重大转变：DRAM取代SRAM

随着添加到系统设计中的功能的增加,以及所要求的代码和数据RAM容量成比例、甚至更可能的按指数规律的增长,DRAM相比于SRAM的每比特成本优势变得更加难以忽略(如图1).     

The Ferroelectric Field Effect within an Integrated Core/Shell Nanowire

The synthesis of cylindrical silicon‐core and ferroelectric oxide perovskite‐shell nanowires and their response characteristics as individual three‐terminal nanoscale electronic devices is reported. The co‐axial nanowire geometry facilitates large ferroelectric field‐effect modulation (>10⁴) of nanowire conductivity following sequential application and removal of an applied dc field. Source‐drain current–voltage traces collected during sweeps of ferroelectric gate potential and switching of the component of shell outward and inward polarization provide direct evidence of ferroelectric coupling on nanowire channel conductance. Despite a very small (1:20) ferroelectric‐to‐semiconductor channel thickness ratio, an unexpectedly strong electrostatic coupling of ferroelectric polarization to channel conductance is observed because of the co‐axial gate geometry and curvature‐induced strain enhancement of ferroelectric polarization.     

Perceptual image hashing via feature points: performance evaluation and tradeoffs.

We propose an image hashing paradigm using visually significant feature points. The feature points should be largely invariant under perceptually insignificant distortions. To satisfy this, we propose an iterative feature detector to extract significant geometry preserving feature points. We apply probabilistic quantization on the derived features to introduce randomness, which, in turn, reduces vulnerability to adversarial attacks. The proposed hash algorithm withstands standard benchmark (e.g., Stirmark) attacks, including compression, geometric distortions of scaling and small-angle rotation, and common signal-processing operations. Content changing (malicious) manipulations of image data are also accurately detected. Detailed statistical analysis in the form of receiver operating characteristic (ROC) curves is presented and reveals the success of the proposed scheme in achieving perceptual robustness while avoiding misclassification.     

A Multiwalled‐Carbon‐Nanotube‐Based Biosensor for Monitoring Microcystin‐LR in Sources of Drinking Water Supplies

A multiwalled carbon nanotube (MWCNT)‐based electrochemical biosensor is developed for monitoring microcystin‐LR (MC‐LR), a toxic cyanobacterial toxin, in sources of drinking water supplies. The biosensor electrodes are fabricated using vertically well‐aligned, dense, millimeter‐long MWCNT arrays with a narrow size distribution, grown on patterned Si substrates by water‐assisted chemical vapor deposition. High temperature thermal treatment (2500 °C) in an Ar atmosphere is used to enhance the crystallinity of the pristine materials, followed by electrochemical functionalization in alkaline solution to produce oxygen‐containing functional groups on the MWCNT surface, thus providing the anchoring sites for linking molecules that allow the immobilization of MC‐LR onto the MWCNT array electrodes. Addition of the monoclonal antibodies specific to MC‐LR in the incubation solutions offers the required sensor specificity for toxin detection. The performance of the MWCNT array biosensor is evaluated using micro‐Raman spectroscopy, including polarized Raman measurements, X‐ray photoelectron spectroscopy, cyclic voltammetry, optical microscopy, and Faradaic electrochemical impedance spectroscopy. A linear dependence of the electron‐transfer resistance on the MC‐LR concentration is observed in the range of 0.05 to 20 μg L^?1, which enables cyanotoxin monitoring well below the World Health Organization (WHO) provisional concentration limit of 1 μg L^?1 for MC‐LR in drinking water.     

An Elastomeric Poly(Thiophene‐EDOT) Composite with a Dynamically Variable Permeability Towards Organic and Water Vapors

An interpenetrating polymer network (IPN) material with controllable nanoporosity is developed for applications such as chemical protection. The IPN material is based on a conducting polymer backbone consisting of thiophene and 3,4 ethylenedioxythiophene (EDOT) repeat units–poly(thiophene‐EDOT)–formed within a soft polyurethane support. The IPN demonstrates reversible, electrochemically switchable nanoporosity in the absence of standard liquid electrolyte, with the oxidized state being the open (high porosity) state and the reduced state being the closed (low porosity) state. The switching of the IPN between its oxidized (open) and reduced (closed) states is actuated using application of ±1.0 V. The variability in the IPN porosity, induced by the electrochemical switching, is revealed by large changes in water vapor diffusivity, as well as changes in the diffusivities of the chemical agent simulants chloroethyl ethyl sulfide (CEES) and methyl salicylate (MeS). The closed state of the IPN is able to decrease CEES diffusivity by ≈99% compared to expanded Teflon (ePTFE), while the open state allows high MVT rates comparable to ePTFE. The IPN's ability to allow high MVT under non‐threat conditions (open state) and high protection from agents under threat conditions (closed state) is a unique and desirable characteristic of this novel IPN material.     

