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Sökning: WFRF:(Allum K. M.)

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1.
  • Strakova, A., et al. (författare)
  • Recurrent horizontal transfer identifies mitochondrial positive selection in a transmissible cancer
  • 2020
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11
  • Tidskriftsartikel (refereegranskat)abstract
    • Autonomous replication and segregation of mitochondrial DNA (mtDNA) creates the potential for evolutionary conflict driven by emergence of haplotypes under positive selection for 'selfish' traits, such as replicative advantage. However, few cases of this phenomenon arising within natural populations have been described. Here, we survey the frequency of mtDNA horizontal transfer within the canine transmissible venereal tumour (CTVT), a contagious cancer clone that occasionally acquires mtDNA from its hosts. Remarkably, one canine mtDNA haplotype, A1d1a, has repeatedly and recently colonised CTVT cells, recurrently replacing incumbent CTVT haplotypes. An A1d1a control region polymorphism predicted to influence transcription is fixed in the products of an A1d1a recombination event and occurs somatically on other CTVT mtDNA backgrounds. We present a model whereby 'selfish' positive selection acting on a regulatory variant drives repeated fixation of A1d1a within CTVT cells.
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  • Lee, J. W.L., et al. (författare)
  • Time-resolved relaxation and fragmentation of polycyclic aromatic hydrocarbons investigated in the ultrafast XUV-IR regime
  • 2021
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Polycyclic aromatic hydrocarbons (PAHs) play an important role in interstellar chemistry and are subject to high energy photons that can induce excitation, ionization, and fragmentation. Previous studies have demonstrated electronic relaxation of parent PAH monocations over 10-100 femtoseconds as a result of beyond-Born-Oppenheimer coupling between the electronic and nuclear dynamics. Here, we investigate three PAH molecules: fluorene, phenanthrene, and pyrene, using ultrafast XUV and IR laser pulses. Simultaneous measurements of the ion yields, ion momenta, and electron momenta as a function of laser pulse delay allow a detailed insight into the various molecular processes. We report relaxation times for the electronically excited PAH*, PAH(+*) and PAH(2+*) states, and show the time-dependent conversion between fragmentation pathways. Additionally, using recoil-frame covariance analysis between ion images, we demonstrate that the dissociation of the PAH(2+) ions favors reaction pathways involving two-body breakup and/or loss of neutral fragments totaling an even number of carbon atoms. Polycyclic aromatic hydrocarbons play an important role in interstellar chemistry, where interaction with high energy photons can induce ionization and fragmentation reactions. Here the authors, with XUV-IR pump-probe experiments, investigate the ultrafast photoinduced dynamics of fluorene, phenanthrene and pyrene, providing insight into their preferred reaction channels.
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  • Garg, D., et al. (författare)
  • Fragmentation Dynamics of Fluorene Explored Using Ultrafast XUV-Vis Pump-Probe Spectroscopy
  • 2022
  • Ingår i: Frontiers in Physics. - : Frontiers Media SA. - 2296-424X. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the use of extreme ultraviolet (XUV, 30.3 nm) radiation from the Free-electron LASer in Hamburg (FLASH) and visible (Vis, 405 nm) photons from an optical laser to investigate the relaxation and fragmentation dynamics of fluorene ions. The ultrashort laser pulses allow to resolve the molecular processes occurring on the femtosecond timescales. Fluorene is a prototypical small polycyclic aromatic hydrocarbon (PAH). Through their infrared emission signature, PAHs have been shown to be ubiquitous in the universe, and they are assumed to play an important role in the chemistry of the interstellar medium. Our experiments track the ionization and dissociative ionization products of fluorene through time-of-flight mass spectrometry and velocity-map imaging. Multiple processes involved in the formation of each of the fragment ions are disentangled through analysis of the ion images. The relaxation lifetimes of the excited fluorene monocation and dication obtained through the fragment formation channels are reported to be in the range of a few tens of femtoseconds to a few picoseconds.
