CERN Document Server

This contribution reviews a selection of findings on atomic density functions and discusses ways for reading chemical information from them. First an expression for the density function for atoms in the multi-configuration Hartree--Fock scheme is established. The spherical harmonic content of the density function and ways to restore the spherical symmetry in a general open-shell case are treated. The evaluation of the density function is illustrated in a few examples. In the second part of the paper, atomic density functions are analyzed using quantum similarity measures. The comparison of atomic density functions is shown to be useful to obtain physical and chemical information. Finally, concepts from information theory are introduced and adopted for the comparison of density functions. In particular, based on the Kullback--Leibler form, a functional is constructed that reveals the periodicity in Mendeleev's table. Finally ...

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A particle detector is provided, the particle detector including a spherical Cherenkov detector, and

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Radial sonic crystals (RSC) are fluidlike structures infinitely periodic along the radial direction that verify the Bloch theorem and are possible only if certain specially designed acoustic metamaterials with mass density anisotropy can be engineered (see Torrent and Sanchez-Dehesa 2009 Phys. Rev. Lett. 103 064301). A comprehensive analysis of two-dimensional (2D) RSC shells is reported here. A given shell is in fact a circular slab with a central cavity. These finite crystal structures contain Fabry-Perot-like resonances and modes strongly localized at the central cavity. Semi-analytical expressions are developed to obtain the quality factors of the different resonances, their symmetry features and their excitation properties. The results reported here are completely general and can be extended to equivalent 3D spherical shells and to their photonic counterparts.

CERN Document Server

We point out that the moduli sector of the $(2,2)$ string compactification with its nonperturbatively preserved non-compact symmetries is a fertile framework to study global topological defects, thus providing a natural source for the large scale structure formation. Based on the target space modular invariance of the nonperturbative superpotential of the four-dimensional N=1 supersymmetric string vacua, topologically stable stringy domain walls are found. They are supersymmetric solutions, thus saturating the Bogomolnyi bound. It is also shown that there are moduli sectors that allow for the global monopole-type and texture-type configurations whose radial stability is ensured by higher derivative terms.

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A detector has been developed and used to measure dose distributions versus linear energy transfer to thin gas targets in spherical geometry from fast neutron irradiation of tissue-equivalent plastic and carbon. The detector is a hemispherical proportional counter with a Cs(T1) scintillator at the center of the hemisphere. The coincidence of the proportional counter signals constrain the measurements to charged particles traversing the radius of the hemisphere. The charged particle energy deposition distributions are directly measured for a known pathlength. The A-150 kerma factor was measured at a neutron energy of 14.8 MeV and is in agreement with tabulated values. The carbon kerma factor measurements are less than the tabulated value at 14.8 MeV. The alpha-particle production in carbon was measured for neutron energies from 14.1 to 14.8 MeV and is compared with existing data.

International Nuclear Information System (INIS)

The experimental study of the proton-rich nuclei close to the N=Z line is a constant challenge for nuclear spectroscopy, mainly due to the difficulty to produce them with the currently available beam/target combinations. Significant advances on this direction were obtained from experiments performed with the GASP array during the last two years: the yrast line of "8"4Mo was extended up to 10"+, "8"8Ru observed for the first time, and the N=Z+1 line was mapped from "8"1Zr to "9"5Ag. These new results allow us to have a more complete image of the transition from the well-deformed shell closure at N,Z=40 to the spherical-shell closure at N,Z=50, and highlights some particular effects that can be observed only in the vicinity of the N=Z line. (orig.)

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We present the results of modeling intended to evaluate the feasibility of using neutrons from induced fission in highly enriched uranium (HEU) as a means of detecting clandestine HEU, even when it is embedded in absorbing surroundings, such as commercial cargo. We characterized radiation from induced fission in HEU, which consisted of delayed neutrons at all energies and prompt neutrons at energies above a threshold. We found that for the candidate detector and for the conditions we considered, a distinctive HEU signature should be detectable, given sufficient detector size, and should be robust over a range of cargo content. In the modeled scenario, an intense neutron source was used to induce fissions in a spherical shell of HEU. To absorb, scatter, and moderate the neutrons, we place one layer of simulated cargo between the source and target and an identical layer between the target and detector. The resulting neutrons ...

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We have performed self-consistent (SC) band structure calculations for the A15 compounds V_3X and Nb_3X, X = Al, Ga, Si, Ge, and Sn, using the augmented-plane-wave (APW) method. Relativistic effects (except the spin-orbit interaction) have been included in each SC cycle, along with corrections to the usual muffin-tin approximation. The latter apply the APW wave functions outside of the muffin-tin spheres to compute the interstitial charge densities and potentials. The resulting interstitial potential has full cubic symmetry (no spherical averaging), although a spherically averaged muffin-tin form is retained inside the spheres. The final SC potentials were used to generate energies and wave functions on a cubic mesh of 35 k points in 1/48th of the Brillouin zone. These results were interpolated onto a finer mesh of 969 k points using a symmetrized Fourier method; the densities of states (DOS), N (E), were determined using ...

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In this paper, we investigate the dynamic behaviors of a two-prey two-predator system with impulsive effect concerning biological and chemical control strategy-periodic releasing natural enemies and spraying pesticide at different fixed time. By applying the Floquet theory of linear periodic impulsive equation and small amplitude perturbation method, we prove that there exists a globally asymptotically stable two-prey-eradication periodic solution when the impulsive period is less than some critical value. The conditions for the permanence of the system are given, and meanwhile the conditions for the extinction of one of the two prey species and permanence of the remaining three species are given. Our results suggest a new approach in pest control. The target pest population can be driven to extinction and the non-target pest can be permanent by choosing impulsive period. With the increasing of the predation rate for the super competitor and ...

CERN Document Server

Both discrete flavour symmetries and Grand Unified symmetries explain apparent structures in the mass sector of the Standard Model. A model that combines both symmetries is therefore very appealing. We construct a model with the $S_4$ flavour symmetry and the Pati-Salam unification. We show that this model can indeed explain many observable relations between the masses of the quarks and leptons and that it is predictive in the neutrino sector. However, the combination of the two symmetries leads to new complications in the Higgs sector and in the running of the renormalisation group equations.

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In this paper, the superfield formulation of quantum gauge theories, recently proposed, is reviewed and developed. The extended BRS symmetry, which comes out quite naturally in this formulation, is investigated.

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The motion of a test particle moving in an interior static spherically symmetric geometry is investigated. The author concludes that an oscillatory motion with the test particle changing its motion from a free fall towards the center to an outward radial motion can not exist for any static interior spherically symmetric model.

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Short communication.

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The electroweak-symmetry-breaking sector of the standard model can be weakly-coupled or can be strongly-coupled, which is characterized by some kinds of strong interaction among the Goldstone bosons of the electroweak-symmetry-breaking sector. In this paper, we summarize an investigation of probing the strong electroweak-symmetry-breaking effects at photon colliders. ((orig.)).

International Nuclear Information System (INIS)

We investigate some aspects of the radiation damage mechanisms in biomolecules, focusing on the modelling of resonant fragmentation caused by the attachment of low-energy electrons (LEEs) initially ejected by biological tissues when exposed to ionizing radiation. Scattering equations are formulated within a symmetry-adapted, single-center expansion of both continuum and bound electrons, and the interaction forces are obtained from a combination of ab initio calculations and a nonempirical model of exchange and correlation effects developed in our group. We present total elastic scattering cross-sections and resonance features obtained for the equilibrium geometries of glycine, alanine, proline and valine. Our results at those geometries of the target molecules are briefly shown to qualitatively explain some of the fragmentation patterns obtained in experiments. We further carry out a one-dimensional (1D) modeling for the dynamics of ...

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High-spin states in the mirror pair nuclei {sup 49}Cr and {sup 49}Mn and their cross-conjugate partners, the mirror pair {sup 47}V and {sup 47}Cr have been investigated using experimental {gamma}-ray spectroscopic techniques. The combination of high-efficiency EUROBALL cluster Germanium detectors and clean exit-channel gating afforded by a 31-element silicon ball used in conjunction with a 15-detector neutron wall allowed a revision and extension to the energy level schemes of all four nuclei up to J{sup {pi}}=31{sup -}/2. The difference in excitation energy between states of equivalent spin in the parent nucleus and its analogue partner have thus been established for both mirror pairs up to the f{sub 7/2}-shell band terminating state for the first time. This difference is assumed to be due almost entirely to the Coulomb effect and is therefore called the Coulomb energy difference (CED). The variation in the CED with spin has been interpreted as reflecting the change in the way the ...

CERN Document Server

Peculiar velocities induce apparent line of sight displacements of galaxies in redshift space, distorting the pattern of clustering in the radial versus transverse directions. On large scales, the amplitude of the distortion yields a measure of the dimensionless linear growth rate \\ff of fluctuations, which is related to the cosmological density \\Omega and the linear bias factor b in linearly biassed standard cosmology by \\ff \\approx \\Omega^{0.6} /b. To make the maximum statistical use of the data in a wide angle redshift survey, and for the greatest accuracy, the spherical character of the distortion needs to be treated properly, rather than in the simpler plane parallel approximation. In the linear regime, the redshift space correlation function is described by a spherical distortion operator acting on the true correlation function. It is pointed out here that there exists an operator, which is essentially the logarithmic derivative with ...

UK PubMed Central (United Kingdom)

The geographical arrangement of people on the surface of the earth is approximated by a mathematical equation of 361 terms. This is a convenient form for comparison with other distributions and for...Full Text Available

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We obtain a symmetry algebra for any unitary minimal model by using the representation of conformal field theories. This symmetry algebra can be interpreted as a quantum group. The generalization to non-unitary minimal models is direct. (orig.).

British Library Electronic Table of Contents (United Kingdom)

We apply the group theory to Kadomtsev-Petviashvili-Burgers (KPBII) equation which is a natural model for the propagation of the two-dimensional damped waves. In correspondence with the generators of the symmetry group allowed by the equation, new types of symmetry reductions are performed. Some new exact solutions are obtained, which can be in the form of solitary waves and periodic waves. Specially, our solutions indicate that the equation may have time-dependent nonlinear shears. Such exact explicit solutions and symmetry reductions are important in both applications and the theory of nonlinear science.

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The model of the supersymmetrical ball in the supersymmetrical Standard Model with additional global U(1) fermion symmetry is presented. We show that the supersymmetry breaking scale (R-parity), the global U(1) fermion symmetry scale and the electroweak symmetry breaking scale are strictly connected to each other. The realistic ball with M[approx]10[sup 5]-10[sup 9] M[sub s]un and the radius R[approx]10[sup 12]-10[sup 14] cm is obtained. Inside the ball all full symmetries are restored. The ball is stabilized by superpartners and right neutrinos which are massless inside. (orig.)

CERN Document Server

Constraints on target chamber first wall and target designs that will enable NIF debris shields to survive

CERN Document Server

An update of the ODEtools Maple package, for the analytical solving of 1st and 2nd order ODEs using Lie group symmetry methods, is presented. The set of routines includes an ODE-solver and user-level commands realizing most of the relevant steps of the symmetry scheme. The package also includes commands for testing the returned results, and for classifying 1st and 2nd order ODEs.

International Nuclear Information System (INIS)

One-velocity angular flux of a neutron field generated by a polarly anisotropic point source in an infinite homogeneous region is calculated in P3 approximation, using the spherical harmonics operator formalism adapted to two-dimensional spherical geometry. The problem is reduced to simple algebraic equations. For weak absorption and linearly anisotropic scattering, the solution is given in closed form. (orig.).

International Nuclear Information System (INIS)

The nucleon decay of subbarrier single-particle states with large angular momentum and parity opposite to that of the shell in soft spherical nuclei is considered. It is shown that the reduced probabilities of the nucleon decay into the ground state (0"+) and into the first excited (2"+) state of the daughter nucleus have qualitatively different energy dependences. (orig.).

International Nuclear Information System (INIS)

Differences of the deformation parameters for the 2"+_1 states of even-even spherical nuclei extracted from electromagnetic excitation #beta#sup(em)_2 and from proton scattering #beta#sup(pp')_2 are discussed. It is found that the ratio #beta#sup(pp')_2/#beta#sup(em)_2 is equal to about unity and that there is a small isotope dependence for several incomplete shell nuclei. (orig.).

International Nuclear Information System (INIS)

This paper provides a brief overview of the young, but rapidly growing field of spintronics. Its primary objective is to explain how as electrons tunnel through simple insulators such as MgO, wavefunctions of certain symmetries are preferentially transmitted. This symmetry filtering property can be converted into a spin-filtering property if the insulator is joined epitaxially to a ferromagnetic electrode with the same two-dimensional symmetry parallel to the interface. A second requirement of the ferromagnetic electrodes is that a wavefunction with the preferred symmetry exists in one of the two spin channels but not in the other. These requirements are satisfied for electrons traveling perpendicular to the interface for Fe-MgO-Fe tunnel barriers. This leads to a large change in the resistance when the magnetic moment of one of the electrodes is rotated relative to those of the other electrode. This ...

