Polarization and frequency disentanglement of photons via stochastic polarization mode dispersion

We investigate the quantum decoherence of frequency and polarization variables of photons via polarization mode dispersion in optical fibers. By observing the analogy between the propagation equation of the field and the Schr\"odinger equation, we develop a master equation under Markovian approximation and analytically solve for the field density matrix. We identify distinct decay behaviors for the polarization and frequency variables for single-photon and two-photon states. For the single photon case, purity functions indicate that complete decoherence for each variable is possible only for infinite fiber length. For entangled two-photon states passing through separate fibers, entanglement associated with each variable can be completely destroyed after characteristic finite propagation distances. In particular, we show that frequency disentanglement is independent of the initial polarization status. For propagation of two photons in a common fiber, the evolution of a polarization singlet state is addressed. We show that while complete polarization disentanglement occurs at a finite propagation distance, frequency entanglement could survive at any finite distance for gaussian states.Comment: 2 figure

Wall slip and flow of concentrated hard-sphere colloidal suspensions

We present a comprehensive study of the slip and flow of concentrated colloidal suspensions using cone-plate rheometry and simultaneous confocal imaging. In the colloidal glass regime, for smooth, non-stick walls, the solid nature of the suspension causes a transition in the rheology from Herschel-Bulkley (HB) bulk flow behavior at large stress to a Bingham-like slip behavior at low stress, which is suppressed for sufficient colloid-wall attraction or colloid-scale wall roughness. Visualization shows how the slip-shear transition depends on gap size and the boundary conditions at both walls and that partial slip persist well above the yield stress. A phenomenological model, incorporating the Bingham slip law and HB bulk flow, fully accounts for the behavior. Microscopically, the Bingham law is related to a thin (sub-colloidal) lubrication layer at the wall, giving rise to a characteristic dependence of slip parameters on particle size and concentration. We relate this to the suspension's osmotic pressure and yield stress and also analyze the influence of van der Waals interaction. For the largest concentrations, we observe non-uniform flow around the yield stress, in line with recent work on bulk shear-banding of concentrated pastes. We also describe residual slip in concentrated liquid suspensions, where the vanishing yield stress causes coexistence of (weak) slip and bulk shear flow for all measured rates

Analyzing and Testing Knowledge Management Complementarity Structures

Recent research on firm level productivity and organizational performance has highlighted the importance of complementarity among organizational practices. A number of studies have developed methods to test the existence of complementarity among such organizational variables. However, despite these advances in the study of industrial organization and management, our understanding of the complementarity structures remains sketchy. In this paper, we seek to advance research on this topic by identifying different classes of complementarity structures and developing a testing procedure for each class. A three-level testing procedure is developed to find complementarity structures which can be categorized into four different classes: non-complementarity, critical complementarity, non-critical asymmetric complementarity, and non-critical symmetrical complementarity. The testing method is illustrated by using an empirical illustration of a range of knowledge management (KM) strategies as they impact on knowledge creation processes in organizations

Does gravity cause load-bearing bridges in colloidal and granular systems?

We study structures which can bear loads, "bridges", in particulate packings. To investigate the relationship between bridges and gravity, we experimentally determine bridge statistics in colloidal packings. We vary the effective magnitude and direction of gravity, volume fraction, and interactions, and find that the bridge size distributions depend only on the mean number of neighbors. We identify a universal distribution, in agreement with simulation results for granulars, suggesting that applied loads merely exploit preexisting bridges, which are inherent in dense packings

