bluuebunny/crossref_metadata_2025 huggingface dataset:
Strained SiGe islands on Si(001): Evolution, motion, dissolution, and plastic relaxation
Authors: Rastelli A. , Stoffel M. , Denker U. , Merdzhanova T. , Schmidt O. G.
Published: November 2006

We report on the morphological evolution of strained SiGe islands epitaxially grown on Si(001). After reviewing the morphological transitions undergone by the islands as their size changes, we present recent results obtained by an approach consisting of “reading the footprints” left by the islands on the Si substrate during growth. Such footprints, which we investigate by a combination of scanning probe microscopy and selective wet chemical etching, are trenches carved in the Si substrate. The study of these trenches allows us to discuss general phenomena occurring during growth or post‐growth annealing, such as coarsening and morphological transitions, surface‐mediated material intermixing and lateral island motion, evolution of plastically relaxed islands and effect on the islands surrounding them. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon nanotube via interconnect technologies: size‐classified catalyst nanoparticles and low‐resistance ohmic contact formation
Authors: Awano Y. , Sato S. , Kondo D. , Ohfuti M. , Kawabata A. , Nihei M. , Yokoyama N.
Published: November 2006

We propose a new approach to fabricating carbon nanotube (CNT) via interconnects for future LSIs, which uses preformed catalyst nanoparticles to grow the CNTs. A newly designed impactor provided size‐classified catalyst particles. For the new approach, we employ a TiN contact layer which is more resistant to oxidation and enables us to form a lower resistance ohmic contact between CNTs and wiring layers. The resultant CNT–via resistance was 0.59 Ω for 2‐µm vias, which is the smallest ever reported. We also study the CNT nucleation process using molecular dynamics and discuss how to remove amorphous carbon from the nucleation process. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preface: phys. stat. sol. (a) 203/14
Authors: Bougeard Dominique , Finley Jonathan , Grayson Matthew , Tornow Marc
Published: November 2006

The present special issue entitled Frontiers in Semiconductor Nanoscience has been prepared to honor Gerhard Abstreiter on the occasion of his 60th birthday and pay tribute to his long career, during which he has consistently operated at the frontiers in semiconductor physics and nanoscience. The twin issues in pss(a) and pss(b) consist of more than forty contributions from leading scientists in four of the general fields of semiconductor and nanostructure physics in which Gerhard has been most active: (i) quantum transport, (ii) optical properties and coherent phenomena, (iii) nano‐biological systems and (iv) novel materials and nanostructures. As discussed by Günther Bauer in his laudatio, Gerhard has consistently made highly significant contributions to each and every one of these fields throughout his career, often leading to new advances that have had a major impact in the fields of semiconductor nanostructures and condensed matter physics.

In addition to providing a fitting tribute to Gerhard's long scientific career, we hope that this issue will stimulate imaginative exploitation of these emerging and rapidly developing fields. We are sure that all contributors, colleagues and collaborators join us in wishing Gerhard a very happy birthday and look forward to working on future problems in the science of semiconductors and their nanostructures. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of Coulomb interactions on electrical conduction through short molecular wires
Authors: Walczak Kamil
Published: November 2006

Electrical conduction through a two‐terminal molecular device is studied using non‐equilibrium Green's function (NEGF) formalism. Such a junction is made of a short linear wire which is connected to the metallic electrodes. The molecule itself is described with the help of the Hückel (tight‐binding) model with the electron interactions treated within the extended Hubbard model (EHM), while the coupling to the electrodes is described with the help of a broad‐band theory. Coulomb interactions within the molecular wire are treated by means of the restricted Hartree–Fock (RHF) approximation. In particular, the influence of short‐range and long‐range Coulomb interactions on electrical transport characteristics is discussed in detail. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The role of density imbalance in the νT = 1 exciton condensate state for electron bilayer systems
Authors: Wiersma R. D. , Lok J. G. S. , Dietsche W. , Klitzing K. von , Schuh D. , Wegscheider W.
Published: November 2006

We report on our experimental work involving the ν T = 1 exciton condensate in independently contacted bilayer two‐dimensional electron systems. A phase diagram between the weakly coupled (ν U = 1/2, ν L = 1/2) phase and the strongly coupled ν T = 1 phase is experimentally investigated as a function of d /ℓB and electron density imbalance Δn (≡ [n L – n U]/n T) using a drag current configuration. For imbalanced electron layer densities, small interlayer imbalances lead to strengthening of the excitonic phase. Here density imbalance leads to a phase boundary in the drag layer which is symmetric around zero imbalance. Surprisingly this behavior is not seen for ϱ drive,xx , where an unusual asymmetric behavior around zero imbalance occurs. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetotransport studies on single and coupled modulation‐doped quantum wires fabricated by cleaved edge overgrowth
Authors: Wegscheider Werner , Rother Martin , Deutschmann Rainer , Feil Thomas
Published: November 2006

