237 results on '"Kazakov, Sergey"'
Search Results
202. Calculation Studies of Operational Faults of Multielement Disk MCG.
- Author
-
Boriskin, Alexander S., Vlasov, Yuri V., Toropova, Tamara A., Demidov, Vasily A., Kazakov, Sergey A., and Shapovalov, Eugeny V.
- Subjects
DETONATORS ,MAGNETIC disks ,MAGNETS ,MAGNETISM ,MAGNETIC fields ,QUASIPARTICLES - Abstract
A calculation simulation of multielement disk magnetocumulative systems is carried out. Effect of failure of one or several detonators in a system of high-explosive (HE) charge initiation and axial shift of the detonators relative to a symmetry plane of the HE charges on the operation efficiency of the multielement disk magnetocumulative generator is considered. The considered models allow explaining the results of the experiments in the case of similar situations. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
203. Disk Magnetocumulative Generator of 480-mm Diameter for Explosive EMIR Facility.
- Author
-
Selemir, Victor D., Demidov, Vasily A., Boriskin, Alexander S., Bulyichev, Sergey V., Vlasov, Yuri V., Garipov, Rinat M., Golosov, Sergey N., Kazakov, Sergey A., Kazakova, Nataliya R., Kutumov, Sergey V., Romanov, Alexander P., Toropova, Tamara A., Shapovalov, Evgenii V., Schetnikov, Evgenii I., and Yanenko, Vladimir A.
- Subjects
MAGNETOHYDRODYNAMIC generators ,X-rays ,RADIATION ,EXPLOSIVES ,PULSED radiation ,QUANTITATIVE research - Abstract
The first test of a disk magnetocumulative generator (DMCG) with high explosive charges of 480-mm diameter was carried out in the frameworks of a program on creation of an explosive EMIR facility, intended for high-power soft X-ray radiation pulses generation. The generator consists of five disk elements. The inductive load was equal to ∼7 nH. The generator was twice larger than model DMCG240, successfully tested earlier. A comparison of calculation and experimental results is carried out. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
204. Study of Thin Films of High Temperature Superconductors Based on YBaCuO by EPMA.
- Author
-
TretyakovRID="*"ID="*" To whom correspondence should be addressed, Vladimir V., Kazakov, Sergey V., Bobyl, Alexander V., and Konnikov, Samuil G.
- Abstract
An analytical model of an effective atomic number, Z
eff , for simultaneous calculation of composition and thickness of films on substrates that allows for backscattering processes is presented. Comparison of dependencies of ϕ(ρ z) parameters for film elements on electron beam energy, on atomic numbers of a film and a substrate and on film thickness was done. The errors inherent in EPMA have been determined by comparing experimental data obtained on YBa2 Cu3 O7−x bulk crystals with model calculations. Possibility of EPMA as an effective technique for investigation of spatially inhomogeneous objects was demonstrated by studying the correlation between composition and local superconducting properties (values of critical temperature and critical current) of these films. [ABSTRACT FROM AUTHOR]- Published
- 2000
- Full Text
- View/download PDF
205. On the possibility of using Kumakhov lenses in x-ray therapy.
- Author
-
Kazakov, Sergey V., Mardynskii, Yulii S., and Sysoev, Alexei S.
- Published
- 2000
- Full Text
- View/download PDF
206. Estimation of the focal spot of x-ray tube with transmission anode.
- Author
-
Ibraimov, Nariman S., Kazakov, Sergey V., Gruev, Dmitrii I., and Lopurko, Kirill N.
- Published
- 2000
- Full Text
- View/download PDF
207. Design, Manufacturing, Assembly, Testing, and Lessons Learned of the Prototype 650 MHz Couplers
- Author
-
Helsper, Josh, Chandrasekaran, Saravan Kumar, Furuta, Fumio, Hanna, Bruce, Kazakov, Sergey, Ozelis, Joseph, Premo, Ken, Solyak, Nikolay, and Wu, Genfa
- Subjects
Accelerator Physics (physics.acc-ph) ,Technology ,FOS: Physical sciences ,Physics - Accelerator Physics ,Accelerator Physics - Abstract
Six 650 MHz high-power couplers will be integrated into the prototype High Beta 650 MHz (HB650) cryomodule for the PIP-II project at Fermilab. The design of the coupler is described, including design optimizations from the previous generation. This paper then describes the coupler life-cycle, including manufacturing, assembly, testing, conditioning and the lessons learned at each stage., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK
- Published
- 1900
208. RD50 status report 2006: Radiation hard semiconductor devices for very high luminosity colliders
- Author
-
Balbuena, Pablo, Campabadal, Francesca, Diez, Sergio, Lozano, Manuel, Pellegrini, Giulio, Rafi, Joan Marc, Ullan, Miguel, Ambrico, Marianna, Creanza, Donato, Palma, Mauro, Ligonzo, Teresa, Manna, Norman, Radicci, Valeria, Schiavulli, Luigi, Kierstead, Jim, Li, Zheng, Cavallini, Anna, Buda, Manuela, Lazanu, Sorina, Pintilie, Lucian, Pintilie, Ioana, Popa, Andreia-Ioana, Lazanu, Ionel, Collins, Paula, Gill, Karl Aaron, Glaser, Maurice, Hoedlmoser, Herbert, Joram, Christian, Moll, Michael, Wright, Victoria, Gossling, Claus, Klingenberg, Reiner, Weber, Jens, Wunstorf, Renate, Roder, Ralf, Stolze, Dieter, Uebersee, Hartmut, Adey, James, Blumenau, A., Coutinho, J., Eberlein, T., Fall, C., Goss, J., Hourahine, B., Jones, Robert, Pinho, N., Coluccia, Rita, Kwan, Simon, Sellberg, Greg, Borchi, Emilio, Bruzzi, Mara, Focardi, Ettore, Lagomarsino, Stefano, Macchiolo, Anna, Menichelli, David, Miglio, Stefania, Scaringella, Monica, Sciortino, Silvio, Tosi, Carlo, Eckert, Simon, Ehrich, Thies, Kuehn, Susanne, Parzefall, Ulrich, Bates, Richard, Blue, Andrew, Bussey, Peter, Craig Buttar, Cunningham, William, Doherty, Freddie, Eklund, Lars, Fleta, Celeste, Bates, Alison G., Haddad, Lina, James, Grant, Mathieson, Keith, Melone, J., O Shea, Val, Parkes, Chris, Pennicard, David, Saavedra, Aldo, Buhmann, Peter, Contarato, Devis, Fretwurst, Eckhart, Honniger, Frank, Lindstrom, Gunnar, Pein, Uwe, Stahl, Jorg, Harkonen, Jaakko, Lassila-Perini, Katri, Luukka, Panja, Nysten, Jukka, Tuominen, Eija, Tuovinen, Esa, Eremin, Vladimir, Ilyashenko, Igor, Ivanov, Alexander, Kalinina, Evgenia, Lebedev, Alexander, Strokan, Nikita, Verbitskaya, Elena, Barcz, Adam, Brzozowski, Andrzej, Kaminski, Pawel, Kozlowski, Roman, Kozubal, Michal, Luczynski, Zygmunt, Nossarzewska-Orlowska, Elzbieta, Surma, Barbara, Zabierowski, Piotr, Boer, Wim, Furgeri, Alex, Hartmann, Frank, Zhukov, Valery, Barabash, L., Dolgolenko, A., Groza, A., Karpenko, A., Khivrich, V., Lastovetsky, V., Litovchenko, P., Polivtsev, L., Brodbeck, Timothy