1,708 research outputs found

    Driving Forces for Digital Transformation – Case Studies of Q-Commerce

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    Companies want to leverage emerging technologies to achieve digital transformation, but most of them are reluctant to take action. This study investigates the driving forces behind digital transformation investment by studying how HKTVmall and Pandamart have invested in new digital technologies to enable q-commerce in Hong Kong, China. Though Pandamart follows a modular approach and HKTVmall follows a staged approach to achieve digital transformation, we have found that in both cases, digital transformation has been driven by economic factors (cost reduction and revenue generation), social factors (changing demographic characteristics and changing customer behavior), and technological factors (proprietary technology advantages and new digital technology capabilities)

    The Omega deformed B-model for rigid N=2 theories

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    We give an interpretation of the Omega deformed B-model that leads naturally to the generalized holomorphic anomaly equations. Direct integration of the latter calculates topological amplitudes of four dimensional rigid N=2 theories explicitly in general Omega-backgrounds in terms of modular forms. These amplitudes encode the refined BPS spectrum as well as new gravitational couplings in the effective action of N=2 supersymmetric theories. The rigid N=2 field theories we focus on are the conformal rank one N=2 Seiberg-Witten theories. The failure of holomorphicity is milder in the conformal cases, but fixing the holomorphic ambiguity is only possible upon mass deformation. Our formalism applies irrespectively of whether a Lagrangian formulation exists. In the class of rigid N=2 theories arising from compactifications on local Calabi-Yau manifolds, we consider the theory of local P2. We calculate motivic Donaldson-Thomas invariants for this geometry and make predictions for generalized Gromov-Witten invariants at the orbifold point.Comment: 73 pages, no figures, references added and typos correcte

    Stable marriage with general preferences

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    We propose a generalization of the classical stable marriage problem. In our model, the preferences on one side of the partition are given in terms of arbitrary binary relations, which need not be transitive nor acyclic. This generalization is practically well-motivated, and as we show, encompasses the well studied hard variant of stable marriage where preferences are allowed to have ties and to be incomplete. As a result, we prove that deciding the existence of a stable matching in our model is NP-complete. Complementing this negative result we present a polynomial-time algorithm for the above decision problem in a significant class of instances where the preferences are asymmetric. We also present a linear programming formulation whose feasibility fully characterizes the existence of stable matchings in this special case. Finally, we use our model to study a long standing open problem regarding the existence of cyclic 3D stable matchings. In particular, we prove that the problem of deciding whether a fixed 2D perfect matching can be extended to a 3D stable matching is NP-complete, showing this way that a natural attempt to resolve the existence (or not) of 3D stable matchings is bound to fail.Comment: This is an extended version of a paper to appear at the The 7th International Symposium on Algorithmic Game Theory (SAGT 2014

    The nucleoporin Nup60p functions as a Gsp1p–GTP-sensitive tether for Nup2p at the nuclear pore complex

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    The nucleoporins Nup60p, Nup2p, and Nup1p form part of the nuclear basket structure of the Saccharomyces cerevisiae nuclear pore complex (NPC). Here, we show that these necleoporins can be isolated from yeast extracts by affinity chromatography on karyopherin Kap95p-coated beads. To characterize Nup60p further, Nup60p-coated beads were used to capture its interacting proteins from extracts. We find that Nup60p binds to Nup2p and serves as a docking site for Kap95p–Kap60p heterodimers and Kap123p. Nup60p also binds Gsp1p–GTP and its guanine nucleotide exchange factor Prp20p, and functions as a Gsp1p guanine nucleotide dissociation inhibitor by reducing the activity of Prp20p. Yeast lacking Nup60p exhibit minor defects in nuclear export of Kap60p, nuclear import of Kap95p–Kap60p-dependent cargoes, and diffusion of small proteins across the NPC. Yeast lacking Nup60p also fail to anchor Nup2p at the NPC, resulting in the mislocalization of Nup2p to the nucleoplasm and cytoplasm. Purified Nup60p and Nup2p bind each other directly, but the stability of the complex is compromised when Kap60p binds Nup2p. Gsp1p–GTP enhances by 10-fold the affinity between Nup60p and Nup2p, and restores binding of Nup2p–Kap60p complexes to Nup60p. The results suggest a dynamic interaction, controlled by the nucleoplasmic concentration of Gsp1p–GTP, between Nup60p and Nup2p at the NPC

    Bose-Einstein condensation and superfluidity of dilute Bose gas in a random potential

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    We develop the dilute Bose gas model with random potential in order to understand the Bose system in random media such as 4He in porous glass. Using the random potential taking account of the pore size dependence, we can compare quantitatively the calculated specific heat with the experimental results, without free parameters. The agreement is excellent at low temperatures, which justifies our model. The relation between Bose condensation and superfluidity is discussed. Our model can predict some unobserved phenomena in this system.Comment: 9 pages, 11 figures, accepted for publication in Phys. Rev.

