Asymmetric Process Research Articles

Cegpy: Modelling with chain event graphs in Python

Chain event graphs (CEGs) are a recent family of probabilistic graphical models that generalise the popular Bayesian networks (BNs) family. Crucially, unlike BNs, a CEG is able to embed, within its graph and its statistical model, asymmetries exhibited by a process. These asymmetries might be in the conditional independence relationships or in the structure of the graph and its underlying event space. Structural asymmetries are common in many domains, and can occur naturally (e.g. a defendant vs prosecutor’s version of events) or by design (e.g. a public health intervention). Whilst two CEG packages exist in R for modelling processes with asymmetric conditional independencies, there currently exists no software that allows a user to leverage the theoretical developments of the CEG model family in modelling processes with structural asymmetries. In this paper, we present cegpy: the first Python implementation of CEGs and the first across all languages to support structurally asymmetric processes. cegpy contains an implementation of Bayesian learning and probability propagation algorithms for CEGs. We illustrate the functionality of cegpy using a structurally asymmetric dataset.

Copper-Catalyzed Dynamic Kinetic Asymmetric P-C Coupling of Secondary Phosphine Oxides and Aryl Iodides.

Transition-metal-catalyzed enantioselective P-C cross-coupling of secondary phosphine oxides (SPOs) is an attractive method for synthesizing P-stereogenic phosphorus compounds, but the development of such a dynamic kinetic asymmetric process remains a considerable challenge. Here we report an unprecedented highly enantioselective dynamic kinetic intermolecular P-C coupling of SPOs and aryl iodides catalyzed by copper complexes ligated by a finely modified chiral 1,2-diamine ligand. The reaction tolerates a wide range of SPOs and aryl iodides, affording P-stereogenic tertiary phosphine oxides (TPOs) in high yields and with good enantioselectivity (average 89.2 % ee). The resulting enantioenriched TPOs were transformed into structurally diverse P-chiral scaffolds, which are highly valuable as ligands and catalysts in asymmetric synthesis.

Copper‐Catalyzed Dynamic Kinetic Asymmetric P−C Coupling of Secondary Phosphine Oxides and Aryl Iodides

AbstractTransition‐metal‐catalyzed enantioselective P−C cross‐coupling of secondary phosphine oxides (SPOs) is an attractive method for synthesizing P‐stereogenic phosphorus compounds, but the development of such a dynamic kinetic asymmetric process remains a considerable challenge. Here we report an unprecedented highly enantioselective dynamic kinetic intermolecular P−C coupling of SPOs and aryl iodides catalyzed by copper complexes ligated by a finely modified chiral 1,2‐diamine ligand. The reaction tolerates a wide range of SPOs and aryl iodides, affording P‐stereogenic tertiary phosphine oxides (TPOs) in high yields and with good enantioselectivity (average 89.2 % ee). The resulting enantioenriched TPOs were transformed into structurally diverse P‐chiral scaffolds, which are highly valuable as ligands and catalysts in asymmetric synthesis.

Asymmetric Radical Bicyclization for Stereoselective Construction of Tricyclic Chromanones and Chromanes with Fused Cyclopropanes.

Asymmetric radical bicyclization processes have been developed via metalloradical catalysis (MRC) to stereoselectively construct chiral chromanones and chromanes bearing fused cyclopropanes. Through optimization of a versatile D2-symmetric chiral amidoporphyrin ligand platform, a Co(II)-metalloradical system can homolytically activate both diazomalonates and α-aryldiazomethanes containing different alkene functionalities under mild conditions for effective radical bicyclization, delivering cyclopropane-fused tricyclic chromanones and chromanes, respectively, in high yields with excellent control of both diastereoselectivities and enantioselectivities. Combined computational and experimental studies, including the electron paramagnetic resonance (EPR) detection and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) trapping of key radical intermediates, shed light on the working details of the underlying stepwise radical mechanisms of the Co(II)-catalyzed bicyclization processes. The two catalytic radical processes provide effective synthetic tools for stereoselective construction of valuable cyclopropane-fused chromanones and chromanes with newly generated contiguous stereogenic centers. As a specific demonstration of synthetic application, the Co(II)-catalyzed radical bicyclization has been employed as a key step for the first asymmetric total synthesis of the natural product (+)-Radulanin J.

