Bimodal Phase Research Articles

A note on the Hendrickson-Lattman phase probability distribution and its equivalence to the generalized von Mises distribution.

Hendrickson & Lattman [Acta Cryst. (1970), B26, 136-143] introduced a method for representing crystallographic phase probabilities defined on the unit circle. Their approach could model the bimodal phase probability distributions that can result from experimental phase determination procedures. It also provided simple and highly effective means to combine independent sources of phase information. The present work discusses the equivalence of the Hendrickson-Lattman distribution and the generalized von Mises distribution of order two, which has been studied in the statistical literature. Recognizing this connection allows the Hendrickson-Lattman distribution to be expressed in an alternative form which is easier to interpret, as it involves the location and concentration parameters of the component von Mises distributions. It also allows clarification of the conditions for bimodality and access to a simplified analytical method for evaluating the trigonometric moments of the distribution, the first of which is required for computing the best Fourier synthesis in the presence of phase, but not amplitude, uncertainty.

Contrarian Voter Model under the Influence of an Oscillating Propaganda: Consensus, Bimodal Behavior and Stochastic Resonance.

We study the contrarian voter model for opinion formation in a society under the influence of an external oscillating propaganda and stochastic noise. Each agent of the population can hold one of two possible opinions on a given issue—against or in favor—and interacts with its neighbors following either an imitation dynamics (voter behavior) or an anti-alignment dynamics (contrarian behavior): each agent adopts the opinion of a random neighbor with a time-dependent probability , or takes the opposite opinion with probability . The imitation probability is controlled by the social temperature T, and varies in time according to a periodic field that mimics the influence of an external propaganda, so that a voter is more prone to adopt an opinion aligned with the field. We simulate the model in complete graph and in lattices, and find that the system exhibits a rich variety of behaviors as T is varied: opinion consensus for , a bimodal behavior for , an oscillatory behavior where the mean opinion oscillates in time with the field for , and full disorder for . The transition temperature vanishes with the population size N as in complete graph. In addition, the distribution of residence times in the bimodal phase decays approximately as . Within the oscillatory regime, we find a stochastic resonance-like phenomenon at a given temperature . Furthermore, mean-field analytical results show that the opinion oscillations reach a maximum amplitude at an intermediate temperature, and that exhibit a lag with respect to the field that decreases with T.

Zealots in multistate noisy voter models.

The noisy voter model is a stylized representation of opinion dynamics. Individuals copy opinions from other individuals, and are subject to spontaneous state changes. In the case of two opinion states this model is known to have a noise-driven transition between a unimodal phase, in which both opinions are present, and a bimodal phase, in which one of the opinions dominates. The presence of zealots can remove the unimodal and bimodal phases in the model with two opinion states. Here we study the effects of zealots in noisy voter models with M>2 opinion states on complete interaction graphs. We find that the phase behavior diversifies, with up to six possible qualitatively different types of stationary states. The presence of zealots removes some of these phases, but not all. We analyze situations in which zealots affect the entire population, or only a fraction of agents, and show that this situation corresponds to a single-community model with a fractional number of zealots, further enriching the phase diagram. Our study is conducted analytically based on effective birth-death dynamics for the number of individuals holding a given opinion. Results are confirmed in numerical simulations.

Schrödinger’s ants: a continuous description of Kirman’s recruitment model

We show how the approach to equilibrium in Kirman’s ants model can be fully characterized in terms of the spectrum of a Schrödinger equation with a Pöschl–Teller (tan2) potential. Among other interesting properties, we have found that in the bimodal phase where ants visit mostly one food site at a time, the switch time between the two sources only depends on the ‘spontaneous conversion’ rate and not on the recruitment rate. More complicated correlation functions can be computed exactly, and involve higher and higher eigenvalues and eigenfunctions of the Schrödinger operator, which can be expressed in terms of hypergeometric functions.

Schrödinger’s Ants: A Continuous Description of Kirman’s Recruitment Model

We show how the approach to equilibrium in Kirman’s ants model can be fully characterized in terms of the spectrum of a Schrodinger equation with a Poschl-Teller (tan2) potential. Among other interesting properties, we have found that in the bimodal phase where ants visit mostly one food site at a time, the switch time between the two sources only depends on the “spontaneous conversion” rate and not on the recruitment rate. More complicated correlation functions can be computed exactly, and involve higher and higher eigenvalues and eigenfunctions of the Schrodinger operator, which can be expressed in terms of hypergeometric functions.

