bluuebunny/crossref_metadata_2025 huggingface dataset:
How mosquitoes fly to man
Authors: Nishimura Masahiko
Published: October 2006

A model is presented to estimate the mosquito density and radius (r) of the attraction range of man as the bait.

Man walked to a spot in the woods and sampled mosquitoes flying to him with a net continuously. The arrival pattern was constant in each mosquito species, and in all species, the number of mosquitoes sampled per five min became constant after ten minutes sampling.

The mosquitoes gathered to man were composed of D: those waiting alight, I: those intruding the attraction range and F: those following man to the spot. They were estimated by means of continuous sampling sets and densities of D and I were calculated.

r s of female and male of A. albopictus and A. japonicus were 4.0, 5.6 and 9.0 m respectively. In these species, most individuals were D, although, in T. bambusa all individuals were I, flying to search for hosts.

How mosquitoes and hosts encounter, is discussed.
Local distribution of two species of Apodemus in Kyushu
Authors: Doi Teruo , Iwamoto Toshitaka
Published: October 2006

Local distributions of two species of Apodemus, A. argenteus and A. speciosus, were studied by the correct estimation of peak density of mice and the detailed description of the habitat. Multiple regression analysis is applied to these distributional data setting with four variables as altitude, forest type, relative cover of shrub layer and age of forest. The local densities of both species and the percentage abundance of A. argenteus can be completely predicted by use of the regression coefficients. The density of A. speciosus correlates with the altitude of habitats, and that of A. argenteus does with the age of forest. The mean relative cover of shrub layer influences the dominancy of A. argenteus when both species occur sympatrically.
Probability functions for components of the Dendroctonus frontalis—Host tree population system and their potential use with population models
Authors: Fargo W. S. , Wagner T. L. , Coulson R. N. , Cover J. D. , McAudle T. , Schowalter T. D.
Published: October 2006

Detailed investigation of the within‐tree population system of Dendroctonus frontalisZimmermann has resulted in a large data base consisting of abundance estimates for various life stages. This data base was used to construct histograms for transformed estimates and several life stage indices. Histograms were also constructed for transformed values of adult residence time, brood development time, and several host‐tree characteristics.

Probability and cumulative density functions of the Weibull distribution were fitted, in tandem, to the scaled frequencies and interval means for each histogram. The inverse cumulative function is known, and with a uniform random number generator, allows the selection of random deviates from each distribution.

This technique can be used for generating initial (starting) values in D. frontalis population models.
Use of a general model to examine control procedures for a cockroach population
Authors: Larter R. J. , Chadwick P. R.
Published: October 2006

A matrix model for populations is described. The model breaks the population into an appropriate number of stadia to allow for reproductive cycles and includes individual daily survival rates and simple density dependence together with migration. Mortality due to insecticidal treatments may be applied on specified days to simulate space spraying while residual insecticides may be simulated with constant or declining effect. The use of the model is exemplified using a simulated population of Blattella germanica with various treatment regimes. This simulation emphasised the importance of immigration.
Age‐specific survivorship analysis of Heliothis spp. Populations on cotton
Authors: Hogg David B. , Nordheim Erik V.
Published: October 2006

Population dynamics of Heliothis virescens (F.) and Heliothis zea (Boddie) (Lepidoptera: Noctuidae) eggs and larvae were studied for two years in a small plot of cotton, Gossypium hirsutum (L.). Due to morphological and ecological similarities, the pooled Heliothis population was considered for most of the analyses. Two generations of Heliothis eggs and larvae were completed during each year. Stage recruitment was estimated for the eggs and larval instars 2–6, and recruitment variances were estimated by a Monte Carlo method. A modified form of the Weibull distribution was developed and used as a model to characterize survivorship curves for each of the four Heliothis generations. A Type I survivorship curve (mortality rate increasing with age) was inferred for both Generation 1 (early season) data sets, whereas a Type II survivorship curve (mortality rate constant and thus independent of age) was inferred for both Generation 2 (late season) data sets. The shapes of the survivorship curves for the individual H. virescens and H. zea populations were inferred to be the same as those for the pooled populations. Analysis of the contributions of various factors to Heliothis stage‐specific mortality indicated that natural enemies (predators and parasites) and the availability of food for larvae were responsible for between‐generation differences in survivorship patterns.
Alternative risk‐taking styles: The case of time‐budgeting strategies of terrestrial gastropods
Authors: Rollo C. D. , Vertinsky I. B. , Wellington W. G. , Kanetkar V. K.
Published: October 2006

The terrestrial slugs Arion ater, Limax maximus and Ariolimax columbianus have similar morphological designs but differ remarkably in their life history tactics and behavioural time budgets. The adaptive value of particular risk‐taking styles was investigated using a comprehensive computer simulation model.

The model allowed each species' success (growth rates, food acquisition) and costs (distance travelled, hydration deficits, injury from aggressive encounters) to be evaluated in various types of weather (benign, harsh and surprise). This was interpreted in terms of the species' life history design. In addition, each species was simulated with the behavioural strategy of the other two species substituted for its natural programming.

The simulation experiments demonstrated how variations in a few simple rules could lead to divergent cost‐benefit consequences. The model also illustrated that coarsely‐tuned sensitivity to the environment may be better than finely‐tuned responses, depending on the animal's ability to respond quickly and the degree of risk.

