bluuebunny/crossref_metadata_2025 huggingface dataset:
Surficial geology of Hecate Strait, British Columbia continental shelf
Authors: Barrie J. V. , Bornhold B. D.
Published: October 2008

Four surficial geological units are defined geophysically for Hecate Strait on the northern British Columbia continental shelf. They consist of Tertiary bedrock (unit 1) unconformably overlain in much of the strait of glacial till (unit 2), which is in turn overlain below 200 m water depth by thick silts (unit 4) and above 200 m by Quaternary sands and gravels (unit 3), except in areas where till or Tertiary bedrock is at or near surface.Glacial ice covered most of the strait at some time in the Pleistocene, but evidence for a Late Wisconsinan advance is more prevalent in the principal troughs of the strait. Sea level was as low as the present-day 180 m isobath during the late Tertiary or early Quaternary and possibly as low as 100 m at the end of the Pleistocene, based on the presence of drainage channels, wave-cut terraces, and both shore-oblique and shore-parallel sand ridges. Sedimentary bedforms found ubiquitously above 100 m appear to be in equilibrium with the present hydrodynamic conditions, and their presence suggests that significant seabed erosion and transport occur within the strait.
Geochemistry of Siluro-Devonian Tobique volcanic belt in northern and central New Brunswick (Canada): tectonic implications
Authors: Dostal J. , Wilson R. A. , Keppie J. D.
Published: October 2008

Siluro-Devonian volcanic rocks of the northwestern mainland Appalachians are found mainly in the Tobique belt of New Brunswick where they consist predominantly of bimodal mafic–felsic suites erupted in a continental-rift environment. The axis of the Tobique rift trends north-northeast – south-southwest, obliquely to the regional northeast–southwest trend of the Appalachians. These geometric relationships are interpreted as being the result of rifting in a sinistral shear regime produced during emplacement of the Avalon terrene. The basaltic rocks are continental tholeiites and transitional basalts derived from a heterogeneous upper-mantle source that was enriched in incompatible elements relative to the primordial mantle. The mantle source was probably affected by the subduction processes.
Contribution palynostratigraphique (dinokystes, pollen et spores) à la connaissance de la mer de Champlain: coupe de Saint-Césaire, Québec
Authors: Vernal Anne de , Goyette Claire , Rodrigues Cyril G.
Published: October 2008

High-resolution continental (pollen and spores) and marine (dinoflagellate cysts) microfloral records were obtained from a section consisting of about 0.5 m of glaciolacustrine and 2.5 m of Champlain Sea deposits at the Saint-Césaire site. The pollen and spore assemblages indicate the existence of a regional open vegetation of shrub tundra to forest tundra. Fluctuations in the percentages of Picea and shrub and herb taxa are related to regional afforestation and paleogeographical evolution of the basin. The Champlain Sea sediments contain an abundant dinocyst flora dominated by Operculodinium centrocarpum, Brigantedinium spp., and Algidasphaeridium? minutum, which indicate cold Arctic conditions in surface waters. Fluctuations in concentration (102–104∙cm−3) and relative abundance of dinocyst species are attributed to changes in dinoflagellate productivity and paleoceanographic conditions, notably paleosalinity. Morphological variations of Operculodinium centrocarpum and Algidasphaeridium? minutum led to this description of the varieties, named "cezare" after the site location.
Paléomagnétisme dans les Hellénides internes: analyse des aimantations superposées par la méthode des cercles de réaimantation
Authors: Surmont Jérôme
Published: October 2008

There are very few reliable and well-dated paleomagnetic data on the internal Hellenides, which were strongly affected by successive tectonic events. We have analysed 268 samples from two separate sedimentary formations of this domain. These correspond to two important moments in the geotectonic evolution of the Hellenides: the Toarcian and the Jurassic– Cretaceous boundary. We show that all the analysed samples probably contain both detrital magnetite and secondary haematite and generally carry at least two components of superimposed magnetization. The diversity and convergence of the remagnetization circles allow us to show that these two components are antiparallel and to determine their directions. Because of tectonic disruption, the calculated declinations are only of local interest. On the other hand, inclinations remain significant for calculating paleolatitudes. These constitute important constraints on reconstructions of the Jurassic paleogeography of the Hellenic domain. In light of our results, two paleogeographic reconstructions are proposed for the Early–Middle Jurassic and Jurassic–Cretaceous boundaries.
New geomagnetic paleosecular-variation results from the Old Crow Basin, Yukon Territory, and their use in stratigraphic correlation
Authors: Gillen K. P. , Evans M. E.
Published: October 2008

A total of 626 fully orientated samples were collected from two laterally equivalent vertical sections (each approximately 20 m thick) in Pleistocene sediments exposed in riverbank outcrops on the Old Crow River, Yukon Territory. The paleomagnetic records recovered reveal a sequence of three features correlatable with results obtained from previously sampled sections some 5 km upstream. This correlation, which is confirmed by magnetic-susceptibility measurements, allows the stratigraphic position of the Old Crow Tephra to be inferred, even though it does not actually occur at this locality; it also provides strong support for the reality of these paleosecular-variation signals. The most prominent of these take the form of repeating linear perturbations, which are here interpreted as evidence of stationary sources of reversely directed flux in the outer core. Such reverse-flux patches exist elsewhere in the modern field, but a simple magnetostatic model suggests that the paleosources were apparently an order of magnitude stronger.
A microseismicity study of the Queen Charlotte Islands region
Authors: Bérubé Joane , Rogers Garry C. , Ellis Robert M. , Hasselgren Elizabeth O.
Published: October 2008

