Positronium formation in porous materials for antihydrogen production

International Nuclear Information System (INIS)

Ferragut, R; Calloni, A; Dupasquier, A; Consolati, G; Giammarchi, M G; Quasso, F; Trezzi, D; Egger, W; Ravelli, L; Petkov, M P; Jones, S M; Wang, B; Yaghi, O M; Jasinska, B; Chiodini, N; Paleari, A

2010-01-01

Positronium (Ps) formation measurements in several porous materials as: Vycor, germanate Xerogel, Metal-Organic Frameworks MOF-177 and Aerogel with two densities (20 and 150 mg/cm 3 ), were performed by means of a variable energy positron beam provided with a Ge detector and a positron lifetime spectrometer. An efficient formation of cooled Ps atoms is a requisite for the production of antihydrogen, with the aim of a direct measurement of the Earth gravitational acceleration g of antimatter, which is a primary scientific goal of AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy). Porous materials are necessary to form a high yield of Ps atoms as well as to cool Ps through collisions with the inner walls of the pores. The different materials were characterized and produce Ps into the pores. Lifetime measurements give an estimation of the typical pores dimension of the substances. A comparative study of the positron lifetime and the Ps fraction values in the above mentioned materials indicates that silica Aerogel, with the appropriate density, is an excellent candidate for an efficient formation of cold Ps atoms for the AEGIS project.

Antihydrogen Beams

Science.gov (United States)

Yamazaki, Yasunori; Doser, Michael; Pérez, Patrice

2018-03-01

Why does our universe consist purely of matter, even though the same amount of antimatter and matter should have been produced at the moment of the Big Bang 13.8 billion years ago? One of the most potentially fruitful approaches to address the mystery is to study the properties of antihydrogen and antiprotons. Because they are both stable, we can in principle make measurement precision as high as we need to see differences between these antimatter systems and their matter counterparts, i.e. hydrogen and protons. This is the goal of cold antihydrogen research. To study a fundamental symmetry-charge, parity, and time reversal (CPT) symmetry-which should lead to identical spectra in hydrogen and antihydrogen, as well as the weak equivalence principle (WEP), cold antihydrogen research seeks any discrepancies between matter and antimatter, which might also offer clues to the missing antimatter mystery. Precision tests of CPT have already been carried out in other systems, but antihydrogen spectroscopy offers the hope of reaching even higher sensitivity to violations of CPT. Meanwhile, utilizing the Earth and antihydrogen atoms as an experimental system, the WEP predicts a gravitational interaction between matter and antimatter that is identical to that between any two matter objects. The WEP has been tested to very high precision for a range of material compositions, but no such precision test using antimatter has yet been carried out, offering hope of a telltale inconsistency between matter and antimatter. In this Discovery book, we invite you to visit the frontiers of cold antimatter research, focusing on new technologies to form beams of antihydrogen atoms and antihydrogen ions, and new ways of interrogating the properties of antimatter.

Slow Antihydrogen

International Nuclear Information System (INIS)

Gabrielse, G.; Speck, A.; Storry, C.H.; Le Sage, D.; Guise, N.; Larochelle, P.C.; Grzonka, D.; Oelert, W.; Schepers, G.; Sefzick, T.; Pittner, H.; Herrmann, M.; Walz, J.; Haensch, T.W.; Comeau, D.; Hessels, E.A.

2004-01-01

Slow antihydrogen is now produced by two different production methods. In Method I, large numbers of H atoms are produced during positron-cooling of antiprotons within a nested Penning trap. In a just-demonstrated Method II, lasers control the production of antihydrogen atoms via charge exchange collisions. Field ionization detection makes it possible to probe the internal structure of the antihydrogen atoms being produced - most recently revealing atoms that are too tightly bound to be well described by the guiding center atom approximation. The speed of antihydrogen atoms has recently been measured for the first time. After the requested overview, the recent developments are surveyed

Antihydrogen synthesis: a progress report

International Nuclear Information System (INIS)

Deutch, B.I.

1992-01-01

The main suggested routes for atomic antihydrogen (anti H) formation will be reviewed in a pedestrian fashion. These are the following reactions: (i) anti p + e + + nhv → anti H + (n+1)hv, (ii) anti p + Ps → anti H + e - , and (iii) anti p + 2e + → anti H + e + . The present status of the projects related to these reactions, as well as the projects' experimental scope, will also be discussed or referred to. Some speculations will be made regarding the physics that can be yielded by an antihydrogen probe. (orig.)

Trapped antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Butler, E., E-mail: eoin.butler@cern.ch [CERN, Physics Department (Switzerland); Andresen, G. B. [Aarhus University, Department of Physics and Astronomy (Denmark); Ashkezari, M. D. [Simon Fraser University, Department of Physics (Canada); Baquero-Ruiz, M. [University of California, Department of Physics (United States); Bertsche, W. [Swansea University, Department of Physics (United Kingdom); Bowe, P. D. [Aarhus University, Department of Physics and Astronomy (Denmark); Cesar, C. L. [Universidade Federal do Rio de Janeiro, Instituto de Fisica (Brazil); Chapman, S. [University of California, Department of Physics (United States); Charlton, M.; Deller, A.; Eriksson, S. [Swansea University, Department of Physics (United Kingdom); Fajans, J. [University of California, Department of Physics (United States); Friesen, T.; Fujiwara, M. C. [University of Calgary, Department of Physics and Astronomy (Canada); Gill, D. R. [TRIUMF (Canada); Gutierrez, A. [University of British Columbia, Department of Physics and Astronomy (Canada); Hangst, J. S. [Aarhus University, Department of Physics and Astronomy (Denmark); Hardy, W. N. [University of British Columbia, Department of Physics and Astronomy (Canada); Hayden, M. E. [Simon Fraser University, Department of Physics (Canada); Humphries, A. J. [Swansea University, Department of Physics (United Kingdom); Collaboration: ALPHA Collaboration; and others

2012-12-15

Precision spectroscopic comparison of hydrogen and antihydrogen holds the promise of a sensitive test of the Charge-Parity-Time theorem and matter-antimatter equivalence. The clearest path towards realising this goal is to hold a sample of antihydrogen in an atomic trap for interrogation by electromagnetic radiation. Achieving this poses a huge experimental challenge, as state-of-the-art magnetic-minimum atom traps have well depths of only {approx}1 T ({approx}0.5 K for ground state antihydrogen atoms). The atoms annihilate on contact with matter and must be 'born' inside the magnetic trap with low kinetic energies. At the ALPHA experiment, antihydrogen atoms are produced from antiprotons and positrons stored in the form of non-neutral plasmas, where the typical electrostatic potential energy per particle is on the order of electronvolts, more than 10{sup 4} times the maximum trappable kinetic energy. In November 2010, ALPHA published the observation of 38 antiproton annihilations due to antihydrogen atoms that had been trapped for at least 172 ms and then released-the first instance of a purely antimatter atomic system confined for any length of time (Andresen et al., Nature 468:673, 2010). We present a description of the main components of the ALPHA traps and detectors that were key to realising this result. We discuss how the antihydrogen atoms were identified and how they were discriminated from the background processes. Since the results published in Andresen et al. (Nature 468:673, 2010), refinements in the antihydrogen production technique have allowed many more antihydrogen atoms to be trapped, and held for much longer times. We have identified antihydrogen atoms that have been trapped for at least 1,000 s in the apparatus (Andresen et al., Nature Physics 7:558, 2011). This is more than sufficient time to interrogate the atoms spectroscopically, as well as to ensure that they have relaxed to their ground state.

Antihydrogen beams

CERN Document Server

Yamazaki, Yasunori; Pérez, Patrice

2018-01-01

Why does our universe consist purely of matter, even though the same amount of antimatter and matter should have been produced at the moment of the Big Bang 13.8 billion years ago? One of the most potentially fruitful approaches to address the mystery is to study the properties of antihydrogen and antiprotons. Because they are both stable, we can in principle make measurement precision as high as we need to see differences between these antimatter systems and their matter counterparts, i.e. hydrogen and protons. This is the goal of cold antihydrogen research. To study a fundamental symmetry—charge, parity, and time reversal (CPT) symmetry—which should lead to identical spectra in hydrogen and antihydrogen, as well as the weak equivalence principle (WEP), cold antihydrogen research seeks any discrepancies between matter and antimatter, which might also offer clues to the missing antimatter mystery. Precision tests of CPT have already been carried out in other systems, but antihydrogen spectroscopy offers t...

Trapped antihydrogen

CERN Document Server

Andresen, G B; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jonsell, S; Jørgensen, L V; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Seif el Nasr, S; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

2010-01-01

Antimatter was first predicted in 1931, by Dirac. Work with highenergy antiparticles is now commonplace, and anti-electrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the bound state of an antiproton and a positron, has been produced at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature’s fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 1014 for the frequency of the 1s-to-2s transition), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen could also be used to study the gravitational be...

Trapped antihydrogen

CERN Document Server

Butler, E; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jonsell, S; Jørgensen, L V; Kemp, S L; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Seif el Nasr, S; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki,Y

2012-01-01

Precision spectroscopic comparison of hydrogen and antihydrogen holds the promise of a sensitive test of the Charge-Parity-Time theorem and matter-antimatter equivalence. The clearest path towards realising this goal is to hold a sample of antihydrogen in an atomic trap for interrogation by electromagnetic radiation. Achieving this poses a huge experimental challenge, as state-of-the-art magnetic-minimum atom traps have well depths of only ∼1 T (∼0.5 K for ground state antihydrogen atoms). The atoms annihilate on contact with matter and must be ‘born’ inside the magnetic trap with low kinetic energies. At the ALPHA experiment, antihydrogen atoms are produced from antiprotons and positrons stored in the form of non-neutral plasmas, where the typical electrostatic potential energy per particle is on the order of electronvolts, more than 104 times the maximum trappable kinetic energy. In November 2010, ALPHA published the observation of 38 antiproton annihilations due to antihydrogen atoms that had been ...

AEgIS at ELENA: outlook for physics with a pulsed cold antihydrogen beam.

Science.gov (United States)

Doser, M; Aghion, S; Amsler, C; Bonomi, G; Brusa, R S; Caccia, M; Caravita, R; Castelli, F; Cerchiari, G; Comparat, D; Consolati, G; Demetrio, A; Di Noto, L; Evans, C; Fanì, M; Ferragut, R; Fesel, J; Fontana, A; Gerber, S; Giammarchi, M; Gligorova, A; Guatieri, F; Haider, S; Hinterberger, A; Holmestad, H; Kellerbauer, A; Khalidova, O; Krasnický, D; Lagomarsino, V; Lansonneur, P; Lebrun, P; Malbrunot, C; Mariazzi, S; Marton, J; Matveev, V; Mazzotta, Z; Müller, S R; Nebbia, G; Nedelec, P; Oberthaler, M; Pacifico, N; Pagano, D; Penasa, L; Petracek, V; Prelz, F; Prevedelli, M; Rienaecker, B; Robert, J; Røhne, O M; Rotondi, A; Sandaker, H; Santoro, R; Smestad, L; Sorrentino, F; Testera, G; Tietje, I C; Widmann, E; Yzombard, P; Zimmer, C; Zmeskal, J; Zurlo, N

2018-03-28

The efficient production of cold antihydrogen atoms in particle traps at CERN's Antiproton Decelerator has opened up the possibility of performing direct measurements of the Earth's gravitational acceleration on purely antimatter bodies. The goal of the AEgIS collaboration is to measure the value of g for antimatter using a pulsed source of cold antihydrogen and a Moiré deflectometer/Talbot-Lau interferometer. The same antihydrogen beam is also very well suited to measuring precisely the ground-state hyperfine splitting of the anti-atom. The antihydrogen formation mechanism chosen by AEgIS is resonant charge exchange between cold antiprotons and Rydberg positronium. A series of technical developments regarding positrons and positronium (Ps formation in a dedicated room-temperature target, spectroscopy of the n =1-3 and n =3-15 transitions in Ps, Ps formation in a target at 10 K inside the 1 T magnetic field of the experiment) as well as antiprotons (high-efficiency trapping of [Formula: see text], radial compression to sub-millimetre radii of mixed [Formula: see text] plasmas in 1 T field, high-efficiency transfer of [Formula: see text] to the antihydrogen production trap using an in-flight launch and recapture procedure) were successfully implemented. Two further critical steps that are germane mainly to charge exchange formation of antihydrogen-cooling of antiprotons and formation of a beam of antihydrogen-are being addressed in parallel. The coming of ELENA will allow, in the very near future, the number of trappable antiprotons to be increased by more than a factor of 50. For the antihydrogen production scheme chosen by AEgIS, this will be reflected in a corresponding increase of produced antihydrogen atoms, leading to a significant reduction of measurement times and providing a path towards high-precision measurements.This article is part of the Theo Murphy meeting issue 'Antiproton physics in the ELENA era'. © 2018 The Author(s).

Calculation of the positronium formation differential cross section for collision of electron with anti-hydrogen atoms

International Nuclear Information System (INIS)

Ghanbari Adivi, E.; Kanjuri, F.; Bolorizadeh, M.

2006-01-01

The positronium formation differential cross sections in collision of the high-energy but non-relativistic electrons with anti-hydrogen atoms are calculated by using the three-body Faddeev-Watson-Lovelace formalism. In a second-order approximation, the inter-nuclear and nuclear-electronic partial amplitudes therein the Faddeev-Watson series are calculated, analytically, in the range of 0-180 degrees of the scattering angles. The presence of the T homas peak a t 45 d egree i s investigated. The results are discussed for 1 and 10 keV impact energies and for electron transition from anti-hydrogen ground state into the different states therein the K-, L- and M- shells of the positronium atoms.

Towards trapped antihydrogen

CERN Document Server

Jorgensen, L V; Bertsche, W; Boston, A; Bowe, P D; Cesar, C L; Chapman, S; Charlton, M; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D R; Hangst, J S; Hayano, R S; Hydomako, R; Jenkins, M J; Kurchaninov, L; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Page, R D; Povilus, A; Robicheaux, F; Sarid, E; Silveira, D M; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

2008-01-01

Substantial progress has been made in the last few years in the nascent field of antihydrogen physics. The next big step forward is expected to be the trapping of the formed antihydrogen atoms using a magnetic multipole trap. ALPHA is a new international project that started to take data in 2006 at CERN’s Antiproton Decelerator facility. The primary goal of ALPHA is stable trapping of cold antihydrogen atoms to facilitate measurements of its properties. We discuss the status of the ALPHA project and the prospects for antihydrogen trapping.

Antihydrogen Production and Precision Experiments The ATHENA Collaboration

CERN Multimedia

Filippini, V

2002-01-01

The ATHENA (AnTiHydrogEN Apparatus) experiment has the goal of producing slow antihydrogen atoms and comparing their physical properties to those of hydrogen. For example, the measurement of the 1S-2S transition offers the possibility for comparing hydrogen and antihydrogen to a precision of 1 part in 10$^{15}$, owing to the long lifetime of the metastable 2S state (122 msec). This would be the most precise test of CPT invariance in the lepton and baryon sector. The first phase of the experiment, which has been installed and commissioned at the Antiproton Decelerator (AD) - is devoted to the study of antihydrogen production. For this purpose, about 10$^{5}$ antiprotons (p=100 MeV/c ) are trapped and cooled to milli-eV energies. Independently, about 10$^{8}$ low energy positrons per minute are collected in the positron accumulator, using a Na-22 source (2 GBq). Formation of antihydrogen will take place in the recombination region, where the antiproton cloud is made to interact with the dense positron plasma tr...

The Fermilab antihydrogen program

CERN Document Server

Mandelkern, M A

1999-01-01

The antihydrogen atom, the bound state of an antiproton and a positron, is the antiparticle of the hydrogen stem. Until very recently no antimatter atoms had been observed. Experiments at CERN and Fermilab have reported observations of small amounts of antihydrogen but are in sharp disagreement. At Fermilab we have produced a background-free sample of 66 atoms. CPT invariance predicts that the spectrum and the lifetimes of antihydrogen states are identical to those of hydrogen. This fundamental symmetry has not been tested in atoms. Experiments for the further study of antihydrogen are planned for both laboratories. At CERN a new antiproton accumulator is expected to facilitate the trapping of cold antihydrogen, followed by high precision spectroscopic measurements. At Fermilab an interferometric technique analogous to measurement of the K/sub S/K/sub L/ mass difference will be used to determine the n =2 antihydrogen spectrum using a beam of high momentum antihydrogen atoms. (11 refs).

Towards Antihydrogen Confinement with the ALPHA Antihydrogen Trap

CERN Document Server

Fujiwara, M.C.; Bertsche, W.; Boston, A.; Bowe, P.D.; Cesar, C.L.; Chapman, S.; Charlton, M.; Chartier, M.; Deutsch, A.; Fajans, J.; Funakoshi, R.; Gill, D.R.; Gomberoff, K.; Hangst, J.S.; Hardy, W.N.; Hayano, R.S.; Hydomako, R.; Jenkins, M.J.; Jorgensen, L.V.; Kurchaninov, L.; Madsen, N.; Nolan, P.; Olchanski, K.; Olin, A.; Page, R.D.; Povilus, A.; Robicheaux, F.; Sarid, E.; Silveira, D.M.; Storey, J.W.; Thompson, R.I.; van der Werf, D.P.; Wurtele, J.S.; Yamazaki, Y.

2006-01-01

ALPHA is an international project that has recently begun experimentation at CERN's Antiproton Decelerator (AD) facility. The primary goal of ALPHA is stable trapping of cold antihydrogen atoms with the ultimate goal of precise spectroscopic comparisons with hydrogen. We discuss the status of the ALPHA project and the prospects for antihydrogen trapping.

Positron cross-field transport due to quasibound states of antihydrogen

International Nuclear Information System (INIS)

Ahat, Y.; Correa, C.E.; Ordonez, C.A.

2007-01-01

Within the past few years, experiments have been reported in which antiprotons produced at the CERN Antiproton Decelerator facility were slowed, trapped in nested Penning traps and made to interact with a positron plasma such that antihydrogen was formed. Classical trajectory simulations of the interactions between the antiprotons and positrons have been reported to indicate that positive-energy, quasibound states of antihydrogen can form at a rate that exceeds the rate of formation of stable Rydberg states. The formation of quasibound states may affect the rate of diffusion of positrons across the magnetic field that confines them in the nested Penning trap. Simulations indicate that a binary interaction associated with the formation and disintegration of a quasibound state can cause a shift of the positron's guiding center that is much larger than the positron cyclotron radius before the interaction. A theory is presented that describes positron cross-magnetic-field diffusion due to quasibound states of antihydrogen

Confinement of antihydrogen for 1000 seconds

CERN Document Server

Andresen, G B; Baquero-Ruiz, M; Bertsche, W; Butler, E; Cesar, C L; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jonsell, S; Kemp, S; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

2011-01-01

Atoms made of a particle and an antiparticle are unstable, usually surviving less than a microsecond. Antihydrogen, made entirely of antiparticles, is believed to be stable, and it is this longevity that holds the promise of precision studies of matter-antimatter symmetry. We have recently demonstrated trapping of antihydrogen atoms by releasing them after a confinement time of 172 ms. A critical question for future studies is: how long can anti-atoms be trapped? Here we report the observation of anti-atom confinement for 1000 s, extending our earlier results by nearly four orders of magnitude. Our calculations indicate that most of the trapped anti-atoms reach the ground state. Further, we report the first measurement of the energy distribution of trapped antihydrogen which, coupled with detailed comparisons with simulations, provides a key tool for the systematic investigation of trapping dynamics. These advances open up a range of experimental possibilities, including precision studies of CPT symmetry and ...

ATRAP - Progress Towards Trapped Antihydrogen

International Nuclear Information System (INIS)

Grzonka, D.; Goldenbaum, F.; Oelert, W.; Sefzick, T.; Zhang, Z.; Comeau, D.; Hessels, E.A.; Storry, C.H.; Gabrielse, G.; Larochelle, P.; Lesage, D.; Levitt, B.; Speck, A.; Haensch, T.W.; Pittner, H.; Walz, J.

2005-01-01

The ATRAP experiment at the CERN antiproton decelerator AD aims for a test of the CPT invariance by a high precision comparison of the 1s-2s transition in the hydrogen and the antihydrogen atom.Antihydrogen production is routinely operated at ATRAP and detailed studies have been performed in order to optimize the production efficiency of useful antihydrogen.For high precision measurements of atomic transitions cold antihydrogen in the ground state is required which must be trapped due to the low number of available antihydrogen atoms compared to the cold hydrogen beam used for hydrogen spectroscopy. To ensure a reasonable antihydrogen trapping efficiency a magnetic trap has to be superposed the nested Penning trap. First trapping tests of charged particles within a combined magnetic/Penning trap have started at ATRAP

ATRAP Progress Towards Trapped Antihydrogen

CERN Document Server

Grzonka, D; Gabrielse, G; Goldenbaum, F; Hänsch, T W; Hessels, E A; Larochelle, P; Le Sage, D; Levitt, B; Oelert, W; Pittner, H; Sefzick, T; Speck, A; Storry, C H; Walz, J; Zhang, Z

2005-01-01

The ATRAP experiment at the CERN antiproton decelerator AD aims for a test of the CPT invariance by a high precision comparison of the 1s‐2s transition in the hydrogen and the antihydrogen atom. Antihydrogen production is routinely operated at ATRAP and detailed studies have been performed in order to optimize the production efficiency of useful antihydrogen. For high precision measurements of atomic transitions cold antihydrogen in the ground state is required which must be trapped due to the low number of available antihydrogen atoms compared to the cold hydrogen beam used for hydrogen spectroscopy. To ensure a reasonable antihydrogen trapping efficiency a magnetic trap has to be superposed the nested Penning trap. First trapping tests of charged particles within a combined magnetic/Penning trap have started at ATRAP.

Search For Trapped Antihydrogen

CERN Document Server

Andresen, Gorm B.; Baquero-Ruiz, Marcelo; Bertsche, William; Bowe, Paul D.; Bray, Crystal C.; Butler, Eoin; Cesar, Claudio L.; Chapman, Steven; Charlton, Michael; Fajans, Joel; Friesen, Tim; Fujiwara, Makoto C.; Gill, David R.; Hangst, Jeffrey S.; Hardy, Walter N.; Hayano, Ryugo S.; Hayden, Michael E.; Humphries, Andrew J.; Hydomako, Richard; Jonsell, Svante; Jorgensen, Lars V.; Kurchaninov, Lenoid; Lambo, Ricardo; Madsen, Niels; Menary, Scott; Nolan, Paul; Olchanski, Konstantin; Olin, Art; Povilus, Alexander; Pusa, Petteri; Robicheaux, Francis; Sarid, Eli; Nasr, Sarah Seif El; Silveira, Daniel M.; So, Chukman; Storey, James W.; Thompson, Robert I.; van der Werf, Dirk P.; Wilding, Dean; Wurtele, Jonathan S.; Yamazaki, Yasunori

2011-01-01

We present the results of an experiment to search for trapped antihydrogen atoms with the ALPHA antihydrogen trap at the CERN Antiproton Decelerator. Sensitive diagnostics of the temperatures, sizes, and densities of the trapped antiproton and positron plasmas have been developed, which in turn permitted development of techniques to precisely and reproducibly control the initial experimental parameters. The use of a position-sensitive annihilation vertex detector, together with the capability of controllably quenching the superconducting magnetic minimum trap, enabled us to carry out a high-sensitivity and low-background search for trapped synthesised antihydrogen atoms. We aim to identify the annihilations of antihydrogen atoms held for at least 130 ms in the trap before being released over ~30 ms. After a three-week experimental run in 2009 involving mixing of 10^7 antiprotons with 1.3 10^9 positrons to produce 6 10^5 antihydrogen atoms, we have identified six antiproton annihilation events that are consist...

Antihydrogen detection in ALPHA

Energy Technology Data Exchange (ETDEWEB)

Hydomako, Richard, E-mail: rhydomako@phas.ucalgary.ca [University of Calgary, Department of Physics and Astronomy (Canada); Bruun Andresen, Gorm [Aarhus University, Department of Physics and Astronomy (Denmark); Ashkezari, Mohammad Dehghani [Simon Fraser University, Department of Physics (Canada); Baquero-Ruiz, Marcelo [University of California, Department of Physics (United States); Bertsche, William [Swansea University, Department of Physics (United Kingdom); Butler, Eoin [CERN, European Laboratory for Particle Physics (Switzerland); Bowe, Paul David [Aarhus University, Department of Physics and Astronomy (Denmark); Cesar, Claudo Lenz [Universidade Federal do Rio de Janeiro, Instituto de Fsica (Brazil); Chapman, Steve [University of California, Department of Physics (United States); Charlton, Michael [Swansea University, Department of Physics (United Kingdom); Fajans, Joel [University of California, Department of Physics (United States); Friesen, Tim; Fujiwara, Makoto C. [University of Calgary, Department of Physics and Astronomy (Canada); Gill, David Russell [TRIUMF (Canada); Hangst, Jeffrey Scott [Aarhus University, Department of Physics and Astronomy (Denmark); Hardy, Walter Newbold [University of British Columbia, Department of Physics and Astronomy (Canada); Hayano, Ryugo S. [University of Tokyo, Department of Physics (Japan); Hayden, Michael Edward [Simon Fraser University, Department of Physics (Canada); Humphries, Andrew James [Swansea University, Department of Physics (United Kingdom); Jonsell, Svante [Stockholm University, Fysikum (Sweden); Collaboration: ALPHA Collaboration; and others

2012-12-15

The ALPHA project is an international collaboration, based at CERN, with the experimental goal of performing precision spectroscopic measurements on antihydrogen. As part of this endeavor, the ALPHA experiment includes a silicon tracking detector. This detector consists of a three-layer array of silicon modules surrounding the antihydrogen trapping region of the ALPHA apparatus. Using this device, the antihydrogen annihilation position can be determined with a spatial resolution of better than 5 mm. Knowledge of the annihilation distribution was a critical component in the recently successful antihydrogen trapping effort. This paper will describe the methods used to reconstruct annihilation events in the ALPHA detector. Particular attention will be given to the description of the background rejection criteria.

ATRAP on the way to trapped Antihydrogen

CERN Document Server

Grzonka, D; Gabrielse, G; Goldenbaum, F; Hänsch, T W; Hessels, E A; Larochelle, P; Le Sage, D; Levitt, B; Oelert, W; Pittner, H; Sefzick, T; Speck, A; Storry, C H; Walz, J; Zhang, Z

2005-01-01

The ATRAP experiment at the CERN antiproton decelerator AD aims for a test of the CPT invariance by a high precision comparison of the 1s‐2s transition in the hydrogen and the antihydrogen atom. Antihydrogen production is routinely operated at ATRAP and detailed studies have been performed in order to optimize the production efficiency of useful antihydrogen. The shape parameters of the antiproton and positron clouds, the n‐state distribution of the produced Rydberg antihydrogen atoms and the antihydrogen velocity have been studied. Furthermore an alternative method of laser controlled antihydrogen production was successfully applied. For high precision measurements of atomic transitions cold antihydrogen in the ground state is required which must be trapped due to the low number of available antihydrogen atoms compared to the cold hydrogen beam used for hydrogen spectroscopy. To ensure a reasonable antihydrogen trapping efficiency a magnetic trap has to be superposed the nested Penning trap. First trappi...

Alpha Antihydrogen Experiment

CERN Document Server

Fujiwara, M C; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bray, C C; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Cesar, C L; Fajans, J; Friesen, T; Gill, D R; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jonsell, S; Kurchaninov, L; Lambo, R; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wilding, D; Wurtele, J S; Yamazaki, Y

2011-01-01

ALPHA is an experiment at CERN, whose ultimate goal is to perform a precise test of CPT symmetry with trapped antihydrogen atoms. After reviewing the motivations, we discuss our recent progress toward the initial goal of stable trapping of antihydrogen, with some emphasis on particle detection techniques.

Fundamental Physics with Antihydrogen

Science.gov (United States)

Hangst, J. S.

Antihydrogen—the antimatter equivalent of the hydrogen atom—is of fundamental interest as a test bed for universal symmetries—such as CPT and the Weak Equivalence Principle for gravitation. Invariance under CPT requires that hydrogen and antihydrogen have the same spectrum. Antimatter is of course intriguing because of the observed baryon asymmetry in the universe—currently unexplained by the Standard Model. At the CERN Antiproton Decelerator (AD) [1], several groups have been working diligently since 1999 to produce, trap, and study the structure and behaviour of the antihydrogen atom. One of the main thrusts of the AD experimental program is to apply precision techniques from atomic physics to the study of antimatter. Such experiments complement the high-energy searches for physics beyond the Standard Model. Antihydrogen is the only atom of antimatter to be produced in the laboratory. This is not so unfortunate, as its matter equivalent, hydrogen, is one of the most well-understood and accurately measured systems in all of physics. It is thus very compelling to undertake experimental examinations of the structure of antihydrogen. As experimental spectroscopy of antihydrogen has yet to begin in earnest, I will give here a brief introduction to some of the ion and atom trap developments necessary for synthesizing and trapping antihydrogen, so that it can be studied.

Observation of relativistic antihydrogen atoms

International Nuclear Information System (INIS)

Blanford, Glenn DelFosse

1998-01-01

An observation of relativistic antihydrogen atoms is reported in this dissertation. Experiment 862 at Fermi National Accelerator Laboratory observed antihydrogen atoms produced by the interaction of a circulating beam of high momentum (3 0 production is outlined within. The cross section corresponds to the process where a high momentum antiproton causes e + e - pair creation near a nucleus with the e + being captured by the antiproton. Antihydrogen is the first atom made exclusively of antimatter to be detected. The observation experiment's results are the first step towards an antihydrogen spectroscopy experiment which would measure the n = 2 Lamb shift and fine structure

Antihydrogen Experiment Gravity Interferometry Spectroscopy

CERN Multimedia

Trezzi, D; Dassa, L; Rienacker, B; Khalidova, O; Ferrari, G; Krasnicky, D; Perini, D; Cerchiari, G; Belov, A; Boscolo, I; Sacerdoti, M G; Ferragut, R O; Nedelec, P; Hinterberger, A; Al-qaradawi, I; Malbrunot, C L S; Brusa, R S; Prelz, F; Manuzio, G; Riccardi, C; Fontana, A; Genova, P; Haider, S; Haug, F; Turbabin, A; Castelli, F; Testera, G; Lagomarsino, V E; Doser, M; Penasa, L; Gninenko, S; Cataneo, F; Zenoni, A; Cabaret, L; Comparat, D P; Zmeskal, J; Scampoli, P; Nesteruk, K P; Dudarev, A; Kellerbauer, A G; Mariazzi, S; Carraro, C; Zavatarelli, S M

The AEGIS experiment (Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy) has the aim of carrying out the first measurement of the gravitational interaction of antimatter to a precision of 1%, by applying techniques from atomic physics, laser spectroscopy and interferometry to a beam of antihydrogen atoms. A further goal of the experiment is to carry out spectroscopy of the antihydrogen atoms in flight.

The ATHENA Antihydrogen Apparatus

CERN Document Server

Amoretti, M; Bonomi, G; Bouchta, A; Bowe, P; Carraro, C; Charlton, M; Collier, M; Doser, Michael; Filippini, V; Fine, K S; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Glauser, A; Grögler, D; Hangst, Jeffrey S; Hayano, R S; Higaki, H; Holzscheiter, Michael H; Joffrain, W; Jørgensen, L V; Lagomarsino, V; Landua, Rolf; Cesar, C L; Lindelöf, D; Lodi-Rizzini, E; Macri, M; Madsen, N; Manuzio, D; Manuzio, G; Marchesotti, M; Montagna, P; Pruys, H S; Regenfus, C; Riedler, P; Rochet, J; Rotondi, A; Rouleau, G; Testera, G; Van der Werf, D P; Variola, A; Watson, T L; Yamazaki, T; Yamazaki, Y

2004-01-01

The ATHENA apparatus that recently produced and detected the first cold antihydrogen atoms is described. Its main features, which are described herein, are: an external positron accumulator, making it possible to accumulate large numbers of positrons; a separate antiproton catching trap, optimizing the catching, colling and handling of antiprotons: a unique high resolution antihydrogen annihilation detector, allowing a clear determination that antihydrogen has been produced; an open, modular design making variations in the experimental approach possible and a "nested" Penning trap situated in a cryogenic, 3T magnetic field environment used for the mixing of the antiprotons and positrons.

ERC supports antihydrogen research

CERN Multimedia

Katarina Anthony

2013-01-01

As part of a Europe-wide effort to promote high-level research, the European Research Council (ERC) has awarded a €2.14 million grant to ALPHA spokesperson Jeffrey Hangst, which will further the collaboration’s study of the antihydrogen spectrum. The grant will be used to purchase laser spectroscopy equipment for the new ALPHA-2 set-up.   ALPHA Spokesperson, Jeffrey Hangst, in front of the new ALPHA-2 set-up. The incorporation of lasers into ALPHA-2 will allow the team to take precise measurements of trapped antihydrogen. Among the new equipment financed by the grant will be a high-precision laser and stabilisation system to study the transition from the ground state to the first excited state in antihydrogen. As this spectral line is very well known in hydrogen, its study in antihydrogen will provide essential data for matter/antimatter symmetry investigations. “The grant has come at a perfect time for us,” says Jeffrey Hangst. “We wil...

The production and investigation of cold antihydrogen atoms

International Nuclear Information System (INIS)

Pittner, H.

2005-04-01

This work reports on experiments in which antihydrogen atoms have been produced in cryogenic Penning traps from antiproton and positron plasmas by two different methods and on experiments that have been carried out subsequently in order to investigate the antihydrogen atoms. By the first method antihydrogen atoms have been formed during the process of positron cooling of antiprotons in so called nested Penning traps and detected via a field ionization method. A measurement of the state distribution has revealed that the antihydrogen atoms are formed in highly excited states. This suggests along with the high production rate that the antihydrogen atoms are formed by three-body recombination processes and subsequent collisional deexcitations. However current theory cannot yet account for the measured state distribution. Typical radii of the detected antihydrogen atoms lie in the range between 0.4 μm and 0.15 μm. The deepest bound antihydrogen atoms have radii below 0.1 μm.The kinetic energy of the weakest bound antihydrogen atoms has been measured to about 200 meV. By the second method antihydrogen atoms have been synthesized in charge-exchange processes. Lasers are used to produce a Rydberg cesium beam within the cryogenic Penning trap that collides with trapped positrons so that Rydberg positronium atoms are formed via charge-exchange reactions. The Rydberg positronium atoms that collide with nearby stored antiprotons form antihydrogen atoms in charge-exchange reactions. So far, 14±4 antihydrogen atoms have been detected background-free via a field-ionization method. The antihydrogen atoms produced via the two-step charge-exchange mechanism are expected to have a temperature of 4.2 K, the temperature of the antiprotons from which they are formed

Production of antihydrogen via double charge exchange

Energy Technology Data Exchange (ETDEWEB)

Muellers, Andreas

2013-02-01

Spectroscopy of the 1S-2S transition of antihydrogen confined in a neutral atom trap and comparison with the equivalent spectral line in hydrogen will provide an accurate test of CPT symmetry and the first one in a mixed baryon-lepton system. Also, with neutral antihydrogen atoms, the gravitational interaction between matter and antimatter can be tested unperturbed by the much stronger Coulomb forces. Antihydrogen is regularly produced at CERN's Antiproton Decelerator by three-body-recombination (TBR) of one antiproton and two positrons. The method requires injecting antiprotons into a cloud of positrons, which raises the average temperature of the antihydrogen atoms produced way above the typical 0.5 K trap depths of neutral atom traps. Therefore only very few antihydrogen atoms can be confined at a time. Precision measurements, like laser spectroscopy, will greatly benefit from larger numbers of simultaneously trapped antihydrogen atoms. Therefore, the ATRAP collaboration developed a different production method that has the potential to create much larger numbers of cold, trappable antihydrogen atoms. Positrons and antiprotons are stored and cooled in a Penning trap in close proximity. Laser excited cesium atoms collide with the positrons, forming Rydberg positronium, a bound state of an electron and a positron. The positronium atoms are no longer confined by the electric potentials of the Penning trap and some drift into the neighboring cloud of antiprotons where, in a second charge exchange collision, they form antihydrogen. The antiprotons remain at rest during the entire process, so much larger numbers of trappable antihydrogen atoms can be produced. Laser excitation is necessary to increase the efficiency of the process since the cross sections for charge-exchange collisions scale with the fourth power of the principal quantum number n. This method, named double charge-exchange, was demonstrated by ATRAP in 2004. Since then, ATRAP constructed a new

Production of antihydrogen via double charge exchange

International Nuclear Information System (INIS)

Muellers, Andreas

2013-01-01

Spectroscopy of the 1S-2S transition of antihydrogen confined in a neutral atom trap and comparison with the equivalent spectral line in hydrogen will provide an accurate test of CPT symmetry and the first one in a mixed baryon-lepton system. Also, with neutral antihydrogen atoms, the gravitational interaction between matter and antimatter can be tested unperturbed by the much stronger Coulomb forces. Antihydrogen is regularly produced at CERN's Antiproton Decelerator by three-body-recombination (TBR) of one antiproton and two positrons. The method requires injecting antiprotons into a cloud of positrons, which raises the average temperature of the antihydrogen atoms produced way above the typical 0.5 K trap depths of neutral atom traps. Therefore only very few antihydrogen atoms can be confined at a time. Precision measurements, like laser spectroscopy, will greatly benefit from larger numbers of simultaneously trapped antihydrogen atoms. Therefore, the ATRAP collaboration developed a different production method that has the potential to create much larger numbers of cold, trappable antihydrogen atoms. Positrons and antiprotons are stored and cooled in a Penning trap in close proximity. Laser excited cesium atoms collide with the positrons, forming Rydberg positronium, a bound state of an electron and a positron. The positronium atoms are no longer confined by the electric potentials of the Penning trap and some drift into the neighboring cloud of antiprotons where, in a second charge exchange collision, they form antihydrogen. The antiprotons remain at rest during the entire process, so much larger numbers of trappable antihydrogen atoms can be produced. Laser excitation is necessary to increase the efficiency of the process since the cross sections for charge-exchange collisions scale with the fourth power of the principal quantum number n. This method, named double charge-exchange, was demonstrated by ATRAP in 2004. Since then, ATRAP constructed a new combined

Antiparticle cloud temperatures for antihydrogen experiments

Science.gov (United States)

Bianconi, A.; Charlton, M.; Lodi Rizzini, E.; Mascagna, V.; Venturelli, L.

2017-07-01

A simple rate-equation description of the heating and cooling of antiparticle clouds under conditions typical of those found in antihydrogen formation experiments is developed and analyzed. We include single-particle collisional, radiative, and cloud expansion effects and, from the modeling calculations, identify typical cooling phenomena and trends and relate these to the underlying physics. Some general rules of thumb of use to experimenters are derived.

The ASACUSA CUSP: an antihydrogen experiment

Energy Technology Data Exchange (ETDEWEB)

Kuroda, N., E-mail: kuroda@phys.c.u-tokyo.ac.jp [University of Tokyo, Graduate School of Arts and Sciences (Japan); Ulmer, S. [RIKEN, Ulmer Initiative Research Unit (Japan); Murtagh, D. J.; Gorp, S. Van [RIKEN, Atomic Physics Laboratory (Japan); Nagata, Y. [Tokyo University of Agriculture and Technology, Department of Applied Physics (Japan); Diermaier, M. [Boltzmangasse 3, Stefan Meyer Institut für Subatomare Physik (Austria); Federmann, S. [CERN (Switzerland); Leali, M. [Università di Brescia & Instituto Nazionale di Fisica Nucleare, Dipartimento di Chimica e Fisica per l’Ingegneria e per i Materiali (Italy); Malbrunot, C. [CERN (Switzerland); Mascagna, V. [Università di Brescia & Instituto Nazionale di Fisica Nucleare, Dipartimento di Chimica e Fisica per l’Ingegneria e per i Materiali (Italy); Massiczek, O. [Boltzmangasse 3, Stefan Meyer Institut für Subatomare Physik (Austria); Michishio, K. [Tokyo University of Science, Department of Physics (Japan); Mizutani, T. [University of Tokyo, Graduate School of Arts and Sciences (Japan); Mohri, A. [Kyoto University, Graduate School of Human and Environmental Sciences (Japan); Nagahama, H.; Ohtsuka, M. [University of Tokyo, Graduate School of Arts and Sciences (Japan); Radics, B. [RIKEN, Atomic Physics Laboratory (Japan); Sakurai, S. [Hiroshima University, Graduate School of Advanced Science of Matter (Japan); Sauerzopf, C.; Suzuki, K. [Boltzmangasse 3, Stefan Meyer Institut für Subatomare Physik (Austria); and others

2015-11-15

In order to test CPT symmetry between antihydrogen and its counterpart hydrogen, the ASACUSA collaboration plans to perform high precision microwave spectroscopy of ground-state hyperfine splitting of antihydrogen atom in-flight. We have developed an apparatus (“cusp trap”) which consists of a superconducting anti-Helmholtz coil and multiple ring electrodes. For the preparation of slow antiprotons and positrons, Penning-Malmberg type traps were utilized. The spectrometer line was positioned downstream of the cusp trap. At the end of the beamline, an antihydrogen beam detector was located, which comprises an inorganic Bismuth Germanium Oxide (BGO) single-crystal scintillator housed in a vacuum duct and surrounding plastic scintillators. A significant fraction of antihydrogen atoms flowing out the cusp trap were detected.

Fast antihydrogen beam spectroscopy

International Nuclear Information System (INIS)

Neumann, R.

1989-01-01

The motivation for production and precision spectroscopy of antihydrogen atoms is outlined. An experimental configuration is considered, concerning laser-microwave spectroscopy of a fast hydrogen beam with characteristics similar to those of an antihydrogen beam emanating from an antiproton-positron overlap region in an antiproton storage ring. In particular, a possible experiment for the measurement of the ground state hyperfine structure splitting is described. (orig.)

Traps for antimatter and antihydrogen production

International Nuclear Information System (INIS)

Holzscheiter, M.H.

1994-01-01

Even though positrons have been captured and stored in ion traps for precision measurements, the recent trapping and cooling of antiprotons may be considered as the beginning of a new era in antimatter research. For the first time all the ingredients to produce the first atom of the antimatter world, the antihydrogen atom, are at hand, and several groups have entered an active discussion on the feasibility of producing antihydrogen as well as on the possibility to perform precision tests on CPT and gravity. At the same time, the trapping of reasonable large numbers of antiprotons has opened up the way for a variety of exciting physics with ultra-low energy antiprotons, ranging from atomic physics issues to nuclear physics and medical applications. I will describe the current status of the work on trapping antiprotons and positrons, discuss possible physics applications of this technique, and describe the two most promising routes to produce antihydrogen for precision spectroscopy. Towards the end a few comments on storing the produced antihydrogen and on utilizing antihydrogen for gravity measurements and for CPT tests are given

First Attempts at Antihydrogen Trapping in ALPHA

CERN Document Server

Andresen, G B; Bowe, P D; Bray, C C; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Fajans, J; Funakoshi, R; Gill, D R; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jørgensen, L V; Kurchaninov, L; Lambo, R; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Page, R D; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Seif El Nasr, S; Silveira, D M; Storey, J W; Thompson, R I; Van der Werf, D P; Wasilenko, L; Wurtele, J S; Yamazaki, Y; Fujiwara, M C

2008-01-01

We discuss aspects of antihydrogen studies, that relate to particle physics ideas and techniques, within the context of the ALPHA experiment at CERN's Antiproton Decelerator facility. We review the fundamental physics motivations for antihydrogen studies, and their potential physics reach. We argue that initial spectroscopy measurements, once antihydrogen is trapped, could provide competitive tests of CPT, possibly probing physics at the Planck Scale. We discuss some of the particle detection techniques used in ALPHA. Preliminary results from commissioning studies of a partial system of the ALPHA Si vertex detector are presented, the results of which highlight the power of annihilation vertex detection capability in antihydrogen studies.

Towards laser spectroscopy of antihydrogen

NARCIS (Netherlands)

Walz, J.; Pahl, A.; Eikema, K.S.E.; Hansch, T.W.

2000-01-01

The development of the first continuous coherent source at 121.56 nm is described. Radiation at this wavelength of Lyman-alpha can be used for laser-cooling of antihydrogen on the strong 1S-2P transition. It also opens up a possibility for precision spectroscopy that requires just a few antihydrogen

Dual levitated coils for antihydrogen production

Science.gov (United States)

Wofford, J. D.; Ordonez, C. A.

2013-04-01

Two coaxial superconducting magnetic coils that carry currents in the same direction and that are simultaneously levitated may serve for antihydrogen plasma confinement. The configuration may be suitable for use by a collaboration at the CERN Antiproton Decelerator facility to test fundamental symmetries between the properties of hydrogen and antihydrogen. Nested Penning traps are currently used to confine recombining antihydrogen plasma. Symmetry studies require the production of sufficiently cold antihydrogen. However, plasma drifts within nested Penning traps can increase the kinetic energy of antiprotons that form antihydrogen atoms. Dual levitated coils may serve to confine relatively large, cold, dense non-drifting recombining antihydrogen plasmas. A minimum-B magnetic field that is produced by the coils could provide for atom trapping. A toroidal plasma is confined between the coils. High density plasmas may be possible, by allowing plasma pressure to balance mechanical pressure to keep the coils apart. Progress is reported on theoretical and experimental efforts. The theoretical effort includes the development of a classical trajectory Monte Carlo simulation of confinement. The experimental effort includes levitation of a NdFeB permanent ring magnet, which produces a magnetic field that is qualitatively similar to the field that would be produced by the two coaxial superconducting magnetic coils. Liquid-nitrogen-cooled Bi-2223 high-temperature-superconducting components, with a critical temperature of 108 K, were used to levitate the ring magnet. An issue concerning keeping the plane of the levitated ring horizontal is discussed.

Antihydrogen for precision tests in physics

CERN Document Server

Charlton, M; Jørgensen, L V; Madsen, N; van der Werf, D P

2008-01-01

The creation of atoms of antihydrogen under controlled conditions has opened up a new era in physics with antimatter. We describe the experimental realisation of low energy antihydrogen, via the mixing of carefully prepared clouds of positrons and antiprotons, and some of the progress that has been made in the last few years in characterising properties of the nascent anti-atoms. Ongoing efforts aimed at trapping the anti-atoms in magnetic field minima are discussed. Some of the motivations for undertaking experiments with antihydrogen are presented.

ATRAP on the road to cold antihydrogen

CERN Multimedia

2001-01-01

The ATRAP collaboration has succeeded in slowing down antiprotons with positrons, the two ingredients of antihydrogen atoms. This is an important step towards capturing and studying antihydrogen. Members of the ATRAP Collaboration with the apparatus that first demonstrated positron cooling. It was in extremis. Last December, during the six short hours of beam remaining to them, ATRAP researchers achieved their initial goal. For the first time, positrons were used to cool antiprotons. To what end, you may ask? The answer is much simpler than the process: physicists think that this is the most effective means of observing antihydrogen. Recall that an antihydrogen atom is composed of an antiproton and a positron. The first atoms of antihydrogen were produced five years ago at LEAR. But their small number and the brevity of their existence made it impossible to study them in depth. However, to understand the subtle nuances between matter and antimatter, which would explain the imbalance in nature between the tw...

Gravitational states of antihydrogen near material surface

Energy Technology Data Exchange (ETDEWEB)

Voronin, Alexei Yu., E-mail: dr.a.voronin@gmail.com [P.N. Lebedev Physical Institute (Russian Federation); Froelich, Piotr [Uppsala University, Department of Quantum Chemistry (Sweden); Nesvizhevsky, Valery V. [Institut Laue-Langevin (ILL) (France)

2012-12-15

We present a theoretical study of the motion of antihydrogen atoms in the Earth's gravitational field near a material surface. We predict the existence of long-living quasistationary states of antihydrogen in a superposition of the gravitational and Casimir-van der Waals potentials of the surface. We suggest an interferometric method of measuring the energy difference between such gravitational states, hence the gravitational mass of antihydrogen.

Collaborative Research: Experimental and Theoretical Study of the Plasma Physics of Antihydrogen Generation and Trapping

Energy Technology Data Exchange (ETDEWEB)

Robicheaux, Francis

2013-03-29

Ever since Dirac predicted the existence of antimatter in 1928, it has excited our collective imagination. Seventy-four years later, two collaborations at CERN, ATHENA and ATRAP, created the first slow antihydrogen. This was a stunning achievement, but the most important antimatter experiments require trapped, not just slow, antihydrogen. The velocity, magnetic moment, and internal energy and state of the antihydrogen depend strongly on how it is formed. To trap antihydrogen, physicists face two broad challenges: (1) Understanding the behavior of the positron and antiprotons plasmas from which the antihydrogen is synthesized; and (2) Understanding the atomic processes by which positrons and antiprotons recombine. Recombination lies on the boundary between atomic and plasma physics, and cannot be studied properly without employing tools from both fields. The proposed collaborative research campaign will address both of these challenges. The collaboration members have unique experience in the relevant fields of experimental and theoretical non-neutral plasma physics, numerical modeling, nonlinear dynamics and atomic physics. This expertise is not found elsewhere amongst antihydrogen researchers. The collaboration members have strong ties already, and seek to formalize them with this proposal. Three of the four PIs are members of the ALPHA collaboration, an international collaboration formed by most of the principal members of the ATHENA collaboration.

Positron Plasma Control Techniques Applied to Studies of Cold Antihydrogen

CERN Document Server

Funakoshi, Ryo

2003-01-01

In the year 2002, two experiments at CERN succeeded in producing cold antihydrogen atoms, first ATHENA and subsequently ATRAP. Following on these results, it is now feasible to use antihydrogen to study the properties of antimatter. In the ATHENA experiment, the cold antihydrogen atoms are produced by mixing large amounts of antiprotons and positrons in a nested Penning trap. The complicated behaviors of the charged particles are controlled and monitored by plasma manipulation techniques. The antihydrogen events are studied using position sensitive detectors and the evidence of production of antihydrogen atoms is separated out with the help of analysis software. This thesis covers the first production of cold antihydrogen in the first section as well as the further studies of cold antihydrogen performed by using the plasma control techniques in the second section.

Simulation of an aperture-based antihydrogen gravity experiment

Directory of Open Access Journals (Sweden)

C. A. Ordonez

2012-03-01

Full Text Available A Monte Carlo simulation is presented of an experiment that could potentially determine whether antihydrogen accelerates vertically up or down as a result of earth's gravity. The experiment would rely on methods developed by existing antihydrogen research collaborations and would employ a Penning trap for the production of antihydrogen within a uniform magnetic field. The axis of symmetry of the cylindrical trap wall would be oriented horizontally, and an axisymmetric aperture (with an inner radius that is smaller than the cylindrical trap wall radius would be present a short distance away from the antihydrogen production region. Antihydrogen annihilations that occur along the cylindrical trap wall would be detected by the experiment. The distribution of annihilations along the wall would vary near the aperture, because some antihydrogen that would otherwise annihilate at the wall would instead annihilate on the aperture. That is, a shadow region forms behind the aperture, and the distribution of annihilations near the boundary of the shadow region is not azimuthally symmetric when the effect of gravity is significant. The Monte Carlo simulation is used together with analytical modeling to determine conditions under which the annihilation distribution would indicate the direction of the acceleration of antihydrogen due to gravity.

Detection of trapped antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Hydomako, Richard [Calgary Univ., AB (Canada). Dept. of Physics and Astronomy

2013-02-01

A landmark thesis describing the first ever trapping of antihydrogen atoms in CERN's ALPHA apparatus. Opens the way to crucial tests of fundamental theories. Nominated as an outstanding contribution by the University of Calgary. In 2010, the ALPHA collaboration achieved a first for mankind: the stable, long-term storage of atomic antimatter, a project carried out a the Antiproton Decelerator facility at CERN. A crucial element of this observation was a dedicated silicon vertexing detector used to identify and analyze antihydrogen annihilations. This thesis reports the methods used to reconstruct the annihilation location. Specifically, the methods used to identify and extrapolate charged particle tracks and estimate the originating annihilation location are outlined. Finally, the experimental results demonstrating the first-ever magnetic confinement of antihydrogen atoms are presented. These results rely heavily on the silicon detector, and as such, the role of the annihilation vertex reconstruction is emphasized.

Numerical Simulations of Hyperfine Transitions of Antihydrogen

CERN Document Server

Kolbinger, B.; Diermaier, M.; Lehner, S.; Malbrunot, C.; Massiczek, O.; Sauerzopf, C.; Simon, M.C.; Widmann, E.

2015-02-04

One of the ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration's goals is the measurement of the ground state hyperfine transition frequency in antihydrogen, the antimatter counterpart of one of the best known systems in physics. This high precision experiment yields a sensitive test of the fundamental symmetry of CPT. Numerical simulations of hyperfine transitions of antihydrogen atoms have been performed providing information on the required antihydrogen events and the achievable precision.

Numerical simulations of hyperfine transitions of antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Kolbinger, B., E-mail: bernadette.kolbinger@oeaw.ac.at; Capon, A.; Diermaier, M.; Lehner, S. [Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences (Austria); Malbrunot, C. [CERN (Switzerland); Massiczek, O.; Sauerzopf, C.; Simon, M. C.; Widmann, E. [Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences (Austria)

2015-08-15

One of the ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration’s goals is the measurement of the ground state hyperfine transition frequency in antihydrogen, the antimatter counterpart of one of the best known systems in physics. This high precision experiment yields a sensitive test of the fundamental symmetry of CPT. Numerical simulations of hyperfine transitions of antihydrogen atoms have been performed providing information on the required antihydrogen events and the achievable precision.

The ALPHA antihydrogen trapping apparatus

Energy Technology Data Exchange (ETDEWEB)

Amole, C. [Department of Physics and Astronomy, York University, Toronto ON Canada, M3J 1P3 (Canada); Andresen, G.B. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Ashkezari, M.D. [Department of Physics, Simon Fraser University, Burnaby, BC Canada, V5A 1S6 (Canada); Baquero-Ruiz, M. [Department of Physics, University of California at Berkeley, Berkeley, CA 94720-7300 (United States); Bertsche, W. [Department of Physics, College of Science, Swansea University, Swansea SA2 8PP (United Kingdom); School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); The Cockcroft Institute, Warrington WA4 4AD (United Kingdom); Bowe, P.D. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Butler, E. [Physics Department, CERN, CH-1211 Geneva 23 (Switzerland); Capra, A. [Department of Physics and Astronomy, York University, Toronto ON Canada, M3J 1P3 (Canada); Carpenter, P.T. [Department of Physics, Auburn University, Auburn, AL 36849-5311 (United States); Cesar, C.L. [Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972 (Brazil); Chapman, S. [Department of Physics, University of California at Berkeley, Berkeley, CA 94720-7300 (United States); Charlton, M.; Deller, A.; Eriksson, S. [Department of Physics, College of Science, Swansea University, Swansea SA2 8PP (United Kingdom); Escallier, J. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Fajans, J. [Department of Physics, University of California at Berkeley, Berkeley, CA 94720-7300 (United States); Friesen, T. [Department of Physics and Astronomy, University of Calgary, Calgary AB, Canada, T2N 1N4 (Canada); Fujiwara, M.C.; Gill, D.R. [TRIUMF, 4004 Wesbrook Mall, Vancouver BC, Canada V6T 2A3 (Canada); Gutierrez, A. [Department of Physics and Astronomy, University of British Columbia, Vancouver BC, Canada V6T 1Z4 (Canada); and others

2014-01-21

The ALPHA collaboration, based at CERN, has recently succeeded in confining cold antihydrogen atoms in a magnetic minimum neutral atom trap and has performed the first study of a resonant transition of the anti-atoms. The ALPHA apparatus will be described herein, with emphasis on the structural aspects, diagnostic methods and techniques that have enabled antihydrogen trapping and experimentation to be achieved.

Direct detection of antihydrogen atoms using a BGO crystal

Energy Technology Data Exchange (ETDEWEB)

Nagata, Y. [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, 184-8588 Tokyo (Japan); Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan); Kuroda, N., E-mail: kuroda@phys.c.u-tokyo.ac.jp [Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8902 Tokyo (Japan); Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan); Ohtsuka, M. [Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8902 Tokyo (Japan); Leali, M.; Lodi-Rizzini, E.; Mascagna, V. [Dipartimento di Ingegneria dell' Informazione, Universitá di Brescia, Brescia 25133 (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Brescia, Brescia 25133 (Italy); Tajima, M.; Torii, H.A. [Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8902 Tokyo (Japan); Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan); Zurlo, N. [Dipartimento di Ingegneria dell' Informazione, Universitá di Brescia, Brescia 25133 (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Brescia, Brescia 25133 (Italy); Matsuda, Y. [Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8902 Tokyo (Japan); Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan); Venturelli, L. [Dipartimento di Ingegneria dell' Informazione, Universitá di Brescia, Brescia 25133 (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Brescia, Brescia 25133 (Italy); Yamazaki, Y. [Atomic Physics Research Unit, RIKEN, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan)

2016-12-21

The ASACUSA collaboration has developed a detector consisting of a large size BGO crystal to detect an atomic antihydrogen beam, and performed the direct detection of antihydrogen atoms. Energy spectra from antihydrogen annihilation on the BGO crystal are discussed in comparison to simulation results from the GEANT4 toolkit. Background mainly originating from cosmic rays were strongly suppressed by analyzing the energy deposited in the BGO and requiring a multiplicity of charged pions. Thus antihydrogen events were identified.

Cold Antihydrogen for Precise Laser Spectroscopy

CERN Multimedia

Gabrielse, G S; Walz, J; Hessels, E A; Tan, J; Oelert, W; George, M C; Grzonka, D J; Kossick, M; Storry, C H; Sefzick, T

2002-01-01

%AD-2 %title\\\\ \\\\The Antihydrogen TRAP Collaboration (ATRAP) seeks to do precise laser spectroscopy of antihydrogen. Comparisons of antihydrogen and hydrogen atoms should provide the most stringent test of CPT invariance involving baryons and leptons. ATRAP is an expansion of the TRAP collaboration that developed the techniques to take CERN antiprotons from an energy of 6 MeV (momentum 100 MeV/c) all the way down to thermal equilibrium at 4 K for storage. This storage energy is lower than realized previously by more than ten orders of magnitude. The TRAP techniques include slowing, capturing, electron cooling and stacking of antiprotons. ATRAP and other collaborations will use antiprotons from the Antiproton Decelerator (AD). This new facility makes sense for such experiments because we showed that antiprotons can be accumulated in a trap at much lower expense than was required in the earlier CERN AC-AA-LEAR complex. In the closest approach yet to the production of cold antihydrogen, collaboration members wer...

Production of cold antihydrogen in a nested trap

International Nuclear Information System (INIS)

Fujiwara, Makoto

2004-01-01

The ATHENA experiment at CERN produced and detected the first cold antihydrogen atoms. Antiprotons and positrons are mixed in a double Penning trap, known as a nested trap. The production of antihydrogen atoms was identified by detecting their annihilations signatures at trap wall. With the ATHENA results subsequently confirmed by another CERN experiment, ATRAP, cold antihydrogen research is entering an exciting era. (author)

The ALPHA Experiment a Cold Antihydrogen Trap

CERN Document Server

Bertsche, W; Bowe, P D; Cesar, C L; Chapman, S; Charlton, M; Chartier, M; Deutsch, A; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D; Gomberoff, K; Grote, D P; Hangst, J S; Hayano, R S; Jenkins, M; Jørgensen, L V; Madsen, N; Miranda, D; Nolan, P; Ochanski, K; Olin, A; Page, R D; Posada, L G C; Robicheaux, F; Sarid, E; Telle, H H; Vay, J L; Wurtele, J; van der Werf, D P; Yamazaki, Y

2005-01-01

The ALPHA experiment aims to trap antihydrogen as the next crucial step towards a precise CPT test, by a spectroscopic comparison of antihydrogen with hydrogen. The experiment will retain the salient techniques developed by the ATHENA collaboration during the previous phase of antihydrogen experiments at the antiproton decelerator (AD) at CERN. The collaboration has identified the key problems in adding a neutral antiatom trap to the previously developed experimental configuration. The solutions identified by ALPHA are described in this paper.

s-wave elastic scattering of antihydrogen off atomic alkali-metal targets

International Nuclear Information System (INIS)

Sinha, Prabal K.; Ghosh, A. S.

2006-01-01

We have investigated the s-wave elastic scattering of antihydrogen atoms off atomic alkali-metal targets (Li, Na, K, and Rb) at thermal energies (10 -16 -10 -4 a.u.) using an atomic orbital expansion technique. The elastic cross sections of these systems at thermal energies are found to be very high compared to H-H and H-He systems. The theoretical models employed in this study are so chosen to consider long-range forces dynamically in the calculation. The mechanism of cooling suggests that Li may be considered to be a good candidate as a buffer gas for enhanced cooling of antihydrogen atoms to ultracold temperature

Precision measurements on trapped antihydrogen in the ALPHA experiment

Science.gov (United States)

Eriksson, S.

2018-03-01

Both the 1S-2S transition and the ground state hyperfine spectrum have been observed in trapped antihydrogen. The former constitutes the first observation of resonant interaction of light with an anti-atom, and the latter is the first detailed measurement of a spectral feature in antihydrogen. Owing to the narrow intrinsic linewidth of the 1S-2S transition and use of two-photon laser excitation, the transition energy can be precisely determined in both hydrogen and antihydrogen, allowing a direct comparison as a test of fundamental symmetry. The result is consistent with CPT invariance at a relative precision of around 2×10-10. This constitutes the most precise measurement of a property of antihydrogen. The hyperfine spectrum of antihydrogen is determined to a relative uncertainty of 4×10-4. The excited state and the hyperfine spectroscopy techniques currently both show sensitivity at the few 100 kHz level on the absolute scale. Here, the most recent work of the ALPHA collaboration on precision spectroscopy of antihydrogen is presented together with an outlook on improving the precision of measurements involving lasers and microwave radiation. Prospects of measuring the Lamb shift and determining the antiproton charge radius in trapped antihydrogen in the ALPHA apparatus are presented. Future perspectives of precision measurements of trapped antihydrogen in the ALPHA apparatus when the ELENA facility becomes available to experiments at CERN are discussed. This article is part of the Theo Murphy meeting issue `Antiproton physics in the ELENA era'.

Aperture-based antihydrogen gravity experiment: Parallel plate geometry

Science.gov (United States)

Rocha, J. R.; Hedlof, R. M.; Ordonez, C. A.

2013-10-01

An analytical model and a Monte Carlo simulation are presented of an experiment that could be used to determine the direction of the acceleration of antihydrogen due to gravity. The experiment would rely on methods developed by existing antihydrogen research collaborations. The configuration consists of two circular, parallel plates that have an axis of symmetry directed away from the center of the earth. The plates are separated by a small vertical distance, and include one or more pairs of circular barriers that protrude from the upper and lower plates, thereby forming an aperture between the plates. Antihydrogen annihilations that occur just beyond each barrier, within a "shadow" region, are asymmetric on the upper plate relative to the lower plate. The probability for such annihilations is determined for a point, line and spheroidal source of antihydrogen. The production of 100,000 antiatoms is predicted to be necessary for the aperture-based experiment to indicate the direction of free fall acceleration of antimatter, provided that antihydrogen is produced within a sufficiently small antiproton plasma at a temperature of 4 K.

Aperture-based antihydrogen gravity experiment: Parallel plate geometry

Energy Technology Data Exchange (ETDEWEB)

Rocha, J. R.; Hedlof, R. M.; Ordonez, C. A. [Department of Physics, University of North Texas, Denton, Texas 76203 (United States)

2013-10-15

An analytical model and a Monte Carlo simulation are presented of an experiment that could be used to determine the direction of the acceleration of antihydrogen due to gravity. The experiment would rely on methods developed by existing antihydrogen research collaborations. The configuration consists of two circular, parallel plates that have an axis of symmetry directed away from the center of the earth. The plates are separated by a small vertical distance, and include one or more pairs of circular barriers that protrude from the upper and lower plates, thereby forming an aperture between the plates. Antihydrogen annihilations that occur just beyond each barrier, within a “shadow” region, are asymmetric on the upper plate relative to the lower plate. The probability for such annihilations is determined for a point, line and spheroidal source of antihydrogen. The production of 100,000 antiatoms is predicted to be necessary for the aperture-based experiment to indicate the direction of free fall acceleration of antimatter, provided that antihydrogen is produced within a sufficiently small antiproton plasma at a temperature of 4 K.

Aperture-based antihydrogen gravity experiment: Parallel plate geometry

Directory of Open Access Journals (Sweden)

J. R. Rocha

2013-10-01

Full Text Available An analytical model and a Monte Carlo simulation are presented of an experiment that could be used to determine the direction of the acceleration of antihydrogen due to gravity. The experiment would rely on methods developed by existing antihydrogen research collaborations. The configuration consists of two circular, parallel plates that have an axis of symmetry directed away from the center of the earth. The plates are separated by a small vertical distance, and include one or more pairs of circular barriers that protrude from the upper and lower plates, thereby forming an aperture between the plates. Antihydrogen annihilations that occur just beyond each barrier, within a “shadow” region, are asymmetric on the upper plate relative to the lower plate. The probability for such annihilations is determined for a point, line and spheroidal source of antihydrogen. The production of 100,000 antiatoms is predicted to be necessary for the aperture-based experiment to indicate the direction of free fall acceleration of antimatter, provided that antihydrogen is produced within a sufficiently small antiproton plasma at a temperature of 4 K.

