Simple Two-dimensional System Research Articles

Cumulus cell co-culture in media drops does not improve rescue in vitro maturation of vitrified-warmed immature oocytes

To assess whether co-culture with vitrified-warmed cumulus cells (CCs) in media drops improves rescue invitro maturation (IVM) of previously vitrified immature oocytes. Previous studies have shown improved rescue IVM of fresh immature oocytes when cocultured with CCs in a three-dimensional matrix. However, the scheduling and workload of embryologists would benefit from a simpler IVM approach, particularly in the setting of time-sensitive oncofertility oocyte cryopreservation (OC) cases. Although the yield of developmentally competent mature metaphase II (MII) oocytes is increased when rescue IVM is performed before cryopreservation, it is unknown whether maturation of previously vitrified immature oocytes is improved after coculture with CCs in a simple system not involving a three-dimensional matrix. Randomized controlled trial. Academic hospital. A total of 320 (160 germinal vesicles [GVs] and 160 metaphase I [MI]) immature oocytes and autologous CC clumps were vitrified from patients who were undergoing planned OC or intracytoplasmic sperm injection from July 2020 until September2021. On warming, the oocytes were randomized to culture in IVM media with CCs (+CC) or without CCs (-CC). Germinal vesicles and MI oocytes were cultured in 25 μL (SAGE IVM medium) for 32 hours and 20-22 hours, respectively. Oocytes with a polar body (MII) were randomized to confocal microscopy for analysis of spindle integrity and chromosomal alignment to assess nuclear maturity or to parthenogenetic activation to assess cytoplasmic maturity. Wilcoxon rank sum tests for continuous variables and the chi square or Fisher's exact test for categorical variables assessed statistical significance. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated. Patient demographic characteristics were similar for both the GV and MI groups after randomization to +CC vs. -CC. No statistically significant differences were observed between +CC vs. -CC groups regarding the percentage of MII from either GV (42.5% [34/80] vs. 52.5% [42/80]; RR 0.81; 95% CI: 0.57-1.15]) or MI (76.3% [61/80]; vs. 72.5% [58/80]; RR 1.05; 95% CI: 0.88-1.26]) oocytes. An increased percentage of GV-matured MIIs underwent parthenogenetic activation in the +CC group (92.3% [12/13] vs. 70.8% [17/24]), but the difference was not statistically significant (RR 1.30; 95% CI: 0.97-1.75), whereas the activation rate was identical for MI-matured oocytes (74.3% [26/35] vs. 75.0% [18/24], CC+ vs. CC-; RR 0.99; 95% CI: 0.74-1.32). No significant differences were observed between +CC vs. -CC groups for cleavage of parthenotes from GV-matured oocytes (91.7% [11/12] vs. 82.4% [14/17]) or blastulation (0 for both) or for MI-matured oocytes (cleavage: 80.8% [21/26] vs. 94.4% [17/18]; blastulation: 0 [0/26] vs. 16.7% [3/18]). Further, no significant differences were observed between +CC vs. -CC for GV-matured oocytes regarding incidence of bipolar spindles (38.9% [7/18] vs. 33.3% [5/15]) or aligned chromosomes (22.2% [4/18] vs. 0.0 [0/15]); or for MI-matured oocytes (bipolar spindle: 38.9% [7/18] vs. 42.9% [2/28]); aligned chromosomes (35.3% [6/17] vs. 24.1% [7/29]). Cumulus cell co-culture in this simple two-dimensional system does not improve rescue IVM of vitrified, warmed immature oocytes, at least by the markers assessed here. Further work is required to assess the efficacy of this system given its potential to provide flexibility in a busy, invitro fertilization clinic.

Self-organized criticality of magnetic avalanches in disordered ferrimagnetic material.