Nineteen land and three ocean-bottom seismographs were operated in the Queen Charlotte Islands region for periods of up to 9 weeks and 5 days, respectively, during the summer of 1983. Three hundred and seventeen seismic events were detected. One hundred and nine earthquakes ranging in size from magnitude −0.5 to 5.1 were well recorded at three or more stations and could be accurately located. Of these, 84 lie on or close to the Queen Charlotte Fault, most within the rupture zone of the great 1949 earthquake (MS = 8.1). The seismic gap, between the rupture zones of the 1949 event and the 1970 earthquake (MS = 7.4) that occurred just south of the Queen Charlotte Islands, exhibited little activity. Eighteen earthquakes, the largest with ML = 3.8, were located east of the fault on northern Graham Island or in adjacent Hecate Strait. Focal depths were generally less than 20 km, and none could be associated with known faults. Composite focal mechanism solutions were obtained for four suites of earthquakes along the Queen Charlotte Fault and for a group east of the fault zone on northern Graham Island. In all cases the solutions indicate thrust mechanisms with the predominant orientation of pressure axes northeast–southwest. The presence of thrust faulting close to the Queen Charlotte Fault suggests that the microseismicity is not occurring on the main transcurrent fault but on subsidiary faults that are moving due to the regional stress regime. Thrust faulting on northern Graham Island can best be interpreted as reflecting the stress field from a locked Pacific and North American boundary.
Fossil marine actinopterygian fishes from the Kaskapau Formation (Upper Cretaceous: Turonian) near Watino, Alberta
Authors: Wilson Mark V. H. , Chalifa Yael
Published: October 2008

Turonian fossil marine fishes occur at several localities near Watino, Alberta, in sandstones and in shale concretions of the Vimy Member, Kaskapau Formation. The actinopterygian fossils in the sandstone facies include Belonostomus, Ichthyodectes, Apateodus, Cimolichthys, Dercetidae, and Enchodus. The sandstone facies also includes abundant chondrichthyan teeth and denticles. Actinopterygian fossils in the concretion facies include Ichthyodectes, Osmeroides, and Leucichthyops. The Watino assemblage is taxonomically similar to other Turonian fish assemblages but is relatively diverse and includes the first North American record of Apateodus and the oldest North American Dercetidae. The fossils in the sandstone facies are often abraded, rounded, and concentrated together with rounded pebbles in lenses and may in part represent lag deposits formed near storm wave base. In the concretion facies, preservation is consistent with the flotation–decay mechanism acting in deeper, quiet water. Some of the differences in taxonomic composition between the sandstone and concretion facies could be caused by taphonomic loss of delicate bones and scales of small teleosts from the former.
Ella Bay Formation: Early Cambrian shelf differentiation in the Franklinian basin, central eastern Ellesmere Island, Arctic Canada
Authors: Long D. G. F.
Published: October 2008

Strata of the Lower Cambrian (Atdabanian) Ella Bay Formation reflect progradation and exposure of a rimmed carbonate platform, subject to intermittent introduction of siliciclastic material from an inshore coastal sand belt or fluviodeltaic source. Initial rapid progradation of platformal carbonates was related to late rift subsidence. Stabilization of depositional sites of oolitic and stromatolitic platform marginal carbonates during middle and late Ella Bay times reflects the earliest phase of differential subsidence of the platform and deep-water basin within the Franklinian mobile belt. Carbonate strata landward of the rim accumulated in a protected shelf setting that was for the most part below effective storm wave base. Towards the end of Ella Bay times, the outer rim became emergent as a result of differential rotation along listric faults as the continental margin began to subside in response to early sea-floor spreading. Dissolution of carbonates along the outer rim during this phase led to the development of distinctive breccia-conglomerates as cave and karst fill. Carbonate production in the lagoon became highly restricted as siliciclastics derived from the inshore clastic belt flooded the area. The pronounced change in style between the Ella Bay Formation and overling clastics of the Ellesmere Group, which consists of a thick sequence of northwesterly prograding clastic wedges, may reflect a change to more rapid subsidence as the ocean began to spread. The local unconformity between the Ella Bay Formation and the Ellesmere Group is thus interpreted as a breakup unconformity.
Auriferous chert, banded iron formation, and related volcanogenic hydrothermal alteration, Atik Lake, Manitoba
Authors: Bernier Louis R. , MacLean Wallace H.
Published: October 2008

