Constant Transition Research Articles

Spatial-confinement synthesis of single-crystal ZrCo nanoparticles for ultrafast and long-life hydrogen/hydrogen isotope storage

ZrCo alloy is a safe and low-cost H-isotope storage material for controlled nuclear fusion, but traditional ZrCo prepared by smelting method suffer from slow gas uptake/release kinetics and serious degradation of cycle performance. Here, a “bottom-up” synthesis method is developed to prepare highly crystalline and high-purity ZrCo micron-/nanoparticles via a spatial-confinement strategy. The size-dependent hydrogen storage performances are systematically investigated from the perspectives of lattice constant, crystallinity, grain boundary, stress, and disproportionation phase transition. Compared with micron-scale polycrystalline smelted-ZrCo, the comprehensive performances of nanoscale ZrCo single crystals are significantly improved, including a 19-fold increase in kinetic rate, a ∼ 50% reduction of disproportionation ratio, and a two-fold improvement in cycle stability. This study provides a promising direction and an efficient synthetic method for the preparation of high-performance ZrCo alloys, which will facilitate their application in controlled nuclear fusion.

Flow Control in Serpentine Inlet Duct Using Vortex Generator Jets

The objective of the present research is to study the effectiveness of steady and pulsed vortex generator jets in reducing inlet flow distortion and in improving pressure recovery by effective secondary flow control in uniform inflow serpentine duct diffuser. The measurements were carried out at a test Reynolds number of 6.5 x 105 based on the diffuser inlet width. Serpentine duct diffuser consisted of two main portions, namely, a square to circular constant area transition duct followed by a circular diffusing duct. Investigations show that the flow in the serpentine diffusing duct suffers from stall on the inner wall and consequently the outflow at AIP has considerable flow distortion due to the combined effect of secondary flow and the inner wall stall. It is observed that the use of vortex generator jets, both in steady and pulsed modes, improve the performance substantially. The number of jets, location of jets, velocity ratios and the pulse frequency are some of the variables that are studied. The results obtained so far suggest that use of pulsed jet not only gives better performance but also reduces the amount of air that is needed to be injected through the jets in comparison to steady jets for similar velocity ratios.

The Flow Matrix Offers a Straightforward Alternative to the Problematic Markov Matrix

The Flow matrix is a novel method to describe and extrapolate transitions among categories. The Flow matrix extrapolates a constant transition size per unit of time on a time continuum with a maximum of one incident per observation during the extrapolation. The Flow matrix extrapolates linearly until the persistence of a category shrinks to zero. The Flow matrix has concepts and mathematics that are more straightforward than the Markov matrix. However, many scientists apply the Markov matrix by default because popular software packages offer no alternative to the Markov matrix, despite the conceptual and mathematical challenges that the Markov matrix poses. The Markov matrix extrapolates a constant transition proportion per time interval during whole-number multiples of the duration of the calibration time interval. The Markov extrapolation allows at most one incident per observation during each time interval but allows repeated incidents per observation through sequential time intervals. Many Markov extrapolations approach a steady state asymptotically through time as each category size approaches a constant. We use case studies concerning land change to illustrate the characteristics of the Flow and Markov matrices. The Flow and Markov extrapolations both deviate from the reference data during a validation time interval, implying there is no reason to prefer one matrix to the other in terms of correspondence with the processes that we analyzed. The two matrices differ substantially in terms of their underlying concepts and mathematical behaviors. Scientists should consider the ease of use and interpretation for each matrix when extrapolating transitions among categories.