Uses of a new asymmetric loss-based process capability index in the electronic industries

This article suggests a novel process capability index (PCI) termed as , which is based on an asymmetric loss function (linear exponential) for a normal process and offers a specific method of incorporating the loss in capability analysis. Next, we estimate the suggested PCI using the moment estimation approach when the process follows a normal distribution, and we compare the effectiveness of the investigated estimation methods in terms of their mean squared errors through simulation analysis. Additionally, the confidence intervals for the index are constructed using the generalized confidence interval (GCI) and parametric bootstrap confidence interval (BCI) approach. Using Monte Carlo simulation, the performance of the GCI and BCI is compared in terms of average width, associated coverage probabilities, and relative coverage. Finally, three real data sets from the electronic industries are re-analyzed to show the usefulness of the suggested index, MOM estimation, GCI and BCI.

Assessment of Deformation Flow in 1050 Aluminum Alloy by the Implementation of Constitutive Model Parameters

The behavior of technically pure aluminum was examined, and this investigation allowed the determination of the material constants by various models. The model parameters derived were subsequently used for the finite element simulations (FEM) of a cold rolling process. To determine the tuning parameters such as the strain-hardening coefficient K, strain-hardening exponent n, or elastic constant E, a tensile test was performed on the heat-treated sheet of 1050 Al alloy and the experimentally observed deformation behavior was compared to the simulated counterpart. The results of the FEM calculations reveal that the strain-hardening characteristics can be alternatively derived from the Brinell indentation. Additionally, the determined constitutive model parameters (E = 69.8 GPa, K = 144.6 MPa, and n = 0.3) were verified by simulating both the symmetric and asymmetric rolling processes. The distribution of the equivalent strain across the sheet thickness was computed by the FEM, and it was found that the modeled deformation profiles tend to reproduce the experimentally observed ones with high accuracy for different strain modes inasmuch as the mentioned rolling trials accommodate diverse amounts of shear and normal strain components.

Green Oxidative Catalytic Processes for the Preparation of APIs and Precursors

Asymmetric oxidation processes have constituted a valuable tool for the synthesis of active pharmaceutical ingredients (APIs), especially for the preparation of optically active sulfoxides, compounds with interesting biological properties. Classical approaches for these oxidative procedures usually require the application of non-sustainable conditions that employ hazardous reagents and solvents. In the last decades, chemists have tried to combine the preparation of valuable compounds of high yields and selectivities with the development of more sustainable protocols. To achieve this objective, greener solvents, reagents, and catalysts are employed, together with the use of novel chemical techniques such as flow catalysis or photocatalysis. The last efforts in the development of greener approaches for the preparation of APIs and their intermediates using oxidative procedure will be reviewed herein. Most of these approaches refer to biocatalytic methods, in which mild reaction conditions and reagents are employed, but other novel techniques such as photocatalysis will be described.

Multivariate Garch Models Comparison in Terms of the Symmetric and Asymmetric Models