The simulations suggested that competition has shaped the time‐budgeting tactics of A. ater and L. maximus. Each species actually performed better in harsh weather, using the behavioural program of the other. L. maximus is an aggressive species with a narrow, nocturnal activity period. The concentrated activity of L. maximus may allow it to displace competitors more effectively, whereas the broader time span of A. ater's activity may be necessary to avoid L. maximus.
Studies on the mating system of the winter cherry bug, Acanthocoris sordidus Thunberg (Heteroptera: Coreidae) II. Harem defence polygyny
Authors: Fujisaki Kenji
Published: October 2006

The mating system of the winter cherry bug, Acanthocoris sordidus, was analyzed precisely. As a result, it was found that male adults of this species establish a small territory for mating on the stem of host plant which harbors females. These males abandoned their territories soon after the disappearance of monopolized females. Thus it was confirned that the cue for the territorial establishment of males is the presence of females per se on the host plant. Moreover, most aggregations of adults observed on the host plant contained only a single male. This one‐male unit in the mating was named a harem. Harem holding males were usually big in body‐size and had a high chance of copulations. The defence behaviors of harem holding males, the mating disparity among males, and the oviposition habit of females in relation to the mating system, were observed. The results obtained were discussed in relation to the sexual selection theories.
The effects of food and density on the nocturnal behaviour of Arion ater and Ariolimax columbianus (Pulmonata: Stylommatophora)
Authors: Hamilton Peter A. , Wellington William G.
Published: October 2006

The effects of food supply and population density on the nocturnal behaviour of Arion ater and Ariolimax columbianus were investigated. Density did not significantly affect A. ater's level of activity or short‐term movement, resting, or feeding. A. columbianus was more active and moved, rested, and fed more frequently when slug density was high. A. ater foraged and rested more often, but fed less when good food was unavailable. Ariolimax's only response to the food regime was to feed more when good food was available. Seasonal changes in the level of activity and behaviour of Arion were evident, whereas Ariolimax's activity and behavioural repertoire were not similarly affected. Arion ater's nightly activity appeared to be mainly food oriented, while Ariolimax columbianus seemed most responsive to slug density during its nocturnal activity periods.
Estimation of the attraction range of a human bait for Aedes albopictus (Diptera, culicidae) adults and its absolute density by a new removal method applicable to populations with immigrants
Authors: Mogi Motoyoshi , Yamamura Norio
Published: October 2006

The attraction range of a human bait for Aedes albopictus (Diptera, Culicidae) adults and its absolute density in the range were estimated by a new removal method which is applicable to populations with immigrants. In this model, the number of mosquitoes removed during the kth collection unit yk, is expressed as
urn:x-wiley:14383896:pope0328:equation:pope0328-math-0001
where x0 is the initial number of mosquitoes in the attraction range, a is an index directly proportional to collection efficiency, b is the number of immgirants per collection unit and s(=e−a) is the survival rate of mosquitoes in the attraction range per collection unit. From the result of successive two collections with various interval distances, it was considered that Aedes albopictus adults are attracted to a human bait from the distance of 4–5 m in the bamboo forest on the calm day. The applicability of this method for the population census of forest mosquitoes was discussed.
Growth and survival rate of the larvae of Hynobius nebulosus Tokyoensis Tago (Amphibia, Hynobiidae)
Authors: Kusano Tamotsu
Published: October 2006

Growth and population density of the larvae, Hynobius nebulosus tokyoensisTago, were estimated in a small pond within the study site settled in Habu village of Hinodemachi, a suburb of Tokyo City, during the period from 1975 to 1980. The mortality factors which influenced the survival rate of larvae were also evaluated from the ecological point of view. Laboratory experiments on the growth of larvae and predation by newts were conducted in pararell with the field survey.

The results showed that growth rate of larvae under the natural condition was very slow, as compared with that under the laboratory condition with sufficient food supply, and mean body size at metamorphosis was negatively correlated with the density at that time. This suggested that food resources were in short supply in the pond, and there occurred a severe intraspecific competition for food among larvae.

The mortality rate of larvae was so high, 80–99% in each year, and the density of larvae survived until metamorphosis varied so greatly from year to year that the larval stage was the most important stage throughout the life cycle to the maintenance of a population for this salamander. The most important factors which contributed to this high mortality were the predation by the newt, Triturus pyrrhogaster pyrrhogasterBoie, and cannibalism. From the laboratory experiment, it was found that predators could attack only small larvae successfully, and successful attack rate decreased sharply as larvae grew larger. This relationship resulted in the characteristic L‐shaped pattern of survivorship curve of larvae; that is, heavy mortality just after hatching period.
On the mode of selection in Escherichia coli
Authors: Kosuda Kazuhiko
Published: October 2006

Competition experiments between a lac+ prototroph and a lac− auxotroph of Escherichia coli were conducted by serial transfer procedure on four levels of sugar concentration. Changes of the relative frequencies of both genotypes were followed and the relative fitness was estimated. Fitness was proved to be density‐dependent. No explicit dependence of fitness upon genotype frequencies could be detected by the simple method ofKosuda (1981).
Comparison of dispersal ability between the green leafhoppers, Nephotettix virescens and N. cincticeps (hemiptera: Cicadellidae) by tethered flight
Authors: Widiarta I Nyoman , Ikeda Tsuyoshi , Fujisaki Kenji , Nakasuji Fusao
Published: October 2006

