bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of host age and host availability on developmental period, adult size, sex ratio, longevity and fecundity in Lariophagus distinguendusFörster (Hymenoptera: Pteromalidae)
Authors: Bellows T. S.
Published: October 2006

The effects of host age on parasitoid reproductive capacity are studied using the pteromalid parasitoid Lariophagus distinguendusFörster and its bruchid hosts, Callosobruchus chinensis (L.) and C. maculatus (F.). A series of experiments were performed to investigate relationships between age and size of host parasitized and the developmental period of pre‐imaginal progeny, sex ratio, female size, longevity, fecundity and oviposition rate. There was no effect of host size on preimaginal parasitoid developmental period. Sex ratio varied from less than 5% females from young (small) hosts to 60% females from mature (large) hosts. Adult size, female longevity, fecundity, and oviposition rate were also positively related to host age. Females provided mature hosts lived longer than those provided either young hosts or no hosts, possibly because of an increased ability to host‐feed from the larger hosts. The implications of these findings to parasitoid population reproductive capacity and host‐parasitoid synchrony are discussed.
Species diversity preserved in different numbers of nature reserves of the same total area
Authors: Kobayashi Shiro
Published: October 2006

Conclusion and Summary

The expected number of species occurring in different numbers of reserves of the same total area is examined on different assumptions of the spatial distribution and the probability of extinction. The advantage of one large reserve or several smaller ones of equal total area depends on the spatial distributions of species and the stage after the establishement of reserves. In general, several smaller reserves maintain more species immediately after the establishments unless the spatial distribution are uniform or random, whereas one large reserve excels several smaller ones after some rare species have gone extinct unless the spatial distributions are strongly contagious. Since the extinction of rare species must be facilitated as the size of each reserve reduces, the area of a reserve should be larger than the critical area that ensures the persistence of the species. Hence it is concluded that one or a few large reserves are a better strategy in order to maintain the species diversity.
Overwintering ecology of two social halictine bees, Lasioglossum duplex and L. problematicum
Authors: Sakagami Shôichi F. , Hoshikawa Kazuo , Fukuda Hiromi
Published: October 2006

Overwintering of two social halictine bees, Lasioglossum duplex (Dalla Torre) and L. problematicum (Blüthgen), was studied. In L. duplex many females stay near the old nests, each female preparing a hibernaculum separated from the natal nest. In L. problematicum most females overwinter communally within the natal nest. This difference in overwintering habits relates to the social structure in the next spring. L. duplex is nearly always solitary in spring although later becoming eusocial, whereas many nests of L. problematicum are polygynous, beginning in early spring. L. duplex overwinters much deeper () in the soil than does L. problematicum (), but both species are safe from drops in soil temperature, which is above 0°C even in midwinter, and the bees' supercooling points are lower than −6°C. This cold resistance and the storage of sufficient food in the crop are reflected in the winter survival, which is much higher (79%) than the rate of successful nests in the spring active phase (25%).
Long adult life spain and polyphagy of a carabid beetle,Leptocarabus kumagaiiin relation to reproduction and survival
Authors: Sota Teiji
Published: October 2006

The reproductive patterns of two different age classes ofLeptocarabus kumagaiiadults, i.e. young beetles which were in the first year of adult stage and old ones which survived for more than two years, were studied in the field. The numbers of eggs laid were compared between young and old females and the effects of food quality and quantity were studied on egg production and maintenance in the laboratory.

Both of the young and old beetles reproduced in the field population. The number of eggs laid did not significantly differ between the two.

The number of eggs laid by female increased with an increase in the amount of miced beef eaten. Plant materials were ineffective for egg production but sufficient for the survival of both male and female beetles.

The two life historical aspects, i.e. repeated reproduction and polyphagy were discussed in relation to environmental fluctuation and limitation of food resources.
Functional response and searching efficiency in Pseudogonatopus flavifemur Esaki and Hash. (Hymenoptera: Dryinidae), a parasite of rice planthoppers
Authors: Chua T. H. , Dyck V. A. , Pena N. B.
Published: October 2006

The functional response of Pseudogonatopus flavifemur E & H (Hym., Dryinidae) was investigated by offering hosts (brown planthopper) at densities ranging from 8 to 160 per cage. The response curve was found to be sigmoid, i. e.Holling's (1959) Type III curve. In experiments involving 310 hosts per cage distributed unevenly in 5 densities (10, 20, 40, 80 and 160 per hill), and a different female parasite density each time (viz. 1, 2, 4, 8 or 16 per cage), the behavioral response was described well by the “random predator equation” ofRoyama (1971) andRoger (1972), which is a convex exponential curve. The area of discovery (a) decreased with an increase in female parasite density (P), and the relationship was described by the equation: log a=−1.0099−0.3638 log P. There was an apparent increase in handling time per host as the number of female parasites increased. Superparasitism, a rare phenomenon under natural conditions, was often observed in the laboratory. The potential of P. flavifemur as a biocontrol agent of the brown planthopper is discussed.
Spatial pattern changes of grazing cattle population I
Authors: Shiyomi Masae , Kubo Sachio
Published: October 2006

A cattle population presents three spatial patterns according to their behaviour. These patterns are as follows: the random spatial pattern which occurs when the cattle move during grazing (feeding), the aggregated spatial pattern which occurs when they rest, and the regular or quasi‐regular spatial pattern which occurs when they separate into two or more subgroups. In this study, these three states of behaviour were represented by a mathematical model, and a method to test the pattern statistically was derived.
One host—one parasitoid system: Seasonal life cycles of Pryeria sinica (Ledipoptera) and Agrothereutes Minousubae (Hymenoptera)
Authors: Shiotsu Yoshifumi , Arakawa Ryo
Published: October 2006

The zygaenid Pryeria sinicaMoore and the ichneumonid Agrothereutes minousubaeNakanishi form a one host—one parasitoid system in nature. Their seasonal life cycles were investigated by laboratory experiments and field observations, and the life‐cycle adaptation of the parasitoid to its host was examined.

