bluuebunny/crossref_metadata_2025 huggingface dataset:
Scanning particle trapped optical microscopy based on two-photon-induced morphology-dependent resonance in a trapped microsphere
Authors: Morrish Dru , Gan Xiaosong , Gu Min
Published: March 2006

We report on scanning particle trapped optical microscopy based on two-photon-induced morphology-dependent resonance (MDR) in a trapped microsphere. In this imaging mode, a femtosecond pulsed laser is adopted for simultaneous laser trapping and two-photon excitation. Due to the localized excitation, MDR is significantly enhanced. As a result, an image contrast enhancement of 9.3% is achieved by the spectral detection of a single on-resonance MDR mode compared with that obtained by the off-resonance MDR mode without compromise in transverse resolution.
Experimental study of moiré method in laser scanning confocal microscopy
Authors: Pan Bing , Xie Huimin , Kishimoto Satoshi , Xing Yongmin
Published: March 2006

By integrating moiré method with laser scanning confocal microscopy (LSCM), a novel class of moiré patterns, i.e., LSCM moiré patterns, is presented and investigated by experiment in this article. The moiré patterns are formed by the interference of a 1200line∕mm cross-line holographic grating and the scanning lines of LSCM. The principles and conditions of forming LSCM moiré are described in detail. The measured parameters of moiré fringes from experimental images agree well with theoretical analysis. The experimental results verify the feasibility and reality of the proposed moiré method to be another effective and high accuracy technique for measuring and observing in-plane microdeformation at micrometer scale.
The calculated infrared spectrum of Cl−H2O using a full dimensional ab initio potential surface and dipole moment surface
Authors: Rheinecker Jaime L. , Bowman Joel M.
Published: March 2006

We report a full dimensional ab initio-based global potential energy surface (PES) and dipole moment surface (DMS) for Cl−H2O. Both surfaces are symmetric with respect to interchange of the H atoms. The PES is a fit to thousands of electronic energies calculated using the coupled-cluster method (CCSD(T)) with a moderately large basis (aug-cc-pVTZ). The infrared spectrum and vibrational dynamics are reported and compared to experiment. These results are analyzed by examination of wave function and the dipole surface.
Electronic structure and excitations in oligoacenes from ab initio calculations
Authors: Kadantsev Eugene S. , Stott M. J. , Rubio Angel
Published: March 2006

Oligoacenes C4n+2H2n+4 (n=2,…,6) are studied using a variety of ab initio methods. Density functional theory (DFT) optimized geometries were in good agreement with experiment. Vertical and adiabatic ionization potentials and electron affinities were computed with DFT and it was found that standard exchange-correlation (xc) functionals underestimate ionization potentials in oligoacenes. Possible reasons for this underestimation are discussed. Low lying electronic excitations were computed using time-dependent density functional theory, configuration interaction singles, and configuration interaction singles with approximate treatment of doubles. In agreement with earlier work, time-dependent DFT in conjunction with standard xc-energy functionals substantially underestimates the lowest (p) singlet-singlet electronic transition.
Model of spin localization in activated carbon fibers
Authors: Kempiński Mateusz , Kempiński Wojciech , Kaszyński Jacek , Śliwińska-Bartkowiak Małgorzata
Published: March 2006

Mechanisms of spin localization in graphitic nanoparticles of activated carbon fibers (ACFs) are discussed. Electronic properties of ACFs are described by the model which is the fusion of two approaches: Langevin paramagnetism represented by Curie law in electron paramagnetic resonance measurements and granular metal model used to describe conducting properties of separated fibers according to metal-insulator transition. This approach shows the possibility of changing the electronic properties of ACFs by temperature or adsorbed molecules as a main factors.
Luminescent enhancement in europium-doped yttria nanotubes coated with yttria
Authors: Bai Xue , Song Hongwei , Pan Guohui , Liu Zhongxin , Lu Shaozhe , Di Weihua , Ren Xingguang , Lei Yanqiang , Dai Qilin , Fan Libo
Published: March 2006

Europium-doped yttria nanotubes were coated with yttria by a simple two-step hydrothermal method, forming the Y2O3:Eu3+∕Y2O3 core-shell composite. Remarkable improvement of photoluminescence was observed in the core-shell composite under both violet and ultraviolet excitations. These characteristics were attributed to the reduced influence of surface defects on host excitation, charge transfer transitions, and f−f inner-shell transitions of the Eu3+ ions. Due to striking red luminescence under ultraviolet excitation, the core-shell structure has potential application in plasma display panel devices.
Study on the short circuit transient process and overcurrent protection of Cockcroft-Walton high voltage power supply
Authors: Zhang Y. M. , Su X. D. , Su H. , Liu J. T. , Lv H. Y. , Su T. L.
Published: March 2006

