One-trial cocaine-induced behavioral sensitization in preweanling rats: Role of contextual stimuli.

Using a one-trial procedure, preweanling rats exhibit robust sensitization regardless of whether drug pretreatment and testing occur in the same or different environments. The purpose of the present study was to determine whether one-trial context-specific and context-independent sensitization of preweanling rats could be dissociated by varying the pretreatment dose of cocaine, by varying the pretreatment drug, or by minimizing interoceptive cues. In Experiments 1a and 1b, rats were pretreated with a broad dose range of cocaine (0–40 mg/kg) before placement in a novel activity chamber or the home cage. In Experiment 2, rats were pretreated with a locomotor-enhancing drug (e.g., methylphenidate, U50,488, or MK-801) before placement in a novel activity or anesthesia chamber. In Experiment 3, rats were anesthetized with isoflurane before cocaine administration to minimize the effects of interoceptive and injection cues. In all experiments, rats were challenged with cocaine on the test day (24 hr later), with locomotion being measured in activity chambers. Results showed that (a) the pretreatment dose of cocaine (10–40 mg/kg) did not differentially affect context-specific and context-independent sensitization; (b) cross-sensitization between methylphenidate and cocaine was observed in the context-specific condition, but not when using a context-independent procedure; and (c) sensitization was evident if injection and interoceptive cues were minimized. One possibility is that associative processes do not modulate the one-trial sensitization of preweanling rats. Alternatively, “unitization” may cause preweanling rats to treat the different environments as equivalent, thus permitting robust sensitization even when drug pretreatment and testing occur in different environments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An agent-based stochastic ruler approach for a stochastic knapsack problem with sequential competition

We examine a situation in which a decision-maker executes a sequence of resource allocation decisions over time, but the availability of the indivisible resources at future epochs is uncertain due to actions of competitors. We cast this problem as a specialized type of stochastic knapsack problem in which the uncertainty of item (resource) availability is induced by competitors concurrently filling their own respective knapsacks. Utilizing a multi-period bounded multiple-choice knapsack framework, we introduce a general discrete stochastic optimization model that allows a nonlinear objective function, cardinality constraints, and a knapsack capacity constraint. Utilizing a set of greedy selection rules and agent-based modeling to simulate the competitors’ actions, we solve the problem with a stochastic ruler approach that incorporates beam search to determine item selection of the types specified by the solution representation. We illustrate the computational effectiveness of our approach on instances motivated by a sports league draft as well as generic problem instances based on the knapsack literature.     

The effects of infrastructure and policy on e-business in Latin America and Sub-Saharan Africa

This study investigates experts' assessments of the pertinent factors affecting e-business in developing countries from a theory-based national infrastructure perspective. We surveyed experts (business people, academicians, and officials of governmental and non-governmental organizations) in e-business in Latin America (LA) and Sub-Saharan Africa (SSA). Our partial least squares analysis shows that experts believed that policies targeted specifically toward e-business are important in affecting e-business capabilities and in obtaining value from e-business, more so than non-specific general information and communication technologies (ICT) policies, which are not significantly influential. ICT infrastructure generally affects e-business capabilities, though this was not found to be the case in Brazil. Experts believed that national government institutions positively affect e-business value in SSA, but not in LA. Experts did not believe that commercial infrastructure significantly affects e-business value. This study theoretically and empirically distinguishes between two different dimensions of e-business outcomes: specific capabilities and value derived from e-business. It operationalizes the effects of national government institutions and commercial infrastructure on e-business outcomes and empirically tests for their effects. The study provides empirical support for conceptual arguments for the need of ICT policies specific to the needs of e-business.     

你的接收率是怎样的?

<正>有时候老方法更适用。以营销测试为例,问问电视界的老人某个新电视节目怎么样?你听到的都将是关于收视率的。     

Visualizing green oil in live algal cells

We report here that BODIPY 505/515, a green lipophilic fluorescent dye, serves as an excellent vital stain for the oil-containing lipid bodies of live algal cells. BODIPY 505/515 vital staining can be used in combination with fluorescent activated cell sorting to detect and isolate algal cells possessing high lipid content.     

Organically modified silicate thin films doped with colourimetric pH indicators methyl red and bromocresol green as pH responsive sol-gel hybrid materials

The colourimetric pH indicators methyl red and bromocresol green have been immobilised in organic-inorganic silica hybrid matrices prepared by a sol-gel method. The optically transparent sol-gel thin films containing encapsualated dye molecules were deposited onto glass substrates using spin-coating and dip-coating techniques. The organic-inorganic hybrid materials were obtained by co-polymerisation of tetraethoxysilane together with glycidoxypropyltrimethoxysilane as an organically modified sol-gel precursor. Matrix polarity and morphology were varied by using solutions containing different ratios of sol-gel precursors and surfactants. Spectral characterisation of the films was performed using ultra-violet and visible absorption spectroscopy, and the spectral changes in different matrices were identified. The effects of the sol-gel mixtures composition on the mechanical stability and homogeneity of the films, and the colourimetric response to solutions of differing pH were studied. The apparent pK_app values of the immobilised pH indicators were also determined in the different matrices.     

Aqueous lateral epitaxy overgrowth of ZnO on (0001) GaN at 90 °C: Part I. Increasing the critical thickness

Thick, epitaxial ZnO thin films have been grown on (0001) GaN buffered Al₂O₃ substrates using an aqueous solution at 90 °C. Films with improved structural, optical and electrical characteristics, were grown using a lateral epitaxial overgrowth (LEO) method. Different photoresist masks were used to enable LEO. The masks included linear windows and two different hexagonal arrays of circular windows. Films that exceeded a critical thickness mechanically failed through buckling, consistent with the large compressive stresses expected due to the mismatch of the ZnO lattice with the underlying GaN substrate. It was shown that improved mechanical stability could be achieved using the LEO method. Without LEO, a film thickness no greater than 4 µm could be grown without buckling. The critical thickness could be increased to 10 µm using linear windows, whereas a critical thickness of 50 μm was achieved with one array of circular windows, and 80 µm for a second array. The two different arrays of circular windows differed relative to their orientation on the substrate. It was also shown that the critical thickness increased with increasing distance between the growth windows. Optical transmission, micro-photoluminescence and Hall Effect measurements showed that the LEO method also results in improved optoelectronic properties.     

Luminescent properties of ZnO structures grown with a vapour transport method

ZnO structures were synthesised on the sapphire (112?0) substrate by a vapour transport method in a gas flowing furnace. The influence of the oxygen content in the gas mixture on the morphology and luminescent properties of ZnO structures grown on a strip-like substrate was investigated, with all other growth parameters being kept nominally identical. Integrated electron microscopy and cathodoluminescence analysis shows gradual variations of structural and optical emission properties for ZnO structures grown on the long substrate. Defect-related green luminescence of ZnO is found to be highly dependent on the oxygen vapour in the growth region of the furnace. Our findings demonstrate that the green luminescence is associated with oxygen deficiency in ZnO.