bluuebunny/crossref_metadata_2025 huggingface dataset:
Inferring the depth distribution of catchability for pelagic fishes and correcting for variations in the depth of longline fishing gear
Authors: Ward Peter , Myers Ransom A
Published: June 2005

We introduce a new method that uses generalized linear mixed models to infer the depth distribution of pelagic fishes. It uses existing data from research surveys and observers on commercial vessels to estimate changes in catchability when longline fishing gear is lengthened to access deeper water. We infer the depth distribution of catchability for 37 fish species that are caught on pelagic longlines in the Pacific Ocean. We show how the estimates of catchability can be used to correct abundance indices for variations in longline depth. Our method facilitates the inclusion of data from early surveys in the time series of commercial catch rates used to estimate abundance. It also resolves inconsistencies in the time series caused by a rapid switch to deep longlining in the 1970s. The catchability distribution does not always match depth preferences derived from tracking studies. Therefore, depth preferences from tracking studies should not be used to correct abundance indices without additional information on feeding behavior.
Stream acidification and mortality of brook trout (Salvelinus fontinalis) in response to timber harvest in Catskill Mountain watersheds, New York, USA
Authors: Baldigo Barry P , Murdoch Peter S , Burns Douglas A
Published: June 2005

Effects of clear-cut and timber-stand improvement (TSI) harvests on water chemistry and mortality of caged brook trout (Salvelinus fontinalis) were evaluated in a study of three Catskill Mountain streams, 19942000. Harvests removed 73% of tree basal area (BA) from a clearcut subbasin, 5% BA from a TSI subbasin, and 14% BA at a site below the confluence of both streams. A fourth nonharvested site served as a control. Water quality and trout mortality were affected only in the clearcut stream. Acidity and concentrations of nitrate and inorganic monomeric aluminum (Alim) increased sharply during high flows after the first growing season (fall 1997). AcidAlim episodes were severe during this period and decreased steadily in magnitude and duration thereafter. All trout at this site died within 7 days during spring 1998 and 85% died during spring 1999. Only background mortality was observed in other years at this site and at the other three sites during all tests. The absence of mortality in TSI watersheds indicates that limited harvests should not harm brook trout populations in acid-sensitive streams. Effects of tree harvests on fish communities are of concern, however, because many stream-dwelling species are more sensitive to acidified waters than brook trout.
Invertebrate resting stages in residual ballast sediment of transoceanic ships
Authors: Bailey Sarah A , Duggan Ian C , Jenkins Philip T , MacIsaac Hugh J
Published: June 2005

Ballast water has been the primary vector of nonindigenous species (NIS) to the Laurentian Great Lakes over the past 45 years. Although ballast water exchange regulations were implemented in 1993 to reduce propagule loads, new NIS continue to be discovered. A possible explanation for this trend is the importance of alternative vectors, such as residual ballast of ships claiming "no ballast on board". We investigate resting stages of invertebrates in residual ballast sediments of transoceanic ships as a possible vector of NIS to the Great Lakes. To model the introduction effort potentially associated with this vector, we collected sediment samples from 39 ships entering the Great Lakes and measured the density, viability, and species richness of resting stages contained therein. Viable resting stages of NIS were found in 32% of ships, at a mean density of 3.0 × 105·ship1. Temperature, salinity, and removal of eggs from sediment during incubation had a significant impact on total abundance and species richness of hatched taxa. A total of 21 NIS were identified, consisting exclusively of rotifers and cladocerans. Salinity of residual ballast water and geographic region of ballast uptake were predictive variables for profiling invasion risk due to ships, although explained variability was low.
Flexible diet and trophic position of dreissenid mussels as inferred from stable isotopes of carbon and nitrogen
Authors: Garton David W , Payne Christopher D , Montoya Joseph P
Published: June 2005

In this study, the trophic position and food-web impacts of invading zebra mussels (Dreissena polymorpha) were investigated by sampling mussels, seston (= phytoplankton), macrophytes, zooplankton, and surficial sediment in two small inland lakes (19992002) and similarly in western Lake Erie (1999 only). Tissues from quagga mussels (Dreissena bugensis) from Lake Erie were also analyzed. Stable-isotope ratios (15N/14N and 13C/12C) were used to identify likely food sources and estimate relative trophic position. For Lake Erie, stable-isotope ratios indicated no diet differences between the two mussel species. For all lakes, zooplankton δ13C was indicative of phytoplanktivory. The 13C stable isotope ratios indicated that seston comprised ~50% of food sources for mussels in Lake Erie, but 73%97% and 52%100% of the diet of mussel populations in Lake Wawasee and Clark Lake, respectively. Stable nitrogen isotope ratios placed zooplankton at trophic levels equal to or higher than those of mussels in seven of eight comparisons. Dreissena polymorpha and D. bugensis are able to exploit suspended detritus as a significant energy source, as well as compete directly with zooplankton for seston as a food source and with each other in areas of sympatry.
Evidence for biomagnification of rubidium in freshwater and marine food webs
Authors: Campbell Linda M , Fisk Aaron T , Wang Xiaowa , Köck Günter , Muir Derek CG
Published: June 2005

