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Biomedical subjects

A Harrison

Publications and source records attributed to A Harrison.

At least 19 recordsLinked to original sources
PubMed2006

HIV risk behaviors and the context of sexual coercion in young adults' sexual interactions: results from a diary study in rural South Africa.

BACKGROUND: Gender inequalities in relationship power may promote unprotected sexual intercourse. GOALS: The goal of this study was to gain insight into the specific gender dynamics in the intimate relationships of rural South African young adults that contribute to risk for HIV infection. STUDY: Using diary methods, 25 female and 25 male secondary school students in rural South Africa provided daily reports (N = 1000) over a 3-week timeframe, including details regarding 466 sexual interactions. RESULTS: Inconsistent condom use was more likely in relationships in which the male partner had ever used threat or force to engage in sex during this period (unadjusted odds ratio, 13.4; 95% confidence interval, 1.57-114.26). Male sexual coercion was more likely in relationships in which alcohol was ever used in conjunction with sex and when a man's desire to engage in sex was perceived as greater than the woman's. CONCLUSION: This study adds to the growing evidence that sexual relationships characterized by gender inequality and sexual coercion are contexts of sexual risk.

Adolescent↗
PubMed2005

A statistical model for HIV-1 sequence classification using the subtype analyser (STAR).

MOTIVATION: HIV-1 antiretroviral drug resistance testing produces large amounts of HIV-1 protease and reverse transcriptase sequences. These provide an excellent resource to study the incidence, spread and clinical significance of HIV-1 subtypes. We have produced a program, Subtype Analyser (STAR) that rapidly and accurately subtypes HIV-1. Here we have determined a robust and statistically validated model for subtype assignment. RESULTS: We have significantly extended our HIV-1 subtyping tool (STAR), such that each query sequence when evaluated against subtype profile alignments, returns a discriminating score based on the ratio of subtype positive to negative amino acid positions. These scores were transformed into a Z-score distribution and evaluated. Of the 141 sequences used to define the subtype alignments, 98% were correctly reclassified. Inclusion of additional recombination detection within STAR increased the detection of known recombinant sequences to 95%. AVAILABILITY: STAR is available as compiled (Linux Fedora 3) or source code from http://pgv19.virol.ucl.ac.uk/download/star_linux.tar CONTACT: p.kellam@ucl.ac.uk SUPPLEMENTARY INFORMATION: http://pgv19.virol.ucl.ac.uk/download/star_supplement

Algorithms↗
PubMed2005

A Java application for tissue section image analysis.

The medical industry has taken advantage of Java and Java technologies over the past few years, in large part due to the language's platform-independence and object-oriented structure. As such, Java provides powerful and effective tools for developing tissue section analysis software. The background and execution of this development are discussed in this publication. Object-oriented structure allows for the creation of "Slide", "Unit", and "Cell" objects to simulate the corresponding real-world objects. Different functions may then be created to perform various tasks on these objects, thus facilitating the development of the software package as a whole. At the current time, substantial parts of the initially planned functionality have been implemented. Getafics 1.0 is fully operational and currently supports a variety of research projects; however, there are certain features of the software that currently introduce unnecessary complexity and inefficiency. In the future, we hope to include features that obviate these problems.

Cytological Techniques↗
PubMed2005

Professional influences on the provision of mental health care for older people within a general hospital ward.

Recent policy initiatives within the United Kingdom have recognized that effective care for older people can only be achieved if health care staff are willing and skilled enough to address patient needs in a holistic way. The preliminary stages of the action research project described here focused on the perceptions of nursing staff regarding the factors that impacted on their ability to address mental health needs within a general hospital ward. A phenomenological approach allowed us to identify the experience of addressing mental health needs in this setting from the perspective of the research participants. A focus group was facilitated with nursing staff whose primary professional focus was the provision of physical health care within an older adult unit. Thematic content analysis was used to analyse the focus group data, and four key themes emerged, namely 'disruption', 'role conflict', 'professional resources' and 'professional distress'. These themes provide a focus for the ongoing development of the action research methods and will embed future work in the experience of those charged with ensuring that mental health care is a key element of their practice. This study highlights the urgent need for further work in this area, as we contend that it is only by addressing the professional needs of the staff concerned, that effective patient-centred care can be ensured.

