DyRAM: An Active Reliable Multicast Framework for Data Distribution

Group communications (multicast) are foreseen to be one of the most critical yet challenging technologies to meet the exponentially growing demands for data distribution in a large variety of applications of the Internet (such as grid computing, web applications and distributed simulations). When reliability is required, there is no straightforward solutions and meeting the objectives of reliable multicast is not an easy task. Active networks open a new perspective in providing more efficient solutions for the problem of reliability. In this context, routers are able to perform customized computations on the packets flowing through them. In this paper, we propose a receiver-based (replier) local recovery multicast protocol with dynamic repliers elected on a per-packet basis. Designed to provide an efficient reliable multicast service without any cache facilities inside the network, our approach, uses low-overhead active services in routers. The current paper addresses the design, evaluation and the implementation of an efficient and scalable reliable multicast protocol noted DyRAM standing for Dynamic Replier Active reliable multicast.     

Object-Oriented Design of QoS Multicast Communications

Multicast (group) communications have been widely recognized by current research and industry. Multicast is very useful for various network applications such as distributed (replicated) database, video/audio conference, information distribution and server locations, etc. But design and implementation of such multicast communication systems in networks are complicated tasks, especially when quality of services (QoS) of applications such as real-time and reliability are desired. To quick design and implement multicast communication, good tools are crucial and must be facilitated. This paper presents a novel object-oriented (O-O) QoS driven approach for the quick design and prototyping of multicast communication systems under certain QoS requirements for multicast message transmission and receptions such as real-time, total ordering, atomicity and fault-tolerance, etc.     

浅论医院绩效反馈环节中存在的问题及对策

绩效反馈是医院绩效管理工作的关键一环,能否达到绩效管理的预期目的,取决于绩效反馈的实施效果。针对目前医院在绩效反馈中存在的一些不足,提出优化方案,以提高绩效反馈效用。     

Molecular Dynamics Simulation of Behaviours of Non-Polar Droplets Merging and Interactions with Hydrophobic Surfaces

This paper presents a molecular dynamics simulation of the behaviours of non-polar droplets merging and also the fluid molecules interacting with a hydrophobic surface. Such behaviours and transport phenomena are popular in general microchannel flow boiling and two-phase flow. The droplets are assumed to be composed of Lennards-Jones type molecules. Periodic boundary conditions are applied in three coordinate directions of a 3-D system, where there exist two liquid droplets and their vapour. The two droplets merge when they come within the prescribed small distance. The merging of two droplets apart from each other at different initial distances is tested and the possible larger （or critical） non-dimensional distance, in which droplets merging can occur, is discussed. The evolution of the merging process is simulated numerically by employing the Molecular Dynamics （MD） method. For interactions with hydrophobic solid wall, a system with fluid confined between two walls is used to study the wetting phenomena of fluid and solid wall. The results are compared with those of hydrophilic wall to show the unique characteristics of hydrophobic interactions by microscopic methods.     

Merging and characterising phenotypic data on conventional and rare traits from dairy cattle experimental resources in three countries

This study set out to demonstrate the feasibility of merging data from different experimental resource dairy populations for joint genetic analyses. Data from four experimental herds located in three different countries (Scotland, Ireland and the Netherlands) were used for this purpose. Animals were first lactation Holstein cows that participated in ongoing or previously completed selection and feeding experiments. Data included a total of 60 058 weekly records from 1630 cows across the four herds; number of cows per herd ranged from 90 to 563. Weekly records were extracted from the individual herd databases and included seven traits: milk, fat and protein yield, milk somatic cell count, liveweight, dry matter intake and energy intake. Missing records were predicted with the use of random regression models, so that at the end there were 44 weekly records, corresponding to the typical 305-day lactation, for each cow. A total of 23 different lactation traits were derived from these records: total milk, fat and protein yield, average fat and protein percentage, average fat-to-protein ratio, total dry matter and energy intake and average dry matter intake-to-milk yield ratio in lactation weeks 1 to 44 and 1 to 15; average milk somatic cell count in lactation weeks 1 to 15 and 16 to 44; average liveweight in lactation weeks 1 to 44; and average energy balance in lactation weeks 1 to 44 and 1 to 15. Data were subsequently merged across the four herds into a single dataset, which was analysed with mixed linear models. Genetic variance and heritability estimates were greater (P < 0.05) than zero for all traits except for average milk somatic cell count in weeks 16 to 44. Proportion of total phenotypic variance due to genotype-by-environment (sire-by-herd) interaction was not different (P > 0.05) from zero. When estimable, the genetic correlation between herds ranged from 0.85 to 0.99. Results suggested that merging experimental herd data into a single dataset is both feasible and sensible, despite potential differences in management and recording of the animals in the four herds. Merging experimental data will increase power of detection in a genetic analysis and augment the potential reference population in genome-wide association studies, especially of difficult-to-record traits.     

