Seed-soil microsite characteristics in relation to weed seed germination

An experimental field, under conventional (fall plowing, spring disking) and reduced (no preplanting soil disturbance) tillage for over 12 years, was sampled with the objectives of determining the distribution of weed seeds in the soil profile and their location in relation to soil structural units. Soil samples were taken at the depths of 0-5, 5-10, and 10-20 cm in the spring and fall of 1982, air-dried, and classified into seven aggregate size-classes by dry rotary-sieving. Sub-samples were deflocculated and washed through sieves to retain large (\u3e 0.9 mm) weed seeds;In the spring, 74% of all seeds in the reduced tillage and 15% of those in the conventional tillage soil were in the 0-5 cm depth layer. Conventional tillage distributed weed seeds uniformly among soil aggregate classes, while reduced tillage produced more seeds in the non-aggregated fraction of the soil. In the fall, the distribution of weed seeds in the profile and among soil structural units was very similar for both tillage regimes;Growth chamber and laboratory experiments evaluated the effects of seed-soil microsite characteristics on weed seed germination. Corn (Zea mays L.), soybean (Glycine max (L.) Merr.), velvetleaf (Abutilon theoprasti Medic.), and giant foxtail (Setaria faberi Herrm.) seeded among soil aggregates \u3e 1.25 cm showed decreased seedling emergence with decreased frequency of irrigation. The same species seeded inside artificially made soil aggregates showed increased seedling emergence with decreased frequency of irrigation. Aggregates made with 0.4 g of soil, incubated in high relative humidity environments, significantly decreased the germination of corn and soybean seeds placed in their centers. Germination of velvetleaf and giant foxtail seeds was significantly reduced by 0.1 g soil aggregates. Rice (Oryza sativa L.) had 68% emergence in 1.0 g fully moist soil peds, while larger seeded corn and soybean had only 20% and 10%, respectively. The inhibition of germination of giant foxtail seeds by fully moist soil peds was partially reversed by incubating seed-containing aggregates in oxygen-enriched atmospheres;The location of weed seeds in relation to soil structural units, the seed-soil microsite, may have an ecological role regulating weed seed germination and dormancy under field conditions

RDF/S)XML Linguistic Annotation of Semantic Web Pages

Although with the Semantic Web initiative much research on web pages semantic annotation has already done by AI researchers, linguistic text annotation, including the semantic one, was originally developed in Corpus Linguistics and its results have been somehow neglected by AI. ..

A COMBINED ANALYSIS OF EXPERIMENTS WHEN TREATMENTS DIFFER AMONG EXPERIMENTS

The advantages of repeating experiments in several locations and years are discussed and standard methods of analysis are reviewed. The methods assume that the same treatments are used in each experiment. This paper discusses a method used for a combined analysis when the treatments represent levels of a quantitative factor but differ among experiments. The method makes use of multiple regression analysis in which a continuous variable represents treatment levels, classification variables represent experiments, and products of the continuous and classification variables represent differences among experiments. The method is illustrated on data from a series of experiments designed to study the relationship of grain yield of soybeans as affected by the density of the weed species velvetleaf. The analysis determined that yield loss was linearly related to weed density but that the slope of the relationship differed among years. The slope differences were correlated with August rainfall, and a model is suggested that accounts for both within-experiment variability due to weed density and between-experiment variability due to August rainfal

STEM Mental Wellness Research

NCSSS and IMSA conducted a survey to gather information regarding how NCSSS member schools handle carious aspects of student mental wellness and mental illness as well as the resources and programming available to address concerns in these areas. Download The 2020 NCSSS Student Mental Health Survey: A Synopsi

