bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spin-liquid phase in the pyrochlore anti-ferromagnet
Authors: Canals B , Garanin D A 
Published: April 2011

Correlation functions (CFs) of the classical Heisenberg anti-ferromagnet on the pyrochlore lattice are studied by solving exactly the infinite-component spin-vector model. As in many fully frustrated lattices, the constraint due to the minimization of the energy and the particular structure based on corner-sharing tetrahedra both contribute to the creation of local degrees of freedom. The resulting degeneracy destroys any magnetic order at all temperatures and we obtain no sign of criticality, even at T = 0. Calculated neutron-scattering cross sections have their maxima beyond the first Brillouin zone and reproduce experimental results obtained on Y(Sc)Mn2 and CsCrNiF6 as well as theoretical predictions previously obtained by classical Monte Carlo simulations. Evidences for thermal and spatial decoupling of the magnetic modes are found so that the magnetic fluctuations in this system can be approximated by S(q,T) [Formula: see text] f(q) h(T). PACS Nos.: 75.10Hk, 75.50Ee, 75.40Cx, 75.40-s
Muon-spin relaxation measurements of geometrically frustrated magnets
Authors: Kojima K M 
Published: April 2011

Muon-spin relaxation (µSR) has been applied to investigations of slow dynamics and quasi-static features of geometrically frustrated spin systems. We take an example in the Kagome-lattice anti-ferromagnets, and briefly review µSR works on S = 1, 3/2, and 5/2 Kagome compounds. PACS No.: 75.30
High-resolution neutron study of the effects of magnetic dilution in the strongly frustrated system SrCrxGa12xO19
Authors: Mondelli C , Mutka H , Payen C 
Published: April 2011

We have pursued the neutron examination of SrCrxGa12xO19, with special emphasis on the role of magnetic dilution in the spin dynamics and freezing. We have examined samples with different levels of magnetic dilution, ranging from 7.0 < x < 8.8, characterized by neutron powder diffraction with Rietveld refinements and bulk susceptibility. The elastic magnetic response examined by high-resolution neutron scattering (µeV range) has confirmed the trend on increasing dilution: the decrease of the freezing temperature as well as of the frozen moment/magnetic site. However, the least diluted sample that we have produced with x = 8.8, deviates from this trend, with a smaller than expected freezing temperature and frozen moment. This suggests that the freezing might be suppressed at the clean limit. PACS Nos.: 75.10Nr, 75.25+z, 75.40Cx, 75.40Gb
Comparison of several tetrahedra-based lattices
Authors: Elhajal M , Canals B , Lacroix C 
Published: April 2011

A comparison of the quantum Heisenberg anti-ferromagnetic model on the pyrochlore lattice, the checkerboard lattice, and the square lattice with crossing interactions is performed. The three lattices are constructed with the same tetrahedral unit cell and this property is used to describe the low-energy spectrum by means of an effective Hamiltonian restricted to the singlet sector. We analyze the structure of the effective Hamiltonian and solve it within a mean-field approximation for the three lattices. PACS No.: 75.10Jm
Anomalous behavior in a three-dimensional frustrated itinerant electron magnet
Authors: Isoda M , Mori S 
Published: April 2011

We present a simple microscopic theory for the magnetic and electronic properties of a three-dimensional frustrated itinerant electron magnet. Based on the single-band Hubbard model, it is investigated in the weak-correlation limit at a half-filling on the pyrochlore lattice. A doubly-degenerate flat band in the bare spectrum emerges as a character of the fully frustrated geometry. The random-phase-approximation dynamical susceptibility reproduces some characters in the low-frequency regime that were found in the neutron inelastic-scattering experiment of the cubic Laves compound Y(Sc)Mn2, especially in the spectral intensity distribution in the reciprocal space and in the almost irrelevant feature of the distribution to frequency. The quasi-particle self-energy shows a peculiarity, resulting from an anomalous frequency dependence in the non-interacting dynamical susceptibility, and then it leads to the breakdown of the Fermi-liquid picture. PACS No.: 75.25+z
7Li NMR studies in magnetically frustrated LiV2O4: Evidence for a spin-liquid ground state?
Authors: Büttgen N , Kaps H , Trinkl W , Loidl A , Klemm M , Horn S 
Published: April 2011

