Understanding soil water repellency under native vegetation in Australia: An empirical and molecular dynamics approach

Soil water repellency (SWR) is a major land management issue across southern Australia and inhibits the infiltration of water into soil with effects on the germination of crops and pastures and run-off in agricultural and forested land. SWR is a natural phenomenon and generally occurs in the surface layers of sandy soils where hydrophobic materials mostly of plant origin occur as particulate organic matter and as waxy coatings on soil particles. Although its incidence and severity have been anecdotally related to the previous native vegetation little is known about the specific organic compounds that may derive from this vegetation. Previous studies have concentrated on characterizing the contribution of soil organic matter, and this and the fact that soils are complex mixtures of a broad range of organic components may have obscured the contribution of a small concentration of compounds from the native species to SWR. Moreover, the precise distribution of these compounds (e.g., as coatings or in interstices between soil particles) and their contribution to SWR has not been quantified. Although analysis of soil solvent extracts can identify the relative amounts of individual compounds, it is often difficult to determine the relative importance of all components in inducing SWR. It is even harder to determine synergistic effects from combinations of components. Experimental studies provide a broad understanding of the bulk effects of hydrophobic molecular coatings but do not provide a molecular level understanding of the coating structure or of its kinetic and/or thermodynamic stability. The molecular arrangement of those organic compounds on the soil particles have been shown to have implications for both the incidence and dynamics of SWR. Thus the present study employed a range of approches to understand SWR in native vegetation: i) quantifying the contribution of canopy derived exudates from native tree species to SWR, ii) discerning the contribution of organic matter in different pools (e.g., on particle surfaces, as interstitial matter) to SWR and iii) examining the physical interaction of the organic molecules (without and with water) with soil mineral surfaces. Canopy derived exudates were captured using an improvised technique, and organic compounds were extracted using nonpolar and polar solvents. In order to discern the contribution of different carbon pools to SWR, soils were separated into mineral and interstitial matter. Soils were extracted using a sonication technique. Individual and combinations of compounds were loaded onto acid washed sand (AWS) using a rotary evaporator. This experimental loading and measurement was complemented by fully atomistic molecular dynamics simulations with Materials Studio v 7.0 to understand the physical interaction of the molecules with mineral surfaces. A range of different organic compounds that are widely reported in the incidence of SWR were detected in the canopy derived exudates and soil extracts. They were mostly long-chain alkanes, fatty acids, phytols, phytanols, amides, aldehydes, ketones, terpenoids, steroids, and some complex ring containing structures. Though there was similarity in the composition of both the nonpolar and polar compounds of exudates of Banksia menziesii, Eucalyptus marginata, Xanthorrhoea preissii and Allocasuarina fraseriana, the concentration level of the chemical species was found to be significantly different. The concentrations were found to differ over the sampling period. For example, docosanoic acid was found to be dominant in the summer for B. menziesii and X. preissii. while in E. marginata and A. fraseriana it was evident in the winter. Moreover, the concentration level of the chemical species derived from the soil extracts were also found to be significantly different between the species of A. fraseriana, E. marginata, E. wandoo and B. menziesii. Notably, the main difference between A. fraseriana and the other three species (E. marginata, E. wandoo and B. menziesii) was the presence of long chain fatty acids and fatty alcohols. The concentration of the compounds was even different in different soil components (e.g., minerals and interstitial matter) of the soil matrix. For example, the concentration level of the individual compound derived from the bulk soil was similar to the total concentration level of the compound derived from both the coarse mineral materials and interstitial matters. The molecular level arrangement of various hydrophobic molecules with mineral surfaces also varied. For example, amphiphilic molecules at surface density of 2.3 molecs/nm2 were found in a tilted arrangement on kaolinite while on quartz surfaces they formed layered arrangements. However, silica did not favor a certain order of arrangement of the molecules due to its amorphous surface. The surface characteristics and polarity (abundance of OH groups) of the substrate (kaolinite > silica) were found to significantly modify the organo-mineral interactions. Different biogenic volatile organic compounds (BVOCs) or terpenoids commonly observed in vegetation smoke or forest fire, were not found to induce SWR. Moreover, the long chain amphiphilic molecules exhibited a balance between molecule-molecule and molecule-surface interactions on the quartz surface that supported surface adhesion, which in turn led to the formation of a hydrophobic layer. Furthermore, soil moisture or the addition of water molecules was found to significantly modify the conformation of molecules at the organo-mineral interfaces. For example, the polar kaolinite and silica surfaces were found to easily wet-up and reorganization of amphiphilic molecules on the surfaces took place following aquation. The stronger interaction between water and organic molecules can thus be inversely correlated to organo-mineral interaction on soil particles

'Just Little Things': Nurses' perceptions of quality of life for people with severe multiple impairments.

