Stabilization of grid frequency through dynamic demand control

Frequency stability in electricity networks is essential to the maintenance of supply quality and security. This paper investigates whether a degree of built-in frequency stability could be provided by incorporating dynamic demand control into certain consumer appliances. Such devices would monitor system frequency (a universally available indicator of supply-demand imbalance) and switch the appliance on or off accordingly, striking a compromise between the needs of the appliance and the grid. A simplified computer model of a power grid was created incorporating aggregate generator inertia, governor action and load-frequency dependence plus refrigerators with dynamic demand controllers. Simulation modelling studies were carried out to investigate the system's response to a sudden loss of generation, and to fluctuating wind power. The studies indicated a significant delay in frequency-fall and a reduced dependence on rapidly deployable backup generation

Pinworms of the red howler monkey (Alouatta seniculus) in Colombia. Gathering the pieces of the pinworm-primate puzzle

Pinworms of primates are believed to be highly host specific parasites, forming co-evolutionary associations with their hosts. In order to assess the strength and reach of such evolutionary links, we need to have a broad understanding of the pinworm diversity associated with primates. Here, we employed an integrative taxonomic approach to assess pinworm diversity in red howler monkeys in Colombia. Molecular and morphological evidence validate the presence of at least four different species of Trypanoxyuris occurring in red howler monkeys: T. minutus, a widely distributed species, and three new species, T. seunimiii n. sp., T. kemuimae n. sp. and T. kotudoi n. sp. The mitochondrial COI gene and the 28S ribosomal gene were used for phylogenetic assessments through Bayesian inference. The three new species were morphologically distinct and formed reciprocally monophyletic lineages. Further molecular lineage subdivision in T. minutus and T. kotudoi n. sp. without morphological correspondence, suggests the potential scenario for the existence of cryptic species. Phylogenetic relationships imply that the different species of Trypanoxyuris occurring in each howler monkey species were acquired through independent colonization events. On-going efforts to uncover pinworm diversity will allow us to test the degree of host specificity and the co-phylogenetic hypothesis, as well as to further unravel the primate-pinworm evolutionary history puzzle

Chemigation Equipment and Safety.

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Self-similar cosmologies in 5D: spatially flat anisotropic models

In the context of theories of Kaluza-Klein type, with a large extra dimension, we study self-similar cosmological models in 5D that are homogeneous, anisotropic and spatially flat. The "ladder" to go between the physics in 5D and 4D is provided by Campbell-Maagard's embedding theorems. We show that the 5-dimensional field equations $R_{AB} = 0$ determine the form of the similarity variable. There are three different possibilities: homothetic, conformal and "wave-like" solutions in 5D. We derive the most general homothetic and conformal solutions to the 5D field equations. They require the extra dimension to be spacelike, and are given in terms of one arbitrary function of the similarity variable and three parameters. The Riemann tensor in 5D is not zero, except in the isotropic limit, which corresponds to the case where the parameters are equal to each other. The solutions can be used as 5D embeddings for a great variety of 4D homogeneous cosmological models, with and without matter, including the Kasner universe. Since the extra dimension is spacelike, the 5D solutions are invariant under the exchange of spatial coordinates. Therefore they also embed a family of spatially {\it inhomogeneous} models in 4D. We show that these models can be interpreted as vacuum solutions in braneworld theory. Our work (I) generalizes the 5D embeddings used for the FLRW models; (II) shows that anisotropic cosmologies are, in general, curved in 5D, in contrast with FLRW models which can always be embedded in a 5D Riemann-flat (Minkowski) manifold; (III) reveals that anisotropic cosmologies can be curved and devoid of matter, both in 5D and 4D, even when the metric in 5D explicitly depends on the extra coordinate, which is quite different from the isotropic case.Comment: Typos corrected. Minor editorial changes and additions in the Introduction and Summary section

Globular clusters and dwarf galaxies in Fornax - I. Kinematics in the cluster core from multi-object spectroscopy

