One of the most persistent debates in the archaeology of the North American Arctic relates to thirteenth-century AD population distributions and movements. Around this time, the final culture of the ...long-lived Paleo-Inuit tradition, known as Late Dorset, was replaced by Thule Inuit, who migrated from Alaska to the Eastern Arctic. Due to the almost complete lack of evidence for direct interaction between Dorset and Thule, there are currently two contrasting models for this transitional period. The first proposes a temporal hiatus between Late Dorset and Thule during which the Eastern Arctic was unoccupied. The second proposes that Late Dorset persisted to at least the late thirteenth century and still occupied some regions of the Eastern Arctic when Thule arrived. Resolution of this question depends largely on radiocarbon dates, particularly for the poorly understood Late Dorset period. This article presents 56 new AMS radiocarbon dates from three Late Dorset sites in the Iqaluktuuq region of southeastern Victoria Island in the Central Arctic. They resolve a significant part of the debate by confirming that Dorset settlement continued in this region later than AD 1300, thus overlapping with Thule settlement in adjacent regions for decades, and perhaps as much as a century.
Un des débats les plus persistants dans l'archéologie de l'Arctique nord-américain concerne les distributions et mouvements de population au 13e siècle. À peu près à ce moment, la culture finale d'une longue tradition paléo-inuite, connue sous le nom de Dorsétien récent, fut remplacée par les Inuit Thuléens, lesquels ont migré en Arctique de l'Est depuis l'Alaska. En raison d'un manque presque complet de preuves pour une interaction directe entre les Dorsétiens et les Thuléens, il y a présentement deux modèles opposés pour cette période transitionnelle. Le premier propose un hiatus temporel entre le Dorsétien récent et le Thuléen durant lequel l'Arctique de l'Est aurait été inoccupé. Le second propose que les Dorsétiens auraient persisté jusqu'au moins la fin du 13e siècle et auraient occupé certaines régions de l'Arctique de l'Est à l'arrivée des Thuléens. La réponse à cette question dépend largement des dates radiocarbones, particulièrement pour la période peu connue du Dorsétien récent. Cet article présente 56 nouvelles dates radiocarbones AMS provenant de trois sites Dorsétiens récents de la région d'Iqaluktuuq dans le Sud-Est de l’île Victoria en Arctique central. Elles résolvent une part significative du débat en confirmant que les établissements dorsétiens se sont poursuivis dans cette région après 1300 après J.-C. et sont conséquemment contemporains aux établissements thuléens dans les régions adjacentes pendant des décennies, voire près d'un siècle.
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BFBNIB, INZLJ, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK, ZRSKP
•Variability in and significance of hunter-gatherer aggregation sites are reviewed.•The Cadfael archaeological site is a Dorset aggregation in the Canadian Arctic.•The aggregation site contains stone ...longhouses as well as ritual features.•Change over time at the site results from interaction between Dorset and Inuit.
Most hunter-gatherer lifeways revolve around periodic large gatherings – aggregations – that serve as social, ritual, and economic anchors for their annual cycles. However, in archaeological contexts they are often difficult to recognize. This paper describes and interprets a particularly large and well-preserved example of a warm season aggregation site dating to the Late Dorset period in the eastern North American Arctic. This site extends for over 750 m along coastal beach ridges and contains four boulder-outlined “longhouses” of up to 38 m in length as well as hundreds of other features used for storage, cooking, and ritual activities. In addition to interpreting the range of activities occurring on the site, this paper discusses the clear evidence for change over time in the ways its inhabitants interacted with the built environment, and with each other. Because these changes took place mainly during the 13th century CE, they likely represent a reaction to the arrival in this region of ancestral Inuit, who migrated from Alaska during this period and ultimately replaced Dorset populations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
3.
The genetic prehistory of the New World Arctic Raghavan, Maanasa; DeGiorgio, Michael; Albrechtsen, Anders ...
Science (American Association for the Advancement of Science),
08/2014, Volume:
345, Issue:
6200
Journal Article
Peer reviewed
Open access
The New World Arctic, the last region of the Americas to be populated by humans, has a relatively well-researched archaeology, but an understanding of its genetic history is lacking. We present ...genome-wide sequence data from ancient and present-day humans from Greenland, Arctic Canada, Alaska, Aleutian Islands, and Siberia. We show that Paleo-Eskimos (~3000 BCE to 1300 CE) represent a migration pulse into the Americas independent of both Native American and Inuit expansions. Furthermore, the genetic continuity characterizing the Paleo-Eskimo period was interrupted by the arrival of a new population, representing the ancestors of present-day Inuit, with evidence of past gene flow between these lineages. Despite periodic abandonment of major Arctic regions, a single Paleo-Eskimo metapopulation likely survived in near-isolation for more than 4000 years, only to vanish around 700 years ago.
