Learning to Plan Near-Optimal Collision-Free Paths

A new approach to find a near-optimal collision-free path is presented. The path planner is an implementation of the adaptive error back-propagation algorithm which learns to plan “good”, if not optimal, collision-free paths from human-supervised training samples. Path planning is formulated as a classification problem in which class labels are uniquely mapped onto the set of maneuverable actions of a robot or vehicle. A multi-scale representational scheme maps physical problem domains onto an arbitrarily chosen fixed size input layer of an error back-propagation network. The mapping does not only reduce the size of the computation domain, but also ensures applicability of a trained network over a wide range of problem sizes. Parallel implementation of the neural network path planner on hypercubes or Transputers based on Parasoft EXPRESS is simple and efficient, Simulation results of binary terrain navigation indicate that the planner performs effectively in unknown environment in the test cases

Portable Asteroids on Hypercube Or Transputers

A multi-player 3D Asteroids video game designed to be used as a testbed for evaluating controller algorithms was described in [l.] The original version of the game and a separate interactive 3D graphics interface for a human player were implemented, based on CrOS III and VERTEX, on an NCUBE-l hypercube equipped with a parallel Real-Time Graphics board. The Asteroids and interactive graphics interface programs are examples of parallel programs which communicate with each other in a space-shared multi-processor environment. We have successfully ported the Asteroids and the interactive graphics interface to run on NCUBE using ParaSoft EXPRESS. The new version of these programs were further ported to run on a SUN 386i with an add-on Transputer board. We present general design considerations that enable easy migration of communicating parallel programs to any other hardware platform that runs EXPRESS. We also report specific experience of porting Asteroids and an associated interactive player interface program on an NCUBE hypercube to a SUN 386i Transputer-based system, with no modification of codes

Exposure to the Dental Environment and Prevalence of Respiratory Illness in Dental Student Populations

Objective: To determine if the prevalence of respiratory disease among dental students and dental residents varies with their exposure to the clinical dental environment. Methods: A detailed questionnaire was administered to 817 students at 3 dental schools. The questionnaire sought information concerning demographic characteristics, school year, exposure to the dental environment and dental procedures, and history of respiratory disease. The data obtained were subjected to bivariate and multiple logistic regression analysis. Results: Respondents reported experiencing the following respiratory conditions during the previous year: asthma (26 cases), bronchitis (11 cases), chronic lung disease (6 cases), pneumonia (5 cases) and streptococcal pharyngitis (50 cases). Bivariate statistical analyses indicated no significant associations between the prevalence of any of the respiratory conditions and year in dental school, except for asthma, for which there was a significantly higher prevalence at 1 school compared to the other 2 schools. When all cases of respiratory disease were combined as a composite variable and subjected to multivariate logistic regression analysis controlling for age, sex, race, dental school, smoking history and alcohol consumption, no statistically significant association was observed between respiratory condition and year in dental school or exposure to the dental environment as a dental patient. Conclusion: No association was found between the prevalence of respiratory disease and a student\u27s year in dental school or previous exposure to the dental environment as a patient. These results suggest that exposure to the dental environment does not increase the risk for respiratory infection in healthy dental health care workers

