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  1. Abstract

    Contemporary whole-body low-field MRI scanners (< 1 T) present new and exciting opportunities for improved body imaging. The fundamental reason is that the reduced off-resonance and reduced SAR provide substantially increased flexibility in the design of MRI pulse sequences. Promising body applications include lung parenchyma imaging, imaging adjacent to metallic implants, cardiac imaging, and dynamic imaging in general. The lower cost of such systems may make MRI favorable for screening high-risk populations and population health research, and the more open configurations allowed may prove favorable for obese subjects and for pregnant women. This article summarizes promising body applications for contemporary whole-body low-field MRI systems, with a focus on new platforms developed within the past 5 years. This is an active area of research, and one can expect many improvements as MRI physicists fully explore the landscape of pulse sequences that are feasible, and as clinicians apply these to patient populations.

     
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  2. Résumé Soit $$E/{\mathbb {Q}}$$ E / Q une courbe elliptique à multiplication complexe et p un nombre premier de bonne réduction ordinaire pour E . Nous montrons que si $${\mathrm{corank}}_{{\mathbb {Z}}_p}{\mathrm{Sel}}_{p^\infty }(E/{\mathbb {Q}})=1$$ corank Z p Sel p ∞ ( E / Q ) = 1 , alors E a un point d’ordre infini. Le point de non-torsion provient d’un point de Heegner, et donc $${{{\mathrm{ord}}}}_{s=1}L(E,s)=1$$ ord s = 1 L ( E , s ) = 1 , ce qui donne une réciproque à un théorème de Gross–Zagier, Kolyvagin, et Rubin dans l’esprit de [49, 54]. Pour $$p>3$$ p > 3 , cela donne une nouvelle preuve du résultat principal de [12], que notre approche étend à tous les nombres premiers. L’approche se généralise aux courbes elliptiques à multiplication complexe sur les corps totalement réels [4]. 
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  3. Abstract During glacial terminations, massive iceberg discharges and meltwater pulses in the North Atlantic triggered a shutdown of the Atlantic Meridional Overturning Circulation (AMOC). Speleothem calcium carbonate oxygen isotope records (δ 18 O Cc ) indicate that the collapse of the AMOC caused dramatic changes in the distribution and variability of the East Asian and Indian monsoon rainfall. However, the mechanisms linking changes in the intensity of the AMOC and Asian monsoon δ 18 O Cc are not fully understood. Part of the challenge arises from the fact that speleothem δ 18 O Cc depends on not only the δ 18 O of precipitation but also temperature and kinetic isotope effects. Here we quantitatively deconvolve these parameters affecting δ 18 O Cc by applying three geochemical techniques in speleothems covering the penultimate glacial termination. Our data suggest that the weakening of the AMOC during meltwater pulse 2A caused substantial cooling in East Asia and a shortening of the summer monsoon season, whereas the collapse of the AMOC during meltwater pulse 2B (133,000 years ago) also caused a dramatic decrease in the intensity of the Indian summer monsoon. These results reveal that the different modes of the AMOC produced distinct impacts on the monsoon system. 
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  4. The Liangzhu culture in the Yangtze River Delta (YRD) was among the world’s most advanced Neolithic cultures. Archeological evidence suggests that the Liangzhu ancient city was abandoned, and the culture collapsed at ~4300 years ago. Here, we present speleothem records from southeastern China in conjunction with other paleoclimatic and archeological data to show that the Liangzhu culture collapsed within a short and anomalously wet period between 4345 ± 32 and 4324 ± 30 years ago, supporting the hypothesis that the city was abandoned after large-scale flooding and inundation. We further show that the demise of Neolithic cultures in the YRD occurred within an extended period of aridity that started at ~4000 ± 45 years ago. We suggest that the major hydroclimatic changes between 4300 and 3000 years ago may have resulted from an increasing frequency of the El Niño–Southern Oscillation in the context of weakened Northern Hemisphere summer insolation. 
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