Large amplitude folding in finely layered viscoelastic rock structures

We analyze folding phenomena in finely layered viscoelastic rock. Fine is meant in the sense that the thickness of each layer is considerably smaller than characteristic structural dimensions. For this purpose we derive constitutive relations and apply a computational simulation scheme (a finite-element based particle advection scheme; see MORESI et al., 2001) suitable for problems involving very large deformations of layered viscous and viscoelastic rocks. An algorithm for the time integration of the governing equations as well as details of the finite-element implementation is also given. We then consider buckling instabilities in a finite, rectangular domain. Embedded within this domain, parallel to the longer dimension we consider a stiff, layered plate. The domain is compressed along the layer axis by prescribing velocities along the sides. First, for the viscous limit we consider the response to a series of harmonic perturbations of the director orientation. The Fourier spectra of the initial folding velocity are compared for different viscosity ratios. Turning to the nonlinear regime we analyze viscoelastic folding histories up to 40% shortening. The effect of layering manifests itself in that appreciable buckling instabilities are obtained at much lower viscosity ratios (1:10) as is required for the buckling of isotropic plates (1:500). The wavelength induced by the initial harmonic perturbation of the director orientation seems to be persistent. In the section of the parameter space considered here elasticity seems to delay or inhibit the occurrence of a second, larger wavelength. Finally, in a linear instability analysis we undertake a brief excursion into the potential role of couple stresses on the folding process. The linear instability analysis also provides insight into the expected modes of deformation at the onset of instability, and the different regimes of behavior one might expect to observe.

The Fornax Cluster Spectroscopic Survey: a sample of confirmed cluster dwarfs

The Fornax Cluster Spectroscopic Survey (FCSS) project utilizes the Two-degree Field (2dF) multi-object spectrograph on the Anglo-Australian Telescope (AAT). Its aim is to obtain spectra for a complete sample of all 14 000 objects with 16 5 less than or equal to b(j) less than or equal to 19 7 irrespective of their morphology in a 12 deg(2) area centred on the Fornax cluster. A sample of 24 Fornax cluster members has been identified from the first 2dF field (3.1 deg(2) in area) to be completed. This is the first complete sample of cluster objects of known distance with well-defined selection limits. Nineteen of the galaxies (with -15.8 < M-B < 12.7) appear to be conventional dwarf elliptical (dE) or dwarf S0 (dS0) galaxies. The other five objects (with -13.6 < M-B < 11.3) are those galaxies which were described recently by Drinkwater et al. and labelled 'ultracompact dwarfs' (UCDs). A major result is that the conventional dwarfs all have scale sizes alpha greater than or similar to 3 arcsec (similar or equal to300 pc). This apparent minimum scale size implies an equivalent minimum luminosity for a dwarf of a given surface brightness. This produces a limit on their distribution in the magnitude-surface brightness plane, such that we do not observe dEs with high surface brightnesses but faint absolute magnitudes. Above this observed minimum scale size of 3 arcsec, the dEs and dS0s fill the whole area of the magnitude-surface brightness plane sampled by our selection limits. The observed correlation between magnitude and surface brightness noted by several recent studies of brighter galaxies is not seen with our fainter cluster sample. A comparison of our results with the Fornax Cluster Catalog (FCC) of Ferguson illustrates that attempts to determine cluster membership solely on the basis of observed morphology can produce significant errors. The FCC identified 17 of the 24 FCSS sample (i.e. 71 per cent) as being 'cluster' members, in particular missing all five of the UCDs. The FCC also suffers from significant contamination: within the FCSS's field and selection limits, 23 per cent of those objects described as cluster members by the FCC are shown by the FCSS to be background objects.

Ultra-compact dwarf galaxies: a new class of compact stellar system discovered in the Fornax Cluster

We have used the 2dF spectrograph on the Anglo-Australian Telescope to obtain a complete spectroscopic sample of all objects in the magnitude range, 16.5 < bj < 19.8, regardless of morphology, in an area centred on the Fornax Cluster of galaxies. Among the unresolved targets are five objects which are members of the Fornax Cluster. They are extremely compact stellar systems with scale lengths less than 40 parsecs. These ultra-compact dwarfs are unlike any known type of stellar system, being more compact and significantly less luminous than other compact dwarf galaxies, yet much brighter than any globular cluster.

A model of seller holdout

We model a buyer who wishes to combine objects owned by two separate sellers in order to realize higher value. Sellers are able to avoid entering into negotiations with the buyer, so that the order in which they negotiate is endogenous. Holdout occurs if at least one of the sellers is not present in the first round of negotiations. We demonstrate that complementarity of the buyer's technology is a necessary condition for equilibrium holdout. Moreover, a rise in complementarity leads to an increased likelihood of holdout, and an increased efficiency loss. Applications include patents, the land assembly problem, and mergers.

