bluuebunny/crossref_metadata_2025 huggingface dataset:
Emergence of Phase- and Shift-Invariant Features by Decomposition of Natural Images into Independent Feature Subspaces
Authors: Hyvärinen Aapo , Hoyer Patrik
Published: July 2002

Olshausen and Field (1996) applied the principle of independence maximization by sparse coding to extract features from natural images. This leads to the emergence of oriented linear filters that have simultaneous localization in space and in frequency, thus resembling Gabor functions and simple cell receptive fields. In this article, we show that the same principle of independence maximization can explain the emergence of phase- and shift-invariant features, similar to those found in complex cells. This new kind of emergence is obtained by maximizing the independence between norms of projections on linear subspaces (instead of the independence of simple linear filter outputs). The norms of the projections on such “independent feature subspaces” then indicate the values of invariant features.
Orientation Tuning Properties of Simple Cells in Area V1 Derived from an Approximate Analysis of Nonlinear Neural Field Models
Authors: Wennekers Thomas
Published: July 2002

We present a general approximation method for the mathematical analysis of spatially localized steady-state solutions in nonlinear neural field models. These models comprise several layers of excitatory and inhibitory cells. Coupling kernels between and inside layers are assumed to be gaussian shaped. In response to spatially localized (i.e., tuned) inputs, such networks typically reveal stationary localized activity profiles in the different layers. Qualitative properties of these solutions, like response amplitudes and tuning widths, are approximated for a whole class of nonlinear rate functions that obey a power law above some threshold and that are zero below. A special case of these functions is the semilinear function, which is commonly used in neural field models. The method is then applied to models for orientation tuning in cortical simple cells: first, to the one-layer model with “difference of gaussians” connectivity kernel developed by Carandini and Ringach (1997) as an abstraction of the biologically detailed simulations of Somers, Nelson, and Sur (1995); second, to a two-field model comprising excitatory and inhibitory cells in two separate layers. Under certain conditions, both models have the same steady states. Comparing simulations of the field models and results derived from the approximation method, we find that the approximation well predicts the tuning behavior of the full model. Moreover, explicit formulas for approximate amplitudes and tuning widths in response to changing input strength are given and checked numerically. Comparing the network behavior for different nonlinearities, we find that the only rate function (from the class of functions under study) that leads to constant tuning widths and a linear increase of firing rates in response to increasing input is the semilinear function. For other nonlinearities, the qualitative network response depends on whether the model neurons operate in a convex (e.g., x2) or concave (e.g., sqrt (x)) regime of their rate function. In the first case, tuning gradually changes from input driven at low input strength (broad tuning strongly depending on the input and roughly linear amplitudes in response to input strength) to recurrently driven at moderate input strength (sharp tuning, supra-linear increase of amplitudes in response to input strength). For concave rate functions, the network reveals stable hysteresis between a state at low firing rates and a tuned state at high rates. This means that the network can “memorize” tuning properties of a previously shown stimulus. Sigmoid rate functions can combine both effects. In contrast to the Carandini-Ringach model, the two-field model further reveals oscillations with typical frequencies in the beta and gamma range, when the excitatory and inhibitory connections are relatively strong. This suggests a rhythmic modulation of tuning properties during cortical oscillations.
Random Embedding Machines for Pattern Recognition
Authors: Baram Yoram
Published: July 2002

Real classification problems involve structured data that can be essentially grouped into a relatively small number of clusters. It is shown that, under a local clustering condition, a set of points of a given class, embedded in binary space by a set of randomly parameterized surfaces, is linearly separable from other classes, with arbitrarily high probability. We call such a data set a local relative cluster. The size of the embedding set is shown to be inversely proportional to the squared local clustering degree. A simple parameterization by embedding hyperplanes, implementing a voting system, results in a random reduction of the nearest-neighbor method and leads to the separation of multicluster data by a network with two internal layers. This represents a considerable reduction of the learning problem with respect to known techniques, resolving a long-standing question on the complexity of random embedding. Numerical tests show that the proposed method performs as well as state-of the-art methods and in a small fraction of the time.
An Alternative Perspective on Adaptive Independent Component Analysis Algorithms
Authors: Girolami Mark
Published: July 2002

This article develops an extended independent component analysis algorithm for mixtures of arbitrary subgaussian and supergaussian sources. The gaussian mixture model of Pearson is employed in deriving a closed-form generic score function for strictly subgaussian sources. This is combined with the score function for a unimodal supergaussian density to provide a computationally simple yet powerful algorithm for performing independent component analysis on arbitrary mixtures of nongaussian sources.
Structure Learning in Conditional Probability Models via an Entropic Prior and Parameter Extinction
Authors: Brand Matthew
Published: July 2002

