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  • Springer  (66,910)
  • 1995-1999  (66,910)
  • 1970-1974
  • 1999  (66,910)
  • 1
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    Insectes sociaux 46 (1999), S. 131-136 
    ISSN: 1420-9098
    Keywords: Key words:Vespula, Polistes, Vespidae, foraging, resource choice.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The role of visual cues provided by resident wasps on resource choice by yellowjacket and paper wasp foragers was investigated. Large spring queen yellowjackets and small early season yellowjacket foragers (Vespula germanica, Vespula maculifrons, and Vespula vidua) were extracted in hexane to remove odors and posed as though feeding at petri dish feeders bearing daisy-like flower models, equipped with microcapillary feeding tubes, and containing 1:3 honey:water solution. An array of five feeders was presented to foragers at a suburban and a woodland site in Saratoga Springs, New York. The visual cues provided by resident wasps influenced resource choice by approaching social wasp foragers. Vespula germanica, an introduced yellowjacket species that tends to dominate at rich resources, was the only wasp visiting the suburban feeders. Foragers of this species preferentially fed on feeders and flowers with posed wasps and fed most often next to large wasps. Polistes fuscatus foragers at the woodland site similarly preferred to feed on occupied feeders and flowers. Vespula maculifrons and V. consobrina preferentially visited unoccupied feeders. Individual V. maculifrons, V. consobrina and V. vidua foragers that landed on occupied feeders all preferentially visited unoccupied flowers on those feeders. Vespula vidua and V. flavopilosa foragers did not demonstrate a feeder preference based on the presence/absence of posed wasps. Vespula consobrina foragers that visited occupied feeders preferred those occupied by extracted V. maculifrons queens and workers; no other wasps showed species based landing preferences.
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  • 2
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    Insectes sociaux 46 (1999), S. 137-145 
    ISSN: 1420-9098
    Keywords: Key words: Mating frequency, polyandry, Apis mellifera sicula, honey bees, microsatellite.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Honey bee queens have been shown to mate with a high number of males, but the evolutionary advantage of this high degree of polyandry is still unclear. Mating data from a number of different Apis species and subspecies are needed to help explain polyandry in honey bees. Pupae of four colonies of Apis mellifera sicula from Sicily were genotyped on three polymorphic microsatellite loci. The genotypes of the queens and fathering drones from these colonies were deduced from the genotypes of the pupae. We found no evidence for polygyny, at least we can exclude more than one functional queen, even super-sister queens, if maternity contributions are equal. The four queens mated with at least 5 to 12 (mean: 9.3 ± 3.0 SE) drones. We estimate the error in our determination of the mating frequency that is caused by limited genetic resolution of the marker loci to be less than 1 mating given that Hardy-Weinberg assumptions are satisfied. However, the drones the single queens mated with may be a non-random sample of the whole population, so that detection error may be more severe. The average pedigree relatedness among workers within the colonies was estimated to be 0.341. These results are within the range of those found in other A. mellifera subspecies and Apis species except A. dorsata. We speculate that mating frequency may be positively correlated with drone density.
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  • 3
    ISSN: 1420-9098
    Keywords: Key words: Worker polymorphism, ant-plant interaction, mutualism, morphometrics.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: We compared intranidal variation in worker size in the two closely related plant-ants Aphomomyrmex afer and Petalomyrmex phylax. Each of these genera is monotypic, and the two appear to be sister species among extant ants. Workers of A. afer are larger on average and exhibit much greater intranidal size variation. Workers of P. phylax are smaller and much less variable in size. Both species show weak allometry for some pairs of characters. Head shape is also different in workers of the two species. We discuss these differences in relation to the ecology of A. afer and P. phylax, and propose a scenario for the evolutionary divergence of worker morphology in these two species. Based on comparisons of these two monotypic genera with related ants, we suggest that reduced intranidal variation in worker size is a derived trait in Petalomyrmex.
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  • 4
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    Insectes sociaux 46 (1999), S. 208-218 
    ISSN: 1420-9098
    Keywords: Key words:Melipona panamica, stingless bees, Apidae, nestmate recognition, worker oviposition.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Nestmate recognition was studied in the Neotropical stingless bee Melipona panamica, a species in which workers “sneak” their own reproductive eggs into 1 % of brood cells. We manipulated four factors that could influence individual recognition cues: the mother queen, the environment during the immature stage, the environment during the early adult stage, and worker age. We also simulated the action of natural enemies on colonies tested for discrimination of such worker characteristics. All factors that we tested affected responses of the discriminating workers, which could recognize sisters, nieces and unrelated workers. Previous exposure of unrelated callow bees to the odor of the host nest greatly increased chances of acceptance by the host colony. Probability of acceptance decreased, however, with increasing age of introduced bees or increasing disturbance of the host colony. These complexities in patterns of nestmate recognition and nest defense are adequately explained from the standpoint of inclusive fitness of the discriminating workers. Differences in nestmate recognition and worker egg laying among Meliponini are also discussed.
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  • 5
    ISSN: 1420-9098
    Keywords: Key words: Termites, nest construction, plant growth suppression, plant abundance.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Termites invest considerable time and energy constructing elaborate mounds out of clay, sand, silt, excreta and saliva, which they defend vigorously against predators and parasites. Termite mounds are fertile and potentially attractive resources for plants, which may threaten the stability of the mound. Field surveys at Boola Boola Forest in SE Australia revealed significantly higher abundance and diversity of vascular plants growing on uninhabited than inhabited mounds of the termite Coptotermes lacteus. These data reveal that the presence of termites affects the establishment and growth of vegetation. Germination experiments indicate that plant growth suppression is not chemically mediated but rather is due to the impenetrable nature of the mound surface. Analyses of soil types suggests that termite workers may choose particular clay minerals for mound construction, which enhances surface impenetrability and thus increases the engineered integrity of the mound.
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  • 6
    ISSN: 1420-9098
    Keywords: Key words: Eusocial aphids, Pseudoregma bambucicola, resource allocation, soldier investment, reproductive schedule.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The reproductive characteristics of the soldier-producing aphid Pseudoregma bambucicola were studied in Kagoshima, Southern Japan, to know the factors affecting soldier production of eusocial aphids. The soldier proportion in aphid colonies was highest from October to November. In some large colonies, soldiers were observed in all seasons except in July when colony size was relatively small. Multiple regression analysis showed that the colony size was a principal factor affecting soldier proportion throughout a year. Other social or environmental factors such as aphid composition, host plant conditions and predator abundance were not always significant. Rearing experiments revealed that large colonies (≥1,000 individuals) produced soldiers in almost all seasons while small colonies (〈1,000) never produced any soldiers. The caste-production schedule of adult females was examined in the field. When solitary females produced both castes, they usually produced normal nymphs first and then soldiers. Females from large colonies tended to produce more soldiers in the earlier period of their lifetime, whereas females from newly established small colonies produced no or only a few soldiers at later times. The average number of soldiers and normal nymphs produced consecutively by a single female was 〉10 and 〉20, respectively. Because they have a small number of ovarioles (〈15 on average), females should alter caste production within the same ovarioles according to changes in environmental conditions. Artificial removal or introduction of predators and reduction of colony size did not affect soldier production over two successive generations, revealing maternal effects on soldier production. Females cannot shift caste production quickly in response to changes in predator abundance and colony size. This is probably due to early developmental determination of castes within the mother's body.
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  • 7
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    Insectes sociaux 46 (1999), S. 315-322 
    ISSN: 1420-9098
    Keywords: Key words:Bombus terrestris, bumble bee, larval feeding, caste differentiation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The duration of feedings received by Bombus terrestris larvae was studied using video-recordings. In the last days of development all larvae received feedings mainly of long duration. Worker larvae of the third brood received significantly longer feedings than worker larvae reared in the other broods. Throughout the development queen larvae and worker larvae received feedings of similar duration. Male larvae received shorter feedings than both kinds of female larvae. Therefore, the duration of feedings seems to be associated to the sex and stage of development of the larvae.¶The causes of the long-duration feedings seem not to be related to the amount of food provided, workers' age and size, to the workers' abdominal contraction or to the amount of pollen in the larval food. Perhaps the feeding duration is caused by the viscosity of the food, which is a consequence of the presence of pollen grains, sugar and glandular material. Although the precise amount of pollen was not measured, the differences in colour showed clearly that the larval food samples contained variable quantities of pollen grains. Some of the samples did not contain any pollen at all.¶It is suggested that the duration of feedings may be related (among other factors) to the presence of glandular material (proteins and enzymes) which is added to the larval food. This could be especially important for queen larvae in the last phase of their development. Because they have a long development and are fed with a high frequency they might receive large amounts of these substances. This could help them to grow more efficiently using a relatively smaller amount of pollen than expected.
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  • 8
    ISSN: 1420-9098
    Keywords: Key words: Pre-mating behaviour, gyne, abdomen enlargement, Melipona beecheii, stingless bee.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The behaviour of gynes of Melipona beecheii in queen-deprived colonies was studied. The period after emergence until acceptance is characterized by agonistic behaviour of workers towards the gynes. The gynes escaped from this worker aggression by hiding in the periphery of the nest, by performing rapid turn-arounds once grabbed by a worker, and "feigning death". Between acceptance and nuptial flight, gynes spent most of their time in pushing, hiding, and antennal contact with workers, and self-grooming or food solicitation. After the nuptial flight the queen's behavioural repertoire shifted to less pushing and food solicitation, to an increase in standing, tapping and antennal contact.¶Accepted gynes had a significantly more prolonged abdomen inflation than gynes that were eliminated.¶An hypothesis is presented to explain how abdomen enlargement and behavioural development influences the acceptance of gynes and the establishment of a dominance relation with workers under queenless conditions.
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  • 9
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    Pure and applied geophysics 154 (1999), S. 57-72 
    ISSN: 1420-9136
    Keywords: Key words: Mining tremors, neural networks, time series.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —Changes of the primary strain-stress state (caused by interaction between natural conditions and mining activity) can result, under special circumstances, to the origin of seismic induced events. The question of induced seismic activity prediction was treated as a problem of time series extrapolation of maximum cumulative amplitudes and numbers of seismic events recorded per day. The treatment was carried out by means of Multilayered Perceptron Neural Networks (MLP NN). The application to mining tremor prediction has been tested and methodological conditions have been obtained. It was proved that the prediction of the number of mining tremors per day is more precise than the prediction of future energy (maximum amplitudes). Further advance, based on the processing of seismo-acoustic activity series, is introduced.
