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11.
Timoney N Baumgart I Johanning M Varón AF Plenio MB Retzker A Wunderlich Ch 《Nature》2011,476(7359):185-188
Trapped atomic ions have been used successfully to demonstrate basic elements of universal quantum information processing. Nevertheless, scaling up such methods to achieve large-scale, universal quantum information processing (or more specialized quantum simulations) remains challenging. The use of easily controllable and stable microwave sources, rather than complex laser systems, could remove obstacles to scalability. However, the microwave approach has drawbacks: it involves the use of magnetic-field-sensitive states, which shorten coherence times considerably, and requires large, stable magnetic field gradients. Here we show how to overcome both problems by using stationary atomic quantum states as qubits that are induced by microwave fields (that is, by dressing magnetic-field-sensitive states with microwave fields). This permits fast quantum logic, even in the presence of a small (effective) Lamb-Dicke parameter (and, therefore, moderate magnetic field gradients). We experimentally demonstrate the basic building blocks of this scheme, showing that the dressed states are long lived and that coherence times are increased by more than two orders of magnitude relative to those of bare magnetic-field-sensitive states. This improves the prospects of microwave-driven ion trap quantum information processing, and offers a route to extending coherence times in all systems that suffer from magnetic noise, such as neutral atoms, nitrogen-vacancy centres, quantum dots or circuit quantum electrodynamic systems. 相似文献
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Bedding TR Mosser B Huber D Montalbán J Beck P Christensen-Dalsgaard J Elsworth YP García RA Miglio A Stello D White TR De Ridder J Hekker S Aerts C Barban C Belkacem K Broomhall AM Brown TM Buzasi DL Carrier F Chaplin WJ Di Mauro MP Dupret MA Frandsen S Gilliland RL Goupil MJ Jenkins JM Kallinger T Kawaler S Kjeldsen H Mathur S Noels A Aguirre VS Ventura P 《Nature》2011,471(7340):608-611
Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertainties in the amount of mass lost at the surface before helium ignition and the amount of internal mixing from rotation and other processes. Progress is hampered by our inability to distinguish between red giants burning helium in the core and those still only burning hydrogen in a shell. Asteroseismology offers a way forward, being a powerful tool for probing the internal structures of stars using their natural oscillation frequencies. Here we report observations of gravity-mode period spacings in red giants that permit a distinction between evolutionary stages to be made. We use high-precision photometry obtained by the Kepler spacecraft over more than a year to measure oscillations in several hundred red giants. We find many stars whose dipole modes show sequences with approximately regular period spacings. These stars fall into two clear groups, allowing us to distinguish unambiguously between hydrogen-shell-burning stars (period spacing mostly ~ 50 seconds) and those that are also burning helium (period spacing ~ 100 to 300 seconds). 相似文献
15.
Arner P Bernard S Salehpour M Possnert G Liebl J Steier P Buchholz BA Eriksson M Arner E Hauner H Skurk T Rydén M Frayn KN Spalding KL 《Nature》2011,478(7367):110-113
Adipose tissue mass is determined by the storage and removal of triglycerides in adipocytes. Little is known, however, about adipose lipid turnover in humans in health and pathology. To study this in vivo, here we determined lipid age by measuring (14)C derived from above ground nuclear bomb tests in adipocyte lipids. We report that during the average ten-year lifespan of human adipocytes, triglycerides are renewed six times. Lipid age is independent of adipocyte size, is very stable across a wide range of adult ages and does not differ between genders. Adipocyte lipid turnover, however, is strongly related to conditions with disturbed lipid metabolism. In obesity, triglyceride removal rate (lipolysis followed by oxidation) is decreased and the amount of triglycerides stored each year is increased. In contrast, both lipid removal and storage rates are decreased in non-obese patients diagnosed with the most common hereditary form of dyslipidaemia, familial combined hyperlipidaemia. Lipid removal rate is positively correlated with the capacity of adipocytes to break down triglycerides, as assessed through lipolysis, and is inversely related to insulin resistance. Our data support a mechanism in which adipocyte lipid storage and removal have different roles in health and pathology. High storage but low triglyceride removal promotes fat tissue accumulation and obesity. Reduction of both triglyceride storage and removal decreases lipid shunting through adipose tissue and thus promotes dyslipidaemia. We identify adipocyte lipid turnover as a novel target for prevention and treatment of metabolic disease. 相似文献
16.
