Chain Transition Research Articles

Economic analysis of the use of in vitro produced embryos transferred during heat stress under dairy herd constraints

The use of embryo transfer helps to improve reproductive performance during periods of heat stress. In vitro produced embryo transfer (IVP-ET) is more expensive than artificial insemination. We hypothesized that the value IVP-ET in seasonal herds depends on herd constraints, such as the maximum number of milking cows and the maximum number of calvings that can be accommodated throughout the year. Therefore, the objective of this study was to estimate how profitability in dairy herds exposed to summer heat stress is affected by the number of months in which IVP-ET is used, the use of IVP-ET in repeat-breeder cows, IVP-ET cost, and herd constraints. We built and used a nonlinear programming model of a dairy herd with young stock and cows with monthly Markov Chain transitions. The model varied the number of heifers calving in each calendar month to maximize herd profitability. We varied IVP-ET cost ($100 or $200), duration of the IVP-ET program (2 or 4 months), and the breeding number in which IVP-ET started (1st or 3rd). In total, 20 scenarios were simulated. Maximum profitability was obtained when IVP-ET was not used, regardless of herd constraints. The 16 scenarios in which IVP-ET was used showed increased seasonality in milk yield, numbers of milking cows, total cows, total calvings, and heifer calvings because the program tried to limit the number of IVP-ET breedings in the summer. The addition of the calving constraint increased the value of IVP-ET. The breakeven cost per IVP-ET ranged from −$6.79 to $24.38 compared with conventional semen cost of $20. In conclusion, the current market costs of IVP-ET did not warrant application with the objective to increase reproductive performance during heat stress. Herd constraints on the maximum allowable seasonality in the monthly number of milking cows and calvings affected the value of IVP-ET during heat stress.

Unraveling the Nature of Exotic Phase Transitions in Quantum Spin Chains

Researchers from Kyushu University have succeeded in identifying a quantum field theory that describes the unusual phase transition in a quantum spin chain composed of spin-1 particles. This was ac...

Melting simulations of poly(ethylene oxide) nanocrystals in amorphous environments

The embedded model has been proposed for simulating melting process of the semicrystalline polymer with a low crystalline fraction. This approach is exemplarily applied to the multiscale coarse-grained (CG) model of poly(ethylene oxide) (PEO) of 14 monomers per chain. When continuously heated to a high temperature, the nanocrystal undergoes great conformational change and disassembly in order. While the specific volume and potential energy of the semicrystalline polymer system capture only glass-rubber transition of amorphous chains, the interaction energy or contact number between the nanocrystal and its amorphous environment allows for precisely identifying glass transition temperature (Tg) and equilibrium melting point (Tm) at the same time. Furthermore, the so-simulated Tg is insensitive to the lateral dimension of the nanocrystal whereas the so-simulated Tm linearly decrease with the inverse of the lateral dimension by the variant of Gibbs-Thomson equation. The extrapolated Tg and Tm for the nanocrystal with infinite lateral dimension compare well with the referenced data. The proposed scheme is quite competitive to the previous ones for a quick and accurate prediction of the Tm of a crystallizing polymer.

Nuclear shape transitions and elastic magnetic electron scattering

Backward elastic electron scattering from odd-$A$ nuclear targets is characterized by magnetic form factors containing precise information on the nuclear structure. We study the sensitivity of the magnetic form factors to structural effects related to the evolution and shape transitions in both isotopic and isotonic chains. Calculations of magnetic form factors are performed in the plane-wave Born approximation. The nuclear structure is obtained from a deformed self-consistent mean-field calculation based on a Skyrme $\mathrm{HF}+\mathrm{BCS}$ formalism. Collective effects are included in the cranking approximation, whereas nucleon-nucleon correlations are taken into account in the coherent density fluctuation model. The evolution of the magnetic form factors is found to exhibit signatures of shape transitions that show up in selected isotopic and isotonic chains involving both stable and unstable nuclei. Several cases are identified as suitable candidates for showing such fingerprints of shape transitions. A new generation of electron scattering experiments involving electron-radioactive beam colliders will be available in the near future, leading to a renewed interest in this field.

Spectral thresholding for the estimation of Markov chain transition operators

We consider nonparametric estimation of the transition operator $P$ of a Markov chain and its transition density $p$ where the singular values of $P$ are assumed to decay exponentially fast. This is for instance the case for periodised, reversible multi-dimensional diffusion processes observed in low frequency. We investigate the performance of a spectral hard thresholded Galerkin-type estimator for $P$ and ${p}$, discarding most of the estimated singular triples. The construction is based on smooth basis functions such as wavelets or B-splines. We show its statistical optimality by establishing matching minimax upper and lower bounds in $L^2$-loss. Particularly, the effect of the dimensionality $d$ of the state space on the nonparametric rate improves from $2d$ to $d$ compared to the case without singular value decay.

