300 research outputs found
Two-neutron halo nuclei in one dimension: dineutron correlation and breakup reaction
We propose a simple schematic model for two-neutron halo nuclei. In this
model, the two valence neutrons move in a one-dimensional mean field,
interacting with each other via a density-dependent contact interaction. We
first investigate the ground state properties, and demonstrate that the
dineutron correlation can be realized with this simple model due to the
admixture of even- and odd-parity single-particle states. We then solve the
time-dependent two-particle Schr\"odinger equation under the influence of a
time-dependent one-body external field, in order to discuss the effect of
dineutron correlation on nuclear breakup processes. The time evolution of
two-particle density shows that the dineutron correlation enhances the total
breakup probability, especially for the two-neutron breakup process, in which
both the valence neutrons are promoted to continuum scattering states. We find
that the interaction between the two particles definitely favours a spatial
correlation of the two outgoing particles, which are mainly emitted in the same
direction.Comment: 17 pages, 11 figure
Nature of eigenstates in a mesoscopic ring coupled to a side branch
We formalize the parity effect of a multichannel ring coupled to a side
branch using the tight binding model. We find that the tight binding model
gives slightly different result from the continuum model. We also show that
some states of the system can be nonmagnetic. In the multichannel ring coupled
to a side branch, the persistent current in the ring does not change sign, over
gigantic fluctuations in N (the number of particles in the ring).Comment: Nine figures available on request. The paper was submitted to Physica
B in January,199
Cooper pair sizes in 11Li and in superfluid nuclei: a puzzle?
We point out a strong influence of the pairing force on the size of the two
neutron Cooper pair in Li, and to a lesser extent also in He. It
seems that these are quite unique situations, since Cooper pair sizes of stable
superfluid nuclei are very little influenced by the intensity of pairing, as
recently reported. We explore the difference between Li and heavier
superfulid nuclei, and discuss reasons for the exceptional situation in
Li.Comment: 9 pages. To be published in J. of Phys. G special issue on Open
Problems in Nuclear Structure (OPeNST
Degeneracies when T=0 Two Body Matrix Elements are Set Equal to Zero and Regge's 6j Symmetry Relations
The effects of setting all T=0 two body interaction matrix elements equal to
a constant (or zero) in shell model calculations (designated as ) are
investigated. Despite the apparent severity of such a procedure, one gets
fairly reasonable spectra. We find that using in single j shell
calculations degeneracies appear e.g. the and
states in Sc are at the same excitation energies; likewise the
I=,,9 and 10 states in Ti. The
above degeneracies involve the vanishing of certain 6j and 9j symbols. The
symmetry relations of Regge are used to explain why these vanishings are not
accidental. Thus for these states the actual deviation from degeneracy are good
indicators of the effects of the T=0 matrix elements. A further indicator of
the effects of the T=0 interaction in an even - even nucleus is to compare the
energies of states with odd angular momentum with those that are even
Relation between the phenomenological interactions of the algebraic cluster model and the effective two--nucleon forces
We determine the phenomenological cluster--cluster interactions of the
algebraic model corresponding to the most often used effective two--nucleon
forces for the O + system.Comment: Latex with Revtex, 1 figure available on reques
Protocol for the isotoxic intensity modulated radiotherapy (IMRT) in stage III non-small cell lung cancer (NSCLC): a feasibility study
Introduction The majority of stage III patients with non-small cell lung cancer (NSCLC) are unsuitable for concurrent chemoradiotherapy, the non-surgical gold standard of care. As the alternative treatment options of sequential chemoradiotherapy and radiotherapy alone are associated with high local failure rates, various intensification strategies have been employed. There is evidence to suggest that altered fractionation using hyperfractionation, acceleration, dose escalation, and individualisation may be of benefit. The MAASTRO group have pioneered the concept of ‘isotoxic’ radiotherapy allowing for individualised dose escalation using hyperfractionated accelerated radiotherapy based on predefined normal tissue constraints. This study aims to evaluate whether delivering isotoxic radiotherapy using intensity modulated radiotherapy (IMRT) is achievable.
