Ontwikkeling van plantenextracten ter bestrijding van droge mollen tot semi-commerciële producten

Droge mollen, veroorzaakt door Verticillium fungicola), vormen een belangrijk probleem in de champignonteelt. Besmetting van een teelt kan een aanzienlijke opbrengstderving tot gevolg hebben en de ziekteverwekker kan door champignonvliegen snel verspreid worden in een kwekerij. Droge mollen kunnen op dit moment nog worden bestreden door het gewasbeschermingsmiddel Sporgon. De verwachting is echter dat Sporgon binnen een termijn van een paar jaar niet meer beschikbaar zal zijn. Om die reden is onderzocht of het mogelijk is om alternatieven voor de bestrijding van droge mollen te ontwikkelen op basis van plantenextracten

Risk of Adverse Perinatal Outcomes in Dizygotic Twins After IVF Pregnancies: A Systematic Review

Background: Since the birth of the first test tube baby, 25 years ago, more than three million babies have been born using assisted reproductive technologies (ART). Twin births by way of ART represent 20-30% of U.S. and European births, as compared to only 1% of natural births. The purpose of this study is to investigate the risk of adverse perinatal outcomes in ART dizigotic twins, compared with non-ART twins. Method: A review of the medical literature available in Pub Med, EBM review, the National Clinical Trials Registry and CINAHL databases. The search was limited to English language sources between 2000 and 2010. Three cohort studies were identified for the final systematic review. The GRADE tool was used to evaluate the evidence. Results: The three cohort studies found no higher risk of low birth weight in ART twins after stratification for maternal age and parity. Birth weight discordance and mortality rates showed similar result as low birth weight. Two of the studies found an increased risk of hospitalization and neonatal intensive care unit admissions and maintained this result after stratification for maternal factors. One study found a higher risk of prematurity in twins conceived by in vitro fertilization; no such association was found in the other study. Conclusion: A review of the evidence found an increased risk of adverse perinatal outcome in twins conceived by in vitro fertilization, compared with twin not conceived by in vitro fertilization. However, no statistically significance differences were found after stratification for maternal confounders, with the exception of hospital and NICU admission. The grade for all outcomes was moderate

The marine geochemistry of the rare earth elements

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1983Novel methods were developed for the determination of 12 of the 14 Rare Earth Elements (REE) in seawater. Initial extractions of the REE by chelating ion exchange chromatography is followed by cation exchange for removal of co-extracted U and remaining traces of major ions. Finally traces of U are removed by anion exchange before irradiation for 8 hours at a flux of 5 x 1013 neutrons.cm-2.sec-l. After post-irradiation separation of 24 Na, the gamma spectra are recorded over four different time intervals with a Ge(Li) detector. An internal standard (144Ce) is carried all along the procedure for improved precision by avoidance of counting geometry errors. Vertical profiles are reported for three stations in respectively the Northwest Atlantic Ocean, the Eastern Equatorial Pacific Ocean and the Cariaco Trench, an anoxic basin. This data set represents the first detailed profiles of Pr, Tb, Ho, Tm and Lu in seawater, together with profiles of La, Ce, Nd, Sm, Eu, Gd and Yb. The first observations of positive Ce anomalies in seawater are ascribed to regeneration of Ce under reducing conditions. The first reported positive Gd anomalies are ascribed to the unique chemical properties of the Gd(III)-cation, which has an exactly half-filled 4f electron shell. Concentrations of the REE range from 0.3 pmol.kg-l (Lu) to 86 pmol.kg-l (Ce) and are among the lowest reported so far for trace elements in seawater. The REE as a group typically exhibit a quasi-linear increase with depth. In the deep water there appears to be some degree of correlation with silicate. Concentration levels in the deep Pacific Ocean are 2-4 times those in deep Atlantic waters. Ce has an opposite behaviour, with very strong depletions in deep Pacific waters. In the Cariaco Trench all REE, but especially Ce, are strongly affected by the chemical changes across the oxic/anoxic interface. The REE distributions normalized versus shales (crustal abundance) exhibit four major features: i) a gradual enrichment of the heavy REE, most strongly developed in the deep Pacific Ocean. This is compatible with the stabilization of heavy REE by stronger inorganic complexation in seawater as predicted by the TURNER- WHITFIELD-DICKSON speciation model. ii) the first description of positive Gd anomalies, in agreement with the anomalously strong complexation of the Gd(III)-cation predicted by the same speciation model. iii) most commonly negative, but sometimes positive, Ce anomalies. iv) a linear Eu/Sm relation for all samples. Distributions of the dissolved REE in ocean waters seem to be dominated by their internal cycling within the ocean basins. With a few notable exceptions, the ultimate external sources (riverine, aeolian, hydrothermal) and sinks (authigenic minerals) appear to have little impact on the spatial distribution of the REE in oceanic water masses. Analogies with distributions of other properties within the oceans suggest that the REE as a group are controlled by two simultaneous processes: A) cycling like or identical to opal and calcium-carbonate, with circumstantial evidence in support of the latter as a possible carrier. B) adsorptive scavenging, possibly by manganese-oxide phases on settling particles. The latter mechanism is strongly supported by the parallels between REE(III) speciation in seawater and the 'typical 1 seawater REE pattern. This general correspondence is highlighted by the very distinct excursions of Gd in both Gd(III) speciation and the observed seawater REE patterns. Combination of both apparent mechanisms, for instance scavenging of REE by adsorptive coatings (Mn oxides) on settling skeletal material, is very well conceivable. Upon dissolution of the shells at or near the seafloor the adsorbed REE fraction would be released into the bottom waters. The observations of positive Ce anomalies in Northwest Atlantic surface waters, enhanced Ce anomalies and Mn levels in the OZ-minimum zone of the Eastern Equatorial Pacific Ocean, and enhanced Ce concentrations in anoxic waters all support the contention that a vigorous cycling driven by oxidation and reduction reactions dominates both Ce and Mn in the ocean basins. Under conditions of thermodynamic equilibrium, Ce tends to become depleted in well-oxygenated open ocean waters, and normal or enriched in waters below a pOZ threshold of about 0.001-0.010 atm partial pressure. The latter threshold level generally lies below the sediment/water interface. However, the kinetics of oxidation (and reduction) of Ce appears to be slow relative to various transport processes. This leads to disequilibria, i.e. a major uncoupling of the pOZ threshold level and the Ce anomaly distribution. The REE are definitely non-conservative in seawater and in general the REE pattern or 143Nd/144Nd isotopic ratio cannot be treated as ideal water mass tracers. The continuous redistribution of Ce within the modern ocean, combined with the likelihood of active diagenesis, precludes the use of Ce anomalies as indicators of oxic versus anoxic conditions in ancient oceans. On the other hand, the Eu/Sm ratio, possibly combined with 143Nd/144Nd , would have potential as a tracer for understanding modern and ancient processes of hydrothermal circulation.This research was supported by Department of Energy contract DE-AS02-76EV03566 and Office of Naval Research Contract NOOOl 4-82-C-00l 9 NR 083-004