John, Campbell, Duncan, Chilingarov, Alexandre, Hughes, Gareth, Jones, Brian Keith, Sloan, Terence, Koski, Miia, Leinonen, Kari, Palviainen, Tanja, Tuuva, Tuure, Allport, Philip, Biagi, Stephen, Bowcock, Themis J. V., Casse, Gianluigi, Vossebeld, Joost, Cindro, Vladimir, Dolenc, Irena, Kramberger, Gregor, Mandic, Igor, Mikuz, Marko, Zavrtanik, Marko, Assouak, Samia, Forton, Eric, Gregoire, Ghislain, Lemaitre, Vincent, Militaru, Otilia, Piotrzkowski, Krzysztof, Rodeghiero, Pierre, Kazuchits, Nikolai, Makarenko, Leonid, Charron, Sebastien, Genest, Marie-Helene, Houdayer, Alain, Lebel, Celine, Leroy, Claude, Golovin, Victor, Grigoriev, Eugene, Karpov, Aleksey, Kazakov, Sergey, Martemianov, Alexander, Rogozhkin, Sergey, Zaluzhny, Alexandre, Andricek, Ladislav, Moser, Hans-Gunther, Richter, Rainer Helmut, Wei, Qingyu, Gorelov, Igor, Hoeferkamp, Martin, Metcalfe, Jessica, Seidel, Sally, Vataga, Elena, Hartjes, Fred, Koffeman, Els, Graaf, Harry, Visschers, Jan, Alfieri, Giovanni, Johansen, Klaus M. H., Kuznetsov, Andrej, Monakhov, Edouard, Svensson, Bengt G., Bisello, Dario, Candelori, Andrea, Khomenkov, Vladimir, Litovchenko, Alexei, Pantano, Devis, Rando, Riccardo, Bilei, Gian Mario, Passeri, Daniele, Petasecca, Marco, Pignatel, Giorgio Umberto, Borrello, Laura, Dutta, Suchandra, Messineo, Alberto, Segneri, Gabriele, Popule, Jiri, Sicho, Petr, Tomasek, Michal, Vrba, Vaclav, Broz, Jan, Dolezal, Zdenek, Kodys, Peter, Tsvetkov, Alexej, Wilhelm, Ivan, Chren, Dominik, Horazdovsky, Tomas, Kohout, Zdenek, Linhart, Vladimir, Pospisil, Stanislav, Solar, Michael, Sopko, Vit, Sopko, Bruno, Uher, Josef, Horisberger, Roland, Rohe, Tilman, Bolla, Gino, Bortoletto, Daniela, Giolo, Kim, Miyamoto, Jun, Rott, Carsten, Roy, Amitava, Shipsey, Ian, Son, Seunghee, Boisvert, Veronique, Demina, Regina, Korjenevski, Sergey, Tipton, Paul, Grillo, Alexander, Sadrozinski, Hartmut, Schumm, Bruce, Seiden, Abraham, Spencer, Ned, Dawson, Ian, Dervan, Paul, Hansen, Thor-Erik, Artuso, Marina, Guskov, J., Marunko, Sergey, Ruzin, Arie, Tylchin, Tamir, Fizzotti, Franco, Garino, Yiuri, Lo Giudice, Alessandro, Manfredotti, Claudio, Boscardin, Maurizio, Dalla Betta, Gian Franco, Gregori, Paolo, Piemonte, Claudio, Pozza, Alberto, Ronchin, Sabina, Zen, Mario, Zorzi, Nicola, Garcia, Carmen, Gonzalez-Sevilla, Sergio, Lacasta, Carlos, Marti I Garcia, Salvador, Minano, Mercedes, Gaubas, Eugenijus, Kadys, Arunas, Kazukauskas, Vaidotas, Sakalauskas, Stanislavas, Storasta, Jurgis, and Vaitkus, Juozas Vidmantis
209. Commissioning and first results from the Fermilab cryomodule test stand
- Author
-
Harms, Elvin, Awida, Mohamed, Baffes, Curtis, Carlson, Kermit, Chandrasekaran, Saravan Kumar, Chase, Brian, Cullerton, Ed, Edelen, Jonathan, Einstein, Joshua, Ginsburg, Camille, Grassellino, Anna, Hansen, Benjamin, Holzbauer, Jeremiah, Kazakov, Sergey, Khabiboulline, Timergali, Kucera, Michael, Leibfritz, Jerry, Lunin, Andrei, McDowell, Dave, McGee, Mike, Nicklaus, Dennis, Orris, Darryl, Ozelis, Joseph, Patrick, James, Petersen, Troy, Pischalnikov, Yuriy, Prieto, Peter, Prokofiev, Oleg, Reid, John, Schappert, Warren, Sergatskov, Dmitri, Solyak, Nikolay, Stanek, Richard, Sun, Ding, White, Michael, Worel, Chuck, and Wu, Genfa
- Subjects
Accelerator Physics (physics.acc-ph) ,3 Technology ,FOS: Physical sciences ,Physics - Accelerator Physics ,Accelerator Physics - Abstract
A new test stand dedicated to Superconducting Radiofrequency (SRF) cryomodule testing, CMTS1, has been commissioned and is now in operation at Fermilab. The first device to be cooled down and powered in this facility is the prototype 1.3 GHz cryomodule assembled at Fermilab for LCLS-II. We describe the demonstrated capabilities of CMTS1, report on steps taken during commissioning, provide an overview of first test results, and survey future plans., Comment: 4 pp. Proceedings of LINAC2016, East Lansing, MI, USA
210. Searches for New Particles, Dark Matter, and Gravitational Waves with SRF Cavities
- Author
-
Berlin, Asher, Belomestnykh, Sergey, Blas, Diego, Frolov, Daniil, Brady, Anthony J., Braggio, Caterina, Carena, Marcela, Cervantes, Raphael, Checchin, Mattia, Contreras-Martinez, Crispin, Tito D Agnolo, Raffaele, Ellis, Sebastian A. R., Eremeev, Grigory, Gao, Christina, Giaccone, Bianca, Grassellino, Anna, Harnik, Roni, Hollister, Matthew, Janish, Ryan, Kahn, Yonatan, Kazakov, Sergey, Kurkcuoglu, Doga Murat, Zhen Liu, Lunin, Andrei, Netepenko, Alexander, Melnychuk, Oleksandr, Pilipenko, Roman, Pischalnikov, Yuriy, Posen, Sam, Romanenko, Alex, Schutte-Engel, Jan, Wang, Changqing, Yakovlev, Vyacheslav, Zhou, Kevin, Zorzetti, Silvia, Zhuang, Quntao, Institut de Physique Théorique - UMR CNRS 3681 (IPHT), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
- Subjects
accelerator ,new physics: search for ,gravitational radiation ,dark matter: density ,quantum chromodynamics: axion ,High Energy Physics - Experiment ,cavity: superconductivity ,coherence ,High Energy Physics - Phenomenology ,quality ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex] ,Physics::Accelerator Physics ,new particle - Abstract
This is a Snowmass white paper on the utility of existing and future superconducting cavities to probe fundamental physics. Superconducting radio frequency (SRF) cavity technology has seen tremendous progress in the past decades, as a tool for accelerator science. With advances spear-headed by the SQMS center at Fermilab, they are now being brought to the quantum regime becoming a tool in quantum science thanks to the high degree of coherence. The same high quality factor can be leveraged in the search for new physics, including searches for new particles, dark matter, including the QCD axion, and gravitational waves. We survey some of the physics opportunities and the required directions of R&D. Given the already demonstrated integration of SRF cavities in large accelerator systems, this R&D may enable larger scale searches by dedicated experiments., Comment: Submitted to the Proceedings of the US Community Study on the Future of Particle Physics (Snowmass 2021). 19 pages, 21 figures
