Continuous Trajectory Research Articles

An integrated decision-execution framework of cooperative control for multi-agent systems via reinforcement learning

Cooperative control is both a crucial and hot research topic for multi-agent systems (MASs). However, most existing cooperative control strategies guarantee tracking stability under various non-ideal conditions, while the path decision capability is often ignored. In this paper, the integrated decision-execution (IDE) framework is newly presented for cooperative control of multi-agent systems (MASs) to accomplish the integrated task of path decision and cooperative execution. This framework includes a decision layer and a control layer. The decision layer generates a continuous trajectory for the virtual leader to reach the target from its initial position in an unknown environment. To achieve the goal of this layer, (1) the Step-based Adaptive Search Q-learning (SASQ-learning) algorithm is proposed based on reinforcement learning to efficiently find the discrete path, (2) an Axis-based Trajectory Fitting (ATF) method is developed to convert the discrete path into a continuous trajectory for mobile agents. In the control layer, this trajectory is used to regulate the following MASs to achieve cooperative tracking control with the presence of input saturation. Simulation experiments are presented to demonstrate the effectiveness of this framework.

Upper limb exoskeleton rehabilitation robot inverse kinematics modeling and solution method based on multi-objective optimization

The inverse kinematics problem of exoskeleton rehabilitation robots is challenging due to the lack of a standard analytical model, resulting in a complex and varied solution process. This complexity is especially pronounced in redundant upper limb exoskeleton robots, where inefficient solutions hinder the robot’s ability to adapt to the kinematic shape of the upper limb. This paper proposes a modeling and solution method based on multi-objective optimization to address the inverse kinematics of upper limb exoskeleton robots. We analyzed and validated this method using a redundant upper limb exoskeleton rehabilitation robot system developed by ourselves. First, we established a multi-objective inverse kinematics solution model by defining the end-position function, joint motion comfort function, system energy consumption function, motion safety, and human-like constraints. Then, the solution was designed based on the Improved Equilibrium Optimization (IEO) algorithm and validated its computational performance in terms of optimization ability, accuracy, and robustness. Finally, we experimentally tested the inverse kinematics solution model with the IEO algorithm on discrete objectives and continuous training trajectories using a redundant upper limb exoskeleton rehabilitation robot system. The results show that by incorporating the joint comfort function, system energy consumption function, and human-like constraints into the inverse kinematics model, we can not only quickly solve the inverse kinematics of redundant upper limb exoskeleton robots but also significantly improve the robot’s motion shape. Furthermore, it has better solution accuracy and stronger robustness than other algorithms when solving this inverse kinematics model based on the IEO algorithm.

Pre-vocational education as a factor in the development of human resources in the healthcare system

Pre-professional medical education in high school provides not only a more in-depth study of individual subjects of general education programs, but also expands the opportunities for self-determination of students, ensures continuity of the educational process, allows boys and girls to adapt more successfully mastering higher medical professional education programs and is the basis for a successful career.Aim. To evaluate the results of the introduction and implementation of the model of pre-professional medical and pharmaceutical education using the example of the Resource Center «Medical Sechenov Pre-University» of the Sechenov First Moscow State Medical University (Sechenov University) (hereinafter referred to as the Pre-University) as a means of developing the human resources potential of the healthcare system on the territory of the Russian Federation.Materials and methods. During the work, a theoretical analysis of domestic and foreign literature on the problem of developing the human resources potential of the healthcare system was carried out. A study was conducted in the comparative aspect of the basic readiness of students in grades 8-11 at the Pre-University and specialized medical and biological classes of regional educational institutions to the choice of medical specialties using a test questionnaire with the identification of three key aspects: readiness to master medical specialties; self-assessment of capabilities and erudition in the field of modern medicine. 1465 people took part in the survey. The reliability of the results was carried using the Mann-Whitney U test. Assessment of the statistical significance of differences between the means was carried out at a critical level of p = 0.05.Results. Studying at the Pre-University of Sechenov University allowed the majority of adolescents to achieve higher levels of formation of the main indicators of basic readiness to choose medical specialties. The share of students with a high level of readiness to master medical specialties at the Pre-University is 13.8 % higher compared to students of specialized medical and biological classes, with high erudition – 13.8 % and 6.7 % higher those who highly assess their prospects for entering a medical university.Conclusion. Pre-professional education based on close interaction between the Pre-University and Sechenov University allows students to develop motivation to choose a medical profession, as well as a clear understanding of the learning process in the chosen profession and is an important link in the system of continuous educational trajectory «pre-university–university–clinic».

