bluuebunny/crossref_metadata_2025 huggingface dataset:
Secretory avocado idioblast oil cells: evidence of their defensive role against a non‐adapted insect herbivore
Authors: Rodriguez‐Saona Cesar , Trumble John T.
Published: October 2003

We tested the hypothesis that avocado idioblast oil cells play a defensive role against herbivorous insects. Toxicities of the intact avocado idioblast oil cells and the extracted idioblast oil were compared for three insect herbivores. Spodoptera exigua (Hübner) larvae are generalists that do not feed on avocados. By contrast, Sabulodes aegrotata (Guenée) and Pseudoplusia includens (Walker) larvae are generalist herbivores that readily feed on avocados. All bioassays were performed at a naturally occurring concentration of idioblast oil cells (2% w/w). Choice experiments showed that S. exigua larvae avoided diet treated with avocado idioblast oil cells and consume more control than treated diet. In contrast, idioblast oil cells had no significant antifeedant effects on the adapted S. aegrotata and P. includens larvae. Subsequent experiments designed to assess resistance mechanisms separated pre‐ingestive (behavioral) and post‐ingestive (physiological) effects of the avocado idioblast oil cells, and the extracted idioblast oil, on the two adapted herbivores. Post‐ingestive adaptation was the mechanism that allows feeding. Because the impact of the avocado idioblast oil cells was greatest on the performance of non‐adapted S. exigua, additional experiments determined that larvae fed diet containing the oil cells had higher mortality and reduced larval growth compared to controls. Developmental times were significantly prolonged for the survivors. Thus, increased mortality, reduced developmental rates, and antifeedant activity in the non‐adapted insect indicate that defense against non‐adapted herbivores may be an important function of idioblast cells in avocados.
Susceptibility of Megalurothrips sjostedti developmental stages to Metarhizium anisopliae and the effects of infection on feeding, adult fecundity, egg fertility and longevity
Authors: Ekesi S. , Maniania N.K.
Published: October 2003

The susceptibility of immature stages of the legume flower thrips, Megalurothrips sjostedti, to the entomopathogenic fungus Metarhizium anisopliae, was investigated under laboratory conditions. The adult stage was found to be more susceptible to infection than the larval and pupal stages. Mortality at all stages was dose‐dependent, with the highest concentration of 1×108 conidia ml−1 producing the highest mortality (26, 46 and 100% for larvae, pupae and adults, respectively) at 8 days post‐inoculation. At the same concentration, daily pollen consumption was significantly reduced at 2 days after treatment in infected adults but more slowly in infected larvae. Fecundity, egg fertility and longevity in adults surviving infection as larvae were significantly reduced compared to the control.
Summer dormancy ensures univoltinism in the predatory bug Picromerus bidens
Authors: Musolin Dmitry L. , Saulich Aida H.
Published: October 2003

The seasonal cycle of Picromerus bidens L. (Heteroptera: Pentatomidae) is usually considered to be univoltine with an obligatory winter egg diapause. Seasonal adaptations of the species were studied in the laboratory and in field experiments. When reared under short‐day photoperiodic conditions (L12:D12 and L14:D10), all females began to lay eggs synchronously soon after their emergence. However, in the females reared under long‐day conditions (L18:D6 and L20:D4) and outdoors in June–July, oviposition was significantly delayed. This delay in reproduction induced by photoperiodic conditions and then spontaneously terminated was considered to be aestivation. Egg batches laid by females in the laboratory and in the field were kept at 25 °C for two months. From 30.8 to 93.8% of batches contained eggs which hatched without cold treatment between day 14 and 60 after oviposition. The proportion of eggs hatched was 17.7 to 20.9% in the short‐day regimes, while it was significantly less (5.7 to 6.0%) under long‐day conditions. It is concluded that in some eggs diapause is of low intensity and that if under natural conditions the first batches had been laid at the end of June, nymphs would have hatched at least from some eggs during the same season even without cold treatment. Such untimely hatching would have resulted in the death of nymphs and adults unprepared for overwintering. A photoperiodic response which induces aestivation in the early emerging adults in June–August may prevent early oviposition and occurrence of a second generation and thus maintains univoltinism in P. bidens.
Interpopulation variation in Chrysoperla carnea reproduction: implications for mass‐rearing and storage
Authors: Chang Yin‐Fu , Tauber Maurice J. , Tauber Catherine A. , Nyrop Jan P.
Published: October 2003

To determine whether diverse populations and biotypes of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) can be mass‐produced and stored under uniform conditions, we assessed reproduction in five North American populations, four from the carnea biotype and one from the mohave biotype. Non‐diapause adults from the carnea biotype varied significantly in only one aspect of reproduction, viz., the preoviposition period, whereas the duration and rate of oviposition, as well as fecundity, did not vary significantly. Relative to the carnea populations, the mohave population typically had delayed oviposition and a lower rate of oviposition; however, its oviposition period was long, and thus its fecundity differed only from that of the most productive carnea populations.

The shelf‐life (= survival during storage, and subsequent survival and reproduction after storage) was evaluated for four populations of the carnea biotype. Survival of diapausing adults during the first 18 weeks of storage was high among all four populations; adults from three populations also showed high survival after 35 weeks of storage. A high incidence of females from all four populations laid some fertile eggs after being stored for up to 31 weeks or longer. After six or more weeks of storage, average fecundity was high and ranged from ∼400–900 eggs/female. Duration of storage (up to 39 weeks) was a significant determinant of fecundity in two of the four populations.