Modelling the Multivariate Generalised Autoregressive Conditional Heteroscedasticity (GARCH) model included both symmetric and asymmetric processes. The information includes monthly data for the Consumer Price Index, Crude Oil Price, Exchange Rate, and Inflation Rate from January 2005 to December 2021. For the analysis, E-view Statistical software was employed. The aforementioned four macroeconomic variables show a tendency for volatility to cluster across time. Both symmetrical and asymmetrical processes had the volatility condition. The residual recursive plot was used to analyse the structural fluctuation in the series. The plot showed continual movement in the inflation rate as well as a downward and upward movement in the consumer price index, exchange rate, and crude oil price. The Akaike Information Criterion (AIC), Hannan-Quinn Information Criterion (HQIC), and Schwarz Information Criterion were chosen as the best models based on information criteria (SIC). Symmetric and asymmetric modelling techniques were used to create the Economic Variables Multivariate GARCH (M-GARCH) models. To calculate the covariance and correlation between the four variables, M-GARCH models were utilised. The main finding of the estimation of all M-GARCH models is that the symmetric models (Diagonal BEKK and Constant Conditional Correlation, or "CCC") have the lowest values of the model information criteria compared to the asymmetric models (Diagonal BEKK and CCC), while the asymmetric models (Diagonal VECH) have the lowest values of the model information criteria compared to the symmetric models (Diagonal VECH). Based on the findings, it was discovered that while analysing the interaction between the four economic variables returns series, the Symmetric Diagonal BEKK and CCC model outperformed the Asymmetric Diagonal VECH model.

Garch Models Comparison with Symmetric and Asymmetric Process for Univariate Econometric Series

The Generalized Autoregressive Conditional Heteroscedasticity (GARCH) model was modeled using both symmetric and asymmetric processes. Secondary data from January 2005 to December 2021 on the Consumer Price Index, Exchange Rate, Crude Oil Price, and Inflation Rate were used for this study. The research was conducted using the statistical software packages Minitab and E-view. The aforementioned four macroeconomic variables show a tendency for volatility to cluster across time. In both symmetric and asymmetric processes, the volatility condition and leverage impact coefficients were present. By contrasting the symmetric models (ARCH, GARCH, and GARCH-M) and the asymmetric models, the best model was chosen using Akaike Information Criteria (E-GARCH, T-GARCH and APARCH). For the investigated univariate economic variables, the results indicated that the found asymmetric model GARCH models outperformed the symmetric model GARCH models. Therefore, these models can be applied to the forecasting of these series of economic indicators. Models include the Asymmetric E-GARCH (1, 1) Model for Consumer Price Index, Crude Oil Price, and Inflation Rate Series and the Asymmetric T-GARCH (1, 1) Model for Exchange Rate Series.

Thermal rectification in thin film metalattice structures: A computational study

Thermal rectification is an asymmetric heat transfer process where directionally dependent transport occurs along a given axis. In this work, geometric parameters that govern thermal rectification in solids composed of various semiconducting materials were investigated utilizing metalattice data for seven materials with pore sizes ranging between 2 and 30 nm. Using numerical simulation, thermal rectification was calculated at different thermal biases in single material systems, including silicon, cubic boron nitride, and diamond, among others. The largest thermal rectification for each material was exhibited in bilayer sample stacks that were thermally matched (i.e., the thermal resistance of each layer in the stack is equal in either forward or reverse direction). Of the materials tested, diamond provided the highest thermal rectification for all cases, with its best case achieving a thermal rectification of 57.2%. This novel thermal functionality will find application in advanced applications for temperature regulation, including resonator systems where thermal effects may significantly alter and/or degrade performance.

Information diversity and anomalous scaling in asymmetric social contagion process on low-dimensional static networks.

To understand how competition affects the diversity of information, we study the social contagion model introduced by Halvorsen-Pedersen-Sneppen (HPS) [G. S. Halvorsen, B. N. Pedersen, and K. Sneppen, Phys. Rev. E 103, 022303 (2021)2470-004510.1103/PhysRevE.103.022303] on one-dimensional (1D) and two-dimensional (2D) static networks. By mapping the information value to the height of the interface, we find that the width W(N,t) does not satisfy the well-known Family-Vicsek finite-size scaling ansatz. From the numerical simulations, we find that the dynamic exponent z should be modified for the HPS model. For 1D static networks, the numerical results show that the information landscape is always rough with an anomalously large growth exponent, β. Based on the analytic derivation of W(N,t), we show that the constant small number of influencers created for unit time and the recruitment of new followers are two processes responsible for the anomalous values of β and z. Furthermore, we also find that the information landscape on 2D static networks undergoes a roughening transition, and the metastable state emerges only in the vicinity of the transition threshold.

