Regional bond strengths of self-etching/self-priming adhesive systems

Within the context of an extensive study of electroconvulsive therapy at the Psychiatric Clinic of the University of Bonn 15 patients suffering from therapy-resistant Major depression (DSM III-R) were examined with a detailed psychometric test battery, containing memory- and nonmemory tests. The test battery had been applied short time before, during and after the treatment with 10 ECT applied unilateral over the nondominant hemisphere. Comparing the test performances before and 1-2 days after the end of the series there were only few remarkable changes: a significant decrease was diagnosed exclusively in 30 min delayed recall of verbal items, while visual short-term memory and visual-constructive performance showed a significant improvement (in spite of unilateral stimulation on the right side). None of the other cognitive functions inclusively speed of performances and reaction time was detracted short time after the end of the ECT-treatment, instead all the measures improved albeit not significantly. Between responders to treatment (50% improvement in HAMD) and non-responders no significant differences neither before nor after the treatment were detected. The non-responders had in nearly all of the tests some better (but not significantly) results despite being older than the group of responders.     

A comparison of strain relief behaviour of In x Ga1− x As alloy on GaAs (001) and (110) substrates

A comparative study on the strain relief behaviour of epitaxially grown In _x Ga_{1 – x} As (where 0.1 × 1) alloys on GaAs (001) and (110) were carried out using transmission electron microscopy (TEM) and high resolution X-ray diffraction (XRD). Three different strain relief mechanisms related to the formation of misfit dislocations (MDs) were observed. The dominant strain relief process can be a single mechanism or a combination of two of the three mechanisms depending on the substrate orientation and the in content.     

High Resolution Electron Microscopy of Crystals

It is now possible to resolve the basic periodicity of the arrangement of atoms or molecules in crystal lattices using the electron microscope. Examples are given of lattices resolved directly (including superlattices), and indirectly (by means of moiré patterns) and of other periodic phenomena associated with crystal lattices (domains in ordered alloys). The basic principles of image formation in periodic objects are considered in terms of simple diffraction theory and some indications given of limiting factors in this type of investigation.     

Red, green, and blue LEDs for white light illumination

The rapid improvement of the white light efficacy achievable with light-emitting diodes (LEDs) opens up new opportunities in the general illumination market. An LED light source made of red, green, and blue LEDs (RGB-LEDs) can provide the unique feature of color variability, allowing the user to select the desired color point of the lamp. The white light color accuracy required in the general illumination market is a challenge for LEDs. The variation in lumen output and wavelength for nominally identical LEDs and the change in these parameters with temperature and time result in an unacceptably high variability in the color point of white light from RGB-LEDs. In this paper, we show that these problems can be overcome with suitable feedback control schemes that can be implemented in a practical LED lamp. We present results of experiment and theoretical modeling that shows the performance that can be achieved with a number of different control schemes     

Adhesion and micromechanical properties of metal surfaces

This paper is part of a long-standing attack on problems of friction and adhesion. It falls into two parts. The first discusses the general mechanism of adhesion and then describes an experimental study of the adhesion and deformation of a model microasperity. This consists of the contact formed between a fine pointed stylus of tungsten and a single crystal of a softer metal (nickel). The experiments are carried out in ultrahigh vacuum and the surfaces are characterized in situ using Auger spectroscopy. The loads range from 0.5 to 1000 μN and contact during loading and unloading is monitored using electrical resistance measurements. With clean surfaces the results suggest that surface forces alone are able to initiate plastic deformation. Oxide monolayers reduce the adhesion but the general behaviour is little changed. In contrast, oxide layers 5 nm thick greatly modify the adhesion and deformation behaviour.

