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The rocky shores of the north-east Atlantic have been long studied. Our focus is from Gibraltar to Norway plus the Azores and Iceland. Phylogeographic processes shape biogeographic patterns of biodiversity. Long-term and broadscale studies have shown the responses of biota to past climate fluctuations and more recent anthropogenic climate change. Inter- and intra-specific species interactions along sharp local environmental gradients shape distributions and community structure and hence ecosystem functioning. Shifts in domination by fucoids in shelter to barnacles/mussels in exposure are mediated by grazing by patellid limpets. Further south fucoids become increasingly rare, with species disappearing or restricted to estuarine refuges, caused by greater desiccation and grazing pressure. Mesoscale processes influence bottom-up nutrient forcing and larval supply, hence affecting species abundance and distribution, and can be proximate factors setting range edges (e.g., the English Channel, the Iberian Peninsula). Impacts of invasive non-native species are reviewed. Knowledge gaps such as the work on rockpools and host–parasite dynamics are also outlined.
Reductions in insulin sensitivity in periparturient dairy cows develop as a means to support lactation; however, excessive mobilization of fatty acids (FA) increases the risk for peripartal metabolic disorders. Our objectives were to investigate the effect of prepartum body condition score (BCS) on systemic glucose and insulin tolerance, and to compare direct and indirect measurements of insulin sensitivity in peripartal lean and overweight dairy cows. Fourteen multiparous Holstein cows were allocated into two groups according to their BCS at day −28 prepartum: lean (n = 7; BCS ≤ 3.0) or overweight; (n = 7; BCS ≥ 4.0). Liver biopsies were performed on day −27, −14 and 4, relative to expected parturition. Intravenous insulin or glucose tolerances tests were performed following each liver biopsy. Relative to lean cows, overweight cows exhibited lower dry matter intake, lost more BCS and displayed increased plasma FA and β-hydroxybutyrate concentrations and elevated liver lipid content during peripartum. Glucose clearance rate was lower for all cows postpartum. Prepartum BCS had minimal effects on insulin and glucose tolerance; however, the ability of the cow to restore blood glucose levels following an insulin challenge was suppressed by increased BCS. Glucose-dependent parameters of insulin and glucose tolerance were not correlated with surrogate indices of insulin sensitivity. We conclude that prepartum BCS had minimal effect on systemic insulin sensitivity following parturition. The observed inconsistency between surrogate indices of insulin sensitivity and direct measurements of insulin and glucose tolerance adds support to growing concerns regarding their usefulness as tools to estimate systemic insulin action in periparturient cows.
Antenna-pattern measurements obtained from a double-metal supra-terahertz-frequency (supra-THz) quantum cascade laser (QCL) are presented. The QCL is mounted within a mechanically micro-machined waveguide cavity containing dual diagonal feedhorns. Operating in continuous-wave mode at 3.5 THz, and at an ambient temperature of ~60 K, QCL emission has been directed via the feedhorns to a supra-THz detector mounted on a multi-axis linear scanner. Comparison of simulated and measured far-field antenna patterns shows an excellent degree of correlation between beamwidth (full-width-half-maximum) and sidelobe content and a very substantial improvement when compared with unmounted devices. Additionally, a single output has been used to successfully illuminate and demonstrate an optical breadboard arrangement associated with a future supra-THz Earth observation space-borne payload. Our novel device has therefore provided a valuable demonstration of the effectiveness of supra-THz diagonal feedhorns and QCL devices for future space-borne ultra-high-frequency Earth-observing heterodyne radiometers.