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In 1928, Dirac published an equation
that combined quantum mechanics and special relativity. Negative-energy solutions to this equation, rather than being unphysical as initially thought, represented ...a class of hitherto unobserved and unimagined particles-antimatter. The existence of particles of antimatter was confirmed with the discovery of the positron
(or anti-electron) by Anderson in 1932, but it is still unknown why matter, rather than antimatter, survived after the Big Bang. As a result, experimental studies of antimatter
, including tests of fundamental symmetries such as charge-parity and charge-parity-time, and searches for evidence of primordial antimatter, such as antihelium nuclei, have high priority in contemporary physics research. The fundamental role of the hydrogen atom in the evolution of the Universe and in the historical development of our understanding of quantum physics makes its antimatter counterpart-the antihydrogen atom-of particular interest. Current standard-model physics requires that hydrogen and antihydrogen have the same energy levels and spectral lines. The laser-driven 1S-2S transition was recently observed
in antihydrogen. Here we characterize one of the hyperfine components of this transition using magnetically trapped atoms of antihydrogen and compare it to model calculations for hydrogen in our apparatus. We find that the shape of the spectral line agrees very well with that expected for hydrogen and that the resonance frequency agrees with that in hydrogen to about 5 kilohertz out of 2.5 × 10
hertz. This is consistent with charge-parity-time invariance at a relative precision of 2 × 10
-two orders of magnitude more precise than the previous determination
-corresponding to an absolute energy sensitivity of 2 × 10
GeV.
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Laser cooling of antihydrogen atoms Baker, C J; Bertsche, W; Capra, A ...
Nature (London),
04/2021, Volume:
592, Issue:
7852
Journal Article
Peer reviewed
Open access
The photon-the quantum excitation of the electromagnetic field-is massless but carries momentum. A photon can therefore exert a force on an object upon collision
. Slowing the translational motion of ...atoms and ions by application of such a force
, known as laser cooling, was first demonstrated 40 years ago
. It revolutionized atomic physics over the following decades
, and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen
, the antimatter atom consisting of an antiproton and a positron. By exciting the 1S-2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-α laser radiation
, we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude-with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S-2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic
and gravitational
studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.
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Improving the oral absorption of compounds with low aqueous solubility is a common challenge that often requires an enabling technology. Frequently, oral absorption can be improved by formulating the ...compound as an amorphous solid dispersion (ASD). Upon dissolution, an ASD can reach a higher concentration of unbound drug than the crystalline form, and often generates a large number of sub-micrometer, rapidly dissolving drug-rich colloids. These drug-rich colloids have the potential to decrease the diffusional resistance across the unstirred water layer of the intestinal tract (UWL) by acting as rapidly diffusing shuttles for unbound drug. In a prior study utilizing a membrane flux assay, we demonstrated that, for itraconazole, increasing the concentration of drug-rich colloids increased membrane flux in vitro. In this study, we evaluate spray-dried amorphous solid dispersions (SDDs) of itraconazole with hydroxypropyl methylcellulose acetate succinate (HPMCAS) to study the impact of varying concentrations of drug-rich colloids on the oral absorption of itraconazole in rats, and to quantify their impact on in vitro flux as a function of bile salt concentration. When Sporanox and itraconazole/AFFINISOL High Productivity HPMCAS SDDs were dosed in rats, the maximum absorption rate for each formulation rank-ordered with membrane flux in vitro. The relative maximum absorption rate in vivo correlated well with the in vitro flux measured in 2% SIF (26.8 mM bile acid concentration), a representative bile acid concentration for rats. In vitro it was found that as the bile salt concentration increases, the importance of colloids for improving UWL permeability is diminished. We demonstrate that drug-containing micelles and colloids both contribute to aqueous boundary layer diffusion in proportion to their diffusion coefficient and drug loading. These data suggest that, for compounds with very low aqueous solubility and high epithelial permeability, designing amorphous formulations that produce colloids on dissolution may be a viable approach to improve oral bioavailability.