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  • 10
    ISSN: 1420-9136
    Keywords: Key words: Asian summer monsoon, systematic errors, temperature, moisture, heat budget, moisture budget.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —The thermodynamic characteristics of the Asian summer monsoon are examined with a global analysis-forecast system. In this study, we investigated the large-scale balances of heat and moisture by making use of operational analyses as well as forecast fields for June, July and August (JJA), 1994. Apart from elucidating systematic errors in the temperature and moisture fields, the study expounds the influence of these errors on the large-scale budgets of heat and moisture over the monsoon region. The temperature forecasts of the model delineate predominant cooling in the middle and lower tropospheres over the monsoon region. Similarly, the moisture forecasts evince a drying tendency in the lower troposphere. However, certain sectors of moderate moistening exist over the peninsular India and adjoining oceanic sectors of the Arabian Sea and Bay of Bengal.¶The broad features of the large-scale heat and moisture budgets represented by the analysis/forecast fields indicate good agreement with the observed aspects of the summer monsoon circulation. The model forecasts fail to retain the analyzed atmospheric variability in terms of the mean circulation, which is indicated by underestimation of various terms of heat and moisture budgets with an increase in the forecast period. Further, the forecasts depict an anomalous diabatic cooling layer in the lower middle troposphere of the monsoon region which inhibits vertical transfer of heat and moisture from the mixed layer of the atmospheric boundary layer to the middle troposphere. In effect, the monsoon circulation is considerably weakened with an increase in the forecast period. The treatment of shallow convection and the use of interactive clouds in the model can reduce the cooling bias considerably.
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  • 11
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    Pure and applied geophysics 154 (1999), S. 467-483 
    ISSN: 1420-9136
    Keywords: Key words: Tsunami, subduction zones, interplate earthquakes, intraplate earthquakes, tsunami earthquakes.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —We classified tsunamigenic earthquakes in subduction zones into three types earth quakes at the plate interface (typical interplate events), earthquakes at the outer rise, within the subducting slab or overlying crust (intraplate events), and "tsunami earthquakes" that generate considerably larger tsunamis than expected from seismic waves. The depth range of a typical interplate earthquake source is 10–40km, controlled by temperature and other geological parameters. The slip distribution varies both with depth and along-strike. Recent examples show very different temporal change of slip distribution in the Aleutians and the Japan trench. The tsunamigenic coseismic slip of the 1957 Aleutian earthquake was concentrated on an asperity located in the western half of an aftershock zone 1200km long. This asperity ruptured again in the 1986 Andreanof Islands and 1996 Delarof Islands earthquakes. By contrast, the source of the 1994 Sanriku-oki earthquake corresponds to the low slip region of the previous interplate event, the 1968 Tokachi-oki earthquake. Tsunamis from intraplate earthquakes within the subducting slab can be at least as large as those from interplate earthquakes; tsunami hazard assessments must include such events. Similarity in macroseismic data from two southern Kuril earthquakes illustrates difficulty in distinguishing interplate and slab events on the basis of historical data such as felt reports and tsunami heights. Most moment release of tsunami earthquakes occurs in a narrow region near the trench, and the concentrated slip is responsible for the large tsunami. Numerical modeling of the 1996 Peru earthquake confirms this model, which has been proposed for other tsunami earthquakes, including 1896 Sanriku, 1946 Aleutian and 1992 Nicaragua.
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  • 12
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    Pure and applied geophysics 154 (1999), S. 677-708 
    ISSN: 1420-9136
    Keywords: Key words: Finite-source rupture models, Chilean tectonics, seismic directivity.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —A finite-source rupture model of the July 30, 1995, M w = 8.1 Antofagasta (Northern Chile) subduction earthquake is developed using body and surface waves that span periods from 20 to 290s. A long-period (150–290s) surface-wave spectral inversion technique is applied to estimate the average finite-fault source properties. Deconvolutions of broadband body waves using theoretical Green’s functions, and deconvolutions of broadband fundamental mode surface waves using empirical Green’s functions provided by a large aftershock, yield effective source time functions containing periods from 20 to 200s for many directivity parameters. The source time functions are used in an inverse radon transform to image a one-dimensional spatial model of the moment rate history. The event produced a predominantly unilateral southward rupture, yielding strong directivity effects on all seismic waves with periods less than a few hundred seconds. The aftershock information, spectral analysis, and moment rate distribution indicate a rupture length of 180–200km, with the largest slip concentrated in the first 120km, a rupture azimuth of 205°± 10° along the Chilean coastline, and a rupture duration of 60–68s with a corresponding average rupture velocity of 3.0–3.2km/s. The overall rupture character is quite smooth, accentuating the directivity effects and reducing the shaking intensity, however there are three regions with enhanced moment rate distributed along the rupture zone near the epicenter, 50 to 80km south of the epicenter, and 110 to 140km south of the epicenter.
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  • 13
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    Pure and applied geophysics 155 (1999), S. 81-92 
    ISSN: 1420-9136
    Keywords: Key words: MONTBLEX, atmospheric surface layer, friction velocity, Monin-Obukhov length scale, turbulent kinetic energy.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —An attempt has been made to study the atmospheric surface layer characteristics such as Richardson number (Ri). Monin-Obukhov length scale (L), friction velocity (U *  ), friction temperature (θ * ), roughness length (Z 0 ), turbulent kinetic energy (TKE), ratio of eddy conductivity to eddy diffusivity (K m  /K h  ) over a semi-moist convective regime. Data which were collected at Varanasi (25°18′N, 83°E) as part of the experiment known as MONTBLEX-90 (Monsoon Trough Boundary Layer Experiment) during the summer monsoon season was used in the present study. The variation of the above parameters with stability has been discussed. The differences within the surface layer are also pointed out. Some broad features are found to coincide with that of Businger et al. (1971). The heterogeneity and the anisotropic turbulence typical of monsoon tropical atmosphere are shown to be responsible for the deviations noticed within the surface layer.
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  • 14
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    Pure and applied geophysics 155 (1999), S. 183-201 
    ISSN: 1420-9136
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  • 15
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    Pure and applied geophysics 154 (1999), S. 405-407 
    ISSN: 1420-9136
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  • 16
    ISSN: 1420-9136
    Keywords: Key words: Central Italy, macroseismic intensity distribution, epicentre, attenuation directions, felt area.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —A study of the intensity distribution of the earthquake of December 5th 1456, which affected a large area of central and southern Italy was carried out, verifying, through a recently proposed methodology, the two hypotheses assumed by different authors for one single seismic event and three distinct and close ones. This methodology is based on a vectorial modelling of the macroseismic intensity distribution which aims at determining the epicentre and the principal (minimum and maximum) attenuation directions.¶The study was structured, considering each of the two assumed hypotheses, in a set of tests obtained for the macroseismic field and the intensity map, by analysing different configurations of the observed intensity distribution.¶The results obtained are in agreement with the hypothesis of the time coexistence of three distinct seismic events, for which the calculated epicentres and the principal attenuation directions are compatible with the observed intensity distribution and with the tectonic trend of the Apennine region, respectively.
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  • 17
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    Pure and applied geophysics 155 (1999), S. 119-129 
    ISSN: 1420-9136
    Keywords: Key words: Capillarity, Wood's metal, surface tension, wettability, porosity.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —A tensiometric method (Wilhelmy plate) is used to study Wood’s metal dynamic wettability on specially prepared surfaces of quartz single crystals at low velocities of immersion (2 to 16 μm/s). After correction for buoyancy, the force exerted on the plate by the molten metal is used to derive the unit work of wetting γ cos θ where γ is the Wood’s metal surface tension and θ is the interfacial contact angle. Tests at different temperatures (85, 120 and 200°C) show that below 120°C, viscosity effects cannot be neglected. At an immersion/emersion rate of 2 μm/s, γ cos θ is in the range 0.417–0.444 N/m at 120°C, and 0.432–0.458 N/m at 200°C. These figures allow the conversion of injection pressures into capillary diameters during Wood’s metal injection tests. The method is promising since it may be used in porous materials to check the sensitivity of the unit work of wetting γ cos θ to parameters such as roughness and mineralogy, which are known to vary in a wide range within the pores and cracks of rocks.
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  • 18
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    Pure and applied geophysics 155 (1999), S. 57-80 
    ISSN: 1420-9136
    Keywords: Key words: Fog prediction, radiation fog, numerical fog modeling.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —A simple one-dimensional numerical-analytical model was developed by Meyer and Rao (1995) to predict the onset of radiation fog. The model computes radiative cooling and turbulent diffusion of heat and vapor through the lower boundary layer and produces heat and vapor fluxes at the soil–atmosphere interface. The model is designed for Air Force forecasters who have access to a personal computer, an early evening surface observation of the dry bulb and dewpoint temperature, wind speed, the lapse rate in the upper boundary layer, and the previous 24-h precipitation amount. These initial data are used to predict the diurnal variation of the dry bulb and dewpoint temperatures at 10 m above the surface. In accordance with conventional synoptic observing practices, fog is defined as a restriction of the surface visibility generally to less than 1000 m. Fog is assumed to occur in the model predictions when the dewpoint depression falls to less than 1°C. Observations, from several Air Force bases for selected days when fog was observed to occur, were used to test the model. The present model with default parameters appears to predict the onset of fog slightly ahead of its occurrence. Better verification results are expected when site-relevant parameters are used in model predictions.
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  • 19
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    Pure and applied geophysics 155 (1999), S. 575-607 
    ISSN: 1420-9136
    Keywords: Key words: Earthquakes, friction, threshold systems, stochastic resonance, nonequilibrium systems, driven dissipative systems.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —Understanding the physics of earthquakes and the space-time patterns they produce is illuminated by the use of coarse-grained models and simulations that capture the basic physical processes, and that are amenable to analysis. We present a summary of ideas that describe the nucleation, growth, and arrest of earthquakes on individual faults. Under shear loading, we find that faults reside in a metastable state near a classical spinodal that governs the nucleation and growth of slip events. The roughness of an associated stress distribution field Σ(x, t) determines whether slip events are confined within the initial high stress patch, or break away and grow to become very large. We find a critical value of roughness that is associated with a first-order, "order–disorder" transition. We also give a number of predictions, examples and applications of these ideas, and indicate how they might be tested through systematic observational programs.
