144 research outputs found
Identité biologique des artisans moustériens de Kebara (Mont Carmel, Israël) Réflexions sur le concept de néanderthalien au Levant méditerranéen
DĂšs les premiĂšres dĂ©couvertes de fossiles humains provenant du Bassin MĂ©diterranĂ©en oriental et datĂ©s du PlĂ©istocĂšne supĂ©rieur, il est apparu Ă©vident que la documentation anthropologique illustrait une hĂ©tĂ©rogĂ©nĂ©itĂ© biologique, suscitant des interprĂ©tations diffĂ©rentes. Par la suite, lâenrichissement de la documentation avec de nouvelles fouilles est venu alimenter, au sein de la communautĂ© scientifique, les discussions portant aussi bien sur les affinitĂ©s phylogĂ©nĂ©tiques des fossiles que sur leur position chronologique. La prise en compte, sur ces fossiles proche-orientaux, de lâoriginalitĂ© de lâassemblage de caractĂšres anatomiques prĂ©sents ne doit pas ĂȘtre sous-estimĂ©e pour une meilleure Ă©valuation des composantes rĂ©gionales. Câest ce qui est proposĂ© Ă propos de Kebara, lâobjectif Ă©tant de favoriser une approche cohĂ©rente de la diversitĂ© biologique des hommes du PalĂ©olithique moyen dans la rĂ©gion, qui nâexclut pas les influences extra-europĂ©ennes.The southern Mediterranean Levant has attracted the attention of the scientific community since the early excavations conducted at the beginning of the 20th century on several sites, which provided a significant sample of Upper Pleistocene hominids. Additional skeletal material, circumscribed geographically and chronologically, raises several questions concerning the biological differences and similarities between the hominid samples represented, and their geographical position at the crossroads of Africa and Eurasia. The excellent state of preservation of the hominid remains enables a new insight into the anatomy of Levantine Middle Palaeolithic populations and provides important data for reconstructing the pattern of human evolution in the Near East. With this in view, re-examination of some skeletal remains recovered at Kebara Cave suggests. that biological differences and similarities may have existed between Neanderthals and Levantine Middle Palaeolithic hominids, strengthening the existence of regional variation
Center-limb dependence of photospheric velocities in regions of emerging magnetic fields on the Sun
We investigate the ratio of the vertical and horizontal velocities of the
photospheric plasma flows in the region of emerging magnetic fields on the Sun.
We carried out a study of photospheric velocities during the first hours of the
appearance of 83 active regions with magnetic flux more than 10^21 Mx with data
acquired by the Michelson Doppler Imager (MDI) on board the Solar and
Heliospheric Observatory (SOHO). The emerging magnetic fluxes under
investigation were isolated from extended concentrations of existing magnetic
fields; they have different spatial scales and are located at different
distances from the solar disk center. We found that the values of maximum
negative Doppler velocities that accompany the emergence of active region
magnetic fields during the first 12 hours increase nonlinearly with the
heliocentric angle. This result shows that the horizontal photospheric
velocities of plasma outflows are higher than the vertical ones of the plasma
upflows during the first hours of the emergence of active regions. The
horizontal velocity component at the site of emerging active regions exceeds
that of convective flows in the quiet Sun. A comparison between the velocities
and the maximum value of the total magnetic flux has not revealed any relation.Comment: 5 pages, 4 figures, accepted in A&
Comments on filament-disintegration and its relation to other aspects of solar activity
Studies of âdisparitions brusquesâ in solar cycles 19 and 20 (to 1969) indicate that such events occur frequently. Approximately 30% of all large filaments in these cycles disintegrated in the course of their transit across the solar disk. âMajorâ flares occurred with above average frequency on the last day on which 141 large disappearing filaments were observed (1958â60; 1966â69). Relationships between a disintegrating filament on July 10â11, 1959, a prior major flare, a newly formed spot, and concomitant growth of Hα plage are presented. Observation of prior descending prominence material apparently directed towards the location of the flare of 1959 July 15 d 19 h 23 m is reported. The development of the filament-associated flare of February 13, 1967 is described.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43723/1/11207_2004_Article_BF00148100.pd
Why dig looted tombs? Two examples and some answers from Keushu (Ancash highlands, Peru)
Looted tombs at Andean archaeological sites are largely the result of a long tradition of trade in archaeological artefacts coupled with the 17th century policy of eradicating ancestor veneration and destroying mortuary evidence in a bid to âextirpate idolatryâ. On the surface, looted funerary contexts often present abundant disarticulated and displaced human remains as well as an apparent absence of mortuary accoutrements. What kind of information can archaeologists and biological anthropologists hope to gather from such contexts? In order to gauge the methodological possibilities and interpretative limitations of targeting looted tombs, we fully excavated two collective funerary contexts at the archaeological site of Keushu (district and province of Yungay, Ancash, Peru; c. 2000 B.C.-A.D. 1600), which includes several dozen tombs, many built under large boulders or rock shelters, all of which appear disturbed by looting. The first is located in the ceremonial sector and excavation yielded information on four individuals; the second, in the funerary and residential sector, held the remains of seventy individuals - adults and juveniles. Here, we present and discuss the recovered data and suggest that careful, joint excavations by archaeologists and biological anthropologists can retrieve evidence of past mortuary practices, aid the biological characterisation of mortuary populations and help distinguish between a broad range of looting practices and post-depositional processes
Svestka's Research: Then and Now
Zdenek Svestka's research work influenced many fields of solar physics,
especially in the area of flare research. In this article I take five of the
areas that particularly interested him and assess them in a "then and now"
style. His insights in each case were quite sound, although of course in the
modern era we have learned things that he could not readily have envisioned.
