bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of Ge substitution in Ni2MnGa1–xGex Heusler alloys and films
Authors: Gościańska I. , Dubowik J. , Kudryavtsev Y. V. , Jezierski A.
Published: January 2006

We present the results on the effect of adding Ge on the magnetic properties of Ni2MnGa1–x Gex (0 < x < 0.4) alloys and thin films deposited by flash‐evaporation from the powdered alloys. It is found that the annealed alloys are single phase with L21 ordering (cubic lattice constant a ≃ 0.581 nm). The Ge addition causes a drastic decrease in the martensitic transformation temperature from T M = 200 K (x = 0) to T M = 50 K (x = 0.4) with almost no effect on the Curie temperature T C ≃ 380 K and magnetization M S (0) ≃ 450–500 G. The magnetic properties of thin films strongly depend on ordering. The ordered films have similar L21 (or B2) ordering and exhibit the magnetic properties similar to the properties of corresponding bulk alloys. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A 55Mn NMR study of the La0.75Sr0.25MnO3 nanoparticles
Authors: Rybicki D. , Sikora M. , Kapusta Cz. , Riedi P.C. , Jirak Z. , Knizek K. , Marysko M. , Pollert E. , Veverka P.
Published: January 2006

We report on a 55Mn NMR study of the La0.75Sr0.25MnO3 nanoparticles of the average grain size 33 nm and 114 nm at 4.2 K and 77 K and at applied field of 0, 0.2 and 0.5T. A dominant signal from the double exchange (DE) controlled metallic ferromagnetic interior of the grains as well as a small signal from insulating ferromagnetic regions is observed. From a comparison with bulk magnetization measurement the thickness of the nonferromagnetic outer layer of the grains and the amount of the ferromagnetic insulating phase was determined. The relative amount of these phases with respect to the ferromagnetic metallic phase increases with decreasing grain size. The DE line in the NMR spectrum shows a frequency shift with applied field according to a full 55Mn gyromagnetic ratio. A value of the demagnetizing field close to zero is obtained, which indicates a single domain state of the nanoparticles. For the sample with larger grains a higher NMR enhancement is observed, which indicates a higher magnetic susceptibility of the sample at the NMR frequencies. A comparison with the NMR data obtained on a microcrystalline material is made. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal expansion of RIn3 compounds with R=Pr,Gd and Lu
Authors: Sołyga M. , Czopnik A. , Pluznikov V. , Ulner J. , Durczewski K. , Kletowski Z.
Published: January 2006

Results of the linear thermal expansion coefficient α (T ) measurements for PrIn3, GdIn3 and LuIn3 are reported. These rare earth intermetallic compounds belong to a large family of RIn3 compounds which crystallize in AuCu3‐type crystal structure. The measurements were made on monocrystalline samples in temperature range 5K ÷ 200 K. The compounds under investigation differ in their magnetic properties: PrIn3 is a typical example of a singlet ground‐state paramagnet in which the interionic interactions are quenched by the crystalline electric field (CEF), whereas GdIn3 is the crystal‐field free antiferromagnet in which the interionic RKKY interactions play essential role and cause the antiferromagnetic structure which is still unknown. The results of the measurements for LuIn3 served as a non‐magnetic background for the separation of the contribution to α (T ) arising from the magnetic interaction. Theoretical considerations concerning the influence of CEF on the thermal expansion are remined. Pertinent Grüneisen parameters will be estimated in a forthcoming paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical properties of carbon doped EuB6
Authors: Bat'ková M. , Bat'ko I. , Mihalik M. , Konovalova E. S. , Shitsevalova N. , Paderno Y.
Published: January 2006

We report results of electrical resistivity and tunnelling spectroscopy studies of carbon doped EuB6 showing a colossal magnetoresistance effect. Performed tunnelling spectroscopy studies confirm a metallic‐like nature of the system. The electrical resistivity studies reveal, it is a spin‐disorder scattering that dominates in the temperature region 10.3–20 K and the magnetic phase transition temperature is T c = 4.1 K. Due to similarities of the temperature dependence of the resistivity with ones reported for stoichiometric and lanthanum substituted EuB6, the resistivity behavior in the intermediate temperature region is expected to be strongly influenced by the formation of magnetic polarons. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure of rare‐earth compounds TmGa3, ErGa3, and CeIn3 studied by positrons
Authors: Samsel‐Czekała M. , Kontrym‐Sznajd G. , Biasini M.
Published: January 2006

The electronic structure of the isostructural rare‐earth systems TmGa3, ErGa3, and CeIn3 has recently been investigated by measurements of two‐dimensional angular correlations of annihilation radiation (2D ACAR). We employ different tomography techniques to reconstruct electron‐positron (e‐p) momentum density ρ (p) from its line projections. In all these compounds we get very specific shape of ρ (p). In order to draw the Fermi surface (FS), we perform conversion from the extended p to reduced k space. In the case of TmGa3 and ErGa3 a nesting feature of the FS consistent with the antiferromagnetic structure is observed. On the other hand, in CeIn3 we cannot detect any link between the FS topology and the vector of the magnetic propagation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure calculations and electrical resistivity of Dy(Co1–xMx)2 (M = Ni, Cu)
Authors: Szajek A. , Kowalczyk A. , Ivanov V. , Falkowski M.
Published: January 2006

