Orientational Correlation Research Articles

The effect of polymorphism on the structural, dynamic and dielectric properties of plastic crystal water: A molecular dynamics simulation perspective.

We have employed molecular dynamics simulations based on the TIP4P/2005 water model to investigate the local structural, dynamical, and dielectric properties of the two recently reported body-centered-cubic and face-centered-cubic plastic crystal phases of water. Our results reveal significant differences in the local orientational structure and rotational dynamics of water molecules for the two polymorphs. The probability distributions of trigonal and tetrahedral order parameters exhibit a multi-modal structure, implying the existence of significant local orientational heterogeneities, particularly in the face-centered-cubic phase. The calculated hydrogen bond statistics and dynamics provide further indications of the existence of a strongly heterogeneous and rapidly interconverting local orientational structural network in both polymorphs. We have observed a hindered molecular rotation, much more pronounced in the body-centered-cubic phase, which is reflected by the decay of the fourth-order Legendre reorientational correlation functions and angular Van Hove functions. Molecular rotation, however, is additionally hindered in the high-pressure liquid compared to the plastic crystal phase. The results obtained also reveal significant differences in the dielectric properties of the polymorphs due to the different dipolar orientational correlation characterizing each phase.

Taking Action or Thinking About It? State Orientation and Rumination Are Correlated in Athletes.

Athletic performance in competitive sports relies heavily on the ability to cope effectively with stressful situations. In contrast, some athletes report that their thoughts revolve around the future or past and not around the actual demands during competitions. In those specific stressful situations, the lack of focus like an unintended fixation on repetitive cognitions can have fatal consequences with regard to the performance. Especially when competitors are close in their athletic capabilities, differences in effectively coping with stress and mental stability may decide about winning and losing. One established factor of performing effectively under pressure is the individual tendency to either focus on taking action (i.e., action orientation) or on focusing on the own emotions (i.e., state orientation). It is widely acknowledged that state-oriented athletes have disadvantages in performing under stress. Moreover, the action control theory claims that state orientation is related to ruminative cognitions, which itself is assumed to impair performance in the long term. We tested this hypothesis in 157 competitive athletes from different sports (including individual and team sports). Regression analysis demonstrates a substantial correlation of failure-related action orientation (i.e., state orientation) with different measures of rumination (including general, clinically relevant, and competition-related rumination). In addition, general (i.e., content independent) rumination also correlated substantially with a rumination scale adapted specifically to sports-related competition. These results suggest (1) that a sports and competition-related ruminative mechanism exists and (2) that ruminative cognitions are related to the cognitive basis of state orientation. While our study does not allow for a causal interpretation, it provides an additional approach to investigate mental factors underlying inter-individual differences in athletic performance under stress and pressure.

Entrepreneurial Orientation of Academic Spin-Offs: Statistical Correlations

The main goal of this article is to present statistical correlations as regards the impact of certain determinants on entrepreneurial orientation of academic spin-off companies. The first part presents the definition of academic spin-offs and the most important elements of entrepreneurial orientation of such companies. The second, empirical, part reports the results regarding statistical correlations of entrepreneurial orientation of academic spin-offs. The research was conducted among 141 academic spin-offs. The test of independence and Cramer’s V coefficient were used to diagnose the correlation.

Solid-liquid transition of skyrmions in a two-dimensional chiral magnet

We study the melting of skyrmions in a two-dimensional Heisenberg chiral magnet with bi-axial Dzyaloshinskii--Moriya interactions. These topological excitations may form at zero temperature a triangular crystal with long-range positional order. However, we show using large-scale Monte Carlo simulations that at small finite temperature, the skyrmions rather form a typical two-dimensional solid: Positional correlations decay with distance as power laws while the orientational correlations remain finite. At higher temperature, we observe a direct transition from this two-dimensional solid to a liquid with short-range correlations. This differs from generic two-dimensional homogeneous particle systems, where a hexatic phase is realized between the solid and the liquid.