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  • 20
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    Pure and applied geophysics 155 (1999), S. 259-278 
    ISSN: 1420-9136
    Keywords: Key words: Seismic gap, seismotectonics, earthquake prediction.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —The test that Kagan and Jackson (1991, 1995) applied to the seismic gap hypothesis did not bring us closer to understanding the generation of large earthquakes. On the contrary, it led some to the conclusion that the rebound theory of earthquake generation should be rejected. We disagree with this point of view and argue that a global test of the simplified gap hypothesis cannot be done because it cannot account for differences in the slip history of fault segments and tectonic differences between separate plate boundaries. Kagan and Jackson did show, however, that the original gap hypothesis was oversimplified and should be refined. We propose that consideration of all the facts, including slip history and seismicity patterns in the Andreanof Islands, show that the concept of seismic gaps and the elastic rebound theory are correct for that segment of the plate boundary. The coseismic slip in the M w 8.7 earthquake that broke this plate boundary segment in 1957 was only 2 m, as published before the repeat earthquake of 1986 (M w 8), and thus, using a plate convergence rate of 7.3 cm/year, the return time in this cycle was expected to be less than 30 years, unless substantial aseismic creep occurs. This supports the time predictable model of mainshock recurrence. In addition, Kisslinger et al. (1985) and Kisslinger (1986) noticed a seismic quiescence in the subsequent source volume before the 1986 earthquake and attempted to predict it. The specific parameters he estimated were not entirely correct although his interpretation of the observed quiescence as a precursor was. We conclude that the 1986, M w 8, Andreanof earthquake was not an example that disproves the seismic gap hypothesis. On the contrary, it shows that the hypothesis that plate motions reload plate boundaries after most of the elastic energy is released in great ruptures was correct in this case. This suggests that great earthquakes occur preferably in mature gaps. We believe the testing of the seismic gap hypothesis by algorithm on a global scale is an example that illustrates that overly simplified tests can lead to erroneous conclusions. To make progress in the actual understanding of the physics of the process of great earthquake ruptures, one must consider all the facts known for case histories.
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  • 21
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    Pure and applied geophysics 155 (1999), S. 443-470 
    ISSN: 1420-9136
    Keywords: Key words: Seismicity pattern, seismic quiescence, Kurile, Hokkaido Toho-Oki, earthquake prediction.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —We have found that the M w = 8.3 Kurile earthquake on October 4, 1994 followed an outstanding seismic quiescence starting 5–6 years before the mainshock near the ruptured area. We have analyzed three independent seismic catalogs Institute of Seismology and Volcanology, Hokkaido University (ISV), Japan Meteorological Agency (JMA) and International Seismology Center (ISC). In spite of selecting different magnitude bands and time windows all three catalogs presented the common feature of the seismic quiescence. This fact strongly suggests that the seismic quiescence should not be a man-made change but actually occurred. Moreover we have confirmed that the seismic quiescence was the most significant and the earthquake was the largest in the past twenty-five years in this region. Therefore we confidently interpret this seismic quiescence as an indication of a preparation process for the M w = 8.3 Kurile earthquake.
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  • 22
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    Pure and applied geophysics 155 (1999), S. 471-507 
    ISSN: 1420-9136
    Keywords: Key words: Causal relationship, ETAS model, modified Omori formula, relative quiescence, season ality of seismicity, space-time models.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —The occurrence times of earthquakes can be considered to be a point process, and suitable modeling of the conditional intensity function of a point process is useful for the investigation of various statistical features of seismic activity. This manuscript summarizes likelihood based methods of analysis of point processes, and reviews useful models for particular analyses of seismicity. Most of the analyses can be implemented by the computer programs published by the author and collaborators.
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  • 23
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    Pure and applied geophysics 155 (1999), S. 207-232 
    ISSN: 1420-9136
    Keywords: Key words: Earthquakes, earthquake prediction, earthquake precursors, physics of earthquakes.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —We re-examine and summarize what is now possible in predicting earthquakes, what might be accomplished (and hence might be possible in the next few decades) and what types of predictions appear to be inherently impossible based on our understanding of earthquakes as complex phenomena. We take predictions to involve a variety of time scales from seconds to a few decades. Earthquake warnings and their possible societal uses differ for those time scales. Earthquake prediction should not be equated solely with short-term prediction—those with time scales of hours to weeks—nor should it be assumed that only short-term warnings either are or might be useful to society. A variety of "consumers" or stakeholders are likely to take different mitigation measures in response to each type of prediction. A series of recent articles in scientific literature and the media claim that earthquakes cannot be predicted and that exceedingly high accuracy is needed for predictions to be of societal value. We dispute a number of their key assumptions and conclusions, including their claim that earthquakes represent a self-organized critical (SOC) phenomenon, implying a system maintained on the edge of chaotic behavior at all times. We think this is correct but only in an uninteresting way, that is on global or continental scales. The stresses in the regions surrounding the rupture zones of individual large earthquakes are reduced below a SOC state at the times of those events and remain so for long periods. As stresses are slowly re-established by tectonic loading, a region approaches a SOC state during the last part of the cycle of large earthquakes. The presence of that state can be regarded as a long-term precursor rather than as an impediment to prediction. We examine other natural processes such as volcanic eruptions, severe storms and climate change that, like earthquakes, are also examples of complex processes, each with its own predictable, possibly predictable and inherently unpredictable elements. That a natural system is complex does not mean that predictions are not possible for some spatial, temporal and size regimes. Long-term, and perhaps intermediate-term, predictions for large earthquakes appear to be possible for very active fault segments. Predicting large events more than one cycle into the future appears to be inherently difficult, if not impossible since much of the nonlinearity in the earthquake process occurs at or near the time of large events. Progress in earthquake science and prediction over the next few decades will require increased monitoring in several active areas.
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    Pure and applied geophysics 155 (1999), S. 409-423 
    ISSN: 1420-9136
    Keywords: Key Words: Earthquake prediction, algorithms M8 and MSc, seismicity, Japan.
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    Topics: Geosciences , Physics
    Notes: Abstract —A succession of precursory changes of seismicity characteristic to earthquakes of magnitude 7.0–7.5 occurred in advance of the Kobe 1995, M = 7.2, earthquake. Using the Japan Meteorological Agency (JMA) regional catalog of earthquakes, the M8 prediction algorithm (Keilies-Borko and Kossobokov, 1987) recognizes the time of increased probability, TIP, for an earthquake with magnitude 7.0–7.5 from July 1991 through June 1996. The prediction is limited to a circle of 280-km radius centered at 33.5°N, 133.75°E. The broad area of intermediate-term precursory rise of activity encompasses a 175 by 175-km square, where the sequence of earthquakes exhibited a specific intermittent behavior. The square is outlined as the second-approximation reduced area of alarm by the "Mendocino Scenario" algorithm, MSc (Kossobokov et al., 1990). Moreover, since the M8 alarm starts, there were no swarms recorded except the one on 9–26 Nov. 1994, located at 34.9°N, 135.4°E. Time, location, and magnitude of the 1995 Kobe earthquake fulfill the M8-MSc predictions. Its aftershock zone ruptured the 54-km segment of the fault zone marked by the swarm, directly in the corner of the reduced alarm area. The Kobe 1995 epicenter is less than 50 km from the swarm and it coincides with the epicenter of the M 3.5 foreshock which took place 11 hours in advance.
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    Pure and applied geophysics 156 (1999), S. 303-318 
    ISSN: 1420-9136
    Keywords: Key words: Borehole seismics, velocity estimation, KTB seismic experiments, vertical receiver array, transmitted wave field, P-to-S conversion.
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    Topics: Geosciences , Physics
    Notes: Abstract —Within the "Integrated Seismics Oberpfalz 1989 (ISO89)" a three-component Moving Source Profiling (MSP) experiment, also named walk-away VSP, was carried out at the drilling site of the "Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland (KTB)" in Germany. Analysis of transmitted waves traveling from the source locations at the surface down to the receiver array in the borehole reveals velocity information about the illuminated part of the subsurface. Complementary to the widely used evaluation of travel-time perturbations to locate velocity inhomogeneities we suggest the use of the directivity of transmitted wave types down in the borehole. To determine the wave-field directivity we focus on transmitted arrivals by employing principles of "Controlled Directional Reception (CDR)." We calculate local slant-stacks for three different depth positions as a function of the source offset, thus obtaining the variation of the vertical slowness (vertical ray parameter) of incident waves along the horizontal source profile and the vertical receiver array. The slowness data combined with travel times are interpreted by forward modeling taking into account geological information of the survey area. Our findings confirm results from gravity measurements which suggest the existence of large amphibolite/metabasite complexes in the vicinity of the borehole. The described method is also used to identify P-to-S converted energy originating from fracture zones above the receiver array and to locate the region in which conversion occurs.
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    Pure and applied geophysics 156 (1999), S. 97-122 
    ISSN: 1420-9136
    Keywords: Key Words: Seismic anisotropy, lower crust, shear-waves, Poisson’s ratio.
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    Topics: Geosciences , Physics
    Notes: Abstract —Seismic anisotropy is often neglected in seismic studies of the earth’s crust. Since anisotropy is a common property of many typically deep crustal rocks, its potential contribution to solving questions of the deep crust is evaluated. The anisotropic seismic velocities obtained from laboratory measurements can be verified by computations based on the elastic constants and on numerical data pertaining to the texture of rock-forming minerals. For typical lower crustal rocks the influence of layering is significantly less important than the influence of rock texture. Surprisingly, most natural lower crustal rocks show a hexagonal type of anisotropy. Maximum anisotropy is observed for rocks with a high content of aligned mica. It seems possible to distinguish between layered intrusives and metasediments on the basis of in situ measurements of anisotropy, which can thus be used to validate different scenarios of crustal evolution.
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    Pure and applied geophysics 156 (1999), S. 173-186 
    ISSN: 1420-9136
    Keywords: Key Words: Variscan basement, 3-D wide-angle data, DEKORP, deep seismic sounding, crustal structure, prestack-migration.
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    Topics: Geosciences , Physics
    Notes: Abstract —In addition to the near normal-incidence observations within the German DEKORP 2 project in 1984, wide-angle observations have been carried out on a parallel profile across the boundary between the Saxothuringian and Moldanubian crust, approximately 50 km NE of the main transect to control three-dimensional variations. Explosion sources have been used for the entire survey, providing excellent conditions for wide-angle registrations. A velocity model has been derived on the basis of in- and off-line refraction measurements using a kinematic raytracer which was extended to three dimensions by interpolation of 2-D velocity fields between parallel sections. Although prestack-migration of the data led to aliasing effects due to large shot and geophone spacing, stable results were obtained by forming envelopes after single-shot migration. The migrated sections reveal a strongly reflective Moho at about 31 km depth and a steeply (50°) dipping intracrustal reflector, which seems to be related to the border between the two Variscan units.
