CERN Document Server

Starting from the original collective Hamiltonian of Bohr and separating the beta and gamma variables as in the X(5) model of Iachello, an exactly soluble model corresponding to a harmonic oscillator potential in the beta-variable (to be called X(5)-$\\beta^2$) is constructed. Furthermore, it is proved that the potentials of the form $\\beta^{2n}$ (with n being integer) provide a ``bridge'' between this new X(5)-$\\beta^2$ model (occuring for n=1) and the X(5) model (corresponding to an infinite well potential in the beta-variable, materialized for n going to infinity. Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are given for the potentials $\\beta^2$, $\\beta^4$, $\\beta^6$, $\\beta^8$, corresponding to E(4)/E(2) ratios of 2.646, 2.769, 2.824, and 2.852 respectively, ...

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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

The interaction of accretion disks with the magnetospheres of young stars can produce X-winds and funnel flows. With the assumption of axial symmetry and steady state flow, the problem can be formulated in terms of quantities that are conserved along streamlines, such as the Bernoulli integral (BI), plus a partial differential equation (PDE), called the Grad-Shafranov equation (GSE), that governs the distribution of streamlines in the meridional plane. The GSE plus BI yields a PDE of mixed type, elliptic before critical surfaces where the flow speed equals certain characteristic wave speeds are crossed and hyperbolic afterward. The computational difficulties are exacerbated by the locations of the critical surfaces not being known in advance. To overcome these obstacles, we consider a variational principle by which the GSE can be attacked by extremizing an action integral, with all other conserved quantities of the problem ...

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 ...

CERN Document Server

The full theory and the semiclassical description of loop quantum cosmology (LQC) have been studied in the Friedmann-Robertson-Walker and Bianchi I models. As an extension to include both anisotropy and intrinsic curvature, this paper investigates the cosmological model of Kantowski-Sachs spacetime with a free massless scalar field at the level of phenomenological dynamics with the LQC discreteness corrections. The LQC corrections are implemented in two different improved quantization schemes. In both schemes, the big bang and big crunch singularities of the classical solution are resolved and replaced by the big bounces when the area or volume scale factor approaches the critical values in the Planck regime measured by the reference of the scalar field momentum. Symmetries of scaling are also noted and suggest that the fundamental spatial scale (area gap) may give rise to a temporal scale. The bouncing scenarios are in an analogous fashion of ...

CERN Document Server

A new mathematical framework is formulated to derive the effective equations of motion for the constrained quantum system which possesses an internal clock. In the realm close to classical behavior, the quantum evolution is approximated by a finite system of coupled but ordinary differential equations adhered to the weakly imposed Hamiltonian constraint. For the simplified version of loop quantum cosmology in the Bianchi I model with a free massless scalar filed, the resulting effective equations of motion affirm the bouncing scenario predicted by the previous studies: The big bang singularity is resolved and replaced by the big bounces, which take place up to three times, once in each diagonal direction, whenever the directional density approaches the critical value in the regime of Planckian density. It is also revealed that back-reaction arises from the quantum corrections and modifies the precise value of the directional density at the bouncing epoch. ...

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.

Energy Technology Data Exchange (ETDEWEB)

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.

International Nuclear Information System (INIS)

Transients induced in nuclear power plants from many sources result in one or more fluid conditions changing with time. Fluid conditions of pressure, inlet temperature, inlet flow, or even system power many change separately or in conjunction with each other. The result of the condition change may be one which induces departure from nucleate boiling. An experimental investigation of transient which were intended to achieve Critical Heat Flux was performed at the Heat Transfer Research Facility of Columbia University for Siemens Nuclear Power Corporation. The transients were set up to include broad ranges of flow and pressure conditions near the operating range of pressurized water reactors. Transient events were dominated by varying single conditions and measuring the response of the system and of the rod thermocouples. Because of coupling effects within the test loop, secondary conditions would also vary. In order to perform controlled tests which achieved the ...

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In this paper we establish that every quantum field theory satisfying some basic axioms possesses a weak quasi Hopf algebra as gauge symmetry. We use a reconstruction theorem to find this symmetry algebra and show how it is sed to build a gauge covariant field algebra. We investigate the question of why this generality is necessary. The non-uniqueness of the reconstruction process is interpreted and a cohomological classification of possible global gauge symmetries is given. (author)

International Nuclear Information System (INIS)

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.)).

Science.gov (United States)

We proposed and numerically investigated the influence of spatial symmetry on the terahertz frequency region response of composite planar metamaterials based on deformed split ring resonators. Compared with the original simple structures, the composite metamaterials with different spatial symmetries exhibited exotic electromagnetic properties. The electromagnetic response of a specific configuration with C4 symmetry was identical to the structure with simple lattice. Especially, for configurations with broken symmetry, very sharp Drude-like resonances with high quality factor were observed. The electric field and current distribution associated the resonances were analyzed for deep understanding of the underlying physical properties.

Energy Technology Data Exchange (ETDEWEB)

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.

Energy Technology Data Exchange (ETDEWEB)

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

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)

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

In models with dynamical electroweak symmetry breaking, this breaking is normally communicated to quarks and leptons by a set of vector bosons with masses generated via sequential breaking of a larger gauge symmetry. In reasonably ultraviolet-complete theories of this type, the number of stages of breaking of the larger gauge symmetry is usually equal to the observed number of quark and lepton generations, $N_{gen.}=3$. Here we investigate the general question of how the construction and properties of these models depend on $N_{gen.}$, regarded as a variable. We build and analyze models with illustrative values of $N_{gen.}$ different from 3 (namely, $N_{gen.}=1,2,4$) that exhibit the necessary sequential symmetry breaking down to a strongly coupled sector that dynamically breaks electroweak symmetry. Our results for variable $N_{gen.}$ show that one can robustly obtain, for this ...

International Nuclear Information System (INIS)

As recently shown the conformal affine Toda models can be obtained via hamiltonian reduction from a two-loop Kac-Moody algebra. In this paper we propose a systematic procedure to analyze the higher spin symmetries of the conformal affine Toda models. The method is based on an explicit construction of infinite towers of extended conformal symmetry generators. Two fundamental building blocks of this construction are special spin-one and -two primary fields characterizing the conformal structure of these models. The connection to the algebra of area preserving diffeomorphisms on a two-manifold (w_#infinity# algebra) is established. (orig.).

UK PubMed Central (United Kingdom)

BackgroundMovement regularities are inherently present in automated goal-directed motions of the primate's arm system. They can provide important signatures of intentional behaviours...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

This is a set of lecture notes given by the author at the Universities of Gottingen and Wroclaw. The text presents the axiomatic approach to field theory and studies in depth the concepts of symmetry and supersymmetry and their associated generators, currents and charges. It is intended as a one- semester course for graduate students in the field of mathematical physics and high energy physics. Contents: Introduction; Example of a Classical and Quantum Scalar Free Field Theory; Scene and Subject of the Drama. Axiom 1 and 2; Subject of the Drama; Principle of Relativity. Causality. Axiom 3, 4 and 5; Irreducibility of the Field Algebra and Scattering Theory. Axiom 6. Axiom O; Preliminaries about Physical Symmetries; Currents and Charges; Global Symmetries and Supersymmetries of the S - Matrix; Representations of the Super-Lie Algebra; The Case of Massless Particles; Fermionic Charges; Concluding Remarks.

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International Nuclear Information System (INIS)

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.

Energy Technology Data Exchange (ETDEWEB)

The authors propose a generalization of the concept of supersymmetry non Riemann surfaces. Generators of this symmetry intermix M fields of different spin. Two types of statistics, i.e., bosonic and fermionic statistics, are allowed for parameters of infinitesimal transformations. They also study the possibility of string models associated with these symmetries. The algebraic structure of a part of generalized supersymmetry is regarded as a sort of an M-th root of the Virasoro algebra.

CERN Document Server

In the GmSUGRA scenario with the high-dimensional operators containing the GUT Higgs fields, we systematically studied the supersymmetry breaking scalar masses, SM fermion Yukawa coupling terms, and trilinear soft terms in the E_6 SUSY GUT model where the gauge symmetry is broken down to the SO(10)\\tm U(1) gauge symmetry, SU(3)_C\\times SU(3)_L \\times SU(3)_R gauge symmetry, SU(6)\\times SU(2)_a (a={\\rm L,R,X}) gauge symmetry, flipped SU(5) gauge symmetry etc. In addition, we considered the scalar and gaugino mass relations, which can be preserved from the GUT scale to the electroweak scale under one-loop RGE running, in the SU(3)_C\\times SU(3)_L \\times SU(3)_R model arising from the E_6 model. With such relations, we may distinguish the mSUGRA and GmSUGRA scenarios if we can measure the supersymmetric particle spectrum at the LHC and ILC.

CERN Document Server

We investigate the relation between the symmetries of a quantum system and its topological quantum numbers, in a general C*-algebraic framework. We prove that, under suitable assumptions on the symmetry algebra, there exists a generalization of the Bloch-Floquet transform which induces a direct-integral decomposition of the algebra of observables. Such generalized transform selects uniquely the set of "continuous sections" in the direct integral, thus yielding a Hilbert bundle. The emerging geometric structure provides some topological invariants of the quantum system. Two running examples provide an Ariadne's thread through the paper. For the sake of completeness, we review two related theorems by von Neumann and Maurin and compare them with our result.

International Nuclear Information System (INIS)

We describe in detail the space of the two Kaehler parameters of the Calabi-Yau manifold P_4"("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.)).

