149 research outputs found
Conceptions about mathematics, its teaching and learning in Compendio Mathematico (1707) written by the Spanish Thomas Vicente Tosca (1651-1723)
No full textThe preface of a book is one of the main examples of paratexts, defined by Gérard Genette as those devices and conventions that enable a text to become a book. It can provide information about aspects such as the author''s motivation and intention, the origin of the presented ideas, the potential readers, etc. In the particular case of a mathematical text devoted to some extent to teaching, the preface can provide information about the author''s conceptions and beliefs about mathematics, its teaching and learning. In this work, we analyze the preface of Compendio Mathematico written by Thomas Vicente Tosca in 1707. This approach will allow us to have a view of how the teaching and learning of mathematics as well as mathematics itself were conceived during Spanish pre-enlightenment.
O prólogo de um livro é um dos múltiplos exemplos de paratextos, definidos por Gérard Genette como esses elementos e convenções que fazem um texto tornar-se um livro. Isso pode fornecer informações sobre aspectos como a motivação e a intenção do autor, a origem das ideias apresentadas, potenciais leitores etc. No caso particular de textos matemáticos dedicados em certa medida ao ensino, o prólogo pode informar as concepções e crenças do autor sobre a matemática, seu ensino e sua aprendizagem. Neste trabalho, analisamos o prólogo do Compendio Mathematico, escrito por Thomas Vicente Tosca em 1707. Essa abordagem nos permitirá obter uma visão sobre como a matemática, seu ensino e sua aprendizagem foi concebida durante a pré-ilustração na Espanha
TuberOus SClerosis registry to increase disease Awareness (TOSCA) – baseline data on 2093 patients
No full textBACKGROUND: Tuberous sclerosis complex (TSC) is a rare autosomal dominant genetic disorder. Many gaps remain in the understanding of TSC because of the complexity in clinical presentation. The TuberOus SClerosis registry to increase disease Awareness (TOSCA) is an international disease registry designed to address knowledge gaps in the natural history and management of TSC. Here, we present the baseline data of TOSCA cohort. METHODS: Patients of any age diagnosed with TSC, having a documented visit for TSC within the preceding 12 months, or newly diagnosed individuals were included. The registry includes a "core" section designed to record detailed background information on each patient including disease manifestations, interventions, and outcomes collected at baseline and updated annually. "Subsections" of the registry recorded additional data related to specific features of TSC. RESULTS: Baseline "core" data from 2093 patients enrolled from 170 sites across 31 countries were available at the cut-off date September 30, 2014. Median age of patients at enrollment was 13 years (range, 0-71) and at diagnosis of TSC was 1 year (range, 0-69). The occurrence rates of major manifestations of TSC included - cortical tubers (82.2%), subependymal nodules (78.2%), subependymal giant cell astrocytomas (24.4%), renal angiomyolipomas (47.2%), lymphangioleiomyomatosis (6.9%), cardiac rhabdomyomas (34.3%), facial angiofibromas (57.3%), forehead plaque (14.1%), ≥ 3 hypomelanotic macules (66.8%), and shagreen patches (27.4%). Epilepsy was reported in 1748 (83.5%) patients, of which 1372 were diagnosed at ≤ 2 years (78%). Intellectual disability was identified in 451 (54.9%) patients of those assessed. TSC-associated neuropsychiatric disorders (TAND) were diagnosed late, and not evaluated in 30-50% of patients. CONCLUSION: TOSCA is the largest clinical case series of TSC to date. It provided a detailed description of the disease trajectory with increased awareness of various TSC manifestations. The rates of different features of TSC reported here reflect the age range and referral patterns of clinics contributing patients to the cohort. Documentation of TAND and LAM was poor. A widespread adoption of the international TSC assessment and treatment guidelines, including use of the TAND Checklist, could improve surveillance. The registry provides valuable insights into the necessity for monitoring, timing, and indications for the treatment of TSC
Corrigendum: Plasma polymers as targets for laser-driven proton-boron fusion
