bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency-dependent capacitance-voltage hysteresis in ferroelectric liquid crystals: An effect of the frequency dependence of dielectric biaxiality
Authors: Rahman Muklesur , Kundu S. K. , Chaudhuri B. K. , Yoshizawa A.
Published: July 2005

Using the concept of the Preisach model for a ferroelectric capacitor, we have analyzed the behavior of frequency (f)-dependent polarization reversal in surface-stabilized ferroelectric liquid crystals (SSFLCs) under an external field. At a fixed temperature, the peak height of the capacitance-voltage hysteresis loop is found to be decreasing with an increasing number of polarization cycles up to a certain typical value of frequency (e.g., fc) being different for different ferroelectric liquid crystals (FLCs). We also observed an inversion (a well instead of a peak) in the hysteresis loops appearing above a typical higher frequency denoted fi. The values of capacitance of the FLC capacitors became almost independent of the voltage for the frequencies between fc and fi. The frequency dependence of dielectric biaxiality in the SSFLCs is directly attributed to the appearance of such behavior.
Saturated domain switching textures and strains in ferroelastic ceramics
Authors: Jones Jacob L. , Hoffman Mark , Bowman Keith J.
Published: July 2005

This paper introduces saturated domain switching textures of three different ferroelastic ceramic crystal systems. The accompanying extrinsic domain switching strain is calculated exclusively using a volume-weighted integral of a single pole figure. In ceramics which are also ferroelectric, the electromechanical response is defined by the domain switching textures, strains, and strain asymmetry, which are found to be functions of the number and directions of possible ferroelastic structural distortions.
Electrochemically controlled transport of lithium through ultrathin SiO2
Authors: Ariel Nava , Ceder Gerbrand , Sadoway Donald R. , Fitzgerald Eugene A.
Published: July 2005

Monolithically integrating the energy supply unit on a silicon integrated circuit (IC) requires the development of a thin-film solid-state battery compatible with silicon IC fabrication methods, materials, and performance. We have envisioned materials that can be processed in a silicon fabrication environment, thus bringing local stored energy to silicon ICs. By incorporating the material directly onto the silicon wafer, the economic parallelism that silicon complementary metal-oxide-semiconductor (CMOS) technology has enjoyed can be brought to power incorporation in each IC on a processed wafer. It is natural to look first towards silicon CMOS materials, and ask which materials need enhancement, which need replacement, and which can be used “as is.” In this study, we begin by using two existing CMOS materials and one unconventional material for the construction of a source of electric power. We have explored the use of thermally grown silicon dioxide (SiO2) as thin as 9nm acting as an electrolyte material candidate in a solid-state power cell integrated on silicon. Other components of the thin-film cell consisted of rf-sputtered lithium cobalt oxide (LiCoO2) as the cathode and highly doped n-type polycrystalline silicon (polysilicon) grown by low-pressure chemical-vapor deposition as the anode. All structures were fabricated using conventional microelectronics fabrication technology. The charge and discharge behaviors of the LiCoO2∕SiO2∕polysilicon cells were studied. On the basis of the impedance measurements an equivalent circuit model of an ultrathin cell was inferred, and its microstructure was characterized by electron microscopy imaging. In spite of its high series resistance (∼4×107Ω), we have shown that an ultrathin layer of an as-deposited Li-free SiO2 is an interesting candidate for an electrolyte or controllable barrier layer in lithium-ion-based devices.
Positive and negative temperature dependences of electron-impact ionization in In0.53Ga0.47As
Authors: Choo K. Y. , Ong D. S.
Published: July 2005

The electron-impact ionization coefficient (α) in In0.53Ga0.47As increases with temperature at electric fields below 200kV∕cm, in contrast to most crystalline semiconductors. It exhibits conventional negative temperature dependence at higher fields. A four-valley analytical band Monte Carlo model is used to study this anomalous behavior. The simulations show that both alloy scattering and the temperature dependence of the impact ionization threshold energy contribute to the temperature dependence of α. At low fields, we find that most ionization events occur in the first conduction band causing an increase of α with temperature in In0.53Ga0.47As. At high fields, α decreases with temperature again because of the reduced hot-electron population in the second conduction band.
Convex-shaped decay curve of carriers in a vertically coupled InAs∕GaAs quantum dot
Authors: Yim J. S. , Jang Y. D. , Lee D. , Lee H. G. , Noh S. K.
Published: July 2005

In a study using time-resolved photoluminescence (PL) to examine the carrier dynamics of a vertically coupled InAs∕GaAs quantum dot (QD) of 20 periods, we observed an initial slow carrier decay followed by a fast decay. The time at which the transition from slow to fast decay occurred increased on going to lower QD states at a fixed excitation power, and increased with increasing excitation intensity at a fixed QD state. This behavior is attributed to the relatively efficient vertical transfer of carriers in the vertically coupled InAs∕GaAs QD. In addition, this vertical carrier transfer makes the rise of the PL signal slower at lower-energy states. This peculiar carrier dynamics behavior was not observed in a single-layered QD or in a vertically uncoupled QD of 20 periods.
Aluminum arsenide cleaved-edge overgrown quantum wires
Authors: Moser J. , Zibold T. , Schuh D. , Bichler M. , Ertl F. , Abstreiter G. , Grayson M. , Roddaro S. , Pellegrini V.
Published: July 2005

