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Sample records for bapang formation hominins

  1. Early Pleistocene lake formation and hominin origins in the Turkana-Omo rift

    Science.gov (United States)

    Lepre, Christopher J.

    2014-10-01

    Prior research has correlated the formation of Plio-Pleistocene lakes in East Africa to global/regional climate changes and interpreted the lacustrine basins as significant settings of hominin evolution. Paleo-Lake Lorenyang from the Turkana-Omo rift is important to these issues, as its marginal deposits contain some of, if not the earliest currently known specimens of Acheulian stone tools and African Homo erectus. Magnetostratigraphic and sedimentological evidence indicates that the oldest preserved paleo-Lake Lorenyang deposits are dated at 2.148-2.128 Ma and derive from the NW Turkana basin, predating those from the Omo basin by ˜100 kyr and the NE Turkana basin by ˜190 kyr. Apparently, the lake expanded asynchronously in the rift, potentially due to a volcano-tectonic influence on the location of drainage networks, depositional slopes, or topographic elevation differences within and between the basins at the time of flooding. The onset of the lake temporally coincides with the eruption of basalt lava flows dated to 2.2-2.0 Ma that blocked the southeast outlet of the Turkana basin. This provides a plausible mechanism for hydrologic closure and lacustrine basin formation through volcano-tectonic impounding. It also points to a non-climatic cause for the initial formation of paleo-Lake Lorenyang at ˜2.14 Ma. First appearances for African H. erectus (˜1.87 Ma) and Acheulian tools (˜1.76 Ma) in the Turkana-Omo rift postdate the lake's initial formation by about 270 kyr and 380 kyr, respectively. Such timing differences contrast with studies that correlate all three to the 400-kyr-eccentricity maximum at 1.8 Ma. Although the Turkana-Omo rift is just one example, it does provide alternative insights to views that link climate, hominin evolution, and lake formation in East Africa.

  2. Bovid ecomorphology and hominin paleoenvironments of the Shungura Formation, lower Omo River Valley, Ethiopia.

    Science.gov (United States)

    Plummer, Thomas W; Ferraro, Joseph V; Louys, Julien; Hertel, Fritz; Alemseged, Zeresenay; Bobe, René; Bishop, L C

    2015-11-01

    The Shungura Formation in the lower Omo River Valley, southern Ethiopia, has yielded an important paleontological and archeological record from the Pliocene and Pleistocene of eastern Africa. Fossils are common throughout the sequence and provide evidence of paleoenvironments and environmental change through time. This study developed discriminant function ecomorphology models that linked astragalus morphology to broadly defined habitat categories (open, light cover, heavy cover, forest, and wetlands) using modern bovids of known ecology. These models used seven variables suitable for use on fragmentary fossils and had overall classification success rates of >82%. Four hundred and one fossils were analyzed from Shungura Formation members B through G (3.4-1.9 million years ago). Analysis by member documented the full range of ecomorph categories, demonstrating that a wide range of habitats existed along the axis of the paleo-Omo River. Heavy cover ecomorphs, reflecting habitats such as woodland and heavy bushland, were the most common in the fossil sample. The trend of increasing open cover habitats from Members C through F suggested by other paleoenvironmental proxies was documented by the increase in open habitat ecomorphs during this interval. However, finer grained analysis demonstrated considerable variability in ecomorph frequencies over time, suggesting that substantial short-term variability is masked when grouping samples by member. The hominin genera Australopithecus, Homo, and Paranthropus are associated with a range of ecomorphs, indicating that all three genera were living in temporally variable and heterogeneous landscapes. Australopithecus finds were predominantly associated with lower frequencies of open habitat ecomorphs, and high frequencies of heavy cover ecomorphs, perhaps indicating a more woodland focus for this genus. PMID:26208956

  3. Connecting Local Environmental Sequences to Global Climate Patterns: Evidence From the Hominin-Bearing Hadar Formation, Ethiopia.

    Science.gov (United States)

    Campisano, C. J.; Feibel, C. S.

    2004-12-01

    Central to the debate surrounding global climate change and Plio-Pleistocene hominin evolution is the degree to which large-scale climate patterns influence low-latitude continental ecosystems and how these global influences can be distinguished from regional tectono-volcanic events and local environmental effects. These isolated factors must then be compared to trends or events in the hominin fossil or archaeological record. The Pliocene Hadar Formation preserves a high-resolution record of hominin paleoenvironments from roughly 3.5 to 2.3 Ma. The chronostratigraphic framework at Hadar, often divisible into sub-50,000 year intervals, provides temporal resolution relevant to evolutionary change within hominins and other taxa. Combined with a high sedimentation rate and abundant faunal remains, this tightly controlled stratigraphic framework allows Hadar to be compared to detailed climate proxies such as marine core isotope, dust, and sapropel records. Preliminary analyses from Hadar suggest that these comparisons can be used to distinguish local versus regional and global environmental change, determine the overall sensitivity of the Hadar system and its fauna to such change, and how this level of sensitively compares to other East African localities. Consistent cycling observed both between and within fluvial and lacustrine depositional environments prior to 2.9 Ma at Hadar appears to be dominantly climatic in nature. However, a significant change in depositional facies after 2.9 Ma to sequences dominated by conglomerate cut-and-fill cycles indicates a strong tectonic signature related to regional developments in the Main Ethiopian Rift (MER). While specific events seen in marine proxy records may have parallels in the Hadar environmental archive, their overall patterns of high versus low variability may be even more relevant. For example, periods of relatively high amplitude climate oscillations between 3.15 and 2.95 Ma may be linked to noted morphological

  4. Comparative morphological and morphometric description of the hominin calvaria from Bukuran (Sangiran, Central Java, Indonesia).

    Science.gov (United States)

    Grimaud-Hervé, Dominique; Widianto, Harry; Détroit, Florent; Sémah, François

    2012-11-01

    We describe the hominin skull (called here "Bukuran") discovered in the lower Kabuh (or "Bapang") series near Sendangbusik, from the Bukuran area in the Sangiran dome. The fossil, heavily mineralized, consists of the parieto-occipital and the left temporal, and the frontal bones. When combined, those two cranial parts represent a rather complete and well-preserved calvaria. Its stratigraphic position was established after the discovery. A detailed description is presented of the morphological and metric features of the Bukuran calvaria, and comparisons are made with Asian Homo erectus from Indonesia and China. The estimated cranial capacity of Bukuran, the general shape of its cranial vault, its ectocranial structures, and its morphological and metrical characters are in the range of Asian Homo erectus, and show clear affinities with other Indonesian members of the species. We discuss the evolutionary status of the Bukuran calvaria and its implication for hominin history on Java.

  5. Early hominin diet included diverse terrestrial and aquatic animals 1.95 Ma in East Turkana, Kenya

    OpenAIRE

    Braun, David R.; Harris, John W. K.; Naomi E. Levin; McCoy, Jack T.; Herries, Andy I. R.; Bamford, Marion K.; Bishop, Laura C.; Richmond, Brian G.; Kibunjia, Mzalendo

    2010-01-01

    The manufacture of stone tools and their use to access animal tissues by Pliocene hominins marks the origin of a key adaptation in human evolutionary history. Here we report an in situ archaeological assemblage from the Koobi Fora Formation in northern Kenya that provides a unique combination of faunal remains, some with direct evidence of butchery, and Oldowan artifacts, which are well dated to 1.95 Ma. This site provides the oldest in situ evidence that hominins, predating Homo erectus, enj...

  6. Earliest hominin occupation of Sulawesi, Indonesia

    DEFF Research Database (Denmark)

    Van Den Bergh, Gerrit D.; Li, Bo; Brumm, Adam;

    2016-01-01

    Sulawesi is the largest and oldest island within Wallacea, a vast zone of oceanic islands separating continental Asia from the Pleistocene landmass of Australia and Papua (Sahul). By one million years ago an unknown hominin lineage had colonized Flores immediately to the south, and by about 50 th...

  7. Early hominin biogeography in Island Southeast Asia.

    Science.gov (United States)

    Larick, Roy; Ciochon, Russell L

    2015-01-01

    Island Southeast Asia covers Eurasia's tropical expanse of continental shelf and active subduction zones. Cutting between island landmasses, Wallace's Line separates Sunda and the Eastern Island Arc (the Arc) into distinct tectonic and faunal provinces. West of the line, on Sunda, Java Island yields many fossils of Homo erectus. East of the line, on the Arc, Flores Island provides one skeleton and isolated remains of Homo floresiensis. Luzon Island in the Philippines has another fossil hominin. Sulawesi preserves early hominin archeology. This insular divergence sets up a unique regional context for early hominin dispersal, isolation, and extinction. The evidence is reviewed across three Pleistocene climate periods. Patterns are discussed in relation to the pulse of global sea-level shifts, as well as regional geo-tectonics, catastrophes, stegodon dispersal, and paleogenomics. Several patterns imply evolutionary processes typical of oceanic islands. Early hominins apparently responded to changing island conditions for a million-and-a-half years, likely becoming extinct during the period in which Homo sapiens colonized the region. PMID:26478140

  8. Tool making, hand morphology and fossil hominins

    OpenAIRE

    Marzke, Mary W.

    2013-01-01

    Was stone tool making a factor in the evolution of human hand morphology? Is it possible to find evidence in fossil hominin hands for this capability? These questions are being addressed with increasingly sophisticated studies that are testing two hypotheses; (i) that humans have unique patterns of grip and hand movement capabilities compatible with effective stone tool making and use of the tools and, if this is the case, (ii) that there exist unique patterns of morphology in human hands tha...

  9. Tool making, hand morphology and fossil hominins.

    Science.gov (United States)

    Marzke, Mary W

    2013-11-19

    Was stone tool making a factor in the evolution of human hand morphology? Is it possible to find evidence in fossil hominin hands for this capability? These questions are being addressed with increasingly sophisticated studies that are testing two hypotheses; (i) that humans have unique patterns of grip and hand movement capabilities compatible with effective stone tool making and use of the tools and, if this is the case, (ii) that there exist unique patterns of morphology in human hands that are consistent with these capabilities. Comparative analyses of human stone tool behaviours and chimpanzee feeding behaviours have revealed a distinctive set of forceful pinch grips by humans that are effective in the control of stones by one hand during manufacture and use of the tools. Comparative dissections, kinematic analyses and biomechanical studies indicate that humans do have a unique pattern of muscle architecture and joint surface form and functions consistent with the derived capabilities. A major remaining challenge is to identify skeletal features that reflect the full morphological pattern, and therefore may serve as clues to fossil hominin manipulative capabilities. Hominin fossils are evaluated for evidence of patterns of derived human grip and stress-accommodation features. PMID:24101624

  10. The earliest securely-dated hominin artefact in Anatolia?

    NARCIS (Netherlands)

    Maddy, D.; Schreve, D.; Demir, T.; Veldkamp, A.; Wijbrans, J.R.; Gorp, van W.; Hinsbergen, van D.J.J.; Dekkers, M.J.; Scaife, R.; Schoorl, J.M.; Stemerdink, C.; Schriek, van der T.

    2015-01-01

    Anatolia lies at the gateway from Asia into Europe and has frequently been favoured as a route for Early Pleistocene hominin dispersal. Although early hominins are known to have occupied Turkey, with numerous finds of Lower Palaeolithic artefacts documented, the chronology of their dispersal has lit

  11. Megadontia, striae periodicity and patterns of enamel secretion in Plio-Pleistocene fossil hominins

    Science.gov (United States)

    Lacruz, Rodrigo S; Dean, M Christopher; Ramirez-Rozzi, Fernando; Bromage, Timothy G

    2008-01-01

    Early hominins formed large and thick-enamelled cheek-teeth within relatively short growth periods as compared with modern humans. To understand better the developmental basis of this process, we measured daily enamel increments, or cross striations, in 17 molars of Plio-Pleistocene hominins representing seven different species, including specimens attributed to early Homo. Our results show considerable variation across species, although all specimens conformed to the known pattern characterised by greater values in outer than inner enamel, and greater cuspal than cervical values. We then compared our results with the megadontia index, which represents tooth size in relation to body mass, for each species to assess the effect of daily growth rates on tooth size. Our results indicate that larger toothed (megadont) taxa display higher rates or faster forming enamel than smaller toothed hominins. By forming enamel quickly, large tooth crowns were able to develop within the constraints of shorter growth periods. Besides daily increments, many animals express long-period markings (striae of Retzius) in their enamel. We report periodicity values (number of cross striations between adjacent striae) in 14 new specimens of Australopithecus afarensis, Paranthropus aethiopicus, Paranthropus boisei, Homo habilis, Homo rudolfensis and Homo erectus, and show that long-period striae express a strong association with male and average male–female body mass. Our results for Plio-Pleistocene hominins show that the biological rhythms that give rise to long-period striae are encompassed within the range of variation known for modern humans, but show a lower mean and modal value of 7 days in australopithecines. In our sample of early Homo, mean and modal periodicity values were 8 days, and therefore similar to modern humans. These new data on daily rates of enamel formation and periodicity provide a better framework to interpret surface manifestations of internal growth markings on

  12. Megadontia, striae periodicity and patterns of enamel secretion in Plio-Pleistocene fossil hominins.

    Science.gov (United States)

    Lacruz, Rodrigo S; Dean, M Christopher; Ramirez-Rozzi, Fernando; Bromage, Timothy G

    2008-08-01

    Early hominins formed large and thick-enamelled cheek-teeth within relatively short growth periods as compared with modern humans. To understand better the developmental basis of this process, we measured daily enamel increments, or cross striations, in 17 molars of Plio-Pleistocene hominins representing seven different species, including specimens attributed to early Homo. Our results show considerable variation across species, although all specimens conformed to the known pattern characterised by greater values in outer than inner enamel, and greater cuspal than cervical values. We then compared our results with the megadontia index, which represents tooth size in relation to body mass, for each species to assess the effect of daily growth rates on tooth size. Our results indicate that larger toothed (megadont) taxa display higher rates or faster forming enamel than smaller toothed hominins. By forming enamel quickly, large tooth crowns were able to develop within the constraints of shorter growth periods. Besides daily increments, many animals express long-period markings (striae of Retzius) in their enamel. We report periodicity values (number of cross striations between adjacent striae) in 14 new specimens of Australopithecus afarensis, Paranthropus aethiopicus, Paranthropus boisei, Homo habilis, Homo rudolfensis and Homo erectus, and show that long-period striae express a strong association with male and average male-female body mass. Our results for Plio-Pleistocene hominins show that the biological rhythms that give rise to long-period striae are encompassed within the range of variation known for modern humans, but show a lower mean and modal value of 7 days in australopithecines. In our sample of early Homo, mean and modal periodicity values were 8 days, and therefore similar to modern humans. These new data on daily rates of enamel formation and periodicity provide a better framework to interpret surface manifestations of internal growth markings on

  13. Archeological insights into hominin cognitive evolution.

    Science.gov (United States)

    Wynn, Thomas; Coolidge, Frederick L

    2016-07-01

    How did the human mind evolve? How and when did we come to think in the ways we do? The last thirty years have seen an explosion in research related to the brain and cognition. This research has encompassed a range of biological and social sciences, from epigenetics and cognitive neuroscience to social and developmental psychology. Following naturally on this efflorescence has been a heightened interest in the evolution of the brain and cognition. Evolutionary scholars, including paleoanthropologists, have deployed the standard array of evolutionary methods. Ethological and experimental evidence has added significantly to our understanding of nonhuman brains and cognition, especially those of nonhuman primates. Studies of fossil brains through endocasts and sophisticated imaging techniques have revealed evolutionary changes in gross neural anatomy. Psychologists have also gotten into the game through application of reverse engineering to experimentally based descriptions of cognitive functions. For hominin evolution, there is another rich source of evidence of cognition, the archeological record. Using the methods of Paleolithic archeology and the theories and models of cognitive science, evolutionary cognitive archeology documents developments in the hominin mind that would otherwise be inaccessible. PMID:27519459

  14. Archeological insights into hominin cognitive evolution.

    Science.gov (United States)

    Wynn, Thomas; Coolidge, Frederick L

    2016-07-01

    How did the human mind evolve? How and when did we come to think in the ways we do? The last thirty years have seen an explosion in research related to the brain and cognition. This research has encompassed a range of biological and social sciences, from epigenetics and cognitive neuroscience to social and developmental psychology. Following naturally on this efflorescence has been a heightened interest in the evolution of the brain and cognition. Evolutionary scholars, including paleoanthropologists, have deployed the standard array of evolutionary methods. Ethological and experimental evidence has added significantly to our understanding of nonhuman brains and cognition, especially those of nonhuman primates. Studies of fossil brains through endocasts and sophisticated imaging techniques have revealed evolutionary changes in gross neural anatomy. Psychologists have also gotten into the game through application of reverse engineering to experimentally based descriptions of cognitive functions. For hominin evolution, there is another rich source of evidence of cognition, the archeological record. Using the methods of Paleolithic archeology and the theories and models of cognitive science, evolutionary cognitive archeology documents developments in the hominin mind that would otherwise be inaccessible.

  15. Earliest hominin occupation of Sulawesi, Indonesia

    Science.gov (United States)

    van den Bergh, Gerrit D.; Li, Bo; Brumm, Adam; Grün, Rainer; Yurnaldi, Dida; Moore, Mark W.; Kurniawan, Iwan; Setiawan, Ruly; Aziz, Fachroel; Roberts, Richard G.; Suyono; Storey, Michael; Setiabudi, Erick; Morwood, Michael J.

    2016-01-01

    Sulawesi is the largest and oldest island within Wallacea, a vast zone of oceanic islands separating continental Asia from the Pleistocene landmass of Australia and Papua (Sahul). By one million years ago an unknown hominin lineage had colonized Flores immediately to the south, and by about 50 thousand years ago, modern humans (Homo sapiens) had crossed to Sahul. On the basis of position, oceanic currents and biogeographical context, Sulawesi probably played a pivotal part in these dispersals. Uranium-series dating of speleothem deposits associated with rock art in the limestone karst region of Maros in southwest Sulawesi has revealed that humans were living on the island at least 40 thousand years ago (ref. 5). Here we report new excavations at Talepu in the Walanae Basin northeast of Maros, where in situ stone artefacts associated with fossil remains of megafauna (Bubalus sp., Stegodon and Celebochoerus) have been recovered from stratified deposits that accumulated from before 200 thousand years ago until about 100 thousand years ago. Our findings suggest that Sulawesi, like Flores, was host to a long-established population of archaic hominins, the ancestral origins and taxonomic status of which remain elusive.

  16. New hominin fossils from Kanapoi, Kenya, and the mosaic evolution of canine teeth in early hominins

    Directory of Open Access Journals (Sweden)

    J. Michael Plavcan

    2012-03-01

    Full Text Available Whilst reduced size, altered shape and diminished sexual dimorphism of the canine–premolar complex are diagnostic features of the hominin clade, little is known about the rate and timing of changes in canine size and shape in early hominins. The earliest Australopithecus, Australopithecus anamensis, had canine crowns similar in size to those of its descendant Australopithecus afarensis, but a single large root alveolus has suggested that this species may have had larger and more dimorphic canines than previously recognised. Here we present three new associated dentitions attributed to A. anamensis, recently recovered from the type site of Kanapoi, Kenya, that provide evidence of canine evolution in early Australopithecus. These fossils include the largest mandibular canine root in the hominin fossil record. We demonstrate that, although canine crown height did not differ between these species, A. anamensis had larger and more dimorphic roots, more like those of extant great apes and Ardipithecus ramidus, than those of A. afarensis. The canine and premolar occlusal shapes of A. anamensis also resemble those of Ar. ramidus, and are intermediary between extant great apes and A. afarensis. A. afarensis achieved Homo-like maxillary crown basal proportions without a reduction in crown height. Thus, canine crown size and dimorphism remained stable during the early evolution of Australopithecus, but mandibular root dimensions changed only later within the A. anamensis–afarensis lineage, coincident with morphological changes in the canine–premolar complex. These observations suggest that selection on canine tooth crown height, shape and root dimensions was not coupled in early hominin evolution, and was not part of an integrated adaptive package.

  17. Early hominin diet included diverse terrestrial and aquatic animals 1.95 Ma in East Turkana, Kenya.

    Science.gov (United States)

    Braun, David R; Harris, John W K; Levin, Naomi E; McCoy, Jack T; Herries, Andy I R; Bamford, Marion K; Bishop, Laura C; Richmond, Brian G; Kibunjia, Mzalendo

    2010-06-01

    The manufacture of stone tools and their use to access animal tissues by Pliocene hominins marks the origin of a key adaptation in human evolutionary history. Here we report an in situ archaeological assemblage from the Koobi Fora Formation in northern Kenya that provides a unique combination of faunal remains, some with direct evidence of butchery, and Oldowan artifacts, which are well dated to 1.95 Ma. This site provides the oldest in situ evidence that hominins, predating Homo erectus, enjoyed access to carcasses of terrestrial and aquatic animals that they butchered in a well-watered habitat. It also provides the earliest definitive evidence of the incorporation into the hominin diet of various aquatic animals including turtles, crocodiles, and fish, which are rich sources of specific nutrients needed in human brain growth. The evidence here shows that these critical brain-growth compounds were part of the diets of hominins before the appearance of Homo ergaster/erectus and could have played an important role in the evolution of larger brains in the early history of our lineage. PMID:20534571

  18. Hominin interbreeding and the evolution of human variation

    OpenAIRE

    Ko, Kwang Hyun

    2016-01-01

    Mitochondrial Eve confirms the “out of Africa” theory, but the evidence also supports interbreeding between Homo sapiens and other hominins: Neanderthals, Denisovans, and Homo heidelbergensis. This article explains how interbreeding between early H. sapiens and archaic hominins occurred. The availability of edible insects in East Asia aided the spread of the unaggressive, highly cooperative Neanderthals, who interbred with H. sapiens in Asia, resulting in a higher admixture of Neanderthal DNA...

  19. A geometric morphometric analysis of hominin upper first molar shape

    OpenAIRE

    Gómez Robles, Aida; Martinón Torres, María; Bermúdez de Castro, José María; Margvelashvili, A.; Bastir, Markus; Arsuaga, Juan Luis; Pérez Pérez, Alejandro; Estebaranz, Ferran; Martínez, Laura M.

    2007-01-01

    Recent studies have revealed interesting differences in upper first molar morphology across the hominin fossil record, particularly significant between H. sapiens and H. neanderthalensis. Usually these analyses have been performed by means of classic morphometric methods, including the measurement of relative cusp areas or the angles defined between cusps. Although these studies have provided valuable information for the morphological characterization of some hominin species, we beli...

  20. Early hominin speciation at the Plio/Pleistocene transition.

    Science.gov (United States)

    Cameron, D W

    2003-01-01

    Over the last half-decade or so, there has been an explosion in the recognition of hominin genera and species. We now have the late Miocene genera Orrorin and Sahelanthropus, the mid Pliocene genus Kenyanthropus, three new Pliocene species of Australopithecus (A. anamensis, A. garhi and A. bahrelghazali) and a sub species of Ardipithecus (Ar. r. kadabba) to contend with. Excepting also the more traditional species allocated to Paranthropus, Australopithecus and early Homo we are approaching around 15 species over 5 million years (excluding hominin evolution over the last one million years). Can such a large number of hominin species be justified? An examination of extant hominid (Gorilla gorilla, Pan troglodytes, and Pan paniscus) anatomical variability indicates that the range of fossil hominin variability supports the recognition of this large number of fossil species. It is also shown that not all hominins are directly related to the emergence of early Homo and as such have become extinct. Indeed the traditional australopithecine species 'A'. anamensis, 'A'. afarensis and 'A'. garhi are considered here to belong to a distinct genus Praeanthropus. They are also argued not be hominins, but rather an as yet undefined hominid group from which the more derived hominins evolved. The first hominin is represented by A. africanus or a hominin very much like it. The Paranthropus clade is defined by a derived heterochronic condition of peramorphosis, associated with sequential progenesis (contraction of successive growth stages) in brain and dental development, but a mixture of peramorphic and paedomorphic features in its craniofacial anatomy. Conversely, Kenyanthropus and Homo both share a pattern of peramorphosis, associated with sequential hypermorphosis (prolongation of successive growth stages) in brain development, and paedomorphosis processes in cranial, facial and dental development. This suggests, that these two clades share an important synapomorphy not

  1. Palaeohydrological corridors for hominin dispersals in the Middle East ∼250-70,000 years ago

    Science.gov (United States)

    Breeze, Paul S.; Groucutt, Huw S.; Drake, Nick A.; White, Tom S.; Jennings, Richard P.; Petraglia, Michael D.

    2016-07-01

    The timing and extent of palaeoenvironmental connections between northeast Africa, the Levant and the Arabian Peninsula during the Middle and Late Pleistocene are critical to debates surrounding dispersals of hominins, including movements of Homo sapiens out of Africa. Although there is evidence that synchronous episodes of climatic amelioration during the late Middle and Late Pleistocene may have allowed connections to form between northern Africa and western Asia, a number of palaeoclimate models indicate the continued existence of an arid barrier between northern Arabia and the Levant. Here we evaluate the palaeoenvironmental setting for hominin dispersals between, and within, northeast Africa and southwest Asia during Marine Isotope Stages (MIS) 7-5 using reconstructions of surface freshwater availability as an environmental proxy. We use remotely sensed data to map palaeohydrological features (lakes, wetlands and rivers) across the presently hyper-arid areas of northern Arabia and surrounding regions, integrating these results with palaeoclimate models, palaeoenvironmental proxy data and absolute dating to determine when these features were active. Our analyses suggest limited potential for dispersals during MIS 7 and 6, but indicate the formation of a palaeohydrological corridor (the 'Tabuk Corridor') between the Levant and the Arabian interior during the MIS 6-5e glacial-interglacial transition and during MIS 5e. A recurrence of this corridor, following a slightly different route, also occurred during MIS 5a. These palaeohydrological and terrestrial data can be used to establish when proposed routes for hominin dispersals became viable. Furthermore, the distribution of Arabian archaeological sites with affinities to Levantine assemblages, some of which are associated with Homo sapiens fossils, and the relative density of Middle Palaeolithic assemblages within the Tabuk Corridor, are consistent with it being utilised for dispersals at various times.

  2. Stepping Out: Investigating Hominin Dispersals Within a Palaeoclimatic Framework.

    Science.gov (United States)

    Hughes, J. K.; Valdes, P.; Mithen, S.; Sellwood, B.

    2004-12-01

    At present the number of well dated early hominin sites (Homo ergaster, Homo erectus etc.) is insufficient to reconstruct the patterns of dispersal and occupation within the Old World. Many questions still remain therefore about the dominant factors influencing the patterns of arrival and their timing. In order to understand these dispersal patterns a modelling framework has been developed, for the late Pliocene, early Pleistocene period (2Ma to 0.5Ma). This time period corresponds to what is believed to be the first expansion of hominin out of Africa. The framework integrates data sets of vegetation patterns, land mass configuration, climate, and orography. In order to estimate vegetation patterns during the simulation a simple method has been developed to combine benthic foraminifera ocean core data with snapshot climate model simulations. The climate estimate produced can then be used to simulate global vegetation patterns using a global vegetation model. The dispersal of hominin is then simulated and the predicted dispersal patterns compared to existing hominin finds.

  3. Interpreting sulci on hominin endocasts: old hypotheses and new findings.

    Science.gov (United States)

    Falk, Dean

    2014-01-01

    Paleoneurologists analyze internal casts (endocasts) of fossilized braincases, which provide information about the size, shape and, to a limited degree, sulcal patterns reproduced from impressions left by the surface of the brain. When interpreted in light of comparative data from the brains of living apes and humans, sulcal patterns reproduced on hominin endocasts provide important information for studying the evolution of the cerebral cortex and cognition in human ancestors. Here, new evidence is discussed for the evolution of sulcal patterns associated with cortical reorganization in three parts of the hominin brain: (1) the parietotemporo-occipital association cortex, (2) Broca's speech area, and (3) dorsolateral prefrontal association cortex. Of the three regions, the evidence regarding the last is the clearest. Compared to great apes, Australopithecus endocasts reproduce a clear middle frontal sulcus in the dorsolateral prefrontal cortex that is derived toward the human condition. This finding is consistent with data from comparative cytoarchitectural studies of ape and human brains as well as shape analyses of australopithecine endocasts. The comparative and direct evidence for all three regions suggests that hominin brain reorganization was underway by at least the time of Australopithecus africanus (~2.5 to 3.0 mya), despite the ape-sized brains of these hominins, and that it entailed expansion of both rostral and caudal association cortices. PMID:24822043

  4. Interpreting sulci on hominin endocasts: Old hypotheses and new findings

    Directory of Open Access Journals (Sweden)

    Dean eFalk

    2014-05-01

    Full Text Available Paleoneurologists analyze internal casts (endocasts of fossilized braincases, which provide information about the size, shape and, to a limited degree, sulcal patterns reproduced from impressions left by the surface of the brain. When interpreted in light of comparative data from the brains of living apes and humans, sulcal patterns reproduced on hominin endocasts provide important information for studying the evolution of the cerebral cortex and cognition in human ancestors. Here, new evidence is discussed for the evolution of sulcal patterns associated with cortical reorganization in three parts of the hominin brain: (1 the parietotemporo-occipital association cortex, (2 Broca’s speech area, and (3 dorsolateral prefrontal association cortex. Of the three regions, the evidence regarding the last is the clearest. Compared to great apes, Australopithecus endocasts reproduce a clear middle frontal sulcus in the dorsolateral prefrontal cortex that is derived toward the human condition. This finding is consistent with data from comparative cytoarchitectural studies of ape and human brains as well as shape analyses of australopithecine endocasts. The comparative and direct evidence for all three regions suggests that hominin brain reorganization was underway by at least the time of Australopithecus africanus (~ 2.5 to 3.0 mya, despite the ape-sized brains of these hominins, and that it entailed expansion of both rostral and caudal association cortices.

  5. Geometric morphometric analysis of the early Pleistocene hominin teeth from Jianshi,Hubei Province,China

    Institute of Scientific and Technical Information of China (English)

    Ronald; CLARKE

    2010-01-01

    Although the early Pleistocene hominin fossils found in East Asia continent are widely recognized as the earliest hominins migrated from Africa, debates remain on the morphology and taxonomy of these fossils. In this study, dental crown shape of the three early Pleistocene hominin teeth (P3, M1, and M1) found in Jianshi, Hubei Province of China was analyzed by means of geometric morphometrics. The comparative samples of fossil hominins from Africa, Asia, and Europe as well as those of modern humans (N=257) were used. The results indicate that the contour, asymmetry, and cusp patterns of these three types of teeth differ obviously between the fossil hominins and modern humans. The crown shape of P3 in most fossil hominins including Australopithecus, African early Homo, and Asian Pleistocene hominins are asymmetric with their crown occlusal contours long and curving elliptic-shaped. The occlusal contour of the fossil hominin M1 is symmetric and rectangle-shaped with no marked cusp protrusion. The crown shape of fossil M1 is characterized by asymmetric contour with slightly projected metaconid and hypoconid. On the contrary, in modern Chinese and some European late Pleistocene hominins, the crowns of P3s show symmetric contours with buccal side wider than lingual side; the crown shape of M1 is asymmetric with lingual cusp distalplaced, especially for hypoconid; the M1 has symmetric and round crown contour. Our study reveals that Australopithecus has wide variations in its crown shape, whereas these dental morphospaces of Asian hominins are closely placed. The crown contour, symmetry, and cusp patterns of these three teeth of Jianshi hominin resemble those of Asian early and middle Pleistocene hominins. No marked difference in dental crown shape is shown between the Jianshi hominin and other Chinese Homo erectus, and there is also no evidence in support of the Jianshi hominin’s closeness to Australopithecus and African early Homo members.

  6. New geochronological, paleoclimatological, and archaeological data from the Narmada Valley hominin locality, central India.

    Science.gov (United States)

    Patnaik, Rajeev; Chauhan, Parth R; Rao, M R; Blackwell, B A B; Skinner, A R; Sahni, Ashok; Chauhan, M S; Khan, H S

    2009-02-01

    The oldest known fossil hominin in southern Asia was recovered from Hathnora in the Narmada Basin, central India in the early 1980's. Its age and taxonomic affinities, however, have remained uncertain. Current estimates place its maximum age at >236ka, but not likely older than the early middle Pleistocene. The calvaria, however, could be considerably younger. We report recent fieldwork at Hathnora and associated Quaternary type-sections that has provided new geological and archaeological insights. The portion of the exposed 'Boulder Conglomerate' within the Surajkund Formation, which forms a relict terrace and has yielded the hominin fossils, contains reworked and stylistically mixed lithic artifacts and temporally mixed fauna. Three mammalian teeth stratigraphically associated with the hominin calvaria were dated by standard electron spin resonance (ESR). Assuming an early uranium uptake (EU) model for the teeth, two samples collected from the reworked surface deposit averaged 49+/-1ka (83+/-2ka, assuming linear uptake [LU]; 196+/-7ka assuming recent uptake [RU]). Another sample recovered from freshly exposed, crossbedded gravels averaged 93+/-5ka (EU), 162+/-8ka (LU) or 407+/-21ka (RU). While linear uptake models usually provide the most accurate ages for this environment and time range, the EU ages represent the minimum possible age for fossils in the deposit. Regardless, the fossils are clearly reworked and temporally mixed. Therefore, the current data constrains the minimum possible age for the calvaria to 49+/-1ka, although it could have been reworked and deposited into the Hathnora deposit any time after 160ka (given the LU uptake ages) or earlier (given the RU ages). At Hathnora, carbonaceous clay, bivalve shells, and a bovid tooth recovered from layers belonging to the overlying Baneta Formation have yielded (14)C ages of 35.66+/-2.54cal ky BP, 24.28+/-0.39cal ky BP, and 13.15+/-0.34ky BP, respectively. Additional surveys yielded numerous lithics and

  7. Hominin-bearing caves and landscape dynamics in the Cradle of Humankind, South Africa

    Science.gov (United States)

    Dirks, Paul H. G. M.; Berger, Lee R.

    2013-02-01

    This paper provides constraints on the evolution of the landscape in the Cradle of Humankind (CoH), UNESCO World Heritage Site, South Africa, since the Pliocene. The aim is to better understand the distribution of hominin fossils in the CoH, and determine links between tectonic processes controlling the landscape and the evolution and distribution of hominins occupying that landscape. The paper is focused on a detailed reconstruction of the landscape through time in the Grootvleispruit catchment, which contains the highly significant fossil site of Malapa and the remains of the hominin species Australopithicus sediba. In the past 4 My the landscape in the CoH has undergone major changes in its physical appearance as a result of river incision, which degraded older African planation surfaces, and accommodated denudation of cover rocks (including Karoo sediments and various sil- and ferricretes) to expose dolomite with caves in which fossils collected. Differentially weathered chert breccia dykes, calibrated with 10Be exposure ages, are used to estimate erosion patterns of the landscape across the CoH. In this manner it is shown that 2 My ago Malapa cave was ˜50 m deep, and Gladysvale cave was first exposed; i.e. landscape reconstructions can provide estimates for the time of opening of cave systems that trapped hominin and other fossils. Within the region, cave formation was influenced by lithological, layer-parallel controls interacting with cross-cutting fracture systems of Paleoproterozoic origin, and a NW-SE directed extensional far-field stress at a time when the African erosion surface was still intact, and elevations were probably lower. Cave geometries vary in a systematic manner across the landscape, with deep caves on the plateau and cave erosion remnants in valleys. Most caves formed to similar depths of 1400-1420 mamsl across much of the CoH, indicating that caves no longer deepened once Pliocene uplift and incision occurred, but acted as passive

  8. Oldowan hominin behavior and ecology at Kanjera South,Kenya.

    Science.gov (United States)

    Plummer, Thomas; Bishop, Laura

    2016-06-20

    The Early Stone Age archaeological record does not become persistent and widespread until approximately 2.0-1.7 million years ago, when Oldowan sites spread across Africa and ultimately into Eurasia. However, good records of hominin behavior from this important time interval are uncommon. Here we describe recent findings from the two million year old Oldowan site of Kanjera South, on the Homa Peninsula of southwestern Kenya. Kanjera South is the oldest Oldowan site with large assemblages of stone artifacts and well-preserved archaeological fauna. Our research indicates that hominin activities were situated in an open habitat within a grassland dominated ecosystem, the first documentation of an archaeological site in such an open setting. Hominins selectively collected and transported stone materials (30% of the lithic assemblage) over longer distances (at least 10 km) than is typical for the Oldowan, reflecting their preference for hard, easily-flaked lithologies unavailable on the northern half of the Homa Peninsula. They deployed different technological strategies to more intensively utilize these hard, non-local raw materials. Artifacts were used for a variety of tasks, including butchering small antelopes probably obtained by hunting, working wood, working soft plant material, and processing underground storage organs. These data suggest that the Kanjera hominins utilized a technological system that allowed them to extract nutrient dense animal and plant foods from their environment. This shift towards the acquisition of nutritious, hard-to-acquire foods in packets large enough to be shared may have facilitated brain and body size expansion in the genus Homo. PMID:27081012

  9. Hominin interbreeding and the evolution of human variation.

    Science.gov (United States)

    Ko, Kwang Hyun

    2016-12-01

    Mitochondrial Eve confirms the "out of Africa" theory, but the evidence also supports interbreeding between Homo sapiens and other hominins: Neanderthals, Denisovans, and Homo heidelbergensis. This article explains how interbreeding between early H. sapiens and archaic hominins occurred. The availability of edible insects in East Asia aided the spread of the unaggressive, highly cooperative Neanderthals, who interbred with H. sapiens in Asia, resulting in a higher admixture of Neanderthal DNA in East Asian populations. Geographical variation in degree of interbreeding between H. sapiens and Neanderthals likely contributed to neurological and behavioral differences in modern humans. Similarly, people with Denisovan genetic admixture were better able to dwell in mountainous regions, allowing their genetic legacy to cross the Himalayas and persist in Southeast Asian and Oceanian H. sapiens. In the Sub-Saharan region, unaffected by Denisovan or Neanderthal interbreeding, H. sapiens interbred with H. heidelbergensis, because high humidity militated against fire-making and allowed the survival of these non-fire-making hominins. PMID:27429943

  10. Carnivore activity in the Sima de los Huesos (Atapuerca, Spain) hominin sample

    Science.gov (United States)

    Sala, Nohemi; Arsuaga, Juan Luis; Martínez, Ignacio; Gracia-Téllez, Ana

    2014-08-01

    The Sima de los Huesos (SH) site is the largest accumulation of human remains from the Middle Pleistocene known to date. Studies in the last two decades have proposed different hypotheses to explain carnivore activity in the SH human sample. This study provides new data in order to test these different interpretations, and therefore to understand the role of the carnivores in site formation at SH. Carnivores are usually not the origin of large accumulations of hominin fossils in the Eurasian record. The results show that marks of carnivore activity in the SH sample appear very infrequently, which we interpret as indicating that carnivore activity was very sporadic at the site. This is in stark contrast with previous studies. The comparison of bone modification patterns at SH to actualistic carnivore data allows us to suggest that bears were likely to have been the carnivore responsible for the modification observed on both human and bear fossils.

  11. Measure, Then Show: Grasping Human Evolution Through an Inquiry-Based, Data-driven Hominin Skulls Lab.

    Science.gov (United States)

    Bayer, Chris N; Luberda, Michael

    2016-01-01

    Incomprehension and denial of the theory of evolution among high school students has been observed to also occur when teachers are not equipped to deliver a compelling case also for human evolution based on fossil evidence. This paper assesses the outcomes of a novel inquiry-based paleoanthropology lab teaching human evolution to high-school students. The inquiry-based Be a Paleoanthropologist for a Day lab placed a dozen hominin skulls into the hands of high-school students. Upon measuring three variables of human evolution, students explain what they have observed and discuss findings. In the 2013/14 school year, 11 biology classes in 7 schools in the Greater New Orleans area participated in this lab. The interviewed teacher cohort unanimously agreed that the lab featuring hominin skull replicas and stimulating student inquiry was a pedagogically excellent method of delivering the subject of human evolution. First, the lab's learning path of transforming facts to data, information to knowledge, and knowledge to acceptance empowered students to themselves execute part of the science that underpins our understanding of deep time hominin evolution. Second, although challenging, the hands-on format of the lab was accessible to high-school students, most of whom were readily able to engage the lab's scientific process. Third, the lab's exciting and compelling pedagogy unlocked higher order thinking skills, effectively activating the cognitive, psychomotor and affected learning domains as defined in Bloom's taxonomy. Lastly, the lab afforded students a formative experience with a high degree of retention and epistemic depth. Further study is warranted to gauge the degree of these effects. PMID:27513927

  12. Age and context of the oldest known hominin fossils from Flores

    DEFF Research Database (Denmark)

    Brumm, Adam; Van Den Bergh, Gerrit D.; Storey, Michael;

    2016-01-01

    Recent excavations at the early Middle Pleistocene site of Mata Menge in the So'a Basin of central Flores, Indonesia, have yielded hominin fossils attributed to a population ancestral to Late Pleistocene Homo floresiensis. Here we describe the age and context of the Mata Menge hominin specimens...

  13. Subocclusal dental morphology of sahelanthropus tchadensis and the evolution of teeth in hominins.

    Science.gov (United States)

    Emonet, Edouard-Georges; Andossa, Likius; Taïsso Mackaye, Hassane; Brunet, Michel

    2014-01-01

    The evolution of the teeth in hominins is characterized by, among other characters, major changes in root morphology. However, little is known of the evolution from a plesiomorphic, ape-like root morphology to the crown hominin morphology. Here we present a study of the root morphology of the Miocene Chadian hominin Sahelanthropus tchadensis and its comparison to other hominins. The morphology of the whole lower dentition (I1 -M3 ) was investigated and described. The comparison with the species Ardipithecus kaddaba and Ardipithecus ramidus indicates a global homogeneity of root morphology in early hominins. This morphology, characterized notably by a reduction of the size and number of the roots of premolars, is a composite between an ape-like morphology and the later hominin morphology. Trends for root evolution in hominins are proposed, including the transition from a basal hominoid to extant Homo sapiens. This study also illustrates the low association between the evolution of tooth root morphology and the evolution of crowns in hominins.

  14. Taxonomic and functional implications of mandibular scaling in early hominins.

    Science.gov (United States)

    Wood, B; Aiello, L C

    1998-04-01

    Body mass estimates for fossil hominin taxa can be obtained from suitable postcranial and cranial variables. However, the nature of the taphonomic processes that winnow the mammalian fossil record are such that these data are usually only available for the minority of the specimens that comprise the hypodigm of a species. This study has investigated the link between species mean body mass and the height and width of the mandibular corpus in a core sample of 23 species of extant simians. The slopes of the least-squares regressions for the whole sample and for the hominoid subset are similar. However, the intercepts differ so that for a given body mass, a hominoid will generally have a smaller mandible than a generalized simian. The same mandibular measurements were taken on 75 early hominin mandibles assigned to eight species groups. When mandibular corpus height- and width-derived estimates of body mass for the fossil taxa were compared with available postcranial and cranial-derived body mass estimates, the eight early hominin species sort into four groups. The first, which includes A. afarensis and A. africanus, has mandibles which follow a "generalized simian" scaling relationship. The second group, which comprises the two "robust" australopithecine species, P. boisei and P. robustus, has mandibles which scale with body mass as if they are "super-simians," for they have substantially larger mandibles than a simian with the same body mass. The two "early Homo" species, H. habilis sensu stricto and H. rudolfensis, make up the third group. It has mandibular scaling relationships that are intermediate between that of the comparative simian sample and that of the hominoid subsample. The last of the four groups comprises H. ergaster and H. erectus; their mandibles scale with body mass as if they were hominoids, so that of the four groups they have the smallest mandibles per unit body mass. These results are related to comparable information about relative tooth size

  15. Reading the landscape: Legible environments and hominin dispersals.

    Science.gov (United States)

    Guiducci, Dario; Burke, Ariane

    2016-05-01

    Wayfinding, or the ability to plan and navigate a course over the landscape, is a subject of investigation in geography, neurophysiology, psychology, urban planning, and landscape design. With the prevalence of GPS-assisted navigation systems, or "wayfinders," computer scientists are also increasingly interested in understanding how people plan their movements and guide others. However, the importance of wayfinding as a process that regulates human mobility has only recently been incorporated into archeological research design. Hominin groups were able to disperse widely during the course of prehistory. The scope of these dispersals speaks to the innate navigation abilities of hominins. Their long-term success must have depended on an ability to communicate spatial information effectively. Here, we consider the extent to which some landscapes may have been more conducive to wayfinding than others. We also describe a tool we have created for quantifying landscape legibility (sensu Gollege), a complex and under-explored concept in archeology, with a view to investigating the impact of landscape structure on human wayfinding and thus, patterns of dispersal during prehistory. To this end, we have developed a method for quantifying legibility using a Geographic Information System (GIS) and apply it to a test case in prehistoric Iberia.

  16. Reading the landscape: Legible environments and hominin dispersals.

    Science.gov (United States)

    Guiducci, Dario; Burke, Ariane

    2016-05-01

    Wayfinding, or the ability to plan and navigate a course over the landscape, is a subject of investigation in geography, neurophysiology, psychology, urban planning, and landscape design. With the prevalence of GPS-assisted navigation systems, or "wayfinders," computer scientists are also increasingly interested in understanding how people plan their movements and guide others. However, the importance of wayfinding as a process that regulates human mobility has only recently been incorporated into archeological research design. Hominin groups were able to disperse widely during the course of prehistory. The scope of these dispersals speaks to the innate navigation abilities of hominins. Their long-term success must have depended on an ability to communicate spatial information effectively. Here, we consider the extent to which some landscapes may have been more conducive to wayfinding than others. We also describe a tool we have created for quantifying landscape legibility (sensu Gollege), a complex and under-explored concept in archeology, with a view to investigating the impact of landscape structure on human wayfinding and thus, patterns of dispersal during prehistory. To this end, we have developed a method for quantifying legibility using a Geographic Information System (GIS) and apply it to a test case in prehistoric Iberia. PMID:27312185

  17. Homo floresiensis and the evolution of the hominin shoulder.

    Science.gov (United States)

    Larson, Susan G; Jungers, William L; Morwood, Michael J; Sutikna, Thomas; Jatmiko; Saptomo, E Wahyu; Due, Rokus Awe; Djubiantono, Tony

    2007-12-01

    The holotype of Homo floresiensis, diminutive hominins with tiny brains living until 12,000 years ago on the island of Flores, is a partial skeleton (LB1) that includes a partial clavicle (LB1/5) and a nearly complete right humerus (LB1/50). Although the humerus appears fairly modern in most regards, it is remarkable in displaying only 110 degrees of humeral torsion, well below modern human average values. Assuming a modern human shoulder configuration, such a low degree of humeral torsion would result in a lateral set to the elbow. Such an elbow joint would function more nearly in a frontal than in a sagittal plane, and this is certainly not what anyone would have predicted for a tool-making Pleistocene hominin. We argue that Homo floresiensis probably did not have a modern human shoulder configuration: the clavicle was relatively short, and we suggest that the scapula was more protracted, resulting in a glenoid fossa that faced anteriorly rather than laterally. A posteriorly directed humeral head was therefore appropriate for maintaining a normally functioning elbow joint. Similar morphology in the Homo erectus Nariokotome boy (KNM-WT 15000) suggests that this shoulder configuration may represent a transitional stage in pectoral girdle evolution in the human lineage. PMID:17692894

  18. A mitochondrial genome sequence of a hominin from Sima de los Huesos.

    Science.gov (United States)

    Meyer, Matthias; Fu, Qiaomei; Aximu-Petri, Ayinuer; Glocke, Isabelle; Nickel, Birgit; Arsuaga, Juan-Luis; Martínez, Ignacio; Gracia, Ana; de Castro, José María Bermúdez; Carbonell, Eudald; Pääbo, Svante

    2014-01-16

    Excavations of a complex of caves in the Sierra de Atapuerca in northern Spain have unearthed hominin fossils that range in age from the early Pleistocene to the Holocene. One of these sites, the 'Sima de los Huesos' ('pit of bones'), has yielded the world's largest assemblage of Middle Pleistocene hominin fossils, consisting of at least 28 individuals dated to over 300,000 years ago. The skeletal remains share a number of morphological features with fossils classified as Homo heidelbergensis and also display distinct Neanderthal-derived traits. Here we determine an almost complete mitochondrial genome sequence of a hominin from Sima de los Huesos and show that it is closely related to the lineage leading to mitochondrial genomes of Denisovans, an eastern Eurasian sister group to Neanderthals. Our results pave the way for DNA research on hominins from the Middle Pleistocene. PMID:24305051

  19. Luminescence dating and palaeomagnetic age constraint on hominins from Sima de los Huesos, Atapuerca, Spain

    OpenAIRE

    Amold, Lee J.; Demuro, Martina; Parés, Josep M.; Arsuaga, Juan Luis; Aramburr, Arantza; Bermúdez de Castro, José María; Carbonell i Roura, Eudald

    2014-01-01

    Establishing a reliable chronology on the extensive hominin remains at Sima de los Huesos is critical for an improved understanding of the complex evolutionary histories and phylogenetic relationships of the European Middle Pleistocene hominin record. In this study, we use a combination of ‘extended-range’ luminescence dating techniques and palaeomagnetism to provide new age constraint on sedimentary infills that are unambiguously associated with the Sima fossil assemblage. Post-i...

  20. Chronostratigraphy of KNM-ER 3733 and other Area 104 hominins from Koobi Fora.

    Science.gov (United States)

    Lepre, Christopher J; Kent, Dennis V

    2015-09-01

    A magnetostratigraphy for ∼ 60 m of Koobi Fora Formation sediment in Area 104 was derived from 46 oriented samples that produced well-resolved characteristic magnetizations from progressive thermal demagnetization. Approximately 59 m below the Morte Tuff, previously dated to ∼ 1.51 Ma (millions of years ago), the Olduvai-Matuyama boundary (∼ 1.78 Ma) was found to be at the level of marker bed A2--inconsistent with the Area 102 type section and thus contrary to fossil dating schemes that utilize temporal equivalence between A2 [104] and A2 [102]. The magnetostratigraphic data, coupled with the Morte Tuff, provide a means to interpolate new ages for marker beds A2 [104] and the White Tuff, as well as multiple Area 104 hominin fossils. Noteworthy is the new date of ∼ 1.63 Ma for KNM-ER 3733, which now implicates KNM-ER 2598 as the sole early African Homo erectus fossil demonstrably older than Dmanisi and Java Homo specimens. Re-dating KNM-ER 3733 creates a ∼ 300-kyr gap at 1.9 to 1.6 Ma in the African fossil record of H. erectus, which might be partially spanned by hand axes recently dated at ∼ 1.76 Ma, if the Acheulian is indeed proprietary to this species. PMID:26190282

  1. Brief communication: Lumbar lordosis in extinct hominins: implications of the pelvic incidence.

    Science.gov (United States)

    Been, Ella; Gómez-Olivencia, Asier; Kramer, Patricia A

    2014-06-01

    Recently, interest has peaked regarding the posture of extinct hominins. Here, we present a new method of reconstructing lordosis angles of extinct hominin specimens based on pelvic morphology, more specifically the orientation of the sacrum in relation to the acetabulum (pelvic incidence). Two regression models based on the correlation between pelvic incidence and lordosis angle in living hominoids have been developed. The mean values of the calculated lordosis angles based on these models are 36°-45° for australopithecines, 45°-47° for Homo erectus, 27°-34° for the Neandertals and the Sima de los Huesos hominins, and 49°-51° for fossil H. sapiens. The newly calculated lordosis values are consistent with previously published values of extinct hominins (Been et al.: Am J Phys Anthropol 147 (2012) 64-77). If the mean values of the present nonhuman hominoids are representative of the pelvic and lumbar morphology of the last common ancestor between humans and nonhuman hominoids, then both pelvic incidence and lordosis angle dramatically increased during hominin evolution from 27° ± 5 to 22° ± 3 (respectively) in nonhuman hominoids to 54° ± 10 and 51° ± 11 in modern humans. This change to a more human-like configuration appeared early in the hominin evolution as the pelvis and spines of both australopithecines and H. erectus show a higher pelvic incidence and lordosis angle than nonhuman hominoids. The Sima de los Huesos hominins and Neandertals show a derived configuration with a low pelvic incidence and lordosis angle. PMID:24615397

  2. Insights into hominin phenotypic and dietary evolution from ancient DNA sequence data.

    Science.gov (United States)

    Perry, George H; Kistler, Logan; Kelaita, Mary A; Sams, Aaron J

    2015-02-01

    Nuclear genome sequence data from Neandertals, Denisovans, and archaic anatomically modern humans can be used to complement our understanding of hominin evolutionary biology and ecology through i) direct inference of archaic hominin phenotypes, ii) indirect inference of those phenotypes by identifying the effects of previously-introgressed alleles still present among modern humans, or iii) determining the evolutionary timing of relevant hominin-specific genetic changes. Here we review and reanalyze published Neandertal and Denisovan genome sequence data to illustrate an example of the third approach. Specifically, we infer the timing of five human gene presence/absence changes that may be related to particular hominin-specific dietary changes and discuss these results in the context of our broader reconstructions of hominin evolutionary ecology. We show that pseudogenizing (gene loss) mutations in the TAS2R62 and TAS2R64 bitter taste receptor genes and the MYH16 masticatory myosin gene occurred after the hominin-chimpanzee divergence but before the divergence of the human and Neandertal/Denisovan lineages. The absence of a functional MYH16 protein may explain our relatively reduced jaw muscles; this gene loss may have followed the adoption of cooking behavior. In contrast, salivary amylase gene (AMY1) duplications were not observed in the Neandertal and Denisovan genomes, suggesting a relatively recent origin for the AMY1 copy number gains that are observed in modern humans. Thus, if earlier hominins were consuming large quantities of starch-rich underground storage organs, as previously hypothesized, then they were likely doing so without the digestive benefits of increased salivary amylase production. Our most surprising result was the observation of a heterozygous mutation in the first codon of the TAS2R38 bitter taste receptor gene in the Neandertal individual, which likely would have resulted in a non-functional protein and inter-individual PTC

  3. Luminescence dating and palaeomagnetic age constraint on hominins from Sima de los Huesos, Atapuerca, Spain.

    Science.gov (United States)

    Arnold, Lee J; Demuro, Martina; Parés, Josep M; Arsuaga, Juan Luis; Aranburu, Arantza; Bermúdez de Castro, José María; Carbonell, Eudald

    2014-02-01

    Establishing a reliable chronology on the extensive hominin remains at Sima de los Huesos is critical for an improved understanding of the complex evolutionary histories and phylogenetic relationships of the European Middle Pleistocene hominin record. In this study, we use a combination of 'extended-range' luminescence dating techniques and palaeomagnetism to provide new age constraint on sedimentary infills that are unambiguously associated with the Sima fossil assemblage. Post-infrared-infrared stimulated luminescence (pIR-IR) dating of K-feldspars and thermally transferred optically stimulated luminescence (TT-OSL) dating of individual quartz grains provide weighted mean ages of 433 ± 15 ka (thousands of years) and 416 ± 19 ka, respectively, for allochthonous sedimentary horizons overlying the hominin-bearing clay breccia. The six replicate luminescence ages obtained for this deposit are reproducible and provide a combined minimum age estimate of 427 ± 12 ka for the underlying hominin fossils. Palaeomagnetic directions for the luminescence dated sediment horizon and underlying fossiliferous clays display exclusively normal polarities. These findings are consistent with the luminescence dating results and confirm that the hominin fossil horizon accumulated during the Brunhes Chron, i.e., within the last 780 ka. The new bracketing age constraint for the Sima hominins is in broad agreement with radiometrically dated Homo heidelbergensis fossil sites, such as Mauer and Arago, and suggests that the split of the H. neanderthalensis and H. sapiens lineages took place during the early Middle Pleistocene. More widespread numerical dating of key Early and Middle Pleistocene fossil sites across Europe is needed to test and refine competing models of hominin evolution. The new luminescence chronologies presented in this study demonstrate the versatility of TT-OSL and pIR-IR techniques and the potential role they could play in helping to refine evolutionary

  4. Locomotion and posture from the common hominoid ancestor to fully modern hominins, with special reference to the last common panin/hominin ancestor.

    Science.gov (United States)

    Crompton, R H; Vereecke, E E; Thorpe, S K S

    2008-04-01

    Based on our knowledge of locomotor biomechanics and ecology we predict the locomotion and posture of the last common ancestors of (a) great and lesser apes and their close fossil relatives (hominoids); (b) chimpanzees, bonobos and modern humans (hominines); and (c) modern humans and their fossil relatives (hominins). We evaluate our propositions against the fossil record in the context of a broader review of evolution of the locomotor system from the earliest hominoids of modern aspect (crown hominoids) to early modern Homo sapiens. While some early East African stem hominoids were pronograde, it appears that the adaptations which best characterize the crown hominoids are orthogrady and an ability to abduct the arm above the shoulder - rather than, as is often thought, manual suspension sensu stricto. At 7-9 Ma (not much earlier than the likely 4-8 Ma divergence date for panins and hominins, see Bradley, 2008) there were crown hominoids in southern Europe which were adapted to moving in an orthograde posture, supported primarily on the hindlimb, in an arboreal, and possibly for Oreopithecus, a terrestrial context. By 7 Ma, Sahelanthropus provides evidence of a Central African hominin, panin or possibly gorilline adapted to orthogrady, and both orthogrady and habitually highly extended postures of the hip are evident in the arboreal East African protohominin Orrorin at 6 Ma. If the traditional idea that hominins passed through a terrestrial 'knuckle-walking' phase is correct, not only does it have to be explained how a quadrupedal gait typified by flexed postures of the hindlimb could have preadapted the body for the hominin acquisition of straight-legged erect bipedality, but we would have to accept a transition from stem-hominoid pronogrady to crown hominoid orthogrady, back again to pronogrady in the African apes and then back to orthogrady in hominins. Hand-assisted arboreal bipedality, which is part of a continuum of orthograde behaviours, is used by modern

  5. Food material properties and early hominin processing techniques.

    Science.gov (United States)

    Zink, Katherine D; Lieberman, Daniel E; Lucas, Peter W

    2014-12-01

    Although early Homo is hypothesized to have used tools more than australopiths to process foods prior to consumption, it is unknown how much the food processing techniques they used altered the material properties of foods, and therefore the masticatory forces they generated, and how well they were able to comminute foods. This study presents experimental data on changes to food material properties caused by mechanical tenderization (pounding with a stone tool) and cooking (dry roasting) of two foods likely to have been important components of the hominin diet: meat and tubers. Mechanical tenderization significantly decreased tuber toughness by 42%, but had no effect on meat toughness. Roasting significantly decreased several material properties of tubers correlated with masticatory effort including toughness (49%), fracture stress (28%) and elastic modulus (45%), but increased the toughness (77%), fracture stress (50%-222%), and elastic modulus of muscle fibers in meat (308%). Despite increasing many material properties of meat associated with higher masticatory forces, roasting also decreased measured energy loss by 28%, which likely makes it easier to chew. These results suggest that the use of food processing techniques by early Homo probably differed for meat and tubers, but together would have reduced masticatory effort, helping to relax selection to maintain large, robust faces and large, thickly enameled teeth.

