| 1. |
- Abbasi, R., et al.
(författare)
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Search for Continuous and Transient Neutrino Emission Associated with IceCube's Highest-energy Tracks: An 11 yr Analysis
- 2024
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 964:1
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Tidskriftsartikel (refereegranskat)abstract
- IceCube alert events are neutrinos with a moderate-to-high probability of having astrophysical origin. In this study, we analyze 11 yr of IceCube data and investigate 122 alert events and a selection of high-energy tracks detected between 2009 and the end of 2021. This high-energy event selection (alert events + high-energy tracks) has an average probability of >= 0.5 of being of astrophysical origin. We search for additional continuous and transient neutrino emission within the high-energy events' error regions. We find no evidence for significant continuous neutrino emission from any of the alert event directions. The only locally significant neutrino emission is the transient emission associated with the blazar TXS 0506+056, with a local significance of 3 sigma, which confirms previous IceCube studies. When correcting for 122 test positions, the global p-value is 0.156 and compatible with the background hypothesis. We constrain the total continuous flux emitted from all 122 test positions at 100 TeV to be below 1.2 x 10-15 (TeV cm2 s)-1 at 90% confidence assuming an E -2 spectrum. This corresponds to 4.5% of IceCube's astrophysical diffuse flux. Overall, we find no indication that alert events in general are linked to lower-energetic continuous or transient neutrino emission.
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| 2. |
- Abbasi, R., et al.
(författare)
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Search for decoherence from quantum gravity with atmospheric neutrinos
- 2024
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Ingår i: Nature Physics. - 1745-2481 .- 1745-2473. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Neutrino oscillations at the highest energies and longest baselines can be used to study the structure of spacetime and test the fundamental principles of quantum mechanics. If the metric of spacetime has a quantum mechanical description, its fluctuations at the Planck scale are expected to introduce non-unitary effects that are inconsistent with the standard unitary time evolution of quantum mechanics. Neutrinos interacting with such fluctuations would lose their quantum coherence, deviating from the expected oscillatory flavour composition at long distances and high energies. Here we use atmospheric neutrinos detected by the IceCube South Pole Neutrino Observatory in the energy range of 0.5-10.0 TeV to search for coherence loss in neutrino propagation. We find no evidence of anomalous neutrino decoherence and determine limits on neutrino-quantum gravity interactions. The constraint on the effective decoherence strength parameter within an energy-independent decoherence model improves on previous limits by a factor of 30. For decoherence effects scaling as E2, our limits are advanced by more than six orders of magnitude beyond past measurements compared with the state of the art. Interactions of atmospheric neutrinos with quantum-gravity-induced fluctuations of the metric of spacetime would lead to decoherence. The IceCube Collaboration constrains such interactions with atmospheric neutrinos.
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| 3. |
- Abazajian, Kevork, et al.
(författare)
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CMB-S4 : Forecasting Constraints on Primordial Gravitational Waves
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 926:1
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Tidskriftsartikel (refereegranskat)abstract
- CMB-S4—the next-generation ground-based cosmic microwave background (CMB) experiment—is set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2–3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5σ, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL.
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| 4. |
- Kim, Hye-Kyung, 1970, et al.
(författare)
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Co-Ion Dependence of DNA Nuclease Activity Suggests Hydrophobic Cavitation as a Potential Source of Activation Energy
- 2001
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Ingår i: European Physical Journal E. - : Springer Science and Business Media LLC. - 1292-8941 .- 1292-895X. ; 4:4, s. 411-417
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Tidskriftsartikel (refereegranskat)abstract
- The source of the activation energy that allows cutting of DNA by restriction enzymes is unclear. A systematic study of the cutting efficiency of the type-II restriction endonuclease EcoRI, with varying background electrolyte ion pair and buffer reported here, shows only a modest dependence of efficiency on cation type. Surprisingly, efficiency does depend strongly on the presumed indifferent anion of the background salt. What emerges is that competition between the background salt anion and the buffer anion for the enzyme and DNA surfaces is crucial. The results are unexpected and counterintuitive from the point of view of conventional electrolyte theory. However, taken together with recent developments in surface chemistry, the results do fall into place and could also suggest a novel mechanism for enzyme activity as an alternative to metal-activated hydrolysis: microscopic cavitation in a hydrophobic pocket might be the source of activation energy.