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ToxA, a necrotrophic effector originally identified from the tan spot fungus Pyrenophora tritici-repentis in 1987, was subsequently identified from Parastagonospora nodorum in 2006. More recently, ...the ToxA gene was identified in the spot blotch fungus Bipolaris sorokiniana in Australia. Here we show that the ToxA gene is also present in the B. sorokiniana population in the winter wheat region of southcentral Texas. Leaves from 'Duster' wheat showing strong necrotic lesions were collected in Castroville, TX. Fifteen single-spore isolates were collected from separate lesions, and 13 of them harbored the BsToxA gene and secreted ToxA in culture based on sensitivity of BG261, the differential line containing the dominant ToxA sensitivity gene, Tsn1. Four isolates harboring BsToxA and one deficient in BsToxA were used to infiltrate two wheat lines harboring Tsn1 as well as their corresponding tsn1 mutant lines. Culture filtrates of the isolate lacking BsToxA did not induce necrosis on any of the lines. Culture filtrates of the four BsToxA-containing isolates induced necrosis on the wild type (Tsn1) lines but not on the corresponding tsn1 mutant lines. Sensitivity to these culture filtrates also mapped to the previously identified location for Tsn1 in the winter wheat mapping population Arina × Forno. Inoculation of one of these ToxA-producing isolates on the same population showed that the Tsn1 locus accounted for 24.4% of the disease variation. All 13 isolates harbored the same BsToxA nucleotide sequence, which was identical to one of the two haplotypes previously identified in Australia. Sensitivity to ToxA is prevalent in popular hard winter wheat cultivars in the central and southcentral winter wheat regions of the United States, showing the potential of a selective advantage for B. sorokiniana isolates that harbor the ToxA gene.
The cold, wet climate of the Arctic has led to the extraordinary preservation of archaeological sites and materials that offer important contributions to the understanding of our common cultural and ...ecological history. This potential, however, is quickly disappearing due to climate-related variables, including the intensification of permafrost thaw and coastal erosion, which are damaging and destroying a wide range of cultural and environmental archives around the Arctic. In providing an overview of the most important effects of climate change in this region and on archaeological sites, the authors propose the next generation of research and response strategies, and suggest how to capitalise on existing successful connections among research communities and between researchers and the public.
KEY MESSAGE : Wheat lines carrying Ug99-effective stem rust resistance gene Sr43 on shortened alien chromosome segments were produced using chromosome engineering, and molecular markers linked to ...Sr43 were identified for marker-assisted selection. Stem rust resistance gene Sr43, transferred into common wheat (Triticum aestivum) from Thinopyrum ponticum, is an effective gene against stem rust Ug99 races. However, this gene has not been used in wheat breeding because it is located on a large Th. ponticum 7el₂ chromosome segment, which also harbors genes for undesirable traits. The objective of this study was to eliminate excessive Th. ponticum chromatin surrounding Sr43 to make it usable in wheat breeding. The two original translocation lines KS10-2 and KS24-1 carrying Sr43 were first analyzed using simple sequence repeat (SSR) markers and florescent genomic in situ hybridization. Six SSR markers located on wheat chromosome arm 7DL were identified to be associated with the Th. ponticum chromatin in KS10-2 and KS24-1. The results confirmed that KS24-1 is a 7DS·7el₂L Robertsonian translocation as previously reported. However, KS10-2, which was previously designated as a 7el₂S·7el₂L-7DL translocation, was identified as a 7DS-7el₂S·7el₂L translocation. To reduce the Th. ponticum chromatin carrying Sr43, a BC₂F₁ population (Chinese Spring//Chinese Spring ph1bph1b*2/KS10-2) containing ph1b-induced homoeologous recombinants was developed, tested with stem rust, and genotyped with the six SSR markers identified above. Two new wheat lines (RWG33 and RWG34) carrying Sr43 on shortened alien chromosome segments (about 17.5 and 13.7 % of the translocation chromosomes, respectively) were obtained, and two molecular markers linked to Sr43 in these lines were identified. The new wheat lines with Sr43 and the closely linked markers provide new resources for improving resistance to Ug99 and other races of stem rust in wheat.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Physicists have long wondered whether the gravitational interactions between matter and antimatter might be different from those between matter and itself. Although there are many indirect ...indications that no such differences exist and that the weak equivalence principle holds, there have been no direct, free-fall style, experimental tests of gravity on antimatter. Here we describe a novel direct test methodology; we search for a propensity for antihydrogen atoms to fall downward when released from the ALPHA antihydrogen trap. In the absence of systematic errors, we can reject ratios of the gravitational to inertial mass of antihydrogen >75 at a statistical significance level of 5%; worst-case systematic errors increase the minimum rejection ratio to 110. A similar search places somewhat tighter bounds on a negative gravitational mass, that is, on antigravity. This methodology, coupled with ongoing experimental improvements, should allow us to bound the ratio within the more interesting near equivalence regime.
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