Sulfuric acid aerosols may have cooled Earth for years. Life certainly could not have been easy for those species which did survive. Fortunately such impacts occur only about once every hundred million years. This shows they became extinct before, or during the event. Mosasaurs, plesiosaurs, pterosaurs and many species of plants and invertebrates also became extinct.
Mammalian and bird groups got through the event with some extinctions. Those that survived became widespread and varied during their later evolutionary radiation. How quickly they died out around the world is an important clue. Scientists also study patterns in rocks to learn the causes. Several impact craters and massive volcanic activity, such as that in the Deccan Traps in India, are dated to about the same time as the extinctions. Saturday, November 13, Sign in. Forgot your password?
Irvine, Daniele L. Pinti, Michel Viso. Contents Search. KT Boundary. The Ce enrichment in spherules from the Mesa-Juan Perez section indicates impact-melted carbonates of the Yucatan carbonate platform as possible precursor rocks. Recent investigations focus on the chemistry of melt rock samples from the PEMEX wells Yucatan-6 and Chicxulub Their average composition mean of data points in wt-percent is These results are in some cases comparable to the geochemistry of ejecta glasses, e.
Since the pioneering study of Alvarez et al. Acta 53, Indian Acad. Earth Planet. Sci , 96, pp. A new Cretaceous-Tertiary boundary locality in the western powder River basin, Wyoming: biological and geological implications. A newly discovered Cretaceous-Tertiary K-T boundary locality in the western Powder River basin, Wyoming, is characterized by a palynologically defined extinction horizon, a fern-spore abundance anomaly, a strong iridium anomaly, and shock-metamorphosed quartz grains.
Detailed microstratigraphic analyses show that about one third of the palynoflora mostly angiosperm pollen disappeared abruptly, placing the K-T boundary within a distinctive, 1- to 2-cm-thick claystone layer.
Shocked quartz grains are concentrated at the top of this layer, and although fern-spore and iridium concentrations are high in this layer, they reach their maximum concentrations in a 2-cm-thick carbonaceous claystone that overlies the boundary claystone layer. The evidence supports the theory that the K-T boundary event was associated with the impact of an extraterrestrial body or bodies.
Palynological analyses of samples from the K-T boundary interval document extensive changes in the flora that resulted from the boundary event. The palynologically and geochemically defined K-T boundary provides a unique time-line of use in regional basin analysis.
Alternative explanations claim that extensive, violent volcanism can account for the Ir, and that other independent causes were responsible for the mass extinctions15, We surmise that the collision of a massive extraterrestrial object with the Earth may have produced a unique organic chemical signature because certain meteorites, and probably comets, contain organic compounds which are either rare or non-existent on the Earth In contrast, no organic compounds would be expected to be associated with volcanic processes.
An extraterrestrial source is the most reasonable explanation for the presence of these amino acids. Planck scale boundary conditions and the Higgs mass. If the LHC does only find a Higgs boson in the low mass region and no other new physics, then one should reconsider scenarios where the Standard Model with three right-handed neutrinos is valid up to Planck scale.
We assume in this spirit that the Standard Model couplings are remnants of quantum gravity which implies certain generic boundary conditions for the Higgs quartic coupling at Planck scale. This leads to Higgs mass predictions at the electroweak scale via renormalization group equations. We find that several physically well motivated conditions yield a range of Higgs masses from - GeV.
Concentric geophysical anomalies associated with enigmatic occurrences of Upper Cretaceous breccias and andesitic rocks led Penfield and Camargo1 to suspect that this structure was a buried impact basin. The Chicxulub melt rocks that we studied contain anomalously high levels of iridium up to Myr, in good agreement with the mean plateau age of Furthermore, these melt rocks acquired a remanent magnetization indicating that they cooled during an episode of reversed geomagnetic polarity.
Mass -conserved volumetric lattice Boltzmann method for complex flows with willfully moving boundaries. In this paper, we develop a mass -conserved volumetric lattice Boltzmann method MCVLBM for numerically solving fluid dynamics with willfully moving arbitrary boundaries. In MCVLBM, fluid particles are uniformly distributed in lattice cells and the lattice Boltzmann equations deal with the time evolution of the particle distribution function. The MCVLBM strictly satisfies mass conservation and can handle irregular boundary orientation and motion with respect to the mesh.
Validation studies are carried out in four cases. The first is to simulate fluid dynamics in syringes focusing on how MCVLBM captures the underlying physics of flow driven by a willfully moving piston.
