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A D McLean

Publications and source records attributed to A D McLean.

At least 19 recordsLinked to original sources

Burns and military clothing.

Burn injury is a ubiquitous threat in the military environment. The risks during combat are well recognised, but the handling of fuel, oil, munitions and other hot or flammable materials during peacetime deployment and training also imposes an inherent risk of accidental burn injury. Over the last hundred years, the burn threat in combat has ranged from nuclear weapons to small shoulder-launched missiles. Materials such as napalm and white phosphorus plainly present a risk of burn, but the threat extends to encompass personnel in vehicles attacked by anti-armour weapons, large missiles, fuel-air explosives and detonations/conflagrations on weapons platforms such as ships. Large numbers of burn casualties were caused at Pearl Harbor, in Hiroshima and Nagasaki, Vietnam, during the Arab/Israeli Wars and in the Falkland Islands conflict. The threat from burns is unlikely to diminish, indeed new developments in weapons seek to exploit the vulnerability of the serviceman and servicewoman to burns. Clothing can be a barrier to some types of burn--both inherently in the properties of the material, but also by trapping air between clothing layers. Conversely, ignition of the clothing may exacerbate a burn. There is hearsay that burnt clothing products within a wound may complicate the clinical management, or that materials that melt (thermoplastic materials) should not be worn if there is a burn threat. This paper explores the incidence of burn injury, the mechanisms of heat transfer to bare skin and skin covered by materials, and the published evidence for the complication of wound management by materials. Even light-weight combat clothing can offer significant protection to skin from short duration flash burns; the most vulnerable areas are the parts of the body not covered--face and hands. Multilayered combat clothing can offer significant protection for short periods from engulfment by flames; lightweight tropical wear with few layers offers little protection. Under high heat loads in the laboratory, combat clothing can ignite, but there is little evidence that clothing ignition is a common occurrence in military burn casualties. Thermoplastic materials have many benefits in civil and military clothing. There is little objective evidence that they exacerbate burns, or complicate burn management. Their use in military clothing must be based on objective evidence, not hearsay.

Burns↗

DNA identification.

Explore the source record for details and available documents.

Blood Grouping and Crossmatching↗

A mucinous tumour of the urachus: adenoma or low grade mucinous cystic tumour of uncertain malignant potential?

We report a case of urachal glandular neoplasia in a male aged 72 years. The lesion had a papillary and villiform structure, and exhibited serrated features as seen in some colorectal neoplasms. The tumour cells expressed carcinoembryonic antigen, whereas the normal urachal epithelium did not. There was a striking resemblance to low grade mucinous cystic tumours of uncertain malignant potential as described in the appendix and elsewhere. Although such lesions in the urachus have been called adenomas, we argue that their potential to cause pseudomyxoma peritonei deserves a different terminology, and that 'mucinous tumour of uncertain malignant potential' is appropriate.

Adenoma↗

Six-year follow-up of the Toronto stentless porcine valve.

Stentless valves in the aortic position have been shown to have superior hemodynamic performance to stented valves and have now been shown to increase survival. We report the medium-term results from a single center of 229 Toronto (SPV) aortic valve replacements between 1994 and 2000. The mean age of the patients was 72 years (range, 41-87 years). The mean Euroscores were 6.2 (+/-0.13) and Parsonnet scores of 16.8 (+/-0.5). Concomitant coronary artery bypass grafting was performed in 125 (55%) of patients, eight patients had additional mitral valve replacements and ten were redo procedures. Hospital mortality was 3.5%. The mean follow-up period was 45 (7-81) months. The actuarial survival was 92.4% (+/-1.4%) at one year and 76.2% (+/-3.5%) at five years. There were 37 late deaths (4.7% per patient years). There were 3 patients with prosthetic valve endocarditis (0.38% per patient years), two of whom died. Stroke occurred in 13 patients (1.6% per patient years), five of whom died. None of these events were known to be valve related. There was no incidence of structural valve dysfunction and no valves have been explanted. At follow-up, the mean transvalvular gradient was 4.2 mm Hg (range, 0.9-12.7 mm Hg). No aortic incompetence (AI) was seen in 88% of patients with trivial or mild AI in 11% of patients and moderate AI in one patient. This series shows acceptable early and medium-term results in an elderly population with a high incidence of coronary artery disease.

Adult↗

Immune monitoring in xenotransplantation: the multiparameter flow cytometric mixed lymphocyte culture assay.