Synthesis of transparent electrospun composite nanofiber membranes by asymmetric solvent evaporation process

Currently, transparent and flexible electrospun nanofiber membranes have attracted considerable attention due to their potential use in electronic displays, solar cells, air filtration, and medical and health fields (i.e., transparent wound dressings). Developing transparent nanofibrous membranes is still very intriguing because of severe light reflection and absorption into the fibrous membranes. Herein, we report a successful fabrication technique of transparent composite nanofibrous membranes by combining electrospinning and a particular post-treatment of the prepared membranes. Firstly, randomly organized polyurethane (PU) nanofibers were prepared via electrospinning. These PU nanofibers mats were then impregnated into different concentrations (i.e., 5, 10, and 15 wt%) and embedded time (i.e., 30 and 60 min) of poly (methyl methacrylate) (PMMA) and polydimethylsiloxane (PDMS) solutions to prepare transparent composite nanofibrous membrane using solution immersion technique. The resulting composite nanofibrous membranes exhibit excellent performance, including optical transparency (i.e., up to 82% for PMMA and ∼ 6% for PDMS), lacking affinity to water, mechanically robust, reasonable water vapor transmission rate (WVTR, ∼ 1 kg/m2 day), and good thermal stability. The composite nanofiber membranes have promising optical transparency, suitable mechanical strength, and high hydrophobicity. Therefore, they have the potential in various applications, including windshields for highly moving objects, displays, and particularly as transparent wound dressings in medicine.

Strengthening a Medium-Carbon Low-Alloy Steel by Nanosized Grains: The Role of Asymmetrical Rolling.

A medium-carbon low-alloy steel was prepared via the asymmetric rolling process with different ratios of upper and down roll velocities. Subsequently, the microstructure and mechanical properties were explored by using SEM, EBSD, TEM, tensile tests and nanoindentation. The results show that asymmetrical rolling (ASR) can significantly improve strength while retaining good ductility compared with conventional symmetrical rolling. The yield strength and tensile strength of the ASR-steel are 1292 ± 10 MPa and 1357 ± 10 MPa, respectively, which are higher than the values of 1113 ± 10 MPa and 1185 ± 10 MPa for the SR-steel. The ASR-steel retains good ductility of 16.5 ± 0.5%. The significant increase in strength is related to the joint actions of the ultrafine grains, dense dislocations and a large number of nanosized precipitates. This is mainly because of the introduction of extra shear stress on the edge under asymmetric rolling, which induces gradient structural changes hence increasing the density of geometrically necessary dislocations.

Development of a Scalable Asymmetric Process for the Synthesis of GLYT1 Inhibitor BI 425809 (Iclepertin)

Development of a Scalable Asymmetric Process for the Synthesis of GLYT1 Inhibitor BI 425809 (Iclepertin)

The Open Universe: Totality, Self-reference and Time

ABSTRACT Before the twentieth century, the Universe was usually imagined as a large spatially extended thing unfolding in time. The past was fixed and the future was open; unfolding was conceived as an asymmetric process of coming into being. Relativity introduced a new vision in which space and time are presented together as a single four-dimensional manifold of events. That, together with the fact that the fundamental laws of our classical theories are symmetric in time, made understanding why the past and future present themselves so differently in our experience one of the central challenges of physics. The last two centuries have seen a great deal of progress in understanding various of the so-called arrows of time: the thermodynamic arrow, the cosmological arrow, the arrow of knowledge or information. There remains an outstanding piece of this puzzle that has seen little progress, one that Roger Penrose described in his beautiful paper Singularities and Time-Asymmetry in 1979 as: “The arrow most difficult to comprehend … namely the feeling of relentless forward temporal progression, according to which potentialities seem to be transformed into actualities.” I will propose that the insight needed to resolve the problem involves taking into account that we are part of the universe and that any attempt to model it as a totality involves self-reference. I will argue specifically that self-reference, against the background of a thermodynamic gradient, creates an instability in an embedded agent’s ability to know the future or even treat it as a potential object of knowledge. That instability captures the sense in which the future remains for her perpetually open and the passage of time resolves openness into the fixity of fact.