It has always been an important and difficult problem for the designer of an intense current Cockcroft-Walton high voltage power supply to quantitatively select appropriate protective resistance so that not only can the power supply be protected reliably once the high voltage output terminal is short circuited but also the negative influence of the protective resistors to the load characteristics of the power supply and the significant but unnecessary power loss on the protective resistors when the power supply runs normally may be reduced to a minimum. In this article, thorough analyses are made to the equivalent circuits in each stage of the short circuit transient process of Cockcroft-Walton circuit. The results indicate that in this process, significant overcurrent only occurs in the rectifiers situated in the locations of the highest and lowest potentials of the voltage multiplier, but there is no significant overvoltage in any component. In order to quantitatively estimate the most possible maximum ∫0∞i2(t)dt value of the rectifiers corresponding to a certain protective resistance, a simplified equivalent circuit based on some reasonable assumptions is given and some formulas, which may enough be reasonably used as a basis of quantitative estimation in engineering design, are deducted.
Development of a 100eV, high-flux ion beam acceleration system
Authors: Yoshida H. , Yokoyama K. , Suzuki S. , Enoeda M. , Akiba M.
Published: March 2006

A new system of electrodes has been developed for a high-flux, steady-state ion source with a large irradiation area to study plasma-wall interaction in fusion reactors at energies in the 100eV range. These electrodes are multiaperture triode electrodes—the sizes of which are smaller as compared with those used in similar applications for previous systems. In particular, these electrodes have a thickness of 0.5mm and an aperture size of 0.9mm in diameter with 0.5mm gaps between them. The influence of the plasma sheath on the beam energy has to be estimated since the plasma sheath potential is comparable to the acceleration voltage in such a low energy region. Source plasma is produced by a hydrogen arc discharge, following which hydrogen ions are extracted by using the new electrode system. Ion fluxes of 1.5×1020–5.3×1020H∕m2s with energies ranging from 28to102eV∕H were obtained. These values are comparable to those of conventional high-flux ion sources with higher energies. This low energy ion beam can be used to investigate the plasma-wall interaction in fusion reactors.
Monitoring of blood sedimentation by a multiplexed light transmission method
Authors: Cab-Cauich Cesar , Alvarado-Gil Juan J. , Leaños-Castañeda Olga L.
Published: March 2006

In this work a method that monitors the dynamics of blood sedimentation using a light transmission method is presented. This technique consists of the illumination of a whole capillary column of blood using a laser and detecting the transmitted light at different heights simultaneously. In order to show the potential of this method, male fish blood samples modified in its composition by the action of several treatments were studied. The experimental groups were a control group, another treated with estradiol, and the third treated with a pesticide dichlorodiphenyl trichloroethane. It is shown that the sedimentation process is strongly dependent on the height of the detection and that this affects the resolution of the measurement.
Development of liquid-environment frequency modulation atomic force microscope with low noise deflection sensor for cantilevers of various dimensions
Authors: Fukuma Takeshi , Jarvis Suzanne P.
Published: March 2006

We have developed a liquid-environment frequency modulation atomic force microscope (FM-AFM) with a low noise deflection sensor for a wide range of cantilevers with different dimensions. A simple yet accurate equation describing the theoretical limit of the optical beam deflection method in air and liquid is presented. Based on the equation, we have designed a low noise deflection sensor. Replaceable microscope objective lenses are utilized for providing a high magnification optical view (resolution: <3μm) as well as for focusing a laser beam (laser spot size: ∼10μm). Even for a broad range of cantilevers with lengths from 35to125μm, the sensor provides deflection noise densities of less than 11fm∕Hz in air and 16fm∕Hz in water. In particular, a cantilever with a length of 50μm gives the minimum deflection noise density of 5.7fm∕Hz in air and 7.3fm∕Hz in water. True atomic resolution of the developed FM-AFM is demonstrated by imaging mica in water.
Silicon carbide nozzle for producing molecular beams
Authors: Patrick Edward L.
Published: March 2006

A resistively heated nozzle of silicon carbide (SiC) ceramic was developed for the production of high speed molecular beams for space environment simulation. The nozzle is able to withstand temperatures in excess of 1800°C and pressures to 30bars. In a seeded beam of 1% argon in 99% hydrogen, a speed of 3.9km∕s was achieved for the argon component at a nozzle temperature of 1150°C and a pressure of 23bars.
In situ frequency calibration technique of FM reflectometer
Authors: Seo Seong-Heon , Lee Dong Ju
Published: March 2006

A frequency modulation (FM) reflectometer is designed to linearly sweep the microwave frequency in order to diagnose the plasma density profile. The static characteristic curve of the frequency versus the control voltage can be easily measured by using a spectrum analyzer. However, it is not guaranteed that the characteristic curve will be the same when the frequency is swept. A technique is devised which measures the dynamic characteristics by using the reflectometer itself. The results show that the shape of the characteristic curve does not depend on the sweep rate but on the time delay between the control voltage of the function generator and the microwave frequency at the detector input. This time delay should be compensated. Based on this measured characteristic curve, the frequency sweep rate and the distance between the antenna and the vacuum chamber are experimentally determined.
Efficient pure-white organic light-emitting diodes with a solution-processed, binary-host employing single emission layer
Authors: Jou Jwo-Huei , Sun Ming-Chen , Chou Hung-Hsing , Li Chien-Hung
Published: March 2006