  6. Middle Pliocene hominin diversity: Australopithecus deyiremeda and Kenyanthropus platyops.

    Science.gov (United States)

    Spoor, Fred; Leakey, Meave G; O'Higgins, Paul

    2016-07-01

    Geometric morphometric shape analyses are used to compare the maxillae of the Kenyanthropus platyops holotype KNM-WT 40000, the Australopithecus deyiremeda holotype BRT-VP-3/1 and other australopiths. The main aim is to explore the relationship between these two specimens and contemporary Australopithecus afarensis Five landmarks placed on lateral views of the maxillae quantify key aspects of the morphology. Generalized Procrustes analyses and principal component analyses of the resulting shape coordinates were performed. The magnitudes of differences in shape and their significances were assessed using Procrustes and Mahalanobis' distances, respectively. Both KNM-WT 40000 and BRT-VP-3/1 show statistically significant differences in maxillary shape from A. afarensis, but do so in dissimilar ways. Moreover, the former differs more from A. afarensis than the latter. KNM-WT 40000 has a more anteriorly positioned zygomatic process with a transversely flat, and more orthognathic subnasal clivus. BRT-VP-3/1 has a more inferiorly positioned zygomatic process, a slightly retracted dental arcade, but without shortening of the anterior maxilla. These findings are consistent with previous conclusions that the two fossils should be attributed to separate species, rather than to A. afarensis, and with the presence of three contemporary hominin species in the Middle Pliocene of eastern Africa.This article is part of the themed issue 'Major transitions in human evolution'. PMID:27298462

  7. Animal movements in the Kenya Rift and evidence for the earliest ambush hunting by hominins.

    Science.gov (United States)

    Kübler, Simon; Owenga, Peter; Reynolds, Sally C; Rucina, Stephen M; King, Geoffrey C P

    2015-01-01

    Animal movements in the Kenya Rift Valley today are influenced by a combination of topography and trace nutrient distribution. These patterns would have been the same in the past when hominins inhabited the area. We use this approach to create a landscape reconstruction of Olorgesailie, a key site in the East African Rift with abundant evidence of large-mammal butchery between ~1.2 and ~0.5 Ma BP. The site location in relation to limited animal routes through the area show that hominins were aware of animal movements and used the location for ambush hunting during the Lower to Middle Pleistocene. These features explain the importance of Olorgesailie as a preferred location of repeated hominin activity through multiple changes in climate and local environmental conditions, and provide insights into the cognitive and hunting abilities of Homo erectus while indicating that their activities at the site were aimed at hunting, rather than scavenging. PMID:26369499

  8. Animal movements in the Kenya Rift and evidence for the earliest ambush hunting by hominins

    Science.gov (United States)

    Kübler, Simon; Owenga, Peter; Reynolds, Sally C.; Rucina, Stephen M.; King, Geoffrey C. P.

    2015-09-01

    Animal movements in the Kenya Rift Valley today are influenced by a combination of topography and trace nutrient distribution. These patterns would have been the same in the past when hominins inhabited the area. We use this approach to create a landscape reconstruction of Olorgesailie, a key site in the East African Rift with abundant evidence of large-mammal butchery between ~1.2 and ~0.5 Ma BP. The site location in relation to limited animal routes through the area show that hominins were aware of animal movements and used the location for ambush hunting during the Lower to Middle Pleistocene. These features explain the importance of Olorgesailie as a preferred location of repeated hominin activity through multiple changes in climate and local environmental conditions, and provide insights into the cognitive and hunting abilities of Homo erectus while indicating that their activities at the site were aimed at hunting, rather than scavenging.

  9. The evolutionary history of the hominin hand since the last common ancestor of Pan and Homo.

    Science.gov (United States)

    Tocheri, Matthew W; Orr, Caley M; Jacofsky, Marc C; Marzke, Mary W

    2008-04-01

    Molecular evidence indicates that the last common ancestor of the genus Pan and the hominin clade existed between 8 and 4 million years ago (Ma). The current fossil record indicates the Pan-Homo last common ancestor existed at least 5 Ma and most likely between 6 and 7 Ma. Together, the molecular and fossil evidence has important consequences for interpreting the evolutionary history of the hand within the tribe Hominini (hominins). Firstly, parsimony supports the hypothesis that the hand of the last common ancestor most likely resembled that of an extant great ape overall (Pan, Gorilla, and Pongo), and that of an African ape in particular. Second, it provides a context for interpreting the derived changes to the hand that have evolved in various hominins. For example, the Australopithecus afarensis hand is likely derived in comparison with that of the Pan-Homo last common ancestor in having shorter fingers relative to thumb length and more proximo-distally oriented joints between its capitate, second metacarpal, and trapezium. This evidence suggests that these derived features evolved prior to the intensification of stone tool-related hominin behaviors beginning around 2.5 Ma. However, a majority of primitive features most likely present in the Pan-Homo last common ancestor are retained in the hands of Australopithecus, Paranthropus/early Homo, and Homo floresiensis. This evidence suggests that further derived changes to the hands of other hominins such as modern humans and Neandertals did not evolve until after 2.5 Ma and possibly even later than 1.5 Ma, which is currently the earliest evidence of Acheulian technology. The derived hands of modern humans and Neandertals may indicate a morphological commitment to tool-related manipulative behaviors beyond that observed in other hominins, including those (e.g. H. floresiensis) which may be descended from earlier tool-making species. PMID:18380869

  10. The first hominin from the early Pleistocene paleocave of Haasgat, South Africa.

    Science.gov (United States)

    Leece, A B; Kegley, Anthony D T; Lacruz, Rodrigo S; Herries, Andy I R; Hemingway, Jason; Kgasi, Lazarus; Potze, Stephany; Adams, Justin W

    2016-01-01

    Haasgat is a primate-rich fossil locality in the northeastern part of the Fossil Hominid Sites of South Africa UNESCO World Heritage Site. Here we report the first hominin identified from Haasgat, a partial maxillary molar (HGT 500), that was recovered from an ex situ calcified sediment block sampled from the locality. The in situ fossil bearing deposits of the Haasgat paleokarstic deposits are estimated to date to slightly older than 1.95 Ma based on magnetobiostratigraphy. This places the hominin specimen at a critical time period in South Africa that marks the last occurrence of Australopithecus around 1.98 Ma and the first evidence of Paranthropus and Homo in the region between ∼2.0 and 1.8 Ma. A comprehensive morphological evaluation of the Haasgat hominin molar was conducted against the current South African catalogue of hominin dental remains and imaging analyses using micro-CT, electron and confocal microscopy. The preserved occlusal morphology is most similar to Australopithecus africanus or early Homo specimens but different from Paranthropus. Occlusal linear enamel thickness measured from micro-CT scans provides an average of ∼2.0 mm consistent with Australopithecus and early Homo. Analysis of the enamel microstructure suggests an estimated periodicity of 7-9 days. Hunter-Schreger bands appear long and straight as in some Paranthropus, but contrast with this genus in the short shape of the striae of Retzius. Taken together, these data suggests that the maxillary fragment recovered from Haasgat best fits within the Australopithecus-early Homo hypodigms to the exclusion of the genus Paranthropus. At ∼1.95 Ma this specimen would either represent another example of late occurring Australopithecus or one of the earliest examples of Homo in the region. While the identification of this first hominin specimen from Haasgat is not unexpected given the composition of other South African penecontemporaneous site deposits, it represents one of the few hominin

  11. A mitochondrial genome sequence of a hominin from Sima de los Huesos

    OpenAIRE

    Meyer, Matthias; Fu, Qiaomei; Aximu Petri, Ayinuer; Glocke, Isabelle; Nickel, Birgit; Arsuaga, Juan Luis; Martínez Mendizábal, Ignacio; Gracia Téllez, Ana; Bermúdez de Castro, José María; Carbonell i Roura, Eudald; Pääbo, Svante

    2014-01-01

    Excavations of a complex of caves in the Sierra de Atapuerca in northern Spain have unearthed hominin fossils that range in age from the early Pleistocene to the Holocene1. One of these sites, the ‘Sima de los Huesos’ (‘pit of bones’), has yielded the world’s largest assemblage of Middle Pleistocene hominin fossils2,3, onsisting of at least 28 individuals4 dated to over 300,000 years ago5. The skeletal remains share a number of morphological features with fossils classifieds Homo heidel...

  12. Craniofacial biomechanics and functional and dietary inferences in hominin paleontology.

    Science.gov (United States)

    Grine, Frederick E; Judex, Stefan; Daegling, David J; Ozcivici, Engin; Ungar, Peter S; Teaford, Mark F; Sponheimer, Matt; Scott, Jessica; Scott, Robert S; Walker, Alan

    2010-04-01

    Finite element analysis (FEA) is a potentially powerful tool by which the mechanical behaviors of different skeletal and dental designs can be investigated, and, as such, has become increasingly popular for biomechanical modeling and inferring the behavior of extinct organisms. However, the use of FEA to extrapolate from characterization of the mechanical environment to questions of trophic or ecological adaptation in a fossil taxon is both challenging and perilous. Here, we consider the problems and prospects of FEA applications in paleoanthropology, and provide a critical examination of one such study of the trophic adaptations of Australopithecus africanus. This particular FEA is evaluated with regard to 1) the nature of the A. africanus cranial composite, 2) model validation, 3) decisions made with respect to model parameters, 4) adequacy of data presentation, and 5) interpretation of the results. Each suggests that the results reflect methodological decisions as much as any underlying biological significance. Notwithstanding these issues, this model yields predictions that follow from the posited emphasis on premolar use by A. africanus. These predictions are tested with data from the paleontological record, including a phylogenetically-informed consideration of relative premolar size, and postcanine microwear fabrics and antemortem enamel chipping. In each instance, the data fail to conform to predictions from the model. This model thus serves to emphasize the need for caution in the application of FEA in paleoanthropological enquiry. Theoretical models can be instrumental in the construction of testable hypotheses; but ultimately, the studies that serve to test these hypotheses - rather than data from the models - should remain the source of information pertaining to hominin paleobiology and evolution. PMID:20227747

  13. Earliest porotic hyperostosis on a 1.5-million-year-old hominin, olduvai gorge, Tanzania.

    Directory of Open Access Journals (Sweden)

    Manuel Domínguez-Rodrigo

    Full Text Available Meat-eating was an important factor affecting early hominin brain expansion, social organization and geographic movement. Stone tool butchery marks on ungulate fossils in several African archaeological assemblages demonstrate a significant level of carnivory by Pleistocene hominins, but the discovery at Olduvai Gorge of a child's pathological cranial fragments indicates that some hominins probably experienced scarcity of animal foods during various stages of their life histories. The child's parietal fragments, excavated from 1.5-million-year-old sediments, show porotic hyperostosis, a pathology associated with anemia. Nutritional deficiencies, including anemia, are most common at weaning, when children lose passive immunity received through their mothers' milk. Our results suggest, alternatively, that (1 the developmentally disruptive potential of weaning reached far beyond sedentary Holocene food-producing societies and into the early Pleistocene, or that (2 a hominin mother's meat-deficient diet negatively altered the nutritional content of her breast milk to the extent that her nursing child ultimately died from malnourishment. Either way, this discovery highlights that by at least 1.5 million years ago early human physiology was already adapted to a diet that included the regular consumption of meat.

  14. Understanding Paleoclimate and Human Evolution Through the Hominin Sites and Paleolakes Drilling Project

    Directory of Open Access Journals (Sweden)

    Kaye Reed

    2009-09-01

    Full Text Available Understanding the evolution of humans and our close relatives is one of the enduring scientific issues of modern times. Since the time of Charles Darwin, scientists have speculated on how and when we evolved and what conditions drove this evolutionary story. The detective work required to address these questions is necessarily interdisciplinary,involving research in anthropology, archaeology, human genetics and genomics, and the earth sciences. In addition to the difficult tasks of finding, describing, and interpreting hominin fossils (the taxonomic tribe which includes Homo sapiens and our close fossil relatives from the last 6 Ma, much of modern geological research associated with paleoanthropology involves understanding the geochronologic and paleoenvironmental context of those fossils. When were they entombed in the sediments? What were the local and regional climatic conditions that early hominins experienced? How did local (watershed scale and regional climate processes combine with regional tectonic boundary conditions to influence hominin food resources, foraging patterns, and demography? How and when did these conditions vary from humid to dry, or cool to warm? Can the history of those conditions (Vrba, 1988; Potts, 1996 be related to the evolution, diversification, stasis, or extinction of hominin species?

  15. A 400,000-year-old mitochondrial genome questions phylogenetic relationships amongst archaic hominins

    DEFF Research Database (Denmark)

    Orlando, Ludovic Antoine Alexandre

    2014-01-01

    By combining state-of-the-art approaches in ancient genomics, Meyer and co-workers have reconstructed the mitochondrial sequence of an archaic hominin that lived at Sierra de Atapuerca, Spain about 400,000 years ago. This achievement follows recent advances in molecular anthropology that delivered...

  16. Nuclear DNA sequences from the Middle Pleistocene Sima de los Huesos hominins.

    Science.gov (United States)

    Meyer, Matthias; Arsuaga, Juan-Luis; de Filippo, Cesare; Nagel, Sarah; Aximu-Petri, Ayinuer; Nickel, Birgit; Martínez, Ignacio; Gracia, Ana; Bermúdez de Castro, José María; Carbonell, Eudald; Viola, Bence; Kelso, Janet; Prüfer, Kay; Pääbo, Svante

    2016-03-24

    A unique assemblage of 28 hominin individuals, found in Sima de los Huesos in the Sierra de Atapuerca in Spain, has recently been dated to approximately 430,000 years ago. An interesting question is how these Middle Pleistocene hominins were related to those who lived in the Late Pleistocene epoch, in particular to Neanderthals in western Eurasia and to Denisovans, a sister group of Neanderthals so far known only from southern Siberia. While the Sima de los Huesos hominins share some derived morphological features with Neanderthals, the mitochondrial genome retrieved from one individual from Sima de los Huesos is more closely related to the mitochondrial DNA of Denisovans than to that of Neanderthals. However, since the mitochondrial DNA does not reveal the full picture of relationships among populations, we have investigated DNA preservation in several individuals found at Sima de los Huesos. Here we recover nuclear DNA sequences from two specimens, which show that the Sima de los Huesos hominins were related to Neanderthals rather than to Denisovans, indicating that the population divergence between Neanderthals and Denisovans predates 430,000 years ago. A mitochondrial DNA recovered from one of the specimens shares the previously described relationship to Denisovan mitochondrial DNAs, suggesting, among other possibilities, that the mitochondrial DNA gene pool of Neanderthals turned over later in their history. PMID:26976447

  17. Fossil hominin shoulders support an African ape-like last common ancestor of humans and chimpanzees.

    Science.gov (United States)

    Young, Nathan M; Capellini, Terence D; Roach, Neil T; Alemseged, Zeresenay

    2015-09-22

    Reconstructing the behavioral shifts that drove hominin evolution requires knowledge of the timing, magnitude, and direction of anatomical changes over the past ∼6-7 million years. These reconstructions depend on assumptions regarding the morphotype of the Homo-Pan last common ancestor (LCA). However, there is little consensus for the LCA, with proposed models ranging from African ape to orangutan or generalized Miocene ape-like. The ancestral state of the shoulder is of particular interest because it is functionally associated with important behavioral shifts in hominins, such as reduced arboreality, high-speed throwing, and tool use. However, previous morphometric analyses of both living and fossil taxa have yielded contradictory results. Here, we generated a 3D morphospace of ape and human scapular shape to plot evolutionary trajectories, predict ancestral morphologies, and directly test alternative evolutionary hypotheses using the hominin fossil evidence. We show that the most parsimonious model for the evolution of hominin shoulder shape starts with an African ape-like ancestral state. We propose that the shoulder evolved gradually along a single morphocline, achieving modern human-like configuration and function within the genus Homo. These data are consistent with a slow, progressive loss of arboreality and increased tool use throughout human evolution. PMID:26351685

  18. Surprising trunk rotational capabilities in chimpanzees and implications for bipedal walking proficiency in early hominins

    Science.gov (United States)

    Thompson, Nathan E.; Demes, Brigitte; O'Neill, Matthew C.; Holowka, Nicholas B.; Larson, Susan G.

    2015-01-01

    Human walking entails coordinated out-of-phase axial rotations of the thorax and pelvis. A long-held assumption is that this ability relies on adaptations for trunk flexibility present in humans, but not in chimpanzees, other great apes, or australopithecines. Here we use three-dimensional kinematic analyses to show that, contrary to current thinking, chimpanzees walking bipedally rotate their lumbar and thoracic regions in a manner similar to humans. This occurs despite differences in the magnitude of trunk motion, and despite morphological differences in truncal ‘rigidity' between species. These results suggest that, like humans and chimpanzees, early hominins walked with upper body rotations that countered pelvic rotation. We demonstrate that even if early hominins walked with pelvic rotations 50% larger than humans, they may have accrued the energetic and mechanical benefits of out-of-phase thoracic rotations. This would have allowed early hominins to reduce work and locomotor cost, improving walking efficiency early in hominin evolution. PMID:26441046

  19. Dynamics of green Sahara periods and their role in hominin evolution.

    Science.gov (United States)

    Larrasoaña, Juan C; Roberts, Andrew P; Rohling, Eelco J

    2013-01-01

    Astronomically forced insolation changes have driven monsoon dynamics and recurrent humid episodes in North Africa, resulting in green Sahara Periods (GSPs) with savannah expansion throughout most of the desert. Despite their potential for expanding the area of prime hominin habitats and favouring out-of-Africa dispersals, GSPs have not been incorporated into the narrative of hominin evolution due to poor knowledge of their timing, dynamics and landscape composition at evolutionary timescales. We present a compilation of continental and marine paleoenvironmental records from within and around North Africa, which enables identification of over 230 GSPs within the last 8 million years. By combining the main climatological determinants of woody cover in tropical Africa with paleoenvironmental and paleoclimatic data for representative (Holocene and Eemian) GSPs, we estimate precipitation regimes and habitat distributions during GSPs. Their chronology is consistent with the ages of Saharan archeological and fossil hominin sites. Each GSP took 2-3 kyr to develop, peaked over 4-8 kyr, biogeographically connected the African tropics to African and Eurasian mid latitudes, and ended within 2-3 kyr, which resulted in rapid habitat fragmentation. We argue that the well-dated succession of GSPs presented here may have played an important role in migration and evolution of hominins. PMID:24146882

  20. Dynamics of green Sahara periods and their role in hominin evolution.

    Directory of Open Access Journals (Sweden)

    Juan C Larrasoaña

    Full Text Available Astronomically forced insolation changes have driven monsoon dynamics and recurrent humid episodes in North Africa, resulting in green Sahara Periods (GSPs with savannah expansion throughout most of the desert. Despite their potential for expanding the area of prime hominin habitats and favouring out-of-Africa dispersals, GSPs have not been incorporated into the narrative of hominin evolution due to poor knowledge of their timing, dynamics and landscape composition at evolutionary timescales. We present a compilation of continental and marine paleoenvironmental records from within and around North Africa, which enables identification of over 230 GSPs within the last 8 million years. By combining the main climatological determinants of woody cover in tropical Africa with paleoenvironmental and paleoclimatic data for representative (Holocene and Eemian GSPs, we estimate precipitation regimes and habitat distributions during GSPs. Their chronology is consistent with the ages of Saharan archeological and fossil hominin sites. Each GSP took 2-3 kyr to develop, peaked over 4-8 kyr, biogeographically connected the African tropics to African and Eurasian mid latitudes, and ended within 2-3 kyr, which resulted in rapid habitat fragmentation. We argue that the well-dated succession of GSPs presented here may have played an important role in migration and evolution of hominins.

  1. A simple rule governs the evolution and development of hominin tooth size.

    Science.gov (United States)

    Evans, Alistair R; Daly, E Susanne; Catlett, Kierstin K; Paul, Kathleen S; King, Stephen J; Skinner, Matthew M; Nesse, Hans P; Hublin, Jean-Jacques; Townsend, Grant C; Schwartz, Gary T; Jernvall, Jukka

    2016-02-25

    The variation in molar tooth size in humans and our closest relatives (hominins) has strongly influenced our view of human evolution. The reduction in overall size and disproportionate decrease in third molar size have been noted for over a century, and have been attributed to reduced selection for large dentitions owing to changes in diet or the acquisition of cooking. The systematic pattern of size variation along the tooth row has been described as a 'morphogenetic gradient' in mammal, and more specifically hominin, teeth since Butler and Dahlberg. However, the underlying controls of tooth size have not been well understood, with hypotheses ranging from morphogenetic fields to the clone theory. In this study we address the following question: are there rules that govern how hominin tooth size evolves? Here we propose that the inhibitory cascade, an activator-inhibitor mechanism that affects relative tooth size in mammals, produces the default pattern of tooth sizes for all lower primary postcanine teeth (deciduous premolars and permanent molars) in hominins. This configuration is also equivalent to a morphogenetic gradient, finally pointing to a mechanism that can generate this gradient. The pattern of tooth size remains constant with absolute size in australopiths (including Ardipithecus, Australopithecus and Paranthropus). However, in species of Homo, including modern humans, there is a tight link between tooth proportions and absolute size such that a single developmental parameter can explain both the relative and absolute sizes of primary postcanine teeth. On the basis of the relationship of inhibitory cascade patterning with size, we can use the size at one tooth position to predict the sizes of the remaining four primary postcanine teeth in the row for hominins. Our study provides a development-based expectation to examine the evolution of the unique proportions of human teeth.

  2. A geometric morphometric analysis of hominin lower molars: Evolutionary implications and overview of postcanine dental variation.

    Science.gov (United States)

    Gómez-Robles, Aida; Bermúdez de Castro, José María; Martinón-Torres, María; Prado-Simón, Leyre; Arsuaga, Juan Luis

    2015-05-01

    Lower molars have been extensively studied in the context of hominin evolution using classic and geometric morphometric analyses, 2D and 3D approaches, evaluations of the external (outer enamel surface) and internal anatomy (dentine, pulp chamber, and radicular canals), and studies of the crown and root variation. In this study, we present a 2D geometric morphometric analysis of the crown anatomy of lower first, second, and third molars of a broad sample of hominins, including Pliocene and Lower, Middle, and Upper Pleistocene species coming from Africa, Asia, and Europe. We show that shape variability increases from first to second and third molars. While first molars tend to retain a relatively stable 5-cusped conformation throughout the hominin fossil record, second and third molars show marked distal reductions in later Homo species. This trend to distal reduction is similar to that observed in previous studies of premolars and upper second and third molars, and points to a correlated reduction of distal areas across the whole postcanine dentition. Results on lower molar variation, as well as on other postcanine teeth, show certain trends in European Pleistocene populations from the Atapuerca sites. Middle Pleistocene hominins from Sima de los Huesos show Neanderthal affinities and strong dental reduction, especially in the most distal molars. The degree of dental reduction in this population is stronger than that observed in classic Neanderthals. Homo antecessor hominins from Gran Dolina-TD6 have primitive lower teeth that contrast with their more derived upper teeth. The evolutionary implications of these dental affinities are discussed in light of recent paleogenetic studies. PMID:25840859

  3. Early hominin foot morphology based on 1.5-million-year-old footprints from Ileret, Kenya.

    Science.gov (United States)

    Bennett, Matthew R; Harris, John W K; Richmond, Brian G; Braun, David R; Mbua, Emma; Kiura, Purity; Olago, Daniel; Kibunjia, Mzalendo; Omuombo, Christine; Behrensmeyer, Anna K; Huddart, David; Gonzalez, Silvia

    2009-02-27

    Hominin footprints offer evidence about gait and foot shape, but their scarcity, combined with an inadequate hominin fossil record, hampers research on the evolution of the human gait. Here, we report hominin footprints in two sedimentary layers dated at 1.51 to 1.53 million years ago (Ma) at Ileret, Kenya, providing the oldest evidence of an essentially modern human-like foot anatomy, with a relatively adducted hallux, medial longitudinal arch, and medial weight transfer before push-off. The size of the Ileret footprints is consistent with stature and body mass estimates for Homo ergaster/erectus, and these prints are also morphologically distinct from the 3.75-million-year-old footprints at Laetoli, Tanzania. The Ileret prints show that by 1.5 Ma, hominins had evolved an essentially modern human foot function and style of bipedal locomotion. PMID:19251625

  4. The bony labyrinth of the middle Pleistocene Sima de los Huesos hominins (Sierra de Atapuerca, Spain).

    Science.gov (United States)

    Quam, Rolf; Lorenzo, Carlos; Martínez, Ignacio; Gracia-Téllez, Ana; Arsuaga, Juan Luis

    2016-01-01

    We performed 3D virtual reconstructions based on CT scans to study the bony labyrinth morphology in 14 individuals from the large middle Pleistocene hominin sample from the site of the Sima de los Huesos (SH) in the Sierra de Atapuerca in northern Spain. The Atapuerca (SH) hominins represent early members of the Neandertal clade and provide an opportunity to compare the data with the later in time Neandertals, as well as Pleistocene and recent humans more broadly. The Atapuerca (SH) hominins do not differ from the Neandertals in any of the variables related to the absolute and relative sizes and shape of the semicircular canals. Indeed, the entire Neandertal clade seems to be characterized by a derived pattern of canal proportions, including a relatively small posterior canal and a relatively large lateral canal. In contrast, one of the most distinctive features observed in Neandertals, the low placement of the posterior canal (i.e., high sagittal labyrinthine index), is generally not present in the Atapuerca (SH) hominins. This low placement is considered a derived feature in Neandertals and is correlated with a more vertical orientation of the ampullar line (LSCm pyramid (LSCm > PPp), and third part of the facial canal (LSCm base, and an archaic pattern of brain allometry. This more general explanation would not necessarily follow taxonomic lines, even though this morphology of the bony labyrinth occurs at high frequencies among Neandertals. While a functional interpretation of the relatively small vertical canals in the Neandertal clade remains elusive, the relative proportions of the semicircular canals is one of several derived Neandertal features in the Atapuerca (SH) crania. Examination of additional European middle Pleistocene specimens suggests that the full suite of Neandertal features in the bony labyrinth did not emerge in Europe until perhaps <200 kya. PMID:26767955

  5. Body mass estimates of hominin fossils and the evolution of human body size.

    Science.gov (United States)

    Grabowski, Mark; Hatala, Kevin G; Jungers, William L; Richmond, Brian G

    2015-08-01

    Body size directly influences an animal's place in the natural world, including its energy requirements, home range size, relative brain size, locomotion, diet, life history, and behavior. Thus, an understanding of the biology of extinct organisms, including species in our own lineage, requires accurate estimates of body size. Since the last major review of hominin body size based on postcranial morphology over 20 years ago, new fossils have been discovered, species attributions have been clarified, and methods improved. Here, we present the most comprehensive and thoroughly vetted set of individual fossil hominin body mass predictions to date, and estimation equations based on a large (n = 220) sample of modern humans of known body masses. We also present species averages based exclusively on fossils with reliable taxonomic attributions, estimates of species averages by sex, and a metric for levels of sexual dimorphism. Finally, we identify individual traits that appear to be the most reliable for mass estimation for each fossil species, for use when only one measurement is available for a fossil. Our results show that many early hominins were generally smaller-bodied than previously thought, an outcome likely due to larger estimates in previous studies resulting from the use of large-bodied modern human reference samples. Current evidence indicates that modern human-like large size first appeared by at least 3-3.5 Ma in some Australopithecus afarensis individuals. Our results challenge an evolutionary model arguing that body size increased from Australopithecus to early Homo. Instead, we show that there is no reliable evidence that the body size of non-erectus early Homo differed from that of australopiths, and confirm that Homo erectus evolved larger average body size than earlier hominins. PMID:26094042

  6. Taxonomic identification of Lower Pleistocene fossil hominins based on distal humeral diaphyseal cross-sectional shape.

    Science.gov (United States)

    Lague, Michael R

    2015-01-01

    The coexistence of multiple hominin species during the Lower Pleistocene has long presented a challenge for taxonomic attribution of isolated postcrania. Although fossil humeri are well-suited for studies of hominin postcranial variation due to their relative abundance, humeral articular morphology has thus far been of limited value for differentiating Paranthropus from Homo. On the other hand, distal humeral diaphyseal shape has been used to justify such generic distinctions at Swartkrans. The potential utility of humeral diaphyseal shape merits larger-scale quantitative analysis, particularly as it permits the inclusion of fragmentary specimens lacking articular morphology. This study analyzes shape variation of the distal humeral diaphysis among fossil hominins (c. 2-1 Ma) to test the hypothesis that specimens can be divided into distinct morphotypes. Coordinate landmarks were placed on 3D laser scans to quantify cross-sectional shape at a standardized location of the humeral diaphysis (proximal to the olecranon fossa) for a variety of fossil hominins and extant hominids. The fossil sample includes specimens attributed to species based on associated craniodental remains. Mantel tests of matrix correlation were used to assess hypotheses about morphometric relationships among the fossils by comparing empirically-derived Procrustes distance matrices to hypothetical model matrices. Diaphyseal shape variation is consistent with the hypothesis of three distinct morphotypes (Paranthropus, Homo erectus, non-erectus early Homo) in both eastern and southern Africa during the observed time period. Specimens attributed to non-erectus early Homo are unique among hominids with respect to the degree of relative anteroposterior flattening, while H. erectus humeri exhibit morphology more similar to that of modern humans. In both geographic regions, Paranthropus is characterized by a morphology that is intermediate with respect to those morphological features that differentiate

  7. Chimpanzee isotopic ecology: a closed canopy C3 template for hominin dietary reconstruction.

    Science.gov (United States)

    Carlson, Bryce A; Kingston, John D

    2014-11-01

    The most significant hominin adaptations, including features used to distinguish and/or classify taxa, are critically tied to the dietary environment. Stable isotopic analyses of tooth enamel from hominin fossils have provided intriguing evidence for significant C4/CAM (crassulacean acid metabolism) resource consumption in a number of Plio-Pleistocene hominin taxa. Relating isotopic tooth signatures to specific dietary items or proportions of C3 versus C4/CAM plants, however, remains difficult as there is an ongoing need to document and quantify isotopic variability in modern ecosystems. This study investigates the ecological variables responsible for carbon isotopic discrimination and variability within the C3-dominated dietary niche of a closed canopy East African hominoid, Pan troglodytes, from Ngogo, Kibale National Park, Uganda. δ(13)C values among C3 resources utilized by Ngogo chimpanzees were highly variable, ranging over 13‰. Infrequent foraging on papyrus (the only C4 plant consumed by chimpanzees at the site) further extended this isotopic range. Variation was ultimately most attributable to mode of photosynthesis (C3 versus C4), food type, and elevation, which together accounted for approximately 78% of the total sample variation. Among C3 food types, bulk carbon values ranged from -24.2‰ to -31.1‰ with intra-plant variability up to 12.1‰. Pith and sapling leaves were statistically more (13)C depleted than pulp, seeds, flowers, cambium, roots, leaf buds, and leaves from mature trees. The effect of elevation on carbon variation was highly significant and equivalent to an approximately 1‰ increase in δ(13)C for every 150 m of elevation gain, likely reflecting habitat variability associated with topography. These results indicate significant δ(13)C variation attributable to food type and elevation among C3 resources and provide important data for hominin dietary interpretations based on carbon isotopic analyses. PMID:24993419

  8. Comparative analysis of the Gran Dolina-TD6 (Spain) and Tighennif (Algeria) hominin mandibles

    OpenAIRE

    Bermúdez de Castro, J.-M.; Martinón-Torres, M.; Gómez-Robles, A.; Prado, L.; Sarmiento, S.

    2011-01-01

    We present a comparative study of the Tighennif (Algeria) and Gran Dolina-TD6 (Spain) hominin mandibles, which represent two geographically near and contemporaneous populations separated by the Mediterranean sea, in order to test the hypothesis that these populations belong to the same evolutionary lineage, as it has been suggested by some authors. The Tighennif mandibles show a clear primitive structural pattern, derived in some features with regard to the oldest Homo specimens from H. habil...

  9. Chimpanzee nest distribution and site reuse in a dry habitat: implications for early hominin ranging.

    Science.gov (United States)

    Hernandez-Aguilar, R Adriana

    2009-10-01

    This paper reports on a 20-month study of chimpanzee nesting patterns in Issa, Ugalla, western Tanzania. Ugalla is one of the driest, most open, and seasonal habitats where chimpanzees are found. The methods used were ethoarchaeological, as the chimpanzees were not habituated and behavioural observations were rare. Systematic data on the spatial and temporal distribution of nests are presented. Places with no nests at the beginning of the study, despite being suitable for nesting, were used as controls. Similar to other chimpanzee study sites, nests were highly concentrated in some parts of the landscape. Issa chimpanzees preferred to nest on slopes. They extensively used the woodland vegetation type of their habitat for nesting throughout the annual cycle. Ninety percent of nest sites were used repeatedly throughout the study period, but none of the control places had nests during this period. The results indicate that chimpanzees ranged more widely during the dry season, when food abundance was lowest, food was available mainly in open vegetation types, and when drinking water was restricted to a few sources. Early hominins in similar habitats may have followed the ranging strategy of Issa chimpanzees. As with a previous study, the distribution of nests was spatially similar to archaeological distributions in early hominin sites. Hominin topography and vegetation type preferences may be misrepresented in the archaeological record. Nest sites may have been the antecedents of carcass processing sites. PMID:19744699

  10. First early hominin from central Africa (Ishango, Democratic Republic of Congo.

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    Isabelle Crevecoeur

    Full Text Available Despite uncontested evidence for fossils belonging to the early hominin genus Australopithecus in East Africa from at least 4.2 million years ago (Ma, and from Chad by 3.5 Ma, thus far there has been no convincing evidence of Australopithecus, Paranthropus or early Homo from the western (Albertine branch of the Rift Valley. Here we report the discovery of an isolated upper molar (#Ish25 from the Western Rift Valley site of Ishango in Central Africa in a derived context, overlying beds dated to between ca. 2.6 to 2.0 Ma. We used µCT imaging to compare its external and internal macro-morphology to upper molars of australopiths, and fossil and recent Homo. We show that the size and shape of the enamel-dentine junction (EDJ surface discriminate between Plio-Pleistocene and post-Lower Pleistocene hominins, and that the Ishango molar clusters with australopiths and early Homo from East and southern Africa. A reassessment of the archaeological context of the specimen is consistent with the morphological evidence and suggest that early hominins were occupying this region by at least 2 Ma.

  11. Conclusions: implications of the Liang Bua excavations for hominin evolution and biogeography.

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    Morwood, M J; Jungers, W L

    2009-11-01

    Excavations at Liang Bua, on the Indonesian island of Flores, have yielded a stratified sequence of stone artifacts and faunal remains spanning the last 95k.yr., which includes the skeletal remains of two human species, Homo sapiens in the Holocene and Homo floresiensis in the Pleistocene. This paper summarizes and focuses on some of the evidence for Homo floresiensis in context, as presented in this Special Issue edition of the Journal of Human Evolution and elsewhere. Attempts to dismiss the Pleistocene hominins (and the type specimen LB1 in particular) as pathological pygmy humans are not compatible with detailed analyses of the skull, teeth, brain endocast, and postcranium. We initially concluded that H. floresiensis may have evolved by insular dwarfing of a larger-bodied hominin species over 880k.yr. or more. However, recovery of additional specimens and the numerous primitive morphological traits seen throughout the skeleton suggest instead that it is more likely to be a late representative of a small-bodied lineage that exited Africa before the emergence of Homo erectus sensu lato. Homo floresiensis is clearly not an australopithecine, but does retain many aspects of anatomy (and perhaps behavior) that are probably plesiomorphic for the genus Homo. We also discuss some of the other implications of this tiny, endemic species for early hominin dispersal and evolution (e.g., for the "Out of Africa 1" paradigm and more specifically for colonizing Southeast Asia), and we present options for future research in the region. PMID:19913680

  12. The larger mammal fauna from the Lower Paleolithic Schöningen Spear site and its contribution to hominin subsistence.

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    Van Kolfschoten, Thijs; Buhrs, Elfi; Verheijen, Ivo

    2015-12-01

    The locality Schöningen (Germany) is an important source of knowledge about Lower Paleolithic hominin subsistence. The locality includes a series of sites dated to the late Middle Pleistocene with a Holsteinian (MIS 11) and Reinsdorf Interglacial (MIS 9) age. One of the youngest sites is Schöningen 13 II-4, the Spear Horizon site also known as the Horse Butchery site. The organic remains excavated here are exceptionally well-preserved as they were embedded in anaerobic, waterlogged sediments in an area where the groundwater is rich in calcium carbonate. The fossil assemblage is ideal for the study of patterns in hominin interference with the mammalian species encountered at the site. The vertebrate record is extensive and very diverse. The fossil larger carnivore guild of the Spear Horizon faunal assemblage includes saber-toothed cat, fox, and wolf. Herbivores are represented by an elephant species, two equid species, two rhinoceros species, two cervid species, and two large bovid species. Evidence of hominin interference presents itself as either marks on skeletal remains related to the use of bones as knapping tools or hammers, or as marks that indicate butchering activities such as skinning, dismembering, defleshing, filleting, and marrow extraction. The humerus of the saber-toothed cat clearly shows that the bone has been used as a knapping tool. The fossil remains of the other larger carnivores do not show any signs of hominin interference or exploitation. This also applies to the limited number of elephant and rhinoceros remains found at the site. The large horse Equus mosbachensis dominates the larger mammal record and played a major role in hominin subsistence. Marks on the horse bones indicate that a large number of carcasses have been butchered. Traces on the fossil remains of both red deer (Cervus elaphus) and the large bovids also indicate exploitation by Lower Paleolithic hominins. PMID:26607346

  13. Lucy's flat feet: the relationship between the ankle and rearfoot arching in early hominins.

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    Jeremy M DeSilva

    Full Text Available BACKGROUND: In the Plio-Pleistocene, the hominin foot evolved from a grasping appendage to a stiff, propulsive lever. Central to this transition was the development of the longitudinal arch, a structure that helps store elastic energy and stiffen the foot during bipedal locomotion. Direct evidence for arch evolution, however, has been somewhat elusive given the failure of soft-tissue to fossilize. Paleoanthropologists have relied on footprints and bony correlates of arch development, though little consensus has emerged as to when the arch evolved. METHODOLOGY/PRINCIPAL FINDINGS: Here, we present evidence from radiographs of modern humans (n = 261 that the set of the distal tibia in the sagittal plane, henceforth referred to as the tibial arch angle, is related to rearfoot arching. Non-human primates have a posteriorly directed tibial arch angle, while most humans have an anteriorly directed tibial arch angle. Those humans with a posteriorly directed tibial arch angle (8% have significantly lower talocalcaneal and talar declination angles, both measures of an asymptomatic flatfoot. Application of these results to the hominin fossil record reveals that a well developed rearfoot arch had evolved in Australopithecus afarensis. However, as in humans today, Australopithecus populations exhibited individual variation in foot morphology and arch development, and "Lucy" (A.L. 288-1, a 3.18 Myr-old female Australopithecus, likely possessed asymptomatic flat feet. Additional distal tibiae from the Plio-Pleistocene show variation in tibial arch angles, including two early Homo tibiae that also have slightly posteriorly directed tibial arch angles. CONCLUSIONS/SIGNIFICANCE: This study finds that the rearfoot arch was present in the genus Australopithecus. However, the female Australopithecus afarensis "Lucy" has an ankle morphology consistent with non-pathological flat-footedness. This study suggests that, as in humans today, there was variation in arch

  14. Hominins, sedges, and termites: new carbon isotope data from the Sterkfontein valley and Kruger National Park.

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    Sponheimer, Matt; Lee-Thorp, Julia; de Ruiter, Darryl; Codron, Daryl; Codron, Jacqui; Baugh, Alexander T; Thackeray, Francis

    2005-03-01

    Stable carbon isotope analyses have shown that South African australopiths did not have exclusively frugivorous diets, but also consumed significant quantities of C4 foods such as grasses, sedges, or animals that ate these foods. Yet, these studies have had significant limitations. For example, hominin sample sizes were relatively small, leading some to question the veracity of the claim for australopith C4 consumption. In addition, it has been difficult to determine which C4 resources were actually utilized, which is at least partially due to a lack of stable isotope data on some purported australopith foods. Here we begin to address these lacunae by presenting carbon isotope data for 14 new hominin specimens, as well as for two potential C4 foods (termites and sedges). The new data confirm that non-C3 foods were heavily utilized by australopiths, making up about 40% and 35% of Australopithecus and Paranthropus diets respectively. Most termites in the savanna-woodland biome of the Kruger National Park, South Africa, have intermediate carbon isotope compositions indicating mixed C3/C4 diets. Only 28% of the sedges in Kruger were C4, and few if any had well-developed rhizomes and tubers that make some sedges attractive foods. We conclude that although termites and sedges might have contributed to the C4 signal in South African australopiths, other C4 foods were also important. Lastly, we suggest that the consumption of C4 foods is a fundamental hominin trait that, along with bipedalism, allowed australopiths to pioneer increasingly open and seasonal environments.

  15. Scavenging by chimpanzees at Ngogo and the relevance of chimpanzee scavenging to early hominin behavioral ecology.

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    Watts, David P

    2008-01-01

    Chimpanzees regularly hunt a variety of prey species. However, they rarely scavenge, which distinguishes chimpanzee carnivory from that of some modern hunter-gatherers and, presumably, at least some Plio-Pleistocene hominins. I use observations made over an 11-year period to document all known opportunities for scavenging encountered by chimpanzees at Ngogo, Kibale National Park, Uganda, and describe all cases of scavenging. I also review data on scavenging from other chimpanzee research sites. Chimpanzees at Ngogo encountered scavenging opportunities only about once per 100 days and ate meat from scavenged carcasses only four times. Scavenging opportunities are also rare at other sites, even where leopards are present (Mahale, Taï, Gombe), and scavenging of leopard kills is known only from Mahale. Feeding on prey that chimpanzees had hunted but then abandoned is the most common form of scavenging reported across study sites. For example, several individuals at Ngogo ate meat from a partially consumed red colobus carcass abandoned after a hunt the previous day. Such behavior probably was not common among Oldowan hominins. Ngogo data and those from other sites also show that chimpanzees sometimes eat meat from carcasses of prey that they did not see killed and that were not killed by chimpanzees, and that scavenging allows access to carcasses larger than those of any prey items. However, chimpanzees ignore relatively many opportunities to obtain meat from such carcasses. Scavenging may be rare because fresh carcasses are rare, because the risk of bacterial infections and zoonoses is high, and because chimpanzees may not recognize certain species as potential prey or certain size classes of prey species as food sources. Its minimal nutritional importance, along with the absence of technology to facilitate confrontational scavenging and rapid carcass processing, apparently distinguishes chimpanzee foraging strategies from those of at least some Oldowan hominins. PMID

  16. Hominin teeth from the Middle Pleistocene site of Yiyuan, Eastern China.

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    Xing, Song; Sun, Chengkai; Martinón-Torres, María; Bermúdez de Castro, José María; Han, Fei; Zhang, Yingqi; Liu, Wu

    2016-06-01

    In 1981-1982, some hominin fossils, including a relatively complete skull and seven isolated teeth, were recovered from the Middle Pleistocene site of Yiyuan in Eastern China. In the present study we provide a detailed metric and morphological comparison of the Yiyuan dental sample in order to characterize better the variability of the human populations that inhabited China during the Middle Pleistocene. Aside from taxonomic and phylogenetic questions, the lack of understanding and/or knowledge about the morphological variability of these populations have caused concern about the human versus non-human nature of some of the hominin dental remains found in East Asia during the Early and the Middle Pleistocene. Thus, our study aims to present a detailed description and comparison of the Yiyuan isolated teeth to 1) discuss and support their human nature and 2) to explore their taxonomic affinities with regard to other penecontemporaneous populations from Asia. Our results clearly differentiate the Yiyuan sample from Pongo specimens and support a human attribution for the Yiyuan material. Our analyses also suggest that the Yiyuan teeth form a morphologically coherent group together with samples from Zhoukoudian, Chaoxian and Hexian. They are different from the more derived specimens from Panxian Dadong, suggesting a pattern of biogeographic isolation and different evolutionary trends between northern and southern China during the Middle Pleistocene. In addition, and despite sharing a common morphological bauplan with Homo erectus sensu stricto (s.s.), the Yiyuan, Zhoukoudian and Hexian teeth are also different from the Indonesian Early Pleistocene samples. In particular, the expression of a highly crenulated or dendritic enamel-dentine surface could be unique to these groups. Our study supports the notion that the taxonomy of the Pleistocene hominins from Asia may have been oversimplified. Future studies should explore the variability of the Asian specimens and

  17. Fossil hominin radii from the Sima de los Huesos Middle Pleistocene site (Sierra de Atapuerca, Spain).

    Science.gov (United States)

    Rodríguez, Laura; Carretero, José Miguel; García-González, Rebeca; Lorenzo, Carlos; Gómez-Olivencia, Asier; Quam, Rolf; Martínez, Ignacio; Gracia-Téllez, Ana; Arsuaga, Juan Luis

    2016-01-01

    Complete radii in the fossil record preceding recent humans and Neandertals are very scarce. Here we introduce the radial remains recovered from the Sima de los Huesos (SH) site in the Sierra de Atapuerca between 1976 and 2011 and which have been dated in excess of 430 ky (thousands of years) ago. The sample comprises 89 specimens, 49 of which are attributed to adults representing a minimum of seven individuals. All elements are described anatomically and metrically, and compared with other fossil hominins and recent humans in order to examine the phylogenetic polarity of certain radial features. Radial remains from SH have some traits that differentiate them from those of recent humans and make them more similar to Neandertals, including strongly curved shafts, anteroposterior expanded radial heads and both absolutely and relatively long necks. In contrast, the SH sample differs from Neandertals in showing a high overall gracility as well as a high frequency (80%) of an anteriorly oriented radial tuberosity. Thus, like the cranial and dental remains from the SH site, characteristic Neandertal radial morphology is not present fully in the SH radii. We also analyzed the cross-sectional properties of the SH radial sample at two different levels: mid-shaft and at the midpoint of the neck length. When standardized by shaft length, no difference in the mid-shaft cross-sectional properties were found between the SH hominins, Neandertals and recent humans. Nevertheless, due to their long neck length, the SH hominins show a higher lever efficiency than either Neandertals or recent humans. Functionally, the SH radial morphology is consistent with more efficient pronation-supination and flexion-extension movements. The particular trait composition in the SH sample and Neandertals resembles more closely morphology evident in recent human males. PMID:26767960

  18. A new early Pleistocene hominin mandible from Atapuerca-TD6, Spain.

    Science.gov (United States)

    Bermúdez de Castro, José María; Pérez-González, Alfredo; Martinón-Torres, María; Gómez-Robles, Aida; Rosell, Jordi; Prado, Leyre; Sarmiento, Susana; Carbonell, Eudald

    2008-10-01

    We present the description of a new mandibular specimen, ATD6-113, recovered in 2006 from the TD6 level of the Gran Dolina cave site in Sierra de Atapuerca, northern Spain. A detailed study of the lithostratigraphy of the top sequence of this level, the section from where all human remains have been recovered so far, is also presented. We have observed that the hominin stratum, previously defined as Aurora Stratum, represents a condensed deposit of at least six layers, which could not be distinguished in the test pit made in 1994-95. Therefore, the human fossil remains were probably deposited during a discrete and undetermined time period. The new mandibular fragment exhibits a very similar morphology to that of the most complete specimen, ATD6-96, which was recovered in 2003 from a different layer. This suggests that both specimens represent the same biological population. The two mandibles, as well as the small mandibular fragment ATD6-5 (which constitutes part of the holotype of Homo antecessor), present a morphological pattern clearly derived with regard to that of the African early Homo specimens usually included in H. habilis and H. rudolfensis, the mandibles D211 and D2735 from Dmanisi, and most of the early Pleistocene mandibles from Sangiran. The TD6 mandibles also exhibit some derived features with regard to the African early Pleistocene specimens included in H. ergaster (or African H. erectus). Thus, the TD6 hominins seem to represent a lineage different from other African and Asian lineages, although some (metric in particular) similarities with Chinese middle Pleistocene mandibles are noted. Interestingly, none of the apomorphic mandibular features of the European middle and early late Pleistocene hominins are present in the TD6 mandibles. PMID:18657300

  19. Metric and geometric morphometric analysis of new hominin fossils from Maba (Guangdong, China).

    Science.gov (United States)

    Xiao, Dongfang; Bae, Christopher J; Shen, Guanjun; Delson, Eric; Jin, Jennie J H; Webb, Nicole M; Qiu, Licheng

    2014-09-01

    We present an analysis of a set of previously unreported hominin fossils from Maba (Guangdong, China), a cave site that is best known for the presence of a partial hominin cranium currently assigned as mid-Pleistocene Homo and that has been traditionally dated to around the Middle-Late Pleistocene transition. A more recent set of Uranium series dates indicate that the Maba travertine may date to >237 ka (thousands of years ago), as opposed to the original U-series date, which placed Maba at 135-129 ka. The fossils under study include five upper first and second molars and a partial left mandible with a socketed m3, all recovered from different parts of the site than the cranium or the dated sediments. The results of our metric and 2D geometric morphometric ('GM') study suggest that the upper first molars are likely from modern humans, suggesting a more recent origin. The upper second molars align more closely with modern humans, though the minimum spanning tree from the 2D GM analysis also connects Maba to Homo neanderthalensis. The patterning in the M2s is not as clear as with the M1s. The m3 and partial mandible are morphometrically intermediate between Holocene modern humans and older Homo sapiens. However, a minimum spanning tree indicates that both the partial mandible and m3 align most closely with Holocene modern humans, and they also may be substantially younger than the cranium. Because questions exist regarding the context and the relationship of the dated travertine with the hominin fossils, we suggest caution is warranted in interpreting the Maba specimens. PMID:25104621

  20. Modularity of the anthropoid dentition: Implications for the evolution of the hominin canine honing complex.

    Science.gov (United States)

    Delezene, Lucas K

    2015-09-01

    In most anthropoid primates, the maxillary canine, mandibular canine, and mesial mandibular premolar form a functional complex that hones the canines. Characters in functional complexes are predicted to covary genetically, which constrains their evolutionary independence. As a result of substantial changes to canine and honing premolar size and shape, hominins are characterized by the apomorphic loss of canine honing. In early hominins, changes in canine and 'honing' premolar size and shape appear to have been uncoordinated, which is unexpected if there is strong genetic covariation coupling these teeth. Using the pattern and magnitude of phenotypic dental size covariation in extant anthropoids, results of this study indicate that certain dimensions of the anthropoid honing complex are characterized by strong size covariation within species and that canine and honing premolar size have evolved in a coordinated manner in both males and females, which undermines arguments that the complex is selectively important only in males. Further, there is no evidence for negative or strong positive covariance between canine and either incisor or postcanine size. If patterns of phenotypic covariation reflect genetic covariation, this suggests that canine reduction was unlikely to have been a dependent change associated with the development of postcanine megadontia or incisor reduction.

  1. Hard-object feeding in sooty mangabeys (Cercocebus atys and interpretation of early hominin feeding ecology.

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    David J Daegling

    Full Text Available Morphology of the dentofacial complex of early hominins has figured prominently in the inference of their dietary adaptations. Recent theoretical analysis of craniofacial morphology of Australopithecus africanus proposes that skull form in this taxon represents adaptation to feeding on large, hard objects. A modern analog for this specific dietary specialization is provided by the West African sooty mangabey, Cercocebus atys. This species habitually feeds on the large, exceptionally hard nuts of Sacoglottis gabonensis, stereotypically crushing the seed casings using their premolars and molars. This type of behavior has been inferred for A. africanus based on mathematical stress analysis and aspects of dental wear and morphology. While postcanine megadontia, premolar enlargement and thick molar enamel characterize both A. africanus and C. atys, these features are not universally associated with durophagy among living anthropoids. Occlusal microwear analysis reveals complex microwear textures in C. atys unlike those observed in A. africanus, but more closely resembling textures observed in Paranthropus robustus. Since sooty mangabeys process hard objects in a manner similar to that proposed for A. africanus, yet do so without the craniofacial buttressing characteristic of this hominin, it follows that derived features of the australopith skull are sufficient but not necessary for the consumption of large, hard objects. The adaptive significance of australopith craniofacial morphology may instead be related to the toughness, rather than the hardness, of ingested foods.

  2. A geometric morphometric analysis of hominin upper premolars. Shape variation and morphological integration.

    Science.gov (United States)

    Gómez-Robles, Aida; Martinón-Torres, María; Bermúdez de Castro, José María; Prado-Simón, Leyre; Arsuaga, Juan Luis

    2011-12-01

    This paper continues the series of articles initiated in 2006 that analyse hominin dental crown morphology by means of geometric morphometric techniques. The detailed study of both upper premolar occlusal morphologies in a comprehensive sample of hominin fossils, including those coming from the Gran Dolina-TD6 and Sima de los Huesos sites from Atapuerca, Spain, complement previous works on lower first and second premolars and upper first molars. A morphological gradient consisting of the change from asymmetric to symmetric upper premolars and a marked reduction of the lingual cusp in recent Homo species has been observed in both premolars. Although percentages of correct classification based on upper premolar morphologies are not very high, significant morphological differences between Neanderthals (and European middle Pleistocene fossils) and modern humans have been identified, especially in upper second premolars. The study of morphological integration between premolar morphologies reveals significant correlations that are weaker between upper premolars than between lower ones and significant correlations between antagonists. These results have important implications for understanding the genetic and functional factors underlying dental phenotypic variation and covariation. PMID:22047673

  3. Possible brucellosis in an early hominin skeleton from sterkfontein, South Africa.

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    Ruggero D'Anastasio

    Full Text Available We report on the paleopathological analysis of the partial skeleton of the late Pliocene hominin species Australopithecus africanus Stw 431 from Sterkfontein, South Africa. A previous study noted the presence of lesions on vertebral bodies diagnosed as spondylosis deformans due to trauma. Instead, we suggest that these lesions are pathological changes due to the initial phases of an infectious disease, brucellosis. The macroscopic, microscopic and radiological appearance of the lytic lesions of the lumbar vertebrae is consistent with brucellosis. The hypothesis of brucellosis (most often associated with the consumption of animal proteins in a 2.4 to 2.8 million year old hominid has a host of important implications for human evolution. The consumption of meat has been regarded an important factor in supporting, directing or altering human evolution. Perhaps the earliest (up to 2.5 million years ago paleontological evidence for meat eating consists of cut marks on animal remains and stone tools that could have made these marks. Now with the hypothesis of brucellosis in A. africanus, we may have evidence of occasional meat eating directly linked to a fossil hominin.

  4. Measures of maturation in early fossil hominins: events at the first transition from australopiths to early Homo.

    Science.gov (United States)

    Dean, M Christopher

    2016-07-01

    An important question in palaeoanthropology is whether, among the australopiths and the first fossil hominins attributed to early Homo, there was a shift towards a more prolonged period of growth that can be distinguished from that of the living great apes and whether between the end of weaning and the beginning of puberty there was a slow period of growth as there is in modern humans. Evidence for the pace of growth in early fossil hominins comes from preserved tooth microstructure. A record of incremental growth in enamel and dentine persists, which allows us to reconstruct tooth growth and compare key measures of dental maturation with modern humans and living great apes. Despite their diverse diets and way of life, it is currently difficult to identify any clear differences in the timing of dental development among living great apes, australopiths and the earliest hominins attributed to the genus Homo There is, however, limited evidence that some early hominins may have attained a greater proportion of their body mass and stature relatively earlier in the growth period than is typical of modern humans today.This article is part of the themed issue 'Major transitions in human evolution'. PMID:27298465

  5. The Hominin Sites and Paleolakes Drilling Project: inferring the environmental context of human evolution from eastern African rift lake deposits

    Science.gov (United States)

    Cohen, A.; Campisano, C.; Arrowsmith, R.; Asrat, A.; Behrensmeyer, A. K.; Deino, A.; Feibel, C.; Hill, A.; Johnson, R.; Kingston, J.; Lamb, H.; Lowenstein, T.; Noren, A.; Olago, D.; Owen, R. B.; Potts, R.; Reed, K.; Renaut, R.; Schäbitz, F.; Tiercelin, J.-J.; Trauth, M. H.; Wynn, J.; Ivory, S.; Brady, K.; O'Grady, R.; Rodysill, J.; Githiri, J.; Russell, J.; Foerster, V.; Dommain, R.; Rucina, S.; Deocampo, D.; Russell, J.; Billingsley, A.; Beck, C.; Dorenbeck, G.; Dullo, L.; Feary, D.; Garello, D.; Gromig, R.; Johnson, T.; Junginger, A.; Karanja, M.; Kimburi, E.; Mbuthia, A.; McCartney, T.; McNulty, E.; Muiruri, V.; Nambiro, E.; Negash, E. W.; Njagi, D.; Wilson, J. N.; Rabideaux, N.; Raub, T.; Sier, M. J.; Smith, P.; Urban, J.; Warren, M.; Yadeta, M.; Yost, C.; Zinaye, B.

    2016-02-01

    The role that climate and environmental history may have played in influencing human evolution has been the focus of considerable interest and controversy among paleoanthropologists for decades. Prior attempts to understand the environmental history side of this equation have centered around the study of outcrop sediments and fossils adjacent to where fossil hominins (ancestors or close relatives of modern humans) are found, or from the study of deep sea drill cores. However, outcrop sediments are often highly weathered and thus are unsuitable for some types of paleoclimatic records, and deep sea core records come from long distances away from the actual fossil and stone tool remains. The Hominin Sites and Paleolakes Drilling Project (HSPDP) was developed to address these issues. The project has focused its efforts on the eastern African Rift Valley, where much of the evidence for early hominins has been recovered. We have collected about 2 km of sediment drill core from six basins in Kenya and Ethiopia, in lake deposits immediately adjacent to important fossil hominin and archaeological sites. Collectively these cores cover in time many of the key transitions and critical intervals in human evolutionary history over the last 4 Ma, such as the earliest stone tools, the origin of our own genus Homo, and the earliest anatomically modern Homo sapiens. Here we document the initial field, physical property, and core description results of the 2012-2014 HSPDP coring campaign.

  6. A geometric morphometric analysis of hominin upper second and third molars, with particular emphasis on European Pleistocene populations.

    Science.gov (United States)

    Gómez-Robles, Aida; Bermúdez de Castro, José María; Martinón-Torres, María; Prado-Simón, Leyre; Arsuaga, Juan Luis

    2012-09-01

    The study of dental morphology by means of geometric morphometric methods allows for a detailed and quantitative comparison of hominin species that is useful for taxonomic assignment and phylogenetic reconstruction. Upper second and third molars have been studied in a comprehensive sample of Plio- and Pleistocene hominins from African, Asian and European sites in order to complete our analysis of the upper postcanine dentition. Intraspecific variation in these two molars is high, but some interspecific trends can be identified. Both molars exhibit a strong reduction of the distal cusps in recent hominin species, namely European Homo heidelbergensis, Homo neanderthalensis and Homo sapiens, but this reduction shows specific patterns and proportions in the three groups. Second molars tend to show four well developed cusps in earlier hominin species and their morphology is only marginally affected by allometric effects. Third molars can be incipiently reduced in earlier species and they evince a significant allometric component, identified both inter- and intraspecifically. European Middle Pleistocene fossils from Sima de los Huesos (SH) show a very strong reduction of these two molars, even more marked than the reduction observed in Neanderthals and in modern human populations. The highly derived shape of SH molars points to an early acquisition of typical Neanderthal dental traits by pre-Neanderthal populations and to a deviation of this population from mean morphologies of other European Middle Pleistocene groups. PMID:22840714

  7. Complex tasks force hand laterality and technological behaviour in naturalistically housed chimpanzees: inferences in hominin evolution.

    Science.gov (United States)

    Mosquera, M; Geribàs, N; Bargalló, A; Llorente, M; Riba, D

    2012-01-01

    Clear hand laterality patterns in humans are widely accepted. However, humans only elicit a significant hand laterality pattern when performing complementary role differentiation (CRD) tasks. Meanwhile, hand laterality in chimpanzees is weaker and controversial. Here we have reevaluated our results on hand laterality in chimpanzees housed in naturalistic environments at Fundació Mona (Spain) and Chimfunshi Wild Orphanage (Zambia). Our results show that the difference between hand laterality in humans and chimpanzees is not as great as once thought. Furthermore, we found a link between hand laterality and task complexity and also an even more interesting connection: CRD tasks elicited not only the hand laterality but also the use of tools. This paper aims to turn attention to the importance of this threefold connection in human evolution: the link between CRD tasks, hand laterality, and tool use, which has important evolutionary implications that may explain the development of complex behaviour in early hominins. PMID:22550466

  8. A revision of hominin fossil teeth from Fontana Ranuccio (Middle Pleistocene, Anagni, Frosinone, Italy).

    Science.gov (United States)

    Rubini, Mauro; Cerroni, Vittorio; Festa, Giulia; Sardella, Raffaele; Zaio, Paola

    2014-12-01

    The Fontana Ranuccio hominin teeth (FR, Latium, Italy) are dated to the Middle Pleistocene. In previous studies these teeth were classified as two lower (left and right) second molars, one lower left central incisor and a badly worn incisor crown, the exact position of which could not be determined. In 2012 these remains were acquired by the Anthropological Service of S.B.A.L. (Italian Ministry of Culture) and for this reason re-analysed. In a thorough revision we have reassessed them both morphologically and dimensionally as two lower (left and right) first molars, one lower left lateral incisor and a possible upper left canine. The comparison with penecontemporaneous and diachronic samples shows that the Fontana Ranuccio teeth are morphologically similar to Atapuerca-Sima de los Huesos, Arago XIII and Neanderthal samples. PMID:25440134

  9. New Radiometric Ages for the BH-1 Hominin from Balanica (Serbia): Implications for Understanding the Role of the Balkans in Middle Pleistocene Human Evolution

    OpenAIRE

    William J Rink; Mercier, Norbert; Mihailović, Dušan; Mike W Morley; Thompson, Jeroen W.; Roksandic, Mirjana

    2013-01-01

    Newly obtained ages, based on electron spin resonance combined with uranium series isotopic analysis, and infrared/post-infrared luminescence dating, provide a minimum age that lies between 397 and 525 ka for the hominin mandible BH-1 from Mala Balanica cave, Serbia. This confirms it as the easternmost hominin specimen in Europe dated to the Middle Pleistocene. Inferences drawn from the morphology of the mandible BH-1 place it outside currently observed variation of European Homo heidelbergen...