Rubidium (Rb), a rarely studied alkali metal, may be an essential ultra-trace element for humans and other organisms. However, very little information exists in regard to the concentrations and distribution of Rb in freshwater and marine food webs. We measured Rb concentrations in freshwater fish from Lake Erie and two Arctic lakes (Lake Hazen and Resolute Lake) and in seabirds, ringed seals, and invertebrates from the marine Northwater Polynya in Baffin Bay. The alkali analogues of Rb, cesium (Cs), and potassium (K) were also analysed in a subset of fish from Lakes Erie and Hazen. Rb and Cs concentrations and Cs:K ratios in the sampled biota are significantly regressed against δ15N values, indicating biomagnification through the food web in diverse ecosystems. However, there is no relationship between K concentrations and δ15N values, indicating a lack of biomagnification and the presence of homeostatistic mechanisms for this essential trace element. Rb must be included with mercury and Cs as metals that consistently biomagnify in diverse food webs and should be considered in multi-element biomagnification studies.
Alternative life-history patterns of estuarine fish: barium in otoliths elucidates freshwater residency
Authors: Elsdon Travis S , Gillanders Bronwyn M
Published: June 2005

Elemental concentrations in fish otoliths (earstones) can reconstruct environmental histories of fish if predictable relationships between the environment and elemental incorporation are established. We assessed whether fresh water occupancy of black bream (Acanthopagrus butcheri) can be inferred from otolith barium concentrations (Ba was standardized to calcium (Ca) and expressed as a ratio, Ba:Ca). Otolith Ba:Ca of fish was correlated with ambient Ba:Ca. Using the natural relationships of increasing ambient and otolith Ba:Ca with decreasing salinity, fish from fresh- and salt-water environments were distinguishable. Fish caught in fresh water had approximately double the otolith Ba:Ca of those from salt-water estuaries, for both summer and winter collections. Fish with otolith Ba:Ca ≤5 µmol·mol1 were classified as resident in salt water, and those with ≥6 µmol·mol1 as resident in fresh water. Transects of Ba:Ca across fish otoliths classified fish to fresh- or salt-water environments. Fish were identified as having migratory patterns typical of residents, migrants with irregular patterns of diadromy, or migrants with cyclic patterns of anadromomy. Multiple migratory behaviours occurred in fish from the same estuary, indicating far more complex migratory behaviours than were previously known. The application of otolith Ba:Ca to infer freshwater occupancy of fish has rarely been studied, yet may provide more accurate classifications of estuarine environments than strontium (Sr) isotopes and otolith Sr:Ca.
A new perspective on the importance of marine-derived nutrients to threatened stocks of Pacific salmon (Oncorhynchus spp.)
Authors: Scheuerell Mark D , Levin Phillip S , Zabel Richard W , Williams John G , Sanderson Beth L
Published: June 2005

Considerable research has highlighted the important role of anadromous salmon in importing marine-derived nutrients to freshwater and riparian ecosystems. These subsidies are thought to support diverse food webs and increase the growth and survival of juvenile salmon during their freshwater residency. Quite recently, however, salmon smolts have been identified as important exporters of nutrients from freshwater ecosystems. Using a mass-balance approach, we examined the phosphorus-transport dynamics by spring/summer Chinook salmon (Oncorhynchus tshawytscha) in the Snake River basin and estimated that net phosphorus transport into the basin over the past 40 years was <2% of historical levels. Furthermore, a nonlinear relationship existed between nutrient import by adults and subsequent export by smolts, such that smolts exported proportionally more phosphorus as spawner abundance decreased. In 12% of years, smolts exported more than adults imported, resulting in a net loss of phosphorus from the ecosystem. This loss of marine subsidies may have caused a state shift in the productivity of the freshwater ecosystem, resulting in strong density-dependent survival observed in juvenile salmon. These results suggest that conserving this threatened stock of salmon requires the need to explicitly address the important role of marine-derived nutrients and energy in sustaining salmon populations.
Present status of the fine-structure frequencies of the 23P helium level
Authors: Giusfredi G , Pastor P Cancio , Natale P De , Mazzotti D , Mauro C de , Fallani L , Hagel G , Krachmalnicoff V , Inguscio M
Published: June 2005

A new measurement of the fine-structure frequencies of the 23 P level in 4He is presented. The result for the largest interval 23 P023 P1 is 29 616 952.7(1.0) kHz, and 2 291 167.7(11.0) kHz for the smallest one, 23 P123 P2. Taking into account this new result, an agreement among different experiments at the 1 kHz level is found. Implications of this situation for the determination of the fine-structure constant α are discussed. PACS Nos.: 31.15.Pf, 31.30.Jv, and 32.10.Hq
Toward high-precision values of the self energy of non-S states in hydrogen and hydrogen-like ions
Authors: Le Bigot E -O , Jentschura U D , Indelicato P , Mohr P J
Published: June 2005

The method and status of a study to provide numerical, high-precision values of the self-energy level shift in hydrogen and hydrogen-like ions is described. Graphs of the self energy in hydrogen-like ions with nuclear charge number between 20 and 110 are given for a large number of states. The self-energy is the largest contribution of quantum electrodynamics (QED) to the energy levels of these atomic systems. These results greatly expand the number of levels for which the self energy is known with a controlled and high precision. Applications include the adjustment of the Rydberg constant and atomic calculations that take into account QED effects.PACS Nos.: 12.20.Ds, 31.30.Jv, 06.20.Jr, 31.15.p
Laser spectroscopy of antiprotonic helium atoms and ions
Authors: Hayano R S
Published: June 2005

