Reasoning and planning in dynamic domains: An experiment with a mobile robot

Progress made toward having an autonomous mobile robot reason and plan complex tasks in real-world environments is described. To cope with the dynamic and uncertain nature of the world, researchers use a highly reactive system to which is attributed attitudes of belief, desire, and intention. Because these attitudes are explicitly represented, they can be manipulated and reasoned about, resulting in complex goal-directed and reflective behaviors. Unlike most planning systems, the plans or intentions formed by the system need only be partly elaborated before it decides to act. This allows the system to avoid overly strong expectations about the environment, overly constrained plans of action, and other forms of over-commitment common to previous planners. In addition, the system is continuously reactive and has the ability to change its goals and intentions as situations warrant. Thus, while the system architecture allows for reasoning about means and ends in much the same way as traditional planners, it also posseses the reactivity required for survival in complex real-world domains. The system was tested using SRI's autonomous robot (Flakey) in a scenario involving navigation and the performance of an emergency task in a space station scenario

Localization Versus Abstraction: A Comparison of Two Search Reduction Techniques

There has been much recent work on the use of abstraction to improve planning behavior and cost. Another technique for dealing with the inherently explosive cost of planning is localization. This paper compares the relative strengths of localization and abstraction in reducing planning search cost. In particular, localization is shown to subsume abstraction. Localization techniques can model the various methods of abstraction that have been used, but also provide a much more flexible framework, with a broader range of benefits

Phase locking below rate threshold in noisy model neurons

The property of a neuron to phase-lock to an oscillatory stimulus before adapting its spike rate to the stimulus frequency plays an important role for the auditory system. We investigate under which conditions neurons exhibit this phase locking below rate threshold. To this end, we simulate neurons employing the widely used leaky integrate-and-fire (LIF) model. Tuning parameters, we can arrange either an irregular spontaneous or a tonic spiking mode. When the neuron is stimulated in both modes, a significant rise of vector strength prior to a noticeable change of the spike rate can be observed. Combining analytic reasoning with numerical simulations, we trace this observation back to a modulation of interspike intervals, which itself requires spikes to be only loosely coupled. We test the limits of this conception by simulating an LIF model with threshold fatigue, which generates pronounced anticorrelations between subsequent interspike intervals. In addition we evaluate the LIF response for harmonic stimuli of various frequencies and discuss the extension to more complex stimuli. It seems that phase locking below rate threshold occurs generically for all zero mean stimuli. Finally, we discuss our findings in the context of stimulus detection

Development of an Expert System for Representing Procedural Knowledge

A high level of automation is of paramount importance in most space operations. It is critical for unmanned missions and greatly increases the effectiveness of manned missions. However, although many functions can be automated by using advanced engineering techniques, others require complex reasoning, sensing, and manipulatory capabilities that go beyond this technology. Automation of fault diagnosis and malfunction handling is a case in point. The military have long been interested in this problem, and have developed automatic test equipment to aid in the maintenance of complex military hardware. These systems are all based on conventional software and engineering techniques. However, the effectiveness of such test equipment is severely limited. The equipment is inflexible and unresponsive to the skill level of the technicians using it. The diagnostic procedures cannot be matched to the exigencies of the current situation nor can they cope with reconfiguration or modification of the items under test. The diagnosis cannot be guided by useful advice from technicians and, when a fault cannot be isolated, no explanation is given as to the cause of failure. Because these systems perform a prescribed sequence of tests, they cannot utilize knowledge of a particular situation to focus attention on more likely trouble spots. Consequently, real-time performance is highly unsatisfactory. Furthermore, the cost of developing test software is substantial and time to maturation is excessive. Significant advances in artificial intelligence (AI) have recently led to the development of powerful and flexible reasoning systems, known as expert or knowledge-based systems. We have devised a powerful and theoretically sound scheme for representing and reasoning about procedural knowledge

Saúde Brasil 2011 : uma análise da situação de saúde e a vigilância da saúde da mulher

