A Nielsen theory for coincidences of iterates

As the title suggests, this paper gives a Nielsen theory of coincidences of iterates of two self maps f, g of a closed manifold. The ideas is, as much as possible, to generalize Nielsen type periodic point theory, but there are many obstacles. Many times we get similar results to the "classical ones" in Nielsen periodic point theory, but with stronger hypotheses.Comment: 30 page

Nevus sebaceus with syringocystadenoma papilliferum, prurigo nodularis, apocrine cystadenoma, basaloid follicular proliferation, and sebaceoma: case report and review of nevus sebaceus-associated conditions

Nevus sebaceus is a benign skin hamartoma of congenital onset that grows during puberty, and in adulthood can develop secondary benign and malignant neoplasms. The most common benign neoplasms occurring in nevus sebaceus are believed to be syringocystadenoma papilliferum, trichilemmoma, and trichoblastoma. A patient with nevus sebaceus developed not only syringocystadenoma papilliferum but also prurigo nodularis within her hamartomatous lesion; multiple biopsies were necessary to establish the diagnoses. Excision of the residual nevus sebaceus also revealed an apocrine cystadenoma, basaloid follicular proliferation, and sebaceoma. Also, it is important to select the appropriate biopsy site and size when evaluating a patient for secondary neoplasms within their nevus sebaceous. Indeed, more than one biopsy may be required if additional diagnoses are suspected

The Escape of Ionizing Photons from the Galaxy

The Magellanic Stream and several high velocity clouds have now been detected in optical line emission. The observed emission measures and kinematics are most plausibly explained by photoionization due to hot, young stars in the Galactic disk. The highly favorable orientation of the Stream allows an unambiguous determination of the fraction of ionizing photons, F_esc, which escape the disk. We have modelled the production and transport of ionizing photons through an opaque interstellar medium. Normalization to the Stream detections requires F_esc = 6%, in reasonable agreement with the flux required to ionize the Reynolds layer. Neither shock heating nor emission within a hot Galactic corona can be important in producing the observed H-alpha emission. If such a large escape fraction is typical of L_* galaxies, star-forming systems dominate the extragalactic ionizing background. Within the context of this model, both the three-dimensional orientation of the Stream and the distances to high-velocity clouds can be determined by sensitive H-alpha observations.Comment: 4 pages; LaTeX2e, emulateapj.sty, apjfonts.sty; 4 encapsulated PS figures. For correct labels, may need to print Fig. 3 separately due to psfig limitation. Astrophysical Journal (Letters), accepte

High temperature reliability of power module substrates

The thermal cycling reliability of candidate copper and aluminium power substrates has been assessed for use at temperatures exceeding 300°C peak using a combination of thermal cycling, nanoindentation and finite element modelling to understand the relative stresses and evolution of the mechanical properties. The results include the relative cycling lifetimes up to 350°C, demonstrating almost an order of magnitude higher lifetime for active metal brazed Al / AlN substrates over Cu / Si3N4, but four times more severe roughening and cracking of the Ni-P plating's on the Al / AlN (DBA) substrates. The nonlinear finite element modelling illustrated that the yield strength of the metal and the thickness of the ceramic are the main stress controlling factors, but comparisons with the cycling lifetime results demonstrated that the fracture toughness (resistance) of the ceramic is the over-riding controlling factor for the overall passive thermal cycling lifetimes. In order to achieve the highest substrate lifetime for the highly stressed high temperature thermal cycled applications, the optimum solution appears to be annealed copper, brazed on to a thicker than normal or higher fracture toughness Si3N4 ceramic

Are Compact High-Velocity Clouds Extragalactic Objects?

Compact high-velocity clouds (CHVCs) are the most distant of the HVCs in the Local Group model and would have HI volume densities of order 0.0003/cm^3. Clouds with these volume densities and the observed neutral hydrogen column densities will be largely ionized, even if exposed only to the extragalactic ionizing radiation field. Here we examine the implications of this process for models of CHVCs. We have modeled the ionization structure of spherical clouds (with and without dark matter halos) for a large range of densities and sizes, appropriate to CHVCs over the range of suggested distances, exposed to the extragalactic ionizing photon flux. Constant-density cloud models in which the CHVCs are at Local Group distances have total (ionized plus neutral) gas masses roughly 20-30 times larger than the neutral gas masses, implying that the gas mass alone of the observed population of CHVCs is about 40 billion solar masses. With a realistic (10:1) dark matter to gas mass ratio, the total mass in such CHVCs is a significant fraction of the dynamical mass of the Local Group, and their line widths would exceed the observed FWHM. Models with dark matter halos fare even more poorly; they must lie within approximately 200 kpc of the Galaxy. We show that exponential neutral hydrogen column density profiles are a natural consequence of an external source of ionizing photons, and argue that these profiles cannot be used to derive model-independent distances to the CHVCs. These results argue strongly that the CHVCs are not cosmological objects, and are instead associated with the Galactic halo.Comment: 30 pages, 14 figures; to appear in The Astrophysical Journa