In practice, diverse populations of C. carnea can be efficiently mass‐produced (with or without storage) under uniform conditions in the insectary. Thus, the choice of which populations to mass‐produce and use in augmentation can be based primarily on the characteristics (e.g., climate, habitat, crop) of the intended area of release, rather than on considerations concerning mass‐rearing.
Effect of host density, temperature, and photoperiod on the fitness of Anagyrus kamali, a parasitoid of the hibiscus mealybug Maconellicoccus hirsutus
Authors: Sagarra L.A. , Vincent C. , Peters N.F. , Stewart R.K.
Published: October 2003

The peformance of the parasitoid Anagyrus kamali Moursi [Hymenoptera: Encyrtidae], as a function of host density, temperature, and photoperiod was investigated with the objective to optimize a mass‐rearing system in the context of a biological control program. The number of hosts parasitized at densities varying from 2–100 hibiscus mealybug (HMB), Maconellicoccus hirsutus Green [Homoptera: Pseudococcidae], corresponded to a type II‐III functional response in fixed‐time conditions and a type III in variable‐time conditions. Twenty‐six percent of the oviposited eggs led to progeny emergence with a sex ratio of 0.49±0.102 (M/F), regardless of host density. Fecundity and oviposition period under six abiotic combinations (i.e., two temperatures (26±2 °C and 32±2 °C) and three photoperiods (L0:D24, L12:D12, L24:D0)) were measured. Lifetime fecundity and reproductive life were significantly affected by temperature and photoperiod conditions. Optimum female parasitoid lifetime fecundity was attained at 26±2 °C, L0:D24 with an average of 116.1±17.43 eggs. At 32±2 °C, L24:D0 and L12:D12, an average of 79.4±34.57 and 85.8±35.81 eggs were laid, respectively. Reproductive longevity was maximal at 26±2 °C, L0:D24 with 12±4.85 days of oviposition. Because the parasite A. kamali can be reared optimally without light, this may save tremendous energy costs.
Metapopulation dynamics in an aphid‐parasitoid system
Authors: Weisser Wolfgang W.
Published: October 2003

Metapopulation theory makes a number of predictions concerning the effects of dispersal on the persistence of predator‐prey or host‐parasitoid systems. While the stabilising effects of dispersal have been shown in a number of laboratory studies, evidence from field studies remains scarce due to a lack of suitable model systems. I describe a host‐parasitoid system that shows a classical metapopulation structure with frequent extinctions and colonisations consisting of the aphidiid Lysiphlebus hirticornis and the aphid Metopeurum fuscoviride. Both the parasitoid and the aphid are specialists on their respective hosts. I followed the dynamics of host and parasitoid on individually marked tansy (Tanacetum vulgare) plants, the host of M. fuscoviride. Dynamics of host and parasitoid populations were characterized by frequent extinctions and colonisations. Mean longevity of aphid colonies was only 3.1 weeks. Parasitism by L. hirticornis was a main cause of extinction for the aphid as rates of parasitism often reached 100%, in particular towards the end of the field season. Patchiness in this system occurs at two spatial scales. Aphid colonies form on single tansy ramets = shoots but movements of aphid individuals among ramets within a particular tansy genet are frequent. Because aphids can persist on a genet for a large numer of generations, it is argued that local populations form on genets rather than ramets. The number of host and parasitoid extinctions described in this study exceeds the number of extinctions usually observed in field studies of host‐parasitoid metapopulations. It is suggested that aphid‐parasitoid systems such as the one studied in this paper may be good models to test the predictions of metapopulation theory.
Influence of previous herbivory on behavior and development of Spodoptera exigua larvae on glanded and glandless cotton
Authors: McAuslane Heather J. , Alborn Hans T.
Published: October 2003

We examined the influence of previous herbivore injury on the feeding behavior, survival and development of larval beet armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae), on glanded and glandless ‘Stoneville 213’ cotton, Gossypium hirsutum L. In a greenhouse study, neonate S. exigua placed on the terminal foliage of glanded cotton plants moved down the plant to feed on older leaves. The location of feeding was more concentrated towards the bottom of the plant on previously damaged plants than on undamaged control plants. In contrast, larval feeding on glandless plants was evenly distributed within the plant and no difference in distribution was noted on plants that had sustained previous herbivore injury when compared to undamaged plants. In a laboratory study, where larvae were offered one type of foliage in a no‐choice situation, survival on young or mature leaves from glanded or glandless plants, with or without previous herbivore injury, did not differ significantly. However, pupae of larvae reared on young leaves of damaged glanded cotton weighed significantly less than pupae from larvae fed all other diets. Pupae from larvae fed young leaves of control glandless plants weighed significantly more than pupae from all other diets. Similar trends were observed in adult weights. In addition, time to pupation and time to adult emergence were significantly longer for larvae fed young leaves from damaged glanded plants compared to all other diets. The experiments reported here link larval feeding behavior of S. exigua to performance. Larval feeding preferences changed following induction of systemic defense such that food choice was optimized for growth.
Biotypes of Dasineura tetensi, differing in ability to gall and develop on black currant genotypes
Authors: Hellqvist Sven
Published: October 2003