We acquired radial velocities of a significant number of globular clusters (GCs) on wide fields between galaxies in the nearby Fornax cluster of galaxies, in order to derive their velocity dispersion radial profile and to probe the dynamics of the cluster. We used FLAMES on the VLT to obtain accurate velocities for 149 GCs, within a ~500x150 kpc strip centered on NGC 1399, the Fornax central galaxy. These objects are at the very bright tail (M_V < -9.5) of the GC luminosity function, overlapping the so-called ``ultra-compact dwarfs'' magnitude range. Eight of the brightest FLAMES-confirmed members indeed show hints of resolution in the subarcsecond pre-imaging data we used for selecting the ~500 targets for FLAMES spectroscopy. Ignoring the GCs around galaxies by applying 3d_25 diameter masks, we find 61 GCs of 20.0 < V < 22.2 lying in the intra-cluster (IC) medium. The velocity dispersion of the population of ICGCs is 200 km/s at ~150 kpc from the central NGC 1399 and rises to nearly 400 km/s at 200 kpc, a value which compares with the velocity dispersion of the population of dwarf galaxies, thought to be infalling from the surroundings of the cluster.Comment: To be published in A&A Letters. 4 pages, 3 figures, 3 table

Stellar models with Schwarzschild and non-Schwarzschild vacuum exteriors

A striking characteristic of non-Schwarzschild vacuum exteriors is that they contain not only the total gravitational mass of the source, but also an {\it arbitrary} constant. In this work, we show that the constants appearing in the "temporal Schwarzschild", "spatial Schwarzschild" and "Reissner-Nordstr{\"o}m-like" exteriors are not arbitrary but are completely determined by star's parameters, like the equation of state and the gravitational potential. Consequently, in the braneworld scenario the gravitational field outside of a star is no longer determined by the total mass alone, but also depends on the details of the internal structure of the source. We show that the general relativistic upper bound on the gravitational potential $M/R < 4/9$, for perfect fluid stars, is significantly increased in these exteriors. Namely, $M/R < 1/2$, $M/R < 2/3$ and $M/R < 1$ for the temporal Schwarzschild, spatial Schwarzschild and Reissner-Nordstr{\"o}m-like exteriors, respectively. Regarding the surface gravitational redshift, we find that the general relativistic Schwarzschild exterior as well as the braneworld spatial Schwarzschild exterior lead to the same upper bound, viz., $Z < 2$. However, when the external spacetime is the temporal Schwarzschild metric or the Reissner-Nordstr{\"o}m-like exterior there is no such constraint: $Z < \infty$. This infinite difference in the limiting value of $Z$ is because for these exteriors the effective pressure at the surface is negative. The results of our work are potentially observable and can be used to test the theory.Comment: 19 pages, 3 figures and caption

Blurred Lines Between Competition and Parasitism

Accurately describing the ecological relationships between species is more than mere semantics-doing so has profound practical and applied implications, not the least of which is that inaccurate descriptions can lead to fundamentally incorrect predicted outcomes of community composition and functioning. Accurate ecological classifications are particularly important in the context of global change, where species interactions can change rapidly following shifts in species composition. Here, we argue that many common ecological interactions-particularly competition and parasitism-can be easily confused and that we often lack empirical evidence for the full reciprocal interaction among species. To make our case and to propose a theoretical framework for addressing this problem, we use the interactions between lianas and trees, whose outcomes have myriad implications for the ecology and conservation of tropical forests (e.g., Schnitzer et al. 2015)

Propagating EUV disturbances in the solar corona : two-wavelength observations

Quasi-periodic EUV disturbances simultaneously observed in 171 Å and 195 Å TRACE bandpasses propagating outwardly in a fan-like magnetic structure of a coronal active region are analysed. Time series of disturbances observed in the different bandpasses have a relatively high correlation coefficient (up to about 0.7). The correlation has a tendency to decrease with distance along the structure: this is consistent with an interpretation of the disturbances in terms of parallel-propagating slow magnetoacoustic waves. The wavelet analysis does not show a significant difference between waves observed in different bandpasses. Periodic patterns of two distinct periods: 2-3 min and 5-8 min are detected in both bandpasses, existing simultaneously and at the same distance along the loop, suggesting the nonlinear generation of the second harmonics