ABSTRACT Notions of quality of life dictate philosophies and policies for services for people with developmental disabilities. There is an abundance of research on quality of life, much of which has influenced the significant amount of study of quality of life for people with developmental disabilities. According to specialist developmental disability nurses, however, this research has little meaning for one group of people with developmental disabilities with whom they work - people with severe multiple impairments. Nevertheless, judgements and decisions about the lives of this group continue to be driven by the idea of quality of life. While the literature review found that researchers are urged to seek the perceptions of people regarding their own quality of life by asking them, some authors have noted the difficulty in pursuing such a method with people, such as people with severe multiple impairments, who are unable to communicate in the usual ways. Given, then, that it is difficult to directly determine the views of people with severe multiple impairments, this study sought the perceptions of nurses about the quality of life of the people with whom they work. In order to discover and conceptualise nurses' views, a symbolic interaction perspective was chosen to guide this study and data were analysed using the grounded theory approach. The study was conducted in two stages. Stage One consisted of semi-structured indepth interviews with expert nurses to explore their perceptions of quality of life for the people with whom they worked. A significant finding in these interviews was that perceptions of quality of life are mediated by interaction. Consequently, Stage Two involved a participant observation study in which the interactions of nurses and people with severe multiple impairments were examined. Specialist developmental disability nurses have a unique view of quality of life for people with severe multiple impairments. They refer to it as 'just little things', a phrase which masks complex nursing knowledge and skills, and which can be described by four interrelated categories which emerged from the data: humans being, supporting, becoming intimate, and situated belonging. As nurses become more intimate with individuals, they perceive that people with severe multiple impairments are humans being as they wish, and that quality resides in supporting their everyday lives in a context of situated belonging. This thesis represents a new conceptualisation of quality of life for people with severe multiple impairments, a conceptualisation which may have significance for other groups and, indeed, for the whole quality of life enterprise. This conceptualisation draws on knowledge not usually related to quality of life, that is, knowledge of the body, of the emotions, of identity and of humanness. Such findings demonstrate the power of an interpretive approach in explicating the meanings nurses have regarding quality of life. Further, these findings have implications for how the question of quality of life is approached, for how different ways of thinking about people impact on quality of life, and for the importance of the life in quality of life

Approximate Analytical Solutions to the Initial Data Problem of Black Hole Binary Systems

We present approximate analytical solutions to the Hamiltonian and momentum constraint equations, corresponding to systems composed of two black holes with arbitrary linear and angular momentum. The analytical nature of these initial data solutions makes them easier to implement in numerical evolutions than the traditional numerical approach of solving the elliptic equations derived from the Einstein constraints. Although in general the problem of setting up initial conditions for black hole binary simulations is complicated by the presence of singularities, we show that the methods presented in this work provide initial data with $l_1$ and $l_\infty$ norms of violation of the constraint equations falling below those of the truncation error (residual error due to discretization) present in finite difference codes for the range of grid resolutions currently used. Thus, these data sets are suitable for use in evolution codes. Detailed results are presented for the case of a head-on collision of two equal-mass M black holes with specific angular momentum 0.5M at an initial separation of 10M. A straightforward superposition method yields data adequate for resolutions of $h=M/4$, and an "attenuated" superposition yields data usable to resolutions at least as fine as $h=M/8$. In addition, the attenuated approximate data may be more tractable in a full (computational) exact solution to the initial value problem.Comment: 6 pages, 5 postscript figures. Minor changes and some points clarified. Accepted for publication in Phys. Rev.

Analysis of ``Gauge Modes'' in Linearized Relativity

By writing the complete set of $3 + 1$ (ADM) equations for linearized waves, we are able to demonstrate the properties of the initial data and of the evolution of a wave problem set by Alcubierre and Schutz. We show that the gauge modes and constraint error modes arise in a straightforward way in the analysis, and are of a form which will be controlled in any well specified convergent computational discretization of the differential equations.Comment: 11pages LaTe

Locating Boosted Kerr and Schwarzschild Apparent Horizons

We describe a finite-difference method for locating apparent horizons and illustrate its capabilities on boosted Kerr and Schwarzschild black holes. Our model spacetime is given by the Kerr-Schild metric. We apply a Lorentz boost to this spacetime metric and then carry out a 3+1 decomposition. The result is a slicing of Kerr/Schwarzschild in which the black hole is propagated and Lorentz contracted. We show that our method can locate distorted apparent horizons efficiently and accurately.Comment: Submitted to Physical Review D. 12 pages and 22 figure