The second and third cases are two-dimensional 2D peristaltic flow and three-dimensional 3D pipe flow, respectively. In each case, we compare the MCVLBM simulation result with the analytical solution and achieve quantitatively good agreements. The fourth case is to simulate blood flow in human aortic arteries with a very complicated irregular boundary.
We study steady flow in two dimensions and unsteady flow via the pulsation of the cardiac cycle in three dimensions. In the 2D case, both vector velocity and. These disturbances are most important within the vicinity of the crater at Chicxulub, Yucatan, Mexico, and 65 million years ago that can be chronologically correlated with the bolide impact postulated by Alvarez et al At all sites the KTB layer shows spatial and temporal differences even within short distances, and the complexity of its characteristic signals includes serious micropaleontological inconsistencies with mixed biotic assemblages that perpetuate divergence of interpretations, thereby they raise doubts on the timing and real causal mechanisms of the biotic turnover that characterizes the boundary.
Indeed, often the biostratigraphic signals are difficult to resolve because of hiatuses, or sediments are highly reworked, and distinct taxonomic successions are not clearly defined. Well defined as well as cryptic primary sedimentary structures within the boundary layer are constant at all outcrops, and they indicate complex, multiphase, subaqueous flow processes that affected sedimentation of the KTB layer at different times.
The structures are known to characterize oscillatory wave processes that affect cohesionless sediments, and such water motion is only known to be associated with seiche as a modern analog that may have generated the amalgamation recorded at the KTB layer.
We believe that "Megaseiche" associated with the KT impact event and its subsequent effects provides a plausible unifying mechanism to explain how various levels of the water column in different large basins can oscillate to develop the structures observed. Because of the magnitude of the bolide impact that generated initial tsunamis and large seismic waves worldwide, megaseiches of different frequencies and nodal modes must have developed in the oceans worldwide to leave different.
This new evidence of youth suggests that a low surface gravity may be sufficient to explain this peculiar feature. Free-breathing navigator-gated two-dimensional radial cine imaging with three-directional multi-point velocity encoding was implemented and fully sampled data were obtained in the aortic arch of healthy volunteers. Velocities were encoded with three different first gradient moments per axis to permit quantification of mean velocity and turbulent kinetic energy.
The seismicity initiating the May 18, catastrophic eruption at Mt. Helens indicates an explosion occurred at depth generating an average pressure of about kbar. Such pressures fall off with distance from the magma chamber although jointing, fractures, etc. Shocked minerals are not to be expected from the magma itself as high temperatures would anneal such features but temperatures fall away rapidly enough from the chamber wall to allow retention even of such possible exotics as stishovite.
The subsequent kinetics of the failure of the north slope support these pressures as do thermodynamic considerations and nucleation kinetics of CO2 exsolution from magmatic melt. Confining pressures e. Unconfined detonations in open air yield pressures to several megabars although some recent arguments asserted to be volcanological would indicate open air bursts greater than one bar to be impossible.
Further, it has been indicated that pressure estimates from ballistic considerations have been too high and large phenocryst content in the discharge material argues against high pressure explosions. In the first instance, sonic choking and volatile diffusion time constraints make these assessments implausible and in the second instance, both theoretical and geological considerations provide for the phenocryst distributions under explosive situations. The geographical breadth of volcanic activity attending the K-T transition e.
Scaling to mantle. Theoretical studies of Higgs production via gluon fusion are frequently carried out in the limit where the top quark mass is much larger than the Higgs mass , an approximation which reduces the top quark loop to an effective vertex.
By examining both inclusive and exclusive quantities, we find that retaining the top- mass dependence results in only a small enhancement of the cross-section. Instead, two phases of Cretaceous species extinctions occur. He did not consider the osmium isotopic signature of the terrestrial mantle, which also has a chondritic evolution of the Re-Os system.
Osmium cannot serve alone as an infallible indicator of the impact theory, but interesting results can be obtained from their investigation. An overview of the values is presented in the table. It shows a very high Ir concentration 66 ppb at the boundary layer and a remarkable Ir enrichment over crustal rocks continuing up to 30 cm above the boundary. We want to evaluate mixing of Os with chondritic ratios with Os from upper crustal rocks. Another goal is to investigate a mobilization of Os.
We expect an even lower value for the boundary clay 0 cm itself not taking into account a contribution of radiogenic osmium from the decay of terrestrial rhenium. Further analysis will be presented at the meeting.