Cleaved Edge Overgrowth is employed to fabricate atomically precise single and coupled quantum wires. Single wires were investigated in the diffusive and ballistic transport regimes. In addition to a detailed understanding of the 1D sublevel structure in the complex CEO devices, clear indications of Luttinger liquid behavior of the one‐dimensional electron systems were obtained. Coupled quantum wires were studied in the two limits of large and small separations. In the first case shallow 1D potentials were chosen and an alternative description for commensurability oscillations in weakly modulated two‐dimensional electron systems could be derived. For the coupled quantum wires with small separations and a large potential modulation the validity of the miniband transport picture leading to negative differential conductivity was demonstrated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measurement, control, and decay of quantum‐dot spins
Authors: Coish W. A. , Golovach Vitaly N. , Egues J. Carlos , Loss Daniel
Published: November 2006

In this review we discuss a recent proposal to perform partial Bell‐state (parity) measurements on two‐electron spin states for electrons confined to quantum dots. The realization of this proposal would allow for a physical implementation of measurement‐based quantum computing. In addition, we consider the primary sources of energy relaxation and decoherence which provide the ultimate limit to all proposals for quantum information processing using electron spins in quantum dots. We give an account of the Hamiltonians used for the most important interactions (spin–orbit and hyperfine) and survey some of the recent work done to understand dynamics, control, and decoherence under the action of these Hamiltonians. We conclude the review with a table of important decay times found in experiment, and relate these time scales to the potential viability of measurement‐based quantum computing. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical control of electron spin dynamics in self‐assembled (In,Ga)As/GaAs quantum dots
Authors: Greilich A. , Oulton R. , Zhukov E. A. , Yugova I. A. , Yakovlev D. R. , Bayer M. , Shabaev A. , Efros Al. L. , Stavarache V. , Reuter D. , Wieck A.
Published: November 2006

Spin coherence has been studied in self‐assembled (In,Ga)As/GaAs quantum dots which contain on average a single electron per dot due to n‐type modulation doping. A magnetic field was applied in the Voigt geometry, in order to study the precession of the electron spins which are oriented normal to the field. Here we address the mechanism by which such a normal orientation can be achieved by resonant excitation with circularly polarized laser pulses. Further, we discuss, how long this coherence is maintained within an ensemble of quantum dots. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural investigation of hierarchically self‐assembled GaAs/AlGaAs quantum dots
Authors: Lenz A. , Timm R. , Eisele H. , Ivanova L. , Martin D. , Voßebürger V. , Rastelli A. , Schmidt O. G. , Dähne M.
Published: November 2006

Recent investigations of self‐organized unstrained inverted GaAs/AlGaAs quantum dots, prepared by a combination of Stranski–Krastanov growth mode and an in situ etching technique, show GaAs quantum dots with large confinement energy and high size homogeneity. Here we present first cross‐sectional scanning tunneling microscopy data of these quantum dots, characterized by a lateral extension of about 35 nm, heights of about 5–6 nm, and a reversed truncated pyramidal shape. We further observe a decomposition of the AlGaAs host layers and a roughening of the AlGaAs/GaAs interfaces. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatial properties and coherence of the high density phase in the microcavity optical parametric oscillator
Authors: Skolnick M. S. , Sanvitto D. , Krizhanovskii D. N. , Love A. P. D. , Whittaker D. M. , Roberts J. S.
Published: November 2006

The special issue entitled “Frontiers in Semiconductor Nanoscience” with a total of more than forty contributions from leading scientists in semiconductor and nanostructure physics has been prepared to honor Gerhard Abstreiter, Technische Universität München. The present Part B contains Feature Articles and Original Papers in the areas of quantum transport, optical properties and coherent phenomena. Part A of the special issue on nano‐biological systems, novel materials and nanostructures is published in phys. stat. sol. (a) 203, No. 14 (2006).

The cover picture has been taken from the Feature Article [1] by Maurice Skolnick et al. It illustrates a calculation of the signal distribution and photonic potential (white contours) in a microcavity optical parametric oscillator with evidence for strong localisation in the potential minima.

This issue also contains articles presented at the 7th International Conference on Excitonic Processes in Condensed Matter held in Winston‐Salem, USA, 26–30 June 2006. They include the Editor's Choice “Optical manipulation of CuCl nanoparticles under an excitonic resonance condition in superfluid helium” by K. Inaba et al. The first author received one of the two EXCON Prizes sponsored by Wiley‐VCH. More contributions from EXCON'06 can be found in phys. stat. sol. (c) 3, No. 10 (2006). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polymer‐filler derived ceramics with low shrinkage using PCS/SiC/Al mixture
Authors: Zhu Y. Z. , Huang Z. R. , Dong S. M. , Yuan M. , Jiang D. L.
Published: November 2006

Active Al and inert SiC powders were dispersed in the polycarbosilane to manufacture SiC ceramic composites by a new process of active‐filler‐controlled pyrolysis of polymer. 40 wt% of active Al fillers, 40 wt% of inert SiC fillers and 20 wt% of PCS, were homogenized. The samples were obtained by pyrolysis at 1100 °C for different soaking time. The results showed that due to the incorporation of active Al fillers, formation of crystallite phases such as Al4C3, Al4Si3 and AlN occured due to the of reaction of Al particles with the polymer decomposition products and the reactive nitrogen atmosphere. The microstructural and mechanical characterization results of the composites are presented in the paper. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A study of the modeling and analysis of software fault‐detection and fault‐correction processes
Authors: Xie M. , Hu Q. P. , Wu Y. P. , Ng S. H.
Published: November 2006

