火灾烟颗粒分形模型和球形模型光散射的比较研究

对烟颗粒的光散射进行模拟计算是研究火灾烟颗粒光散射特性的重要手段,目前对于火灾烟颗粒光散射的数值计算多采用球形或椭球模型.实际上,火灾烟颗粒的形貌与球形和椭球均存在着显著差异.扫描电子显微镜图像表明,烟颗粒具有近似分形的结构.本文利用离散偶极近似方法计算了随机取向的火灾烟颗粒分形凝团以及同体积的球形颗粒的光散射Muller矩阵,并对两者的归一化Muller矩阵元素随散射角的分布进行了比较.研究表明:火灾烟颗粒分形模型和球形模型的归一化矩阵元素F₁₁(θ)/     

Drinfeld Twists and Algebraic Bethe Ansatz of the Supersymmetric Model Associated with U q (gl(m|n))

We construct the Drinfeld twists (or factorizing F-matrices) of the super-symmetric model associated with quantum superalgebra U_q(gl(m|n)), and obtain the completely symmetric representations of the creation operators of the model in the F-basis provided by the F-matrix. As an application of our general results, we present the explicit expressions of the Bethe vectors in the F-basis for the U_q(gl(2|1))-model (the quantum t-J model).     

Drinfeld twist and the domain wall partition function of the eight-vertex model

With the help of the F-basis provided by the Drinfeld twist or factorising F-matrix for the spatial optical soliton model associated with the eight-vertex model, we calculate the partition function for the eight-vertex model on an N × N square lattice with domain wall boundary condition.     

Duality in non-linear BF models: equivalence between self-dual and topologically massive Born–Infeld BF models

We study the dual equivalence between the non-linear generalization of the self-dual (NSD_BF) and the topologically massive BF models with particular emphasis on the non-linear electrodynamics proposed by Born and Infeld. This is done through a dynamical gauge embedding of the non-linear self-dual model yielding to a gauge invariant and dynamically equivalent theory. We clearly show that non-polinomial NSD_BF models can be map, through a properly defined duality transformation into TM_BF actions. The general result obtained is then particularized for a number of examples, including the Born–Infeld-BF (BIBF) model that has experienced a revival in the recent literature.     

Excimer Fluorescence as a Tool for Monitoring Protein Domain Dynamics Applied to Actin Conformation Changes Based on Circulary Polarized Fluorescence Spectroscopy

Fluorescence-detected circular dichroism (FDCD) was introduced into the study of protein conformation changes. Actin was used as a model protein which undergoes dynamic conformation changes as it polymerizes. Actin labeled with N-(1-pyrene)iodoacetamide (PIA) showed monomer fluorescence peak at 386 and 410 nm, and excimer fluorescence peak at around 480 nm. Excimer was formed by PIA-dimers labeled to different sites of amino acid residues. New information concerned with actin structural changes were monitored by fluorescence emission spectra excited with left- and right-circulary polarized light at 355 nm. FDCD intensities were shown as the difference in the fluorescence emission ΔF, where ΔF=(F _L−F _R)/(F _L+F _R) denoting F _L and F _R as emissions obtained by excitation with left- and right-circulary polarized light. When solvent conditions of PIA-actin were changed by addition of NaCl, TFE, or ATP, ΔF showed sensitive responses to these compounds. From the analysis of ΔF _M and ΔF _E which represent the peaks of ΔF at the monomer- and excimer-emission band, the information concerned with the actin intrastructural changes were obtained. This method based on monitoring the excimer fluorescence with FDCD could be used for other proteins to extract finer structural changes that cannot be detected by the normal fluorescence spectroscopy.     

Perturbation treatment of non-linear transport via the Robertson statistical formalism

A perturbation solution is found for the differential equation defining an operator Tˆ used by Robertson to relate the information-theoretic phase-space distribution σ to the solution ρ of the classical Liouville equation. This relation provides a closure, used in obtaining an exact equation for σ. Multiplying the latter equation by F, a phase-space function odd under momentum reversal, of which heat and diffusion fluxes are among the examples, one gets an exact equation for ∂〈F〉/∂t. 〈F〉 is the phase space integral of ρF. The dissipative terms in ∂〈F〉/∂t can be expanded, like Tˆ, in successive orders O(〈F〉ⁿ). For a model in which equilibrium ensemble fluctuations relax exponentially, terms linear and O(〈F〉³) are calculated. The non-linear terms exhibit an explicit time-dependence for short times. In a steady state induced by external driving forces, the explicit time-dependence disappears, in agreement with existing phenomenology. For simplicity, spatial uniformity is assumed. A generalization is required for large temperature or velocity gradients.     

