Step Transition Research Articles

Approximate verification of geometric ergodicity for multiple-step Metropolis transition kernels

In many applications involving discrete time Markov chains, the autocorrelation between states corresponding to nearby time points is too high to use all of these states as part of an approximate random sample from a specified target distribution. In these situations, it is common to use the output of a thinned chain, where we take samples every $h$ steps, and $h$ is a positive integer, in order to reduce autocorrelation. In order to justify using central limit theorems in analyses based on the output of a thinned chain, it is necessary to show that the thinned chain is geometrically ergodic. A common way to do this is to show that the chain satisfies a minorization condition and an associated drift condition. In this manuscript, we extend previous results pertaining to one-step transition kernels to handle numerical estimation of minorization and drift coefficients for $h$-step transition kernels for Metropolis algorithms.

Influence of Cooling Rate on Ice Crystallization and Melting in Sucrose-Water System

The ice crystallization and melting in systems where the equilibrium state is difficult to reach is one of the growing areas in pharmaceutical freeze-drying research. The quality of the final freeze-dried product depends on the parameters of the cooling step, which affect the ice nucleation and growth. In this paper, we present a DSC study of ice crystallization and melting in a sucrose-water system. Using two different types of thermal cycles, we examine the influence of cooling and heating rates on the thermal behavior of sucrose-water solutions with water contents between 50 and 100 wt%.The DSC results show that low cooling rates provide crystallization at higher temperatures and lead to lower amount of non-freezing water. Consequently, the glass transition and ice melting properties observed upon heating depend on the cooling conditions in the preceding step. Based on the experimental results, we investigate the reasons for the existence of the two steps on DSC heating curves in sucrose-water systems: the glass transition step and the onset of ice melting. We show that diffusion of water can be the limiting factor for ice growth and melting in the sucrose-water system when the amorphous phase is in a liquid state. In particular, when the diffusion coefficient drops below 10−14 m2/sec, the ice crystals growth or melting becomes strongly suppressed even above the glass transition temperature. Understanding the diffusion limitations in the sucrose-water system can be used for the optimization of the freeze-drying protocols for proteins and probiotics.

Direct additive manufacturing of melt growth Al2O3-ZrO2 functionally graded ceramics by laser directed energy deposition

Functionally graded ceramics (FGC), which combine properties of different ceramics in one part, usually have better comprehensive function and structural efficiency. In this study, four different gradient transition Al2O3-ZrO2 FGC samples were prepared by laser directed energy deposition (LDED) method. The results show that there is an obvious interface in direct transition sample. The transition section bears tensile stress caused by difference of thermophysical properties of materials, resulting in significant longitudinal cracks. Element transition in interface region shows a step sharp transition. The direct transition sample shows intergranular fracture and the bonding strength is very low. Gradient transition mode can effectively suppress cracks, and avoid the step transition of microstructure and elements. Elements, microhardness of 25, 20 wt% FGC samples realized a nearly linear smooth transition. The interface fracture of FGC samples changed to transgranular fracture, bonding strength was significantly improved, and the maximum flexural strength reached 160.19 MPa.

Multiple Sub-State Structures of SERCA2b Reveal Conformational Overlap at Transition Steps During the Catalytic Cycle

Multiple Sub-State Structures of SERCA2b Reveal Conformational Overlap at Transition Steps During the Catalytic Cycle

Lock-In, Fixation and the Extinction of Technologies: A Design-Theoretic View of Sustainable Transitions

In this viewpoint article we discuss the challenges to achieving sustainability transitions from the perspective of theories of design and of technology. We first introduce the environmental issues that face industrial civilization, noting the differences in viewpoints concerning whether planetary limits are largely insurmountable or if they may be alleviated through human ingenuity. We then give an overview of theoretical perspectives on the nature of technology and of technological change and innovation before discussing the implications of these theoretical perspectives for possible approaches to sustainability transition. In particular, we note the importance of the maturity of technologies and the challenges of increasing technological complexity. We then introduce a selection of theoretical perspectives on the nature of design, before discussing the implications of these, especially the knowledge requirements in identifying feasible transition steps, and the inherent conflict between different viewpoints on planetary limits. We emphasize the risk of fixation and the importance of trade-offs. We conclude by proposing a five-fold set of actions.

