2,056 research outputs found
Divisibility of the Conway polynomial of links
No full textThe Conway polynomial ∇K = c0 + c1z + c2z2...of a link K is an invariant of links. In this paper we extend a theorem of J. Levine [5] regarding divisibility of the Conway polynomial by monomials of the form zi.
Three different definitions of finite type invariants of links are presented, including a definition of surgery finite type. When the coefficients ci are considered as finite type invariants, the type of these invariants is closely related to the degree of the monomials which can be factored out of ∇K.
With this in mind, we prove an extension of a conjecture by T. Cochran and P. Melvin [2] concerning the divisibility of an alternating sum sum S<L ∇K(Sigma S) of Conway polynomials of an algebraically split link K in various surgered spheres. This result was also proved for a more general case in which the link K is not necessarily algebraically split.
Finally, corollaries relate these theorems to the type of the coefficients ci, considered as finite type invariants
Opportunities for linking young surveyors across professional surveying member organisations and FIG
No full textChildren\u27s/Young Adult (YA) Author Event: Tim Green Author Visit
No full textThe Children’s/Young Adult Author Committee at Olivet Nazarene University received a $2500 Community Engagement Grant from the university. Because of this grant, the university hosted Tim Green, a former NFL football player who is now authoring books of primary interest to fourth through eighth graders. The success of this grant is difficult to measure, but in numbers, more than 3200 4th - 8th grade students and their teachers attended his speaking events during his two day visit. Green autographed more than 400 books for the attendees. Regarding reading motivation, area teachers have and still are reporting students, boys in particular, who in the past have never read a whole book, but when the teachers give them one of Tim Green’s books, they return and ask for more of his books to read. The Children’s/Young Adult Author Committee plans to continue bringing authors of quality literature to the community
The terraces of the Conway Coast, North Canterbury: Geomorphology, sedimentary facies and sequence stratigraphy
No full textA basin analysis was conducted at the Conway Flat coast (Marlborough Fault Zone, South Island, New Zealand) to investigate the interaction of regional and local structure in a transpressional plate boundary and its control on basin formation. A multi-tiered approach has been employed involving: (i) detailed analysis of sedimentary deposits; (ii) geomorphic mapping of terraces, fault traces and lineaments; (iii) dating of deposits by 14C and OSL and (iv) the integration of data to form a basin-synthesis in a sequence stratigraphy framework.
A complex thrust fault zone (the Hawkswood Thrust Fault Zone), originating at the hinge of the thrust-cored Hawkswood anticline, is interpreted to be a result of west-dipping thrust faults joining at depth with the Hundalee Fault and propagating eastwards. The faults uplift and dissect alluvial fans to form terraces along the Conway Flat coast that provide the necessary relief to form the fan deltas. These terrace/fan surfaces are ~9 km long and ~3 km wide, composite features, with their upper parts representing sub-aerial alluvial fans. These grade into delta plains of Quaternary Gilbert-style fan deltas. Uplift and incision have created excellent 3D views of the underlying Gilbert-style fan delta complexes from topsets to prodelta deposits.
Erosive contacts between the Medina, Rafa, Ngaroma and modern Conway fan delta deposits, coupled with changes in terrace elevations allow an understanding of the development of multiple inset terraces along the Conway Flat coast. These terraces are divided into five stages of evolution based on variations in sedimentary facies and geomorphic mapping: Stage I involves the uplift of the Hawkswood Range and subsequent increased sedimentation rate such that alluvial fans prograded to the sea to form the Medina fan delta Terrace. Stage II began with a period of incision, from lowering sea level or changes in the uplift and sedimentation rate and continued with the deposition of the Dawn and Upham fan deltas. Stage III starts with the incision of the Rafa Terrace and deposition of aggradational terraces in the upper reaches. Stage IV initiated by a period of incision followed by deposition of estuarine facies at ~8ka and Stage V began with a period of incision and continues today with the infilling of the incised valley by the modern fan delta of the Conway River and its continued progradation.
