1,490 research outputs found
Extended Partial Geometries: Dual 2-Designs
The study of EpGs (extended partial geometries) is continued from [5]; here we consider extended dual 2-designs (EDDs), especially one-point and triangular structures. We concentrate on three interesting cases: semibiplanes, which are extensions of the duals of trivial 2-designs (Section 4); extensions of dual projective geometries (Section 7); extensions of dual affine geometries (Section 8). We find non-existence theorems, examples, uniqueness theorems, and many open questions
Recommended from our members
Diode and final-focus simulations for DARHT
Beam dynamics calculations for the injector and final-focus region of a 4 kA, 20 MeV linear induction accelerator are presented. The injector is a low-emittance 4 MeV thermionic or photocathode diode designed to produce four 70 ns pulses over 2 {micro}sec. Due to the long total pule length, the authors have kept the field stress to < 200 kV/cm over the cathode electrode, and to {approx} 50 kV/cm on the radial insulator stacks. The normalized edge emittance produced by the diode is only {approx} 0.019 cm-rad. In the final-focus region, the authors have modeled the effect of ion emission from the target. The intense electric field of the beam at the 1-mm-diameter focal spot produces substantial ion velocities, and, if the space-charge-limited current density can be supplied, significant focal spot degradation may occur due to ion space-charge. Calculations for the existing Integrated Test Stand, which has a larger focal spot, show that the effect should be observable for H{sup +} and C{sup +} ion species. The effect is lessened if there is insufficient ion density on the target to supply the space-charge-limited current density, or if the ion charge-to-mass ratio is sufficiently small
Block-Transitive Designs in Affine Spaces
This paper deals with block-transitive - designs in affine
spaces for large , with a focus on the important index case. We
prove that there are no non-trivial 5- designs admitting a
block-transitive group of automorphisms that is of affine type. Moreover, we
show that the corresponding non-existence result holds for 4- designs,
except possibly when the group is one-dimensional affine. Our approach involves
a consideration of the finite 2-homogeneous affine permutation groups.Comment: 10 pages; to appear in: "Designs, Codes and Cryptography
Aluminium and Acacia plant growth on coal mine dumps
Colonising native and introduced plant species present on old abandoned dumps in the Collie coal field in south-west Western Australia provide a potential resource for rehabilitation. Coal waste dumps are more acidic than the surrounding forest soils, indicating a potentially toxic presence of aluminium. Some plants exhibit tolerance, and may accumulate, avoid or exclude aluminium. Excluders restrict translocation of the metal bound in root cells. Evolution of tolerance to metal stress may be comparatively rapid and although aluminium has many adverse affects on growth, plants tolerant of its presence also tend to be drought tolerant, an advantage for survival on dumps over dry summers.
Progeny of a dump population of Acacia decurrens are contrasted with a non-dump population. Seedlings were subjected to varied concentrations of aluminium in solution and harvested at 10 weeks. A. decurrens tolerated low levels of applied aluminium but severe effects on growth were observed at 500 ppm. Plants of dump origin failed to produce greater plant biomass than non-dump plants. However, dump origin plants took up less total aluminium than non-dump plants, indicating an avoidance mechanism. Dump progeny held more of the absorbed aluminium within roots, translocating lower quantities to foliage, suggesting an exclusion mechanism. Decreased tissue nitrogen, phosphorus and calcium coincided with increased aluminium supplied. Calcium decline was the most severe. Trace element and manganese concentrations increased with added aluminium.
Despite an inability to out-perform non-dump progeny, the pattern of nutrient uptake indicates a real difference between the two accessions. In the long run survivors are likely to persist and reproduce if they have successfully avoided uptake of deleterious elements beyond the root systems. It is therefore recommended that collection of seed for use on coal-mine rehabilitation sites should be made from established plants growing on dumps
Образ міста у творчості О. Іваненко (на матеріалі казки “Чарівна квітка”)
Авторка статті досліджує образ міста у творчості відомої письменниці ХХ ст.
Оксани Іваненко. Автор робить спробу виокремити особливості творів, що характерні для її
манери письма. Приділяється увага тематиці творів письменниці, портретній характеристиці її
героїв. Дослідниця робить спробу схарактеризувати образ міста на матеріалі казок “Чарівна
квітка”. “Місто боягузів” у казці “Чарівна квітка” О. Іваненко є точкою відліку в казковому часі, не має логіки у взаємозв’язку з дійсністю. Результатом дослідження є висновок про те, що
письменниця досліджує процес становлення і розвитку дитини, вивчає особливості психології
персонажів.
