Voidites in pure type IaB diamonds

Abstract

Electron microscopy of five pure type IaB diamonds (showing no trace whatever of a B′ infrared absorption peak due to {001} platelets) reveals voidite distributions unlike any reported before. In three of the crystals the voidites are distributed at random, and are not associated with degraded platelets, which themselves are not present in these specimens. These observations show that voidite formation and platelet degradation are distinct independent phenomena. The other two speamens showed only arrays of dislocations that patently resulted from plastic deformation: no voidites were seen. The non-formation of platelets in diamonds showing such an advanced stage of nitrogen aggregation is unexpected, and places these diamonds in a category distinct from that called ‘irregular’, in which platelets have indeed formed, but then experienced, to some degree, a process of transformation to perfect dislocation loops.     

An Adaptive Logic Based on Jaśkowskiˈs Approach to Paraconsistency

In this paper, I present the modal adaptive logic AJ ^r (based on S5) as well as the discussive logic D ^r ₂ that is defined from it. D ^r ₂ is a (non-monotonic) alternative for Jaśkowski’s paraconsistent system D ₂ . Like D ₂ , D ^r ₂ validates all single-premise rules of Classical Logic. However, for formulas that behave consistently, D ^r ₂ moreover validates all multiple-premise rules of Classical Logic. Importantly, and unlike in the case of D ₂ , this does not require the introduction of discussive connectives. It is argued that this has clear advantages with respect to one of the main application contexts of discussive logics, namely the interpretation of discussions.*Research for this paper was indirectly supported by the Flemish Minister responsible for Science and Technology (contract BIL1/8). The author is indebted to Leon Horsten, Jo?o Marcos, Jerzy Perzanowski, Liza Verhoeven, and especially to the referee and to Diderik Batens for comments and suggestions.     

The Geometry of Enhancement in Multiple Regression

In linear multiple regression, “enhancement” is said to occur when R ²=b′r>r′r, where b is a p×1 vector of standardized regression coefficients and r is a p×1 vector of correlations between a criterion y and a set of standardized regressors, x. When p=1 then b≡r and enhancement cannot occur. When p=2, for all full-rank R _xx≠I, R _xx=E[xx′]=V Λ V′ (where V Λ V′ denotes the eigen decomposition of R _xx; λ ₁>λ ₂), the set B₁:={b_i:R²=b_i￠r_i=r_i￠r_i;0 < R² ￡ 1}\boldsymbol{B}_{1}:=\{\boldsymbol{b}_{i}:R^{2}=\boldsymbol{b}_{i}'\boldsymbol{r}_{i}=\boldsymbol{r}_{i}'\boldsymbol{r}_{i};0R² ￡ 1;R²l_p ￡ r_i￠r_i < R²}0p≥3 (and λ ₁>λ ₂>⋯>λ _p ), both sets contain an uncountably infinite number of vectors. Geometrical arguments demonstrate that B ₁ occurs at the intersection of two hyper-ellipsoids in ℝ ^p . Equations are provided for populating the sets B ₁ and B ₂ and for demonstrating that maximum enhancement occurs when b is collinear with the eigenvector that is associated with λ _p (the smallest eigenvalue of the predictor correlation matrix). These equations are used to illustrate the logic and the underlying geometry of enhancement in population, multiple-regression models. R code for simulating population regression models that exhibit enhancement of any degree and any number of predictors is included in Appendices A and B.     

Some Results on Mean Square Error for Factor Score Prediction

For the confirmatory factor model a series of inequalities is given with respect to the mean square error (MSE) of three main factor score predictors. The eigenvalues of these MSE matrices are a monotonic function of the eigenvalues of the matrix Γ _p = Φ ^1/2 Λ _p ′Ψ _p ⁻¹ Λ _p Φ ^1/2. This matrix increases with the number of observable variables p. A necessary and sufficient condition for mean square convergence of predictors is divergence of the smallest eigenvalue of Γ _p or, equivalently, divergence of signal-to-noise (Schneeweiss & Mathes, 1995). The same condition is necessary and sufficient for convergence to zero of the positive definite MSE differences of factor predictors, convergence to zero of the distance between factor predictors, and convergence to the unit value of the relative efficiencies of predictors. Various illustrations and examples of the convergence are given as well as explicit recommendations on the problem of choosing between the three main factor score predictors. The author is obliged to Maarten Speekenbrink and Peter van Rijn for their assistance with plotting the figures. In addition, I am obliged to the referees for their stimulating remarks.     

