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排序方式: 共有2448条查询结果,搜索用时 15 毫秒
1.
M. Fernando Gonzalez-Zalba Chiara Ciccarelli Liviu P. Zarbo Andrew C. Irvine Richard C. Campion Bryan L. Gallagher Tomas Jungwirth Andrew J. Ferguson Joerg Wunderlich 《PloS one》2015,10(4)
We propose a novel hybrid single-electron device for reprogrammable low-power logic operations, the magnetic single-electron transistor (MSET). The device consists of an aluminium single-electron transistor with a GaMnAs magnetic back-gate. Changing between different logic gate functions is realized by reorienting the magnetic moments of the magnetic layer, which induces a voltage shift on the Coulomb blockade oscillations of the MSET. We show that we can arbitrarily reprogram the function of the device from an n-type SET for in-plane magnetization of the GaMnAs layer to p-type SET for out-of-plane magnetization orientation. Moreover, we demonstrate a set of reprogrammable Boolean gates and its logical complement at the single device level. Finally, we propose two sets of reconfigurable binary gates using combinations of two MSETs in a pull-down network. 相似文献
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Halasz Norbert; Nowycky Martha C.; Shepherd Gordon M.; Hofelt Tomas 《Chemical senses》1985,10(2):203-218
aftographic exeperiments on the localization of radiolabelednoradrenaline, dopamine and dopa, as well as immunohistochemicalstudies on hydroxylase-like activity, are summarized and comparedin both rat and turtle olfactory bulbs. Evoked field potentialstudies on effects of dopamine are also discussed. The histochemicalstudies suggest that dopaminergic periglomerular neurons arethe most significant cellular component of the catecholaminergicsystem in the olfactory bulb of both species. Scattered fluorescentcell group was also present in the internal plexiform layerand superficial granule cell layer of the turtle olfactory bulb.Other fibres, not related to intrinsic bulbar neuronal cellbodies, were also labeled, mostly in the granule cell layerbut also in the external plexiform layer. These might belongto a centrifugal catecholaminergic system from brain stem neurons.In the in vitro turtle olfactory bulb, dopamine and apomorphinedepressed the amplitude of field potentials evoked by a singlevolley in the olfactory nerve or lateral olfactory tract, andreduced the depression and latency of reponses when paired volleywere delivered. It is suggested that catecholaminergic systemsplay a key role in modulating mitral cell activity through actionsin both superficial (glomerular) and deep (granule) layers.This may involve direct actions, or other, non-catecholaminergicinterneurons. 相似文献
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Unicellular, diazotrophic cyanobacteria temporally separate dinitrogen (N2) fixation and photosynthesis to prevent inactivation of the nitrogenase by oxygen. This temporal segregation is regulated by a circadian clock with oscillating activities of N2 fixation in the dark and photosynthesis in the light. On the population level, this separation is not always complete, since the two processes can overlap during transitions from dark to light. How do single cells avoid inactivation of nitrogenase during these periods? One possibility is that phenotypic heterogeneity in populations leads to segregation of the two processes. Here, we measured N2 fixation and photosynthesis of individual cells using nanometer-scale secondary ion mass spectrometry (nanoSIMS) to assess both processes in a culture of the unicellular, diazotrophic cyanobacterium Crocosphaera watsonii during a dark-light and a continuous light phase. We compared single-cell rates with bulk rates and gene expression profiles. During the regular dark and light phases, C. watsonii exhibited the temporal segregation of N2 fixation and photosynthesis commonly observed. However, N2 fixation and photosynthesis were concurrently measurable at the population level during the subjective dark phase in which cells were kept in the light rather than returned to the expected dark phase. At the single-cell level, though, cells discriminated against either one of the two processes. Cells that showed high levels of photosynthesis had low nitrogen fixing activities, and vice versa. These results suggest that, under ambiguous environmental signals, single cells discriminate against either photosynthesis or nitrogen fixation, and thereby might reduce costs associated with running incompatible processes in the same cell. 相似文献
6.
This paper describes the sediment and soils responses in a very long-running study of the capacity of a natural peatland to remove nutrients from treated wastewater. Data are here presented and analyzed from three decades of full-scale operation (1978–2007), during which large changes in the wetland soils occurred. An average of 600,000 m3 y−1 of treated water was discharged each warm season to the Porter Ranch peatland near the community of Houghton Lake, Michigan. This discharge was seasonal, commencing no sooner than May 1 and ending no later than October 31. During the winter half-year, treated wastewater was stored at the lagoon site. This water contained 3.5 mg/L of total phosphorus, and 7 mg/L of dissolved inorganic nitrogen. Nutrients were stored in the 100 ha irrigation area, which removed 94% of the phosphorus (53 t) and 95% of the dissolved inorganic nitrogen. Phosphorus was stored in new biomass, increased soil sorption, and accretion of new soils and sediments, with accretion being dominant. Peat probings, water level increases and topographical surveys established quantitative measures of soil accretion. Over 30 cm of new soil developed, in which nutrient storage occurred. Phosphorus concentrations in the new soil were approximately 2000 mg P/kg, and the nitrogen concentration was 2–3%DW. The removal of TSS was effective, but minor in comparison to the internal generation and cycling of produced particulates. Later in the project history, the interior portion of impacted area became a floating mat. Sedimentation processes then occurred with no exposure to above-mat detrital processes. Trace element analyses showed no appreciable accumulation of heavy metals, other than the calcium and iron that characterized the antecedent wetland and the incoming water. Biomass cycling models were found to produce reasonable estimates of the measured nutrient accumulations. The light loadings of nutrients to this system produced dramatic effects in the ecosystem, but were lower than the range seen in some other treatment wetlands. Insufficient nitrogen was added to support the new biomass, and nitrogen fixation was identified as a possible compensatory mechanism. 相似文献
7.
