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

Comments on "Vortex Glass and Lattice Melting Transitions in a YNi_2B_2C Single Crystal"

Recently, Mun et.al. (Phys. Rev. Lett., 76, 2790 (1996)) have published their results on single crystal YNi_2B_2C, claiming that their experimental observations can be explained in terms of formation of Vortex Glass and Lattice melting. Our experiments, carried out on samples obtained from the SAME source, reveal a much richer phase diagram and span wider regions of experimental parameter space than Mun et. al. that encompasses most of their observations. We speculate that this material has anomalous intrinsic properties and the results cannot be explained by simple models about the flux lattice.Comment: 1 page, LaTeX type, 1 PostScript figure, Uses PRABIB.STY file, 600 dpi PS file available at http://sagar.physics.neu.edu/preprints.html To appear in Physical Review Letter

Direct in situ GDD measurement in optical coating process

In the presented work a fast frequency domain measurement system to determine group delay (GD) and group delay dispersion (GDD) of optical coatings is proposed. The measurements are performed in situ directly on moving substrates during the thin film coating process. The method is based on a Michelson interferometer, which is equipped with a high power broad band light source and a fast spectrometer. Especially for the production of chirped mirrors it is advantageous to obtain group delay and group delay dispersion data of the last layers. This additional information allows for online corrections of coating errors to enhance the precision of complex interference filters for short pulse applications. © 2015 SPIE

Moved by the tears of others: emotion networking in the heritage sphere

There is no heritage without emotional sharing and clashing. This article explores the involvement of divergent emotions in heritage making by discussing the debate series of Imagine IC and the Reinwardt Academy and zooming in on the commemoration of slavery and imagery of ‘Black Pete’ in the Netherlands. We introduce ‘emotion networking’ as a methodology to approach present-day heritage production, aiming for a novel approach to engage with ‘the collective’

Critical State Flux Penetration and Linear Microwave Vortex Response in YBa_2Cu_3O_{7-x} Films

The vortex contribution to the dc field (H) dependent microwave surface impedance Z_s = R_s+iX_s of YBa_2Cu_3O_{7-x} thin films was measured using suspended patterned resonators. Z_s(H) is shown to be a direct measure of the flux density B(H) enabling a very precise test of models of flux penetration. Three regimes of field-dependent behavior were observed: (1) Initial flux penetration occurs on very low field scales H_i(4.2K) 100Oe, (2) At moderate fields the flux penetration into the virgin state is in excellent agreement with calculations based upon the field-induced Bean critical state for thin film geometry, parametrized by a field scale H_s(4.2K) J_c*d 0.5T, (3) for very high fields H >>H_s, the flux density is uniform and the measurements enable direct determination of vortex parameters such as pinning force constants \alpha_p and vortex viscosity \eta. However hysteresis loops are in disagreement with the thin film Bean model, and instead are governed by the low field scale H_i, rather than by H_s. Geometric barriers are insufficient to account for the observed results.Comment: 20 pages, LaTeX type, Uses REVTeX style files, Submitted to Physical Review B, 600 dpi PostScript file with high resolution figures available at http://sagar.physics.neu.edu/preprints.htm

Heritability of Daytime Ambulatory Blood Pressure in an Extended Twin Design.

The present study estimated the genetic influences on ambulatory systolic and diastolic blood pressure, and on hypertensive status derived from ambulatory levels, in a family sample of 535 twins and 257 singleton siblings. This "extended twin design" was used to explicitly test the possibility that results obtained in singleton siblings are different from those obtained in twins. To examine the effects of excluding (medicated) hypertensive subjects, the genetic analyses were first performed under strict exclusion (medication and/or blood pressure > 135/85 mm Hg), then without the medicated subjects, and, finally, without any exclusion. For the latter analysis, the untreated blood pressure values in subjects using antihypertensive medication were estimated by augmenting the observed blood pressure by the published efficacy of the specific antihypertensive medication used. No evidence was found for differential means, variances, or covariances of ambulatory blood pressure in singletons compared with twins. This indicates that estimates of heritability of ambulatory blood pressure from twin studies can be generalized to the singleton population. Heritability of hypertension, defined as a mean daytime blood pressure > 135/85 mm Hg or antihypertensive medication use, was 61%. Genetic contribution to ambulatory blood pressure was highest when all subjects were included (systolic, 44% to 57%; diastolic, 46% to 63%) and lowest under strict exclusion (systolic, 32% to 50%; diastolic, 31% to 55%). We conclude that exclusion of (medicated) hypertensives removes part of the true genetic variance in ambulatory blood pressure