Dependence of |V ub/Vcb| on Fermi momentump F in ACCMM model

The Gaussian width of Fermi momentum,p _F, is the most important parameter of the ACCMM model, and its value is essential in the determination of |V _ub/V_cb| because the experimental analysis is allowed only at the end-point region of inclusive semileptonicB-decay spectrum. We extract the value of |V _ub/V_cb| as a function ofp _F. We also calculate the parameterp _F in the relativistic quark model using the variational method, and obtainp _F=0.54 GeV which is much larger than the commonly used value, ∼0.3 GeV, in experimental analyses. When we usep _F=0.5 GeV instead of 0.3 GeV, the value of |V _ub/V_cb| from ACCMM model is increased by a factor 1.81, and can give a good agreement with Isgur et al. model.     

A study of the variable moment of inertia models

The variable moment of inertia (VMI) model proposed by Holmberg and Lipas has been shown to be a special case of the VMI model of Mariscottiet al. The solution of Mariscotti’s model is expressed in terms of hypergeometric functions, which directly give the rotational energies or their expansions in terms of the quantityF(F+1), whereF is the total angular momentum. The present way of looking at the VMI model also tells us how to write the general dependence of the vibrational energy and the moment of inertia on the energyE _J.     

Maximal atmospheric neutrino mixing in an <Emphasis Type="Italic">SU</Emphasis>(5) model

We show that maximal atmospheric and large solar neutrino mixing can be implemented in SU(5) gauge theories, by making use of the U(1) _F symmetry associated with a suitably defined family number F, together with a Z₂ symmetry which does not commute with F. U(1) _F is softly broken by the mass terms of the right-handed neutrino singlets, which are responsible for the seesaw mechanism; in additio n, U(1) _F is also spontaneously broken at the electroweak scale. In our scenario, lepton mixing stems exclusively from the right-handed-neutrino Majorana mass matrix, whereas the CKM matrix originates solely in the up-type-quark sector. We show that, despite the non-supersymmetric character of our model, unification of the gauge couplings can be achieved at a scale 10¹⁶ GeV < m _U < 10¹⁹ GeV; indeed, we have found a particula r solution to this problem which yields results almost identical to the ones of the minimal supersymmetric standard model. Received: 29 November 2002 / Published online: 3 March 2003 RID="a" ID="a" e-mail: walter.grimus@univie.ac.at RID="b" ID="b" e-mail: balio@cfif.ist.utl.pt     

Bianchi Type V magnetized string dust cosmological models with Petrov-type degenerate

Bianchi Type V massive string cosmological models with free gravitational field of Petrov Type degenerate in the presence of magnetic field with variable magnetic permeability are investigated. The magnetic field is due to an electric current produced along the x-axis. The F ₂₃ is the only non-vanishing component of electromagnetic field tensor F _ij . Maxwell’s equations F _[ij;k] = 0 and F _;j ^ij = 0 are satisfied by F ₂₃ = constant. The behaviour of the model in the presence and absence of magnetic field and other physical aspects are also discussed.      

<Emphasis Type="Italic">O</Emphasis>(12) limit and complete classification of symmetry schemes in proton-neutron interacting boson model

It is shown that the proton-neutron interacting boson model (pnIBM) admits new symmetry limits withO(12) algebra which breakF spin but preserves theF _z quantum numberM _F. The generators ofO(12) are derived and the quantum numberU ofO(12) for a given boson numberN is determined by identifying the corresponding quasi-spin algebra. TheO(12) algebra generates two symmetry schemes and for both of them, complete classification of the basis states and typical spectra are given. With theO(12) algebra identified, complete classification of pnIBM symmetry limits with goodM _F is established.     

Griffith–Kelly–Sherman Correlation Inequalities for Generalized Potts Model

Inspired by the work of D.G.Kelly and S.Sherman on general Griffiths inequalities on correlations in Ising ferromagnets, we formulate and prove Griffith–Kelly–Sherman-type inequalities for the ferromagnetic Potts model with a general number q of local states. We take as local state space for the q-state Potts model the set F ^c  = { − l, − l + 1, ⋯ ,l − 1,l},where l=\fracq-12l=\frac{q-1}{2}. The important properties of F ^c for what follows are that |F ^c | = q and F ^c  = − F ^c .     

Chiral SU(4) × SU(4) breaking: masses and decay constants of charmed hadrons

The (4, 4*) ⊕ (4*, 4) model of broken chiral SU (4) × SU (4) symmetry has been used to calculate the third-order coupling constants involving charmed and ordinary pseudoscalar mesons. These coupling constants are exploited to derive some interesting new relations among the masses and decay constants of these charmed particles. Using the known masses and decay constants as inputs, we exploit these relations to predict:F _D = −1·41F _π ,F _F = −1·13F _π ,F _D/F_F = 1·25,m(D _s) = 1·43 GeV,m(F _s) = 1·39 GeV andm(K _s) = 1·02 GeV.     