  10. Homo erectus and Middle Pleistocene hominins: brain size, skull form, and species recognition.

    Science.gov (United States)

    Rightmire, G Philip

    2013-09-01

    Hominins that differ from Homo erectus, the Neanderthals, and recent humans are known from Middle Pleistocene localities across the Old World. The taxonomic status of these populations has been clouded by controversy. Perhaps the most critical problem has been an incomplete understanding of variation in skull form. Here, both H. erectus and later mid-Pleistocene hominins are the focus of an investigation aimed at clarifying the relationships among brain volume, basicranial dimensions, neurocranial shape, and certain facial characters. Brain size in H. erectus averages about 950 cm(3), while in a series of Middle Pleistocene crania from Africa and Europe, volume is about 1230 cm(3). If encephalization is the primary mechanism operating in the mid-Pleistocene, then diverse aspects of cranial form cannot all be treated as independent variables. Correlation is utilized to examine the associations among measurements for more than 30 H. erectus crania that are reasonably well preserved. A similar approach is used with the Middle Pleistocene sample. Patterns of covariation are compared in order to assess integration. Next, factor analysis is applied to the H. erectus specimens in an attempt to identify modules, tightly integrated traits that can evolve independently. Studies of the variation within H. erectus are followed by direct comparisons with the Middle Pleistocene population. Discriminant functions facilitate the description of intergroup differences. Traits that vary independently from brain volume include anterior frontal broadening, lateral expansion of the parietal vault, elevation of the lambda-inion chord, and rounding of the sagittal contour of the occipital. This finding helps to resolve the problem of species recognition. Neurocranial proportions as well as characters from the cranial base and face can be incorporated into a differential diagnosis for the mid-Pleistocene sample. Evidence presented here supports arguments for speciation in the Middle

  11. Landscapes and their relation to hominin habitats: case studies from Australopithecus sites in eastern and southern Africa.

    Science.gov (United States)

    Reynolds, Sally C; Bailey, Geoff N; King, Geoffrey C P

    2011-03-01

    We examine the links between geomorphological processes, specific landscape features, surface water drainage, and the creation of suitable habitats for hominins. The existence of mosaic (i.e., heterogeneous) habitats within hominin site landscape reconstructions is typically explained using models of the riverine and gallery forest settings, or the pan or lake setting. We propose a different model: the Tectonic Landscape Model (TLM), where tectonic faulting and volcanism disrupts existing pan or river settings at small-scales (∼10-25 km). Our model encompasses the interpretation of the landscape features, the role of tectonics in creating these landscapes, and the implications for hominins. In particular, the model explains the underlying mechanism for the creation and maintenance of heterogeneous habitats in regions of active tectonics. We illustrate how areas with faulting and disturbed drainage patterns would have been attractive habitats for hominins, such as Australopithecus, and other fauna. Wetland areas are an important characteristic of surface water disturbance by fault activity; therefore we examine the tectonically-controlled Okavango Delta (Botswana) and the Nylsvley wetland (South Africa) as modern examples of how tectonics in a riverine setting significantly enhance the faunal and floral biodiversity. While tectonic landscapes may not have been the only type of attractive habitats to hominins, we propose a suite of landscape, faunal, and floral indicators, which when recovered together suggest that site environments may have been influenced by tectonic and/or volcanic activity while hominins were present. For the fossil sites, we interpret the faulting and landscapes around australopithecine-bearing sites of the Middle Awash (Ethiopia) and Makapansgat, Taung, and Sterkfontein (South Africa) to illustrate these relationships between landscape features and surface water bodies. Exploitation of tectonically active landscapes may explain why the

  12. Identification of a new hominin bone from Denisova Cave, Siberia using collagen fingerprinting and mitochondrial DNA analysis

    Science.gov (United States)

    Brown, Samantha; Higham, Thomas; Slon, Viviane; Pääbo, Svante; Meyer, Matthias; Douka, Katerina; Brock, Fiona; Comeskey, Daniel; Procopio, Noemi; Shunkov, Michael; Derevianko, Anatoly; Buckley, Michael

    2016-03-01

    DNA sequencing has revolutionised our understanding of archaic humans during the Middle and Upper Palaeolithic. Unfortunately, while many Palaeolithic sites contain large numbers of bones, the majority of these lack the diagnostic features necessary for traditional morphological identification. As a result the recovery of Pleistocene-age human remains is extremely rare. To circumvent this problem we have applied a method of collagen fingerprinting to more than 2000 fragmented bones from the site of Denisova Cave, Russia, in order to facilitate the discovery of human remains. As a result of our analysis a single hominin bone (Denisova 11) was identified, supported through in-depth peptide sequencing analysis, and found to carry mitochondrial DNA of the Neandertal type. Subsequent radiocarbon dating revealed the bone to be >50,000 years old. Here we demonstrate the huge potential collagen fingerprinting has for identifying hominin remains in highly fragmentary archaeological assemblages, improving the resources available for wider studies into human evolution.

  13. The Jaramillo Bottleneck for Migration of Hominins with Megaherbivores Into Europe via the Danube-Po Gateway

    Science.gov (United States)

    Muttoni, G.; Kent, D. V.; Scardia, G.

    2015-12-01

    Based on ongoing magnetostratigraphic work and updated critical reviews of sites bearing hominin remains and/or tools from greater Europe, including the Balkans and Greece, we maintain that the only compelling evidence of hominin presence in these regions was after the Jaramillo subchron (0.99 Ma), at about the time of the climatic late Early Pleistocene revolution (EPR) and the onset of enhanced glacial/interglacial activity from MIS 22 onward. Europe may have become initially populated during the EPR when, possibly for the first time in the Pleistocene, vast and exploitable ecosystems were generated along the Danube-Po Gateway in the Balkan peninsula and northern Italy. These newly formed settings, characterized by low-lands with open grasslands and reduced woody cover during glacial/interglacial transitions, represented the closest analogues to the savanna environment to which several large mammals linked with hominins in a common food web were adapted and could use as a migratory corridor. We acknowledge that lack of evidence may not be a compelling argument, but the absence of the Jaramillo and out-of-sequence cosmogenic nuclide dates with wide error margins in key sections preclude the use of such evidence to substantiate the presence of humans (and presumably associated biostratigraphic markers) prior to the Jaramillo, and thus logically deny applying such conclusions to other systems.

  14. Bovid mortality profiles in paleoecological context falsify hypotheses of endurance running-hunting and passive scavenging by early Pleistocene hominins

    Science.gov (United States)

    Bunn, Henry T.; Pickering, Travis Rayne

    2010-11-01

    The world's first archaeological traces from 2.6 million years ago (Ma) at Gona, in Ethiopia, include sharp-edged cutting tools and cut-marked animal bones, which indicate consumption of skeletal muscle by early hominin butchers. From that point, evidence of hominin meat-eating becomes increasingly more common throughout the Pleistocene archaeological record. Thus, the substantive debate about hominin meat-eating now centers on mode(s) of carcass resource acquisition. Two prominent hypotheses suggest, alternatively, (1) that early Homo hunted ungulate prey by running them to physiological failure and then dispatching them, or (2) that early Homo was relegated to passively scavenging carcass residues abandoned by carnivore predators. Various paleontologically testable predictions can be formulated for both hypotheses. Here we test four predictions concerning age-frequency distributions for bovids that contributed carcass remains to the 1.8 Ma. old FLK 22 Zinjanthropus (FLK Zinj, Olduvai Gorge, Tanzania) fauna, which zooarchaeological and taphonomic data indicate was formed predominantly by early Homo. In all but one case, the bovid mortality data from FLK Zinj violate test predictions of the endurance running-hunting and passive scavenging hypotheses. When combined with other taphonomic data, these results falsify both hypotheses, and lead to the hypothesis that early Homo operated successfully as an ambush predator.

  15. Hominin stature, body mass, and walking speed estimates based on 1.5 million-year-old fossil footprints at Ileret, Kenya.

    Science.gov (United States)

    Dingwall, Heather L; Hatala, Kevin G; Wunderlich, Roshna E; Richmond, Brian G

    2013-06-01

    The early Pleistocene marks a period of major transition in hominin body form, including increases in body mass and stature relative to earlier hominins. However, because complete postcranial fossils with reliable taxonomic attributions are rare, efforts to estimate hominin mass and stature are complicated by the frequent albeit necessary use of isolated, and often fragmentary, skeletal elements. The recent discovery of 1.52 million year old hominin footprints from multiple horizons in Ileret, Kenya, provides new data on the complete foot size of early Pleistocene hominins as well as stride lengths and other characteristics of their gaits. This study reports the results of controlled experiments with habitually unshod Daasanach adults from Ileret to examine the relationships between stride length and speed, and also those between footprint size, body mass, and stature. Based on significant relationships among these variables, we estimate travel speeds ranging between 0.45 m/s and 2.2 m/s from the fossil hominin footprint trails at Ileret. The fossil footprints of seven individuals show evidence of heavy (mean = 50.0 kg; range: 41.5-60.3 kg) and tall individuals (mean = 169.5 cm; range: 152.6-185.8 cm), suggesting that these prints were most likely made by Homo erectus and/or male Paranthropus boisei. The large sizes of these footprints provide strong evidence that hominin body size increased during the early Pleistocene. PMID:23522822

  16. Hominin reactions to herbivore distribution in the Lower Palaeolithic of the Southern Levant

    Science.gov (United States)

    Devès, Maud; Sturdy, Derek; Godet, Nan; King, Geoffrey C. P.; Bailey, Geoffrey N.

    2014-07-01

    We explore the relationship between the edaphic potential of soils and the mineral properties of the underlying geology as a means of mapping the differential productivity of different areas of the Pleistocene landscape for large herbivores. These factors strongly control the health of grazing animals irrespective of the particular types of vegetation growing on them, but they have generally been neglected in palaeoanthropological studies in favour of a more general emphasis on water and vegetation, which provide an incomplete picture. Taking the Carmel-Galilee-Golan region as an example, we show how an understanding of edaphic potential provides insight into how animals might have exploited the environment. In order to simplify the analysis, we concentrate on the Lower Palaeolithic period and the very large animals that dominate the archaeofaunal assemblages of this period. Topography and the ability of soils to retain water also contribute to the differential productivity and accessibility of different regions and to patterns of seasonal movements of the animals, which are essential to ensure a supply of healthy fodder throughout the year, especially for large animals such as elephants, which require substantial regions of good grazing and browsing. Other animals migrating in groups have similar needs. The complex topography of the Southern Levant with frequent sudden and severe changes in gradient, and a wide variety of landforms including rocky outcrops, cliffs, gorges, and ridges, places major limits on these patterns of seasonal movements. We develop methods of mapping these variables, based on the geology and our substantial field experience, in order to create a framework of landscape variation that can be compared with the locations and contents of archaeological sites to suggest ways in which early hominins used the variable features of the landscape to target animal prey, and extend the analysis to the consideration of smaller mammals that were exploited

  17. Hominin responses to environmental changes during the Middle Pleistocene in Central and Southern Italy

    Directory of Open Access Journals (Sweden)

    R. Orain

    2012-10-01

    Full Text Available The palaeobotanical record of early Palaeolithic sites from Western Europe indicates that hominins settled in different kinds of environments. During the "Mid-Pleistocene Transition (MPT", from about 1 to 0.6 Ma, the transition from 41-ka to 100-ka dominant climatic oscillations, occurring within a long-term cooling trend, was associated with an aridity crisis which strongly modified the ecosystems. Starting from the MPT the more favorable climate of central and southern Italy provided propitious environmental conditions for long-term human occupations even during the glacial times. In fact, the human strategy of territory occupation was certainly driven by the availabilities of resources. Prehistoric sites such as Notarchirico (ca. 680–600 ka, La Pineta (ca. 600–620 ka, Gaudo San Nicola (ca. 380–350 ka or Ceprano (ca. 345–355 ka testify to a preferential occupation of the central and southern Apennines valleys during interglacial phases, while later interglacial occupations were oriented towards the coastal plains, as attested by the numerous settlements of the Roma basin (ca. 300 ka. Faunal remains indicate that human subsistence behaviors benefited of a diversity of exploitable ecosystems, from semi-open to closed environments. In central and southern Italy, several palynological records have already illustrated the regional and local scale vegetation dynamic trends. During the Middle Pleistocene climate cycles, mixed mesophytic forests developed during the interglacial periods and withdrew in response to increasing aridity during the glacial episodes. New pollen data from the Boiano basin (Molise, Italy, attest to the evolution of vegetation and climate between OIS 13 and 9 (ca. 500 to 300 ka. In this basin, the persistence of high edaphic humidity, even during the glacial phases, could have favored the establishment of a refuge area for the arboreal flora and provided subsistence resources for the animal and hominin communities

  18. Ecomorphology of radii in Canidae: Application to fragmentary fossils from Plio-Pleistocene hominin assemblages

    Directory of Open Access Journals (Sweden)

    Carlo Meloro

    2015-12-01

    Full Text Available Fragmentary long bone material from fossil Carnivora is rarely considered to support palaeoenvironmental reconstructions. Here, we use morphometry of the radius in extant carnivorans of the dog family (Canidae to reconstruct the palaeobiology of extinct canids from Olduvai Gorge, Tanzania (Bed I and II and Koobi Fora, Kenya. We use radius morphometrics to predict adaptation to prey size and introduce a new method for quantifying canid habitat adaptations based on the geographic distributions of the extant species sampled. Linear Discriminant Function Analyses (DFA and cluster neighbour-joining algorithms are employed to investigate radial morphometrics as described by 29 linear measurements. Results of our analyses suggest that a phylogenetic signal is present in radial morphometrics, even if it does not allow us to accurately discriminate among genera. A binary prey size categorisation of “small-medium” versus “large” prey can be more accurately predicted than a habitat categorisation scheme (Open, Mixed, Closed. The East African fossil specimens examined show morphometric affinities with the golden jackal (Canis aureus and coyote (Canis latrans and are likely attributable to the genus Canis. Fragmentary fossil specimens from Olduvai Gorge are predicted as habitat generalists (Open for Bed I and Mixed for Bed II adapted for hunting small-medium prey, whereas the specimen from Koobi Fora was predicted as inhabiting mixed habitats and adapted for killing large prey. This study supports the inclusion of fossil Canidae in palaeoecological analyses attempting to clarify the palaeoenvironment of early hominin fossil sites.

  19. Form and function of the human and chimpanzee forefoot: implications for early hominin bipedalism.

    Science.gov (United States)

    Fernández, Peter J; Holowka, Nicholas B; Demes, Brigitte; Jungers, William L

    2016-01-01

    During bipedal walking, modern humans dorsiflex their forefoot at the metatarsophalangeal joints (MTPJs) prior to push off, which tightens the plantar soft tissues to convert the foot into a stiff propulsive lever. Particular features of metatarsal head morphology such as "dorsal doming" are thought to facilitate this stiffening mechanism. In contrast, chimpanzees are believed to possess MTPJ morphology that precludes high dorsiflexion excursions during terrestrial locomotion. The morphological affinity of the metatarsal heads has been used to reconstruct locomotor behavior in fossil hominins, but few studies have provided detailed empirical data to validate the assumed link between morphology and function at the MTPJs. Using three-dimensional kinematic and morphometric analyses, we show that humans push off with greater peak dorsiflexion angles at all MTPJs than do chimpanzees during bipedal and quadrupedal walking, with the greatest disparity occurring at MTPJ 1. Among MTPJs 2-5, both species exhibit decreasing peak angles from medial to lateral. This kinematic pattern is mirrored in the morphometric analyses of metatarsal head shape. Analyses of Australopithecus afarensis metatarsals reveal morphology intermediate between humans and chimpanzees, suggesting that this species used different bipedal push-off kinematics than modern humans, perhaps resulting in a less efficient form of bipedalism. PMID:27464580

  20. Variability in an early hominin percussive tradition: the Acheulean versus cultural variation in modern chimpanzee artefacts.

    Science.gov (United States)

    Gowlett, J A J

    2015-11-19

    Percussion makes a vital link between the activities of early human ancestors and other animals in tool-use and tool-making. Far more of the early human actions are preserved as archaeology, since the percussion was largely used for making hard tools of stone, rather than for direct access to food. Both primate tools and early hominin tools, however, offer a means to exploring variability in material culture, a strong focus of interest in recent primate studies. This paper charts such variability in the Acheulean, the longest-lasting tool tradition, extant form about 1.7 to about 0.1 Ma, and well known for its characteristic handaxes. The paper concentrates on the African record, although the Acheulean was also known in Europe and Asia. It uses principal components and discriminant analysis to examine the measurements from 66 assemblages (whole toolkits), and from 18 sets of handaxes. Its review of evidence confirms that there is deep-seated pattern in the variation, with variability within a site complex often matching or exceeding that between sites far distant in space and time. Current techniques of study allow comparisons of handaxes far more easily than for other components, stressing a need to develop common practice in measurement and analysis. The data suggest, however, that a higher proportion of traits recurs widely in Acheulean toolkits than in the chimpanzee record. PMID:26483536

  1. Embodied niche construction in the hominin lineage: semiotic structure and sustained attention in human embodied cognition.

    Science.gov (United States)

    Stutz, Aaron J

    2014-01-01

    Human evolution unfolded through a rather distinctive, dynamically constructed ecological niche. The human niche is not only generally terrestrial in habitat, while being flexibly and extensively heterotrophic in food-web connections. It is also defined by semiotically structured and structuring embodied cognitive interfaces, connecting the individual organism with the wider environment. The embodied dimensions of niche-population co-evolution have long involved semiotic system construction, which I hypothesize to be an evolutionarily primitive aspect of learning and higher-level cognitive integration and attention in the great apes and humans alike. A clearly pre-linguistic form of semiotic cognitive structuration is suggested to involve recursively learned and constructed object icons. Higher-level cognitive iconic representation of visually, auditorily, or haptically perceived extrasomatic objects would be learned and evoked through indexical connections to proprioceptive and affective somatic states. Thus, private cognitive signs would be defined, not only by their learned and perceived extrasomatic referents, but also by their associations to iconically represented somatic states. This evolutionary modification of animal associative learning is suggested to be adaptive in ecological niches occupied by long-lived, large-bodied ape species, facilitating memory construction and recall in highly varied foraging and social contexts, while sustaining selective attention during goal-directed behavioral sequences. The embodied niche construction (ENC) hypothesis of human evolution posits that in the early hominin lineage, natural selection further modified the ancestral ape semiotic adaptations, favoring the recursive structuration of concise iconic narratives of embodied interaction with the environment. PMID:25136323

  2. New actualistic data on the ecology and energetics of hominin scavenging opportunities.

    Science.gov (United States)

    Pobiner, Briana L

    2015-03-01

    For decades, the 'hunting-scavenging debate' has been an important research focus in Plio-Pleistocene hominin behavioral ecology. Here I present new data on potential scavenging opportunities from fresh carnivore kills on a conservancy in central Kenya. This ecosystem is dominated by felids (mainly lions) and has a different carnivore guild than in many earlier studies of scavenging opportunities that took place in areas such as Ngorongoro and Serengeti in Tanzania and Maasai Mara in Kenya, where lions face high levels of inter-specific competition from bone-crunching hyenas. I found that while scavenging opportunities vary among carcasses, most carcasses retained some scavengeable resources. Excluding within-bone resources, even the scavengeable meat on 'defleshed' larger sized prey carcasses is usually substantial enough to meet the total daily caloric requirements of at least one adult male Homo erectus individual. I argue, as others have before me, that scavenging opportunities in a particular ecosystem will vary in part due to carnivore taxon, density and guild composition; prey size, biomass and community structure; and habitat (e.g., vegetation, physiography). We should expect variability in scavenging opportunities in different locales and should focus our research efforts on identifying which variables condition these differences in order to make our findings applicable to the diversity of ecological settings characterizing the past. PMID:25563408

  3. Enamel hypoplasias and physiological stress in the Sima de los Huesos Middle Pleistocene hominins.

    Science.gov (United States)

    Cunha, E; Rozzi, F Ramirez; Bermúdez de Castro, J M; Martinón-Torres, M; Wasterlain, S N; Sarmiento, S

    2004-11-01

    This study presents an analysis of linear enamel hypoplasias (LEH) and plane-form defects (PFD) in the hominine dental sample from the Sima de los Huesos (SH) Middle Pleistocene site in Atapuerca (Spain). The SH sample comprises 475 teeth, 467 permanent and 8 deciduous, belonging to a minimum of 28 individuals. The method for recording PFD and LEH is discussed, as well as the definition of LEH. The prevalence of LEH and PFD in SH permanent dentition (unilateral total count) is 4.6% (13/280). Only one deciduous tooth (lower dc) showed an enamel disruption. Prevalence by individual ranges from 18.7-30%. The most likely explanation for the relatively low LEH and PFD prevalence in the SH sample suggests that the SH population exhibited a low level of developmental stress. The age at occurrence of LEH and PFD was determined by counting the number of perikymata between each lesion and the cervix of the tooth. Assuming a periodicity of nine days for the incremental lines, the majority of LEH in the SH sample occurred during the third year of life and may be related to the metabolic stress associated with weaning. PMID:15386251

  4. Archaeology and age of a new hominin from Flores in eastern Indonesia.

    Science.gov (United States)

    Morwood, M J; Soejono, R P; Roberts, R G; Sutikna, T; Turney, C S M; Westaway, K E; Rink, W J; Zhao, J-X; van den Bergh, G D; Due, Rokus Awe; Hobbs, D R; Moore, M W; Bird, M I; Fifield, L K

    2004-10-28

    Excavations at Liang Bua, a large limestone cave on the island of Flores in eastern Indonesia, have yielded evidence for a population of tiny hominins, sufficiently distinct anatomically to be assigned to a new species, Homo floresiensis. The finds comprise the cranial and some post-cranial remains of one individual, as well as a premolar from another individual in older deposits. Here we describe their context, implications and the remaining archaeological uncertainties. Dating by radiocarbon (14C), luminescence, uranium-series and electron spin resonance (ESR) methods indicates that H. floresiensis existed from before 38,000 years ago (kyr) until at least 18 kyr. Associated deposits contain stone artefacts and animal remains, including Komodo dragon and an endemic, dwarfed species of Stegodon. H. floresiensis originated from an early dispersal of Homo erectus (including specimens referred to as Homo ergaster and Homo georgicus) that reached Flores, and then survived on this island refuge until relatively recently. It overlapped significantly in time with Homo sapiens in the region, but we do not know if or how the two species interacted. PMID:15510146

  5. Embodied niche construction in the hominin lineage: semiotic structure and sustained attention in human embodied cognition.

    Science.gov (United States)

    Stutz, Aaron J

    2014-01-01

    Human evolution unfolded through a rather distinctive, dynamically constructed ecological niche. The human niche is not only generally terrestrial in habitat, while being flexibly and extensively heterotrophic in food-web connections. It is also defined by semiotically structured and structuring embodied cognitive interfaces, connecting the individual organism with the wider environment. The embodied dimensions of niche-population co-evolution have long involved semiotic system construction, which I hypothesize to be an evolutionarily primitive aspect of learning and higher-level cognitive integration and attention in the great apes and humans alike. A clearly pre-linguistic form of semiotic cognitive structuration is suggested to involve recursively learned and constructed object icons. Higher-level cognitive iconic representation of visually, auditorily, or haptically perceived extrasomatic objects would be learned and evoked through indexical connections to proprioceptive and affective somatic states. Thus, private cognitive signs would be defined, not only by their learned and perceived extrasomatic referents, but also by their associations to iconically represented somatic states. This evolutionary modification of animal associative learning is suggested to be adaptive in ecological niches occupied by long-lived, large-bodied ape species, facilitating memory construction and recall in highly varied foraging and social contexts, while sustaining selective attention during goal-directed behavioral sequences. The embodied niche construction (ENC) hypothesis of human evolution posits that in the early hominin lineage, natural selection further modified the ancestral ape semiotic adaptations, favoring the recursive structuration of concise iconic narratives of embodied interaction with the environment.

  6. Using Isotopes to Reconstruct Mammalian Diet, Migration and Paleoenvironment for Hominin Sites in Indonesia

    Science.gov (United States)

    Wershow, H.; Janssen, R.; Vonhof, H.; Lubbe, J. V. D.; Joordens, J. J.; Koutamanis, D. S.; Puspaningrum, M. R.; de Vos, J.; Reijmer, J.

    2015-12-01

    Climate plays a prominent role in ecosystem development in the biodiversity hotspot Sundaland (Malaysia and western Indonesia) throughout the Quaternary. Recurrent isolation and connection of the islands to mainland Asia due to sea level fluctuations has enabled repeated biotic migrations and encouraged genetic speciation. These migration waves also brought Homo erectus to Java. Together with extensive and well-documented collections of other terrestrial species, these hominin fossils form faunal assemblages of which the paleoenvironmental and paleogeographical background is poorly known. Using carbon, oxygen and strontium isotopes, we have reconstructed the paleoenvironmental and paleoecological conditions of several Holocene and Pleistocene fossil sites on Sumatra and Java, Indonesia. Carbon (∂13C) and oxygen (∂18O) isotope analysis of well-preserved herbivore teeth enamel reveals a marked contrast between C3-dominated diets in warmer periods, and C4-dominated diets in cooler periods, reflecting the distinct changes in Sundaland vegetation cover between glacials and interglacials. These isotope patterns allow us to assign the appropriate climatic background to some of the older fossil assemblages from Java, for which dating uncertainty does not allow direct assignment to glacial or interglacial conditions. The stable isotope signatures of herbivores from Trinil and Sangiran, sites well-known for the fossil occurrence of Homo erectus, indicate glacial conditions. The isotope data of several H. erectus fossils from these sites seem to be in line with such an interpretation. Furthermore, we applied strontium (87Sr/86Sr) isotope analyses to a sample subset. The preliminary data show distinct Sr-isotope ratios for different sites, providing clues for the applicability of this isotope technique in detecting climate-related mobility of Sundaland fossil faunas.

  7. Embodied Niche Construction in the Hominin Lineage: Semiotic Structure and Sustained Attention in Human Embodied Cognition

    Directory of Open Access Journals (Sweden)

    Aaron Jonas Stutz

    2014-08-01

    Full Text Available Human evolution unfolded through a rather distinctive, dynamically constructed ecological niche. The human niche is not only generally terrestrial in habitat, while being flexibly and extensively heterotrophic in food-web connections. It is also defined by semiotically structured and structuring embodied cognitive interfaces, connecting the individual organism with the wider environment. The embodied dimensions of niche-population co-evolution have long involved semiotic system construction, which I hypothesize to be an evolutionarily primitive aspect of learning and higher-level cognitive integration and attention in the great apes and humans alike. A clearly pre-linguistic form of semiotic cognitive structuration is suggested to involve recursively learned and constructed object icons. Higher-level cognitive iconic representation of visually, auditorily, or haptically perceived extrasomatic objects would be learned and evoked through indexical connections to proprioceptive and affective somatic states. Thus, private cognitive signs would be defined, not only by their learned and perceived extrasomatic referents, but also by their associations to iconically represented somatic states. This evolutionary modification of animal associative learning is suggested to be adaptive in ecological niches occupied by long-lived, large-bodied ape species, facilitating memory construction and recall in highly varied foraging and social contexts, while sustaining selective attention during goal-directed behavioral sequences. The embodied niche construction (ENC hypothesis of human evolution posits that in the early hominin lineage, natural selection further modified the ancestral ape semiotic adaptations, favoring the recursive structuration of concise iconic narratives of embodied interaction with the environment.

  8. Mosaic evolution and the pattern of transitions in the hominin lineage.

    Science.gov (United States)

    Foley, Robert A

    2016-07-01

    Humans are uniquely unique, in terms of the extreme differences between them and other living organisms, and the impact they are having on the biosphere. The evolution of humans can be seen, as has been proposed, as one of the major transitions in evolution, on a par with the origins of multicellular organisms or the eukaryotic cell (Maynard Smith & Szathmáry 1997 Major transitions in evolution). Major transitions require the evolution of greater complexity and the emergence of new evolutionary levels or processes. Does human evolution meet these conditions? I explore the diversity of evidence on the nature of transitions in human evolution. Four levels of transition are proposed-baseline, novel taxa, novel adaptive zones and major transitions-and the pattern of human evolution considered in the light of these. The primary conclusions are that changes in human evolution occur continuously and cumulatively; that novel taxa and the appearance of new adaptations are not clustered very tightly in particular periods, although there are three broad transitional phases (Pliocene, Plio-Pleistocene and later Quaternary). Each phase is distinctive, with the first based on ranging and energetics, the second on technology and niche expansion, and the third on cognition and cultural processes. I discuss whether this constitutes a 'major transition' in the context of the evolutionary processes more broadly; the role of behaviour in evolution; and the opportunity provided by the rich genetic, phenotypic (fossil morphology) and behavioural (archaeological) record to examine in detail major transitions and the microevolutionary patterns underlying macroevolutionary change. It is suggested that the evolution of the hominin lineage is consistent with a mosaic pattern of change.This article is part of the themed issue 'Major transitions in human evolution'. PMID:27298474

  9. Chew Bahir: A Key Site within the Hominin Sites and Paleolakes Drilling Project, towards a Half Million-Year Climate Record from Southern Ethiopia

    Science.gov (United States)

    Schaebitz, F.; Asrat, A.; Lamb, H. F.; Trauth, M. H.; Foerster, V. E.; Junginger, A.; Raub, T. D.; Gromig, R.; Viehberg, F. A.; Roberts, H. M.; Cohen, A.

    2015-12-01

    Chew Bahir, a saline mudflat today, is one of the five sites in East Africa, drilled within the framework of HSPDP (Hominin Site and Paleolakes Drilling Project). It is also one of the key sites of the Collaborative Research Centre (CRC-806) "Our way to Europe" aiming at the reconstruction of environmental conditions in the source region of modern man (H. sapiens). It is suggested that a changing environment could have triggered the mobility and dispersal of modern man. The oldest known fossils of anatomical modern humans (~195 ka BP) were found in the Omo basin, not more than 90km westwards of our drill site. The deposits in the tectonic basin of Chew Bahir in southern Ethiopia were cored in Nov. 2014 in two boreholes down to 280 m and 260 m below surface respectively. The overlapping long cores (drilled ~20 m apart from each other), were opened, scanned, described and sampled in low resolution in April 2015. The recovered sediments mostly contain green-greyish to light coloured and brown to reddish clays and silty clays, interbedded with some laminated mica-rich sand layers and occurrences of carbonate concretions and nodules, which decrease upcore. Here we will present a first set of results on the composite core, comprising mainly lithology and magnetic susceptibility (MS). Based on known sedimentation rates from pre-studies performed on short cores across the basin, we anticipate the deep drilled cores to cover at least 500 ka BP. Moreover, new insights into the role of post-depositional alteration, especially of clay minerals and zeolites, will be presented as a contribution to an improved understanding of formation processes. The results support the identification of wet and dry climate periods in the past. Those pronounced variations of moisture availability, are thought to have influenced the evolution and mobility of Homo sapiens sapiens.

  10. The naming of new species in hominin evolution: A radical proposal--A temporary cessation in assigning new names.

    Science.gov (United States)

    Quintyn, C

    2009-01-01

    The species problem is one of the most complex and enduring problems plaguing evolutionary biology in general and human paleontology in particular. In the past 50 years, conceptions of species have diverged and speciated analogous to the present, largely accepted view of the hominin phylogeny. Conventional wisdom supports a "bushy" hominin phylogeny. However, chaos reigns because there is no agreed-upon methodology used to delimit species taxa in paleontology. This dispute is complicated by the ever-present intraspecific and interspecific morphological variation, which is itself exacerbated by other types of variation, including behavioral, ecological, geographical and temporal. When two or more of these forms of variation are used to delimit "new" extant or fossil species, any decision arrived at might be construed as arbitrary. This paper proposes that temporary cessation in assigning new names should be considered based on several critical problems: (1) the explosion of conceptions of a "species" arising from disagreements regarding species definitions, (2) differing interpretations of population variation, which lead to difficulty in interpreting hybridization in nature, leading in turn to the underestimation or overestimation of species, (3) the problem of modes of speciation being confounded with criteria used to distinguish among species, e.g., punctuated equilibrium posits high-speciation rates, and (4) the most common of all human traits, vanity. PMID:19573870

  11. On the Relationships of Postcanine Tooth Size with Dietary Quality and Brain Volume in Primates: Implications for Hominin Evolution

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    Juan Manuel Jiménez-Arenas

    2014-01-01

    Full Text Available Brain volume and cheek-tooth size have traditionally been considered as two traits that show opposite evolutionary trends during the evolution of Homo. As a result, differences in encephalization and molarization among hominins tend to be interpreted in paleobiological grounds, because both traits were presumably linked to the dietary quality of extinct species. Here we show that there is an essential difference between the genus Homo and the living primate species, because postcanine tooth size and brain volume are related to negative allometry in primates and show an inverse relationship in Homo. However, when size effects are removed, the negative relationship between encephalization and molarization holds only for platyrrhines and the genus Homo. In addition, there is no general trend for the relationship between postcanine tooth size and dietary quality among the living primates. If size and phylogeny effects are both removed, this relationship vanishes in many taxonomic groups. As a result, the suggestion that the presence of well-developed postcanine teeth in extinct hominins should be indicative of a poor-quality diet cannot be generalized to all extant and extinct primates.

  12. Rates of anterior tooth wear in Middle Pleistocene hominins from Sima de los Huesos (Sierra de Atapuerca, Spain)

    Science.gov (United States)

    de Castro, J. M. Bermúdez; Martinón-Torres, M.; Sarmiento, S.; Lozano, M.; Arsuaga, J. L.; Carbonell, E.

    2003-01-01

    This study presents quantitative data on the rates of anterior tooth wear in a Pleistocene human population. The data were obtained for the hominin sample of the Sima de los Huesos site in Atapuerca, Spain. The fossil record belongs to a minimum of 28 individuals of the same biological population, assigned to the species Homo heidelbergensis. We have estimated the original and the preserved crown height of the mandibular incisors (I1 and I2) of 11 individuals, whose age at death can be ascertained from the mineralization stage and tooth eruption. Results provide a range of 0.276–0.348 and 0.288–0.360 mm per year for the mean wear rate of the mandibular I1 and I2, respectively, in individuals ≈16–18 years old. These data suggest that incisors' crowns would be totally worn out toward the fifth decade of life. Thus, we expect the life expectancy of this population to be seriously limited. These data, which could be contrasted with results obtained on hominins at other sites, could be of interest for estimating the death age of adult individuals. PMID:14528001

  13. Taphonomic analysis of the hominin remains from Swabian Jura and their implications for the mortuary practices during the Upper Paleolithic

    Science.gov (United States)

    Sala, Nohemi; Conard, Nicholas

    2016-10-01

    The symbolic behavior of human beings usually is manifested in different ways such as figurative art, musical traditions, spoken language or complex funerary behavior. The Paleolithic sites of the Swabian Jura contain a rich archaeological record including the oldest evidence of musical instruments and figurative art which indicates complex cognitive abilities of the Paleolithic Homo sapiens that colonized Europe. Nevertheless, there is no evidence for burials in the Swabian caves during the Paleolithic. This raises questions regarding the kind of mortuary practices that existed in this region during the Paleolithic. In this paper, we address these questions from a taphonomic perspective by analyzing the hominin remains recovered in caves of the Swabian Jura. Whatever the funerary behavior was during the Early and Middle Upper Paleolithic, we have no evidence to document these practices. The Magdalenian hominin remains from Brillenhöhle, however, display anthropic modifications that have been hotly debated in the past. Our taphonomic analysis indicates that the assemblage displays traces of butchery similar to those recorded in the faunal remains. In addition to the cut marks, we have documented intentional breakage and human tooth marks, suggesting that the consumption of human corpses took place during the Magdalenian at Brillenhöhle. Similar anthropic modifications have also been documented in Magdalenian horizon at Hohle Fels. This suggests that the cannibalism practices during the Magdalenian were more common than previously expected during the Magdalenian in the Swabian Jura.

  14. Rates of anterior tooth wear in Middle Pleistocene hominins from Sima de los Huesos (Sierra de Atapuerca, Spain).

    Science.gov (United States)

    Bermúdez de Castro, J M; Martinón-Torres, M; Sarmiento, S; Lozano, M; Arsuaga, J L; Carbonell, E

    2003-10-14

    This study presents quantitative data on the rates of anterior tooth wear in a Pleistocene human population. The data were obtained for the hominin sample of the Sima de los Huesos site in Atapuerca, Spain. The fossil record belongs to a minimum of 28 individuals of the same biological population, assigned to the species Homo heidelbergensis. We have estimated the original and the preserved crown height of the mandibular incisors (I1 and I2) of 11 individuals, whose age at death can be ascertained from the mineralization stage and tooth eruption. Results provide a range of 0.276-0.348 and 0.288-0.360 mm per year for the mean wear rate of the mandibular I1 and I2, respectively, in individuals approximately 16-18 years old. These data suggest that incisors' crowns would be totally worn out toward the fifth decade of life. Thus, we expect the life expectancy of this population to be seriously limited. These data, which could be contrasted with results obtained on hominins at other sites, could be of interest for estimating the death age of adult individuals. PMID:14528001

  15. Trabecular architecture in the StW 352 fossil hominin calcaneus.

    Science.gov (United States)

    Zeininger, Angel; Patel, Biren A; Zipfel, Bernhard; Carlson, Kristian J

    2016-08-01

    Australopithecus africanus has been interpreted as having a rigid lateral foot. One mechanism contributing to a rigid foot during push-off in humans is a calcaneocuboid joint (CCJ) with limited dorsiflexion and a "close-packed" talocalcaneal joint (TCJ). In contrast, apes likely have a greater CCJ range of motion and lack a close-packed TCJ. Differences in tarsal arthrokinematics may result in different joint loading environments. In Homo sapiens, we tested the hypothesis that dorsal and plantar CCJ and the TCJ show evidence of predictable habitual loading. In Pan troglodytes, Gorilla gorilla, Gorilla beringei, and Papio ursinus, we tested the hypothesis that only the dorsal CCJ shows evidence of predictable loading. Specifically, we predicted similarity in trabecular properties across the dorsal and plantar CCJ in H. sapiens, but dissimilarity in non-humans. Additionally, we investigated trabecular properties of an A. africanus calcaneus (StW 352) to evaluate joint loading patterns in this hominin and ultimately address the evolution of these properties in H. sapiens. Contrary to predictions, the H. sapiens dorsal CCJ has a significantly higher elongation index, bone volume fraction, trabecular thickness, and trabecular number than the plantar CCJ, while trabecular properties in non-humans do not always differ as predicted between regions. H. sapiens exhibits trabecular morphology indicative of less variable TCJ loading than other groups, having the most anisotropic and rod-like struts oriented in line with predicted principal loads. Multivariate analysis shows that the StW 352 dorsal CCJ matches P. ursinus best, while the plantar CCJ matches G. beringei best and the TCJ matches that of G. gorilla best. Overall patterns suggest that the StW 352 calcaneus experienced more variable loading than H. sapiens, but less variable loading than P. troglodytes, G. gorilla, G. beringei, and P. ursinus, consistent with a large range of foot movements, probably

  16. Orangutan fish eating, primate aquatic fauna eating, and their implications for the origins of ancestral hominin fish eating.

    Science.gov (United States)

    Russon, Anne E; Compost, Alain; Kuncoro, Purwo; Ferisa, Agnes

    2014-12-01

    This paper presents new evidence of fish eating in rehabilitant orangutans living on two Bornean islands and explores its contributions to understanding nonhuman primates' aquatic fauna eating and the origins of ancestral hominin fish eating. We assessed the prevalence of orangutans' fish eating, their techniques for obtaining fish, and possible contributors (ecology, individual differences, humans). We identified 61 events in which orangutans tried to obtain fish, including 19 in which they ate fish. All the orangutans were juvenile-adolescent; all the fish were disabled catfish; and most were obtained and eaten in drier seasons in or near shallow, slow-moving water. Orangutans used several techniques to obtain fish (inadvertent, opportunistic and deliberate hand-catch, scrounge, tool-assisted catch) and probably learned them in that order. Probable contributing factors were orangutan traits (age, pre-existing water or tool skills), island features (social density, water accessibility), and local human fishing. Our review of primates' aquatic fauna eating showed orangutans to be one of 20 species that eat aquatic fauna, one of nine confirmed to eat fish, and one of three that use tools to obtain fish. Primate fish eating is also site-specific within species, partly as a function of habitat (e.g., marine-freshwater, seasonality) and human influence (possibly fostered eating fish or other aquatic fauna at most sites, clearly induced it at some). At tropical freshwater sites, fish eating occurred most often in drier seasons around shallow water. Orangutan and primate findings are generally consistent with Stewart's (2010) reconstruction of the origins of ancestral hominin fish eating, but suggest that it, and tool-assisted fish catching, were possible much earlier. PMID:25038033

  17. Hominin Sites and Paleolakes Drilling Project. Chew Bahir, southern Ethiopia: How to get from three tonnes of sediment core to > 500 ka of continuous climate history?

    Science.gov (United States)

    Foerster, Verena; Asrat, Asfawossen; Cohen, Andrew S.; Gromig, Raphael; Günter, Christina; Junginger, Annett; Lamb, Henry F.; Schaebitz, Frank; Trauth, Martin H.

    2016-04-01

    In search of the environmental context of the evolution and dispersal of Homo sapiens and our close relatives within and beyond the African continent, the ICDP-funded Hominin Sites and Paleolakes Drilling Project (HSPDP) has recently cored five fluvio-lacustrine archives of climate change in East Africa. The sediment cores collected in Ethiopia and Kenya are expected to provide valuable insights into East African environmental variability during the last ~3.5 Ma. The tectonically-bound Chew Bahir basin in the southern Ethiopian rift is one of the five sites within HSPDP, located in close proximity to the Lower Omo River valley, the site of the oldest known fossils of anatomically modern humans. In late 2014, the two cores (279 and 266 m long respectively, HSPDP-CHB14-2A and 2B) were recovered, summing up to nearly three tonnes of mostly calcareous clays and silts. Deciphering an environmental record from multiple records, from the source region of modern humans could eventually allow us to reconstruct the pronounced variations of moisture availability during the transition into Middle Stone Age, and its implications for the origin and dispersal of Homo sapiens. Here we present the first results of our analysis of the Chew Bahir cores. Following the HSPDP protocols, the two parallel Chew Bahir sediment cores have been merged into one single, 280 m long and nearly continuous (>90%) composite core on the basis of a high resolution MSCL data set (e.g., magnetic susceptibility, gamma ray density, color intensity transects, core photographs). Based on the obvious cyclicities in the MSCL, correlated with orbital cycles, the time interval covered by our sediment archive of climate change is inferred to span the last 500-600 kyrs. Combining our first results from the long cores with the results from the accomplished pre-study of short cores taken in 2009/10 along a NW-SE transect across the basin (Foerster et al., 2012, Trauth et al., 2015), we have developed a hypothesis

  18. Papio Cranium from the Hominin-Bearing Site of Malapa: Implications for the Evolution of Modern Baboon Cranial Morphology and South African Plio-Pleistocene Biochronology.

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    Christopher C Gilbert

    Full Text Available A new partial cranium (UW 88-886 of the Plio-Pleistocene baboon Papio angusticeps from Malapa is identified, described and discussed. UW 88-886 represents the only non-hominin primate yet recovered from Malapa and is important both in the context of baboon evolution as well as South African hominin site biochronology. The new specimen may represent the first appearance of modern baboon anatomy and coincides almost perfectly with molecular divergence date estimates for the origin of the modern P. hamadryas radiation. The fact that the Malapa specimen is dated between ~2.026-2.36 million years ago (Ma also has implications for the biochronology of other South African Plio-Pleistocene sites where P. angusticeps is found.

  19. New radiometric ages for the BH-1 hominin from Balanica (Serbia: implications for understanding the role of the Balkans in Middle Pleistocene human evolution.

    Directory of Open Access Journals (Sweden)

    William J Rink

    Full Text Available Newly obtained ages, based on electron spin resonance combined with uranium series isotopic analysis, and infrared/post-infrared luminescence dating, provide a minimum age that lies between 397 and 525 ka for the hominin mandible BH-1 from Mala Balanica cave, Serbia. This confirms it as the easternmost hominin specimen in Europe dated to the Middle Pleistocene. Inferences drawn from the morphology of the mandible BH-1 place it outside currently observed variation of European Homo heidelbergensis. The lack of derived Neandertal traits in BH-1 and its contemporary specimens in Southeast Europe, such as Kocabaş, Vasogliano and Ceprano, coupled with Middle Pleistocene synapomorphies, suggests different evolutionary forces acting in the east of the continent where isolation did not play such an important role during glaciations.

  20. A description of the geological context, discrete traits, and linear morphometrics of the Middle Pleistocene hominin from Dali, Shaanxi Province, China.

    Science.gov (United States)

    Wu, Xinzhi; Athreya, Sheela

    2013-01-01

    In 1978, a nearly complete hominin fossil cranium was recovered from loess deposits at the site of Dali in Shaanxi Province, northwestern China. It was subsequently briefly described in both English and Chinese publications. Here we present a comprehensive univariate and nonmetric description of the specimen and provide comparisons with key Middle Pleistocene Homo erectus and non-erectus hominins from Eurasia and Africa. In both respects we find affinities with Chinese H. erectus as well as African and European Middle Pleistocene hominins typically referred to as Homo heidelbergensis. Specifically, the Dali specimen possesses a low cranial height, relatively short and arched parietal bones, an angled occipital bone, and a nonprominent articular tubercle relative to the preglenoid surface all of which distinguish it from Afro/European Middle Pleistocene Homo and align it with Asian H. erectus. At the same time, it displays a more derived morphology of the supraorbital torus and supratoral sulcus and a thinner tympanic plate than H. erectus, a relatively long upper (lambda-inion) occipital plane with a clear separation of inion and opisthocranion, and an absolute and relative increase in brain size, all of which align it with African and European Middle Pleistocene Homo. Finally, traits such as the form of the frontal keel and the relatively short, broad midface align Dali specifically with other Chinese specimens from the Middle Pleistocene and Late Pleistocene, including H. erectus, and differentiate these from the Afro/European specimens of this time period. PMID:23283667

  1. The environment of the Ethiopian highlands at the Mid Pleistocene Transition: Fauna, flora and hominins in the 850-700 ka sequence of Gombore II (Melka Kunture)

    Science.gov (United States)

    Mussi, M.; Altamura, F.; Bonnefille, R.; De Rita, D.; Melis, R. T.

    2016-10-01

    Environment, climatic change and human evolution have been debated over the last 50 years giving special attention to the Plio-Pleistocene sites of the Rift Valley. In this paper we discuss the environment and the limits of hominin adaptability based on evidence from Melka Kunture, at 2000 m asl on the Ethiopian highlands, and specifically on the ∼850 ka to ∼700 ka sequence at sub-site Gombore II. Human fossils and multiple Acheulean occurrences, as well as hippo remains and footprints, combined with palynological analysis, provide a highly detailed chronological resolution of the changing local environmental conditions during the last ∼150 ka of the MPT (Mid Pleistocene Transition), including the sequence of events after a volcanic eruption. Layers containing footprints and fossils are evidence of near-continuous occupation by hippos and their recolonization of the area after a disruptive volcanic eruption. Conversely, Acheulean implements and human fossils suggest that peopling by hominins occurred at a different and discontinuous pace even when the flora and fauna were re-established and the environment was rather stable. Most notably, the assembled evidence points to the limits of Homo erectus s.l. adaptability. Apparently, this hominin could no longer live at 2000 m asl when the climate deteriorated during glacial isotopic stage 20, becoming markedly colder than it is today, but re-colonized the area when the climate turned warmer again during isotopic stage 19.

  2. The Acheulian site of Gesher Benot Ya'aqov, Israel: environment, hominin culture, subsistence and adaptation on the shores of the paleo-Hula Lake

    Science.gov (United States)

    Goren-Inbar, N.

    2014-12-01

    The Acheulian site of Gesher Benot Ya'aqov (GBY), located in the Hula Valley, northern sector of the Dead Sea transform, stretches along 3.5 km of the Jordan River and its banks. The accumulation of tilted lake-margin sediments interfingered with basalt flows began 1.1 Ma and ended after 0.6 Ma. The excavations (1989-1997) exposed 34 m thick deposits that provide unique data sets on climate, environment, biology, culture and hominin behavior. Hominin presence is known throughout the sequence, providing information on Acheulian technology and cognition along the time trajectory, but the richest sites (15 in number) occur above the M/B Chron Boundary. Reconstructions of paleoenvironment and habitats are based on fossil remains yielding an extremely rich typically Mediterranean biomass of diverse biogeographic origins. Macro and micro organic material (over 140 identified taxa) exhibits a typical Mediterranean environment similar to the extant flora, with few extinctions (20 species). The rich fossil faunal include molluscs, ostracods, fish, amphibians, reptiles, birds, micromammals and medium-sized to large mammals (over 237 taxa), predominantly Palearctic in biogeographic origin. Many of these taxa are still extant, attesting to stable habitats and paleoclimatic conditions. Hominin occupations are documented by thousands of lithic artifacts (flint, limestone and basalt), all assigned to the Large Flake Acheulian culture. These assemblages show a continuous cultural tradition of the same tool kit along the time trajectory. The lithic reduction required developed cognitive abilities and communication abilities, interpreted as language. Evidence of hominin subsistence includes data on carcass processing including extraction of marrow, with a preference for consumption of fallow deer, elephant, hippopotamus and fish. Edible plant remains include nuts, USO, fruits, seeds and vegetables in association with stone artifacts and animal bones. Fire, present throughout, was

  3. The Homo sapiens Cave hominin site of Mulan Mountain,Jiangzhou District,Chongzuo,Guangxi with emphasis on its age

    Institute of Scientific and Technical Information of China (English)

    JIN ChangZhu; PAN WenShi; ZHANG YingQi; CAI YanJun; XU QinQi; TANG ZhiLu; WANG Wei; WANG Yuan; LIU JinYi; QIN DaGong; R.Lawrence Edwards; CHENG Hai

    2009-01-01

    One of the most hotly debated and frontal issues in paleoanthropology focuses on the origins of modern humans.Recently,an incomplete hominin mandible with a distinctly weaker mental protuberance than modern human and a great variety of coexisting fossil mammals were unearthed from the Homo sapiens Cave of Mulan Mountain,Chongzuo,Guangxi.The mammalian fauna from the Homo sapiens Cave characterized by the combination of Elephas kiangnanensis,first occurring Elephas maixmus,and Megatapirus augustus,and strikingly different from the Early Pleistocene Gigantopithecus fauna and the Middle Pleistocene Ailuropoda-Stogodon fauna of South China could be regarded as an early representive of the typical Asian elephant fauna.Faunal analysis,biostratigraphic correlation,and,most importantly,U-series dating all consistently support an estimate of ca.110 ka for the age of the fossil Homo sapiens and coexisting mammalian fauna,that is,the early Late Pleistocene.The fauna is mainly made up of tropical-subtropical elements,but grassland elements have a much greater variety than forest elements,which probably indicates a drier climate at that time.This discovery of early Homo sapiens at the Mulan Mountain will play a significant role in the study of the origin and its environmental background of modern humans.

  4. Tool-composite reuse in wild chimpanzees (Pan troglodytes): archaeologically invisible steps in the technological evolution of early hominins?

    Science.gov (United States)

    Carvalho, Susana; Biro, Dora; McGrew, William C; Matsuzawa, Tetsuro

    2009-10-01

    Recent etho-archaeological studies of stone-tool use by wild chimpanzees have contributed valuable data towards elucidating the variables that influenced the emergence and development of the first lithic industries among Plio-Pleistocene hominins. Such data help to identify potential behaviours entailed in the first percussive technologies that are invisible in archaeological records. The long-term research site of Bossou in Guinea features a unique chimpanzee community whose members systematically use portable stones as hammers and anvils to crack open nuts in natural as well as in field experimental settings. Here we present the first analysis of repeated reuse of the same tool-composites in wild chimpanzees. Data collected over 5 years of experimental nut-cracking sessions at an "outdoor laboratory" site were assessed for the existence of systematic patterns in the selection of tool-composites, at group and at individual levels. Chimpanzees combined certain stones as hammer and anvil more often than expected by chance, even when taking into account preferences for individual stones by themselves. This may reflect an ability to recognise the nut-cracker as a single tool (composed of two elements, but functional only as a whole), as well as discrimination of tool quality-effectiveness. Through repeatedly combining the same pairs of stones--whether due to preferences for particular composites or for the two elements independently--tool-users may amplify use-wear traces and increase the likelihood of fracturing the stones, and thus of detaching pieces by battering. PMID:19680699

  5. The ICDP-Hominin Sites and Paleolakes Drilling Project (HSPDP): new data from the Chew Bahir site in Ethiopia

    Science.gov (United States)

    Leng, Melanie; Dean, Jonathan; Asrat, Asfawossen; Cohen, Andrew; Foerster, Verena; Just, Janna; Klasen, Nicole; Lamb, Henry; Schäbitz, Frank; Trauth, Martin; Viehberg, Finn; Wagner, Bernd

    2016-04-01

    There are currently few long, continuous, Pleistocene records from East Africa, meaning it has been difficult to establish the relative influence of low- versus high-latitude forcing on East African climate and climatic conditions at the time of anatomically modern human origin and subsequent dispersal. We have been attempting to address these gaps in our knowledge by analysing lake sediments taken from Chew Bahir, an area of playa mudflats in southern Ethiopia close to the site of the oldest-known anatomically modern human fossils at Omo-Kibish. In March 2014, Chew Bahir was cored to a depth of ~40 metres, and the resulting sediment sequence is estimated to cover the last ~115ka. In December 2014, a nearby site was drilled to a depth of ~280 metres as part of the International Continental scientific Drilling Programme - Hominin Sites and Paleolakes Drilling Project (HSPDP). The oxygen and carbon isotope composition of endogenic calcite and other data from these cores will be presented. The data show some significant changes in water balance variability, the period prior to 70ka appears very unstable with some significant periods of drought and flood. Between 70-20ka the lake was stable and evaporative. The last 20ka years was wetter.

  6. Shared human-chimpanzee pattern of perinatal femoral shaft morphology and its implications for the evolution of hominin locomotor adaptations.

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    Naoki Morimoto

    Full Text Available BACKGROUND: Acquisition of bipedality is a hallmark of human evolution. How bipedality evolved from great ape-like locomotor behaviors, however, is still highly debated. This is mainly because it is difficult to infer locomotor function, and even more so locomotor kinematics, from fossil hominin long bones. Structure-function relationships are complex, as long bone morphology reflects phyletic history, developmental programs, and loading history during an individual's lifetime. Here we discriminate between these factors by investigating the morphology of long bones in fetal and neonate great apes and humans, before the onset of locomotion. METHODOLOGY/PRINCIPAL FINDINGS: Comparative morphometric analysis of the femoral diaphysis indicates that its morphology reflects phyletic relationships between hominoid taxa to a greater extent than taxon-specific locomotor adaptations. Diaphyseal morphology in humans and chimpanzees exhibits several shared-derived features, despite substantial differences in locomotor adaptations. Orangutan and gorilla morphologies are largely similar, and likely represent the primitive hominoid state. CONCLUSIONS/SIGNIFICANCE: These findings are compatible with two possible evolutionary scenarios. Diaphyseal morphology may reflect retained adaptive traits of ancestral taxa, hence human-chimpanzee shared-derived features may be indicative of the locomotor behavior of our last common ancestor. Alternatively, diaphyseal morphology might reflect evolution by genetic drift (neutral evolution rather than selection, and might thus be more informative about phyletic relationships between taxa than about locomotor adaptations. Both scenarios are consistent with the hypothesis that knuckle-walking in chimpanzees and gorillas resulted from convergent evolution, and that the evolution of human bipedality is unrelated to extant great ape locomotor specializations.

  7. The Hominin Sites and Paleolakes Drilling Project (HSPDP): Understanding the paleoenvironmental and paleoclimatic context of human origins through continental drilling

    Science.gov (United States)

    Cohen, Andrew S.; Campisano, Christopher; Asrat, Asfawossen; Arrowsmith, Ramon; Deino, Alan; Feibel, Craig; Hill, Andrew; Kingston, John; Lamb, Henry; Lowenstein, Tim; Olago, Daniel; Bernhart Owen, R.; Renaut, Robin; Schabitz, Frank; Trauth, Martin

    2015-04-01

    The influence of climate and environmental history on human evolution is an existential question that continues to be hotly debated, in part because of the paucity of high resolution records collected in close proximity to the key fossil and archaeological evidence. To address this issue and transform the scientific debate, the HSPDP was developed to collect lacustrine sediment drill cores from basins in Kenya and Ethiopia that collectively encompass critical time intervals and locations for Plio-Quaternary human evolution in East Africa. After a 17 month campaign, drilling was completed in November, 2014, with over 1750m of core collected from 11 boreholes from five areas (1930m total drilling length, avg. 91% recovery). The sites, from oldest to youngest, include 1) N. Awash, Ethiopia (~3.5-2.9Ma core interval); 2) Baringo-Tugen Hills, Kenya (~3.3-2.5Ma); 3) West Turkana, Kenya (~1.9-1.4Ma); L. Magadi, Kenya (0.8-0Ma) and the Chew Bahir Basin, Ethiopia (~0.5-0Ma). Initial core description (ICD) and sampling for geochronology, geochemistry and paleoecology studies had been completed by mid2014, with the two remaining sites (Magadi and Chew Bahir) scheduled for ICD work in early 2015. Whereas the primary scientific targets were the lacustrine deposits from the hominin-bearing basin depocenters, many intervals of paleosols (representative of low lake stands and probable arid periods) were also encountered in drill cores. Preliminary analyses of drill core sedimentology and geochemistry show both long-term lake level changes and cyclic variability in lake levels, both of which may be indicative of climatic forcing events of interest to paleoanthropologists. Authors of this abstract also include the entire HSPDP field team.

  8. The hominins: a very conservative tribe? Last common ancestors, plasticity and ecomorphology in Hominidae. Or, What's in a name?

    Science.gov (United States)

    Crompton, Robin Huw

    2016-04-01

    In the early 20th century the dominant paradigm for the ecological context of the origins of human bipedalism was arboreal suspension. In the 1960s, however, with recognition of the close genetic relationship of humans, chimpanzees and bonobos, and with the first field studies of mountain gorillas and common chimpanzees, it was assumed that locomotion similar to that of common chimpanzees and mountain gorillas, which appeared to be dominated by terrestrial knuckle-walking, must have given rise to human bipedality. This paradigm has been popular, if not universally dominant, until very recently. However, evidence that neither the knuckle-walking or vertical climbing of these apes is mechanically similar to human bipedalism, as well as the hand-assisted bipedality and orthograde clambering of orang-utans, has cast doubt on this paradigm. It now appears that the dominance of terrestrial knuckle-walking in mountain gorillas is an artefact seen only in the extremes of their range, and that both mountain and lowland gorillas have a generalized orthogrady similar to that seen in orang-utans. These data, together with evidence for continued arboreal competence in humans, mesh well with an increasing weight of fossil evidence suggesting that a mix of orang-utan and gorilla-like arboreal locomotion and upright terrestrial bipedalism characterized most australopiths. The late split date of the panins, corresponding to dates for separation of Homo and Australopithecus, leads to the speculation that competition with chimpanzees, as appears to exist today with gorillas, may have driven ecological changes in hominins and perhaps cladogenesis. However, selection for ecological plasticity and morphological conservatism is a core characteristic of Hominidae as a whole, including Hominini. PMID:26729562

  9. Pleistocene Hominins as a Resource for Carnivores: A c. 500,000-Year-Old Human Femur Bearing Tooth-Marks in North Africa (Thomas Quarry I, Morocco.

