M. J. Taylor

Adaptive skin segmentation via feature-based face detection

Variations in illumination can have significant effects on the apparent colour of skin, which can be damaging to the efficacy of any colour-based segmentation approach. We attempt to overcome this issue by presenting a new adaptive approach, capable of generating skin colour models at run-time. Our approach adopts a Viola-Jones feature-based face detector, in a moderate-recall, high-precision configuration, to sample faces within an image, with an emphasis on avoiding potentially detrimental false positives. From these samples, we extract a set of pixels that are likely to be from skin regions, filter them according to their relative luma values in an attempt to eliminate typical non-skin facial features (eyes, mouths, nostrils, etc.), and hence establish a set of pixels that we can be confident represent skin. Using this representative set, we train a unimodal Gaussian function to model the skin colour in the given image in the normalised rg colour space – a combination of modelling approach and colour space that benefits us in a number of ways. A generated function can subsequently be applied to every pixel in the given image, and, hence, the probability that any given pixel represents skin can be determined. Segmentation of the skin, therefore, can be as simple as applying a binary threshold to the calculated probabilities. In this paper, we touch upon a number of existing approaches, describe the methods behind our new system, present the results of its application to arbitrary images of people with detectable faces, which we have found to be extremely encouraging, and investigate its potential to be used as part of real-time systems.

γ -ray linear polarization measurements and (g9/2) −3 neutron alignment in 91Ru

The authors would like to thank the operators of the GANIL cyclotrons for providing the 36Ar beam. We would also like to thank the EXOGAM Collaboration for use of the clover Ge detector array, the DIAMANT Collaboration for use of the charged particle detector system, and the European gamma-ray Spectroscopy Pool for use of the neutron detector system. We acknowledge funding support from the French-Polish LEA COPIGAL and the IN2P3-Polish laboratories COPIN Agreement No. 06-122, from the UK STFC, from the Swedish Research Council (Contracts No. 2007-4067 and No. 2008-5793), from the Goran Gustafsson Foundation, from the OTKA under Contract No. K100835, and from the Bolyai Janos Foundation. AG has been supported by the Generalitat Valenciana, Spain, under Grant No. PROMETEO/2010/101 and by MINECO, Spain, under Grants No. AIC-D-2011-0746 and No. FPA2011-29854. AJ acknowledge financial support from the Spanish Ministerio de Ciencia e Innovacion under Contract No. FPA2011-29854-C04. ZY acknowledges the support from the Chinese Academy of Sciences, China.

Re-examining the transition into the N = 20 island of inversion: Structure of 30Mg

Abstract Intermediate energy single-neutron removal from 31Mg has been employed to investigate the transition into the N = 20 island of inversion. Levels up to 5 MeV excitation energy in 30Mg were populated and spin-parity assignments were inferred from the corresponding longitudinal momentum distributions and γ-ray decay scheme. Comparison with eikonal-model calculations also permitted spectroscopic factors to be deduced. Surprisingly, the 0 2 + level in 30Mg was found to have a strength much weaker than expected in the conventional picture of a predominantly 2 p − 2 h intruder configuration having a large overlap with the deformed 31Mg ground state. In addition, negative parity levels were identified for the first time in 30Mg, one of which is located at low excitation energy. The results are discussed in the light of shell-model calculations employing two newly developed approaches with markedly different descriptions of the structure of 30Mg. It is concluded that the cross-shell effects in the region of the island of inversion at Z = 12 are considerably more complex than previously thought and that n p − n h configurations play a major role in the structure of 30Mg.