We report conductance measurements in quantum wires made of aluminum arsenide, a heavy-mass, multivalley one-dimensional (1D) system. Zero-bias conductance steps are observed as the electron density in the wire is lowered, with additional steps observable upon applying a finite dc bias. We attribute these steps to depopulation of successive 1D subbands. The quantum conductance is substantially reduced with respect to the anticipated value for a spin- and valley-degenerate 1D system. This reduction is consistent with disorder-induced, intrawire backscattering that suppresses the transmission of 1D modes. Calculations are presented to demonstrate the role of strain in the 1D states of this cleaved-edge structure.
Instabilities of multiphase wave trains in coupled nonlinear Schrödinger equations: A bisymplectic framework
Authors: Laine-Pearson F. E.
Published: July 2005

Hamiltonian systems, with bisymplectic structure, are known to model a wide range of interesting phenomena occurring in optics, oceanography, biochemistry, geology, and materials science. Examples of such systems are nonlinear Schrödinger (NLS) equations and Klein-Gordon (KG) equations. The paper focuses on a general class of the former and presents a linear stability theory for the interaction of a basic class of periodic traveling wave solutions, which exploits the geometric structure of the system. A criterion for linear instability is derived. Additionally, for the qualitatively tractable cases, criteria for linear instability are given explicitly in terms of: the amplitudes of the modes; the parameters of the system that characterize the medium as well as the interaction between component modes; and, when the solutions of the system are both time-and space dependent, the wave numbers. An extension to the coupled NLS equations case study is introduced, namely the consideration of a related class of coupled KG equations, which has the potential to lead to further development for the underlying bisymplectic systems theory.
THz parallel plate photonic waveguides
Authors: Bingham Adam , Zhao Yuguang , Grischkowsky D.
Published: July 2005

We have observed narrowband transmission or rejection in the frequency spectra of THz pulses transmitted through air-spaced parallel plate photonic waveguides. These waveguides have one of the metal plates covered by a silicon plate with a metallic photonic band gap (PBG) surface precisely fabricated by lithographic techniques. We use two different PBG surface types: an array of metallic cylindrical pillars, and an array of metallic cylindrical holes. With the inversion of the PBG structures from cylinders to holes, the output spectra changes from narrow bandpass to narrow band-reject filtering. These photonic waveguides show extremely sharp spectral responses in regions as large as 1 THz, with stop bands or transmission bands having contrasts of as much as 90 dB.
Nanocrystals of cerium and europium trifluorides generated by coaxial Taylor cone electrospray of aqueous solutions at room temperature
Authors: de Cárcer I. Aguirre , Herrero P. , Landa-Cánovas A. R. , Sobolev B.
Published: July 2005

Cerium and europium trifluoride nanocrystals have been obtained in a Taylor’s double-cone electrospray by chemical reactions of precipitation from two miscible aqueous solutions of rare earth (RE=Ce,Eu) nitrates and HF. The products of the chemical reactions CeF3 and EuF3 have a very low solubility precipitating as nanocrystals of controllable size and composition. The change of the starting concentration, from 0.13 M Ce(NO3)3 to 0.01 M Eu(NO3)3, seems to have influence on the morphology of the nanoparticles, producing well crystallized EuF3 nanocrystals for the dilute solution and mosaic-like multidomain CeF3 nanocrystals for the more concentrated solution. This procedure can be used for the production of a great variety of inorganic compounds. The low-solubility requirement of the products of chemical reactions is the only key and it assures a high rate of insoluble crystals formation.
Electronic transport properties of pentacene single crystals upon exposure to air
Authors: Jurchescu Oana D. , Baas Jacob , Palstra Thomas T. M.
Published: July 2005

We report the effect of air exposure on the electronic properties of pentacene single crystals. Air can diffuse reversibly in and out of the crystals and influences the physical properties. We discern two competing mechanisms that modulate the electronic transport. The presence of oxygen increases the hole conduction, as in dark four O2 molecules introduce one charge carrier. This effect is enhanced by the presence of visible light. Contrarily, water, present in ambient air, is incorporated in the crystal lattice and forms trapping sites for injected charges.
Hydrothermal growth and photoluminescence property of textured CdWO4 scintillator films
Authors: Shang H. M. , Wang Y. , Bliss M. , Cao G. Z.
Published: July 2005

Cadmium tungstate (CWO) films on glass substrate have been first prepared by hydrothermal method at temperatures ranging from 120 to 180 °C from cadmium nitrite and tungstic acid in hydrogen peroxide solution. Crack free and dense CWO films with textured structure and thickness up to 8 μm were formed at 150 and 180 °C as revealed by x-ray diffraction (XRD) and scanning electron microscopy (SEM) studied. Photoluminescence (PL) measurements revealed that highly textured CWO thick films possess better PL property. The growth mechanism and preferred orientation or textured structure as well as the relations between textured structure and PL property have been discussed.
Grain size effect on the semiconductor-metal phase transition characteristics of magnetron-sputtered VO2 thin films
Authors: Brassard D. , Fourmaux S. , Jean-Jacques M. , Kieffer J. C. , El Khakani M. A.
Published: July 2005