Variation in damage levels on certain black currant, Ribes nigrum L., genotypes, caused by the black currant leaf midge, Dasineura tetensi (Rübs.) (Diptera: Cecidomyiidae), has been observed in northern Sweden. I investigated whether this variation is due to variation in virulence among midges. From a field population of midges, I successfully selected for virulence and avirulence, respectively, on the resistant black currant genotype cultivar ‘Storklas’ (called resistant genotype). The performance of avirulent and virulent midge larvae on two black currant genotypes were studied in experiments where first or second instar larvae were artificially transferred. There were no differences in larval survival and developmental rate between the two midge types when transferred to the susceptible currant genotype ‘7801–31’ (called susceptible genotype). Larvae of the virulent strain established galls and developed on ‘Storklas’ but development was initially slower there than on the susceptible currant genotype. Larvae of the avirulent strain suffered high mortality or remained in first instar on that same currant genotype when transferred alone, but developed readily if transferred together with virulent larvae. Larvae transferred in second instar to host plants susceptible to the larvae resumed feeding and developed further to maturity. Second instar larvae were also able to establish new galls even though these galls were not as well developed as those caused by first instar larvae. Black currant plantations in northern Sweden were surveyed and local midge populations were found to be composed of either avirulent, virulent or a mixture of both midge types. Virulent midges were not restricted to plantations where resistant currant genotypes were grown. I conclude that, at least, two biotypes of the midge exist, and that those two are distinguished by the ability to gall and survive on ‘Storklas’.
Is the parasitization capacity of Trichogramma cordubensis influenced by the age of the females?
Authors: Garcia Patrícia Ventura , Wajnberg Eric , Oliveira Maria Luísa Melo , Tavares João
Published: October 2003

We investigated the parasitization capacity of Trichogramma cordubensis Vargas & Cabello (Hymenoptera: Trichogrammatidae) females aged 24 h, 48 h, 72 h, 96 h, 120 h, and 144 h, using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs as hosts. Wasps were held without hosts during the period of ageing, therefore being increasingly time‐limited with respect to parasitization as they got older. The total number of parasitized hosts decreased as the age of the parasitoid increased. However, the proportion of lifetime parasitism carried out on the first day increased with wasp age, up to 120‐h old females. These results show that the parasitization capacity of ageing T. cordubensis females changes as they become time‐limited. The consequences of such changes for biological control programs are discussed.
Prostephanus truncatus mate choice on contact: does pheromone signalling by males affect their mating success?
Authors: Birkinshaw L.A. , Smith R.H.
Published: October 2003

Prostephanus truncatus is an economically important beetle pest of stored maize and cassava in the tropics. Male beetles signal using an aggregation pheromone that attracts both female and male beetles over large distances. Females preferentially orientate towards the pheromone signals of particular males when given a choice. The influence of pheromone signalling on courtship and mating success was investigated using pheromone biossays and mating trials in both of which a female made a choice between two males. Signalling was manipulated by exposing males to a Female Factor that inhibits pheromone production. The relative attractiveness of males to females based on pheromone bioassays was found not to influence short‐range courtship behaviour or mating success.
Comparative sensitivity of larval mosquitoes to vegetable polyphenols versus conventional insecticides
Authors: Rey D. , David J.P. , Besnard G. , Jullien J.L. , Lagneau C. , Meyran J.C.
Published: October 2003

The larvicidal effects of polyphenols of natural crude decomposed alder leaf litter and commercially available tannic acid were experimentally compared with those of two common conventional insecticides (Bacillus thuringiensis ssp. israelensis: microbial insecticide; temephos: organophosphate insecticide). Comparative standard bioassays using third instar larval Aedes aegypti, A. albopictus, Culex pipiens and Coquillettidia richiardii as references indicated that Aedes and Culex taxa are far more sensitive to alder leaf litter than to tannic acid and conventional insecticides. C. richiardii is far more resistant to conventional insecticides than Aedes and Culex taxa, but its sensitivity to tannic acid is close to that of those taxa. Dietary vegetable polyphenols are thus proposed as new, practical, alternative chemicals for mosquito control when conventional insecticides are difficult and costly to be used (e.g., in the management of Aedes and Culex populations in man‐made breeding sites and Coquillettidia control strategy).
Temperature and humidity responses of the arctic‐alpine seed bug Nysius groenlandicus
Authors: Böcher Jens , Nachman Gösta
Published: October 2003

Field observations in Greenland as well as arena choice experiments showed that the arctic‐alpine seed bug Nysius groenlandicus (Zetterstedt) (Heteroptera: Lygaeidae) is markedly xerophilous and thermophilous, preferring temperatures around 30 °C. Some variation in thermo‐preference was found among individuals from different localities in Greenland. Individuals from an inland locality (Søndre Strømfjord/Kangerlussuaq) had the highest temperature preference. Exposing individuals to rising temperature showed very high thresholds for excessive activity (ca. 41 °C), heat stupor (ca. 51 °C) and death (ca. 52 °C). All stages initially preferred the lowest humidity obtainable but gradually changed to higher humidities. The youngest nymph stages were most tolerant to desiccation. The observed preferences are interpreted as adaptations to a habitat where a warm and dry microclimate allows this obligatorily univoltine species to complete its life cycle within one year. The paper presents some general statistical approaches to analyses of behavioural responses to environmental gradients.
Host frass as arrestant chemicals in locating host Mythimna separata by the tachinid fly Exorista japonica
Authors: Tanaka Chiharu , Kainoh Yooichi , Honda Hiroshi
Published: October 2003