Variants of shadowing properties for iterated function systems on uniform spaces

In this paper, the notions of topological shadowing, topological ergodic shadowing, topological chain transitivity and topological chain mixing are introduced and studied for an iterated function system (IFS) on uniform spaces. It is proved that if an IFS has topological shadowing property and is topological chain mixing, then it has topological ergodic shadowing and it is topological mixing. Moreover, if an IFS has topological shadowing property and is topological chain transitive, then it is topologically ergodic and hence topologically transitive. Also, these notions are studied for the product IFS on uniform spaces.

Dielectric Performance of Silica-Filled Nanocomposites Based on Miscible (PP/PP-HI) and Immiscible (PP/EOC) Polymer Blends

This study compares different polymer-nanofiller blends concerning their suitability for application as insulating thermoplastic composites for High Voltage Direct Current (HVDC) cable application. Two polymer blends, PP/EOC (polypropylene/ethylene-octene copolymer) and PP/PP-HI (polypropylene/ propylene - ethylene copolymer) and their nanocomposites filled with 2 wt.% of fumed silica modified with 3-aminopropyltriethoxysilane were studied. Morphology, thermal stability, crystallization behavior dynamic relaxation, conductivity, charge trap distribution and space charge behavior were studied respectively. The results showed that the comprehensive performance of the PP/PP-HI composite is better than the one of the PP/EOC composite due to better polymer miscibility and flexibility, as well as lower charging current density and space charge accumulation. Nanosilica addition improves the thermal stability and dielectric properties of both polymer blends. The filler acts as nucleating agent increasing the crystallization temperature, but decreasing the degree of crystallinity. Dynamic mechanical analysis results revealed three polymer relaxation transitions: PP glass transition ( $\beta$ ), weak crystal reorientation ( $\alpha 1$ ) and melting ( $\alpha 2$ ). The nanosilica introduced deep traps in the polymer blends and suppressed space charge accumulation, but slightly increased the conductivity. A hypothesis for the correlation of charge trap distribution and polymer chain transition peaks is developed: In unfilled PP/EOC and PP/PP-HI matrices, charges are mostly located at the crystalline-amorphous interface, whereas in the filled PP/EOC/silica and PP/PP-HI /silica composites, charges are mostly located at the nanosilica-polymer interface. Overall, the PP/PP-HI (55/45) nanocomposite with 2 wt.% modified silica and 0.3 wt.% of antioxidants making it $a$ promising material for PP based HVDC cable insulation application with $a$ reduced space charge accumulation and good mechanical properties.

Convergence of Markov chain transition probabilities

Consider a discrete time Markov chain with rather general state space which has an invariant probability measure $\mu$. There are several sufficient conditions in the literature which guarantee convergence of all or $\mu$-almost all transition probabilities to $\mu$ in the total variation (TV) metric: irreducibility plus aperiodicity, equivalence properties of transition probabilities, or coupling properties. In this work, we review and improve some of these criteria in such a way that they become necessary and sufficient for TV convergence of all respectively $\mu$-almost all transition probabilities. In addition, we discuss so-called generalized couplings.

Evolution of collectivity in Xe118

A recoil-distance Doppler shift experiment has been performed using the $^{102}\mathrm{Pd}(^{19}\mathrm{F},p2n$) reaction at a beam energy of 73 MeV to measure the lifetime of excited states in $^{118}\mathrm{Xe}$. The differential decay-curve method using $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidences and a gating procedure that allows to extract the lifetime without feeding assumptions has been employed. The lifetimes obtained for the yrast states up to spin-parity ${8}^{+}$ are compared with interacting boson model calculations and $^{118}\mathrm{Xe}$ can be classified as a transitional nucleus between the spherical and a deformed shape. Systematics of the $B(E2)$ values for the ${2}^{+}\ensuremath{\rightarrow}{0}^{+}$ and ${4}^{+}\ensuremath{\rightarrow}{2}^{+}$ transitions in the isotopic chains of tin, tellurium and xenon are presented. It is proposed that a ``critical point'' exists at which the $B(E2;{4}^{+}\ensuremath{\rightarrow}{2}^{+})/B(E2;{2}^{+}\ensuremath{\rightarrow}{0}^{+})$ ratio drops to unity for lower neutron numbers within the isotopic chain. The position of the ``critical point'' varies with proton number, i.e., it is presumed to be located at the same mass number $A=114$ in the Sn, Te, and Xe isotopes.

