2,631 research outputs found
Searching and Stopping: An Analysis of Stopping Rules and Strategies
Searching naturally involves stopping points, both at a query level (how far down the ranked list should I go?) and at a session level (how many queries should I issue?). Understanding when searchers stop has been of much interest to the community because it is fundamental to how we evaluate search behaviour and performance. Research has shown that searchers find it difficult to formalise stopping criteria, and typically resort to their intuition of what is "good enough". While various heuristics and stopping criteria have been proposed, little work has investigated how well they perform, and whether searchers actually conform to any of these rules. In this paper, we undertake the first large scale study of stopping rules, investigating how they influence overall session performance, and which rules best match actual stopping behaviour. Our work is focused on stopping at the query level in the context of ad-hoc topic retrieval, where searchers undertake search tasks within a fixed time period. We show that stopping strategies based upon the disgust or frustration point rules - both of which capture a searcher's tolerance to non-relevance - typically result in (i) the best overall performance, and (ii) provide the closest approximation to actual searcher behaviour, although a fixed depth approach also performs remarkably well. Findings from this study have implications regarding how we build measures, and how we conduct simulations of search behaviours
Semiclassical Quantization for the Spherically Symmetric Systems under an Aharonov-Bohm magnetic flux
The semiclassical quantization rule is derived for a system with a
spherically symmetric potential and an
Aharonov-Bohm magnetic flux. Numerical results are presented and compared with
known results for models with . It is shown that the
results provided by our method are in good agreement with previous results. One
expects that the semiclassical quantization rule shown in this paper will
provide a good approximation for all principle quantum number even the rule is
derived in the large principal quantum number limit . We also discuss
the power parameter dependence of the energy spectra pattern in this
paper.Comment: 13 pages, 4 figures, some typos correcte
Site investigation for the effects of vegetation on ground stability
The procedure for geotechnical site investigation is well established but little attention is currently given to investigating the potential of vegetation to assist with ground stability. This paper describes how routine investigation procedures may be adapted to consider the effects of the vegetation. It is recommended that the major part of the vegetation investigation is carried out, at relatively low cost, during the preliminary (desk) study phase of the investigation when there is maximum flexibility to take account of findings in the proposed design and construction. The techniques available for investigation of the effects of vegetation are reviewed and references provided for further consideration. As for general geotechnical investigation work, it is important that a balance of effort is maintained in the vegetation investigation between (a) site characterisation (defining and identifying the existing and proposed vegetation to suit the site and ground conditions), (b) testing (in-situ and laboratory testing of the vegetation and root systems to provide design parameters) and (c) modelling (to analyse the vegetation effects)
Kir5.1 regulates Nedd4-2-mediated ubiquitination of Kir4.1 in distal nephron.
Kir4.1/5.1 heterotetramer participates in generating the negative cell membrane potential in distal convoluted tubule (DCT) and plays a critical role in determining the activity of Na-Cl cotransporter (NCC). Kir5.1 contains a phosphothreonine motif at its COOH terminus (AA249-252). Coimmunoprecipitation showed that Nedd4-2 was associated with Kir5.1 in HEK293 cells cotransfected with Kir5.1 or Kir4.1/Kir5.1. GST pull-down further confirmed the association between Nedd4-2 and Kir5.1. Ubiquitination assay showed that Nedd4-2 increased the ubiquitination of Kir4.1/Kir5.1 heterotetramer in the cells cotransfected with Kir4.1/Kir5.1, but it has no effect on Kir4.1 or Kir5.1 alone. Patch-clamp and Western blot also demonstrated that coexpression of Nedd4-2 but not Nedd4-1 decreased K currents and Kir4.1 expression in the cells cotransfected with Kir4.1 and Kir5.1. In contrast, Nedd4-2 fails to inhibit Kir4.1 in the absence of Kir5.1 or in the cells transfected with the inactivated form of Nedd4-2 (Nedd4-2C821A). Moreover, the mutation of TPVT motif in the COOH terminus of Kir5.1 largely abolished the association of Nedd4-2 with Kir5.1 and abolished the inhibitory effect of Nedd4-2 on K currents in HEK293 cells transfected with Kir4.1 and Kir5.1 mutant (Kir5.1T249A). Finally, the basolateral K conductance in the DCT and Kir4.1 expression is significantly increased in the kidney-specific Nedd4-2 knockout or in Kir5.1 knockout mice in comparison to their corresponding wild-type littermates. We conclude that Nedd4-2 binds to Kir5.1 at the phosphothreonine motif of the COOH terminus, and the association of Nedd4-2 with Kir5.1 facilitates the ubiquitination of Kir4.1, thereby regulating its plasma expression in the DCT
Extended States in a One-dimensional Generalized Dimer Model