Most of the models for software reliability analysis are based on reliability growth models which deal with the fault detection process. This is done either by assuming that faults are corrected immediately after being detected or the time to correct a fault is not counted. Some models have been developed to relax this assumption. However, unlike the fault‐detection process, few published data sets are available to support the modeling and analysis of both the fault detection and removal processes. In this paper, some useful approaches to the modeling of both software fault‐detection and fault‐correction processes are discussed. Further analysis on the software release time decision that incorporates both a fault‐detection model and fault‐correction model is also presented. This procedure is easy to use and useful for practical applications. The approach is illustrated with an actual set of data from a software development project. Copyright © 2006 John Wiley & Sons, Ltd.
Reliable determination of oxygen and hydrogen isotope ratios in atmospheric water vapour adsorbed on 3A molecular sieve
Authors: Han Liang‐Feng , Gröning Manfred , Aggarwal Pradeep , Helliker Brent R.
Published: November 2006

The isotope ratio of atmospheric water vapour is determined by wide‐ranging feedback effects from the isotope ratio of water in biological water pools, soil surface horizons, open water bodies and precipitation. Accurate determination of atmospheric water vapour isotope ratios is important for a broad range of research areas from leaf‐scale to global‐scale isotope studies. In spite of the importance of stable isotopic measurements of atmospheric water vapour, there is a paucity of published data available, largely because of the requirement for liquid nitrogen or dry ice for quantitative trapping of water vapour. We report results from a non‐cryogenic method for quantitatively trapping atmospheric water vapour using 3A molecular sieve, although water is removed from the column using standard cryogenic methods. The molecular sieve column was conditioned with water of a known isotope ratio to ‘set’ the background signature of the molecular sieve. Two separate prototypes were developed, one for large collection volumes (3 mL) and one for small collection volumes (90 µL). Atmospheric water vapour was adsorbed to the column by pulling air through the column for several days to reach the desired final volume. Water was recovered from the column by baking at 250 °C in a dry helium or nitrogen air stream and cryogenically trapped. For the large‐volume apparatus, the recovered water differed from water that was simultaneously trapped by liquid nitrogen (the experimental control) by 2.6‰ with a standard deviation (SD) of 1.5‰ for δ2H and by 0.3‰ with a SD of 0.2‰ for δ18O. Water‐vapour recovery was not satisfactory for the small volume apparatus. Copyright © 2006 John Wiley & Sons, Ltd.
Robust discrete‐time nonlinear sliding mode state estimation of uncertain nonlinear systems
Authors: Veluvolu K. C. , Soh Y. C. , Cao W.
Published: November 2006

In this paper, we propose a discrete‐time nonlinear sliding mode observer for state and unknown input estimations of a class of single‐input/single‐output nonlinear uncertain systems. The uncertainties are characterized by a state‐dependent vector and a scalar disturbance/unknown input. The discrete‐time model is derived through Taylor series expansion together with nonlinear state transformation. A design methodology that combines the discrete‐time sliding mode (DSM) and a nonlinear observer design is adopted, and a strategy is developed to guarantee the convergence of the estimation error to a bound within the specified boundary layer. A relation between sliding mode gain and boundary layer is established for the existence of DSM, and the estimation is made robust to external disturbances and uncertainties. The unknown input or disturbance can also be estimated through the sliding mode. The conditions for the asymptotical stability of the estimation error are analysed. Application to a bioreactor is given and the simulation results demonstrate the effectiveness of the proposed scheme. Copyright © 2006 John Wiley & Sons, Ltd.
Parsimonious analysis of time‐dependent effects in the Cox model
Authors: Lehr Stephan , Schemper Michael
Published: November 2006

Cox's proportional hazards model can be extended to accommodate time‐dependent effects of prognostic factors. We briefly review these extensions along with their varying degrees of freedom. Spending more degrees of freedom with conventional procedures (a prioridefined interactions with simple functions of time, restricted natural splines, piecewise estimation for partitions of the time axis) allows the fitting of almost any shape of time dependence but at an increased risk of over‐fit. This results in increased width of confidence intervals of time‐dependent hazard ratios and in reduced power to confirm any time‐dependent effect or even any effect of a prognostic factor. By means of comparative empirical studies the consequences of over‐fitting time‐dependent effects have been explored. We conclude that fractional polynomials, and similarly penalized likelihood approaches, today are the methods of choice, avoiding over‐fit by parsimonious use of degrees of freedom but also permitting flexible modelling if time dependence of a usuallya prioriunknown shape is present in a data set. The paradigm of a parsimonious analysis of time‐dependent effects is exemplified by means of a gastric cancer study. Copyright © 2006 John Wiley & Sons, Ltd.
Content and distribution of arsenic in soils, sediments and groundwater environments of the southern Pampa region, Argentina
Authors: Blanco M. del C. , Paoloni J. D. , Morrás H. J. M. , Fiorentino C. E. , Sequeira M.
Published: November 2006