Efficient white light-emitting diodes were fabricated with a solution-processed single emission layer composing a molecular and polymeric materials mixed binary host. The main host used was a molecule of 4,4′-bis-(carbazol-9-yl) biphenyl and the assisting host used was a blue light-emitting polyfluorene-derived copolymer of poly[(9,9-dioctylfluo-renyl-2,7-diyl)-alt-co-(9-hexyl-3,6-carbazole)]. The hosts were doped via solution-mixing a green dye of tris(2-phenylpyridine) iridium (III) and a red dye of bis[2-(2′-benzo-thienyl)-pyridi-nato-N,C3,](acetylacetonate) iridium (III). One resultant device having a pure white emission of Commission Internationale de l’Eclairage (0.33, 0.33) has a maximum power efficiency of 4.2lm∕W at 802cd∕m2 and a maximum brightness of 11800cd∕m2. The better efficiency performance may be attributed to the addition of the assisting host, which halves the energy barrier for holes to inject into the light-emitting zone.
Probe for measurements of density/conductivity in flows of conducting fluids
Authors: Fan Xuejun , Brown Garry L.
Published: March 2006

A probe utilizing the bipolar pulse method to measure the density of a conducting fluid has been developed. The probe is specially designed such that the concentration of a stream tube can be sampled continuously. The density was determined indirectly from the measurement of solution conductivity. The probe was calibrated using standard NaCl solutions of varying molarity and was able to rapidly determine the density of a fluid with continuously varying conductance. Measurements of the conductivity profiles, corresponding density profiles, and their fluctuation levels are demonstrated in a channel flow with an electrolyte injected from a slot in one wall.
Construction of multiphoton laser scanning microscope based on dual-axis acousto-optic deflector
Authors: Lv Xiaohua , Zhan Chen , Zeng Shaoqun , Chen Wei R. , Luo Qingming
Published: March 2006

The construction of a multiphoton laser scanning microscope based on a dual-axis acousto-optic deflector (AOD) is described. Without mechanical inertia and physical movement of the scanner, this system has a high random-addressing and data-acquisition rate of 10μspixel. By proper compensation of the dispersion of the AODs, the spatial resolution of the system is 0.5μm for lateral direction and 1.5μm for axial direction. Fluorescence images are acquired to demonstrate these imaging performances.
Fabrication of ruby phosphor sheet for the fluorescence thermometer application
Authors: Aizawa H. , Sekiguchi M. , Katsumata T. , Komuro S. , Morikawa T.
Published: March 2006

A fluorescence thermometer using the temperature dependence of the phase shift of fluorescence response was developed using a ruby phosphor sheet. The ruby phosphor sheet was compounded of ruby powder and silicone resin. The fluorescence lifetime from the ruby phosphor sheet was measured with a phase shift measurement technique. The phase shift of the fluorescence response from the ruby phosphor sheet decreased linearly with temperature from 270to350K. The ruby phosphor sheet is found to be powerful tool for temperature measurement, and can be used for noncontact temperature measurement.
Dual beam experiment for simultaneous irradiation of surfaces with ion species of gaseous and solid-state elements
Authors: Bizyukov I. , Krieger K.
Published: March 2006

The effects occurring under simultaneous bombardment of surfaces by ions of gaseous and solid elements is a new field for research, which is of great interest for applications ranging from cold plasma technologies to nuclear fusion in magnetically confined plasmas. A multitude of new effects has been observed originating from mixing of incident ion species and bulk material at the surface and, in some cases, from additional complex chemical interactions between the mixing species. To study these effects under controlled conditions a new dual beam experiment has been commissioned, particularly suited for in situ studies of surface sputtering and ion implantation processes. Thin films with negligible impurity level and surface roughness are used as targets. High energy ion beam analysis is used as a means of nondestructive elemental depth profiling and concentration measurements. This allows for the first time the fast quantification of the elemental composition change of a target sample in intervals between ion irradiation. The article describes the details of design and operation, as well as the accessible range of experimental conditions.
Second-order aberration corrected electron energy loss spectroscopy attachment for scanning electron microscopes
Authors: Luo T. , Khursheed A.
Published: March 2006

At present transmission electron energy loss spectrum (EELS) analysis is only carried out in dedicated research instruments such as transmission electron microscopes (TEMs) or scanning transmission electron microscopes. This article presents a new design of second-order geometric aberration corrected EELS spectrometer attachment using split plates, which enables conventional scanning electron microscopes (SEMs) to provide TEM-like EELS spectra. Correction to a third-order dominant geometric aberration pattern has been achieved, which indicates that most of the second-order geometric aberration component is eliminated. This second-order aberration corrected spectrometer attachment design can enable SEMs to provide transmission EELS spectrums.
Monolayers and nanoparticles on nickel silicide for molecular electronics
Authors: Marx Eike , Chiesa Marco , Borg Malin , Bengtsson Stefan , Less Robert J. , Raithby Paul R. , Ford Christopher J. B. , Greenham Neil C.
Published: March 2006