211. A New Representative of the Cubic Parkerites Family: Synthesis, Crystal and Electronic Structure of Pt3Bi2Se2.
- Author
-
Zakharova, Elena Yu., Kazakov, Sergey M., and Kuznetsov, Alexey N.
- Subjects
- *
ATOMIC structure , *ELECTRON transport , *CHEMICAL synthesis , *CRYSTAL structure , *CRYSTAL growth , *CRYSTALLIZATION , *PHASE equilibrium , *PHYSICAL & theoretical chemistry - Abstract
Pt3Bi2Se2 is prepared by annealing of the elements in stoichiometric quantities (evacuated silica ampoule, 1. 750 °C, 10 d, 2. 650 °C, 10 d). The intermetallic compound crystallizes in the cubic space group I213 (Z = 4, powder XRD), represents a rare example of the cubic parkerite structure, and is isotypic with Pd3Bi2S2. DFT calculations indicate metallic properties and Pauli-like paramagnetic behavior. A combination of Bader's QTAIM approach and the topological analysis of electron localizability indicators reveal a 3D framework based on covalent Pt--Se and polar covalent Pt--Bi pairwise interactions. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
212. A New Representative of the Cubic Parkerites Family: Synthesis, Crystal and Electronic Structure of Pt3Bi2Se2.
- Author
-
Zakharova, Elena Yu., Kazakov, Sergey M., and Kuznetsov, Alexey N.
- Published
- 2015
- Full Text
- View/download PDF
213. ChemInform Abstract: Ternary Arsenides Based on Platinum-Indium and Palladium-Indium Fragments of the Cu3Au Type: Crystal Structures and Chemical Bonding.
- Author
-
Zakharova, Elena Yu., Andreeva, Natalia A., Kazakov, Sergey M., and Kuznetsov, Alexey N.
- Published
- 2015
- Full Text
- View/download PDF
214. ChemInform Abstract: Multiple Cation and Anion Substitutions into the Structures of Bi2WO6 and PbBi3WO8Cl.
- Author
-
Charkin, Dmitri O., Lebedev, Dmitri N., and Kazakov, Sergey M.
- Published
- 2012
- Full Text
- View/download PDF
215. ChemInform Abstract: Uranium Substitution for Tungsten in the Bi2WO6—Bi2UO6System: Formation of a Broad High‐Temperature Solid Solution.
- Author
-
Charkin, Dmitri O., Lebedev, Dmitri N., Stefanovich, Sergey Yu., and Kazakov, Sergey M.
- Abstract
A broad Bi2W1‐xUxO6solid solution with the Aurivillius‐type structure exists in the title system.
- Published
- 2011
- Full Text
- View/download PDF
216. Synthesis, Crystal Structure, Transport, and Magnetic Properties of Novel Ternary Copper Phosphides, A2Cu6P5 (A = Sr, Eu) and EUCU4P3.
- Author
-
Charkin, Dmitri O., Urmanov, Arthur V., Kazakov, Sergey M., Batuk, Dmitri, Abakumov, Artem M., Knöner, Stephan, Gati, Elena, Wolf, Bernd, Lang, Michael, Shevelkov, Andrey V., Van Tendeloo, Gustaaf, and Antipov, Evgeni V.
- Subjects
- *
COPPER compounds synthesis , *CRYSTAL structure , *MAGNETIC properties , *PHOSPHIDES , *FERROMAGNETISM , *SUPERCONDUCTIVITY , *TEMPERATURE effect - Abstract
Three new ternary copper phosphides, Sr2Cu6P5, Eu2Cu6P5, and EuCu4P3, have been synthesized from the elements in evacuated silica capsules. Eu2Cu6Ps and Sr2Cu6P5 adopt the Ca2Cu6P5-type structure while EuCu4P3 is isostructural to BaMg4Si3 and still remains the only representative of this structure type among the ternary Cu pnictides. All three materials show metallic conductivity in the temperature range 2 K ≤ T ≤ 290 K, with no indication for superconductivity. For Eu2Cu6P5 and EuCu4P3, long-range magnetic order was observed, governed by 4f local moments on the Eu atoms with predominant ferromagnetic interactions. While Eu2Cu6P5 shows a single ferromagnetic transition at TC = 34 K, the magnetic behavior of EuCu4P3 is more complex, giving rise to three consecutive magnetic phase transitions at 70, 43, and 18 K. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
217. Preparation and crystal structures of novel LaOAgS-type copper and silver fluoride chalcogenides
- Author
-
Charkin, Dmitri O., Urmanov, Arthur V., and Kazakov, Sergey M.