Dissecting the dynamic cellular transcriptional atlas of adult teleost testis development throughout the annual reproductive cycle.

Teleost testis development during the annual cycle involves dramatic changes in cellular compositions and molecular events. In this study, the testicular cells derived from adult black rockfish at distinct stages - regressed, regenerating and differentiating - were meticulously dissected via single-cell transcriptome sequencing. A continuous developmental trajectory of spermatogenic cells, from spermatogonia to spermatids, was delineated, elucidating the molecular events involved in spermatogenesis. Subsequently, the dynamic regulation of gene expression associated with spermatogonia proliferation and differentiation was observed across spermatogonia subgroups and developmental stages. A bioenergetic transition from glycolysis to mitochondrial respiration of spermatogonia during the annual developmental cycle was demonstrated, and a deeper level of heterogeneity and molecular characteristics was revealed by re-clustering analysis. Additionally, the developmental trajectory of Sertoli cells was delineated, alongside the divergence of Leydig cells and macrophages. Moreover, the interaction network between testicular micro-environment somatic cells and spermatogenic cells was established. Overall, our study provides detailed information on both germ and somatic cells within teleost testes during the annual reproductive cycle, which lays the foundation for spermatogenesis regulation and germplasm preservation of endangered species.

Continuous planning for inertial-aided systems

Inertial-aided systems require continuous motion excitation among other reasons to characterize the measurement biases that will enable accurate integration required for localization frameworks. This paper proposes the use of informative path planning to find the best trajectory for minimizing the uncertainty of IMU biases and an adaptive traces method to guide the planner towards trajectories that aid convergence. The key contribution is a novel regression method based on Gaussian Process (GP) to enforce continuity and differentiability between waypoints from a variant of the RRT∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {RRT}^*$$\\end{document} planning algorithm. We employ linear operators applied to the GP kernel function to infer not only continuous position trajectories, but also velocities and accelerations. The use of linear functionals enable velocity and acceleration constraints given by the IMU measurements to be imposed on the position GP model. The results from both simulation and real-world experiments show that planning for IMU bias convergence helps minimize localization errors in state estimation frameworks.

Exploring crystallized and fluid intelligence in down syndrome using graph theory

This cross-sectional study examined the cognitive performance of crystallized intelligence (Gc) and fluid intelligence (Gf) in 340 individuals, comparing adults (aged 22-45) to adolescents (aged 16-21) in two groups of etiologies. Down syndrome (DS) and non-specific intellectual disability (NSID). The aim was to estimate whether their cognitive performance reflected accelerated, stable, or continuous trajectories. Participants were assessed using the Vocabulary, Similarities, Block Design, and Raven Matrix tests. ANOVA analysis indicated that adults exhibited higher scores than adolescents on three of the crystallized and fluid intelligence tests, with similar trends observed in the Raven Matrix test, thus supporting the Compensation Age Theory. Participants with NSID exhibited higher scores in Vocabulary than participants with DS. Participants with DS exhibited higher scores in Block Design and Raven than participants with NSID. There was no difference between the groups in Similarities, suggesting that the verbal ability of individuals with DS is not so impaired relative to participants with NSID. Graph analysis demonstrated divergent Gc-Gf networks between the two groups of etiologies. The DS etiology revealed more coherent connections between crystallized and fluid intelligence, especially in adulthood, compared to the diffuse and absent connections seen in adults with NSID. Thus, the relative strength in Similarities and the more coherent Gc-Gf interconnections in the DS etiology suggested a more coherent and not-so-impaired profile in a clear diagnostic etiology such as DS, especially in adulthood, compared to unclear genetic etiologies such as NSID. The findings hold educational implications for adults with ID with and without Down syndrome at least until their 40’s as a time for growth and development, perhaps serving as a protective factor against possible cognitive decline in the future.

