Control and measurement of three-qubit entangled states     

Roos CF  Riebe M  Häffner H  Hänsel W  Benhelm J  Lancaster GP  Becher C  Schmidt-Kaler F  Blatt R 《Science (New York, N.Y.)》2004,304(5676):1478-1480

We report the deterministic creation of maximally entangled three-qubit states-specifically the Greenberger-Horne-Zeilinger (GHZ) state and the W state-with a trapped-ion quantum computer. We read out one of the qubits selectively and show how GHZ and W states are affected by this local measurement. Additionally, we demonstrate conditional operations controlled by the results from reading out one qubit. Tripartite entanglement is deterministically transformed into bipartite entanglement by local operations only. These operations are the measurement of one qubit of a GHZ state in a rotated basis and, conditioned on this measurement result, the application of single-qubit rotations.  相似文献   

Structure of a NHEJ polymerase-mediated DNA synaptic complex     

Brissett NC  Pitcher RS  Juarez R  Picher AJ  Green AJ  Dafforn TR  Fox GC  Blanco L  Doherty AJ 《Science (New York, N.Y.)》2007,318(5849):456-459

Nonhomologous end joining (NHEJ) is a critical DNA double-strand break (DSB) repair pathway required to maintain genome stability. Many prokaryotes possess a minimalist NHEJ apparatus required to repair DSBs during stationary phase, composed of two conserved core proteins, Ku and ligase D (LigD). The crystal structure of Mycobacterium tuberculosis polymerase domain of LigD mediating the synapsis of two noncomplementary DNA ends revealed a variety of interactions, including microhomology base pairing, mismatched and flipped-out bases, and 3' termini forming hairpin-like ends. Biochemical and biophysical studies confirmed that polymerase-induced end synapsis also occurs in solution. We propose that this DNA synaptic structure reflects an intermediate bridging stage of the NHEJ process, before end processing and ligation, with both the polymerase and the DNA sequence playing pivotal roles in determining the sequential order of synapsis and remodeling before end joining.  相似文献   

PDZ domain binding selectivity is optimized across the mouse proteome     

Stiffler MA  Chen JR  Grantcharova VP  Lei Y  Fuchs D  Allen JE  Zaslavskaia LA  MacBeath G 《Science (New York, N.Y.)》2007,317(5836):364-369

PDZ domains have long been thought to cluster into discrete functional classes defined by their peptide-binding preferences. We used protein microarrays and quantitative fluorescence polarization to characterize the binding selectivity of 157 mouse PDZ domains with respect to 217 genome-encoded peptides. We then trained a multidomain selectivity model to predict PDZ domain-peptide interactions across the mouse proteome with an accuracy that exceeds many large-scale, experimental investigations of protein-protein interactions. Contrary to the current paradigm, PDZ domains do not fall into discrete classes; instead, they are evenly distributed throughout selectivity space, which suggests that they have been optimized across the proteome to minimize cross-reactivity. We predict that focusing on families of interaction domains, which facilitates the integration of experimentation and modeling, will play an increasingly important role in future investigations of protein function.  相似文献   

Perspectives: signal transduction. Cell survival demands some Rsk     

Nebreda AR  Gavin AC 《Science (New York, N.Y.)》1999,286(5443):1309-1310

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Intestinal microbiota promote enteric virus replication and systemic pathogenesis     

Kuss SK  Best GT  Etheredge CA  Pruijssers AJ  Frierson JM  Hooper LV  Dermody TS  Pfeiffer JK 《Science (New York, N.Y.)》2011,334(6053):249-252

Intestinal bacteria aid host health and limit bacterial pathogen colonization. However, the influence of bacteria on enteric viruses is largely unknown. We depleted the intestinal microbiota of mice with antibiotics before inoculation with poliovirus, an enteric virus. Antibiotic-treated mice were less susceptible to poliovirus disease and supported minimal viral replication in the intestine. Exposure to bacteria or their N-acetylglucosamine-containing surface polysaccharides, including lipopolysaccharide and peptidoglycan, enhanced poliovirus infectivity. We found that poliovirus binds lipopolysaccharide, and exposure of poliovirus to bacteria enhanced host cell association and infection. The pathogenesis of reovirus, an unrelated enteric virus, also was more severe in the presence of intestinal microbes. These results suggest that antibiotic-mediated microbiota depletion diminishes enteric virus infection and that enteric viruses exploit intestinal microbes for replication and transmission.  相似文献   

Socio-economic differences in fruit and vegetable consumption among Australian adolescents and adults     

Giskes K  Turrell G  Patterson C  Newman B 《Public health nutrition》2002,5(5):663-669

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The Source of Anthropogenic Heavy Metals in Fluvial Sediments of a Rural Catchment: Coxs River,Australia     

Birch  Gavin  Siaka  Made  Owens  Christopher 《Water, air, and soil pollution》2001,126(1-2):13-35

A serious health scare involving thesupply of drinking water to Sydney, Australia hasrecently focussed attention on the environmentalstatus of river catchments of the main reservoir, LakeBurragorang. Although the Coxs River – a majorcatchment of Lake Burragorang – comprises mainlyforests and grazing land, it supports a moderate sizedtown, power stations and coal mines. The heavy metal content of stream-bed sedimentscharacterises environmental impact in this ruralcatchment and sources of contamination. Sediment in acreek flowing through a country town (population 12 000) is markedly enriched in Cr, Pb and Zn (3×, 18×and 52×, respectively) over background, probably dueto a long history of metal-based industry. The highestCu, Pb and Zn concentrations (204, 332 and2460 μg g^-1, respectively) in fluvialsediment in the town are, however associated withdischarges from a sewage treatment plant. Twocoal-based power stations in the catchment contributeconsiderable Cu and Ni (maximum concentrations 562 and157 μg g^-1, respectively) to ambient fluvialsediments, possibly from cooling towers and coalstorage areas. The highest Co and Cr concentrations(113 and 490 μg g^-1) in fluvial sediments ofthis catchment are associated with coal-miningactivities. Selective extraction indicates that about50% of the anthropogenic fraction may bebioavailable, whereas sequential extraction proceduressuggest that <25% is associated with the easilyexchangeable/adsorbed phase.Two dams restrict the migration of heavy metals downthe Coxs River and sediment discharging into LakeBurragorang is low in metals.  相似文献   