References Alekseyev A. Effects of K and Ca doping on twin boundary energy of cupperate superconductors. Ab-initio calculations under GGA approximation have been employed to find out the effect Ba substitution by K and Ca on the structural and electronic properties twined and untwined YBCO system.
Our results show that despite the structural changes the presence of K Ca modifies substantially density of levels at the Fermi level, which could be responsible for empirical reports of decreasing the critical temperature Tc by increasing the K Ca content. In addition, reduction of the carrier density occurs at twin boundary in CuO2 layer for the substituted system with respect to the untwined YBCO system.
Our results would be noticeable in conjunction with the experimentally reported twinned and alkali substituted superconductive properties of the YBCO samples. Measurement of electron effective mass ratios in Hg1-xCdxTe for 0. Measured effective masses diverge further from the theoretical formulations as temperature increases which appears to be due to a thermal excitation effect that is not accounted for in theoretical calculations.
Carrier concentrations were measured using Hall or van der Pauw tests. Soldered contacts to high mobility materials like HgCdTe using even the purest indium solder inevitably result in contamination that can add significant numbers of impurity carriers to the material and severely decrease mobility. A simple method of burnishing contacts to the material without heat using indium solder is presented.
These cold contacts do not effect the material properties and are very effective in n-type HgCdTe making good physically strong contacts that remain ohmic to at least 10 K. This is a review paper. This dinocyst pattern is interpreted to reflect an invasion of this species into the southwest Pacific, in the aftermath of the Chicxulub impact. In the New Zealand sections, two earliest Paleocene intervals with dominance of T.
The sudden acme of P. A second period with warm-surface water is observed c. The end of the main marine recovery period is marked by a gradual arrival of new suite of dinocyst species and oligotrophic conditions. Mass extinctions: Ecological selectivity and primary production.
If mass extinctions were caused by reduced primary productivity, then extinctions should be concentrated among animals with starvation-susceptible feeding modes, active lifestyles, and high-energy budgets.
Measurement of the mass difference between t and t quarks. We make an event by event estimate of the mass difference to construct templates for top quark pair signal events and background events. The resulting mass difference distribution of data is compared to templates of signals and background using a maximum likelihood fit. From a sample corresponding to an integrated luminosity of 5.
Terrestrial ecosystem collapse associated to the K -Pg boundary and dinosaur extinction: palynological evidences. Bercovici, A. We report here the discovery of the stratigraphically youngest in situ dinosaur specimen. This ceratopsian brow horn was found in southeastern Montana, in the Western Interior of the United States in a poorly rooted, silty mudstone floodplain deposit and only 13 centimeters below the palynologically defined K -Pg boundary.
The boundary is identified using three criteria: 1 substantial decrease in diversity and abundance of Cretaceous pollen and spore taxa that completely disappear from the palynological record a few meters above the boundary , 2 the presence of a "fern spike", and 3 palynostratigraphical correlation to a nearby section where primary extraterrestrial impact markers are present e. The palynological record in the rock sequence immediately following the K -Pg boundary consistently indicates a sudden and major loss of the Cretaceous components across the North American record.
During this rapid decline, the palynological assemblages are dominated by freshwater ferns Azolla and algae usually Pediastrum sp. The onset of the Paleocene sedimentation is subsequently announced by the presence of variegated beds, multiple lignite seams and small scale meandering river systems, starting with palynological associations that attest for reworking and erosion.
The destabilization of terrestrial ecosystems is coincident with the markers of the K -Pg boundary , supporting a catastrophic event taking place over a very short duration. The in situ ceratopsian brow horn demonstrates that a gap devoid of non-avian dinosaur fossils in the last meters of the Cretaceous is artificial and thus inconsistent with the hypothesis that non-avian dinosaurs were extinct prior to the K -Pg boundary asteroid impact event.
Is there evidence for Cretaceous-Tertiary boundary -age deep-water deposits in the Caribbean and Gulf of Mexico? Current-bedded volcaniclastic sedimentary rocks at Deep Sea Drilling Project DSDP Sites and , which were previously interpreted as impact-generated megawave deposits of K-T boundary age, are biostratigraphically of pre- K-T boundary age and probably represent turbidite or gravity-How deposits. The top 10 to 20 cm of this deposit at Site contains very rare Micula prinsii, the uppermost Maastrichtian index taxon, as well as low values of Ir 0.
These indicate possible reworking of sediments of K-T boundary age at the hiatus. Absence of continuous sediment accumulation across the K-T boundary in the 16 Gulf of Mexico and Caribbean sections examined prevents their providing evidence of impact-generated megawave deposits in this region. Our study indicates that the most complete trans- K-T stratigraphic records may be found in onshore marine sections of Mexico, Cuba, and Haiti.
