392 research outputs found
A Svarc-Milnor lemma for monoids acting by isometric embeddings
We continue our programme of extending key techniques from geometric group
theory to semigroup theory, by studying monoids acting by isometric embeddings
on spaces equipped with asymmetric, partially-defined distance functions. The
canonical example of such an action is a cancellative monoid acting by
translation on its Cayley graph. Our main result is an extension of the
Svarc-Milnor Lemma to this setting.Comment: 11 page
Quasi-morphisms and L^p-metrics on groups of volume-preserving diffeomorphisms
Let M be a smooth compact connected oriented manifold of dimension at least
two endowed with a volume form. We show that every homogeneous quasi-morphism
on the identity component of the group of volume preserving
diffeomorphisms of M, which is induced by a quasi-morphism on the fundamental
group, is Lipschitz with respect to the L^p-metric on the group
. As a consequence, assuming certain conditions on the
fundamental group, we construct bi-Lipschitz embeddings of finite dimensional
vector spaces into .Comment: This is a published versio
The Determination of the Homogeneity of a Vitis vinif era L. cv. Cape Riesling Vineyard
The value of Principal Component and Stepwise Discriminant analyses in selecting uniform plants for experimental purposes is discussed. Twenty seven variables were taken into account to establish the homogeniety (uniform plants) of 297 Vitis vinifera L. cv. Cape Riesling vines. A detailed study of the relationship and interrelationship of these variables resulted in 208 vines being selected as a uniform population. This selection provides the researcher with the possibility of using single vines as experimental units. However, it must be pointed out that Principal Component and Stepwise Discriminant analyses can only be used as an aid to normal statistical evaluation of experimental results and not as substitute for statistical experimental design
A Comparative Anatomical Study of the Grapevine, Shoot and Cane: II: Periderm and Secondary Phloem
The taxonomic value of ten periderm and secondary phloem features of canes of different grapevine species was investigated. A scatter diagram showed that with few exceptions the American cultivars have a larger periderm with smaller secondary phloem, while the reverse was true for European cultivars. Crosses tend to cluster with one of their parents. It has been found that the largest intercultivar variation occurs at either the middle of the shoot length or the ventral sides of the basal part of the shoots
Thermoelectrochemistry for harvesting waste heat
Current devices to harvest heat have significant limitations, and typically consist of intricate mechanical systems, such as either a petrol engine or a steam turbine. Thermoelectrochemistry is a simple, scalable technique for the direct electrochemical conversion of thermal energy into useful electricity.1, 2 It is driven by the entropy change associated with a redox process, resulting in a temperature dependence of the electrode potential (the Seebeck effect).1 The greater this dependence (the larger the Seebeck effect) the more efficient the power generation through this method.3 If there is a temperature difference between two identical electrodes, this difference can be converted into electricity using electrochemistry; such systems are ideal for harvesting low-grade heat that would otherwise go to waste.2 Ionic liquids have solvent properties appropriate for thermoelectrochemical systems such as wide liquid temperature ranges, low vapour pressure, low flamability and favourable interactions with charged, redox active species which can lead to a large entropy change.2
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A Comparative Anatomical Study of the Grapevine Shoot: I Epidermis
Material gathered from three positions on the shoot and cane during veraison and two weeks after harvest were investigated for taxonomic features concerning the epidermis. Stomata and lenticels were present in all the cultivars studied, but trichomes were frequently present only on 99 Richter. Based on epidermal characteristics a dendogram giving the percentage similarity between cultivars, was constructed, and from this was concluded that concerning taxonomic features on Vitis vinifera L. cultivars tend to have a more than 90% similarity irrespective of the position on the shoot
Strongly bounded groups and infinite powers of finite groups
We define a group as strongly bounded if every isometric action on a metric
space has bounded orbits. This latter property is equivalent to the so-called
uncountable strong cofinality, recently introduced by G. Bergman.
Our main result is that G^I is strongly bounded when G is a finite, perfect
group and I is any set. This strengthens a result of Koppelberg and Tits. We
also prove that omega_1-existentially closed groups are strongly bounded.Comment: 10 pages, no figure. Versions 1-3 were entitled "Uncountable groups
with Property (FH)". To appear in Comm. Algebr
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