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J H Potgieter

Publications and source records attributed to J H Potgieter.

6 recordsLinked to original sources
PubMed2006

Distribution of atmospheric marine salt depositions over Continental Western Europe.

This contribution describes the distribution of marine salt aerosols in Belgium, France and Spain, as obtained from applying a kriging model to a set of data. The data was collected over a period of nine years and included wet as well as dry deposition results. It was found that the concentration of the salt particles decreased the fastest in Spain and the slowest in Belgium with increasing inland distance from the sea. These findings have implications for the degradation of monuments and historical buildings as a result of salt attack and ingress that often accompany degradation due to air pollution.

Aerosols↗
PubMed2005

Micro-structural characterization of black crust and laser cleaning of building stones by micro-Raman and SEM techniques.

Research concerning the formation and removal of black crusts on various historical objects is approached from many different angles. The so-called "yellowing effect", observed after laser treatment for cleaning purposes, has also received a lot of attention. Evidence regarding this phenomenon differs considerably and the actual mechanisms are still speculated on by researchers. In an attempt to elucidate the processes involved in the yellowing effect associated with laser cleaning, a new analytical technique has been used to investigate the black crust, a region of the sample cleaned by laser irradiation at 1064 nm and another region of the same sample subjected to further laser irradiation at 355 nm, on a limestone sample from the cathedral of Seville in Spain. Micro-Raman spectrometry offers the advantage of spatial chemical characterization of the stone, based upon its molecular makeup and was performed on the bulk body of the stone. Raman and scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDXS) results indicate that the surfaces cleaned by irradiation at 1064 nm and by double irradiation at 1064 and 355 nm differed in terms of their calcium sulphate, calcium oxalate and iron oxide content, and that this could contribute to the difference in colour observed.

Calcium Carbonate↗
PubMed2005

A comparison of the steady-state pharmacokinetics and pharmacodynamics of a novel rapid-acting insulin analog, insulin glulisine, and regular human insulin in healthy volunteers using the euglycemic clamp technique.

Insulin glulisine is a new rapid-acting insulin analog. The aim of this study was to assess the glucodynamic efficacy of insulin glulisine compared with regular human insulin (RHI) using a manual euglycemic clamp technique. Steady-state pharmacokinetics of insulin glulisine, and its cardiac safety (ECG) and tolerability after intravenous administration, were also determined. This was a single center, randomized, open-label, two-way crossover study in healthy male subjects (n = 16). At the treatment visits subjects received an intravenous infusion of the study drug at a rate of 0.8 mU kg (-1) . min (-1) for 2 hours. Individual baseline glucose concentrations were targeted for euglycaemia and maintained with a manual adjusted 20 % glucose solution over the clamp period of a maximum 6 hours. A glulisine-specific antibody was used to quantify glulisine concentrations by radioimmunoassay, while a non-specific insulin antibody and C-peptide based correction for endogenous insulin was used to estimate exogenous human insulin (RHI). At steady state (90 - 120 min), insulin glulisine and RHI had equivalent glucose utilization (GIR-AUC (SS), 209 [corrected] mg . kg (-1) for glulisine, 214 [corrected] mg . kg (-1) for RHI) and infusion rates (GIR (SS), 7.0 and 7.2 [corrected] mg . kg (-1) . [corrected] min (-1) . kg (-1)). Both insulins also presented equal total glucose disposal (GIR-AUC (0 - clamp end), 995 and 1050 [corrected] mg . kg (-1)) and onset of activity within 20 min. Insulin glulisine and RHI showed parallel time concentration profiles with similar distribution and elimination, but the different antibodies employed for radioimmunoassay impeded a quantitative comparison. There were no noteworthy individual or within-group changes in cardiac repolarisation parameters measured by 12-lead ECG during insulin glulisine infusion. In conclusion, insulin glulisine and RHI show similar distribution and elimination profiles and equivalent glucodynamic efficacy on a molar, unit-per-unit basis.

Adult↗
PubMed2005

Insulin glulisine, a new rapid-acting insulin analogue, displays a rapid time-action profile in obese non-diabetic subjects.

AIMS/HYPOTHESIS: This study compared the pharmacokinetics and pharmacodynamics of insulin glulisine, insulin lispro, and regular human insulin in obese subjects. METHODS: In this single-dose, randomized, double-blind, crossover euglycaemic clamp study, 18 non-diabetic subjects (mean body mass index [BMI] 34.7 kg . m (-2)) were randomized to receive subcutaneous injections of each insulin (0.3 U . kg (-1)) in pre-determined sequences. RESULTS: Insulin glulisine and insulin lispro had more rapid-acting profiles than regular human insulin. Fractional glucose infusion rate (GIR)-area under curves (AUC) of the GIR curve and maximum GIR were greater for insulin glulisine and insulin lispro versus regular human insulin. Total glucose disposal was slightly greater with insulin glulisine than with regular human insulin, and was comparable to insulin lispro, although it decreased with increasing insulin resistance (HOMA index) with all insulins. Time to 20 % (early glucose disposal) and 80 % (bulk of activity) of total GIR-AUC were shorter for insulin glulisine and insulin lispro versus regular human insulin. This was corroborated by more rapid and shorter residing pharmacokinetic profiles of insulin glulisine and insulin lispro versus regular human insulin, evidenced by shorter times to 20 % of total INS-AUC, INS-C (max) (INS-t (max)), and mean residence time. Moreover, time to 20 % of total GIR-AUC demonstrated a less rapid-acting profile for insulin lispro versus insulin glulisine, which was consistent with the slightly less rapid pharmacokinetic profile of insulin lispro. There was no significant correlation between BMI or subcutaneous fat thickness and pharmacokinetic or pharmacodynamic profiles for insulin glulisine, unlike insulin lispro and regular human insulin. CONCLUSIONS/INTERPRETATION: Insulin glulisine and insulin lispro demonstrated substantially more rapid time-action profiles than regular human insulin in obese non-diabetic subjects, which prevailed with insulin glulisine irrespective of BMI and subcutaneous fat thickness.

Adult↗
PubMed1999

Evaluation of a new type of direct digital radiography machine.

OBJECTIVE: To evaluate a recently developed low-dose, large-field, direct digital X-ray scanning system for medical use. METHOD: Radiation dose, image quality, diagnostic capability and clinical utility of the unit were compared with those of conventional radiography. RESULTS: Radiation doses ranged from 3% to 5% of conventional radiographic values, and a mean of 1 line-pair per millimetre could be detected. Ease of use, anatomical coverage and tolerance to patient motion were advantages. However, image quality was inferior to that of conventional radiographs, with limited fine detail visibility and penetration. Only 67 of 156 (42.9%) pathological features seen on conventional radiographs were detected, including 13 of 41 fractures (31.7%) and 11 of 18 pneumothoraces (61.1%). CONCLUSION: Although image quality and diagnostic performance were not ideal, potential roles in triage, foreign body detection and possibly screening were promising. Radiographic factors may have affected sensitivity. This machine demonstrated useful attributes that may, with improvement, be beneficial in the imaging of trauma and other patients.

Adolescent↗