Laser spectroscopy of an antiprotonic helium ([Formula: see text]He+) atom, a neutral three-body Coulomb system consisting of an antiproton, a helium nucleus, and an electron has so far contributed to the determination of antiproton mass and charge to a precision of 10-8. Recently, we have succeeded in producing long-lived (τ [Formula: see text] 100 ns) antiprotonic helium ions (two-body system: [Formula: see text]He++). This was done by stopping ∼50 keV antiprotons decelerated by using an "inverse linac" (RFQD) in a very low-density helium gas target and selectively populating the ionic level by using laser tagging. It may be possible to use this two-body ion for future high-precision work.PACS Nos.: 36.10.k, 34.90.+q, 25.43.+t
A new measurement of the decay rate of the negative positronium ion:status and preliminary results
Authors: Fleischer F , Degreif K , Gwinner G , Lestinsky M , Liechtenstein V , Plenge F , Scheit H , Schwalm D
Published: June 2005

A great number of theoretical papers have been published dealing with the negative positronium ion Ps. On the other hand, experimental data on this purely leptonic three-body system (e+ee) is very limited. Apart from a first observation, a lifetime measurement with an accuracy of 4% has been published. We have built a set-up to produce Ps making use of moderated positrons from a 22Na source, and we are presently running an experiment to improve on its decay rate. This paper discusses the status of the project as well as the possibilities of extending these investigations to other properties of Ps, the latter becoming possible using the NEPOMUC positron source at the FRM II reactor in Munich.PACS No.: 36.10.Dr
A new determination of the proton-to-deuteron ratio of magnetic moments
Authors: Karshenboim S G , Ivanov V G , Neronov Yu. I , Nikolaev B P , Tolparov Yu. N
Published: June 2005

Nuclear magnetic resonance (NMR) spectroscopy of hydrogen deuteride (HD) is an attractive tool for a determination of the proton-to-deuteron ratio of magnetic moments. Potentially, it may provide a result an order of magnitude more accurate than the present value based on the study of atomic hydrogen and deuterium. NMR spectroscopy does not deal with single molecules but with a molecular gas and here we study the pressure dependence of the results.PACS Nos.: 12.20Ds, 21.20Ky, 27.10+h, 31.30Gs, 76.60Cq, 82.56Hg
Three-loop radiative-recoil corrections to hyperfine splitting in muonium
Authors: Eides Michael I , Grotch Howard , Shelyuto Valery A
Published: June 2005

We consider three-loop radiative-recoil corrections to hyperfine splitting in muonium. These corrections are enhanced by the large logarithm of the electronmuon mass ratio. The leading logarithm-cubed and logarithm-squared contributions were obtained a long time ago. We calculate the single-logarithmic and nonlogarithmic contributions of order α3(m/M)EF generated by gauge invariant sets of diagrams with one- and two-loop polarization insertions in diagrams with two exchanged photons and radiative photons, and by diagrams with one-loop radiative photon insertions both in the electron and muon lines. The results of this paper constitute a next step in the implementation of the program of reduction of the theoretical uncertainty of hyperfine splitting below 10 Hz. They improve the theory of hyperfine splitting, and affect the value of the electronmuon mass ratio extracted from experimental data on the muonium hyperfine splitting.PACS Nos.: 12.20.Ds, 31.30.Jv, 32.10.Fn, 36.10.Dr
Nucleon deformation and atomic spectroscopy
Authors: Buchmann A J
Published: June 2005

Recent ineleastic electronproton scattering experiments have led to rather accurate values for the N → Δ transition quadrupole moment QN→Δ. The experimental results imply a prolate (cigar-shaped) intrinsic deformation of the nucleon. The nonsphericity of the proton's charge distribution might be seen in the spectrum of atomic hydrogen. The possibilities and limitations for determining the geometric shape of the nucleon in an atomic physics experiment are discussed. PACS Nos.: 13.40.f, 21.10.k, 31.30.Gs
Precision measurements of fine and hyperfine structure in lithium I and II
Authors: van Wijngaarden W A
Published: June 2005

Recent advances in modeling Li I and II in conjunction with improved experimental techniques have enabled precise tests of quantum electrodynamics. For Li+, the hyperfine intervals of the 1s2s 3S1 and 1s2p 3P0,1,2 states are in excellent agreement with theory. A recent measurement of the 1s2p 3P1,2 fine-structure interval also agrees well with the calculated value and resolves a discrepancy found by two prior experiments. For neutral lithium, discrepancies exist among the results of various experiments for the 6,7Li D1 isotope shift and the 2P fine structure. However, all of the fine-structure measurements are several MHz larger than the theoretical value. Prospects for future experiments to improve the determination of the fine-structure constant and the relative 6,7Li nuclear charge radii are discussed. PACS Nos.: 32.10.Fn, 31.30.Gs, 42.62.Fi
New approach to many-body quantum-electrodynamics calculations:merging quantum electrodynamics with many-body perturbation
Authors: Lindgren Ingvar , Salomonson Sten , Hedendahl Daniel
Published: June 2005

A new method for bound-state quantum electrodynamics (QED) calculations on many-electron systems is presented that is a combination of the non-QED many-body technique for quasi-degenerate systems and the newly developed covariant-evolution-operator technique for QED calculations. The latter technique has been successfully applied to the fine structure of excited states of medium-heavy heliumlike ions, and it is expected that the new method should be applicable also to light elements, hopefully down to neutral helium. PACS Nos.: 31.30.Jv, 31.15.Md, 31.25.Jf, 33.15.Pw
A new path to ultracold hydrogen
Authors: deCarvalho R , Brahms N , Newman B , Doyle J M , Kleppner D , Greytak T
Published: June 2005