CERN Document Server

Both Grand Unified symmetries and discrete flavour symmetries are appealing ways to describe apparent structures in the gauge and flavour sectors of the Standard Model. Both symmetries put constraints on the high energy behaviour of the theory. This can give rise to unexpected interplay when building models that possess both symmetries. We investigate on the possibility to combine a Pati-Salam model with the discrete flavour symmetry S4 that gives rise to quark-lepton complementarity. Under appropriate assumptions at the GUT scale, the model reproduces fermion masses and mixings both in the quark and in the lepton sectors (the Beauty). We show that in particular the Higgs sector and the running Yukawa couplings are strongly affected by the combined constraints of the Grand Unified and family symmetries (the Beast). This in turn reduces the phenomenologically ...

International Nuclear Information System (INIS)

Full text: In case of lanthanide (Ln) compounds the bis(trimethylsilyl)amido (btmsa) ligand is considered as a steric and electronic equivalent of the bis(trimethylsilyl)methanido (btmsm) group . Because of their extreme air and moisture sensitivity the chemistry of Ln(btmsm)_3 is very poor, whereas that of comparatively stable Ln(btmsa)_3 is much more developed. As we wish to extend the chemistry of Ln(btmsm)_3 and plan to derive and to parameterize the crystal field (CF) splitting patterns of the target molecules, it is recommended to study in advance the electronic structures of the corresponding compounds derived from Ln(btmsa)_3 . Beside (btmsa)_3 Nd(m-Cl)Li(THF)_3 a number of mono base adducts [(btmsa)_3 Ln.B] with sterically less demanding bases such as OPPh_3 , NCtBu or CNtBu have been described and were partly structurally characterized. Considering only the immediately coordinating atoms, the effective CF is of C_3_v symmetry. ...

British Library Electronic Table of Contents (United Kingdom)

Spherical nano-sized YSZ (yttria stabilized ZrO2) powders were successfully synthesized via a reverse microemulsion system. The water droplets in the microemulsion system of yclohexane/water/span85/Triton X-100/hexyl alcohol can act as the nano-reactors which solubilize zirconium oxychloride and ammonia water separately. The minute original reactors are favor to the formation of nano-sized spherical YSZ powders and the dispersibility of the powders can be controlled effectually by adjusting the weight ratio of the LiNO3 molten salt to the precursor. The phase transformation from cubic to monoclinic starts at and 500??C and finally monoclinic and cubic phase with increased crytallinity coexist at 800??C. The effect of LiNO3 molten salt in the formation of YSZ powders was also discussed.

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A new principle of particle trapping in the simple spherical cavity using both electric and magnetic components of radiofrequency electromagnetic field is proposed. The electric component of H {sub 12} oscillating mode drives the fast particle oscillations, while the magnetic component synchronously bends the trajectories to the cavity center. A specially developed theory of particle stability predicts dense and energetic electron cluster in the trap. Numerical simulations of particle dynamics in the complete electromagnetic field taking into account both space charge and particle-induced magnetic field are in good agreement with the analytic results, giving a density of 2.6*10{sup 1} electrons/cm{sup 3} and an average kinetic energy of around 30 keV at an operating frequency of 3 GHz. Being used at lower frequency, spherical cavity can trap protons and heavier ions too, but with lower density and kinetic energy.

CERN Document Server

Modifications of low-energy theorems for the scattering of longitudinally polarized W and Z bosons in an alternative model of electroweak symmetry breaking are discussed. The symmetry breaking pattern SU(4)/SU(2) leads to light (compared to 1 TeV) pseudo-Goldstone bosons. Their interactions with electroweak gauge bosons are described by chiral (or effective) lagrangian. Tree-level contribution of the pseudo-Goldstone bosons to the scattering amplitudes are computed. Comparison with the Standard Model is given.

International Nuclear Information System (INIS)

The equivalence of representations of symmetry groups operating upon wave-functions in configuration space is studied with regard to the (intuitive) notion of physical equivalence. A refinement of the usual projective equivalence relation is introduced, called gauge equivalence, for which the allowed unitary equivalence transformations are gauge transformations. For a Euclidean as well as for Newton-Hooke symmetry group the gauge equivalence classes of unitary multiplier representations are determined. These examples support the assertion that equivalence from a physical viewpoint corresponds better to this new gauge equivalence concept than to the usual notion of projective equivalence. (author).

CERN Document Server

This paper presents three non-linear asymptotic observers corresponding to three examples of engineering interest: a chemical reactor, a non-holonomic car, and an inertial navigation system. For each example, the design is based on physical symmetries. This motivates the theoretical development of invariant observers, i.e, symmetry-preserving observers. We consider an observer to consist in a copy of the system equation and a correction term, and we give a constructive method (based on the Cartan moving-frame method) to find all the symmetry-preserving correction terms. They rely on an invariant frame (a classical notion) and on an invariant output-error, a less standard notion precisely defined here. For each example, the convergence analysis relies also on symmetries consideration with a key use of invariant state-errors. For the non-holonomic car and the inertial navigation system, the invariant ...

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We consider the Pauli theorem on the spin-statistics connection for faster-than-light particles. As the consequence of the unlocalizability of tachyons in space we conclude that their spin-statistics correlations are inverted.

Science.gov (United States)

Feb 7, 2011 ... The potentials of the spherical sensor and nearby conductors are controlled ... Incoming data are continuously monitored by algorithms in the software ... together with FM8 (Tango) by a Soyuz-Fregat rocket from Baikonur. ...

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An analysis is made of the manner in which the process of primordial black-hole formation and the subsequent accretion of gas depend on the equation of state. On the assumption that the process is spherically symmetric, the problem is solved numerically.

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This report describes mathematical predictions for the migration of radionuclides from an emplaced radioactive waste container. The model assumes a spherical-equivalent waste solid surrounded by backfill but neglects the effect of decay heat. 7 refs., 2 tabs. (TEM)

International Nuclear Information System (INIS)

To investigate the magnetic fluctuations and for further transport study, the poloidal and radial magnetic field measurement is conducted on the Sino United Spherical Tokamak (SUNIST). Auto-power spectral density indicates that the magnetic fluctuation energy mainly concentrates in the frequency region lower than 10 kHz. The magnetic field oscillations, which are characterized by harmonic frequencies of 40 kHz, are observed in the scrape-off layer; by contrast, in the plasma core, the magnetic fluctuations are of Gaussian type. The time-frequency profiles show that the poloidal magnetic fluctuations are temporally intermittent. The autocorrelation calculation indicates that the fluctuations in decorrelation time vary between the core and the edge. (authors)

International Nuclear Information System (INIS)

The spherical harmonic analysis of cosmic ray neutron data from the worldwide network neutron monitor stations during the years 1966 to 1969 was carried out. The second zonal harmonic component obtained from the analysis corresponds to the Pole-Equator anisotropy of the cosmic ray neutron intensity. Such an anisotropy makes a semiannual variation. In addition to this, it is shown that the Pole-Equator anisotropy makes a variation depending on the interplanetary magnetic field (IMF) sector polarities around the passages of the IMF sector boundary. A mechanism to interpret these results is also discussed.

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All microRNA (miRNA) target—finder algorithms return lists of candidate target genes. How valid is that output in a biological setting? Transcriptome analysis has proven to be a useful approach...Full Text Available

Science.gov (United States)

We examine the electric and magnetic strange form factors of the nucleon in the pseudoscalar-vector SU(3) Skyrme model, with special emphasis on the effects of isospin symmetry breaking (ISB). It is found that ISB has a nontrivial effect on the strange vector form factors of the nucleon and its contribution to the nucleon strangeness is significantly larger than one might naively expect. Our calculations and discussions may be of some significance for the experimental extraction of the authentic strangeness.

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The hierarchy of integrable nonlinear equations associated with the quadratic bundle is considered. The expressions for the solution of linearization of these equations and their conservation law in the terms of solutions of corresponding Lax pairs are found. It is shown for the first member of the hierarchy that the conservation law is connected with the solution of linearized equation due to the Noether's theorem. The local hierarchy and three nonlocal ones of the infinitesimal symmetries and conservation laws explicitly expressed through the variables of the nonlinear equations are derived. (author)

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The irreducible representations associated with states of dipole symmetry have been calculated for the space groups O/sub h//sup 3/, the space group with the correct symmetry for A-15 phase compounds. Also assembled are the character tables of the O/sub h/3 group. Thus all thedirect interband dipole-transition selection rules for A-15 compounds can easily be determined.

CERN Document Server

We apply the permutation symmetry S3 to both charged-lepton and neutrino mass matrices, and suggest a useful symmetry-breaking scheme, in which the flavor symmetry is explicitly broken down via S3 -> Z3 -> nothing in the charged-lepton sector and via S3 -> Z2 -> nothing in the neutrino sector. Such a two-stage breaking scenario is reasonable in the sense that both Z3 and Z2 are the subgroups of S3, while Z3 and Z2 only have a trivial subgroup. In this scenario, we can naturally obtain a relatively large value of the smallest neutrino mixing angle, e.g., theta13 ~ 9 degrees, which is compatible with the recent result from T2K experiment and will be precisely measured in the ongoing Double Chooz and Daya Bay reactor neutrino experiments. Moreover, the maximal atmospheric mixing angle theta23 ~ 45 degrees can also be obtained while the best-fit value of solar mixing angle theta12 ~ 34 degrees is assumed, which ...

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The MiniBooNE experiment [1] is motivated by the LSND observation, [2] which has been interpreted as {nu}{sub {mu}} {yields} {nu}{sub e} oscillations, and by the atmospheric neutrino deficit, [3,4,5] which may be ascribed to {nu}{sub {mu}} oscillations into another type of neutrino. MiniBooNE is a single-detector experiment designed to: obtain {approx} 1000 {nu}{sub {mu}} {yields} {nu}{sub e} events if the LSND signal is due to {nu}{sub {mu}} {yields} {nu}{sub e} oscillations, establishing the oscillation signal at the > 5{sigma} level as shown in Fig. 1.1; extend the search for {nu}{sub {mu}} {yields} {nu}{sub e} oscillations significantly beyond what has been studied previously if no signal is observed; search for {nu}{sub {mu}} disappearance to address the atmospheric neutrino deficit with a signal that is a suppression of the rate of {nu}{sub {mu}}C {yields} {mu}N events from the expected 600,000 per year; measure the oscillation parameters as shown in Fig. 1.2 if ...

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We describe in detail the space of the two Kaehler parameters of the Calabi-Yau manifold P[sub 4][sup (1,1,1,6,9)][D. R. Morrison, 1993] by exploiting mirror symmetry. The large complex structure limit of the mirror, which corresponds to the classical large radius limit, is found by studying the monodromy of the periods about the discriminant locus, the boundary of the moduli space corresponding to singular Calabi-Yau manifolds. A symplectic basis of periods is found and the action of the Sp(6, Z) generators of the modular group is determined. From the mirror map we compute the instanton expansion of the Yukawa couplings and the generalized N=2 index, arriving at the numbers of instantons of genus zero and genus one of each bidegree. We find that these numbers can be negative, even in genus zero. We also investigate an SL(2, Z) symmetry that acts on a boundary of the moduli space. ((orig.))

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A theoretical analysis of formation and symmetry transformations is presented for Wigner molecules with N = 2,..., 20 electrons confined in quantum dots at high magnetic fields. Using the unrestricted Hartree-Fock method with the multicentre Gaussian basis, we have found that Wigner molecules with N {>=} 6 abruptly change their shape and symmetry with an associated jump in the first derivative of the ground-state energy, i.e. they undergo phase transitions. In particular, the phases of the Wigner molecules obtained just after emerging from the maximum-density droplet (MDD) phase possess a different symmetry from that formed at a high magnetic field. We show that the properties of the electron-electron interaction energy demonstrate very well both the breakdown of the MDD and the quasi-classical character of the Wigner molecule in the high magnetic field. Possible mechanisms of the MDD decay are discussed.

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We discuss the renormalisation properties of the complete set of {delta}B=2 four-quark operators with the heavy quark treated in the static approximation. We elucidate the role of heavy quark symmetry and other symmetry transformations in constraining their mixing under renormalisation. By employing the Schroedinger functional, a set of non-perturbative renormalisation conditions can be defined in terms of suitable correlation functions. As a first step in a fully non-perturbative determination of the scale-dependent renormalisation factors, we evaluate these conditions in lattice perturbation theory at one loop. Thereby we verify the expected mixing patterns and determine the anomalous dimensions of the operators at NLO in the Schroedinger functional scheme. Finally, by employing twisted-mass QCD it is shown how finite subtractions arising from explicit chiral symmetry breaking can be avoided completely. (Orig.)