- Subjects
- *
CRYSTAL structure , *CHALCOGENIDES , *FLUORIDES , *TRANSITION metal compounds , *LANTHANUM compounds , *CHEMICAL bonds , *QUALITATIVE research - Abstract
Abstract: Systematic studies of LaOAgS-type alkaline earth–Cu/Ag fluoride chalcogenides revealed six new compounds SrFCuTe, SrFAgS, SrFAgSe, SrFAgTe, BaFAgS, and BaFAgSe. Crystal structures have been determined for these as well as for BaFCuS. Based on trends in the bond distances within the PbO- and FeS-type layers, a semi-qualitative approach is suggested to predict new members of the LaOAgS family. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
218. Development of a dual-layered dielectric-loaded accelerating structure
- Author
-
Jing, Chunguang, Kanareykin, Alexei, Kazakov, Sergey, Liu, Wanming, Nenasheva, Elizaveta, Schoessow, Paul, and Gai, Wei
- Subjects
- *
PARTICLE acceleration , *DIELECTRICS , *OPTICAL reflection , *CRYSTALLOGRAPHY - Abstract
Abstract: rf Power attenuation is a critical problem in the development of dielectric-loaded structures for particle acceleration. In a previous paper [C. Jing, W. Liu, W. Gai, J. Power, T. Wong, Nucl. Instr. Meth. A 539 (2005) 445] we suggested the use of a Multilayer Dielectric-Loaded Accelerating Structure (MDLA) as a possible approach for reducing the rf losses in a single layer device. The MDLA is based on the principle of Bragg reflection familiar from optics that is used to partially confine the fields inside the dielectric layers and reduce the wall current losses at the outer boundary. We report here on the design, construction and testing of a prototype X-band double-layer structure (2DLA). The measurements show an rf power attenuation for the 2DLA more than ten times smaller than that of a comparable single-layer structure, in good agreement with the analytic results. Testing and operation of MDLAs also requires efficient power coupling from test equipment or rf power systems to the device. We describe the design and construction of two novel structures: a TM03 mode launcher for cold testing and a power coupler for planned high-gradient experiments. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
219. Pt5Mn2Si, the first platinum-rich ternary intermetallic of the Rh5Ge3 structure type: Synthesis, crystal and electronic structure, and magnetic properties.
- Author
-
Makhaneva, Anastasiya Yu., Zakharova, Elena Yu., Nesterenko, Sergey N., Kazakov, Sergey M., Lyssenko, Konstantin A., Efimov, Nikolay N., and Kuznetsov, Alexey N.
- Subjects
- *
PLATINUM , *CRYSTAL structure , *MAGNETIC properties , *MAGNETIC transitions , *SINGLE crystals , *MAGNETIC measurements , *ELECTRONIC structure - Abstract
New ternary intermetallic Pt 5 Mn 2 Si was obtained in the form of single crystals and phase-pure polycrystalline bulk samples. This compound is only the second one found in the Pt–Mn–Si system. Pt 5 Mn 2 Si (space group Pbam , a = 5.4355(3) Å, b = 10.5955(7) Å, c = 4.0024(3) Å, Z = 2) is isotypic with the Rh 5 Ga 2 As structure, an ordered ternary variation of the Rh 5 Ge 3 structure type. This structure type is fairly rare, and Pt 5 Mn 2 Si is only the second ternary intermetallic adopting this structure. Magnetic measurements show that the compound has magnetic transition at ca. 80 K, most likely attributed to ferrimagnetic ordering of manganese spins. DFT calculations predict Pt 5 Mn 2 Si to be a metallic conductor. Chemical bonding analysis shows a pattern of localized pairwise-like Pt–Mn and Pt–Si bonds. [Display omitted] • Ternary intermetallic Pt 5 Mn 2 Si was obtained as single crystals and bulk. • Its crystal structure was determined from X-ray diffraction data. • Pt 5 Mn 2 Si belongs to the rare subtype of the Rh 5 Ge 3 structure type. • DFT calculations indicate metallic properties and localized bonding. • Pt 5 Mn 2 Si has a transition to ferrimagnetic state at ca. 80 K. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
220. New clathrate-like compound Eu7Cu44Sb23-δ: synthesis, crystal and electronic structure, and the effect of As-for-Sb substitution on the magnetic properties.
- Author
-
Plokhikh, Igor V., Charkin, Dmitry O., Kuznetsov, Alexey N., Verchenko, Valery Yu, Ignatiev, Ivan A., Kazakov, Sergey M., Tsirlin, Alexander A., and Shevelkov, Andrei V.
- Subjects
- *
INTERMETALLIC compounds , *CLATHRATE compounds , *ANTIMONIDES , *FERROMAGNETISM , *PARAMAGNETISM - Abstract
A new intermetallic compound, ternary antimonide Eu 7 Cu 44 Sb 23-δ [ Fm -3m, a = 17.4346(1)Å, δ = 0.5(1)] is reported. The compound forms a continuous substitutional solid solution with its Eu 7 Cu 44 As 23 archetype. The gradual substitution of Sb for As evokes partial disorder in the copper–pnictogen framework that becomes more pronounced with an increase of the Sb content and changes magnetic properties. Whereas Eu 7 Cu 44 As 23 is metallic ferromagnet below 17 K, Eu 7 Cu 44 Sb 23-δ shows paramagnetic behavior down to 1.8 K according to the magnetic measurements, while retaining metallic properties according to the DFT calculations. The origin of the disorder, the structure-property relationships, as well as prospects of further substitution in the anionic sublattice are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
221. One disorder out of two orders: Synthesis and crystal structures of cation-ordered PbNaF2NO3, anion-ordered Pb2OFNO3, and continuous disordered (Pb, Na)2(O,F)2-δNO3 solid solution with Sillén-derived structures.
- Author
-
Charkin, Dmitri O., Plokhikh, Igor V., Zaloga, Aleksandr N., Lobanov, Maxim V., and Kazakov, Sergey M.
- Subjects
- *
CHEMICAL synthesis , *CRYSTAL structure , *BISMUTH compounds , *HALIDES , *FLUORIDES - Abstract
Two new Sillén–like layered lead fluoride nitrates, PbNaF 2 NO 3 and Pb 2 OFNO 3 , have been prepared at 300 °C. PbNaF 2 NO 3 is a structural analog of alkaline earth – bismuth oxyhalides, BaBiO 2 X and SrBiO 2 X (X = Cl – I), but not the corresponding nitrates, SrBiO 2 NO 3 or BaBiO 2 NO 3 . Pb 2 OFNO 3 is analogous to the corresponding halides, Pb 2 OFX (X = Cl, Br, I). Both structures belong to orthorhombic symmetry and demonstrate Na/Pb and O/F ordering, respectively. A continuous solid solution is formed between PbNaF 2 NO 3 and Pb 2 OFNO 3 which demonstrates neither cation nor anion ordering; the structure of intermediate composition Pb 1.5 Na 0.5 F 1.5 O 0.5 NO 3 was refined in tetragonal symmetry and is indeed very close to that of PbBiO 2 NO 3 and CaBiO 2 NO 3 . In PbNaF 2 NO 3 , the O:F ratio may be varied to a slight extent, PbNaF 2-2y O yy NO 3 , which also breaks the Na – Pb cation ordering. Analogous fluoride halides could not be prepared. Structural analogies to lead, bismuth, and antimony oxyhalides are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
222. Effect of Transition Metal Substitution on the Structure and Properties of a Clathrate-Like Compound Eu7Cu44As23.
- Author
-
Plokhikh, Igor V., Charkin, Dmitri O., Verchenko, Valeriy Yu., Ignatyev, Ivan A., Kazakov, Sergey M., Sobolev, Alexey V., Presniakov, Igor A., Tsirlin, Alexander A., and Shevelkov, Andrei V.