Aged↗
PubMed2004

Prevalence of dihydropteroate synthase mutants in HIV-infected South African children with Pneumocystis jiroveci pneumonia.

BACKGROUND: Pneumocystis jiroveci (formerly Pneumocystis carinii) pneumonia (PCP) is a major cause of mortality in human immunodeficiency virus (HIV)-infected infants in Africa, but the prevalence of mutations in the gene encoding dihydropteroate synthase (DHPS) in isolates from Africa has not been reported. METHODS: This study investigated the prevalence of DHPS mutations in P. jiroveci isolates from South African HIV-infected children with PCP by amplifying DNA using 2 different polymerase chain reactions. RESULTS: P. jiroveci DNA from 30 respiratory specimens was amplified; 26 specimens (86.7%) contained wild-type DHPS alleles. Of the 4 samples (13.3%) with DHPS mutations, 2 contained a homogenous population with single DHPS mutations, 1 contained a homogenous population with 2 DHPS mutations, and the fourth contained a heterogenous population of organisms with both wild-type and single-mutant DHPS genotypes. Only 1 child was receiving trimethoprim-sulphamethoxazole (TMP-SMZ) prophylaxis; this patient was infected with wild-type P. jiroveci. The mortality rate (overall, 20 [66.7%] of 30 children) was not significantly different between children infected with wild-type P. jiroveci (17 [65.4%] of 26) and those infected with mutant strains (3 [75%] of 4; P=.8). CONCLUSIONS: DHPS mutations are uncommon in P. jiroveci isolates from South Africa. However, increasing use of TMP-SMZ prophylaxis may result in widespread development of mutations.

AIDS-Related Opportunistic Infections↗
PubMed2004

Evidence for negative association of the chemokine receptor CCR5 d32 polymorphism with rheumatoid arthritis.

BACKGROUND: Ligands of chemokine receptor CCR5, including MIP-1 alpha, MIP-1 beta, and RANTES, have been implicated in rheumatoid arthritis. OBJECTIVE: To test whether CCR5 d32 polymorphism has a negative association with rheumatoid arthritis in a New Zealand cohort. METHODS: 516 white patients with rheumatoid arthritis and 985 healthy controls were investigated by PCR amplification of the region flanking the known CCR5 d32 deletion, and the frequencies of CCR5 d32 compared. An early rheumatoid arthritis (ERA) cohort of 92 patients was followed prospectively for two years; disease severity and outcome were correlated with CCR5 d32 status. RESULTS: 12 control subjects (1.2%) were homozygous for d32; no d32 homozygous rheumatoid patients were detected (p = 0.012); 56 patients (10.9%) were heterozygous for the d32 polymorphism (d32/wt), compared with 169 controls (17.2%) (p = 0.0011). The CCR5 d32 allele frequency was lower in the rheumatoid patients than in the controls (frequencies of 0.054 and 0.098, respectively; p = 3.7 x 10(-5)). The frequency of CCR5 d32 did not differ significantly according to disease severity or outcome in the prospective ERA cohort, nor with HLA-DRB1 status. CONCLUSIONS: This study provides further evidence for a protective effect of the CCR5 d32 variant on rheumatoid arthritis, consistent with a role for CCR5 and its ligands in disease pathogenesis.

Arthritis, Rheumatoid↗
PubMed2004

Consultant nurses in mental health: a discussion of the historical and policy context of the role.

This paper provides a platform for the discussion of the recent development of the nursing leadership role of consultant nurse. It focuses on the implementation of this role in mental health. The discussion is partially informed by evidence from personal reflections from consultant nurses obtained from semistructured interviews undertaken as part of a pilot study aimed at explaining the influences and context of nursing leadership in mental health. The authors believe that more in depth consideration needs to be given to the interpretation and implementation of such professional policy initiatives in to mental health nursing. Further thought also needs to be given to how consultant nurses in mental health can operationalize their expert clinical practice.

