Dimensionality Of Structure Research Articles

Bis(benzimidazole)-based ligands-directed the various dimensionality of metal–organic complexes based on carboxylates co-ligands: Syntheses, structures and properties

Four new metal–organic complexes [Co2(bbix)4(2,6-pdc)2]·4H2O (1), [Co(bbbm)1.5(2,6-pdc)]·2H2O (2), [Ni(bbmmb)2(dnba)2(H2O)2] (3) and [Ni(bbbm)1.5(dnba)2(H2O)]·(0.5bbbm)(H2O) (4) (bbix=1,4-bis(benzimidazol-1-ylmethyl)benzene, bbbm=1,1′-(1,4-butanediyl)bis-1H-benzimidazole, bbmmb=4,4′-bis(benzimidazol-1-ylmethyl)biphenyl, 2,6-H2pdc=2,6-pyridinedicarboxylic acid and Hdnba=3,5-dinitrobenzoic acid) constructed from bis(benzimidazole)-based ligands with different flexibility and organic carboxylates co-ligands have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction analysis. Complex 1 possesses a binuclear Co2(bbix)2 ring. The adjacent binuclear units are packed into a one-dimensional (1D) supramolecular chain through very weak π–π stacking interactions. Complex 2 shows a two-dimensional (2D) 3-connected (63) topology connected by the flexible bbbm ligands. Complex 3 features a discrete mononuclear structure. The adjacent mononuclear units are linked by the H-bond interactions to form a 1D supramolecular chain. Complex 4 exhibits a 1D infinite chain formed by the Ni2(bbbm)2 rectangular macrocycles and bbbm ligands. The results clearly reveal that the flexibility of bis(benzimidazole)-based ligands have a great influence on the dimensionality and final structures of 1–4. The electrochemical and fluorescence properties for 1–4 have been investigated.

Particle coordinates and discrete molecular description: a geometric point of view on a twofold dimensionality environment

In the present study a specific kind of widespread mathematical objects: descriptor matrices are defined and studied. These are matrices connected with several problems concerning many fields of interest in theoretical chemistry, classical and quantum mechanics, or quantitative structure-properties relations. The twofold dimensionality structure of descriptor matrices is analyzed and the properties of descriptor matrices are also disclosed with respect origin shifts and rotations. A tensor to study schematically the three dimensional nature of many particle structures, the characteristic form tensor is defined. The construction of similarity matrices from descriptor matrices and the connection with quantum similarity are finally discussed.

Methodological artifacts in dimensionality assessment of the Hospital Anxiety and Depression Scale (HADS)

ObjectiveThe Hospital Anxiety and Depression Scale (HADS) is a brief, self-administered questionnaire for the assessment of anxiety and depression in hospital patients. A recent review [7] discussed the disagreement among different studies with respect to the dimensionality of the HADS, leading Coyne and Van Sonderen [8] to conclude from this disagreement that the HADS must be abandoned. Our study argues that the disagreement is mainly due to a methodological artifact, and that the HADS needs revision rather than abandonment. MethodWe used Mokken scale analysis (MSA) to investigate the dimensionality of the HADS items in a representative sample from the Dutch non-clinical population (N=3643) and compared the dimensionality structure with the results that Emons, Sijtsma, and Pedersen [11] obtained in a Dutch cardiac-patient sample. ResultsWe demonstrated how MSA can retrieve either one scale, two subscales, or three subscales, and that the result not only depends on the data structure but also on choices that the researcher makes. Two 5-item HADS scales for anxiety and depression seemed adequate. Four HADS items constituted a weak scale and contributed little to reliable measurement. ConclusionsWe argued that several psychometric methods show only one level of a hierarchical dimensionality structure and that users of psychometric methods are often unaware of this phenomenon and miss information about other levels. In addition, we argued that a theory about the attribute may guide the researcher but that well-tested theories are often absent.

