Local Rules and Fitness Landscapes: A Catastrophe Model

This paper examines the imposition of local rules in five mail delivery centres of Australia Post. Local rules are patterns of behaviour used by subunits of an organization to optimise their payoff. These local rules may ultimately benefit the total organization. Fitness landscapes are used to examine the emergence of local rules in this workplace. This research examined the relationship between the time taken to sort the mail and the volume of this mail. Work rates show a clear catastrophe shift; that is, work rates suddenly drop when the volume of mail exceeds a certain level, as Postal Delivery Officers apply local rules to maximise gains inherent in the pay structures. Such behaviour is close to that predicted by Kauffman (1995) in computer simulations of lattices and may be indicative of the application of local rules in organizations. The implications of the use of local rules are that behaviour in social systems may be dictated by systemic and emergent processes which are outside immediate management control. A further implication is that organizations may be structured to a significant extent by such local rules.     

Homoclinic bifurcation in a Hodgkin-Huxley model of thermally sensitive neurons

We study global bifurcations of the chaotic attractor in a modified Hodgkin-Huxley model of thermally sensitive neurons. The control parameter for this model is the temperature. The chaotic behavior is realized over a wide range of temperatures and is visualized using interspike intervals. We observe an abrupt increase of the interspike intervals in a certain temperature region. We identify this as a homoclinic bifurcation of a saddle-focus fixed point which is embedded in the chaotic attractors. The transition is accompanied by intermittency, which obeys a universal scaling law for the average length of trajectory segments exhibiting only short interspike intervals with the distance from the onset of intermittency. We also present experimental results of interspike interval measurements taken from the crayfish caudal photoreceptor, which qualitatively demonstrate the same bifurcation structure. (c) 2000 American Institute of Physics.     

A phase I, randomized study of combined IL-2 and therapeutic immunisation with antiretroviral therapy

Background  

Fully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection.     

Synthesis and characterization of [MCl2(nPr-N(Ph2P)2] (M?=?Pt, Pd) complexes and hydroformylation of 1-octene using [PtCl2(R-N(Ph2P)2)] (R?=?benzyl, 2-picolyl, nPr) complexes

The synthesis and characterization of platinum(II) and palladium(II) complexes of the type [PtX₂( ⁿ Pr-N(Ph₂P)₂)] (X = Cl, I) and [PdCl₂(R-N(Ph₂P)₂)] {R =  ⁿ Pr, p-OMe(C₆H₄)} containing aminodiphosphine P,P-bidentate ligands is described. Complexes of the type [PtCl₂(R-N(Ph₂P)₂)] (where R = benzyl, 2-picolyl and ⁿ Pr) catalyzed the hydroformylation of 1-octene, albeit at low activities and slightly elevated regioselectivities toward the linear aldehyde, when compared with analogous compounds containing small bite angles.     

Constraints on the fundamental string coupling from B-mode experiments

We study signatures of cosmic superstring networks containing strings of multiple tensions and Y junctions, on the cosmic microwave background (CMB) temperature and polarization spectra. Focusing on the crucial role of the string coupling constant g(s), we show that the number density and energy density of the scaling network are dominated by different types of string in the g(s) ~ 1 and g(s) ? 1 limits. This can lead to an observable shift in the position of the B-mode peak--a distinct signal leading to a direct constraint on g(s). We forecast the joint bounds on g(s) and the fundamental string tension μ(F) from upcoming and future CMB polarization experiments, as well as the signal to noise in detecting the difference between B-mode signals in the limiting cases of large and small g(s). We show that such a detectable shift is within reach of planned experiments.     

Investigation of slow light enhanced nonlinear transmission for all-optical regeneration in silicon photonic crystal waveguides at 10 Gbit/s

We demonstrate bit error rate improvement, corroborated by eye diagram measurements, of a (10 MHz) amplitude distorted 10 Gbit/s data signal in silicon photonic crystal waveguides. This demonstration exploits a power clamping nonlinear transfer function, provided by slow light enhancement of nonlinear absorption in these waveguides.     

Group invariant solution for a pre-existing fluid-driven fracture in impermeable rock

The propagation of a two-dimensional fluid-driven fracture in impermeable rock is considered. The fluid flow in the fracture is laminar. By applying lubrication theory a partial differential equation relating the half-width of the fracture to the fluid pressure is derived. To close the model the PKN formulation is adopted in which the fluid pressure is proportional to the half-width of the fracture. By considering a linear combination of the Lie point symmetries of the resulting non-linear diffusion equation the boundary value problem is expressed in a form appropriate for a similarity solution. The boundary value problem is reformulated as two initial value problems which are readily solved numerically. The similarity solution describes a preexisting fracture since both the total volume and length of the fracture are initially finite and non-zero. Applications in which the rate of fluid injection into the fracture and the pressure at the fracture entry are independent of time are considered.     

Group invariant solution for a pre-existing fluid-driven fracture in impermeable rock

The propagation of a two-dimensional fluid-driven fracture in impermeable rock is considered. The fluid flow in the fracture is laminar. By applying lubrication theory a partial differential equation relating the half-width of the fracture to the fluid pressure is derived. To close the model the PKN formulation is adopted in which the fluid pressure is proportional to the half-width of the fracture. By considering a linear combination of the Lie point symmetries of the resulting non-linear diffusion equation the boundary value problem is expressed in a form appropriate for a similarity solution. The boundary value problem is reformulated as two initial value problems which are readily solved numerically. The similarity solution describes a preexisting fracture since both the total volume and length of the fracture are initially finite and non-zero. Applications in which the rate of fluid injection into the fracture and the pressure at the fracture entry are independent of time are considered.     

Human neuronal stargazin-like proteins, γ2, γ3 and γ4; an investigation of their specific localization in human brain and their influence on CaV2.1 voltage-dependent calcium channels expressed in Xenopus oocytes.

Background  

Stargazin (γ₂) and the closely related γ₃, and γ₄ transmembrane proteins are part of a family of proteins that may act as both neuronal voltage-dependent calcium channel (VDCC) γ subunits and transmembrane α-amino-3-hydroxy-5-methyl-4-isoxazoleproponinc (AMPA) receptor regulatory proteins (TARPs). In this investigation, we examined the distribution patterns of the stargazin-like proteins γ₂, γ₃, and γ₄ in the human central nervous system (CNS). In addition, we investigated whether human γ₂ or γ₄ could modulate the electrophysiological properties of a neuronal VDCC complex transiently expressed in Xenopus oocytes.