Auction price anomalies: Evidence from wool auctions in Australia

Using detailed Australian wool auction data we test for further evidence of pricing anomalies at sequential auctions. We find that an anomaly frequently exists and order is frequently endogenously determined. Moreover, prices increase through some sales and decrease through others. We examine whether it is possible to explain the variation in the anomaly across sales and conclude that there is no systematic relationship between the direction of the price anomaly and the characteristics of the wool or the auction. We do, however, find evidence that an anomaly, is more likely in longer sales.

Auctions with synergies and asymmetric buyers

In this paper we consider sequential auctions with synergies where one player wants two objects and the remaining players want one object each. We show that expected prices may not necessarily decrease as predicted by Branco [Econ. Lett. 54 (1997) 159]. Indeed we show that expected prices can actually increase. (C) 2004 Elsevier B.V All rights reserved.

The Parkes half-jansky flat-spectrum sample

We present a new sample of Parkes half-jansky flat-spectrum radio sources, having made a particular effort to find any previously unidentified sources. The sample contains 323 sources selected according to a flux limit of 0.5 Jy at 2.7 GHz, a spectral index measured between 2.7 and 5.0 GHz of alpha(2.7/5.0) > -0.5, where S(nu) proportional to nu(alpha), Galactic latitude \b\ > 20 degrees and -45 degrees < declination (B1950) < +10 degrees. The sample was selected from a region 3.90 steradians in area. We have obtained accurate radio positions for all the unresolved sources in this sample, and combined these with accurate optical positions from digitized photographic sky survey data to check all the optical identifications. We report new identifications based on R- and Kn-band imaging and new spectroscopic measurements of many of the sources. We present a catalogue of the 323 sources, of which 321 now have identified optical counterparts and 277 have measured spectral redshifts.

The Edinburgh-Cape Blue Object Survey - I. Description of the survey

The Edinburgh-Cape Blue Object Survey is a major survey to discover blue stellar objects brighter than B similar to 18 in the southern sky. It is planned to cover an area of sky of 10 000 deg(2) with \b\ > 30 degrees and delta < 0 degrees. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy are being obtained with the SAAO telescopes to classify objects brighter than B = 16.5. This paper describes the survey, the techniques used to extract the blue stellar objects, the photometric methods and accuracy, the spectroscopic classification, and the limits and completeness of the survey.

Sequential asymmetric auctions with endogenous participation

In this paper we suggest a model of sequential auctions with endogenous participation where each bidder conjectures about the number of participants at each round. Then, after learning his value, each bidder decides whether or not to participate in the auction. In the calculation of his expected value, each bidder uses his conjectures about the number of participants for each possible subgroup. In equilibrium, the conjectured probability is compatible with the probability of staying in the auction. In our model, players face participation costs, bidders may buy as many objects as they wish and they are allowed to drop out at any round. Bidders can drop out at any time, but they cannot come back to the auction. In particular we can determine the number of participants and expected prices in equilibrium. We show that for any bidding strategy, there exists such a probability of staying in the auction. For the case of stochastically independent objects, we show that in equilibrium every bidder who decides to continue submits a bid that is equal to his value at each round. When objects are stochastically identical, we are able to show that expected prices are decreasing.

A polydnavirus-encoded protein of an endoparasitoid wasp is an immune suppressor

The molecular mechanism by which polydnaviruses of endoparasitoid wasps disrupt cell-mediated encapsulation reactions of host insects is largely unknown. Here we show that a polydnavirus-encoded protein, produced from baculovirus and plasmid expression vectors, prevents cell surface exposure of lectin-binding sites and microparticle formation during immune stimulation of haemocytes. The inactivation of immune-related cellular processes by this protein was analysed using a specific lectin and annexin V and shown to be virtually identical to polydnavirus-mediated effects on haemocytes. Cytochalasin D application has similar effects on haemocytes, suggesting that the immune suppression by the polydnavirus protein is caused by the destabilization of actin filaments. Since the exposure of cell surface glycoproteins and the formation of microparticles are part of an immune response to foreign objects or microorganisms and a prerequisite for cell-mediated encapsulation of microorganisms and parasites, the virus-encoded protein may become an important tool for the inactivation of cellular immune reactions in insects and an essential component in understanding immune suppression in parasitized host insects.

Folding processes and solitary waves in structural geology

Evolution of localized folding patterns in layered elastic and visco-elastic materials is reviewed in the context of compressed geological systems. The thin strut or plate embedded in a visco-elastic medium is used as an archetypal example to describe localized buckles which, in contrast to those from earlier formulations, appear in the absence of triggering imperfections. Structural and material effects are surveyed and important nonlinear characteristics are identified. A brief review of possible methods of analysis is conducted.

Asymmetric page split generalized index search trees for formal concept analysis

Formal Concept Analysis is an unsupervised machine learning technique that has successfully been applied to document organisation by considering documents as objects and keywords as attributes. The basic algorithms of Formal Concept Analysis then allow an intelligent information retrieval system to cluster documents according to keyword views. This paper investigates the scalability of this idea. In particular we present the results of applying spatial data structures to large datasets in formal concept analysis. Our experiments are motivated by the application of the Formal Concept Analysis idea of a virtual filesystem [11,17,15]. In particular the libferris [1] Semantic File System. This paper presents customizations to an RD-Tree Generalized Index Search Tree based index structure to better support the application of Formal Concept Analysis to large data sources.