Introdução: No Brasil, ocorrem cerca de 3 milhões de nascimentos ao ano, sendo grande parte deles por meio de cesarianas. Entender como se distribui esse procedimento no País é relevante para a reflexão sobre o papel das políticas públicas nesse contexto. Objetivos: a) Descrever: magnitude e tendência da taxa de cesáreas*1 no País; morbimortalidade materna e neonatal associada a tipo de parto; e características dos hospitais; b) analisar o preenchimento das variáveis da nova versão da Declaração de Nascido Vivo (DNV) que permitirão monitoramento das indicações de cesárea; c) descrever as respostas institucionais para o enfrentamento do problema. Métodos: Estudo descritivo de série histórica da taxa de cesarianas, no País e macrorregiões, segundo características sociodemográficas, morbimortalidade e tipo de provedor, com fonte em bancos de dados oficiais. Analisou-se a completitude de variáveis da versão da DNV de 2010 para monitoramento das indicações de cirurgia. Foram pesquisados documentos oficiais, visando identificar iniciativas para qualificar a atenção a partos e nascimentos e reduzir cesarianas desnecessárias. Resultados: A taxa de cesarianas foi de 32%, em 1994, e de 52%, em 2010, sendo menor no Norte e Nordeste. Mulheres submetidas a cesáreas tiveram 3,5 vezes mais probabilidade de morrer (entre 1992–2010) e 5 vezes mais de ter infecção puerperal (entre 2000–2011) que as de parto normal. No período, a proporção de prematuros se elevou, mais nas cesáreas (7,8%, sendo 6,4% nos partos normais em 2010). Em 2010, hospitais não públicos apresentaram taxas maiores (63,6%) e maior aumento no período de 2006 a 2010 (14,0%); para os públicos, as taxas foram de 47,8% (federais), de 39,6% (estaduais) e de 34,0% (municipais). Conclusão: A cesariana é frequente e sua proporção ascende no País, sendo muito elevada no setor de Saúde Suplementar. Para reverter essa tendência, serão necessárias várias medidas, incluindo a qualificação da informação para monitorar a efetividade das medidas propostas

Motoneuron membrane potentials follow a time inhomogeneous jump diffusion process

Stochastic leaky integrate-and-fire models are popular due to their simplicity and statistical tractability. They have been widely applied to gain understanding of the underlying mechanisms for spike timing in neurons, and have served as building blocks for more elaborate models. Especially the Ornstein–Uhlenbeck process is popular to describe the stochastic fluctuations in the membrane potential of a neuron, but also other models like the square-root model or models with a non-linear drift are sometimes applied. Data that can be described by such models have to be stationary and thus, the simple models can only be applied over short time windows. However, experimental data show varying time constants, state dependent noise, a graded firing threshold and time-inhomogeneous input. In the present study we build a jump diffusion model that incorporates these features, and introduce a firing mechanism with a state dependent intensity. In addition, we suggest statistical methods to estimate all unknown quantities and apply these to analyze turtle motoneuron membrane potentials. Finally, simulated and real data are compared and discussed. We find that a square-root diffusion describes the data much better than an Ornstein–Uhlenbeck process with constant diffusion coefficient. Further, the membrane time constant decreases with increasing depolarization, as expected from the increase in synaptic conductance. The network activity, which the neuron is exposed to, can be reasonably estimated to be a threshold version of the nerve output from the network. Moreover, the spiking characteristics are well described by a Poisson spike train with an intensity depending exponentially on the membrane potential

The impact of childhood cancer on parents' socio-economic situation-A systematic review.

OBJECTIVE: Taking care of children diagnosed with cancer may have considerable consequences on parents' socio-economic situation. Our systematic review aimed to evaluate and synthesise the evidence on the impact of childhood cancer on parents' socio-economic situation. METHODS: Systematic literature searches for articles published between January 2000 and January 2019 were performed in PubMed, Scopus, and PsycINFO. Findings of eligible articles were narratively synthesised and quality appraised. RESULTS: Our systematic review included 35 eligible articles. Childhood cancer had a substantial impact on parents' socio-economic situation across all studies. This impact varied largely by geographical region. We observed a high prevalence of disruptions in parental employment such as job quitting or job loss, particularly among mothers. The associated income losses further contributed to families' perceived financial burden in addition to increased cancer-related expenses. Adverse socio-economic consequences were most pronounced shortly after diagnosis, however, persisted into early survivorship for certain groups of parents. We identified families of children diagnosed with haematological cancers, younger age at diagnosis, and lower parental socio-economic position to be at particular risk for adverse socio-economic consequences. CONCLUSIONS: Following the child's cancer diagnosis, parents experience a broad range of adverse socio-economic consequences. Further effort is needed to systematically implement an assessment of financial hardship in paediatric oncology together with appropriate support services along the cancer trajectory

Confronting system barriers for ST- elevation MI in low and middle income countries with a focus on India

© 2017 Our previous research found seven specific factors that cause system delays in ST-elevation Myocardial infarction management in developing countries. These delays, in conjunction with a lack of organized STEMI systems of care, result in inefficient processes to treat AMI in developing countries. In our present opinion paper, we have specifically explored the three most pertinent causes that afflict the seven specific factors responsible for system delays. In doing so, we incorporated a unique strategy of global STEMI expertise. With this methodology, the recommendations were provided by expert Indian cardiologist and final guidelines were drafted after comprehensive discussions by the entire group of submitting authors. We expect these recommendations to be utilitarian in improving STEMI care in developing countries