48 research outputs found
Characterization and selection of interspecific hybrids of Brachiaria decumbens for seed production in Campo Grande - MS
The Aguablanca Ni–(Cu) sulfide deposit, SW Spain: geologic and geochemical controls and the relationship with a midcrustal layered mafic complex
The Aguablanca Ni–(Cu) sulfide deposit is
hosted by a breccia pipe within a gabbro–diorite pluton.
The deposit probably formed due to the disruption of a
partially crystallized layered mafic complex at about 12–
19 km depth and the subsequent emplacement of melts and
breccias at shallow levels (<2 km). The ore-hosting breccias
are interpreted as fragments of an ultramafic cumulate,
which were transported to the near surface along with a
molten sulfide melt. Phlogopite Ar–Ar ages are 341–
332 Ma in the breccia pipe, and 338–334 Ma in the layered
mafic complex, and are similar to recently reported U–Pb
ages of the host Aguablanca Stock and other nearby calcalkaline
metaluminous intrusions (ca. 350–330 Ma). Ore
deposition resulted from the combination of two critical
factors, the emplacement of a layered mafic complex deep
in the continental crust and the development of small
dilational structures along transcrustal strike-slip faults that
triggered the forceful intrusion of magmas to shallow
levels. The emplacement of basaltic magmas in the lower
middle crust was accompanied by major interaction with
the host rocks, immiscibility of a sulfide melt, and the
formation of a magma chamber with ultramafic cumulates
and sulfide melt at the bottom and a vertically zoned mafic
to intermediate magmas above. Dismembered bodies of
mafic/ultramafic rocks thought to be parts of the complex
crop out about 50 km southwest of the deposit in a
tectonically uplifted block (Cortegana Igneous Complex,
Aracena Massif). Reactivation of Variscan structures that
merged at the depth of the mafic complex led to sequential
extraction of melts, cumulates, and sulfide magma. Lithogeochemistry
and Sr and Nd isotope data of the Aguablanca
Stock reflect the mixing from two distinct reservoirs, i.e.,
an evolved siliciclastic middle-upper continental crust and a
primitive tholeiitic melt. Crustal contamination in the deep
magma chamber was so intense that orthopyroxene
replaced olivine as the main mineral phase controlling the early fractional crystallization of the melt. Geochemical
evidence includes enrichment in SiO2 and incompatible
elements, and Sr and Nd isotope compositions (87Sr/86Sri
0.708–0.710; 143Nd/144Ndi 0.512–0.513). However, rocks
of the Cortegana Igneous Complex have low initial
87Sr/86Sr and high initial 143Nd/144Nd values suggesting
contamination by lower crustal rocks. Comparison of the
geochemical and geological features of igneous rocks in the
Aguablanca deposit and the Cortegana Igneous Complex
indicates that, although probably part of the same magmatic
system, they are rather different and the rocks of the
Cortegana Igneous Complex were not the direct source of
the Aguablanca deposit. Crust–magma interaction was a
complex process, and the generation of orebodies was
controlled by local but highly variable factors. The model
for the formation of the Aguablanca deposit presented in
this study implies that dense sulfide melts can effectively
travel long distances through the continental crust and that
dilational zones within compressional belts can effectively
focus such melt transport into shallow environments
The Genomic Ancestry of Individuals from Different Geographical Regions of Brazil Is More Uniform Than Expected
Based on pre-DNA racial/color methodology, clinical and pharmacological trials have traditionally considered the different geographical regions of Brazil as being very heterogeneous. We wished to ascertain how such diversity of regional color categories correlated with ancestry. Using a panel of 40 validated ancestry-informative insertion-deletion DNA polymorphisms we estimated individually the European, African and Amerindian ancestry components of 934 self-categorized White, Brown or Black Brazilians from the four most populous regions of the Country. We unraveled great ancestral diversity between and within the different regions. Especially, color categories in the northern part of Brazil diverged significantly in their ancestry proportions from their counterparts in the southern part of the Country, indicating that diverse regional semantics were being used in the self-classification as White, Brown or Black. To circumvent these regional subjective differences in color perception, we estimated the general ancestry proportions of each of the four regions in a form independent of color considerations. For that, we multiplied the proportions of a given ancestry in a given color category by the official census information about the proportion of that color category in the specific region, to arrive at a “total ancestry” estimate. Once such a calculation was performed, there emerged a much higher level of uniformity than previously expected. In all regions studied, the European ancestry was predominant, with proportions ranging from 60.6% in the Northeast to 77.7% in the South. We propose that the immigration of six million Europeans to Brazil in the 19th and 20th centuries - a phenomenon described and intended as the “whitening of Brazil” - is in large part responsible for dissipating previous ancestry dissimilarities that reflected region-specific population histories. These findings, of both clinical and sociological importance for Brazil, should also be relevant to other countries with ancestrally admixed populations
Population ecology of the sea lamprey (Petromyzon marinus) as an invasive species in the Laurentian Great Lakes and an imperiled species in Europe
The sea lamprey Petromyzon marinus (Linnaeus) is both an invasive non-native species in the Laurentian Great Lakes of North America and an imperiled species in much of its native range in North America and Europe. To compare and contrast how understanding of population ecology is useful for control programs in the Great Lakes and restoration programs in Europe, we review current understanding of the population ecology of the sea lamprey in its native and introduced range. Some attributes of sea lamprey population ecology are particularly useful for both control programs in the Great Lakes and restoration programs in the native range. First, traps within fish ladders are beneficial for removing sea lampreys in Great Lakes streams and passing sea lampreys in the native range. Second, attractants and repellants are suitable for luring sea lampreys into traps for control in the Great Lakes and guiding sea lamprey passage for conservation in the native range. Third, assessment methods used for targeting sea lamprey control in the Great Lakes are useful for targeting habitat protection in the native range. Last, assessment methods used to quantify numbers of all life stages of sea lampreys would be appropriate for measuring success of control in the Great Lakes and success of conservation in the native range
Apical transportation associated with ProTaper® Universal F1, F2 and F3 instruments in curved canals prepared by undergraduate students
Objective: This study evaluated apical transportation associated with ProTaper® Universal F1, F2 and F3 rotary files in curved canals prepared by undergraduate students. Material and Methods: Twenty mesial roots of mandibular molars with curvatures ranging between 25° and 35° were selected. Mesiobuccal canals were instrumented by twenty students with the ProTaper® system (Dentsply-Maillefer, Ballaigues, Switzerland) according to the manufacturer’s instructions. Pre-flaring was performed with S1 and SX files. A #15 K-file was inserted into the root canal up to the working length (WL), and an initial digital radiograph was taken in a buccolingual direction (baseline). Afterwards, the S1, S2, F1, F2, and F3 files were employed up to the WL. Other radiographies were taken in the same
orientation of the baseline after the use of the F1, F2, and F3 files, with each file inserted into the root canal. The radiographic images were overlapped, and the Image J software was used to measure the distance between the rotary files’ ends and the #15 K-file’s end, characterizing the apical transportation. Data were analyzed by Repeated Measure ANOVA and by the SNK post hoc test (P<0.05). Results: It was verified that file size affected apical transportation significantly (P<0.001). The F3 file showed higher apical transportation than F1 and F2, while between these last files there was no difference. Conclusion: The undergraduate students produced lower apical transportation in curved canals when they did not use the F3 rotary file