We observe multiple steplike jumps in a Dy-Fe-Ga-based ferrimagnetic alloy in its magnetic hysteresis curve at 2K. The observed jumps are found to have a stochastic character with respect to their magnitude and the field position, and the jumps do not correlate with the duration of the field. The distribution of jump size follows a power law variation indicating the scale invariance nature of the jumps. We have invoked a simple two-dimensional random bond Ising-type spin system to model the dynamics. Our computational model can qualitatively reproduce the jumps and their scale-invariant character. It also elucidates that the flipping of antiferromagnetically coupled Dy and Fe clusters is responsible for the observed jumps in the hysteresis loop. These features are described in terms of the self-organized criticality.

P-147 Cumulus cell co-culture in media drops does not improve in vitro maturation of vitrified warmed immature oocytes

Abstract Study question Does co-culture with vitrified warmed cumulus cells (CC) in media drops improve in vitro maturation (IVM) of previously vitrified immature oocytes? Summary answer CC co-culture in this simple two-dimensional system does not improve IVM of vitrified warmed immature oocytes. What is known already Previous studies have shown improved IVM of fresh immature oocytes when co-cultured with cumulus cells in a three-dimensional (3D) matrix. However, scheduling and workload of embryologists would benefit from a simpler IVM approach, particularly in the setting of time-sensitive oncofertility oocyte cryopreservation cases. Although yield of developmentally competent mature (metaphase II, MII) oocytes is increased if IVM is performed before cryopreservation, it is unknown whether maturation of previously vitrified immature oocytes is improved following co-culture with CCs in a simple system not involving a 3D matrix. Study design, size, duration A randomized controlled trial was performed where 320 immature oocytes (160 GV and 160 MI) and autologous CC clumps were vitrified from 7/2020 to 9/2021. Upon warming, the oocytes were randomized to culture in IVM media with cumulus cells (+CC) or without cumulus cells (-CC) and then assessed for nuclear maturation using confocal microscopy and for cytoplasmic maturation following parthenogenetic activation. Participants/materials, setting, methods GV and MI oocytes were cultured in 25µL (SAGE IVM medium) for 32 and 20-22 hours, respectively. Oocytes with a polar body (MII) were randomized to confocal microscopy for analysis of spindle integrity and chromosomal alignment or parthenogenetic activation to assess cytoplasmic maturity. Wilcoxon rank sum tests for continuous variables and chi square or Fisher’s Exact test for categorical variables assessed statistical significance. Relative risks (RR) and 95% confidence intervals (CI) were calculated. Main results and the role of chance Patient demographic characteristics were similar for both GV and MI groups after randomization to +CC vs -CC. No statistically significant differences were observed between +CC versus -CC groups regarding the % MII from either GV [42.5% (34/80) vs 52.5% (42/80); RR 0.81 95% CI: 0.57-1.15] or MI [76.3% (61/80;) vs 72.5% (58/80); RR 1.05 95% CI: 0.88-1.26] oocytes. There was more parthenogenetic activation of GV-matured MIIs in the +CC group [92.3% (12/13) vs 70.8% (17/24)], but the difference was not statistically significant (RR 0.77 95% CI: 0.57-1.03). There was no difference for MI-matured oocytes [74.3% (26/35) vs 75.0% (18/24), CC+ vs CC-; RR 1.01 95% CI: 0.76-1.35]. No significant differences were observed between +CC vs -CC groups for parthenotes from GV-matured oocytes for cleavage [91.7% (11/12) vs 82.4% (14/17)] or blastulation (0% for both); or for MI-matured oocytes [cleavage: 80.8% (21/26) vs 94.4% (17/18); blastulation: 0% (0/26) vs 16.7% (3/18)]. Further, no significant differences were observed between +CC vs -CC for GV-matured oocytes regarding incidence of bipolar spindles [38.9% (7/18) vs 33.3% (5/15)] or aligned chromosomes [22.2% (4/18) vs 0.0% (0/15)]; or for MI-matured oocytes [bipolar spindle: 38.9% (7/18) vs 42.9% (2/28); aligned chromosomes: 35.3% (6/17) vs 24.1% (7/29)]. Limitations, reasons for caution One person performed the vitrification, thaw, co-culture and parthenogenetic activation experiments so scheduling capacity required the culture duration to be shorter than the optimum of at least 36 hours. Small sample sizes for the parthenogenetic activation and confocal analyses limit reliability of definitive conclusions. Wider implications of the findings Warmed CCs and immature oocytes co-cultured in medium drops may not result in improvements in nuclear and cytoplasmic maturity, at least by the markers assessed here. Further work is required to assess the efficacy of this system given its potential to provide flexibility in a busy IVF clinic. Trial registration number not applicable