- Subjects
- *
TRANSITION metals , *CLATHRATE compounds , *CRYSTAL structure , *EUROPIUM compounds synthesis , *FERROMAGNETIC materials - Abstract
A series of substitutional solid solutions—Eu7Cu44−xTxAs23 (T = Fe, Co, Ni)—based on a recently discovered clathrate-like compound (Eu7Cu44As23) were synthesized from the elements at 800 °C. Almost up to 50% of Cu can be substituted by Ni, resulting in a linear decrease of the cubic unit cell parameter from a = 16.6707(1) Å for the ternary compound to a = 16.3719(1) Å for the sample with the nominal composition Eu7Cu24Ni20As23. In contrast, Co and Fe can only substitute less than 20% of Cu. Crystal structures of six samples of different composition were refined from powder diffraction data. Despite very small differences in scattering powers of Cu, Ni, Co, and Fe, we were able to propose a reasonable model of dopant distribution over copper sites based on the trends in interatomic distances as well as on Mössbauer spectra for the iron-substituted compound Eu7Cu36Fe8As23. Ni doping increases the Curie temperature to 25 K with respect to the parent compound, which is ferromagnetically ordered below 17.5 K, whereas Fe doping suppresses the ferromagnetic ordering in the Eu sublattice. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
223. Synthesis and crystal structures of novel LaOAgS-type alkaline earth – Zinc, manganese, and cadmium fluoride pnictides.
- Author
-
Charkin, Dmitri O., Urmanov, Arthur V., Plokhikh, Igor V., Korshunov, Alexander D., Kuznetsov, Alexey N., and Kazakov, Sergey M.
- Subjects
- *
LANTHANUM compounds , *ALKALINE earth metals , *CRYSTAL structure , *ZINC , *MANGANESE , *CADMIUM - Abstract
Highlights: [•] Sight new alkaline earth – Mn, Zn, Cd fluoride pnictides were prepared. [•] All new compounds adopt the LaOAgS structure type. [•] Bond distances in their structures are transferable within 2–3%. [•] Very close similarities are observed in structural chemistry of LaOAgS- and HfCuSi2-type compounds of Mn, Cu, Zn, Ag, and Cd. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
224. Probable Mechanisms of Doxorubicin Antitumor Activity Enhancement by Ginsenoside Rh2.
- Author
-
Popov, Alexander, Klimovich, Anna, Styshova, Olga, Tsybulsky, Alexander, Hushpulian, Dmitry, Osipyants, Andrey, Khristichenko, Anna, Kazakov, Sergey, Ahuja, Manuj, Kaidery, Navneet, Thomas, Bobby, Tishkov, Vladimir, Brown, Abraham, Gazaryan, Irina, and Poloznikov, Andrey
- Subjects
- *
GINSENOSIDES , *ANTINEOPLASTIC agents , *DOXORUBICIN , *TUMOR growth , *CELL adhesion , *METASTASIS - Abstract
Ginsenoside Rh2 increases the efficacy of doxorubicin (DOX) treatment in murine models of solid and ascites Ehrlich's adenocarcinoma. In a solid tumor model (treatment commencing 7 days after inoculation), DOX + Rh2 co-treatment was significantly more efficacious than DOX alone. If treatment was started 24 h after inoculation, the inhibition of tumor growth of a solid tumor for the DOX + Rh2 co-treatment group was complete. Furthermore, survival in the ascites model was dramatically higher for the DOX + Rh2 co-treatment group than for DOX alone. Mechanisms underlying the combined DOX and Rh2 effects were studied in primary Ehrlich's adenocarcinoma-derived cells and healthy mice's splenocytes. Despite the previously established Rh2 pro-oxidant activity, DOX + Rh2 co-treatment revealed no increase in ROS compared to DOX treatment alone. However, DOX + Rh2 treatment was more effective in suppressing Ehrlich adenocarcinoma cell adhesion than either treatment alone. We hypothesize that the benefits of DOX + Rh2 combination treatment are due to the suppression of tumor cell attachment/invasion that might be effective in preventing metastatic spread of tumor cells. Ginsenoside Rh2 was found to be a modest activator in a Neh2-luc reporter assay, suggesting that Rh2 can activate the Nrf2-driven antioxidant program. Rh2-induced direct activation of Nrf2 might provide additional benefits by minimizing DOX toxicity towards non-cancerous cells. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
225. Structure and magnetic properties of a new anion-deficient perovskite Pb2Ba2BiFe4ScO13 with crystallographic shear structure.
- Author
-
Batuk, Maria, Tyablikov, Oleg A., Tsirlin, Alexander A., Kazakov, Sergey M., Rozova, Marina G., Pokholok, Konstantin V., Filimonov, Dmitry S., Antipov, Evgeny V., Abakumov, Artem M., and Hadermann, Joke
- Subjects
- *
LEAD compounds synthesis , *ANIONS , *PEROVSKITE , *CRYSTAL structure , *MAGNETIC properties of metals , *CRYSTALLOGRAPHY , *SOLID state chemistry - Abstract
Highlights: [•] Pb2Ba2BiFe4ScO13 was obtained by solid state synthesis. [•] Its structure was refined from combination of XPD and TEM. [•] It is a new member of the perovskite-related homologous series A n B n O3n−2 with n =5. [•] Pb2Ba2BiFe4ScO13 is antiferromagnetically ordered below T N ≈350K. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
226. Uranium substitution for tungsten in the Bi2WO6–Bi2UO6 system: Formation of a broad high-temperature solid solution
- Author
-
Charkin, Dmitri O., Lebedev, Dmitri N., Stefanovich, Sergey Yu., and Kazakov, Sergey M.