The health of a large rural population in the southern Pampa (Argentina) is at risk owing to newly detected areas where As‐groundwater exceeds 0.01 mg/L standard (WHO (1995) Guidelines for drinking water quality, 2nd edition. pp 43–45). Currently, devitrification of volcanic glass is invoked to interpret the origin of arsenic in the aquifers hosted in a sequence of pampean loess (Plio‐Pleistocene) juxtaposed with postpampean loess (Holocene). Our data suggest that arsenic is not specifically associated with volcanic glass and that other minerals contribute to As‐release into groundwater. The goals were (1) to understand As‐groundwater spatial variability, (2) to explore soils/sediments/water relationships and to identify the probable As‐provenance. Comparable As concentrations of the light and the heavy sand fractions suggest that though detrital glass is a major light constituent, other existing primary minerals are As‐bearers that contribute to As‐release into groundwater. Grouping of materials according to their As‐content indicated spatial variability in the sedimentary distribution pattern leading to differences in the frequencies of occurrence of As‐bearing minerals. Phreatic waters were Ca + Mg bicarbonate and devoid of As in the intake areas (Ventania System) and Na‐carbonate but As‐rich towards the discharge (Atlantic coast and local depressions). As‐groundwater reflects a patchy distribution within the pampean landscape. A correspondence between As‐high groundwater, EC >1 dSm, CO3H−, alkaline pH and a longer water residence time do exist triggering As extraction from the loess sand fraction and desorption from charged fine particles which lead to As‐toxicity towards groundwater discharge. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 561–574, 2006.
Oral toxicity of the cyanobacterial toxin cylindrospermopsin in mice: Long‐term exposure to low doses
Authors: Sukenik A. , Reisner M. , Carmeli S. , Werman M.
Published: November 2006

The hepatotoxin cylindrospermopsin, a sulfated‐guanidinium alkaloid with substituted dioxypyrimidine (uracil) moiety, was isolated from several cyanobacteria species. The acute toxicity of cylindrospermopsin was well established based on intraperitoneal and oral exposure; however, only a few long‐term subacute exposure studies were performed to permit a reliable guideline value for cylindrospermopsin in drinking water. In the study reported herein, female and male mice were exposed to cylindrospermopsin in their drinking water. Cylindrospermopsin‐containing, Aphanizomenon ovalisporum (cyanobacterium)‐free medium was provided as the only source of drinking water, whereas a control group was given a fresh medium for cyanobacteria as drinking water. Over a period of 42 weeks, experiment groups were exposed to cylindrospermopsin concentration, gradually increased from 100 to 550 μg L−1 (daily exposure ranged between 10 and 55 μg kg−1 day−1). Body and organ weights were recorded, and serum and hematology analyses were performed 20 and 42 weeks after the beginning of the experiment. The most pronounced effect of cylindrospermopsin was elevated hematocrit levels in both male and female mice after 16 weeks of exposure to cylindrospermopsin. The observed changes in the hematocrit level were accompanied by deformation of red blood cells, which were changed into acanthocyte. Based on these results, a daily cylindrospermopsin dose of 20 μg kg−1 day−1 (equivalent to 200 μg L−1) is proposed as the lowest‐observed‐adverse‐effect level for both male and female mice. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 575–582, 2006.
Impacts per unit weight in catch by two types of fisheries on a chub mackerel population
Authors: Matsuda Hiroyuki , Fukase Kenjiro , Mitani Isamu , Asano Kenji
Published: November 2006

By using data on the age‐specific annual fecundity and catches‐at‐age by each fishery in a chub mackerel (Scomber japonicus) population in the Pacific Ocean off Japan during 1970 to 1992, we evaluated the long‐term fluctuation in impacts of two types of fisheries on the chub mackerel population. The purse‐seine fishery consistently had a larger impact on the population than did the dip‐net fishery, mainly because the catch by the former was much larger than that by the latter. To evaluate impact per unit weight in catch, we calculated the average reproductive value per unit weight over individuals caught by each fishery as an indicator of efficient use of bioresource. Because the proportion of immature fish caught by the purse‐seine fishery was usually larger than that by the dip‐net fishery, the impact per unit weight in catch by the purse‐seine fishery was not always less than that by the dip‐net fishery.
Demographic attributes of an introduced herbivorous lady beetle
Authors: Ohgushi Takayuki , Sawada Hiroichi
Published: November 2006

Demographic attributes of the adults of an introduced herbivorous lady beetle Epilachna niponica (Coleoptera: Coccinellidae) were investigated from 1975 to 1981 in the Botanical Garden of Kyoto University. Population growth rate varied from 4.8 to 16.8 throughout the study period. Fecundity and mortality in the late larval period contributed most to annual changes in the population growth rate. Population growth rate was negatively correlated with the density of overwintering adults. Adult survival from emergence to the reproductive season, which varied from 0.03 to 0.36 throughout the study, was almost completely determined by survival during the pre‐hibernation period. Adult survival to the preproductive season changed in a size‐ and sex‐dependent manner. Larger adults survived better than smaller individuals; male‐biased mortality occurred from adult emergence to the reproductive age. Severe intraspecific competition among late instar larvae due to host plant defoliation produced a higher proportion of small‐sized adults, resulting in lower adult survival to hibernation. The introduced population had a higher population growth rate and a lower adult survival to the reproductive season than the source population.
Sexual differences in natal dispersal and philopatry of the grey‐sided vole
Authors: Saitoh Takashi
Published: November 2006

