4,446 research outputs found
Subject searching requirements : the HILT II experience
The HILT Phase II project aimed to develop a pilot terminologies server with a view to improving cross-sectoral information retrieval. In order to inform this process, it was first necessary to examine how a representative group of users approached a range of information-related tasks. This paper focuses on exploratory interviews conducted to investigate the proposed ideal and actual strategies of a group of 30 users in relation to eight separate information tasks. In addition, users were asked to give examples of search terms they may employ and to describe how they would formulate search queries in each scenario. The interview process undertaken and the results compiled are outlined, and associated implications for the development of a pilot terminologies server are discussed
Greening information management: final report
As the recent JISC report on âthe âgreeningâ of ICT in education [1] highlights, the increasing reliance on ICT to underpin the business functions of higher education institutions has a heavy environmental impact, due mainly to the consumption of electricity to run computers and to cool data centres. While work is already under way to investigate how more energy efficient ICT can be introduced, to date there has been much less focus on the potential environmental benefits to be accrued from reducing the demand âat sourceâ through better data and information management. JISC thus commissioned the University of Strathclyde to undertake a study to gather evidence that establishes the efficacy of using information management options as components of Green ICT strategies within UK Higher Education environments, and to highlight existing practices which have the potential for wider replication
Particle number conservation in quantum many-body simulations with matrix product operators
Incorporating conservation laws explicitly into matrix product states (MPS)
has proven to make numerical simulations of quantum many-body systems much less
resources consuming. We will discuss here, to what extent this concept can be
used in simulation where the dynamically evolving entities are matrix product
operators (MPO). Quite counter-intuitively the expectation of gaining in speed
by sacrificing information about all but a single symmetry sector is not in all
cases fulfilled. It turns out that in this case often the entanglement imposed
by the global constraint of fixed particle number is the limiting factor.Comment: minor changes, 18 pages, 5 figure
Infinite boundary conditions for matrix product state calculations
We propose a formalism to study dynamical properties of a quantum many-body
system in the thermodynamic limit by studying a finite system with infinite
boundary conditions (IBC) where both finite size effects and boundary effects
have been eliminated. For one-dimensional systems, infinite boundary conditions
are obtained by attaching two boundary sites to a finite system, where each of
these two sites effectively represents a semi-infinite extension of the system.
One can then use standard finite-size matrix product state techniques to study
a region of the system while avoiding many of the complications normally
associated with finite-size calculations such as boundary Friedel oscillations.
We illustrate the technique with an example of time evolution of a local
perturbation applied to an infinite (translationally invariant) ground state,
and use this to calculate the spectral function of the S=1 Heisenberg spin
chain. This approach is more efficient and more accurate than conventional
simulations based on finite-size matrix product state and density-matrix
renormalization-group approaches.Comment: 10 page
Strontium and neodymium isotopic variations in early Archean gneisses affected by middle to late Archean high-grade metamorphic processes: West Greenland and Labrador
Relicts of continental crust formed more than 3400 Ma ago are preserved fortuitously in most cratons. The cratons provide the most direct information about crust and mantle evolutionary processes during the first billion years of Earth history. In view of their polymetamorphic character, these terrains are commonly affected by subsequent tectonothermal events. Hence, their isotope systematics may be severely disturbed as a result of bulk chemical change or local isotopic homogenization. This leads to equivocal age and source information for different components within these terrains. The Sr and Nd isotopic data are presented for early Archean gneisses from the North Atlantic Craton in west Greenland and northern Labrador which were affected by younger metamorphic events
Enhancement of pulmonary tumour seeding by human coagulation factors II, IX, X--an investigation into the possible mechanisms involved.
Warfarin inhibits metastasis in the animal model and injection of the Warfarin-dependent coagulation factor complex II, IX, X enhances pulmonary metastasis in the same model. We have studied two possible mechanisms responsible for the observed effect. Mtln3, rat mammary carcinoma cells, radiolabelled with 5-(125) Iodo-2'-deoxyuridine (IUDR) were injected intravenously in female Fisher 344 rats either alone or in combination with factor complex II, IX, X or bovine serum albumin. Following sacrifice at various intervals, measured lung radioactivity was significantly higher (20%) in animals administered cells with the factor complex than in the other two groups (P less than 0.001, ANOVA and Student's t-test). These results indicate increased entrapment of tumour cells in the pulmonary microcirculation. In a second experiment, rat factor complex II, IX, X was prepared, and Mtln3 cells were then injected in female Fisher 344 rats alone or in combination with either human factor complex or rat factor complex. Following sacrifice, the number of pulmonary nodules in animals receiving cells with rat factor complex was similar to that in animals receiving human factor complex, and significantly higher than that in the control (P less than 0.001, ANOVA and Mann-Whitney), indicating that the observed enhancement of pulmonary seeding is unrelated to the xenogeneic properties of the human factor complex
On the Nature of Precursors in the Radio Pulsar Profiles
In the average profiles of several radio pulsars, the main pulse is
accompanied by the preceding component. This so called precursor is known for
its distinctive polarization, spectral, and fluctuation properties. Recent
single-pulse observations hint that the sporadic activity at the extreme
leading edge of the pulse may be prevalent in pulsars. We for the first time
propose a physical mechanism of this phenomenon. It is based on the induced
scattering of the main pulse radiation into the background. We show that the
scattered component is directed approximately along the ambient magnetic field
and, because of rotational aberration in the scattering region, appears in the
pulse profile as a precursor to the main pulse. Our model naturally explains
high linear polarization of the precursor emission, its spectral and
fluctuation peculiarities as well as suggests a specific connection between the
precursor and the main pulse at widely spaced frequencies. This is believed to
stimulate multifrequency single-pulse studies of intensity modulation in
different pulsars.Comment: 5 pages, no figures. Accepted for publication in MNRAS Letter
Residential Load Variability and Diversity at Different Sampling Time and Aggregation Scales
The increasing use of large-scale intermittent distributed renewable energy resources on the electrical power system introduces uncertainties in both network planning and management. In addition to architectural changes to the power system, the applications of demand side response (DSR) also add a dimension of complexity - thereby converting the traditionally passive customers into active prosumers (customers that both produce and consume electricity). It has therefore become important to conduct detailed studies on system load profiles to uncover the nature of the system load. These studies could help distribution network operators (DNOs) to adopt relevant strategies that can accommodate new resources such as distributed generation and energy storage on the evolving distribution network and ensure updated design and management approaches. This paper investigates the relationship between both the system load diversity and variability when different customers are aggregated at different scales. Additionally, the implication of sampling time scales is investigated to capture its effect on load diversity and variability. The study looks at the diversity and variability that is observable from the viewpoint of higher power levels, when interconnecting different sized groupings of customers, at different sampling resolutions. The paper thus concludes that the per-customer capacity requirement of the network decreases as the size of customer groupings increases. The load variability also decreases as the aggregation level increases. For active network management, faster time scales are required at lower aggregation scales due to high load variability
From density-matrix renormalization group to matrix product states
In this paper we give an introduction to the numerical density matrix
renormalization group (DMRG) algorithm, from the perspective of the more
general matrix product state (MPS) formulation. We cover in detail the
differences between the original DMRG formulation and the MPS approach,
demonstrating the additional flexibility that arises from constructing both the
wavefunction and the Hamiltonian in MPS form. We also show how to make use of
global symmetries, for both the Abelian and non-Abelian cases.Comment: Numerous small changes and clarifications, added a figur
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