A 2-categorial Generalization of the Concept of Institution

After defining, for each many-sorted signature Σ = (S, Σ), the category Ter(Σ), of generalized terms for Σ (which is the dual of the Kleisli category for \mathbb T_S{\mathbb {T}_{\bf \Sigma}}, the monad in Set ^S determined by the adjunction T_S \dashv G_S{{\bf T}_{\bf \Sigma} \dashv {\rm G}_{\bf \Sigma}} from Set ^S to Alg(Σ), the category of Σ-algebras), we assign, to a signature morphism d from Σ to Λ, the functor d_à{{\bf d}_\diamond} from Ter(Σ) to Ter(Λ). Once defined the mappings that assign, respectively, to a many-sorted signature the corresponding category of generalized terms and to a signature morphism the functor between the associated categories of generalized terms, we state that both mappings are actually the components of a pseudo-functor Ter from Sig to the 2-category Cat. Next we prove that there is a functor Tr^Σ, of realization of generalized terms as term operations, from Alg(Σ) × Ter(Σ) to Set, that simultaneously formalizes the procedure of realization of generalized terms and its naturalness (by taking into account the variation of the algebras through the homomorphisms between them). We remark that from this fact we will get the invariance of the relation of satisfaction under signature change. Moreover, we prove that, for each signature morphism d from Σ to Λ, there exists a natural isomorphism θ ^d from the functor Tr^L °(Id ×d_à){{{\rm Tr}^{\bf {\bf \Lambda}} \circ ({\rm Id} \times {\bf d}_\diamond)}} to the functor Tr^S °(d^* ×Id){{\rm Tr}^{\bf \Sigma} \circ ({\bf d}^* \times {\rm Id})}, both from the category Alg(Λ) × Ter(Σ) to the category Set, where d* is the value at d of the arrow mapping of a contravariant functor Alg from Sig to Cat, that shows the invariant character of the procedure of realization of generalized terms under signature change. Finally, we construct the many-sorted term institution by combining adequately the above components (and, in a derived way, the many-sorted specification institution), but for a strict generalization of the standard notion of institution.     

Mobility of c dislocations in Ti3, Al

Abstract

The rôle of dislocations with Burgers vectors, b, given by b = [0001] during deformation of samples of the intermetallic compound Ti₃Al has been assessed. At room temperature, the experimental evidence is consistent with these dislocations being sessile, their density and morphology being similar to that in undeformed samples. In samples deformed at 650°C and above, it is concluded that motion of these dislocations is effected by dislocation climb. The line directions of the various segments of dislocations with b= [0001] are shown to be perpendicular to planes that contain sheets of Ti atoms, with an expected tendency to exhibit a high Peierls stress.     

Stability of the F2-(Al-Pd-Mn) phase

The stability of the F2-(Al-Pd-Mn) phase has been studied by in-situ neutron diffraction on a single quasicrystal with composition Al_69.8Pd_21.4Mn_8.8. We find that the F2 phase is not stable and corresponds to a transient state in the process of the transformation of the icosahedral phase to the F2_M phase. The icosahedral-to-F2_Mphase transition occurs at around 715^oC. In the F2 phase a large amount of diffuse scattering is located close to the icosahedral Bragg reflection in place of the S ₁ superstructure reflections characteristic of the F2_m phase.     

Intermediate logics with the same disjunctionless fragment as intuitionistic logic

Given an intermediate prepositional logic L, denote by L ^–d its disjuctionless fragment. We introduce an infinite sequence {J _n}_n1 of propositional formulas, and prove:(1)For any L: L ^–d =I ^–d (I=intuitionistic logic) if and only if J _n L for every n 1.Since it turns out that L{J _{n} n}1 = Ø for any L having the disjunction property, we obtain as a corollary that L ^–d = I ^–d for every L with d.p. (cf. open problem 7.19 of [5]). Algebraic semantic is used in the proof of the if part of (1). In the last section of the paper we provide a characterization in Kripke's semantic for the logics J _n =I+ +J _n (n 1).     