Optimising the analysis of transcript data using high density oligonucleotide arrays and genomic DNA-based probe selection

Background: Affymetrix GeneChip arrays are widely used for transcriptomic studies in a diverse range of species. Each gene is represented on a GeneChip array by a probe-set, consisting of up to 16 probe-pairs. Signal intensities across probe-pairs within a probe-set vary in part due to different physical hybridisation characteristics of individual probes with their target labelled transcripts. We have previously developed a technique to study the transcriptomes of heterologous species based on hybridising genomic DNA (gDNA) to a GeneChip array designed for a different species, and subsequently using only those probes with good homology. Results: Here we have investigated the effects of hybridising homologous species gDNA to study the transcriptomes of species for which the arrays have been designed. Genomic DNA from Arabidopsis thaliana and rice (Oryza sativa) were hybridised to the Affymetrix Arabidopsis ATH1 and Rice Genome GeneChip arrays respectively. Probe selection based on gDNA hybridisation intensity increased the number of genes identified as significantly differentially expressed in two published studies of Arabidopsis development, and optimised the analysis of technical replicates obtained from pooled samples of RNA from rice. Conclusion: This mixed physical and bioinformatics approach can be used to optimise estimates of gene expression when using GeneChip arrays

Reconciling diverse lacustrine and terrestrial system response to penultimate deglacial warming in southern Europe

Unlike the most recent deglaciation, the regional expression of climate changes during the penultimate deglaciation remains understudied, even though it led into a period of excess warmth with estimates of global average temperature 1–2 °C, and sea level ∼6 m, above pre-industrial values. We present the first complete high-resolution southern European diatom record capturing the penultimate glacial-interglacial transition, from Lake Ioannina (northwest Greece). It forms part of a suite of proxies selected to assess the character and phase relationships of terrestrial and aquatic ecosystem response to rapid climate warming, and to resolve apparent conflicts in proxy evidence for regional paleohydrology. The diatom data suggest a complex penultimate deglaciation driven primarily by multiple oscillations in lake level, and provide firm evidence for the regional influence of abrupt changes in North Atlantic conditions. There is diachroneity in lake and terrestrial ecosystem response to warming at the onset of the last interglacial, with an abrupt increase in lake level occurring ∼2.7 k.y. prior to sustained forest expansion with peak precipitation. We identify the potentially important role of direct input of snow melt and glacial meltwater transfer to the subterranean karst system in response to warming, which would cause rising regional groundwater levels. This explanation, and the greater sensitivity of diatoms to subtle changes in temperature, reconciles the divergent lacustrine and terrestrial proxy evidence and highlights the sensitivity of lakes situated in mountainous karstic environments to past climate warming

Detection, attribution, and sensitivity of trends toward earlier streamflow in the Sierra Nevada

Observed changes in the timing of snowmelt dominated streamflow in the western United States are often linked to anthropogenic or other external causes. We assess whether observed streamflow timing changes can be statistically attributed to external forcing, or whether they still lie within the bounds of natural (internal) variability for four large Sierra Nevada (CA) basins, at inflow points to major reservoirs. Streamflow timing is measured by “center timing” (CT), the day when half the annual flow has passed a given point. We use a physically based hydrology model driven by meteorological input from a global climate model to quantify the natural variability in CT trends. Estimated 50-year trends in CT due to natural climate variability often exceed estimated actual CT trends from 1950 to 1999. Thus, although observed trends in CT to date may be statistically significant, they cannot yet be statistically attributed to external influences on climate. We estimate that projected CT changes at the four major reservoir inflows will, with 90% confidence, exceed those from natural variability within 1–4 decades or 4–8 decades, depending on rates of future greenhouse gas emissions. To identify areas most likely to exhibit CT changes in response to rising temperatures, we calculate changes in CT under temperature increases from 1 to 5°. We find that areas with average winter temperatures between −2°C and −4°C are most likely to respond with significant CT shifts. Correspondingly, elevations from 2000 to 2800 m are most sensitive to temperature increases, with CT changes exceeding 45 days (earlier) relative to 1961–1990