International Nuclear Information System (INIS)

The UTST (University of Tokyo Spherical Tokamak) device was constructed for the purpose of exploring the formation of ultra-high beta ST (Spherical Tokamak) plasma using the double null plasma merging method. When two plasmas merge together to form a single plasma, magnetic field lines reconnect, and the magnetic field energy is converted to the plasma kinetic energy, increasing the plasma beta. The merging start-up has been demonstrated in the TS-3/4, START and MAST devices using coils inside the vacuum vessel and TS-3 plasma obtained 50% beta. In order to demonstrate the start-up in a more reactor relevant situation, UTST has all poloidal field coils outside the vacuum vessel. The first plasma experiment on the UTST was performed from December, 2007. In the result, the plasma obtained 10 kA by using only outer PF coils and single ST was generated at the lower area (z=-0.3 - -1.0[m]) close to a washer gun. This result suggests that another ...

International Nuclear Information System (INIS)

... reactions selenium 74 target selenium 77 target strontium 84 target strontium

UK PubMed Central (United Kingdom)

In order to identify novel high value antibacterial targets it is desirable to delineate whether the inactivation of the target enzyme will lead to bacterial death or stasis. This knowledge is particularly...Full Text Available

British Library Electronic Table of Contents (United Kingdom)

The shock stand-off distance of a spherical model flying with transonic speeds is determined through numerical simulations. The model decelerates due to drag forces caused by the pressure and viscous shear stress at the model surface. Two-dimensional axisymmetric numerical codes with numerical grids fixed to the flying spherical model are used in the simulations. Numerically determined shock stand-off distances are compared with experimental data obtained in a previous study as well as with those obtained in our ballistic-range experiments. The numerical results and the experimental data are found to be in good agreement. In addition, the time-dependent shock stand-off distance of a decelerating model is investigated.

International Nuclear Information System (INIS)

The use of X-ray diffraction line profile analysis for the study of nanocrystalline powders is described. The fundamentals of the theory are presented in terms of crystallite/domain size, size distribution, lattice distortion, dislocations density and stacking faults. Line profile parameters and the methods of pattern fitting introduced to overcome the diffraction-line overlap problem are discussed. The approaches based of the integral breadth of the measured line profiles and the Fourier method are discussed. In addition, simplified approaches are also commented. Representative examples are selected to illustrate various cases of microstructure, such as nanomaterials with strain-free spherical nano crystallites, strain-free crystallites with anisotropic crystallite shape, anisotropic crystallites with microstrains and spherical crystallites with dislocation densities and crystallite size distributions. (author)

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Formulas are obtained for calculation of the energies and B(Elambda) values of T/sub greater-than/ giant resonances in the quasiparticle-phonon model of the nucleus. Characteristics of giant dipole resonances are calculated in several spherical nuclei and the correct location is obtained for T/sub less-than/ and T/sub greater-than/ collective 1/sup -/ states. The calculated ratios sigma/sub -/1(T/sub greater-than/)/sigma/sub -/1(T/sub less-than/) agree with the experimental data for /sup 88/Sr, /sup 90/Zr, and /sup 92/Mo and are 3 times larger than the experimental values for /sup 116,120,124/Sn. The decrease of the cross sections sigma/sub -/1(T/sub greater-than/) in /sup 124/Sn in comparison with /sup 116/Sn is correctly reproduced.

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A fast multipole transformation is adapted to the evaluation of summations that occur in global climate calculations when transforming between spatial and spherical harmonic representations. For each summation, the timing of the fast multipole transformation scales linearly with the number of latitude gridpoints, but the timing for direct evaluations scales quadratically. In spite of a larger computational overhead, this scaling advantage renders the fast multipole method faster than direct evaluation for transformations involving greater than approximately 300 to 500 gridpoints. Convergence of the fast multipole transformation is accurate to machine precision. As the resolution in global climate calculations continues to increase, an increasingly large fraction of the computational work involves the transformation between spatial and spherical harmonic representations. The fast multipole transformation offers a significant reduction in ...

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A review of recent work in nuclear physics is presented. The paper gives a broad discussion of research goals in nuclear structure, quark-gluon degrees of freedom, quark-gluon plasma, symmetries, and rare decays. (DWL)

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I review the physics prospects for high energy photon photon colliders, emphasizing results presented at the LBL Gamma Gamma Collider Workshop. Advantages and difficulties are reported for studies of QCD, the electroweak gauge sector, supersymmetry, and electroweak symmetry breaking. ((orig.)).

International Nuclear Information System (INIS)

I review the physics prospects for high energy photon photon colliders, emphasizing results presented at the LBL Gamma Gamma Collider Workshop. Advantages and difficulties are reported for studies of QCD, the electroweak gauge sector, supersymmetry, and electroweak symmetry breaking. ((orig.)).

Science.gov (United States)

We consider a symmetric boundary integral formulation associated with a mixed boundary value problem defined on a domain Omega is an element of the set of real numbers(2) with piecewise smooth boundary Gamma. We assume that Omega is mapped onto itself by ...

CERN Document Server

Koide's mass formula is an empirical relation among the charged lepton masses which holds with a striking precision. We present a model of charged lepton sector based on U(3)\\times SU(2) family gauge symmetry, which predicts Koide's formula within the present experimental accuracy. Radiative corrections as well as other corrections to Koide's mass formula are kept under control. We adopt a known mechanism, through which the charged lepton spectrum is determined by the vacuum expectation value of a 9-component scalar field \\Phi. On the basis of this mechanism, we implement the following mechanisms into our model: (1) The radiative correction induced by family gauge interaction cancels the QED radiative correction to Koide's mass formula, assuming a scenario in which the U(3) family gauge symmetry and SU(2)_L weak gauge symmetry are unified at 10^2-10^3 TeV scale; (2) A simple potential of \\Phi invariant under U(3)\\times ...

CERN Document Server

Within the type-I seesaw framework with three heavy right chiral neutrinos and in the basis where the latter and the charged leptons are mass diagonal, a near `mu-tau' symmetry in the neutrino sector is strongly suggested by the neutrino oscillation data. There is further evidence for a close to the tribimaximal mixing pattern which subsumes `mu-tau' symmetry. On the other hand, the assumption of a (maximally allowed) four zero texture in the Yukawa coupling matrix Y_nu in the same basis leads to a highly constrained and predictive theoretical scheme. We show that the requirement of an exact `mu-tau' symmetry, coupled with observational constraints, reduces the `seventy two' allowed textures in such a `Y_nu' to 'only four' corresponding to just two different forms of the light neutrino mass matrix `m_nu'. The effect of each of these on measurable quantities can be described, apart from an overall factor of the neutrino mass ...

International Nuclear Information System (INIS)

Firstly the so called 'conformal relativity' in the 6-dimensional conformal space is formulated. In particular the concept of dilatational degree of freedom - scale - is introduced. The special conformal transformations are interpreted as the transformations connecting dilatationally moving frames (and objects). The ideas, similar to those by Kaluza and Klein, can be applied to the conformal space to obtain a unification of gravitation and electromagnetism. Lastly the conformal symmetry is extended to imaginary scales and to negative scales. Particles having imaginary scales are shown to be tachyons, whilst particles with negative scales correspond to antiparticles. (Auth.).

International Nuclear Information System (INIS)

Because of limitation on neutron-incident data, it is difficult to obtain global optical model potential for neutrons. In contrast, there are some global optical model potentials for proton in detail. It is interesting to convert the proton-incident global optical potentials into neutron-incident ones. In this study we introduce (N-Z)/A dependent symmetry potential terms into the global proton-incident optical potentials, and then obtain neutron-incident ones. The neutron potentials reproduce total cross sections in an acceptable degree. However, a comparison with potentials proposed by other authors brings about a confused situation in the sign of the symmetry terms. (author).

CERN Document Server

It is shown that the direct Fourier synthesization of light beams allows one to create polarity-asymmetric waves, which are able, in the process of nonlinear interaction with a medium, to break its inversion symmetry. As a result, these "polar" waves may show the effect of optical rectification in nonlinear centrosymmetric media by generating light-induced dc electric polarization. At the same time, the waves of this type, due to their unusual symmetry properties, can be used for detecting the direction and sign of a dc electric field applied to the medium. The prospects of application of polar waves to data recording and processing are discussed.

Energy Technology Data Exchange (ETDEWEB)

Starting with two supersymmetric dual theories, we imagine adding a chiral perturbation that breaks supersymmetry dynamically. At low energy we then get two theories with soft supersymmetry-breaking terms that are generated dynamically. With a canonical K{umlt a}hler potential, some of the scalars of the ``magnetic`` theory typically have negative mass-squared, and the vector-like symmetry is broken. Since for large supersymmetry breaking the ``electric`` theory becomes ordinary QCD, the two theories are then incompatible. For small supersymmetry breaking, if duality still holds, the magnetic theory analysis implies specific patterns of chiral symmetry breaking in supersymmetric QCD with small soft masses.

CERN Document Server

We consider the alternating sign matrices of the odd order that have some kind of central symmetry. Namely, we deal with matrices invariant under the half-turn, quarter-turn and flips in both diagonals. In all these cases, there are two natural structures in the centre of the matrix. For example, for the matrices invariant under the half-turn the central element is equal $\\pm 1$. It was recently found that $A^+_{HT}(2m+1)/A^-_{HT}(2m+1)$=(m+1)/m. We conjecture that similar very simple relations are valid in the two remaining cases.

UK PubMed Central (United Kingdom)

In an effort to develop octahedral metal complexes as chemotherapeutic and diagnostic agents targeted to DNA, it is critical to optimize the properties of their cellular uptake. Appending d-octaarginine...Full Text Available

Science.gov (United States)

... L. Sutton. 2000. Is the aquatic weed hygrophila, Hygrophila polysperma (Polemoniales: Acanthaceae), a suitable target for classical biological ... ...

Science.gov (United States)

By W. Wayne Scott. Langley Research Center. SUMMARY. Thin- and thick-target bremsstrahlung spectra are presented for electron energies up to 7.0 MeV. ...

International Nuclear Information System (INIS)

The National Ignition Facility (NIF) is a proposed Department of Energy facility which will contribute to the resolution of important Defense Program and inertial fusion energy issues for energy production in the future. The NIF will consist of a laser system with 192 independent beamlets transported to a target chamber. The target chamber is a multi-purpose structure that provides the interface between the target and the laser optics. The chamber must be capable of achieving moderate vacuum levels in reasonable times; it must remain dimensionally stable within micron tolerances, provide support for the optics, diagnostics, and target positioner; it must minimize the debris from the x-ray and laser light environments; and it must be capable of supporting external neutron shielding. The chamber must also be fabricated from a low neutron activation material. The fusion reaction in the ...

International Nuclear Information System (INIS)

The nuclear shapes of transitional Mo isotopes are calculated by means of a model based on the cranking approximation and the Strutinksy method. The recent experimental results of the high-spin spectroscopy and lifetime measurement of "8"7Mo are studied in detail and explained by the evolution of the #gamma#-deformation with the quasiparticle configurations. The shape calculations with the modified-harmonic-oscillator potential give a critical neutron number N #>=# 47 for the spherical shape of the Mo isotopes. (orig.).

Energy Technology Data Exchange (ETDEWEB)

Spherical {beta}-Ni(OH){sub 2} was modified by a low-cost method of normal ball milling (NBM), and the physical properties of both ball-milled and un-milled Ni(OH){sub 2} were characterized by transmission electron microscopy, specific surface area, particle size distribution and X-ray diffraction. It was found that NBM could obviously increase the surface area, decrease the particle and crystallite size, and reduce the crystallinity of {beta}-Ni(OH){sub 2}, which were advantageous to the improvement of the electrochemical activity of Ni(OH){sub 2}. NBM also lowered the packing density and flowability of Ni(OH){sub 2}, as revealed by the measurements of tapping density and angle of repose. Electrochemical performances of pasted nickel electrodes with an addition of ball-milled Ni(OH){sub 2} to spherical Ni(OH){sub 2} as the active material were investigated, and were compared with those of the pure spherical Ni(OH){sub 2} ...

Energy Technology Data Exchange (ETDEWEB)

The evaluated data testing for Si, Zr, Nb and Fe materials has been performed through the analyses of the neutron leakage spectrum from spherical assemblies measured in integral benchmark experiments with (d,t) and Cf fission neutron sources. Intercomparisons of the calculated from BROND-2, ENDF/B-6 and JENDL-3 data files with experimental results are presented.

Energy Technology Data Exchange (ETDEWEB)

The authors report an extension of the source imaging method for analyzing three-dimensional sources from three-dimensional correlations. The technique consists of expanding the correlation data and the underlying source function in spherical harmonics and inverting the resulting system of one-dimensional integral equations. With this strategy, they can image the source function quickly, even with the extremely large data sets common in three-dimensional analyses.