No full textA Corrigendum on Plasma polymers as targets for laser-driven proton-boron fusion by Tosca M, Molloy D, McNamee A, Pleskunov P, Protsak M, Biliak K, Nikitin D, Kousal J, Krtouš Z, Hanyková L, Hanuš J, Biederman H, Foster T, Nersisyan G, Martin P, Ho C, Macková A, Mikšová R, Borghesi M, Kar S, Istokskaia V, Levy Y, Picciotto A, Giuffrida L, Margarone D and Choukourov A (2023). Front. Phys. 11:1227140. doi: 10.3389/fphy.2023.1227140In the published article, there was an error in Affiliations 6, 7, and 8.Author Valeriia Istokskaia should be affiliated with “2, 7” instead of “2, 6”.Author Yoann Levy should be affiliated with “8” instead of “7”.The authors apologize for these errors and state that this does not change the scientific conclusions of the article in any way. The original article has been updated
An integrated view of the chemistry and mineralogy of martian soils
No full textThe mineralogical and elemental compositions of the martian soil are indicators of chemical and physical weathering processes. Using data from the Mars Exploration Rovers, we show that bright dust deposits on opposite sides of the planet are part of a global unit and not dominated by the composition of local rocks. Dark soil deposits at both sites have similar basaltic mineralogies, and could reflect either a global component or the general similarity in the compositions of the rocks from which they were derived. Increased levels of bromine are consistent with mobilization of soluble salts by thin films of liquid water, but the presence of olivine in analysed soil samples indicates that the extent of aqueous alteration of soils has been limited. Nickel abundances are enhanced at the immediate surface and indicate that the upper few millimetres of soil could contain up to one per cent meteoritic material.Additional co-authors: Thanasis E Economou, Amitabha Ghosh, Brian C Hahn, Kenneth E Herkenhoff, Larry A Haskin, Joel A Hurowitz, Bradley L Joliff, Jeffrey R Johnson, Göstar Klingelhöfer, Morten Bo Madsen, Scott M McLennan, Harry Y McSween, Lutz Richter, Rudi Rieder, Daniel Rodionov, Larry Soderblom, Steven W Squyres, Nicholas J Tosca, Alian Wang, Michael Wyatt, Jutta Zipfe
Small shelly fossil preservation and the role of early diagenetic redox in the early Triassic
No full textMinute fossils from a variety of different metazoan clades, collectively referred to as small shelly fossils, represent a distinctive taphonomic mode that is most commonly reported from the Cambrian Period. Lower Triassic successions of the western United States, deposited in the aftermath of the end-Permian mass extinction, provide an example of small shelly style preservation that significantly post-dates Cambrian occurrences. Glauconitized and phosphatized echinoderms and gastropods are preserved in the insoluble residues of carbonates from the Virgin Limestone Member of the Moenkopi Formation. Echinoderm plates, spines and other skeletal elements are preserved as stereomic molds; gastropods are preserved as steinkerns. All small shelly style fossils are preserved in the small size fractions of the residues (177 to 420 μm), which is consistent with the size selection of small shelly fossils in the Cambrian. Energy-dispersive X-ray spectra of individual fossils coupled with X-ray diffraction of residues confirm that the fossils are dominantly preserved by apatite and glauconite, and sometimes a combination of the two minerals. The nucleation of both of these minerals requires that pore water redox oscillated between oxic and anoxic conditions, which, in turn, implies that Lower Triassic carbonates periodically experienced oxygen depletion after deposition and during early diagenesis. Long-term oxygen depletion persisted through the Early Triassic, creating diagenetic conditions that were instrumental in the preservation of small shelly fossils in Triassic and, likely, Paleozoic examples
Evidence for anoxic shallow oceans at 2.45 Ga: Implications for the rise of oxygenic photosynthesis
