Photonic signal processing offers the prospect of realizing extremely high multigigahertz sampling frequencies, overcoming inherent electronic limitations. This stems from the intrinsic excellent delay properties of optical delay lines. These processors provide new capabilities for realizing high time-bandwidth operation and high-resolution performance. In-fiber signal processors are inherently compatible with fiber-optic microwave systems and can provide connectivity with built-in signal conditioning. Fundamental principles of photonic signal processing, including sampling, tuning, and noise, are discussed. Structures that can extend the performance of photonic signal processors are presented, including methods for improving the filter shape characteristics of interference mitigation filters, techniques to increase the stopband attenuation of bandpass filters, and methods to achieve large free spectral range. Several photonic signal processors, including high-resolution microwave filters, widely tunable filters, arbitrary waveform generators, and fast signal correlators, are discussed. Techniques to solve the fundamental noise problem in photonic signal processors are described, and coherence-free structures for few-tap notch filters are discussed. Finally, a new concept for realizing multiple-tap coherence-free processor filters, based on a new frequency-shifting technique, is presented. The structure not only eliminates the phase-induced intensity noise limitation, but can also generate a large number of taps to enable the achievement of processors with high performance and high resolution.

Photonic signal processing of microwave signals

Mounting of the acute inflammatory response is crucial for host defense and pivotal to the development of chronic inflammation, fibrosis, or abscess formation versus the protective response and the need of the host tissues to return to homeostasis. Within self-limited acute inflammatory exudates, novel families of lipid mediators are identified, named resolvins (Rv), protectins, and maresins, which actively stimulate cardinal signs of resolution, namely, cessation of leukocytic infiltration, counterregulation of proinflammatory mediators, and the uptake of apoptotic neutrophils and cellular debris. The biosynthesis of these resolution-phase mediators in sensu stricto is initiated during lipid-mediator class switching, in which the classic initiators of acute inflammation, prostaglandins and leukotrienes (LTs), switch to produce specialized proresolving mediators (SPMs). In this work, we review recent evidence on the structure and functional roles of these novel lipid mediators of resolution. Together, these show that leukocyte trafficking and temporal spatial signals govern the resolution of self-limited inflammation and stimulate homeostasis.

/pdf/lipid-mediators-in-the-resolution-of-inflammation-16p8f9iuvq.pdf

Lipid Mediators in the Resolution of Inflammation

Amplifiers are ubiquitous in electronics and play a fundamental role in a wide range of scientific measurements. From a user's perspective, an ideal amplifier has very low noise, operates over a broad frequency range, and has a high dynamic range - it is capable of handling strong signals with little distortion. Unfortunately, it is difficult to obtain all of these characteristics simultaneously. For example, modern transistor amplifiers offer multi-octave bandwidths and excellent dynamic range. However, their noise remains far above the fundamental limit set by the uncertainty principle of quantum mechanics. Parametric amplifiers, which predate transistor amplifiers and are widely used in optics, exploit a nonlinear response to transfer power from a strong pump tone to a weak signal. If the nonlinearity is purely reactive, ie. nondissipative, in theory the amplifier noise can reach the quantum-mechanical limit. Indeed, microwave frequency superconducting Josephson parametric amplifiers do approach the quantum limit, but generally are narrow band and have very limited dynamic range. In this paper, we describe a superconducting parametric amplifier that overcomes these limitations. The amplifier is very simple, consisting only of a patterned metal film on a dielectric substrate, and relies on the nonlinear kinetic inductance of a superconducting transmission line. We measure gain extending over 2 GHz on either side of an 11.56 GHz pump tone, and we place an upper limit on the added noise of the amplifier of 3.4 photons at 9.4 GHz. Furthermore, the dynamic range is very large, comparable to microwave transistor amplifiers, and the concept can be applied throughout the microwave, millimeter-wave and submillimeter-wave bands.

/pdf/a-wideband-low-noise-superconducting-amplifier-with-high-5gmsu34n36.pdf

A wideband, low-noise superconducting amplifier with high dynamic range

Stereolithography is a solid freeform technique (SFF) that was introduced in the late 1980s Although many other techniques have been developed since then, stereolithography remains one of the most powerful and versatile of all SFF techniques It has the highest fabrication accuracy and an increasing number of materials that can be processed is becoming available In this paper we discuss the characteristic features of the stereolithography technique and compare it to other SFF techniques The biomedical applications of stereolithography are reviewed, as well as the biodegradable resin materials that have been developed for use with stereolithography Finally, an overview of the application of stereolithography in preparing porous structures for tissue engineering is given

A review on stereolithography and its applications in biomedical engineering

Diameter-controlled Growth of Single-crystalline In2O3 Nanowires and Their Electronic Properties

This paper describes the design, fabrication, and testing of a novel microstrip superconducting delay line. The structure of the delay line is a double-spiral meander line. The device is patterned from a YBa 2 Cu 3 O 7-δ (YBCO) thin film deposited on both sides of a 2-in-diameter LaAIO 3 substrate with a thickness of 0.25 mm. It exhibits low insertion loss up to 20 GHz. At 10 GHz, the measured attenuation is 0.031 dB/ns at 30 K, 0.049 dB/ns at 60 K, and 0.118 dB/ns at 77 K. The magnitudes of the ripples are below 2 dB across the entire band. The total delay at low frequency is approximately 29 ns.

Wide-band superconducting microstrip delay line

Diplexers are three-port filtering devices with a junction connecting two channel filters; the common port connects to an antenna which serves the two channel filters bearing the second and the third port. Conventionally, diplexers are designed using transmission line based junctions or circulators, but recently a new approach of designing diplexers with resonant junctions was introduced and this led to a reduction in the total number of components needed in the system or reduction in size. Such techniques are reported in [1] where two novel multiplexer topologies based on all-resonator structures were implemented at X-band using waveguide technology. In [2], a diplexer with a resonant star-junction and a triplexer with a non-resonant node star-junction were presented using synthesis approach. [3] presented a diplexer with asplit-ring resonator (SRR) as a common resonator and signal splitter. In [4], an FDD diplexer with a T-shaped junction resonator was presented. This work presents a diplexer that uses a SRR as a common resonator to connect two channel filters. The SRR comprises two nested open-loop resonators resonating at different frequencies corresponding to the two passbands of the diplexer. This differs with [3] in that the nested resonators are synchronously tuned in [3], whereas these are asynchronously tuned in this work resulting in more widely separated channels. The two channels at 2 GHz and 3 GHz each with a 4% fractional bandwidth were separately designed and joined together using the SRR. The SRR was used to replace the first resonator of each filter, resulting in reduced circuit size. Fig. 1(a) illustrates the coupling topology of the SRR where the resonator 1 and 2 represents the resonator of low and high frequency respectively. Resonator 2 is nested in resonator 1 thereby allowing all external couplings to be made with resonator 1. Fig. 1(b) illustrates the coupling topology of the proposed diplexer.

A Diplexer with a split-ring resonator junction

In this paper a coupling matrix synthesis procedure based on a combination of global and local optimisations has been presented. The coupling matrices of two high-order triple-band filters have been synthesized to demonstrate its applicability for cross-coupled filters with complex topologies and frequency responses. Convergence of the optimisation is fast and no initial values for control parameters are required. This technique can be used to synthesize many other multiple-passband filters. These coupling matrices can be used to produce practical filters with any resonator.

Yi Wang

Papers

Wide-band superconducting microstrip delay line

A Diplexer with a split-ring resonator junction

Coupling matrix synthesis of triple-passband filters using optimisation