Different Perspectives on IT Business Value: An Integrative Approach

Despite growing evidence of a positive impact of Information Technology (IT) investments on firm performance, the variations in the results across organisations are still significant. This research takes a fresh approach by addressing complementarity impacts of organisational practices on three different dimensions of IT business value (ITBV). The goal is to identify important organisational practices and empirically test the synergistic relationships among them and their impacts on different dimensions of IT business value. We implemented an integrative approach to analyse the complex interactions among multiple organisational practices. First, we categorised ITBV into four dimensions based on different management objectives: strategic, informational, transactional and organisational transformation. Second, organisational configuration for each ITBV dimension is identified using regression trees. Third, a formal complementarity test was performed on each configuration pattern. Our findings indicate that the set of organisational practices affecting each dimension of ITBV is different. Hence, IT complementary factors that affect particular dimensions of ITBV do not necessarily have the same effect on other dimensions

Enhancement of oligomeric stability by covalent linkage and its application to the human p53tet domain: thermodynamics and biological implications

Abstract The formation of oligomeric proteins proceeds at a major cost of reducing the translational and rotational entropy for their subunits in order to form the stabilizing interactions found in the oligomeric state. Unlike site-directed mutations, covalent linkage of subunits represents a generically applicable strategy for enhancing oligomeric stability by reducing the entropic driving force for dissociation. Although this can be realized by introducing de novo disulfide cross-links between subunits, issues with irreversible aggregation limit the utility of this approach. In contrast, tandem linkage of subunits in a single polypeptide chain offers a universal method of pre-paying the entropic cost of oligomer formation. In the present paper, thermodynamic, structural and experimental aspects of designing and characterizing tandem-linked oligomers are discussed with reference to engineering a stabilized tetramer of the oligomerization domain of the human p53 tumour-suppressor protein by tandem dimerization

Scaling of dynamics with the range of interaction in short-range attractive colloids

We numerically study the dependence of the dynamics on the range of interaction $\Delta$ for the short-range square well potential. We find that, for small $\Delta$, dynamics scale exactly in the same way as thermodynamics, both for Newtonian and Brownian microscopic dynamics. For interaction ranges from a few percent down to the Baxter limit, the relative location of the attractive glass line and the liquid-gas line does not depend on $\Delta$. This proves that in this class of potentials, disordered arrested states (gels) can be generated only as a result of a kinetically arrested phase separation.Comment: 4 pages, 4 figure

Ab-initio density functional studies of stepped TaC surfaces

We report on density functional total energy calculations of the step formation and interaction energies for vicinal TaC(001) surfaces. Our calculations show that double and triple-height steps are favored over single-height steps for a given vicinal orientation, which is in agreement with recent experimental observations. We provide a description of steps in terms of atomic displacements and charge localization and predict an experimentally observable rumpled structure of the step-edges, where the Ta atoms undergo larger displacements compared to the C atoms.Comment: 4 pages, 4 figure

Influence of polydispersity on the critical parameters of an effective potential model for asymmetric hard sphere mixtures

We report a Monte Carlo simulation study of the properties of highly asymmetric binary hard sphere mixtures. This system is treated within an effective fluid approximation in which the large particles interact through a depletion potential (R. Roth {\em et al}, Phys. Rev. E{\bf 62} 5360 (2000)) designed to capture the effects of a virtual sea of small particles. We generalize this depletion potential to include the effects of explicit size dispersity in the large particles and consider the case in which the particle diameters are distributed according to a Schulz form having degree of polydispersity 14%. The resulting alteration (with respect to the monodisperse limit) of the metastable fluid-fluid critical point parameters is determined for two values of the ratio of the diameters of the small and large particles: $q\equiv\sigma_s/\bar\sigma_b=0.1$ and $q=0.05$. We find that inclusion of polydispersity moves the critical point to lower reservoir volume fractions of the small particles and high volume fractions of the large ones. The estimated critical point parameters are found to be in good agreement with those predicted by a generalized corresponding states argument which provides a link to the known critical adhesion parameter of the adhesive hard sphere model. Finite-size scaling estimates of the cluster percolation line in the one phase fluid region indicate that inclusion of polydispersity moves the critical point deeper into the percolating regime. This suggests that phase separation is more likely to be preempted by dynamical arrest in polydisperse systems.Comment: 11 pages, 10 figure