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Biomedical subjects

A McNab

Publications and source records attributed to A McNab.

15 recordsLinked to original sources
PubMed2004

A high power ultrasonic array based test cell.

This paper describes the use of finite element (FE) analysis as a tool in the design process for laboratory based ultrasonic test cells. The system was designed to incorporate an array of ultrasonic transducers to provide a pressure focus in the centre of the cell and importantly, operate both above and below the cavitation threshold of the load medium. Furthermore, the cell incorporates a coolant jacket to accommodate temperature control of the load material associated with the process. A 2D FE model corresponding to a slice through the operational plane of the cell was developed and used to investigate the influence of cell wall material and thickness, transducer configuration, rotation of a metallic stirrer blade and heat transfer fluid on the cell acoustic response. Importantly, experimentally measured pressure field maps demonstrate good correlation with the FE predicted fields. A final manufactured test cell is shown to produce a highly focussed region of cavitation. Finally, the importance in accurately representing the acoustic properties of the constituent materials used in such FE models is demonstrated through an illustrated example.

Journal Article↗
PubMed2003

The design of a high power ultrasonic test cell using finite element modelling techniques.

This paper will describe the application of a finite element (FE) code to design a test cell, in which a single transducer is used to generate acoustic cavitation. The FE model comprises a 2-D slice through the centre of the test cell and was used to evaluate the generated pressure fields as a function of frequency. Importantly, the pressure fields predicted by FE modelling are used to indicate the position of pressure peaks, or 'hot-spots', and nulls enabling the systems design engineer to visualise both the potential cavitation areas, corresponding to the 'hot-spots', and areas of low acoustic pressure. Through this design process, a rectangular test cell was constructed from perspex for use with a 40 kHz Tonpilz transducer. A series of experimental measurements was conducted to evaluate the cavitation threshold as a function of temperature and viscosity/surface tension, for different fluid load media. The results indicate the potential of the FE design approach and assist the design engineer in understanding the influence of the fluid load medium on the cell's ability to produce a strong cavitation field.

Acoustics↗
PubMed2002

1-3 connectivity composite material made from lithium niobate and cement for ultrasonic condition monitoring at elevated temperatures.

We have designed, manufactured and tested a piezoelectric composite material to operate at temperatures above 400 degrees C. The material is a 1-3 connectivity composite with pillars of Z-cut lithium niobate in a matrix of alumina cement. The composite material produced shorter pulses than a monolithic plate of lithium niobate and remained intact upon cooling. Results are presented from room temperature and high temperature testing. This material could be bonded permanently to a test object, making it possible to carry out condition monitoring over an extended period. A new excitation method was also developed to enable remote switching between array elements.

Journal Article↗
PubMed2002

The national strategy for sexual health and HIV: implications for genitourinary medicine.

The first ever national strategy for sexual health and HIV in England was published in July 2001 and proposes a comprehensive and holistic model for dealing with an increasing public health problem. The strategy covers the issues of prevention, service provision, commissioning of services, and the necessary requirements to support change. This paper concentrates on service issues and developments in relation to genitourinary medicine/HIV services, and outlines a model for providing these which attempts to do so around patients' needs, delivered through comprehensive and interlinked local networks of services.

Comprehensive Health Care↗
PubMed2001

Ocular adnexal lymphoproliferative disease: a series of 73 cases.