Tests of fundamental symmetries with trapped antihydrogen

DEFF Research Database (Denmark)

Rasmussen, Chris Ørum

2016-01-01

Antihydrogen is the simplest pure antimatter atomic system, and it allows for direct tests of CPT symmetry as well as the weak equivalence principle. Furthermore the study of antihydrogen may provide clues to the matter- antimatter asymmetry observed in the universe - one of the major unanswered...

Measurement of the ground-state hyperfine splitting of antihydrogen

CERN Document Server

Juhász, B; Federmann, S

2011-01-01

The ASACUSA collaboration at the Antiproton Decelerator of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic beam line, consisting of a cusp trap as a source of partially polarized antihydrogen atoms, a radiofrequency spin-flip cavity, a superconducting sextupole magnet as spin analyser, and an antihydrogen detector. This will be a measurement of the antiproton magnetic moment, and also a test of the CPT invariance. Monte Carlo simulations predict that the antihydrogen ground-state hyperfine splitting can be determined with a relative precision of ~10−7. The first preliminary measurements of the hyperfine transitions will start in 2011.

Towards antihydrogen trapping and spectroscopy at ALPHA

International Nuclear Information System (INIS)

Butler, E.; Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Bray, C. C.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayano, R. S.; Hayden, M. E.; Humphries, A. J.; Hydomako, R.

2011-01-01

Spectroscopy of antihydrogen has the potential to yield high-precision tests of the CPT theorem and shed light on the matter-antimatter imbalance in the Universe. The ALPHA antihydrogen trap at CERN’s Antiproton Decelerator aims to prepare a sample of antihydrogen atoms confined in an octupole-based Ioffe trap and to measure the frequency of several atomic transitions. We describe our techniques to directly measure the antiproton temperature and a new technique to cool them to below 10 K. We also show how our unique position-sensitive annihilation detector provides us with a highly sensitive method of identifying antiproton annihilations and effectively rejecting the cosmic-ray background.

Towards Antihydrogen Trapping and Spectroscopy at ALPHA

CERN Document Server

Butler, Eoin; Ashkezari, Mohammad.D.; Baquero-Ruiz, Marcelo; Bertsche, William; Bowe, Paul D.; Bray, Crystal C.; Cesar, Claudio L.; Chapman, Steven; Charlton, Michael; Fajans, Joel; Friesen, Tim; Fujiwara, Makoto C.; Gill, David R.; Hangst, Jeffrey S.; Hardy, Walter N.; Hayano, Ruyugo S.; Hayden, Michael E.; Humphries, Andrew J.; Hydomako, Richard; Jonsell, Svante; Kurchaninov, Leonid; Lambo, Ricardo; Madsen, Niels; Menary, Scott; Nolan, Paul; Olchanski, Konstantin; Olin, Art; Povilus, Alexander; Pusa, Petteri; Robicheaux, Francis; Sarid, Eli; Silveira, Daniel M.; So, Chukman; Storey, James W.; Thompson, Robert I.; van der Werf, Dirk P.; Wilding, Dean; Wurtele, Jonathan S.; Yamazaki, Yasunori

2011-01-01

Spectroscopy of antihydrogen has the potential to yield high-precision tests of the CPT theorem and shed light on the matter-antimatter imbalance in the Universe. The ALPHA antihydrogen trap at CERN's Antiproton Decelerator aims to prepare a sample of antihydrogen atoms confined in an octupole-based Ioffe trap and to measure the frequency of several atomic transitions. We describe our techniques to directly measure the antiproton temperature and a new technique to cool them to below 10 K. We also show how our unique position-sensitive annihilation detector provides us with a highly sensitive method of identifying antiproton annihilations and effectively rejecting the cosmic-ray background.

Characterization of the 1S–2S transition in antihydrogen

DEFF Research Database (Denmark)

Ahmadi, M.; Alves, B. X. R.; Baker, C. J.

2018-01-01

makes its antimatter counterpart—the antihydrogen atom—of particular interest. Current standard-model physics requires that hydrogen and antihydrogen have the same energy levels and spectral lines. The laser-driven 1S–2S transition was recently observed 8 in antihydrogen. Here we characterize one...... of the hyperfine components of this transition using magnetically trapped atoms of antihydrogen and compare it to model calculations for hydrogen in our apparatus. We find that the shape of the spectral line agrees very well with that expected for hydrogen and that the resonance frequency agrees...

A Spin-Flip Cavity for Microwave Spectroscopy of Antihydrogen

CERN Document Server

Federmann, Silke; Widmann, Eberhard

The present thesis is a contribution to the Asacusa (Atomic Spectroscopy And Collisions Using Slow Antiprotons) experiment. The aim of this experiment is to measure the ground-state hyperfine structure of antihydrogen. This is done using a Rabi-like spectrometer line consisting of an antihydrogen source, a microwave cavity, a sextupole magnet and a detector. The cavity induces spin-flip transitions in the ground-state hyperfine levels of antihydrogen whereas the sextupole magnet selects the antihydrogen atoms according to their spin state. Such a configuration allows the measurements of the hyperfine transition in antihydrogen with very high precision. A comparison with the corresponding transitions in hydrogen would thus provide a very sensitive test of the charge-parity-time (Cpt) symmetry. In the context of this thesis, the central piece of this spectrometer line, the spin flip cavity, was designed and implemented. The delicacy of this task was achieving the required field homogeneity: It needs to be bette...

Physics with Trapped Antihydrogen

Science.gov (United States)

Charlton, Michael

2017-04-01

For more than a decade antihydrogen atoms have been formed by mixing antiprotons and positrons held in arrangements of charged particle (Penning) traps. More recently, magnetic minimum neutral atom traps have been superimposed upon the anti-atom production region, promoting the trapping of a small quantity of the antihydrogen yield. We will review these advances, and describe some of the first physics experiments performed on anrtihydrogen including the observation of the two-photon 1S-2S transition, invesigation of the charge neutrailty of the anti-atom and studies of the ground state hyperfine splitting. We will discuss the physics motivations for undertaking these experiments and describe some near-future initiatives.

Progress towards antihydrogen hyperfine spectroscopy in a beam

Energy Technology Data Exchange (ETDEWEB)

Widmann, Eberhard [Stefan Meyer Institute for Subatomic Physics, Vienna (Austria); Collaboration: ASACUSA CUSP collaboration

2014-07-01

The spectroscopy of antihydrogen promises one of the most precise tests of CPT symmetry. The ASACUSA CUSP collaboration at the Antiproton Decelerator of CERN is preparing an experiment to measure the ground-state hyperfine structure GS-HFS of antihydrogen, since this quantity is one of the most precisely determined transitions in ordinary hydrogen (relative accuracy ∝10{sup -12}). The experiment uses a Rabi-type atomic beam apparatus consisting of a source of spin-polarized antihydrogen (a so-called cusp trap), a microwave cavity to induce a spin flip, a superconducting sextuple magnet for spin analysis, and an antihydrogen detector. In this configuration, a relative accuracy of better than 10{sup -6} can be obtained. This precision will already allow to be sensitive to finite size effects of the antiproton, provided its magnetic moment will measured to higher precision, which is in progress by two collaborations at the AD. The recent progress in producing a beam of antihydrogen atoms and in the development of the apparatus as well as ways to further improve the accuracy by using the Ramsey method of separated oscillatory fields are presented.

ASACUSA: the first beam of anti-hydrogen atoms

International Nuclear Information System (INIS)

2014-01-01

The ASACUSA experiment at CERN has produced for the first time a beam of anti-hydrogen atoms, 80 atoms of anti-hydrogen have been detected at a distance of 2.7 meters away from their production place which is the true achievement of this experiment. The ASACUSA team has developed an innovative device that allows the transfer of the anti-hydrogen atoms in a place where they can be studied in flight, away from the intense magnetic field that was necessary to produce them but affect their spectroscopic properties. Anti-hydrogen atoms are made up of anti-electrons and anti-protons, according to the theory their spectrum must be identical to that of hydrogen atoms and any difference that might be detected by the ASACUSA experiment may shed light on the matter-antimatter asymmetry issue. (A.C.)

The ASACUSA antihydrogen and hydrogen program: results and prospects

Science.gov (United States)

Malbrunot, C.; Amsler, C.; Arguedas Cuendis, S.; Breuker, H.; Dupre, P.; Fleck, M.; Higaki, H.; Kanai, Y.; Kolbinger, B.; Kuroda, N.; Leali, M.; Mäckel, V.; Mascagna, V.; Massiczek, O.; Matsuda, Y.; Nagata, Y.; Simon, M. C.; Spitzer, H.; Tajima, M.; Ulmer, S.; Venturelli, L.; Widmann, E.; Wiesinger, M.; Yamazaki, Y.; Zmeskal, J.

2018-03-01

The goal of the ASACUSA-CUSP collaboration at the Antiproton Decelerator of CERN is to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. A milestone was achieved in 2012 through the detection of 80 antihydrogen atoms 2.7 m away from their production region. This was the first observation of `cold' antihydrogen in a magnetic field free region. In parallel to the progress on the antihydrogen production, the spectroscopy beamline was tested with a source of hydrogen. This led to a measurement at a relative precision of 2.7×10-9 which constitutes the most precise measurement of the hydrogen hyperfine splitting in a beam. Further measurements with an upgraded hydrogen apparatus are motivated by CPT and Lorentz violation tests in the framework of the Standard Model Extension. Unlike for hydrogen, the antihydrogen experiment is complicated by the difficulty of synthesizing enough cold antiatoms in the ground state. The first antihydrogen quantum states scan at the entrance of the spectroscopy apparatus was realized in 2016 and is presented here. The prospects for a ppm measurement are also discussed. This article is part of the Theo Murphy meeting issue `Antiproton physics in the ELENA era'.

Antiproton annihilation in very low-energy antihydrogen scattering by simple atoms and molecules

International Nuclear Information System (INIS)

Armour, E.A.G.; Gregory, M.R.; Liu, Y.

2006-01-01

The aim of experimentalists currently working on the preparation of antihydrogen is to trap it at very low temperatures so that its properties can be studied. Of concern to experimentalists are processes that lead to a loss of antihydrogen through annihilation. The dominant annihilation process that leads to the loss of antihydrogen is the annihilation of the antiproton with nuclei through the strong interaction. A recent scattering calculation of antihydrogen with hydrogen at very low energy, using the complex strong interaction potential of Kohno and Weise, has found an average annihilation cross-section of 0.13E -1/2 a 0 -2 , where E is the energy of relative motion. The antihydrogen-helium system is of particular interest to experimentalists as helium may be present as an impurity in the trap. Also there is interest in the possibility of using it to cool antihydrogen. We present a treatment of antihydrogen scattering with helium at very low temperatures. The annihilation cross-sections obtained are much larger than antihydrogen-hydrogen scattering cross-section, making it very unlikely that helium can be used to cool antihydrogen

Antiproton annihilation in very low-energy antihydrogen scattering by simple atoms and molecules

Energy Technology Data Exchange (ETDEWEB)

Armour, E.A.G. [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Gregory, M.R. [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)]. E-mail: mark.gregory@maths.nottingham.ac.uk; Liu, Y. [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

2006-06-15

The aim of experimentalists currently working on the preparation of antihydrogen is to trap it at very low temperatures so that its properties can be studied. Of concern to experimentalists are processes that lead to a loss of antihydrogen through annihilation. The dominant annihilation process that leads to the loss of antihydrogen is the annihilation of the antiproton with nuclei through the strong interaction. A recent scattering calculation of antihydrogen with hydrogen at very low energy, using the complex strong interaction potential of Kohno and Weise, has found an average annihilation cross-section of 0.13E{sup -1/2}a{sub 0}{sup -2}, where E is the energy of relative motion. The antihydrogen-helium system is of particular interest to experimentalists as helium may be present as an impurity in the trap. Also there is interest in the possibility of using it to cool antihydrogen. We present a treatment of antihydrogen scattering with helium at very low temperatures. The annihilation cross-sections obtained are much larger than antihydrogen-hydrogen scattering cross-section, making it very unlikely that helium can be used to cool antihydrogen.

Production of antihydrogen at reduced magnetic field for anti-atom trapping

CERN Document Server

Andresen, G.B.; Boston, A.; Bowe, P.D.; Cesar, C.L.; Chapman, S.; Charlton, M.; Chartier, M.; Deutsch, A.; Fajans, J.; Fujiwara, M.C.; Funakoshi, R.; Gill, D.R.; Gomberoff, K.; Hangst, J.S.; Hayano, R.S.; Hydomako, R.; Jenkins, M.J.; Jorgensen, L.V.; Kurchaninov, L.; Madsen, N.; Nolan, P.; Olchanski, K.; Olin, A.; Page, R.D.; Povilus, A.; Robicheaux, F.; Sarid, E.; Silveira, D.M.; Storey, J.W.; Thompson, R.I.; van der Werf, D.P.; Wurtele, J.S.; Yamazaki, Y.

2008-01-01

We have demonstrated production of antihydrogen in a 1$,$T solenoidal magnetic field. This field strength is significantly smaller than that used in the first generation experiments ATHENA (3$,$T) and ATRAP (5$,$T). The motivation for using a smaller magnetic field is to facilitate trapping of antihydrogen atoms in a neutral atom trap surrounding the production region. We report the results of measurements with the ALPHA (Antihydrogen Laser PHysics Apparatus) device, which can capture and cool antiprotons at 3$,$T, and then mix the antiprotons with positrons at 1$,$T. We infer antihydrogen production from the time structure of antiproton annihilations during mixing, using mixing with heated positrons as the null experiment, as demonstrated in ATHENA. Implications for antihydrogen trapping are discussed.

Particle Physics Aspects of Antihydrogen Studies with ALPHA at CERN

CERN Document Server

Fujiwara, M.C.; Bertsche, W.; Bowe, P.D.; Bray, C.C.; Butler, E.; Cesar, C.L.; Chapman, S.; Charlton, M.; Fajans, J.; Funakoshi, R.; Gill, D.R.; Hangst, J.S.; Hardy, W.N.; Hayano, R.S.; Hayden, M.E.; Humphries, A.J.; Hydomako, R.; Jenkins, M.J.; Jorgensen, L.V.; Kurchaninov, L.; Lai, W.; Lambo, R.; Madsen, N.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; Seif El Nasr, S.; Silveira, D.M.; Storey, J.W.; Thompson, R.I.; van der Werf, D.P.; Wasilenko, L.; Wurtele, J.S.; Yamazaki, Y.

2008-01-01

We discuss aspects of antihydrogen studies, that relate to particle physics ideas and techniques, within the context of the ALPHA experiment at CERN's Antiproton Decelerator facility. We review the fundamental physics motivations for antihydrogen studies, and their potential physics reach. We argue that initial spectroscopy measurements, once antihydrogen is trapped, could provide competitive tests of CPT, possibly probing physics at the Planck Scale. We discuss some of the particle detection techniques used in ALPHA. Preliminary results from commissioning studies of a partial system of the ALPHA Si vertex detector are presented, the results of which highlight the power of annihilation vertex detection capability in antihydrogen studies.

The detection of cold antihydrogen atoms

International Nuclear Information System (INIS)

Zhang, Zhongdong

2007-01-01

The ATRAP experiment at CERN's antiproton decelerator (AD) aims for a test of CPT violation and Lorentz invariance by a comparison of hydrogen to antihydrogen atom spectroscopy and a measurement of the gravitational force on antimatter atoms. The experiment is divided into two parts: ATRAP-I, where successfully antihydrogen atoms were produced and intensive studies on the charged clouds of positrons and antiprotons were performed, and ATRAP-II which was commissioned during the beam-time 2006. ATRAP-II includes a much larger superconducting solenoid bore allowing the installation of an extended detection system as well as an optimized combined Penning-Ioffe trap. Another essential part is a new positron accumulator and delivery system which will increase the ATRAP-II efficiency drastically. Thus ATRAP-II now allows for much larger flexibility, increased performance, higher robustness, and better efficiency for the production and storage of cold antihydrogen atoms. A general overview of the experimental setup for the second phase of the ATRAP experiment will be presented in this thesis. The antiproton annihilation detector system, consisting of several layers of scintillating fibers, counts the antihydrogen atoms and determines the annihilation vertex of the atoms. This diagnostic element will allow to optimize the production of cold antihydrogen sufficiently to permit optical observations and measurements. Extensive Monte Carlo simulations concerning the track fitting and vertex reconstruction have been developed during the planned interruption of antiproton production at AD in the year 2005. Different event generators, magnetic field distributions as well as data reconstruction algorithms on simulated data were established and the results were compared to data in 2006. To improve the detector position resolution, a constraint-fit procedure was adopted. Further possible improvements, by applying certain cuts on the data, were investigated. Real-time measurements

A source of antihydrogen for in-flight hyperfine spectroscopy

CERN Document Server

Kuroda, N; Murtagh, D J; Van Gorp, S; Nagata, Y; Diermaier, M; Federmann, S; Leali, M; Malbrunot, C; Mascagna, V; Massiczek, O; Michishio, K; Mizutani, T; Mohri, A; Nagahama, H; Ohtsuka, M; Radics, B; Sakurai, S; Sauerzopf, C; Suzuki, K; Tajima, M; Torii, H A; Venturelli, L; Wünschek, B; Zmeskal, J; Zurlo, N; Higaki, H; Kanai, Y; Lodi Rizzini, E; Nagashima, Y; Matsuda, Y; Widmann, E; Yamazaki, Y

2014-01-01

Antihydrogen, a positron bound to an antiproton, is the simplest antiatom. Its counterpart—hydrogen—is one of the most precisely investigated and best understood systems in physics research. High-resolution comparisons of both systems provide sensitive tests of CPT symmetry, which is the most fundamental symmetry in the Standard Model of elementary particle physics. Any measured difference would point to CPT violation and thus to new physics. Here we report the development of an antihydrogen source using a cusp trap for in-flight spectroscopy. A total of 80 antihydrogen atoms are unambiguously detected 2.7 m downstream of the production region, where perturbing residual magnetic fields are small. This is a major step towards precision spectroscopy of the ground-state hyperfine splitting of antihydrogen using Rabi-like beam spectroscopy.

Progress towards microwave spectroscopy of trapped antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Ashkezari, Mohammad D., E-mail: mdehghan@cern.ch [Simon Fraser University, Department of Physics (Canada); Andresen, Gorm B. [Aarhus University, Department of Physics and Astronomy (Denmark); Baquero-Ruiz, Marcelo [University of California, Department of Physics (United States); Bertsche, Wil [Swansea University, Department of Physics (United Kingdom); Bowe, Paul D. [Aarhus University, Department of Physics and Astronomy (Denmark); Butler, Eoin [CERN, Physics Department (Switzerland); Cesar, Claudio L. [Universidade Federal do Rio de Janeiro, Instituto de Fisica (Brazil); Chapman, Steve [University of California, Department of Physics (United States); Charlton, Michael; Deller, Adam; Eriksson, Stefan [Swansea University, Department of Physics (United Kingdom); Fajans, Joel [University of California, Department of Physics (United States); Friesen, Tim; Fujiwara, Makoto C. [University of Calgary, Department of Physics and Astronomy (Canada); Gill, Dave R. [TRIUMF (Canada); Gutierrez, Andrea [University of British Columbia, Department of Physics and Astronomy (Canada); Hangst, Jeffrey S. [Aarhus University, Department of Physics and Astronomy (Denmark); Hardy, Walter N. [University of British Columbia, Department of Physics and Astronomy (Canada); Hayano, Ryugo S. [University of Tokyo, Department of Physics (Japan); Hayden, Michael E. [Simon Fraser University, Department of Physics (Canada); Collaboration: ALPHA Collaboration; and others

2012-12-15

Precision comparisons of hyperfine intervals in atomic hydrogen and antihydrogen are expected to yield experimental tests of the CPT theorem. The CERN-based ALPHA collaboration has initiated a program of study focused on microwave spectroscopy of trapped ground-state antihydrogen atoms. This paper outlines some of the proposed experiments, and summarizes measurements that characterize microwave fields that have been injected into the ALPHA apparatus.

Progress towards microwave spectroscopy of trapped antihydrogen

CERN Document Server

Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jonsell, S; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki,Y

2012-01-01

Precision comparisons of hyperfine intervals in atomic hydrogen and antihydrogen are expected to yield experimental tests of the CPT theorem. The CERN-based ALPHA collaboration has initiated a program of study focused on microwave spectroscopy of trapped ground-state antihydrogen atoms. This paper outlines some of the proposed experiments, and summarizes measurements that characterize microwave fields that have been injected into the ALPHA apparatus.

An experimental limit on the charge of antihydrogen

CERN Document Server

Amole, C; Baquero-Ruiz, M; Bertsche, W; Butler, E; Capra, A; Cesar, C L; Charlton, M; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Menary, S; Napoli, S C; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Tharp, T D; Thompson, R I; Van der Werf, D P; Vendeiro, Z; Wurtele, J S; Zhmoginov, A I; Charman, A E

2014-01-01

The properties of antihydrogen are expected to be identical to those of hydrogen, and any differences would constitute a profound challenge to the fundamental theories of physics. The most commonly discussed antiatom-based tests of these theories are searches for antihydrogen-hydrogen spectral differences (tests of CPT (charge-parity-time) invariance) or gravitational differences (tests of the weak equivalence principle). Here we, the ALPHA Collaboration, report a different and somewhat unusual test of CPT and of quantum anomaly cancellation. A retrospective analysis of the influence of electric fields on antihydrogen atoms released from the ALPHA trap finds a mean axial deflection of 4.1±3.4 mm for an average axial electric field of 0.51 V mm−1. Combined with extensive numerical modelling, this measurement leads to a bound on the charge Qe of antihydrogen of Q=(−1.3±1.1±0.4) × 10−8. Here, e is the unit charge, and the errors are from statistics and systematic effects.

Antimatter Plasmas in a Multipole Trap for Antihydrogen

CERN Document Server

Andresen, G B; Boston, A; Bowe, P D; Cesar, C L; Chapman, S; Charlton, M; Chartier, M; Deutsch, A; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D R; Gomberoff, K; Hangst, J S; Hayano, R S; Hydomako, R; Jenkins, M J; Jørgensen, L V; Kurchaninov, L; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Robicheaux, F; Sarid, E; Silveira, D M; Storey, J W; Telle, H H; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

2007-01-01

We have demonstrated storage of plasmas of the charged constituents of the antihydrogen atom, antiprotons and positrons, in a Penning trap surrounded by a minimum-B magnetic trap designed for holding neutral antiatoms. The neutral trap comprises a superconducting octupole and two superconducting, solenoidal mirror coils. We have measured the storage lifetimes of antiproton and positron plasmas in the combined Penning-neutral trap, and compared these to lifetimes without the neutral trap fields. The magnetic well depth was 0.6 T, deep enough to trap ground state antihydrogen atoms of up to about 0.4 K in temperature. We have demonstrated that both particle species can be stored for times long enough to permit antihydrogen production and trapping studies.

Antimatter plasmas in a multipole trap for antihydrogen.

Science.gov (United States)

Andresen, G; Bertsche, W; Boston, A; Bowe, P D; Cesar, C L; Chapman, S; Charlton, M; Chartier, M; Deutsch, A; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D R; Gomberoff, K; Hangst, J S; Hayano, R S; Hydomako, R; Jenkins, M J; Jørgensen, L V; Kurchaninov, L; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Robicheaux, F; Sarid, E; Silveira, D M; Storey, J W; Telle, H H; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

2007-01-12

We have demonstrated storage of plasmas of the charged constituents of the antihydrogen atom, antiprotons and positrons, in a Penning trap surrounded by a minimum-B magnetic trap designed for holding neutral antiatoms. The neutral trap comprises a superconducting octupole and two superconducting, solenoidal mirror coils. We have measured the storage lifetimes of antiproton and positron plasmas in the combined Penning-neutral trap, and compared these to lifetimes without the neutral trap fields. The magnetic well depth was 0.6 T, deep enough to trap ground state antihydrogen atoms of up to about 0.4 K in temperature. We have demonstrated that both particle species can be stored for times long enough to permit antihydrogen production and trapping studies.

Resonant quantum transitions in trapped antihydrogen atoms.

Science.gov (United States)

Amole, C; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Capra, A; Cesar, C L; Charlton, M; Deller, A; Donnan, P H; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Menary, S; Napoli, S C; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Shields, C R; Silveira, D M; Stracka, S; So, C; Thompson, R I; van der Werf, D P; Wurtele, J S

2012-03-07

The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom's stature lies in its simplicity and in the accuracy with which its spectrum can be measured and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and--by comparison with measurements on its antimatter counterpart, antihydrogen--the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves.

Proposal to measure the Gravitational Behaviour of Antihydrogen at Rest

CERN Document Server

Chardin, G; Lunney, D; Manea, V; Badertscher, A; Crivelli, P; Curioni, A; Marchionni, A; Rossi, B; Rubbia, A; Nesvizhevsky, V; Hervieux, P-A; Manfredi, G; Comini, P; Debu, P; Dupré, P; Liszkay, L; Mansoulié, B; Pérez, P; Rey, J-M; Ruiz, N; Sacquin, Y; Voronin, A; Biraben, F; Cladé, P; Douillet, A; Gérardin, A; Guellati, S; Hilico, L; Indelicato, P; Lambrecht, A; Guérout, R; Karr, J-P; Nez, F; Reynaud, S; Tran, V-Q; Mohri, A; Yamazaki, Y; Charlton, M; Eriksson, S; Madsen, N; van der Werf, D-P; Kuroda, N; Torii, H; Nagashima, Y; CERN. Geneva. SPS and PS Experiments Committee; SPSC

2011-01-01

We propose an experiment to measure the free fall acceleration of neutral antihydrogen atoms in order to test the Weak Equivalence Principle. The originality of this path is to first produce the antihydrogen ion Hbar+ (or anti H-). The ion is formed through two charge exchange processes involving the interaction of an antiproton with positronium to produce antihydrogen, followed by the interaction of this atom with positronium. The ion is then sympathetically cooled with laser cooled Be+ ions down to μK temperatures (i.e. m/s velocities). The excess positron can then be laser detached in order to recover the neutral antihydrogen atom. The laser pulse will give the start time for the antihydrogen free fall measurement. The stop will be determined by the detection of the charged pions coming from the annihilation of the antiprotons on a plate placed at a known distance from the initial position of the atoms. From the free fall time and distance one will can extract the value of g. Our goal is a measurement at ...

Electron plasmas as a diagnostic tool for hyperfine spectroscopy of antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Friesen, T.; Thompson, R. I. [Department of Physics and Astronomy, University of Calgary, Calgary AB, T2N 1N4 (Canada); Amole, C.; Capra, A.; Menary, S. [Department of Physics and Astronomy, York University, Toronto ON, M3J 1P3 (Canada); Ashkezari, M. D.; Hayden, M. E. [Department of Physics, Simon Fraser University, Burnaby BC, V5A 1S6 (Canada); Baquero-Ruiz, M.; Fajans, J.; Little, A.; So, C.; Wurtele, J. S. [Department of Physics, University of California, Berkeley, CA 94720-7300 (United States); Bertsche, W. [School of Physics and Astronomy, University of Manchester, M13 9PL Manchester, UK and The Cockcroft Institute, WA4 4AD Warrington (United Kingdom); Bowe, P. D.; Hangst, J. S.; Rasmussen, C. O. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Butler, E. [Physics Department, CERN, CH-1211 Geneva 23 (Switzerland); Cesar, C. L.; Silveira, D. M. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972 (Brazil); Charlton, M. [Department of Physics, College of Science, Swansea University, Swansea SA2 8PP (United Kingdom); and others

2013-03-19

Long term magnetic confinement of antihydrogen atoms has recently been demonstrated by the ALPHA collaboration at CERN, opening the door to a range of experimental possibilities. Of particular interest is a measurement of the antihydrogen spectrum. A precise comparison of the spectrum of antihydrogen with that of hydrogen would be an excellent test of CPT symmetry. One prime candidate for precision CPT tests is the ground-state hyperfine transition; measured in hydrogen to a precision of nearly one part in 10{sup 12}. Effective execution of such an experiment with trapped antihydrogen requires precise knowledge of the magnetic environment. Here we present a solution that uses an electron plasma confined in the antihydrogen trapping region. The cyclotron resonance of the electron plasma is probed with microwaves at the cyclotron frequency and the subsequent heating of the electron plasma is measured through the plasma quadrupole mode frequency. Using this method, the minimum magnetic field of the neutral trap can be determined to within 4 parts in 10{sup 4}. This technique was used extensively in the recent demonstration of resonant interaction with the hyperfine levels of trapped antihydrogen atoms.

Laser-Ablated Beryllium Ions for Cold Antihydrogen in ALPHA

CERN Document Server

Sameed, Muhammed; Charlton, Michael

One of the best ways to study antimatter is to investigate antihydrogen, the bound state of an antiproton and a positron. Antihydrogen atoms do not exist naturally and must be synthesized in the lab by merging carefully-prepared plasmas of positrons and antiprotons. If the atoms are created in a magnetic trap like the one used by the ALPHA experiment at CERN, then a fraction of the coldest atoms remain trapped, while the rest escape and annihilate on the trap walls. The trapped atoms may then be probed using microwaves or lasers to make high-precision comparisons with hydrogen. Increasing the trapping rate would allow us to perform precision measurements on antihydrogen in a shorter period of time and with better systematics. Particle simulations indicate that by sympathetically cooling positrons using laser-cooled beryllium ions, we have the ability to improve the antihydrogen trapping rate by up to two orders of magnitude. This thesis describes the effort to design and qualify a beryllium ion source that is...

An improved limit on the charge of antihydrogen from stochastic acceleration

CERN Document Server

Ahmadi, M; Bertsche, W; Butler, E; Capra, A; Carruth, C; Cesar, C L; Charlton, M; Charman, A E; Eriksson, S; Evans, L T; Evetts, N; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Isaac, C A; Ishida, A; Jones, S A; Jonsell, S; Kurchaninov, L; Madsen, N; Maxwell, D; McKenna, J T K; Menary, S; Michan, J M; Momose, T; Munich, J J; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sacramento, R L; Sameed, M; Sarid, E; Silveira, D M; So, C; Tharp, T D; Thompson, R I; van der Werf, D P; Wurtele, J S; Zhmoginov, A I

2016-01-01

Antimatter continues to intrigue physicists because of its apparent absence in the observable Universe. Current theory requires that matter and antimatter appeared in equal quantities after the Big Bang, but the Standard Model of particle physics offers no quantitative explanation for the apparent disappearance of half the Universe. It has recently become possible to study trapped atoms of antihydrogen to search for possible, as yet unobserved, differences in the physical behaviour of matter and antimatter. Here we consider the charge neutrality of the antihydrogen atom. By applying stochastic acceleration to trapped antihydrogen atoms, we determine an experimental bound on the antihydrogen charge, Qe, of |Q| < 0.71 parts per billion (one standard deviation), in which e is the elementary charge. This bound is a factor of 20 less than that determined from the best previous measurement of the antihydrogen charge. The electrical charge of atoms and molecules of normal matter is known to be no greater than...

Tests of CPT, Lorentz invariance and the WEP with antihydrogen

International Nuclear Information System (INIS)

Holzscheiter, M.H.

1999-01-01

Antihydrogen atoms, produced near rest, trapped in a magnetic well, and cooled to the lowest possible temperature (kinetic energy) could provide an extremely powerful tool for the search of violations of CPT and Lorentz invariance. Equally well, such a system could be used for searches of violations of the Weak Equivalence Principle (WEP) at high precision. The author describes his plans to form a significant number of cold, trapped antihydrogen atoms for comparative precision spectroscopy of hydrogen and antihydrogen and comment on possible first experiments

Inelastic Transitions in Slow Collisions of Anti-Hydrogen with Hydrogen Atoms

Science.gov (United States)

Harrison, Robert; Krstic, Predrag

2007-06-01

We calculate excited adiabatic states and nonadiabatic coupling matrix elements of a quasimolecular system containing hydrogen and anti-hydrogen atoms, for a range of internuclear distances from 0.2 to 20 Bohrs. High accuracy is achieved by exact diagonalization of the molecular Hamiltionian in a large Gaussian basis. Nonadiabatic dynamics was calculated by solving MOCC equations. Positronium states are included in the consideration.

Towards the measurement of the ground-state hyperfine splitting of antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Juhasz, Bertalan, E-mail: bertalan.juhasz@oeaw.ac.at [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria)

2012-12-15

The ASACUSA collaboration at the Antiproton Decelerator of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic beam line, which will consist of a superconducting cusp trap as a source of partially polarized antihydrogen atoms, a radiofrequency spin-flip cavity, a superconducting sextupole magnet as spin analyser, and an antihydrogen detector. This will be a measurement of the antiproton magnetic moment, and also a test of the CPT invariance. Monte Carlo simulations predict that the antihydrogen ground-state hyperfine splitting can be determined with a relative precision of better than {approx} 10{sup - 6}. The first preliminary measurements of the hyperfine transitions will start in 2011.

Experimental and computational study of the injection of antiprotons into a positron plasma for antihydrogen production

International Nuclear Information System (INIS)

Amole, C.; Capra, A.; Menary, S.; Ashkezari, M. D.; Hayden, M. E.; Baquero-Ruiz, M.; Little, A.; So, C.; Zhmoginov, A.; Bertsche, W.; Butler, E.; Cesar, C. L.; Silveira, D. M.; Charlton, M.; Deller, A.; Eriksson, S.; Isaac, C. A.; Madsen, N.; Napoli, S. C.; Shields, C. R.

2013-01-01

One of the goals of synthesizing and trapping antihydrogen is to study the validity of charge–parity–time symmetry through precision spectroscopy on the anti-atoms, but the trapping yield achieved in recent experiments must be significantly improved before this can be realized. Antihydrogen atoms are commonly produced by mixing antiprotons and positrons stored in a nested Penning-Malmberg trap, which was achieved in ALPHA by an autoresonant excitation of the antiprotons, injecting them into the positron plasma. In this work, a hybrid numerical model is developed to simulate antiproton and positron dynamics during the mixing process. The simulation is benchmarked against other numerical and analytic models, as well as experimental measurements. The autoresonant injection scheme and an alternative scheme are compared numerically over a range of plasma parameters which can be reached in current and upcoming antihydrogen experiments, and the latter scheme is seen to offer significant improvement in trapping yield as the number of available antiprotons increases.

Experimental and computational study of the injection of antiprotons into a positron plasma for antihydrogen production

Energy Technology Data Exchange (ETDEWEB)

Amole, C.; Capra, A.; Menary, S. [Department of Physics and Astronomy, York University, Toronto, M3J 1P3 Ontario (Canada); Ashkezari, M. D.; Hayden, M. E. [Department of Physics, Simon Fraser University, Burnaby, V5A 1S6 British Columbia (Canada); Baquero-Ruiz, M.; Little, A.; So, C.; Zhmoginov, A. [Department of Physics, University of California, Berkeley, California 94720 (United States); Bertsche, W. [Department of Physics, College of Science, Swansea University, SA2 8PP Swansea (United Kingdom); School of Physics and Astronomy, University of Manchester, M13 9PL Manchester (United Kingdom); Daresbury Laboratory, Cockcroft Institute, WA4 4AD Warrington (United Kingdom); Butler, E. [Physics Department, CERN, CH-1211 Geneva 23 (Switzerland); Cesar, C. L.; Silveira, D. M. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941 (Brazil); Charlton, M.; Deller, A.; Eriksson, S.; Isaac, C. A.; Madsen, N.; Napoli, S. C.; Shields, C. R. [Department of Physics, College of Science, Swansea University, SA2 8PP Swansea (United Kingdom); Collaboration: ALPHA Collaboration; and others

2013-04-15

One of the goals of synthesizing and trapping antihydrogen is to study the validity of charge-parity-time symmetry through precision spectroscopy on the anti-atoms, but the trapping yield achieved in recent experiments must be significantly improved before this can be realized. Antihydrogen atoms are commonly produced by mixing antiprotons and positrons stored in a nested Penning-Malmberg trap, which was achieved in ALPHA by an autoresonant excitation of the antiprotons, injecting them into the positron plasma. In this work, a hybrid numerical model is developed to simulate antiproton and positron dynamics during the mixing process. The simulation is benchmarked against other numerical and analytic models, as well as experimental measurements. The autoresonant injection scheme and an alternative scheme are compared numerically over a range of plasma parameters which can be reached in current and upcoming antihydrogen experiments, and the latter scheme is seen to offer significant improvement in trapping yield as the number of available antiprotons increases.

Measurement of the hyperfine structure of antihydrogen in a beam

Energy Technology Data Exchange (ETDEWEB)

Widmann, E., E-mail: ew@antihydrogen.at; Diermaier, M. [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria); Juhasz, B. [Lufthansa Systems Hungaria Kft. (Hungary); Malbrunot, C.; Massiczek, O.; Sauerzopf, C.; Suzuki, K.; Wuenschek, B.; Zmeskal, J. [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria); Federmann, S. [CERN (Switzerland); Kuroda, N. [University of Tokyo, Institute of Physics (Japan); Ulmer, S.; Yamazaki, Y. [RIKEN Advanced Science Institute (Japan)

2013-03-15

A measurement of the hyperfine structure of antihydrogen promises one of the best tests of CPT symmetry. We describe an experiment planned at the Antiproton Decelerator of CERN to measure this quantity in a beam of slow antihydrogen atoms.

CERN experiment provides first glimpse inside cold antihydrogen

CERN Multimedia

2002-01-01

"The ATRAP experiment at the Antiproton Decelerator at CERN has detected and measured large numbers of cold antihydrogen atoms. Relying on ionization of the cold antiatoms when they pass through a strong electric field gradient, the ATRAP measurement provides the first glimpse inside an antiatom, and the first information about the physics of antihydrogen. The results have been accepted for publication in Physical Review Letters" (1 page).

Towards a precise measurement of the antihydrogen ground state hyperfine splitting in a beam: the case of in-flight radiative decays

Science.gov (United States)

Lundmark, R.; Malbrunot, C.; Nagata, Y.; Radics, B.; Sauerzopf, C.; Widmann, E.

2015-09-01

The ASACUSA antihydrogen setup at the CERN Antiproton Decelerator (AD) consists of an antihydrogen source (cusp magnet coupled to a positron source and an antiproton catching magnet) followed by a spectrometer beamline. After production in the cusp, the antihydrogen atoms decay while they escape the trap leading to changes in their effective magnetic moment which in turn affect their trajectories in the beamline. Those sequential decays in the presence of a varying magnetic field strength from their production point in the cusp to their detection at the end of the spectrometer line can in principle greatly affect the prospects for a precision measurement of the antihydrogen hyperfine splitting given the so-far relatively low number of available anti-atoms. The impact of the antihydrogen decay in this context has for the first time been simulated. The implementation of atomic radiative decay has been done in Geant4 to extend the particle tracking capabilities originally embedded in Geant4 to excited atoms, and to allow studies of the effect of dynamic atomic properties on trajectories. This new tool thus allows the study of particle-matter interaction via the Geant4 toolkit while properly taking into account the atomic nature of the object under study. The implementation as well as impacts on the experimental sensitivity for antihydrogen spectroscopy are discussed in this paper.

Antihydrogen physics: gravitation and spectroscopy in AEgIS

CERN Document Server

Ferragut, R; Stroke, H H; Dassa, L; Rohne, O; Hogan, S D; Cialdi, S; Al-Qaradawi, I Y; Formaro, L; Sandaker, H; Testera, G; Stepanov, S V; Folegati, P; Morhard, C; Warring, U; Prelz, F; Belov, A S; Bonomi, G; Consolati, G; Ferrari, G; Lagomarsino, V; Krasnicky, D; Drobychev, G; Giammarchi, M G; Heyne, R; Zenoni, A; Castelli, F; Mariazzi, S; Cabaret, L; Fischer, A; Boscolo, I; Sillou, D; Villa, F; Perini, D; Djourelov, N; Zavatarelli, S; Oberthaler, M K; Manuzio, G; Carraro, C; Matveev, V A; Jorgensen, L V; Nedelec, P; Prevedelli, M; Comparat, D; Dupasquier, A; Turbabin, A V; Zvezhinskij, D S; Fontana, A; Kellerbauer, A; Canali, C; Dudarev, A; Petracek, V; Riccardi, C; Nebbia, G; Gninenko, S N; Brusa, R S; Rotondi, A; Sacerdoti, M; Calloni, A; Doser, M; Byakov, V M; Quasso, F; Trezzi, D

2011-01-01

AEgIS (Antimatter experiment: gravity, interferometry, spectroscopy) is an experiment approved by CERN with the goal of studying antihydrogen physics. In AEgIS, antihydrogen will be produced by charge exchange reactions of cold antiprotons with positronium atoms excited in a Rydberg state (n > 20). In the first phase of the experiment, controlled acceleration by an electric field gradient (Stark effect) and subsequent measurement of free fall in a Moire deflectometer will allow a test of the weak equivalence principle. In a second phase, the antihydrogen will be slowed, confined, and laser-cooled to perform CPT studies and detailed spectroscopy. In the present work, after a general description of the experiment, the present status of advancement will be reviewed, with special attention to the production and excitation of positronium atoms.

Two-species mixing in a nested Penning trap for antihydrogen trapping

International Nuclear Information System (INIS)

Ordonez, C. A.; Weathers, D. L.

2008-01-01

There exists an international quest to trap neutral antimatter in the form of antihydrogen for scientific study. One method that is being developed for trapping antihydrogen employs a nested Penning trap. Such a trap serves to mix positrons and antiprotons so as to produce low energy antihydrogen atoms. Mixing is achieved when the confinement volumes of the two species overlap one another. In the work presented here, a theoretical understanding of the mixing process is developed by analyzing a mixing scheme that was recently reported [G. Gabrielse et al., Phys. Rev. Lett. 100, 113001 (2008)]. The results indicate that positron space charge or collisions among antiprotons may substantially reduce the fraction of antiprotons that have an energy suitable for antihydrogen trapping

Production and detection of cold antihydrogen atoms

CERN Multimedia

Amoretti, M; Bonomi, G; Bouchta, A; Bowe, P; Carraro, C; Cesar, C L; Charlton, M; Collier, M; Doser, Michael; Filippini, V; Fine, K S; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Holzscheiter, M H; Jørgensen, L V; Lagomarsino, V; Landua, Rolf; Landua, Rolf; Lindelöf, D; Lodi-Rizzini, E; Macri, M; Madsen, N; Manuzio, G; Marchesotti, M; Montagna, P; Pruys, H S; Regenfus, C; Riedler, P; Rochet, J; Rotondi, A; Rouleau, G; Testera, G; Van der Werf, D P; Variola, A; Watson, T L; CERN. Geneva

2002-01-01

A theoretical underpinning of the standard model of fundamental particles and interactions is CPT invariance, which requires that the laws of physics be invariant under the combined discrete operations of charge conjugation, parity and time reversal. Antimatter, the existence of which was predicted by Dirac, can be used to test the CPT theorem experimental investigations involving comparisons of particles with antiparticles are numerous. Cold atoms and anti-atoms, such as hydrogen and anti-hydrogen, could form the basis of a new precise test, as CPT invariance implies that they must have the same spectrum. Observations of antihydrogen in small quantities and at high energies have been reported at the European Organization for Nuclear Research (CERN) and at Fermilab, but were not suited to precision comparison measurements. Here we demonstrate the production of antihydrogen atoms at very low energy by mixing trapped antiprotons and positrons in a cryogenic environment. The neutral anti-atoms have been detected...

Low Temperature Hydrogen Antihydrogen Interactions

International Nuclear Information System (INIS)

Armour, E. A. G.; Chamberlain, C. W.

2001-01-01

In view of current interest in the trapping of antihydrogen (H-bar) atoms at low temperatures, we have carried out a full four-body variational calculation to determine s-wave elastic phase shifts for hydrogen antihydrogen scattering, using the Kohn Variational Principle. Terms outside the Born-Oppenheimer approximation have been taken into account using the formalism of Kolos and Wolniewicz. As far as we are aware, this is the first time that these terms have been included in an H H-bar scattering calculation. This is a continuation of earlier work on H-H-bar interactions. Preliminary results differ substantially from those calculated using the Born-Oppenheimer approximation. A method is outlined for reducing this discrepancy and taking the rearrangement channel into account.

Second CERN group produces cold atoms of antihydrogen

CERN Document Server

Levi-Goss, Barbara

2003-01-01

A new experiment, by CERN's ATRAP collaboration, which introduced a technique for determining the quantum state in which antihydrogen atoms are formed was discussed. To make antihydrogen, antiprotons were taken from CERN's Antiproton Decelerator, further slowed down, and trapped with a configuration of electric fields. The evidence gathered confirmed that the H over bar atoms formed in the experiment occupy highly excited Rydberg states. (Edited abstract) 5 Refs.

Towards the production of an ultra cold antihydrogen beam with the AEGIS apparatus

Energy Technology Data Exchange (ETDEWEB)

Storey, James William, E-mail: james.storey@cern.ch [University of Zurich, Physik-Institut (Switzerland); Collaboration: AEGIS Collaboration

2012-12-15

The AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) experiment is an international collaboration, based at CERN, with the experimental goal of performing the first direct measurement of the Earth's gravitational acceleration on antihydrogen. In the first phase of the experiment, a gravity measurement with 1% precision will be performed by passing a beam of ultra cold antihydrogen atoms through a classical Moire deflectometer coupled to a position sensitive detector. The key requirements for this measurement are the production of ultra cold (T{approx}100 mK) Rydberg state antihydrogen and the subsequent Stark acceleration of these atoms. The aim is to produce Rydberg state antihydrogen by means of the charge exchange reaction between ultra cold antiprotons (T{approx}100 mK) and Rydberg state positronium. This paper will present details of the developments necessary for the successful production of the ultra cold antihydrogen beam, with emphasis on the detector that is required for the development of these techniques. Issues covered will include the detection of antihydrogen production and temperature, as well as detection of the effects of Stark acceleration.

In-beam measurement of the hydrogen hyperfine splitting and prospects for antihydrogen spectroscopy.

Science.gov (United States)

Diermaier, M; Jepsen, C B; Kolbinger, B; Malbrunot, C; Massiczek, O; Sauerzopf, C; Simon, M C; Zmeskal, J; Widmann, E

2017-06-12

Antihydrogen, the lightest atom consisting purely of antimatter, is an ideal laboratory to study the CPT symmetry by comparison with hydrogen. With respect to absolute precision, transitions within the ground-state hyperfine structure (GS-HFS) are most appealing by virtue of their small energy separation. ASACUSA proposed employing a beam of cold antihydrogen atoms in a Rabi-type experiment, to determine the GS-HFS in a field-free region. Here we present a measurement of the zero-field hydrogen GS-HFS using the spectroscopy apparatus of ASACUSA's antihydrogen experiment. The measured value of ν HF =1,420,405,748.4(3.4) (1.6) Hz with a relative precision of 2.7 × 10 -9 constitutes the most precise determination of this quantity in a beam and verifies the developed spectroscopy methods for the antihydrogen HFS experiment to the p.p.b. level. Together with the recently presented observation of antihydrogen atoms 2.7 m downstream of the production region, the prerequisites for a measurement with antihydrogen are now available within the ASACUSA collaboration.

Geneva University: On our way to anti-hydrogen at rest

CERN Multimedia

Geneva University

2010-01-01

Ecole de physique Département de physique nucléaire et corspusculaire 24, quai Ernest-Ansermet 1211 GENEVA 4 Tel: (022) 379 62 73 Fax: (022) 379 69 92 Wednesday 28 April 2010 PARTICLE PHYSICS SEMINAR at 17.00 hrs – Stückelberg Auditorium On our way to anti-hydrogen at rest Prof. Walter Oelert, Research Center Jülich, Germany Trapped cold atoms of anti-hydrogen are optimal for testing possible CPT violations in comparison of spectral lines and gravitational effects on matter and anti-matter. For this reason it is mandatory to optimize the properties of the clouds of anti-protons and positrons used to produce the anti-hydrogen atoms. The ATRAP-collaboration at CERNs AD did perform such experiments by studying the temperature of these clouds and their stability at different conditions. Though detailed tests have been performed to verify the trapping of anti-hydrogen atoms in a magnetic gradient field no statistically significant signal was detected yet. Re...

Temperature dependence of anti-hydrogen production in the ATHENA experiment

CERN Document Server

Bonomi, G; Amsler, Claude; Bouchta, A; Bowe, P; Carraro, C; Cesar, C L; Charlton, M; Doser, Michael; Filippini, V; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Lagomarsino, V; Landua, Rolf; Lindelöf, D; Lodi-Rizzini, E; Macri, M; Madsen, N; Montagna, P; Pruys, H S; Regenfus, C; Riedler, P; Rotondi, A; Testera, G; Variola, A; Van der Werf, D P

2004-01-01

The ATHENA experiment recently produced the first sample of cold anti-hydrogen atoms by mixing cold plasmas of anti-protons and positrons. The temperature of the positron plasma was increased by controlled RF heating and the anti-hydrogen production rate was measured. Preliminary results are presented. (8 refs).

GBAR. Graviational behavior of antihydrogen at rest

Energy Technology Data Exchange (ETDEWEB)

Debu, Pascal, E-mail: pascal.debu@cea.fr [CEA/DSM/IRFU (France); Collaboration: GBAR Collaboration

2012-12-15

The GBAR project aims to perform the first test of the Equivalence Principle with antimatter by measuring the free fall of ultra-cold antihydrogen atoms. The objective is to measure the gravitational acceleration to better than a percent in a first stage, with a long term perspective to reach a much higher precision using gravitational quantum states of antihydrogen. The production of {approx}20 {mu}K atoms proceeds via sympathetic cooling of H-bar{sup +} ions by Be{sup +} ions. H-bar{sup +} ions are produced via a two-step process, involving the interaction of bursts of 10{sup 7} slow antiprotons from the AD (or ELENA upgrade) at CERN with a dense positronium cloud. In order to produce enough positronium, it is necessary to realize an intense source of slow positrons, a few 10{sup 8} per second. This is done with a small electron linear accelerator. A few 10{sup 10} positrons are accumulated every cycle in a Penning-Malmberg trap before they are ejected onto a positron-to-positronium converter. The overall scheme of the experiment is described and the status of the installation of the prototype positron source at Saclay is shown. The accumulation scheme of positrons is given, and positronium formation results are presented. The estimated performance and efficiency of the various steps of the experiment are given.

Review of Plasma Techniques Used to Trap Antihydrogen

Science.gov (United States)

Fajans, Joel

2011-10-01

Recently, the ALPHA collaboration at CERN trapped antihydrogen atoms. To date, over three hundred antiatoms have been confined, some for as long as 1000s. This was the first time that antiatoms had ever been trapped. The ultimate goal of the ALPHA collaboration is to test CPT invariance by comparing the spectra of hydrogen and antihydrogen, and to measure the gravitational attraction between matter and antimatter. Such studies might resolve the baryogenesis problem: why is there very little antimatter in the Universe? The ALPHA experiment brought together techniques from many different fields of physics, but the crucial breakthroughs were in plasma physics. The essential problem is this: How does one combine two Malmberg-Penning trapped plasmas, one made from antiprotons, and the other positrons, which have opposite electrostatic potentials of nearly one volt, in such a manner that the antiprotons traverse the positrons with kinetic energies of less than 40 μeV, this latter being the depth of the superimposed neutral antihydrogen trap? The plasma techniques ALPHA developed to accomplish this include: Minimizing the effects of the neutral trap multipole fields on the positron and antiproton plasma confinement. Compressing antiprotons down to less than 0.5mm. Using autoresonance to inject antiprotons into the positrons with very little excess energy. Evaporative cooling of the electrons and antiprotons to record low temperatures. Development of charge, radial profile, temperature, and antiproton loss location diagnostics. Careful and lengthy manipulations to finesse the plasmas into the best states for optimal antihydrogen production and trapping. The plasma techniques necessary to trap antihydrogen will be reviewed in this talk. This work was supported by DOE and NSF, and is reported on behalf of the ALPHA collaboration.

Hydrogen-Antihydrogen Collisions at Cold Temperatures

Science.gov (United States)

Zygelman, Bernard

2001-05-01

With the CERN anti-proton de-accelerator now on line, it is anticipated that antihydrogen ( \\overline H) atoms will be created, cooled, and stored in large numbers (M. H. Holzscheitner and M. Charlton, Rep. Prog. Phys. 62),1 (1999). It has recently been proposed that the introduction of cold, spin-polarized, hydrogen atoms into a gas of trapped anti-hydrogen could allow the sympathetic cooling of the anti-hydrogen into the sub-Kelvin regime (P. Froelich, S. Jonsell, A.Saenz, B. Zygelman, and A. Dalgarno, Phys. Rev. Lett. 84), 4577 (2000). In this talk we will present the results of calculations that estimate the rate of elastic scattering of H with \\overline H, and compare that to the rate in which the fragmentation reaction, H + \\overline H arrow p \\overline p + e^+ e^- occurs and limits the utility of sympathetic cooling. Unlike the ground state of the H2 system, the H \\overline H system possesses a non-vanishing electric dipole moment (B. Zygelman, A. Saenz, P. Froelich, S. Jonsell and A. Dalgarno, Phys. Rev. A, in Press (2001).) that allows for the additional inelastic reaction H + \\overline H arrow H\\overline H^* + h ν , where H \\overline H^* is a quasi-bound state of the hydrogen-antihydrogen complex. The rate for radiative association into quasi-bound states of the H \\overline H^* complex will be presented and we will explore the viability for the spectroscopic study of this novel four-body matter-antimatter system. Collaborators in this study include, A. Dalgarno, P. Froelich, A. Saenz and S. Jonsell. I wish to thank the Institute for Theoretical Atomic and Molecular Physics (ITAMP) for their hospitality and support during sabbatical leave where part of this work was done. Partial support was provided by NSF grants to the Smithsonian Institution and Harvard University for ITAMP.

Characterization of a transmission positron/positronium converter for antihydrogen production

Science.gov (United States)

Aghion, S.; Amsler, C.; Ariga, T.; Bonomi, G.; Brusa, R. S.; Caccia, M.; Caravita, R.; Castelli, F.; Cerchiari, G.; Comparat, D.; Consolati, G.; Demetrio, A.; Di Noto, L.; Doser, M.; Ereditato, A.; Evans, C.; Ferragut, R.; Fesel, J.; Fontana, A.; Gerber, S.; Giammarchi, M.; Gligorova, A.; Guatieri, F.; Haider, S.; Hinterberger, A.; Holmestad, H.; Kellerbauer, A.; Krasnický, D.; Lagomarsino, V.; Lansonneur, P.; Lebrun, P.; Malbrunot, C.; Mariazzi, S.; Matveev, V.; Mazzotta, Z.; Müller, S. R.; Nebbia, G.; Nedelec, P.; Oberthaler, M.; Pacifico, N.; Pagano, D.; Penasa, L.; Petracek, V.; Povolo, L.; Prelz, F.; Prevedelli, M.; Ravelli, L.; Resch, L.; Rienäcker, B.; Robert, J.; Røhne, O. M.; Rotondi, A.; Sacerdoti, M.; Sandaker, H.; Santoro, R.; Scampoli, P.; Simon, M.; Smestad, L.; Sorrentino, F.; Testera, G.; Tietje, I. C.; Widmann, E.; Yzombard, P.; Zimmer, C.; Zmeskal, J.; Zurlo, N.; Andersen, S. L.; Chevallier, J.; Uggerhøj, U. I.; Lyckegaard, F.

2017-09-01

In this work a characterization study of forward emission from a thin, meso-structured silica positron/positronium (Ps) converter following implantation of positrons in light of possible antihydrogen production is presented. The target consisted of a ∼1 μm thick ultraporous silica film e-gun evaporated onto a 20 nm carbon foil. The Ps formation and emission was studied via Single Shot Positron Annihilation Lifetime Spectroscopy measurements after implantation of pulses with 3 - 4 ·107 positrons and 10 ns temporal width. The forward emission of implanted positrons and secondary electrons was investigated with a micro-channel plate - phosphor screen assembly, connected either to a CCD camera for imaging of the impinging particles, or to a fast photomultiplier tube to extract information about their time of flight. The maximum Ps formation fraction was estimated to be ∼10%. At least 10% of the positrons implanted with an energy of 3.3 keV are forward-emitted with a scattering angle smaller than 50° and maximum kinetic energy of 1.2 keV. At least 0.1-0.2 secondary electrons per implanted positron were also found to be forward-emitted with a kinetic energy of a few eV. The possible application of this kind of positron/positronium converter for antihydrogen production is discussed.

AEgIS antihydrogen production trap

CERN Multimedia

Caraban Gonzalez, Noemi

2017-01-01

During technical stop 2017 the AEgIS experiment was open for upgrades and maintenance. We had the opportunity to take some 360 images from inside and see where antiprotons are ¨trapped¨ and anti-Hydrogen produced.

Design of a 1.42 GHZ spin-flip cavity for antihydrogen atoms

CERN Document Server

Caspers, F; Juhasz, B; Mahner, E; Widmann, E

2010-01-01

The ground state hyperfine transition frequency of hydrogen is known to a very high precision and therefore the measurement of this transition frequency in antihydrogen is offering one of the most accurate tests of CPT symmetry. The ASACUSA collaboration at CERN will run an experiment designed to produce ground state antihydrogen atoms in a cusp trap. These antihydrogen atoms will pass with a low rate in the order of 1 per second through a spin-flip cavity where they get excited depending on their polarization by a 1.42 GHz magnetic field. Due to the small amount of antihydrogen atoms that will be available the requirement of good field homogeneity is imposed in order to obtain an interaction with as many antihydrogen atoms as possible. This leads to a requirement of an RF field deviation of less than ±10% transverse to the beam direction over a beam aperture with 10 cm diameter. All design aspects of this new spin-flip cavity, including the required field homogeneity and vacuum aspects, are discussed.

Alternative method for reconstruction of antihydrogen annihilation vertices

Energy Technology Data Exchange (ETDEWEB)

Amole, C., E-mail: chanpreet.amole@cern.ch [York University, Department of Physics and Astronomy (Canada); Ashkezari, M. D. [Simon Fraser University, Department of Physics (Canada); Andresen, G. B. [Aarhus University, Department of Physics and Astronomy (Denmark); Baquero-Ruiz, M. [University of California, Department of Physics (United States); Bertsche, W. [Swansea University, Department of Physics (United Kingdom); Bowe, P. D. [Aarhus University, Department of Physics and Astronomy (Denmark); Butler, E. [CERN, Physics Department (Switzerland); Cesar, C. L. [Universidade Federal do Rio de Janeiro, Instituto de Fisica (Brazil); Chapman, S. [University of California, Department of Physics (United States); Charlton, M.; Deller, A.; Eriksson, S. [Swansea University, Department of Physics (United Kingdom); Fajans, J. [University of California, Department of Physics (United States); Friesen, T.; Fujiwara, M. C. [University of Calgary, Department of Physics and Astronomy (Canada); Gill, D. R. [TRIUMF (Canada); Gutierrez, A. [University of British Columbia, Department of Physics and Astronomy (Canada); Hangst, J. S. [Aarhus University, Department of Physics and Astronomy (Denmark); Hardy, W. N. [University of British Columbia, Department of Physics and Astronomy (Canada); Hayano, R. S. [University of Tokyo, Department of Physics (Japan); Collaboration: ALPHA Collaboration; and others

2012-12-15

The ALPHA experiment, located at CERN, aims to compare the properties of antihydrogen atoms with those of hydrogen atoms. The neutral antihydrogen atoms are trapped using an octupole magnetic trap. The trap region is surrounded by a three layered silicon detector used to reconstruct the antiproton annihilation vertices. This paper describes a method we have devised that can be used for reconstructing annihilation vertices with a good resolution and is more efficient than the standard method currently used for the same purpose.

Alternative method for reconstruction of antihydrogen annihilation vertices

CERN Document Server

Amole, C; Andresen , G B; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jonsell, S; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki,Y

2012-01-01

The ALPHA experiment, located at CERN, aims to compare the properties of antihydrogen atoms with those of hydrogen atoms. The neutral antihydrogen atoms are trapped using an octupole magnetic trap. The trap region is surrounded by a three layered silicon detector used to reconstruct the antiproton annihilation vertices. This paper describes a method we have devised that can be used for reconstructing annihilation vertices with a good resolution and is more efficient than the standard method currently used for the same purpose.

Antihydrogen synthesis in a double-CUSP trap towards test of the CPT-symmetry

Energy Technology Data Exchange (ETDEWEB)

Radics, B., E-mail: balint.radics@cern.ch [ETH Zürich, Institute for Particle Physics (Switzerland); Ishikawa, S.; Kuroda, N. [University of Tokyo, Institute of Physics, Graduate School of Arts and Sciences (Japan); Murtagh, D. J.; Nagata, Y. [RIKEN, Atomic Physics Laboratory (Japan); Tajima, M. [University of Tokyo, Institute of Physics, Graduate School of Arts and Sciences (Japan); Gorp, S. Van [RIKEN, Atomic Physics Laboratory (Japan); Abo, Y. [Hiroshima University, Graduate School of Advanced Sciences of Matter (Japan); Dupre, P. [RIKEN, Atomic Physics Laboratory (Japan); Higashi, Y. [University of Tokyo, Institute of Physics, Graduate School of Arts and Sciences (Japan); Kaga, C. [Hiroshima University, Graduate School of Advanced Sciences of Matter (Japan); Leali, M.; Mascagna, V.; Venturelli, L.; Zurlo, N. [Universita di Brescia, Dipartimento di Ingegneria dell Informazione (Italy); Breuker, H. [CERN (Switzerland); Higaki, H. [Hiroshima University, Graduate School of Advanced Sciences of Matter (Japan); Kanai, Y. [RIKEN, Atomic Physics Laboratory (Japan); Rizzini, E. Lodi [Universita di Brescia, Dipartimento di Ingegneria dell Informazione (Italy); Matsuda, Y. [University of Tokyo, Institute of Physics, Graduate School of Arts and Sciences (Japan); and others

2016-12-15

The aim of the ASACUSA-CUSP experiment at CERN is to produce a cold, polarised antihydrogen beam and perform a high precision measurement of the ground-state hyperfine transition frequency of the antihydrogen atom and compare it with that of the hydrogen atom using the same spectroscopic beam line. Towards this goal a significant step was successfully accomplished: synthesised antihydrogen atoms have been produced in a CUSP magnetic configuration and detected at the end of our spectrometer beam line in 2012 [1]. During a long shut down at CERN the ASACUSA-CUSP experiment had been renewed by introducing a new double-CUSP magnetic configuration and a new semi-cylindrical tracking detector (AMT) [2], and by improving the transport feature of low energy antiproton beams. The new tracking detector monitors the antihydrogen synthesis during the mixing cycle of antiprotons and positrons. In this work the latest results and improvements of the antihydrogen synthesis will be presented including highlights from the last beam time.

Spectroscopy Apparatus for the Measurement of The Hyperfine Structure of Antihydrogen

CERN Document Server

Malbrunot, C.; Diermaier, M.; Dilaver, N.; Friedreich, S.; Kolbinger, B.; Lehner, S.; Lundmark, R.; Massiczek, O.; Radics, B.; Sauerzopf, C.; Simon, M.; Widmann, E.; Wolf, M.; Wünschek, B.; Zmeskal, J.

2014-02-04

The ASACUSA CUSP collaboration at the Antiproton Decelerator (AD) of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. We describe here the latest developments on the spectroscopy apparatus developed to be coupled to the antihydrogen production setup (CUSP).