R(Co1–x Mx )2 (R = rare earth; M = transition metal) alloys exhibit interesting magnetic properties because of the differing nature of magnetism (localized and band) of their constituents. Results of measurements of the magnetic susceptibility, electrical resistivity of intermetallic compounds Dy(Co1–x Mx)2 (M = Ni, Cu) are presented. The effect of partial substitution of Co by M is reflected in a change of TC and in the temperature dependence of electrical resistivity. The ab initio calculations show that impurities reduce magnetic moments on Co atoms. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic and magnetic properties of cobalt between titanium layers – ab‐initio calculations
Authors: Jezierski A.
Published: January 2006

The influence of the local environment on the electronic and magnetic properties of Co atom between Ti layers is presented., using (i) a layer model and (ii) a chain model. The effect of surface on the electronic and magnetic properties of Co‐Ti system and the magnetic properties of the chain of the cobalt atoms between titanium layers is studied by ab‐initio LMTO method. The results indicate that the cobalt between titanium layers has a small magnetic moment. In the chain of cobalt atoms between titanium layers the magnetic moment of Co is strongly reduced near the titanium layer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic spectra and magnetic properties of RB6, RB12 and RB2C2 borides
Authors: Baranovskiy A. E. , Grechnev G. E. , Logosha A. V. , Svechkarev I. V. , Filippov V. B. , Shitsevalova N. Yu. , Żogał O. J. , Eriksson O.
Published: January 2006

The electronic structures of R B6, R B12 and R B2C2 borides are studied ab initio by using the full‐potential linear muffin‐tin orbital method. This study includes the promising materials for spin electronics with reported high temperature ferromagnetism, namely, doped divalent hexaborides CaB6, SrB6, BaB6, and the CaB2C2 compound, as well as Kondo semiconductors, SmB6 and YbB12. For CaB6 and SrB6 a semiconducting band structure has been obtained, whereas a semimetallic ground state is revealed for CaB2C2 and doped hexaborides. For YB6, LaB6, CaB2C2 and the semimetallic Ba1–x Lax B6 alloys we have performed spin‐polarized band structure calculations in an external field to evaluate the induced spin and orbital magnetic moments. These calculations indicate a feasibility of the field‐induced weak ferromagnetic phase in CaB2C2 and the La doped hexaborides. The LSDA and GGA calculations for different spin configurations of YbB12 point to a possibility of antiferromagnetic coupling between Yb3+ ions. For SmB6 and YbB12 our LSDA, GGA, and LSDA+U calculations have not revealed the hybridization gap for configurations with trivalent Sm3+ and Yb3+. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐principles electronic structure and magnetic properties of M/GaAs/M (001) heterostructures with M = Fe or Co
Authors: Vlaic P.
Published: January 2006

The electronic structure and magnetic properties of M/GaAs/M/ multilayer systems with M = Fe or Co have been studied by means of a first‐principles Green's function technique. The results show that the magnetic behaviour of interface Fe atoms is sensitive to the terminations of the GaAs semiconducting spacer. Thus, in case of Ga terminations the iron magnetic moment increases over its bulk value while for As terminations it remains almost unchanged. At the Co/GaAs interfaces the cobalt magnetic moment is reduced compared with corresponding bulk value and it seems to be less sensitive to the terminations. The exchange coupling between M magnetic slabs is also influenced by terminations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ab‐initio electronic structure calculations for Pr3Co13B2 and Pr5Co19B6 compounds
Authors: Szajek A.
Published: January 2006

Recently synthesized compounds Pr3Co13B2 and Pr5Co19B6 belong to the Rm+nCo5m+3nB2n family with (m = 2, n = 1) and (m = 2, n = 3), respectively. They are studied because of their possible use as permanent magnets. The electronic structure is investigated by the tight binding version of the linear muffin‐tin orbital method in the atomic sphere approximation (TB‐LMTO ASA). The cobalt atoms occupying distinct sites have different types and number of neighbouring atoms and as a consequence the magnetic moments are different. The calculated values are compared with the results of bulk measurements. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Superfluidity in condensed excitons below 20 K
Authors: Wachter P. , Bucher B.
Published: January 2006

In the condensed excitonic phase of intermediate valent TmSe0.45Te0.55 the heat conductivity and the thermal diffusivity have been obtained between 300 K and 1.5 K and between ambient pressure and 17 kbar (1.7 GPa), as a first experiment of its kind. Pressure and temperature are used to navigate in three different phases of the material, the intermediate valent semiconducting phase, the condensed excitonic phase and the intermediate valent metallic phase. In the condensed excitonic phase the heat conductivity λ increases strongly below about 20 K, suggesting a superfluid phase for the lowest temperatures. In a solid under equilibrium conditions this has never been seen before. Also the thermal diffusivity a strongly increases below 20 K, giving evidence for second sound. The quotient λ/ρa represents the specific heat, which thus can be calculated, for the first time as a function of pressure and for a large temperature range. When entering the condensed excitonic phase under pressure and from high temperatures (100 K–250 K), the Dulong‐Petit value of the specific heat drops precipitously to about half its value. Also this phenomenon is unprecedented. In addition the longitudinal sound velocity has been measured under pressure and as a function of temperature. Entering the excitonic phase the sound velocity drastically increases by about a factor two. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Monte Carlo study of the spinless Falicov‐Kimball model in the perturbative regime: preliminary results
Authors: Wojtkiewicz Jacek , Musiał Grzegorz , Dębski Lech
Published: January 2006

