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Träfflista för sökning "WFRF:(Penfold J.) "

Sökning: WFRF:(Penfold J.)

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1.
  • Edelson, R. A., et al. (författare)
  • Multiwavelength observations of short-timescale variability in NGC 4151. IV. Analysis of multiwavelength continuum variability
  • 1996
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 470:1, s. 364-377377
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>For pt.III see ibid., vol.470, no.1, p.349-63 (1996). Combines data from the three preceding papers in order to analyze the multi wave-band variability and spectral energy distribution of the Seyfert 1 galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA=6%) variations (uncorrelated with those at lower energies) were seen at soft gamma-ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 Aring. These data do not probe extreme ultraviolet (1200 Aring to 0.1 keV) or hard X-ray (250 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of lsim0.15 day between 1275 Aring and the other ultraviolet bands, lsim0.3 day between 1275 Aring and 1.5 keV, and lsim1 day between 1275 and 5125 Aring. These tight limits represent more than an order of magnitude improvement over those determined in previous multi-wave-band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (ales-2.5)</p>
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2.
  • Crenshaw, D. M., et al. (författare)
  • Multiwavelength observations of short-timescale variability in NGC 4151. I. Ultraviolet observations
  • 1996
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 470:1, s. 322-335335
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Presents the results of an intensive ultraviolet monitoring campaign on the Seyfert 1 galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously with the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra every ~70 minutes, and during 4 hr periods for 4 days prior to and 5 days after the continuous-monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy. The continuum fluxes in bands from 1275 to 2688 Aring went through four significant and well-defined ldquoeventsrdquo of duration 2-3 days during the continuous-monitoring period. The authors find that the amplitudes of the continuum variations decrease with increasing wavelength, which extends a general trend for this and other Seyfert galaxies to smaller timescales (i.e., a few days). The continuum variations in all the UV bands are simultaneous to within an accuracy of ~0.15 days, providing a strict constraint on continuum models. The emission-line light curves show only one major event during the continuous monitoring (a slow rise followed by a shallow dip) and do not correlate well with continuum light curves over the short duration of the campaign, because the timescale for continuum variations is apparently smaller than the response times of the emission lines</p>
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6.
  • Szlachetko, Jakub, et al. (författare)
  • Establishing nonlinearity thresholds with ultraintense X-ray pulses
  • 2016
  • Ingår i: Scientific Reports. - 2045-2322 .- 2045-2322. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>X-ray techniques have evolved over decades to become highly refined tools for a broad range of investigations. Importantly, these approaches rely on X-ray measurements that depend linearly on the number of incident X-ray photons. The advent of X-ray free electron lasers (XFELs) is opening the ability to reach extremely high photon numbers within ultrashort X-ray pulse durations and is leading to a paradigm shift in our ability to explore nonlinear X-ray signals. However, the enormous increase in X-ray peak power is a double-edged sword with new and exciting methods being developed but at the same time well-established techniques proving unreliable. Consequently, accurate knowledge about the threshold for nonlinear X-ray signals is essential. Herein we report an X-ray spectroscopic study that reveals important details on the thresholds for nonlinear X-ray interactions. By varying both the incident X-ray intensity and photon energy, we establish the regimes at which the simplest nonlinear process, two-photon X-ray absorption (TPA), can be observed. From these measurements we can extract the probability of this process as a function of photon energy and confirm both the nature and sub-femtosecond lifetime of the virtual intermediate electronic state.</p>
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7.
  • Buchan, Sarah L., et al. (författare)
  • Antibodies to Costimulatory Receptor 4-1BB Enhance Anti-tumor Immunity via T Regulatory Cell Depletion and Promotion of CD8 T Cell Effector Function
  • 2018
  • Ingår i: Immunity. - Cell Press. - 1074-7613. ; 49:5, s. 958-970
  • Tidskriftsartikel (refereegranskat)abstract
    • The costimulatory receptor 4-1BB is expressed on activated immune cells, including activated T cells. Antibodies targeting 4-1BB enhance the proliferation and survival of antigen-stimulated T cells in vitro and promote CD8 T cell-dependent anti-tumor immunity in pre-clinical cancer models. We found that T regulatory (Treg) cells infiltrating human or murine tumors expressed high amounts of 4-1BB. Intra-tumoral Treg cells were preferentially depleted by anti-4-1BB mAbs in vivo. Anti-4-1BB mAbs also promoted effector T cell agonism to promote tumor rejection. These distinct mechanisms were competitive and dependent on antibody isotype and FcγR availability. Administration of anti-4-1BB IgG2a, which preferentially depletes Treg cells, followed by either agonistic anti-4-1BB IgG1 or anti-PD-1 mAb augmented anti-tumor responses in multiple solid tumor models. An antibody engineered to optimize both FcγR-dependent Treg cell depleting capacity and FcγR-independent agonism delivered enhanced anti-tumor therapy. These insights into the effector mechanisms of anti-4-1BB mAbs lay the groundwork for translation into the clinic.
