<Emphasis Type="Italic">Comment on</Emphasis>¶Low temperature specific heat of blue bronze K <Emphasis Type="Bold">0.30</Emphasis>MoO <Emphasis Type="Bold">3</Emphasis>, by J. Odin,J.C. Lasjaunias,K. Biljaković, K. Hasselbach,and P. Monceau

Eur. Phys. J. B 24, 315 (2001) Here we comment on a recently published paper on the presence of a phason contribution in the low temperature heat capacity data of the charge-density-wave compounds K_0.3MoO₃ and (TaSe₄)₂I. We have shown that the anomaly in the C _P / T ³ data reported by Odin et al. is straightforwardly interpreted in terms of low energy phonon modes resulting from the peculiar topology of these compounds. Received 21 February 2002 Published online 19 July 2002     

Generalized Noether's theorem. I. theory

This article is a theoretical investigation of generalized Noether's theorem, which, though unconcerned with considerations such as coordinate transformations, symmetry, and invariance, is the basic mechanism of conventional Noether's theorem, its extensions, and its inverse. The generalized theorem is a completely new approach to the subject—formally, conceptually, and practically. It is an association, for a set of field equations, of field variations with conserved currents. The theorem is stated from two points of view and analyzed with regard to its interpretation and its formal and conceptual relation to conventional Noether's theorem and extensions, transformation groups, and Hamilton's principle. The inverse theorem is also treated. The role of coordinate transformations in conventional Noether's theorem is analyzed.     

Electrical properties of polycrystalline TiO<Subscript>2</Subscript>. Prolonged oxidation kinetics

The equilibration kinetics for polycrystalline TiO₂ was monitored during prolonged oxidation at 1,323 K and p(O₂)=75 kPa using the measurements of the electrical conductivity and thermoelectric power. The determined kinetic data indicate the presence of two kinetics regimes; the Regime I (rapid kinetics) and the Regime II (slow kinetics). The prolonged oxidation of TiO₂ is considered in terms of the formation of Ti vacancies at the surface and their subsequent transport into the bulk. This effect, also observed for TiO₂ single crystal, allows to obtain p-type TiO₂ without the incorporation of acceptor-type foreign ions into the TiO₂ lattice. This project was performed as part of the University of New South Wales Research and Development programme on solar-hydrogen.     

Mikrophysikalische Bestimmung elektronenkinetischer Kenngrößen im binären Molekül-Mischplasma von Stickstoff und Wasserstoff. II. Elektronenstoßfrequenzen für die Anregung und Ionisierung langlebiger elektronischer Molekülzustände und die Energieverlustraten der Elektronenkomponente des Mischplasmas

In this second part of the in [l] started paper the results of microphysical determined collision frequencies of the electrons for the excitation and ionization of metastable molecules, excited in electronic states, and of the energy loss rates of the electrons due to elastic collisions, vibrational excitation, electronic excitation, dissociation and ionization of the molecules in a N₂ - H₂ -plasma are represented and discussed. These investigations are related to a low ionized, homogeneous and stationary plasma in a mixture and are performed for the range 6- 100 V/(cm Torr) of the reduced electric field strength and for any composition of the N₂ - H₂-mixture.     

Studies on toxicity of aluminum oxide (Al<Subscript>2</Subscript>O<Subscript>3</Subscript>) nanoparticles to microalgae species: <Emphasis Type="Italic">Scenedesmus</Emphasis> sp. and <Emphasis Type="Italic">Chlorella</Emphasis> sp.

