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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Variation in stomatal conductance is typically explained in relation to environmental conditions. However, tree height may also contribute to the variability in mean stomatal conductance. Mean canopy stomatal conductance of individual tree crowns (GSi) was estimated using sap flux measurements in Fagus sylvatica L., and the hypothesis that GSi decreases with tree height was tested. Over 13 d of the growing season during which soil moisture was not limiting, GSi decreased linearly with the natural logarithm of vapour pressure deficit (D), and increased exponentially to saturation with photosynthetic photon flux density (Qo). Under conditions of D= 1 kPa and saturating Qo, GSi decreased by approximately 60% with 30 m increase in tree height. Over the same range in height, sapwood-to-leaf area ratio (AS:AL) doubled. A simple hydraulic model explained the variation in GSi based on an inverse relationship with height, and a linear relationship with AS:AL. Thus, in F. sylvatica, adjustments in AS:AL partially compensate for the negative effect of increased flow-path length on leaf conductance. Furthermore, because stomata with low conductance are less sensitive to D, gas exchange of tall trees is reduced less by high D. Despite these compensations, decreasing hydraulic conductance with tree height in F. sylvatica reduces carbon uptake through a corresponding decrease in stomatal conductance.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Responses of stomatal conductance (gs) to increasing vapour pressure deficit (D) generally follow an exponential decrease described equally well by several empirical functions. However, the magnitude of the decrease – the stomatal sensitivity – varies considerably both within and between species. Here we analysed data from a variety of sources employing both porometric and sap flux estimates of gs to evaluate the hypothesis that stomatal sensitivity is proportional to the magnitude of gs at low D (≤ 1 kPa). To test this relationship we used the function gs=gsref–m· lnD where m is the stomatal sensitivity and gsref=gs at D= 1 kPa. Regardless of species or methodology, m was highly correlated with gsref (average r2= 0·75) with a slope of approximately 0·6. We demonstrate that this empirical slope is consistent with the theoretical slope derived from a simple hydraulic model that assumes stomatal regulation of leaf water potential. The theoretical slope is robust to deviations from underlying assumptions and variation in model parameters. The relationships within and among species are close to theoretical predictions, regardless of whether the analysis is based on porometric measurements of gs in relation to leaf-surface D (Ds), or on sap flux-based stomatal conductance of whole trees (GSi), or stand-level stomatal conductance (GS) in relation to D. Thus, individuals, species, and stands with high stomatal conductance at low D show a greater sensitivity to D, as required by the role of stomata in regulating leaf water potential.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1569-8041
    Keywords: neuroblastoma ; prognosis ; telomerase activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Treatment of neuroblastoma has remained a major challenge in pediatric oncology because the assessment of the individual prognosis, particularly in disseminated disease is still obscure. Previous studies have correlated clinical outcome with activity levels of telomerase, a cellular reverse transcriptase which has been detected in the majority of human malignant tumors. Patients and methods: In this blind-trial study, a non-radioactive telomeric repeat amplification protocol (TRAP) with an internal telomerase-assay standard was used on an automated laser fluorescence sequencer for the detection and semiquantitative analysis of telomerase activity (TA) in 67 neuroblastomas of all clinical stages from the German Neuroblastoma Trial and 2 ganglioneuromas. TA levels were correlated with event-free and overall survival rates and established prognostic markers such as MYCN. Results: TA was present in 14 of 69 (20%) samples, including 3 of 22 stage IVS, 8 of 14 stage IV, 1 of 10 stage III, 1 of 7 stage II and 1 of 14 stage I neuroblastomas and 0 of 2 ganglioneuromas. We found a strong statistical correlation between the presence of TA and poor clinical prognosis with regard to all tumor stages. Multivariate analysis revealed TA as an independent prognostic marker. In particular, the analysis of TA in IVS neuroblastomas distinguished two different prognostic groups. Conclusions: Our data suggest that TA is an independent prognostic marker in neuroblastoma which, in combination with other markers such as MYCN, may proof useful in assessing the individual patient's prognosis.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 61 (1995), S. 249-251 
    ISSN: 1432-0649
    Keywords: 42.68 ; 42.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The combination of remote sensing methods like Doppler lidar and FTIR offers the possibility to determine mass fluxes of gases remotely. Doppler lidar measures the three-dimensional wind vector in the vicinity of diffuse sources or the velocity of air in a chimney plume if an industrial complex is monitored. FTIR is a multi-component remote sensing method for gas concentrations. The Fourier transformation of an interferogram of a Michelson interferometer within a FTIR system converts the recorded intensity (function of optical path length) to a spectral signal (function of wavenumber). Both information, velocity and concentration, give the mass fluxes of the tracer (gas). A first test was performed at Munich-North power station with FTIR and cw-Doppler lidar. Fluxes of CO2, CO, NO, and HC1 were determined. The results are in good agreement with the fluxes measured by in-situ instruments of the power station. The method can be used to control industrial complexes from an outside observation site.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 68 (1999), S. 321-324 