The objective of this study was to investigate the impact of the most commonly cited factors that may have influenced infants’ gut microbiota profiles at one year of age: mode of delivery, breastfeeding duration and antibiotic exposure. Barcoded V3/V4 amplicons of bacterial 16S-rRNA gene were prepared from the stool samples of 52 healthy 1-year-old Australian children and sequenced using the Illumina MiSeq platform. Following the quality checks, the data were processed using the Quantitative Insights Into Microbial Ecology pipeline and analysed using the Calypso package for microbiome data analysis. The stool microbiota profiles of children still breastfed were significantly different from that of children weaned earlier (P<0.05), independent of the age of solid food introduction. Among children still breastfed, Veillonella spp. abundance was higher. Children no longer breastfed possessed a more ‘mature’ microbiota, with notable increases of Firmicutes. The microbiota profiles of the children could not be differentiated by delivery mode or antibiotic exposure. Further analysis based on children’s feeding patterns found children who were breastfed alongside solid food had significantly different microbiota profiles compared to that of children who were receiving both breastmilk and formula milk alongside solid food. This study provided evidence that breastfeeding continues to influence gut microbial community even at late infancy when these children are also consuming table foods. At this age, any impacts from mode of delivery or antibiotic exposure did not appear to be discernible imprints on the microbial community profiles of these healthy children.
The aim of this retrospective review was to assess the overall burden and trend in spinal tuberculosis (TB) at tertiary hospitals in the Western Cape Province of South Africa. All spinal TB cases seen at the province's three tertiary hospitals between 2012 and 2015 were identified and clinical records of each case assessed. Cases were subsequently classified as bacteriologically confirmed or clinically diagnosed and reported with accompanying clinical and demographic information. Odds ratios (OR) for severe spinal disease and corrective surgery in child vs. adult cases were calculated. A total of 393 cases were identified (319 adults, 74 children), of which 283 (72%) were bacteriologically confirmed. Adult cases decreased year-on-year (P = 0.04), however there was no clear trend in child cases. Kyphosis was present in 60/74 (81%) children and 243/315 (77%) adults with available imaging. Corrective spinal surgery was performed in 35/74 (47%) children and 80/319 (25%) adults (OR 2.7, 95% confidence interval 1.6–4.5, P = 0.0003). These findings suggest that Western Cape tertiary hospitals have experienced a substantial burden of spinal TB cases in recent years with a high proportion of severe presentation, particularly among children. Spinal TB remains a public health concern with increased vigilance required for earlier diagnosis, especially of child cases.
We investigate the onset of three-dimensional hydrothermal waves in a low-capillary-number liquid layer of arbitrary depth, bounded by a free liquid–gas interface from above and a partial slip, rigid surface from below. A selection of two- and three-dimensional hydrothermal waves, longitudinal rolls and longitudinal travelling waves, form the preferred mode of instability, which depends intricately on the magnitude of the basal slip. Partial slip is destabilizing for all modes of instability. Specifically, the minimal Marangoni number required for the onset of instability follows
for each mode, where
is the slip parameter. In the limit of free slip, longitudinal travelling waves disappear in favour of longitudinal rolls. With increasing slip, it is common for two-dimensional hydrothermal waves to exchange stability in favour of longitudinal rolls and oblique hydrothermal waves. Two types of oblique hydrothermal waves appear under partial slip, which exchange stability with increasing slip. The oblique mode that is preferred under no slip persists and remains near longitudinal for small slip parameters.
Let G be a group and H be a subgroup of G. We say that H is left relatively convex in G if the left G-set G/H has at least one G-invariant order; when G is left orderable, this holds if and only if H is convex in G under some left ordering of G. We give a criterion for H to be left relatively convex in G that generalizes a famous theorem of Burns and Hale and has essentially the same proof. We show that all maximal cyclic subgroups are left relatively convex in free groups, in right-angled Artin groups, and in surface groups that are not the Klein-bottle group. The free-group case extends a result of Duncan and Howie. More generally, every maximal m-generated subgroup in a free group is left relatively convex. The same result is valid, with some exceptions, for compact surface groups. Maximal m-generated abelian subgroups in right-angled Artin groups are left relatively convex. If G is left orderable, then each free factor of G is left relatively convex in G. More generally, for any graph of groups, if each edge group is left relatively convex in each of its vertex groups, then each vertex group is left relatively convex in the fundamental group; this generalizes a result of Chiswell.
