Full field of view super-resolution imaging based on two static gratings and white light illumination

The usage of two static gratings for obtaining super-resolved imaging dates back to the work by Bachl and Lukosz in 1967. However, in their approach a severe reduction in the field of view was the necessary condition for improving the resolution. We present an approach based on two static gratings without sacrificing the field of view. The key idea for not paying with the field of view is to use white light illumination to average the ghost images obtained outside the region of interest since the positions of those images are wavelength dependent. Moreover, large magnification is achieved by using a commercial microscope objective instead of a test system with a unity magnification as presented in previous works. Because of the large magnification, the second grating has a low spatial period. This allows us to create an intermediate image and use a second imaging lens with low resolution capability while still obtaining an imaging quality as good as that provided by the first imaging lens. This is an important improvement in comparison with the original super-resolving method with two fixed gratings.     

Manipulating light waves: introduction

This special Applied Optics issue pays tribute to an extraordinary teacher, scientist, and friend who revolutionized several fields of optics, such as holography, microscopy, and biomedical imaging, by contributing his unique and simplified perspective on complicated phenomena. We thank all the authors who have contributed papers to this special feature as a manifestation of the long and unique career of Emmett Leith.     

Luminescent quantum dots fluorescence resonance energy transfer-based probes for enzymatic activity and enzyme inhibitors

The paper describes the development and characterization of analytical properties of quantum dot-based probes for enzymatic activity and for screening enzyme inhibitors. The luminescent probes are based on fluorescence resonance energy transfer (FRET) between luminescent quantum dots that serve as donors and rhodamine acceptors that are immobilized to the surface of the quantum dots through peptide linkers. Peptide-coated CdSe/ZnS quantum dots were prepared using a one-step ligand exchange process in which RGDC peptide molecules replace trioctylphosphine oxide (TOPO) molecules as the capping ligands of the quantum dots. The peptide molecules were bound to the surface of the CdSe/ZnS quantum dots through the thiol group of the peptide cysteine residue. The peptide-coated quantum dots were labeled with rhodamine to form the FRET probes. The emission quantum yield of the quantum dot FRET probes was 4-fold lower than the emission quantum yield of TOPO-capped quantum dots. However, the quantum dot FRET probes were sufficiently bright to enable quantitative enzyme and enzyme inhibition assays. The probes were used first to test the enzymatic activity of trypsin in solution based on FRET signal changes of the quantum dot-based enzymatic probes in the presence of proteolytic enzymes. For example, exposure of the quantum dot FRET probes to 500 microg/mL trypsin for 15 min resulted in 60% increase in the photoluminescence of the quantum dots and a corresponding decrease in the emission of the rhodamine molecules. These changes resulted from the release of rhodamine molecules from the surface of the quantum dots due to enzymatic cleavage of the peptide molecules. The quantum dot FRET-based probes were used to monitor the enzymatic activity of trypsin and to screen trypsin inhibitors for their inhibition efficiency.     

Transverse resolution improvement using rotating-grating time-multiplexing approach

The ability to improve the limited resolving power of optical imaging systems while approaching the theoretical diffraction limit has been an attractive discipline with growing interest over the last years due to its benefits in many applied optics systems. This paper presents a new approach to achieve transverse superresolution in far-field imaging systems, with direct application in both digital microscopy and digital holographic microscopy. Theoretical analysis and computer simulations show the validity of the presented approach.     

Extractors for varieties

We study the task of randomness extraction from sources that are distributed uniformly on an unknown algebraic variety. In other words, we are interested in constructing a function (an extractor) whose output is close to uniform even if the input is drawn uniformly from the set of solutions of an unknown system of low degree polynomials. This problem generalizes the problem of extraction from affine sources which has drawn a considerable amount of interest lately. We present two constructions of explicit extractors for varieties. The first works for varieties of any size (including one-dimensional varieties or curves) and requires field size that is exponential in the overall dimension of the space. Our second extractor allows the field size to be polynomial in the degree of the equations defining the variety, but works only for varieties whose size is at least the square root of the total size of the space.     

