Electrical impedance spectroscopy of the human prostate

Tissue electrical impedance is a function of its architecture and has been used to differentiate normal and cancer tissues in a variety of organs including breast, cervix, skin, and bladder. This paper investigates the possibility of differentiating normal and malignant prostate tissue using bioimpedance spectra. A probe was designed to measure impedance spectra over the range of 10 kHz to 1 MHz. The probe was fully characterized using discrete loads and saline solutions of different concentrations. Impedance spectra of five ex vivo prostates were measured in the operating room immediately following radical prostatectomy. Wilcoxon signed-rank tests were used to compare the normal and malignant findings. The impedance probe had a signal-to-noise ratio (SNR) > 84 dB across the entire spectrum and measured a tissue volume of approximately 46 mm(3). At 10 kHz, prostate conductivity (or) ranged from 0.232 S/m to 0.310 S/m for tumor and from 0.238 S/m to 0.901 S/m for normal tissue. At 1 MHz the ranges were 0.301 S/m to 0.488 S/m for tumor and 0.337 S/m to 1.149 S/m for normal. Prostate permittivity (epsilonr) ranged from 6.64 x10(4) to 1.25 x 10(5) for tumor and from 9.08 x 10(4) to 4.49 x 10(5) for normal tissues at 10 kHz. And, at 1 MHz the er ranges were 9.23 x 10(2) to 1.88 x 10(3) for tumor and 1.16 x 10(3) to 2.18 x 10(3) for normal tissue. Both sigma and epsilonr of tumor tissue were found to be significantly lower than that of normal tissue (P < 0.0001). Conductivity and permittivity are both higher in normal prostate tissues than they are in malignant tissue making them suitable parameters for tissue differentiation. This is in agreement with trends observed in other tissues reported in much of the literature. Expanded studies are needed to further validate this finding and to explore the biological mechanism responsible for generating the results.     

新型PSVA像素结构中液晶配向的研究

研究了一种新型的PSVA(聚合物稳定垂直配向)像素结构,与传统的的像素结构相比,该新型结构具有更高的穿透率。钝化(Passivation,PV)层的沟槽深度是新型像素结构中的一个关键参数,液晶的方位角和倾斜角与沟槽深度具有很强的相关性。通过模拟和实验研究了液晶的在该结构中的配向行为。     

The Effect of Nanotube Content and Orientation on the Mechanical Properties of Polymer–Nanotube Composite Fibers: Separating Intrinsic Reinforcement from Orientational Effects

We have measured the mechanical properties of coagulation‐spun polymer–nanotube composite fibers. Both the fiber modulus, Y, and strength, σ_B, scale linearly with volume fraction, V_f, up to V_f ～10%, after which these properties remain constant. We measured dY/dV_f = 254 GPa and dσ_B/dV_f = 2.8 GPa in the linear region. By drawing fibers with V_f < 10% to a draw ratio of ～60%, we can increase these values to dY/dV_f = 600 GPa and dσ_B/dV_f = 7 GPa. Raman measurements show the Herman's orientation parameter, S, to increase with drawing, indicating that significant nanotube alignment occurs. Raman spectroscopy also shows that the nanotube effective modulus, Y_Eff, also increases with drawing. We have calculated an empirical relationship between the nanotube orientation efficiency factor, η_o, and S. This allows us to fit the data for Y_Eff versus η_o, showing that the fiber modulus scales linearly with η_o, as predicted theoretically by Krenchel. From the fit, we estimate the nanotube modulus to be; Y_NT = 480 GPa. Finally, we show that the fiber strength also scales linearly with η_o, giving an effective interfacial stress transfer of τ = 40 MPa and a nanotube critical length of l_c=1250 nm. This work demonstrates the validity of the Cox‐Krenchel rule of mixtures and shows that continuum theory still applies at the near‐molecular level.     

Gas Diffusion,Energy Transport,and Thermal Accommodation in Single‐Walled Carbon Nanotube Aerogels

The thermal conductivity of gas‐permeated single‐walled carbon nanotube (SWCNT) aerogel (8 kg m^?3 density, 0.0061 volume fraction) is measured experimentally and modeled using mesoscale and atomistic simulations. Despite the high thermal conductivity of isolated SWCNTs, the thermal conductivity of the evacuated aerogel is 0.025 ± 0.010 W m^?1 K^?1 at a temperature of 300 K. This very low value is a result of the high porosity and the low interface thermal conductance at the tube–tube junctions (estimated as 12 pW K^?1). Thermal conductivity measurements and analysis of the gas‐permeated aerogel (H₂, He, Ne, N₂, and Ar) show that gas molecules transport energy over length scales hundreds of times larger than the diameters of the pores in the aerogel. It is hypothesized that inefficient energy exchange between gas molecules and SWCNTs gives the permeating molecules a memory of their prior collisions. Low gas‐SWCNT accommodation coefficients predicted by molecular dynamics simulations support this hypothesis. Amplified energy transport length scales resulting from low gas accommodation are a general feature of CNT‐based nanoporous materials.     