We discuss the connection between Chevalley’s definition of a covering space and the usual definition given in an introductory topology course. Then we indicate how some theorems about the covering groups of a topological group can be proved from the global point of view, without using local isomorphisms between topological groups.
This is a summary, written by the first-named author, of his joint work with Ross Geoghegan over the past years. Most of the material is available in detail in the preprint “Limit sets for modules over groups on cat(0) spaces – from the Euclidean to the hyperbolic,” available at http://arxiv.org/abs/1306.3403, and I will occasionally refer to specific detail in that paper. Other parts of our joint work - results mostly concerned with extending concepts and results from that paper to higher dimensions – will also be mentioned but are still in preparation.
Let G be a group, and let S be a finite subset of G that generates G as a monoid. The co-word problem is the collection of words in the free monoid S∗ that represent non-trivial elements of G. A current conjecture, based originally on a conjecture of Lehnert and modified into its current form by Bleak, Matucci, and Neunhöffer, says that Thompson’s group V is a universal group with context-free co-word problem. It is thus conjectured that a group has a context-free co-word problem exactly if it is a finitely generated subgroup of V. Hughes introduced the class FSS of groups that are determined by finite similarity structures. An FSS group acts by local similarities on a compact ultrametric space. Thompson’s group V is a representative example, but there are many others.We show that FSS groups have context-free co-word problem under a minimal additional hypothesis. As a result, we can specify a subfamily of FSS groups that are potential counterexamples to the conjecture.
Let G be a finitely generated group, and Σ a finite subset that generates G as a monoid. The word problem of G with respect to Σ consists of all words in the free monoid Σ* that are equal to the identity in G. The co-word problem of G with respect to Σ is the complement in Σ* of the word problem. We say that a group G is coCF if its co-word problem with respect to some (equivalently, any) finite generating set Σ is a context-free language. We describe a generalized Thompson group V(G,θ) for each finite group G and homomorphism θ: G → G. Our group is constructed using the cloning systems introduced by Witzel and Zaremsky. We prove that V(G,θ) is coCF for any homomorphism θ and finite group G by constructing a pushdown automaton and showing that the co-word problem of V(G,θ) is the cyclic shift of the language accepted by our automaton. Demonstrative subgroups of V, introduced by Bleak and Salazar-Diaz, can be used to construct embeddings of certain wreath products and amalgamated free products into V. We extend the class of known finitely generated demonstrative subgroups of V to include all virtually cyclic groups.
An important “stability” theorem in shape theory, due to D. A. Edwards and R. Geoghegan, characterizes those compacta having the same shape as a finite CW complex. In this chapter we present a straightforward and self-contained proof of that theorem.
We give a simple technique to compute the distance between two points in an n-dimensional Euclidean simplex, where the points are given in barycentric coordinates, using only the edge lengths of that simplex. We then use this technique to verify a few computations which will be used in subsequent papers. The most important application is a formula for intrinsically computing the volume of a Euclidean simplex, which is more efficient (and more natural) than any previously documented methods.
We explore the ideal structure of the reduced C∗-algebra of R. Thompson’s group T. We show that even though T has trace, one cannot use the Kesten Condition to verify that the reduced C∗-algebra of T is simple. At the time of the initial writing of this chapter, there had been no example group for which it was known that the Kesten Condition would fail to prove simplicity, even though the group has trace. Motivated by this first result, we describe a class of groups where even if the group has trace, one cannot apply the Kesten Condition to verify the simplicity of those groups' reduced C∗-algebras. We also offer an apparently weaker condition to test for the simplicity of a group's reduced C∗-algebra, and we show this new test is still insufficient to show that the reduced C∗-algebra of T is simple. Separately, we find a controlled version of a Ping-Pong Lemma which allows one to find non-abelian free subgroups in groups of homeomorphisms of the circle generated by elements with rational rotation number. We use our Ping-Pong Lemma to find a simple converse to a theorem of Uffe Haagerup and Kristian Knudsen Olesen.