1,403 research outputs found
International Capital Taxation.
Globalization carries profound implications for tax systems, yet most tax systems, including that of the UK, still retain many features more suited to closed economies. The purpose of this chapter is to assess how tax policy should reflect the changing international economic environment. Institutional barriers to the movement of goods, services, capital, and (to a lesser extent) labour have fallen dramatically since the Meade Report (Meade, 1978) was published. So have the costs of moving both real activity and taxable profits between tax jurisdictions. These changes mean that capital and taxable profits in particular are more mobile between jurisdictions than they used to be. Our focus is on the taxation of capital and our main conclusions may be summarized as follows
Photon storage in Lambda-type optically dense atomic media. II. Free-space model
In a recent paper [Gorshkov et al., Phys. Rev. Lett. 98, 123601 (2007)], we
presented a universal physical picture for describing a wide range of
techniques for storage and retrieval of photon wave packets in Lambda-type
atomic media in free space, including the adiabatic reduction of the photon
group velocity, pulse-propagation control via off-resonant Raman techniques,
and photon-echo based techniques. This universal picture produced an optimal
control strategy for photon storage and retrieval applicable to all approaches
and yielded identical maximum efficiencies for all of them. In the present
paper, we present the full details of this analysis as well some of its
extensions, including the discussion of the effects of non-degeneracy of the
two lower levels of the Lambda system. The analysis in the present paper is
based on the intuition obtained from the study of photon storage in the cavity
model in the preceding paper [Gorshkov et al., Phys. Rev. A 76, 033804 (2007)].Comment: 26 pages, 8 figures. V2: significant changes in presentation, new
references, higher resolution of figure
Fouling of an anion exchange chromatography operation in a monoclonal antibody process: Visualization and kinetic studies
Fouling of chromatographic resins over their operational lifetimes can be a significant problem for commercial bioseparations. In this article, scanning electron microscopy (SEM), batch uptake experiments, confocal laser scanning microscopy (CLSM) and small-scale column studies were applied to characterize a case study where fouling had been observed during process development. The fouling was found to occur on an anion exchange (AEX) polishing step following a protein A affinity capture step in a process for the purification of a monoclonal antibody. Fouled resin samples analyzed by SEM and batch uptake experiments indicated that after successive batch cycles, significant blockage of the pores at the resin surface occurred, thereby decreasing the protein uptake rate. Further studies were performed using CLSM to allow temporal and spatial measurements of protein adsorption within the resin, for clean, partially fouled and extensively fouled resin samples. These samples were packed within a miniaturized flowcell and challenged with fluorescently labeled albumin that enabled in situ measurements. The results indicated that the foulant has a significant impact on the kinetics of adsorption, severely decreasing the protein uptake rate, but only results in a minimal decrease in saturation capacity. The impact of the foulant on the kinetics of adsorption was further investigated by loading BSA onto fouled resin over an extended range of flow rates. By decreasing the flow rate during BSA loading, the capacity of the resin was recovered. These data support the hypothesis that the foulant is located on the particle surface, only penetrating the particle to a limited degree. The increased understanding into the nature of the fouling can help in the continued process development of this industrial example
Photon storage in Lambda-type optically dense atomic media. I. Cavity model
In a recent paper [Gorshkov et al., Phys. Rev. Lett. 98, 123601 (2007)], we
used a universal physical picture to optimize and demonstrate equivalence
between a wide range of techniques for storage and retrieval of photon wave
packets in Lambda-type atomic media in free space, including the adiabatic
reduction of the photon group velocity, pulse-propagation control via
off-resonant Raman techniques, and photon-echo-based techniques. In the present
paper, we perform the same analysis for the cavity model. In particular, we
show that the retrieval efficiency is equal to C/(1+C) independent of the
retrieval technique, where C is the cooperativity parameter. We also derive the
optimal strategy for storage and, in particular, demonstrate that at any
detuning one can store, with the optimal efficiency of C/(1+C), any smooth
input mode satisfying T C gamma >> 1 and a certain class of resonant input
modes satisfying T C gamma ~ 1, where T is the duration of the input mode and 2
gamma is the transition linewidth. In the two subsequent papers of the series,
we present the full analysis of the free-space model and discuss the effects of
inhomogeneous broadening on photon storage.Comment: 16 pages, 2 figures. V2: significant changes in presentation, new
references, higher resolution of figure
Self-adapting method for the localization of quantum critical points using Quantum Monte Carlo techniques
A generalization to the quantum case of a recently introduced algorithm (Y.