Single-phase vanadium dioxide (VO2) thin films have been grown on Si3N4∕Si substrates by means of a well-controlled magnetron sputtering process. The deposited VO2 films were found to exhibit a semiconductor-to-metal transition (SMT) at ∼69°C with a resistivity change as high as 3.2 decades. A direct and clear-cut correlation is established between the SMT characteristics (both amplitude and abruptness of the transition) of the VO2 films and their crystallite size.
Spiroconjugation-enhanced intermolecular charge transport
Authors: Wu Chung-Chih , Liu Wei-Guang , Hung Wen-Yi , Liu Tsung-Li , Lin Yu-Ting , Lin Hao-Wu , Wong Ken-Tsung , Chien Yuh-Yih , Chen Ruei-Tang , Hung Tsung-Hsi , Chao Teng-Chih , Chen You-Ming
Published: July 2005

We report charge-transport and related physical properties of terfluorenes with various C9 substitutions. Results show that by introducing slight spiroconjugation between a core chromophore and conjugated substitutions through spiro-linking, the bulky substitution not only serves as a spatial hindrance to enhance morphological stability and emission efficiency in thin films, but also bridges and enhances intermolecular charge transport under certain situations. Interestingly, such characteristics are acquired without altering major electronic properties of core chromophores, rendering it a flexible molecular scheme for tuning characteristics of functional molecules to meet various demands of different applications.
Cracking diamond anvil cells by compressed nanographite sheets near the contact edge
Authors: Zhang Bin , Guo Wanlin
Published: July 2005

Uniformly cold-compressed nanographite sheets in diamond anvil cells (DAC) are found to transform from soft into hard phase at about 17 GPa using molecular dynamics simulations. The hard phase can reach the compressive strength of about 150 GPa. Finite element analyses show that high stress concentrations occur along the boundary of interface on the diamond-anvil culets contacted with the nanographite sheets. The concentrated compressive stress can exceed the strength of diamond in a ring region with the width about 0.2μm, when the average pressure in the graphite sample is 17 GPa as in [W. L. Mao et al., Science 302, 425 (2003)]. Within the narrow ring, superhard carbon phase can be formed from the nanographite sheets, which leads to cracking of the DAC near the contact edge.
Optimizing boron junctions through point defect and stress engineering using carbon and germanium co-implants
Authors: Moroz Victor , Oh Yong-Seog , Pramanik Dipu , Graoui Houda , Foad Majeed A.
Published: July 2005

We report the fabrication of p+∕n junctions using Ge+, C+, and B+ co-implantation and a spike anneal. The best junction exhibits a depth of 26nm, vertical abruptness of 3nm∕decade, and sheet resistance of 520Ohm∕square. The junction location is defined by where the boron concentration drops to 1018cm−3. These junctions are close to the International Technology Roadmap specifications for the 65nm technology node and are achieved by careful engineering of amorphization, stresses, and point defects. Advanced simulation of boron diffusion is used to understand and optimize the process window. The simulations show that the optimum process completely suppresses the transient-enhanced diffusion of boron and the formation of boron-interstitial clusters. This increases the boron solubility to 20% above the equilibrium solid-state solubility.
Field electron emission of Si nanotips with apexes of various compositions
Authors: She J. C. , Zhao K. , Deng S. Z. , Chen J. , Xu N. S.
Published: July 2005

We report procedure with use of self-assembled silicon carbide (SiC) nanomasks for preparation of ultrahigh-density Si nanotips. Si nanotips with SiC apex may be firstly prepared in a CH4∕H2 plasma treatment and in a subsequent H2 plasma etching a SiC apex may be converted into an amorphous silicon (a-Si) one with an additional function of sharpening the nanotips. A comparative study of the field electron emission from the Si nanotips with apexes of SiC, a-Si and pure Si is carried out, and shows that nanotips with a-Si apexes have not only the highest field enhancement factor but also the best emission uniformity. The physical origins for the above two improvements in field emission are discussed.
High mobility two-dimensional electron system on hydrogen-passivated silicon(111) surfaces
Authors: Eng K. , McFarland R. N. , Kane B. E.
Published: July 2005

We have fabricated and characterized a field-effect transistor in which an electric field is applied through an encapsulated vacuum cavity and induces a two-dimensional electron system on a hydrogen-passivated Si(111) surface. This vacuum cavity preserves the ambient sensitive surface and is created via room temperature contact bonding of two Si substrates. Hall measurements are made on the H–Si(111) surface prepared in aqueous ammonium fluoride solution. We obtain electron densities up to 6.5×1011cm−2 and peak mobilities of ∼8000cm2∕Vs at 4.2K.
Growth and characterization of GaN PiN rectifiers on free-standing GaN
Authors: Cao X. A. , Lu H. , LeBoeuf S. F. , Cowen C. , Arthur S. D. , Wang W.
Published: July 2005

GaN PiN rectifiers with high structural quality were grown on free-standing GaN substrates using metalorganic chemical vapor deposition. The lattice mismatch between the substrate and the epitaxial GaN was found to be ∼1×10−4. The full width at half maximum of the (0002) rocking curve was 79arcs compared to 230arcs for similar materials grown on sapphire. The incorporation of C, H, and O impurities in the homoepitaxial drift layer was reduced by a factor of 2–4. The rectifiers on GaN demonstrated rectification to −265V, which represents a 1.6× improvement over the rectifiers on sapphire and corresponds to a critical electric field ∼2.7MV∕cm. The homoepitaxial rectifiers also showed two orders of magnitude lower reverse leakage and a smaller negative temperature coefficient for breakdown voltage, consistent with a reduced defect density in the drift region.
The origin of n-type conductivity in undoped In2O3
Authors: Tomita Takumi , Yamashita Kazuyoshi , Hayafuji Yoshinori , Adachi Hirohiko
Published: July 2005