7Li NMR measurements were performed in the metallic spinel LiV2O4. The temperature dependence of the spin-lattice relaxation rate is documented in the temperature range 100 mK < T < 280 K. A comparison with the spin-glass behavior of Li1xZnxV2O4 for small concentrations of x is given. For low temperatures T < 1 K we observe a maximum for the spin-lattice relaxation rate in LiV2O4. The frequency dependence of this maximum is indicative for a slowing down of spin fluctuations. The NMR results can be explained by a spin-liquid behavior and the opening of a spin gap of the order 1 K. PACS Nos.: 75.20Hr, 75.50Lk, 76.60Es, 76.60-k
Geometric frustration in the RMn2 Laves phase compounds
Authors: Ballou R 
Published: April 2011

An overview of neutron-scattering investigations of the geometrically frustrated Mn itinerant-electron magnetism in the RMn2 Laves phase compounds is given. Magnetic structures of magnetically ordered compounds are briefly described, in particular the mixed phases where magnetic and nonmagnetic Mn coexist. Magnetic correlations in the paramagnetic phase of YMn2 and in (Y0.97Sc0.03)Mn2, where the substitution of Sc for Y inhibits the magnetic order down to the lowest temperatures, are then discussed. An unusual neutron-scattering function S(Q, ω) is measured, which appear to arise from an itinerant-electron spin liquid. PACS Nos.: 71.27+a, 75.40Gb, 75.50Ee
Magnetic ordering and excitation in triangulated anti-ferromagnet Cu9Cl2(cpa)6·nH2O
Authors: Mekata M , Abdulla M , Kubota M , Oohara Y 
Published: April 2011

The Cu2+ ions in Cu9Cl2(cpa)6 · nH2O (cpa is the anion of 2-carboxy pentonic acid) form a slightly deformed Kagome lattice with a smaller triangle plaquette in each triangle of a Kagome lattice showing strong frustration. The anomalous features of magnetism are the reduction of the Curie constant below 50 K, fractional saturation even in a field of 38 T, and nonlinear magnetic susceptibility below 5 K. We performed inelastic neutron scattering measurements on powder samples and observed dispersionless scattering around 6.5 meV with a full width of about 8 meV indicating a single-site excitation with E/kB [Formula: see text] 70 K. The scattering is less conspicuous above 50 K. These results are interpreted in terms of the plaquette-ordering model that assumes a 120° arrangement of three moments on each triangular plaquette and a random freezing of the remaining paramagnetic moments below 5 K. PACS No.: 75.10Hk
Magnetic-ordering process in SrCr9(Ga-In)3O19
Authors: Mekata M , Yamada Y 
Published: April 2011

To investigate the anomalous magnetic properties of SrCr9xGa3+xO19, we synthesized SrCr9x(Ga0.95In0.05)3+xO19 compounds including the x = 0 compounds and carried out magnetic and µSR measurements. The results show clearly the insignificant role of the defects in the magnetic Cr lattice. Based on the results, a classical Heisenberg spin model, the plaquette-ordering model, is presented. Below 60 K, seven moments on a bi-tetrahedron plaquette correlate anti-ferromagnetically to give one moment, so that the Curie constant decreases to 1/9 at low temperatures. The surviving moments forming a triangular lattice do not exhibit long-range order due to frustration but the c-components of the moments are frozen randomly below Tf. The muoniums formed in the compound combine with the oxygen ions connecting Cr3+ ions and are subject to transferred hyperfine fields from Cr moments. This field is shielded by the electrons of the muonium so as to be hardly decoupled by external fields. PACS Nos.: 75.40Cx, 75.50Ee
Magnets with strong geometric frustration
Authors: Moessner R 
Published: April 2011