In view of increasing commercial applications of metal oxide nanoparticles their toxicity assessment becomes important. Alumina (Al₂O₃) nanoparticles have wide range of applications in industrial as well as personal care products. In the absence of prior report on toxicological impact of alumina nanoparticles to microalgae, the principal objective of this study was to demonstrate the effect of the nanoparticles on microalgae isolated from aquatic environment (Scenedesmus sp. and Chlorella sp.). The growth inhibitory effect of alumina nanoparticles was observed for both the species (72 h EC₅₀ value, 45.4 mg/L for Chlorella sp.; 39.35 mg/L for Scenedesmus sp.). Bulk alumina also showed toxicity though to a lesser extent (72 h EC₅₀ value, 110.2 mg/L for Chlorella sp.; 100.4 mg/L for Scenedesmus sp.). A clear decrease in chlorophyll content was observed in the treated cells compared to the untreated ones, more effect being notable in the case of nanoparticles. Preliminary results based on FT-IR studies, optical and scanning electron microscopic images suggest interaction of the nanoparticles with the cell surface.     

Streuung elektromagnetischer Oberflächen- und Volumenwellen an rauhen Oberflächen. Teil II. Die Streulichtverteilung; Ein- und Auskopplung von Oberflächenwellen

Scattering of Electromagnetic Surface and Bulk Waves from Rough Surfaces. Part II. The Indicatrix of Scattering; the Coupling of Surface and Bulk Waves In this paper, we present the calculation of the spectral power density of light scattered from homogenously isotropic and rough surfaces which are influenced by bulk or surface waves. A classification of all possible scattering cases in dependence on the wave types which arise in the regions z > O and z < O is given. The dependence of scattered light on scattering angles for the different possibilities of polarisation variantes (∥ and ?) will be presented. The relationship between the correlation function of roughness and the efficiency of coupling between bulk and surface modes will be discussed and compared with the results of other authors.     

Ionenschallinstabilitäten in Edelgas-Gleichstromentladungen bei niedrigen Drücken. I. Meßanordnung und experimentelle Ergebnisse

An experimental study of self-excited ion acoustic waves with wavelengths greater than the radius of the discharge tube in a de-low pressure column is presented. The propagation of this type of waves was observed over a pressure range of 5 · 10^?4 torr ≦ p ≦ 10^?1 torr and currents of 0,02 A ≦ i ≦ 0,6 A in various gases (argon, neon, helium, and hydrogen) in cylindrical glass tubes with diameters of d = 2;4 and 6 cm. The Dispersion behaviour and the existence range were measured in dependence of the internal parameters of the discharge (characteristic velocities and collision frequencies) and the geometry of the discharge tube. It is shown, that the existence range depends not only on gas pressure and current but is influenced also by the geometry of the discharge tube. The minimum wavelengths which belong to the upper cut-off frequencies correlate with the radius of the discharge tube at currents higher than i ～ 0,2 A and increasing pressure.     

Diffusionstheoretische Beschreibung der Dissoziation und des Ionenhaushaltes im schwachionisierten Säulenplasma der Wasserstoffentladung. I. Reaktionsmechanismen — Bilanzgleichungssystem und Lösungsmethode

After the discussion of the main reaction mechanisms as ionization, dissociation, dissociative recombination, ion-molecule-reactions and chemical reactions between neutral particles a system of balance equations for the ions H⁺, H₂⁺, H₃⁺, and H₅⁺, for the atoms, for the mixture of neutral particles, for charge neutrality and the discharge current is given in the framework of the diffusion theory. The numerical method for the solution of this system is explained. In the following parts of this paper detailed results of the numerical calculation will be dicussed in comparison with some experimental investigations.     

Comment on “Critique of multinomial coefficient method for evaluating Tsallis and Rényi entropies” by A.S. Parvan

Parvan [A.S. Parvan, Critique of multinomial coefficients method for evaluating Tsallis and Rényi entropies, Physica A 389 (2010) 5645] has recently presented some calculations in order to demonstrate the incorrectness of the results obtained from the generalized multinomial coefficients (GMC) presented in Oikonomou (2007) [1]. According to Parvan, the aforementioned approach of studying maximum entropy probability distributions is erroneous. In this comment I demonstrate that Parvan’s arguments do not hold true and that the obtained results from GMC do not present either mathematical or physical discrepancies.     

