Upconverting Nanoparticle Relays for Resonance Energy Transfer Networks

Networks of fluorophores arranged at the nanoscale can perform basic computation using resonance energy transfer (RET) to transport and manipulate information in the form of excitons. As excitons travel through RET circuits, they are red‐shifted due to vibrational energy loss at each transfer event. This loss prohibits RET circuits from being cascaded to form larger, more computationally complex systems. To address this issue, a nanoassembly capable of converting three or more low energy excitons into a single high energy exciton is designed and fabricated. Deemed the RET relay, this device uses upconverting nanoparticles to achieve anti‐Stokes energy transfer from near‐infrared excited fluorophores to visibly excited fluorophores. In this work, the relay is explored by first breaking it into its halves. Each fluorophore's ability to donate energy to or from the nanoparticle is characterized by a series of photoluminescence experiments. The adsorption of these fluorophores to the particle is modeled as a Langmuir process, revealing the fractional occupancy of each dye that optimizes energy transfer. A fully functional relay is then demonstrated by exciting the near‐infrared dye and extracting the visible dye's fluorescence. Lastly, the performance of the entire construct is optimized over a small sampling of assembly reaction coordinates.     

电能计量IC配合闪存单片机,实现灵活创新的电表设计

近年来,市场上固定功能的电表集成电路（IC）不断增多,这使得在电表设计方面保持竞争力变得越来越困难。许多模拟前端（AFE）电能计量IC都采用Δ-∑ADC,并通过基于ROM的固定功能状态机来计算功率输出。这些IC不能进行修改,也不能用于电能测量之外的其他功能。     

Semi-empirical model for millimetre-wave vegetation attenuationrates

An improved empirical model of the attenuation rates due to propagation through vegetation at millimetre-wave frequencies is described. The measured vegetation attenuation rates of 38 GHz signals were fitted to a two-parameter model with a final slope of 0 dB/m, to give an improvement in fit over the current ITU recommendation. However, this final slope is not a typical characteristic and is not seen at other frequencies. A new three-parameter model has been developed, which may have a nonzero final slope, giving the model greater freedom and therefore a better fit to measured data at all frequencies     

High aperture efficiency symmetric reflector antennas with up to60° field of view

A microwave single-reflector scanning antenna derived from an ellipse (rather than the usual parabola) which gives a much greater field of view is presented. This reflector combines reasonable scanning in one plane with good focusing in the other, and its scanning ability is superior to the torus and other single reflectors because it has much greater aperture efficiency and is thus smaller while having the same performance. The reflector surface is derived in two steps: a fourth-order even polynomial profile curve in the scan plane is found using least squares to minimize the scanned ray errors; then even polynomial terms in x and y that minimize astigmatism for both the unscanned and maximally scanned beams are added to form the three-dimensional surface. Numerical simulations of radiation patterns for a variety of antenna diameter and field-of-view cases give excellent results. The 60° scan case with 30-λ-diameter aperture has only 0.2-dB peak gain deviation from ideal and first sidelobe levels below 14 dB down from peak gain. The 17°, 500-λ case has only 0.8-dB gain variation and -14 to -11 dB sidelobe levels for approximately ±68 beamwidths of scan, with focal length to aperture diameter ratio equal to about one     

从PC至移动应用,DisplayPort技术方兴未艾

未来几年内,HDMI与DisplayPort将作为两种消费者可用的数字视频接口同时主宰市场.HDMI将继续在消费视频产品中存在,而DisplayPort则将取代VGA和DVI,成为PC显示器接口.     

Radar cross section of trihedral corner reflectors using PO and MEC

Physical optics (po) and the method of equivalent currents (mec) are used for the formulation and calculation of the backscatter cross section of both the triangular and square trihedral corner reflectors. Scattering from a trihedral corner reflector is dominated by single, double, and triple reflections by the interior walls. A physical optics integration is performed on the entire surface of each plate for the evaluation of the singly reflected fields. Doubly and triply reflected fields are evaluated by first using geometrical optics (go) at initial reflections to calculate the incident plane wave on the plate where the last reflection occurs. Physical optics is then applied on the illuminated area of that plate. First-order diffractions, which are based on the fringe current expressions for the exterior edges of the trihedral, are also included in the analysis. Predictions compare very well with both experimental and fdtd data.     