Design and experimental verification of an S-shaped continuous weft insertion system for soft–hard blended preform narrow channels

To address the limitations of the existing weft insertion technology in inserting carbon fiber bundles into the narrow channels of soft–hard blended preform, a proposed solution is to use a continuous weft insertion trajectory based on an S-shaped path for narrow channels. A weft insertion system that meets the process requirements has been designed. The analysis of the functional requirements for the continuous weft insertion system has identified five key nodes for the system, and the motion paths of each mechanism have been established. Through design methods such as analytical methods, rigid inversion methods, and mechanical analysis, the modular design of the system and the planning of the timing sequence for multiple mechanisms have been completed. Weft insertion experiments have been conducted on a continuous weft insertion system experimental platform, and the results demonstrate that the weft insertion system can effectively introduce carbon fiber bundles into the narrow channels, forming the expected S-shaped continuous weft insertion trajectory. This study verifies the feasibility of the designed weft insertion system and the accuracy of the continuous weft insertion theory, providing a viable solution for continuous weft insertion in the narrow channels of soft–hard blended preforms.

Jerk limited continuous tool path generation for flexible systems in non-cartesian coordinate systems

Inspired by computer numerical control (CNC) technology and drastic changes in the world of electronics and microcontrollers, the idea of using non-cartesian coordinate system for CNC machines became a topic of interest. Non-cartesian coordinate systems provide freedom of movement in systems with large working spaces where high dimensional accuracy is not a prime concern. Applications of such systems can be found in murals, where a painting is applied to a large wall of any arbitrary build material. In the present paper, a new design was introduced to automate the process of drawing murals on large surfaces. The proposed mechanism utilized chain and sprocket to overcome the size limitations of traditionally available x-y tables. In addition to that, the developed mechanism does not utilize the common robust structures used in the conventional CNC systems and the tool motion is created using flexible arms that are not heavily constrained. The effect of systems unwanted vibration has been eliminated using continuous trajectory and kinematic profiles. Parametric curve interpolation algorithms for trajectory planning were implemented to increase the flexibility of drawing complex curves. Parametric curves such as B-spline and non-uniform rational B-spline (NURBS) were employed to generate a jerk limited trajectory for motion control and extraction of kinematic profiles. Such trajectory constrains the jerk of the system and guarantees a smooth motion free of feed-rate fluctuations. Compared to other methods available for extracting the kinematic profiles, jerk limited method decreases the travel time and trajectory error. Ultimately, motion commands were produced by using kinematic profiles and the second order Taylor interpolator. STM32746ZG card was used as the main processor and two stepper motors controlled by a Bit Pattern interpolation algorithm were utilized to drive the proposed mechanism. The input pulses of stepper motors were stored as binary bits and transmitted to drivers in real-time. The feedback was also evaluated by two rotary encoders, placed at the end of the motors’ shafts. Encoder data were acquired and transmitted using a TCP/IP protocol to guarantee zero data loss during the transmission.

Trajectory optimization of spacecraft autonomous far-distance rapid rendezvous based on deep reinforcement learning

This paper investigates the application of Deep Reinforcement Learning (DRL) in the trajectory optimization of spacecraft far-distance rapid rendezvous, and uses the most advanced DRL method Proximal Policy Optimization (PPO) to solve the continuous high-thrust minimum-fuel trajectory optimization problem. The space J2 perturbation was considered, its impact on the spacecraft’s on-orbit operation and trajectory design was analyzed, and the effectiveness and accuracy of the proposed method were verified in two far-distance rapid rendezvous missions. In order to ensure the safety of the subsequent close-range operation phase, a safe area reward framework is proposed, and sparse and dense safe area reward functions are designed. The dense safe area reward function significantly improves the training efficiency of the algorithm on the basis of ensuring terminal performance. In addition, the modeling and analysis of possible uncertainties in the spacecraft’s orbit operation, including observation uncertainty, state uncertainty and control uncertainty, is carried out to verify the performance of the proposed method through simulation. For uncertainties, the closed-loop performance of the policy is also evaluated by performing Monte Carlo simulations. The results show that the PPO algorithm can effectively deal with the rendezvous problem in uncertainty environments. These preliminary results demonstrate the great potential of the DRL method in achieving autonomous guidance of spacecraft.