The natal dispersal distance of the grey‐sided vole, Clethrionomys rufocanus (Sundevall), was measured in a large outdoor enclosure (2.1 ha) in Hokkaido, Japan. Voles in about half of the enclosure (1 ha) were fed. Distance from the natal site to the site of reproduction was significantly greater in males (64.9 m) than in females (35.3 m). In males, 24.8% settled within one home range length of their natal site and 49.6% settled further than two range lengths from their natal site. In femles, the respective percentages were reversed: 51.2% and 22.0%. The timing of large movements (≥50 m) was related to body mass in both sexes. The population density was always higher on the fed grid than on the control grid, which resulted in the frequency of large movements being greater on the fed grid that on the control grid. Thus, the percentage of voles performing a large movement was not different between the grids in both sexes.
Emergent and effective properties in ecology and evolution
Authors: Kawata Masakado
Published: November 2006

Emergent properties are often discussed in arguments concerning relationships among different levels. However, the different definitions of emergent properties sometimes confuse the arguments about macro‐level phenomena, since some authors regard emergent properties not only as observable global patterns but as properties that affect and cause change in ecological and evolutionary processes. Thus it is important to distinguish higher‐level or larger‐scale properties that can influence particular ecological and evolutionary processes from those that cannot. I call the former properties effective properties. I gave examples that show why the distinctions between effective and non‐effective properties are important.
Factors and consequences of a non‐functional alary polymorphism in Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)
Authors: Honěk Alois
Published: November 2006

Functional alary polymorphisms have been studied rather extensively in several insect species. This review article deals with factors controlling wing polymorphism in a flightless species, Pyrrhocoris apterus (L.), and discusses its adaptive significance and mechanisms for their persistence under natural conditions. The macropterous morph is determined by a recessive allele whose penetrance depends on photoperiod and temperature. Natural populations of this species contain a small fraction of flightless macropters. The disadvantages of being a macropter (increase of development time, decrease of fecundity) are minimal, while the benefit may consist in the tendency to prereproductive arrest of ovarian development in teneral females. It prevents establishing a second generation which would mostly die during the next winter. The mechanism of alary morph regulation may be an ancestral trait linking P. apterus with other polymorphic Heteroptera, while its decreased penetrance may be a derivative character. Variation in fitness due to alary morphs is small compared to the one associated with differences in body size. The latter is environmentally determined, and not linked to the genetic basis of wing polymorphism. In the “mosaic” of phenotypes of various size the significance of the genetic macroptery may be close to neutral.
The dynamics of laboratory populations of Callosobruchus chinensis and C. Maculatus (Coleoptera: Bruchidae) in patchy environments
Authors: Hassell M. P. , Taylor V. A. , Reader P. M.
Published: November 2006

Experiments are described showing the long‐term dynamics of two species of bruchid beetles (Callosobruchus chinensis and C. maculatus) in arenas in which the resource of 50 black‐eyed beans is divided between 5, 10 or 50 ‘patches’. Both species of adult beetles exhibit clumped distributions between patches. Within a patch there is a tendency for a density dependent reduction in (1) eggs laid per female, (2) the proportion of eggs hatching per bean (C. chinensis only) and (3) larval survival which is strongly overcompensating (particularly in C. maculatus). A discrete generation model is used as a framework to draw these results together and show how the different factors affecting natality and mortality can influence the population dynamics. Finally, the importance of the resource renewal interval in influencing the period of the population cycles is discussed.
A simulation study of population interaction between the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae), and the parasitoid Encarsia formosa gahan (Hymenoptera: Aphelinidae) I. Description of the model
Authors: Yano Eizi
Published: November 2006

A simple simulation model was developed to simulate the population dynamics of the system of the greenhouse whitefly (Trialeurodes vaporariorumWestwood) and the parasitoid Encarsia formosaGahan. On the assumption that temperature is constant, the whitefly population was described as theLeslie Matrix model. Parasitization and host feeding by the parasitoid population were modelled by means of a modified disc equation. The validity of the model was demonstrated by comparing the predictions of the model with the observed values obtained in greenhouse experiments.
A simulation study of population interaction between the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) and the parasitoid Encarsia formosaGahan (Hymenoptera: Aphelinidae) II. Simulation analysis of population dynamics and strategy of biological control
Authors: Yano Eizi
Published: November 2006

Simulation studies were performed to analyze factors affecting the population dynamics of the system with the greenhouse whitefly (Trialeurodes vaporariorumWestwood) and the parasitoid Encarsia formosaGahan and to develop strategies for the introduction of E. formosa. The reduction of parasitization efficiency with an increase in parasitoid density promotes the stability of the system, which coincides with the prediction from current theory. The stability of the system is also shown to be promoted by the effect of host feeding. The population levels of the system are remarkably suppressed with an increase in searching efficiency and a decrease in host oviposition. The control effect of the parasitoids is enhanced when the number of parasitoids is divided among many introductions. An optimal time, an optimal density ratio of parasitoids to hosts and optimal densities of hosts and parasitoids exist in the introduction programme of parasitoids.
Density‐dependent predation of the antLasius niger(Hymenoptera: Formicidae) on two attended aphidsLachnus tropicalisandMyzocallis kuricola(Homoptera: Aphididae)
Authors: Sakata Hiroshi
Published: November 2006