The transmission coefficient for a one dimensional system is given in terms
of Chebyshev polynomials using the tight-binding model. This result is applied
to a system composed of two impurities located between sites of a host
lattice. It is found that the system has extended states for several values of
the energy. Analytical expressions are given for the impurity site energy in
terms of the electron's energy. The number of resonant states grows like the
number of host sites between the impurities. This property makes the system
interesting since it is a simple task to design a configuration with resonant
energy very close to the Fermi level .Comment: 4 pages, 3 figure
Magnetic-Field Induced First-Order Transition in the Frustrated XY Model on a Stacked Triangular Lattice
The results of extensive Monte Carlo simulations of magnetic-field induced
transitions in the xy model on a stacked triangular lattice with
antiferromagnetic intraplane and ferromagnetic interplane interactions are
discussed. A low-field transition from the paramagnetic to a 3-state (Potts)
phase is found to be very weakly first order with behavior suggesting
tricriticality at zero field. In addition to clarifying some long-standing
ambiguity concerning the nature of this Potts-like transition, the present work
also serves to further our understanding of the critical behavior at ,
about which there has been much controversy.Comment: 10 pages (RevTex 3.0), 4 figures available upon request, CRPS-93-0
Global Incidence and mortality of oesophageal cancer and their correlation with socioeconomic indicators temporal patterns and trends in 41 countries
Oesophageal cancers (adenocarcinomas [AC] and squamous cell carcinomas [SCC]) are characterized by high incidence/mortality in many countries. We aimed to delineate its global incidence and mortality, and studied whether socioeconomic development and its incidence rate were correlated. The age-standardized rates (ASRs) of incidence and mortality of this medical condition in 2012 for 184 nations from the GLOBOCAN database; national databases capturing incidence rates, and the WHO mortality database were examined. Their correlations with two indicators of socioeconomic development were evaluated. Joinpoint regression analysis was used to generate trends. The ratio between the ASR of AC and SCC was strongly correlated with HDI (r = 0.535 [men]; r = 0.661 [women]) and GDP (r = 0.594 [men]; r = 0.550 [women], both p < 0.001). Countries that reported the largest reduction in incidence in male included Poland (Average Annual Percent Change [AAPC] = −7.1, 95%C.I. = −12,−1.9) and Singapore (AAPC = −5.8, 95%C.I. = −9.5,−1.9), whereas for women the greatest decline was seen in Singapore (AAPC = −12.3, 95%C.I. = −17.3,−6.9) and China (AAPC = −5.6, 95%C.I. = −7.6,−3.4). The Philippines (AAPC = 4.3, 95%C.I. = 2,6.6) and Bulgaria (AAPC = 2.8, 95%C.I. = 0.5,5.1) had a significant mortality increase in men; whilst Columbia (AAPC = −6.1, 95%C.I. = −7.5,−4.6) and Slovenia (AAPC = −4.6, 95%C.I. = −7.9,−1.3) reported mortality decline in women. These findings inform individuals at increased risk for primary prevention
Defect and anisotropic gap induced quasi-one-dimensional modulation of local density of states in YBaCuO
Motivated by recent angle-resolved photoemission spectroscopy (ARPES)
measurement that superconducting YBaCuO (YBCO) exhibits a
-symmetry gap, we show possible quasi-one-dimensional
modulations of local density of states in YBCO. These aniostropic gap and
defect induced stripe structures are most conspicuous at higher biases and
arise due to the nesting effect associated with a Fermi liquid. Observation of
these spectra by scanning tunneling microscopy (STM) would unify the picture
among STM, ARPES, and inelastic neutron scattering for YBCO.Comment: 4 pages, 4 figure
Melting transition of an Ising glass driven by magnetic field
The quantum critical behavior of the Ising glass in a magnetic field is
investigated. We focus on the spin glass to paramagnet transition of the
transverse degrees of freedom in the presence of finite longitudinal field. We
use two complementary techniques, the Landau theory close to the T=0 transition
and the exact diagonalization method for finite systems. This allows us to
estimate the size of the critical region and characterize various crossover
regimes. An unexpectedly small energy scale on the disordered side of the
critical line is found, and its possible relevance to experiments on metallic
glasses is briefly discussed.Comment: 4 pages, 3 figure
The fermion dynamical symmetry model for the even--even and even--odd nuclei in the Xe--Ba region
The even--even and even--odd nuclei Xe-Xe and
Ba-Ba are shown to have a well-realized fermion dynamical symmetry. Their low-lying energy levels can be
described by a unified analytical expression with two (three) adjustable
parameters for even--odd (even--even) nuclei that is derived from the fermion
dynamical symmetry model. Analytical expressions are given for wavefunctions
and for transition rates that agree well with data. The distinction
between the FDSM and IBM limits is discussed. The experimentally
observed suppression of the the energy levels with increasing quantum
number can be explained as a perturbation of the pairing interaction on
the symmetry, which leads to an Pairing effect for nuclei.Comment: submitted to Phys. Rev. C, LaTeX, 31 pages, 8 figures with postscript
files available on request at [email protected]
- …