Small-scale alteration pipes and stratiform alteration in Archean glomeroporphyritic tholeiitic basalts at Atik Lake, Manitoba, stratigraphically underlie silicate-oxide banded iron formation (BIF) and auriferous sulfide-bearing chert. The auriferous chert is locally interbedded with graphitic argillite, indicating euxinic conditions during deposition. Cordierite–gedrite rocks formed by recrystallization of alteration assemblages during the lower amphibolite-facies metamorphism (T = 550 °C, P = 2.5 kbar). Al2O3, TiO2, Zr, and Nb, which were relatively immobile during alteration, have been used to monitor igneous differentiation and alteration. Volcanogenic hydrothermal alteration resulted in depletion of Ca, Si, Mg, Na, and Sr in the altered basalt and the addition of K, Fe, Rb, and Ba. This was accompanied by mass and volume losses of up to 25%. The mineralizing fluid was reducing and somewhat acidic. Rare-earth-element (REE) profiles of BIF and graphitic argillite, normalized to Archean shale, are less steep ((La/Lu)N = 0.51 and 0.49 respectively), than those of both mineralized chert ((La/Lu)N = 0.04) and recent sea-floor, siliceous, gold-enriched massive sulfides ((La/Lu)N = 0.11). REE profiles and Boström's plot suggest that the auriferous, sulfide-bearing chert formed by mixing of hydrothermal and detrital components. The overall chemical changes in the Atik Lake alteration system are comparable to those in Noranda-type massive-sulfide deposits. The trace-metal association in the auriferous chert is similar to that at some modern sea-floor hydrothermal sites.
Gravity and magnetic signatures of the Ackley Granite Suite, southeastern Newfoundland: implications for magma emplacement
Authors: Miller H. G. , Tuach J.
Published: October 2008

A detailed gravity survey (255 stations over an area of 3000 km2) over the posttectonic, Devonian, Ackley Granite Suite in southeastern Newfoundland suggests that a set of northwest-trending geophysical lineations, interpreted as faults, controlled the bottom morphology of the magma chamber during emplacement.The main negative Bouguer gravity anomaly over the Ackley Granite Suite trends in a north–south direction across the trace of the Dover – Hermitage Bay Fault, the boundary between the Gander and Avalon terranes. Inversion of the gravity and density data indicates that the thickness of the granite suite varies between 2 and 8 km.Magnetic interpretation and modelling suggest that the southeast portion of the suite is underlain by mafic volcanic rocks typical of the Avalon Terrane. The magnetically determined depth to the top of these is consistent with that calculated from the gravity data.The combined geophysical models are indicative of a process of megablock stoping in which large crustal blocks were displaced downwards in midcrustal regions to permit the emplacement of what is now the Ackley Granite Suite and associated plutons.
Cimolopteryx sp. (Aves, Charadriiformes) from the Frenchman Formation (Maastrichtian), Saskatchewan
Authors: Tokaryk Tim T. , James Paul C.
Published: October 2008

Cimolopteryx sp. (Aves, Charadriiformes) is reported from the Frenchman Formation (late Maastrichtian) of Saskatchewan, providing the first record of a latest Cretaceous bird from nonmarine sediments of western Canada.
U–Pb zircon ages of volcanism and plutonism in the Mishibishu greenstone belt near Wawa, Ontario
Authors: Turek A. , Keller R. , Schmus W. R. Van
Published: October 2008

The Mishibishu greenstone belt, located 40 km west of Wawa, is a typical Archean greenstone belt and is probably an extension of the Michipicoten belt. This belt is composed of basic to felsic metavolcanic rocks of tholeiitic to calc-alkaline affinity and of metasedimentary rocks ranging from conglomerate to argillite. Granitoids, diorites, and gabbros intrude and embay supracrustal rocks as internal and external plutons.Six U–Pb zircon ages have been obtained on rocks in this area. The oldest is 2721 ± 4 Ma for the Jostle Lake tonalite. The bulk of the volcanic rocks formed by 2696 ± 17 Ma, which is the age of the Chimney Point porphyry at the top of the volcanic pile. The Pilot Harbour granite has a similar age of 2693 ± 7 Ma. The age of the Tee Lake tonalite is 2673 ± 12 Ma, and the age of the Iron. Lake gabbro is 2671 ± 4 Ma. The youngest age for volcanics in this part of the Superior Province is 2677 ± 7 Ma, obtained from, the David Lakes pyroclastic breccia. these ages agree with those reported for the adjacent Michipicoten and Gamitagama belts.
Influence of the location of production wells in unconfined groundwater basins: an analysis by numerical simulation
Authors: Ophori Duke , Tóth József
Published: October 2008

Development potential of groundwater resources under continuous production is calculated by numerical simulation for models of unit basins for the plains regions of Alberta, Canada, in order to analyze the relations between the location of water wells on the one hand, and well yield and basin stability, on the other. These relations are expressed in terms of two basin hydrologic parameters, namely the transitional basin yield (TBY) and the sustainable basin yield (SBY). TBY is the net cumulative inflow of water into the system, induced by and during development at a particular site, from an initial to a final steady-state condition. SBY, on the other hand, is the amount of water captured from precipitation due to production at a particular site under the newly established steady-state conditions. TBY is highest for well locations in the discharge area and decreases gradually as the sites are moved toward the recharge area. This is so because more of the naturally discharging, and thus otherwise lost, water is captured by wells located in discharge areas than by wells in recharge areas. On the other hand, SBY is greater if the wells are located in recharge areas than if they are in the discharge areas because an increasing percentage of precipitation is converted to infiltration by production wells as their locations are moved upslope in the basin. From a regional hydrological viewpoint, these are key relations in optimizing the development potential of the groundwater resources in extensive unconfined basins. Precipitation rate, simulated as maximum potential infiltration rate, is assumed to be constant over time. It is shown also that under conditions of restricted rainfall, a recharge-area development results in unstable basin-hydrological conditions sooner than when development takes place in the discharge area. Regional groundwater exploitation should, therefore, be initiated in discharge areas and moved towards recharge regions gradually, and only for compelling reasons. Factors such as precipitation rates and positions of aquifers within a basin affect TBY and SBY to various degrees, thereby influencing the optimal location of well sites in the basin.
Evidence of cryostatic desiccation processes associated with sand intraclasts within diamictons, southern Ontario, Canada
Authors: Menzies John
Published: October 2008