A Landscape of Circadian and Ultradian Alternative Splicing Events in Mammalian Tissues

Mounting evidence points to a role of the circadian clock in the temporal regulation of alternative splicing (AS). In this study, we carried out a systematic analysis of circadian and ultradian transcriptional rhythms to characterize the landscape of rhythmic AS events in 76 tissues from mouse and baboon. We found a bimodal phase distribution of splicing factors with 24-h rhythmic expression across tissues and species and identified putative oscillating AS events in murine tissues and pairs of differentially rhythmic splice isoforms of the same gene in baboon tissues that peaked at opposing times of the day. Genes with phase-shifted isoforms included oncogenes and tumor suppressors. We further explored these findings using a new circadian data-set of human colorectal cancer cell lines. Rhythmic isoform expression patterns differed between the primary tumor and the metastatic cell line, indicating a functional role of rhythmic AS that might be implicated in tumor progression.

The noisy voter model under the influence of contrarians

The influence of contrarians on the noisy voter model is studied at the mean-field level. The noisy voter model is a variant of the voter model where agents can adopt two opinions, optimistic or pessimistic, and can change them by means of an imitation (herding) and an intrinsic (noise) mechanisms. An ensemble of noisy voters undergoes a finite-size phase transition, upon increasing the relative importance of the noise to the herding, form a bimodal phase where most of the agents share the same opinion to a unimodal phase where almost the same fraction of agent are in opposite states. By the inclusion of contrarians we allow for some voters to adopt the opposite opinion of other agents (anti-herding). We first consider the case of only contrarians and show that the only possible steady state is the unimodal one. More generally, when voters and contrarians are present, we show that the bimodal-unimodal transition of the noisy voter model prevails only if the number of contrarians in the system is smaller than four, and their characteristic rates are small enough. For the number of contrarians bigger or equal to four, the voters and the contrarians can be seen only in the unimodal phase. Moreover, if the number of voters and contrarians, as well as the noise and herding rates, are of the same order, then the probability functions of the steady state are very well approximated by the Gaussian distribution.

Regulation of Pol II Pausing Is Involved in Daily Gene Transcription in the Mouse Liver.

The circadian clock orchestrates gene expression rhythms. Regulation at the level of gene transcription is essential for molecular and cellular rhythms. Pol II pause release is a critical step of transcription regulation. However, whether and how Pol II pause release is regulated during daily transcription have not been characterized. In this study, we performed Pol II ChIP-seq across the day in the mouse liver and quantitatively analyzed binding signals within the transcription start site (TSS) region and the gene body. We frequently found discordant changes between Pol II near the TSS ([Pol II]TSS, paused Pol II) and that within the gene body ([Pol II]GB, transcribing Pol II) across the genome, with only [Pol II]GB always reflecting transcription of clock and clock-controlled genes. Accordingly, Pol II traveling ratios of more than 7000 genes showed significant daily changes (>1.5-fold). Therefore, there is widespread regulation of Pol II pausing in the mouse liver. Interestingly, gene transcription rhythms exhibited a bimodal phase distribution. The transcription of ~400 genes peaked near ZT0, coincident with a genome-wide increase in [Pol II]TSS and traveling ratio (TR). The transcription of ~300 other genes peaked ~12 h later, when there was a global decrease in [Pol II]TSS and TR. ChIP-seq against TATA-binding protein (Tbp), a preinitiation complex (PIC) component, revealed that Pol II recruitment mainly played an indirect role in transcriptional output, with transcriptional termination and pause release functioning prominently in determining the fate of initiated Pol II and its pausing status. Taken together, our results revealed a critical, albeit complex role of Pol II pausing control in regulating the temporal output of gene transcription.