Francisco José González Minero Isabel Iglesias Victoria Jato Maria Jesús Aira Pilar Candau Julia Morales Carmen Tomas 《Aerobiologia》1998,14(2-3):117-129
A comparative study is presented of the pollen emissions of Urticaceae, Plantaginaceae and Poaceae, collected during 1995
with Hirst samplers (Burkard or Lanzoni) at five sites in western Spain: two Mediterranean sites located in the south (Huelva
and Seville) and three Atlantic sites in the north (Orense, Vigo and Santiago). The annual pollen of Poaceae and Plantaginaceae
collected in the Atlantic cities was found to be twice that in the Mediterranean sites, and the total amount of Urticaceae
was higher at sites with an urban environment and subject to sea influence (Vigo, Huelva and Seville). At all the sites, the
start of the main pollination periods (MPP) took place in the following order: Urticaceae, Plantaginaceae and Poaceae. It
was also observed that the MPP of these three pollen types began earlier in Huelva and Seville, where the mean temperatures
necessary for the beginning of pollen emissions are recorded very early. Regarding the variation in pollen concentrations
throughout the year, Urticaceae presented peaks of maximum concentration in March (Huelva, Seville, Vigo and Orense) and June
(Santiago); Plantaginaceae in March (south) and June (north); and Poaceae in May (south) and June–July (north). At northern
sites, pollen emissions of Urticaceae and Plantaginaceae continued throughout the summer, while in the south they decreased
considerably from May onwards. From the allergenic point of view, the indices of reactivity described for Urticaceae and Poaceae
were exceeded more often at northern sites, in particular at Vigo. The meteorological conditions associated with periods of
highest pollen emission of these three herbaceous types are a rise in mean temperature, light or absent rainfall, and abundant
sunshine. The statistical correlations between pollen emissions and meteorological factors were not well-defined, either for
the stations or for all the taxa, although they were clearer for the Atlantic cities and for Urticaceae. 相似文献
8.
9.
Ross A. Robinson Samuel C. Griffiths Lieke L. van de Haar Tomas Malinauskas Eljo Y. van Battum Pavol Zelina Rebekka A. Schwab Dimple Karia Lina Malinauskaite Sara Brignani Marleen H. van den Munkhof Özge Düdükcü Anna A. De Ruiter Dianne M.A. Van den Heuvel Benjamin Bishop Jonathan Elegheert A. Radu Aricescu R. Jeroen Pasterkamp Christian Siebold 《Cell》2021,184(8):2103-2120.e31
10.
Tomas Majtan Angel L. Pey Roberto Fernández José A. Fernández Luis A. Martínez-Cruz Jan P. Kraus 《PloS one》2014,9(8)
Cystathionine beta-synthase (CBS) is a key regulator of sulfur amino acid metabolism diverting homocysteine, a toxic intermediate of the methionine cycle, via the transsulfuration pathway to the biosynthesis of cysteine. Although the pathway itself is well conserved among eukaryotes, properties of eukaryotic CBS enzymes vary greatly. Here we present a side-by-side biochemical and biophysical comparison of human (hCBS), fruit fly (dCBS) and yeast (yCBS) enzymes. Preparation and characterization of the full-length and truncated enzymes, lacking the regulatory domains, suggested that eukaryotic CBS exists in one of at least two significantly different conformations impacting the enzyme’s catalytic activity, oligomeric status and regulation. Truncation of hCBS and yCBS, but not dCBS, resulted in enzyme activation and formation of dimers compared to native tetramers. The dCBS and yCBS are not regulated by the allosteric activator of hCBS, S-adenosylmethionine (AdoMet); however, they have significantly higher specific activities in the canonical as well as alternative reactions compared to hCBS. Unlike yCBS, the heme-containing dCBS and hCBS showed increased thermal stability and retention of the enzyme’s catalytic activity. The mass-spectrometry analysis and isothermal titration calorimetry showed clear presence and binding of AdoMet to yCBS and hCBS, but not dCBS. However, the role of AdoMet binding to yCBS remains unclear, unlike its role in hCBS. This study provides valuable information for understanding the complexity of the domain organization, catalytic specificity and regulation among eukaryotic CBS enzymes. 相似文献