The moth is univoltine. The larva hatches from mid‐February to mid‐March and feeds on leaf buds and young leaves of ever green Euonymus japonicusThunb. The thermal constants for completing the 1st, 2nd, 3rd, 4th larval instars and prepupal stage were 85.6, 80.5, 85.2, 177,0 and 197.6 degree‐days, respectively. The prepupa and pupa vulnerable to the attack by the parasitoid occurred from mid‐April to early May and from mid‐ to late May, respectively.

Diapause in the parasitoid is facultative and occurs in the eonymphal stage. The photoperiodic response for this diapause was a long‐day type with a critical photoperiod of 13 hr 40 min at 20°C, but it was not expressed at 25°C, most larvae entering diapause irrespective of photoperiod. About 19, 120, 82 and 112 degree‐days above 7°C were required to complete the egg, larval, prepupal and pupal development, respectively. These data were superimposed on the photothermograph of Fukuoka, and it is predicted that the 1st adult eclosion would occur in late April and the partial 2nd adult eclosion in early June. The prediction was supported by field observations.

The adult eclosion of the parasitoid synchronized well with the apperance of prepupae and pupae of the moth. The parasitoid has two types of seasonal life cycle, one generation and two generations a year. Both types have an extremely long dormant period of 10–11 months due to aestivo‐hibernation. This seasonal life cycle enables the parasitoid to maintain its population when the host is in short supply.
Factors governing the evolution of eusociality through kin selection
Authors: Kasuya Eiiti
Published: October 2006

The evolution of eusociality through kin selection was analyzed by simple population genetical models. Models were solved analytically with no approximation. The main results are

Sex ratio in reproductives in a colony of haplodiploid species does not affect the direction of evolution, contrary to the hypothesis ofTrivers andHare (1976). Female biased sex ratio increases the rate of evolution irrespective of its direction.

The only factor that determines the direction of evolution is the balance of benefit and cost of altruism of workers.

The value of ratio of benefit to cost of altruism of workers when the change of gene frequency of altruistic allele does not take place is unity in both haplodiploid and diploid species. There is no theoretical reason that the eusociality through kin selection evolves more easily in haplodiploidy than in diploidy, contrary to the hypotheses ofHamilton (1964) andTrivers andHare (1976).

The larger the colony size is, the lower the rate of evolution is irrespective of its direction.

It was concluded that discussion on the evolution of altruism which depended on only the values of the degrees of relatedness is misleading. The importance of life history structure, oviposition of workers and number of relating gene(s) in the evolution of eusociality were discussed.
Spatial distribution of greenhouse whitefly (Trialeurodes vaporariorumWestwood) and a suggested sampling plan for estimating its density in greenhouses
Authors: Yano Eizi
Published: October 2006

Spatial distribution of the greenhouse whitefly population infesting tomato plants in greenhouses was analyzed. A leaf of tomato consists of 7 leaflets, each being used as a basic sampling unit. Distribution patterns between plants, between leaves and between leaflets were analyzed by the analysis of variance and the method.

It was found that populations of all the developmental stages were composed of contagiously distributed colonies or individuals between leaves and between leaflets. On the other hand, they showed random distribution of colonies between plants. On leaflets, egg populations were distributed as colonies, each consisting of several eggs, while in larval and adult populations, individuals were distributed rather independently of each other.

A three‐stage sampling plan was developed to estimate the density at the assigned level of precision.
Relative importance of direct and indirect interaction among individual snails
Authors: Kawata Masakado
Published: October 2006

Individual organisms interact directly through behavior, and indirectly through resource consumption and environment modification. The effects of different kinds of interactions on individual growth and reproduction will differ. Freshwater snails may interact directly for food resources and indirectly through substances dissolved in water. I separated the effects of the direct behavioral interaction and indirect interaction through waters using laboratory experiments with freshwater snails Physa acuta. Behavioral direct interaction have negative effects on the growth, but indirect interaction through water environments has positive effect on the growth. The importance of distinction of different kinds of interactions were discussed.
Neurotrophic property of geniposide for inducing the neuronal differentiation of PC12 cells
Authors: Liu Jianhui , Zheng Xuxu , Yin Fei , Hu Yinhe , Guo Lixia , Deng Xiaohong , Chen Gang , Jiajia Jing , Zhang Heng
Published: October 2006