通过线性状态反馈使四种群Lotka—Volterra模型永久持续生存

本文研究了四种群Lotka0-Volterra模型的永久持续生存问题,给出了通过线性状态反馈使四种群Lotka-Volterra模型永久持续生存的一些充分和必要条件。     

具有分布式反馈控制的阶段结构捕食-食饵系统的持久与周期解(英文)

讨论了一个具有时滞与分布式反馈控制的阶段结构捕食-食饵系统,该模型考虑到了两类种群的个体都被划分为幼体与成体这一特征。通过应用比较定理以及重合度理论,获得了一组保证系统持久并存在正周期解的充分条件.     

Feedback Control of an Achiral Robotic Microswimmer

Magnetic microswimmers are useful for navigating and performing tasks at small scales.To demonstrate effective control over such microswimmers,we implemented feedback control of the three-bead achiral microswimmers in both simulation and experiment.The achiral microswimmers with the ability to swim in bulk fluid are controlled wirelessly using magnetic fields generated from electromagnetic coils.The achirality of the microswimmers introduces unknown handedness resulting in uncertainty in swimming direction.We use a combination of rotating and static magnetic fields generated from an approximate Helmholtz coil system to overcome such uncertainty.There are also movement uncertainties due to environmental factors such as unsteady flow conditions.A kinematic model based feedback controller was created based on data fitting of experimental data.However,the controller was unable to yield satisfactory performance due to uncertainties from environmental factors;i.e.,the time to reach target pose under adverse flow condition is too long.Following the implementation of an integral controller to control the microswimmers' swimming velocity,the microswimmers were able to reach the target in roughly half the time.Through simulation and experiments,we show that the feedback control law can move an achiral microswimmer from any initial conditions to a target pose.     

植被变化对气候的反馈机制及调节效应

植被通过光合作用固定大气中的CO₂来减缓温室效应,同时植被也通过改变地表能量收支影响温室效应。在过去的气候-植被研究中,大多关注气候变化对植被的影响,而植被对气候反馈的研究相对较少。植被通过调节地表能量收支、水通量等重要地气过程影响局地、区域乃至全球气候,在气候变化中的作用十分重要。因此,需要厘清植被对气候的反馈效应机制及其结果,并识别其地域差异。从生物地球物理和生物地球化学过程两方面分析植被与气候之间的作用机制,对全球及关键区域内植被变化对局地、区域乃至全球的气候反馈效应进行了系统总结：（1）生物地球物理反馈的区域特征明显,生物地球化学反馈则表现在全球尺度上,二者相互作用但难以统一;（2）植被破坏带来的气候影响在气温效应方面与生态系统的类型及地理分布相关：热带森林破坏带来增温效应,北方森林破坏带来降温效应,温带森林破坏则会通过增加森林反照率抵消丢失的固碳降温效应,气温效应表现不明显;（3）当前研究对关键过程机制考虑不够完善,不同研究方法的结果差异较大,且缺乏高质量观测数据的验证;同时考虑生物地球物理和生物地球化学的净气候反馈研究尚无法支撑植树造林对气候变化单一减缓作用的常规理解。本文可为科学评估植树造林对气候变化作用的方向与强度提供理论依据。     

A Model for Mechano-Electrical Feedback Effects on Atrial Flutter Interval Variability

Atrial flutter is a supraventricular arrhythmia, based on a reentrant mechanism mainly confined to the right atrium. Although atrial flutter is considered a regular rhythm, the atrial flutter interval (i.e., the time interval between consecutive atrial activation times) presents a spontaneous beat-to-beat variability, which has been suggested to be related to ventricular contraction and respiration by mechano-electrical feedback. This paper introduces a model to predict atrial activity during atrial flutter, based on the assumption that atrial flutter variability is related to the phase of the reentrant activity in the ventricular and respiratory cycles. Thus, atrial intervals are given as a superimposition of phase-dependent ventricular and respiratory modulations. The model includes a simplified atrioventricular (AV) branch with constant refractoriness and conduction times, which allows the prediction of ventricular activations in a closed-loop with atrial activations. Model predictions are quantitatively compared with real activation series recorded in 12 patients with atrial flutter. The model predicts the time course of both atrial and ventricular time series with a high beat-to-beat agreement, reproducing 96±8% and 86±21% of atrial and ventricular variability, respectively. The model also predicts the existence of phase-locking of atrial flutter intervals during periodic ventricular pacing and such results are observed in patients. These results constitute evidence in favor of mechano-electrical feedback as a major source of cycle length variability during atrial flutter.     

Feedback regulation between autophagy and PKA

Protein kinase A (PKA) controls diverse cellular processes and homeostasis in eukaryotic cells. Many processes and substrates of PKA have been described and among them are direct regulators of autophagy. The mechanisms of PKA regulation and how they relate to autophagy remain to be fully understood. We constructed a reporter of PKA activity in yeast to identify genes affecting PKA regulation. The assay systematically measures relative protein-protein interactions between the regulatory and catalytic subunits of the PKA complex in a systematic set of genetic backgrounds. The candidate PKA regulators we identified span multiple processes and molecular functions (autophagy, methionine biosynthesis, TORC signaling, protein acetylation, and DNA repair), which themselves include processes regulated by PKA. These observations suggest the presence of many feedback loops acting through this key regulator. Many of the candidate regulators include genes involved in autophagy, suggesting that not only does PKA regulate autophagy but that autophagy also sends signals back to PKA.     

