Calibration of the whole body counter at PSI

Abstract. At the Paul Scherrer Institut (PSI), measurements with the whole body counter are routinely carried out for occupationally exposed persons and occasionally for individuals of the population suspected of radioactive intake. In total about 400 measurements are performed per year. The whole body counter is based on a p-type high purity germanium (HPGe) coaxial detector mounted above a canvas chair in a shielded small room. The detector is used to detect the presence of radionuclides that emit photons with energies between 50 keV and 2 MeV. The room itself is made of iron from old railway rails to reduce the natural background radiation to 24 nSv/h. The present paper describes the calibration of the system with the IGOR phantom. Different body sizes are realized by different standardized configurations of polyethylene bricks, in which small tubes of calibration sources can be introduced. The efficiency of the detector was determined for four phantom geometries (P1, P2, P4 and P6) simulating human bodies in sitting position of 12 kg, 24 kg, 70 kg and 110 kg, respectively. The measurements were performed serially using five different radionuclide sources ( Eu) within the phantom bricks. Based on results of the experiment, an efficiency curve for each configuration and the detection limits for relevant radionuclides were determined. For routine measurements, the efficiency curve obtained with the phantom geometry P4 was chosen. The detection limits range from 40 Bq to 1000 Bq for selected radionuclides applying a measurement time of 7 min. The proper calibration of the system, on the one hand, is essential for the routine measurements at PSI. On the other hand, it serves as a benchmark for the already initiated characterisation of the system with Monte Carlo simulations

Research priorities in light of current trends in microsurgical training: revalidation, simulation, cross-training, and standardisation.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly citedPlastic surgery training worldwide has seen a thorough restructuring over the past decade, with the introduction of formal training curricula and work-based assessment tools. Part of this process has been the introduction of revalidation and a greater use of simulation in training delivery. Simulation is an increasingly important tool for educators because it provides a way to reduce risks to both trainees and patients, whilst facilitating improved technical proficiency. Current microsurgery training interventions are often predicated on theories of skill acquisition and development that follow a 'practice makes perfect' model. Given the changing landscape of surgical training and advances in educational theories related to skill development, research is needed to assess the potential benefits of alternative models, particularly cross-training, a model now widely used in non-medical areas with significant benefits. Furthermore, with the proliferation of microsurgery training interventions and therefore diversity in length, cost, content and models used, appropriate standardisation will be an important factor to ensure that courses deliver consistent and effective training that achieves appropriate levels of competency. Key research requirements should be gathered and used in directing further research in these areas to achieve on-going improvement of microsurgery training

Tebentafusp in Patients with Metastatic Uveal Melanoma: A Real-Life Retrospective Multicenter Study

Background: Tebentafusp has recently been approved for the treatment of metastatic uveal melanoma (mUM) after proving to have survival benefits in a first-line setting. Patients and Methods: This retrospective, multicenter study analyzed the outcomes and safety of tebentafusp therapy in 78 patients with mUM. Results: Patients treated with tebentafusp had a median PFS of 3 months (95% CI 2.7 to 3.3) and a median OS of 22 months (95% CI 10.6 to 33.4). In contrast to a published Phase 3 study, our cohort had a higher rate of patients with elevated LDH (65.4% vs. 35.7%) and included patients with prior systemic and local ablative therapies. In patients treated with tebentafusp following ICI, there was a trend for a longer median OS (28 months, 95% CI 26.9 to 29.1) compared to the inverse treatment sequence (24 months, 95% CI 13.0 to 35.0, p = 0.257). The most common treatment-related adverse events were cytokine release syndrome in 71.2% and skin toxicity in 53.8% of patients. Tumor lysis syndrome occurred in one patient. Conclusions: Data from this real-life cohort showed a median PFS/OS similar to published Phase 3 trial data. Treatment with ICI followed by tebentafusp may result in longer PFS/OS compared to the inverse treatment sequence

Spatially resolved spectroscopy of monolayer graphene on SiO2

We have carried out scanning tunneling spectroscopy measurements on exfoliated monolayer graphene on SiO$_2$ to probe the correlation between its electronic and structural properties. Maps of the local density of states are characterized by electron and hole puddles that arise due to long range intravalley scattering from intrinsic ripples in graphene and random charged impurities. At low energy, we observe short range intervalley scattering which we attribute to lattice defects. Our results demonstrate that the electronic properties of graphene are influenced by intrinsic ripples, defects and the underlying SiO$_2$ substrate.Comment: 6 pages, 7 figures, extended versio

Single-Pion Production in pp Collisions at 0.95 GeV/c (II)

The single-pion production reactions $pp\to d\pi^+$, $pp\to np\pi^+$ and $pp\to pp\pi^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \approx$ 400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts. Thus all pion production channels were recorded with 1-4 overconstraints. Main emphasis is put on the presentation and discussion of the $np\pi^+$ channel, since the results on the other channels have already been published previously. The total and differential cross sections obtained are compared to theoretical calculations. In contrast to the $pp\pi^0$ channel we find in the $np\pi^+$ channel a strong influence of the $\Delta$ excitation already at this energy close to threshold. In particular we find a $(3 cos^2\Theta + 1)$ dependence in the pion angular distribution, typical for a pure s-channel $\Delta$ excitation and identical to that observed in the $d\pi^+$ channel. Since the latter is understood by a s-channel resonance in the $^1D_2$ $pn$ partial wave, we discuss an analogous scenario for the $pn\pi^+$ channel

