Casimir energy of a non-uniform string

The Casimir energy of a non-uniform string built up from two pieces with different speed of sound is calculated. A standard procedure of subtracting the energy of an infinite uniform string is applied, the subtraction being interpreted as the renormalization of the string tension. It is shown that in the case of a homogeneous string this method is completely equivalent to the zeta renormalization.Comment: 11 pages, REVTeX, no figures and table

Black hole solutions in F(R) gravity with conformal anomaly

In this paper, we consider $F(R)=R+f(R)$ theory instead of Einstein gravity with conformal anomaly and look for its analytical solutions. Depending on the free parameters, one may obtain both uncharged and charged solutions for some classes of $F(R)$ models. Calculation of Kretschmann scalar shows that there is a singularity located at $r=0$, which the geometry of uncharged (charged) solution is corresponding to the Schwarzschild (Reissner-Nordstr\"om) singularity. Further, we discuss the viability of our models in details. We show that these models can be stable depending on their parameters and in different epoches of the universe.Comment: 12 pages, one figur

Early soil knowledge and the birth and development of soil science

Soils knowledge dates to the earliest known practice of agriculture about 11,000 BP Civilizations all around the world showed various levels of soil knowledge by the 4th century AD, including irrigation, the use of terraces to control erosion, various ways of improving soil fertility, and ways to create productive artificial soils. Early soils knowledge was largely based on observations of nature: experiments to test theories were not conducted. Many famous scientists, for example, Francis Bacon, Robert Boyle, Charles Darwin, and Leonardo da Vinci worked on soils issues. Soil science did not become a true science, however, until the 19th century with the development of genetic soil science, led by Vasilii V Dokuchaev In the 20th century, soil science moved beyond its agricultural roots and soil information is now used in residential development, the planning of highways, building foundations, septic systems, wildlife management, environmental management, and many other applications in addition to agricultur

Geodiversity and Geopedology in a Logarithmic Universe

Zinck, J.A., Metternicht, G., del Valle, H.F., Angelini, M. (eds)Pedology and geomorphology are considered independent scientific disciplines, but form in fact a single indivisible system. Diversity analysis of natural resources tries to account for the variety of forms and spatial patterns that are displayed in the natural bodies, biotic and abiotic, appearing at the earth’s surface. The application of mathematical tools to diversity analysis requires a classification of the universe concerned. Biodiversity studies have a long tradition in comparison to those in earth sciences. Recently pedologists started paying attention to soil diversity using the same mathematical tools as ecologists and finding interesting relations between the spatial patterns of soil and vegetation. So far geodiversity studies are primarily concerned with the preservation of geological heritage, bypassing most of the aspects related to its spatial distribution and the quantitative estimation of geodiversity. Vegetation scientists have developed a classification that links climate and plant communities, the so-called syntaxonomic system. The purpose of this chapter is to explore a perspective for joining soils, geoforms, climate, and biocenoses in an integrated and comprehensive approach to describe the structure and diversity of earth surface systems. Likewise, a meta-analysis of the findings detected to date was carried out considering the scales of geographical space, a Paretian perspective and the cognitive processing of the data by the human mind.Peer reviewe

The use of multivariate statistical analysis and soil quality indices as tools to be included in regional management plans. A case study from the Mashhad Plain, Iran