Positional information as a universal predictor of freezing

Variation of positional information, measured by the two-body excess entropy , is studied across the liquid-solid equilibrium transition in a simple two-dimensional system. Analysis reveals a master relation between and the freezing temperature T 1, from which a scaling law is extracted, . Theoretical and practical implications of the observed universality are discussed.

Chaos Driven Evolutionary Algorithm: a Novel Approach for Optimization

This research deals with the initial investigations on the concept of a chaos-driven evolutionary algorithm Differential evolution. This paper is aimed at the embedding of simple two-dimensional chaotic system, which is Lozi map, in the form of chaos pseudo random number generator for Differential Evolution. The chaotic system of interest is the discrete dissipative system. Repeated simulations were performed on standard benchmark Schwefel’s test function in higher dimensions. Finally, the obtained results are compared with canonical Differential Evolution.

Counterexample to a Lyapunov Condition for Uniform Asymptotic Partial Stability

Partial stability characterizes dynamical systems for which only a part of the state variables exhibits a stable behavior. In his book on partial stability, Vorotnikov proposed a sufficient condition to establish this property through a Lyapunov-like function whose total derivative is upper-bounded by a negative definite function involving only the sub-state of interest. In this note, we show with a simple two-dimensional system that this statement is wrong in general. More precisely, we show that the convergence rate of the relevant state variables may not be uniform in the initial state. We also discuss the impact of this lack of uniformity on the connected issue of robustness with respect to exogenous disturbances.

A Simple Nonautonomous Hidden Chaotic System with a Switchable Stable Node-Focus

This paper presents a simple two-dimensional nonautonomous system, which possesses piecewise linearity constructed by a simple absolute value function. The nonautonomous system has only one switchable equilibrium state with a stable node-focus in the considered control parameter region but can generate periodic, chaotic and coexisting attractors. Therefore, the presented simple two-dimensional nonautonomous system always operates with hidden oscillations, which is not similar to any example reported in the literature. Furthermore, specific hidden dynamical behaviors are numerically disclosed by employing one-dimensional and two-dimensional bifurcation plots, phase plane plots, Poincaré mappings, local attraction basins, and complexity plots. In addition, by utilizing the circuit module of the absolute value function, a multiplierless analog circuit is designed, based on which breadboard experiments are performed to validate the numerically simulated phase plane plots of coexisting attractors.

Development of Initial Perturbations in the Problem of Motion of a Cylinder in Circulation Flow

The stability of a cylinder in circulation flow of an inviscid incompressible fluid is considered. The investigation of stability in the simple two-dimensional system is of considerable interest since in this problem the analytical solution can be obtained in both spectral and initial problems. The investigation of the critical layer region in which the phase perturbation velocity coincides with the velocity of mean flow is of particular interest since just in this region the perturbations are concentrated and grow indefinitely.

Modeling Electron Transfer in Diffusive Multidimensional Electrochemical Systems

We analyze different stochastic approaches for simulating electron transfer and potential sweep experiments in diffusive multidimensional electrochemical systems. In particular, we focus on a simple two-dimensional system, where one dimension is a traditional mass diffusion coordinate moving reactants from bulk solution to an electrode, and a second dimension represents a reorganization coordinate capturing solvent motion. We find that this multidimensional system can indeed be reduced to a simpler one-dimensional model, provided certain circumstances pertaining to separability between the two coordinates are met. Our results should begin to bridge the gap between continuum models of electrochemical dynamics/transport and ab initio models of surface electronic structure.