Structural and optical properties of InP1-xSbx/n-InAs epilayers grown by gas source molecular beam epitaxy

High-resolution x-ray diffraction (HR-XRD), photoluminescence (PL), synchrotron radiation extended x-ray absorption fine-structure (SR-EXAFS) measurements are methodically analyzed for assessing the optical and structural properties of InP1−xSbx/n-InAs epifilms grown by gas-source molecular-beam epitaxy method. For InP0.63Sb0.37/n-InAs sample, the PL study has revealed two A1, A2 energy bands. The A1 band prevalent at low temperature is attributed to the recombination of carriers trapped in the tail states. The A2 band with nearly constant transition energy ∼ 0.46 eV is virtually temperature independent. In InP1−xSbx alloys, the energy peak of A1 band redshifted with temperature and showed strong compositional disorder. The A2 band, dominant at higher temperature with Gaussian-like line shape is ascribed to the deep-level transition as its behavior coincided with the signature of a configuration coordinate model. The deep level responsible for A2 band is possibly linked to the “vacancy-impurity” like complexes having ground and excited states in the energy band gap. The composition dependent analysis of SR-EXAFS data for InP1−xSbx/InAs samples has confirmed the maintenance of nearest neighbor In-P, In-Sb shell distances within the range of bulk binary materials’ bond lengths. We feel that our results of HR-XRD, PL and SR-EXAFS techniques have provided valuable information on the structural and optical characteristics of the InP1−xSbx/n-InAs (001) epilayers and can be extended to many other technologically important materials.

From Warlords to Politicians: Transforming Rebel Movements Into Political Parties

Over the past few decades, African countries have faced a new phenomenon in political life – the ascent to power of former warlords – leaders of insurgent anti-government movements or tribal militias, who become presidents, vice presidents, prime ministers and members of parliament. Warlords seek to translate their wartime gains into material wealth and social status and gain political office to consolidate their military exploits. To achieve this, they employ many different strategies: transforming their armed groups into political parties, joining existing political organizations, establishing totally new parties, or conducting individual political activity. In societies where power is accumulated through the expansion of social networks – political, economic, military, ethnic, religious, regional, etc. – it becomes extremely useful for a politician to play several leadership roles. Access to various networks allows leaders to expand their base of support: this partly explains why African political elites are represented not only by politicians, but also by businessmen, priests, football players and former warlords. Since most African countries since independence have been in a constant transition from authoritarian to “democratic” governance, from public sector dominance to liberal economies, from limited violence to large-scale warfare, elites have constantly had to invent new roles for themselves in order to maintain political power. If they were unable to achieve the transformation that the situation required, they risked becoming marginalized figures. In this sense, recent warlords intuitively felt it inadvisable to distance themselves from their past wartime activities. Depending on the audience and circumstances, they either emphasized their former merits as field commanders, or, on the contrary, diligently portrayed themselves as vigorous peacemakers. The literature on peacebuilding and post-war reconstruction, with rare exceptions, ignores such an important aspect as the influence of former warlords on post-conflict electoral processes, focusing almost exclusively on organizational issues, the level of effectiveness of state institutions, intra- and inter-party struggles, methods of ensuring security, and the degree of readiness of polling stations. The present paper aims at filling this gap.

Managing resource allocation for the recruitment stocking problem

This paper revisits the Recruitment Stocking Problem (RSP), in which a prescribed total number of kits must be allocated across multiple distribution sites, where streams of subjects arrive for kit pickup. A kit can be a test-kit for a new pharmaceutical drug, a medical device, a vaccine, a humanitarian relief survival kit, etc. RSP seeks to minimize the expected recruitment time — the time to recruit a prescribed target number of kits — by identifying an optimal or near-optimal kit allocation across all locations. To this end, we first develop a computational method for evaluating the expected recruitment time using the so-called Randomization Procedure. Specifically, since the recruitment process forms a finite-state continuous-time Markov process, the Randomization Procedure transforms the Markov process with varied transition rates from different states into one with a constant transition rate across all states, and thus substantially simplifies the RSP statistics computation. Further, we develop two search heuristics to efficiently search for optimal or near-optimal kit allocations, especially for large RSP models that are too computationally expensive to optimize by exhaustive search. Finally, we illustrate the efficacy of the proposed heuristics by numerical experiments, and then discuss practical implications and provide managerial insights.

