Influence of poly(acrylic acid) molar mass on the fracture properties of glass polyalkenoate cements

The failure behaviour of glass polyalkenoate cements was investigated using a linear elastic fracture mechanics (LEFM) approach. Cements were based on four model glasses with varying reactivity and four poly(acrylic acid)s (PAA)s with number average molar masses (Mn) ranging from 3.25 × 104 to 1.08 × 105. Cement properties were studied at time intervals of one, seven and twenty eight days. Compressive strengths (c) of the cements increased with increasing fluorine content of the glass, with increased molar mass of the PAA and with ageing time. The Young's moduli increased with time, but were lower for cements based on the fluorine free glass. Moduli values were independant of PAA molar mass. The un-notched fracture strength (f) of the cement increased with the molar mass of the PAA and with ageing time. Glass composition did not appreciably influence the un-notched fracture strength. The fracture toughness (KIC) increased with the molar mass of the PAA and with ageing time, but reduced with increasing fluorine content of the glass. The toughness (GIC) was dependant on molar mass. The influence of molar mass was not as great as predicted by the reptation chain pull-out model for fracture. The molar mass dependence of toughness was greatest with the lower fluorine content glasses. The plastic zone size at the crack tip increased with the molar mass of the PAA. However the plastic zone size decreased with ageing time for all the cements studied and was smaller for the more reactive higher fluorine content glasses.     

Multi-level hierarchical interface-based supervisory control

Hierarchical Interface-Based Supervisory Control employs interfaces that allow properties of a monolithic system to be verified through local analysis. By avoiding the need to verify properties globally, significant computational savings can be achieved. In this paper we provide local requirements for a multi-level architecture employing command-pair type interfaces. This multi-level architecture allows for a greater reduction in complexity and improved reconfigurability over the two-level case that has been previously studied since it allows the global system to be partitioned into smaller modules. This paper also provides results for synthesizing supervisors in the multi-level architecture that are locally maximally permissive with respect to a given specification and set of interfaces.     

Photolithography of amorphous films of (η5-C5H5)2Ti(N3)2 on silicon (111) resulting in TiO2: The mechanism of the photodeposition reaction

Photolithography to produce TiO₂ patterns from amorphous films of (⁵-C₅H₅)₂Ti(N₃)₂ has been demonstrated. The efficiency of the reaction has been measured yielding a quantum yield of 0.025. The mechanism of the photoreactions of (⁵-C₅H₅)₂Ti(N₃)₂ has been studied using Fourier transform-infrared spectroscopy in both a low-temperature 1,2-epoxyethylbenzene glass and as surface films. In each case the primary photochemical process was found to be loss of a single azido group. The result of subsequent photolysis was found to be dependent upon medium and temperature. In the low-temperature glass no further photochemistry was observed. The exhaustive photolysis of films at 20 K, or room temperature, under a vacuum or in air led to loss of all ligands and the formation of TiO₂.     

The dielectric properties of a commercial polyvinylchloride

The dielectric response of a commercial polyvinylchloride is examined in terms of the cluster model of dielectric relaxation, and compared with a sample from which the plasticizer had been extracted. An interpretation of the approach to the glass transition in terms of scaling concepts is outlined and related to the hierarchical dynamics of the cluster model. In this picture the dynamics goes over naturally to the dynamics on small size scales. The plasticizer is shown to contribute a quasi-d.c. electrical transport above the glass transition, which at higher temperatures causes the formation of an electrode barrier layer.     

Psychotherapy with high-achieving adolescent girls.

The "overnurtured child" is the label applied to adolescent girls whose strong mother-identification and oedipal attachment to father may be associated with a variety of achievement-related conflicts following puberty. Symptoms include anxiety, depression, vague feelings of inadequacy, loneliness, and isolation from peers. These patients suffer from a form of identity diffusion in which pressures to continue achieving at their present rate of excellence collide with pressures to be more "feminine," social, and affiliative. Therapy is conceptualized as a kind of resocialization process aimed at facilitating separation from family and the development of an independent identity. In treatment, the therapist plays a variety of interrelated roles such as role model, family counselor, and teacher. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The electroactive species in the catalysis of cyclohexadiene to benzene by Rh2(TM4) 4 +2 (TM4=2,5-diisocyano-2,5-dimethylhexane)

