Discounted cost optimality problem: stability with respect to weak metrics

We find inequalities to estimate the stability (robustness) of a discounted cost optimization problem for discrete-time Markov control processes on a Borel state space. The one stage cost is allowed to be unbounded. Unlike the known results in this area we consider a perturbation of transition probabilities measured by the Kantorovich metric, closely related to the weak convergence. The results obtained make possible to estimate the vanishing rate of the stability index when approximation is made through empirical measures.     

On the approximate controllability of stochastic stokes systems

In this paper, we analyze the approximate controllability in quadratic mean of some systems governed by stochastic partial differential equations of the Stokes kind. When the noise is state-independent, we obtain satisfactory results, similar to those known for the corresponding deterministic system. In the more complicate case of a multiplicative noise, we are able to give (only) partial results. More precisely, we prove in this case that approximate controllability is equivalent to the unique continuation property for a particular backward (adjoint) stochastic system     

Ordered representations of spaces of integrable functions

Let X be a Banach space, (Ω,Σ) a measurable space and let m : Σ → X be a (countably additive) vector measure. Consider the corresponding space of integrable functions L¹(m). In this paper we analyze the set of (countably additive) vector measures n satisfying that L¹(n) = L¹(m). In order to do this we define a (quasi) order relation on this set to obtain under adequate requirements the simplest representation of the space L¹(m) associated to downward directed subsets of the set of all the representations. This research has been partially supported by La Junta de Andalucía. The support of D.G.I. under project MTM2006–11690–C02 (M.E.C. Spain) and FEDER is gratefully acknowledged.     

Persistence, Ontic Vagueness and Identity: Towards a Substantialist Four–dimensionalism

Four-dimensionalism, the stage theory version in particular, has been defended as the best solution for avoiding vagueness in regards to composition, persistence and identity. Stage theory is highly problematic by itself, and the two views usually packed with it, unrestricted composition and counterpart theory, are a heavy burden. However, dispensing with these two views, four-dimensionalism could avoid vague persistence by issuing a criterion that would establish sharp temporal boundaries for the existence of genuine entities (simples, molecules and living organisms). This would avoid vague existence and vague identity, but in a way that is still compatible with endurantism. Nevertheless, a minimal (substantialist) four-dimensionalism, a worm perdurantist ontology, would fit better with the unique way in which organisms persist: by retaining both identity and intrinsic change.     

Investigation of Catalyst Fragmentation in Gas‐Phase Olefin Polymerisation: A Novel Short Stop Reactor

Summary: A short stop reactor (SSR) was developed to study nascent particle morphology and reaction kinetics in the gas‐phase polymerisation of olefins on supported catalysts. It is shown that the SSR provides a useful means to look into important phenomena such as catalyst fragmentation and catalyst site activation and deactivation that take place during the very early stages of the heterogeneous polymerisation of olefins. New experimental results obtained from gas‐phase polymerisation of ethylene show that, depending on the type of catalyst system and on the reaction conditions, different kinds of morphologies can be obtained for the nascent polymer (e.g., cracks and folded chain). Experimental data also indicate that the growth of the polymer chains occur at a non‐steady state during the very early stages of the polymerisation.

SEM image showing the morphology of a polymer/catalyst particle after 2 seconds of polymerisation at 8 bars of ethylene on an MgCl₂‐supported Ziegler‐Natta catalyst.     

Differential modulation of cellular death and survival pathways by conjugated bile acids

Background  

The liver-derived McNtcp.24 cells transport bile acids and show distinctive responses to the two classes of conjugated bile acids. Whereas taurine-conjugated bile acids are non-toxic, glycine-conjugated bile acids efficiently induce apoptosis. The aim of this study was to determine if the differential sensitivity is limited to cells that normally transport bile acids and if bile acid binding proteins could reduce bile acid-mediated apoptosis. The apical sodium/bile acid co-transporter (asbt) was expressed in Chinese hamster ovary (CHO) cells to establish active bile acid transport in a non-liver-derived cell model (CHO.asbt). A high-affinity bile acid binder was expressed in McNtcp.24 cells.     

Structural, Spectroscopic, and Thermal Behaviour of Bis-(thiosaccharinate)-aqua-cadmium(II)

Summary.  The crystal structure of the title complex, [Cd(tsac)₂(H₂O)], has been determined by single crystal X-ray diffraction methods. It crystallizes in the monoclinic space group C2/c (a = 12.236(3), b = 8.919(3), c = 16.655(3) ?, β = 96.18(2)°, Z = 4). The molecular structure was solved from 1705 independent reflections with I > σ(I) and refined to R ₁ = 0.0489. Infrared and Raman spectra of the complex were recorded and are briefly discussed. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis. Received December 18, 2000. Accepted February 19, 2001     

High-spin spectroscopy of 63 31Ga32 and 65 31Ga34

High-spin states in the nuclei ⁶³Ga and ⁶⁵Ga were studied following the reaction ³²S + ⁴⁰Ca at a reaction energy of 125 MeV and using the GASP γ-ray spectrometer in combination with the ISIS charged-particle detector system. In addition to low-lying negative-parity states with single-particle character, rotational-like cascades built on the 9/2⁺ and 19/2^- states have been observed in both nuclei. Sidebands with negative parity in ⁶³Ga and positive parity in ⁶⁵Ga could be established. The experimental results are compared with Total Routhian Surface calculations which describe the nuclei as moderately deformed (β₂≈ 0.25) and γ soft at low rotational frequencies. The highest experimentally observed positive-parity state in ⁶⁵Ga (41/2⁺) is in good agreement with the calculated crossing of the collective band with a non-collective one terminating at this spin. Received: 20 December 2000 / Accepted: 2 May 2001     

High-spin states in 208Pb

High-spin states in ²⁰⁸Pb have been studied by γ-ray-spectroscopy methods in deep inelastic reactions induced by beams of ²⁰⁸Pb, ¹³⁶Xe and ⁷⁶Ge beams on a thick ²⁰⁸Pb target. The 11⁺ ₂ state and new γ-transitions between the one-particle one-hole states of highest spin have been found and electromagnetic matrix elements verified. High-spin states of two-particle two-hole structure have been detected for the first time. The results are compared to shell model calculations with realistic interactions in the complete Kuo-Herling space. Received: 31 October 2000 / Accepted: 26 March 2001