Toward in vivo nanoscale communication networks: utilizing an active network architecture

A safe and reliable in vivo nanoscale communication network will be of great benefit for medical diagnosis and monitoring as well as medical implant communication. This review article provides a brief introduction to nanoscale and molecular networking in general and provides opinions on the role of active networking for in vivo nanoscale information transport. While there are many in vivo communication mechanisms that can be leveraged, for example, forms of cell signaling, gap junctions, calcium and ion signaling, and circulatory borne communication, this review examines two in particular: molecular motor transport and neuronal information communication. Molecular motors transport molecules representing information and neural coding operates by means of the action potential; these mechanisms are reviewed within the theoretical framework of an active network. This review suggests that an active networking paradigm is necessary at the nanoscale along with a new communication constraint, namely, minimizing the communication impact upon the living environment. The goal is to assemble efficient nanoscale and molecular communication channels while minimizing disruption to the host organism.     

Toward in vivo nanoscale communication networks: utilizing an active network architecture

A safe and reliable in vivo nanoscale communication network will be of great benefit for medical diagnosis and monitoring as well as medical implant communication. This review article provides a brief introduction to nanoscale and molecular networking in general and provides opinions on the role of active networking for in vivo nanoscale information transport. While there are many in vivo communication mechanisms that can be leveraged, for example, forms of cell signaling, gap junctions, calcium and ion signaling, and circulatory borne communication, this review examines two in particular: molecular motor transport and neuronal information communication. Molecular motors transport molecules representing information and neural coding operates by means of the action potential; these mechanisms are reviewed within the theoretical framework of an active network. This review suggests that an active networking paradigm is necessary at the nanoscale along with a new communication constraint, namely, minimizing the communication impact upon the living environment. The goal is to assemble efficient nanoscale and molecular communication channels while minimizing disruption to the host organism.     

一种新型的井下无线通信组网方式

介绍了一种适合煤矿井下工作特点的无线通信组网方式。组网采用小区制频率复用技术 ,每个小区的基站用 1个载频 ,小区半径为 5 0 0m ,小区基站有 3个话音信道、1个专用信令信道 ,多址采用TDMA方式。为改善呼损率和提高通信系统可靠性以防基站故障时出现盲区 ,设计了直通方式 ,使在 0 .5km距离内移动台之间的话音数据可以不通过基站 ,并且各自还能接收本小区基站的信令以响应高级别的呼叫     

High-speed electrical signaling: overview and limitations

Advances in IC fabrication technology, coupled with aggressive circuit design, have led to exponential growth of IC speed and integration levels. For these improvements to benefit overall system performance, the communication bandwidth between systems and ICs must scale accordingly. Currently, communication links in various applications approach Gbps data rates. These applications include computer-to-peripheral connections, local area networks, memory buses, and multiprocessor interconnection networks. Designers are concerned that these links will soon reach the fundamental limits of electrical signaling. In this article, we examine the limitations of CMOS implementations of highspeed links and show that the links' performance should continue to scale with technology. To handle the interconnects' finite bandwidth, however requires more sophisticated signaling methods. CMOS circuits, typically slower than circuits implemented in nonmainstream technologies, are particularly attractive for common applications because of their lower cost. The overall system cost is further reduced when signaling components are implemented as macro cells, integrated on the same die with a microprocessor or signal processing block     

ON A LOGISTIC-HIDDEN MARKOV MODEL FOR COMMUNICATION SYSTEMS

This article proposes an extension of hidden Markov models for communication systems by allowing the Markovian transitions between the channel's states to be influenced by an external “catalyzer” (i.e., environmental or experimental conditions). The stochastic influence of the catalyzer is expressed by logistic link functions. The model can be useful for modeling communication channels, for example, in predicting single-ion channel behavior for cell signaling. A simulation study is provided in order to explore how trainable the model is. We prove that the Logistic-Hidden Markov model can be very well trained by means of the maximum likelihood method, assisted by a modified Baum–Welch algorithm.     

Cell motion and recovery in a two-stream microfluidic device

The motion of cells in a two-stream microfluidic device designed to extract cryoprotective agents from cell suspensions was tested under a range of conditions. Jurkat cells (lymphoblasts) in a 10% dimethylsulfoxide solution were driven in parallel with phosphate-buffered saline solution wash streams through single rectangular channel sections and multiple sections in series. The influence of cell-stream flow rate and cell volume fraction (CVF) on cell viability and recovery were examined. The channel depth was 500 μm, and average cell stream velocity within the channels was varied from 3.6 to 8.5 mm/s corresponding with cell stream Reynolds numbers of 2.6–6.0. Cell viability measured at device outlets was high for all cases examined indicating no significant cell damage within the device. Downstream of a single stage, cell recoveries measured 90–100% for average cell stream velocities ≥6 mm/s and for CVFs up to 20%. Cell recovery downstream of multistage devices also measured 90–100% after a critical device population time. This time was found to be five times the average cell residence time within the device. The measured recovery values were significantly larger than those typically obtained using conventional cell washing methods.     