The lived housing experience of the urban poor in Chengdu: Four distinct periods in the urban housing career

AbstractCurrent research on the housing careers of urban low‐income groups, dominated by quantitative modelling, has discussed the housing predicament faced by the urban poor at length. While much is known about the factors influencing their housing careers, these studies have failed to provide a satisfactory understanding of the intricacy and depth of human struggles those vulnerable groups experienced in the urban housing market. This contributes a four‐period model, through a dialogue with the established life cycle/life course theories, to the reconceptualization of housing career of the urban poor and depicts a vivid and continuous housing trajectory by analysing their lived experiences at each period. This paper finds that, in a highly constrained and segregated housing market, the housing problems experienced by low‐income earners and their coping strategies are far more complex and variegated than traditional life cycle/course theory would predict. Factors at individual, household, community and even national levels are often interwoven and, more importantly, the combinations of these influences are constantly changing, sometimes repeating along their housing career forming a nuanced dynamism that has been largely overlooked by existing research.

Further analysis of tuberculosis in eight high-burden countries based on the Global Burden of Disease Study 2021 data

BackgroundsMost significant findings from the Global Tuberculosis (TB) Report 2023 indicate that India, Indonesia, China, the Philippines, Pakistan, Nigeria, Bangladesh, and the Democratic Republic of the Congo (DRC) collectively contribute to approximately two-thirds of global TB cases. This study aims to provide crucial data-driven insights and references to improve TB control measures through a comprehensive analysis of these eight high-burden countries.MethodsThe eight high-burden TB countries analyzed in this study include India, Indonesia, China, the Philippines, Pakistan, Nigeria, Bangladesh, and the DRC. Age-standardized incidence rates (ASIR) of TB were derived from the Global Burden of Diseases Study 2021 data. Temporal trends were analyzed using Joinpoint regression. An age-period-cohort model was applied to examine the risk ratios (RR) of TB across diverse age groups, periods, and birth cohorts. A Bayesian age-period-cohort framework was employed to predict the ASIR of TB by 2030.ResultsThe study found that the Philippines (average annual percentage change = 3.1%, P < 0.001) exhibited an upward trend from 1990 to 2021. In India, the Philippines, Pakistan, and Bangladesh, the RR of TB incidence exceeded 1 after individuals reached 25 years old. Notably, the RR has shown a consistent upward trend since 2001, peaking during the period of 2017–2021 with an estimated RR of 1.5 (P < 0.001) in the Philippines. Similarly, the highest RR was observed during the period of 2017–2021 reaching 1.1 (P < 0.001) in the DRC. In the Philippines, the markedly increasing RR values for TB have been observed among individuals born after 1997–2001. Projections suggest that the ASIR of TB is expected to follow a continued upward trajectory, with an estimated rate of 392.9 per 100,000 by 2030 in the Philippines; India and Indonesia are projected to achieve less than 20.0% of the target set by the World Health Organization (WHO).ConclusionsAmong the eight high-burden countries, the Philippines, India and Indonesia are diverging from the goals set by the WHO, and the risk of TB in the Philippines and the DRC shows a trend toward affecting younger populations, which suggests that the management strategies for TB patients need to be further strengthened.Graphical

Abstract A044: Persistence of fetal splanchnic gene signature defines a tumor-restraining fibroblast subtype in pancreatic cancer

