A homotopy double groupoid of a Hausdorff space II: a van Kampen theorem

This paper is the second in a series exploring the properties of a functor which assigns a homotopy double groupoid with connections to a Hausdorff space. We show that this functor satisfies a version of the van Kampen theorem, and so is a suitable tool for nonabelian, 2-dimensional, local-to-global problems. The methods are analogous to those developed by Brown and Higgins for similar theorems for other higher homotopy groupoids. An integral part of the proof is a detailed discussion of commutative cubes in a double category with connections, and a proof of the key result that any composition of commutative cubes is commutative. These results have recently been generalised to all dimensions by Philip Higgins.Comment: 19 pages, uses picte

Evaluation of the gust-alleviation characteristics and handling qualities of a free-wing aircraft

Dynamic characteristics of aircraft with wings free to pivot spanwise axi

The Abundances of Light Neutron-Capture Elements in Planetary Nebulae III. The Impact of New Atomic Data on Nebular Selenium and Krypton Abundance Determinations

The detection of neutron(n)-capture elements in several planetary nebulae (PNe) has provided a new means of investigating s-process nucleosynthesis in low-mass stars. However, a lack of atomic data has inhibited accurate trans-iron element abundance determinations in astrophysical nebulae. Recently, photoionization and recombination data were determined for Se and Kr, the two most widely detected n-capture elements in nebular spectra. We have incorporated these new data into the photoionization code Cloudy. To test the atomic data, numerical models were computed for 15 PNe that exhibit emission lines from multiple Kr ions. We found systematic discrepancies between the predicted and observed emission lines that are most likely caused by inaccurate photoionization and recombination data. These discrepancies were removed by adjusting the Kr$^+$--Kr$^{3+}$ photoionization cross sections within their cited uncertainties and the dielectronic recombination rate coefficients by slightly larger amounts. From grids of models spanning the physical conditions encountered in PNe, we derive new, broadly applicable ionization correction factor (ICF) formulae for calculating Se and Kr elemental abundances. The ICFs were applied to our previous survey of near-infrared [Kr III] and [Se IV] emission lines in 120 PNe. The revised Se and Kr abundances are 0.1-0.3 dex lower than former estimates, with average values of [Se/(O, Ar)]=0.12$\pm$0.27 and [Kr/(O, Ar)]=0.82$\pm$0.29, but correlations previously found between their abundances and other nebular and stellar properties are unaffected. We also find a tendency for high-velocity PNe that can be associated with the Galactic thick disk to exhibit larger s-process enrichments than low-velocity PNe belonging to the thin disk population.Comment: 73 pages, 6 figures, 18 tables, accepted for publication in ApJ

Experiments with modified techniques for the determination of purity and viability of Bluegrass seed, Poa Pratensis L.

1. Determination of absolute purity in small seeded grasses with multiple florets, such as bluegrass, is possible experimentally but is a practical impossibility and when applied by different seed laboratories results in variations much greater than may be expected from homogeneous sub-samples of seed. 2. A close approximation of pure bluegrass seed may be obtained by a modified method of procedure which involves separation of unattached infertile florets or infertile spikelets from fertile florets by means of a uniform speed motor and fan and a vertical air blast separator of the Holland type. The only hand labor involved is that .of removing pieces of stem, grit, stones, weeds and other crop seeds from the heavy portion. A glass tube of the Kny-Scheerer type may be equally satisfactory, but breakage is too frequent. 3. Application of the chi-square test to four or more sub-samples drawn from the same lot and analyzed by the modified method shows that, in general, the percentages of heavy and pure seed fractions fall within the range of natural variability, thus indicating that the uniform speed motor and fan provide a reasonably constant air pressure. 4. Uniform performance of the motor and fan was also demonstrated by germination tests of the pure seed fractions from duplicate sub-samples of seven different lots in which no significant differences in germination of the replicates were obtained. 5. An additional evidence of uniform performance of the motor and fan was noted in the fairly uniform number of normal sprouts obtained in the inert fractions of samples having different weights per bushel. 6. Samples ranging in bushel weight from 16 to 27 pounds responded similarly to the same treatment thereby suggesting that weight per bushel for the samples studied was controlled more by the amount of empty florets present than by immature or light weight seed. Seed weighing 10 pounds required a stronger air blast than did heavier seed in order to remove infertile florets, although possibly a longer time at the standard opening might accomplish the same result. 7. Eight seed laboratories using the modified method of procedure, each with a similar sub-sample previously blown to aid in calibration of each blower, obtained purity percentages within the range of natural variability. 8. The adoption of the modified method of analyzing bluegrass for purity would involve the following: a. Installation of a standard control machine in a laboratory where frequent checks on samples could be made for all laboratories with similar equipment. b. Purchase of a scale and use of graduated vials for determining weight per bushel of small samples. c. Acceptance of the principle of approximate purity by a uniform method of procedure as a substitute for the ideal of absolute purity. d. Regular examination of pure seed remnants with a binocular or reflected light to check the reliability of the fan. 9. The use of a standard method of procedure based on the principle of separation of fertile and infertile florets by air pressure, as developed and maintained by a uniform speed motor, would solve one of the most difficult labeling and analytical problems now faced by the seed trade and seed analysts, respectively, and in addition provide uniform pure seed fractions for germination, which should automatically reduce some of the differences obtained in germination tests. 10. Germination tests of non-fresh seed of bluegrass representing 15 different lots each in quadruplicate indicate that sterile sand in petri dishes saturated with distilled water furnishes a slightly superior sub-stratum to filter paper moistened with distilled water or with .2% KN03 solution. Limited trials with copper trays equipped with wicks to maintain a constant supply of water indicate that they are equal to sand. 11. Total germination of bluegrass seed from 15 lots was significantly higher on sand than on filter papers at 10, 15 and 20 days after the tests were started. Mean germination at the end of 15 days on sand was practically equal to that on filter papers at the end of 28 days