A nontechnical introduction to the theory of magnets with strong geometric frustration is given, concentrating on magnets on corner-sharing (Kagome, pyrochlore, SCGO, and GGG) lattices. Their rich behaviour is traced back to a large ground-state degeneracy in model systems, which renders them highly unstable towards perturbations. A systematic classification according to properties of their ground states is discussed. Other topics addressed in this overview article include a general theoretical framework for thermal order-by-disorder, the dynamics of how the vast regions of phase space accessible at low temperature are explored, the origin of the featureless magnetic susceptibility fingerprint of geometric frustration, the role of perturbations, and spin ice. The rich field of quantum frustrated magnets is also touched on. PACS No.: 75.50-y
Dependence on crystallographic orientation of trapping properties in a polished MgO single crystal
Authors: Dammak N , Kallel A , Fakhfakh Z , Tréheux D 
Published: April 2011

It is well known that the presence of space charges in an insulator is correlated with electric breakdown. Many studies have been carried out on the experimental characterization of space charges and on phenomenological models of trapping and detrapping. In this paper, we outline the dependence on crystallographic orientations of the charge-trapping phenomenon in polished MgO. The charging phenomenon was characterized during and after electron injection by using a scanning electron microscope (SEM). It was shown that the trapping ability depends on the dislocation network of different crystallographic orientations. PACS No.: 72.20Jv
Scattering from a spherical shell with a circular aperature using neural network approach
Authors: Hamid A -K 
Published: April 2011

A neural network is developed for the problem of scattering from a spherical shell with a circular aperture. The neural network is used to predict the backscattering cross section without the need to solve the vector field equations. The neural network is trained to model the nonlinear relation between the electrical radius of the sphere, half aperture angle, and the backscattering cross section using experimental data. This method is proven to be faster than standard methods and consumes less CPU time. Numerical results are presented graphically for backscattering cross section with electrical radii and half aperture angles different from those are used for training. PACS Nos. 41.10H, 41.90
The ponderomotive four-momentum
Authors: Gao J , Bagayoko D , Guo D -S 
Published: April 2011

Using classical mechanics and classical field theory, we confirm that the ponderomotive momentum exists as a counterpart of the ponderomotive energy to form the ponderomotive four-momentum when an electron interacts with a light plane wave. As a solution to the equations of motion, a time-dependent four-momentum on the electron (rest) mass shell is obtained in a coordinate-free form. By taking out the quiver motion, we find that the nonoscillating part of the four-momentum is not on the electron mass shell. We show mathematically that the decomposition of the nonoscillating four-momentum into an on-mass-shell four-momentum and a lightlike four-momentum along the light-propagation direction is unique. The time-component of the lightlike four-momentum is exactly the ponderomotive energy, while the space-component is the ponderomotive momentum. We discuss the critical role of the ponderomotive four-momentum in lightelectron scattering processes due to the lightlike property and the uniqueness of the decomposition of a four-momentum. Two pieces of experimental evidence of the ponderomotive momentum are identified in the discussion. PACS No. 32.80Rm
Single quantum pair annihilation of a bound particleparticleantiparticle system
Authors: Darewych J W , Biswas P 
Published: April 2011

A relativistic coupled channel formalism is presented for the description of a quasi-bound three-body state.The annihilation of a particleparticleantiparticle system into a particle and a single quantum is studied in the scalar Yukawa model, in which scalar "nucleons" (ϕ) and "antinucleons" ([Formula: see text]) interact via scalar "meson" χ exchange. A three-Fock-state trial state is used to derive variational equations that describe the quasi-bound [Formula: see text] system as a resonance in the χ ϕ collision channel. These equations are solved approximately to yield the [Formula: see text] decay width. This width is found to be negligible compared with the two-quantum pair annihilation width if the coupling is weak (α << 1), but is found to be of comparable magnitude for strong coupling (α [Formula: see text] 1). Relativistic effects on the width are pronounced and cannot be neglected at strong coupling. Order of magnitude comparison is made with the Ps¯ system for the massless-χ case, and to nuclear [Formula: see text] systems for the massive-χcase. PACS Nos. 11.10Qr and 11.10st
Formal theory of multiphoton double ionization: Sequential and direct
Authors: Altzman Jerry B , Mittleman Marvin H 
Published: April 2011