We introduce an entropic prior for multinomial parameter estimation problems and solve for its maximum a posteriori (MAP) estimator. The prior is a bias for maximally structured and minimally ambiguous models. In conditional probability models with hidden state, iterative MAP estimation drives weakly supported parameters toward extinction, effectively turning them off. Thus, structure discovery is folded into parameter estimation. We then establish criteria for simplifying a probabilistic model's graphical structure by trimming parameters and states, with a guarantee that any such deletion will increase the posterior probability of the model. Trimming accelerates learning by sparsifying the model. All operations monotonically and maximally increase the posterior probability, yielding structure-learning algorithms only slightly slower than parameter estimation via expectation-maximization and orders of magnitude faster than search-based structure induction. When applied to hidden Markov model training, the resulting models show superior generalization to held-out test data. In many cases the resulting models are so sparse and concise that they are interpretable, with hidden states that strongly correlate with meaningful categories.
Calibrating Visual Path Integration in VEs
Authors: Bakker Niels H. , Werkhoven Peter J. , Passenier Peter O.
Published: July 2002

When moving around in the world, humans can use the motion sensations provided by their kinesthetic, vestibular, and visual senses to maintain their sense of direction. Previous research in virtual environments (VEs) has shown that this so-called path integration process is inaccurate in the case that only visual motion stimuli are present, which may lead to disorientation. In an experiment, we investigated whether participants can calibrate this visual path integration process for rotations; in other words, can they learn the relation between visual flow and the angle that they traverse in the VE? Results show that, by providing participants with knowledge of results (KR), they can indeed calibrate the biases in their path integration process, and also maintain their improved level of performance on a retention test the next day.
Cooperative Strategies and the Evolution of Communication
Authors: Wagner Kyle
Published: July 2002

Using communication is not the only cooperative strategy that can evolve when organisms need to solve a problem together. This article describes a model that extends MacLennan and Burghardt's [37] synthetic ethology simulation to show that using a spatial world in a simulation allows a wider range of strategies to evolve in response to environmental demands. The model specifically explores the interaction between population density and resource abundance and their effect on the kinds of cooperative strategies that evolve. Signaling strategies evolve except when population density is high or resource abundance is low.
Water Resources in Life‐Cycle Impact Assessment: Considerations in Choosing Category Indicators
Authors: Owens J. W.
Published: July 2002

Water is one of many resources, wastes, and pollutants considered in life‐cycle assessment (LCA). The widely used indicator for water resources, the total input of water used, is not adequate to assess water resources from a sustainability perspective. More detailed indicators are proposed for water resources in two areas essential to water sustainability: water quantity and water quality. The governing principles for a consideration of water quantity are that (1) the water sources or LCA inputs are renewable and sustainable and (2) the volume of water released or LCA outputs are returned to humans or ecosystems for further use downstream. The governing principle for a consideration of water quality is that the utility of the returned water is not impaired for either humans or ecosystems downstream. Water quantity indicators are defined for water use, consumption, and depletion to reveal the sustainable or nonsustainable nature of the sources. A flexible set of water quality indicators for various factors that may impair water quality are then discussed, including the LCA study choices, technical challenges, and trade‐offs involved with such indicators. Indicator selection from this set involves the underlying concern or endpoint represented by the indicator and the level and accuracy of decision‐making information that the indicator must provide. With significant differences in emissions among systems studied using LCA and different purposes of the LCA studies themselves, a single, default set of water quality indicators applicable to all systems studied with LCA is problematic. The proposed water quantity and quality indicators for LCA studies are also intended to be compatible with environmental management and reporting systems so that data needs are not duplicated and interpretation for one does not contradict or sow confusion for the other.
From Cradle to Grave: Extended Producer Responsibility for Household Hazardous Wastes in British Columbia
Authors: Driedger Ronald J.
Published: July 2002

Household hazardous wastes (HHWs), the discarded pesticides, solvents, paints, lubricating oil, and similar products common to residences throughout the industrial world, create problems for governments charged with managing solid waste. When disposed of improperly in landfills or incinerators or if dumped illegally, HHW may contribute to soil and water contamination. A most common management tool for HHW is a special collection effort that segregates HHW from normal trash and disposes of it in an approved manner, all at a higher cost to the governmental jurisdiction. The Canadian province of British Columbia (BC) has undertaken a different approach, based on the use of extended producer responsibility (EPR).

BC's efforts began in 1992 with adoption of a regulation on used lubricating oil (lube oil). More than 40 million liters (L) of used lube oil have been collected annually through the EPR system established under this regulation. A regulation establishing producer responsibility for postconsumer paints followed in 1994. BC enacted an additional regulation establishing EPR in 1997 for solvents/flammable liquids, domestic pesticides, gasoline, and pharmaceuticals.

As a result of the application of EPR to HHW, local government costs for managing HHW and the amount of HHW identified in municipal waste have declined. Although the regulations appear to have mixed success in prompting consumers to avoid products that result in HHW, there are indications that they may be more effective than conventional management efforts.