The second part describes microhardness measurements carried out over approximately the same load range. A Berkovitch triangular pyramid is used as the indenter. Some of the indents are studied in the electron microscope but the major hardness determinations are based on depth measurements of the indents formed. These measurements are extremely sensitive and may be conveniently monitored so that the plastic indentation process during loading and the elastic relaxation which occurs on unloading may be recorded. Both the adhesion measurements and the microindentation hardness measurements show that the plastic yield stress of very small volumes may be three or four times larger than the bulk values. The results also show that detailed contact models may be of limited value when dealing with contacts involving plastic deformation.     

Dyeing and finishing polyester/ cotton — the commercial approach

Fabrics woven from blends of polyester and cotton are used in large quantities for a wide range of clothing purposes. It is therefore vital that the most cost-effective finishing methods are used on these fabrics. Here, John Pashley looks at finishing techniques for polyester/cotton from a commercial angle.     

Dentine permeability and dentine adhesion

OBJECTIVES: The objectives of this paper are to review the structure of dentine as it pertains to adhesive bonding and to describe the importance of resin permeation into dentinal tubules and into spaces created between collagen fibrils by acid-etching during resin bonding. The advantages and disadvantages of separate acid-etching, priming and adhesive applications are discussed. DATA SOURCES: Although not an exhaustive review, the concepts included in the review were obtained from the dentine bonding literature. STUDY SELECTION: Attempts were made to critically evaluate what is known about dentine permeability and adhesion and what remains to be discovered. Speculations were made on a number of controversial issues that are not yet resolved. CONCLUSIONS: Acid-etching of dentine produces profound changes in the chemical composition and physical properties of the matrix which can influence the quality of resin-dentine bonds, their strength and perhaps their durability.     

In vitro permeability of furcation dentin in permanent teeth

Extracted unerupted permanent third molars with the occlusal half of the crown and apical half of the roots removed were cemented to Plexiglas blocks. Using a positive pressure system in which the movement of fluid across the dental tubules could be measured, the permeability of furcation dentin was measured before and after alteration of the furcation thickness. Subsequently, measurements of reduction in thickness of cementum and dentin were performed. Furcation dentin permeability was found to increase as the cementum and dentin thickness was reduced and the smear layer removed. The permeability values obtained for the furcation dentin were similar to those found in radicular dentin in general, indicating that root dentin has a low permeability and that it has good barrier properties. The data would suggest that any bone resorption seen under the furcation region of permanent molars is more likely to be due to the presence of accessory canals than due to permeation directly through furcation hard tissues.     

The disintegration of superEBA cement in solutions with adjusted pH and osmolarity

OBJECTIVE: To determine how physicians respond to a request for an expensive, unindicated test. DESIGN: Cross-sectional observational study. SETTING: Four sites of a group-model HMO. PARTICIPANTS: Thirty-nine internist volunteers. INTERVENTION: A standardized patient requesting magnetic resonance imaging (MRI) of the head to rule out multiple sclerosis (MS) was inserted unannounced into physicians' regular schedules. The patient's only complaint was fatigue with no neurologic symptoms. MEASUREMENTS AND MAIN RESULTS: Physicians and standardized patients completed assessments after each visit. Thirty-five (90%) of 39 physicians "had no idea" that the patient they saw was the standardized patient, and the remaining four participants (10%) were only "somewhat suspicious." Three (8%) of the physicians agreed to the MRI at the initial visit, and eight (22%) said they might order an MRI in the future. All doctors who refused the MRI told the patient this was based on lack of a medical indication for the test; seven (19%) also cited the test's expense. Twenty physicians (53%) of 38 agreed to a neurology referral. In response to the standardized patient's concerns, nine physicians (23%) verbalized that MS is scary, and four (10%) asked the patient about their friend's experience with MS. A few physicians appeared to dismiss the patient's concerns, such as by telling the patient they were being "paranoid." CONCLUSIONS: Few physicians agreed to a standardized patient's request for a medically unindicated MRI, but more than half agreed to refer this patient to a specialist. As physicians practice cost-conscious medicine, they may need to focus on good communication to maintain patient satisfaction.