A Small-Step Operational Semantics for GP 2

The operational semantics of a programming language is said to be small-step if each transition step is an atomic computation step in the language. A semantics with this property faithfully corresponds to the implementation of the language. The previous semantics of the graph programming language GP 2 is not fully small-step because the loop and branching commands are defined in big-step style. In this paper, we present a truly small-step operational semantics for GP 2 which, in particular, accurately models diverging computations. To obtain small-step definitions of all commands, we equip the transition relation with a stack of host graphs and associated operations. We prove that the new semantics is non-blocking in that every computation either diverges or eventually produces a result graph or the failure state. We also show the finite nondeterminism property, viz. that each configuration has only a finite number of direct successors. The previous semantics of GP 2 is neither non-blocking nor does it have the finite nondeterminism property. We also show that, for a program and a graph that terminate, both semantics are equivalent, and that the old semantics can be simulated with the new one.

The N-glycosylation-related genes as potential targets for RNAi-mediated pest control of the Colorado potato beetle (Leptinotarsa decemlineata).

N-glycosylation is one of the most common and important post-translational modifications in the eukaryotic cell. The study of protein N-glycosylation in several model insects confirmed the importance of this process in insect development, immunity, survival and fertility. The Colorado potato beetle (Leptinotarsa decemlineata) (CPB) is a common pest of Solanaceae crops. With the infamous title of champion of insecticide resistance, novel pest control strategies for this insect are needed. Luckily this pest insect is reported as very sensitive for the post-genomic technology of RNA interference (RNAi). In this project, we investigated the importance of N-glycosylation in the survival and development of CPB using RNAi-mediated gene silencing of N-glycosylation-related genes (NGRGs) during the different transition steps from the larva, through the pupa to the adult stage. High mortality was observed in the larval stage with the silencing of early NGRGs, as STT3a, DAD1 and GCS1. With dsRNA against middle NGRGs, abnormal phenotypes at the ecdysis process and adult formation were observed, while the silencing of late NGRGs did not cause mortality. The lethal phenotypes observed on silencing of the genes involved in the early processing steps of the N-glycosylation pathway suggest these genes are good candidates for RNAi-mediated control of CPB. Next to the gene-specific mechanism of RNAi for biosafety and possible implementation in integrated pest management, we believe these early NGRGs provide a possible alternative to the well-known target genes Snf7 and vacuolar ATPases that are now used in the first commercial RNAi-based products and thus they may be useful in the context of proactive resistance management. © 2021 Society of Chemical Industry.

Reliability modelling for linear and circular [formula omitted]-out-of-[formula omitted]: F systems with shared components

Reliability analysis for k-out-of-n systems has received much attention in the field of reliability due to its practical importance. In this work, models for linear and circular k-out-of-n: F systems with shared components, consisting of m subsystems, are discussed. The finite Markov chain imbedding approach cannot be used directly to derive reliability of the considered systems because of the common area existing between adjacent subsystems. For this reason, we first derive the probability that the number of failed components is a given value in the m common areas. Then, all disjoint cases, each of which is regarded as a series system consisting of m subsystems with different initial state probability distributions, are obtained, with which the nith step transition rate matrix is calculated by using the Markov chain technique, for i=1,2,…,m. Finally, the reliability of the system is obtained by summing the reliabilities of all cases along with the finite Markov chain imbedding approach. Some numerical examples are presented to illustrate the efficiency of the proposed reliability evaluation method.

Participation and engagement of a rural community in Ciclov\xeda: progressing from research intervention to community adoption

BackgroundOpen streets events, where roads are temporarily closed to motorized vehicles, can provide safe spaces for physical activity (PA) and become sustainable community infrastructure. Since 2016, we have collaborated with a rural community to implement an open streets event, named ciclovía. In 2019, ciclovía was adopted as a community-wide program. This paper describes the process of building and progressing a ciclovía from a research intervention to a community-adopted program and participation of a rural community in ciclovía.MethodsWe used community-based participatory research to foster bidirectional learning on how to optimize the content and implementation of ciclovía to be feasible and acceptable for rural communities. The community-academic partnership focused on: 1) understanding the science of ciclovía; 2) learning the implementation process; 3) creating tools to facilitate planning, implementation, and evaluation of ciclovía; and 4) developing transition steps from a research intervention to a community-adopted program.ResultsThe progression of the research intervention to community adoption spanned 2 years. First, the partnership met quarterly to discuss the science of ciclovía, its utility, and its adaptation for rural communities. Second, the partnership studied processes that facilitated ciclovía implementation. Third, the partnership created the ciclovía planning guide and tools for communities to establish their own ciclovía. The guide included forming a planning committee, setting meeting and communication plans, marketing and promotion, and selecting evaluation tools. Fourth, the transition steps from research intervention to community adoption included creating roles and responsibilities, implementing ciclovía using the planning guide, and convening listening sessions for improvement on implementation. Community attendance at ciclovía doubled from 189 individuals (126 children and 63 adults) when it was a research intervention to 394 individuals (277 children and 117 adults) when it was a community program.ConclusionsThe progression from a research intervention to a community-adopted program encompasses multiple steps that involve bidirectional learning and partnership with the community. Lessons learned from this study are integrated into a disseminatable ciclovía planning guide.