Dynamic mode decomposition with exogenous input for data-driven modeling of unsteady flows

This work proposes a data-driven reduced-order modeling algorithm for complex, high-dimensional, and unsteady fluid systems with exogenous input and control. This algorithm is a variant of dynamic mode decomposition (DMD), which is an equation-free method for identifying coherent structures and modeling complex flow dynamics. Compared with existing methods, the proposed method improves the capability of predicting the flow evolution near the unstable equilibrium state. The method is achieved by two steps. First, the system matrix without input is identified by standard DMD to represent the intrinsic flow dynamics. Second, the input term, represented by a state space equation, is identified through existing methods for DMD with control effects. The whole system with input is described by the superposition of both the system matrix and the input term. The proposed method is validated by one simple two-dimensional dynamic system and two test cases of unsteady flow, including flow past a circular cylinder at Reynolds number 45 and flow past a NACA0012 airfoil at an angle of attack 25°. Results indicate that the proposed method gives more accurate description on the flow evolution with or without external forcing.

On-Line two dimensional liquid chromatography based on skeleton type molecularly imprinted column for selective determination of sulfonylurea additive in Chinese patent medicines or functional foods

Substandard and counterfeit anti-diabetic medicines directly influence the health and impose a great danger to individual patients and to public health. Counterfeiting has become a serious and underreported problem in the pharmaceutical industry. There are a large number of counterfeit medicines flooded in anti-diabetic markets which effect human health directly and indirectly. Therefore, some novel analytical techniques are necessary to be established for detecting these counterfeit drugs. In this study, a novel skeleton type molecularly imprinted column was successfully prepared. Based on the column, a simple, fast and reliable two-dimensional chromatography analytical system was established for selective determination of the illegal sulfonylurea additive in traditional Chinese patent medicines and functional foods. The developed method was validated. The linearitiesof the method were tested with calibration curves using ten calibration points in the concentration range of 0.25–12.5μg/g. The LODs were 0.0125μg/g and 0.01μg/g for tolbutamide and glibenclamide respectively. The five batches of Chinese patent medicines and dietary supplements obtained from different markets and online websites were tested by the validated method. With good retention time and spectral confirmation, chemical anti-diabetic substances were identified and quantified in traditional Chinese medicine and in dietary supplements.

Refining Dynamic Risk Stratification and Prognostic Groups for Differentiated Thyroid Cancer With TERT Promoter Mutations.

Currently, no recurrence or mortality risk systems consider molecular testing when predicting thyroid cancer outcomes. We developed an integrative prognostic system that incorporates telomerase reverse transcription (TERT) promoter mutations into the recently proposed risk reclassification system after initial therapy [dynamic risk stratification (DRS)] to better categorize and predict outcomes. A total of 357 differentiated thyroid cancer (DTC) patients without initial distant metastasis were enrolled. Among patients with mutated TERT and wild-type, recurrence-free survival (RFS) was compared according to DRS grouping. Cox regression was used to calculate adjusted hazard ratios (AHRs) to derive AHR groups. Performance of the AHR grouping system with respect to prediction of structural recurrence and cancer-specific survival (CSS) was assessed against the current DRS system and the tumor/node/metastasis (TNM) classification. Among 357 patients, there were 90 recurrences and 15 cancer-related deaths during a median of 14 years of follow-up. Patients in higher AHR groups were at higher risk of recurrence (10-year RFS for AHR 1, 2, 3, and 4: 94.9%, 82.7%, 50.2%, and 23.1%; P < 0.001) and cancer-related death (10-year CSS: 100.0%. 98.7%, 94.2%, and 76.9%; P < 0.001). The proportions of variance explained (PVEs) for the ability of AHR and DRS grouping to predict recurrence were 22.4% and 18.5%. PVEs of AHR and TNM system to predict cancer-related deaths were 11.5% and 7.4%. The AHR grouping system, a simple two-dimensional prognostic system, is as effective as DRS at predicting structural recurrence and provides clinical implication for long-term CSS in patients with nonmetastatic DTC.