A continuous-flow polymerase chain reaction microchip with regional velocity control

This paper presents a continuous-flow polymerase chain reaction (PCR) microchip with a serpentine microchannel of varying width for "regional velocity control." Varying the channel width by incorporating expanding and contracting conduits made it possible to control DNA sample velocities for the optimization of the exposure times of the sample to each temperature phase while minimizing the transitional periods during temperature transitions. A finite element analysis (FEA) and semi-analytical heat transfer model was used to determine the distances between the three heating assemblies that are responsible for creating the denaturation (96/spl deg/C), hybridization (60/spl deg/C), and extension (72/spl deg/C) temperature zones within the microchip. Predictions from the thermal FEA and semi-analytical model were compared with temperature measurements obtained from an infrared (IR) camera. Flow-field FEAs were also performed to predict the velocity distributions in the regions of the expanding and contracting conduits to study the effects of the microchannel geometry on flow recirculation and bubble nucleation. The flow fields were empirically studied using micro particle image velocimetry (/spl mu/-PIV) to validate the flow-field FEA's and to determine experimental velocities in each of the regions of different width. Successful amplification of a 90 base pair (bp) bacillus anthracis DNA fragment was achieved.     

Computer networking for the robotic neural and sensory systems

At the present time, robotic systems are composed mainly of mechanical functions connected for the purpose of achieving a specific form of automation. An overall plan for the robotic system computer architecture is described to investigate optimal, efficient and cost effective mimicking of human nervous system functions in the robotic system. The following component analogies are drawn between the computer network and the human nervous system: computer node to soma (cell body), input communication channels (links) to dendrites, output communication channels to axons and communications processor ports to buttons. The robotic nervous system therefore is structured as a larger internetwork (similar to the DARPA internetwork) of gateway nodes (controlling neuron cell bodies) which connect neuron intranetworks together. As in the human body, the robotic nervous system is the controlling system for visual and sensory functions.     

Calculations of distance distributions and probabilities of binding by ligands between parallel plane membranes comprising receptors

Cell communication through biochemical signaling pathways is a key determinant of tissue responses to radiation. Several molecules, such as the transforming growth factor β$\beta$ (TGFβ$\beta$), are implicated in radiation-induced signaling between cells. Brownian Dynamics (BD) algorithms have recently been used to simulate the interaction of ligands with receptors and to elucidate signal transduction and autocrine loops in ligand–receptors systems. In this paper, we discuss the simulation of particle diffusion and binding kinetics in a space bounded by two parallel plane membranes, using an exact algorithm to sample the propagator (Green’s function) of a particle located between 2 membranes. We also show that the simulation results are independent of the number of time steps used, in accordance with time discretization equations. These simulations could be used to simulate the motion and binding of ligand molecules in a cell culture, and possibly in neuronal synapses.     

品质升级的衡量与评价——基于对转型时期我国耐用品的实证分析

品质升级是一个常见现象,认识品质升级的基础是如何衡量品质升级速度。如果直接用价格来衡量品质升级就会有所偏差,而品质恩格尔曲率则提供了一个良好的研究工具和研究视角。本文首先测算了我国各类耐用品的品质恩格尔曲率,然后,以品质恩格尔曲率为工具变量估计1998～2006年我国各类耐用品的品质升级速度。分析结果表明,我国各类耐用品品质都有升级的特征,但是品质升级速度在不同耐用品之间存在明显的差异。     

Prediction of traveling front behavior in a lattice-gas cellular automaton model for tumor invasion

Cancer invasion is the process of cells detaching from a primary tumor and infiltrating the healthy tissue. Cancer invasion has been recognized as a complex system, since a tumor’s invasive behavior emerges from the combined effect of tumor cell proliferation, tumor cell migration and cell–microenvironment interactions. Cellular automata (CA) provide simple models of self-organizing complex systems in which collective behavior can emerge out of an ensemble of many interacting “simple” components. Here, we introduce a lattice-gas cellular automaton (LGCA) model of tumor cell proliferation, necrosis and tumor cell migration. The impact of the tumor environment on tumor cells has been investigated in a previous study. Our analysis aims at predicting the velocity of the traveling invasion front, which depends upon fluctuations that arise from the motion of the discrete cells at the front. We find an excellent agreement between the velocities measured in simulations of the LGCA and an analytical estimate derived in the cut-off mean-field approximation via the discrete Lattice Boltzmann equation and its linearization. In particular, we predict the front velocity to scale with the square root of the product of probabilities for mitosis and the migration coefficient. Finally, we calculate the width of the traveling front which is found to be proportional to the front velocity.     