Modified Macdonald polynomials and the multispecies zero-range process: I

In this paper we prove a new combinatorial formula for the modified Macdonald polynomials H ˜ λ (X;q,t), motivated by connections to the theory of interacting particle systems from statistical mechanics. The formula involves a new statistic called queue inversions on fillings of tableaux. This statistic is closely related to the multiline queues which were recently used to give a formula for the Macdonald polynomials P λ (X;q,t). In the case q=1 and X=(1,1,⋯,1), that formula had also been shown to compute stationary probabilities for a particle system known as the multispecies ASEP on a ring, and it is natural to ask whether a similar connection exists between the modified Macdonald polynomials and a suitable statistical mechanics model. In a sequel to this work, we demonstrate such a connection, showing that the stationary probabilities of the multispecies totally asymmetric zero-range process (mTAZRP) on a ring can be computed using tableaux formulas with the queue inversion statistic. This connection extends to arbitrary X=(x 1 ,⋯,x n ); the x i play the role of site-dependent jump rates for the mTAZRP.

Boosting Electrocatalytic Urea Production via Promoting Asymmetric C–N Coupling

Open AccessCCS ChemistryRESEARCH ARTICLES10 Jan 2023Boosting electrocatalytic urea production via promoting asymmetric C-N coupling Mengyi Qiu, Xiaorong Zhu, Shuowen Bo, Kai Cheng, Nihan He, Kaizhi Gu, Dezhong Song, Chen Chen, Xiaoxiao Wei, Dongdong Wang, Yingying Liu, Shuang Li, Xiaojin Tu, Yafei Li, Qinghua Liu, Conggang Li and Shuangyin Wang Mengyi Qiu Google Scholar More articles by this author , Xiaorong Zhu Google Scholar More articles by this author , Shuowen Bo Google Scholar More articles by this author , Kai Cheng Google Scholar More articles by this author , Nihan He Google Scholar More articles by this author , Kaizhi Gu Google Scholar More articles by this author , Dezhong Song Google Scholar More articles by this author , Chen Chen Google Scholar More articles by this author , Xiaoxiao Wei Google Scholar More articles by this author , Dongdong Wang Google Scholar More articles by this author , Yingying Liu Google Scholar More articles by this author , Shuang Li Google Scholar More articles by this author , Xiaojin Tu Google Scholar More articles by this author , Yafei Li Google Scholar More articles by this author , Qinghua Liu Google Scholar More articles by this author , Conggang Li Google Scholar More articles by this author and Shuangyin Wang Google Scholar More articles by this author https://doi.org/10.31635/ccschem.023.202202408 SectionsSupplemental MaterialAboutPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail The electrocatalytic C-N coupling shows great potential in direct and sustainable urea synthesis. However, the mechanism of interaction between catalytic sites and intermediate species is unclear currently, and the corresponding strategies to boost urea synthesis are urgent to be explored. Herein, we demonstrated that the multihole structure could preserve the Cu+ component of Cu2O spheres under electrochemical reduction conditions. The in-situ formed Cu0-Cu+ site promoted the asymmetric coupling process of *CO and *NO thermodynamically and kinetically, conducive to boost the urea production. The impressive urea yield rates of 29.2 mmol h-1 g-1 and 114.0 mmol h-1 g-1 were realized for electrochemical coupling of CO2 with nitrate and nitrite respectively. The multihole-Cu2O exhibits both superior activity and long-term stability compared to the electrocatalysts with reconstructed Cu0-dominated surface. This work provides insights into the identification and design of the active site for C-N coupling and urea synthesis. Download figure Download PowerPoint Previous articleNext article FiguresReferencesRelatedDetails Issue AssignmentVolume 0Issue jaPage: 1-63Supporting Information Copyright & Permissions© 2023 Chinese Chemical Society Downloaded 133 times PDF downloadLoading ...