The rate parameters for double multiphoton ionization are obtained as functions of T matrices, which are derived from the S matrix by a generalization of the Fermi Golden Rule. The different T's appear, and are distinguished from each other as coefficients of different energy singularities, principal parts as well as delta functions, in S. These are connected to the rate parameters, which appear in threecoupled-rate equations. New terms are shown to contribute to the direct ionization process and new interference terms are also found to contribute to the direct ionization rate. A new interpretation of the shake-off term is given, and it is found to be a sequential process. {PACS Nos.: 32.80F, 32.80K}
Article
Authors: Kent R D , Schlesinger M , Wybourne B G 
Published: April 2011

The role of Lie groups and algebras in symmetry-based models of the genetic code is considered. The two schemes, based upon the symplectic group Sp(6) and the exceptional group G(2) are shown to correspond to different embeddings in the group SO(14). Some possible alternative schemes are sketched. Problems with considering codons being represented as fermionic or bosonic are noted. A complete listing is given of all 64-dimensional irrecducible representations that can arise in the symmetric and alternating groups. PACS Nos.: 87.10 and 02.20
Article
Authors: Burgess M , Carrington M , Kunstatter G 
Published: April 2011

The initial value problem of wave motion is considered for two immiscible layersof incompressible fluids in the presence of a porous wave maker immersed vertically in thetwo uids, which are periodic in the horizontal direction along the wave maker as well as intime. The resulting motion is investigated using the method of generalized functions, and anasymptotic analysis for large values of time and distance is given for the depression of thefree surface and the surface of separation between the two fluids. The generated fluid patternis discussed for different values of the wave number of the oscillations of the wave makervelocity in the horizontal direction. PACS No.: 47.35
Article
Authors: Toyama F M , Nogami Y 
Published: April 2011

This is a sequel to two earlier papers in which the behaviour of the nonlinear Dirac soliton in an external potential in 1+1 dimensions is examined. Regarding the Lorentz transformation properties there are three types of potentials: vector (V), scalar (S), and pseudoscalar (PS). In this paper we consider the PS potential. Unlike the V and S potentials that we considered earlier, the PS potential has no obvious counterpart in classical mechanics. Still the soliton behaves like a point particle in relativistic classical mechanics with a certain Hamiltonian. Close scrutiny, however, reveals that the soliton undergoes Zitterbewegung. PACS Nos.: 02.30, 03.40Kf, 03.65-w
Article
Authors: Wang Lixen , Jones W E 
Published: April 2011

In-situ real time CARS (coherent anti-Stokes Raman spectroscopy) spectra of the nu1 mode of SF6 were recorded in a discharge tube with varying delay times between the discharge pulse and the CARS detection pulse. Theoretical CARS spectra were calculated for the nu1 mode of SF6 at various vibrational temperatures. Based on relationships between line width, frequency shift, and temperature, a best fit method was developed to extract the temperatures from experimental line shapes instead of peak intensities. The kinetic behaviour of the vibrational temperature of SF6 during the discharge pulse was thus obtained. This method is useful for examination of chemical and physical processes in which the total population in a specific vibrational mode changes. PACS No.:33.20f
Atomic interface structure-property investigations
Authors: Kavanagh K L 
Published: April 2011