Abstract The pancreas is composed of the epithelial and mesenchymal cells. While mesenchymal fibroblasts are a minor component of the normal pancreas, fibroblast population expands drastically during tumorigenesis. In pancreatic ductal adenocarcinoma (PDAC), cancer associated fibroblasts (CAFs) play critical and complex roles in the tumor microenvironment. This study sought to define the origin, heterogeneity and function of pancreatic cancer associated fibroblasts. Recently we performed a series of lineage tracing studies in genetically engineered mouse models. This identified the splanchnic mesenchyme (a tissue layer adjacent to the developing fetal pancreatic epithelium) as the fetal origin of the adult pancreatic resident fibroblasts and pancreatic CAFs. Single cell transcriptomic analysis indicated persistent and dynamic gene expressions along the pancreatic mesenchymal trajectory during development, homeostasis, precancer and cancer. Intriguingly, we found that two splanchnic transcription factors, GATA6 and FOXF1, are expressed in only subsets of adult pancreatic fibroblasts in temporally and spatially distinct patterns. Similar patterns were observed in both mouse models and human patient samples. To determine the role of GATA6 in fibroblasts during tumorigenesis, we constructed a dual DNA recombinase mouse genetic model. DNA recombinase FlpO directs expression of an oncogene Kras (G12D mutation) and loss of a tumor suppressor p53 in pancreatic epithelial cells to induce spontaneous tumor formation in the pancreas, and DNA recombinase Cre deletes Gata6 specifically in fibroblasts. This fibroblast specific Gata6 deletion resulted in altered number and gene expression of CAFs as well as increased tumor burden in the pancreas. This suggests a non-cell autonomous function of GATA6 within CAFs to restrain pancreatic cancer progression. In summary, this study delineated a continuous cell trajectory of the mesenchymal lineage in the pancreas across different life stages. Additionally, this study provides evidence that persistent and selective gene expressions along the mesenchymal trajectory contributes to pancreatic CAF heterogeneity and such persistence may constitute an inherent host defense mechanism to restrain pancreatic cancer. The enhancement of this mechanism could be explored further for therapeutic benefits. Citation Format: Lu Han, Tom Walter, Joseph Beaudet, Caroline Everett, Gustavo Leone, Michael Ostrowski. Persistence of fetal splanchnic gene signature defines a tumor-restraining fibroblast subtype in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A044.

A Hierarchical Control Method for Trajectory Tracking of Aerial Manipulators Arms

To address the control challenges of an aerial manipulator arm (AMA) mounted on a drone under conditions of model inaccuracy and strong disturbances, this paper proposes a hierarchical control architecture. In the upper-level control, Bézier curves are first used to generate smooth and continuous desired trajectory points, and the theory of singular trajectory lines along with a Radial Basis Function Neural Network (RBFNN) is introduced to construct a highly accurate multi-configuration inverse kinematic solver. This solver not only effectively avoids singular solutions but also enhances its precision online through data-driven methods, ensuring the accurate calculation of joint angles. The lower-level control focuses on optimizing the dynamic model of the manipulator. Using a Model Predictive Control (MPC) strategy, the dynamic behavior of the manipulator is predicted, and a rolling optimization process is executed to solve for the optimal control sequence. To enhance system robustness, an RBFNN is specifically introduced to compensate for external disturbances, ensuring that the manipulator maintains stable performance in dynamic environments and computes the optimal control commands. Physical prototype testing results show that this control strategy achieves a root mean square (RMS) error of 0.035, demonstrating the adaptability and disturbance rejection capabilities of the proposed method.

Optimal Joint Design on Continuous Trajectory and Power Control for UAV-Assisted Energy Constrained Communications

Optimal Joint Design on Continuous Trajectory and Power Control for UAV-Assisted Energy Constrained Communications

Sex differences in mobility recovery after hip fracture: a time series analysis.