Marine ecosystem science and the media: Exploring ways to improve news coverage through journalist–scientist working relations     

Komathi Kolandai-Matchett  Maria Armoudian  Simon Thrush  Jenny Hillman  Luitgard Schwendenmann  Julia Jakobsson  Tim Haggitt  Caitlin O'Hara Blain  Gavin Lear 《水产资源保护:海洋与淡水生态系统》2021,31(11):3034-3055

1. The ocean's remoteness, ecological complexities, lengthy ecosystem processes, and vulnerability to multiple and cumulative anthropogenic threats make marine conservation communication particularly difficult. Both scientists and journalists face unique challenges in explaining the science of these often out-of-sight ecosystems. Given the inadequacies of marine news, improvement appeared necessary. However, the experiences and views of journalists and scientists have hardly been examined within marine news contexts. Thus, this study sought the perspectives of these two professional groups to provide a discussion on ways to improve news coverage of complex ocean issues through enhanced journalist–scientist working relations.
2. Both journalists and scientists rated the quantity, breadth and quality of marine news as average and were receptive to alternative ways for reporting ecosystem complexities. Although some frustrations remain, both valued impactful news stories resulting from their working relations and preferred direct contact with each other over indirect methods such as press releases and science news platforms. Both groups generally agreed on what to include in marine news, but scientists favoured a collaborative approach to news content decision-making more strongly than journalists.
3. Journalists' and scientists' commonly shared views and goals concerning marine news identified in this study could serve as a common ground for uniting the two professions. Institutional policies that permit one-on-one journalist–scientist interactions could lead to mutual understandings about the contexts of their relationship challenges. More trustful and mutually beneficial relationships, in turn, could be a basis for a more collaborative news generation process. Compiling and making marine visuals readily accessible to journalists; training programmes that enhance journalists' and scientists' understanding of the influence of media message framing on conservation actions; media appreciation of marine ecosystem complexities' newsworthiness; and the notion of media's social responsibility in reporting marine conservation issues could contribute to more impactful coverage.

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Impact of spectral composition on larval haddock,Melanogrammus aeglefinus L., growth and survival     

Gavin Downing 《Aquaculture Research》2002,33(4):251-259

In a small‐scale culture experiment, larval haddock, Melanogrammus aeglefinus L., were raised under various combinations of light quality [blue (470 nm), green (530 nm) or full‐spectrum white light] and light intensity [low (0.3–0.4 µmol  s^?1  m^?2) or high (1.7–1.9 µmol  s^?1  m^?2)], and in total darkness (both fed, and starved). Larval growth (0.9% day^?1 in standard length; 2.4% day^?1 in body area) was not significantly different between any combination of coloured light. At the time of total mortality in the starved treatment, survival was significantly reduced under low intensity, full‐spectrum white light (13%) vs. all other coloured light treatments (68%). Larvae raised under both continuous dark treatments (fed and starved) exhibited morphological changes associated with irreversible starvation (point‐of‐no‐return). Lack of a pronounced effect of light quality on larval haddock growth probably results from a combination of plasticity in early larval vision, and enhanced encounter rates between larvae and prey at the relatively high prey densities used in aquaculture.  相似文献   

Effect of extender composition and freezing rate on post-thaw motility and fertility of Arctic char, Salvelinus alpinus (L.), spermatozoa     

Nabil Mansour  Gavin F Richardson  & Mary A McNiven 《Aquaculture Research》2006,37(9):862-868

The effects of extender composition and freezing rate on motility and fertility of frozen‐thawed Arctic char, Salvelinus alpinus, spermatozoa were investigated. Three freezing rates, two semen diluents and three cryoprotectants were tested. Semen frozen in 0.3 mol L^?1 glucose diluent with 10% methanol as a cryoprotectant or in a diluent described by Lahnsteiner with 10%N,N‐dimethylacetamide (DMA) resulted in the highest sperm motility. Fertility was the highest for semen frozen in a glucose–methanol extender but was not significantly different than that for semen frozen in Lahnsteiner's diluent with 10% DMA. Dimethyl sulphoxide (DMSO) at 10% was a relatively ineffective cryoprotectant with either semen diluent. Semen frozen at 6 cm above the surface of liquid nitrogen resulted in a higher post‐thaw sperm motility and fertility than semen frozen at 5 cm. The addition of 7% fresh egg yolk to glucose diluent containing methanol or DMSO did not improve the fertility of frozen‐thawed spermatozoa. However, the addition of 7% fresh egg yolk to glucose–DMA extender significantly improved the fertilization percentages of frozen‐thawed spermatozoa. In conclusion, dilution of semen 1:3 in 0.3 mol L^?1 glucose with 10% methanol and freezing 6 cm above the surface of liquid nitrogen (freezing rate of 40±8°C min^?1, mean±SD from ?5 to ?55°C) is a promising protocol for cryopreservation of Arctic char semen.  相似文献