Developing a Novel Two-Dimensional Culture System to Enrich Human Prostate Luminal Progenitors that Can Function as a Cell of Origin for Prostate Cancer.

Elucidating the cell of origin of cancer has great significance in stratifying patients into appropriate treatment groups and for developing novel targeted therapies. Early studies demonstrate that only stem‐like basal cells in the normal human prostate (NHP) can function as the cell of origin for prostate cancer (PCa). Here, we show that the organoids derived from bulk NHP luminal cells can also be tumorigenically transformed. We further show that the WIT medium, which is used to culture human mammary epithelial progenitor cells, when combined with the ROCK inhibitor, can readily propagate a population of progenitor‐like cells from the primary NHP luminal cell isolates. Such functionally defined luminal progenitors can be transformed by distinct sets of genetic perturbations (i.e., AR+AKT/ERG or c‐MYC+PTEN knockout) to form tumor glands. Genome‐wide RNA‐Seq analysis of freshly purified unperturbed human benign prostatic basal and luminal cells and culture‐expanded lineage‐specific stem/progenitor populations reveals that the luminal progenitors possess a distinct gene expression profile that is greatly enriched in advanced, castration‐resistant, and metastatic PCa, and it associates with poor patient survival. The ability of the simple two‐dimensional culture system reported herein to greatly enrich NHP progenitor‐like cells should facilitate biological and biochemical studies as well as high‐throughput screening in these cells and in progenitor‐like PCa cells. Stem Cells Translational Medicine 2017;6:748–760

Computing the optimal path in stochastic dynamical systems.

In stochastic systems, one is often interested in finding the optimal path that maximizes the probability of escape from a metastable state or of switching between metastable states. Even for simple systems, it may be impossible to find an analytic form of the optimal path, and in high-dimensional systems, this is almost always the case. In this article, we formulate a constructive methodology that is used to compute the optimal path numerically. The method utilizes finite-time Lyapunov exponents, statistical selection criteria, and a Newton-based iterative minimizing scheme. The method is applied to four examples. The first example is a two-dimensional system that describes a single population with internal noise. This model has an analytical solution for the optimal path. The numerical solution found using our computational method agrees well with the analytical result. The second example is a more complicated four-dimensional system where our numerical method must be used to find the optimal path. The third example, although a seemingly simple two-dimensional system, demonstrates the success of our method in finding the optimal path where other numerical methods are known to fail. In the fourth example, the optimal path lies in six-dimensional space and demonstrates the power of our method in computing paths in higher-dimensional spaces.

Nesting an incompressible-flow code within a compressible-flow code: A two-dimensional study

We consider numerical algorithms appropriate for one- and two-way coupling between meso-scale and micro-scale fluid-dynamics codes for wind energy computing. At the meso-scale is a numerical weather-prediction code, which is typically based on the compressible-flow Euler equations. At the micro-scale, surrounding one or more wind turbines, is a computational fluid dynamics code, which is typically based on the incompressible-flow Navier–Stokes equations. When calculating short-duration flow around wind turbines, one-way coupling is sufficient, where the meso-scale computational model drives the micro-scale model. However, in long-duration simulations involving large wind farms, the influence of the wind farm on the meso-scale weather may no longer be insignificant and two-way coupling is warranted. In this study, we focus on a simple two-dimensional system, for which our goal is to devise one- and two-way coupling algorithms that can effectively transport a vortex propagating in laminar flow from one domain to the other. Two coupling schemes and their numerical implementation are described: partial-boundary coupling and projection coupling. In the former, the micro-scale-domain boundary is decomposed, based on the meso-scale solution, into sections corresponding to inflow and outflow. The micro-scale model has Dirichlet- and Neumann-type boundary conditions on these sections, respectively. In projection coupling, the meso-scale solution is projected onto the incompressible-flow solution space in the micro-scale domain, from which Dirichlet-type boundary conditions are derived. In these simulations, the uncoupled meso-scale solution is taken as the reference, and the best coupling method is that which produces solutions that deviate the least from the reference. In one-way coupling, under a simple two-dimensional laminar-flow test case, partial-boundary coupling was more effective than projection coupling. However, in two-way coupling, projection coupling was the best performer.