Feedback inhibition of ecdysone production by 20-hydroxyecdysone in Pieris brassicae pupae

The effects of exogenous moulting hormones, ecdysone and 20-hydroxyecdysone on ecdysteroid production were studied in vivo in Pieris brassicae pupae. Both hormones inhibit ecdysteroid production; however, 20-hydroxyecdysone is much more efficient than ecdysone, and it is likely that the ecdysone effect is due to its partial conversion into 20-hydroxyecdysone. These results suggest that 20-hydroxyecdysone acts on ecdysteroid production as a negative-feedback regulator. Furthermore, since 20-hydroxyecdysone elicits inhibition in headless pupae, it is suggested that 20-hydroxyecdysone acts directly upon the prothoracic glands.     

不确定时滞组合系统的动态输出反馈无源控制

无源性不仅是系统的一个重要性质,而且是控制一个系统的重要途径.本文研究不确定时滞关联大系统的无源控制问题.利用Lyapunov泛函方法,通过求解线性矩阵不等式得到了无源控制器的显示表达,保证闭环系统稳定且严格无源.由于控制器采用动态输出反馈得到,因而控制器的设计也容易实现.最后用数值例子说明了得到定理的有效性.     

A Lightweight,Headphones-based System for Manipulating Auditory Feedback in Songbirds

Experimental manipulations of sensory feedback during complex behavior have provided valuable insights into the computations underlying motor control and sensorimotor plasticity¹. Consistent sensory perturbations result in compensatory changes in motor output, reflecting changes in feedforward motor control that reduce the experienced feedback error. By quantifying how different sensory feedback errors affect human behavior, prior studies have explored how visual signals are used to recalibrate arm movements^2,3 and auditory feedback is used to modify speech production^4-7. The strength of this approach rests on the ability to mimic naturalistic errors in behavior, allowing the experimenter to observe how experienced errors in production are used to recalibrate motor output.Songbirds provide an excellent animal model for investigating the neural basis of sensorimotor control and plasticity^8,9. The songbird brain provides a well-defined circuit in which the areas necessary for song learning are spatially separated from those required for song production, and neural recording and lesion studies have made significant advances in understanding how different brain areas contribute to vocal behavior^9-12. However, the lack of a naturalistic error-correction paradigm - in which a known acoustic parameter is perturbed by the experimenter and then corrected by the songbird - has made it difficult to understand the computations underlying vocal learning or how different elements of the neural circuit contribute to the correction of vocal errors¹³.The technique described here gives the experimenter precise control over auditory feedback errors in singing birds, allowing the introduction of arbitrary sensory errors that can be used to drive vocal learning. Online sound-processing equipment is used to introduce a known perturbation to the acoustics of song, and a miniaturized headphones apparatus is used to replace a songbird''s natural auditory feedback with the perturbed signal in real time. We have used this paradigm to perturb the fundamental frequency (pitch) of auditory feedback in adult songbirds, providing the first demonstration that adult birds maintain vocal performance using error correction¹⁴. The present protocol can be used to implement a wide range of sensory feedback perturbations (including but not limited to pitch shifts) to investigate the computational and neurophysiological basis of vocal learning.     

Tuning Dopant Distribution for Stabilizing the Surface of High-Nickel Layered Oxide Cathodes for Lithium-Ion Batteries

Layered oxide cathodes with a high-nickel (Ni ≥ 0.9) content exhibit great potential for enabling high-energy-density lithium-ion batteries. However, their practical feasibility and cycle life are hampered by severe surface reactivity with the electrolyte. A LiNi_0.90Co_0.05Al_0.05O₂ cathode is presented enriched with Al on the surface (S-NCA) and benchmark it against a LiNi_0.90Co_0.05Al_0.05O₂ cathode obtained by a conventional co-precipitation method that has a uniform Al distribution throughout the bulk (B-NCA). The S-NCA cathode greatly outperform with an impressive capacity retention of 84% after 1000 cycles in pouch full cells with graphite anode compared to 62% retention for B-NCA. Advanced surface characterization methodologies, including time-of-flight secondary-ion mass spectrometry, reveal that the Al-enriched surface morphology facilitates the formation of a robust, thin electrode-electrolyte interphase (EEI), effectively suppressing the oxidative decomposition of the electrolyte, gas generation, and metallic dead lithium formation on graphite anode. The results illustrate that surface reactivity with the electrolyte is the primary factor limiting the cycle of cells with high-Ni cathodes. The work provides valuable insights toward the practical viability of ultrahigh-Ni cathodes in lithium-ion batteries.     

RNA-Mediated Feedback Control of Transcriptional Condensates

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L-亮氨酸发酵过程氮源反馈与非反馈控制的初步研究

氮源可直接影响氨基酸发酵过程中菌体生长与氨基酸生成。但是关于氨基酸发酵过程中氮源控制的研究报道并不多。本文作者在L-亮氨酸发酵过程碳源流加研究及动力学特征分析基础上,比较了几种非反馈型、反馈型补加硫酸铵的发酵结果,提出了较佳的控制方法。