This study explores the origin of the native donor in undoped In2O3. The electronic structure of various point defects in In2O3 clusters is studied using the first-principles molecular orbital calculation. The results show that an oxygen vacancy cannot act as a native donor, because the defect level formed is much lower than the bottom of the conduction band. However, interstitial indium can generate a shallow donor level, close to the conduction band, and an even shallower donor level is formed when it associates with an oxygen vacancy. It is concluded that the origin of the native donor in undoped In2O3 is interstitial indium, but also that the existence of an oxygen vacancy is absolutely essential for carrier generation.
Screening of external electric field by photoinduced carriers in Bragg multiple quantum wells
Authors: Puller V. I. , Deych L. I. , Erementchouk M. V. , Lisyansky A. A.
Published: July 2005

We study screening of external bias in a multiple-quantum-well structure by optically injected excess carriers. By solving self-consistently the Poisson equation and the equations for the electron and hole densities, we analyze how realization of different screening regimes depends on the applied bias, excitation power, temperature, and the parameters of the structure. Our calculations show the feasibility of using the proposed setup as an optically controlled electric switch in photonic circuits.
Lattice distortion and polarization switching in calcium copper titanate
Authors: Chung Sung-Yoon
Published: July 2005

It is shown that CaCu3Ti4O12 grains in a polycrystalline specimen have domains and comparatively thick domain walls. The orientations of the domains within a grain were observed to be slightly tilted toward each other, suggesting the presence of lattice distortions. Multiple reflection spots in the electron diffraction pattern and misfit dislocations were also found in the domain walls. Kelvin probe force microscopy showed the variation in the surface potential of a grain by external electric fields, demonstrating the polarization of dipole moments. The influence of the local distortions on the formation of dipole moments is discussed in terms of the deviation from the cubic symmetry due to the small misfit between domains in a single grain of CaCu3Ti4O12 polycrystals.
Contesting and Surviving Memory: Space, Nation, and Nostalgia in Les Lieux de Mémoire
Authors: Legg Stephen
Published: July 2005

In this paper I explore the writings of Pierre Nora on lieux de mémoire (realms of memory). Nora's work is a standard reference in geographical writings on memory, yet there are various assumptions in his work that often go unchallenged. An investigation of the concept of nostalgia allows certain levels of yearning to be made clear in Nora's writings. A melancholic nostalgia for ‘real environments of memory’ and for the unifying power of the nation-state pervades this work. However, Nora hints at the possibility for the survival of memory in the body, and for its defence through the mobilisation of counterhistorical narratives. I conclude through using interdisciplinary theories on embodied memory and sites of countermemory to expand the range of spaces in which the memories of a nation might be constructed, contained, and contested.
‘The Tears of Portugal’: Empire, Identity, ‘Race’, and Destiny in Portuguese Geopolitical Narratives
Authors: Sidaway James D , Power Marcus
Published: July 2005

Geopolitical discourses are constitutive moments within the expression and construction of ‘national’ identities. Approaching geopolitics and identities as contested and fluid domains, we examine the relationships between geopolitical narratives and visions of Portugueseness ( Portugalidade). The focus is on the frames of geopolitical thought developed in 20th-century Portugal, with particular reference to the post-1945 period and with some consideration of the transformations since 1974 accompanying the collapse of what was both the first and the most enduring European overseas empire. This study of Portuguese geopolitical discourses leads to a conclusion in which we reflect on the significance of relations between the ‘colonial’ and the ‘postcolonial’ and the articulations of East–West and North–South in geopolitical discourses. This permits wider critique concerning the location of geopolitics within 20th-century and contemporary imperialisms.
Occidentalism and Plural Modernities: Or How Fukuzawa and Tagore Invented the West
Authors: Bonnett Alastair
Published: July 2005

The conflation of the West with modernity is being challenged by new critical interventions on the themes of ‘occidentalism’ and ‘plural modernities’. In this paper I bring these themes together into an account of the way the idea of the West has been employed and deployed in the construction of non-Western modernities. This is done in the company of two important figures in the articulation and invention of the West, the Japanese ‘Westerniser’ Fukuzawa Yukichi and the Indian poet and advocate of spiritual Asia Rabindranath Tagore. Fukuzawa and Tagore developed contrasting narratives both of the West and of Asia, narratives which they employed to express novel and distinctive visions of the nature of modern life.
Religious Schools: For Spirit, (f)or Nation
Authors: Kong Lily
Published: July 2005