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  • Lee, J. W. L., et al. (författare)
  • The kinetic energy of PAH dication and trication dissociation determined by recoil-frame covariance map imaging
  • 2022
  • Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:38, s. 23096-23105
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated the dissociation of dications and trications of three polycyclic aromatic hydrocarbons (PAHs), fluorene, phenanthrene, and pyrene. PAHs are a family of molecules ubiquitous in space and involved in much of the chemistry of the interstellar medium. In our experiments, ions are formed by interaction with 30.3 nm extreme ultraviolet (XUV) photons, and their velocity map images are recorded using a PImMS2 multi-mass imaging sensor. Application of recoil-frame covariance analysis allows the total kinetic energy release (TKER) associated with multiple fragmentation channels to be determined to high precision, ranging 1.94-2.60 eV and 2.95-5.29 eV for the dications and trications, respectively. Experimental measurements are supported by Born-Oppenheimer molecular dynamics (BOMD) simulations.
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  • Allum, F., et al. (författare)
  • A localized view on molecular dissociation via electron-ion partial covariance
  • 2022
  • Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Inner-shell photoelectron spectroscopy provides an element-specific probe of molecular structure, as core-electron binding energies are sensitive to the chemical environment. Short-wavelength femtosecond light sources, such as Free-Electron Lasers (FELs), even enable time-resolved site-specific investigations of molecular photochemistry. Here, we study the ultraviolet photodissociation of the prototypical chiral molecule 1-iodo-2-methylbutane, probed by extreme-ultraviolet (XUV) pulses from the Free-electron LASer in Hamburg (FLASH) through the ultrafast evolution of the iodine 4d binding energy. Methodologically, we employ electron-ion partial covariance imaging as a technique to isolate otherwise elusive features in a two-dimensional photoelectron spectrum arising from different photofragmentation pathways. The experimental and theoretical results for the time-resolved electron spectra of the 4d(3/2) and 4d(5/2) atomic and molecular levels that are disentangled by this method provide a key step towards studying structural and chemical changes from a specific spectator site. Coincidence experiments at free-electron lasers enable time resolved site-specific investigations of molecular photochemistry at high signal rates, but isolating individual dissociation processes still poses a considerable technical challenge. Here, the authors use electron-ion partial covariance imaging to isolate otherwise elusive chemical shifts in UV-induced photofragmentation pathways of the prototypical chiral molecule 1-iodo-2-methylbutane.
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  • Allum, W., et al. (författare)
  • ECCO essential requirements for quality cancer care: Oesophageal and gastric cancer
  • 2018
  • Ingår i: Critical reviews in oncology/hematology. - : Elsevier BV. - 1040-8428. ; 122, s. 179-193
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: ECCO essential requirements for quality cancer care (ERQCC) are checklists and explanations of organisation and actions that are necessary to give high-quality care to patients who have a specific type of cancer. They are written by European experts representing all disciplines involved in cancer care. ERQCC papers give oncology teams, patients, policymakers and managers an overview of the elements needed in any healthcare system to provide high quality of care throughout the patient journey. References are made to clinical guidelines and other resources where appropriate, and the focus is on care in Europe. Oesophageal and gastric: essential requirements for quality care: • Oesophageal and gastric (OG) cancers are a challenging tumour group with a poor prognosis and wide variation in outcomes among European countries. Increasing numbers of older people are contracting the diseases, and treatments and care pathways are becoming more complex in both curative and palliative settings.• High-quality care can only be a carried out in specialised OG cancer units or centres which have both a core multidisciplinary team and an extended team of allied professionals, and which are subject to quality and audit procedures. Such units or centres are far from universal in all European countries.• It is essential that, to meet European aspirations for comprehensive cancer control, healthcare organisations implement the essential requirements in this paper, paying particular attention to multidisciplinarity and patient-centred pathways from diagnosis, to treatment, to survivorship. Conclusion: Taken together, the information presented in this paper provides a comprehensive description of the essential requirements for establishing a high-quality OG cancer service. The ERQCC expert group is aware that it is not possible to propose a ‘one size fits all’ system for all countries, but urges that access to multidisciplinary units or centres must be guaranteed for all those with OG cancer.
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