- Subjects
- *
SOLID solutions , *URANIUM compounds , *TUNGSTEN , *HOMOGENEITY , *BISMUTH compounds , *TUNGSTEN oxides , *URANIUM oxides , *MOLECULAR structure - Abstract
Abstract: Polythermic studies of Bi2WO6–Bi2UO6 system revealed existence of a broad Bi2W1−x U x O6 solid solution with the Aurivillius-type structure. Below 750 °C, the homogeneity area is narrow (x ≤ 0.12) but extends significantly at higher temperatures (up to ca. 75% Bi2UO6 at 1025 °C). The solid solution retains orthorhombic symmetry over the entire compositional range, but substitution of U for W results in significant lowering of second harmonic intensity and Curie point suggesting, at high substitution degrees, a very close approach to the archetypic body-centered tetragonal centrosymmetric structure. The known Bi2WO6-based solid solutions are discussed in terms of thermal stability, and a general geometrical explanation is suggested. Incorporation of large cations into the B perovskitic positions of [Bi2O2][An −1 Bn O3n+1] Aurivillius structures seems yet to be restricted by the n = 1 case. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
227. Electrochemical equilibria in copper/cryolite-alumina melt systems
- Author
-
Filatov, Alexander Yu., Borzenko, Marina I., Kuzminova, Zoya V., Vassiliev, Sergey Yu., Kazakov, Sergey M., Antipov, Evgeny V., and Lunin, Valerii V.
- Subjects
- *
ALUMINUM oxide , *ANALYTICAL chemistry , *SOLUTION (Chemistry) , *MIXTURES - Abstract
Temperature and cryolite ratio effects on copper redox potentials in alumina-cryolite melts are reported in relation to the prospects of metal-containing anodes for aluminum electrolysis. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
228. NaZr 2 (PO 4 ) 3 - a cubic langbeinite-type sodium-ion solid conductor.
- Author
-
Marshenya SN, Scherbakov AG, Dembitskiy AD, Golubnichiy AA, Trussov IA, Savina AA, Kazakov SM, Aksyonov DA, Antipov EV, and Fedotov SS
- Abstract
The synthesis of langbeinite-type phosphates with small cations such as Li
+ or Na+ via a high-temperature solid-state reaction is a challenging task due to the predominant formation of a related NaSICON-type phase. This work reports on the synthesis route, crystal structure, thermal behavior, and Na-conductive properties of the langbeinite-type NaZr2 (PO4 )3 prepared by a mechanochemically activated ion-exchange reaction between hydrothermally prepared NH4 Zr2 (PO4 )3 and NaNO3 . The crystal structure of NaZr2 (PO4 )3 is refined based on X-ray diffraction data and validated by Fourier-transformed infrared spectroscopy. NaZr2 (PO4 )3 is found to be stable up to 730 °C, undergoing a transformation into the NaSICON phase with further heating. Notably, in the 25-500 °C range, the material shows negative thermal expansion. The Na+ conductivity within the range of 50-225 °C amounts to 1.7 × 10-8 S cm-1 at 50 °C and 1 × 10-6 S cm-1 at 225 °C with an activation energy of 0.44 eV, accompanied by a sufficiently low (∼10-12 S cm-1 ) electronic conductivity. The bandgap of 4.44 eV and the electrochemical stability window covering the 1.39-4.18 V vs. Na/Na+ range are calculated using density functional theory. The obtained results open up opportunities for designing langbeinite-structured phosphates as potential solid electrolytes for Na-ion batteries.- Published
- 2024
- Full Text
- View/download PDF
229. Degradation Kinetics of Disulfide Cross-Linked Microgels: Real-Time Monitoring by Confocal Microscopy.
- Author
-
Mercer IG, Italiano AN, Gazaryan IG, Steiner AB, and Kazakov SV
- Abstract
Although biodegradable microgels represent a useful drug delivery system, questions remain regarding the kinetics of gel degradation and subsequent drug release. Spherical microgels (~Ø10-300 µm) were synthesized using an inverse suspension polymerization method. Specifically, acrylamide and acrylonitrile monomers were thermally co-polymerized with N , N '-bis(acryloyl)cystamine as a cross-linker with disulfide bridges. The kinetics and mechanism of degradation of these cross-linked, degradable, fluorescently labeled microgels (PAAm-AN-BAC-FA) were quantitatively studied under confocal microscopy at various concentrations of glutathione (reducing agent) ranging from 0.06 to 91.8 mM. It was found that polymer network degradation via the cleavage of disulfide bonds was accompanied by two overlapping processes: diffusion-driven swelling and dissolution-driven erosion. A slow increase in microgel size (swelling) resulted from partial de-cross-linking in the bulk of the microgel, whereas a faster decrease in fluorescence intensity (erosion) resulted from the complete cleavage of disulfide bonds and the release of uncleaved polymeric chains from the microgel immediate surface into the solution. Swelling and erosion exhibited distinct kinetics and characteristic times. Importantly, the dependence of kinetics on glutathione concentration for both swelling and erosion suggests that degradation would occur faster in cancer cells (higher concentration of reductants) than in normal cells (lower concentration of reductants), such that drug release profiles would be correspondingly different. A greater comprehension of microgel degradation kinetics would help in (i) predicting the drug release profiles for novel multifunctional drug delivery systems and (ii) using redox-sensitive degradable hydrogel particles to determine the concentrations of reducing agents either in vitro or in vivo.
- Published
- 2023
- Full Text
- View/download PDF
230. Structure-Activity Relationships and Transcriptomic Analysis of Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitors.
- Author
-
Poloznikov AA, Nikulin SV, Hushpulian DM, Khristichenko AY, Osipyants AI, Asachenko AF, Shurupova OV, Savin SS, Lee SH, Gaisina IN, Thatcher GRJ, Narciso A, Chang EP, Kazakov SV, Krucher N, Tishkov VI, Thomas B, and Gazaryan IG
- Abstract
To evaluate the differences in action of commercially available 2-oxoglutarate mimetics and "branched-tail" oxyquinoline inhibitors of hypoxia-inducible factor prolyl hydroxylase (HIF PHD), the inhibitors' IC
50 values in the activation of HIF1 ODD-luciferase reporter were selected for comparative transcriptomics. Structure-activity relationship and computer modeling for the oxyquinoline series of inhibitors led to the identification of novel inhibitors, which were an order of magnitude more active in the reporter assay than roxadustat and vadadustat. Unexpectedly, 2-methyl-substitution in the oxyquinoline core of the best HIF PHD inhibitor was found to be active in the reporter assay and almost equally effective in the pretreatment paradigm of the oxygen-glucose deprivation in vitro model. Comparative transcriptomic analysis of the signaling pathways induced by HIF PHD inhibitors showed high potency of the two novel oxyquinoline inhibitors (#4896-3249 and #5704-0720) at 2 μM concentrations matching the effect of 30 μM roxadustat and 500 μM dimethyl oxalyl glycine in inducing HIF1 and HIF2-linked pathways. The two oxyquinoline inhibitors exerted the same activation of HIF-triggered glycolytic pathways but opposite effects on signaling pathways linked to alternative substrates of HIF PHD 1 and 3, such as p53, NF-κB, and ATF4. This finding can be interpreted as the specificity of the 2-methyl-substitute variant for HIF PHD2.- Published