    ISSN: 1432-0630
    Keywords: PACS: 42.70; 66.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: 3 by diffusion doping is investigated by means of secondary neutral mass spectrometry and secondary ion mass spectrometry. The diffusion of praseodymium in LiNbO3 can be described by Fick’s laws of diffusion with a concentration-independent diffusion coefficient and a limited solubility of praseodymium in LiNbO3 increasing exponentially with rising temperature. The diffusion depends on the Li2O content of the LiNbO3 crystal. For LiNbO3 crystals with a nominal slight difference in the congruent composition, the diffusion constants and activation energies for Z-cut LiNbO3 are 3.28×10-5 cm2/s and 2.27 eV, and 1.39×10-5 cm2/s and 2.24 eV, respectively. Titanium-doped waveguides are formed in Pr:LiNbO3 and characterised in relation to waveguide loss and absorption in the visible and near infrared.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1437-9813
    Keywords: Key words Mechanical ileus ; Small-bowel atresia ; Meconium ileus ; Intestinal feeding ; Short-bowel syndrome ; Extracorporeal stool transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Between May 1994 and June 1995, nine newborns underwent surgery due to mechanical ileus or intrauterine perforation of the small bowel. Three were very-low-birth-weight infants weighing between 520 and 1,200 g. Surgery was performed in the first 2 days of life and split ileo- or jejunostomas were implanted. Early oral nutrition was initiated. To avoid non-use of the distal bowel and short-bowel syndrome, the aboral stoma was irrigated a few days later with the proximal feces. A new technique was applied to transport the chyle continuously from the oral to the aboral stoma: the stool was collected in an especially constructed stoma bag and transported distally by a roller pump. No major complications were seen. The general outcome was excellent in all cases, and reanastomosis under optimal bowel conditions was achieved in all patients without further problems.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1437-9813
    Keywords: Mechanical ileus ; Smallbowel atresia ; Meconium ileus ; Intestinal feeding ; Short-bowel syndrome ; Extracorporeal stool transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Between May 1994 and June 1995, nine newborns underwent surgery due to mechanical ileus or intrauterine perforation of the small bowel. Three were very-low-birth-weight infants weighing between 520 and 1,200 g. Surgery was performed in the first 2 days of life and split ileo- or jejunostomas were implanted. Early oral nutrition was initiated. To avoid non-use of the distal bowel and shortbowel syndrome, the aboral stoma was irrigated a few days later with the proximal feces. A new technique was applied to transport the chyle continuously from the oral to the aboral stoma: the stool was collected in an especially constructed stoma bag and transported distally by a roller pump. No major complications were seen. The general outcome was excellent in all cases, and reanastomosis under optimal bowel conditions was achieved in all patients without further problems.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0827
    Keywords: Key words: Apolipoprotein E — Genetic — Bone fracture — Hemodialysis — Vitamin K.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. This investigation of 219 hemodialysis patients relates the history and prospective risk of bone fractures to apolipoprotein E (apoE) genotype. A greater percentage of the 41 patients with the E3/4 and E4/4 genotypes than of the 38 patients with the E2/3 and E2/2 genotypes had a history of bone fractures at the time of recruitment (44% versus 16%, P 〈 0.005). During the 4 years following recruitment, more of the patients with apoE genotypes E3/4 and E4/4 than with apoE genotypes E2/3 and E2/2 suffered bone fractures, but this difference was not statistically significant (17.1 versus 5.3%, P 〈 0.1). ApoE genotype appears to be an important genetic risk factor for bone fracture, possibly due to its previously reported influence on vitamin K concentrations in blood.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1106
    Keywords: Key words Neurotrophic factor ; Growth factor ; GDNF ; Neurite outgrowth ; Postnatal development ; Enteric nervous system ; Myenteric plexus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Glial cell-line-derived neurotrophic factor (GDNF), a member of the transforming growth-factor- (TGF-) β-family, is an essential factor for the development of the enteric nervous system (ENS) during embryogenesis. In the present study, the effects of GDNF on postnatal ENS development were investigated using cultures of myenteric plexus from the small intestine of newborn albino rats of different developmental phases (P1, P7, P14). Myenteric plexus was dissociated and cultivated as mixed cultures of enteric neurons and glial cells. After seeding, the cultures were kept for 24 h or 7 days in serum-free medium containing various doses (1, 10, 100 ng/ml) of GDNF. The effect of the neurotrophic factor was evaluated using parameters such as cell size, neuronal survival, or neurite elongation. While neither glial-cell nor neuronal size was influenced by GDNF, there was an observable effect upon neuronal survival and neurite elongation. The cultures treated with GDNF displayed increased neurite outgrowth. The promoting effect was dose- and age-dependent, decreasing clearly during the early postnatal period. Already after 24 h, neuronal survival was increased in P1 and P7, but not in P14 cultures. In long-term cultures, a marked tendency to form cell aggregates and dense fiber networks was observed when treated with GDNF. These observations suggest that GDNF plays an important role not only in pre-, but also in postnatal development of the enteric nervous system.
    Type of Medium: Electronic Resource
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