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R Ceulemans

Publications and source records attributed to R Ceulemans.

32 records · Page 2Linked to original sources
PubMed2000

Respiration as the main determinant of carbon balance in European forests.

Carbon exchange between the terrestrial biosphere and the atmosphere is one of the key processes that need to be assessed in the context of the Kyoto Protocol. Several studies suggest that the terrestrial biosphere is gaining carbon, but these estimates are obtained primarily by indirect methods, and the factors that control terrestrial carbon exchange, its magnitude and primary locations, are under debate. Here we present data of net ecosystem carbon exchange, collected between 1996 and 1998 from 15 European forests, which confirm that many European forest ecosystems act as carbon sinks. The annual carbon balances range from an uptake of 6.6 tonnes of carbon per hectare per year to a release of nearly 1 t C ha(-1) yr(-1), with a large variability between forests. The data show a significant increase of carbon uptake with decreasing latitude, whereas the gross primary production seems to be largely independent of latitude. Our observations indicate that, in general, ecosystem respiration determines net ecosystem carbon exchange. Also, for an accurate assessment of the carbon balance in a particular forest ecosystem, remote sensing of the normalized difference vegetation index or estimates based on forest inventories may not be sufficient.

Atmosphere↗
PubMed2000

Effects of ozone exposure in open-top chambers on poplar (Populus nigra) and beech (Fagus sylvatica): a comparison.

Rooted cuttings of poplar (Populus nigra) and seedlings of beech (Fagus sylvatica) were exposed to ozone in open-top chambers for one growing season. Three treatments were applied: charcoal-filtered (CF), non-filtered (NF) and non-filtered air plus 30 ppb (nl l(-1)) ozone (NF+). Extra ozone was only added on clear days, from 09:00 until 17:00-20:00. The AOT40s (accumulated exposure over a threshold of 40 ppb), calculated from April to September were 4055 ppb.h for the NF and 8880 ppb.h for the NF+ treatments. For poplar ozone exposure caused highly significant reductions in growth rate, light-saturated net CO(2) assimilation rate, stomatal conductance, F(v)/F(m) and chlorophyll content. The largest effects were observed in August at which time ozone concentrations were elevated. A reduction was noticed in new leaf production, while accelerated ageing and visible damage to leaves caused high leaf losses. For beech the responses were similar but less pronounced: ozone exposure resulted in non-significant growth reductions, slight changes in light-saturated photosynthesis and accelerated leaf abscission. The chlorophyll content of beech leaves was not affected by the ozone treatments. The results confirmed previous observations that fast-growing tree species, such as most poplar species and hybrids, are more sensitive and responsive to tropospheric ozone than slower-growing species, such as beech. The growth reductions observed and reported here for beech were within the range of those reported in relationship to the AOT40 (accumulated exposure over a threshold of 40 ppb) critical level for ozone.

Journal Article↗
PubMed2000

Benefit of emergency haemorrhoidectomy: a comparison with results after elective operations.

OBJECTIVE: To compare the outcome of emergency and elective haemorrhoidectomy. DESIGN: Retrospective study. SETTING: Teaching hospital, Belgium. SUBJECT: 104 patients who had haemorrhoidectomy for acutely ulcerated or strangulated haemorrhoids, and 545 who had elective haemorrhoidectomy. RESULTS: Early complications (26/104, 25%), reoperation (7/104, 7%) and late anal stenosis (7/104, 7%) were more common after emergency than elective haemorrhoidectomy, for which the corresponding figures were 74/545 (3.6%), 9 (1.7%) and 1/545 (0.2%). Late outcome was similar for the two groups. CONCLUSIONS: Emergency haemorrhoidectomy is indicated for the treatment of the acute complications of haemorrhoids.

Acute Disease↗
PubMed2000

A simple method to determine leaf angles of grass species.

There are several very accurate methods to determine leaf angles in closed canopies. However, these are generally very time-consuming or require special equipment. Average canopy leaf angles were derived from simple height and blade length measurements. An exponential relationship between the height/length ratio and the average blade leaf angle was used. The method was tested for two grass species, Dactylis glomerata and Festuca arundinacea, grown under different UV-B levels. The results clearly show that the method is reasonably accurate and able to identify UV-B induced changes in leaf angle. To get these results only 50 measurements of leaf blade height and length were necessary to calculate the allometric relationship, after which 10 length and height measurements from a canopy were used to calculate the average canopy leaf angle.

Plant Leaves↗
PubMed1997

Imaging of primary tumors and tumor-like conditions of the lumbosacral osseous spine.

Primary tumors of the osseous spine are rare. This article illustrates some aspects of imaging of tumoral pathology of the osseous spine. Plain film and CT scan still remain the initial imaging modalities in the work-up of tumoral pathology of the osseous spine. MR imaging however has proven its potentials in the detection of lesions in areas with superimposing structures which hamper reliable reading of the plain films or in areas with a complex bony anatomy such as the sacrum. MR imaging is exquisite in determining the local extent of tumoral lesions and in defining the relationship to adjacent central nervous system structures. In some tumors or tumor-like lesions, MR imaging allows to make a correct tissue-related diagnosis or to strengthen the diagnosis made on plain film/CT observations. In other case MR imaging only has a role in staging or may have definitely no role at all.

