Physical Sciences and Mathematics Commons^™

Comment On “Direct Observation Of Stretched-Exponential Relaxation In Low-Temperature Lennard-Jones Systems Using The Cage Correlation Function”, Ulrich Zürcher, T. Keyes

Physics Faculty Publications

A Comment on the Letter by Eran Rabani, J. Daniel Gezelter, and D. J. Berne, Phys. Rev. Lett. 82, 3649 (1999). The authors of the Letter offer a Reply.

Redshift-Distance Survey Of Early-Type Galaxies: Dipole Of The Velocity Field, L. N. Da Costa, M. Bernardi, M. V. Alonso, G. Wegner

Dartmouth Scholarship

We use the recently completed redshift-distance survey of nearby early-type galaxies (ENEAR) to measure the dipole component of the peculiar velocity field to a depth of cz ~ 6000 km s-1. The sample consists of 1145 galaxies brighter than mB = 14.5 and with cz ≤ 7000 km s-1, uniformly distributed over the whole sky, and 129 fainter cluster galaxies within the same volume. Most of the Dn-σ distances were obtained from new spectroscopic and photometric observations conducted by this project, ensuring the homogeneity of the data over the whole sky. These 1274 galaxies are objectively assigned …

Plasma Oscillations And Expansion Of An Ultracold Neutral Plasma, Scott D. Bergeson, S. Kulin, T. C. Killian, S. L. Rolston

Faculty Publications

We report the observation of plasma oscillations in an ultracold neutral plasma. With this collective mode we probe the electron density distribution and study the expansion of the plasma as a function of time. For classical plasma conditions, i.e., weak Coulomb coupling, the expansion is dominated by the pressure of the electron gas and is described by a hydrodynamic model. Discrepancies between the model and observations at low temperature and high density may be due to strong coupling of the electrons.

Orbital Period Of The Low‐Inclination Sw Sextantis Star V442 Ophiuchi, D. W. Hoard, John R. Thorstensen, Paula Szkody

Dartmouth Scholarship

V442 Ophiuchi is a low-inclination (noneclipsing) nova-like cataclysmic variable. We have obtained medium resolution (1-3.5 Å), time-resolved optical spectroscopy of this interacting binary star spanning an interval of 4 yr, from 1995 August to 1999 June. Using an Hα radial velocity curve constructed from our combined spectroscopic data sets, we have determined that Porb = 0.1243 days for V442 Oph, breaking the long-standing 1 day alias ambiguity in its orbital period. V442 Oph shares many of the characteristics of the group of cataclysmic variables known as the SW Sextantis stars. Its Doppler tomograms and orbital phase-dependent emission-line behavior, including …

Analytic Inversion Of Emission Lines Of Arbitrary Optical Depth For The Structure Of Supernova Ejecta., R. Ignace, M. A. Hendry

Richard Ignace

We derive a method for inverting emission line profiles formed in supernova ejecta. The derivation assumes spherical symmetry and homologous expansion (i.e., v(r)∝r), is analytic, and even takes account of occultation by a pseudo-photosphere. Previous inversion methods have been developed which are restricted to optically thin lines, but the particular case of homologous expansion permits an analytic result for lines of arbitrary optical depth. In fact, we show that the quantity that is generically retrieved is the run of line intensity Iλ with radius in the ejecta. This result is quite general, and so could be applied to resonance lines, …

Kinetic Energy Release In Electron-Induced Decay Reactions Of Molecular Ions: C3h8+ And C3h7+, S. Matt, Olof E. Echt, A. Stamatovic, T. D. Mark

Physics & Astronomy

We have measured the kinetic energy release (KER) distributions for electron-induced dissociation of mass-selected molecular parent and fragment ions of propane. They are compared with distributions determined for spontaneous (metastable) dissociation. The average KER for induced dissociation of C3H8+ into C3H7+ is 13.2 +/- 1.2 meV, about 42% larger than for the spontaneous reaction. This large difference is attributed to the dramatically reduced time at which the induced reaction can be sampled. In contrast, the KER for dissociation of C3H7+ into C3H5+, which is characterized by a large reverse activation energy, is hardly affected by the experimental time scale. (C) …

Static Quark Potential In Three Flavor Qcd, James E. Hetrick, C. Bernard

All Faculty Articles - School of Engineering and Computer Science

We study the effects of dynamical quarks on the static quark potential at distances shorter than those where string breaking is expected. Quenched calculations and calculations with three flavors of dynamical quarks are done on sets of lattices with the lattice spacings matched within about one percent. The effect of the sea quarks on the shape of the potential is clearly visible. We investigate the consequences of these effects in a very crude model, namely solving Schrödinger’s equation in the resulting potential.

Interaction Of Mitochondrial Elongation Factor Tu With Aminoacyl-Trna And Elongation Factor Ts, Ying Chun Cai, James M. Bullard, Nancy L. Thompson, Linda L. Spremulli

Chemistry Faculty Publications and Presentations

Elongation factor (EF) Tu promotes the binding of aminoacyl-tRNA (aa-tRNA) to the acceptor site of the ribosome. This process requires the formation of a ternary complex (EF-Tu·GTP·aa-tRNA). EF-Tu is released from the ribosome as an EF-Tu·GDP complex. Exchange of GDP for GTP is carried out through the formation of a complex with EF-Ts (EF-Tu·Ts). Mammalian mitochondrial EF-Tu (EF-Tu_mt) differs from the corresponding prokaryotic factors in having a much lower affinity for guanine nucleotides. To further understand the EF-Tu_mt subcycle, the dissociation constants for the release of aa-tRNA from the ternary complex (K _tRNA) and for …

Ammonite Biostratigraphy, Lithofacies Variations, And Paleoceanographic Implications For Barremian-Aptian Sequences Of Northeastern Mexico, Ricardo Barragan

FIU Electronic Theses and Dissertations

Two Barremian-Aptian sequences studied in Durango and Nuevo Leon States, northeastern Mexico include three lithic units which have been described as the Cupido Formation of Barremian-early Early Aptian age, its lateral equivalent, the Lower Tamaulipas Formation, and the La Pena Formation extending through the early Albian.