Ultracold hydrogen offers unique possibilities for precision spectroscopy, studies of atomic interactions, and the creation of quantum fluids containing mixtures of hydrogen and deuterium. Current techniques for trapping and cooling hydrogen have produced large condensates with N ∼ 109 atoms, but suffer from a variety of experimental limitations. Among these are the slow evaporative cooling rate due to the small HH elastic-scattering cross section, the need for a superfluid helium film in the initial thermalization process, a geometry that severely limits detection efficiency, and the inability to trap deuterium. We are constructing a new apparatus based on buffer-gas cooling that will overcome these problems. To accelerate evaporative cooling, the thermalization rate is increased by simultaneously loading lithium and hydrogen into a 4.2 T anti-Helmholtz trap. Lithium accelerates evaporative cooling because the LiH elastic-scattering cross section is ∼1200 times larger than that of HH. Hydrogen and lithium will be produced by laser ablation of solid LiH in a 3He buffer gas held at temperatures of ∼350 mK. Because no wall collisions are needed for initial thermalization, ablating a solid sample of LiD should enable studies of deuterium. The apparatus is in the final stages of construction. We report on results of initial tests and discuss the new scientific opportunities made possible by this approach.PACS No.: 32.80.Pj
The 2s hyperfine structure in hydrogen and deuterium: a precision test of bound state quantum electrodynamics
Authors: Karshenboim S G , Fendel P , Ivanov V G , Kolachevsky N N , Hänsch T W
Published: June 2005

New experimental results for the 2s hyperfine interval in hydrogen and deuterium have been obtained by optical frequency measurement of the 1s2s two-photon transition for different spin states in a zero magnetic field. The accuracy exceeds that of earlier microwave measurements. Together with the precisely known ground-state hyperfine splitting, we obtain a value of D21 = 8vhfs(2s)  vhfs(1s), which permits a test of quantum electrodynamics without suffering from large unknown nuclear structure effects. The theory of D21 in hydrogen and deuterium is also presented in this paper. PACS Nos.: 12.20Fv, 32.10Fn, 32.30Jc, 42.62Fi
High-precision measurements in few-electron highly charged ions at the HeidelbergElectron Beam Ion Trap (EBIT)
Authors: López-Urrutia J.R. Crespo , Braun J , Brenner G , Bruhns H , Draganič I N , Martínez AJ González , Lapierre A , Mironov V , Osborne C , Sikler G , Orts R Soria , Tawara H , Ullrich J , Tupitsyn I I , Shabaev V M
Published: June 2005

The research program at the Heidelberg Electron Beam Ion Trap (EBIT) has concentrated mainly on precision measurements relevant to quantum electrodynamics (QED) and nuclear physics. Spectroscopic measurements in the optical region have delivered the most accurate wavelengths ever reported for highly charged ions, extracting even isotopic shifts. The forbidden transitions of B-like Ar XIV and Be-like Ar XV ions were studied. They are especially interesting, since the QED contributions are as large as 0.2%. Improved atomic structure calculations allowed for the determination of their values with growing accuracy. The lifetimes of the corresponding metastable levels have also been measured with an uncertainty of less than 0.5% thus becoming sensitive to the influence of the bound electron anomalous magnetic moment, so far an almost experimentally unexplored QED effect. A new laser spectroscopic setup aims at facilitating future studies of the hyperfine structure of heavy hydrogenic ions. Through the study of the dielectronic recombination, information on rare processes, such as two-electron-one-photon transitions in Ar16+, or the interference effects between dielectronic and radiative recombination in Hg77+, and accurate values for the excitation energies of very heavy HCI have been obtained. A novel X-ray crystal spectrometer allowing absolute X-ray wavelength measurements in the range up to 15 keV with very high precision and reproducibility is currently used to study the Lyman series of H-like ions of medium-Z ions and the 2s2p transitions of very heavy Li-like ions. PACS Nos.: 31.30.Jv, 32.80.Fb, 32.80.Dz, 32.30.Jv, 32.30.Rj, 95.30.Dr
The muonic hydrogen Lamb-shift experiment
Authors: Pohl R , Antognini A , Amaro F D , Biraben F , Cardoso J MR , Conde C AN , Dax A , Dhawan S , Fernandes L MP , Hänsch T W , Hartmann F J , Hughes V W , Huot O , Indelicato P , Julien L , Knowles P E , Kottmann F , Liu Y -W , Ludhova L , Monteiro C MB , Mulhauser F , Nez F , Rabinowitz P , dos Santos J MF , Schaller L A , Schwob C , Taqqu D , Veloso JF CA
Published: June 2005

The charge radius of the proton, the simplest nucleus, is known from electron-scattering experiments only with a surprisingly low precision of about 2%. The poor knowledge of the proton charge radius restricts tests of bound-state quantum electrodynamics (QED) to the precision level of about 6 × 106, although the experimental data themselves (1S Lamb shift in hydrogen) have reached a precision of 2 × 106. The determination of the proton charge radius with an accuracy of 103 is the main goal of our experiment, opening a way to check bound-state QED predictions to a level of 107. The principle is to measure the 2S2P energy difference in muonic hydrogen (µp) by infrared laser spectroscopy. The first data were taken in the second half of 2003. Muons from our unique very-low-energy muon beam are stopped at a rate of ~100 s1 in 0.6 mbar H2 gas where the lifetime of the formed µp(2S) atoms is about 1.3 µs. An incoming muon triggers a pulsed multistage laser system that delivers ~0.2 mJ at λ ≈ 6 µm. Following the laser excitation µp(2S) → µp(2P) we observe the 1.9 keV X-rays from 2P1S transitions using large area avalanche photodiodes. The resonance frequency, and, hence, the Lamb shift and the proton radius, is determined by measuring the intensity of these X-rays as a function of the laser wavelength. A broad range of laser frequencies was scanned in 2003 and the analysis is currently under way. PACS Nos.: 36.10.Dr, 14.20.Dh, 42.62.Fi
Including the strong nuclear force in antihydrogen-scattering calculations
Authors: Jonsell S , Saenz A , Froelich P , Zygelman B , Dalgarno A
Published: June 2005