The emerging data show that the insulinotrophic hormone glucagon‐like peptide‐1(GLP‐1) and its agonist extendin‐4 have neurotrophic function to inducing neuronal differentiation of PC12 cells and prevent neurons damage challenged by oxidative stress. Here, with the model of high throughput screen for GLP‐1 receptor agonists, we screen and identify that geniposide is a novel agonist for GLP‐1 receptor. Furthermore, geniposide induces the neuronal differentiation of PC12 cells with resulting neurites outgrowth; we also observe an increase in expression of growth‐associated protein‐43. U0126, a selective MEK inhibitor, prevents neurites out growth and phosphorylation of mitogen‐activated kinase proteins in PC12 cells induced by geniposide. All these results show that activation of GLP‐1 receptor by geniposide to induce the neuronal differentiation of PC12 cells involves in MAPK signaling cascade.
The circuitous path to the comparison of simulated values from crop models with field observations
Authors: WEISS A. , WILHELM W. W.
Published: October 2006

The Journal of Agricultural Science, Cambridge has been a fixture in dissemination of crop simulation models and the concepts and data upon which they are built since the inception of computers and computer modelling in the mid-20th century. To quantify the performance of a crop simulation model, model outputs are compared with observed values using statistical measures of bias, i.e. the difference between simulated and observed values. While applying these statistical measures is unambiguous for the experienced user, the same cannot always be said of determining the observed or simulated values. For example, differences in accessing crop development can be due to the subjectivity of an observer or to a definition that is difficult to apply in the field. Methods of determining kernel number, kernel mass, and yield can vary among researchers, which can add errors to comparisons between experimental observations and simulated results. If kernel moisture is not carefully determined and reported it can add error to values of grain yield and kernels per unit area regardless of the protocol used to collect these data. Inaccurate determination of kernel moisture will also influence computation of grain protein or oil content. Problems can also be associated with input data to the simulation models. Under-reporting of precipitation values from tipping bucket rain gauges, commonly found on automated weather stations, can introduce errors in results from crop simulation models. Using weather data collected too far from an experimental site may compound problems with input data. The importance of accurate soil and weather input data increases as the environment becomes more limiting for plant growth and development. Problems can also arise from algorithms that calculate important parameters in a model, such as daylength, which is used to determine a photoperiod response. Errors in the calculation of photoperiod can be related to the definition of sunrise and sunset and the inclusion or exclusion of civil twilight or to the improper calculation of the solar declination. Even the simple calculation of the daily mean air temperature can have an impact on the results from a non-linear algorithm. During a period when crop simulation modelling is moving in the difficult direction of incorporating genomic-based inputs, the critical importance of careful and accurate collection and reporting of field data and the need to develop robust algorithms that accommodate readily available or easily acquired input data should not be forgotten. As scientists we have an obligation to provide the best available knowledge and understanding as possible. Avoiding potential pitfalls will assist us as we develop new knowledge and understanding and incorporate these concepts into new or modified crop simulation models.
Is there objective evidence that septal surgery improves nasal airflow?
Authors: Singh A , Patel N , Kenyon G , Donaldson G
Published: October 2006

Objective: To identify any prospective, controlled trials providing objective evidence of a reduction in nasal airway resistance following nasal septal surgery, and to undertake a meta-analysis of available data.

Methods: A systematic review with meta-analysis of data was undertaken. A systematic review of the literature using a defined search strategy was conducted to identify papers that used objective methods of airway assessment to evaluate the benefit of septal surgery. Accepted techniques for objective airway assessment included acoustic rhinometry, active anterior rhinomanometry and peak nasal inspiratory airflow. Papers were included based on pre-defined criteria, which included standardization of techniques as outlined in the guidelines of the 1984 committee report on the standardization of rhinomanometry.

Results: We identified 942 articles, of which 13 were prospective studies evaluating the objective benefit of nasal septal surgery. Only three of these studies conformed to the inclusion criteria. A meta-analysis on these papers was performed using the Mantel–Haenszel method, and this demonstrated an overall reduction in nasal airway resistance following septal surgery for nasal obstruction (p=0.018).

Conclusions: The majority of studies evaluating the objective benefit of septal surgery did not conform to the recommendations of the committee report on the standardization of rhinomanometry. Only three prospective controlled trials, with pooled data from 141 cases, were identified for meta-analysis. The conclusions that can be drawn concerning objective improvement in airway function following nasal septal surgery are therefore limited. More long-term studies, adhering to standardized techniques, are needed to provide more convincing data.
A new methodology for the determination of the workspace of six-DOF redundant parallel structures actuated by nine wires
Authors: Ferraresi Carlo , Paoloni Marco , Pescarmona Francesco
Published: October 2006

The WiRo-6.3 is a six-degrees of freedom (six-DOF) robotic parallel structure actuated by nine wires, whose characteristics have been thoroughly analyzed in previous papers in reference. It is thought to be a master device for teleoperation; thus, it is moved by an operator through a handle and can convey a force reflection on the operator's hand. A completely new method for studying the workspace of this device, and of virtually any nine-wire parallel structure actuated by wire is presented and discussed, and its results are given in a graphical form.
Locomotion control of a hydraulically actuated hexapod robot by robust adaptive fuzzy control and dead-zone compensation
Authors: Barai Ranjit Kumar , Nonami Kenzo
Published: October 2006