Models to Evaluate the Role of Stress in Periodontal Disease

We evaluated the association of stress, distress, and coping behaviors with periodontal disease in 1,426 subjects, aged 25 to 74, in Erie County, NY. Demographic characteristics, medical and dental history, and tobacco and alcohol consumption, as well as clinical assessments of supragingival plaque, subgingival flora, gingival bleeding, calculus, probing depth, clinical attachment level (CAL), and radiographic alveolar bone loss (ABL) were obtained for each subject. Subjects also completed a set of 5 psychosocial instruments that measured life events, daily strains, hassles and uplifts, distress, and coping behaviors. Internal consistencies of all subscales on the instruments were high, with Cronbach’s alpha ranging from 0.88 to 0.99. Logistic regression indicated that financial strain was significantly associated with greater attachment and alveolar bone loss (OR 1.70; 95% CI, 1.09–2.65; and 1.68; 95% CI, 1.20–2.37, respectively) after adjusting for age, gender, and smoking. When those with financial strain were stratified with respect to coping behaviors, it was found that those who exhibited high emotion‐focused coping (inadequate coping) had an even higher risk of having more severe attachment loss (OR 2.24; 95% CI, 1.15–4.38) and alveolar bone loss (OR 1.91; 95% CI, 1.15–3.17) than those with low levels of financial strain within the same coping group, after adjustment for age, gender, and cigarette smoking. After further adjusting for number of visits to the dentist, those with financial strain who were high emotion‐focused copers still had higher levels of periodontal disease based on CAL (OR 2.12; 95% CI, 1.07–4.18). In contrast, subjects with high levels of financial strain who reported high levels of problem‐based coping (good coping) had no more periodontal disease than those with low levels of financial strain. Salivary cortisol levels were higher in a test group exhibiting severe periodontitis, a high level of financial strain, and high emotion‐focused coping, as compared to a control group consisting of those with little or no periodontal disease, low financial strain, and low levels of emotion‐focused coping (11.04 ± 4.4 vs. 8.6 ± 4.1 nmol/L salivary cortisol, respectively). These findings suggest that psychosocial measures of stress associated with financial strain are significant risk indicators for periodontal disease in adults. Further prospective studies are needed to help establish the time course of stress, distress, and inadequate coping on the onset and progression of periodontal disease, as well as to evaluate the mechanisms by which stress exerts its effects on periodontal infections. Ann Periodontol 1998;3:288–302.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142261/1/aape0288.pd

A chemical genetic approach reveals distinct EphB signaling mechanisms during brain development.

EphB receptor tyrosine kinases control multiple steps in nervous system development. However, it remains unclear whether EphBs regulate these different developmental processes directly or indirectly. In addition, given that EphBs signal through multiple mechanisms, it has been challenging to define which signaling functions of EphBs regulate particular developmental events. To address these issues, we engineered triple knock-in mice in which the kinase activity of three neuronally expressed EphBs can be rapidly, reversibly and specifically blocked. We found that the tyrosine kinase activity of EphBs was required for axon guidance in vivo. In contrast, EphB-mediated synaptogenesis occurred normally when the kinase activity of EphBs was inhibited, suggesting that EphBs mediate synapse development by an EphB tyrosine kinase-independent mechanism. Taken together, our data indicate that EphBs control axon guidance and synaptogenesis by distinct mechanisms and provide a new mouse model for dissecting EphB function in development and disease

Genetic Diversity, Latency and Co-Infections

Alphaherpesviruses are highly prevalent in equine populations and co- infections with more than one of these viruses’ strains frequently diagnosed. Lytic replication and latency with subsequent reactivation, along with new episodes of disease, can be influenced by genetic diversity generated by spontaneous mutation and recombination. Latency enhances virus survival by providing an epidemiological strategy for long-term maintenance of divergent strains in animal populations. The alphaherpesviruses equine herpesvirus 1 (EHV-1) and 9 (EHV-9) have recently been shown to cross species barriers, including a recombinant EHV-1 observed in fatal infections of a polar bear and Asian rhinoceros. Little is known about the latency and genetic diversity of EHV-1 and EHV-9, especially among zoo and wild equids. Here, we report evidence of limited genetic diversity in EHV-9 in zebras, whereas there is substantial genetic variability in EHV-1. We demonstrate that zebras can be lytically and latently infected with both viruses concurrently. Such a co- occurrence of infection in zebras suggests that even relatively slow-evolving viruses such as equine herpesviruses have the potential to diversify rapidly by recombination. This has potential consequences for the diagnosis of these viruses and their management in wild and captive equid populations. View Full- Tex