We describe the use of nickel silicide as an electrode in molecular electronics applications. Formation of monolayers of aliphatic and aromatic hydrocarbons on nickel silicide is demonstrated, and these monolayers are used to link CdSe nanocrystals to the substrate. Using the conjugated linker molecule 1,4-ethynylphenyl-2′-nitro-1-benzene-dithiolate, scanning tunneling spectroscopy measurements at 120K show evidence of Coulomb blockade and resonant tunneling behavior associated with the nanocrystals. These measurements demonstrate the feasibility of using nickel silicide as an electrode in molecular electronic devices.
Electrically switchable, two-color quantum cascade laser emitting at 1.39 and 2.3THz
Authors: Scalari Giacomo , Walther Christoph , Faist Jérôme , Beere Harvey , Ritchie David
Published: March 2006

A quantum cascade laser emitting at 1.39 and 2.3THz is demonstrated. The structure is based on a large single quantum well and multiwavelength operation is obtained by selectively injecting carriers by resonant tunneling in the excited states of the well. A magnetic field applied perpendicularly to the layers increases the gain enabling laser action. Extremely low values of the threshold current density (below 30A∕cm2) are observed for both wavelengths. A study of the dependence of the laser emission intensity as a function of the applied magnetic field is also presented.
Zn
Ga
2
O
4
nanotubes with sharp cathodoluminescence peak
Authors: Li Y. J. , Lu M. Y. , Wang C. W. , Li K. M. , Chen L. J.
Published: March 2006

Single-crystal ZnGa2O4 nanotubes were grown using well-aligned ZnO nanorods as templates by a vapor transport method. Ga and O vapors were reacted with ZnO to form ZnO∕ZnGa2O4 core-shell nanostructure, and single-crystal ZnGa2O4 nanotubes were obtained by the removal of ZnO cores with a dilute HCl solution. The cathodoluminescence spectra indicate that the ZnGa2O4 nanotubes emit near ultraviolet (UV) and blue lights (380 and 464nm). The sharp near UV peak shall be beneficial for optical applications.
Analysis of graphene nanoribbons as a channel material for field-effect transistors
Authors: Obradovic B. , Kotlyar R. , Heinz F. , Matagne P. , Rakshit T. , Giles M. D. , Stettler M. A. , Nikonov D. E.
Published: March 2006

Electronic properties of graphene (carbon) nanoribbons are studied and compared to those of carbon nanotubes. The nanoribbons are found to have qualitatively similar electron band structure which depends on chirality but with a significantly narrower band gap. The low- and high-field mobilities of the nanoribbons are evaluated and found to be higher than those of carbon nanotubes for the same unit cell but lower at matched band gap or carrier concentration. Due to the inverse relationship between mobility and band gap, it is concluded that graphene nanoribbons operated as field-effect transistors must have band gaps <0.5eV to achieve mobilities significantly higher than those of silicon and thus may be better suited for low power applications.
On-chip photoconductive excitation and detection of pulsed terahertz radiation at cryogenic temperatures
Authors: Wood C. , Cunningham J. , Upadhya P. C. , Linfield E. H. , Hunter I. C. , Davies A. G. , Missous M.
Published: March 2006

We report on measurements of the excitation, propagation, and detection of picosecond duration electrical pulses at cryogenic (∼4K) temperatures in a microstrip circuit. A reduction is observed in the measured excitation and propagating pulse widths at low temperatures, compared with room temperature. The results indicate both that the electrical properties of low-temperature-grown GaAs make it suitable for photoconductive excitation and detection in cryogenic optoelectric circuits and that an organic polymer is a good transmissive medium for terahertz (THZ) frequency range excitations at low temperatures. This work will prove an invaluable starting point for future guided wave terahertz experiments at cryogenic temperatures.
Negative differential thermal resistance and thermal transistor
Authors: Li Baowen , Wang Lei , Casati Giulio
Published: March 2006

We report on the first model of a thermal transistor to control heat flow. Like its electronic counterpart, our thermal transistor is a three-terminal device with the important feature that the current through the two terminals can be controlled by small changes in the temperature or in the current through the third terminal. This control feature allows us to switch the device between “off” (insulating) and “on” (conducting) states or to amplify a small current. The thermal transistor model is possible because of the negative differential thermal resistance.
Translation-related domain boundaries form to relieve strain in a thin alumina film on NiAl (110)
Authors: McCarty Kevin F. , Pierce John P. , Carter C. Barry
Published: March 2006

We examine how translation-related domains form in thin alumina films synthesized by oxidizing a NiAl (110) surface. Low-energy electron microscopy observations reveal that translation-related domains (sometimes called antiphase domains in the literature) are created within isolated alumina islands as they grow or are annealed. Thus, the domains do not originate when islands with displaced lattices impinge, as frequently assumed in models of film growth. Even though the planar defects that bound the translation-related domains cost energy, the misfit dislocations that terminate the domain boundaries lower the film’s strain energy.
Copper drift in high-dielectric-constant tantalum oxide thin films under bias temperature stress
Authors: Jain Pushkar , Juneja Jasbir S. , Mallikarjunan A. , Rymaszewski E. J. , Lu T.-M.
Published: March 2006