Methods and analysis Isotoxic IMRT is a multicentre feasibility study. From June 2014, a total of 35 patients from 7 UK centres, with a proven histological or cytological diagnosis of inoperable NSCLC, unsuitable for concurrent chemoradiotherapy will be recruited. A minimum of 2 cycles of induction chemotherapy is mandated before starting isotoxic radiotherapy. The dose of radiation will be increased until one or more of the organs at risk tolerance or the maximum dose of 79.2 Gy is reached. The primary end point is feasibility, with accrual rates, local control and overall survival our secondary end points. Patients will be followed up for 5 years.
Ethics and dissemination The study has received ethical approval (REC reference: 13/NW/0480) from the National Research Ethics Service (NRES) Committee North West—Greater Manchester South. The trial is conducted in accordance with the Declaration of Helsinki and Good Clinical Practice (GCP). The trial results will be published in a peer-reviewed journal and presented internationally.
Trial registration number NCT01836692; Pre-result
Symmetry-breaking skyrmion states in fractional quantum Hall systems
We calculate in an analyical fashion the energies and net spins of skyrmions
in fractional quantum Hall systems, based on the suggestion that skyrmion
states are spontaneously and symmetry-breaking states. The
quasihole-skyrmion state with a charge around = 1/3, where the
ground state is known as a spin-polarized ferromagnetic state, is found to
exist even in high magnetic fields up to about 7 T for GaAs samples.Comment: There is conceptual change. To appear in Phys. Rev.
Ground state particle-particle correlations and double beta decay
A self-consistent formalism for the double beta decay of Fermi type is
provided. The particle-particle channel of the two-body interaction is
considered first in the mean field equations and then in the QRPA. The
resulting approach is called the QRPA with a self-consistent mean field
(QRPASMF). The mode provided by QRPASMF, does not collapse for any strength of
the particle-particle interaction. The transition amplitude for double beta
decay is almost insensitive to the variation of the particle-particle
interaction. Comparing it with the result of the standard pnQRPA, it is smaller
by a factor 6. The prediction for transition amplitude agrees quite well with
the exact result. The present approach is the only one which produces a strong
decrease of the amplitude and at the same time does not alter the stability of
the ground state.Comment: 23 pages, 7 figure
Radiation dose differences between thoracic radiotherapy planning CT and thoracic diagnostic CT scans
Purpose: To compare the absorbed dose from computed tomography (CT) in radiotherapy planning (RP CT) against those from diagnostic CT (DG CT) examinations and to explore the possible reasons for any dose differences.
Method: Two groups of patients underwent CT-scans of the thorax with either DG-CT (n=55) or RP-CT (n=55). Patients from each group had similar weight and body mass index (BMI) and were divided into low (25). Parameters including CTDIvol, DLP and scan length were compared.
Results: The mean CTDIvol and DLP values from RP-CT (38.1 mGy, 1472 mGy·cm) are approximately four times higher than for DG-CT (9.63 mGy, 376.5 mGy·cm). For low BMI group, the CTDIvol in the RP-CT scans (36.4 mGy) is 6.3 times higher than the one in the DG-CT scans (5.8 mGy). For high BMI group, the CTDIvol in the RP-CT (39.6 mGy) is 2.5 times higher than the one in the DG-CT scans (15.8 mGy). In the DG-CT scans a strong negative linear correlation between noise index (NI) and mean CTDIvol was observed (r =-0.954, p=0.004); the higher NI, the lower CTDIvol. This was not the case in the RP-DG scans.
Conclusion: The absorbed radiation dose is significantly higher and less BMI dependent for RP-CT scans compared to DG-CT. Image quality requirements of the examinations should be researched to ensure that radiation doses are not unnecessarily high
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