Energy Technology Data Exchange (ETDEWEB)

We proposed a solid and a mercury target concepts through the preliminary conceptual design. To feasible these concepts, analysis and experimental works are being carried out. This paper introduces an outline of present status of target R and D such as heat transfer augmentation experiments for the solid target, mercury flow tests with a loop of maximum flow rate of 15L/min, flow pattern measurements for a cold source moderator etc. as well as preliminary conceptual design works. (author)

Energy Technology Data Exchange (ETDEWEB)

Short communication.

KoreaScience (Korea)

Full Text Available

CERN Document Server

We use a superspin Hamiltonian defined on an infinite-dimensional Fock space with positive definite scalar product to study localization and delocalization of noninteracting spinless quasiparticles in quasi-one-dimensional quantum wires perturbed by weak quenched disorder. Past works using this approach have considered a single chain. Here, we extend the formalism to treat a quasi-one-dimensional system: a quantum wire with an arbitrary number of channels coupled by random hopping amplitudes. The computations are carried out explicitly for the case of a chiral quasi-one-dimensional wire with broken time-reversal symmetry (chiral-unitary symmetry class). By treating the space direction along the chains as imaginary time, the effects of the disorder are encoded in the time evolution induced by a single site superspin (non-Hermitian) Hamiltonian. We obtain the density of states near the band center of an infinitely long quantum wire. Our results ...

CERN Document Server

While dealing with molecular systems, it is highly advantageous to work with a basis set which has definite total spin and also belongs to a definite irreducible representation of its symmetry (point) group. But unfortunately, there hadn't been any general simple technique to deal with the problem, especially when molecule possesses non-Abelian point group symmetry. In a previous paper \\cite{sahoo}, we presented a general technique which is a hybrid method based on Valence Bond basis and the basis of z-component of the total spin. The technique is applicable to all types of point groups and is easy to implement on computer. We illustrated the power of the method by applying it to a molecular magnetic system. Here we extend the method to electronic systems and demonstrate this extended technique by applying it to a model icosahedral half-filled electronic system (12 sites). Reasons we took this model are, its a system with huge Hilbert space ...

CERN Document Server

In culture migrating and interacting amoeboid cells can form nematic liquid crystal phases. A polar nematic liquid crystal is formed if the interaction has a polar symmetry. One type of white blood cells (granulocytes) form clusters where the cells are oriented towards the center. The core of such an orientational defect (disclination) is either a granulocyte forced to be in an isotropic state or another cell type like a monocyte. An apolar nematic liquid crystal is formed if the interaction has an apolar symmetry. Different cell types like human melanocytes (=pigment cells of the skin), human fibroblasts (=connective tissue cells), human osteoblasts (=bone cells), human adipocytes (= fat cells) etc., form an apolar nematic liquid crystal. The orientational elastic energy is derived and the orientational defects (disclination) of nematic liquid crystals are investigated. The existence of half-numbered disclinations show that the nematic phase ...

CERN Document Server

Some properties of the universe are fixed by physics derived from mathematical symmetries, others may have been selected from an ensemble of possibilities. Some successes and failures of anthropic reasoning in this context are reviewed in the light of recent developments in astrobiology, cosmology and unification physics. Specific issues raised include our spacetime location (including the reason for the present age of the universe), the timescale of biological evolution, the tuning of global cosmological parameters, the origin of the Large Numbers of astrophysics, and the parameters of the Standard Model. Out of the twenty parameters of the Standard Model,the basic behavior and structures of the world (nucleons, nuclei,atoms, molecules, planets, stars, galaxies) depend mainly on five of them: $m_e,m_u,m_d,\\alpha,\\alpha_G$, three of which are independent in the context of Grand Unified Theories (that is, not related by any known symmetry). ...

CERN Document Server

One hope to solve the cosmological constant problem is to identify a symmetry principle, based on which the cosmological constant can be reduced either to zero, or to a tiny value. Here, we note that requiring that the vacuum state is Lorentz invariant significantly reduces the theoretical value of the vacuum energy density. Hence, this also reduces the discrepancy between the observed value of the cosmological constant and its theoretical expectation, down from 123 orders of magnitude to 56 orders of magnitude. We find that, at one loop level, massless particles do not yield any contribution to the cosmological constant. Another important consequence of Lorentz symmetry is stabilization of the gravitational hierarchy: the cosmological constant (divided by Newton's constant) does not run as the quartic power of the renormalization group scale, but instead only logarithmically.

CERN Document Server

When one uses the Coleman-Weinberg renormalization condition, the effective potential $V$ in the massless $\\phi_4^4$ theory with O(N) symmetry is completely determined by the renormalization group functions. It has been shown how the $(p+1)$ order renormalization group function fix the N$^{p}$LL order contribution to $V$. We discuss here how, in addition to fixing the N$^{p}$LL contribution to $V$, the $(p+1)$ order renormalization group functions also can be used to determine portions of the N$^{p+n}$LL contributions to $V$. When these contributions are summed to all orders, the singularity structure of \\mcv is altered. An alternate approach to fixing \\mcv in terms of the renormalization group functions is shown to eliminate dependence on the background field if spontaneous symmetry breaking occurs.

CERN Document Server

A generalized relativistic harmonic oscillator for spin 1/2 particles is studied. The Dirac Hamiltonian contains a scalar, $S$, and a vector, $V$, quadratic potentials in the radial coordinate, as well as a tensor potential, $U$, linear in $r$. Setting either or both combinations $\\Sigma=S+V$ and $% \\Delta=V-S$ to zero, analytical solutions for bound states of the corresponding Dirac equations are found. The eigenenergies and wave functions are presented and particular cases are discussed, devoting a special attention to the non-relativistic limit and the case $\\Sigma=0$, for which pseudospin symmetry is exact. We also show that the case $U=\\Delta=0$ is the most natural generalization of the non-relativistic harmonic oscillator. The radial node structure of the Dirac spinor is studied for several combinations of harmonic oscillator potentials, and that study allows us to explain why nuclear intruder levels cannot be described in the framework of the ...

International Nuclear Information System (INIS)

Highly ordered arrays of Ni nanoholes and Fe20Ni80 antidots have been prepared, respectively, by replica/antireplica processing and sputtering techniques using nanoporous alumina membranes as templates. Geometrical characteristics as nanohole/antidot diameter, interpore distance and the overall hexagonal symmetry of arrays are controlled through the original templates. Experimental data on their hysteresis and magnetic domain structure have been taken by vibrating sample magnetometry and magnetic force microscopy, respectively. An analysis of the magnetization process, resulting magnetic anisotropy and magnetic domain structure is summarized considering the influence of those geometry aspects. In particular, the hexagonal symmetry and the density of nanohole/antidots determine the overall magnetic behavior, which is of interest in future high-density magnetic storage systems.

CERN Document Server

In these lecture notes we derive a generic holographic string theory realization of a p-wave superconductor and superfluid. For this purpose we also review basic D-brane physics, gauge/gravity methods at finite temperature, key concepts of superconductivity and recent progress in distinct realizations of holographic superconductors and superfluids. Then we focus on a D3/D7-brane construction yielding a superconducting or superfluid vector-condensate. The corresponding gauge theory is 3+1-dimensional N=2 supersymmetric Yang-Mills theory with SU(N) color and SU(2) flavor symmetry. It shows a second order phase transition to a phase in which a U(1) subgroup of the SU(2) symmetry is spontaneously broken and typical superconductivity signatures emerge, such as a conductivity (pseudo-)gap and the Meissner-Ochsenfeld effect. Condensates of this nature are comparable to those recently found experimentally in p-wave superconductors such as a ruthenate ...

International Nuclear Information System (INIS)

An extensive analysis of the 1/N expansion of O(N)-symmetric lambdaphi"4 theory in four dimensions shows it to be a consistent approximation method. It is confirmed that the ground state of the theory is O(N(-symmetric, and that spontaneous symmetry breaking is not possible in the large-N limit. The Green's functions are free of tachyons if constructed relative to this ground state. A natural upper bound is derived for the parameters of the theory to ensure the existence of a ground state. In the strong-coupling domain there exist a bound state and a resonance in the identity representation of the O(N) group, which disappear in the weak-coupling regime. It is shown that, to leading order in N, a zero-mass interacting ''charged'' boson cannot be sustained in this theory. If the boson mass goes to zero, the model becomes a free-field theory.

Energy Technology Data Exchange (ETDEWEB)

The results of X-ray and neutron diffraction experiments on molten alkali halides in which some data of our experiments by X-ray diffraction such as those of molten LiCl, NaCl, KCl, LiBr and KBr are included were summarized. The first peak positions in the radial distribution function in molten alkali halides by X-ray or neutron diffraction experiments are always longer than those by computer simulations and the differences of 0.1 -- 0.3 A exceed the experimental error. It seems to be due to the deformation of the electron shell. In the computer simulation, the shell model which has the spherical deformation was expected to have a closer value of the first peak position to the experimental one than the rigid ion model by taking the polarization of ions. However, no change in the first peak position was found. Therefore, the non-spherical deformation of electron shell at the point where ions are in contact with each other has to be taken into ...

International Nuclear Information System (INIS)

Spherical nanostructured Si/C composite was prepared by spray drying technique, followed by heat treatment, in which nanosized silicon and fine graphite particles were homogeneously embedded in carbon matrix pyrolyzed by phenol formaldehyde resin. Cyclic voltammetry tests showed two pairs of redox peaks corresponding to lithiation and delithiation of Si/C composite. The Si/C composite exhibited a reversible capacity of 635 mAh g"-"1 and good cycle performance used in lithium ion batteries. To improve cycle performance of this Si/C composite further, the carbon-coated Si/C composite was synthesized by the second spray drying and heat treatment processing. The cycle performance of carbon-coated Si/C composite was improved significantly, which was attributed to the formation of stable SEI passivation layers on the outer surface of carbon shell which protected the bared silicon from exposing to electrolyte directly.

Energy Technology Data Exchange (ETDEWEB)

Transmission electron microscopy studies on solution-annealed Alloy 800 revealed small (100-200 nm), spherical-shaped titanium carbide (face centered cubic structure) and large (200 nm-5 {mu}m), faceted titanium nitride (hexagonal structure) particles randomly distributed in the austenite matrix. The volume fraction of former particles was found to be greater than that of the latter. Corrosion studies of the alloy in acidic, chlorides and acidic chloride environments at room temperature indicated that the passivity of Alloy 800 was adversely affected by the addition Cl{sup -} ions. X-ray photoelectron spectroscopy revealed that the surface film formed on the alloy at the onset of passivity consisted of Cr{sup 3+} (as Cr{sub 2}O{sub 3}), without any Fe{sup 3+}/Fe{sup 2+} or Ni{sup 2+}. Scanning electron microscopy studies indicated initiation of pitting at large, faceted particles, not at small, spherical-shaped ones.

International Nuclear Information System (INIS)

A numerical investigation of the mixing of gaseous uranium and hydrogen inside an open-cycle gas core nuclear rocket engine (spherical geometry) is presented. The gaseous uranium fuel is injected near the centerline of the spherical engine cavity at a constant mass flow rate, and the hydrogen propellant is injected around the periphery of the engine at a five degree angle to the wall, at a constant mass flow rate. The main objective is to seek ways to minimize the mixing of uranium and hydrogen by choosing a suitable injector geometry for the mixing of light and heavy gas streams. Three different uranium inlet areas are presented, and also three different turbulent models (k-var-epsilon model, RNG k-var-epsilon model, and RSM model) are investigated. The commercial CFD code, FLUENT, is used to model the flow field. Uranium mole fraction, axial mass flux, and radial mass flux contours are obtained. copyright 1997 American Institute of Physics.

International Nuclear Information System (INIS)

Small-angle X-ray scattering method recognised to be very useful in the studies of structural problems of materials in homogeneous in nanoscale. Studies by small-angle X-ray scattering on the Al-Ag alloys are presented. The size distributions of spherical Guinier-Person zones were calculated using Vonk's and Glatter's methods. Small-angle X-ray scattering studies were performed on Al-5.0 at.%Ag alloy containing Guinier-Preson zones in the #eta#-state. For this alloy one can assume that scattering particles are of spherical shape, have uniform electron density and scatter independently. Moreover, the size distributions were calculated for Al-1.6 at.%Ag alloy containing Guinier-Preston zones in #epsilon#-state (scattering particles with not uniform electron density). Both, Vonk's and Glatter's, methods gave similar size distributions. Profiles of size distributions for Guinier-Preston zones in #epsilon#-state are more complex in comparison to ...

