Improving the quantity, quality and transparency of data used to derive radionuclide transfer parameters for animal products. 2. Cow milk

Under the International Atomic Energy Agency (IAEA) MODARIA (Modelling and Data for Radiological Impact Assessments) Programme, there has been an initiative to improve the derivation, provenance and transparency of transfer parameter values for radionuclides from feed to animal products that are for human consumption. A description of the revised MODARIA 2016 cow milk dataset is described in this paper. As previously reported for the MODARIA goat milk dataset, quality control has led to the discounting of some references used in IAEA's Technical Report Series (TRS) report 472 (IAEA, 2010). The number of Concentration Ratio (CR) values has been considerably increased by (i) the inclusion of more literature from agricultural studies which particularly enhanced the stable isotope data of both CR and Fm and (ii) by estimating dry matter intake from assumed liveweight. In TRS 472, the data for cow milk were 714 transfer coefficient (Fm) values and 254 CR values describing 31 elements and 26 elements respectively. In the MODARIA 2016 cow milk dataset, Fm and CR values are now reported for 43 elements based upon 825 data values for Fm and 824 for CR. The MODARIA 2016 cow milk dataset Fm values are within an order of magnitude of those reported in TRS 472. Slightly bigger changes are seen in the CR values, but the increase in size of the dataset creates greater confidence in them. Data gaps that still remain are identified for elements with isotopes relevant to radiation protection

Improving the quantity, quality and transparency of data used to derive radionuclide transfer parameters for animal products. 1. Goat milk

Under the MODARIA (Modelling and Data for Radiological Impact Assessments Programme of the International Atomic Energy Agency), there has been an initiative to improve the derivation, provenance and transparency of transfer parameter values for radionuclides. The approach taken for animal products is outlined here and the first revised table for goat milk is provided. Data from some references used in TRS 472 were removed and reasons given for removal. Particular efforts were made to improve the number of CR (concentration ratio) values which have some advantages over transfer coefficients. There is little difference in most of the new CR and Fm (transfer coefficient) values for goat milk compared with those in TRS 472. In TRS 472, 21 CR values were reported for goat milk. In the 2015 dataset for goat milk CR values for a further 14 elements are now included. The CR and Fm values for only one element (Co) were removed

Clinical placements in private practice for physiotherapy students are perceived as safe and beneficial for students, private practices and universities: a national mixed-methods study

Question: What are the extent and characteristics of clinical placements in private practice for physiotherapy students? What do university clinical education managers perceive to be the benefits, risks, barriers and enablers of clinical placements in private practice for physiotherapy students? What training and support are available for private practitioners? Design: Mixed methods study combining a national survey and in-depth, semi-structured focus group interviews. Participants: Twenty clinical education managers from Australian universities who had graduating students in entry-level physiotherapy programs in 2017 (95% response rate) responded to the survey with data on 2,000 students. Twelve clinical education managers participated in the focus groups. Results: It was found that 44% of physiotherapy graduates in Australia in 2017 completed a 5-week private practice placement. Private practice placement experiences were perceived to be safe and beneficial for students, private practices and universities. The main risks identified by clinical education managers were related to the quality and consistency of the student's experience on placement and not risks to service or clients. The main perceived barriers were time costs (both practitioner and university clinical education managers) and perceived lost earning capacity. Clinical education managers emphasised that more time and resources to establish and support private practitioners would enable them to reduce risk and overcome barriers to increasing private practice placement capacity and quality. Engaging private practitioners and working collaboratively appear vital for establishing, monitoring and supporting private practice placements. Conclusion: By working collaboratively, universities and private practice physiotherapists can enhance private practice placement capacity and quality

Quasiparticle photoemission intensity in doped two-dimensional quantum antiferromagnets

Using the self-consistent Born approximation, and the corresponding wave function of the magnetic polaron, we calculate the quasiparticle weight corresponding to destruction of a real electron (in contrast to creation of a spinless holon), as a funtion of wave vector for one hole in a generalized $t-J$ model and the strong coupling limit of a generalized Hubbard model. The results are in excellent agreement with those obtained by exact diagonalization of a sufficiently large cluster. Only the Hubbard weigth compares very well with photoemission measurements in Sr_2CuO_2Cl_2.Comment: 11 pages, latex, 3 figure

