Coherent two-dimensional nanoscopy     

Aeschlimann M  Brixner T  Fischer A  Kramer C  Melchior P  Pfeiffer W  Schneider C  Strüber C  Tuchscherer P  Voronine DV 《Science (New York, N.Y.)》2011,333(6050):1723-1726

We introduce a spectroscopic method that determines nonlinear quantum mechanical response functions beyond the optical diffraction limit and allows direct imaging of nanoscale coherence. In established coherent two-dimensional (2D) spectroscopy, four-wave-mixing responses are measured using three ingoing waves and one outgoing wave; thus, the method is diffraction-limited in spatial resolution. In coherent 2D nanoscopy, we use four ingoing waves and detect the final state via photoemission electron microscopy, which has 50-nanometer spatial resolution. We recorded local nanospectra from a corrugated silver surface and observed subwavelength 2D line shape variations. Plasmonic phase coherence of localized excitations persisted for about 100 femtoseconds and exhibited coherent beats. The observations are best explained by a model in which coupled oscillators lead to Fano-like resonances in the hybridized dark- and bright-mode response.  相似文献   

Two-dimensional Mott-Hubbard electrons in an artificial honeycomb lattice     

Singha A  Gibertini M  Karmakar B  Yuan S  Polini M  Vignale G  Katsnelson MI  Pinczuk A  Pfeiffer LN  West KW  Pellegrini V 《Science (New York, N.Y.)》2011,332(6034):1176-1179

Artificial crystal lattices can be used to tune repulsive Coulomb interactions between electrons. We trapped electrons, confined as a two-dimensional gas in a gallium arsenide quantum well, in a nanofabricated lattice with honeycomb geometry. We probed the excitation spectrum in a magnetic field, identifying collective modes that emerged from the Coulomb interaction in the artificial lattice, as predicted by the Mott-Hubbard model. These observations allow us to determine the Hubbard gap and suggest the existence of a Coulomb-driven ground state.  相似文献   

Atom Harvest     

Pfeiffer JE 《Science (New York, N.Y.)》1956,124(3218):409

  相似文献   

Implications of global and regional patterns of highly pathogenic avian influenza virus H5N1 clades for risk management     

Pfeiffer DU  Otte MJ  Roland-Holst D  Inui K  Nguyen T  Zilberman D 《Veterinary journal (London, England : 1997)》2011,(3):309-316

This paper analyses the publicly available data on the distribution and evolution of highly pathogenic avian influenza virus (HPAIV) H5N1 clades, whilst acknowledging the biases resulting from the non-random selection of isolates for gene sequencing. The data indicate molecular heterogeneity in the global distribution of HPAIV H5N1, in particular in different parts of East and Southeast Asia. Analysis of the temporal pattern of haemagglutinin clade data shows a progression from clade 0 (the ‘dominant’ clade between 1996 and 2002) to clade 1 (2003–2005) and then to clade 2.3.4 (2005 onwards). This process continuously produces variants, depending on the frequency of virus multiplication in the host population, which is influenced by geographical variation in poultry density, poultry production systems and also HPAI risk management measures such as vaccination. Increased multilateral collaboration needs to focus on developing enhanced disease surveillance and control targeted at evolutionary ‘hotspots’.  相似文献   

Follow-up of mercury levels in fish,human hair and urine in the Madeira and Tapajós basins,Amazon, Brazil     

Malm  O  Guimarães  JRD  Castro  MB  Bastos  WR  Viana  JP  Branches  FJP  Silveira  EG  Pfeiffer  WC 《Water, air, and soil pollution》1997,97(1-2):45-51