International Nuclear Information System (INIS)

The shell integrity near peak compression of spherical implosions using the 60-beam, 30-kJ UV OMEGA laser system [Opt. Commun. 133, 495 (1997)] has been measured. Hot core emission backlights a shell with a thin titanium-doped layer that is imaged at x-ray photon energies above and below the titanium K edge. The x-ray intensity ratio between the two images is related to perturbations in the cold, or absorbing, part of the shell. The measured cold-shell areal-density modulations, integrated over the time of peak compression, are of the order of 25% to 50% with nonuniformity spectra peaked at spatial wavelengths of 30 to 50 #mu#m and with the smallest detectable nonuniformity features extending down to spatial wavelengths of 12 to 15 #mu#m. Hot-shell areal-density modulations of the emitting part of the shell (inner edge) are of the order of 13% to 20%. The measured shell modulations are in agreement with the results of two-dimensional simulations that include ...

British Library Electronic Table of Contents (United Kingdom)

The effect of particle/matrix interface debonding on composites consisting of elastic particles and viscoelastic matrix is studied. The interface debonding is represented by a nonlinear cohesive law for the high explosive PBX 9501. The Mori-Tanaka method gives the constitutive relation of the composite in terms of the properties of elastic particles, viscoelastic matrix, and nonlinear cohesive law for interfaces. For the example of a composite with spherical particles subject to hydrostatic tension, simple analytical expressions of the composite stress-strain relation are obtained. The strain rate and temperature have strong effects on the composite behavior. High strain rate and low temperature give high strength of the composite. However, the rate and temperature effects decrease as the ...

Energy Technology Data Exchange (ETDEWEB)

For light water reactors, loss of coolant is an important point in safety analysis, whereas for gas-cooled reactors the ingress of water into the core region is an incident of safety relevance. The applicability of the computer code system GAMTEREX to pebble beds of spherical high-temperature gas-cooled reactor fuel elements with simulated water ingress is verified by experiment. The measurements were performed at a Siemens-Argonaut reactor, using its ring core as a driver zone for a pebble-bed core in the center of the reactor.

CERN Document Server

The paper deals with Hawking radiation related to non-static spherically symmetric black hole. Quantum corrections are incorporated using Hamilton-Jacobi method beyond semi-classical approximation. It is found that different order correction terms satisfy identical differential equation as the semiclassical action and are solved by a typical technique. It has been shown that with proper choice of the proportionality factors, one loop back reaction effect in the space time can be obtained. Finally, using the law of black hole mechanics, a general modified form of the black hole entropy is obtained considering modified Hawking temperature.

International Nuclear Information System (INIS)

In laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), the properties of laser-generated aerosols, such as size and composition, are crucial for matrix-independent quantification. In this study, the aerosol particle morphology and elemental composition generated by two state-of-the-art laser systems (ArF excimer nanosecond-UV laser and Ti:sapphire femtosecond-IR laser) were investigated by electron microscopic techniques. Electrostatic sampling of the aerosols directly onto transmission electron microscopy (TEM) grids allowed us to study the morphology and elemental composition of the aerosols using TEM and TEM-EDX (energy dispersive X-ray spectroscopy) analyses, respectively. The results of the electron microscopic studies were finally compared to the LA-ICPMS signals of the main matrix components. The investigations were carried out for non-conducting materials (glass and zircon), metallic samples (steel and brass) and semiconductors (sulfides). The studies ...

Energy Technology Data Exchange (ETDEWEB)

Fission reaction rates for four nuclides were measured in the leakage spectrum outside spherical water moderators of various radii surrounding a {sup 252}Cf neutron source. Using the MCNP transport code, matching calculations were made with highly detailed modeling of the measurement apparatus. The calculations predicted significantly higher leakage of neutrons in the epicadmium energy range than was found in the measurements. A discrepancy of the same sign but weaker magnitude was found for thermal neutrons. These discrepancies may be relevant to problems with criticality calculations in special cases.

Energy Technology Data Exchange (ETDEWEB)

High-current implantation of Cu{sup {minus}} ions into silica glasses has been demonstrated using mA-class negative ion beams at 60 keV. Negative ion implantation has an advantage to alleviate specimen charging for insulating substrates and has attained high dose rates, up to 260 {micro}A/cm{sup 2}. Spherical Cu colloids form in the silica glasses without additional thermal annealing. Optical absorption and reflection of the implanted specimens vary with the current density, even at a fixed dose level. A beam-induced surface plasma may affect the high current implantation.

Energy Technology Data Exchange (ETDEWEB)

Several fast neutral pressure gauges have been installed on NSTX [National Spherical Torus Experiment] to measure the vessel and divertor pressure during inductive and coaxial helicity injected (CHI) plasma operations. Modified, PDX [Poloidal Divertor Experiment]-type Penning gauges have been installed on the upper and lower divertors. Neutral pressure measurements during plasma operations from these and from two shielded fast Micro ion gauges at different toroidal locations on the vessel mid-plane are described. A new unshielded ion gauge, referred to as the In-vessel Neutral Pressure (INP) gauge is under development.

Energy Technology Data Exchange (ETDEWEB)

Average emittance data for ion beams extracted from cesium-sputter negative ion sources equipped with spherical, ellipsoidal, and cylindrical geometry cesium-surface ionizers are presented. The attributes of the respective source geometries are described in terms of their cesium ion optical properties. The results of recent measurement of the emittances of momentum-analyzed beams extracted from the ellipsoidal geometry source are also presented. These measurements indicate the presence of a species-dependent effect. The effect is believed to be attributable to differences in the energy spreads of the respective negative ion beams introduced by the sputter generation process.

International Nuclear Information System (INIS)

A nanoparticle generator based on the principle of electrical discharge (PALAS GFG-1000) was used to produce nanoparticles of different chemical natures. The fractions of electrically neutral particles were then measured by means of a Spectrometre de Mobilite Electrique Circulaire (SMEC, i.e. radial-flow mobility analyzer) for different operating conditions. The experimental results were compared with the theoretical values calculated from the Fuchs extended charge equilibrium model for spherical particles and agglomerates. For the smallest particles (below 20 nm), the deviations observed remain below 10%, and tend towards 20% for larger particles (over 35 nm).

Energy Technology Data Exchange (ETDEWEB)

After having studied the shape that a tachyon T (e.g., intrinsically spherical) would take up, we show in an explicit example that the characteristics of classical tachyons are similar to those of the ordinary (slower-than-light) quantum particles. In particular, a realistic tachyon is associated with a ''phase speed'' V(V/sup 2/>c/sup 2/), but with a ''group speed'' upsilon=c/sup 2//V (upsilon/sup 2/

UK PubMed Central (United Kingdom)

PurposeWe conducted a comparative study of Clinical Target Volume (CTV) definition of pelvic lymph nodes by multiple GU radiation oncologists looking at the levels...Full Text Available

UK PubMed Central (United Kingdom)

The role of IGF-I in the negative regulation of GH expression and release is demonstrated by in vitro and in vivo models; however, the targets and mechanisms of IGF-I...Full Text Available

UK PubMed Central (United Kingdom)

The goal of ultrasonic molecular imaging is the detection of targeted contrast agents bound to receptors on endothelial cells. We propose imaging methods that can distinguish adherent microbubbles...Full Text Available

UK PubMed Central (United Kingdom)

The phenomenon of antibiotic resistance has created a need for the development of novel antibiotic classes with non-classical cellular targets. Unfortunately, target-based drug discovery against...Full Text Available

UK PubMed Central (United Kingdom)

Peroxisomes, glyoxysomes, glycosomes, and hydrogenosomes have each been classified as microbodies, i.e., subcellular organelles with an electron-dense matrix that is bound by a single membrane. We investigated...Full Text Available

UK PubMed Central (United Kingdom)

Histone Arg methylation and Lys acetylation have been found to cooperatively regulate the expression of p53 target genes. Peptidylarginine deiminase 4 (PAD4) is an enzyme that citrullinates...Full Text Available

UK PubMed Central (United Kingdom)

Cytokinesis in animal and fungal cells utilizes a contractile actomyosin ring (AMR). However, how myosin II is targeted to the division site and promotes AMR assembly, and how the AMR coordinates with...Full Text Available

International Nuclear Information System (INIS)

... transitions lutetium 175 target mev range 10-100 multipolarity neutrons parity

Science.gov (United States)

... Tanzania, and the attack on the USS COLE. ... vis another has no bearing on the legality of the attack. If the person attacked is a combatant, the use of ...

Science.gov (United States)

... hazards. One study targeted the effects of common household disinfectants on virus inactivation (Butcher and Ulaeto, 2005). ...

Energy Technology Data Exchange (ETDEWEB)

The production of polarized negative ion beams by ''collisional pumping'' is described. Collisional pumping utilizes repeated charge changing collisions in a thick electron-spin-polarized gas or vapor target to form a polarized fast atom beam. The polarized fast atom beam is then partially converted into a polarized negative ion beam in a vapor target. Analysis is presented for a hydrogen beam passing through either a thick polarized H atom target or a thick polarized alkali target. Large polarizations and large currents may be possible.

KoreaScience (Korea)

Full Text Available

Energy Technology Data Exchange (ETDEWEB)

While there is growing interest in Real Time Pricing as a competitive tool, its adoption to date has been constrained by wariness on the part of many utilities and many of their customers. That wariness is not misplaced, for Real Time Pricing is not for everyone. In order for both utilities and their customers to benefit, the pricing system must be properly tailored for, and offered to, the appropriate audience. This paper discusses needs for identifying targets, implications of targeting of Real Time Pricing to various types of customers, and implications for design and marketing of such pricing systems. Examples from utility experiences are provided, and recommendations are offered for development of improved targeting of Real Time Pricing.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

International Nuclear Information System (INIS)

... 98 target molybdenum 99 niobium 91 photoneutrons photonuclear reactions

Energy Technology Data Exchange (ETDEWEB)

We apply the framework developed in Target space duality I: general theory. We show that both nonabelian duality and Poisson-Lie duality are examples of the general theory. We propose how the formalism leads to a systematic study of duality by studying few scenarios that lead to open questions in the theory of Lie algebras. We present evidence that there are probably new examples of irreducible target space duality.

Energy Technology Data Exchange (ETDEWEB)

This paper illustrates how the techniques developed by the authors for capital cost targeting of mass exchange networks can be applied to determination of capital investment targets for reduction in effluent for existing systems involving mass exchange. The results is an impact diagram which shows the relationship between effluent reduction and capital investment, indicating a region of limiting return on investment as well as the maximum possible reduction in effluent. (au)

Energy Technology Data Exchange (ETDEWEB)

A portable fiber optic detector that senses the presence of specific target chemicals by electrostatically attracting the target chemical to an aromatic compound coating on an optical fiber. Attaching the target chemical to the coated fiber reduces the fluorescence so that a photon sensing detector records the reduced light level and activates an appropriate alarm or indicator.

Science.gov (United States)

...2010-10-01 2010-10-01 false Energy Policy Act target group certification...Acquisition Regulations System DEPARTMENT OF ENERGY CLAUSES AND FORMS SOLICITATION...Provisions and Clauses 952.226-73 Energy Policy Act target group...

British Library Electronic Table of Contents (United Kingdom)

The work is devoted to a microscopic analysis of the reactive capacity of chitin. An algorithm for modeling the deacetylation reaction in a monomeric unit of chitin is described. The reaction coordinate and the potential energy surface topography are determined taking into account the electron-vibrational interaction and low-symmetry perturbations within Jahn-Teller theory. Based on this algorithm, the topological modeling of the deacetylation process is performed for the first time and a mechanism of the biological activity of chitosan is proposed.

International Nuclear Information System (INIS)

The method of inversion of the eigenvalue problem previously developped for nuclei with axial symmetry is extended to asymmetric equilibrium shapes. This new approach to the asymmetric rotator model is applied to the odd-mass Iridium isotopes. A satisfactory and coherent description of the observed energy spectra is obtained, especially for the lighter isotopes. (orig.).

International Nuclear Information System (INIS)

The fluorescence, absorption, infrared and Raman spectra of Sm_3Ga_5O_1_2 have been investigated. The energy-level schemes in the energy range 3000-16000 cm"-"1 have been determined. The number and symmetries of the Sm_3Ga_5O_1_2 crystal normal mode have been obtained by the molecular site group analysis and their comparison with the experiment has been made.

International Nuclear Information System (INIS)

An alternative and graphical representation of the magnetic moment and the effective paramagnetic moment for polycrystalline Ce compounds with tetragonal site symmetry is described. The reduced moments can be calculated by means of standard perturbation theory. The calculated values deduced from the ground states of CeCu_2Si_2, CeRu_2Si_2, and CePd_2Si_2 polycrystals are compared with experimental magnetic moments.

Energy Technology Data Exchange (ETDEWEB)

Considering the radial motion of a test particle in the Schwarzschild field in the hypothesis of local rotational invariance, the authors discuss the conditions to be satisfied by a physically acceptable model of broken SO(3,1) symmetry, and shown in particular that to preserve causality a breaking, even infinitesimal, makes necessarily impenetrable the interior of the Schwarzschild sphere.

