On chlorosulphonation and the electron microscopy of polyethylene

It is shown that chlorosulphonation is a major aid to the electron microscopy of polyethylene for various samples which had mostly been crystallized at high pressures and included at least a proportion of the so-called chain-extended form. It is confirmed that sheets of excess electron density are produced at lamellar surfaces, but also including lateral surfaces. This is due primarily to the incorporation of chlorine and sulphur rather than to added uranium. The time to achieve an overall reaction varies sensitively with morphology, decreasing as the number of diffusion channels increases. Crystallinity is gradually lost, but sufficient crystals remain when a sample has become uniform, and in their initial orientations, for diffraction studies to be possible. The technique has been used to demonstrate that, during melt crystallization, the thickness of one lamella changes in response to altered growth conditions. This is direct confirmation that lamellar thickness is determined by secondary nucleation at the growth front. The tapered profile of a growing lamella previously observed in thick crystals of various polymers has been observed for chain-folded polyethylene lamellae, providing further evidence that this is a general feature of melt growth.     

A distributed fuzzy logic controller for an autonomous vehicle

Autonomous vehicles can be used in a variety of applications such as hazardous environments or intelligent highway systems. Fuzzy logic is an appropriate choice for this application as it can describe human behavior well. This paper proposes two fuzzy logic controllers for the steering and the velocity control of an autonomous vehicle. The two controllers are divided into separate modules to mimic the way humans think while driving. The steering controller is divided into four modules; one module drives the vehicle toward the target while another module avoids collision with obstacles. A third module drives the vehicle through mazes. The fourth module adjusts the final orientation of the target. The velocity controller is divided into three modules; the first module speeds up the vehicle to reach the target and slows it down as it moves toward the target. The second module controls the velocity in the neighborhood of obstacles. A third module controls the velocity of the vehicle as it turns sharp corners. A method for automatic tuning of the first module of the velocity controller is proposed to stabilize the velocity of the vehicle as it approaches the target. Two examples to demonstrate the interaction among the seven control modules are included. Results of the simulation are compared with those in the literature. © 2004 Wiley Periodicals, Inc.     

An agent-based approach to multisensor coordination

This paper presents an automated system for multiple sensor placement based on the coordinated decisions of independent, intelligent agents. The problem domain is such that a single sensor system would not provide adequate information for a given sensor task. Hence, it is necessary to incorporate multiple sensors in order to obtain complete information. The overall goal of the system is to provide the surface coverage necessary to perform feature inspection on one or more target objects in a cluttered scene. This is accomplished by a group of cooperating intelligent sensors. In this system, the sensors are mobile, the target objects are stationary and each agent controls the position of a sensor and has the ability to communicate with other agents in the environment. By communicating desires and intentions, each agent develops a mental model of the other agents' preferences, which is used to avoid or resolve conflict situations. In this paper we utilize cameras as the sensors. The experimental results illustrate the feasibility of the autonomous deployment of the sensors and that this deployment can occur with sufficient accuracy as to allow the inspection task to be performed.     

A simple method for holding electron microscope grids during autoradiography of serial sections

A simple, reliable, and inexpensive method is described for holding electron microscope grids during the application of photographic emulsion and during subsequent storage and processing. This method has proved to be especially useful in autoradiographic studies using serial sections.     

Increased anxiety and altered responses to anxiolytics in mice deficient in the 65-kDa isoform of glutamic acid decarboxylase

The larger isoform of the enzyme glutamate decarboxylase, GAD67, synthesizes >90% of basal levels of gamma-aminobutyric acid (GABA) in the brain. In contrast, the smaller isoform, GAD65, has been implicated in the fine-tuning of inhibitory neurotransmission. Mice deficient in GAD65 exhibit increased anxiety-like responses in both the open field and elevated zero maze assays. Additionally, GAD65-deficient mice have a diminished response to the anxiolytics diazepam and pentobarbital, both of which interact with GABA-A receptors in a GABA-dependent fashion to facilitate GABAergic neurotransmission. Loss of GAD65-generated GABA does not appear to result in compensatory postsynaptic GABA-A receptor changes based on radioligand receptor binding studies, which revealed no change in the postsynaptic GABA-A receptor density. Furthermore, mutant and wild-type animals do not differ in their behavioral response to muscimol, which acts independently of the presence of GABA. We propose that stress-induced GABA release is impaired in GAD65-deficient mice, resulting in increased anxiety-like responses and a diminished response to the acute effects of drugs that facilitate the actions of released GABA.     

Evaluation of the hot corrosion behavior of thermal barrier coatings

Calcium silicate and yttria-stabilized ZrO₂/(MCrAlY) thermal barrier coating systems on air-cooled specimens were exposed to sodium-plus vanadium- doped Mach 0.3 combustion gases. The thermal barrier coating endurance was determined to be a strong inverse function of the ceramic coating thickness. Coating system durability was increased through the use of NiCrAlY and CoCrAlY bond coatings with high chronium and aluminum contents. Chemical and electron microprobe analyses supported the predictions of condensate compositions and the determination of their roles in causing spalling of the ceramic coatings.     

Evaluation of the Canadian Coordinating Office for Health Technology Assessment

The Canadian Coordinating Office for Health Technology Assessment (CCOHTA) was recently evaluated. We summarize the evaluation process, report, and 17 recommendations for enhancing CCOHTA's effectiveness. This paper may be useful for evaluators of agencies for technology assessment.     

Acquisition, retention, and extinction of operant discriminations in rats with nucleus basalis magnocellularis lesions.

Effects of bilateral ibotenic acid lesions of nucleus basalis magnocellularis (NBM) and scopolamine treatment on different aspects of learning and memory in an operant discrimination task were assessed. In Experiment 1, NBM lesions impaired acquisition performance. In Experiment 2, scopolamine lowered response rates but did not affect discrimination accuracy in lesioned or control rats. In Experiment 3, although pretrained rats showed transient increases in commission errors, percentage correct responding remained above chance levels after lesion. During extinction in Experiment 4, operant responding diminished more quickly in pretrained NBM-lesioned rats than in controls, but subsequent reacquisition performance was equivalent in both groups. Results suggest the NBM is importantly involved in discrimination learning, but cholinergic activity may be less critical for memory retention than for acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)