Exploring the organisational culture construct for small and medium enterprises in the ecotourism of emerging economies

Considerable research is being conducted to examine the culture of the resort operators to ensure that they are adhering to good practices for protecting the environment. Undoubtedly, it is essential for the effective and effi cient operation of the tourism industry that the ecotourism businesses engage in the wise usage and properly run management of the natural environment. However, little attention has been given to the development and the validation of the instruments used to conceptualise organisational cultures in the context of ecotourism. The present study fi lls this gap by validating the scale items and examining the dimensionality, reliability and factor structures used to measure organisational cultures of small and medium enterprise resort operators in the ecotourism areas of emerging economies. Three factors have emerged for organisational values and four factors for organisational practices as a result of this study. The results show the unique features of the organisational culture model based on the specifi cations of ecotourism and the culture of Malaysian small and medium enterprises. The direction for future improvement strategies is presented at the end of the paper.

Ab initio thermal transport properties of nanostructures from density functional perturbation theory

We present a comprehensive first-principles study of the thermal transport properties of low-dimensional nanostructures such as polymers and nanowires. An approach is introduced where the phonon quantum conductance is computed from the combination of accurate plane-wave density functional theory electronic structure calculations, the evaluation of the interatomic force constants through density functional perturbation theory for lattice dynamics, and the calculation of transport properties by a real-space Green’s function method based on the Landauer formalism. This approach is computationally very efficient, can be straightforwardly implemented as a post-processing step in a standard electronic structure calculation (Quantum ESPRESSO and WanT in the present implementation), and allows us to directly link the thermal transport properties of a device to the coupling, dimensionality, and atomistic structure of the system. It provides invaluable insight into the mechanisms that govern heat flow at the nanoscale and paves the way to the fundamental understanding of phonon engineering in nanostructures.

Simulation of laser radiation effects on low dimensionality structures

This paper presents a study on a system comprised of a low-dimensional structure (Ga1-xAlxAs and GaAs quantum well wire), an intense laser field and an applied magnetic field in axial direction, resulting in a modified structure by interaction with the laser field. A variation of the concentration of aluminum is considered. So, the characteristics of the semiconductor such as the effective mass and width of the forbidden band vary due to the aluminum concentration. The electronic Landé factor control by changing of both intensity and frequency of a laser field on cylindrical quantum well wire was also reported. We use the laser dressed approximation for the treated "quantum wire + laser" system as quantum wire in the absence of radiation but with parameter (electronic barrier height and electronic effective mass) renormalized by laser effects. We consider a magnetic field applied in the parallel direction of symmetric axis of the quantum well wire. We take into account non-parabolicity and anisotropy effects on the conduction band by Ogg-McCombe Hamiltonian.

Learning embedded lines of attraction by self organization for pose and expression invariant face recognition

Algorithms that mimic the computation and learning capabilities of the human brain are feasible solutions to many information-processing problems. We present a theoretical model based on the observation that images of similar visual perceptions reside in a complex manifold in an image space. To model the pattern manifold, we present a novel learning algorithm using a recurrent neural network based on the behavior of the brain. In designing a recurrent neural network, convergence dynamics of the network needs special consideration. We propose to modify this picture: If the brain remembers by converging to the state representing familiar patterns, it should also diverge from such states when presented with an unknown encoded representation of a visual image belonging to a different category. Based on this, we have developed a self-organizing line attractor to learn new patterns. A nonlinear dimensionality reduction technique is used to embed the points to a lower dimensional space that preserves the intrinsic dimensionality and metric structure of the data to enable fast and accurate recognition. Experiments performed on UMIST, CMU AMP, FRGC version-2, Japanese female face expression, and Essex Grimace databases show the effectiveness of the proposed approach in accurate recognition of complex patterns.

Phonon engineering in nanostructures: Controlling interfacial thermal resistance in multilayer-graphene/dielectric heterojunctions

Using calculations from first principles and the Landauer approach for phonon transport, we study the Kapitza resistance in selected multilayer graphene/dielectric heterojunctions (hexagonal BN and wurtzite SiC) and demonstrate (i) the resistance variability (∼50−700×10−10 m2K/W) induced by vertical coupling, dimensionality, and atomistic structure of the system and (ii) the ability of understanding the intensity of the thermal transmittance in terms of the phonon distribution at the interface. Our results pave the way to the fundamental understanding of active phonon engineering by microscopic geometry design.