- 2022
- Full Text
- View/download PDF
231. HIF Prolyl Hydroxylase Inhibitors for COVID-19 Treatment: Pros and Cons.
- Author
-
Poloznikov AA, Nersisyan SA, Hushpulian DM, Kazakov EH, Tonevitsky AG, Kazakov SV, Vechorko VI, Nikulin SV, Makarova JA, and Gazaryan IG
- Abstract
The review analyzes the potential advantages and problems associated with using HIF prolyl hydroxylase inhibitors as a treatment for COVID-19. HIF prolyl hydroxylase inhibitors are known to boost endogenous erythropoietin (Epo) and activate erythropoiesis by stabilizing and activating the hypoxia inducible factor (HIF). Recombinant Epo treatment has anti-inflammatory and healing properties, and thus, very likely, will be beneficial for moderate to severe cases of COVID-19. However, HIF PHD inhibition may have a significantly broader effect, in addition to stimulating the endogenous Epo production. The analysis of HIF target genes reveals that some HIF-targets, such as furin, could play a negative role with respect to viral entry. On the other hand, HIF prolyl hydroxylase inhibitors counteract ferroptosis, the process recently implicated in vessel damage during the later stages of COVID-19. Therefore, HIF prolyl hydroxylase inhibitors may serve as a promising treatment of COVID-19 complications, but they are unlikely to aid in the prevention of the initial stages of infection., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Poloznikov, Nersisyan, Hushpulian, Kazakov, Tonevitsky, Kazakov, Vechorko, Nikulin, Makarova and Gazaryan.)
- Published
- 2021
- Full Text
- View/download PDF
232. Nickel - p-block metal mixed chalcogenides based on AuCu 3 -type fragments: iodine-assisted synthesis as a way of obtaining new structures.
- Author
-
Stroganova EA, Kazakov SM, Efimov NN, Khrustalev VN, Keilholz S, Götze A, Kohlmann H, and Kuznetsov AN
- Abstract
Two new mixed nickel-gallium chalcogenides, Ni9.39Ga2S2 and Ni5.80GaTe2, and a new mixed nickel-indium telluride, Ni5.78InTe2, have been synthesized by a high-temperature ampoule route with the addition of iodine, and characterized from single-crystal or powder diffraction data. They belong to the relatively uncommon Ni7-xMQ2/Ni10-xM2Q2 type of structures (M = Ge, Sn, Sb, In), and are built from p-block metal-centered nickel cuboctahedra, alternating along the c axis with defective Cu2Sb-type nickel-chalcogen ones. Both tellurium-containing compounds show a small degree of orthorhombic distortion with respect to the idealized tetragonal structure, only detectable in the powder diffraction data. No phase transition to the tetragonal structure was detected for Ni5.80GaTe2 by the in situ powder diffraction measurements from room temperature to 550 °C. DFT calculations show close relationships of electronic structures of these ternary compounds to their parent intermetallics, Ni3M (M = Ga, In). Metallic conductivity and paramagnetic properties are predicted for all three with the latter confirmed by magnetic measurements. The bonding patterns, investigated via the ELF topological analysis, show multi-centered nickel - p-block metal bonds in the AuCu3-type fragments and pairwise covalent interactions in the nickel-chalcogen fragments. Both Ni7-xMTe2 compounds showed no structural or compositional changes upon high-temperature mid-pressure hydrogenation.
- Published
- 2020
- Full Text
- View/download PDF
233. De novo mutations in FLNC leading to early-onset restrictive cardiomyopathy and congenital myopathy.
- Author
-
Kiselev A, Vaz R, Knyazeva A, Khudiakov A, Tarnovskaya S, Liu J, Sergushichev A, Kazakov S, Frishman D, Smolina N, Pervunina T, Jorholt J, Sjoberg G, Vershinina T, Rudenko D, Arner A, Sejersen T, Lindstrand A, and Kostareva A
- Subjects
- Adolescent, Cardiomyopathy, Restrictive physiopathology, Child, Preschool, Congenital Abnormalities physiopathology, DNA Mutational Analysis, Female, Humans, Infant, Infant, Newborn, Male, Muscular Diseases physiopathology, Mutation, Pedigree, Phenotype, Cardiomyopathy, Restrictive genetics, Congenital Abnormalities genetics, Filamins genetics, Muscular Diseases genetics
- Abstract
Mutations in FLNC for a long time are known in connection to neuromuscular disorders and only recently were described in association with various cardiomyopathies. Here, we report a new clinical phenotype of filaminopathy in four unrelated patients with early-onset restrictive cardiomyopathy (RCM) in combination with congenital myopathy due to FLNC mutations (NM_001458.4:c.3557C>T, p.A1186V, rs1114167361 in three probands and c.[3547G>C; 3548C>T], p.A1183L, rs1131692185 in one proband). In all cases, concurrent myopathy was confirmed by neurological examination, electromyography, and morphological studies. Three of the patients also presented with arthrogryposis. The pathogenicity of the described missense variants was verified by cellular and morphological studies and by in vivo modeling in zebrafish. Combination of in silico and experimental approaches revealed that FLNC missense variants localized in Ig-loop segments often lead to development of RCM. The described FLNC mutations associated with early-onset RCMP extend cardiac spectrum of filaminopathies and facilitate the differential diagnosis of restrictive cardiac phenotype associated with neuromuscular involvement in children., (© 2018 Wiley Periodicals, Inc.)
- Published
- 2018
- Full Text
- View/download PDF
234. Draft Genome Sequence of Coxiella burnetii Historical Strain Leningrad-2, Isolated from Blood of a Patient with Acute Q Fever in Saint Petersburg, Russia.
- Author
-
Freylikhman O, Kiselev A, Kazakov S, Sergushichev A, Panferova Y, Tokarevich N, and Kostareva A
- Abstract
This is the announcement of a draft genome sequence of Coxiella burnetii strain Leningrad-2, phase I. The strain, which is mildly virulent in infected guinea pigs, was isolated in 1957 from the blood of a patient with acute Q fever in Leningrad (now Saint Petersburg), Russia., (Copyright © 2018 Freylikhman et al.)