The Effect of Bending Rigidity on Polymers

AbstractThe conformations of chromatin are influenced by many factors. In the regulation of gene expression the bending rigidity of the chromatin polymer and its heterogeneity play an important role for the possible conformations. To elucidate this, the effect of bending rigidity as well as its heterogeneity on various polymer properties is investigated. In the context of chromatin organization, the contact probability is an important measure. It is analyzed whether there is any ambiguity in the definition of a contact. The results show that the contact probability does not depend on the range of contact in the limit of a large contour length between monomers. Further, the persistence length as a function of the bending rigidity is computed in the homogeneous and heterogeneous cases. The persistence length is systematically smaller in the heterogeneous case. Chromosomes are confined by each other in the nucleus and by looking at specific loci, the environment changes much more slowly than the local chromatin part. In conjunction with bending rigidity, polymers in rectangular confinements with several aspect ratios are simulated. Due to the spiraling behavior when the box size is small enough, an oscillation in the contact probability and the orientational correlation function is found.

Thermodynamic picture of vitrification of water through complex specific heat and entropy: A journey through "no man's land".

We investigate thermodynamic properties of supercooled water across the "no man's land" onto the formation of amorphous ice. The calculations are aided by very long computer simulations, often more than 50 μs long, with the TIP4P/2005 model potential. Density fluctuations that arise from the proximity to a putative liquid-liquid (LL) transition at 228 K, cast a long shadow on the properties of water, both above and below the LL transition. We carry out the calculations of the quantum mechanical static and frequency-dependent specific heats by combining seminal studies of Lebowitz, Percus, and Verlet and Grest and Nagel with the harmonic approximation for the density of states. The obtained values are in quantitative agreement with all available experimental and numerical results of specific heats for both supercooled water and ice. We calculate the entropy at all the state points by integrating the specific heat. We find that the quantum corrected-contributions of intermolecular vibrational entropy dominate the excess entropy of amorphous phases over the crystal over a wide range of temperatures. Interestingly, the vibrational entropy lowers the Kauzmann temperature, TK, to 130 K, just below the experimental glass-to-liquid water transition temperature, Tg, of 136 K and the calculated Tg of 135 K in our previous study. A straightforward extrapolation of high temperature entropy from 250 K to below however would give a much higher value of TK ∼ 190 K. The calculation of Lindemann ratios shows the melting of amorphous ice ∼135 K. The amorphous state exhibits an extremely short correlation length for the distance dependence of orientational correlation.

Cosmological-scale coherent orientations of quasar optical polarization vectors in thePlanckera

Gigaparsec scale alignments of the quasar optical polarization vectors have been proven to be robust against a scenario of contamination by the Galactic interstellar medium (ISM). This claim has been established by means of optical polarization measurements of the starlight surrounding the lines of sight of the 355 quasars for which reliable optical polarization measurements are available. In this paper, we take advantage of the full-sky and high quality polarization data released by thePlancksatellite to provide an independent, complementary, and up-to-date estimation of the contamination level of the quasar optical polarization data by the Galactic dust. Our analysis reveals signatures of Galactic dust contamination at the two sigma level for about 30 percent of the quasar optical polarization data sample. The remaining 70 percent of the lines of sight do not show Galactic dust contamination above the two sigma level, suggesting low to negligible contamination of the quasar optical polarization signal. We further found arguments suggesting that Galactic thermal dust cannot fully account for the reported quasar optical polarization alignments. Based on the measurements of the ratio of the polarized intensity of the dust in the submillimeter to the degree of linear polarization of the quasar in the optical, we provide a new and independent quality criteria to apply to the quasar optical polarization sample. We argue that, unless correction is applied, such a criterion should be imposed on the data for future investigations in the framework of the cosmological-scale correlations of quasar optical polarization vector orientations that still could compete with the isotropic principle of the cosmological paradigm.