Near-infrared transitions of LiNdP4O12 and LiErYP4O12

Abstract

Fluorescence transitions in LiNdP₄O₁₂: ⁴ F_3/2→⁴I_9/2 (0·90μm), ⁴F_3/2→⁴I_11/2 (1·05μm), ⁴F_3/2→⁴I_13/2 (1·32μm), ⁴F_3/2→⁴I_15/2 (1·77μm), and in LiErYP₄O₁₂: ⁴S_3/2→⁴I_11/2 (1·3μm), ⁴I_13/2→⁴I_15/2 (1·53μm), have been obtained at room temperature. The positions of the energy levels related to the excitation, nonradiative and radiative processes have been established from complementary absorption measurements. The fluorescence lifetimes of the above-mentioned transitions have been determined from single exponential decays.     

The soft X-ray emission spectra of Zn,Ga and Ge

Abstract

The experimental L_α1,2 and L_β1 X-ray emission spectra of Zn, Ga and Ge are presented. The high-energy satellite structure of the lines is considered. It appears that the intensity of these satellites relative to the main lines is much larger for Zn than for Ga and Ge. This enhancement effect is interpreted as arising mainly from the 2p^?1 _1/2 → 2p^?1 _3/23d^?1 _3/2,5/2 Coster-Kronig transition occurring in metallic Zn, which is absent in the case of Ga and Ge. Furthermore, for all these elements it is suggested that a significant contribution to the high-energy satellites of the L_α1,2; X-ray emission band arises from the 2s^?1 _1/2 → 2p^?1 _3/23d^?1 _3/2,5/2 Coster-Kronig process, whereas in the case of the satellites of the L_β1 X-ray emission spectrum the main cause would be the 2s^?1 _1/2 → 2p^?1 _1/23d^?1 _3/2,5/2transition.     

A thermodynamic model for nanocrystallization in bulk metallic glasses

The structural complexity of glass-forming alloys, which generally contain more than three components, can lead by partial crystallization during annealing to a dispersion of nanocrystals in an amorphous matrix, giving the material a very high mechanical strength. In the present study, the evolution of the driving force for crystallization is expressed as a function of the composition and the chemical potentials of the components. Application to Zr₆₀Al₁₀Cu₃₀ and Zr₆₀Al₁₀Cu₂₀Pd₁₀ bulk metallic glasses shows that the first crystallization step leads to a metastable equilibrium between nanocrystals of an intermetallic and a percolating amorphous phase. The effects of the number of components and of chemical bonding on the fraction crystallized is analysed and discussed.     

Conduction-electron mediated 1H nuclear spin-lattice relaxation in Ti45Zr38Ni17H x icosahedral quasicrystals

Nuclear magnetic resonance spin-lattice relaxation rates for ¹H in quasicrystalline Ti₄₅Zr₃₈Ni₁₇H _x are presented as a function of temperature and hydrogen concentration x. The temperature dependence demonstrates that the relaxation is via interaction with conduction electrons. The relaxation rate is extremely sensitive to hydrogen content, with the rate changing by a factor of as much as two for samples that differ in x     

Approximant phases,phason planes and domain-boundary networks in Al−Ni−Rh alloys

Structurally complicated ξ′- and ξ-phases have been found, for the first time, in as-cast Al₇₃Ni₅Rh₂₂ and Al₇₅Ni₁₅Rh₁₀ alloys. The lattice parameters of these two phases were determined by means of electron diffraction and high-resolution transmission electron microscopy (HREM). These two phases have similar orthorhombic structures but with different lattice parameters of a?=?23.2?Å, b?=?16.4?Å, c?=?12.0?Å for the ξ′-phase and a?=?20.3?Å, b?=?16.4?Å, c?=?14.8?Å for the ξ-phase. A new two-dimensional domain-boundary network has also been observed in these two phases. Domain boundaries with normals closely parallel to the [001] direction are actually phason planes represented by a translation vector of r?=(1/2)a?+(1/2τ)c in the ξ′-phase and r=±(1/2τ²) a?+(τ/2)c in the ξ-phase, whereas the newly-found wide and zigzag boundaries perpendicular to the above set were attributed from the step-like boundary structures of domains related by a translation vector of r?=(1/τ)((1/2)a?+(1/2τ)c). The structural difference between the two types of planar faults is discussed.     