Mechanical properties of tungsten alloys with Y2O3 and titanium additions

In this research the mechanical behaviour of pure tungsten (W) and its alloys (2 wt.% Ti–0.47 wt.% Y2O3 and 4 wt.% Ti–0.5 wt.% Y2O3) is compared. These tungsten alloys, have been obtained by powder metallurgy. The yield strength, fracture toughness and elastic modulus have been studied in the temperature interval of 25 °C to 1000 °C. The results have shown that the addition of Ti substantially improves the bending strength and toughness of W, but it also dramatically increases the DBTT. On the other hand, the addition of 0.5% Y2O3, is enough to improve noticeably the oxidation behaviour at the higher temperatures. The grain size, fractography and microstructure are studied in these materials. Titanium is a good grain growth inhibitor and effective precursor of liquid phase in HIP. The simultaneous presence of Y2O3 and Ti permits to obtain materials with low pores presenc

Local freedom in the gravitational field revisited

Maartens {\it et al.}\@ gave a covariant characterization, in a 1+3 formalism based on a perfect fluid's velocity, of the parts of the first derivatives of the curvature tensor in general relativity which are ``locally free'', i.e. not pointwise determined by the fluid energy momentum and its derivative. The full decomposition of independent curvature derivative components given in earlier work on the spinor approach to the equivalence problem enables analogous general results to be stated for any order: the independent matter terms can also be characterized. Explicit relations between the two sets of results are obtained. The 24 Maartens {\it et al.} locally free data are shown to correspond to the $\nabla \Psi$ quantities in the spinor approach, and the fluid terms are similarly related to the remaining 16 independent quantities in the first derivatives of the curvature.Comment: LaTeX. 13 pp. To be submitted to Class. Quant. Gra

The Internationalisation of the Spanish food industry: The home market effect and European market integration

The objective of this study was to analyse, from a long-term perspective, the factors determining the process of the internationalisation of the Spanish agrifood industry. The paper concentrates on the empirical verification of the existence of a home market effect in the food and drink industries in Spain and on the effects on trade flows of integration into the European Union. With this aim in mind, we took into account the latest contributions to the estimation of the gravity equation for a sample of export flows from 13 agrifood subsectors between 1970 and 2012, with a destination of 175 markets. From the results of the study the existence of the “home market effect” stands out as the determining factor of the increasing process of internationalisation in the majority of the subsectors of the food industry. On this point, the presence of this effect is remarkable in the most dynamic industries, where the process of restructuring caused by the development of the internal market was more intense. Furthermore, the influence of the process of European integration has been shown by the literature to be a very important factor. Our results qualify in part the results of previous studies, since the positive effect appeared later than expected. The positive effects did not appear until the completion of the process of transition by the dismantling of the barriers established in the treaty of accession to the European Union

Epicrania fugax with backward radiation: clinical characteristics of nine new cases

Epicrania fugax (EF) is a novel syndrome, described as a paroxysmal and brief head pain, starting in posterior cranial regions and rapidly spreading forward ipsilateral eye, nose or forehead. Two patients with comparable clinical features stemming from frontal scalp to ipsilateral posterior regions have been recently described and proposed as backward radiation epicrania fugax (BREF). We report a new series of nine BREF and compare their clinical characteristics with 18 forward radiation EF (FREF). Since first description of BREF in February 2010 we have assessed nine patients (four males, five females) with this clinical picture at an outpatient headache office in a Tertiary Hospital. Comparison is established with 18 FREF patients (6 males, 12 females), attended since the publication of first series of EF in March 2008. We found no differences between BREF and FREF, respectively, in age at onset (43.4 ± 13.1 vs. 42.5 ± 17.7 years), female/male ratio (5/4 vs. 12/6), pain intensity (6.9 ± 2.1 vs. 6.8 ± 2.1 in a 0–10 visual analogical scale), duration (7.1 ± 4.9 vs. 5.7 ± 4.3 s) and frequency of episodes per day (7 ± 8.4 vs. 9.9 ± 15.4). Patients in BREF group presented less frequently interictal pain in stemming point (22.2 vs. 55.5%) and accompanying autonomic signs (33.3 vs. 55.5%), but without statistical significance in both the cases. This series reinforces the proposal of EF as a new headache variant or a new headache syndrome. Clinical picture of brief pain paroxysms starting in the anterior scalp and radiating backwards does not fit known headaches or neuralgias and might correspond to a reverse variant of EF, clinical characteristics of which are comparable to FREF