Finite‐temperature properties of the Falicov‐Kimball model on the square lattice have been studied in the perturbative regime, i.e. in the case: t = U ≪ 1, where t is the hopping constant and U denotes the Coulomb interaction strength. In our study, we have determined the phase diagram of the model in the second‐order of the perturbation theory, where the antiferromagnetic Ising model in the magnetic field emerges, and partially in the fourth‐order, where it constitutes the Ising model with more complicated frustrated antiferromagnetic interactions. The Monte Carlo method was employed, which proved its accuracy in recent analyses of other spin models, like Ashkin‐Teller model. To determine the type of ordering and phase boundaries, the behavior of Binder cumulants, based on the order parameters under consideration, was analyzed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron‐quasiparticle interaction in van Heusler alloy Cu2MnAl
Authors: Pristáš G. , Reiffers M. , Šebek J. , Šantavá E. , Courtois P. , Andersen K.H. , Hamelin B.
Published: January 2006

Electron‐quasiparticle interaction in single crystal van Heusler ferromagnetic alloy Cu2MnAl (TC = 630 K) has been studied. The temperature dependence of the electrical resistivity ρ (T ) shows normal metallic behaviour with a shoulder at T ≈ 10 K. Point‐contact measurements were carried out at the temperature 4.2 K and in magnetic fields up to 1 T. d 2V/dI 2 (eV ) dependences in spectroscopic regime show the characteristic energies of the electron‐quasiparticle interaction in Cu2MnAl. Moreover, an asymmetric behaviour of dV/dI (eV ) has been detected. The observed behaviour is probably due to partial spin polarisation at the Fermi energy or thermopower effect. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Imaging magnetic microstructures with the use of electrons
Authors: Szmaja Witold , Balcerski Józef , Makita Ken
Published: January 2006

The paper presents investigations of magnetic microstructures by techniques which make use of electrons. In this context, we refer to the examples of magnetic microstructure images of cobalt monocrystals, Nd–Fe–B permanent magnet and a thin permalloy film, while the methods used are the type‐I magnetic contrast technique of scanning electron microscopy (SEM), the colloid‐SEM method and the Fresnel mode of transmission electron microscopy (TEM). It is shown that the SEM type‐I magnetic contrast and the colloid‐SEM method have quite different probing depths and consequently provide useful complementary information on the magnetic microstructure at the surface of bulk materials which exhibit an out‐of‐plane component of magnetization. It is also demonstrated that TEM is a powerful tool for investigating the magnetic microstructure of thin magnetic films. Some improvements over previous results are presented. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and magnetic anisotropy evolution in Au/Co/Au sandwiches upon thermal treatment
Authors: Wawro A. , Kurant Z. , Baczewski L.T. , Pankowski P. , Pełka J.B. , Maneikis A. , Bójko A. , Zablotskii V. , Maziewski A.
Published: January 2006

The correlation between structural and magnetic properties of Au(111)/Co(0001)/Au(111) sandwiches with perpendicular magnetic anisotropy, grown by molecular beam epitaxy, has been studied in details. Thermal treatment in the range between room temperature and 300 °C at various stages of samples growth process as well as after its completion is applied as a factor modifying the structure of studied specimens. Annealing at 150 °C does not affect substantially either crystalline structure or perpendicular magnetic anisotropy. At 250 °C the RHEED pattern of Co layers reveals the loss of the lattice coherence with Au underlayer and the analysis of synchrotron radiation reflectometry leads to the conclusion that the continuity of Co layers is lost. Structural evolution upon thermal treatment is well correlated with changes of magnetic anisotropy studied by magnetooptical Kerr effect. After annealing at 250 °C magnetization switches from out‐of‐plane to in‐plane orientation, which is explained in terms of interfacial and magnetoelastic contributions to the sample magnetic anisotropy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
[Ni(Prixa)2 (pyr)]n – Low‐dimensional S = 1 Heisenberg magnet
Authors: Orendáčová A. , Zorkovská A. , Park J.‐H. , Orendáč M. , Trávníček Z. , Feher A. , Meisel M. W.
Published: January 2006

[Ni(Prixa)2(pyr)]n was previously identified as a S = 1 Heisenberg chain with intrachain interaction J /k B ≅ –2.7 K and subcritical single‐ion anisotropy D. Specific heat measurements conducted from 100 mK to 9 K in zero magnetic field revealed the presence of a λ‐like anomaly at T c = 2.2 K, which can be associated with a phase transition to the ordered state. Magnetic entropy removed above T c indicates a low‐dimensional character of the magnetic system. Observed deviations between the specific heat data and predictions from a S = 1 Heisenberg chain model with various D /J ratios can be ascribed to the presence of additional exchange coupling mediated by a set of hydrogen bonds. These interactions together with the intrachain coupling potentially form a two‐dimensional distorted triangular S = 1 Heisenberg lattice which might approximate magnetic behaviour above T c. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of non‐stoichiometric U1+xNi1+yAl compounds
Authors: Zentko A. , Kováč J. , Kavečanský V. , Maťaš S. , Mihalik M. , Zentková M. , Svoboda P.
Published: January 2006