AEgIS experiment: Towards antihydrogen beam production for antimatter gravity measurements

CERN Document Server

Mariazzi, Sebastiano; Amsler, Claude; Ariga, Akitaka; Ariga, Tomoko; Belov, Alexandre S; Bonomi, Germano; Bräunig, Philippe; Brusa, Roberto S; Bremer, Johan; Cabaret, Louis; Canali, Carlo; Caravita, Ruggero; Castelli, Fabrizio; Cerchiari, Giovanni; Cialdi, Simone; Comparat, Daniel; Consolati, Giovanni; Dassa, Luca; Derking, Jan Hendrik; Di Domizio, Sergio; Di Noto, Lea; Doser, Michael; Dudarev, Alexey; Ereditato, Antonio; Ferragut, Rafael; Fontana, Andrea; Genova, Pablo; Giammarchi, Marco; Gligorova, Angela; Gninenko, Sergei N; Hogan, Stephen D; Haider, Stefan; Jordan, Elena; Jørgensen, Lars V; Kaltenbacher, Thomas; Kawada, Jiro; Kellerbauer, Alban; Kimura, Mitsuhiro; Knecht, Andreas; Krasnický, Daniel; Lagomarsino, Vittorio; Lehner, Sebastian; Malbrunot, Chloe; Matveev, Viktor A; Merkt, Frederic; Moia, Fabio; Nebbia, Giancarlo; Nédélec, Patrick; Oberthaler, Markus K; Pacifico, Nicola; Petráček, Vojtech; Pistillo, Ciro; Prelz, Francesco; Prevedelli, Marco; Regenfus, Christian; Riccardi, Cristina; Røhne, Ole; Rotondi, Alberto; Sandaker, Heidi; Scampoli, Paola; Storey, James; Subieta Vasquez, Martin A.; Spaček, Michal; Czech Technical U. in Prague - FNSPE - B\\oehova 7 - 11519 - Praha 1 - Czech Aff25 Testera, Gemma; Vaccarone, Renzo; Villa, Fabio; Widmann, Eberhard; Zavatarelli, Sandra; Zmeskal, Johann

2014-01-01

AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is an experiment that aims to perform the first direct measurement of the gravitational acceleration g of antihydrogen in the Earth’s field. A cold antihydrogen beam will be produced by charge exchange reaction between cold antiprotons and positronium excited in Rydberg states. Rydberg positronium (with quantum number n between 20 and 30) will be produced by a two steps laser excitation. The antihydrogen beam, after being accelerated by Stark effect, will fly through the gratings of a moir ́ e deflectometer. The deflection of the horizontal beam due to its free fall will be measured by a position sensitive detector. It is estimated that the detection of about 10 3 antihydrogen atoms is required to determine the gravitational acceleration with a precision of 1%. In this report an overview of the AEgIS experiment is presented and its current status is described. Details on the production of slow positronium and its excitation with lasers ar...

Measuring g with a beam of antihydrogen (AEgIS)

CERN Document Server

Canali, C

2011-01-01

The gravitational interaction between matter and antimatter has never been tested experimentally. According to some attempts to unify gravity with the other forces, the possibility that $g(p) 6= g\\bar{(p)}$ cannot be excluded 1 . The AEGIS experiment 2 intends to measure for the first time the gravitational acceleration of antimatter using cold antihydrogen atoms. Antihydrogen atoms will be obtained trough a charge exchange process between Rydberg positronium atoms and antiprotons. Once $\\bar{H}$ are accelerated to form a horizontal beam, they travel through a Moire deflectometer, able to measure the vertical displacement of atoms due to gravity. Knowing the velocity of the antiatoms from the time of flight measurement and the length of the flight path allows to estimate the gravity acceleration g for antihydrogen. With this setup an initial precision on the measure of g of 1% is expected.

An improved limit on the charge of antihydrogen from stochastic acceleration.

Science.gov (United States)

Ahmadi, M; Baquero-Ruiz, M; Bertsche, W; Butler, E; Capra, A; Carruth, C; Cesar, C L; Charlton, M; Charman, A E; Eriksson, S; Evans, L T; Evetts, N; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Isaac, C A; Ishida, A; Jones, S A; Jonsell, S; Kurchaninov, L; Madsen, N; Maxwell, D; McKenna, J T K; Menary, S; Michan, J M; Momose, T; Munich, J J; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sacramento, R L; Sameed, M; Sarid, E; Silveira, D M; So, C; Tharp, T D; Thompson, R I; van der Werf, D P; Wurtele, J S; Zhmoginov, A I

2016-01-21

Antimatter continues to intrigue physicists because of its apparent absence in the observable Universe. Current theory requires that matter and antimatter appeared in equal quantities after the Big Bang, but the Standard Model of particle physics offers no quantitative explanation for the apparent disappearance of half the Universe. It has recently become possible to study trapped atoms of antihydrogen to search for possible, as yet unobserved, differences in the physical behaviour of matter and antimatter. Here we consider the charge neutrality of the antihydrogen atom. By applying stochastic acceleration to trapped antihydrogen atoms, we determine an experimental bound on the antihydrogen charge, Qe, of |Q| < 0.71 parts per billion (one standard deviation), in which e is the elementary charge. This bound is a factor of 20 less than that determined from the best previous measurement of the antihydrogen charge. The electrical charge of atoms and molecules of normal matter is known to be no greater than about 10(-21)e for a diverse range of species including H2, He and SF6. Charge-parity-time symmetry and quantum anomaly cancellation demand that the charge of antihydrogen be similarly small. Thus, our measurement constitutes an improved limit and a test of fundamental aspects of the Standard Model. If we assume charge superposition and use the best measured value of the antiproton charge, then we can place a new limit on the positron charge anomaly (the relative difference between the positron and elementary charge) of about one part per billion (one standard deviation), a 25-fold reduction compared to the current best measurement.

Interaction of antihydrogen with ordinary atoms and solid surfaces

Energy Technology Data Exchange (ETDEWEB)

Froelich, Piotr, E-mail: piotr.froelich@kvac.uu.se; Voronin, Alexei [P.N. Lebedev Physical Institute (Russian Federation)

2012-12-15

The characteristic features of cold atom-antiatom collisions and antiatom-surface interactions are discussed and illustrated by the results for hydrogen-antihydrogen scattering and for quantum reflection of ultracold antihydrogen from a metallic surface. We discuss in some detail the case of spin-exchange in ultracold H-bar - H collisions, exposing the interplay of Coulombic, strong and dispersive forces, and demonstrating the sensitivity of the spin-exchange cross sections to hypothetical violations of Charge-Parity-Time (CPT) symmetry.

Trapping of antiprotons -- a first step on the way to antihydrogen

International Nuclear Information System (INIS)

Holzscheiter, M.H.

1993-01-01

A first step towards producing and effectively utilizing antihydrogen atoms consists of trapping antiprotons. The immediate next step must then be to control, i.e. trap the produced antihydrogen. The current state of the art in trapping antiprotons and positrons is reviewed, and the challenges in trapping the resulting neutral particles are discussed

The four-body system made up of hydrogen and antihydrogen

International Nuclear Information System (INIS)

Armour, E.A.G.; Chamberlain, C.W.

2002-01-01

In view of current interest in the trapping of antihydrogen (H) atoms at low temperatures, we have investigated the reasons for considering that H-H does not have a bound state. We go on to carry out a four-body variational calculation for s-wave hydrogen-antihydrogen scattering, using the Kohn variational method. This is a continuation of earlier work on H-H interactions. Refs. 21 (author)

Real-time Detection of Antihydrogen Annihilations and Applications to Spectroscopy

Directory of Open Access Journals (Sweden)

Stracka Simone

2014-04-01

Full Text Available A detection scheme based on real-time measurement of antihydrogen annihilations during radiation injection is presented, which allows an efficient use of the trapped atoms for laser and microwave spectroscopy. The application of real-time detection of H¯$\\bar H$ annihilations to microwave spectroscopy, which yielded the first evidence of microwave induced spin-flip transitions in trapped antihydrogen [1], is reported.

Very low-energy hydrogen-antihydrogen scattering

International Nuclear Information System (INIS)

Armour, E.A.G.; Chamberlain, C.W.

2003-01-01

In view of current interest in the trapping of antihydrogen (H-bar) atoms at very low temperatures, we have carried out a calculation of s-wave hydrogen-antihydrogen scattering at very low energies, using the Kohn variational method, taking into account rearrangement scattering into the three channels that contain positronium in its ground state and lie closest to threshold. We find that our values for the elastic cross section are in good agreement with the values obtained by Jonsell et al. [2001 Phys. Rev. A 64 052712] using a distorted wave approximation. However, our values for the total rearrangement cross section are much larger than their values and we predict that cooling of H-bar by cold H would be considerably less efficient than was found to be the case by Jonsell et al.. (author)

Observation of the hyperfine spectrum of antihydrogen.

Science.gov (United States)

Ahmadi, M; Alves, B X R; Baker, C J; Bertsche, W; Butler, E; Capra, A; Carruth, C; Cesar, C L; Charlton, M; Cohen, S; Collister, R; Eriksson, S; Evans, A; Evetts, N; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Isaac, C A; Ishida, A; Johnson, M A; Jones, S A; Jonsell, S; Kurchaninov, L; Madsen, N; Mathers, M; Maxwell, D; McKenna, J T K; Menary, S; Michan, J M; Momose, T; Munich, J J; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sacramento, R L; Sameed, M; Sarid, E; Silveira, D M; Stracka, S; Stutter, G; So, C; Tharp, T D; Thompson, J E; Thompson, R I; van der Werf, D P; Wurtele, J S

2017-08-02

The observation of hyperfine structure in atomic hydrogen by Rabi and co-workers and the measurement of the zero-field ground-state splitting at the level of seven parts in 10 13 are important achievements of mid-twentieth-century physics. The work that led to these achievements also provided the first evidence for the anomalous magnetic moment of the electron, inspired Schwinger's relativistic theory of quantum electrodynamics and gave rise to the hydrogen maser, which is a critical component of modern navigation, geo-positioning and very-long-baseline interferometry systems. Research at the Antiproton Decelerator at CERN by the ALPHA collaboration extends these enquiries into the antimatter sector. Recently, tools have been developed that enable studies of the hyperfine structure of antihydrogen-the antimatter counterpart of hydrogen. The goal of such studies is to search for any differences that might exist between this archetypal pair of atoms, and thereby to test the fundamental principles on which quantum field theory is constructed. Magnetic trapping of antihydrogen atoms provides a means of studying them by combining electromagnetic interaction with detection techniques that are unique to antimatter. Here we report the results of a microwave spectroscopy experiment in which we probe the response of antihydrogen over a controlled range of frequencies. The data reveal clear and distinct signatures of two allowed transitions, from which we obtain a direct, magnetic-field-independent measurement of the hyperfine splitting. From a set of trials involving 194 detected atoms, we determine a splitting of 1,420.4 ± 0.5 megahertz, consistent with expectations for atomic hydrogen at the level of four parts in 10 4 . This observation of the detailed behaviour of a quantum transition in an atom of antihydrogen exemplifies tests of fundamental symmetries such as charge-parity-time in antimatter, and the techniques developed here will enable more-precise such tests.

Getting to grips with antihydrogen

CERN Multimedia

Katarina Anthony

2012-01-01

In June 2011, the ALPHA Collaboration announced that they had successfully managed to trap and hold atoms of antimatter for 1000 seconds. Last week they announced that their success in changing the internal state of antihydrogen and made the first ever measurement of its spectrum. The Collaboration is now installing an all-new experimental set-up – ALPHA-2 – and shows no signs of slowing down its investigations into the anti-world.   The ALPHA experiment hall. Newspapers and magazines around the world described the recent ALPHA announcement as the first step towards explaining why antimatter and matter did not cancel each other out in the first instances of creation, that is, why our universe of matter exists. Understanding the behaviour of matter and antimatter can help scientists solve this conundrum. With this in mind, the ALPHA collaboration has begun the study of the antihydrogen spectrum. So far, the Collaboration has been focused on proving that they can alter the ...

Antihydrogen annihilation reconstruction with the ALPHA silicon detector

Energy Technology Data Exchange (ETDEWEB)

Andresen, G.B. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Ashkezari, M.D. [Department of Physics, Simon Fraser University, Burnaby, BC, Canada V5A 1S6 (Canada); Bertsche, W. [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); Bowe, P.D. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Butler, E. [European Laboratory for Particle Physics, CERN, CH-1211 Geneva 23 (Switzerland); Cesar, C.L. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972 (Brazil); Chapman, S. [Department of Physics, University of California, Berkeley, CA 94720-7300 (United States); Charlton, M.; Deller, A.; Eriksson, S. [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); Fajans, J. [Department of Physics, University of California, Berkeley, CA 94720-7300 (United States); Friesen, T. [Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada T2N 1N4 (Canada); Fujiwara, M.C. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, Canada V6T 2A3 (Canada); Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada T2N 1N4 (Canada); Gill, D.R. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, Canada V6T 2A3 (Canada); Gutierrez, A. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada V6T 1Z4 (Canada); Hangst, J.S. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Hardy, W.N. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada V6T 1Z4 (Canada); Hayden, M.E. [Department of Physics, Simon Fraser University, Burnaby, BC, Canada V5A 1S6 (Canada); Hayano, R.S. [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Humphries, A.J. [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); and others

2012-08-21

The ALPHA experiment has succeeded in trapping antihydrogen, a major milestone on the road to spectroscopic comparisons of antihydrogen with hydrogen. An annihilation vertex detector, which determines the time and position of antiproton annihilations, has been central to this achievement. This detector, an array of double-sided silicon microstrip detector modules arranged in three concentric cylindrical tiers, is sensitive to the passage of charged particles resulting from antiproton annihilation. This article describes the method used to reconstruct the annihilation location and to distinguish the annihilation signal from the cosmic ray background. Recent experimental results using this detector are outlined.

Antihydrogen annihilation reconstruction with the ALPHA silicon detector

CERN Document Server

Andresen, G B; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D.R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Hayano, R S; Humphries, A J; Hydomako, R; Jonsell, S; Jorgensen, L V; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Sarid, E; Seif el Nasr, S; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Yamazaki, Y

2012-01-01

The ALPHA experiment has succeeded in trapping antihydrogen, a major milestone on the road to spectroscopic comparisons of antihydrogen with hydrogen. An annihilation vertex detector, which determines the time and position of antiproton annihilations, has been central to this achievement. This detector, an array of double-sided silicon microstrip detector modules arranged in three concentric cylindrical tiers, is sensitive to the passage of charged particles resulting from antiproton annihilation. This article describes the method used to reconstruct the annihilation location and to distinguish the annihilation signal from the cosmic ray background. Recent experimental results using this detector are outlined.

Antihydrogen spectroscopy and fundamental symmetry tests

DEFF Research Database (Denmark)

Ximenez Rodrigues Alves, Bruno

2018-01-01

The baryon asymmetry remains an important unanswered question in physics nowadays. The Standard Model of Particle Physics predicts that matter and antimatter should have been created in equal amounts in early stages of the universe. However, our universe seems to be pretty much empty of antimat......- ter. This discrepancy between theory and observation triggers scientists to investigate the properties of antimatter. A comparison between matter and antimatter properties constitutes a test of the charge conjugation-parity-time reversal (CPT) symmetry and any violation of this symmetry can open...... the doors for new physics and a possible explanation for the baryon asymmetry. Antihydrogen, the bound state of a positron and an antiproton, is the simplest anti-atom one can make. This thesis reports on the measurement of the resonance frequency of the 1S–2S transition in magnetically trapped antihydrogen...

Production and detection of cold anti-hydrogen atoms A first step towards high precision CPT test

CERN Document Server

Variola, A; Bonomi, G; Boutcha, A; Bowe, P; Carraro, C; Cesar, C L; Charlton, M; Doser, Michael; Filippini, V; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Lagomarsino, V; Landua, Rolf; Lindelöf, D; Lodi-Rizzini, E; Macri, M; Madsen, N; Manuzio, G; Montagna, P; Pruys, H S; Regenfus, C; Rotondi, A; Riedler, P; Testera, G; Van der Werf, D P

2003-01-01

Observations of anti-hydrogen in small quantities have been reported at CERN and at FermiLab, but these experiments were not suited to spectroscopy experiments. In 2002 the ATHENA collaboration reported the production and detection of very low energy anti-hydrogen atoms produced in cryogenic environment. This is the first major step in the study of antiatom's internal structure and it can lead to a high precision test of the CPT fundamental symmetry. The method of production and detection of cold anti-hydrogen will be introduced. The absolute rate of anti-hydrogen production and the signal to background ratio in the ATHENA experiment will be discussed. (7 refs) .

Fundamental symmetry tests with antihydrogen

International Nuclear Information System (INIS)

Hughes, R.J.

1992-01-01

The prospects for testing CPT invariance and the weak equivalence principle (WEP) for antimatter with spectroscopic measurements on antihydrogen are discussed. The potential precisions of these tests are compared with those from other measurements. The arguments involving energy conservation, the behavior of neutral kaons in a gravitational field and the equivalence principle for antiparticles are reviewed in detail

Investigation of two-frequency Paul traps for antihydrogen production

Energy Technology Data Exchange (ETDEWEB)

Leefer, Nathan; Krimmel, Kai, E-mail: kkrimmel@students.uni-mainz.de [Helmholtz-Institut Mainz (Germany); Bertsche, William [University of Manchester (United Kingdom); Budker, Dmitry [Helmholtz-Institut Mainz (Germany); Fajans, Joel [University of California at Berkeley, Department of Physics (United States); Folman, Ron [Ben-Gurion University of the Negev, Department of Physics (Israel); Häffner, Hartmut [University of California at Berkeley, Department of Physics (United States); Schmidt-Kaler, Ferdinand [Helmholtz-Institut Mainz (Germany)

2017-11-15

Radio-frequency (rf) Paul traps operated with multifrequency rf trapping potentials provide the ability to independently confine charged particle species with widely different charge-to-mass ratios. In particular, these traps may find use in the field of antihydrogen recombination, allowing antiproton and positron clouds to be trapped and confined in the same volume without the use of large superconducting magnets. We explore the stability regions of two-frequency Paul traps and perform numerical simulations of small samples of multispecies charged-particle mixtures of up to twelve particles that indicate the promise of these traps for antihydrogen recombination.

Prospects for measuring the gravitational free-fall of antihydrogen with emulsion detectors

CERN Document Server

Aghion, S.; Amsler, C.; Ariga, A.; Ariga, T.; Belov, A.S.; Bonomi, G.; Bräunig, P.; Bremer, J.; Brusa, R.S.; Cabaret, L.; Canali, C.; Caravita, R.; Castelli, F.; Cerchiari, G.; Cialdi, S.; Comparat, D.; Consolati, G.; Derking, J.H.; Di Domizio, S.; Di Noto, L.; Doser, M.; Dudarev, A.; Ereditato, A.; Ferragut, R.; Fontana, A.; Genova, P.; Giammarchi, M.; Gligorova, A.; Gninenko, S.N.; Haider, S.; Harasimovicz, J.; Hogan, S.D.; Huse, T.; Jordan, E.; Jørgensen, L.V.; Kaltenbacher, T.; Kawada, J.; Kellerbauer, A.; Kimura, M.; Knecht, A.; Krasnický, D.; Lagomarsino, V.; Magnani, A.; Mariazzi, S.; Matveev, V.A.; Moia, F.; Nebbia, G.; Nédélec, P.; Oberthaler, M.K.; Pacifico, N.; Petráček, V.; Pistillo, C.; Prelz, F.; Prevedelli, M.; Regenfus, C.; Riccardi, C.; Røhne, O.; Rotondi, A.; Sandaker, H.; Scampoli, P.; Sosa, A.; Storey, J.; Subieta Vasquez, M.A.; Špaček, M.; Testera, G.; Trezzi, D.; Vaccarone, R.; Welsch, C.P.; Zavatarelli, S.

2013-01-01

The main goal of the AEgIS experiment at CERN is to test the weak equivalence principle for antimatter. AEgIS will measure the free-fall of an antihydrogen beam traversing a moir\\'e deflectometer. The goal is to determine the gravitational acceleration g for antihydrogen with an initial relative accuracy of 1% by using an emulsion detector combined with a silicon micro-strip detector to measure the time of flight. Nuclear emulsions can measure the annihilation vertex of antihydrogen atoms with a precision of about 1 - 2 microns r.m.s. We present here results for emulsion detectors operated in vacuum using low energy antiprotons from the CERN antiproton decelerator. We compare with Monte Carlo simulations, and discuss the impact on the AEgIS project.

Experimental and computational study of the injection of antiprotons into a positron plasma for antihydrogen production

DEFF Research Database (Denmark)

Amole, C.; Ashkezari, M.D.; Baquero-Ruiz, M.

2013-01-01

One of the goals of synthesizing and trapping antihydrogen is to study the validity of charge-parity-time symmetry through precision spectroscopy on the anti-atoms, but the trapping yield achieved in recent experiments must be significantly improved before this can be realized. Antihydrogen atoms...... and upcoming antihydrogen experiments, and the latter scheme is seen to offer significant improvement in trapping yield as the number of available antiprotons increases....

Antihydrogen production and precision experiments

International Nuclear Information System (INIS)

Nieto, M.M.; Goldman, T.; Holzscheiter, M.H.

1996-01-01

The study of CPT invariance with the highest achievable precision in all particle sectors is of fundamental importance for physics. Equally important is the question of the gravitational acceleration of antimatter. In recent years, impressive progress has been achieved in capturing antiprotons in specially designed Penning traps, in cooling them to energies of a few milli-electron volts, and in storing them for hours in a small volume of space. Positrons have been accumulated in large numbers in similar traps, and low energy positron or positronium beams have been generated. Finally, steady progress has been made in trapping and cooling neutral atoms. Thus the ingredients to form antihydrogen at rest are at hand. Once antihydrogen atoms have been captured at low energy, spectroscopic methods can be applied to interrogate their atomic structure with extremely high precision and compare it to its normal matter counterpart, the hydrogen atom. Especially the 1S-2S transition, with a lifetime of the excited state of 122 msec and thereby a natural linewidth of 5 parts in 10 16 , offers in principle the possibility to directly compare matter and antimatter properties at a level of 1 part in 10 16

Study of the anti-hydrogen atom and ion formation in the collisions antiproton-positronium

International Nuclear Information System (INIS)

Comini, Pauline

2014-01-01

The future CERN experiment called GBAR intends to measure the gravitational acceleration of antimatter on Earth using cold (neV) anti-hydrogen atoms undergoing a free fall. The experiment scheme first needs to cool anti-hydrogen positive ions, obtained thanks to two consecutive reactions occurring when an antiproton beam collides with a dense positronium cloud.The present thesis studies these two reactions in order to optimise the production of the anti-ions. The total cross sections of both reactions have been computed in the framework of a perturbation theory model (Continuum Distorted Wave - Final State), in the range 0 to 30 keV antiproton kinetic energy; several excited states of positronium have been investigated. These cross sections have then been integrated to a simulation of the interaction zone where antiprotons collide with positronium; the aim is to find the optimal experimental parameters for GBAR. The results suggest that the 2P, 3D or, to a lower extend, 1S states of positronium should be used, respectively with 2, less than 1 or 6 keV antiprotons. The importance of using short pulses of antiprotons has been underlined; the positronium will have to be confined in a tube of 20 mm length and 1 mm diameter. In the prospect of exciting the 1S-3D two-photon transition in positronium at 410 nm, a pulsed laser system had already been designed. It consists in the frequency doubling of an 820 nm pulsed titanium-sapphire laser. The last part of the thesis has been dedicated to the realisation of this laser system, which delivers short pulses (9 ns) of 4 mJ energy at 820 nm. (author) [fr

CPT-symmetry studies with antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Lehnert, Ralf, E-mail: ralehner@indiana.edu [Indiana University Center for Spacetime Symmetries (United States)

2012-05-15

Various approaches to physics beyond the Standard Model can lead to small violations of CPT invariance. Since CPT symmetry can be measured with ultra-high precision, CPT tests offer an interesting phenomenological avenue to search for underlying physics. We discuss this reasoning in more detail, comment on the connection between CPT and Lorentz invariance, and review how CPT breaking would affect the (anti)hydrogen spectrum.

ATHENA: an actual antihydrogen annihilation

CERN Multimedia

2002-01-01

This is an image of an actual matter-antimatter annihilation due to an atom of antihydrogen in the ATHENA experiment, located on the Antiproton Decelerator (AD) at CERN since 2001. The antiproton produces four charged pions (yellow) whose positions are given by silicon microstrips (pink) before depositing energy in CsI crystals (yellow cubes). The positron also annihilates to produce back-to-back gamma rays (red).

Confinement of antihydrogen for 1,000 seconds

DEFF Research Database (Denmark)

Bruun Andresen, Gorm; Ashkezari, M.D.; Baquero-Ruiz, M.

2011-01-01

Atoms made of a particle and an antiparticle are unstable, usually surviving less than a microsecond. Antihydrogen, made entirely of antiparticles, is believed to be stable, and it is this longevity that holds the promise of precision studies of matter–antimatter symmetry. We have recently...

Axial to transverse energy mixing dynamics in octupole-based magnetostatic antihydrogen traps

Science.gov (United States)

Zhong, M.; Fajans, J.; Zukor, A. F.

2018-05-01

The nature of the trajectories of antihydrogen atoms confined in an octupole minimum-B trap is of great importance for upcoming spectroscopy, cooling, and gravity experiments. Of particular interest is the mixing time between the axial and transverse energies for the antiatoms. Here, using computer simulations, we establish that almost all trajectories are chaotic, and then quantify the characteristic mixing time between the axial and transverse energies. We find that there are two classes of trajectories: for trajectories whose axial energy is higher than about 20% of the total energy, the axial energy substantially mixes within about 10 s, whereas for trajectories whose axial energy is lower than about 10% of the total energy, the axial energy remains nearly constant for 1000 s or longer.

Resonant quantum transitions in trapped antihydrogen atoms

CERN Document Server

Amole, C; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Capra, A; Cesar, C L; Charlton, M; Deller, A; Donnan, P H; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Menary, S; Napoli, S C; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Shields, C R; Silveira, D M; Stracka, S; So, C; Thompson, R I; van der Werf, D P; Wurtele, J S

2012-01-01

The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom’s stature lies in its simplicity and in the accuracy with which its spectrum can be measured1 and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and—by comparison with measurements on its antimatter counterpart, antihydrogen—the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state2, 3 of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave...

Polish Acadaemy of Sciences Positronium for Antihydrogen Production in the AEGIS Experiment

CERN Document Server

Consolati, G; Amsler, C; Bonomi, G; Brusa, R S; Caccia, M; Caravita, R; Castelli, F; Cerchiari, G; Comparat, D; Demetrio, A; Di Noto, L; Doser, M; Evans, C; Fanì, M; Ferragut, R; Fesel, J; Fontana, A; Gerber, S; Giammarchi, M; Gligorova, A; Guatieri, F; Haider, S; Hinterberger, A; Holmestad, H; Kellerbauer, A; Khalidova, O; Krasnicky, D; Lagomarsino, V; Lansonneur, P; Lebrun, P; Malbrunot, C; Mariazzi, S; Marton, J; Matveev, V; Mazzotta, Z; Müller, S R; Nebbia, G; Nedelec, P; Oberthaler, M; Pacifico, N; Pagano, D; Penasa, L; Petracek, V; Prelz, F; Prevedelli, M; Ravelli, L; Rienaecker, B; Robert, J; Røhne, O M; Rotondi, A; Sandaker, H; Santoro, R; Smestad, L; Sorrentino, F; Testera, G; Tietje, I C; Widmann, E; Yzombard, P; Zimmer, C; Zmeskal, J; Zurlo, N

2017-01-01

The primary goal of the Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy (AEGIS) collaboration is to measure for the first time precisely the gravitational acceleration of antihydrogen, H¯ , a fundamental issue of contemporary physics, using a beam of antiatoms. Indeed, although indirect arguments have been raised against a different acceleration of antimatter with respect to matter, nevertheless some attempts to formulate quantum theories of gravity, or to unify gravity with the other forces, consider the possibility of a non-identical gravitational interaction between matter and antimatter. We plan to generate H¯ through a charge-exchange reaction between excited Ps and antiprotons coming from the Antiproton Decelerator facility at CERN. It offers the advantage to produce sufficiently cold antihydrogen to make feasible a measurement of gravitational acceleration with reasonable uncertainty (of the order of a few percent). Since the cross-section of the above reaction increases with n 4 , n b...

Discriminating between antihydrogen and mirror-trapped antiprotons in a minimum-B trap

CERN Document Server

Amole, C; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Hydomako, R; Kurchaninov, L; Jonsell, S; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S

2012-01-01

Recently, antihydrogen atoms were trapped at CERN in a magnetic minimum (minimum-B) trap formed by superconducting octupole and mirror magnet coils. The trapped antiatoms were detected by rapidly turning off these magnets, thereby eliminating the magnetic minimum and releasing any antiatoms contained in the trap. Once released, these antiatoms quickly hit the trap wall, whereupon the positrons and antiprotons in the antiatoms annihilated. The antiproton annihilations produce easily detected signals; we used these signals to prove that we trapped antihydrogen. However, our technique could be confounded by mirror-trapped antiprotons, which would produce seemingly-identical annihilation signals upon hitting the trap wall. In this paper, we discuss possible sources of mirror-trapped antiprotons and show that antihydrogen and antiprotons can be readily distinguished, often with the aid of applied electric fields, by analyzing the annihilation locations and times. We further discuss the general properties of antipr...

Detailed calculations on low-energy positron-hydrogen-molecule and helium-antihydrogen scattering

Energy Technology Data Exchange (ETDEWEB)

Armour, E A G; Cooper, J N; Gregory, M R; Todd, A C [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Jonsell, S [Department of Physics, University of Swansea, Swansea SA2 8PP (United Kingdom); Plummer, M, E-mail: edward.armour@nottingham.ac.u [Computational Science and Engineering, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom)

2010-01-01

In this paper, we consider two scattering processes: low-energy positron-hydrogen-molecule and helium-antihydrogen scattering. In the positron-hydrogen-molecule scattering calculations, we use the Kohn variational method to calculate Z{sub eff}, the number of target electrons available to the positron for annihilation. In the helium-antihydrogen scattering calculations, we use the Rayleigh-Ritz variational method to calculate a wave function for the leptons as a function of the distance between the helium and the antihydrogen. This is used, together with the associated nuclear wave function and the wave function for {alpha} p-bar + Ps{sup -}, to calculate the cross section for the rearrangement reaction He + H-bar {yields} {alpha} p-bar + Ps{sup -}, using the T-matrix and a form of the distorted wave approximation. For both processes, positron-electron correlation is taken into account accurately using Hylleraas-type functions.

Matter-antimatter interactions involving antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Armour, E.A.G. [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)]. E-mail: edward.armour@nottingham.ac.uk; Jonsell, S. [Department of Physics, Umeaa University, SE-90187 Umeaa (Sweden); Liu, Y. [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Todd, A.C. [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

2006-06-15

We review theoretical results for low-energy scattering of antihydrogen and atomic hydrogen and helium. Various inelastic channels, such as rearrangement and annihilation, as well as elastic scattering, are considered. In particular we give a progress report on our He-H-bar calculations and give preliminary results for the low-energy cross section for rearrangement into positronium and antiprotonic helium. As far as we are aware, this is the first time that these cross sections have been calculated.

Mexican hat curve for hydrogen and antihydrogen-states in natural atom H

CERN Document Server

Van Hooydonk, G

2004-01-01

Molecular band spectra as well as atomic line spectra reveal a left-right symmetry for atoms (Van Hooydonk, Spectrochim. Acta A, 2000, 56, 2273 and CERN-Ext-2002-041). We now extract a Mexican hat shaped or double well curve from the line spectrum (Lyman ns1/2 singlets) of natural atom H. An H CSB theory and its oscillator contribution (1-0.5pi/n)esp2/nexp2 lead to unprecedented results for antihydrogen physics, ahead of the CERN AD-project on artificial antihydrogen.

Characterization of the 1S-2S transition in antihydrogen.

Science.gov (United States)

Ahmadi, M; Alves, B X R; Baker, C J; Bertsche, W; Capra, A; Carruth, C; Cesar, C L; Charlton, M; Cohen, S; Collister, R; Eriksson, S; Evans, A; Evetts, N; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Hangst, J S; Hardy, W N; Hayden, M E; Isaac, C A; Johnson, M A; Jones, J M; Jones, S A; Jonsell, S; Khramov, A; Knapp, P; Kurchaninov, L; Madsen, N; Maxwell, D; McKenna, J T K; Menary, S; Momose, T; Munich, J J; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sacramento, R L; Sameed, M; Sarid, E; Silveira, D M; Stutter, G; So, C; Tharp, T D; Thompson, R I; van der Werf, D P; Wurtele, J S

2018-05-01

In 1928, Dirac published an equation 1 that combined quantum mechanics and special relativity. Negative-energy solutions to this equation, rather than being unphysical as initially thought, represented a class of hitherto unobserved and unimagined particles-antimatter. The existence of particles of antimatter was confirmed with the discovery of the positron 2 (or anti-electron) by Anderson in 1932, but it is still unknown why matter, rather than antimatter, survived after the Big Bang. As a result, experimental studies of antimatter 3-7 , including tests of fundamental symmetries such as charge-parity and charge-parity-time, and searches for evidence of primordial antimatter, such as antihelium nuclei, have high priority in contemporary physics research. The fundamental role of the hydrogen atom in the evolution of the Universe and in the historical development of our understanding of quantum physics makes its antimatter counterpart-the antihydrogen atom-of particular interest. Current standard-model physics requires that hydrogen and antihydrogen have the same energy levels and spectral lines. The laser-driven 1S-2S transition was recently observed 8 in antihydrogen. Here we characterize one of the hyperfine components of this transition using magnetically trapped atoms of antihydrogen and compare it to model calculations for hydrogen in our apparatus. We find that the shape of the spectral line agrees very well with that expected for hydrogen and that the resonance frequency agrees with that in hydrogen to about 5 kilohertz out of 2.5 × 10 15 hertz. This is consistent with charge-parity-time invariance at a relative precision of 2 × 10 -12 -two orders of magnitude more precise than the previous determination 8 -corresponding to an absolute energy sensitivity of 2 × 10 -20 GeV.

Experimental limit on the ratio of the gravitational mass to the inertial mass of antihydrogen

Science.gov (United States)

Fajans, Joel; Wurtele, Jonathan; Charman, Andrew; Zhmoginov, Andrey

2012-10-01

Physicists have long wondered if the gravitational interactions between matter and antimatter might be different from those between matter and itself. While there are many indirect indications that no such differences exist, i.e., that the weak equivalence principle holds, there have been no direct, free-fall style, experimental tests of gravity on antimatter. By searching for a propensity for antihydrogen atoms to fall downward when released from the ALPHA antihydrogen trap, we have determined that we can reject ratios of the gravitational mass to the inertial mass of antihydrogen greater than about 100 at a statistical significance level of 5%. A similar search places somewhat lower limits on a negative gravitational mass, i.e., on antigravity.

Antihydrogen atoms may have been drifters

CERN Multimedia

Reich, Eugenie Samuel

2003-01-01

"It is a mystery of cosmic proportions: why is the universe filled with matter and not antimatter? Physicists hoping to find the answer have been left scratching their heads this week by an analysis which claims that some antihydrogen atoms created last year may not be normal antiatoms after all. Instead, they may sit on the blurry line between atoms and plasma" (1 page)

AEGIS at CERN: Measuring Antihydrogen Fall

CERN Document Server

Giammarchi, Marco G.

2011-01-01

The main goal of the AEGIS experiment at the CERN Antiproton Decelerator is the test of fundamental laws such as the Weak Equivalence Principle (WEP) and CPT symmetry. In the first phase of AEGIS, a beam of antihydrogen will be formed whose fall in the gravitational field is measured in a Moire' deflectometer; this will constitute the first test of the WEP with antimatter.

Observation of the hyperfine spectrum of antihydrogen

Science.gov (United States)

Ahmadi, M.; Alves, B. X. R.; Baker, C. J.; Bertsche, W.; Butler, E.; Capra, A.; Carruth, C.; Cesar, C. L.; Charlton, M.; Cohen, S.; Collister, R.; Eriksson, S.; Evans, A.; Evetts, N.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Isaac, C. A.; Ishida, A.; Johnson, M. A.; Jones, S. A.; Jonsell, S.; Kurchaninov, L.; Madsen, N.; Mathers, M.; Maxwell, D.; McKenna, J. T. K.; Menary, S.; Michan, J. M.; Momose, T.; Munich, J. J.; Nolan, P.; Olchanski, K.; Olin, A.; Pusa, P.; Rasmussen, C. Ø.; Robicheaux, F.; Sacramento, R. L.; Sameed, M.; Sarid, E.; Silveira, D. M.; Stracka, S.; Stutter, G.; So, C.; Tharp, T. D.; Thompson, J. E.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.

2017-08-01

The observation of hyperfine structure in atomic hydrogen by Rabi and co-workers and the measurement of the zero-field ground-state splitting at the level of seven parts in 1013 are important achievements of mid-twentieth-century physics. The work that led to these achievements also provided the first evidence for the anomalous magnetic moment of the electron, inspired Schwinger’s relativistic theory of quantum electrodynamics and gave rise to the hydrogen maser, which is a critical component of modern navigation, geo-positioning and very-long-baseline interferometry systems. Research at the Antiproton Decelerator at CERN by the ALPHA collaboration extends these enquiries into the antimatter sector. Recently, tools have been developed that enable studies of the hyperfine structure of antihydrogen—the antimatter counterpart of hydrogen. The goal of such studies is to search for any differences that might exist between this archetypal pair of atoms, and thereby to test the fundamental principles on which quantum field theory is constructed. Magnetic trapping of antihydrogen atoms provides a means of studying them by combining electromagnetic interaction with detection techniques that are unique to antimatter. Here we report the results of a microwave spectroscopy experiment in which we probe the response of antihydrogen over a controlled range of frequencies. The data reveal clear and distinct signatures of two allowed transitions, from which we obtain a direct, magnetic-field-independent measurement of the hyperfine splitting. From a set of trials involving 194 detected atoms, we determine a splitting of 1,420.4 ± 0.5 megahertz, consistent with expectations for atomic hydrogen at the level of four parts in 104. This observation of the detailed behaviour of a quantum transition in an atom of antihydrogen exemplifies tests of fundamental symmetries such as charge-parity-time in antimatter, and the techniques developed here will enable more-precise such tests.

Compression of Antiproton Clouds for Antihydrogen Trapping

CERN Document Server

Andresen, G B; Bowe, P D; Bray, C C; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D R; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Hydomako, R; Jenkins, M J; Jørgensen, L V; Kurchaninov, L; Lambo, R; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Seif El Nasr, S; Silveira, D M; Storey, J W; Thompson, R I; Van der Werf, D P; Wurtele, J S; Yamazaki, Y

2008-01-01

Control of the radial profile of trapped antiproton clouds is critical to trapping antihydrogen. We report the first detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial profile and its relation to that of the electron plasma.

Why We Already Know that Antihydrogen is Almost Certainly NOT Going to Fall "Up"

CERN Document Server

Menary, Scott

2012-01-01

The ALPHA collaboration (of which I am a member) has made great strides recently in trapping antihydrogen and starting down the path of making spectroscopic measurements. The primary goal of the experiment is to test CPT invariance but there is also interest in testing another fundamental issue -- the gravitational interaction between matter and antimatter (the so-called question of "antigravity"). As well as the other antihydrogen trapping experiments -- ASACUSA and ATRAP -- there is also a new experiment in the Antiproton Decelerator hall at CERN called AEGIS which is dedicated to testing the gravitional interaction between antihydrogen and the Earth. It has been claimed in the literature that there "is no compelling evidence or theoretical reason to rule out such a difference (i.e., between $g$ and $\\bar{g}$) at the 1% level." I argue in this short paper that bending of light by the sun provides a more stringent limit than this.

Limit on the electric charge of antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Capra, A., E-mail: acapra@triumf.ca; Amole, C. [York University, Department of Physics and Astronomy (Canada); Ashkezari, M. D. [Simon Fraser University, Department of Physics (Canada); Baquero-Ruiz, M. [University of California at Berkeley, Department of Physics (United States); Bertsche, W. [University of Manchester, School of Physics and Astronomy (United Kingdom); Butler, E. [Imperial College, Centre for Cold Matter (United Kingdom); Cesar, C. L. [Universidade Federal do Rio de Janeiro, Instituto de Física (Brazil); Charlton, M.; Eriksson, S. [Swansea University, Department of Physics, College of Science (United Kingdom); Fajans, J. [University of California at Berkeley, Department of Physics (United States); Friesen, T. [University of Calgary, Department of Physics and Astronomy (Canada); Fujiwara, M. C.; Gill, D. R. [TRIUMF (Canada); Gutierrez, A. [University of British Columbia, Department of Physics and Astronomy (Canada); Hangst, J. S. [CERN, Physics Department (Switzerland); Hardy, W. N. [University of British Columbia, Department of Physics and Astronomy (Canada); Hayden, M. E. [Simon Fraser University, Department of Physics (Canada); Isaac, C. A. [Swansea University, Department of Physics, College of Science (United Kingdom); Jonsell, S. [Stockholm University, Department of Physics (Sweden); Kurchaninov, L. [TRIUMF (Canada); and others

2017-11-15

The ALPHA collaboration has successfully demonstrated the production and the confinement of cold antihydrogen, H̅. An analysis of trapping data allowed a stringent limit to be placed on the electric charge of the simplest antiatom. Charge neutrality of matter is known to a very high precision, hence a neutrality limit of H̅ provides a test of CPT invariance. The experimental technique is based on the measurement of the deflection of putatively charged H̅ in an electric field. The tendency for trapped H̅ atoms to be displaced by electrostatic fields is measured and compared to the results of a detailed simulation of H̅ dynamics in the trap. An extensive survey of the systematic errors was performed, and this work focuses on those due to the silicon vertex detector, which is the device used to determine the H̅ annihilation position. The limit obtained on the charge of the H̅ atom is Q = (−1.3 ± 1.8 ± 0.4) × 10{sup −8}, representing the first precision measurement with H̅ [1].

Cold Antimatter Plasmas, and Aspirations for Cold Antihydrogen

Science.gov (United States)

2002-06-24

UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012494 TITLE: Cold Antimatter Plasmas, and Aspirations for Cold...part numbers comprise the compilation report: ADP012489 thru ADP012577 UNCLASSIFIED Cold Antimatter Plasmas, and Aspirations for Cold Antihydrogen G...and positrons. The antiprotons come initially from the new Antiproton Decel- erator facility at CERN. Good control of such cold antimatter plasmas is

Description and first application of a new technique to measure the gravitational mass of antihydrogen

Science.gov (United States)

Alpha Collaboration; Amole, C.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Butler, E.; Capra, A.; Cesar, C. L.; Charlton, M.; Eriksson, S.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Isaac, C. A.; Jonsell, S.; Kurchaninov, L.; Little, A.; Madsen, N.; McKenna, J. T. K.; Menary, S.; Napoli, S. C.; Nolan, P.; Olin, A.; Pusa, P.; Rasmussen, C. Ø.; Robicheaux, F.; Sarid, E.; Silveira, D. M.; So, C.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Zhmoginov, A. I.; Charman, A. E.

2013-04-01

Physicists have long wondered whether the gravitational interactions between matter and antimatter might be different from those between matter and itself. Although there are many indirect indications that no such differences exist and that the weak equivalence principle holds, there have been no direct, free-fall style, experimental tests of gravity on antimatter. Here we describe a novel direct test methodology; we search for a propensity for antihydrogen atoms to fall downward when released from the ALPHA antihydrogen trap. In the absence of systematic errors, we can reject ratios of the gravitational to inertial mass of antihydrogen >75 at a statistical significance level of 5% worst-case systematic errors increase the minimum rejection ratio to 110. A similar search places somewhat tighter bounds on a negative gravitational mass, that is, on antigravity. This methodology, coupled with ongoing experimental improvements, should allow us to bound the ratio within the more interesting near equivalence regime.

Description and first application of a new technique to measure the gravitational mass of antihydrogen

CERN Document Server

Charman, A E; Menary, S; Capra, A; Baquero-Ruiz, M; Fajans, J; Ashkezari, M D; Bertsche, W; Butler, E; Cesar, C L; Charlton, M; Eriksson, S; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Napoli, S C; Nolan, P; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Thompson, R I; Van der Werf, D P; Wurtele, J S; Zhmoginov, A I

2013-01-01

Physicists have long wondered whether the gravitational interactions between matter and antimatter might be different from those between matter and itself. Although there are many indirect indications that no such differences exist and that the weak equivalence principle holds, there have been no direct, free-fall style, experimental tests of gravity on antimatter. Here we describe a novel direct test methodology; we search for a propensity for antihydrogen atoms to fall downward when released from the ALPHA antihydrogen trap. In the absence of systematic errors, we can reject ratios of the gravitational to inertial mass of antihydrogen >75 at a statistical significance level of 5%; worst-case systematic errors increase the minimum rejection ratio to 110. A similar search places somewhat tighter bounds on a negative gravitational mass, that is, on antigravity. This methodology, coupled with ongoing experimental improvements, should allow us to bound the ratio within the more interesting near equivalence regim...

Frequency Fine-tuning of a Spin-flip Cavity for Antihydrogen Atoms

CERN Document Server

Federmann, S; Mahner, E; Juhasz, B; Widmann, E

2012-01-01

As part of the ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) physics program a spin-flip cavity, for measurements of the ground-state hyperfine transition frequency of antihydrogen atoms, is needed. The purpose of the cavity is to excite antihydrogen atoms depending on their polarisation by a microwave field operating at 1.42 GHz. The delicacy of designing such a cavity lies in achieving and maintaining the required properties of this field over a large aperture of 10 cm and for a long period of time (required amplitude stability is 1% over 12 h). This paper presents the frequency fine tuning techniques developed to obtain the desired centre frequency of 1.42GHz with a Q value below 500 as well as the circuit used for the frequency sweep over a bandwidth of 6MHz.

Narrowband solid state vuv coherent source for laser cooling of antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Michan, J. Mario [TRIUMF (Canada); Polovy, Gene; Madison, Kirk W. [The University of British Columbia, Department of Physics and Astronomy (Canada); Fujiwara, Makoto C. [TRIUMF (Canada); Momose, Takamasa, E-mail: momose@chem.ubc.ca [The University of British Columbia, Department of Chemistry, Department of Physics and Astronomy (Canada)

2015-11-15

We describe the design and performance of a solid-state pulsed source of narrowband (< 100 MHz) Lyman-α radiation designed for the purpose of laser cooling magnetically trapped antihydrogen. Our source utilizes an injection seeded Ti:Sapphire amplifier cavity to generate intense radiation at 729.4 nm, which is then sent through a frequency doubling stage and a frequency tripling stage to generate 121.56 nm light. Although the pulse energy at 121.56 nm is currently limited to 12 nJ with a repetition rate of 10 Hz, we expect to obtain greater than 0.1 μJ per pulse at 10 Hz by further optimizing the alignment of the pulse amplifier and the efficiency of the frequency tripling stage. Such a power will be sufficient for cooling a trapped antihydrogen atom from 500 mK to 20mK.

Observation of Hyperfine Transitions in Trapped Ground-State Antihydrogen

CERN Document Server

Olin, Arthur

2015-01-01

This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that these transitions are consistent with the values in hydrogen to within 4~parts~in~$10^3$. Simulations of the trapped antiatoms in a microwave field are consistent with our measurements.

Observation of hyperfine transitions in trapped ground-state antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Collaboration: A. Olin for the ALPHA Collaboration

2015-08-15

This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that these transitions are consistent with the values in hydrogen to within 4 parts in 10{sup 3}. Simulations of the trapped antiatoms in a microwave field are consistent with our measurements.

Analysis of time-dependent effects when operating nested-well plasma traps for achieving antihydrogen recombination

International Nuclear Information System (INIS)

Chang Yongbin; Dolliver, D. D.; Ordonez, C. A.

1999-01-01

In the work reported, time-dependent effects are considered which affect the prospect of getting two oppositely signed plasmas to overlap the same region while trapped within a solenoidal magnetic field. Parameters that are relevant to future experimental attempts at producing cold antihydrogen atoms using nested-well plasma traps are considered. It is found that the timescale over which an overlap remains, without changing the electrode voltages, can be much larger than the timescale over which the overlap plasma recombines. Hence, it does not appear necessary to use time-dependent electrode voltages to maintain the overlap while antihydrogen atoms are being produced

Collisions between low-energy antihydrogen and atoms

International Nuclear Information System (INIS)

Armour, E.A.G.; Chamberlain, C.W.; Liu, Y.; Martin, G.D.R.

2004-01-01

Antihydrogen is currently the subject of great interest as cold H-bar has recently been prepared at CERN by the ATHENA and ATRAP projects. This work is described elsewhere in this volume. In this paper, we describe a calculation that we have carried out recently for very low-energy HH-bar scattering using the Kohn variational method and including three rearrangement channels in addition to the elastic channel. We also consider the He-H-bar system and give a progress report on the calculation that we are currently carrying out for this system

Collisions between low-energy antihydrogen and atoms

Energy Technology Data Exchange (ETDEWEB)

Armour, E.A.G. E-mail: edward.armour@nottingham.ac.uk; Chamberlain, C.W.; Liu, Y.; Martin, G.D.R

2004-07-01

Antihydrogen is currently the subject of great interest as cold H-bar has recently been prepared at CERN by the ATHENA and ATRAP projects. This work is described elsewhere in this volume. In this paper, we describe a calculation that we have carried out recently for very low-energy HH-bar scattering using the Kohn variational method and including three rearrangement channels in addition to the elastic channel. We also consider the He-H-bar system and give a progress report on the calculation that we are currently carrying out for this system.

Antihydrogen Production in $ \\bar{p} $ Z - interaction

CERN Multimedia

2002-01-01

% PS210 \\\\ \\\\ The production of the antihydrogen atom $ \\bar {H}^0 \\equiv \\bar{p}e $ as the simplest atomic bound state of antimatter has been studied. Nine $ \\bar {H}^0 $ have been observed.\\\\ \\\\ The production of $ \\bar {H}^0 $ is predominantly mediated by the two-photon mechanism in the antiproton-nucleus interaction. In principle $ \\bar {H}^0 $ is well suited for investigations of fundamental CPT violation studies under different forces, however, in the present experiment we concentrated on the production of this antimatter object, since so far it never had been observed.

Collisions between low-energy antihydrogen and atoms

CERN Document Server

Armour, E A G; Liu, Y; Martin, G D R

2004-01-01

Antihydrogen is currently the subject of great interest as cold H has recently been prepared at CERN by the ATHENA and ATRAP projects. This work is described elsewhere in this volume. In this paper, we describe a calculation that we have carried out recently for very low-energy HH scattering using the Kohn variational method and including three rearrangement channels in addition to the elastic channel. We also consider the He-H system and give a progress report on the calculation that we are currently carrying out for this system.

Prospects for Lorentz and CPT tests with hydrogen and antihydrogen

CERN Document Server

Becker, Tobias Frederic

2017-01-01

As a summer student for 13 weeks in the ASACUSA-CUSP collaboration, under the supervision of Chloé Malbrunot, my project consisted in a first part on the theoretical treatment of Lorentz and CPT violation in hydrogen & antihydrogen in the framework of the Standard Model Extension SME and in second part on experimental measurements on a hydrogen beam.

Des atomes d'antihydrogene produits en quantites substantielles au CERN

CERN Multimedia

Sevestre, G

2002-01-01

"Des quantites relativement substantielles d'atomes d'antihydrogene a basse temperature ont ete produites cet ete au Laboratoire europeen de physique des particules, le CERN a Geneve, ouvrant la voie a une etude approfondie de cette antimatiere qui pourrait remettre en cause les theories actuelles, a annonce mercredi sur le site Internet de la revue Nature une equipe internationale de chercheurs" (1 page).

Collisions involving antiprotons and antihydrogen: an overview

Science.gov (United States)

Jonsell, S.

2018-03-01

I give an overview of experimental and theoretical results for antiproton and antihydrogen scattering with atoms and molecules (in particular H, He). At low energies (>1 keV) there are practically no experimental data available. Instead I compare the results from different theoretical calculations, of various degrees of sophistication. At energies up to a few tens of eV, I focus on simple approximations that give reasonably accurate results, as these allow quick estimates of collision rates without embarking on a research project. This article is part of the Theo Murphy meeting issue `Antiproton physics in the ELENA era'.

Inclusion of the strong interaction in low-energy hydrogen-antihydrogen scattering using a complex potential

International Nuclear Information System (INIS)

Armour, E A G; Liu, Y; Vigier, A

2005-01-01

The aim of experimentalists currently working on the preparation of antihydrogen is to trap it at very low temperatures so that its properties can be studied. Any process that can lead to loss of antihydrogen is thus of great concern to them. In view of this, we have carried out a calculation of the antiproton annihilation cross section in very low-energy hydrogen-antihydrogen scattering using a complex potential to represent the strong interaction that brings about the annihilation. The potential takes into account the isotopic spin state of the proton and the antiproton and the possibility that they may be in either a singlet or a triplet spin state. The results for the annihilation cross section and the percentage change in the elastic cross section due to the inclusion of the strong interaction are similar to those obtained in a recent calculation (Jonsell et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 1195), using an effective range expansion. They are smaller by a factor of 2 and 3, respectively, than those obtained in an earlier calculation (Voronin and Carbonell 2001 Nucl. Phys. A 689 529c), using a coupled channel method and a complex strong interaction potential. (letter to the editor)

Antimatter plasmas and antihydrogen

International Nuclear Information System (INIS)

Greaves, R.G.; Surko, C.M.

1997-01-01

Recent successes in confining antimatter in the form of positron and antiproton plasmas have created new scientific and technological opportunities. Plasma techniques have been the cornerstone of experimental work in this area, and this is likely to be true for the foreseeable future. Work by a number of groups on trapping antimatter plasmas is summarized, and an overview of the promises and challenges in this field is presented. Topics relating to positron plasmas include the use of positrons to study the unique properties of electron endash positron plasmas, the interaction between positrons and ordinary matter, and the laboratory modeling of positron-annihilation processes in interstellar media. The availability of cold, trapped antiprotons and positrons makes possible the production of neutral antimatter in the form of antihydrogen. This is expected to enable precise comparisons of the properties of matter and antimatter, including tests of fundamental symmetries and the measurement of the interaction of antimatter with gravity. copyright 1997 American Institute of Physics

Hydrogen-antihydrogen oscillations: Signature of intermediate mass scales in GUTs

Directory of Open Access Journals (Sweden)

Uptal Sarkar

1983-01-01

Full Text Available Hydrogen-antihydrogen oscillations and the double nucleon decay (pp, np and nn into two antileptons are discussed in the context of SO(10, E(6 and SU(16 GUTs. It is shown that the intermediate mass scales of the GUTs concerned govern the amplitude of these processes which are found to compete with the other baryon nonconserving processes in SU(16 GUT.

First step in the process of calculating the cross section for muonic antihydrogen

CERN Document Server

Maher, Niamh

2016-01-01

The end goal of the project is to measure the charge radius of the antiproton with muons. However a necessary step first is to calculate cross section of Muonium and antiprotons in the production of antihydrogen to determine the feasibility of such an experiment.

Towards Measuring the Ground State Hyperfine Splitting of Antihydrogen -- A Progress Report

CERN Document Server

Sauerzopf, C.

2016-06-20

We report the successful commissioning and testing of a dedicated field-ioniser chamber for measuring principal quantum number distributions in antihydrogen as part of the ASACUSA hyperfine spectroscopy apparatus. The new chamber is combined with a beam normalisation detector that consists of plastic scintillators and a retractable passivated implanted planar silicon (PIPS) detector.

Emulsion detectors for the antihydrogen detection in AEgIS

Energy Technology Data Exchange (ETDEWEB)

Pistillo, C., E-mail: ciro.pistillo@cern.ch [University of Bern, Albert Einstein Center for Fundamental Physics, Laboratory for High Energy Physics (Switzerland); Aghion, S. [Politecnico of Milano (Italy); Amsler, C.; Ariga, A.; Ariga, T. [University of Bern, Albert Einstein Center for Fundamental Physics, Laboratory for High Energy Physics (Switzerland); Belov, A. [Institute for Nuclear Research of the Russian Academy of Science (Russian Federation); Bonomi, G. [University of Brescia, Department of Mechanical and Industrial Engineering (Italy); Bräunig, P. [Heidelberg University, Kirchhoff-Institute for Physics (Germany); Bremer, J. [CERN, Physics Department (Switzerland); Brusa, R. S. [University of Trento, Department of Physics (Italy); Cabaret, L. [University of Paris-Sud, Laboratory Aim Cotton, CNRS (France); Caccia, M. [INFN Milano (Italy); Caravita, R. [University of Genova, Department of Physics (Italy); Castelli, F. [INFN Milano (Italy); Cerchiari, G. [Max Planck Institute for Nuclear Physics (Germany); Chlouba, K. [Czech Technical University (Czech Republic); Cialdi, S. [INFN Milano (Italy); Comparat, D. [University of Paris-Sud, Laboratory Aim Cotton, CNRS (France); Consolati, G. [Politecnico of Milano (Italy); Demetrio, A. [Heidelberg University, Kirchhoff-Institute for Physics (Germany); and others

2015-08-15

The AEgIS experiment at CERN aims to perform the first direct measurement of gravitational interaction between matter and antimatter by measuring the deviation of a cold antihydrogen beam in the Earth gravitational field. The design of the experiment has been recently updated to include emulsion films as position sensitive detector. The submicrometric position accuracy of emulsions leads indeed to a significant improvement of the experimental sensitivity. We present results of preliminary tests and discuss perspectives for the final measurement.

A reliable cw Lyman-{alpha} laser source for future cooling of antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Kolbe, Daniel, E-mail: kolbed@uni-mainz.de; Beczkowiak, Anna; Diehl, Thomas; Koglbauer, Andreas; Sattler, Matthias; Stappel, Matthias; Steinborn, Ruth; Walz, Jochen [Johannes Gutenberg-Universitaet, Institut fuer Physik (Germany)

2012-12-15

We demonstrate a reliable continuous-wave (cw) laser source at the 1 S-2 P transition in (anti)hydrogen at 121.56 nm (Lyman-{alpha}) based on four-wave sum-frequency mixing in mercury. A two-photon resonance in the four-wave mixing scheme is essential for a powerful cw Lyman-{alpha} source and is well investigated.

A reliable cw Lyman-α laser source for future cooling of antihydrogen

International Nuclear Information System (INIS)

Kolbe, Daniel; Beczkowiak, Anna; Diehl, Thomas; Koglbauer, Andreas; Sattler, Matthias; Stappel, Matthias; Steinborn, Ruth; Walz, Jochen

2012-01-01

We demonstrate a reliable continuous-wave (cw) laser source at the 1 S–2 P transition in (anti)hydrogen at 121.56 nm (Lyman-α) based on four-wave sum-frequency mixing in mercury. A two-photon resonance in the four-wave mixing scheme is essential for a powerful cw Lyman-α source and is well investigated.

Development of mini linac-based positron source and an efficient positronium convertor for positively charged antihydrogen production

Science.gov (United States)

Muranaka, T.; Debu, P.; Dupré, P.; Liszkay, L.; Mansoulie, B.; Pérez, P.; Rey, J. M.; Ruiz, N.; Sacquin, Y.; Crivelli, P.; Gendotti, U.; Rubbia, A.

2010-04-01

We have installed in Saclay a facility for an intense positron source in November 2008. It is based on a compact 5.5 MeV electron linac connected to a reaction chamber with a tungsten target inside to produce positrons via pair production. The expected production rate for fast positrons is 5·1011 per second. The study of moderation of fast positrons and the construction of a slow positron trap are underway. In parallel, we have investigated an efficient positron-positronium convertor using porous silica materials. These studies are parts of a project to produce positively charged antihydrogen ions aiming to demonstrate the feasibility of a free fall antigravity measurement of neutral antihydrogen.

Development of mini linac-based positron source and an efficient positronium convertor for positively charged antihydrogen production

International Nuclear Information System (INIS)

Muranaka, T; Debu, P; Dupre, P; Liszkay, L; Mansoulie, B; Perez, P; Rey, J M; Ruiz, N; Sacquin, Y; Crivelli, P; Gendotti, U; Rubbia, A

2010-01-01

We have installed in Saclay a facility for an intense positron source in November 2008. It is based on a compact 5.5 MeV electron linac connected to a reaction chamber with a tungsten target inside to produce positrons via pair production. The expected production rate for fast positrons is 5·10 11 per second. The study of moderation of fast positrons and the construction of a slow positron trap are underway. In parallel, we have investigated an efficient positron-positronium convertor using porous silica materials. These studies are parts of a project to produce positively charged antihydrogen ions aiming to demonstrate the feasibility of a free fall antigravity measurement of neutral antihydrogen.

Development of mini linac-based positron source and an efficient positronium convertor for positively charged antihydrogen production

Energy Technology Data Exchange (ETDEWEB)

Muranaka, T; Debu, P; Dupre, P; Liszkay, L; Mansoulie, B; Perez, P; Rey, J M; Ruiz, N; Sacquin, Y [Irfu, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex (France); Crivelli, P; Gendotti, U; Rubbia, A, E-mail: tomoko.muranaka@cea.f [Institut fuer TelichenPhysik, ETHZ, CH-8093 Zuerich (Switzerland)

2010-04-01

We have installed in Saclay a facility for an intense positron source in November 2008. It is based on a compact 5.5 MeV electron linac connected to a reaction chamber with a tungsten target inside to produce positrons via pair production. The expected production rate for fast positrons is 5{center_dot}10{sup 11} per second. The study of moderation of fast positrons and the construction of a slow positron trap are underway. In parallel, we have investigated an efficient positron-positronium convertor using porous silica materials. These studies are parts of a project to produce positively charged antihydrogen ions aiming to demonstrate the feasibility of a free fall antigravity measurement of neutral antihydrogen.

Anti-hydrogen: The cusp between quantum mechanics and general relativity

International Nuclear Information System (INIS)

Noyes, H.P.

1992-09-01

We argue that the crossing (CPT) symmetry of relativistic quantum mechanics requires that both the coulombic and the Newtonian force between pairs of particles will reverse when one is replaced by its anti-particle. For consistency, this requires a theory in which both the equivalence principles and gauge invariance are abandoned. thus whether anti-hydrogen ''falls'' up or down will provide an experiment crusis separating general relativity and gauge invariance from this version of quantum mechanics

Possibilities for achieving antihydrogen recombination and trapping using a nested Penning trap and a magnetic well

International Nuclear Information System (INIS)

Ordonez, C.A.; Dolliver, D.D.; Chang Yongbin; Correa, J. R.

2002-01-01

A theoretical study is presented regarding some possibilities for achieving antihydrogen recombination and trapping using a nested Penning trap and a magnetic well. The work reported consists of a review, an extension, and applications of the relevant knowledge base. A nested Penning trap produces a magnetic field, which provides plasma confinement perpendicular to the magnetic field, and an electric field associated with a nested-well potential profile. The nested-well potential profile provides plasma confinement parallel to the magnetic field for oppositely signed plasma species that can have overlapping confinement regions. A configuration is considered in which the electric field is applied in two regions of uniform magnetic field that reside on opposite sides of a magnetic well region. The electric field confines overlapping positron and antiproton plasmas, which thread the magnetic well region. The magnetic well region would serve to trap a fraction of any antihydrogen atoms that are formed. Two different methods are considered for achieving overlap of positron and antiproton plasmas. For each, a set of conditions is predicted for achieving antihydrogen recombination and trapping. Although the study reported specifically considers simultaneous confinement of positron and antiproton plasmas in nested Penning traps, much of the information presented is also relevant to the prospect of merging other pairs of oppositely signed plasmas (e.g., electron and positron plasmas)

Towards measuring the ground state hyperfine splitting of antihydrogen – a progress report

Energy Technology Data Exchange (ETDEWEB)

Sauerzopf, C., E-mail: clemens.sauerzopf@oeaw.ac.at; Capon, A. A.; Diermaier, M. [Stefan Meyer Institute for subatomic physics, Austrian Academy of Sciences (Austria); Dupré, P. [Atomic Physics Laboratory, RIKEN (Japan); Higashi, Y. [University of Tokyo, Institute of Physics, Graduate School of Arts and Sciences (Japan); Kaga, C. [Hiroshima University, Graduate School of Advanced Sciences of Matter (Japan); Kolbinger, B. [Stefan Meyer Institute for subatomic physics, Austrian Academy of Sciences (Austria); Leali, M. [Università di Brescia, Dipartimento di Ingegneria dell’ Informazione (Italy); Lehner, S. [Stefan Meyer Institute for subatomic physics, Austrian Academy of Sciences (Austria); Rizzini, E. Lodi [Università di Brescia, Dipartimento di Ingegneria dell’ Informazione (Italy); Malbrunot, C. [Stefan Meyer Institute for subatomic physics, Austrian Academy of Sciences (Austria); Mascagna, V. [Università di Brescia, Dipartimento di Ingegneria dell’ Informazione (Italy); Massiczek, O. [Stefan Meyer Institute for subatomic physics, Austrian Academy of Sciences (Austria); Murtagh, D. J.; Nagata, Y.; Radics, B. [Atomic Physics Laboratory, RIKEN (Japan); Simon, M. C.; Suzuki, K. [Stefan Meyer Institute for subatomic physics, Austrian Academy of Sciences (Austria); Tajima, M. [University of Tokyo, Institute of Physics, Graduate School of Arts and Sciences (Japan); Ulmer, S. [Ulmer Initiative Research Unit, RIKEN (Japan); and others

2016-12-15

We report the successful commissioning and testing of a dedicated field-ioniser chamber for measuring principal quantum number distributions in antihydrogen as part of the ASACUSA hyperfine spectroscopy apparatus. The new chamber is combined with a beam normalisation detector that consists of plastic scintillators and a retractable passivated implanted planar silicon (PIPS) detector.

