916 research outputs found
Investigations on alternative substances for control of apple scab - results from sanitation trials
The intention of this research project, which was supported within the "Bundesprogramm Ökologischer
Landbau", was to look for alternatives in organic fruit growing to control apple scab, Venturia
inaequalis. One important part of the investigations was the application of different substances like
microbiological nutrient media, enzymes usually used for production of fruit juices and organic fertilizers
on their effect on the ascospore potential on depots of fallen leaves. Some substances like
TRYPTIC SOY BROTH increased the decomposition of the leaves significantly, other like BACTOFIL B
and HUMOFIX showed nearly no effect on the decomposition, but reduced the ascospore potential in
early spring by 80 % compared to the untreated control
Investigations on alternative substances for control of apple scab - Results from Conidia germinating tests and experiments with plant extracts
The intention of this research project, which was supported within the "Bundesprogramm Ökologischer
Landbau", was to find alternatives for the control of Venturia inaequalis for the organic fruitgrower.
Beside the investigations on reducing the ascospore potential on fallen leaves, experiments
were conducted in laboratory, greenhouses and in orchard to test direct control of scab with different
plant extracts, concentrations and methods of extraction. Extracts from Inula viscosa, Quillaja
saponaria-bark, citrus-species (AGROMIL) and Saponaria officinalis revealed a distinct efficacy
against apple scab in greenhouse studies on apple seedlings. ELOT-VIS, CHITOPLANT, COMCAT,
MOOSEXTRAKT, SILIOPLANT und FZB 24 did not show sufficient efficacy with the application schedule
used for control of scab. Mixtures of Quillaja-saponine and sulphur reduced effectively apple scab
incidence. In an experiment concerning rain stability Citrus-extract and Quillaja-saponine showed a
lower efficacy against scab after a simulated rain of 5 mm. The screening of different supplements
to Citrus-extract as surfactants and adhesives revealed GREEMAX and BIOPLUSS as promising additives.
Both combinations showed an efficacy comparable to copperoxychloride corresponding to
400 g elementary copper per ha
Tone-activated, remote, alert communication system
Pocket sized transmitter, frequency modulated by crystal derived tones, with integral loop antenna provides police with easy operating alert signal communicator which uses patrol car radio to relay signal. Communication channels are time shared by several patrol units
Telescopic actions
A group action H on X is called "telescopic" if for any finitely presented
group G, there exists a subgroup H' in H such that G is isomorphic to the
fundamental group of X/H'.
We construct examples of telescopic actions on some CAT[-1] spaces, in
particular on 3 and 4-dimensional hyperbolic spaces. As applications we give
new proofs of the following statements:
(1) Aitchison's theorem: Every finitely presented group G can appear as the
fundamental group of M/J, where M is a compact 3-manifold and J is an
involution which has only isolated fixed points;
(2) Taubes' theorem: Every finitely presented group G can appear as the
fundamental group of a compact complex 3-manifold.Comment: +higher dimension
Toward a script theory of guidance in computer-supported collaborative learning
This article presents an outline of a script theory of guidance for computer-supported collaborative learning (CSCL). With its four types of components of internal and external scripts (play, scene, role, and scriptlet) and seven principles, this theory addresses the question how CSCL practices are shaped by dynamically re-configured internal collaboration scripts of the participating learners. Furthermore, it explains how internal collaboration scripts develop through participation in CSCL practices. It emphasizes the importance of active application of subject matter knowledge in CSCL practices, and it prioritizes transactive over non-transactive forms of knowledge application in order to facilitate learning. Further, the theory explains how external collaboration scripts modify CSCL practices and how they influence the development of internal collaboration scripts. The principles specify an optimal scaffolding level for external collaboration scripts and allow for the formulation of hypotheses about the fading of external collaboration scripts. Finally, the article points towards conceptual challenges and future research questions
Exact analytic results for the Gutzwiller wave function with finite magnetization
We present analytic results for ground-state properties of Hubbard-type
models in terms of the Gutzwiller variational wave function with non-zero
values of the magnetization m. In dimension D=1 approximation-free evaluations
are made possible by appropriate canonical transformations and an analysis of
Umklapp processes. We calculate the double occupation and the momentum
distribution, as well as its discontinuity at the Fermi surface, for arbitrary
values of the interaction parameter g, density n, and magnetization m. These
quantities determine the expectation value of the one-dimensional Hubbard
Hamiltonian for any symmetric, monotonically increasing dispersion epsilon_k.