The stratigraphic records of these areas should be investigated further for evidence of impact deposits. Neutrino oscillation physics potential of the T 2 K experiment. T2K Collaboration; Abe, K. With an exposure of 7. Impact models and experiments combined with estimates of volatiles in the projectile and target rocks predict that over gigatons Gt each of SO2 and water vapor, and over Gt of CO2, were globally distributed in the stratosphere by the impact.
The inducement of planetary boundary layer mass convergence associated with varying vorticity beneath tropospheric wind maximum. The effects of the vorticity distribution are applied to study planetary boundary layer mass convergence beneath free tropospheric wind maximum. For given forcing by viscous and pressure gradient forces beneath a wind maximum, boundary layer cross stream mass transport is increased by anticyclonic vorticity on the right flank and decreased by cyclonic vorticity on the left flank.
Such frictionally forced mass transport induces boundary layer mass convergence beneath the relative wind maximum. This result is related to the empirical rule that the most intense convection and severe weather frequently develop beneath the mb zero relative vorticity isopleth.
Current high-throughput top-down proteomic platforms provide routine identification of proteins less than 25 k Da with 4-D separations. This short communication reports the application of technological developments over the past few years that improve protein identification and characterization for masses greater than 25 k Da.
Advances in separation science have allowed increased numbers of proteins to be identified, especially by nanoliquid chromatography nLC prior to mass spectrometry MS analysis. Normally, large proteins greater than 50 k Da are identified and characterized by top-down proteomics through fraction collection and direct infusion at relatively low throughput.
Further, other MS-based techniques provide top-down protein characterization, however at low resolution for intact mass measurement. The separation platform reduced the complexity of the protein matrix so that, at Further, the results document routine identification of proteins at improved throughput based on accurate mass measurement less than 10 ppm mass error of precursor and fragment ions for proteins up to 50 k Da.
The School Attendance Boundary Information System is a social science data infrastructure project that assembles, processes, and distributes spatial data delineating K through 12th grade school attendance boundaries for thousands of school districts in U. Although geography is a fundamental organizing feature of K to 12 education, until now school attendance boundary data have not been made readily available on a massive basis and in an easy-to-use format.
The School Attendance Boundary Information System removes these barriers by linking spatial data delineating school attendance boundaries with tabular data describing the demographic characteristics of populations living within those boundaries. This paper explains why a comprehensive GIS database of K through 12 school attendance boundaries is valuable, how original spatial information delineating school attendance boundaries is collected from local agencies, and techniques for modeling and storing the data so they provide maximum flexibility to the user community.
An important goal of this paper is to share the techniques used to assemble the SABINS database so that local and state agencies apply a standard set of procedures and models as they gather data for their regions. The School Attendance Boundary Information System is a social science data infrastructure project that assembles, processes, and distributes spatial data delineating K through 12 th grade school attendance boundaries for thousands of school districts in U.
Individual Dynamical Masses of Ultracool Dwarfs. We present the full results of our decade-long astrometric monitoring programs targeting 31 ultracool binaries with component spectral types M7- T 5.
We derive a precise, mass -calibrated spectral type-effective temperature relation covering K. We determine a median age of 1. We discover two triple-brown-dwarf systems, the first with directly measured masses and eccentricities. We examine the eccentricity distribution, carefully considering biases and completeness, and find that low-eccentricity orbits are significantly more common among ultracool binaries than solar-type binaries, possibly indicating the early influence of long-lived dissipative gas disks.
Overall, this work represents a major advance in the empirical view of very low- mass stars and brown dwarfs. This family is the source of meteoroids and near-Earth asteroids and likely caused an asteroid shower of impactors on our Earth. Masiero et al. Also, Reddy et al. Unfortunately, Reddy et al. At this site, the first kyrs after the boundary is represented by an extended carbonate section [1]. The strange interval is important for evaluating the immediate changes in climate, ocean circulation, and evolutionary dynamics that accompanied K-T impact in the Pacific Ocean.
Here we present measurements of extraterrestrial 3He at site for the first one million year following the K-T impact event at a resolution of 2. Our goal is to better constrain the timescale of climatic and biotic events during this interval of time. Accumulation rates of interplanetary dust particles IDPs , as traced by extraterrestrial 3He [2], provide a tool with which to investigate sedimentation rates at high resolution.