Extending transmission bandwidth of air-core photonic bandgap fibers

Air-core photonic bandgap fibers offer many unique properties and are critical to many emerging applications. A notable property is the high nonlinear threshold which provides a foundation for applications at high peak powers. The strong interaction of light and air is also essential for a number of emerging applications, especially those based on nonlinear interactions and spectroscopy. For many of those applications, much wider transmission bandwidths are desired to accommodate a wider tuning range or the large number of optical wavelengths involved. Presently, air-core photonic bandgap fibers have a cladding of hexagonal lattice. The densely packed geometry of hexagonal stacking does not allow large nodes in the cladding, which would provide a further increase of photonic bandgaps. On the other hand, a photonic cladding with a square lattice can potentially provide much larger nodes and consequently wider bandgap. In this work, the potentials of much wider bandgap with square lattice cladding is theoretically studied and experimentally demonstrated.     

Nanoimprint lithography fabrication of waveguide-integrated optical gratings with inexpensive stamps

We demonstrate that a replica grating can be effectively used as an inexpensive stamp for nanoimprint lithography to pattern diffractive optical couplers integrated with planar optical waveguides. Imprinted grating patterns were integrated with silicon oxynitride waveguide films to be used as an evanescent wave sensor in the input grating-coupler configuration. An anti-adhesion layer using an inexpensive, two-step chemical functionalization was developed for the stamps. The stamps were able to withstand imprint temperatures ranging from 140 to 190 °C and high fidelity imprints were obtained. The groove pattern was integrated in waveguide films by etch transfer and light-coupling properties of gratings with 1.2 μm pitch were tested using a λ = 1.55 μm laser. Compared to etched silicon masters, replica optical gratings provide uniform pattern density over their entire surface with no unstructured regions, are inexpensive, and readily available for R&D use.     

Modified Goodness-of-Fit Tests for Gamma Distributions with Unknown Location and Scale Parameters

The common Kolmogorov-Smirnov, Anderson-Darling, and Cramer-von Mises goodness-of-fit tests require continuous underlying distributions with known parameters. This paper gives tables of critical values for these tests for gamma distributions with unknown location and scale parameters and known shape parameters. The powers of these tests are given for a number of alternative distributions. A relation between the critical values and the inverse square of the shape parameter is presented. For larger sample sizes, the modified CvM test is usually the most powerful of the three tests. One exception is for the alternative of a lognormal distribution where the modified AD test is most powerful. The equation, C = ao + a1(1/?2) describes the relation between critical value and shape parameter quite well.     

Measurement of Ventricular Volume by Intracardiac Impedance: Theoretical and Empinrcal Approaches

The most widely used equation, V = pL2/R, is developed for the computation of ventricular volume from catheter based impedance measurements. The assumptions implicit in this derivation are examined and found to be generally invalid. An empirical discrete resistor model is described which includes the impedance of the myocardial tissue and the adjoining ventricular blood volume. Once the parameters of this model are determined for individual canine hearts, the model predicts stroke volume from measured impedances. Due to the difficulty involved in determining the parameters of the empirical model, a numerical model is developed which solves the equation V ?a V U + F = 0 in a three-dimensional volume. This model is then used to determine the effect of parallel tissue resistance, catheter position, and contraction of the other ventricle on volumes computed by intracardiac impedance. Parallel tissue resistance is found to have the greatest impact on absolute volume measurements. However, stroke volume computations are relatively unaffected by any of the three factors.     

Nanochannel electroporation delivers precise amounts of biomolecules into living cells

Many transfection techniques can deliver biomolecules into cells, but the dose cannot be controlled precisely. Delivering well-defined amounts of materials into cells is important for various biological studies and therapeutic applications. Here, we show that nanochannel electroporation can deliver precise amounts of a variety of transfection agents into living cells. The device consists of two microchannels connected by a nanochannel. The cell to be transfected is positioned in one microchannel using optical tweezers, and the transfection agent is located in the second microchannel. Delivering a voltage pulse between the microchannels produces an intense electric field over a very small area on the cell membrane, allowing a precise amount of transfection agent to be electrophoretically driven through the nanochannel, the cell membrane and into the cell cytoplasm, without affecting cell viability. Dose control is achieved by adjusting the duration and number of pulses. The nanochannel electroporation device is expected to have high-throughput delivery applications.