20,463 research outputs found
Biodiversity performance of organic farms in Austria - results from eight years of biodiversity assessment
Assessing the biodiversity performance of agricultural farms has gained importance in recent years since conserving and promoting biodiversity and associated ecosystem functions in cultural landscapes is a key aspect in making agriculture more sustainable ā a demand expressed in science, politics and society. This contribution presents results from eight years of biodiversity assessments on organic farms in Austria applying a method developed at FiBL that estimates the biodiversity potential of agricultural farms (Schader et al. 2014)
Bubbles emerging from a submerged granular bed
This paper explores the phenomena associated with the emergence of gas bubbles from a submerged granular bed. While there are many natural and industrial applications, we focus on the particular circumstances and consequences associated with the emergence of methane bubbles from the beds of lakes and reservoirs since there are significant implications for the dynamics of lakes and reservoirs and for global warming. This paper describes an experimental study of the processes of bubble emergence from a granular bed. Two distinct emergence modes are identified, mode 1 being simply the percolation of small bubbles through the interstices of the bed, while mode 2 involves the cumulative growth of a larger bubble until its buoyancy overcomes the surface tension effects. We demonstrate the conditions dividing the two modes (primarily the grain size) and show that this accords with simple analytical evaluations. These observations are consistent with previous studies of the dynamics of bubbles within porous beds. The two emergence modes also induce quite different particle fluidization levels. The latter are measured and correlated with a diffusion model similar to that originally employed in river sedimentation models by Vanoni and others. Both the particle diffusivity and the particle flux at the surface of the granular bed are measured and compared with a simple analytical model. These mixing processes can be consider applicable not only to the grains themselves, but also to the nutrients and/or contaminants within the bed. In this respect they are shown to be much more powerful than other mixing processes (such as the turbulence in the benthic boundary layer) and could, therefore, play a dominant role in the dynamics of lakes and reservoirs
Emerging roles in plant biotechnology for the second messenger cGMP - guanosine 3ā, 5ā-cyclic monophosphate
Second messengers are small transient molecules that transmit and/or modulate environmental or hormonal signals linking them to complex and often systemic physiological responses. Recent reports have renewed interest in the second messenger guanosine 3ā, 5ā-cyclic monophosphate (cGMP) since it has been shown to directly mediate an ever increasing number of plant responses ranging from themodification of cyclic nucleotide gated ion channels to the regulation of tran scription of many cGMPresponsive genes. Here some of these cGMP dependent responses will be reviewed emphasising their role in plant stress responses. Finally, potential applications of cGMP in plant biotechnology will be discussed
CW and pulsed electrically detected magnetic resonance spectroscopy at 263 GHz/12 T on operating amorphous silicon solar cells
Here we describe a new high frequency/high field continuous wave and pulsed
electrically detected magnetic resonance (CW EDMR and pEDMR) setup, operating
at 263 GHz and resonance fields between 0 and 12 T. Spin dependent transport in
illuminated hydrogenated amorphous silicon p-i-n solar cells at 5 K and 90 K
was studied by in operando 263 GHz CW and pEDMR alongside with complementary
X-band CW EDMR. Benefiting from the superior resolution at 263 GHz, we were
able to better resolve EDMR signals originating from spin dependent hopping and
recombination processes. 5 K EDMR spectra were found to be dominated by
conduction and valence band tale states involved in spin dependent hopping,
with additional contributions from triplet exciton states. 90 K EDMR spectra
could be assigned to spin pair recombination involving conduction band tail
states and dangling bonds as dominating spin dependent transport process, with
additional contributions from valence band tail and triplet exciton states.Comment: 8 pages, 4 figure
Structure factor and thermodynamics of rigid dendrimers in solution
The ''polymer reference interaction site model'' (PRISM) integral equation
theory is used to determine the structure factor of rigid dendrimers in
solution. The theory is quite successful in reproducing experimental structure
factors for various dendrimer concentrations. In addition, the structure factor
at vanishing scattering vector is calculated via the compressibility equation
using scaled particle theory and fundamental measure theory. The results as
predicted by both theories are systematically smaller than the experimental and
PRISM data for platelike dendrimers.Comment: 7 pages, 5 figures, submitte
Information requirements for supersonic transport operation Final report
Effects of meteorological parameters and instrument errors on vertical flight performance of supersonic transport
- ā¦