An analysis of lateralized neural crest marker expression across development in the Mexican tetra, Astyanax mexicanus.

The biological basis of lateralized cranial aberrations can be rooted in early asymmetric patterning of developmental tissues. However, precisely how development impacts natural cranial asymmetries remains incompletely understood. Here, we examined embryonic patterning of the cranial neural crest at two phases of embryonic development in a natural animal system with two morphotypes: cave-dwelling and surface-dwelling fish. Surface fish are highly symmetric with respect to cranial form at adulthood, however adult cavefish harbor diverse cranial asymmetries. To examine if lateralized aberrations of the developing neural crest underpin these asymmetries, we used an automated technique to quantify the area and expression level of cranial neural crest markers on the left and right sides of the embryonic head. We examined the expression of marker genes encoding both structural proteins and transcription factors at two key stages of development: 36hpf (∼mid-migration of the neural crest) and 72hpf (∼early differentiation of neural crest derivatives). Interestingly, our results revealed asymmetric biases at both phases of development in both morphotypes, however consistent lateral biases were less common in surface fish as development progressed. Additionally, this work provides the information on neural crest development, based on whole-mount expression patterns of 19 genes, between stage-matched cave and surface morphs. Further, this study revealed 'asymmetric' noise as a likely normative component of early neural crest development in natural Astyanax fish. Mature cranial asymmetries in cave morphs may arise from persistence of asymmetric processes during development, or as a function of asymmetric processes occurring later in the life history.

Molecular mechanism of core planar cell polarity complex function elucidated with single-molecule methods.

The planar cell polarity (PCP) signaling pathway polarizes epithelial cells along an axis parallel to the epithelial sheet in order to generate front-back asymmetry at the tissue level. Failures in PCP signaling underlie developmental defects and diseases such as neural tube and heart defects, deafness and contribute to cancer. Six core PCP proteins assemble into large, asymmetric complexes at cell-cell junctions, with Vang and Prickle recruited to one side of the cell-cell junction while Frizzled and Dishevelled are recruited to the other. How this asymmetric assembly process occurs is not known. Genetic evidence suggests that the process of symmetry breaking at PCP clusters is coupled to cluster formation. To test how this occurs, we developed a method to count the number of each of the six core proteins in individual PCP complexes. Specifically, by analyzing bleaching traces obtained with a high frame rate in live Drosophila wing cells imaged using total internal reflection microscopy, we quantify the intensity of single fluorophores in each complex and thereby calculate the molecular number in the corresponding PCP complex. Using this approach, we find that the molecular size distribution of PCP complexes follows an exponential function, indicating a single underlying growth mechanism. We report that specifically, the number of Vang molecules in PCP complexes increases from 15 hours after puparium formation until reaching a steady state around 28 hours. Besides, we measure the asymmetry as a function of cluster size and test the dependence of the observed relationship by introducing gain and loss of function mutations that perturb cluster assembly. In conclusion, our findings provide a detailed understanding of how the PCP mechanism generates stable polarization during embryonic development.

Asymmetric attractive zero-range processes with particle destruction at the origin

We investigate the macroscopic behavior of asymmetric attractive zero-range processes on Z where particles are destroyed at the origin at a rate of order Nβ, where β∈R and N∈N is the scaling parameter. We prove that the hydrodynamic limit of this particle system is described by the unique entropy solution of a hyperbolic conservation law, supplemented by a boundary condition depending on the range of β. Namely, if β⩾0, then the boundary condition prescribes the particle current through the origin, whereas if β<0, the destruction of particles at the origin has no macroscopic effect on the system and no boundary condition is imposed at the hydrodynamic limit.