Mogućnost zamene aluminijuma magnezijumom u kompozitnim raketnim gorivima

Composite solid propellants based on ammonium perchlorate/hydroxyterminated polybutadiene/isophorone dyisocyanate including two metal components: aluminium and magnesium with different contents have been represented in this paper. The mass of metal powder has increased in relation to oxidant, with constant bimodal fraction ratio and total solid phase. Parameters of burning rate laws, apparent viscosity, uniaxial mechanical characteristic, density and energetic values have been determined and compared in accordance to the propellants of the smoke reduction research.

Observation of the Photon-Blockade Breakdown Phase Transition

Non-equilibrium phase transitions exist in damped-driven open quantum systems, when the continuous tuning of an external parameter leads to a transition between two robust steady states. In second-order transitions this change is abrupt at a critical point, whereas in first-order transitions the two phases can co-exist in a critical hysteresis domain. Here we report the observation of a first-order dissipative quantum phase transition in a driven circuit quantum electrodynamics (QED) system. It takes place when the photon blockade of the driven cavity-atom system is broken by increasing the drive power. The observed experimental signature is a bimodal phase space distribution with varying weights controlled by the drive strength. Our measurements show an improved stabilization of the classical attractors up to the milli-second range when the size of the quantum system is increased from one to three artificial atoms. The formation of such robust pointer states could be used for new quantum measurement schemes or to investigate multi-photon quantum many-body phases.

Metabolic Analysis of Red Blood Cells Stored at High Temperature

According to standard practice, red blood cells stored for transfusion are kept at 4°C for up to 42 days. Studies on these RBC units therefore require over a month of experimental work. At higher temperatures, dynamics proceed at an increased rate, creating the potential for faster experiments. In this study, twelve RBC units were stored in SAGM at 4°C, 13°C, 22°C, and 37°C and profiled using quantitative metabolomics throughout storage in order to determine whether the metabolic RBC response is similar at higher temperatures.In order to obtain a rate for each measurement, the profiles were fit as either linear or nonlinear. A quarter of the data (26%) was classified as linear, while approximately half of the measurements (48%) were classified and fit as nonlinear. The remaining 26% of the measurements were either noisy or exhibited no clear trend and were excluded from further calculations. Once a rate was calculated for each measurement, it was plotted on a log2(rate) vs. temperature plot. Linear regression was used to calculate the slope, from which the temperature coefficient (Q10) was calculated (Fig. 1a). The resulting distribution of temperature coefficients shows consistent values in the 2 to 3 range, the typical estimate for biological systems (Fig. 1b); the median Q10 of the linear fits was 2.64 (mean = 2.64), and the median Q10 of the nonlinear fits was 2.44 (mean = 2.52). A complete list of all linear and nonlinear fitted measurements with corresponding Q10 values is provided in Table 1.Principal component analysis (PCA) was performed on the data, yielding consistent baseline behavior in three components: one component was highly correlated with time (~50% contribution), one bimodal phase correlated with oxidative measurements (~10% contribution), and one component represented bag variance (~5-10% contribution). The component that was correlated with oxidative measurements and 2,3-diphosphoglyceric acid depletion displays the same qualitative behavior when plotted against the time component at all four temperatures (Fig. 1c). As temperature increased, the trend was accelerated.Looking at specific pathway behavior, we observed a significant accumulation of metabolites in the nucleotide salvage pathway (e.g., xanthine, hypoxanthine, uridine) at higher temperatures, while concentrations were fairly steady at low temperatures. The same behavior was observed for intracellular citric acid. Several metabolites proved to be outliers in scaling behavior, notably intracellular xanthine and extracellular oxidized glutathione, which had the highest calculated Q10 values (4.84 and 6.75, respectively).Metabolite profiling for RBCs in storage at different temperatures show that the rate of change of metabolite profiles approximately double for every 10°C of change in storage temperature. The increased metabolism causes a pronounced accumulation or depletion of certain metabolites at 22°C and 37°C, while the behavior at 13°C was similar to that at 4°C. These results indicate that for metabolic studies, storage at temperatures as high as 13°C provides a similar but accelerated system that could reduce the time required to complete experiments. [Display omitted] [Display omitted] DisclosuresBordbar:Sinopia Biosciences: Employment, Patents & Royalties. Palsson:Sinopia Biosciences: Equity Ownership.

Janus Mesoporous Nanodisc from Gelable Triblock Copolymer.

