Detecting sub-MeV neutrons in solid plastic scintillator with gamma-ray discrimination

We report on recent efforts to design a solid plastic scintillation hodoscope to measure neutron production cross sections at low energies. Our program includes not only the development of the detector itself, but also a set of auxiliary measurements which will help characterize its low-energy response. A novel scintillation counter has been developed to detect sub-MeV neutrons while rejecting gamma-ray backgrounds with good efficiency. The detector uses multiple layers of thin solid scintillator, with optical isolation between the adjacent layers. Incident low-energy neutrons produce ionizing recoil particles which remain within just one of the scintillator layers, while background gamma rays create electrons which most often cross the boundary between layers. By observing the trigger pattern within the layers, most gamma-ray backgrounds can be distinguished from the low-energy neutrons of interest. We report on the results of our Monte Carlo studies of this design, as well as on the operation of a prototype detector unit. We also have undertaken a new measurement of the neutron-proton total cross section below 1 MeV. Calculations of the efficiency for detecting low energy neutrons in plastic scintillator rely on accurate low energy n-p cross sections, yet surprisingly few such data currently exist. New measurements which span the region from 150 to 800 keV neutron (lab) energy are reported and discussed. Additionally, we have measured the light response of BC 418 scintillator for recoil proton energies as low as 100 keV. Recoil protons are produced at a known energy in the scintillator by placing it in a neutron beam and detecting in coincidence the elastically scattered neutrons at fixed angle. Our new results extend the energy range of previous measurements of the light response of solid organic scintillators, and may indicate a significantly modified response at the lowest observed energies.United States. Dept. of Energy (Grant No. DE-FG52-10NA29651

Swift X-Ray Observations of Classical Novae. II. The Super Soft Source sample

The Swift GRB satellite is an excellent facility for studying novae. Its rapid response time and sensitive X-ray detector provides an unparalleled opportunity to investigate the previously poorly sampled evolution of novae in the X-ray regime. This paper presents Swift observations of 52 Galactic/Magellanic Cloud novae. We included the XRT (0.3-10 keV) X-ray instrument count rates and the UVOT (1700-8000 Angstroms) filter photometry. Also included in the analysis are the publicly available pointed observations of 10 additional novae the X-ray archives. This is the largest X-ray sample of Galactic/Magellanic Cloud novae yet assembled and consists of 26 novae with super soft X-ray emission, 19 from Swift observations. The data set shows that the faster novae have an early hard X-ray phase that is usually missing in slower novae. The Super Soft X-ray phase occurs earlier and does not last as long in fast novae compared to slower novae. All the Swift novae with sufficient observations show that novae are highly variable with rapid variability and different periodicities. In the majority of cases, nuclear burning ceases less than 3 years after the outburst begins. Previous relationships, such as the nuclear burning duration vs. t_2 or the expansion velocity of the eject and nuclear burning duration vs. the orbital period, are shown to be poorly correlated with the full sample indicating that additional factors beyond the white dwarf mass and binary separation play important roles in the evolution of a nova outburst. Finally, we confirm two optical phenomena that are correlated with strong, soft X-ray emission which can be used to further increase the efficiency of X-ray campaigns.Comment: Accepted to ApJ Supplements. Full data for Table 2 and Figure 17 available in the electronic edition. New version of the previously posted paper since the earlier version was all set in landscape mod

Participatory transport planning the experience of eight european metropolitan regions

This chapter presents experience with participatory transport planning in eight European metropolitan regions: Ljubljana, Oslo, Gothenburg, Helsinki, Budapest, Rome, Porto and Barcelona. These metropolitan regions answered the questionnaire on strengths, weaknesses and needs and an in-depth questionnaire on participatory transport planning. The results were presented at a workshop, where representatives from these eight metropolitan regions shared their experience in two workshop sessions, one dealing with the key stakeholders in participatory transport planning and the other dealing with ways to get them involved. The findings show that stakeholder involvement differs between the local and regional levels. Participants engagement is greater at the local level, where measures are more concrete and less abstract. The participatory planning process takes longer than the traditional planning processes, but it can ease the implementation of the project/measure to the extent that it justifies the additional resources and time. It is of crucial importance to include all the relevant stakeholders, to provide an experienced facilitator and, above all, to include the results in the final plans and policies. Although there are differences in the participatory planning culture between the countries and regions involved, the use of participatory methods in transport planning is becoming increasingly important. Document type: Part of book or chapter of boo

Design and prototyping of an interactive virtual environment to foster citizen participation and creativity in urban design

Public Participation encounters great challenges in the domain of urban design concerning decision making and citizens’ appropriation of a future place. Many tools and methods have been proposed to ease the participation process. In this paper we are targeting artefacts used in face-to-face workshops, in which citizens are asked to make design proposals for a public space. We claim that current state of the art can be improved (i) by better articulating digital artefacts with participatory processes and (ii) by providing interfaces that enhance citizen’s spatial awareness and comprehension as well as collective creativity in urban design projects. We present the design and prototyping of an interactive virtual environment that follow the design-science research guidelines.U_CODE project (H2020 No 688873

ATX-Konzerne: Mit einem Bein im Steuersumpf? [ATX companies: With one foot in the tax swamp?]

Policy brie

Activity of the unique X-ray transient CI Cam (XTE J0421+560)

The variations of the source of optical light appear to be related to those of X-ray source. The 1998 outburst can be explained by thermal instability of the accretion disk

Interpretation of the 1998 outburst of the unique X-ray transient CI Camelopardalis (XTE J0421+560)

We present an analysis of the photometric observations of the peculiar X-ray binary and X-ray transient CI Cam. The similarities between CI Cam and the microquasar LS 5039/RX J1826-1450 are discusse

Selective Mediator dependence of cell-type-specifying transcription

The Mediator complex directs signals from DNA-binding transcription factors to RNA polymerase II (Pol II). Despite this pivotal position, mechanistic understanding of Mediator in human cells remains incomplete. Here we quantified Mediator-controlled Pol II kinetics by coupling rapid subunit degradation with orthogonal experimental readouts. In agreement with a model of condensate-driven transcription initiation, large clusters of hypophosphorylated Pol II rapidly disassembled upon Mediator degradation. This was accompanied by a selective and pronounced disruption of cell-type-specifying transcriptional circuits, whose constituent genes featured exceptionally high rates of Pol II turnover. Notably, the transcriptional output of most other genes was largely unaffected by acute Mediator ablation. Maintenance of transcriptional activity at these genes was linked to an unexpected CDK9-dependent compensatory feedback loop that elevated Pol II pause release rates across the genome. Collectively, our work positions human Mediator as a globally acting coactivator that selectively safeguards the functionality of cell-type-specifying transcriptional networks