On distributed finite‐time observer design and finite‐time coordinated tracking of multiple double integrator systems via local interactions

This paper studies finite‐time coordinated tracking problem for multiple double integrator systems with a time‐varying leader's velocity and bounded external disturbances. We consider the dynamic feedback designs for two different cases. In the first case, the velocities of the followers and the leader are assumed to be unavailable, and the communication topology is assumed to be undirected and fixed. In the second case, the velocities of the followers and the leader are assumed to be available, and the communication topology is assumed to be directed and switching. Distributed finite‐time observers are designed, respectively, to obtain the velocity information in the first case and the relative state information in the second case. The states of these observers are then used to design control inputs that achieve finite time robust coordinated tracking of multiple double integrator systems in the presence of bounded disturbances for these two cases. Simulation results are provided to validate the effectiveness of these theoretical results. Copyright © 2013 John Wiley & Sons, Ltd.     

On-chip manipulation of nonmagnetic particles in paramagnetic solutions using embedded permanent magnets

This study develops a method for embedding permanent magnets into poly(dimethylsiloxane) (PDMS)-based microfluidic chips. Magnets can be brought very close to the planar microchannels for enhanced magnetic field and field gradients, which enables on-chip continuous-flow manipulation of nonmagnetic particles in typical paramagnetic solutions. We performed a systematic study of the transport of polystyrene particles suspended in manganese (II) chloride (MnCl₂) solutions through a rectangular microchannel. Owing to their smaller magnetization than the suspending fluid, particles experience negative magnetophoresis and are deflected away from the magnet. The effects of particle position (relative to the magnet), particle size, MnCl₂ salt concentration, and fluid flow velocity on the horizontal magnetophoretic deflection are examined using a combined experimental and theoretical approach. The experimental results agree quantitatively with the predictions of an analytical model. The demonstrated nonmagnetic particle deflection may be used with the potential to focus and sort cells in lab-on-a-chip for bio-applications.     

VC-method: high-speed navigation of a uniformly braking mobile robot using position-velocity configuration space

This paper considers the problem of fast autonomous mobile robot navigation between obstacles while attempting to maximize velocity subject to safe braking constraints. The paper introduces position-velocity configuration space. Within this space, keeping a uniform braking distance from the obstacles can be modeled as forbidden regions called vc-obstacles. Using Morse Theory, the paper characterizes the critical position-velocity points where two vc-obstacles meet and locally disconnect the free position-velocity space. These points correspond to critical events where the robot’s velocity becomes too large to support safe passage between neighboring obstacles. The velocity dependent critical points induce a cellular decomposition of the free position-velocity space into cells. Each cell is associated with a particular range of velocities that can be safely followed by the robot. The vc-method searches the cells’ adjacency graph for a maximum velocity path. The method outputs a pseudo time optimal path which maintains safe braking distance from the obstacles throughout the robot motion. Simulations and experiments demonstrate the method and highlight the usefulness of taking the path’s velocity into account during the path planning process.     

Microvalve and liquid membrane double-controlled integrated microfluidics for observing the interaction of breast cancer cells

The methodical development of cell biology has resulted in significant advancements in the study of breast tumors. However, the dynamic investigation of the self-seeding process remains largely out of reach. In the present study, we describe a microvalve and liquid membrane double-controlled integrated microfluidic device that provides for the versatile assessment of breast tumor cell invasion dynamics. The liquid membrane formation was first optimized to obtain a high level of control, and was then applied to different types of homotypic and heterotypic cell seeding with precise selective positioning for monoculture and coculture. Using this device, the interaction between breast cancer cells MDA231-LM2 and MDA-MB231 was successfully observed to investigate self-seeding dynamics, including migration, infiltration, and coexistence. The results quantitatively demonstrate the mutual signal-induced attraction between MDA-MB231 and MDA231-LM2 cells, as well as the progressive infiltration of MDA231-LM2 cells into the MDA-MB231 cell population. These results are valuable in the development of spatiotemporal-controlled microfluidic systems and to many microscale-based biological and diagnostic studies involving cell growth, cell differentiation, cell interaction, and cell signal.     