The polymer/inorganic composite trilayered Janus mesoporous nanodiscs are synthesized by coassembly of gelable poly(ethylene oxide)-block-poly(3-triethoxysilylpropyl methacrylate)-block-polystyrene (PEO-b-PTEPM-b-PS) and PEO-b-PS via a sol-gel process at an emulsion interface. Bimodal phase separations are responsible for the formation of isolated nanodiscs and mesopores within the discs. The Janus mesoporous nanodiscs are amphiphilic to form superstructures in dispersions. They can serve as a solid surfactant to stabilize emulsions.

A discussion on the performance of seven existing models proposed to describe induced polarization

Many types of classical models of the induced polarization (IP) effects of rock ore have been introduced in previous studies. Our focus is on determining the most effective model for describing the rock ore IP effects based on a numerical simulation calculation and a rock mineral spectrum experiment. We have constructed a Delphi 7 program for seven models to calculate the complex resistivity spectrum of phase. We have also evaluated the influences of the parameters on the spectrum and the spectral scope. More than 50 pieces of various natural rock ore samples from 16 regions were selected, and the frequency sweep measurements were completed using an SI-1260 Solartron spectrometer. Another program of seven models was developed using a differential evolution algorithm and least-squares for fitting the experimental spectral data. The purpose was to evaluate the ability of these models for fitting the IP effects. The results found that the influence laws on the spectrum of the different parameters, as well as the spectral scope of the models, were different. The natural samples measured revealed unimodal and bimodal phase spectra. Dias and multi-Cole-Cole models were optimal for characterizing the unimodal and bimodal phase spectra of the selected metal minerals, with the highest fitting precision root-mean-square (rms) error of 2.5% and 1.16%, respectively. Warburg, Cole-Cole, and generalized Cole-Cole models were suitable for the unimodal phase spectra, with the highest fitting precision of 3.67%, 3.01%, and 3.27%, respectively. Madden and Cantwell model was suitable for characterizing the silver-ore- and gold-bearing pyrite, but the rms was [Formula: see text] for other samples. The Debye model had an rms [Formula: see text] for characterizing all our experimental samples.

On Localized Vapor Pressure Gradients Governing Condensation and Frost Phenomena.

Interdroplet vapor pressure gradients are the driving mechanism for several phase-change phenomena such as condensation dry zones, interdroplet ice bridging, dry zones around ice, and frost halos. Despite the fundamental nature of the underlying pressure gradients, the majority of studies on these emerging phenomena have been primarily empirical. Using classical nucleation theory and Becker-Döring embryo formation kinetics, here we calculate the pressure field for all possible modes of condensation and desublimation in order to gain fundamental insight into how pressure gradients govern the behavior of dry zones, condensation frosting, and frost halos. Our findings reveal that in a variety of phase-change systems the thermodynamically favorable mode of nucleation can switch between condensation and desublimation depending upon the temperature and wettability of the surface. The calculated pressure field is used to model the length of a dry zone around liquid or ice droplets over a broad parameter space. The long-standing question of whether the vapor pressure at the interface of growing frost is saturated or supersaturated is resolved by considering the kinetics of interdroplet ice bridging. Finally, on the basis of theoretical calculations, we propose that there exists a new mode of frost halo that is yet to be experimentally observed; a bimodal phase map is developed, demonstrating its dependence on the temperature and wettability of the underlying substrate. We hope that the model and predictions contained herein will assist future efforts to exploit localized vapor pressure gradients for the design of spatially controlled or antifrosting phase-change systems.

Exhaustive study of the noise-induced phase transition in a stochastic model of self-catalyzed reactions

We completely investigate the stationary distribution density in the space of relative concentrations for the three-parameter stochastic Horsthemke–Lefever model of a binary self-catalyzed cyclic chemical reaction with perturbations produced by thermal fluctuations of reagents taken into account. This model is a stationary diffusion random process generated by a stochastic equation with the Stratonovich differential, whose marginal distribution density admits a bifurcation restructuring from the unimodal to the bimodal phase with increasing noise intensity, which is interpreted physically as a dynamical phase transition induced by fluctuations in the system.

Dual-pumped degenerate Kerr oscillator in a silicon nitride microresonator.