Development of a simple two-dimensional optical measurement system for linear guideways

In this study, a simple two-dimensional measurement system based on optical design was developed to measure the motion errors of the linear guideway. Compared with the transitional methods about the linear guideway for measuring the motion errors, our proposed two-dimensional optical measurement system can simultaneously measure horizontal and vertical running straightness errors for the linear guideway. Calibration results showed that the residual error of the two-dimensional optical measurement system is less than 0.5 µm. Measurement results showed that the three tests for the motion errors of the linear guideway are almost coincident with the laser interferometer within 1000 mm. The standard deviations of the horizontal and vertical straightness measurement systems are 0.9 and 1.2 µm.

A simple two-dimensional model system to study electrostatic-self-assembly

This paper surveys the variables controlling the lattice structure and charge in macroscopic Coulombic crystals made from electrically charged, millimeter-sized polymer objects (spheres, cubes, and cylinders). Mechanical agitation of these objects inside planar, bounded containers caused them to charge electrically through contact electrification, and to self-assemble. The processes of electrification and self-assembly, and the characteristics of the assemblies, depended on the type of motion used for agitation, on the type of materials used for the objects and the dish, on the size and shape of the objects and the dish, and on the number of objects. Each of the three different materials in the system (of the dish and of the two types of spheres) influenced the electrification. Three classes of structures formed by self-assembly, depending on the experimental conditions: two-dimensional lattices, one-dimensional chains, and zero-dimensional ‘rosettes’. The lattices were characterized by their structure (disordered, square, rhombic, or hexagonal) and by the electrical charges of individual objects; the whole lattices were approximately electrically neutral. The lattices observed in this study were qualitatively different from ionic crystals; the charge of objects had practically continuous values which changed during agitation and self-assembly, and depended on experimental conditions which included the lattice structure itself. The relationship between charge and structure led to the coexistence of regions with different lattice structures within the same assembly, and to transformations between different lattice structures during agitation.

Estimation of Rotor Position and Speed of Permanent Magnet Synchronous Motors With Guaranteed Stability

The control algorithms used in high performance ac drives require the knowledge of rotor position and, in the case of speed regulation, also of speed. Since in many applications rotational transducers cannot be installed, their reconstruction is needed. The use of observers is stymied by the fact that the dynamics of electrical machines are highly nonlinear and does not belong to the class studied by the nonlinear control community. In this paper solutions to both problems, which are particularly tailored for the widely popular permanent magnet synchronous motors, are provided. A key step for the design of both observers is the choice of a suitable set of coordinates. The position observer is a standard gradient search whose detailed analysis reveals outstanding (global asymptotic) stability properties. Furthermore, the analysis clearly exhibits the interplay between rotor speed and the gain of the gradient search-that (essentially) determines its convergence rate. The position observer is a simple two-dimensional nonlinear system, hence is easily implementable. The speed observer is designed following the immersion and invariance technique and is also shown to be globally convergent. Simulation and experimental results of the position observer, used together with a classical field-oriented control algorithm, are presented.

Two-Dimensional Local Vector Magnetic Property Measurements by Use of Simple Transducers

A new simple two-dimensional local magnetic property measurement system is presented. In this paper, we developed a new transducer whose two amorphous cores enables measure in a high magnetic induction range. Experimental results show very good agreements with ones of conventional 2-D measurement system.

Transient growth and why we should care about it

The phrases ‘transient growth’ and ‘non-normality’ have become common parlance in fluid mechanics nowadays. We present these ideas with a simple two-dimensional system, to enable the reader to look for transient growth, as a trigger for nonlinear behaviour to set in, in a variety of situations probably having nothing to do with fluid mechanics. The article is aimed at undergraduate students of science, engineering, finance, etc., and the material is based completely on the excellent books of Trefethen and Embree, and Schmid and Henningson [1,2].