Controlling shop floor operations in a multi-family, multi-cell manufacturing environment through constant work-in-process

This paper discusses pertinent issues in applying CONstant Work-In-Process (CONWIP) principles to control shop floor operations in a manufacturing environment characterized by several product families processed along different routes in several production cells. The approach we take is to simultaneously answer two major questions: (1) what is the best WIP level? and (2) how to arrange the backlog list for a given system? The problem is posed as a mathematical programming model and solved via a simulated annealing heuristic. We design an experiment that captures essential elements of the systems under investigation. We then execute an extensive simulation to evaluate the effectiveness of various control schemes in a multi-cell, multi-family production environment. Specifically, we compare two variants of CONWIP control, one where containers are restricted to stay within given cells all the time and the other where containers are allowed to move through the entire system. We demonstrate the superiority of the latter in all the simulated scenarios.     

A note on Rooted Survivable Networks

The (undirected) Rooted Survivable Network Design (Rooted SND) problem is: given a complete graph on node set V with edge-costs, a root sV, and (node-)connectivity requirements , find a minimum cost subgraph G that contains r(t) internally-disjoint st-paths for all tT. For large values of k=max_tTr(t) Rooted SND is at least as hard to approximate as Directed Steiner Tree [Y. Lando, Z. Nutov, Inapproximability of survivable networks, Theoret. Comput. Sci. 410 (21–23) (2009) 2122–2125]. For Rooted SND, [J. Chuzhoy, S. Khanna, Algorithms for single-source vertex-connectivity, in: FOCS, 2008, pp. 105–114] gave recently an approximation algorithm with ratio O(k²logn). Independently, and using different techniques, we obtained at the same time a simpler primal–dual algorithm with the same ratio.     

Stereochemical Control in Palladium-catalyzed Allylic Etherification

Two alternative approaches for increasing the stereospecificity of Pd(0)-catalyzed allylic etherification are presented, both of which also suppress product isomerization and elimination. One of them involves addition of chlorotrimethylsilane to a benzene reaction mixture. In the model reaction studied, it increases the ratio of the two stereoisomeric products, arising from either retention or inversion of configuration at the allylic carbon, from 3:1 to 9:1, respectively. The second approach involves the employment of both donor- and acceptor-chelating ligands. Essentially 100% stereospecificity (retention of configuration) was achieved when the reaction was carried out in benzene at 60°C in the presence of Pd₂(dba)₃ and bis-1,2-diphenylphosphinoethane.     

Intensity-based statistical scorer for tandem mass spectrometry

We describe a new statistical scorer for tandem mass spectrometry. The scorer is based on the probability that fragments with given chemical properties create measured intensity levels in the experimental spectrum. The scorer's parameters are computed using a fully automated procedure. Benchmarking the new scorer on a large set of experimental spectra, we show that it performs significantly better than the widely used cross-correlation scoring algorithm of Eng et al. (Eng, J. K; McKormack, A. L.; Yates, J. R. J. Am. Soc. Mass Spectrom. 1994, 5, 976-989.).     

Castor oil biodiesel and its blends as alternative fuel

Intensive production and commercialization of biodiesel from edible-grade sources have raised some critical environmental concerns. In order to mitigate these environmental consequences, alternative oilseeds are being investigated as biodiesel feedstocks. Castor (Ricinus communis L.) is one of the most promising non-edible oil crops, due to its high annual seed production and yield, and since it can be grown on marginal land and in semi-arid climate. Still, few studies are available regarding its fuel-related properties in its pure form or as a blend with petrodiesel, many of which are due to its extremely high content of ricinoleic acid. In this study, the specifications in ASTM D6751 and D7467 which are related to the fatty acid composition of pure castor methyl esters (B100) and its blend with petrodiesel in a 10% vol ratio (B10) were investigated. Kinematic viscosity and distillation temperature of B100 (15.17 mm² s⁻¹ and 398.7 °C respectively) were the only two properties which did not meet the appropriate standard limits. In contrast, B10 met all the specifications. Still, ASTM D7467 requires that the pure biodiesel meets the requirements of ASTM D6751. This can limit the use of a wide range of feedstocks, including castor, as alternative fuel, especially due to the fact that in practice vehicles normally use low level blends of biodiesel and petrodiesel. These issues are discussed in depth in the present study.