Annihilation detector for an in-beam spectroscopy apparatus to measure the ground state hyperfine splitting of antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Sauerzopf, Clemens, E-mail: clemens.sauerzopf@oeaw.ac.at [Stefan Meyer Institute for subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Wien (Austria); Capon, Aaron A.; Diermaier, Martin; Fleck, Markus; Kolbinger, Bernadette [Stefan Meyer Institute for subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Wien (Austria); Malbrunot, Chloé [Stefan Meyer Institute for subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Wien (Austria); Organisation Européenne pour la Recherche Nucléaire (CERN), 1211 Geneva 23 (Switzerland); Massiczek, Oswald; Simon, Martin C.; Vamosi, Stefan; Zmeskal, Johann; Widmann, Eberhard [Stefan Meyer Institute for subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Wien (Austria)

2017-02-11

The matter-antimatter asymmetry observed in the universe today still lacks a quantitative explanation. One possible mechanism that could contribute to the observed imbalance is a violation of the combined Charge-, Parity- and Time symmetries (CPT). A test of CPT symmetry using anti-atoms is being carried out by the ASACUSA-CUSP collaboration at the CERN Antiproton Decelerator using a low temperature beam of antihydrogen—the most simple atomic system built only of antiparticles. While hydrogen is the most abundant element in the universe, antihydrogen is produced in very small quantities in a laboratory framework. A detector for in-beam measurements of the ground state hyperfine structure of antihydrogen has to be able to detect very low signal rates within high background. To fulfil this challenging task, a two layer barrel hodoscope detector was developed. It is built of plastic scintillators with double sided readout via Silicon Photomultipliers (SiPMs). The SiPM readout is done using novel, compact and cost efficient electronics that incorporate power supply, amplifier and discriminator on a single board. This contribution will evaluate the performance of the new hodoscope detector. - Highlights: • A novel detector for Antihydrogen was successfully commissioned. • A time of flight resolution of better than 1 ns was achieved. • Rudimentary 3D tracking is possible without bar segmentation.

(Anti)hydrogen recombination studies in a nested Penning trap

International Nuclear Information System (INIS)

Quint, W.; Kaiser, R.; Hall, D.; Gabrielse, G.

1993-01-01

Extremely cold antiprotons, stored in Penning trap at 4 K, open the way toward the production and study of cold antihydrogen. We have begun experimentally investigating the possibility to recombine cold positrons and antiprotons within nested Penning traps. Trap potentials are adjusted to allow cold trapped protons (and positive helium ions) to pass through cold trapped electrons. Electrons, protons and ions are counted by ejecting them to a cold channel plate and by nondestructive radiofrequency techniques. The effect of the space charge of one trapped species upon another trapped species passing through is clearly observed. (orig.)

Nonneutral plasma diagnostic commissioning for the ALPHA Antihydrogen experiment

Science.gov (United States)

Konewko, S.; Friesen, T.; Tharp, T. D.; Alpha Collaboration

2017-10-01

The ALPHA experiment at CERN creates antihydrogen by mixing antiproton and positron plasmas. Diagnostic measurements of the precursor plasmas are performed using a diagnostic suite, colloquially known as the ``stick.'' This stick has a variety of sensors and is able to move to various heights to align the desired diagnostic with the beamline. A cylindrical electrode, a faraday cup, an electron gun, and a microchannel-plate detector (MCP) are regularly used to control and diagnose plasmas in ALPHA. We have designed, built, and tested a new, upgraded stick which includes measurement capabilities in both beamline directions.

Description and first application of a new technique to measure the gravitational mass of antihydrogen

DEFF Research Database (Denmark)

Amole, C.; Ashkezari, M.D.; Baquero-Ruiz, M.

2013-01-01

of the gravitational to inertial mass of antihydrogen >75 at a statistical significance level of 5%; worst-case systematic errors increase the minimum rejection ratio to 110. A similar search places somewhat tighter bounds on a negative gravitational mass, that is, on antigravity. This methodology, coupled...

Strong equivalence, Lorentz and CPT violation, anti-hydrogen spectroscopy and gamma-ray burst polarimetry

International Nuclear Information System (INIS)

Shore, Graham M.

2005-01-01

The strong equivalence principle, local Lorentz invariance and CPT symmetry are fundamental ingredients of the quantum field theories used to describe elementary particle physics. Nevertheless, each may be violated by simple modifications to the dynamics while apparently preserving the essential fundamental structure of quantum field theory itself. In this paper, we analyse the construction of strong equivalence, Lorentz and CPT violating Lagrangians for QED and review and propose some experimental tests in the fields of astrophysical polarimetry and precision atomic spectroscopy. In particular, modifications of the Maxwell action predict a birefringent rotation of the direction of linearly polarised radiation from synchrotron emission which may be studied using radio galaxies or, potentially, gamma-ray bursts. In the Dirac sector, changes in atomic energy levels are predicted which may be probed in precision spectroscopy of hydrogen and anti-hydrogen atoms, notably in the Doppler-free, two-photon 1s-2s and 2s-nd (n∼10) transitions

Professor Walter Oelert, leader of the team which created the first atoms of antihydrogen at the Low Energy Antiproton Ring (LEAR) in January 1996

CERN Document Server

Laurent Guiraud

1996-01-01

Antiparticles were predicted in the work of Paul Dirac in the 1920's, since when physicists have identified all the necessary antiparticle constituents of an antiparticle atom - antielectrons (positrons), antiprotons and antineutrons. However, an antihydrogen atom wasn't produced until the PS210 experiment at CERN in 1995. PS210 used the LEAR accelerator, which was then nearing the end of its lifetime, so everything in the experiment had to work first time. After installing the equipment in spring 1995, the experiment took place in the autumn, in two hour periods over 4 weeks. The experiment team collided energetic antiprotons from LEAR with a heavy element, a challenge for them as well as the LEAR operators. Proving that antihydrogen atoms had been formed required several more weeks of data analysis, but the announcement that nine antihydrogen atoms had been produced came on 4 January 1996.

Hydrogen-antihydrogen interactions

International Nuclear Information System (INIS)

Armour, E.A.G.; Carr, J.M.

1998-01-01

A small number of antihydrogen (AH) atoms have recently been prepared at CERN and at Fermilab. However, these atoms were travelling at speeds close to that of light. It is intended to carry out experiments on AH by trapping it at very low temperature ( 2 and He with energies up to room temperature. However, these reactions are not easy to treat theoretically. In this paper we consider the interaction between AH and H. This has already received some attention. Initially, in a collision between AH and H the electron is bound to the proton and the positron is bound to the antiproton. Clearly, if the proton and antiproton coincide they cannot bind the two light particles. There exists a critical value, R c , of the internuclear distance, probably not very much below a 0 , below which the electron and the positron can attain a lower energy by separating from the nuclei and forming positronium. As a first stage in our work on the H-AH interaction, we are carrying out variational calculations of the energy of the H-AH system for internuclear separations a short distance above R c . The aim is to determine R c as accurately as possible. The basis set used is similar to that of a previous calculation by W. Kolos, D.L. Morgan, D.M. Schrader, L. Wolniewiez (1975). However, it also contains a function to represent weakly bound positronium. Initial results suggest that R c 0 . (orig.)

An investigation of antiprotons collisions with positronium atom in Debye plasma environments

International Nuclear Information System (INIS)

Pandey, M. K.; Lin, Y.-C.; Ho, Y. K.

2015-01-01

The effects of Debye plasmas on antihydrogen formation and ionization processes are investigated in antiprotons (p ¯ ) and positronium (Ps) collisions. The classical trajectory Monte Carlo method with Debye Hückel potentials has been used for cross section calculations. In this process, antihydrogen formation and ionization cross sections have been calculated in unscreened as well as in Debye plasmas conditions in energies ranging from 1 to 500 keV. Partial cross sections for antihydrogen formation are also calculated which show the largest cross sections correspond to production of antihydrogen in the n = 2 (2s, 2p) states. Comparative study has been carried out to determine the differences of cross sections in screening and unscreening cases. The results show that the cross sections for both antihydrogen formation and positronium ionization depend on Debye screening lengths as well as on collision energies. The effects of plasmas conditions on antihydrogen formation and positronium ionization are explained in terms of classical trajectory framework. Our results for the unscreened case are in agreement with previously reported results

An investigation of antiprotons collisions with positronium atom in Debye plasma environments

Energy Technology Data Exchange (ETDEWEB)

Pandey, M. K., E-mail: pandey@pub.iams.sinica.edu.tw; Lin, Y.-C.; Ho, Y. K., E-mail: ykho@pub.iams.sinica.edu.tw [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan (China)

2015-05-15

The effects of Debye plasmas on antihydrogen formation and ionization processes are investigated in antiprotons (p{sup ¯}) and positronium (Ps) collisions. The classical trajectory Monte Carlo method with Debye Hückel potentials has been used for cross section calculations. In this process, antihydrogen formation and ionization cross sections have been calculated in unscreened as well as in Debye plasmas conditions in energies ranging from 1 to 500 keV. Partial cross sections for antihydrogen formation are also calculated which show the largest cross sections correspond to production of antihydrogen in the n = 2 (2s, 2p) states. Comparative study has been carried out to determine the differences of cross sections in screening and unscreening cases. The results show that the cross sections for both antihydrogen formation and positronium ionization depend on Debye screening lengths as well as on collision energies. The effects of plasmas conditions on antihydrogen formation and positronium ionization are explained in terms of classical trajectory framework. Our results for the unscreened case are in agreement with previously reported results.

Proposal for making a beam of antihydrogen by two charge exchange events

International Nuclear Information System (INIS)

Robicheaux, F

2010-01-01

We have performed calculations of two successive charge transfers in a geometry that could generate a beam of antihydrogen atoms (H-bar) or reliably produce cold H-bar without having to reach extremely cold plasma temperatures. The basic idea is similar to that proposed by Hessels et al (1998 Phys. Rev. A 57 1668) except that the order of the charge transfers is reversed. A beam of highly-excited (Rydberg) Cs atoms passes through an antiproton (p-bar) plasma where a charge transfer can take place; the result is an exotic Rydberg atom (Cs + ion and a bound p-bar) which has approximately the original velocity of the Cs atom since the Cs + mass is much greater than that of the p-bar. This exotic Rydberg atom travels into a positron plasma where a second charge exchange gives antihydrogen (H-bar). The velocity distribution of the resulting H-bar is directly related to the original velocity of the Rydberg Cs atom. The binding energy of the H-bar is roughly that of the original Cs Rydberg atom; thus, the starting state of the H-bar can be controlled by choosing the initial state of the Cs atom. Because the p-barCs + binding energy can be controlled in the charge transfer, this first step, by itself, could be of interest to the exotic atom community.

An atomic hydrogen beam to test ASACUSA's apparatus for antihydrogen spectroscopy

CERN Document Server

Diermaier, Martin; Kolbinger, Bernadette; Malbrunot, Chloé; Massiczek, Oswald; Sauerzopf, Clemens; Simon, Martin C.; Wolf, Michael; Zmeskal, Johann; Widmann, Eberhard

2015-01-01

The ASACUSA collaboration aims to measure the ground state hyperfine splitting (GS-HFS) of antihydrogen, the antimatter pendant to atomic hydrogen. Comparisons of the corresponding transitions in those two systems will provide sensitive tests of the CPT symmetry, the combination of the three discrete symmetries charge conjugation, parity, and time reversal. For offline tests of the GS-HFS spectroscopy apparatus we constructed a source of cold polarised atomic hydrogen. In these proceedings we report the successful observation of the hyperfine structure transitions of atomic hydrogen with our apparatus in the earth's magnetic field.

CPT symmetry tests with cold anti {rho} and antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Yamazaki, Yasunori [RIKEN, Atomic Physics Laboratory, 2-1 Hirosawa, Wako, Saitama, 351-0198 (Japan); Ulmer, Stefan [RIKEN, Ulmer Initiative Research Unit, 2-1 Hirosawa, Wako, Saitama, 351-0198 (Japan)

2013-07-15

Precision comparisons of the properties of particles and their corresponding antiparticles are highly relevant because the Standard Model of elementary particle physics, a local, Lorentz-invariant field theory, is necessarily symmetric with respect to the combined CPT operation. This symmetry defines exact equality between the fundamental properties of particles and their anti-images. Any measured and confirmed violation constitutes a significant challenge to the Standard Model. Recent results of different CPT-tests are summarized, with emphasis to the high-precision measurement of the magnetic moment of the proton and the antiproton, as well as the precision investigation of antihydrogen ground state hyperfine splitting. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

New Interpretations of Measured Antihydrogen Velocities and Field Ionization Spectra

International Nuclear Information System (INIS)

Pohl, T.; Sadeghpour, H. R.; Gabrielse, G.

2006-01-01

We present extensive Monte Carlo simulations, showing that cold antihydrogen (H) atoms are produced when antiprotons (p) are gently heated in the side wells of a nested Penning trap. The observed H with high energies, that had seemed to indicate otherwise, are instead explained by a surprisingly effective charge-exchange mechanism. We shed light on the previously measured field-ionization spectrum, and reproduce both the characteristic low-field power law as well as the enhanced H production at higher fields. The latter feature is shown to arise from H atoms too deeply bound to be described as guiding center atoms, atoms with internally chaotic motion

Evaporative cooling of antiprotons for the production of trappable antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Silveira, D. M.; Cesar, C. L. [Instituto de Fisica - Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro (Brazil); Andresen, G. B.; Bowe, P. D.; Hangst, J. S. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Ashkezari, M. D.; Hayden, M. E. [Department of Physics, Simon Fraser University, Burnaby BC, V5A 1S6 (Canada); Baquero-Ruiz, M.; Chapman, S.; Fajans, J.; Povilus, A.; So, C.; Wurtele, J. S. [Department of Physics, University of California, Berkeley, California 94720-7300 (United States); Bertsche, W. [School of Physics and Astronomy, University of Manchester, M13 9PL Manchester (United Kingdom) and Cockroft Institute, WA4 4AD Warrington (United Kingdom); Butler, E. [CERN, PH Department, CH-1211 Geneva 23 (Switzerland); Charlton, M.; Madsen, N.; Werf, D. P. van der [Department of Physics, College of Science, Swansea University, Swansea SA2 8PP (United Kingdom); Friesen, T.; Hydomako, R. [Department of Physics and Astronomy, University of Calgary AB, T2N 1N4 (Canada); and others

2013-03-19

We describe the implementation of evaporative cooling of charged particles in the ALPHA apparatus. Forced evaporation has been applied to cold samples of antiprotons held in Malmberg-Penning traps. Temperatures on the order of 10 K were obtained, while retaining a significant fraction of the initial number of particles. We have developed a model for the evaporation process based on simple rate equations and applied it succesfully to the experimental data. We have also observed radial re-distribution of the clouds following evaporation, explained by simple conservation laws. We discuss the relevance of this technique for the recent demonstration of magnetic trapping of antihydrogen.

Extrasolar planets formation, detection and dynamics

CERN Document Server

Dvorak, Rudolf

2008-01-01

This latest, up-to-date resource for research on extrasolar planets covers formation, dynamics, atmospheres and detection. After a look at the formation of giant planets, the book goes on to discuss the formation and dynamics of planets in resonances, planets in double stars, atmospheres and habitable zones, detection via spectra and transits, and the history and prospects of ESPs as well as satellite projects.Edited by a renowned expert in solar system dynamics with chapters written by the leading experts in the method described -- from the US and Europe -- this is an ideal textbook for g

An atomic hydrogen beam to test ASACUSA’s apparatus for antihydrogen spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Diermaier, M., E-mail: martin.diermaier@oeaw.ac.at; Caradonna, P.; Kolbinger, B. [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria); Malbrunot, C. [CERN (Switzerland); Massiczek, O.; Sauerzopf, C.; Simon, M. C.; Wolf, M.; Zmeskal, J.; Widmann, E. [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria)

2015-08-15

The ASACUSA collaboration aims to measure the ground state hyperfine splitting (GS-HFS) of antihydrogen, the antimatter counterpart to atomic hydrogen. Comparisons of the corresponding transitions in those two systems will provide sensitive tests of the CPT symmetry, the combination of the three discrete symmetries charge conjugation, parity, and time reversal. For offline tests of the GS-HFS spectroscopy apparatus we constructed a source of cold polarised atomic hydrogen. In these proceedings we report the successful observation of the hyperfine structure transitions of atomic hydrogen with our apparatus in the earth’s magnetic field.

International Workshop on Exotic Hadronic Atoms, Deeply Bound Kaonic Nuclear States and Antihydrogen : Present Results, Future Challenges

CERN Document Server

Widmann, E; Curceanu, C; Trento 2006; Trento06

2006-01-01

These are the miniproceedings of the workshop "Exotic hadronic atoms, deeply bound kaonic nuclear states and antihydrogen: present results, future challenges," which was held at the European Centre for Theoretical Nuclear Physics and Related Studies (ECT*), Trento (Italy), June 19-24, 2006. The document includes a short presentation of the topics, the list of participants, and a short contribution from each speaker.

Plasma turbulence. Structure formation, selection rule, dynamic response and dynamics transport

International Nuclear Information System (INIS)

Ito, Sanae I.

2010-01-01

The five-year project of Grant-in-Aid for Specially Promoted Research entitled general research on the structure formation and selection rule in plasma turbulence had brought many outcomes. Based on these outcomes, the Grant-in-Aid for Scientific Research (S) program entitled general research on dynamic response and dynamic transport in plasma turbulence has started. In the present paper, the state-of-the-art of the research activities on the structure formation, selection rule and dynamics in plasma turbulence are reviewed with reference to outcomes of these projects. (author)

Design of a spin-flip cavity for the measurement of the antihydrogen hyperfine structure

CERN Document Server

Kroyer, T

2008-01-01

In the framework of the ASACUSA collaboration at the CERN Antiproton Decelerator an experiment for precisely testing the CPT invariance of the hydrogen hyperfine structure is currently being designed. An integral part of the set-up is the 1.42 GHz spin-flipping cavity, which should have a good field homogeneity over the large aperture of the antihydrogen beam. After the evaluation of various approaches a structure based on a resonant stripline is proposed as a concrete cavity design. For this structure the field homogeneity, undesired modes, coupling and power issues are discussed in detail.

Born-Oppenheimer potential energy for interaction of antihydrogen with molecular hydrogen

International Nuclear Information System (INIS)

Strasburger, Krzysztof

2005-01-01

Inelastic collisions with hydrogen molecules are claimed to be an important channel of antihydrogen Hbar losses (Armour and Zeman 1999 Int. J. Quantum Chem. 74 645). In the present work, interaction energies for the H 2 -Hbar system in the ground state have been calculated within the Born-Oppenheimer approximation. The leptonic problem was solved variationally with the basis of explicitly correlated Gaussian functions. The geometry of H 2 was fixed at equilibrium geometry and the Hbar atom approached the molecule from two directions-along or perpendicularly to the bond axis. Purely attractive potential energy curve has been obtained for the first nuclear configuration, while a local maximum (lower than the energy at infinite separation) has been found for the second one

Born Oppenheimer potential energy for interaction of antihydrogen with molecular hydrogen

Science.gov (United States)

Strasburger, Krzysztof

2005-09-01

Inelastic collisions with hydrogen molecules are claimed to be an important channel of antihydrogen (\\overlineH) losses (Armour and Zeman 1999 Int. J. Quantum Chem. 74 645). In the present work, interaction energies for the H_{2}\\--\\overlineH system in the ground state have been calculated within the Born-Oppenheimer approximation. The leptonic problem was solved variationally with the basis of explicitly correlated Gaussian functions. The geometry of H2 was fixed at equilibrium geometry and the \\overlineH atom approached the molecule from two directions—along or perpendicularly to the bond axis. Purely attractive potential energy curve has been obtained for the first nuclear configuration, while a local maximum (lower than the energy at infinite separation) has been found for the second one.

Characterization of the 1S–2S transition in antihydrogen

DEFF Research Database (Denmark)

Ahmadi, M.; Alves, B. X. R.; Baker, C. J.

2018-01-01

In 1928, Dirac published an equation 1 that combined quantum mechanics and special relativity. Negative-energy solutions to this equation, rather than being unphysical as initially thought, represented a class of hitherto unobserved and unimagined particles—antimatter. The existence of particles...... of antimatter was confirmed with the discovery of the positron 2 (or anti-electron) by Anderson in 1932, but it is still unknown why matter, rather than antimatter, survived after the Big Bang. As a result, experimental studies of antimatter3–7, including tests of fundamental symmetries such as charge...... of the hyperfine components of this transition using magnetically trapped atoms of antihydrogen and compare it to model calculations for hydrogen in our apparatus. We find that the shape of the spectral line agrees very well with that expected for hydrogen and that the resonance frequency agrees...

Shaping the distribution of vertical velocities of antihydrogen in GBAR

Energy Technology Data Exchange (ETDEWEB)

Dufour, G.; Lambrecht, A.; Reynaud, S. [CNRS, ENS, UPMC, Laboratoire Kastler-Brossel, Paris (France); Debu, P. [CEA-Saclay, Institut de Recherche sur les lois Fondamentales de l' Univers, Gif-sur-Yvette (France); Nesvizhevsky, V.V. [Institut Max von Laue-Paul Langevin, Grenoble (France); Voronin, A.Yu. [P.N. Lebedev Physical Institute, Moscow (Russian Federation)

2014-01-15

GBAR is a project aiming at measuring the freefall acceleration of gravity for antimatter, namely antihydrogen atoms (H). The precision of this timing experiment depends crucially on the dispersion of initial vertical velocities of the atoms as well as on the reliable control of their distribution.We propose to use a new method for shaping the distribution of the vertical velocities of H, which improves these factors simultaneously. The method is based on quantum reflection of elastically and specularly bouncing H with small initial vertical velocity on a bottom mirror disk, and absorption of atoms with large initial vertical velocities on a top rough disk.We estimate statistical and systematic uncertainties, and we show that the accuracy for measuring the free fall acceleration g of H could be pushed below 10{sup -3} under realistic experimental conditions. (orig.)

Shaping the distribution of vertical velocities of antihydrogen in GBAR

CERN Document Server

Dufour, G.; Lambrecht, A.; Nesvizhevsky, V.V.; Reynaud, S.; Voronin, A.Yu.

2014-01-30

GBAR is a project aiming at measuring the free fall acceleration of gravity for antimatter, namely antihydrogen atoms ($\\overline{\\mathrm{H}}$). Precision of this timing experiment depends crucially on the dispersion of initial vertical velocities of the atoms as well as on the reliable control of their distribution. We propose to use a new method for shaping the distribution of vertical velocities of $\\overline{\\mathrm{H}}$, which improves these factors simultaneously. The method is based on quantum reflection of elastically and specularly bouncing $\\overline{\\mathrm{H}}$ with small initial vertical velocity on a bottom mirror disk, and absorption of atoms with large initial vertical velocities on a top rough disk. We estimate statistical and systematic uncertainties, and show that the accuracy for measuring the free fall acceleration $\\overline{g}$ of $\\overline{\\mathrm{H}}$ could be pushed below $10^{-3}$ under realistic experimental conditions.

A scheme to produce a dense positronium plasma for an antihydrogen experiment

Energy Technology Data Exchange (ETDEWEB)

Perez, P. [CEA Saclay, DSM/IRFU, 91191 Gif-sur-Yvette Cedex (France)], E-mail: patrice.perez@cea.fr; Liszkay, L.; Rey, J.-M.; Delferrierre, O.; Blideanu, V.; Carty, M.; Curtoni, A.; Ruiz, N.; Sauce, Y. [CEA Saclay, DSM/IRFU, 91191 Gif-sur-Yvette Cedex (France)

2008-10-31

A 6 MeV industrial electron linac with 0.2 mA average current will be installed in December 2007 in CEA-Saclay. Equipped with a tungsten target and moderator, it is aimed at producing rates of order 10{sup 8} s{sup -1} slow positrons. This setup is part of a project to demonstrate the feasibility of an experiment to produce the H-bar{sup +} ion for a free fall measurement of H-bar. The energy is below the neutron activation threshold. Its small size and cost could be of interest for a university laboratory or industry, and could be envisaged as a replacement source for the antihydrogen experiments at CERN.

Theoretical motivation for gravitation experiments on ultra-low energy antiprotons and antihydrogen

International Nuclear Information System (INIS)

Nieto, M.M.

1995-01-01

It is known that the generally accepted theories of gravity and quantum mechanics are fundamentally incompatible. Thus, when one tries to combine these theories, one must beware of physical pitfalls. Modern theories of quantum gravity are trying to overcome these problems. Any ideas must confront the present agreement with general relativity, but yet be free to wonder about not understood phenomena, such as the dark matter problem. This all has led some open-quotes intrepidclose quotes theorists to consider a new gravitational regime, that of antimatter. Even more open-quotes daringclose quotes experimentalists are attempting, or considering attempting, the measurement of the gravitational force on antimatter, including low-energy antiprotons and, perhaps most enticing, antihydrogen

Evaporative cooling of antiprotons and efforts to trap antihydrogen

CERN Document Server

Andresen, Gorm Bruun

Evaporative cooling has proven to be an invaluable technique in atomic physics, allowing for the study of effects such as Bose-Einstein condensation. One main topic of this thesis is the first application of evaporative cooling to cold non-neutral plasmas stored in an ion trap. We (the ALPHA collaboration) have achieved cooling of a cloud of antiprotons to a temperature as low as 9 K, two orders of magnitude lowerthan ever directly measured previously. The measurements are well-described by appropriate rate equations for the temperature and number of particles. The technique has direct application to the ongoing attempts to produce trapped samples of antihydrogen. In these experiments the maximum trap depths are ex tremely shallow (~0.6 K for ground state atoms), and careful control of the trapped antiprotons and positrons used to form the (anti)atoms is essential to succes. Since 2006 powerful tools to diagnose and manipulate the antiproton and positron plasmas in the ALPHA apparatus have been developed and ...

Self-consistent static analysis of using nested-well plasma traps for achieving antihydrogen recombination

International Nuclear Information System (INIS)

Dolliver, D. D.; Ordonez, C. A.

1999-01-01

The use of a Malmberg-Penning type trap with nested electric potential wells to confine overlapping antiproton and positron plasmas for the purpose of producing low temperature antihydrogen is studied. Two approaches for confining antiproton and positron plasmas with a region of overlap are considered. In one approach the two components have a large temperature difference. In the other, one of the components is in a nonequilibrium 'antishielding' plasma state. A finite differences algorithm is used to solve Poisson's equation based on a simultaneous overrelaxation numerical approach. Self-consistent numerical results for required trap potentials and possible particle density profiles are presented

A Moire-deflectometer as gravimeter for antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Haupert, Fabienne Catherine

2012-02-02

AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) - one of the experiments carried out at CERN - aims to examine fundamental physical properties of antimatter, in order to promote knowledge about the incompatibility of gravitation with other forces. As part of achieving this knowledge, the experiment will measure in its first phase the gravitational acceleration g of antihydrogen with a precision of 1% and hence, provide data for a deeper understanding of antimatter in general. A Moire-deflectometer is applied as gravimeter for this measurement. Its design and construction are carried out in Heidelberg. In order to test and characterise this deflectometer to its best achieveable sensitivity, a high-flux source of metastable argon atoms as well as a Faraday cup to detect these atoms are built. An additional optical Mach-Zehnder interferometer controls the stability of the apparatus. The major components of the deflectometer, the deflection gratings, are manufactured out of six-inch silicon wafers. Their prototypes together with the entire apparatus are designed and built with due care to account for the experimental conditions given by the apparatus at CERN. A first gravitational measurement with the test setup at Heidelberg yields g=(9.5{+-}1.9)(m)/(s{sup 2}) and opens up a huge number of potential improvements.

Ultracold Anions for High-Precision Antihydrogen Experiments.

Science.gov (United States)

Cerchiari, G; Kellerbauer, A; Safronova, M S; Safronova, U I; Yzombard, P

2018-03-30

Experiments with antihydrogen (H[over ¯]) for a study of matter-antimatter symmetry and antimatter gravity require ultracold H[over ¯] to reach ultimate precision. A promising path towards antiatoms much colder than a few kelvin involves the precooling of antiprotons by laser-cooled anions. Because of the weak binding of the valence electron in anions-dominated by polarization and correlation effects-only few candidate systems with suitable transitions exist. We report on a combination of experimental and theoretical studies to fully determine the relevant binding energies, transition rates, and branching ratios of the most promising candidate La^{-}. Using combined transverse and collinear laser spectroscopy, we determined the resonant frequency of the laser cooling transition to be ν=96.592 713(91)  THz and its transition rate to be A=4.90(50)×10^{4}  s^{-1}. Using a novel high-precision theoretical treatment of La^{-} we calculated yet unmeasured energy levels, transition rates, branching ratios, and lifetimes to complement experimental information on the laser cooling cycle of La^{-}. The new data establish the suitability of La^{-} for laser cooling and show that the cooling transition is significantly stronger than suggested by a previous theoretical study.

Electron-cooled accumulation of $4 × 10^9$ positrons for production and storage of antihydrogen atoms

CERN Document Server

Fitzakerley, DW; Hessels, E A; Skinner, T D G; Storry, C H; Weel, M; Gabrielse, G; Hamley, C D; Jones, N; Marable, K; Tardiff, E; Grzonka, D; Oelert, W; Zielinski, M

2016-01-01

Four billion positrons (e+) are accumulated in a Penning–Ioffe trap apparatus at 1.2 K and <6 × 10−17 Torr. This is the largest number of positrons ever held in a Penning trap. The e+ are cooled by collisions with trapped electrons (e−) in this first demonstration of using e− for efficient loading of e+ into a Penning trap. The combined low temperature and vacuum pressure provide an environment suitable for antihydrogen ($\\bar{{\\rm{H}}}$) production, and long antimatter storage times, sufficient for high-precision tests of antimatter gravity and of CPT.

TIME-VARYING DYNAMICAL STAR FORMATION RATE

Energy Technology Data Exchange (ETDEWEB)

Lee, Eve J.; Chang, Philip; Murray, Norman, E-mail: evelee@berkeley.edu [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, Toronto, ON M5S 3H8 (Canada)

2015-02-10

We present numerical evidence of dynamic star formation in which the accreted stellar mass grows superlinearly with time, roughly as t {sup 2}. We perform simulations of star formation in self-gravitating hydrodynamic and magnetohydrodynamic turbulence that is continuously driven. By turning the self-gravity of the gas in the simulations on or off, we demonstrate that self-gravity is the dominant physical effect setting the mass accretion rate at early times before feedback effects take over, contrary to theories of turbulence-regulated star formation. We find that gravitational collapse steepens the density profile around stars, generating the power-law tail on what is otherwise a lognormal density probability distribution function. Furthermore, we find turbulent velocity profiles to flatten inside collapsing regions, altering the size-line width relation. This local flattening reflects enhancements of turbulent velocity on small scales, as verified by changes to the velocity power spectra. Our results indicate that gas self-gravity dynamically alters both density and velocity structures in clouds, giving rise to a time-varying star formation rate. We find that a substantial fraction of the gas that forms stars arrives via low-density flows, as opposed to accreting through high-density filaments.

Magnetic multipole induced zero-rotation frequency bounce-resonant loss in a Penning–Malmberg trap used for antihydrogen trapping

CERN Document Server

Andresen, G B; Bray, C; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Fajans, J; Fujiwara, M C; Gill, D R; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jørgensen, L V; Kerrigan, S J; Keller, J; Kurchaninov, L; Lambo, R; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Seif El Nasr, S; Silveira, D M; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

2009-01-01

In many antihydrogen trapping schemes, antiprotons held in a short-well Penning–Malmberg trap are released into a longer well. This process necessarily causes the bounce-averaged rotation frequency $\\overline{\\Omega}_r$ of the antiprotons around the trap axis to pass through zero. In the presence of a transverse magnetic multipole, experiments and simulations show that many antiprotons (over 30% in some cases) can be lost to a hitherto unidentified bounce-resonant process when $\\overline{\\Omega}_r$ is close to zero.

Dynamical Formation and Merger of Binary Black Holes

Science.gov (United States)

Stone, Nicholas

2017-01-01

The advent of gravitational wave (GW) astronomy began with Advanced LIGO's 2015 discovery of GWs from coalescing black hole (BH) binaries. GW astronomy holds great promise for testing general relativity, but also for investigating open astrophysical questions not amenable to traditional electromagnetic observations. One such question concerns the origin of stellar mass BH binaries in the universe: do these form primarily from evolution of isolated binaries of massive stars, or do they form through more exotic dynamical channels? The best studied dynamical formation channel involves multibody interactions of BHs and stars in dense globular cluster environments, but many other dynamical scenarios have recently been proposed, ranging from the Kozai effect in hierarchical triple systems to BH binary formation in the outskirts of Toomre-unstable accretion disks surrounding supermassive black holes. The BH binaries formed through these processes will have different distributions of observable parameters (e.g. mass ratios, spins) than BH binaries formed through the evolution of isolated binary stars. In my talk I will overview these and other dynamical formation scenarios, and summarize the key observational tests that will enable Advanced LIGO or other future detectors to determine what formation pathway creates the majority of binary BHs in the universe. NCS thanks NASA, which has funded his work through Einstein postdoctoral grant PF5-160145.

Dynamic Membrane Formation in Anaerobic Dynamic Membrane Bioreactors: Role of Extracellular Polymeric Substances.

Directory of Open Access Journals (Sweden)

Hongguang Yu

Full Text Available Dynamic membrane (DM formation in dynamic membrane bioreactors plays an important role in achieving efficient solid-liquid separation. In order to study the contribution of extracellular polymeric substances (EPS to DM formation in anaerobic dynamic membrane bioreactor (AnDMBR processes, EPS extraction from and re-addition to bulk sludge were carried out in short-term filtration tests. DM formation behaviors could be well simulated by cake filtration model, and sludge with EPS re-addition showed the highest resistance coefficient, followed by sludge after EPS extraction. The DM layers exhibited a higher resistance and a lower porosity for the sludge sample after EPS extraction and for the sludge with EPS re-addition. Particle size of sludge flocs decreased after EPS extraction, and changed little with EPS re-addition, which was confirmed by interaction energy analysis. Further investigations by confocal laser scanning microscopy (CLSM analysis and batch tests suggested that the removal of in-situ EPS stimulated release of soluble EPS, and re-added EPS were present as soluble EPS rather than bound EPS, which thus improved the formation of DM. The present work revealed the role of EPS in anaerobic DM formation, and could facilitate the operation of AnDMBR processes.

Mantle dynamics following supercontinent formation

Science.gov (United States)

Heron, Philip J.

This thesis presents mantle convection numerical simulations of supercontinent formation. Approximately 300 million years ago, through the large-scale subduction of oceanic sea floor, continental material amalgamated to form the supercontinent Pangea. For 100 million years after its formation, Pangea remained relatively stationary, and subduction of oceanic material featured on its margins. The present-day location of the continents is due to the rifting apart of Pangea, with supercontinent dispersal being characterized by increased volcanic activity linked to the generation of deep mantle plumes. The work presented here investigates the thermal evolution of mantle dynamics (e.g., mantle temperatures and sub-continental plumes) following the formation of a supercontinent. Specifically, continental insulation and continental margin subduction are analyzed. Continental material, as compared to oceanic material, inhibits heat flow from the mantle. Previous numerical simulations have shown that the formation of a stationary supercontinent would elevate sub-continental mantle temperatures due to the effect of continental insulation, leading to the break-up of the continent. By modelling a vigorously convecting mantle that features thermally and mechanically distinct continental and oceanic plates, this study shows the effect of continental insulation on the mantle to be minimal. However, the formation of a supercontinent results in sub-continental plume formation due to the re-positioning of subduction zones to the margins of the continent. Accordingly, it is demonstrated that continental insulation is not a significant factor in producing sub-supercontinent plumes but that subduction patterns control the location and timing of upwelling formation. A theme throughout the thesis is an inquiry into why geodynamic studies would produce different results. Mantle viscosity, Rayleigh number, continental size, continental insulation, and oceanic plate boundary evolution are

The performance model of dynamic virtual organization (VO) formations within grid computing context

International Nuclear Information System (INIS)

Han Liangxiu

2009-01-01

Grid computing aims to enable 'resource sharing and coordinated problem solving in dynamic, multi-institutional virtual organizations (VOs)'. Within the grid computing context, successful dynamic VO formations mean a number of individuals and institutions associated with certain resources join together and form new VOs in order to effectively execute tasks within given time steps. To date, while the concept of VOs has been accepted, few research has been done on the impact of effective dynamic virtual organization formations. In this paper, we develop a performance model of dynamic VOs formation and analyze the effect of different complex organizational structures and their various statistic parameter properties on dynamic VO formations from three aspects: (1) the probability of a successful VO formation under different organizational structures and statistic parameters change, e.g. average degree; (2) the effect of task complexity on dynamic VO formations; (3) the impact of network scales on dynamic VO formations. The experimental results show that the proposed model can be used to understand the dynamic VO formation performance of the simulated organizations. The work provides a good path to understand how to effectively schedule and utilize resources based on the complex grid network and therefore improve the overall performance within grid environment.

Antiproton cross-field diffusion in antihydrogen production experiments due to anisotropic binary interactions

International Nuclear Information System (INIS)

Ordonez, C.A.; Correa, J.R.

2007-01-01

Collisional processes in electrostatic ion storage rings and reflecting-beam-type electrostatic ion traps can be associated with anisotropic binary interactions, because shielding of the Coulomb interactions may not take place in one or more dimensions. Collisional scattering theory has recently been developed for describing the velocity-space scattering processes in such systems [J.R. Correa, Y. Chang, C.A. Ordonez, Phys. Plasmas 12 (2005) 084505]. The theory is extended to enable the effect of a magnetic field to be included. The theory is intended to be applicable, for example, to antiproton scattering within nested Penning traps that are used to produce antihydrogen [M. Amoretti et al., Nature 419 (2002) 456; G. Gabrielse et al., Phys. Rev. Lett. 89 (2002) 213401]. The theory is applied for considering the cross-magnetic-field diffusion of the antiprotons

Centrifugal Separation and Equilibration Dynamics in an Electron-Antiproton Plasma

International Nuclear Information System (INIS)

Andresen, G. B.; Bowe, P. D.; Hangst, J. S.; Ashkezari, M. D.; Hayden, M. E.; Baquero-Ruiz, M.; Chapman, S.; Fajans, J.; Povilus, A.; So, C.; Bertsche, W.; Butler, E.; Charlton, M.; Deller, A.; Eriksson, S.; Humphries, A. J.; Madsen, N.; Werf, D. P. van der; Cesar, C. L.; Friesen, T.

2011-01-01

Charges in cold, multiple-species, non-neutral plasmas separate radially by mass, forming centrifugally separated states. Here, we report the first detailed measurements of such states in an electron-antiproton plasma, and the first observations of the separation dynamics in any centrifugally separated system. While the observed equilibrium states are expected and in agreement with theory, the equilibration time is approximately constant over a wide range of parameters, a surprising and as yet unexplained result. Electron-antiproton plasmas play a crucial role in antihydrogen trapping experiments.

Centrifugal separation and equilibration dynamics in an electron-antiproton plasma

CERN Document Server

Andresen, G B; Baquero-Ruiz, Marcelo; Bertsche, William; Bowe, Paul D; Butler, Eoin; Cesar, Claudio L; Chapman, Steven; Charlton, Michael; Deller, A; Eriksson, S; Fajans, Joel; Friesen, Tim; Fujiwara, Makoto C; Gill, David R; Gutierrez, A; Hangst, Jeffrey S; Hardy, Walter N; Hayden, Michael E; Humphries, Andrew J; Hydomako, Richard; Jonsell, Svante; Madsen, Niels; Menary, Scott; Nolan, Paul; Olin, Art; Povilus, Alexander; Pusa, Petteri; Robicheaux, Francis; Sarid, Eli; Silveira, Daniel M; So, Chukman; Storey, James W; Thompson, Robert I; van der Werf, Dirk P; Wurtele, Jonathan S; Yamazaki, Yasunori

2011-01-01

Charges in cold, multiple-species, non-neutral plasmas separate radially by mass, forming centrifugally-separated states. Here, we report the first detailed measurements of such states in an electron-antiproton plasma, and the first observations of the separation dynamics in any centrifugally-separated system. While the observed equilibrium states are expected and in agreement with theory, the equilibration time is approximately constant over a wide range of parameters, a surprising and as yet unexplained result. Electron-antiproton plasmas play a crucial role in antihydrogen trapping experiments.

Dynamic Scaling of Colloidal Gel Formation at Intermediate Concentrations.

Science.gov (United States)

Zhang, Qingteng; Bahadur, Divya; Dufresne, Eric M; Grybos, Pawel; Kmon, Piotr; Leheny, Robert L; Maj, Piotr; Narayanan, Suresh; Szczygiel, Robert; Ramakrishnan, Subramanian; Sandy, Alec

2017-10-27

We have examined the formation and dissolution of gels composed of intermediate volume-fraction nanoparticles with temperature-dependent short-range attractions using small-angle x-ray scattering, x-ray photon correlation spectroscopy, and rheology to obtain nanoscale and macroscale sensitivity to structure and dynamics. Gel formation after temperature quenches to the vicinity of the rheologically determined gel temperature, T_{gel}, was characterized via the slowdown of dynamics and changes in microstructure observed in the intensity autocorrelation functions and structure factor, respectively, as a function of quench depth (ΔT=T_{quench}-T_{gel}), wave vector, and formation time t_{f}. We find the wave-vector-dependent dynamics, microstructure, and rheology at a particular ΔT and t_{f} map to those at other ΔTs and t_{f}s via an effective scaling temperature, T_{s}. A single T_{s} applies to a broad range of ΔT and t_{f} but does depend on the particle size. The rate of formation implied by the scaling is a far stronger function of ΔT than expected from the attraction strength between colloids. We interpret this strong temperature dependence in terms of cooperative bonding required to form stable gels via energetically favored, local structures.

AEg¯$\\overline {\\rm{g}}$IS Experiment: Measuring the acceleration g of the earth’s gravitational field on antihydrogen beam

Directory of Open Access Journals (Sweden)

Subieta Vasquez M. A.

2014-04-01

Full Text Available The AEg¯ $\\overline {\\rm{g}}$IS experiment [1] aims at directly measuring the gravitational acceleration g on a beam of cold antihydrogen (H¯$\\overline {\\rm{H}}$ to a precision of 1%, performing the first test with antimatter of the (WEP Weak Equivalence Principle. The experimental apparatus is sited at the Antiproton Decelerator (AD at CERN, Geneva, Switzerland. After production by mixing of antiprotons with Rydberg state positronium atoms (Ps, the H¯$\\overline {\\rm{H}}$ atoms will be driven to fly horizontally with a velocity of a few 100 ms−1 for a path length of about 1 meter. The small deflection, few tens of μm, will be measured using two material gratings (of period ∼ 80 μm coupled to a position-sensitive detector working as a moiré deflectometer similarly to what has been done with matter atoms [2]. The shadow pattern produced by the H¯$\\overline {\\rm{H}}$ beam will then be detected by reconstructing the annihilation points with a spatial resolution (∼ 2 μm of each antiatom at the end of the flight path by the sensitive-position detector. During 2012 the experimental apparatus has been commissioned with antiprotons and positrons. Since the AD will not be running during 2013,during the refurbishment of the CERN accelerators, the experiment is currently working with positrons, electrons and protons, in order to prepare the way for the antihydrogen production in late 2014.

Imaging antimatter with a Micromegas detector

Science.gov (United States)

Mäckel, V.; Radics, B.; Dupre, P.; Higaki, H.; Kanai, Y.; Kuroda, N.; Matsuda, Y.; Nagata, Y.; Tajima, M.; Widmann, E.; Yamazaki, Y.

2018-05-01

The ASACUSA collaboration aims at measuring the ground state hyperfine splitting of antihydrogen for probing fundamental symmetries. A cryogenic trap for mixing antiprotons and positrons serves as an antihydrogen source for in-flight spectroscopy. In order to be able to monitor the antihydrogen formation process, a dedicated Micromegas tracking detector has been designed and built to record the annihilation distribution in the trap. In this paper, we present the first results from antiproton annihilation data recorded with the Micromegas, together with a description of the event reconstruction algorithm.

Formation Learning Control of Multiple Autonomous Underwater Vehicles With Heterogeneous Nonlinear Uncertain Dynamics.

Science.gov (United States)

Yuan, Chengzhi; Licht, Stephen; He, Haibo

2017-09-26

In this paper, a new concept of formation learning control is introduced to the field of formation control of multiple autonomous underwater vehicles (AUVs), which specifies a joint objective of distributed formation tracking control and learning/identification of nonlinear uncertain AUV dynamics. A novel two-layer distributed formation learning control scheme is proposed, which consists of an upper-layer distributed adaptive observer and a lower-layer decentralized deterministic learning controller. This new formation learning control scheme advances existing techniques in three important ways: 1) the multi-AUV system under consideration has heterogeneous nonlinear uncertain dynamics; 2) the formation learning control protocol can be designed and implemented by each local AUV agent in a fully distributed fashion without using any global information; and 3) in addition to the formation control performance, the distributed control protocol is also capable of accurately identifying the AUVs' heterogeneous nonlinear uncertain dynamics and utilizing experiences to improve formation control performance. Extensive simulations have been conducted to demonstrate the effectiveness of the proposed results.

Dynamics of Research Team Formation in Complex Networks

Science.gov (United States)

Sun, Caihong; Wan, Yuzi; Chen, Yu

Most organizations encourage the formation of teams to accomplish complicated tasks, and vice verse, effective teams could bring lots benefits and profits for organizations. Network structure plays an important role in forming teams. In this paper, we specifically study the dynamics of team formation in large research communities in which knowledge of individuals plays an important role on team performance and individual utility. An agent-based model is proposed, in which heterogeneous agents from research communities are described and empirically tested. Each agent has a knowledge endowment and a preference for both income and leisure. Agents provide a variable input (‘effort’) and their knowledge endowments to production. They could learn from others in their team and those who are not in their team but have private connections in community to adjust their own knowledge endowment. They are allowed to join other teams or work alone when it is welfare maximizing to do so. Various simulation experiments are conducted to examine the impacts of network topology, knowledge diffusion among community network, and team output sharing mechanisms on the dynamics of team formation.

Further evidence for low-energy protonium production in vacuum

CERN Document Server

Lodi Rizzini, E; Zurlo, N; Charlton, M; Amsler, C; Bonomi, G; Canali, C; Carraro, C; Fontana, A; Genova, P; Hayano, R; Jorgensen, L V; Kellerbauer, A; Lagomarsino, V; Landua, R; Macri, M; Manuzio, G; Montagna, P; Regenfus, C; Rotondi, A; Testera, G; Variola, A; van der Werf, D P

2012-01-01

We describe an experiment performed in the ATHENA apparatus in which there is evidence that the antiproton-proton bound state, protonium, has been produced at very low energies in vacuum following the interaction of cold antiprotons with a trapped cloud of molecular hydrogen ions. The latter were confined in a centrifugally separated belt outside a positron plasma used for antihydrogen formation. Studies have been performed at low positron plasma temperatures in which the protonium annihilation signal has been identified along with that from antihydrogen, and we discuss how their contributions can be disentangled. With the positron plasma heated to around 10000 K the ions become distributed in the positrons, and the majority of the annihilation signal can be explained in terms of protonium formation, as antihydrogen creation is heavily suppressed. In this case we compare the observed protonium formation rate with expectations from theory and find reasonable accord, when experimental systematics are taken into...

Dynamical scenario of intermediary mass fragments formation in heavy ion collisions

International Nuclear Information System (INIS)

Ayik, S.; Belkacem, M.; Gregoire, C.; Stryjewski, J.; Suraud, E.

1989-01-01

We briefly remind the possible dynamical scenario of fragments formation in heavy-ion collisions at some tens fo MeV/A. We discuss how present day dynamical models can describe fragment formation. We next turn to the Boltzmann-Langevin formalism which provides a well defined theoretical framework for the understanding of the growing of the dynamical instabilities leading to multifragmentation. We present a first numerical solution of the Boltzmann-Langevin equation and we apply the formalism to the onset of multifragmentation of the 40 Ca + 40 Ca system between 20 and 60 MeV/A beam energy [fr

The dynamics of fragment formation

International Nuclear Information System (INIS)

Keane, D.

1994-09-01

We demonstrate that in the Quantum Molecular Dynamics model, dynamical correlations can result in the production rate for final state nucleon clusters (and hence composite fragments) being higher than would be expected if statistics and the available phase space were dominant in determining composite formation. An intranuclear cascade or a Boltzmann-Uehling-Uhlenbeck model, combined with a statistical approach in the late stage of the collision to determine composites, provides an equivalent description only under limited conditions of centrality and beam energy. We use data on participant fragment production in Au + Au collisions in the Bevalac's BOS time projection chamber to map out the parameter space where statistical clustering provides a good description. In particular, we investigate momentum-space densities of fragments up to 4 He as a function of fragment transverse momentum, azimuth relative to the reaction plane, rapidity, multiplicity and beam energy

Formation dynamics of FeN thin films on Cu(100)

KAUST Repository

Heryadi, Dodi

2012-01-01

To investigate the structural and magnetic properties of thin films of FeN we have performed ab initio molecular dynamics simulations of their formation on Cu(100) substrates. The iron nitride layers exhibit a p4gm(2 × 2) reconstruction and order ferromagnetically in agreement with experiment. We establish the dynamics and time scale of the film formation as a function of the film thickness. The process is split in two phases: formation of almost flat FeN layers and optimization of the distance to the substrate. Our calculated magnetic moments are 1.67 μ B, 2.14 μ B, and 2.21 μ B for one, two, and three monolayers of iron nitride. © 2011 Elsevier B.V. All rights reserved.

Two-state approximation applied to hydrogen formation by proton impact on positronium

Directory of Open Access Journals (Sweden)

E Ghanbari Adivi

2009-09-01

Full Text Available Although there is no experimental data available for antihydrogen formation following antiprotons impact on positroium atoms, as a charge transfer reaction, at incident energies which are suitable for antimatter high-precision spectroscopic studies, measurements were carried out for its charge-conjugate reaction i. e. hydrogen formation, by protons impact on positronium. In this study, a two-state approximation method is applied to charge exchange process in proton-positronium collision system. The nonorthogonality of initial and final states and its effects on the angular distribution of the differential cross sections is taken into account by using this method. The state-to-state differential cross sections are reported for transition from ground state of positronium into the ground and a few lowest excited states of the formed hydrogen. Integrated cross sections are presented as well.

Cloud-particle galactic gas dynamics and star formation

International Nuclear Information System (INIS)

Roberts, W.W. Jr.

1983-01-01

Galactic gas dynamics, spiral structure, and star formation are discussed in the context of N-body computational studies based on a cloud-particle model of the interstellar medium. On the small scale, the interstellar medium appears to be cloud-dominated and supernova-perturbed. The cloud-particle model simulates cloud-cloud collisions, the formation of stellar associations, and supernova explosions as dominant local processes. On the large scale in response to a spiral galactic gravitational field, global density waves and galactic shocks develop with large-scale characteristics similar to those found in continuum gas dynamical studies. Both the system of gas clouds and the system of young stellar associations forming from the clouds share in the global spiral structure. However, with the attributes of neither assuming a continuum of gas (as in continuum gas dynamical studies) nor requiring a prescribed equation of state such as the isothermal condition so often employed, the cloud-particle picture retains much of the detail lost in earlier work: namely, the small-scale features and structures so important in understanding the local, turbulent state of the interstellar medium as well as the degree of raggedness often observed superposed on global spiral structure. (Auth.)

Slowing down of 100 keV antiprotons in Al foils

Directory of Open Access Journals (Sweden)

K. Nordlund

2018-03-01

Full Text Available Using energy degrading foils to slow down antiprotons is of interest for producing antihydrogen atoms. I consider here the slowing down of 100 keV antiprotons, that will be produced in the ELENA storage ring under construction at CERN, to energies below 10 keV. At these low energies, they are suitable for efficient antihydrogen production. I simulate the antihydrogen motion and slowing down in Al foils using a recently developed molecular dynamics approach. The results show that the optimal Al foil thickness for slowing down the antiprotons to below 5 keV is 910 nm, and to below 10 keV is 840 nm. Also the lateral spreading of the transmitted antiprotons is reported and the uncertainties discussed. Keywords: Antiprotons, Stopping power, Slowing down, Molecular dynamics

Biological Dynamics Markup Language (BDML): an open format for representing quantitative biological dynamics data.

Science.gov (United States)

Kyoda, Koji; Tohsato, Yukako; Ho, Kenneth H L; Onami, Shuichi

2015-04-01

Recent progress in live-cell imaging and modeling techniques has resulted in generation of a large amount of quantitative data (from experimental measurements and computer simulations) on spatiotemporal dynamics of biological objects such as molecules, cells and organisms. Although many research groups have independently dedicated their efforts to developing software tools for visualizing and analyzing these data, these tools are often not compatible with each other because of different data formats. We developed an open unified format, Biological Dynamics Markup Language (BDML; current version: 0.2), which provides a basic framework for representing quantitative biological dynamics data for objects ranging from molecules to cells to organisms. BDML is based on Extensible Markup Language (XML). Its advantages are machine and human readability and extensibility. BDML will improve the efficiency of development and evaluation of software tools for data visualization and analysis. A specification and a schema file for BDML are freely available online at http://ssbd.qbic.riken.jp/bdml/. Supplementary data are available at Bioinformatics online. © The Author 2014. Published by Oxford University Press.

Advanced Concepts for Ultrahigh Brightness and Low Temperature Beams. Final Report

Energy Technology Data Exchange (ETDEWEB)

Wurtele, Jonathan S. [Univ. of California, Berkeley, CA (United States); Fajans, Joel [Univ. of California, Berkeley, CA (United States)

2015-06-01

This grant supported research on techniques to manipulate and combine positrons and antiprotons to synthesize, and to probe, antihydrogen. The majority of the research was conducted as part of the ALPHA Collaboration at CERN. Using ideas and techniques from accelerator physics, we proposed a new method for measuring the the gravitational attraction of antihydrogen to the Earth's field. ALPHA reported the first precision charge measurement on antihydrogen and a crude bound on its gravitational dynamics in the Earth's field. We proposed using a stochastic acceleration method to measure any putative charge of antihydrogen and built numerical models of the mixing of antiprotons and positrons. Further research included proposing the radiator-first concept for operating an X-ray free electron laser driven by a high repetition rate bunch source and studying scattering in passive foil-based ion focusing systems.

Advanced Concepts for Ultrahigh Brightness and Low Temperature Beams. Final Report

International Nuclear Information System (INIS)

Wurtele, Jonathan S.; Fajans, Joel

2015-01-01

This grant supported research on techniques to manipulate and combine positrons and antiprotons to synthesize, and to probe, antihydrogen. The majority of the research was conducted as part of the ALPHA Collaboration at CERN. Using ideas and techniques from accelerator physics, we proposed a new method for measuring the the gravitational attraction of antihydrogen to the Earth's field. ALPHA reported the first precision charge measurement on antihydrogen and a crude bound on its gravitational dynamics in the Earth's field. We proposed using a stochastic acceleration method to measure any putative charge of antihydrogen and built numerical models of the mixing of antiprotons and positrons. Further research included proposing the radiator-first concept for operating an X-ray free electron laser driven by a high repetition rate bunch source and studying scattering in passive foil-based ion focusing systems.

Dynamics of exciplex formation in rare gas media

International Nuclear Information System (INIS)

Rojas-Lorenzo, German; Rubayo-Soneira, Jesus; Alberti, Sebastian Fernandez

2009-01-01

A hopping-surface algorithm has been used to simulate the dynamics induced in rare gas matrices due to the photoexcitation ( 1 S 0 → 3 P 1 ) of atomic mercury embedded in them. Especially, the study of the dynamics of an exciplex formation in a model system consisting of solid xenon doped with atomic mercury. The process starts upon the photoexcitation of the Hg atom to its 3 P 1 electronic excited state. Diatomics-in-Molecule approach has been used for constructing the adiabatic potential surfaces. In all trajectories we show that a triatomic Xe-Hg * -Xe complex is formed, but in two conformations: bent and linear. The mechanisms leading to the formation of one or the other are identified. Mainly, are noted the thermal fluctuations of the Hg impurity and the shape of the potential surfaces. Furthermore, we show that non-radiative intrastate relaxation occurs via a conical intersection between the excited state surfaces. The simulated spectra are in very good agreement with the experimental data.

A natural experiment of social network formation and dynamics.

Science.gov (United States)

Phan, Tuan Q; Airoldi, Edoardo M

2015-05-26

Social networks affect many aspects of life, including the spread of diseases, the diffusion of information, the workers' productivity, and consumers' behavior. Little is known, however, about how these networks form and change. Estimating causal effects and mechanisms that drive social network formation and dynamics is challenging because of the complexity of engineering social relations in a controlled environment, endogeneity between network structure and individual characteristics, and the lack of time-resolved data about individuals' behavior. We leverage data from a sample of 1.5 million college students on Facebook, who wrote more than 630 million messages and 590 million posts over 4 years, to design a long-term natural experiment of friendship formation and social dynamics in the aftermath of a natural disaster. The analysis shows that affected individuals are more likely to strengthen interactions, while maintaining the same number of friends as unaffected individuals. Our findings suggest that the formation of social relationships may serve as a coping mechanism to deal with high-stress situations and build resilience in communities.

Dynamic Trap Formation and Elimination in Colloidal Quantum Dots

KAUST Repository

Voznyy, O.; Thon, S. M.; Ip, A. H.; Sargent, E. H.

2013-01-01

Using first-principles simulations on PbS and CdSe colloidal quantum dots, we find that surface defects form in response to electronic doping and charging of the nanoparticles. We show that electronic trap states in nanocrystals are dynamic entities, in contrast with the conventional picture wherein traps are viewed as stable electronic states that can be filled or emptied, but not created or destroyed. These traps arise from the formation or breaking of atomic dimers at the nanoparticle surface. The dimers' energy levels can reside within the bandgap, in which case a trap is formed. Fortunately, we are also able to identify a number of shallow-electron-affinity cations that stabilize the surface, working to counter dynamic trap formation and allowing for trap-free doping. © 2013 American Chemical Society.

Dynamic Trap Formation and Elimination in Colloidal Quantum Dots

KAUST Repository

Voznyy, O.

2013-03-21

Using first-principles simulations on PbS and CdSe colloidal quantum dots, we find that surface defects form in response to electronic doping and charging of the nanoparticles. We show that electronic trap states in nanocrystals are dynamic entities, in contrast with the conventional picture wherein traps are viewed as stable electronic states that can be filled or emptied, but not created or destroyed. These traps arise from the formation or breaking of atomic dimers at the nanoparticle surface. The dimers\\' energy levels can reside within the bandgap, in which case a trap is formed. Fortunately, we are also able to identify a number of shallow-electron-affinity cations that stabilize the surface, working to counter dynamic trap formation and allowing for trap-free doping. © 2013 American Chemical Society.

The self-adaptation to dynamic failures for efficient virtual organization formations in grid computing context

International Nuclear Information System (INIS)

Han Liangxiu

2009-01-01

Grid computing aims to enable 'resource sharing and coordinated problem solving in dynamic, multi-institutional virtual organizations (VOs)'. However, due to the nature of heterogeneous and dynamic resources, dynamic failures in the distributed grid environment usually occur more than in traditional computation platforms, which cause failed VO formations. In this paper, we develop a novel self-adaptive mechanism to dynamic failures during VO formations. Such a self-adaptive scheme allows an individual and member of VOs to automatically find other available or replaceable one once a failure happens and therefore makes systems automatically recover from dynamic failures. We define dynamic failure situations of a system by using two standard indicators: mean time between failures (MTBF) and mean time to recover (MTTR). We model both MTBF and MTTR as Poisson distributions. We investigate and analyze the efficiency of the proposed self-adaptation mechanism to dynamic failures by comparing the success probability of VO formations before and after adopting it in three different cases: (1) different failure situations; (2) different organizational structures and scales; (3) different task complexities. The experimental results show that the proposed scheme can automatically adapt to dynamic failures and effectively improve the dynamic VO formation performance in the event of node failures, which provide a valuable addition to the field.

A Preliminary Formation Flying Orbit Dynamics Analysis for Leonardo-BRDF

Science.gov (United States)

Hughes, Steven P.; Mailhe, Laurie M.

2001-01-01

Leonardo-BRDF is a NASA mission concept proposed to allow the investigation of radiative transfer and its effect on the Earth's climate and atmospheric phenomenon. Enabled by the recent developments in small-satellite and formation flying technology, the mission is envisioned to be composed of an array of spacecraft in carefully designed orbits. The different perspectives provided by a distributed array of spacecraft offer a unique advantage to study the Earth's albedo. This paper presents the orbit dynamics analysis performed in the context of the Leonardo-BRDF science requirements. First, the albedo integral is investigated and the effect of viewing geometry on science return is studied. The method used in this paper, based on Gauss quadrature, provides the optimal formation geometry to ensure that the value of the integral is accurately approximated. An orbit design approach is presented to achieve specific relative orbit geometries while simultaneously satisfying orbit dynamics constraints to reduce formation-keeping fuel expenditure. The relative geometry afforded by the design is discussed in terms of mission requirements. An optimal two-burn initialization scheme is presented with the required delta-V to distribute all spacecraft from a common parking orbit into their appropriate orbits in the formation. Finally, formation-keeping strategies are developed and the associated delta-V's are calculated to maintain the formation in the presence of perturbations.

Dynamics of biofilm formation in a model drinking water distribution system

DEFF Research Database (Denmark)

Boe-Hansen, Rasmus; Albrechtsen, Hans-Jørgen; Arvin, Erik

2002-01-01

The dynamics of biofilm formation in non-chlorinated groundwater-based drinking water was studied in a model distribution system. The formation of biofilm was closely monitored for a period of 522 days by total bacterial counts (AODC), heterotrophic plate counts (R2A media), and ATP content...

Designing a Robust Nonlinear Dynamic Inversion Controller for Spacecraft Formation Flying

Directory of Open Access Journals (Sweden)

Inseok Yang

2014-01-01

Full Text Available The robust nonlinear dynamic inversion (RNDI control technique is proposed to keep the relative position of spacecrafts while formation flying. The proposed RNDI control method is based on nonlinear dynamic inversion (NDI. NDI is nonlinear control method that replaces the original dynamics into the user-selected desired dynamics. Because NDI removes nonlinearities in the model by inverting the original dynamics directly, it also eliminates the need of designing suitable controllers for each equilibrium point; that is, NDI works as self-scheduled controller. Removing the original model also provides advantages of ease to satisfy the specific requirements by simply handling desired dynamics. Therefore, NDI is simple and has many similarities to classical control. In real applications, however, it is difficult to achieve perfect cancellation of the original dynamics due to uncertainties that lead to performance degradation and even make the system unstable. This paper proposes robustness assurance method for NDI. The proposed RNDI is designed by combining NDI and sliding mode control (SMC. SMC is inherently robust using high-speed switching inputs. This paper verifies similarities of NDI and SMC, firstly. And then RNDI control method is proposed. The performance of the proposed method is evaluated by simulations applied to spacecraft formation flying problem.

Shock Dynamics in Stellar Outbursts. I. Shock Formation

Energy Technology Data Exchange (ETDEWEB)

Ro, Stephen; Matzner, Christopher D., E-mail: ro@astro.utoronto.ca [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)

2017-05-20

Wave-driven outflows and non-disruptive explosions have been implicated in pre-supernova outbursts, supernova impostors, luminous blue variable eruptions, and some narrow-line and superluminous supernovae. To model these events, we investigate the dynamics of stars set in motion by strong acoustic pulses and wave trains, focusing on nonlinear wave propagation, shock formation, and an early phase of the development of a weak shock. We identify the shock formation radius, showing that a heuristic estimate based on crossing characteristics matches an exact expansion around the wave front and verifying both with numerical experiments. Our general analytical condition for shock formation applies to one-dimensional motions within any static environment, including both eruptions and implosions. We also consider the early phase of shock energy dissipation. We find that waves of super-Eddington acoustic luminosity always create shocks, rather than damping by radiative diffusion. Therefore, shock formation is integral to super-Eddington outbursts.

Dynamics of exciplex formation in rare gas media

Energy Technology Data Exchange (ETDEWEB)

Rojas-Lorenzo, German, E-mail: grojas37@gmail.com [Departamento de Fisica General y Matematicas, Instituto Superior de Tecnologias y Ciencias Aplicadas, La Habana (Cuba)] [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain); Rubayo-Soneira, Jesus [Departamento de Fisica General y Matematicas, Instituto Superior de Tecnologias y Ciencias Aplicadas, La Habana (Cuba); Alberti, Sebastian Fernandez [Centro de Estudios e Investigaciones, Universidad Nacional de Quilmes, Roque Saenz Pena 180, Bernal B1876BXD (Argentina)

2009-07-30

A hopping-surface algorithm has been used to simulate the dynamics induced in rare gas matrices due to the photoexcitation ({sup 1}S{sub 0} {yields} {sup 3}P{sub 1}) of atomic mercury embedded in them. Especially, the study of the dynamics of an exciplex formation in a model system consisting of solid xenon doped with atomic mercury. The process starts upon the photoexcitation of the Hg atom to its {sup 3}P{sub 1} electronic excited state. Diatomics-in-Molecule approach has been used for constructing the adiabatic potential surfaces. In all trajectories we show that a triatomic Xe-Hg{sup *}-Xe complex is formed, but in two conformations: bent and linear. The mechanisms leading to the formation of one or the other are identified. Mainly, are noted the thermal fluctuations of the Hg impurity and the shape of the potential surfaces. Furthermore, we show that non-radiative intrastate relaxation occurs via a conical intersection between the excited state surfaces. The simulated spectra are in very good agreement with the experimental data.

