2,673 research outputs found
Efficiently Storing Well-Composed Polyhedral Complexes Computed Over 3D Binary Images
A 3D binary image I can be naturally represented
by a combinatorial-algebraic structure called cubical complex
and denoted by Q(I ), whose basic building blocks are
vertices, edges, square faces and cubes. In Gonzalez-Diaz
et al. (Discret Appl Math 183:59–77, 2015), we presented a
method to “locally repair” Q(I ) to obtain a polyhedral complex
P(I ) (whose basic building blocks are vertices, edges,
specific polygons and polyhedra), homotopy equivalent to
Q(I ), satisfying that its boundary surface is a 2D manifold.
P(I ) is called a well-composed polyhedral complex over the
picture I . Besides, we developed a new codification system
for P(I ), encoding geometric information of the cells
of P(I ) under the form of a 3D grayscale image, and the
boundary face relations of the cells of P(I ) under the form
of a set of structuring elements. In this paper, we build upon
(Gonzalez-Diaz et al. 2015) and prove that, to retrieve topological
and geometric information of P(I ), it is enough to
store just one 3D point per polyhedron and hence neither
grayscale image nor set of structuring elements are needed.
From this “minimal” codification of P(I ), we finally present
a method to compute the 2-cells in the boundary surface of
P(I ).Ministerio de Economía y Competitividad MTM2015-67072-
Encoding Specific 3D Polyhedral Complexes Using 3D Binary Images
We build upon the work developed in [4] in which we presented
a method to “locally repair” the cubical complex Q(I) associated
to a 3D binary image I, to obtain a “well-composed” polyhedral complex
P(I), homotopy equivalent to Q(I). There, we developed a new codification
system for P(I), called ExtendedCubeMap (ECM) representation,
that encodes: (1) the (geometric) information of the cells of P(I) (i.e.,
which cells are presented and where), under the form of a 3D grayscale
image gP ; (2) the boundary face relations between the cells of P(I),
under the form of a set BP of structuring elements.
In this paper, we simplify ECM representations, proving that geometric
and topological information of cells can be encoded using just a 3D
binary image, without the need of using colors or sets of structuring
elements. We also outline a possible application in which well-composed
polyhedral complexes can be useful.Junta de Andalucía FQM-369Ministerio de Economía y Competitividad MTM2012-32706Ministerio de Economía y Competitividad MTM2015-67072-
Spatiotemporal Barcodes for Image Sequence Analysis
Taking as input a time-varying sequence of two-dimensional
(2D) binary images, we develop an algorithm for computing a spatiotemporal
0–barcode encoding lifetime of connected components on the image
sequence over time. This information may not coincide with the one provided
by the 0–barcode encoding the 0–persistent homology, since the
latter does not respect the principle that it is not possible to move backwards
in time. A cell complex K is computed from the given sequence,
being the cells of K classified as spatial or temporal depending on whether
they connect two consecutive frames or not. A spatiotemporal path is
defined as a sequence of edges of K forming a path such that two edges
of the path cannot connect the same two consecutive frames. In our
algorithm, for each vertex v ∈ K, a spatiotemporal path from v to the
“oldest” spatiotemporally-connected vertex is computed and the corresponding
spatiotemporal 0–bar is added to the spatiotemporal 0–barcode.Junta de Andalucía FQM-369Ministerio de Economía y Competitividad MTM2012-3270
Distribution of critical metals in evolving pyrite from massive sulfide ores of the Iberian Pyrite Belt
Acknowledgements
This research is a contribution to the projects CGL2016-79204-R,
PID2019-111715GB-I00 which are supported by the Spanish Government,
and 18/IF/6347 granted by Science Foundation Ireland (SFI). The
authors thank Cambridge Minerals for access to drill core, sampling
assistance and the ongoing collaboration. We are also grateful to Teodosio
Donaire for his constructive suggestions in petrogenetic aspects of
volcanogenic rocks in the IPB as well as Dany Savard and Audrey Lavoie
of LabMaTer, UQAC, for their assistance during the laser ablation analyses.