Dynamic Dipole and Quadrupole Phase Transitions in the Kinetic Spin-3/2 Model

The dynamic phase transition has been studied, within a mean-field approach, in the kinetic spin-3/2 Ising model Hamiltonian with arbitrary bilinear and biquadratic pair interactions in the presence of a time dependent oscillating magnetic field by using the Glauber-type stochastic dynamics. The nature (first- or second-order) of the transition is characterized by investigating the behavior of the thermal variation of the dynamic order parameters and as well as by using the Liapunov exponents. The dynamic phase transitions (DPTs) are obtained and the phase diagrams are constructed in the temperature and magnetic field amplitude plane and found nine fundamental types of phase diagrams. Phase diagrams exhibit one, two or three dynamic tricritical points, and besides a disordered (D) and the ferromagnetic-3/2 (F_3/2) phases, six coexistence phase regions, namely F _3/2+ F _1/2, F _3/2+ D, F _3/2+ F _1/2+ FQ, F _3/2+ FQ, F _3/2+ FQ + D and FQ + D, exist in which depending on the biquadratic interaction. PACS number(s): 05.50.+q, 05.70.Fh, 64.60.Ht, 75.10.Hk     

Scaling properties of dynamic response in orientational glasses

The freezing transition in dipolar and quadrupolar glasses is characterized by the presence of local random electric and strain fields generated by substitutional disorder. The dynamic response in the ergodic phase above the freezing temperature T_F is studied in terms of Langevin dynamics applied to the recently formulated symmetry-adapted random-bond-random-field (SARBRF) model of orientational glasses. Following the theory of spin glasses it is assumed that for T≥T_F the response can be written in a dynamic scaling form by introducing a scaling exponent v and a frequency scaling variable. The value of v(T) is explicitly evaluated for the quadrupolar (100) SARBRF model, and its relation to the experimentally observed effective exponent u_eFF(T) in dipolar and quadrupolar glasses is discussed.     

Excited state absorption and energy transfer losses in thulium doped fluoroindogallate glass

Thulium doped fluoroindogallate glass was characterized by means of excited state absorption experiment in the 0.95 to 1.55 μm spectral range. The three bands corresponding to the electronic transitions ³ F ₄→³ F ₂ (at 1.05 μm), ³ F ₄→³ F ₃ (at 1.125 μm), and ³ F ₄→³ H ₄ (at 1.45 μm) were observed. The energy transfer microscopic parameters for the reverse cross relaxation process ³ F ₄, ³ F ₄→³ H ₆, ³ H ₄ were calculated for different multipolar interaction mechanisms using the Kushida model, and it was verified that the probability of this process is 100 times lower than that of the direct ³ H ₄, ³ H ₆→³ F ₄, ³ F ₄ cross relaxation, responsible for the 1.8 μm emission pumping. PACS 78.20.-e; 78.55.Qr; 42.70.Hj; 42.55.Wd     

Composition formulae of ideal metallic glasses and their relevant eutectics established by a cluster-resonance model

Composition formulae for ideal metallic glasses are explored by combining the cluster-plus-glue-atom model with the global resonance model, termed the cluster-resonance model for short. The former model gives the [cluster]₁(glue atom) _x cluster formulae, stressing the local cluster order of a glassy structure; the latter model extends the local cluster order to a medium-range one by introducing spherical periodicity that relates the cluster size with Fermi vector, k _F. Such a correlation allows the calculation of Fermi energy, E _F, and electrochemical potential of electrons of the system from any local clusters. The cluster-resonance model also implies the equilibrium of the electrochemical potentials of electrons between different clusters so that the number of glue atoms matching one cluster (x in the cluster formula) can be determined. Examples in the Cu–Zr–Al and B–Co–Si–Ta systems are given to show the effectiveness of the proposed model and the resulting cluster formulae in interpreting multicomponent metallic-glass compositions as well as their relevant binary eutectic points.     

Nonlinear Hanle effect in Cs vapor under strong laser excitation

We report results of a theoretical and experimental study of the ground state nonlinear Hanle effect under strong laser excitation. It is shown that besides the well-known zero-magnetic field suppression of absorption on F _g = F→F _e = F - 1 transitions caused by population trapping, an optical pumping induced enhanced absorption occurs on F _g = F→F _e = F + 1 transitions for small B-fields. The latter effect becomes more pronounced for high F values. The experiment with atomic vapor of Cs (D₂ line, F _g = 4) confirms an increase of the spectrally unresolved fluorescence yield at zero magnetic field and 600 mW/cm² laser intensity by 9% or 42%, when excitation occurs with linearly or circularly polarized light, respectively. The results of the experiment agree with numerical simulation studies using equations of motion for a density matrix. Received 24 November 2001 / Received in final form 25 March 2002 Published online 24 September 2002     

Output from an atom laser: theory vs. experiment

Atom lasers based on rf-outcoupling can be described by a set of coupled generalized Gross–Pitaevskii equations (GPE). We compare the theoretical predictions obtained by numerically integrating the time-dependent GPE of an effective one-dimensional model with recently measured experimental data for the F=2 and F=1 states of Rb-87. We conclude that the output of a rf atom-laser can be described by this model in a satisfactory way. Received: 15 June 1999 / Revised version: 9 September 1999 / Published online: 10 November 1999