We have studied the magnetic and electrical properties of non‐stoichiometric U1+x Ni1+y Al compounds. It has been shown that both the positive and negative deviations from the stoichiometry lead to suppression of magnetically ordered state, to the broadening of the phase transition and to the occurrence of a region with high degree of short range magnetic ordering between 20 K and 50 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and magnetic properties of Sm‐Ni‐Cu compounds after mechanical treatment
Authors: Szlaferek A. , Andrzejewski B. , Toliński T. , Kowalczyk A.
Published: January 2006

We have investigated the influence of mechanical alloying on structural changes and magnetic properties of the SmNi4Cu compound. This compound crystallizes in the hexagonal structure of CaCu5, space group P6/mmm. SmNi4Cu is ferromagnetic with the Curie temperature of 34 K and the saturation magnetic moment of 0.36 µ B at 4.2 K. The decrease of intensity and broadening of the diffraction lines have been detected after milling as a consequence of the grains' size reduction. The analysis of the as‐prepared sample using EDAX has revealed a stable composition without a presence of any additional phases and elements. The obtained results show that the magnetic properties significantly depend on the milling time. The temperature and magnetic field dependences of the magnetization exhibit a presence of antiferromagnetic‐like behavior of the milled samples. The transition temperature does not vary as a function of the milling time. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The RKKY interaction in the presence of an external magnetic field
Authors: Balcerzak T.
Published: January 2006

The Ruderman‐Kittel‐Kasuya‐Yosida (RKKY) interaction has been extended to the case when an external magnetic field is taken into account. It has been shown that the RKKY Hamiltonian should contain the Zeeman‐like term in which the effective gyromagnetic factor occurs. This effective gyromagnetic factor contains a correction term which is linearly dependent on the contact potential between the localized spins and conduction electrons. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the short range order (SRO) on electrical resistivity of magnetic alloys
Authors: Lipowczan M. , Borgieł W. , Stysiak D.
Published: January 2006

The model of the magnetic binary alloy which contains interacting itinerant electrons and localized spins was considered. The interaction between both kinds of electrons was assumed in the simple local exchange form. The complicated many body problem was reduced to the one particle one with the help of Coherent Potential Approximation (CPA ). Itinerant electron selfenergy was calculated using standard Green's function technique with taking into account short range order (SRO ) within the localized spin system. Electron's states were strongly affected by the correlations (SRO , when T > T C) within localized moments system. The DC electrical conductivity σ in the paramagnetic region expressed by Kubo‐Grennwood alloy formula was calculated. The resistivity ρ = 1/σ and its derivative over the temperature have the structure near T C, which depends on the number of the electrons in the band and the interaction strength between two subsystems. The quantities ρ , $ { {\partial \rho} \over {\partial T} }$ were not constant vs. temperature as it is in the simple models. The influence of the important model parameters on the DC conductivity was also discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deviation from Matthiessen rule in magnetic disordered alloys–theoretical investigation
Authors: Stysiak D. , Borgieł W. , Deniszczyk J.
Published: January 2006

The model of the magnetic disordered alloys, including the itinerant electrons, localized spins and phonons, was elaborated in details in the paramagnetic region with the use of the Coherent Potential Approximation (CPA) approach. The expression for the DC electrical conductivity was taken from the Kubo‐Greenwood formula for an alloys. The separate (residual, phonon and magnetic) contributions to the resistivity for the temperatures above Curie transition temperature, different sets of the model parameters were calculated. The linear temperature dependence of the phonon contribution to the resistivity was reproduced except from the anomalous behavior observed for the parameters sets for which the Fermi level locates near the band's edges. For the same parameters sets our calculations showed the largest percentage deviations from the Matthiessen's rule. Our model calculations confirmed the Matthiessen's rule generalized to the case of the three, residual, phonon and magnetic contributions to the resistivity of the magnetic disordered alloys with the partially filled band when the Fermi level locates far from the bands edges. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quasi‐one‐dimensional S = 1/2 magnet Pb[Cu(SO4)(OH)2]: frustration due to competing in‐chain exchange
Authors: Baran M. , Jedrzejczak A. , Szymczak H. , Maltsev V. , Kamieniarz G. , Szukowski G. , Loison C. , Ormeci A. , Drechsler S.‐L. , Rosner H.
Published: January 2006

Zero‐field susceptibility and specific heat of Pb[Cu(SO4)(OH)2] (linarite) single crystal were measured. In order to verify that linarite is a quasi‐one‐dimensional system with competing nearest‐neighbour and next‐nearest‐neighbour in‐chain exchange interaction (J1 ≈ –30 K, J2 ≈ 15 K), theoretical results based on electronic structure calculations within the LDA and a phenomenological modelling using the finite‐temperature transfer‐matrix method are taken into account. The possibility of various ground states is discussed in terms of the screened onsite repulsion U s: commensurate Neel or spin‐Peierls phases versus incommensurate spiral states with acute or obtuse pitch angles. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New spin configurations in nano‐sized magnets near reorientation phase transition
Authors: Kisielewski M. , Maziewski A. , Zablotskii V.
Published: January 2006

The cover picture of this issue of physica status solidi (c) has been taken from the article [1].
On the performance of turbo equalization for precoded ISI channels
Authors: Ghrayeb Ali , El‐Tarhuni Mohamed
Published: January 2006

