A cellular resolution atlas of Broca's area.

Brain cells are arranged in laminar, nuclear, or columnar structures, spanning a range of scales. Here, we construct a reliable cell census in the frontal lobe of human cerebral cortex at micrometer resolution in a magnetic resonance imaging (MRI)-referenced system using innovative imaging and analysis methodologies. MRI establishes a macroscopic reference coordinate system of laminar and cytoarchitectural boundaries. Cell counting is obtained with a digital stereological approach on the 3D reconstruction at cellular resolution from a custom-made inverted confocal light-sheet fluorescence microscope (LSFM). Mesoscale optical coherence tomography enables the registration of the distorted histological cell typing obtained with LSFM to the MRI-based atlas coordinate system. The outcome is an integrated high-resolution cellular census of Broca's area in a human postmortem specimen, within a whole-brain reference space atlas.

Rapid head-pose detection for automated slice prescription of fetal-brain MRI.

In fetal-brain MRI, head-pose changes between prescription and acquisition present a challenge to obtaining the standard sagittal, coronal and axial views essential to clinical assessment. As motion limits acquisitions to thick slices that preclude retrospective resampling, technologists repeat ~55-second stack-of-slices scans (HASTE) with incrementally reoriented field of view numerous times, deducing the head pose from previous stacks. To address this inefficient workflow, we propose a robust head-pose detection algorithm using full-uterus scout scans (EPI) which take ~5 seconds to acquire. Our ~2-second procedure automatically locates the fetal brain and eyes, which we derive from maximally stable extremal regions (MSERs). The success rate of the method exceeds 94% in the third trimester, outperforming a trained technologist by up to 20%. The pipeline may be used to automatically orient the anatomical sequence, removing the need to estimate the head pose from 2D views and reducing delays during which motion can occur.

Earliest stone-tipped projectiles from the Ethiopian rift date to >279,000 years ago.

Projectile weapons (i.e. those delivered from a distance) enhanced prehistoric hunting efficiency by enabling higher impact delivery and hunting of a broader range of animals while reducing confrontations with dangerous prey species. Projectiles therefore provided a significant advantage over thrusting spears. Composite projectile technologies are considered indicative of complex behavior and pivotal to the successful spread of Homo sapiens. Direct evidence for such projectiles is thus far unknown from >80,000 years ago. Data from velocity-dependent microfracture features, diagnostic damage patterns, and artifact shape reported here indicate that pointed stone artifacts from Ethiopia were used as projectile weapons (in the form of hafted javelin tips) as early as >279,000 years ago. In combination with the existing archaeological, fossil and genetic evidence, these data isolate eastern Africa as a source of modern cultures and biology.

Time scales of critical events around the Cretaceous-Paleogene boundary.

Mass extinctions manifest in Earth's geologic record were turning points in biotic evolution. We present (40)Ar/(39)Ar data that establish synchrony between the Cretaceous-Paleogene boundary and associated mass extinctions with the Chicxulub bolide impact to within 32,000 years. Perturbation of the atmospheric carbon cycle at the boundary likely lasted less than 5000 years, exhibiting a recovery time scale two to three orders of magnitude shorter than that of the major ocean basins. Low-diversity mammalian fauna in the western Williston Basin persisted for as little as 20,000 years after the impact. The Chicxulub impact likely triggered a state shift of ecosystems already under near-critical stress.

Refined age estimates and Paleoanthropological investigation of the Manyara Beds, Tanzania.

The Manyara Beds in the area of Makuyuni Village in the Lake Manyara Basin, Tanzania have been studied for nearly a century, but interpretations of their age have ranged from Middle Pleistocene to Late Pliocene. New geological, paleontological and archeological fieldwork was conducted at the site and has provided siginificant new evidence, including refined stratigraphy, radiometric age estimates, preliminary paleomagnetic analysis, significant new faunal collections, as well as stratigraphic context for some of the lithic artifacts in stratigraphic context. These efforts have succesfully constrained the geological age estimates for the Manyara Beds to between less than 0.63 to 1.3 Ma, and the age of the two hominin bearing localities to between 0.63 and 0.78 Ma. This new chronology may impact the taxonomic interpretation of the hominin remains recovered from the site. They also suggest that two mammalian taxa, Metridiochoerus compactus and Eurygnathohippus, may have some of their youngest known occurences in the Manyara Beds. Acheulean lithics were also found in stratigraphic context during this more narrow time interval. Furthermore, the presence of potential cut-marks on the surface of a bovid mandible may represent the first evidence for human modification of bones from the Manyara Beds.