In particular for nearest-neighbor hopping and densities away from half filling
the Gutzwiller wave function is found to predict ferromagnetic behavior for
sufficiently large interaction U.Comment: REVTeX 4, 32 pages, 8 figure
S-COL: A Copernican turn for the development of flexibly reusable collaboration scripts
Collaboration scripts are usually implemented as parts of a particular collaborative-learning platform. Therefore, scripts of demonstrated effectiveness are hardly used with learning platforms at other sites, and replication studies are rare. The approach of a platform-independent description language for scripts that allows for easy implementation of the same script on different platforms has not succeeded yet in making the transfer of scripts feasible. We present an alternative solution that treats the problem as a special case of providing support on top of diverse Web pages: In this case, the challenge is to trigger support based on the recognition of a Web page as belonging to a specific type of functionally equivalent pages such as the search query form or the results page of a search engine. The solution suggested has been implemented by means of a tool called S-COL (Scripting for Collaborative Online Learning) and allows for the sustainable development of scripts and scaffolds that can be used with a broad variety of content and platforms. The tool’s functions are described. In order to demonstrate the feasibility and ease of script reuse with S-COL, we describe the flexible re-implementation of a collaboration script for argumentation in S-COL and its adaptation to different learning platforms. To demonstrate that a collaboration script implemented in S-COL can actually foster learning, an empirical study about the effects of a specific script for collaborative online search on learning activities is presented. The further potentials and the limitations of the S-COL approach are discussed
Thermodynamically consistent equilibrium properties of normal-liquid Helium-3
The high-precision data for the specific heat C_{V}(T,V) of normal-liquid
Helium-3 obtained by Greywall, taken together with the molar volume V(T_0,P) at
one temperature T_0, are shown to contain the complete thermodynamic
information about this phase in zero magnetic field. This enables us to
calculate the T and P dependence of all equilibrium properties of normal-liquid
Helium-3 in a thermodynamically consistent way for a wide range of parameters.
The results for the entropy S(T,P), specific heat at constant pressure
C_P(T,P), molar volume V(T,P), compressibility kappa(T,P), and thermal
expansion coefficient alpha(T,P) are collected in the form of figures and
tables. This provides the first complete set of thermodynamically consistent
values of the equilibrium quantities of normal-liquid Helium-3. We find, for
example, that alpha(T,P) has a surprisingly intricate pressure dependence at
low temperatures, and that the curves alpha(T,P) vs T do not cross at one
single temperature for all pressures, in contrast to the curves presented in
the comprehensive survey of helium by Wilks.
Corrected in cond-mat/9906222v3: The sign of the coefficient d_0 was
misprinted in Table I of cond-mat/9906222v1 and v2. It now correctly reads
d_0=-7.1613436. All results in the paper were obtained with the correct value
of d_0. (We would like to thank for E. Collin, H. Godfrin, and Y. Bunkov for
finding this misprint.)Comment: 19 pages, 19 figures, 9 tables; published version; note added in
proof; v3: misprint correcte
Loss of the mechanotransducer zyxin promotes a synthetic phenotype of vascular smooth muscle cells.
BACKGROUND: Exposure of vascular smooth muscle cells (VSMCs) to excessive cyclic stretch such as in hypertension causes a shift in their phenotype. The focal adhesion protein zyxin can transduce such biomechanical stimuli to the nucleus of both endothelial cells and VSMCs, albeit with different thresholds and kinetics. However, there is no distinct vascular phenotype in young zyxin-deficient mice, possibly due to functional redundancy among other gene products belonging to the zyxin family. Analyzing zyxin function in VSMCs at the cellular level might thus offer a better mechanistic insight. We aimed to characterize zyxin-dependent changes in gene expression in VSMCs exposed to biomechanical stretch and define the functional role of zyxin in controlling the resultant VSMC phenotype.
METHODS AND RESULTS: DNA microarray analysis was used to identify genes and pathways that were zyxin regulated in static and stretched human umbilical artery-derived and mouse aortic VSMCs. Zyxin-null VSMCs showed a remarkable shift to a growth-promoting, less apoptotic, promigratory and poorly contractile phenotype with ≈90% of the stretch-responsive genes being zyxin dependent. Interestingly, zyxin-null cells already seemed primed for such a synthetic phenotype, with mechanical stretch further accentuating it. This could be accounted for by higher RhoA activity and myocardin-related transcription factor-A mainly localized to the nucleus of zyxin-null VSMCs, and a condensed and localized accumulation of F-actin upon stretch.
CONCLUSIONS: At the cellular level, zyxin is a key regulator of stretch-induced gene expression. Loss of zyxin drives VSMCs toward a synthetic phenotype, a process further consolidated by exaggerated stretch
- …