BACKGROUND: This study involved 73 patients with lymphoproliferative lesions of the ocular adnexa. The lesions were categorized using the Revised European American Lymphoma classification of lymphoid tissues and analysed to determine the frequency and prognostic impact of tumour type, location, stage and patient's age and sex. METHODS: The clinical, histopathological, immunohistochemical and phenotypic analysis by flow cytometry and follow-up data were studied. RESULTS: The ocular adnexal lymphoproliferative lesions included 70 lymphomas and six reactive lymphoid hyperplasia. Seventy-nine per cent had stage IE disease, 4% stage II, 1.5% stage III and 15.5% stage IV. Five patients (7%) had a past history of systemic lymphoma. Major histological types were extranodal marginal zone lymphoma (MZL) in 44 (63%), follicular (FL) in 12 (17%), diffuse large B-cell (DLBCL) in eight (11%), mantle cell (MCL) in two (3%), B-cell chronic lymphocytic leukaemia (CLL)/small lymphocytic lymphoma in two (3%), peripheral T-cell lymphoma (PTCL) one (1.5%) and natural killer cell lymphoma (NKCL) in one (1.5%). Longest survival was seen in those with low-grade lymphomas (MZL and FL) and worst in PTCL and NKCL. Lymphoma-related mortality was 2% for MZL, 33% for FL, 38% for DLBCL, and 100% for MCL, PTCL and NKCL. Systemic lymphoma was present prior to, at presentation or at subsequent follow up in 26/68 (39%) of all lymphoma patients, 17% for MZL, 38% for DLBCL, 83% for FL, and 100% for MCL, CLL, PTCL and NKCL. CONCLUSION: The majority of ocular adnexal lymphomas were low-grade B-cell lymphomas (MZL). Multivariate analysis showed that the only significant independent predictors of all causes of mortality were the histological type of lymphoma and the stage of disease at presentation.

Adult↗
PubMed1998

Drug-induced ocular cicatricial pemphigoid: a series of clinico-pathological reports.

Ocular cicatricial pemphigoid is a slowly progressive disease of mucous membranes and skin of unknown but presumed autoimmune aetiology. We describe eight cases of presumed drug-induced cicatrising conjunctival changes simulating ocular cicatricial pemphigoid, following the chronic use of topical glaucoma medication. In three of four patients who underwent conjunctival biopsy of the inferior fornix, this revealed histopathological changes similar to ocular cicatricial pemphigoid.

Aged↗
PubMed1995

Hydroxyapatite orbital implants. Experience with 100 cases.

BACKGROUND: The hydroxyapatite (HA) intraorbital implant is a relatively new implant made from the porous skeleton of a coral species which allows fibrovascular ingrowth and therefore tissue integration. After fibrovascular ingrowth, a hole can be drilled in the implant and a motility peg inserted to increase movements of the prosthesis by coupling the implant to the prosthesis. METHOD: The records of the first 100 cases of HA intraorbital implants inserted by the one surgeon were analysed for complications, pain and nausea postoperatively, length of hospital stay, and further surgical procedures required. A series of acrylic implants inserted by the same surgeon was used for comparison. RESULTS: Twenty-five primary and 75 secondary HA implants were performed in patients ranging from six to 74 years of age. All were covered in donor sclera. Follow-up was three to 34 months (mean 16.9, median 17.0). Complications occurred in 15 patients and included too large an implant (seven cases) requiring surgical reduction, scleral exposure in three (repair required in one), an early small exposure of the coral in one case, late thinning of the conjunctiva and later exposure of the implant in one, and shallowing of the inferior fornix requiring mucous membrane grafting in three. No implants migrated, extruded or became infected. Of 80 patients beyond six months follow-up, 28 (35%) had insertion of motility pegs, and six (7.5%) of these suffered minor complications related to the peg. Compared to patients having acrylic implants, the postoperative analgesic requirements and length of hospital stay were significantly greater for the HA patients. CONCLUSIONS: Hydroxyapatite intraorbital implants represent a significant advance over other implants and offer a more stable, safe alternative. They also offer the possibility of improved prosthesis motility. The additional cost of the implant, prolonged hospital stay and postoperative pain, should be considered in recommending such implants to patients either as primary or secondary implants.

Acrylates↗
PubMed1985

The structural proteins of the autonomous parvovirus feline panleukopenia virus.

Approximately 80% of the genome of feline panleukopenia virus was cloned into the plasmid pBR322. The entire 3943 nucleotide sequence of the cloned portion of FPV was determined. This DNA includes the gene which codes for the structural proteins of the virus. Portions of this gene were expressed in E. coli as fusion proteins with bacterial proteins. Some of the fusion proteins were capable of raising neutralizing antibodies in guinea pigs. Through the use of deletion mapping, monoclonal antibodies, and synthetic peptides, attempts were made to localize the portion of the protein responsible for raising these antibodies.