    Directory of Open Access Journals (Sweden)

    Camille Daujeard

    Full Text Available In many Middle Pleistocene sites, the co-occurrence of hominins with carnivores, who both contributed to faunal accumulations, suggests competition for resources as well as for living spaces. Despite this, there is very little evidence of direct interaction between them to-date. Recently, a human femoral diaphysis has been recognized in South-West of Casablanca (Morocco, in the locality called Thomas Quarry I. This site is famous for its Middle Pleistocene fossil hominins considered representatives of Homo rhodesiensis. The bone was discovered in Unit 4 of the Grotte à Hominidés (GH, dated to c. 500 ky and was associated with Acheulean artefacts and a rich mammalian fauna. Anatomically, it fits well within the group of known early Middle Pleistocene Homo, but its chief point of interest is that the diaphyseal ends display numerous tooth marks showing that it had been consumed shortly after death by a large carnivore, probably a hyena. This bone represents the first evidence of consumption of human remains by carnivores in the cave. Whether predated or scavenged, this chewed femur indicates that humans were a resource for carnivores, underlining their close relationships during the Middle Pleistocene in Atlantic Morocco.

  10. Pleistocene Hominins as a Resource for Carnivores: A c. 500,000-Year-Old Human Femur Bearing Tooth-Marks in North Africa (Thomas Quarry I, Morocco).

    Science.gov (United States)

    Daujeard, Camille; Geraads, Denis; Gallotti, Rosalia; Lefèvre, David; Mohib, Abderrahim; Raynal, Jean-Paul; Hublin, Jean-Jacques

    2016-01-01

    In many Middle Pleistocene sites, the co-occurrence of hominins with carnivores, who both contributed to faunal accumulations, suggests competition for resources as well as for living spaces. Despite this, there is very little evidence of direct interaction between them to-date. Recently, a human femoral diaphysis has been recognized in South-West of Casablanca (Morocco), in the locality called Thomas Quarry I. This site is famous for its Middle Pleistocene fossil hominins considered representatives of Homo rhodesiensis. The bone was discovered in Unit 4 of the Grotte à Hominidés (GH), dated to c. 500 ky and was associated with Acheulean artefacts and a rich mammalian fauna. Anatomically, it fits well within the group of known early Middle Pleistocene Homo, but its chief point of interest is that the diaphyseal ends display numerous tooth marks showing that it had been consumed shortly after death by a large carnivore, probably a hyena. This bone represents the first evidence of consumption of human remains by carnivores in the cave. Whether predated or scavenged, this chewed femur indicates that humans were a resource for carnivores, underlining their close relationships during the Middle Pleistocene in Atlantic Morocco.

  11. Man the Fat Hunter: The Demise of Homo erectus and the Emergence of a New Hominin Lineage in the Middle Pleistocene (ca. 400 kyr) Levant

    Science.gov (United States)

    Ben-Dor, Miki; Gopher, Avi; Hershkovitz, Israel; Barkai, Ran

    2011-01-01

    The worldwide association of H. erectus with elephants is well documented and so is the preference of humans for fat as a source of energy. We show that rather than a matter of preference, H. erectus in the Levant was dependent on both elephants and fat for his survival. The disappearance of elephants from the Levant some 400 kyr ago coincides with the appearance of a new and innovative local cultural complex – the Levantine Acheulo-Yabrudian and, as is evident from teeth recently found in the Acheulo-Yabrudian 400-200 kyr site of Qesem Cave, the replacement of H. erectus by a new hominin. We employ a bio-energetic model to present a hypothesis that the disappearance of the elephants, which created a need to hunt an increased number of smaller and faster animals while maintaining an adequate fat content in the diet, was the evolutionary drive behind the emergence of the lighter, more agile, and cognitively capable hominins. Qesem Cave thus provides a rare opportunity to study the mechanisms that underlie the emergence of our post-erectus ancestors, the fat hunters. PMID:22174868

  12. Man the fat hunter: the demise of Homo erectus and the emergence of a new hominin lineage in the Middle Pleistocene (ca. 400 kyr Levant.

    Directory of Open Access Journals (Sweden)

    Miki Ben-Dor

    Full Text Available The worldwide association of H. erectus with elephants is well documented and so is the preference of humans for fat as a source of energy. We show that rather than a matter of preference, H. erectus in the Levant was dependent on both elephants and fat for his survival. The disappearance of elephants from the Levant some 400 kyr ago coincides with the appearance of a new and innovative local cultural complex--the Levantine Acheulo-Yabrudian and, as is evident from teeth recently found in the Acheulo-Yabrudian 400-200 kyr site of Qesem Cave, the replacement of H. erectus by a new hominin. We employ a bio-energetic model to present a hypothesis that the disappearance of the elephants, which created a need to hunt an increased number of smaller and faster animals while maintaining an adequate fat content in the diet, was the evolutionary drive behind the emergence of the lighter, more agile, and cognitively capable hominins. Qesem Cave thus provides a rare opportunity to study the mechanisms that underlie the emergence of our post-erectus ancestors, the fat hunters.

  13. Exploring the Potential of Laser Ablation Carbon Isotope Analysis for Examining Ecology during the Ontogeny of Middle Pleistocene Hominins from Sima de los Huesos (Northern Spain.

    Directory of Open Access Journals (Sweden)

    Nuria Garcia

    Full Text Available Laser ablation of tooth enamel was used to analyze stable carbon isotope compositions of teeth of hominins, red deer, and bears from middle Pleistocene sites in the Sierra de Atapuerca in northern Spain, to investigate the possibility that this technique could be used as an additional tool to identify periods of physiological change that are not detectable as changes in tooth morphology. Most of the specimens were found to have minimal intra-tooth variation in carbon isotopes (< 2.3‰, suggesting isotopically uniform diets through time and revealing no obvious periods of physiological change. However, one of the two sampled hominin teeth displayed a temporal carbon isotope shift (3.2‰ that was significantly greater than observed for co-occurring specimens. The δ13C value of this individual averaged about -16‰ early in life, and -13‰ later in life. This isotopic change occurred on the canine crown about 4.2 mm from the root, which corresponds to an approximate age of two to four years old in modern humans. Our dataset is perforce small owing to the precious nature of hominid teeth, but it demonstrates the potential utility of the intra-tooth isotope profile method for extracting ontogenetic histories of human ancestors.

  14. Exploring the Potential of Laser Ablation Carbon Isotope Analysis for Examining Ecology during the Ontogeny of Middle Pleistocene Hominins from Sima de los Huesos (Northern Spain).

    Science.gov (United States)

    Garcia, Nuria; Feranec, Robert S; Passey, Benjamin H; Cerling, Thure E; Arsuaga, Juan Luis

    2015-01-01

    Laser ablation of tooth enamel was used to analyze stable carbon isotope compositions of teeth of hominins, red deer, and bears from middle Pleistocene sites in the Sierra de Atapuerca in northern Spain, to investigate the possibility that this technique could be used as an additional tool to identify periods of physiological change that are not detectable as changes in tooth morphology. Most of the specimens were found to have minimal intra-tooth variation in carbon isotopes (< 2.3‰), suggesting isotopically uniform diets through time and revealing no obvious periods of physiological change. However, one of the two sampled hominin teeth displayed a temporal carbon isotope shift (3.2‰) that was significantly greater than observed for co-occurring specimens. The δ13C value of this individual averaged about -16‰ early in life, and -13‰ later in life. This isotopic change occurred on the canine crown about 4.2 mm from the root, which corresponds to an approximate age of two to four years old in modern humans. Our dataset is perforce small owing to the precious nature of hominid teeth, but it demonstrates the potential utility of the intra-tooth isotope profile method for extracting ontogenetic histories of human ancestors. PMID:26673156

  15. Comparative morphology of the hominin and African ape hyoid bone, a possible marker of the evolution of speech.

    Science.gov (United States)

    Steele, James; Clegg, Margaret; Martelli, Sandra

    2013-10-01

    This study examines the morphology of the hyoid in three closely related species, Homo sapiens, Pan troglodytes, and Gorilla gorilla. Differences and similarities between the hyoids of these species are characterized and used to interpret the morphology and affi nities of the Dikika A. afarensis, Kebara 2 Neanderthal, and other fossil hominin hyoid bones. Humans and African apes are found to have distinct hyoid morphologies. In humans the maximum width across the distal tips of the articulated greater horns is usually slightly greater than the maximum length (distal greater horn tip to most anterior point of the hyoid body in the midline). A different pattern is usually found in the African ape hyoids, which have much greater maximum lengths. In humans, the hyoid body is also much more anteroposteriorly shallow in proportion to its height and width, and this is true for all age classes. The Dikika australopithecine hyoid body proportions are chimpanzeelike. A discriminant function analysis, using a larger subadult sample from the three extant species than that reported by Alemseged et al. (2006), confirms this finding. The Kebara hyoid dimensions (body alone, and articulated body and greater horns) are almost all within the observed range for human hyoids. Discriminant functions clearly distinguish human from African ape hyoids and classify the Kebara 2 hyoid as human (confirming the finding of Arensburg et al. 1989). Our virtual dissection of a chimpanzee air sac system shows its subhyoid extension into the dorsal hyoid body. Following Alemseged et al. (2006), the expanded bulla characteristic of the African ape and australopithecine hyoid body is therefore interpreted as refl ecting the presence of such a laryngeal air sac extension. Its absence in the human, Neanderthal, and H. heidelbergensis (Atapuerca SH) hyoids implicates the loss of the laryngeal air sacs as a derived Neanderthal and modern human trait, which evolved no later than the middle Pleistocene. If

  16. Comparative morphology of the hominin and African ape hyoid bone, a possible marker of the evolution of speech.

    Science.gov (United States)

    Steele, James; Clegg, Margaret; Martelli, Sandra

    2013-10-01

    This study examines the morphology of the hyoid in three closely related species, Homo sapiens, Pan troglodytes, and Gorilla gorilla. Differences and similarities between the hyoids of these species are characterized and used to interpret the morphology and affi nities of the Dikika A. afarensis, Kebara 2 Neanderthal, and other fossil hominin hyoid bones. Humans and African apes are found to have distinct hyoid morphologies. In humans the maximum width across the distal tips of the articulated greater horns is usually slightly greater than the maximum length (distal greater horn tip to most anterior point of the hyoid body in the midline). A different pattern is usually found in the African ape hyoids, which have much greater maximum lengths. In humans, the hyoid body is also much more anteroposteriorly shallow in proportion to its height and width, and this is true for all age classes. The Dikika australopithecine hyoid body proportions are chimpanzeelike. A discriminant function analysis, using a larger subadult sample from the three extant species than that reported by Alemseged et al. (2006), confirms this finding. The Kebara hyoid dimensions (body alone, and articulated body and greater horns) are almost all within the observed range for human hyoids. Discriminant functions clearly distinguish human from African ape hyoids and classify the Kebara 2 hyoid as human (confirming the finding of Arensburg et al. 1989). Our virtual dissection of a chimpanzee air sac system shows its subhyoid extension into the dorsal hyoid body. Following Alemseged et al. (2006), the expanded bulla characteristic of the African ape and australopithecine hyoid body is therefore interpreted as refl ecting the presence of such a laryngeal air sac extension. Its absence in the human, Neanderthal, and H. heidelbergensis (Atapuerca SH) hyoids implicates the loss of the laryngeal air sacs as a derived Neanderthal and modern human trait, which evolved no later than the middle Pleistocene. If

  17. Terrestrial nest-building by wild chimpanzees (Pan troglodytes): implications for the tree-to-ground sleep transition in early hominins.

    Science.gov (United States)

    Koops, Kathelijne; McGrew, William C; Matsuzawa, Tetsuro; Knapp, Leslie A

    2012-07-01

    Nest-building is a great ape universal and arboreal nesting in chimpanzees and bonobos suggests that the common ancestor of Pan and Homo also nested in trees. It has been proposed that arboreal nest-building remained the prevailing pattern until Homo erectus, a fully terrestrial biped, emerged. We investigated the unusual occurrence of ground-nesting in chimpanzees (Pan troglodytes), which may inform on factors influencing the tree-to-ground sleep transition in the hominin lineage. We used a novel genetic approach to examine ground-nesting in unhabituated chimpanzees at Seringbara in the Nimba Mountains, Guinea. Previous research showed that ground-nesting at Seringbara was not ecologically determined. Here, we tested a possible mate-guarding function of ground-nesting by analyzing DNA from shed hairs collected from ground nests and tree nests found in close proximity. We examined whether or not ground-nesting was a group-level behavioral pattern and whether or not it occurred in more than one community. We used multiple genetic markers to identify sex and to examine variation in mitochondrial DNA control region (HV1, HV2) sequences. Ground-nesting was a male-biased behavior and males constructed more elaborate ("night") nests than simple ("day") nests on the ground. The mate-guarding hypothesis was not supported, as ground and associated tree nests were built either by maternally-related males or possibly by the same individuals. Ground-nesting was widespread and likely habitual in two communities. We suggest that terrestrial nest-building may have already occurred in arboreally-adapted early hominins before the emergence of H. erectus. PMID:22460549

  18. When felids and hominins ruled at Olduvai Gorge: A machine learning analysis of the skeletal profiles of the non-anthropogenic Bed I sites

    Science.gov (United States)

    Arriaza, Mari Carmen; Domínguez-Rodrigo, Manuel

    2016-05-01

    In the past twenty years, skeletal part profiles, which are prone to equifinality, have not occupied a prominent role in the interpretation of early Pleistocene sites on Africa. Alternatively, taphonomic studies on bone surface modifications and bone breakage patterns, have provided heuristic interpretations of some of the best preserved archaeological record of this period; namely, the Olduvai Bed I sites. The most recent and comprehensive taphonomic study of these sites (Domínguez-Rodrigo et al., 2007a) showed that FLK Zinj was an anthropogenic assemblage in which hominins acquired carcasses via primary access. That study also showed that the other sites were palimpsests with minimal or no intervention by hominins. The FLK N, FLK NN and DK sequence seemed to be dominated by single-agent (mostly, felid) or multiple-agent (mostly, felid-hyenid) processes. The present study re-analyzes the Bed I sites focusing on skeletal part profiles. Machine learning methods, which incorporate complex algorithms, are powerful predictive and classification methods and have the potential to better extract information from skeletal part representation than past approaches. Here, multiple algorithms (via decision trees, neural networks, random forests and support vector machines) are combined to produce a solid interpretation of bone accumulation agency at the Olduvai Bed I sites. This new approach virtually coincides with previous taphonomic interpretations on a site by site basis and shows that felids were dominant accumulating agents over hyenas during Bed I times. The recent discovery of possibly a modern lion-accumulated assemblage at Olduvai Gorge (Arriaza et al., submitted) provides a very timely analog for this interpretation.

  19. Macromammalian faunas, biochronology and palaeoecology of the early Pleistocene Main Quarry hominin-bearing deposits of the Drimolen Palaeocave System, South Africa.

    Science.gov (United States)

    Adams, Justin W; Rovinsky, Douglass S; Herries, Andy I R; Menter, Colin G

    2016-01-01

    The Drimolen Palaeocave System Main Quarry deposits (DMQ) are some of the most prolific hominin and primate-bearing deposits in the Fossil Hominids of South Africa UNESCO World Heritage Site. Discovered in the 1990s, excavations into the DMQ have yielded a demographically diverse sample of Paranthropus robustus (including DNH 7, the most complete cranium of the species recovered to date), early Homo, Papio hamadryas robinsoni and Cercopithecoides williamsi. Alongside the hominin and primate sample is a diverse macromammalian assemblage, but prior publications have only provided a provisional species list and an analysis of the carnivores recovered prior to 2008. Here we present the first description and analysis of the non-primate macromammalian faunas from the DMQ, including all 826 taxonomically identifiable specimens catalogued from over two decades of excavation. We also provide a biochronological interpretation of the DMQ deposits and an initial discussion of local palaeoecology based on taxon representation.The current DMQ assemblage consists of the remains of minimally 147 individuals from 9 Orders and 14 Families of mammals. The carnivore assemblage described here is even more diverse than established in prior publications, including the identification of Megantereon whitei, Lycyaenops silberbergi, and first evidence for the occurrence of Dinofelis cf. barlowi and Dinofelis aff. piveteaui within a single South African site deposit. The cetartiodactyl assemblage is dominated by bovids, with the specimen composition unique in the high recovery of horn cores and dominance of Antidorcas recki remains. Other cetartiodactyl and perissodactyl taxa are represented by few specimens, as are Hystrix and Procavia; the latter somewhat surprisingly so given their common occurrence at penecontemporaneous deposits in the region. Equally unusual (particularly given the size of the sample) is the identification of single specimens of giraffoid, elephantid and aardvark

  20. Niche partitioning in sympatric Gorilla and Pan from Cameroon: implications for life history strategies and for reconstructing the evolution of hominin life history.

    Directory of Open Access Journals (Sweden)

    Gabriele A Macho

    Full Text Available Factors influencing the hominoid life histories are poorly understood, and little is known about how ecological conditions modulate the pace of their development. Yet our limited understanding of these interactions underpins life history interpretations in extinct hominins. Here we determined the synchronisation of dental mineralization/eruption with brain size in a 20th century museum collection of sympatric Gorilla gorilla and Pan troglodytes from Central Cameroon. Using δ13C and δ15N of individuals' hair, we assessed whether and how differences in diet and habitat use may have impacted on ape development. The results show that, overall, gorilla hair δ13C and δ15N values are more variable than those of chimpanzees, and that gorillas are consistently lower in δ13C and δ15N compared to chimpanzees. Within a restricted, isotopically-constrained area, gorilla brain development appears delayed relative to dental mineralization/eruption [or dental development is accelerated relative to brains]: only about 87.8% of adult brain size is attained by the time first permanent molars come into occlusion, whereas it is 92.3% in chimpanzees. Even when M1s are already in full functional occlusion, gorilla brains lag behind those of chimpanzee (91% versus 96.4%, relative to tooth development. Both bootstrap analyses and stable isotope results confirm that these results are unlikely due to sampling error. Rather, δ15N values imply that gorillas are not fully weaned (physiologically mature until well after M1 are in full functional occlusion. In chimpanzees the transition from infant to adult feeding appears (a more gradual and (b earlier relative to somatic development. Taken together, the findings are consistent with life history theory that predicts delayed development when non-density dependent mortality is low, i.e. in closed habitats, and with the "risk aversion" hypothesis for frugivorous species as a means to avert starvation. Furthermore, the

  1. 广西平乐鸡母岩发现的晚更新世人类牙齿化石%LATE PLEISTOCENE HOMININ TEETH FROM THE JIMUYAN CAVE,PINGLE COUNTY, GUANGXI,SOUTH CHINA

    Institute of Scientific and Technical Information of China (English)

    王頠; 黄超林; 谢绍文; 鄢成林

    2011-01-01

    Five hominin teeth are recently discovered at the Jimuyan Cave in Pingle County, Southern China. The Jimuyan Cave is located at Juntang Village(24° 29' 52. 8" N,110° 50' 0. 79" E) ,20km southeast to the Pingle Town,with 163. 2m above the sea level. Mammalian fauna of the cave consists of eleven species,including: Macaca sp. ,Pongo pygmaeus weidenreichi, Hystrix cf. Subcristata, Ursus thibetanus ,Ahuropoda melanoleuca baconi ,Stegodon orhentalis, Tapirus sinensis,Sus scrofa,Muntiacus sp.,Cervus sp. And Bovidae gen. Et sp. Indet. This faunal assemblage contains four genera that are either extinct or no longer present in this region, including Stegodon, Tapirus, Ailuropoda and Pongo, which is distinctly different from that of Holocene, however similar to that of Late Pleistocene in Southern China. Thus, age of this fauna is dated to Late Pleistocene by biostratigraphy comparison. The hominin teeth in Jimuyan Cave are morphologically different from those of already known Homo erectus and Early Homo sapiens, nevertheless, similar to those of Late Homo sapiens in South China. This finding presents significant fossil evidence for the study of modern hunan origin and evolution in East Asia.The origin of modern humans is a controversial scientific topic at present. Based on fossil evidence of Homo sapiens in Africa are more ancient than that in Eastern Asia. With the results of molecular biology analysis, most of the anthropologists and geneticists support the hypothesis of modern humans originated in Africa. So far,the oldest fossils come from Omo-Kibish and Herto in Ethiopia, with the age of 160ka and 190ka respectively. The characteristics of these fossil skulls are intervenient between Homo sapiens and Homo heidelbergensis. Some of the hominin fossils,dated to 74 ~ 134ka,have been discovered at Klasies estuary in South Africa, but it is difficult to confirm whether these materials belong to modern human. Fossil hominin unearthed at Qafzeh and Skhul in Israel, Middle

  2. On the tool use behavior of the bonobo-chimpanzee last common ancestor, and the origins of hominine stone tool use.

    Science.gov (United States)

    Haslam, Michael

    2014-10-01

    The last common ancestor (LCA) shared by chimpanzees (Pan troglodytes) and bonobos (P. paniscus) was an Early Pleistocene African ape, which, based on the behavior of modern chimpanzees, may be assumed to be a tool-using animal. However, the character of tool use in the Pan lineage prior to the 20th century is largely unknown. Here, I use available data on wild bonobo tool use and emerging molecular estimates of demography during Pan evolution to hypothesise the plausible tool use behavior of the bonobo-chimpanzee LCA (or "Pancestor") at the start of the Pleistocene, over 2 million years ago. This method indicates that the common ancestor of living Pan apes likely used plant tools for probing, sponging, and display, but it did not use stone tools. Instead, stone tool use appears to have been independently invented by Western African chimpanzees (P. t. verus) during the Middle Pleistocene in the region of modern Liberia-Ivory Coast-Guinea, possibly as recently as 200,000-150,000 years ago. If this is the case, then the LCA of humans and chimpanzees likely also did not use stone tools, and this trait probably first emerged among hominins in Pliocene East Africa. This review also suggests that the consistently higher population sizes of Central African chimpanzees (P. t. troglodytes) over the past million years may have contributed to the increased complexity of wild tool use seen in this sub-species today. PMID:24710771

  3. Speleology and magnetobiostratigraphic chronology of the GD 2 locality of the Gondolin hominin-bearing paleocave deposits, North West Province, South Africa.

    Science.gov (United States)

    Herries, Andy I R; Adams, Justin W; Kuykendall, Kevin L; Shaw, John

    2006-12-01

    Speleological, paleomagnetic, mineral magnetic, and biochronological analyses have been undertaken at the Gondolin hominin-bearing paleocave, North West Province, South Africa. Two fossiliferous but stratigraphically separate sequences, GD2 and GD1/3, which were once part of a large cavern system, have been identified. Although some comparative paleomagnetic samples were taken from the GD 1, 3, and 4 localities that are currently under investigation, the research presented here focuses on the fossil-rich, in situ deposits at locality GD 2, excavated by E.S. Vrba in 1979. The GD 2 deposits are dominated by normal-polarity calcified clastic deposits that are sandwiched between clastic-free flowstone speleothems. The lower flowstone has a sharp contact with the red siltstone deposits and is of reversed polarity. The capping flowstone shows a change from normal to reversed polarity, thereby preserving a polarity reversal. While the paleomagnetic work indicates that the GD 2 fossil material was deposited during a normal-polarity period, the shortness of the sequence made matching of the magnetostratigraphy to the geomagnetic polarity time scale (GPTS) impossible without the aid of biochronology. While lacking multiple time-sensitive taxa, the recovery of specimens attributable to Stage III Metridiochoerus andrewsi is consistent with a deposition date between 1.9 and 1.5 Ma. A comparison of the magnetostratigraphy with the GPTS therefore suggests that the fauna-bearing siltstone of GD 2 date to the Olduvai normal-polarity event, which occurred between 1.95 and 1.78 Ma, and that the reversal from normal to reversed polarity identified in the capping flowstone dates to 1.78 Ma. The main faunal layers therefore date to slightly older than 1.78 Ma. Deposits from the GD 1 locality are dominated by reversed directions of magnetization, which show that this deposit is not of the same age as the faunal layers from the GD 2 locality. PMID:16949648

  4. Stellar formation

    CERN Document Server

    Reddish, V C

    1978-01-01

    Stellar Formation brings together knowledge about the formation of stars. In seeking to determine the conditions necessary for star formation, this book examines questions such as how, where, and why stars form, and at what rate and with what properties. This text also considers whether the formation of a star is an accident or an integral part of the physical properties of matter. This book consists of 13 chapters divided into two sections and begins with an overview of theories that explain star formation as well as the state of knowledge of star formation in comparison to stellar structure

  5. Galaxy formation

    International Nuclear Information System (INIS)

    Galaxy formation is at the forefront of observation and theory in cosmology. An improved understanding is essential for improving our knowledge both of the cosmological parameters, of the contents of the universe, and of our origins. In these lectures intended for graduate students, galaxy formation theory is reviewed and confronted with recent observational issues. In lecture 1, the following topics are presented: star formation considerations, including IMF, star formation efficiency and star formation rate, the origin of the galaxy luminosity function, and feedback in dwarf galaxies. In lecture 2, we describe formation of disks and massive spheroids, including the growth of supermassive black holes, negative feedback in spheroids, the AGN-star formation connection, star formation rates at high redshift and the baryon fraction in galaxies.

  6. Galaxy formation

    CERN Document Server

    Silk, Joseph; Dvorkin, Irina

    2015-01-01

    Galaxy formation is at the forefront of observation and theory in cosmology. An improved understanding is essential for improving our knowledge both of the cosmological parameters, of the contents of the universe, and of our origins. In these lectures intended for graduate students, galaxy formation theory is reviewed and confronted with recent observational issues. In Lecture 1, the following topics are presented: star formation considerations, including IMF, star formation efficiency and star formation rate, the origin of the galaxy luminosity function, and feedback in dwarf galaxies. In Lecture 2, we describe formation of disks and massive spheroids, including the growth of supermassive black holes, negative feedback in spheroids, the AGN-star formation connection, star formation rates at high redshift and the baryon fraction in galaxies.

  7. Paleoenvironments of the Shungura Formation (Plio-Pleistocene: Ethiopia) based on ecomorphology of the bovid astragalus.

    Science.gov (United States)

    Barr, W Andrew

    2015-11-01

    The Shungura Formation in southwestern Ethiopia preserves a long and relatively continuous record of eastern African mammalian and hominin evolution. This study reconstructs habitat preferences of the Shungura Formation bovids from ca. 3.4-1.9 Ma (million years ago), based on the ecomorphology of fossil bovid astragali. Habitat predictions are made using a Discriminant Function Analysis informed by functional analysis of the astragalus that controls for body size and phylogenetic signal. The high abundance of astragali in the Shungura record allows for habitat reconstructions on sub-unit timescales, rather than aggregating samples at the level of geological member. During much of the time period examined, the lower Omo Valley was dominated by relatively mesic habitats in close proximity to the ancestral Omo River. Previous research has suggested that environmental change at ∼ 2.85 Ma caused significant habitat change at Shungura, but the astragalar data do not support major habitat change at this time. However, there are significant fluctuations in inferred habitats, with more open habitats indicated in sub-units C-08 and C-09 (∼ 2.56 Ma), and in unit F-01 (just after 2.36 Ma). The cause of sub-unit fluctuations in habitat signal is difficult to determine, but local factors, including spatial habitat heterogeneity around the river channel and in its floodplain, may play a contributing role. In the light of faunal evidence from elsewhere in the greater Omo-Turkana Basin, hominins in the area likely had access to a variety of heterogeneous habitats. PMID:26049924

  8. Soil formation.

    NARCIS (Netherlands)

    Breemen, van N.; Buurman, P.

    1998-01-01

    Soil Formation deals with qualitative and quantitative aspects of soil formation (or pedogenesis) and the underlying chemical, biological, and physical processes. The starting point of the text is the process - and not soil classification. Effects of weathering and new formation of minerals, mobilis

  9. A Pleistocene palaeovegetation record from plant wax biomarkers from the Nachukui Formation, West Turkana, Kenya.

    Science.gov (United States)

    Uno, Kevin T; Polissar, Pratigya J; Kahle, Emma; Feibel, Craig; Harmand, Sonia; Roche, Hélène; deMenocal, Peter B

    2016-07-01

    Reconstructing vegetation at hominin fossil sites provides us critical information about hominin palaeoenvironments and the potential role of climate in their evolution. Here we reconstruct vegetation from carbon isotopes of plant wax biomarkers in sediments of the Nachukui Formation in the Turkana Basin. Plant wax biomarkers were extracted from samples from a wide range of lithologies that include fluvial-lacustrine sediments and palaeosols, and therefore provide a record of vegetation from diverse depositional environments. Carbon isotope ratios from biomarkers indicate a highly dynamic vegetation structure (ca 5-100% C4 vegetation) from 2.3 to 1.7 Ma, with an overall shift towards more C4 vegetation on the landscape after about 2.1 Ma. The biomarker isotope data indicate ca 25-30% more C4 vegetation on the landscape than carbon isotope data of pedogenic carbonates from the same sequence. Our data show that the environments of early Paranthropus and Homo in this part of the Turkana Basin were primarily mixed C3-C4 to C4-dominated ecosystems. The proportion of C4-based foods in the diet of Paranthropus increases through time, broadly paralleling the increase in C4 vegetation on the landscape, whereas the diet of Homo remains unchanged. Biomarker isotope data associated with the Kokiselei archaeological site complex, which includes the site where the oldest Acheulean stone tools to date were recovered, indicate 61-97% C4 vegetation on the landscape.This article is part of the themed issue 'Major transitions in human evolution'.

  10. A Pleistocene palaeovegetation record from plant wax biomarkers from the Nachukui Formation, West Turkana, Kenya.

    Science.gov (United States)

    Uno, Kevin T; Polissar, Pratigya J; Kahle, Emma; Feibel, Craig; Harmand, Sonia; Roche, Hélène; deMenocal, Peter B

    2016-07-01

    Reconstructing vegetation at hominin fossil sites provides us critical information about hominin palaeoenvironments and the potential role of climate in their evolution. Here we reconstruct vegetation from carbon isotopes of plant wax biomarkers in sediments of the Nachukui Formation in the Turkana Basin. Plant wax biomarkers were extracted from samples from a wide range of lithologies that include fluvial-lacustrine sediments and palaeosols, and therefore provide a record of vegetation from diverse depositional environments. Carbon isotope ratios from biomarkers indicate a highly dynamic vegetation structure (ca 5-100% C4 vegetation) from 2.3 to 1.7 Ma, with an overall shift towards more C4 vegetation on the landscape after about 2.1 Ma. The biomarker isotope data indicate ca 25-30% more C4 vegetation on the landscape than carbon isotope data of pedogenic carbonates from the same sequence. Our data show that the environments of early Paranthropus and Homo in this part of the Turkana Basin were primarily mixed C3-C4 to C4-dominated ecosystems. The proportion of C4-based foods in the diet of Paranthropus increases through time, broadly paralleling the increase in C4 vegetation on the landscape, whereas the diet of Homo remains unchanged. Biomarker isotope data associated with the Kokiselei archaeological site complex, which includes the site where the oldest Acheulean stone tools to date were recovered, indicate 61-97% C4 vegetation on the landscape.This article is part of the themed issue 'Major transitions in human evolution'. PMID:27298466

  11. Galaxy Formation

    DEFF Research Database (Denmark)

    Sparre, Martin

    Galaxy formation is an enormously complex discipline due to the many physical processes that play a role in shaping galaxies. The objective of this thesis is to study galaxy formation with two different approaches: First, numerical simulations are used to study the structure of dark matter and how...... galaxies form stars throughout the history of the Universe, and secondly it is shown that observations of gamma-ray bursts (GRBs) can be used to probe galaxies with active star formation in the early Universe. A conclusion from the hydrodynamical simulations is that the galaxies from the stateof-the-art...

  12. Bulge Formation

    CERN Document Server

    Combes, F

    1999-01-01

    The currently discussed theories of bulge formation are reviewed, including the primordial scenario, where bulges form rapidly and then accrete disks, the secular scenario, where bulges are formed by dynamical evolution of disks through bars and galaxy interactions, and some combinations of both, where formation of bulges and disks are more continuous and interleaved. The various scenarios make specific predictions about the relative masses, angular momenta, colours, metallicities of bulges relative to disks, and the bulge-to-disk ratio as a function of time. Dynamical processes relevant to the formation of bulges (bar instabilities, mergers) are described and tested against observed statistics. Current data suggest a dynamical feedback from gravitational instabilities in bulge and disk formation. It is very difficult to discriminate between the various scenarios from surveys at z=0 only, and observations at high redshift are presently the best hope for large progress.

  13. Cement Formation

    DEFF Research Database (Denmark)

    Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten;

    2012-01-01

    Cement production has been subject to several technological changes, each of which requires detailed knowledge about the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including......−liquid reactions are discussed, as are the influences of particles sizes on clinker phase formation. Furthermore, a mechanism for clinker phase formation in an industrial rotary kiln reactor is outlined....

  14. Star formation

    Energy Technology Data Exchange (ETDEWEB)

    Woodward, P.R.

    1978-09-27

    Theoretical models of star formation are discussed beginning with the earliest stages and ending in the formation of rotating, self-gravitating disks or rings. First a model of the implosion of very diffuse gas clouds is presented which relies upon a shock at the edge of a galactic spiral arm to drive the implosion. Second, models are presented for the formation of a second generation of massive stars in such a cloud once a first generation has formed. These models rely on the ionizing radiation from massive stars or on the supernova shocks produced when these stars explode. Finally, calculations of the gravitational collapse of rotating clouds are discussed with special focus on the question of whether rotating disks or rings are the result of such a collapse. 65 references.

  15. Star formation

    International Nuclear Information System (INIS)

    Theoretical models of star formation are discussed beginning with the earliest stages and ending in the formation of rotating, self-gravitating disks or rings. First a model of the implosion of very diffuse gas clouds is presented which relies upon a shock at the edge of a galactic spiral arm to drive the implosion. Second, models are presented for the formation of a second generation of massive stars in such a cloud once a first generation has formed. These models rely on the ionizing radiation from massive stars or on the supernova shocks produced when these stars explode. Finally, calculations of the gravitational collapse of rotating clouds are discussed with special focus on the question of whether rotating disks or rings are the result of such a collapse. 65 references

  16. Galaxy formation.

    Science.gov (United States)

    Peebles, P J

    1998-01-01

    It is argued that within the standard Big Bang cosmological model the bulk of the mass of the luminous parts of the large galaxies likely had been assembled by redshift z approximately 10. Galaxy assembly this early would be difficult to fit in the widely discussed adiabatic cold dark matter model for structure formation, but it could agree with an isocurvature version in which the cold dark matter is the remnant of a massive scalar field frozen (or squeezed) from quantum fluctuations during inflation. The squeezed field fluctuations would be Gaussian with zero mean, and the distribution of the field mass therefore would be the square of a random Gaussian process. This offers a possibly interesting new direction for the numerical exploration of models for cosmic structure formation.

  17. Pattern Formation

    Science.gov (United States)

    Hoyle, Rebecca

    2006-03-01

    From the stripes of a zebra and the spots on a leopard's back to the ripples on a sandy beach or desert dune, regular patterns arise everywhere in nature. The appearance and evolution of these phenomena has been a focus of recent research activity across several disciplines. This book provides an introduction to the range of mathematical theory and methods used to analyse and explain these often intricate and beautiful patterns. Bringing together several different approaches, from group theoretic methods to envelope equations and theory of patterns in large-aspect ratio-systems, the book also provides insight behind the selection of one pattern over another. Suitable as an upper-undergraduate textbook for mathematics students or as a fascinating, engaging, and fully illustrated resource for readers in physics and biology, Rebecca Hoyle's book, using a non-partisan approach, unifies a range of techniques used by active researchers in this growing field. Accessible description of the mathematical theory behind fascinating pattern formation in areas such as biology, physics and materials science Collects recent research for the first time in an upper level textbook Features a number of exercises - with solutions online - and worked examples

  18. 湖北郧西白龙洞洞穴发育与古人类生存环境探讨%PRELIMINARY STUDY ON THE CAVE DEVELOPMENT AND ENVIRONMENTAL BACKGROUND OF HOMININ OCCUPATION AT BAILONG CAVE,YUNXI COUNTY, HUBEI PROVINCE

    Institute of Scientific and Technical Information of China (English)

    李潇丽; 武仙竹; 裴树文

    2012-01-01

    ,algal limestone, and biological frame limestone of Shaping Formation were the surrounding rock of the cave. The Bailong cave was formed first by the fracture water dissolution along the unconformity fissure in the early stage, and then transferred to vertical vadose,which became the dominant resorption pattern of the karst development. Eight stratigraphic layers were identified at the site during the 2007 text excavation, and had a total thickness of more than 240cm. Archaeological materials were mainly unearthed from the 2nd layer, a layer of red clay with a thickness of 50 ~ 60cm. In order to interpret the possible environmental background, especially the impact on human activities at Bailong cave, a systematic analysis of the particle size, magnetic susceptibility, clay minerals, oxides, as well as mammalian fauna from sediments were carried out by the authors in this paper. It can be inferred from the systematic analysis that the climate and environment were optimal as a warm and humid one to some degree, indicating the climate background in the transitional zone between north subtropical zone and warm temperate zone. It should be noted that the human fossils, stone artifacts, and mammalian fossils were mainly distributed in the layer 2 of red clay( upper part of the section) , where the environment were exhibited relatively warm and humid than the lower part of the section. In addition, the climate and environment were optimal as a warm temperature with flourishing of grass and forest, as well as animals, which may lead to the intensified occupation of early hominins during the formation of layer 2 in Middle Pleistocene. In brief, the study of human activity environment at Bailong cave bears great significance in the research of human occupation environment in the northeast margin of Three Gorges-West Hubei area during Middle Pleistocene.

  19. Common File Formats.

    Science.gov (United States)

    Mills, Lauren

    2014-03-21

    An overview of the many file formats commonly used in bioinformatics and genome sequence analysis is presented, including various data file formats, alignment file formats, and annotation file formats. Example workflows illustrate how some of the different file types are typically used.

  20. Extreme Star Formation

    OpenAIRE

    Turner, JL

    2010-01-01

    Extreme star formation includes star formation in starbursts and regions forming super star clusters. We survey the current problems in our understanding of the star formation process in starbursts and super star clusters - initial mass functions, cluster mass functions, star formation efficiencies, and radiative feedback into molecular clouds - that are critical to our understanding of the formation and survival of large star clusters, topics that will be the drivers of the observations of t...

  1. Formate Formation and Formate Conversion in Biological Fuels Production

    Directory of Open Access Journals (Sweden)

    Bryan R. Crable

    2011-01-01

    Full Text Available Biomethanation is a mature technology for fuel production. Fourth generation biofuels research will focus on sequestering CO2 and providing carbon-neutral or carbon-negative strategies to cope with dwindling fossil fuel supplies and environmental impact. Formate is an important intermediate in the methanogenic breakdown of complex organic material and serves as an important precursor for biological fuels production in the form of methane, hydrogen, and potentially methanol. Formate is produced by either CoA-dependent cleavage of pyruvate or enzymatic reduction of CO2 in an NADH- or ferredoxin-dependent manner. Formate is consumed through oxidation to CO2 and H2 or can be further reduced via the Wood-Ljungdahl pathway for carbon fixation or industrially for the production of methanol. Here, we review the enzymes involved in the interconversion of formate and discuss potential applications for biofuels production.

  2. Star Formation in Galaxies

    Science.gov (United States)

    1987-01-01

    Topics addressed include: star formation; galactic infrared emission; molecular clouds; OB star luminosity; dust grains; IRAS observations; galactic disks; stellar formation in Magellanic clouds; irregular galaxies; spiral galaxies; starbursts; morphology of galactic centers; and far-infrared observations.

  3. Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia

    Science.gov (United States)

    Wynn, Jonathan G.; Sponheimer, Matt; Kimbel, William H.; Alemseged, Zeresenay; Reed, Kaye; Bedaso, Zelalem K.; Wilson, Jessica N.

    2013-06-01

    The enhanced dietary flexibility of early hominins to include consumption of C4/crassulacean acid metabolism (CAM) foods (i.e., foods derived from grasses, sedges, and succulents common in tropical savannas and deserts) likely represents a significant ecological and behavioral distinction from both extant great apes and the last common ancestor that we shared with great apes. Here, we use stable carbon isotopic data from 20 samples of Australopithecus afarensis from Hadar and Dikika, Ethiopia (>3.4-2.9 Ma) to show that this species consumed a diet with significant C4/CAM foods, differing from its putative ancestor Au. anamensis. Furthermore, there is no temporal trend in the amount of C4/CAM food consumption over the age of the samples analyzed, and the amount of C4/CAM food intake was highly variable, even within a single narrow stratigraphic interval. As such, Au. afarensis was a key participant in the C4/CAM dietary expansion by early australopiths of the middle Pliocene. The middle Pliocene expansion of the eastern African australopith diet to include savanna-based foods represents a shift to use of plant food resources that were already abundant in hominin environments for at least 1 million y and sets the stage for dietary differentiation and niche specialization by subsequent hominin taxa.

  4. Star Formation for Predictive Primordial Galaxy Formation

    CERN Document Server

    Milosavljevic, Milos

    2015-01-01

    The elegance of inflationary cosmology and cosmological perturbation theory ends with the formation of the first stars and galaxies, the initial sources of light that launched the phenomenologically rich process of cosmic reionization. Here we review the current understanding of early star formation, emphasizing unsolved problems and technical challenges. We begin with the first generation of stars to form after the Big Bang and trace how they influenced subsequent star formation. The onset of chemical enrichment coincided with a sharp increase in the overall physical complexity of star forming systems. Ab-initio computational treatments are just now entering the domain of the predictive and are establishing contact with local observations of the relics of this ancient epoch.

  5. Star Formation for Predictive Primordial Galaxy Formation

    Science.gov (United States)

    Milosavljević, Miloš; Safranek-Shrader, Chalence

    The elegance of inflationary cosmology and cosmological perturbation theory ends with the formation of the first stars and galaxies, the initial sources of light that launched the phenomenologically rich process of cosmic reionization. Here we review the current understanding of early star formation, emphasizing unsolved problems and technical challenges. We begin with the first generation of stars to form after the Big Bang and trace how they influenced subsequent star formation. The onset of chemical enrichment coincided with a sharp increase in the overall physical complexity of star forming systems. Ab-initio computational treatments are just now entering the domain of the predictive and are establishing contact with local observations of the relics of this ancient epoch.

  6. The Conic Benchmark Format

    DEFF Research Database (Denmark)

    Friberg, Henrik A.

    This document constitutes the technical reference manual of the Conic Benchmark Format with le extension: .cbf or .CBF. It unies linear, second-order cone (also known as conic quadratic) and semidenite optimization with mixed-integer variables. The format has been designed with benchmark libraries...... in mind, and therefore focuses on compact and easily parsable representations. The problem structure is separated from the problem data, and the format moreover facilitate benchmarking of hotstart capability through sequences of changes....

  7. High-resolution record of the Matuyama-Brunhes transition constrains the age of Javanese Homo erectus in the Sangiran dome, Indonesia.

    Science.gov (United States)

    Hyodo, Masayuki; Matsu'ura, Shuji; Kamishima, Yuko; Kondo, Megumi; Takeshita, Yoshihiro; Kitaba, Ikuko; Danhara, Tohru; Aziz, Fachroel; Kurniawan, Iwan; Kumai, Hisao

    2011-12-01

    A detailed paleomagnetic study conducted in the Sangiran area, Java, has provided a reliable age constraint on hominid fossil-bearing formations. A reverse-to-normal polarity transition marks a 7-m thick section across the Upper Tuff in the Bapang Formation. The transition has three short reversal episodes and is overlain by a thick normal polarity magnetozone that was fission-track dated to the Brunhes chron. This pattern closely resembles another high-resolution Matuyama-Brunhes (MB) transition record in an Osaka Bay marine core. In the Sangiran sediments, four successive transitional polarity fields lie just below the presumed main MB boundary. Their virtual geomagnetic poles cluster in the western South Pacific, partly overlapping the transitional virtual geomagnetic poles from Hawaiian and Canary Islands' lavas, which have a mean (40)Ar/(39)Ar age of 776 ± 2 ka. Thus, the polarity transition is unambiguously the MB boundary. A revised correlation of tuff layers in the Bapang Formation reveals that the hominid last occurrence and the tektite level in the Sangiran area are nearly coincident, just below the Upper Middle Tuff, which underlies the MB transition. The stratigraphic relationship of the tektite level to the MB transition in the Sangiran area is consistent with deep-sea core data that show that the meteorite impact preceded the MB reversal by about 12 ka. The MB boundary currently defines the uppermost horizon yielding Homo erectus fossils in the Sangiran area. PMID:22106291

  8. Usage Record Format Recommendation

    CERN Document Server

    Nilsen, J.K.; Muller-Pfeerkorn, R

    2013-01-01

    For resources to be shared, sites must be able to exchange basic accounting and usage data in a common format. This document describes a common format which enables the exchange of basic accounting and usage data from different resources. This record format is intended to facilitate the sharing of usage information, particularly in the area of the accounting of jobs, computing, memory, storage and cloud usage but with a structure that allows an easy extension to other resources. This document describes the Usage Record components both in natural language form and annotated XML. This document does not address how these records should be used, nor does it attempt to dictate the format in which the accounting records are stored. Instead, it denes a common exchange format. Furthermore, nothing is said regarding the communication mechanisms employed to exchange the records, i.e. transport layer, framing, authentication, integrity, etc.

  9. Challenges in Planet Formation

    CERN Document Server

    Morbidelli, Alessandro

    2016-01-01

    Over the past two decades, large strides have been made in the field of planet formation. Yet fundamental questions remain. Here we review our state of understanding of five fundamental bottlenecks in planet formation. These are: 1) the structure and evolution of protoplanetary disks; 2) the growth of the first planetesimals; 3) orbital migration driven by interactions between proto-planets and gaseous disk; 4) the origin of the Solar System's orbital architecture; and 5) the relationship between observed super-Earths and our own terrestrial planets. Given our lack of understanding of these issues, even the most successful formation models remain on shaky ground.

  10. Methemoglobin formation by paraquat.

    Directory of Open Access Journals (Sweden)

    Watanabe,Shinsaku

    1982-12-01

    Full Text Available Paraquat is a broad spectrum herbicide known to be highly lethal to man and animals. Its toxicity is characterized by acute lung injury. Paraquat produces such toxic effects through the generation of the superoxide anion according to one proposed mechanism. The present experiment, methemoglobin formation was demonstrated after incubation of oxyhemoglobin with paraquat. The generation of the superoxide anion through the interaction of oxyhemoglobin with paraquat was suggested by chemiluminescence of luminol. Superoxide dismutase (SOD and catalare inhibited methemoglobin formation. The generation of the superoxide anion is discussed in regard to methemoglobin formation by paraquat.

  11. Manuel UNIMARC format bibliographique

    CERN Document Server

    2007-01-01

    This manual is the French translation of the second edition of UNIMARC Manual: bibliographic format published in English in 1994 and completed by 5 updates published from 1996 to 2005. This 5th French edition is composite. It reproduces identically a part of the 4th edition published in 2002 and, for the fields of the format modified in the Update 5, it offers a new more structured presentation. This is a handbook dedicated to French-speaking users of the UNIMARC format for bibliographic descriptions.

  12. Formation of planetary systems

    Science.gov (United States)

    Lin, Douglas N. C.

    The discovery of extrasolar planets and the determination of their orbital properties have provided golden opportunities for new advancements in the quest to understand the origin and evolution of planets and planetary systems. While their bizarre variety presents a challenge for the existing theories, their ubiquity suggests that planetary formation is a robust process. Combining data obtained from solar system exploration, star formation studies and the searches for extra solar planets, we address some outstanding issues concerning critical processes of grain condensation, planetesimal coagulation, and gas accretion. Some implications of these investigations are: 1) the about of heavy elements available for planetary formation in protostellar disks is retained at a similar level as that empirically inferred for the primordial solar nebula, through self regulated processes and 2) the critical stages of planet formation, from grain condensation, planetesimal coagulation, to gas accretion, proceed on the timescale of a few million years.

  13. Notes on Star Formation

    CERN Document Server

    Krumholz, Mark R

    2015-01-01

    This book provides an introduction to the field of star formation at a level suitable for graduate students or advanced undergraduates in astronomy or physics. The structure of the book is as follows. The first two chapters begin with a discussion of observational techniques, and the basic phenomenology they reveal. The goal is to familiarize students with the basic techniques that will be used throughout, and to provide a common vocabulary for the rest of the book. The next five chapters provide a similar review of the basic physical processes that are important for star formation. Again, the goal is to provide a basis for what follows. The remaining chapters discuss star formation over a variety of scales, starting with the galactic scale and working down to the scales of individual stars and their disks. The book concludes with a brief discussion of the clearing of disks and the transition to planet formation. The book includes five problem sets, complete with solutions.

  14. LANDFORM,LOESS DEPOSIT AND PALEOENVIRONMENTAL CHANGES IN THE SOUTH LUOHE RIVER(CENTRAL CHINA) DURING THE HOMININ OCCUPATIONS%中国中部南洛河流域地貌、黄土堆积与更新世古人类生存环境

    Institute of Scientific and Technical Information of China (English)

    鹿化煜; 弋双文; 马萧林; Ming Wei; 张红艳; 孙雪峰; 王社江; Richard Cosgrove; Chen Shen; 张文超; 张小兵; 王先彦

    2012-01-01

    Over the past 20 years, more than 300 Paleolithic sites have been found in catchment of South Luohe River, Central China. This river is located at the environmental boundary between North and South China. To its south, climate is characterized by the subtropical monsoon; to the north,it is a warm temperate climate. Many lithic artifacts are scattered on the surface of various landforms and buried in aeolian loess deposits and cave sediments. The Paleolithic artifacts are made up of chopper-chopping ( Mode 1 ) assemblages such as cores, flakes, choppers, scrapers and points and Acheulian-like large-cutting tools (Mode 2) such as hand-axes, cleavers, trihedrals, knives. The region contains both small tools reminiscent of North China and biface technology produced on large pebbles characteristic of South China. It appears that early humans repeatedly occupied this region.In summer of 2004, our interdisciplinary team was set up and field exploration focussed on different landforms, particularly loess deposits that reflected past environmental changes, was undertaken. Eight archaeological sites were excavated, and sediment samples were taken from 14 loess-paleosol sections. Over 20000 lithic artefacts were collected and more than 10 thousand loess samples have been obtained and studied.In this paper, we discuss recent findings during 2009 -2011 on understanding landform evolution, the loess-paleosol record, paleoenvironmental reconstruction and relationship between hominines behavior and these landforms. The results show that the landforms of the South Luohe River can be divided into two parts; the upper part is characterized by mountains and intermountain basins,with gorges and narrow rivers,where the channel gradient ratio is greater and the river current is relatively swift. The lower part is characterised by a piedmont plain with a smaller stream channel gradient ratio, where the river is braided with relatively slow flowing water. There is an extensive loess cover

  15. New 1.5 million-year-old Homo erectus maxilla from Sangiran (Central Java, Indonesia).

    Science.gov (United States)

    Zaim, Yahdi; Ciochon, Russell L; Polanski, Joshua M; Grine, Frederick E; Bettis, E Arthur; Rizal, Yan; Franciscus, Robert G; Larick, Roy R; Heizler, Matthew; Aswan; Eaves, K Lindsay; Marsh, Hannah E

    2011-10-01

    Sangiran (Solo Basin, Central Java, Indonesia) is the singular Homo erectus fossil locale for Early Pleistocene Southeast Asia. Sangiran is the source for more than 80 specimens in deposits with (40)Ar/(39)Ar ages of 1.51-0.9 Ma. In April 2001, we recovered a H. erectus left maxilla fragment (preserving P(3)- M(2)) from the Sangiran site of Bapang. The find spot lies at the base of the Bapang Formation type section in cemented gravelly sands traditionally called the Grenzbank Zone. Two meters above the find spot, pumice hornblende has produced an (40)Ar/(39)Ar age of 1.51 ± 0.08 Ma. With the addition of Bpg 2001.04, Sangiran now has five H. erectus maxillae. We compare the new maxilla with homologs representing Sangiran H. erectus, Zhoukoudian H. erectus, Western H. erectus (pooled African and Georgian specimens), and Homo habilis. Greatest contrast is with the Zhoukoudian maxillae, which appear to exhibit a derived pattern of premolar-molar relationships compared to Western and Sangiran H. erectus. The dental patterns suggest distinct demic origins for the earlier H. erectus populations represented at Sangiran and the later population represented at Zhoukoudian. These two east Asian populations, separated by 5000 km and nearly 800 k.yr., may have had separate origins from different African/west Eurasian populations.

  16. Primordial Planet Formation

    CERN Document Server

    Schild, Rudolph E

    2010-01-01

    Recent spacecraft observations exploring solar system properties impact standard paradigms of the formation of stars, planets and comets. We stress the unexpected cloud of microscopic dust resulting from the DEEP IMPACT mission, and the existence of molten nodules in STARDUST samples. And the theory of star formation does not explain the common occurrence of binary and multiple star systems in the standard gas fragmentation scenario. No current theory of planet formation can explain the iron core of the earth, under oceans of water. These difficulties are avoided in a scenario where the planet mass objects form primordially and are today the baryonic dark matter. They have been detected in quasar microlensing and anomalous quasar radio brightening bursts. The primordial planets often concentrate together to form a star, with residual matter seen in pre-stellar accretion discs around the youngest stars. These primordial planet mass bodies were formed of hydrogen-helium, aggregated in dense clumps of a trillion...

  17. Solar System formation

    CERN Document Server

    Crida, A

    2009-01-01

    In this review, three major changes in our understanding of the early history of the Solar System are presented. 1) Early differentiation: A few recent results support the idea that protoplanet formation and differentiation occurred partly simultaneously than CAI formation. First, some iron meteorites, eucrites, and angrites older than the chondrules or even than the CAI have been found. Second, iron meteorites could be debris of early disrupted differentiated planetesimals, scattered from the terrestrial planet region to the Main Belt. Finally, chondrules contain fragments of planetesimal material. 2) Earth and Moon: An equilibration mechanism explains the identical Oxygen isotopic composition of the Earth and the Moon. In addition, it has been shown that the Earth and the Moon mantles have the same 182^W anomaly, in contrast to what was believed before. Consequently, the Moon forming impact should have occurred after the extinction of the 182Hf radioactivity, about 60 Myr after Solar System formation. This ...

  18. Meningococcal biofilm formation

    DEFF Research Database (Denmark)

    Lappann, M.; Haagensen, Janus Anders Juul; Claus, H.;

    2006-01-01

    We show that in a standardized in vitro flow system unencapsulated variants of genetically diverse lineages of Neisseria meningitidis formed biofilms, that could be maintained for more than 96 h. Biofilm cells were resistant to penicillin, but not to rifampin or ciprofloxacin. For some strains......, microcolony formation within biofilms was observed. Microcolony formation in strain MC58 depended on a functional copy of the pilE gene encoding the pilus subunit pilin, and was associated with twitching of cells. Nevertheless, unpiliated pilE mutants formed biofilms showing that attachment and accumulation......X alleles was identified among genetically diverse meningococcal strains. PilX alleles differed in their propensity to support autoaggregation of cells in suspension, but not in their ability to support microcolony formation within biofilms in the continuous flow system....

  19. Densities and Kinematic Viscosities for the Systems Benzene + Methyl Formate, Benzene + Ethyl Formate, Benzene + Propyl Formate, and Benzene + Butyl Formate

    DEFF Research Database (Denmark)

    Emmerling, Uwe; Rasmussen, Peter

    1998-01-01

    Densities and kinematic viscosities have been measured for the system benzene + methyl formate at 20°C and for the systems benzene + ethyl formate, benzene + propyl formate, and benzene + butyl formate from 20°C to 50°C. The results for the system benzene + methyl formate have been correlated using...... a Redlich-Kister type of expression with temperature-independent parameters and the data for the systems benzene + ethyl formate, benzene + propyl formate, and benzene + butyl formate with temperature-dependent parameters. The viscosities have furthermore been compared to values predicted by means of the GC...

  20. The formation of stars

    CERN Document Server

    Stahler, Steven W

    2008-01-01

    This book is a comprehensive treatment of star formation, one of the most active fields of modern astronomy. The reader is guided through the subject in a logically compelling manner. Starting from a general description of stars and interstellar clouds, the authors delineate the earliest phases of stellar evolution. They discuss formation activity not only in the Milky Way, but also in other galaxies, both now and in the remote past. Theory and observation are thoroughly integrated, with the aid of numerous figures and images. In summary, this volume is an invaluable resource, both as a text f

  1. Tea aroma formation

    Directory of Open Access Journals (Sweden)

    Chi-Tang Ho

    2015-03-01

    Full Text Available Besides water, tea is one of the most popular beverages around the world. The chemical ingredients and biological activities of tea have been summarized recently. The current review summarizes tea aroma compounds and their formation in green, black, and oolong tea. The flavor of tea can be divided into two categories: taste (non-volatile compounds and aroma (volatile compounds. All of these aroma molecules are generated from carotenoids, lipids, glycosides, etc. precursors, and also from Maillard reaction. In the current review, we focus on the formation mechanism of main aromas during the tea manufacturing process.

  2. Formats and data storage

    International Nuclear Information System (INIS)

    The currently used ENDF-6 format has a number of shortcomings that originate from the punch-card legacy. Some, such as redundancy, counting lines, too short MAT number and too many options could be resolved within the current format. The more critical issues, such as rigidity to extensions, limited accuracy due to fixed number of digits, difficulty of reading by humans, lack of native software support, and lack of integration with EXFOR and ENSDF libraries, would require such considerable efforts that migration to a new and modern format, offering additional advantages, is a more attractive option. Actually, such an option is even more justified by the existence of the well advanced General Nuclear Data (GND) format being developed by LLNL. This XML based framework is easily extensible, its numerical precision is not fixed, it is easier to edit, can store additional information (e.g. renormalized experimental data used in the evaluation), allows for storing various versions side by side (e.g. reconstructed data, group-wise data, alternative evaluations), it may include hyperlinks to documentation or another set of data (e.g. covariances). Two additional advantages are the possibility of using native Python support software and already available conversion (in both directions) to the binary HDF5 format which allows to organize, store, access, analyze, share, and preserve data huge in both size and complexity. The GND format comes with the processing software FUDGE, whose class structure mirrors the GND format. It provides for arbitrary alteration of the data, energy deposition/kermas, data checking, translation to different format (ENDF-6, HDF5, ENDL), grouping, resonance reconstruction, visualization and sampling from covariances. It is deemed advantageous to the Nuclear Data community to adopt this new system and develop interfaces to the currently used processing codes and retrieval systems to take full advantage of the evolving technology. Such modernization is

  3. Sensitivity Data File Formats

    Energy Technology Data Exchange (ETDEWEB)

    Rearden, Bradley T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-04-01

    The format of the TSUNAMI-A sensitivity data file produced by SAMS for cases with deterministic transport solutions is given in Table 6.3.A.1. The occurrence of each entry in the data file is followed by an identification of the data contained on each line of the file and the FORTRAN edit descriptor denoting the format of each line. A brief description of each line is also presented. A sample of the TSUNAMI-A data file for the Flattop-25 sample problem is provided in Figure 6.3.A.1. Here, only two profiles out of the 130 computed are shown.

  4. Terrestrial planet formation

    OpenAIRE

    Righter, K.; D. P. O’Brien

    2011-01-01

    Advances in our understanding of terrestrial planet formation have come from a multidisciplinary approach. Studies of the ages and compositions of primitive meteorites with compositions similar to the Sun have helped to constrain the nature of the building blocks of planets. This information helps to guide numerical models for the three stages of planet formation from dust to planetesimals (∼106 y), followed by planetesimals to embryos (lunar to Mars-sized objects; few × 106 y), and finally e...