CERN Document Server

A novel algebraic topology approach to supersymmetry (SUSY) and symmetry breaking in quantum field and quantum gravity theories is presented with a view to developing a wide range of physical applications. These include: controlled nuclear fusion and other nuclear reaction studies in quantum chromodynamics, nonlinear physics at high energy densities, dynamic Jahn-Teller effects, superfluidity, high temperature superconductors, multiple scattering by molecular systems, molecular or atomic paracrystal structures, nanomaterials, ferromagnetism in glassy materials, spin glasses, quantum phase transitions and supergravity. This approach requires a unified conceptual framework that utilizes extended symmetries and quantum groupoid, algebroid and functorial representations of non-Abelian higher dimensional structures pertinent to quantized spacetime topology and state space geometry of quantum operator algebras. Fourier transforms, generalized ...

UK PubMed Central (United Kingdom)

Hyperglycemia frequently occurs with acute medical illness, especially among patients with cardiovascular disease, and has been linked to increased morbidity and mortality in critically ill patients....Full Text Available

Science.gov (United States)

transmitted to the Ozone Secretariat of the United Nations Environment Programme (UNEP) its sixth nomination for a critical use exemption (CUE) from the phaseout of methyl...

Energy Technology Data Exchange (ETDEWEB)

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 ...

CERN Document Server

We explore the structure of a new family gauge symmetry U(3) and show its experimental signatures to search for. U(3) gauge bosons obviate an unwelcome deviation of the charged lepton mass formula with the running masses from that with the pole masses. The current structure of this model leads to flavor number violations via exchange of extra gauge bosons. We obtain bounds on the masses of the gauge bosons from rare kaon decay searches and muonium-antimuonium oscillation searches. We propose attractive signatures at LHC and lepton colliders and discuss feasibility of their discovery.

CERN Document Server

Attention is paid to the production mechanisms of light scalars that reveal their nature. We reveal the chiral shielding of the \\sigma(600) meson. We show that the kaon loop mechanism of the \\phi radiative decays, ratified by experiment, points to the four-quark nature of light scalars. We show also that the light scalars are produced in the two photon collisions via four-quark transitions in contrast to the classic P wave tensor q\\bar q mesons that are produced via two-quark transitions $\\gamma\\gamma\\to q\\bar q$. The history of spontaneous breaking of symmetry in quantum physics is discussed in Appendix.

International Nuclear Information System (INIS)

A complete electron paramagnetic resonance power pattern characterization of Fe"3"+ in cubic sites in presented. A one-to-one correspondence among the peaks appearing in the powder pattern and the outer fine-structure transitions (Mnot = 1/2 ) observed in the single crystal along the , , and directions is shown. It is shown that the process of mechanically grinding the single crystal to a powder (particle size approx.1--10 #mu#) does not remove the cubic symmetry sites. No axial or lower symmetry sites which may be induced by lattice distortion of the crystallites due to strain have been observed.

CERN Document Server

If fourth family condensates are responsible for electroweak symmetry breaking then they may also break approximate global symmetries. Among the resulting pseudo-Goldstone bosons are those that can have diquark quantum numbers. We describe the variety of diquarks and their decay modes, and we find aspects that are particular to the fourth family framework. Spectacular signatures at the LHC appear and are explored for color sextet diquarks with 600 GeV mass. We consider a simple search strategy which avoids diquark reconstruction. We also consider 350 GeV mass diquarks that are accessible at the Tevatron.

CERN Document Server

In the generalized minimal supergravity (GmSUGRA) scenario, we systematically study the supersymmetry breaking scalar masses, Standard Model fermion Yukawa coupling terms, and trilinear soft terms in SU(5) models with the Higgs fields in the {\\bf 24} and {\\bf 75} representations, and in SO(10) models where the gauge symmetry is broken down to the Pati-Salam SU(4)_C X SU(2)_L X SU(2)_R gauge symmetry, SU(3)_C X SU(2)_L X SU(2)_R X U(1)_{B-L} gauge symmetry, George-Glashow SU(5) X U(1)' gauge symmetry, flipped SU(5) X U(1)_X gauge symmetry, and SU(3)_C X SU(2)_L X U(1)_1 X U(1)_2 gauge symmetry. Most importantly, we for the first time consider the scalar and gaugino mass relations, which can be preserved from the unification scale to the electroweak scale under one-loop renormalization group equation running, in the SU(5) models, the Pati-Salam models and ...

KoreaScience (Korea)

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Science.gov (United States)

This paper presents a systematic study on the stability of a two-dimensional vibration isolation floating raft system with a time-delayed feedback control. Based on the generalized Sturm criterion, the critical control gain for the delay-independent stability region and critical time delays for the stability switches are derived. The critical conditions can provide a theoretical guidance of chaotification design for line spectra reduction. Numerical simulations verify the correctness of the approach. Bifurcation analyses reveal that chaotification is more likely to occur in unstable region defined by these critical conditions, and the stiffness of the floating raft and mass ratio are the sensitive parameters to reduce critical control gain.

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)

This paper describes a functional slide rule that provides a readily usable ?in-hand? method for estimating nuclear criticality accident information from sliding graphs, thereby permitting (1) the rapid estimation of pertinent criticality accident information without laborious or sophisticated calculations in a nuclear criticality emergency situation, (2) the appraisal of potential fission yields and external personnel radiation exposures for facility safety analyses, and (3) a technical basis for emergency preparedness and training programs at nonreactor nuclear facilities. The slide rule permits the estimation of neutron and gamma dose rates and integrated doses based upon estimated fission yields, distance from the fission source, and time-after criticality accidents for five different critical systems. Another sliding graph permits the estimation of critical ...

UK PubMed Central (United Kingdom)

BackgroundWe investigated the influence of parenteral glucose infusion on insulin-driven tight glucose control (4.4–6.1 mmol/liter) in the critically ill by appraising kinetic...Full Text Available

International Nuclear Information System (INIS)

Most superconductors are quite sensitive to irradiation defects. Critical temperatures may be depressed, critical currents may be increased, by irradiation, but other behaviours may be encountered. In compounds, the sublattice in which defects are created is of significant importance. 24 refs.

UK PubMed Central (United Kingdom)

Vulnerable periods during the development of the nervous system are sensitive to environmental insults because they are dependent on the temporal and regional emergence of critical developmental processes...Full Text Available

UK PubMed Central (United Kingdom)

An integrated system of micro-and mini-computers is described to acquire, analyze, store and report data on the total activity of the heart of a critically ill patient. Real-time beat and rhythm diagnoses...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

A liquid-fillet is formed in front of a rotor blade in the cylinder of a horizontal agitated thin-film evaporator. Its thickness varies due to the gravity while the blade revolves inside the cylinder. In the critical condition, the amplitude of the oscillation becomes infinite and the phase advances 180 degrees. Prior to the critical condition, the experimental data agrees fairly well with the predictions. Near the critical condition, the amplitutde increases and the phase advances 60 degrees. In other words, the transition to the critical condition occurs continuously. (6 figs, 1 ref)

International Nuclear Information System (INIS)

... Tohoku University, Graduate School of Engineering, Sendai, Miyagi (Japan)

International Nuclear Information System (INIS)

Monte Carlo criticality calculations have been performed for over 50 years for reactor physics and criticality safety applications. With today's faster computers, these calculations are being carried out to greater precision (smaller uncertainties) in keff, and detailed distributions of power and reaction rates are being computed routinely. This paper provides a review of the fundamental theory of Monte Carlo criticality calculations, with guidance on practical methods for: (1) assuring convergence of both keff and the source distribution, (2) minimizing the bias in keff and reaction rate distributions, and (3) dealing with the under-prediction bias in uncertainties for keff and reaction rate distributions. (authors)

British Library Electronic Table of Contents (United Kingdom)

The glasses with the composition of 37.5Li2O?(25?x)Fe2O3?xNb2O5?37.5P2O5 (mol%) (x=5,10,15) are prepared, and it is found that the addition of Nb2O5 is effective for the glass formation in the lithium iron phosphate system. The glass?ceramics consisting of Nasicon-type Li3Fe2(PO4)3 crystals with an orthorhombic structure are developed through conventional crystallization in an electric furnace, showing electrical conductivities of 3?10?6?Scm?1 at room temperature and the activation energies of 0.48?eV (x=5) and 0.51?eV (x=10) for Li+ ion conduction in the temperature range of 30?200??C. A continuous wave Nd:YAG laser (wavelength: 1064?nm) with powers of 0.14?0.30?W and a scanning speed of 10??m/s is irradiated onto the surface of the glasses, and the formation of Li3Fe2(PO4)3 crystals is c...

Energy Technology Data Exchange (ETDEWEB)

I discuss several examples of critical phenomena in O(N) models where topological excitations play an important role at criticality. I focus particular attention on the O(2) model in 3D, where recent measurements of the vortex string length distribution in equilibrium suggest the existence of a quantitative picture of the critical behavior in terms of defects. The compatibility of this perspective with renormalization group predictions is examined.

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The theoretical treatment of the relation between the critical angle of planar channeling and the characteristics of crystal lattice defects is carried out. The predictions are made about some typical forms of the critical angle dependence on the mean-square static displacement produced by defects, and then these predictions are detailed for the cases of homogeneous disordering, spherical clusters of point defects and dislocation loops. Analytical results are supported by the exact computer calculations for the defects in the intermetallic A-15 compounds.

International Nuclear Information System (INIS)

The effect of severe plastic deformation by cold high pressure torsion (HPT) on radio frequency (RF) plasma nitriding of pure iron, as well as St2K50 and X5CrNi1810 steels was investigated. Nitriding was carried out for 3 h in a nitrogen atmosphere at a pressure of 10"-"5 bar and temperatures of 350 and 400 deg. C. Nitrided specimens were analysed by scanning electron microscopy (SEM), X-ray diffraction and micro hardness measurements. It was found that HPT enhances the effect of nitriding leading almost to doubling of the thickness of the nitrided layer for pure iron and the high alloyed steel. The largest increase in hardness was observed when HPT was combined with RF plasma nitriding at 350 deg. C. In the case of pure iron, the X-ray diffraction spectra showed the formation of #epsilon# and #gamma#' nitrides in the compound layer, with a preferential formation of #gamma#' at the expense of the #alpha#-phase at the higher nitriding ...

