{Surficial shell accumulations from shallow marine settings are typically averaged over centennial-to-millennial time scales and dominated by specimens that died in the most recent centuries, resulting in strongly right-skewed age-frequency distributions (AFDs). However, AFDs from modern offshore settings (outer shelf and uppermost continental slope) still need to be explored. Using individually dated shells (14C-calibrated amino acid racemization), we compared AFDs along an onshore-offshore gradient across the southern Brazilian shelf, with sites ranging from the inner shelf, shallow-water (\< 40 m) to offshore, deep-water (ġt; 100 m) settings. The duration of time averaging is slightly higher in deeper water environments, and the AFD shapes change along the depositional profile. The inner shelf AFDs are strongly right-skewed due to the dominance of shells from the most recent millennia (median age range: 0–3 ka). In contrast, on the outer shelf and the uppermost continental slope, AFDs are symmetrical to left-skewed and dominated by specimens that died following the Last Glacial Maximum (median age range: 15–18 ka). The onshore-offshore changes in the observed properties of AFDs—increased median age and decreased skewness, but only slightly increased temporal mixing—likely reflect changes in sea level and concurrent water depth-related changes in biological productivity. These results suggest that on a passive continental margin subject to post-glacial sea-level changes, the magnitude of time-averaging of shell assemblages is less variable along the depositional profile than shell assemblage ages and the shapes of AFDs.}

Multiscale methods for second order elliptic equations based on non-overlapping domain decomposition schemes have great potential to take advantage of multi-core, state-of-the-art parallel computers. These methods typically involve solving local boundary value problems followed by the solution of a global interface problem. Known iterative procedures for the solution of the interface problem have typically slow convergence, increasing the overall cost of the multiscale solver. To overcome this problem we develop a scalable recursive solution method for such interface problem that replaces the global problem by a family of small interface systems associated with adjacent subdomains, in a hierarchy of nested subdomains. Then, we propose a novel parallel algorithm to implement our recursive formulation in multi-core devices using the Multiscale Robin Coupled Method by Guiraldello et al. (2018) [26], that can be seen as a generalization of several multiscale mixed methods. Through several numerical studies we show that the new algorithm is very fast and exhibits excellent strong and weak scalability. We consider very large problems, that can have billions of discretization cells, motivated by the numerical simulation of subsurface flows.

{The study of sambaquis (ancient shell mounds) in conservation paleobiology is a complicated subject, especially when comparing body sizes of current and past mollusk valves to observe possible changes. There is a lack of information regarding how ancient fisher-gardeners collected these shellfish. Another obstacle is finding the hypothesis tests and data that can be used to compare current and past body sizes. To this end, we use the t-test (tt), Mann-Whitney (mw), and Bootstrap (bt) analyses to determine data scenarios for yellow clam (Amarilladesma mactroides) shells from two sambaquis units, and from two transects along the beaches of Rio Grande do Sul in southern Brazil. The study finds that the average body size of an Amarilladesma mactroides adult specimen is greater in sambaquis than the current valves across all tests (tt

The direct carbonate procedure for accelerator mass spectrometry radiocarbon (AMS 14C) dating of submilligram samples of biogenic carbonate without graphitization is becoming widely used in a variety of studies. We compare the results of 153 paired direct carbonate and standard graphite 14C determinations on single specimens of an assortment of biogenic carbonates. A reduced major axis regression shows a strong relationship between direct carbonate and graphite percent Modern Carbon (pMC) values (m = 0.996; 95% CI [0.991–1.001]). An analysis of differences and a 95% confidence interval on pMC values reveals that there is no significant difference between direct carbonate and graphite pMC values for 76% of analyzed specimens, although variation in direct carbonate pMC is underestimated. The difference between the two methods is typically within 2 pMC, with 61% of direct carbonate pMC measurements being higher than their paired graphite counterpart. Of the 36 specimens that did yield significant differences, all but three missed the 95% significance threshold by 1.2 pMC or less. These results show that direct carbonate 14C dating of biogenic carbonates is a cost-effective and efficient complement to standard graphite 14C dating.

In the Southern Brazil ShelfSouthern Brazil Shelf (SBS), surface bioclastic concentrationsBioclastic concentrations are associated with putative paleo-shorelines formed where wave ravinement surfaces are probably present. From the late Last Glacial Maximum, the SBS can be considered a sediment-starved passive margin continental shelf, with its morphostructural development fairly known. There, fourteen molluscan shell samples from near shelf-break deposits (“distal shell-rich”), eleven from proximal, low depth bioclastic deposits (“proximal shell-rich”) and ten samples from sandy substrate (“shell-poor”) were evaluated for taphonomic damage accordingly to updated protocols. Multivariate statistical analysis showed significant differences between the three groups of shelly samples. Low-intensity damage states (such as natural bright and ornamentation) dominate samples from the distal shell-rich deposit, whereas the inverse occurs in the proximal deposit (samples from the shell-poor locations present an intermediate damage pattern). This pattern is consistent either with onlap/toplap and backlap shell bedShell bed formation, according to characteristics determined in the literature. The condition of these three areas may reflect degrees of exposure at the taphonomically-active zone, the magnitude of time averagingTime-averaging and duration of shell accumulation, and even the lack of shelf accommodation space, which in turn is related to glacioeustatic sea-level oscillations.