Ключові слова: казка, логіка, образ, місто, тематика, реальність, персонажі.Автор статьи исследует образ города в творчестве известной писательницы ХХ века
Оксаны Иваненко. Автор статьи делает попытку выделить особенности произведений,
характерные ее письму. Уделяется внимание тематике произведений писательницы, портретной
характеристике ее героев. Исследователь делает попытку охарактеризовать образ города на
материале сказки “Волшебный цветок”. “Город боягузов” в сказке “Волшебный цветок”
Оксаны Иваненко является точкой отсчета в сказочном времени, не имеет логики со
взаимосвязью с действительностью. Результатом исследования является вывод о том, что
писательница исследует процесс становления и развития юного читателя, изучает особенности
психологии персонажей.
Ключевые слова: сказка, логика, образ, город, тематика, реальность, персонажи.The author of the article investigates the figure of the city in the O. Ivanenko’s works, the
famous writer of the XX th century. The author tries to define the peculiarities of her works. There are
paid attentions to the portrait characteristics of the main characters in “Magic flower”, to the themes of
her works. The investigator tries to characterise the figure of the city in the “Magic flower”. The “city of
timorous people” in the “Magic flower” by O. Ivanenko is the beginning in the time of the tale, it does not
have logic. This investigation proves that the writer investigates the process of the child’s growing and
growing, studies the psychological peculiarities of the main characters.
Keywords: tale, logic, figure, city, themes, reality, main characters
Steiner t-designs for large t
One of the most central and long-standing open questions in combinatorial
design theory concerns the existence of Steiner t-designs for large values of
t. Although in his classical 1987 paper, L. Teirlinck has shown that
non-trivial t-designs exist for all values of t, no non-trivial Steiner
t-design with t > 5 has been constructed until now. Understandingly, the case t
= 6 has received considerable attention. There has been recent progress
concerning the existence of highly symmetric Steiner 6-designs: It is shown in
[M. Huber, J. Algebr. Comb. 26 (2007), pp. 453-476] that no non-trivial
flag-transitive Steiner 6-design can exist. In this paper, we announce that
essentially also no block-transitive Steiner 6-design can exist.Comment: 9 pages; to appear in: Mathematical Methods in Computer Science 2008,
ed. by J.Calmet, W.Geiselmann, J.Mueller-Quade, Springer Lecture Notes in
Computer Scienc
Description of superdeformed nuclei in the interacting boson model
The interacting boson model is extended to describe the spectroscopy of
superdeformed bands. Microscopic structure of the model in the second minimum
is discussed and superdeformed bosons are introduced as the new building
blocks. Solutions of a quadrupole Hamiltonian are implemented through the
expansion method. Effects of the quadrupole parameters on dynamic moment of
inertia and electric quadrupole transition rates are discussed and the results
are used in a description of superdeformed bands in the Hg-Pb and Gd-Dy
regions.Comment: 18 pages revtex, 9 figures available upon reques
In vitro neuroprotective activities of two distinct probiotic consortia
Neurodegeneration has been linked to changes in the gut microbiota and this study compares the neuroprotective capability of two bacterial consortia, known as Lab4 and Lab4b, using the established SH-SY5Y neuronal cell model. Firstly, varying total antioxidant capacities (TAC) were identified in the intact cells from each consortia and their secreted metabolites, referred to as conditioned media (CM). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Crystal Violet (CV) assays of cell viability revealed that Lab4 CM and Lab4b CM could induce similar levels of proliferation in SH-SY5Y cells and, despite divergent TAC, possessed a comparable ability to protect undifferentiated and retinoic acid-differentiated cells from the cytotoxic actions of rotenone and undifferentiated cells from the cytotoxic actions of 1-methyl-4-phenylpyridinium iodide (MPP+). Lab4 CM and Lab4b CM also had the ability to attenuate rotenone-induced apoptosis and necrosis with Lab4b inducing the greater effect. Both consortia showed an analogous ability to attenuate intracellular reactive oxygen species accumulation in SH-SY5Y cells although the differential upregulation of genes encoding glutathione reductase and superoxide dismutase by Lab4 CM and Lab4b CM, respectively, implicates the involvement of consortia-specific antioxidative mechanisms of action. This study implicates Lab4 and Lab4b as potential neuroprotective agents and justifies their inclusion in further in vivo studies
Quantifying the levitation picture of extended states in lattice models
The behavior of extended states is quantitatively analyzed for two
dimensional lattice models. A levitation picture is established for both
white-noise and correlated disorder potentials. In a continuum limit window of
the lattice models we find simple quantitative expressions for the extended
states levitation, suggesting an underlying universal behavior. On the other
hand, these results point out that the Quantum Hall phase diagrams may be
disorder dependent.Comment: 5 pages, submitted to PR
- …