Shore bluffs at Mohawk Bay, southern Ontario, reveal, within a complex mélange of glacial sediments, brecciated diamicton surrounding sand-block intraclasts. Typically, each intraclast has an aureole (50–65 cm) of brecciated diamicton. It is thought that a causal link exists between the origin of the intraclasts and the deposition of the diamicton. A hypothesis is developed in which sand deposits are thought to have been frozen, eroded, entrained, and eventually deposited within a deforming subglacial or glacio-aquatic debris layer. These sand blocks remained frozen after being deposited, forming intraclasts encased within the diamicton. It is proposed that differential cryostatic stresses developed at the interface between the frozen blocks and the diamicton, causing tensile stresses to develop over short distances and fracturing (brecciation) of the rapidly cooling diamicton. To test this hypothesis, a simple heat-flow-simulation program (COLDSPOT) was run using parameters akin to those found at Mohawk Bay. Results from the simulation are compatible with field observations. The findings from Mohawk Bay have significant implications for glacial sedimentology and glacier bed conditions.
FINITE GLUON FUSION AMPLITUDE IN THE GAUGE-HIGGS UNIFICATION
Authors: MARU NOBUHITO
Published: October 2008

We show that the gluon fusion amplitude in the gauge-Higgs unification scenario is finite in any dimension regardless of its nonrenormalizability. This result is supported by the fact that the local operator describing the gluon fusion process is forbidden by the higher dimensional gauge invariance. We explicitly calculate the gluon fusion amplitude in an arbitrary dimensional gauge-Higgs unification model and indeed obtain the finite result.
DO THE FUNDAMENTAL CONSTANTS CHANGE WITH TIME?
Authors: KANEKAR NISSIM
Published: October 2008

Comparisons between the redshifts of spectral lines from cosmologically-distant galaxies can be used to probe temporal changes in low-energy fundamental constants like the fine structure constant and the proton–electron mass ratio. Here, we review the results from, and the advantages and disadvantages of, the best techniques using this approach, before focussing on a new method, based on conjugate satellite OH lines, that appears to be less affected by systematic effects and hence holds much promise for the future.
PREDICTION OF LOOP REGIONS IN PROTEIN SEQUENCE
Authors: DOVIDCHENKO NIKITA V. , BOGATYREVA NATALYA S. , GALZITSKAYA OXANA V.
Published: October 2008

We suggest an algorithm that inputs a protein sequence and outputs a decomposition of the protein chain into a regular part including secondary structures and a nonregular part corresponding to loop regions. We have analyzed loop regions in a protein dataset of 3,769 globular domains and defined the optimal parameters for this prediction: the threshold between regular and nonregular regions and the optimal window size for averaging procedures using the scale of the expected number of contacts in a globular state and entropy scale as the number of degrees of freedom for the angles φ, ψ, and χ for each amino acid. Comparison with known methods demonstrates that our method gives the same results as the well-known ALB method based on physical properties of amino acids (the percentage of true predictions is 64% against 66%), and worse prediction for regular and nonregular regions than PSIPRED (Protein Structure Prediction Server) without alignment of homologous proteins (the percentage of true predictions is 73%). The potential advantage of the suggested approach is that the predicted set of loops can be used to find patterns of rigid and flexible loops as possible candidates to play a structure/function role as well as a role of antigenic determinants.
MODELING OF GLYCEROL-3-PHOSPHATE TRANSPORTER SUGGESTS A POTENTIAL 'TILT' MECHANISM INVOLVED IN ITS FUNCTION
Authors: TSIGELNY IGOR F. , GREENBERG JERRY , KOUZNETSOVA VALENTINA , NIGAM SANJAY K.
Published: October 2008