Exploratory Mokken Scale Analysis as a Dimensionality Assessment Tool

The assessment of the number of dimensions and the dimensionality structure of questionnaire data is important in scale evaluation. In this study, the authors evaluate two dimensionality assessment procedures in the context of Mokken scale analysis (MSA), using a so-called fixed lowerbound. The comparative simulation study, covering various theoretically and empirically relevant conditions, indicates that the MSA procedures may result in scales that are inconsistent with the dimensionality of the data set at hand. That is, a single Mokken scale can be multidimensional, and two Mokken scales can pertain to a single dimension. In an illustrative evaluation, MSA using a range of lowerbounds, rather than a fixed lowerbound, was shown to have some benefits, but not to solve all limitations. The results of this study imply that MSA is perfectly suitable to create Mokken scales. However, MSA appears of limited value as a dimensionality assessment method.

Significance testing in ridge regression for genetic data.

BackgroundTechnological developments have increased the feasibility of large scale genetic association studies. Densely typed genetic markers are obtained using SNP arrays, next-generation sequencing technologies and imputation. However, SNPs typed using these methods can be highly correlated due to linkage disequilibrium among them, and standard multiple regression techniques fail with these data sets due to their high dimensionality and correlation structure. There has been increasing interest in using penalised regression in the analysis of high dimensional data. Ridge regression is one such penalised regression technique which does not perform variable selection, instead estimating a regression coefficient for each predictor variable. It is therefore desirable to obtain an estimate of the significance of each ridge regression coefficient.ResultsWe develop and evaluate a test of significance for ridge regression coefficients. Using simulation studies, we demonstrate that the performance of the test is comparable to that of a permutation test, with the advantage of a much-reduced computational cost. We introduce the p-value trace, a plot of the negative logarithm of the p-values of ridge regression coefficients with increasing shrinkage parameter, which enables the visualisation of the change in p-value of the regression coefficients with increasing penalisation. We apply the proposed method to a lung cancer case-control data set from EPIC, the European Prospective Investigation into Cancer and Nutrition.ConclusionsThe proposed test is a useful alternative to a permutation test for the estimation of the significance of ridge regression coefficients, at a much-reduced computational cost. The p-value trace is an informative graphical tool for evaluating the results of a test of significance of ridge regression coefficients as the shrinkage parameter increases, and the proposed test makes its production computationally feasible.

Multi-ferroic and magnetoelectric materials and interfaces

The existence of multiple ferroic orders in the same material and the coupling between them have been known for decades. However, these phenomena have mostly remained the theoretical domain owing to the fact that in single-phase materials such couplings are rare and weak. This situation has changed dramatically recently for at least two reasons: first, advances in materials fabrication have made it possible to manufacture these materials in structures of lower dimensionality, such as thin films or wires, or in compound structures such as laminates and epitaxial-layered heterostructures. In these designed materials, new degrees of freedom are accessible in which the coupling between ferroic orders can be greatly enhanced. Second, the miniaturization trend in conventional electronics is approaching the limits beyond which the reduction of the electronic element is becoming more and more difficult. One way to continue the current trends in computer power and storage increase, without further size reduction, is to use multi-functional materials that would enable new device capabilities. Here, we review the field of multi-ferroic (MF) and magnetoelectric (ME) materials, putting the emphasis on electronic effects at ME interfaces and MF tunnel junctions.

