Application of micro-FTIR imaging in the Earth sciences

In this paper we describe recent applications of micro-infrared imaging in the Earth sciences. We address, in particular, the use of Fourier-transform infrared (FTIR) spectroscopy in characterizing the zoning and speciation of H and C in a variety of geological materials, including microporous minerals, nominally anhydrous volcanic minerals (NAMs), and crystal inclusions. These investigations show that use of the modern techniques of FTIR imaging enables detection of the zoning of volatile species across the studied samples, and possible configuration changes of structurally-bound carbon molecular species (e.g., CO₂ vs CO₃) during crystal growth. Such features, which are not accessible with other micro-analytical techniques, may provide information about the physicochemical properties which act as constraints in the genesis of the samples, and important information about the evolution of the geological system. Tests performed with focal-plane-array detectors (FPA) show that resolution close to the diffraction limit can be achieved if the amounts of the target molecules in the sample are substantially different. We also point out the possibility of using FTIR imaging for investigations under non-ambient conditions.     

Determination and assessment of the contents of essential and potentially toxic elements in Ayurvedic medicine formulations by inductively coupled plasma-optical emission spectrometry

Traditional Ayurvedic remedies are easily available nowadays not only in India, their country of origin, but also in Western countries. Some of these products contain high concentrations of potentially toxic elements as main or secondary ingredients, in addition to elements essential for human health; for these reasons, it is interesting to determine their elemental composition. In this study we assessed the concentrations of fifteen elements (Al, As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Pb, Si and Zn) in five products of the Parpati family, a group of Ayurvedic medicines containing high concentrations of mercury, manufactured in various places in India. Concentrations were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) or (for Pb and Cd) by graphite furnace atomic absorption spectrometry (GF-AAS) after sample mineralization. We compared the calculated daily intake of each element with reference values, considering maximum tolerable intake levels or recommended nutrient amounts. The experimental results were treated with chemometric pattern recognition techniques. We found differences in the composition of products of the same denomination manufactured by different companies and strong correlations among groups of variables. As expected, the daily intake of mercury upon consumption of Parpati medicines largely exceeded the tolerable intake level of this element.     

Effect of some physico-chemical conditions on an immunoassay for viable Escherichia coli

Viable Escherichia coli can be detected by an immunoassay in which live bacteria captured on antibody-coated paramagnetic beads are induced to synthesize the enzyme β-galactosidase, which catalyzes the hydrolysis of the slightly fluorescent substrate 4-methyl umbelliferyl-β-d-galactoside to the highly fluorescent product 7-hydroxy-4-methylcoumarin for detection. The effects of bacterial strain, presence of dead bacteria, and some environmental stresses on assay performance were evaluated.     

Compatibility of a closed singular universe with present observational data

The influence of the constant term A on the cosmological equations is investigated. It is shown that a closed singular universe is possible even with the presently known matter and radiation densities, provided that the universe age is restricted to a suitable range.     

On Graphlike k-Dissimilarity Vectors

Let \({\mathcal{G} = (G, w)}\) be a positive-weighted simple finite connected graph, that is, let G be a simple finite connected graph endowed with a function w from the set of edges of G to the set of positive real numbers. For any subgraph \({G^\prime}\) of G, we define \({w(G^\prime)}\) to be the sum of the weights of the edges of \({G^\prime}\) . For any i ₁, . . . , i _k vertices of G, let \({D_{\{i_1,..., i_k\}} (\mathcal{G})}\) be the minimum of the weights of the subgraphs of G connecting i ₁, . . . , i _k . The \({D_{\{i_1,..., i_k\}}(\mathcal{G})}\) are called k-weights of \({\mathcal{G}}\) . Given a family of positive real numbers parametrized by the k-subsets of {1, . . . , n}, \({{\{D_I\}_{I} \in { \{1,...,n\} \choose k}}}\) , we can wonder when there exist a weighted graph \({\mathcal{G}}\) (or a weighted tree) and an n-subset {1, . . . , n} of the set of its vertices such that \({D_I (\mathcal{G}) = D_I}\) for any \({I} \in { \{1,...,n\} \choose k}\) . In this paper we study this problem in the case k =  n?1.     

On the estimation of the curvatures and bending rigidity of membrane networks via a local maximum-entropy approach

We present a meshfree method for the curvature estimation of membrane networks based on the local maximum entropy approach recently presented in [1]. A continuum regularization of the network is carried out by balancing the maximization of the information entropy corresponding to the nodal data, with the minimization of the total width of the shape functions. The accuracy and convergence properties of the given curvature prediction procedure are assessed through numerical applications to benchmark problems, which include coarse grained molecular dynamics simulations of the fluctuations of red blood cell membranes [2], [3]. We also provide an energetic discrete-to-continuum approach to the prediction of the zero-temperature bending rigidity of membrane networks, which is based on the integration of the local curvature estimates. The local maximum entropy approach is easily applicable to the continuum regularization of fluctuating membranes, and the prediction of membrane and bending elasticities of molecular dynamics models.     

Large-scale anisotropy in scalar turbulence

The effect of anisotropy on the statistics of a passive tracer transported by a turbulent flow is investigated. We show that under broad conditions an arbitrarily small amount of anisotropy propagates to the large scales where it eventually dominates the structure of the concentration field. This result is obtained analytically in the framework of an exactly solvable model and confirmed by numerical simulations of scalar transport in two-dimensional turbulence.     

Some new results on the two-dimensional kinetic Ising model in the phase coexistence region

We consider a Glauber dynamics reversible with respect to the two-dimensional Ising model in a finite square of sideL with open boundary conditions, in the absence of an external field and at large inverse temperature . We prove that the gap in the spectrum of the generator restricted to the invariant subspace of functions which are even under global spin flip is much larger than the true gap. As a consequence we are able to show that there exists a new time scalet _even, much smaller than the global relaxation timet _rel, such that, with large probability, any initial configuration first relaxes to one of the two phases in a time scale of ordert _even and only after a time scale of the order oft _rel does it reach the final equilibrium by jumping, via a large deviation, to the opposite phase. It also follows that, with large probability, the time spent by the system during the first jump from one phase to the opposite one is much shorter than the relaxation time.