Beyond similarity: A network approach for identifying and delimiting biogeographical regions

Biogeographical regions (geographically distinct assemblages of species and communities) constitute a cornerstone for ecology, biogeography, evolution and conservation biology. Species turnover measures are often used to quantify biodiversity patterns, but algorithms based on similarity and clustering are highly sensitive to common biases and intricacies of species distribution data. Here we apply a community detection approach from network theory that incorporates complex, higher order presence-absence patterns. We demonstrate the performance of the method by applying it to all amphibian species in the world (c. 6,100 species), all vascular plant species of the USA (c. 17,600), and a hypothetical dataset containing a zone of biotic transition. In comparison with current methods, our approach tackles the challenges posed by transition zones and succeeds in identifying a larger number of commonly recognised biogeographical regions. This method constitutes an important advance towards objective, data derived identification and delimitation of the world's biogeographical regions.Comment: 5 figures and 1 supporting figur

Excitonic effects in the optical properties of CdSe nanowires

Using a first-principle approach beyond density functional theory we calculate the electronic and optical properties of small diameter CdSe nanowires.Our results demonstrate how some approximations commonly used in bulk systems fail at this nano-scale level and how indispensable it is to include crystal local fields and excitonic effects to predict the unique optical properties of nanowires. From our results, we then construct a simple model that describes the optical gap as a function of the diameter of the wire, that turns out to be in excellent agreement with experiments for intermediate and large diameters.Comment: submitte

Construction of the B88 exchange-energy functional in two dimensions

We construct a generalized-gradient approximation for the exchange-energy density of finite two-dimensional systems. Guided by non-empirical principles, we include the proper small-gradient limit and the proper tail for the exchange-hole potential. The observed performance is superior to that of the two-dimensional local-density approximation, which underlines the usefulness of the approach in practical applications

Friction of human skin against different hospital fabrics for different contact conditions

Knowledge on tribology of human skin is essential to improve and optimise surfaces and materials in contact with the skin, as well in the design process of consumer products. Besides that, friction between the human skin and textiles are critical factors in the formation of skin injuries (irritations, abrasions, decubitus and blisters), which are caused if the loads and shear forces are high enough and/or over long periods of time. This factor is of particular importance in bedridden patients since they are not moving about or are confined to wheelchairs (and may be aggravated by incontinence or perspiration). Decubitus ulcers are one of the most frequently reported iatrogenic injuries in developed countries. The risk of developing decubitus ulcers can be predicted by using the “Braden Scale for Predicting Pressure Ulcer Risk” that was developed in 1987 [1], and contains 6 areas of risk (cognitiveperceptual, immobility, inactivity, moisture, nutrition, friction/shear), although there are limitations to the use of such tools. The coefficient of friction of textiles against skin is mainly influenced by: the nature of the textile, skin moisture content and ambient humidity. This study will investigate how skin friction (different anatomical regions) varies, rubbing against different type of contacting materials (i.e. synthetic and natural fabrics) under different contact conditions and their relation with the decubitus ulcers formation. The results will be compared with a reference hospital fabric

Two-dimensional dispersion analytical approach: Eddy diffusivities depending on source distance

An analytical air quality dispersion approach based on the steadystate two-dimensional advection-diffusion equation is presented. The solution employs a spectral method and is analytical in the sense that no approximation is made along its derivation. The approach is valid for homogeneous turbulence and for situations of uniform mean wind speed, and for practical purposes, to elevated releases that occur in neutral stability conditions without strong buoyancy. To simulate and compare the results of this approach against observed ground-level crosswind-integrated concentration two eddy diffusivities are considered. The first eddy diffusivity depends on the distance from the source while the second one assumes a constant value independent of the source distance. It is found that the memory effect contained in the eddy diffusivity, which is a function of downwind distance from the source, allows a better description of the turbulent dispersion of atmospheric contaminants released by an elevated continuous point source

Co‐existing monophasic teratoma and uterine adenocarcinoma in a female dog

Ovarian teratomas are occasionally reported in dogs; the rarest type is the monophasic teratoma,composed of tissues originating from only one germ layer. Canine endometrial adenocarcinomas are also rare in dogs and mainly affect geriatric females. This report describes case of co-existing ovarian teratoma and uterine adenocarcinoma in a 10-year old nulliparous female Boxer presented with lethargy, anorexia and purulent vaginal discharge. Abdominal ultrasonography evidenced pyometra and a mass in the left ovary. This was composed of a uniform whitish tissue with multiple cystic structures. The histology revealed an atrophy of the ovarian parenchyma, compressed by a proliferation of well-differentiated nervous tissue staining positively to vimentin, S100 and neuronal specific enolase (NSE), and negatively to keratin and inhibin. The left uterine horn, whose diameter was markedly increased, showed foci of endometrial cellular atypia, evident nucleoli and mitoses, at light microscopy. To our best knowledge, this is the first report of a coexisting ovarian monophasic teratoma and endometrial adenocarcinoma, two rare reproductive neoplasia in dogs

Mechanical and tribological characterization of four commercial braking formulation materials

Organic friction materials for brake linings, namely brake pads are polymer matrix composites usually containing numerous macroscopic as well as microscopic constituents such as filamentary reinforcements, solid lubricants, abrasives and fillers. Their main objective of the these composite system are that a constant and stable coefficient of friction (COF) is provided irrespective of environmental conditions such as pressure, sliding velocity, temperature, humidity etc. Brake pads performance should be maintained over a wide range of stress conditions. Although the wear of the brake pad is inevitable, it should be minimized as far as possible. While cast iron has been the dominant material for brake discs, brake pad materials are constantly evolving into more complex composites. The main objectives of the present work is to characterize the physical and the tribological behavior of four commercial braking pads material formulations. For all compositions the studied factors are normal pressure and sliding speed, considering one braking-test protocol designed with temperature and friction load data acquisition. A double pad-on-disc tribological test configuration was used to determine tribological properties of brake pad for heavy vehicles commercial. Three wear tests via increased severity of rubbing conditions for a constant braking distance.The authors acknowledge Auto Travões Viseu-recondicionamento de Travões e embraiagens Lda the support through the provision of the frictrion linning materials presented in the study

On the violation of a local form of the Lieb-Oxford bound

In the framework of density-functional theory, several popular density functionals for exchange and correlation have been constructed to satisfy a local form of the Lieb-Oxford bound. In its original global expression, the bound represents a rigorous lower limit for the indirect Coulomb interaction energy. Here we employ exact-exchange calculations for the G2 test set to show that the local form of the bound is violated in an extensive range of both the dimensionless gradient and the average electron density. Hence, the results demonstrate the severity in the usage of the local form of the bound in functional development. On the other hand, our results suggest alternative ways to construct accurate density functionals for the exchange energy.Comment: (Submitted on 27 April 2012