Playing safe: Assessing the risk of sexual abuse to elite child athletes

Young athletes frequently suffer from being seen as athletes first and children second. This has consequences for their legal, civil and human rights as children (Kelly et al., 1995) and for the way in which sport organisations choose to intervene on their behalf to protect them from physical, psychological and sexual abuses (Brackenridge, 1994). Sport careers peak at different ages depending on the sport: in some, children as young as 12 or 13 may reach the highest levels of competitive performance; in others, full maturity as an athlete may come late into adulthood or even middle age. Recognition of this variation has given rise to the concept of ‘sport age’ (Kirby, 1986) referring to sport-specific athlete development. This concept is of significance in helping to identify the developmental process in terms of athletic, rather than chronological, maturity. The risk of sexual abuse in sport, formerly ignored or denied, has now been documented in a number of studies, using both quantitative and qualitative methods (Kirby & Greaves, 1996; Brackenridge, 1997; Volkwein, 1996). Drawing on data from these studies and from the previous work on sport age and athletic maturation, this paper proposes a possible means of identifying and assessing relative risk of sexual abuse to elite young athletes in selected sports. The concept of a ‘stage of imminent achievement’ (SIA) is proposed as the period of peak vulnerability of young athletes to sexual abuse

Dispersion of a single hole in the t-J model

The dispersion of a single hole in the t-J model obtained by the exact result of 32 sites and the results obtained by self-consistent Born approximation and the Green function Monte Carlo method can be simply derived by a mean-field theory with d-RVB and antiferromagnetic order parameters. In addition, it offers a simple explanation for the difference observed between those results. The presence of the extended van Hove region at (pi,0) is a consequence of the d-RVB pairing independenct of the antiferromagnetic order. Results including t' and t" are also presented and explained consistently in a similar way.Comment: LaTex file, 5 pages with 5 embedded eps figure

Electron momentum distribution in underdoped cuprates

We investigate the electron momentum distribution function (EMD) in a weakly doped two-dimensional quantum antiferromagnet (AFM) as described by the t-J model. Our analytical results for a single hole in an AFM based on the self-consistent Born approximation (SCBA) indicate an anomalous momentum dependence of EMD showing 'hole pockets' coexisting with a signature of an emerging large Fermi surface. The position of the incipient Fermi surface and the structure of the EMD is determined by the momentum of the ground state. Our analysis shows that this result remains robust in the presence of next-nearest neighbor hopping terms in the model. Exact diagonalization results for small clusters are with the SCBA reproduced quantitatively.Comment: 5 pages, submitted to PR

Quasiparticle vanishing driven by geometrical frustration

We investigate the single hole dynamics in the triangular t-J model. We study the structure of the hole spectral function, assuming the existence of a 120 magnetic Neel order. Within the self-consistent Born approximation (SCBA) there is a strong momentum and t sign dependence of the spectra, related to the underlying magnetic structure and the particle-hole asymmetry of the model. For positive t, and in the strong coupling regime, we find that the low energy quasiparticle excitations vanish outside the neighbourhood of the magnetic Goldstone modes; while for negative t the quasiparticle excitations are always well defined. In the latter, we also find resonances of magnetic origin whose energies scale as (J/t)^2/3 and can be identified with string excitations. We argue that this complex structure of the spectra is due to the subtle interplay between magnon-assisted and free hopping mechanisms. Our predictions are supported by an excellent agreement between the SCBA and the exact results on finite size clusters. We conclude that the conventional quasiparticle picture can be broken by the effect of geometrical magnetic frustration.Comment: 6 pages, 7 figures. Published versio

Spin-charge separation in the single hole doped Mott antiferromagnet

The motion of a single hole in a Mott antiferromagnet is investigated based on the t-J model. An exact expression of the energy spectrum is obtained, in which the irreparable phase string effect [Phys. Rev. Lett. 77, 5102 (1996)] is explicitly present. By identifying the phase string effect with spin backflow, we point out that spin-charge separation must exist in such a system: the doped hole has to decay into a neutral spinon and a spinless holon, together with the phase string. We show that while the spinon remains coherent, the holon motion is deterred by the phase string, resulting in its localization in space. We calculate the electron spectral function which explains the line shape of the spectral function as well as the ``quasiparticle'' spectrum observed in angle-resolved photoemission experiments. Other analytic and numerical approaches are discussed based on the present framework.Comment: 16 pages, 9 figures; references updated; to appear in Phys. Rev.

Doping and temperature dependence of incommensurate antiferromagnetism in underdoped lanthanum cuprates

The doping, temperature and energy dependence of the dynamical spin structure factors of the underdoped lanthanum cuprates in the normal state is studied within the t-J model using the fermion-spin transformation technique. Incommensurate peaks are found at $[(1\pm\delta)\pi,\pi]$, $[\pi,(1\pm\delta)\pi]$ at relatively low temperatures with $\delta$ linearly increasing with doping at the beginning and then saturating at higher dopings. These peaks broaden and weaken in amplitude with temperature and energy, in good agreement with experiments. The theory also predicts a rotation of these peaks by $\pi/4$ at even higher temperatures, being shifted to $[(1\pm \delta/\sqrt{2})\pi,(1\pm \delta/\sqrt{2})\pi]$.Comment: 11 pages, PDF file, six figures are included, accepted for publication in Physical Review