The present work improves the existing ammonite Aptian biozonation by considering constraints associated with a discontinuous spatial and temporal record of the different taxa within the La Pena Formation.

Four ammonite biozones are established: 1) The Dufrenoyia justinae Zone for the late Early Aptian, 2) The Burckhardtites nazasensis/Rhytidoplites robertsi Zone for the middle Aptian, …

Monitoring Relative Abundance Of American Shad In Virginia's Rivers Annual Report 1999, John E. Olney Sr., John M. Hoenig

Reports

A moratorium on the taking of American shad (Alosa sapidissima) in the Chesapeake Bay and its tributaries was established by the Virginia Marine Resources Commission (VMRC) beginning 1 January 1994. The prohibition applied to both recreational and commercial fishers. The moratorium was imposed at a time when commercial catch rates of American shad in Virginia's rivers were experiencing declines. Data from the commercial fishery were the best available for assessing the status of individual stocks. Catch-per-unit-effort (CPUE) data were compiled from logbooks that recorded landings by commercial fishermen using staked gill nets at various locations throughout the middle reaches of …

Accurate, Critically Sampled Characteristic Waveform Surface Construction For Waveform Interpolation Decomposition, N. R. Chong-White, I. Burnett

Faculty of Informatics - Papers (Archive)

A waveform-matched waveform interpolation (WMWI) technique is presented which offers improved signal analysis over standard WI coders and, in the unquantised case, perfect reconstruction. In WMWI, an accurate representation of speech evolution is formed by extracting consecutive pitch periods of a time-warped, constant pitch residual. A pitch track optimisation technique is described which ensures that the critically sampled pitch periods can be effectively decomposed into a slowly evolving and rapidly evolving waveform, allowing efficient quantisation.

Integration And Querying Of Heterogeneous, Autonomous, Distributed Database Systems, Rukshan Indika Athauda

FIU Electronic Theses and Dissertations

Today, databases have become an integral part of information systems. In the past two decades, we have seen different database systems being developed independently and used in different applications domains. Today's interconnected networks and advanced applications, such as data warehousing, data mining & knowledge discovery and intelligent data access to information on the Web, have created a need for integrated access to such heterogeneous, autonomous, distributed database systems. Heterogeneous/multidatabase research has focused on this issue resulting in many different approaches. However, a single, generally accepted methodology in academia or industry has not emerged providing ubiquitous intelligent data access from heterogeneous, …

Iron Acquisition Systems And The Effect Of Iron On Virulence, Amy E. Noles

Honors Theses

No abstract provided.

Performance Analysis Of Qos Mechanisms In Ip Networks, D. Jia, E. Dutkiewicz, Joe F. Chicharo

Faculty of Informatics - Papers (Archive)

Integrated services IP networks are expected to provide a variety of services with differentiated QoS. This requires the implementation of mechanisms that can discriminate service classes in terms of QoS. The IETF has recently proposed a differentiated services (Diffserv) framework for provision of QoS. In this paper we analyse the performance of two Diffserv mechanisms: threshold dropping and priority scheduling in terms of packet loss and mean packet delay. A comparison of the two mechanisms is carried out with the requirement that both mechanisms provide the same level of packet loss for the preferred flow. This comparison extends the results …

Effective Surface Debye Temperature For Nimnsb.100. Epitaxial Films, C.N. Borca, Takashi Komesu, Hae-Kyung Jeong, Peter A. Dowben, D. Ristoiu, Ch. Hordequin, J. Pierre, J. P. Nozie`Res

Peter Dowben Publications

The surface Debye temperature of the NiMnSb (100) epitaxial films has been obtained using low energy electron diffraction, inverse photoemission, and core-level photoemission. The normal dynamic motion of the (100) surface results in a value for the effective surface Debye temperature of 145613 K. This is far smaller than the bulk Debye temperature of 31265 K obtained from wave vector dependent inelastic neutron scattering. The large difference between these measures of surface and bulk dynamic motion indicates a soft and compositionally different (100) surface. © 2000 American Institute of Physics. [S0003-6951(00)05127-5]

Quantum Computation Through Entangling Single Photons In Multipath Interferometers, John C. Howell, John A. Yeazell

Mathematics, Physics, and Computer Science Faculty Articles and Research

Single-photon interferometry has been used to simulate quantum computations. Its use has been limited to studying few-bit applications due to rapid growth in physical size with numbers of bits. We propose a hybrid approach that employs n photons, each having L degrees of freedom yielding Lⁿ basis states. The photons are entangled via a quantum nondemolition measurement. This approach introduces the essential element of quantum computing, that is, entanglement into the interferometry. Using these techniques, we demonstrate a controlled-NOT gate and a Grover's search circuit. These ideas are also applicable to the study of nonlocal correlations in many dimensions.

Coastal Forested Wetland Walk, Virginia Institute Of Marine Science

Miscellaneous

Booklet describes resident trees, plants and animals along the walk on the VIMS campus.