Viscoelastic shear stress relaxation in two-dimensional glass-forming liquids

Translational dynamics of 2D glass-forming fluids is strongly influenced by soft, long-wavelength fluctuations first recognized by D. Mermin and H. Wagner. As a result of these fluctuations, characteristic features of glassy dynamics, such as plateaus in the mean-squared displacement and the self-intermediate scattering function, are absent in two dimensions. In contrast, Mermin-Wagner fluctuations do not influence orientational relaxation, and well-developed plateaus are observed in orientational correlation functions. It has been suggested that, by monitoring translational motion of particles relative to that of their neighbors, one can recover characteristic features of glassy dynamics and thus disentangle the Mermin-Wagner fluctuations from the 2D glass transition. Here we use molecular dynamics simulations to study viscoelastic relaxation in two and three dimensions. We find different behavior of the dynamic modulus below the onset of slow dynamics (determined by the orientational or cage-relative correlation functions) in two and three dimensions. The dynamic modulus for 2D supercooled fluids is more stretched than for 3D supercooled fluids and does not exhibit a plateau, which implies the absence of glassy viscoelastic relaxation. At lower temperatures, the 2D dynamic modulus starts exhibiting an intermediate time plateau and decays similarly to the 2D dynamic modulus. The differences in the glassy behavior of 2D and 3D glass-forming fluids parallel differences in the ordering scenarios in two and three dimensions.

Membrane-Protein-Hydration Interaction of α-Synuclein with Anionic Vesicles Probed via Angle-Resolved Second-Harmonic Scattering.

Amyloid formation of the protein α-synuclein promotes neurodegeneration in Parkinson's disease. The normal function of α-synuclein includes synaptic vesicle transport and fusion, and the protein binds strongly to negatively charged vesicles in vitro. Here, we demonstrate that nonresonant angle-resolved second-harmonic scattering detects α-synuclein binding to liposomes through changes in water orientational correlations and can thus be used as a high-accuracy and high-throughput label-free probe of protein-liposome interactions. The obtained results support a binding model in which the N-terminus of α-synuclein adopts an α-helical conformation that lies flat on the vesicle surface while the negatively charged C-terminus remains in solution.

Correlation of Students’ Interpersonal Orientation, Experience and Motivation for Livingin a Dormitory

One of the indicators of psychological adjustment of adolescents is interpersonal orientation (attitudes to generalised others). Tis paper deals with interpersonal orientation of college students facing specifc challenges during studying – living in a dormitory. Te aim of the research was to examine the correlation between interpersonal orientation of students, their previous experience in coeval collective accommodation (peer-to-peer housing) and their motivation for living in a dormitory. Scale of interpersonal orientation (Bezinović, 2002), applied to 221 students, at the age of 18 to 28, who came from other towns to Sarajevo to study and who were living in one of dormitories of „Studentski centar’’ and Foundation for improvement of education and culture „Source of Hope’’. Two items are included in the questionnaire to examine the experience of housing in a collective accommodation and motivation for living in a dormitory. Te results indicate that there is a statistically signifcant correlation of interpersonal orientation of the students and their previous experience in coeval collective accommodation, as well as their motivation for living in a dormitory. Students with developed positive (philanthropic) orientation have predominantly pleasant experience, but students with developed negative (misanthropic) orientation have predominantly unpleasant experience while staying in coeval collective accommodation (peer-to-peer housing). It is proved that students who claim that the main reason for living in a dormitory is living with a peer group, have the highest philanthropic and the lowest misanthropic orientation. Students, who have not had the possibility to choose a place of housing, have the lowest philanthropic and the highest misanthropic orientation.

Manifestation of dipole-induced disorder in self-assembly of ferroelectric and ferromagnetic nanocubes.

The colloidal processing of nearly monodisperse and highly crystalline single-domain ferroelectric or ferromagnetic nanocubes is a promising route to produce superlattice structures for integration into next-generation devices, whereas controlling the local behaviour of nanocrystals is imperative for fabricating highly-ordered assemblies. The current picture of nanoscale polarization in individual nanocrystals suggests a potential presence of a significant dipolar interaction, but its role in the condensation of nanocubes is unknown. We simulate the self-assembly of colloidal dipolar nanocubes under osmotic compression and perform the microstructural characterization of their densified ensembles. Our results indicate that the long-range positional and orientational correlations of perovskite nanocubes are highly sensitive to the presence of dipoles.