The antLasius nigerwas observed collecting honeydew and preying on the two aphid speciesLachnus tropicalisandMyzocallis kuricolaon the chestnut treesCastanea crenata. Observation determined how the antL. nigercontrolled their predation on the aphids in response to the density and honeydew‐productivity of the aphids.Lachnus tropicaliswas a better honeydew source thanM. kuricolaforL. nigerin terms of the amount of honeydew collected per unit time by the ants. The number of foraging workers on a tree increased with the number ofL. tropicalison the tree, but not with the number ofM. kuricola. The density ofL. tropicalisperL. nigerworker on a tree had a positive effect on the predation activity ofL. nigeron both aphids, whereas the density ofM. kuricolaper ant did not have any significant effect. The predation pressure by the ant which increased withL. tropicalisdensity, however, directed toM. kuricolarather than toL. tropicalis. These facts suggest (1) thatL. nigercontrol their predation activities on aphids with regards to the densities of the attended aphids per worker, and (2) that the ants prey on the aphid species producing less honeydew. The effects of the ant predation on aphids and the importance of these predation effect in antaphids interactions were discussed.
Variation in offspring size within a population of the web‐building spider Agelena limbata
Authors: Tanaka Koichi
Published: November 2006

Within a population of the web‐building spider Agelena limbata, the weight of the first instar nymphs ranged from 1.187 to 6.559 mg. Both intraclutch and interclutch variation were recorded. The mean weights were different among clutches and the coefficients of variation within a clutch ranged from 3.3 to 29.2%. Variation in the nymphal weight was certainly derived from variation in the egg weight because there was a high correlation between the two weights. Factors affecting interclutch variation in nymphal weight were examined by multiple regression analysis. Nymphal weight was positively correlated with the body size and food conditions of female parents, and negatively correlated with the clutch size. Among these three factors, the food conditions of female parents had the largest apparent effect on the interclutch variation. The results suggest that females with larger body size and more food produce larger offspring, and that there is a trade‐off between offspring size and clutch size. Heavier nymphs had larger body size (carapace width) and may have larger energy reserves. Heavier nymphs survived experimental starvation for a significantly longer period.
The role of the brown‐eared bulbul Hypsypetes amaurotis as a seed dispersal agent
Authors: Fukui Akiko W.
Published: November 2006

The role of the brown‐eared bulbul, Hypsypetes amaurotis, as a dispersal agent for seeds of fruiting plants was studied by field observations for two years, in parallel with laboratory experiments on seed germination. Bulbuls consumed fruits of 53 species from 24 plant families. The fruits of these plants had similar color and size, and these characteristics were likely to enhance the feeding efficiency of the frugivore. Laboratory experiments on 20 food plant species demonstrated that: (1) no seeds were injured by passing through the bulbul's gut; (2) seeds that had passed through the bulbul's gut were still able to germinate and (3) fruit pulp reduced germination ability. When pulp was removed by passing through bulbul's gut, or by hand, germination was improved. An estimate of the home range of six bulbuls suggested that they may transport seeds for at least 300 m.
The outbreak mechanisms of the green rice leafhopper, Nephotettix cincticeps Uhler, in northern Japan
Authors: Hirano Kohji , Fujii Koichi
Published: November 2006

Intraspecific regulatory processes keep the population of Nephotettix cincticeps stable at a low density in southern Japan. In northern Japan, however, the yearly population density of the insect fluctuates violently, and large outbreaks occasionally take place. To clarify the difference in the population dynamics between the two regions, we analyzed light‐trap and sweep‐net sampling records from prefectural and national agricultural experimental stations. The survival rate of the overwintering population decreased with increases in the period of continuous snow cover (PCSC) in the north, and initial population densities in the years of long PCSC were too low for populations to reach equilibrium density by the end of the active breeding season. This made yearly population fluctuations in the north much larger than in the south. The equilibrium density in the north was higher than in the south. The higher equilibrium density presumably permits the higher population density and larger yearly population fluctuations in the north. A major factor responsible for the difference in equilibrium densities between the two regions is the difference in heading dates of the host plant (rice). Qualitative differences among rice plant varieties, and among biotypes of N. cincticeps, may also be important.
Enzymatic extraction of mustard seed and rice bran
Authors: Sengupta R. , Bhattacharyya D. K.
Published: November 2006

Aqueous enzymatic extraction was investigated for recovery of oil from mustard seed and rice bran. The extraction process was reproducible based on statistical analysis of extraction data under different extraction conditions. The most significant factors for extraction were the time of digestion with enzymes, seed or bran concentration in water, volume of hexane added before recovery, and amount of enzyme(s) used. The pretreatment steps of each material before enzyme digestion influenced oil yield.