  5. Kepler Planet Formation

    Science.gov (United States)

    Lissauer, Jack J.

    2015-01-01

    Kepler has vastly increased our knowledge of planets and planetary systems located close to stars. The new data shows surprising results for planetary abundances, planetary spacings and the distribution of planets on a mass-radius diagram. The implications of these results for theories of planet formation will be discussed.

  6. Gravitational Structure Formation

    OpenAIRE

    Labini, Francesco Sylos; Baertschiger, Thierry

    2005-01-01

    We discuss the formation of the first structures in gravitational N-body simulations. The role of two-body interaction is found to be a crucial element and an analogy with the dynamics of the Coulomb lattice, well-studied in solid state physics, is discussed.

  7. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted

  8. Airship formation control

    OpenAIRE

    Bicho, E.; Moreira, André; Diegues, Sérgio; Carvalheira, Manuel Pereira; Monteiro, Sérgio

    2006-01-01

    This paper addresses the problem underlying the control and coordination of multiple autonomous airships that must travel maintaining a desired geometric formation and simultaneously avoid collisions with moving or stationary obstacles. The control architecture is based on the attractor dynamics approach to behaviour generation. The airship physical model is presented and the mathematical background for the control architecture is explained. Simulations (with perturbations) ...

  9. Syntactic Formats for Free

    DEFF Research Database (Denmark)

    Klin, Bartek; Sobocinski, Pawel

    2003-01-01

    A framework of Plotkin and Turi’s, originally aimed at providing an abstract notion of bi-simulation, is modified to cover other operational equivalences and preorders. Combined with bi-algebraic methods, it yields a technique for the derivation of syntactic formats for transition system specific...

  10. Generic file format

    Science.gov (United States)

    Felgate, Nick

    2002-11-01

    The Generic File Format (GFF) is a file format developed within the UK ASW community for the interchange and storage of underwater sonar data. Originally developed for the interchange of time-series data between analysis systems, it has been extended to provide for storage of processed acoustic data (e.g., power and DEMON spectrum, lofargram grey-scale), nonacoustic data (e.g., own-ship dynamics, sensor configuration) and event data (e.g., tracker output, sonar intercepts). The format employs the chunk concept, as used in the WAV and AIFF file formats, to provide extendability (including local variants) while providing a measure of backward compatability. However, the basic concept has been adapted to allow for the mixing in the one file of multiple channels of different sample-rates and data-types through the inclusion of a data frame concept and multiple data blocks. Chunk cross-referencing has been employed to ensure data consistency. A provision is made in the header of the file to store details of the sensor and processing for the data (e.g., the number of hydrophones, beam direction, FFT size) so that an analysis system does not need to know about the sensor or other system from which the data originated.

  11. Multispectral Thermal Imagery and Its Application to the Geologic Mapping of the Koobi Fora Formation, Northwestern Kenya

    Energy Technology Data Exchange (ETDEWEB)

    Green, Mary K. [Univ. of New Mexico, Albuquerque, NM (United States)

    2005-12-01

    The Koobi Fora Formation in northwestern Kenya has yielded more hominin fossils dated between 2.1 and 1.2 Ma than any other location on Earth. This research was undertaken to discover the spectral signatures of a portion of the Koobi Fora Formation using imagery from the DOE's Multispectral Thermal Imager (MTI) satellite. Creation of a digital geologic map from MTI imagery was a secondary goal of this research. MTI is unique amongst multispectral satellites in that it co-collects data from 15 spectral bands ranging from the visible to the thermal infrared with a ground sample distance of 5 meters per pixel in the visible and 20 meters in the infrared. The map was created in two stages. The first was to correct the base MTI image using spatial accuracy assessment points collected in the field. The second was to mosaic various MTI images together to create the final Koobi Fora map. Absolute spatial accuracy of the final map product is 73 meters. The geologic classification of the Koobi Fora MTI map also took place in two stages. The field work stage involved location of outcrops of different lithologies within the Koobi Fora Formation. Field descriptions of these outcrops were made and their locations recorded. During the second stage, a linear spectral unmixing algorithm was applied to the MTI mosaic. In order to train the linear spectra unmixing algorithm, regions of interest representing four different classes of geologic material (tuff, alluvium, carbonate, and basalt), as well as a vegetation class were defined within the MTI mosaic. The regions of interest were based upon the aforementioned field data as well as overlays of geologic maps from the 1976 Iowa State mapping project. Pure spectra were generated for each class from the regions of interest, and then the unmixing algorithm classified each pixel according to relative percentage of classes found within the pixel based upon the pure spectra values. A total of four unique combinations of geologic

  12. Symbol Formation Reconsidered

    DEFF Research Database (Denmark)

    Wagoner, Brady

    2013-01-01

    Werner and Kaplan’s Symbol formation was published 50 years ago but its insights have yet to be adequately explored by psychology and other social sciences. This special issue aims to revisit this seminal work in search of concepts to work on key issues facing us today. This introductory article...... them vis-à-vis other research at Clark and in American psychology more generally. The second two articles analyse Werner and Kaplan’s notions of ‘distancing’ and ‘physiognomic metaphor’, showing their roots in naturphilosophie and comparing them with contemporary theories. The last four articles apply...... the organismic-developmental approach to fields only touched in Symbol formation, such as magical practices, social structures, pictures and gesture....

  13. Simulating Cosmic Structure Formation

    CERN Document Server

    Weinberg, D H; Hernquist, L E; Weinberg, David H.; Katz, Neal; Hernquist, Lars

    1997-01-01

    We describe cosmological simulation techniques and their application to studies of cosmic structure formation, with particular attention to recent hydrodynamic simulations of structure in the high redshift universe. Collisionless N-body simulations with Gaussian initial conditions produce a pattern of sheets, filaments, tunnels, and voids that resembles the observed large scale galaxy distribution. Simulations that incorporate gas dynamics and dissipation form dense clumps of cold gas with sizes and masses similar to the luminous parts of galaxies. Models based on inflation and cold dark matter predict a healthy population of high redshift galaxies, including systems with star formation rates of 20 M_{\\sun}/year at z=6. At z~3, most of the baryons in these models reside in the low density intergalactic medium, which produces fluctuating Lyman-alpha absorption in the spectra of background quasars. The physical description of this ``Lyman-alpha forest'' is particularly simple if the absorption spectrum is viewe...

  14. Emptiness Formation Probability

    Science.gov (United States)

    Crawford, Nicholas; Ng, Stephen; Starr, Shannon

    2016-08-01

    We present rigorous upper and lower bounds on the emptiness formation probability for the ground state of a spin-1/2 Heisenberg XXZ quantum spin system. For a d-dimensional system we find a rate of decay of the order {exp(-c L^{d+1})} where L is the sidelength of the box in which we ask for the emptiness formation event to occur. In the {d=1} case this confirms previous predictions made in the integrable systems community, though our bounds do not achieve the precision predicted by Bethe ansatz calculations. On the other hand, our bounds in the case {d ≥ 2} are new. The main tools we use are reflection positivity and a rigorous path integral expansion, which is a variation on those previously introduced by Toth, Aizenman-Nachtergaele and Ueltschi.

  15. Plasma formation in TBR

    International Nuclear Information System (INIS)

    In this work are presented and discussed results of the formation and equilibrium of the plasma current in TBR, a small tokamak, designed and contructed at the Instituto de Fisica of Universidade de Sao Paulo. The measured breakdown curves for H2, A and He are compared with the predictions of a simple model with reasonable agreement. The influence of stray magnetic fields in the plasma formation is investigated and conditions are chosen to facilitate the breakdown. The time profile of loop voltage and plasma current for shots with plasma equilibrium are shown. A comparison is made between experimental results and analytical-numerical model for tokamaks discharges with ohmic heating. Reasonable agreement is obtained when Z, effective atomic number, is assumed as a parameter. (Author)

  16. Induced galaxy formation

    CERN Document Server

    Dokuchaev, V; Rubin, S; Dokuchaev, Vyacheslav; Eroshenko, Yury; Rubin, Sergei

    2004-01-01

    We describe the model of protogalaxy formation around the cluster of primordial black holes with a minimum extension of standard cosmological model. Namely, it is supposed, that a mass fraction of the universe ~10^-3 is composed of the compact clusters of primordial (relict) black holes produced during the phase transitions in the early universe. These clusters are the centers of the dark matter (DM) condensations. As a result the protogalaxies with a mass 2x10^8Msun form at the redshift z=15. These induced protogalaxies contain the central black holes of mass ~10^5Msun and look like the dwarf spheroidal galaxies with a central density spike. Subsequent merging of the induced protogalaxies and ordinary DM haloes leads to the standard scenario of the large scale structure formation. Black holes merging gives the nowadays supermassive black holes and reproduces the observed correlations between their masses and velocity dispersions in the bulges.

  17. Formation of multiple networks

    DEFF Research Database (Denmark)

    Magnani, Matteo; Rossi, Luca

    2013-01-01

    While most research in Social Network Analysis has focused on single networks, the availability of complex on-line data about individuals and their mutual heterogenous connections has recently determined a renewed interest in multi-layer network analysis. To the best of our knowledge, in this paper...... we introduce the first network formation model for multiple networks. Network formation models are among the most popular tools in traditional network studies, because of both their practical and theoretical impact. However, existing models are not sufficient to describe the generation of multiple...... networks. Our model, motivated by an empirical analysis of real multi-layered network data, is a conservative extension of single-network models and emphasizes the additional level of complexity that we experience when we move from a single- to a more complete and realistic multi-network context....

  18. Modeling river delta formation

    OpenAIRE

    Seybold, Hansjörg; Andrade, José S.; Herrmann, Hans J.

    2007-01-01

    A model to simulate the time evolution of river delta formation process is presented. It is based on the continuity equation for water and sediment flow and a phenomenological sedimentation/erosion law. Different delta types are reproduced by using different parameters and erosion rules. The structures of the calculated patterns are analyzed in space and time and compared with real data patterns. Furthermore, our model is capable of simulating the rich dynamics related to the switching of the...

  19. Frost formation with salt

    OpenAIRE

    Guadarrama-Cetina, J.; Mongruel, A. (Anne); González-Viñas, W.; Beysens, D.A. (Daniel A.)

    2015-01-01

    The formation of frost in presence of salt (NaCl) crystal is experimentally investigated on a hydrophobic surface. It presents several remarkable features due to the interplay of salty-water saturation pressure evolution, initially lower than the saturation pressure of ice and water, and the percolating propagation of ice dendrites from defects throughout the supercooled water droplet pattern. In particular, it is remarkable that nucleation of supercooled water and/or ice is prevented around ...

  20. Formate-assisted pyrolysis

    Science.gov (United States)

    DeSisto, William Joseph; Wheeler, Marshall Clayton; van Heiningen, Adriaan R. P.

    2015-03-17

    The present invention provides, among other thing, methods for creating significantly deoxygenated bio-oils form biomass including the steps of providing a feedstock, associating the feedstock with an alkali formate to form a treated feedstock, dewatering the treated feedstock, heating the dewatered treated feedstock to form a vapor product, and condensing the vapor product to form a pyrolysis oil, wherein the pyrolysis oil contains less than 30% oxygen by weight.

  1. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet

  2. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet age:

  3. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet

  4. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet age:

  5. Formation of transient lamellipodia.

    Directory of Open Access Journals (Sweden)

    Juliane Zimmermann

    Full Text Available Cell motility driven by actin polymerization is pivotal to the development and survival of organisms and individual cells. Motile cells plated on flat substrates form membrane protrusions called lamellipodia. The protrusions repeatedly appear and retract in all directions. If a lamellipodium is stabilized and lasts for some time, it can take over the lead and determine the direction of cell motion. Protrusions traveling along the cell perimeter have also been observed. Their initiation is in some situations the effect of the dynamics of the pathway linking plasma membrane receptors to actin filament nucleation, e.g. in chemotaxis. However, lamellipodia are also formed in many cells incessantly during motion with a constant state of the signaling pathways upstream from nucleation promoting factors (NPFs, or spontaneously in resting cells. These observations strongly suggest protrusion formation can also be a consequence of the dynamics downstream from NPFs, with signaling setting the dynamic regime but not initiating the formation of individual protrusions. A quantitative mechanism for this kind of lamellipodium dynamics has not been suggested yet. Here, we present a model exhibiting excitable actin network dynamics. Individual lamellipodia form due to random supercritical filament nucleation events amplified by autocatalytic branching. They last for about 30 seconds to many minutes and are terminated by filament bundling, severing and capping. We show the relevance of the model mechanism for experimentally observed protrusion dynamics by reproducing in very good approximation the repetitive protrusion formation measured by Burnette et al. with respect to the velocities of leading edge protrusion and retrograde flow, oscillation amplitudes, periods and shape, as well as the phase relation between protrusion and retrograde flow. Our modeling results agree with the mechanism of actin bundle formation during lamellipodium retraction suggested by

  6. Egg Formation in Lepidoptera

    OpenAIRE

    William H. Telfer

    2009-01-01

    Reproductive biology in the Twentieth Century produced comprehensive descriptions of the mechanisms of egg formation in most of the major orders of insects. While many general principles of ovarian development and physiology emerged, every order turned out to have a set of its own special motifs. Discovery of the lepidopteran motifs is summarized in this essay. The emphasis is on developmental mechanisms, beginning with the early growth and differentiation of female germ cells and ending, aft...

  7. Isothermal Martensite Formation

    DEFF Research Database (Denmark)

    Villa, Matteo

    are chosen to investigate time dependent martensite formation. Among them, a Fe-11wt%Ni-0.6wt%C model alloy and Fe-1.6wt%Cr-1wt%C (AISI 52100), Fe-17wt%Cr-7wt%Ni (AISI 631) and Fe-16wt%Cr-5wt%Ni (AISI 630) commercial steels. The investigation was performed with in situ magnetometry, dilatometry, synchrotron...

  8. Galaxy Formation and Evolution

    Science.gov (United States)

    Nagamine, Kentaro; Reddy, Naveen; Daddi, Emanuele; Sargent, Mark T.

    2016-07-01

    In this chapter, we discuss the current status of observational and computational studies on galaxy formation and evolution. In particular, a joint analysis of star-formation rates (SFRs), stellar masses, and metallicities of galaxies throughout cosmic time can shed light on the processes by which galaxies build up their stellar mass and enrich the environment with heavy elements. Comparison of such observations and the results of numerical simulations can give us insights on the physical importance of various feedback effects by supernovae and active galactic nuclei. In Sect. 1, we first discuss the primary methods used to deduce the SFRs, stellar masses, and (primarily) gas-phase metallicities in high-redshift galaxies. Then, we show how these quantities are related to each other and evolve with time. In Sect. 2, we further examine the distribution of SFRs in galaxies following the `Main Sequence' paradigm. We show how the so-called `starbursts' display higher specific SFRs and SF efficiencies by an order of magnitude. We use this to devise a simple description of the evolution of the star-forming galaxy population since z ˜3 that can successfully reproduce some of the observed statistics in the infrared (IR) wavelength. We also discuss the properties of molecular gas. In Sect. 3, we highlight some of the recent studies of high-redshift galaxy formation using cosmological hydrodynamic simulations. We discuss the physical properties of simulated galaxies such as luminosity function and escape fraction of ionizing photons, which are important statistics for reionization of the Universe. In particular the escape fraction of ionizing photons has large uncertainties, and studying gamma-ray bursts (which is the main topic of this conference) can also set observational constraints on this uncertain physical parameter as well as cosmic star formation rate density.

  9. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    <正>The format for citations in text and for bibliographic references follows GB/T 7714—2005.The citation should be ordered in number as it appears in the text of the submitted article.For journal article Sun,Y.,Li,B.,&Qu,J.F.Design and implementation of library intelligent IM reference robot.New Technology of Library and Information Service(in Chinese),

  10. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    <正>The format for citations in text and for bibliographic references follows GB/T 7714—2005.The citation should be ordered in number as it appears in the text of the submitted article.For journal article Sun,Y.,Li,B.,&Qu,J.F.Design and implementation of library intelligent IM reference robot.New Technology of Library and Information Service(in Chinese),2011,205:88–92.

  11. Unemployment and Household formation

    OpenAIRE

    Ebrahim, Amina; Woolard, Ingrid; Leibbrandt, Murray

    2013-01-01

    In comparison to other continents, Africa has received little scholarly attention with regard to household composition. Household composition is endogenous to a variety of welfare issues and little is understood about the determinants of this composition. Understanding the household composition and formation decision may improve our understanding of how the unemployed gain access to resources and how household composition could provide a safety net to the unemployed. However, increasingly, mo...

  12. Cyst formation by Methanosarcina

    Energy Technology Data Exchange (ETDEWEB)

    Zhilina, T.N.; Zavarzin, G.A.

    1979-05-01

    The morphology of a coccoid, methane producing bacterium growing on acetate was studied. The organism is capable of forming morphologically differentiated cells, microcysts, whose structure resembles that of bacterial surviving cells. The organism forms peculiar macrocysts in the enrichment culture. In its other characteristics, the organism is similar to Methanococcus mazei. However, it classified as Methanosarcina, biotype 3, due to the characteristic formation of multicellular pseudococci.

  13. Terrestrial planet formation.

    Science.gov (United States)

    Righter, K; O'Brien, D P

    2011-11-29

    Advances in our understanding of terrestrial planet formation have come from a multidisciplinary approach. Studies of the ages and compositions of primitive meteorites with compositions similar to the Sun have helped to constrain the nature of the building blocks of planets. This information helps to guide numerical models for the three stages of planet formation from dust to planetesimals (~10(6) y), followed by planetesimals to embryos (lunar to Mars-sized objects; few 10(6) y), and finally embryos to planets (10(7)-10(8) y). Defining the role of turbulence in the early nebula is a key to understanding the growth of solids larger than meter size. The initiation of runaway growth of embryos from planetesimals ultimately leads to the growth of large terrestrial planets via large impacts. Dynamical models can produce inner Solar System configurations that closely resemble our Solar System, especially when the orbital effects of large planets (Jupiter and Saturn) and damping mechanisms, such as gas drag, are included. Experimental studies of terrestrial planet interiors provide additional constraints on the conditions of differentiation and, therefore, origin. A more complete understanding of terrestrial planet formation might be possible via a combination of chemical and physical modeling, as well as obtaining samples and new geophysical data from other planets (Venus, Mars, or Mercury) and asteroids. PMID:21709256

  14. The Star Formation Camera

    CERN Document Server

    Scowen, Paul A; Beasley, Matthew; Calzetti, Daniela; Desch, Steven; Fullerton, Alex; Gallagher, John; Lisman, Doug; Macenka, Steve; Malhotra, Sangeeta; McCaughrean, Mark; Nikzad, Shouleh; O'Connell, Robert; Oey, Sally; Padgett, Deborah; Rhoads, James; Roberge, Aki; Siegmund, Oswald; Shaklan, Stuart; Smith, Nathan; Stern, Daniel; Tumlinson, Jason; Windhorst, Rogier; Woodruff, Robert

    2009-01-01

    The Star Formation Camera (SFC) is a wide-field (~15'x19, >280 arcmin^2), high-resolution (18x18 mas pixels) UV/optical dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited images at lambda > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. Our aim is to conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems, and to investigate and understand the range of environments, feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. This program addresses the origins and evolution of stars, galaxies, and cosmic structure and has direct relevance for the formation and survival of planetary systems like our Solar System and planets like Earth. We present the design and performance specifications resulting from the implementation study of the camera, conducted ...

  15. Formation of Lunar Swirls

    CERN Document Server

    Bamford, R A; Cruz, F; Kellett, B J; Fonseca, R A; Silva, L O; Trines, R M G M; Halekas, J S; Kramer, G; Harnett, E; Cairns, R A; Bingham, R

    2015-01-01

    In this paper we show a plausible mechanism that could lead to the formation of the Dark Lanes in Lunar Swirls, and the electromagnetic shielding of the lunar surface that results in the preservation of the white colour of the lunar regolith. We present the results of a fully self-consistent 2 and 3 dimensional particle-in-cell simulations of mini-magnetospheres that form above the lunar surface and show that they are consistent with the formation of `lunar swirls' such as the archetypal formation Reiner Gamma. The simulations show how the microphysics of the deflection/shielding of plasma operates from a kinetic-scale cavity, and show that this interaction leads to a footprint with sharp features that could be the mechanism behind the generation of `dark lanes'. The physics of mini-magnetospheres is described and shown to be controlled by space-charge fields arising due to the magnetized electrons and unmagnetized ions. A comparison between model and observation is shown for a number of key plasma parameters...

  16. Bouyei word formation

    Directory of Open Access Journals (Sweden)

    Attasith Boonsawasd

    2012-12-01

    Full Text Available The Bouyei language is divided into three vernaculars, the southern vernacular, the central vernacular and the southwestern vernacular. This paper aims to describe the lexicology of the southern vernacular of the Bouyei language focusing on word formation process. Bouyei words are formed by affixing, compounding and reduplicating. First, the affixation consists of prefixing and suffixing. Infixing is not found in this language. Second, the compound is divided into the semantic and syntactic compound. Finally, the reduplication is divided into the simple and complex reduplication. The simple reduplication is normally used to emphasize the meaning of the root or to indicate plurality.

  17. Modeling river delta formation

    CERN Document Server

    Seybold, Hansjörg; Herrmann, Hans J

    2007-01-01

    A new model to simulate the time evolution of river delta formation process is presented. It is based on the continuity equation for water and sediment flow and a phenomenological sedimentation/ erosion law. Different delta types are reproduced using different parameters and erosion rules. The structures of the calculated patterns are analyzed in space and time and compared with real data patterns. Furthermore our model is capable to simulate the rich dynamics related to the switching of the mouth of the river delta. The simulation results are then compared with geological records for the Mississippi river.

  18. Modeling river delta formation.

    Science.gov (United States)

    Seybold, Hansjörg; Andrade, José S; Herrmann, Hans J

    2007-10-23

    A model to simulate the time evolution of river delta formation process is presented. It is based on the continuity equation for water and sediment flow and a phenomenological sedimentation/erosion law. Different delta types are reproduced by using different parameters and erosion rules. The structures of the calculated patterns are analyzed in space and time and compared with real data patterns. Furthermore, our model is capable of simulating the rich dynamics related to the switching of the mouth of the river delta. The simulation results are then compared with geological records for the Mississippi River. PMID:17940031

  19. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet age:A citation analysis of computer science literature.Information Processing and Management,2001,37:661-675.2 Fernandez,M.,Kadiyska,Y.,&Suciu,D.,et al.SilkRoute:A framework for publishing

  20. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet age:A citation analysis of computer science literature.Information Processing and Manage-

  1. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5th Ed.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet age:A citation analysis of computer science literature.Information Processing and Management,2001,37:661-675.

  2. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet age:A citation analysis of computer science literature.Information Processing and Management,2001,37:661-675.2 Fernandez.M

  3. Formation control of AAUSHIP

    DEFF Research Database (Denmark)

    Østergaard, Nick; Dam, Jeppe; Larsen, Jesper Abildgaard

    2015-01-01

    Many maritime mapping tasks are today carried out by large research ships, which are very costly to operate. As a way to overcome this, a number of small surveying vessels have been developed called AAUSHIP. In order to efficiently map the an area with such smaller vessels, it is important that s...... that several vessels are able to corporate on the task at hand. In this paper, the developed formation control strategy for the AAUSHIP series of vessels is presented, along with simulation results, which confirms, that the algorithm works as intended....

  4. The Star Formation Camera

    OpenAIRE

    Scowen, Paul A.; Jansen, Rolf; Beasley, Matthew; Calzetti, Daniela; Desch, Steven; Fullerton, Alex; Gallagher, John; Lisman, Doug; Macenka, Steve; Malhotra, Sangeeta; McCaughrean, Mark; Nikzad, Shouleh; O'Connell, Robert; Oey, Sally; Padgett, Deborah

    2009-01-01

    The Star Formation Camera (SFC) is a wide-field (~15'x19, >280 arcmin^2), high-resolution (18x18 mas pixels) UV/optical dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited images at lambda > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. Our aim is to conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and ...

  5. Star Formation in Irregular Galaxies.

    Science.gov (United States)

    Hunter, Deidre; Wolff, Sidney

    1985-01-01

    Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

  6. Parametrising Star Formation Histories

    CERN Document Server

    Simha, Vimal; Conroy, Charlie; Dave, Romeel; Fardal, Mark; Katz, Neal; Oppenheimer, Benjamin D

    2014-01-01

    We examine the star formation histories (SFHs) of galaxies in smoothed particle hydrodynamics (SPH) simulations, compare them to parametric models that are commonly used in fitting observed galaxy spectral energy distributions, and examine the efficacy of these parametric models as practical tools for recovering the physical parameters of galaxies. The commonly used tau-model, with SFR ~ exp(-t/tau), provides a poor match to the SFH of our SPH galaxies, with a mismatch between early and late star formation that leads to systematic errors in predicting colours and stellar mass-to-light ratios. A one-parameter lin-exp model, with SFR ~ t*exp(-t/tau), is much more successful on average, but it fails to match the late-time behavior of the bluest, most actively star-forming galaxies and the passive, "red and dead" galaxies. We introduce a 4-parameter model, which transitions from lin-exp to a linear ramp after a transition time, which describes our simulated galaxies very well. We test the ability of these paramet...

  7. Formation of planetary systems

    International Nuclear Information System (INIS)

    It seemed appropriate to devote the 1980 School to the origin of the solar system and more particularly to the formation of planetary systems (dynamic accretion processes, small bodies, planetary rings, etc...) and to the physics and chemistry of planetary interiors, surface and atmospheres (physical and chemical constraints associated with their formation). This Summer School enabled both young researchers and hard-nosed scientists, gathered together in idyllic surroundings, to hold numerous discussions, to lay the foundations for future cooperation, to acquire an excellent basic understanding, and to make many useful contacts. This volume reflects the lectures and presentations that were delivered in this Summer School setting. It is aimed at both advanced students and research workers wishing to specialize in planetology. Every effort has been made to give an overview of the basic knowledge required in order to gain a better understanding of the origin of the solar system. Each article has been revised by one or two referees whom I would like to thank for their assistance. Between the end of the School in August 1980 and the publication of this volume in 1982, the Voyager probes have returned a wealth of useful information. Some preliminary results have been included for completeness

  8. The Planet Formation Imager

    Science.gov (United States)

    Kraus, S.; Buscher, D. F.; Monnier, J. D.; PFI Science, the; Technical Working Group

    2014-04-01

    Among the most fascinating and hotly-debated areas in contemporary astrophysics are the means by which planetary systems are assembled from the large rotating disks of gas and dust which attend a stellar birth. Although important work is being done both in theory and observation, a full understanding of the physics of planet formation can only be achieved by opening observational windows able to directly witness the process in action. The key requirement is then to probe planet-forming systems at the natural spatial scales over which material is being assembled. By definition, this is the so-called Hill Sphere which delineates the region of influence of a gravitating body within its surrounding environment. The Planet Formation Imager project has crystallized around this challenging goal: to deliver resolved images of Hill-Sphere-sized structures within candidate planet-hosting disks in the nearest star-forming regions. In this contribution we outline the primary science case of PFI and discuss how PFI could significantly advance our understanding of the architecture and potential habitability of planetary systems. We present radiation-hydrodynamics simulations from which we derive preliminary specifications that guide the design of the facility. Finally, we give an overview about the interferometric and non-interferometric technologies that we are investigating in order to meet the specifications.

  9. Thiol isomerases in thrombus formation

    OpenAIRE

    Furie, Bruce; Flaumenhaft, Robert

    2014-01-01

    Protein disulfide isomerase, ERp5 and ERp57, among perhaps other thiol isomerases, are important for the initiation of thrombus formation. Using the laser injury thrombosis model in mice to induce in vivo arterial thrombus formation, it was shown that thrombus formation is associated with PDI secretion by platelets, that inhibition of PDI blocked platelet thrombus formation and fibrin generation, and that endothelial cell activation leads to PDI secretion. Similar results using this and other...

  10. Designing for informed group formation

    DEFF Research Database (Denmark)

    Nicolajsen, Hanne Westh; Juel Jacobsen, Alice; Riis, Marianne

    2012-01-01

    A new design ―project preparation‖ preparing for the group formation in problem based project work is proposed and investigated. The main problem is to overcome group formation based on existing relations. The hypothesis is that theme development and group formation are somewhat counterproductive...

  11. Social Network Formation with Consent

    NARCIS (Netherlands)

    Gilles, R.P.; Sarangi, S.

    2004-01-01

    We investigate the equilibria of game theoretic models of network formation that are based on individual actions only.Our approach is grounded in three simple and realistic principles: (1) Link formation should be a binary process of consent.(2) Link formation should be costly.(3) The class of netwo

  12. Cosmological Structure Formation

    CERN Document Server

    Primack, Joel R

    2015-01-01

    LCDM is remarkably successful in predicting the cosmic microwave background and large-scale structure, and LCDM parameters have been determined with only mild tensions between different types of observations. Hydrodynamical simulations starting from cosmological initial conditions are increasingly able to capture the complex interactions between dark matter and baryonic matter in galaxy formation. Simulations with relatively low resolution now succeed in describing the overall galaxy population. For example, the EAGLE simulation in volumes up to 100 cubic Mpc reproduces the observed local galaxy mass function nearly as well as semi-analytic models. It once seemed that galaxies are pretty smooth, that they generally grow in size as they evolve, and that they are a combination of disks and spheroids. But recent HST observations combined with high-resolution hydrodynamic simulations are showing that most star-forming galaxies are very clumpy; that galaxies often undergo compaction which reduces their radius and ...

  13. Synapse formation and remodeling

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Synapses are specialized structures that mediate information flow between neurons and target cells,and thus are the basis for neuronal system to execute various functions,including learning and memory.There are around 1011 neurons in the human brain,with each neuron receiving thousands of synaptic inputs,either excitatory or inhibitory.A synapse is an asymmetric structure that is composed of pre-synaptic axon terminals,synaptic cleft,and postsynaptic compartments.Synapse formation involves a number of cell adhesion molecules,extracellular factors,and intracellular signaling or structural proteins.After the establishment of synaptic connections,synapses undergo structural or functional changes,known as synaptic plasticity which is believed to be regulated by neuronal activity and a variety of secreted factors.This review summarizes recent progress in the field of synapse development,with particular emphasis on the work carried out in China during the past 10 years(1999-2009).

  14. Dislocation Formation in Alloys

    Science.gov (United States)

    Minami, Akihiko; Onuki, Akira

    2006-05-01

    An interaction between dislocations and phase transitions is studied by a phase field model both in two and three dimensional systems. Our theory is a simple extension of the traditional linear elastic theory, and the elastic energy is a periodic function of local strains which is reflecting the periodicity of crystals. We find that the dislocations are spontaneously formed by quenching. Dislocations are formed from the interface of binary alloys, and slips are preferentially gliding into the soft metals. In three dimensional systems, formation of dislocations under applied strain is studied in two phase state. We find that the dislocation loops are created from the surface of hard metals. We also studied the phase separation above the coexisting temperature which is called as the Cottrell atmosphere. Clouds of metals cannot catch up with the motion of dislocations at highly strained state.

  15. Determinants for gallstone formation

    DEFF Research Database (Denmark)

    Shabanzadeh, Daniel Monsted; Sorensen, Lars Tue; Jørgensen, Torben

    2016-01-01

    . Gallstone incidence was assessed through repeated ultrasound examinations. Body mass index (BMI), blood pressure, self-rated health, lifestyle variables, blood lipids, and use of female sex hormones were measured at the baseline examination. Statistical analyses included logistic regression. Based...... on a prospective protocol, a systematic review of the literature was performed identifying all articles dealing with determinants of incident gallstones. Meta-analyses of comparable determinants were performed through fixed effect models. Results: Participants with no gallstones at baseline and with at least one...... associations were found for blood pressure, smoking, alcohol consumption, HDL cholesterol, or triglycerides in meta-analyses. Conclusions: Age, female sex, BMI, non-HDL cholesterol, and polyps are independent determinants for gallstone formation. Incident gallstones and the metabolic syndrome share common risk...

  16. Physics of amniote formation.

    Science.gov (United States)

    Fleury, Vincent; Murukutla, Ameya Vaishnavi; Chevalier, Nicolas R; Gallois, Benjamin; Capellazzi-Resta, Marina; Picquet, Pierre; Peaucelle, Alexis

    2016-08-01

    We present a detailed study of the formation of the amniotic sac in the avian embryo, and a comparison with the crocodile amniotic sac. We show that the amniotic sac forms at a circular line of stiffness contrast, separating rings of cell domains. Cells align at this boundary, and this in turn orients and concentrates the tension forces. The tissue fold which forms the amniotic sac is locked exactly along this line due to the colocalization of the stiffness contrast and of the tensile force. In addition, the tensile force plays a regenerative role when the amniotic sac is cut. The fold forming the ventral side of the embryo displays the same characteristics. This work shows that amniote embryogenesis consists of a cascade of buckling events taking place at the boundaries between regions of differing mechanical properties. Hence, amniote embryogenesis relies on a simple and robust biomechanical scheme used repeatedly, and selected ancestrally. PMID:27627351

  17. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet age:A citation analysis of computer science literature.Information Processing and Management,2001,37:661-675.2 Fernandez,M.,Kadiyska,Y.,&Suciu,D.,et al.SilkRoute:A framework for publishing relational data in XML.ACM Transactions on Database Systems,2002,27(4):438-493.

  18. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet age:A citation analysis of computer science literature.Information Processing and Management,2001,37:661-675.2 Fernandez,M.,Kadiyska,Y.,&Suciu,D.,et al.SilkRoute:A framework for publishing relational data in XML.ACM Transactions on Database Systems,2002,27(4):438-493.

  19. Reference Citation Format

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    <正>The format for citations in text and for bibliographic references follows the Publication Manual of the American Psychological Association(5thEd.,2001)and GB/T 7714-2005.The citation of printed word should be ordered in number as it appears in the text of the submitted article.For journal article1 Goodrum,A.A.,McCain,K.W.,&Lawrence,S.,et al.Scholarly publishing in the Internet age:A citation analysis of computer science literature.Information Processing and Management,2001,37:661-675.2 Fernandez,M.,Kadiyska,Y.,&Suciu,D.,et al.SilkRoute:A framework for publishing relational data in XML.ACM Transactions on Database Systems,2002,27(4):438-493.

  20. Recipes for planet formation

    Science.gov (United States)

    Meyer, Michael R.

    2009-11-01

    Anyone who has ever used baking soda instead of baking powder when trying to make a cake knows a simple truth: ingredients matter. The same is true for planet formation. Planets are made from the materials that coalesce in a rotating disk around young stars - essentially the "leftovers" from when the stars themselves formed through the gravitational collapse of rotating clouds of gas and dust. The planet-making disk should therefore initially have the same gas-to-dust ratio as the interstellar medium: about 100 to 1, by mass. Similarly, it seems logical that the elemental composition of the disk should match that of the star, reflecting the initial conditions at that particular spot in the galaxy.

  1. Group Formation in Economics

    Science.gov (United States)

    Demange, Gabrielle; Wooders, Myrna

    2005-01-01

    Broad and diverse ranges of activities are conducted within and by organized groups of individuals, including political, economic and social activities. These activities have recently become a subject of intense interest in economics and game theory. Some of the topics investigated in this collection are models of networks of power and privilege, trade networks, co-authorship networks, buyer-seller networks with differentiated products, and networks of medical innovation and the adaptation of new information. Other topics are social norms on punctuality, clubs and the provision of club goods and public goods, research and development and collusive alliances among corporations, and international alliances and trading agreements. While relatively recent, the literature on game theoretic studies of group formation in economics is already vast. This volume provides an introduction to this important literature on game-theoretic treatments of situations with networks, clubs, and coalitions, including some applications.

  2. Nuclear Pasta Formation

    CERN Document Server

    Schneider, A S; Hughto, J; Berry, D K

    2013-01-01

    The formation of complex nonuniform phases of nuclear matter, known as nuclear pasta, is studied with molecular dynamics simulations containing 51200 nucleons. A phenomenological nuclear interaction is used that reproduces the saturation binding energy and density of nuclear matter. Systems are prepared at an initial density of 0.10fm$^{-3}$ and then the density is decreased by expanding the simulation volume at different rates to densities of 0.01 fm$^{-3}$ or less. An originally uniform system of nuclear matter is observed to form spherical bubbles ("swiss cheese"), hollow tubes, flat plates ("lasagna"), thin rods ("spaghetti") and, finally, nearly spherical nuclei with decreasing density. We explicitly observe nucleation mechanisms, with decreasing density, for these different pasta phase transitions. Topological quantities known as Minkowski functionals are obtained to characterize the pasta shapes. Different pasta shapes are observed depending on the expansion rate. This indicates non equilibrium effects...

  3. Chinese Affixes and Word Formation

    Directory of Open Access Journals (Sweden)

    Fu Ruomei

    2014-05-01

    Full Text Available Chinese language is one of the typical isolated languages. It lacks morphological variation; part of speech has no morphological signs; the additional component of word formation is less; and the roots never change their forms. The major method of Chinese word formation is the combination of roots according to certain grammatical relations. Although the affix word formation is not part of mainstream Chinese word formation, affix-formation is still an integral part of the Chinese word-formation. Article used literature review, summarized the types and meanings of Chinese affixes. And meanwhile, article analyzed word formation function of Chinese Affixes and quasi-affixes. The Chinese quasi-affixes have stronger capabilities in forming new words, but development direction of Chinese quasi-affixes has to stand the test of time.

  4. Gas formation. Formation temperatures of thermogenic and biogenic methane.

    Science.gov (United States)

    Stolper, D A; Lawson, M; Davis, C L; Ferreira, A A; Santos Neto, E V; Ellis, G S; Lewan, M D; Martini, A M; Tang, Y; Schoell, M; Sessions, A L; Eiler, J M

    2014-06-27

    Methane is an important greenhouse gas and energy resource generated dominantly by methanogens at low temperatures and through the breakdown of organic molecules at high temperatures. However, methane-formation temperatures in nature are often poorly constrained. We measured formation temperatures of thermogenic and biogenic methane using a "clumped isotope" technique. Thermogenic gases yield formation temperatures between 157° and 221°C, within the nominal gas window, and biogenic gases yield formation temperatures consistent with their comparatively lower-temperature formational environments (<50°C). In systems where gases have migrated and other proxies for gas-generation temperature yield ambiguous results, methane clumped-isotope temperatures distinguish among and allow for independent tests of possible gas-formation models. PMID:24970083

  5. Modeling Formation of Globular Clusters: Beacons of Galactic Star Formation

    CERN Document Server

    Gnedin, Oleg Y

    2010-01-01

    Modern hydrodynamic simulations of galaxy formation are able to predict accurately the rates and locations of the assembly of giant molecular clouds in early galaxies. These clouds could host star clusters with the masses and sizes of real globular clusters. I describe current state-of-the-art simulations aimed at understanding the origin of the cluster mass function and metallicity distribution. Metallicity bimodality of globular cluster systems appears to be a natural outcome of hierarchical formation and gradually declining fraction of cold gas in galaxies. Globular cluster formation was most prominent at redshifts z>3, when massive star clusters may have contributed as much as 20% of all galactic star formation.

  6. Formation of "bound

    Science.gov (United States)

    Nowak, K.; Kästner, M.; Miltner, A.

    2009-04-01

    During degradation of organic pollutants in soil, metabolites, microbial biomass, CO2and "bound" residues ("non-extractable" residues in soil organic matter) are formed. Enhanced transformation of these contaminants into "bound" residues has been proposed as an alternative remediation method for polluted soils. However, this kind of residues may pose a potential risk for the environment due to their chemical structure and possible remobilization under different conditions. Therefore particular attention is given actually to "bound" residues. Part of these non-extractable residues may be "biogenic," because microorganisms use the carbon from the pollutant to form their biomass components (fatty acids, amino acids, amino sugars), which subsequently may be incorporated into soil organic matter. Furthermore, the CO2 originating from mineralization of xenobiotics, can be re-assimilated by microorganisms and also incorporated into "biogenic residue". The hazard posed by "bound" residues may be overestimated because they are "biogenic" (contain microbial fatty acids and amino acids). The knowledge about the pathways of "biogenic residue" formation is necessary for a proper assessment of the fate of tested pollutants and their turnover in the soil environment. Moreover, these data are needed to establish the realistic degradation rates of the contaminants in soil. The main objectives of this study are: to quantify the extent of "biogenic residue" (fatty acids, amino acids, amino sugars) formation during the degradation of a model pollutant (2,4-dichlorophenoxyacetic acid = 2,4-D) and during CO2 assimilation by microorganisms and to evaluate which components are mainly incorporated into "bound" residues. To investigate the extent of "biogenic residue" formation in soil during the degradation of 2,4-D, experiments with either 14C-U-ring and 13C6-2,4-D or carboxyl-14C 2,4-D were performed. The incubation experiments were performed according to OECD test guideline 307, in the

  7. ISLET FORMATION AND REGENERATION

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Objective To explore the mechanisms of differentiation and development of pancreatic endocrine cells as well as pancreatic regeneration. Methods Human embryonic pancreatic tissue at 7-14 weeks of gestation was collected. Diabetes mellitus rat model was induced with 65 mg/kg of streptozotocin. Insulin, glucagon, somatostatin, nestin, and cytokeratin 19 (CK19)of pancreatic tissues were observed by immunohistochemistry. Results At 9 weeks of gestation, pancreatic epithelial cells began to co-express insulin, glucagon, somatostatin, and CK19 before migration. Islet cells gradually congregated along with the increase of aging, and at 14 weeks of gestation histological examination showed islet formation. At 12 weeks of gestation, nestin-positive cells could be seen in the pancreatic mesenchyme. During early embryogenesis, islet cells of pancreatic ducts co-expressed insulin, glucagon, and somatostatin. During pancreatic regeneration after damage, nestin expression of islet cells increased. Conclusion In the early stage of embryogenesis, islet cells of primary pancreatic ducts can be differentiated to multipotential endocrine cells before migration. During tissue regeneration, pancreatic stem cells may differentiate and proliferate to form pancreatic islet.

  8. 巨猿、化石人和智人牙齿的波动不对称:人类进化中压力源变化的意义%Fluctuating Dental Asymmetry in Great Apes, Fossil Hominins, and Modern Humans: Implications for Changing Stressors during Human Evolution

    Institute of Scientific and Technical Information of China (English)

    Michael J. Frederick; Gordon G. Gallup, Jr.

    2007-01-01

    Fluctuating asymmetry (FA), defined by random, stress-induced deviations from perfect bilateral symmetry, is an indication of the inability to buffer against developmental disturbances, such as poor early nutrition. One method of measuring FA involves comparing individual tooth sizes on opposing sides of the mouth. In this study tooth measurements were compiled for 296 individuals from 10 species, including chimpanzees (Pan troglodytes),orangutans (Pongo pygmaeus), gorillas (Gorilla gorilla), modern humans (Homo sapiens), and a number of fossil hominins. The orangutan sample had significantly lower levels of dental FA than the gorilla, chimpanzee, Homo erectus, neandertal, or modern human samples. In contrast, the human and neandertal samples had significantly higher dental FA levels than any of the great ape samples. Some explanations relating to relaxed selection pressures are suggested.%波动不对称(FA)是压力的随机性引发双侧完美对称偏离的现象,这是个体无力免受发展中不利因素(如早期营养不良)侵害的一个标志.比较个体口腔两侧牙齿的大小是一种测量FA的方法.本研究汇集了10个物种共296名个体的牙齿测量结果,测量对象包括黑猩猩(学名Pan troglodytes)、猩猩(学名Pongo pygmaeus)、大猩猩(学名Gorilla gorilla)、智人(学名Homo sapiens),以及许多化石人.分析发现,猩猩样本牙齿的FA水平要显著低于大猩猩、黑猩猩、直立人、尼安德特人和智人样本的FA水平.而与之相反的是,智人与尼安德特人样本的牙齿FA水平要显著高于其它任何一种巨猿样本的FA水平.该文提出了有关缓和的选择压力的解释.

  9. The KEA image file format

    Science.gov (United States)

    Bunting, Peter; Gillingham, Sam

    2013-08-01

    There are a large number of image formats already in use within the remote sensing community but currently there is no format that provides the features of: compression, support for large file sizes, ground control points, raster attribute tables and inbuilt image pyramids. Therefore, a new image format, named KEA, after the New Zealand bird, has been proposed. The KEA format provides a full implementation of the GDAL data model and is implemented within a HDF5 file. A software library with a GDAL driver have been freely provided to the community allowing use through any GDAL based software. The new format has comparable performance with existing formats while producing smaller file sizes and is already within active use for a number of projects within Landcare Research, New Zealand, and the wider community.

  10. Earth and Terrestrial Planet Formation

    OpenAIRE

    Jacobson, Seth A.; Walsh, Kevin J.

    2015-01-01

    The growth and composition of Earth is a direct consequence of planet formation throughout the Solar System. We discuss the known history of the Solar System, the proposed stages of growth and how the early stages of planet formation may be dominated by pebble growth processes. Pebbles are small bodies whose strong interactions with the nebula gas lead to remarkable new accretion mechanisms for the formation of planetesimals and the growth of planetary embryos. Many of the popular models for ...

  11. Spray formation: an inverse cascade

    CERN Document Server

    Ling, Yue; Tryggvason, Gretar; zaleski, Stephane

    2015-01-01

    We present a study of droplet formation in a gas-liquid mixing layer using direct numerical simulation. It is seen that two mechanisms compete to generate the droplets: fingering at the tip of the waves and hole formation in the thin liquid sheet. The three dimensional liquid structures are much shorter than the longitudinal wavelength of the instability at the first instant of their formation. As time evolves, the structures evolves to larger and larger scales, in a way similar to the inverse cascade of length scales in droplet impact and impact crown formation.

  12. Formation of Bidisperse Particle Clouds

    Science.gov (United States)

    Er, Jenn Wei; Zhao, Bing; Law, Adrian W. K.; Adams, E. Eric

    2014-11-01

    When a group of dense particles is released instantaneously into water, their motion has been conceptualized as a circulating particle thermal (Ruggerber 2000). However, Wen and Nacamuli (1996) observed the formation of particle clumps characterized by a narrow, fast moving core shedding particles into wakes. They observed the clump formation even for particles in the non-cohesive range as long as the source Rayleigh number was large (Ra > 1E3) or equivalently the source cloud number (Nc) was small (Nc < 3.2E2). This physical phenomenon has been investigated by Zhao et al. (2014) through physical experiments. They proposed the theoretical support for Nc dependence and categorized the formation processes into cloud formation, transitional regime and clump formation. Previous works focused mainly on the behavior of monodisperse particles. The present study further extends the experimental investigation to the formation process of bidisperse particles. Experiments are conducted in a glass tank with a water depth of 90 cm. Finite amounts of sediments with various weight proportions between coarser and finer particles are released from a cylindrical tube. The Nc being tested ranges from 6E-3 to 9.9E-2, which covers all the three formation regimes. The experimental results showed that the introduction of coarse particles promotes cloud formation and reduce the losses of finer particles into the wake. More quantitative descriptions of the effects of source conditions on the formation processes will be presented during the conference.

  13. The formation of Pangea

    Science.gov (United States)

    Stampfli, G. M.; Hochard, C.; Vérard, C.; Wilhem, C.; vonRaumer, J.

    2013-05-01

    The making of Pangea is the result of large-scale amalgamation of continents and micro-continents, which started at the end of the Neoproterozoic with the formation of Gondwana. As pieces were added to Gondwana on its South-American, Antarctica and Australia side, ribbon-like micro-continents were detached from its African and South-Chinese side: Cadomia in the late Neoproterozoic, Avalonia and Hunia in the Ordovician, Galatia in the Devonian and Cimmeria in the Permian. Cadomia was re-accreted to Gondwana, but the other ribbon-continents were accreted to Baltica, North-China, Laurussia or Laurasia. Finding the origin of these numerous terranes is a major geological challenge. Recently, a global plate tectonic model was developed together with a large geological/geodynamic database, at the Lausanne University, covering the last 600 Ma of the Earth's history. Special attention was given to the placing of Gondwana derived terranes in their original position, using all possible constraints. We propose here a solution for the Variscan terranes, another paper deals with the Altaids. The Galatian super-terrane was detached from Gondwana in the Devonian, during the opening of Paleotethys, and was quickly separated into four sub-terranes that started to by-pass each other. The leading terranes collided at the end of the Devonian with the Hanseatic terrane detached from Laurussia. In the Carboniferous, Gondwana started to impinge onto the amalgamated terranes, creating the Variscan chain and the Pangean super-continent. East of Spain Paleotethys remained opened until the Triassic, subducting northward under Laurasia. Roll-back of the Paleotethyan slab triggered the collapse of most of the European Variscan orogen, which was replaced by series of Permian rifts, some of them becoming oceanized back-arc basins during the Triassic. Major force changes at the Pangean plate limits at the end of the Triassic provoked its break-up, through the opening of the proto

  14. Target-point formation control

    NARCIS (Netherlands)

    Mou, Shaoshuai; Cao, Ming; Morse, A. Stephen

    2015-01-01

    In this paper a new distributed feedback strategy is proposed for controlling a rigid, acyclic formation of kinematic point-modeled mobile autonomous agents in the plane. The strategy makes use of a new concept called a "target point" and is applicable to any two-dimensional, acyclic formation whose

  15. Identity formation in multiparty negotiations

    NARCIS (Netherlands)

    Swaab, R; Postmes, T.; Spears, R.

    2008-01-01

    Based on the recently proposed Interactive Model of Identity Formation, we examine how top-down deductive and bottom-up inductive identity formations influence intentions and behaviour in multiparty negotiations. Results show that a shared identity can be deduced from the social context through reco

  16. Pathogenesis of postoperative adhesion formation

    NARCIS (Netherlands)

    Hellebrekers, B.W.J.; Kooistra, T.

    2011-01-01

    Background: Current views on the pathogenesis of adhesion formation are based on the "classical concept of adhesion formation", namely that a reduction in peritoneal fibrinolytic activity following peritoneal trauma is of key importance in adhesion development. Methods: A non-systematic literature s

  17. Portable File Format (PFF) specifications.

    Energy Technology Data Exchange (ETDEWEB)

    Dolan, Daniel H.,

    2015-02-01

    Created at Sandia National Laboratories, the Portable File Format (PFF) allows binary data transfer across computer platforms. Although this capability is supported by many other formats, PFF files are still in use at Sandia, particularly in pulsed power research. This report provides detailed PFF specifications for accessing data without relying on legacy code.

  18. Formative assessments as pedagogic tools

    Directory of Open Access Journals (Sweden)

    Ashwin Kumar

    2013-03-01

    Full Text Available This article aims at presenting a state of the art status of formative assessment as a pedagogic tool. To this end, a brief developmental account of different modes of assessment over the last decades will be presented first. Then, formative assessment will be discussed in its constructivist guise. The present literature on assessment suggests that assessment for learning (formative assessment not only represents an assessment tool but it also serves as a pedagogic tool to enhance learning and thinking. It has also gone to lengths to affect the design of classroom tasks and activities. Attempts have been made to delineate the underlying principles of formative assessment which can be used to picture the formation process of learners’ knowledge and development. Subsequently, alternative assessment techniques of which the present article will give an account have been suggested by scholars to operationalize these principles.

  19. Physics of primordial star formation

    Science.gov (United States)

    Yoshida, Naoki

    2012-09-01

    The study of primordial star formation has a history of nearly sixty years. It is generally thought that primordial stars are one of the key elements in a broad range of topics in astronomy and cosmology, from Galactic chemical evolution to the formation of super-massive blackholes. We review recent progress in the theory of primordial star formation. The standard theory of cosmic structure formation posits that the present-day rich structure of the Universe developed through gravitational amplification of tiny matter density fluctuations left over from the Big Bang. It has become possible to study primordial star formation rigorously within the framework of the standard cosmological model. We first lay out the key physical processes in a primordial gas. Then, we introduce recent developments in computer simulations. Finally, we discuss prospects for future observations of the first generation of stars.

  20. Formation depths of Fraunhofer lines

    CERN Document Server

    Gurtovenko, E A

    2015-01-01

    We have summed up our investigations performed in 1970--1993. The main task of this paper is clearly to show processes of formation of spectral lines as well as their distinction by validity and by location. For 503 photospheric lines of various chemical elements in the wavelength range 300--1000 nm we list in Table the average formation depths of the line depression and the line emission for the line centre and on the half-width of the line, the average formation depths of the continuum emission as well as the effective widths of the layer of the line depression formation. Dependence of average depths of line depression formation on excitation potential, equivalent widths, and central line depth are demonstrated by iron lines.

  1. Dwarf galaxy formation with H2-regulated star formation

    CERN Document Server

    Kuhlen, M; Madau, P; Smith, B; Wise, J

    2011-01-01

    We describe cosmological galaxy formation simulations with the adaptive mesh refinement code Enzo that incorporate a star formation prescription regulated by the local abundance of molecular hydrogen. We show that this H2-regulated prescription leads to a suppression of star formation in low mass halos (M_h 4, alleviating some of the dwarf galaxy problems faced by theoretical galaxy formation models. H2 regulation modifies the efficiency of star formation of cold gas directly, rather than indirectly reducing the cold gas content with "supernova feedback". We determine the local H2 abundance in our most refined grid cells (76 proper parsec in size at z=4) by applying the model of Krumholz, McKee, & Tumlinson, which is based on idealized 1D radiative transfer calculations of H2 formation-dissociation balance in ~100 pc atomic--molecular complexes. Our H2-regulated simulations are able to reproduce the empirical (albeit lower z) Kennicutt-Schmidt relation, including the low Sigma_gas cutoff due to the transi...

  2. SOME QUESTIONS CONCERNING PSYCHOANALYTICAL FORMATION

    Directory of Open Access Journals (Sweden)

    Orlando Soeiro Cruxên

    2009-12-01

    Full Text Available The psychoanalytical formation is a question without a definitive answer. The development of its study requests treatment of the evolution of the clinical theory. This work begins with a distinction between analytical and academic formation. It includes Jacques Lacan’s approach concerning the question of psychoanalytical formation. It discusses the relationship between the named intentional and extensional psychoanalysis. This article resumes some theoretical aspects of a post-doctoral investigation developed in the clinical-school of Psychology (Universidade Federal do Ceará e SAP ( Pontifícia Universidade Católica do Rio Grande doSul.

  3. AGN feedback in galaxy formation

    CERN Document Server

    Antonuccio-Delogu, Vincenzo

    2010-01-01

    During the past decade, convincing evidence has been accumulated concerning the effect of active galactic nuclei (AGN) activity on the internal and external environment of their host galaxies. Featuring contributions from well-respected researchers in the field, and bringing together work by specialists in both galaxy formation and AGN, this volume addresses a number of key questions about AGN feedback in the context of galaxy formation. The topics covered include downsizing and star-formation time scales in massive elliptical galaxies, the connection between the epochs of supermassive black h

  4. Free-format RPG IV

    CERN Document Server

    Martin, Jim

    2013-01-01

    This how-to guide offers a concise and thorough introduction to the increased productivity, better readability, and easier program maintenance that comes with the free-format style of programming in RPG IV. Although free-format information is available in IBM manuals, it is not separated from everything else, thereby requiring hours of tedious research to track down the information needed. This book provides everything one needs to know to write RPG IV in the free-format style, and author Jim Martin not only teaches rules and syntax but also explains how this new style of coding has the pot

  5. Portfolio Optimization under Habit Formation

    CERN Document Server

    Naryshkin, Roman

    2008-01-01

    The "standard" Merton formulation of optimal investment and consumption involves optimizing the integrated lifetime utility of consumption, suitably discounted, together with the discounted future bequest. In this formulation the utility of consumption at any given time depends only on the amount consumed at that time. However, it is both theoretically and empirically reasonable that an individuals utility of consumption would depend on past consumption history. Economists term this "Habit Formation". We introduce a new formulation of habit formation which allows non-addictive consumption patterns for a wide variety of utility specification. In this paper we construct a simple mathematical description of this habit formation and present numerical solutions. We compare the results with the standard ones and draw insights obtained from the habit formation. The consumption path tends to increase with time and be less sensitive to the market fluctuations, which perfectly reflects the existence of habit persistenc...

  6. The multifaceted planetesimal formation process

    CERN Document Server

    Johansen, Anders; Tanaka, Hidekazu; Ormel, Chris; Bizzarro, Martin; Rickman, Hans

    2014-01-01

    Accumulation of dust and ice particles into planetesimals is an important step in the planet formation process. Planetesimals are the seeds of both terrestrial planets and the solid cores of gas and ice giants forming by core accretion. Left-over planetesimals in the form of asteroids, trans-Neptunian objects and comets provide a unique record of the physical conditions in the solar nebula. Debris from planetesimal collisions around other stars signposts that the planetesimal formation process, and hence planet formation, is ubiquitous in the Galaxy. The planetesimal formation stage extends from micrometer-sized dust and ice to bodies which can undergo run-away accretion. The latter ranges in size from 1 km to 1000 km, dependent on the planetesimal eccentricity excited by turbulent gas density fluctuations. Particles face many barriers during this growth, arising mainly from inefficient sticking, fragmentation and radial drift. Two promising growth pathways are mass transfer, where small aggregates transfer u...

  7. Robust Decentralized Formation Flight Control

    Directory of Open Access Journals (Sweden)

    Zhao Weihua

    2011-01-01

    Full Text Available Motivated by the idea of multiplexed model predictive control (MMPC, this paper introduces a new framework for unmanned aerial vehicles (UAVs formation flight and coordination. Formulated using MMPC approach, the whole centralized formation flight system is considered as a linear periodic system with control inputs of each UAV subsystem as its periodic inputs. Divided into decentralized subsystems, the whole formation flight system is guaranteed stable if proper terminal cost and terminal constraints are added to each decentralized MPC formulation of the UAV subsystem. The decentralized robust MPC formulation for each UAV subsystem with bounded input disturbances and model uncertainties is also presented. Furthermore, an obstacle avoidance control scheme for any shape and size of obstacles, including the nonapriorily known ones, is integrated under the unified MPC framework. The results from simulations demonstrate that the proposed framework can successfully achieve robust collision-free formation flights.

  8. Problem of professional personality formation

    Directory of Open Access Journals (Sweden)

    Pryazhnikova E.Yu.

    2012-09-01

    Full Text Available The article presents the current approaches to the problem of professional personality formation. It ana-lyzes the impact of professional identity of students on the choice of the specialist field they make. The article highlights certain aspects of the educational environment which promote to formation of compe-tences in students, relating to their choice of professional occupations. The article presents the analysis of students’ internal and external strivings after graduation from the university and their fulfillment.

  9. Electronic formation of a contract:

    OpenAIRE

    Kežmah, Urška

    2001-01-01

    This paper analysis main legal problems that are related to formation of e-contracts. Because of the different legal consequences it is highly important for parties to be aware and understand the basic phases of contract formation process. For a contract to exist, usually one party must have made offer, and the other must have accepted it. Once acceptance takes effect, a contract will usually be binding on both parties. A variety of procedures are available for forming an electronic contract,...

  10. EPR dosimetric properties of formates

    International Nuclear Information System (INIS)

    As a part of a program to develop an electron paramagnetic resonance (EPR) dosimeter suited for clinical use (doses in the cGy range), polycrystalline samples of lithium formate monohydrate (HCO2Li·H2O), magnesium formate dihydrate (C2H2O4Mg·2H2O), and calcium formate (C2H2O4Ca) have been examined. L-Alanine was included for comparison and reference. Samples were irradiated with 60Co γ-rays and 60-220 kV X-rays. The dosimeter response was assessed using the peak-to-peak amplitude of the first-derivative EPR spectrum. Dose-response curves for the 60Co γ-irradiated samples were constructed, and the dependences of the response on the photon energy, microwave power, and modulation amplitude were studied. Stability of the irradiation products upon storage (signal fading) was also investigated. Lithium formate monohydrate is by far the best candidate of the tested formates, suitable for measuring doses down to approximately 0.1 Gy. Lithium formate monohydrate is more sensitive than alanine by a factor of 5.6-6.8 in the tested photon energy range, it exhibits no zero-dose signal and shows a linear dose response in the dose range from 0.2 to 1000 Gy. Its EPR signal was found unchanged in shape and intensity 1 week after irradiation to 10 Gy. Various less favorable properties rendered the other formates generally unsuitable, although calcium formate exhibits some interesting EPR dosimetric properties

  11. Political parties and network formation

    OpenAIRE

    Miettinen, Topi; Poutvaara, Panu

    2006-01-01

    We argue that anti-corruption laws may provide an efficiency rationale for why political parties should meddle in the distribution of political nominations and government contracts. Anti-corruption laws forbid trade in spoils that politicians distribute. However, citizens may pay for gaining access to politicians and, thereby, to become potential candidates for nominations. Such rent-seeking results in excessive network formation. Political parties may reduce wasteful network formation, thank...

