82 research outputs found
The Locomotion of Babakotia radofilai Inferred From Epiphyseal and Diaphyseal Morphology of the Humerus and Femur
Palaeopropithecids, or âsloth lemurs,â are a
diverse clade of large-bodied Malagasy subfossil primates
characterized by their inferred suspensory positional
behavior. The most recently discovered genus of the
palaeopropithecids is Babakotia, and it has been
described as more arboreal than Mesopropithecus, but
less than Palaeopropithecus. In this article, the withinbone
and between-bones articular and cross-sectional
diaphyseal proportions of the humerus and femur of
Babakotia were compared to extant lemurs, Mesopropithecus
and Palaeopropithecus in order to further understand
its arboreal adaptations. Additionally, a sample of
apes and sloths (Choloepus and Bradypus) are included
as functional outgroups composed of suspensory adapted
primates and non-primates. Results show that Babakotia
and Mesopropithecus both have high humeral/femoral
shaft strength proportions, similar to extant great apes
and sloths and indicative of forelimb suspensory behavior,
with Babakotia more extreme in this regard. All three
subfossil taxa have relatively large femoral heads, also
associated with suspension in modern taxa. However,
Babakotia and Mesopropithecus (but not Palaeopropithecus)
have relatively small femoral head surface area to
shaft strength proportions suggesting that hind-limb positioning
in these taxa during climbing and other behaviors
was different than in extant great apes, involving
less mobility. Knee and humeral articular dimensions
relative to shaft strengths are small in Babakotia and
Mesopropithecus, similar to those found in modern sloths
and divergent from those in extant great apes and
lemurs, suggesting more sloth-like use of these joints during
locomotion. Mesopropithecus and Babakotia are more
similar to Choloepus in humerofemoral head and length
proportions while Palaeopropithecus is more similar to
Bradypus. These results provide further evidence of the
suspensory adaptations of Babakotia and further highlight
similarities to both extant suspensory primates and
non-primate slow arboreal climbers and hangers
Dendritic reidite from the Chesapeake Bay impact horizon, Ocean Drilling Program Site 1073 (offshore northeastern USA): A fingerprint of distal ejecta?
High-pressure minerals provide records of processes not normally preserved in Earthâs crust. Reidite, a quenchable polymorph of zircon, forms at pressures >20 GPa during shock compression. However, there is no broad consensus among empirical, experimental, and theoretical studies on the nature of the polymorphic transformation. Here we decipher a multistage history of reidite growth recorded in a zircon grain in distal impact ejecta (offshore northeastern United States) from the ca. 35 Ma Chesapeake Bay impact event which, remarkably, experienced near-complete conversion (89%) to reidite. The grain displays two distinctive reidite habits: (1) intersecting sets of planar lamellae that are dark in cathodoluminescence (CL); and (2) dendritic epitaxial overgrowths on the lamellae that are luminescent in CL. While the former is similar to that described in literature, the latter has not been previously reported. A two-stage growth model is proposed for reidite formation at >40 GPa in Chesapeake Bay impact ejecta: formation of lamellar reidite by shearing during shock compression, followed by dendrite growth, also at high pressure, via recrystallization. The dendritic reidite is interpreted to nucleate on lamellae and replace damaged zircon adjacent to lamellae, which may be amorphous ZrSiO4 or possibly an intermediate phase, all before quenching. These results provide new insights on the microstructural evolution of the highpressure polymorphic transformation over the microseconds-long interval of reidite stability during meteorite impact. Given the formation conditions, dendritic reidite may be a unique indicator of distal ejecta
Titles versus titles and abstracts for initial screening of articles for systematic reviews
PMC3933432BACKGROUND:
There is no consensus on whether screening titles alone or titles and abstracts together is the preferable strategy for inclusion of articles in a systematic review.
METHODS:
TWO METHODS OF SCREENING ARTICLES FOR INCLUSION IN A SYSTEMATIC REVIEW WERE COMPARED: titles first versus titles and abstracts simultaneously. Each citation found in MEDLINE or Embase was reviewed by two physician reviewers for prespecified criteria: the citation included (1) primary data; (2) the exposure of interest; and (3) the outcome of interest.