In this paper, we present a semi‐analytical approach for analyzing the serial concatenation (SCC) of a high rate convolutional code and a precoded intersymbol interference (ISI) channel. The significance of the proposed approach is that it can be used to identify, for a given outer high rate code and fixed ISI channel, the precoder that results in the lowest error rate floor. In estimating the bit error performance in the floor region, we use analytical techniques developed for trellis codes to compute the overall system minimum squared Euclidean distance, and then use a semi‐analytical approach to find the corresponding multiplicity. We also demonstrate via simulations that the proposed technique may be extended to fading ISI channels with favorable results. We give examples that support our analysis. Copyright © 2006 John Wiley & Sons, Ltd.
Two Interpretations of the Discrimination Parameter
Authors: Tuerlinckx Francis , Boeck Paul De
Published: January 2006

In this paper we propose two interpretations for the discrimination parameter in the two-parameter logistic model (2PLM). The interpretations are based on the relation between the 2PLM and two stochastic models. In the first interpretation, the 2PLM is linked to a diffusion model so that the probability of absorption equals the 2PLM. The discrimination parameter is the distance between the two absorbing boundaries and therefore the amount of information that has to be collected before a response to an item can be given. For the second interpretation, the 2PLM is connected to a specific type of race model. In the race model, the discrimination parameter is inversely related to the dependency of the information used in the decision process. Extended versions of both models with person-to-person variability in the difficulty parameter are considered. When fitted to a data set, it is shown that a generalization of the race model that allows for dependency between choices and response times (RTs) is the best-fitting model.
Comparing Latent Structures of the Grade of Membership, Rasch, and Latent Class Models
Authors: Erosheva Elena A.
Published: January 2006

This paper focuses on model interpretation issues and employs a geometric approach to compare the potential value of using the Grade of Membership (GoM) model in representing population heterogeneity. We consider population heterogeneity manifolds generated by letting subject specific parameters vary over their natural range, while keeping other population parameters fixed, in the marginal space (based on marginal probabilities) and in the full parameter space (based on cell probabilities). The case of a 2 × 2 contingency table is discussed in detail, and a generalization to 2J tables with J ≥ 3 is sketched. Our approach highlights the main distinction between the GoM model and the probabilistic mixture of classes by demonstrating geometrically the difference between the concepts of partial and probabilistic memberships. By using the geometric approach we show that, in special cases, the GoM model can be thought of as being similar to an item response theory (IRT) model in representing population heterogeneity. Finally, we show that the GoM item parameters can provide quantities analogous to more general logistic IRT item parameters. As a latent structure model, the GoM model might be considered a useful alternative for a data analysis when both classes of extreme responses, and additional heterogeneity that cannot be captured by those latent classes, are expected in the population.
Probabilistic Subset Conjunction
Authors: Kohli Rajeev , Jedidi Kamel
Published: January 2006

The authors introduce subset conjunction as a classification rule by which an acceptable alternative must satisfy some minimum number of criteria. The rule subsumes conjunctive and disjunctive decision strategies as special cases.

Subset conjunction can be represented in a binary-response model, for example, in a logistic regression, using only main effects or only interaction effects. This results in a confounding of the main and interaction effects when there is little or no response error. With greater response error, a logistic regression, even if it gives a good fit to data, can produce parameter estimates that do not reflect the underlying decision process. The authors propose a model in which the binary classification of alternatives into acceptable/unacceptable categories is based on a probabilistic implementation of a subset-conjunctive process. The satisfaction of decision criteria biases the odds toward one outcome or the other. The authors then describe a two-stage choice model in which a (possibly large) set of alternatives is first reduced using a subset-conjunctive rule, after which an alternative is selected from this reduced set of items. They describe methods for estimating the unobserved consideration probabilities from classification and choice data, and illustrate the use of the models for cancer diagnosis and consumer choice. They report the results of simulations investigating estimation accuracy, incidence of local optima, and model fit.
Application of Sequential Interval Estimation to Adaptive Mastery Testing
Authors: Chang Yuan-chin Ivan
Published: January 2006

In this paper, we apply sequential one-sided confidence interval estimation procedures with β-protection to adaptive mastery testing. The procedures of fixed-width and fixed proportional accuracy confidence interval estimation can be viewed as extensions of one-sided confidence interval procedures. It can be shown that the adaptive mastery testing procedure based on a one-sided confidence interval with β-protection is more efficient in terms of test length than a testing procedure based on a two-sided/fixed-width confidence interval. Some simulation studies applying the one-sided confidence interval procedure and its extensions mentioned above to adaptive mastery testing are conducted. For the purpose of comparison, we also have a numerical study of adaptive mastery testing based on Wald's sequential probability ratio test. The comparison of their performances is based on the correct classification probability, averages of test length, as well as the width of the “indifference regions.” From these empirical results, we found that applying the one-sided confidence interval procedure to adaptive mastery testing is very promising.
Clinical trials update from the American Heart Association: REPAIR‐AMI, ASTAMI, JELIS, MEGA, REVIVE‐II, SURVIVE, and PROACTIVE
Authors: Cleland John G.F. , Freemantle Nick , Coletta Alison P. , Clark Andrew L.
Published: December 2005