Relative dynamics and motion control of nanosatellite formation flying

Science.gov (United States)

Pimnoo, Ammarin; Hiraki, Koju

2016-04-01

Orbit selection is a necessary factor in nanosatellite formation mission design/meanwhile, to keep the formation, it is necessary to consume fuel. Therefore, the best orbit design for nanosatellite formation flying should be one that requires the minimum fuel consumption. The purpose of this paper is to analyse orbit selection with respect to the minimum fuel consumption, to provide a convenient way to estimate the fuel consumption for keeping nanosatellite formation flying and to present a simplified method of formation control. The formation structure is disturbed by J2 gravitational perturbation and other perturbing accelerations such as atmospheric drag. First, Gauss' Variation Equations (GVE) are used to estimate the essential ΔV due to the J2 perturbation and atmospheric drag. The essential ΔV presents information on which orbit is good with respect to the minimum fuel consumption. Then, the linear equations which account for J2 gravitational perturbation of Schweighart-Sedwick are presented and used to estimate the fuel consumption to maintain the formation structure. Finally, the relative dynamics motion is presented as well as a simplified motion control of formation structure by using GVE.

Neural dynamics of social tie formation in economic decision-making.

Science.gov (United States)

Bault, Nadège; Pelloux, Benjamin; Fahrenfort, Johannes J; Ridderinkhof, K Richard; van Winden, Frans

2015-06-01

The disposition for prosocial conduct, which contributes to cooperation as arising during social interaction, requires cortical network dynamics responsive to the development of social ties, or care about the interests of specific interaction partners. Here, we formulate a dynamic computational model that accurately predicted how tie formation, driven by the interaction history, influences decisions to contribute in a public good game. We used model-driven functional MRI to test the hypothesis that brain regions key to social interactions keep track of dynamics in tie strength. Activation in the medial prefrontal cortex (mPFC) and posterior cingulate cortex tracked the individual's public good contributions. Activation in the bilateral posterior superior temporal sulcus (pSTS), and temporo-parietal junction was modulated parametrically by the dynamically developing social tie-as estimated by our model-supporting a role of these regions in social tie formation. Activity in these two regions further reflected inter-individual differences in tie persistence and sensitivity to behavior of the interaction partner. Functional connectivity between pSTS and mPFC activations indicated that the representation of social ties is integrated in the decision process. These data reveal the brain mechanisms underlying the integration of interaction dynamics into a social tie representation which in turn influenced the individual's prosocial decisions. © The Author (2014). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

Antimatter annihilation detection with AEgIS

CERN Document Server

Gligorova, Angela

2015-01-01

AE ̄ gIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is an antimatter exper- iment based at CERN, whose primary goal is to carry out the first direct measurement of the Earth’s gravitational acceleration on antimatter. A precise measurement of antimatter gravity would be the first precision test of the Weak Equivalence Principle for antimatter. The principle of the experiment is based on the formation of antihydrogen through a charge exchange reaction between laser excited (Rydberg) positronium and ultra-cold antiprotons. The antihydrogen atoms will be accelerated by an inhomogeneous electric field (Stark acceleration) to form a pulsed cold beam. The free fall of the antihydrogen due to Earth’s gravity will be measured using a moiré de- flectometer and a hybrid position detector. This detector is foreseen to consist of an active silicon part, where the annihilation of antihydrogen takes place, followed by an emulsion part coupled to a fiber time-of-flight detector. This overview prese...

Construction and Operational Experience with a Superconducting Octupole Used to Trap Antihydrogen

Energy Technology Data Exchange (ETDEWEB)

Wanderer P.; Escallier, J.; Marone, A.; Parker, B.

2011-09-06

A superconducting octupole magnet has seen extensive service as part of the ALPHA experiment at CERN. ALPHA has trapped antihydrogen, a crucial step towards performing precision measurements of anti-atoms. The octupole was made at the Direct Wind facility by the Superconducting Magnet Division at Brookhaven National Laboratory. The magnet was wound with a six-around-one NbTi cable about 1 mm in diameter. It is about 300 mm long, with a radius of 25 mm and a peak field at the conductor of 4.04 T. Specific features of the magnet, including a minimal amount of material in the coil and coil ends with low multipole content, were advantageous to its use in ALPHA. The magnet was operated for six months a year for five years. During this time it underwent about 900 thermal cycles (between 4K and 100K). A novel operational feature is that during the course of data-taking the magnet was repeatedly shut off from its 950 A operating current. The magnet quenches during the shutoff, with a decay constant of 9 ms. Over the course of the five years, the magnet was deliberately quenched many thousands of times. It still performs well.

Slowing down of 100 keV antiprotons in Al foils

Science.gov (United States)

Nordlund, K.

2018-03-01

Using energy degrading foils to slow down antiprotons is of interest for producing antihydrogen atoms. I consider here the slowing down of 100 keV antiprotons, that will be produced in the ELENA storage ring under construction at CERN, to energies below 10 keV. At these low energies, they are suitable for efficient antihydrogen production. I simulate the antihydrogen motion and slowing down in Al foils using a recently developed molecular dynamics approach. The results show that the optimal Al foil thickness for slowing down the antiprotons to below 5 keV is 910 nm, and to below 10 keV is 840 nm. Also the lateral spreading of the transmitted antiprotons is reported and the uncertainties discussed.

Dynamics of crater formations in immersed granular materials

Science.gov (United States)

Varas, G.; Vidal, V.; Géminard, J.

2009-12-01

Craters are part of the widespread phenomena observed in nature. Among the main applications to natural phenomena, aside from meteorite impact craters, are the formation and growth of volcanic edifices, by successive ejecta emplacement and/or erosion. The time evolution and dynamics play a crucial role here, as the competition between volcanic-jet mass-flux (degassing and ejecta) and crater-size evolution may control directly the eruptive regime. Crater morphology in dry granular material has been extensively studied, both experimentally and theoretically. Most of these studies investigate the final, steady crater shape resulting from the collision of solid bodies with the material surface and scaling laws are derived. In immersed granular material, craters generated by an underwater vortex ring, or underwater impact craters generated by landslide, have been reported. In a previous experimental study, Gostiaux et al. [Gran. Matt., 2002] have investigated the dynamics of air flowing through an immersed granular layer. They reported that, depending on the flow rate, the system exhibits two qualitatively different regimes: At small flow rate, the bubbling regime during which bubbles escape the granular layer independently one from another; At large flow rate, the open-channel regime which corresponds to the formation of a channel crossing the whole thickness of the granular bed through which air escapes almost continuously. At intermediate flow rate, a spontaneous alternation between these two regimes is observed. Here, we report the dynamics of crater formations at the free surface of an immersed granular bed, locally crossed by an ascending gas flow. We reproduce the experimental conditions of Gostiaux et al. (2002) in two dimensions: In a vertical Hele-Shaw cell, the crater consists of two sand piles which develop around the location of the gas emission. We observe that the typical size of the crater increases logarithmically with time, independently of the gas

Dynamic properties of anhydrites, marls and salts of the Gachsaran evaporitic formation, Iran

International Nuclear Information System (INIS)

Gorjian, M; Memarian, H; Moosavi, M; Mehrgini, B

2013-01-01

A large carbonate oil field in Iran is suffering from severe casing collapses and related operational problems in anhydrite, marl and salt sequences of the Gachsaran cap rock formation. To investigate the causes and cures of operational problems, specifically casing collapse, knowing geomechanical properties of anhydrite, marl and salt of this formation is a prerequisite. However, taking cores in this formation is virtually impossible due to high solubility and weakness of the rocks. Moreover, there are insufficient well log data in this formation and the only available running well log is V p . In this paper, in order to obtain the dynamic parameters of the Gachsaran formation, V p , V s and ρ b in anhydrite, marl and salt cores, which had been taken from depths up to 300 m, were measured. Moreover, V p and V s in salt cores under different triaxial and hydrostatic stress conditions were obtained. The V p –V s, (V p /V s )–V p and V p –ρ b relations in anhydrite, marl and salt were investigated. The established relations in these anhydrite samples were verified by the data derived from limited cores which were taken from 3600 m depth. The relations between dynamic properties of salt with lateral and hydrostatic stresses were investigated. In conclusion, V s , ρ b and the ratio of V p /V s in anhydrite and marl can be estimated through the established relations and having V p logs in the Gachsaran formation. As a result, the dynamic properties of these rocks can be calculated in different depths of this evaporitic formation. Furthermore, the dynamic properties of salt rock seem to be constant in various depths and under differing triaxial and hydrostatic stress conditions. (paper)

Dynamics of intense laser channel formation in an underdense plasma

International Nuclear Information System (INIS)

Davis, J.; Petrov, G.M.; Velikovich, A.L.

2005-01-01

Efficient guiding and propagation of multi-keV x-rays in plasmas can be achieved by dynamically modifying the media through plasma channel formation. The dynamics of plasma channel formation is studied in preformed underdense plasma irradiated by a high intensity laser. This is done by a two-dimensional model coupling laser propagation to a relativistic particle-in-cell model. For laser intensity of 10 20 W/cm 2 and a laser beam width of 5 μm the channel formation proceeds on a time scale of 60-70 fs in uniform plasma with density 10 18 cm -3 . The channel closes shortly after the rear of the laser pulse has passed due to Coulomb attraction from the ion core. Electron cavitation occurs only if the laser intensity is above a certain threshold intensity and the laser pulse duration exceeds 100 fs. X-ray generation and propagation is feasible for ultrarelativistic laser pulses with small beam width, less than ∼20 μm, and duration of more than 100 fs

Local-heterogeneous responses and transient dynamics of cage breaking and formation in colloidal fluids.

Science.gov (United States)

Nag, Preetom; Teramoto, Hiroshi; Li, Chun-Biu; Terdik, Joseph Z; Scherer, Norbert F; Komatsuzaki, Tamiki

2014-09-14

Quantifying the interactions in dense colloidal fluids requires a properly designed order parameter. We present a modified bond-orientational order parameter, ψ̄6, to avoid problems of the original definition of bond-orientational order parameter. The original bond-orientational order parameter can change discontinuously in time but our modified order parameter is free from the discontinuity and, thus, it is a suitable measure to quantify the dynamics of the bond-orientational ordering of the local surroundings. Here we analyze ψ̄6 in a dense driven monodisperse quasi-two-dimensional colloidal fluids where a single particle is optically trapped at the center. The perturbation by the trapped and driven particle alters the structure and dynamics of the neighboring particles. This perturbation disturbs the flow and causes spatial and temporal distortion of the bond-orientational configuration surrounding each particle. We investigate spatio-temporal behavior of ψ̄6 by a Wavelet transform that provides a time-frequency representation of the time series of ψ̄6. It is found that particles that have high power in frequencies corresponding to the inverse of the timescale of perturbation undergo distortions of their packing configurations that result in cage breaking and formation dynamics. To gain insight into the dynamic structure of cage breaking and formation of bond-orientational ordering, we compare the cage breaking and formation dynamics with the underlying dynamical structure identified by Lagrangian Coherent Structures (LCSs) estimated from the finite-time Lyapunov exponent (FTLE) field. The LCSs are moving separatrices that effectively divide the flow into distinct regions with different dynamical behavior. It is shown that the spatial distribution of the FTLE field and the power of particles in the wavelet transform have positive correlation, implying that LCSs provide a dynamic structure that dominates the dynamics of cage breaking and formation of the

Pore Scale Dynamics of Microemulsion Formation.

Science.gov (United States)

Unsal, Evren; Broens, Marc; Armstrong, Ryan T

2016-07-19

Experiments in various porous media have shown that multiple parameters come into play when an oleic phase is displaced by an aqueous solution of surfactant. In general, the displacement efficiency is improved when the fluids become quasi-miscible. Understanding the phase behavior oil/water/surfactant systems is important because microemulsion has the ability to generate ultralow interfacial tension (microemulsion formation and the resulting properties under equilibrium conditions. However, the majority of applications where microemulsion is present also involve flow, which has received relatively less attention. It is commonly assumed that the characteristics of an oil/water/surfactant system under flowing conditions are identical to the one under equilibrium conditions. Here, we show that this is not necessarily the case. We studied the equilibrium phase behavior of a model system consisting of n-decane and an aqueous solution of olefin sulfonate surfactant, which has practical applications for enhanced oil recovery. The salt content of the aqueous solution was varied to provide a range of different microemulsion compositions and oil-water interfacial tensions. We then performed microfluidic flow experiments to study the dynamic in situ formation of microemulsion by coinjecting bulk fluids of n-decane and surfactant solution into a T-junction capillary geometry. A solvatochromatic fluorescent dye was used to obtain spatially resolved compositional information. In this way, we visualized the microemulsion formation and the flow of it along with the excess phases. A complex interaction between the flow patterns and the microemulsion properties was observed. The formation of microemulsion influenced the flow regimes, and the flow regimes affected the characteristics of the microemulsion formation. In particular, at low flow rates, slug flow was observed, which had profound consequences on the pore scale mixing behavior and resulting microemulsion properties.

Effects of internal friction on contact formation dynamics of polymer chain

Science.gov (United States)

Bian, Yukun; Li, Peng; Zhao, Nanrong

2018-04-01

A theoretical framework is presented to study the contact formation dynamics of polymer chains, in accompany with an electron-transfer quenching. Based on a non-Markovian Smoluchowski equation supplemented with an exponential sink term, we derive the mean time of contact formation under Wilemski-Fixman approximation. Our particular attentions are paid to the effect of internal friction. We find out that internal friction induces a novel fractional viscosity dependence, which will become more remarkable as internal friction increases. Furthermore, we clarify that internal friction inevitably promotes a diffusion-controlled mechanism by slowing the chain relaxation. Finally, we apply our theory to rationalise the experimental investigation for contact formation of a single-stranded DNA. The theoretical results can reproduce the experimental data very well with quite reasonable estimation for the intrinsic parameters. Such good agreements clearly demonstrate the validity of our theory which has appropriately addressed the very role of internal friction to the relevant dynamics.

Dynamics of gradient formation by intracellular shuttling

Energy Technology Data Exchange (ETDEWEB)

Berezhkovskii, Alexander M. [Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892 (United States); Shvartsman, Stanislav Y. [Department of Chemical and Biological Engineering and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544 (United States)

2015-08-21

A number of important cellular functions rely on the formation of intracellular protein concentration gradients. Experimental studies discovered a number of mechanisms for the formation of such gradients. One of the mechanisms relies on the intracellular shuttling of a protein that interconverts between the two states with different diffusivities, under the action of two enzymes, one of which is localized to the plasma membrane, whereas the second is uniformly distributed in the cytoplasm. Recent work reported an analytical solution for the steady state gradient in this mechanism, obtained in the framework of a one-dimensional reaction-diffusion model. Here, we study the dynamics in this model and derive analytical expressions for the Laplace transforms of the time-dependent concentration profiles in terms of elementary transcendental functions. Inverting these transforms numerically, one can obtain time-dependent concentration profiles of the two forms of the protein.

Formation dynamics of FeN thin films on Cu(100)

KAUST Repository

Heryadi, Dodi; Schwingenschlö gl, Udo

2012-01-01

To investigate the structural and magnetic properties of thin films of FeN we have performed ab initio molecular dynamics simulations of their formation on Cu(100) substrates. The iron nitride layers exhibit a p4gm(2 × 2) reconstruction and order

Cloud fluid models of gas dynamics and star formation in galaxies

Science.gov (United States)

Struck-Marcell, Curtis; Scalo, John M.; Appleton, P. N.

1987-01-01

The large dynamic range of star formation in galaxies, and the apparently complex environmental influences involved in triggering or suppressing star formation, challenges the understanding. The key to this understanding may be the detailed study of simple physical models for the dominant nonlinear interactions in interstellar cloud systems. One such model is described, a generalized Oort model cloud fluid, and two simple applications of it are explored. The first of these is the relaxation of an isolated volume of cloud fluid following a disturbance. Though very idealized, this closed box study suggests a physical mechanism for starbursts, which is based on the approximate commensurability of massive cloud lifetimes and cloud collisional growth times. The second application is to the modeling of colliding ring galaxies. In this case, the driving processes operating on a dynamical timescale interact with the local cloud processes operating on the above timescale. The results is a variety of interesting nonequilibrium behaviors, including spatial variations of star formation that do not depend monotonically on gas density.

Dynamical and photometric models of star formation in tidal tails

International Nuclear Information System (INIS)

Wallin, J.F.

1990-01-01

An investigation into the causes of star formation in tidal tails has been conducted using a restricted three-body dynamical model in conjunction with a broadband photometric evolutionary code. Test particles are initially placed in circular orbits around a softened point mass and then perturbed by a companion passing in a parabotic orbit. During the passage, the density evolution of the galaxy is examined both in regions within the disk and in selected comoving regions in the tidal features. Even without the inclusion of self-gravity and hydrodynamics, regions of compression form inside the disk, along the tidal tail, and in the tidal bridge causing local density increases of up to 500 percent. By assuming that the density changes relate to the star-formation rate via a Schmidt (1959) law, limits on the density changes needed to make detectable changes in the colors are calculated. A spiral galaxy population is synthesized and the effects of modest changes in the star-formation rate are explored using a broadband photometric evolutionary code. Density changes similar to those found in the dynamical models will cause detectable changes in the colors of a stellar population. From these models, it is determined that the blue colors and knotty features observed in the tidal features of some galaxies result from increased rates of star formation induced by tidally produced density increases. Limitations of this model are discussed along with photometric evolutionary models based on the density evolution in the tails. 52 refs

Liquid crystal droplet formation and anchoring dynamics in a microfluidic device

Science.gov (United States)

Steinhaus, Ben; Shen, Amy; Feng, James; Link, Darren

2004-11-01

Liquid crystal drops dispersed in a continuous phase of silicon oil are generated with a narrow distribution in droplet size in microfluidic devices both above and below the nematic to isotropic transition temperature. For these two cases, we observe not only the different LC droplet generation and coalescence dynamics, but also distinct droplet morphology. Our experiments show that the nematic liquid crystalline order is important for the LC droplet formation and anchoring dynamics.

Dynamical entanglement formation and dissipation effects in two double quantum dots

Energy Technology Data Exchange (ETDEWEB)

Contreras-Pulido, L D [Centro de Investigacion CientIfica y de Educacion Superior de Ensenada, Apartado Postal 2732, Ensenada, BC 22860 (Mexico); Rojas, F [Departamento de Fisica Teorica, Centro de Ciencias de la Materia Condensada, Universidad Nacional Autonoma de Mexico, Ensenada, Baja California 22800 (Mexico)

2006-11-01

We study the static and dynamic formation of entanglement in charge states of a two double quantum dot array with two mobile electrons under the effect of an external driving field. We include dissipation via contact with a phonon bath. By using the density matrix formalism and an open quantum system approach, we describe the dynamical behaviour of the charge distribution (polarization), concurrence (measure of the degree of entanglement) and Bell state probabilities (two qubit states with maximum entanglement) of such a system, including the role of dot asymmetry and temperature effects. Our results show that it is possible to obtain entangled states as well as a most probable Bell state, which can be controlled by the driving field. We also evaluate how the entanglement formation based on charge states deteriorates as the temperature or asymmetry increases.

Dynamics of blood flow and thrombus formation in a multi-bypass microfluidic ladder network.

Science.gov (United States)

Zilberman-Rudenko, Jevgenia; Sylman, Joanna L; Lakshmanan, Hari H S; McCarty, Owen J T; Maddala, Jeevan

2017-02-01

The reaction dynamics of a complex mixture of cells and proteins, such as blood, in branched circulatory networks within the human microvasculature or extravascular therapeutic devices such as extracorporeal oxygenation machine (ECMO) remains ill-defined. In this report we utilize a multi-bypass microfluidics ladder network design with dimensions mimicking venules to study patterns of blood platelet aggregation and fibrin formation under complex shear. Complex blood fluid dynamics within multi-bypass networks under flow were modeled using COMSOL. Red blood cells and platelets were assumed to be non-interacting spherical particles transported by the bulk fluid flow, and convection of the activated coagulation factor II, thrombin, was assumed to be governed by mass transfer. This model served as the basis for predicting formation of local shear rate gradients, stagnation points and recirculation zones as dictated by the bypass geometry. Based on the insights from these models, we were able to predict the patterns of blood clot formation at specific locations in the device. Our experimental data was then used to adjust the model to account for the dynamical presence of thrombus formation in the biorheology of blood flow. The model predictions were then compared to results from experiments using recalcified whole human blood. Microfluidic devices were coated with the extracellular matrix protein, fibrillar collagen, and the initiator of the extrinsic pathway of coagulation, tissue factor. Blood was perfused through the devices at a flow rate of 2 µL/min, translating to physiologically relevant initial shear rates of 300 and 700 s -1 for main channels and bypasses, respectively. Using fluorescent and light microscopy, we observed distinct flow and thrombus formation patterns near channel intersections at bypass points, within recirculation zones and at stagnation points. Findings from this proof-of-principle ladder network model suggest a specific correlation between

Formation and field-driven dynamics of nematic spheroids.

Science.gov (United States)

Fu, Fred; Abukhdeir, Nasser Mohieddin

2017-07-19

Unlike the canonical application of liquid crystals (LCs), LC displays, emerging technologies based on LC materials are increasingly leveraging the presence of nanoscale defects. The inherent nanoscale characteristics of LC defects present both significant opportunities as well as barriers for the application of this fascinating class of materials. Simulation-based approaches to the study of the effects of confinement and interface anchoring conditions on LC domains has resulted in significant progress over the past decade, where simulations are now able to access experimentally-relevant length scales while simultaneously capturing nanoscale defect structures. In this work, continuum simulations were performed in order to study the dynamics of micron-scale nematic LC spheroids of varying shape. Nematic spheroids are one of the simplest inherently defect-containing LC structures and are relevant to polymer-dispersed LC-based "smart" window technology. Simulation results include nematic phase formation and external field-switching dynamics of nematic spheroids ranging in shape from oblate to prolate. Results include both qualitative and quantitative insight into the complex coupling of nanoscale defect dynamics and structure transitions to micron-scale reorientation. Dynamic mechanisms are presented and related to structural transitions in LC defects present in the nematic domain. Domain-averaged metrics including order parameters and response times are determined for a range of experimentally-accessible electric field strengths. These results have both fundamental and technological relevance, in that increased understanding of LC dynamics in the presence of defects is a key barrier to continued advancement in the field.

The ASACUSA Micromegas Tracker: A cylindrical, bulk Micromegas detector for antimatter research

Energy Technology Data Exchange (ETDEWEB)

Radics, B., E-mail: balint.radics@riken.jp; Nagata, Y.; Yamazaki, Y. [Atomic Physics Laboratory, RIKEN, Saitama 351-0198 (Japan); Ishikawa, S.; Kuroda, N.; Matsuda, Y. [Institute of Physics, Graduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902 (Japan); Anfreville, M.; Aune, S.; Boyer, M.; Chateau, F.; Combet, M.; Granelli, R.; Legou, P.; Mandjavidze, I.; Procureur, S.; Riallot, M.; Vallage, B.; Vandenbroucke, M. [Irfu, CEA, Centre de Saclay, 91191 Gif sur Yvette (France)

2015-08-15

The ASACUSA Micromegas Tracker (AMT; ASACUSA: Atomic Spectroscopy and Collisions Using Slow Antiprotons) was designed to be able to reconstruct antiproton-nucleon annihilation vertices in three dimensions. The goal of this device is to study antihydrogen formation processes in the ASACUSA cusp trap, which was designed to synthesise a spin-polarised antihydrogen beam for precise tests of Charge, Parity, and Time (CPT) symmetry invariance. This paper discusses the structure and technical details of an AMT detector built into such an environment, its data acquisition system and the first performance with cosmic rays.

The ASACUSA Micromegas Tracker: A cylindrical, bulk Micromegas detector for antimatter research.

Science.gov (United States)

Radics, B; Nagata, Y; Yamazaki, Y; Ishikawa, S; Kuroda, N; Matsuda, Y; Anfreville, M; Aune, S; Boyer, M; Chateau, F; Combet, M; Granelli, R; Legou, P; Mandjavidze, I; Procureur, S; Riallot, M; Vallage, B; Vandenbroucke, M

2015-08-01

The ASACUSA Micromegas Tracker (AMT; ASACUSA: Atomic Spectroscopy and Collisions Using Slow Antiprotons) was designed to be able to reconstruct antiproton-nucleon annihilation vertices in three dimensions. The goal of this device is to study antihydrogen formation processes in the ASACUSA cusp trap, which was designed to synthesise a spin-polarised antihydrogen beam for precise tests of Charge, Parity, and Time (CPT) symmetry invariance. This paper discusses the structure and technical details of an AMT detector built into such an environment, its data acquisition system and the first performance with cosmic rays.

Formation, evolution, and dynamics of young solar systems

CERN Document Server

Gressel, Oliver

2017-01-01

This book's interdisciplinary scope aims at bridging various communities: 1) cosmochemists, who study meteoritic samples from our own solar system, 2) (sub-) millimetre astronomers, who measure the distribution of dust and gas of star-forming regions and planet-forming discs, 3) disc modellers, who describe the complex photo-chemical structure of parametric discs to fit these to observation, 4) computational astrophysicists, who attempt to decipher the dynamical structure of magnetised gaseous discs, and the effects the resulting internal structure has on the aerodynamic re-distribution of embedded solids, 5) theoreticians in planet formation theory, who aim to piece it all together eventually arriving at a coherent holistic picture of the architectures of planetary systems discovered by 6) the exoplanet observers, who provide us with unprecedented samples of exoplanet worlds. Combining these diverse fields the book sheds light onto the riddles that research on planet formation is currently confronted with, a...

Terrestrial Planet Formation: Dynamical Shake-up and the Low Mass of Mars

Science.gov (United States)

Bromley, Benjamin C.; Kenyon, Scott J.

2017-05-01

We consider a dynamical shake-up model to explain the low mass of Mars and the lack of planets in the asteroid belt. In our scenario, a secular resonance with Jupiter sweeps through the inner solar system as the solar nebula depletes, pitting resonant excitation against collisional damping in the Sun’s protoplanetary disk. We report the outcome of extensive numerical calculations of planet formation from planetesimals in the terrestrial zone, with and without dynamical shake-up. If the Sun’s gas disk within the terrestrial zone depletes in roughly a million years, then the sweeping resonance inhibits planet formation in the asteroid belt and substantially limits the size of Mars. This phenomenon likely occurs around other stars with long-period massive planets, suggesting that asteroid belt analogs are common.

Community helping services: dynamic of formation and expressiveness of the cultural care.

Science.gov (United States)

Landim, Fátima Luna Pinheiro

2006-01-01

Community helping services is an expression used by the social movements to designate families that live in shacks installed in a public area intended for building of own house at a community helping system. Studies in ethnonursing that aimed: in order to detail dynamic configuration in a community helping service. It took place in an community helping area located in the outskirts of Fortaleza, Ceará. The community members acting as general informants from the local culture, while eight (8) women heads-of-families, working as key informers. The data collect used the Observation-Participation-Reflection Model. The analyses were processing by the time that the dates were collected, considering the categories: inserting in the community helping culture to obtain their history; community helping is not a slum -describing the formation dynamic. Established that the formation dynamic of the community helping go on the own house representation as a symbol of " a better life". To assimilate such expression introducing in own cultural universe is a challenge for the nursing to assist a care culture congruent.

Excimer Formation Dynamics of Dipyrenyldecane in Structurally Different Ionic Liquids.

Science.gov (United States)

Yadav, Anita; Pandey, Siddharth

2017-12-07

Ionic liquids, being composed of ions alone, may offer alternative pathways for molecular aggregation. These pathways could be controlled by the chemical structure of the cation and the anion of the ionic liquids. Intramolecular excimer formation dynamics of a bifluorophoric probe, 1,3-bis(1-pyrenyl)decane [1Py(10)1Py], where the fluorophoric pyrene moieties are separated by a long decyl chain, is investigated in seven different ionic liquids in 10-90 °C temperature range. The long alkyl separator allows for ample interaction with the solubilizing milieu prior to the formation of the excimer. The ionic liquids are composed of two sets, one having four ionic liquids of 1-butyl-3-methylimidazolium cation ([bmim + ]) with different anions and the other having four ionic liquids of bis(trifluoromethylsulfonyl)imide anion ([Tf 2 N - ]) with different cations. The excimer-to-monomer emission intensity ratio (I E /I M ) is found to increase with increasing temperature in sigmoidal fashion. Chemical structure of the ionic liquid controls the excimer formation efficiency, as I E /I M values within ionic liquids with the same viscosities are found to be significantly different. The excited-state intensity decay kinetics of 1Py(10)1Py in ionic liquids do not adhere to a simplistic Birk's scheme, where only one excimer conformer forms after excitation. The apparent rate constants of excimer formation (k a ) in highly viscous ionic liquids are an order of magnitude lower than those reported in organic solvents. In general, the higher the viscosity of the ionic liquid, the more sensitive is the k a to the temperature with higher activation energy, E a . The trend in E a is found to be similar to that for activation energy of the viscous flow (E a,η ). Stokes-Einstein relationship is not followed in [bmim + ] ionic liquids; however, with the exception of [choline][Tf 2 N], it is found to be followed in [Tf 2 N - ] ionic liquids suggesting the cyclization dynamics of 1Py(10)1Py

H-bar and H-bar + production cross sections for the GBAR experiment

International Nuclear Information System (INIS)

Comini, P; Hervieux, P-A

2013-01-01

The production and cooling of the H-bar + ion is the key point of the GBAR experiment (Gravitational Behaviour of Antihydrogen at Rest), which aims at performing the free fall of antihydrogen atoms to measure g-bar , the acceleration of antimatter on Earth. H-bar + ions will be obtained from collisions between a positronium cloud and antiprotons delivered by the AD/ELENA facility at CERN, with intermediate formation of antihydrogen atoms. In order to optimise the experimental production of H-bar + ions, we computed the total cross sections of the two corresponding reactions, within the same theoretical framework of the Continuum Distorted Wave – Final State (CDW-FS) model. The different contributions of the H-bar excited states have been systematically investigated for different states of Ps. The results exhibit an increase of the H-bar production toward low kinetic energies, in agreement with experimental data and previous calculations, whereas the largest H-bar + production is obtained with low energy ground-state antihydrogen atoms. These theoretical predictions suggest that the overall production of H-bar + could be optimal for 2 keV antiproton impact energy, using positronium atoms prepared in the 2p state.

Brownian dynamics simulations of insulin microspheres formation

Science.gov (United States)

Li, Wei; Chakrabarti, Amit; Gunton, James

2010-03-01

Recent experiments have indicated a novel, aqueous process of microsphere insulin fabrication based on controlled phase separation of protein from water-soluble polymers. We investigate the insulin microsphere crystal formation from insulin-PEG-water systems via 3D Brownian Dynamics simulations. We use the two component Asakura-Oosawa model to simulate the kinetics of this colloid polymer mixture. We first perform a deep quench below the liquid-crystal boundary that leads to fractal formation. We next heat the system to obtain a break-up of the fractal clusters and subsequently cool the system to obtain a spherical aggregation of droplets with a relatively narrow size distribution. We analyze the structure factor S(q) to identify the cluster dimension. S(q) crosses over from a power law q dependence of 1.8 (in agreement with DLCA) to 4 as q increases, which shows the evolution from fractal to spherical clusters. By studying the bond-order parameters, we find the phase transition from liquid-like droplets to crystals which exhibit local HCP and FCC order. This work is supported by grants from the NSF and Mathers Foundation.

Finite element simulation of dynamic wetting flows as an interface formation process

KAUST Repository

Sprittles, J.E.; Shikhmurzaev, Y.D.

2013-01-01

A mathematically challenging model of dynamic wetting as a process of interface formation has been, for the first time, fully incorporated into a numerical code based on the finite element method and applied, as a test case, to the problem

Dynamics of Semantic and Word-Formation Subsystems of the Russian Language: Historical Dynamics of the Word Family

Directory of Open Access Journals (Sweden)

Olga Ivanovna Dmitrieva

2015-09-01

Full Text Available The article provides comprehensive justification of the principles and methods of the synchronic and diachronic research of word-formation subsystems of the Russian language. The authors also study the ways of analyzing historical dynamics of word family as the main macro-unit of word-formation system. In the field of analysis there is a family of words with the stem 'ход-' (the meaning of 'motion', word-formation of which is investigated in different periods of the Russian literary language. Significance of motion-verbs in the process of forming a language picture of the world determined the character and the structure of this word family as one of the biggest in the history of the Russian language. In the article a structural and semantic dynamics of the word family 'ход-' is depicted. The results of the study show that in the ancient period the prefixes of verbal derivatives were formed, which became the apex-branched derivational paradigms existing in modern Russian. The old Russian period of language development is characterized by the appearance of words with connotative meaning (with suffixes -ishk-, -ichn-, as well as the words with possessive semantics (with suffixes –ev-, -sk-. In this period the verbs with the postfix -cz also supplement the analyzed word family. The period of formation of the National Russian language was marked by the loss of a large number of abstract nouns and the appearance of neologisms from some old Russian abstract nouns. The studied family in the modern Russian language is characterized by the following processes: the appearance of terms, the active semantic derivation, the weakening of word-formation variability, the semantic differentiation of duplicate units, the development of subsystem of words with connotative meanings, and the preservation of derivatives in all functional styles.

THE RELATION BETWEEN DYNAMICS AND STAR FORMATION IN BARRED GALAXIES

International Nuclear Information System (INIS)

Martinez-Garcia, Eric E.; Gonzalez-Lopezlira, Rosa A.

2011-01-01

We analyze optical and near-infrared data of a sample of 11 barred spiral galaxies, in order to establish a connection between star formation and bar/spiral dynamics. We find that 22 regions located in the bars and 20 regions in the spiral arms beyond the end of the bar present azimuthal color/age gradients that may be attributed to star formation triggering. Assuming a circular motion dynamic model, we compare the observed age gradient candidates with stellar population synthesis models. A link can then be established with the disk dynamics that allows us to obtain parameters like the pattern speed of the bar or spiral as well as the positions of resonance radii. We subsequently compare the derived pattern speeds with those expected from theoretical and observational results in the literature (e.g., bars ending near corotation). We find a tendency to overestimate bar pattern speeds derived from color gradients in the bar at small radii, away from corotation; this trend can be attributed to non-circular motions of the young stars born in the bar region. In spiral regions, we find that ∼50% of the color gradient candidates are 'inverse', i.e., with the direction of stellar aging contrary to that of rotation. The other half of the gradients found in spiral arms have stellar ages that increase in the same sense as rotation. Of the nine objects with gradients in both bars and spirals, six (67%) appear to have a bar and a spiral with similar Ω p , while three (33%) do not.

Magnetic cusp and electric nested- or single-well configurations for high density antihydrogen and fusion nonneutral plasma applications

International Nuclear Information System (INIS)

Ordonez, C. A.

1999-01-01

Malmberg-Penning traps have had limited uses for applications that require high density nonneutral plasma confinement. For such traps, the density is severely limited because a magnetic field is used to provide a radially inward force to balance both self-electric and centrifugal radially outward forces. A possible way to confine higher density nonneutral plasmas is to use a magnetic cusp configuration. An annular nonneutral plasma would be confined in the radial magnetic field of a magnetic cusp such that radial confinement is provided by an externally produced electric potential well while axial confinement is provided by the magnetic field. In addition, a radial electric potential profile having a nested-well configuration can be used to simultaneously confine two oppositely signed plasma species (e.g., positrons and antiprotons) that overlap. In the work reported, various aspects of using magnetic cusp configurations and electric nested-well configurations are considered. Plasma confinement with these configurations may be useful for obtaining fast antihydrogen recombination and trapping rates and for achieving practical fusion power production

Magnetic Cusp and Electric Nested- or Single-Well Configurations for High Density Antihydrogen and Fusion Nonneutral Plasma Applications

International Nuclear Information System (INIS)

C.A. Ordonez

1999-01-01

Malmberg-Penning traps have had limited uses for applications that require high density nonneutral plasma confinement. For such traps, the density is severely limited because a magnetic field is used to provide a radially inward force to balance both self-electric and centrifugal radially outward forces. A possible way to confine higher density nonneutral plasmas is to use a magnetic cusp configuration. An annular nonneutral plasma would be confined in the radial magnetic field of a magnetic cusp such that radial confinement is provided by an externally produced electric potential well while axial confinement is provided by the magnetic field. In addition, a radial electric potential profile having a nested-well configuration can be used to simultaneously confine two oppositely signed plasma species (e.g., positrons and antiprotons) that overlap. In the work reported, various aspects of using magnetic cusp configurations and electric nested-well configurations are considered. Plasma confinement with these configurations may be useful for obtaining fast antihydrogen recombination and trapping rates and for achieving practical fusion power production

Dynamic Stall Vortex Formation of OA-209 Airfoil at Low Reynolds Number

OpenAIRE

Aung Myo Thu; Sang Eon Jeon; Yung Hwan Byun; Soo Hyung Park

2014-01-01

The unsteady flow field around oscillating OA-209 airfoil at a Reynolds number of 3.5×105 were investigated. Three different reduced frequencies were tested in order to see how it affects the hysteresis loop of an airfoil. At a reduced frequency of 0.05 the deep dynamic stall phenomenon was observed. Lift overshooting was observed as a result of dynamic stall vortex (DSV) shedding. Further investigation was carried out to find out the cause of DSV formation and shedding over airfoil. Particle...

Extracellular matrix dynamics during vertebrate axis formation.

Science.gov (United States)

Czirók, András; Rongish, Brenda J; Little, Charles D

2004-04-01

The first evidence for the dynamics of in vivo extracellular matrix (ECM) pattern formation during embryogenesis is presented below. Fibrillin 2 filaments were tracked for 12 h throughout the avian intraembryonic mesoderm using automated light microscopy and algorithms of our design. The data show that these ECM filaments have a reproducible morphogenic destiny that is characterized by directed transport. Fibrillin 2 particles initially deposited in the segmental plate mesoderm are translocated along an unexpected trajectory where they eventually polymerize into an intricate scaffold of cables parallel to the anterior-posterior axis. The cables coalesce near the midline before the appearance of the next-formed somite. Moreover, the ECM filaments define global tissue movements with high precision because the filaments act as passive motion tracers. Quantification of individual and collective filament "behaviors" establish fate maps, trajectories, and velocities. These data reveal a caudally propagating traveling wave pattern in the morphogenetic movements of early axis formation. We conjecture that within vertebrate embryos, long-range mechanical tension fields are coupled to both large-scale patterning and local organization of the ECM. Thus, physical forces or stress fields are essential requirements for executing an emergent developmental pattern-in this case, paraxial fibrillin cable assembly.

Explaining formation of Astronomical Jets using Dynamic Universe Model

Science.gov (United States)

Naga Parameswara Gupta, Satyavarapu

2016-07-01

Astronomical jets are observed from the centres of many Galaxies including our own Milkyway. The formation of such jet is explained using SITA simulations of Dynamic Universe Model. For this purpose the path traced by a test neutron is calculated and depicted using a set up of one densemass of the mass equivalent to mass of Galaxy center, 90 stars with similar masses of stars near Galaxy center, mass equivalents of 23 Globular Cluster groups, 16 Milkyway parts, Andromeda and Triangulum Galaxies at appropriate distances. Five different kinds of theoretical simulations gave positive results The path travelled by this test neutron was found to be an astronomical jet emerging from Galaxy center. This is another result from Dynamic Universe Model. It solves new problems like a. Variable Mass Rocket Trajectory Problem b. Explaining Very long baseline interferometry (VLBI) observations c. Astronomical jets observed from Milkyway Center d. Prediction of Blue shifted Galaxies e. Explaining Pioneer Anomaly f. Prediction of New Horizons satellite trajectory etc. Dynamic Universe Model never reduces to General relativity on any condition. It uses a different type of mathematics based on Newtonian physics. This mathematics used here is simple and straightforward. As there are no differential equations present in Dynamic Universe Model, the set of equations give single solution in x y z Cartesian coordinates for every point mass for every time step

Molecular-dynamics simulation of defect formation energy in boron nitride nanotubes

International Nuclear Information System (INIS)

Moon, W.H.; Hwang, H.J.

2004-01-01

We investigate the defect formation energy of boron nitride nanotubes (BNNTs) using molecular dynamics simulation. Although the defect with tetragon-octagon pairs (TOP) is favored in the flat BNNTs cap, BN clusters, and the growth of BNNTs, the formation energy of the TOP defect is significantly higher than that of the pentagon-heptagon pairs (PHP) defect in BNNTs. The PHP defect reduces the effect of the structural distortion caused by the TOP defect, in spite of homoelemental bonds. The instability of the TOP defect generates the structural transformation into BNNTs with no defect at about 1500 K. This mechanism shows that the TOP defect is less favored in case of BNNTs

Preliminary Design of the AEGIS Test Facility

CERN Document Server

Dassa, Luca; Cambiaghi, Danilo

2010-01-01

The AEGIS experiment is expected to be installed at the CERN Antiproton Decelerator in a very close future, since the main goal of the AEGIS experiment is the measurement of gravity impact on antihydrogen, which will be produced on the purpose. Antihydrogen production implies very challenging environmental conditions: at the heart of the AEGIS facility 50 mK temperature, 1e-12 mbar pressure and a 1 T magnetic field are required. Interfacing extreme cryogenics with ultra high vacuum will affect very strongly the design of the whole facility, requiring a very careful mechanical design. This paper presents an overview of the actual design of the AEGIS experimental facility, paying special care to mechanical aspects. Each subsystem of the facility – ranging from the positron source to the recombination region and the measurement region – will be shortly described. The ultra cold region, which is the most critical with respect to the antihydrogen formation, will be dealt in detail. The assembly procedures will...

Development and data analysis of a position detector for AE$\\bar{g}$IS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy)

CERN Document Server

Gligorova, Angela; Doser, Michael; Pacifico, Nicola

2015-03-13

AE$\\mathrm{\\bar{g}}$IS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is an antimatter experiment based at CERN, the European Organization for Nuclear Research, whose goal is to carry out the first direct measurement of the Earth’s gravitational acceleration on antimatter. The outcome of such measurement would be the first precision test of the Weak Equivalence Principle in a completely new area. According to WEP, all bodies fall with the same acceleration regardless of their mass and composition. AE$\\mathrm{\\bar{g}}$IS will attempt to achieve its aim by measuring the gravitational acceleration ($\\bar{g}$) for antihydrogen with 1$\\%$ relative precision. The first step towards the final goal is the formation of a pulsed, cold antihydrogen beam, which will be performed by a charge exchange reaction between laser excited (Rydberg) positronium and cold (100 mK) antiprotons. The antihydrogen atoms will be accelerated by an inhomogeneous electric field (Stark acceleration) to form a beam whose fr...

Probing antimatter gravity – The AEGIS experiment at CERN

Directory of Open Access Journals (Sweden)

Kellerbauer A.

2016-01-01

Full Text Available The weak equivalence principle states that the motion of a body in a gravitational field is independent of its structure or composition. This postulate of general relativity has been tested to very high precision with ordinary matter, but no relevant experimental verification with antimatter has ever been carried out. The AEGIS experiment will measure the gravitational acceleration of antihydrogen to ultimately 1% precision. For this purpose, a pulsed horizontal antihydrogen beam with a velocity of several 100 m s−1 will be produced. Its vertical deflection due to gravity will be detected by a setup consisting of material gratings coupled with a position-sensitive detector, operating as a moiré deflectometer or an atom interferometer. The AEGIS experiment is installed at CERN’s Antiproton Decelerator, currently the only facility in the world which produces copious amounts of low-energy antiprotons. The construction of the setup has been going on since 2010 and is nearing completion. A proof-of-principle experiment with antiprotons has demonstrated that the deflection of antiparticles by a few μm due to an external force can be detected. Technological and scientific development pertaining to specific challenges of the experiment, such as antihydrogen formation by positronium charge exchange or the position-sensitive detection of antihydrogen annihilations, is ongoing.

Dynamical barrier for the formation of solitary waves in discrete lattices

International Nuclear Information System (INIS)

Kevrekidis, P.G.; Espinola-Rocha, J.A.; Drossinos, Y.; Stefanov, A.

2008-01-01

We consider the problem of the existence of a dynamical barrier of 'mass' that needs to be excited on a lattice site to lead to the formation and subsequent persistence of localized modes for a nonlinear Schroedinger lattice. We contrast the existence of a dynamical barrier with its absence in the static theory of localized modes in one spatial dimension. We suggest an energetic criterion that provides a sufficient, but not necessary, condition on the amplitude of a single-site initial condition required to form a solitary wave. We show that this effect is not one-dimensional by considering its two-dimensional analog. The existence of a sufficient condition for the excitation of localized modes in the non-integrable, discrete, nonlinear Schroedinger equation is compared to the dynamics of excitations in the integrable, both discrete and continuum, version of the nonlinear Schroedinger equation

Changing Dynamics of Cross-Border Intimate Partnership Formations in Scandinavia

DEFF Research Database (Denmark)

Singla, Rashmi

Intimate partnership formations across the borders at various levels challenge stereotypes and lead to enhanced social diversity but are understudied in Scandinavia. Our workshop presents and discusses these phenomena through research, practice and policy issues from Denmark and Finland within...... interdisciplinary framework. It explores processes related to "us and them" redefinitions and minority-majority relations through focus on motivations,identity, life course,gender,family dynamics especially intergenerational conflicts, diaspora and policy effects.  ...

Dynamics of alliance formation and the egalitarian revolution.

Directory of Open Access Journals (Sweden)

Sergey Gavrilets

Full Text Available BACKGROUND: Arguably the most influential force in human history is the formation of social coalitions and alliances (i.e., long-lasting coalitions and their impact on individual power. Understanding the dynamics of alliance formation and its consequences for biological, social, and cultural evolution is a formidable theoretical challenge. In most great ape species, coalitions occur at individual and group levels and among both kin and non-kin. Nonetheless, ape societies remain essentially hierarchical, and coalitions rarely weaken social inequality. In contrast, human hunter-gatherers show a remarkable tendency to egalitarianism, and human coalitions and alliances occur not only among individuals and groups, but also among groups of groups. These observations suggest that the evolutionary dynamics of human coalitions can only be understood in the context of social networks and cognitive evolution. METHODOLOGY/PRINCIPAL FINDINGS: Here, we develop a stochastic model describing the emergence of networks of allies resulting from within-group competition for status or mates between individuals utilizing dyadic information. The model shows that alliances often emerge in a phase transition-like fashion if the group size, awareness, aggressiveness, and persuasiveness of individuals are large and the decay rate of individual affinities is small. With cultural inheritance of social networks, a single leveling alliance including all group members can emerge in several generations. CONCLUSIONS/SIGNIFICANCE: We propose a simple and flexible theoretical approach for studying the dynamics of alliance emergence applicable where game-theoretic methods are not practical. Our approach is both scalable and expandable. It is scalable in that it can be generalized to larger groups, or groups of groups. It is expandable in that it allows for inclusion of additional factors such as behavioral, genetic, social, and cultural features. Our results suggest that a rapid

Autonomy in action: linking the act of looking to memory formation in infancy via dynamic neural fields.

Science.gov (United States)

Perone, Sammy; Spencer, John P

2013-01-01

Looking is a fundamental exploratory behavior by which infants acquire knowledge about the world. In theories of infant habituation, however, looking as an exploratory behavior has been deemphasized relative to the reliable nature with which looking indexes active cognitive processing. We present a new theory that connects looking to the dynamics of memory formation and formally implement this theory in a Dynamic Neural Field model that learns autonomously as it actively looks and looks away from a stimulus. We situate this model in a habituation task and illustrate the mechanisms by which looking, encoding, working memory formation, and long-term memory formation give rise to habituation across multiple stimulus and task contexts. We also illustrate how the act of looking and the temporal dynamics of learning affect each other. Finally, we test a new hypothesis about the sources of developmental differences in looking. Copyright © 2012 Cognitive Science Society, Inc.

Cylindrical Penning traps with dynamic orthogonalized anharmonicity compensation for precision experiments

International Nuclear Information System (INIS)

Fei Xiang; Snow, W.M.

1999-01-01

Harmonic potentials can be produced in cylindrical ion traps by means of dynamic orthogonalized anharmonicity compensation with use of two (or multiple) sets of compensation electrodes. One special example is for traps with multiple identical electrodes which are not only easy to construct and allow access to the center region of the trap for particle loading and releasing, laser beams, and microwaves, but also flexible in forming harmonic potential wells in many locations. The nested trap configuration and the side-by-side trap configuration are readily available in this special scheme. Analytical solutions for cylindrical traps with multiple sets of compensation potentials are presented. This work will be useful for studies involving Penning trap diagnostics, atomic and molecular interactions (including the production of antihydrogen atoms), accurate mass measurements of exotic particles, and precision measurements of the spin precession frequencies of trapped particles

Cylindrical Penning traps with dynamic orthogonalized anharmonicity compensation for precision experiments

CERN Document Server

Fei Xiang

1999-01-01

Harmonic potentials can be produced in cylindrical ion traps by means of dynamic orthogonalized anharmonicity compensation with use of two (or multiple) sets of compensation electrodes. One special example is for traps with multiple identical electrodes which are not only easy to construct and allow access to the center region of the trap for particle loading and releasing, laser beams, and microwaves, but also flexible in forming harmonic potential wells in many locations. The nested trap configuration and the side-by-side trap configuration are readily available in this special scheme. Analytical solutions for cylindrical traps with multiple sets of compensation potentials are presented. This work will be useful for studies involving Penning trap diagnostics, atomic and molecular interactions (including the production of antihydrogen atoms), accurate mass measurements of exotic particles, and precision measurements of the spin precession frequencies of trapped particles.

Dynamical barrier for the formation of solitary waves in discrete lattices

Energy Technology Data Exchange (ETDEWEB)

Kevrekidis, P.G. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003 (United States)], E-mail: kevrekid@math.umass.edu; Espinola-Rocha, J.A. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003 (United States); Drossinos, Y. [European Commission, Joint Research Centre, I-21020 Ispra (Vatican City State, Holy See,) (Italy); School of Mechanical and Systems Engineering, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU (United Kingdom); Stefanov, A. [Department of Mathematics, University of Kansas, 1460 Jayhawk Blvd., Lawrence, KS 66045-7523 (United States)

2008-03-24

We consider the problem of the existence of a dynamical barrier of 'mass' that needs to be excited on a lattice site to lead to the formation and subsequent persistence of localized modes for a nonlinear Schroedinger lattice. We contrast the existence of a dynamical barrier with its absence in the static theory of localized modes in one spatial dimension. We suggest an energetic criterion that provides a sufficient, but not necessary, condition on the amplitude of a single-site initial condition required to form a solitary wave. We show that this effect is not one-dimensional by considering its two-dimensional analog. The existence of a sufficient condition for the excitation of localized modes in the non-integrable, discrete, nonlinear Schroedinger equation is compared to the dynamics of excitations in the integrable, both discrete and continuum, version of the nonlinear Schroedinger equation.

Muon, positron and antiproton interactions with atoms and molecules

Energy Technology Data Exchange (ETDEWEB)

Armour, Edward A G, E-mail: edward.armour@nottingham.ac.u [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

2010-04-01

In this paper, a description is given of some interesting processes involving the interaction of a muon, a positron, or an antiproton with atoms and molecules. The process involving a muon is the resonant formation of the muonic molecular ion, dt{mu}, in the muon catalyzed fusion cycle. In the case of a positron, the process considered is positron annihilation in low-energy positron scattering by the hydrogen molecule. The antiproton is considered as the nucleus of an antihydrogen atom interacting with simple atoms. Attention is given to antiproton annihilation through the strong interaction. An outline is given of proposed tests of fundamental physics to be carried out using antihydrogen.

Formation Dynamics of Oral Oil Coatings and Their Effect on Subsequent Sweetness Perception of Liquid Stimuli

NARCIS (Netherlands)

Camacho, S.; Eck, van Arianne; De Velde, Van Fred; Stieger, M.A.

2015-01-01

Knowledge of the formation of oral coatings and their influence on subsequent taste perception is necessary to understand possible taste-masking effects by oil coatings. This study investigated (a) the dynamics of the formation of oral oil coatings formed by o/w emulsions and (b) the effect of oral

Hg-Xe exciplex formation in mixed Xe/Ar matrices: molecular dynamics and luminescence study.

Science.gov (United States)

Lozada-García, Rolando; Rojas-Lorenzo, Germán; Crépin, Claudine; Ryan, Maryanne; McCaffrey, John G

2015-03-19

Luminescence of Hg((3)P1) atoms trapped in mixed Ar/Xe matrices containing a small amount of Xe is reported. Broad emission bands, strongly red-shifted from absorption are recorded which are assigned to strong complexes formed between the excited mercury Hg* and xenon atoms. Molecular dynamics calculations are performed on simulated Xe/Ar samples doped with Hg to follow the behavior of Hg* in the mixed rare gas matrices leading to exciplex formation. The role of Xe atoms in the first solvation shell (SS1) around Hg was investigated in detail, revealing the formation of two kinds of triatomic exciplexes; namely, Xe-Hg*-Xe and Ar-Hg*-Xe. The first species exists only when two xenon atoms are present in SS1 with specific geometries allowing the formation of a linear or quasi-linear exciplex. In the other geometries, or in the presence of only one Xe in SS1, a linear Ar-Hg*-Xe exciplex is formed. The two kinds of exciplexes have different emission bands, the most red-shifted being that involving two Xe atoms, whose emission is very close to that observed in pure Xe matrices. Simulations give a direct access to the analysis of the experimental absorption, emission, and excitation spectra, together with the dynamics of exciplexes formation.

Fixed geometric formation structure in formation control problem for group of robots with dynamically changing number of robots in the group

Directory of Open Access Journals (Sweden)

N. S. Morozova

2015-01-01

Full Text Available The article considers a problem of the decentralization-based approach to formation control of a group of agents, which simulate mobile autonomous robots. The agents use only local information limited by the covering range of their sensors. The agents have to build and maintain the formation, which fits to the defined target geometric formation structure with desired accuracy during the movement to the target point. At any point in time the number of agents in the group can change unexpectedly (for example, as a result of the agent failure or if a new agent joins the group.The aim of the article is to provide the base control rule, which solves the formation control problem, and to develop its modifications, which provide the correct behavior in case the agent number in the group is not equal to the size of the target geometric formation structure. The proposed base control rule, developed by the author, uses the method of involving virtual leaders. The coordinates of the virtual leaders and also the priority to follow the specific leader are calculated by each agent itself according to specific rules.The following results are presented in the article: the base control rule for solving the formation control problem, its modifications for the cases when the number of agents is greater/less than the size of the target geometric formation structure and also the computer modeling results proving the efficiency of the modified control rules. The specific feature of the control rule, developed by the author, is that each agent itself calculates the virtual leaders and each agent performs dynamic choice of the place within the formation (there is no predefined one-to-one relation between agents and places within the geometric formation structure. The results, provided in this article, can be used in robotics for developing control algorithms for the tasks, which require preserving specific relational positions among the agents while moving. One of the

Propagation dynamics and X-pulse formation in phase-mismatched second-harmonic generation

International Nuclear Information System (INIS)

Valiulis, G.; Jukna, V.; Jedrkiewicz, O.; Clerici, M.; Rubino, E.; DiTrapani, P.

2011-01-01

This paper concerns the theoretical, numerical, and experimental study of the second-harmonic-generation (SHG) process under conditions of phase and group-velocity mismatch and aims to demonstrate the dimensionality transition of the SHG process caused by the change of the fundamental wave diameter. We show that SHG from a narrow fundamental beam leads to the spontaneous self-phase-matching process with, in addition, the appearance of angular dispersion for the off-axis frequency components generated. The angular dispersion sustains the formation of the short X pulse in the second harmonic (SH) and is recognized as three-dimensional (3D) dynamics. On the contrary, the large-diameter fundamental beam reduces the number of the degrees of freedom, does not allow the generation of the angular dispersion, and maintains the so-called one-dimensional (1D) SHG dynamics, where the self-phase-matching appears just for axial components and is accompanied by the shrinking of the SH temporal bandwidth, and sustains a long SH pulse formation. The transition from long SH pulse generation typical of the 1D dynamics to the short 3D X pulse is illustrated numerically and experimentally by changing the conditions from the self-defocusing to the self-focusing regime by simply tuning the phase mismatch. The numerical and experimental verification of the analytical results are also presented.

Nanoparticles dynamics on a surface: fractal pattern formation and fragmentation

DEFF Research Database (Denmark)

Dick, Veronika V.; Solov'yov, Ilia; Solov'yov, Andrey V.

2010-01-01

In this paper we review our recent results on the formation and the post-growth relaxation processes of nanofractals on surface. For this study we developed a method which describes the internal dynamics of particles in a fractal and accounts for their diffusion and detachment. We demonstrate...... that these kinetic processes determine the final shape of the islands on surface after post-growth relaxation. We consider different scenarios of fractal relaxation and analyze the time evolution of the island's morphology....

Game Design Document Format For Video Games With Passive Dynamic Difficulty Adjustment

Directory of Open Access Journals (Sweden)

Pratama Wirya Atmaja

2016-07-01

satisfaction of its players is the primary mean to measure its quality. One important element of player’s satisfaction is a proper difficulty level, which is neither too easy nor too hard. The current state-of-the-art way to implement it is with Dynamic Difficulty Adjustment (DDA, which allows the difficulty level of a video game to be adjusted at run-time. Currently, the most popular type of DDA is the passive one. Meanwhile, Game Design Document (GDD is an important artefact in the development process of a video game software, and there is still no GDD format that supports the design of passive DDA mechanism. The aim of this research was to find a new GDD format that supports the mechanism. We modified a general purpose GDD format by adding new parts for designing passive DDA mechanism. We tested the usefulness of the modified format in a testing process involving developers and players. The developers developed video games using the modified GDD format and the general purpose one. Their development processes were observed and evaluated to know if there were any difficulties. The resulting video games were played by the players to find which are better in terms of passive DDA mechanism. The result of developer testing showed that the modified format is better than the general purpose one. The result of player testing showed that the video games made with the modified format are better than their counterparts, albeit by an insignificant margin. Based on the results, we declare that the modified GDD format is successful.Keywords: Video game, requirement engineering, game design document, dynamic difficulty adjustment, software development.

The structure, dynamics, and star formation rate of the Orion nebula cluster

International Nuclear Information System (INIS)

Da Rio, Nicola; Tan, Jonathan C.; Jaehnig, Karl

2014-01-01

The spatial morphology and dynamical status of a young, still-forming stellar cluster provide valuable clues to the conditions during the star formation event and the processes that regulated it. We analyze the Orion Nebula Cluster (ONC), utilizing the latest censuses of its stellar content and membership estimates over a large wavelength range. We determine the center of mass of the ONC and study the radial dependence of angular substructure. The core appears rounder and smoother than the outskirts, which is consistent with a higher degree of dynamical processing. At larger distances, the departure from circular symmetry is mostly driven by the elongation of the system, with very little additional substructure, indicating a somewhat evolved spatial morphology or an expanding halo. We determine the mass density profile of the cluster, which is well fitted by a power law that is slightly steeper than a singular isothermal sphere. Together with the interstellar medium density, which is estimated from average stellar extinction, the mass content of the ONC is insufficient by a factor ∼1.8 to reproduce the observed velocity dispersion from virialized motions, in agreement with previous assessments that the ONC is moderately supervirial. This may indicate recent gas dispersal. Based on the latest estimates for the age spread in the system and our density profiles, we find that at the half-mass radius, 90% of the stellar population formed within ∼5-8 free-fall times (t ff ). This implies a star formation efficiency per t ff of ε ff ∼ 0.04-0.07 (i.e., relatively slow and inefficient star formation rates during star cluster formation).

Bifurcation and spatial pattern formation in spreading of disease with incubation period in a phytoplankton dynamics

Directory of Open Access Journals (Sweden)

Randhir Singh Baghel

2012-02-01

Full Text Available In this article, we propose a three dimensional mathematical model of phytoplankton dynamics with the help of reaction-diffusion equations that studies the bifurcation and pattern formation mechanism. We provide an analytical explanation for understanding phytoplankton dynamics with three population classes: susceptible, incubated, and infected. This model has a Holling type II response function for the population transformation from susceptible to incubated class in an aquatic ecosystem. Our main goal is to provide a qualitative analysis of Hopf bifurcation mechanisms, taking death rate of infected phytoplankton as bifurcation parameter, and to study further spatial patterns formation due to spatial diffusion. Here analytical findings are supported by the results of numerical experiments. It is observed that the coexistence of all classes of population depends on the rate of diffusion. Also we obtained the time evaluation pattern formation of the spatial system.

Towards a dynamical description of intermediate mass fragment formation in heavy-ion collisions at some tens of MeV/A

International Nuclear Information System (INIS)

Suraud, E.

1990-01-01

We briefly remind the possible dynamical scenario of fragments formation in central heavy-ion collisions at some tens of MeV/A. We discuss how present day dynamical models can describe fragment formation. We show that particle methods provide a reasonable solution of Boltzman-like equations. We next turn to the Boltzmann-Langevin formalism which gives a well defined framework for the understanding of Intermediate Mass Fragments formation. We present a first numerical solution of this equation and show the importance of fluctuations in the dynamics of the collision. We finally apply the formalism to the onset of multifragmentation in the 40 Ca + 40 Ca system between 20 and 60 MeV/A beam energy

OCCURRENCE OF ACCELERATING FIELD, FORMATION AND DYNAMICS OF RELATIVISTIC ELECTRON BEAM NEAR JUPITER

Directory of Open Access Journals (Sweden)

V. I. Maslov

2018-06-01

Full Text Available The possible dynamics of the electron beam, formed in the vicinity of Io, the natural satellite of Jupiter, and injected toward Jupiter, has been investigated analytically. When a beam penetrates the Jupiter plasma to a certain depth, the beam-plasma instability can be developed. In this case, the distribution function of electrons is expanded additionally by excited oscillations. These electrons, when their energy is of order of a required certain value, cause UV polar light. For closing of a current, the formation of a double electric layer is necessary. The necessary parameters and conditions for the formation of a double layer with a large jump of an electric potential at a certain height have been formulated, its properties, stability, behavior over time and beam reflection in its field for closing of a current have been described. Reflection of the beam can lead to its vortex dynamics.

Distributed Consensus-Based Robust Adaptive Formation Control for Nonholonomic Mobile Robots with Partial Known Dynamics

Directory of Open Access Journals (Sweden)

Zhaoxia Peng

2014-01-01

Full Text Available This paper investigates the distributed consensus-based robust adaptive formation control for nonholonomic mobile robots with partially known dynamics. Firstly, multirobot formation control problem has been converted into a state consensus problem. Secondly, the practical control strategies, which incorporate the distributed kinematic controllers and the robust adaptive torque controllers, are designed for solving the formation control problem. Thirdly, the specified reference trajectory for the geometric centroid of the formation is assumed as the trajectory of a virtual leader, whose information is available to only a subset of the followers. Finally, numerical results are provided to illustrate the effectiveness of the proposed control approaches.

Vesicles and vesicle gels - structure and dynamics of formation

International Nuclear Information System (INIS)

Gradzielski, M

2003-01-01

Vesicles constitute an interesting morphology formed by self-aggregating amphiphilic molecules. They exhibit a rich structural variety and are of interest both from a fundamental point of view (for studying closed bilayer systems) and from a practical point of view (whenever one is interested in the encapsulation of active molecules). In many circumstances vesicular structures have to be formed by external forces, but of great interest are amphiphilic systems, where they form spontaneously. Here the question arises of whether this means that they are also thermodynamically stable structures, which at least in some systems appears to be the case. If such vesicles are well defined in size, it is possible to pack them densely and thereby form vesicle gels that possess highly elastic properties even for relatively low volume fractions of amphiphile. Conditions for the formation and the microstructure of such vesicle gels have been studied in some detail for the case of unilamellar vesicles. Another important and topical issue is the dynamics of vesicle formation/breakdown, as the understanding of the transition process will open the way to a deeper understanding of their stability and also allow controlling of the structures formed, by means of their formation processes. Significant progress in the study of the transformation processes has been achieved, in particular by means of time-resolved scattering experiments. (topical review)

Molecular dynamics and density functional simulations of tungsten nanostructure formation by helium plasma irradiation

International Nuclear Information System (INIS)

Ito, A.M.; Takayama, A.; Oda, Y.