This investigation presents locomotion control of a hydraulically actuated six-legged humanitarian demining robot by robust adaptive fuzzy control in conjunction with the dead zone compensation technique within independent joint control framework. For proper locomotion of the demining robot, accurate tracking of the desired joint trajectory is very important. However, high degree of nonlinearity, the uncertainties due to changing hydraulic properties, and delay due to the flow of oil and dead zone of the proportional electromagnetic control valve results into an inaccurate plant model for the hydraulically actuated robotic joints. Consequently, model-based classical control techniques result into a large tracking error. Therefore, adaptive fuzzy control technique, being a model independent control paradigm for complex and uncertain systems, is a good choice for such systems. In this work, a hydraulic dead zone compensated robust adaptive fuzzy control law has been proposed for locomotion control of hydraulically actuated hexapod demining robot. The experimental results exhibit a fairly accurate trajectory tracking of the leg joints and, consequently, very stable locomotion of the walking robot.
Socioeconomic constraints, environmental impacts and drivers of change in the Congo Basin as perceived by logging companies
Authors: PÉREZ MANUEL RUIZ , DE BLAS DRISS EZZINE , NASI ROBERT , SAYER JEFFREY A. , KARSENTY ALAIN , SASSEN MARIEKE , ANGOUÉ CLAUDINE , GAMI NORBERT , NDOYE OUSSEYNOU , NGONO GRÉGOIRE , NGUINGUIRI JEAN-CLAUDE , NZALA DONATIEN , TOIRAMBE BENJAMIN , YALIBANDA YVES
Published: October 2006

The external factors that influence the environmental, social and economic performance of logging companies were studied using a questionnaire submitted to 30 logging concessions in five countries of the Congo Basin. This paper analyses socioeconomic constraints and environmental impacts experienced by these concessions, as well as their response to major external drivers of change. Concessionaires considered investment and operating finance their main constraint, followed by insufficient technical and human capacities, and inconsistent application of official regulations. Environmental problems directly produced by concessions' operations represented around one-third of the total score for environmental problems reported. Damage caused by construction of logging roads and erosion were identified as the main issues. Induced problems (two-thirds of the total score) were dominated by hunting, with encroachment and illegal logging perceived as much less significant. Policies, infrastructure, markets and technology are key external drivers of change in concessions' practices, while regional and international forestry institutions reportedly have the least influence, reflecting an emerging scepticism about the proliferation of international institutions and initiatives promoting sustainable forestry.
Spatiotemporal structure of the reconnecting magnetosphere under By‐dominated interplanetary magnetic cloud conditions
Authors: Sandholt P. E. , Farrugia C. J.
Published: October 2006

In this study we discuss the spatiotemporal structure of the reconnecting magnetosphere under a steady external field which was pointing southward (Bz = −5 nT), but with a strong eastward component (By = 20 nT; clock angle = 100°). The relevant conditions refer to a three hour long interval midway through the passage at Earth of an interplanetary magnetic cloud on 17 April 1999. The quasi‐steady parameters provided by the magnetic cloud is what allow us to probe the detailed magnetospheric/ionospheric structure under these conditions. We document the presence of a specific configuration of cusp and oval‐aligned polar arcs with associated merging and lobe convection cells in both hemispheres. Strong signatures of pulsed ionospheric flows (PIFs) are present in high‐latitude ground magnetometer records from Svalbard and Greenland. Particle data obtained from Polar/HYDRA during an overflight of the southern hemisphere cusp at 0800–0900 MLT show the presence of polar arcs and an inverse energy versus latitude dispersion of precipitating ions on the poleward side of the merging cell and the plasma regimes of mantle, cusp, and BPS. Furthermore, observations by Polar, DMSP, and SuperDARN document the precipitation, field‐aligned current and ion flow pattern in the south. The presence of “double cusp” in the north and polar arcs in both hemispheres (mirror images about noon) during the actual IMF Bz negative (By‐dominated) conditions and the implications on solar wind‐magnetosphere coupling are discussed. The magnetic cloud conditions at ACE included a very low proton plasma β (∼0.01) and a low Alfven Mach number (∼2) near the center of the cloud. We speculate that these conditions may have given rise to a plasma depletion at the high‐latitude magnetopause and favored the excitation of lobe reconnection under the prevailing Bz negative conditions. The reported observations are placed in the context of recent studies of the spatiotemporal structure of the dayside aurora.
Tropopause characteristics over a southern subtropical site, Reunion Island (21°S, 55°E): Using radiosonde‐ozonesonde data
Authors: Sivakumar V. , Baray J.‐L. , Baldy S. , Bencherif H.
Published: October 2006

In this paper, we present tropopause characteristics using in situ radiosonde‐ozonesonde observations carried out over the past 13 years (September 1992 to February 2005) from a southern subtropical site, Reunion Island (21°S, 55°E). Three kinds of tropopause definitions, namely, cold‐point tropopause (CPT), lapse rate tropopause (LRT), and ozone tropopause (OT), are characterized. The ozone tropopause for Reunion is appropriately defined as the height at which the vertical gradient of the ozone mixing ratio exceeds 55 ppbv/km and the ozone mixing ratio is over 75 ppbv. The overall height distribution of the three kinds of tropopause ranges in between 12.5 and 18.5 km. Of the three definitions, CPT follows higher heights of distribution, followed by LRT and then OT. The sharpness of tropopause height detection for LRT and OT has been examined, and it has been found that the detection frequency of a definite OT is larger than that for LRT. The results also showed no indefinite OT for a subtropical station in comparison to the results obtained for Northern Hemisphere midlatitude and high‐latitude stations. After adopting a few modifications in the sharpness of ozone tropopause detection, the result remains the same, with a single indefinite case. The indefinite ozone tropopause case was identified when Reunion Island was located nearer to the divergence zone of wind as well as in the anticyclonic region of jet stream entrance. The LRT sharpness results are found to be in good agreement with the other published definition.
Thermocline flux exchange during the Pinatubo event
Authors: Douglass D. H. , Knox R. S. , Pearson B. D. , Clark A.
Published: October 2006