O capítulo pretende apresentar a primeira parte de uma análise da teoria cartesiana da percepção sensível na Dióptrica, inserindo-as, tanto quanto possível, no contexto do debate sobre esses temas em na primeira metade do século XVII. Neste texto, ressalto os pontos de contato entre essa teoria e a ótica de Kepler, cuja influência na dióptrica cartesiana é manifesta, mas também em que sentindo ela propicia uma resposta à ótica de Christoph Scheiner, matemático jesuíta que promove uma reforma na concepção tomista da percepção sensível para acomodar as teses da ótica de Kepler, sem, todavia, abandonar os conceitos de similitude e de species.

In the marine realm, the interpretation of taphofacies relies heavily on how oceanographic and sedimentary conditions affect the preservation state of fossils. Several taphonomic variables either covary with depth or are directly influenced by depth. Facies-level factors rather than broad, basin-scale parameters influence the taphonomic profile of mollusc death assemblages according to actualistic and experimental evidence. To determine the possible relation between depth and the taphonomic conditions of multiple species of bivalve remains, we used seven samples gathered over a comprehensive bathymetric gradient (from 7 to 150 m below mean sea level; topmost 10- to 20-cm layer, roughly corresponding to the taphonomically active zone). We selected samples from predominantly muddy facies on the southern Brazilian shelf (SBS). The taphonomic damage profile (TDP) was measured using site samples based on a standard taphonomic analysis (categorical scoring system) of shells and fragments larger than 4 mm, to identify site damage patterns. Restricting the sedimentary grain size (samples from fine sediments) enabled the determination of the variation in damage with depth among the samples. Constrained analysis of proximities (CAP) revealed that up to 46% of the taphonomic variation observed was related to variation in depth (with approximately 28% unexplained by environmental factors). Part of the unexplained fraction was due to the effect of temporal mixing, which is predictable along large-scale patches but is inversely linked to the TDP. Our results show that taphonomic analysis, considering large spatial scales in recent environments, can explain the variations present in shell beds that formed during distinct time periods of the evolution of a Quaternary sedimentary basin. © 2018 Lethaia Foundation. Published by John Wiley & Sons Ltd

The degree to which a group of fossils reflects the original community from which it was derived can be estimated by comparing living communities with locally accumulated dead remains. Such live–dead approaches (LA/DA) can provide important baseline information on the ecological structure of ancient freshwater systems. This study explored variations in composition, richness, evenness and rank-abundance in live and dead mollusk assemblages recovered from the Ibicuí River Basin, southern Brazil. LA/DA was related to topography, river size, and sediment grain size, separated respectively into plain (altitude 0–100 m) versus slope (100–500 m), small versus medium-large stream orders, and gravel versus sand substrate. Positive correlation between LA and DA species composition was significant only in large rivers. Slope areas showed LA/DA species compositions that were significantly different, whereas the communities from sand and gravel substrates were quite similar. Important factors that affected live/dead similarity in the study area included (1) destruction of thin, fragile shells of dead animals by acidic waters that are common in the region, (2) downstream drift of small spherical shells from species common in slope areas, such as Potamolithus sp., and (3) high abundances of invasive species in the local death assemblage, especially in large rivers. High fidelity in large rivers is caused by the presence of favorable habitats for bivalve communities. Coarse sediments are an important driver of macro invertebrate diversity, acting as shell traps that slow the downstream drift of bivalve remains and improve the preservation of fluvial mollusks. The preservation potential of dead assemblages of the Ibicuí River showed that fossil assemblages are useful tools for recognizing ancient riverscapes, such as flat areas with sandy substrates.

In the marine realm, the interpretation of taphofacies relies heavily on how oceanographic and sedimentary conditions affect the preservation state of fossils. Several taphonomic variables either covary with depth or are directly influenced by depth. Facies‐level factors rather than broad, basin‐scale parameters influence the taphonomic profile of mollusc death assemblages according to actualistic and experimental evidence. To determine the possible relation between depth and the taphonomic conditions of multiple species of bivalve remains, we used seven samples gathered over a comprehensive bathymetric gradient (from 7 to 150 m below mean sea level; topmost 10‐ to 20‐cm layer, roughly corresponding to the taphonomically active zone). We selected samples from predominantly muddy facies on the southern Brazilian shelf (SBS). The taphonomic damage profile (TDP) was measured using site samples based on a standard taphonomic analysis (categorical scoring system) of shells and fragments larger than 4 mm, to identify site damage patterns. Restricting the sedimentary grain size (samples from fine sediments) enabled the determination of the variation in damage with depth among the samples. Constrained analysis of proximities (CAP) revealed that up to 46{%} of the taphonomic variation observed was related to variation in depth (with approximately 28{%} unexplained by environmental factors). Part of the unexplained fraction was due to the effect of temporal mixing, which is predictable along large‐scale patches but is inversely linked to the TDP. Our results show that taphonomic analysis, considering large spatial scales in recent environments, can explain the variations present in shell beds that formed during distinct time periods of the evolution of a Quaternary sedimentary basin.

This work presents a comparison among three different control strategies for multivariable processes. The techniques were implemented in a pilot plant with coupled control loops, where all steps used to design the controllers were described allowing to establish a trade-off between algorithm complexity, information needed from the process and achieved performance. Two data-driven control techniques are used: multivariable ultimate point method to design a decentralized PID controller and virtual reference feedback tuning to design a centralized PID controller. A mathematical model of the process is obtained and used to design a model-based generalized predictive controller. Experimental results allow us to evaluate the performance achieved for each method, as well as to infer on their advantages and disadvantages.