Many major facilitator superfamily (MFS) transporters have similar 12-transmembrane α-helical topologies with two six-helix halves connected by a long loop. In humans, these transporters participate in key physiological processes and are also, as in the case of members of the organic anion transporter (OAT) family, of pharmaceutical interest. Recently, crystal structures of two bacterial representatives of the MFS family — the glycerol-3-phosphate transporter (GlpT) and lac-permease (LacY) — have been solved and, because of assumptions regarding the high structural conservation of this family, there is hope that the results can be applied to mammalian transporters as well. Based on crystallography, it has been suggested that a major conformational "switching" mechanism accounts for ligand transport by MFS proteins. This conformational switch would then allow periodic changes in the overall transporter configuration, resulting in its cyclic opening to the periplasm or cytoplasm. Following this lead, we have modeled a possible "switch" mechanism in GlpT, using the concept of rotation of protein domains as in the DynDom program17and membranephilic constraints predicted by the MAPAS program.23We found that the minima of energies of intersubunit interactions support two alternate positions consistent with their transport properties. Thus, for GlpT, a "tilt" of 9°–10° rotation had the most favorable energetics of electrostatic interaction between the two halves of the transporter; moreover, this confirmation was sufficient to suggest transport of the ligand across the membrane. We conducted steered molecular dynamics simulations of the GlpT-ligand system to explore how glycerol-3-phosphate would be handled by the "tilted" structure, and obtained results generally consistent with experimental mutagenesis data. While biochemical data remain most consistent with a single-site alternating access model, our results raise the possibility that, while the "rocker switch" may apply to certain MFS transporters, intermediate "tilted" states may exist under certain circumstances or as transitional structures. Although wet lab experimental confirmation is required, our results suggest that transport mechanisms in this transporter family should probably not be assumed to be conserved simply based on standard structural homology considerations. Furthermore, steered molecular dynamics elucidating energetic interactions of ligands with amino acid residues in an appropriately modeled transporter may have predictive value in understanding the impact of mutations and/or polymorphisms on transporter function.
UBIQUITOUS REASSORTMENTS IN INFLUENZA A VIRUSES
Authors: WAN XIU-FENG , OZDEN MUFIT , LIN GUOHUI
Published: October 2008

The influenza A virus is a negative-stranded RNA virus composed of eight segmented RNA molecules, including polymerases (PB2, PB1, PA), hemagglutinin (HA), nucleoprotein (NP), neuraminidase (NA), matrix protein (MP), and nonstructure gene (NS). The influenza A viruses are notorious for rapid mutations, frequent reassortments, and possible recombinations. Among these evolutionary events, reassortments refer to exchanges of discrete RNA segments between co-infected influenza viruses, and they have facilitated the generation of pandemic and epidemic strains. Thus, identification of reassortments will be critical for pandemic and epidemic prevention and control. This paper presents a reassortment identification method based on distance measurement using complete composition vector (CCV) and segment clustering using a minimum spanning tree (MST) algorithm. By applying this method, we identified 34 potential reassortment clusters among 2,641 PB2 segments of influenza A viruses. Among the 83 serotypes tested, at least 56 (67.46%) exchanged their fragments with another serotype of influenza A viruses. These identified reassortments involve 1,957 H2N1 and 1,968 H3N2 influenza pandemic strains as well as H5N1 avian influenza virus isolates, which have generated the potential for a future pandemic threat. More frequent reassortments were found to occur in wild birds, especially migratory birds. This MST clustering program is written in Java and will be available upon request.
THE EFFECTS OF ETHNICITY, FAMILIES AND CULTURE ON ENTREPRENEURIAL EXPERIENCE: AN EXTENSION OF SUSTAINABLE FAMILY BUSINESS THEORY
Authors: DANES SHARON M. , LEE JINHEE , STAFFORD KATHRYN , HECK RAMONA KAY ZACHARY
Published: October 2008

Entrepreneurs have been traditionally epitomized as rugged individuals garnering creative forces of innovation and technology. Applying this traditional, limited, and narrow view of entrepreneurship to ethnic firm creation and growth is to ignore or discount core cultural values of the ethnic contexts in which these firms operate. It is no longer possible to depend solely on human capital theory and household characteristic descriptions to understand the complex and interdependent relationships between the ethnic-owning family, its firm, and the community context in which the firm operates. This paper addresses the complex dynamic of ethnic firms with three purposes: (a) to provide a cultural context for the three ethnic groups composing the National Minority Business Owner Study; (b) to extend the Sustainable Family Business Theory, a dynamic, behaviorally-based, multi-dimensional family firm theory, by clarifying how it accommodates ethnic firm complexities within their cultural context, and (c) to derive implications for research, education and consulting with worldwide applications.
ON THE NUMBER OF SOLUTIONS TO THE EQUATION (x1 + ⋯ + xn)2 = ax1 ⋯ xn IN A FINITE FIELD
Authors: BAOULINA IOULIA
Published: October 2008

Let Nq be the number of solutions to the equation [Formula: see text] over the finite field 𝔽q = 𝔽ps. L. Carlitz found formulas for Nq when n = 3 or 4. In an earlier paper, we found formulas for Nq when d = gcd (n - 2, q - 1) = 1 or 2 or 3 or 4; and when there exists an ℓ such that pℓ ≡ -1 (mod d). In our other paper, the cases d = 7 or 14, p ≡ 2 or 4 (mod 7) were considered. Recently, we obtained formulas for Nq when d = 8. In this paper, we find formulas for Nq when d = 2t, t ≥ 4, p ≡ 3 or 5 (mod 8) or p ≡ 9 (mod 16).
POINTS OF BOUNDED HEIGHT ON SCHUBERT VARIETIES
Authors: THUNDER JEFFREY LIN
Published: October 2008

Growth estimates and asymptotic estimates are given for the number of rational points of bounded height on Schubert varieties defined over number fields.
Incremental tensor analysis
Authors: Sun Jimeng , Tao Dacheng , Papadimitriou Spiros , Yu Philip S. , Faloutsos Christos
Published: October 2008

How do we find patterns in author-keyword associations, evolving over time? Or in data cubes (tensors), with product-branchcustomer sales information? And more generally, how to summarize high-order data cubes (tensors)? How to incrementally update these patterns over time? Matrix decompositions, like principal component analysis (PCA) and variants, are invaluable tools for mining, dimensionality reduction, feature selection, rule identification in numerous settings like streaming data, text, graphs, social networks, and many more settings. However, they have only two orders (i.e., matrices, like author and keyword in the previous example).