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    Pure and applied geophysics 156 (1999), S. 503-524 
    ISSN: 1420-9136
    Keywords: Key Words: Optical turbulence, thermosonde, isoplanometer, isoplanatic angle.
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    Topics: Geosciences , Physics
    Notes: Abstract —A comparison of isoplanatic angles θ 0 derived from (1) balloon-borne in situ measurements of the index of refraction structure constant (C n 2) profiles and (2) ground-based optical measurements of stellar intensity fluctuations using an isoplanometer is presented. Concurrent data taken over a six-day period in the spring of 1986 show reasonably good agreement between the mean values determined by the two methods. Comparisons in light of meteorological conditions suggest an isoplanatic angle behavior consistent with the Kelvin-Helmholtz instability where the best correlation was found between the optically-measured isoplanatic angle and the layer-averaged wind shear. Differences between the two measurement methods are largest for isoplanometer azimuth angles perpendicular to the balloon trajectory and for lower values of mean shear.
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    Notes: Abstract —To determine the average relationship among the Fourier spectrum of horizontal acceleration FSA(f), moment magnitude M W and hypocentral distance R for Kamchatka earthquakes, we analyzed 44 analog strong-motion records recorded here in 1969–1993. The records of acceleration and velocity meters were obtained at 11 rock to medium-ground sites from 36 earthquakes with M W = 4.5–7.8, at distances R = 30–250 km and depths 0–80 km. Amplitude spectra FSA(f) were calculated from digitized, baseline corrected records of 81 horizontal components, and then divided by instrumental transfer function. After smoothing the values were picked at a set of fixed frequencies. With the scarce amount of data at hand it was impossible to determine reliably the entire FSA(M W , R| f) average trend surface. Hence we first performed distance equalization with distance corrections calculated on a theoretical basis, and thus reduced the observed data to the reference distance of R 0 = 100 km. The model of distance attenuation applied included point source decay terms (1/R plus attenuation specified by Q(f) = 250 f 0.8) and finite source correction (using the formula for a disc-shaped incoherent source, its size depending on M W ); its general applicability was later checked by analysis of residuals. After reduction we determined the FSA(M W , R 0|f) vs. M W trends. To do this we employed a multiple regression procedure with ground type and station dummy variables. The M W dependence was assumed to consist of two linear branches intersecting at M W = 6.5. The result of multiple regression represents the first systematic description of spectral properties of destructive ground motion for Kamchatka earthquakes. The empirical FSA vs. M W trend flattens as frequency increases. This flattening persists even between 3 and 16 Hz, suggesting the decrease of source-related f max with increasing magnitude.
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    Pure and applied geophysics 156 (1999), S. 631-649 
    ISSN: 1420-9136
    Keywords: Key Words: H/V ratio, spectral ratio, site response, microtremor, resonant frequency, amplification.
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    Topics: Geosciences , Physics
    Notes: Abstract —The applicability of the single-station H/V method, based on the spectral ratio between the horizontal and the vertical components of strong ground motions, is examined for site-response estimation using the high quality data from the 1994 Northridge earthquake sequence. Instead of using Rayleigh-wave data from microtremors, the large amplitude-wave part of the S-wave data is used and based on the 1994 Northridge mainshock and aftershock recordings. We have found that upon averaging over a number of recordings for a given station, the station site responses, derived both from the single-station H/V ratio and from the standard spectral ratio (with respect to a reference rock-site station) are sufficiently close for practical purposes. We therefore conclude that the H/V ratio can reasonably predict the resonant frequency and the amplification level of a site response, especially for sites in the neighborhood of the epicenters. In the absence of a reference rock-site station, the H/V ratio provides a practical alternative to the standard site-response estimation.
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  • 31
    ISSN: 1420-9136
    Keywords: Key Words: Bengal basin, crystalline basement, crustal structure, gravity high, Moho configuration, wide-angle reflections.
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    Notes: Abstract —The crustal structure in the West Bengal basin, India has been investigated by means of wide-angle reflection data recorded along (i) Bishnupur-Palashi-Kandi, 227-km long profile in the north-south direction and (ii) Taki-Arambagh, 120-km long profile in the east-west direction. The data were acquired using multichannel digital seismic instruments with close station spacing. The crustal model, initially derived by 1-D forward modeling of the wide-angle reflection data, has been iteratively refined by 2-D ray tracing and modeling of travel-time observations and the corresponding synthetic seismograms computation. The structural contour map of the Moho prepared from the present data set, indicates the crustal thickness of about 37 km in the western margin of the basin, thinning to about 28 km in the east with an upwarp in the Moho boundary. The upwarp in the Moho and the inferred structural features may be indicative of crustal rifting. The well-known gravity anomaly in the West Bengal basin, ‘Calcutta gravity high,’ appears to have resulted from the Moho upwarp in combination with the huge thickness of sediments deposited east of the steep flexure of the crystalline basement representing the ‘Hinze zone.’
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    Pure and applied geophysics 156 (1999), S. 187-206 
    ISSN: 1420-9136
    Keywords: Key Words: Prestack migration, instantaneous slowness, migration artefact, crystalline crust, DEKORP.
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    Topics: Geosciences , Physics
    Notes: Abstract —Prestack migration finds increasing application in processing crustal seismic data. However, less effort has been made to incorporate slowness information in the imaging process. The combination of slowness information with migration leads to an improved image in the depth domain, especially by reducing migration artefacts and noise. A slowness-driven isochrone migration scheme is introduced for migration of 2-D seismic data. Instantaneous slowness information p(x, t) is extracted from the data using correlation analysis in moving time and space windows. Slowness values resulting from spatial coherent energy (signal) and incoherent background noise are distinguished by the simultaneous evaluation of an instantaneous coherence criterion g(x, t). In slowness-driven isochrone migration this information is used for locally weighting the amplitude A(x, t) smearing on the isochrone surface. In particular, slowness p and coherence criterion g determine position and sharpness of a Gaussian weighting function. The method is demonstrated using two synthetic data examples and is subsequently applied to two deep crustal data sets, one wide-angle (along DEKORP4) and one steep-angle reflection seismic observation (KTB8506). Both data sets were collected in the surroundings of the KTB drill site, Oberpfalz, as part of the German DEKORP project.
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    Pure and applied geophysics 156 (1999), S. 421-443 
    ISSN: 1420-9136
    Keywords: Key Words: Potassic magmatism, upper mantle, metasomatism, geophysical-geochemical models, central-southern Italy.
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    Notes: Abstract —The Italian peninsula shows high complexity of the mantle-crust system and of the Plio-Quaternary magmatism. The lithospheric thickness has remarkable lateral variations from about 110 km to about 30 km. Intermediate and deep-focus earthquakes indicate the presence of a lithospheric slab under the Aeolian-Calabrian area and at the southern end of Campania. Much less extensive intermediate-depth seismicity characterizes the Roman-Tuscany region, where the existence of a relic slab has been hypothesized. The deep seismicity in the southern Tyrrhenian Sea is associated with active calcalkaline to shoshonitic volcanism in the Aeolian arc. Alkaline potassic volcanism occurs in central Italy, and potassic lamproitic magmatism coexists with crustal anatectic and various types of hybrid rocks in the Tuscany area.¶The parallelism between changing magmatism and variation of the structure of the crust-mantle system makes central-southern Italy a key place where petrological and geophysical data can be used to work out an integrated model of the structure and composition of the upper mantle. Beneath Tuscany the upper mantle has been affected by intensive subduction-related metasomatism. This caused the formation of phlogopite-rich veins that cut through residual spinel-harzburgite and dunite. These veins, possibly partially molten, may explain the unusually soft mechanical properties that are detected just below the Moho. In the Roman Province, the upper mantle is formed by a relatively thin lid (the mantle part of the lithosphere) and by metasomatic fertile peridotite, probably connected with the upraise of an asthenospheric mantle wedge above the Apennines subduction zone. Geochemical data indicate that metasomatism, though still related to subduction, had different characteristics and age than in Tuscany. In the eastern sector of the Aeolian arc and in the Neapolitan area, the upper mantle appears to be distinct from the Roman and Tuscany areas and is probably formed by fertile peridotite contaminated by the presently active subduction of the Ionian Sea floor.¶The overall picture is that of a mosaic of various mantle domains that have undergone different evolutionary history in terms of both metasomatism and pre-metasomatic events. The coexistence side by side of these sectors is a key factor that has to be considered by models of the geodynamic evolution of the Central Mediterranean area.
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    Pure and applied geophysics 156 (1999), S. 543-555 
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    Pure and applied geophysics 156 (1999), S. 395-420 
    ISSN: 1420-9136
    Keywords: Key Words: Block-structure dynamics, Vrancea, block motions.
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    Topics: Geosciences , Physics
    Notes: Abstract —The dependence of synthetic earthquake catalog obtained by numerical modelling of block-structure dynamics for the Vrancea (Romania) seismoactive region on values of the model parameters is studied. The features of the synthetic seismicity, such as the spatial distribution of epicentres, the level of seismic activity, the relative activity of the different faults, are considered as functions of the directions of motions of the different blocks of the structure. The likelihood of the features of the synthetic and of the real seismicity could be used as criterion for the reconstruction of the direction of the tectonic motions.
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  • 36
    ISSN: 1420-9136
    Keywords: Key Words: Bay of Bengal, tropical cyclone, Arakawa-Schubert, simulation.
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    Topics: Geosciences , Physics
    Notes: Abstract —A ten-level axi-symmetric primitive equation model with cylindrical coordinates is used to simulate the tropical cyclone evolution from a weak vortex for the Bay of Bengal region. The physics of the model comprises the parameterization schemes of Arakawa-Schubert cumulus convection (Lord et al., 1982) and Deardorff’s (1972) planetary boundary layer. The initial conditions have been taken from the climate mean data for November of Port Blair (92.4 E, 11.4 N) in the Bay of Bengal, published by the India Meteorological Department. An initial vortex has been designed to have tangential wind maximum of 10 m/s at 120-km radius with a central surface pressure of 1008 hPa. As a control experiment, referred to as ASBB1, the model is integrated for 240 h maintaining the sea-surface temperature (SST) constant at 301 K. The results of the control experiment reveal a slow decrease of the Central Surface Pressure (CSP) from the initial value of 1008 hPa to 970 hPa at 156 h. After 156 h the CSP decreased sharply until 186 h, attaining 890 hPa. The tangential wind at 1 km level attained the Cyclone Threshold Intensity (CTI) of 17 m/s around 78 h and a maximum of 87 m/s was found at 210 h. These features indicate a predeveloping stage up to 156 h, a deepening stage of 30 h from 156–186 h followed by the mature stage. The mature stage is characterized by the simulation of the central eye region, warm core, strong cyclonic circulation in the central 300 km with low-level inflow; strong vertical motion at the eye wall and outflow aloft. The convection features of the different cloud types conform with the circulation features. The control experiment clearly indicates the evolution of a cyclone with hurricane intensity from a weak vortex. In part two of the paper, results from sensitivity experiments with respect to variations in latitude, SST and initial thermodynamic state have been presented.
