Pressure viscosity behavior of various fluids

Abstract

Many works have been published on the pressure viscosity dependence of liquids. The difficulty to fit experimental results with a simple and universal law has been often put in evidence. According to our experimental results, we show that a power law is an acceptable alternative to the common Barus law.     

Determination of trace elements in archaeological ceramics and application of Kernel Density Estimates: Implications for the definition of production locations

Summary Chemistry fingerprint of materials helps determine provenance and technological production techniques, and, therefore, is useful way to study interaction between prehistoric people. In this work 38 ceramic fragments from Justino and S?o José sites, in Brazilian northeast, were analyzed using instrumental neutron activation analysis (INAA). The recognition of the compositionally homogeneous group within of the database was performed by means of principal component (PC). The PC scores were calculated on the matrix covariance of the log base 10 transformed concentration values, and grouping was sought in the PC scores using Kernel Density Estimates (KDE). By using KDE from PC scores two chemically different groups were found. Discriminant analysis was performed to assess the groups' validity. Despite of the pottery from Justino and S?o José sites present same technical profile, different of the Tupiguarani and Aratu traditions, it was obtained that Justino and S?o José samples are constitute of distinct ceramic pastes. This result can be understood in terms of the cultural influences in the preparation of the ceramic past and that potteries analyzed are originate locally.     

Infinitesimal index: cohomology computations

In this note we study the equivariant cohomology with compact supports of the zeroes of the moment map for the cotangent bundle of a linear representation of a torus and some of its notable subsets, using the theory of the infinitesimal index, developed in [8]. We show that, in analogy to the case of equivariant K-theory dealt with in [7] using the index of transversally elliptic operators, we obtain isomorphisms with notable spaces of splines studied in [2], [3].     

The multiplicities of the equivariant index of twisted Dirac operators

In this note, we give a geometric expression for the multiplicities of the equivariant index of a Dirac operator twisted by a line bundle.     

L’indice équivariant des opérateurs transversalement elliptiques

Rèsumé. Dans cet article, nous montrons que l’indice cohomologique (construit dans [11]) d’un symbole transversalement elliptique satisfait certaines propriétés fonctorielles. Nous calculons d’autre part l’indice cohomologique pour certains symboles transversalement elliptiques particuliers. En reprenant les arguments donnés par Atiyah dans [1], on en déduit que l’indice cohomologique du symbole d’un opérateur transversalement elliptique P est égal à l’indice analytique de P.

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Oblatum 24-VII-1995     

The archaeometry study of the chemical and mineral composition of pottery from Brazil’s Northeast

Chemical and mineralogical analysis was performed on ceramics and clay samples from Barracão archaeological site located in Baixo São Francisco River by means of instrumental neutron activation analysis (INAA) and by differential scanning calorimetry (DSC). The data set was studied by means of cluster analysis (CA) and discriminant analysis (DA). The results showed that the raw material used in ceramics is not local. By using DSC it was possible to discover that the principal minerals in the samples are quartz, feldspars, mica and kaolinite.     

Sharp Error Terms for Return Time Statistics under Mixing Conditions

We describe the statistics of repetition times of a string of symbols in a stochastic process. Denote by τ _A the time elapsed until the process spells a finite string A and by S _A the number of consecutive repetitions of A. We prove that, if the length of the string grows unboundedly, (1) the distribution of τ _A , when the process starts with A, is well approximated by a certain mixture of the point measure at the origin and an exponential law, and (2) S _A is approximately geometrically distributed. We provide sharp error terms for each of these approximations. The errors we obtain are point-wise and also allow us to get approximations for all the moments of τ _A and S _A . To obtain (1) we assume that the process is φ-mixing, while to obtain (2) we assume the convergence of certain conditional probabilities.      

Large temporal narrowing of subnanosecond pulses in a low-birefringence optical fiber

A temporal shortening by a factor higher than 10 of subnanosecond pulses launched into a low-birefringence optical fiber is achieved by polarization filtering at the output. By means of the theoretical approach, in good agreement with experimental measurements, the impact of the nonlinear polarization rotation and of the coherent coupling phenomena is pointed out.