We propose to envision such higher-order data as tensors, and tap the vast literature on the topic. However, these methods do not necessarily scale up, let alone operate on semi-infinite streams. Thus, we introduce a general framework, incremental tensor analysis (ITA), which efficiently computes a compact summary for high-order and high-dimensional data, and also reveals the hidden correlations. Three variants of ITA are presented: (1) dynamic tensor analysis (DTA); (2) streaming tensor analysis (STA); and (3) window-based tensor analysis (WTA). In paricular, we explore several fundamental design trade-offs such as space efficiency, computational cost, approximation accuracy, time dependency, and model complexity.

We implement all our methods and apply them in several real settings, such as network anomaly detection, multiway latent semantic indexing on citation networks, and correlation study on sensor measurements. Our empirical studies show that the proposed methods are fast and accurate and that they find interesting patterns and outliers on the real datasets.
Mixing source and bytecode
Authors: Kats Lennart C.L. , Bravenboer Martin , Visser Eelco
Published: October 2008

Language extensions increase programmer productivity by providing concise, often domain-specific syntax, and support for static verification of correctness, security, and style constraints. Language extensions can often be realized through translation to the base language, supported by preprocessors and extensible compilers. However, various kinds of extensions require further adaptation of a base compiler's internal stages and components, for example to support separate compilation or to make use of low-level primitives of the platform (e.g., jump instructions or unbalanced synchronization). To allow for a more loosely coupled approach, we propose an open compiler model based on normalization steps from a high-level language to a subset of it, the core language. We developed such a compiler for a mixed Java and (core) bytecode language, and evaluate its effectiveness for composition mechanisms such as traits, as well as statement-level and expression-level language extensions.
Tolerating memory leaks
Authors: Bond Michael D. , McKinley Kathryn S.
Published: October 2008

Type safety and garbage collection in managed languages eliminate memory errors such as dangling pointers, double frees, and leaks of unreachable objects. Unfortunately, a program still leaks memory if it maintains references to objects it will never use again. Leaked objects decrease program locality and increase garbage collection frequency and workload. A growing leak will eventually exhaust memory and crash the program.

This paper introduces a
leak tolerance
approach called
Melt
that safely eliminates performance degradations and crashes due to leaks of dead but reachable objects in managed languages, given sufficient disk space to hold leaking objects. Melt (1) identifies
stale
objects that the program is not accessing; (2) segregates in-use and stale objects by storing stale objects to disk; and (3) preserves safety by activating stale objects if the program subsequently accesses them. We design and build a prototype implementation of Melt in a Java VM and show it adds overhead low enough for production systems. Whereas existing VMs grind to a halt and then crash on programs with leaks, Melt keeps many of these programs running much longer without significantly degrading performance. Melt provides users the illusion of a fixed leak and gives developers more time to fix leaky programs.
QVM
Authors: Arnold Matthew , Vechev Martin , Yahav Eran
Published: October 2008

Coping with software defects that occur in the post-deployment stage is a challenging problem: bugs may occur only when the system uses a specific configuration and only under certain usage scenarios. Nevertheless, halting production systems until the bug is tracked and fixed is often impossible. Thus, developers have to try to reproduce the bug in laboratory conditions. Often the reproduction of the bug consists of the lion share of the debugging effort.

In this paper we suggest an approach to address the aforementioned problem by using a specialized runtime environment (QVM, for
Quality Virtual Machine
). QVM efficiently detects defects by continuously monitoring the execution of the application in a production setting. QVM enables the efficient checking of violations of user-specified correctness properties, e.g., typestate safety properties, Java assertions, and heap properties pertaining to ownership.

QVM is markedly different from existing techniques for continuous monitoring by using a novel overhead manager which enforces a user-specified overhead budget for quality checks. Existing tools for error detection in the field usually disrupt the operation of the deployed system. QVM, on the other hand, provides a balanced trade off between the cost of the monitoring process and the maintenance of sufficient accuracy for detecting defects. Specifically, the overhead cost of using QVM instead of a standard JVM, is low enough to be acceptable in production environments.