Sex differences are commonly reported for hip fracture incidence rates and recovery. Current knowledge about mobility recovery after hip fracture involves clinical assessments of physical capacity or patient-reported outcomes. Information on mobility performance during daily life is missing but relevant to evaluate patients' recovery. Hence, it remains unclear whether sex differences exist in the longitudinal progression of mobility performance in hip fracture patients. To investigate this, we pooled data from four studies in Germany and Norway. In all studies, real-world mobility was assessed continuously over 1 to 7 days using a sensor fixed to the unaffected frontal thigh. All studies assessed mobility at different time points that were allocated to three distinct phases: Acute and post-acute phase (week 1-6), extended recovery (7-26), and long-term recovery (27-52). Sex-specific continuous trajectories of the median (50th percentile) as well as the 1st (25th percentile) and 3rd quartile (75th percentile) were estimated using quantile regression models with splines for daily walking and standing duration; number of sit-to-stand-to-walk transfers and walking bouts; mean walking bout duration; maximum number of steps per walking bout. There were 5,900 valid observation days from n = 717 participants (mean age = 83.4 years, SD 6.1). The majority was female (75.3%), with similar sex distribution across all studies. Demographics of both sexes were comparable, but a higher percentage of women was living alone (69.0% compared to 40.9% in men) and had experienced an indoor fall leading to the fracture (74.3% compared to 67.4% in men). There were clear sex differences in mobility recovery. Women improved their mobility faster than men, but men showed larger increases later in the year after surgery. At the end of the first year, both sexes reached comparable levels in almost all mobility parameters. We identified varying aspects of mobility recovery between men and women, i.e., timely development of mobility recovery shows different patterns. Our findings support the consideration of sex differences in planning and implementing rehabilitation measures for hip fracture patients and highlight the need to provide adapted support at different time points. The underlying mechanisms of these sex differences need further investigation.

ScDiffusion: conditional generation of high-quality single-cell data using diffusion model.

Single-cell RNA sequencing (scRNA-seq) data are important for studying the laws of life at single-cell level. However, it is still challenging to obtain enough high-quality scRNA-seq data. To mitigate the limited availability of data, generative models have been proposed to computationally generate synthetic scRNA-seq data. Nevertheless, the data generated with current models are not very realistic yet, especially when we need to generate data with controlled conditions. In the meantime, diffusion models have shown their power in generating data with high fidelity, providing a new opportunity for scRNA-seq generation. In this study, we developed scDiffusion, a generative model combining the diffusion model and foundation model to generate high-quality scRNA-seq data with controlled conditions. We designed multiple classifiers to guide the diffusion process simultaneously, enabling scDiffusion to generate data under multiple condition combinations. We also proposed a new control strategy called Gradient Interpolation. This strategy allows the model to generate continuous trajectories of cell development from a given cell state. Experiments showed that scDiffusion could generate single-cell gene expression data closely resembling real scRNA-seq data. Also, scDiffusion can conditionally produce data on specific cell types including rare cell types. Furthermore, we could use the multiple-condition generation of scDiffusion to generate cell type that was out of the training data. Leveraging the Gradient Interpolation strategy, we generated a continuous developmental trajectory of mouse embryonic cells. These experiments demonstrate that scDiffusion is a powerful tool for augmenting the real scRNA-seq data and can provide insights into cell fate research. scDiffusion is openly available at the GitHub repository https://github.com/EperLuo/scDiffusion or Zenodo https://zenodo.org/doi/10.5281/zenodo.13268742.

Development of Internalizing Mental Health Symptoms from Early Childhood to Late Adolescence.

Children's mental health symptoms' development can be characterized by both continuity and discontinuity. However, existing studies ignore the potential discontinuity in children's internalizing symptoms' development. Hence, the current study examines continuous and discontinuous developmental trajectories using representative data from a sample of 2792 children (49.10% females) from the Growing Up in Australia cohort assessed seven times (ages 4, 6, 8, 10, 12, 14, 16). Longitudinal measurement invariance analyses revealed that internalizing symptoms were comparable over time. Linear, quadratic, and piecewise latent growth curve models were deployed to estimate the trajectory of internalizing symptoms from early childhood to late adolescence. The analyses showed that internalizing symptoms were characterized by a quadratic-quadratic piecewise growth curve comprising two distinct phases of upward concave growth. Internalizing scores reduced steadily between ages 4 and 8 years but exhibited a slight upward curvature between ages 8 and 10 years. By age 14 years, the trajectory remained relatively stable but spiked between age 14 and 16 years. The two phases of internalizing symptoms' development were largely unrelated. Overall, the study adds to the knowledge about the development of internalizing mental health from early childhood to late adolescence and highlights the need for additional support in late adolescence.