Several methods have been used to model reality and explain soil pedogenesis and evolution. However, there is a lack of information about which soil properties truly condition soil quality indicators and indices particularly at the pedon scale and at different soil depths to be used in land management planning. Thus, the main goals of this research were: i) to assess differences in soil properties (particle size, saturation point, bulk density, soil organic carbon, pH and electrical conductivity) at different soil depths (0-30 and 30-60 cm); ii) to check their statistical correlation with soil quality indicators (CEC, total N, Olsen-P, available K, exchangeable Na, calcium carbonate equivalent, Fe, Mn, Zn, and Cu); and, iii) to elaborate a soil quality index and maps for each soil layer. To achieve this, forty-eight soil samples were analysed in the laboratory and subjected to statistical analyses by ANOVA, Spearman Rank coefficients and Principal Component Analyses. Finally, a soil quality index was developed based on indicators of sensitivity. The study was conducted in a semiarid catchment in northeast Iran with irrigated farming and well-documented land degradation issues. We found that: i) organic carbon and bulk density were not similar in the topsoil and subsoil; ii) calcium carbonate and sand content conditioned organic carbon content and bulk density; iii) organic carbon showed the highest correlations with soil quality indicators; iv) particle size conditioned cation-exchange capacity; and, v) heavy metals such as Mn and Cu were highly correlated with organic carbon due to non-suitable agricultural practices. Based on the communality analysis to map of soil quality, CEC, Mn, Zn, and Cu had the highest weights (≥0.11) at both depths, coinciding with the same level of relevance in the multivariate analysis. Exchangeable Na, CaCO3, and Fe had the lowest weights (≤0.1) and N, P, and K had intermediate weights (0.1- 0.11). In general, the map of the soil quality index shows a lower soil quality in the subsoil increment than in the topsoil.Muchos métodos permiten modelizar la realidad para tratar de explicar la formación y evolución del suelo. Sin embargo, a una escala suelo y a diferentes profundidades, no existe una gran cantidad de estudios que también mencionen los indicadores de calidad para ser incluidos en la ordenación del territorio. Por lo tanto, los principales objetivos de esta investigación son: i) evaluar las diferencias entre propiedades del suelo (tamaño de partículas, punto de saturación, densidad aparente, materia orgánica, pH y conductividad eléctrica) a diferentes profundidades (0-30 cm y 30-60 cm); ii) su posible correlación estadística con indicadores de calidad de suelo (capacidad de intercambio catiónico, N total, Olsen-P, K disponible, Na intercambiable, carbonato cálcico equivalente, Fe, Mn, Zn y Cu); y, iii) elaborar un índice de calidad del suelo con su respectivo mapa para cada capa estudiada. Para alcanzar dicho objetivo, 48 muestras fueron recogidas y analizadas en el laboratorio, comparadas con diferentes métodos estadísticos (ANOVA, correlación de Spearman y análisis de componentes principales) y utilizadas para la creación de un índice de calidad del suelo en una cuenca de un ambiente semiárido al Noreste de Irán, caracterizada por una agricultura por irrigación y documentados procesos de degradación. Las principales conclusiones alcanzadas fueron: i) la materia orgánica y la densidad aparente fueron diferentes para cada profundidad; ii) el carbonato cálcico y el contenido en arenas estaba altamente correlacionado con la materia orgánica y la densidad aparente; iii) el contenido en materia orgánica mostró la mejor correlación con los indicadores de calidad del suelo; iv) el tamaño de las partículas del suelo condicionó la capacidad de intercambio catiónico; y, v) los metales pesados como el Mn y el Cu estuvieron fuertemente correlacionados con el carbono orgánico debido, posiblemente, a las malas prácticas agrícolas. Basados en el análisis de comunalidad del índice de calidad del suelo, para ambas profundidades, la capacidad de intercambio catiónico, Mn, Zn y Cu obtuvieron los mayores pesos, coincidiendo con su importancia dentro del análisis multivariante realizado anteriormente. Por el contrario, el Na intercambiable, CaCo3 y el Fe obtuvieron los valores más bajos. N, P y K alcanzaron valores intermedios. En general el mapa de calidad del suelo mostró valores menores en el horizonte sub-superficial que en la capa superficial

Land System Diversity, Scaling Laws, and Polygons Map Analysis

Numerous lines of evidence have been presented in the literature that show the patterns of pedodiversity and biodiversity are very similar. One of the most corroborated patterns lies in the fits of the relationships between biodiversity and soil diversity to power laws according to the increase in study area. Several authors have analysed the presence of fractal and multifractal features in pedodiversity and biodiversity analyses. Similarly, it has also been found that valuable information can be extracted from the polygons of soil and vegetation maps, which also have surprising similarities. These approac hes concern information on the spatial distribution of natural resources. However, other more artificial but interesting maps and their comparison have been neglected by such studies. Land systems maps and their georeferenced databases fall into this latter category, and they include most of the soil-forming factors. In this paper a georeferenced land system database and map were analysed and the results compared with those obtained in previous pedodiversity and biodiversity studies, primarily the spatial patterns of the polygons. The results showed that the analysed land system map units followed the same patterns that were previously found in pedod iversity and biodiversity studies; that is, the power law concerning richness–area relationships. The same patterns occur with the number of polygons. Some geographers claim there is a “law” that states that there are far more small things/objects than larger ones across several orders of magnitude in geographic space and thus this regularity conforms to scaling laws, independent of the resource involved. The results obtained corroborate this conjecture irrespective of whether natural resources or artificial cartographies were analysed. This paper represents a first test of land use maps; additional work in this area is needed.Peer reviewe