3,596 research outputs found
Neutron Charge Radius: Relativistic Effects and the Foldy Term
The neutron charge radius is studied within a light-front model with
different spin coupling schemes and wave functions. The cancellation of the
contributions from the Foldy term and Dirac form factor to the neutron charge
form factor is verified for large nucleon sizes and it is independent of the
detailed form of quark spin coupling and wave function. For the physical
nucleon our results for the contribution of the Dirac form factor to the
neutron radius are insensitive to the form of the wave function while they
strongly depend on the quark spin coupling scheme.Comment: 12 pages, 5 figures, Latex, Int. J. Mod. Phys.
Feynman versus Bakamjian-Thomas in Light Front Dynamics
We compare the Bakamjian-Thomas (BT) formulation of relativistic few-body
systems with light front field theories that maintain closer contact with
Feynman diagrams. We find that Feynman diagrams distinguish Melosh rotations
and other kinematical quantities belonging to various composite subsystem
frames that correspond to different loop integrals. The BT formalism knows only
the rest frame of the whole composite system, where everything is evaluated.Comment: 5 page
Dynamical description of vesicle growth and shape change
We systematize and extend the description of vesicle growth and shape change
using linear nonequilibrium thermodynamics. By restricting the study to shape
changes from spheres to axisymmetric ellipsoids, we are able to give a
consistent formulation which includes the lateral tension of the vesicle
membrane. This allows us to generalize and correct a previous calculation. Our
present calculations suggest that, for small growing vesicles, a prolate
ellipsoidal shape should be favored over oblate ellipsoids, whereas for large
growing vesicles oblates should be favored over prolates. The validity of this
prediction is examined in the light of the various assumptions made in its
derivation.Comment: 6 page
Quality of herbage at different latitudes.
In a cooperative experiment, yield and herbage quality of timothy was measured during the uninterrupted growth of the 1st cut at 6 lat. (51-69 deg N). Rate of production was greatest at Tromso (69 deg N), apparently because of the long day and rapid reproductive development. Digestibility of OM declined faster at higher lat. because stem development proceeded faster and less leaf DM was produced. At the same morphological stage, digestibility of the whole crop was better at higher lat. because of the better digestibility of the cell walls from the stems. It was concluded that rate of lignification could not keep pace with the rapid rate of stem development. (Abstract retrieved from CAB Abstracts by CABI’s permission
Scaling Bounded Model Checking By Transforming Programs With Arrays
Bounded Model Checking is one the most successful techniques for finding bugs
in program. However, model checkers are resource hungry and are often unable to
verify programs with loops iterating over large arrays.We present a
transformation that enables bounded model checkers to verify a certain class of
array properties. Our technique transforms an array-manipulating (ANSI-C)
program to an array-free and loop-free (ANSI-C) program thereby reducing the
resource requirements of a model checker significantly. Model checking of the
transformed program using an off-the-shelf bounded model checker simulates the
loop iterations efficiently. Thus, our transformed program is a sound
abstraction of the original program and is also precise in a large number of
cases - we formally characterize the class of programs for which it is
guaranteed to be precise. We demonstrate the applicability and usefulness of
our technique on both industry code as well as academic benchmarks
Personalised digital interventions for reducing hazardous and harmful alcohol consumption in community-dwelling populations
This is the protocol for a review and there is no abstract. The objectives are as follows: The main objective is to assess the effectiveness and cost effectiveness of digital interventions for reducing hazardous and harmful alcohol consumption and/or alcohol-related problems in community-dwelling populations. We envisage two comparator groups: (1) no intervention (or minimal input) controls; and (2) another active intervention for delivering preventive advice or counselling to reduce hazardous or harmful alcohol consumption. Specifically, we will address two questions: (1) Are digital interventions superior to no intervention (or minimal input) controls? This question is important for individuals accessing interventions through their own motivation or interest. These individuals will be unlikely to experience active practitioner input and it is important to understand whether digital interventions are better than general material they might seek out on the internet or via mobile phone-based apps etc. (2) Are digital interventions at least equally effective as face-to-face brief alcohol interventions? Practitioner delivered brief interventions are generally accepted to be the best alternative in secondary preventive care in health, workplace, educational or community settings. However, time constraints can impede face-to-face delivery of such interventions and it is important to know whether digitally provided input can yield comparable effects to interventions delivered by trained practitioners. We will also identify the most effective component behaviour change techniques of such interventions and their mechanisms of action. Secondary objectives are as follows: 1.To assess whether outcomes differ between trials where the digital intervention targets participants attending health, social care, education or other community-based settings and those where it is offered remotely via the internet or mobile phone platforms; 2.To develop a taxonomy of interventions according to their mode of delivery (e.g. functionality features) and assess their impact on outcomes; 3.To identify theories or models that have been used in the development and/or evaluation of the intervention – this will inform intervention development work
The role of the rigged Hilbert space in Quantum Mechanics
There is compelling evidence that, when continuous spectrum is present, the
natural mathematical setting for Quantum Mechanics is the rigged Hilbert space
rather than just the Hilbert space. In particular, Dirac's bra-ket formalism is
fully implemented by the rigged Hilbert space rather than just by the Hilbert
space. In this paper, we provide a pedestrian introduction to the role the
rigged Hilbert space plays in Quantum Mechanics, by way of a simple, exactly
solvable example. The procedure will be constructive and based on a recent
publication. We also provide a thorough discussion on the physical significance
of the rigged Hilbert space.Comment: 29 pages, 2 figures; a pedestrian introduction to the rigged Hilbert
spac
Thermodynamics of vesicle growth and instability
We describe the growth of vesicles, due to the accretion of lipid molecules
to their surface, in terms of linear irreversible thermodynamics. Our treatment
differs from those previously put forward by consistently including the energy
of the membrane in the thermodynamic description. We calculate the critical
radius at which the spherical vesicle becomes unstable to a change of shape in
terms of the parameters of the model. The analysis is carried out both for the
case when the increase in volume is due to the absorption of water and when a
solute is also absorbed through the walls of the vesicle.Comment: To be published in Phys. Rev.
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