No full textGeochemical proxies indicate that atmospheric oxygen levels were <10–5 times present atmospheric levels (10–5 × PAL) until the start of the Great Oxidation Event (GOE; 2.33 Ga). However, trace metal and isotopic data from sedimentary rocks have been interpreted to reflect the presence of oxygenated surface oceans ≥2.5 b.y. ago, implying decoupling of the atmosphere and shallow marine systems. Evidence for oxygen in shallow oceans has fueled the idea that oxygenic photosynthesis evolved long before the GOE and that oxygen did not accumulate in the atmosphere because it was scavenged by reductants such as dissolved Fe2+, a process thought by some to have formed banded iron formations (BIFs). Here we present high-resolution microscopy showing that 2.45 Ga shallow-water BIFs were deposited as ferrous iron-rich muds dominantly composed of greenalite; these muds were rapidly cemented by silica on the seafloor, and subsequently eroded and redeposited as intraformational chert clasts. Our experimental results and kinetic models show that the accumulation of greenalite required seawater oxygen concentrations <10–6 × PAL on the shallow shelf. We infer that oxygen levels of the surface oceans and atmosphere were not decoupled 2.45 b.y. ago, but that both were exceedingly low (<10–5 × PAL). Our findings support the hypothesis that oxygenic photosynthesis evolved shortly before atmospheric oxygenation and was a direct cause of the GOE
Products of the iron cycle on the early Earth
No full textTraditional models for pre-GOE oceans commonly view iron as a critical link to multiple biogeochemical cycles, and an important source of electrons to primary producers. However, an accurate and detailed understanding of the ancient iron cycle has been limited by: (1) our ability to constrain primary depositional processes through observations of the ancient sedimentary rock record, and (2) a quantitative understanding of the aqueous geochemistry of ferrous iron. Recent advances in high resolution petrography and experimental geochemistry, however, have contributed to a new understanding of certain aspects of the early Fe cycle. Most importantly, high resolution petrographic studies of late Archean/early Paleoproterozoic iron formation have documented the prolific deposition of Fe(II)-silicate-rich chemical muds from a dominantly anoxic ocean. At the same time, recent experimental work has shed new light on processes likely to have controlled steady state Fe concentrations in Archean oceans. These studies suggest that spontaneous precipitation of Fe(II)-carbonate was probably rare in Archean oceans, and that Fe(II)-carbonate would have more commonly precipitated on the surfaces of suitable mineral substrates within clastic and chemical sediments, consistent with petrographic observations. In addition, although experimental investigations suggest that maximum Fe concentrations in Archean oceans would have been limited by authigenic Fe(II)-silicate production (rather than Fe(II)-carbonate), the rock record indicates that this process was rarely operative. Instead, sedimentology, stratigraphy, and geochemical modelling suggest that much of the precursor sediment to late Archean iron formation was produced as hydrothermal effluent interacted with seawater in close proximity to seafloor vents. Together, these observations help define a new topology for the ancient Fe cycle. In this view, hydrothermal effluent-seawater mixing would have strongly attenuated the flux of dissolved Fe2+andnbsp;to Archean oceans, and early diagenetic siderite formation may have balanced globally averaged riverine and hydrothermal Fe2+andnbsp;input fluxes. In contrast to previous models, this emerging picture of the early Fe cycle suggests that Fe played only a negligible role in supporting anoxygenic phototrophs, reinforcing the concept that electron donors were in comparatively limited supply before the advent of oxygenic photosynthesis.</p
Experimental constraints on Mg isotope fractionation during clay formation: Implications for the global biogeochemical cycle of Mg
No full textThe direction and magnitude of magnesium (Mg) isotope fractionation attendant to the formation of clay minerals is fundamental to the use of Mg isotopes to decipher the biogeochemical cycling of Mg in the critical zone and for the oceanic Mg budget. This study provides experimental data on the Mg fractionation factor for two smectite-group minerals (stevensite and saponite) at temperatures relevant for Earth surface processes. The resultant solids were characterised by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) to confirm the mineralogy and crystallinity of the product. A series of experiments were performed to asses the impact of temperature and pH on isotope fractionation. Bulk solid samples were treated with ammonium chloride to remove exchangeable Mg in order to distinguish the Mg isotopic fractionation between these sites and octahedral sites. All