Tomita and Y. Okabe, Phys. Rev. Lett. {\bf 86}, 572 (2001)) for the
determination of the critical temperature of classical spin models is proposed.
We describe a simple method to automatically locate critical points in
(Quantum) Monte Carlo simulations. The algorithm assumes the existence of a
finite correlation length in at least one of the two phases surrounding the
quantum critical point. We illustrate these ideas on the example of the
critical inter-chain coupling for which coupled antiferromagnetic S=1 spin
chains order at T=0. Finite-size scaling relations are used to determine the
exponents, and in agreement with previous
estimates.Comment: 5 pages, 3 figures, published versio
Dilation of the Giant Vortex State in a Mesoscopic Superconducting Loop
We have experimentally investigated the magnetisation of a mesoscopic
aluminum loop at temperatures well below the superconducting transition
temperature . The flux quantisation of the superconducting loop was
investigated with a -Hall magnetometer in magnetic field intensities
between . The magnetic field intensity periodicity observed in
the magnetization measurements is expected to take integer values of the
superconducting flux quanta . A closer inspection of the
periodicity, however, reveal a sub flux quantum shift. This fine structure we
interpret as a consequence of a so called giant vortex state nucleating towards
either the inner or the outer side of the loop. These findings are in agreement
with recent theoretical reports.Comment: 12 pages, 5 figures. Accepted for publication in Phys. Rev.
Failure Processes in Elastic Fiber Bundles
The fiber bundle model describes a collection of elastic fibers under load.
the fibers fail successively and for each failure, the load distribution among
the surviving fibers change. Even though very simple, the model captures the
essentials of failure processes in a large number of materials and settings. We
present here a review of fiber bundle model with different load redistribution
mechanism from the point of view of statistics and statistical physics rather
than materials science, with a focus on concepts such as criticality,
universality and fluctuations. We discuss the fiber bundle model as a tool for
understanding phenomena such as creep, and fatigue, how it is used to describe
the behavior of fiber reinforced composites as well as modelling e.g. network
failure, traffic jams and earthquake dynamics.Comment: This article has been Editorially approved for publication in Reviews
of Modern Physic
β-Microseminoprotein Endows Post Coital Seminal Plasma with Potent Candidacidal Activity by a Calcium- and pH-Dependent Mechanism
The innate immune factors controlling Candida albicans are mostly unknown. Vulvovaginal candidiasis is common in women and affects approximately 70–75% of all women at least once. Despite the propensity of Candida to colonize the vagina, transmission of Candida albicans following sexual intercourse is very rare. This prompted us to investigate whether the post coital vaginal milieu contained factors active against C. albicans. By CFU assays, we found prominent candidacidal activity of post coital seminal plasma at both neutral and the acid vaginal pH. In contrast, normal seminal plasma did not display candidacidal activity prior to acidification. By antifungal gel overlay assay, one clearing zone corresponding to a protein band was found in both post coital and normal seminal plasma, which was subsequently identified as β-microseminoprotein. At neutral pH, the fungicidal activity of β-microseminoprotein and seminal plasma was inhibited by calcium. By NMR spectroscopy, amino acid residue E71 was shown to be critical for the calcium coordination. The acidic vaginal milieu unleashed the fungicidal activity by decreasing the inhibitory effect of calcium. The candidacidal activity of β-microseminoprotein was mapped to a fragment of the C-terminal domain with no structural similarity to other known proteins. A homologous fragment from porcine β-microseminoprotein demonstrated calcium-dependent fungicidal activity in a CFU assay, suggesting this may be a common feature for members of the β-microseminoprotein family. By electron microscopy, β-microseminoprotein was found to cause lysis of Candida. Liposome experiments demonstrated that β-microseminoprotein was active towards ergosterol-containing liposomes that mimic fungal membranes, offering an explanation for the selectivity against fungi. These data identify β-microseminoprotein as an important innate immune factor active against C. albicans and may help explain the low sexual transmission rate of Candida
An aqueous non-heme Fe(iv)oxo complex with a basic group in the second coordination sphere
The Fe(IV)oxo complex of a coordinatively flexible multidentate mono-carboxylato ligand is obtained by the one electron oxidation of a low spin Fe(III) precursor in water
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