Authors would also like to acknowledge the use of Servicio General
de Apoyo a la Investigación-SAI, Universidad de Zaragoza.Supplementary data to this article can be found online at https://doi.
org/10.1016/j.oregeorev.2022.105275.With >90 known deposits containing original reserves of >2400 Mt of sulfide ore, the Iberian Pyrite Belt (IPB) is the largest volcanogenic massive sulfide (VMS) province on Earth. In these evolving mineral systems, texturally different pyrite exhibits characteristic mineralogy and trace element fingerprints. Pyrite (Py-1), which is well preserved in the polymetallic ores that crystallized at the earliest stage of VMS deposit formation, consists of kernels of pyrite framboids surrounded by concentric colloform bands and ended by faceted outlines. It is rich in some metals like Pb, Zn, Sb and As (mostly hosted as nano-to-micron-sized particles, including galena, tetrahedrite and arsenopyrite) but depleted in Cu, Co and Bi. In contrast, pyrite from the pyritic and Cu-rich ore overprinted by late fluids exhibits spongy-looking (Py-2) or homogenous (Py-3) cores surrounded by external facets with crystallographic continuity across the whole single grains due to re-crystallization. Py-2 is depleted in most trace elements with the exception of Au and Bi, which occur both in solid solutions and as nano-to-micron-sized inclusions. Py-3 has the highest Cu, Ag, Co and Ni (mainly associated to nano-to-micron-sized particles of tennantite, chalcopyrite and gersdorffite) and the lowest Au contents in the form of native gold. The progressive increase in metal contents from inner to outer parts of Py-1 matches with the onset of the economic metal endowment of VMS deposits in the IPB, whereas Py-2 and Py-3 are associated with metal shoot processes that led to both leached and high-grade ores, very likely when mafic rocks were emplaced into the footwall of the deposits.Projects CGL2016-79204-R, PID2019-111715GB-I00 which are supported by the Spanish Government, and 18/IF/6347 granted by Science Foundation Ireland (SFI
Nanomaterial accumulation in boiling brines enhances epithermal bonanzas
This work benefited from Grant NANOMET PID2022-138768OB-I00 funded by MCIN/AEI/10.13039/50110001133 and by “ERDF A way of making Europe” by the “European Union”, Grant IN 218323 funded by PAPIIT-DGAPA-UNAM, and Grant PID 2019-105625RB-C21 funded by MCIN/AEI/10.13039/501100011033. Additional funding was Granted by CONAHCyT (ongoing Ph.D. grant) and the Geological Society of America (Grant Number 13570-22) to the first author. Xavier Llovet, Laura Casado, Isabel Rivas, María del Mar Abad, and Cecilia de la Prada are acknowledged for their assistance during EPMA, FIB-SEM, and HRTEM analyses. We thank UNAM academicians Juan Tomás Vásquez and Edith Fuentes Guzmán for their help during sample preparation. We also thank Baltazar Chávez, Senén Benítez, and the team at Natividad (Oaxaca) for their assistance during the stay at the mine facilities. The manuscript has strongly benefited from insightful reviews by two anonymous reviewers and the handling Editor, Dr. Dan Zhu.Epithermal bonanza-type ores, characterized by weight-percent contents of e.g., gold and silver in a few mm to cm, are generated by mixtures of magmatic-derived hydrothermal brines and external fluids (e.g., meteoric) that transport a variety of metals to the site of deposition. However, the low solubilities of precious metals in hydrothermal fluids cannot justify the high concentrations necessary to produce such type of hyper-enriched metal ore. Here we show that boiling metal-bearing brines can produce, aggregate, and accumulate metal nanomaterials, ultimately leading to focused gold + silver ± copper over-enrichments. We found direct nano-scale evidence of nanoparticulate gold- and/or silver-bearing ores formed via nonclassical growth (i.e., nanomaterial attachment) during boiling in an intermediate-sulfidation epithermal bonanza. The documented processes may explain the generation of bonanzas in metal-rich brines from a range of mineral deposit types.MCIN/AEI/10.13039/50110001133: NANOMET PID2022-138768OB-I00ERDF A way of making Europe, European UnionPAPIIT-DGAPA-UNAM: IN 218323CONAHCyTGeological Society of America 13570-22Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México
MCIN/AEI/10.13039/501100011033, PID 2019-105625RB-C21 DGAPA, UNA
Unraveling the Effects of Melt–Mantle Interactions on the Gold Fertility of Magmas
We thank Tony Lanzirotti and Matt Newville for assistance with μ-XANES analyses at the GeoSoilEnviroCars (Sector 13), Advanced Photon Source (APS), Argonne National Laboratory.The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/feart.2020.00029/full#supplementary-materialThe oxidation state of the Earth’s mantle and its partial melting products exert a key control on the behavior and distribution of sulfur and chalcophile and siderophile elements between the mantle and crust, underpinning models of ore deposit formation. Whether the oxidized nature of magmas is inherited from the asthenospheric mantle source or acquired during ascent and differentiation is vigorously debated, limiting our understanding of the mechanisms of extraction of sulfur and metals from the mantle. Here, we focused on the redox-sensitive behavior of sulfur in apatite crystallized from quenched alkaline basaltic melts preserved within a peridotite xenolith from the El Deseado Massif auriferous province in southern Patagonia. We took advantage of this unique setting to elucidate the redox evolution of melts during their ascent through the subcontinental lithospheric mantle (SCLM) and grasp the inner workings of the Earth’s mantle during gold metallogenesis. Our data reveal that an initially reduced silicate melt (ΔFMQ −2.2 to −1.2) was oxidized to ΔFMQ between 0 and 1.2 during percolation and interaction with the surrounding peridotite wall-rock (ΔFMQ 0 to +0.8). This process triggered changes in sulfur speciation and solubility in the silicate melt, boosting the potential of the melt to scavenge ore metals such as gold. We suggest that large redox gradients resulting from the interaction between ascending melts and the surrounding mantle can potentially modify the oxidation state of primitive melts and enhance their metallogenic fertility. Among other factors including an enriched metal source and favorable geodynamic conditions, redox gradients in the mantle may exert a first-order control on the global-scale localization of crustal provinces endowed with gold deposits.This study was funded by the Iniciativa Científica Milenio through Millennium Nucleus for Metal Tracing along Subduction Grant NC130065. Additional funding for analytical work was provided by the FONDAP project 15090013 “Centro de Excelencia en Geotermia de Los Andes, CEGA.” ST acknowledges CONICYT for support through a Ph.D. scholarship #21170857. Grants RTI2018-099157-A-100 and RYC-2015-1796 provided funding for sample preparation and EPMA analyses. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The DID-UACh project #S-201505 financed the fieldwork
¿Esférulas de hierro y vítreas subducidas en el manto superior?
Spherules are documented in ophiolitic
mantle rocks such as peridotites
and associated chromitites. They
consist of: (1) native iron having
variable amounts of Ni with/without
inclusions of silicate glass or oxides
(wüstite), (2) dendritic intergrowth of
oxides (magnetite, wüstite and hematite)
with/without silicate glass and,
(3) silicate glass. Consensually, they
are interpreted as indigenous to chromitites
and related with high-temperature
processes operating in the
Earth’s upper mantle. However, their
similarity with terrestrial and extraterrestrial
spherules found in other
settings of the geological record is
remarkable. We raise the question on
such indigenous origin, relating them
to volcanic and cosmic material recycled
back to the mantle wedge where
chromitites form during subduction.Rocas del manto superior ofiolitico tales
como peridotitas y cromititas contienen esferas.
Estas consisten de: (1) hierro native con
cantidades variables de Ni con y sin inclusiones
de vidrio silicatdo y óxidos (wüstite),
(2) intercrecimientos dendríticos de óxidos
(magnetita, wüstita y hematites) con o sin
vidrio silicatado y, (2) vidrio silicatado.
Unísonamente, estas esferulas se interpretan
como indígenas a las cromititas y relacionadas
con procesos de alta temperatura que
tienen lugar en el manto superior terrestre.
