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Search Results: 1 - 10 of 555223 matches for " K?hler A "
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First report of Elasmus polistis Burks (Hymenoptera: Eulophidae) recovered from Polistes versicolor (Olivier) (Hymenoptera: Vespidae) nests in Brazil
Dorfey, C;Khler, A;
Neotropical Entomology , 2011, DOI: 10.1590/S1519-566X2011000400019
Abstract: the first record of elasmus polistis burks in polistes versicolor (olivier) nests in the rio grande do sul state and in brazil is provided. a total of 173 specimens of p. versicolor and 790 specimens of e.polistis were collected from two nests from gramado and santa cruz do sul, rs, brazil.
Towards ground-truthing of spaceborne estimates of above-ground life biomass and leaf area index in tropical rain forests
P. K hler,A. Huth
Biogeosciences (BG) & Discussions (BGD) , 2010,
Abstract: The canopy height h of forests is a key variable which can be obtained using air- or spaceborne remote sensing techniques such as radar interferometry or LIDAR. If new allometric relationships between canopy height and the biomass stored in the vegetation can be established this would offer the possibility for a global monitoring of the above-ground carbon content on land. In the absence of adequate field data we use simulation results of a tropical rain forest growth model to propose what degree of information might be generated from canopy height and thus to enable ground-truthing of potential future satellite observations. We here analyse the correlation between canopy height in a tropical rain forest with other structural characteristics, such as above-ground life biomass (AGB) (and thus carbon content of vegetation) and leaf area index (LAI) and identify how correlation and uncertainty vary for two different spatial scales. The process-based forest growth model FORMIND2.0 was applied to simulate (a) undisturbed forest growth and (b) a wide range of possible disturbance regimes typically for local tree logging conditions for a tropical rain forest site on Borneo (Sabah, Malaysia) in South-East Asia. In both undisturbed and disturbed forests AGB can be expressed as a power-law function of canopy height h (AGB = a · hb) with an r2 ~ 60% if data are analysed in a spatial resolution of 20 m × 20 m (0.04 ha, also called plot size). The correlation coefficient of the regression is becoming significant better in the disturbed forest sites (r2 = 91%) if data are analysed hectare wide. There seems to exist no functional dependency between LAI and canopy height, but there is also a linear correlation (r2 ~ 60%) between AGB and the area fraction of gaps in which the canopy is highly disturbed. A reasonable agreement of our results with observations is obtained from a comparison of the simulations with permanent sampling plot (PSP) data from the same region and with the large-scale forest inventory in Lambir. We conclude that the spaceborne remote sensing techniques such as LIDAR and radar interferometry have the potential to quantify the carbon contained in the vegetation, although this calculation contains due to the heterogeneity of the forest landscape structural uncertainties which restrict future applications to spatial averages of about one hectare in size. The uncertainties in AGB for a given canopy height are here 20–40% (95% confidence level) corresponding to a standard deviation of less than ± 10%. This uncertainty on the 1 ha-scale is much smaller than in the analysis of 0.04 ha-scale data. At this small scale (0.04 ha) AGB can only be calculated out of canopy height with an uncertainty which is at least of the magnitude of the signal itself due to the natural spatial heterogeneity of these forests.
