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141.
Trotzky S Cheinet P Fölling S Feld M Schnorrberger U Rey AM Polkovnikov A Demler EA Lukin MD Bloch I 《Science (New York, N.Y.)》2008,319(5861):295-299
Quantum mechanical superexchange interactions form the basis of quantum magnetism in strongly correlated electronic media. We report on the direct measurement of superexchange interactions with ultracold atoms in optical lattices. After preparing a spin-mixture of ultracold atoms in an antiferromagnetically ordered state, we measured coherent superexchange-mediated spin dynamics with coupling energies from 5 hertz up to 1 kilohertz. By dynamically modifying the potential bias between neighboring lattice sites, the magnitude and sign of the superexchange interaction can be controlled, thus allowing the system to be switched between antiferromagnetic and ferromagnetic spin interactions. We compare our findings to predictions of a two-site Bose-Hubbard model and find very good agreement, but are also able to identify corrections that can be explained by the inclusion of direct nearest-neighbor interactions. 相似文献
142.
Ceccarelli Viviana Lastra Sphyros Loor Solrzano Rey Gastn Chacn Walter Wenceslao Nolasco Mario Sotomayor Cantos Ignacio Antonio Plaza Avelln Luis Fernando Lpez Diana Aracelly Fernndez Anchundia Fabian Marcelo Dessauw Dominique Orozco-Aguilar Luis Thomas Evert 《Genetic Resources and Crop Evolution》2022,69(3):1283-1302
Genetic Resources and Crop Evolution - Cacao (Theobroma cacao L.) is among the most important cash crops in tropical countries. The existing cacao genetic diversity represents a key resource to... 相似文献
143.
G. Rozas P. Rey M. V. Rozados E. Rebolledo M. Aldegunde 《Fish physiology and biochemistry》1992,9(5-6):463-471
The levels of tryptophan (Trp), 5-hydroxytryptamine (serotonin, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in two brain regions (hypothalamus and medulla oblongata) of rainbow trout (Oncorhynchus mykiss) were measured throughout the year using a sensitive high performance liquid chromatographic method with electrochemical detection. Trp was also quantified in serum, liver and brain regions. Trp concentrations were higher in sera than in tissues (brain and liver) throughout the year. Hypothalamic and medullary Trp offered similar annual patterns showing two peaks, the first on 10 May and the second on 15 June. 5-HT levels were always higher in the hypothalamus than in the medulla and much higher than the 5-HIAA levels in both regions. Moreover hypothalamic and medullar serotonin patterns were very different, in the latter region few variations were observed. In addition, the 5-HIAA/5-HT ratio was different in the brain regions, the hypothalamus showed two peaks (April 8 and June 15) whereas the equivalent was not observed in the medulla. All measured compounds showed significant variations during the year. 相似文献
144.
Swallows MD Bishof M Lin Y Blatt S Martin MJ Rey AM Ye J 《Science (New York, N.Y.)》2011,331(6020):1043-1046
Optical lattice clocks with extremely stable frequency are possible when many atoms are interrogated simultaneously, but this precision may come at the cost of systematic inaccuracy resulting from atomic interactions. Density-dependent frequency shifts can occur even in a clock that uses fermionic atoms if they are subject to inhomogeneous optical excitation. However, sufficiently strong interactions can suppress collisional shifts in lattice sites containing more than one atom. We demonstrated the effectiveness of this approach with a strontium lattice clock by reducing both the collisional frequency shift and its uncertainty to the level of 10(-17). This result eliminates the compromise between precision and accuracy in a many-particle system; both will continue to improve as the number of particles increases. 相似文献
145.
Sánchez S García-Sánchez A Martínez R Blanco J Blanco JE Blanco M Dahbi G Mora A Hermoso de Mendoza J Alonso JM Rey J 《Veterinary journal (London, England : 1997)》2009,180(3):384-388
Shiga toxin-producing Escherichia coli (STEC) are an important group of emerging pathogens, with ruminants recognised as their main natural reservoir. The aim of this work was to establish the prevalence of non-O157 STEC in free-ranging wild ruminants in the Extremadura region of Spain and to characterise them phenogenotypically. Faecal samples were collected from 243 wild ruminants, including Cervus elaphus, Capreolus capreolus, Dama dama and Ovis musimon and were examined for STEC using both phenotypic (Vero cells) and genotypic (PCR and PFGE) methods.Shiga toxin-producing Escherichia coli were isolated from 58 (23.9%) of the samples and a total of 65 isolates were characterised. A PCR method indicated that 11 (16.9%) strains carried the stx1 gene, 44 (67.7%) carried the stx2 gene and 10 (15.4%) carried both these genes. The ehxA gene was detected in 37 (57%) of the isolates but none contained either the eae or saa genes. The isolates were from a total of 12 ‘O’ serogroups, although 80% were restricted to the O2, O8, O128, O146, O166 and O174 serogroups. The most commonly isolated STEC bacteria, which were from the O146 serogroup, exhibited a high degree of polymorphism as indicated by PFGE. Shiga toxin-producing Escherichia coli isolates of serogroups O20, O25, O166, O171, O174 and O176 had not previously been found in wild ruminants. This is the first study to confirm that wild ruminants in Spain are a reservoir of STEC and are thus a potential source of human infection. 相似文献