7,237 research outputs found
Covers of Point-Hyperplane Graphs
We construct a cover of the non-incident point-hyperplane graph of projective
dimension 3 for fields of characteristic 2. If the cardinality of the field is
larger than 2, we obtain an elementary construction of the non-split extension
of SL_4 (F) by F^6.Comment: 10 pages, 3 figure
Curvaton Scenario with Affleck-Dine Baryogenesis
We discuss the curvaton scenario with the Affleck-Dine baryogenesis. In this
scenario, non-vanishing baryonic entropy fluctuation may be generated even
without primordial fluctuation of the Affleck-Dine field. Too large entropy
fluctuation is inconsistent with the observations and hence constraints on the
curvaton scenario with the Affleck-Dine baryogenesis are obtained. We calculate
the baryonic entropy fluctuation (as well as other cosmological density
fluctuations) in this case and derive constraints. Implications to some of the
models of the curvaton are also discussed.Comment: 16 pages,2 figure
Substrate induction and glucose repression of maltose utilization by Streptomyces coelicolor A3(2) is controlled by malR, a member of the lacI-galR family of regulatory genes
malR of Strepomyces coelicolor A3(2) encodes a homologue of the Lacl/Galr family of repressor proteins, and is divergently transcribed from the malEFG gene cluster, which encodes components of an ATP-dependent transport system that is required for maltose utilization. Transcription of malE was induced by maltose and repressed by glucose. Disruption or deletion of malR resulted in constitutive, glucose-insensitive malE transcription at a level markedly above that observed in the parental malR+ strain, and overproduction of MalR prevented growth on maltose as carbon source. Consequently, MalR plays a crucial role in both substrate induction and glucose repression of maltose utilization. MalR is expressed from a single promoter with transcription initiating at the first G of the predicted GTG translataion start codon
Disease suppressive soilless culture systems; characterisation of its microflora
The trend in glasshouse horticulture has always been to start culture systems as aseptic as possible. However, several root diseases still cause problems under these conditions. The present paper shows the importance of the microflora to suppress Pythium aphanidermatum, a fungal root pathogen which is a serious threat in cucumber. Introduced single antagonists as well as the indigenous microflora suppressed pythium root and crown rot. Pseudomonas fluorescens, Streptomyces griseoviridis, Pythium oligandrum, and 2 isolates of Trichoderma harzianum reduced the disease occurrence by 60 ␘r more in several, but not all, of the experiments. The indigenous microflora showed a very constant disease suppression of 50 to 100 &Eth;This was tested in experiments where P. aphanidermatum was added to sterilised and non-sterilised rockwool, and to sterilised rockwool that had been recolonised with the original microflora. Suppressiveness correlated with the number of filamentous actinomycetes present in the nutrient solution in the rockwool slabs. If a beneficial microflora is present in the cropping system, it should not be disturbed or eradicated by treatments such as disinfection of the recirculated nutrient solution. Therefore, the effects of different disinfection procedures on the composition of the microflora were compared. Numbers of filamentous actinomycetes in the nutrient solution in the tank after the disinfection treatment were highest without disinfection, intermediate after slow filtration, and lowest after UV treatment. Numbers of actinomycetes in the slabs, i.e. around the roots, were not distinctly different between the treatments. The implication of potential shifts in the microbial populations due to certain treatments for the disease development is not known. Increased knowledge on the beneficial microflora and the treatments that influence the composition of such a microflora, will stimulate the exploitation of microbially balanced and optimised soilless culture systems
Detectie van Lysobacter spp. in de bodem; het dilemma van te veel of te weinig meten
Onderzoek van de afgelopen jaren heeft aangetoond dat de aanwezigheid van de antagonistische bacterie Lysobacter correleert met ziektewering in bodems tegen Rhizoctonia solani-aantasting. Het betreft de nauw verwante soorten L. antibioticus, L. capsici en L. gummosus. Voor verder onderzoek naar stimulering van deze antagonistische Lysobacter-soorten in de bodem zijn detectietechnieken nodig, zodat de invloed van teeltmaatregelen op de populatieomvang van Lysobacter bepaald kan worde
Study of the Growth of Entropy Modes in MSSM Flat Directions Decay: Constraints on the Parameter Space
We study how the resonant decay of moduli fields arising in the Minimal
Supersymmetric Standard Model (MSSM) could affect large scale curvature
perturbations in the early universe. It has been known for some time that the
presence of entropy perturbations in a multi-component system can act as seeds
for the curvature perturbations on all scales. These entropy perturbations
could be amplified exponentially if one of the moduli decays via stochastic
resonance, affecting the curvature power spectrum in the process. By imposing
the COBE normalization on this power spectrum, one could put constraints on the
masses and couplings of the underlying particle physics model without having to
rely on collider experiments. We discuss in detail the case of the MSSM but
this method could be applied to other theories beyond the Standard Model.Comment: 6 pages, 1 figure, revtex4, comments added in section II, 1 reference
adde
Ziektewering van bodemgebonden pathogenen en functionele diversiteit van de bodemmicroflora
Dit onderzoek richt zich op het vinden van micro-organismen of hun eigenschappen die correleren met ziektewering op verschillende bedrijfstypen en grondsoorten
- …