We implemented QVM on top of IBM's J9 Java Virtual Machine and used it to detect and fix various errors in real-world applications.
Dynamic optimization for efficient strong atomicity
Authors: Schneider Florian T. , Menon Vijay , Shpeisman Tatiana , Adl-Tabatabai Ali-Reza
Published: October 2008

Transactional memory (TM) is a promising concurrency control alternative to locks. Recent work has highlighted important memory model issues regarding TM semantics and exposed problems in existing TM implementations. For safe, managed languages such as Java, there is a growing consensus towards strong atomicity semantics as a sound, scalable solution. Strong atomicity has presented a challenge to implement efficiently because it requires instrumentation of non-transactional memory accesses, incurring significant overhead even when a program makes minimal or no use of transactions. To minimize overhead, existing solutions require either a sophisticated type system, specialized hardware, or static whole-program analysis. These techniques do not translate easily into a production setting on existing hardware. In this paper, we present novel dynamic optimizations that significantly reduce strong atomicity overheads and make strong atomicity practical for dynamic language environments. We introduce analyses that optimistically track which non-transactional memory accesses can avoid strong atomicity instrumentation, and we describe a lightweight speculation and recovery mechanism that applies these analyses to generate speculatively-optimized but safe code for strong atomicity in a dynamically-loaded environment. We show how to implement these mechanisms efficiently by leveraging existing dynamic optimization infrastructure in a Java system. Measurements on a set of transactional and non-transactional Java workloads demonstrate that our techniques substantially reduce the overhead of strong atomicity from a factor of 5x down to 10% or less over an efficient weak atomicity baseline.
jStar
Authors: Distefano Dino , Parkinson J Matthew J.
Published: October 2008

In this paper we introduce a novel methodology for verifying a large set of Java programs which builds on recent theoretical developments in program verification: it combines the idea of abstract predicate families and the idea of symbolic execution and abstraction using separation logic. The proposed technology has been implemented in a new automatic verification system, called jStar, which combines theorem proving and abstract interpretation techniques. We demonstrate the effectiveness of our methodology by using jStar to verify example programs implementing four popular design patterns (subject/observer, visitor, factory, and pooling). Although these patterns are extensively used by object-oriented developers in real-world applications, so far they have been highly challenging for existing object-oriented verification techniques.
Enabling static analysis for partial java programs
Authors: Dagenais Barthélémy , Hendren Laurie
Published: October 2008

Software engineering tools often deal with the source code of programs retrieved from the web or source code repositories. Typically, these tools only have access to a subset of a program's source code (one file or a subset of files) which makes it difficult to build a complete and typed intermediate representation (IR). Indeed, for incomplete object-oriented programs, it is not always possible to completely disambiguate the syntactic constructs and to recover the declared type of certain expressions because the declaration of many types and class members are not accessible.

We present a framework that performs partial type inference and uses heuristics to recover the declared type of expressions and resolve ambiguities in partial Java programs. Our framework produces a complete and typed IR suitable for further static analysis. We have implemented this framework and used it in an empirical study on four large open source systems which shows that our system recovers most declared types with a low error rate, even when only one class is accessible.
Analyzing the performance of code-copying virtual machines
Authors: Prokopski Gregory B. , Verbrugge Clark
Published: October 2008

Many popular programming languages use interpreter-based execution for portability, supporting dynamic or reflective properties, and ease of implementation.
Code-copying
is an optimization technique for interpreters that reduces the performance gap between interpretation and
JIT
compilation, offering significant speedups over direct-threading interpretation. Due to varying language features and virtual machine design, however, not all languages benefit from codecopying to the same extent. We consider here properties of interpreted languages, and in particular bytecode and virtual machine construction that enhance or reduce the impact of code-copying. We implemented code-copying and compared performance with the original direct-threading virtual machines for three languages, Java (SableVM), OCaml, and Ruby (Yarv), examining performance on three different architectures, ia32 (Pentium 4), x86_64 (AMD64) and PowerPC (G5). Best speedups are achieved on ia32 by OCaml (maximum 4.88 times, 2.81 times on average), where a small and simple bytecode design facilitates improvements to branch prediction brought by code-copying. Yarv only slightly improves over direct-threading; large working sizes of bytecodes, and a relatively small fraction of time spent in the actual interpreter loop both limit the application of codecopying and its overall net effect. We are able to show that simple ahead of time analysis of VM and execution properties can help determine the suitability of code-copying for a particular VM before an implementation of code-copying is even attempted.
Multiple dispatch in practice
Authors: Muschevici Radu , Potanin Alex , Tempero Ewan , Noble James
Published: October 2008

Multiple dispatch uses the run time types of more than one argument to a method call to determine which method body to run. While several languages over the last 20 years have provided multiple dispatch, most object-oriented languages still support only single dispatch forcing programmers to implement multiple dispatch manually when required. This paper presents an empirical study of the use of multiple dispatch in practice, considering six languages that support multiple dispatch, and also investigating the potential for multiple dispatch in Java programs. We hope that this study will help programmers understand the uses and abuses of multiple dispatch; virtual machine implementors optimise multiple dispatch; and language designers to evaluate the choice of providing multiple dispatch in new programming languages.
An improved DFA for fast regular expression matching
Authors: Ficara Domenico , Giordano Stefano , Procissi Gregorio , Vitucci Fabio , Antichi Gianni , Di Pietro Andrea
Published: October 2008

Modern network devices need to perform deep packet inspection at high speed for security and application-specific services. Finite Automata (FAs) are used to implement regular expressions matching, but they require a large amount of memory. Many recent works have proposed improvements to address this issue.