In this paper I draw attention to the study of ‘unofficially sacred’ sites in geographies of religion, which provide significant insights into the construction of religious identity and community, and the intersections of sacred and secular. I show that such sites deserve as much attention as places of worship (the more conventional focus in the geographical study of religion) in our understanding of the place of religion in contemporary urban society. In particular, using the case of Islamic religious schools in Singapore, I examine how Muslim identities and community are negotiated within multicultural and multireligious contexts, and particularly within one in which there is a highly ‘educative’ state [Gramsci, 1971 Selections from the Prison Notebooks of Antonio Gramsci (International Publishers, New York)] that seeks to guide nation formation and the manufacture of consensus, and which strives to achieve a secular, modernist vision of society, characterized by economic progress and development. The specific analysis focuses, first, on the role of the state in the social construction of ‘schools’—particularly the ways in which state-constructed definitions of multiculturalism, multiracialism, multireligiosity, and modernity shape Singapore schools and education. Second, I examine the ways in which religious schools ( madrasahs) are a means by which some Singapore Muslims maintain and enhance their religious life. Further, I analyze state–religion relations, state strategies of nation-building, strategies of identity and community construction among Muslims in Singapore, as well as the fractured nature of the Muslim community by studying the divergent meanings invested in schools by state and religious groups.
Symbolic Spaces of Difference: Contesting the Eruv in Barnet, London and Tenafly, New Jersey
Authors: Watson Sophie
Published: July 2005

In this paper I explore discourses and resistances mobilized around the construction of an Orthodox Jewish symbolic and material concrete space, the ‘eruv’, in two localities (one in the United Kingdom, one in the USA) where it has been at the center of heated debate and contestation. Conflicts around the reordering and redefining of this public space expose some of the limits of living with difference and normative versions of multiculturalism in the city. Through a detailed examination of two case studies in the United Kingdom and the United States I conclude that the multicultural city necessitates a recognition of symbolic as well as material spaces—and the interconnections between these—and that the notion of public space warrants interrogation as to how it is imagined, read, and experienced in multiple ways.
The Street as Locus of Collective Memory
Authors: Hebbert Michael
Published: July 2005

In discussing the role of streets and urban spaces as a locus of collective memory, I draw a distinction between overt commemoration of public memory and the accumulation of group memories in the setting of the everyday street. Community struggles over postwar street clearances stimulated interest in the physical layout of the public realm as a gestalt for shared memory, a theme of earlier work on memory and urbanism by Maurice Halbwachs. I show how Aldo Rossi and colleagues put the concept onto a practical footing by making morphological analysis the basis for urban infill, repair, and extension, most ambitiously and controversially in the ‘critical reconstruction’ of modern Berlin.
The Critical Geopolitics of Danger in Uzbekistan and Kyrgyzstan
Authors: Megoran Nick
Published: July 2005

Drawing on critical security studies and critical geopolitics, I examine how geopolitical discourses of danger circulate in Kyrgyzstan and Uzbekistan. Whereas some work in this field risks reinscribing the discursive articulation of danger as an inevitable condition of political formation, in this paper I emphasise the need to disaggregate the concept of danger carefully to highlight its operation in specific contexts. I explore these processes across a range of discursive sites from official media to popular music, contrasting findings with material from focus groups composed of socially marginalised populations. I demonstrate the role of discursive constructions of danger or safety in the production and maintenance of the political identity of the new states, and how this is inseparable from material conditions of elite power struggle. I conclude by echoing Hewitt's call for a critical geography that confronts and challenges the domestic exercise of state terror.
Triterpenoid Esters from Bruguiera cylindrica
Authors: Karalai Chatchanok , Laphookhieo Surat
Published: July 2005

Three new pentacyclic triterpenoid esters 1–3 together with six known lupane-type triterpenoids were isolated from Bruguiera cylindrica. The structures of the new compounds were elucidated by spectroscopic methods and were characterized as 3α-E-coumaroyllupeol 1, 3α-Z-coumaroyllupeol 2, and 3α-E-caffeoyltaraxerol 3.
Direct Synthesis and Catalytic Reactivity of Highly Ordered Large-Pore Methylaminopropyl-Functionalized SBA-15 Materials
Authors: Wang Xueguang , Cheng Soofin
Published: July 2005

Highly ordered large-pore SBA-15 materials functionalized with a high loading of amino groups were synthesized for the first time by co-condensation of tetraethyl orthosilicate (TEOS) and [3-(methylamino)propyl]trimethoxysilane (MAPTMS) using an amphiphilic block copolymer. Addition of inorganic salt to the initial mixture greatly enhanced the mesostructure ordering and stability of the mesoporous materials. The materials thus obtained showed high catalytic activity and selectivity for the synthesis of flavanones by means of the Claisen–Schmidt condensation in the absence of solvent.
Surfactant-Assisted Controlled Synthesis of Antimony and Bismuth Three-Dimensional Superstructures in Different Hydrothermal Emulsion Systems
Authors: Zhang Meng , Wang Zhenghua , Ma Dekun , Zhang Rui , Qian Yitai
Published: July 2005

This paper describes a surfactant-assisted hydrothermal reduction pathway toward various kinds of antimony and bismuth three-dimensional superstructures, containing hollow spheres composed of nanostrips, peony-like architecture, radial sub-micrometer rod bundles, and a shale-like pattern. These three-dimensional superstructures were obtained through the reduction of SbCl3 or Bi(NO3)3·5H2O by aluminum powder in different emulsion systems at 120°C. The formation mechanism for Sb three-dimensional superstructures has been formally proposed. Some influencing factors on the morphology of the final products have also been discussed. We expect this convenient method can be extended to prepare three-dimensional superstructures of other inorganic materials, which have similar layered structures to Sb and Bi.
Synthesis and NMR Spectroscopic Characterization of Some Fluoro-2H-1-Benzopyran Derivatives
Authors: Teral Yannick , Roubaud Gabriel , Aubert Claude , Faure Robert , Campredon Mylène
Published: July 2005