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.

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.

Energy Technology Data Exchange (ETDEWEB)

Evaluations were done to determine conditions that could permit nuclear criticality with fissile uranium in low-level waste (LLW) facilities and to estimate potential radiation exposures to personnel if there were such an accident. Simultaneous hydrogeochemical and nuclear criticality studies were done (1) to identity realistic scenarios for uranium migration and concentration increase at LLW disposal facilities, (2) to model groundwater transport of uranium and subsequent concentration via sorption or precipitation, (3) to evaluate the potential for nuclear criticality resulting from potential increases in uranium concentration over disposal limits, and (4) to estimate potential radiation exposures to personnel resulting from criticality consequences. This paper presents the details of the radiation exposure calculations relying on the conditions as determined from the preceding studies detailed in a ...

British Library Electronic Table of Contents (United Kingdom)

Abstract In this paper, a Cognitive Radio Based Medium Access Control (CR-MAC) protocol for Wireless Sensor Body Area Networks (WSBAN) that utilizes cognitive radio transmission is proposed. In this proposal, the sensor nodes are classified into nodes of life-critical health information and nodes of non-critical health information. The CR-MAC protocol prioritizes the critical packets access to the transmission medium by transmitting them with higher power while transmitting lower priority packets using lower transmission power. At the receiver, a higher priority packet experiences collision only when there are more than one critical packet transmission at the same transmission slot while non critical packets experience collision when there are more than one transmission at the same transmi...

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A technique and a particular apparatus for an inductive measurement of critical currents as a function of temperature and magnetic field in thin-film superconductors are described. The technique has been found to be particularly useful for high-field A-15 compounds 2 to 3 ..mu..m thick. Samples with lower critical current densities would have to be correspondingly thicker to measure over the same broad range of temperature and field. The design of the apparatus is detailed showing that the film can be taken directly from the deposition chamber and mounted without electrical contacts so samples can be changed easily. The principles of operation are developed based on the Critical State Model. These principles are tested by measurements which verify that the measured value of critical curent is independent of the amplitudes and frequency of the small ac magnetic field which is added to a much larger ...

Energy Technology Data Exchange (ETDEWEB)

This paper described the application of an AC surface probe, similar to presently used eddy current probes, to the measurement of DC transport critical currents and critical state dissipation in high {Tc} superconductors. It has been shown that the probe can provide quantitative measurement of the full field penetration in superconducting samples by measuring the response of AC induced screening currents for superconducting materials in the form of tapes with overlayers of silver. In this manner, the AC probe can be used to replace the contact DC probe for determining critical currents in a noncontacting and local manner suitable for scanning over or along the sample.

Energy Technology Data Exchange (ETDEWEB)

This paper described the application of an AC surface probe, similar to presently used eddy current probes, to the measurement of DC transport critical currents and critical state dissipation in high [Tc] superconductors. It has been shown that the probe can provide quantitative measurement of the full field penetration in superconducting samples by measuring the response of AC induced screening currents for superconducting materials in the form of tapes with overlayers of silver. In this manner, the AC probe can be used to replace the contact DC probe for determining critical currents in a noncontacting and local manner suitable for scanning over or along the sample.

Energy Technology Data Exchange (ETDEWEB)

Minimum critical fissile concentrations are calculated for U-233, U-235, Pu-239, and Am-242m mixed homogeneously with hydrogen at temperatures to 15,000K. Minimum critical masses of the same mixtures in a 1000 liter sphere are also calculated. It is shown that propellent efficiencies of a gas core fizzler engine using Am-242m as fuel would exceed those in a solid core engine as small as 1000L operating at 100 atmospheres pressure. The same would be true for Pu-239 and possibly U-233 at pressures of 1000 atm. or at larger volumes.

UK PubMed Central (United Kingdom)

BackgroundProfessionalism is a critical quality for physicians to possess. Physician professionalism has received increased attention in recent years, with many authorities suggesting...Full Text Available

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

UK PubMed Central (United Kingdom)

Motivation: Automatic recognition of cell identities is critical for quantitative measurement, targeting and manipulation of cells of model animals at single-cell resolution. It has been...Full Text Available

UK PubMed Central (United Kingdom)

For some neurotoxic chemicals, neurobehavioral effects are now considered to be among the most sensitive end points yet detected, particularly if exposures occur during critical windows of vulnerability....Full Text Available

CERN Document Server

The celebrated Kuramoto model captures various synchronization phenomena in biological and man-made dynamical systems of coupled oscillators. It is well-known that there exists a critical coupling strength among the oscillators at which a phase transition from incoherency to synchronization occurs. This paper features three contributions. First, we characterize and distinguish the different notions of synchronization used throughout the literature and formally introduce the concept of phase cohesiveness as an analysis tool and performance index for synchronization. Second, we review the vast literature providing necessary, sufficient, implicit, and explicit estimates of the critical coupling strength in the finite and infinite-dimensional case. Finally, we present the first explicit necessary and sufficient condition on the critical coupling strength to achieve synchronization in the finite-dimensional Kuramoto model for an ...

Energy Technology Data Exchange (ETDEWEB)

A brief article considers the possible result of the enquiry into Nirex`s plan to build an underground rock laboratory at Sellafield in relation to radioactive waste disposal in the UK. (UK).

Energy Technology Data Exchange (ETDEWEB)

We compare the effect of isotropic point defects vis a vis extended defects on the inter and intra grain properties of superconducting MgB{sub 2} thin films. In a recent paper Gandikota et al. [Appl. Phys. Lett. 86 (2005) 012508] reported that after 200 MeV {alpha} particle irradiation intergrain connectivity remains unaffected. Our results on the contrary indicate that connectivity does depend on irradiation dose and type of ions used. We ascertain that extended defects alter the {sigma} band properties of this two-band superconductor more effectively than the point defects. The improvement in upper critical field and critical current density is intricately related to the type and density of defects created.

UK PubMed Central (United Kingdom)

Motivation: Inference of haplotypes from genotype data is crucial and challenging for many vitally important studies. The first, and most critical step, is the ascertainment of a biologically...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundGender is a critically important moderator of psychopathology. However, gender similarities and differences in body dysmorphic disorder (BDD) have received...Full Text Available

Science.gov (United States)

A method for determining the critical debond size between the facesheet and the core in composite sandwich panels under in-plane compression is described. The approach uses fracture mechanics together with a buckling criterion for a debonded faceskin. The technique yields predictions for the critical in-plane compressive load for debond propagation as a function of core-to-faceskin debond size, faceskin thickness, lay-up, composite material properties, and honeycomb properties and geometry. A computer program, developed in this work, calculates the critical buckling load and facesheet deformed shape by solving an eigenvalue problem. The output predicts, for several cases, critical initial debond lengths comparable to those that have been observed on tests on sandwich panels.

UK PubMed Central (United Kingdom)

Given growing interest in Functional Data Analysis (FDA) as a useful method for analyzing human movement data, it is critical to understand the effects of standard FDA procedures, including...Full Text Available

UK PubMed Central (United Kingdom)

ObjectiveEpidemiological studies indicate that experimentation with addictive drugs and onset of addictive disorders is primarily concentrated in adolescence and...Full Text Available

Science.gov (United States)

May 11, 2007 ... "Deforestation in the tropics accounts for nearly 20 per cent of carbon emissions due to human activities," Dr. Canadell says. ...

UK PubMed Central (United Kingdom)

Many microbial pathogens recognize oligosaccharides displayed on the surface of host cells as receptors for toxins and adhesins. These ligand-receptor interactions are critical for disease pathogenesis,...Full Text Available

UK PubMed Central (United Kingdom)

It is one of the central aims of the philosophy of science to elucidate the meanings of scientific terms and also to think critically about their application. The focus of this essay is the scientific...Full Text Available

UK PubMed Central (United Kingdom)

AMPA receptors (AMPARs) are critical for synaptic plasticity, and are subject to alterations based on subunit composition and receptor trafficking to and from the plasma membrane. One of the...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundMitochondrial DNA (mtDNA) is being analyzed by an increasing number of laboratories in order to investigate its potential role as an active marker of tumorigenesis...Full Text Available

CERN Document Server

The matter spectrum of the MSSM, including three right-handed neutrino supermultiplets and one pair of Higgs-Higgs conjugate superfields, can be obtained by compactifying the E_{8} x E_{8} heterotic string and M-theory on Calabi-Yau manifolds with specific SU(4) vector bundles. These theories have the standard model gauge group 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 previous papers, we presented the results of a quasi-analytic renormalization group analysis showing that B-L gauge symmetry is indeed radiatively broken with an appropriate B-L/electroweak hierarchy. In this paper, we extend these results by 1) enlarging the initial parameter space and 2) explicitly calculating all renormalization group equations numerically, without approximation. The regions of the initial parameter ...

Energy Technology Data Exchange (ETDEWEB)

The spectroscopic properties of Eu{sup 3+} doped into two lanthanum chlorotungstates matrices, namely LaWO{sub 4}Cl (1-1) and La{sub 3}WO{sub 6}Cl{sub 3}(3-1), are investigated. The fluorescence spectra of these compounds, recorded at room and liquid nitrogen temperatures, show that the lanthanide ion occupies only one site with the low symmetry, C{sub s}, in both cases. From the energy level schemes of the {sup 7}F{sub J} levels (J = 0, 1, 2, 3, 4, 5), two sets of crystal field parameters (cfp) are deduced, in a C{sub 2v} approximated point symmetry (i.e., 9 cfp), simulating the experimental data, correctly. Furthermore, for the 3-1 compound, the data is complete enough to extend the calculations to the real point group, C{sub s} (14 cfp).

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 ...

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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 ...