Informal economy of gold mining has contaminated some important river basins in Amazon. Follow-up studies on critical compartments showed some areas with high Hg levels in fish as well as in human hair samples. Average Hg in piscivorous fish in the Madeira river itself was 846 ppb (N=284) with a maximum of 3921 ppb. Mercury in fish from non polluted areas in this basin shows high variability, even for single species. A seasonal variation in Hg content was observed, with higher values at the end of the dry season. In the upper Tapajós basin comparable values were found for fish but with a definite decreasing trend downstream. Average value for piscivorous fish in the whole Tapajós basin is 482 ppb (N=122) with a maximum value of 3770 ppb. Hair Hg was higher in fishing villages in the Tapajós (average: 17 ppm; with N=432 and maximum value of 176 ppm) than in the Madeira (average: 9 ppm; N=169; maximum 71 ppm), and data from some areas of the Tapajós suggest a decrease with time. Mercury was much higher in urine of goldshop workers in Santarém (low Tapajós) than in Alta Floresta (high Tapajbs) and show a decreasing trend in both cases, probably related to the significant decline in gold mining activities during the study period (1986–1994).  相似文献   

Arsenic Contamination and Dispersion in the Engenho Inlet,Sepetiba Bay,SE, Brazil     

Magalhães  V. F.  Carvalho  C. E. V.  Pfeiffer  W. C. 《Water, air, and soil pollution》2001,129(1-4):83-90

Arsenic distribution and dispersion in sediments of the EngenhoInlet and the Sepetiba Bay were investigated in order to evaluate the extent of the contamination caused by a metallurgical plant installed in the Sepetiba Bay watershed. The ore used in the smelting process, the soil around the plant, and ore waste collected inside the plant were also analyzed for As. Very high As concentrations in the stronglyand weakly bound fractions (up to 63 000 and 52 700 μgg^-1, respectively) were found in the ore waste. The soilsalso contained high concentrations of both the strongly andweakly bound fractions (748 and 636 μg g^-1, repectively), although the ore itself contained lower levelsof the two fractions (63 and 13 μg g^-1, respectively).The sediments of the Engenho Inlet had a high degree of contamination (up to 347 μg g^-1) decreasing toward Sepetiba Bay where the lowest concentrations were found (up to 50 μg g^-1). Altough lower concentrations were found in the Sepetiba Bay sediments, they are 5 times higher than the world average. The results showed that there is an As transport from the Engenho Inlet to the Sepetiba Bay. These results suggests that the bay's fish and mollusk stock my be contaminated. This contamination may adversely affect the health of the local population, whose main protein supply is seafood.  相似文献   

Gastrointestinal Strongyloides in cattle: strategic treatment of grazing calves in early summer and following stabling     

H J Bürger  A Pfeiffer  M S Rahman 《Berliner und Münchener tier?rztliche Wochenschrift》1970,83(17):329-335

  相似文献   

Electromyographic studies on healthy pigs and pigs with protracted atrophy of the posterior femoral musculature     

G Buschmann  K Bickhardt  H J Reinhard  H J Chevalier  A Pfeiffer 《Berliner und Münchener tier?rztliche Wochenschrift》1970,83(24):477-480

  相似文献   

A case study of capture-recapture methodology using scrapie surveillance data in Great Britain     

del Rio Vilas VJ  Sayers R  Sivam K  Pfeiffer D  Guitian J  Wilesmith JW 《Preventive veterinary medicine》2005,67(4):303-317

We applied capture–recapture methodology (CRC) to data from three surveillance sources (statutory notification, abattoir survey (AS) and fallen stock (FS) survey) to estimate the number of holdings infected with scrapie in Great Britain and to assess the sensitivity of the surveillance network. Between January 1, 2002 and March 31, 2003, 144 holdings were identified by the three sources. Using CRC modelling techniques, we estimated a minimum lower bound for the total number of holdings infected as 642. A biologically plausible positive dependence between the statutory reporting and the fallen stock survey was found statistically significant. The sensitivity of the three sources combined was very low. The integration of the three overlapping sources provided a better understanding of the interactions within the surveillance network. However, the scarcity of the data and reduced overlapping among sources only allowed for very cautious inferences to be drawn about the true proportion of scrapie affected holdings in the national population. Future surveys and surveillance activities should be planned such that the resulting data can be used more effectively as part of CRC modelling approaches.  相似文献   

Effects of veterinary board disciplinary actions on veterinarians licensed in multiple states     

Babcock S  Mantese T  Pfeiffer CL 《Journal of the American Veterinary Medical Association》2005,227(12):1906-1909

  相似文献