This article provides information and a commentary on trials presented at the American Heart Association meeting held in November 2005, relevant to the pathophysiology, prevention and treatment of heart failure. All reports should be considered as preliminary data, as analyses may change in the final publication. In REPAIR‐AMI an improvement in ejection fraction was observed in post‐MI patients following infusion of bone marrow stem cells. However, the ASTAMI study showed no benefit of stem cell implantation in a similar patient cohort. The JELIS study reported a reduction in major coronary events in patients receiving statins plus fish oil compared to statins alone. MEGA showed that low dose statins in a low risk population reduce the incidence of major cardiovascular events. Two studies of levosimendan in acute heart failure gave conflicting results, in the REVIVE‐II study levosimendan was reported to have a superior effect on the composite primary outcome compared to placebo, however, in SURVIVE despite a trend to early benefit with levosimendan, there was no difference in effect on long‐term outcome versus dobutamine. The PROACTIVE study showed encouraging results for the use of pioglitazone in post‐myocardial infarction patients with concomitant type 2 diabetes.
Dressing up for the deep: agglutinated protists adorn an irregular urchin
Authors: Levin Lisa A. , Gooday Andrew J. , James David W.
Published: January 2006

A specimen of the deep-water, spatangoid urchin, Cystochinus loveni, wearing a costume of agglutinated protists, was collected from 3088 m in the Gulf of Alaska, north-east Pacific. Over 24 putative taxa of living and dead foraminiferans and xenophyophores, as well as a sipunculan, polychaete, tanaid, and two isopods, were collected from the dorsal surface of this single individual. This is the first report of a deep-sea urchin using rhizopod protists and it is proposed that the urchin acquires camouflage or benefits from increased specific gravity associated with the protistan cloak.
ASSOCIATIONS BETWEEN OBSESSIVE-COMPULSIVE PHENOMENA, AFFECT AND BELIEFS: CROSS-CULTURAL COMPARISONS OF AUSTRALIAN AND ITALIAN DATA
Authors: Kyrios Michael , Sanavio Ezio , Bhar Sunil , Liguori Lia
Published: January 2006

Consistent with cognitive-behavioural formulations of Obsessive-Compulsive Disorder (OCD), recent
research has supported the association between obsessive-compulsive phenomena, specific dysfunctional beliefs and
negative affective states. However, such research has not been conducted across sufficiently different cultural contexts
using the same measures in comparable samples. In the present study, university psychology students from Australia and Italy completed questionnaire measures of obsessive-compulsive phenomena, inflated responsibility, perfectionism, guilt, depression, and anxiety. Australian and Italian cultures can be seen to differ in a number of ways that could impact on the pattern of expected interrelations between these measures. Similarities in the factor structure and psychometric properties of the measures were apparent across the two cultural contexts, suggesting the appropriateness of cross-cultural comparisons in the pattern of intercorrelations. Significant interrelations were found between the measure of obsessive-compulsive phenomena, dysfunctional beliefs and negative affect in both cultural contexts. While there were some differences in the specific patterns of interrelations, these were few in number and, generally, could be explained by sociocultural factors or stereotypes, although the overall pattern of intercorrelations was stronger for the Australian cohort. The results suggest that cognitive-behavioural formulations of OCD can be generalized across these two different cultural contexts, although idiosyncratic cultural factors may need to be considered in developing cognitive-behavioural treatments.
THE REVISED COGNITIVE THERAPY SCALE (CTS-R): PSYCHOMETRIC PROPERTIES
Authors: Blackburn Ivy-Marie , James Ian A. , Milne Derek L. , Baker Chris , Standart Sally , Garland Anne , Reichelt F. Katharina
Published: January 2006

The existing scale for assessing competence in cognitive therapy (CTS) dates from 1988 and only the
previous version of 1980 has been validated to any extent. A revised version, the CTS-R, was devised to improve on
the CTS by: eliminating overlap between items, improving on the scaling system, and defining items more clearly.
Kolb's well-known educational model was used as a guideline. In the new 14-item scale, three new items measure
general therapeutic flair, the facilitation of emotional expression, and therapist's non-verbal behaviours (optional). We hypothesized that the CTS-R would prove more user friendly and demonstrate satisfactory reliability and validity. Twenty-one mental health professionals undergoing training in cognitive therapy provided 102 video-tapes of therapy
with 34 patients, reflecting three stages of therapy. The tapes were rated by four expert raters, in a balanced design.
The CTS-R showed high internal consistency and adequate average inter-rater reliability. Reliability for individual
items varied widely among pairs of raters. Validity was demonstrated by improved ratings of competence for trainees
who saw patients early and later during the course of training. Although raters found the CTS-R a more useful tool
than the CTS and satisfactory reliability and validity were demonstrated, more refinement is needed in item definition.
The study has led to modifications in the CTS-R, which are in the process of evaluation.
“Letztes Halbjahr stand ich zwei”
Authors: Dickhäuser Oliver , Plenter Insa
Published: January 2006

Zusammenfassung: Pädagogisch-psychologische Studien verwenden oft die von Schülern selbst berichteten Noten als Leistungsindikatoren. In der vorliegenden Studie wurde die Akkuratheit dieser Selbstangaben überprüft, indem selbst berichtete Mathematiknoten der letzten Klassenarbeit und des letzten Zeugnisses mit den Lehrerangaben verglichen wurden. Es zeigen sich hohe Korrelationen, allerdings wurden die Noten im Mittel überschätzt. Die Akkuratheit der Selbsteinschätzung ist praktisch unabhängig von Geschlecht, mathematischem Fähigkeitsselbstkonzept und mathematischer Leistung (erfasst über Items aus dem TIMSS-Instrumentarium).
Wissenschafts-Praxis-Forum
Authors: Brandstätter Hermann , Riedl Johannes
Published: January 2006