Based on BC's experience with EPR, key factors for successful implementation include maintaining flexibility in program design, creating viable funding alternatives, aggressive enforcement to provide a level playing field, and adopting policies that maximize diversion of HHW from landfills, while minimizing waste generation, setting targets for reuse and recycling, promoting consumer awareness and convenience, involving local government jurisdictions, and monitoring outcomes.
Rethinking the Role of Ideology in International Politics During the Cold War
Authors: Gould-Davies Nigel
Published: July 2002

The partial opening of East-bloc archives has sparked renewed interest in the study of ideological influences in Soviet foreign policy. The task of weighing the relative importance of ideology is complicated, however, by the failure of most scholars to develop sound evaluative criteria. This article discusses the shortcomings of previous analyses of Soviet ideology and puts forth a more theoretically coherent approach, based on three explicit criteria for assessing ideological and security-seeking goals. A Few Unresolved Mysteries about Stalin and the Cold War in Europe: A Modest Agenda for Research
THE CANONICAL FUNCTION OF 2 PETER
Authors: Wall Robert
Published: July 2002

During the modern period, the authority of 2 Peter for Christian theological formation has been challenged by the reconstructions of historical criticism. The verdict of biblical scholarship has been largely negative: the theological conception of 2 Peter comes from a person and for a setting that does not easily cohere with the rest of the New Testament writings. The present essay seeks to rehabilitate the status of 2 Peter for use in biblical theology, independent of the historical problem it poses for the interpreter, by approaching its theological subject matter within the setting of the New Testament canon, where its theological perspective functions as complementary to and integral with 1 Peter in forming Scripture's Petrine witness to the faith.
FROM THE LION THRONE: POLITICAL AND SOCIAL DYNAMICS OF THE VIJAYANAGARA EMPIRE
Authors: Sinopoli Carla
Published: July 2002

The fourteenth- through seventeenth-century A.D. Vijayanagara empire of south India spanned a vast area and incorporated diverse ethnic, linguistic, socioeconomic and political groups. Beyond the imperial bounds, Vijayanagara was also part of complex subcontinental political and cultural nexus, with cooperative and antagonistic relations with neighboring states and empires. In this paper, I examine both scales of these relations: the local responses to empire and the nature and creation of an imperial identity within the broader framework of subcontinental politics. As inhabitants of incorporated regions within the empire maintained aspects of their regional identities, they were also drawn into the broader polity through both economic and symbolic practices. And even as it incorporated local traditions of conquered states, Vijayanagara's court also forged a distinctive imperial identity by adopting and adapting cultural, political, and military elements from a larger subcontinental framework.
The Development of Children's Beliefs about Prayer
Authors: Woolley Jacqueline , Phelps Katrina
Published: July 2002

In this study we explored the development of children's beliefs about the concept of prayer. Three- to 8-year-old children were given a combination of tasks and structured interview questions designed to assess a number of basic aspects of their concepts of prayer. We also considered potential relations between children's concepts of prayer and two other explanatory systems — naïve psychology and magic — by probing understanding of the roles of knowledge and thinking in prayer and by comparing beliefs in prayer to beliefs in wishing. Results revealed significantly more sophisticated concepts of prayer than found in previous studies, including an earlier understanding of its mentalistic nature. We propose a new developmental trajectory for children's understanding of prayer and discuss interrelations between children's religious beliefs and their developing ontologies.
Age structure and growth pattern in two populations of the golden-striped salamander Chioglossa lusitanica (Caudata, Salamandridae)
Authors: Ferrand  , Lima  , Arntzen
Published: July 2002

We studied age structure and growth in two populations of the golden-striped salamander, Chioglossa lusitanica, in northern Portugal by cohort analysis and skeletochronology. Lines of Arrested Growth (LAG) deposited during the larval phase could be distinguished from LAG deposited after metamorphosis. One or two LAG were found in larvae, with counts corresponding to age in years as predicted from larval size distributions. Post-metamorphic modal age was 5 to 6 years and longevity was 8 years. Von Bertalanffy growth curves for males and females from both populations were different from one another. Sexual maturity was reached 4 to 5 years after metamorphosis and corresponded with a snout-vent length of 43-44 mm in both sexes. A tendency was observed for females to be older than males. Mature females were on average larger than mature males. Larval growth was higher in spring than in winter and differed between populations and years. The population in which larvae grew relatively slowly was characterized by large young adults and vice versa, perhaps reflecting contrasting aquatic and terrestrial feeding conditions. The knowledge here presented is important for the better understanding of the population dynamics and ecological and conservation requirements of the golden-striped salamander.
ACOUSTICAL INTERFERENCE IN THE ADVERTISEMENT CALLS OF THE MIDWIFE TOADS (ALYTES OBSTETRICANS AND ALYTES CISTERNASII)
Authors: Bosch Jaime , Marquez Rafael
Published: July 2002

We address the issue of whether call alternation is a mechanism for diminishing call overlap between male midwife toads who are competing acoustically. Additionally, we study the effect of call overlap on the calling behavior of males and on female preferences. In both species, naturally interacting males emitted calls that did not overlap less than expected when males called randomly. Interactive playback calls showed that males increase their calling rate when responded to by a non-overlapping call, and that they do not increase their calling rate when responded to by calls that overlap with their own calls. In phonotaxis tests, females discriminated against duets of males that overlapped their calls. Furthermore, when calling males overlapped the males' calls, females did not discriminate between the male who was leading a calling duet and the follower. We conclude, therefore, that call overlap plays an important role in communication, since overlapping calls are less attractive to females. However, timing of male calling interactions does not diminish the overlap between calls.
VARIATION IN LEKKING COSTS IN BLACKBUCK (ANTILOPE CERVICAPRA): RELATIONSHIP TO LEK-TERRITORY LOCATION AND FEMALE MATING PATTERNS
Authors: Isvaran Kavita , Jhala Yadavendradev
Published: July 2002