Multifunctional Reversible Self-Assembled Structures of Cellulose-Derived Phase-Change Nanocrystals.

Owing to advantageous properties attributed to well-organized structures, multifunctional materials with reversible hierarchical and highly ordered arrangement in solid-state assembled structures have drawn tremendous interest. However, such materials rarely exist. Based on the reversible phase transition of phase-change materials (PCMs), phase-change nanocrystals (C18-UCNCs) are presented herein, which are capable of self-assembling into well-ordered hierarchical structures. C18-UCNCs have a core-shell structure consisting of a cellulose crystalline core that retains the basic structure and a soft shell containing octadecyl chains that allow phase transition. The distinct core-shell structure and phase transition of octadecyl chains allow C18-UCNCs to self-assemble into flaky nano/microstructures. These self-assembled C18-UCNCs exhibit efficient thermal transport and light-to-thermal energy conversion, and thus are promising for thermosensitive imaging. Specifically, flaky self-assembled nano/microstructures with manipulable surface morphology, surface wetting, and optical properties are thermoreversible and show thermally induced self-healing properties. By using phase-change nanocrystals as a novel group of PCMs, reversible self-assembled multifunctional materials can be engineered. This study proposes a promising approach for constructing self-assembled hierarchical structures by using phase-change nanocrystals and thereby significantly expands the application of PCMs.

Ballistic-to-diffusive transition in spin chains with broken integrability

We study the ballistic-to-diffusive transition induced by the weak breaking of integrability in a boundary-driven XXZ spin-chain. Studying the evolution of the spin current density $\mathcal J^s$ as a function of the system size $L$, we show that, accounting for boundary effects, the transition has a non-trivial universal behavior close to the XX limit. It is controlled by the scattering length $L^*\propto V^{-2}$, where $V$ is the strength of the integrability breaking term. In the XXZ model, the interplay of interactions controls the emergence of a transient "quasi-ballistic" regime at length scales much shorter than $L^*$. This parametrically large regime is characterized by a strong renormalization of the current which forbids a universal scaling, unlike the XX model. Our results are based on Matrix Product Operator numerical simulations and agree with perturbative analytical calculations.

MSMPathfinder: Identification of Pathways in Markov State Models.

Markov state models represent a popular means to interpret biomolecular processes in terms of memoryless transitions between metastable conformational states. To gain insight into the underlying mechanism, it is instructive to determine all relevant pathways between initial and final states of the process. Currently available methods, such as Markov chain Monte Carlo and transition path theory, are convenient for identifying the most frequented pathways. They are less suited to account for the typically huge amount of pathways with low probability which, though, may dominate the cumulative flux of the reaction. On the basis of a systematic construction of all possible pathways, the here proposed method MSMPathfinder is able to characterize the multitude of unique pathways (say, up to 1010) in a complex system and to quantitatively calculate their correct weights and associated waiting times with predefined accuracy. Adopting the chiral transitions of a peptide helix and the folding of the villin headpiece as model problems, mechanisms and associated waiting times of these processes are discussed using a kinetic network representation. The analysis reveals that the waiting time distribution may yield only little insight into the diversity of pathways, because the measured folding times do typically not reflect the most probable path lengths but rather the cumulative effect of many different pathways.

Dynamics of Induced Maps on the Space of Probability Measures

For a continuous self-map f on a compact metric space X, we provide two simple examples: the first confirms that shadowing of (X, f) is not inherited by $$({\mathcal {M}}(X),{\hat{f}})$$ in general, and the other satisfies that both (X, f) and $$({\mathcal {M}}(X),{\hat{f}})$$ have no Li–Yorke pair, where $${\mathcal {M}}(X)$$ be the space of all Borel probability measures on X. Then we prove that chain transitivity of (X, f) implies chain mixing of $$({\mathcal {M}}(X),{\hat{f}})$$ , and provide an example to deny the converse. For a non-autonomous system $$(X,f_{0,\infty })$$ , we prove that weak mixing of $$({\mathcal {M}}(X),\hat{f}_{0,\infty })$$ implies that of $$(X,f_{0,\infty })$$ , and give an example to deny the converse, where $$f_{0,\infty }=\{f_n\}_{n=0}^\infty $$ is a sequence of continuous self-maps on X. We also prove that if $$f_n$$ is surjective for all $$n\ge 0$$ , then chain mixing of $$({\mathcal {M}}(X),{\hat{f}}_{0,\infty })$$ always holds true, and shadowing of $$({\mathcal {M}}(X),{\hat{f}}_{0,\infty })$$ implies mixing of $$(X, f_{0,\infty })$$ . If $$X=I$$ is an interval, we obtain a sharp condition such that transitivity is equivalent between (I, f) and $$({\mathcal {M}}(I),{\hat{f}})$$ . Although $$({\mathcal {M}}(I),{\hat{f}})$$ has infinite topological entropy for any transitive system (I, f), we give an example such that $$(I,f_{0,\infty })$$ is transitive but $$({\mathcal {M}}(I),{\hat{f}}_{0,\infty })$$ has zero topological entropy.

