Hydrophobicity of peritoneal tissues in the rat

In this study, an inventory of the hydrophobicity of peritoneal tissues in the living rat was made. Peritoneal tissues were divided into mesentery (i.e., omentum) and parietal and visceral peritoneum and their hydrophobicity was determined by the sessile drop method. All peritoneal tissues were hydrophilic with water contact angles varying from 0 degrees to 61 degrees. Mesentery and visceral peritoneum covering the intestines were significantly more hydrophilic than parietal and other visceral peritoneal tissues. In general, visceral peritoneum was the most hydrophobic tissue, and visceral peritoneum covering the kidneys (61 degrees) and the stomach (54 degrees) was less hydrophilic than that covering the rest of the organs, i.e., spleen (49 degrees), liver (45 degrees), and bladder (41 degrees). In summary, peritoneal tissues involved in adsorptive and exchange functions and requiring lubrication are more hydrophilic than tissues with more important and protective functions.     

Finite Element Matrix Sequences: the Case of Rectangular Domains

In the present paper, we consider a preconditioning strategy for Finite Element (FE) matrix sequences {A _n (a)} _n discretizing the elliptic problem $$\left\{ \begin{gathered} A_a u \equiv ( - )^k \nabla ^k [a(x,y)\nabla ^k u(x,y)] = f(x,y),{ }(x,y) \in \Omega = (0,1)^2 , \hfill \\ \left. {\left( {\frac{{\partial ^s }}{{\partial v^s }}u(x,y)} \right)} \right|_{\partial \Omega } \equiv 0,{ }s = 0,...,k - 1,{ }^{^{^{^{^{^{(1)} } } } } } \hfill \\ \end{gathered} \right.$$ with a(x,y) being a uniformly positive function and ν denoting the unit outward normal direction. More precisely, in connection with preconditioned conjugate gradient (PCG) like methods, we define the preconditioning sequence: {P _n (a)} _n , P _n (a):= $$\widetilde D$$ _n ^1/2(a)A _n (1) $$\widetilde D$$ _n ^1/2(a), where $$\widetilde D$$ _n (a) is the suitable scaled main diagonal of A _n (a). In fact, under the mild assumption of Lebesgue integrability of a(x), the weak clustering at the unity of the corresponding preconditioned sequence is proved. Moreover, if a(x,y) is regular enough and if a uniform triangulation is considered, then the preconditioned sequence shows a strong clustering at the unity so that the sequence {P _n (a)} _n turns out to be a superlinear preconditioning sequence for {A _n (a)} _n . The computational interest is due to the fact that the computation with A _n (a) is reduced to computations involving diagonals and two-level Toeplitz structures {A _n (1)} _n with banded pattern. Some numerical experimentations confirm the efficiency of the discussed proposal.     

Cold rolling mill process: a numerical procedure for industrial applications

The paper proposes a model for a cold rolling mill process in the full-film regime that uses lubricant emulsion sprayed on at the entrance of the strip. The aim of the model is to forecast the reduction of strip thickness versus the flow rate of lubricant given the other operation parameters. The model includes strip plastic deformation, lubricant flow and lubricant viscosity depending on pressure. The mathematical problem is a free boundary one and a numerical procedure, applied to an industrial plant, is presented with some results.     

A Monte Carlo Method for the Simulation of First Passage Times of Diffusion Processes

A reliable Monte Carlo method for the evaluation of first passage times of diffusion processes through boundaries is proposed. A nested algorithm that simulates the first passage time of a suitable tied-down process is introduced to account for undetected crossings that may occur inside each discretization interval of the stochastic differential equation associated to the diffusion. A detailed analysis of the performances of the algorithm is then carried on both via analytical proofs and by means of some numerical examples. The advantages of the new method with respect to a previously proposed numerical-simulative method for the evaluation of first passage times are discussed. Analytical results on the distribution of tied-down diffusion processes are proved in order to provide a theoretical justification of the Monte Carlo method.     