Adaptation and conservation insights from the koala genome

The koala, the only extant species of the marsupial family Phascolarctidae, is classified as ‘vulnerable’ due to habitat loss and widespread disease. We sequenced the koala genome, producing a complete and contiguous marsupial reference genome, including centromeres. We reveal that the koala’s ability to detoxify eucalypt foliage may be due to expansions within a cytochrome P450 gene family, and its ability to smell, taste and moderate ingestion of plant secondary metabolites may be due to expansions in the vomeronasal and taste receptors. We characterized novel lactation proteins that protect young in the pouch and annotated immune genes important for response to chlamydial disease. Historical demography showed a substantial population crash coincident with the decline of Australian megafauna, while contemporary populations had biogeographic boundaries and increased inbreeding in populations affected by historic translocations. We identified genetically diverse populations that require habitat corridors and instituting of translocation programs to aid the koala’s survival in the wild

Spin dynamics simulations of the magnetic dynamics of RbMnF3_3 and direct comparison with experiment

Spin-dynamics techniques have been used to perform large-scale simulations of the dynamic behavior of the classical Heisenberg antiferromagnet in simple cubic lattices with linear sizes $L\leq 60$. This system is widely recognized as an appropriate model for the magnetic properties of RbMnF$_3$. Time-evolutions of spin configurations were determined numerically from coupled equations of motion for individual spins using a new algorithm implemented by Krech {\it etal}, which is based on fourth-order Suzuki-Trotter decompositions of exponential operators. The dynamic structure factor was calculated from the space- and time-displaced spin-spin correlation function. The crossover from hydrodynamic to critical behavior of the dispersion curve and spin-wave half-width was studied as the temperature was increased towards the critical temperature. The dynamic critical exponent was estimated to be $z=(1.43\pm 0.03)$, which is slightly lower than the dynamic scaling prediction, but in good agreement with a recent experimental value. Direct, quantitative comparisons of both the dispersion curve and the lineshapes obtained from our simulations with very recent experimental results for RbMnF$_3$ are presented.Comment: 30 pages, RevTex, 9 figures, to appear in PR

A Chemical Genetic Approach Reveals Distinct Mechanisms of EphB Signaling During Brain Development

EphB receptor tyrosine kinases control multiple steps in nervous system development. However, it remains unclear whether EphBs regulate these different developmental processes directly or indirectly. In addition, as EphBs signal through multiple mechanisms, it has been challenging to define which signaling functions of EphBs regulate particular developmental events. To address these issues, we engineered triple knockin mice in which the kinase activity of three neuronally expressed EphBs can be rapidly, reversibly, and specifically blocked. Using these mice we demonstrate that the tyrosine kinase activity of EphBs is required for axon guidance in vivo. By contrast, EphB-mediated synaptogenesis occurs normally when the kinase activity of EphBs is inhibited suggesting that EphBs mediate synapse development by an EphB tyrosine kinase-independent mechanism. Taken together, these experiments reveal that EphBs control axon guidance and synaptogenesis by distinct mechanisms, and provide a new mouse model for dissecting EphB function in development and disease

Bad influence? – an investigation into the purported negative influence of foreign domestic helpers on children's second language English acquisition

This paper explores the purported negative influence of foreign domestic helpers (FDHs) on child second language acquisition (SLA) by studying Hong Kong Cantonese children's listening ability in second language (L2) English. 31 kindergarten third graders aged 4;6 to 6, and 29 first year secondary students aged 11-14 who have had a Filipino domestic helper at home took part in the study. In addition, 34 youngsters (20 in kindergarten, 14 in secondary) who did not have a Filipino helper participated as controls. Results from two listening tasks (picture choosing task, sound discrimination task) suggest that informants do not differ from the control in their abilities to listen to American-, British-, and Hong Kong English, and that they are better at listening to Filipino-accented English than the control. These findings cast doubts on the anecdotal belief of the harmful effect FDHs have on children's language acquisition including an L2. Moreover, the additional effect of being familiar with another variety of English is arguably a desirable outcome given that English is used as a lingua franca among non-native speakers on a daily basis in this highly globalised world