Science-policy-practice Interfaces for City Climate Change Transitions: A Case Study of Canberra, Australia

ABSTRACT Science indicates that cities are central to society’s capacity to avoid catastrophic and irreversible climate change, that rapid transitions to climate wise practices are needed and that transition steps will face implementation challenges. Lessons learned from reform experience can build understanding of the knowledge, policy and practices required for further transitions. This paper identifies lessons learned from renewable energy and resilience reforms in the city of Canberra, Australia. It finds that attention to science-policy-practice interfaces contributes important insights for the design of planned transitions and for integrative and implementation-focused reforms needed to overcome local barriers.

Wnt Signaling Pathway Is among the Drivers of Liver Metastasis

Liver metastasis, originating either from a primary liver or other cancer types, represent a large cancer-related burden. Therefore, studies that add to better understanding of its molecular basis are needed. Herein, the role of the Wnt signaling pathway in liver metastasis is outlined. Its role in hepatocellular carcinoma (HCC) epithelial-mesenchymal transition (EMT), motility, migration, metastasis formation, and other steps of the metastatic cascade are presented. Additionally, the roles of the Wnt signaling pathway in the liver metastasis formation of colorectal, breast, gastric, lung, melanoma, pancreatic, and prostate cancer are explored. The special emphasis is given to the role of the Wnt signaling pathway in the communication between the many of the components of the primary and secondary cancer microenvironment that contribute to the metastatic outgrowth in the liver. The data presented herein are a review of the most recent publications and advances in the field that add to the idea that the Wnt pathway is among the drivers of liver metastasis and that its targeting could potentially relieve liver metastasis–related complications.

Toward Convergence in Free Energy Calculations for Protein Conformational Changes: A Case Study on the Thin Gate of Mhp1 Transporter.

It has been challenging to obtain reliable free energies for protein conformational changes from all-atom molecular dynamics simulations, despite the availability of many enhanced sampling techniques. To alleviate the difficulties associated with the enormous complexity of the conformational space, here we propose a few practical strategies for such calculations, including (1) a stringent method to examine convergence by comparing independent simulations starting from different initial coordinates, (2) adoption of multistep schemes in which the complete conformational change consists of multiple transition steps, each sampled using a distinct reaction coordinate, and (3) application of boundary restraints to simplify the conformational space. We demonstrate these strategies on the conformational changes between the outward-facing and outward-occluded states of the Mhp1 membrane transporter, obtaining the equilibrium thermodynamics of the relevant metastable states, the kinetic rates between these states, and the reactive trajectories that reveal the atomic details of spontaneous transitions. Our approaches thus promise convergent and reliable calculations to examine intuition-based hypotheses and to eventually elucidate the underlying molecular mechanisms of reversible conformational changes in complex protein systems.

First-principles investigation of the metal-insulator transition in rutile RuO2

The electronic and magnetic properties of rutile ruthenium dioxide (RuO2) are extensively investigated by employing density functional theory. The material RuO2 is observed as a nonmagnetic metal. The sharing of a single Ru 4d electron by the dyz/xz orbitals is responsible for the metallicity of RuO2. The ground-state properties of this material change significantly upon the application of on-site Coulomb interaction U. RuO2 preserves its nonmagnetic metallic character up to U=3 eV. Nevertheless, RuO2 encounters a first step transition from nonmagnetic metal to a ferromagnetic metal (FM) at U=4 eV. The present system remains in its FM phase till U=5 eV. It exhibits a second step transition from the FM to a half-metallic ferromagnetic phase at U=6 eV. Eventually, RuO2 encounters metal-insulator transition (MIT) at U=7 eV with a band gap of Eg ∼0.3 eV upholding ferromagnetism. It is revealed that the spin polarization arising from the strong dynamical electron correlation due to the application of U is responsible for the metal to half-metal and MIT in RuO2.