Spectroscopy, docking and molecular dynamics studies on the interaction between cis and trans palladium-alanine complexes with calf-thymus DNA and antitumor activities

The present article investigates whether the cis and trans isomers of the same compound affect their antitumor and DNA-binding properties. Thus, we have synthesized cis-[Pd(L-Ala)2] (I) and trans-[Pd(L-Ala)2] (II) (Ala = L-alanine) complexes by modifications to improve the reported procedure. Cytotoxicity tests of these two isomers along with carboplatin (as a known drug) against MCF-7 and HCT-116 (as cancerous) and MCF10A and CCD-841 (as normal cell lines) were performed under the same experimental conditions. The results follow the sequence I > II > carboplatin for both cell lines. DNA-binding studies were carried out in a medium similar to that of physiological conditions (pH = 7 and 0.02 M NaCl). Results of UV–vis absorption provides apparent binding constant, K app, and midpoint transition of native CT-DNA to refolded structure, L1/2, suggesting interaction at quite low concentrations of these metal complexes. Fluorescence emission intensity of the CT-DNA-EB system demonstrates static quenching predominates in the binding process. Moreover, negative values of ΔH 0 and ΔS 0 suggested that the hydrogen bonds and van der Waals forces are the interaction forces between the complexes with the CT-DNA groove. Other studies include gel electrophoresis, viscosity experiments, partition coefficient, computational energy minimization, molecular docking and molecular dynamics simulations. All these studies indicate that the cis isomer has better interaction towards CT-DNA and are in accord with fluorescence, UV–vis and cytotoxicity studies. The present work gives valuable indications for further design of cis and trans metal-based isomers as potential anticancer agents.

On the gain of entrainment in the n-dimensional ribosome flow model.

The ribosome flow model (RFM) is a phenomenological model for the flow of particles along a one-dimensional chain of n sites. It has been extensively used to study ribosome flow along the mRNA molecule during translation. When the transition rates along the chain are time-varying and jointly T-periodic the RFM entrains, i.e. every trajectory of the RFM converges to a unique T-periodic solution that depends on the transition rates, but not on the initial condition. In general, entrainment to periodic excitations like the 24 h solar day or the 50 Hz frequency of the electric grid is important in numerous natural and artificial systems. An interesting question, called the gain of entrainment (GOE) in the RFM, is whether proper coordination of the periodic translation rates along the mRNA can lead to a larger average protein production rate. Analysing the GOE in the RFM is non-trivial and partial results exist only for the RFM with dimensions n = 1, 2. We use a new approach to derive several results on the GOE in the general n-dimensional RFM. Perhaps surprisingly, we rigorously characterize several cases where there is no GOE, so to maximize the average production rate in these cases, the best choice is to use constant transition rates all along the chain.

Hitting times, number of jumps, and occupation times for continuous-time finite state Markov chains

In this paper we discuss three random variables associated with a finite state continuous-time Markov chain having a constant transition rate matrix: the number of jumps between two different states, the amount of time spent in a given state, known as an occupation time, and the time it takes for the Markov chain to first reach a particular state, known as a hitting time or first passage time. First, we calculate expected values for each of these random variables. We then derive the moment generating functions for these variables. Our approach is to use the vector/matrix representations of the various processes. Each solution is written in terms of an integral of the exponential of a matrix.

Историко-культурная динамика формирования идентичности

The paper analyzes the historical and cultural dynamics of identity formation from antiquity to the present. Identity and identity processes occupy one of the central places in history and culture, as they provide an answer to the such fundamental questions as: Who am I? With whom am I? Who are “ours” and who are “theirs”? The methodological basis includes the theory of symbolic interactionism; the sociology of knowledge; the cultural approach. The novelty of the author's approach is an integrated historical and cultural approach to the processes of identification/identity; as well as identifying the mechanisms of its formation through common memories in the context of development from “We” to “I” and “I”. The author concludes that the dynamics of the process of identity formation is not based on the transition from one type of identity to another, but on the expansion of different forms of identification. The main mechanism of identification is the transition from identification based on blood kinship and unity of territory to professional, group, religious identification (in the Middle Ages) to national, ethnic, cultural, civilizational identity in the new time and (in Modern Times). As a leitmotif of the acquisition of identity one may take transitions from identification in archaic times as a prescription in a rigid and direct form, to “loyalty and service” in the Middle Ages, gradual formation of personal identity in the Renaissance, the 19th century, when the subject received the right to choose, and up to the need to choose in the second half of the 19th and in the 20th centuries. And such choice is a constant transition from one identity to another depending on the circumstances.