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  • 37
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    Keywords: Key Words: Magnitude-intensity relationships, distribution-free statistics, regionalization, Mediterranean, seismicity.
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    Notes: Abstract —A distribution-free statistical approach is proposed for tackling the problem of regionalization devoted to the study of magnitude-intensity relationships in the Mediterranean area. The training-set constitutes a compilation of more than 2000 earthquakes which occurred in the Mediterranean region since the end of the nineteenth century, when instrumental data became available, with epicentral or maximum intensity ≥ VI and MS magnitude values. Firstly an empirical magnitude-intensity correspondence has been computed for each intensity class by using the entire data set in the assumption of homogeneity at the regional scale. Residuals of such relation have been analyzed by a distribution-free statistical approach in order to evaluate the opportunity of a regionalization able to locally improve the performances of magnitude-intensity relationships. The analysis indicates that data concerning larger earthquakes (intensity ≥ VII) do not suggest the opportunity of zonation, and that unbiased estimates of macroseismic magnitude can also be obtained in the assumption that magnitude-intensity correspondences are uniform over the entire Mediterranean area. Therefore, better constrained relations determined for the entire Mediterranean region should be preferred to ill-defined local ones. As concerns smaller events (intensity VI), the procedure suggests that medium/small-scale lateral variations (on a wavelength lower than 102 km) should be taken into account if an efficient estimate of magnitudes from maximum observed intensity is pursued, but that data presently available are not sufficient to suggest any reliable zonation of the area under study.
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    Journal of mathematical fluid mechanics 1 (1999), S. 24-61 
    ISSN: 1422-6952
    Keywords: Keywords. Water waves, bifurcations, spectral theory, dynamical systems.
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    Topics: Mathematics , Physics
    Notes: Abstract. The mathematical study of 2D travelling waves in the potential flow of two superposed layers of perfect fluid, with free surface and interfaces (with or without surface tensions) and with the bottom layer of infinite depth, is set as an ill-posed reversible evolution problem, where the horizontal space variable plays the role of a “time”. We give the structure of the spectrum of the linearized operator near equilibrium. This spectrum contains a set of isolated eigenvalues of finite multiplicities, a small number of which lie near or on the imaginary axis, and the entire real axis constitutes the essential spectrum, where there is no eigenvalue, except 0 in some cases. We give a general constructive proof of bifurcating periodic waves, adapting the Lyapunov-Schmidt method to the present (reversible) case where 0 (which is “resonant”) belongs to the continuous spectrum. In particular we give the results for the generic case and for the 1 : 1 resonance case.
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    Journal of mathematical fluid mechanics 1 (1999), S. 168-186 
    ISSN: 1422-6952
    Keywords: Keywords. Navier-Stokes equations, heat-conducting fluids, steady states, asymptotic behaviour.
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    Topics: Mathematics , Physics
    Notes: Abstract. We prove that any solution to the full Navier-Stokes system of equations of heat-conducting compressible fluid stabilizes to an equilibrium when time tends to infinity.
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    Journal of mathematical fluid mechanics 1 (1999), S. 282-308 
    ISSN: 1422-6952
    Keywords: Keywords. Viscous, compressible, heat conducting fluid, liquid—solid phase transition, free boundary, classical solution.
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    Notes: Abstract. A new model for liquid—solid phase transitions within the frame of complete Navier—Stokes equations in a liquid phase is proposed. It takes into account such properties of liquid as compressibility, viscosity, and heat conductivity. The local existence and uniqueness of a smooth solution to the related initial-boundary value problem is proved.
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    Journal of mathematical fluid mechanics 1 (1999), S. 356-387 
    ISSN: 1422-6952
    Keywords: Keywords. Navier—Stokes equations, initial-boundary value problems, partial regularity, Hausdorff's dimension.
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    Notes: Abstract. We prove a criterion of local Hölder continuity for suitable weak solutions to the Navier—Stokes equations. One of the main part of the proof, based on a blow-up procedure, has quite general nature and can be applied to other problems in spaces of solenoidal vector fields.
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    Journal of mathematical fluid mechanics 1 (1999), S. 235-281 
    ISSN: 1422-6952
    Keywords: Keywords. The modified Navier—Stokes equations, initial-boundary value problems, interior regularity, Hausdorff's dimension.
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    Notes: Abstract. We discuss interior regularity of solutions to the three-dimensional modified Navier—Stokes equations. In particular, we formulate sufficient conditions that guarantee the local Hölder continuity of the velocity gradient.
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    Journal of mathematical fluid mechanics 1 (1999), S. 388-408 
    ISSN: 1422-6952
    Keywords: Keywords. Lagrange functional, stationary points, C2 solutions of the Euler equation.
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    Notes: Abstract. We show in detail in which sense the following two properties of a time dependent, C 2-smooth, divergence-free vector field v are equivalent:¶a) v satisfies the Euler equation of hydrodynamics (with some pressure function p)¶b) v is a stationary point of a suitable Lagrange functional.¶Important steps are the study of surjectivity properties of the derivative of the action functional, and the identification of vector fields orthogonal to the divergence-free fields as gradients, in the sense of classical differentiability. Thus, a foundation of the Euler equation from a variational principle is provided in a form which, to the author's knowledge, was not available so far.
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    The chemical educator 4 (1999), S. 238-241 
    ISSN: 1430-4171
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The potential of Artificial Intelligence (AI) in the development of intelligent machines is widely recognized. It is less widely appreciated that the methods which computer scientists use in their work on AI are also applicable to the solution of numerous problems in science. In many cases, AI methods are preferable to more conventional approaches, being superior in terms of time, quality of solution, or both. Most AI tools are comparatively simple to understand, despite their power, and computer programs to implement them can be written by anyone with average programming skills. This series of papers will demonstrate how AI methods are of value in science, why they work, and how they can be introduced into the syllabus as undergraduate research projects; suggestions of projects, illustrative programs and Java source code will be provided. This paper introduces the topic of AI and explains some of the ways in which an AI program differs from a conventional program.
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    The chemical educator 4 (1999), S. 3-5 
    ISSN: 1430-4171
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    Topics: Chemistry and Pharmacology
    Notes: Abstract While the balanced chemical equations for a multireaction system are generally not unique, the minimum number of independent equations, R, is a characteristic property of the system. Deleting one nonspectator species from the system leads to a system with R reduced by one. In this way each system can be reduced to a single-reaction system and ultimately to a no-reaction system. The least number of chemical species that can be deleted to obtain a no-reaction system equals R. Every multireaction system, therefore, can be reduced to a number of single-reaction equations which can be balanced by any one of the standard techniques. Some examples are given where balancing by inspection is employed.
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    The chemical educator 4 (1999), S. 6-11 
    ISSN: 1430-4171
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    Topics: Chemistry and Pharmacology
    Notes: Abstract We suggest a one-term course project based on a light-induced “worm” that can improve students’ understanding of several major principles, such as the material-balance equation, light absorption, and line broadening in laser spectroscopy. A description of the effect of the light-induced worm is presented along with the results for a trial run of the project and plans for future enhancements.
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    Topics: Chemistry and Pharmacology
    Notes: Abstract To provide an application for the method of linear least squares to data collected in a laboratory, a beaker with water is heated in a microwave oven, and the water temperature is measured as a function of heating variables (time and oven setting). This procedure enables a student to obtain a regression line for each oven setting, and to evaluate the intercept and slope of this line and compare them with the initial temperature of the water and the heating versus oven setting relationship described in the microwave’s manufacturer’s manual. They also are asked to identify any sources of errors observed in this experiment.
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    The chemical educator 4 (1999), S. 259-267 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract On December 10, 1998, the 102nd anniversary of Alfred Nobel’s death, in Stockholm’s Konserthus (Concert Hall), Sweden’s King Carl XVI Gustav awarded one half of the 1998 Nobel Prize in Chemistry (3,800,000 kronor, about $489,000) to Professor John A. Pople, 73, of Northwestern University, Evanston, Illinois “for his development of computational methods in quantum chemistry.”The remaining half of the prize, the ne plus ultra of chemistry, was awarded to Professor Walter Kohn, 75, of the University of California, Santa Barbara “for his development of the density-functional theory” [1–9]. Because of health problems in his family, Kohn was unable to attend the ceremony but presented his Nobel lecture in Stockholm on January 28, 1999. According to the Royal Swedish Academy of Sciences: “The laureates have each made pioneering contributions in developing methods that can be used for theoretical studies of the properties of molecules and the chemical processes in which they are involved” [7].
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    The chemical educator 4 (1999), S. 214-218 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Many general chemistry courses spend little time on descriptive inorganic chemistry. An approach used, which has met with considerable interest by students, is to select a different chemical each week as the Chemical of the Week. A 15 minutes presentation of this chemical is given at the end of the last lecture of the week. Compounds are chosen which appeal to students based on health, environmental, or current media interest. The chemicals discussed, in order, are ozone, Freons, nitrogen dioxide, sulfur dioxide, sulfuric acid, ammonia, nitric acid, phosphoric acid, lead, mercury, and cisplatin. The presentations are arranged so that later chemicals build on information from earlier chemicals. Each presentation usually follows a general format of the chemical’s synthesis, its environmental impact, practical applications, and personal relevance. Details of each presentation are given.
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    Notes: Abstract A laboratory exercise that introduces differential scanning calorimetry (DSC) is presented. In order to connect this basic physical chemistry technique with an application in the biological sciences, students investigated the thermodynamic properties of lipid-bilayer model compounds. DSC was used to characterize the gel-to-liquid-crystal transition for three phosphatidylcholines of varying acyl chain length. The laboratory exercise is suitable only for students with some background in physical chemistry and biochemistry.
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    The chemical educator 4 (1999), S. 23-27 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Algebraic equations were derived for plotting theoretical titration curves involving argentometric titration of binary halide mixtures. These generic equations are applied to three cases of binary halide mixtures in spreadsheet programs. The results are presented graphically as plots of half-cell potential versus volume of the titrant. This approach may serve as a more effective and logical method of showing students how to simulate a complex system involving multiple equilibria.