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8.
  • Czapla-Masztafiak, Joanna, et al. (författare)
  • Investigating DNA Radiation Damage Using X-Ray Absorption Spectroscopy
  • 2016
  • Ingår i: Biophysical Journal. - 0006-3495 .- 1542-0086. ; 110:6, s. 1304-1311
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The biological influence of radiation on living matter has been studied for years; however, several questions about the detailed mechanism of radiation damage formation remain largely unanswered. Among all biomolecules exposed to radiation, DNA plays an important role because any damage to its molecular structure can affect the whole cell and may lead to chromosomal rearrangements resulting in genomic instability or cell death. To identify and characterize damage induced in the DNA sugar-phosphate backbone, in this work we performed x-ray absorption spectroscopy at the P K-edge on DNA irradiated with either UVA light or protons. By combining the experimental results with theoretical calculations, we were able to establish the types and relative ratio of lesions produced by both UVA and protons around the phosphorus atoms in DNA.</p>
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9.
  • Donetto, S., et al. (författare)
  • Nursing work and sensory experiences of hospital design : A before and after qualitative study following a move to all-single room inpatient accommodation
  • 2017
  • Ingår i: Health and Place. - Elsevier. - 1353-8292 .- 1873-2054. ; 46, s. 121-129
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The embodied experience of nursing practice is rarely studied. Drawing on data from an internationally relevant larger study conducted in 2013–14, here we explore the sensory dimension of the embodied experiences of nursing staff working on two acute NHS hospital wards before and after a move to all-single room inpatient accommodation. We undertook a secondary analysis of 25 interviews with nursing staff (12 before and 13 after the move with half [13/25] using photographs taken by participants) from a mixed-method before-and-after study. This analysis focused on the sensory dimensions of nursing staff's experiences of their working practices and the effect of the built environment upon these. Drawing on Pallasmaa's theoretocal insights, we report how the all-single room ward design prioritises ‘focused vision’ and hinders peripheral perception, whilst the open ward environment is rich in contextual and preconscious information. We suggest all-single room accommodation may offer staff an impoverished experience of caring for patients and of working with each other. </p>
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10.
  • El Nahhas, A., et al. (författare)
  • X-ray absorption spectroscopy of ground and excited rhenium-carbonyl- diimine complexes : Evidence for a two-center electron transfer
  • 2013
  • Ingår i: Journal of Physical Chemistry A. - The American Chemical Society (ACS). - 1089-5639. ; 117:2, s. 361-369
  • Tidskriftsartikel (refereegranskat)abstract
    • Steady-state and picosecond time-resolved X-ray absorption spectroscopy is used to study the ground and lowest triplet states of [ReX(CO) 3 (bpy)] n+ , X = Etpy (n = 1), Cl, or Br (n = 0). We demonstrate that the transient spectra at both the Re L 3 -and Br K-edges show the emergence of a pre-edge feature, absent in the ground-state spectrum, which is associated with the electron hole created in the highest occupied molecular orbital following photoexcitation. Importantly, these features have the same dynamics, confirming previous predictions that the low-lying excited states of these complexes involve a two-center charge transfer from both the Re and the ligand, X. We also demonstrate that the DFT optimized ground and excited structures allow us to reproduce the experimental XANES and EXAFS spectra. The ground-state structural refinement shows that the Br atom contributes very little to the latter, whereas the Re-C-O scattering paths are dominant due to the so-called focusing effect. For the excited-state spectrum, the Re-X bond undergoes one of the largest changes but still remains a weak contribution to the photoinduced changes of the EXAFS spectrum.
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  • Resultat 1-10 av 20
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