91 research outputs found
Uncertainty-Aware Imitation Learning using Kernelized Movement Primitives
During the past few years, probabilistic approaches to imitation learning
have earned a relevant place in the literature. One of their most prominent
features, in addition to extracting a mean trajectory from task demonstrations,
is that they provide a variance estimation. The intuitive meaning of this
variance, however, changes across different techniques, indicating either
variability or uncertainty. In this paper we leverage kernelized movement
primitives (KMP) to provide a new perspective on imitation learning by
predicting variability, correlations and uncertainty about robot actions. This
rich set of information is used in combination with optimal controller fusion
to learn actions from data, with two main advantages: i) robots become safe
when uncertain about their actions and ii) they are able to leverage partial
demonstrations, given as elementary sub-tasks, to optimally perform a higher
level, more complex task. We showcase our approach in a painting task, where a
human user and a KUKA robot collaborate to paint a wooden board. The task is
divided into two sub-tasks and we show that using our approach the robot
becomes compliant (hence safe) outside the training regions and executes the
two sub-tasks with optimal gains.Comment: Submitted to IROS1
Serum Levels of FGF-21 Are Increased in Coronary Heart Disease Patients and Are Independently Associated with Adverse Lipid Profile
BACKGROUND: Fibroblast growth factor 21 (FGF-21) is a metabolic regulator with multiple beneficial effects on glucose homeostasis and lipid metabolism in animal models. The relationship between plasma levels of FGF-21 and coronary heart disease (CHD) in unknown. METHODOLOGY/PRINCIPAL FINDINGS: This study aimed to investigate the correlation of serum FGF-21 levels and lipid metabolism in the patients with coronary heart disease. We performed a logistic regression analysis of the relation between serum levels of FGF-21 and CHD patients with and without diabetes and hypertension. This study was conducted in the Departments of Endocrinology and Cardiovascular Diseases at two University Hospitals. Participants consisted of one hundred and thirty-five patients who have been diagnosed to have CHD and sixty-one control subjects. Serum FGF-21 level and levels of fasting blood glucose; triglyceride; apolipoprotein B100; HOMA-IR; insulin; total cholesterol; HDL-cholesterol; LDL-cholesterol; and C-reactive protein were measured. We found that median serum FGF-21 levels were significantly higher in CHD than that of control subjects (P<0.0001). Serum FGF-21 levels in CHD patients with diabetes, hypertension, or both were higher than that of patients without these comorbidities. Serum FGF-21 levels correlated positively with triglycerides, fasting blood glucose, apolipoprotein B100, insulin and HOMA-IR but negatively with HDL-C and apolipoprotein A1 after adjusting for BMI, diabetes and hypertension. Logistic regression analysis demonstrated that FGF-21 showed an independent association with triglyceride and apolipoprotein A1. CONCLUSIONS/SIGNIFICANCE: High levels of FGF-21 are associated with adverse lipid profiles in CHD patients. The paradoxical increase of serum FGF-21 in CHD patients may indicate a compensatory response or resistance to FGF-21
Circulating FGF21 Levels Are Progressively Increased from the Early to End Stages of Chronic Kidney Diseases and Are Associated with Renal Function in Chinese
Fibroblast growth factor 21 (FGF21) is a hepatic hormone involved in the regulation of lipid and carbohydrate metabolism. This study aims to test the hypothesis that elevated FGF21 concentrations are associated with the change of renal function and the presence of left ventricular hypertrophy (LVH) in the different stages of chronic kidney disease (CKD) progression.0.05).Plasma FGF21 levels are significantly increased with the development of early- to end-stage CKD and are independently associated with renal function and adverse lipid profiles in Chinese population. Understanding whether increased FGF21 is associated with myocardial hypertrophy in CKD requires further study
Towards Orientation Learning and Adaptation in Cartesian Space
As a promising branch of robotics, imitation learning emerges as an important
way to transfer human skills to robots, where human demonstrations represented
in Cartesian or joint spaces are utilized to estimate task/skill models that
can be subsequently generalized to new situations. While learning Cartesian
positions suffices for many applications, the end-effector orientation is
required in many others. Despite recent advances in learning orientations from
demonstrations, several crucial issues have not been adequately addressed yet.
For instance, how can demonstrated orientations be adapted to pass through
arbitrary desired points that comprise orientations and angular velocities? In
this paper, we propose an approach that is capable of learning multiple
orientation trajectories and adapting learned orientation skills to new
situations (e.g., via-points and end-points), where both orientation and
angular velocity are considered. Specifically, we introduce a kernelized
treatment to alleviate explicit basis functions when learning orientations,
which allows for learning orientation trajectories associated with
high-dimensional inputs. In addition, we extend our approach to the learning of
quaternions with angular acceleration or jerk constraints, which allows for
generating smoother orientation profiles for robots. Several examples including
experiments with real 7-DoF robot arms are provided to verify the effectiveness
of our method.Comment: Accepted for publication at IEEE Transactions on Robotic
A Cytokinin Analog Thidiazuron Suppresses Shoot Growth in Potted Rose Plants via the Gibberellic Acid Pathway.
Application of thidiazuron (N-phenyl-N'-1,2,3-thiadiazol-5-ylurea, TDZ), a cytokinin analog, to inhibit the leaf yellowing that occurs after pinching potted rose plants, resulted in compact plants with shorter shoots and thicker internodes. Two weeks after treatment with 100 μM of TDZ, new shoots were half as long as those in control plants, and stem diameters were about 40% greater. This effect of TDZ is associated with changes in cell architecture. Although TDZ treatment stimulated ethylene production by the plants, inhibitors of ethylene biosynthesis (2-aminoethoxyvinyl glycine) or action (silver thiosulfate) did not affect the response of plants to TDZ. We found that TDZ treatment significantly suppressed the expression of bioactive gibberellic acid (GA) biosynthesis genes encoding GA3 and GA20 oxidases and slightly increased the expression of GA catabolism genes encoding GA2 oxidase. Application of GA3 and TDZ together resulted in normal elongation growth, although stem diameters were still somewhat thicker. Our results suggest that TDZ regulates shoot elongation and stem enlargement in potted rose plants through the modulation of bioactive GA biosynthesis
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