  12. Immigration, Integration and Ghetto Formation

    Science.gov (United States)

    Meyer-Ortmanns, Hildegard

    We study ghetto formation in a population with natives and immigrants in the framework of the two-dimensional Ising-model with Kawasaki-exchange dynamics. It is the phase structure of the Ising model, the integration speed and the immigration rate which determine whether ghetto formation between natives and immigrants can be avoided or not. Our simulations are performed in- and out-of-equilibrium.

  13. Immigration, integration and ghetto formation

    OpenAIRE

    Meyer-Ortmanns, Hildegard

    2002-01-01

    We study ghetto formation in a population with natives and immigrants in the framework of the two-dimensional Ising-model with Kawasaki-exchange dynamics. It is the phase structure of the Ising model, the integration speed and the immigration rate which determine whether ghetto formation between natives and immigrants can be avoided or not. Our simulations are performed in and out-of equilibrium.

  14. Chain formation of metal atoms

    DEFF Research Database (Denmark)

    Bahn, Sune Rastad; Jacobsen, Karsten Wedel

    2001-01-01

    The possibility of formation of single-atomic chains by manipulation of nanocontacts is studied for a selection of metals (Ni, Pd, Pt, Cu, Ag, Au). Molecular dynamics simulations show that the tendency for chain formation is strongest for Au and Pt. Density functional theory calculations indicate...... that the metals which form chains exhibit pronounced many-atom interactions with strong bonding in low coordinated systems....

  15. Treating tar sands formations with karsted zones

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J. (Bellaire, TX); Karanikas, John Michael (Houston, TX)

    2010-03-09

    Methods for treating a tar sands formation are described herein. The tar sands formation may have one or more karsted zones. Methods may include providing heat from one or more heaters to one or more karsted zones of the tar sands formation to mobilize fluids in the formation. At least some of the mobilized fluids may be produced from the formation.

  16. Loss of air sacs improved hominin speech abilities

    NARCIS (Netherlands)

    B. de Boer

    2012-01-01

    In this paper, the acoustic-perceptual effects of air sacs are investigated. Using an adaptive hearing experiment, it is shown that air sacs reduce the perceptual effect of vowel-like articulations. Air sacs are a feature of the vocal tract of all great apes, except humans. Because the presence or a

  17. Star formation and structure formation in galaxy collisions

    CERN Document Server

    Bournaud, Frederic

    2009-01-01

    A number of theoretical and simulation results on star and structure formation in galaxy interactions and mergers is reviewed, and recent hydrodynamic simulations are presented. The role of gravity torques and ISM turbulence in galaxy interactions, in addition to the tidal field, is highlighted. Interactions can drive gas inflows towards the central kpc and trigger a central starburst, the intensity and statistical properties of which are discussed. A kinematically decoupled core and a supermassive central black hole can be fueled. Outside of the central kpc, many structures can form inside tidal tails, collisional ring, bridges, including super star clusters and tidal dwarf galaxies. The formation of super star clusters in galaxy mergers can now be directly resolved in hydrodynamic simulations. Their formation mechanisms and long-term evolution are reviewed, and the connection with present-day early-type galaxies is discussed.

  18. The dynamics of latifundia formation.

    Science.gov (United States)

    Chaves, Luis Fernando

    2013-01-01

    Land tenure inequity is a major social problem in developing nations worldwide. In societies, where land is a commodity, inequities in land tenure are associated with gaps in income distribution, poverty and biodiversity loss. A common pattern of land tenure inequities through the history of civilization has been the formation of latifundia [Zhuāngyuán in chinese], i.e., a pattern where land ownership is concentrated by a small fraction of the whole population. Here, we use simple Markov chain models to study the dynamics of latifundia formation in a heterogeneous landscape where land can transition between forest, agriculture and recovering land. We systematically study the likelihood of latifundia formation under the assumption of pre-capitalist trade, where trade is based on the average utility of land parcels belonging to each individual landowner during a discrete time step. By restricting land trade to that under recovery, we found the likelihood of latifundia formation to increase with the size of the system, i.e., the amount of land and individuals in the society. We found that an increase of the transition rate for land use changes, i.e., how quickly land use changes, promotes more equitable patterns of land ownership. Disease introduction in the system, which reduced land profitability for infected individual landowners, promoted the formation of latifundia, with an increased likelihood for latifundia formation when there were heterogeneities in the susceptibility to infection. Finally, our model suggests that land ownership reforms need to guarantee an equitative distribution of land among individuals in a society to avoid the formation of latifundia. PMID:24376597

  19. The dynamics of latifundia formation.

    Directory of Open Access Journals (Sweden)

    Luis Fernando Chaves

    Full Text Available Land tenure inequity is a major social problem in developing nations worldwide. In societies, where land is a commodity, inequities in land tenure are associated with gaps in income distribution, poverty and biodiversity loss. A common pattern of land tenure inequities through the history of civilization has been the formation of latifundia [Zhuāngyuán in chinese], i.e., a pattern where land ownership is concentrated by a small fraction of the whole population. Here, we use simple Markov chain models to study the dynamics of latifundia formation in a heterogeneous landscape where land can transition between forest, agriculture and recovering land. We systematically study the likelihood of latifundia formation under the assumption of pre-capitalist trade, where trade is based on the average utility of land parcels belonging to each individual landowner during a discrete time step. By restricting land trade to that under recovery, we found the likelihood of latifundia formation to increase with the size of the system, i.e., the amount of land and individuals in the society. We found that an increase of the transition rate for land use changes, i.e., how quickly land use changes, promotes more equitable patterns of land ownership. Disease introduction in the system, which reduced land profitability for infected individual landowners, promoted the formation of latifundia, with an increased likelihood for latifundia formation when there were heterogeneities in the susceptibility to infection. Finally, our model suggests that land ownership reforms need to guarantee an equitative distribution of land among individuals in a society to avoid the formation of latifundia.

  20. RELATIONSHIP BETWEEN FORMATION OF THE FEMORAL BICONDYLAR ANGLE AND TROCHLEAR SHAPE. INDEPENDENCE OF DIAPHYSEAL AND EPIPHYSEAL GROWTH

    OpenAIRE

    Tardieu, Christine; Glard, Yann; Garron, Emmanuelle; Boulay, Christophe; Jouve, Jean-Luc; Dutour, Olivier; Boëtsch, Gilles; Bollini, Gérard

    2005-01-01

    During hominin evolution, an increase in the femoral bicondylar angle was the initial change that led to selection for protuberance of the lateral trochlear lip and elliptical profile of the lateral condyle. No correlation is found during ontogeny between the degree of femoral obliquity and of the prominence of the lateral trochlear lip. Might there be then a relationship with the elliptical profile of the lateral condyle ? On intact femoral diaphyses of juvenile humans and great apes, we com...

  1. PCDF formation from PAH reactions

    Energy Technology Data Exchange (ETDEWEB)

    Fullana, A.; Nakka, H.; Sidhu, S. [Dayton Univ., OH (United States). Environmental Engineering

    2004-09-15

    It is clear that PAHs play an important role in PCDF formation. It does not matter if PCDF are formed from carbonaceous material or from PAH adsorbed on the carbon surface. The role of PAH in the formation of PCDF has been studied by several authors. Probably one of the most complete investigations was conducted by Wilhelm et al. They investigated PCDF formation from twelve different PAHs with structures similar to the PCDF. The results of this study showed that biphenyl-like structures can be easily converted to PCDFs. Although the biphenyl-like structures are clearly involved in PCDF formation, there are several aspects of this formation pathway that are not well understood. Iino et al. found that higher PCDF yields could be obtained from pyrene than phenanthrene, contradicting biphenyl intermediate formation pathway theory as phenantrene structure can more easily be converted to biphenyl than pyrene. All previous PCDD/F formation studies from PAHs were conducted using CuCl{sub 2} as model fly ash. CuCl{sub 2} is highly volatile and probably not present in any significant quantities in the actual fly ash. High temperature oxidative conditions in the high temperature zone are able to oxidize all transition metals to their oxides. Therefore, Cu in actual fly ash is most probably present as CuO or Cu2O. Also in previous studies, PAH - model fly ash mixtures were prepared at room temperature and then heated to experimental temperatures. This experimental method can lead to some uncertainties because depending on PAH boiling point, various amounts of different PAHS would have evaporated by the time experimental temperatures were achieved. The main objective of this study is to address all the above issues and develop a better understanding of the role of biphenyl structures in PCDF formation. The salient features of this study are: Use of CuO+HCl as model fly ash instead of CuCl{sub 2} which was traditionally used in earlier De Novo studies. Study major non

  2. Star formation in Galactic flows

    Science.gov (United States)

    Smilgys, Romas; Bonnell, Ian A.

    2016-06-01

    We investigate the triggering of star formation in clouds that form in Galactic scale flows as the interstellar medium passes through spiral shocks. We use the Lagrangian nature of smoothed particle hydrodynamics simulations to trace how the star-forming gas is gathered into self-gravitating cores that collapse to form stars. Large-scale flows that arise due to Galactic dynamics create shocks of the order of 30 km s-1 that compress the gas and form dense clouds (n > several × 102 cm-3) in which self-gravity becomes relevant. These large-scale flows are necessary for creating the dense physical conditions for gravitational collapse and star formation. Local gravitational collapse requires densities in excess of n > 103 cm-3 which occur on size scales of ≈1 pc for low-mass star-forming regions (M 103 M⊙). Star formation in the 250 pc region lasts throughout the 5 Myr time-scale of the simulation with a star formation rate of ≈10-1 M⊙ yr-1 kpc-2. In the absence of feedback, the efficiency of the star formation per free-fall time varies from our assumed 100 per cent at our sink accretion radius to values of <10-3 at low densities.

  3. Resolving the Formation of Protogalaxies

    CERN Document Server

    Wise, John H

    2007-01-01

    Cosmic structure originated from minute density perturbations in an almost homogeneous universe. The first stars are believed to be very massive and luminous, providing the first ionizing radiation and heavy elements to the universe and forming 100 million years after the Big Bang. The impact from primordial stellar radiation is far reaching and affects subsequent star and galaxy formation. In this thesis, we present results from adaptive mesh refinement calculations of the formation of the first galaxies. We gradually introduce important physical processes, such as molecular hydrogen cooling and stellar feedback, to base models that only consider atomic hydrogen and helium cooling. In these base models, we find that gas in dark matter halos with masses ~10^8 solar masses centrally collapse before multiple fragmentation occurs in a global disc. We then investigate the importance of molecular hydrogen cooling in early structure formation in the presence of a soft ultraviolet radiation background. We find that ...

  4. Black holes and galaxy formation

    CERN Document Server

    Propst, Raphael J

    2010-01-01

    Galaxies are the basic unit of cosmology. The study of galaxy formation is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning. The physics of galaxy formation is complicated because it deals with the dynamics of stars, thermodynamics of gas and energy production of stars. A black hole is a massive object whose gravitational field is so intense that it prevents any form of matter or radiation to escape. It is hypothesized that the most massive galaxies in the universe- "elliptical galaxies"- grow simultaneously with the supermassive black holes at their centers, giving us much stronger evidence that black holes control galaxy formation. This book reviews new evidence in the field.

  5. Formation of porous gas hydrates

    CERN Document Server

    Salamatin, Andrey N

    2015-01-01

    Gas hydrates grown at gas-ice interfaces are examined by electron microscopy and found to have a submicron porous texture. Permeability of the intervening hydrate layers provides the connection between the two counterparts (gas and water molecules) of the clathration reaction and makes further hydrate formation possible. The study is focused on phenomenological description of principal stages and rate-limiting processes that control the kinetics of the porous gas hydrate crystal growth from ice powders. Although the detailed physical mechanisms involved in the porous hydrate formation still are not fully understood, the initial stage of hydrate film spreading over the ice surface should be distinguished from the subsequent stage which is presumably limited by the clathration reaction at the ice-hydrate interface and develops after the ice grain coating is finished. The model reveals a time dependence of the reaction degree essentially different from that when the rate-limiting step of the hydrate formation at...

  6. Spatial competition and price formation

    Science.gov (United States)

    Nagel, Kai; Shubik, Martin; Paczuski, Maya; Bak, Per

    2000-12-01

    We look at price formation in a retail setting, that is, companies set prices, and consumers either accept prices or go someplace else. In contrast to most other models in this context, we use a two-dimensional spatial structure for information transmission, that is, consumers can only learn from nearest neighbors. Many aspects of this can be understood in terms of generalized evolutionary dynamics. In consequence, we first look at spatial competition and cluster formation without price. This leads to establishement size distributions, which we compare to reality. After some theoretical considerations, which at least heuristically explain our simulation results, we finally return to price formation, where we demonstrate that our simple model with nearly no organized planning or rationality on the part of any of the agents indeed leads to an economically plausible price.

  7. Bundle Formation in Biomimetic Hydrogels.

    Science.gov (United States)

    Jaspers, Maarten; Pape, A C H; Voets, Ilja K; Rowan, Alan E; Portale, Giuseppe; Kouwer, Paul H J

    2016-08-01

    Bundling of single polymer chains is a crucial process in the formation of biopolymer network gels that make up the extracellular matrix and the cytoskeleton. This bundled architecture leads to gels with distinctive properties, including a large-pore-size gel formation at very low concentrations and mechanical responsiveness through nonlinear mechanics, properties that are rarely observed in synthetic hydrogels. Using small-angle X-ray scattering (SAXS), we study the bundle formation and hydrogelation process of polyisocyanide gels, a synthetic material that uniquely mimics the structure and mechanics of biogels. We show how the structure of the material changes at the (thermally induced) gelation point and how factors such as concentration and polymer length determine the architecture, and with that, the mechanical properties. The correlation of the gel mechanics and the structural parameters obtained from SAXS experiments is essential in the design of future (synthetic) mimics of biopolymer networks.

  8. Dense Cloud Formation and Star Formation in a Barred Galaxy

    CERN Document Server

    Nimori, M; Sorai, K; Watanabe, Y; Hirota, A; Namekata, D

    2012-01-01

    We investigate the properties of massive, dense clouds formed in a barred galaxy and their possible relation to star formation, performing a two-dimensional hydrodynamical simulation with the gravitational potential obtained from the 2Mass data from the barred spiral galaxy, M83. Since the environment for cloud formation and evolution in the bar region is expected to be different from that in the spiral arm region, barred galaxies are a good target to study the environmental effects on cloud formation and the subsequent star formation. Our simulation uses for an initial 80 Myr an isothermal flow of non-self gravitating gas in the barred potential, then including radiative cooling, heating and self-gravitation of the gas for the next 40 Myr, during which dense clumps are formed. We identify many cold, dense gas clumps for which the mass is more than $10^4M_{\\odot}$ (a value corresponding to the molecular clouds) and study the physical properties of these clumps. The relation of the velocity dispersion of the i...

  9. Formation of the first stars

    International Nuclear Information System (INIS)

    Understanding the formation of the first stars is one of the frontier topics in modern astrophysics and cosmology. Their emergence signalled the end of the cosmic dark ages, a few hundred million years after the Big Bang, leading to a fundamental transformation of the early Universe through the production of ionizing photons and the initial enrichment with heavy chemical elements. We here review the state of our knowledge, separating the well understood elements of our emerging picture from those where more work is required. Primordial star formation is unique in that its initial conditions can be directly inferred from the Λ cold dark matter (ΛCDM) model of cosmological structure formation. Combined with gas cooling that is mediated via molecular hydrogen, one can robustly identify the regions of primordial star formation, the so-called minihalos, having total masses of ∼106 M⊙ and collapsing at redshifts z ≃ 20–30. Within this framework, a number of studies have defined a preliminary standard model, with the main result that the first stars were predominantly massive. This model has recently been modified to include a ubiquitous mode of fragmentation in the protostellar disks, such that the typical outcome of primordial star formation may be the formation of a binary or small multiple stellar system. We will also discuss extensions to this standard picture due to the presence of dynamically significant magnetic fields, of heating from self-annihalating WIMP dark matter, or cosmic rays. We conclude by discussing possible strategies to empirically test our theoretical models. Foremost among them are predictions for the upcoming James Webb space telescope (JWST), to be launched ∼2018, and for ‘stellar archaeology’, which probes the abundance pattern in the oldest, most-metal poor stars in our cosmic neighborhood, thereby constraining the nucleosynthesis inside the first supernovae. (review article)

  10. Conductive Anodic Filament (CAF) Formation

    Science.gov (United States)

    Caputo, Antonio

    Conductive anodic filament (CAF) is a failure mode in printed wiring boards (PWBs) which occurs under high humidity and high voltage gradient conditions. The filament, a copper salt, grows from anode to cathode along the epoxy-glass interface. Ready and Turbini (2000) identified this copper salt as the Cu 2(OH)3Cl, atacamite compound. This work has investigated the influence of polyethylene glycol (PEG) and polyethylene propylene glycol (PEPG) fluxing agents on the chemical nature of CAF. For coupons processed with PEPG flux, with and without chloride, a copper-chloride containing compound was formed in the polymer matrix. This compound was characterized using x-ray photoelectron spectroscopy (XPS) as CuCl and an electrochemical mechanism for the formation of the chloride-containing CAF has been proposed. For PEG flux, with and without chloride, it has been shown that CAF only formed, but no copper containing compound formed in the matrix. It appears for PEG fluxed coupons, a PEG-Cu-Cl complex forms, binds the available Cu and acts as a barrier to the formation of CuCl in the polymer matrix. Meeker and Lu Valle (1995) have previously proposed that CAF failure is best represented by two competing reactions -- the formation of a copper chloride corrosion compound (now identified as Cu2(OH)3Cl) and the formation of innocuous trapped chlorine compounds. Since no evidence of any trapped chloride compounds has been found, we propose that the formation of CAF is best represented by a single non-reversible reaction. For coupons processed with a high bromide-containing flux, bromide containing CAF was created and characterized using transmission electron microscopy (TEM) to be Cu2(OH)3Br. In addition, a copper-containing compound was formed in the polymer matrix and characterized using XPS as CuBr. An electrochemical mechanism for the formation of bromide-containing CAF has been proposed based on the XPS data.

  11. Prediction of tar ball formation

    Energy Technology Data Exchange (ETDEWEB)

    Khelifa, A.; Gamble, L. [Environment Canada, Ottawa, ON (Canada). Emergencies Science and Technology Division, Environmental Technology Centre, Science and Technology Branch

    2006-07-01

    The presence of small tar balls ranging in size from less than a millimetre to 60 centimetres have been observed during cleanup assessment operations following accidental oil spills on water. The tar balls are composed of heavy oil residues and suspended particulate matter (SPM) from the water column. They can be found on shorelines, settled on the seafloor and floating at or near the water surface. Their abundance on the shorelines varies from site to site and depends on the conditions of the spill and mixing conditions. Aggregation between SPM and micro-sized oil droplets occurs naturally in coastal waters and enhances the dispersion of spilled oil. Although tar balls are among the important end states of spilled oil in the marine environment, no model exists to estimate the percentage of the spilled oil that becomes tar balls. This paper offered some insight into the modeling of tar ball formation. Current modeling understanding of oil-SPM aggregate formation was used to predict tar ball formation. The formation of oil droplets was examined with respect to a range of conditions under which the formation of large droplets is expected. The role of aggregation was then presented to demonstrate the effects of concentration and type of SPM on the buoyancy of tar balls. Good agreement was found between modeling results and field data reported in the literature regarding the size and density of tar balls. Oil viscosity and mixing energy were found to be the main factors controlling the formation of tar balls. The aggregation of tar balls with SPM and shoreline material results in significant increases or decreases in density, depending on the type and concentration of SPM. 42 refs., 2 tabs., 6 figs.

  12. Formation of the First Stars

    OpenAIRE

    Bromm, Volker

    2005-01-01

    How and when did the first generation of stars form at the end of the cosmic dark ages? Quite generically, within variants of the cold dark matter model of cosmological structure formation, the first sources of light are expected to form in ~ 10^{6} M_sun dark matter potential wells at redshifts z > 20. I discuss the physical processes that govern the formation of the first stars. These so-called Population~III stars are predicted to be predominantly very massive, and to have contributed sign...

  13. Pattern formations and oscillatory phenomena

    CERN Document Server

    Kinoshita, Shuichi

    2013-01-01

    Patterns and their formations appear throughout nature, and are studied to analyze different problems in science and make predictions across a wide range of disciplines including biology, physics, mathematics, chemistry, material science, and nanoscience. With the emergence of nanoscience and the ability for researchers and scientists to study living systems at the biological level, pattern formation research has become even more essential. This book is an accessible first of its kind guide for scientists, researchers, engineers, and students who require a general introduction to thi

  14. High-Mass Star Formation

    CERN Document Server

    Schilke, Peter

    2016-01-01

    A review on current theories and observations of high-mass star formation is given. Particularly the influence of magnetic fields and feedback mechanisms, and of varying initial conditions on theories are discussed. The, in my biased view, most important observations to put strong constraints on models of high-mass star formation are pres ented, in particular bearing on the existence and properties of high-mass starless cores, the role of filaments in the mass transport to high-mass cores, and the propertie s of disks around high-mass stars.

  15. Magnetohydrodynamic mechanism for pedestal formation.

    Science.gov (United States)

    Guazzotto, L; Betti, R

    2011-09-16

    Time-dependent two-dimensional magnetohydrodynamic simulations are carried out for tokamak plasmas with edge poloidal flow. Differently from conventional equilibrium theory, a density pedestal all around the edge is obtained when the poloidal velocity exceeds the poloidal sound speed. The outboard pedestal is induced by the transonic discontinuity, the inboard one by mass redistribution. The density pedestal follows the formation of a highly sheared flow at the transonic surface. These results may be relevant to the L-H transition and pedestal formation in high performance tokamak plasmas.

  16. Star formation and gas supply

    Science.gov (United States)

    Catinella, B.

    2016-06-01

    A detailed knowledge of how gas cycles in and around galaxies, and how it depends on galaxy properties such as stellar mass and star formation rate, is crucial to understand galaxy formation and evolution. We take advantage of the most sensitive surveys of cold gas in massive galaxies, GASS and COLD GASS, as well as of the state-of-the-art HI blind survey ALFALFA to investigate how molecular and atomic hydrogen reservoirs vary along and across the main sequence of star-forming galaxies.

  17. Strategy Formation in Eastern Jutland

    DEFF Research Database (Denmark)

    Olesen, Kristian

    2008-01-01

      In Eastern Jutland a strategy formation process has been initiated with the aim of developing a strategic spatial plan for the city region.  An organisation has been set up to deal with the first phase of the process, which is to carry out three functional analyses and prepare a common vision...... on which level a serious strategy formation process can take place.  There is a danger that a common strategic spatial plan is more an expression of the lowest common denominator and the municipalities request for infrastructure investments rather than being a spatial strategy with transformative power. ...

  18. Exciton Formation in Disordered Semiconductors

    DEFF Research Database (Denmark)

    Klochikhin, A.; Reznitsky, A.; Permogorov, S.;

    1999-01-01

    Stationary luminescence spectra of disordered solid solutions can be accounted by the model of localized excitons. Detailed analysis of the long time decay kinetics of luminescence shows that exciton formation in these systems is in great extent due to the bimolecular reaction of separated carrie...

  19. Constraints on galaxy formation theories

    Science.gov (United States)

    Szalay, A. S.

    1986-01-01

    The present theories of galaxy formation are reviewed. The relation between peculiar velocities, temperature fluctuations of the microwave background and the correlation function of galaxies point to the possibility that galaxies do not form uniformly everywhere. The velocity data provide strong constraints on the theories even in the case when light does not follow mass of the universe.

  20. The EPRDATA Format: A Dialogue

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Henry Grady III [Los Alamos National Laboratory

    2015-08-18

    Recently the Los Alamos Nuclear Data Team has communicated certain issues of concern in relation to the new electron/photon/relaxation ACE data format as released in the eprdata12 library. In this document those issues are parsed, analyzed, and answered.

  1. Earth and Terrestrial Planet Formation

    CERN Document Server

    Jacobson, Seth A

    2015-01-01

    The growth and composition of Earth is a direct consequence of planet formation throughout the Solar System. We discuss the known history of the Solar System, the proposed stages of growth and how the early stages of planet formation may be dominated by pebble growth processes. Pebbles are small bodies whose strong interactions with the nebula gas lead to remarkable new accretion mechanisms for the formation of planetesimals and the growth of planetary embryos. Many of the popular models for the later stages of planet formation are presented. The classical models with the giant planets on fixed orbits are not consistent with the known history of the Solar System, fail to create a high Earth/Mars mass ratio, and, in many cases, are also internally inconsistent. The successful Grand Tack model creates a small Mars, a wet Earth, a realistic asteroid belt and the mass-orbit structure of the terrestrial planets. In the Grand Tack scenario, growth curves for Earth most closely match a Weibull model. The feeding zon...

  2. Genetic analysis of symbiosome formation

    NARCIS (Netherlands)

    Ovchinnikova, E.

    2012-01-01

    Endosymbiotic interactions form a fundament of life as we know it and are characterized by the formation of new specialized membrane compartments, in which the microbes are hosted inside living plant cells. A striking example is the symbiosis between legumes and nitrogen-fixing Rhizobium bacteria (r

  3. Stereotype Formation : Biased by Association

    NARCIS (Netherlands)

    Le Pelley, Mike E.; Reimers, Stian J.; Calvini, Guglielmo; Spears, Russell; Beesley, Tom; Murphy, Robin A.

    2010-01-01

    We propose that biases in attitude and stereotype formation might arise as a result of learned differences ill the extent its which social groups have previously been predictive elf behavioral or physical properties Experiments 1 and 2 demonstrate that differences in the experienced predictiveness o

  4. Star formation in Galactic flows

    CERN Document Server

    Smilgys, R

    2016-01-01

    We investigate the triggering of star formation in clouds that form in Galactic scale flows as the ISM passes through spiral shocks. We use the Lagrangian nature of SPH simulations to trace how the star forming gas is gathered into self-gravitating cores that collapse to form stars. Large scale flows that arise due to Galactic dynamics create shocks of order 30 km/s that compress the gas and form dense clouds $(n> $several $\\times 10^2$ cm$^{-3}$) in which self-gravity becomes relevant. These large-scale flows are necessary for creating the dense physical conditions for gravitational collapse and star formation. Local gravitational collapse requires densities in excess of $n>10^3$ cm$^{-3}$ which occur on size scales of $\\approx 1$ pc for low-mass star forming regions ($M10^3 M_{\\odot}$). Star formation in the 250 pc region lasts throughout the 5 Myr timescale of the simulation with a star formation rate of $\\approx 10^{-1} M_{\\odot}$ yr$^{-1}$ kpc$^{-2}$. In the absence of feedback, the efficiency of the sta...

  5. Formative Assessment in Dance Education

    Science.gov (United States)

    Andrade, Heidi; Lui, Angela; Palma, Maria; Hefferen, Joanna

    2015-01-01

    Feedback is crucial to students' growth as dancers. When used within the framework of formative assessment, or assessment for learning, feedback results in actionable next steps that dancers can use to improve their performances. This article showcases the work of two dance specialists, one elementary and one middle school teacher, who have…

  6. Formation of Rationally Heterogeneous Expectations

    NARCIS (Netherlands)

    Pfajfar, D.

    2012-01-01

    Abstract: This paper models expectation formation by taking into account that agents produce heterogeneous expectations due to model uncertainty, informational frictions and different capacities for processing information. We show that there are two general classes of steady states within this frame

  7. The Road to Galaxy Formation

    CERN Document Server

    Keel, William C

    2007-01-01

    The formation of galaxies is one of the greatest puzzles in astronomy, the solution is shrouded in the depths of space and time, but has profound implications for the universe we observe today. The book discusses the beginnings of the process from cosmological observations and calculations, considers the broad features of galaxies that we need to explain and what we know of their later history. The author compares the competing theories for galaxy formation and considers the progress expected from new generations of powerful telescopes both on earth and in space. In this second edition the author has retained the observationally-based approach of the first edition, a feature which was particularly well-reviewed: Writing in Nature, Carlton Baugh noted in February 2003 that “It is refreshing, in a market dominated by theorists, to come across a book on galaxy formation written from an observational perspective. The Road to Galaxy Formation should prove to be a handy primer on observations for graduate student...

  8. Control over Administrative Contract Formation

    Directory of Open Access Journals (Sweden)

    Frane Staničić

    2016-02-01

    Full Text Available Administrative contracts in Croatian legislation represent a novelty introduced into the General Administration Procedure Act in 2010. This is a novelty which has not proved to be successful in practice. Control over administrative contract formation is inevitable and is very significant for a number of reasons. Firstly, public legal bodies which form them do so by exercising their own public powers which are without doubt subject to legality control; secondly, in forming administrative contracts, public funds are used which must be controlled; thirdly, forming administrative contracts often touches on using public goods. Due to the restrictive interpretation of administrative contracts in Croatian legislation, this institute is indisputably only regulated in the General Taxation Act. However, for more than two decades contracts which satisfy all presumptions have existed in our law in order to be considered as administrative contracts. It is for this reason that control over contracts will be dealt with for contracts considered by the author to be administrative contracts. These are contracts on concessions and contracts on public procurement. How inadequate today’s regulation of control of administrative contract formation is will be demonstrated, particularly regarding contracts on concession and public procurement. Legislative changes will be proposed which should result in a more quality system of control over administrative contract formation. How control over administrative contract formation cannot be considered as separate from control over administrative contract execution will also be shown.

  9. Wintertime Haze Formation in Beijing

    Science.gov (United States)

    Levy Zamora, M. E.

    2015-12-01

    Recent severe haze events in China have attracted significant public attention due to the severely reduced visibility and unprecedentedly high pollutant concentrations. Particular attention has been given to the high concentrations of particulate matter with a diameter less than 2.5 microns (PM2.5), which can exceed several hundred micrograms per cubic meter over several days. During January and February of 2015, a suite of aerosol instruments was deployed in Beijing to directly measure a comprehensive set of aerosol properties, including the particle size distribution, effective density, and chemical composition. In this presentation, we will discuss the particulate matter formation mechanisms, the evolution of aerosol properties throughout the event, and how the winter formation mechanisms compare with the warmer seasons. We show that the periodic cycles of severe haze episodes in Beijing are largely driven by meteorological conditions. During haze events, stagnation typically develops as a result of a low planetary boundary layer and weak southerly wind from polluted industrial source regions. Stronger northerly winds were frequently observed during the clean period, which carry unpolluted air masses from the less populated northern mountainous areas. Nucleation consistently occurs on clean days, producing a high number concentration of nano particles. The particle mass concentration exceeding several hundred micrograms per cubic meter is attributed to the continuous size growth from the nucleation-mode particles (diameter less than 10 nm) over multiple days to produce a high concentration of larger particles (diameter greater than 100 nm). The particle chemical composition in Beijing is similar to those commonly measured in other urban centers, which is indicative of chemical constituents dominated by secondary aerosol formation. Our results reveal that the severe haze formation in Beijing during the wintertime is similar to the mechanism of haze formation

  10. Sedimentary pyrite formation: An update

    Science.gov (United States)

    Berner, Robert A.

    1984-04-01

    Sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time. The amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter, dissolved sulfate, and reactive detrital iron minerals. Organic matter appears to be the major control on pyrite formation in normal (non-euxinic) terrigenous marine sediments where dissolved sulfate and iron minerals are abundant. By contrast, pyrite formation in non-marine, freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic-rich fresh water shales from marine shales. Under marine euxinic conditions sufficient H 2S is produced that the dominant control on pyrite formation is the availability of reactive iron minerals. Calculations, based on a sulfur isotope model, indicate that over Phanerozoic time the worldwide average organic carbon-to-pyrite sulfur ratio of sedimentary rocks has varied considerably. High C/S ratios during Permo-Carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time. Low C/S ratios, compared to today, during the early Paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean. The latter could have been due to lower oceanic oxygen levels and/or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time.

  11. Consensus formation on coevolving networks: groups' formation and structure

    International Nuclear Information System (INIS)

    We study the effect of adaptivity on a social model of opinion dynamics and consensus formation. We analyse how the adaptivity of the network of contacts between agents to the underlying social dynamics affects the size and topological properties of groups and the convergence time to the stable final state. We find that, while on static networks these properties are determined by percolation phenomena, on adaptive networks the rewiring process leads to different behaviors: adaptive rewiring fosters group formation by enhancing communication between agents of similar opinion, though it also makes possible the division of clusters. We show how the convergence time is determined by the characteristic time of link rearrangement. We finally investigate how the adaptivity yields nontrivial correlations between the internal topology and the size of the groups of agreeing agents

  12. Stratigraphy and dissolution of the Rustler Formation

    International Nuclear Information System (INIS)

    This report describes the physical stratigraphy of the Rustler Formation, because the Waste Isolation Pilot Plant will be constructed in salt beds that underlie this formation. Described are subdivisions of the formations, the major karst features, and a proposed method for the formation of Nash Draw. 2 refs., 2 figs

  13. Transparent Format Migration of Preserved Web Content

    OpenAIRE

    Rosenthal, David S. H.; Lipkis, Thomas; Robertson, Thomas; Morabito, Seth

    2005-01-01

    The LOCKSS digital preservation system collects content by crawling the web and preserves it in the format supplied by the publisher. Eventually, browsers will no longer understand that format. A process called format migration converts it to a newer format that the browsers do understand. The LOCKSS program has designed and tested an initial implementation of format migration for Web content that is transparent to readers, building on the content negotiation capabilities of HTTP.

  14. Treating tar sands formations with dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J.; Karanikas, John Michael

    2010-06-08

    Methods for treating a tar sands formation are described herein. The tar sands formation may include dolomite and hydrocarbons. Methods may include providing heat at less than the decomposition temperature of dolomite from one or more heaters to at least a portion of the formation. At least some of the hydrocarbon fluids are mobilized in the formation. At least some of the hydrocarbon fluids may be produced from the formation.

  15. Controlled Irradiative Formation of Penitentes

    CERN Document Server

    Bergeron, V; Betterton, M D

    2006-01-01

    Spike-shaped structures are produced by light-driven ablation in very different contexts. Penitentes 1-4 m high are common on Andean glaciers, where their formation changes glacier dynamics and hydrology. Laser ablation can produce cones 10-100 microns high with a variety of proposed applications in materials science. We report the first laboratory generation of centimeter-scale snow and ice penitentes. Systematically varying conditions allows identification of the essential parameters controlling the formation of ablation structures. We demonstrate that penitente initiation and coarsening requires cold temperatures, so that ablation leads to sublimation rather than melting. Once penitentes have formed, further growth of height can occur by melting. The penitentes intially appear as small structures (3 mm high) and grow by coarsening to 1-5 cm high. Our results are an important step towards understanding and controlling ablation morphologies.

  16. Photophoresis boosts giant planet formation

    CERN Document Server

    Teiser, Jens

    2013-01-01

    In the core accretion model of giant planet formation, a solid protoplanetary core begins to accrete gas directly from the nebula when its mass reaches about 5 earth masses. The protoplanet has at most a few million years to reach runaway gas accretion, as young stars lose their gas disks after 10 million years at the latest. Yet gas accretion also brings small dust grains entrained in the gas into the planetary atmosphere. Dust accretion creates an optically thick protoplanetary atmosphere that cannot efficiently radiate away the kinetic energy deposited by incoming planetesimals. A dust-rich atmosphere severely slows down atmospheric cooling, contraction, and inflow of new gas, in contradiction to the observed timescales of planet formation. Here we show that photophoresis is a strong mechanism for pushing dust out of the planetary atmosphere due to the momentum exchange between gas and dust grains. The thermal radiation from the heated inner atmosphere and core is sufficient to levitate dust grains and to ...

  17. Singularities formation, structure, and propagation

    CERN Document Server

    Eggers, J

    2015-01-01

    Many key phenomena in physics and engineering are described as singularities in the solutions to the differential equations describing them. Examples covered thoroughly in this book include the formation of drops and bubbles, the propagation of a crack and the formation of a shock in a gas. Aimed at a broad audience, this book provides the mathematical tools for understanding singularities and explains the many common features in their mathematical structure. Part I introduces the main concepts and techniques, using the most elementary mathematics possible so that it can be followed by readers with only a general background in differential equations. Parts II and III require more specialised methods of partial differential equations, complex analysis and asymptotic techniques. The book may be used for advanced fluid mechanics courses and as a complement to a general course on applied partial differential equations.

  18. New Paradigms For Asteroid Formation

    CERN Document Server

    Johansen, Anders; Cuzzi, Jeffrey N; Morbidelli, Alessandro; Gounelle, Matthieu

    2015-01-01

    Asteroids and meteorites provide key evidence on the formation of planetesimals in the Solar System. Asteroids are traditionally thought to form in a bottom-up process by coagulation within a population of initially km-scale planetesimals. However, new models challenge this idea by demonstrating that asteroids of sizes from 100 to 1000 km can form directly from the gravitational collapse of small particles which have organised themselves in dense filaments and clusters in the turbulent gas. Particles concentrate passively between eddies down to the smallest scales of the turbulent gas flow and inside large-scale pressure bumps and vortices. The streaming instability causes particles to take an active role in the concentration, by piling up in dense filaments whose friction on the gas reduces the radial drift compared to that of isolated particles. In this chapter we review new paradigms for asteroid formation and compare critically against the observed properties of asteroids as well as constraints from meteo...

  19. Complexity of Formation in Holography

    CERN Document Server

    Chapman, Shira; Myers, Robert C

    2016-01-01

    It was recently conjectured that the quantum complexity of a holographic boundary state can be computed by evaluating the gravitational action on a bulk region known as the Wheeler-DeWitt patch. We apply this complexity=action duality to evaluate the `complexity of formation' (arXiv:1509.07876, arXiv:1512.04993), i.e., the additional complexity arising in preparing the entangled thermofield double state with two copies of the boundary CFT compared to preparing the individual vacuum states of the two copies. We find that for boundary dimensions $d>2$, the difference in the complexities grows linearly with the thermal entropy at high temperatures. For the special case $d=2$, the complexity of formation is a fixed constant, independent of the temperature. We compare these results to those found using the complexity=volume duality.

  20. Magnetic Diffusion in Star Formation

    CERN Document Server

    Basu, Shantanu

    2010-01-01

    Magnetic diffusion plays a vital role in star formation. We trace its influence from interstellar cloud scales down to star-disk scales. On both scales, we find that magnetic diffusion can be significantly enhanced by the buildup of strong gradients in magnetic field structure. Large scale nonlinear flows can create compressed cloud layers within which ambipolar diffusion occurs rapidly. However, in the flux-freezing limit that may be applicable to photoionized molecular cloud envelopes, supersonic motions can persist for long times if driven by an externally generated magnetic field that corresponds to a subcritical mass-to-flux ratio. In the case of protostellar accretion, rapid magnetic diffusion (through Ohmic dissipation with additional support from ambipolar diffusion) near the protostar causes dramatic magnetic flux loss. By doing so, it also allows the formation of a centrifugal disk, thereby avoiding the magnetic braking catastrophe.

  1. Star Cluster Formation and Feedback

    CERN Document Server

    Krumholz, Mark R; Arce, Hector G; Dale, James E; Gutermuth, Robert; Klein, Richard I; Li, Zhi-Yun; Nakamura, Fumitaka; Zhang, Qizhou

    2014-01-01

    Stars do not generally form in isolation. Instead, they form in clusters, and in these clustered environments newborn stars can have profound effects on one another and on their parent gas clouds. Feedback from clustered stars is almost certainly responsible for a number of otherwise puzzling facts about star formation: that it is an inefficient process that proceeds slowly when averaged over galactic scales; that most stars disperse from their birth sites and dissolve into the galactic field over timescales $\\ll 1$ Gyr; and that newborn stars follow an initial mass function (IMF) with a distinct peak in the range $0.1 - 1$ $M_\\odot$, rather than an IMF dominated by brown dwarfs. In this review we summarize current observational constraints and theoretical models for the complex interplay between clustered star formation and feedback.

  2. Othering, identity formation and agency

    Directory of Open Access Journals (Sweden)

    Sune Qvotrup Jensen

    2011-10-01

    Full Text Available The article examines the potentials of the concept of othering to describe identity formation among ethnic minorities. First, it outlines the history of the concept, its contemporary use, as well as some criticisms. Then it is argued that young ethnic minority men in Denmark are subject to intersectional othering, which contains elements of exoticist fascination of the other. On the basis of ethnographic material, it is analysed how young marginalized ethnic minority men react to othering. Two types of reactions are illustrated: 1 capitalization on being positioned as the other, and 2 refusing to occupy the position of the other by disidentification and claims to normality. Finally, it is argued that the concept of othering is well suited for understanding the power structures as well as the historic symbolic meanings conditioning such identity formation, but problematic in terms of agency.

  3. Restucturing the Project Work Format

    DEFF Research Database (Denmark)

    Dupont, Søren

    2015-01-01

    The chapter is based on an evaluation of a pedagogical experiment at Roskilde University, the Antology Experiment. The objective of the experiment was to develop and expand the framework for project work through the production of anthologies compiled collectively by a number of project groups....... The novel aspects of the Anthology Experiment were most notably its magnitude and complexity. In this experiment the groups were totalling some 50 students who were working together. The experiment used a well-known publishing format from research, namely the anthology form, which usually focuses....... The organization was complex, the written product changed from project to article format, the students had to concentrate on working in their own project group as well as in the so-called clusters, and the form of exam was radically changed...

  4. Formation of Supermassive Black Holes

    CERN Document Server

    Volonteri, Marta

    2010-01-01

    Evidence shows that massive black holes reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that central MBHs, while much less massive than the host (~ 0.1%), are linked to the evolution of galactic structure. In hierarchical cosmologies, a single big galaxy today can be traced back to the stage when it was split up in hundreds of smaller components. Did MBH seeds form with the same efficiency in small proto-galaxies, or did their formation had to await the buildup of substantial galaxies with deeper potential wells? I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I will discuss black hole formation processes for `seed' black holes that are likely to place at early cosmic epochs, and possible observational tests of these scenarios.

  5. Cophasing the Planet Formation Imager

    CERN Document Server

    Petrov, Romain G; Elhalkouj, Thami; Monnier, John; Ireland, Michael; Kraus, Stefan

    2016-01-01

    The Planet Formation Imager (PFI) is a project for a very large optical interferometer intended to obtain images of the planet formation process at scales as small as the Hill sphere of giant exoplanets. Its main science instruments will work in the thermal infrared but it will be cophased in the near infrared, where it requires also some capacity for scientific imaging. PFI imaging and resolution specifications imply an array of 12 to 20 apertures and baselines up to a few kilometers cophased at near infrared coherent magnitudes as large as 10. This paper discusses various cophasing architectures and the corresponding minimum diameter of individual apertures, which is the dominant element of PFI cost estimates. From a global analysis of the possible combinations of pairwise fringe sensors, we show that conventional approaches used in current interferometers imply the use of prohibitively large telescopes and we indicate the innovative strategies that would allow building PFI with affordable apertures smaller...

  6. Shock Formation in Lovelock Theories

    CERN Document Server

    Reall, Harvey S; Way, Benson

    2014-01-01

    We argue that Lovelock theories of gravity suffer from shock formation, unlike General Relativity. We consider the propagation of (i) a discontinuity in curvature, and (ii) weak, high frequency, gravitational waves. Such disturbances propagate along characteristic hypersurfaces of a "background" spacetime and their amplitude is governed by a transport equation. In GR the transport equation is linear. In Lovelock theories, it is nonlinear and its solutions can blow up, corresponding to the formation of a shock. We show that this effect is absent in some simple cases e.g. a flat background spacetime, and demonstrate its presence for a plane wave background. We comment on weak cosmic censorship, the evolution of shocks, and the nonlinear stability of Minkowski spacetime, in Lovelock theories.

  7. Biofilm formation on abiotic surfaces

    DEFF Research Database (Denmark)

    Tang, Lone

    2011-01-01

    Bacteria can attach to any surface in contact with water and proliferate into complex communities enclosed in an adhesive matrix, these communities are called biofilms. The matrix makes the biofilm difficult to remove by physical means, and bacteria in biofilm can survive treatment with many...... antibiotics, disinfectants and cleaning agents. Biofilms are therefore very difficult to eradicate, and an attractive approach to limit biofilm formation is to reduce bacterial adhesion. In this thesis it was shown that lowering the surface roughness had a greater effect on bacterial retention compared....... The ability to form biofilms, the amount of eDNA produced, and the importance of eDNA for biofilm formation or stability did not correlate and varied from strain to strain. Finally, a method was developed for immobilization of living bacteria for analysis by atomic force microscopy (AFM). AFM is used...

  8. Formation of quasiparallel Alfven solitons

    Science.gov (United States)

    Hamilton, R. L.; Kennel, C. F.; Mjolhus, E.

    1992-01-01

    The formation of quasi-parallel Alfven solitons is investigated through the inverse scattering transformation (IST) for the derivative nonlinear Schroedinger (DNLS) equation. The DNLS has a rich complement of soliton solutions consisting of a two-parameter soliton family and a one-parameter bright/dark soliton family. In this paper, the physical roles and origins of these soliton families are inferred through an analytic study of the scattering data generated by the IST for a set of initial profiles. The DNLS equation has as limiting forms the nonlinear Schroedinger (NLS), Korteweg-de-Vries (KdV) and modified Korteweg-de-Vries (MKdV) equations. Each of these limits is briefly reviewed in the physical context of quasi-parallel Alfven waves. The existence of these limiting forms serves as a natural framework for discussing the formation of Alfven solitons.

  9. Coevolutionary modeling in network formation

    KAUST Repository

    Al-Shyoukh, Ibrahim

    2014-12-03

    Network coevolution, the process of network topology evolution in feedback with dynamical processes over the network nodes, is a common feature of many engineered and natural networks. In such settings, the change in network topology occurs at a comparable time scale to nodal dynamics. Coevolutionary modeling offers the possibility to better understand how and why network structures emerge. For example, social networks can exhibit a variety of structures, ranging from almost uniform to scale-free degree distributions. While current models of network formation can reproduce these structures, coevolutionary modeling can offer a better understanding of the underlying dynamics. This paper presents an overview of recent work on coevolutionary models of network formation, with an emphasis on the following three settings: (i) dynamic flow of benefits and costs, (ii) transient link establishment costs, and (iii) latent preferential attachment.

  10. Star Formation in Satellite Galaxies

    CERN Document Server

    Funes, S J; Prada, F; Azzaro, M; Ribeiro, M B; SJ, Jose G. Funes; Gutierrez, Carlos M.; Prada, Francisco; Azzaro, Marco; Ribeiro, Marcelo B.

    2003-01-01

    The study of satellite galaxies can provide information on the merging and aggregation processes which, according to the hierarchical clustering models, form the larger spiral galaxies we observe. With the aim of testing hierarchical models of galaxy formation, we have conducted an observational program which comprises H$\\alpha$ imaging for both the parent and the satellite galaxies, taken from the compilation by Zaritsky et al. (1997) that contains 115 galaxies orbiting 69 primary isolated spiral galaxies. We have observed a subsample of 37 spiral and irregular galaxies taken from the compilation mentioned above. The aim of this study is to determine star formation properties of the sample galaxies. In this work we present the preliminary results of this program that we have carried out with the 1.8-m Vatican Telescope (VATT).

  11. THE BLACK HOLE FORMATION PROBABILITY

    International Nuclear Information System (INIS)

    A longstanding question in stellar evolution is which massive stars produce black holes (BHs) rather than neutron stars (NSs) upon death. It has been common practice to assume that a given zero-age main sequence (ZAMS) mass star (and perhaps a given metallicity) simply produces either an NS or a BH, but this fails to account for a myriad of other variables that may effect this outcome, such as spin, binarity, or even stochastic differences in the stellar structure near core collapse. We argue that instead a probabilistic description of NS versus BH formation may be better suited to account for the current uncertainties in understanding how massive stars die. We present an initial exploration of the probability that a star will make a BH as a function of its ZAMS mass, P BH(M ZAMS). Although we find that it is difficult to derive a unique P BH(M ZAMS) using current measurements of both the BH mass distribution and the degree of chemical enrichment by massive stars, we demonstrate how P BH(M ZAMS) changes with these various observational and theoretical uncertainties. We anticipate that future studies of Galactic BHs and theoretical studies of core collapse will refine P BH(M ZAMS) and argue that this framework is an important new step toward better understanding BH formation. A probabilistic description of BH formation will be useful as input for future population synthesis studies that are interested in the formation of X-ray binaries, the nature and event rate of gravitational wave sources, and answering questions about chemical enrichment

  12. Biofilm formation by Clostridium difficile

    OpenAIRE

    Dapa, Tanja; Unnikrishnan, Meera

    2013-01-01

    Clostridium difficile infection (CDI) is a major healthcare-associated disease worldwide. Recurring infections and increasing antibiotic resistance have complicated treatment of CDI. While C. difficile spores are important for transmission and persistence of CDI, other factors such as gut colonization and formation of bacterial communities in the gut may also contribute to pathogenesis and persistence, but have not been well investigated. Recently, we reported that important clinical C. diffi...

  13. Formation of artificial ionospheric ducts

    OpenAIRE

    Milikh, G. M.; Papadopoulos, K.; Shroff, H; Chang, C. L.; Wallace, T; E. V. Mishin; Parrot, Michel; Berthelier, Jean-Jacques

    2008-01-01

    International audience It is well known that strong electron heating by a powerful HF-facility can lead to the formation of electron and ion density perturbations that stretch along the magnetic field line. Those density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents the first experimental evidence of plasma modifications associated with ion outflows due to HF heating. The experiments were conducted using the HAARP heater during t...

  14. Cycling Behavior and Memory Formation

    OpenAIRE

    Gerstner, Jason R.; Lyons, Lisa C.; Wright, Kenneth P.; Loh, Dawn H; Rawashdeh, Oliver; Eckel-Mahan, Kristin L.; Roman, Gregg W.

    2009-01-01

    Circadian research has spent considerable effort in the determining clock output pathways, including identifying both physiological and behavioral processes that demonstrate significant time-of-day variation. Memory formation and consolidation represent notable processes shaped by endogenous circadian oscillators. To date, very few studies on memory mechanisms have considered potential confounding effects of time-of-day and the organism’s innate activity cycles (e.g., nocturnal, diurnal, or c...

  15. Cataract formation following vitreoretinal procedures

    OpenAIRE

    Feng H; Adelman RA

    2014-01-01

    Hao Feng, Ron A Adelman Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, CT, USA Purpose: To evaluate the incidence and prevalence of cataract formation, progression, and extraction in patients that underwent vitreoretinal procedures and to evaluate factors that can potentially predispose patients to postoperative cataracts.Materials and methods: The medical records of consecutive patients who underwent vitreoretinal surgery at the Yale Eye Cent...

  16. Formation of binary radio pulsars

    International Nuclear Information System (INIS)

    In the framework of the standard scenario of the evolution of massive binary stars a study is made of the formation of final binary systems in which at least one of the components is a neutron star. It is found that about every fortieth radio pulsar must be a member of a close binary system. This is confirmed by observations. Radio pulsars are not formed in wide binary systems, possibly because of the very slow rotation of the presupernova stars

  17. Neutron Stars: Formation and Structure

    OpenAIRE

    Kutschera, Marek

    1998-01-01

    A short introduction is given to astrophysics of neutron stars and to physics of dense matter in neutron stars. Observed properties of astrophysical objects containing neutron stars are discussed. Current scenarios regarding formation and evolution of neutron stars in those objects are presented. Physical principles governing the internal structure of neutron stars are considered with special emphasis on the possible spin ordering in the neutron star matter.

  18. UNION FORMATION IN FRAGILE FAMILIES*

    OpenAIRE

    Carlson, Marcia; McLanahan, Sara; England, Paula

    2004-01-01

    In this paper, we use data from a new longitudinal survey—the Fragile Families and Child Wellbeing Study—to examine union formation among unmarried parents who have just had a child together. We use multinomial logistic regression to estimate the effects of economic, cultural/interpersonal, and other factors on whether (relative to having no romantic relationship) parents are romantically involved living apart, cohabiting, or married to each other about one year after the child’s birth. Net o...

  19. Memory Formation Shaped by Astroglia

    OpenAIRE

    Zorec, Robert; Horvat, Anemari; Vardjan, Nina; VERKHRATSKY, ALEXEI

    2015-01-01

    Astrocytes, the most heterogeneous glial cells in the central nervous system (CNS), execute a multitude of homeostatic functions and contribute to memory formation. Consolidation of synaptic and systemic memory is a prolonged process and hours are required to form long-term memory. In the past, neurons or their parts have been considered to be the exclusive cellular sites of these processes, however, it has now become evident that astrocytes provide an important and essential contribution to ...

  20. Hydrodynamics of catheter biofilm formation

    CERN Document Server

    Sotolongo-Costa, Oscar; Rodriguez-Perez, Daniel; Martinez-Escobar, Sergio; Fernandez-Barbero, Antonio

    2009-01-01

    A hydrodynamic model is proposed to describe one of the most critical problems in intensive medical care units: the formation of biofilms inside central venous catheters. The incorporation of approximate solutions for the flow-limited diffusion equation leads to the conclusion that biofilms grow on the internal catheter wall due to the counter-stream diffusion of blood through a very thin layer close to the wall. This biological deposition is the first necessary step for the subsequent bacteria colonization.

  1. Non cooperative Stackelberg network formation

    Directory of Open Access Journals (Sweden)

    Juan M.C Larrosa

    2014-12-01

    Full Text Available Non-cooperative network formation games in industrial organizations analyze how firms create links. We assume that links portray cost-reducing information and that access to this information is not reciprocal. We study the consequences in terms of profits if one firm can move first in establishing a link. A classic model of exogenous Stackelberg leadership is developed and first-mover advantage is observed.

  2. Formation of Cosmic Dust Bunnies

    OpenAIRE

    Matthews, Lorin S.; Hayes, Ryan L.; Freed, Michael S.; Hyde, Truell W.

    2007-01-01

    Planetary formation is an efficient process now thought to take place on a relatively short astronomical time scale. Recent observations have shown that the dust surrounding a protostar emits more efficiently at longer wavelengths as the protoplanetary disk evolves, suggesting that the dust particles are coagulating into fluffy aggregates, "much as dust bunnies form under a bed." One poorly understood problem in this coagulation process is the manner in which micron-sized, charged grains form...

  3. Simulation of primordial object formation

    CERN Document Server

    Fuller, T M; Fuller, Todd M.

    2000-01-01

    We have included the chemical rate network responsible for the formation ofmolecular Hydrogen in the N-body hydrodynamic code, Hydra, in order to studythe formation of the first cosmological at redshifts between 10 and 50. We havetested our implementation of the chemical and cooling processes by comparingN-body top hat simulations with theoretical predictions from a semi-analyticmodel and found them to be in good agreement. We find that post-virializationproperties are insensitive to the initial abundance of molecular hydrogen. Ourmain objective was to determine the minimum mass ($M_{SG}(z)$) of perturbationsthat could become self gravitating (a prerequisite for star formation), and theredshift at which this occurred. We have developed a robust indicator fordetecting the presence of a self-gravitating cloud in our simulations and findthat we can do so with a baryonic particle mass-resolution of 40 solar masses.We have performed cosmological simulations of primordial objects and find thatthe object's mass and ...

  4. Illusory contour formation survives crowding.

    Science.gov (United States)

    Lau, Jonathan Siu Fung; Cheung, Sing-Hang

    2012-06-12

    Flanked objects are difficult to identify using peripheral vision due to visual crowding, which limits conscious access to target identity. Nonetheless, certain types of visual information have been shown to survive crowding. Such resilience to crowding provides valuable information about the underlying neural mechanism of crowding. Here we ask whether illusory contour formation survives crowding of the inducers. We manipulated the presence of illusory contours through the (mis)alignment of the four inducers of a Kanizsa square. In the inducer-aligned condition, the observers judged the perceived shape (thin vs. fat) of the illusory Kanizsa square, manipulated by small rotations of the inducers. In the inducer-misaligned condition, three of the four inducers (all except the upper-left) were rotated 90°. The observers judged the orientation of the upper-left inducer. Crowding of the inducers worsened observers' performance significantly only in the inducer-misaligned condition. Our findings suggest that information for illusory contour formation survives crowding of the inducers. Crowding happens at a stage where the low-level featural information is integrated for inducer orientation discrimination, but not at a stage where the same information is used for illusory contour formation.

  5. Modeling of Dynamic FRC Formation

    Science.gov (United States)

    Mok, Yung; Barnes, Dan; Dettrick, Sean

    2010-11-01

    We have developed a 2-D resistive MHD code, Lamy Ridge, to simulate the entire FRC formation process in Tri Alpha's C2 device, including initial formation, translation, merging and settling into equilibrium. Two FRC's can be created simultaneously, and then translated toward each other so that they merge into a single FRC. The code couples the external circuits around the formation tubes to the partially ionized plasma inside. Plasma and neutral gas are treated as two fluids. Dynamic and energetic equations, which take into account ionization and charge exchange, are solved in a time advance manner. The geometric shape of the vessel is specified by a set of inputs that defines the boundaries, which are handled by a cut-cell algorithm in the code. Multiple external circuits and field coils can be easily added, removed or relocated through individual inputs. The design of the code is modular and flexible so that it can be applied to future devices. The results of the code are in reasonable agreement with experimental measurements on the C2 device.

  6. Pattern formation in optical resonators

    International Nuclear Information System (INIS)

    We review pattern formation in optical resonators. The emphasis is on 'particle-like' structures such as vortices or spatial solitons. On the one hand, similarities impose themselves with other fields of physics (condensed matter, phase transitions, particle physics, fluds/super fluids). On the other hand the feedback is led by the resonator mirrors to bi- and multi-stability of the spatial field structure, which is the basic ingredient for optical information processing. The spatial dimension or the 'parallelism' is the strength of optics compared to electronics (and will have to be employed to fully use the advantages optics offers in information processing). But even in the 'serial' processing tasks of telecoms (e.g. information buffering) spatial resonator solitons can do better than the schemes proposed so far-including 'slow light'. Pattern formation in optical resonators will likely be the key to brain-like information processing like cognition, learning and association; to complement the precise but limited algorithmic capabilities of electronic processing. But even in the short term it will be useful for solving serial optical processing problems. The prospects for technical uses of pattern formation in resonators are one motivation for this research. The fundamental similarities with other fields of physics, on the other hand, inspire transfer of concepts between fields; something that has always proven fruitful for gaining deeper insights or for solving technical problems

  7. Star Formation in Satellite Galaxies

    CERN Document Server

    Gutíerrez, C M; Funes, J G; Ribeiro, M B

    2006-01-01

    We present narrow-band observations of the H$\\alpha$ emission in a sample of 31 satellite orbiting isolated giant spiral galaxies. The sample studied spans the range $-19formation rates are 0.68 and 3.66 M$_\\sun$ yr$^{-1}$ respectively. Maps of the spatial distribution of ionized gas are presented. The star-forming regions show a rich structure in which frequently discrete complexes are imposed over more diffuse structures. In general, the current star formation rates are smaller that the mean values in the past obtained from the current stellar content; this probably indicates a declining rhythm with time in the generation of new stars. However, the reserve of gas is enough to continue fueling the current levels of star formation activity for at least another Hubble time. Four of the o...