Dispersal propensity of green leafhoppers was compared between a tropical species, Nephotettix virescens, and a temperate species, N. cincticeps. The flight ability was measured with tethered flight technique under laboratory conditions (25°C, 16L‐8D). The pre‐flight period was shorter and the flight duration was longer in N. virescens than in N. cincticeps in both sexes. No significant correlations were found between the flight activity and morphometric characters for either of the two species. The results suggested that dispersal propensity of N. virescens is higher than that of N. cincticeps.
Closed Rupture of the Flexor Tendons of the Index Finger Caused by A Pathological Fracture Secondary to an Intraosseous Ganglion in the Lunate
Authors: YAMAZAKI H. , KATO H. , MURAKAMI N.
Published: October 2006

We report a rare occurrence of attritional rupture of both flexor tendons of the right index finger in a 71 year-old man with a pathological fracture of the lunate arising from an intraosseous ganglion.
Antimicrobial resistance in non-typhoidal salmonellas from humans in Northern Ireland, 2001–2003: standardization needed for better epidemiological monitoring
Authors: ONG G. , WILSON I. , SMYTH B. , ROONEY P.
Published: October 2006

This study investigated the identification and antimicrobial susceptibility testing of Salmonella isolates in Northern Ireland during 2001–2003. All six participating hospital laboratories used similar methods. Identification and antimicrobial resistance of human enteric (n=897) Salmonella isolates were analysed by retrospective collation of laboratory records. Resistance of human Salmonella isolates to nalidixic acid was 16% but resistance to ciprofloxacin or cefotaxime was rare (<1%). Minor inter-laboratory variations in sensitivity testing practices make it difficult to compare antimicrobial sensitivity results reliably and also to monitor for epidemic clones such as S. Typhimurium DT104 with the ACSSuT resistance pattern. The outcome of this study was the adoption of a standardized regional approach to the isolation of salmonella antimicrobial resistance. This should improve epidemiological monitoring of epidemic clones and assure optimum treatment options are available. In cases of treatment failure, MICs to third-generation cephalosporins and ciprofloxacin should be determined.
Importance of planktonic community respiration on the carbon balance of the East China Sea in summer
Authors: Chen Chung‐Chi , Chiang Kuo‐Ping , Gong Gwo‐Ching , Shiah Fuh‐Kwo , Tseng Chun‐Mao , Liu Kon‐Kee
Published: October 2006

The East China Sea (ECS) is one of the largest continental shelves in the world; however, the role that biota plays in the carbon fluxes of this shelf ecosystem is still obscure. To evaluate the organic carbon balance and the roles played by planktonic communities in organic carbon consumption, two cruises with stations covering almost the entire shelf were conducted during the high productivity and high river flow season of the ECS in June (the early summer) and August (the middle summer) 2003. Results showed that biological activity was significantly higher in the early summer. To flourish in the early summer, plankton need a significant fluvial input of dissolved inorganic nutrients and organic matter from the Chinese coast, especially from the Changjiang (aka Yangtze River), might be one of the main driving forces. Further analysis showed that most planktonic community respiration (PCR) could be attributed to phytoplankton and bacterioplankton, which accounted for over 96% of the total planktonic biomass (in carbon units) in summer. This might partially explain why mean PCR was higher in June (∼114 mg C m−3 d−1), with higher phytoplankton biomass, than in August (∼40 mg m−3 d−1). The ratio of integrated primary production to PCR (i.e., the P/R ratio) was, however, less than 1, with a mean ± SD value of 0.35 ± 0.41 for all the pooled data. This indicates a significant amount of organic carbon has been regenerated through planktonic activity in the water column. The sea‐air difference in fCO2, however, changed from a mean value of −64.5 ± 61.3 ppm in June to 10.0 ± 37.5 ppm in August. To explain the contradictory results between PCR and fCO2, we suggest that the dissolved inorganic carbon regenerated through planktonic respiration could be stored in the subsurface layer and may affect the fCO2 in the surface water, which is what controls the shelf sea either as an atmospheric CO2 sink or as a source, depending on the prevailing physical forces. These results also suggest that the controversy between atmospheric CO2 sink or source in the ECS shelf needs further exploration.
Production of giant marine diatoms and their export at oceanic frontal zones: Implications for Si and C flux from stratified oceans
Authors: Kemp A. E. S. , Pearce R. B. , Grigorov I. , Rance J. , Lange C. B. , Quilty P. , Salter I.
Published: October 2006

From a synthesis of recent oceanic observations and paleo‐data it is evident that certain species of giant diatoms includingRhizosoleniaspp.Thalassiothrixspp. andEthmodiscus rexmay become concentrated at oceanic frontal zones and subsequently form episodes of mass flux to the sediment. Within the nutrient bearing waters advecting towards frontal boundaries, these species are generally not dominant, but they appear selectively segregated at fronts, and thus may dominate the export flux. AncientThalassiothrixdiatom mat deposits in the eastern equatorial Pacific and beneath the Polar Front in the Southern Ocean record the highest open ocean sedimentation rates ever documented and represent vast sinks of silica and carbon. Several of the species involved are adapted to a stratified water column and may thrive in Deep Chlorophyll Maxima. Thus in oceanic regions and/or at times prone to enhanced surface water stratification (e.g., during meltwater pulses) they provide a mechanism for generating substantial biomass at depth and its subsequent export with concomitant implications for Si export and C drawdown. This ecology has important implications for ocean biogeochemical models suggesting that more than one diatom “functional type” should be used. In spite of the importance of these giant diatoms for biogeochemical cycling, their large size coupled with the constraints of conventional oceanographic survey schemes and techniques means that they are undersampled. An improved insight into these key species will be an important prerequisite for enhancing our understanding of marine biogeochemical cycling and for assessing the impacts of climate change on ocean export production.
Vegetation patterns induced by random climate fluctuations
Authors: D'Odorico Paolo , Laio Francesco , Ridolfi Luca
Published: October 2006