We studied variation in lekking costs in an Indian antelope, the blackbuck Antilope cervicapra, in relation to female mating patterns. We tested the hypothesis that central males had a higher mating success and faced higher costs than peripheral males. We used continuous focal animal sampling to estimate time-activity budgets of individually identified central and peripheral lekking males and bachelor males. Scan sampling was used to estimate the time spent on the lek by central and peripheral males and to monitor female visits to the lek. We mapped lek-territories and monitored territory additions, territory turnover, and the location of matings. We found that central males faced higher costs than peripheral males. Central males foraged less, spent more time on the lek and tended to have higher fighting rates than peripheral males. Corresponding to this difference in costs, mating benefits were also greater for central males. Our results suggest that lek-territory location may be an important cue in female choice. Male mating success was skewed and 90% of matings observed occurred in the lek-centre. Furthermore, three of the five most successful males previously held territories in the lek-periphery where they were not observed to mate. Territory turnover was higher in the centre than in the periphery and males tended to move towards the centre while shifting territories. Based on these findings, we suggest that central and peripheral males follow two different strategies in response to a female preference for central territories: while central males may try to maximise encounters with oestrous females by investing heavily in lekking, peripheral males seem to attempt to maximise their chances of gaining central territories by not compromising on foraging time and investing less in lekking. Since we did not directly measure male phenotype, its role in explaining the patterns we found remains to be studied.
SOCIAL BONDS AND THE COHERENCE OF MOUNTAIN BABOON TROOPS
Authors: Henzi  , Lycett  , Weingrill  , Piper
Published: July 2002

Female chacma baboons (Papio cynocephalus ursinus) in the Drakensberg mountains, experiencing neither predation nor within-group competition, structure their social relationships with other females in order to sustain reciprocated grooming (Henzi et al., 1997b). To do so, they cap, where time constraints demand, the size of their grooming cliques. From this we have assumed that the social orientation of mountain baboon females is primarily towards other females and that fission is a consequence of the increasing differentiation of cliques, leading to one or a few females following a male 'friend' when he departs. An alternative argument (Barton et al., 1996) is that, where predation or within-group competition do not occur, neither should female-bonded groups. In this view, females under such conditions should be 'cross-bonded' to males, each group male associating with a few females in the manner of hamadryas baboons (P. c. hamadryas). We test this prediction of 'cross-bonding' at both troop and individual level and find no evidence to support it. We then present data on fission events which argue for fission in the Drakensberg being due to the departure of small one-male units. However, the data do not support, unequivocally, the proposal that females leave with male 'friends'. They do, however, always leave with a male who has fathered at least one of their non-adult offspring.
MATING SUCCESS AND MALE COURTSHIP BEHAVIORS IN THREE POPULATIONS OF THE THREESPINE STICKLEBACK
Authors: Ishikawa Masaki , Mori Seiichi
Published: July 2002

Genetic and morphological studies indicated the existence of two phylogenetically distinct groups in the threespine stickleback, Gasterosteus aculeatus, around Japan. These two morphotypes were named as the Pacific Ocean group and the Japan Sea group, respectively. In the Pacific Ocean group, there are anadromous populations and populations that reside permanently in freshwater. This study presented the results of mate choice tests among three allopatric populations of Japanese threespine sticklebacks and we found significant evidence of assortative mating. A total of 226 mate choice test was carried out in 1995 and 1996. Ten courtship behaviors were collected and comparisons were made among three intrapopulational pairings. It was concluded that the Pacific Ocean group and the Japan Sea group have distinct behavioral characteristics. We also found effects of male size and female size on the probability of mating success between populations.
MICROGEOGRAPHIC SONG DIALECTS IN THE ORANGE-TUFTED SUNBIRD (NECTARINIA OSEA)
Authors: Leader Noam , Wright Jonathan , Yom-Tov Yoram
Published: July 2002

In a study of male song in the orange-tufted sunbird (Nectarinia osea) in an urban neighborhood in Ramat-Aviv, Israel, we discovered the occurrence of song variation on a microgeographic scale in the form of two distinct dialects with a sharp boundary between them. The main distinction between the two song dialects is the frequency of the trill, which comprises the terminal part of the song. A large difference of 2-3 kHz in the peak frequency of the trill was discovered between the two dialects, which could be easily distinguished by ear. Thirtyseven males were recorded singing the 'low' dialect and 21 birds sang the 'high' dialect. Four other birds sang both dialects or 'hybrid' songs. Along the boundary that separated the two dialect populations, neighboring birds sang different dialect songs, although they were only 20-30 meters apart. All four 'bilingual' birds occupied territories near the dialect boundary. The historical processes leading to the formation of this dialect system may result from the pattern of human settlement at the time of the establishment of this neighborhood in the early 1950's. The spatial distribution of the two sunbird dialect populations, and the apparent low dispersal rates of birds from their natal dialect area, suggest the existence of a mechanism, which currently maintains these dialects at the current boundaries.
NO EVIDENCE OF FEMALE CHOICE FOR A CONDITION-DEPENDENT TRAIT IN THE AGAMID LIZARD, CTENOPHORUS ORNATUS
Authors: Lebas Natasha , Marshall N. Justin
Published: July 2002