    An Oral Selective Alpha-1A Adrenergic Receptor Agonist Prevents Doxorubicin Cardiotoxicity

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    Alpha-1 adrenergic receptors (α1-ARs) play adaptive and protective roles in the heart. Dabuzalgron is an oral selective α1A-AR agonist that was well tolerated in multiple clinical trials of treatment for urinary incontinence, but has never been used to treat heart disease in humans or animal models. In this study, the authors administered dabuzalgron to mice treated with doxorubicin (DOX), a widely used chemotherapeutic agent with dose-limiting cardiotoxicity that can lead to heart failure (HF). Dabuzalgron protected against DOX-induced cardiotoxicity, likely by preserving mitochondrial function. These results suggest that activating cardiac α1A-ARs with dabuzalgron, a well-tolerated oral agent, might represent a novel approach to treating HF

    Conserving and Gapless Approximations for an Inhomogeneous Bose Gas at Finite Temperatures

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    We derive and discuss the equations of motion for the condensate and its fluctuations for a dilute, weakly interacting Bose gas in an external potential within the self--consistent Hartree--Fock--Bogoliubov (HFB) approximation. Account is taken of the depletion of the condensate and the anomalous Bose correlations, which are important at finite temperatures. We give a critical analysis of the self-consistent HFB approximation in terms of the Hohenberg--Martin classification of approximations (conserving vs gapless) and point out that the Popov approximation to the full HFB gives a gapless single-particle spectrum at all temperatures. The Beliaev second-order approximation is discussed as the spectrum generated by functional differentiation of the HFB single--particle Green's function. We emphasize that the problem of determining the excitation spectrum of a Bose-condensed gas (homogeneous or inhomogeneous) is difficult because of the need to satisfy several different constraints.Comment: plain tex, 19 page

    Two-Photon, Two-gluon and Radiative Decays of Heavy Flavoured Mesons

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    Here we present the two-photon and two-gluon decay widths of the S-wave (ηQ∈c,b\eta_{Q\in c,b}) and P-wave (χQ∈c,bJ\chi_{Q\in c,bJ}) charmonium and bottonium states and the radiative transition decay widths of ccˉc\bar c, bbˉb\bar b and cbˉc\bar b systems based on Coulomb plus power form of the inter-quark potential (CPPνCPP_\nu) with exponent ν\nu. The Schro¨\ddot{o}dinger equation is solved numerically for different choices of the exponent ν\nu. We employ the masses of different states and their radial wave functions obtained from the study to compute the two-photon and two-gluon decay widths and the E1 and M1 radiative transitions. It is found that the quarkonia mass spectra and the E1 transition can be described by the same interquark model potential of the CPPνCPP_\nu with ν=1.0\nu=1.0 for ccˉc\bar c and ν=0.7\nu=0.7 for bbˉb\bar b systems, while the M1 transition (at which the spin of the system changes) and the decay rates in the annihilation channel of quarkonia are better estimated by a shallow potential with ν<1.0\nu<1.0.Comment: 27 Pages, 8 figure

    Landau-Khalatnikov two-fluid hydrodynamics of a trapped Bose gas

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    Starting from the quantum kinetic equation for the non-condensate atoms and the generalized Gross-Pitaevskii equation for the condensate, we derive the two-fluid hydrodynamic equations of a trapped Bose gas at finite temperatures. We follow the standard Chapman-Enskog procedure, starting from a solution of the kinetic equation corresponding to the complete local equilibrium between the condensate and the non-condensate components. Our hydrodynamic equations are shown to reduce to a form identical to the well-known Landau-Khalatnikov two-fluid equations, with hydrodynamic damping due to the deviation from local equilibrium. The deviation from local equilibrium within the thermal cloud gives rise to dissipation associated with shear viscosity and thermal conduction. In addition, we show that effects due to the deviation from the diffusive local equilibrium between the condensate and the non-condensate (recently considered by Zaremba, Nikuni and Griffin) can be described by four frequency-dependent second viscosity transport coefficients. We also derive explicit formulas for all the transport coefficients. These results are used to introduce two new characteristic relaxation times associated with hydrodynamic damping. These relaxation times give the rate at which local equilibrium is reached and hence determine whether one is in the two-fluid hydrodynamic region.Comment: 26 pages, 3 postscript figures, submitted to PR

    Hexatic-Herringbone Coupling at the Hexatic Transition in Smectic Liquid Crystals: 4-ϵ\epsilon Renormalization Group Calculations Revisited

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    Simple symmetry considerations would suggest that the transition from the smectic-A phase to the long-range bond orientationally ordered hexatic smectic-B phase should belong to the XY universality class. However, a number of experimental studies have constantly reported over the past twenty years "novel" critical behavior with non-XY critical exponents for this transition. Bruinsma and Aeppli argued in Physical Review Letters {\bf 48}, 1625 (1982), using a 4−ϵ4-\epsilon renormalization-group calculation, that short-range molecular herringbone correlations coupled to the hexatic ordering drive this transition first order via thermal fluctuations, and that the critical behavior observed in real systems is controlled by a `nearby' tricritical point. We have revisited the model of Bruinsma and Aeppli and present here the results of our study. We have found two nontrivial strongly-coupled herringbone-hexatic fixed points apparently missed by those authors. Yet, those two new nontrivial fixed-points are unstable, and we obtain the same final conclusion as the one reached by Bruinsma and Aeppli, namely that of a fluctuation-driven first order transition. We also discuss the effect of local two-fold distortion of the bond order as a possible missing order parameter in the Hamiltonian.Comment: 1 B/W eps figure included. Submitted to Physical Review E. Contact: [email protected]
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