Electrostatics and Dimensions of Space

The principles of electrostatics are applied to dimensions both lower and higher than 3. Specifically, Laplace’s equations are solved in n dimensions subject to hyper-spherical symmetry in order to obtain the electric potential and hence the electric field. The physical problems associated with these solutions in 3-dimensional space are identified. The radial dependences of the potential and electric field are scrutinized. The successively lower radial dependences of the multipole fields are obtained by differentiating those of the multi-poles of the immediately lower order. The same results are also obtained by considering the hyper-surfaces of hyper-spheres in n dimensions. This study reaffirms the principles of electrostatics and provides a glimpse of the notion of higher dimensions

Improved timber harvest techniques maintain biodiversity in tropical forests

Tropical forests are selectively logged at 20 times the rate at which they are cleared, and at least a fifth have already been disturbed in this way. In a recent pan-tropical assessment, Burivalova et al. demonstrate the importance of logging intensity as a driver of biodiversity decline in timber estates. Their analyses reveal that species richness of some taxa could decline by 50% at harvest intensities of 38 m3 ha-1. However, they did not consider the extraction techniques that lead to these intensities. Here, we conduct a complementary meta-analysis of assemblage responses to differing logging practices: conventional logging and reduced-impact logging. We show that biodiversity impacts are markedly less severe in forests that utilise reduced-impact logging, compared to those using conventional methods. While supporting the initial findings of Burivalova et al., we go on to demonstrate that best practice forestry techniques curtail the effects of timber extraction regardless of intensity. Therefore, harvest intensities are not always indicative of actual disturbance levels resulting from logging. Accordingly, forest managers and conservationists should advocate practices that offer reduced collateral damage through best practice extraction methods, such as those used in reduced-impact logging. Large-scale implementation of this approach would lead to improved conservation values in the 4 million km2 of tropical forests that are earmarked for timber extraction

‘Shaken, but not stirred’: six decades defining social innovation

Ingenio Working Paper SeriesThis paper examines the evolution in the conceptualization of Social Innovation (SI) under the assumption of SI as a trans-disciplinary construct which comprises a diversity of discourses from different fields and actors. We performed a comprehensive and systematic literature review along six decades (1950-2014), extracting definitions of SI through a search of 2,339 documents in various languages retrieved from Web of Science, SCOPUS and Google scholar. To guide the inductive analysis of pluri-vocal discourses we assume innovation to be a learning-based process, introducing the notion of social practice linked to its intertwined institutional and sociocultural dimensions. We applied mixed qualitative methodologies, combining content analysis based on a social constructionist/interpretivist ontology with cognitive mapping techniques. Our findings identify some core and secondary elements underpinning two complementary perspectives (transformative and instrumental) of SI as scientific construct. They also point to a number of promising avenues for research towards the advancement of a socio-technical theory of innovation.This work has been partly funded by the JAE-Doc grant for the programme ‘Junta para la Ampliación de Estudios’, co-financed by the European Social Fund and the Spanish Ministry of Science (2011-2014).N

Spermatogenesis Associated Retrogenes Are Expressed in the Human Ovary and Ovarian Cancers

BACKGROUND: Ovarian cancer is the second most prevalent gynecologic cancer in women. However, it is by far the most lethal. This is generally attributed to the absence of easily detectable markers specific to ovarian cancers that can be used for early diagnosis and specific therapeutic targets. METHODOLOGY/PRINCIPAL FINDINGS: Using end point PCR we have found that a family of retrogenes, previously thought to be expressed only in the male testis during spermatogenesis in man, are also expressed in normal ovarian tissue and a large percentage of ovarian cancers. In man there are at least eleven such autosomal retrogenes, which are intronless copies of genes on the X chromosome, essential for normal spermatogenesis and expressed specifically in the human testis. We tested for the expression of five of the known retrogenes, UTP14C, PGK2, RPL10L, RPL39L and UBL4B in normal human ovary and ovarian cancers. CONCLUSIONS/SIGNIFICANCE: We propose that the activation of the testis specific retrogenes in the ovary and ovarian cancers is of biological significance in humans. Because these retrogenes are specifically expressed in the ovary and ovarian cancers in the female they may prove useful in developing new diagnostic and/or therapeutic targets for ovarian cancer