RESULTS:
There were 2965 unique citations. The titles first strategy resulted in an immediate rejection of 2558 (86%) of the records after reading the title alone, requiring review of 239 titles and abstracts, and subsequently 176 full text articles. The simultaneous titles and abstracts review led to rejection of 2782 citations (94%) and review of 183 full text articles. Interreviewer agreement to include an article for full text review using the titles-first screening strategy was 89%-94% (kappa = 0.54) and 96%-97% (kappa = 0.56) for titles and abstracts combined. The final systematic review included 13 articles, all of which were identified by both screening strategies (yield 100%, burden 114%). Precision was higher in the titles and abstracts method (7.1% versus 3.2%) but recall was the same (100% versus 100%), leading to a higher F-measure for the titles and abstracts approach (0.1327 versus 0.0619).
CONCLUSION:
Screening via a titles-first approach may be more efficient than screening titles and abstracts together.JH Libraries Open Access Fun
(U-Th)/He zircon dating of Chesapeake Bay distal impact ejecta from ODP site 1073
Single crystal (UâTh)/He dating has been undertaken on 21 detrital zircon grains extracted from a core sample from Ocean Drilling Project (ODP) site 1073, which is located ~390 km northeast of the center of the Chesapeake Bay impact structure. Optical and electron imaging in combination with energy dispersive Xâray microanalysis (EDS) of zircon grains from this late Eocene sediment shows clear evidence of shock metamorphism in some zircon grains, which suggests that these shocked zircon crystals are distal ejecta from the formation of the ~40 km diameter Chesapeake Bay impact structure. (UâTh/He) dates for zircon crystals from this sediment range from 33.49 ± 0.94 to 305.1 ± 8.6 Ma (2Ï), implying crystalâtoâcrystal variability in the degree of impactârelated resetting of (UâTh)/He systematics and a range of different possible sources. The two youngest zircon grains yield an inverseâvariance weighted mean (UâTh)/He age of 33.99 ± 0.71 Ma (2Ï uncertainties n = 2; mean square weighted deviation = 2.6; probability [P] = 11%), which is interpreted to be the (UâTh)/He age of formation of the Chesapeake Bay impact structure. This age is in agreement with K/Ar, 40Ar/39Ar, and fission track dates for tektites from the North American strewn field, which have been interpreted as associated with the Chesapeake Bay impact event
Transition to self-management among emerging adults with type 1 diabetes: a mixed methods study
IntroductionEmerging adulthood is challenging for young people with type 1 diabetes (T1D). This study evaluated transition to diabetes self-management and perceptions of care transfer using mixed methods.MethodsAn online survey queried demographics, management characteristics, diabetes knowledge, self-care readiness, adherence, and diabetes distress. T-tests compared survey scores between those with self-reported target A1c <7.0% versus â„7.0%. Pearson correlations assessed associations between A1c and diabetes distress, stratified by A1c <7.0% versus â„7.0%. Qualitative semi-structured interviews elicited perceptions of young adults; transcripts were analyzed using directed qualitative content analysis.ResultsOf 141 participants (30% male, 84% non-Hispanic white) completing the survey, 41% self-reported target A1c <7.0%. Diabetes knowledge and self-care readiness scores did not differ between those with A1c <7.0% versus â„7.0%, while diabetes distress was lower (45 ± 20 vs 52 ± 20, p=0.01) and adherence higher (77 ± 12 vs 71 ± 14, p=0.02) in those with A1c <7.0% versus â„7.0%. Diabetes distress was significantly associated with glycemic outcomes in those reporting A1c â„7.0% (R=0.36, p<0.01). Qualitative analysis (24 participants) revealed five themes and two sub-themes, notable for need for more mental health support, support from others with T1D, benefits of technology for care autonomy, and challenges of obtaining diabetes supplies.DiscussionEmerging adults with self-reported target A1c endorsed lower diabetes distress and higher adherence than those with elevated A1c. Mental health access, support from others with T1D, technology use, and guidance for supply acquisition may improve transition to self-management and care transfer for emerging adults with T1D
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