Science.gov (United States)

We investigate the form factors of the chiral-odd nucleon matrix element of the tensor current. In particular, we aim at the anomalous tensor magnetic form factors of the nucleon within the framework of the SU(3) and SU(2) chiral quark-soliton model. We consider 1/N{sub c} rotational corrections and linear effects of SU(3) symmetry breaking with the symmetry-conserving quantization employed. We first obtain the results of the anomalous tensor magnetic moments for the up and down quarks: {kappa}{sub T}{sup u}=3.56 and {kappa}{sub T}{sup d}=1.83, respectively. The strange anomalous tensor magnetic moment is yielded to be {kappa}{sub T}{sup s}=0.2{approx}-0.2, that is compatible with zero. We also calculate the corresponding form factors {kappa}{sub T}{sup q}(Q{sup 2}) up to a momentum transfer Q{sup 2{<=}}1 GeV{sup 2} at a renormalization scale of 0.36 GeV{sup 2}.

Energy Technology Data Exchange (ETDEWEB)

The effect of severe plastic deformation by cold high pressure torsion (HPT) on radio frequency (RF) plasma nitriding of pure iron, as well as St2K50 and X5CrNi1810 steels was investigated. Nitriding was carried out for 3 h in a nitrogen atmosphere at a pressure of 10{sup -5} bar and temperatures of 350 and 400 deg. C. Nitrided specimens were analysed by scanning electron microscopy (SEM), X-ray diffraction and micro hardness measurements. It was found that HPT enhances the effect of nitriding leading almost to doubling of the thickness of the nitrided layer for pure iron and the high alloyed steel. The largest increase in hardness was observed when HPT was combined with RF plasma nitriding at 350 deg. C. In the case of pure iron, the X-ray diffraction spectra showed the formation of {epsilon} and {gamma}' nitrides in the compound layer, with a preferential formation of {gamma}' at the expense of the {alpha}-phase at the ...

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.

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.

Energy Technology Data Exchange (ETDEWEB)

The rare earth antimonates RE{sub 3}Sb{sub 5}O{sub 12} constitute an isostructural series, where the rare earth site symmetry is S{sub 4}. The spectroscopic properties of pure or doped compounds of this family are studied in order to derive their energy level schemes and to simulate them through the crystal field theory, by using the approximated D{sub 2d} potential. The paramagnetic susceptibilities are calculated with the derived wavefunctions and compared to experiment.

CERN Document Server

The problem of spectra formation in hydrodynamic approach to A+A collisions is discussed. It is analyzed in terms of the two different objects: distribution and emission functions. We show that though the process of particle liberation, described by the emission function, is, usually, continuous in time, the observable spectra can be also expressed by means of the Landau/Cooper-Frye prescription. We argue that such an approximate duality results from some symmetry properties that systems in A+A collisions reach to the end of hydrodynamic evolution and reduction of the collision rate at post hydrodynamic stage

International Nuclear Information System (INIS)

Muonic-atom energy levels and wave functions are calculated. The results are corrected for nearly all important static effects, including finite nuclear size as produced by a user-specified nuclear charge distribution. Fourth-order Runge-Kutta integration of the radial Dirac equations, with the secant method determining the eigenvalues. Corrections are either included as potentials in the Dirac equations or computed as first-order perturbations. The code assumes spherical symmetry, so that effects of nuclear deformation may be treated only as static first-order perturbations. Dynamic muon-electron and muon-nuclear effects are neglected (the latter are calculated by RURP). (Auth.).

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.

Energy Technology Data Exchange (ETDEWEB)

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.

Energy Technology Data Exchange (ETDEWEB)

Polarized antiprotons produced by spin filtering with an internal polarized gas target provide access to a wealth of single- and double-spin observables, thereby opening a window to physics uniquely accessible with the HESR at FAIR. This includes a first measurement of the transversity distribution of the valence quarks in the proton, and a first measurement of the moduli and the relative phase of the time-like electric and magnetic form factors G{sub E,M} of the proton. In polarized and unpolarized pp-bar elastic scattering open questions like the contribution from the odd charge-symmetry Landshoff-mechanism at large |t| and spin-effects in the extraction of the forward scattering amplitude at low |t| can be addressed.

International Nuclear Information System (INIS)

We construct a phenomenological model which describes the dynamical chiral symmetry breaking (DCSB) of a QCD vacuum and reproduces meson spectra. Quark condensates, the pion decay constant, and meson spectra are well reproduced by the phenomenological interaction which consists of a linear confining potential, a Coulombic potential, and the close-quote t Hooft determinant interaction. In this model, the close-quote t Hooft determinant interaction plays an important role to not only the mass difference between the #eta# and #eta#"' mesons, but other meson masses through DCSB. copyright 1997 The American Physical Society.

International Nuclear Information System (INIS)

The average single-particle field shows a very small pseudo-spin-orbit splitting in the pseudo-spin representation. If this splitting is neglected, pseudo-spin becomes a good quantum number and the resulting scheme (the pseudo-Nilsson model) has a very simple interpretation. The pseudo-spin symmetry embodied in the realistic deformed average field is explored by comparing the single-particle energies and wave functions of the deformed Woods-Saxon model with the corresponding results of the pseudo-Nilsson model. The scheme is used to calculate the magnetic moments of deformed odd-A nuclei of the rare-earth region. (orig.).

Energy Technology Data Exchange (ETDEWEB)

It is shown that when a quantum mechanical oscillator is parametrically excited there are special values of the parameters for which the system will pass periodically through a lattice of coherent states associated with the modular group [Gamma]. It is shown that these [Gamma] transits can be used to determine unknown parameters. A method is given for detecting the transits experimentally and is made possible by the existence of three families of states associated with modular forms that are orthogonal to the lattice. For isotropic states the three families occur in [ital D]-mode systems with [ital D][gt]10, 14, and 26.

International Nuclear Information System (INIS)

The combined magnetic braking-ambipolar diffusion problem in weakly ionized, rigidly rotating disks is studied. An analytical solution is presented for a disk whose angular velocity and magnetic yield vectors are aligned with the symmetry axis, illustrating the effects of the relative azimuthal drift of neutrals and ions. The effects of radial drift are added, commenting on the ratio of the characteristic ambipolar diffusion and magnetic braking time scales in high-mass and low-mass disks. A numerical calculation is used to show the combined action of these two processes. 31 references.

International Nuclear Information System (INIS)

The self-consistent relativistic linearized-augmented-plane-wave method is applied to local-density calculation of electronic structure of TmS. It is found that thulium monosulphide is a compound with a trivalent state of thulium. The influence of spin-orbital interaction is shown for different symmetry states of electrons. Calculated densities of states are used for the estimation of the electron-phonon coupling constant. And in conclusion it is shown that TmS is a high temperature Kondo-like system. (author).

CERN Document Server

We show that in the Landau gauge of the SU(2) Yang-Mills theory the residual global symmetry supports existence of the topological vortices which resemble disclination defects in the nematic liquid crystals and the Alice (half-quantum) vortices in the superfluid heluim 3 in the A-phase. The theory also possesses half-integer and integer charged monopoles which are analogous to the point-like defects in the nematic crystal and in the liquid helium. We argue that the deconfinement phase transition in the Yang-Mills theory in the Landau gauge is associated with the proliferation of these vortices and/or monopoles. The disorder caused by these defects is suggested to be responsible for the confinement of quarks in the low-temperature phase.

CERN Document Server

We study the production of gravitational waves from cosmic domain walls created during phase transition in the early universe. We investigate the process of formation and evolution of domain walls by running three dimensional lattice simulations. If we introduce an approximate discrete symmetry, walls become metastable and finally disappear. We calculate the spectrum of gravitational waves produced by collapsing metastable domain walls. Extrapolating the numerical results, we find the signal of gravitational waves produced by domain walls whose energy scale is around 10^10-10^12GeV will be observable in the next generation gravitational wave interferometers.

Energy Technology Data Exchange (ETDEWEB)

The E1 and E3 transition operators in the sdf-IBA model are discussed. An effective E1 operator containing one- and two-body terms explains very well the E1 data in transitional and rotational nuclei. The E1 parameters for rotational nuclei are obtained by imposing a constraint on the IBA model namely, the validity of Alaga rules for ``pure K`` states. The systematic behavior of the octupole strength is well reproduced using a one-body octupole operator. The anomalously large fragmentation of the low-energy octupole strength in non-rotational nuclei is shown to be a signature of the O(6) dynamical symmetry.

Energy Technology Data Exchange (ETDEWEB)

For the determination of top dead center (TDC) of a running engine a measuring system using microwaves was developed by AEG and Volkswagen AG. The measuring method utilizes the Doppler shift of the microwaves, which were reflected at the up and down moving piston, and the varying resonance properties of the combustion chamber. The system works with a frequency of 61.4 GHz and can be used as well for spark ignition as form compression ignition engines, particularly for direct injection engines. The output signal is symmetrical to TDC. For data acquisition and data processing, i.e. the calculation of the point of symmetry, the computer system FARES is used in a special assembly.

International Nuclear Information System (INIS)

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.

Energy Technology Data Exchange (ETDEWEB)

We consider the dynamics toward the initial singularity of Bianchi type IX vacuum and orthogonal perfect fluid models with a linear equation of state. The 'Bianchi type IX attractor theorem' states that the past asymptotic behavior of generic type IX solutions is governed by Bianchi type I and II vacuum states (Mixmaster attractor). We give a comparatively short and self-contained new proof of this theorem. The proof we give is interesting in itself, but more importantly it illustrates and emphasizes that type IX is special, and to some extent misleading when one considers the broader context of generic models without symmetries.

CERN Document Server

We consider the dynamics towards the initial singularity of Bianchi type IX vacuum and orthogonal perfect fluid models with a linear equation of state. The `Bianchi type IX attractor theorem' states that the past asymptotic behavior of generic type IX solutions is governed by Bianchi type I and II vacuum states (Mixmaster attractor). We give a comparatively short and self-contained new proof of this theorem. The proof we give is interesting in itself, but more importantly it illustrates and emphasizes that type IX is special, and to some extent misleading when one considers the broader context of generic models without symmetries.

