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G Ayoub

Publications and source records attributed to G Ayoub.

13 recordsLinked to original sources
PubMed2002

An optimisation model for regional integrated solid waste management I. Model formulation.

Increased environmental concerns and the emphasis on material and energy recovery are gradually changing the orientation of MSW management and planning. In this context, the application of optimisation techniques have been introduced to design the least cost solid waste management systems, considering the variety of management processes. This study presents a model that was developed and applied to serve as a solid waste decision support system for MSW management taking into account both socio-economic and environmental considerations. The model accounts for solid waste generation rates, composition, collection, treatment, disposal as well as potential environmental impacts of various MSW management techniques. The model follows a linear programming formulation with the framework of dynamic optimisation. The model can serve as a tool to evaluate various MSW management alternatives and obtain the optimal combination of technologies for the handling, treatment and disposal of MSW in an economic and environmentally sustainable way. The sensitivity of various waste management policies will be also addressed. The work is presented in a series of two papers: (I) model formulation, and (II) model application and sensitivity analysis.

Conservation of Natural Resources↗
PubMed2002

An optimisation model for regional integrated solid waste management II. Model application and sensitivity analyses.

Increased environmental concerns and the emphasis on material and energy recovery are gradually changing the orientation of MSW management and planning. In this context, the application of optimisation techniques have been introduced to design the least cost solid waste management systems, considering the variety of management processes (recycling, composting, anaerobic digestion, incineration, and landfilling), and the existence of uncertainties associated with the number of system components and their interrelations. This study presents a model that was developed and applied to serve as a solid waste decision support system for MSW management taking into account both socio-economic and environmental considerations. The model accounts for solid waste generation rates, composition, collection, treatment, disposal as well as potential environmental impacts of various MSW management techniques. The model follows a linear programming formulation with the framework of dynamic optimisation. The model can serve as a tool to evaluate various MSW management alternatives and obtain the optimal combination of technologies for the handling, treatment and disposal of MSW in an economic and environmentally sustainable way. The sensitivity of various waste management policies is also addressed. The work is presented in a series of two papers: (I) model formulation, and (II) model application and sensitivity analysis.

Conservation of Natural Resources↗
PubMed1998

Transport-mediated release of endogenous glutamate in the vertebrate retina.

In the present study we measured calcium-dependent, vesicular glutamate release, and calcium-independent, transport-mediated glutamate release patterns in the vertebrate retina to better understand the sources of elevated glutamate in neural tissue under ischemic conditions. A potassium concentration of 40 mM, which mimics the extracellular potassium concentration in the central nervous system during ischemia, was applied to the bathing medium of a retinal slice prepared from zebrafish. High external potassium evoked release of endogenous glutamate that was measured using a glutamate-specific fluorometric assay applied to the bath. The slice was visualized under 668 nm light using Normarski optics and fluorescent images were captured using a cooled charge-coupled device (CCD) camera. Following the elevation of external potassium to 40 mM several bands of glutamate fluorescence, reflecting the spatial distribution of glutamate release, were observed. A calcium-dependent cloud of glutamate was observed in the inner plexiform layer, that was antagonized by bath-applied nifedipine. A relatively dense glutamate cloud (1-10 microM) was observed over the ganglion cell layer, which was blocked by dihydrokainate, a glutamate transport antagonist. In contrast, nifedipine, an inhibitor of calcium-dependent neurotransmitter release in the retina, failed to block the cloud of released glutamate in the ganglion cell layer. These data suggest that under pathological conditions in the eye where glutamate levels are elevated surrounding retinal ganglion cells, such as observed in some forms of glaucoma, a possible source of the elevated glutamate is through a glutamate transporter operating in a reversed direction. A likely candidate for mediating this reversed transport of glutamate is the retinal Muller cell.

ATP-Binding Cassette Transporters↗
PubMed1984

HLA studies in acquired immune deficiency syndrome patients with Kaposi's sarcoma.

To investigate the possible contribution of genetic susceptibility to Kaposi's sarcoma associated with acquired immune deficiency syndrome (AIDS-KS), 21 patients were typed for HLA-A, B, C, and DR antigens. Significantly increased frequencies of HLA-Aw23, and HLA-Bw49 antigens were observed in the Caucasian AIDS-KS group. In this same group, the frequencies of HLA-DR5 and HLA-Bw44 antigens were increased at the P less than 0.1 level. Increased frequencies of HLA-A29 and HLA-Cw4 antigens and a decreased frequency of HLA-B8 antigen were also noted, but with P greater than 0.1, in the Caucasian AIDS-KS group.