Dryland vegetation is known for its ability to exhibit high degrees of spatial organization with well‐defined patterns of vegetated and unvegetated soil patches. Deterministic dynamics are usually invoked to explain the emergence of these patterns in arid ecosystems, while the effect of noise on the process of pattern formation has seldom been investigated. Relatively strong interannual rainfall fluctuations are a typical feature of dryland climates. Rainfall variability is commonly interpreted as a source of random disturbances for arid and semiarid vegetation, while its ability to play a more fundamental role in the process of vegetation pattern formation remains poorly understood. Here we show how random interannual climate fluctuations may indeed cause the emergence of vegetation patterns through the random alternation of stressed (i.e., water limited) and unstressed conditions. Thus, patterns emerge as a noise‐induced phenomenon from a mechanism of climate‐driven random switching of deterministic dynamics. Moreover, pattern formation is observed even when the deterministic dynamics of unstressed and stressed vegetation would ‐ separately ‐ lead to uniform spatial distributions of vegetation or bare soil.
Denitrification in the Arctic winter 2004/2005: Observations from ACE‐FTS
Authors: Jin J. J. , Semeniuk K. , Manney G. L. , Jonsson A. I. , Beagley S. R. , McConnell J. C. , Rinsland C. P. , Boone C. D. , Walker K. A. , Bernath P. F.
Published: October 2006

Arctic denitrification in the winter 2004/2005 is analyzed using measurements from the satellite instrument ACE‐FTS. Two methods based on changes in the correlations of odd nitrogen (NOy) versus methane and versus an artificial long‐lived tracer are employed. The observations show that significant denitrification occurred in the region 15 km–20 km and that it was spatially inhomogeneous within the polar vortex. Before the vortex breakup in mid‐March 2005 a maximum denitrification of 8 ± 0.8 ppbv, accounting for a relative reduction of over 50%, was observed at ∼450 K (∼17 km) using both methods. When averaged over the polar vortex for the first half of March, the denitrification at this level was about 4.4 ppbv and 5.0 ppbv from the artificial tracer method and the correlation method, respectively.
Modeling global O+ substorm injection using analytic magnetic field model
Authors: Jones S. T. , Fok M.‐C. , Brandt P. C.
Published: October 2006

During storm‐time substorms the IMAGE/High‐Energy Neutral Atom (HENA) global magnetospheric plasma imager observes dramatic rise and fall of the oxygen energetic neutral atom (ENA) fluxes in the 29–180 keV range that are well correlated with substorm onsets. The corresponding hydrogen ENA flux (10–198 keV) shows a much more gradual rise and fall. We use a three‐dimensional test particle code in time varying electric and magnetic fields to study mechanisms causing the dramatic oxygen variation. Consistent with our previous work, we find that nonadiabatic heating occurs during the dipolarization of the geomagnetic field. The simulation model reproduces key features including the high‐altitude increase of the ENA flux and enhancement timescale.
Changes in the vertical profile of the Indonesian Throughflow during Termination II: Evidence from the Timor Sea
Authors: Xu Jian , Kuhnt Wolfgang , Holbourn Ann , Andersen Nils , Bartoli Gretta
Published: October 2006

We use a multiproxy approach to monitor changes in the vertical profile of the Indonesian Throughflow as well as monsoonal wind and precipitation patterns in the Timor Sea on glacial‐interglacial, precessional, and suborbital timescales. We focus on an interval of extreme climate change and sea level variation: marine isotope (MIS) 6 to MIS 5e. Paleoproductivity fluctuations in the Timor Sea follow a precessional beat related to the intensity of the Australian (NW) monsoon. Paired Mg/Ca and δ18O measurements of surface‐ and thermocline‐dwelling planktonic foraminifers (G. ruber and P. obliquiloculata) indicate an increase of >4°C in both surface and thermocline water temperatures during Termination II. Tropical sea surface temperature changed synchronously with ice volume (benthic δ18O) during deglaciation, implying a direct coupling of high‐ and low‐latitude climate via atmospheric and/or upper ocean circulation. Substantial cooling and freshening of thermocline waters occurred toward the end of Termination II and during MIS 5e, indicating a change in the vertical profile of the Indonesian Throughflow from surface‐ to thermocline‐dominated flow.
Diatom productivity in the equatorial Pacific Ocean from the last glacial period to the present: A test of the silicic acid leakage hypothesis
Authors: Bradtmiller L. I. , Anderson R. F. , Fleisher M. Q. , Burckle L. H.
Published: October 2006