Prior work has shown that the accretion rate of IDPs across the K-T boundary is constant [2], allowing us to invert the extraterrestrial 3He flux for instantaneous sedimentation rates.
Sedimentation rates derived from extraterrestrial 3He for the first 1. For a brief period, between Tektites in cretaceous-tertiary boundary rocks on Haiti and their bearing on the Alvarez impact extinction hypothesis. Observational and geochemical data for glass objects recently discovered, by Izett et al. The presence of tektites, which are of terrestrial impact origin, in the same bed with a Pt-metal abundance anomaly and shocked mineral grains enormously strengthens the impact component of the Alvarez K-T impact extinction hypothesis.
Shocked quartz grains in samples of the Haitian K-T boundary marker bed are about the same size as those at the K-T boundary sites in western North America. Petrographic observations indicate that the K-T marker bed on Haiti is not a primary air fall unit composed entirely of impact ejecta. It contains a small volcanogenic component of locally derived material admixed with the impact ejecta during deposition on the seafloor.
The major and trace element composition of the Haitian tektites, in particular, the high Rb and REE content, suggests that the target material melted during the K-T impact was sedimentary with an average composition of andesite, not mafic or ultramafic oceanic crust. Gorman, Andrew R. Hamish; Vennell, Ross; Holbrook, W. Steven; Frew, Russell. The Subtropical and Subantarctic Fronts, which separate Subtropical, Subantarctic, and Antarctic Intermediate Waters, are diverted to the south of New Zealand by the submerged continental landmass of Zealandia.
In the upper ocean of this region, large volumes of dissolved or suspended material are intermittently transported across the Subtropical Front; however, the mechanisms of such transport processes are enigmatic.
Understanding these oceanic boundaries in three dimensions generally depends on measurements collected from stationary vessels and moorings. The details of these data sets, which are critical for understanding how water masses interact and mix at the fine-scale masses have been produced using petroleum industry data. These seismic sections clearly show three main water masses , the boundary zones fronts between them, and associated thermohaline fine structure that may be related to the mixing of water masses in this region.
Interpretations of the data suggest that the Subtropical Front in this region is a landward-dipping zone, with a width that can vary between 20 and 40 km. The boundary zone between Subantarctic Waters and the underlying Antarctic Intermediate Waters is also observed to dip landward. Several isolated lenses have been identified on the three data sets, ranging in size from 9 to 30 km in diameter. These lenses are interpreted to be mesoscale eddies that form at relatively shallow depths along the south side of the Subtropical Front.
Evidence for a single impact at the Cretaceous-Tertiary boundary from trace elements. Eight enriched elements at 7 K-T sites were compared and it was found that: All have fairly constant proportions to Ir and Kilauea invoked as an example of a volcanic source of Ir by opponents of the impact theory has too little of 7 of these 8 elements to account for the boundary enrichments.
The distribution of trace elements at the K-T boundary was reexamined using data from 11 sites for which comprehensive are available. The meteoritic component can be assessed by first normalizing the data to Ir, the most obviously extraterrestrial element, and then to Cl chondrites. The double normalization reduces the concentration range from 11 decades to 5 and also facilitates the identification of meteoritic elements. Elemental carbon is also enriched by up to 10, x in boundary clay from 5 K-T sides and is correlated with Ir across the boundary at Woodside Creek.
While biomass would appear to be the primary fuel source for this carbon a contribution from a fossil fuel source may be necessary in order to account for the observed C abundance.
Ar to Ar ages of the large impact structures Kara and Manicouagan and their relevance to the Cretaceous-Tertiary and the Triassic-Jurassic boundary. Since the discovery of the Ir enrichment in Cretaceous-Tertiary boundary clays in , the effects of a km asteroid impacting on the Earth 65 Ma ago have been discussed as the possible reason for the mass extinction--including the extinction of the dinosaurs--at the end of the Cretaceous.
Geologists have dated this period to about When physicist Luis Alvarez and geologist Walter Alvarez studied the K-T boundary around the world, they found that it had a much higher concentration of iridium than normal — between times the amount of iridium you would expect. Iridium is rare on Earth because it sank down into the center of the planet as it formed, but iridium can still be found in large concentrations in asteroids. When they compared the concentrations of iridium in the K-T boundary, they found it matched the levels found in meteorites.
The researchers were even able to estimate what kind of asteroid must have impacted the Earth They estimated that the impactor must have been about 10 km in diameter, and release the energy equivalent of trillion tons of TNT.
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