168 research outputs found
Frustrated antiferromagnetic quantum spin chains for spin length S > 1
We investigate frustrated antiferromagnetic Heisenberg quantum spin chains at
T=0 for S=3/2 and S=2 using the DMRG method. We localize disorder and Lifshitz
points, confirming that quantum disorder points can be seen as quantum remnants
of classical phase transitions. Both in the S=3/2 and the S=2 chain, we observe
the disappearance of effectively free S=1/2 and S=1 end spins respectively. The
frustrated spin chain is therefore a suitable system for clearly showing the
existence of free end spins S'=[S/2] also in half-integer antiferromagnetic
spin chains with S>1/2. We suggest that the first order transition found for
S=1 in our previous work is present in all frustrated spin chains with S>1/2,
characterized by the disappearance of effectively free end spins with S'=[S/2].Comment: 6 pages, 8 ps figures, uses RevTeX, submitted to PR
The Inhalation Characteristics of Patients When They Use Different Dry Powder Inhalers
Background: The characteristics of each inhalation maneuver when patients use dry powder inhalers (DPIs) are important, because they control the quality of the emitted dose.
Methods: We have measured the inhalation profiles of asthmatic children [CHILD; n=16, mean forced expiratory volume in 1 sec (FEV1) 79% predicted], asthmatic adults (ADULT; n=53, mean predicted FEV1 72%), and chronic obstructive pulmonary disease (COPD; n=29, mean predicted FEV1 42%) patients when they inhaled through an Aerolizer, Diskus, Turbuhaler, and Easyhaler using their “real-life” DPI inhalation technique. These are low-, medium-, medium/high-, and high-resistance DPIs, respectively. The inhalation flow against time was recorded to provide the peak inhalation flow (PIF; in L/min), the maximum pressure change (ΔP; in kPa), acceleration rates (ACCEL; in kPa/sec), time to maximum inhalation, the length of each inhalation (in sec), and the inhalation volume (IV; in liters) of each inhalation maneuver.
Results: PIF, ΔP, and ACCEL values were consistent with the order of the inhaler's resistance. For each device, the inhalation characteristics were in the order ADULT>COPD>CHILD for PIF, ΔP, and ACCEL (p4 L and ΔP >4 kPa.
Conclusion: The large variability of these inhalation characteristics and their range highlights that if inhalation profiles were used with compendial in vitro dose emission measurements, then the results would provide useful information about the dose patients inhale during routine use. The inhalation characteristics highlight that adults with asthma have greater inspiratory capacity than patients with COPD, whereas children with asthma have the lowest. The significance of the inhaled volume to empty doses from each device requires investigation
Variational and DMRG studies of the Frustrated Antiferromagnetic Heisenberg S=1 Quantum Spin Chain
We study a frustrated antiferromagnetic isotropic Heisenberg chain
using a variational ansatz and the DMRG. At , there is a
disorder point of the second kind, marking the onset of incommensurate
correlations in the chain. At there is a Lifshitz point,
at which the excitation spectrum develops a doubly degenerate structure. These
points are the quantum remnants of the transition from antiferromagnetic to
spiral order in the classical frustrated chain. At there
is a first order phase transition from an AKLT phase to a next-nearest neighbor
generalization of the AKLT model. At the transition, the string order parameter
shows a discontinuous jump of 0.085 to 0; the correlation length and the gap
are both finite at the transition. The problem of edge states in open
frustrated chains is discussed at length.Comment: 37 pages, 14 figures, submitted to Phys.Rev.
Quantum spherical model with competing interactions
We analyze the phase diagram of a quantum mean spherical model in terms of
the temperature , a quantum parameter , and the ratio ,
where refers to ferromagnetic interactions between first-neighbor
sites along the directions of a hypercubic lattice, and is
associated with competing antiferromagnetic interactions between second
neighbors along directions. We regain a number of known results for
the classical version of this model, including the topology of the critical
line in the space, with a Lifshitz point at , for , and
closed-form expressions for the decay of the pair correlations in one
dimension. In the T=0 phase diagram, there is a critical border,
for , with a singularity at the Lifshitz point if
. We also establish upper and lower critical dimensions, and analyze
the quantum critical behavior in the neighborhood of .Comment: 18 pages, 3 figures, refs added, minor modifications to match
published versio
The Exercise Intensity-Music-Tempo Preference Relationship: A Decennial Revisit.
