Phone-level pronunciation scoring and assessment for interactive language learning

This paper investigates a method of automatic pronunciation scoring for use in computer-assisted language learning (CALL) systems. The method utilizes a likelihood-based `Goodness of Pronunciation' (GOP) measure which is extended to include individual thresholds for each phone based on both averaged native confidence scores and on rejection statistics provided by human judges. Further improvements are obtained by incorporating models of the subject's native language and by augmenting the recognition networks to include expected pronunciation errors. The various GOP measures are assessed using a specially recorded database of non-native speakers which has been annotated to mark phone-level pronunciation errors. Since pronunciation assessment is highly subjective, a set of four performance measures has been designed, each of them measuring different aspects of how well computer-derived phone-level scores agree with human scores. These performance measures are used to cross-validate the reference annotations and to assess the basic GOP algorithm and its refinements. The experimental results suggest that a likelihood-based pronunciation scoring metric can achieve usable performance, especially after applying the various enhancements.

Random lasing in a bistable smectic A liquid crystal

In this work, we examine the phenomenon of random lasing from the smectic A liquid crystal phase. We summarise our results to date on random lasing from the smectic A phase including the ability to control the output from the sample using applied electric fields. In addition, diffuse random lasing is demonstrated from the electrohydrodynamic instabilities of a smectic A liquid crystal phase that has been doped with a low concentration of ionic impurities. Using a siloxane-based liquid crystal doped with ionic impurities and a laser dye, nonresonant random laser emission is observed from the highly scattering texture of the smectic A phase which is stable in zero-field. With the application of a low frequency alternating current electric field, turbulence is induced due to motion of the ions. This is accompanied by a decrease in the emission linewidth and an increase in the intensity of the laser emission. The benefit in this case is that a field is not required to maintain the texture as the scattering and homeotropic states are both stable in zero field. This offers a lower power consumption alternative to the electric-field induced static scattering sample.

Red-Green-Blue 2D tuneable liquid crystal laser devices

In this paper, we review our recent experimental work on coherent and blue phase liquid crystal lasers.We will present results on thin-film photonic band edge lasing devices using dye-doped low molar mass liquid crystals in self-organised chiral nematic and blue phases. We show that high Q-factor lasers can be achieved in these materials and demonstrate that a single mode output with a very narrow line width can be readily achievable in well-aligned mono-domain samples. Further, we have found that the performance of the laser, i.e. the slope efficiency and the excitation threshold, are dependent upon the physical parameters of the low molar mass chiral nematic liquid crystals. Specifically, slope efficiencies greater than 60% could be achieved depending upon the materials used and the device geometry employed. We will discuss the important parameters of the liquid crystal host/dye guest materials and device configuration that are needed to achieve such high slope efficiencies. Further we demonstrate how the wavelength of the laser can be tuned using an in-plane electric field in a direction perpendicular to the helix axis via a flexoelectric mechanism as well as thermally using thermochromic effects. We will then briefly outline data on room temperature blue phase lasers and further show how liquid crystal/lenslet arrays have been used to demonstrate 2D laser emission of any desired wavelength. Finally, we present preliminary data on LED/incoherent pumping of RG liquid crystal lasers leading to a continuous wave output. © 2009 SPIE.

Effect of stocking density on the production of common carp (Cyprinus carpio Lin.) in cages at Kaptai lake, Bangladesh

Growth, survival and food conversion ratio (FCR) of Cyprinus carpio in cages at different stocking density were studied in Kaptai lake. Fingerlings of common carp (12.47 ± 4.29 g) were stocked at 25/m2 , 50/m2 and 75/m2 each with replication in six floating net cages each of Sm x Sm x 4m and reared for 240 days. The growth rate was inversely related to the stocking density with the mean weights of 325.5 ± 11.74 g, 268.99± 8.44 g and 167.0 ± 11.66 g at low, medium and high densities, respectively. At harvest, standing crop biomass averaged 7 .82, 12.83 and 11.58 kg with the survival of 98.9%, 97.6% and 94.4% and food conversion ratios of 4.51, 3.82 and 4.21 for the above three densities, respectively. Weight gain and production at density 25 fish/m 2 were significantly different (p< 0.01) from other two densities. Water quality was not affected in the cages having different stocking densities.