2014-10-01

For the purposes of long-term use of tungsten diverter walls, it is necessary to suppress the surface deterioration due to the helium ash which induces the formations of helium bubbles and tungsten fuzzy nanostructures. In the present paper, the formation mechanisms of helium bubbles and tungsten fuzzy nanostructures were explained by the four-step process which is composed of the penetration process, the diffusion and agglomeration process, the helium bubble growth process and the tungsten fuzzy nanostructure formation process. The first to third step processes of the four-step process were investigated by using binary collision approximation, density functional theory and molecular dynamics, respectively. Furthermore, newly developed molecular dynamics and Monte-Carlo hybrid simulation has successfully reproduced the early formation process of tungsten fuzzy nanostructure. From these simulations, we here suggest the following key mechanisms of the formations of helium bubbles and tungsten fuzzy nanostructures: (1) By comparison between helium, neon, argon and hydrogen, the noble gas atoms can agglomerate limitlessly not only at a vacancy but also at an interstitial site. In particular, at the low incident energy, only helium atoms bring about the nucleation for helium bubble. (2) In the helium bubble growth process, the strain of the tungsten material around a helium atom is released as a dislocation loop, which is regarded as the loop punching phenomenon. (3) In the tungsten nanostructure formation process, the bursting of a helium bubble forms cavity and convexity in the surface. The helium bubbles tend to be grown and to burst at the cavity region, and then the difference of height between the cavity and convexity on the surface are enhanced. Consequently, the tungsten fuzzy nanostructure is formed. (author)

Dynamical Formation of Low-mass Merging Black Hole Binaries like GW151226

Energy Technology Data Exchange (ETDEWEB)

Chatterjee, Sourav; Rodriguez, Carl L.; Kalogera, Vicky; Rasio, Frederic A., E-mail: sourav.chatterjee@northwestern.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) Physics and Astronomy, Northwestern University, Evanston, IL 60202 (United States)

2017-02-20

Using numerical models for star clusters spanning a wide range in ages and metallicities (Z) we study the masses of binary black holes (BBHs) produced dynamically and merging in the local universe ( z ≲ 0.2). After taking into account cosmological constraints on star formation rate and metallicity evolution, which realistically relate merger delay times obtained from models with merger redshifts, we show here for the first time that while old, metal-poor globular clusters can naturally produce merging BBHs with heavier components, as observed in GW150914, lower-mass BBHs like GW151226 are easily formed dynamically in younger, higher-metallicity clusters. More specifically, we show that the mass of GW151226 is well within 1 σ of the mass distribution obtained from our models for clusters with Z/Z{sub ⊙} ≳ 0.5. Indeed, dynamical formation of a system like GW151226 likely requires a cluster that is younger and has a higher metallicity than typical Galactic globular clusters. The LVT151012 system, if real, could have been created in any cluster with Z/Z{sub ⊙} ≲ 0.25. On the other hand, GW150914 is more massive (beyond 1 σ ) than typical BBHs from even the lowest-metallicity (Z/Z{sub ⊙} = 0.005) clusters we consider, but is within 2 σ of the intrinsic mass distribution from our cluster models with Z/Z{sub ⊙} ≲ 0.05; of course, detection biases also push the observed distributions toward higher masses.

Simultaneous measurement of amyloid fibril formation by dynamic light scattering and fluorescence reveals complex aggregation kinetics.

Directory of Open Access Journals (Sweden)

Aaron M Streets

Full Text Available An apparatus that combines dynamic light scattering and Thioflavin T fluorescence detection is used to simultaneously probe fibril formation in polyglutamine peptides, the aggregating subunit associated with Huntington's disease, in vitro. Huntington's disease is a neurodegenerative disorder in a class of human pathologies that includes Alzheimer's and Parkinson's disease. These pathologies are all related by the propensity of their associated protein or polypeptide to form insoluble, β-sheet rich, amyloid fibrils. Despite the wide range of amino acid sequence in the aggregation prone polypeptides associated with these diseases, the resulting amyloids display strikingly similar physical structure, an observation which suggests a physical basis for amyloid fibril formation. Thioflavin T fluorescence reports β-sheet fibril content while dynamic light scattering measures particle size distributions. The combined techniques allow elucidation of complex aggregation kinetics and are used to reveal multiple stages of amyloid fibril formation.

Merging constitutional and motional covalent dynamics in reversible imine formation and exchange processes.

Science.gov (United States)

Kovaříček, Petr; Lehn, Jean-Marie

2012-06-06

The formation and exchange processes of imines of salicylaldehyde, pyridine-2-carboxaldehyde, and benzaldehyde have been studied, showing that the former has features of particular interest for dynamic covalent chemistry, displaying high efficiency and fast rates. The monoimines formed with aliphatic α,ω-diamines display an internal exchange process of self-transimination type, inducing a local motion of either "stepping-in-place" or "single-step" type by bond interchange, whose rate decreases rapidly with the distance of the terminal amino groups. Control of the speed of the process over a wide range may be achieved by substituents, solvent composition, and temperature. These monoimines also undergo intermolecular exchange, thus merging motional and constitutional covalent behavior within the same molecule. With polyamines, the monoimines formed execute internal motions that have been characterized by extensive one-dimensional, two-dimensional, and EXSY proton NMR studies. In particular, with linear polyamines, nondirectional displacement occurs by shifting of the aldehyde residue along the polyamine chain serving as molecular track. Imines thus behave as simple prototypes of systems displaying relative motions of molecular moieties, a subject of high current interest in the investigation of synthetic and biological molecular motors. The motional processes described are of dynamic covalent nature and take place without change in molecular constitution. They thus represent a category of dynamic covalent motions, resulting from reversible covalent bond formation and dissociation. They extend dynamic covalent chemistry into the area of molecular motions. A major further step will be to achieve control of directionality. The results reported here for imines open wide perspectives, together with other chemical groups, for the implementation of such features in multifunctional molecules toward the design of molecular devices presenting a complex combination of

Dynamics of C2 formation in laser-produced carbon plasma in helium environment

International Nuclear Information System (INIS)

Al-Shboul, K. F.; Harilal, S. S.; Hassanein, A.; Polek, M.

2011-01-01

We investigated the role of helium ambient gas on the dynamics of C 2 species formation in laser-produced carbon plasma. The plasma was produced by focusing 1064 nm pulses from an Nd:YAG laser onto a carbon target. The emission from the C 2 species was studied using optical emission spectroscopy, and spectrally resolved and integrated fast imaging. Our results indicate that the formation of C 2 in the plasma plume is strongly affected by the pressure of the He gas. In vacuum, the C 2 emission zone was located near the target and C 2 intensity oscillations were observed both in axial and radial directions with increasing the He pressure. The oscillations in C 2 intensity at higher pressures in the expanding plume could be caused by various formation zones of carbon dimers.

Dynamical hindrance to compound nucleus formation in heavy ion reactions

International Nuclear Information System (INIS)

Blocki, J.; Feldmeier, H.; Swiatecki, W.J.

1987-01-01

A large number of dynamical trajectories corresponding to colliding nuclei, as represented by an idealized, sharp-surfaced liquid-drop model with one-body dissipation are examined. The objective was to delineate quantitatively, within this model, the behaviour of the extra-extra-push energy E XX in its dependence on the mass /or charge/ numbers of the colliding nuclei. Qualitatively, the results are as anticipated on the basis of earlier studies: the appearance of a dynamical limitation on compound nucleus formation beyond a certain threshold locus in the A 1 . A 2 plane, with the energy E XX rising smoothly but rapidly beyond the threshold. The reduction of the two-dimensional function E XX /A 1 ,A 2 / to a one-dimensional function of a mean fissility x m appears possible as a rough approximation. As expected, the mean fissility x and the entrance channel fissility x 0 . The optimum choice appears to be one in which x is given about twice the weight of x 0

Particle concentration and flux dynamics in the atmospheric boundary layer as the indicator of formation mechanism

DEFF Research Database (Denmark)

Lauros, J.; Sogachev, Andrey; Smolander, S.

2011-01-01

the atmospheric boundary layer during nucleation event days shows a highly dynamical picture, where particle formation is coupled with chemistry and turbulent transport. We have demonstrated the suitability of our turbulent mixing scheme in reproducing the most important characteristics of particle dynamics...... within the boundary layer. Deposition and particle flux simulations show that deposition affects noticeably only the smallest particles...

Motion of guiding center drift atoms in the electric and magnetic field of a Penning trap

International Nuclear Information System (INIS)

Kuzmin, S.G.; O'Neil, T.M.

2005-01-01

The ApparaTus for High precision Experiment on Neutral Antimatter and antihydrogen TRAP collaborations have produced antihydrogen atoms by recombination in a cryogenic antiproton-positron plasma. This paper discusses the motion of the weakly bound atoms in the electric and magnetic field of the plasma and trap. The effective electric field in the moving frame of the atom polarizes the atom, and then gradients in the field exert a force on the atom. An approximate equation of motion for the atom center of mass is obtained by averaging over the rapid internal dynamics of the atom. The only remnant of the atom internal dynamics that enters this equation is the polarizability for the atom. This coefficient is evaluated for the weakly bound and strongly magnetized (guiding center drift) atoms understood to be produced in the antihydrogen experiments. Application of the approximate equation of motion shows that the atoms can be trapped radially in the large space charge field near the edge of the positron column. Also, an example is presented for which there is full three-dimensional trapping, not just radial trapping. Even untrapped atoms follow curved trajectories, and such trajectories are discussed for the important class of atoms that reach a field ionization diagnostic. Finally, the critical field for ionization is determined as an upper bound on the range of applicability of the theory

Eberhard Widmann (Stefan Meyer Institute, Vienna) and Silke Federmann (Ph.D. Student from Vienna in the CERN-Austrian Ph.D. program) together with a microwave cavity developed by Silke at CERN. The cavity will be used for the first time to look for spin-flip transitions of antihydrogen atoms later this year.

CERN Multimedia

Maximilien Brice

2011-01-01

Eberhard Widmann (Stefan Meyer Institute, Vienna) and Silke Federmann (Ph.D. Student from Vienna in the CERN-Austrian Ph.D. program) together with a microwave cavity developed by Silke at CERN. The cavity will be used for the first time to look for spin-flip transitions of antihydrogen atoms later this year.

Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations.

Science.gov (United States)

He, Rongxing; Li, Lei; Zhong, Jie; Zhu, Chongqin; Francisco, Joseph S; Zeng, Xiao Cheng

2016-04-26

Solar emission produces copious nitrosonium ions (NO(+)) in the D layer of the ionosphere, 60 to 90 km above the Earth's surface. NO(+) is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200-220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates-tetrahydrate NO(+)(H2O)4 and pentahydrate NO(+)(H2O)5-are identified and shown to be responsible for HONO formation in the ionosphere. The critical tetrahydrate NO(+)(H2O)4 exhibits a chain-like structure through which all of the lowest-energy isomers must go. However, most lowest-energy isomers of pentahydrate NO(+)(H2O)5 can be converted to the HONO-containing product, encountering very low barriers, via a chain-like or a three-armed, star-like structure. Although these structures are not the global minima, at 220 K, most lowest-energy NO(+)(H2O)4 and NO(+)(H2O)5 isomers tend to channel through these highly populated isomers toward HONO formation.

Satellite formation flying relative dynamics, formation design, fuel optimal maneuvers and formation maintenance

CERN Document Server

Wang, Danwei; Poh, Eng Kee

2017-01-01

This book systematically describes the concepts and principles for multi-satellite relative motion, passive and near passive formation designs, trajectory planning and control for fuel optimal formation maneuvers, and formation flying maintenance control design. As such, it provides a sound foundation for researchers and engineers in this field to develop further theories and pursue their implementations. Though satellite formation flying is widely considered to be a major advance in space technology, there are few systematic treatments of the topic in the literature. Addressing that gap, the book offers a valuable resource for academics, researchers, postgraduate students and practitioners in the field of satellite science and engineering.

Statistical analysis of dimer formation in supersaturated metal vapor based on molecular dynamics simulation

Science.gov (United States)

Korenchenko, Anna E.; Vorontsov, Alexander G.; Gelchinski, Boris R.; Sannikov, Grigorii P.

2018-04-01

We discuss the problem of dimer formation during the homogeneous nucleation of atomic metal vapor in an inert gas environment. We simulated nucleation with molecular dynamics and carried out the statistical analysis of double- and triple-atomic collisions as the two ways of long-lived diatomic complex formation. Close pair of atoms with lifetime greater than the mean time interval between atom-atom collisions is called a long-lived diatomic complex. We found that double- and triple-atomic collisions gave approximately the same probabilities of long-lived diatomic complex formation, but internal energy of the resulted state was essentially lower in the second case. Some diatomic complexes formed in three-particle collisions are stable enough to be a critical nucleus.

Phase separation like dynamics during Myxococcus xanthus fruiting body formation

Science.gov (United States)

Liu, Guannan; Thutupalli, Shashi; Wigbers, Manon; Shaevitz, Joshua

2015-03-01

Collective motion exists in many living organisms as an advantageous strategy to help the entire group with predation, forage, and survival. However, the principles of self-organization underlying such collective motions remain unclear. During various developmental stages of the soil-dwelling bacterium, Myxococcus xanthus, different types of collective motions are observed. In particular, when starved, M. xanthus cells eventually aggregate together to form 3-dimensional structures (fruiting bodies), inside which cells sporulate in response to the stress. We study the fruiting body formation process as an out of equilibrium phase separation process. As local cell density increases, the dynamics of the aggregation M. xanthus cells switch from a spatio-temporally random process, resembling nucleation and growth, to an emergent pattern formation process similar to a spinodal decomposition. By employing high-resolution microscopy and a video analysis system, we are able to track the motion of single cells within motile collective groups, while separately tuning local cell density, cell velocity and reversal frequency, probing the multi-dimensional phase space of M. xanthus development.

Stochastic Dynamics of Clay Translocation and Formation of Argillic Horizons

Science.gov (United States)

Calabrese, S.; Richter, D. D., Jr.; Porporato, A. M.

2017-12-01

The formation of argillic horizons in vertical soil profiles is mainly attributed to lessivage, namely the transport of clay from an upper E horizon to a deeper illuviated horizon. Because of the long timescales involved in this phenomenon, quantitative modeling is useful to explore the role of clay lessivage on soil formation and sub-surface clay accumulation. The limitations of detailed models of colloidal transport to short timescales make it necessary to resort to simple models. Here, we present a parsimonious model of clay transport in which lessivage is interpreted stochastically. Clay particles approach the soil surface at a speed equal to the erosion rate and are intermittently transported to deeper soil layers when percolation events occur or removed by erosion. Along with the evolution of clay particles trajectories, the model predicts the vertical clay profile, the depth of the B horizon, and the mean time to erosion. Dimensional analysis reveals the two dimensionless parameters governing the dynamics, leading to a new classification of soil types based on erosion rates and intensity of lessivage.

Robust Optimization Approach for Design for a Dynamic Cell Formation Considering Labor Utilization: Bi-objective Mathematical Mode

Directory of Open Access Journals (Sweden)

Hiwa Farughi

2016-05-01

Full Text Available In this paper, robust optimization of a bi-objective mathematical model in a dynamic cell formation problem considering labor utilization with uncertain data is carried out. The robust approach is used to reduce the effects of fluctuations of the uncertain parameters with regards to all the possible future scenarios. In this research, cost parameters of the cell formation and demand fluctuations are subject to uncertainty and a mixed-integer programming (MIP model is developed to formulate the related robust dynamic cell formation problem. Then the problem is transformed into a bi-objective linear one. The first objective function seeks to minimize relevant costs of the problem including machine procurement and relocation costs, machine variable cost, inter-cell movement and intra-cell movement costs, overtime cost and labor shifting cost between cells, machine maintenance cost, inventory, holding part cost. The second objective function seeks to minimize total man-hour deviations between cells or indeed labor utilization of the modeled.

Dynamics of seed magnetic island formation due to geometrically coupled perturbations

International Nuclear Information System (INIS)

Hegna, C.C.; Callen, J.D.; LaHaye, R.J.

1998-06-01

Seed magnetic island formation due to a dynamically growing external source in toroidal confinement devices is modeled as an initial value forced reconnection problem. For an external source whose amplitude grows on a time scale quickly compared to the Sweet-Parker time of resistive magnetohydrodynamics, the induced reconnection is characterized by a current sheet and a reconnected flux amplitude which lags in time the source amplitude. This suggests that neoclassical tearing modes, whose excitation requires a seed magnetic island, are more difficult to cause in high Lundquist number plasmas

Global format for energy-momentum based time integration in nonlinear dynamics

DEFF Research Database (Denmark)

Krenk, Steen

2014-01-01

A global format is developed for momentum and energy consistent time integration of second‐order dynamic systems with general nonlinear stiffness. The algorithm is formulated by integrating the state‐space equations of motion over the time increment. The internal force is first represented...... of mean value products at the element level or explicit use of a geometric stiffness matrix. An optional monotonic algorithmic damping, increasing with response frequency, is developed in terms of a single damping parameter. In the solution procedure, the velocity is eliminated and the nonlinear...

Ab initio calculations of scattering cross sections of the three-body system (p ¯,e+,e- ) between the e-+H ¯(n =2 ) and e-+H ¯(n =3 ) thresholds

Science.gov (United States)

Valdes, Mateo; Dufour, Marianne; Lazauskas, Rimantas; Hervieux, Paul-Antoine

2018-01-01

The ab initio method based on the Faddeev-Merkuriev equations is used to calculate cross sections involving the (p ¯,e+,e-) three-body system, with an emphasis on antihydrogen formation (H ¯) via antiproton (p ¯) scattering on positronium. This system is studied in the energy range between the e-+H ¯(n =2 ) and the e-+H ¯(n =3 ) thresholds, where precisely calculated cross sections can be useful for future experiments (GBAR, AEGIS, etc.) aiming to produce antihydrogen atoms. A special treatment is developed to take into account the long-range charge-dipole interaction effect on the wave function. Emphasis is placed on the impact of Feshbach resonances and Gailitis-Damburg oscillations appearing in the vicinity of the p ¯+Ps (n =2 ) threshold.

Molecular dynamics simulations of polyelectrolyte brushes under poor solvent conditions: origins of bundle formation.

Science.gov (United States)

He, Gui-Li; Merlitz, Holger; Sommer, Jens-Uwe

2014-03-14

Molecular dynamics simulations are applied to investigate salt-free planar polyelectrolyte brushes under poor solvent conditions. Starting above the Θ-point with a homogeneous brush and then gradually reducing the temperature, the polymers initially display a lateral structure formation, forming vertical bundles of chains. A further reduction of the temperature (or solvent quality) leads to a vertical collapse of the brush. By varying the size and selectivity of the counterions, we show that lateral structure formation persists and therefore demonstrate that the entropy of counterions being the dominant factor for the formation of the bundle phase. By applying an external compression force on the brush we calculate the minimal work done on the polymer phase only and prove that the entropy gain of counterions in the bundle state, as compared to the homogeneously collapsed state at the same temperature, is responsible for the lateral microphase segregation. As a consequence, the observed lateral structure formation has to be regarded universal for osmotic polymer brushes below the Θ-point.

Spontaneous formation and dynamics of half-skyrmions in a chiral liquid-crystal film

Science.gov (United States)

Nych, Andriy; Fukuda, Jun-Ichi; Ognysta, Uliana; Žumer, Slobodan; Muševič, Igor

2017-12-01

Skyrmions are coreless vortex-like excitations emerging in diverse condensed-matter systems, and real-time observation of their dynamics is still challenging. Here we report the first direct optical observation of the spontaneous formation of half-skyrmions. In a thin film of a chiral liquid crystal, depending on experimental conditions including film thickness, they form a hexagonal lattice whose lattice constant is a few hundred nanometres, or appear as isolated entities with topological defects compensating their charge. These half-skyrmions exhibit intriguing dynamical behaviour driven by thermal fluctuations. Numerical calculations of real-space images successfully corroborate the experimental observations despite the challenge because of the characteristic scale of the structures close to the optical resolution limit. A thin film of a chiral liquid crystal thus offers an intriguing platform that facilitates a direct investigation of the dynamics of topological excitations such as half-skyrmions and their manipulation with optical techniques.

Formation Dynamics of Potassium-Based Graphite Intercalation Compounds: An Ab Initio Study

Science.gov (United States)

Jiang, Xiankai; Song, Bo; Tománek, David

2018-04-01

This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. We use ab initio molecular dynamics simulations to study the microscopic dynamics of potassium intercalation in graphite. Upon adsorbing on graphite from the vapor phase, K atoms transfer their valence charge to the substrate. K atoms adsorbed on the surface diffuse rapidly along the graphene basal plane and eventually enter the interlayer region following a "U -turn" across the edge, gaining additional energy. This process is promoted at higher coverages associated with higher K pressure, leading to the formation of a stable intercalation compound. We find that the functionalization of graphene edges is an essential prerequisite for intercalation since bare edges reconstruct and reconnect, closing off the entry channels for the atoms.

Cooper pair formation dynamics in Bi2Sr2CaCu2O8+δ

International Nuclear Information System (INIS)

Kaindl, R.A.; Carnahan, M.A.; Orenstein, J.; Chemla, D.S.; Oh, S.; Eckstein, J.N.

2003-01-01

We utilize ultrafast terahertz pulses to monitor the carrier dynamics in the high-TC superconductor Bi2Sr2CaCu2O8+delta. The temperature, density and time dependence distinctly exposes a bimolecular recombination process of quasiparticles which underlies formation of Cooper pairs

Ion Dynamics at Shocks: Ion Reflection and Beam Formation at Quasi-perpendicular Shocks

International Nuclear Information System (INIS)

Kucharek, Harald; Moebius, Eberhard

2005-01-01

The physics of collisionless shocks is controlled by the ion dynamics. The generation of gyrating ions by reflection as well as the formation of field-aligned ion beams are essential parts of this dynamic. On the one hand reflection is most likely the first interaction of ions with the shock before they undergo the downstream thermalization process. On the other hand field-aligned ion beams, predominately found at the quasi-perpendicular bow shock, propagate into the distant foreshock region and may create wave activity. We revisit ion reflection, the source and basic production mechanism of field-aligned ion beams, by using multi-spacecraft measurements and contrast these observations with existing theories. Finally, we propose an alternative production mechanism

Reversible formation of aminals: a new strategy to control the release of bioactive volatiles from dynamic mixtures.

Science.gov (United States)

Godin, Guillaume; Levrand, Barbara; Trachsel, Alain; Lehn, Jean-Marie; Herrmann, Andreas

2010-05-14

Dynamic mixtures generated by reversible aminal formation of fragrance aldehydes with N,N-dibenzyl alkyldiamines in aqueous systems were found to be suitable delivery systems for the controlled release of bioactive volatiles.

Finite element simulation of dynamic wetting flows as an interface formation process

KAUST Repository

Sprittles, J.E.

2013-01-01

A mathematically challenging model of dynamic wetting as a process of interface formation has been, for the first time, fully incorporated into a numerical code based on the finite element method and applied, as a test case, to the problem of capillary rise. The motivation for this work comes from the fact that, as discovered experimentally more than a decade ago, the key variable in dynamic wetting flows - the dynamic contact angle - depends not just on the velocity of the three-phase contact line but on the entire flow field/geometry. Hence, to describe this effect, it becomes necessary to use the mathematical model that has this dependence as its integral part. A new physical effect, termed the \\'hydrodynamic resist to dynamic wetting\\', is discovered where the influence of the capillary\\'s radius on the dynamic contact angle, and hence on the global flow, is computed. The capabilities of the numerical framework are then demonstrated by comparing the results to experiments on the unsteady capillary rise, where excellent agreement is obtained. Practical recommendations on the spatial resolution required by the numerical scheme for a given set of non-dimensional similarity parameters are provided, and a comparison to asymptotic results available in limiting cases confirms that the code is converging to the correct solution. The appendix gives a user-friendly step-by-step guide specifying the entire implementation and allowing the reader to easily reproduce all presented results, including the benchmark calculations. © 2012 Elsevier Inc.

Femtosecond dynamics of excitons in π-conjugated oligomers: the role of intrachain two-exciton states in the formation of interchain species

Science.gov (United States)

Klimov, Victor I.; McBranch, Duncan W.; Barashkov, Nikolay N.; Ferraris, John P.

1997-10-01

We report femtosecond transient absorption results for solutions and thin films of a substituted oligomer of poly(para-phenylene vinylene) performed over wide spectral and pump-intensity ranges. Solutions and films exhibit a photoinduced absorption (PA) band with dynamics matching those of the stimulated emission, demonstrating unambiguously that these features originate from intrachain singlet excitons. Thin films exhibit an additional short-wavelength PA band with pump-independent dynamics, indicating the formation of non-emissive interchain excitons. Correlations in the dynamics of the two PA features, as well as the intensity-dependence, provide strong evidence that the formation of interchain excitons is mediated by intrachain two-exciton states.

PSEUDOBULGE FORMATION AS A DYNAMICAL RATHER THAN A SECULAR PROCESS

Energy Technology Data Exchange (ETDEWEB)

Guedes, Javiera; Mayer, Lucio; Carollo, Marcella [Institute for Astronomy, ETH Zuerich, Wolgang-Pauli-Strasse 27, 8093 Zurich (Switzerland); Madau, Piero [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

2013-07-20

We investigate the formation and evolution of the pseudobulge in 'Eris', a high-resolution N-body + smoothed particle hydrodynamic cosmological simulation that successfully reproduces a Milky-Way-like massive late-type spiral in an cold dark matter universe. At the present epoch, Eris has a virial mass M{sub vir} {approx_equal} 8 Multiplication-Sign 10{sup 11} M{sub Sun }, a photometric stellar mass M{sub *} = 3.2 Multiplication-Sign 10{sup 10} M{sub Sun }, a bulge-to-total ratio B/T = 0.26, and a weak nuclear bar. We find that the bulk of the pseudobulge forms quickly at high redshift via a combination of non-axisymmetric disk instabilities and tidal interactions or mergers, both occurring on dynamical timescales, not through slow secular processes at lower redshift. Its subsequent evolution is not strictly secular either, and is closely intertwined with the evolution of the stellar bar. In fact, the structure that we recognize as a pseudobulge today evolved from a stellar bar that formed at high redshift due to tidal interactions with satellites, was destroyed by minor mergers at z {approx} 3, re-formed shortly after, and weakened again following a steady gas inflow at z {approx}< 1. The gradual dissolution of the bar ensued at z {approx} 1 and continues until the present without increasing the stellar velocity dispersion in the inner regions. In this scenario, the pseudobulge is not a separate component from the inner disk in terms of formation path; rather, it is the first step in the inside-out formation of the baryonic disk, in agreement with the fact that pseudobulges of massive spiral galaxies typically have a dominant old stellar population. If our simulations do indeed reproduce the formation mechanisms of massive spirals, then the progenitors of late-type galaxies should have strong bars and small photometric pseudobulges at high redshift.

Dynamics of Hippocampal Protein Expression During Long-term Spatial Memory Formation*

Science.gov (United States)

Borovok, Natalia; Nesher, Elimelech; Levin, Yishai; Reichenstein, Michal; Pinhasov, Albert

2016-01-01

trafficking, enhancement of metabolic activity, and Wnt signaling pathway during the steep phase of memory formation; and (3) cytoskeleton organization proteins. Taken together, this study clearly demonstrates dynamic assembly and disassembly of protein-protein interaction networks depending on the stage of memory formation engrams. PMID:26598641

Dynamics of Hippocampal Protein Expression During Long-term Spatial Memory Formation.

Science.gov (United States)

Borovok, Natalia; Nesher, Elimelech; Levin, Yishai; Reichenstein, Michal; Pinhasov, Albert; Michaelevski, Izhak

2016-02-01

trafficking, enhancement of metabolic activity, and Wnt signaling pathway during the steep phase of memory formation; and (3) cytoskeleton organization proteins. Taken together, this study clearly demonstrates dynamic assembly and disassembly of protein-protein interaction networks depending on the stage of memory formation engrams. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Habit Formation in Natural Cheese Consumption An Approach Based on Dynamic Demand Analysis

OpenAIRE

WAKABAYASHI, Katsufumi

2010-01-01

In expectation of growing cheese consumption, natural cheese production is being increased to reduce surplus milk and create high added value in raw milk. Other studies found positive trends in cheese consumption. However, those studies neither clarified recent trends, nor distinguished natural cheese from processed cheese. The purpose of this paper is to discuss the structure of natural cheese consumption, focusing on habit formation. We test structural changes in cheese demand using dynamic...

The formation of continuous opinion dynamics based on a gambling mechanism and its sensitivity analysis

Science.gov (United States)

Zhu, Yueying; Alexandre Wang, Qiuping; Li, Wei; Cai, Xu

2017-09-01

The formation of continuous opinion dynamics is investigated based on a virtual gambling mechanism where agents fight for a limited resource. We propose a model with agents holding opinions between -1 and 1. Agents are segregated into two cliques according to the sign of their opinions. Local communication happens only when the opinion distance between corresponding agents is no larger than a pre-defined confidence threshold. Theoretical analysis regarding special cases provides a deep understanding of the roles of both the resource allocation parameter and confidence threshold in the formation of opinion dynamics. For a sparse network, the evolution of opinion dynamics is negligible in the region of low confidence threshold when the mindless agents are absent. Numerical results also imply that, in the presence of economic agents, high confidence threshold is required for apparent clustering of agents in opinion. Moreover, a consensus state is generated only when the following three conditions are satisfied simultaneously: mindless agents are absent, the resource is concentrated in one clique, and confidence threshold tends to a critical value(=1.25+2/ka ; k_a>8/3 , the average number of friends of individual agents). For fixed a confidence threshold and resource allocation parameter, the most chaotic steady state of the dynamics happens when the fraction of mindless agents is about 0.7. It is also demonstrated that economic agents are more likely to win at gambling, compared to mindless ones. Finally, the importance of three involved parameters in establishing the uncertainty of model response is quantified in terms of Latin hypercube sampling-based sensitivity analysis.

ALMA OBSERVATIONS OF A HIGH-DENSITY CORE IN TAURUS: DYNAMICAL GAS INTERACTION AT THE POSSIBLE SITE OF A MULTIPLE STAR FORMATION

Energy Technology Data Exchange (ETDEWEB)

Tokuda, Kazuki; Onishi, Toshikazu [Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Saigo, Kazuya; Kawamura, Akiko [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Fukui, Yasuo; Inutsuka, Shu-ichiro; Tachihara, Kengo [Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan); Matsumoto, Tomoaki [Faculty of Humanity and Environment, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160 (Japan); Machida, Masahiro N. [Department of Earth and Planetary Sciences, Kyushu University, Fukuoka 812-8581 (Japan); Tomida, Kengo, E-mail: s_k.tokuda@p.s.osakafu-u.ac.jp [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2014-07-01

Starless dense cores eventually collapse dynamically, forming protostars inside them, and the physical properties of the cores determine the nature of the forming protostars. We report ALMA observations of dust continuum emission and molecular rotational lines toward MC27 or L1521F, which is considered to be very close to the first protostellar core phase. We found a few starless high-density cores, one of which has a very high density of ∼10{sup 7} cm{sup –3}, within a region of several hundred AU around a very low-luminosity protostar detected by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few hundred years was found toward the protostar. The molecular line observation shows several cores with an arc-like structure, possibly due to the dynamical gas interaction. These complex structures revealed in the present observations suggest that the initial condition of star formation is highly dynamical in nature, which is considered to be a key factor in understanding fundamental issues of star formation such as the formation of multiple stars and the origin of the initial mass function of stars.

Development of a new molecular dynamics method for tribochemical reaction and its application to formation dynamics of MoS2 tribofilm

International Nuclear Information System (INIS)

Morita, Yusuke; Onodera, Tasuku; Suzuki, Ai; Sahnoun, Riadh; Koyama, Michihisa; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Del Carpio, Carlos A.; Shin-yoshi, Takatoshi; Nishino, Noriaki; Suzuki, Atsushi; Miyamoto, Akira

2008-01-01

Recently we have developed a novel molecular dynamics program NEW-RYUDO-CR, which can deal with chemical reactions. The developed method has been applied to the study of tribochemical reaction dynamics of MoS 2 tribofilm on iron surface. The initially amorphous MoS 2 layer self-organized its structure as result of the tribochemical reactions and formed layered MoS 2 tribofilm. The friction coefficient significantly decreased as the MoS 2 tribofilm was formed. Besides, sliding was observed between sulfur layers of MoS 2 tribofilms which occurred due to repulsive Coulombic interaction forces between sulfur atoms. This indicates that the formation of the layered MoS 2 tribofilm is important to achieve better lubrication properties

Aperiodic dynamics in a deterministic adaptive network model of attitude formation in social groups

Science.gov (United States)

Ward, Jonathan A.; Grindrod, Peter

2014-07-01

Adaptive network models, in which node states and network topology coevolve, arise naturally in models of social dynamics that incorporate homophily and social influence. Homophily relates the similarity between pairs of nodes' states to their network coupling strength, whilst social influence causes coupled nodes' states to convergence. In this paper we propose a deterministic adaptive network model of attitude formation in social groups that includes these effects, and in which the attitudinal dynamics are represented by an activato-inhibitor process. We illustrate that consensus, corresponding to all nodes adopting the same attitudinal state and being fully connected, may destabilise via Turing instability, giving rise to aperiodic dynamics with sensitive dependence on initial conditions. These aperiodic dynamics correspond to the formation and dissolution of sub-groups that adopt contrasting attitudes. We discuss our findings in the context of cultural polarisation phenomena. Social influence. This reflects the fact that people tend to modify their behaviour and attitudes in response to the opinions of others [22-26]. We model social influence via diffusion: agents adjust their state according to a weighted sum (dictated by the evolving network) of the differences between their state and the states of their neighbours. Homophily. This relates the similarity of individuals' states to their frequency and strength of interaction [27]. Thus in our model, homophily drives the evolution of the weighted ‘social' network. A precise formulation of our model is given in Section 2. Social influence and homophily underpin models of social dynamics [21], which cover a wide range of sociological phenomena, including the diffusion of innovations [28-32], complex contagions [33-36], collective action [37-39], opinion dynamics [19,20,40,10,11,13,15,41,16], the emergence of social norms [42-44], group stability [45], social differentiation [46] and, of particular relevance

Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation

Science.gov (United States)

Shiraiwa, Manabu; Yee, Lindsay D.; Schilling, Katherine A.; Loza, Christine L.; Craven, Jill S.; Zuend, Andreas; Ziemann, Paul J.; Seinfeld, John H.

2013-01-01

Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process. PMID:23818634

Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation.

Science.gov (United States)

Shiraiwa, Manabu; Yee, Lindsay D; Schilling, Katherine A; Loza, Christine L; Craven, Jill S; Zuend, Andreas; Ziemann, Paul J; Seinfeld, John H

2013-07-16

Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process.

Dynamic-stochastic modeling of snow cover formation on the European territory of Russia

OpenAIRE

A. N. Gelfan; V. M. Moreido

2014-01-01

A dynamic-stochastic model, which combines a deterministic model of snow cover formation with a stochastic weather generator, has been developed. The deterministic snow model describes temporal change of the snow depth, content of ice and liquid water, snow density, snowmelt, sublimation, re-freezing of melt water, and snow metamorphism. The model has been calibrated and validated against the long-term data of snow measurements over the territory of the European Russia. The model showed good ...

Dynamic of ozone formation in nanosecond microwave discharges

International Nuclear Information System (INIS)

Akhmedzhanov, R.A.; Vikharev, A.L.; Gorbachev, A.M.

1995-01-01

Nanosecond gas discharges are efficient sources of chemically active plasma. Studies of the nanosecond microwave discharge are interesting for remote modification of the chemical composition of the atmosphere in term of its purification, for diagnostics of impurities and ozone replenishment in the regions of local open-quotes ozone holesclose quotes. In this connection a study of plasma chemical processes in such a discharge seems appropriate, as well as modeling of ecological consequences of the effect of powerful microwave radiation on the atmosphere. The present paper contains generalized results of studying the process of ozone formation in a pulse-periodic freely localized nanosecond microwave discharge. The experiments were performed in a wide range of parameters: microwave radiation wavelength λ = 0.8 and 3cm, pulse duration τ = 6 and 500ns, pulse power P = 50kW and 20MW, pulse repetition rate F = 1-10 3 Hz. The working gases were air and oxygen under pressure P = 10-100Torr. As a source of the microwave radiation a pulse magnetron was used with a device for pulse compression based on the waveguide resonator, and a relativistic microwave generator. The discharge was produced in the focus of the parabolic mirror and had the form of homogeneous cylinder. The plasma chemical processes were studied in two cases. The discharge was created either in the quartz tube placed along the focal line of the mirror or in the free air. Dynamics of formation of ozone and nitrogen oxides in the discharge was studied by means of absorption spectroscopy in the regime of accumulation of the products of chemical reactions (in a closed volume) and their diffusion spreading

S-Lagrangian dynamics of many-body systems and behavior of social groups: Dominance and hierarchy formation

Science.gov (United States)

Sandler, U.

2017-11-01

In this paper, we extend our generalized Lagrangian dynamics (i.e., S-Lagrangian dynamics, which can be applied equally to physical and non-physical systems as per Sandler (2014)) to many-body systems. Unlike common Lagrangian dynamics, this is not a trivial task. For many-body systems with S-dependent Lagrangians, the Lagrangian and the corresponding Hamiltonian or energy become vector functions, conjugated momenta become second-order tensors, and the system inevitably develops a hierarchical structure, even if all bodies initially have similar status and Lagrangians. As an application of our theory, we consider dominance and hierarchy formation, which is present in almost all communities of living species. As a biological basis for this application, we assume that the primary motivation of a groups activity is to attempt to cope with stress arising as pressure from the environment and from intrinsic unmet needs of individuals. It has been shown that the S-Lagrangian approach to a group's evolution naturally leads to formation of linear or despotic dominance hierarchies, depending on differences between individuals in coping with stress. That is, individuals that cope more readily with stress take leadership roles during the evolution. Experimental results in animal groups which support our assumption and findings are considered.

More Than Filaments and Cores: Statistical Study of Structure Formation and Dynamics in Nearby Molecular Clouds

Science.gov (United States)

Chen, How-Huan; Goodman, Alyssa

2018-01-01

In the past decade, multiple attempts at understanding the connection between filaments and star forming cores have been made using observations across the entire epectrum. However, the filaments and the cores are usually treated as predefined--and well-defined--entities, instead of structures that often come at different sizes, shapes, with substantially different dynamics, and inter-connected at different scales. In my dissertation, I present an array of studies using different statistical methods, including the dendrogram and the probability distribution function (PDF), of structures at different size scales within nearby molecular clouds. These structures are identified using observations of different density tracers, and where possible, in the multi-dimensional parameter space of key dynamic properties--the LSR velocity, the velocity dispersion, and the column density. The goal is to give an overview of structure formation in nearby star-forming clouds, as well as of the dynamics in these structures. I find that the overall statistical properties of a larger structure is often the summation/superposition of sub-structures within, and that there could be significant variations due to local physical processes. I also find that the star formation process within molecular clouds could in fact take place in a non-monolithic manner, connecting potentially merging and/or transient structures, at different scales.

Strain-Mediated Interfacial Dynamics during Au–PbS Core–Shell Nanostructure Formation

KAUST Repository

Niu, Kai-Yang; Liu, Miao; Persson, Kristin A.; Han, Yu; Zheng, Haimei

2016-01-01

An understanding of the hierarchical nanostructure formation is of significant importance for the design of advanced functional materials. Here, we report the in situ study of lead sulfide (PbS) growth on gold (Au) nanorod seeds using liquid cell transmission electron microscopy (TEM). By tracking the formation dynamics of Au-PbS core-shell nanoparticles, we found the preferential heterogeneous nucleation of PbS on the ends of a Au nanorod prior to the development of a complete PdS shell. During PbS shell growth, drastic sulfidation of Au nanorod was observed, leading to large volume shrinkage (up to 50%) of the initial Au nanorod seed. We also captured intriguing wavy interfacial behavior, which can be explained by our DFT calculation results that the local strain gradient at the core-shell interface facilitates the mass transport and mediates reversible phase transitions of Au ↔ Au2S during the PbS shell growth. © 2016 American Chemical Society.

UAV formation control design with obstacle avoidance in dynamic three-dimensional environment.

Science.gov (United States)

Chang, Kai; Xia, Yuanqing; Huang, Kaoli

2016-01-01

This paper considers the artificial potential field method combined with rotational vectors for a general problem of multi-unmanned aerial vehicle (UAV) systems tracking a moving target in dynamic three-dimensional environment. An attractive potential field is generated between the leader and the target. It drives the leader to track the target based on the relative position of them. The other UAVs in the formation are controlled to follow the leader by the attractive control force. The repulsive force affects among the UAVs to avoid collisions and distribute the UAVs evenly on the spherical surface whose center is the leader-UAV. Specific orders or positions of the UAVs are not required. The trajectories of avoidance obstacle can be obtained through two kinds of potential field with rotation vectors. Every UAV can choose the optimal trajectory to avoid the obstacle and reconfigure the formation after passing the obstacle. Simulations study on UAV are presented to demonstrate the effectiveness of proposed method.

Predictive modeling of multicellular structure formation by using Cellular Particle Dynamics simulations

Science.gov (United States)

McCune, Matthew; Shafiee, Ashkan; Forgacs, Gabor; Kosztin, Ioan

2014-03-01

Cellular Particle Dynamics (CPD) is an effective computational method for describing and predicting the time evolution of biomechanical relaxation processes of multicellular systems. A typical example is the fusion of spheroidal bioink particles during post bioprinting structure formation. In CPD cells are modeled as an ensemble of cellular particles (CPs) that interact via short-range contact interactions, characterized by an attractive (adhesive interaction) and a repulsive (excluded volume interaction) component. The time evolution of the spatial conformation of the multicellular system is determined by following the trajectories of all CPs through integration of their equations of motion. CPD was successfully applied to describe and predict the fusion of 3D tissue construct involving identical spherical aggregates. Here, we demonstrate that CPD can also predict tissue formation involving uneven spherical aggregates whose volumes decrease during the fusion process. Work supported by NSF [PHY-0957914]. Computer time provided by the University of Missouri Bioinformatics Consortium.

Strain-Mediated Interfacial Dynamics during Au–PbS Core–Shell Nanostructure Formation

KAUST Repository

Niu, Kai-Yang

2016-05-23

An understanding of the hierarchical nanostructure formation is of significant importance for the design of advanced functional materials. Here, we report the in situ study of lead sulfide (PbS) growth on gold (Au) nanorod seeds using liquid cell transmission electron microscopy (TEM). By tracking the formation dynamics of Au-PbS core-shell nanoparticles, we found the preferential heterogeneous nucleation of PbS on the ends of a Au nanorod prior to the development of a complete PdS shell. During PbS shell growth, drastic sulfidation of Au nanorod was observed, leading to large volume shrinkage (up to 50%) of the initial Au nanorod seed. We also captured intriguing wavy interfacial behavior, which can be explained by our DFT calculation results that the local strain gradient at the core-shell interface facilitates the mass transport and mediates reversible phase transitions of Au ↔ Au2S during the PbS shell growth. © 2016 American Chemical Society.

Laboratory studies of the dynamic of resonance cones formation in magnetized plasmas

Energy Technology Data Exchange (ETDEWEB)

Nazarov, V. V.; Starodubtsev, M. V.; Kostrov, A. V. [Russian Academy of Sciences, Institute of Applied Physics, Nizhny Novgorod (Russian Federation)

2013-03-15

The paper is devoted to experimental studies of formation of resonance cones in magnetized plasmas by pulsed RF source in the lower-hybrid (whistler) and the upper-hybrid frequency ranges. It is shown that in both frequency ranges, resonance cones exhibit similar dynamics after switching-on the RF source: at first, wide maxima of radiation are formed in non-resonance directions, which then become narrower, with their direction approaching the resonance one. While the resonance cones are being formed, one observes a fine structure in the form of secondary radiation maxima. It is shown that the characteristic formation time of stationary resonance cones is determined by the minimal value of the group velocity of the quasi-electrostatic waves excited by the antenna. In the low-temperature plasma, this value is limited in the lower-hybrid frequency range by the spatial spectrum of the emitting antenna and in the upper-hybrid range, by the effects of spatial plasma dispersion.

Deracemization of Axially Chiral Nicotinamides by Dynamic Salt Formation with Enantiopure Dibenzoyltartaric Acid (DBTA

Directory of Open Access Journals (Sweden)

Fumitoshi Yagishita

2013-11-01

Full Text Available Dynamic atroposelective resolution of chiral salts derived from oily racemic nicotinamides and enantiopure dibenzoyltartaric acid (DBTA was achieved by crystallization. The absolute structures of the axial chiral nicotinamides were determined by X-ray structural analysis. The chirality could be controlled by the selection of enantiopure DBTA as a chiral auxiliary. The axial chirality generated by dynamic salt formation was retained for a long period after dissolving the chiral salt in solution even after removal of the chiral acid. The rate of racemization of nicotinamides could be controlled based on the temperature and solvent properties, and that of the salts was prolonged compared to free nicotinamides, as the molecular structure of the pyridinium ion in the salts was different from that of acid-free nicotinamides.

Low-energy experiments that measure fundamental constants and test basic symmetries

CERN Multimedia

CERN. Geneva. Audiovisual Unit

2002-01-01

Cold Antihydrogen: Are We There? Cold antihydrogen offers the possibility to precisely compare the structure of antihydrogen and hydrogen atoms, using the well developed tools of laser spectroscopy with antihydrogen atoms cold enough to be trapped in the minimum of a magnetic field gradient. Progress made at CERN's new Antiproton Decelerator will be discussed, along with goals and aspirations, such as measuring the anti-Rydberg constant. ATRAP has observed and studied the interaction of low energy antiprotons and positrons for more than a year, and ATHENA hopes to soon make antiprotons and positrons to interact as well.

The GBAR antimatter gravity experiment

Energy Technology Data Exchange (ETDEWEB)

Perez, Patrice [IRFU, CEA Saclay (France)

2015-07-01

The GBAR project (Gravitational Behaviour of Antihydrogen at Rest) at CERN, will measure the free fall acceleration of ultracold neutral antihydrogen atoms in the terrestrial gravitational field. The experiment consists in preparing antihydrogen ions (one antiproton and two positrons) and sympathetically cool them with Be{sup +} ions to a few 10 microK. The ultracold ions will then be photo-ionized just above threshold, and the free-fall time over a known distance measured. I describe the project, the accuracy that can be reached by standard techniques, and with possible improvements using quantum reflection of antihydrogen on surfaces.

On the Appearance of Thresholds in the Dynamical Model of Star Formation

Science.gov (United States)

Elmegreen, Bruce G.

2018-02-01

The Kennicutt–Schmidt (KS) relationship between the surface density of the star formation rate (SFR) and the gas surface density has three distinct power laws that may result from one model in which gas collapses at a fixed fraction of the dynamical rate. The power-law slope is 1 when the observed gas has a characteristic density for detection, 1.5 for total gas when the thickness is about constant as in the main disks of galaxies, and 2 for total gas when the thickness is regulated by self-gravity and the velocity dispersion is about constant, as in the outer parts of spirals, dwarf irregulars, and giant molecular clouds. The observed scaling of the star formation efficiency (SFR per unit CO) with the dense gas fraction (HCN/CO) is derived from the KS relationship when one tracer (HCN) is on the linear part and the other (CO) is on the 1.5 part. Observations of a threshold density or column density with a constant SFR per unit gas mass above the threshold are proposed to be selection effects, as are observations of star formation in only the dense parts of clouds. The model allows a derivation of all three KS relations using the probability distribution function of density with no thresholds for star formation. Failed galaxies and systems with sub-KS SFRs are predicted to have gas that is dominated by an equilibrium warm phase where the thermal Jeans length exceeds the Toomre length. A squared relation is predicted for molecular gas-dominated young galaxies.

Thermal domains in inhomogeneous current-carrying superconductors. Current-voltage characteriscs and dynamics of domain formation after current jumps

International Nuclear Information System (INIS)

Bezuglyj, A.I.; Shklovskij, V.A.

1984-01-01

The static and dynamic behavior of thermal domains in inhomogeneous superconducting films, where the inhomogeneity behaves like a portion of the film with a reduced critical current, have been studied theoretically within the framework of the phenomenological approach, using the heat balance equation and the dependence of the superconductor critical current on temperature. Depending on the size of the inhomogeneity (local or extended) and on the relative values of parameters of the homogeneous and inhomogeneous regions, different types of current-voltage characteristics are obtained. The nonstationary problem of thermal domain formation near the inhomogeneity after a current jump has been solved, and the domain boundary (kink) dynamics at a distance from the inhomogeneity has been analyzed. A combination of the results allows one to describe the whole process of normal phase formation and its spread throughout the superconducting film

Bacterial Selection during the Formation of Early-Stage Aerobic Granules in Wastewater Treatment Systems Operated Under Wash-Out Dynamics

OpenAIRE

Weissbrodt, David G.; Lochmatter, Samuel; Ebrahimi, Sirous; Rossi, Pierre; Maillard, Julien; Holliger, Christof

2012-01-01

Aerobic granular sludge is attractive for high-rate biological wastewater treatment. Biomass wash-out conditions stimulate the formation of aerobic granules. Deteriorated performances in biomass settling and nutrient removal during start-up have however often been reported. The effect of wash-out dynamics was investigated on bacterial selection, biomass settling behavior, and metabolic activities during the formation of early-stage granules from activated sludge of two wastewater treatment pl...

Physics Colloquium - Tight-binding in a new light: Photons in optical lattices

CERN Multimedia

Ecole de Physique - Université de Genève

2011-01-01

Geneva University Physics Department 24, Quai Ernest Ansermet CH-1211 Geneva 4   Lundi 21 mars 2011, 17h00 Ecole de Physique, Auditoire Stueckelberg Tight-binding in a new light: Photons in optical lattices Dr. Niels Madsen Department of Physics, Swansea University, Singleton Park, Swansea, United Kingdom   Antihydrogen, the bound state of an antiproton and a positron, has been produced at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature's fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom, subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen co...

Dewetting dynamics of a gold film on graphene: implications for nanoparticle formation.

Science.gov (United States)

Namsani, Sadanandam; Singh, Jayant K

2016-01-01

The dynamics of dewetting of gold films on graphene surfaces is investigated using molecular dynamics simulation. The effect of temperature (973-1533 K), film diameter (30-40 nm) and film thickness (0.5-3 nm) on the dewetting mechanism, leading to the formation of nanoparticles, is reported. The dewetting behavior for films ≤5 Å is in contrast to the behavior seen for thicker films. The retraction velocity, in the order of ∼300 m s(-1) for a 1 nm film, decreases with an increase in film thickness, whereas it increases with temperature. However at no point do nanoparticles detach from the surface within the temperature range considered in this work. We further investigated the self-assembly behavior of nanoparticles on graphene at different temperatures (673-1073 K). The process of self-assembly of gold nanoparticles is favorable at lower temperatures than at higher temperatures, based on the free-energy landscape analysis. Furthermore, the shape of an assembled structure is found to change from spherical to hexagonal, with a marked propensity towards an icosahedral structure based on the bond-orientational order parameters.

Function and Dynamics of Tetraspanins during Antigen Recognition and Immunological Synapse Formation

Directory of Open Access Journals (Sweden)

Vera eRocha-Perugini

2016-01-01

Full Text Available Tetraspanin-enriched microdomains (TEMs are specialized membrane platforms driven by protein-protein interactions that integrate membrane receptors and adhesion molecules. Tetraspanins participate in antigen recognition and presentation by antigen presenting cells (APCs through the organization of pattern recognition receptors (PRRs and their downstream induced-signaling, as well as the regulation of MHC-II-peptide trafficking. T lymphocyte activation is triggered upon specific recognition of antigens present on the APC surface during immunological synapse (IS formation. This dynamic process is characterized by a defined spatial organization involving the compartmentalization of receptors and adhesion molecules in specialized membrane domains that are connected to the underlying cytoskeleton and signaling molecules. Tetraspanins contribute to the spatial organization and maturation of the IS by controlling receptor clustering and local accumulation of adhesion receptors and integrins, their downstream signaling and linkage to the actin cytoskeleton. This review offers a perspective on the important role of TEMs in the regulation of antigen recognition and presentation, and in the dynamics of IS architectural organization.

Function and Dynamics of Tetraspanins during Antigen Recognition and Immunological Synapse Formation

Science.gov (United States)

Rocha-Perugini, Vera; Sánchez-Madrid, Francisco; Martínez del Hoyo, Gloria

2016-01-01

Tetraspanin-enriched microdomains (TEMs) are specialized membrane platforms driven by protein–protein interactions that integrate membrane receptors and adhesion molecules. Tetraspanins participate in antigen recognition and presentation by antigen-­presenting cells (APCs) through the organization of pattern-recognition receptors (PRRs) and their downstream-induced signaling, as well as the regulation of MHC-II–peptide trafficking. T lymphocyte activation is triggered upon specific recognition of antigens present on the APC surface during immunological synapse (IS) formation. This dynamic process is characterized by a defined spatial organization involving the compartmentalization of receptors and adhesion molecules in specialized membrane domains that are connected to the underlying cytoskeleton and signaling molecules. Tetraspanins contribute to the spatial organization and maturation of the IS by controlling receptor clustering and local accumulation of adhesion receptors and integrins, their downstream signaling, and linkage to the actin cytoskeleton. This review offers a perspective on the important role of TEMs in the regulation of antigen recognition and presentation and in the dynamics of IS architectural organization. PMID:26793193

Is Adolescence a Period of Identity Formation for All Youth? Insights from a Four-Wave Longitudinal Study of Identity Dynamics in Japan

Science.gov (United States)

Hatano, Kai; Sugimura, Kazumi

2017-01-01

In the present study, we examined changes in identity dynamics during adolescence using the Dimensions of Identity Development Scale (DIDS), focusing on social and cultural factors possibly affecting identity formation. Identity formation among adolescents outside Western countries is largely unexplored; therefore, we focused on adolescents in…

A biplanar X-ray approach for studying the 3D dynamics of human track formation.

Science.gov (United States)

Hatala, Kevin G; Perry, David A; Gatesy, Stephen M

2018-05-09

Recent discoveries have made hominin tracks an increasingly prevalent component of the human fossil record, and these data have the capacity to inform long-standing debates regarding the biomechanics of hominin locomotion. However, there is currently no consensus on how to decipher biomechanical variables from hominin tracks. These debates can be linked to our generally limited understanding of the complex interactions between anatomy, motion, and substrate that give rise to track morphology. These interactions are difficult to study because direct visualization of the track formation process is impeded by foot and substrate opacity. To address these obstacles, we developed biplanar X-ray and computer animation methods, derived from X-ray Reconstruction of Moving Morphology (XROMM), to analyze the 3D dynamics of three human subjects' feet as they walked across four substrates (three deformable muds and rigid composite panel). By imaging and reconstructing 3D positions of external markers, we quantified the 3D dynamics at the foot-substrate interface. Foot shape, specifically heel and medial longitudinal arch deformation, was significantly affected by substrate rigidity. In deformable muds, we found that depths measured across tracks did not directly reflect the motions of the corresponding regions of the foot, and that track outlines were not perfectly representative of foot size. These results highlight the complex, dynamic nature of track formation, and the experimental methods presented here offer a promising avenue for developing and refining methods for accurately inferring foot anatomy and gait biomechanics from fossil hominin tracks. Copyright © 2018 Elsevier Ltd. All rights reserved.

Molecular dynamic simulation on boron cluster implantation for shallow junction formation

International Nuclear Information System (INIS)

Yuan Li; Yu Min; Li Wei; Ji Huihui; Ren Liming; Zhan Kai; Huang Ru; Zhang Xing; Wang Yangyuan; Zhang Jinyu; Oka, Hideki

2006-01-01

Boron cluster ion implantation is a potential technology for shallow junction formation in integrated circuits manufacture. A molecular dynamic method for cluster implantation simulation, aiming at microelectronics application, is presented in this paper. Accurate geometric structures of boron clusters are described by the model, and the H atoms in clusters are included. A potential function taking the form of combining the ZBL and the SW potentials is presented here to model interaction among the atoms in the boron cluster. The impact of these models on cluster implantation simulation is investigated. There are notable impact on dopant distribution and amount of implantation defects with consideration of these models. The simulation on the distributions of B and H are verified by SIMS data

Violent Relaxation, Dynamical Instabilities and the Formation of Elliptical Galaxies

Science.gov (United States)

Aguilar, L. A.

1990-11-01

RESUMEN: El problema de la formaci6n de galaxias elfpticas por medjo de colapso gravitacional sin disipaci6n de energfa es estudiado usando un gran numero de simulaciones numericas. Se muestra que este tipo de colapsos, partiendo de condiciones iniciales frfas donde la energfa cinetica inicial representa s6lo un 5%, 0 , de a potencial inicial, produce sistemas relajados de forma triaxial muy similares a las galaxias elfpticas reales en sus formas y perfiles de densidad en proyecci6i . La forina triaxial resulta de la acci6n de una inestabilidad dinamica que aparece en sistemas 'inicos dominados por movimientos radiales, mientras que el perfil de densidad final Cs debido al llamado relajamiento violento que tiende a producir una distribuci6n en espacio fase unica. Estos dos fen6menos tienden a borrar los detalles particulares sobre las condiciones iniciales y dan lugar a una evoluci6n convergente hacia sistemas realistas, esto innecesario el uso de condiciones iniciales especiales (excepto por Ia condici6i de que estas deben ser frfas). Las condiciones iniciales frfas producen los movimientos radiales y fluctuaciones de la energfa potencial requeridos por ambos fen6menos. ABSTRACT: The problem of formation of elliptical galaxies via dissipationless collapse is studied using a large set of numerical simulations. It is shown that dissipationless collapses from cold initial conditions, where the total initial kinetic energy is less than 5% ofthe initial potential energy, lead to relaxed triaxial systems ery similar to real elliptical galaxies ii projected shape and density profiles. The triaxial shape is due to the of a dynamical instability that appears on systems dominated by radial orbits, while final density profile is due to violent relaxation that tends to produce a unique distribution iii space. These two phenomena erase memory of the initial prodtice a convergent evolution toward realistic systems, thus making unnecessary use o[special initial conditions (other

Mediating Dynamic Supply Chain Formation by Collaborative Single Machine Earliness/Tardiness Agents in Supply Mesh

Directory of Open Access Journals (Sweden)

Hang Yang

2014-01-01

Full Text Available Nowadays, a trend of forming dynamic supply chains with different trading partners over different e-marketplaces has emerged. These supply chains, which are called “supply mesh,” generally refer to heterogeneous electronic marketplaces in which dynamic supply chains, as per project (often make-to-order, are formed across different parties. Conceptually, in a supply mesh a dynamic supply chain is formed vertically, mediating several companies for a project. Companies that are on the same level horizontally are either competitors or cohorts. A complex scenario such as this makes it challenging to find the right group of members for a dynamic supply chain. Earlier on, a multiagent model called the collaborative single machine earliness/tardiness (CSET model was proposed for the optimal formation of make-to-order supply chains. This paper contributes the particular agent designs, for enabling the mediation of CSET in a supply mesh, and the possibilities are discussed. It is demonstrated via a computer simulation, based on samples from the U.S. textile industry, that by using intelligent agents under the CSET model it is possible to automatically find an ideal group of trading partners from a supply mesh.

ATHENA - Ready to go!

CERN Multimedia

2001-01-01

Making antihydrogen is one thing - detecting it is another. After a three year construction period, the ATHENA antihydrogen detector has now been commissioned. With this last major component installed, the ATHENA experiment has all the ingredients it needs for producing and detecting slow antihydrogen atoms.   Installing the new ATHENA antihydrogen detector. The recipe for making antihydrogen atoms appears simple: capture antiprotons, cool them, bring them together with a cloud of cold positrons - and voila! But, even when antiprotons and positrons are moving slowly, they still don't like to stick together. Large numbers are therefore important, and the ATHENA apparatus provides the means to accumulate large amounts of cold antiprotons and positrons. In the first part of 2001, several bunches of antiprotons from the AD were stacked, yielding more than 50,000 antiprotons in the antiproton trap. These were then cooled and held for more than one hour. In the dedicated positron accumulator, about 35 ...

AEgIS experiment commissioning at CERN

Energy Technology Data Exchange (ETDEWEB)

Krasnicky, D. [University of Genoa, Dept of Physics, Via Dodecaneso 33, 16146 Genova, Italy and Istituto Nazionale di Fisica Nucleare, Sez. di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Aghion, S. [Politecnico di Milano, LNESS and Dept of Physics, Via Anzani 42, 22100 Como, Italy and Istituto Nazionale di Fisica Nucleare, Sez. di Milano, Via Celoria 16, 20133 Milano (Russian Federation); Amsler, C.; Ariga, A.; Ariga, T.; Ereditato, A.; Kawada, J.; Kimura, M.; Pistillo, C.; Scampoli, P.; Storey, J. [Albert Einstein Center for Fundamental Physics, University of Bern, 3012 Bern (Switzerland); Belov, A. S.; Gninenko, S. N. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 117312 (Russian Federation); Bonomi, G.; Subieta Vasquez, M. A. [University of Brescia, Dept of Mech. and Indust. Engineering, Via Branze 38, 25133 Brescia, Italy and Istituto Nazionale di Fisica Nucleare, Sez. di Pavia, Via Agostino Bassi 6, 27100 Pavia (Italy); Braeunig, P.; Oberthaler, M. K. [University of Heidelberg, Kirchhoff Institute for Physics, Im Neuenheimer Feld 227, 69120 Heidelberg (Germany); Brusa, R. S.; Di Noto, L.; Mariazzi, S. [Dipartimento di Fisica, Universita di Trento and INFN, Gruppo collegato di Trento, Via Sommarive 14, 38050 Povo, Trento (Italy); and others

2013-03-19

The AEgIS Experiment is an international collaboration based at CERN whose aim is to perform the first direct measurement of the gravitational acceleration g of antihydrogen in the gravitational field of the Earth. Cold antihydrogen will be produced with a pulsed charge exchange reaction in a cylindrical Penning trap where antiprotons will be cooled to 100mK. The cold antihydrogen will be produced in an excited Rydberg state and subsequently formed into a beam. The deflection of the antihydrogen beam will be measured by using Moire deflectometer gratings. After being approved in late 2008, AEgIS started taking data in a commissioning phase early 2012. This report presents an overview of the AEgIS experiment, describes its current status and shows the first measurements on antiproton catching and cooling in the 5 T Penning catching trap. We will also present details on the techniques needed for the 100mK antihydrogen production, such as pulsed positronium production and its excitation with lasers.

Dynamic expression reveals a two-step patterning of WUS and CLV3 during axillary shoot meristem formation in Arabidopsis.

Science.gov (United States)

Xin, Wei; Wang, Zhicai; Liang, Yan; Wang, Yonghong; Hu, Yuxin

2017-07-01

Seed plants have a remarkable capability to produce axillary meristems (AM) in the leaf axils, however, the dynamic establishment of a stem cell niche in AM is largely uncharacterized. We comprehensively examined the dynamic patterning of WUSCHEL (WUS) and CLAVATA3 (CLV3), the two key marker genes defining the shoot stem cell niches, during AM formation in Arabidopsis, and we found that a two-step patterning of WUS and CLV3 occurred during AM stem cell niche establishment. Our further work on the wus and clv3 mutants implicates that such two-step patterning is likely critical for the maintenance of AM progenitor cells and the specification of AM stem cell niche. These data provide a cytological frame for how a stem cell niche is established during AM formation. Copyright © 2017 Elsevier GmbH. All rights reserved.

A novel antiproton radial diagnostic based on octupole induced ballistic loss

International Nuclear Information System (INIS)

Andresen, G. B.; Bowe, P. D.; Hangst, J. S.; Bertsche, W.; Butler, E.; Charlton, M.; Humphries, A. J.; Jenkins, M. J.; Joergensen, L. V.; Madsen, N.; Werf, D. P. van der; Bray, C. C.; Chapman, S.; Fajans, J.; Povilus, A.; Wurtele, J. S.; Cesar, C. L.; Lambo, R.; Silveira, D. M.; Fujiwara, M. C.

2008-01-01

We report results from a novel diagnostic that probes the outer radial profile of trapped antiproton clouds. The diagnostic allows us to determine the profile by monitoring the time history of antiproton losses that occur as an octupole field in the antiproton confinement region is increased. We show several examples of how this diagnostic helps us to understand the radial dynamics of antiprotons in normal and nested Penning-Malmberg traps. Better understanding of these dynamics may aid current attempts to trap antihydrogen atoms

A novel antiproton radial diagnostic based on octupole induced ballistic loss

CERN Document Server

Andresen, G.B.; Bowe, P.D.; Bray, C.C.; Butler, E.; Cesar, C.L.; Chapman, S.; Charlton, M.; Fajans, J.; Fujiwara, M.C.; Funakoshi, R.; Gill, D.R.; Hangst, J.S.; Hardy, W.N.; Hayano, R.S.; Hayden, M.E.; Humphries, A.J.; Hydomako, R.; Jenkins, M.J.; Jorgensen, L.V.; Kurchaninov, L.; Lambo, R.; Madsen, N.; Nolan, P.; Olchanski, K.; Olin, A.; Page, R.D.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; Seif El Nasr, S.; Silveira, D.M.; Storey, J.W.; Thompson, R.I.; van der Werf, D.P.; Wurtele, J.S.; Yamazaki, Y.

2008-01-01

We report results from a novel diagnostic that probes the outer radial profile of trapped antiproton clouds. The diagnostic allows us to determine the profile by monitoring the time-history of antiproton losses that occur as an octupole field in the antiproton confinement region is increased. We show several examples of how this diagnostic helps us to understand the radial dynamics of antiprotons in normal and nested Penning-Malmberg traps. Better understanding of these dynamics may aid current attempts to trap antihydrogen atoms.

Relationships between and formation dynamics of the microbiota of consumers, producers, and the environment in an abalone aquatic system.