Testing the quality of seeds for farm and garden

The yield and quality of a crop to be harvested depend in part on the quality of the seed that is planted. Seed quality is a relative term. It is based on a number of conditions, the more important of which are purity of the seed as expressed in terms of freedom from weed seed and other impurities, viability, freedom from seed-borne organisms and ability to resist infection by soil-borne organisms. Many factors and conditions affect seed quality, including crop sequence, type and frequency of cultivation, climate, time of harvesting, genetic constitution of the seed, variety of seed planted, storage, age and treatment of seed. The purpose of this bulletin is to discuss some of the factors which affect seed quality, to outline methods employed in a seed laboratory to determine seed quality and to illustrate how the results of seed laboratory tests may be applied in the planting of seeds

Germinability of treated and untreated lots of vegetable seed in Pythium-infested soil and in the field

Seed lots of beans, beets, carrots, onions, peas, popcorn, soybeans, spinach, sweet corn and tomatoes were obtained from several sources. Tests with treated and untreated seed were made in sand, blotters or towels using the standard methods recommended in rules for seed testing. In addition, tests were made in soil naturally infested with Pythium debaryanum Hesse and Pythium graminicola Subr. as well as in the field. Temperature and moisture conditions in the field were occasionally optimum or nearly so but more frequently the temperature-moisture relationship was such as to provide an environment far below the optimum for germination. The data obtained from the several tests are summarized herewith

Weeds Are on the Spot

Iowa and most other states have a real weed problem. Canada thistle, quack grass, horse nettle and field bindweed (creeping jennie) have spread rapidly in the last 10 years in Iowa, and other new but equally serious weeds have become established

Testing farm seed

Iowa is a major crop- and seed-producing area. More acres of corn and oats are grown in Iowa than in any other state, and most of the seed of these crops for Iowa farmers is produced within the state. Furthermore, in 1943 over 95 percent of the corn acreage was planted with hybrid seed, and over 60 percent of the oat. acreage was planted with seed of new rust-resistant varieties. Other seed crops of importance in Iowa are soybeans, bluegrass, timothy, wheat, flax, bromegrass, red clover, sweet clover, sudan grass, sweet corn, watermelon and sorghum. The yield and quality of a crop harvested each year is dependent in part on the quality of the seed that is planted and the only, way to know the quality factors of purity, vitality, weed seed content and sanitation is to test seed prior to planting. The purpose of this bulletin is to provide teachers and farmers with information about the need for clean seed and methods of testing seed with special emphasis on determination of pure seed, identification of weed and crop seeds, germination tests and use of seed disinfectants for the control of molds that cause disease

On the Hα\alpha emission from the β\beta Cephei system

Be stars, which are characterised by intermittent emission in their hydrogen lines, are known to be fast rotators. This fast rotation is a requirement for the formation of a Keplerian disk, which in turn gives rise to the emission. However, the pulsating, magnetic B1IV star $\beta$ Cephei is a very slow rotator that still shows H$\alpha$ emission episodes like in other Be stars, contradicting current theories. We investigate the hypothesis that the H$\alpha$ emission stems from the spectroscopically unresolved companion of $\beta$ Cep. Spectra of the two unresolved components have been separated in the 6350-6850\AA range with spectro-astrometric techniques, using 11 longslit spectra obtained with ALFOSC at the Nordic Optical Telescope, La Palma. We find that the H$\alpha$ emission is not related to the primary in $\beta$ Cep, but is due to its 3.4 magnitudes fainter companion. This companion has been resolved by speckle techniques, but it remains unresolved by traditional spectroscopy. The emission extends from about $-$400 to +400 km s$^{-1}$. The companion star in its 90-year orbit is likely to be a classical Be star with a spectral type around B6-8. By identifying its Be-star companion as the origin of the H$\alpha$ emission behaviour, the enigma behind the Be status of the slow rotator $\beta$ Cep has been resolved.Comment: 4 pages, 3 figures. Accepted by A&A Letter