The use of high-dielectric-constant (high-κ) materials for embedded capacitors is becoming increasingly important. Tantalum oxide (Ta2O5) is a prominent candidate as a high-κ material for embedded capacitor use. Metal drift in Ta2O5 (κ∼25) was investigated by bias temperature stress and triangular voltage sweep testing techniques on metal/Ta2O5∕SiO2∕Si structures. At a temperature of 300°C and 0.75MV∕cm bias conditions, Al, Ta, and Ti do not diffuse in Ta2O5, but Cu clearly showed a drift. The Cu drift is attributed to the lack of a stable Cu oxide which can limit Cu ion generation and penetration.
Generating random surfaces with desired autocorrelation length
Authors: Zhang Yilei , Sundararajan Sriram
Published: March 2006

A versatile surface processing method based on electrostatic deposition of particles and subsequent dry etching is shown to be able to tailor the autocorrelation length of a random surface by varying particle size and coverage. An explicit relation between final autocorrelation length, surface coverage of the particles, particle size, and etch depth is built. The autocorrelation length of the final surface closely follows a power law decay with particle coverage, the most significant processing parameter. Experimental results on silicon substrates agree reasonably well with model predictions.
Electric field tuning characteristics of a ferrite-piezoelectric microwave resonator
Authors: Fetisov Y. K. , Srinivasan G.
Published: March 2006

The fabrication and characterization of an electric field-tunable yttrium iron garnet (YIG)-lead zirconate titanate (PZT) microwave resonator are discussed. The device is based on ferromagnetic resonance for YIG. The tunability is accomplished through magnetoelectric interactions. For an electric field E=10kV∕cm across PZT, a frequency shift of 18–25MHz that was an order of magnitude higher the frequency width of the absorption profile for the resonator was measured. Upon reversal of the direction of E, the shift also reversed. The YIG-PZT bilayer structures could form the basis for rapid, electric field tunable, passive microwave resonators and filters.
Study on vacancy formation in ferroelectric PbTiO3 from ab initio
Authors: Zhang Zhen , Wu Ping , Lu Li , Shu Chang
Published: March 2006

Formation energies of possible vacancies under different oxygen partial pressures were studied using an ab initio density functional theory and supercell approach. Under oxygen-rich conditions, lead vacancies are the stable ones throughout the band gap, and their ionization level locates at 0.56eV from the top of valence band, which may contribute to p-type conduction. Under oxygen-poor conditions, oxygen vacancies are the stable ones at the top of the valence band. It is a deep donor that may not only dilute the acceptor carriers to weaken the p-type conduction but hardly contribute to n-type conduction.
Quantum size effects in the volume plasmon excitation of bismuth nanoparticles investigated by electron energy loss spectroscopy
Authors: Wang Y. W. , Kim J. S. , Kim G. H. , Kim Kwang S.
Published: March 2006

Quantum size effects in volume plasmon excitation of bismuth nanoparticles with diameters ranging from 5to500nm have been studied by electron energy loss spectroscopy. The Bi nanoparticles were prepared by reducing Bi3+ with sodium borohydride in the presence of poly(vinylpyrroldone). The volume plasmon energy and its peak width increase with decreasing nanoparticle diameter, due to the quantum size effect. For the particles with diameter less than 40nm, the increase of the volume plasmon energy is proportional to the inverse square of the nanoparticle diameter, confirming the semimetal to semiconductor transition in Bi nanoparticles.
Voltage gain dependence of the negative differential conductance width in silicon single-hole transistors
Authors: Miyaji Kousuke , Saitoh Masumi , Hiramoto Toshiro
Published: March 2006

The full width at half maximum (FWHM) of the negative differential conductance (NDC) characteristics in room temperature (RT)-operating silicon single-hole transistors (SHTs) has been studied by experiments and calculations. It is found that when the voltage gain of the SHT is higher, sharper NDC and smaller FWHM are achieved. Lower drain coupling is considered to be the main reason for the small FWHM in a resonant tunneling system of RT-operating SHTs. FWHM of NDC of as small as 95mV has been obtained in a SHT with the gain of as high as 5.2 at RT, which is the highest value of the gain ever reported. The device is in the form of an ultranarrow wire channel metal oxide semiconductor field-effect transistor, which shows large Coulomb blockade oscillations at RT and has extremely small drain capacitance due to its ultranarrow channel structure. NDC can now be designed by device parameters, showing further potential for application to low-voltage, low-power NDC circuits.
Space, Power, and Mobility: Car Traffic as a Controversial Issue in Neighbourhood Regeneration
Authors: Fotel Trine
Published: March 2006

Mobility, especially for car traffic, is a contested spatial phenomenon in contemporary cities. It contributes to processes of segregation and inequality, and the power-geometry of mobility is an integral part of the conflicting rationalities inherent in contemporary urban space wars. Internationally, Copenhagen is often seen as a successfully planned city. However, a case study of a participatory planning initiative in Copenhagen reveals inert and unequal power relations. It illustrates how residents experience their living conditions as being reduced by heavy car traffic, and how they oppose the multidimensional side effects caused by traffic overload. To increase the welfare of everyday life, urban policies thus ought to focus much more on the spatial distribution of mobility and the ways that mobility influences place-bound living conditions. Integrating bottom-up initiatives and participatory planning processes oriented towards empowerment could be a vital part of democratic urban planning.
Housing as a Heuristic Condition in the Simultaneous Projection of Population and Households
Authors: Akkerman Abraham
Published: March 2006