Energy Technology Data Exchange (ETDEWEB)

We have obtained optically clear samples of LuAP:Ce from the Institute of Physical Research, Ashtarak, Armenia, measuring up to 5x5x40 mm{sup 3}. The photo electron yield for a number of theses samples was measured with a Philips XP2020Q photomultiplier tube, and 556 photo electrons per MeV was obtained for the best samples. This is comparable to what is obtained from BGO crystals under the same condition, but a factor of 5 less than what is obtained with an LSO sample of similar dimensions. The light in LuAP:Ce increases with cerium concentration between 0.13 and 0.47%.

Energy Technology Data Exchange (ETDEWEB)

The mass generation in the Standard Model of Particles Physics relies on a spontaneous symmetry breaking mechanism. Its implementation is recalled, along with its constraints, both theoretical (Naturalness, Stability, Triviality, Unitarity) and experimental (limits of direct and indirect searches, prospects). Calculation techniques for observables evaluation in Perturbative Field Theory are described, particularly Helicity Amplitude method, which is given in details: fermions and vector bosons, massless and massive. Monte-Carlo integration, and structure functions approximations (which allows non-perturbative calculations) are also detailed. With these tools, a process giving to Physics beyond the Standard Model is studied: it leads to an experimental prediction for the LEP collision ring, taking the classical background into account. Technical aspects of a future photon linear collider are reviewed. The production of heavy vector bosons, either the classical Z for ...

Energy Technology Data Exchange (ETDEWEB)

An analysis of the energy level structure of Cr{sup 3+} ions in Cs{sub 2}NaAlF{sub 6} crystal is performed using the exchange charge model (ECM) together with the crystal field analysis/microscopic spin Hamiltonian (CFA/MSH) computer package. Utilizing the crystal structure data, our approach enables modelling of the crystal field parameters (CFPs) and thus the energy level structure for Cr{sup 3+} ions at the two crystallographically inequivalent sites in Cs{sub 2}NaAlF{sub 6}. Using the ECM initial adjustment procedure, the CFPs are calculated in the crystallographic axis system centred at the Cr{sup 3+} ion at each site. Additionally the CFPs are also calculated using the superposition model (SPM). The ECM and SPM predicted CFP values match very well. Consideration of the symmetry aspects for the so-obtained CFP datasets reveals that the latter axis system matches the symmetry-adapted axis system related directly to the six Cr-F bonds well. ...

Energy Technology Data Exchange (ETDEWEB)

Small-scale methods for determining the reaction rates of explosives that make it possible to predict safe temperatures for using them, and methods for testing the accuracy of these predictions were developed. Each different size and shape of each different explosive has its own critical temperature. The ability to predict these critical temperatures is required before high-energy materials can be used safely.

Science.gov (United States)

Only a small number of radiation accidents in the United States have been severe enough to result in multi-organ failure (MOF). Medical details of selected medical misadministration and criticality cases are reviewed, with an emphasis on pathophysiology. The four criticality cases are particularly relevant for analysis of MOF, since medical treatment was supportive and did not appreciably alter the clinical evolution of radiation injury. PMID:15975871

Energy Technology Data Exchange (ETDEWEB)

Pitting corrosion is localized accelerated dissolution of metal that occurs as a result of a breakdown of the otherwise protective passive film on the metal surface. This paper provides an overview of the critical factors influencing the pitting corrosion of metals. The phenomenology of pitting corrosion is discussed, including the effects of alloy composition, environment, potential, and temperature. A summary is then given of studies that have focused on various stages of the pitting process, including breakdown of the passive film, metastable pitting, and pit growth. 120 refs.

Energy Technology Data Exchange (ETDEWEB)

Improvements in critical current capacity for superconducting film structures are disclosed and include the use of a superconducting RE-BCO layer including a mixture of rare earth metals, e.g., yttrium and europium, where the ratio of yttrium to europium in the RE-BCO layer ranges from about 3 to 1 to from about 1.5 to 1.

Energy Technology Data Exchange (ETDEWEB)

The critical concentrations correspond to contamination thresholds of environments over which noxious effects can occur and deteriorate soils, water and vegetation. They are defined according to the type of pollutants and their mode of action. The aim of this document is to provide a scientific framework to the policies of reduction of atmospheric pollution negotiated at Geneva`s convention. The methodology of evaluation, the results obtained for surface waters and forest soils, the perspectives of French research and the integration of French knowledge in the European database are presented. (J.S.)

International Nuclear Information System (INIS)

Critical power characteristics of tight lattice rod assembly was investigated using a simple-shaped experimental apparatus. An electrically heated rod with four spacers was placed in a circular tube, and boiling transition condition for a rod in an annular geometry was clarified varing annulus clearance. It was found that critical heat flux depends strongly on the clearance accoding as the gap becomes smaller. This results was compared with KfK correlation and the trends were well correlated. (author).

Science.gov (United States)

...Critical habitat units are depicted for Baldwin County, Alabama, on the maps below...paragraph (2) of this entry, over 2005 Baldwin County, Alabama color photography (UTM...ER30JA07.000(6) Unit 1: Fort Morgan, Baldwin County, Alabama.(i) General...

International Nuclear Information System (INIS)

The dynamics of a general Bianchi type-IX model with three scale factors is examined. The matter content of the model is assumed to be comoving dust plus a positive cosmological constant. The model presents a critical point of saddle-center-center type in the finite region of phase space. This critical point engenders in the phase space dynamics the topology of stable and unstable four dimensional tubes RxS"3, where R is a saddle direction and S"3 is the manifold of unstable periodic orbits in the center-center sector. A general characteristic of the dynamical flow is an oscillatory mode about orbits of an invariant plane of the dynamics which contains the critical point and a Friedmann-Robertson-Walker (FRW) singularity. We show that a pair of tubes (one stable, one unstable) emerging from the neighborhood of the critical point towards the FRW singularity have homoclinic transversal crossings. The ...

International Nuclear Information System (INIS)

The Fast Flux Test Facility (FFTF) was designed to test fast-reactor fuels and other nonfuel materials. In its 37 reactor cycles of operations, the FFTF reactor has performed very well and successfully completed all the irradiation testings with an operating efficiency factor as high as 98%. Since FFTF is an experimental reactor, its core loading changed from cycle to cycle. Depending on the number of test assemblies in the core and their location, the core loading can change significantly from an essentially homogeneous core loading to a relatively nonhomogeneous or even highly localized heterogeneous loading. Consequently, the core reload design and initial criticality analyses were required for each operating cycle. The zero power initial critical control rod bank height was predicted before each reactor startup. The initial critical prediction depends on the reactivity conditions at the end of the previous cycle, the ...

Science.gov (United States)

The theory of a method of determination of reactivity from power spectral density measurements with /sup 252/Cf and the results of experiments with a critical assembly mockup of a liquid-metal fast breeder reactor (LMFBR) and with uranium (93.2 wt % /sup 235/U) metal cylinders and a sphere are presented. This method of reactivity determination has an advantage over existing methods in that it determines the reactivity only from properties of the reactor at the subcritical state of interest and thus does not require a calibration near delayed criticality. In these experiments, the reactivity was varied by changing the fissile loading or the amount of neutron absorber inserted; for the LMFBR mockup, the reactivity varied to approximately 75 dollars subcritical, and for the uranium metal assemblies to approximately 30 dollars subcritical. These experiments verified for the first time the predictions of theory that could be tested in the ...

Energy Technology Data Exchange (ETDEWEB)

This is a report on the results of creep tests of large extent on samples of welded joints. The possibilities of minimising the reduction in creep strength which occurs are also shown. The range of the pipe welded joints examined extends from superheater pipes 31.8 diam x 5 mm to hot steam pipelines 240 diam x 29 mm. The steels used are: X 20 CrMoV 12-1, X 10 CrMoVNb 9-1 and X 10 CrWMoVnB 9-2. (orig./MM) [Deutsch] Es wird ueber Ergebnisse von in groesserem Umfang laufenden Zeitstandversuchen an Proben aus Schweissverbindungen berichtet. Ausserdem werden Moeglichkeiten aufgezeigt, den eintretenden Zeitstandfestigkeitsabfall zu minimieren. Die Spanne der in Untersuchung befindlichen Rohrschweissverbindungen reicht dabei vom Ueberhitzerrohr diameter 31,8 x 5 mm bis zum Heissdampfleitungsrohr diameter 240 x 29 mm. Die verwendeten Staehle sind: X 20 CrMoV 12 -1; X 10 CrMoVnB 9-1; X 10 CrWMoVnb 9-2. ...

International Nuclear Information System (INIS)

The effects of extended source-to-surface distance (SSD) on the electron beam dose profiles were evaluated for various electron beam energies - 6, 9, 12, 15 and 20 MeV - and the accuracy of various output correction methods was analysed on a Mitsubishi linear accelerator using a radiation field analyser (RFA). The dose fall-off region of the central axis depth-dose curves was nearly independent for SSDs up to 120 cm where as in the build-up region, a marginal reduction of surface dose was observed, particularly for lower energies and for smaller field sizes. Effective SSDs and virtual source distances were evaluated for field sizes ranging from 5x5 to 15x15 cm"2 for various energies. Curve fitting was done with the measured outputs with various equations and coefficients were evaluated. The accuracy of the derived output correction factors by effective SSD, virtual source distance and curve-fit methods was assessed by evaluating correlation ...