Female choice has rarely been documented in reptiles. In this study we examined the variation, condition-dependence and female preference for a range of male morphological and colour traits in the agamid lizard, Ctenophorus ornatus. Colour traits were measured with reflectance spectrophotometry which allows the accurate quantification of colour traits independent of the human visual system. All the colour traits varied greatly in brightness but only the throat showed high variation in the spectral shape. For the morphological traits, chest patch size showed the highest amount of variation and was also condition-dependent. Males with a larger chest patch also had a patch which was a darker black. Female mate choice trials were conducted on male chest patch size and body size, which is the trait females have preferred in other lizard species. Females showed no preference, measured as spatial association, for larger males or males with bigger chest patches. In post-hoc tests females did not prefer males with brighter throats or darker chests. Our findings suggest that females show no spatial discrimination between males on the basis of a range of traits most expected to influence female choice.
Sperm Competition in a Nuptial Feeding Spider, Pisaura Mirabilis
Authors: Drengsgaard Inger , Toft Soren
Published: July 2002

The paper tests two hypotheses about sperm priority in the spider Pisaura mirabilis. A 'phylogenetic constraints hypothesis' states that since the females have conduit spermathecae, first male priority should prevail. On the other hand, males offer nuptial prey to the females and females mate with multiple males. The evolution of these traits is most easily understood if late mating males also have a substantial fertilization success. The results indicate a compromise solution. Sterile-male technique with double-mated females indicated a first male priority pattern (P1 = ca 70%, after adjusting for sterilization damage and experimental mortality). However, the success of the fourth male of quadroublemated females was unexpectedly high (adjusted P4 = ca 24%, not different from P of 2 two-male matings). This lends support to a supplementary hypothesis of constant last male success, which may turn an initial first-male advantage into a last-male advantage, when the number of males mating with a female raises above a certain number. Independent of mating order, males may increase their share of fertilizations by long copulation times. It was tested whether female choice for symmetric males might account for differential male success. However, fluctuating asymmetry (FA) in male leg length showed no relationships with fertilization success or copulation duration.
EXTRA-HAREM PATERNITY IN THE WHITE-LINED BAT SACCOPTERYX BILINEATA (EMBALLONURIDAE)
Authors: Heckel Gerald , Voigt Christian , Mayer Frieder , Von Helversen Otto
Published: July 2002

We studied the paternity in a colony of the harem-polygynous white-lined bat Saccopteryx bilineata by microsatellite typing and compared the data with group composition and stability. Although we recorded a high stability for harem groups, neither spatial proximity of males to harem females nor harem ownership allowed us to predict the paternity of the next year's harem offspring. Eight out of 28 juveniles were fathered by holders of the harem in which they were born, while the other 20 represent Extra-Harem-Young (EHY). 50% of EHY were fathered by males from outside the colony and 50% by other harem holders or peripheral males of the colony. On average, reproductive success of harem holders (1.2 offspring/year) was higher compared with peripheral males (0.4 offspring/year). Harem size seemed not to influence reproductive success of harem holders. Although maintaining of a territory seems to be costly for a harem male, his ability to control the females of his harem may be restricted; instead female Saccopteryx bilineata appear to have a high potential for female choice.
A uniform representation for the plan of organisation of nematodes of the order Tylenchida
Authors: Milton Jack , Diederich Jim , Fortuner Renaud
Published: July 2002

The need for a uniform method of describing structures (organs and sub-organs) of taxa prior to building a database for nematode identification and other computer applications is discussed. The classical representation of characters (entity - attribute - value) does not assure uniformity and guidelines are needed for a truly uniform representation of morphological-anatomical entities, i.e., the organs and sub-organs of nematodes or other biological groups. Views and other relationships are proposed to manage specific aspects of representation such as perspectives (e.g., front vs lateral view), junction between two organs, structural overlaps, grouping of organs, sub-organs contained in several organs, and organs that could be arranged in more than one system. The value of the proposed character representation is discussed for identification, taxonomy (homologies), and other uses. Une représentation uniformisée du plan d'organisation des nématodes de l'ordre Tylenchida - L'article considère la nécessité d'une méthode uniformisée pour la description des structures des taxons dans le cadre de la construction d'une base de données pour l'identification assistée par ordinateur et d'autres applications informatiques. La représentation classique des caractères (entité - attribut - valeur) ne suffit pas à elle seule à assurer l'uniformité et des directives sont nécessaires pour aboutir à une décomposition réellement uniforme. La représentation uniforme des "entités" morpho-anatomiques est discutée, les entités en question étant les organes et sous-organes des nématodes et d'autres groupes biologiques. Des vues (au sens informatique) et d'autres relations sont proposées pour gérer des aspects spécifiques de la représentation tels que les différentes perspectives (vue de face et vue latérale par exemple), les jonctions entre deux organes, les recouvrements structurels, l'association de plusieurs organes, la présence d'un même sous-organe dans plusieurs organes et les organes qui appartiennent à plusieurs systèmes. La valeur de la représentation des caractères proposée dans cet article est discutée pour l'identification, la taxinomie (homologies) et d'autres utilisations informatiques en biologie.
Potato cyst nematode hatching activity and hatching factors in inter-specific Solanum hybrids
Authors: Devine Ken , Jones Peter
Published: July 2002