Our current understanding of the relationship between interfacialstructure and the resulting properties remains very rudimentary.This is a concern for many fields and applications, includingmetal/semiconductor contacts, insulator/semiconductor field effectjunctions, magnetic multilayers, ferroelectric thin films, andsemiconductor heterostructures. The situation is slightly improvedin the case of epitaxial growth where a deposited layer followsthe structure of the underlying substrate. However, even withthese systems the interfacial properties are difficult to predictaccurately, even when impurities and defects can be ignored. Thispaper highlights a number of recent examples of interfacestructure-property investigations that have attempted tounderstand how the interface formation determines the relevantfilm or interface property. PACS Nos.: 68.55.Jk, 68.55.Ln, 68.65.+g
Effect of nitric oxide synthase inhibition on cardiovascular and hormonal regulation during pregnancy in the rat
Authors: Zhang Yunlong , Kaufman Susan 
Published: April 2011

Recent studies have shown that nitric oxide (NO) biosynthesis increases in pregnancy and that inhibition of nitric oxide synthase (NOS) induces some pathological processes characteristic of preeclampsia. The current project sought to study the effect of the NOS inhibitor Nω-nitro-L-arginine methyl ester (L-NAME, 10 µg·min-1, sc for 7 days) on plasma volume, plasma atrial natriuretic factor (ANF), plasma endothelin-1 (ET), and plasma renin activity (PRA) during gestation in conscious rats. NOS inhibition caused mean arterial pressure to increase in both virgin and 21-day pregnant rats. Plasma volume fell in the pregnant rats [L-NAME, 4.5 ± 0.3 mL·100 g-1 body wt. (n = 7) vs. D-NAME, 6.8 ± 0.2 mL·100 g-1 body wt. (n = 10); P < 0.05] but not in the virgin rats [L-NAME, 4.3 ± 0.1 mL·100 g-1 body wt. (n = 6) vs. D-NAME, 4.8 ± 0.2 mL·100 g-1 body wt. (n = 8)]. There was no effect of NOS inhibition on plasma ANF levels or PRA in either the virgin or pregnant rats. However, L-NAME did decrease plasma ET levels in the pregnant rats [L-NAME, 19.6 ± 1.6 pg·mL-1 (n = 8) vs. D-NAME, 11.6 ± 2.5 pg·mL-1 (n = 9); P < 0.05]. Our results confirm that NO is involved in cardiovascular homeostasis in pregnancy; NOS inhibition selectively reduces plasma volume in pregnant rats, thus mimicking a major pathophysiological perturbation of preeclampsia. However, it does not induce the hormonal changes characteristic of preeclampsia, namely the decrease in PRA and increase in plasma ET and ANF levels. Key words: plasma volume, preeclampsia, endothelin, atrial natriuretic factor, plasma renin activity.
THE INFLUENCE OF FOOD WHEAST® AND RELATED SACCHAROMYCES FRAGILIS YEAST PRODUCTS ON THE FECUNDITY OF CHRYSOPA CARNEA (NEUROPTERA: CHRYSOPIDAE)
Authors: Hagen K. S. , Tassan R. L. 
Published: April 2011

AbstractHigh fecundity from Chrysopa carnea was obtained from an inexpensive diet containing a commercially available product of dried, inactive Saccharomyces fragilis yeast and whey proteins. The effective diet consists of this product mixed with sucrose and water. S. fragilis autolysed 17 hours was more effective in diets than when autolysed for 36 hours or unautolysed, and was as effective as autolysed brewers’ yeast, S. cerevisiae.
A NEW EULOPHID PARASITE (HYMENOPTERA: CHALCIDOIDEA) FROM EGGS OF THE NURSERY PINE SAWFLY, DIPRION FRUTETORUM (HYMENOPTERA: TENTHREDINOIDEA)
Authors: Yoshimoto Cari. M. 
Published: April 2011