We investigated the response of the tachinid fly, Exorista japonica (Townsend), to host frass or its extracts in order to clarify the host location mechanisms of female flies in a potential host habitat. Host searching time in a patch and the number of patch visits were analyzed by using a frass‐containing patch which was excreted by host larvae, Mythimna separata (Walker) (Lepidoptera: Noctuidae), and patches to which host frass extracts were applied. E. japonica females were arrested in response to the host‐frass‐containing patch after contacting the frass with their front tarsi, thereby spending most of the time to search the patch and to revisit the host‐frass patch. While host‐searching time in the patch by the females was longest at their first visit of a patch with host frass, searching time decreased with successive visits. The female flies also exhibited area‐restricted searching with methanol extracts of the host frass. Area‐restricted searching activity increased with the concentration of host‐frass extract, i.e., total searching time in the patch and the number of patch visits varied in a dose‐dependent manner. E. japonica females likely employ chemicals in host frass as arrestants in host location.
Electronic tags for the tracking of insects in flight: effect of weight on flight performance of adult Colorado potato beetles
Authors: Boiteau Gilles , Colpitts Bruce
Published: October 2003

The wing loading of the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), was found to decrease slightly with increasing size over a wide range of individual sizes and independent of sex. This makes it possible to use tags of the same weight for beetles of all sizes and suggests that if the addition of light electronic tags has any effect on the beetle's flight it will be similar across beetle size. The wing loading of individual potato beetles ranged from an average minimum 10.9 N m−2 to an average maximum of 15.6 N m−2 as their weights fluctuated over time following water and food uptake or dispersal. However, tests carried out in flight chambers indicate that beetles become incapable of upward flight as they go beyond an average wing loading of 11.8 N m−2, that is 101 μN (10.3 mg) beyond their minimum weight. It is estimated from our results that electronic tags should weigh no more than 23–33% of the potato beetle's acceptable extra loading for the technique to have no or minimal impact on the number and quality of upward flights taken.
Plant‐mediated interactions between the rice water weevil and fall armyworm in rice
Authors: Tindall Kelly V. , Stout Michael J.
Published: October 2003

Greenhouse studies were conducted to investigate plant‐mediated interactions between an above‐ground and a below‐ground herbivore when sharing a common host plant, rice (Oryza sativa L). Two common pests of rice were used: the rice water weevil (RWW), Lissorhoptrus oryzophilus Kuschel, as the root herbivore, and the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) as the foliage‐feeding herbivore. Rice water weevil larval performance was assessed by measuring larval density and average weight in response to different levels of defoliation by FAW larvae. The reciprocal experiment was done to evaluate FAW performance (growth rate) in response to RWW feeding. Severe defoliation by FAW decreased RWW densities by 32% and reduced larval weights by 48% compared to larvae on roots of non‐defoliated plants. Effects in the converse experiments were not as strong. FAW growth rates were reduced 9–37% when feeding on rice leaves from plants damaged by RWW compared to larvae feed leaves from the no damage treatment. These reciprocal negative effects show that RWW and FAW are potential competitors when sharing a rice plant. Because RWW and FAW did not interact directly, competition was plant‐mediated.
Oviposition and larval survival of Dasineura tetensi on four blackcurrant Ribes cultivars
Authors: Crook D.J. , Cross J. , Birch A.N.E. , Brennan R.M. , Mordue (Luntz) A.J.
Published: October 2003

Monitoring of an unsprayed infested fieldsite using watertraps in S.E. Kent revealed four generations of Dasineura tetensi (Rubs) (Diptera: Cecidomyiidae) occurring between April and September 1996. Ribes nigrum L. cultivars ‘Baldwin’ (susceptible), ‘Ben Alder’ (susceptible) and ‘Ben Connan’ (resistant) were sampled for eggs in the field and assessed for midge damage throughout the season. Oviposition was indiscriminate, but plant damage varied significantly between cultivars. In laboratory choice experiments, mated female midges showed no preference between susceptible shoots of ‘Ben Alder’ and resistant shoots of ‘Ben Connan’ for oviposition. Olfactory responses of D. tetensi to leaf volatiles of ‘Ben Alder’ and ‘Ben Connan’ were also tested in a 4‐way olfactometer. Mated females did not discriminate between volatiles of susceptible and resistant host plants. Larvae reared on cv. ‘Ben Connan’ shoots were significantly smaller than those reared on shoots of cv. ‘Ben Alder’. Larval antibiosis and not female antixenosis appears to be the main mechanism for resistance to D. tetensi in ‘Ben Connan’.
Evaluation of an improved method for mass‐rearing of thrips and a thrips parasitoid
Authors: Murai Tamotsu , Loomans Antoon J.M.
Published: October 2003

