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31.
Adriano BattagliaNicoletta Calace Elisa NardiBianca Maria Petronio Marco Pietroletti 《Microchemical Journal》2003,75(2):97-102
Paper mill sludge (characterized by 29.0% of organic substances such as cellulose, lignin and tannins and 71.0% of inorganic substances such as kaolinite and carbonates) was studied in a mixture with soil in order to evaluate its effects on soil capability for retaining heavy metals. Attention was focused on cadmium and lead sorption and two parameters were investigated, the contact time of paper mill sludge-soil mixture and the paper mill sludge-soil ratio in the mixture. Results showed that paper mill sludge and soil interact to form ‘new’ sorbing sites. Taking into account sorption results of lead, the retention of which by soil is substantially increased by sludge addition, can highlight this modification. Also, the amount of sorbed cadmium was increased by sludge addition. 相似文献
32.
Starting from the (apparently) elementary problem of deciding how many different topological spaces can be obtained by gluing
together in pairs the faces of an octahedron, we will describe the central r?le played by hyperbolic geometry within three-dimensional
topology. We will also point out the striking difference with the two dimensional case, and we will review some of the results
of the combinatorial and computational approach to three-manifolds developed by different mathematicians over the last several
years.
Lecture held by Carlo Petronio in the Seminario Matematico e Fisico di Milano on April 23, 2007 相似文献
33.
We generalize Turaev's definition of torsion invariants of pairs (M,&\xi;), where M is a 3-dimensional manifold and &\xi; is an Euler structure on M (a non-singular vector field up to homotopy relative to ∂M and modifications supported in a ball contained in Int(M)). Namely, we allow M to have arbitrary boundary and &\xi; to have simple (convex and/or concave) tangency circles to the boundary. We prove that
Turaev's H
1(M)-equivariance formula holds also in our generalized context. Using branched standard spines to encode vector fields we show
how to explicitly invert Turaev's reconstruction map from combinatorial to smooth Euler structures, thus making the computation
of torsions a more effective one. Euler structures of the sort we consider naturally arise in the study of pseudo-Legendrian
knots (i.e.~knots transversal to a given vector field), and hence of Legendrian knots in contact 3-manifolds. We show that torsion, as
an absolute invariant, contains a lifting to pseudo-Legendrian knots of the classical Alexander invariant. We also precisely
analyze the information carried by torsion as a relative invariant of pseudo-Legendrian knots which are framed-isotopic.
Received: 3 October 2000 / Revised version: 20 April 2001 相似文献
34.
An analytical method based on graphite-furnace atomic-absorption spectrophotometry employing a suitable signal-enhancing medium for determination of inorganic tin and two of its trisubstituted organic derivatives in sea-water has been established. This method allows determination of triphenyltin and tributyltin compounds down to 2 x 10(-12) and 2.8 x 10(-12)M respectively by means of enrichment by collection on graphitized carbon black (enrichment factor up to 8 x 10(4)) and a separation on a small silica-gel column. Inorganic tin, which is not adsorbed on the graphitized carbon black, is isolated from the matrix by liquid-liquid extraction of its pyrrolidinedithiocarbamate complex into dichloromethane. The method gives good recovery (95%) and precision ( less, similar5%) at the ng/l. level. 相似文献
35.
In this work a new analytical approach is proposed for the recovery of humin present in soil and sediments. The procedure is based on microwave oven treatment for humin deashing. In this way both the treatment time and the concentration of the HCl/HF mixture are significantly reduced (minutes rather than hours, 10% rather than concentrated). By means of the proposed scheme organic matter present in sediment and soil samples can be subdivided into the different fractions (hydrophobic and hydrophilic compounds, fulvic and humic acids, humin) making up the balance of organic carbon. Results obtained for samples characterised by different organic carbon content showed a loss of carbon ranging between 20% and 30%, consistent with previous reports about humin deashing. 相似文献
36.
