Generation of indistinguishable and pure heralded single photons with tunable bandwidth

We describe a new scheme to fully control the joint spectrum of paired photons generated in spontaneous parametric down-conversion. We show the capability of this method to generate frequency-uncorrelated photon pairs that are pure and indistinguishable, and whose bandwidth can be readily tuned. Importantly, the scheme we propose here can be implemented in any nonlinear crystal and frequency band of interest.Comment: 3 pages, 3 figure

Broadening the bandwidth of entangled photons: a step towards the generation of extremely short biphotons

We demonstrate a technique that allows to fully control the bandwidth of entangled photons independently of the frequency band of interest and of the nonlinear crystal. We show that this technique allows to generate nearly transform-limited biphotons with almost one octave of bandwidth (hundreds of THz) which corresponds to correlation times of just a few femtoseconds. The presented method becomes an enabling tool for attosecond entangled-photons quantum optics. The technique can also be used to generate paired photons with a very high degree of entanglement.Comment: 4 page

A Grey Interval Relational Degree-Based Dynamic Multiattribute Decision Making Method and Its Application in Investment Decision Making

The purpose of this paper is to propose a three-dimensional grey interval relational degree model for dynamic Multiattribute decision making. In the model, the observed values are interval grey numbers. Elements are selected in the system as the points in an m-dimensional linear space. Then observation data of each element to different time and objects are as the coordinates of point. An optimization model is employed to obtain each scheme’s affiliate degree for the positive and negative ideal schemes. And a three-dimensional grey interval relational degree model based on time, index, and scheme is constructed in the paper. The result shows that the three-dimensional grey relational degree simplifies the traditional dynamic multiattribute decision making method and can better resolve the dynamic multiattribute decision making problem of interval numbers. The example illustrates that the method presented in the paper can be used to deal with problems of uncertainty such as dynamic multiattribute decision making

A Strategy for Modelling Mechanochemically Induced Unzipping and Scission of Chemical Bonds in Double-Network Polymer Composite

A molecular mechanics model for covalent and ionic double-network polymer composites was developed in this study to investigate mechanisms of mechanochemically induced unzipping and scission of chemical bonds. Morse potential function was firstly applied to investigate mechanical unzipping of the covalent bonds, and then stress-dependent mechanical energy for the interatomic covalent bonds was discussed. A new mechanochemical model was formulated for describing the mechanically induced ionic bond scissions based on the Morse potential model and equations for electrostatic forces. Based on this newly proposed model, mechanochemical behaviors of several common interatomic interaction types (e.g., A+B-, A2+B2-/A2+2B-/2A+B2- and A3+B3-/A3+3B-/3A+B3-) of the ionic bonds have been quantitatively described and analyzed. Finally, mechanochemical unzipping of the covalent bonds and dissociation of the ionic bonds have been characterized and analyzed based on the molecular mechanics model, which has well predicted the chemical and mechanochemical activations in the covalent and ionic double-network polymer composites

Shaping the waveform of entangled photons

We demonstrate experimentally the tunable control of the joint spectrum, i.e. waveform and degree of frequency correlations, of paired photons generated in spontaneous parametric downconversion. This control is mediated by the spatial shape of the pump beam in a type-I noncollinear configuration. We discuss the applicability of this technique to other sources of frequency entangled photons, such as electromagnetically induced Raman transitions.Comment: 5 Pages, 4 Figure

A phenomenological model for dynamic response of double-network hydrogel composite undergoing transient transition

We present a phenomenological model for dynamic deformation and mechanical response of double-network (with short-chained ionic network and long-chained covalent network) hydrogel composite based on theory of transient networks. Molecular structures and stress-strain relations of the hydrogel composite were investigated based on thermomechanical properties of the individual network. Constitutive relations were derived for its nonlinear viscoelastic responses and annihilation/reformation rates of active short chains were determined by means of Eyring formula. An extended Volokh model was proposed to separate effects of large strain hysteresis and anomalous viscoelastic relaxation on the hydrogel composite after strain reversal. Experimental results from rate-independent tests are well in agreement with that of the numerical simulations. This study provides a fundamental simulation tool for modelling and predicting mechanics and mechanisms of viscoelastic response and mechanical responses in double-network hydrogel composite

The impact of species phylogenetic relatedness on invasion varies distinctly along resource versus non-resource environmental gradients

1. Understanding why some, but not other, plant communities are vulnerable to alien invasive species is essential for predicting and managing biological invasions. Darwin proposed two seemingly contradictory hypotheses on how native-invader relatedness influences invasion success, emphasizing, respectively, the importance of environmental filtering and competition between natives and invaders. Despite much recent empirical research on this topic, reconciling these two hypotheses, known as Darwin's naturalization conundrum, remains a challenge. 2. Using plot-level data from natural forests along elevational transects covering strong environmental gradients, we examined whether the invasion of the globally invasive species crofton weed (Ageratina adenophora) can be explained by environmental filtering and/or competition from closely related species linked to environmental gradients. 3. Abundant precipitation, warm temperatures, open canopies and postfire environments facilitated A. adenophora invasion, whereas resident taxonomic richness suppressed its invasion. Importantly, we found that invader-resident relatedness had a strong negative effect on invader cover under resource scarcity conditions (e.g. low water availability), but not under non-resource environmental stress gradients (e.g. low temperature). 4. Synthesis and applications. Our results suggest that the impact of species phylogenetic relatedness on invasion success varies distinctly along resource versus non-resource environmental gradients. These results help to reconcile Darwin's naturalization conundrum, thereby improving the ability to predict the success of alien plant invasions in a changing world. Our study stresses the need to consider adjusting forest species composition to strengthen their resistance to invasion, while taking into account resource and non-resource environmental gradients, particularly after wildfires

Optimized sample preparation for two-dimensional gel electrophoresis of soluble proteins from chicken bursa of Fabricius

<p>Abstract</p> <p>Background</p> <p>Two-dimensional gel electrophoresis (2-DE) is a powerful method to study protein expression and function in living organisms and diseases. This technique, however, has not been applied to avian bursa of Fabricius (BF), a central immune organ. Here, optimized 2-DE sample preparation methodologies were constructed for the chicken BF tissue. Using the optimized protocol, we performed further 2-DE analysis on a soluble protein extract from the BF of chickens infected with virulent avibirnavirus. To demonstrate the quality of the extracted proteins, several differentially expressed protein spots selected were cut from 2-DE gels and identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS).</p> <p>Results</p> <p>An extraction buffer containing 7 M urea, 2 M thiourea, 2% (w/v) 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS), 50 mM dithiothreitol (DTT), 0.2% Bio-Lyte 3/10, 1 mM phenylmethylsulfonyl fluoride (PMSF), 20 U/ml Deoxyribonuclease I (DNase I), and 0.25 mg/ml Ribonuclease A (RNase A), combined with sonication and vortex, yielded the best 2-DE data. Relative to non-frozen immobilized pH gradient (IPG) strips, frozen IPG strips did not result in significant changes in the 2-DE patterns after isoelectric focusing (IEF). When the optimized protocol was used to analyze the spleen and thymus, as well as avibirnavirus-infected bursa, high quality 2-DE protein expression profiles were obtained. 2-DE maps of BF of chickens infected with virulent avibirnavirus were visibly different and many differentially expressed proteins were found.</p> <p>Conclusion</p> <p>These results showed that method C, in concert extraction buffer IV, was the most favorable for preparing samples for IEF and subsequent protein separation and yielded the best quality 2-DE patterns. The optimized protocol is a useful sample preparation method for comparative proteomics analysis of chicken BF tissues.</p