Xenotransplantation requires monitoring of complex cellular interactions in vitro. A tool to monitor cell proliferation in detail would be instrumental in understanding these cellular interactions in heterogeneous xenogeneic lymphocyte cultures and in patients after xenotransplantation. To accomplish this, we used a fluorescent cell proliferation marker, 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE), in combination with flow cytometry. CFSE, a green fluorescent molecule, binds covalently to intracellular macromolecules. Each cell division reduces the fluorescent intensity per cell by half and shows a characteristic multipeak pattern in flow cytometric analysis. For this study, human lymphocytes were labeled with CFSE and cultured in the presence of irradiated porcine lymphocytes. Cell proliferation was detected in CFSE-labeled lymphocytes in both a single and a multiparameter flow cytometry setting. Concurrently, tritiated ((3)H) thymidine incorporation, a common method to measure gross cell proliferation, was assessed. The kinetics of CFSE-labeled cell proliferation correlated with (3)H-thymidine incorporation in that both methods showed a lag phase for days 1-3 and a log phase for days 4-7. Multiparameter flow cytometric monitoring of mixed lymphocyte cultures allowed phenotyping and assessment of viability of proliferating populations in heterogeneous xenogeneic stimulated human lymphocyte cultures and complemented the classical (3)H-thymidine incorporation assay. The use of this technique will allow a wide array of immunologic parameters to be measured in a heterogeneous xenogeneic mixed lymphocyte culture. The information gained from these assays is essential to understanding the biological significance of xenogeneic cellular interaction and for monitoring the immune status of the xenotransplanted patient.

Cell Division↗

Replacement of graft-resident donor-type antigen presenting cells alters the tempo and pathogenesis of murine cardiac allograft rejection.

BACKGROUND: Graft-resident antigen presenting cells (APCs) are potent stimulators of the alloresponse. To test whether replacement of graft-resident donor-type APCs with those of recipient-type alters allorecognition and the pathogenesis of both acute and chronic rejection, we created chimeric hearts for transplantation into naive recipients. METHODS: To replace donor-type APCs with those of recipient-type, chimeric animals were created by bone marrow transplantation (BMT) in fully allogeneic mouse and rat strain combinations. The degree of APC replacement in chimeric organs was assessed phenotypically and functionally. Chimeric hearts were transplanted heterotopically into untreated recipients. RESULTS: Flow cytometric and immunohistochemical analysis did not detect residual bone marrow recipient-type APCs in mouse BMT chimeras. Although semi-quantitative reverse transcription polymerase chain reaction detected 0.001-0.01% residual cells, APCs isolated from chimeric organs were functionally unable to stimulate donor-type cells. When transplanted into naive recipients, chimeric mouse hearts had significantly prolonged survival but were nevertheless rejected acutely. Similar results were obtained in the ACI --> LEW rat strain combination. However, in the PVG --> DA rat model, the majority of chimeric hearts survived >100 days and all long-surviving hearts developed cardiac allograft vasculopathy. CONCLUSIONS: BMT leads to near complete replacement of organ-resident APCs. The virtual absence of donor-type APCs in chimeric hearts delays or prevents acute rejection in a strain-dependent manner. In contrast, this type of graft modification does not prevent cardiac allograft vasculopathy. This suggests that, although the CD4+ direct pathway may play a role in acute rejection, it is not essential for the development of chronic rejection in rodent cardiac allografts.

Acute Disease↗

Early experience of intra-ureteric capsaicin infusion in loin pain haematuria syndrome.

OBJECTIVES: To evaluate early results of the intra-ureteric instillation of capsaicin for the treatment of loin pain haematuria syndrome (LPHS). PATIENTS AND METHODS: Ten patients with LPHS were treated using intra-ureteric capsaicin instillation. A solution of capsaicin was infused into the affected ureter through an embolectomy catheter, under anaesthesia. The success of the treatment was assessed using patient questionnaires and the quantitative reduction in the patients' analgesic requirements measured. RESULTS: During a mean follow-up of 6 months, six of the 10 patients had short- to medium-term symptomatic relief after one or more treatments; four had no relief from their symptoms. One patient had a mucosal ulceration in the bladder after extravasation of the capsaicin solution. Two patients subsequently underwent simple nephrectomy for symptomatic nonfunctioning kidneys. CONCLUSION: These results are consistent with other preliminary reports of the efficacy of capsaicin treatment in LPHS and such treatment therefore has a definite therapeutic role in this difficult condition. We are uncertain if the treatment contributed to the deterioration of the excised kidneys. This early experience suggests a need for careful consideration when contemplating this treatment, with attention directed to both the initial diagnosis and possibly the technique of capsaicin/instillation. We include a protocol to follow when preparing patients for capsaicin treatment.

Administration, Topical↗

New calculations on the ion-molecule processes C2H2(+) + H2 --> C2H3(+) + H and C2H2(+) + H2 --> C2H4+.

New high-level quantum chemical calculations have been undertaken to understand the rates and mechanisms of the reactive and associative channels for the reactants C2H2(+) + H2. The reactive channel, which produces C2H3(+) + H, has been shown to be slightly endothermic, confirming earlier calculations at a somewhat lower level and in agreement with some recent experimental work. The associative channel, leading to C2H4+, has been shown to proceed via a transition state with negative energy relative to the reactants, so that association is predicted to be efficient. This result is in conflict with an earlier theoretical study but in agreement with low-temperature experimental measurements.

Hydrocarbons↗

Calculations concerning interstellar isomeric abundance ratios for C3H and C3H2.

