Global Deposits of \u3cem\u3ein situ\u3c/em\u3e Upper Cambrian microbialites: Implications for a Cohesive Model of Origins

The existence of in situ microbialites of biological origin located in upper Cambrian rocks in western Utah presents some problems for creationists as they seek to define the boundary that separates pre-Flood deposits from those that were deposited during the Flood event itself. These microbialites are extensive in nature, covering an area of at least 2600 km2, and are stacked one atop the other in multiple beds that span a thickness of at least 300 m, but could be as thick as several km (intercalated between wackestone wedges). Other microbialites found throughout similar upper Cambrian rocks in Nevada and California are most likely representative of those in western Utah. Upper Cambrian microbialite beds have also been described from other areas in North America that circumscribe what appears to be the ancient coast of the North American craton associated with Laurentia. A total of 24 different locations span North America starting in Newfoundland, traveling down to the New York area, crossing the southern United States to Texas, then moving over to the region around Utah, California and Nevada, before continuing the trail northward through Idaho, Alberta and on into the Northwest Territories of Canada. If these microbialites indeed are in situ, then they represent vast environments that require time frames greater than the one-year period of Noah’s Flood

The Growth and Ecology of Upper Cambrian Microbialite Biostromes from the Notch Peak Formation in Utah

Exposure of carbonate rocks within the uplifted mountains of southwestern Utah presents a unique opportunity to study the growth, morphology and ecology of two upper Cambrian microbialite reefs located within the Hellnmaria Member of the Notch Peak Formation. The first reef contains meter-length, strongly elongate microbialites that grew in a deep, subtidal marine environment. These elongate microbialites formed as a result of coalescence of round ‘algal’ heads, a process known to produce compound microbialite structures in shallow water, but seldom explored as a key factor in the elongation of deep, subtidal forms that grew in ancient environments. The second reef contains lithistid sponge-microbial ‘stromatolites,’ a new type of metazoan bio-structure that has only been described from the Carboniferous and Triassic periods. This discovery has important implications when reconstructing middle to upper Cambrian reef-building communities, as these periods are assumed to have a very low diversity of metazoan reefal components. Taken together, both reefs shed light on the paleoecology and paleoenvironment of upper Cambrian microbialite reef-building communities

Using Stromatolites to Rethink the Precambrian-Cambrian Pre-Flood/Flood Boundary

The 550-meter-thick upper Cambrian (Furongian Epoch) Notch Peak Formation of western Utah has over a dozen horizons of meter- to multiple-meter-thick sequences of stromatolites that have been correlated with similar stromatolitic beds in the Drum Mountains to the north and the Wah Wah mountains to the south, providing a total geographic distribution greater than 2,600 square kilometres. Cambrian stromatolitic beds have also been described from other areas in North America that circumscribe what appears to be the ancient coast of the North American craton associated with Laurentia. A total of 24 different locations span North America starting in Newfoundland, traveling down to the New York area, crossing the southern United States to Texas, then moving over to the region around Utah, California, and Nevada, before continuing the trail northward through Idaho, Alberta and on into the Northwest Territories of Canada. These growth structures challenge the majority creationist consensus that places the onset of the Flood at, or near, the Proterozoic/Paleozoic boundary. For this latter position to be valid, thick, and geographically widespread sequences of stromatolites would necessarily have had to have grown during the initial stages of the Flood (in just months), when, according to many creationists upwards of 1000 meters of continental crust was being eroded from the craton at almost the same time. For this reason, I propose that processes related to the erosion of the craton and associated with the Great Unconformity be placed within Creation Week, thus removing its place as a primary marker for the onset of the Flood

Mechanisms Underlying Insulin Deficiency-Induced Acceleration of β-Amyloidosis in a Mouse Model of Alzheimer's Disease

Although evidence is accumulating that diabetes mellitus is an important risk factor for sporadic Alzheimer's disease (AD), the mechanisms by which defects in insulin signaling may lead to the acceleration of AD progression remain unclear. In this study, we applied streptozotocin (STZ) to induce experimental diabetes in AD transgenic mice (5XFAD model) and investigated how insulin deficiency affects the β-amyloidogenic processing of amyloid precursor protein (APP). Two and half months after 5XFAD mice were treated with STZ (90 mg/kg, i.p., once daily for two consecutive days), they showed significant reductions in brain insulin levels without changes in insulin receptor expression. Concentrations of cerebral amyloid-β peptides (Aβ40 and Aβ42) were significantly increased in STZ-treated 5XFAD mice as compared with vehicle-treated 5XFAD controls. Importantly, STZ-induced insulin deficiency upregulated levels of both β-site APP cleaving enzyme 1 (BACE1) and full-length APP in 5XFAD mouse brains, which was accompanied by dramatic elevations in the β-cleaved C-terminal fragment (C99). Interestingly, BACE1 mRNA levels were not affected, whereas phosphorylation of the translation initiation factor eIF2α, a mechanism proposed to mediate the post-transcriptional upregulation of BACE1, was significantly elevated in STZ-treated 5XFAD mice. Meanwhile, levels of GGA3, an adapter protein responsible for sorting BACE1 to lysosomal degradation, are indistinguishable between STZ- and vehicle-treated 5XFAD mice. Moreover, STZ treatments did not affect levels of Aβ-degrading enzymes such as neprilysin and insulin-degrading enzyme (IDE) in 5XFAD brains. Taken together, our findings provide a mechanistic foundation for a link between diabetes and AD by demonstrating that insulin deficiency may change APP processing to favor β-amyloidogenesis via the translational upregulation of BACE1 in combination with elevations in its substrate, APP

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

First Sagittarius A* Event Horizon Telescope results. II. EHT and multiwavelength observations, data processing, and calibration

We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5–11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ∼50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.http://iopscience.iop.org/2041-8205Physic

First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration

We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5–11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ∼50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*’s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior