10 results on '"Vaz, David"'
Search Results
2. Morphostructural mapping of Borealis Planitia, Mercury.
- Author
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Cardinale, Marco, Vaz, David A., D'Incecco, Piero, Mari, Nicola, Filiberto, Justin, Eggers, Gabriel L., and Di Achille, Gaetano
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MERCURY (Planet) ,INSPECTION & review ,CLASSIFICATION algorithms ,DATABASES ,MAPS ,MERCURY ,IMPACT craters - Abstract
Orbital data from the MESSENGER spacecraft show that a significant portion of Mercury’s northern hemisphere is covered by smooth plains, which are interpreted to be flood volcanic material and/or impact melt. The smooth plains show pervasive tectonic structures and encompass a broad raised bulge of uncertain geophysical interpretation. In this work, we focus on the mapping of all the morphostructures within the northern smooth plains, aiming at providing a useful dataset for further studies about the mapped area. The structural map is obtained through a twofold process: first with an automatic mapping, using an algorithm to identify all the lineaments from a DEM; and second with a visual inspection and classification of the results of the algorithm in a GIS environment. The final maps are drafted at two different scales, 1:300,000 and 1:600,000. With this approach, we mapped and characterized more than fifty thousand lines marking scarps on the surface, creating a database with several morphometric attributes for each of the identified scarps (e.g. length, azimuth, and height), which can be used for geostatistical study of smooth plains tectonics. Our structural map reveals that: (i) the area is broadly dominated by wrinkle ridges, ghost crater assemblages of lineaments, and scarps related to impact crater processes (e.g. radial faults, secondary crater chains, ejecta emplacement) and that (ii) the amount of strain was not evenly accommodated throughout the northern smooth plains. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
3. A review of panic buying: the mediation of illusory truth effect and persistence due to herd mentality and confirmation bias.
- Author
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Susie Woo, Khan, Muhammad Samir, Vaz, David, Bhavsar, Daivat, and Mardon, Austin
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THOUGHT & thinking ,SOCIAL media ,CONSUMER attitudes ,PANIC disorders ,FEAR ,SHOPPING ,PERCEPTUAL illusions ,DECISION making ,ANXIETY ,MISINFORMATION ,DECEPTION ,COVID-19 pandemic ,PSYCHOLOGICAL stress - Abstract
In the early stages of the COVID-19 pandemic, the public has been experiencing severe stress and feelings of anxiety. Social media in particular has been shown in the literature to be a major contributing medium for the widespread distribution of misinformation concerning COVID-19. The rapid dissemination of fake news concerning supply shortages of certain essential items has increased pandemic-related behaviours such as panic buying. Factors that have led to panic buying include: perceived threat of an event, perceived product scarcity, fear of the unknown, and coping methods to gain control. Although these factors are prevalent reasons that induce panic buying behaviours, they do not explain the mechanisms of perception formation. It is possible that heuristics (i.e. availability, and affect), which are reinforced by social media posts, aid in the development of the illusory truth effect. This psychological phenomenon may be the root cause of the public's false perceptions of pandemic-related events. This paper reviews the impact of the illusory truth effect as a mediator in processing misinformation from social media and the news as truths that inevitably encourages panic buying behaviour. Furthermore, this paper examines the persistence of the illusory truth effect due to herd mentality and confirmation bias in the perpetual cycle of irrational decision making. In conclusion, the illusory truth effect has been demonstrated to be a key cognitive bias that strengthens with repetitive exposure to adverse sentiments related to COVID-19, and is likely to be maintained through herd mentality and confirmation bias in social situations. Although more research must be conducted to solidify this theory, the current review aims to serve as a basis for further research on the illusory truth effect and potentiate solutions in the prevention of adherence to this effect. [ABSTRACT FROM AUTHOR]
- Published
- 2022
4. Effectiveness of global rural teleoncology and future routes for teleoncology research in the context of Canadian rural areas: a narrative review of the literature.
- Author
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Rahimpoor-Marnani, Parmin, Kannan, Vivek, Vaz, David, Bhavsar, Daivat, Singh, Jasrita, and Mardon, Austin
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EVALUATION of medical care ,HEALTH services accessibility ,SYSTEMATIC reviews ,SEARCH engines ,RURAL health ,CANCER patient medical care ,TELEMEDICINE - Abstract
Background: To limit the risk of transmitting the COVID-19 virus during in person interactions, modes of telemedicine, such as teleoncology, have been on the rise more than ever. This narrative review examines the effectiveness of current Canadian teleoncology services in providing adequate services to the residents of Canadian rural areas. This paper also seeks to analyze current international research and models of teleoncology and how they may be applicable in a Canadian rural context. The paper additionally provides well-supported and appropriate suggestions for future developments of Canadian rural teleoncology and future research directions within the field. Methods: Through a literature search on platforms like Google Scholar, 14 Canadian and international pieces of literature have been selected and reviewed. Common trends of teleoncology strengths and weaknesses have been retrieved, analyzed and summarized. Results: Upon analysis of advantages and disadvantages, it can be stated that teleoncology is a relevant mode of healthcare delivery in the current Canadian context. Despite its limitations, teleoncology can enhance and diversify the quality and types of services delivered to Canadians, especially those in rural areas. Conclusion: Overall, it can be safely deduced that teleoncology has the potential of becoming a prominent aspect of the future of healthcare especially in Canadian rural contexts. The next step towards enhancing the Canadian rural teleoncology system is to gain a better understanding of this system through more recent, standardized research. This can be followed by careful examination of the international status of teleoncology for potential inspirations for change and areas of research. In its analysis, the paper at hand provides a series of suggestions for future areas of research in this topic and potential methodologies for enhancing current Canadian rural teleoncology. [ABSTRACT FROM AUTHOR]
- Published
- 2022
5. Widespread Megaripple Activity Across the North Polar Ergs of Mars.
- Author
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Chojnacki, Matthew, Vaz, David A., Silvestro, Simone, and Silva, David C. A.
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SAND dunes ,ERGS (Landforms) ,RIPPLES (Fluid dynamics) ,MORPHOLOGY ,MARS (Planet) - Abstract
The most expansive dune fields on Mars surround the northern polar cap where various aeolian bedform classes are modified by wind and ice. The morphology and dynamics of these ripples, intermediate‐scale bedforms (termed megaripples and Transverse Aeolian Ridges [TARs]), and sand dunes reflect information regarding regional boundary conditions. We found that populations of polar megaripples and larger TARs are distinct in terms of their morphology, spatial distribution, and mobility. Whereas regionally restricted TARs appeared degraded and static in long‐baseline observations, polar megaripples were not only widespread but migrating at relatively high rates (0.13 ± 0.03 m/Earth year) and possibly more active than other regions on Mars. This high level of activity is somewhat surprising since there is limited seasonality for aeolian transport due to surficial frost and ice during the latter half of the martian year. A comprehensive analysis of an Olympia Cavi dune field estimated that the advancement of megaripples, ripples, and dunes avalanches accounted for ∼1%, ∼10%, and ∼100%, respectively, of the total aeolian system's sand fluxes. This included dark‐toned ripples that migrated the average equivalent of 9.6 ± 6 m/yr over just 22 days in northern summer—unprecedented rates for Mars. While bedform transport rates are some of the highest yet reported on Mars, the sand flux contribution between the different bedforms does not substantially vary from equatorial sites with lower rates. Seasonal off‐cap sublimation winds and summer‐time polar storms are attributed as the cause for the elevated activity, rather than cryospheric processes. Plain Language Summary: "Megaripples" are distinct wind‐driven bedforms that occur on the surface of Earth and Mars, often with sizes between that of smaller ripples and larger dunes. Recent work has found the thin martian atmosphere can mobilize some coarse‐grained megaripples, overturning prior notions that these were static relic landforms from a past climate. We mapped megaripples and adjacent bedforms across the north polar sand seas, the most expansive collection of dune fields on Mars. Megaripples were found to be widespread across the region and migrating at relatively high rates relative to other sites on Mars that are at lower latitudes. This enhanced activity is likely related to the greater sand fluxes found for neighboring dunes which are driven by summer‐time seasonal winds when polar ice is sublimating. In contrast, other megaripples appear to be stabilized, a likely result of intergranular ice within low wind areas. Key Points: Abundant megaripple populations were identified across the north polar ergs of Mars and found to be migrating with dunes and ripplesPolar megaripple dynamics and sand fluxes are enhanced relative to lower‐latitude sites, despite the shorter migration season due to iceSeasonal sublimation winds and polar storms were attributed as the cause for the elevated activity rather than cryospheric processes [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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6. A Better View Over Titan Drainage Networks Through RGB Fusion of Cassini SAR Images.
- Author
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Alves, Eduardo I., Andrade, Ana I. A. S. S., and Vaz, David A.
- Abstract
We present a simple method to enhance the view of Titan drainage networks, thus allowing extracting relevant hydrological parameters. The method uses RGB fusion of three Cassini synthetic aperture radar images acquired at different times, and is tested on one drainage network. Comparison with previous studies of the same network shows an increase in all the measured parameters. The present results help constrain previous estimates of erosion times, terrain, and tectonic models for the area and indicate that, whenever possible, geomorphological inference from drainage network geometry should be drawn on multiply sampled scenes. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
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7. Dune‐Yardang Interactions in Becquerel Crater, Mars.
- Author
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Urso, Anna, Chojnacki, Matthew, and Vaz, David A.
