Directed Molecular Collection by E‐Jet Printed Microscale Chemical Potential Wells in Hydrogel Films

A facile approach to locally concentrate analytes of interest will significantly enhance miniaturized, integrated chemical‐analysis systems. Here, the directed analyte transport and concentration using ≈200 µm‐diameter E‐jet printed chemical potential wells in a polyacrylamide hydrogel is demonstrated. Using a cationic well as the model system, anionic analytes are accumulated into a microscale area with a local concentration enhancement of >50‐fold relative to the surrounding area. By downscaling the diameter of the chemical potential well from a few millimeters to 100s of micrometers, it is found, using both fluorescence and Raman microscopy, that the molecular collection capacity of the well is greatly improved. Additionally, it is shown that molecules can be simultaneously transported and concentrated to arrays of microscale regions using an array of microscale chemical potential wells. This approach enhances many‐fold the limit of detection, enables the formation of microscale potential well arrays with a variety of chemical properties, and provides a novel microscale molecular manipulation technique as an alternative to traditional microfluidic‐based systems.     

A survey of the theory of source coding with a fidelity criterion

The purpose of this paper is threefold: 1) to acquaint the reader with the types of problems that have been considered in the area of source coding with a fidelity criterion; 2) to survey results that have been obtained on these problems; and 3) to outline future research trends in the area     

Embedded image compression based on wavelet pixel classification and sorting

The method of modeling and ordering in wavelet domain is very important to design a successful algorithm of embedded image compression. In this paper, the modeling is limited to "pixel classification," the relationship between wavelet pixels in significance coding. Similarly, the ordering is limited to "pixel sorting," the coding order of wavelet pixels. We use pixel classification and sorting to provide a better understanding of previous works. The image pixels in wavelet domain are classified and sorted, either explicitly or implicitly, for embedded image compression. A new embedded image code is proposed based on a novel pixel classification and sorting (PCAS) scheme in wavelet domain. In PCAS, pixels to be coded are classified into several quantized contexts based on a large context template and sorted based on their estimated significance probabilities. The purpose of pixel classification is to exploit the intraband correlation in wavelet domain. Pixel sorting employs several fractional bit-plane coding passes to improve the rate-distortion performance. The proposed pixel classification and sorting technique is simple, yet effective, producing an embedded image code with excellent compression performance. In addition, our algorithm is able to provide either spatial or quality scalability with flexible complexity.     

Comparison of SeaWiFS measurements of the Moon with the U.S. Geological Survey lunar model

The Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) has made monthly observations of the Moon since 1997. Using 66 monthly measurements, the SeaWiFS calibration team has developed a correction for the instrument's on-orbit response changes. Concurrently, a lunar irradiance model has been developed by the U.S. Geological Survey (USGS) from extensive Earth-based observations of the Moon. The lunar irradiances measured by SeaWiFS are compared with the USGS model. The comparison shows essentially identical response histories for SeaWiFS, with differences from the model of less than 0.05% per thousand days in the long-term trends. From the SeaWiFS experience we have learned that it is important to view the entire lunar image at a constant phase angle from measurement to measurement and to understand, as best as possible, the size of each lunar image. However, a constant phase angle is not required for using the USGS model. With a long-term satellite lunar data set it is possible to determine instrument changes at a quality level approximating that from the USGS lunar model. However, early in a mission, when the dependence on factors such as phase and libration cannot be adequately determined from satellite measurements alone, the USGS model is critical to an understanding of trends in instruments that use the Moon for calibration. This is the case for SeaWiFS.     

Universal lossless compression via multilevel pattern matching

A universal lossless data compression code called the multilevel pattern matching code (MPM code) is introduced. In processing a finite-alphabet data string of length n, the MPM code operates at O(log log n) levels sequentially. At each level, the MPM code detects matching patterns in the input data string (substrings of the data appearing in two or more nonoverlapping positions). The matching patterns detected at each level are of a fixed length which decreases by a constant factor from level to level, until this fixed length becomes one at the final level. The MPM code represents information about the matching patterns at each level as a string of tokens, with each token string encoded by an arithmetic encoder. From the concatenated encoded token strings, the decoder can reconstruct the data string via several rounds of parallel substitutions. A O(1/log n) maximal redundancy/sample upper bound is established for the MPM code with respect to any class of finite state sources of uniformly bounded complexity. We also show that the MPM code is of linear complexity in terms of time and space requirements. The results of some MPM code compression experiments are reported     

Grammar-based codes: a new class of universal lossless source codes

We investigate a type of lossless source code called a grammar-based code, which, in response to any input data string x over a fixed finite alphabet, selects a context-free grammar G_x representing x in the sense that x is the unique string belonging to the language generated by G_x. Lossless compression of x takes place indirectly via compression of the production rules of the grammar G_x. It is shown that, subject to some mild restrictions, a grammar-based code is a universal code with respect to the family of finite-state information sources over the finite alphabet. Redundancy bounds for grammar-based codes are established. Reduction rules for designing grammar-based codes are presented     

Comparison of two optimum rates for noiseless encoding of anonstationary information source

A nonstationary finite-alphabet information source μ is noiselessly encoded, first by adaptive block to variable-length codes and then by finite-state codes of this kind. It is shown that if μ belongs to a certain class of sources that includes those with finite-order Markov memory, then a stationary input-restricted channel exists such that in the first case the optimum encoding rate is equal to the largest conditional entropy for channel input given channel output, whereas in the second case it is the largest channel output entropy. A sufficient condition for the two rates to be equal is also given     

超短高功率脉冲激光与物质相互作用及其应用

超短高功率脉冲激光系统的小型化实用化极大地促进了激光与物质相互作用的物理和应用研究。回顾加拿大魁北克大学国立科学研究院材料研究所（简称ＩＮＲＳ）的超短高功率脉冲激光产生高温高密度等离子体的最新研究成果及其在分子物理和辐射约束高温高密度等离子体物理中的应用。     

Guaranteed recursive non‐linear state bounding using interval analysis

The problem considered here is state estimation in the presence of unknown but bounded state perturbations and measurement noise. In this context, most available results are for linear models, and the purpose of the present paper is to deal with the non‐linear case. Based on interval analysis and the notion of set inversion, a new state estimator is presented, which evaluates a set estimate guaranteed to contain all values of the state that are consistent with the available observations, given the perturbation and noise bounds and a set containing the initial value of the state. To the best of our knowledge, it is the first estimator for which this claim can be made. The precision of the set estimate can be improved, at the cost of more computation. Theoretical properties of the estimator are studied, and computer implementation receives special attention. A simple illustrative example is treated. Copyright © 2002 John Wiley & Sons, Ltd.