An ARPES view on the high-<Emphasis Type="Italic">T</Emphasis><Subscript>c</Subscript> problem: Phonons <Emphasis Type="Italic">vs.</Emphasis> spin-fluctuations

We review the search for a mediator of high-T _c superconductivity focusing on ARPES experiment. In case of HTSC cuprates, we summarize and discuss a consistent view of electronic interactions that provides natural explanation of both the origin of the pseudogap state and the mechanism for high temperature superconductivity. Within this scenario, the spin-fluctuations play a decisive role in formation of the fermionic excitation spectrum in the normal state and are sufficient to explain the high transition temperatures to the superconducting state while the pseudogap phenomenon is a consequence of a Peierls-type intrinsic instability of electronic system to formation of an incommensurate density wave. On the other hand, a similar analysis being applied to the iron pnictides reveals especially strong electron-phonon coupling that suggests important role of phonons for high-T _c superconductivity in pnictides.     

Selective photoinactivation of <Emphasis Type="Italic">C. albicans</Emphasis> and <Emphasis Type="Italic">C. dubliniensis</Emphasis> with hypericin

The genus Candida includes different species that have the potential to invade and colonize the human body and C. albicans is the most common cause of skin, nail and mucous infections. The increasing resistance against antifungal drugs has renewed the search for new treatment procedures and antimicrobial photodynamic inactivation (PDI) is a propitious candidate. Hypericin (HY) has several wanted properties to be used as a photosensitizer in this technique including a high quantum yield of singlet oxygen generation, a high extinction coefficient near 600 nm, and a relatively low dark toxicity. Although the phototoxicity of HY on several tumor cells has been reported, the data concerning its photoactivity on microorganisms are scarce. The aim of this study was to obtain the experimental parameters to achieve an acceptable selective hypericinphotoinactivation of two species of Candida comparing with fibroblasts and epithelial cells which are the constituents of some potential host tissues, such mucosas, skin and cavities. Microorganisms and cells were incubated with the same HY concentrations and short incubation time followed by irradiation with equal dose of light. The best conditions to kill just Candida were very low HY concentration (0.1–0.4 μg ml⁻¹) incubated by 10 min and irradiated with LED 590 nm with 6 J cm⁻².     

Reply to: “Comment on: ‘Epidemic spreading on heterogeneous networks with identical infectivity’ [Phys. Lett. A 364 (2007) 189]” [Phys. Lett. A 372 (2008) 1722]

In a recent Letter [R. Yang, B.H. Wang, J. Ren, W.J. Bai, Z.W. Shi, W.X. Wang, T. Zhou, Phys. Lett. A 364 (2007) 189], we proposed a modified susceptible-infected-recovered (SIR) model, in which each node is assigned with an identical capability of active contact, A, at each time step. We found a threshold value λc=1/A in uncorrelated and unlocalized networks. A corresponding Comment, raised by Alberto d'Onofrio, claimed that (i) our model is not biologically relevant; (ii) our model does not have a threshold behavior for recovered population; (iii) the analytical result λc=1/A is incorrect being considered as a threshold for epidemic outbreak, because of an improper approximation of the initial configuration. In this Reply, I show that, by debating from point to point, our analysis and conclusion are solid and reasonable.     

On Polynomials Interpolating Between the Stationary State of a <Emphasis Type="Italic">O</Emphasis>(<Emphasis Type="Italic">n</Emphasis>) Model and a Q.H.E. Ground State

We obtain a family of polynomials defined by vanishing conditions and associated to tangles. We study more specifically the case where they are related to a O(n) loop model. We conjecture that their specializations at z _i = 1 are positive in n. At n = 1, they coincide with the Razumov-Stroganov integers counting alternating sign matrices. We derive the CFT modular invariant partition functions labelled by Coxeter-Dynkin diagrams using the representation theory of the affine Hecke algebras.     

