Material properties of nanoclay PVC composites

Nanocomposites of poly(vinyl chloride) have been prepared using both hectorite- and bentonite-based organically-modified clays. The organic modification used is tallow-triethanol-ammonium ion. The morphology of the systems was investigated using X-ray diffraction and transmission electron microscopy and these systems show that true nanocomposites, both intercalated and exfoliated systems, are produced. The mechanical properties have been evaluated and the modulus increases upon nanocomposite formation without a significant decrease in tensile strength or elongation at break. Thermal analysis studies using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis were conducted. Thermal stability of the PVC systems was assessed using a standard thermal process evaluating the evolution of hydrogen chloride and by color development through the yellowness index. Cone calorimetry was used to measure the fire properties and especially to evaluate smoke evolution. The addition of an appropriately-modified bentonite or hectorite nanoclay leads to both a reduction in the total smoke that is evolved, and an increase in the length of time over which smoke is evolved. Along with this, a reduction in the peak heat release rate is seen. It is likely that the presence of the clay in some way interferes with the cyclization of the conjugated system formed upon HCl loss

Bladrandjes en Ca bij tomaat: Fysiologische achtergronden van cel- en weefselstevigheid in relatie tot het ontstaan van bladrandjes en infectie met Botrytis cinerea L.

Tip burn of tomato leaves is often seen by growers as indication for maximum crop performance, however grey mould (botrytis), can easily infect through the necrotic leaf edges. In this desk study factors that are influencing the occurrence of tip burn and calcium (Ca) deficiency were studied. Cells formed during periods of Ca shortage have weaker membranes and walls and ‘burst’ after a climatic shock resulting in plasmolysis and disintegration of the membranes. Possibly the disruption of the Ca homeostasis in the cytoplasm. Botrytis uses dead tissue as an entrance to infect the plant. The weak cell walls and solute leaking caused by disruption of the membranes facilitates the infection process of the fungus. Ca uptake and transport are affected by high fruit load, EC and K/Ca in the root environment and transpiration and root pressure. These factors sometimes interact and sometimes are independently effective, resulting in a complex situation. Thus preventing heavy fruit loads in susceptible periods and stimulating Ca uptake and distribution will alleviate the problem. This, in combination with the prevention of climate shocks will help to reduce the occurrence of tip burn in tomato

A strategy for the characterization of minute chromosome rearrangements using multiple color fluorescence in situ hybridization with chromosome-specific DNA libraries and YAC clones

The identification of marker chromosomes in clinical and tumor cytogenetics by chromosome banding analysis can create problems. In this study, we present a strategy to define minute chromosomal rearrangements by multicolor fluorescence in situ hybridization (FISH) with whole chromosome painting probes derived from chromosome-specific DNA libraries and Alu-polymerase chain reaction (PCR) products of various region-specific yeast artificial chromosome (YAC) clones. To demonstrate the usefulness of this strategy for the characterization of chromosome rearrangements unidentifiable by banding techniques, an 8p+ marker chromosome with two extra bands present in the karyotype of a child with multiple anomalies, malformations, and severe mental retardation was investigated. A series of seven-color FISH experiments with sets of fluorochrome-labeled DNA library probes from flow-sorted chromosomes demonstrated that the additional segment on 8p+ was derived from chromosome 6. For a more detailed characterization of the marker chromosome, three-color FISH experiments with library probes specific to chromosomes 6 and 8 were performed in combination with newly established telomeric and subtelomeric YAC clones from 6q25, 6p23, and 8p23. These experiments demonstrated a trisomy 6pter6p22 and a monosomy 8pter8p23 in the patient. The present limitations for a broad application of this strategy and its possible improvements are discusse

The origin of human chromosome 2 analyzed by comparative chromosome mapping with a DNA microlibrary