Assessment of tinnitus-related impairments and disabilities using the German THI-12: Sensitivity and stability of the scale over time

Objective: To evaluate the reliability, dimensionality, predictive validity, construct validity, and sensitivity to change of the THI-12 total and sub-scales as diagnostic aids to describe and quantify tinnitus-evoked reactions and evaluate treatment efficacy. Design: Explorative analysis of the German tinnitus handicap inventory (THI-12) to assess potential sensitivity to tinnitus therapy in placebo-controlled randomized studies. Correlation analysis, including Cronbach's coefficient α and explorative common factor analysis (EFA), was conducted within and between assessments to demonstrate the construct validity, dimensionality, and factorial structure of the THI-12. Study sample: N = 618 patients suffering from subjective tinnitus who were to be screened to participate in a randomized, placebo-controlled, 16-week, longitudinal study. Results: The THI-12 can reliably diagnose tinnitus-related impairments and disabilities and assess changes over time. The test–retest coefficient for neighboured visits was r > 0.69, the internal consistency of the THI-12 total score was α ≤ 0.79 and α ≤ 0.89 at subsequent visits. Predictability of THI-12 total score and overall variance increased with successive measurements. The three-factorial structure allowed for evaluation of factors that affect aspects of patients’ health-related quality of life. Conclusions: The THI-12, with its three-factorial structure, is a simple, reliable, and valid instrument for the diagnosis and assessment of tinnitus and associated impairment over time.SumarioObjetivo: Evaluar la confiabilidad, dimensionalidad, validez predictiva, validez de la estructura y sensibilidad de cambio del total del THI-12 y las subescalas, como ayuda diagnóstica para describir y cuantificar las reacciones con acúfeno evocado y para evaluar la eficacia del tratamiento. Diseño: Análisis exploratorio del Cuestionario Alemán de Desventaja por Acúfeno (THI-12) para evaluar la sensibilidad potencial de la terapia del acúfeno en estudios al azar, controlados con placebo. Se realizó un análisis de correlación incluyendo el coeficiente a de Cronbach’s y un análisis exploratorio de factor común de análisis (EFA), en y entre evaluaciones, para demostrar la validez de la estructura, la dimensionalidad y la estructura factorial del THI-12. Muestra: N = 618 pacientes con acúfeno subjetivo fueron tamizados para participar en un estudio al azar, controlado por placebo, de 16 semanas y longitudinal. Resultados: El THI-12 puede confiablemente diagnosticar los impedimentos y discapacidades relacionados con el acúfeno y evaluar los cambios en el tiempo. El coeficiente test-retest para visitas cercanas fue de r > 0.69 y la consistencia interna de la puntuación total del THI-12 fue de a ≤ 0.79 y de a ≤ 0.89, en visitas subsecuentes. La previsibilidad de la puntuación total del THI-12 y la variancia global se incrementó con mediciones sucesivas. La estructura factorial triple permitió la evaluación de factores que afectan aspectos que relacionados con la salud y calidad de vida de los pacientes. Conclusiones: El THI-12, con su estructura factorial triple es un instrumento simple, confiable y válido para el diagnóstico y la evaluación del acúfeno y de la discapacidad que con él se asocia, a lo largo del tiempo.

Detecting and Deterring Insufficient Effort Responding to Surveys

Responses provided by unmotivated survey participants in a careless, haphazard, or random fashion can threaten the quality of data in psychological and organizational research. The purpose of this study was to summarize existing approaches to detect insufficient effort responding (IER) to low-stakes surveys and to comprehensively evaluate these approaches. In an experiment (Study 1) and a nonexperimental survey (Study 2), 725 undergraduates responded to a personality survey online. Study 1 examined the presentation of warnings to respondents as a means of deterrence and showed the relative effectiveness of four indices for detecting IE responses: response time, long string, psychometric antonyms, and individual reliability coefficients. Study 2 demonstrated that the detection indices measured the same underlying construct and showed the improvement of psychometric properties (item interrelatedness, facet dimensionality, and factor structure) after removing IE respondents identified by each index. Three approaches (response time, psychometric antonyms, and individual reliability) with high specificity and moderate sensitivity were recommended as candidates for future application in survey research. The identification of effective IER indices may help researchers ensure the quality of their low-stake survey data. This study is a first attempt to comprehensively evaluate IER detection methods using both experimental and nonexperimental designs. Results from both studies corroborated each other in suggesting the three more effective approaches. This study also provided convergent validity evidence regarding various indices for IER.

