441 research outputs found
Sensitivity of a cavityless optomechanical system
We study the possibility of revealing a weak coherent force by using a
pendular mirror as a probe, and coupling this to a radiation field, which acts
as the meter, in a cavityless configuration. We determine the sensitivity of
such a scheme and show that the use of an entangled meter state greatly
improves the ultimate detection limit. We also compare this scheme with that
involving an optical cavity.Comment: 4 pages, RevTex file, 2 eps figures, provisionally accepted by Phys.
Rev.
Trapping cold atoms near carbon nanotubes: thermal spin flips and Casimir-Polder potential
We investigate the possibility to trap ultracold atoms near the outside of a
metallic carbon nanotube (CN) which we imagine to use as a miniaturized
current-carrying wire. We calculate atomic spin flip lifetimes and compare the
strength of the Casimir-Polder potential with the magnetic trapping potential.
Our analysis indicates that the Casimir-Polder force is the dominant loss
mechanism and we compute the minimum distance to the carbon nanotube at which
an atom can be trapped.Comment: 8 pages, 3 figure
Inter-species variation in the oligomeric states of the higher plant Calvin cycle enzymes glyceraldehyde-3-phosphate dehydrogenase and phosphoribulokinase
In darkened leaves the Calvin cycle enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) form a regulatory multi-enzyme complex with the small chloroplast protein CP12. GAPDH also forms a high molecular weight regulatory mono-enzyme complex. Given that there are different reports as to the number and subunit composition of these complexes and that enzyme regulatory mechanisms are known to vary between species, it was reasoned that protein-protein interactions may also vary between species. Here, this variation is investigated. This study shows that two different tetramers of GAPDH (an A2B2 heterotetramer and an A4 homotetramer) have the capacity to form part of the PRK/GAPDH/CP12 complex. The role of the PRK/GAPDH/CP12 complex is not simply to regulate the 'non-regulatory' A4 GAPDH tetramer. This study also demonstrates that the abundance and nature of PRK/GAPDH/CP12 interactions are not equal in all species and that whilst NAD enhances complex formation in some species, this is not sufficient for complex formation in others. Furthermore, it is shown that the GAPDH mono-enzyme complex is more abundant as a 2(A2B2) complex, rather than the larger 4(A2B2) complex. This smaller complex is sensitive to cellular metabolites indicating that it is an important regulatory isoform of GAPDH. This comparative study has highlighted considerable heterogeneity in PRK and GAPDH protein interactions between closely related species and the possible underlying physiological basis for this is discussed. © 2011 The Author(s)
First measurement of the Kân âÎÏânon-resonant transition amplitude below threshold
We present the analysis of Kâabsorption processes on He4 leading to ÎÏâfinal states, measured with the KLOE spectrometer at the DAΊNE e+eâcollider and extract, for the first time, the modulus of the non-resonant Kân âÎÏâdirect production amplitude about 33 MeV below the KâŸN threshold. This analysis also allows to disentangle the Kânuclear absorption at-rest from the in-flight capture, for Kâmomenta of about 120 MeV. The data are interpreted with the help of a phenomenological model, and the modulus of the non-resonant Kân âÎÏâamplitude for Kâabsorption at-rest is found to be |AKânâÎÏâ|=(0.334±0.018statâ0.058+0.034syst)fm
Riflessioni e strumenti per l\u2019orientamento scolastico e universitario
Il libro costituisce un manuale di consultazione per quanti vogliano farsi un'idea sullo stato dell'arte in materia di orientamento scolastico e alle profession
Redox homeostasis in photosynthetic organisms: Novel and established thiol-based molecular mechanisms
Redox homeostasis consists of an intricate network in which reactive molecular species (RMS), redox modifications and redox proteins act in concert to allow both physiological responses and adaptation to stress conditions. This review highlights established and novel thiol-based regulatory pathways underlying the functional facets and significance of redox biology in photosynthetic organisms. This cannot be all-encompassing, but is intended to provide a comprehensive overview on the structural/molecular mechanisms governing the most relevant thiol switching modifications with emphasis on the large genetic and functional diversity of redox controllers (i.e. redoxins). We also summarize the different proteomic-based approaches aimed at investigating the dynamics of redox modifications and the recent evidence that extends the possibility to monitor the cellular redox state in vivo. Lastly, the physiological relevance of redox transitions is discussed based on reverse genetic studies confirming the importance of redox homeostasis in plant growth, development, and stress responses
Spatial decoherence near metallic surfaces
Published versio
Gains and losses of coral skeletal porosity changes with ocean acidification acclimation
Ocean acidification is predicted to impact ecosystems reliant on calcifying organisms, potentially reducing the socioeconomic benefits these habitats provide. Here we investigate the acclimation potential of stony corals living along a pH gradient caused by a Mediterranean CO(2) vent that serves as a natural long-term experimental setting. We show that in response to reduced skeletal mineralization at lower pH, corals increase their skeletal macroporosity (features >10âÎŒm) in order to maintain constant linear extension rate, an important criterion for reproductive output. At the nanoscale, the coral skeleton's structural features are not altered. However, higher skeletal porosity, and reduced bulk density and stiffness may contribute to reduce population density and increase damage susceptibility under low pH conditions. Based on these observations, the almost universally employed measure of coral biomineralization, the rate of linear extension, might not be a reliable metric for assessing coral health and resilience in a warming and acidifying ocean
Measurement of the atmospheric muon depth intensity relation with the NEMO Phase-2 tower
The results of the analysis of the data collected with the NEMO Phase-2
tower, deployed at 3500 m depth about 80 km off-shore Capo Passero (Italy), are
presented. Cherenkov photons detected with the photomultipliers tubes were used
to reconstruct the tracks of atmospheric muons. Their zenith-angle distribution
was measured and the results compared with Monte Carlo simulations. An
evaluation of the systematic effects due to uncertainties on environmental and
detector parameters is also included. The associated depth intensity relation
was evaluated and compared with previous measurements and theoretical
predictions. With the present analysis, the muon depth intensity relation has
been measured up to 13 km of water equivalent.Comment: submitted to Astroparticle Physic
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