The genetic diversity and geographical separation study of Oncomelania hupensis populations in mainland China using microsatellite loci

© 2016 Guan et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. The attached file is the published version of the article.NHM Repositor

Electro -absorptive and electro -optic quantum well modulators using surface acoustic wave

The characteristics of Al0.3Ga0.7As/GaAs QW acousto-absorption and acousto-optic modulators using the interaction between Surface Acoustic Wave (SAW) and quantum well (QW) optical waveguide structures are analyzed here theoretically. The QW structures are optimized by maximizing the optical confinement of modal field in the active region and the piezoelectric effect of SAW on QWs. The electric field induced by SAW reduces non-uniformly in depth, which limits in the development of high efficiency modulators, especially for devices with a large number of QWs in the active region. We present the results of the analysis of a range of QW SQW modulators using between one and 25 QWs in the active region. For devices with thin active regions, the QW structures are designed so that at the top surface strong SAW effects can be obtained while for the 25 periods structure, the QWs located at a depth of 2/3 SAW wavelength in order to obtain an uniform SAW induced electric field. The results show that the single and five QW devices are suitable for absorptive modulation and optical modulation respectively while the 25-QW modulators can shorten the modulation interaction length and thus increase modulation bandwidth. The effective index change of these devices are at least 10 times larger than the conventional surface acoustic wave devices. These results make the quantum-well modulators more attractive for the development of acousto-optic device applications.published_or_final_versio

Asymmetric double-quantum-well phase modulator using surface acoustic waves

An AlGaAs-GaAs asymmetric double-quantum-well (DQW) optical phase modulator using surface acoustic waves is investigated theoretically. The optimization steps of the DQW structure, which so far have not been reported in detail, are discussed here. The optimized phase modulator structure is found to contain a five-period QDW active region. A surface acoustic wave induces a potential field which provides the phase modulation. Analysis of the modulation characteristics show that by using the asymmetric DQW, the large change of the induced potential at the surface and thus large modification of the quantum-well (QW) structure can be utilized. The modification of each QW structure is consistent, although this consistency is not always preserved in typical surface acoustic wave devices. Consequently, the change of refractive index in each of the five DQW's is almost identical. Besides, the change of effective refractive index is ten times larger here in comparison to a modulator with a five-period single QW as the active region and thus produces a larger phase modulation. In addition, a long wavelength and a low surface acoustic wave power required here simplify the fabrication of surface acoistic wave transducer and the acoustooptic phase modulator.published_or_final_versio

Electro-optic and electro-absorptive modulations of AlGaAs/GaAs quantum well using surface acoustic wave

The surface acoustic wave produced electron absorptive and electro-optic modulation in AlGaAs/ GaAs quantum well structures are theoretically analyzed. The quantum well structures are optimized by maximizing the optical confinement of the modal field in the active region and the piezoelectric effect of surface acoustic wave on the quantum wells. The effect of penetration depth of the surface acoustic wave on the number (1-25 periods) of quantum wells, serving as the active region, is being studied. For 1-5 period structures, the quantum wells are designed on the top surface so that a strong piezoelectric effect can be obtained. For the 25-period structure, the quantum wells locate at a depth of two-thirds the acoustic-wave wavelength in order to obtain a uniform surface acoustic-wave-induced electric field. The results show that the single and five quantum well devices are suitable for absorptive modulation and optical modulation, respectively, while a general advantage of the 25-period quantum well modulator can shorten the modulation interaction length and increase the modulation bandwidth. The effective index change of these devices are at least ten times larger than the conventional surface acoustic wave devices. These results make the surface acoustic wave quantum well modulators more attractive for the development of acousto-optic device applications. © 1998 American Institute of Physics.published_or_final_versio

Aqueous oxidation of dimethyl phthalate in a Fe(VI)-TiO?-UV reaction system

2007-2008 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Eigenstates and absorption spectra of interdiffused AlGaAs-GaAs multiple-quantum-well structures

published_or_final_versio

AlGaAs-GaAs quantum-well electrooptic phase modulator with disorder delineated optical confinement

Waveguide phase modulators, with 0.5- and 1-μm quantum-well (QW) active regions which are defined by impurity-induced disordering are investigated theoretically. By controlling the extent of the interdiffusion in the lateral claddings, the refractive index difference between the core and claddings is used to provide single-mode operation. Strong optical confinement, which is required to produce single-mode high-efficiency modulation, requires the peak impurity concentration to be at the center of the QW active region. Moreover, the annealing time needs to be optimized so that single mode can be maintained at the desired bias field. A low dopant concentration is also expected to minimize the destruction of the modulator structure. The results show that since the core/cladding interface is graded, the width of the metal contact is important. A comparison of modulation efficiency for active layer thicknesses of 0.5 and 1.0 μm shows that the 0.5-μm one is a more efficient structure and its absorption loss can be reduced by increasing the applied field from 50 to 100 kV/cm.published_or_final_versio

Electroabsorption enhancement in disordered, strained InGaAs/GaAs quantum well

The results of modeling the application of an external electric field to disordered, strained InGaAs/GaAs single quantum well are presented. An error function profile is used to model the constituent atoms composition after interdiffusion. Results indicate that the exciton Stark shift in the disordered quantum well is greater than in the as-grown 10 nm wide In0.2Ga0.8As well, and that the change in electroabsorption near the fundamental exciton absorption peak is enhanced by 30% in the disordered quantum well for a 30 kV/cm electric field applied perpendicular to the well. These results may be used to achieve optical modulators with improved performance characteristics in strained quantum well structures. © 1995 American Institute of Physics.published_or_final_versio

Ferrate(VI) enhanced photocatalytic oxidation of pollutants in aqueous TiO?suspensions

Author name used in this publication: Nigel J. D. Graham2009-2010 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

MESSI: metabolic engineering target selection and best strain identification tool

Metabolic engineering and synthetic biology are synergistically related fields for manipulating target pathways and designing microorganisms that can act as chemical factories. Saccharomyces cerevisiae’s ideal bioprocessing traits make yeast a very attractive chemical factory for production of fuels, pharmaceuticals, nutraceuticals as well as a wide range of chemicals. However, future attempts of engineering S. cerevisiae’s metabolism using synthetic biology need to move towards more integrative models that incorporate the high connectivity of metabolic pathways and regulatory processes and the interactions in genetic elements across those pathways and processes. To contribute in this direction, we have developed Metabolic Engineering target Selection and best Strain Identification tool (MESSI), a web server for predicting efficient chassis and regulatory components for yeast bio-based production. The server provides an integrative platform for users to analyse ready-to-use public high-throughput metabolomic data, which are transformed to metabolic pathway activities for identifying the most efficient S. cerevisiae strain for the production of a compound of interest. As input MESSI accepts metabolite KEGG IDs or pathway names. MESSI outputs a ranked list of S. cerevisiae strains based on aggregation algorithms. Furthermore, through a genome-wide association study of the metabolic pathway activities with the strains’ natural variation, MESSI prioritizes genes and small variants as potential regulatory points and promising metabolic engineering targets. Users can choose various parameters in the whole process such as (i) weight and expectation of each metabolic pathway activity in the final ranking of the strains, (ii) Weighted AddScore Fuse or Weighted Borda Fuse aggregation algorithm, (iii) type of variants to be included, (iv) variant sets in different biological levels. Database URL: http://sbb.hku.hk/MESSI