Zusammenfassung. Es wird über die Bewährung eines Auswahlverfahrens für Schulleiter/innen berichtet, das seit Mitte der 90er-Jahre vom Landesschulrat für Oberösterreich angewendet wird. Berufsrelevante biographischen Daten, Beurteilungen in einem Hearing vor den Lehrern und den Elternvertretern der Schule, AC-Beurteilungen und Persönlichkeitsscores wurden zu einer Eignungspunktezahl als Entscheidungskriterium verrechnet. Verschiedene Aspekte der beruflichen Bewährung wurden zwei bis vier Jahre später von den zuständigen Schulinspektoren, den Lehrern der betroffenen Schule, den Elternvertretern und den Schuldirektoren selbst beurteilt. Eine Summe aus optimal gewichteten Punktwerten von Biographie, Hearing, AC und Persönlichkeit (Normgebundenheit, Belastbarkeit und Extraversion) erreicht eine Validität von R = .40 (R = .54 nach Korrektur des Ausleseeffekts), wobei der AC-Beurteilung und den Persönlichkeitsskalen neben berufsbiographischen Daten und Hearingbeurteilungen eine signifikante zusätzliche Validität zukommt.
Psychologie im Beruf
Authors: Stock Armin
Published: January 2006

Zusammenfassung. Erkenntnisse über die berufliche Bedeutung von Lehrinhalten des Psychologiestudiums sind in Zeiten einer erhöhten Akademikerarbeitslosigkeit sowie anstehender Umstrukturierungen der Hochschulen im Rahmen des Bologna-Prozesses von hohem Interesse. In einer deutschlandweiten E-Mail-Befragung konnten insgesamt 50 Firmen und Verwaltungen dafür gewonnen werden, Auskunft über verschiedene Aspekte ihrer Personalauswahl zu geben sowie unterschiedliche, vorwiegend arbeits- und organisationspsychologische, aber auch allgemeine Kompetenzen hinsichtlich ihrer Wichtigkeit für die Arbeit im Unternehmen zu beurteilen. Die Ergebnisse zeigen unter anderem, dass ein Großteil der Fachkenntnisse in der Arbeits- und Organisationspsychologie vom Arbeitsmarkt positiv aufgenommen werden. Je nachdem, ob man Wirtschaftsunternehmen oder Verwaltungen betrachtet, ist es möglich, die Berufschancen durch den Nachweis bestimmter Qualifikationen zusätzlich zu erhöhen. Die durch diese Studie erworbenen Arbeitsmarktkenntnisse können auch zur Entscheidungshilfe bei der Konzeption künftiger Bachelor- und Masterstudiengänge dienen.
Neuronale Netze: Nichtlineare Methoden der statistischen Urteilsbildung in der psychologischen Eignungsdiagnostik
Authors: Häusler Joachim , Sommer Markus
Published: January 2006

Zusammenfassung. Künstliche Neuronale Netze stellen eine innovative und attraktive Form der statistischen Urteilsbildung dar, da sie im Gegensatz zu herkömmlichen Methoden auch nichtlineare Zusammenhänge modellieren können, ohne dass diese a priori bekannt sein müssen. In der vorliegenden Arbeit soll die Annahme, dass durch explorative, nichtlineare Modellierung die Validität der Vorhersage verbessert werden kann, anhand eines Methodenvergleichs zwischen linearen und nichtlinearen Methoden der statistischen Urteilsbildung überprüft werden. Hierzu wurde eine Reanalyse der Daten von Schmidt-Atzert, Deter und Jaeckel (2004 ) durchgeführt. Das Künstliche Neuronale Netz erweist sich dabei im Vergleich zu linearen Methoden wie der Diskriminanzanalyse mit Validitäten von R = 0.645 für den theoretischen Teil und R = 0.586 für die praktischen Teil der Lehrabschlussprüfung als leistungsfähiger bei der Vorhersage der beiden Indikatoren des Ausbildungserfolgs. Gleichzeitig konnte die Befürchtung, Künstliche Neuronale Netze führten zwangsläufig zu einer Überanpassung an die vorliegenden Daten, entkräftet werden. Die Ergebnisse bleiben sowohl nach der Jackknife-Validierung als auch in einer internen Bootstrap-Validierung stabil. Die Vorhersage mittels nichtlinearer Klassifikationsmethoden erweist sich daher als nützlicher Fortschritt in der psychologischen Eignungsdiagnostik, sodass eine generelle Methodologie zum Umgang mit auf Künstlichen Neuronalen Netzen basierenden diagnostischen Expertensystemen abgeleitet werden kann.
Response of the ITCZ to Northern Hemisphere cooling
Authors: Broccoli Anthony J. , Dahl Kristina A. , Stouffer Ronald J.
Published: January 2006