The silicic acid leakage hypothesis (SALH) suggests that during glacial periods, unused silicic acid escaped the Southern Ocean into the equatorial oceans, causing an ecological shift favoring diatoms relative to coccolithophorids and a drawdown of CO2. The 230Th normalized opal fluxes and 231Pa/230Th ratios were measured in eleven equatorial Pacific cores to reconstruct diatom productivity over the past 30 kyr and to test the SALH. Holocene spatial patterns of opal flux are strongly correlated with 231Pa/230Th ratios and with satellite estimates of primary productivity. Down‐core opal flux records do not support the SALH but show Holocene opal burial to exceed that of the late glacial period by 35%, or 2.8 Gt opal/kyr, across the equatorial Pacific. This suggests that the SALH may not account for lower atmospheric CO2 levels during the late glacial. However, the data do support results from previous studies that invoke increased El Niño–like conditions during this time.
Development of time resolved x-ray spectroscopy in high intensity laser-plasma interactions
Authors: Notley M. M. , Weber R. L. , Fell B. , Jeffries J. , Freeman R. R. , Mackinnon A. J. , Dickson R. , Hey D. , Khattak F. , Saiz E. Garcia , Gregori G.
Published: October 2006

This article discusses the design of a novel time resolved von Hamos Bragg spectrometer to provide spectra in the region around the titanium K-α and He-α lines. The instrument consists of a highly oriented pyrolitic graphite mosaic crystal coupled to a picosecond x-ray streak camera. Measurements of the time dependent behavior from Ti foils illuminated with intense laser pulses can be used to improve the understanding of recombination dynamics, electron transport, and phase transitions in strongly coupled dense plasma. This is important for the modeling of the compression phase in inertial confinement fusion research and the study of astrophysical environments.
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measurements using electron Bernstein wave thermal emission on NSTX
Authors: Diem S. J. , Taylor G. , Efthimion P. C. , LeBlanc B. P. , Carter M. , Caughman J. , Wilgen J. B. , Harvey R. W. , Preinhaelter J. , Urban J.
Published: October 2006

The National Spherical Torus Experiment (NSTX) routinely studies overdense plasmas with ne of (1–5)×1019m−3 and total magnetic field of <0.6T, so that the first several electron cyclotron harmonics are overdense. The electrostatic electron Bernstein wave (EBW) can propagate in overdense plasmas, exhibits strong absorption, and is thermally emitted at electron cyclotron harmonics. These properties allow thermal EBW emission to be used for local Te measurement. A significant upgrade to the previous NSTX EBW emission diagnostic to measure thermal EBW emission via the oblique B-X-O mode conversion process has been completed. The new EBW diagnostic consists of two remotely steerable, quad-ridged horn antennas, each of which is coupled to a dual channel radiometer. Fundamental (8–18GHz) and second and third harmonic (18–40GHz) thermal EBW emission and polarization measurements can be obtained simultaneously.
Bayesian design of plasma diagnostics
Authors: Dreier H. , Dinklage A. , Fischer R. , Hirsch M. , Kornejew P.
Published: October 2006

A framework for diagnostics design based on Bayesian probability theory is introduced. The design is assessed in figures of an expected utility which measures the information gain from measurements. The approach is applied on design studies for a multichord interferometer for Wendelstein 7-X.
Electron Bernstein wave simulations and comparison to preliminary NSTX emission data
Authors: Preinhaelter Josef , Urban Jakub , Pavlo Pavol , Taylor Gary , Diem Steffi , Vahala Linda , Vahala George
Published: October 2006

Simulations indicate that during flattop current discharges the optimal angles for the aiming of the National Spherical Torus Experiment (NSTX) antennae are quite rugged and basically independent of time. The time development of electron Bernstein wave emission (EBWE) at particular frequencies as well as the frequency spectrum of EBWE as would be seen by the recently installed NSTX antennae are computed. The simulation of EBWE at low frequencies (e.g., 16GHz) agrees well with the recent preliminary EBWE measurements on NSTX. At high frequencies, the sensitivity of EBWE to magnetic field variations is understood by considering the Doppler broadened electron cyclotron harmonics and the cutoffs and resonances in the plasma. Significant EBWE variations are seen if the magnetic field is increased by as little as 2% at the plasma edge. The simulations for the low frequency antenna are compared to preliminary experimental data published separately by Diem et al. [Rev. Sci. Instrum.77 (2006)]
Anomalous transport fluctuations in a model of irregular media
Authors: Ourrad O. , Erochenkova G. , Lima R. , Vittot M.
Published: October 2006

We consider a diffusion model with stochastic porosity for which the average solution exhibits an abnormal transport. In this paper we investigate the relation of such an anomalous diffusive property of the mean value with the behavior of the solution corresponding to each realization of the stochastic porosity. Such a solution will correspond to the actual measurements in an experiment made on a particular tube. The most relevant result of our work is that, although the concentration corresponding to each realization diffuses normally for large times, it experiments on large deviations from the mean value during intermediate times.
Multireference correlation in long molecules with the quadratic scaling density matrix renormalization group
Authors: Hachmann Johannes , Cardoen Wim , Chan Garnet Kin-Lic
Published: October 2006