Enhanced microphase separation of thin films of low molecular weight block copolymer by the addition of an ionic liquid.

We report on the use of a selective, non-volatile ionic liquid (IL) to enhance the self-assembly via solvent annealing of a low molecular weight block copolymer (BCP) of styrene and 2-vinylpyridine (2VP) suitable for generating sub-10 nm features. Diblock and triblock copolymers of different molecular weights of styrene and 2VP are individually blended with the IL and then solvent annealed in acetone, a non-preferential solvent for the BCPs. Differential scanning calorimetry indicates that the IL selectively resides in the 2VP block of the BCP, resulting in a decrease of the block's Tg and an increase of the effective Flory-Huggins parameter (χeff) of the BCP. The influence of the IL on the non-preferential window of a random copolymer brush used to treat the substrate for self-assembly of the BCPs is also analyzed. Well-defined lamellar patterns form when the optimal weight ratio of IL (∼1%) is added to the BCPs. A detailed analysis of the orientational correlation length and pitch size of the BCPs quantitatively shows that the addition of the IL enhanced the microphase separation of the low molecular weight version of the BCP. Subsequent treatment of the self-assembled BCP with sequential infiltration synthesis yields sub-10 nm AlOx lines.

Improving the accuracy of Cu(ii)-nitroxide RIDME in the presence of orientation correlation in water-soluble Cu(ii)-nitroxide rulers.

Orientation selection is a challenge in distance determination with double electron electron resonance (DEER) spectroscopy of rigid molecules. The problem is reduced when applying the Relaxation-Induced Dipolar Modulation Enhancement (RIDME) experiment. Here we present an in-depth study on nitroxide-detected RIDME in Cu(ii)-nitroxide spin pairs using two Cu(ii)-nitroxide rulers that are both water soluble and have comparable spin-spin distances. They differ in the type of the ligand (TAHA and PyMTA) for the Cu(ii) ion which results in different contributions of exchange coupling. Both rulers feature substantial orientation correlation between the molecular frames of the Cu(ii) complex and the nitroxide. We discuss how the spin-spin couplings can be accurately measured and how they can be correlated to the nitroxide resonance frequencies. In that, we pay particular attention to the suppression of nuclear modulation and of echo crossing artefacts, to background correction, and to orientation averaging. With a nitroxide observer sequence based on chirp pulses, we achieve wideband detection of all nitroxide orientations. Two-dimensional Fourier transformation of data obtained in this manner affords observer-EPR correlated RIDME spectra that enable visual understanding of the orientation correlation. The syntheses of the Cu(ii)-nitroxide rulers are presented. The synthetic route is considered to be of general use for the preparation of [metal ion complex]-nitroxide rulers, including water soluble ones.

Excess Cesium Iodide Induces Spinodal Decomposition of CsPbI2Br Perovskite Films.

We report an exploratory study on the crystal formation behavior of CsPbI2Br perovskite films by adding excess cesium iodide (CsI). Surprisingly, facile co-crystallization of CsI and CsPbI2Br in the form of spinodal decomposition is observed. Significantly, the two phases spontaneously form morphing into a remarkably uniform bicontinuous nanoscale blend with high orientational correlation through the well-matched (110) plane of CsI and the (200) plane of CsPbI2Br. The CsPbI2Br films produced by the spinodal decomposition method not only enjoy a compact surface, low defect concentration, and long carrier lifetimes, they also retain their excellent charge transport property. By employing such a CsPbI2Br film for carbon-based perovskite solar cells, power conversion efficiency exceeding 10% is achieved with remarkable thermal stability. Our results provide valuable insight into the role of CsI in perovskite crystallization and a promising approach for designing inorganic halide perovskite-based devices.