International Nuclear Information System (INIS)

The field algebra of the minimal models of W-algebras is amenable to a very simple description as a polynomial algebra generated by a few elementary fields, corresponding to order parameters. Using this description, the complete Landau-Ginzburg lagrangians for these models are obtained. Perturbing these lagrangians we can explore their phase diagrams, which correspond to multicritical points with D_n symmetry. In particular, it is shown that there is a perturbation for which the phase structure is similar to that of the IRF models of Jimbo et al. (orig.).

International Nuclear Information System (INIS)

The governor model is extended to include the asymmetric shape of nuclei which allows a simultaneous analysis of the data for both the ground state and the #gamma#-vibrational bands in deformed even-even nuclei. The rotationally invariant core is assumed to be a spheroid with an axis of symmetry parallel to the axis of rotation. The calculations are carried out under the assumption of no stretching. The static #gamma#-deformation results are compared with the VMI(ARM) and Krutov values, and the calculated energies are in good agreement with the experimental data.

Energy Technology Data Exchange (ETDEWEB)

Straightforward, though formal, arguments are presented to establish that the effective action and potential are gauge covariant at the symmetry-breaking point. We establish that in certain classes of gauge, covariant and axial gauges for Abelian theories and axial gauges for non-Abelian theories, the Nielsen equation for the effective potential can be put into closed form. Scalar electrodynamics is presented in detail in covariant and axial gauges.

Energy Technology Data Exchange (ETDEWEB)

We present a study of the crystal field in PrNiAl, NdNiAl, ErNiAl and ErCuAl intermetallic compounds based on inelastic neutron spectroscopy. These compounds crystallize in the ZrNiAl-type hexagonal structure with an orthorhombic symmetry on rare-earth sites. The results are compared with the specific-heat data, and the lower parts of the crystal-field energy-level schemes are determined. (orig.)

International Nuclear Information System (INIS)

Constraining the SL(3) WZW-model we construct a reduced theory which is invariant with respect to the new chiral algebra W_3"2. This symmetry is generated by the stress-energy tensor, two bosonic currents with spins 3/2 and the U(1) current. We conjecture a Kac formula that describes the highly reducible representation for this algebra. We also discuss the quantum Hamiltonian reduction for the general type of constraints that leads to the new extended conformal algebras. (orig.).

International Nuclear Information System (INIS)

On the basis of symmetry way of texture description a calculation method of elastic moduli of two-phase titanium alloys with rolling texture has been suggested. Efficiency of the calculation formulas is checked by comparing the calculation results of Young modulus anisotropy in the sheet plane of (#alpha#+#beta#)-titanium alloy VT23 with the experimental data.

Energy Technology Data Exchange (ETDEWEB)

The dimensionally reduced effective action of the bosonic sector of the heterotic string in critical dimensions is employed to derive a Wheeler-DeWitt equation for the Bianchi type-IX cosmology. An exact solution is found that becomes strongly peaked around the isotropic limit as the volume of the three-geometry increases. In principle the global O(6,6) symmetry of the effective action can be employed to generate new solutions from the one presented here.

CERN Document Server

We study the high energy behaviour of Yang-Mills theory under the inclusion of gravity. In the weak-gravity limit, the running gauge coupling receives no contribution from the gravitational sector, if all symmetries are preserved. This holds true with and without cosmological constant. We also show that asymptotic freedom persists in general field-theory-based gravity scenarios including gravitational shielding as well as asymptotically safe gravity.

International Nuclear Information System (INIS)

Target materials for inertial fusion energy (IFE) power plant designs might be selected for a wide variety of reasons including wall absorption of driver energy, material opacity, cost and ease of fabrication. While each of these issues are of great importance, target materials should also be selected based upon their safety and environmental (S and E) characteristics. The present work focuses on the recycling, waste management and accident dose characteristics of potential target materials. If target materials are recycled so that the quantity is small, isotopic separation may be economically viable. Therefore, calculations have been completed for all stable isotopes for all elements from lithium to polonium. The results of these calculations are used to identify specific isotopes and elements that are most likely to be offensive as well as those most likely to be acceptable in terms of their S and E ...

Energy Technology Data Exchange (ETDEWEB)

A simple electromagnetic transport system was constructed to identify very rare positrons produced in a powerful laser beam interaction with a target. Testing experiments were carried out with CO[sub 2]-laser (10[sup 12] W/cm[sup 2]) beam pulses ([tau] = 50 ns, f = 0.01 Hz) focused on the copper target, as well as with a 96 MeV alpha-particle beam irradiated carbon target. The results showed that the developed system could be effectively used for positron identification and evaluation of their energy by means of a time-of-flight method. The computerized system to deal with this problem, together with others related to the power laser beam interaction with targets, has been constructed. (orig.).

Science.gov (United States)

Using static Michelson interferometer to get the spectrum information of measurement targets for spectrum identification, under the condition that the interference length is constant, the system can be optimized by BP neural network algorithm for the mixed spectral separation process. Thereby it can realize improving the recognition probability of camouflage target. Collecting the spectrum information in field of view (FOV) by the interferometer and linear array CCD detector, composing the set of mixed spectrum data, with known absorption spectrum of the material as a hidden layer of rules, it used BP neural network to separate the mixed spectrum data. Experiment with different distances, different combinations of mixed background spectrum as the initial data, using steel target (size: 1.5 m x 1.5 m) made of four kinds, the recognition probability of non-camouflage target is about 90% by BP neural ...

International Nuclear Information System (INIS)

Purpose: Various published reports involving intensity-modulated radiotherapy (IMRT) plans developed using automated optimization (inverse planning) have demonstrated highly conformal plans. These reported conformal IMRT plans involve significant target dose inhomogeneity, including both overdosage and underdosage within the target volume. In this study, we demonstrate the development of optimized beamlet IMRT plans that satisfy rigorous dose homogeneity requirements for all target volumes (e.g., #+-#5%), while also sparing the parotids and other normal structures. Methods and Materials: The treatment plans of 15 patients with oropharyngeal cancer who were previously treated with forward-planned multisegmental IMRT were planned again using an automated optimization system developed in-house. The optimization system allows for variable sized beamlets computed using a three-dimensional convolution/superposition dose ...

Energy Technology Data Exchange (ETDEWEB)

The production methods for seven radioisotopes, Ga-67, Sr-85, Pd-103, In-111, Tm-167, Hg-197 and Pb-203, by using a classical 1.5m cyclotron in the Institute of Physics and Power Engineering, Obninsk, USSR, are described. At present, more than 50 cyclotrons in different countries are used for the production of radioisotopes applied to medicine. Radioisotopes are produced with the cyclotron in the I.Ph.P.E. in the form of irradiated targets, which are delivered to Moscow radiopharmaceutical factory, where radiopharmaceuticals are produced on the base of these targets. The cyclotron is operated in two regimes providing the acceleration of protons, deuterons and alpha -particles. Two types of target assemblies are used for irradiation, the one is intended for the internal beam, and the other is for the external beam. The reactions used for the production of seven radioisotopes described above, the types of ...

Energy Technology Data Exchange (ETDEWEB)

The theory of ..cap alpha.. decay in first-order perturbation theory is presented. The theory is designed for a strongly deformed nucleus in an isomeric state which changes its deformation dynamically through decay from a very deformed to an almost spherical shape. It is shown that other channels are not coupled to the ..cap alpha.. channel in first-order perturbation theory. The collective degrees of freedom of the daughter nucleus are described by shape vibrational states, eigenstates of a Hamiltonian whose potential has two minima. The parent nucleus is described by dynamically coupling the vibrational degrees of freedom to the ..cap alpha..-particle motion and also taking rotations into account. The ..cap alpha.. particle is taken to be a point-like particle. The theory is applied to the ..cap alpha.. decay of the isomeric state of /sub 95//sup 242/Am.

Science.gov (United States)

The present study numerically investigates the enhancement of forced convective heat transfer from a single circular cylinder embedded in a packed bed of spherical particles confined by two impermeable parallel plates. The heat transfer results from the heated cylinder, with and without the presence of a porous medium, are compared. The results show that the presence of the porous particles enhances the heat transfer from the cylinder; however, the significant heat transfer augmentation is produced at high Re due to the effect of thermal dispersion. In addition, the effect of Re on Nut is much greater than that of kr and Bi in the porous channel. It is also found that the %?p is much higher than %HTE producing from packing the empty channel.

International Nuclear Information System (INIS)

Ceramic fuel element is one of the most important items of HTGR technology, and the corrosion resistance of is matrix materials is vital to the operational performance of HTGR. In the paper, based on the oxidation study of the matrix materials, it has been proposed that the corrosion resistance of the matrix materials might be improved through forming carbon -ceramic composite. The experiment results have shown that the corrosion resistance of matrix materials has been improved by addition of SiC superfine powders, and that the matrix materials containing SiC superfine powders and heat-treated at 1600 deg. C had an oxidation rate lower than the general one containing no SiC superfine powder and heat-treated at 1950 deg. C. (author). 5 refs, 8 figs.

Energy Technology Data Exchange (ETDEWEB)

This paper attempts to explain the peculiarities of the radial-distribution function of metal glasses without involving ideas of the amorphous structure. On a computer, the radial atomic density for a spherical eutectic single crystal of the composition Fe/sub 84/C/sub 16/ of radius 15 A formed by alternating small crystals of e-Fe and Fe/sub 3/C of cubic form with the edge of the cube ca 10 A. For the sake of clarity, the diagram of such a quasisingle crystal is shown and has been given a cubic boundary. The change in the relationship between the heights of the subpeaks of the second maximum of the radial distribution function of atoms in the Fe-B glasses with a change in the concentration of boron can be explained by the change in the space group of the Fe/sub 3/B metastable boride which is formed in this system.

Energy Technology Data Exchange (ETDEWEB)

We study some aspects of the experimental behaviour of tachyons, in particular by finding out their <> shape. A Superluminal particle, which in its own rest frame is spherical or ellipsoidal (and with an infinite lifetime), would <> to a laboratory frame as occupying the whole region of space bound by a double cone and a two sheeted hyperboloid. Such a structure (the tachyon <>) rigidly travels with the speed of the tachyon. However, if the Superluminal particle has a finite lifetime in its rest frame, then in the laboratory frame it gets a finite space extension. As a by-product, we are able to interpret physically the imaginary units entering - as is well known - the transverse co-ordinates in the Superluminal Lorentz transformations. The various particular or limiting cases of the tachyon shape are thoroughly considered. Finally, some brief considerations concerning possible experiments to look for ...

Energy Technology Data Exchange (ETDEWEB)

Aqueous radioactive high-level waste slurries are combined during processing steps that ultimately produce a stable borosilicate glass waste form. Chemically treated waste slurries are combined with each other and with glass frit-water slurries to produce the melter feed. Understanding the evolution of the rheological properties of the slurries is an important aspect of removing and treating the stored waste. To a first approximation, combinations of colloidal waste slurry with {approx}0.1-mm mean diameter glass frit or glass beads act in an analogous matter to slurries of spherical beads in Newtonian liquids. The non-Newtonian rheological properties of the waste slurries without frit, however, add complexity to the hydrodynamic analysis. The use of shear rate dependent apparent viscosities with the modified Einstein equation was used to model the rheological properties of aqueous frit-waste slurries.

Science.gov (United States)

Polysomaty analysis of the succulent portulaca (Portulaca grandiflora Hook.) plant was carried out using flow cytometry. For both diploid and tetraploid plants, mature leaf tissue was found to have a higher level of polysomaty than young leaf tissue. Mesophyll (MP), bundle sheath (BSP) and water storage protoplasts (WSP) were isolated from leaf tissues of diploid portulaca plants. WSP had a higher degree of endopolyploidization than MP and BSP. The ploidy distribution was also variable in different floral organs. Tetraploid plants artificially induced by colchicine treatment showed a decline in the degree of polysomaty compared to diploid plants. Tetraploid plants had more spherical leaves, a larger number of petals and lower pollen fertility than diploid plants. PMID:10936528

CERN Document Server

A method for systematically including topological degrees of freedom in perturbation theory is developed. This is not bound by the restrictions of semi-classical techniques. The Yang-Mills theory in three Euclidean dimensions is considered here. A well-defined separation of the topological and the ``spin wave'' degrees of freedom is obtained, motivated by a singular gauge. This has ``photons'' distorting the spherically symmetric magnetic fields of Dirac monopoles, and massless charged vector bosons ``W'' scattering off the latter. It is explicitly shown that the Dirac string does not contribute. The mode of the charged vector bosons with total angular momentum J=0 provides precisely the core to give a finite energy to the monopole. The radial equation for W is remarkably simplified and only two polarization states survive exactly for the anomalous magnetic moment required by the Yang-Mills interaction.