We investigate two methods to include the strong nuclear force in hydrogenantihydrogen scattering calculations. First, we construct a model optical potential with parameters determined by the measured shift and width of the protonium ground state. Although this potential is a very crude model for the strong nuclear force, its parameters may be adjusted to reproduce both bound states and low-energy annihilation cross sections to within the experimental accuracy. It is then shown that this potential may be reduced to a short-distance boundary condition in terms of the protonantiproton strong-interaction scattering length. Elastic and annihilation cross sections for ground-state hydrogenantihydrogen scattering are calculated for s- and p-waves, and collision energies up to 1 atomic unit. The two methods are found to agree to within about 1%. The main source of discrepancy is that the scattering-length approach does not account for vacuum polarization, relativistic, and finite-size corrections. We verify that the range of the strong interaction potential does not affect the hydrogenantihydrogen s-wave scattering properties, and that the strong interaction has negligible influence on p-wave scattering. PACS Nos.: 36.10.-k, 34.90.+q
Some recent advances in bound-state quantum electrodynamics
Authors: Jentschura U D , Evers J
Published: June 2005

We discuss recent progress in various problems related to bound-state quantum electrodynamics: the bound-electron g factor, two-loop self-energy corrections, and the laser-dressed Lamb shift. The progress relies on various advances in the bound-state formalism, including ideas inspired by effective field theories such as nonrelativistic quantum electrodynamics. Radiative corrections in dynamical processes represent a promising field for further investigations. PACS Nos.: 31.15.p, 12.20.Ds
Test of time dilation by laser spectroscopy on fast ions
Authors: Saathoff G , Reinhardt S , Buhr H , Carlson L A , Schwalm D , Wolf A , Karpuk S , Novotny C , Huber G , Gwinner G
Published: June 2005

The laser-spectroscopic frequency measurement of Doppler-shifted optical lines in the forward and backward directions of a fast ion beam permits a sensitive test of the relativistic Doppler formula and, hence, the relativistic time-dilation factor γSR = 1/[Formula: see text]. An experiment on 7Li+, stored at a velocity of v = 0.065c in the Heidelberg heavy-ion storage ring TSR, has confirmed time dilation with unprecedented accuracy limiting deviations to below 2.2 × 107. Ongoing improvements on the experimental setup will further tighten this limit.PACS Nos.: 03.30.+p, 06.30.Ft, and 42.62.Fi
Isotope shifts and nuclear radius measurements for helium and lithium
Authors: Drake G WF , Nörtershäuser W , Yan Z -C
Published: June 2005

It is now well established that accurate relative values of the rms nuclear charge radius for light atoms can be extracted from a comparison between high-precision theory and experiment for the isotope shift in atomic transition frequencies. Results are available for isotopes of helium and lithium. This paper reviews and updates the interpretation of earlier measurements for 3He relative to 4He, and 6Li relative to 7Li. New results are presented for the quantum electrodynamic recoil corrections. Recent measurements for the halo nucleus 6He, and the short-lived nuclei 8Li, and 9Li are discussed. The derived nuclear charge radii of 2.054(14), 2.30(4), and 2.24(4)~fm, respectively, are compared with the predictions of various nuclear structure models.PACS Nos.: 31.15.Pf, 31.30.Jv, and 32.10.Hq
Lithium transition energies and isotopic shift: three correlated electron states
Authors: Tomaselli M
Published: June 2005

Energies of the 1s22s2S1/2 and the 1s23s2S1/2 of the lithium isotopes are calculated in a dynamic correlation model. With the evaluated configuration mixing wave functions the polarization effects resulting from an extended nuclear charge distribution are evaluated. A relative large contribution for 7Li is observed.PACS Nos.: 32.10.Fn, 21.10.Ft, 27.20.+n
ELECTRONIC STRUCTURE CALCULATIONS OF LOW-DIMENSIONAL SEMICONDUCTOR STRUCTURES USING B-SPLINE BASIS FUNCTIONS
Authors: DIKMEN BORA , TOMAK MEHMET
Published: June 2005

An efficient method for the low-dimensional semiconductor structure is investigated. The method is applied to symmetric double rectangular quantum well as an example. A basis set of Cubic B-Splines is used as localized basis functions. The method compares well with analytical solutions and the finite difference method.
MASS DISTRIBUTION OF A TWO-DIMENSIONAL FRAGMENTATION PROCESS
Authors: ARARIPE L. E. , DIEHL A. , ANDRADE J. S. , COSTA FILHO R. N.
Published: June 2005

We perform extensive molecular dynamics simulations to study the mass size distribution of a two-dimensional fragmentation process. Our model consists of a large number of particles interacting through the Lennard–Jones potential. The fragmentation is induced by suddenly imposing a radial component on the particles' velocities, in order to mimic an explosion phenomenon. We then investigate the effect of the input energy on the resulting mass distribution of fragments.
STRUCTURAL AND ELECTRONIC PROPERTIES OF (CnLi)+ CLUSTER IONS
Authors: YAZGAN EFE , ERKOÇ ŞAKIR
Published: June 2005