A chronological framework for a long and persistent archaeological record: Melka Kunture, Ethiopia.

New (40)Ar/(39)Ar geochronological data for several volcanic ash horizons from Melka Kunture, Ethiopia, allow for significantly more precise age constraints to be placed upon the lithostratigraphy, archaeology and paleontology from this long record. Ashes from the Melka Kunture Formation at Gombore yielded the most reliable age constraints, from 1.393 ± 0.162 Ma(2) (millions of years ago) near the base of the section to 0.709 ± 0.013 Ma near the top. Dating the Garba section proved more problematic, but the base of the section, which contains numerous Oldowan obsidian artifacts, may be >1.719 ± 0.199 Ma, while the top is securely dated to 0.869 ± 0.020 Ma. The large ignimbrite from the Kella Formation at Kella and Melka Garba is dated to 1.262 ± 0.034 Ma and pre-dates Acheulean artifacts in the area. The Gombore II site, which has yielded two Homo skull fragments, 'twisted bifaces,' and a preserved butchery site, is now constrained between 0.875 ± 0.010 Ma and 0.709 ± 0.013 Ma. Additional ashes from these and other sites further constrain the timing of deposition throughout the section. Integration with previously published magnetostratigraphy has allowed for the first time a relatively complete, reliable timeline for the deposition of sediments, environmental changes, archaeology, and paleontology at Melka Kunture.

Polymerization profile analysis of resin composite dental restorative materials in real time.

OBJECTIVES: In this study, the hypothesis that the polymerization shrinkage profile of "low shrinkage" non-methacrylate based composite; Silorane and "low shrinkage" high molecular mass methacrylate based composite; Kalore is not different from that of three conventional methacrylate based composites (Gradia Direct X, Filtek Supreme XT and Beautifil II) was tested. METHODS: Five commercially available composites were analysed: one "low shrinkage" non-methacrylate based composite (Silorane); one "low shrinkage" high molecular mass methacrylate based composite (Kalore) and three conventional methacrylate based composites (Gradia Direct X, Filtek Supreme XT and Beautifil II). Polymerization shrinkage was measured using an electromagnetic balance which recorded changes in composite buoyancy occurring due to volumetric changes during polymerization. This instrument allowed real time volumetric shrinkage measurements to be made at 40 ms intervals. RESULTS: All five resin composites demonstrated a similar volumetric shrinkage profile during polymerization. The rate of shrinkage of all five composites decreased from t=0 at a rate approximating x=t. After 170 s the rate of shrinkage of all five composites was at or below 0.01%/s. During the initial 5s of light exposure Silorane and Kalore exhibited a significantly lower (p<0.05) rate of contraction relative to the three conventional methacrylate composites. After 640 s of analysis, Silorane exhibited a significantly lower (p<0.05) percentage volumetric contraction compared to the other four analysed materials. CONCLUSIONS: The newly developed "low shrinkage" composites (Silorane, Kalore) in the present study demonstrated significantly lower (p<0.05) shrinkage rates and shrinkage volumes compared to the three conventional methacrylate composites. Investigation to identify whether polymerization shrinkage profile analysis is a good predictor of relative polymerization contraction stress levels generated by different composites, is warranted. CLINICAL SIGNIFICANCE: Clinicians making a resin composite selection with the view to minimizing the clinical effects of polymerization shrinkage must consider the rate of polymerization as well as the total volumetric shrinkage of a composite. Silorane (non methacrylate composite) and Kalore (high molecular mass methacrylate composite) have the ability to exhibit lower shrinkage rates and lower shrinkage volumes compared to conventional methacrylate composites.