We demonstrate a degenerate parametric oscillator in a silicon nitride microresonator. We use two frequency-detuned pump waves to perform parametric four-wave mixing and operate in the normal group-velocity dispersion regime to produce signal and idler fields that are frequency degenerate. Our theoretical modeling shows that this regime enables generation of bimodal phase states, analogous to the χ(2)-based degenerate OPO. Our system offers potential for realization of CMOS-chip-based coherent optical computing and an all-optical quantum random number generator.

Representation of higher-order statistical structures in natural scenes via spatial phase distributions

Natural scenes contain richer perceptual information in their spatial phase structure than their amplitudes. Modeling phase structure of natural scenes may explain higher-order structure inherent to the natural scenes, which is neglected in most classical models of redundancy reduction. Only recently, a few models have represented images using a complex form of receptive fields (RFs) and analyze their complex responses in terms of amplitude and phase. However, these complex representation models often tacitly assume a uniform phase distribution without empirical support. The structure of spatial phase distributions of natural scenes in the form of relative contributions of paired responses of RFs in quadrature has not been explored statistically until now. Here, we investigate the spatial phase structure of natural scenes using complex forms of various Gabor-like RFs. To analyze distributions of the spatial phase responses, we constructed a mixture model that accounts for multi-modal circular distributions, and the EM algorithm for estimation of the model parameters. Based on the likelihood, we report presence of both uniform and structured bimodal phase distributions in natural scenes. The latter bimodal distributions were symmetric with two peaks separated by about 180°. Thus, the redundancy in the natural scenes can be further removed by using the bimodal phase distributions obtained from these RFs in the complex representation models. These results predict that both phase invariant and phase sensitive complex cells are required to represent the regularities of natural scenes in visual systems.

Trapping citronellal in a microporous polyethylene matrix

The Flory–Huggins theory was used to model the phase behaviour of linear low density polyethylene–citronellal binary mixtures. The model parameters were obtained from fitting the bimodal phase envelope using data points from cloud point determinations. This allowed the prediction of the melting point depression curve as well as the location of the spinodal region. A microporous polyethylene matrix was obtained by quenching homogeneous liquid mixtures at temperatures well below the spinodal phase boundary. This strategy makes it possible to trap, and effectively solidify, large amounts of citronellal in a polyethylene (LLDPE) matrix. This has potential implications for the development of long-lasting insect repellent bracelets and anklets.

Effect of particle size distribution on the separation efficiency in liquid chromatography

In this work, the influence of the width of particle size distribution (PSD) on chromatographic efficiency is studied. The PSD is described by lognormal distribution. A theoretical framework is developed in order to calculate heights equivalent to a theoretical plate in case of different PSDs. Our calculations demonstrate and verify that wide particle size distributions have significant effect on the separation efficiency of molecules. The differences of fully porous and core–shell phases regarding the influence of width of PSD are presented and discussed. The efficiencies of bimodal phases were also calculated. The results showed that these packings do not have any advantage over unimodal phases.

Formation of a bimodal structure in ultrafine Ti–Fe–Nb alloys with high-strength and enhanced ductility

Bulk (Ti70.5Fe29.5)100−xNbx (x=0, 3, 5 and 7at%) alloys were prepared by cold crucible levitation melting, and their mechanical properties were tested in compression at room temperature. A (Ti70.5Fe29.5)97Nb3 alloy specimen in compression exhibited an ultimate compressive strength of 2.53GPa and a compressive plastic strain of 15%. Electron microscope observations indicated that lamellar structures present in the eutectic Ti70.5Fe29.5 alloy could be modified by the addition of Nb to obtain a bimodal structure. The improvement of the mechanical properties is attributed to two factors: (1) the bimodal phase size distribution with micrometer-sized primary β-Ti dendrites embedded inside a matrix of refined ultrafine eutectics (β-Ti+TiFe), and (2) the larger lattice mismatches between the β-Ti and TiFe phases in Nb-modified eutectic Ti–Fe alloys that introduce coherency strain at the interface. The orientation relationship of A2 β-Ti with B2 TiFe in binary and Nb-modified Ti–Fe alloys is TiFe (110)[001] || β-Ti (110)[001].