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    The chemical educator 4 (1999), S. 28-35 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract On December 10, 1997, the 101st anniversary of Alfred Nobel’s death, in Stockholm’s Concert Hall Swedish King Carl XVI Gustav awarded one half of the 1997 Nobel Prize in Chemistry (3.75 million kronor, about $500,000) to Professor Emeritus Paul Delos Boyer, age 79, of the University of California, Los Angeles and Dr. John Ernest Walker, age 56, of the Medical Research Council Laboratory of Molecular Biology, Cambridge, England “for their elucidation of the enzymatic mechanism underlying the synthesis of adenosine triphosphate (ATP)” and one half (3.75 million kronor, about $500,000) to Professor Emeritus Jens Christian Skou, age 79, of Århus University, Århus, Denmark “for the first discovery of an ion-transporting enzyme, Na+, K+-ATPase.”
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    The chemical educator 4 (1999), S. 51-57 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The properties of the Joule-Thomson coefficient are discussed in general for pure gases, and the possibility of a nonlinear effect in binary mixtures is analyzed using the First Law of Thermodynamics and some common cubic equations of state. It is shown that although theoretically a binary mixture of gases may exhibit a Joule-Thomson effect different from the molar-weighted mean of the pure-component effects, the possibility of observing a positive difference is very low.
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    The chemical educator 4 (1999), S. 58-62 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The Principle of Le Châtelier is analyzed for the case of reactions taking place with real gases. The Principle, as usually stated in textbooks, is true only for ideal gas mixtures, and may be violated when the nonideal behavior of a gas is taken into consideration.
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    Notes: Abstract A laboratory experiment suitable for second- or higher-year chemistry students uses thymol blue, an organic dye, for investigating the fraction of each colored species present as a function of pH. Visible color changes in the vivid, highly absorbing dye permit students to “see” relative amounts of acid, base, and ampholyte species during the titration, while potentiometric measurement of pH and spectroscopic determination of concentrations permit quantitation of the species present. A standard Beer’s law calibration curve is constructed for known concentrations of the pure forms of each species at a pH where that species is present as nearly 100% of the total analytical concentration of the dye. Using the molar absorptivities of the three species computed from the calibration curves, simultaneous determination of concentration by species is performed on a set of solutions having constant total concentration of dye such that each solution represents one point in the range pH 0 to pH 13. A mathematical software application is used to solve the simultaneous equations and determine the fraction of each species present. Students then use a spreadsheet application to plot the fractions as functions of pH (the alpha functions). The significance of the isosbestic points in the spectra is also explored.
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    Notes: Abstract Beer’s law plots are commonly straight-line graphs in which absorbance is plotted versus concentration. The errors in such a plot are accentuated in the high-absorbance region due to the logarithmic transformation. This paper discusses the errors inherent in all Beer’s law plots and the choices the student has available: the use of either linear or nonlinear plotting methods. An experiment is described in which student Beer’s law data are treated in several ways to find out if transformation errors are significant. The conclusion is that if the absorbance values obtained for the calibration data exceed A=1, then nonlinear regression or weighted linear regression is indicated.
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    The chemical educator 4 (1999), S. 123-124 
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    The chemical educator 4 (1999), S. 94-101 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract In this experiment the unfolding of the protein, myoglobin, will be monitored using both fluorescence and UV-vis absorption spectroscopy. Changes in the absorbance at 409.5 nm, the absorption maximum of the native state, will be monitored in order to probe changes in the protein conformation after initiation of unfolding by addition of a chemical denaturant. Protein unfolding will also be monitored after exciting the sample at 280 nm and following protein fluorescence emission at 345 nm, the fluorescence maximum for the unfolded state. The absorption run follows the time-dependent decrease in the concentration of the native-state species, whereas the fluorescence experiment monitors the increase in the concentration of the unfolded state. Kinetic rate constants obtained using the two techniques will be compared.
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    The chemical educator 4 (1999), S. 134-136 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract This undergraduate laboratory experiment challenges students to use their combined knowledge of organic reaction mechanisms and spectroscopic analysis to determine the product of a reaction that has several possible outcomes. The result is that students gain the “real-life” experience, commonly encountered by most research chemists, of characterizing and identifying an unknown organic substance.
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    Notes: Abstract A simple procedure to be used in an analytical chemistry laboratory by undergraduate students to prepare a potentiometric biosensor for D-amygdalin is given. The membrane material is prepared by simple compression of a solid sensing mixture (β-glucosidase mixed with Ag2S and AgI). This new technology has some advantages. It presents a simple way to prepare a biosensor membrane and this methodology adapts well to mass production technology. Simple polishing before each new measurement can renew the membrane. This type of biosensor produced by consolidated biocomposites can serve as a base material for different biosensing schemes. Using this technique, students can easily envision the functioning of a potentiometric biosensor where the classic detection mechanism as of an I-ISE is combined with the biological recognition of an enzyme.
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    The chemical educator 4 (1999), S. 147-156 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract This article is dedicated to the memory of Professor Yurii Nikolaevich Kukushkin (1931–1998), who died suddenly of a stroke on November 30, 1998, during its composition.
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    The chemical educator 4 (1999), S. 158-167 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract This study examined the mental representations of chemical reactions used by six students (three male, three female) who achieved above-average grades in a college freshman chemistry class at a large midwestern university. The representations expressed by the students in structured interviews were categorized as microscopic, macroscopic, or symbolic representations of chemical reactions. The study revealed that the participants did make at least some use of each of the three representations; however, there were wide variations among participants in the sophistication of the various representations they used and in their understanding of the relationships between representations. Also, participants receiving very similar course grades sometimes demonstrated very different conceptual understandings of chemical reactions.
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    The chemical educator 4 (1999), S. 173-176 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract One-dimensional (1H, 13C, DEPT), and two-dimensional (COSY, HETCOR) NMR experiments are used to assemble the chemical structures of monoterpene unknowns assigned to senior instrumental analysis students. Students were asked to use their knowledge of NMR to deduce the structure of their assigned compound.
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    The chemical educator 4 (1999), S. 211-213 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The simple statistical treatment of the temperature equilibration of two two-level systems provides an easily understandable example of changes in entropy during reversible and irreversible processes. This treatment yields the fundamental formula dS = dqrev/T; thus, it provides a useful link between the classical (macroscopic) and statistical (microscopic) view of thermodynamic processes.
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    The chemical educator 4 (1999), S. 219-220 
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    Topics: Chemistry and Pharmacology
    Notes: Abstract 2-Methoxyanthracene (target), a non-natural polycyclic aromatic compound, was obtained from the commercially available phthalic anhydride (starting material) through familiar reactions but a new approach.
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    Requirements engineering 4 (1999), S. 92-102 
    ISSN: 1432-010X
    Keywords: Key words:Fixed-point theorem – Grounded theory – Grounded systems engineering methodology – GSEM – Information systems requirements – Qualitative methodology – Qualitative scenarios – Requirements engineering
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    Topics: Computer Science
    Notes: In this paper, we argue that information systems requirements are inherently dynamic, and that a methodology that caters for such dynamicity must enable the evaluation of requirements, as they evolve, against dynamic contexts. Moreover, information systems contexts are soft, ambiguous, and are thus mainly characterised by qualitative data. We present an analytical technique, based on the grounded theory method for developing qualitative scenarios against which statements of requirements can be evaluated.
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    Requirements engineering 4 (1999), S. 165-168 
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    Requirements engineering 4 (1999), S. 134-151 
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    Keywords: Key words:Empirical study – Legacy systems – Medical information systems – Non-functional requirements – Process history – RE practice – Requirements validation – Usability
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    Topics: Computer Science
    Notes: A case study of requirements engineering practice is reported. The application, a decision support system for the Greek Ministry of Health, was investigated by studying the process of requirements analysis through to design and implementation. A usability analysis was then conducted on the designed system with the users. Several usability problems were discovered, and interviews uncovered further problems with the system that could be attributed to failure in requirements engineering (RE). Even though requirements were explicitly stated and the system was an evolution from an existing legacy system, functionality was defective and usability was poor. The client’s prime concern for redeveloping the system was to improve usability; unfortunately communications problems in the RE process meant that the developers did not appreciate this. The implications for RE methods and understanding the RE process are discussed.
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    Requirements engineering 4 (1999), S. 188-197 
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    Keywords: Key words:Memory systems – Parallel applications – Predicate calculus
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    Topics: Computer Science
    Notes: Shared memory provides a convenient programming model for parallel applications. However, such a model is provided on physically distributed memory systems at the expense of efficiency of execution of the applications. For this reason, applications can give minimum consistency requirements on the memory system, thus allowing alternatives to the shared memory model to be used which exploit the underlying machine more efficiently. To be effective, these requirements need to be specified in a precise way and to be amenable to formal analysis. Most approaches to formally specifying consistency conditions on memory systems have been from the viewpoint of the machine rather than from the application domain.  In this paper we show how requirements on memory systems can be given from the viewpoint of the application domain formally in a first-order theory MemReq, to improve the requirements engineering process for such systems. We show the general use of MemReq in expressing major classes of requirements for memory systems and conduct a case study of the use of MemReq in a real-life parallel system out of which the formalism arose.
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    Requirements engineering 4 (1999), S. 19-37 
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    Keywords: Key words: Formal methods; Specification languages; Statecharts; Visual languagesRID=""ID="" 〈E5〉Correspondence and offprint requests to〈/E5〉: D.A. Lamb, Computing and Information Science, Queen’s University, Kingston, Ontario, Canada K7L 3N6. Email: dalamb@qucis.queensu.ca
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    Notes: paper introduces the idea of a software behavioural view: intuitively, this is a complete description of the behaviour of the system observable from a specific point of view. We believe that a fully developed methodology based on views would significantly reduce the complexity of creating and understanding software requirements. In this paper we take the first steps towards such a methodology. We define a formal notation, Viewcharts, with a well-defined semantics based on Statecharts. Viewcharts gives a means for precisely describing views and their compositions. We show that Viewcharts reasonably capture the informal idea of a view by giving an example: a manufacturing control system. We show that Viewcharts have some advantages over Statecharts; in particular, Viewcharts add name space control to limit the scope of broadcast communication, solving a problem with Statecharts presented by Harel.