We have devised a local ab initio density matrix renormalization group algorithm to describe multireference correlations in large systems. For long molecules that are extended in one of their spatial dimensions, we can obtain an exact characterization of correlation, in the given basis, with a cost that scales only quadratically with the size of the system. The reduced scaling is achieved solely through integral screening and without the construction of correlation domains. We demonstrate the scaling, convergence, and robustness of the algorithm in polyenes and hydrogen chains. We converge to exact correlation energies (in the sense of full configuration interaction, with 1–10μEh precision) in all cases and correlate up to 100 electrons in 100 active orbitals. We further use our algorithm to obtain exact energies for the metal-insulator transition in hydrogen chains and compare and contrast our results with those from conventional quantum chemical methods.
Electron-electron and electron-nucleus correlation effects on exponent values of Gaussian-type functions for quantum protons and deuterons
Authors: Ishimoto Takayoshi , Tachikawa Masanori , Nagashima Umpei
Published: October 2006

Electron-electron and electron-nucleus correlation effects on exponent (α) values of Gaussian-type functions (GTFs) for quantum protons and deuterons in BH3, CH4, NH3, H2O, and HF molecular systems and their deuterated counterparts were analyzed using the second-order Møller-Plesset (MP2) level of theory of the multicomponent molecular orbital (MCMO-MP2) method. This method can simultaneously determine both nuclear and electronic wave functions. Results showed that the average α value (αave) of the optimized α in single s-type ([1s]) GTF for a proton and a deuteron is similar to that determined using the Hartree-Fock level of the MCMO (MCMO-HF) method. In contrast, due to the electron-nucleus correlation effect, the s- and p-type ([1s1p]) GTFs are delocalized compared with those determined using the MCMO-HF method. For the H-bonded complexes, differences in the interaction energy induced by the H/D isotope effect were clearly evident because the D⋯Y bond distance for D complex is longer than the H⋯Y for H complex. Also, the basis set superposition error for the interaction energy in every H complex was similar to that in every D complex. The results here clearly demonstrate that the protonic and deuteronic basis functions based on αave values for correlation effects can be applied to the detailed analysis of the quantum effects of protons and the H/D isotope effect in widespread fields that involve H bonds and weak interactions, such as the function of biological molecules, chemical reaction processes, and the design of new materials.
Photodissociation of 1-bromo-2-butene, 4-bromo-1-butene, and cyclopropylmethyl bromide at 234nm studied using velocity map imaging
Authors: Lau Kai-Chung , Liu Yi , Butler Laurie J.
Published: October 2006

We present photofragment imaging experiments to characterize potential photolytic precursors of three C4H7 radical isomers: 1-methylallyl, cyclopropylmethyl, and 3-buten-1-yl radicals. The experiments use 2+1 resonance enhanced multiphoton ionization (REMPI) with velocity map imaging to state-selectively detect the Br(P3∕22) and Br(P1∕22) atoms as a function of their recoil velocity imparted upon photodissociation of 1-bromo-2-butene, cyclopropylmethyl bromide, and 4-bromo-1-butene at 234nm as well as the angular distributions of the photofragments. Energy and momentum conservation allows the internal energy distribution of the nascent momentum-matched radicals to be derived. The radicals are detected with single photon photoionization at 157nm. In the case of the 1-methylallyl radical the photoionization cross section is expected to be independent of internal energy in the range of 7–30kcal∕mol. Thus, comparison of the product recoil kinetic energy distribution derived from the measurement of the 1-methylallyl velocity distribution, detecting the radicals with 157nm photoionization, with a linear combination of the Br atom recoil kinetic energy distributions allows us to derive reliable REMPI line strength ratios for the detection of Br atoms and to test the assumption that the photoionization cross section does not strongly depend on the internal energy of the radical. This line strength ratio is then used to determine the branching to the Br(P3∕22) and Br(P1∕22) product channels for the other two photolytic systems and to determine the internal energy distribution of their momentum-matched radicals. (We also revisit earlier work on the photodissociation of cyclobutyl bromide which detected the Br atoms and momentum-matched cyclobutyl radicals.) This allows us to test whether the 157nm photoionization of these radicals is insensitive to internal energy for the distribution of total internal (vibrational+rotational) energy produced. We find that 157nm photoionization of cyclopropylmethyl radicals is relatively insensitive to internal energy, while 3-buten-1-yl radicals show a photoionization cross section that is markedly dependent on internal energy with the lowest internal energy radicals not efficiently detected by photoionization at 157nm. We present electronic structure calculations of the radicals and their cations to understand the experimental results.
Kinetics of droplet condensation through a double free-energy barrier
Authors: Valencia Antoni
Published: October 2006

Results are presented for the kinetics of nucleation of liquid droplets from a one-component vapor phase on a planar lyophobic substrate patterned with a large number of easily wettable (lyophilic) circular domains. If the wettability of these lyophilic domains is characterized by a contact angle smaller than π∕2, for intermediate values of the supersaturation, the condensation of a droplet on a lyophilic domain occurs through a free-energy barrier with two maxima, that is, through a double barrier. A simple model is proposed for the kinetics of droplet condensation through a double barrier that combines Kramers’s [Physica (Utrecht) 7, 284 (1940)] transition rate theory with known results of nucleation theory. In the framework of this model, the solution is derived for the steady-state limit of the nucleation process. The number of lyophilic domains available for droplet condensation reduces with time as domains are occupied by droplets. The problem of droplet condensation through a double barrier is solved taking into account the effect of the time-dependent depletion in the number of available lyophilic domains.
Condensed phase ionic polarizabilities from plane wave density functional theory calculations
Authors: Heaton Robert J. , Madden Paul A. , Clark Stewart J. , Jahn Sandro
Published: October 2006