British Library Electronic Table of Contents (United Kingdom)

Starch from the fruits of sweetsop (Anonna squamosa) and soursop (Anonna muricata) were isolated and purified and the fat, ash, phosphorus and protein contents measured. The amount of amylose present was determined spectrophotometrically and found to be very similar (19%) for both starches. Scanning electron microscopy showed very small indented and spherical granules from both with an average granule size of 4.84mm and 4.72mm, respectively. The physicochemical properties, namely the swelling power, solubility, pasting characteristics, paste clarity and freeze-thaw stability were studied to assess the functionality of the starch pastes as hydrocolloids. The sweetsop starch showed higher swelling power and solubility compared to soursop starch and had a lower gelatinization temperature indi...

International Nuclear Information System (INIS)

Synthesis, morphology, structural and optical characteristics of SiC NWs and SiC/C nanocomposites with an inverse opal lattice have been investigated. The samples were prepared by carbothermal reduction of silica (SiC NWs) and by thermo-chemical treatment of opal matrices (SiC/C) filled with carbon compounds which was followed by silicon dioxide dissolution. It was shown that the nucleation of SiC NWs occurs at the surface of carbon fibers felt. It was observed three preferred growth direction of the NWs: [111], [110] and [112]. HRTEM studies revealed the mechanism of the wires growth direction change. SiC/C- HRTEM revealed in the structure of the composites, except for silicon carbide, graphite and amorphous carbon, spherical carbon particles containing concentric graphite shells (onion-like particles).

British Library Electronic Table of Contents (United Kingdom)

By choosing appropriate microemulsion systems, hexagonal cobalt (Co) and cobalt-nickel (1:1) alloy nanoparticles have been obtained with cetyltrimethylammonium bromide as a cationic surfactant at 500degreeC. This method thus stabilizes the hcp cobalt even at sizes (<10nm) at which normally fcc cobalt is predicted to be stable. On annealing the hcp cobalt nanoparticles in H2 at 700degreeC we could transform them to fcc cobalt nanoparticles. Microscopy studies show the formation of spherical nanoparticles of hexagonal and cubic forms of cobalt and Co-Ni (1:1) alloy nanoparticles with the average size of 4, 8 and 20nm, respectively. Electrochemical studies show that the catalytic property towards oxygen evolution is dependent on the applied voltage. At low voltage (less than 0.65V) the Co (he...

Energy Technology Data Exchange (ETDEWEB)

The performance of spherical Resorcinol-Formaldehyde ion-exchange resin for the removal of cesium from alkaline radioactive waste solutions has been investigated through computer modeling. Cesium adsorption isotherms were obtained by fitting experimental data using a thermodynamic framework. Results show that ion-exchange is an efficient method for cesium removal from highly alkaline radioactive waste solutions. On average, two 1300 liter columns operating in series are able to treat 690,000 liters of waste with an initial cesium concentration of 0.09 mM in 11 days achieving a decontamination factor of over 50,000. The study also tested the sensitivity of ion-exchange column performance to variations in flow rate, temperature and column dimensions. Modeling results can be used to optimize design of the ion exchange system.

CERN Document Server

The confining effect of a spherical substrate inducing anchoring (normal to the surface) of rod-like liquid crystal molecules contained in a thin film spread over it has been investigated with regard to possible changes in the nature of the isotropic-to-nematic phase transition as the sample is cooled. The focus of these Monte Carlo simulations is to study the competing effects of the homeotropic anchoring due to the surface inducing orientational ordering in the radial direction and the inherent uniaxial order promoted by the intermolecular interactions. By adopting entropic sampling procedure, we could investigate this transition with a high temperature precision, and we studied the effect of the surface anchoring strength on the phase diagram for a specifically chosen geometry. We find that there is a threshold anchoring strength of the surface below which uniaxial nematic phase results, and above which the isotropic fluid cools to a radially ordered nematic ...

Energy Technology Data Exchange (ETDEWEB)

Multi-kilo-electron-volt x-ray microscopy will be an important laser-produced plasma diagnostic at future megajoule facilities such as the National Ignition Facility (NIF). However, laser energies and plasma characteristics imply that x-ray microscopy will be more challenging at NIF than at existing facilities. We use analytical estimates and numerical ray tracing to investigate several instrumentation options in detail, and we conclude that near-normal-incidence single spherical or toroidal crystals may offer the best general solution for high-energy x-ray microscopy at NIF and similar large facilities. Apertured Kirkpatrick{endash}Baez microscopes using multilayer mirrors may also be good options, particularly for applications requiring one-dimensional imaging over narrow fields of view. {copyright} 1998 Optical Society of America

British Library Electronic Table of Contents (United Kingdom)

Intrinsic spherical aberrations of electron lenses have been the major resolution limiting factor in electron microscopes for several decades. While effective correctors have recently been implemented, an alternative to correct these aberrations is to circumvent them by scaling down lens dimensions by several orders of magnitude. We have fabricated electrostatic lenses exhibiting one micrometer diameter apertures and evaluated their beam forming properties against predictions from numerical ray tracing simulations. It turns out that it is routinely possible to shape a paraxial low-energy electron beam by such micron-sized lenses. Beam profiles have been measured both at a distant detector as well as in a plane close to the lens. It is shown that the lens can form a parallel beam extending ...

Energy Technology Data Exchange (ETDEWEB)

In calibration measurements with low energy X-rays, a double peak effect appears in low pressure proportional counters with a helix, when used for simulation of tissue equivalent diameters considerably larger than 2 m. An interpretation of this phenomenon is discussed, based upon electron capture and electric field perturbation at the counter helix. A description of the physical processes is presented showing that the double peak effect is a problem in the case of helix counters (called also Rossi counters) for all simulated diameters. Conclusions are drawn on systematic errors introduced by the counter helix into microdosimetric spectra and anti y/sub D/ of photons and neutrons. The authors recommend to use cylindrical counters with optimized geometrical and electronic parameters rather than the spherical counters with a helix discussed.

Energy Technology Data Exchange (ETDEWEB)

The authors describe a small doubly reflecting research furnace. Its optical components, a heliostat and a concentrating array of hexagonal-in-plan-form mirrors, focus sunlight at the aperture of a cavity receiver. A perfect paraboloid of revolution would have given higher concentration ratios. But large paraboloids are difficult to make and manipulate. Small hexagons are convenient and can be close packed. Spherical mirrors centered on a sphere simplified construction and were economical. In this note they use a simple model to describe the radial distribution of the normal flux at the focus of such an array. A schematic representation of a cross section of the concentrator mirror array in a plane which includes its axis is shown.

CERN Document Server

E8 X E8 heterotic string and M-theory, when appropriately compactified, can give rise to realistic, N=1 supersymmetric particle physics. In particular, the exact matter spectrum of the MSSM, including three right-handed neutrino supermultiplets, one per family, and one pair of Higgs-Higgs conjugate superfields is obtained by compactifying on Calabi-Yau manifolds admitting specific SU(4) vector bundles. These "heterotic standard models" have the SU(3)_{C} X SU(2)_{L} X U(1)_{Y} gauge group of the standard model augmented by an additional gauged U(1)_{B-L}. Their minimal content requires that the B-L gauge symmetry be spontaneously broken by a vacuum expectation value of at least one right-handed sneutrino. In a previous paper, we presented the results of a renormalization group analysis showing that B-L gauge symmetry is indeed radiatively broken with a B-L/electroweak hierarchy of O(10) to O(10^{2}). In this paper, we present the details of ...

International Nuclear Information System (INIS)

The high resolution absorption, luminescence and excitation spectra of the orthorhombic potassium lanthanum praseodymium ternary chloride, K_2La_1_-_xPr_xCl_5, (0.02 #<=# x #<=# 0.15) single crystals were recorded at 4, 77 and 293 K with different excitation sources. The experimental 4f"2 energy level scheme of the Pr"3"+ ion in K_2LaCl_5 derived from the absorption and emission spectra consisted of 86 (out of 91) Stark components. This energy level scheme was simulated by using a phenomenological crystal field (cf) model which included eight free ion and nine cf parameters according to the C_2_v symmetry. Despite the approximate C_2_v point symmetry instead of the real C_s one, the simulation yielded a very satisfactory rms deviation of 17 cm"-"1 between the experimental and calculated energy level schemes. The results, especially the weak cf strength, are discussed taking into account the bonding characteristics in K_2LaCl_5.

Energy Technology Data Exchange (ETDEWEB)

Absorption and emission measurements at liquid-helium temperature, liquid-nitrogen temperature and room temperature have been performed on tetragonal scheelite-type rare earth sodium double molybdates Na[sub 5]RE(MoO[sub 4])[sub 4] and on RE-doped Na[sub 5]Gd(MoO[sub 4])[sub 4] samples. The rare earth occupies one single crystallographic position with S[sub 4] as point symmetry. The spectra were analysed according to the crystal field theory. From the experimental data, nearly complete energy level schemes of the Pr[sup 3+] and Nd[sup 3+], on the 4f [sup 2] and 4f [sup 3] configurations were derived. Very good correlation was obtained between the experimental and simulated energy level schemes, first for the approximated D[sub 2d] and then for the true S[sub 4] symmetries. The crystal field parameters vary smoothly with the atomic number of the rare earth, when compared with those determined previously for Eu[sup 3+] in the same matrix. ...

CERN Document Server

We consider a family of chiral non-Hermitian Gaussian random matrices in the unitarily invariant symmetry class. The eigenvalue distribution in this model is expressed in terms of Laguerre polynomials in the complex plane. These are orthogonal with respect to a non-Gaussian weight including a modified Bessel function of the second kind, and we give an elementary proof for this. In the large $n$ limit, the eigenvalue statistics at the spectral edge close to the real axis are described by the same family of kernels interpolating between Airy and Poisson that was recently found by one of the authors for the elliptic Ginibre ensemble. We conclude that this scaling limit is universal, appearing for two different non-Hermitian random matrix ensembles with unitary symmetry. As a second result we give an equivalent form for the interpolating Airy kernel in terms of a single real integral, similar to representations for the asymptotic kernel in the bulk ...

International Nuclear Information System (INIS)

The perturbations of the L.R.S. class A spatially homogeneous spacetimes are treated using Hamiltonian methods in conjunction with techniques from the theory of Lie group harmonic analysis. These latter techniques lead to a simple way of handling any set of tensor equations on these background spacetimes which has the same symmetry group as the space-time metric. Once this approach is developed, the Hamiltonian formulation is used to recover in a clean way the Bonanos equations for the perturbations of the perfect fluid models of the class of spacetimes under consideration. The conserved quantities associated with the four-dimensional symmetry group are evaluated and their role in the linearized Hamiltonian dynamics is discussed. The time-dependent linear canonical transformation of the linearized vacuum gravitational phase space adapted to Moncrief's gauge invariant decomposition is described in general for these models and evaluated ...

CERN Document Server

The detailed formulation for loop quantum cosmology (LQC) in the Bianchi I model with a scalar massless field has been constructed. In this paper, its effective dynamics is studied in two improved strategies for implementing the LQC discreteness corrections. Both schemes show that the big bang is replaced by the big bounces, which take place up to three times, once in each diagonal direction, when the area or volume scale factor approaches the critical values in the Planck regime measured by the reference of the scalar field momentum. These two strategies give different evolutions: In one scheme, the effective dynamics is independent of the choice of the finite sized cell prescribed to make Hamiltonian finite; in the other, the effective dynamics reacts to the macroscopic scales introduced by the boundary conditions. Both schemes reveal interesting symmetries of scaling, which are reminiscent of the relational interpretation of quantum mechanics and also suggest ...

Energy Technology Data Exchange (ETDEWEB)

We find instanton/cosmological solutions with biaxial Bianchi-IX symmetry, involving nontrivial spatial dependence of the CP{sup 1}-CP{sup 2}-sigma-models coupled to gravity. Such manifolds arise in N = 1, d 4 supergravity with supermatter actions and hence the solutions can be embedded in supergravity. There is a natural way in which the standard coordinates of these manifolds can be mapped into the four-dimensional physical space. Due to its special symmetry, we start with CP{sup 2} with its corresponding scalar ansatz; this further requires the spacetime to be SU(2) x U(1)-invariant. The problem then reduces to a set of ordinary differential equations whose analytical properties and solutions are discussed. Among the solutions there is a surprising, special family of exact solutions which owe their existence to the nontrivial topology of CP{sup 2} and are in 1-1 correspondence with matter-free Bianchi-IX metrics. These solutions can also be ...

