Electric utilities are looking for novel methods to increase the transmission capacity of existing transmission lines. The conversion of conventional AC towers to hybrid AC/DC lines allows for ...significantly more power and reduces the need for new rights of way. Still, due to the fixed geometry, there will be coupling effects between the AC and DC systems. Corona effects, such as audible noise, which are crucial for public acceptance, must be controlled to obtain crucial public acceptance. An outdoor test setup is used to investigate the corona audible noise and partial discharges of parallel AC and DC bundles. The effect of a DC bias on the AC corona as well as an AC ripple on DC corona are studied for varying surface gradients and weather conditions. The AC and DC audible noise clearly increased for most cases of a DC bias or AC ripple, respectively. The relative increase was found higher if the conductor was only slightly above corona as it happens in dry conditions with light pollution. Still, the highest level of AC audible noise was observed during wet weather and for DC during dry conditions.
In Valais, Switzerland, Scots pines (Pinus sylvestris L.) are declining, mainly following drought. To assess the impact of drought on tree growth and survival, an irrigation experiment was initiated ...in 2003 in a mature pine forest, approximately doubling the annual precipitation. Tree crown transparency (lack of foliage) and leaf area index (LAI) were annually assessed. Seven irrigated and six control trees were felled in 2006, and needles, stem discs and branches were taken for growth analysis. Irrigation in 2004 and 2005, both with below-average precipitation, increased needle size, area and mass, stem growth and, with a 1-year delay, shoot length. This led to a relative decrease in tree crown transparency (–14%) and to an increase in stand LAI (+20%). Irrigation increased needle length by 70%, shoot length by 100% and ring width by 120%, regardless of crown transparency. Crown transparency correlated positively with mean needle size, shoot length and ring width and negatively with specific leaf area. Trees with high crown transparency (low growth, short needles) experienced similar increases in needle mass and growth with irrigation than trees with low transparency (high growth, long needles), indicating that seemingly declining trees were able to ‘recover’ when water supply became sufficient. A simple drought index before and during the irrigation explained most of the variation found in the parameters for both irrigated and control trees.
Dupuytren's disease (DD) is a progressive fibromatosis that causes the formation of nodules and cords in the palmar aponeurosis leading to flexion contracture of affected fingers. The ...etiopathogenesis is multifactorial with a strong genetic predisposition. It is the most frequent genetic disorder of connective tissues. We have collected clinical data from 736 unrelated individuals with DD who underwent surgical treatment from Germany and Switzerland. We evaluated a standardised questionnaire, assessed the importance of different risk factors and compared subgroups with and without positive family history. We found that family history clearly had the strongest influence on the age at first surgery compared to environmental factors, followed by male sex. Participants with a positive family history were on average 55.9 years of age at the first surgical intervention, 5.2 years younger than probands without known family history (p = 6.7 × 10−8). The percentage of familial cases decreased with age of onset from 55% in the 40–49 years old to 17% at age 80 years or older. Further risk factors analysed were cigarettes, alcohol, diabetes, hypertension, and epilepsy. Our data pinpoint the importance of genetic susceptibility for DD, which has long been underestimated.
Global climate change is expected to increase annual temperatures and decrease summer precipitation in Central Europe. Little is known of how forests respond to the interaction of these climate ...factors and if their responses depend on soil conditions. In a 3‐year lysimeter experiment, we investigated the growth response of young mixed oak stands, on either acidic or calcareous soil, to soil water regime, air‐warming and drought treatments corresponding to an intermediate climate change scenario. The air‐warming and drought treatments were applied separately as well as in combination. The air‐warming treatment had no effect on soil water availability, evapotranspiration or stand biomass. Decreased evapotranspiration from the drought‐exposed stands led to significantly higher air and soil temperatures, which were attributed to impaired transpirational cooling. Water limitation significantly reduced the stand foliage, shoot and root biomass as droughts were severe, as shown in low leaf water potentials. Additional air warming did not enhance the drought effects on evapotranspiration and biomass, although more negative leaf water potentials were observed. After re‐watering, evapotranspiration increased within a few days to pre‐drought levels. Stands not subjected to the drought treatment produced significantly less biomass on the calcareous soil than on the acidic soil, probably due to P or Mn limitation. There was no difference in biomass and water regime between the two soils under drought conditions, indicating that nutrient availability was governed by water availability under these conditions. The results demonstrate that young oak stands can cope with severe drought and therefore can be considered for future forestry.
Seasonal trends in leaf gas exchange and ozone-induced visible foliar injury were investigated for three ozone sensitive woody plant species. Seedlings of
Populus nigra L.,
Viburnum lantana L., and
...Fraxinus excelsior L. were grown in charcoal-filtered chambers, non-filtered chambers and open plots. Injury assessments and leaf gas exchange measurements were conducted from June to October during 2002. All species developed typical ozone-induced foliar injury. For plants exposed to non-filtered air as compared to the charcoal-filtered air, mean net photosynthesis was reduced by 25%, 21%, and 18% and mean stomatal conductance was reduced by 25%, 16%, and 8% for
P. nigra,
V. lantana, and
F. excelsior, respectively. The timing and severity of the reductions in leaf gas exchange were species specific and corresponded to the onset of visible foliar injury.
Reductions in leaf gas exchange corresponded to the onset of ozone-induced visible foliar injury for seedlings exposed to ambient ozone exposures.