SCIENTIFIC COSMISM AND POSTNONCLASSICAL SCIENCE: ANTHROPOLOGICAL CONTEXT OF INTERACTION

The ideas of human-dimensional scientific knowledge originated more than 100 years ago in the thoughts of the cosmists of М. Umov, V. Vernadsky, K. Tsiolkovsky, O. Chizhevsky, who wrote about the cosmic origin of man, the influence of his creative activity on cosmic processes are represented in the introduction. At the end of the XXth-at the beginning of the XXIst cc., they were developed by natural scientists who are investigating the origin of the universe and living conditions in it with the help of modern high technologies. It actualizes the philosophical conception of the correlation of the anthropological orientation of scientific cosmism and postnonclassical science. Hence the task of the article is to identify the connections between the philosophy of cosmism (its scientific direction) of the end of the XIXth and early XXth centuries and post-nonclassical science in the aspect of their anthropological dimension. For this purpose, philosophical-anthropological, cultural-historical and comparative methodological approaches and research methods of cultural-semantic analysis and interdisciplinary research are used. On the basis of the study and comparison of the anthropocosmic ideas of the native cosmists of the conditions for the origin of man in the cosmos and the influence of space processes on man's life, of the possibility of transformation of the biosphere into the noosphere in the process of human activity, the author of the article within research results substantiates the position of the relationship of these ideas with the scientific concepts of representatives of postclassical science. In these concepts, man himself is scientifically proven to become one of the factors of further evolution of nature in the part of the universe inhabited by him. And the laws of nonequilibrium thermodynamics, discovered by a scientific school under the direction of I. Prygozhin, confirm the hypotheses of cosmic scientists about the possibilities of the origin of life in the cosmos through the birth of living from nonliving and further - the higher forms of organization of living matter in the universe because of the emergence of instability in extremely unbalanced conditions. The discussion analyzes the results of the research of anthropological ideas of cosmic scientists and contemporary natural scientists, carried out by M. Wallerstein, V. Kazyutinsky, M. Moiseyev, I. Mochalov, V. Onoprienko, N. Popkova, V. Stepin, S. Yahodzinskyi and others. These researchers are shown in the article not to aim to compare the anthropological views of representatives of cosmism and postnonclassical science. The conclusions prove that the leading idea of anthropocosmism is to understand man as an integral part of the cosmos, his role and place in the world evolutionary processes - has become quite promising for the science of the late XXth - early XXIth centuries, has generated a large number of new hypotheses regarding the origin, formation and development of the universe, the planet Earth and man as a special species of living organisms. It discovers the laws of functioning of self-organized systems that represent non-linear, stochastic, cooperative, and other properties of such systems, which are all components of the space process, including the social world and man himself.

Demonstrating the potential of accurate absolute cross-grain stress and orientation correlation using electron backscatter diffraction

We report a first exploration of High-angular-Resolution Electron Backscatter Diffraction, without using simulated Electron Backscatter Diffraction patterns as a reference, for absolute stress and orientation measurements in polycrystalline materials. By co-correlating the pattern center and fully exploiting crystal symmetry and plane-stress, simultaneous correlation of all overlapping regions of interest in multiple direct-electron-detector, energy-filtered Electron Backscatter Diffraction patterns is achieved. The potential for highly accurate measurement of absolute stress, crystal orientation and pattern center is demonstrated on a virtual polycrystalline case-study, showing errors respectively below 20 MPa (or 10−4 in strain), 7 × 10−5 rad and 0.06 pixels.

Orientational Pair Correlations in a Dipolar Molecular Liquid: Time-Resolved Resonant and Nonresonant Pump-Probe Spectroscopies.

Orientational pair correlations (OPCs), when they are sufficiently strong in a liquid, contain information on the interplay between structure and dynamics that arise from intermolecular interactions. Consequently, the quantification of OPCs remains a subject of substantial interest in current experimental and theoretical works. In the case of benzonitrile, the importance of OPCs remains ambiguous, owing to the use of model-dependent analyses or reliance on a single spectroscopic technique. Here, IR polarization-selective pump-probe (PSPP) and optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments were used to quantify OPCs in benzonitrile. These methods measure single molecule and collective orientational relaxation dynamics, respectively. A comparison of the orientational correlation function (PSPP) of the naturally abundant 13CN stretching mode and the polarizability anisotropy relaxation (OHD-OKE) of the liquid revealed that the collective reorientation time was a factor of 1.56 ± 0.08 slower than the single molecule reorientation time. The two types of measurements on dilute benzonitrile in carbon tetrachloride were the same within experimental error. These results support the proposition that OPCs exist and arise from the formation of parallel-aligned intermolecular structures in the neat liquid.

