Agrostis ambatoensis Asteg.

Sierra de Ambato (Falda E, subiendo desde El Rodeo), cerca de la Cumbre del Cerro ManchadopublishedVersio

Hexabromocyclododecane and hexachlorocyclohexane: How lessons learnt have led to improved regulation

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2014 Taylor & Francis.The use of chemicals by society has many benefits but contamination of the environment is an unintended consequence. One example is the organochlorine compound hexachlorocyclohexane (HCH). During the 1980s, when HCH was banned in many countries, the brominated flame retardant, hexabromocyclododecane (HBCD), found increasing use. The persistent, bioaccumulative, and toxic characteristics of HBCD are, 30 years later, likely to warrant global action on production and use under the Stockholm Convention on persistent organic pollutants. Historical lessons have taught us that we need to control the use of chemicals and programs are in place worldwide in an attempt to do so.Tertiary Education Trust Fund, Nigeri

Fire-cracked Rock Use and Reuse in the Hueco Bolson, Fort Bliss, Texas

The Center for Archaeological Research of The University of Texas at San Antonio conducted an analysis of 29,058 pieces of fire-cracked rock and burned caliche selected from a sample of hundreds of features tested as part of the Hueco Mountain Archaeological Project at Fort Bliss, Texas. Feature and non-feature material included in this analysis were collected from site FB 13237 located on the proximal fan, FB 12719 within the basin area, and FB 12412 situated in the transitional zone between the two. The goal of the analysis was to identify patterns of attribute variability in burned rock that could be used to infer function of the various features and sites in the sample. Specific burned rock attributes used in the study were material type, size, weight, and the presence or absence of fracturing, cortex, and discoloration. These attributes were recorded and compared in various combinations at course- and fme-grained levels of intensity to address issues of reuse, recycling, feature function, thermally induced morphological variability, and how these variables might relate to specific land forms through time. Through these comparisons, patterns relating to expedient material selection, feature type, reuse and feature function were identified

Free Fermionic Heterotic Model Building and Root Systems

We consider an alternative derivation of the GSO Projection in the free fermionic construction of the weakly coupled heterotic string in terms of root systems, as well as the interpretation of the GSO Projection in this picture. We then present an algorithm to systematically and efficiently generate input sets (i.e. basis vectors) in order to study Landscape statistics with minimal computational cost. For example, the improvement at order 6 is approximately 10^{-13} over a traditional brute force approach, and improvement increases with order. We then consider an example of statistics on a relatively simple class of models.Comment: Standard Latex, 12 page

Fracture Unclogging: A Numerical Study of Seismically Induced Viscous Shear Stresses in Fluid‐Saturated Fractured Rocks

Dynamic shaking imposed by passing seismic waves is able to promote various hydrological processes in fractured reservoirs. This is often associated with seismically‐induced fracture unclogging due to mobilization of deposited colloids in the fracture network which, in turn, affects permeability at the reservoir scale. Numerous laboratory and field studies pointed out that fracture unclogging can be initiated when viscous shear stresses in the fracture fluid are in the range of 0.1‐1 Pascals. In this numerical study, we compute viscous shear stress in a fluid‐saturated fractured medium due to the action of passing P‐ and S‐waves. We perform a sensitivity analysis in terms of fluid, fracture, and host rock physical properties as well as seismic wave characteristics. Our results show that seismically‐induced viscous shearing increases with frequency and seismic strain and can be in the order of those initiating fracture unclogging for typical seismic strains and frequencies. S‐waves tend to produce viscous shearing approximately two times larger than P‐waves and, for anisotropic distribution of fractures, it is extremely dependent on the direction of wave propagation. Moreover, larger viscous shearing is expected for more viscous fluids and stiffer host rocks. Regarding the fracture network distribution, for the same fracture density, the presence of longer fractures drastically increases the potential of fracture unclogging at seismic frequencies. The fracture aperture distribution, on the other hand, can also affect the development of viscous shearing. Fractures with correlated distributions of contact areas exhibit an order of magnitude larger viscous shearing than uncorrelated ones

Effects of halothane, sevoflurane and propofol on left ventricular diastolic function in humans during spontaneous and mechanical ventilation

Background. There is limited knowledge of the effects of anaesthetics on left ventricular (LV) diastolic function in humans. Our aim was to evaluate these effects in humans free from cardiovascular disease. Methods. Sixty patients (aged 18-47 yr) who had no history or signs of cardiovascular disease were randomized to receive general anaesthesia with halothane, sevoflurane or propofol. Echocardiography was performed at baseline and during spontaneous respiration at 1 minimum alveolar concentration (MAC) of the inhalational agents or propofol 4 µg ml−1 (step 1), and repeated during positive-pressure ventilation with 1 and 1.5 MAC of the inhalational agents or with propofol 4 and 6 µg ml−1 (steps 2a and 2b). Analysis of echocardiographic measurements focused on heart rate corrected isovolumic relaxation time (IVRTc) and early diastolic peak velocity of the lateral mitral annulus (Ea). Results. IVRTc decreased from baseline to step 1 in the halothane group (82 [95% CI, 76-88] ms and 74 [95% CI, 68-80] ms respectively; P=0.02), remained stable in the sevoflurane group (78 [95% CI, 72-83] ms and 73 [95% CI, 67-81] ms; n.s.) and increased in the propofol group (80 [95% CI, 74-86] ms and 92 [95% CI, 84-102] ms; P=0.02). Ea decreased in the propofol group only (18.8 [95% CI, 16.5-19.9] cm s−1 and 16.0 [95% CI, 14.9-17.9] cm s−1; P=0.003). From step 2a to step 2b, IVRTc increased further in the propofol group (109 [95% CI, 99-121] ms and 119 [95% CI, 99-135] ms; P=0.04) but remained stable in the other two groups. Ea did not change from step 2a to step 2b. Conclusions. Halothane and sevoflurane did not impair LV relaxation, whereas propofol caused a mild impairment. However, the impairment by propofol was of a magnitude that is unlikely to cause clinical diastolic dysfunctio

Heat kernel estimates and spectral properties of a pseudorelativistic operator with magnetic field

Based on the Mehler heat kernel of the Schroedinger operator for a free electron in a constant magnetic field an estimate for the kernel of E_A is derived, where E_A represents the kinetic energy of a Dirac electron within the pseudorelativistic no-pair Brown-Ravenhall model. This estimate is used to provide the bottom of the essential spectrum for the two-particle Brown-Ravenhall operator, describing the motion of the electrons in a central Coulomb field and a constant magnetic field, if the central charge is restricted to Z below or equal 86