We analyze the temperature anomaly of the Pinatubo eruption using an exact mathematical solution of a standard energy balance model that includes coupling between the mixed layer and the thermocline. Our solution yields a short response time τ = 4.4 months and a small climate sensitivity λ = 0.22 C/(W/m2), implying short‐term negative feedback. Also, our analysis determines a value of the effective eddy diffusion constant κ = 2 × 10−6 m2/s that is much smaller than that assumed in many climate models. We find for this model that the heat flux to the thermocline reverses sign and integrates to zero for any forcing of finite duration. This effect should be observable in any future Pinatubo‐type event.
Offshore transport episodes of anthropogenic sulfur in northern Chile: Potential impact on the stratocumulus cloud deck
Authors: Huneeus N. , Gallardo L. , Rutllant J. A.
Published: October 2006

An outstanding meteorological feature appearing off the coast in Central and Northern Chile is the persistent stratus cloud deck under the subtropical Pacific High. It has a large impact on the regional and global energy balance and atmospheric circulation. In connection with mid‐latitude synoptic‐scale disturbances, subsiding easterly flow down the subtropical Andes often occurs in Northern Chile allowing large anthropogenic emissions of oxidized sulfur that take place in the region to reach the stratus deck. We explore the potential impact of anthropogenic emitted sulfur on the stratus deck associated with strong easterly flow events that occur on the average 4 to 8 times per year. A representative transport event is simulated using a 3‐D transport chemistry model and the results are compared with satellite observations of cloud droplet number concentration. Although not conclusive, this preliminary study reveals a potential perturbation of the subtropical stratocumulus deck due to anthropogenic sulfur aerosols.
Estimation of peak electron density in upper ionosphere of Mars at high latitude (50°–70°N) using MGS ACC data
Authors: Seth S. P. , Jayanthi U. B. , Haider S. A.
Published: October 2006

Under photochemical equilibrium condition, electron density near peak varies as the square root of total peak ionization rate. Thus by averaging the longitudinal variation of latter, the mean primary and secondary peak electron densities in upper ionosphere of Mars using measured mass densities at LST 16 hrs are estimated to be ∼8.56 × 104 cm−3 and ∼1.81 × 104 cm−3. On comparison with mean electron densities at LST 3–4 hrs for observational period Dec. 24–31, 1998, at same solar zenith angle, it is found that the estimated primary peak electron density at LST 16 hrs is more by a factor of ∼1.06. With this analogy, the estimated secondary peak electron density should be ∼3.76 × 104 cm−3 instead of ∼1.81 × 104 cm−3. Thus, in order to obtain the estimated secondary peak electron density of ∼3.76 × 104 cm−3, soft X‐ray flux should be increased by a factor of ∼4.31.
Observational evidence of changes in water vapor, clouds, and radiation at the ARM SGP site
Authors: Dong Xiquan , Xi Baike , Minnis Patrick
Published: October 2006

Characterizing water vapor and cloud effects on the surface radiation budget is critical for understanding the current climate because water vapor is the most important greenhouse gas in the atmosphere and clouds are one of the largest sources of uncertainty in predicting potential future climate change. Several studies have shown that insolation over land declined until 1990 then increased until the present. Using 8 years of data collected at the ARM Southern Great Plains (SGP) surface site, we found that the insolation increased from 1997 to 2000, but significantly decreased from 2001 to 2004, changes that exactly mirror the variation in the second‐order fit of cloud fraction. Under clear‐sky conditions, the rates of change of water vapor, insolation and downwelling longwave (LW) flux are −0.0166 cm/yr, 0.48 Wm−2/yr, and −1.16 Wm−2/yr, respectively, indicating that water vapor changes are more important for LW flux than for insolation.
Laser-based platform for studying material hydrodynamics under heated and shocked conditions
Authors: Lanier N. E. , Holmes R. L. , Workman J. , Graham P. , Chambers D. M. , Moore A.
Published: October 2006

Understanding how target defects and surface finish perturbations affect ignition capsule mixing is a critical goal of the inertial confinement fusion (ICF) community. While initial characterization of these features is essential to understanding the physics of ICF implosions, it is the condition of the features at the time of shock passage that ultimately dictates their impact on capsule performance. The Off-Hugoniot experiment was designed to quantify the evolution of material interfaces under heated and subsequently shocked conditions. The platform uses tin L-shell radiation to uniformly heat an epoxy/foam-layered package. As the epoxy expands into the foam, an independently controlled shock impacts the evolving interface. The resulting hydrodynamics are imaged via x-ray radiography. Beyond the flexibility of independent heating and shock control, the epoxy can be configured with any desired features, such as gaps, chamfers, and single and multimode perturbations. An overview of the experimental platform, data from the ongoing OMEGA campaign, and future plans are presented.
Jet cooled spectroscopy of H2DO+: Barrier heights and isotope-dependent tunneling dynamics from H3O+ to D3O+
Authors: Dong Feng , Nesbitt David J.
Published: October 2006

