477 research outputs found
Stratifying derived categories of cochains on certain spaces
In recent years, Benson, Iyengar and Krause have developed a theory of
stratification for compactly generated triangulated categories with an action
of a graded commutative Noetherian ring. Stratification implies a
classification of localizing and thick subcategories in terms of subsets of the
prime ideal spectrum of the given ring. In this paper two stratification
results are presented: one for the derived category of a commutative
ring-spectrum with polynomial homotopy and another for the derived category of
cochains on certain spaces. We also give the stratification of cochains on a
space a topological content.Comment: 27 page
Interaction between toothbrushes and toothpaste abrasive particles in simulated tooth cleaning
There are currently many toothbrush designs on the market incorporating different
filament configurations such as filaments at various angles and different lengths and
made from several different materials. In order to understand how the tooth cleaning
process occurs there is a need to investigate in detail how the abrasive particles in a
toothpaste interact with the filaments in a teeth cleaning contact and cause material
removal from a plaque or stain layer.
The following describes the development of optical apparatus to enable the
visualisation of simulated teeth cleaning contacts. Studies have been carried out using
the apparatus to investigate particle entrainment into the contact and how it differs
with varying bristle configurations. The effects of filament stiffness and tip shape
were also investigated. Various types of electric toothbrushes were also tested.
The studies have shown how particles are trapped at the tips of toothbrush filaments.
Particles, suspended in fluid, approach the filament tips, as they pass through they
may become trapped. Greater particle entrainment into the filament tip contact occurs
with a reciprocating action at low filament loads and deflections than with a sliding
motion. Large particles are less likely to enter tip contacts and are trapped between
tips or under the filament bend at higher loads.
Whether the particles are likely to be trapped and how long they remain so depends
on the filament stiffness and degree of splay on loading and the filament
configuration. The direction the filaments point in, the number of filaments in a tuft,
the spacing of the tufts and the way the filaments splay when deflected all have an
influence on entrainment of particles. Tufts with tightly packed stiff filaments which
deflected together on loading were more effective at trapping particles than more flexible filaments that splayed out on loading as they present more of a barrier to
particle entry and exit from the tip region
On the algebraic K-theory of the complex K-theory spectrum
Let p>3 be a prime, let ku be the connective complex K-theory spectrum, and
let K(ku) be the algebraic K-theory spectrum of ku. We study the p-primary
homotopy type of the spectrum K(ku) by computing its mod (p,v_1) homotopy
groups. We show that up to a finite summand, these groups form a finitely
generated free module over a polynomial algebra F_p[b], where b is a class of
degree 2p+2 defined as a higher Bott element.Comment: Revised and expanded version, 42 pages
Experimental infection of sheep with ovine and bovine Dichelobacter nodosus isolates
AbstractThe aim of this study was, under experimental conditions, to investigate infection of Norwegian White sheep with ovine and bovine isolates of Dichelobacter nodosus of varying virulence. In addition, the efficacy of gamithromycin as a treatment for the experimentally induced infections was examined. The study was performed as a single foot inoculation using a boot. Four groups, each with six lambs, were inoculated with four different challenge strains (Group 1: benign bovine strain; Group 2: virulent bovine strain; Group 3: benign ovine strain; Group 4: virulent ovine strain). The main criterion to determine that infection was transferred was that D. nodosus isolate was obtained by culture. After the trial all lambs were treated with gamithromycin. Clinical symptoms of footrot developed in all groups, and when removing the boots two weeks after challenge, D. nodosus was isolated from 5 of 24 experimental lambs. All lambs tested negative for D. nodosus by PCR within six weeks after treatment with gamithromycin. This study strongly indicates that D. nodosus isolates from both sheep and cattle can be transferred to sheep under experimental conditions. The study also indicates that gamithromycin may be effective against D. nodosus
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