Energy Technology Data Exchange (ETDEWEB)

Ternary diagrams are commonly used to provide a graphic representation of equilibrium fluid phase behavior for systems as diverse as distillation columns and miscible gas floods of oil reservoirs. The phase envelope, and the position of the critical point on it, are important to enhanced oil recovery engineers who are involved with miscible gas flood design. In the past, phase equilibrium data were laboriously plotted on the ternary diagram and special graphic techniques were utilized to locate the critical point on the phase envelope. This work presents a computerized curve fitting method to generate the phase envelope from a given set of phase equilibrium data and then use the tie-line slopes to position the critical point. Experimental data are included and show excellent agreement with this new method.

International Nuclear Information System (INIS)

Electron-beam codeposition of the elements to form certain high critical temperature superconducting materials, in particular A-15 compounds, has proven to be very useful in research directed at understanding and improving their superconducting properties. This work has used the close control of three or more evaporant sources to reproducibly make specimens that permit studies across selected regions of composition and phase space. The effect of composition and phase, together with the temperature and rate of deposition, on the growth morphology and superconducting properties has been studied. The superconducting properties measured include the critical temperature, ac loss, critical current density, and tunnel junction characteristics. The particular compounds studied include Nb_3Sn, Nb_3Ge, and V_3Si.

CERN Document Server

A recurrent idea in the study of complex systems is that optimal information processing is to be found near bifurcation points or phase transitions. However, this heuristic hypothesis has few (if any) concrete realizations where a standard and biologically relevant quantity is optimized at criticality. Here we give a clear example of such a phenomenon: a network of excitable elements has its sensitivity and dynamic range maximized at the critical point of a non-equilibrium phase transition. Our results are compatible with the essential role of gap junctions in olfactory glomeruli and retinal ganglionar cell output. Synchronization and global oscillations also appear in the network dynamics. We propose that the main functional role of electrical coupling is to provide an enhancement of dynamic range, therefore allowing the coding of information spanning several orders of magnitude. The mechanism could provide a microscopic neural basis for ...

British Library Electronic Table of Contents (United Kingdom)

We investigated the magnet field dependence of the X-ray pulse height and the critical current of a Ti/Au bilayer TES micro-calorimeter. The pulse height was strongly affected by the magnetic field intensity applied perpendicularly to the TES surface. We found that the critical current at zero temperature, I c0, decreased by a factor of two by applying a magnet field of ?10??T. Our data are consistent with a TES sensitivity proportional to (I/I c0)?2/3, as predicted by the Ginzburg-Landau theory. This fact implies that the shape of the R?T curve of the TES is partly determined by the critical current of the superconductor. In order to make our TES microcalorimeters less sensitive to the external magnetic field, we fabricated devices equipped with on-chip magnetic shielding. One device has ...

International Nuclear Information System (INIS)

Using indigenously developed computer program, coupled neutron gamma multi-group libraries have been generated from MA TXS-NJOY files. The MATXS format contains all the details for each reaction. Temperature and dilution factor dependent cross-sections have been generated and used in discrete ordinates method for benchmark studies of fast critical experiments. We have analyzed criticality benchmarks, which includes CSEWG fast critical benchmarks, "2"3"3U and Pu spheres and enriched uranium spheres using 30-group neutron cross-sections. Neutron and gamma spectra for spheres with point neutron source at the center, are also calculated with 42-group coupled neutron gamma cross-sections. (author)

International Nuclear Information System (INIS)

The report presents the results of experimental studies conducted to provide a description of the conditions which lead to the occurrence of critical heat flux (CHF), in Combustion Engineering (C-E) fuel assemblies using the C-E standard spacer grid. A CHF correlation is presented which is based on CHF data obtained in tests with electrically heated rod bundles representative of the C-E 14 x 14 and 16 x 16 array fuel assemblies. The results reported are for a uniform axial heat flux distribution. The experiments were conducted in the Medium Pressure Heat Transfer Flow Loop at the Chemical Engineering Research Laboratories at Columbia University.

Energy Technology Data Exchange (ETDEWEB)

We study the three-nucleon force in chiral effective field theory with explicit {delta}-resonance degrees of freedom. We show that up to next-to-next-to-leading order, the only contribution to the isospin symmetric three-nucleon force involving the spin-3/2 degrees of freedom is given by the two-pion-exchange diagram with an intermediate delta, frequently called the Fujita-Miyazawa force. We also analyze the leading isospin-breaking corrections due to the delta. For that, we give the first quantitative analysis of the delta quartet mass splittings in chiral effective field theory including the leading electromagnetic corrections. The charge-symmetry breaking three-nucleon force due to an intermediate delta excitation is small, of the order of a few keV.

CERN Document Server

Chiral symmetry in QCD can be simultaneously in Wigner and Goldstone modes, depending on the part of the spectrum examined. The transition regime between both, exploiting for example the onset of parity doubling in the high baryon spectrum, can be used to probe the running quark mass in the mid-IR power-law regime. In passing we also argue that three-quark states naturally group into same-flavor quartets, split into two parity doublets, all splittings decreasing high in the spectrum. We propose that a measurement of masses of high-partial wave Delta* resonances should be sufficient to unambiguously establish the approximate degeneracy and see the quark mass running. We test these concepts with the first computation of the spectrum of high-J excited baryons in a chiral-invariant quark model.

International Nuclear Information System (INIS)

HAMILTON is a computer code performing all algebraic operations necessary for an analytic determination of the power series of the Hamiltonian equations of motion in the electromagnetic fields with at least one plane of symmetry. It is written entirely in FORTRAN in order to achieve fast machine performance, a requirement which is essential due to the complexity of the equations of motion in higher orders. HAMILTON is considerably faster than common more versatile formula manipulators and uses noticeably less storage. Besides the mere solution of the equations of motion, HAMILTON also produces FORTRAN code compatible with the program COSY 5.0 allowing the computation of matrix elements of individual optical elements and their concatenation. The produced FORTRAN code is highly optimized and on average requires only 30% of the execution time of a handwritten comparable code. (orig.).

CERN Document Server

Non-linear realisations of the groups SU(2), SO(1,4) and SO(2,4) are analysed, described by the coset spaces SU(2)/U(1), SO(1,4)/SO(1,3) and SO(2,4)/SO(1,3) x SO(1,1). The Lie algebras of certain special unitary and special orthogonal groups are studied and their projection operators are determined in order to facilitate the above analyses, in particular that of SO(2,4)/SO(l,3) x SO(1,1). The analysis consists of determining the transformation properties of the Goldstone bosons, constructing the most general possible Lagrangian for the realisations and finding the metric of the coset space.

CERN Document Server

The predictions of the MSSM are discussed in the light of recent LEP and SLD precision data. The full supersymmetric one loop corrections to the effective weak mixing angle, experimentally determined in LEP and SLD experiments, are considered. It is demonstrated, both analytically and numerically, that, potentially dangerous, large logarithmic sparticle corrections are cancelled. The relative difference factor \\Delta k between the mixing angle defined as a ratio of couplings and the experimentally obtained angle is discussed. It is found that \\Delta k is dominated by the oblique corrections, while the non-oblique overall supersymmetric EW and SQCD corrections are negligible. The comparison of the MSSM with radiative electroweak symmetry breaking to the LEP precision data indicates that rather large values of the soft breaking parameter M_{1/2} in the region greater than 500 GeV are preferred.

Energy Technology Data Exchange (ETDEWEB)

In this systematic examination of some of the spectroscopic properties of the f-elements we deal with both the trivalent lanthanides and actinides. We summarize the present status of our energy level calculations in single crystal matrices and in aqueous solution, and compare the predicted crystal-field structure in certain low-symmetry sites with that observed. Some interesting new structural insights are thereby gained. The state eigenvectors from these calculations are then used in part in reassessing and interpreting the intensities of transitions in aqueous solution via the Judd-Ofelt theory. The parameters of this theory derived from fitting experimental data are compared with those computed from model considerations. Finally, we discuss some recent contributions to the interpretation of excited state relaxation processes in aqueous solution. 79 references, 23 figures, 17 tables.

Energy Technology Data Exchange (ETDEWEB)

The spectroscopic properties of Pr{sup 3+} doping two lanthanum chlorotungstate hosts: the orthorhombic LaWO4Cl (1-1) and the hexagonal La3WO4Cl6 (3-1), as well as those of PrWO4Cl and Pr3wO613 have been investigated. The simulations of the energy level schemes are carried out within the crystal field theory frame. Each simulation involves 7 free ion parameters and 14 non-zero crystal field parameters (cfps), corresponding to the C{sub s} point symmetry of the site occupied by the rare earth, in both structures.

CERN Document Server

The use of a running coupling constant in renormalizable theories is well known, but the implementation of this idea for effective field theories with a dimensional coupling constant is in general less useful. Nevertheless there are multiple attempts to define running couplings including the effects of gravity, with varying conclusions. We sort through many of the issues involved, most particularly the idea of operator mixing and also the kinematics of crossing, using calculations in Yukawa and lambda phi^4 theory as illustrative examples. We remain in the perturbative regime. In some theories with a high permutation symmetry, such as lambda phi^4, a reasonable running coupling can be defined. However in most cases, such as Yukawa and gauge theories, a running coupling fails to correctly account for the energy dependence of the interaction strength. As a byproduct we also contrast on-shell and off-shell renormalizaton schemes and show that operators which are ...

CERN Document Server

We study the renormalization group running of the tri-bimaximal mixing predicted by the two typical $S_4$ flavor models at leading order. Although the textures of the mass matrices are completely different, the evolution of neutrino mass and mixing parameters is found to display approximately the same pattern. For both normal hierarchy and inverted hierarchy spectrum, the quantum corrections to both atmospheric and reactor neutrino mixing angles are so small that can be neglected. The evolution of solar mixing angle $\\theta_{12}$ depends on $\\tan\\beta$ and mass spectrum, the deviation from its tri-bimaximal value could be large. Taking into account the renormalization group running effect, the neutrino spectrum is constrained by experimental data on $\\theta_{12}$ and the inverted hierarchy spectrum is disfavored for large $\\tan\\beta$. The evolution of light neutrino masses is approximately described by a common scaling factor.