Form-stable flexible composite multi-phase change material with high latent heat and enhanced thermal conductivity for thermal management

Form-stable flexible composite phase change materials (PCMs) are widely studied on the application of thermal management of batteries. Usually, the latent heat of composite PCMs is lower than that of pure PCMs due to the existence of additive materials. More composite PCMs are needed when their latent heat is too low to meet the requirements, which limits the development of the compact structure of the thermal management system. In this work, a novel paraffin (PA) -based composite multi-phase change material (m-PCM) with high latent heat was fabricated for thermal management. PA thickened by adding styrene ethylene butene styrene block copolymer (SEBS) and expanded graphite (EG) as enhanced thermal conductivity material were loaded in phase change polymer skeleton (PPS) synthesized from polyethylene glycol (PEG). One side, PPS not only played a role on preventing the leakage of paraffin as supporting material, but also provided the extra latent heat of phase change for the composite m-PCM. On the other side, SEBS was added by increasing the viscosity of PA to solve the problem of poor compatibility between the polymer skeleton and PA. Benefiting from the additional latent heat provided by PPS and the addition of EG, the composite m-PCM exhibited the phase change enthalpies as high as about 221.3 J·g−1 while ensuring the thermal conductivity as high as 1.46 W·m−1·K−1. When heated, the composite m-PCM exhibited the excellent shape-stability and flexibility. After 200 thermal cycles, the composite m-PCM performed the almost constant phase transition properties. The results demonstrate the composite m-PCM has extensive application prospects for efficient thermal management.

Electrical conductivity and relaxation in lithium-doped barium vanadate glasses investigated by impedance spectroscopy

We present herein a detailed study of the electric and dielectric properties of glasses with the composition 60V2O5–(40–x)BaO–xLi2O, where x = 10, 15, 20, or 25 mol%. The conduction and relaxation mechanisms have been studied by impedance spectroscopy over the frequency range from 40 Hz to 10 MHz and at various temperatures. With constant transition metal oxide content, the conductivity variation in the glasses is assumed to be mainly due to an ionic contribution. The dependence of electrical conductivity on frequency has been analysed using Jonscher's power law. Properties of the glasses, such as electric modulus loss and relaxation mechanism, have been analysed in terms of electric modulus using the Kohlrausch–William–Watts (KWW) equation, which describes the relaxation behaviour of the mobile ions as non-Debye in nature. Scaling of ac conductivity and electric modulus data has shown that conductivity relaxation is independent of temperature. The non-monotonic variation in the stretching parameter β has been found to show a positive correlation with various activation energies, namely electrical activation energy, relaxation activation energy, and the activation energy from the Anderson–Stuart model. The anomalous behaviour of activation energy with respect to conductivity has been substantiated through structural insight. The conductivity was found to be highest in glasses with 25 mol% Li2O, while coupling between the mobile ions was best for glasses with 20 mol% Li2O.

Cu triggered phase transitions in Fe7S8@NS-C anode: A neglected factor affecting the electrochemical performance of sodium storage

Iron sulfide (Fe7S8) with high theoretical capacity and abundant natural resource is an attractive anode candidate in sodium-ion batteries (SIBs). However, its abnormal capacity variation in ether-based electrolytes is inexplicable. Herein, N,S co-doped carbon-coated Fe7S8 (Fe7S8@NS-C) is constructed. As an anode for SIBs, the Na-storage capacity of Fe7S8@NS-C increases significantly from 503.9 to 565.8 mAh/g at 1 A/g after 120 cycles. Comprehensive characterizations demonstrate this capacity growth not only originates from the reduced FeSx particle size, but also from the Cu-triggered phase transition to form Cu5FeS4 and CuSx. Subsequently, the unstable Cu5FeS4 is converted to CuSx and FeSx, and the resultant capacity maintains relatively stable. Remarkably, Cu2O and Cu0 gradually appear as the cycle number increases, which may result from the side reactions of Cu+ with some electrolyte components. The constant Cu-related phase transition accelerates the corrosion of Cu foil, which weakens the adhesion of active materials on it and induces a capacity attenuation after ∼ 550 cycles. This work is helpful to understand the capacity variation of Fe7S8 anode during sodiation/desodiation processes in ether-based systems, which is of great significance for the design and application of metal sulfide materials in electrochemical energy storage.