bulk and residual solids were enriched in 24Mg compared to the initial solution and δ 26Mg values of the exchangeable pool were lower than, or within error of, the initial solution. Final solutions were either within error of, or enriched in, 26Mg compared to the initial solution, depending on the fraction of Mg removed from solution (f M g ). For experiments with small or negligible f M g , increasing the pH resulted in a higher reaction rate and reduced fractionation from the initial solution. This could point to a kinetic effect, but the composition of the residual solid (Mg/(Li+Mg) ratio) was also dependent on pH. The change in the composition was reflected in the wavenumber of the Mg3-OH stretch in FT-IR data, which is a proxy for bond strength, and suggests an equilibrium control. An equilibrium control is further supported by the observation of reduced fractionation compared to the initial solution with increasing temperature. Rayleigh and batch fractionation models were fitted to the data giving fractionation factors of 0.9991 and 0.9990 respectively. We compare our results with existing field and experimental data and suggest that the apparent contradictions surrounding the direction of Mg isotope fractionation into phyllosilicate minerals could be due to the similarity of Mg bond lengths between clay octahedral sites and dissolved Mg. Thus small changes in mineral structure or initial solution conditions may result in a change in bond length sufficient to alter the direction of fractionation, implying that the magnitude and direction of Mg isotope fractionation into clay minerals could be dependent on local field conditions. Alternatively, if the precipitation of secondary clay minerals in the field preferentially incorporates light Mg, as observed in this experimental study, this implies the contribution of carbonate weathering to dissolved Mg fluxes has been underestimated, with major implications for the global biogeochemical cycle of Mg
Temperature–time relationships and their implications for thermal history and modelling of silica diagenesis in deep-sea sediments
No full text67 Ocean Drilling Program and Deep Sea Drilling Project sites were investigated to determine the relationship between temperature and time for silica diagenesis. The selected sites cover a variety of settings where the opal-A to opal-CT transition zone lies in Cenozoic sediments. The opal-A to opal-CT transition leads to abrupt changes in the sediment petrophysics which are used to identify the diagenetic interval at the study sites. This transition zone is a thin interval ranging in thickness from 10 to 40 m. Controls on transition zone thickness are analysed and temperature was found to be the fundamental driver. This study extends “the time–temperature stability field of Hein et al. (1978)” for the onset of opal-CT precipitation more generally. Active silica diagenesis persists over a long period of time (>35 m.y.) at low temperatures (55 °C) regardless of burial depth. Geothermal gradients and sediment accumulation rates are the principal controls of the rate of silica diagenesis transformation. Sites 794 and 795 in the Japan Sea, as typical cases of deep-sea boreholes capturing active transitions, were selected for further understanding the temperature–time control on silica diagenesis. The reconstructed thermal evolution of sediments from these representative sites demonstrates that the rapid increase in temperatures from the Late Miocene onwards occurred in response to high accumulation rates in the opal-A interval. The higher burial temperatures achieved for the opal-A sediment under higher sedimentation rates and a steeper thermal gradient led to an earlier transition at Site 795 (~5 m.y.) as compared to Site 794 (~8 m.y.). Kinetic-based models are formulated to illustrate the time–temperature dependence of biogenic silica diagenesis. One of the main findings based on this model is that although opal-CT precipitation reaches its peak levels across the transition zone at 8 and 5 m.y. after initial deposition of opal-A at Sites 794 and 795, respectively, the transformation is not completed until 14 m.y. at Site 794 and ca. 9.5 m.y. at Site 795 after initial sedimentation. Given the temperature and elapsed time, the model allows the transformation state of opal-containing sediments to be successfully predicted at any depth in these two sites
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