Fluorescencein situ hybridization (FISH) of microlibraries established from distinct chromosome subregions can test the evolutionary conservation of chromosome bands as well as chromosomal rearrangements that occurred during primate evolution and will help to clarify phylogenetic relationships. We used a DNA library established by microdissection and microcloning from the entire long arm of human chromosome 2 for fluorescencein situ hybridization and comparative mapping of the chromosomes of human, great apes (Pan troglodytes, Pan paniscus, Gorilla gorilla, Pongo pygmaeus) and Old World monkeys (Macaca fuscata andCercopithecus aethiops). Inversions were found in the pericentric region of the primate chromosome 2p homologs in great apes, and the hybridization pattern demonstrates the known phylogenetically derived telomere fusion in the line that leads to human chromosome 2. The hybridization of the 2q microlibrary to chromosomes of Old World monkeys gave a different pattern from that in the gorilla and the orang-utan, but a pattern similar to that of chimpanzees. This suggests convergence of chromosomal rearrangements in different phylogenetic lines

Goed Gietwater: Werkpakket 2: Kwaliteit gietwater en groeiprestaties

Referaat De opkweeksector stelt hoge eisen aan de kwaliteit van gietwater ter voorkoming van groeiremming en ziekten. Lozingen en emissies zijn soms een uitweg om risico’s te mijden. Het project Goed Gietwater beoogt de ontwikkeling van een duurzame watertechnologie voor opkweekbedrijven in de glastuinbouw. Hiermee moet de emissie geminimaliseerd worden. In dit verslag over werkpakket 2 wordt een geselecteerd aantal factoren die de kwaliteit van het gietwater negatief kunnen beïnvloeden nader onderzocht. Het gaat om een ontsmettingsmiddel (natrium hypochoriet), twee organische stoffen (POW-humus en kokoschips) een remstof (Alar) en een vloeier. Deze stoffen worden in meetreeksen getest op groeiremming. Natrium hypochloriet laat groeiremming zien vanaf 45 mg/l, ook Alar (Daminozide) remt de groei vanaf 45 mg/l. De organische stoffen en de vloeier vertonen geen groeiremming. Een hoog gehalte aan organische stof beïnvloedt wel de groei van micro-organismen en kan verstorend werken bij de UV-ontsmetting. In een tweede reeks testen is gekenen naar het tenietdoen van de groeiremming met geavanceerde oxidatie. Geavanceerde oxidatie (AOX) lijkt geen oplossing te bieden voor afbraak van natrium hypochloriet, humus en exudaat van kokoschips bij de in de praktijk toegepaste UVc-dosis (maximaal 250 mJ/cm2). Vloeier in demiwater wordt bij een hoge dosis peroxide (30ppm) en 240mJ/cm2 UVc tot 45% afgebroken. AOX leidt niet tot substantiele afbraak van remstoffen. Abstract The propagation sector demands a very high quality of irrigation water to prevent negative growth effects and diseases. Discharge of nutrient solution is sometimes used to avoid risks for the crop. The project Goed Gietwater (Good Irrigation Water) aims to develop sustainable water technology for nurseries in greenhouse horticulture. The underlying aim is to reduce the emission of nutrients and crop protection agents. This report decribes how in Work Package 2 a selected number of quality determining factors was investigated in laboratory experiments. The tested materials were a disinfectant (sodium hypochlorite), two organic compounds (POW-humic and coconut chips) a growth control agent (Alar) and a surfactant as used in rockwool. Sodium hypochlorite gave growth inhibition from 45 mg/l on, Alar (Daminozide) reduced growth from 45 mg/l. The organic substances and surfactant showed no growth inhibition. In a subsewuent series of tests advanced oxidation (AOX) seems no solution to destruct sodium hypochlorite or POW humus or the exudate of coir chips when applied in practical UVc doses (up to 250 mJ/cm2). Surfactant with a high dose peroxide (30 ppm) and 240mJ/cm2 UVc is broken down up to 45%. AOX does not readily destrcut growth control agents

Vermindering wortelproblemen Miltonia (Miltoniopsis)