Quality of enzyme‐extracted mustard oil was better with respect to color and odor than commercial expeller‐extracted and Soxhlet‐extracted oils. Most of the characteristics of rice bran oil were identical to those of commercial solvent‐extracted oils, but rice bran oil had a lower content of colored substances and higher acidity (free fatty acid). Enzymatic extraction led to recovery of a protein concentrate with increased protein and reduced fiber and ash contents in the mustard and rice bran meals.
Analysis of the volatile fraction from sunflower oil extracted under pressure
Authors: Bocci F. , Frega N.
Published: November 2006

This study concerns the analysis of volatile components that may contribute to the formation of the flavor of the oil extracted from sunflower seeds. The compounds were trapped on a charcoal cartridge, then desorbed and analyzed by gas chromatography/mass spectrometry. The principal compounds were terpenes (about 225 mg/L) consisting of α‐pinene (80%), limonene (5%), sabinene (3.3%), β‐pinene (1.8%), 1,2,6,6‐tetramethyl‐1,3‐cyclohexadiene (1.5%), and camphene (1.2%). There were also a small amount of hexanal (1.3%) and traces (<1%) of unidentified compounds, which probably correspond to other terpenic hydrocarbons and to terpenic alcohols and/or aldehydes.
Potential margarine oils from genetically modified soybeans
Authors: List G. R. , Mounts T. L. , Orthoefer F. , Neff W. E.
Published: November 2006

Genetically modified soybeans were processed into finished, refined, bleached, and deodorized oils. Fatty acid composition was determined by gas‐liquid chromatography. Glyceride structure was characterized according to degree of unsaturation by high‐performance liquid chromatography, lipase hydrolysis, and gas‐liquid chromatography. Compared to common varieties with 15% saturated acids, genetically modified soybeans yielded oils containing 24–40% saturated acids. Several varieties were examined, including the Pioneer A‐90, Hartz HS‐1, and Iowa State A‐6 lines. Pioneer A‐90 contained 17% stearic acid, had a solid fat index (SFI) of 6.0 at 10°C (50°F) and zero from 21.1 to 40°C (70 to 104°F), and therefore lacked sufficient solids for tub‐type margarine. To improve its plastic range, the Pioneer oil was blended with palm oil, randomized palm oil, or interesterified palm/soy trisaturate basestock. After blending with 10–40% of these components, the high‐stearic acid oil had an SFI profile suitable for soft tube margarine. The A‐6 varieties, 32–38% saturates, showed SFI profiles with sufficient solids at 10°C (50°F) and 21.1°C (70°F) to qualify as a stick‐type margarine oil, but lacked sufficient solids at 33.3°C (92°F); however, after small amounts (2–3%) of cottonseed or soybean hardstocks were added, the A‐6 oils qualified as stick margarine oil. The HS‐1 variety, when blended with small amounts (2–3%) of hardstock, possessed sufficient solids at 10°–33.3°C (50–92°F) to prepare soft tub margarine oil.
A high‐field1H nuclear magnetic resonance study of the minor components in virgin olive oils
Authors: Sacchi R. , Patumi M. , Fontanazza G. , Barone P. , Fiordiponti P. , Mannina L. , Rossi E. , Segre A. L.
Published: November 2006

High‐field (600 MHz) nuclear magnetic resonance (NMR) spectroscopy was applied to the direct analysis of virgin olive oil. Minor components were studied to assess oil quality and genuineness. Unsaturated and saturated aldehyde resonances, as well as those related to other volatile compounds, were identified in the low‐field region of the spectrum by two‐dimensional techniques. Unsaturated aldehydes can be related to the sensory quality of oils. Other unidentified peaks are due to volatile components, because they disappear after nitrogen fluxing. The statistical analysis performed on the intensity of these peaks in several oil samples, obtained from different olive varieties, allows clustering and identification of oils arising from the same olive variety. Diacylglycerols, linolenic acid, other volatile components, water, acetic acid, phenols, and sterols can be detected simulteneously, suggesting a useful application of high‐field NMR in the authentication and quality assessment of virgin olive oil.
Conifer seeds: Oil content and fatty acid composition
Authors: Wolff Robert L. , Deluc Laurent G. , Marpeau Anne M.
Published: November 2006