Climate simulations, using models with different levels of complexity, indicate that the north‐south position of the intertropical convergence zone (ITCZ) responds to changes in interhemispheric temperature contrast. Paleoclimate data on a variety of timescales suggest a similar behavior, with southward displacements of the ITCZ and associated changes in tropical atmospheric circulation during cold periods in the Northern Hemisphere. To identify a mechanism by which ITCZ displacements can be forced from the extratropics, we use a climate model with idealized geography and a simple slab ocean. We cool the northern extratropics and warm the southern extratropics to represent the asymmetric temperature changes associated with glacial‐interglacial and millennial‐scale climate variability. A southward shift in the ITCZ occurs, along with changes in the trade winds and an asymmetric response of the Hadley circulation. Changes in atmospheric heat exchange between the tropics and midlatitudes are the likely cause of this response, suggesting that this mechanism may play an important role in ITCZ displacements on timescales from decadal to glacial‐interglacial.
The importance of atmospheric precipitation in storm‐time relativistic electron flux drop outs
Authors: Clilverd Mark A. , Rodger Craig J. , Ulich Thomas
Published: January 2006

During the sudden decrease of geosynchronous electron flux (>2 MeV) of 17:10–17:20 UT, January 21, 2005 large‐scale precipitation into the atmosphere was observed. Estimates from ground‐based radio propagation experiments at L∼5 in the Northern and Southern hemispheres suggest that the atmospheric precipitation was less than 1/10 of the flux apparently lost during this 10 minute period. However, continuing precipitation losses from 4 < L < 6, observed for the next 2.7 hours, provides about 1/2 of the total relativistic electron content lost.
Simulation and inversion of borehole temperature profiles in surrogate climates: Spatial distribution and surface coupling
Authors: González‐Rouco J. F. , Beltrami H. , Zorita E. , von Storch H.
Published: January 2006

A heat‐conduction forward model driven by ground surface temperature from three 1000‐year climate simulations with the state‐of‐the‐art ECHO‐g model has been used to simulate underground temperature perturbation profiles. An inversion approach has been applied to reconstruct ground surface temperature histories from the simulated profiles and to compare them with the climate model temperatures. Results support the skill of borehole inversion methods to retrieve long‐term temperature trends, and the robustness of using the present‐day borehole network for reconstructing SAT variations.
Thermodynamic structure of collision‐dominated expanding plasma: Heating of interplanetary coronal mass ejections
Authors: Liu Y. , Richardson J. D. , Belcher J. W. , Kasper J. C. , Elliott H. A.
Published: January 2006

We investigate the thermodynamic structure of interplanetary coronal mass ejections (ICMEs) using combined surveys of the ejecta between 0.3 and 20 AU. ICMEs are shown to have a moderate expansion in the solar wind compared with theoretical predictions. The expansion seems to be governed by a polytrope with γ ∼ 1.3 in this distance range. We find that Coulomb collisions are important contributors to the ion‐ion equilibration process in the ICME plasma. The alpha‐proton differential speed quickly drops to below 10 km s−1 due to strong Coulomb collisions. However, the two species of particles are far from thermal equilibrium with a temperature ratio Tα/Tp = 4–6, suggestive of a preferential heating of alpha particles. The plasma heating rate as a function of heliocentric distance required for the temperature profile is deduced by taking into account the expansion and energy transfer between protons and alphas via Coulomb collisions. The turbulence dissipation rate is also inferred from the inertial range power spectrum of magnetic fluctuations within ICMEs. Comparison of the turbulence dissipation rate with the required heating rate shows that turbulence dissipation seems sufficient to explain the ICME heating. Sources powering the turbulence are also investigated by examining the instabilities induced by temperature anisotropies and energy deposition by pickup ions.
Paleoseismologic investigation of the fault rupture of the 14 April 1928 Chirpan earthquake (M 6.8), southern Bulgaria
Authors: Vanneste K. , Radulov A. , De Martini P. , Nikolov G. , Petermans T. , Verbeeck K. , Camelbeeck T. , Pantosti D. , Dimitrov D. , Shanov S.
Published: January 2006

Seventy‐five years after the destructive Chirpan earthquake of 14 April 1928, we conducted a paleoseismologic study of the causative fault combining a review of contemporary literature, geomorphology, geophysical prospecting, and trenching. We reidentified the fault scarp in the field, and mapped it over a distance of 12.5 km. Geophysical profiles and boreholes demonstrate that Chirpan scarp is the surface expression of a normal fault that was active throughout the Pleistocene and Holocene. In 2002, we excavated a paleoseismologic trench to study the faulting history. A narrow fault zone separates Plio‐Pleistocene alluvial sand in the footwall from Holocene alluvial and colluvial silt in the hanging wall. The 1928 earthquake is recorded by 0.45 m vertical offset of the topsoil, in accordance with contemporary descriptions. We identified three colluvial wedge‐like units in the hanging wall sediments next to the fault, evidencing at least three surface‐rupturing paleoearthquakes since the Atlantic. Their timing could only be loosely constrained using pollen. The penultimate event had an offset of 0.40–0.45 m and occurred after circa 2600 calibrated years before present (cal years B.P.). Event 3 displaced a Subboreal semiarid calcic soil 0.55–0.70 m between circa 5750 and 2600 cal years B.P. The fourth event had a minimal offset of 0.50–0.70 m and occurred between circa 8900 cal years B.P. and 4900 B.C., when the region was first settled. We obtain a Holocene fault slip rate of 0.22 ± 0.12 mm/yr and an average recurrence interval of 2350 ± 643 years for earthquakes comparable to or larger than the 1928 event.