- Published
- 2018
- Full Text
- View/download PDF
235. Assemblathon 2: evaluating de novo methods of genome assembly in three vertebrate species.
- Author
-
Bradnam KR, Fass JN, Alexandrov A, Baranay P, Bechner M, Birol I, Boisvert S, Chapman JA, Chapuis G, Chikhi R, Chitsaz H, Chou WC, Corbeil J, Del Fabbro C, Docking TR, Durbin R, Earl D, Emrich S, Fedotov P, Fonseca NA, Ganapathy G, Gibbs RA, Gnerre S, Godzaridis E, Goldstein S, Haimel M, Hall G, Haussler D, Hiatt JB, Ho IY, Howard J, Hunt M, Jackman SD, Jaffe DB, Jarvis ED, Jiang H, Kazakov S, Kersey PJ, Kitzman JO, Knight JR, Koren S, Lam TW, Lavenier D, Laviolette F, Li Y, Li Z, Liu B, Liu Y, Luo R, Maccallum I, Macmanes MD, Maillet N, Melnikov S, Naquin D, Ning Z, Otto TD, Paten B, Paulo OS, Phillippy AM, Pina-Martins F, Place M, Przybylski D, Qin X, Qu C, Ribeiro FJ, Richards S, Rokhsar DS, Ruby JG, Scalabrin S, Schatz MC, Schwartz DC, Sergushichev A, Sharpe T, Shaw TI, Shendure J, Shi Y, Simpson JT, Song H, Tsarev F, Vezzi F, Vicedomini R, Vieira BM, Wang J, Worley KC, Yin S, Yiu SM, Yuan J, Zhang G, Zhang H, Zhou S, and Korf IF
- Abstract
Background: The process of generating raw genome sequence data continues to become cheaper, faster, and more accurate. However, assembly of such data into high-quality, finished genome sequences remains challenging. Many genome assembly tools are available, but they differ greatly in terms of their performance (speed, scalability, hardware requirements, acceptance of newer read technologies) and in their final output (composition of assembled sequence). More importantly, it remains largely unclear how to best assess the quality of assembled genome sequences. The Assemblathon competitions are intended to assess current state-of-the-art methods in genome assembly., Results: In Assemblathon 2, we provided a variety of sequence data to be assembled for three vertebrate species (a bird, a fish, and snake). This resulted in a total of 43 submitted assemblies from 21 participating teams. We evaluated these assemblies using a combination of optical map data, Fosmid sequences, and several statistical methods. From over 100 different metrics, we chose ten key measures by which to assess the overall quality of the assemblies., Conclusions: Many current genome assemblers produced useful assemblies, containing a significant representation of their genes and overall genome structure. However, the high degree of variability between the entries suggests that there is still much room for improvement in the field of genome assembly and that approaches which work well in assembling the genome of one species may not necessarily work well for another.
- Published
- 2013
- Full Text
- View/download PDF
236. Physicochemical characterization of natural ionic Microreservoirs: Bacillus subtilis dormant spores.
- Author
-
Kazakov S, Bonvouloir E, and Gazaryan I
- Subjects
- Cell Membrane metabolism, Chemistry, Physical methods, Ions, Kinetics, Microchemistry, Bacillus subtilis cytology, Cell Membrane Permeability, Potentiometry, Protons, Spores, Bacterial metabolism
- Abstract
The kinetics of proton exchange between dormant spores and aqueous environment was examined by time-resolved micropotentiometry, the method we recently introduced for hydrogel particles of micro- and nanometer diameter (J. Phys. Chem. B 2006, 110, 15107). In this work, the method was applied to the suspensions of dormant Bacillus subtilis spore of different concentrations to show that proton uptake kinetics was a multistep process involving a number of successively approximately 10-fold slower steps of proton penetration into the bulk and their binding to the ionizable groups within different layers of a spore structure. By analyzing the proton equilibrium binding to ionizable groups inside a spore, it was shown that each Bacillus subtilis spore behaves like almost infinite ionic reservoir capable of accumulating billions of protons (N approximately 2 x 10(10) per spore). The obtained pK(a) value of 4.7 for the spores studied is the first quantitative indication on carboxyl groups as the major ionizable groups fixed in a spore matrix. In general, proton equilibrium binding within the spore matrix obeys the fundamental law of the Langmuir isotherm. The proton binding to the ionizable groups slows down the free proton diffusion within a spore, but this effect is substantially weakened by increasing the initial concentration of protons added. On the basis of the diffusion time analysis, it was found that the effective diffusion coefficient for hydrogen ions within the spore core can be up to 3 orders of magnitude lower than that within the coats and cortex. We speculate that the spore inner membrane which separates core from cortex and coats in a dormant spore is a major permeability barrier for protons to penetrate into a lockbox of the genetic information (core).
- Published
- 2008
- Full Text
- View/download PDF
237. Ion concentration of external solution as a characteristic of micro- and nanogel ionic reservoirs.
- Author
-
Kazakov S, Kaholek M, Gazaryan I, Krasnikov B, Miller K, and Levon K
- Subjects
- Hydrogen-Ion Concentration, Ions chemistry, Kinetics, Models, Chemical, Osmolar Concentration, Particle Size, Polyvinyls, Sensitivity and Specificity, Solutions chemistry, Time Factors, Hydrogels chemistry, Imidazoles chemistry, Vinyl Compounds chemistry
- Abstract
Ion-sensitive hydrogel is regarded as an ionic reservoir, i.e., a system capable of changing the external pH or ionic strength by accumulating or releasing ions. The concept of a hydrogel ionic reservoir was demonstrated for hydrogel particles of three different size ranges: macrogel (1000-6000 microm), microgel (approximately 20-200 microm), and nanogel (approximately 0.2 microm). Ion sensitivity of poly(N-isopropylacrylamide-co-1-vinylimidazole) (PNIPA-VI) microgels with imidazolyl (ionizable) groups was confirmed by the pH dependence of their volume, while nanogels were characterized by dynamic light scattering. On the contrary, the volume of poly(N-isopropylacrylamide) (PNIPA) microgels without ionizable groups was pH independent in the whole range of pH from 10 to 2. Four distinct regions of pH-behavior were observed for PNIPA-VI hydrogel micro- and nanoparticles using potentiometric titration of their suspensions. Time-resolved measurements of ion concentrations in the suspension of hydrogel particles revealed a substantial difference in kinetics of pH equilibration for (i) ion-sensitive hydrogels (PNIPA-VI) vs hydrogels without ionizable groups (PNIPA) and (ii) PNIPA-VI hydrogels of different sizes. On the basis of the experimental observations, a two-step mechanism affecting the kinetics of proton uptake into the hydrogel particles with ionizable groups was proposed: (1) fast binding of ions to the immediate surface of each particle and (2) a slower successive diffusion of bound sites into the next inner layer of polymer network. In accord with the mechanism proposed, a quasi-chemical kinetic model of pH relaxation to equilibrium was developed to fit the experimental data for the time course of proton uptake by macro-, micro-, and nanogels into two exponentials with the characteristic times of tau(1) and tau(2). We believe the same kinetic model will be pertinent to describe phenomenological and molecular mechanisms controlling proton transport in/out bacteria, cells, organelles, drug delivery vehicles, and other natural or artificial multifunctional ionic containers. The approach can be easily extended for the other ions (e.g., Na(+), K(+), and Ca(2+)).
- Published
- 2006
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.