Conventional population projections regard individuals, rather than households, as population units of reference. Such an approach has been questioned on both methodological and empirical grounds. Furthermore, in applications to smaller populations, conventional population projections have repeatedly yielded poor results. The simultaneous projection of population and households, on the other hand, regards households as population units of reference, but, in applications based on the notion of the household composition matrix, it has occasionally yielded analytically infeasible results. In the present study I examine the simultaneous projection of population and households in a etropolitan area, under feasibility constraints. A housing-market specification is expressed as a feasibility condition against multipliers of the household composition matrix, extracted here for the Cleveland Consolidated Metropolitan Statistical Area (CMSA), 1990. The feasibility condition is shown to function as a gateway to exogenous considerations regarding the transfer of headship in households, and is exemplified in a forecast of population and households for the Cleveland CMSA.
Migration to Urban and Rural Destinations in Post-Soviet Estonia: A Multilevel Event-History Analysis
Authors: Kulu Hill , Billari Francesco C
Published: March 2006

Researchers are divided on the trends and causes of internal migration in postsocialist Central and Eastern Europe. Theories run in opposite directions: some scholars argue that increasing similarities with Western market economies are explaining the migration processes, whereas others claim that specific developments during the postsocialist socioeconomic restructuring are playing a major role. In this paper we contribute to the existing discussion by providing an analysis of personal and contextual determinants of migration to urban and rural destinations in post-Soviet Estonia. We base our study on the data of the Estonian Labour Force Survey from 1995. Our research population consists of 8480 people aged 15 years to 68 years in early 1989. We analyze the intensity of urban-bound and rural-bound migration from January 1989 to December 1994, using the techniques of multilevel event-history analysis. We show that personal characteristics (age, marital status, employment status, education, and ethnicity) and contextual factors (unemployment level and the share of ethnic minorities) are both important in shaping the intensity of migration to urban and rural destinations in post-Soviet Estonia. Although the differences in migration behaviour by demographic characteristics in Estonia are in line with universalistic explanations, the regionally varying effect of socioeconomic status on migration is specific to developments in postsocialist countries, as a result of general economic hardship during the socioeconomic transition.
A catchment-based approach to recharge estimation in the Liverpool Plains, NSW, Australia
Authors: Sun H. , Cornish P. S.
Published: March 2006

This study investigated drainage and shallow groundwater change in a headwater catchment of the Liverpool Plains in north-western New South Wales. A catchment model, SWAT (Soil and Water Assessment Tool), was used to explore rain-fed drainage to shallow groundwater and its relationship to land use. Drainage was predicted along with the prediction of runoff on a catchment and land-use basis over a simulation period of 44 years. Predicted drainage in the catchment was 8 mm/year for the 44 years, which essentially matched estimates derived from bore data observed in the catchment over a 22-year period. These estimates of drainage are much lower than published estimates based on scaling up to the catchment using estimates of drainage derived from point-scale models for different land uses. Estimates of drainage for the different land uses, derived from the catchment model, were also generally lower than simulated drainages from other studies in the area using point-scale models.
The investigation demonstrates a place for catchment-based modelling for estimating drainage at the catchment scale. This is mainly because observed catchment runoff is used as an error controller in catchment recharge modelling, whereas scaled-up point-scale modelling generally does not use observed catchment runoff to derive the catchment drainage. Modelling on the Liverpool Plains catchment also suggests that some of the drainage entering the vadose zone and groundwater is later lost via evapotranspiration, a process not generally simulated in crop models, and requiring further investigation to improve understanding of recharge processes and accuracy of modelling.
The performance of lucerne - wheat rotations on Western Australian duplex soils
Authors: Latta R. A. , Lyons A.
Published: March 2006

In field experiments on duplex soils in the south-eastern and central Western Australian wheatbelt, lucerne (Medicago sativa L.) was compared with subterranean clover (Trifolium subterraneum L.) in pasture–crop rotations. Comparative pasture plant densities and biomass, soil water content, available soil nitrogen, wheat grain yield, and protein content were measured during 2 and 3 years of pasture followed by 2 and 1 year of wheat, respectively. Lucerne densities declined by 60–90% over the 3-year pasture phase but produced up to 3 times more total annual biomass than weed-dominant annual pastures and similar total annual biomass when annual pastures were legume dominant. Lower soil water contents were measured under lucerne than under annual pastures from 6 months after establishment, with deficits up to 60 mm in the 0–1.6 m soil profile. However, significant rain events and volunteer perennial weeds periodically negated comparative deficits. Wheat yields were lower following lucerne (1.3 t/ha) than following an annual pasture (1.8 t/ha) in a low-rainfall season, higher (3.7 v. 2.9 t/ha) in a high-rainfall season, and much higher when the previous annual pastures were grass dominant (3.4 v. 1.5 t/ha). Grain protein contents were 1–2% higher in response to the lucerne pasture phase. Overcropping wheat into a lucerne pasture of 19 plants/m2 reduced wheat grain yields, but a lucerne density of 4 plants/m2 reduced yields only where rainfall was low. The study has shown that lucerne–wheat rotations provide a productive farming system option on duplex, sodic soils in both the south-eastern and central cropping regions of Western Australia. This was most evident in seasons of above-average summer and growing-season rainfall and when compared with grass-dominant annual pastures.
Using soil, climate, and agronomy to predict soil water use by lucerne compared with soil water use by annual crops or pastures
Authors: Ward P. R. , Micin S. F. , Dunin F. X.
Published: March 2006