Improved laboratory methods are described in detail for mass rearing of various thrips species, such as Frankliniella occidentalis, Frankliniella intonsa, Thrips palmi, Thrips tabaci (Thysanoptera: Thripidae) and a thrips parasitoid, Ceranisus menes (Hymenoptera: Eulophidae), using various foods. In one method, plant pollen and honey solution are used as food sources. In a second method, germinated broad bean seeds are used. Eggs, produced in large numbers in water, are collected by a suction funnel onto a filter paper and incubated in a Petri dish. Large numbers of larvae that hatch are collected by using food traps (plant pollen). Larvae can be reared on pollen or on germinated broad bean seeds until adult emergence without additional water and food. This method has been found useful for producing even‐aged thrips at different densities (up to 500 larvae in a cage of 80 mm diameter) with relatively low mortality rates. Evaluation of this rearing method for F. intonsa, shows that during 2 weeks at 20 °C per 100 females more than 4000 females could be produced in the next generation. About 5 min per day is required to achieve this productivity of mass production. The method is also suitable for producing large numbers of the solitary endoparasitoid of thrips larvae, C. menes.
Variable-range hopping conductivity in thin film of the ladder compound [Ca1+δCu2O3]4
Authors: Lisunov K. G. , Raquet B. , Rakoto H. , Broto J. M. , Arushanov E. , Xu X. Z. , El Alami H. , Deville Cavellin C.
Published: October 2003

Low-temperature charge transport in [Ca1+δCu2O3]4 films with δ=0 and 0.08 is investigated at T=1.4–290 K in magnetic fields of B=0–30 T. Between Tv≈20 and 40 K, depending on δ, and Tv′≈2–3 K three-dimensional (3D) Mott variable-range hopping (VRH) conductivity is observed. Deviations from 3D Mott VRH conductivity below Tv′ can be attributed to the onset of the Shklovskii–Efros VRH regime, accompanied by violation of the 3D hopping condition, Rh≪d (where Rh is the mean hopping length and d is the thickness of the film). The density of the localized states (DOS) at the Fermi level, g3(μ)≈4.4×1020 eV−1 cm−3, the values of the localization radius, α≈46 and 34 Å, the concentration of sites involved in hopping charge transfer, N≈9.9×1018 and 9.0×1018 cm−3, the width of the band of localized electron states, 2W≈22 and 20 meV, and the width of the Coulomb gap in the DOS spectrum, 2Δ≈1 and 1.6 meV are obtained for films with δ=0 and 0.08, respectively. These values characterize the films as being near the 3D metal–insulator transition given by the critical concentration NC≈1.3×1019 cm−3.
Off-resonant two-dimensional fifth-order Raman spectroscopy of liquid CS2: Detection of anharmonic dynamics
Authors: Saito Shinji , Ohmine Iwao
Published: October 2003

Off-resonant two-dimensional (2-D) fifth-order Raman signal of liquid CS2 is calculated by using a molecular dynamics (MD) simulation based on the fifth-order response function, which is characterized by a three-time correlation function of polarizability with the stability matrix of the phase space dynamics. The physical origin of the 2-D Raman signal pattern is investigated by analyzing anharmonic and nonlinear polarizability contributions. It is found that a rotation–rotation dynamical coupling arising from anharmonic dynamics is a dominant contribution to the fifth-order response function on the axis of the second time duration, t2. This coupling yields a novel feature of the signal, that is, a change in sign or a ridge in the vicinity along the t2 axis. The echo signal along t1=t2 obtained by the MD simulation accounting for the full dynamic effect, becomes blurred in comparison with that obtained by a harmonic description. The 2-D Raman signal at a very low temperature is also examined to find how the signal changes when structural transitions are suppressed. The 2-D Raman signal is also evaluated with a nonequilibrium MD simulation, which is found to be very similar to that with the equilibrium MD simulation based on the nonlinear response function formalism.
Modeling alkane+perfluoroalkane interactions using all-atom potentials: Failure of the usual combining rules
Authors: Song W. , Rossky P. J. , Maroncelli M.
Published: October 2003

We have tested the ability of the OPLS–AA models (optimized potentials for liquid simulations) of alkanes and perfluoroalkanes recently developed by Jorgensen and co-workers to represent the unusual mixing behavior of alkane+perfluoroalkane systems. We find that these all-atom Lennard-Jones (6-12)+Coulomb representations, together with the usual Lorentz–Berthelot combining rules, fail to reproduce the weaker-than-anticipated interactions between these two classes of molecules. Systematic disagreements with experiment are found in the case of second pressure virial coefficients, gas solubilities, and liquid–liquid mixing properties. These discrepancies are not specific to the choice of OPLS–AA potentials, but are rather linked to the failure of the geometric mean combining rule for relating unlike atom interactions. In all cases examined, a reduction in the strength of cross H+F interactions by ∼25% relative to the geometric mean is required in order to achieve reasonable agreement with experiment. Several less commonly used combining rules were also examined. Although some of these rules are able to provide a reasonable description of the interactions among perfluoroalkane and alkane species, they fail to provide a consistent treatment when atoms other than C, H, and F are considered, as is necessary for modeling the interaction of the former molecules with rare-gas atoms.
Plethysms and interacting boson models
Authors: Castilho Alcarás J. A. , Tambergs J. , Krasta T. , Ruža J. , Katkevičius O.
Published: October 2003