Health Policy↗
PubMed2004

The effect of a range of disinfectants on the dimensional accuracy of some impression materials.

In this study the dimensional accuracy of two model materials; dental stone and plaster of Paris, reproduced from three commonly used impression materials; alginate, polyether and addition-cured silicone, retained by their adhesives in acrylic resin trays and exposed to four disinfectant solutions was evaluated. Ninety casts were used to investigate the effect of the four disinfectants on the dimensional accuracy of alginate, polyether and addition-cured silicone impression material. For each impression material 30 impressions were taken, half were poured in dental stone and half in plaster of Paris. The disinfectants used were Dimenol, Perform-ID, MD-520, and Haz-tabs. Measurements were carried out using a High Precision Reflex Microscope. For the alginate impressions only those disinfected by 5-minute immersion in Haz-tabs solution and in full-strength MD 520 were not adversely affected by the disinfection treatment. All polyether impressions subjected to immersion disinfection exhibited a clinically acceptable expansion. Disinfected addition-cured silicone impressions produced very accurate stone casts. Those disinfected by spraying with fill-strength Dimenol produced casts that were very similar to those left as controls, but those treated by immersion disinfection exhibited negligible and clinically acceptable expansion. The results of the studied demonstrated that the various disinfection treatments had different effects on the impression materials. It is important that an appropriate disinfectant is used for each type of impression material.

2-Propanol↗
PubMed2003

The effect of the addition of poly(methyl methacrylate) fibres on some properties of high strength heat-cured acrylic resin denture base material.

The self-reinforcement of acrylic resin with butadiene styrene surface treated poly(methyl methacrylate) fibres has been reported to have the potential to substantially improve the transverse bend strength of conventional heat-cured acrylic resin. The aim of this study was to investigate the effect of the addition of butadiene styrene surface treated poly(methyl methacrylate) fibres in cross-ply arrangement to high impact acrylic resin on the transverse and impact strength. Specimens were prepared as specified in the International Standard Organization and British Standards for the Testing of Denture Base Resins (ISO 1567, 1988; BS 2487, 1989) and the British Standard Specification for Orthodontic resins (BS 6747, 1987) for transverse bend and impact testing. The impact strength was measured using a Zwick pendulum impact tester and the transverse bend strength measured using a Lloyds Instruments testing machine. The results showed that the impact strength was not improved with the addition of fibres, high impact acrylic resin with fibres (LF) 11.1 kJ m-2 and high impact acrylic resin (L) (12.5 kJ m-2). The modulus of rupture was decreased with the addition of fibres (57.8 MPa) for (LF) compared with (60.4 MPa) for (L). The modulus of elasticity was also reduced with the addition of fibres (1834.9 MPa) (LF) and 2086.2 MPa (L) as was the peak load (LF) (50.8 N) and (L) (55.8 N). It was concluded that the addition of surface treated poly(methyl methacrylate) fibres in cross-ply arrangement to high strength acrylic resin did not produce an improvement in the impact or transverse strength and cannot be recommended as a method of reinforcement.

Acrylic Resins↗
PubMed2003

The effect of the addition of poly (methyl methacrylate) fibres on the transverse strength of repaired heat-cured acrylic resin.

The aim of the present study was to investigate the effect of addition of an experimental poly (methyl methacrylate) (PMMA) fibre in linear form, 0.75 mm in diameter on the transverse strength of repaired heat-cured poly (methyl methacrylate) denture base material. Specimens of heat-cured PMMA were repaired with an autopolymerizing acrylic resin and an autopolymerizing acrylic resin together with the addition of untreated and surface-treated PMMA fibres in different arrangements. The transverse bend test was carried out using a LIoyd's Instrument Material Testing Machine. From the results, it can be concluded that the box incorporated into the repair joint produced a significant decrease in the moduli of elasticity and rupture which may be due to stress concentration effects. The addition of one layer of untreated PMMA fibres significantly decreased the modulus of rupture. The addition of two layers of untreated fibres produced a slight but statistically non-significant increase in the modulus of rupture. The addition of surface-treated (with butadiene styrene latex emulsion) fibres into the repair complex gave no improvement compared with the addition of untreated fibres in terms of transverse strength. There was an insignificant decrease in the modulus of rupture compared with the untreated fibres.