New dates from within the Gilbert-type fan deltas along the Conway Flat coast are presented, using OSL and 14C dating techniques. Faulting at the Conway Flat coast began ~ 94 ka, based on the development of the Medina Terrace fan delta with uplift rates ~1.38~1.42 m/ka. The interplay of tectonics and sea level fluctuations continued as the ~79 ka Rafa Terrace fan deltas were created, with uplift rates calculated at ~1.39 m/ka. Detailed 14C ages from paleoforest (~8.4-~6.4 ka) in the Ngaroma Terrace and from the mouths of smaller streams have established uplift rates during the Holocene ~1-3 m/ka, depending on sea level
The GEOTRACES Intermediate Data Product 2017
No full textThe GEOTRACES Intermediate Data Product 2017 (IDP2017) is the second publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2016. The IDP2017 includes data from the Atlantic, Pacific, Arctic, Southern and Indian oceans, with about twice the data volume of the previous IDP2014. For the first time, the IDP2017 contains data for a large suite of biogeochemical parameters as well as aerosol and rain data characterising atmospheric trace element and isotope (TEI) sources. The TEI data in the IDP2017 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at crossover stations. The IDP2017 consists of two parts: (1) a compilation of digital data for more than 450 TEIs as well as standard hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing an on-line atlas that includes more than 590 section plots and 130 animated 3D scenes. The digital data are provided in several formats, including ASCII, Excel spreadsheet, netCDF, and Ocean Data View collection. Users can download the full data packages or make their own custom selections with a new on-line data extraction service. In addition to the actual data values, the IDP2017 also contains data quality flags and 1-σ data error values where available. Quality flags and error values are useful for data filtering and for statistical analysis. Metadata about data originators, analytical methods and original publications related to the data are linked in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2017 as section plots and rotating 3D scenes. The basin-wide 3D scenes combine data from many cruises and provide quick overviews of large-scale tracer distributions. These 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of tracer plumes near ocean margins or along ridges. The IDP2017 is the result of a truly international effort involving 326 researchers from 25 countries. This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017.
This article is part of a special issue entitled: Cycles of trace elements and isotopes in the ocean – GEOTRACES and beyond - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González
Evaluating Citebase, an open access Web-based citation-ranked search and impact discovery service
No full textCitebase is a new citation-ranked search and impact discovery service that measures citations of scholarly research papers which are openly accessible on the Web, i.e. papers that are assessable continuously online. Other services, such as ResearchIndex, have emerged in recent years to offer citation indexing of Web research papers. In the first detailed user evaluation of an open access Web citation indexing service, Citebase has been evaluated by nearly 200 users from different backgrounds. The paper details the procedures used in the evaluation, and analyses the results of this study, which took place between June and October 2002. It was found that within the scope of its primary components, the search interface and services available from its rich bibliographic records, Citebase can be used simply and reliably for the purpose intended, and that it compares favourably with other bibliographic services. It is shown tasks can be accomplished efficiently with Citebase regardless of the background of the user. More data need to be collected and the process refined before it is as reliable for measuring citation impact of indexed papers. Better explanations and guidance are required for first-time users. Coverage is seen as a limiting factor, even though Citebase indexes over 200,000 papers from arXiv. Non-physicists were frustrated at the lack of papers from other sciences. The principle of citation searching of open access archives has thus been demonstrated and need not be restricted to current users. Since the evaluation, Citebase has become a featured service of the ArXiv physics eprint archives
Distinct iron isotopic signatures and supply from marine sediment dissolution