Adult↗
PubMed1997

Epidermoid cyst.

Explore the source record for details and available documents.

Adult↗
PubMed1995

[Infraclinical breast carcinoma].

Early detection of breast cancer is gaining importance because it leads to reduction of morbidity and mortality rates of this disease. Detection of infraclinical tumors is best accomplished by mammography because of its high sensitivity. Ultrasonography and MR mammography play a complementary role. Ductal carcinoma in situ as well as small invasive tumors can be clinically occult malignant tumors. Preoperative marking should be performed in suspected breast lesions, preferentially by means of a hookwire or carbon. Surgical removal of the lesion is to be verified by intraoperative specimen radiography.

Adenocarcinoma↗
PubMed1993

Adamantinoma of the tibia: MRI documentation.

We report two cases of adamantinoma of the tibia, for which an MR examination was performed. Each patient was initially investigated with plain radiography and in case 2, a computerized tomography was also performed. The MR characteristics of this tumor are scarcely documented in the even few case reports of this tumor. MRI does not add to the (differential) diagnosis but does have significance in the preoperative staging because it allows adequate delineation of tumor, which is essential for a complete and curative resection of the tumor.

Adolescent↗
PubMed1991

The solitary hyperdynamic pulsating superior mesenteric artery: an additional dynamic sonographic feature of midgut volvulus.

Midgut malrotation complicated by volvulus is a surgical emergency. The diagnosis is often suspected clinically and usually confirmed by barium meal. In this case the diagnosis of malrotation with midgut volvulus is made by ultrasound. We describe the solitary hyperdynamic pulsating superior mesenteric artery as an additional dynamic sonographic feature of midgut volvulus.

Humans↗
PubMedDate not supplied

Genetic variation of the bud and leaf phenology of seventeen poplar clones in a short rotation coppice culture.

Leaf phenology of 17 poplar ( Populus spp.) clones, encompassing spring phenology, length of growth period and end-of-year phenology, was examined over several years of different rotations. The 17 poplar clones differed in their latitude of origin (45 degrees 30'N to 51 degrees N) and were studied on a short rotation experimental field plantation, situated in Boom (province of Antwerpen, Belgium; 51 degrees 05'N, 04 degrees 22'E). A similar, clear pattern of bud burst was observed during the different years of study for all clones. Clones Columbia River, Fritzi Pauley, Trichobel (Populus trichocarpa) and Balsam Spire (Populus trichocarpa x Populus balsamifera) from 45 degrees 30'N to 49 degrees N reached bud burst (expressed as day of the year or degree day sums) almost every year earlier than clones Wolterson (Populus nigra), Gaver, Gibecq and Primo (Populus deltoides x Populus nigra) (50 degrees N to 51 degrees N). This observation could not be generalised to end-of-season phenology, for which a yearly returning pattern for all clones was lacking. Late bud burst and early leaf fall of some clones (Beaupré, Boelare, IBW1, IBW2, IBW3) was brought about by increasing rust incidence during the years of observation. For these clones, the variability in leaf phenology was reflected in high coefficients of variation among years. The patterns of genetic variation in leaf phenology have implications for short rotation intensive culture forestry and management of natural populations. Moreover, the variation in phenology reported here is relevant with regard to the genetic mapping of poplar.

Genetic Variation↗
PubMedDate not supplied

Laparoscopic surgery for cancer: are we ready?

Following feasibility studies more and more large prospective reports even randomised trials document the treatment of digestive cancer using a laparoscopic approach. While the spectre of port-site recurrences, once so alarming has faded, it has become a challenge for laparoscopic surgeons to provide long-term follow-up. There is good class II and III evidence that staging laparoscopy (SL) has a value for oesophageal, gastric, pancreatic and hepatobiliary cancer as well as for intra-abdominal lymphomas since it adds to primary staging and often alters the clinical stage of the disease and hence the management of the individual patient. For minimally invasive oesophagectomy and gastric cancer surgery several series have demonstrated shorter perioperative morbidity and hospital stay however at present most studies report smaller numbers of selected patients and long term follow up is rare. The laparoscopic resection of pancreatic malignancies is not reported to be feasible, safe or potentially beneficial for the patient while the curative resection of suspected early gallbladder cancer is a poor indication. Nevertheless laparoscopy is documented to be safe and applicable for small malignant liver lesions and the Lacy trial was significantly in favour of laparoscopy-assisted colectomy, predominantly for stage III disease. Bearing in mind that in many fields of digestive cancer surgery, laparoscopy should still be conducted as part of a trial, it is safe to say that "we are ready" for this revolution to arise.

Abdominal Neoplasms↗