Estudio epidemiológico de la litiasis en Armilla (Granada) (T. C)

Se estudia la incidencia de la litiasis renal en población completa. La unidad elegida ha sido Armilla y en este estudio además de relacionar la incidencia con diversos parámetros, tales como edad, sexo, recidivas, etc., se comparan los resultados obtenidos con los de otros autores en distintas partes del mundo.In this study we have pointed out the incidence of the lithiasis at a whole poblation and as the town of Armilla (Granada - Spain). We have shown the relationships between the nephritic calculi and several parameters such as Age. sex. etc. We have also compared out results with other of differents authors several parts of the world

Extended Lifetime in Computational Evolution of Isolated Black Holes

Solving the 4-d Einstein equations as evolution in time requires solving equations of two types: the four elliptic initial data (constraint) equations, followed by the six second order evolution equations. Analytically the constraint equations remain solved under the action of the evolution, and one approach is to simply monitor them ({\it unconstrained} evolution). The problem of the 3-d computational simulation of even a single isolated vacuum black hole has proven to be remarkably difficult. Recently, we have become aware of two publications that describe very long term evolution, at least for single isolated black holes. An essential feature in each of these results is {\it constraint subtraction}. Additionally, each of these approaches is based on what we call "modern," hyperbolic formulations of the Einstein equations. It is generally assumed, based on computational experience, that the use of such modern formulations is essential for long-term black hole stability. We report here on comparable lifetime results based on the much simpler ("traditional") $\dot g$ - $\dot K$ formulation. We have also carried out a series of {\it constrained} 3-d evolutions of single isolated black holes. We find that constraint solution can produce substantially stabilized long-term single hole evolutions. However, we have found that for large domains, neither constraint-subtracted nor constrained $\dot g$ - $\dot K$ evolutions carried out in Cartesian coordinates admit arbitrarily long-lived simulations. The failure appears to arise from features at the inner excision boundary; the behavior does generally improve with resolution.Comment: 20 pages, 6 figure

Three-dimensional adaptive evolution of gravitational waves in numerical relativity

Adaptive techniques are crucial for successful numerical modeling of gravitational waves from astrophysical sources such as coalescing compact binaries, since the radiation typically has wavelengths much larger than the scale of the sources. We have carried out an important step toward this goal, the evolution of weak gravitational waves using adaptive mesh refinement in the Einstein equations. The 2-level adaptive simulation is compared with unigrid runs at coarse and fine resolution, and is shown to track closely the features of the fine grid run.Comment: REVTeX, 7 pages, including three figures; submitted to Physical Review

Effective catalytic deoxygenation of palm fatty acid distillate for green diesel production under hydrogen-free atmosphere over bimetallic catalyst CoMo supported on activated carbon

Palm fatty acid distillate (PFAD) is considered as an inedible and renewable feedstock for the production of green diesel. In the current study, green diesel was successfully synthesised via catalytic deoxygenation of PFAD in an environment free of H2 using a mesoporous activated carbon (AC) supported CoMo catalyst with various molybdenum (Mo) concentrations (5–20 wt%). Based on the study results, bimetallic catalyst Co10Mo10/AC formulation exhibited excellent catalytic performance with 92% hydrocarbon components (C8-C20) yield and 89% selectivity for n-(C15 + C17) with a total acid number of 24 mg KOH mg−1 . Based on a comparison study with various supports (AC, γ-Al2O3, TiO2), the AC-supported CoMo catalyst showed higher deoxygenation activity than both Co10Mo10/γ-Al2O3 and Co10Mo10/TiO2 owing to the super acid-base sites as a result of synergism between the CoMo and AC support. The Co10Mo10/AC catalyst demonstrated excellent stability during the study as it maintained the hydrocarbon components yield and selectivity of n-(C15 + C17) > 80% until the sixth run

Generic Tracking of Multiple Apparent Horizons with Level Flow

We report the development of the first apparent horizon locator capable of finding multiple apparent horizons in a ``generic'' numerical black hole spacetime. We use a level-flow method which, starting from a single arbitrary initial trial surface, can undergo topology changes as it flows towards disjoint apparent horizons if they are present. The level flow method has two advantages: 1) The solution is independent of changes in the initial guess and 2) The solution can have multiple components. We illustrate our method of locating apparent horizons by tracking horizon components in a short Kerr-Schild binary black hole grazing collision.Comment: 13 pages including figures, submitted to Phys Rev