The dorsomedial visual areas in New World and Old World monkeys: homology and function

The extrastriate cortex near the dorsal midline has been described as part of an 'express' pathway that provides visual input to the premotor cortex. This pathway is considered important for the integration of sensory information about the visual field periphery and the skeletomotor system, especially in relation to the control of arm movements. However, a better understanding of the functional contributions of different parts of this complex has been hampered by the lack of data on the extent and boundaries of its constituent visual areas. Recent studies in macaques have provided the first detailed view of the topographical organization of this region in Old World monkeys. Despite differences in nomenclature, a comparison of the visuotopic organization, myeloarchitecture and connections of the relevant visual areas with those previously studied in New World monkeys reveals a remarkable degree of similarity and helps to clarify the subdivision of function between different areas of the dorsomedial complex. A caudal visual area, named DM or V6, appears to be important for the detection of coherent patterns of movement across wide regions of the visual field, such as those induced during self-motion. A rostral area, named M or V6A, is more directly involved with visuomotor integration. This area receives projections both from DM/V6 and from a separate motion analysis channel, centred on the middle temporal visual area (or V5), which detects the movement of objects in extrapersonal space. These results support the suggestion, made earlier on the basis of more fragmentary evidence, that the areas rostral to the second visual area in dorsal cortex are homologous in all simian primates. Moreover, they emphasize the importance of determining the anatomical organization of the cortex as a prerequisite for elucidating the function of different cortical areas.

The equilibrium penetration of monolayers. Is equilibrium really established?

In studying the penetration of water-soluble surfactants into water-insoluble monolayers the main theoretical problem is to find a relationship that would enable the amount of surfactant that has entered the monolayer to be calculated from a set of equilibrium surface pressure-area isotherms. Despite many attempts, no current theory gives satisfactory results when applied to experimental data (Langmuir 14 (1998) 2148). One possible reason is that equilibrium had not been established when the surface pressure-area curves were measured. The three experiments reported here suggest that equilibrium is extremely difficult to establish in such systems when the area is low or the surface pressure is high. The essence of these experiments is to try to reach the same final condition by two different routes. In the first route, the one nearly always used in equilibrium penetration measurements, the surfactant is injected under the expanded monolayer, which is then slowly compressed in steps, with time allowed at each step for a steady surface pressure to be attained. In the second procedure, the monolayer is first compressed to a high surface pressure and the surfactant then injected. A stepped expansion isotherm may then be observed. Surface pressure-area per monolayer molecule isotherms, reflection spectra, and slow neutron reflectivity data all show the same pattern: if the surfactant was allowed to penetrate while the monolayer was in an expanded state, it was not completely removed when the monolayer was compressed; but if the monolayer was in a highly compressed state when exposed to the surfactant little penetration took place until the film was expanded. There thus appear to be very large energy barriers to the ejection of surfactant from a compressed monolayer and to the penetration of surfactant into a compressed monolayer. Although these experiments have some limitations, it now seems likely that at least some of the penetration data used in evaluating the various thermodynamic treatments of equilibrium penetration were not equilibrium data. (C) 2001 Elsevier Science B.V. All rights reserved.

Four new species of Macropodinium (Ciliophora : Litostomatea) from Australian wallabies and pademelons

Samples of Macropodinium spp. were collected from 3 new macropodid species: from 21 of 28 (75%) black-striped wallabies (Macropus dorsalis); 10 of 11 (91%) swamp wallabies (Wallabia bicolor); and 22 of 43 (51%) Tasmanian pademelons (Thylogale billardierii). The examination of ciliate morphology by silver impregnation and scanning electron microscopy led to the redescription of the genus Macropodinium and the description of 4 new species: Ma. tricresta sp. nov. and Ma. spinosus sp. nov. from M. dorsalis; Ma. maira sp. nov. from T. billardierii; and M. bicolor sp. nov. from W. bicolor; each species was strictly host specific. Cellular orientation was reinterpreted on the basis of vestibular morphology and it is concluded that Macropodinium spp. are laterally rather than dorso-ventrally compressed. The striated groove is thus dorso-ventral rather than lateral. Oral ciliation consisted of up to three bands: an adoral band composed of oblique kineties; a vestibular band of longitudinal kineties; and a preoral band of longitudinal kineties. Somatic ciliation occurred in two longitudinal bands: a dense band composed of several parallel kineties on the left side of the dorso-ventral groove; and a sparse band composed of a single kinety on the right internal side of the dorso-ventral groove. Few structures were homologous to those of other litostome ciliates, and thus the relationship of Macropodinium to other litostomes cannot yet be clearly defined.