In studies using three sibling F1 clones from each of five crosses between Solanum tuberosum and different wild tuberbearing Solanum species, root leachate hatching activity towards each of the two potato cyst nematode (PCN) species, Globodera rostochiensis and G. pallida, segregated independently. Sephadex G-10 fractionation of the leachates of S. sucrense-hybrid clones revealed differences between clones in the hatching factor elution profiles for the two PCN species. Analysis of individual hatching factors indicated examples both of selectivity (both PCN species hatched in response to a particular hatching factor, but at different levels of hatching response) and of specificity (only one PCN species hatched in response to a particular hatching factor) of hatching factors. The hatching factor profiles of the S. sucrense-hybrids indicated segregation of hatching factors from the parents, but also detected novel factors unique to specific hybrid clones. Total hatching activity of the root leachate of the S. sucrense clones was positively correlated with the proportion of S. tuberosum-derived hatching factors.
The association of two Diplogasteroides species (Secernentea: Diplogastrina) and cockchafers (Melolontha spp., Scarabaeidae)
Authors: Kiontke Karin , Manegold Albrecht
Published: July 2002

The life cycle of two morphologically very similar Diplogasteroides species and their association with cockchafers in southern Germany was investigated. 70-100% of cockchafer grubs and 95% of the imagines carried Diplogasteroides spp. dauer juveniles. The nematodes were almost exclusively found on the external cuticle of the insects and usually not in the body cavity or the intestine. Diplogasteroides spp. dauer juveniles embark on the grub and accumulate during its development. There was some indication that dauer juveniles are transmitted from male to female beetle during copulation. The dauer juveniles resume development only after the death of the beetle, feeding on the cadaver (necromeny). Former hypotheses, assuming the nematode species to be parasitic and to cause the death of cockchafer grubs, can be refuted.
Diagenetic evolution of crystallite thickness distribution of illitic material in Carpathian shales, studied by the Bertaut-Warren-Averbach XRD method (MudMaster computer program)
Authors: Kotarba M. , Środoń J.
Published: July 2002

The MudMaster computer program, based on the modified Bertaut-Warren- Averbach (BWA) XRD method, was used in the study of diagenetic evolution of illitic material in shales. The illitic material was characterized by XRD as a mixture of illite-smectite (I-S) and discrete illite. The experimental conditions for complete dehydration of swelling clays, necessary in this method, were established for a climate of high relative humidity (RH >40%). It was found that the distribution of crystallite thickness of dehydrated illitic material of shales is described by the lognormal law, as was established earlier by the BWA method for pure I-S from pyroclastic rocks. The parameters characterizing this distribution evolve with depth: the mean crystallite thickness (Te), the distribution broadening (DW) and the parameter of a lognormal distribution (β2) increase, whereas the percentage of the most frequent crystallite thickness decreases. The observed scatter of values is not random but indicates fluctuations in the characteristics of the illitic material of shales. The results imply that the modified Scherrer technique of measuring mean crystal thickness from the broadening of XRD reflections can be extended at least to some shales.
Time-dependent changes of adsorption and wetting properties of pillared montmorillonites
Authors: Dékány I. , Seefeld V. , Lagaly G.
Published: July 2002

The changes of adsorption properties of uncalcined Al-pillared montmorillonite were studied. A soda-activated bentonite from Slovakia was reacted with polymeric hydroxoaluminium salt solutions. During storagein air at room temperature for three years, the basal spacing decreased by 0.15–0.2 nm; the specific surface area was reduced by 80% and the total pore volume by 40–60%. Adsorption experiments from ethanol-cyclohexane mixtures revealed the decreasing adsorption capacity and the increasing hydrophobicity. The changing surface character was also evident in the decrease in enthalpy of immersion in ethanol from 65.3 J/g to 8.3 J/g (sample B) and from 37.8 J/g to 5.2 J/g (sample C). The alteration probably arises from gradual formation of gibbsite-like interlayers and the redistribution of charges.
ATEM investigation of experimentally annealed sillimanite: new constraints for the SiO2–Al2O3 join
Authors: Raterron P. , Carpenter M. , Doukhan J.-C.
Published: July 2002