Hermitian formulation of multiple scattering induced topological phases in metamaterial crystals

In this article we develop an analog to the SSH model in tight-binding chains of resonators and an innovative Hermitian matrix formulation to describe the topological phases induced by multiple scattering at subwavelength scales in one-dimensional structured and locally resonant metamaterial crystals. We first start from a set of coupled dipole equations capturing the nature of the wave-matter interactions, i.e., hybridization between locally dispersive resonances and a continuum as well as infinite long range multiple scattering coupling, to analytically derive a matrix operator ${H}_{\mathrm{MS}}$, which is found to be Hermitian when evaluated on propagative bands. This new operator straightforwardly highlights how the composition, structure, scattering resonance, and Bloch periodicity together set in the chain macroscopic properties, in particular its topology. We analytically confirm the existence of a structure based topological transition in chiral-symmetric biperiodic metamaterial crystal chains, characterized by a winding number. We further demonstrate that chiral symmetry breaking in metamaterial crystal chains prevents us from defining a proper topological invariant. We finally numerically confirm, in the microwave domain, the existence of the topological transition in a chiral symmetric metamaterial crystal chain through the study of topological interface modes and their robustness to disorder.

Superconducting phase transition in inhomogeneous chains of superconducting islands

We study one dimensional chains of superconducting islands with a particular emphasis on the regime in which every second island is switched into its normal state, thus forming a superconductor-insulator-normal metal (S-I-N) repetition pattern. As is known since Giaever tunneling experiments, tunneling charge transport between a superconductor and a normal metal becomes exponentially suppressed, and zero-bias resistance diverges, as the temperature is reduced and the energy gap of the superconductor grows larger than the thermal energy. Here we demonstrate that this physical phenomenon strongly impacts transport properties of inhomogeneous superconductors made of weakly coupled islands with fluctuating values of the critical temperature. We observe a non-monotonous dependence of the chain resistance on both temperature and magnetic field, with a pronounced resistance peak at temperatures at which some but not all islands are superconducting. We explain this phenomenon by the inhomogeneity of the chains, in which neighboring superconducting islands have slightly different critical temperatures. We argue that the Giaever's resistance divergence can also occur in the zero-temperature limit. Such quantum transition can occur if the magnetic field is tuned such that it suppresses superconductivity in the islands with the weaker critical field, while the islands with stronger energy gap remain superconducting. In such a field, the system acts as a chain of S-I-N junctions.

Long-Range Multibody Interactions and Three-Body Antiblockade in a Trapped Rydberg Ion Chain.

Trapped Rydberg ions represent a flexible platform for quantum simulation and information processing that combines a high degree of control over electronic and vibrational degrees of freedom. The possibility to individually excite ions to high-lying Rydberg levels provides a system where strong interactions between pairs of excited ions can be engineered and tuned via external laser fields. We show that the coupling between Rydberg pair interactions and collective motional modes gives rise to effective long-range and multibody interactions consisting of two, three, and four-body terms. Their shape, strength, and range can be controlled via the ion trap parameters and strongly depends on both the equilibrium configuration and vibrational modes of the ion crystal. By focusing on an experimentally feasible quasi one-dimensional setup of ^{88}Sr^{+} Rydberg ions, we demonstrate that multibody interactions are enhanced by the emergence of soft modes associated with, e.g., a structural phase transition. This has a striking impact on many-body electronic states and results-for example-in a three-body antiblockade effect that can be employed as a sensitive probe to detect structural phase transitions in Rydberg ion chains. Our study unveils the possibilities offered by trapped Rydberg ions for studying exotic phases of matter and quantum dynamics driven by enhanced multibody interactions.