Society, segregation and freedom: The transformation of the female image in Iranian cinema

Talking about the figure of women in Iranian cinema during the post-revolutionary era is controversial, due to the factors that have influenced its appearance and its tense relationship with the norms imposed by the Islamic theocracy; In this sense, this feminine semblance goes beyond the arts, since the restrictions or censorship towards them would not begin there, but rather the fact in question stems from a restrictive and confessional regimentation of public life, which in the case of the cinema, it would even have an impact on the private orbit. To understand the process of women in Iranian cinematography, it is convenient to go back many years, when the woman in the image had completely different roles than those that the Islamic Republic now wanted to encourage, given that the role of the female gender during the Pahlavi monarchy contradicted Iranian values, not only from the perspective of Islam, but also from traditional ones. In accordance with the previous description of the historical transition, during the conformation, consolidation and acceptance —by authorities and the Iranian society itself—.Women in cinema through the years continues in constant transition, which refuses to forget what an Iranian woman has lived through during the several processes constants of transformation by a society that adheres to the norms and laws that the sharia law allows, but that in turn, with the creativity that many filmmakers (today many more women in the profession) have managed to mitigate different views about of women in society.

Birth-death chains on a spider: Spectral analysis and reflecting-absorbing factorization

We consider discrete-time birth-death chains on a spider, i.e. a graph consisting of N discrete half lines on the plane that are joined at the origin. This process can be identified with a discrete-time quasi-birth-death process on the state space N0×{1,2,…,N}, represented by a block tridiagonal transition probability matrix. We prove that we can analyze this process by using spectral methods and obtain the n-step transition probabilities in terms of a weight matrix and the corresponding matrix-valued orthogonal polynomials (the so-called Karlin-McGregor formula). We also study under what conditions we can get a reflecting-absorbing factorization of the birth-death chain on a spider which can be seen as a stochastic UL block factorization of the transition probability matrix of the quasi-birth-death process. With this factorization we can perform a discrete Darboux transformation and get new families of “almost” birth-death chains on a spider. The spectral matrix associated with the Darboux transformation will be a Geronimus transformation of the original spectral matrix. Finally, we apply our results to the random walk on a spider, i.e. with constant transition probabilities.

Asymptotic properties of the maximum likelihood estimator in regime-switching models with time-varying transition probabilities

Summary Time-varying transition probability (TVTP) regime-switching models extend the constant regime transition probability in Markov-switching models to include information from observations. We show consistency and asymptotic normality of the maximum likelihood estimator (MLE) in general TVTP regime-switching models where the conditional distribution of $Y_t$ depends on lagged regimes. Consistency of the MLE is also shown under misspecification. The assumptions are verified in regime-switching autoregressive models with widely applied TVTP specifications. A simulation study examines the finite-sample distributions of the MLE and compares the asymptotic variance estimates constructed from the Hessian matrix and the outer product of the score. The simulation results favour the latter. As an empirical example, we compare three leading economic indicators in terms of describing U.S. industrial production.

Prediction of high-temperature polymer dielectrics using a Bayesian molecular design model

Machine learning has shown its great potential in the accelerated discovery of advanced materials in the field of computational molecular design. High-temperature polymer dielectrics are urgently required with the emerging applications of energy-storage dielectric film capacitors under high-temperature conditions. Here, we demonstrate the successful prediction of polymers with a high dielectric constant (ɛ) and high glass transition temperature (Tg) using a Bayesian molecular design model. The model is trained on a joint data set containing 382 computed ɛ values using density functional perturbation theory and experimentally measured Tg values of ∼7000 polymers to build relative quantitative structure–property relationships and identify the promising polymers with specific desired range of dielectric constant and glass transition temperature. From the hypothetical polymer candidates, ten promising polymers are proposed based on their predicted properties and synthetic accessibility score for high-temperature dielectric film capacitors’ application. Moreover, 250k novel polymer structures are generated with the model to support future polymer informatics research. This work contributes to the successful prediction of high-temperature polymer dielectrics using machine learning models.