Experimental determination of the complete spin structure for anti-proton + proton -> anti-\Lambda + \Lambda at anti-proton beam momentum of 1.637 GeV/c

The reaction anti-proton + proton -> anti-\Lambda + \Lambda -> anti-proton + \pi^+ + proton + \pi^- has been measured with high statistics at anti-proton beam momentum of 1.637 GeV/c. The use of a transversely-polarized frozen-spin target combined with the self-analyzing property of \Lambda/anti-\Lambda decay allows access to unprecedented information on the spin structure of the interaction. The most general spin-scattering matrix can be written in terms of eleven real parameters for each bin of scattering angle, each of these parameters is determined with reasonable precision. From these results all conceivable spin-correlations are determined with inherent self-consistency. Good agreement is found with the few previously existing measurements of spin observables in anti-proton + proton -> anti-\Lambda + \Lambda near this energy. Existing theoretical models do not give good predictions for those spin-observables that had not been previously measured.Comment: To be published in Phys. Rev. C. Tables of results (i.e. Ref. 24) are available at http://www-meg.phys.cmu.edu/~bquinn/ps185_pub/results.tab 24 pages, 16 figure

On the Production of π+π+\pi^+\pi^+ Pairs in pp Collisions at 0.8 GeV

Data accumulated recently for the exclusive measurement of the $pp\to pp\pi^+\pi^-$ reaction at a beam energy of 0.793 GeV using the COSY-TOF spectrometer have been analyzed with respect to possible events from the $pp \to nn\pi^+\pi^+$ reaction channel. The latter is expected to be the only $\pi\pi$ production channel, which contains no major contributions from resonance excitation close to threshold and hence should be a good testing ground for chiral dynamics in the $\pi\pi$ production process. No single event has been found, which meets all conditions for being a candidate for the $pp \to nn \pi^+\pi^+$ reaction. This gives an upper limit for the cross section of 0.16 $\mu$b (90% C.L.), which is more than an order of magnitude smaller than the cross sections of the other two-pion production channels at the same incident energy

Measurement of Spin Transfer Observables in Antiproton-Proton -> Antilambda-Lambda at 1.637 GeV/c

Spin transfer observables for the strangeness-production reaction Antiproton-Proton -> Antilambda-Lambda have been measured by the PS185 collaboration using a transversely-polarized frozen-spin target with an antiproton beam momentum of 1.637 GeV/c at the Low Energy Antiproton Ring at CERN. This measurement investigates observables for which current models of the reaction near threshold make significantly differing predictions. Those models are in good agreement with existing measurements performed with unpolarized particles in the initial state. Theoretical attention has focused on the fact that these models produce conflicting predictions for the spin-transfer observables D_{nn} and K_{nn}, which are measurable only with polarized target or beam. Results presented here for D_{nn} and K_{nn} are found to be in disagreement with predictions from existing models. These results also underscore the importance of singlet-state production at backward angles, while current models predict complete or near-complete triplet-state dominance.Comment: 5 pages, 3 figure

Evaluering av tiltak for å fremme bærekraftig sameksistens mellom fiskeri og havbruksnæring (ProCoEx)

Fiskeri- og havbruksnæringen har felles interesser i kystnære farvann, næringene må i størst mulig grad se nytten i å samarbeide om bruken av områdene uten urimelig forringelse av felles næringsgrunnlag. Økt tilstedeværelse av havbruk vil føre til økte interessekonflikter i kystnære farvann. Mye erfaringsbasert viten ligger til grunn for denne situasjonsbeskrivelsen, og de senere år har området også vært tema for forskningsbaserte tilnærminger. Målsettingen med dette prosjektet er å skaffe til veie kunnskap som kan danne grunnlag for utvikling av tiltak for å bedre sameksistens mellom næringene med tilknytning til kystsonen, hovedsakelig fiskeri- og havbruksnæringene. Vesentlig i denne sammenhengen er å redusere negative og forsterke positive sider ved bruken av felles arealer. Siden erfaringene og kunnskapen er mangelfulle, og sameksistensen i noen grad preges av påstander som ikke er dokumenterte, utgjør en oppsummering av tilgjengelig kunnskap rundt tema en viktig del av prosjektet. Vi har dokumentert at filétkvaliteten på villfisk som har spist laksefôr over noe tid er påvirket negativt, men at denne effekten er begrenset om fangsten håndteres optimalt. Hvilket redskap, og hvordan disse benyttes, har også betydning for kvaliteten. Vi har også belyst mulige effekter på reproduksjon som følge av økt tilgang på laksefôr hos villfisk som beiter ved oppdrettsanlegg