A short review of the plethysm technique aiming to its application in finding branching rules for the reduction of an irreducible representation of a group under the restriction to one of its subgroups is given. The algebraic structure of the interacting boson model and some of its extensions is given together with the branching rules needed to classify their basis states, obtained by the use of plethysms.
Spectroscopic characterization of naturally and chemically oxidized silicon surfaces
Authors: Tsunoda Kazuaki , Ohashi Emiko , Adachi Sadao
Published: October 2003

We have determined the thicknesses of naturally and chemically grown oxides on HF-cleaned silicon surfaces in ambient air and in NH4OH/H2O2/H2O solution, respectively, using spectroscopic ellipsometry. The naturally grown oxide thickness versus air-exposure time plots yield a rate constant of 3.5±0.5 Å/decade in ambient air. Chemical oxidation occurs immediately upon immersing the sample in the chemical solution and leaves the sample surface terminated with ∼6 Å of a chemical oxide. Photoreflectance intensity is found to be strongly dependent on such surface processing, and results are explained by the different degree of surface (interface) states.
Time-resolved CARS measurements of the vibrational decoherence of I2 isolated in an Ar matrix
Authors: Karavitis M. , Segale D. , Bihary Z. , Pettersson M. , Apkarian V. A.
Published: October 2003

Time-resolved coherent anti-Stokes Raman scattering is applied to prepare and interrogate vibrational coherences on the ground electronic surface of molecular iodine isolated in Ar matrices. The coherence decay time shows a linear dependence on vibrational quantum numbers for v=3–15. The temperature dependence of decoherence rates is negligible for v<7 in the experimental range T=18–32 K. For a v=13, 14 superposition, the temperature dependence indicates dephasing by a 66 cm−1 pseudo-local phonon, just outside the Debye edge of the solid. The accuracy of the data is limited due to two-photon induced dissociation of the molecule, a process which is characterized using polarized fields. The T→0 limit of dephasing is discussed.
Determination of carrier density in Te-doped Bi nanowires
Authors: Lin Yu-Ming , Dresselhaus M. S.
Published: October 2003

A promising approach is presented to characterize the carrier density in Te-doped Bi nanowires from their temperature-dependent resistance measurements, based on the comparison of the scattering rates due to charged impurity scattering and due to other scattering mechanisms that are independent of the carrier density. The result shows that the Te doping efficiency δe is only about 10%–15% for Te-doped Bi nanowires synthesized in an alumina template by molten-metal pressure injection. This analysis technique can be extended to other nanowire systems to provide valuable information regarding the carrier concentration and the Fermi energy for use in controlling and optimizing nanowire properties for specific applications.
Cathode fall characteristics in a dc atmospheric pressure glow discharge
Authors: Shi J. J. , Kong M. G.
Published: October 2003

Atmospheric pressure glow discharges are attractive for a wide range of material-processing applications largely due to their operation flexibility afforded by removal of the vacuum system. These relatively new atmospheric plasmas are nonequilibrium plasmas with gas temperature around 100 °C and electron temperature in the 1–10 eV range. Their appearance is characteristically diffuse and uniform, and their temporal features are repetitive and stable. Of the reported numerical studies of atmospheric glow discharges, most are based on the hydrodynamic approximation in which electrons are assumed to be in equilibrium with the local electric field. Spectroscopic and electrical measurements suggest however that the cathode fall region is fundamentally nonequilibrium. To this end we consider a hybrid model that treats the cathode fall region kinetically but retains a hydrodynamic description for the region between the thin cathode fall layer and the anode. Using this hybrid model, a helium discharge system excited at dc is studied numerically for a very wide current density range that spans from Townsend dark discharge, through normal glow discharge, to abnormal glow discharge. Numerical results confirm many distinct characteristics of glow discharges and compare well with that of low-pressure glow discharges. Generic relationships, such as that between the electric field and the current density, are also established and are in good agreement with experimental data. This hybrid model is simple and insightful as a theoretical tool for atmospheric pressure glow discharges.
A central extension of Uq sl(2|2)(1) and R-matrices with a new parameter
Authors: Yamane Hiroyuki
Published: October 2003

In this paper, using a quantum superalgebra associated with the universal central extension of sl(2|2)(1), we introduce new R-matrices having an extra parameter x. As x→0, they become those associated with the symmetric and antisymmetric tensor products of the copies of the vector representation of Uq sl(2|2)(1).
Phase space methods for particles on a circle
Authors: Zhang S. , Vourdas A.
Published: October 2003

The phase space S×Z for a particle on a circle is considered. Displacement operators in this phase space are introduced and their properties are studied. Wigner and Weyl functions in this context are also considered and their physical interpretation and properties are discussed. All results are compared and contrasted with the corresponding ones for the harmonic oscillator in the R×R phase space.
Surface degradation of InxGa1−xN thin films by sputter-anneal processing: A scanning photoemission microscope study
Authors: Downes James E. , Smith Kevin E. , Matsuura A. Y. , Lindau Ingolf , Iliopoulos Eleftherios , Moustakas Theodore D.
Published: October 2003