The seed oils from twenty‐five Conifer species (from four families—Pinaceae, Cupressaceae, Taxodiaceae, and Taxaceae) have been analyzed, and their fatty acid compositions were established by capillary gas‐liquid chromatography on two columns with different polarities. The oil content of the seeds varied from less than 1% up to 50%. Conifer seed oils were characterized by the presence of several Δ5‐unsaturated polymethylene‐interrupted polyunsaturated fatty acids (Δ5‐acids) with either 18 (cis‐5,cis‐9, 18∶2,cis‐5,cis‐9,cis‐12 18∶3, andcis‐5,cis‐9,cis‐12,cis‐15 18∶4 acids) or 20 carbon atoms (cis‐5,cis‐11 20∶2,cis‐5,cis‐11,cis‐14, 20∶3, andcis‐5,cis‐11,cis‐14,cis‐17 20∶4 acids). Pinaceae seed oils contained 17–31% of Δ5‐acids, mainly with 18 carbon atoms. The 20‐carbon acids present were structurally derived from 20∶1n‐9 and 20∶2n‐6 acids. Pinaceae seed oils were practically devoid of 18∶3n‐3 acid and did not contain either Δ5‐18∶4 or Δ5‐20∶4 acids. Several Pinaceae seeds had a Δ5‐acid content higher than 50 mg/g of seed. The only Taxaceae seed oil studied (Taxus baccata) had a fatty acid composition related to those of Pinaceae seed oils. Cupressaceae seed oils differed from Pinaceae seed oils by the absence of Δ5‐acids with 18 carbon atoms and high concentrations in 18∶3n‐3 acid and in Δ5‐acids with 20 carbon atoms (Δ5‐20∶3 and Δ5‐20∶4 acids). Δ5‐18∶4 Acid was present in minute amounts. The highest level of Δ5‐20∶4 acid was found inJuniperus communis seed oil, but the best source of Δ5‐acids among Cupressaceae wasThuja occidentalis. Taxodiaceae seed oils had more heterogeneous fatty acid compositions, but the distribution of Δ5‐acids resembled that found in Cupressaceae seed oils. Except forSciadopytis verticillata, other Taxodiaceae species are not interesting sources of Δ5‐acids. The distribution profile of Δ5‐acids among different Conifer families appeared to be linked to the occurrence of 18∶3n‐3 acid in the seed oils.
Ambient‐temperature extraction of rice bran oil with hexane and isopropanol
Authors: Proctor A. , Bowen D. J.
Published: November 2006

Hexane and isopropanol were compared as solvents for use in ambient‐temperature equilibrium extraction of rice bran oil (RBO). Isopropanol was as effective as hexane in extracting RBO when 20 mL of solvent was used to extract 2 g of bran. Free fatty acid levels were 2–3% in both solvents and similar to that previously reported for hexane extraction of RBO hexane extraction by this method. Larger‐scale extractions with 30 g of bran and 150 mL of solvent produced oil with a similar free fatty acid content and a phosphorus level of approximately 500 ppm. The oil extracted with isopropanol was significantly more stable to heat‐induced oxidation than hexane‐extracted oil. Antioxidants that are more easily extracted by isopropanol than hexane may be responsible for the increased stability.
Comparative performance of steam and nitrogen as stripping gas in physical refining of edible oils
Authors: Ruiz‐Méndez M. V. , Márquez‐Ruiz G. , Dobarganes M. C.
Published: November 2006

Olive, sunflower, and soybean oils were physically refined in a discontinuous laboratory system with either nitrogen or steam as stripping gas during the deodorization step. Comparative assays were also carried out on olive oil in a 10‐MT discontinuous industrial plant. Vaporization efficiency of free fatty acids was calculated, and quality of refined oils and composition of deodorizer distillates were analyzed. Results indicated that, in all assays, the efficiency of free fatty acid distillation was higher when nitrogen was used. The amount of nitrogen needed was much lower than that of steam for refined oils of similar high quality. The results also suggested that the amount of stripping gas had a clear influence on the composition of deodorizer distillates because lower quantities of triglycerides and unsaponifiable matter were found when nitrogen was employed.
Chemical and thermal characteristics of milk‐fat fractions isolated by a melt crystallization
Authors: Dimick P. S. , Reddy S. Yella , Ziegler G. R.
Published: November 2006

Anhydrous milk fat (AMF) was fractionated by a two‐stage dry fractionation process to produce three fractions: high melting (HMF), middle melting (MMF), and low melting (LMF). The HMF (m.p. 42°C) exhibited a broad melting range similar to a plastic fat. The MMF (m.p. 33°C) resembled the original AMF (m.p. 31°C), but with slightly higher solid fat content. The LMF (m.p. 16°C) was liquid at ambient temperature. Differences in the thermal properties of these fractions were attributed to the triacylglycerols (TAG) and their fatty acid composition. Saturated TAG with carbon numbers of 36–54 were concentrated in the HMF; whereas unsaturated TAG of carbon number 36–54 predominated in the LMF. Likewise, the long‐chain saturated fatty acids were significantly higher and the long‐chain unsaturated fatty acids were significantly lower in the HMF fraction. Binary blends of milk‐fat fractions with a range of melting profiles were produced by mixing HMF with AMF, MMF, or LMF. Laboratory‐prepared fractions were similar to commercially available fractions.
Supercritical carbon dioxide extraction ofDimorphotheca pluvialis oil seeds
Authors: Cuperus F. Petrus , Boswinkel Gerard , Muuse Bart G. , Derksen Johannes T. P.
Published: November 2006

The possibility of extraction ofDimorphotheca oil with supercritical carbon dioxide is demonstrated in this article. Before extraction, the seeds have to be pretreated to improve extraction yield. Experiments showed that the best pretreatment procedure forDimorphotheca was heating the seeds under reduced pressure to 100°C for 60 min, followed by flaking or milling. To give an impression about the efficiency of the supercritical extraction, a mathematical model has been developed to estimate the overall mass transfer coefficient (ApK). Also, an empirical relation betweenApK and the interstitial velocity has been found. The physical properties of the supercriticalDimorphotheca oil are in good agreement with those of conventionally extracted oil, except for a lower phospholipid content. It is expected that further refining of supercriticalDimorphotheca oil will be marginal.