Molecular diversity of arbuscular mycorrhizal fungi in onion roots from organic and conventional farming systems in the Netherlands

Diversity and colonization levels of naturally occurring arbuscular mycorrhizal fungi (AMF) in onion roots were studied to compare organic and conventional farming systems in the Netherlands. In 2004, 20 onion fields were sampled in a balanced survey between farming systems and between two regions, namely, Zeeland and Flevoland. In 2005, nine conventional and ten organic fields were additionally surveyed in Flevoland. AMF phylotypes were identified by rDNA sequencing. All plants were colonized, with 60% for arbuscular colonization and 84% for hyphal colonization as grand means. In Zeeland, onion roots from organic fields had higher fractional colonization levels than those from conventional fields. Onion yields in conventional farming were positively correlated with colonization level. Overall, 14 AMF phylotypes were identified. The number of phylotypes per field ranged from one to six. Two phylotypes associated with the Glomus mosseae-coronatum and the G. caledonium-geosporum species complexes were the most abundant, whereas other phylotypes were infrequently found. Organic and conventional farming systems had similar number of phylotypes per field and Shannon diversity indices. A few organic and conventional fields had larger number of phylotypes, including phylotypes associated with the genera Glomus-B, Archaeospora, and Paraglomus. This suggests that farming systems as such did not influence AMF diversity, but rather specific environmental conditions or agricultural practice

MEMS based hair flow-sensors as model systems for acoustic perception studies

Arrays of MEMS fabricated flow sensors inspired by the acoustic flow-sensitive hairs found on the cerci of crickets, have been designed, fabricated and characterized. The hairs consist of up to 1 mm long SU-8 structures mounted on suspended membranes with normal translational and rotational degrees of freedom. Electrodes on the membrane and on the substrate form variable capacitors allowing for capacitive read-out. Capacitance versus voltage, frequency dependency and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept. The sensors form a model-system allowing for investigations on sensory acoustics by their arrayed nature, their adaptivity via electrostatic interaction (frequency tuning and parametric amplifica- tion) and their susceptibility to noise (stochastic resonance

Micromachined two dimensional resistor arrays for determination of gas parameters

A resistive sensor array is presented for two dimensional temperature distribution measurements in a micromachined flow channel. This allows simultaneous measurement of flow velocity and fluid parameters, like thermal conductivity, diffusion coefficient and viscosity. More general advantages of measuring temperature distributions are the inherent compensation of heat losses to the support and the insensitivity to variations in the temperature coefficient of resistance

Optimizing an Intermittent Stretch Paradigm Using ERK1/2 Phosphorylation Results in Increased Collagen Synthesis in Engineered Ligaments

Dynamic mechanical input is believed to play a critical role in the development of functional musculoskeletal tissues. To study this phenomenon, cyclic uniaxial mechanical stretch was applied to engineered ligaments using a custom-built bioreactor and the effects of different stretch frequency, amplitude, and duration were determined. Stretch acutely increased the phosphorylation of p38 (3.5±0.74-fold), S6K1 (3.9±0.19-fold), and ERK1/2 (2.45±0.32-fold). The phosphorylation of ERK1/2 was dependent on time, rather than on frequency or amplitude, within these constructs. ERK1/2 phosphorylation was similar following stretch at frequencies from 0.1 to 1?Hz and amplitudes from 2.5% to 15%, whereas phosphorylation reached maximal levels at 10?min of stretch and returned toward basal within 60?min of stretch. Following a single 10-min bout of cyclic stretch, the cells remained refractory to a second stretch for up to 6?h. Using the phosphorylation of ERK1/2 as a guide, the optimum stretch paradigm was hypothesized to be 10?min of stretch at 2.5% of resting length repeated every 6?h. Consistent with this hypothesis, 7 days of stretch using this optimized intermittent stretch program increased the collagen content of the grafts more than a continuous stretch program (CTL=3.1%±0.44%; CONT=4.8%±0.30%; and INT=5.9%±0.56%). These results suggest that short infrequent bouts of loading are optimal for improving engineered tendon and ligament physiology.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98478/1/ten%2Etea%2E2011%2E0336.pd