Ultrafast switching liquid crystals for electro-optic transmissive and reflective displays and microscopic lasers

We have used novel liquid crystals with extremely large flexoelectric coefficients in a range of ultra-fast photonic/display modes, namely 1) the uniform lying helix, that leads to in-plain switching, birefringence based displays with 100 μs switching times at low fields, i.e.2-5 V/μm, wide viewing angle and analogue or grey scale capability, 2) the uniform standing helix, using planar surface alignment and in-plane fields, with sub ms response times and optical contrasts in excess of 5000:1 with a perfect black "off state", 3) the wide temperature range blue phase that leads to field controlled reflective color and 4) high slope efficiency, wide wavelength range tunable narrow linewidth microscopic liquid crystal lasers.

Trade-off between reciprocal mutualists: local resource availability-oriented interaction in fig/fig wasp mutualism

The mechanisms that prevent competition (conflict) between the recipient and co-operative actor in co-operative systems remain one of the greatest problems for evolutionary biology. Previous hypotheses suggest that self-restraint, dispersal or spatial con

A unique group of inactive serine protease homologues from snake venom

A number of inactive serine protease homologues (SPHs), which have poorly understood functions, have been identified in invertebrates and vertebrates. Recently, several SPH transcripts have been reported from snake venom glands, which provide potential ne

The limits of flexoelectricity in liquid crystals

The flexoelectric conversion of mechanical to electrical energy in nematic liquid crystals is investigated using continuum theory. Since the electrical energy produced cannot exceed the mechanical energy supplied, and vice-versa, upper bounds are imposed on the magnitudes of the flexoelectric coefficients in terms of the elastic and dielectric coefficients. For conventional values of the elastic and dielectric coefficients, it is shown that the flexoelectric coefficients may not be larger than a few tens of pC/m. This has important consequences for the future use of such flexoelectric materials in devices and the related energetics of distorted equilibrium structures. © 2011 Author(s).

Simple and functional photonic devices from printable liquid crystal lasers

In this paper we demonstrate laser emission from emulsion-based polymer dispersed liquid crystals. Such lasers can be easily formed on single substrates with no alignment layers. Remarkably, it is shown that there can exist two radically different laser emission profiles, namely, photonic band-edge lasing and non-resonant random lasing. The emission is controlled by simple changes in the emulsification procedure. Low mixing speeds generate larger droplets that favor photonic band edge lasing with the requisite helical alignment produced by film shrinkage. Higher mixing speeds generate small droplets, which facilitate random lasing by a non-resonant scattering feedback process. Lasing thresholds and linewidth data are presented showing the potential of controllable linewidth lasing sources. Sequential and stacked layers demonstrate the possibility of achieving complex, simultaneous multi-wavelength and "white-light" laser output from a wide variety of substrates including glass, metallic, paper and flexible plastic. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Wavelength-tuneable liquid crystal lasers from the visible to the near-infrared