The incorporation of perennials in general, and lucerne in particular, into farming systems of southern Australia has been proposed as a possible means to slow or stop the spread of dryland salinity. In order to be effective, lucerne roots must remove substantially more water from the soil than roots produced by annual crops and pastures. The term ‘buffer’ is used here to denote the extra water storage created by lucerne in addition to that normally created by an annual crop or pasture. In trials across southern Australia, lucerne has proved variable in its ability to create a buffer. In this research, we established 3 new trials, and collated results from current and published trials across Australia, to determine the effect of various edaphic (soil pH, texture, depth, and density for A and B horizons), climatic (average and actual seasonal rainfall), and agronomic (lucerne age, plant density, dry matter production, and rooting depth) factors on buffer size created by lucerne. Data from 26 trials were analysed, representing 84 site × year comparisons. The mean lucerne buffer for all comparisons was 91 mm, and increased with lucerne age. Buffers were generally greater for heavier-textured soils, but standard deviations of the means were large. Within a broad soil type, regression equations were developed to predict buffer size from climatic, edaphic, and agronomic factors, with r2 values ranging between 0.96 and 0.84, and standard errors ranging between 40 and 44 mm. For all soil types, average summer rainfall (but not actual summer rainfall) was a significant component of the regression, suggesting that management of the lucerne stand, in terms of maintaining leaf area during summer, may have an important role in buffer development.
Nitrogen use and crop type affect the water use of annual crops in south-eastern Australia
Authors: Norton R. M. , Wachsmann N. G.
Published: March 2006

The effect of management and crop selection on water use and profile drying was investigated using 2 series of experiments conducted in the Victorian Wimmera. The effect of applied nitrogen on growth and water use of canola was assessed from 3 field experiments on a Vertosol soil. Across these sites, 140 kg N/ha increased crop water use by a mean of 30 mm, and the biological response averaged 3.68 t/ha of shoot dry matter and seed yield increased by 73% from 1.46 to 2.52 t/ha. The additional nitrogen enabled roots to go deeper into the soil and also to extract water to higher tensions, but the increases in water use were far less than the growth and yield responses. Estimated average soil evaporation was 120 mm across these experiments, but ranged from 26 to 57% of total water use. It was concluded that increased crop vigour in response to applied nitrogen does increase total water use, but the main way that water-use efficiency increases is through reduced soil evaporation.
In a second series of experiments, the growth, yield, and water use of wheat, canola, linseed, mustard, and safflower were compared across 4 sites with differing soil moisture contents. Wheat was the highest yielding crop at all sites. Mustard and canola produced similar amounts of biomass and seed yields, whereas linseed produced seed yields that were generally less than the brassica oilseeds. Safflower grew well and produced large amounts of biomass at all sites, but this increased growth did not necessarily translate into increased seed yields. Safflower yielded less seed than all other crops at the 2 dry sites, but yields were similar to canola at the wetter sites. On 2 drier sites, soil water extraction occurred to approximately 1 m for all crops, and all available water was used within that zone by all crops. Where the soil was wet beyond 1 m, safflower was able to extract water from deeper in the profile than the other crops and generated a soil water deficit of about 100 mm more than the other crops at maturity. This deficit persisted into the subsequent autumn–winter period. The potential of using safflower as a management option to extract water from deep in the profile, and so create a soil buffer, is discussed.
Prologue: Amending agricultural water use to maintain production while affording environmental protection through control of outflow
Authors: Dunin Frank , Passioura John
Published: March 2006

The long-standing debate about the problem of dryland salinity in Australia has been increasingly well informed. We chart here the deepening understanding of the processes involved in how plants use water and what this means for flows in the regolith, from the introduction of the idea of the soil–plant–atmosphere continuum 50 years ago, through the comparative patterns of water use by annual and perennial vegetation and the variety of their hydrological effects in different landscapes, to the realisation, as demonstrated by many of the papers in this special issue of AJAR, that the era of unviable simplistic solutions to dryland salinity is behind us. The mood now is one of cautious optimism that we will be able to develop a wide range of options for maintaining economically viable farming systems that protect the environment by controlling outflow well enough to arrest the spread of dryland salinity.
Turing instability mediated by voltage and calcium diffusion in paced cardiac cells
Authors: Shiferaw Yohannes , Karma Alain
Published: March 2006