A method is presented to allow the calculation of the dipole polarizabilities of ions and molecules in a condensed-phase coordination environment. These values will be useful for understanding the optical properties of materials and for developing simulation potentials which incorporate polarization effects. The reported values are derived from plane wave density functional theory calculations, though the method itself will apply to first-principles calculations on periodic systems more generally. After reporting results of test calculations on atoms to validate the procedure, values for the polarizabilities of the oxide ion and various cations in a range of materials are reported and compared with experimental information as well as previous theoretical results.
Ultraviolet photoluminescence from Gd-implanted AlN epilayers
Authors: Zavada J. M. , Nepal N. , Lin J. Y. , Jiang H. X. , Brown E. , Hömmerich U. , Hite J. , Thaler G. T. , Abernathy C. R. , Pearton S. J. , Gwilliam R.
Published: October 2006

Deep ultraviolet emission from gadolinium (Gd)-implanted AlN thin films has been observed using photoluminescence (PL) spectroscopy. The AlN epilayers were ion implanted with Gd to a total dose of ∼6×1014cm−2. Using the output at 197nm from a quadrupled Ti:sapphire laser, narrow PL emission was observed at 318nm, characteristic of the trivalent Gd ion. A broader emission band, also centered at 318nm, was measured with excitation at 263nm. The PL emission intensity decreased by less than a factor of 3 over the sample temperature range of 10–300K and decay transients were of the order of nanoseconds.
Electronic delocalization and resonant transmission in symmetric metallic nanowires
Authors: Zhang R. L. , Peng R. W. , Cao L. S. , Wang Z. , Tang Z. H. , Zhang X. F. , Wang Mu , Hu A.
Published: October 2006

We report here the theoretical studies on electronic delocalization and resonant transmission in symmetric metallic nanowires (SMNs). Resonant transmissions, which are characterized by multiple perfect transmission peaks, have been found in the electronic band gap. The resonant energy and the number of modes of resonant transmission therein can be manipulated, and the quality factor of the perfect transmission peak can be exponentially increased. We suggest that the resonant transmission originates from the electronic delocalization in SMNs, which is characterized by the extended wave function of electrons around the resonant energy. These features open a unique way to control quantum transport in nanodevices.
Defect structure in micropillars using x-ray microdiffraction
Authors: Maaβ R. , Grolimund D. , Van Petegem S. , Willimann M. , Jensen M. , Van Swygenhoven H. , Lehnert T. , Gijs M. A. M. , Volkert C. A. , Lilleodden E. T. , Schwaiger R.
Published: October 2006

White beam x-ray microdiffraction is used to investigate the microstructure of micron-sized Si, Au, and Al pillars fabricated by focused ion beam (FIB) machining. Comparison with a Laue pattern obtained from a Si pillar made by reactive ion etching reveals that the FIB damages the Si structure. The Laue reflections obtained from the metallic pillars fabricated by FIB show continuous and discontinuous streakings, demonstrating the presence of strain gradients.
Silicon micromachined periodic structures for optical applications at λ=1.55μm
Authors: Barillaro G. , Diligenti A. , Benedetti M. , Merlo S.
Published: October 2006

In this letter, the authors report the design, fabrication, and characterization of a silicon micromachined periodic structure for optical applications at λc=1.55μm. The microstructure, which can be envisioned as a one-dimensional photonic crystal, is composed of a periodic array of 1-μm-thick silicon walls and 2-μm-wide air gaps, each one corresponding to a different odd number of quarter wavelength at λc (hybrid quarter wavelength). The fabrication is based on the electrochemical etching of silicon, yielding parallel trenches with depths up to 100μm. Preliminary reflectivity measurements show the presence of a band gap at λc=1.55μm, as theoretically expected.
Theoretical analysis of electric field effect on Young’s modulus of nanowires
Authors: Zheng Xiaojing , Zhu Linli
Published: October 2006

The effect of an applied electric field on Young’s modulus of nanowires is investigated in this letter. The exact and analytical expressions of the transverse and axial Young moduli of a nanowire in an applied electric field are derived with the aid of the surface energy arising from the charges distributed on the surfaces of the nanowire. The results reveal that the transverse and axial Young moduli of a nanowire in an applied electric field are different from those of a nanowire in the absence of the field. The effect of the electric field on Young modulus is related to the intensity of the field, the size of the wire, and the direction of the wire.
Controlled growth of Co nanoparticle assembly on nanostructured template Al2O3∕NiAl(100)
Authors: Lin Wen-Chin , Wong Shen-Shing , Huang Po-Chun , Wu Chii-Bin , Xu Bin-Rui , Chiang Cheng-Tien , Yen Hong-Yu , Lin Minn-Tsong
Published: October 2006

Based on the systematic studies of the growth temperature, deposition rate, and annealing effects, the control of Co nanoparticle density, size, and alignment is demonstrated to be feasible on a nanostructured template Al2O3∕NiAl(100). At 140–170K, a slow deposition rate (0.027ML∕min) promises both the linear alignment and the high particle density. 1.5 ML Co nanoparticle assembly sustains the density of ∼260∕104nm2 even after 800–1090K annealing. This study also indicates the possibilities of the controlled growth for nanoparticles of different materials.
Utilization of water/alcohol-soluble polyelectrolyte as an electron injection layer for fabrication of high-efficiency multilayer saturated red-phosphorescence polymer light-emitting diodes by solution processing
Authors: Wang Lei , Liang Bo , Huang Fei , Peng Junbiao , Cao Yong
Published: October 2006

