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T Holst

Publications and source records attributed to T Holst.

11 recordsLinked to original sources
PubMed2005

Net radiation balance for two forested slopes on opposite sides of a valley.

Measurements of the net radiation balance of two forested sites on the opposite slopes of a valley in south-western Germany, made over 3 years, are presented in this study. Radiation sensors were mounted horizontally on two measurement towers above two beech stands. The direct part of the measured short-wave incoming radiation was adjusted according to the slope's angle to convert horizontally measured radiation data into surface-parallel radiation fluxes. During periods when contemporaneous measurements of slope-parallel and horizontal radiation fluxes were available, the calculation of surface-parallel radiation fluxes from the horizontally recorded net radiation components were compared with measured values. The net radiative fluxes parallel to the slopes were calculated for a period of 36 months and analysed. Results show that the different aspects of both sites cause significant differences of the net radiation balance. In June, when the elevation of the sun is highest, incoming solar radiation K downward arrow received on the NE-slope was 9% lower than K downward arrow received on the SW-slope. During the winter months, the differences were much greater and incoming solar radiation to the NE-slope was 50% of that to the SW-slope. Due to the differing solar irradiance, net radiation fluxes were significantly higher on the SW-slope than on the NE-slope. For long-wave radiation only small differences between both slopes could be found. Since radiative fluxes determine the energy balance and hence the microclimate and water balance of a forest stand, these differences in the net radiation balance between the slopes are important for the vegetation.

Altitude↗
PubMed2004

Measuring and modelling plant area index in beech stands.

For some beech ( Fagus sylvatica L.) stands with different stand densities the plant area index (PAI) was measured by means of a Licor LAI-2000 plant canopy analyser. The stands are located on the slopes of a valley in south-west Germany and had been treated by different types of silvicultural management (heavy shelterwood felling, light shelterwood felling, control plot). The analyser was used (a) to investigate the light conditions on plots of the same thinning regime, (b) to quantify the differences between the different treatments and (c) to obtain absolute values of PAI for interdisciplinary research. PAI was measured at three different phenological stages (leafless, leaf-unfolding and fully leafed season in 2000) and was found to be about 5.2 for the fully developed canopy on the control plots, 3.2 on the light fellings and about 2.0 for the heavy fellings. In the leafless period PAI was between 1.1 (control) and 0.4 (heavy felling). Measurements made in summer 2000 and summer 2002 were compared, and showed an increase of PAI, especially on the thinned plots. Measurements of photosynthetically active radiation (PAR) above and below the canopy in combination with measured PAI were used to apply Beer's Law of radiation extinction to calculate the extinction coefficient k for different sky conditions and for the different growing seasons on the control plots. The extinction coefficient k for the beech stands was found to be between 0.99 and 1.39 in the leafless period, 0.62 to 0.91 during leaf unfolding and between 0.68 and 0.83 in the fully leafed period. Using PAR measurements and the k values obtained, the annual cycle of PAI was modelled inverting Beer's Law.

Environmental Monitoring↗
PubMed2001

Mineralisation studies of 14C-labelled metsulfuron-methyl, tribenuron-methyl, chlorsulfuron and thifensulfuron-methyl in one Danish soil and groundwater sediment profile.

Bacterial mineralisation of four sulfonylurea herbicides at 20 microg kg(-1) in a sandy soil from nine different depths in a sandy soil horizon (5-780 cm) was investigated in laboratory studies. Metsulfuron-methyl, chlorsulfuron, and tribenuron-methyl were 14C-labelled in the sulfonamide ring, while thifensulfuron-methyl was labelled in the thiophene ring. The highest mineralised amount in 126 days was observed for metsulfuron-methyl (40%) followed by tribenuron-methyl (25%), and thifensulfuron-methyl (11%). Chlorsulfuron showed low mineralisation in all the soils tested (<4%). Mineralisation of the herbicides metsulfuron-methyl and tribenuron-methyl varied according to soil depth (upper profile: 5-70 cm, and lower profile: 165-780 cm) and were proven faster in soil taken from depths 5-7 and 30-35 cm, and slower in depths 45-50 and 70-75 cm. Mineralisation was absent in the lower profile (165-780 cm). As an indicator of microbial activity bacterial counts were taken at the experimental start; these counts grouped in three levels: highest in the surface layer (5-7 cm), slightly lower in the depths 30-75 cm, and lowest in the lower profile (165-780 cm). Residual concentrations of metsulfuron-methyl correlated to the accumulated amount mineralised, with high residual concentrations in soil showing low mineralisation. Also chlorsulfuron showed high residual concentrations with increasing depth in the upper profile, but the relatively high dissipation at 30-35 cm and lower one at 45-50 cm could not be related with the lack of mineralisation. This shows that hydrolysis occurs, but mineralisation of the chloro-substituted sulfonamide is restricted. Tribenuron-methyl and thifensulfuron-methyl could not be detected due to interference with other compounds.

Arylsulfonates↗
PubMed1998

Endoscopic therapy of a pancreatic effusion caused by chronic pancreatitis.

A 36-year-old patient was hospitalized because of an extensive right pleural effusion. He complained of increasing dyspnea, moderate weight loss and night sweats. The pleural aspirate was hemorrhagic and, surprisingly, excessively elevated lipase activity (57,000 U/L) was measured. An ultrasound examination of the epigastric area revealed several cystic structures in the upper retroperitoneum, and CT scan additionally showed diffuse pancreatic calculi. After conservative treatment had failed, ERCP was performed. A pseudocyst and the indistinct outline of a stenosis of the pancreatic duct could be seen. A few fragments of calculi were removed and a pancreatic duct stent was positioned. Because of stent occlusion ERCP was repeated and some more calculi were extracted, after which the pleural effusion and the pseudocysts completely regressed. In cases of pleural effusion on unclear etiology, a pancreatic pleural effusion should be included in the differential diagnosis. In patients with this clinical picture ERCP can provide not only diagnostic information, but also opportunities for new modes of treatment.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1995

Categorising [s], [integral of] and intermediate electropalatographic patterns: neural networks and other approaches.

We consider two approaches to the interpretation of EPG data, using materials designed for the investigation of [s]-[integral of] assimilations across word boundaries, as in boss Shep. A contact index is based on electrode contact in different row groups, whereas a neural network is used to determine patterns of contact. Both approaches are speaker sensitive, reflecting the wide variation in [s] and [integral of] articulation between speakers. The advantage of the neural net analysis is that the investigator need not make any assumptions about the relative value of specific electrodes or groups of electrodes. We found that the 'hand-selected' index, in general, modelled linguopalatal movement for all degrees of [s]-[integral of] assimilation better than the neural net. However, the neural net very successfully characterised stable /s/ and /integral of/ and has the potential to give an accurate representation of intermediate assimilatory cases, if trained on a more varied input set than the rather limited one used in this experiment.

Electrodiagnosis↗
PubMed1994

Detection of atrial fusion systole in patients with dual chamber pacemakers by 24-hour esophagus ECG.

We performed ambulatory 24-hour esophagus ECG in nine patients with dual chamber pacemakers suspect of transient arrhythmias in order to achieve correct and reliable P wave identification during daily life activities. In all patients episodes were observed with varying atrial artifact to left atrial depolarization sequences. These episodes probably reflected presence of atrial fusion systole, an ECG phenomenon which should be taken into account when analyzing ambulatory esophagus ECG. Thus, the ambulatory esophagus ECG revealed its ability to detect spontaneous atrial depolarization in the presence of pacemaker artifact in patients with DDD(R) pacemakers.

Activities of Daily Living↗