Acquired Immunodeficiency Syndrome↗
PubMed1982

HLA-DR matching in multicenter, single-typing laboratory data.

The results of 370 transplants done at 11 transplant centers in Los Angeles over the past 4 years is summarized for DR matching and transfusions. Among 28 patients with two HLA-DR antigens matched, the 1-year transplant survival rate was 75% as compared with 47% for those patients with no matched HLA-DR antigen (P less than 0.0025). Therefore, in this multicenter single-typing laboratory trial, HLA-DR typing had a significant effect on transplant outcome. The effect of pretransplant transfusions was additive. Patients with fewer than five transfusions had a 1-year survival rate of 45% compared with 69% for those with five or more transfusions (P less than 0.0005). In patients with two DR antigens matched and five or more transfusions, the survival rate was 86%. Similarly, patients with zero or one DR antigen match had a higher graft survival rate if they had previously been transfused with more than four units of blood. We conclude that two-DR antigen-matched transplants have a higher change of success than those with a zero or one antigen match and that this effect is additive with transfusions.

Adult↗
PubMed1982

Association of anti-F(ab')2 antibodies with higher kidney transplant survival rates.

When the pretransplant sera of cadaver donor transplant patients were divided into 132 with anti-F(ab')2 (Fab) antibodies and 121 without anti-Fab antibodies, those patients with the antibodies had a 2-year graft survival rate of 59.7 +/- 4.6% (+/- SE) as compared with 34.0 +/- 5.0 % (+/- SE) for those without antibodies (P less than 0.001). This difference was greater when the patients were further classified by whether they had antibodies reactive to B lymphocytes in the cold. Patients with anti-Fab antibodies and B-cold antibodies had a 2-year graft survival of 81.3 +/- 9.8% as compared with 15.7 +/- 7.9% for patients without anti-Fab antibodies and with B-cold antibodies. We suggest that these anti-immunoglobulin antibodies may function in some immunoregulatory role. The number of transfusions was not directly related to the frequency of occurrence of these antibodies.

Antibodies, Anti-Idiotypic↗
PubMed1982

Prediction of negative crossmatch: an aid for cost-effective kidney sharing.

Prospective kidney transplant recipients, who have broadly reactive cytotoxic antibodies, are currently at a considerable disadvantage in competing for shared kidneys since they tend not to be considered as candidates because of the likelihood of kidney wastage subsequent to positive crossmatch tests. Alternative to extensive shipping, storage and crossmatch testing by the harvesting center, is the prediction of crossmatch outcome on the basis of donor HLA type and recipient sera characteristics. A prediction method was developed that yields approximately 85% correct predictions. The method was validated by predicting crossmatch outcome of 67 consecutive cadaveric donors tested against 87 recipients and is suggested as useful for guiding kidney sharing programs.

ABO Blood-Group System↗
PubMed1981

Improved DR typing of cadaver donor by lymphocyte incubation.

Of 39 consecutive cadaver donors tested, DR antigens could not be detected in 17. Following 3 h incubation of the B lymphocytes at 37 degrees C, eight of the donors with no detectable DR antigens had two DR antigens and nine had one DR antigen. In addition, there were nine cases in which a potential cadaver donor had one antigen before incubation and two DR antigens following incubation. The simple technique of pre-incubating B lymphocytes before testing has helped considerably in prospectively typing cadaver donors for HLA-DR.

B-Lymphocytes↗
PubMed1980

B cell antibodies and crossmatching.

Over 200 cadaver donor transplants were crossmatched against T and B lymphocytes at 5 and 37 C. Of 54 positive B cell crossmatches, one-half had cold antibodies and one-half had warm antibodies. The 1-year transplant survival was 58% for B-cold-positive crossmatches and 42% for B-warm-positive crossmatches. The B-warm-positive crossmatches, when subdivided into those with strong HLA-DR antibodies showed a 27% 1-year transplant survival rate. We conclude that B cell-positive crossmatches with HLA-DR antibodies are deleterious and that those with cold anti-IgM antibodies may enhance graft survival.

Absorption↗