Lifetime measurements of unbound nuclear states

A Differential Plunger device for measuring the lifetimes of Unbound Nuclear States (DPUNS) is currently being built at the University of Manchester. The plunger has been designed to be able to work with the proton-, alpha-, beta- and isomer-tagging methods using the JUROGAM II - RITU - GREAT setup at the University of Jyvaskyla, Finland. Valuable nuclear-structure information can be investigated from the measurement of lifetimes in proton-and alpha-unbound nuclei. To date, nuclear structure information from proton emission has been obtained from a comparison of the experimentally measured half-life with that predicted from various tunnelling calculations. A crucial parameter required to perform these calculations is the deformation of the parent nucleus involved in the decay, which in all cases to date, has only ever been estimated or calculated from theory. DPUNS aims to address this logical weakness through the measurement of the lifetimes of excited states in these unbound nuclei. The first measurement of a lifetime in a proton-unbound nucleus was recently obtained for 109I. The results from this measurement were discussed along with the future physics programme that can be performed with DPUNS.

A new differential plunger to measure lifetimes of unbound states in tagged exotic nuclei

A new differential plunger is being designed and built at the University of Manchester to measure lifetimes of unbound states in exotic nuclei approaching the proton drip‐line. The device is designed to work in both vacuum and gas environments and will primarily be used in conjunction with the gas filled separator RITU at the University of Jyvaskyla, Finland. This will enable the accurate measurement of excited state lifetimes identified via isomer and charged‐particle tagging. The plunger will be used to address many key facets of nuclear structure physics with particular emphasis on the effect of deformation on proton emission rates.

Lifetime measurements of excited states in 172Pt and the variation of quadrupole transition strength with angular momentum

Lifetimes of the first excited 2^{+} and 4^{+} states in the extremely neutron-deficient nuclide ^{172}Pt have been measured for the first time using the recoil-distance Doppler shift and recoil-decay tagging techniques. An unusually low value of the ratio B(E2:4_{1}^{+}→2_{1}^{+})/B(E2:2_{1}^{+}→0_{gs}^{+})=0.55(19) was found, similar to a handful of other such anomalous cases observed in the entire Segré chart. The observation adds to a cluster of a few extremely neutron-deficient nuclides of the heavy transition metals with neutron numbers N≈90-94 featuring the effect. No theoretical model calculations reported to date have been able to explain the anomalously low B(E2:4_{1}^{+}→2_{1}^{+})/B(E2:2_{1}^{+}→0_{gs}^{+}) ratios observed in these cases. Such low values cannot, e.g., be explained within the framework of the geometrical collective model or by algebraic approaches within the interacting boson model framework. It is proposed that the group of B(E2:4_{1}^{+}→2_{1}^{+})/B(E2:2_{1}^{+}→0_{gs}^{+}) ratios in the extremely neutron-deficient even-even W, Os, and Pt nuclei around neutron numbers N≈90-94 reveal a quantum phase transition from axa0seniority-conserving structure to a collective regime as a function of neutron number. Although a system governed by seniority symmetry is the only theoretical framework for which such an effect may naturally occur, the phenomenon is highly unexpected for these nuclei that are not situated near closed shells.

Level structure above the 17+ isomeric state in Tm8369152

B. S. Nara Singh,1,* D. M. Cullen,1 M. J. Taylor,1,2 P. C. Srivastava,3,4 P. Van Isacker,3 O. Beeke,1 B. Dodson,1 C. Scholey,5 D. O’Donell,6 U. Jakobson,5,7 T. Grahn,5 P. T. Greenlees,5 P. M. Jones,5,8 R. Julin,5 S. Khan,1 M. Leino,5 A.-P. Leppänen,5,9 S. Eeckhaudt,5 K. Mäntyniemi,5 J. Pakarinen,5 P. Peura,5,10 P. Rahkila,5 J. Sarén,5 J. Sorri,5,11 J. Uusitalo,5 and M. Venhart12 1Schuster Building, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, United Kingdom 2Division of Cancer Sciences, The Univserity of Manchester, Manchester M13 9PL, United Kingdom 3Grand Accélérateur National d’Ions Lourds, CEA/DRF-CNRS/IN2P3, Boulevard Henri Becquerel, F-14076 Caen, France 4Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247 667, India 5University of Jyvaskyla, Department of Physics, P.O. Box 35, FI-40014 University of Jyvaskyla, Finland 6School of Computing, Engineering and Physical Sciences, University of the West of Scotland, Paisley, PA1 2BE, United Kingdom 7Department of Chemistry-Radiochemistry, P.O. Box 55, FI-00014 University of Helsinki, Finland 8Department of Nuclear Physics, iThemba Laboratory for Accelerator Based Sciences, P.O. Box 722, Somerset West 7129, South Africa 9STUK, Radiation and Nuclear Safety Authority, Finland 10Helsinki Institute of Physics, FI-00014, University of Helsinki, Finland 11University of Oulu, Sodankylä Geophysical Observatory, Tähteläntie 62, FI-99600 Sodankylä, Finland 12Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 845 11 Bratislava, Slovakia