The synthesis of some new fluoro-2H-1-benzopyran derivatives utilizing a reaction between titanium phenolates and β-phenylcinnamaldehydes in toluene is reported. These compounds were characterized by NMR and UV/visible spectroscopy as well as mass spectrometry. In solution all the compounds are photochromic. Complete assignment of the 1H and 13C resonances was achieved by concerted application of homonuclear (gs-COSY), proton-detected (C, H) one-bond (gs-HMQC), and long-range (gs-HMBC) heteronuclear two-dimensional chemical shift correlation experiments using a 500 MHz NMR spectrometer equipped with a cryoplatform and a 5 mm cryoprobe. The mass spectra of the different compounds were characterized by intense molecular and high fragment ions. The introduction of an atom of fluorine as a molecular probe is of interest in determining the mechanistic aspects of the photochemical process.
A Chemoenzymatic Total Synthesis of the Undecenolide ( - )-Cladospolide C
Authors: Banwell Martin G. , Loong David T. J. , Willis Anthony C.
Published: July 2005

The (−)-enantiomer, ent-3, of the natural product (+)-cladospolide C (3) has been prepared for the first time using the monochiral cis-1,2-dihydrocatechol 5 as starting material. Key steps include coupling of the derived acid 6 with the enzymatically generated (S)-(+)-4-penten-2-ol (7) and ring-closing metathesis (RCM) of the resultant doubly unsaturated ester 8 to give lactone 9. The structure of this last compound has been confirmed by single-crystal X-ray analysis. This work has established that the absolute configuration of (+)-cladospolide C has been correctly assigned and is as illustrated in structure 3.
Structural Analysis of a Potent Seed Germination Stimulant
Authors: Flematti Gavin R. , Ghisalberti Emilio L. , Dixon Kingsley W. , Trengove Robert D. , Skelton Brian W. , White Allan H.
Published: July 2005

A single-crystal X-ray crystallographic study of a seed germination stimulant isolated from plant-derived smoke confirms it to be 3-methyl-2H-furo[2,3-c]pyran-2-one 1.
Electrooxidative Conversion of Dibenzoylbenzene Dihydrazones into the Corresponding Bis-diazo Compounds and Bis-dimethyl Acetals
Authors: Okimoto Mitsuhiro , Numata Kaori , Tomozawa Kenta , Shigemoto Takamasa , Hoshi Masayuki , Takahashi Yukio
Published: July 2005

Several dibenzoylbenzene dihydrazones were electrochemically oxidized into the corresponding bis-dimethyl acetals in a methanolic solution containing sodium methoxide and a catalytic amount of KI. During electrolysis, the anolyte exhibited a characteristic deep purple colour, which strongly suggests the formation of a diazo compound as an intermediate. Such intermediates have been isolated in the electrooxidation of two dihydrazones.
Use of otolith weight in length-mediated estimation of proportions at age
Authors: Francis R. I. C. Chris , Harley Shelton J. , Campana Steven E. , Doering-Arjes Peer
Published: July 2005

Each year almost a million fish are aged from otoliths, primarily to estimate proportions at age for use in stock assessments. The preparation and reading of otoliths is time-consuming and thus expensive. Two techniques have been proposed to reduce costs. The first is length-mediated estimation, in which the length distribution from a large sample of fish is converted to an age distribution, using information (usually in the form of an age–length key) from a smaller sample containing length and age data. The second is to infer age from otolith weight (and/or other otolith measurements). These two cost-saving ideas are combined in a new method, length-mediated mixture analysis. It requires three samples – one with lengths only, one with lengths and otolith measurements, and one with lengths, otolith measurements and ages – and estimation is by maximum likelihood. The use of this method, which can be thought of as a generalisation of three established methods of age inference, is illustrated in two simulation experiments in a cost-benefit framework.
Variation in the periodicity and timing of increment formation in red throat emperor (Lethrinus miniatus) otoliths
Authors: Williams A. J. , Davies C. R. , Mapstone B. D.
Published: July 2005

Marginal increment analysis was used to validate the periodicity of opaque increment formation in red throat emperor (Lethrinus miniatus) otoliths and to test for variation in the periodicity and timing of increment formation across age classes, years and regions of the Great Barrier Reef (GBR). Marginal increment analysis demonstrated that opaque increments were deposited on an annual basis, a result supported by a preliminary experiment on a chemically tagged captive fish, although significant regional and temporal variation in the timing of increment formation was observed. Marginal increment analysis revealed a clear annual periodicity in increment formation for all age classes in the southern region but a more ambiguous pattern for most age classes in the northern region of the species distribution on the GBR. Opaque increments appeared to form 1 month earlier in the southern region than in the northern region and, in the southern region, formed 2 months earlier in 1999 than in 2000. No significant variation was observed in the timing of increment formation between age classes. Based on knowledge of the timing of otolith increment formation and spawning season of L. miniatus, an algorithm was developed for the estimation of age in months, irrespective of the time or location of capture.
Distinguishing aquaculture and wild yellowtail kingfish via natural elemental signatures in otoliths
Authors: Gillanders Bronwyn M. , Joyce Tanya C.
Published: July 2005