5d-level energies of Ce and the crystalline environment. IV. Aluminates and “simple” oxides

Information on the energy of 5d-levels of Ce³⁺ ions in aluminates and “simple” oxides has been collected. The crystal field splitting of the 5d-levels is interpreted in terms of the type and size of anion polyhedron coordinating the Ce³⁺ ion. The centroid (barycenter) shift of the 5d-configuration is analyzed by a ligand polarization model providing values for the spectroscopic polarizability α_sp of the anion ligands. The data provide evidence that the centroid shift behaves independently from the crystal field splitting. By combining centroid shift and crystal field splitting, the “spectroscopic” redshift of the first electric dipole-allowed fd transition of Ce³⁺-doped in the compounds will be interpreted. The large crystal field splitting in garnet compounds and the small splitting in perovskite compounds will be discussed.     

Soft Dynamics simulation. 2. Elastic spheres undergoing a T<Subscript>1</Subscript> process in a viscous fluid

Robust empirical constitutive laws for granular materials in air or in a viscous fluid have been expressed in terms of timescales based on the dynamics of a single particle. However, some behaviours such as viscosity bifurcation or shear localization, observed also in foams, emulsions, and block copolymer cubic phases, seem to involve other micro-timescales which may be related to the dynamics of local particle reorganizations. In the present work, we consider a T₁ process as an example of a rearrangement. Using the Soft Dynamics simulation method introduced in the first paper of this series, we describe theoretically and numerically the motion of four elastic spheres in a viscous fluid. Hydrodynamic interactions are described at the level of lubrication (Poiseuille squeezing and Couette shear flow) and the elastic deflection of the particle surface is modeled as Hertzian. The duration of the simulated T₁ process can vary substantially as a consequence of minute changes in the initial separations, consistently with predictions. For the first time, a collective behaviour is thus found to depend on a parameter other than the typical volume fraction of particles.     

Influence of Bi<Superscript>3+</Superscript> ions on low temperature D.C. conductivity of Na<Subscript>2</Subscript>SiCuO<Subscript>4</Subscript> glasses

Sodium silicate glasses doped with CuO and mixed with different contents of Bi₂O₃ (ranging from 4 to 16 mol%) were prepared. D.C. conductivity studies over a range of temperature from 225 to 325 K have been carried out. The conductivity is observed to decrease linearly with increase of Bi₂O₃ concentration. The results are analyzed using optical absorption, ESR, and IR spectral data. The spectroscopic studies have indicated that there is a gradual reduction divalent copper ions to monovalent ions with increase of Bi₂O₃ concentration. These studies have also indicated that such Cu⁺ ions participate in the glasses network forming and increase the polymerization of the glass network. The analysis of the results of D.C. conductivity indicated that in temperature region T > θ _D/2, the small polaron hoping model is valid, and the conduction is predicted to be adiabatic type. The analysis of the results has further revealed that there is a gradual change over of conduction mechanism from ionic to electronic with increase of Bi₂O₃ concentration. The low temperature part of D.C. conductivity is explained using variable range hopping (VRH) model.     

CaCuMn<Subscript>6</Subscript>O<Subscript>12</Subscript> vs. CaCu<Subscript>2</Subscript>Mn<Subscript>5</Subscript>O<Subscript>12</Subscript>: A comparative study

The ferrimagnetic compounds Ca(Cu_xMn_3?x)Mn₄O₁₂ of the double distorted perovskites AC₃B₄O₁₂ family exhibit a rapid increase of the ferromagnetic component in magnetization at partial substitution of square coordinated (Mn³⁺)_C for (Cu²⁺)_C. In the transport properties, this is seen as a change of the semiconducting type of resistivity for the metallic one. The evolution of magnetic properties of Ca(Cu_xMn_3?x)Mn₄O₁₂ is driven by strong antiferromagnetic exchange interaction of (Cu²⁺)_C with (Mn³⁺/Mn⁴⁺)_B coordinated octahedra. The competing interactions of (Mn³⁺)_C with (Mn³⁺/Mn⁴⁺)_B lead to the formation of noncollinear magnetic structures that can be aligned by magnetic fields.     

