6,738 research outputs found

    A Macroeconomic Overview of Public Enterprise in the Philippines, 1975-84

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    This paper provides an overview of the macroeconomic role and impact of Philippine public enterprises. In particular, it deals with its economic contribution on value-added, investment and employment. It also discusses the sector’s deficit and the impact of its finance on the national budget and borrowings. Its efficiency, as indicated by financial profitability is measured as well.public debt, public enterprise, employment opportunities, gross value added

    Active redundancy allocation in systems

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    An effective way of improving the reliability of a system is the allocation of active redundancy. Let X1X_{1}, X2X_{2} be independent lifetimes of the components C1C_{1} and C2C_{2}, respectively, which form a series system. Let denote U1=min(max(X1,X),X2)U_{1} = \min ( \max (X_{1},X),X_{2}) and U2=min(X1,max(X2,X))U_{2} = \min (X_{1},\max (X_{2},X)), where X is the lifetime of a redundancy (say S) independent of X1X_{1} and X2X_{2}. That is U1(U2)U_{1}(U_{2}) denote the lifetime of a system obtained by allocating S to C1(C2)C_{1}(C_{2}) as an active redundancy. Singh and Misra (1994) considered the criterion where C1C_{1} is preferred to C2C_{2} for redundancy allocation if P(U1>U2)P(U2>U1)P(U_{1} > U_{2})\geq P(U_{2} > U_{1}). In this paper we use the same criterion of Singh and Misra (1994) and we investigate the allocation of one active redundancy when it differs depending on the component with which it is to be allocated. We find sufficient conditions for the optimization which depend on the components and redundancies probability distributions. We also compare the allocation of two active redundancies (say S1S_{1} and S2S_{2}) in two different ways, that is S1S_{1} with C1C_{1} and S2S_{2} with C2C_{2} and viceversa. For this case the hazard rate order plays an important role. We obtain results for the allocation of more than two active redundancies to a k-out-of-n systems

    Quantum MERA Channels

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    Tensor networks representations of many-body quantum systems can be described in terms of quantum channels. We focus on channels associated with the Multi-scale Entanglement Renormalization Ansatz (MERA) tensor network that has been recently introduced to efficiently describe critical systems. Our approach allows us to compute the MERA correspondent to the thermodynamic limit of a critical system introducing a transfer matrix formalism, and to relate the system critical exponents to the convergence rates of the associated channels.Comment: 4 pages, 2 figure

    Quantum relative positioning in Hilbert space

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    A new class of state transformations that are quantum mechanically prohibited is introduced. These can be seen as the generalization of the universal-NOT transformation which, for all pure inputs state of a given Hilbert space produces pure outputs whose projection on the original state is fixed to a value smaller than one. The case of not pure output states is also addressed. We give an application of these transformations in the context of separability criteria.Comment: 5 pages, 1 figure; new material added: in particular we present an application of quantum movers in the context of separability criteria. Typos corrected. Phys. Rev. A, accepted for publicatio

    Unifying approach to the quantification of bipartite correlations by Bures distance

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    The notion of distance defined on the set of states of a composite quantum system can be used to quantify total, quantum and classical correlations in a unifying way. We provide new closed formulae for classical and total correlations of two-qubit Bell-diagonal states by considering the Bures distance. Complementing the known corresponding expressions for entanglement and more general quantum correlations, we thus complete the quantitative hierarchy of Bures correlations for Bell-diagonal states. We then explicitly calculate Bures correlations for two relevant families of states: Werner states and rank-2 Bell-diagonal states, highlighting the subadditivity which holds for total correlations with respect to the sum of classical and quantum ones when using Bures distance. Finally, we analyse a dynamical model of two independent qubits locally exposed to non-dissipative decoherence channels, where both quantum and classical correlations measured by Bures distance exhibit freezing phenomena, in analogy with other known quantifiers of correlations.Comment: 18 pages, 4 figures; published versio

    Relations between entanglement and purity in non-Markovian dynamics

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    Knowledge of the relationships among different features of quantumness, like entanglement and state purity, is important from both fundamental and practical viewpoints. Yet, this issue remains little explored in dynamical contexts for open quantum systems. We address this problem by studying the dynamics of entanglement and purity for two-qubit systems using paradigmatic models of radiation-matter interaction, with a qubit being isolated from the environment (spectator configuration). We show the effects of the corresponding local quantum channels on an initial two-qubit pure entangled state in the concurrence-purity diagram and find the conditions which enable dynamical closed formulas of concurrence, used to quantify entanglement, as a function of purity. We finally discuss the usefulness of these relations in assessing entanglement and purity thresholds which allow noisy quantum teleportation. Our results provide new insights about how different properties of composite open quantum systems behave and relate each other during quantum evolutions.Comment: 16 Pages, 10 Figures. One author added. Improved version with more references and comment

    Dopamine receptor expression and function in the normal and pathological hypothalamus-pituitary-adrenal axis

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    __Abstract__ Dopamine is the predominant catecholamine neurotransmitter in the human central nervous system, where it controls a variety of functions including cognition, emotion, locomotor activity, food intake and endocrine regulation. Dopamine also plays multiple roles in the periphery as a modulator of cardiovascular and renal function, gastrointestinal motility and the endocrine system (1). Dopamine exerts its functions via the binding with dopamine receptors (1). Dopamine receptors belong to the family of seven transmembrane domain G protein-coupled receptors and include five different receptor subtypes, named D1-Ds. The members of dopamine receptor family are encoded by genes localized on different chromosome loci, displaying a considerable homology in their protein structure and function. The analysis of dopamine receptor structure and function suggests the existence of two different groups of receptors: D1-like, including D1 and D5 receptors, associated to a stimulatory function, and Dz-like, including Dz, D3 and D4 receptors, associated to an inhibitory function. The D1 and Ds receptors are encoded by intronless genes and share an 80% homology in their transmembrane domains. The Dz receptor shares a 75% homology with the D3 and a 53% homology with the D4 transmembrane domains and all three receptor subtypes are encoded by genes, which are interrupted by introns. The Dz receptor exists in two main variants, called Dzlong and Dzshort, generated by an alternative splicing of an 87 base pairs exon. These two D2 receptor isoforms differ for the presence or absence of a stretch of 29 amino acids in the third cytoplasmic loop in their protein structure. Splicing variants of the D3 receptor encoding nonfunctional proteins have been also identified. The analysis of the D4 receptor reveals the existence of polymorphic variations within the coding sequence, being a 48 base pairs sequence existent as a direct repeat sequence (D4.1), fourfold (D4.4), sevenfold (D4.7) or eleven fold (D4.11) repeat sequence. Therefore, the D4 receptor isoforms differ for the length of the third cytoplasmic loop and have one, four, seven or eleven times the same insert of a stretch of 19 amino acids in their protein structure. The Ds receptor has two related pseudogenes, which share a 95% homology with the gene and encode for truncated non functional forms of the receptor (1). The molecular characteristics of human dopamine receptor family are summarized in Table 1. A schematic representation of the human dopamine receptor is shown in Fig. 1

    Superconducting Fluctuation Corrections to the Thermal Current in Granular Metals

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    The first-order superconducting fluctuation corrections to the thermal conductivity of a granular metal are calculated. A suppression of thermal conductivity proportional to Tc/(TTc)T_c/(T-T_c) is observed in a region not too close to the critical temperature TcT_c. As TTcT\simeq T_c, a saturation of the correction is found, and its sign depends on the ratio between the barrier transparency and the critical temperature. In both regimes, the Wiedemann-Franz law is violated.Comment: 9 pages, 7 figures. Replaced with published version. Important change
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