  8. Hypothesis Formation, Paradigms, and Openness

    Directory of Open Access Journals (Sweden)

    Conrad P. Pritscher

    2008-01-01

    Full Text Available A part of hypothesis formation, while necessary for scientific investigation, is beyond direct observation. Powerful hypothesis formation is more than logical and is facilitated by mind­opening. As Percy Bridgeman, Nobel laureate, said, science is: “Nothing more than doing one's damnedest with one's mind, no holds barred.” This paper suggests more open schooling helps generate more open hypothesizing which helps one do one's damnedest with one's mind. It is hypothesized that a more open process of hypothesis formation may help schools and society forge new ways of living and learning so that more people more often can do their damnedest with their mind. This writing does not offer a new paradigm but rather attempts to elaborate on the notion that new paradigms are difficult to form without openness to what was previously quasi­unthinkable. More on these topics and issues is included in the author's Reopening Einstein's Thought: About What Can't Be Learned From Textbooks ­­to be published by Sense Publishers in June 2008.

  9. Kinetic competition during glass formation

    Energy Technology Data Exchange (ETDEWEB)

    Perepezko, J.H., E-mail: perepezk@engr.wisc.edu [University of Wisconsin-Madison, Department of Materials Science and Engineering, 1509 University Ave., Madison, WI 53706 (United States); Santhaweesuk, C.; Wang, J.Q. [University of Wisconsin-Madison, Department of Materials Science and Engineering, 1509 University Ave., Madison, WI 53706 (United States); Imhoff, S.D. [Los Alamos National Laboratory, Materials Science and Technology Div., Los Alamos, NM 87545 (United States)

    2014-12-05

    Highlights: • The kinetics of glass formation has been elucidated in an Fe and Au-base alloy. • A critical cooling rate range should be considered for glass formation. • Wedge casting, calorimetry and upquenching data are used to model TTT curves. - Abstract: For vitrification of an alloy melt during cooling there is a kinetic competition with the nucleation and growth of metastable and stable crystalline phases. Many of the measures of glass forming ability (GFA) attempt to capture some of the features of the kinetic competition, but the GFA metrics are static measures and the kinetic processes are dynamic in nature. In fact, the critical cooling rate for glass formation should be viewed in terms of a critical cooling rate range to acknowledge the stochastic nature of crystal nucleation behavior. Direct measurements of the critical cooling rate range confirm this behavior and also provide useful input for kinetics analysis. Usually kinetics analyses are based upon crystallization behavior that is measured either isothermally or upon heating to temperatures near the crystallization onset, T{sub x} and the results are extrapolated to much higher temperatures. This practice is based upon a number of assumptions about transport behavior in the undercooled liquid. With rapid up-quenching of amorphous samples, the high temperature crystallization behavior can be measured and used to refine the kinetics analysis and provide useful insight on the kinetic competition and glass forming ability.

  10. NSDF: Neuroscience Simulation Data Format.

    Science.gov (United States)

    Ray, Subhasis; Chintaluri, Chaitanya; Bhalla, Upinder S; Wójcik, Daniel K

    2016-04-01

    Data interchange is emerging as an essential aspect of modern neuroscience. In the areas of computational neuroscience and systems biology there are multiple model definition formats, which have contributed strongly to the development of an ecosystem of simulation and analysis tools. Here we report the development of the Neuroscience Simulation Data Format (NSDF) which extends this ecosystem to the data generated in simulations. NSDF is designed to store simulator output across scales: from multiscale chemical and electrical signaling models, to detailed single-neuron and network models, to abstract neural nets. It is self-documenting, efficient, modular, and scalable, both in terms of novel data types and in terms of data volume. NSDF is simulator-independent, and can be used by a range of standalone analysis and visualization tools. It may also be used to store variety of experimental data. NSDF is based on the widely used HDF5 (Hierarchical Data Format 5) specification and is open, platform-independent, and portable. PMID:26585711

  11. Theory of Remote Image Formation

    Science.gov (United States)

    Blahut, Richard E.

    2004-11-01

    In many applications, images, such as ultrasonic or X-ray signals, are recorded and then analyzed with digital or optical processors in order to extract information. Such processing requires the development of algorithms of great precision and sophistication. This book presents a unified treatment of the mathematical methods that underpin the various algorithms used in remote image formation. The author begins with a review of transform and filter theory. He then discusses two- and three-dimensional Fourier transform theory, the ambiguity function, image construction and reconstruction, tomography, baseband surveillance systems, and passive systems (where the signal source might be an earthquake or a galaxy). Information-theoretic methods in image formation are also covered, as are phase errors and phase noise. Throughout the book, practical applications illustrate theoretical concepts, and there are many homework problems. The book is aimed at graduate students of electrical engineering and computer science, and practitioners in industry. Presents a unified treatment of the mathematical methods that underpin the algorithms used in remote image formation Illustrates theoretical concepts with reference to practical applications Provides insights into the design parameters of real systems

  12. Kinetic competition during glass formation

    International Nuclear Information System (INIS)

    Highlights: • The kinetics of glass formation has been elucidated in an Fe and Au-base alloy. • A critical cooling rate range should be considered for glass formation. • Wedge casting, calorimetry and upquenching data are used to model TTT curves. - Abstract: For vitrification of an alloy melt during cooling there is a kinetic competition with the nucleation and growth of metastable and stable crystalline phases. Many of the measures of glass forming ability (GFA) attempt to capture some of the features of the kinetic competition, but the GFA metrics are static measures and the kinetic processes are dynamic in nature. In fact, the critical cooling rate for glass formation should be viewed in terms of a critical cooling rate range to acknowledge the stochastic nature of crystal nucleation behavior. Direct measurements of the critical cooling rate range confirm this behavior and also provide useful input for kinetics analysis. Usually kinetics analyses are based upon crystallization behavior that is measured either isothermally or upon heating to temperatures near the crystallization onset, Tx and the results are extrapolated to much higher temperatures. This practice is based upon a number of assumptions about transport behavior in the undercooled liquid. With rapid up-quenching of amorphous samples, the high temperature crystallization behavior can be measured and used to refine the kinetics analysis and provide useful insight on the kinetic competition and glass forming ability

  13. Dioxin formation from waste incineration.

    Science.gov (United States)

    Shibamoto, Takayuki; Yasuhara, Akio; Katami, Takeo

    2007-01-01

    There has been great concern about dioxins-polychlorinated dibenzo dioxins (PCDDs), polychlorinated dibenzo furans (PCDFs), and polychlorinated biphenyls (PCBs)-causing contamination in the environment because the adverse effects of these chemicals on human health have been known for many years. Possible dioxin-contamination has received much attention recently not only by environmental scientists but also by the public, because dioxins are known to be formed during the combustion of industrial and domestic wastes and to escape into the environment via exhaust gases from incinerators. Consequently, there is a pressing need to investigate the formation mechanisms or reaction pathways of these chlorinated chemicals to be able to devise ways to reduce their environmental contamination. A well-controlled small-scale incinerator was used for the experiments in the core references of this review. These articles report the investigation of dioxin formation from the combustion of various waste-simulated samples, including different kinds of paper, various kinds of wood, fallen leaves, food samples, polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), polyvinylidene chloride, polyethylene tetraphthalate (PET), and various kinds of plastic products. These samples were also incinerated with inorganic chlorides (NaCl, KCl, CuCI2, MgCl2, MnCl2, FeCl2, CoCl2, fly ash, and seawater) or organic chlorides (PVC, chlordane, and pentachlorophenol) to investigate the role of chlorine content and/or the presence of different metals in dioxin formation. Some samples, such as newspapers, were burned after they were impregnated with NaCl or PVC, as well as being cocombusted with chlorides. The roles of incineration conditions, including chamber temperatures, O2 concentrations, and CO concentrations, in dioxin formation were also investigated. Dioxins (PCDDs, PCDFs, and coplanar-PCBs) formed in the exhaust gases from a controlled small-scale incinerator, where experimental waste

  14. Core formation in silicate bodies

    Science.gov (United States)

    Nimmo, F.; O'Brien, D. P.; Kleine, T.

    2008-12-01

    Differentiation of a body into a metallic core and silicate mantle occurs most efficiently if temperatures are high enough to allow at least the metal to melt [1], and is enhanced if matrix deformation occurs [2]. Elevated temperatures may occur due to either decay of short-lived radio-isotopes, or gravitational energy release during accretion [3]. For bodies smaller than the Moon, core formation happens primarily due to radioactive decay. The Hf-W isotopic system may be used to date core formation; cores in some iron meteorites and the eucrite parent body (probably Vesta) formed within 1 My and 1-4~My of solar system formation, respectively [4]. These formation times are early enough to ensure widespread melting and differentiation by 26Al decay. Incorporation of Fe60 into the core, together with rapid early mantle solidification and cooling, may have driven early dynamo activity on some bodies [5]. Iron meteorites are typically depleted in sulphur relative to chondrites, for unknown reasons [6]. This depletion contrasts with the apparently higher sulphur contents of cores in larger planetary bodies, such as Mars [7], and also has a significant effect on the timing of core solidification. For bodies of Moon-size and larger, gravitational energy released during accretion is probably the primary cause of core formation [3]. The final stages of accretion involve large, stochastic collisions [8] between objects which are already differentiated. During each collision, the metallic cores of the colliding objects merge on timescales of a few hours [9]. Each collision will reset the Hf-W isotopic signature of both mantle and core, depending on the degree to which the impactor core re-equilibrates with the mantle of the target [10]. The re-equilibration efficiency depends mainly on the degree to which the impactor emulsifies [11], which is very uncertain. Results from N-body simulations [8,12] suggest that significant degrees of re- equilibration are required [4,10]. Re

  15. MHD turbulence, cloud formation and star formation in the ISM

    CERN Document Server

    Vázquez-Semadeni, E; Pouquet, A

    1996-01-01

    We discuss the role of turbulence in cloud and star formation, as observed in numerical simulations of the interstellar medium. Turbulent compression at the interfaces of colliding gas streams is responsible for the formation of intermediate (\\simlt 100 pc) and small clouds (a few tens of pc), although the smallest clouds can also form from fragmentation of expanding shells around stellar heating centers. The largest cloud complexes (several hundred pc) seem to form by slow, gravitational instability-driven merging of individual clouds, which can actually be described as a large-scale tendency towards homogenization of the flow due to gravity rather than cloud collisions. These mechanisms operate as well in the presence of a magnetic field and rotation, although slight variations on the compressibility and cloud morphology are present which depend on the strength and topology of the field. In summary, the role of turbulence in the life-cycle of clouds appears to be twofold: small-scale modes contribute to clo...

  16. Package Formats for Preserved Digital Material

    DEFF Research Database (Denmark)

    Zierau, Eld

    2012-01-01

    This paper presents an investigation of the best suitable package formats for long term digital preservation. The choice of a package format for preservation is crucial for future access, thus a thorough analysis of choice is important. The investigation presented here covers setting up...... requirements for package formats used for long term preserved digital material, and using these requirements as the basis for analysing a range of package formats. The result of the concrete investigation is that the WARC format is the package format best suited for the listed requirements. Fulfilling...

  17. DIKE FORMATION WITH SUBMERGED VANE

    Institute of Scientific and Technical Information of China (English)

    Umesh P.GUPTA; C.S.P.OJHA; Nayan SHARMA

    2006-01-01

    Submerged vanes are submerged foils constructed in a river at an angle of attack to induce horizontal circulation in the downstream flow. The initial height of vanes is 0.2 - 0.4 times the local water depth (d) at the design stage. Its length expressed as a multiple of the height to length ratio (H/L) normally is 0.25 to 0.5. With the use of a submerged vane in straight channels, dikes (heaps of sediment) were formed downstream. At an optimal angle of attack of 40o and at a Froude number of 0.25, the formation of the dike starts at some distance from the trailing edge of the rectangular and trapezoidal submerged vanes with a collar. A significant scour hole results at the trailing edge of a vane with a collar. A typical dike formed along the vane on the suction side with a symmetric bell-shaped profile. The dike formation phenomenon triggered by a vane close to the bank-line at a flow with a relatively higher Froude number, such as 0.25, does not seem to follow a straight alignment, but has a sort of curvilinear shape bent towards the suction side. The dike formation process for a flow with a smaller Froude number, such as 0.13, is observed to not be appreciable. With the same installation height of H, a vane without a collar was dislodged by the flow at a Froude number of 0.25, whereas it was stable at a Froude number of 0.13.

  18. Massive neutrinos and galaxy formation

    CERN Document Server

    Ma Chung Pei

    1994-01-01

    We report the most recent results from high-resolution numerical simulations of structure formation in two flat cold+hot dark matter models with neutrino mass densities \\onu=0.2 and 0.3. We find that structure forms too late in all CDM+HDM models with \\onu>0.2 to account for the amount of dense neutral gas in high-redshift damped Lyman-\\alpha systems. The \\onu=0.2 model at z\\approx0 provides a better match to observations than the pure CDM model.

  19. Branch formation during organ development

    Science.gov (United States)

    Gjorevski, Nikolce; Nelson, Celeste M.

    2010-01-01

    Invertebrates and vertebrates use branching morphogenesis to build epithelial trees to maximize the surface area of organs within a given volume. Several molecular regulators of branching have recently been discovered, a number of which are conserved across different organs and species. Signals that control branching at the cellular and tissue levels are also starting to emerge, and are rapidly unveiling the physical nature of branch development. Here we discuss the molecular, cellular and physical processes that govern branch formation and highlight the major outstanding questions in the field. PMID:20890968

  20. Biofilm formation and microbial corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Goldstein, R.; Porcella, D.

    1992-07-01

    Biofilms-colonies of microorganisms growing on surfaces - can greatly accelerate the corrosion rates of metals and alloys in utility water systems. Fundamental EPRI research is showing how mechanisms of biofilm formation, interactions between bacterial species, and metabolic activities control such biofilm properties as corrosive potential This research is identifying methods to control biofilm development and prevent microbially influenced corrosion. The results should also apply to the control of other processes involving biological consortia, including the bioremediation of contaminated groundwater and soil and the biodesulfurization of coal.

  1. Formation flight astronomical survey telescope

    Science.gov (United States)

    Tsunemi, Hiroshi

    2012-03-01

    Formation Flight Astronomical Survey Telescope (FFAST) is a project for hard X-ray observation. It consists of two small satellites; one (telescope satellite) has a super mirror covering the energy range up to 80 keV while the other (detector satellite) has an scintillator deposited CCD (SDCCD) having good spatial resolution and high efficiency up to 100 keV. Two satellites will be put into individual Kepler orbits forming an X-ray telescope with a focal length of 20 m. They will be not in pointing mode but in survey mode to cover a large sky region.

  2. Adsorption-induced step formation

    DEFF Research Database (Denmark)

    Thostrup, P.; Christoffersen, Ebbe; Lorensen, Henrik Qvist;

    2001-01-01

    Through an interplay between density functional calculations, Monte Carlo simulations and scanning tunneling microscopy experiments, we show that an intermediate coverage of CO on the Pt(110) surface gives rise to a new rough equilibrium structure with more than 50% step atoms. CO is shown to bind...... so strongly to low-coordinated Pt atoms that it can break Pt-Pt bonds and spontaneously form steps on the surface. It is argued that adsorption-induced step formation may be a general effect, in particular at high gas pressures and temperatures....

  3. XML Format for SESAME and LEOS

    Energy Technology Data Exchange (ETDEWEB)

    Durrenberger, J K; Neely, J R; Sterne, P A

    2009-04-29

    The objective of this document is to describe the XML format used by LLNL and LANL to represent the equation-of-state and related material information in the LEOS and SESAME data libraries. The primary purpose of this document is to describe a specific XML format for representing EOS data that is tailored to the nature of the underlying data and is amenable to conversion to both legacy SESAME and LEOS binary formats. The secondary purpose is to describe an XML format that lends itself to a 'natural' representation in a binary file format of the SESAME, pdb or hdf5 form so that this format and related tools can be used for the rapid and efficient development and implementation of prototype data structures. This document describes the XML format only. A working knowledge of LEOS and SESAME formats is assumed.

  4. The Current Status of Galaxy Formation

    OpenAIRE

    Silk, Joe; Mamon, Gary A.

    2012-01-01

    Understanding galaxy formation is one of the most pressing issues in cosmology. We review the current status of galaxy formation from both an observational and a theoretical perspective, and summarise the prospects for future advances.

  5. Multilevel Modulation formats for Optical Communication

    DEFF Research Database (Denmark)

    Jensen, Jesper Bevensee

    2008-01-01

    This thesis studies the use of multilevel modulation formats for optical communication systems. Multilevel modulation is an attractive method of increasing the spectral efficiency of optical communication systems. Various modulation formats employing phase modulation, amplitude modulation...

  6. SAR polar format implementation with MATLAB.

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Grant D.; Doerry, Armin Walter

    2005-11-01

    Traditional polar format image formation for Synthetic Aperture Radar (SAR) requires a large amount of processing power and memory in order to accomplish in real-time. These requirements can thus eliminate the possible usage of interpreted language environments such as MATLAB. However, with trapezoidal aperture phase history collection and changes to the traditional polar format algorithm, certain optimizations make MATLAB a possible tool for image formation. Thus, this document's purpose is two-fold. The first outlines a change to the existing Polar Format MATLAB implementation utilizing the Chirp Z-Transform that improves performance and memory usage achieving near realtime results for smaller apertures. The second is the addition of two new possible image formation options that perform a more traditional interpolation style image formation. These options allow the continued exploration of possible interpolation methods for image formation and some preliminary results comparing image quality are given.

  7. On the modelling of river delta formation

    NARCIS (Netherlands)

    Geleynse, N.

    2013-01-01

    This thesis presents approaches to the modelling of river delta formation. In particular, it provides results of numerical stratigraphic-morphodynamic modelling of river delta formation under various environmental forcings.

  8. Molecular mechanism of bone formation and regeneration

    Institute of Scientific and Technical Information of China (English)

    Akira Yamaguchi

    2008-01-01

    @@ Bone formation and regeneration are mediated by the coordinate action of various factors. Among these, bone morphogenetic protein (BMP) and runt-related gene 2 (Runx2) play crucial roles in bone formation.

  9. FORMATE-BASED FLUIDS: FORMULATION AND APPLICATION

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    2008-12-01

    Full Text Available Formate-based fluids has been successfully used in over hunders HPHT well operations since they introduced in field practice. They have many advantages when compared with conventional HPHT drilling and completion fluids such as: minimal formation damage, maintenance of additve properties at high temperatures, reduced hydraulic flow resistance, low potential for differential sticking, naturally lubricating, very low corrosion rates, biodegradable and pose little risk to the environment etc. Formate-based fluids can be applied during deep slim hole drilling, shale drilling, reservoir drilling, salt and gas hydrate formations drilling. The laboratory research was carried out to evaluate the rheological behavior of formate-based fluids as a function of temperature. Formate-based fluids were formulated using potassium formate brine, xanthan polymer, PAC, starch and calcium carbonate. Experimental results show that potassium formate improves the thermal stability of polymers.

  10. Choosing to write the paper format thesis.

    Science.gov (United States)

    Morris, H M; Tipples, G

    1998-04-01

    Graduate students today may be faced with the option of writing either a traditional format thesis or a paper format thesis. In contrast to the traditional format in which the text body consists of four or five chapters, the body of the paper format thesis can be comprised of an introductory chapter, two or more papers written as publishable manuscripts, and a conclusion. In this article, an overview of the paper format thesis is presented and contrasted with the traditional format thesis. The description of the paper format thesis is followed by its advantages and disadvantages for writers and readers. It is by weighing all possible pros and cons, as well as considering one's individual situation, that the graduate student will be able to decide which format of thesis to write.

  11. Enamel formation and amelogenesis imperfecta.

    Science.gov (United States)

    Hu, Jan C-C; Chun, Yong-Hee P; Al Hazzazzi, Turki; Simmer, James P

    2007-01-01

    Dental enamel is the epithelial-derived hard tissue covering the crowns of teeth. It is the most highly mineralized and hardest tissue in the body. Dental enamel is acellular and has no physiological means of repair outside of the protective and remineralization potential provided by saliva. Enamel is comprised of highly organized hydroxyapatite crystals that form in a defined extracellular space, the contents of which are supplied and regulated by ameloblasts. The entire process is under genetic instruction. The genetic control of amelogenesis is poorly understood, but requires the activities of multiple components that are uniquely important for dental enamel formation. Amelogenesis imperfecta (AI) is a collective designation for the variety of inherited conditions displaying isolated enamel malformations, but the designation is also used to indicate the presence of an enamel phenotype in syndromes. Recently, genetic studies have demonstrated the importance of genes encoding enamel matrix proteins in the etiology of isolated AI. Here we review the essential elements of dental enamel formation and the results of genetic analyses that have identified disease-causing mutations in genes encoding enamel matrix proteins. In addition, we provide a fresh perspective on the roles matrix proteins play in catalyzing the biomineralization of dental enamel.

  12. Simulations for terrestrial planets formation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Niu; JI JiangHui

    2009-01-01

    In this paper, the formation of terrestrial planets in the late stage of planetary formation is Investigated using the two-planet model. At that time, the protostar formed for about 3 Ma and the gas disk dissipated. In the model, the perturbations from Jupiter and Saturn are considered. Variations of the mass of outer planet, and the initial eccentricities and inclinations of embryos and planetesimals are also considered. Our results show that, terrestrial planets are formed in 50 Ma, and the accretion rate is about 60%-80%. In each simulation, 3-4 terrestrial planets are formed inside "Jupiter" with masses of 0.15-3.6 M(⊙). In the 0.5-4 AU, when the eccentricities of planetesimals are excited, planetesimals are able to accrete material from wide radial direction. The plenty of water material of the terrestrial planet in the Habitable Zone may be transferred from the farther places by this mechanism. Accretion could also happen a few times between two major planets only if the outer planet has a moderate mass and the small terrestrial planet could survive at some resonances over time scale of 108a. In one of our simulations, commensurability of the orbital periods of planets is very common. Moreover, a librating-circulating 3:2 configuration of mean motion resonance is found.

  13. Simulations for terrestrial planets formation

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper,the formation of terrestrial planets in the late stage of planetary formation is investigated using the two-planet model.At that time,the protostar formed for about 3 Ma and the gas disk dissipated.In the model,the perturbations from Jupiter and Saturn are considered.Variations of the mass of outer planet,and the initial eccentricities and inclinations of embryos and planetesimals are also considered.Our results show that,terrestrial planets are formed in 50 Ma,and the accretion rate is about 60%-80%.In each simulation,3-4 terrestrial planets are formed inside"Jupiter"with masses of 0.15 -3.6M⊕.In the 0.5-4 AU,when the eccentricities of planetesimals are excited,planetesimals are able to accrete material from wide radial direction.The plenty of water material of the terrestrial planet in the Habitable Zone may be transferred from the farther places by this mechanism.Accretion could also happen a few times between two major planets only if the outer planet has a moderate mass and the small terrestrial planet could survive at some resonances over time scale of 10 8 a.In one of our simulations,commensurability of the orbital periods of planets is very common.Moreover,a librating-circulating 3:2 configuration of mean motion resonance is found.

  14. Radical formation by heavy metals

    Energy Technology Data Exchange (ETDEWEB)

    Beuter, W.

    1982-09-01

    Certain reduced heavy metal ions can convert oxygen to a ''reactive oxygen species'' by donation of an electron. The reactive oxygen then attacks structures susceptible to oxidation, in particular unsaturated fatty acids, and peroxidizes them in a radical reaction. This process is inhibited by the presence of vitamin E and by other means. Peroxidized lipids decay forming free radicals in the process which themselves can peroxidise neighbouring lipids in a radical chain reaction. This decay is, moreover, catalysed by reduced heavy metal ions but on the other hand retarded by selenium-containing glutathione peroxidase. Radical formation by heavy metals is considerably involved in (i) the production of parenteral iron poisoning of the piglet (ii) haemolytic crisis occurring in ruminants through chronic copper poisoning (iii) the production of lead poisoning in ruminants and other animals. These types of poisonings are made worse by a deficiency of vitamin E and/or selenium. Factors which increase the bio-availability of the free heavy metal ion or reduce the redox potential thereof can aid radical formation as well as factors which lead to a reduction of the heavy metal ion e.g. cysteine, ascorbic acid or glucose.

  15. Tube Formation in Nanoscale Materials

    Directory of Open Access Journals (Sweden)

    Yan Chenglin

    2008-01-01

    Full Text Available Abstract The formation of tubular nanostructures normally requires layered, anisotropic, or pseudo-layered crystal structures, while inorganic compounds typically do not possess such structures, inorganic nanotubes thus have been a hot topic in the past decade. In this article, we review recent research activities on nanotubes fabrication and focus on three novel synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. Specifically, thermal oxidation method based on gas–solid reaction to porous CuO nanotubes has been successfully established, semiconductor ZnS and Nb2O5nanotubes have been prepared by employing sacrificial template strategy based on liquid–solid reaction, and an in situ template method has been developed for the preparation of ZnO taper tubes through a chemical etching reaction. We have described the nanotube formation processes and illustrated the detailed key factors during their growth. The proposed mechanisms are presented for nanotube fabrication and the important pioneering studies are discussed on the rational design and fabrication of functional materials with tubular structures. It is the intention of this contribution to provide a brief account of these research activities.

  16. Characteristic Scales in Galaxy Formation

    CERN Document Server

    Dekel, A

    2004-01-01

    Recent data, e.g. from SDSS and 2dF, reveal a robust bi-modality in the distribution of galaxy properties, with a characteristic transition scale at stellar mass M_*~3x10^{10} Msun (near L_*), corresponding to virial velocity V~100 km/s. Smaller galaxies tend to be blue disks of young populations. They define a "fundamental line" of decreasing surface brightness, metallicity and velocity with decreasing M_*, which extends to the smallest dwarf galaxies. Galaxies above the critical scale are dominated by red spheroids of old populations, with roughly constant high surface brightens and metallicity, and they tend to host AGNs. A minimum in the virial M/L is obtained at the same magic scale. This bi-modality can be the combined imprint of several different physical processes. On smaller scales, disks are built by cold flows, and supernova feedback is effective in regulating star formation. On larger scales, the infalling gas is heated by a virial shock and star formation can be suppressed by AGN feedback. Anothe...

  17. The formation of flashbulb memories.

    Science.gov (United States)

    Conway, M A; Anderson, S J; Larsen, S F; Donnelly, C M; McDaniel, M A; McClelland, A G; Rawles, R E; Logie, R H

    1994-05-01

    A large group of subjects took part in a multinational test-retest study to investigate the formation of flashbulb (FB) memories for learning the news of the resignation of the British prime minister, Margaret Thatcher. Over 86% of the U.K. subjects were found to have FB memories nearly 1 year after the resignation; their memory reports were characterized by spontaneous, accurate, and full recall of event details, including minutiae. In contrast, less than 29% of the non-U.K. subjects had FB memories 1 year later; memory reports in this group were characterized by forgetting, reconstructive errors, and confabulatory responses. A causal analysis of secondary variables showed that the formation of FB memories was primarily associated with the level of importance attached to the event and level of affective response to the news. These findings lend some support to the study by R. Brown and Kulik (1977), who suggest that FB memories may constitute a class of autobiographical memories distinguished by some form of preferential encoding.

  18. The Formation of Very Massive Stars

    OpenAIRE

    Krumholz, Mark R

    2014-01-01

    In this chapter I review theoretical models for the formation of very massive stars. After a brief overview of some relevant observations, I spend the bulk of the chapter describing two possible routes to the formation of very massive stars: formation via gas accretion, and formation via collisions between smaller stars. For direct accretion, I discuss the problems of how interstellar gas may be prevented from fragmenting so that it is available for incorporation into a single very massive st...

  19. Formation of embryoid bodies using dielectrophoresis

    OpenAIRE

    Agarwal, Sneha; Sebastian, Anil; Forrester, Lesley M; Markx, Gerard H

    2012-01-01

    Embryoid body (EB) formation forms an important step in embryonic stem cell differentiation invivo. In murine embryonic stem cell (mESC) cultures EB formation is inhibited by the inclusion of leukaemic inhibitory factor (LIF) in the medium. Assembly of mESCs into aggregates by positive dielectrophoresis (DEP) in high field regions between interdigitated oppositely castellated electrodes was found to initiate EB formation. Embryoid body formation in aggregates formed with DEP occurred at a mor...

  20. Treating nahcolite containing formations and saline zones

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J

    2013-06-11

    A method for treating a nahcolite containing subsurface formation includes removing water from a saline zone in or near the formation. The removed water is heated using a steam and electricity cogeneration facility. The heated water is provided to the nahcolite containing formation. A fluid is produced from the nahcolite containing formation. The fluid includes at least some dissolved nahcolite. At least some of the fluid is provided to the saline zone.

  1. Towards the Rosetta Stone of planet formation

    OpenAIRE

    Schmidt T.O.B.; Roell T.; Raetz St.; Pribulla T.; Moualla M.; Marka C.; Kramm U.; Hohle M.; Ginski Ch.; Fiedler S.; Eisenbeiss T.; Berndt A.; Adam Ch.; Mugrauer M.; Errmann R.

    2011-01-01

    Transiting exoplanets (TEPs) observed just about 10 Myrs after formation of their host systems may serve as the Rosetta Stone for planet formation theories. They would give strong constraints on several aspects of planet formation, e.g. time-scales (planet formation would then be possible within 10 Myrs), the radius of the planet could indicate whether planets form by gravitational collapse (being larger when young) or accretion growth (being smaller when young). We present a survey, the main...

  2. Supermassive Black Holes and Galaxy Formation

    OpenAIRE

    Silk, Joseph

    2001-01-01

    The formation of supermassive black holes (SMBH) is intimately related to galaxy formation, although precisely how remains a mystery. I speculate that formation of, and feedback from, SMBH may alleviate problems that have arisen in our understanding of the cores of dark halos of galaxies.

  3. Formation of tax culture in Russia

    Directory of Open Access Journals (Sweden)

    Halikova Je.A.

    2014-11-01

    Full Text Available This article deals with the mechanism of the formation of tax culture in Russia, moral and ethical principles, on which based the work of the tax authorities, given the author's idea of the formation of tax culture. We consider the institution of tax advice, its interaction with the tax authorities and its impact on the formation of tax culture.

  4. Diet History Questionnaire II: Size Formats

    Science.gov (United States)

    Two serving size formats are used on the NCI versions of the DHQ as shown below. Format 1 is used for nearly all serving size questions. Format 2 is used only in special cases, where 'never' is allowed as a response.

  5. String Formatting Considered Harmful for Novice Programmers

    Science.gov (United States)

    Hughes, Michael C.; Jadud, Matthew C.; Rodrigo, Ma. Mercedes T.

    2010-01-01

    In Java, "System.out.printf" and "String.format" consume a specialised kind of string commonly known as a format string. In our study of first-year students at the Ateneo de Manila University, we discovered that format strings present a substantial challenge for novice programmers. Focusing on their first laboratory we found that 8% of all the…

  6. Formation of tax culture in Russia

    OpenAIRE

    Halikova Je.A.; Ginijatullina D.R.

    2014-01-01

    This article deals with the mechanism of the formation of tax culture in Russia, moral and ethical principles, on which based the work of the tax authorities, given the author's idea of the formation of tax culture. We consider the institution of tax advice, its interaction with the tax authorities and its impact on the formation of tax culture.

  7. ENDF/B-5 formats manual 1984

    International Nuclear Information System (INIS)

    The ENDF-5 Format, originally the format of the US Evaluated Nuclear Data File ENDF/B-5, was internationally recommended for the computer storage, processing and exchange of evaluated neutron nuclear data. The present document contains the original Formats Manual of 1979, updated with revisions of Nov. 1983. (author)

  8. A new PICL trace file format

    Energy Technology Data Exchange (ETDEWEB)

    Worley, P.H.

    1992-10-01

    A trace file format is described that will be used in future releases of the Portable Instrumented Communication Library (PICL) and ParaGraph. The new format provides improved support for tracing and profiling PICL communication primitives and user-defined events. The new format is also easily extended and may be useful in other instrumentation packages and performance visualization tools.

  9. Tree Formation Using Coordinate Method

    Directory of Open Access Journals (Sweden)

    Monika Choudhary

    2015-06-01

    Full Text Available In this paper we are introducing a new method of tree formation, we propose a coordinate based method by which we can store and access tree structures. As we know in NLP, parsing is the most important module. The output of this module is generally parsed trees. Currently, TAG (Tree Adjoining Grammar is widely used grammar due to its linguistic and formal nature. It is simply tree generating system. The unit structure used in TAG is structured trees. So we used our new method to store trees where we worked on English to Hindi language. We worked on different sentences from English to Hindi, our method is the easiest way to manipulate tree. We have implemented within small corpus and for finite number of structures and further can be extended in future.

  10. Mud Volcanoes Formation And Occurrence

    Science.gov (United States)

    Guliyev, I. S.

    2007-12-01

    Mud volcanoes are natural phenomena, which occur throughout the globe. They are found at a greater or lesser scale in Azerbaijan, Turkmenistan, Georgia, on the Kerch and Taman peninsulas, on Sakhalin Island, in West Kuban, Italy, Romania, Iran, Pakistan, India, Burma, China, Japan, Indonesia, Malaysia, New Zealand, Mexico, Colombia, Trinidad and Tobago, Venezuela and Ecuador. Mud volcanoes are most well-developed in Eastern Azerbaijan, where more than 30% of all the volcanoes in the world are concentrated. More than 300 mud volcanoes have already been recognized here onshore or offshore, 220 of which lie within an area of 16,000 km2. Many of these mud volcanoes are particularly large (up to 400 m high). The volcanoes of the South Caspian form permanent or temporary islands, and numerous submarine banks. Many hypotheses have been developed regarding the origin of mud volcanoes. Some of those hypotheses will be examined in the present paper. Model of spontaneous excitation-decompaction (proposed by Ivanov and Guliev, 1988, 2002). It is supposed that one of major factors of the movement of sedimentary masses and formation of hydrocarbon deposits are phase transitions in sedimentary basin. At phase transitions there are abnormal changes of physical and chemical parameters of rocks. Abnormal (high and negative) pressure takes place. This process is called as excitation of the underground environment with periodicity from several tens to several hundreds, or thousand years. The relationship between mud volcanism and the generation of hydrocarbons, particularly methane, is considered to be a critical factor in mud volcano formation. At high flow rates the gas and sediment develops into a pseudo-liquid state and as flow increases the mass reaches the "so-called hover velocity" where mass transport begins. The mass of fluid moves as a quasi-uniform viscous mass through the sediment pile in a piston like manner until expelled from the surface as a "catastrophic eruption

  11. The formation of postcolonial theory

    Directory of Open Access Journals (Sweden)

    Lazare S. Rukundwa

    2007-05-01

    Full Text Available The purpose of this article is to outline certain options and struggles, which gave rise to postcolonial theory. The author deals with various experiences of anti-slavery and anti-colonial movements in Western and tricontinental countries, comprising the development of postcolonial theory. It is argued that postcolonial theory provides a means of defiance by which any exploitative and discriminative practices, regardless of time and space, can be challenged. The article consists of a section in which terminology is clarified, secondly a discussion of the elements that functioned as justification of the formation of postcolonial theory, namely a humanitarian, economic, political, and religious justification. The role of feminism and anti-colonialism is discussed in the third instance, followed by a reflection on the concept “hybrid identities”.

  12. Positronium formation in condensed matter

    International Nuclear Information System (INIS)

    AMOC (age-momentum correlation) studies of the slowing-down of positronium in condensed matter have demonstrated that positronium formation does not require special sites (e.g., 'free volumes') and diffusion of thermalized e+ to these sites. The differences in the energies E0 at which ps becomes 'permanent' (i.e., does no longer break up into its constituents) between disordered (e.g., organic liquids) and highly ordered (e.g., rare-gas crystals) Ps-formers are explained by the different character of the forces acting on the constituents. It is proposed that information on the break-up may be obtained from the relaxation of the positron spin polarization and that very long slowing-down times may be investigated by ACAR-based AMOC measurements. (orig.)

  13. New Office Software course format

    CERN Multimedia

    HR Department

    2010-01-01

    Always interested to anticipate your training needs, the Technical Training service is pleased to propose two new Office Software course formats : “Focus on... ” : On a monthly basis we will propose a theme such as “Sharepoint Collaboration Workspace” or “Word 2007” or “charts” etc. You will have to send us in advance your questions regarding the proposed topic and register for the course through our Training Catalogue. During the session, our trainer will answer all the questions received and participants will increase their knowledge thanks to the solutions discussed for everyone. The course will last two hours, from 09h00 to 11h00 - with open questions on the proposed topic at the end. “Office software Individual coaching”: If one or several particular topics cause you sleepless nights, you can get the help of our trainer who will come to your workplace for a multiple of 1-hour slots . All fields ...

  14. Formation of $\\phi$ mesic nuclei

    CERN Document Server

    Yamagata-Sekihara, J; Vacas, M J Vicente; Hirenzaki, S

    2010-01-01

    We study the structure and formation of the $\\phi$ mesic nuclei to investigate the in-medium modification of the $\\phi$-meson spectral function at finite density. We consider (${\\bar p},\\phi$), ($\\gamma,p$) and ($\\pi^-,n$) reactions to produce a $\\phi$-meson inside the nucleus and evaluate the effects of its medium modifications to the reaction cross sections. We also estimate the consequences of the uncertainties of the ${\\bar K}$ selfenergy in medium to the $\\phi$-nucleus interaction. We find that it may be possible to see a peak structure in the reaction spectra for the strong attractive potential cases. On the other hand, for strong absorptive interaction cases with relatively weak attractions, it is very difficult to observe clear peaks and we may need to know the spectrum shape in a wide energy region to deduce the properties of $\\phi$.

  15. Foam formation in low gravity

    Science.gov (United States)

    Wessling, Francis C.; Mcmanus, Samuel P.; Matthews, John; Patel, Darayas

    1990-01-01

    An apparatus that produced the first polyurethane foam in low gravity has been described. The chemicals were mixed together in an apparatus designed for operation in low gravity. Mixing was by means of stirring the chemicals with an electric motor and propeller in a mixing chamber. The apparatus was flown on Consort 1, the first low-gravity materials payload launched by a commercial rocket launch team. The sounding rocket flight produced over 7 min of low gravity during which a polyurethane spheroidal foam of approximately 2300 cu cm was formed. Photographs of the formation of the foam during the flight show the development of the spheroidal form. This begins as a small sphere and grows to approximately a 17-cm-diam spheroid. The apparatus will be flown again on subsequent low-gravity flights.

  16. The Formation of Lake Stars

    CERN Document Server

    Tsai, Victor C

    2007-01-01

    Star patterns, reminiscent of a wide range of diffusively controlled growth forms from snowflakes to Saffman-Taylor fingers, are ubiquitous features of ice covered lakes. Despite the commonality and beauty of these ``lake stars'' the underlying physical processes that produce them have not been explained in a coherent theoretical framework. Here we describe a simple mathematical model that captures the principal features of lake-star formation; radial fingers of (relatively warm) water-rich regions grow from a central source and evolve through a competition between thermal and porous media flow effects in a saturated snow layer covering the lake. The number of star arms emerges from a stability analysis of this competition and the qualitative features of this meter-scale natural phenomena are captured in laboratory experiments.

  17. Glass formation in eutectic alloys

    International Nuclear Information System (INIS)

    We have analyzed the glass forming ability around eutectic composition in terms of the competitive growth/formation of primary dendrites, eutectic and glass. It is concluded that the glass forming ability of a eutectic alloy system depends on the type of the eutectics, i.e. symmetric or asymmetric eutectic coupled zone. For the alloy systems with symmetric eutectic coupled zone, the best glass forming alloys should be at or very close to the eutectic composition. For the alloys with asymmetric eutectic coupled zone, which is associated with the irregular eutectic, the best glass forming alloys should be at off-eutectic compositions, probably towards the side of the faceted phase with a high entropy in the phase diagram. (orig.)

  18. MDF: Magnetic Particle Imaging Data Format

    CERN Document Server

    Knopp, Tobias; Bringout, Gael; Ahlborg, Mandy; Rahmer, Jürgen; Hofmann, Martin

    2016-01-01

    Magnetic particle imaging (MPI) is a tomographic method to determine the spatial distribution of magnetic nanoparticles. In this document a file format for the standardized storage of MPI data is introduced. The aim of the Magnetic Particle Imaging Data Format (MDF) is to provide a coherent way of exchanging MPI data acquired with different MPI scanners worldwide. The focus of the file format is on sequence parameters, raw measurement data, calibration data, and reconstruction data. The format is based on the hierarchical document format (HDF) in version 5 (HDF5).

  19. Uranium price formation. Final report

    International Nuclear Information System (INIS)

    The modern uranium industry came into existence in 1946. Until 1966, its sole customer was the Atomic Energy Commission, whose needs for U3O8 relative to industry capacity declined over the years. The development of the commercial market after 1965 coincided with a period of excess capacity and falling nominal and real prices. Gradually in 1973 and dramatically thereafter, market conditions changed and prices rose as utilities sought larger quantities of U3O8 and longer term contracts. Questions about availability of long-run supplies were raised, given the known reserve base. The response of the supply of U3O8 to incentives offered first by the AEC and later by the utilities in the context of new and developing market conventions is examined. The methodology used is microeconomic analysis, qualitatively applied to the history of price formation in the market. Because the study emphasizes the implications of the history of uranium price formation for forecasting supply response, the study presents many different kinds of data and evaluates their quality and appropriateness for forecasting. A simple, very-useful framework for analyzing the history of the market for U3O8 was developed and used to describe supply responses in selected important periods of the industry's development. It is concluded that the response of supply of U3O8 to rising prices or to expectations of demand growth has been impressively strong. The potential reserve inventory is large enough to meet the needs for nuclear power generation through the end of this century. The price necessary to induce producers to find and produce these reserves is uncertain, partly because of problems inherent in estimating long-run supply curves and partly because recent inflation has created major uncertainties about the cost of future supplies

  20. Drill cuttings mount formation study

    Science.gov (United States)

    Teh, Su Yean; Koh, Hock Lye

    2014-07-01

    Oil, Gas and Energy sector has been identified as an essential driving force in the Malaysian Economic Transformation Programs (ETP). Recently confirmed discovery of many offshore oil and gas deposits in Malaysian waters has ignited new confidence in this sector. However, this has also spurred intense interest on safeguarding the health and environment of coastal waters in Malaysia from adverse impact resulting from offshore oil and gas production operation. Offshore discharge of spent drilling mud and rock cuttings is the least expensive and simplest option to dispose of large volumes of drilling wastes. But this onsite offshore disposal may have adverse environmental impacts on the water column and the seabed. It may also pose occupational health hazards to the workers living in the offshore platforms. It is therefore important to model the transport and deposition of drilling mud and rock cuttings in the sea to enable proper assessment of their adverse impacts on the environment and the workers. Further, accumulation of drill particles on the seabed may impede proper operation of pipelines on the seabed. In this paper, we present an in-house application model TUNA-PT developed to cater to local oil and gas industry needs to simulate the dispersion and mount formation of drill cuttings by offshore oil and gas exploration and production platforms. Using available data on Malaysian coastal waters, simulation analyses project a pile formation on the seabed with a maximum height of about 1 m and pile radius of around 30 to 50 m. Simulated pile heights are not sensitive to the heights of release of the cuttings as the sensitivity has been mitigated by the depth of water.

  1. Engram Formation in Psychiatric Disorders

    Directory of Open Access Journals (Sweden)

    Peter J. Gebicke-Haerter

    2014-05-01

    Full Text Available Environmental factors substantially influence beginning and progression of mental illness, reinforcing or reducing the consequences of genetic vulnerability. Often initiated by early traumatic events, engrams or memories are formed that may give rise to a slow and subtle progression of psychiatric disorders. The large delay between beginning and time of onset (diagnosis may be explained by efficient compensatory mechanisms observed in brain metabolism that use optional pathways in highly redundant molecular interactions.To this end, research has to deal with mechanisms of learning and long-term memory formation, which involves a epigenetic changes, b altered neuronal activities and c changes in neuron-glia communication. On the epigenetic level, apparently DNA-methylations are more stable than histone modifications, although both closely interact. Neuronal activities basically deliver digital information, which clearly can serve as basis for memory formation (LTP. However, research in this respect has long time neglected the importance of glia. They are more actively involved in the control of neuronal activities than thought before. They can both reinforce and inhibit neuronal activities by transducing neuronal information from frequency-encoded to amplitude and frequency-modulated calcium wave patterns spreading in the glial syncytium by use of gap junctions. In this way, they serve integrative functions. In conclusion, we are dealing with two concepts of encoding information that mutually control each other and synergize: a digital (neuronal and a wave-like (glial computing, forming neuron-glia functional units with inbuilt feedback loops to maintain balance of excitation and inhibition. To better understand mental illness, we have to gain more insight into the dynamics of adverse environmental impact on those cellular and molecular systems. This report summarizes existing knowledge and draws some outline about further research in molecular

  2. Biomineralization: mineral formation by organisms

    Science.gov (United States)

    Addadi, Lia; Weiner, Steve

    2014-09-01

    Organisms form many different types of minerals, with diverse shapes and sizes. These minerals fulfill a variety of functions. Inspired by the late H A Lowenstam, Steve Weiner and Lia Addadi have addressed many questions that relate to the mechanisms by which biological organisms produce these mineral phases and how their structures relate to their functions. Addadi and Weiner have explored the manner in which macromolecules extracted from mineralized tissues can interact with some crystal planes and not others, how these macromolecules can be occluded inside the forming crystals residing preferentially on specific crystal planes, and how they can induce one polymorph of calcium carbonate and not another to nucleate. Addadi and Weiner have also identified a novel strategy used by the sea urchin to form its smooth and convoluted mineralized skeletal elements. The strategy involves the initial production by cells of a highly disordered mineral precursor phase in vesicles, and then the export of this so-called amorphous phase to the site of skeletal formation, where it crystallizes. This strategy is now known to be used by many different invertebrate phyla, as well as by vertebrates to build bones and teeth. One of the major current research aims of the Weiner--Addadi group is to understand the biomineralization pathways whereby ions are extracted from the environment, are transported and deposited inside cells within vesicles, how these disordered phases are then transferred to the site of skeletal formation, and finally how the so-called amorphous phase crystallizes. Biology has clearly evolved unique strategies for forming crystalline minerals. Despite more than 300 years of research in this field, many challenging questions still remain unanswered.

  3. Formation and Evolution of Protoatmospheres

    Science.gov (United States)

    Massol, H.; Hamano, K.; Tian, F.; Ikoma, M.; Abe, Y.; Chassefière, E.; Davaille, A.; Genda, H.; Güdel, M.; Hori, Y.; Leblanc, F.; Marcq, E.; Sarda, P.; Shematovich, V. I.; Stökl, A.; Lammer, H.

    2016-09-01

    The origin and evolution of planetary protoatmospheres in relation to the protoplanetary disk is discussed. The initial atmospheres of planets can mainly be related via two formation scenarios. If a protoplanetary core accretes mass and grows inside the gas disk, it can capture H2, He and other gases from the disk. When the gas of the disk evaporates, the core that is surrounded by the H2/He gas envelope is exposed to the high X-ray and extreme ultraviolet flux and stellar wind of the young host star. This period can be considered as the onset of atmospheric escape. It is shown that lower mass bodies accrete less gas and depending on the host stars radiation environment can therefore lose the gaseous envelope after tens or hundreds of million years. Massive cores may never get rid of their captured hydrogen envelopes and remain as sub-Neptunes, Neptunes or gas giants for their whole life time. Terrestrial planets which may have lost the captured gas envelope by thermal atmospheric escape, or which accreted after the protoplanetary nebula vanished will produce catastrophically outgassed steam atmospheres during the magma ocean solidification process. These steam atmospheres consist mainly of water and CO2 that was incorporated into the protoplanet during its accretion. Planets, which are formed in the habitable zone, solidify within several million years. In such cases the outgassed steam atmospheres cool fast, which leads to the condensation of water and the formation of liquid oceans. On the other hand, magma oceans are sustained for longer if planets form inside a critical distance, even if they outgassed a larger initial amount of water. In such cases the steam atmosphere could remain 100 million years or for even longer. Hydrodynamic atmospheric escape will then desiccate these planets during the slow solidification process.

  4. Format SPARQL Query Results into HTML Report

    Directory of Open Access Journals (Sweden)

    Dr Sunitha Abburu

    2013-07-01

    Full Text Available SPARQL is one of the powerful query language for querying semantic data. It is recognized by the W3C as a query language for RDF. As an efficient query language for RDF, it has defined several query result formats such as CSV, TSV and XML etc. These formats are not attractive, understandable and readable. The results need to be converted in an appropriate format so that user can easily understand. The above formats require additional transformations or tool support to represent the query result in user readable format. The main aim of this paper is to propose a method to build HTML report dynamically for SPARQL query results. This enables SPARQL query result display, in HTML report format easily, in an attractive understandable format without the support of any additional or external tools or transformation.

  5. Improving the Formatting Tools of CDS Invenio

    CERN Document Server

    Caffaro, J; Pu Faltings, Pearl

    2006-01-01

    CDS Invenio is the web-based integrated digital library system developed at CERN. It is a strategical tool that supports the archival and open dissemination of documents produced by CERN researchers. This paper reports on my Master’s thesis work done on BibFormat, a module in CDS Invenio, which formats documents metadata. The goal of this project was to implement a completely new formatting module for CDS Invenio. In this report a strong emphasis is put on the user-centered design of the new BibFormat. The bibliographic formatting process and its requirements are discussed. The task analysis and its resulting interaction model are detailed. The document also shows the implemented user interface of BibFormat and gives the results of the user evaluation of this interface. Finally the results of a small usability study of the formats included in CDS Invenio are discussed.

  6. Formation Flying for Distributed InSAR

    Science.gov (United States)

    Scharf, Daniel P.; Murray, Emmanuell A.; Ploen, Scott R.; Gromov, Konstantin G.; Chen, Curtis W.

    2006-01-01

    We consider two spacecraft flying in formation to create interferometric synthetic aperture radar (InSAR). Several candidate orbits for such in InSar formation have been previously determined based on radar performance and Keplerian orbital dynamics. However, with out active control, disturbance-induced drift can degrade radar performance and (in the worst case) cause a collision. This study evaluates the feasibility of operating the InSAR spacecraft as a formation, that is, with inner-spacecraft sensing and control. We describe the candidate InSAR orbits, design formation guidance and control architectures and algorithms, and report the (Delta)(nu) and control acceleration requirements for the candidate orbits for several tracking performance levels. As part of determining formation requirements, a formation guidance algorithm called Command Virtual Structure is introduced that can reduce the (Delta)(nu) requirements compared to standard Leader/Follower formation approaches.

  7. Fibril formation from pea protein and subsequent gel formation.

    Science.gov (United States)

    Munialo, Claire Darizu; Martin, Anneke H; van der Linden, Erik; de Jongh, Harmen H J

    2014-03-19

    The objective of this study was to characterize fibrillar aggregates made using pea proteins, to assemble formed fibrils into protein-based gels, and to study the rheological behavior of these gels. Micrometer-long fibrillar aggregates were observed after pea protein solutions had been heated for 20 h at pH 2.0. Following heating of pea proteins, it was observed that all of the proteins were hydrolyzed into peptides and that 50% of these peptides were assembled into fibrils. Changes on a structural level in pea proteins were studied using circular dichroism, transmission electron microscopy, and particle size analysis. During the fibril assembly process, an increase in aggregate size was observed, which coincided with an increase in thioflavin T binding, indicating the presence of β-sheet aggregates. Fibrils made using pea proteins were more branched and curly. Gel formation of preformed fibrils was induced by slow acidification from pH 7.0 to a final pH of around pH 5.0. The ability of pea protein-based fibrillar gels to fracture during an amplitude sweep was comparable to those of soy protein and whey protein-based fibrillar gels, although gels prepared from fibrils made using pea protein and soy protein were weaker than those of whey protein. The findings show that fibrils can be prepared from pea protein, which can be incorporated into protein-based fibrillar gels.

  8. Magnetic Assisted Colloidal Pattern Formation

    Science.gov (United States)

    Yang, Ye

    Pattern formation is a mysterious phenomenon occurring at all scales in nature. The beauty of the resulting structures and myriad of resulting properties occurring in naturally forming patterns have attracted great interest from scientists and engineers. One of the most convenient experimental models for studying pattern formation are colloidal particle suspensions, which can be used both to explore condensed matter phenomena and as a powerful fabrication technique for forming advanced materials. In my thesis, I have focused on the study of colloidal patterns, which can be conveniently tracked in an optical microscope yet can also be thermally equilibrated on experimentally relevant time scales, allowing for ground states and transitions between them to be studied with optical tracking algorithms. In particular, I have focused on systems that spontaneously organize due to particle-surface and particle-particle interactions, paying close attention to systems that can be dynamically adjusted with an externally applied magnetic or acoustic field. In the early stages of my doctoral studies, I developed a magnetic field manipulation technique to quantify the adhesion force between particles and surfaces. This manipulation technique is based on the magnetic dipolar interactions between colloidal particles and their "image dipoles" that appear within planar substrate. Since the particles interact with their own images, this system enables massively parallel surface force measurements (>100 measurements) in a single experiment, and allows statistical properties of particle-surface adhesion energies to be extracted as a function of loading rate. With this approach, I was able to probe sub-picoNewton surface interactions between colloidal particles and several substrates at the lowest force loading rates ever achieved. In the later stages of my doctoral studies, I focused on studying patterns formed from particle-particle interaction, which serve as an experimental model of

  9. Cataract formation following vitreoretinal procedures

    Directory of Open Access Journals (Sweden)

    Feng H

    2014-09-01

    Full Text Available Hao Feng, Ron A Adelman Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, CT, USA Purpose: To evaluate the incidence and prevalence of cataract formation, progression, and extraction in patients that underwent vitreoretinal procedures and to evaluate factors that can potentially predispose patients to postoperative cataracts.Materials and methods: The medical records of consecutive patients who underwent vitreoretinal surgery at the Yale Eye Center with at least 6 months of follow-up and no prior intraocular surgery were obtained. Preoperative, intraoperative, and postoperative data were recorded and analyzed in this retrospective observational study. The main outcome measures were defined as cataract extraction, formation, and progression after vitreoretinal procedures. The lens status of the surgical eye was recorded preoperatively and at 1 month, 3 months, 6 months, 12 months, 24 months, and 36 months postoperatively.Results: A total of 193 eyes of 180 patients fulfilled the inclusion criteria. The percentages of eyes with mild lens change were 96% after 20-gauge pars plana vitrectomy (PPV, 72% after small gauge (23- and 25-gauge PPV, 38% after scleral buckle (SB, 38% after pneumatic retinopexy (PR, and 91% after PPV plus SB (PPV+SB. Posterior subcapsular and nuclear sclerotic cataracts were the most common with almost all developing within 24 months. There was no statistically significant difference (P=1.00 between the rate of cataract extraction after 20-gauge (41% and small gauge PPV (42%, but there was a statistically significant difference between PPV and non-PPV (SB, 6%; PR, 7%; P<0.001 and PPV and PPV+SB groups (69%; P=0.0063.Conclusion: Cataracts were common following PPV regardless of the gauge. SB and PR led to the lowest while PPV+SB led to the highest risk of postoperative cataracts. Keywords: cataracts, vitreoretinal surgery, vitrectomy, scleral buckle, pneumatic retinopexy

  10. Pattern Formation and Complexity Emergence

    Science.gov (United States)

    Berezin, Alexander A.

    2001-03-01

    Success of nonlinear modelling of pattern formation and self-organization encourages speculations on informational and number theoretical foundations of complexity emergence. Pythagorean "unreasonable effectiveness of integers" in natural processes is perhaps extrapolatable even to universal emergence "out-of-nothing" (Leibniz, Wheeler). Because rational numbers (R = M/N) are everywhere dense on real axis, any digital string (hence any "book" from "Library of Babel" of J.L.Borges) is "recorded" infinitely many times in arbitrary many rationals. Furthermore, within any arbitrary small interval there are infinitely many Rs for which (either or both) integers (Ms and Ns) "carry" any given string of any given length. Because any iterational process (such as generation of fractal features of Mandelbrot Set) is arbitrary closely approximatable with rational numbers, the infinite pattern of integers expresses itself in generation of complexity of the world, as well as in emergence of the world itself. This "tunnelling" from Platonic World ("Platonia" of J.Barbour) to a real (physical) world is modern recast of Leibniz's motto ("for deriving all from nothing there suffices a single principle").

  11. Collagen fibril formation during development

    International Nuclear Information System (INIS)

    Studies with embryonic skin and bone suggested that the aminopropeptide (AP) and carboxylpropeptide (CP) of type I pro-callagen (pro-col) play a role in fibril formation. Chick leg metatarsal tendons were studied by electron microscopy. AP and CP of type I pro-col were purified from chick leg tendons; antibodies developed in rabbits and purity tested by radioimmunoassays. Antibodies were used for immunofluorescence microscopy (IFM) and immunoblotting (IB). The peritendineum, consisting of thin 20-30 nm fibrils, revealed the AP of type I and type III procol. In the tendon area, collagen fibrils were arranged within small compartments and were of uniform diameter at 10d, 14d and 18d. However, beyond 21d, there was confluency of the compartments and a wide range of fibril diameters. IFM revealed fine streaks of collagen, staining with the AP of type I throughout the tendon. The CP was mainly intracellular with only a small amount present in the extracellular space. IB revealed procollagen, pN-collagen (AP+collagen) and pC-collagen, (CP+collagen) at all stages of development. Ratios of pN/pC collagen, determined by spectrophotometric scanning of autoradiographs, correlated well with the distribution of fibril diameter. This study suggests the hypothesis that AP initiates fibrillogenesis while CP may regulate additional fibril growth

  12. Fertilization and early seed formation.

    Science.gov (United States)

    Dumas, Christian; Rogowsky, Peter

    2008-10-01

    The double fertilization of flowering plants is a complex process, encompassing multiple steps. From its discovery more than a century ago, many useful descriptive approaches have been employed to better unveil specific steps/mechanisms. More recently, the development of an in vitro assay developed in our laboratory, has allowed a better understanding of this phenomenon. However, in vitro methods may show some limitations. The search for complementary strategies, especially with the search of mutants affected in the fertilization step allowed one to elucidate this critical and unique phenomenon in living organisms. Genes involved in pollen tube guidance or pollen discharge in synergids have been identified, as well as genes exhibiting differential expression in sperm, egg and central cells before and after fertilization. A calcium wave proved to correspond to the first cellular event seen after cytoplasmic fusion in the fertilized egg cell or zygote, which develops into a multi-cellular organism with an elaborate body plan. The development of the fertilized central cell into a nourishing tissue (endosperm) starts with the formation of the coenocyte, a multinuclear single cell unique in the plant kingdom, cellularization occurring later on. The balance of the paternal and maternal genomes, which is under the control of the FIS polycomb group complex, was found to be of the utmost importance for the successful development of the seed.

  13. New Office Software course format!

    CERN Multimedia

    HR Department

    Always keen to anticipate your  training needs, the Technical Training service is pleased to propose two new Office Software course formats: “Focus on... ”:  On a monthly basis we will propose a theme such as “Sharepoint Collaboration Workspace” or “Word 2007” or “charts”, etc.  You will be invited to send us in advance your questions regarding the proposed topic and register  for the course through our Training Catalogue. During the session, our trainer will answer all the questions received and participants will increase their knowledge thanks to the solutions discussed for everyone. The course will last two hours, from 9-00 to 11-00 a.m. - with open questions on the proposed topic at the end.   “Office software Individual coaching”: If one or more specific topics are causing you sleepless nights, you can get the help of our trainer who will ...

  14. New Office Software course format!

    CERN Multimedia

    HR Department

    2009-01-01

    Always keen to anticipate your  training needs, the Technical Training service is pleased to propose two new Office Software course formats: “Focus on... ”:  On a monthly basis we will propose a theme such as “Sharepoint Collaboration Workspace” or “Word 2007” or “charts”, etc.  You will be invited to send us in advance your questions regarding the proposed topic and register  for the course through our Training Catalogue. During the session, our trainer will answer all the questions received and participants will increase their knowledge thanks to the solutions discussed for everyone. The course will last two hours, from 9-00 to 11-00 a.m. - with open questions on the proposed topic at the end.   “Office software Individual coaching”: If one or more specific topics are causing you sleepless nights, you can get the help of our trainer who will ...