Sicardy B Ortiz JL Assafin M Jehin E Maury A Lellouch E Hutton RG Braga-Ribas F Colas F Hestroffer D Lecacheux J Roques F Santos-Sanz P Widemann T Morales N Duffard R Thirouin A Castro-Tirado AJ Jelínek M Kubánek P Sota A Sánchez-Ramírez R Andrei AH Camargo JI da Silva Neto DN Gomes AR Martins RV Gillon M Manfroid J Tozzi GP Harlingten C Saravia S Behrend R Mottola S Melendo EG Peris V Fabregat J Madiedo JM Cuesta L Eibe MT Ullán A Organero F Pastor S de Los Reyes JA Pedraz S Castro A 《Nature》2011,478(7370):493-496
The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1?AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163?±?6?kilometres, density 2.52?±?0.05 grams per cm(3) and a high visible geometric albedo, Pv = 0.96(+0.09)(-0.04). No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ~1?nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun. 相似文献
17.
A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse 总被引:1,自引:0,他引:1
Rosengren Pielberg G Golovko A Sundström E Curik I Lennartsson J Seltenhammer MH Druml T Binns M Fitzsimmons C Lindgren G Sandberg K Baumung R Vetterlein M Strömberg S Grabherr M Wade C Lindblad-Toh K Pontén F Heldin CH Sölkner J Andersson L 《Nature genetics》2008,40(8):1004-1009
In horses, graying with age is an autosomal dominant trait associated with a high incidence of melanoma and vitiligo-like depigmentation. Here we show that the Gray phenotype is caused by a 4.6-kb duplication in intron 6 of STX17 (syntaxin-17) that constitutes a cis-acting regulatory mutation. Both STX17 and the neighboring NR4A3 gene are overexpressed in melanomas from Gray horses. Gray horses carrying a loss-of-function mutation in ASIP (agouti signaling protein) had a higher incidence of melanoma, implying that increased melanocortin-1 receptor signaling promotes melanoma development in Gray horses. The Gray horse provides a notable example of how humans have cherry-picked mutations with favorable phenotypic effects in domestic animals. 相似文献
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Rodríguez-Muñoz M Sánchez-Blázquez P Vicente-Sánchez A Bailón C Martín-Aznar B Garzón J 《Cellular and molecular life sciences : CMLS》2011,68(17):2933-2949
A series of pharmacological and physiological studies have demonstrated the functional cross-regulation between MOR and NMDAR.
These receptors coexist at postsynaptic sites in midbrain periaqueductal grey (PAG) neurons, an area implicated in the analgesic
effects of opioids like morphine. In this study, we found that the MOR-associated histidine triad nucleotide-binding protein
1 (HINT1) is essential for maintaining the connection between the NMDAR and MOR. Morphine-induced analgesic tolerance is prevented
and even rescued by inhibiting PKC or by antagonizing NMDAR. However, in the absence of HINT1, the MOR becomes supersensitive
to morphine before suffering a profound and lasting desensitization that is refractory to PKC inhibition or NMDAR antagonism.
Thus, HINT1 emerges as a key protein that is critical for sustaining NMDAR-mediated regulation of MOR signaling strength.
Thus, HINT1 deficiency may contribute to opioid-intractable pain syndromes by causing long-term MOR desensitization via mechanisms
independent of NMDAR. 相似文献
20.
Lopez-Castejón G Baroja-Mazo A Pelegrín P 《Cellular and molecular life sciences : CMLS》2011,68(18):3095-3107
Plasticity is a well-known property of macrophages that is controlled by different changes in environmental signals. Macrophage
polarization is regarded as a spectrum of activation phenotypes adjusted from one activation extreme, the classic (M1), to
the other, the alternative (M2) activation. Here we show, in vitro and in vivo, that both M1 and M2 macrophage phenotypes
are tightly coupled to specific patterns of gene expression. Novel M2-associated markers were characterized and identified
as genes controlling the extracellular metabolism of ATP to generate pyrophosphates (PPi). Stimulation of M1 macrophages with
PPi dampens both NLR and TLR signaling and thus mediates cytokine production. In this context extracellular PPi enhanced the
resolution phase of a murine peritonitis model via a decrease in pro-inflammatory cytokine production. Therefore, our study
reveals an additional level of plasticity modulating the resolution of inflammation. 相似文献