Advanced optical tweezers for the study of cellular and molecular biomechanics

Optical tweezers are an important tool for studying cellular and molecular biomechanics. We present a robust optical tweezers device with advanced features including: multiple optical traps, acousto-optic trap steering, and back focal plane interferometry position detection. We integrate these features into an upright microscope, with no compromise to its capabilities (differential interference contrast microscopy, fluorescence microscopy, etc.). Acousto-optic deflectors (AODs) steer each beam and can create multiple time-shared traps. Position detection, force calibrations and AOD performance are presented. The system can detect subnanometer displacements and forces below 0.1 pN.     

朗讯重新定义服务概念

朗讯科技（中国）公司借上海“2005年中国国际信息通信展览会”之机,于2005年6月21日在沪举办了“2005通信服务高层论坛-朗讯服务解决方案研讨会”,邀请国内政府机构、运营商以及企业代表与来自国际知名运营商和朗讯全球服务部（IWS）的专家们一道,共同探讨通信业务和通信服务面临的挑战、未来发展方向以及相关的服务解决方案。     

Dynamic behavior of an electrohydraulic valve: Typology of characteristic curves

The majority of off-road vehicles employed in agriculture are equipped with a hydraulic steering. An efficient way of automating the steering mechanism of these vehicles is by controlling the electrohydraulic valve that operates the steering cylinder. Electronically-controlled hydraulic valves often behave nonlinearly and, consequently, they introduce certain complexities in the analysis of the hydraulic system. Therefore, it is necessary to understand their behavior before designing a control system that is able to auto-steer an agricultural machine safely and efficiently. The objective of this work was to characterize the performance of an electrohydraulic valve with the aid of a set of experiments conducted on a hardware-in-the-loop electrohydraulic simulator. The operation of the valve was classified in four types (I, II, III, and IV) according to the valve characteristic curves and the properties of the input signal. The phenomena of deadband, hysteresis, and saturation helped to discriminate between types. The input signal, especially its frequency, was crucial in studying the functioning of the valve. The hardware-in-the-loop simulator was fed with signals that imitated the auto-steering action. The outcomes obtained from this research provide some critically supporting information for designing high performance steering controllers for agricultural vehicles.     

Detailed Balance Broken by Catch Bond Kinetics Enables Mechanical-Adaptation in Active Materials

Unlike nearly all engineered materials which contain bonds that weaken under load, biological materials contain “catch” bonds which are reinforced under load. Consequently, materials, such as the cell cytoskeleton, can adapt their mechanical properties in response to their state of internal, non-equilibrium (active) stress. However, how large-scale material properties vary with the distance from equilibrium is unknown, as are the relative roles of active stress and binding kinetics in establishing this distance. Through course-grained molecular dynamics simulations, the effect of breaking of detailed balance by catch bonds on the accumulation and dissipation of energy within a model of the actomyosin cytoskeleton is explored. It is found that the extent to which detailed balance is broken uniquely determines a large-scale fluid-solid transition with characteristic time-reversal symmetries. The transition depends critically on the strength of the catch bond, suggesting that active stress is necessary but insufficient to mount an adaptive mechanical response.     

Ultrasensitive Strain Gauges Enabled by Graphene‐Stabilized Silicone Emulsions

Here, an approach is presented to incorporate graphene nanosheets into a silicone rubber matrix via solid stabilization of oil‐in‐water emulsions. These emulsions can be cured into discrete, graphene‐coated silicone balls or continuous, elastomeric films by controlling the degree of coalescence. The electromechanical properties of the resulting composites as a function of interdiffusion time and graphene loading level are characterized. With conductivities approaching 1 S m^?1, elongation to break up to 160%, and a gauge factor of ≈20 in the low‐strain linear regime, small strains such as pulse can be accurately measured. At higher strains, the electromechanical response exhibits a robust exponential dependence, allowing accurate readout for higher strain movements such as chest motion and joint bending. The exponential gauge factor is found to be ≈20, independent of loading level and valid up to 80% strain; this consistent performance is due to the emulsion‐templated microstructure of the composites. The robust behavior may facilitate high‐strain sensing in the nonlinear regime using nanocomposites, where relative resistance change values in excess of 10⁷ enable highly accurate bodily motion monitoring.     

A New Prototype Two‐Phase (TiNi)–(β‐W) SMA System with Tailorable Thermal Hysteresis

The Ti–Ni–W two‐phase shape memory alloy (SMA) thin film system is presented as a prototype for new SMAs with tailorable thermal transformation hysteresis (ΔT). The concept is to combine the SMA TiNi with almost insoluble W to create the two‐phase system (TiNi)–(β‐W). This system behaves like a pseudobinary TiNi system. Phase transformation behavior for compositions above the solubility limit of W in TiNi exhibit a B2–R phase transformation with characteristically small ΔT. Moreover, ΔT is dependent on the amount of W and it can be tailored to zero and even negative. This phenomenon is rationalized as being due to the mechanical interaction between the phases B2‐TiNi and β‐W. The presented results are very promising for the development of high‐speed Ti–Ni‐based SMA actuators.