Highly efficient multilayer red polymer light-emitting diodes were fabricated by solution process-ing from iridium complex, bis(1-(3-(9,9-dimethyl-fluorene-2-yl)phenyl)isoquinoline-C2,N′) iridium(III)acetylacetonate, doped into polyfluorene as a host and with a water/alcohol-soluble polymer, poly[(9,9-bis(3′-((N,N-dimethyl)-N-ethylammonium)propyl)-2,7-fluorene)-2,7-(9,9-dioctylfluorene)-4,7-(2,1,3-benzoselenadiazole)]dibromide (PFN) as electron injection layer. The device with the structure ITO∕PEDOT-PSS(50nm)∕PVK(40nm)∕PFO:PBD:Ir(DMFPQ)2acac(2%,75nm)∕PFN(20nm)∕Ba(4.5nm)∕Al(150nm) showed an external quantum efficiency of 18.0% and luminance efficiency of 9.8Cd∕A at a current density of 1.1mA∕cm2, a peak emission at λmax=636nm, and Commission International de I’Eclairage coordinates of (0.665, 0.319). The efficiency remained as high as QE=11.1%, and LE=6.0cd∕A, at a current density of 100mA∕cm2, and a luminance of 6140cd∕m2.
Band gap properties of Zn1−xCdxO alloys grown by molecular-beam epitaxy
Authors: Wang X. J. , Buyanova I. A. , Chen W. M. , Izadifard M. , Rawal S. , Norton D. P. , Pearton S. J. , Osinsky A. , Dong J. W. , Dabiran Amir
Published: October 2006

Optical absorption and reflectance measurements are performed to evaluate compositional and temperature dependences of band gap energies of Zn1−xCdxO alloys grown by molecular-beam epitaxy. The compositional dependence of the band gap energy, determined by taking into account excitonic contributions, is shown to follow the trend Eg(x)=3.37−2.82x+0.95x2. Incorporation of Cd was also shown to somewhat slow down thermal variation of the band gap energies, beneficial for future device applications.
X-ray photoelectron spectroscopy study of dielectric constant for Si compounds
Authors: Hirose K. , Kihara M. , Kobayashi D. , Okamoto H. , Shinagawa S. , Nohira H. , Ikenaga E. , Higuchi M. , Teramoto A. , Sugawa S. , Ohmi T. , Hattori T.
Published: October 2006

The authors measure the difference of core-level binding energy shifts for Si 1s and Si 2p, ΔE1s-ΔE2p, for various Si compounds using high-resolution high-energy synchrotron radiation. They find that the ΔE1s-ΔE2p values are in very good correlation with the dielectric constant values of the Si compounds. Using this relation, they deduce the local dielectric constant for each of the Si intermediate oxidation states formed at the SiO2∕Si interface. The results are in good agreement with values predicted by a first-principles calculation.
The Measurement of Migration, from Census Data and other Sources
Authors: Rees P H
Published: October 2006

In the first part of the paper a general classification of migration measures is introduced. The rates corresponding to these measures are defined together with the associated populations at risk. A particular problem in migration analysis is then tackled. The questions asked in the British censuses of 1966 and 1971 about migration generate tabulations of migrants over the one year, and over the five years, preceding the census date. It is often observed that the numbers of migrants in the two periods are not linearly related; that is, the number of migrants over five years is less than five times the number over one year. A simple stochastic model embodying population-accounting principles is developed to show why this is the case, and that the relationship between one-year and five-year figures is a complex one involving some multiple migrations, some return migrations, and some deaths.
Optimum and Market Equilibrium in a Model of a City without a Predetermined Center
Authors: Borukhov E , Hochman O
Published: October 2006

Most of the recent theoretical literature on the internal structure of cities has assumed that a city is organized around a predetermined center, and that all traffic in the city is oriented toward that point. This is an oversimplification. It is not correct that all traffic in modern cities either goes to the center or comes from the center. In this paper we assume that every individual travels to every location in the city. The individuals choose locations that minimize the sum of their transportation and housing expenditures. Results are obtained for a social optimization and for a competitive equilibrium. In both cases there is a center where the density and land prices are higher; the density decreases with distance from this center. The optimal city is more dense than the ‘competitive’ one owing to externalities which are not taken into account in the latter case.
Measuring Accessibility: A Review and Proposal
Authors: Pirie G H
Published: October 2006

An attempt is made to clarify some of the confusion about the notion of accessibility by examining the limitations, strengths, and conceptual bases of distance, topological, gravity, and cumulative-opportunity measures of accessibility. In their aggregate and disaggregate states the measures are practical, enabling measurement into the future and measurement with a minimum of data, but the assumptions that all nodes are potential destinations and that all origins are known severely restrict the meaning and uses of the measures. Time—space measures of accessibility do not make these assumptions although they are data hungry, retrospective, and share with the other measures the narrow conception of accessibility as a property of the built environment. It is proposed that accessibility be thought of as a vacancy in an activity routine and that it be measured in terms of the disruption involved in creating it.