Two‐, One‐, and Zero‐Dimensional Elemental Nanostructures Based on Ge9‐Clusters

We investigated the structural principles of novel germanium modifications derived by oxidative coupling of Zintl-type [Ge(9)](4-)clusters in various ways. The structures, stabilities, and electronic properties of the predicted {(2) (infinity)[Ge(9)](n)} sheet, {(1) (infinity)[Ge(9)](n)} nanotubes, and fullerene-like {Ge(9)}(n) cages were studied by using quantum chemical methods. The polyhedral {Ge(9)}(n) cages are energetically comparable with bulk-like nanostructures of the same size, in good agreement with previous experimental findings. Three-dimensional structures derived from the structures of lower dimensionality are expected to shed light on the structural characteristics of the existing mesoporous Ge materials that possess promising optoelectronic properties. Furthermore, 3D networks derived from the polyhedral {Ge(9)}(n) cages lead to structures that are closely related to the well-known LTA zeolite framework, suggesting further possibilities for deriving novel mesoporous modifications of germanium. Raman and IR spectra and simulated X-ray diffraction patterns of the predicted materials are given to facilitate comparisons with experimental results. The studied novel germanium modifications are semiconducting, and several structure types possess noticeably larger band gaps than bulk alpha-Ge.

Eight‐Coordinate Endohedral Rhenium, Osmium and Iridium Atoms in Rare‐Earth Halide Cluster Complexes

AbstractEndohedral (interstitial) atoms are essential for almost all of the rare‐earth halide cluster complexes. Most of these contain octahedral clusters, some are isolated, but the majority exhibits condensation by common edges to structures of higher dimensionality. Higher coordination numbers of the endohedral atoms are rare. Four examples of extended cluster complexes with eight‐coordinate endohedral atoms of sixth‐period elements (Re, Os, Ir) are presented. In the quasi‐isostructural, non‐isotypic halides {ReGd4}Br4 and {OsSc4}Cl4, square antiprisms of gadolinium and scandium atoms, respectively, are connected by two common faces to chains, surrounded and loosely connected by halogenido ligands. The Re and Os atoms build a slightly bent chain with only little bonding interactions. Chemical bonding is dominated by endohedral atom–cluster atom and cluster atom–halide interactions. The same is true for the two scandium bromides {Ir3Sc12}Br16 and {Os3Sc12}Br16Sc, which contain chains of face‐sharing square antiprisms and cubes in a ratio of 2:1. Metal–metal bonding is attested by short distances between those endohedral Ir and Os atoms, respectively, which center the square antiprisms (283 pm and 290 pm, respectively). Magnetic and conductivity measurements on {Ir3Sc12}Br16 reveal paramagnetism and a small‐band‐gap semiconductor. This is in accord with electronic structure calculations.

Synthesis, Structure, and Transformation Studies in a Family of Inorganic−Organic Hybrid Framework Structures Based on Indium

Eight new open-framework inorganic-organic hybrid compounds based on indium have been synthesized employing hydrothermal methods. All of the compounds have InO(6), C(2)O(4), and HPO(3)/HPO(4)/SO(4) units connected to form structures of different dimensionality. Thus, the compounds have zero- (I), two- (II, III, IV, V, VII, and VIII), and three-dimensionally (VI) extended networks. The formation of the first zero-dimensional hybrid compound is noteworthy. In addition, concomitant polymorphic structures have been observed in the present study. The molecular compound, I, was found to be reactive, and the transformation studies in the presence of a base (pyridine) give rise to the polymorphic structures of II and III, while the addition of an acid (H(3)PO(3)) gives rise to a new indium phosphite with a pillared layer structure (T1). Preliminary density functional theory calculations suggest that the stabilities of the polymorphs are different, with one of the forms (II) being preferred over the other, which is consistent with the observed experimental behavior. The oxalate units perform more than one role in the present structures. Thus, the oxalate units connect two In centers to satisfy the coordination requirements as well as to achieve charge balance in compounds II, IV, and VI. The terminal oxalate units observed in compounds I, IV, and V suggest the possibility of intermediate structures. Both in-plane and out-of-plane connectivity of the oxalate units were observed in compound VI. The compounds have been characterized by powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and (31)P NMR studies.