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    Requirements engineering 4 (1999), S. 65-76 
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    Keywords: Key words:Global organisations – Object technology – Requirements – Use cases
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    Topics: Computer Science
    Notes: The increasingly global nature of financial markets and institutions means that the collection and management of information on which decisions might be based are increasingly complex. There is a growing requirement for the integration of information flows at individual and departmental levels, and across processes and organisational boundaries. Effective information management is an important contributory factor in the efficiency of such institutions, though there are many associated problems that do not have obvious or simple answers. This paper discusses the problem of information gathering in complex business environments and considers how use cases can help to alleviate the problem using an example of a multinational organisation. Such organisations often require information systems that can support regional differences. However, management requires consistent and uniform representation of information. The example shows that use cases can be a helpful mechanism for capturing user requirements that accommodate both regional properties as well as their organisational commonalties.
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    Requirements engineering 4 (1999), S. 103-114 
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    Keywords: Key words:Industrial democracy – Participatory design – Systems development – Work organisation
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    Topics: Computer Science
    Notes: This paper is predicated on requirements analysis as the Achilles heel of information systems development, and accepts that information systems often disappoint. Most design paradigms can be located within a rationalistic framework polarised by requirements analysis and system delivery. Such traditional design paradigms are seen as palliatives that prevent us moving toward more satisfying information systems. It is argued that this rationalistic framework forces us to identify, and attempt to solve, problems that are symptomatic of the approach adopted. A pluralistic framework for information system development is presented which rejects the notions of requirements analysis and system optimality. Participatory design, derived from the field of human computer interaction, is located within this framework and identified as a possible paradigm for information system development. A case study is conducted to assess the benefits of participatory design techniques and to evaluate the extent to which participatory design can overcome the failings of traditional methodologies.
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    Requirements engineering 4 (1999), S. 198-209 
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    Keywords: Key words:Animation of specifications – Inheritance – Object-oriented methods – Requirements engineering
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    Topics: Computer Science
    Notes: Dynamic logic (DL) provides a suitable formal framework to model actions and reasoning about them. 〈$〉\cal OASIS〈$〉 is a language for the specification of object-oriented conceptual models. In our model, specialisation is a relation between classes that defines an inheritance mechanism through static and dynamic partitions. A variant of DL (including the deontic operators for permission, prohibition and obligation) is the formalism used in 〈$〉\cal OASIS〈$〉 to deal with changes of state, triggers, preconditions, protocols and operations. The animation of conceptual models in order to validate the specification is an interesting topic. We have worked on translating 〈$〉\cal OASIS〈$〉 specifications automatically to concurrent environments in order to obtain a prototype useful to validate specifications by animation. The aim of this paper is to show that it is feasible to translate static and dynamic partitions automatically into dynamic logic formulae. Thus, using the same developed schema of animation it is possible to execute 〈$〉\cal OASIS〈$〉 specifications including inheritance.
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    Development genes and evolution 209 (1999), S. 48-58 
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    Keywords: Key words Glycogen synthase kinase-3 binding protein ; Dorso-ventral axis ; Zebrafish ; Wnt signaling ; T cell factor
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    Topics: Biology
    Notes: Abstract  The mechanism of early dorso-ventral axis specification in zebrafish embryos is not well understood. While β-catenin has been clearly implicated as a determinant of the axis, the factors upstream and downstream of β-catenin in this system are not defined. Unlike in Xenopus, where a sperm-induced cortical rotation is used to localize β-catenin on the future dorsal side of the embryo, zebrafish do not have an obviously similar morphogenetic movement. Recently, a GSK-3 (Glycogen Synthase Kinase-3) binding protein (GBP) was identified as a novel member of the Wnt pathway required for maternal dorsal axis formation in Xenopus. GBP stabilizes β-catenin levels by inhibiting GSK-3 and potentially provides a link between cortical rotation and β-catenin regulation. Since zebrafish may use a different mechanism for regulating β-catenin, we asked whether zebrafish also express a maternal GBP. We report the isolation of the zebrafish GBP gene and show that it is maternally expressed and is present as mRNA ubiquitously throughout early embryonic development. Over-expression of zebrafish GBP in frogs and fish leads to hyper-dorsalized phenotypes, similar to the effects resulting from over-expression of β-catenin, indicating that components upstream of β-catenin are conserved between amphibians and teleosts. We also examined whether Tcf (T cell factor) functions in zebrafish embryos. As in frogs, ectopic expression of a dominant negative form of XTcf-3 ventralizes zebrafish embryos. In addition, ectopic β-catenin expression activates the promoter of the Tcf-dependent gene siamois, indicating that the step immediately downstream of β-catenin is also conserved between fish and frogs.
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    Notes: Abstract  We describe two modifications of the popular reporter green fluorescent protein (GFP) which have short half-lives in our system, the cellular slime mould Dictyostelium discoideum. One of these bears an N-terminal ubiquitin; this GFP was originally planned to be a substrate of the ”N-end-rule” pathway, but deubiquitination does not seem to occur, and a degradation by the UFD (ubiquitin-fusion-degradation pathway seems more probable. The protein half-life is about 3–5 h. The second construct has an N-terminus derived from the L11 ribosomal protein; it is transported to the nucleus and broken down much more rapidly than the ubiquitin fusion (protein half-life about 30 min). We show examples of the use of these reporters in the study of gene expression in Dictyostelium.
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    Keywords: Key words Scutoid ; escargot ; snail ; Basic helix-loop-helix protein ; Neurogenesis
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    Topics: Biology
    Notes: Abstract  Scutoid is a classical dominant gain-of-function mutation of Drosophila, causing a loss of bristles and roughening of the compound eye. Previous genetic and molecular analyses have shown that Scutoid is associated with a chromosomal transposition resulting in a fusion of no-oceli and snail genes. How this gene fusion event leads to the defects in neurogenesis was not known until now. Here have found that snail is ectopically expressed in the eye-antennal and wing imaginal discs in Scutoid larvae, and that this expression is reduced in Scutoid revertants. We have also shown that the expressivity of Scutoid is enhanced by zeste mutations. snail and escargot encode evolutionarily conserved zinc-finger proteins involved in the development of mesoderm and limbs. Snail and Escargot proteins share a common target DNA sequence with the basic helix-loop-helix (bHLH) type proneural gene products. When expressed in the developing external sense organ precursors of the thorax and the eye, these proteins cause a loss of mechanosensory bristles in the thorax and perturbed the development of the compound eye. Such phenotypes resemble those associated with Scutoid. Furthermore, the effect of ectopic Escargot on bristle development is antagonized by coexpression of the bHLH gene asense. Thus, our results suggest that the Scutoid phenotype is due to an ectopic snail expression under the control of no-oceli enhancer, antagonizing neurogenesis through its inhibitory interaction with bHLH proteins.
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    Keywords: Key words Irregular chiasm-C-roughest ; Immunoglobulin domain superfamily ; Adhesion molecules ; Olfactory sense organs ; Antennal disc
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    Topics: Biology
    Notes: Abstract  We describe a role for Irregular chiasmC-roughest (IrreC-rst), an immunoglobulin (Ig) superfamily member, in patterning sense organs on the Drosophila antenna. IrreC-rst protein is initially expressed homogeneously on apical profiles of ectodermal cells in regions of the antennal disc. During specification of founder cells (FCs), the intracellular protein distribution changes and becomes concentrated in regions where specific intercellular contacts presumably occur. Loss of function mutations as well as misexpression of irreC-rst results in an altered arrangement of FCs within the disc compared to wildtype. Sense organ development occurs normally, although spacing is affected. Unlike its role in interommatidial spacing, irreC-rst does not affect apoptosis during antennal development. We propose that IrreC-rst affects the spatial relationship between sensory and ectodermal cells during FC delamination.
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    Development genes and evolution 209 (1999), S. 634-634 
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    Development genes and evolution 209 (1999), S. 635-635 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 89
    ISSN: 1432-041X
    Keywords: Key words Amphibian haematopoiesis ; Leukocytes ; Activin ; Basic fibroblast growth factor ; Bone morphogenetic proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Cultures of Xenopus blastula animal caps were used to explore the haematopoietic effects of three candidate inducers of mesoderm: basic fibroblast growth factor (bFGF), bone morphogenetic proteins (BMPs) and activin A. In response to either bFGF or activin A, explants expanded into egg-shaped structures, and beneath an outer layer of epidermis, a ventral mesodermal lining surrounded a fluid-filled cavity containing ”blood-like cells”. Immunocytochemistry identified some of these cells as early leukocytes, but erythrocytes were rare. BMP-2 or BMP-4 induced primitive erythrocytes as well as leukocytes, and a high concentration was required for these cells to differentiate in only a small proportion of explants. BMP-2 but not BMP-4 induced ventral mesoderm concomitantly. High concentrations of activin A dorsalized explants, which contained infrequent leukocytes, and an optimal combination of activin A and bFGF caused differentiation of muscle with few blood cells. By contrast, BMP-2 or BMP-4 plus activin A synergistically increased the numbers of both leukocytes and erythrocytes. Explants treated with BMPs plus activin contained a well organized cell mass in which yolk-rich cells mixed with blood cells and pigmented cells did not. BMP-2 plus bFGF also induced numerous leukocytes and fewer erythrocytes, but BMP-4 antagonized the leukopoietic effect of bFGF. The data suggest that the signalling pathways these three factors use to induce leukopoiesis overlap and that erythropoiesis may be activated when inducers are present in combination.
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  • 90
    ISSN: 1432-041X
    Keywords: Key words Evolution ; DiI ; Engrailed ; Neuroblast ; Neurogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Cell lineages of identified midline cells were traced in the amphipod Orchestia cavimana (Crustacea, Malacostraca) by in vivo labelling. Midline cells are a common phenomenon in the germ band of crustaceans and insects. Studies in midline cells of Drosophila showed an origin from separate, paired anlagen and a differentiation into three types of cells. The in vivo labelling of midline cells of Orchestia demonstrates that they originate from the same material as the neural and epidermal ectoderm, divide in a stereotyped cell division pattern and give rise to at least two different types of cells. During the following evolutionarily derived mode of germ band elongation in Orchestia, a morphogenetic process is intercalated that separates germ band halves. On the level of single cells, it can be shown that midline cells are the only ectodermal cells that bridge the large distance between the separated parts. The cells are stretched extensively but do not proliferate. Comparing the midline cells of Orchestia with non-malacostracan crustaceans and insects, the results favour the hypothesis that midline cells are a distinct population of cells homologous in crustaceans and insects.