No full textIron (Fe) inputs to the surface ocean may stimulate photosynthesis and have an impact on the uptake of carbon dioxide in the ocean on glacial to inter-glacial timescales of climate change1. Global ocean reservoir-flux models2 indicate that 90% of Fe used by marine phytoplankton in the present day surface ocean is supplied from the deep water below, but the sources of dissolved Fe to this deep water are still poorly constrained. Therefore, quantifying and tracking iron supplied to the ocean will provide key information to resolve climate models and sensitivity to the Fe cycle3, 4.Measurable differences in the isotopic composition of Fe between various sources to the ocean have prompted widespread interest in seawater Fe isotope determintions5, 6, 7, which can potentially be used to track Fe inputs and assess the relative importance of different sources of dissolved Fe to the oceanic reservoir. Microbial sediment respiration supports a major flux of dissolved and isotopically light Fe to the global ocean8, 9, 10, by catalysing the reductive dissolution (RD) of Fe oxyhydroxide minerals during organic matter decomposition11. Reduction of Fe oxyhydroxide enriches soluble Fe(II)(aq) in sediment pore water, which diffuses into bottom water when the oxygenated layer of surface sediment is adequately shallow9, 12, most notably from oxygen-deficient continental margins8, 9, 10. Benthic fluxes of Fe are mixed in bottom waters and can be transported to open ocean and surface waters13, 14, where Fe may control the efficacy of the biological carbon pump15, 16.Dissolved Fe(II)(aq) produced by RD initially has ?56Fe values 0.5–2.0‰ lighter than the original substrates17, and at isotopic equilibrium, experiments show ?56Fe(II)(aq) is ?1.05 to ?3.99‰ relative to the common reactive Fe oxides haematite17, goethite18 and ferrihydrite17, 19, 20. Similar light ?56Fe values (?1.82 to ?3.45‰) have been observed in both the pore waters21, 22, 23 and overlying seawater9, 24 of river-dominated and dysoxic margins, and light Fe isotopic compositions are recorded in ocean basin sediments coeval with past episodes of ocean oxygen deficiency, consistent with seawater transport of light Fe from ferruginous shelf sediments to ocean basins25. Thus, benthic fluxes of isotopically light Fe appear to be distinguishable from other sources of Fe to the ocean, such as atmospheric dust dissolution (?56Fe=+0.13±0.18‰)26 and river discharge (?56Fe=+0.14±0.28‰)27.Paradoxically, however, equatorial Pacific seawater originating from the continental margin of New Guinea contains elevated Fe concentrations with heavy Fe isotopic compositions (?56Fe=+0.37±0.15‰)28. These and other seawater isotope measurements have led to the proposition of an additional ‘non-reductive dissolution’ (NRD) mechanism for Fe28, 29, albeit with existing Fe isotope evidence from continental margin sediments indicating otherwise9, 24. These findings coincide with a growing need to evaluate the geographical variability of benthic Fe fluxes to effectively model carbon cycling in the ocean3, 4, where models presently rely on global extrapolations from potentially unrepresentative regions.Here we characterise the pore water isotopic composition and corresponding flux of dissolved Fe from the Cape margin, South Africa—a semi-arid passive margin derived from deeply weathered saprolite soils and surrounded by oxygenated South Atlantic seawater. These sites are distinct from most previous sites of benthic Fe flux investigation, which have focused on active margins next to areas of rapid uplift with oxygen-deficient shelf waters (Fig. 1). This study reveals that the amount of dissolved Fe released from the Cape margin is less than predicted by benthic Fe flux relationships8 widely used to model ocean Fe–CO2 interaction3, 4. We report solid-phase compositional data that suggests that the small pore water Fe flux reflects geological and hydro-climatic influences on reactive Fe substrate delivery to the shelf. Isotopically heavy Fe present in ‘oxidizing’ pore waters of the Cape margin—a zone previously beyond analytical resolution—provides in situ evidence for the role of ‘NRD’ of Fe proposed by Radic et al.28 These discoveries have implications for past and present oceanic Fe cycles and the parameterization of ocean biogeochemical models
Catholic Comments Podcast.
No full textAuthor Tim Rinaldi discusses his mission work in Honduras and how it changed his life and perspective
Accepting Optimally in Automated Negotiation with Incomplete Information (abstract)
No full textIntelligent SystemsElectrical Engineering, Mathematics and Computer Scienc
Nostalgia: content, triggers, functions
No full textSeven methodologically diverse studies addressed 3 fundamental questions about nostalgia. Studies 1 and 2 examined the content of nostalgic experiences. Descriptions of nostalgic experiences typically featured the self as a protagonist in interactions with close others (e.g., friends) or in momentous events (e.g., weddings). Also, the descriptions contained more expressions of positive than negative affect and often depicted the redemption of negative life scenes by subsequent triumphs. Studies 3 and 4 examined triggers of nostalgia and revealed that nostalgia occurs in response to negative mood and the discrete affective state of loneliness. Studies 5, 6, and 7 investigated the functional utility of nostalgia and established that nostalgia bolsters social bonds, increases positive self-regard, and generates positive affect. These findings demarcate key landmarks in the hitherto uncharted research domain of nostalgi
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