This paper presents a new representation for deterministic finite automata (orthogonal to previous solutions), called Delta Finite Automata (δFA), which considerably reduces states and transitions and requires a transition per character only, thus allowing fast matching. Moreover, a new state encoding scheme is proposed and the comprehensive algorithm is tested for use in the packet classification area.
The resource pooling principle
Authors: Wischik Damon , Handley Mark , Braun Marcelo Bagnulo
Published: October 2008

Since the ARPAnet, network designers have built localized mechanisms for statistical multiplexing, load balancing, and failure resilience, often without understanding the broader implications. These mechanisms are all types of resource pooling whichmeans making a collection of resources behave like a single pooled resource. We believe that the natural evolution of the Internet is that it should achieve resource pooling by harnessing the responsiveness of multipath-capable end systems. We argue that this approach will solve the problems and limitations of the current piecemeal approaches.
W4A 2008
Authors: Sloan David , Yesilada Yeliz
Published: October 2008

The 5
th
annual International Cross-disciplinary Conference on Web Accessibility (W4A for short) took place alongside WWW 2008 in Beijing, in April 2008. The conference venue was Beijing's International Convention Centre, next door to the Bird's Nest Olympic Stadium, and given the closeness of the conference - in location and timing - to the world's most famous sporting event, it was fitting that the conference theme looked at how accessibility can be addressed as Web user become more active, as content creators. Our theme was "One World, One Web: Surfers become Designers?
KPC-Toolbox
Authors: Zhang Eddy Zheng , Casale Giuliano , Smirni Evgenia
Published: October 2008

We present the KPC-Toolbox, a set of MATLAB scripts for fitting workload traces into Markovian Arrival Processes (MAPs) in an automatic way. Given that the MAP parameterization space can be very large, we focus on first determining the order of the smallest MAP that can fit the trace well using the Bayesian Information Criterion (
BIC
). Having determined the order of the target MAP, the KPC-Toolbox automatically derives a MAP that captures accurately the moments and temporal dependence of the trace. We present experiments showing the effectiveness of the KPC-Toolbox in fitting traces that are well-documented in the literature as very challenging ones to fit.
Design of an object-based storage device based on I/O processor
Authors: He Shuibing , Feng Dan
Published: October 2008

Object-based Storage Device (OSD) is the foundation of the Object-based Storage System (OBSS).As the petabyte-scale OBSS includes thousands of OSDs, the performance, cost and power of single OSD must be considered together to build such a huge storage system The existing OSD based on server and general-purposed PC platform cannot have an excellent tradeoff among the three factor as they are not designed specifically for storage applications. An original OSD architecture based on the Intel IOP315 I/O processor chipset is presented in this paper. The I/O processor makes it powerful for the OSD to process the network communication protocol and the unique switch fabric of the chipset can further improve the I/O performance through parallel data transfer in multiple I/O channels. The experimental results show that the OSD performs well for system performance. Moreover, it provides characteristic of low cost and power.
On adaptive replacement based on LRU with working area restriction algorithm
Authors: Midorikawa Edson T. , Piantola Ricardo L. , Cassettari Hugo H.
Published: October 2008

Adaptive algorithms are capable of modifying their own behavior through time, depending on the execution characteristics. Recently, we have proposed LRU-WAR, an adaptive replacement algorithm whose objective is to minimize failures detected in LRU policy, preserving its simplicity and low overhead. In this paper, we present our contribution to the study of adaptive replacement algorithms describing their behavior under a number of workloads. Simulations include an analysis of the performance sensibility with the variation of the control parameters and its application in a multiprogrammed environment. In order to address LRU-WAR weakness as a global policy, we also introduce LRU-WARlock. The simulation results show that substantial performance improvements can be obtained.
A three pronged approach to teaching undergraduate operating systems
Authors: Robbins Steven
Published: October 2008

This paper describes an approach to teaching an undergraduate operating systems course that relies on three aspects. First, a standard textbook is used for the basic theoretical material. Second, programming projects are used to reinforce some of the material covered from the textbook. Lastly, simulators are used to illustrate other material. A key to the approach is to use experimentation by the student to enhance understanding and prepare them for research. Although no formal evaluation has been done, students seem to enjoy using the simulators and student performance on exams has increased since the simulators were introduced.
A Wiki that knows where it is being used
Authors: Plummer Maria , Plotnick Linda , Hiltz Starr Roxanne , Jones Quentin
Published: October 2008

With the advent of extensive wireless networks that blanket physically compact urban enclaves such as office complexes, shopping centers, or university campuses, it is possible to create software applications that provide location-based mobile/online services. One such application is CampusWiki, which integrates location information into a wiki structure. In the design science research reported in this paper, we employed a form of "action research" in which we engaged users as participants in an iterative process of designing and evaluating CampusWiki. Two qualitative studies were undertaken early in the design process in which semi-structured interviews were used to assess potential users' reactions to CampusWiki. Through this research, the designers were able to assess whether their intentions matched the mental models of potential users of the application. The results showed that although many of the perceived benefits were as designed by the developers, a misunderstanding of the location-aware feature led users to unanticipated concerns and expectations. These findings are important in guiding designers and implementers on the desirable and possibly undesirable features of such systems.