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  • 91
    ISSN: 1432-041X
    Keywords: Key words Thermobia domestica ; Thysanura ; teashirt ; HOM-C ; Insect evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  During embryogenesis of the fruit fly, Drosophila melanogaster, the homeotic genes are required to specify proper cell fates along the anterior-posterior axis of the embryo. We cloned partial cDNAs of homologues of the Drosophila homeotic gene teashirt and five of the homeotic-complex (HOM-C) genes from the thysanuran insect, Thermobia domestica, and assayed their embryonic expression patterns. The HOM-C genes we examined were labial, Antennapedia, Ultrabithorax, abdominal-A and Abdominal-B. As the expression pattern of these HOM-C genes is largely conserved among insects and as Thermobia is a member of a phylogenetically basal order of insects, we were able to infer their ancestral expression patterns in insects. We compare the expression patterns of the Thermobia HOM-C genes with their expression in Drosophila and other insects and discuss the potential roles these genes may have played in insect evolution. Interestingly, the teashirt homologue shows greater variability between Thermobia and Drosophila than any of the HOM-C genes. In particular, teashirt is not expressed strongly in the Thermobia abdomen, unlike Drosophila teashirt. We propose that teashirt expression has expanded posteriorly in Drosophila and contributed to a homogenization of the Drosophila larval thorax and abdomen.
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  • 92
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    Development genes and evolution 209 (1999), S. 126-131 
    ISSN: 1432-041X
    Keywords: Key words Globin genes ; Transcription pattern ; Erythropoiesis ; Zebrafish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In a search for novel, developmentally regulated genes we screened randomly picked cDNA clones, obtained from zebrafish mRNA, by in situ hybridization with digoxigenin-labelled riboprobes. Out of 150 clones tested, 1 codes for a new β-globin gene and is expressed during embryogenesis. Here we describe its pattern of expression and its use as a marker for early zebrafish erythropoiesis.
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  • 93
    ISSN: 1432-041X
    Keywords: Key words Genomic imprinting ; Allele-specific ; In situ hybridisation ; Random inactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The IGF2 and H19 genes are genomically imprinted and expressed preferentially from the paternal and maternal alleles, respectively, during human prenatal development. The exact role of the parental imprint(s), however, is not known. To explore this issue in some detail, we have examined human androgenetic cells which by definition should be incapable of allelic discrimination given the paternal origin of both genomes. Allele-specific in situ hybridisation analysis of dispermic complete hydatidiform moles shows that IGF2 and H19 can be found to be transcriptionally active in a variegated manner, which results in the generation of random monoallelic expression patterns. This data shows that imprinted genes can be expressed monoallelically in the absence of discriminating parental marks and raises the question whether or not mechanisms underlying monoallelic expression preceded the acquisition of parental imprints during evolution.
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  • 94
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    Development genes and evolution 209 (1999), S. 120-125 
    ISSN: 1432-041X
    Keywords: Key words Mouse chromosome 10 and 14 ; Maternal transcript ; Mouse Expressed Sequence Tag (EST)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  As part of a large scale mouse Expressed Sequence Tag (EST) project to identify molecules involved in the initiation of mammalian development, a homolog of the Drosophila cornichon gene was detected as a mouse maternal transcript present in the two-cell embryo. Cornichon is a multigene family in the mouse: the new gene, Cnih, maps to mouse chromosome 10, another cornichon homolog, Cnil, maps to chromosome 14 and two additional cornichon-related loci, possibly pseudogenes, localize to chromosomes 3 and 10, respectively. Cnih encodes an open reading frame (ORF) of 144 amino acids that is 93% homologous (68% identical) to the Drosophila protein, whereas the ORF of Cnil contains two extra polypeptide regions not found in these other proteins. Transcripts of Cnih are highly abundant in the full grown oocyte and the ovulated unfertilized egg, while Cnil message is only detectable after activation of the embryonic genome at the eight-cell stage. In situ hybridization shows specific localization of Cnih transcripts to ovarian oocytes. The lack of cytoplasmic polyadenylation of the maternally inherited Cnih transcript suggests that Cnih mRNA is translated in the full grown oocyte before, but not after, ovulation. In Drosophila, cornichon is involved in the establishment of both anterior-posterior and dorso-ventral polarity via the epidermal growth factor (EGF)-receptor signaling pathway. Finding Cnih in the mammalian oocyte opens a new perspective on the investigation of EGF-signaling in the oocyte.
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  • 95
    ISSN: 1432-041X
    Keywords: Key words Imaginal disc ; Axonal trajectories ; Ultrastructure ; Chaoborus (Insecta ; Diptera)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In one of his classical studies on insect metamorphosis, Weismann compared the imaginal anlagen of the ancestral phantom midge, Chaoborus, with those of advanced brachycerans. We have expanded his findings on the relationships between larval and imaginal organs using electron microscopy and cobalt backfilling of the antenna and leg anlagen and the axonal trajectories of corresponding larval sensilla. We show that both primordia are confluent with the larval antennae and ”leg” sensilla (an ancestral Keilin organ), respectively. These fully developed larval organs represent the distal tips of the imaginal anlagen rather than separate cell clusters. The axons of the larval antenna and leg sensilla project across the corresponding anlagen to their target neuromeres within the central nervous system (CNS). Within the discs, nerves composed of these larval axons, developing afferent fibres and efferences ascending from the CNS are found. Both the structure of the primordia and the axonal trajectories thus relate the situation found in advanced brachycerans with that seen in more ancestral insects. In addition, the larval antennae, legs, wings and even the eyes possess very similar afferent pioneer trajectories supporting the idea that the described pattern is generally used in the ontogeny of sensory systems.
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  • 96
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    Development genes and evolution 209 (1999), S. 132-134 
    ISSN: 1432-041X
    Keywords: Key words Xenopus ; Homeobox ; Pharyngeal endoderm ; Facial cartilage and visceral musculature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In Drosophila, the bagpipe homeobox gene is expressed in a subset of dorsal mesodermal cells and in the absence of bagpipe gene function, development of the visceral musculature is disrupted. In Xenopus, one bagpipe-related gene, Xbagpipe (Xbap) has previously been described. Here we report the isolation of a second Xenopus homologue named zampogna (zax). zax is transcribed within the muscular layer of the forming midgut as well as in the embryonic head, where zax transcripts mark both the pharyngeal endoderm and the future infrarostral cartilage.
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  • 97
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    Development genes and evolution 209 (1999), S. 135-144 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  To analyse the proliferative abilities of cells within particular regions of the zebrafish neural plate, injections of fluorescein-dextran were made into single cells at either medial or intermediary positions in the neural plate region of two-somite stage embryos. The resulting cell clones were analysed in 3.5-day-old embryos. Clones with similar compositions were found among those derived from injections in both regions, and these were grouped into classes. 78 clones 29 obtained following injections in the medial region, and 22 of 59 cell clones derived from injections in the intermediary region, were classifiable into 9 and 10 different classes, respectively, each comprising a variable number of clones. Several identified cell types, as well as each of the clone classes themselves, were specific for the regions of the neural plate from which they derived, i.e. they were not represented among the clones derived from the other region. These results suggest that the composition of the lineages derived from particular cells is constant in different animals.
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  • 98
    ISSN: 1432-041X
    Keywords: Key words Notch pathway ; Antagonist ; Hairless ; Orthologue ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Hairless is a member of the Notch signalling pathway, where it acts as antagonist by binding to Suppressor of Hairless [Su(H)], thereby inhibiting Notch target gene activation. The pathway and its members are highly conserved in metazoans from worms to humans. However, a Hairless orthologue from another species has not yet been identified. The identification of Hairless in largely diverged species by cross-hybridization has failed so far probably due to a low degree of conservation. Therefore, we turned to D. hydei where a Hairless mutation has been described before. The D. hydei Hairless orthologue is reasonably well conserved with regard to gene structure and expression. The prospective Hairless protein orthologues share several highly conserved regions which are separated by quite diverged stretches. As to be expected, the largest region of high conservation corresponds to the Su(H) binding domain. This region is also functionally conserved, since this D. hydei protein domain binds very strongly to the D. melanogaster Su(H) protein. The other conserved regions support our earlier structure-function analysis since they nicely correspond to previously defined, functionally important protein domains. Most notably, the very C-terminal domain which is very sensitive to structural alterations, is nearly identical between the two species. In summary, this evolutionary study improves the knowledge on functionally significant domains of the Hairless protein, and may be helpful for the future identification of homologues in other animals, especially in vertebrates.
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  • 99
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    Development genes and evolution 209 (1999), S. 312-316 
    ISSN: 1432-041X
    Keywords: Key words Vasa-like gene ; Germ cell ; Bombyx mori
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A cDNA for a vasa-like gene (BmVLG) was isolated from Bombyx mori. As with vasa in Drosophila, the expression is restricted to the germline in the larval (and pupal and adult?) stage, and the maternal transcript exists. However, the maternal transcript shows localized (germ anlage) distribution patterns, and after degradation of the transcript during germband formation the transcript within cells clustering in the midst of the germ anlage, which eventually give rise to germ cells, remains and continues to be expressed during subsequent embryogenesis; this contrasts to the case of vasa in Drosophila. These results not only indicate the usefulness of BmVLG as a germ cell marker but also suggest the usefulness of this gene (family) in the study of insect germ anlage formation.
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  • 100
    ISSN: 1432-041X
    Keywords: Key words Delta ; Notch ; Follicle cells ; Oogenesis ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  During Drosophila oogenesis the body axes are determined by signaling between the oocyte and the somatic follicle cells that surround the egg chamber. A key event in the establishment of oocyte anterior-posterior polarity is the differential patterning of the follicle cell epithelium along the anterior-posterior axis. Both the Notch and epithelial growth factor (EGF) receptor pathways are required for this patterning. To understand how these pathways act in the process we have analyzed markers for anterior and posterior follicle cells accompanying constitutive activation of the EGF receptor, loss of Notch function, and ectopic expression of Delta. We find that a constitutively active EGF receptor can induce posterior fate in anterior but not in lateral follicle cells, showing that the EGF receptor pathway can act only on predetermined terminal cells. Furthermore, Notch function is required at both termini for appropriate expression of anterior and posterior markers, while loss of both the EGF receptor and Notch pathways mimic the Notch loss-of-function phenotype. Ectopic expression of the Notch ligand, Delta, disturbs EGF receptor dependent posterior follicle cell differentiation and anterior-posterior polarity of the oocyte. Our data are consistent with a model in which the Notch pathway is required for early follicle cell differentiation at both termini, but is then repressed at the posterior for proper determination of the posterior follicle cells by the EGF receptor pathway.
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