Tempo is a key determinant of the motivational effects of music during exercise and has been the focus of numerous empirical studies (e.g., Karageorghis & Jones, 2014). The present study sought to address the limitations of previous related work and revisit the relationship between exercise intensity and music-tempo preference using unfamiliar, non-lyrical music (to isolate the tempo manipulation). A within-within experimental design was employed to test hypotheses pertaining to the non-linear relationship and associated psychological outcomes (e.g., core affect and state attention). Twenty-four participants (Mage = 20.6 years, SD = .92 years) exercised at five intensities (10% of peak VO2 below ventilatory threshold [VT]; 5% of peak VO2 below VT, at VT, midway between VT and the respiratory compensation point [RCP], and at RCP) during which they were administered music tracks at four tempi (90 bpm, 110 bpm, 130 bpm and 150 bpm) and a no-music control. A music liking item, measures of core affect (valence and arousal), attentional focus and perceived exertion were recorded during the exercise bouts. Results indicated that unlike previous findings with familiar, lyrical music, there was no discernible relationship between exercise intensity and preference for music tempo. The most positive psychological outcomes were associated with fast-tempo music. In accord with previous findings, slow-tempo music attracted low liking scores and the least desirable psychological outcomes at every exercise intensity. The present findings have implications for the use of unfamiliar, non-lyrical music during exercise. Specifically, that such music should be ∼10 bpm faster than familiar, lyrical music
Q methodology and rural research
Traditionally, rural scholarship has been limited in its methodological approach. This has begun to change in recent years as rural researchers have embraced a range of different methodological tools. The aim of this article is to contribute to greater methodological pluralism in rural sociology by introducing readers to a method of research that is rarely engaged in the field, that is, Q methodology. The article describes the defining features of the approach as well as providing examples of its application to argue that it is a method that offers particular opportunities and synergies for rural social science research
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The EU societal awareness of landscape indicator: a review of its meaning, utility and performance across different scales
There is increasing recognition that agricultural landscapes meet multiple societal needs and demands beyond provision of economic and environmental goods and services. Accordingly, there have been significant calls for the inclusion of societal, amenity and cultural values in agri-environmental landscape indicators to assist policy makers in monitoring the wider impacts of land-based policies. However, capturing the amenity and cultural values that rural agrarian areas provide, by use of such indicators, presents significant challenges. The EU social awareness of landscape indicator represents a new class of generalized social indicator using a top-down methodology to capture the social dimensions of landscape without reference to the specific structural and cultural characteristics of individual landscapes. This paper reviews this indicator in the context of existing agri-environmental indicators and their differing design concepts. Using a stakeholder consultation approach in five case study regions, the potential and limitations of the indicator are evaluated, with a particular focus on its perceived meaning, utility and performance in the context of different user groups and at different geographical scales. This analysis supplements previous EU-wide assessments, through regional scale assessment of the limitations and potentialities of the indicator and the need for further data collection. The evaluation finds that the perceived meaning of the indicator does not vary with scale, but in common with all mapped indicators, the usefulness of the indicator, to different user groups, does change with scale of presentation. This indicator is viewed as most useful when presented at the scale of governance at which end users operate. The relevance of the different sub-components of the indicator are also found to vary across regions
Demonstration of the temporal matter-wave Talbot effect for trapped matter waves
We demonstrate the temporal Talbot effect for trapped matter waves using
ultracold atoms in an optical lattice. We investigate the phase evolution of an
array of essentially non-interacting matter waves and observe matter-wave
collapse and revival in the form of a Talbot interference pattern. By using
long expansion times, we image momentum space with sub-recoil resolution,
allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure
Kaon Production and Kaon to Pion Ratio in Au+Au Collisions at \snn=130 GeV
Mid-rapidity transverse mass spectra and multiplicity densities of charged
and neutral kaons are reported for Au+Au collisions at \snn=130 GeV at RHIC.
The spectra are exponential in transverse mass, with an inverse slope of about
280 MeV in central collisions. The multiplicity densities for these particles
scale with the negative hadron pseudo-rapidity density. The charged kaon to
pion ratios are and
for the most central collisions. The ratio is lower than the same
ratio observed at the SPS while the is higher than the SPS result.
Both ratios are enhanced by about 50% relative to p+p and +p
collision data at similar energies.Comment: 6 pages, 3 figures, 1 tabl
Mid-rapidity anti-proton to proton ratio from Au+Au collisions at GeV
We report results on the ratio of mid-rapidity anti-proton to proton yields
in Au+Au collisions at \rts = 130 GeV per nucleon pair as measured by the
STAR experiment at RHIC. Within the rapidity and transverse momentum range of
and 0.4 1.0 GeV/, the ratio is essentially independent of
either transverse momentum or rapidity, with an average of for minimum bias collisions. Within errors, no
strong centrality dependence is observed. The results indicate that at this
RHIC energy, although the -\pb pair production becomes important at
mid-rapidity, a significant excess of baryons over anti-baryons is still
present.Comment: 5 pages, 3 figures, accepted by Phys. Rev. Let
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