Canton Ticino in southern Switzerland is exposed to some of the highest concentrations of tropospheric ozone in Europe. During recent field surveys in Canton Ticino, foliar symptoms identical to ...those caused by ozone have been documented on native tree and shrub species. In Europe, the critical ozone level for forest trees has been defined at an AOT40 of 10 ppm.h O3 (10 ppm.h accumulated exposure of ozone over a threshold of 40 ppb) during daylight hours over a six-month growing season. The objective of this study was to determine the amount of ambient ozone required to induce visible foliar symptoms on various forest plant species in southern Switzerland. Species were grown within eight open-top chambers and four open plots at the Vivaio Lattecaldo Cantonal Forest Nursery in Ticino, Switzerland. Species differed significantly in terms of the ppb.h exposures needed to cause visible symptoms. The most to least symptomatic species grown within open-plots in this study rank as Prunus serotina, Salix viminalis, Vibrnum lantana, Rhamnus cathartica, Betula pendula, Rumex obtusifolius, Sambucus racemosa, Morus nigra, Prunus avium, Fraxinus excelsior, Rhamnus frangula, Alnus viridis, Fagus sylvatica and Acer pseudoplatanus. Similar rankings were obtained in the non-filtered chamber plots. The ranking of species sensitivity closely follows AOT values for the occurrence of initial symptoms and symptom progression across the remainder of the exposure season. Species that first showed evidence of foliar injury also demonstrated the most sensitivity throughout the growing season, with symptoms rapidly advancing over ca. 25-30% of the total plant leaf surfaces by the end of the observation period. Conversely, those species that developed symptoms later in the season had far less total injury to plant foliage by the end of the observation period (1.5 to < 5% total leaf area injured). The current European ambient ozone standard may be insufficient to protect native plant species from visible foliar injury, and many more native species may be sensitive to ozone-induced foliar injury than are currently known.
Current-year seedlings of beech, ash, Norway spruce and Scots pine were exposed during one growing season to different, but moderate, ozone (O(3)) scenarios representative for Switzerland (50, 85, ...100% ambient, 50% ambient+30 nl l(-1)) in open-top chambers (OTCs) and to ambient O(3) concentrations in the field. Biomass significantly decreased with increasing O(3) dose in all species except for spruce. Losses of 25.5% (ash), 17.4% (beech), 9.9% (Scots pine) were found per 10 microl l(-1) h accumulated O(3) exposure over a threshold concentration of 40 nl l(-1) during daylight hours (AOT40). Ratios of root/shoot biomass (RSR) also significantly decreased with increasing AOT40 levels in beech and ash, but not in Norway spruce and Scots pine. The data show that the deciduous species beech and ash were more susceptible to O(3) with respect to RSR and biomass than the coniferous species Norway spruce and Scots pine.
The aetiology of the carpal tunnel syndrome is unknown in most cases. Among our patients we found four with acute thrombosis occurring in a persistent median artery which led to acute carpal tunnel ...symptoms. The purpose of this study was to compare our cases with those from the literature and to show possible causes for the thrombosis. In conclusion, thrombosis of a persistent median artery as a cause of acute carpal tunnel syndrome is certainly very rare. Sudden onset of pain, local tenderness at the palm and decreased sensation in the median nerve distribution may provide clues for the diagnosis. Prior to surgery ultrasound can be performed to confirm the diagnosis.
Visible ozone-induced foliar injury on native forest species of Switzerland was identified and confirmed under ambient OTC-conditions and related to the current European AOT40 standard.
The ...objectives of this study were to examine the foliar sensitivity to ozone exposure of 12 tree, shrub, and herbaceous species native to southern Switzerland and determine the seasonal cumulative ozone exposures required to induce visible foliar injury. The study was conducted from the beginning of May through the end of August during 2000 and 2001 using an open-top chamber research facility located within the Lattecaldo Cantonal Forest Nursery in Canton Ticino, southern Switzerland (600 m asl). Plants were examined daily and dates of initial foliar injury were recorded in order to determine the cumulative AOT40 ppb h ozone exposure required to cause visible foliar injury. Plant responses to ozone varied significantly among species; 11 species exhibited visible symptoms typical of exposures to ambient ozone. The symptomatic species (from most to least sensitive) were
Populus nigra, Viburnum lantana, Salix alba, Crataegus monogyna, Viburnum opulus, Tilia platyphyllos, Cornus alba, Prunus avium, Fraxinus excelsior, Ribes alpinum, and
Tilia cordata;
Clematis spp. did not show foliar symptoms. Of the 11 symptomatic species, five showed initial injury below the critical level AOT40 10 ppmh O
3 in the 2001 season.
Studies were conducted during the period 1993–1996 to determine the extent of foliar injury on native plant species and black cherry as may be induced by ambient ozone exposures throughout ...Switzerland. Particular emphasis was placed on determining foliar injury in Canton Ticino (Ti.) situated in the sub-Alpine region of southern Switzerland. Surveys revealed black cherry to be very sensitive exhibiting an adaxial foliar stipple and leaf reddening at higher elevation plots in the southern-most parts of Ti. Open-top chamber investigations confirmed the foliar response as being due to ambient ozone. Surveys of natural vegetation in proximity to air quality monitoring stations throughout the whole of Switzerland revealed many native plants symptomatic with ozone-like foliar injury. Fumigation studies within CSTR chambers are being used to determine ozone-induced exposure/response relationships. Of the species thus far tested,
Viburnum lantana, Morus nigra, Betula pendula, Rumex acetosa and
Prunus serotina appear most sensitive.
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