Towards ground-truthing of spaceborne estimates of above-ground biomass and leaf area index in tropical rain forests
P. Khler,A. Huth
Biogeosciences Discussions , 2010, DOI: 10.5194/bgd-7-3227-2010
Abstract: The canopy height of forests is a key variable which can be obtained using air- or spaceborne remote sensing techniques such as radar interferometry or lidar. If new allometric relationships between canopy height and the biomass stored in the vegetation can be established this would offer the possibility for a global monitoring of the above-ground carbon content on land. In the absence of adequate field data we use simulation results of a tropical rain forest growth model to propose what degree of information might be generated from canopy height and thus to enable ground-truthing of potential future satellite observations. We here analyse the correlation between canopy height in a tropical rain forest with other structural characteristics, such as above-ground biomass (AGB) (and thus carbon content of vegetation) and leaf area index (LAI). The process-based forest growth model FORMIND2.0 was applied to simulate (a) undisturbed forest growth and (b) a wide range of possible disturbance regimes typically for local tree logging conditions for a tropical rain forest site on Borneo (Sabah, Malaysia) in South-East Asia. It is found that for undisturbed forest and a variety of disturbed forests situations AGB can be expressed as a power-law function of canopy height h (AGB=a·hb) with an r2~60% for a spatial resolution of 20 m×20 m (0.04 ha, also called plot size). The regression is becoming significant better for the hectare wide analysis of the disturbed forest sites (r2=91%). There seems to exist no functional dependency between LAI and canopy height, but there is also a linear correlation (r2~60%) between AGB and the area fraction in which the canopy is highly disturbed. A reasonable agreement of our results with observations is obtained from a comparison of the simulations with permanent sampling plot data from the same region and with the large-scale forest inventory in Lambir. We conclude that the spaceborne remote sensing techniques have the potential to quantify the carbon contained in the vegetation, although this calculation contains due to the heterogeneity of the forest landscape structural uncertainties which restrict future applications to spatial averages of about one hectare in size. The uncertainties in AGB for a given canopy height are here 20–40% (95% confidence level) corresponding to a standard deviation of less than ±10%. This uncertainty on the 1 ha-scale is much smaller than in the analysis of 0.04 ha-scale data. At this small scale (0.04 ha) AGB can only be calculated out of canopy height with an uncertainty which is at least of the m
Dielectric and conductivity relaxation in mixtures of glycerol with LiCl
M. Khler,P. Lunkenheimer,A. Loidl
Physics , 2008, DOI: 10.1140/epje/i2008-10357-8
Abstract: We report a thorough dielectric characterization of the alpha relaxation of glass forming glycerol with varying additions of LiCl. Nine salt concentrations from 0.1 - 20 mol% are investigated in a frequency range of 20 Hz - 3 GHz and analyzed in the dielectric loss and modulus representation. Information on the dc conductivity, the dielectric relaxation time (from the loss) and the conductivity relaxation time (from the modulus) is provided. Overall, with increasing ion concentration, a transition from reorientationally to translationally dominated behavior is observed and the translational ion dynamics and the dipolar reorientational dynamics become successively coupled. This gives rise to the prospect that by adding ions to dipolar glass formers, dielectric spectroscopy may directly couple to the translational degrees of freedom determining the glass transition, even in frequency regimes where usually strong decoupling is observed.
A hidden reservoir of Fe/FeS in interstellar silicates?
M. Khler,A. Jones,N. Ysard
Physics , 2014, DOI: 10.1051/0004-6361/201423985
Abstract: The depletion of iron and sulphur into dust in the interstellar medium and the exact nature of interstellar amorphous silicate grains is still an open question. We study the incorporation of iron and sulphur into amorphous silicates of olivine- and pyroxene-type and their effects on the dust spectroscopy and thermal emission. We used the Maxwell-Garnett effective-medium theory to construct the optical constants for a mixture of silicates, metallic iron, and iron sulphide. We also studied the effects of iron and iron sulphide in aggregate grains. Iron sulphide inclusions within amorphous silicates that contain iron metal inclusions shows no strong differences in the optical properties of the grains. A mix of amorphous olivine- and pyroxene-type silicate broadens the silicate features. An amorphous carbon mantle with a thickness of 10 nm on the silicate grains leads to an increase in absorption on the short-wavelength side of the 10 $\mu$m silicate band. The assumption of amorphous olivine-type and pyroxene-type silicates and a 10 nm thick amorphous carbon mantle better matches the interstellar silicate band profiles. Including iron nano-particles leads to an increase in the mid-IR extinction, while up to 5 ppm of sulphur can be incorporated as Fe/FeS nano inclusions into silicate grains without leaving a significant trace of its presence.