Cultural Experience Tourist Motives Dimensionality: A Cross-Cultural Study

This empirical research of tourists' cultural experiences aims to advance theory by developing a measurement model of tourists' motives towards attending cultural experiences for samples of Western and Asian tourists visiting Melbourne, Australia. Drawing upon Iso-Ahola's (1989) seeking/avoiding dichotomy theory for tourist motivation dimensions, the hypothesized dimensions primarily included escape and seeking-related dimensions, and some hedonic dimensions because of their relevance to aesthetic products (Hirschman & Holbrook, 1982; Holbrook & Hirschman, 1982), which are the context for this study. Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were used to cross-validate the underlying dimensionality structure of cultural experience motives. A four-factor model was extracted from the EFA consistent with some theoretical formulations and was retained in the CFA. Specific cultural language group differences for the motive dimensions were also hypothesized between Western and Asian tourist samples, and within the Chinese- and Japanese-speaking Asian tourist samples, but not within the different cultural groups of English-speaking Western tourists. These cross-cultural hypotheses were tested for the motive dimension measurement model using invariance testing in CFA. The findings for the motive dimensions differing by cultural group were not as expected. Significant cultural differences between Western and Asian tourists were not found, but a new finding of this study was significant differences between English-speaking tourists in their motives for attending cultural experiences. Marketing implications of these findings are also presented.

Grain boundary segregation and thermodynamically stable binary nanocrystalline alloys

A free-energy function for binary polycrystalline solid solutions is developed based on pairwise nearest-neighbor interactions. The model permits intergranular regions to exhibit unique energetics and compositions from grain interiors, under the assumption of random site occupation in each region. For a given composition, there is an equilibrium grain size, and the alloy configuration in equilibrium generally involves solute segregation. The present approach reduces to a standard model of grain boundary segregation in the limit of infinite grain size, but substantially generalizes prior thermodynamic models for nanoscale alloy systems. In particular, the present model allows consideration of weakly segregating systems, systems away from the dilute limit, and is derived for structures of arbitrary dimensionality. A series of solutions for the equilibrium alloy configuration and grain size are also presented as a function of simple input parameters, including temperature, alloy interaction energies, and component grain boundary energies.

Strong anisotropic thermal expansion in borates

AbstractThe paper summarizes results of high‐temperature single crystal X‐ray diffraction studies for six borate structures and high‐temperature powder X‐ray diffraction data for about 50 borates. The characteristics on thermal expansion of 50 borates of univalent, bivalent and trivalent metals of different dimensionality and anion structure are listed. The basic principles of high‐temperature borate crystal chemistry emerge from these studies and the regularities of borate thermal behavior are revealed. On heating the BO3 and BO4 polyhedra and rigid groups consisting of these polyhedra practically do not change their configuration and size but sometimes rotate like hinges exhibiting greatly anisotropic thermal expansion including linear negative expansion. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

An investigation of the dimensionality of the Pittsburgh Sleep Quality Index in Australian adults

The Pittsburgh Sleep Quality Index (PSQI) is widely used to assess subjective sleep quality in clinical and non-clinical settings. Although the PSQI is routinely scored to provide a single sleep quality factor, two recent studies suggest that multiple factor scoring methods could be more appropriate. As a consequence, the present study investigated for the dimensionality and factor structure of the PSQI in 364 Australian adults aged 18 to 59 years. The results demonstrate that two factor and three factor scoring models were favored statistically over the single factor model. These results add to recent findings and suggest that scoring the PSQI in relation to multiple factors could facilitate the assessment of sleep problems, which are increasingly common in society.