Upon further investigation of the recently reported electrocatalytic oxidation of 1,4-cyclohexadiene to benzene by Rh₂(TM4) ₄ ⁺² (TM4=2,5-diisocyano-2,5-dimethylhexane), we have obtained data which strongly implicates the 2e^– oxidized d⁷-d⁷ complex as the electroactive species. This contrasts with the original report which suggested that the le^– oxidized d⁷-d⁸ radical acted as the key species via hydrogen atom abstraction from 1,4-cyclohexadiene. A possible mechanism for the catalysis is proposed.     

Surface texture analysis based upon the visually acquired perturbation of surface normals

A novel technique has been developed for the textural analysis of Lambertian surfaces while in the presence of a variable albedo. The method has direct application for the surface quality determination of cosmetically sensitive components, and has particular application where more traditional methods may prove unsatisfactory. A photometric stereo technique is used to facilitate the isolation of localised irregular features, such as scratching, indentations or small protrusions, which may be obscured by a coincident, regular or random surface albedo. A generic lighting arrangement is employed, which obviates the need for a customised lighting configuration. This represents a significant advantage for the configuration of industrial vision-based inspection systems. Promising experimental results have been obtained using example components, and are presented in the paper.     

Physical and Sexual Intimate Partner Violence Among Women in Methadone Maintenance Treatment.

Although several studies have examined the relationship between intimate partner violence (IPV) and drug use among women in drug treatment programs, more information is needed to delineate differences, as a function of the specific drug used. Data from a random sample of 416 women attending methadone programs were analyzed to elucidate the differential associations between IPV and use of the following: marijuana only, cocaine only, heroin only, or cocaine and heroin. Prevalence of IPV among this sample far exceeded estimates from the general population. After adjusting for sociodemographic variables, use of cocaine only was significantly associated with an increased likelihood of experiencing IPV compared with no drug use. Similar results were found for women using both cocaine and heroin. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detection of Porphyrins in Hair Using Capillary Liquid Chromatography-Mass Spectrometry

Unlike humans, some animals have evolved a physiological ability to deposit porphyrins, which are pigments produced during heme synthesis in cells, in the skin and associated integument such as hair. Given the inert nature and easiness of collection of hair, animals that present porphyrin-based pigmentation constitute unique models for porphyrin analysis in biological samples. Here we present the development of a simple, rapid, and efficient analytical method for four natural porphyrins (uroporphyrin I, coproporphyrin I, coproporphyrin III and protoporphyrin IX) in the Southern flying squirrel Glaucomys volans, a mammal with hair that fluoresces and that we suspected has porphyrin-based pigmentation. The method is based on capillary liquid chromatography-mass spectrometry (CLC-MS), after an extraction procedure with formic acid and acetonitrile. The resulting limits of detection (LOD) and quantification (LOQ) were 0.006–0.199 and 0.021–0.665 µg mL⁻¹, respectively. This approach enabled us to quantify porphyrins in flying squirrel hairs at concentrations of 3.6–353.2 µg g⁻¹ with 86.4–98.6% extraction yields. This method provides higher simplicity, precision, selectivity, and sensitivity than other methods used to date, presenting the potential to become the standard technique for porphyrin analysis.     

Friction Measurements on Contact Lenses in Their Operating Environment

An important issue concerning the use of soft contact lenses is comfort, which, among other factors, has been related to the level of friction between the anterior side of the lens and the inner eyelid. Although several studies have been carried out to investigate the frictional properties of contact lenses, these have not taken the physiological environment of the eye into account. In use, lenses are in contact with proteins present in tears, with corneal cells and with the palpebral conjunctiva (clear membrane on inner eyelid). The focus of this study was to establish a biologically relevant measurement protocol for the investigation of friction of contact lenses that would mimic the eye’s physiological environment. By optimizing parameters such as the composition of the friction counter surface, the lubricant solution, the normal load and the velocity, an ideal protocol and setup for microtribological testing could be established and used to perform a comparative study of various commercially available soft contact lenses.