The syntheses of interstellar c-C3H2, H2CCC, c-C3H, and HCCC, where "c" stands for the cyclic isomer, are thought to proceed via dissociative recombination of the precursor ions c-C3H3+ and H2CCCH+, which are themselves produced mainly via the radiative association reaction between C3H+ and H2. We have utilized ab initio methods to study the potential energy surface (PES) for the association of the linear ion C3H+ and H2 to form the isomers c-C3H3+ and H2CCCH+. The overall rate coefficient for radiative association has been calculated as a function of temperature via the phase space method. Our ab initio calculations show that the H2CCCH+ isomer is formed directly without an activation barrier from reactants, and that isomerization between the two isomers can occur readily via a low-energy pathway consisting of two transition states (saddle points on the PES) and one intermediate (local minimum on the PES). Calculations of the equilibrium coefficient for the isomerization H2CCCH+ <-> c-C3H3+ as a function of energy shows that equal abundances of these two ions should be produced as relaxation proceeds, in agreement with experimental measurements at high pressure. Our results confirm the important point that a simple ion-molecule association reaction can produce a cyclic hydrocarbon. If dissociative recombination reactions involving c-C3H3+ and H2CCCH+ maintain the carbon skeletal structure of the ions and produce roughly similar C3H/C3H2 branching ratios, then abundance ratios of unity are produced between the cyclic and noncyclic isomers of C3H and C3H2 via this mechanism. The large abundance ratio of c-C3H2 to H2CCC observed in TMC-1 can then be explained by differential destruction rates.

Astronomical Phenomena↗

Calculations on the competition between association and reaction for C3H(+) + H2.

A potential energy surface has been calculated for the competing associative and reactive ion-molecule processes involving the reactants C3H(+) + H2. Our ab initio results show that the linear ion C3H+ and H2 can directly access the deep potential well of the propargyl ion H2CCCH+, which is calculated to lie 390 kJ mol-1 below the zero-point energy of the reactants. Isomerization between the propargyl ion and the lower energy, cyclic C3H3+ ion, calculated to lie 501 kJ mol-1 below the zero-point energy of reactants, can subsequently occur via two pathways. One of these pathways involves a transition state lying 22 kJ mol-1 below the energy of the reactants while the other, which occurs at much lower energies, involves two transition states and an intermediate. The dissociation of c-C3H3+ into c-C3H2(+) + H is calculated to occur directly, without any intermediate potential energy maximum, but the energy of the products lies 7.3 kJ mol-1 above the energy of the reactants. Using the minimum energy potential pathway and properties of the stationary point structures determined via ab initio methods, we have calculated both the association rate coefficient to produce C3H3+ as a function of density and the branching ratio between the propargyl and cyclic structures of the ion. Our results are in good agreement with some experimental results and in conflict with others. Specifically, we agree with the 1:1 branching ratio measured for the propargyl and cyclic isomers of C3H3+ at 80 and 300 K and we agree with the rate coefficient for radiative association measured at 80 K. We cannot reproduce reported measurements that the reactive channel (C3H2(+) + H) is the dominant channel at 80 K and at low gas densities, or that the association channel at high densities saturates at an effective rate coefficient well below the Langevin value -2x10(-11) cm3 s-1 at 300K and 1x10(-10) cm3 s-1 at 80K.

Astronomical Phenomena↗

Improved collisional excitation rates for interstellar water.

Theoretical rate constants among the lowest 45 para and 45 ortho rotational levels of water in collisions with He atoms have been calculated for temperatures between 20 and 2000 K using a recently improved theoretical interaction potential. These values are about 30%-40% larger than those reported previously (Palma et al. 1988b) but relative sizes of different state-to-state rates have not changed significantly. Successive improvements to the theoretical description of this system now appear to have converged.

Astronomical Phenomena↗

Ab initio predictions on the rotational spectra of carbon-chain carbene molecules.

We predict rotational constants for the carbon-chain molecules H2C=(C=)nC, n=3-8, using ab initio computations, observed values for the earlier members in the series, H2CCC and H2CCCC with n=1 and 2, and empirical geometry corrections derived from comparison of computation and experiment on related molecules. H2CCC and H2CCCC have already been observed by radioastronomy; higher members in the series, because of their large dipole moments, which we have calculated, are candidates for astronomical searches. Our predictions can guide searches and assist in both astronomical and laboratory detection.

Astronomical Phenomena↗

Calculations of ion-molecule deuterium fractionation reactions involving HD.

Gas-phase chemical models of deuterium fractionation in dense interstellar clouds utilize a small number of exothermic reactions to achieve fractionation. Although HD is a major repository of deuterium, it appears not to exchange deuterium with many molecular ions. Useful semiquantitative reasons have been given for the unusual lack of reactivity of exothermic ion-HD deuterium exchange systems, but quantum chemical studies are needed to understand these ideas in more detail and to determine if the lack of reactivity pertains at very low temperatures not studied in the laboratory, or whether tunneling can drive the reactions. Accordingly, the potential energy surfaces of three representative ion-molecule exchange reactions involving protonated ions (H3+, CH3+, HCO+) and HD have been investigated with ab initio quantum chemical techniques. Our results generally confirm the semiquantitative picture as to which reactions are likely to occur and show that tunneling at low temperatures is unlikely to alter this picture.

Astronomy↗