Effects of acid rain on soil humic compounds 总被引:1,自引:0,他引:1
The modifications induced by acid rain on the solubility, molecular configuration and molecular weight distribution of humic (HA) and fulvic (FA) acids were studied. A natural soil was subjected to simulated acid rain until a soil pH of 4 was obtained; HA and FA acids were then extracted and characterised. The results obtained were compared both with those of natural soil and with those of a soil subjected to acid rain. Elute analysis indicates the continuous release of soluble organic compounds as a consequence of acid rain simulation, although no relationship was found with the process of soil acidification. The yields of HA and FA show that HA values are the same while FA amount is higher in the natural soil; in acid soils their water solubility increases. The molecular weight distribution shows that HA consist of a mixture of compounds of different molecular weights; they are molecules for the most part larger than 100 kDa and their distribution is not changed by soil acidification. FA can be considered to form a much more homogeneous system; in natural soil, the molecules are larger than 50 kDa, while in acidified soil they are for the most part smaller than 3 kDa. 相似文献
37.
Antonelli M. L. Calace N. Fortini C. Petronio B. M. Pietroniro B. M. Pusceddu P. 《Journal of Thermal Analysis and Calorimetry》2002,70(1):291-297
In the present paper we studied the complexation capacity towards copper ion of fulvic acids extracted from Arno River and
Lake Como sediments, as well as Antarctic Sea water at different pHs in order to evaluate the interaction of different complexing
groups of fulvic acids with copper ions. The binding capacity studies were carried out by means of titration with a copper-selective
electrode and calorimetric measurements. For the same purpose, the heat of reaction in the complexation of copper ions with
small molecules containing functional groups similar to fulvic acid was also determined. Titration results indicated that
the fraction of bound metal increases with increasing pH (from 5 to 7). This may be accounted for by the increase in the ionisation
of the fulvic acid molecule. Results obtained from calorimetric measurements show that the quantity of total heat involved
in the metal ion-fulvate interactions determines a decreasing exothermic response with increasing pH values.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
38.
We investigate the notion of complexity for finitely presented groups and the related notion of complexity for three‐dimensional manifolds. We give two‐sided estimates on the complexity of all the Milnor groups (the finite groups with free action on S3), as well as for all finite Abelian groups. The ideas developed in the process also allow to construct two‐sided bounds for the values of the so‐called T ‐invariant (introduced by Delzant) for the above groups, and to estimate from below the value of T ‐invariant for an arbitrary finitely presented group. Using the results of this paper and of previous ones, we then describe an infinite collection of Seifert threemanifolds for which we can asymptotically determine the complexity in an exact fashion up to linear functions. We also provide similar estimates for the complexity of several infinite families of Milnor groups. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
39.
We compute for all orientable irreducible geometric 3-manifolds certain complexity functions that approximate from above Matveev's
natural complexity, known to be equal to the minimal number of tetrahedra in a triangulation. We can show that the upper bounds
on Matveev's complexity implied by our computations are sharp for thousands of manifolds, and we conjecture they are for infinitely
many, including all Seifert manifolds. Our computations and estimates apply to all the Dehn fillings of M
6
1
3
(the complement of the three-component chain-link, conjectured to be the smallest triply cusped hyperbolic manifold), whence
to infinitely many among the smallest closed hyperbolic manifolds. Our computations are based on the machinery of the decomposition
into ‘bricks’ of irreducible manifolds, developed in a previous paper. As an application of our results we completely describe
the geometry of all 3-manifolds of complexity up to 9. 相似文献
40.
We describe a natural strategy to enumerate compact hyperbolic 3-manifolds with geodesic boundary in increasing order of complexity.
We show that the same strategy can be applied in order to analyze simultaneously compact manifolds and finite-volume manifolds
with toric cusps. In contrast, we show that if one allows annular cusps, the number of manifolds grows very rapidly and our
strategy cannot be employed to obtain a complete list. We also carefully describe how to compute the volume of our manifolds,
discussing formulas for the volume of a tetrahedron with generic dihedral angles in hyperbolic space. 相似文献