Rebuttal on “anti-gravitation” by S. Hossenfelder

Hossenfelder proposes in [S. Hossenfelder, Phys. Lett. B 636 (2006) 119] and [S. Hossenfelder, gr-qc/0605083] a symmetry between gravitating and anti-gravitating particles by superposing a negative charge to classical relativity. This Letter explicitly shows that the latter proposal does not address any of the difficulties that arise in such context. On the contrary, the “world-lines” of the anti-gravitating particles are defined as observer-dependent entities and no attempt whatsoever to dynamically restore local boost invariance is made. Both papers simply focus on the erroneous construction of a new bundle attached to a preferred timelike vector field, although the author gives the impression that no such preference is needed.     

Orientational dynamics of superfluid He: A “two-fluid” model. II. Orbital dynamics

We present a phenomenological theory of the homogeneous orbital dynamics of the class of “separable” anisotropic superfluid phases which includes the ABM state generally identified with ³He-A. The theory is developed by analogy with the spin dynamics described in the first paper of this series; the basic variables are the orientation of the Cooper-pair wavefunction (in the ABM phase, the l-vector) and a quantity K which we visualize as the “pseudo-angular momentum” of the Cooper pairs but which must be distinguished, in general, from the total orbital angular momentum of the system. In the ABM case l is the analog of d in the spin dynamics and K of the “superfluid spin” S_p. Important points of difference from the spin case which are taken into account include the fact that a rotation of l without a simultaneous rotation of the normal-component distribution strongly increases the energy of the system (“normal locking”), and that the equilibrium value of K is zero even for finite total angular momentum. The theory does not claim to handle correctly effects associated with any intrinsic angular momentum arising from particle-hole asymmetry, but it is shown that the magnitude of this quantity can be estimated directly from experimental data and is extremely small; also, the Landau damping does not emerge automatically from the theory, but can be put in in an ad hoc way. With these provisos the theory should be valid for all frequencies irrespective of the value of ωτ. (Δ = gap parameter, τ = quasi-particle relaxation time.) It disagrees with all existing phenomenological theories of comparable generality, although the disagreement with that of Volovik and Mineev is confined to the “gapless” region very close to T_c.The phenomenological equations of motion, which are similar in general form to those of the spin dynamics with damping, involve an “orbital susceptibility of the Cooper pairs” χ_orb(T). We give a possible microscopic definition of the variable K and use it to calculate χ_orb(T) for a general phase of the “separable” type. The theory is checked by inserting the resulting formula in the phenomenological equations for ωτ 1 and comparing with the results of a fully microscopic calculation based on the collisionless kinetic equation; precise agreement is obtained for both the ABM and the (real) polar phase, showing that the complex nature of the ABM phase and the associated “pair angular momentum” is largely irrelevant to its orbital dynamics. We note also that the phenomenological theory gives a good qualitative picture even when ω Δ(T), e.g., for the flapping mode near T_c. Our theory permits a simple and unified calculation of (1) the Cross-Anderson viscous torque in the overdamped regime, (2) the flapping-mode frequency near zero temperature, (3) orbital effects on the NMR, both at low temperatures and near T_c, (4) the orbit wave spectrum at zero temperature (this requires a generalization to inhomogeneous situations which is possible at T = 0 but probably not elsewhere). We also discuss the possibility of experiments of the Einstein-de Haas type. Generally speaking, our results for any one particular application can be also obtained from some alternative theory, but in the case of orbital and spin relaxation very close to T_c (within the “gapless” region) our predictions, while somewhat tentative and qualitative, appear to disagree with those of all existing theories. We discuss briefly how our approach could be extended to apply to more general phases.