Influence of computed tomography angiography reconstruction software on anatomic measurements and endograft component selection for endovascular abdominal aortic aneurysm repair

ObjectiveThree-dimensional (3D) centerline reconstruction of computed tomography angiography (CTA) images permits detailed anatomic characterization of abdominal aortic aneurysms and facilitates planning of endovascular repair. Although several programs for 3D CTA reconstruction and measurement are available, direct comparisons have not been published, and reliability between software platforms has not been characterized. We evaluated agreement between anatomic measurements obtained from 3D CTA reconstructions using three commercially available software programs and characterized concordance between the programs for endograft component selection.MethodsImages from 92 CTA studies performed before abdominal aortic aneurysm repair were reconstructed and measured using three different software programs: independent reconstruction with proprietary software (Preview; M2S Inc, Lebanon, NH), surgeon-based reconstruction with proprietary software (AquariusNet Thin Client; TeraRecon Inc, San Mateo, Calif), and surgeon-based reconstruction with open-source software (Osirix MD; Pixmeo, Geneva, Switzerland). Agreement between outer wall diameter and length measurements obtained from centerline reconstructions created with each program was evaluated using scatter plots, intraclass correlation coefficients, and Bland-Altman plots. Concordance between aortic and iliac endograft component diameters selected from measurements with each program based on published instructions for use was examined using weighted κ statistics.ResultsDiameter measurements were generally similar between programs. Mean diameters at all locations were within ≤1 mm of one another, and mean length measurements were within ≤10 mm of one another for all pairwise comparisons. Intraclass correlations coefficients between programs for diameter measurements were comparable between programs (≥0.82 for all diameter comparisons and ≥0.88 for all length comparisons) and indicated good correlation. Pair-wise comparisons indicated similar rates of identical and adjacent size endograft component selection without an obvious trend toward superior agreement for any two programs. Rates of identical proximal endograft diameter selection ranged from 46% to 59%, whereas 89% to 100% of proximal endograft diameters selected between programs were within one adjacent (smaller or larger) size of each other. For iliac endograft selection, rates of identical component diameter selection between programs ranged from 36% to 69%, and 58% to 99% of selected iliac endograft diameters were within one adjacent size.ConclusionsOuter wall diameter and centerline length measurements obtained from 3D CTA reconstructions demonstrated good correlation between imaging analysis software programs, and graft diameter selections based on these measurements were reasonably similar. Comparable 3D CTA reconstruction measurements can be generated from independent and surgeon-based approaches using proprietary and open-source software, and the selection of a method to interpret images for endograft planning can be individualized according to operator experience and available resources while retaining sufficient accuracy

On the mechanisms of DC conduction in electrospun PLZT/PVDF nanocomposite membranes

Designing dielectric nanocomposite films with excellent dielectric properties is of strategic importance for a variety of applications requiring pressure sensing, energy harvesting and storing, and biomedical technology. Hence, the present investigation aims at studying the dielectric properties of lead lanthanum zirconate titanate (PLZT)/poly(vinylidene fluoride) (PVDF) nanocomposite based membranes fabricated using traditional electrospinning techniques. The composites were investigated for structural and electrical conductivity properties at varying temperatures. While the Scanning Electron microscope revealed beaded and unannealed micro/nanofibers, the observations of temperature-dependent electrical conductivity imply that the charge carrier transport phenomena involve more than one conduction mechanism. This is an interesting observation and can be explained in terms of the contents and porosity of the composites. As compared to PVDF, PLZT/PVDF nanocomposite films have somewhat better conductivity. The space charge limited current was the dominant mechanism at high voltages, while the Schottky–Richardson conduction mechanism was dominating at high temperature, according to observed J–V characteristics. The DC activation energy was found to be different, as expected, due to the dynamically heterogeneous nature of PLZT aggregates within the polymer matrix; however, the films exhibit the well-known Arrhenius relationship. This indicates that the dominant conduction mechanism is observed to be electronic and thermally activated. Graphical abstract: [Figure not available: see fulltext.]</p