The first high resolution spectroscopic data for jet cooled H2DO+ are reported, specifically via infrared laser direct absorption in the OH stretching region with a slit supersonic jet discharge source. Transitions sampling upper (0−) and lower (0+) tunneling states for both symmetric (ν1+←0+, ν1−←0−, and ν1−←0+) and antisymmetric (ν3+←0+ and ν3−←0−) OH stretching bands are observed, where +/− refers to wave function reflection symmetry with respect to the planar umbrella mode transition state. The spectra can be well fitted to a Watson asymmetric top Hamiltonian, revealing band origins and rotational constants for benchmark comparison with high-level ab initio theory. Of particular importance are detection and assignment of the relatively weak band (ν1−←0+) that crosses the inversion tunneling gap, which is optically forbidden in H3O+ or D3O+, but weakly allowed in H2DO+ by lowering of the tunneling transition state symmetry from D3h to C2v. In conjunction with other H2DO+ bands, this permits determination of the tunneling splittings to within spectroscopic precision for each of the ground [40.518(10)cm−1], ν1=1 [32.666(6)cm−1], and ν3=1 [25.399(11)cm−1] states. A one-dimensional zero-point energy corrected potential along the tunneling coordinate is constructed from high-level ab initio CCSD(T) calculations (AVnZ, n=3,4,5) and extrapolated to the complete basis set limit to extract tunneling splittings via a vibrationally adiabatic treatment. Perturbative scaling of the potential to match splittings for all four isotopomers permits an experimental estimate of ΔV0=652.9(6)cm−1 for the tunneling barrier, in good agreement with full six-dimensional ab initio results of Rajamaki, Miani, and Halonen (RMH) [J. Chem. Phys. 118, 10929 (2003)]. (ΔV0RMH=650cm−1). The 30%–50% decrease in tunneling splitting observed upon ν1 and ν3 vibrational excitations arises from an increase in OH stretch frequencies at the planar transition state, highlighting the transition between sp2 and sp3 hybridizations of the OH∕D bonds as a function of inversion bending angle.
Variance estimators for the Lempel-Ziv entropy rate estimator
Authors: Amigó José M. , Kennel Matthew B.
Published: October 2006

Lempel and Ziv’s 1976 algorithm provides an easy-to-compute way to automatically estimate the entropy rate for symbolic time series, requiring no free parameters. Here we derive an analytical variance estimate for the Lempel-Ziv entropy rate estimator that is easily computable from observations with negligible extra effort beyond the entropy rate itself, and compare to another procedure, a time-series-based bootstrap method. These provide a justified “error bar” quantifying the size of expected fluctuations on the estimate itself, given by the single time series of symbols.
Probabilistic analysis of turbulent structures from two-dimensional plasma imaging
Authors: Müller S. H. , Diallo A. , Fasoli A. , Furno I. , Labit B. , Plyushchev G. , Podestà M. , Poli F. M.
Published: October 2006

A method is presented to construct object-related structure observables, such as size, mass, shape, and trajectories from two-dimensional plasma imaging data. The probability distributions of these observables, deduced from measurements of many realizations, provide a robust framework in which the fluctuations, the turbulence, and the related transport are characterized. The results for imaging data recorded in the presence of drift-interchange instabilities and turbulence on the TORPEX toroidal plasma experiment [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)] are discussed.
Orientational dynamics of isotopically diluted H2O and D2O
Authors: Rezus Y. L. A. , Bakker H. J.
Published: October 2006

We use femtosecond midinfrared pump-probe spectroscopy to compare the ultrafast dynamics of HDO dissolved in D2O and H2O. For both systems the vibrational energy relaxation proceeds through an intermediate state. The relaxation leads to heating of the sample, which is observed in the transient spectra. In order to obtain the correct anisotropy decay, the ingrowing heating signal is subtracted from the raw data. For the OD vibration this procedure works well. For the OH vibration, however, we find an additional effect that leads to a severe distortion of the anisotropy. We show that this effect can be explained by a slightly faster reorientation of excited molecules during their relaxation as compared to unexcited molecules. We construct a model that includes this effect and is able to reproduce the experimental data. Using this model we show how the distorted anisotropy can be corrected.
Cumulative reaction probabilities: A comparison between quasiclassical and quantum mechanical results
Authors: Aoiz F. J. , Brouard M. , Eyles C. J. , Castillo J. F. , Sáez Rábanos V.
Published: October 2006