Sin embargo, su parecido con aquellas esferas
de origen terrestre y extraterrestre descritas en
otros contextos geológicos es reseñable. En
este trabajo cuestionamos el origen autóctono
de las esferas en las rocas mantélicas,
interpretándolas como material de origen
volcánico y cósmico que ha sido reciclado
atraves de la cuña de manto superior donde
ser forman las cromititas durante los procesos
de subducción.Junta de Andaluci
Torsion of rational elliptic curves over quadratic fields II
Let E be an elliptic curve defined over Q and let G=E(Q)_tors be the associated torsion group. In a previous paper, the authors studied, for a given G, which possible groups G\leq H could appear such that H=E(K)_tors, for [K:Q]=2. In the present paper, we go further in this study and compute, under this assumption and for every such G, all the possible situations where G\neq H. The result is optimal, as we also display examples for every situation we state as possible. As a consequence, the maximum number of quadratic number fields K such that E(Q)_tors\neq E(K)_tors is easily obtained.Ministerio de Economía y CompetitividadJunta de Andalucí
Comparação de três sistemas de medição diferentes para avaliar a altura do salto vertical
Introduction: The numerous instruments used to measure jump height use different technologies and
calculations that can provide variable results. Objective: This study compared the countermovement jump
(CMJ) height assessed with a wearable 3D inertial measurement unit (IMU), using flight time and the numerical
integration method with a force platform and photocells. Methods: Forty CMJs were analysed, starting from an
upright standing position with the hands placed on the waist. Twenty healthy volunteers completed 2 CMJs,
which were simultaneously assessed using an IMU placed on the subject’s sacrum, a force platform (considered
the gold standard method) and photocells. The maximum height of each CMJ was measured. Results: The results
showed a significant overestimation (p<0.001) in jump height for the IMU using the numerical integration
method when compared to the force platform (+7 cm). Excellent intraclass correlation coefficients (ICCs) were
obtained with the flight time equations for the different types of measurement equipment. Fair to good ICCs
were obtained with the IMU using the numerical integration method and force platform. Conclusion: In conclusion,
the jump height obtained with the IMU using the numerical integration method showed the poorest
agreement compared to the force platform.Introducción: Los numerosos instrumentos usados para medir la altura del salto emplean diferentes tecnologías y cálculos
que pueden suministrar resultados variables. Objetivo: Este estudio comparó la altura del salto contramovimiento (SCM) con
una un sistema inercial 3D (IMU) portátil, usando el tiempo de vuelo y el método de integración numérica, con plataforma
de fuerza y fotocélulas. Métodos: Cuarenta SCMs fueron analizados a partir de la posición ortostática con las manos en la
cintura. Veinte voluntarios saludables concluyeron dos SCMs que fueron evaluados simultáneamente con un IMU colocada
en el sacro del individuo, una plataforma de fuerza (considerado el método de referencia) y fotocélulas. Fue medida la altura
máxima de cada SCM. Resultados: Los resultados mostraron una sobreestimación significativa (p <0,001) de la altura del salto
para la IMU con el método de integración numérica, en comparación con la plataforma de fuerza (+7 cm). Fueron obtenidos
excelentes coeficientes de correlación intraclase (ICCs) con las ecuaciones de tiempo de vuelo entre los equipamientos de
medición. Fueron obtenidos resultados de regulares a buenos de ICC con la IMU por el método de integración numérica y la
plataforma de fuerza. Conclusión: La altura de salto obtenida con la IMU con el método de integración numérica mostró la
peor concordancia en comparación con la plataforma de fuerza.Introdução: Os numerosos instrumentos usados para medir a altura de salto empregam diferentes tecnologias e cálculos
que podem fornecer resultados variáveis. Objetivo: Este estudo comparou a altura de salto contramovimento (SCM)
com uma unidade de medida inercial 3D (UMI) portátil, usando o tempo de voo e o método de integração numérica, com
plataforma de força e fotocélulas. Métodos: Quarenta SCMs foram analisados a partir da posição ortostática com as mãos
na cintura. Vinte voluntários saudáveis concluíram 2 SCMs que foram avaliados simultaneamente com uma UMI colocada
no sacro do indivíduo, uma plataforma de força (considerado o método de referência) e fotocélulas. A altura máxima de
cada SCM foi medida. Resultados: Os resultados mostraram uma superestimação significativa (p < 0,001) da altura do
salto para a UMI com o método de integração numérica, em comparação com a plataforma de força (+7 cm). Foram
obtidos excelentes coeficientes de correlação intraclasse (ICCs) com as equações de tempo de voo entre os equipamentos
de medição. Foram obtidos resultados de regulares a bons de ICC com a UMI pelo método de integração numérica e a
plataforma de força. Conclusão: A altura de salto obtida com a UMI com o método de integração numérica mostrou a pior
concordância em comparação com a plataforma de força.This work was funded by the Ministry of Education, Culture and
Sports of Spain by grants (ref. FPU13/00162)
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