Animals↗
PubMed1981

Differential expression of the globin genes in human leukemia K562(S) cells induced to differentiate by hemin or butyric acid.

Human leukemia K562(S) cells were induced to differentiate by 50 microM hemin or 1.4 mM butyric acid, and the types of hemoglobins synthesized were compared. In both cases, embryonal hemoglobins [Portland, Gower 1, Hb X, and fetal hemoglobin (Hb-F)] were detected. Butyric acid-treated K562(S) cells contained mostly Hb Gower 1 (zeta 2 epsilon 2) and a hemoglobin with the electrophoretic characteristics of Portland (gamma 2 zeta 2). For hemin-treated K562(S), the most abundant hemoglobin synthesized by Hb X (epsilon 2 gamma 2), and the second most abundant was Bart's (gamma 4). Traces of Gower 1 were observed in nontreated K562(S) cells. The kinetics of hemoglobin induction as a result of the two treatments differed; increased hemoglobin synthesis was detected after only 24 hr of hemin treatment, whereas 4 days were required in butyric acid-treated cells. Both hemin and butyric acid were able to induce their respective patterns of hemoglobin synthesis independent of the presence of serum in the K562(S) growth medium. Analysis of the globin chains in induced K562(S) cells induced to differentiate indicated that, with both inducers, adult alpha- but not beta-globin chains were present. Karyotype analysis of K562(S) cells revealed a nearly triploid chromosome complement with a modal number of 68 chromosomes. Three copies of chromosome 11 and four copies of chromosome 16 (coding for the beta-like and alpha-like globin genes, respectively) were present. A large marked chromosome, involving chromosome 7, and a Philadelphia chromosome were also seen. These data characterize the K562(S) subline and also indicate that hemin and butyric acid differ in their effects on the expression of embryonal globin genes.

Butyrates↗
PubMed1981

Growth and differentiation of human and murine erythroleukemia cell lines in serum-free synthetic medium.

Only two chemicals (transferrin and selenium dioxide) are required to supplement serum-free Roswell Park Memorial Institute Medium 1640 for long-term growth and for spontaneous and induced differentiation of established lines of human and mouse erythroleukemia cells. We describe here two serum-free media (a minimal synthetic medium and a high-density synthetic medium) that support the growth and differentiation of human K562(S) and mouse clones 745, 707, and 3TCl 12 erythroleukemia cell lines in long-term culture. The doubling times of the erythroleukemic cell populations are longer in minimal synthetic medium that in serum-containing medium. Cell saturation density in minimal growth medium is one-half that obtained in serum-containing medium for clone 745, whereas for K562(S) it is approximately the same. Cell saturation density in high-density medium (containing albumin) is greater than that achieved in serum-containing medium for K562(S), whereas for clone 745 cell saturation density increases for cells in midlogarithmic growth, although not to the density of cells grown in serum-containing medium. The differences in saturation density are due to a decreased doubling time as well as to better survival of the cells 3 or 4 days after plating. The cells can grow in the synthetic media and be passaged for as many generations as desired without impairment of growth capabilities. In the minimal synthetic medium, spontaneous differentiation of erythroleukemia cells continues to occur, indicating that spontaneously differentiating cells are the result of intracellular mechanisms controlling the expression of a genetic program of some of the cells at any given time. Hemoglobin synthesis can be induced in cells growing in synthetic medium by using lower concentrations of the same inducers that are effective in serum-containing medium, indicating that these chemicals do not depend on serum factors to initiate the process of differentiation. The percentage of benzidine-positive cells and the concentration of hemoglobin per cell, however, are less in the synthetic medium than in serum-containing medium, suggesting that serum factors do play a role in modulating the extent of hemoglobin synthesis. The types of hemoglobins synthesized by cells in synthetic medium are identical to those reported in serum-containing medium.

Animals↗