AbstractA new genus and new species, Peckelachertus diprioni, is described and illustrated. Material was reared from eggs of the nursery pine sawfly, Diprion frutetorum (Fabricius) in Quebec, Canada.
DESCRIPTIONS OF THREE NEW SPECIES IN THE GENERA AMBLYSEIUS BERLESE AND TYPHLODROMUS SCHEUTEN (ACARINA: PHYTOSEIIDAE) IN CANADA, WITH DESCRIPTIONS OF MALES OF NINE OTHER SPECIES, AND SOME NEW COLLECTION RECORDS
Authors: Chant D. A. , Shaul E. Yoshida 
Published: April 2011

AbstractThree new species, two in the genus Amblyseius Berlese and one in the genus Typhlodromus Scheuten, collected in Canada are described. Three additional Amblyseius species and one Typhlodromus species are recorded for the first time in Canada. The previously unknown males of 9 species are described. These new records bring the total numbers of species in the genera Amblyseius and Typhlodromus in Canada to 53 and 22 respectively.
SUPPRESSION OF CODLING MOTH, LASPEYRESIA POMONELLA (LEPIDOPTERA: OLETHREUTIDAE), BY RELEASE OF STERILE AND PARTIALLY STERILE MOTHS
Authors: Proverbs M.D. , Newton J.R. , Logan D.M. 
Published: April 2011

AbstractBecause laboratory and field cage experiments had shown that partially sterile (25 krad dose) male codling moths were sexually more competitive than sterile (40 krad) ones, a study was made in a British Columbia orchard in 1970 to determine whether release of 25 krad moths of mixed sexes would suppress this pest more effectively than release of 40 krad moths. Approximately 75,000 moths/ha were released from 24 April to 25 September for each dose level. In the 25 krad moth release plot, the percentage of apple fruits damaged by this pest at harvest was reduced from 0.21 in 1969 to 0.08 in 1970, whereas in the 40 krad plot damage was reduced from 0.04 in 1969 to 0.02 in 1970.Release of 25 krad moths was also compared with insecticide sprays for codling moth suppression in two small areas at Cawston and Olalla, B.C. At Cawston, the percentage of apples damaged at harvest was reduced from 1.0 in 1969, after three sprays of phosalone, to 0.1 in 1970 after release of irradiated insects. In contrast, per cent damage in a nearby apple orchard, sprayed twice with azinphos-methyl in 1969 and 1970, increased from 2.0 in 1969 to 8.1 in 1970. At Olalla, per cent damage was about the same (0.5) in 1969, after three phosalone sprays, as in 1970 (0.6) after release of irradiated insects. In a neighboring apple orchard, sprayed twice with phosalone in 1969 and 1970, per cent damage was about the same (1.0–1.2) each year.
TRAFFIC THROUGH THE NEST ENTRANCE OF A COLONY OF VESPULA ARENARIA (HYMENOPTERA: VESPIDAE)
Authors: Pallett M. J. , Plowright R. C. 
Published: April 2011

AbstractStatistical analysis of traffic data at the nest entrance of a colony of the yellowjacket, Vespula arenaria (F.), showed no evidence for the operation of social facilitation of the type described by Blackith (1957). As in bumble bees, the appearance of contagion in the temporal distribution of exits and sorties is the result of overall change in flight activity and is not due to social interaction between wasps.
A NEW GENUS OF EURYTOMIDAE (CHALCIDOIDEA: EURYTOMIDAE, AXIMINAE) FROM BRAZIL
Authors: Yoshimoto Carl M. , Gibson Gary A. P. 
Published: April 2011

An interesting, highly unusual chalcidoid wasp was found recently for Dr. L. Masner in material collected for him by Mr. F. M. Oliveira from Brazil. This unique specimen proved to belong to an undescribed genus in the subfamily Aximinae of the family Eurytomidae. It keys to the genera Axima Walker and Conoaxima Brues in Burks’ (1971) key to the genera of Eurytomidae, but differs in a number of morphological characters discussed below.The structure and sculpture of this unique female specimen are illustrated by scanning electron photographs, the wings and antennae by macrophotography.