Abstract ID: 171 A Monte Carlo study to reduce range uncertainty in proton beam therapy via prompt gamma-ray detection

In proton beam therapy precise knowledge of the proton beam range is essential to guarantee the treatments efficacy and to avoid unnecessary toxicities. Unlike photon beams, protons stop inside the patients body, therefore a direct detection of the distal fall-off is impossible. One technique to determine the beam range is to detect the prompt gamma (PG) rays emitted from the nuclei de-exciting following proton bombardment [1]. PG emission is almost instantaneous and has a high-production rate. The aim of this project is to develop a new method, based on an optimized PG detector system, which can achieve 3D range determination with an uncertainty of no more than 2u202fmm. The presented method is based on the detection of discrete gamma-rays. As a first step, the position reconstruction capability of the PG detector system was examined by means of Geant4 simulations. The prototype system is comprised of 12 LaBr3(Ce) detectors. The information recorded by each individual detector is fed into a reconstruction algorithm to determine the gamma-ray emission point in 3 dimensions. The development of the algorithm, proof-of-principle and simulation validation, have all been conducted using a sealed 60Co source. Our simulations demonstrate that an ideal detector system with the current reconstruction algorithm is capable of determining the source position with sub-millimetre accuracy. Having obtained proof-of-principle for the reconstruction algorithm the next stage is to investigate how implementing a realistic detector system affects the reconstruction performance. In addition, the ability of the detector system to discriminate between multiple sources in different positions is under evaluation.

How sharp is the transition into the N=20 island of inversion for the Mg isotopes ?

The N=20 island of inversion is an excellent playground for testing shell model calculations. The Mg chain is a region of shell evolution still far from being well understood. In this paper we present preliminary results of a single-neutron knockout experiment from 31Mg performed at GANIL to study the structure of 31Mg and of the core 30Mg. The level scheme and longitudinal momentum distributions were mesured and spectroscopic factors were deduced. Negative parity states arise at low energy and the spectroscopic factor for the isomeric in 30Mg was determined to be smaller than foreseen in the standard picture. The preliminary experimental results are compared to state-of the art shell model calculations revealing opposed interpretations.

X(5) critical-point symmetries in 138Gd

The lifetimes of low-lying transitions in 138Gd have been measured using the recoil-distance Doppler-shift technique. The resultant reduced transition probabilities have been compared to X(5) critical-point calculations to assess the potential phase-transitional behaviour of 138Gd. The X(5) symmetry describes the first order phase transition between sphericity, U(5) and an axially deformed nuclear shape, SU(3). Although a high degree of correspondence is observed between the experimental and theoretical excitation energies, the large uncertainties of the experimental B(E2) values cannot preclude contributions from either vibrational or rotational modes of excitation. In order to further examine the nature of low-lying states in 138Gd, ongoing work is aiming to derive solutions to the Bohr Hamiltonian using a more general potential that is not restricted to the X(5) critical point. These results, in parallel to more extensive IBM-1 calculations, will eventually be compared to the experimental results to more accurately locate 138Gd along the U(5) − SU(3) arm of the structure triangle.