Neogene fluvial landscape evolution in the hyperarid core of the Atacama Desert

Dating of extensive alluvial fan surfaces and fluvial features in the hyperarid core of the Atacama Desert, Chile, using cosmogenic nuclides provides unrivalled insights about the onset and variability of aridity. The predominantly hyperarid conditions help to preserve the traces of episodic climatic and/or slow tectonic change. Utilizing single clast exposure dating with cosmogenic 10Be and 21Ne, we determine the termination of episodes of enhanced fluvial erosion and deposition occurring at ~19, ~14, ~9.5 Ma; large scale fluvial modification of the landscape had ceased by ~2–3 Ma. The presence of clasts that record pre-Miocene exposure ages (~28 Ma and ~34 Ma) require stagnant landscape development during the Oligocene. Our data implies an early onset of (hyper-) aridity in the core region of the Atacama Desert, interrupted by wetter but probably still arid periods. The apparent conflict with interpretation that favour a later onset of (hyper-) aridity can be reconciled when the climatic gradients within the Atacama Desert are considered

Extending Properly n-REA Sets

In [5] Soare and Stob prove that if $A$ is an r.e. set which isn't computable then there is a set of the form $A \oplus W^A_e$ which isn't of r.e. Turing degree. If we define a properly $n+1$-REA set to be an $n+1$-REA set which isn't Turing equivalent to any $n$-REA set (and identify 0-REA sets with the computable sets) this result shows that every properly 1-REA set can be extended to a properly 2-REA set. This result was extended in [1] by Cholak and Hinman who proved that every 2-REA set can be extended to a properly 3-REA set. This leads naturally to the hypothesis that every properly $n$-REA set can be extended to a properly $n+1$-REA set. In this paper, we show this hypothesis is false and that there is a properly $3$-REA set which can't be extended to a properly $4$-REA set

Precambrian isotopic sources of the Anti-Atlas, Morocco

The isotopic data stored in detrital and magmatic zircons are crucial for assessing magma sources, terrane correlation, paleogeography and plate reconstructions. In many cases the comparison of the zircon age and isotope signature of a terrane of unknown provenance with the signature of possible sources, generally old cratonic areas, can resolve questions of origin and paleoposition. Obviously, a precise knowledge of the zircon characteristics of these old areas is essential for reliable comparisons. One of the major sources of sediments of the peri-Gondwanan terranes and of the European Variscan Belt is the West African craton. The northern boundary of this craton is the Pan- African Anti-Atlas belt, which is therefore an ideal place to better constrain the zircon isotopic features of sediments sourced from it. With that aim, we obtained LA-ICM-MS U-Pb and Hf isotopic data of more than 600 zircons separated from six samples of siliciclastic sedimentary rocks from the main Neoproterozoic stratigraphic units of the Anti-Atlas belt, from the Sirwa and Zenaga inliers. The data suggest that the north part of the West African craton formed during three cycles of juvenile crust formation, with variable amount of reworking of older crust. The youngest group of zircons, with a main population clustering around 610 Ma, has a predominantly juvenile character and evidence of moderate mixing with Paleoproterozoic crust, suggesting that the igneous and metamorphic rocks in which the zircons originally crystallized were formed in an ensialic magmatic arc environment. A group of zircons with ages in the range 1.79–2.3 Ga corresponds to the major crust forming event in the West African craton: the Eburnian- Birimian orogeny. The isotopic data indicate that the provenance area should represent a crustal domain that separated from a mantle reservoir at ∼2050–2300 Ma, and further evolved with a time-integrated 176Lu/177Hf of ∼0.013, characteristic of continental crust. The evolution of the Eburnian orogeny is apparently dominated by new crust formation in a magmatic arc environment. The Lower Paleoproterozoic and Neoarchean evolution (2.3–2.75 Ga) involves a group of detrital zircon ages that has not been identified up to now in the igneous or metamorphic rocks of the north West African craton basement. Their Hf isotopic signature points to reworking of juvenile crust mixed with moderate amounts of Archean crust. The significance of these ages is uncertain: they could represent a tectonothermal event not discovered yet in the Reguibat Shield or the zircons can be far-travelled from an unknown source.Peer Reviewe