Model parameters influencing the cost-effectiveness of sacubitril/valsartan in heart failure: evidence from a systematic literature review

ObjectivesTo summarize cost-effectiveness (CE) evidence of sacubitril/valsartan for the treatment of heart failure (HF) patients with reduced ejection fraction (HFrEF). The impact of different modeling approaches and parameters on the CE results is also described.MethodsWe conducted a systematic literature review using multiple databases: Embase®; MEDLINE®; MEDLINE®-In Process; NIHR CRD database including DARE, NHS EED, and HTA databases; and the Cost Effectiveness Analysis registry. We also reviewed HTA countries’ websites to identify CE reports of sacubitril/valsartan, published up to 25-July-2021. Articles published in English as full-texts, conference-abstracts, or HTA reports were included.ResultsWe included 44 CE models [39 from 37 publications (22 full-texts; 15 conference-abstracts) and 5 HTAs; Europe, n = 20; North and South Americas, n = 14; Asia and Australia, n = 10]. Most models adopted a Markov structure with constant transition probabilities of events (n = 27) or a mix of Markov and regression-based models (n = 16), with variations in structural assumptions and chosen parameters. Study authors concluded sacubitril/valsartan to be a cost-effective therapy in 37/41 models in chronic HFrEF patients and 2/3 models in hospitalized patients stabilized after an acute decompensation for HF. CE models showing sacubitril/valsartan not to be a cost-effective treatment generally modeled a shorter time horizon. Effect of sacubitril/valsartan on cardiovascular and all-cause mortality, cost, duration of effect and time horizon was the main model drivers.ConclusionsMost evidence indicated sacubitril/valsartan is cost-effective in HFrEF. The use of a lifetime horizon is recommended in future models as HF is a chronic disease. Data on the CE of sacubitril/valsartan in the inpatient setting were limited and further research is warranted.

Molecular design of monomers by considering the dielectric constant and stability of the polymer

AbstractThe dielectric constant (DC) and glass transition temperature (Tg) properties were used to design polymers by quantitative structure–property relationship (QSPR). Using polymer data sets that included homopolymers and copolymers, property prediction models were constructed using the polymer properties and molecular descriptors calculated from monomer structures. The best combination of regression methods, types of descriptors, and preprocessing methods for constructing regression models were determined, and thus, DC and Tg prediction models with a high prediction accuracy could be constructed. Then, theoretical monomer structures, and theoretical copolymers with different combinations of monomer structures and composition ratios were generated, and the DC and Tg of the generated structures were predicted using the constructed models. Candidate structures met the desired DC and Tg values, and the proposed method could select promising monomer structures and composition ratios. Thus, monomer structures that would produce polymers with a high or low DC and high Tg were designed.

Similarity of competing risks models with constant intensities in an application to clinical healthcare pathways involving prostate cancer surgery

The recent availability of routine medical data, especially in a university-clinical context, may enable the discovery of typical healthcare pathways, that is, typical temporal sequences of clinical interventions or hospital readmissions. However, such pathways are heterogeneous in a large provider such as a university hospital, and it is important to identify similar care pathways that can still be considered typical pathways. We understand the pathway as a temporal process with possible transitions from a single initial treatment state to hospital readmission of different types, which constitutes a competing risks setting. In this article, we propose a multi-state model-based approach to uncover pathway similarity between two groups of individuals. We describe a new bootstrap procedure for testing the similarity of constant transition intensities from two competing risk models. In a large simulation study, we investigate the performance of our similarity approach with respect to different sample sizes and different similarity thresholds. The studies are motivated by an application from urological clinical routine and we show how the results can be transferred to the application example.