CERN Document Server

In light of the recent discovery of the importance of the isovector EMC effect for the interpretation of the NuTeV determination of sin^2 theta_W, it seems timely to reassess the central value and the errors on this fundamental Standard Model parameter derived from the NuTeV data. We also include earlier work on charge symmetry violation and the recent limits on a possible asymmetry between s and \\bar{s} quarks. With these corrections we find a revised NuTeV result of sin^2 theta_W = 0.2232 \\pm 0.0013(stat) \\pm 0.0024(syst), which is in excellent agreement with the running of sin^2 theta_W predicted by the Standard Model.

Energy Technology Data Exchange (ETDEWEB)

The non-perturbative validity of covariant BRST-quantization of gauge theories on compact Euclidean space-time manifolds is reviewed. BRST-quantization is related to the construction of a Topological Quantum Field Theory (TQFT) of Witten type on the gauge group. The criterion for the non-perturbative validity of the quantization is that the partition function of the corresponding TQFT does not vanish and that its (equi-variant) BRST-algebra is free of anomalies. I sketch the construction of a TQFT whose partition function is proportional to the generalized Euler-characteristic of the coset space S U (n){sub gauge} / SU(n){sub global} with an associated equi-variant BRST-algebra that manifestly preserves translational symmetry. Some non-perturbative consequences of this approach are discussed. (author)

International Nuclear Information System (INIS)

We analyze the potential of the e"+e"- linear colliders, operating in the e#gamma# and #gamma##gamma# modes, to probe anomalous quartic vector-boson interactions through the multiple production of W's and Z's. We examine all SU(2)_L(circle times)U(1)_Y chiral operators of order p"4 that lead to new four-gauge-boson interactions but do not alter trilinear vertices. We show that the e#gamma# and #gamma##gamma# modes are able not only to establish the existence of a strongly interacting symmetry breaking sector but also to probe for anomalous quartic couplings of the order of 10"-"2 at 90% C.L. Moreover, the information gathered in the e#gamma# mode can be used to reduce the ambiguities of the e"+e"- mode.

Science.gov (United States)

Generally the photonic band gap (PBG) is a multi-variable function of several parameters related to the shape and size of the dielectric columns of photonic crystals (PhCs), and a time-consuming step-by-step scanning process for each parameter has to be used to find their best combination yielding maximum PBG. In this letter, the widely used Nelder-Mead simplex algorithm is introduced to optimize these parameters simultaneously to find a larger PBG for a new kind of two-dimensional (2D) hexagonal GaAs-Air PhC. This structure can be conveniently produced by the single-exposure holographic lithography, and the specific holographic design is also systematically investigated. This study reveals that the band gaps of PhCs made by holographic lithography may be widened by introducing irregularity of the columns and lowering the symmetry of the structure.

International Nuclear Information System (INIS)

The problem in perturbation theory in general relativity is finding a natural gauge which simplifies the equations considerably. We solved the first and second order perturbation equations in the ''Lorentz gauge'' using the two-timing method. The equations were deduced from the equations of Einstein in the presence of a matter energy-momentum tensor of a perfect fluid with equation of state p = (#gamma#-1) rho. It is found that the 0--0 component of the first order equations together with the gauge conditions are consistent with the Bianchi type V model, without axial symmetry. It represents a ''ground state'' situation of the Bianchi type IX model (Mixmaster model.) The second order equations, describing the reaction back of the gravitational waves on the slowly varying background, give rise to rotation and will disturb the isotropization mechanism. The numerical solutions show all the features which are expected to appear. Moreover, it is found that the frequency ...

Science.gov (United States)

Mixed convection in a rectangular channel (width/height = 2) with bottom-heated and top-cooled sections is studied by laser Doppler anemometry in nitrogen at Ra = 22,200 and Re = 18.75, 36, and 54. At the lower Re values, symmetry breaking is observed in steady but spatially oscillating flows that prevail over a certain distance from the leading edge of the differentially heated section. Further downstream, unsteady flows are found even for Re = 18.75. Numerical models are used to investigate the effects of adiabatic, conducting (with a conductive-convective heat transfer coefficient), and perfectly conducting side walls; channel tilts and Prandtl number dependence. Good agreement between calculations and experiment is obtained for longitudinal convective roll velocities. The transverse velocities are found to be independent of Re.

Science.gov (United States)

We propose a new algorithm for two-dimensional magnetotelluric (MT) inversion. Our algorithm is an MT inversion based on the steepest descent method, borrowed from the backpropagation technique of seismic inversion or reverse time migration, introduced in the middle 1980s by Lailly and Tarantola. The steepest descent direction can be calculated efficiently by using the symmetry of numerical Green's function derived from a mixed finite element method proposed by Nedelec for Maxwell's equation, without calculating the Jacobian matrix explicitly. We construct three different objective functions by taking the logarithm of the complex apparent resistivity as introduced in the recent waveform inversion algorithm by Shin and Min. These objective functions can be naturally separated into amplitude inversion, phase inversion and simultaneous inversion. We demonstrate our algorithm by showing three inversion results for synthetic data.

Energy Technology Data Exchange (ETDEWEB)

Magnetic properties of polycrystalline samples of RPd/sub 2/Si compounds (R = Gd, Tb, Dy, Ho and Er) are presented. The Gd and Tb based compounds are antiferromagnetic with Neel temperatures of 13.5 and 21 K respectively. For both compounds a metamagnetic transition is observed in low field. Moreover, in TbPd/sub 2/Si a transition between two different antiferromagnetic phases is observed at 8.5 K. The Dy, Ho and Er based compounds are ferromagnetic with Curie temperatures of 9, 3.5 ad 2.8 K respectively. The observed properties result from indirect exchange interactions and crystal field effects acting on rare earth ions which lie in a very low symmetry site.

Energy Technology Data Exchange (ETDEWEB)

We have succeeded in aligning self-assembled structures by using a lithographically defined stripe. The 140 nm wide by 100 nm high SiO{sub 2} strip is shown to guide the assembly of 500 nm latex spheres so that spheres are aligned along the strip and are in registration on either side of the strip. This method can be used to increase long-range ordering in magnetic storage systems without compromising the density. Inverse sphere Ni arrays were made by electrodeposition through the latex template. We also show that the hexagonal symmetry of the resulting inverse sphere Ni arrays can be simulated using the approach presented below.

British Library Electronic Table of Contents (United Kingdom)

We have succeeded in aligning self-assembled structures by using a lithographically defined stripe. The 140nm wide by 100nm high SiO2 strip is shown to guide the assembly of 500nm latex spheres so that spheres are aligned along the strip and are in registration on either side of the strip. This method can be used to increase long-range ordering in magnetic storage systems without compromising the density. Inverse sphere Ni arrays were made by electrodeposition through the latex template. We also show that the hexagonal symmetry of the resulting inverse sphere Ni arrays can be simulated using the approach presented below.

Energy Technology Data Exchange (ETDEWEB)

The advent of carbon nanotubes, which are graphite layers convoluted in cylinders several nanometers in diameter and several micrometers in length, as well as the experiments on implanting metal atoms in such tubes open the way to producing nanoconductors and other materials with unique properties. For theorists, the basic challenge is interpreting and predicting the structure and properties of these systems. The linearized augmented-plane-wave method (LAPW) is one of the most accurate methods in the theory of the electronic structure of solids. A generalization of this method for quasi-two-dimensional systems, surface electronic states, and layered crystals is known. The LAPW theory for quasi-unidimensional systems, which exhibit translational symmetry in one direction, has been absent thus far. In this paper, the authors suggest a version of such a theory and use this method to calculate the electronic structure of carbyne (a linear chain of carbon atoms) and ...

International Nuclear Information System (INIS)

The optical emission of excited H reflected from clean Cu(110) after impingement of H"+ and H_2"+ in the energy range of 250 eV to 20 keV per nucleon at 70"0 angle of incidence to the surface normal was measured. For incident 10 keV H_2"+, the highest excited hydrogen state detected was the n=10 level. The Hsub(#alpha#) yield was found to be fluence and energy dependent. This effect is attributed either to fast sputtered hydrogen, surface roughness or to an increase with hydrogen concentration in electron states of p-like symmetry near the Fermi level of copper. The Hsub(#alpha#) yield per reflected nucleon shows approximately an exponential dependence on both projectile energy per nucleon and scattered particle reciprocal velocity perpendicular to the surface. (orig.).

CERN Document Server

Jahn-Teller theorem, proposed in 1937, predicts a distortional instability for a molecule that has symmetry based degenerate electronic states. In 1939 Krishnan emphasized the importance of this theorem for the arrangement of water molecules around the transition metal or rare earth ions in aqueous solutions and hydrated saltes, in a short and interesting paper published in Nature by pointing out atleast four existing experimental results in support of the theorem. This paper of Krishnan has remained essentially unknown to the practitioners of Jahn-Teller effect, eventhough it pointed to the best experimental results that were available, in the 30's and 40's, in support of Jahn-Teller theorem. Some of the modern day experiments are also in conformity with some specific suggestions of Krishnan.

Energy Technology Data Exchange (ETDEWEB)

The present conference on lens design encompasses physical and geometrical optics, diffractive optics, the optimization of optical design, software packages, ray tracing, the use of artificial intelligence, the achromatization of materials, zoom optics, microoptics and GRIN lenses, and IR lens design. Specific issues addressed include diffraction-performance calculations in lens design, the optimization of the optical transfer function, a rank-down method for automatic lens design, applications of quadric surfaces, the correction of aberrations by using HOEs in UV and visible imaging systems, and an all-refractive telescope for intersatellite communications. Also addressed are automation techniques for optics manufacturing, all-reflective phased-array imaging telescopes, the thermal aberration analysis of a Nd:YAG laser, the analysis of illumination systems, athermalized FLIR optics, and the design of array systems using shared symmetry.