Four samples of Fe-bearing prismatic sillimanite, containing ∼1 wt.% Fe2O3, were annealed experimentally at temperatures of 1465 and 1675°C, and pressures between 1 atm and 30 kbar. Transmission electron microscopy (TEM) and analytical TEM (ATEM) investigation of the samples reveal that the starting material partly transformed into mullite during the annealing, and that this process was assisted by partial melting. The exsolved partial melt (now a glass), observed at triple junctions and in the form of small precipitates (∼10–1000 nm in size) within the sillimanite matrix, contains >80 wt.% SiO2. It also contains ∼11 wt.% Al2O3, some FeO and detectable amounts of K2O and CaO. Dissociated c dislocations in sillimanite are preferential nucleation sites for SiO2-rich precipitates. The equilibrium compositions of residual sillimanite-mullite were measured with a 2 nm wide probe at the interface with the SiO2-rich glass in each sample after heat treatment. We used these equilibrium compositions to constrain the parameters of a point defect model for sillimanite mullitization proposed by Raterron et al. (1999). With the revised parameterization, it is now possible to calculate the position of the boundary between fields of mullite + melt and mullite in the SiO2–Al2O3 phase diagram, and to predict the effect of pressure on this boundary. However, to be used as a standard, this model still needs to be calibrated in the pure SiO2–Al2O3 system (without impurities such as iron).
Three compositional varieties of perovskite from kimberlites of the Lac de Gras field (Northwest Territories, Canada)
Authors: Chakhmouradian A. R. , Mitchell R. H.
Published: July 2002

In hypabyssal and crater-facies kimberlites of the Lac de Gras kimberlite field, perovskite occurs as reaction-induced rims on earlier-crystallized Ti-bearing minerals (magnesian ilmenite and priderite), inclusions in atoll spinels and discrete crystals in a serpentine-calcite mesostasis. The mineral is associated with spinels, apatite, monticellite, phlogopite, baryte, Fe-Ni sulphides, ilmenite, diopside and zircon. Uncommon accessory phases found in an assemblage with perovskite include titanite, monazite- (Ce), witherite, strontium-apatite, khibinskite, djerfisherite, wollastonite, pectolite, suolunite, hydroxyapophyllite and bultfonteinite. Three types of perovskite can be distinguished on the basis of composition: (I) REE-Nb-Al-poor perovskite with relatively high Sr and K contents (up to 2.2 and 0.6 wt.% oxides, respectively) occurring as mantles on priderite and inclusions in atoll spinels; (II) perovskite with elevated Al, Fe, Nb and LREE (up to 1.4, 8.3, 9.1 and 17.0 wt.% oxides, respectively) found as discrete crystals and rims on macrocrystic ilmenite; (III) perovskite significantly enriched in Na, Sr, Nb and LREE (up to 3.3, 3.4, 13.0 and 22.6 wt.% oxides, respectively) found as rims on perovskite I and II. The overwhelming majority of perovskite is represented by discrete crystals of type II. In some occurrences, this type of perovskite also has high Th contents (up to 5.5 wt.% ThO2) and Zr contents (up to 3.7 wt.% ZrO2). Textural evidence indicates that perovskite shows an overall evolutionary trend from the most primitive type I towards type III showing the highest Na, Nb and LREE contents. Perovskite of type I probably crystallized under relatively high pressures prior to the precipitation of MUM spinels. Perovskite II crystallized after magnesiochromite, pleonaste and MUM (magnesian ulvöspinel-magnetite) spinels, under increasing fO2. The most compositionally evolved type III formed during near-solidus re-equilibration of the earlier-crystallized perovskite. The compositional variation of the Lac de Gras perovskite can be adequately characterized in terms of five major end-members: CaTiO3 (perovskite), CeFeO3, NaNbO3 (lueshite), Na0.5LREE0.5TiO3 (loparite), and CaFe0.5Nb0.5O3 (latrappite).
Lattice defects in lawsonite: a TEM investigation
Authors: Cámara F. , Doukhan J. C. , Carpenter M. A.
Published: July 2002

Lattice defects in lawsonite have been studied by transmission electron microscopy. It is proposed that twinning and easy glide systems are 1/2[110] {110}; the easy glide planes are coincident with twin planes. This mineral displays high sensitivity to the electron beam, even at low temperatures. In situ precipitates appear as a consequence of beam irradiation. The precipitation takes places first on dislocations, then on twin boundaries and then in the matrix, causing ‘coffee-bean’ contrast features typical of precipitates. The studies were performed at low temperature (∼110 K) in order to investigate the low temperature displacive transitions from space group Cmcm to Pmcn and P21cn and elucidate their microscopic character. No characteristic microstructural texture, such as antiphase domains associated with the transition, were observed, however. This is probably due to the high mobility of protons under the electron beam. The development of regularly spaced dislocations along twin planes is hypothesized as the only evidence that a phase transition takes place at a nanoscale.
Discontinuation of fucose therapy in LADII causes rapid loss of selectin ligands and rise of leukocyte counts
Authors: Lühn Kerstin , Marquardt Thorsten , Harms Erik , Vestweber Dietmar
Published: July 2002