This article presents a quasiclassical trajectory (QCT) method for determining the cumulative reaction probability (CRP) as a function of the total energy. The method proposed is based on a discrete sampling using integer values of the total and orbital angular momentum quantum numbers for each trajectory and on the development of equations that have a clear counterpart in the quantum mechanical (QM) case. The calculations comprise cumulative reaction probabilities at a given total angular momentum J, as well as those summed over J. The latter are used to compute QCT rate constants. The method is illustrated by comparing QCT and exact QM results for the H+H2, H+D2, D+H2, and H+HD reactions. The agreement between QCT and QM results is very good, with small discrepancies between the two data sets indicating some genuine quantum effects. The most important of these involves the value of the CRP at low energies which, due to the absence of tunneling, is lower in the QCT calculations, causing the corresponding rate constants to be smaller. The second is the steplike structure that is clearly displayed in the QM CRP for J=0, which is much smoother in the corresponding QCT results. However, when the QCT density of reactive states, i.e., the derivatives of the QCT CRP with respect to the energy, is calculated, a succession of maxima and minima is obtained which roughly resembles those found in the QM calculations, although the latter are considerably sharper. The analysis of the broad peaks in the QCT density of reactive states indicates that the distributions of collision times associated with the maxima are somewhat broader, with a tail extending to larger collision times, than those associated with the minima. In addition, the QM and QCT dynamics of the isotopic variants mentioned above are compared in the light of their CRPs. Issues such as the compliance of the QCT CRP with the law of microscopic reversibility, as well as the similarity between the CRPs for ortho and para species in the QM and QCT cases, are also addressed.
One-dimensional magnetic grating structure made easy
Authors: Kim J. B. , Lee G. J. , Lee Y. P. , Rhee J. Y. , Kim K. W. , Yoon C. S.
Published: October 2006

A simple and easy method of the fabrication of one-dimensional magnetic grating structure is developed. By using the interference pattern of two femtosecond laser beams, a selective-area annealing of as-deposited Co2MnSi film was achieved and one-dimensional magnetic grating structures were fabricated. The as-deposited films exhibit no magnetic response at room temperature. Several microscopies were applied to confirm the periodic crystalline and magnetic structures. The Faraday-like rotation of the polarization of the zeroth- and first-order diffracted beams were measured, and that of the first-order diffracted beam is nearly six times larger than that of the zeroth-order beam.
Complete wetting of curved microscopic channels
Authors: Bruschi Lorenzo , Fois Giovanni , Mistura Giampaolo , Tormen Massimo , Garbin Valeria , di Fabrizio Enzo , Gerardino Annamaria , Natali Marco
Published: October 2006

We have measured the adsorption of argon films on arrays of microscopic nonlinear cusps and of semicircular channels. In the former case, we observe a distinct crossover from a planarlike to a geometry dependent growth behavior near liquid-vapor bulk coexistence, characterized by a growth exponent χ equal to −0.96±0.04 in very good agreement with the predictions of a recent scaling theory [C. Rascon and A. O. Parry, J. Chem. Phys. 112, 5175 (2000)]. The crossover location is also consistent with theory. Instead, on the concave channels we find a much steeper growth near saturation that may signal the formation of two menisci at both sides of the channel bottom.
Freezing of hard spheres confined in narrow cylindrical pores
Authors: Gordillo M. C. , Martínez-Haya B. , Romero-Enrique J. M.
Published: October 2006

Monte Carlo simulations for the equation of state and phase behavior of hard spheres confined inside very narrow hard tubes are presented. For pores whose radii are greater than 1.1 hard sphere diameters, a sudden change in the density and the microscopic structure of the fluid is neatly observed, indicating the onset of freezing. In the high-density structure the particles rearrange in such a way that groups of three particles fit in sections across the pore.
Superconductivity in metal-mixed ion-implanted polymer films
Authors: Micolich A. P. , Tavenner E. , Powell B. J. , Hamilton A. R. , Curry M. T. , Giedd R. E. , Meredith P.
Published: October 2006

Ion implantation of normally insulating polymers offers an alternative to depositing conjugated organics onto plastic films to make electronic circuits. We used a 50keV nitrogen ion beam to mix a thin 10nm Sn∕Sb alloy film into the subsurface of polyetheretherketone and report the low temperature properties of this material. We observed metallic behavior, and the onset of superconductivity below 3K. There are strong indications that the superconductivity does not result from a residual thin film of alloy, but instead from a network of alloy grains coupled via a weakly conducting, ion-beam carbonized polymer matrix.
Individual classification of buried transistors in live microprocessors by functional infrared emission spectral microscopy
Authors: Oblefias Wilma , Soriano Maricor , Tarun Alvarado , Saloma Caesar
Published: October 2006

The authors classify good, leaky, and broken field effect transistors (FET’s) in a live 90nm flip-chip microprocessor using functional infrared emission spectral microscopy. The FET’s are in the active layer that is sandwiched between a thick heat-absorbing silicon material and a highly reflecting grid of metal interconnects. Together they are optically imaged only as a single bright blob. They classify FET’s individually from their distinct electroluminescence spectra that are recovered efficiently by spectral decomposition of the detected composite spectrum. Leaky FET’s have no apparent structural damage and are detectable only in live microprocessors.
Nonlinear absorption of femtosecond laser on a metal surface embedded by metallic nanoparticles
Authors: Ahmad Amir , Tripathi V. K.
Published: October 2006

Metal surface with nanosize roughness is modeled as a plane surface embedded with clusters. A high power femtosecond laser pulse normally incident on the metal surface undergoes field enhancement when laser frequency equals the frequency of surface charge oscillations of the clusters. The enhanced field causes increased absorption of the laser pulse. The model suggests that the increase in absorption decreases with the increase of the laser power. The results are in line with recent observations.
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characteristics of Au∕Ni Schottky diodes on GaN with SiNx nanonetwork
Authors: Xie Jinqiao , Fu Yi , Ni Xianfeng , Chevtchenko Serguei , Morkoç Hadis
Published: October 2006