The effects of nitrogen ion sputtering and thermal anneal processing on the surface electronic structure of the ternary III–V semiconductor In0.12Ga0.88N have been studied using scanning photoemission microscopy. No phase separation of the material is observed for annealing temperatures up to 650 °C. However, samples annealed at 700 °C for 5 h show clear evidence of phase separation. Furthermore, annealing at these temperatures with the sample surface directly exposed to ultrahigh vacuum produces a surface greatly deficient in In and with considerable surface roughness. This can be circumvented by using a sacrificial sample in physical contact with the film to artificially increase the local vapor pressure of Ga, In, and N during annealing.
A class of vector coherent states defined over matrix domains
Authors: Thirulogasanthar K. , Twareque Ali S.
Published: October 2003

A general scheme is proposed for constructing vector coherent states, in analogy with the well-known canonical coherent states, and their deformed versions, when these latter are expressed as infinite series in powers of a complex variable z. In the present scheme, the variable z is replaced by matrix valued functions over appropriate domains. As particular examples, we analyze the quaternionic extensions of the canonical coherent states and the Gilmore–Perelomov and Barut–Girardello coherent states arising from representations of SU(1,1). Possible physical applications are indicated.
Alteration of exchange anisotropy and magnetoresistance in Co/Cu/Co/FeMn spin valves by ion bombardment
Authors: Engel D. , Krug I. , Schmoranzer H. , Ehresmann A. , Paetzold A. , Röll K. , Ocker B. , Maass W.
Published: October 2003

The dose dependence of the exchange bias field and magnetoresistance by 10 keV-He ion bombardment in an applied magnetic field were investigated for Co/Cu/Co/FeMn top spin valves. The exchange bias field Heb of the pinned Co layer can be enhanced, reversed, and reduced similarly to an exchange biased bilayer system. Additionally, upon ion bombardment, the free Co layer couples increasingly strong to the pinned Co layer until they act magnetically as one single pinned layer. The magnetoresistance decreases exponentially with increasing ion dose, caused by a higher sheet resistance due to increasing defect density and increasing coupling between the free and the pinned ferromagnetic layer. A phenomenological model is extended to describe the ion bombardment-induced changes of Heb of ferromagnet/antiferromagnet exchange biased bilayers by including saturation effects. This model is compared to available experimental data.
The generalized MIC-Kepler system
Authors: Mardoyan Levon
Published: October 2003

This paper deals with the dynamical system that generalizes the MIC-Kepler system. It is shown that the Schrödinger equation for this generalized MIC-Kepler system can be separated in spherical and parabolic coordinates. The spectral problem in spherical and parabolic coordinates is solved.
Backward wave oscillator regime of the whistler cyclotron instability in an inhomogeneous magnetic field
Authors: Demekhov A. G. , Nunn D. , Trakhtengerts V. Y.
Published: October 2003

A linear theory for the backward wave oscillator generation regime of whistler waves in the Earth’s magnetosphere is presented. Using a parabolic profile of the magnetic field and a linear expression for the resonant current in the case of a zeroth order distribution function with a step discontinuity in the velocity component parallel to the magnetic field, the modes of the system are investigated by means of a search procedure. The existence of at least one mode exponentially growing in time is indicative of absolute instability, and such modes have been found. Therefore, an earlier prediction of such a regime, based on the homogeneous magnetic field model, is confirmed. The dependence of growth rates on the frequency mismatch and energetic electron density has been studied. These results yield the characteristic spatial profile and temporal growth rate of small-amplitude whistler-wave disturbances, which are likely to be the seeds for chorus emissions.
Formation of stacking faults containing microtwins in (111) chemical-vapor-deposited diamond homoepitaxial layers
Authors: Kasu M. , Makimoto T. , Ebert W. , Kohn E.
Published: October 2003

Stacking faults containing microtwins in (111)-oriented diamond layers grown on a high-pressure high-temperature (HPHT)-synthesized diamond substrate by chemical vapor deposition start to form just on the substrate. The microtwins in the stacking faults form on the {1̄11} plane, not on the (111) substrate plane. To explain these results, we propose an atomic-scale model in which a foreign atom remains on the HPHT substrate surface and a C atom on the foreign atom cannot form a covalent bond with it. Therefore, twinning of the C atom occurs on the {1̄11} plane. The next C atoms bond with the twinned C atom in an untwinned (normal crystalline) relation. Consequently, the formation of stacking faults that contain microtwins occurs.
Improvement of near-ultraviolet InGaN/GaN light-emitting diodes by inserting an in situ rough SiNx interlayer in n-GaN layers
Authors: Tu Ru-Chin , Chuo Chang-Cheng , Pan Shyi-Ming , Fan Yu-Mei , Tsai Ching-En , Wang Te-Chung , Tun Chun-Ju , Chi Gou-Chung , Lee Bing-Chi , Lee Chien-Ping
Published: October 2003