The structural and electronic properties of ( C n Li )+ cluster ions with n =1–6 and n =20 have been investigated by performing density functional theory calculations at B3LYP level. The vibrational frequencies of the clusters are also calculated.
SCALING PROPERTIES OF STRONG AVALANCHES IN SAND-PILE
Authors: SHAPOVAL A. B. , SHNIRMAN M. G.
Published: June 2005

We introduced strong avalanches in the two-dimensional sand-pile and investigated the distributions F(·, L) of their size corresponding to the different system lengths L. Being appropriately scaled, these distributions coincide. The inverse map F-1as the function on L sets up the correspondence between the avalanches associated with different L. As to the strong avalanches, with any fixed first argument δ, the map F-1(δ, L) is proportional to a power function, where the exponent varies from 2 to 3 depending on δ, while F-1(δ, L) is proportional to L2for the other avalanches.
CHOICE OF Bi2223 UNIT CELL FOR TEXTURE STUDIES USING ORIENTATION DETERMINATION IN THE SCANNING ELECTRON MICROSCOPE
Authors: LIN D. , LIU W. , GODFREY A. , LIU Q.
Published: June 2005

Existing proposals for the crystal structure of the high temperature superconducting Bi 2 Sr 2 Ca 2 Cu 3 O 7-x ( Bi 2223) phase have been reviewed. For the purpose of automated orientation determination in the scanning electron microscope using electron backscatter pattern (EBSP) analysis, a new crystal structure is proposed, where the unit cell is assumed to be tetragonal with P4/mmm point-group symmetry. Simulated EBSP images corresponding to the various unit cells exhibit significant differences, confirming the importance of choosing the correct unit-cell information. The suitability of various choices of the unit cell for automated orientation determination using EBSP analysis has been investigated using experimental data. The newly proposed unit cell is superior to the other unit cells for each of the criteria used to assess the indexing ability.
MAGNETIC PROPERTIES OF AMORPHOUS Fe40Ni38B18Mo4 RIBBONS CONTAINING NANOCRYSTALLITES
Authors: TIVAKORNASITHORN K. , NILPAIRUCH S. , VATANAYON S. , TANG I. M.
Published: June 2005

Cut Fe 40 Ni 38 B 18 Mo 4 ribbons were annealed for two hours at various temperatures Ta between 400 and 540°C. All the ribbons were subjected to XRD, VSM (vibrating sample magnetometer) and ME (Mossbauer effect spectroscopy) investigations. A differential thermal analysis scan of an as-cast ribbon showed the presence of two exothermic peaks, the first beginning at 419.9°C and peaking at 429.7°C and the second beginning at 497.3°C and ending at 546.2°C. The XRD patterns of the ribbons showed the formation of FeNi 3 nanocrystallites in the lower T'a ribbons and (Fe, Ni, Mo) 23 B 6 crystallites in the ribbons annealed above 470°C. Different behaviors of the saturation magnetization were seen in the ribbons annealed between 400 and 450°C, between 450 and 490°C, and between 490 and 540°C. The ME spectra of the ribbons annealed in the three different temperature ranges also pointed to the presence of three crystalline Fe-compounds in these ranges. The XRD patterns and the coercivities (Hc) of the lower Ta ribbons point to the formation of nanocrystallites in these ribbons.
IMPLICATIONS OF Gd DESTROYING HIGH-TEMPERATURE SUPERCONDUCTIVITY
Authors: DOW JOHN D. , HARSHMAN DALE R.
Published: June 2005

The magnetic ion Gd +3, having L = 0 and J ≠ 0, is unsplit by crystal fields and, unlike the other trivalent L ≠ 0 rare-earth ions (which are crystal-field split), is a pair-breaker in high-temperature superconductors. Consequently two-layer compounds with Gd (i.e., Gd 2-z Ce z CuO 4 and Ba 2 GdRu 1-u Cu u O 6) do not superconduct, but their sister compounds without unsplit and pair-breaking Gd , do superconduct (e.g., Nd 2-z Ce z CuO 4, with crystal-field split Nd , and Sr 2 YRu 1-u Cu u O 6, with L = 0 Y , both superconduct). The superconductivity clearly originates in the oxygen of the SrO or BaO layers, or in interstitial oxygen, not in the CuO 2 planes.
ON THE STOCHASTIC VARIATIONAL APPROACH TO LOWER BOUNDS FOR ENERGY EIGENVALUES OF FEW-BODY QUANTUM SYSTEMS
Authors: SOLDATOV A. V.
Published: June 2005

It is shown that the method of intermediate problems, which provides improvable convergent lower bounds for eigenvalues of linear half-bound Hermitian operators in Hilbert space, can be linked in a natural way to the stochastic variational method, thus resulting in an effective tool for analytical and numerical investigation of the energy spectrum and eigenstates of various few-body quantum systems, among them quantum dots with relatively large numbers of electrons.
SPECTRAL APPROACH TO CHAOS AND QUANTUM-CLASSICAL CORRESPONDENCE IN QUANTUM MAPS
Authors: GARCÍA-MATA IGNACIO , SARACENO MARCOS
Published: June 2005