Energy Technology Data Exchange (ETDEWEB)

We investigate ordering properties of two-dimensional granular materials using several shapes created by welding ball bearings together. Ordered domains form much more easily in two than in three dimensions, even when configurations lack long-range order. The onset of ordered domains occurs near a packing density of 0.8, a phenomenon observed previously for disks. One of our shapes, the trapezoid, has packings that remain disordered and near the transition density even after annealing by shaking. Although random packings are unstable for disks and many other shapes in two dimensions, trapezoid packings provide an approach to studying two-dimensional randomness. We also find that the rotational symmetry of a shape is an excellent predictor of how easily it orders, and a potential guide to identifying two-dimensional shapes that remain random after annealing.

Energy Technology Data Exchange (ETDEWEB)

The authors report experimental results on a high gradient 17 GHz RF photocathode gun. The photocathode RF gun is a novel electron beam source intended to meet the requirements set by future high-energy linear colliders and next generation free electron lasers. A coupled pair of pillbox TM{sub 010}-like resonators is excited by sidewall coupled microwaves at 17 GHz. A picosecond ultraviolet laser pulse illuminates one wall of the structure at the axis of symmetry. Electrons are released by the photoelectric effect and are accelerated by the electric field of the microwaves in the cavity. The high frequency of operation raises the RF breakdown limit allowing strong electric fields to be used. In turn, the intense fields result in rapid acceleration of the electrons to relativistic speeds and reduced space charge induced emittance growth.

British Library Electronic Table of Contents (United Kingdom)

We report the first band structure calculations of the quasi-one-dimensional [MnTPP][TCNE] compounds (TPP?=?meso-tetraphenylporphyrinato, TCNE?=?tetracyanoethylene), based on Density Functional Theory (DFT) methods, in order to interpret the magnetic ordering in these prototypic systems. We compare and contrast the results of broken-symmetry DFT calculations for extended systems, with periodic boundary conditions, and for finite systems, magnetic dimers modeling the actual molecular magnets. By varying systematically the main angles, we are able to determine the geometry dependence of the exchange interaction. Structure?properties correlations in these charge-transfer salts reveal the determinant role of the Mn-(N?C)TCNE bond angle on the strength of the ferrimagnetic coupling between the ...

Energy Technology Data Exchange (ETDEWEB)

We study the localized tachyon condensation of non-supersymmetric orbifold backgrounds in their mirror Landau-Ginzburg picture. We first show that the R-charges of chiral primaries increase under the process of condensing the tachyon in the same chiral ring. Then, utilizing the existence of four copies of (2,2) worldsheet supersymmetry, we show that the minimal tachyon mass in twisted sectors increases in CFT and type 0 string and it plays the role of the c-function of the twisted sectors. We also study the GSO projection in detail and show that type II decays to only to type II while type 0 can mix with type 0 and II under the RG-flow.

CERN Document Server

We consider 4-dimensional space-times which are asymptotically flat at spatial infinity and show that, in the first order framework, action principle is well-defined \\emph{without the need of infinite counter terms.} It naturally leads to a covariant phase space in which the Hamiltonians generating asymptotic symmetries provide the total energy-momentum and angular momentum of the space-time. We address the subtle but important problems that arise because of logarithmic translations and super-translations both in the Langrangian and Hamiltonian frameworks. As a forthcoming paper will show, the treatment of higher dimensions is considerably simpler. Our first order framework also suggests a new direction for generalizing the spectral action of non-commutative geometry.

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Spectroscopy based on the Andreev reflection (AR) process at the interface between the normal metal tip and the superconductor has become one of the very successful methods for studies in novel exotic superconductors. The method is capable to address the size, symmetry as well as multiplicity of the superconducting order parameter. The method provided one of the first evidences of the two-gap superconductivity in MgB{sub 2} with a detailed temperature dependence of the both gaps. A theory treating the Andreev reflection spectroscopy in the mixed state is missing. We analyse the AR spectra of MgB{sub 2} in the mixed state via modelling the magnetic pair-breaking by the increasing spectral broadening parameter {gamma}. As a result a non-trivial pair breaking effect in the {pi}-band is found.

CERN Document Server

This paper offers a conceptually straightforward method for the calculation of stresses in polarisable media based on the notion of a drive form and its property of being closed in spacetimes with symmetry. After an outline of the notation required to exploit the powerful exterior calculus of differential forms, a discussion of the relation between Killing isometries and conservation laws for smooth and distributional drive forms is given. Instantaneous forces on isolated spacetime domains and regions with interfaces are defined, based on manifestly covariant equations of motion. The remaining sections apply these notions to media that sustain electromagnetic stresses, with emphasis on homogeneous magnetoelectric material. An explicit calculation of the average pressure exerted by a monochromatic wave normally incident on a homogeneous, magnetoelectric slab in vacuo is presented and the concluding section summarizes how this pressure depends on the parameters in ...

Energy Technology Data Exchange (ETDEWEB)

A theoretical framework for the hierarchical multiscale modeling of inelastic response of heterogeneous materials has been presented. Within this multiscale framework, the second gradient is used as a non local kinematic link between the response of a material point at the coarse scale and the response of a neighborhood of material points at the fine scale. Kinematic consistency between these scales results in specific requirements for constraints on the fluctuation field. The wryness tensor serves as a second-order measure of strain. The nature of the second-order strain induces anti-symmetry in the first order stress at the coarse scale. The multiscale ISV constitutive theory is couched in the coarse scale intermediate configuration, from which an important new concept in scale transitions emerges, namely scale invariance of dissipation. Finally, a strategy for developing meaningful kinematic ISVs and the proper free energy functions and evolution kinetics is ...

UK PubMed Central (United Kingdom)

The mechanisms that contribute to the extinction of previously acquired memories are not well understood. These processes, often referred to as inhibitory learning, are thought to be parallel...Full Text Available

UK PubMed Central (United Kingdom)

This paper summarizes the deliberations of a work group charged with addressing specific questions relevant to risk estimation in developmental neurotoxicology. We focused on eight questions. a) Does...Full Text Available

UK PubMed Central (United Kingdom)

A critical research priority for our field is to develop treatments that enhance cognitive functioning in schizophrenia and thereby attenuate the functional losses associated with the illness. In this...Full Text Available

UK PubMed Central (United Kingdom)

The hemagglutinin (HA) glycoprotein of influenza virus performs two critical roles during infection: it binds virus to cell surface sialic acids, and under mildly acidic conditions it induces fusion...Full Text Available

UK PubMed Central (United Kingdom)

Synaptic vesicle endocytosis is critical to maintain synaptic communication during intense stimulation. Here we describe Tweek, a conserved protein that is required for synaptic vesicle recycling....Full Text Available

UK PubMed Central (United Kingdom)

BackgroundProcessing of multimodal information is a critical capacity of the human brain, with classic studies showing bimodal stimulation either facilitating or interfering in perceptual...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

The temperature dependence of the dislocation mobility threshold is investigated on the basis of a dislocation model suggested by Frenkel-Kontorova. The critical value is obtained for the stress/temperature, corresponding to the dislocation depinning from its equilibrium position. The universal behaviour of a barrier height at finite stress and temperature is revealed and investigated.

UK PubMed Central (United Kingdom)

Thyroid hormone is a critical regulator of growth, development and metabolism in virtually all tissues, and altered thyroid status affects many organs and systems. Although for many years testis...Full Text Available

UK PubMed Central (United Kingdom)

By analysis of crossovers in key recombinant families and by homozygosity analysis of inbred families, the Friedreich ataxia (FRDA) locus was localized in a 300-kb interval between the X104 gene and...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundRasbora tawarensis is an endemic freshwater fish in Lake Laut Tawar, Aceh Province, Indonesia. Unfortunately, its status is regarded as critical endangered...Full Text Available

International Nuclear Information System (INIS)

A calculation program (URA 6.F4) was elaborated on FORTRAN IV language, that through finite differences solves the unidimensional scalar Helmholtz equation, assuming only one energy group, in spherical cylindrical or plane geometry. The purpose is the determination of the flow distribution in a reactor of spherical cylindrical or plane geometry and the critical dimensions. Feeding as entrance datas to the program the geometry, diffusion coefficients and macroscopic transversals cross sections of absorption and fission for each region. The differential diffusion equation is converted with its boundary conditions, to one system of homogeneous algebraic linear equations using the box integration technique. The investigation on criticality is converted then in a succession of eigenvalue problems for the critical eigenvalue. In general, only is necessary to solve the first eigenvalue and its corresponding eigenvector, employing ...

Energy Technology Data Exchange (ETDEWEB)

Three dispersants (stearic acid, oleic acid, and poly-(12-hydroxystearic acid)) are compared for their ability to produce low-viscosity suspensions of zirconia in kerosene. Rheological measurements and sediment packing density measurements show that poly(12-hydroxystearic acid) is a better dispersant than stearic acid or oleic acid; this is explained in terms of the longer tail of the poly-(12-hydroxystearic acid) surfactant molecule. The amount of dispersant can be optimized to reduce viscosity and yield point of the suspension, and to eliminate thixotropic hysteresis. The use of a dispersion medium of lower viscosity than the dispersant makes it easy to detect when complete monolayer coverage has been achieved. The loss of pseudoplasticity, brought about by a higher degree of deflocculation, can be recovered by increasing the volume fraction of solids of a suspension and this is beneficial in the plastic forming of ceramics. Rheological measurements showed that these suspensions ...

Energy Technology Data Exchange (ETDEWEB)

The energy strategy of the UK Overseas Development Administration is outlined with specific emphasis on energy efficiency and renewable energies. Based on 29 case studies concerning projects and programmes in both developed and developing countries, critical success factors for renewable energy projects are identified. UK)