His own views about his research life have been published recently in this
journal, to which he contributed so much, and his memoir contains much
additional scientific and personal information (Svestka, 2010).Comment: Invited review for "Solar and Stellar Flares," a conference in honour
of Prof. Zden\v{e}k \v{S}vestka, Prague, June 23-27, 2014. This is a
contribution to a Topical Issue in Solar Physics, based on the presentations
at this meeting (Editors Lyndsay Fletcher and Petr Heinzel
A Prescription for Improving Drug Formulary Decision Making
Gordon Schiff and colleagues present a new tool and checklist to help formularies make decisions about drug inclusion and to guide rational drug use
Control of Centrin Stability by Aurora A
Aurora A is an oncogenic serine/threonine kinase which can cause cell transformation and centrosome amplification when over-expressed. Human breast tumors show excess Aurora A and phospho-centrin in amplified centrosomes. Here, we show that Aurora A mediates the phosphorylation of and localizes with centrin at the centrosome, with both proteins reaching maximum abundance from prophase through metaphase, followed by their precipitous loss in late stages of mitosis. Over-expression of Aurora A results in excess phospho-centrin and centrosome amplification. In contrast, centrosome amplification is not seen in cells over-expressing Aurora A in the presence of a recombinant centrin mutant lacking the serine phosphorylation site at residue 170. Expression of a kinase dead Aurora A results in a decrease in mitotic index and abrogation of centrin phosphorylation. Finally, a recombinant centrin mutation that mimics centrin phosphorylation increases centrin's stability against APC/C-mediated proteasomal degradation. Taken together, these results suggest that the stability of centrin is regulated in part by Aurora A, and that excess phosphorylated centrin may promote centrosome amplification in cancer
Dynamism in the solar core
Recent results of a mixed shell model heated asymmetrically by transient
increases in nuclear burning indicate the transient generation of small hot
spots inside the Sun somewhere between 0.1 and 0.2 solar radii. These hot
bubbles are followed by a nonlinear differential equation system with finite
amplitude non-homologous perturbations which is solved in a solar model. Our
results show the possibility of a direct connection between the dynamic
phenomena of the solar core and the atmospheric activity. Namely, an initial
heating about DQ_0 ~ 10^{31}-10^{37} ergs can be enough for a bubble to reach
the outer convective zone. Our calculations show that a hot bubble can arrive
into subphotospheric regions with DQ_final ~ 10^{28} - 10^{34} ergs with a high
speed, up to 10 km s-1, approaching the local sound speed. We point out that
the developing sonic boom transforms the shock front into accelerated particle
beam injected upwards into the top of loop carried out by the hot bubble above
its forefront traveling from the solar interior. As a result, a new perspective
arises to explain flare energetics. We show that the particle beams generated
by energetic deep-origin hot bubbles in the subphotospheric layers have masses,
energies, and chemical compositions in the observed range of solar
chromospheric and coronal flares. It is shown how the emergence of a hot bubble
into subphotospheric regions offers a natural mechanism that can generate both
the eruption leading to the flare and the observed coronal magnetic topology
for reconnection. We show a list of long-standing problems of solar physics
that our model explains. We present some predictions for observations, some of
which are planned to be realized in the near future.Comment: 44 pages, 20 figure
Soft solar X-rays and solar activity
Minor Hα activity, consisting of small brightenings and small, surgelike spikes, was observed to take place above an active center at the solar limb in good time-association with small fluctuations in the soft X-ray background flux, suggesting that even small dynamical events seen optically are associated with coronal heating. The ratio of Hα flux to soft X-ray flux in some of the surges was approximately the same as the ratio already established for flares. The total energy dissipated by the events in a 24-hour period is estimated; it is approximately equivalent to that released by one flare of imp 1 per day.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43719/1/11207_2004_Article_BF00155785.pd
Study of the post-flare loops on 29 July 1973
We present revised values of temperature and density for the flare loops of 29 July 1973 and compare the revised parameters with those obtained aboard the SMM for the two-ribbon flare of 21 May 1980. The 21 May flare occurred in a developed sunspot group; the 29 July event was a spotless two-ribbon flare. We find that the loops in the spotless flare extended higher (by a factor of 1.4â2.2), were less dense (by a factor of 5 or more in the first hour of development), were generally hotter, and the whole loop system decayed much slower than in the spotted flare (i.e. staying at higher temperature for a longer time). We also align the hot X-ray loops of the 29 July flare with the bright Hα ribbons and show that the Hα emission is brightest at the places where the spatial density of the hot elementary loops is enhanced.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43753/1/11207_2004_Article_BF00151609.pd
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