Correspondence in quantum chaotic systems is lost in short time scales. Introducing some noise we study the spectrum of the resulting coarse-grained propagator of density matrices. Some different methods to compute the spectrum are reviewed. The relationship between the eigenvalues of the coarse-grained superoperator and the classical Ruelle–Pollicott resonances is remarked on. As a consequence, classical decay rates in quantum time-dependent quantities appear.
REPRESENTING BUSINESS CONTRACTS INRuleML
Authors: GOVERNATORI GUIDO
Published: June 2005

This paper presents an approach for the specification and implementation of translating contracts from a human-oriented form into an executable representation for monitoring. This will be done in the setting of RuleML. The task of monitoring contract execution and performance requires a logical account of deontic and defeasible aspects of legal language; currently such aspects are not covered by RuleML; accordingly we show how to extend it to cover such notions. From its logical form, the contract will thus be transformed into a machine readable rule notation and eventually implemented as executable semantics via any mark-up languages depending on the client's preference, for contract monitoring purposes.
EXTENDING CHOREOGRAPHY WITH BUSINESS CONTRACT CONSTRAINTS
Authors: BERRY ANDREW , MILOSEVIC ZORAN
Published: June 2005

Business contracts play a central role in governing commercial interactions between organizations. It is increasingly recognized that business contract conditions need to be closely linked to internal and external business processes, both to reduce the risk of contract violations and to ensure compliance with legislative regimes. Recent research has proposed contract languages allowing the specification of obligations, permissions and prohibitions in business contracts. Business processes that cross-organizational boundaries can be specified in choreography and coordination languages but these do not provide appropriate abstractions for contract constraints. In this paper, we examine the transformation of contract constraints in a business contract language into expressions in a choreography language. An example cross-organizational process is presented, along with a specification of the process in a choreography language and a specification of a set of contract conditions for the process in a business contract language. The contract terms are then translated into choreography expressions that govern the process to ensure compliance. Subsequent discussion explores a number of business and technology issues related to the results. We conclude that cross-organizational business processes can be monitored and enforced according to business contract specifications through the transformation of a contract definition to constraints on process behavior.
AUTOMATING SUPPORT FOR E-BUSINESS CONTRACTS
Authors: LININGTON PETER F.
Published: June 2005

If e-business contracts are to be widely used, they need to be supported by the IT infrastructure of the organizations concerned. This implies that the interactions between systems in different organizations must be guided by the contract and there must be sufficiently strong checks and balances to ensure that the contract is in fact obeyed. This includes facilities for the unbiased monitoring of correct behaviour and the reporting of exceptions.

One of the ways to provide this support is to generate it directly from the agreed contract. This paper considers the steps necessary to provide sufficient automation in the support and checking of e-Business contracts for them to offer efficiency gains and so to become widely used. It focuses on the role of models, taking a model-driven approach to development and discussing both the source and target models and the transformational pathways needed to support the contract-based business processes.
COUNTERACTING SHILL BIDDING IN ONLINE ENGLISH AUCTION
Authors: BHARGAVA BHARAT , JENAMANI MAMATA , ZHONG YUHUI
Published: June 2005

The popularity of online auctions and the associated frauds have led to many auction sites preferring English auction over other auction mechanisms. The ease of adopting multiple fake identities over the Internet nourishes shill bidding by fraudulent sellers in English auction. In this paper, we derive an equilibrium bidding strategy to counteract shill bidding in an online English auction. An algorithm based on this strategy is developed. We conduct experiments to evaluate the strategy in a simulated eBay like auction environment. Five popular bidding strategies are compared with the proposed one. In the simulation, bidders compete to buy a product in the presence of a shill. Each bidder is randomly assigned a bidding strategy. She draws her valuation from a uniform distribution. The experiments show hat the average expected utility of agents with proposed strategy is the highest when the auction continues for a longer duration.
The Intra-Industry Effect of Share Repurchase Deregulation: Evidence from Taiwan
Authors: Chang Shao-Chi , Lai Jung-Ho , Yu Chen-Hsiang
Published: June 2005

Share repurchases were deregulated in Taiwan in 2000. The regulatory provisions and the government's stated aim of market stabilization provide a setting in which share repurchases are exclusively motivated by undervaluation. This study investigates if deregulation of share repurchases is an effective method of market stabilization by investigating the intra-industry effects of repurchase deregulation in Taiwan. We find that repurchasing firms and their corresponding rivals both experience strong value creation upon the repurchase announcements. The evidence suggests that the intra-industry effect of share repurchases is negatively associated with rivals' firm size, and positively associated with the announcing firm's abnormal return, the size of share repurchases and the similarity of business operation between rivals and repurchasing firms. These findings hold even after taking into account other effects that could influence the valuation of the rival firms.
Stock Market Reaction to Mergers and Acquisitions in Anticipation of a Subsequent Related Significant Event: Evidence from the Korean Telecommunications Industry
Authors: Nam Changi , Yang Dong-Hoon , Park Myeong-Cheol , Oh Gil-Hwan , Park Jong-Hyun
Published: June 2005

The objective of this paper is to assess the effect of mergers and acquisitions on shareholder wealth when subsequent related significant events are anticipated. We identify a particular merger and acquisition between telecommunication companies in Korea and examine whether it conveys good or bad news to stock market participants. We hypothesize and find that mergers and acquisitions are interpreted as good news by the marketplace when they are expected to be accompanied by a subsequent related significant event, in our case granting of a government license for the IMT-2000 mobile service.
FLEXURAL AND LOCAL BUCKLING INTERACTION OF STEEL ANGLES
Authors: MOHAN S. J. , RAO N. PRASAD , LAKSHMANAN N.
Published: June 2005