Naturally occurring elemental signatures (or composition) of otoliths may enable aquaculture and wild-caught yellowtail kingfish (Seriola lalandi) to be distinguished from one another, so that in the event of aquaculture escapes, escaped fish could be identified. Yellowtail kingfish were obtained from aquaculture ventures in three regions of Spencer Gulf and from nine areas external to aquaculture throughout the inner and outer Spencer Gulf, South Australia. Elemental signatures (Mg, Mn, Sr, Ba) of otoliths were analysed via LA-ICP-MS (laser ablation-inductively coupled plasma-mass spectrometry). A highly significant difference was detected between elemental signatures of the aquaculture and wild-caught fish, but this difference was largely attributable to wild fish from Port Augusta being different from the other groupings. For individual elements, it was difficult to detect differences between aquaculture and wild-caught fish, as there was considerable variation between locations within each group. When comparisons between aquaculture and wild fish were made of the inner and outer Spencer Gulf, aquaculture fish could be distinguished from wild fish and classified correctly with a high degree of accuracy (82–100%); the same level of accuracy was not achieved with wild fish. Comparison of elemental transects showed considerable variability between locations, with no features distinguishing aquaculture or wild-caught fish. It would be beneficial to combine naturally occurring signatures with other identification approaches (e.g. artificial elemental signatures) to accurately distinguish aquaculture from wild-caught fish. The impacts of escaped fish could then be determined.
Retrospective determination of natal habitats for an estuarine fish with otolith strontium isotope ratios
Authors: Hobbs James A. , Yin Qing-zhu , Burton Jessica , Bennett William A.
Published: July 2005

We investigated the ability of strontium isotope ratios (87Sr/86Sr) in otolith cores to record the natal habitats of juvenile delta smelt Hypomesus transpacificus from the San Francisco Estuary, USA. Young delta smelt (<60 days old) were collected during the California Department of Fish and Game 20-mm Survey in May and June of 1999 at several potential natal areas: Napa River, Suisun Marsh, West Delta, North Delta, Central Delta, South Delta and East Delta. The core region of sagittal otoliths was assayed with laser ablation-multicollector inductively coupled plasma mass spectroscopy. The laser ablation technique provided precise estimates of 87Sr : 86Sr ratios with relative standard deviation of 0.003% (one sigma). Isotope ratios ranged from 0.7065 to 0.708 and were different among natal habitats. However, natal habitats within the delta region were not discernable among each other, and reflect the mixing of the two major rivers, Sacramento River and San Joaquin River within the delta. We will therefore be able to determine natal habitats for delta smelt by assaying the core region of the otoliths. The application of strontium isotope ratios (87Sr/86Sr) in fish otoliths will greatly improve conservation efforts for this protected species.
Fluctuating asymmetry in fish otoliths and heterozygosity in stressful estuarine environments (West Africa)
Authors: Panfili Jacques , Durand Jean-Dominique , Diop Khady , Gourène Béatrice , Simier Monique
Published: July 2005

Fluctuating asymmetry (FA) is assumed to reflect the developmental instability caused by environmental or genetic stress. Fish otoliths represent a very good tool for investigating the consequence of different effects on FA. Otolith FA analysis, coupled with genetic analysis, has been undertaken on two common West African estuarine species, Ethmalosa fimbriata (EFI) and Sarotherodon melanotheron (SME), in two neighbouring estuaries, in order to highlight the impact of salinity on developmental stability. The Gambia estuary has a normal functioning and the Saloum estuary is inverse (saltier waters in the upper river), reaching extremely high salinities (>100 psu) and constituting severe environmental stress. Five sub-populations of EFI and six of SME were studied along a salinity gradient. The differences between right and left otoliths were estimated with image processing by measuring five dimensions (area, perimeter, diameter, rostrum and posterior radii). Analyses of genetic differentiation at three EPIC and one anonymous nuclear gene loci for EFI and six polymorphic enzymatic loci for SME were carried out to measure the level of heterozygosity. Absolute FA in all otolith traits examined was unaffected by gender but increased significantly with fish size. Size-corrected absolute FA did not show any significant difference among sites differing largely in salinity, although a higher asymmetry in otolith area was recorded in the saltiest site. These findings suggest that otolith asymmetry is a poor indicator of osmotic stress. The individual heterozygosity level did not seem to have an effect on otolith FA for either species, even though a slight correlation appeared with otolith area or perimeter. Otolith FA cannot be considered to be a useful indicator for estimating changes linked with environmental or genetic stress in these estuaries.
Short-term decoupling of otolith and somatic growth induced by food level changes in postlarval Baltic sprat, Sprattus sprattus
Authors: Baumann Hannes , Peck Myron A. , Herrmann Jens-Peter
Published: July 2005

We studied the effects of food level changes on otolith and somatic growth in postlarval Baltic sprat reared initially for a period of 11 days under zero, low, and ad libitum feeding conditions. During a subsequent 11 day period, feeding regimes were reversed in half of the low and ad libitum feeding treatments, and starved fish were re-fed ad libitum rations. Somatic growth rates under low and ad libitum food rations ranged between 0.15–0.22 mm day−1 and 0.48–0.63 mm day−1, respectively, and led to significant differences in length and weight between feeding regimes. Previously starved fish, however, grew only 0.25–0.28 mm day−1 under ad libitum conditions. During the first period, significant linear relationships were found for otolith v. length and v. weight growth across all treatments. After changing feeding regimes, increment widths failed to significantly predict somatic growth for 9 days, after which a significant relationship between otolith and somatic growth became re-established. Recent otolith growth was a good predictor of fish condition after the first, but not after the second period. The results suggest that perturbations in environmental conditions can temporarily decouple otolith from somatic growth in postlarval sprat, which needs to be considered in field studies.
Quality control of age data at the Alaska Fisheries Science Center
Authors: Kimura Daniel K. , Anderl Delsa M.
Published: July 2005

