A comparison between neural networks and k-nearest neighbours for blood cells taxonomy

Constitutive properties of living cells are able to withstand physiological environment as well as mechanical stimuli occurring within and outside the body. Any deviation from these properties would undermine the physical integrity of the cells as well as their biological functions. Thus, a quantitative study in single cell mechanics needs to be conducted. In this paper we will examine fluid flow and Neo–Hookean deformation related to the rolling effect. A mechanical model to describe the cellular adhesion with detachment is here proposed. We develop a first finite element method (FEM) analysis, simulating blood cells attached on vessel wall. Restricting the interest on the contact surface and elaborating again the computational results, we develop an equivalent spring model. Our opinion is that the simulation notices deformation inhomogeneities, i.e., areas with different concentrations having different deformation values. This important observation should be connected with a specific form of the stored energy deformation. In this case, it loses the standard convexity to show a non-monotone deformation law. Consequently, we have more minima and the variational problem seems more difficult. Several numerical simulations have been carried out, involving a number of human cells with different mechanical properties. All the collected data have been subsequently used to train and test suitable soft computing models in order to classify the kind of cell. Obtained results assure good performances (4.7% of classification error) of the implemented classifier, with very interesting applications.     

First Hitting Time Analysis of the Independence Metropolis Sampler

In this paper, we study a special case of the Metropolis algorithm, the Independence Metropolis Sampler (IMS), in the finite state space case. The IMS is often used in designing components of more complex Markov Chain Monte Carlo algorithms. We present new results related to the first hitting time of individual states for the IMS. These results are expressed mostly in terms of the eigenvalues of the transition kernel. We derive a simple form formula for the mean first hitting time and we show tight lower and upper bounds on the mean first hitting time with the upper bound being the product of two factors: a “local” factor corresponding to the target state and a “global” factor, common to all the states, which is expressed in terms of the total variation distance between the target and the proposal probabilities. We also briefly discuss properties of the distribution of the first hitting time for the IMS and analyze its variance. We conclude by showing how some non-independence Metropolis–Hastings algorithms can perform better than the IMS and deriving general lower and upper bounds for the mean first hitting times of a Metropolis–Hastings algorithm.     

Citronens?ure

Ohne Zusammenfassung     

A mixed integer linear programming formulation of the optimal mean/Value-at-Risk portfolio problem

In this paper, we consider an extension of the Markovitz model, in which the variance has been replaced with the Value-at-Risk. So a new portfolio optimization problem is formulated. We showed that the model leads to an NP-hard problem, but if the number of past observation T or the number of assets K are low, e.g. fixed to a constant, polynomial time algorithms exist. Furthermore, we showed that the problem can be formulated as an integer programming instance. When K and T are large and α^VaR is small—as common in financial practice—the computational results show that the problem can be solved in a reasonable amount of time.     

Kinetics of the reaction of O3 with selected benzenediols

The kinetics of the reaction of O₃ with the aromatic vicinal diols 1,2‐benzenediol, 3‐methyl‐1,2‐benzenediol, and 4‐methyl‐1,2‐benzenediol have been investigated using a relative rate technique. The rate coefficients were determined in a 1080‐L smog chamber at 298 K and 1 atm total pressure of synthetic air using propene and 1,3‐butadiene as reference compounds. The following O₃ reaction rate coefficients (in units of cm³ molecule^?1 s^?1) have been obtained: k(1,2‐benzenediol) = (9.60 ± 1.12) × 10^?18, k(3‐methyl‐1,2‐benzenediol) = (2.81 ± 0.23) × 10^?17, k(4‐methyl‐1,2‐benzenediol) = (2.63 ± 0.34) × 10^?17. Absolute measurements of the O₃ rate coefficient have also been carried out by measuring the decay of the dihydroxy compound in an excess of O₃. The results from these experiments are in good agreement with the relative determinations. Atmospheric implications are discussed. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 223–230, 2003     

Yellow-to-blue frequency upconversion in Pr-doped aluminium fluoride glasses

Rare-earth-doped fluoride glasses are attractive materials for photonics, since they combine a transmission region from ultraviolet to infrared and low vibrational cut-off energy. We report on the spectroscopic properties of aluminium fluorophosphate glasses doped with 0.1, 0.6, 1, 3 and 10 mol% Pr³⁺. Yellow-to-blue upconversion was observed upon pulsed and continuous-wave (CW) excitation at 575 nm. The temporal evolution of the upconverted fluorescence is characterised by rise and decay times depending on Pr³⁺ concentration. The upconversion intensity has a quadratic dependence on incident pump power, indicating a two-step process. The upconversion emission is described in the framework of a two-ion energy transfer mechanism. Emission in the second telecom window (1.3 μm) was measured upon excitation at 976 nm.     

The trapping of j,x-biradicals,photochemically produced,with 4-cyanopyridine in neutral and acidic medium

4-Cyanopyridine is able to trap 1,x-biradicals produced by direct photochemical excitation of some ketones, showing in some cases that unaspected species are formed and pyridine producs which are not explainable on the basis of actual knowledge.