Substructure in the Coma Cluster: Giants vs Dwarfs

The processes that form and shape galaxy clusters, such as infall, mergers and dynamical relaxation, tend to generate distinguishable differences between the distributions of a cluster's giant and dwarf galaxies. Thus the dynamics of dwarf galaxies in a cluster can provide valuable insights into its dynamical history. With this in mind, we look for differences between the spatial and velocity distributions of giant (b18) galaxies in the Coma cluster. Our redshift sample contains new measurements from the 2dF and WYFFOS spectrographs, making it more complete at faint magnitudes than any previously studied sample of Coma galaxies. It includes 745 cluster members - 452 giants and 293 dwarfs. We find that the line-of-sight velocity distribution of the giants is significantly non-Gaussian, but not that for the dwarfs. A battery of statistical tests of both the spatial and localised velocity distributions of the galaxies in our sample finds no strong evidence for differences between the giant and dwarf populations. These results rule out the cluster as a whole having moved significantly towards equipartition, and they are consistent with the cluster having formed via mergers between dynamically-relaxed subclusters.Comment: 23 pages, 6 figures, to appear in Ap

Avoiding bias in mixed model inference for fixed effects

Analysis of a large longitudinal study of children motivated our work. The results illustrate how accurate inference for fixed effects in a general linear mixed model depends on the covariance model selected for the data. Simulation studies have revealed biased inference for the fixed effects with an underspecified covariance structure, at least in small samples. One underspecification common for longitudinal data assumes a simple random intercept and conditional independence of the within-subject errors (i.e., compound symmetry). We prove that the underspecification creates bias in both small and large samples, indicating that recruiting more participants will not alleviate inflation of the Type I error rate associated with fixed effect inference. Enumerations and simulations help quantify the bias and evaluate strategies for avoiding it. When practical, backwards selection of the covariance model, starting with an unstructured pattern, provides the best protection. Tutorial papers can guide the reader in minimizing the chances of falling into the often spurious software trap of nonconvergence. In some cases, the logic of the study design and the scientific context may support a structured pattern, such as an autoregressive structure. The sandwich estimator provides a valid alternative in sufficiently large samples. Authors reporting mixed-model analyses should note possible biases in fixed effects inference because of the following: (i) the covariance model selection process; (ii) the specific covariance model chosen; or (iii) the test approximation

Sequence and gene content of a large fragment of a lizard sex chromosome and evaluation of candidate sex differentiating gene R-spondin 1

Background: Scant genomic information from non-avian reptile sex chromosomes is available, and for only a few lizards, several snakes and one turtle species, and it represents only a small fraction of the total sex chromosome sequences in these species. Results: We report a 352 kb of contiguous sequence from the sex chromosome of a squamate reptile, Pogona vitticeps, with a ZZ/ZW sex microchromosome system. This contig contains five protein coding genes (oprd1, rcc1, znf91, znf131, znf180), and major families of repetitive sequences with a high number of copies of LTR and non-LTR retrotransposons, including the CR1 and Bov-B LINEs. The two genes, oprd1 and rcc1 are part of a homologous syntenic block, which is conserved among amniotes. While oprd1 and rcc1 have no known function in sex determination or differentiation in amniotes, this homologous syntenic block in mammals and chicken also contains R-spondin 1 (rspo1), the ovarian differentiating gene in mammals. In order to explore the probability that rspo1 is sex determining in dragon lizards, genomic BAC and cDNA clones were mapped using fluorescence in situ hybridisation. Their location on an autosomal microchromosome pair, not on the ZW sex microchromosomes, eliminates rspo1 as a candidate sex determining gene in P. vitticeps. Conclusion: Our study has characterized the largest contiguous stretch of physically mapped sex chromosome sequence (352 kb) from a ZZ/ZW lizard species. Although this region represents only a small fraction of the sex chromosomes of P. vitticeps, it has revealed several features typically associated with sex chromosomes including the accumulation of large blocks of repetitive sequences

Resonances of the cusp family

We study a family of chaotic maps with limit cases the tent map and the cusp map (the cusp family). We discuss the spectral properties of the corresponding Frobenius--Perron operator in different function spaces including spaces of analytic functions. A numerical study of the eigenvalues and eigenfunctions is performed.Comment: 14 pages, 3 figures. Submitted to J.Phys.