Entanglement of orbital angular momentum for the signal and idler beams in parametric down-conversion

We calculate the anticipated correlation between measurements of the orbital angular momentum of the signal and idler beams for parametric down-conversion. These calculations apply to the experiments where the orbital angular momentum state is measured by the use of computer-generated holograms. Displacement of these holograms with respect to the beam axis allows the measurement of superpositions of Laguerre—Gaussian modes. The correlations between such superposition modes of the signal and idler beams show their entanglement and could be used for Bell-type tests of nonlocality.     

Separately balanced realization of two-dimensional separable-denominator transfer functions†

In this paper a method is developed for the computation of a separately balanced state-space model for a given two-dimensional transfer function with separable denominator. The procedure relies on the eigenvalue/eigenvector decomposition (or singular-value decomposition) of two real symmetric matrices determined directly from the given transfer function.     

HYDRODYNAMIC COUPLING AND NON-EQUILIBRIUM DISTRIBUTION IN PORE DIFFUSION OF NONSPHERICAL FINE PARTICLES

ABSTRACT

A detailed investigation is presented of a model problem describing diffusion of a thin rod between parallel walls. Analysis proceeds by formulation of the exact diffusion equation in spatial and angular coordinates, and therefore accounts for all translational and rotational modes of transport. It is shown that the presence of a longitudinal concentration gradient produces cross-sectional forcing because of hydrodynamic anisotropy, and thereby leads to a steady-state, configuration-dependent distribution that does not relax to the uniform equilibrium distribution. A general formula derived for the effective dif-fusivity D¯ shows that the configuration-average longitudinal diffusivity is modified by an additive contribution arising from hydrodynamic coupling. Calculation of the latter term requires solution of a transtational-rotational diffusion problem. Thus, determination of D¯ cannot generally be achieved by integration alone. Boundary-layer analysis, augmented by a finite-difference calculation, reveals the asymptotic structure of the coupling effect and leads to an explicit expression for D¯ applicable to relatively small particles.     

ON BROWNIAN DYNAMICS WITH HYDRODYNAMIC WALL EFFECTS: A PROBLEM IN DIFFUSION NEAR A FIBER,AND THE MEANING OF THE NO-FLUX BOUNDARY CONDITION

An analysis is presented of the steady-state diffusion of spherical Brownian partcles through an effectively infinite expanse of fluid perforated by a circular cylindrical fiber. Detailed Stokes-flow calculations quantify the solute-fiber hydrodynamic interaction in three regimes covering the full range of solute-fiber separations, and lead to an approximate expression for the position-dependent diffusion dyadic. Thereafter, solution of the pertinent Brownian dynamic problem yields the perturbation caused by the fiber to a linear variation of the solute concentration. The results illustrate a general conclusion, derivable by simple scaling arguments, that the normal derivative of the solute concentration must tend to zero with decreasing solute-wall gap ε as [ln(1/ε)]^?1     

Controlled Decontrolling: Involution and Democratisation in Dutch Rural Planning

The debate between proponents of collaborative planning theory and their critics on the dynamics of power in planning highlights a discrepancy between the norms and the practices of democratic planning. According to the norm of democratic planning, all participants should have an equal opportunity to influence and to realise a plan's objectives, but practice has shown that power is unequally divided between people, privileging some and excluding others. This raises the important issue of how normative aspirations of deliberative planning can be reconciled with actual planning practices. This article discusses this question, exploring the power relationships and institutional transformations that influence planning using two case studies about conflicts over Dutch rural land use.     

Minireview: C2- and C4-position 17β-estradiol metabolites and their relation to breast cancer

C2- and C4-position 17β-estradiol metabolites play an important role in breast carcinogenesis. 2-Hydroxyestradiol and 4-hydroxyestradiol are implicated in tumorigenesis via two pathways. These pathways entail increased cell proliferation and the formation of reactive oxygen species that trigger an increase in the likelihood of deoxyribonucleic acid mutations.
2-Methoxyestradiol, a 17β-estradiol metabolite, however, causes induction of apoptosis in transformed and tumor cells; thus exhibiting an antiproliferative effect on tumor growth. The 4-hydroxyestradiol:2- methoxyestradiol and 2-hydroxyestradiol:2-methoxyestradiolratios therefore ought to be taken into account as possible indicators of carcinogenesis.     

Calorimetric Measurement of the Plastic Vtork of Fatigue Crack Propagation in 4140 Steel

A calorimetric technique has been developed for measurement of the effective surface energy of fatigue crack propagation,U, and the cyclic plastic work in the plastic zone,Q. The technique has several distinct advantages over existing methods. Measurements on 4140 steel (650 °C temper) show thatU andQ are direct functions of the stress intensity factor,hK, and indirect functions of crack growth rate,daldN. Measurement of the change ofU andQ after the application of a tensile overload supports this conclusion and provides strong evidence supporting crack closure theories. Formerly with the Materials Science and Engineering Department and Materials Research Center, Northwestern University, Evanston, IL.     

Pyruvate Metabolism in Saccharomyces cerevisiae

In yeasts, pyruvate is located at a major junction of assimilatory and dissimilatory reactions as well as at the branch-point between respiratory dissimilation of sugars and alcoholic fermentation. This review deals with the enzymology, physiological function and regulation of three key reactions occurring at the pyruvate branch-point in the yeast Saccharomyces cerevisiae: (i) the direct oxidative decarboxylation of pyruvate to acetyl-CoA, catalysed by the pyruvate dehydrogenase complex, (ii) decarboxylation of pyruvate to acetaldehyde, catalysed by pyruvate decarboxylase, and (iii) the anaplerotic carboxylation of pyruvate to oxaloacetate, catalysed by pyruvate carboxylase. Special attention is devoted to physiological studies on S. cerevisiae strains in which structural genes encoding these key enzymes have been inactivated by gene disruption.