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Biomedical subjects

P Coppin

Publications and source records attributed to P Coppin.

11 recordsLinked to original sources
PubMed2005

Allometry and evaluation of in situ optical LAI determination in Scots pine: a case study in Belgium.

We evaluated several optical methods for in situ estimation of leaf area index (LAI) in a Belgian Scots pine (Pinus sylvestris L.) stand. The results obtained were compared with LAI determined from allometric relationships established in the same stand. We found high correlations between branch cross-sectional area, diameter at breast height (DBH) and basal area as dependent variables, and leaf mass, needle area and crown projection as independent variables. We then compared LAI estimated by allometry with LAI determined by three optical methods (LAI-2000, TRAC and digital hemispherical photography) both before and after corrections for blue light scattering, clumping and non-leafy material. Estimates of stand LAI of Scots pine ranged from 1.52 for hemispherical photography to 3.57 for the allometric estimate based on DBH. There was no significant difference (alpha = 0.01) between the allometric LAI estimates and the optical LAI values corrected for blue light scattering, clumping and interception by non-leafy material. However, we observed high sensitivity of the optical LAI estimates to the various conversion factors, particularly to the clumping factor, indicating the need for caution when correcting LAI measured by optical methods.

Belgium↗
PubMed2001

Geographical and genetic distances among zooplankton populations in a set of interconnected ponds: a plea for using GIS modelling of the effective geographical distance.

In systems of interconnected ponds or lakes, the dispersal of zooplankton may be mediated by the active population component, with rivulets and overflows functioning as dispersal pathways. Using a landscape-based approach, we modelled the effective geographical distance among a set of interconnected ponds (De Maten, Genk, Belgium) in a Geographic Information System (GIS) environment. The first model (the Landscape Model; LM) corrects for the presence of direct connections among ponds and was based on the existing landscape structure (i.e. network of connecting elements among ponds, travelling distance and direction of the current). A second model (the Flow Rate Model; FRM) also incorporated field data on flow rates in the connecting elements as the driving force for the passive dispersal of the active zooplankton population component. Finally, the third model (the Dispersal Rate Model; DRM) incorporated field data on zooplankton dispersal rates. An analysis of the pattern of genetic differentiation among Daphnia ambigua populations inhabiting 10 ponds in the pond complex reveals that the effective geographical distance as modelled by the flow rate and the dispersal rate model provide a better approximation of the true rates of genetic exchange among populations than mere Euclidean geographical distances or the landscape model that takes into account solely the presence of physical connections.

Alleles↗
PubMed1988

A possible misdiagnosis in patients presenting with acute HBsAg-negative hepatitis: the role of hepatitis delta virus.

We describe here two cases of delta hepatitis (a coinfection and a superinfection) presenting as acute HBsAg-negative hepatitis. The first patient, a parenteral drug abuser, had a biphasic course of the disease, with HBsAg detectable transiently only during the relapse. Testing for delta markers on stored sera gave evidence of HBV/HDV coinfection. The other patient, a hospital nurse, chronic asymptomatic carrier of HBsAg, developed fulminant hepatitis with the transient appearance of antibody to HBsAg. She survived massive liver necrosis, and serological analysis of HDV markers documented a hepatitis delta virus superinfection. These cases demonstrate the possible substantial repression of HBV gene products exerted by the replication of delta virus, with a likely misdiagnosis if delta markers are not determined in serial serum samples.

Acute Disease↗