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| 5. |
- McKinley, A. W., et al.
(författare)
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DNA Sequence and Ancillary Ligand Modulate the Biexponential Emission Decay of Intercalated [Ru(L)2dppz]2+ Enantiomers
- 2012
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Ingår i: Chemistry - A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 18:47, s. 15142-15150
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Tidskriftsartikel (refereegranskat)abstract
- The bi-exponential emission decay of [Ru(L)2dppz]2+ (L=N,N'-diimine ligand) bound to DNA has been studied as a function of polynucleotide sequence, enantiomer, and nature of L (phenanthroline vs. bipyridine). The lifetimes (ti) and pre-exponential factors (ai) depend on all three parameters. With [poly(dA-dT)]2, the variation of ai with [Nu]/[Ru] has little dependence on L for ?-[Ru(L)2dppz]2+ but a substantial dependence for ?-[Ru(L)2dppz]2+. With [poly(dG-dC)]2, by contrast, the ?-enantiomer ai values depend strongly on the nature of L, whereas those of the ?-enantiomer are relatively unaffected. DNA-bound linked dimers show similar photophysical behaviour. The lifetimes are identified with two geometries of minor-groove intercalated [Ru(L)2dppz]2+, resulting in differential water access to the phenazine nitrogen atoms. Interplay of cooperative and anti-cooperative binding resulting from complexcomplex and complexDNA interactions is responsible for the observed variations of ai with binding ratio. [Ru(phen)2dppz]2+ emission is quenched by guanosine in DMF, which may further rationalise the shorter lifetimes observed with guanine-rich DNA.
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| 6. |
- McKinley, A. W., et al.
(författare)
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Environmental effects on the photophysics of transition metal complexes with dipyrido 2,3-a:3 ',2 '-c phenazine (dppz) and related ligands
- 2011
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Ingår i: Coordination Chemistry Reviews. - : Elsevier BV. - 0010-8545. ; 255:21-22, s. 2676-2692
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Tidskriftsartikel (refereegranskat)abstract
- This review primarily covers studies of ruthenium(II) complexes with the dppz (dipyrido[2,3-a:3',2'-c]phenazine) ligand; in solution, in polymers and surfactant/lipid media, and when bound to DNA. Related studies with other transition metals, and with extended ligands that can form bimetallic as well as monometallic complexes are discussed. The review focuses on photophysics of these complexes with particular attention devoted to the nature of the excited states that give rise to emission, their dependence on solvent environment, and the behavior of the complexes as luminescent probes for DNA.
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| 7. |
- McKinley, A. W., et al.
(författare)
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Sensitivity of Ru(phen)(2)dppz (2+) light switch emission to ionic strength, temperature, and DNA sequence and conformation
- 2013
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:11, s. 4081-4090
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Tidskriftsartikel (refereegranskat)abstract
- The luminescence of DNA-bound [Ru(phen)(2)dppz](2+) is shown to be highly sensitive to environmental conditions such as ionic strength, temperature, and the sequence and secondary structure of the nucleic acid, although not to bulky DNA substituents in the major groove. Each enantiomer has two characteristic lifetimes with any polynucleotide and their relative amplitudes vary as a function of binding ratio. For [poly(dA-dT)](2) as a model sequence, the longer lifetime for Delta-[Ru(phen)(2)dppz](2+) has been assigned to canted intercalation of the complex and the shorter lifetime is ascribed to symmetric intercalation. At a fixed binding ratio, the longer lifetime amplitude increases with increasing ionic strength, without significant change in lifetimes. Increasing temperature has a similar effect, but also affects lifetimes. In general, emission is strongest with AT-rich polynucleotides and with higher-order secondary structures, with intensity increasing as single-stranded
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