Bij de teelt van Miltonia (Miltoniopsis) komen veel wortelproblemen voor. Planten komen los op de pot te staan en vallen weg. Onderzoek gefinancierd door het Productschap Tuinbouw heeft laten zien dat de sterke zuigkracht van sphagnum er voor zorgt dat de sphagnumplug opgepot in bark of Allure na een watergift veel water aan zuigt en daarna te lang nat blijft. Daardoor ontstaat zuurstofgebrek bij de wortels en sterven wortels af. In een proef met de huidige opkweek- en teeltsubstraten was de kwaliteit van de wortels bij een partij planten op bark beter dan bij een partij planten op Allure en een watergift van 1 x 5 liter was beter dan een watergift van 2 x 3 liter per m2. Tijdens de koeling droogden de potten minder snel af dan tijdens de opkweek. Als de watergeeffrequentie dan onvoldoende aangepast wordt, kunnen de wortelproblemen in de koeling verergeren. Het meten van het gewicht van de potten kan een goed hulpmiddel zijn om de watergeeffrequentie op de juiste manier aan te passen en wortelproblemen te verminderen. De beste manier om wortelproblemen te voorkomen is een nieuwe combinatie van opkweek- en teeltsubstraat waarvan de eigenschappen meer in elkaars verlengde liggen. Abstract Many Miltonia (Miltoniopsis) growers suffer plant losses, as a result of root problems. Research financed by the Dutch Product Board of Horticulture has shown that when the sphagnum plug containing the young plant is potted in bark or ‘Allure’ (a new orchid substrate) the plug remains wet for too long after irrigation. This causes a lack of oxygen to the roots and roots die. In a trial with the current substrates, the quality of the roots on bark was better than on ‘allure’ and an irrigation with 1 x 5 litres was better than an irrigation with 2 x 3 litres per m2. During the generative phase, pots dried less rapidly than during the vegetative phase. If the irrigation is not adjusted, the substrate becomes wetter and root problems can increase in the generative phase. Measuring the weight of the pots can be a good tool to adjust the irrigation frequency and decrease root problems. The best solution to solve these root problems would be a new combination of propagation and growing substrate with similar properties for both media

A Model-Based Analysis of GC-Biased Gene Conversion in the Human and Chimpanzee Genomes

GC-biased gene conversion (gBGC) is a recombination-associated process that favors the fixation of G/C alleles over A/T alleles. In mammals, gBGC is hypothesized to contribute to variation in GC content, rapidly evolving sequences, and the fixation of deleterious mutations, but its prevalence and general functional consequences remain poorly understood. gBGC is difficult to incorporate into models of molecular evolution and so far has primarily been studied using summary statistics from genomic comparisons. Here, we introduce a new probabilistic model that captures the joint effects of natural selection and gBGC on nucleotide substitution patterns, while allowing for correlations along the genome in these effects. We implemented our model in a computer program, called phastBias, that can accurately detect gBGC tracts about 1 kilobase or longer in simulated sequence alignments. When applied to real primate genome sequences, phastBias predicts gBGC tracts that cover roughly 0.3% of the human and chimpanzee genomes and account for 1.2% of human-chimpanzee nucleotide differences. These tracts fall in clusters, particularly in subtelomeric regions; they are enriched for recombination hotspots and fast-evolving sequences; and they display an ongoing fixation preference for G and C alleles. They are also significantly enriched for disease-associated polymorphisms, suggesting that they contribute to the fixation of deleterious alleles. The gBGC tracts provide a unique window into historical recombination processes along the human and chimpanzee lineages. They supply additional evidence of long-term conservation of megabase-scale recombination rates accompanied by rapid turnover of hotspots. Together, these findings shed new light on the evolutionary, functional, and disease implications of gBGC. The phastBias program and our predicted tracts are freely available. © 2013 Capra et al

Cat or Dog Ownership and Seroprevalence of Ehrlichiosis, Q Fever, and Cat-Scratch Disease

Concerns have been raised about the role of domestic cats or dogs in the acquisition of zoonoses, in particular in pregnant women or immune-suppressed persons. We report that cat or dog ownership is not associated with an increased seroprevalence of antibodies to Anaplasma phagozytophilum, Coxiella burnetii, and Bartonella henselae in symptom-free persons in Styria, Austria