Investigating morphological changes in treated vs. untreated stone building materials by x-ray micro-CT

Calcareous stones have been largely used to build historical buildings. Among these, the calcarenites are usually characterized by a high content of calcite and a high open porosity, which make them very sensitive to the weathering caused by physical and chemical agents. In order to prevent their deterioration and to retard their decay, different protective products—mainly polymers—are applied on the stone artefact surfaces. In this work we apply the methodology tested in a preliminary study to investigate the morphological changes of the internal structure of a biocalcarenite (Lecce stone) by micro x-ray computed tomography (μ-CT). The porosity and other morphological parameters of the rock before and after the conservation treatment were calculated on a significant number of samples. The Student’s t test was applied for statistical comparison. The results reveal that the treatment with Paraloid B72 (PB 72) is homogenously distributed and causes small changes to the natural properties of the rock, whereas the application of a fluoroelastomer (NH) causes an appreciable decrease in porosity and variation in terms of wall thickness distribution, probably resulting from its inhomogeneous distribution. Figure Porosity and other morphological parameters of Lecce stone were investigated by μ-CT: the effect of conservation treatment with fluoroelastomer on wall thickness distribution is illustrated     

Evaluation of the Effect of Pear Stone Cells on the Recovery of Multi-Class Pesticides

The widespread sample preparation method for the extraction of pesticide residues, the QuEChERS method, sometimes yields different pesticide recovery values for different food matrices. Pear (Pyrus communis L.) is an example of a matrix that can be characterized with somewhat lower pesticide recoveries. In order to investigate the reason for this result, the most characteristic structural feature of pears, the stone cells, possessing a specific surface due to their greater cellulose and lignin contents, were isolated and purified. The isolated stone cells were used for the preparation of a model sample in combination with tomato, a food matrix showing high pesticide recovery values, in a pesticide spiking experiment. Eleven multi-class pesticides were selected for the study where the quantification was carried out with HPLC-ESI-MS/MS. No significant differences were found between the pesticide recoveries obtained from the tomato and the combined tomato-pear stone cells matrices, which indicates the reason behind the lower pesticide recoveries in pear matrices is still to be determined.     

Stone型定理

本文在Hilbert C~*-模框架下获得了Stone型定理,使得经典的Stone定理是其特例。     

The existence of free ultrafilters on ω does not imply the extension of filters on ω to ultrafilters

Let X be an infinite set and let and denote the propositions “every filter on X can be extended to an ultrafilter” and “X has a free ultrafilter”, respectively. We denote by the Stone space of the Boolean algebra of all subsets of X. We show:

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Analysis of stone column-supported geosynthetic-reinforced embankments

In the present paper, the behavior of stone column-supported geosynthetic-reinforced embankments has been studied. The soil arching effect is incorporated in the study to determine the stresses acting on stone columns as well as soft soil. The effect of stiffness of the stone column is also incorporated in the present study. Based on the stress action in the improved ground, stress concentration ratio, axial strain of geosynthetic reinforcement, tension developed in it and settlement of the improved soft ground are determined by using the developed methodology. Present analytical method is also verified with several current design methods. It is observed from parametric studies that modular ratio or stiffness of the stone columns, spacing to diameter ratio, height of the embankment, depth of the soft soil, stiffness of the geosynthetic reinforcement significantly affect the behavior of geosynthetic-reinforced stone column-supported embankments resting on soft soil.     

A mathematical model to study the soil arching effect in stone column-supported embankment resting on soft foundation soil

Soil arching is a common phenomena in pile or columnar (vibroconcrete columns, soil–cement columns by mixing or grouting, stone columns) supported geosynthetic-reinforced or unreinforced embankments resting on soft soil. Due to soil arching, stress acting on soft soil or geosynthetic reinforcement decreases and stress on piles or columns increases. In this paper, using mechanical elements (such as spring, dashpot), a generalized mathematical model has been developed to study the soil arching effect in stone column-supported geosynthetic-reinforced and unreinforced embankments resting on soft soil. Pasternak model concept has been used to model the embankment soil. The soft soil has been idealized by spring-dashpot system to include the time-dependent behavior. The stone columns and geosynthetic reinforcement are idealized by stiffer nonlinear springs and rough elastic membrane, respectively. The consolidation effect of soft soil due to inclusions of stone columns has also been included in the model to study its effect on soil arching. Plane strain condition has been considered in the analysis. A finite difference scheme has been used to solve the governing differential equations and results are presented in non-dimensional form. It has been observed that the height of embankment, degree of consolidation of soft soil, stiffness of the stone column material, spacing between the stone columns, use of geosynthetic reinforcement and properties of soft and embankment soils (such as ultimate bearing capacity of soft soil, shear modulus and ultimate shearing resistance of embankment soil) significantly influence the degree of soil arching.     

R_0-代数的Stone拓扑表示定理

研究R0-代数中极大滤子的结构性质,通过引入有限平方交性质的概念证明了素理想定理;在全体极大滤子之集上引入了Stone拓扑,研究了Stone空间的性质;在R0-代数中引入了Boole-元的概念,证明了R0-代数的Stone拓扑表示定理,即,全体Boole-元作为Boole代数同构于该R0-代数的Stone空间中的全体既开又闭子集构成的Boole代数。Boole代数的Stone拓扑表示定理可作为该表示定理的特例而给出。     

The characterization of certain quantum stochastic stationary process

In this paper we will obtain a Stone type theorem under the frame of Hilbert C＊-module, such that the classical Stone theorem is our special case. Then we use it as a main tool to obtain a spectrum decomposition theorem of certain stationary quantum stochastic process. In the end, we will give it an interpretation in statistical mechanics of multi-linear response.     

Endoprimal algebras

An algebra A is endoprimal if, for all the only maps from A ^k to A which preserve the endomorphisms of A are its term functions. One method for finding finite endoprimal algebras is via the theory of natural dualities since an endodualisable algebra is necessarily endoprimal. General results on endoprimality and endodualisability are proved and then applied to the varieties of sets, vector spaces, distributive lattices, Boolean algebras, Stone algebras, Heyting algebras, semilattices and abelian groups. In many classes the finite endoprimal algebras turn out to be endodualisable. We show that this fails in general by proving that , regarded as either a bounded semilattice or upper-bounded semilattice is dualisable, endoprimal but not endodualisable. Received May 16, 1997; accepted in final form November 6, 1997.     

Band gap tuning of defective silicon carbide nanotubes under external electric field: Density functional theory

We have theoretically investigated the effect of applying longitudinal and transverse electric field on silicon carbide nanotubes with different orientations of Stone Wales defects. We found that each type of Stone Wales defects maintained different formation energy. We have also successfully proved that the orientation of Stone Wales defects in silicon carbide nanotubes response quite differently upon applying external electric field, whereas, two important and interesting phenomena were observed. First, the semiconductor-metal phase transition occurred in silicon carbide nanotubes as well as the three types of Stone Wales defects. However, clear band gap variations were observed in all silicon carbide nanotubes under study. Second, the band gap variations in pristine silicon carbide nanotubes and nanotubes with different orientations of Stone Wales defects have the same trend, even though all silicon carbide nanotubes have clear band gap values under different strengths of the applied external electric field. However, band gap tuning under longitudinal electric field is less significant compared to band gap tuning under the transverse electric field.