Relaxation of curvature induced elastic stress by the Asaro-Tiller-Grinfeld instability
C. Khler,R. Backofen,A. Voigt
Physics , 2015, DOI: 10.1209/0295-5075/111/48006
Abstract: A two-dimensional crystal on the surface of a sphere experiences elastic stress due to the incompatibility of the crystal axes and the curvature. A common mechanism to relax elastic stress is the Asaro-Tiller-Grinfeld (ATG) instability. With a combined numerical and analytical approach we demonstrate, that also curvature induced stress in surface crystals can be relaxed by the long wave length ATG instability. The numerical results are obtained using a surface phase-field crystal (PFC) model, from which we determine the characteristic wave numbers of the ATG instability for various surface coverages corresponding to different curvature induced compressions. The results are compared with an analytic expression for the characteristic wave number, obtained from a continuum approach which accounts for hexagonal crystals and intrinsic PFC symmetries. We find our numerical results in accordance with the analytical predictions.
Nuclear Saturation and Correlations
H. S. Khler,S. A. Moszkowski
Physics , 2007,
Abstract: The relation between nuclear saturation and NN-correlations is examined. Nucleons bound in a nucleus have a reduced effective mass due to the mean field. This results in off-energy-shell scatterings modifying the free-space NN-interaction by a dispersion correction. This is a major contribution to the density-dependence of the effective in-medium force and to saturation. Low-momentum effective interactions have been derived by renormalisation methods whereby correlations may be reduced by effectively cutting off high momentum components of the interaction. The effect of these cut-offs on dispersive corrections and on saturation is the main focus of this paper. The role of the tensor-force, its strength and its effect on correlations is of particular interest. The importance of the definition of the mean field in determining saturation as well as compressibility is also pointed out. With a cut-off below $\sim 2.6 fm^{-1}$ there is no saturation but at lower density the binding energy is still well approximated suggesting that such a force may be useful in nuclear structure calculations of (small) finite nuclei if saturation is not an issue. A separable interaction that fits experimental phase-shifts exactly by inverse scattering methods is used. Recent experiments measure short ranged correlations (SRC's) to be 0.23 for $^{56}Fe$. Other experiments have obtained a depletion of occupation-numbers in $^{208}Pb$ to be $\sim 0.2$. For nuclear matter with the separable interaction and a continuous spectrum we obtain the related quantity $\kappa$ to be 0.175 with the Bonn-B deuteron parameters, while Machleidt's gets $\kappa= 0.125$ for the Bonn-B potential and a continuous spectrum.
Aerosol-cloud-precipitation effects over Germany as simulated by a convective-scale numerical weather prediction model
A. Seifert, C. K hler,K. D. Beheng
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: Possible aerosol-cloud-precipitation effects over Germany are investigated using the COSMO model in a convection-permitting configuration close to the operational COSMO-DE. Aerosol effects on clouds and precipitation are modeled by using an advanced two-moment microphysical parameterization taking into account aerosol assumptions for cloud condensation nuclei (CCN) as well as ice nuclei (IN). Simulations of three summer seasons have been performed with various aerosol assumptions, and are analysed regarding surface precipitation, cloud properties, and the indirect aerosol effect on near-surface temperature. We find that the CCN and IN assumptions have a strong effect on cloud properties, like condensate amounts of cloud water, snow and rain as well as on the glaciation of the clouds, but the effects on surface precipitation are – when averaged over space and time – small. This robustness can only be understood by the combined action of microphysical and dynamical processes. On one hand, this shows that clouds can be interpreted as a buffered system where significant changes to environmental parameters, like aerosols, have little effect on the resulting surface precipitation. On the other hand, this buffering is not active for the radiative effects of clouds, and the changes in cloud properties due to aerosol perturbations may have a significant effect on radiation and near-surface temperature.