Science.gov (United States)

Jiang, Jing-Zhe; Zhao, Wang; Liu, Guang-Feng; Wang, Jiang-Yong

2017-01-01

An ecosystem is a community comprising living and nonliving components of the environment. Microbes are ubiquitous elements in each of these components. The dynamics of microbiota formation in an ecosystem is important to elucidate, because how the different components of a system exchange microbes, and how the microbes control ecological processes remain unresolved. In this study, an abalone, Haliotis diversicolor, seed-nursing pond was used as a model system. We first examined changes in bacterial communities during the seedling cultivation of this herbivorous juvenile aquatic invertebrate animal. Denaturing gradient gel electrophoresis (DGGE) and pyrosequencing were used to analyze bacterial community dynamics and spatio-temporal interactions of different system components: consumers (abalone), producers (algae or a substrate), and the environment (water). DGGE fingerprints revealed that the developmental stages of abalone influences bacterial communities of both the abalone and substrate. Although the communities in water fluctuated daily, they could be divided into two clusters that coincided with abalone stages, reflecting the transition from larva to juvenile at around day 21. Pyrosequencing showed that the microbiota in the abalone and substrate had more operational taxonomic units in common than that of either with water. The Bray-Curtis similarity index was used to quantify the formation dynamics of microbiota among the various components of the system. The bacterial communities in producers and consumers showed similar changes. These communities were unstable at the beginning and then slowly stabilized over time. The environmental bacterial community was more stable than the bacterial communities in consumers and producers, and may have been the basis for stability in the system. Our research provides insights into the dynamics of microbiota formation in various biotic elements of a system that will contribute to predictive systems modeling.

Relationships between and formation dynamics of the microbiota of consumers, producers, and the environment in an abalone aquatic system.

Directory of Open Access Journals (Sweden)

Jing-Zhe Jiang

Full Text Available An ecosystem is a community comprising living and nonliving components of the environment. Microbes are ubiquitous elements in each of these components. The dynamics of microbiota formation in an ecosystem is important to elucidate, because how the different components of a system exchange microbes, and how the microbes control ecological processes remain unresolved. In this study, an abalone, Haliotis diversicolor, seed-nursing pond was used as a model system. We first examined changes in bacterial communities during the seedling cultivation of this herbivorous juvenile aquatic invertebrate animal. Denaturing gradient gel electrophoresis (DGGE and pyrosequencing were used to analyze bacterial community dynamics and spatio-temporal interactions of different system components: consumers (abalone, producers (algae or a substrate, and the environment (water. DGGE fingerprints revealed that the developmental stages of abalone influences bacterial communities of both the abalone and substrate. Although the communities in water fluctuated daily, they could be divided into two clusters that coincided with abalone stages, reflecting the transition from larva to juvenile at around day 21. Pyrosequencing showed that the microbiota in the abalone and substrate had more operational taxonomic units in common than that of either with water. The Bray-Curtis similarity index was used to quantify the formation dynamics of microbiota among the various components of the system. The bacterial communities in producers and consumers showed similar changes. These communities were unstable at the beginning and then slowly stabilized over time. The environmental bacterial community was more stable than the bacterial communities in consumers and producers, and may have been the basis for stability in the system. Our research provides insights into the dynamics of microbiota formation in various biotic elements of a system that will contribute to predictive systems

A dynamic programming–enhanced simulated annealing algorithm for solving bi-objective cell formation problem with duplicate machines

Directory of Open Access Journals (Sweden)

Mohammad Mohammadi

2015-04-01

Full Text Available Cell formation process is one of the first and the most important steps in designing cellular manufacturing systems. It consists of identifying part families according to the similarities in the design, shape, and presses of parts and dedicating machines to each part family based on the operations required by the parts. In this study, a hybrid method based on a combination of simulated annealing algorithm and dynamic programming was developed to solve a bi-objective cell formation problem with duplicate machines. In the proposed hybrid method, each solution was represented as a permutation of parts, which is created by simulated annealing algorithm, and dynamic programming was used to partition this permutation into part families and determine the number of machines in each cell such that the total dissimilarity between the parts and the total machine investment cost are minimized. The performance of the algorithm was evaluated by performing numerical experiments in different sizes. Our computational experiments indicated that the results were very encouraging in terms of computational time and solution quality.

Atomic physics of the antimatter explored with slow antiprotons

International Nuclear Information System (INIS)

Torii, Hiroyuki A.

2010-01-01

Frontiers of antimatter physics are reviewed, with a focus on our ASACUSA collaboration, doing research on 'Atomic Spectroscopy And Collisions Using Slow Antiprotons' at the 'Antiproton Decelerator' facility at CERN. Antiprotonic helium atoms give a unique test ground for testing CPT invariance between particles and antiparticles. Laser spectroscopy of this exotic atom has reached a precision of a few parts per billion in determation of the antiproton mass. We also have developed techniques to decelerate antiprotons and cool them to sub-eV energies in an electromagnetic trap at ultra-high vacuum and extract them as an ultra-slow beam at typically 250 eV. This unique low-energy beam opens up the possibility to study ionization and formation of antiprotonic atoms. The antihydrogen has been synthesized at low temperature in nested Penning traps by ATRAP and ATHENA(presently ALPHA) collaborations. Confinement of this neutral anti-atoms in a trap with magnetic field gradient is being studied, with an aim of 1S-2S laser spectroscopy in the future. ASACUSA has prepared a cusp trap for production of antihydrogen atoms, and aims at microwave spectroscopy between the hyperfine states of spin-polarized antihydrogen. A wide variety of low-energy antiproton physics also includes measurement of nuclear scattering, radiational biological effects, and gravity test of antimatter. (author)

A genetic algorithm for a bi-objective mathematical model for dynamic virtual cell formation problem

Science.gov (United States)

Moradgholi, Mostafa; Paydar, Mohammad Mahdi; Mahdavi, Iraj; Jouzdani, Javid

2016-09-01

Nowadays, with the increasing pressure of the competitive business environment and demand for diverse products, manufacturers are force to seek for solutions that reduce production costs and rise product quality. Cellular manufacturing system (CMS), as a means to this end, has been a point of attraction to both researchers and practitioners. Limitations of cell formation problem (CFP), as one of important topics in CMS, have led to the introduction of virtual CMS (VCMS). This research addresses a bi-objective dynamic virtual cell formation problem (DVCFP) with the objective of finding the optimal formation of cells, considering the material handling costs, fixed machine installation costs and variable production costs of machines and workforce. Furthermore, we consider different skills on different machines in workforce assignment in a multi-period planning horizon. The bi-objective model is transformed to a single-objective fuzzy goal programming model and to show its performance; numerical examples are solved using the LINGO software. In addition, genetic algorithm (GA) is customized to tackle large-scale instances of the problems to show the performance of the solution method.

A numerical study on the dynamics of droplet formation in a microfluidic double T-junction.

Science.gov (United States)

Ngo, Ich-Long; Dang, Trung-Dung; Byon, Chan; Joo, Sang Woo

2015-03-01

In this study, droplet formations in microfluidic double T-junctions (MFDTD) are investigated based on a two-dimensional numerical model with volume of fluid method. Parametric ranges for generating alternating droplet formation (ADF) are identified. A physical background responsible for the ADF is suggested by analyzing the dynamical stability of flow system. Since the phase discrepancy between dispersed flows is mainly caused by non-symmetrical breaking of merging droplet, merging regime becomes the alternating regime at appropriate conditions. In addition, the effects of channel geometries on droplet formation are studied in terms of relative channel width. The predicted results show that the ADF region is shifted toward lower capillary numbers when channel width ratio is less than unity. The alternating droplet size increases with the increase of channel width ratio. When this ratio reaches unity, alternating droplets can be formed at very high water fraction (wf = 0.8). The droplet formation in MFDTD depends significantly on the viscosity ratio, and the droplet size in ADF decreases with the increase of the viscosity ratio. The understanding of underlying physics of the ADF phenomenon is useful for many applications, including nanoparticle synthesis with different concentrations, hydrogel bead generation, and cell transplantation in biomedical therapy.

The 4-particle hydrogen-anti-hydrogen system revisited. Twofold molecular Hamiltonian symmetry and natural atom anti-hydrogen

International Nuclear Information System (INIS)

Van Hooydonk, G.

2005-01-01

The historical importance of the original quantum mechanical bond theory proposed by Heitler and London in 1927 as well as its pitfalls are reviewed. Modern ab initio treatments of H-H-bar systems are inconsistent with the logic behind algebraic Hamiltonians H ± = H 0 ± ΔH for charge-symmetrical and charge-asymmetrical 4 unit charge systems like H 2 and HH-bar. Their eigenvalues are exactly those of 1927 Heitler-London (HL) theory. Since these 2 Hamiltonians are mutually exclusive, only the attractive one can apply for stable natural molecular H 2 . A wrong choice leads to problems with anti-atom H-bar. In line with earlier results on band and line spectra, we now prove that HL chose the wrong Hamiltonian for H 2 . Their theory explains the stability of attractive system H 2 with a repulsive Hamiltonian H 0 + ΔH instead of with the attractive one H 0 - ΔH, representative for charge-asymmetrical system HH-bar. A new second order symmetry effect is detected in this attractive Hamiltonian, which leads to a 3-dimensional structure for the 4-particle system. Repulsive HL Hamiltonian H + applies at long range but at the critical distance, attractive charge-inverted Hamiltonian H - takes over and leads to bond H 2 but in reality, HH-bar, for which we give an analytical proof. This analysis confirms and generalizes an earlier critique of the wrong long range behavior of HL-theory by Bingel, Preuss and Schmidtke and by Herring. Another wrong asymptote choice in the past also applies for atomic anti-hydrogen H-bar, which has hidden the Mexican hat potential for natural hydrogen. This generic solution removes most problems, physicists and chemists experience with atomic H-bar and molecular HH-bar, including the problem with antimatter in the Universe. (author)

Role of Fluid-Dynamics in Soot Formation and Microstructure in Acetylene-Air Laminar Diffusion Flames

Directory of Open Access Journals (Sweden)

Praveen Pandey

2015-03-01

Full Text Available Residence time and thermo-chemical environment are important factors in the soot-formation process in flames. Studies have revealed that flow-dynamics plays a dominant role in soot formation process. For understanding the effect of flow dynamics on soot formation and physical structure of the soot formed in different combustion environments two types of laminar diffusion flames of Acetylene and air, a normal diffusion flame (NDF and an inverse diffusion flame (IDF have been investigated. The fuel and air supply in the reaction zone in two flame types were kept constant but the interchange of relative position of fuel and air altered the burner exit Reynolds and Froude numbers of gases, fuel/air velocity ratio and flame shape. Soot samples were collected using thermophoretic sampling on transmission electron microscope (TEM grids at different flame heights and were analyzed off-line in a Transmission Electron Microscope. Soot primary particle size, soot aggregate size and soot volume fraction were measured using an image analysis software. In NDF the maximum flame temperature was about 1525 K and 1230 K for IDF. The soot primary particles are distinctly smaller in size in IDF (between 19 – 26 nm compared to NDF (between 29–34 nm. Both NDF and IDF show chainlike branched structure of soot agglomerate with soot particles of a nearly spherical shape. The average number of soot primary particles per aggregate in NDF was in the range of 24 to 40 and in IDF it varied between 16 to 24. Soot volume fraction was between 0.6 to 1.5 ppm in NDF where as it was less than 0.2 ppm in IDF. The change in sooting characteristics of the two flame types is attributed to changed fuel/air velocity ratio, entrainment of gas molecules and thermophoresis on soot particles.

The AEGIS experiment at CERN

Energy Technology Data Exchange (ETDEWEB)

Kellerbauer, A., E-mail: a.kellerbauer@cern.ch [Max Planck Institute for Nuclear Physics (Germany); Allkofer, Y.; Amsler, C. [University of Zurich, Physics Institute (Switzerland); Belov, A. S. [Institute for Nuclear Research of the Russian Academy of Sciences (Russian Federation); Bonomi, G. [University of Brescia, Department of Mechanical and Industrial Engineering (Italy); Braeunig, P. [University of Heidelberg, Kirchhoff Institute for Physics (Germany); Bremer, J. [European Organisation for Nuclear Research, Physics Department (Switzerland); Brusa, R. S. [University of Trento, Department of Physics (Italy); Burghart, G. [European Organisation for Nuclear Research, Physics Department (Switzerland); Cabaret, L. [Centre national de la recherche scientifique, Laboratoire Aime Cotton (France); Canali, C. [University of Zurich, Physics Institute (Switzerland); Castelli, F. [University of Milano, Department of Physics (Italy); Chlouba, K. [Czech Technical University in Prague, Department of Physics (Czech Republic); Cialdi, S. [University of Milano, Department of Physics (Italy); Comparat, D. [Centre national de la recherche scientifique, Laboratoire Aime Cotton (France); Consolati, G. [Politecnico di Milano, Department of Physics (Italy); Dassa, L. [University of Brescia, Department of Mechanical and Industrial Engineering (Italy); Noto, L. Di [University of Trento, Department of Physics (Italy); Donzella, A. [University of Brescia, Department of Mechanical and Industrial Engineering (Italy); Doser, M. [European Organisation for Nuclear Research, Physics Department (Switzerland); Collaboration: AEGIS Collaboration; and others

2012-05-15

After the first production of cold antihydrogen by the ATHENA and ATRAP experiments ten years ago, new second-generation experiments are aimed at measuring the fundamental properties of this anti-atom. The goal of AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is to test the weak equivalence principle by studying the gravitational interaction between matter and antimatter with a pulsed, cold antihydrogen beam. The experiment is currently being assembled at CERN's Antiproton Decelerator. In AEGIS, antihydrogen will be produced by charge exchange of cold antiprotons with positronium excited to a high Rydberg state (n > 20). An antihydrogen beam will be produced by controlled acceleration in an electric-field gradient (Stark acceleration). The deflection of the horizontal beam due to its free fall in the gravitational field of the earth will be measured with a moire deflectometer. Initially, the gravitational acceleration will be determined to a precision of 1%, requiring the detection of about 10{sup 5} antihydrogen atoms. In this paper, after a general description, the present status of the experiment will be reviewed.

Prospects for Studies of the Free Fall and Gravitational Quantum States of Antimatter

Directory of Open Access Journals (Sweden)

G. Dufour

2015-01-01

Full Text Available Different experiments are ongoing to measure the effect of gravity on cold neutral antimatter atoms such as positronium, muonium, and antihydrogen. Among those, the project GBAR at CERN aims to measure precisely the gravitational fall of ultracold antihydrogen atoms. In the ultracold regime, the interaction of antihydrogen atoms with a surface is governed by the phenomenon of quantum reflection which results in bouncing of antihydrogen atoms on matter surfaces. This allows the application of a filtering scheme to increase the precision of the free fall measurement. In the ultimate limit of smallest vertical velocities, antihydrogen atoms are settled in gravitational quantum states in close analogy to ultracold neutrons (UCNs. Positronium is another neutral system involving antimatter for which free fall under gravity is currently being investigated at UCL. Building on the experimental techniques under development for the free fall measurement, gravitational quantum states could also be observed in positronium. In this contribution, we report on the status of the ongoing experiments and discuss the prospects of observing gravitational quantum states of antimatter and their implications.

Droplet formation in microfluidic T-junction generators operating in the transitional regime. III. Dynamic surfactant effects.

Science.gov (United States)

Glawdel, Tomasz; Ren, Carolyn L

2012-08-01

This study extends our previous work on droplet generation in microfluidic T-junction generators to include dynamic interfacial tension effects created by the presence of surfactants. In Paper I [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016322 (2012)], we presented experimental findings regarding the formation process in the squeezing-to-transition regime, and in Paper II [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016323 (2012)] we developed a theoretical model that describes the performance of T-junction generators without surfactants. Here we study dynamic interfacial tension effects for two surfactants, one with a small molecular weight that adsorbs quickly, and the other with a large molecular weight that adsorbs slowly. Using the force balance developed in Paper II we extract the dynamic interfacial tension from high speed videos obtained during experiments. We then develop a theoretical model to predict the dynamic interfacial tension in microfluidic T-junction generators as a function of the surfactant properties, flow conditions, and generator design. This model is then incorporated into the overall model for generator performance to effectively predict the size of droplets produced when surfactants are present.

Optimization of detectors positioning with respect to flying dynamics for future formation flight missions

Science.gov (United States)

Civitani, Marta; Djalal, Sophie; Chipaux, Remi

2009-08-01

In a X-ray telescope in formation flight configuration, the optics and the focal-plane detectors reside in two different spacecraft. The dynamics of the detector spacecraft (DSC) with respect to the mirror spacecraft (MSC, carrying the mirrors of the telescope) changes continuously the arrival positions of the photons on the detectors. In this paper we analyze this issue for the case of the SIMBOL-X hard X-ray mission, extensively studied by CNES and ASI until 2009 spring. Due to the existing gaps between pixels and between detector modules, the dynamics of the system may produce a relevant photometric effect. The aim of this work is to present the optimization study of the control-law algorithm with respect to the detector's geometry. As the photometric effect may vary depending upon position of the source image on the detector, the analysis-carried out using the simuLOS (INAF, CNES, CEA) simulation tool-is extended over the entire SIMBOL-X field of view.

Territorial dynamics and stable home range formation for central place foragers.

Directory of Open Access Journals (Sweden)

Jonathan R Potts

Full Text Available Uncovering the mechanisms behind territory formation is a fundamental problem in behavioural ecology. The broad nature of the underlying conspecific avoidance processes are well documented across a wide range of taxa. Scent marking in particular is common to a large range of terrestrial mammals and is known to be fundamental for communication. However, despite its importance, exact quantification of the time-scales over which scent cues and messages persist remains elusive. Recent work by the present authors has begun to shed light on this problem by modelling animals as random walkers with scent-mediated interaction processes. Territories emerge as dynamic objects that continually change shape and slowly move without settling to a fixed location. As a consequence, the utilisation distribution of such an animal results in a slowly increasing home range, as shown for urban foxes (Vulpes vulpes. For certain other species, however, home ranges reach a stable state. The present work shows that stable home ranges arise when, in addition to scent-mediated conspecific avoidance, each animal moves as a central place forager. That is, the animal's movement has a random aspect but is also biased towards a fixed location, such as a den or nest site. Dynamic territories emerge but the probability distribution of the territory border locations reaches a steady state, causing stable home ranges to emerge from the territorial dynamics. Approximate analytic expressions for the animal's probability density function are derived. A programme is given for using these expressions to quantify both the strength of the animal's movement bias towards the central place and the time-scale over which scent messages persist. Comparisons are made with previous theoretical work modelling central place foragers with conspecific avoidance. Some insights into the mechanisms behind allometric scaling laws of animal space use are also given.

Dynamical Stability of Imaged Planetary Systems in Formation: Application to HL Tau

Science.gov (United States)

Tamayo, D.; Triaud, A. H. M. J.; Menou, K.; Rein, H.

2015-06-01

A recent Atacama Large Millimeter/Submillimeter Array image revealed several concentric gaps in the protoplanetary disk surrounding the young star HL Tau. We consider the hypothesis that these gaps are carved by planets, and present a general framework for understanding the dynamical stability of such systems over typical disk lifetimes, providing estimates for the maximum planetary masses. We collect these easily evaluated constraints into a workflow that can help guide the design and interpretation of new observational campaigns and numerical simulations of gap opening in such systems. We argue that the locations of resonances should be significantly shifted in massive disks like HL Tau, and that theoretical uncertainties in the exact offset, together with observational errors, imply a large uncertainty in the dynamical state and stability in such disks. This presents an important barrier to using systems like HL Tau as a proxy for the initial conditions following planet formation. An important observational avenue to breaking this degeneracy is to search for eccentric gaps, which could implicate resonantly interacting planets. Unfortunately, massive disks like HL Tau should induce swift pericenter precession that would smear out any such eccentric features of planetary origin. This motivates pushing toward more typical, less massive disks. For a nominal non-resonant model of the HL Tau system with five planets, we find a maximum mass for the outer three bodies of approximately 2 Neptune masses. In a resonant configuration, these planets can reach at least the mass of Saturn. The inner two planets’ masses are unconstrained by dynamical stability arguments.

Formation Dynamics of CH3NH3PbI3 Perovskite Following Two-Step Layer Deposition.

Science.gov (United States)

Patel, Jay B; Milot, Rebecca L; Wright, Adam D; Herz, Laura M; Johnston, Michael B

2016-01-07

Hybrid metal-halide perovskites have emerged as a leading class of semiconductors for optoelectronic devices because of their desirable material properties and versatile fabrication methods. However, little is known about the chemical transformations that occur in the initial stages of perovskite crystal formation. Here we follow the real-time formation dynamics of MAPbI3 from a bilayer of lead iodide (PbI2) and methylammonium iodide (MAI) deposited through a two-step thermal evaporation process. By lowering the substrate temperature during deposition, we are able to initially inhibit intermixing of the two layers. We subsequently use infrared and visible light transmission, X-ray diffraction, and photoluminescence lifetime measurements to reveal the room-temperature transformations that occur in vacuum and ambient air, as MAI diffuses into the PbI2 lattice to form MAPbI3. In vacuum, the transformation to MAPbI3 is incomplete as unreacted MAI is retained in the film. However, exposure to moist air allows for conversion of the unreacted MAI to MAPbI3, demonstrating that moisture is essential in making MAI more mobile and thus aiding perovskite crystallization. These dynamic processes are reflected in the observed charge-carrier lifetimes, which strongly fluctuate during periods of large ion migration but steadily increase with improving crystallinity.

Opinion formation models in static and dynamic social networks

Science.gov (United States)

Singh, Pramesh

We study models of opinion formation on static as well as dynamic networks where interaction among individuals is governed by widely accepted social theories. In particular, three models of competing opinions based on distinct interaction mechanisms are studied. A common feature in all of these models is the existence of a tipping point in terms of a model parameter beyond which a rapid consensus is reached. In the first model that we study on a static network, a node adopts a particular state (opinion) if a threshold fraction of its neighbors are already in that state. We introduce a few initiator nodes which are in state '1' in a population where every node is in state '0'. Thus, opinion '1' spreads through the population until no further influence is possible. Size of the spread is greatly affected by how these initiator nodes are selected. We find that there exists a critical fraction of initiators pc that is needed to trigger global cascades for a given threshold phi. We also study heuristic strategies for selecting a set of initiator nodes in order to maximize the cascade size. The structural properties of networks also play an important role in the spreading process. We study how the dynamics is affected by changing the clustering in a network. It turns out that local clustering is helpful in spreading. Next, we studied a model where the network is dynamic and interactions are homophilic. We find that homophily-driven rewiring impedes the reaching of consensus and in the absence of committed nodes (nodes that are not influenceable on their opinion), consensus time Tc diverges exponentially with network size N . As we introduce a fraction of committed nodes, beyond a critical value, the scaling of Tc becomes logarithmic in N. We also find that slight change in the interaction rule can produce strikingly different scaling behaviors of T c . However, introducing committed agents in the system drastically improves the scaling of the consensus time regardless of

Dynamical Analysis of a Continuous Stirred-Tank Reactor with the Formation of Biofilms for Wastewater Treatment

Directory of Open Access Journals (Sweden)

Karen López Buriticá

2015-01-01

Full Text Available This paper analyzes the dynamics of a system that models the formation of biofilms in a continuous stirred-tank reactor (CSTR when it is utilized for wastewater treatment. The growth rate of the microorganisms is modeled using two different kinetics, Monod and Haldane kinetics, with the goal of studying the influence of each in the system. The equilibrium points are identified through a stability analysis, and the bifurcations found are characterized.

Double Dynamic Supramolecular Polymers of Covalent Oligo-Dynamers

NARCIS (Netherlands)

Schaeffer, Gaël; Buhler, Eric; Candau, Sauveur Jean; Lehn, Jean-Marie

2013-01-01

Double-dynamic polymers, incorporating both molecular and supramolecular dynamic features (“double dynamers”) have been generated, where these functions are present in a nonstoichiometric ratio in the main chain of the polymer. It has been achieved by (1) the formation of covalent oligo-dynamers in

Development of a buffer gas trap for the confinement of positrons and study of positronium production in the GBAR experiment

CERN Document Server

AUTHOR|(CDS)2101248; van der Werf, Dirk

The GBAR experiment relies on the production of antihydrogen positive ions to achieve its goal of measuring the gravitational acceleration of antimatter at rest. The ANTION project, included in the GBAR enterprise, is responsible for the production of these antimatter ions. Moreover, it also aims to measure the cross section of antihydrogen production throughout the collision of antiprotons and positronium atoms, as well as the matter cross sections of hydrogen and the hydrogen negative ion. These experiments imply the formation of a very dense positronium cloud, thus a large amount of positrons will be implanted on a positron/positronium converter material. This thesis reports the construction of a three stage buffer gas trap with the goal of trapping and accumulating positrons for the ANTION project. The combination of the Penning-type trap with a LINAC source constitutes a unique experimental setup. The trap was commissioned and optimized and is now fully operational. Trapping protocols were studied and...

Transient β-hairpin formation in α-synuclein monomer revealed by coarse-grained molecular dynamics simulation

Energy Technology Data Exchange (ETDEWEB)

Yu, Hang; Ma, Wen [Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Han, Wei [Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Schulten, Klaus, E-mail: kschulte@ks.uiuc.edu [Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2015-12-28

Parkinson’s disease, originating from the intrinsically disordered peptide α-synuclein, is a common neurodegenerative disorder that affects more than 5% of the population above age 85. It remains unclear how α-synuclein monomers undergo conformational changes leading to aggregation and formation of fibrils characteristic for the disease. In the present study, we perform molecular dynamics simulations (over 180 μs in aggregated time) using a hybrid-resolution model, Proteins with Atomic details in Coarse-grained Environment (PACE), to characterize in atomic detail structural ensembles of wild type and mutant monomeric α-synuclein in aqueous solution. The simulations reproduce structural properties of α-synuclein characterized in experiments, such as secondary structure content, long-range contacts, chemical shifts, and {sup 3}J(H{sub N}H{sub C{sub α}})-coupling constants. Most notably, the simulations reveal that a short fragment encompassing region 38-53, adjacent to the non-amyloid-β component region, exhibits a high probability of forming a β-hairpin; this fragment, when isolated from the remainder of α-synuclein, fluctuates frequently into its β-hairpin conformation. Two disease-prone mutations, namely, A30P and A53T, significantly accelerate the formation of a β-hairpin in the stated fragment. We conclude that the formation of a β-hairpin in region 38-53 is a key event during α-synuclein aggregation. We predict further that the G47V mutation impedes the formation of a turn in the β-hairpin and slows down β-hairpin formation, thereby retarding α-synuclein aggregation.

Synaptic scaling enables dynamically distinct short- and long-term memory formation.

Directory of Open Access Journals (Sweden)

Christian Tetzlaff

2013-10-01

Full Text Available Memory storage in the brain relies on mechanisms acting on time scales from minutes, for long-term synaptic potentiation, to days, for memory consolidation. During such processes, neural circuits distinguish synapses relevant for forming a long-term storage, which are consolidated, from synapses of short-term storage, which fade. How time scale integration and synaptic differentiation is simultaneously achieved remains unclear. Here we show that synaptic scaling - a slow process usually associated with the maintenance of activity homeostasis - combined with synaptic plasticity may simultaneously achieve both, thereby providing a natural separation of short- from long-term storage. The interaction between plasticity and scaling provides also an explanation for an established paradox where memory consolidation critically depends on the exact order of learning and recall. These results indicate that scaling may be fundamental for stabilizing memories, providing a dynamic link between early and late memory formation processes.

Synaptic scaling enables dynamically distinct short- and long-term memory formation.

Science.gov (United States)

Tetzlaff, Christian; Kolodziejski, Christoph; Timme, Marc; Tsodyks, Misha; Wörgötter, Florentin

2013-10-01

Memory storage in the brain relies on mechanisms acting on time scales from minutes, for long-term synaptic potentiation, to days, for memory consolidation. During such processes, neural circuits distinguish synapses relevant for forming a long-term storage, which are consolidated, from synapses of short-term storage, which fade. How time scale integration and synaptic differentiation is simultaneously achieved remains unclear. Here we show that synaptic scaling - a slow process usually associated with the maintenance of activity homeostasis - combined with synaptic plasticity may simultaneously achieve both, thereby providing a natural separation of short- from long-term storage. The interaction between plasticity and scaling provides also an explanation for an established paradox where memory consolidation critically depends on the exact order of learning and recall. These results indicate that scaling may be fundamental for stabilizing memories, providing a dynamic link between early and late memory formation processes.

Monitoring intra-annual dynamics of wood formation with microcores and dendrometers in Picea abies at two different altitudes.

Science.gov (United States)

Cocozza, Claudia; Palombo, Caterina; Tognetti, Roberto; La Porta, Nicola; Anichini, Monica; Giovannelli, Alessio; Emiliani, Giovanni

2016-07-01

Seasonal analyses of cambial cell production and day-by-day stem radial increment can help to elucidate how climate modulates wood formation in conifers. Intra-annual dynamics of wood formation were determined with microcores and dendrometers and related to climatic signals in Norway spruce (Picea abies (L.) Karst.). The seasonal dynamics of these processes were observed at two sites of different altitude, Savignano (650 m a.s.l.) and Lavazè (1800 m a.s.l.) in the Italian Alps. Seasonal dynamics of cambial activity were found to be site specific, indicating that the phenology of cambial cell production is highly variable and plastic with altitude. There was a site-specific trend in the number of cells in the wall thickening phase, with the maximum cell production in early July (DOY 186) at Savignano and in mid-July (DOY 200) at Lavazè. The formation of mature cells showed similar trends at the two sites, although different numbers of cells and timing of cell differentiation were visible in the model shapes; at the end of ring formation in 2010, the number of cells was four times higher at Savignano (106.5 cells) than at Lavazè (26.5 cells). At low altitudes, microcores and dendrometers described the radial growth patterns comparably, though the dendrometer function underlined the higher upper asymptote of maximum growth in comparison with the cell production function. In contrast, at high altitude, these functions exhibited different trends. The best model was obtained by fitting functions of the Gompertz model to the experimental data. By combining radial growth and cambial activity indices we defined a model system able to synchronize these processes. Processes of adaptation of the pattern of xylogenesis occurred, enabling P. abies to occupy sites with contrasting climatic conditions. The use of daily climatic variables in combination with plant functional traits obtained by sensors and/or destructive sampling could provide a suitable tool to better

[First time revealed small formations of lungs (under 2 cm in diameter). Dynamic follow-up or surgery?

Science.gov (United States)

Pavlov, Yu V; Rybin, V K

To develop the treatment algorithm in patients with first time revealed lung lesions smaller than 2 cm. The study included 110 patients with pathological lung lesions with small dimensions who have been treated in the Burdenko Clinic of Faculty Surgery for the period 1997-2013. All patients underwent surgical removal of lung tissue using different surgical approaches: 44 cases of videothoracoscopic resections, 43 video-assisted minithoracotomies, 23 minithoracotomies. There were 25 patients with lung cancer, 38 cases of benign tumours (hamartoma and tuberculoma) and 10 patients with disseminated tuberculosis thar required special treatment. Small pulmonary formations (from 0.5 to 2 cm) can be removed without morphological verification prior to surgery. Optimal surgical approach should be selected depending on the amount and size of formations. Management of solitary lung formation smaller than 0.5 cm that was newly diagnosed by computed tomography should include dynamic follow-up and performance of computed tomography in 3-6-12 months.

Evidence for Dynamically Driven Formation of the GW170817 Neutron Star Binary in NGC 4993

Energy Technology Data Exchange (ETDEWEB)

Palmese, A.; et al.

2017-11-09

We present a study of NGC 4993, the host galaxy of the GW170817 gravitational wave event, the GRB170817A short gamma-ray burst (sGRB) and the AT2017gfo kilonova. We use Dark Energy Camera imaging, AAT spectra and publicly available data, relating our findings to binary neutron star (BNS) formation scenarios and merger delay timescales. NGC4993 is a nearby (40 Mpc) early-type galaxy, with $i$-band S\\'ersic index $n=4.0$ and low asymmetry ($A=0.04\\pm 0.01$). These properties are unusual for sGRB hosts. However, NGC4993 presents shell-like structures and dust lanes indicative of a recent galaxy merger, with the optical transient located close to a shell. We constrain the star formation history (SFH) of the galaxy assuming that the galaxy merger produced a star formation burst, but find little to no on-going star formation in either spatially-resolved broadband SED or spectral fitting. We use the best-fit SFH to estimate the BNS merger rate in this type of galaxy, as $R_{NSM}^{gal}= 5.7^{+0.57}_{-3.3} \\times 10^{-6} {\\rm yr}^{-1}$. If star formation is the only considered BNS formation scenario, the expected number of BNS mergers from early-type galaxies detectable with LIGO during its first two observing seasons is $0.038^{+0.004}_{-0.022}$, as opposed to $\\sim 0.5$ from all galaxy types. Hypothesizing that the binary system formed due to dynamical interactions during the galaxy merger, the subsequent time elapsed can constrain the delay time of the BNS coalescence. By using velocity dispersion estimates and the position of the shells, we find that the galaxy merger occurred $t_{\\rm mer}\\lesssim 200~{\\rm Myr}$ prior to the BNS coalescence.

Evidence for Dynamically Driven Formation of the GW170817 Neutron Star Binary in NGC 4993

Science.gov (United States)

Palmese, A.; Hartley, W.; Tarsitano, F.; Conselice, C.; Lahav, O.; Allam, S.; Annis, J.; Lin, H.; Soares-Santos, M.; Tucker, D.; Brout, D.; Banerji, M.; Bechtol, K.; Diehl, H. T.; Fruchter, A.; García-Bellido, J.; Herner, K.; Levan, A. J.; Li, T. S.; Lidman, C.; Misra, K.; Sako, M.; Scolnic, D.; Smith, M.; Abbott, T. M. C.; Abdalla, F. B.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Davis, C.; DePoy, D. L.; Desai, S.; Dietrich, J. P.; Doel, P.; Drlica-Wagner, A.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gaztanaga, E.; Gerdes, D. W.; Giannantonio, T.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D. J.; Jeltema, T.; Johnson, M. W. G.; Johnson, M. D.; Krause, E.; Kron, R.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; March, M.; Marshall, J. L.; McMahon, R. G.; Menanteau, F.; Miller, C. J.; Miquel, R.; Neilsen, E.; Ogando, R. L. C.; Plazas, A. A.; Reil, K.; Romer, A. K.; Sanchez, E.; Schindler, R.; Smith, R. C.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Thomas, R. C.; Walker, A. R.; Weller, J.; Zhang, Y.; Zuntz, J.

2017-11-01

We present a study of NGC 4993, the host galaxy of the GW170817 gravitational-wave event, the GRB 170817A short gamma-ray burst (sGRB), and the AT 2017gfo kilonova. We use Dark Energy Camera imaging, AAT spectra, and publicly available data, relating our findings to binary neutron star (BNS) formation scenarios and merger delay timescales. NGC 4993 is a nearby early-type galaxy, with an I-band Sérsic index n = 4.0 and low asymmetry (A = 0.04 ± 0.01). These properties are unusual for sGRB hosts. However, NGC 4993 presents shell-like structures and dust lanes indicative of a recent galaxy merger, with the optical transient located close to a shell. We constrain the star formation history (SFH) of the galaxy assuming that the galaxy merger produced a star formation burst, but find little to no ongoing star formation in either spatially resolved broadband SED or spectral fitting. We use the best-fit SFH to estimate the BNS merger rate in this type of galaxy, as {R}{NSM}{gal}={5.7}-3.3+0.57× {10}-6{{yr}}-1. If star formation is the only considered BNS formation scenario, the expected number of BNS mergers from early-type galaxies detectable with LIGO during its first two observing seasons is {0.038}-0.022+0.004, as opposed to ˜0.5 from all galaxy types. Hypothesizing that the binary formed due to dynamical interactions during the galaxy merger, the subsequent time elapsed can constrain the delay time of the BNS coalescence. By using velocity dispersion estimates and the position of the shells, we find that the galaxy merger occurred t mer ≲ 200 Myr prior to the BNS coalescence.

Dynamic Price Vector Formation Model-Based Automatic Demand Response Strategy for PV-Assisted EV Charging Stations

Energy Technology Data Exchange (ETDEWEB)

Chen, Qifang; Wang, Fei; Hodge, Bri-Mathias; Zhang, Jianhua; Li, Zhigang; Shafie-Khah, Miadreza; Catalao, Joao P. S.

2017-11-01

A real-time price (RTP)-based automatic demand response (ADR) strategy for PV-assisted electric vehicle (EV) Charging Station (PVCS) without vehicle to grid is proposed. The charging process is modeled as a dynamic linear program instead of the normal day-ahead and real-time regulation strategy, to capture the advantages of both global and real-time optimization. Different from conventional price forecasting algorithms, a dynamic price vector formation model is proposed based on a clustering algorithm to form an RTP vector for a particular day. A dynamic feasible energy demand region (DFEDR) model considering grid voltage profiles is designed to calculate the lower and upper bounds. A deduction method is proposed to deal with the unknown information of future intervals, such as the actual stochastic arrival and departure times of EVs, which make the DFEDR model suitable for global optimization. Finally, both the comparative cases articulate the advantages of the developed methods and the validity in reducing electricity costs, mitigating peak charging demand, and improving PV self-consumption of the proposed strategy are verified through simulation scenarios.

Dark energy with a gradient coupling to the dark matter fluid: cosmological dynamics and structure formation

Science.gov (United States)

Dutta, Jibitesh; Khyllep, Wompherdeiki; Tamanini, Nicola

2018-01-01

We consider scalar field models of dark energy interacting with dark matter through a coupling proportional to the contraction of the four-derivative of the scalar field with the four-velocity of the dark matter fluid. The coupling is realized at the Lagrangian level employing the formalism of Scalar-Fluid theories, which use a consistent Lagrangian approach for relativistic fluid to describe dark matter. This framework produces fully covariant field equations, from which we can derive unequivocal cosmological equations at both background and linear perturbations levels. The background evolution is analyzed in detail applying dynamical systems techniques, which allow us to find the complete asymptotic behavior of the universe given any set of model parameters and initial conditions. Furthermore we study linear cosmological perturbations investigating the growth of cosmic structures within the quasi-static approximation. We find that these interacting dark energy models give rise to interesting phenomenological dynamics, including late-time transitions from dark matter to dark energy domination, matter and accelerated scaling solutions and dynamical crossing of the phantom barrier. Moreover we obtain possible deviations from standard ΛCDM behavior at the linear perturbations level, which have an impact on the dynamics of structure formation and might provide characteristic observational signatures.

Simulations of NLC formation using a microphysical model driven by three-dimensional dynamics

Science.gov (United States)

Kirsch, Annekatrin; Becker, Erich; Rapp, Markus; Megner, Linda; Wilms, Henrike

2014-05-01

Noctilucent clouds (NLCs) represent an optical phenomenon occurring in the polar summer mesopause region. These clouds have been known since the late 19th century. Current physical understanding of NLCs is based on numerous observational and theoretical studies, in recent years especially observations from satellites and by lidars from ground. Theoretical studies based on numerical models that simulate NLCs with the underlying microphysical processes are uncommon. Up to date no three-dimensional numerical simulations of NLCs exist that take all relevant dynamical scales into account, i.e., from the planetary scale down to gravity waves and turbulence. Rather, modeling is usually restricted to certain flow regimes. In this study we make a more rigorous attempt and simulate NLC formation in the environment of the general circulation of the mesopause region by explicitly including gravity waves motions. For this purpose we couple the Community Aerosol and Radiation Model for Atmosphere (CARMA) to gravity-wave resolving dynamical fields simulated beforehand with the Kuehlungsborn Mechanistic Circulation Model (KMCM). In our case, the KMCM is run with a horizontal resolution of T120 which corresponds to a minimum horizontal wavelength of 350 km. This restriction causes the resolved gravity waves to be somewhat biased to larger scales. The simulated general circulation is dynamically controlled by these waves in a self-consitent fashion and provides realistic temperatures and wind-fields for July conditions. Assuming a water vapor mixing ratio profile in agreement with current observations results in reasonable supersaturations of up to 100. In a first step, CARMA is applied to a horizontal section covering the Northern hemisphere. The vertical resolution is 120 levels ranging from 72 to 101 km. In this paper we will present initial results of this coupled dynamical microphysical model focussing on the interaction of waves and turbulent diffusion with NLC-microphysics.

Multishell structure formation in Ni nanowire under uniaxial strain along <0 0 1> crystallographic direction: A molecular dynamics simulation

Energy Technology Data Exchange (ETDEWEB)

Wang Li, E-mail: wanglihxf@sdu.edu.c [School of Mechanical and Electrical Engineering, Shandong University at Weihai, 180 Wenhuaxi Road, Weihai 264209 (China); Peng Chuanxiao [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Gong Jianhong [School of Mechanical and Electrical Engineering, Shandong University at Weihai, 180 Wenhuaxi Road, Weihai 264209 (China)

2010-04-01

Molecular dynamics simulations based upon embedded-atom-method potential are employed to explore the fracture behavior of Ni nanowire along <0 0 1> crystallographic direction at temperature of 300 K. We find the formation of (5,5) multishell structure (MS), which is transformed from (6,5) MS at the necking region of nanowire under the strain rate of 0.02%ps{sup -1}. A reorientation transformation from <0 0 1> to <1 1 0> is first detected before formation of (6,5) MS. The formed (5,5) MS is more stable and can be tensioned longer as lower strain rate is loaded.

Mechanical Model of Geometric Cell and Topological Algorithm for Cell Dynamics from Single-Cell to Formation of Monolayered Tissues with Pattern

KAUST Repository

Kachalo, Së ma; Naveed, Hammad; Cao, Youfang; Zhao, Jieling; Liang, Jie

2015-01-01

development, and other emerging behavior. Here we describe a cell model and an efficient geometric algorithm for studying the dynamic process of tissue formation in 2D (e.g. epithelial tissues). Our approach improves upon previous methods by incorporating

Consensus formation on coevolving networks: groups' formation and structure

International Nuclear Information System (INIS)

Kozma, Balazs; Barrat, Alain

2008-01-01

We study the effect of adaptivity on a social model of opinion dynamics and consensus formation. We analyse how the adaptivity of the network of contacts between agents to the underlying social dynamics affects the size and topological properties of groups and the convergence time to the stable final state. We find that, while on static networks these properties are determined by percolation phenomena, on adaptive networks the rewiring process leads to different behaviors: adaptive rewiring fosters group formation by enhancing communication between agents of similar opinion, though it also makes possible the division of clusters. We show how the convergence time is determined by the characteristic time of link rearrangement. We finally investigate how the adaptivity yields nontrivial correlations between the internal topology and the size of the groups of agreeing agents

Dynamics of dendritic spines in the mouse auditory cortex during memory formation and memory recall.

Science.gov (United States)

Moczulska, Kaja Ewa; Tinter-Thiede, Juliane; Peter, Manuel; Ushakova, Lyubov; Wernle, Tanja; Bathellier, Brice; Rumpel, Simon

2013-11-05

Long-lasting changes in synaptic connections induced by relevant experiences are believed to represent the physical correlate of memories. Here, we combined chronic in vivo two-photon imaging of dendritic spines with auditory-cued classical conditioning to test if the formation of a fear memory is associated with structural changes of synapses in the mouse auditory cortex. We find that paired conditioning and unpaired conditioning induce a transient increase in spine formation or spine elimination, respectively. A fraction of spines formed during paired conditioning persists and leaves a long-lasting trace in the network. Memory recall triggered by the reexposure of mice to the sound cue did not lead to changes in spine dynamics. Our findings provide a synaptic mechanism for plasticity in sound responses of auditory cortex neurons induced by auditory-cued fear conditioning; they also show that retrieval of an auditory fear memory does not lead to a recapitulation of structural plasticity in the auditory cortex as observed during initial memory consolidation.

Lattice dynamical study of omega phase formation in Zr-Al system

International Nuclear Information System (INIS)

Ghosh, P.S.; Arya, A.; Kulkarni, U.D.; Dey, G.K.

2011-01-01

The hexagonal ω phase occurs in the alloys in which the high temperature β phase (bcc) is stabilized with respect to the martensitic β -> ω transformation. The compositional ranges over which the ω phase can be stabilized is the characteristic of the alloy system under consideration. The formation of ordered ω (B8 2 -Zr 2 Al) phase, having space group P6 3 /mmc has been viewed in terms of a superimposition of displacive and replacive components of phase transformation. While the lattice collapse mechanism of β -> ω transformation is displacive in nature; a replacive transformation involving diffusion is required for decorating different sublattice sites by different atomic species. Although, the extent of overlap of these transformations in the formation of ordered ω phase has not been established so far; attempts have been made to explore this aspect by examining the sequential formation of several intermediate stable/metastable phases. The partial collapse of 2nd - 3rd and 5th - 6th planes along (111) direction leads to intermediate trigonal ω ' phase upto which the transformation is purely displacive in nature. A chemical ordering sets in after this step leading to B82 structure via ω'' structure. Density functional plane wave based calculations using the projector augmented wave (PAW) potentials are employed under the generalized gradient approximation to exchange and correlation to study (a) relative ground state stabilities of these phases, (b) variation of total energy as a function of displacement (z, z = 0 to 1/12) and (c) Frozen-phonon calculations for 2/3 longitudinal phonon along (111) direction. The energy-displacement curve for the B2 structure shows nearly harmonic behavior for small displacements but shows strong anharmonic behavior for large displacements making trigonal ω ' structure metastable with respect to this kind of transformations. The phonon dispersion of B2 structure exhibits imaginary frequencies along (111) making it a

Research on Formation Mechanism of Dynamic Response and Residual Stress of Sheet Metal Induced by Laser Shock Wave

Science.gov (United States)

Feng, Aixin; Cao, Yupeng; Wang, Heng; Zhang, Zhengang

2018-01-01

In order to reveal the quantitative control of the residual stress on the surface of metal materials, the relevant theoretical and experimental studies were carried out to investigate the dynamic response of metal thin plates and the formation mechanism of residual stress induced by laser shock wave. In this paper, the latest research trends on the surface residual stress of laser shock processing technology were elaborated. The main progress of laser shock wave propagation mechanism and dynamic response, laser shock, and surface residual stress were discussed. It is pointed out that the multi-scale characterization of laser and material, surface residual stress and microstructure change is a new hotspot in laser shock strengthening technology.

Coevolutionary modeling in network formation

KAUST Repository

Al-Shyoukh, Ibrahim

2014-12-03

Network coevolution, the process of network topology evolution in feedback with dynamical processes over the network nodes, is a common feature of many engineered and natural networks. In such settings, the change in network topology occurs at a comparable time scale to nodal dynamics. Coevolutionary modeling offers the possibility to better understand how and why network structures emerge. For example, social networks can exhibit a variety of structures, ranging from almost uniform to scale-free degree distributions. While current models of network formation can reproduce these structures, coevolutionary modeling can offer a better understanding of the underlying dynamics. This paper presents an overview of recent work on coevolutionary models of network formation, with an emphasis on the following three settings: (i) dynamic flow of benefits and costs, (ii) transient link establishment costs, and (iii) latent preferential attachment.

Coevolutionary modeling in network formation

KAUST Repository

Al-Shyoukh, Ibrahim; Chasparis, Georgios; Shamma, Jeff S.

2014-01-01

Network coevolution, the process of network topology evolution in feedback with dynamical processes over the network nodes, is a common feature of many engineered and natural networks. In such settings, the change in network topology occurs at a comparable time scale to nodal dynamics. Coevolutionary modeling offers the possibility to better understand how and why network structures emerge. For example, social networks can exhibit a variety of structures, ranging from almost uniform to scale-free degree distributions. While current models of network formation can reproduce these structures, coevolutionary modeling can offer a better understanding of the underlying dynamics. This paper presents an overview of recent work on coevolutionary models of network formation, with an emphasis on the following three settings: (i) dynamic flow of benefits and costs, (ii) transient link establishment costs, and (iii) latent preferential attachment.

Mechanical Model of Geometric Cell and Topological Algorithm for Cell Dynamics from Single-Cell to Formation of Monolayered Tissues with Pattern

KAUST Repository

Kachalo, Sëma

2015-05-14

Geometric and mechanical properties of individual cells and interactions among neighboring cells are the basis of formation of tissue patterns. Understanding the complex interplay of cells is essential for gaining insight into embryogenesis, tissue development, and other emerging behavior. Here we describe a cell model and an efficient geometric algorithm for studying the dynamic process of tissue formation in 2D (e.g. epithelial tissues). Our approach improves upon previous methods by incorporating properties of individual cells as well as detailed description of the dynamic growth process, with all topological changes accounted for. Cell size, shape, and division plane orientation are modeled realistically. In addition, cell birth, cell growth, cell shrinkage, cell death, cell division, cell collision, and cell rearrangements are now fully accounted for. Different models of cell-cell interactions, such as lateral inhibition during the process of growth, can be studied in detail. Cellular pattern formation for monolayered tissues from arbitrary initial conditions, including that of a single cell, can also be studied in detail. Computational efficiency is achieved through the employment of a special data structure that ensures access to neighboring cells in constant time, without additional space requirement. We have successfully generated tissues consisting of more than 20,000 cells starting from 2 cells within 1 hour. We show that our model can be used to study embryogenesis, tissue fusion, and cell apoptosis. We give detailed study of the classical developmental process of bristle formation on the epidermis of D. melanogaster and the fundamental problem of homeostatic size control in epithelial tissues. Simulation results reveal significant roles of solubility of secreted factors in both the bristle formation and the homeostatic control of tissue size. Our method can be used to study broad problems in monolayered tissue formation. Our software is publicly

Dynamic Transition and Pattern Formation in Taylor Problem

Institute of Scientific and Technical Information of China (English)

Tian MA; Shouhong WANG

2010-01-01

The main objective of this article is to study both dynamic and structural transitions of the Taylor-Couette flow,by using the dynamic transition theory and geometric theory of incompressible flows developed recently by the authors.In particular,it is shown that as the Taylor number crosses the critical number,the system undergoes either a continuous or a jump dynamic transition,dictated by the sign of a computable,nondimensional parameter R.In addition,it is also shown that the new transition states have the Taylor vortex type of flow structure,which is structurally stable.

Expectation formation in dynamic market experiments

NARCIS (Netherlands)

Heemeijer, P.

2009-01-01

People often make mistakes when predicting economic variables such as prices. It is important to understand how these predictions are formed, since people's expectations have a large impact on the development and stability of economic systems. In this thesis the expectation formation of individuals

Planetary Formation and Dynamics in Binary Systems

Science.gov (United States)

Xie, J. W.

2013-01-01

As of today, over 500 exoplanets have been detected since the first exoplanet was discovered around a solar-like star in 1995. The planets in binaries could be common as stars are usually born in binary or multiple star systems. Although current observations show that the planet host rate in multiple star systems is around 17%, this fraction should be considered as a lower limit because of noticeable selection effects against binaries in planet searches. Most of the current known planet-bearing binary systems are S-types, meaning the companion star acts as a distant satellite, typically orbiting the inner star-planet system over 100 AU away. Nevertheless, there are four systems with a smaller separation of 20 AU, including the Gamma Cephei, GJ 86, HD 41004, and HD 196885. In addition to the planets in circumprimary (S-type) orbits discussed above, planets in circumbinary (P-type) orbits have been found in only two systems. In this thesis, we mainly study the planet formation in the S-type binary systems. In chapter 1, we first summarize current observational facts of exoplanets both in single-star and binary systems, then review the theoretical models of planet formation, with special attention to the application in binary systems. Perturbative effects from stellar companions render the planet formation process in binary systems even more complex than that in single-star systems. The perturbations from a binary companion can excite planetesimal orbits, and increase their mutual impact velocities to the values that might exceed their escape velocity or even the critical velocity for the onset of eroding collisions. The intermediate stage of the formation process---from planetesimals to planetary embryos---is thus the most problematic. In the following chapters, we investigate whether and how the planet formation goes through such a problematic stage. In chapter 2, we study the effects of gas dissipation on the planetesimals' mutual accretion. We find that in a

Advanced Accelerator Concepts Final Report

Energy Technology Data Exchange (ETDEWEB)

Wurtele, Jonathan S.

2014-05-13

A major focus of research supported by this Grant has been on the ALPHA antihydrogen trap. We first trapped antihydrogen in 2010 and soon thereafter demonstrated trapping for 1000s. We now have observed resonant quantum interactions with antihydrogen. These papers in Nature and Nature Physics report the major milestones in anti-atom trapping. The success was only achieved through careful work that advanced our understanding of collective dynamics in charged particle systems, the development of new cooling and diagnostics, and in- novation in understanding how to make physics measurements with small numbers of anti-atoms. This research included evaporative cooling, autoresonant excitation of longitudinal motion, and centrifugal separation. Antihydrogen trapping by ALPHA is progressing towards the point when a important theories believed by most to hold for all physical systems, such as CPT (Charge-Parity-Time) invariance and the Weak Equivalence Principle (matter and antimatter behaving the same way under the influence of gravity) can be directly tested in a new regime. One motivation for this test is that most accepted theories of the Big Bang predict that we should observe equal amounts of matter and antimatter. However astrophysicists have found very little antimatter in the universe. Our experiment will, if successful over the next seven years, provide a new test of these ideas. Many earlier detailed and beautiful tests have been made, but the trapping of neutral antimatter allows us to explore the possibility of direct, model-independent tests. Successful cooling of the anti atoms, careful limits on systematics and increased trapping rates, all planned for our follow-up experiment (ALPHA-II) will reach unrivaled precision. CPT invariance implies that the spectra of hydrogen and antihydrogen should be identical. Spectra can be measured in principle with great precision, and any di erences we might observe would revolutionize fundamental physics. This is the

Design and Testing of 100 mK High-voltage Electrodes for AEgIS (Proc. 25th ICEC & ICMC2014 conference)

NARCIS (Netherlands)

Derking, J.H.; Liberadzka, Joanna; Koettig, T.; Bremer, J.

2015-01-01

The AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) experiment at CERN has as main goal to perform the first direct measurement of the Earth's gravitational acceleration on antihydrogen atoms within 1% precision. To reach this precision, the antihydrogen should be cooled down to

Simbol-X Formation Flight and Image Reconstruction

Science.gov (United States)

Civitani, M.; Djalal, S.; Le Duigou, J. M.; La Marle, O.; Chipaux, R.

2009-05-01

Simbol-X is the first operational mission relying on two satellites flying in formation. The dynamics of the telescope, due to the formation flight concept, raises a variety of problematic, like image reconstruction, that can be better evaluated via a simulation tools. We present here the first results obtained with Simulos, simulation tool aimed to study the relative spacecrafts navigation and the weight of the different parameters in image reconstruction and telescope performance evaluation. The simulation relies on attitude and formation flight sensors models, formation flight dynamics and control, mirror model and focal plane model, while the image reconstruction is based on the Line of Sight (LOS) concept.

Living on the edge: contrasted wood-formation dynamics in Fagus sylvatica and Pinus sylvestris under Mediterranean conditions

Directory of Open Access Journals (Sweden)

Edurne eMartinez Del Castillo

2016-03-01

Full Text Available Wood formation in European beech (Fagus sylvatica L. and Scots pine (Pinus sylvestris L. was intra-annually monitored to examine plastic responses of the xylem phenology according to altitude in one of the southernmost areas of their distribution range, i.e. in the Moncayo Natural Park, Spain. The monitoring was done from 2011 to 2013 at 1180 and 1580 m a.s.l., corresponding to the lower and upper limits of European beech forest in this region. Microcores containing phloem, cambium and xylem were collected biweekly from twenty-four trees from the beginning of March to the end of November to assess the different phases of wood formation. The samples were prepared for light microscopy to observe the following phenological phases: onset and end of cell production, onset and end of secondary wall formation in xylem cells and onset of cell maturation. The temporal dynamics of wood formation widely differed among years, altitudes and tree species. For Fagus sylvatica, the onset of cambial activity varied between the first week of May and the third week of June. Cambial activity then slowed down and stopped in summer, resulting in a length of growing season of 48–75 days. In contrast, the growing season for Pinus sylvestris started earlier and cambium remained active in autumn, leading to a period of activity varying from 139-170 days. The intra-annual wood-formation pattern is site and species-specific. Comparison with other studies shows a clear latitudinal trend in the duration of wood formation, positive for Fagus sylvatica and negative for Pinus sylvestris.

Equation of State Dependent Dynamics and Multi-messenger Signals from Stellar-mass Black Hole Formation

Science.gov (United States)

Pan, Kuo-Chuan; Liebendörfer, Matthias; Couch, Sean M.; Thielemann, Friedrich-Karl

2018-04-01

We investigate axisymmetric black hole (BH) formation and its gravitational wave (GW) and neutrino signals with self-consistent core-collapse supernova simulations of a non-rotating 40 M ⊙ progenitor star using the isotropic diffusion source approximation for the neutrino transport and a modified gravitational potential for general relativistic effects. We consider four different neutron star (NS) equations of state (EoS): LS220, SFHo, BHBΛϕ, and DD2, and study the impact of the EoS on BH formation dynamics and GW emission. We find that the BH formation time is sensitive to the EoS from 460 to >1300 ms and is delayed in multiple dimensions for ∼100–250 ms due to the finite entropy effects. Depending on the EoS, our simulations show the possibility that shock revival can occur along with the collapse of the proto-neutron star (PNS) to a BH. The gravitational waveforms contain four major features that are similar to previous studies but show extreme values: (1) a low-frequency signal (∼300–500 Hz) from core-bounce and prompt convection, (2) a strong signal from the PNS g-mode oscillation among other features, (3) a high-frequency signal from the PNS inner-core convection, and (4) signals from the standing accretion shock instability and convection. The peak frequency at the onset of BH formation reaches to ∼2.3 kHz. The characteristic amplitude of a 10 kpc object at peak frequency is detectable but close to the noise threshold of the Advanced LIGO and KAGRA, suggesting that the next-generation GW detector will need to improve the sensitivity at the kHz domain to better observe stellar-mass BH formation from core-collapse supernovae or failed supernovae.

Torque controlled rotary-shear experiments reveal pseudotachilites formation-dynamics and precursor events

Science.gov (United States)

Tisato, Nicola; Cordonnier, Benoit; De Siena, Luca; Lavier, Luc; Di Toro, Giulio

2017-04-01

Except few cases, rotary shear tests, which are designed to study dynamic friction and strengthening/weakening mechanisms in seismogenic faults, are performed by imposing, to the specimens, a slipping velocity that is pre-defined. This approach has been adopted from engineering that typically, tests man-made objects that, when functioning, spin or slide at a pre-defined velocity under a pre-defined load. On the other hand, natural earthquakes are the effect of a rupture that nucleates, propagates and arrests in the subsurface. These three phases, and the consequent emerging fault slipping velocity, are controlled by the accumulated and released energy around the seismogenic fault before, during and after the earthquake. Thus, imposing the slipping velocity in laboratory experiments might not represent the best option to uncover many aspects of earthquake nucleation and fault slipping dynamics. Here we present some experiments performed with an innovative rotary shear apparatus that uses a clock-spring that when winded provides to the rotating sample a linearly increasing torque. Thus, the nucleation of simulated events occur spontaneously when the shear stress on the slipping surface overcomes the static friction times the normal load that is controlled by a deadweight. In addition, this method allows studying precursory seismic events resembling natural slow-slip earthquakes. We report some preliminary results for a transparent polymer that has melting point 340 K and allows observing the slipping surface (i.e., the contact between the two samples). By coupling: i) the rotary shear apparatus, ii) a video camera recording at 60 fps and a iii) laser pointer we observed the formation and evolution of a melt film that forms in the slipping surface after a phase of "dry" stick-slip. After each seismic event the melt layer solidify forming a pseudotachilite that partially welds the slipping surfaces. We also present the mechanical data that show rupture strengthening in

Dynamics of bubble formation in highly viscous liquids.

Science.gov (United States)

Pancholi, Ketan; Stride, Eleanor; Edirisinghe, Mohan

2008-04-15

There has recently been considerable interest in the development of devices for the preparation of monodisperse microbubble suspensions for use as ultrasound contrast agents and drug delivery vehicles. These applications require not only a high degree of bubble uniformity but also a maximum bubble size of 8 mum, and this provides a strong motivation for developing an improved understanding of the process of bubble formation in a given device. The aim of this work was to investigate bubble formation in a T-junction device and determine the influence of the different processing parameters upon bubble size, in particular, liquid viscosity. Images of air bubble formation in a specially designed T-junction were recorded using a high-speed camera for different ratios of liquid to gas flow rate (Ql/Qg) and different liquid viscosities (microl). It was found that theoretical predictions of the flow profile in the focal region based on analysis of axisymmetric Stokes flow were accurate to within 6% when compared with the experimental data, indicating that this provided a suitable means of describing the bubble formation process. Both the theoretical and experimental results showed that Ql/Qg and mul had a significant influence upon bubble formation and eventual size, with higher flow rates and higher viscosities producing smaller bubbles. There were, however, found to be limiting values of Ql/Qg and mul beyond which no further reduction in bubble size was achieved.

Golden Jubilee photos: Welcome to the antiworld

CERN Multimedia

2004-01-01

Professor Walter Oelert, leader of the team which created the first atoms of antihydrogen at the LEAR (Low Energy Antiproton Ring).Antiparticles were predicted in the work of Paul Dirac in the 1920's, since when physicists have identified all the necessary antiparticle constituents of an antiparticle atom - antielectrons (positrons), antiprotons and antineutrons. However, an antihydrogen atom wasn't produced until the PS210 experiment at CERN in 1995. PS210 used the LEAR accelerator, which was then nearing the end of its lifetime (see Bulletin 28/04), so everything in the experiment had to work first time. After installing the equipment in spring 1995, the experiment took place in the autumn, in two hour periods over 4 weeks. The experiment team collided energetic antiprotons from LEAR with a heavy element, a challenge for them as well as the LEAR operators. Proving that antihydrogen atoms had been formed required several more weeks of data analysis, but the announcement that nine antihydrogen atoms had been ...

Studying antimatter with laser precision

CERN Multimedia

Katarina Anthony

2012-01-01

The next generation of antihydrogen trapping devices, ALPHA-2, is moving into CERN’s Antiproton Decelerator (AD) hall. This brand-new experiment will allow the ALPHA collaboration to conduct studies of antimatter with greater precision. ALPHA spokesperson Jeffrey Hangst was recently awarded a grant by the Carlsberg Foundation, which will be used to purchase equipment for the new experiment.   A 3-D view of the new magnet (in blue) and cryostat. The red lines show the paths of laser beams. LHC-type current leads for the superconducting magnets are visible on the top-right of the image. The ALPHA collaboration has been working to trap and study antihydrogen since 2006. Using antiprotons provided by CERN’s Antiproton Decelerator (AD), ALPHA was the first experiment to trap antihydrogen and to hold it long enough to study its properties. “The new ALPHA-2 experiment will use integrated lasers to probe the trapped antihydrogen,” explains Jeffrey Hangst, ALP...

Dynamics of protein aggregation and oligomer formation governed by secondary nucleation

Energy Technology Data Exchange (ETDEWEB)

Michaels, Thomas C. T., E-mail: tctm3@cam.ac.uk; Lazell, Hamish W.; Arosio, Paolo; Knowles, Tuomas P. J., E-mail: tpjk2@cam.ac.uk [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

2015-08-07

The formation of aggregates in many protein systems can be significantly accelerated by secondary nucleation, a process where existing assemblies catalyse the nucleation of new species. In particular, secondary nucleation has emerged as a central process controlling the proliferation of many filamentous protein structures, including molecular species related to diseases such as sickle cell anemia and a range of neurodegenerative conditions. Increasing evidence suggests that the physical size of protein filaments plays a key role in determining their potential for deleterious interactions with living cells, with smaller aggregates of misfolded proteins, oligomers, being particularly toxic. It is thus crucial to progress towards an understanding of the factors that control the sizes of protein aggregates. However, the influence of secondary nucleation on the time evolution of aggregate size distributions has been challenging to quantify. This difficulty originates in large part from the fact that secondary nucleation couples the dynamics of species distant in size space. Here, we approach this problem by presenting an analytical treatment of the master equation describing the growth kinetics of linear protein structures proliferating through secondary nucleation and provide closed-form expressions for the temporal evolution of the resulting aggregate size distribution. We show how the availability of analytical solutions for the full filament distribution allows us to identify the key physical parameters that control the sizes of growing protein filaments. Furthermore, we use these results to probe the dynamics of the populations of small oligomeric species as they are formed through secondary nucleation and discuss the implications of our work for understanding the factors that promote or curtail the production of these species with a potentially high deleterious biological activity.