The use of an aircraft test stand for VTOL handling qualities studies

The VTOL flight tests stand for testing control concepts on the X-14B VSS aircraft in hover, is described. This stand permits realistic and safe piloted evaluation and checkout of various control systems and of parameter variations within each system to determine acceptability to the pilot. Pilots can use it as a practical training tool to practice procedures and flying techniques and become familiar with the aircraft characteristics. Some examples of test experience are given. The test stand allows the X14B to maneuver in hover from centered position + or - 9.7 deg in roll and + or - 9.3 deg in pitch, about + or - 6 deg in yaw, and + or - 15 cm in vertical translation. The unique vertical free flight freedom enables study of liftoffs and landings with power conditions duplicated. The response on the stand agrees well with that measured in free hovering flight, and pilot comments confirm this

Tracing the cryptic Sardic (Ordovician) metamorphism across Alpine Europe: the Krndija region in the Slavonian Mountains, Croatia

Results of a combined petrological, geochemical and geochronological study suggest that metasedimentary rock units in the Krndija region of the Slavonian Mountains, Croatia, were affected by at least three major tectonometamorphic imprints: during the Middle Ordovician (Sardic event), the early Carboniferous (Variscan event), and the Cretaceous (Alpine event). All three metamorphic phases are established by electron microprobe-based in-situ U–Th–Pb dating of monazite grains. The Sardic metamorphic event is additionally confirmed by a precise Lu–Hf garnet-whole-rock isochron age of 466.0 ± 2.3 Ma. Taken together, the data unveil a relatively large and well-preserved piece of the cryptic Sardic orogen in central Krndija, that we name the Kutjevo Zone. A Sardic subduction-related metamorphic event (ca. 540-580 ℃, 8–11 kbar) at ca. 466 Ma is manifested in the mineral paragenesis Ca-rich garnet plus rutile. A low degree of retrograde reequilibration suggests a subsequent fast exhumation. Low-Ca cores in some garnets and staurolite relics record a pre-HP metamorphic event that involves isobaric heating from 570 to 610 ℃ at ~ 7 kbar. We attribute this (so far undated) event to mid-crustal contact metamorphism caused by early Sardic magmatism. Southern parts of Krndija (the Gradište Zone) experienced an (additional?) clockwise PT evolution in Variscan times at ca. 350 Ma. Garnet formed with ilmenite during a PT increase from 580 ℃/5 kbar to 600 ℃/6 kbar and underwent later strong retrograde resorption. Slow Variscan exhumation resulted in andalusite formation at < 550 ℃/ < 3.8 kbar. Penetrative Alpine metamorphism was observed in low-grade phyllites in the north. The lithology and metamorphic history of the Kutjevo Zone is similar to what has been reported from the Sardic Strona-Ceneri Zone in the western Alps. Both areas expose metapelitic (metagreywacke) rocks with a pre-middle Ordovician formation age. These metasedimentary rocks are inter-layered with numerous small amphibolitic units as well as metagranitoids and were likely deposited along the active Gondwana margin, perhaps in a fore-arc position, prior to their subduction during the middle Ordovician. According to recent palaeogeographic reconstructions, both the Kutjevo Zone and the Strona-Ceneri Zone have once resided in an eastern sector of the northern Gondwana margin (i.e., in E-Armorica). We conclude that in the Middle Ordovician, important subduction activities took place in this E-Armorican segment of north Gondwana, which is today exposed in the Alps. The W-Armorican segment of north Gondwana (now exposed in the French, German, and Czech Variscides) had probably already mutated from a (Cadomian) subduction setting to an extensional (transtensional–transpressional) setting by the late Cambrian

Mechanisms of fast-ice development in the south-eastern Laptev Sea: a case study for winter of 2007/08 and 2009/10