Overview of damped least-squares methods for inverse kinematics of robot manipulators

In this paper, we present a tutorial report of the literature on the damped-least squares method which has been used for computing velocity inverse kinematics of robotic manipulators. This is a local optimization method that can prevent infeasible joint velocities near singular configurations by using a damping factor to control the norm of the joint velocity vector. However, the exactness of the inverse kinematic solution has to be sacrificed in order to achieve feasibility.The damping factor is an important parameter in this technique since it determines the trade-off between the accuracy and feasibility of the inverse kinematic solution. Various methods that have been proposed to compute an appropriate damping factor are described.Redundant manipulators, possessing extra degrees of freedom, afford more choice of inverse kinematic solutions than do non-redundant ones. The damped least-squares method has been used in conjunction with redundancy resolution schemes to compute feasible joint velocities for redundant arms while performing an additional subtask. We outline the different techniques that have been proposed to achieve this objective. In addition, we introduce an iterative method to compute the optimal damping factor for one of the redundancy resolution techniques.     

Distribution and Variation of Glacier Velocity in Himalayas based on ALOS PALSAR

Based on the 12 scenes ALOS PALSAR data from December 2007 to February 2010,combined with SRTM,we estimated the glacier velocityof the Himalayasin three periods by feature tracking method.The results show that glacier velocity of the winter of 2007,the summer of 2009 and the winter of 2009 were between 0~300 m·a^-1,and accumulation area of the glacier have obvious movement only in summer,butthe movement of the glacier tongue is obviousin any season.Long tongue glacier velocity decreasesslowlyalong the mainstream line,while the short tongue glacier velocity fluctuatesalong the mainstream line,and even increases.The glacier in east aspecthas the largest velocity.The glaciervelocity in southeast aspect and the southwest aspect are second,and glacier velocity is minimum in the north aspect.In addition to climatic factors,it also closely relates to terrain factors.In terms of the slope of the four aspects,the north aspecthas the smallest slope,andit is one of the main causes of the smallest glacier velocity in the north aspect.There is an inter-annual variation of glaciers,that is,mean velocity of glaciers increases in winter,and the increased velocities are between -5~18 m·(2a).The glacier with small areavaries greatly,and the glacier with large area varies little.Meanwhile,the glacier velocity also has seasonal variation.The overall velocity in summer is larger than that in winter.The velocity in mainstream line fluctuates strongly in summer,and there are many peaks,but velocity in winteris gentle.However,the seasonal variation of the mean velocity in mainstream line is not obvious.The inter-annual variation and seasonal variation of the four typical glacier velocities are similar to those of the glaciers in the study area.There is a close relationship between velocity and climate and the shape of the glacier.The characteristics of glacier advance and retreat are not obvious,and the glaciers in the study area are in equilibrium.     

Sequential droplet manipulation via vibrating ratcheted microchannels

This work reports on a simple scheme for transport and sequential manipulation of droplets using ratchet-shaped microchannels. Once subjected to lateral vibration through a sinusoidal shaker with a controllable frequency and amplitude, droplets move along the direction of least resistance with velocities depending on vibration parameters (amplitude and frequency), channel geometry and material properties, and the angle between the channel and vibration direction (lateral offset angle). Using channels having different lateral offset angles, we achieved a controllable time delay between the transports of various droplets. Based on the same principal, we also designed a multi-functional droplet manipulation platform with the capability to transport, collect, mix, and discharge several droplets.     

Attitude Synchronization of a Group of Spacecraft Without Velocity Measurements

We consider the coordinated attitude control problem for a group of spacecraft, without velocity measurements. Our approach is based on the introduction of auxiliary dynamical systems (playing the role of velocity observers in a certain sense) to generate the individual and relative damping terms in the absence of the actual angular velocities and relative angular velocities. Our main focus, in this technical note, is to address the following two problems: 1) Design a velocity-free attitude tracking and synchronization control scheme, that allows the team members to align their attitudes and track a time-varying reference trajectory (simultaneously). 2) Design a velocity-free synchronization control scheme, in the case where no reference attitude is specified, and all spacecraft are required to reach a consensus by aligning their attitudes with the same final time-varying attitude. In this work, one important and novel feature (besides the non-requirement of the angular velocity measurements), consists in the fact that the control torques are naturally bounded and the designer can arbitrarily assign the desired bounds on the control torques, a priori, through the control gains, regardless of the angular velocities. Throughout this technical note, the communication flow between spacecraft is assumed to be undirected. Simulation results of a scenario of four spacecraft are provided to show the effectiveness of the proposed control schemes.