Learning landmark triples by experimentation

This article describes a method for learning a set of landmarks suitable for place navigation. The approach is novel in that it exploits the ability of a robot to learn through active perception in the task environment, similar to the learning by experimentation technique developed for LEX (Mitchell et al., 1990). The proposed strategy uses heuristics to select and rank candidate triples, then generates test cases to confirm that the best triple is sufficient. The method supports the use of multiple sensors with different computational and energy costs, where a utility function captures the tradeoff between navigational performance ranking and cost.

Over 100 data points were collected on a mobile robot using a laser barcode reader and computer vision to identify landmarks. The results indicated that active perception and experimentation identified triples with better navigational properties. Furthermore, the learning process is proactive: it was shown to prevent the robot from learning a triple which was not visible over the entire navigational space and/or was not sufficient in practice.     

Transmitter-induced calcium responses differ in astrocytes acutely isolated from rat brain and in culture

Glial fibrillary acid protein (GFAP)-positive astrocytes isolated from the cerebral cortices of 3-10-day-old rats frequently showed increased intracellular Ca2+ concentration responses to L-glutamate and glutamate analogues. However, few of the acutely isolated cells responded to ATP, and no such cells responded to serotonin [5-hydroxytryptamine (5-HT)]. The same cell that failed to respond to ATP or 5-HT often responded to glutamate. Culturing acutely isolated cells in media containing horse serum decreased Ca2+ responses to glutamate but increased the responses to ATP and induced responses to 5-HT. In primary cultures prepared from the cerebral cortices of 1-day-old rats and cultured in horse serum, fewer of the cells responded to glutamate, but almost all cells responded to ATP and 5-HT. The lack of or limited response to, 5-HT or ATP in the acutely isolated cells seems unlikely to be due to selective damage to the respective receptors because acutely isolated GFAP-negative cells showed responses to ATP, several different proteases and mechanical dissociation yielded cells that also responded to glutamate but not to ATP, and exposure of primary cultures to papain did not abolish Ca2+ responses to several transmitters. The responses of the acutely isolated cells to glutamate but limited or lack of responses to ATP and 5-HT also correspond to what has been seen so far for astrocytes in situ. Thus, the present studies provide direct evidence that some of the receptors seen in primary astrocyte cultures may reflect a response to culture conditions and that, in the context of the relevant information so far available, acutely isolated astrocytes seem to reflect better the in vivo state.     

企业如何规避言行不一的陷阱

避开言行不一的陷阱的方法是：听其言，观其行，积极了解多方情况，认真观察实际情况     

Altered functional responsiveness of thymocyte subsets from CD3delta-deficient mice to TCR-CD3 engagement

CD3delta-deficient (delta degrees) mice are defective in alphabeta T cell development. Here we explore the capacity of TCR-CD3 signaling complexes expressed on delta degrees thymocytes to mediate the following functional outcomes in response to antibody cross-linking: (i) the transition from the CD4-CD8- to CD4+CD8+ stage, (ii) the transition from the CD4+CD8+ to CD4+CD8- or CD4-CD8+ stages and (iii) the induction of apoptosis. We provide evidence that CD3deltaepsilon complexes are dispensable for mediating the anti-CD3-mediated CD4-CD8- to CD4+CD8+ transition. On the other hand, CD3delta is critical at the CD4+CD8+ stage. We demonstrate that CD4+CD8+ thymocytes from delta degrees mice, unlike delta degrees CD4-CD8- thymocytes and wild-type CD4+CD8+ thymocytes, require prolonged or consecutive stimuli to elicit functional responses. Depending on the nature of the secondary stimulus, delta degrees thymocytes can be induced to undergo apoptosis or preferential maturation to the CD4-CD8+ stage. Taken together these results indicate that the signaling capacity of the TCR-CD3 complex is noticeably altered in the absence of CD3delta. The essential role of CD3delta at the CD4+CD8+ stage of development correlates with the onset of TCRalpha rearrangement, consistent with a critical structural and/or functional relationship between CD3delta and TCRalpha.     

Validity of the isotropic-distribution approximation in solar energy estimations

Results of numerical simulation are presented for the diffuse and direct energy passing through a Sun-facing flat surface located at the bottom of plane-parallel models of non-absorbing, homogeneous atmospheres. Computations of the diffuse component were carried out with a high degree of accuracy, and also were carried out using the well-known, isotropic-distribution approximation for the sky energy. It is shown that the results obtained with the isotropic-distribution approximation are consistently smaller than those obtained with the exact procedure. These two sets of results can differ by a factor 1–6 depending upon the optical characteristics of the model and the position of the Sun.     

Interviews as catalysts in a community setting.

Examined the effects of interviews about community experience on subsequent attitudes and behavior of adult residents in 2 new condominium communities. Volunteer (23 households) and randomly selected experimental (17 households) groups of respondents were interviewed in their homes. Questionnaires about community experience were administered shortly after the interviews (at 1 condominium) and 6 mo later (at both), and observers rated the activism of community leaders during the interim. Interviewed respondents gave less socially desirable and more extreme responses to the first questionnaire, reported more involvement in the community, and were rated more active in community affairs than uninterviewed controls (103 households). The dynamics of interviews as catalytic events are considered, and the implications of these findings for future use of interviews are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characteristics and Composition of Seeds and Oil of Diplocyclos palmatus (L.) C. Jaffery from Gujarat,India

The seed of Diplocyclos palmatus (L.) C. Jaffery contained 12% oil and 40% protein. The seed oil has iodine value of 171.5, saponification value of 208.3, peroxide value of 0.3 and acid value of 2.9. The fatty acid composition (wt.%) as determined by gas liquid chromatography (GLC) is: C₁₆:₀,23.0; C₁₈:₀, 5.0; C₁₈:₂, 27.5; and C₁₈;₃, 3.5.     

Subnanometer Analysis and Modeling of MBE Grown InP Based MODFETs

InGaAs/InAlAs double-doped double-strained modulation-doped field-effect transistors OD-SMODFETs)1 were grown by solid source molecular beam epitaxy. The structures were characterized using high resolution x-ray diffraction, Hall effect, and cross-sectional scanning tunneling microscopy. A record two-dimensional electron gas (2DEG) sheet density of 8.5 × 10¹²/cm² and 8.1 × 10¹²/cm² for 300 and 77K, respectively, was achieved. The mobility was 6500 and 12000 cm²/ Vs for 300 and 77K, respectively. To the author’s knowledge,² the previous record 2DEG result was 6.58 × 10¹²/cm². The electron mobility was limited by alloy scattering and interface roughness caused by the presence of “clustering.” Using cross-sectional scanning tunneling microscopy to verify the presence of these clusters, we have the first images of the lattice matched InAlAs (spacer)-InGaAs (quantum well) interface. These images reveal clusters that have approximate spherical or cylindrical shapes with equivalent cubic dimensions ranging from 25 to 45Å.