The study of band-edge lasing from dye-doped chiral nematic liquid crystals has thus far been largely restricted to visible wavelengths. In this paper, a wide range of commercially available laser dyes are examined for their suitability as infrared emitters within a chiral nematic host. Problems such as poor solubility and reduced quantum efficiencies are overcome, and successful band-edge lasing is demonstrated within the range of 735-850 nm, using the dyes LD800, HITC-P and DOTC-P. This paper also reports on progress towards widely tuneable liquid crystal lasers, capable of emission in the region 460- 850 nm. Key to this is the use of common pump source, capable of simultaneously exciting all of the dyes (both infrared and visible) that are present within the system. Towards this aim, we successfully demonstrate near-infrared lasing (800 nm) facilitated by Förster energy transfer between the visible dye DCM, and the infra-red dye LD800, enabling pump wavelengths anywhere between 420 and 532 nm to be used. These results demonstrate that small and low-cost tuneable visible to near-infrared laser sources are achievable, using a single common pump source. Such devices are envisaged to have wide-ranging applications including medical imaging (including optical coherence tomography), point-of-care optical medical diagnostics (such as flow cytometry), telecommunications, and optical signatures for security coatings. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

黔东南小香羊与贵州原有其它山羊品种的线粒体DNA 多态性比较

用B am H É、B g lÉ、B g lÊ、D raÉ、E coR É、E coR Í、H indË、Kp nÉ、 P stÉ、P vuÊ、S acÉ、S a lÉ、Sm aÉ、S tuÉ、X hoÉ 15 种识别6 碱基的限制性内 切酶对黔东南小香羊和贵州原有3 个地方山羊品种的93 只个体的m tDNA 进行分 析表明, B am H É、H indË 和S a lÉ 3 种酶表现多态性; 共检出18 种限制性多态型, 归纳得到3 种单倍型, 以单倍型É 和Ê 为基本单倍型。根据此2 种基本单倍型在所 比较各品种中的不同分布比例, 以及遗传距离分析和品种间的聚类关系, 表明黔东 南小香羊的群体遗传构成与贵州省原有其它3 个山羊品种不同, 从而为进一步确认 其为一独立的品种提供了必要的分子生物学依据。

Molecular phylogenetic systematics of twelve species of acipenseriformes based on mtDNA ND4L-ND4 gene sequence analysis

Acipenseriformes is an endangered primitive fish group, which occupies a special place in the history of ideas concerning fish evolution, even in vertebrate evolution. However, the classification and evolution of the fishes have been debated. The mitochondrial DNA (mtDNA) ND4L and partial ND4 genes were first sequenced in twelve species of the order Acipenseriformes, including endemic Chinese species. The following points were drawn from DNA sequences analysis: (i) the two species of Huso can be ascribed to Acipenser; (ii) A. dabryanus is the mostly closely related to A. sinensis, and most likely the landlocked form of A. sinensis; (iii) genus Acipenser in trans-Pacific region might have a common origin; (iv) mtDNA ND4L and ND4 genes are the ideal genetic markers for phylogenetic analysis of the order Acipenseriformes.

Mitochondrial DNA variation, effective female population size and population history of the endangered Chinese sturgeon, Acipenser sinensis

The anadromous Chinese sturgeon (Acipenser sinensis), mainly endemic to the Yangtze River in China, is an endangered fish species. The natural population has declined since the Gezhouba Dam blocked its migratory route to the spawning grounds in 1981. In the near future, the completion of the Three Gorges Dam, the world's largest hydroelectric project, may further impact this species by altering the water flow of the Yangtze River. Little is currently known about the population genetic structure of the Chinese sturgeon. In this study, DNA sequence data were determined from the control region (D-loop) of the mitochondrial genome of adult sturgeons (n = 106) that were collected between 1995-2000. The molecular data were used to investigate genetic variation, effective female population size and population history of the Chinese sturgeon in the Yangtze River. Our results indicate that the reduction in abundance did not change genetic variation of the Chinese sturgeon, and that the population underwent an expansion in the past. AMOVA analysis indicated that 98.7% of the genetic variability occurred within each year's spawning populations, the year of collection had little influence on the diversity of annual temporary samples. The relative large effective female population size (N-ef) indicates that good potential exists for the recovery of this species in the future. Strikingly, the ratio of N-ef to the census female population size (N-f) is unusually high (0.77-0.93). This may be the result of a current bottleneck in the population of the Chinese sturgeon that is likely caused by human intervention.