112,673 research outputs found

    The Number of Hierarchical Orderings

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    An ordered set-partition (or preferential arrangement) of n labeled elements represents a single ``hierarchy''; these are enumerated by the ordered Bell numbers. In this note we determine the number of ``hierarchical orderings'' or ``societies'', where the n elements are first partitioned into m <= n subsets and a hierarchy is specified for each subset. We also consider the unlabeled case, where the ordered Bell numbers are replaced by the composition numbers. If there is only a single hierarchy, we show that the average rank of an element is asymptotic to n/(4 log 2) in the labeled case and to n/4 in the unlabeled case.Comment: 7 page

    Cloning a Qutrit

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    We investigate several classes of state-dependent quantum cloners for three-level systems. These cloners optimally duplicate some of the four maximally-conjugate bases with an equal fidelity, thereby extending the phase-covariant qubit cloner to qutrits. Three distinct classes of qutrit cloners can be distinguished, depending on two, three, or four maximally-conjugate bases are cloned as well (the latter case simply corresponds to the universal qutrit cloner). These results apply to symmetric as well as asymmetric cloners, so that the balance between the fidelity of the two clones can also be analyzed.Comment: 14 pages LaTex. To appear in the Journal of Modern Optics for the special issue on "Quantum Information: Theory, Experiment and Perspectives". Proceedings of the ESF Conference, Gdansk, July 10-18, 200

    Studying Intermediate pT Hadron Production with Fluctuations

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    Mechanisms for particle production at intermediate pT in nuclear collisions at RHIC are discussed, emphasizing the differences in associated jet-like correlations between color-neutral and colored production. An alternative production mechanism involving both recombination and fragmentation is suggested, which might simultaneously lead to an enhancement of baryons and to jet-like correlations. To gain more insight into the relative importance of different mechanisms a study of constrained distributions of associated multiplicity is proposed. In a simple model it is shown that these multiplicity distributions may change significantly, if the nature of the production mechanism fluctuates from event to event.Comment: 7 pages, 4 figures, talk at Hot Quarks 2004 conferenc

    Total plankton respiration in the Chesapeake Bay plume

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    Total plankton respiration (TPR) was measured at 17 stations within the Chesapeake Bay plume off the Virginia coast during March, June, and October 1980. Elevated rates of TPR, as well as higher concentrations of chlorophyll a and phaeopigment a, were found to be associated with the Bay plume during each survey. The TPR rates within the Bay plume were close to those found associated with the Hudson River plume for comparable times of the year. The data examined indicate that the Chesapeake Bay plume stimulates biological activity and is a source of organic loading to the contiguous shelf ecosystem

    Harvest Scheduling as a Timber Appraisal Tool

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    Appraisers often value a forest that contains many different timber stands that can vary due to factors such as age, stocking, species, and site index. Many assumptions are possible on how the various stands will be harvested and what subsequent cash flows might be generated. We describe harvest scheduling methodology that is widely used to obtain the net present value of such a forest under optimal conditions. We illustrate how a popular software package can be used by appraisers to obtain optimal discounted cash flows using harvest scheduling and resulting timber stand values. ChristopherProduction Economics,

    Vitreous GeO2 response to shock loading

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    Shock wave profiles in vitreous GeO2 (6.56 Mg/m^3) under planar loading were measured using stress gauges to 14 GPa. New and previous data yield Hugoniot: D=0.974 (km/s)+1.711 u for shocks of 6 to 40 GPa. We show that the phase change from 4- to 6-fold coordination of Ge+4 with O–2 in vitreous GeO2 occurs from 4 to 15 GPa. Hugoniots of vitreous GeO2 and SiO2 are found to approximately coincide if the pressure in SiO2 is scaled by the ratio of SiO2 to GeO2 initial density

    Role of the community matron in advance care planning and ‘do not attempt CPR’ decision-making: a qualitative study

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    The community matron (CM) is often the key worker caring for patients with chronic, life-limiting, long-term conditions, but these patients are not always recognised as palliative cases. This study explored the experiences of CMs with regard to advance care planning (ACP) and ‘do not attempt cardiopulmonary resuscitation’ (DNACPR) decision-making to understand whether or not they felt adequately prepared for this aspect of their role, and why. Qualitative data were generated from six CMs using a broad interpretive phenomenological approach. Face-to-face recorded interviews were analysed using template analysis. The study found that although participants faced complex ethical situations around ACP and DNACPR almost on a daily basis, none had received any formal training despite the emphasis on training in national and local guidelines. Participants often struggled to get their patients accepted on to the Gold Standards Framework. The research found variability and complexity of cases to be the main barriers to clear identification of the palliative phase
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