A linear conservative extension of Zermelo-Fraenkel set theory

In this paper, we develop the system LZF of set theory with the unrestricted comprehension in full linear logic and show that LZF is a conservative extension of ZF^– i.e., the Zermelo-Fraenkel set theory without the axiom of regularity. We formulate LZF as a sequent calculus with abstraction terms and prove the partial cut-elimination theorem for it. The cut-elimination result ensures the subterm property for those formulas which contain only terms corresponding to sets in ZF^–. This implies that LZF is a conservative extension of ZF^– and therefore the former is consistent relative to the latter. Hiroakira Ono     

Interpretation of the low-temperature photoconductivity in a-Si

Abstract

The paper is concerned with the interpretation of steady-state photoconductivity results on undoped a-Si at temperatures of 50K and below which lead to an essentially constant value of the (photogeneration efficiency x mobility x lifetime) product νμτ?10^?11 cm² V^?1. Measurements on p⁺-i-n⁺ junctions and Cr-i-n⁺ barriers were carried out to determine the above parameters separately: (i) steadystate reverse saturation currents gave a generation efficiency of ν? 5×10-² below 50K, suggesting that geminate recombination limits the generation process. (ii) the electron drift mobility μ_e through the tail states and the charge extracted from the absorption region of the incident light were investigated by transient experiments, these showed that μ_eτ_a is limited to about 3×10^?10cm²V^?1 at low T. The independent results account for the observed νμτ values and suggest that, contrary to the interpretation of Hoheisel, Carius and Fuhs (1984), the main contribution to the low-temperature photoconductivity arises from transport in tail states.     

Transmission electron microscopy of dislocations in SrTiO3

Dislocations have been introduced in SrTiO₃ by Vickers indentation at room temperature and analysed by transmission electron microscopy. The slip systems in SrTiO₃ were identified as ?110?-{110}. ?110? dislocations are dissociated into two partial dislocations. The stacking-fault energy γSF was determined to be 136 ± 15 mJm^-2.     

The temperature dependence of the optical dispersion parameters in Si and Ge

Abstract

In Si and Ge, the optical dispersion parameters (single-oscillator energy E_o , dispersion energy E_d and bond energy gap E_g developed by Wemple and DiDomenico, and Phillips) have been analysed in the temperature range 100-300 K using data obtained by Icenogle et al. E_o and E_g exhibit a very small temperature dependence in both materials. The thermal coefficients of the dispersion energy, dE_d/dT, have opposite signs (Si, –41·9 × 10^?4eVK^?1; Ge, +37·7 × 10^?4eVK^?1).     

Dislocation dissociation and stacking-fault energies in Ge1-xSix alloys

Dislocations in deformed Ge_1-xSi_x alloys in the whole range 0 < x < 1 have been investigated by means of weak-beam transmission electron microscopy. They are dissociated into Shockley partial dislocations bounding intrinsic stacking-faults. The intrinsic stacking-fault energy in the alloys decreases from 61 +/- 10 to 55 +/- 10 mJm^-2 with increasing Si content.     

Secondary-ion mass spectrometry of superconducting YBa2Cu3 O7 and insulating La2 CuO4 materials

Abstract

The superconducting compound YBa₂ Cu₃O₇ and the insulating material La₂CuO₄ have been examined using liquid-metal ion-induced secondary-ion mass spectrometry. The results revealed surface reactions with moisture as well as some contamination by hydrocarbons. These surface layers were readily sputtered away, but the apparent presence of yttrium, barium and lanthanum hydroxides could play a significant part in their surface conduction characteristics. The relative intensity of the sputtered ion MO⁺ was found to be a logarithmic function of its dissociation energy.     

Phason elastic constants of the icosahedral Al-Pd-Mn phase derived from diffuse scattering measurements

The diffuse scattering in the diffraction pattern of the icosahedral Al-Pd-Mn quasicrystalline phase has been measured on an absolute scale by X-ray and neutron scattering on single-grain samples. Most of the diffuse scattering can be interpreted in the framework of the elasticity theory of icosahedral quasicrystals considering only phason fluctuations. At room temperature the absolute values of the K₁/k_BT and K₂/k_B T phason elastic constants are of the order of 0.06 and 0.031atom^-1. The amount of diffuse scattering intensity is insensitive to the sample annealing treatment.