Daily changes in global cloud cover and Earth transits of the heliospheric current sheet

Changes in cloud cover are found to occur for periods of a few days following Earth transits of the heliospheric current sheet (HCS), provided also that the transits occur in years of high stratospheric aerosol loading. Using global cloud products from the International Satellite Cloud Climatology Project (ISCCP) D1 data series, epoch superposition analyses were made for various samples of HCS events. For the period August 1991 to June 1994 for the stratospheric aerosol loading due to the Pinatubo eruption, the analysis of the data in 30° geomagnetic latitude intervals revealed that cloud anomalies that were significant and negative were located in the Southern Hemisphere high and middle latitudes, and anomalies that were significant and positive were found in both hemispheres at low latitudes. When the key days in the superposed epoch analysis were determined by minima in the relativistic electron flux, rather than by the HCS crossings, the location of the significant negative anomalies was in the northern high latitudes, and the location of the significant positive anomalies was in middle latitudes in the Northern Hemisphere. The spatial and temporal patterns of these cloud cover variations are in broad agreement with the expected opposite variations at high and low latitudes of the current density Jz in the global electric circuit caused by the relativistic electron flux variations, during periods when the aerosol loading has made a large increase in stratospheric resistivity

Spherical alterations of handles: embedding the manifold plus construction

A key tool in our earlier work on ends of manifolds high-dimensional manifolds was an ability to embed cobordisms provided by the Quillen Plus Construction into those ends. Here we develop a `spherical modification' trick which provides a constructive approach to obtaining such embeddings. More importantly, this approach allows for more general embedding results. In this paper we develop generalizations of the plus construction and show how the corresponding cobordisms can be embedded in manifolds satisfying appropriate fundamental group properties. Results obtained here play an important role in our ongoing study of noncompact manifolds.Comment: This final version will appear in Algebraic & Geometric Topology. Small corrections, including a fix to the statement of Theorem 5.3. 22 pages, 4 figure

Environmental constraints influencing survival of an African parasite in a north temperate habitat: effects of temperature on egg development

SUMMARYFactors affecting survival of parasites introduced to new geographical regions include changes in environmental temperature. Protopolystoma xenopodis is a monogenean introduced with the amphibian Xenopus laevis from South Africa to Wales (probably in the 1960s) where low water temperatures impose major constraints on life-cycle processes. Effects were quantified by maintenance of eggs from infections in Wales under controlled conditions at 10, 12, 15, 18, 20 and 25°C. The threshold for egg viability/ development was 15°C. Mean times to hatching were 22 days at 25°C, 32 days at 20°C, extending to 66 days at 15°C. Field temperature records provided calibration of transmission schedules. Although egg production continues year-round, all eggs produced during >8 months/ year die without hatching. Output contributing significantly to transmission is restricted to 10 weeks (May-mid-July). Host infection, beginning after a time lag of 8 weeks for egg development, is also restricted to 10 weeks (July-September). Habitat temperatures (mean 15·5°C in summer 2008) allow only a narrow margin for life-cycle progress: even small temperature increases, predicted with 'global warming', enhance infection. This system provides empirical data on the metrics of transmission permitting long-term persistence of isolated parasite populations in limiting environments

Environmental constraints influencing survival of an African parasite in a north temperate habitat: effects of temperature on development within the host

The monogenean Protopolystoma xenopodis has been established in Wales for >40 years following introduction with Xenopus laevis from South Africa. This provides an experimental system for determining constraints affecting introduced species in novel environments. Parasite development post-infection was followed at 15, 20 and 25 °C for 15 weeks and at 10 °C for51 year and correlated with temperatures recorded inWales. Development was slowed/arrested at410 °C which reflects habitat conditions for >6 months/year. There was wide variation in growth at constant temperature (body size differing by >10 times) potentially attributable in part to genotype-specific host-parasite interactions. Parasite density had no effect on size but host sex did: worms in males were 1·8 times larger than in females. Minimum time to patency was 51 days at 25 °C and 73 days at 20 °C although some infections were still not patent at both temperatures by 105 days p.i. In Wales, fastest developing infections may mature within one summer (about 12 weeks), possibly accelerated by movements of hosts into warmer surface waters. Otherwise, development slows/stops in October–April, delaying patency to about 1 year p.i., while wide variation in developmental rates may impose delays of 2 years in some primary infections and even longer in secondary infections

Manifolds with non-stable fundamental groups at infinity, II

In this paper we continue an earlier study of ends non-compact manifolds. The over-arching goal is to investigate and obtain generalizations of Siebenmann's famous collaring theorem that may be applied to manifolds having non-stable fundamental group systems at infinity. In this paper we show that, for manifolds with compact boundary, the condition of inward tameness has substatial implications for the algebraic topology at infinity. In particular, every inward tame manifold with compact boundary has stable homology (in all dimensions) and semistable fundamental group at each of its ends. In contrast, we also construct examples of this sort which fail to have perfectly semistable fundamental group at infinity. In doing so, we exhibit the first known examples of open manifolds that are inward tame and have vanishing Wall finiteness obstruction at infinity, but are not pseudo-collarable.Comment: Published by Geometry and Topology at http://www.maths.warwick.ac.uk/gt/GTVol7/paper7.abs.htm