Leukocyte adhesion deficiency type II (LADII) is a rare inherited disorder of fucose metabolism. Patients with LADII lack fucosylated glycoconjugates, including the carbohydrate ligands of the selectins, leading to an immunodeficiency caused by the lack of selectin-mediated leukocyte-endothelial interactions. A simple and effective therapy has recently been described for LADII, based on the administration of oral fucose. Parallel to this treatment the lack of E- and P-selectin ligands on neutrophils was corrected, and high peripheral neutrophil counts were reduced to normal levels. This study reports that discontinuation of this therapy leads to the complete loss of E-selectin ligands within 3 days and of P-selectin ligands within 7 days. Peripheral neutrophil counts increased parallel to the decrease of selectin ligands. Selectin ligands reappeared promptly after resumption of the fucose therapy, demonstrating a causal relationship between fucose treatment and selectin ligand expression and peripheral neutrophil counts.
A novel regulator of G-protein signaling bearing GAP activity for Gαi and Gαq in megakaryocytes
Authors: Nagata Yuka , Oda Masaaki , Nakata Hiroko , Shozaki Yuka , Kozasa Tohru , Todokoro Kazuo
Published: July 2002

The regulator of G-protein signaling (RGS) negatively regulates the α subunit of G proteins by accelerating their intrinsic guanosine triphosphatase (GTPase) activity. Here are reported the isolation and characterization of a novel mouse RGS, termed RGS18, which is a new member of RGS subfamily B. Northern blot analysis showed that RGS18 messenger RNA was detected predominantly in spleen and hematopoietic cells, and immunohistochemical studies demonstrated that RGS18 was expressed in megakaryocytes, platelets, granulocytes/monocytes, and, weakly, in hematopoietic stem cells, but not in lymphocytes or erythrocytes. Although various subcellular localizations of RGS have been reported, RGS18 was found to be localized in cytoplasm in megakaryocytes. In vitro binding assays of RGS18 with megakaryocyte cell lysates with or without AlF4− treatment demonstrated that RGS18 specifically binds to 2 α subunits of the G protein, Gαi and Gαq. Furthermore, RGS18 clearly exhibited GTPase-activating protein (GAP) activity for Gαi and Gαq but not for Gαs or Gα12. In addition, chemokine stromal-derived factor 1 (SDF-1), which has been reported to stimulate megakaryocyte colony formation in the presence of thrombopoietin, affected the binding of RGS18 to Gαi but not to Gαq. Therefore, the newly isolated RGS18 turned out to be a new member of the RGS family bearing GAP activity for Gαi, which might be stimulated by SDF-1 in megakaryocytes, as well as for Gαq. Thus, RGS18 may play an important role in proliferation, differentiation, and/or migration of megakaryocytes.
Immune thrombocytopenia resulting from sensitivity to metabolites of naproxen and acetaminophen
Authors: Bougie Daniel , Aster Richard
Published: July 2002

In patients suspected of having drug-induced immune thrombocytopenia, antibodies reactive with normal platelets in the presence of the suspect drug can sometimes be identified, but negative results are often obtained. One reason for this is that drug metabolites, formed in vivo, can be the sensitizing agents, but very little is known about the specific metabolites that can cause this complication. Five patients were studied who developed thrombocytopenia after taking the nonsteroidal anti-inflammatory drug naproxen (3 cases) or acetaminophen (2 cases) but in whom drug-dependent antibodies could not be detected by means of the unmodified drugs. In each case, antibodies that reacted with normal target platelets in the presence of a known drug metabolite (naproxen glucuronide or acetaminophen sulfate) were identified. Four of the antibodies were specific for the glycoprotein (GP) IIb/IIIa complex, but one acetaminophen sulfate–dependent antibody reacted preferentially with GPIb/IX/V. In patients with a clinical picture suggestive of drug-induced immune thrombocytopenia, tests for metabolite-dependent antibodies can be helpful in identifying the responsible agent.
Interferon-inducible protein 10, monokine induced by interferon gamma, and interferon-inducible T-cell alpha chemoattractant are produced by thymic epithelial cells and attract T-cell receptor (TCR) αβ+CD8+ single-positive T cells, TCRγδ+ T cells, and natural killer–type cells in human thymus
Authors: Romagnani Paola , Annunziato Francesco , Lazzeri Elena , Cosmi Lorenzo , Beltrame Chiara , Lasagni Laura , Galli Grazia , Francalanci Michela , Manetti Roberto , Marra Fabio , Vanini Vittorio , Maggi Enrico , Romagnani Sergio
Published: July 2002

Strong reactivity for interferon-inducible protein 10 (IP-10), monokine induced by interferon gamma (Mig), and interferon-inducible T-cell alpha chemoattractant (I-TAC) was found in epithelial cells mainly localized to the medulla of postnatal human thymus. The CXC chemokine receptor common to the 3 chemokines (CXCR3) was also preferentially expressed in medullary areas of the same thymuses and appeared to be a property of 4 distinct populations: CD3+T-cell receptor (TCR) αβ+CD8+ single-positive (SP) T cells, TCRγδ+ T cells, natural killer (NK)–type cells, and a small subset of CD3+(low)CD4+CD8+TCRαβ+double-positive (DP) T cells. IP-10, Mig, and I-TAC showed chemoattractant activity for TCRαβ+CD8+ SP T cells, TCRγδ+ T cells, and NK-type cells, suggesting their role in the migration of different subsets of mature thymocytes during human thymus lymphopoiesis.