Long cold winters give higher stream water dissolved organic carbon (DOC) concentrations during snowmelt
A. ?gren,M. Haei,S. Khler,K. Bishop
Biogeosciences Discussions , 2010, DOI: 10.5194/bgd-7-4857-2010
Abstract: We show that long cold winters enhanced the stream water dissolved organic carbon (DOC) concentrations during the following spring flood. Using a 15 year stream record from a boreal catchment, we demonstrate that the interannual variation in DOC concentrations during spring flood was related to the discharge, and winter climate. That discharge is important for DOC concentration agrees with previous studies. By controlling for discharge we could detect that the winter climatic conditions during the preceding winter affected the soil water DOC concentrations, which in turn affected the concentrations in the stream. The results from the stream time-series were also supported by a riparian soil frost experiment, which showed that a long period of soil frost promoted high DOC concentrations in the soil water.
Machbarkeit und Effizienz einer extramuralen Nachsorge von Patienten mit dekompensierter Herzinsuffizienz - das Tiroler Modell
P?lzl G,Metzler B,Khler A,Schindelwig K
Journal für Kardiologie , 2007,
Abstract: Dekompensierte Herzinsuffizienz ist die h ufigste Ursache für station re Behandlung bei lteren Patienten. Die Wiederaufnahmerate innerhalb der ersten Monate betr gt bis zu 50 %. Durch ein umfassendes Patientenmanagement kann die Zahl der Krankenhauswiederaufnahmen reduziert werden. In der vorliegenden Pilotstudie sollen neben Machbarkeit und Effizienz auch die konomischen Konsequenzen einer auf den Gro raum Innsbruck zugeschnittenen Ambulanz-basierten Heimbetreuung von lteren Patienten mit Herzinsuffizienz (HI) durch speziell geschultes Pflegepersonal untersucht werden. Von Juli bis September 2003 wurden 17 Patienten, die wegen dekompensierter HI an der Universit tsklinik Innsbruck station r behandelt wurden, in die Studie eingeschlossen. Nach intensiver Schulung durch speziell ausgebildete "HI-Schwestern" und Therapieoptimierung in der HI-Ambulanz wurden acht Patienten einer Interventionsgruppe und neun Patienten einer Kontrollgruppe randomisiert zugeordnet. Patienten der Interventionsgruppe wurden nach der Entlassung und in weiterer Folge in variablen Abst nden von der "HI-Schwester" zu Hause besucht und die Therapie in Absprache mit der HI-Ambulanz angepa t. Patienten der Kontrollgruppe wurden dem niedergelassenen Arzt zur weiteren Betreuung zugewiesen. Die Wiederaufnahmerate innerhalb von sechs Monaten betrug in der Interventionsgruppe 37 %, in der Kontrollgruppe 78 % (p 0,05). Die Zeit bis zur Wiederaufnahme (127 ± 24 vs. 84 ± 23 Tage) war in der Interventionsgruppe tendenziell l nger als in der Kontrollgruppe. Ebenso zeigte sich in der Interventionsgruppe nach sechs Monaten ein Trend zu einer verbesserten neurohumoralen Therapie. Die Reduktion der Krankenhauswiederaufnahmen ist nach Abzug der Kosten für die HI-Schwester mit einer Kosteneinsparung von 2266/Patient/Jahr verbunden. Auf das gesamte Bundesland Tirol hochgerechnet würde ein derartiges Hybrid-Betreuungsmodell eine Kosteneinsparung von ca. 1,172.820 j hrlich bedeuten. Diese Pilotstudie zeigt die Machbarkeit einer Ambulanz-basierten Nachbetreuung von lteren Patienten mit schwerer Herzinsuffizienz durch eine mobile Pflegekraft unter Berücksichtigung der in sterreich notwendigen gesetzlichen Voraussetzungen. Mit diesem Hybrid- Betreuungsmodell ist eine Reduktion der Krankenhauswiederaufnahmen und damit eine Senkung der krankheitsbezogenen Kosten m glich.
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