Kinetic study of the crystallization of ZSM-5 under organic template-free conditions

Here, the ZSM-5 zeolite was prepared under organic template-free conditions at different reaction temperatures and initial gel compositions using a hydrothermal process. A kinetic study of the synthesis of Zeolite was performed based on crystal growth. The crystallinity degree of the prepared samples was calculated from the PXRD and FT-IR results and then the crystallization curves were obtained. From these curves, the kinetic parameters were computed. The obtained results showed that by increasing the Na+ content of the initial gel composition, the activation energy for the crystal growth was reduced and as a result, the crystallization rate of ZSM-5 zeolite was enhanced due to the structure-directing role of Na+ cation. The activation energy of the induction step, transition step and crystal growth step are 122.8, 46.2, and 48.5 kJ/mol respectively for the molar ratios of 29Na2O:63SiO2:Al2O3:2400H2O:16H2SO4 and 141.0, 70.4, and 80.8 kJ/mol respectively for the molar ratios of 16Na2O:31SiO2:Al2O3:2400H2O:16H2SO4.

Decoding the Structural Dynamics and Conformational Alternations of DNA Secondary Structures by Single-Molecule FRET Microspectroscopy.

In addition to the canonical double helix form, DNA is known to be extrapolated into several other secondary structural patterns involving themselves in inter- and intramolecular type hydrogen bonding. The secondary structures of nucleic acids go through several stages of multiple, complex, and interconvertible heterogeneous conformations. The journey of DNA through these conformers has significant importance and has been monitored thoroughly to establish qualitative and quantitative information about the transition between the unfolded, folded, misfolded, and partially folded states. During this structural interconversion, there always exist specific populations of intermediates, which are short-lived or sometimes even do not accumulate within a heterogeneous population and are challenging to characterize using conventional ensemble techniques. The single-molecule FRET(sm-FRET) microspectroscopic method has the advantages to overcome these limitations and monitors biological phenomena transpiring at a measurable high rate and balanced stochastically over time. Thus, tracing the time trajectory of a particular molecule enables direct measurement of the rate constant of each transition step, including the intermediates that are hidden in the ensemble level due to their low concentrations. This review is focused on the advantages of the employment of single-molecule Forster’s resonance energy transfer (sm-FRET), which is worthwhile to access the dynamic architecture and structural transition of various secondary structures that DNA adopts, without letting the donor of one molecule to cross-talk with the acceptor of any other. We have emphasized the studies performed to explore the states of folding and unfolding of several nucleic acid secondary structures, for example, the DNA hairpin, Holliday junction, G-quadruplex, and i-motif.

Extended Migdal-Watson formula to evaluate background strength in binary breakup reactions

A new formula to evaluate the nonresonant background for binary breakup is proposed by extending the Migdal-Watson (MW) formula, which was originally developed for $s$-wave breakup in charge neutral systems. The strength of the direct breakup, which is assumed by a one step transition from the initial bound state, is simulated by the complex scaling method (CSM) in binary cluster systems. The extended MW formula is applied to the direct breakup of $^{20}\mathrm{Ne}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}\ensuremath{\alpha}+^{16}\mathrm{O}$, and we have found that the formula nicely reproduces the strength of the direct breakup evaluated by CSM. We have demonstrated that new parameters introduced in the extended MW formula have a close connection to the spatial size of the initial wave packet, which is given by the product of the initial wave function and the external field. The application of the new formula to the direct breakup of $^{12}\mathrm{Be}$ into $\ensuremath{\alpha}+^{8}\mathrm{He}$ is also discussed.

US Medical Licensing Exam Performance and American Board of Surgery Qualifying and Certifying Examinations