Adhesion and Surface Interactions of a Self‐Healing Polymer with Multiple Hydrogen‐Bonding Groups

The surface properties and self‐adhesion mechanism of self‐healing poly(butyl acrylate) (PBA) copolymers containing comonomers with 2‐ureido‐4[1H]‐pyrimidinone quadruple hydrogen bonding groups (UPy) are investigated using a surface forces apparatus (SFA) coupled with a top‐view optical microscope. The surface energies of PBA–UPy4.0 and PBA–UPy7.2 (with mole percentages of UPy 4.0% and 7.2%, respectively) are estimated to be 45–56 mJ m^?2 under dry condition by contact angle measurements using a three probe liquid method and also by contact and adhesion mechanics tests, as compared to the reported literature value of 31–34 mJ m^?2 for PBA, an increase that is attributed to the strong UPy–UPy H‐bonding interactions. The adhesion strengths of PBA–UPy polymers depend on the UPy content, contact time, temperature and humidity level. Fractured PBA–UPy films can fully recover their self‐adhesion strength to 40, 81, and 100% in 10 s, 3 h, and 50 h, respectively, under almost zero external load. The fracture patterns (i.e., viscous fingers and highly “self‐organized” parallel stripe patterns) have implications for fabricating patterned surfaces in materials science and nanotechnology. These results provide new insights into the fundamental understanding of adhesive mechanisms of multiple hydrogen‐bonding polymers and development of novel self‐healing and stimuli‐responsive materials.     

Matrix Metalloproteinase Responsive,Proximity‐Activated Polymeric Nanoparticles for siRNA Delivery

Small interfering RNA (siRNA) has significant potential to evolve into a new class of pharmaceutical inhibitors, but technologies that enable robust, tissue‐specific intracellular delivery must be developed before effective clinical translation can be achieved. A pH‐responsive, smart polymeric nanoparticle (SPN) with matrix metalloproteinase (MMP)‐7‐dependent proximity‐activated targeting (PAT) is described here. The PAT‐SPN is designed to trigger cellular uptake and cytosolic delivery of siRNA once activated by MMP‐7, an enzyme whose overexpression is a hallmark of cancer initiation and progression. The PAT‐SPN is composed of a corona‐forming polyethylene glycol (PEG) block, an MMP‐7‐cleavable peptide, a cationic siRNA‐condensing block, and a pH‐responsive, endosomolytic terpolymer block that drives self‐assembly and forms the PAT‐SPN core. With this novel design, the PEG corona shields cellular interactions until it is cleaved in MMP‐7‐rich environments, shifting the SPN ζ‐potential from +5.8 to +14.4 mV and triggering a 2.5 fold increase in carrier internalization. The PAT‐SPN exhibits pH‐dependent membrane disruptive behavior that enables siRNA escape from endo‐lysosomal pathways. Intracellular siRNA delivery and knockdown of the model enzyme luciferase in R221A‐Luc mammary tumor cells is significantly increased by MMP‐7 pre‐activation (p < 0.05). These combined data indicate that the PAT‐SPN provides a promising new platform for tissue‐specific, proximity‐activated siRNA delivery to MMP‐rich pathological environments.     

Data-delay evaluation in integrated wireless networks based on local product-form solutions for voice occupancy

In this paper we consider the evaluation of data-packet delay in wireless integrated voice/data networks. In networks that support voice in the classical circuit-switched fashion, the voice occupancy process satisfies a product-form solution under reasonable modeling assumptions. Although this product-form solution provides an accurate characterization of equilibrium voicetraffic behavior, it does not directly provide a method to evaluate data-packet delay. However, examination of each link separately in a manner that incorporates interaction with the rest of the network permits us to take advantage of the wireless nature of the network and obtain a three-flow characterization of each link, which also satisfies a product-form solution and is hence termed a mini-product-form solution. By matching the values of these flows to the average values obtained from the product-form solution of the entire network, we obtain a three-dimensional Markov chain characterization of the voice occupancy state on the link, which permits a simpler evaluation of data-packet delay. A further reduction is possible by converting the three-dimensional chain to a single-dimensional one. Performance results demonstrate that these models provide satisfactory delay estimates that also appear to be upper bounds on delay.C.M. Barnhart was at the Naval Research Laboratory when this paper was written.     

选择高压场效应管实现节能

高压金属氧化物半导体场效应晶体管（MOSFET）技术在过去几年中经历了很大的变化,这为电源工程师提供了许多选择。了解不同MOSFET器件的细微差别及不同切换电路的应力,能够帮助工程师避免许多问题,并实现效率最大化。经验证明,采用新型的MOSFET器件取代旧式MOSFET,除简单地导通电阻上的差异之外,更重要的是,还能实现更高的电流强度与更快的切换速度以及其他优越性能。