Room temperature and temperature dependent current-voltage characteristics of Ni∕Au Schottky diodes fabricated on undoped GaN prepared with and without in situ SiNx nanonetwork by metal organic chemical vapor deposition have been studied. The features of the Schottky diodes depend strongly on the SiNx deposition conditions, namely, its thickness. Reduction in the point and line defect densities caused the Schottky barrier height to increase to 1.13eV for 5min SiNx deposition time as compared to 0.78eV without SiNx nanonetwork. Similarly, the breakdown voltage also improved from 76V for the reference to 250V when SiNx nanonetwork was used. With optimized SiNx nanonetwork, full width at half maximum values of (0002) and (101¯2) x-ray rocking curves improved to 217 and 211arcsec, respectively, for a 5.5μm thick layer, as compared to 252 and 405arcsec for a reference sample of the same thickness, which are comparable to literature values. The photoluminescence linewidth also reduced to 2.5meV at 15K with free excitons A and B clearly resolvable.
Optically pumped semiconductor disk laser with graded and step indices
Authors: Saas Florian , Talalaev Vadim , Griebner Uwe , Tomm Jens W. , Zorn Martin , Knigge Andrea , Weyers Markus
Published: October 2006

Results of a study of different gain section designs in nonresonantly optically pumped vertically emitting semiconductor disk lasers (SCDLs) are presented. Clear superiority of structures with barriers based on graded-gap layers is demonstrated. This finding is assigned to the lack of absorption saturation within the barriers caused by the efficient carrier collection capabilities of graded structures compared to ungraded ones. Transient photoluminescence experiments providing direct access to the carrier transfer from the barrier to the quantum-well active region confirm this explanation. Consequently, the authors propose graded designs for SCDLs.
Rubrene single crystal field-effect transistor with epitaxial BaTiO3 high-k gate insulator
Authors: Hiroshiba Nobuya , Kumashiro Ryotaro , Tanigaki Katsumi , Takenobu Taishi , Iwasa Yoshihiro , Kotani Kenta , Kawayama Iwao , Tonouchi Masayoshi
Published: October 2006

High quality BaTiO3 thin-film epitaxially grown on a Nb-doped SrTiO3 (BTO/Nb-STO) substrate by a laser ablation technique is employed as a high-k gate insulator for a field-effect transistor of a rubrene single crystal in order to search for the possibility of high carrier accumulation. The high dielectric constant ϵ of 280esu for the prepared BaTiO3 thin-film accumulates 0.1holes∕rubrene-molecule, which is 2.5 times as high as the maximum carrier number of 0.04holes∕rubrene-molecule attained in the case of SiO2. This is the highest carrier number so far obtained in organic field-effect transistors (FETs). Other important parameters of rubrene single crystal FETs on BTO/Nb-STO are described in comparison with those on SiO2/doped-Si.
Design of midinfrared photodetectors enhanced by surface plasmons on grating structures
Authors: Yu Zongfu , Veronis Georgios , Fan Shanhui , Brongersma Mark L.
Published: October 2006

The authors propose to exploit the unique properties of surface plasmons to enhance the signal-to-noise ratio of midinfrared photodetectors. The proposed photodetector consists of a slit in a metallic slab filled with absorptive semiconductor material. Light absorption in the slit is enhanced due to Fabry-Perot resonances. Further absorption enhancement is achieved by surrounding the slit with a series of periodic grooves that enable the excitation of surface plasmons that carry electromagnetic energy towards the slit. Using this scheme, they design and optimize a photodetector operating at λ0=9.8μm with a roughly 250 times enhancement in the absorption per unit of volume of semiconductor material compared to conventional photodetectors operating at the same wavelength.
Temperature dependence of threshold current in p-doped quantum dot lasers
Authors: Sandall I. C. , Smowton P. M. , Thomson J. D. , Badcock T. , Mowbray D. J. , Liu H.-Y. , Hopkinson M.
Published: October 2006

The authors measure the temperature dependence of the components of threshold current of 1300nm undoped and p-doped quantum dot lasers and show that the temperature dependence of the injection level necessary to achieve the required gain is the largest factor in producing the observed negative T0 in p-doped quantum dot lasers.
Colossal electroresistance and current induced switching in ferromagnetic insulating state of La0.82Ca0.18MnO3
Authors: Jain Himanshu , Raychaudhuri A. K. , Mukovskii Ya. M. , Shulyatev D.
Published: October 2006

Colossal electroresistance and current induced resistivity switching have been measured in the ferromagnetic insulating (FMI) state of single crystal manganite La0.82Ca0.18MnO3. The sample has a Curie transition temperature TC=165K and the FMI state is realized for temperatures T<100K. The electroresistance (ER), arising from a strong nonlinear resistivity, attains a large value (≈100%) in the FMI state. However, this is accompanied by a collapse of the magnetoresistance (MR) to a small value even in magnetic field (H) of 10T. This demonstrates that the mechanisms that give rise to ER and MR are effectively decoupled.