  15. STAR FORMATION IN DENSE CLUSTERS

    International Nuclear Information System (INIS)

    A model of core-clump accretion with equally likely stopping describes star formation in the dense parts of clusters, where models of isolated collapsing cores may not apply. Each core accretes at a constant rate onto its protostar, while the surrounding clump gas accretes as a power of protostar mass. Short accretion flows resemble Shu accretion and make low-mass stars. Long flows resemble reduced Bondi accretion and make massive stars. Accretion stops due to environmental processes of dynamical ejection, gravitational competition, and gas dispersal by stellar feedback, independent of initial core structure. The model matches the field star initial mass function (IMF) from 0.01 to more than 10 solar masses. The core accretion rate and the mean accretion duration set the peak of the IMF, independent of the local Jeans mass. Massive protostars require the longest accretion durations, up to 0.5 Myr. The maximum protostar luminosity in a cluster indicates the mass and age of its oldest protostar. The distribution of protostar luminosities matches those in active star-forming regions if protostars have a constant birthrate but not if their births are coeval. For constant birthrate, the ratio of young stellar objects to protostars indicates the star-forming age of a cluster, typically ∼1 Myr. The protostar accretion luminosity is typically less than its steady spherical value by a factor of ∼2, consistent with models of episodic disk accretion.

  16. Dark Energy and Structure Formation

    International Nuclear Information System (INIS)

    We study the gravitational dynamics of dark energy configurations. We report on the time evolution of the dark energy field configurations as well as the time evolution of the energy density to demonstrate the gravitational collapse of dark energy field configurations. We live in a Universe which is dominated by Dark Energy. According to current estimates about 75% of the Energy Density is in the form of Dark Energy. Thus when we consider gravitational dynamics and Structure Formation we expect Dark Energy to play an important role. The most promising candidate for dark energy is the energy density of fields in curved space-time. It therefore become a pressing need to understand the gravitational dynamics of dark energy field configurations. We develop and describe the formalism to study the gravitational collapse of fields given any general potential for the fields. We apply this formalism to models of dark energy motivated by particle physics considerations. We solve the resulting evolution equations which determine the time evolution of field configurations as well as the dynamics of space-time. Our results show that gravitational collapse of dark energy field configurations occurs and must be considered in any complete picture of our universe.

  17. Dark Energy and Structure Formation

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Anupam, E-mail: morisi@ific.uv.es [Physics Department, L.N. Mittal I.I.T, Jaipur, Rajasthan (India)

    2010-11-01

    We study the gravitational dynamics of dark energy configurations. We report on the time evolution of the dark energy field configurations as well as the time evolution of the energy density to demonstrate the gravitational collapse of dark energy field configurations. We live in a Universe which is dominated by Dark Energy. According to current estimates about 75% of the Energy Density is in the form of Dark Energy. Thus when we consider gravitational dynamics and Structure Formation we expect Dark Energy to play an important role. The most promising candidate for dark energy is the energy density of fields in curved space-time. It therefore become a pressing need to understand the gravitational dynamics of dark energy field configurations. We develop and describe the formalism to study the gravitational collapse of fields given any general potential for the fields. We apply this formalism to models of dark energy motivated by particle physics considerations. We solve the resulting evolution equations which determine the time evolution of field configurations as well as the dynamics of space-time. Our results show that gravitational collapse of dark energy field configurations occurs and must be considered in any complete picture of our universe.

  18. Pattern formation in centrosome assembly.

    Science.gov (United States)

    Mahen, Robert; Venkitaraman, Ashok R

    2012-02-01

    A striking but poorly explained feature of cell division is the ability to assemble and maintain organelles not bounded by membranes, from freely diffusing components in the cytosol. This process is driven by information transfer across biological scales such that interactions at the molecular scale allow pattern formation at the scale of the organelle. One important example of such an organelle is the centrosome, which is the main microtubule organising centre in the cell. Centrosomes consist of two centrioles surrounded by a cloud of proteins termed the pericentriolar material (PCM). Profound structural and proteomic transitions occur in the centrosome during specific cell cycle stages, underlying events such as centrosome maturation during mitosis, in which the PCM increases in size and microtubule nucleating capacity. Here we use recent insights into the spatio-temporal behaviour of key regulators of centrosomal maturation, including Polo-like kinase 1, CDK5RAP2 and Aurora-A, to propose a model for the assembly and maintenance of the PCM through the mobility and local interactions of its constituent proteins. We argue that PCM structure emerges as a pattern from decentralised self-organisation through a reaction-diffusion mechanism, with or without an underlying template, rather than being assembled from a central structural template alone. Self-organisation of this kind may have broad implications for the maintenance of mitotic structures, which, like the centrosome, exist stably as supramolecular assemblies on the micron scale, based on molecular interactions at the nanometer scale. PMID:22245706

  19. Clumpy Disc and Bulge Formation

    CERN Document Server

    Perez, J; Tissera, P; Michel-Dansac, L

    2013-01-01

    We present a set of hydrodynamical/Nbody controlled simulations of isolated gas rich galaxies that self-consistently include SN feedback and a detailed chemical evolution model, both tested in cosmological simulations. The initial conditions are motivated by the observed star forming galaxies at z ~ 2-3. We find that the presence of a multiphase interstellar media in our models promotes the growth of disc instability favouring the formation of clumps which in general, are not easily disrupted on timescales compared to the migration time. We show that stellar clumps migrate towards the central region and contribute to form a classical-like bulge with a Sersic index, n > 2. Our physically-motivated Supernova feedback has a mild influence on clump survival and evolution, partially limiting the mass growth of clumps as the energy released per Supernova event is increased, with the consequent flattening of the bulge profile. This regulation does not prevent the building of a classical-like bulge even for the most ...

  20. Rowing sportswomen motor actions formation

    Directory of Open Access Journals (Sweden)

    Volodymyr Bogush

    2015-08-01

    Full Text Available Purpose: to study the formation of motor action sportswomen different ages depending on the level of sportsmanship. Material and Methods: girls which are specialized in a boat-racing in age groups 13–14 years inspected, 15–16 years, 17–18 years, in every group was for 20–25 persons, in all 72 sportswomen. Motive actions were probed on the method of measuring of training effect developed by us an action, and also the functional state was determined by methods: measuring of sensorimotor reaction is on sound and light irritants, speed of current of air, exactness of implementation of the set muscular effort. Results: testing showed the dynamics of forming motive, namely technique of mastering of receptions and actions, reliability, presence of errors, efficiency of active voice of consciousness in correct implementation of motion in a biomechanics relation. Conclusions: application of this method in the process of sporting preparation will allow to define quality of mastering of technique of the proper motive actions, forming of abilities, subsequent learning and becoming of more difficult motive skills

  1. Testing Models for Structure Formation

    CERN Document Server

    Kaiser, N

    1993-01-01

    I review a number of tests of theories for structure formation. Large-scale flows and IRAS galaxies indicate a high density parameter $\\Omega \\simeq 1$, in accord with inflationary predictions, but it is not clear how this meshes with the uniformly low values obtained from virial analysis on scales $\\sim$ 1Mpc. Gravitational distortion of faint galaxies behind clusters allows one to construct maps of the mass surface density, and this should shed some light on the large vs small-scale $\\Omega$ discrepancy. Power spectrum analysis reveals too red a spectrum (compared to standard CDM) on scales $\\lambda \\sim 10-100$ $h^{-1}$Mpc, but the gaussian fluctuation hypothesis appears to be in good shape. These results suggest that the problem for CDM lies not in the very early universe --- the inflationary predictions of $\\Omega = 1$ and gaussianity both seem to be OK; furthermore, the COBE result severely restricts modifications such as tilting the primordial spectrum --- but in the assumed matter content. The power s...

  2. Autonomous Formations of Multi-Agent Systems

    Science.gov (United States)

    Dhali, Sanjana; Joshi, Suresh M.

    2013-01-01

    Autonomous formation control of multi-agent dynamic systems has a number of applications that include ground-based and aerial robots and satellite formations. For air vehicles, formation flight ("flocking") has the potential to significantly increase airspace utilization as well as fuel efficiency. This presentation addresses two main problems in multi-agent formations: optimal role assignment to minimize the total cost (e.g., combined distance traveled by all agents); and maintaining formation geometry during flock motion. The Kuhn-Munkres ("Hungarian") algorithm is used for optimal assignment, and consensus-based leader-follower type control architecture is used to maintain formation shape despite the leader s independent movements. The methods are demonstrated by animated simulations.

  3. Giant Planet Formation, Evolution, and Internal Structure

    CERN Document Server

    Helled, Ravit; Podolak, Morris; Boley, Aaron; Meru, Farzana; Nayakshin, Sergei; Fortney, Jonathan J; Mayer, Lucio; Alibert, Yann; Boss, Alan P

    2013-01-01

    The large number of detected giant exoplanets offers the opportunity to improve our understanding of the formation mechanism, evolution, and interior structure of gas giant planets. The two main models for giant planet formation are core accretion and disk instability. There are substantial differences between these formation models, including formation timescale, favorable formation location, ideal disk properties for planetary formation, early evolution, planetary composition, etc. First, we summarize the two models including their substantial differences, advantages, and disadvantages, and suggest how theoretical models should be connected to available (and future) data. We next summarize current knowledge of the internal structures of solar- and extrasolar- giant planets. Finally, we suggest the next steps to be taken in giant planet exploration.

  4. Stereoregularity Drives Precipitation in Polyelectrolyte Complex Formation

    Science.gov (United States)

    Tirrell, Matthew; Perry, Sarah; Leon, Lorraine; Kade, Matthew; Priftis, Dimitris; Black, Katie; Hoffman, Kyle; Whitmer, Jonathan; Qin, Jian; de Pablo, Juan

    2014-03-01

    This study investigates the effect of stereoregularity on the formation of polypeptide-based complex formation and assembly into micelles, hydrogels and ordered phases. We demonstrate that fluid complex coacervate formation (rather than solid complex precipitation) between oppositely charged polypeptides requires at least one racemic partner in order to disrupt backbone hydrogen bonding networks and prevent the hydrophobic collapse of the polymers into compact, fibrillar secondary structures. Computer simulations bear this out and enable visualization of the molecular structure of the complexes. The ability to choose between conditions of fluid phase formation and solid phase formation is a useful tool in developing new self-assembled materials based on polyelectrolyte complex formation. Support from the Argonne National Laboratory Laboratory Research and Development Program (2011-217) is gratefully acknowledged.

  5. Formation temperatures of thermogenic and biogenic methane

    Science.gov (United States)

    Stolper, D.A.; Lawson, M.; Davis, C.L.; Ferreira, A.A.; Santos Neto, E. V.; Ellis, G.S.; Lewan, M.D.; Martini, A.M.; Tang, Y.; Schoell, M.; Sessions, A.L.; Eiler, J.M.

    2014-01-01

    Methane is an important greenhouse gas and energy resource generated dominantly by methanogens at low temperatures and through the breakdown of organic molecules at high temperatures. However, methane-formation temperatures in nature are often poorly constrained. We measured formation temperatures of thermogenic and biogenic methane using a “clumped isotope” technique. Thermogenic gases yield formation temperatures between 157° and 221°C, within the nominal gas window, and biogenic gases yield formation temperatures consistent with their comparatively lower-temperature formational environments (<50°C). In systems where gases have migrated and other proxies for gas-generation temperature yield ambiguous results, methane clumped-isotope temperatures distinguish among and allow for independent tests of possible gas-formation models.

  6. Molecular hydrogen formation in the interstellar medium

    CERN Document Server

    Cazaux, S

    2002-01-01

    We have developed a model for molecular hydrogen formation under astrophysically relevant conditions. This model takes fully into account the presence of both physisorbed and chemisorbed sites on the surface, allows quantum mechanical diffusion as well as thermal hopping for absorbed H-atoms, and has been benchmarked versus recent laboratory experiments on H2 formation on silicate surfaces. The results show that H2 formation on grain surface is efficient in the interstellar medium up to some 300K. At low temperatures (<100K), H2 formation is governed by the reaction of a physisorbed H with a chemisorbed H. At higher temperatures, H2 formation proceeds through reaction between two chemisorbed H atoms. We present simple analytical expressions for H2 formation which can be adopted to a wide variety of surfaces once their surfaces characteristics have been determined experimentally.

  7. Black-hole formation from stellar collapse

    International Nuclear Information System (INIS)

    I review the end-state of massive stellar evolution, following the evolution of these massive stars from the onset of collapse through the formation of a compact remnant and the possible supernova or hypernova explosion. In particular, I concentrate on the formation of black holes from stellar collapse: the fraction of stars that form black holes, the black-hole mass distribution and the velocities these black-hole remnants may receive during their formation process

  8. Models of formation of lignin polymer

    OpenAIRE

    Gričar, Jožica; Oven, Primož; Čufar, Katarina

    2005-01-01

    In paper, two models of formation of lignin macromolecule are described. Random coupling model suggests lignin formation process through coupling of monomer radicals to growing lignin polymer in a near-random fashion. According to the dirigent protein model, process of lignin polymerization is fully controlled by specific dirigent proteins that direct formation of individual bonds. Critical judgements and scientific opinions of both models are given.

  9. Education, values and union formation in Sweden

    OpenAIRE

    Thomson, Elizabeth; Bernhardt, Eva

    2007-01-01

    Education provides opportunities for as well as barriers and alternatives to the formation of intimate unions. In this study, we consider the several mechanisms through which educational attainment may delay or speed up union formation. As do most other studies, we include both educational enrolment and attainment, the former viewed as a constraint on union formation, the latter facilitating the accumulation of resources that enable young couples to establish their own household. A third comp...

  10. Massive Star Formation : the Role of Disks

    OpenAIRE

    Fallscheer, Cassandra

    2010-01-01

    In this thesis, I study three different evolutionary stages of the massive star formation process looking for supporting evidence for an accretion-based formation scenario of massive stars. The first source studied, the Infrared Dark Cloud IRDC 18223-3, is at one of the earliest observable phases of massive star formation. This source is characterized by a cone-shaped molecular outflow component which is used to establish the outflow orientation. A velocity gradient traced by the molecule ...

  11. Control of star formation by supersonic turbulence

    OpenAIRE

    Mac Low, Mordecai-Mark; Klessen, Ralf S.

    2003-01-01

    Understanding the formation of stars in galaxies is central to much of modern astrophysics. For several decades it has been thought that stellar birth is primarily controlled by the interplay between gravity and magnetostatic support, modulated by ambipolar diffusion. Recently, however, both observational and numerical work has begun to suggest that support by supersonic turbulence rather than magnetic fields controls star formation. In this review we outline a new theory of star formation re...

  12. Formation temperatures of thermogenic and biogenic methane

    OpenAIRE

    Stolper, D. A.; Lawson, M.; Davis, C. L.; Ferreira, A. A.; Santos Neto, E. V.; Ellis, G.S.; Lewan, M.D.; Martini, A. M.; Tang, Y.; Schoell, M.; Sessions, A.L.; Eiler, J. M.

    2014-01-01

    Methane is an important greenhouse gas and energy resource generated dominantly by methanogens at low temperatures and through the breakdown of organic molecules at high temperatures. However, methane-formation temperatures in nature are often poorly constrained. We measured formation temperatures of thermogenic and biogenic methane using a “clumped isotope” technique. Thermogenic gases yield formation temperatures between 157° and 221°C, within the nominal gas window, and biogenic gases yiel...

  13. Entanglement of Formation for Quantum States

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hui; WANG Zhi-Xi

    2007-01-01

    We investigate the entanglement of formation for a class of high-dimensional quantum mixed states. We present a kind of generalized concurrence for a class of high-dimensional quantum pure states such that the entanglement of formation is a monotonically increasing convex function of the generalized concurrence. From the monotonicity and convexity the entanglement of formation for a class of high-dimensional mixed states has been calculated analytically.

  14. COOPERATIVE TEAM FORMATION USING DISTRIBUTED DECOMPOSITION KNOWLEDGE

    OpenAIRE

    Carpenter, Martin Richard John

    2010-01-01

    Cooperative team formation using distributed decomposition knowledgeA thesis submitted in August 2010 by Martin Carpenter to the University ofManchester for the degree of Doctor of Philosophy. In recent years, the problem of automating the formation of Virtual Organisations (VO) has risen to prominence. Work in this area has typically considered the process of VO formation to be a centralised process driven by a company with responsibility for the business opportunity.Such systems use two mai...

  15. Precursors of Young Women's Family Formation Pathways

    OpenAIRE

    Amato, Paul R.; Landale, Nancy S.; Havasevich, Tara C.; Booth, Alan; Eggebeen, David J.; Schoen, Robert; McHale, Susan M.

    2008-01-01

    We used latent class analysis to create family formation pathways for women between the ages of 18 and 23. Input variables included cohabitation, marriage, parenthood, full-time employment, and attending school. Data (n = 2,290) came from Waves I and III of the National Longitudinal Study of Adolescent Health (Add Health). The analysis revealed seven latent pathways: college-no family formation (29%), high school-no family formation (19%), cohabitation without children (15%), married mothers ...

  16. Complications and mortality following stoma formation.

    OpenAIRE

    Harris, D. A.; Egbeare, D.; Jones, S; Benjamin, H; Woodward, A; Foster, M E

    2005-01-01

    INTRODUCTION: As stoma formation is thought to be declining, we performed a study to evaluate the rate of stoma formation and the impact on stoma complication rates, together with risk factors for complications. PATIENTS AND METHODS: Stoma incidence, individual complications and mortality rates were retrieved from a stoma nurse database of 345 stomas created over an 8-year period. RESULTS: Stoma formation increased over the study period, although the incidence of complications declined. Stoma...

  17. New Particle Formation Study Final Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Smith, JN; McMurry, PH [University of Minnesota

    2015-01-01

    The scientific foci of the New Particle Formation Study were the formation and evolution of atmospheric aerosols and the impacts of newly formed particles on cloud processes. Specifically, we planned to: (1) to identify the species and mechanisms responsible for the initial steps of new particle formation, i.e., the formation of thermodynamically stable clusters; (2) investigate the role of acid-base chemistry in new particle growth through measurements of ammonia and amines as well as organic and inorganic acids in both atmospheric nanoparticles and the gas phase; (3) investigate the contribution of other surface area or volume-controlled processes to nanoparticle formation and growth; (4) create a comprehensive dataset related to new particle formation and growth that can be used as input for our own thermodynamic models as well as the modeling efforts by our Department of Energy (DOE) Aerosol Life Cycle working group collaborators; (5) characterize the increase of the number and activity of cloud condensation nuclei (CCN) due to particle formation and growth; (6) determine the regional extent of new particle formation to address the role that atmospheric transport plays in determining the impacts, if any, of new particle formation on cloud number and properties.

  18. Cellular chain formation in Escherichia coli biofilms

    DEFF Research Database (Denmark)

    Vejborg, Rebecca Munk; Klemm, Per

    2009-01-01

    In this study we report on a novel structural phenotype in Escherichia coli biofilms: cellular chain formation. Biofilm chaining in E. coli K-12 was found to occur primarily by clonal expansion, but was not due to filamentous growth. Rather, chain formation was the result of intercellular......; type I fimbriae expression significantly reduced cellular chain formation, presumably by steric hindrance. Cellular chain formation did not appear to be specific to E coli K-12. Although many urinary tract infection (UTI) isolates were found to form rather homogeneous, flat biofilms, three isolates...

  19. Antagonistic formation motion of cooperative agents

    Institute of Scientific and Technical Information of China (English)

    卢婉婷; 代明香; 薛方正

    2015-01-01

    This paper investigates a new formation motion problem of a class of first-order multi-agent systems with antagonis-tic interactions. A distributed formation control algorithm is proposed for each agent to realize the antagonistic formation motion. A sufficient condition is derived to ensure that all agents make an antagonistic formation motion in a distributed manner. It is shown that all agents can be spontaneously divided into several groups, and agents in the same group collab-orate while agents in different groups compete. Finally, a numerical simulation is included to demonstrate our theoretical results.

  20. On the Formation of Brown Dwarfs

    CERN Document Server

    Jiang, I G; Lin, D N C; Jiang, Ing-Guey

    2004-01-01

    The observational properties of brown dwarfs pose challenges to the theory of star formation. Because their mass is much smaller than the typical Jeans mass of interstellar clouds, brown dwarfs are most likely formed through secondary fragmentation processes, rather than through the direct collapse of a molecular cloud core. In order to prevent substantial post-formation mass accretion, young brown dwarfs must leave the high density formation regions in which they form. We propose here that brown dwarfs are formed in the circumbinary disks. Through post-formation dynamical interaction with their host binary stars, young brown dwarfs are either scattered to large distance or removed, with modest speed, from their cradles.

  1. Processes and problems in secondary star formation

    International Nuclear Information System (INIS)

    Recent developments relating the conditions in molecular clouds to star formation triggered by a prior stellar generation are reviewed. Primary processes are those that lead to the formation of a first stellar generation. The secondary processes that produce stars in response to effects caused by existing stars are compared and evaluated in terms of the observational data presently available. We discuss the role of turbulence to produce clumpy cloud structures and introduce new work on colliding inter-cloud gas flows leading to non-linear inhomogeneous cloud structures in an intially smooth cloud. This clumpy morphology has important consequences for secondary formation. The triggering processes of supernovae, stellar winds, and H II regions are discussed with emphasis on the consequences for radiation driven implosion as a promising secondary star formation mechanism. Detailed two-dimensional, radiation-hydrodynamic calculations of radiation driven implosion are discussed. This mechanism is shown to be highly efficient in synchronizing the formation of new stars in congruent to 1-3 x 104 years and could account for the recent evidence for new massive star formation in several UCHII regions. It is concluded that, while no single theory adequately explains the variety of star formation observed, a uniform description of star formation is likely to involve several secondary processes. Advances in the theory of star formation will require multiple dimensional calculations of coupled processes. The important non-linear interactions include hydrodynamics, radiation transport, and magnetic fields

  2. Heats of formation of binary semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, V.; Sastry, B.S.R. [Department of Electronics and Instrumentation Indian School of Mines, Dhanbad 826 004 (India)

    2005-03-01

    Heats of formation of tetrahedrally coordinated II-VI and III-V groups of binary semiconductors have been calculated using plasmon energy data. Two simple relations between plasmon energy and heats of formation have been proposed. One is based on spectroscopic model of Phillips and Van Vechten and other is based on the best-fit data of heats of formation. The calculated values of heats of formation from both the equations are compared with the experimental values and the values reported by earlier workers. A fairly good agreement has been obtained between them. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. A Glimpse at Different File Formats

    Science.gov (United States)

    Shortridge, K.

    2015-09-01

    The image display program AAOGlimpse has recently been extended to provide support for files using both HDF5 and NDF/HDS formats. Loosely defined formats present problems. Given an input file, what should be displayed? A FITS file may contain multiple images, and for the more flexible hierarchical formats things are even less clear: which of the many arrays in a structure actually represents the data of interest? Where is the wavelength or other WCS data? With HDF5 files, this becomes quite complex. This paper describes the way AAOGlimpse handles these questions, and emphasises the importance of agreeing conventions for how file formats are used.

  4. Heating systems for heating subsurface formations

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Scott Vinh (Houston, TX); Vinegar, Harold J. (Bellaire, TX)

    2011-04-26

    Methods and systems for heating a subsurface formation are described herein. A heating system for a subsurface formation includes a sealed conduit positioned in an opening in the formation and a heat source. The sealed conduit includes a heat transfer fluid. The heat source provides heat to a portion of the sealed conduit to change phase of the heat transfer fluid from a liquid to a vapor. The vapor in the sealed conduit rises in the sealed conduit, condenses to transfer heat to the formation and returns to the conduit portion as a liquid.

  5. Treating tar sands formations with dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J.; Karanikas, John Michael

    2013-10-15

    A method for treating a karsted formation containing heavy hydrocarbons and dolomite includes providing heat to at least part of one or more karsted layers in the formation from one or more heaters located in the karsted layers. A temperature in at least one of the karsted layers is allowed to reach a decomposition temperature of dolomite in the formation. The dolomite is allowed to decompose and at least some hydrocarbons are produced from at least one of the karsted layers of the formation.

  6. Processes and problems in secondary star formation

    Energy Technology Data Exchange (ETDEWEB)

    Klein, R.I.; Whitaker, R.W.; Sandford M.T. II

    1984-03-01

    Recent developments relating the conditions in molecular clouds to star formation triggered by a prior stellar generation are reviewed. Primary processes are those that lead to the formation of a first stellar generation. The secondary processes that produce stars in response to effects caused by existing stars are compared and evaluated in terms of the observational data presently available. We discuss the role of turbulence to produce clumpy cloud structures and introduce new work on colliding inter-cloud gas flows leading to non-linear inhomogeneous cloud structures in an intially smooth cloud. This clumpy morphology has important consequences for secondary formation. The triggering processes of supernovae, stellar winds, and H II regions are discussed with emphasis on the consequences for radiation driven implosion as a promising secondary star formation mechanism. Detailed two-dimensional, radiation-hydrodynamic calculations of radiation driven implosion are discussed. This mechanism is shown to be highly efficient in synchronizing the formation of new stars in congruent to 1-3 x 10/sup 4/ years and could account for the recent evidence for new massive star formation in several UCHII regions. It is concluded that, while no single theory adequately explains the variety of star formation observed, a uniform description of star formation is likely to involve several secondary processes. Advances in the theory of star formation will require multiple dimensional calculations of coupled processes. The important non-linear interactions include hydrodynamics, radiation transport, and magnetic fields.

  7. Format requirements of thermal neutron scattering data in a nuclear data format to succeed the ENDF format

    Energy Technology Data Exchange (ETDEWEB)

    Brown, D. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2014-03-31

    In November 2012, the Working Party on Evaluation Cooperation Subgroup 38 (WPEC-SG38) began with the task of developing a nuclear data format and supporting infrastructure to replace the now nearly 50 year old ENDF format. The first step in this process is to develop requirements for the new format and infrastructure. In this talk, I will review the status of ENDF's Thermal Scattering Law (TSL) formats as well as support for this data in the GND format (from which the new format is expected to evolve). Finally, I hope to begin a dialog with members of the thermal neutron scattering community so that their data needs can be accurately and easily accommodated by the new format and tools, as captured by the requirements document. During this discussion, we must keep in mind that the new tools and format must; Support what is in existing data files; Support new things we want to put in data files; and Be flexible enough for us to adapt it to future unanticipated challenges.

  8. Film formation from latex blends

    Science.gov (United States)

    Tang, Jiansheng

    2000-10-01

    Film formation from hard/soft (i.e., high Tg/low Tg) latex blends consisting of hard polystyrene (PS) and soft poly(n-butyl methacrylate-co-n-butyl acrylate) [P(BMA/BA)] latex particles were studied with an emphasis on the influence of the carboxyl groups present on the latex particles. A theoretical model was developed to calculate the optimal surfactant and monomer feed rates for a semicontinuous polymerization process to synthesize monodisperse carboxylated latex particles and independently control the particle size and degree of carboxylation. An important finding obtained from the drying studies is that the drying rate from the edge zone is much faster than the rate obtained from the latex pool. It was also found that the presence of carboxyl groups on the latex particles retarded the drying rate. Utilizing PS particles with a low density of carboxyl groups present on the particle surfaces (e.g., 10% surface coverage) resulted in an even distribution of these particles in the soft copolymer matrix, and thus, good film gloss was achieved. However, the use of hard particles with a high density of carboxyl groups present (e.g., 65% coverage) resulted in a less even distribution of PS particles and poor gloss. A cluster model and a hydrogen bonding mechanism were proposed to explain these phenomena. The presence of the carboxyl groups on the PS particles significantly enhanced the Young's modulus and the yield strength, but did not influence the ultimate mechanical properties. A quantitative model was proposed to predict the Young's modus of the latex blend films as a function of the carboxyl group coverage on the hard particles. There was a good fit between model and the experimental data. The stability of the precipitated calcium carbonate (PCC) particles in the P(BMA/BA) latexes was determined by the charge on pigment surface which, in turn, was influenced by the presence of sodium polyacrylate stabilizer. It was found that the wetting ability of the soft

  9. Formation of parting in quartz

    Science.gov (United States)

    Jørgen Kjøll, Hans; Eske Sørensen, Bjørn

    2014-05-01

    and two, possibly three, planar structures; two evident, one more obscure. The most prominent of the three appears to cut across the recrystallization, offsetting the recrystallization textures with varying distances. We propose a very late formation of the parting due to its crosscutting relationship with all features, such as recrystallized quartz, secondary fluid inclusion trails and twins. The parting develops in crystals that are optimally oriented with respect to σ1 in a fast, low temperature deformation event.

  10. Unit Monitors Manchester-Format Data Buses

    Science.gov (United States)

    Amador, Jose J.

    1994-01-01

    Circuit card converts data signals into convenient hexadecimal form for troubleshooting. Bus-monitoring unit converts data signals from Manchester II format used on data bus into hexadecimal format. Monitoring circuit causes hexadecimal words to display on video terminal, where test engineer compares them with hexadecimal records for troubleshooting. Circuit monitors one bus or two buses simultaneously.

  11. Distributed formation control for autonomous robots

    NARCIS (Netherlands)

    Garcia de Marina Peinado, Hector Jesús

    2016-01-01

    This thesis addresses several theoretical and practical problems related to formation-control of autonomous robots. Formation-control aims to simultaneously accomplish the tasks of forming a desired shape by the robots and controlling their coordinated collective motion. This kind of robot performan

  12. Cadmium Modulates Biofilm Formation by Staphylococcus epidermidis

    NARCIS (Netherlands)

    Wu, Xueqing; Santos, Regiane R.; Fink-Gremmels, Johanna

    2015-01-01

    The aim of the study was to evaluate the effect of cadmium exposure on Staphylococcus epidermidis (ATCC 35984) biofilm formation. Bacteria were cultured in the absence or presence of different concentrations (0-50 mu M) of cadmium. Biofilm formation and bacterial viability were assessed. Quantitativ

  13. Nature and nurture in galaxy formation simulations

    NARCIS (Netherlands)

    Haas, Marcel Richard

    2010-01-01

    We study several aspects of the formation of galaxies, using numerical simulations. We investigate the influence of about thirty different sub-grid physics recipes for cooling, star formation, supernova feedback, AGN feedback etc. on the resulting galaxy populations with large SPH simulations. We in

  14. Formation of communication skills of aviation specialists

    OpenAIRE

    Коваленко, Ольга Олександрівна

    2012-01-01

    Culture of the professional communication is the basis of the professional activity. It is spoken about the process of formation of the professional communication culture, where communication, professionalism of the communication are foundation of it in personal oriented studying by means of creative technologies; examined about peculiarities, and defined conditions of formation of professional oral skills culture of future aviation specialists.

  15. Star formation history in forming dwarf galaxies

    Science.gov (United States)

    Berczik, P.; Kravchuk, S. G.

    The processes of formation and evolution of isolated dwarf galaxies over the Hubble timescale is followed by means of SPH techniques. As an initial protogalaxy perturbation we consider an isolated, uniform, solid -- body rotated sphere involved into the Hubble flow and made of dark and baryonic matter in a 10:1 ratio. The simulations are carried out for the set of models having spin parameters lambda in the range from 0.01 to 0.08 and the total mass of dark matter 1011 M_odot . Our model includes gasdynamics, radiative processes, star formation, supernova feedback and simplified chemistry. The application of modified star formation criterion which accounts for chaotic motions and the time lag between initial development of suitable conditions for star formation and star formation itself (Berczik P.P, Kravchuk S.G. 1997, Ap.Sp.Sci.) provides the realistic description of the process of galaxy formation and evolution. Two parameters: total mass and initial angular momentum of the dwarf protogalaxy play the crucial role in its star formation activity. After the 15 Gyr of the evolution the rapidly rotated dwarf galaxies manifest themselves as an extremly gasrich, heavy element deficient objects showing the initial burst of star formation activity in several spatially separated regions. Slowly rotating objects manifest themselves finally as typical evolved dwarf galaxies.

  16. On the kinetics of platinum silicide formation

    NARCIS (Netherlands)

    Faber, Erik J.; Wolters, Rob A.M.; Schmitz, Jurriaan

    2011-01-01

    In this work, the kinetics of platinum silicide formation for thin Pt films (50 nm) on monocrystalline <100> silicon is investigated via in situ resistance measurements under isothermal (197–275 °C) conditions. For Pt2Si diffusion limited growth was observed. For PtSi formation, however, no linear r

  17. Automatic 3D video format detection

    Science.gov (United States)

    Zhang, Tao; Wang, Zhe; Zhai, Jiefu; Doyen, Didier

    2011-03-01

    Many 3D formats exist and will probably co-exist for a long time even if 3D standards are today under definition. The support for multiple 3D formats will be important for bringing 3D into home. In this paper, we propose a novel and effective method to detect whether a video is a 3D video or not, and to further identify the exact 3D format. First, we present how to detect those 3D formats that encode a pair of stereo images into a single image. The proposed method detects features and establishes correspondences between features in the left and right view images, and applies the statistics from the distribution of the positional differences between corresponding features to detect the existence of a 3D format and to identify the format. Second, we present how to detect the frame sequential 3D format. In the frame sequential 3D format, the feature points are oscillating from frame to frame. Similarly, the proposed method tracks feature points over consecutive frames, computes the positional differences between features, and makes a detection decision based on whether the features are oscillating. Experiments show the effectiveness of our method.

  18. Soft thrombus formation in radiofrequency catheter ablation

    NARCIS (Netherlands)

    Demolin, JM; Eick, OJ; Munch, K; Koullick, E; Nakagawa, H; Wittkampf, FHM

    2002-01-01

    During RF catheter ablation, local temperature elevation can result in coagulum formation on the ablation electrode, resulting in impedance rise. A recent study has also demonstrated the formation of a so-called soft thrombus during experimental ablations. This deposit poorly adhered to the catheter

  19. Problems of Kazakh Literary Criticism Formation

    Directory of Open Access Journals (Sweden)

    Zhandos Smagulov

    2013-01-01

    Full Text Available Тhe article is concerned with the problem of scientific research of Kazakh literature formation in national science. Kazakh literature, having long history of formation is classified by periods. Besides, the article thoroughly considers the principles of the study of methodology, theory, history of spiritual heritage in Kazakh literary criticism

  20. Stone Formation in the Infected Pediatric Enterocystoplasty

    NARCIS (Netherlands)

    R.B. Mathoera (Rejiv)

    2003-01-01

    markdownabstract__Abstract__ Proteus mirabilis is one of the most frequent bacterial agents that can induce infection stone formation by urease production. In recent years the influence of Proteus mirabilis on stone formation in enterocystoplasties has been primarily related to the presence of ure

  1. Learning Progressions that Support Formative Assessment Practices

    Science.gov (United States)

    Alonzo, Alicia C.

    2011-01-01

    Black, Wilson, and Yao (this issue) lay out a comprehensive vision for the way that learning progressions (or other "road maps") might be used to inform and coordinate formative and summative purposes of assessment. As Black, Wilson, and others have been arguing for over a decade, the effective use of formative assessment has great potential to…

  2. Formative Assessment in the High School IMC

    Science.gov (United States)

    Edwards, Valerie A.

    2007-01-01

    In this article, the author discusses how she uses formative assessments of information literacy skills in the high school IMC. As a result of informal observation and conversations with individual students--a form of formative assessment itself--the author learned that students were not using indexes to locate relevant information in nonfiction…

  3. Mechanism of formation of curved Kikuchi lines

    Science.gov (United States)

    Karakhanyan, R. K.; Karakhanyan, K. R.

    2008-07-01

    The mechanism of formation of curved Kikuchi lines, observed at displacement of point reflections from their normal positions, is proposed. Curving of Kikuchi lines is explained taking into account the participation of diffracted electron beams in the formation of Kikuchi electron diffraction patterns.

  4. Pedagogical Formation Education via Distance Education

    Science.gov (United States)

    Ozcan, Deniz; Genc, Zeynep

    2016-01-01

    The purpose of this research is to identify the perceptions of the efficacy of curriculum development on the part of pedagogical formation students, their views regarding their professional attitudes, and their attitudes towards the pedagogical formation education they receive via distance education. The study sample includes 438 Near East…

  5. Lean Data Strategies for Formative Evaluation.

    Science.gov (United States)

    Baker, Eva L.

    The intent of formative evaluation is to improve programs as well as to justify their continuation. It is critical to separate clearly those functions of the evaluation which are political from those which may lead the way to instructional improvement. Data for formative evaluation should be gathered in an interpretable way at the level at which…

  6. Dynamic formation control for autonomous underwater vehicles

    Institute of Scientific and Technical Information of China (English)

    燕雪峰; 古锋; 宋琛; 胡晓琳; 潘毅

    2014-01-01

    Path planning and formation structure forming are two of the most important problems for autonomous underwater vehicles (AUVs) to collaborate with each other. In this work, a dynamic formation model was proposed, in which several algorithms were developed for the complex underwater environment. Dimension changeable particle swarm algorithm was used to find an optimized path by dynamically adjusting the number and the distribution of the path nodes. Position relationship based obstacle avoidance algorithm was designed to detour along the edges of obstacles. Virtual potential point based formation-keeping algorithm was employed by incorporating dynamic strategies which were decided by the current states of the formation. The virtual potential point was used to keep the formation structure when the AUV or the formation was deviated. Simulation results show that an optimal path can be dynamically planned with fewer path nodes and smaller fitness, even with a concave obstacle. It has been also proven that different formation-keeping strategies can be adaptively selected and the formation can change its structure in a narrow area and restore back after passing the obstacle.

  7. Identity formation in the New Testament

    OpenAIRE

    Markus Cromhout

    2009-01-01

    This article is a review of the book entitled Identity Formation in the New Testament (edited by Bengt Holmberg and Mikael Winninge, Mohr Siebeck, Tübingen, 2008). It is a collection of various articles using intertextuality, literary theory (and social identity approaches), gender studies and postcolonial theory when investigating identity formation in the New Testament.

  8. Identity formation in the New Testament

    Directory of Open Access Journals (Sweden)

    Markus Cromhout

    2009-11-01

    Full Text Available This article is a review of the book entitled Identity Formation in the New Testament (edited by Bengt Holmberg and Mikael Winninge, Mohr Siebeck, Tübingen, 2008. It is a collection of various articles using intertextuality, literary theory (and social identity approaches, gender studies and postcolonial theory when investigating identity formation in the New Testament.

  9. An Existentialist Account of Identity Formation.

    Science.gov (United States)

    Bilsker, Dan

    1992-01-01

    Gives account of Marcia's identity formation model in language of existentialist philosophy. Examines parallels between ego-identity and existentialist approaches. Describes identity in terms of existentialist concepts of Heidegger and Sartre. Argues that existentialist account of identity formation has benefits of clarification of difficult…

  10. Chemostratigraphy of Neoproterozoic Banded Iron Formation (BIF)

    DEFF Research Database (Denmark)

    Gaucher, Claudio; Sial, Alcides N.; Frei, Robert

    2015-01-01

    Sawawin BIF (Saudi Arabia), and the Jucurutu Formation of the Seridó Belt (NE Brazil). Lake Superior type BIFs are represented by the Tonian Shilu Group (South China) and the late Ediacaran Arroyo del Soldado Group (Yerbal and Cerro Espuelitas formations, Uruguay). Useful chemostratigraphic tools...

  11. Network Formation under the Threat of Disruption

    NARCIS (Netherlands)

    Hoyer, B.

    2013-01-01

    The studies in this thesis are focused on the impact the presence of a network disruptor has on network formation models. In particular, we build two theoretical models to study the effect of network disruption on network formation and test the effect network disruption has on equilibrium selection

  12. Gas-Phase Infrared; JCAMP Format

    Science.gov (United States)

    SRD 35 NIST/EPA Gas-Phase Infrared; JCAMP Format (PC database for purchase)   This data collection contains 5,228 infrared spectra in the JCAMP-DX (Joint Committee for Atomic and Molecular Physical Data "Data Exchange") format.

  13. Hormonal Regulation of Tuber Formation in Potato

    NARCIS (Netherlands)

    Aksenova, N.P.; Sergeeva, L.; Kolachevskaya, O.O.; Romanov, G.A.

    2013-01-01

    Tubers of potato (Solanum tuberosum L.) plants serve as organs for vegetative propagation and stock of matter and energy for the next generation. Tuber formation is a complex process involving several successive stages: stolon formation and growth, induction of tuberization, tuber initiation and fur

  14. When sticking influences H2 formation

    NARCIS (Netherlands)

    Cazaux, S.; Morisset, S.; Spaans, M.; Allouche, A.

    2011-01-01

    Aims: Because of their catalytic properties, interstellar dust grains are crucial to the formation of H2, the most abundant molecule in the Universe. The formation of molecular hydrogen strongly depends on the ability of H atoms to stick on dust grains. In this study we determine the sticking coeffi

  15. Formative and Summative Assessment in the Classroom

    Science.gov (United States)

    Dixson, Dante D.; Worrell, Frank C.

    2016-01-01

    In this article, we provide brief overviews of the definitions of formative and summative assessment and a few examples of types of formative and summative assessments that can be used in classroom contexts. We highlight the points that these two types of assessment are complementary and the differences between them are often in the way these…

  16. Salicylic acid electrooxidation. A surface film formation

    Energy Technology Data Exchange (ETDEWEB)

    Baturova, M.D.; Vedenjapin, A.; Baturova, M.M. [N.D. Zelinsky Inst. of Organic Chemistry, Russian Academy of Sciences, Moscow (Russian Federation); Weichgrebe, D.; Danilova, E.; Rosenwinkel, K.H. [Univ. of Hannover, Inst. of Water Quality and Waste Management Hannover (Germany); Skundin, A. [A.N. Frumkin Inst. of Electrochemistry, Russian Academy of Sciences, Moscow (Russian Federation)

    2003-07-01

    A possibility to use electrochemical treatment for salicylic acid (SA) removal from waste water was studied. It was found that SA can be oxidized at platinum anode with formation of harmless products. Features of anodic process, in particular, formation of solid film on anode surface as well as properties of the film were investigated. (orig.)

  17. Compressed Multiple-Row Storage Format

    CERN Document Server

    Koza, Zbigniew; Szkoda, Sebastian; Mirosław, Łukasz

    2012-01-01

    A new format for storing sparse matrices is proposed for efficient sparse matrix-vector (SpMV) product calculation on modern throughput-oriented computer architectures. This format extends the standard compressed row storage (CRS) format and is easily convertible to and from it without any memory overhead. Computational performance of an SpMV kernel for the new format is determined for over 140 sparse matrices on two Fermi-class graphics processing units (GPUs) and the efficiency of the kernel, which peaks at 36 and 25 GFLOPS at single and double precision, respectively, is compared with that of five existing generic algorithms and industrial implementations. The efficiency of the new format is also measured as a function of the mean (\\mu) and of the standard deviation (\\sigma) of the number of matrix nonzero elements per row. The largest speedup is found for matrices with \\mu > 20 and \\mu > \\sigma > 1.5 and can be as high as 43%.

  18. Coordinated formation control of multiple nonlinear systems

    Institute of Scientific and Technical Information of China (English)

    Wei KANG; Ning XI; Jindong TAN; Yiwen ZHAO; Yuechao WANG

    2005-01-01

    A general method of controller design is developed for the purpose of formation keeping and reconfiguration of nonlinear systems with multiple subsystems,such as the formation of multiple aircraft,ground vehicles,or robot arms.The model consists of multiple nonlinear systems.Controllers are designed to keep the subsystems in a required formation and to coordinate the subsystems in the presence of environmental changes.A step-by-step algorithm of controller design is developed.Sufficient conditions for the stability of formation tracking are proved.Simulations and experiments are conducted to demonstrate some useful coordination strategies such as movement with a leader,simultaneous movement,series connection of formations,and human-machine interaction.

  19. Storage format for personalized broadcasting content consumption

    Science.gov (United States)

    Jin, Sung Ho; Jang, Jea-Seok; Min, Hyun-Seok; Ro, Yong Man; Kim, Hui Yong

    2007-01-01

    In this paper, we propose a storage format which binds digital broadcasts with related data such as TV-Anytime metadata, additional multimedia resources, and personal viewing history. The goal of the proposed format is to make it possible to offer personalized content consumption after recording broadcasting contents to storage devices, e.g., HD-DVD and Blu-ray Disc. To achieve that, we adopt MPEG-4 file format as a container and apply a binary format for scenes (BIFS) for representing and rendering personal viewing history. In addition, TV-Anytime metadata is used to describe broadcasts and to refer to the additional multimedia resources, e.g, images, audio clips, and short video clips. To demonstrate the usefulness of the proposed format, we introduce an application scenario and test it on that scenario.

  20. On the interplay between star formation and feedback in galaxy formation simulations

    OpenAIRE

    Agertz, Oscar; Kravtsov, Andrey V.

    2014-01-01

    We investigate the star formation-feedback cycle in cosmological galaxy formation simulations, focusing on progenitors of Milky Way (MW)-sized galaxies. We find that in order to reproduce key properties of the MW progenitors, such as semi-empirically derived star formation histories and the shape of rotation curves, our implementation of star formation and stellar feedback requires 1) a combination of local early momentum feedback via radiation pressure and stellar winds and subsequent effici...

  1. Digital forensics formats: seeking a digital preservation storage format for web archiving

    OpenAIRE

    Kim, Y.; Ross, S

    2011-01-01

    In this paper we discuss archival storage formats from the point of view of digital curation and preservation. Considering established approaches to data management as our jumping off point, we selected seven format attributes which are core to the long term accessibility of digital materials. These we have labeled core preservation attributes. These attributes are then used as evaluation criteria to compare file formats belonging to five common categories: formats for archiving s...

  2. PROBA-3: Precise formation flying demonstration mission

    Science.gov (United States)

    Llorente, J. S.; Agenjo, A.; Carrascosa, C.; de Negueruela, C.; Mestreau-Garreau, A.; Cropp, A.; Santovincenzo, A.

    2013-01-01

    Formation Flying (FF) has generated a strong interest in many space applications, most of them involving a significant complexity for building for example on-board large "virtual structures or distributed observatories". The implementation of these complex formation flying missions with critical dependency on this new, advanced and critical formation technology requires a thorough verification of the system behaviour in order to provide enough guarantees for the target mission success. A significant number of conceptual or preliminary designs, analyses, simulations, and HW on-ground testing have been performed during the last years, but still the limitations of the ground verification determine that enough confidence of the behaviour of the formation flying mission will only be possible by demonstration in flight of the concept and the associated technologies. PROBA-3 is the mission under development at ESA for in-flight formation flying demonstration, dedicated to obtain that confidence and the necessary flight maturity level in the formation flying technologies for those future target missions. PROBA-3 will demonstrate technologies such as formation metrology sensors (from very coarse to highest accuracy), formation control and GNC, system operability, safety, etc. During the last years, PROBA-3 has evolved from the initial CDF study at ESA, to two parallel phase A studies, followed by a change in the industrial configuration for the Bridging step between A and B phases. Currently the SRR consolidation has been completed, and the project is in the middle of the phase B. After the phase A study SENER and GMV were responsible for the Formation Flying System, within a mission core team completed by OHB-Sweden, QinetiQ Space and CASA Espacio. In this paper an overview of the PROBA-3 mission is provided, with a more detailed description of the formation flying preliminary design and results.

  3. Star Formation in Henize 206

    Science.gov (United States)

    2004-01-01

    from that explosion impacted a cloud of nearby hydrogen gas, compressed it, and started a new generation of star formation. The death of one star led to the birth of many new stars. This is particularly evident in the MIPS inset, where the 24-micron emission peaks correspond to newly formed stars. The ultraviolet and visible-light photons from the new stars are absorbed by surrounding dust and re-radiated at longer infrared wavelengths, where it is detected by Spitzer. This emission nebula was cataloged by Karl Henize (HEN-eyes) while spending 1948-1951 in South Africa doing research for his Ph.D. dissertation at the University of Michigan. Henize later became a NASA astronaut and, at age 59, became the oldest rookie to fly on the Space Shuttle during an eight-day flight of the Challenger in 1985. He died just short of his 67th birthday in 1993 while attempting to climb the north face of Mount Everest, the world's highest peak.

  4. MAGNETIC FIELDS AND GALACTIC STAR FORMATION RATES

    International Nuclear Information System (INIS)

    The regulation of galactic-scale star formation rates (SFRs) is a basic problem for theories of galaxy formation and evolution: which processes are responsible for making observed star formation rates so inefficient compared to maximal rates of gas content divided by dynamical timescale? Here we study the effect of magnetic fields of different strengths on the evolution of giant molecular clouds (GMCs) within a kiloparsec patch of a disk galaxy and resolving scales down to ≃0.5 pc. Including an empirically motivated prescription for star formation from dense gas (nH>105 cm−3) at an efficiency of 2% per local free-fall time, we derive the amount of suppression of star formation by magnetic fields compared to the nonmagnetized case. We find GMC fragmentation, dense clump formation, and SFR can be significantly affected by the inclusion of magnetic fields, especially in our strongest investigated B-field case of 80 μG. However, our chosen kiloparsec-scale region, extracted from a global galaxy simulation, happens to contain a starbursting cloud complex that is only modestly affected by these magnetic fields and likely requires internal star formation feedback to regulate its SFR

  5. What triggers star formation in galaxies?

    CERN Document Server

    Elmegreen, Bruce G

    2012-01-01

    Processes that promote the formation of dense cold clouds in the interstellar media of galaxies are reviewed. Those that involve background stellar mass include two-fluid instabilities, spiral density wave shocking, and bar accretion. Young stellar pressures trigger gas accumulation on the periphery of cleared cavities, which often take the form of rings by the time new stars form. Stellar pressures also trigger star formation in bright-rim structures, directly squeezing the pre-existing clumps in nearby clouds and clearing out the lower density gas between them. Observations of these processes are common. How they fit into the empirical star formation laws, which relate the star formation rate primarily to the gas density, is unclear. Most likely, star formation follows directly from the formation of cold dense gas, whatever the origin of that gas. If the average pressure from the weight of the gas layer is large enough to produce a high molecular fraction in the ambient medium, then star formation should fo...

  6. Inviscid Analysis of Extended Formation Flight

    Science.gov (United States)

    Kless, James; Aftosmis, Michael J.; Ning, Simeon Andrew; Nemec, Marian

    2012-01-01

    Flying airplanes in extended formations, with separation distances of tens of wingspans, significantly improves safety while maintaining most of the fuel savings achieved in close formations. The present study investigates the impact of roll trim and compressibility at fixed lift coefficient on the benefits of extended formation flight. An Euler solver with adjoint-based mesh refinement combined with a wake propagation model is used to analyze a two-body echelon formation at a separation distance of 30 spans. Two geometries are examined: a simple wing and a wing-body geometry. Energy savings, quantified by both formation drag fraction and span efficiency factor, are investigated at subsonic and transonic speeds for a matrix of vortex locations. The results show that at fixed lift and trimmed for roll, the optimal location of vortex impingement is about 10% inboard of the trailing airplane s wing-tip. Interestingly, early results show the variation in drag fraction reduction is small in the neighborhood of the optimal position. Over 90% of energy benefits can be obtained with a 5% variation in transverse and 10% variation in crossflow directions. Early results suggest control surface deflections required to achieve trim reduce the benefits of formation flight by 3-5% at subsonic speeds. The final paper will include transonic effects and trim on extended formation flight drag benefits.

  7. Influence of fluorosurfactants on hydrate formation rates

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.U.; Jeong, K.E.; Chae, H.J.; Jeong, S.Y. [Korea Reasearch Inst. of Chemical Technology, Alternative Chemicals/Fuel Research Center, Yuseong-Gu, Daejon (Korea, Republic of)

    2008-07-01

    Gas hydrates, or clathrates, are ice-like solids that forms when natural gas is in contact with liquid water or ice under high pressure and low temperature. There is significant interest in studying the storage and transportation of gas in the form of hydrates. However, a critical problem impacting the industrial application of gas hydrates for storage and transportation of natural gas is the slow formation rate of natural gas hydrate. Researchers have previously reported on the promotion effect of some additives on gas hydrate formation and hydrate gas content. Fluorosurfactants are significantly superior to nonfluorinated surfactants in wetting action, as well as stability in harsh environments, both thermal and chemical. This paper discussed an experimental investigation into the effects of fluorosurfactants with different ionic types on the formation of methane hydrate. The surfactants used were FSN-100 of DuPont Zonyl as non-ionic surfactant and FC-143 of DuPont as anionic surfactant. The paper discussed the experimental apparatus for methane hydrate formation. It also discussed hydrate formation kinetics and the series of hydrate formation experiments that were conducted in the presence of fluorosurfactants. Last, the paper explored the results of the study. It was concluded that anionic fluorosurfactant of FC-143 had a better promoting effect on methane hydrate formation compared with nonionic surfactant of FSN-100. 8 refs., 2 tabs., 2 figs.

  8. Formation Feedback Applied to Behavior-Based Approach to Formation Keeping

    Institute of Scientific and Technical Information of China (English)

    苏治宝; 陆际联

    2004-01-01

    Approaches to the study of formation keeping for multiple mobile robots are analyzed and a behavior-based robot model is built in this paper. And, a kind of coordination architecture is presented, which is similar to the infantry squad organization and is used to realize multiple mobile robots to keep formations. Simulations verify the validity of the approach to keep formation, which combines the behavior-based method and formation feedback. The effects of formation feedback on the performance of the system are analyzed.

  9. Star Formation Histories of the Galactic Satellites

    CERN Document Server

    Gilmore, G; Valls-Gabaud, D; Gilmore, Gerard; Hernandez, Xavier; Valls-Gabaud, David

    1999-01-01

    Late accretion models for formation of the Galactic halo require that many Galactic satellite galaxies have been cannibalised into the halo field. Comparison of the metallicity and age distribution function of stars in the surviving satellites with the apparently exclusively old stars in the field halo can constrain the importance of any such process. We have developed a new objective technique to determine star formation histories in dSph galaxies. We apply this technique to the surviving Galactic satellites, deducing an approximately uniform distribution of ages for the constituents, quite unlike the halo field stars. Thus, late accretion did not play a substantial part in Galactic halo formation.

  10. The formation of compact groups of galaxies

    Institute of Scientific and Technical Information of China (English)

    马駬; 俞允强

    1999-01-01

    In the compact group of galaxies the galaxies can merge into a few massive ones in a very short time, so they must be formed very recently. On the other hand, according to the theory of structure formation, the denser system should form earlier. By analyzing the apparent paradox, we suggest that the merging process of CDM halo plays an important role in the formation of the compact groups of galaxies: it delays the formation of compact groups of galaxies, and makes the groups of galaxies much denser.

  11. Geologic formation prospect of uranium Irian Jaya

    International Nuclear Information System (INIS)

    This paper was resulted from compilation of regional geologic mapping and uranium prospection in which it was considered in making exploration program. Method used was literary study of geologic information which was connected with uranium deposit occurrence. From the 26 formations identified as a formation based on physical characteristics and U grade in stream sediments and rocks, there were 2 specific formation groups which were good enough to be dealt in exploration program that is Kemblangan Group and Aifam Group. (author); 8 refs; 4 figs

  12. Metonymy and word-formation revisited

    OpenAIRE

    Janda, Laura Alexis

    2014-01-01

    Brdar and Brdar-Szabó (this volume) offer a critique of Janda (2011). Janda (2011) found that the same cognitive strategy that facilitates metonymy, namely use of a conceptual source to access a target, can also be invoked in many patterns of affixal word-formation. In other words, many cases of word-formation appear to be motivated by metonymic association. Brdar and Brdar-Szabó claim that it is incorrect to refer to word-formational processes as metonymies. In addition to the robust paralle...

  13. Radiation Driven Implosion and Triggered Star Formation

    CERN Document Server

    Bisbas, T G; Wünsch, R; Hubber, D A; Walch, S

    2010-01-01

    We present simulations of initially stable isothermal clouds exposed to ionizing radiation from a discrete external source, and identify the conditions that lead to radiatively driven implosion and star formation. We use the Smoothed Particle Hydrodynamics code SEREN (Hubber et al. 2010) and the HEALPix-based photoionization algorithm described in Bisbas et al. (2009). We find that the incident ionizing flux is the critical parameter determining the evolution: high fluxes simply disperse the cloud, whereas low fluxes trigger star formation. We find a clear connection between the intensity of the incident flux and the parameters of star formation.

  14. Subjectivities as Centers of Citizen Formation

    Directory of Open Access Journals (Sweden)

    ANGÉLICA MARÍA OCAMPO-TALERO

    2008-12-01

    Full Text Available The article presents academic reflections resulting from the teaching work of the authors with students of the Psychology career at the Javeriana University.Beginning from Latinamerica’s sociopolitical reality, it is pointed out that complex views of citizenship are needed that permit the confrontation of the region’s crises, particularly in Colombia, from the educational scenarios. Formative implications of that view for the professional work of Psychologists are reviewed, proposing subject and subjectivity as the heart of formative practices. Finally, some significant challenges to the Psychologists’ task inthe field of civic formation in educational contexts are outlined.

  15. Turbulence, Feedback, and Slow Star Formation

    OpenAIRE

    Krumholz, Mark R.

    2006-01-01

    One of the outstanding puzzles about star formation is why it proceeds so slowly. Giant molecular clouds convert only a few percent of their gas into stars per free-fall time, and recent observations show that this low star formation rate is essentially constant over a range of scales from individual cluster-forming molecular clumps in the Milky Way to entire starburst galaxies. This striking result is perhaps the most basic fact that any theory of star formation must explain. I argue that a ...

  16. Extrasolar planets formation, detection and dynamics

    CERN Document Server

    Dvorak, Rudolf

    2008-01-01

    This latest, up-to-date resource for research on extrasolar planets covers formation, dynamics, atmospheres and detection. After a look at the formation of giant planets, the book goes on to discuss the formation and dynamics of planets in resonances, planets in double stars, atmospheres and habitable zones, detection via spectra and transits, and the history and prospects of ESPs as well as satellite projects.Edited by a renowned expert in solar system dynamics with chapters written by the leading experts in the method described -- from the US and Europe -- this is an ideal textbook for g

  17. File format for storage of scalable video

    Institute of Scientific and Technical Information of China (English)

    BAI Gang; SUN Xiao-yan; WU Feng; YIN Bao-cai; LI Shi-peng

    2006-01-01

    A file format for storage of scalable video is proposed in this paper. A generic model is presented to enable a codec independent description of scalable video stream. The relationships, especially the dependencies, among sub-streams in a scalable video stream are specified sufficiently and effectively in the proposed model. Complying with the presented scalable video stream model, the file format for scalable video is proposed based on ISO Base Media File Format, which is simple and flexible enough to address the demands of scalable video application as well as the non-scalable ones.

  18. Binary Modulation Formats in Optical Access Networks

    Directory of Open Access Journals (Sweden)

    Vladimir Tejkal

    2010-01-01

    Full Text Available In this paper the binary modulation formats and their application in passive optical networks have been discussed. Passive optical networks are characterized by dividing the optical signal between several end users by using passive splitters, which added a significant attenuation to the network. The performance of the selected modulation formats, depending on the transmitter power in order to verify that there is no signal distortion, has been examined in our simulations. A minimal error rate of the system for each modulation format has been also examined. Finding a suitable modulation, which would allow extension of the distance and splitting ration in current passive optical networks, has been the main aim.

  19. Spur Reaction Model of Positronium Formation

    DEFF Research Database (Denmark)

    Mogensen, O. E.

    1974-01-01

    A new model of positronium (Ps) formation is proposed. Positronium is assumed to be formed by a reaction between a positron and an electron in the positron spur. Ps formation must compete with electron‐ion recombination and electron or positron reactions with solvent molecules and scavenger...... impurities. It is also influenced by electron and positron solvation. The model correlates the measured Ps formation probabilities with the spur electron properties determined in radiation chemistry. The predictions of the model are shown to be in good agreement with experimental results for liquids and...

  20. Biofilm formation in a hot water system

    DEFF Research Database (Denmark)

    Bagh, L.K.; Albrechtsen, Hans-Jørgen; Arvin, Erik;

    2002-01-01

    The biofilm formation rate was measured in situ in a hot water system in an apartment building by specially designed sampling equipment, and the net growth of the suspended bacteria was measured by incubation of water samples with the indigeneous bacteria. The biofilm formation rate reached......, in the sludge, or in the water from the distribution system was negligible. This indicated that bacterial growth took place on the inner surfaces in the hot water system and biofilm formation and detachment of bacteria could account for most of the suspended bacteria actually measured in hot water. Therefore...