In cardiac cells, the coupling between the voltage across the cell membrane (
V
m
) and the release of calcium (Ca) from intracellular stores is a crucial ingredient of heart function. Under abnormal conditions and/or rapid pacing, both the action potential duration and the peak Ca concentration in the cell can exhibit well known period-doubling oscillations referred to as “alternans,” which have been linked to sudden cardiac death. Fast diffusion of
V
m
keeps action potential duration alternans spatially synchronized over the ≈150-μm-length scale of a cell, but slow diffusion of Ca ions allows Ca alternans within a cell to become spatially asynchronous, as observed in some experiments. This finding raises the question: When are Ca alternans spatially in-phase or out-of-phase on subcellular length scales? This question is investigated by using a spatially distributed model of Ca cycling coupled to
V
m
. Our main finding is the existence of a Turing-type symmetry breaking instability mediated by
V
m
and Ca diffusion that causes Ca alternans to become spontaneously out-of-phase at opposite ends of a cardiac cell. Pattern formation is governed by the interplay of short-range activation of Ca alternans, because of a dynamical instability of Ca cycling, and long-range inhibition of Ca alternans by
V
m
alternans through Ca-sensitive membrane ionic currents. These results provide a striking example of a Turing instability in a biological context where the morphogens can be clearly identified, as well as a potential link between dynamical instability on subcellular scales and life-threatening cardiac disorders.
A mechanism for diversity in warning signals: Conspicuousness versus toxicity in poison frogs
Authors: Darst Catherine R. , Cummings Molly E. , Cannatella David C.
Published: March 2006

Many animals advertise their chemical defense to predators with conspicuous coloration and unpalatability, but little is known about the information in these signal elements. To effectively avoid predation, is it more advantageous to invest in increased conspicuousness or greater noxiousness, or to allocate equally to both signal modalities? Using natural variation among poison frog species measured with spectral reflectance and toxicity assays, we tested the relative importance of warning signal components with predator-learning and avoidance experiments. We demonstrate that closely related species use alternative strategies: increasing either conspicuousness or toxicity affords equivalent avoidance by predators and provides protection to nontoxic mimic species. These equally effective predator avoidance tactics demonstrate different aposematic solutions for two potentially costly signal components, providing a mechanism for natural diversity in warning signals.
Cultivation and genetics ofArtemisia annuaL. for increased production of the antimalarial artemisinin
Authors: Ferreira J.F.S. , Laughlin J. C. , Delabays N. , de Magalhães P.M.
Published: March 2006

Malaria has been treated for over 350 years with quinine and quinine-derived drugs. However, in several areas of the world, some strains of the malarial parasitePlasmodium falciparumhave developed resistance against these drugs. Recently, the World Health Organization (WHO) recommended the use of artemisinin-combination treatments (ACT) as the first-line treatment for multidrug-resistant falciparum malaria. The WHO estimates that current supplies of artemisinin are sufficient for only 30 million ACT, and is foreseeing the need for 130–220 million ACT in 2005 (WHO, 2004). Current research on the production of synthetic artemisinin-like compounds by the Roll Back Malaria project, pharmaceutical companies and academia resulted in a promising synthetic artemisinin-like compound (OZ277) which is currently undergoing phase I clinical trials. In about 5 years this drug is expected to be approved and made available to the public, however, meeting current global demands for ACT depends on the immediate availability of affordable artemisinin-derived drugs. This will involve expansion of the area under cultivation ofArtemisia annuaand improved methods of cultivation and processing of raw material, associated with more efficient methods for extraction and purification of artemisinin from plant material. This review addresses the agricultural, environmental and genetic aspects that may be useful in the successful large-scale cultivation ofA. annuaand for producing the antimalarial artemisinin in areas where it is urgently needed today. It also includes geographic aspects (latitude and altitude), which will help make decisions about crop establishment in tropical countries, and includes a list of Good Agricultural and Collection Practices forA. annua.
Somaclonal variation in seed germination of dallisgrass biotypes
Authors: Pitman W.D. , Croughan S.S. , Nash J.L. , Venuto B.C.
Published: March 2006

Dallisgrass (Paspalum dilatatum Poir.) is an important pasture grass on moist fertile sites in warm climates, however, it is limited in use by periodic low seed quality and resulting erratic availability and establishment difficulties. Due to apomictic reproduction, common pentaploid dallisgrass has not been responsive to traditional plant improvement approaches. Recent research has shown potential for some improvement in forage production and plant persistence with apomictic hexaploid varieties of dallisgrass. Tissue-culture regeneration has been reported to produce somaclonal variation in seed germination of common pentaploid dallisgrass and has recently resulted in availability of potentially useful regenerants of hexaploid dallisgrass. Seed of selected plants from both field and greenhouse environments was evaluated in replicated germination trials to determine whether hexaploid tissue-culture regenerants responded similarly to regenerants from common dallisgrass and to determine whether regenerants expressing potential agronomic usefulness as indicated by preliminary observations differed in germination. The eight germination trials included 299 regenerants with 57 of these being duplicate entries among trials. Germination did not differ among sources of regenerants. Within sources germination differed among regenerants with a few individuals exceeding germination percentage of parent lines in one evaluation of greenhouse-produced seed. Individual regenerants with agronomic potential and high percentage seed germination were identified. The results demonstrate that tissue-culture regeneration can be used to produce improved germination in agronomically useful genotypes of apomictic dallisgrass and suggest that such potential may exist for other recalcitrant plant species.