Modification of os calcis bone mineral profiles during bedrest

The mineral content of the left central os calcis was determined using the photon absorptiometric technique modified for the space missions to permit area scanning, and was compared with total body calcium balance changes. The instrument consists of a rectilinear scanner that is programmed by a specially designed control module to move a low energy X-ray emitting radionuclide placed in opposition to a detector to scan the foot which is places between them. The foot is placed in a plexiglas box filled with water to provide tissue equivalence and to compensate for irregularities in thickness of tissue cover that surrounds the bone. The mineral content is obtained from basic attenuation equation

Limit on T-violating P-conserving rhoNN interaction from the gamma decay of Fe-57

We use the experimental limit on the interference of M1 and E2 multipoles in the γ decay of 57Fe to bound the time-reversal-violating parity-conserving ρNN vertex. Our approach is a large-basis shell-model calculation of the interference. We find an upper limit on the parameter g¯ρ, the relative strength of the T-violating ρNN vertex, of close to 10^(-2), a value similar to the best limits from other experiments

Representation of entanglement by negative quasi-probabilities

Any bipartite quantum state has quasi-probability representations in terms of separable states. For entangled states these quasi-probabilities necessarily exhibit negativities. Based on the general structure of composite quantum states, one may reconstruct such quasi-propabilities from experimental data. Because of ambiguity, the quasi-probabilities obtained by the bare reconstruction are insufficient to identify entanglement. An optimization procedure is introduced to derive quasi-probabilities with a minimal amount of negativity. Negativities of optimized quasi-probabilities unambiguously prove entanglement, their positivity proves separability.Comment: 9 pages, 2 figures; An optimization procedure for the quasi-probabilities has been adde

Evaluation of the InDUCKtion project at UCL

Executive summary: There is evidence that a good induction to university life can help with student retention; however, there is also a danger of overwhelming students during the intense period of fresher’s week. Under the auspices of a small grant from the Higher Education Academy’s ‘Changing the Learning Landscape’ funding stream, staff at two universities (University College London and Southampton Solent University) collaborated to produce an innovative and engaging induction project entitled ‘InDUCKtion’, based on the idea of an induction duck being a fun character for students to interact with. At UCL, the InDUCKtion duck existed in the form of a physical plastic duck included in international postgraduate student induction packs, and they were encouraged to take photos of themselves in and around UCL and London as part of a photo challenge using social media. It was anticipated that this would enable students to familiarise themselves with the locale, make friends and have fun at the same time. The InDUCKtion duck was also evident on flyers and posters with QR codes advertising an online tour to enable students to gain an accelerated familiarisation with the campus and its facilities. Within UCL, the project was a collaborative, cross-departmental venture instigated by members of UCL’s E-Learning Environments (ELE) working in partnership with the Centre for the Advancement of Learning and Teaching (CALT) and Student Support and Wellbeing (SSW). The logistics of the project meant that the team members also had to liaise with a number of other individuals and departments around UCL, to help promote and implement the project. Despite a rapid following on Twitter in a relatively short period, a reasonable hit rate on the QR code for the main page of the online tour resource, and some engagement with the photo challenges using social media, participation in the project was lower than anticipated. Lessons learned from an evaluation perspective revealed that adding another activity to an already overwhelming fresher’s week was problematic, despite its innovative and interactive nature. The use of QR codes was problematic for a number of reasons, and the project needed more buy-in from student representatives and academics to provide institutional endorsement. Recommendations for future instances of the project include securing student representation and academic endorsement, integrating the activity with parallel induction activities – particularly with academic departments, replacing QR codes with an alternative technology-enhanced learning approach and optimising the learning design to better motivate students and promote groupwork

Necessary and sufficient conditions for bipartite entanglement

Necessary and sufficient conditions for bipartite entanglement are derived, which apply to arbitrary Hilbert spaces. Motivated by the concept of witnesses, optimized entanglement inequalities are formulated solely in terms of arbitrary Hermitian operators, which makes them useful for applications in experiments. The needed optimization procedure is based on a separability eigenvalue problem, whose analytical solutions are derived for a special class of projection operators. For general Hermitian operators, a numerical implementation of entanglement tests is proposed. It is also shown how to identify bound entangled states with positive partial transposition.Comment: 7 pages, 2 figur

Radiative corrections in neutrino-deuterium disintegration

The radiative corrections of order alpha for the charged- and neutral-current neutrino-deuterium disintegration for energies relevant to the SNO experiment are evaluated. Particular attention is paid to the issue of the bremsstrahlung detection threshold. It is shown that the radiative corrections to the total cross section for the charged current reaction are independent of that threshold, as they must be for consistency, and amount to a slowly decreasing function of the neutrino energy E-nu, varying from about 4% at low energies to 3% at the end of the B-8 spectrum. The differential cross section corrections, on the other hand, do depend on the bremsstrahlung detection threshold. Various choices of the threshold are discussed. It is shown that for a realistic choice of the threshold and for the actual electron energy threshold of the SNO detector, the deduced B-8 nu(e) flux should be decreased by about 2%. The radiative corrections to the neutral-current reaction are also evaluated

System Size and Energy Dependence of Dilepton Production in Heavy-Ion Collisions at SIS Energies

We study the dilepton production in heavy-ion collisions at energies of 1-2 AGeV as well as in proton induced pp, pn, pd and p+A reactions from 1 GeV up to 3.5 GeV. For the analysis we employ three different transport models - the microscopic off-shell Hadron-String-Dynamics (HSD) transport approach, the Isospin Quantum Molecular Dynamics (IQMD) approach as well as the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) approach. We confirm the experimentally observed enhancement of the dilepton yield (normalized to the multiplicity of neutral pions $N_{\pi^0}$) in heavy-ion collisions with respect to that measured in $NN = (pp+pn)/2$ collisions. We identify two contributions to this enhancement: a) the $pN$ bremsstrahlung which scales with the number of collisions and not with the number of participants, i.e. pions; b) the dilepton emission from intermediate $\Delta$'s which are part of the reaction cycles $\Delta \to \pi N ; \pi N \to \Delta$ and $NN\to N\Delta; N\Delta \to NN$. With increasing system size more generations of intermediate $\Delta$'s are created. If such $\Delta$ decays into a pion, the pion can be reabsorbed, however, if it decays into a dilepton, the dilepton escapes from the system. Thus, experimentally one observes only one pion (from the last produced $\Delta$) whereas the dilepton yield accumulates the contributions from all $\Delta$'s of the cycle. We show as well that the Fermi motion enhances the production of pions and dileptons in the same way. Furthermore, employing the off-shell HSD approach, we explore the influence of in-medium effects like the modification of self-energies and spectral functions of the vector mesons due to their interactions with the hadronic environment.Comment: 46 pages, 48 figures, version to be published in Phys. Rev.