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Abstract: Isolated landscapes largely shaped by aeolian processes can occur on Earth, while the majority of Mars' recent history has been dominated by wind‐driven activity. Resultantly, Martian landscapes often exhibit large‐scale aeolian features, including yardang landforms carved from sedimentary‐layered deposits. High‐resolution orbital monitoring has revealed that persistent bedform activity is occurring with dune and ripple migration implying ongoing abrasion of the surface. However, little is known about the interaction between dunes and the topography surrounding them. Here we explore dune‐yardang interactions in Becquerel crater in an effort to better understand local landscape evolution. Dunes there occur on the north and south sides of a 700 m tall sedimentary deposit, which displays numerous superposed yardangs. Dune and yardang orientations are congruent, suggesting that they both were formed under a predominantly northerly wind regime. Migration rates and sediment fluxes decrease as dunes approach the deposit and begin to increase again downwind of the deposit where the effect of topographic sheltering decreases. Estimated sand abrasion rates (16–40 μm yr
−1 ) would yield a formation time of 1.8–4.5 Myr for the 70 m deep yardangs. This evidence for local aeolian abrasion also helps explain the young exposure ages of deposit surfaces, as estimated by the crater size‐frequency distribution. Comparisons to terrestrial dune activity and yardang development begin to place constraints on yardang formation times for both Earth and Mars. These results provide insight into the complexities of sediment transport on uneven terrain and are compelling examples of contemporary aeolian‐driven landscape evolution on Mars. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
8. User Defined Indexing.
- Author
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Vaz, David, Costa, Vítor Santos, and Ferreira, Michel
- Abstract
Logic programming provides an ideal framework for tackling complex data, such as the multi-dimensional vector-based data used to represent spatial databases. Unfortunately, the usefulness of logic programming systems if often hampered by the fact that most of these systems have to rely on a single unification-based mechanism as the only way to search in the database. While unification can usually take effective advantage of hash-based indexing, it is often the case that queries over more complex and structured data, such as the vectorial terms stored in spatial databases, cannot. We propose a new extension to Prolog indexing: User Defined Indexing (UDI). In this mechanism, the programmer may add extra information to Prolog indices so that only interesting fragments of the database will be selected. UDI provides a general extension of indexing, and can be used for both instantiated and constrained variables. As a test case, we demonstrate how UDI can be combined with a constraint system to provide an elegant and efficient mechanism to generate and execute range queries and spatial queries. Experimental evaluation shows that this mechanism can achieve orders of magnitude speedups on non-trivial datasets. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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9. Spatial-Yap: A Logic-Based Geographic Information System.
- Author
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Hutchison, David, Kanade, Takeo, Kittler, Josef, Kleinberg, Jon M., Mattern, Friedemann, Mitchell, John C., Naor, Moni, Nierstrasz, Oscar, Pandu Rangan, C., Steffen, Bernhard, Sudan, Madhu, Terzopoulos, Demetri, Tygar, Doug, Vardi, Moshe Y., Weikum, Gerhard, Dahl, Véronica, Niemelä, Ilkka, Vaz, David, Ferreira, Michel, and Lopes, Ricardo
- Abstract
Coupled deductive database systems join together logic programming systems and relational database management systems, in order to combine the best of both worlds. The current state-of-the-art of these interfaces is restricted to access extensional data in databases in Datalog form, disallowing access to compound terms. However, recent years have seen the evolution of relational database management systems in order to enable them to store and manage more complex information. Of this complex data, one of the most interesting and fast growing is that of spatial data. In this paper we describe the application of the MYDDAS deductive database system to the handling of spatial data, and the needed extensions, namely the ability to handle vectorial geometric attributes from database relations, the definition of spatial operators, and a visualization framework, in order to obtain a spatial deductive database system, that can be used as a geographic information system. We argue that such a system can improve the state-of-the-art of spatial data handling in all of its aspects, namely in spatial data modeling, spatial querying and spatial data mining. We describe, in particular, the application of such a logic-powered geographic information system to two real-world problems. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
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10. BigYAP: Exo-compilation meets UDI.
- Author
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SANTOS COSTA, VÍTOR, VAZ, DAVID, Lamma, Evelina, and Swift, Terrance
- Subjects
BIG data ,COMPUTER programming ,LOGIC programming ,DATABASES ,PROLOG (Computer program language) ,SQL ,COMPUTER performance - Abstract
The widespread availability of large data-sets poses both an opportunity and a challenge to logic programming. A first approach is to couple a relational database with logic programming, say, a Prolog system with MySQL. While this approach does pay off in cases where the data cannot reside in main memory, it is known to introduce substantial overheads. Ideally, we would like the Prolog system to deal with large data-sets in an efficient way both in terms of memory and of processing time. Just In Time Indexing (JITI) was mainly motivated by this challenge, and can work quite well in many application.Exo-compilation, designed to deal with large tables, is a next step that achieves very interesting results, reducing the memory footprint over two thirds. We show that combining exo-compilation with Just In Time Indexing can have significant advantages both in terms of memory usage and in terms of execution time.An alternative path that is relevant for many applications is User-Defined Indexing (UDI). This allows the use of specialized indexing for specific applications, say the spatial indexing crucial to any spatial system. The UDI sees indexing as pluggable modules, and can naturally be combined with Exo-compilation. We do so by using UDI with exo-data, and incorporating ideas from the UDI into high-performance indexers for specific tasks. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
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