Program directors use US Medical Licensing Exam (USMLE) scores as criteria for ranking applicants. First-time pass rates of the American Board of Surgery (ABS) Qualifying (QE) and Certifying (CE) Examinations have become important measures of residency program quality. USMLE Step 1 will become pass/fail in2022. American Board of Surgery QE and CE success rates were assessed considering multiple characteristics of highly ranked (top 20) applicants to 22 general surgery programs in 2011. Chi-square, t-test, Wilcoxon Rank sum, linear and logistic regression were used, as appropriate. The QE and CE first attempt pass rates were 96% (235/244) and 86% (190/221), respectively. QE/CE success was not significantly associated with sex, race, research experience, or publications. Alpha Omega Alpha (AΩA) status was associated with success on the index CE (98% vs 83%; p= 0.008). Step 1 and Step 2 Clinical Knowledge (CK) scores of surgeons who passed QE on their first attempt were higher than scores of those who failed (Step 1: 233 vs 218; p= 0.016); (Step 2CK: 244 vs 228, p= 0.009). For every 10-point increase in Step 1 and 2CK scores, the odds of passing CE on the first attempt increased 1.5 times (95% CI 1.12, 2.0; p= 0.006) and 1.5 times (95% CI 1.11, 2.02, p= 0.008), respectively. For every 10-point increase in Steps 1 and 2CK scores, the odds of passing the QE on the first attempt increased 1.85 times (95% CI 1.11, 3.09; p= 0.018) and 1.86 times (95% CI 1.14, 3.06, p= 0.013), respectively. USMLE Step 1 and Step 2 CK examination scores correlate with American Board of Surgery QE and CE performance and success. The USMLE decision to transition Step 1 to a pass/fail examination will require program directors to identify other factors that predict ABS performance for ranking applicants.

The influence of age and fall history on single transition step kinematics

BackgroundThe risk of falls during locomotion increases with age, and step negotiation is one of the most hazardous types of gait for older adults. Further, a history of a fall is one of the strongest predictors of a future fall; and women fall more frequently, and incur greater medical costs, compared to men. The purpose of the study was to identify lower extremity kinematic factors associated with transition step clearance and foot placement in young women and older women with and without a fall history.MethodsForty-five female participants (15 per group) completed trials that consisted of walking barefoot along a raised walkway at a self-selected speed, descending a 17 cm step, and continued level ground walking. Variables of interest included lead and trail limb minimum step clearance and foot placement, and bilateral lower extremity joint positions at step clearance and at lead foot initial contact.FindingsSignificant group differences, with large effect sizes, were found in lead foot placement and knee flexion position at initial contact. Both older groups landed more closely to the step and made initial contact with the lead knee in a more flexed position compared to the young group.InterpretationThe kinematic differences may be a strategy utilized by older adults to create an early landing to minimize time in single limb stance and compensate for age-related loss of lower extremity strength, range of motion, and/or balance. However, the greater knee flexion may also increase the risk a fall due to lead limb collapse.

Optimal Non-Markovian Search Strategies with n-Step Memory.

Stochastic search processes are ubiquitous in nature and are expected to become more efficient when equipped with a memory, where the searcher has been before. A natural realization of a search process with long-lasting memory is a migrating cell that is repelled from the diffusive chemotactic signal that it secretes on its way, denoted as an autochemotactic searcher. To analyze the efficiency of this class of non-Markovian search processes, we present a general formalism that allows one to compute the mean first-passage time (MFPT) for a given set of conditional transition probabilities for non-Markovian random walks on a lattice. We show that the optimal choice of the n-step transition probabilities decreases the MFPT systematically and substantially with an increasing number of steps. It turns out that the optimal search strategies can be reduced to simple cycles defined by a small parameter set and that mirror-asymmetric walks are more efficient. For the autochemotactic searcher, we show that an optimal coupling between the searcher and the chemical reduces the MFPT to 1/3 of the one for a Markovian random walk.

Petri Net-Based Semi-Compiled Code Generation for Programmable Logic Controllers

Industrial discrete event dynamic systems (DEDSs) are commonly modeled by means of Petri nets (PNs). PNs have the capability to model behaviors such as concurrency, synchronization, and resource sharing, compared to a step transition function chart or GRAphe Fonctionnel de Commande Etape Transition (GRAFCET) which is a particular case of a PN. However, there is not an effective systematic way to implement a PN in a programmable logic controller (PLC), and so the implementation of such a controller outside a PLC in some external software that will communicate with the PLC is very common. There have been some attempts to implement PNs within a PLC, but they are dependent on how the logic of places and transitions is programmed for each application. This work proposes a novel application-independent and platform-independent PN implementation methodology. This methodology is a systematic way to implement a PN controller within industrial PLCs. A great portion of the code will be validated automatically prior to PLC implementation. Net structure and marking evolution will be checked on the basis of PN model structural analysis, and only net interpretation will be manually coded and error-prone. Thus, this methodology represents a systematic and semi-compiled PN implementation method. A use case supported by a digital twin (DT) is shown where the automated solution required by a manufacturing system is carried out and executed in two different devices for portability testing, and the scan cycle periods are compared for both approaches.