CERN Document Server

We consider a class of nonlinear Schrodinger / Gross-Pitaevskii (NLS/GP) equations with periodic potentials, having an even symmetry. We construct "solitons", centered about any point of symmetry of the potential. For focusing (attractive) nonlinearities, these solutions bifurcate from the zero state at the lowest band edge frequency, into the semi-infinite spectral gap. Our results extend to bifurcations into finite spectral gaps, for focusing or defocusing (repulsive) nonlinearities under more restrictive hypotheses. Soliton nonlinear bound states with frequencies near a band edge are well-approximated by a slowly decaying solution of a homogenized NLS/GP equation, with constant homogenized effective mass tensor and effective nonlinear coupling coefficient, modulated by a Bloch state. For the critical NLS equation with a periodic potential, e.g. the cubic two dimensional NLS/GP with a periodic potential, our results imply that the limiting ...

CERN Document Server

The aim of this set of lectures is to review different avenues of electroweak symmetry breaking explored over the years. This constitutes a timely exercise as the world's largest and the highest energy particle accelerator, namely, the Large Hadron Collider (LHC) at CERN near Geneva, is all set to start running whose primary mission is to unravel the mysteries of electroweak phase transition. In the beginning, we discuss the Standard Model Higgs mechanism. After that we review the Higgs sector of the Minimal Supersymmetric Standard Model. Then we take up three relatively recent ideas: Little Higgs, Gauge-Higgs Unification, and Higgsless scenarios. For the latter three cases, we present the basic ideas and restrict our illustrations to some instructive toy models, as our intention is rather to provide an intuitive feel of the underlying dynamics than to get into an in-depth analysis of realistic scenarios. Wherever possible, we provide enough pedagogical details, ...

CERN Document Server

The HARP experiment at CERN is performing extensive measurements of hadron production cross sections and secondary particle yields, in the momentum range 1.5-15 GeV/c, over the full solid angle and using a large set of cryogenic and solid targets. First measurements of hadron production cross-sections in the forward region are reported using an aluminium target 5% of an interaction length thick and a proton beam of 12.9 GeV/c. A preliminary analysis in the large angle region of elastic scattering events produced with the cryogenic hydrogen target at 3 GeV/c beam momentum is also presented.

International Nuclear Information System (INIS)

Carrier-free radioisotopes of tungsten, "1"7"6","1"7"7W, and their corresponding daughter radionuclides "1"7"6","1"7"7Ta, have been produced in holmium target by heavy ion activation with "1"6O"5"+ beam. An attempt has been made to separate these carrier-free radionuclides from bulk holmium target through LLX using cation exchanger HDEHP. (author)

International Nuclear Information System (INIS)

A simple highly efficient procedure has been developed for recovery of thallium radioisotopes from lead and bismuth targets irradiated by 1-GeV protons. The procedure is based on the use of extraction chromatography. The cross-sections have been determined for formation of "2"0"0Pb, "2"0"1Pb, "2"0"2"mPb, and "2"0"3Pb radioisotopes in targets from lead with natural isotopic composition, irradiated by 1-GeV protons.

British Library Electronic Table of Contents (United Kingdom)

A modified variable structure interacting multiple model (M-VSIMM) estimator for complex hybrid maneuver target tracking is presented. The M-VSIMM could potentially be applied to fire control systems (FCS) used on warships. Target model groups were designed using 3D dimensional dynamic target models. Optimal model group selection logic was proposed, contrary to the activation and termination logic in the original VSIMM. The system will respond faster with optimal model group selection logic. After performing simulations, the tracking performances of the Kalman, ?-?(-?), VDIE, IMM and M-VSIMM filters were compared under various maneuvering conditions.

Energy Technology Data Exchange (ETDEWEB)

The velocity distribution of electrons ejected close to the forward direction by 0.8-2 MeV/A ions traversing various solid targets, including a Au monocrystal, is measured in coincidence with emerging charge-selected ions. The velocity spectrum is observed to be independent of outgoing projectile velocity and charge state for polycrystalline targets. Measurements on the Au crystal under channeling conditions show dependences on final charge state, and are tentatively explained by assuming that the main contribution to the production yield comes from the non-channeled fraction of the ions. A simple model for the creation of the forward-ejected electrons is proposed, which accounts for most of the experimental findings.

Energy Technology Data Exchange (ETDEWEB)

The centroid and envelope dynamics of a high-intensity charged particle beam are investigated as a beam smoothing technique to achieve uniform illumination over a suitably chosen region of the target for applications to ion-beam-driven high energy density physics and heavy ion fusion. The motion of the beam centroid projected onto the target follows a smooth pattern to achieve the desired illumination, for improved stability properties during the beam-target interaction. The centroid dynamics is controlled by an oscillating "wobbler", a set of electrically-biased plates driven by RF voltage. __________________________________________________

CERN Document Server

An electroweak model with running coupling constants described by an energy dependent entire function is utraviolet complete and avoids unitarity violations for energies above 1 TeV. The action contains no physical scalar fields and no Higgs particle and the physical electroweak model fields are local and satisfy microcausality. The $W$ and $Z$ masses are compatible with a symmetry breaking $SU(2)_L\\times U(1)_Y \\rightarrow U(1)_{\\rm em}$, which retains a massless photon. The vertex couplings possess an energy scale $\\Lambda_W > 1$ TeV predicting scattering amplitudes that can be tested at the LHC.

International Nuclear Information System (INIS)

It is shown that the Cherenkov radiation of tachyons (CRT) in general case cannot possess axial symmetry with respect to velocity v. This implies that tachyons must be vector particles. Electric dipole is used as a vector characterising the tachyon. Formulas describing the CRT spectrum are derived taking into account the asymmetry for charged tachyon and neutral tachyon dipole with arbitrary orientation with respect to v. It is shown that both types of CRT possess the same integral characteristics. A new integral of motion specific for tachyons is found. Negative results of all attempts to detect the CRT are explained.

CERN Document Server

Supersymmetry, a new symmetry that relates bosons and fermions in particle physics, still escapes observation. Search for SUSY is one of the main aims of the recently launched Large Hadron Collider. The other possible manifestation of SUSY is the Dark Matter in the Universe. The present lectures contain a brief introduction to supersymmetry in particle physics. The main notions of supersymmetry are introduced. The supersymmetric extension of the Standard Model - the Minimal Supersymmetric Standard Model - is considered in more detail. Phenomenological features of the MSSM as well as possible experimental signatures of SUSY at the LHC are described. The DM problem and its possible SUSY solution is presented.

Energy Technology Data Exchange (ETDEWEB)

Strains in multivalley semiconductors can destroy the strict equivalence of the valleys that is demanded by cubic symmetry. Significant changes in the properties of a semiconductor may result. A proposed implementation of quantum computing with donor atoms in silicon would suffer from alterations of the donor wave functions caused by strains that are produced by fabrication processes. Deliberately straining the silicon to an extent that removed all but one valley from participation in the lowest donor state, would prevent further changes in the wave function by strain. The strain required can be achieved with established technology for depositing silicon on SiGe alloys. (author)

CERN Document Server

It has been proposed that a hidden conformal field theory (CFT) governs the dynamics of low frequency scattering in a general Kerr black hole background. We further investigate this correspondence by mapping higher order corrections to the massless wave equations in a Kerr background to an expansion within the CFT in terms of higher dimension operators. This implies the presence of infinite towers of CFT primary operators with positive conformal dimensions compatible with unitarity. The exact Kerr background softly breaks the conformal symmetry and the scaling dimensions of these operators run with frequency. The scale-invariant fixed point is dual to a degenerate case of flat spacetime.

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I review recent developments in quark-hadron duality in inclusive electron-nucleon scattering. Matrix elements of twist-4 operators extracted from moments of the spin-dependent g1 structure function suggest that duality violating higher twists are small above Q2 {approx} 1 GeV2. The x dependence of local duality is analyzed within a quark model framework, and mechanisms are identified for spin-flavor symmetry breaking which underpin the behavior of structure functions at large x.

International Nuclear Information System (INIS)

Impurity effects on the photon-assisted spin-polarized transport through armchair carbon nanotubes connected with ferromagnetic leads are investigated theoretically. The impurity induces one resonant state whose position depends on the impurity strength, which can break the electron-hole symmetry. Whether the impurity suppresses or enhances the spin-coherent current depends on the nanotube length. When the microwave fields are applied on the nanotube, additional small side peaks caused by the photon-assisted tunneling are found. With increasing the impurity strength, one new current peak appears under the influence of both the microwave fields and the impurity.

CERN Document Server

By using a model independent Monte Carlo approach, we study the possible structure of charged and neutral lepton mass matrices, under the assumption of an U(2) horizontal symmetry (additional to the usual Standard Model ones) involving the light fermion generations. We assume the most general Majorana mass matrix for neutrinos. We update the results of our previous similar study, by inserting in the analysis the recent KamLAND data, that contributed to find a final solution to the Solar neutrino problem. The introduction of the new experimental data reduce the allowed regions in the nine dimensional space parameters, and show that our procedure gives stable solutions.

British Library Electronic Table of Contents (United Kingdom)

Electrostatic torsional micro-mirrors have wide spread use in different industries for diverse purposes. This paper investigates the development of superharmonics and chaotic responses in electrostatic torsional micro-mirrors near the pull-in condition. Appearance of nonlinear phenomena is investigated in models accounting for and disregarding the coupling of torsional and flexural deflections. Analysis of the system response to step and harmonic excitation reveals the appearance of DC and AC symmetry breaking. Increasing the amplitude of harmonic excitation, the response in the form of distinct superharmonics changes to a broad band response, where there is loss of periodicity and the response becomes chaotic. Accounting for flexural deflections in coupled model reduces the voltage thresh...

Energy Technology Data Exchange (ETDEWEB)

This guide is applied for the reload pattern's formation for mirror symmetry of a core room and in accordance with the Control Cell core technique (of the english Control Cell Core - CCC) for the PRESTO-B code. (Author)

British Library Electronic Table of Contents (United Kingdom)

We have successfully grown single crystalline Formula Not Shown with the range of Formula Not Shown using the floating-zone method. All compounds show orthorhombic symmetry in this substitution range, but the difference between lattice constants a and b decreases with increasing Sr concentration and becomes almost zero at Formula Not Shown . Characteristic temperatures, which correspond to antiferromagnetic ordering and structural transition, decrease with increasing Sr concentration. The value of the magnetic susceptibility below 30K increases with increasing Sr concentration. The temperature dependence of the electrical resistivity revealed that Sr substitution significantly suppresses the highly anisotropic electric structure of Formula Not Shown .

International Nuclear Information System (INIS)

In CsCdBr_3, Tm"3"+ substitutes for Cd"2"+. It predominately forms symmetric dimer centers and single-ion centers, both of trigonal symmetry. The energy level schemes of both centers were determined by EPR and site-selective laser spectroscopy. To describe the spectra term dependent crystal-field parameters were deduced on the basis of a microscopic model taking into account the local lattice deformation induced by the impurity centers and the quasi-resonant virtual scattering of intrinsic lattice excitations by the Tm"3"+ ions. (orig.)

CERN Document Server

We carry out a Lie group analysis of the Sachs equations for a time-dependent axisymmetric non-rotating space-time in which the Ricci tensor vanishes. These equations, which are the first two members of the set of Newman-Penrose equations, define the characteristic initial-value problem for the space-time. We find a particular form for the initial data such that these equations admit a Lie symmetry, and so defines a geometrically special class of such spacetimes. These should additionally be of particular physical interest because of this special geometric feature.

International Nuclear Information System (INIS)

The composite wave variational version of the APW (augmented plane wave) method is used to obtain the electronic band structure of the compounds boron phosphide and boron arsenide at the high symmetry points #GAMMA#, X, and L. The tight binding interpolation scheme of Slater and Koster is used to calculate the rest of the band structure. The results show that both these materials are indirect band gap semiconductors. The density of states, and the imaginary part of the dielectric constant is also calculated. The theoretical results are compared with the reported experimental and theoretical data. (author).

International Nuclear Information System (INIS)

The symmetry properties of the Coulomb potential allow for a dynamical spin-1/2 description of any fixed n level of a hydrogenlike atom in a time-dependent sufficiently weak electric and/or magnetic field. An explicit expression for the time dependence of the l,m amplitudes pertaining to a general n level is derived. The derivation follows on purely algebraic operations. Based on the derivation, we give analytical n-independent solutions to established and proposed schemes for driving the atom into a high angular-momentum state.

Energy Technology Data Exchange (ETDEWEB)

The geodesic equation for space-like objects moving along a circular trajectory in the expanding universe is considered. Our analysis leads to the conclusion that ancient cosmological tachyons may exist in the present-day world and may play an important role in (i) the internal structure of hadrons conceived as nonlocal objects called strings, (ii) the T-symmetry violation observed in the weak K-decays, (iii) the multidimensional unified field theories of Kaluza-Klein type, and in (iv) the classical models of charged particles which combine ordinary electromagnetism with a self-interacting version of Newtonian gravity. 18 refs.