Orientational dynamics of a heated Janus particle.

Using large scale molecular dynamics simulations, we study the orientational dynamics of a heated Janus particle which exhibits self-propulsion. The asymmetry in the microscopic interaction of the colloid with the solvent is implemented by choosing different wetting parameters for the two halves of the sphere. This choice leads to a different microscopic Kapitza resistance across the solid-fluid boundary of the two halves of the sphere, and consequently a gradient in temperature is created across the poles of the sphere. It is this self-created temperature gradient which leads to a self-propulsion along the direction of the symmetry axis. In this article, we look at the orientational dynamics of such a system, as well as the subsequent enhancement of the translational diffusivity of the heated Janus colloid at late times. The orientational correlation of the symmetry axis is measured from the simulation and provides a direct access to the rotational diffusion constant. The heating leads to an increase in the rotational diffusivity of the colloid. We quantify this increase in rotational diffusion D r against the temperature difference δT ≡ T(R, 0) - T(R, π) across the poles of the Janus sphere as well as the average surface temperature difference ΔT ≡ T(R) - T(∞) from the ambient fluid. Since the rotational diffusion is determined by the complete flow field in the solvent, we illustrate that comparing D r against δT is misleading and is better quantified when compared against ΔT. The later quantification results in a data collapse for different choices of the microscopic interaction. The average propulsion velocity is also measured for different choices of the wetting parameter. The directionality of self-propulsion changes depending on the microscopic interaction. We show that whenever the attractive interaction of the colloid with the solvent is switched off, the phoretic mobility changes sign. Furthermore, the propulsion velocity is zero for heating below a certain threshold value. This is also corroborated by the probability distribution of the angle between the displacement vector Δr(t) ≡ r(t) - r(0) and the symmetry axis. Finally, we combine the measured propulsion velocity and the rotational diffusion time τ r = 1/2D r to estimate the enhancement in the long time diffusion coefficient of the particle.

Velocity alignment promotes motility-induced phase separation

We study the phase behavior of polar active Brownian particles moving in two-spatial dimensions and interacting through volume exclusion and velocity alignment. We combine particle-based simulations of the microscopic model with a simple mean-field kinetic model to understand the impact of velocity alignment on the motility-induced phase separation of self-propelled disks. We show that, as the alignment strength is increased, approaching the onset of collective motion from below, orientational correlations grow, rendering the diffusive reorientation dynamics slower. As a consequence, the tendency of particles to aggregate into isotropic clusters is enhanced, favoring the complete de-mixing of the system into a low and high-density phase.

A Monte Carlo study of the electrical double layer of a shape-asymmetric electrolyte around a spherical colloid.

In this paper, we present a Monte Carlo simulation study on the structure of the electrical double layer around a spherical colloid surrounded by a binary electrolyte composed of spherical and non-spherical ions. Results are provided for the radial distribution functions between the colloid and ions, the orientation correlations between the colloid and non-spherical particles, and the integrated charge. Work is reported mainly for non-spherical particles modeled as spherocylinders, although a particular comparison is made between spherocylindrical particles and dimers. For the conditions investigated here, spherocylinders and dimers produce essentially the same structural information. Additionally, it is shown that spherocylinders mostly orient tangentially to the colloid at its surface; this preferred orientation disappears for larger distances. We also evidence that, near the colloid, the integrated charge attenuates monotonically when the macroparticle is highly charged, whereas for intermediate and low charged states of the colloid, the integrated charge can display charge reversal, overcharging, or both, with magnitudes that are sensitive to the salt concentration and to the localization of charge inside the spherocylinders.