An improved scheme for accelerating the convergence of the simulated annealing algorithm applied to real world problems

When formulated in mathematical terms, the problem of zoning a protected natural area subject to both box and spatial constraints results in a large combinatorial optimization problem belonging to the NP-hard class. These facts suggest the need to apply a heuristic approach. In this contribution a new proposal to decrease the control parameter, known as temperature, in the simulated annealing algorithm is presented. The strategy is based on that proposed by Lundy and Mees [4], and developed in order to decrease the running time of the algorithm applied to large scale problems. When applied to solving small-size simulated problems, results were indistinguishable from those obtained via an exact, enumerative method. A coarse-scale zoning of Talampaya National Park (Argentina) rendered maps remarkably similar to those produced by subject area experts using a non-quantitative consensus-seeking approach. Results are encouraging and show particular potential for the periodical update of zoning of protected natural areas. Such a capability is crucial for application in developing countries where both human and financial resources are usually scarce but still critical for updating zoning and management plans. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and preliminary in vivo evaluations of polyurethane microstructures for transdermal drug delivery

ABSTRACT: BACKGROUND: Polymers have been considered as important materials in fabrication of microstructures for various medical purposes including drug delivery. This study evaluates polyurethane as material for hollow microstructures preparation. RESULTS: Polyurethane microstructures were obtained by interfacial polyaddition combined with spontaneous emulsification and present slightly acid pH values. Scanning electron microscopy revealed the existence of irregular shapes and agglomerated microstructures. The material is heat resistant up to 280 [DEGREE SIGN]C. Good results were recorded on murine skin tests in case of polyurethane microstructures based on isophorone diisocyanate. Mesenchymal stem cells viability presents good results for the same sample after 48 hours based on the Alamar Blue test. CONCLUSIONS: The research revealed the reduced noxiousness of this type of microstructures and consequently the possibility of their use for therapeutic purposes.     

The Compound Poisson Limit Ruling Periodic Extreme Behaviour of Non-Uniformly Hyperbolic Dynamics

We prove that the distributional limit of the normalised number of returns to small neighbourhoods of periodic points of certain non-uniformly hyperbolic dynamical systems is compound Poisson. The returns to small balls around a fixed point in the phase space correspond to the occurrence of rare events, or exceedances of high thresholds, so that there is a connection between the laws of Return Times Statistics and Extreme Value Laws. The fact that the fixed point in the phase space is a repelling periodic point implies that there is a tendency for the exceedances to appear in clusters whose average sizes is given by the Extremal Index, which depends on the expansion of the system at the periodic point. We recall that for generic points, the exceedances, in the limit, are singular and occur at Poisson times. However, around periodic points, the picture is different: the respective point processes of exceedances converge to a compound Poisson process, so instead of single exceedances, we have entire clusters of exceedances occurring at Poisson times with a geometric distribution ruling its multiplicity. The systems to which our results apply include: general piecewise expanding maps of the interval (Rychlik maps), maps with indifferent fixed points (Manneville-Pomeau maps) and Benedicks-Carleson quadratic maps.     

Iridium(I) Hydroxides: Powerful Synthons for Bond Activation

A family of iridium(I) hydroxides of the form [Ir(cod)(NHC)(OH)] (cod=1,5‐cyclooctadiene, NHC=N‐heterocyclic carbene) is reported. Single‐crystal X‐ray analyses and computational methods were used to explore the structural characteristics and steric properties of these new complexes. The model complex [Ir(cod)(IiPr)(OH)] (IiPr=1,3‐(diisopropyl)imidazol‐2‐ylidene) undergoes reaction with a wide variety of substrates including boronic acids and silicon compounds. In addition, O? H, N? H and C? H bond activation was achieved with alcohols, carboxylic acids, amines and various sp‐, sp²‐ and sp³‐hybridised carbon centres, giving access to a wide range of new Ir^I complexes. These studies have allowed us to explore the exciting reactivity of this motif, revealing a versatile and useful synthon capable of activating important chemical bonds under mild (typically room temperature) conditions. No additives were required and, in the case of X? H bond activation, water was the only waste product, rendering this an atom efficient procedure for bond activation. This system has great potential for the construction of new catalytic cycles for organic synthesis and small‐molecule activation.