Near-ultraviolet 400-nm InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with and without an in situ rough SiNx interlayer inserted into the n-GaN underlying layer were grown on c-face sapphire substrates by metalorganic vapor phase epitaxy. Inserting the SiNx interlayer into the n-GaN underlying layer slightly reduced leakage current induced by reducing the defect density. Additionally, an enhancement of light extraction for the LED with a SiNx interlayer is expected because of the increased intensity of light scattered on the SiNx nanomask, changing the directions of propagation of light. Consequently, the emission efficiency of an LED with an in situ rough SiNx interlayer doubles that without a SiNx interlayer.
Influence of the doping concentration of Y1−yCayBa2Cu3O7−δ drain-source channels on the properties of superconducting field-effect devices
Authors: Logvenov G. Yu. , Sawa A. , Schneider C. W. , Mannhart J.
Published: October 2003

Systematic electric-field-effect studies of the charge transport in doped YBa2Cu3O7−δ films were conducted. For overdoped drain-source channels, the normal-state resistance and the critical temperature Tc decrease with electric-field-induced enhancements of the hole concentration n. For underdoped channels, the resistance decreases, but Tc increases with n. For chemically optimally doped channels, the resistance decreases with n, however, Tc shifts are less pronounced compared with underdoped and overdoped films. The results verify that the superconducting properties of YBa2Cu3O7−δ can be controlled by electric fields, as predicted by the generic phase diagram of the cuprates.
Titanium metal quantum-dot composite induced by subplantation
Authors: Zhao J. P. , Huang D. X. , Jacobson A. J. , Rabalais J. W.
Published: October 2003

Crystalline titanium nanodots have been formed in the subsurface layer of single-crystal SiO2, i.e., a Ti-based metal quantum dot composite, by subplantation of 9 keV Ti+ ions. Transmission electron microscopy images show that the Ti nanodots have a single, uniform size distribution of ∼3–4 nm, they are single crystals of mainly the Ti bcc β-phase, and their position in the subsurface is controllable through the ion energy. The unique features of subplantation for promoting the precipitation/clustering of crystalline Ti nanodots are discussed. These results confirm previous findings based on the linear optical properties of Ti in SiO2.
Second-harmonic green generation from two-dimensional χ(2) nonlinear photonic crystal with orthorhombic lattice structure
Authors: Peng L.-H. , Hsu C.-C. , Shih Y.-C.
Published: October 2003

We report the synthesis of nonlinear photonic crystals (NPCs) with a periodical distribution of inverted χ(2) nonlinearity having an orthorhombic lattice structure on Z-cut congruent-grown lithium niobate (LiNbO3) substrate. The quasiphase-matching (QPM) mechanism of nonlinear wave interaction is examined by monitoring the far-field emission pattern of second-harmonic generation (SHG) as the NPC is pumped by a Nd:yttritium–aluminum–garnet laser beam. We observe (i) a series distribution of green SHG in a direction transverse to the fundamental beam, and (ii) an increase of phase-matching temperature in the SHG peak signal with the azimuth rotation angle in the x–y plane. These observations are ascribed to the high-order reciprocal lattice vectors assisted QPM–SHG process in a NPC that has a distribution of χ(2) nonlinearity with an orthorhombic crystal symmetry.
Formation of low resistance and transparent ohmic contacts to p-type GaN using Ni–Mg solid solution
Authors: Song June-O , Leem Dong-Seok , Seong Tae-Yeon
Published: October 2003

We report on the formation of Ni–Mg solid solution/Au ohmic contacts on p-GaN (5×1017 cm−3). The as-deposited Ni–Mg solid solution (8 nm)/Au (8 nm) contact shows near-linear I–V characteristics. However, oxidizing the contacts at 450 and 550 °C for 1 min in air results in a dramatic improvement in their I–V behaviors, producing specific contact resistance of ∼10−6 Ω cm2, which is much better than the conventional oxidized Ni/Au contacts. The light transmittance of the Ni–Mg solid solution/Au contacts annealed at 550 °C is measured to be better than 79% at a wavelength of 460 nm. Based on the I–V measurements, Auger electron spectroscopy, and x-ray photoemission spectroscopy results, possible ohmic formation mechanisms are described.
Cyclotron resonance at microwave frequencies in two-dimensional hole system in AlGaAs/GaAs quantum wells
Authors: Pan W. , Lai K. , Bayrakci S. P. , Ong N. P. , Tsui D. C. , Pfeiffer L. N. , West K. W.
Published: October 2003

Cyclotron resonance at the microwave frequency is used to measure the band edge mass (mb) in the two-dimensional hole (2DH) system, confined in 30 nm quantum wells in the Al0.1Ga0.9As/GaAs/Al0.1Ga0.9As heterostructures. We find that for 2DH density p⩽1.0×1010 cm−2, mb is nearly constant, ∼0.35me. It increases with increasing density, to ∼0.5me at p=7.4×1010 cm−2.
Electric-field-induced quenching effect of Raman scattering in Mg-doped p-GaN
Authors: Jeong T. S. , Youn C. J. , Han M. S. , Yang J. W. , Lim K. Y.
Published: October 2003

We have studied the influence of electric fields on the Mg-doped p-GaN by using Raman scattering and photocurrent (PC) measurement. It has been observed that the E2 (LO) mode was quenched upon increasing the electric field. To explain this effect, the combined results obtained from the electric-field-induced Raman scattering and the PC measurement were analyzed. As a result, we have found that the damping of E2 (LO) mode is caused to the phonon–hole scattering due to a strong interaction between the phonons and the photogenerated hole carriers with increasing the applied electric field.