The Alaska Fisheries Science Center operates a 14-person Age and Growth Program that specialises in the ageing of various groundfish species using otoliths. In 1983, a quality control programme was established whereby a random subsample of 20% of the total of aged samples is re-aged by a second age reader. The purpose of this programme is to assure, to the greatest extent possible, that ages used in stock assessment are based on consistent ageing criteria. This age data is entered into our AGEDATA Microsoft ACCESS™ database where it can be easily updated, corrected and analysed. VISUAL BASIC computer programmes AGREE (a precision estimating programme) and RANGES (an outlier searching programme) were written to routinely analyse age data before data are released to end-users. The statistical relationship between average percentage error and coefficient of variation is described, as well as an interpretation of Bowker’s test for symmetry. Discrepancies between the reader and tester are reconciled while viewing the problematic otoliths using a dual-headed microscope, and reconciled ages are assigned. When necessary, all questionable otoliths in a troublesome sample may be re-aged.
Improved interpretation of labelled fish otoliths: a cost-effective tool in sustainable fisheries management
Authors: Niva T. , Keränen P. , Raitaniemi J. , Berger H. M.
Published: July 2005

A total of 222 pairs of alizarin red S (ARS)-labelled and 75 pairs of unlabelled sagittal otoliths from six hatchery-reared species, including Arctic charr (Salvelinus alpinus (L.)), lake trout (Salvelinus namaycush (Walbaum)), salmon (Salmo salar L.), brown trout (Salmo trutta L.), whitefish (Coregonus sp.) and pikeperch (Sander lucioperca (L.)), were used in blind tests to determine whether sawing a 0.4-mm thick slice from the otolith would improve the interpretation of labelled otoliths. The fish were labelled in 1995–2002. Fish age at labelling varied from two weeks to three months, immersion time from three to six hours and concentration of ARS 50–100 ppm. Blind tests were arranged so that sawed slices were contrasted with entire otoliths using stereomicroscope under UV epi-illumination. According to blind tests, the accuracy of interpretation of ARS-labelled otoliths was 97.0% from the slices and 92.3% from entire otoliths. The role of different filters in detecting false marks owing to autofluorescence is discussed. Cost-benefits of the method are discussed briefly.
Testing larval fish dispersal hypotheses using maximum likelihood analysis of otolith chemistry data
Authors: Sandin Stuart A. , Regetz James , Hamilton Scott L.
Published: July 2005

Otolith chemical analyses enable researchers to follow the dispersal pathways of individual fish through time. Given that water masses have spatially or temporally variable chemical signatures (or correlates thereof) and that this variability can be modelled statistically, we have the potential to describe a fish’s dispersal history by examining a temporal transect of elemental concentrations throughout the otolith generated from laser ablation inductively coupled plasma mass spectrometry. Statistical analyses tend to focus on temporal trajectories of individual elements or analyse multiple elements at single points in time. We have developed a customised statistical technique allowing detailed exploration of elemental signatures using maximum likelihood methods. The benefit of this approach is the ability to model chronological series of otolith measurements for all sampled fish and all elements simultaneously, while providing explicit treatment of variability in the data. We used data from a Caribbean fish population to compare traditional analysis techniques with this likelihood-based approach, showing their relative capacities to test among alternative hypotheses regarding the dispersal trajectories of individual fish. By incorporating information specific to the species’ natural history and to the analytical techniques, we can explore more detailed models of fish movement than were possible using pre-existing approaches.
Impact of environmental factors on survival of larval and juvenile Cape anchovy Engraulis encrasicolus (G.) in the southern Benguela upwelling region, determined from hatchdate distributions: implications for recruitment
Authors: Wilhelm M. R. , Painting S. J. , Field J. G. , Kerstan M. , Durholtz M. D.
Published: July 2005

March larval and May juvenile Cape anchovy of the unusually strong 1999/2000 year-class were collected off South Africa. Age estimates were obtained from daily increment counts on otoliths using light microscopy for March larvae (14–70 mm standard length, SL, n = 193, 92% success rate), and scanning electron microscopy for May juveniles (52–110 mm SL, n = 80, 22% success rate). Differences between March and May hatchdate distributions were related to the prevailing temperatures. March larval hatchdate distributions showed slight modes in October/November 1999 and January/February 2000, each a month later than May juvenile hatchdate distributions (September/October and November/December). Thus, mortality rates of larvae hatched after mid-December seem to have been higher. Large areas of warm water (19–26°C sea surface temperature) on the Agulhas Bank, mid-November 1999 to March 2000, indicated conditions conducive to spawning and reduced offshore advection of spawning products. A period of strong upwelling, March to May 2000, is likely to have increased availability of planktonic food for older larvae; also causing offshore dispersal of younger larvae and food patches required by these, possibly leading to starvation mortality of younger larvae during strong upwelling. The critical period thus seemed to be later than at first-feeding.