Dynamic model based on voltage transfer curve for pattern formation in dielectric barrier glow discharge

Energy Technology Data Exchange (ETDEWEB)

Li, Ben; He, Feng; Ouyang, Jiting, E-mail: jtouyang@bit.edu.cn [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Duan, Xiaoxi [Research Center of Laser Fusion, CAEP, Mianyang 621900 (China)

2015-12-15

Simulation work is very important for understanding the formation of self-organized discharge patterns. Previous works have witnessed different models derived from other systems for simulation of discharge pattern, but most of these models are complicated and time-consuming. In this paper, we introduce a convenient phenomenological dynamic model based on the basic dynamic process of glow discharge and the voltage transfer curve (VTC) to study the dielectric barrier glow discharge (DBGD) pattern. VTC is an important characteristic of DBGD, which plots the change of wall voltage after a discharge as a function of the initial total gap voltage. In the modeling, the combined effect of the discharge conditions is included in VTC, and the activation-inhibition effect is expressed by a spatial interaction term. Besides, the model reduces the dimensionality of the system by just considering the integration effect of current flow. All these greatly facilitate the construction of this model. Numerical simulations turn out to be in good accordance with our previous fluid modeling and experimental result.

Water ordering controls the dynamic equilibrium of micelle-fibre formation in self-assembly of peptide amphiphiles.

Science.gov (United States)

Deshmukh, Sanket A; Solomon, Lee A; Kamath, Ganesh; Fry, H Christopher; Sankaranarayanan, Subramanian K R S

2016-08-24

Understanding the role of water in governing the kinetics of the self-assembly processes of amphiphilic peptides remains elusive. Here, we use a multistage atomistic-coarse-grained approach, complemented by circular dichroism/infrared spectroscopy and dynamic light scattering experiments to highlight the dual nature of water in driving the self-assembly of peptide amphiphiles (PAs). We show computationally that water cage formation and breakage near the hydrophobic groups control the fusion dynamics and aggregation of PAs in the micellar stage. Simulations also suggest that enhanced structural ordering of vicinal water near the hydrophilic amino acids shifts the equilibrium towards the fibre phase and stimulates structure and order during the PA assembly into nanofibres. Experiments validate our simulation findings; the measured infrared O-H bond stretching frequency is reminiscent of an ice-like bond which suggests that the solvated water becomes increasingly ordered with time in the assembled peptide network, thus shedding light on the role of water in a self-assembly process.

Hot spot formation and chemical reaction initiation in shocked HMX crystals with nanovoids: a large-scale reactive molecular dynamics study.

Science.gov (United States)

Zhou, Tingting; Lou, Jianfeng; Zhang, Yangeng; Song, Huajie; Huang, Fenglei

2016-07-14

We report million-atom reactive molecular dynamic simulations of shock initiation of β-cyclotetramethylene tetranitramine (β-HMX) single crystals containing nanometer-scale spherical voids. Shock induced void collapse and subsequent hot spot formation as well as chemical reaction initiation are observed which depend on the void size and impact strength. For an impact velocity of 1 km s(-1) and a void radius of 4 nm, the void collapse process includes three stages; the dominant mechanism is the convergence of upstream molecules toward the centerline and the downstream surface of the void forming flowing molecules. Hot spot formation also undergoes three stages, and the principal mechanism is kinetic energy transforming to thermal energy due to the collision of flowing molecules on the downstream surface. The high temperature of the hot spot initiates a local chemical reaction, and the breakage of the N-NO2 bond plays the key role in the initial reaction mechanism. The impact strength and void size have noticeable effects on the shock dynamical process, resulting in a variation of the predominant mechanisms leading to void collapse and hot spot formation. Larger voids or stronger shocks result in more intense hot spots and, thus, more violent chemical reactions, promoting more reaction channels and generating more reaction products in a shorter duration. The reaction products are mainly concentrated in the developed hot spot, indicating that the chemical reactivity of the hmx crystal is greatly enhanced by void collapse. The detailed information derived from this study can aid a thorough understanding of the role of void collapse in hot spot formation and the chemical reaction initiation of explosives.

Dynamics of uranium ore formation in the basement and frame of the Streltsovskaya Caldera

International Nuclear Information System (INIS)

Petrov, V.; Schukin, S.

2014-01-01

The analysis of geological-geophysical, paleo-geodynamics, mineralogical, geochemical, isotope, geochronological, and thermo-baro-geochemical data allow us to offer a model of uranium ore formation dynamics in the basement and frame of the Streltsovskaya Caldera connected to activity of the fluid-conducting fault zones network with the aim to identify prospective areas The most ancient fluid-conducting structures are inter-block NE-SW, NNE-submeridional, NW-SE and, probably, WNW-sub-latitudinal faults. The oldest NE-SW faults and schistosity zones were formed during Proterozoic tectonic cycle (TC) with reactivation in T3-J2 time due to global reorganization of stress field and reactivation of tectonic movements. The NNE-submeridional and NW-SE faults were extended with increased fluid permeability during Caledonian and Variscan TCs. They also were reactivated in the process of Late Mesozoic tectonic and magmatic activation (TMA). Thus already at early stages of geotectonic evolution within the intersection of NE-SW (N-Urulyunguyevskiy fault) and NNE-submeridional (Chindachinskaya zone) faults the areas of increased fluid and magmatic activity were formed. The dynamics of fault formation in the basement and frame of the Streltsovskaya caldera and its volcano-sedimentary cover differs. In the basement and granite framework NE-SW, NNEsubmeridional and NW-SE faults are interblock structures of the I rank. Their intersection formed areas of long-term circulation of hydrothermal solutions and telescopic appearance of multi-age metasomatites that created conditions for localizing of vein-stockwork mineralization. In volcanosedimentary cover the NE-SW and NNE-submeridional faults should be considered as interblock structures of the I rank where intersections provided inflow of ore-bearing solutions and their redistribution within the cover. Here the main ore distributing role belongs to NW-SE shears. They are intrablock II rank structures which were formed due to dextral

Control of Polymer Glass Formation Behaviour Using Molecular Diluents and Dynamic Interfaces

Science.gov (United States)

Mangalara, Jayachandra Hari

The end use application of polymeric materials is mainly determined by their viscosity, thermal stability and processability. These properties are primarily determined by the segmental relaxation time (taualpha) of the polymer and its glass state modulus, which determines its glassy mechanical response. Developing design principles to obtain rational control over these properties would enable fabrication of new polymers or polymer blends with improved thermal stability, enhanced processability and better mechanical robustness of the material. Introduction of diluents and nanostructuring of the material serve as invaluable tools for altering polymers' glass transition and associated dynamic and mechanical properties. Besides providing guidelines for technologically important improvements in processability, glassy mechanical properties, and transport behavior, diluent effects and behavior of nanostructured materials can provide insights into the fundamental physics of the glass transition, for example, by elucidating the interrelation between high- and low-frequency structural relaxation processes. It has been previously suggested that there exists a similarity between how diluents and interfaces impact the glass formation behavior of the polymer, raising the possibility that the effects of these two polymer modifications may be separate manifestations of a common set of physics in glass forming polymers. Here we address several interrelated questions in the understanding of glass formation in polymer/diluent blends and nanostructured polymers. First, what is the relationship between a diluent's molecular structure and its impact on a polymer's glass formation behavior? How does this compare to the effect of interfaces? Second, how does the introduction of diluents impact the role of interfaces in modifying polymer glass formation? Third, how does the introduction of interfaces impact metrology of the polymer glass transition? Finally, we address a major open

Molecular dynamics study of amorphous pocket formation in Si at low energies and its application to improve binary collision models

International Nuclear Information System (INIS)

Santos, Ivan; Marques, Luis A.; Pelaz, Lourdes; Lopez, Pedro

2007-01-01

In this paper, we present classical molecular dynamics results about the formation of amorphous pockets in silicon for energy transfers below the displacement threshold. While in binary collision simulations ions with different masses generate the same number of Frenkel pairs for the same deposited nuclear energy, in molecular dynamics simulations the amount of damage and its complexity increase with ion mass. We demonstrate that low-energy transfers to target atoms are able to generate complex damage structures. We have determined the conditions that have to be fulfilled to produce amorphous pockets, showing that the order-disorder transition depends on the particular competition between melting and heat diffusion processes. We have incorporated these molecular dynamics results in an improved binary collision model that is able to provide a good description of damage with a very low computational cost

Characterizing Suspension Plasma Spray Coating Formation Dynamics through Curvature Measurements

Science.gov (United States)

Chidambaram Seshadri, Ramachandran; Dwivedi, Gopal; Viswanathan, Vaishak; Sampath, Sanjay

2016-12-01

Suspension plasma spraying (SPS) enables the production of variety of microstructures with unique mechanical and thermal properties. In SPS, a liquid carrier (ethanol/water) is used to transport the sub-micrometric feedstock into the plasma jet. Considering complex deposition dynamics of SPS technique, there is a need to better understand the relationships among spray conditions, ensuing particle behavior, deposition stress evolution and resultant properties. In this study, submicron yttria-stabilized zirconia particles suspended in ethanol were sprayed using a cascaded arc plasma torch. The stresses generated during the deposition of the layers (termed evolving stress) were monitored via the change in curvature of the substrate measured using an in situ measurement apparatus. Depending on the deposition conditions, coating microstructures ranged from feathery porous to dense/cracked deposits. The evolving stresses and modulus were correlated with the observed microstructures and visualized via process maps. Post-deposition bi-layer curvature measurement via low temperature thermal cycling was carried out to quantify the thermo-elastic response of different coatings. Lastly, preliminary data on furnace cycle durability of different coating microstructures were evaluated. This integrated study involving in situ diagnostics and ex situ characterization along with process maps provides a framework to describe coating formation mechanisms, process parametrics and microstructure description.

Experiments with low-energy antimatter

Directory of Open Access Journals (Sweden)

Consolati G.

2015-01-01

Full Text Available Investigations on antimatter allow us to shed light on fundamental issues of contemporary physics. The only antiatom presently available, antihydrogen, is produced making use of the Antiproton Decelerator (AD facility at CERN. International collaborations currently on the floor (ALPHA, ASACUSA and ATRAP have succeeded in producing antihydrogen and are now involved in its confinement and manipulation. The AEGIS experiment is currently completing the commissioning of the apparatus which will generate and manipulate antiatoms. The present paper, after a report on the main results achieved with antihydrogen physics, gives an overview of the AEGIS experiment, describes its current status and discusses its first target.

Temporal dynamic of wood formation in Pinus cembra along the alpine treeline ecotone and the effect of climate variables.

Science.gov (United States)

Gruber, Andreas; Baumgartner, Daniel; Zimmermann, Jolanda; Oberhuber, Walter

2009-06-01

We determined the temporal dynamic of cambial activity and xylem development of stone pine (Pinus cembra L.) throughout the treeline ecotone. Repeated micro-sampling of the developing tree ring was carried out during the growing seasons 2006 and 2007 at the timberline (1950 m a.s.l.), treeline (2110 m a.s.l.) and within the krummholz belt (2180 m a.s.l.) and the influence of climate variables on intra-annual wood formation was determined.At the beginning of both growing seasons, highest numbers of cambial and enlarging cells were observed at the treeline. Soil temperatures at time of initiation of cambial activity were c. 1.5 °C higher at treeline (open canopy) compared to timberline (closed canopy), suggesting that a threshold root-zone temperature is involved in triggering onset of above ground stem growth.The rate of xylem cell production determined in two weekly intervals during June through August 2006-2007 was significantly correlated with air temperature (temperature sums expressed as degree-days and mean daily maximum temperature) at the timberline only. Lack of significant relationships between tracheid production and temperature variables at the treeline and within the krummholz belt support past dendroclimatological studies that more extreme environmental conditions (e.g., wind exposure, frost desiccation, late frost) increasingly control tree growth above timberline.Results of this study revealed that spatial and temporal (i.e. year-to-year) variability in timing and dynamic of wood formation of Pinus cembra is strongly influenced by local site factors within the treeline ecotone and the dynamics of seasonal temperature variation, respectively.

Synergistic enhancement of micro-bubble formation in ultrasound irradiated H2O-CH3OH mixtures probed by dynamic light scattering

International Nuclear Information System (INIS)

Pai, M.R.; Hassan, P.A.; Bharadwaj, S.R.; Kulshreshtha, S.K.

2008-01-01

This report investigates the formation of micro-bubbles in water-methanol mixtures upon ultrasound irradiation and its correlation with the yield of H 2 obtained as a result of sono-chemical splitting of water. The yield of hydrogen produced by sono-chemical reaction is monitored at different compositions of water-methanol mixtures. The evidence for the formation of micro-bubbles upon ultrasound irradiation is obtained by the dynamic light scattering technique. Micro-bubble formation during ultrasound irradiation of water-methanol mixtures, their stability and size distribution, has been quantitatively estimated. The effect of composition of the water-methanol mixture and duration of irradiation on the extent of bubble formation has been inferred from the changes in the light scattering intensity and its time correlation function. Exceptional stability of micro-bubbles without any additives is observed at a certain composition of the water-methanol mixture (4:3, v/v). The extent of micro-bubbles formed in the mixture correlates well with the yield of hydrogen detected. (authors)

μCT-based, in vivo dynamic bone histomorphometry allows 3D evaluation of the early responses of bone resorption and formation to PTH and alendronate combination therapy.

Science.gov (United States)

de Bakker, Chantal M J; Altman, Allison R; Tseng, Wei-Ju; Tribble, Mary Beth; Li, Connie; Chandra, Abhishek; Qin, Ling; Liu, X Sherry

2015-04-01

Current osteoporosis treatments improve bone mass by increasing net bone formation: anti-resorptive drugs such as bisphosphonates block osteoclast activity, while anabolic agents such as parathyroid hormone (PTH) increase bone remodeling, with a greater effect on formation. Although these drugs are widely used, their role in modulating formation and resorption is not fully understood, due in part to technical limitations in the ability to longitudinally assess bone remodeling. Importantly, it is not known whether or not PTH-induced bone formation is independent of resorption, resulting in controversy over the effectiveness of combination therapies that use both PTH and an anti-resorptive. In this study, we developed a μCT-based, in vivo dynamic bone histomorphometry technique for rat tibiae, and applied this method to longitudinally track changes in bone resorption and formation as a result of treatment with alendronate (ALN), PTH, or combination therapy of both PTH and ALN (PTH+ALN). Correlations between our μCT-based measures of bone formation and measures of bone formation based on calcein-labeled histology (r=0.72-0.83) confirm the accuracy of this method. Bone remodeling parameters measured through μCT-based in vivo dynamic bone histomorphometry indicate an increased rate of bone formation in rats treated with PTH and PTH+ALN, together with a decrease in bone resorption measures in rats treated with ALN and PTH+ALN. These results were further supported by traditional histology-based measurements, suggesting that PTH was able to induce bone formation while bone resorption was suppressed. Copyright © 2014 Elsevier Inc. All rights reserved.

Modularity in New Market Formation

DEFF Research Database (Denmark)

Sanchez, Ron; Hang, Chang Chieh

2017-01-01

In this paper we appraise the ways in which use of closed-system proprietary product architectures versus open-system modular product architectures is likely to influence the dynamics and trajectory of new product market formation. We compare the evolutions of new markets in China for gas......-powered two-wheeled vehicles (G2WVs) based (initially) on closed-system proprietary architectures and for electric-powered two-wheeled vehicles (E2WVs) based on open-system modular architectures. We draw on this comparison to suggest ways in which the use of the two different kinds of architectures...... as the basis for new kinds of products may result in very different patterns and speeds of new market formation. We then suggest some key implications of the different dynamics of market formation associated with open-system modular architectures for both the competence-based strategic management (CBSM...

Dynamic behavior of a social model for opinion formation

Science.gov (United States)

Bordogna, Clelia M.; Albano, Ezequiel V.

2007-12-01

The dynamic behavior of a social group influenced by both a strong leader and the mass media, which is modeled according to the social impact theory, is studied under two situations: (i) The strong leader changes his/her state of opinion periodically while the mass media are not considered. In this case, the leader is capable of driving the group between a dynamically ordered state with a weak leader-group coupling (high-frequency regime) and a dynamically disordered state where the group follows the opinion of the leader (low-frequency regime). (ii) The mass-media change periodically their message and have to compete with a strong leader that keeps his/her state of opinion unchanged. In this case, the mass media require an amplitude threshold in order to overcome the influence of the leader and drive the system into a dynamically disordered state. The dynamic behavior characteristic of the studied social opinion model shares many features of physical systems that are relevant in the fields of statistical mechanics and condensed matter.

Spontaneous and Flow-Driven Interfacial Phase Change: Dynamics of Microemulsion Formation at the Pore Scale.

Science.gov (United States)

Tagavifar, Mohsen; Xu, Ke; Jang, Sung Hyun; Balhoff, Matthew T; Pope, Gary A

2017-11-14

The dynamic behavior of microemulsion-forming water-oil-amphiphiles mixtures is investigated in a 2.5D micromodel. The equilibrium phase behavior of such mixtures is well-understood in terms of macroscopic phase transitions. However, what is less understood and where experimental data are lacking is the coupling between the phase change and the bulk flow. Herein, we study the flow of an aqueous surfactant solution-oil mixture in porous media and analyze the dependence of phase formation and spatial phase configurations on the bulk flow rate. We find that a microemulsion forms instantaneously as a boundary layer at the initial surface of contact between the surfactant solution and oil. The boundary layer is temporally continuous because of the imposed convection. In addition to the imposed flow, we observe spontaneous pulsed Marangoni flows that drag the microemulsion and surfactant solution into the oil stream, forming large (macro)emulsion droplets. The formation of the microemulsion phase at the interface distinguishes the situation from that of the more common Marangoni flow with only two phases present. Additionally, an emulsion forms via liquid-liquid nucleation or the Ouzo effect (i.e., spontaneous emulsification) at low flow rates and via mechanical mixing at high flow rates. With regard to multiphase flow, contrary to the common belief that the microemulsion is the wetting liquid, we observe that the minor oil phase wets the solid surface. We show that a layered flow pattern is formed because of the out-of-equilibrium phase behavior at high volumetric flow rates (order of 2 m/day) where advection is much faster than the diffusive interfacial mass transfer and transverse mixing, which promote equilibrium behavior. At lower flow rates (order of 30 cm/day), however, the dynamic and equilibrium phase behaviors are well-correlated. These results clearly show that the phase change influences the macroscale flow behavior.

ON THE STAR FORMATION LAW FOR SPIRAL AND IRREGULAR GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Elmegreen, Bruce G., E-mail: bge@us.ibm.com [IBM Research Division, T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States)

2015-12-01

A dynamical model for star formation on a galactic scale is proposed in which the interstellar medium is constantly condensing to star-forming clouds on the dynamical time of the average midplane density, and the clouds are constantly being disrupted on the dynamical timescale appropriate for their higher density. In this model, the areal star formation rate scales with the 1.5 power of the total gas column density throughout the main regions of spiral galaxies, and with a steeper power, 2, in the far outer regions and in dwarf irregular galaxies because of the flaring disks. At the same time, there is a molecular star formation law that is linear in the main and outer parts of disks and in dIrrs because the duration of individual structures in the molecular phase is also the dynamical timescale, canceling the additional 0.5 power of surface density. The total gas consumption time scales directly with the midplane dynamical time, quenching star formation in the inner regions if there is no accretion, and sustaining star formation for ∼100 Gyr or more in the outer regions with no qualitative change in gas stability or molecular cloud properties. The ULIRG track follows from high densities in galaxy collisions.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Pulsed formation and readout of dynamic holograms in a photorefractive GaAs:Cr crystal

Science.gov (United States)

Andreeva, N. P.; Barashkov, M. S.; Bel'dyugin, Igor'M.; Kruzhilin, Yu I.; Petnikova, V. M.; Umnov, A. F.; Kharchenko, M. A.; Shuvalov, Vladimir V.

1989-12-01

An experimental investigation was made of the energy (diffraction efficiency) and time (formation, storage, readout) parameters of four-wave mixing in GaAs:Cr. An investigation of the dynamics of the leading edge of a nonlinear response pulse could become an effective method for pulsed spectroscopy of photorefractive materials.

Dynamical formation of spatially localized arrays of aligned nanowires in plastic films with magnetic anisotropy.

Science.gov (United States)

Fragouli, Despina; Buonsanti, Raffaella; Bertoni, Giovanni; Sangregorio, Claudio; Innocenti, Claudia; Falqui, Andrea; Gatteschi, Dante; Cozzoli, Pantaleo Davide; Athanassiou, Athanassia; Cingolani, Roberto

2010-04-27

We present a simple technique for magnetic-field-induced formation, assembling, and positioning of magnetic nanowires in a polymer film. Starting from a polymer/iron oxide nanoparticle casted solution that is allowed to dry along with the application of a weak magnetic field, nanocomposite films incorporating aligned nanocrystal-built nanowire arrays are obtained. The control of the dimensions of the nanowires and of their localization across the polymer matrix is achieved by varying the duration of the applied magnetic field, in combination with the evaporation dynamics. These multifunctional anisotropic free-standing nanocomposite films, which demonstrate high magnetic anisotropy, can be used in a wide field of technological applications, ranging from sensors to microfluidics and magnetic devices.

A dynamic capacity degradation model and its applications considering varying load for a large format Li-ion battery

International Nuclear Information System (INIS)

Ouyang, Minggao; Feng, Xuning; Han, Xuebing; Lu, Languang; Li, Zhe; He, Xiangming

2016-01-01

Highlights: • A dynamic capacity degradation model for large format Li-ion battery is proposed. • The change of the model parameters directly link with the degradation mechanisms. • The model can simulate the fading behavior of Li-ion battery under varying loads. • The model can help evaluate the longevity of a battery system under specific load. • The model can help predict the evolution of cell variations within a battery pack. - Abstract: The capacity degradation of the lithium ion battery should be well predicted during battery system design. Therefore, high-fidelity capacity degradation models that are suitable for the task of capacity prediction are required. This paper proposes a novel capacity degradation model that can simulate the degradation dynamics under varying working conditions for large-format lithium ion batteries. The degradation model is built based on a mechanistic and prognostic model (MPM) whose parameters are closely linked with the degradation mechanisms of lithium ion batteries. Chemical kinetics was set to drive the parameters of the MPM to change as capacity degradation continues. With the dynamic parameters of the MPM, the capacity predicted by the degradation model decreases as the cycle continues. Accelerated aging tests were conducted on three types of commercial lithium ion batteries to calibrate the capacity degradation model. The good fit with the experimental data indicates that the model can capture the degradation mechanisms well for different types of commercial lithium ion batteries. Furthermore, the calibrated model can be used to (1) evaluate the longevity of a battery system under a specific working load and (2) predict the evolution of cell variations within a battery pack when different cell works at different conditions. Correlated applications are discussed using the calibrated degradation model.

Non-adiabatic molecular dynamics investigation of photoionization state formation and lifetime in Mn²⁺-doped ZnO quantum dots.

Science.gov (United States)

Fischer, Sean A; Lingerfelt, David B; May, Joseph W; Li, Xiaosong

2014-09-07

The unique electronic structure of Mn(2+)-doped ZnO quantum dots gives rise to photoionization states that can be used to manipulate the magnetic state of the material and to generate zero-reabsorption luminescence. Fast formation and long non-radiative decay of this photoionization state is a necessary requirement for these important applications. In this work, surface hopping based non-adiabatic molecular dynamics are used to demonstrate the fast formation of a metal-to-ligand charge transfer state in a Mn(2+)-doped ZnO quantum dot. The formation occurs on an ultrafast timescale and is aided by the large density of states and significant mixing of the dopant Mn(2+) 3dt2 levels with the valence-band levels of the ZnO lattice. The non-radiative lifetime of the photoionization states is also investigated.

Quantum dynamics of the Eley-Rideal hydrogen formation reaction on graphite at typical interstellar cloud conditions.

Science.gov (United States)

Casolo, Simone; Martinazzo, Rocco; Bonfanti, Matteo; Tantardini, Gian Franco

2009-12-31

Eley-Rideal formation of hydrogen molecules on graphite, as well as competing collision induced processes, are investigated quantum dynamically at typical interstellar cloud conditions, focusing in particular on gas-phase temperatures below 100 K, where much of the chemistry of the so-called diffuse clouds takes place on the surface of bare carbonaceous dust grains. Collisions of gas-phase hydrogen atoms with both chemisorbed and physisorbed species are considered using available potential energy surfaces (Sha et al., J. Chem. Phys.2002 116, 7158), and state-to-state, energy-resolved cross sections are computed for a number of initial vibrational states of the hydrogen atoms bound to the surface. Results show that (i) product molecules are internally hot in both cases, with vibrational distributions sharply peaked around few (one or two) vibrational levels, and (ii) cross sections for chemisorbed species are 2-3x smaller than those for physisorbed ones. In particular, we find that H(2) formation cross sections out of chemically bound species decrease steadily when the temperature drops below approximately 1000 K, and this is likely due to a quantum reflection phenomenon. This suggests that such Eley-Rideal reaction is all but efficient in the relevant gas-phase temperature range, even when gas-phase H atoms happen to chemisorb barrierless to the surface as observed, e.g., for forming so-called para dimers. Comparison with results from classical trajectory calculations highlights the need of a quantum description of the dynamics in the astrophysically relevant energy range, whereas preliminary results of an extensive first-principles investigation of the reaction energetics reveal the importance of the adopted substrate model.

Nonlinear dynamics of pattern formation and pattern recognition in the rabbit olfactory bulb

Science.gov (United States)

Baird, Bill

1986-10-01

A mathematical model of the process of pattern recognition in the first olfactory sensory cortex of the rabbit is presented. It explains the formation and alteration of spatial patterns in neural activity observed experimentally during classical Pavlovian conditioning. On each inspiration of the animal, a surge of receptor input enters the olfactory bulb. EEG activity recorded at the surface of the bulb undergoes a transition from a low amplitude background state of temporal disorder to coherent oscillation. There is a distinctive spatial pattern of rms amplitude in this oscillation which changes reliably to a second pattern during each successful recognition by the animal of a conditioned stimulus odor. When a new odor is paired as conditioned stimulus, these patterns are replaced by new patterns that stabilize as the animal adapts to the new environment. I will argue that a unification of the theories of pattern formation and associative memory is required to account for these observations. This is achieved in a model of the bulb as a discrete excitable medium with spatially inhomogeneous coupling expressed by a connection matrix. The theory of multiple Hopf bifurcations is employed to find coupled equations for the amplitudes of competing unstable oscillatory modes. These may be created in the system by proper coupling and selectively evoked by specific classes of inputs. This allows a view of limit cycle attractors as “stored” fixed points of a gradient vector field and thereby recovers the more familiar dynamical systems picture of associative memory.

Andreev Bound States Formation and Quasiparticle Trapping in Quench Dynamics Revealed by Time-Dependent Counting Statistics.

Science.gov (United States)

Souto, R Seoane; Martín-Rodero, A; Yeyati, A Levy

2016-12-23

We analyze the quantum quench dynamics in the formation of a phase-biased superconducting nanojunction. We find that in the absence of an external relaxation mechanism and for very general conditions the system gets trapped in a metastable state, corresponding to a nonequilibrium population of the Andreev bound states. The use of the time-dependent full counting statistics analysis allows us to extract information on the asymptotic population of even and odd many-body states, demonstrating that a universal behavior, dependent only on the Andreev state energy, is reached in the quantum point contact limit. These results shed light on recent experimental observations on quasiparticle trapping in superconducting atomic contacts.

Traction force dynamics predict gap formation in activated endothelium

International Nuclear Information System (INIS)

Valent, Erik T.; Nieuw Amerongen, Geerten P. van; Hinsbergh, Victor W.M. van; Hordijk, Peter L.

2016-01-01

In many pathological conditions the endothelium becomes activated and dysfunctional, resulting in hyperpermeability and plasma leakage. No specific therapies are available yet to control endothelial barrier function, which is regulated by inter-endothelial junctions and the generation of acto-myosin-based contractile forces in the context of cell-cell and cell-matrix interactions. However, the spatiotemporal distribution and stimulus-induced reorganization of these integral forces remain largely unknown. Traction force microscopy of human endothelial monolayers was used to visualize contractile forces in resting cells and during thrombin-induced hyperpermeability. Simultaneously, information about endothelial monolayer integrity, adherens junctions and cytoskeletal proteins (F-actin) were captured. This revealed a heterogeneous distribution of traction forces, with nuclear areas showing lower and cell-cell junctions higher traction forces than the whole-monolayer average. Moreover, junctional forces were asymmetrically distributed among neighboring cells. Force vector orientation analysis showed a good correlation with the alignment of F-actin and revealed contractile forces in newly formed filopodia and lamellipodia-like protrusions within the monolayer. Finally, unstable areas, showing high force fluctuations within the monolayer were prone to form inter-endothelial gaps upon stimulation with thrombin. To conclude, contractile traction forces are heterogeneously distributed within endothelial monolayers and force instability, rather than force magnitude, predicts the stimulus-induced formation of intercellular gaps. - Highlights: • Endothelial monolayers exert dynamic- and heterogeneous traction forces. • High traction forces correlate with junctional areas and the F-actin cytoskeleton. • Newly formed inter-endothelial gaps are characterized by opposing traction forces. • Force stability is a key feature controlling endothelial permeability.

Traction force dynamics predict gap formation in activated endothelium

Energy Technology Data Exchange (ETDEWEB)

Valent, Erik T.; Nieuw Amerongen, Geerten P. van; Hinsbergh, Victor W.M. van; Hordijk, Peter L., E-mail: p.hordijk@vumc.nl

2016-09-10

In many pathological conditions the endothelium becomes activated and dysfunctional, resulting in hyperpermeability and plasma leakage. No specific therapies are available yet to control endothelial barrier function, which is regulated by inter-endothelial junctions and the generation of acto-myosin-based contractile forces in the context of cell-cell and cell-matrix interactions. However, the spatiotemporal distribution and stimulus-induced reorganization of these integral forces remain largely unknown. Traction force microscopy of human endothelial monolayers was used to visualize contractile forces in resting cells and during thrombin-induced hyperpermeability. Simultaneously, information about endothelial monolayer integrity, adherens junctions and cytoskeletal proteins (F-actin) were captured. This revealed a heterogeneous distribution of traction forces, with nuclear areas showing lower and cell-cell junctions higher traction forces than the whole-monolayer average. Moreover, junctional forces were asymmetrically distributed among neighboring cells. Force vector orientation analysis showed a good correlation with the alignment of F-actin and revealed contractile forces in newly formed filopodia and lamellipodia-like protrusions within the monolayer. Finally, unstable areas, showing high force fluctuations within the monolayer were prone to form inter-endothelial gaps upon stimulation with thrombin. To conclude, contractile traction forces are heterogeneously distributed within endothelial monolayers and force instability, rather than force magnitude, predicts the stimulus-induced formation of intercellular gaps. - Highlights: • Endothelial monolayers exert dynamic- and heterogeneous traction forces. • High traction forces correlate with junctional areas and the F-actin cytoskeleton. • Newly formed inter-endothelial gaps are characterized by opposing traction forces. • Force stability is a key feature controlling endothelial permeability.

Molecular dynamics study of methane hydrate formation at a water/methane interface.

Science.gov (United States)

Zhang, Junfang; Hawtin, R W; Yang, Ye; Nakagava, Edson; Rivero, M; Choi, S K; Rodger, P M

2008-08-28

We present molecular dynamics simulation results of a liquid water/methane interface, with and without an oligomer of poly(methylaminoethylmethacrylate), PMAEMA. PMAEMA is an active component of a commercial low dosage hydrate inhibitor (LDHI). Simulations were performed in the constant NPT ensemble at temperatures of 220, 235, 240, 245, and 250 K and a pressure of 300 bar. The simulations show the onset of methane hydrate growth within 30 ns for temperatures below 245 K in the methane/water systems; at 240 K there is an induction period of ca. 20 ns, but at lower temperatures growth commences immediately. The simulations were analyzed to calculate hydrate content, the propensity for hydrogen bond formation, and how these were affected by both temperature and the presence of the LDHI. As expected, both the hydrogen bond number and hydrate content decreased with increasing temperature, though little difference was observed between the lowest two temperatures considered. In the presence of PMAEMA, the temperature below which sustained hydrate growth occurred was observed to decrease. Some of the implications for the role of PMAEMA in LDHIs are discussed.

Real time observation of the excimer formation dynamics of a gas phase benzene dimer by picosecond pump-probe spectroscopy.

Science.gov (United States)

Miyazaki, Mitsuhiko; Fujii, Masaaki

2015-10-21

We observed the real-time excimer (EXC) formation dynamics of a gas phase benzene dimer (Bz2) cluster after photo-excitation to the S1 state by applying an ionization detected picosecond transient absorption method for probing the visible EXC absorption for the first time. The time evolution of the EXC absorption from the S1 0(0) level shows a rise that is well fitted by a single exponential function with a time constant of 18 ± 2 ps. The structure of the Bz dimer has a T-shaped structure in the ground electronic state, and that in the EXC state is a parallel sandwich (SW) structure. Thus, the observed rise time corresponds to the structural change from the T to the SW structures, which directly shows the EXC formation. On the other hand, the EXC formation after excitation of the S1 6(1) vibrational level of the stem site showed a faster rise of the time constant of 10 ± 2 ps. Supposing equilibrium between the EXC and the local excited states, it followed that the intramolecular vibrational energy redistribution rate of the 6(1) level is largely enhanced and becomes faster than the EXC formation reaction.

Tensegrity Models and Shape Control of Vehicle Formations

OpenAIRE

Nabet, Benjamin; Leonard, Naomi Ehrich

2009-01-01

Using dynamic models of tensegrity structures, we derive provable, distributed control laws for stabilizing and changing the shape of a formation of vehicles in the plane. Tensegrity models define the desired, controlled, multi-vehicle system dynamics, where each node in the tensegrity structure maps to a vehicle and each interconnecting strut or cable in the structure maps to a virtual interconnection between vehicles. Our method provides a smooth map from any desired planar formation shape ...

Formation dynamics of UV and EUV induced hydrogen plasma

NARCIS (Netherlands)

Dolgov, A.A.; Lee, Christopher James; Yakushev, O.; Lopaev, D.V.; Abrikosov, A.; Krivtsun, V.M.; Zotovich, A.; Bijkerk, F.

2014-01-01

The comparative study of the dynamics of ultraviolet (UV) and extreme ultraviolet (EUV) induced hydrogen plasma was performed. It was shown that for low H2 pressures and bias voltages, the dynamics of the two plasmas are significantly different. In the case of UV radiation, the plasma above the

Multicolor photometry of the merging galaxy cluster A2319: Dynamics and star formation properties

Energy Technology Data Exchange (ETDEWEB)

Yan, Peng-Fei; Yuan, Qi-Rong [Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023 (China); Zhang, Li [QuFu Education Bureau, QuFu 273100 (China); Zhou, Xu, E-mail: pfyan0822@sina.com, E-mail: yuanqirong@njnu.edu.cn [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2014-05-01

Asymmetric X-ray emission and a powerful cluster-scale radio halo indicate that A2319 is a merging cluster of galaxies. This paper presents our multicolor photometry for A2319 with 15 optical intermediate filters in the Beijing-Arizona-Taiwan-Connecticut (BATC) system. There are 142 galaxies with known spectroscopic redshifts within the viewing field of 58' × 58' centered on this rich cluster, including 128 member galaxies (called sample I). A large velocity dispersion in the rest frame, 1622{sub −70}{sup +91} km s{sup –1}, suggests merger dynamics in A2319. The contour map of projected density and localized velocity structure confirm the so-called A2319B substructure, at ∼10' northwest to the main concentration A2319A. The spectral energy distributions (SEDs) of more than 30,000 sources are obtained in our BATC photometry down to V ∼ 20 mag. A u-band (∼3551 Å) image with better seeing and spatial resolution, obtained with the Bok 2.3 m telescope at Kitt Peak, is taken to make star-galaxy separation and distinguish the overlapping contamination in the BATC aperture photometry. With color-color diagrams and photometric redshift technique, 233 galaxies brighter than h {sub BATC} = 19.0 are newly selected as member candidates after an exclusion of false candidates with contaminated BATC SEDs by eyeball-checking the u-band Bok image. The early-type galaxies are found to follow a tight color-magnitude correlation. Based on sample I and the enlarged sample of member galaxies (called sample II), subcluster A2319B is confirmed. The star formation properties of cluster galaxies are derived with the evolutionary synthesis model, PEGASE, assuming a Salpeter initial mass function and an exponentially decreasing star formation rate (SFR). A strong environmental effect on star formation histories is found in the manner that galaxies in the sparse regions have various star formation histories, while galaxies in the dense regions are found to have

3D time-lapse analysis of Rab11/FIP5 complex: spatiotemporal dynamics during apical lumen formation.

Science.gov (United States)

Mangan, Anthony; Prekeris, Rytis

2015-01-01

Fluorescent imaging of fixed cells grown in two-dimensional (2D) cultures is one of the most widely used techniques for observing protein localization and distribution within cells. Although this technique can also be applied to polarized epithelial cells that form three-dimensional (3D) cysts when grown in a Matrigel matrix suspension, there are still significant limitations in imaging cells fixed at a particular point in time. Here, we describe the use of 3D time-lapse imaging of live cells to observe the dynamics of apical membrane initiation site (AMIS) formation and lumen expansion in polarized epithelial cells.

Prospects for comparison of matter and antimatter gravitation with ALPHA-g

Science.gov (United States)

Bertsche, W. A.

2018-03-01

The ALPHA experiment has recently entered an expansion phase of its experimental programme, driven in part by the expected benefits of conducting experiments in the framework of the new AD + ELENA antiproton facility at CERN. With antihydrogen trapping now a routine operation in the ALPHA experiment, the collaboration is leading progress towards precision atomic measurements on trapped antihydrogen atoms, with the first excitation of the 1S-2S transition and the first measurement of the antihydrogen hyperfine spectrum (Ahmadi et al. 2017 Nature 541, 506-510 (doi:10.1038/nature21040); Nature 548, 66-69 (doi:10.1038/nature23446)). We are building on these successes to extend our physics programme to include a measurement of antimatter gravitation. We plan to expand a proof-of-principle method (Amole et al. 2013 Nat. Commun. 4, 1785 (doi:10.1038/ncomms2787)), first demonstrated in the original ALPHA apparatus, and perform a precise measurement of antimatter gravitational acceleration with the aim of achieving a test of the weak equivalence principle at the 1% level. The design of this apparatus has drawn from a growing body of experience on the simulation and verification of antihydrogen orbits confined within magnetic-minimum atom traps. The new experiment, ALPHA-g, will be an additional atom-trapping apparatus located at the ALPHA experiment with the intention of measuring antihydrogen gravitation. This article is part of the Theo Murphy meeting issue 'Antiproton physics in the ELENA era'.

Prospects for comparison of matter and antimatter gravitation with ALPHA-g.

Science.gov (United States)

Bertsche, W A

2018-03-28

The ALPHA experiment has recently entered an expansion phase of its experimental programme, driven in part by the expected benefits of conducting experiments in the framework of the new AD + ELENA antiproton facility at CERN. With antihydrogen trapping now a routine operation in the ALPHA experiment, the collaboration is leading progress towards precision atomic measurements on trapped antihydrogen atoms, with the first excitation of the 1S-2S transition and the first measurement of the antihydrogen hyperfine spectrum (Ahmadi et al. 2017 Nature 541 , 506-510 (doi:10.1038/nature21040); Nature 548 , 66-69 (doi:10.1038/nature23446)). We are building on these successes to extend our physics programme to include a measurement of antimatter gravitation. We plan to expand a proof-of-principle method (Amole et al. 2013 Nat. Commun. 4 , 1785 (doi:10.1038/ncomms2787)), first demonstrated in the original ALPHA apparatus, and perform a precise measurement of antimatter gravitational acceleration with the aim of achieving a test of the weak equivalence principle at the 1% level. The design of this apparatus has drawn from a growing body of experience on the simulation and verification of antihydrogen orbits confined within magnetic-minimum atom traps. The new experiment, ALPHA-g, will be an additional atom-trapping apparatus located at the ALPHA experiment with the intention of measuring antihydrogen gravitation.This article is part of the Theo Murphy meeting issue 'Antiproton physics in the ELENA era'. © 2018 The Authors.

Trajectories of Identity Formation Modes and Their Personality Context in Adolescence.

Science.gov (United States)

Topolewska-Siedzik, Ewa; Cieciuch, Jan

2018-04-01

Identity formation is a dynamic process during adolescence. Trajectories of identity formation were assessed longitudinally in early and middle adolescents, taking into account the personality underpinnings of this process. Identity formation was conceptualized according to the circumplex of identity formation modes. The model distinguishes basic modes rooted in Marcia's categories of exploration and commitment. Plasticity and stability, the two higher order Big Five meta-traits, were used to assess personality underpinnings. This study includes five measurement waves over 1.5 years and involves 1,839 Polish participants; 914 early adolescents (53.9% girls) and 925 middle adolescents (63.8% girls). The results suggest that (1) the four identity formation modes change dynamically, showing linear and curvilinear growth and that (2) identity formation mode trajectories are more dynamic in middle adolescence than in early adolescence. The results also showed that, in the conditional model, (3) the higher-order personality factors and gender affect the growth factors of identity formation modes. Overall, trajectories of identity formation modes are more linear during early adolescence and more curvilinear during middle adolescence. The initial levels in identity trajectories are influenced by the personality metatraits but only plasticity is related to change among early adolescents.

Modeling of tethered satellite formations using graph theory

DEFF Research Database (Denmark)

Larsen, Martin Birkelund; Smith, Roy S; Blanke, Mogens

2011-01-01

satellite formation and proposes a method to deduce the equations of motion for the attitude dynamics of the formation in a compact form. The use of graph theory and Lagrange mechanics together allows a broad class of formations to be described using the same framework. A method is stated for finding...

The role of reconsolidation and the dynamic process of long-term memory formation and storage

Directory of Open Access Journals (Sweden)

Cristina M Alberini

2011-03-01

Full Text Available It is becoming increasingly clear that the processes of memory formation and storage are exquisitely dynamic. Elucidating the nature and temporal evolution of the biological changes that accompany encoding, storage and retrieval is key to understand memory formation. For explicit or medial temporal lobe-dependent memories that form after a discrete event and are stored for a long time, the physical changes underlying the encoding and processing of the information (memory trace or engram remain in a fragile state for some time. However, over time, the new memory becomes increasingly resistant to disruption until it is consolidated. Retrieval or reactivation of an apparently consolidated memory can render the memory labile again, and reconsolidation is the process that occurs to mediate its restabilization. Reconsolidation also evolves with the age of the memory: Young memories are sensitive to postreactivation disruption, but older memories are more resistant. Why does a memory become labile again if it is retrieved or reactivated? Here I suggest that the main function of reconsolidation is to contribute to the lingering consolidation process and mediate memory strengthening. I also discuss the literature and results regarding the influence of the passage of time on the reconsolidation of memory. These points have important implications for the use of reconsolidation in therapeutic settings.

Effects of cell culture media on the dynamic formation of protein-nanoparticle complexes and influence on the cellular response.

Science.gov (United States)

Maiorano, Gabriele; Sabella, Stefania; Sorce, Barbara; Brunetti, Virgilio; Malvindi, Maria Ada; Cingolani, Roberto; Pompa, Pier Paolo

2010-12-28

The development of appropriate in vitro protocols to assess the potential toxicity of the ever expanding range of nanoparticles represents a challenging issue, because of the rapid changes of their intrinsic physicochemical properties (size, shape, reactivity, surface area, etc.) upon dispersion in biological fluids. Dynamic formation of protein coating around nanoparticles is a key molecular event, which may strongly impact the biological response in nanotoxicological tests. In this work, by using citrate-capped gold nanoparticles (AuNPs) of different sizes as a model, we show, by several spectroscopic techniques (dynamic light scattering, UV-visible, plasmon resonance light scattering), that proteins-NP interactions are differently mediated by two widely used cellular media (i.e., Dulbecco Modified Eagle's medium (DMEM) and Roswell Park Memorial Institute medium (RPMI), supplemented with fetal bovine serum). We found that, while DMEM elicits the formation of a large time-dependent protein corona, RPMI shows different dynamics with reduced protein coating. Characterization of these nanobioentities was also performed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and mass spectroscopy, revealing that the average composition of protein corona does not reflect the relative abundance of serum proteins. To evaluate the biological impact of such hybrid bionanostructures, several comparative viability assays onto two cell lines (HeLa and U937) were carried out in the two media, in the presence of 15 nm AuNPs. We observed that proteins/NP complexes formed in RPMI are more abundantly internalized in cells as compared to DMEM, overall exerting higher cytotoxic effects. These results show that, beyond an in-depth NPs characterization before cellular experiments, a detailed understanding of the effects elicited by cell culture media on NPs is crucial for standardized nanotoxicology tests.

Chain formation of metal atoms

DEFF Research Database (Denmark)

Bahn, Sune Rastad; Jacobsen, Karsten Wedel

2001-01-01

The possibility of formation of single-atomic chains by manipulation of nanocontacts is studied for a selection of metals (Ni, Pd, Pt, Cu, Ag, Au). Molecular dynamics simulations show that the tendency for chain formation is strongest for Au and Pt. Density functional theory calculations indicate...... that the metals which form chains exhibit pronounced many-atom interactions with strong bonding in low coordinated systems....

Autonomous Formations of Multi-Agent Systems

Science.gov (United States)

Dhali, Sanjana; Joshi, Suresh M.

2013-01-01

Autonomous formation control of multi-agent dynamic systems has a number of applications that include ground-based and aerial robots and satellite formations. For air vehicles, formation flight ("flocking") has the potential to significantly increase airspace utilization as well as fuel efficiency. This presentation addresses two main problems in multi-agent formations: optimal role assignment to minimize the total cost (e.g., combined distance traveled by all agents); and maintaining formation geometry during flock motion. The Kuhn-Munkres ("Hungarian") algorithm is used for optimal assignment, and consensus-based leader-follower type control architecture is used to maintain formation shape despite the leader s independent movements. The methods are demonstrated by animated simulations.

Challenges in analysing and visualizing large-scale molecular dynamics simulations: domain and defect formation in lung surfactant monolayers

International Nuclear Information System (INIS)

Mendez-Villuendas, E; Baoukina, S; Tieleman, D P

2012-01-01

Molecular dynamics simulations have rapidly grown in size and complexity, as computers have become more powerful and molecular dynamics software more efficient. Using coarse-grained models like MARTINI system sizes of the order of 50 nm × 50 nm × 50 nm can be simulated on commodity clusters on microsecond time scales. For simulations of biological membranes and monolayers mimicking lung surfactant this enables large-scale transformation and complex mixtures of lipids and proteins. Here we use a simulation of a monolayer with three phospholipid components, cholesterol, lung surfactant proteins, water, and ions on a ten microsecond time scale to illustrate some current challenges in analysis. In the simulation, phase separation occurs followed by formation of a bilayer fold in which lipids and lung surfactant protein form a highly curved structure in the aqueous phase. We use Voronoi analysis to obtain detailed physical properties of the different components and phases, and calculate local mean and Gaussian curvatures of the bilayer fold.

Rethinking pattern formation in reaction-diffusion systems

Science.gov (United States)

Halatek, J.; Frey, E.

2018-05-01

The present theoretical framework for the analysis of pattern formation in complex systems is mostly limited to the vicinity of fixed (global) equilibria. Here we present a new theoretical approach to characterize dynamical states arbitrarily far from (global) equilibrium. We show that reaction-diffusion systems that are driven by locally mass-conserving interactions can be understood in terms of local equilibria of diffusively coupled compartments. Diffusive coupling generically induces lateral redistribution of the globally conserved quantities, and the variable local amounts of these quantities determine the local equilibria in each compartment. We find that, even far from global equilibrium, the system is well characterized by its moving local equilibria. We apply this framework to in vitro Min protein pattern formation, a paradigmatic model for biological pattern formation. Within our framework we can predict and explain transitions between chemical turbulence and order arbitrarily far from global equilibrium. Our results reveal conceptually new principles of self-organized pattern formation that may well govern diverse dynamical systems.

Backstepping Based Formation Control of Quadrotors with the State Transformation Technique

Directory of Open Access Journals (Sweden)

Keun Uk Lee

2017-11-01

Full Text Available In this paper, a backstepping-based formation control of quadrotors with the state transformation technique is proposed. First, the dynamics of a quadrotor is derived by using the Newton–Euler formulation. Next, a backstepping-based formation control for quadrotors using a state transformation technique is presented. In the position control, which is the basis of formation control, it is possible to derive the reference attitude angles employing a state transformation technique without the small angle assumption or the simplified dynamics usually used. Stability analysis based on the Lyapunov theorem shows that the proposed formation controller can provide a quadrotor formation error system that is asymptotically stabilized. Finally, we verify the performance of the proposed formation control method through comparison simulations.

Managing digitally formatted diagnostic image data

International Nuclear Information System (INIS)

Templeton, A.W.; Dwyer, S.J.

1985-01-01

Diagnostic radiologists are very comfortable using analog radiographic film and interpreting its recorded images. To improve patient care, the radiologist has sought the finest quality radiographic film for use with the best radiographic imaging systems. The proper choice and use of x-ray tubes, generators, film-screen combinations, and contrast media has occupied the professional attention of the radiologist since the inception of radiology. Image quality can be significantly improved with digitally formatted diagnostic imaging systems by providing dynamic ranges in excess of those possible with analog x-ray films. In a CT scanner, the digital acquisition and reconstruction system can obtain a dynamic range (contrast resolution) of 10,000 to 1. Digital subtraction angiography systems achieve 10-bit dynamic ranges for each of the acquired television frames. Increases in the dynamic ranges of the various imaging modalities have been coupled with improved spatial resolution. A digitally formatted image is a two-dimensional, numerical array of discrete image elements. Each picture element is called a pixel. Each pixel has a discrete size. Figure 15.1 illustrates a digitally formatted image depicting the spatial resolution, array size, and quantization or numerical range of the pixel values. Currently, 512 x 512 image arrays are standard. Development of 1024 x 1024 digital arrays are underway. Significant improvements have also been achieved in the rates at which digital diagnostic imaging data can be acquired, manipulated, and archived

Compression of a mixed antiproton and electron non-neutral plasma to high densities

Science.gov (United States)

Aghion, Stefano; Amsler, Claude; Bonomi, Germano; Brusa, Roberto S.; Caccia, Massimo; Caravita, Ruggero; Castelli, Fabrizio; Cerchiari, Giovanni; Comparat, Daniel; Consolati, Giovanni; Demetrio, Andrea; Di Noto, Lea; Doser, Michael; Evans, Craig; Fanì, Mattia; Ferragut, Rafael; Fesel, Julian; Fontana, Andrea; Gerber, Sebastian; Giammarchi, Marco; Gligorova, Angela; Guatieri, Francesco; Haider, Stefan; Hinterberger, Alexander; Holmestad, Helga; Kellerbauer, Alban; Khalidova, Olga; Krasnický, Daniel; Lagomarsino, Vittorio; Lansonneur, Pierre; Lebrun, Patrice; Malbrunot, Chloé; Mariazzi, Sebastiano; Marton, Johann; Matveev, Victor; Mazzotta, Zeudi; Müller, Simon R.; Nebbia, Giancarlo; Nedelec, Patrick; Oberthaler, Markus; Pacifico, Nicola; Pagano, Davide; Penasa, Luca; Petracek, Vojtech; Prelz, Francesco; Prevedelli, Marco; Rienaecker, Benjamin; Robert, Jacques; Røhne, Ole M.; Rotondi, Alberto; Sandaker, Heidi; Santoro, Romualdo; Smestad, Lillian; Sorrentino, Fiodor; Testera, Gemma; Tietje, Ingmari C.; Widmann, Eberhard; Yzombard, Pauline; Zimmer, Christian; Zmeskal, Johann; Zurlo, Nicola; Antonello, Massimiliano

2018-04-01

We describe a multi-step "rotating wall" compression of a mixed cold antiproton-electron non-neutral plasma in a 4.46 T Penning-Malmberg trap developed in the context of the AEḡIS experiment at CERN. Such traps are routinely used for the preparation of cold antiprotons suitable for antihydrogen production. A tenfold antiproton radius compression has been achieved, with a minimum antiproton radius of only 0.17 mm. We describe the experimental conditions necessary to perform such a compression: minimizing the tails of the electron density distribution is paramount to ensure that the antiproton density distribution follows that of the electrons. Such electron density tails are remnants of rotating wall compression and in many cases can remain unnoticed. We observe that the compression dynamics for a pure electron plasma behaves the same way as that of a mixed antiproton and electron plasma. Thanks to this optimized compression method and the high single shot antiproton catching efficiency, we observe for the first time cold and dense non-neutral antiproton plasmas with particle densities n ≥ 1013 m-3, which pave the way for an efficient pulsed antihydrogen production in AEḡIS.

Neural dynamics of social tie formation in economic decision-making

NARCIS (Netherlands)

Bault, N.; Pelloux, B.; Fahrenfort, J.J.; Ridderinkhof, K.R.; van Winden, F.

2015-01-01

The disposition for prosocial conduct, which contributes to cooperation as arising during social interaction, requires cortical network dynamics responsive to the development of social ties, or care about the interests of specific interaction partners. Here, we formulate a dynamic computational

Chromatin dynamics during cell cycle mediate conversion of DNA damage into chromatid breaks and affect formation of chromosomal aberrations: Biological and clinical significance

International Nuclear Information System (INIS)

Terzoudi, Georgia I.; Hatzi, Vasiliki I.; Donta-Bakoyianni, Catherine; Pantelias, Gabriel E.

2011-01-01

The formation of diverse chromosomal aberrations following irradiation and the variability in radiosensitivity at different cell-cycle stages remain a long standing controversy, probably because most of the studies have focused on elucidating the enzymatic mechanisms involved using simple DNA substrates. Yet, recognition, processing and repair of DNA damage occur within the nucleoprotein complex of chromatin which is dynamic in nature, capable of rapid unfolding, disassembling, assembling and refolding. The present work reviews experimental work designed to investigate the impact of chromatin dynamics and chromosome conformation changes during cell-cycle in the formation of chromosomal aberrations. Using conventional cytogenetics and premature chromosome condensation to visualize interphase chromatin, the data presented support the hypothesis that chromatin dynamic changes during cell-cycle are important determinants in the conversion of sub-microscopic DNA lesions into chromatid breaks. Consequently, the type and yield of radiation-induced chromosomal aberrations at a given cell-cycle-stage depends on the combined effect of DNA repair processes and chromatin dynamics, which is cell-cycle-regulated and subject to up- or down-regulation following radiation exposure or genetic alterations. This new hypothesis is used to explain the variability in radiosensitivity observed at various cell-cycle-stages, among mutant cells and cells of different origin, or among different individuals, and to revisit unresolved issues and unanswered questions. In addition, it is used to better understand hypersensitivity of AT cells and to provide an improved predictive G2-assay for evaluating radiosensitivity at individual level. Finally, experimental data at single cell level obtained using hybrid cells suggest that the proposed hypothesis applies only to the irradiated component of the hybrid.

Hyper-massive cloud, shock and stellar formation efficiency

International Nuclear Information System (INIS)

Louvet, Fabien

2014-01-01

O and B types stars are of paramount importance in the energy budget of galaxies and play a crucial role enriching the interstellar medium. However, their formation, unlike that of solar-type stars, is still subject to debate, if not an enigma. The earliest stages of massive star formation and the formation of their parent cloud are still crucial astrophysical questions that drew a lot of attention in the community, both from the theoretical and observational perspective, during the last decade. It has been proposed that massive stars are born in massive dense cores that form through very dynamic processes, such as converging flows of gas. During my PhD, I conducted a thorough study of the formation of dense cores and massive stars in the W43-MM1 supermassive structure, located at 6 kpc from the sun. At first, I showed a direct correlation between the star formation efficiency and the volume gas density of molecular clouds, in contrast with scenarios suggested by previous studies. Indeed, the spatial distribution and mass function of the massive dense cores currently forming in W43-MM1 suggests that this supermassive filament is undergoing a star formation burst, increasing as one approaches its center. I compared these observational results with the most recent numerical and analytical models of star formation. This comparison not only provides new constraints on the formation of supermassive filaments, but also suggests that understanding star formation in high density, extreme ridges requires a detailed portrait of the structure of these exceptional objects. Second, having shown that the formation of massive stars depends strongly on the properties of the ridges where they form, I studied the formation processes of these filaments, thanks of the characterization of their global dynamics. Specifically, I used a tracer of shocks (SiO molecule) to disentangle the feedback of local star formation processes (bipolar jets and outflows) from shocks tracing the pristine

Robust combined position and formation control for marine surface craft

DEFF Research Database (Denmark)

Ihle, Ivar-Andre F.; Jouffroy, Jerome; Fossen, Thor I.

We consider the robustness properties of a formation control system for marine surface vessels. Intervessel constraint functions are stabilized to achieve the desired formation configuration. We show that the formation dynamics is Input-to-State Stable (ISS) to both environmental perturbations th...

Dimer formation enhances structural differences between amyloid β-protein (1-40 and (1-42: an explicit-solvent molecular dynamics study.

Directory of Open Access Journals (Sweden)

Bogdan Barz

Full Text Available Amyloid β-protein (Aβ is central to the pathology of Alzheimer's disease. A 5% difference in the primary structure of the two predominant alloforms, Aβ(1-40 and Aβ(1-42, results in distinct assembly pathways and toxicity properties. Discrete molecular dynamics (DMD studies of Aβ(1-40 and Aβ(1-42 assembly resulted in alloform-specific oligomer size distributions consistent with experimental findings. Here, a large ensemble of DMD-derived Aβ(1-40 and Aβ(1-42 monomers and dimers was subjected to fully atomistic molecular dynamics (MD simulations using the OPLS-AA force field combined with two water models, SPCE and TIP3P. The resulting all-atom conformations were slightly larger, less compact, had similar turn and lower β-strand propensities than those predicted by DMD. Fully atomistic Aβ(1-40 and Aβ(1-42 monomers populated qualitatively similar free energy landscapes. In contrast, the free energy landscape of Aβ(1-42 dimers indicated a larger conformational variability in comparison to that of Aβ(1-40 dimers. Aβ(1-42 dimers were characterized by an increased flexibility in the N-terminal region D1-R5 and a larger solvent exposure of charged amino acids relative to Aβ(1-40 dimers. Of the three positively charged amino acids, R5 was the most and K16 the least involved in salt bridge formation. This result was independent of the water model, alloform, and assembly state. Overall, salt bridge propensities increased upon dimer formation. An exception was the salt bridge propensity of K28, which decreased upon formation of Aβ(1-42 dimers and was significantly lower than in Aβ(1-40 dimers. The potential relevance of the three positively charged amino acids in mediating the Aβ oligomer toxicity is discussed in the light of available experimental data.

A position sensitive silicon detector for AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy)

CERN Multimedia

Gligorova, A

2014-01-01

The AEḡIS experiment (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is located at the Antiproton Decelerator (AD) at CERN and studies antimatter. The main goal of the AEḡIS experiment is to carry out the first measurement of the gravitational acceleration for antimatter in Earth’s gravitational field to a 1% relative precision. Such a measurement would test the Weak Equivalence Principle (WEP) of Einstein’s General Relativity. The gravitational acceleration for antihydrogen will be determined using a set of gravity measurement gratings (Moiré deflectometer) and a position sensitive detector. The vertical shift due to gravity of the falling antihydrogen atoms will be detected with a silicon strip detector, where the annihilation of antihydrogen will take place. This poster presents part of the development process of this detector.

Development and validation of a dynamical atmosphere-vegetation-soil HTO transport and OBT formation model

Energy Technology Data Exchange (ETDEWEB)

Ota, Masakazu, E-mail: ohta.masakazu@jaea.go.jp [Research Group for Environmental Science, Division of Environment and Radiation, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (Japan); Nagai, Haruyasu [Research Group for Environmental Science, Division of Environment and Radiation, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (Japan)

2011-09-15

A numerical model simulating transport of tritiated water (HTO) in atmosphere-soil-vegetation system, and, accumulation of organically bound tritium (OBT) in vegetative leaves was developed. Characteristic of the model is, for calculating tritium transport, it incorporates a dynamical atmosphere-soil-vegetation model (SOLVEG-II) that calculates transport of heat and water, and, exchange of CO{sub 2}. The processes included for calculating tissue free water tritium (TFWT) in leaves are HTO exchange between canopy air and leaf cellular water, root uptake of aqueous HTO in soil, photosynthetic assimilation of TFWT into OBT, and, TFWT formation from OBT through respiration. Tritium fluxes at the last two processes are input to a carbohydrate compartment model in leaves that calculates OBT translocation from leaves and allocation in them, by using photosynthesis and respiration rate in leaves. The developed model was then validated through a simulation of an existing experiment of acute exposure of grape plants to atmospheric HTO. Calculated TFWT concentration in leaves increased soon after the start of HTO exposure, reaching to equilibrium with the atmospheric HTO within a few hours, and then rapidly decreased after the end of the exposure. Calculated non-exchangeable OBT amount in leaves linearly increased during the exposure, and after the exposure, rapidly decreased in daytime, and, moderately nighttime. These variations in the calculated TFWT concentrations and OBT amounts, each mainly controlled by HTO exchange between canopy air and leaf cellular water and by carbohydrates translocation from leaves, fairly agreed with the observations within average errors of a factor of two. - Highlights: > TFWT retention and OBT formation in leaves were modeled > The model fairly well calculates TFWT concentration after an acute HTO exposure > The model well assesses OBT formation and attenuation of OBT amount in leaves.

Starting mechanisms and dynamics of bubble formation induced by a Ho:Yttrium aluminum garnet laser in water

Science.gov (United States)

Frenz, Martin; Könz, Flurin; Pratisto, Hans; Weber, Heinz P.; Silenok, Alexander S.; Konov, Vitaly I.

1998-12-01

The starting mechanisms and dynamics of laser-induced bubble formation at a submerged fiber tip in distilled water were experimentally investigated using pressure measurements and fast flash videography. A fiber guided Ho:YAG laser operating in the free running (τ=200 μs) and Q-switched (τ=45 ns) mode at a wavelength of λ=2.12 μm was used as a light source. It is shown that the beam profile at the distal fiber tip (multimode fiber d=300 μm) exhibits hot spots that result in an inhomogeneous temperature distribution in the heated water volume. Depending on the laser irradiance, three different bubble formation processes are distinguished: bubble formation by heating, by rarefraction (cavitation), and by a combination of these two processes. For laser irradiances of less than 0.5 MW/ cm2 bubble formation takes place at temperatures near the critical point of water (T=280 °C). A rapid decrease in the threshold temperature for bubble formation was found for laser irradiances between 0.5 and 1 MW/cm 2. At laser irradiances higher than 3 MW/cm2, microbubbles with radii of up to 20 μm were formed at the front of the laser pulse even though the average water temperature was far below 100 °C. The water temperature distribution during the laser pulse was determined by numerical simulation. Simultaneous pressure measurements revealed that each subablative laser spike induces a bipolar pressure transient. The onset of the bubble expansion was found to be correlated with a characteristic pressure increase that can be used for on-line monitoring of the ablation process. The distortion of the temporal profile of the pressure wave is shown to be an effect of diffraction. The reduction of pressure by the negative part of the bipolar pressure transients leads to a lowering of the evaporation pressure and therefore to the initiation of bubbles by cavitation. With increasing irradiance this mechanism becomes more efficient.

Rock-salt structure lithium deuteride formation in liquid lithium with high-concentrations of deuterium: a first-principles molecular dynamics study

Science.gov (United States)

Chen, Mohan; Abrams, T.; Jaworski, M. A.; Carter, Emily A.

2016-01-01

Because of lithium’s possible use as a first wall material in a fusion reactor, a fundamental understanding of the interactions between liquid lithium (Li) and deuterium (D) is important. We predict structural and dynamical properties of liquid Li samples with high concentrations of D, as derived from first-principles molecular dynamics simulations. Liquid Li samples with four concentrations of inserted D atoms (LiDβ , β =0.25 , 0.50, 0.75, and 1.00) are studied at temperatures ranging from 470 to 1143 K. Densities, diffusivities, pair distribution functions, bond angle distribution functions, geometries, and charge transfer between Li and D atoms are calculated and analyzed. The analysis suggests liquid-solid phase transitions can occur at some concentrations and temperatures, forming rock-salt LiD within liquid Li. We also observe formation of some D2 molecules at high D concentrations.

Complex Pattern Formation from Current-Driven Dynamics of Single-Layer Epitaxial Islands on Crystalline Conducting Substrates

Science.gov (United States)

Kumar, Ashish; Dasgupta, Dwaipayan; Maroudas, Dimitrios

We report a systematic study of complex pattern formation resulting from the driven dynamics of single-layer homoepitaxial islands on face-centered cubic (FCC) crystalline conducting substrate surfaces under the action of an externally applied electric field. The analysis is based on an experimentally validated nonlinear model of mass transport via island edge atomic diffusion, which also accounts for edge diffusional anisotropy. We analyze the morphological stability and simulate the field-driven evolution of rounded islands for an electric field oriented along the fast diffusion direction. For larger than critical island sizes on {110} and {100} FCC substrates, we show that multiple necking instabilities generate complex island patterns, including void-containing islands, mediated by sequences of breakup and coalescence events and distributed symmetrically with respect to the electric field direction. We analyze the dependence of the formed patterns on the original island size and on the duration of application of the external field. Starting from a single large rounded island, we characterize the evolution of the number of daughter islands and their average size and uniformity. The analysis reveals that the pattern formation kinetics follows a universal scaling relation. Division of Materials Sciences & Engineering, Office of Basic Energy Sciences, U.S. Department of Energy (Award No.: DE-FG02-07ER46407).