Accurate representation of fast ice in numerical models is important for realistic simulation of numerous sea-ice and ocean variables. In order to simulate seasonal and interannual variability of fast-ice extent, the mechanisms controlling fast-ice development need to be thoroughly understood. The objective of this paper is to investigate mechanisms contributing to the advance of fast-ice edge to its winter location in the south-eastern Laptev Sea. The study is based on time series of synthetic aperture radar (SAR) imagery for winter 2007/08 and 2009/10. A detailed examination of SAR-based ice drift showed that several grounded ice features are formed offshore prior to fast-ice expansion. These features play a key role in offshore advance of the fast-ice edge and serve as stabilizing points for surrounding pack ice as it becomes landfast. Electromagnetic ice thickness measurements suggest that the grounded ice ridges over water depths of ca. 20 m water might be responsible for interannual variations in fast-ice edge position. Contrary to previous studies, we conclude that grounding is a key mechanism of fast-ice development in the south-eastern Laptev Sea

The time-dependent localization of Ki 67 antigen-positive cells in human skin wounds

A total of 77 human skin wounds with a post-infliction interval between 3 h and 7 months were investigated and the proliferation marker antigen Ki 67 was visualized in paraffin sections using a specific monoclonal antibody (MIB). The re-built epidermal layer covering the former lesional area showed only a few basal cells positively staining for Ki 67 antigen. No enhanced reactivity was found when compared to uninjured skin. In basal cells of the epidermis adjacent to the wound area, however, varying numbers of positive cells occurred, but no information useful for a reliable time estimation of skin wounds could be obtained due to the considerable variability in the number of Ki 67 positive epidermal basal cells found in non-damaged skin. Fibroblastic cells in the wound area revealed an increased number of Ki 67-positive sites which could first be detected in a 1.5-day-old skin lesion. Positive results could be obtained in every specimen investigated after a post-infliction interval of 6 days up to 1.5 months. Only the scar tissue of the oldest wound examined (wound age 7 months) revealed no increase in the number of positively staining fibroblasts. Therefore, positive results indicate a wound age of at least approximately 1.5 days and the lack of an increased number of positive fibroblastic cells in a sufficient number of specimens indicates at a wound age of less than 6 days, but cannot totally exclude longer post-infliction intervals

Using Theory to Develop Healthy Choices in Motion, a Comprehensive, Experiential Physical Activity Curriculum.

Background: Research has shown that engaging in regular physical activity supports physiologic, metabolic, and immunologic processes, as well as quality of life. However, few youth in the United States meet the U.S. Department of Health and Human Services recommendation of 60 min of moderate-to-vigorous physical activity every day. School-based programs can be an effective avenue for engaging youth in physical activity, particularly when the design of the health education is based on theory, research, and practice. The purpose of this study was to design, implement, and evaluate a theory-driven physical activity curriculum for the Shaping Healthy Choices Program (SHCP) using a systematic approach. Methods: The experiential, inquiry-based physical activity curriculum, Healthy Choices in Motion (HCIM), was developed with an optional technology enhancement using Backward Design. A questionnaire to assess the curriculum's effect on physical activity knowledge was developed and assessed for content validity, internal consistency (α = 0.84), and test-retest reliability (r = 0.73). The curriculum was piloted in two phases among upper elementary-aged youth: to ensure the learning goals were met (Pilot I) and to determine the curriculum's impact on physical activity knowledge, behavior, and self-efficacy (Pilot II). Pilot II was implemented among eight 4th and 5th-grade classrooms participating in the UC CalFresh Nutrition Education Program: (1) Comparison (no intervention) (n = 25); (2) SHCP only (n = 22); (3) SHCP + HCIM (n = 42); (4) SHCP + HCIM with technology enhancement (n = 47). Analyses included unadjusted ANOVA and Bonferroni for multiple comparisons and paired t-test (p &lt; 0.05). Results: Through the use of a methodical design approach, a comprehensive physical activity curriculum, called HCIM, was developed. Youth participating in HCIM improved physical activity knowledge compared to youth receiving no intervention (+2.8 points, p = 0.009) and youth only in the SHCP (+3.0 points, p = 0.007). Youth participating in HCIM with technology enhancement demonstrated improvements compared to youth only in the SHCP (+2.3 points, p = 0.05). Conclusion: Improvements in physical activity knowledge in youth participating in HCIM may contribute to improvements in physical activity and should be further explored in conjunction with behavioral measurements