The column buckling equation and plate buckling equation are merged to obtain a graphical relation in the elastic and inelastic buckling ranges. This graphical relation has been used to classify all possible modes of hot rolled angle sections investigated by previous researchers in their experimental works. Forced plate buckling experiments have been carried out to verify the graphical relation for plate buckling. Design practices adopted by various standards for design of steel angles, have been compared with respect to this graphical relation and discussed. The importance of width to thickness ratio has been used to emphasize the buckling characteristics of hot rolled angle sections. The objective of this paper is to discuss the plate buckling failures of the angle sections recorded during full scale testing of transmission towers at Tower Testing and Research Station, SERC, Chennai, India. The plate buckling failures in tower testing for the past eighteen years have been analyzed and suggestions are given to avoid such failures in real structures and during testing.
FREE VIBRATION OF AN ORTHOTROPIC HOLLOW BODY OF REVOLUTION
Authors: REDEKOP D.
Published: June 2005

A method is developed to determine the natural frequencies of vibration of an orthotropic hollow body of revolution of constant thickness but of arbitrary smooth meridian. Equations are derived using the linear three-dimensional theory of elasticity, and a numerical solution is obtained using the differential quadrature method. The geometric generality of the solution is attained by delaying definition of local geometric parameters until the solution stage. Validation is by comparison with previously published results, including results for a hollow orthotropic cylinder. Sample results are given for orthotropic hollow cylinders and spherical segments, and conclusions are drawn.
COLLAPSE OF CORRUGATED CIRCULAR CYLINDERS UNDER UNIFORM EXTERNAL PRESSURE
Authors: ROSS CARL T. F.
Published: June 2005

The paper describes a finite element investigation into the buckling, under uniform external pressure, of four submarine pressure hulls. Two of these hulls were traditional ring-stiffened types, but two of these hulls were in the form of corrugated circular cylinders. The latter design was based on an invention by the present author. The investigation found that the new design was structurally efficient and in the case of the smaller vessel, it was found to be structurally more efficient than the conventional design.

Another investigation, based on axisymmetric plastic buckling, was conducted on the two corrugated vessels, to determine if they were prone to collapse through the bellows' mode of failure. This investigation was carried out because former critics of this work stated that the corrugated circular cylinders would fail by the bellows' mode of failure. Neither of the two corrugated pressure hulls was found to fail through the bellows' mode of failure, thereby completely vindicating the present author. The author, however, concludes that the bellows' mode of failure can occur if the cone angles were too large.

Two of the finite element theories were based on the author's work, but the giant computer package ANSYS was also used to study non-symmetric bifurcation buckling. This work was carried out to vindicate the author's in-house computer programs, which were simpler to use than ANSYS.
A FURTHER STUDY OF FLEXURAL-TORSIONAL BUCKLING OF ELASTIC ARCHES
Authors: PI Y.-L. , BRADFORD M. A. , TRAHAIR N. S. , CHEN Y. Y.
Published: June 2005

This paper uses both a virtual work approach and a static equilibrium approach to study the elastic flexural-torsional buckling of circular arches under uniform bending, or under uniform compression. In most studies of the elastic flexural-torsional buckling of arches under uniform compression produced by uniformly-distributed radial loads, the directions of the radial loads are conventionally assumed not to change but to remain parallel to their initial directions during buckling. In practice, the uniform compression may be produced by hydrostatic loads or by uniformly-distributed radial loads that are directed to a specific point during buckling. In addition, there are discrepancies between existing solutions for the elastic flexural-torsional buckling moment and load of arches under uniform bending or under uniform compression which need to be clarified. Closed form solutions for the buckling moment and load are developed. The discrepancies among the existing solutions for the elastic flexural-torsional buckling moment and load of arches are clarified and the sources for the discrepancies are identified. It is found that the lateral components of hydrostatic loads and of uniformly-distributed radial loads that are always directed toward the center of the arch increase the flexural-torsional buckling resistance of an arch under uniform compression. It is also found that first-order buckling deformations are sufficient for static equilibrium approaches for the flexural-torsional buckling analysis of arches. The rational static equilibrium approach for the flexural-torsional buckling in the present study is effective.
A LINEAR THERMOELASTIC BUCKLING BEHAVIOR OF FUNCTIONALLY GRADED HEMISPHERICAL SHELL WITH A CUT-OUT AT APEX IN THERMAL ENVIRONMENT
Authors: BHANGALE RAJESH K. , GANESAN N.
Published: June 2005

In this paper, a finite element formulation based on first-order shear deformation theory (FSDT) is used to study the thermal buckling behavior of functionally graded material (FGM) hemispherical shells with a cut-out at apex in a high temperature environment. A Fourier series expansion for the displacement variable in the circumferential direction is used to model the FGM hemispherical shell. The material properties of FGM hemispherical shells are functionally graded in the thickness direction according to a volume fraction power law distribution. Temperature-dependent material properties are considered to carry out a linear thermal buckling analysis. The hemispherical shell is assumed to be clamped–clamped and has a high temperature specified on the inner surface while the outer surface is at ambient temperature. The one-dimensional heat conduction equation is applied along the thickness of the shell to determine the temperature distribution and thereby material properties. Converged critical buckling temperatures are computed for two cases of thermal loads, namely, under uniform temperature rise and temperature gradient across the thickness. Numerical studies include the influence of, power law index, base to radius ratios, and different cut-out angles at the apex on the magnitude of thermal buckling temperature.