Acrylic Resins↗
PubMed2003

The effect of the addition of different fibres on the transverse and impact strength of acrylic resin denture base material.

The aim of the present study was to investigate the effect of the addition of different types of fibres on the transverse and impact strength of acrylic resin denture base material. The addition of glass fibres (strand) and polyethylene fibres produced a non significant increase in the modulus of elasticity, compared with the control of conventional heat-cured acrylic resin. The addition of glass fibres (woven and strand), polyethylene and carbon fibres to acrylic resin produced a non significant increase in the modulus of rupture. The addition of carbon, glass (strand) and polyethylene fibres produced a significant increase in the impact strength. Within the limitations of this study the addition of silk fibres did not produce an improvement in the mechanical properties.

Acrylic Resins↗
PubMed2002

An investigation into the transverse and impact strength of "high strength" denture base acrylic resins.

A range of materials, often marketed as high strength resins is available. These materials are often expensive options to conventional heat-cured acrylic resin. The aim of this study was to investigate transverse and impact strength of five "high strength" acrylic resin denture base materials. A conventional heat-cured acrylic resin was used as a control. Specimens were prepared as specified in the International Standard Organization (ISO 1567: 1988) and British standards for the Testing of Denture Base Resins (BS 2487: 1989) and the British Standard Specification for Orthodontic resins (BS 6747: 1987) for transverse bend and impact testing. The impact strength was measured using a Zwick pendulum impact tester and the transverse bend strength measured using a Lloyds Instruments testing machine. The results showed that Metrocryl Hi, Luctitone 199 and N.D.S. Hi all had an impact strength which was significantly higher than the control. For the modulus of rupture, there was a significant difference between Sledgehammer and the other groups. There was no significant difference between the other groups and the control. For the modulus of elasticity, Sledgehammer produced the highest value followed by the control. The remaining four materials had a modulus of elasticity less than the control.

Acrylic Resins↗
PubMed2002

The selection of anterior teeth appropriate for the age and sex of the individual. How variable are dental staff in their choice?

As part of the development of a guide to aid the undergraduate in the selection of artificial teeth, the aim of this study was to investigate the variability in choice of dental staff to select teeth appropriate to the age and sex of the individual with the aid of a series of three-dimensional guides. Four three-dimensional guides were produced for use in the study. Fifty dentists were asked to complete a questionnaire designed to assess the variability in selection of anterior teeth appropriate for the age and sex of an individual. From this study it can be concluded that there was little consistency in the selection of the shade, mould and arrangement of anterior teeth appropriate for the age and sex of the individual by qualified dental staff. The development and implementation of an aesthetic proforma to guide dental staff, dental undergraduates and patients through the process of choosing tooth mould, shade and arrangement based on age and sex may be helpful.

Adult↗
PubMed2001

Spin dynamics of the 2D spin 1/2 quantum antiferromagnet copper deuteroformate tetradeuterate (CFTD).

The magnetic excitation spectrum in the two-dimensional (2D) S = 1/2 Heisenberg antiferromagnet copper deuteroformate tetradeuterate has been measured for temperatures up to T approximately J/2, where J = 6.31+/-0.02 meV is the 2D exchange coupling. For T<<J, a dispersion of the zone boundary energy is observed, which is attributed to a wave vector dependent quantum renormalization. At higher temperatures, spin-wavelike excitations persist, but are found to broaden and soften. By combining our data with numerical calculations, and with existing theoretical work, a consistent description of the behavior of the model system is found over the whole temperature interval investigated.

Journal Article↗