Respiratory motion-corrected T1 mapping of the abdomen.

The purpose of this study was to investigate an approach for motion-corrected T1 mapping of the abdomen that allows for free breathing data acquisition with 100% scan efficiency. Data were acquired using a continuous golden radial trajectory and multiple inversion pulses. For the correction of respiratory motion, motion estimation based on a surrogate was performed from the same data used for T1 mapping. Image-based self-navigation allowed for binning and reconstruction of respiratory-resolved images, which were used for the estimation of respiratory motion fields. Finally, motion-corrected T1 maps were calculated from the data applying the estimated motion fields. The method was evaluated in five healthy volunteers. For the assessment of the image-based navigator, we compared it to a simultaneously acquired ultrawide band radar signal. Motion-corrected T1 maps were evaluated qualitatively and quantitatively for different scan times. For all volunteers, the motion-corrected T1 maps showed fewer motion artifacts in the liver as well as sharper kidney structures and blood vessels compared to uncorrected T1 maps. Moreover, the relative error to the reference breathhold T1 maps could be reduced from up to 25% for the uncorrected T1 maps to below 10% for the motion-corrected maps for the average value of a region of interest, while the scan time could be reduced to 6-8s. The proposed approach allows for respiratory motion-corrected T1 mapping in the abdomen and ensures accurate T1 maps without the need for any breathholds.

Non-unique Hamiltonians for discrete symplectic dynamics.

An outstanding property of any Hamiltonian system is the symplecticity of its flow, namely, the continuous trajectory preserves volume in phase space. Given a symplectic but discrete trajectory generated by a transition matrix applied at a fixed time-increment (τ > 0), it was generally believed that there exists a unique Hamiltonian producing a continuous trajectory that coincides at all discrete times (t = nτ with n integers) as long as τ is small enough. However, it is now exactly demonstrated that, for any given discrete symplectic dynamics of a harmonic oscillator, there exist an infinite number of real-valued Hamiltonians for any small value of τ and an infinite number of complex-valued Hamiltonians for any large value of τ. In addition, when the transition matrix is similar to a Jordan normal form with the supradiagonal element of 1 and the two identical diagonal elements of either 1 or -1, only one solution to the Hamiltonian is found for the case with the diagonal elements of 1, but no solution can be found for the other case.

The Association Between Trajectories of Self-reported Psychotic Experiences and Continuity of Mental Health Care in a Longitudinal Cohort of Adolescents and Young Adults.

Young people (YP) with psychotic experiences (PE) have an increased risk of developing a psychiatric disorder. Therefore, knowledge on continuity of care from child and adolescent (CAMHS) to adult mental health services (AMHS) in relation to PE is important. Here, we investigated whether the self-reported trajectories of persistent PE were associated with likelihood of transition to AMHS and mental health outcomes. In this prospective cohort study, interviews and questionnaires were used to assess PE, mental health, and service use in 763 child and adolescent mental health service users reaching their service's upper age limit in 8 European countries. Trajectories of self-reported PE (3 items) from baseline to 24-month follow-up were determined using growth mixture modeling (GMM). Associations were assessed with auxiliary variables and using mixed models. Study results. At baseline, 56.7% of YP reported PE. GMM identified 5 trajectories over 24 months: medium increasing (5.2%), medium stable (11.7%), medium decreasing (6.5%), high decreasing (4.2%), and low stable (72.4%). PE trajectories were not associated with continuity of specialist care or transition to AMHS. Overall, YP with PE reported more mental health problems at baseline. Persistence of PE or an increase was associated with poorer outcomes at follow-up. PE are common among CAMHS users when reaching the upper age limit of CAMHS. Persistence or an increase of PE was associated with poorer mental health outcomes, poorer prognosis, and impaired functioning, but were less discriminative for continuity of care.