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- 2017
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 96:2
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Dey, Lankeswar, et al.
(författare)
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Authenticating the Presence of a Relativistic Massive Black Hole Binary in OJ 287 Using Its General Relativity Centenary Flare : Improved Orbital Parameters
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 866:1
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Tidskriftsartikel (refereegranskat)abstract
- Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (GWs). We show that observations associated with the binary black hole (BBH) central engine of blazar OJ 287 demand the inclusion of gravitational radiation reaction effects beyond the quadrupolar order. It turns out that even the effects of certain hereditary contributions to GW emission are required to predict impact flare timings of OJ 287. We develop an approach that incorporates this effect into the BBH model for OJ 287. This allows us to demonstrate an excellent agreement between the observed impact flare timings and those predicted from ten orbital cycles of the BBH central engine model. The deduced rate of orbital period decay is nine orders of magnitude higher than the observed rate in PSR 1913+16, demonstrating again the relativistic nature of OJ 287's central engine. Finally, we argue that precise timing of the predicted 2019 impact flare should allow a test of the celebrated black hole no-hair theorem at the 10% level.
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| 3. |
- Nagaraja, Ch., et al.
(författare)
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Opening remarks
- 2016
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Konferensbidrag (refereegranskat)
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| 4. |
- Gopakumar, Deepu A., et al.
(författare)
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Carbon dioxide plasma treated PVDF electrospun membrane for the removal of crystal violet dyes and iron oxide nanoparticles from water
- 2019
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Ingår i: Nano-Structures and Nano-Objects. - : Elsevier BV. - 2352-507X. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Here we reported a reactive plasma treatment of polyvinylidene fluoride (PVDF) electrospun membrane by using carbon dioxide (CO 2 ) plasma in order to reduce the hydrophobicity of the PVDF membrane and thereby used to remove toxic crystal violet dye (CV) and iron oxide (Fe 2 O 3 ) nanoparticles from water. The demonstrated plasma treated PVDF electrospun membrane showed a decrement in the hydrophobicity after plasma treatment. Most of the microfiltration membranes based on PVDF were fabricated via phase inversion technique and solvent casting. The main drawback of these methods is that to obtain membranes with uniform pore size. Moreover, the membranes fabricated via phase inversion and solvent casting process have low surface area whereas in the membranes via electrospinning technique have interconnected pore structure with high surface area and uniform pore size. The contact angle of the neat PVDF electrospun membrane and plasma treated PVDF electrospun membrane were 141°and 102°respectively. FTIR studies revealed that, after CO 2 plasma treatment, highly negative carboxylate (COO-) groups were formed on the surface of the PVDF electrospun membrane. With the 10 mg/L of crystal violet (CV) aqueous solution, the dye adsorption capacity was 1.368 mg/g of the membrane for neat PVDF membrane and 3.84 mg/g of the membrane for plasma treated PVDF membrane. It was found that, the CO 2 plasma treated PVDF membrane had two- or three-times greater adsorption capacity then neat PVDF membrane against crystal violet dyes which was due to the strong electrostatic interaction between the highly negative carboxyl groups on the surface of plasma treated PVDF electrospun membrane and protonated CV dye. Both neat PVDF membrane and plasma treated PVDF membrane showed excellent filtration capacity against Fe 2 O 3 nanoparticles. The demonstrated plasma treated PVDF membrane could successfully remove iron oxide nanoparticles and crystal violet dyes from water via size exclusion and adsorption mechanism respectively.
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| 5. |
- Gopakumar, Geethanjali, 1992-, et al.
(författare)
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X-ray Induced Fragmentation of Protonated Cystine
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Protein structure determination using high-intensity X-ray sources induces damage in the protein. Disulfide bridges, formed between two cysteine amino acid residues stabilize the protein structure. Owing to the higher absorption cross-section of sulfur for X-ray photons, and a large number of electrons released from sulfur atoms, these disulfide bridges are hot spots for a higher level of noise in structural studies. But it is yet to be understood how exactly the damage occurs through the interaction of the disulfide bridges with photons. Here we study the fragmentation of protonated cystine in the gas phase, which is the dimer of cysteine, by irradiation with X-rays across the sulfur L-edge using an electrospray ionization source (ESI) in combination with an ion trap. This is complemented with the calculation of the sulfur NEXAFS spectrum on the level of Restricted Open-Shell Configuration Interaction (ROCIS) and Density Functional Theory (DFT) calculations for molecular orbital visualization as well as Molecular Dynamics (MD) simulations for the fragmentation of triply charged cystine ions. We have deduced a possible pathway of fragmentation upon excitation and ionization of S 2p electrons by combining the experiments and simulations. The disulfide bridge breaks for resonant excitation at lower energies but remains intact upon higher energy resonant excitation and upon ionization of S 2p. The larger fragments formed subsequently break into smaller fragments.
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| 6. |
- Kaiser, L., et al.
(författare)
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Angular emission distribution of O 1s photoelectrons of uniaxially oriented methanol
- 2020
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:19
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Tidskriftsartikel (refereegranskat)abstract
- The angular distribution of O 1s photoelectrons emitted from uniaxially oriented methanol is studied experimentally and theoretically. We employed circularly polarized photons of an energy ofh nu= 550 eV for our investigations. We measured the three-dimensional photoelectron angular distributions of methanol, with the CH3-OH axis oriented in the polarization plane, by means of cold target recoil ion momentum spectroscopy. The experimental results are interpreted by single active electron calculations performed with the single center method. A comparative theoretical study of the respective molecular-frame angular distributions of O 1s photoelectrons of CO, performed for the same photoelectron kinetic energy and for a set of different internuclear distances, allows for disentangling the role of internuclear distance and the hydrogen atoms of methanol as compared to carbon monoxide.
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