Mapping the environmental footprints of nations partnering the Belt and Road Initiative

Over the past few years, the Belt and Road Initiative (BRI) proposed by China has made a notable contribution to the rapid growth of cross-border trade. This however has been accompanied by unexpected burden shifting of resource extractions and environmental emissions to less developed countries. Given that little attention has been paid to the trade-embodied resources and emissions throughout the BRI, this paper, for the first time, accounts for the water, land, carbon, nitrogen and phosphorus footprints of 65 BRI nations and traces the flows embodied in international trade between the BRI and remaining 124 economies by employing a global multi-regional input–output model. Overall, distribution of the BRI's environmental footprints shows strong spatial heterogeneity, amongst China, India and Russia have the highest total environmental footprints. Furthermore, reverse patterns of spatial distribution can be observed between the total and per capita footprints of BRI nations. When it comes to the global scale, the BRI as a whole is found to be a net exporter of trade-embodied flows except for virtual water. Remarkably, 29% of the BRI nations experience a role transition in supply chains across scales, either from net exporters on the BRI level to net importers on the global level, or in reverse. Our findings provide a holistic picture of environmental footprints at scales ranging from single nations, regions, BRI, and even globe, highlighting the significance of a global view in finding ways to tackle environmental challenges and fulfill the Sustainable Development Goals throughout the BRI countries by 2030.

The impact of R&D and innovation on global supply chain transition: GTAP analysis on Japan's public R&D investment.

Policymaking for science, technology, and innovation (R&D) is stepping into a new era in the twenty-first century within a highly integrated production network, making it more challenging to capture the impact of R&D investment from an evidence-based approach. To unfold the paradox of the R&D spillover effect spared in the global supply chain, we use computable general equilibrium model with the GTAP database v10 to analyze the impact of Japan’s public R&D investment to the world focus on key sectors of global supply chain, namely chemical and pharmaceutical, electronic equipment, machinery, and transportation equipment to examine its output, external trades, and welfare. The productivity parameters triggered by public R&D investment are calibrated from the SciREX Policymaking Intelligent Assistance System—Economic Simulator (SPIAS-e). The simulation results show significant increase in Japan’s output and export for chemical and pharmaceutical, electronic equipment, and transportation equipment. The GDP growth was stimulated by 0.6% and substantial welfare improvement by USD 78,000 million, while other countries such as Malaysia and Taiwan by 0.4–0.6%. In contrast, the economic indicators of China reveal a negative impact, implying a structural change in the composition of the production network. It is notable to see a higher economic integration of Oceania within the region through its vibrant production and trades. The study provides comprehensive global analysis on production networks and insights for evaluating the R&D investment spillover effects.

A Combined Markov Chain and Reinforcement Learning Approach for Powertrain-Specific Driving Cycle Generation

<div class="section abstract"><div class="htmlview paragraph">Driving cycles are valuable tools for emissions calibration at engine and powertrain test beds. While generic velocity profiles were sufficient in the past, legislative changes and increasing complexity of powertrain and exhaust aftertreatment systems require a new approach: Realistically transient cycles - which include critical driving maneuvers and can be tailored to a specific powertrain configuration - are needed to optimize the emission behavior of the said powertrain.</div><div class="htmlview paragraph">For the generation of realistic velocity profiles, the Markov chain approach has been widely used and described in literature. However, this approach, so far, has only been used to generate cycles that are statistically representative of a large database of real driving trips, which is typically not available during the early stages of development of a new powertrain.</div><div class="htmlview paragraph">The work at hand combines a Markov chain approach for driving cycle generation with Q-learning - a reinforcement learning algorithm - to generate driving cycles that meet user-defined criteria and include critical driving maneuvers reflecting individual powertrain development targets.</div><div class="htmlview paragraph">Using simplified models of the powertrain, vehicle and driver and an iterative process, the generated driving cycles are evaluated regarding the fulfillment of the set criteria. The learning algorithm then adapts the Markov chain transition probability matrix to increase the occurrence of the desired critical driving maneuvers and reduce the share of undesired stochastic elements.</div><div class="htmlview paragraph">Exemplary results show that the proposed method is indeed able to generate driving cycles with certain realistic properties that include the desired maneuvers with the expected statistical variance.</div></div>

Many-body localization transition in large quantum spin chains: The mobility edge

This work shows the existence of many-body mobility edge in large disordered Heisenberg chain. The time dynamics of initial product states reveal that the transition between localized and extended phases depends on the average energy of the initial states.