicker emitted from conventional low-frequency fluorescent lights (LF; 100 Hz in Europe, 120 Hz in the U.S.A.). These lights are commonly used in the housing of captive birds and this may affect both their welfare and performance in experiments. We carried out mate choice experiments on European starlings, Sturnus vulgaris, under both low- and high-frequency fluorescent lights (HF; > 30 kHz, at which flicker is imperceptible). Indicators of male condition and size, together with the reflectance spectra and length of the males' throat feathers, were also recorded to ascertain which variables correlated with female preference. Females ranked males consistently under HF, but not LF, lighting, and individual females chose different males under the two lighting types. Under HF lighting, females chose to spend more time with males that had longer throat feathers. The flicker rate of the light clearly affected the choices made by the females, possibly because of nonspecific stress effects or decreased discrimination ability. Our results imply that careful interpretation of mate choice experiments is needed, especially with regard to the lighting types used, to elucidate the real cause behind any variation shown. (c) 2006 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Does the flicker frequency of fluorescent lighting affect the welfare of captive European starlings?

It is common practice for captive birds to be kept under fluorescent lighting, which typically flickers at either 100Hz (UK) or 120 Hz (USA). Such lighting was developed for human vision and it is thought that birds may be able to detect higher frequencies of flicker than humans. For humans, 100Hz fluorescent lighting has been linked to eyestrain, headaches and migraine, even though this rate of flicker is above the human perceptual flicker-fusion frequency of around 60 Hz. Keeping birds under 100 Hz lighting is therefore potentially detrimental to their welfare. We studied the preferences of wild-caught European starlings, Sturnus vulgaris, for high-frequency (HF, >30 kHz) fluorescent lighting versus conventional low-frequency (LF, 100 Hz) fluorescent lighting. The flicker frequency of the HF lighting would be undetectable to the nervous system of any animal. We also exposed starlings to either HF or LF light for 2 weeks, and investigated the degree of stress caused by each environment by monitoring their behaviour and plasma corticosterone levels. Groups of starlings showed a preference for HF lighting over LF lighting (P < 0.001), which indicates that they can detect a difference between the two lighting conditions and find the HF lighting preferable. However, there were no measurable differences in behaviour or plasma corticosterone levels when the birds were housed under either HF or LF for 2 weeks, thus providing initial evidence that housing starlings under 100Hz lighting may not be detrimental to the welfare of starlings during early captivity. (C) 2003 Elsevier B.V. All rights reserved.

Potential antiarrhythmic and cardioprotective agents based on adenosine

N-Ethylcarboxamidoadenosine (12) was synthesised from adenosine (1) and the 6-chloro-2’,3’-O-isopropylidene-AT-ethylcarboxamidoadenosine (25) was synthesised from inosine (19). Employing molecular modelling techniques and the results from previous structure activity relationships it was possible to design and synthesise a N6-substituted N-ethylcarboxamidoadenosines which possessed an oxygen in the N6-substituent either in the form of an epoxide (which was obtained by cpoxidising an alkene with m-CPBA or dimethyldioxirane) or in the form of a cyclic ether as was the case for N6-((tetrahydro-2H--pyran--2-yl)methyl-N-ethylcarboxamidoadenosine (78). These compounds were tested for their biological activity at the A1 adenosine receptor by their ability to inhibit cAMP accumulation in DDT, MF2 cells. The EC50 values obtained indicated that the N6-(norborn-5-en-2-yl)-N-ethylcarboxamidoadenosines were the most potent. Of theseN6-(S-endo-norbrn-5-en-2-yI)-N-ethylcarboxaniidoadenosine (56) was the most potent (0.2 nM). N6-(exo-norborn-5-en-2-yl)-2-iodo-N-ethylcarboxamidoadenosine (79) was synthesised from guanosine (22) and was also evaluated for its potency at the A, receptor (24.8 ± 1.5 nM). At present 79 is being evaluated for its selectivity for the A1 receptor compared to the other three receptor subtypes (A2a, A2b, A3). A series of N6-(benzyl)-N-ethylcarboxamidoadenosines were synthesised with substitutions at the 4-position of the phenyl ring. Another series of compounds were synthesised which replaced the methylene spacer between the N6H and the N6-aromatic or lipophilic substituent The replacement groups -were carbonyl and trans-2- cyclopropyl moieties. The N6-acyl compounds were obtained by reacting 2’,3’-O- di(tert-butyldimethylsilyl)-AT-ethylcarboxamidoadenosinc (59) with the appropriate acid chloride and then deprotecting with lelrabutylammonium fluoride in tetrahydrofuran. The compound N6-(4-(1,2-dihydroxy)ethyl)benzyl-N- ethylcarboxamidoadenosine (125) was synthesised by the reaction of 4-(1,2-0- isopropylidene-ethyl)benzyl aminc (123) with 6-chloro-2,3-0-isopropylidene-N- ethylcarboxamidoadenosine (25). Compound 123 was synthesised from an epoxidation of vinylbenzyl phthalimide (118) followed by an acidic ring opening to yield the diol which was isopropylidenated to yield 4-(l,2-O-isopropylidene- elhyl)benzyl phlhalimide (122), It was hoped that the presence of the diol functionality in 125 would increase water solubility whilst maintaining potency at the A3 receptor.