1,721,326 research outputs found
Italian law on assisted conception: clinical and research implications
No full textThe Italian law 40/2004 regulating the use of assisted conception will remain on the statutes after the failure of the referendum in June 2005. Italy is now one of the most restrictive countries in the world in the field of assisted conception. It is thought that the new regulations, which have already increased 'reproductive tourism' in Italian subfertile couples, will also have clinical and research implications
Optical profiles with 180 micron resolution of objects hidden in scattering media
No full textWe measure the time-of-flight distributions of near-infrared photons emerging from thick scattering media within a collection angle of 0.6 mrad about the incident light direction by means of a time-correlated single-photon counting apparatus endowed with <35 ps resolution. These measurements, which are performed with a picosecond laser beam, allow us to isolate the weakly scattered (ballisticsnake) photons from the multiply scattered ones. By scanning the incidence position across a target we find variations in the fraction of detected unscattered photons that are significative of local changes in the optical parameters of the target. In particular, if either opaque, light diffusing, or transparent objects are embedded in the scattering medium, their profiles can be reconstructed and their nature can be assessed. Opaque objects embedded in realistic tissue phantoms are detected with <180 μm spatial resolution. © 2007 American Institute of Physics
DNA-ligand binding-mode discrimination by characterizing fluorescence resonant energy transfer through lifetime measurements with picosecond resolution
No full textWe describe a method for distinguishing between minor groove binders and base intercalators that is based on measurements of the fluorescence lifetime of a donor (D) in the presence of an acceptor (A). The D-A pair is separated by a short double helix DNA with which the ligands interact. By plotting the D fluorescence lifetime as a function of the ligand-to-base pair concentration ratio we find a clear signature that distinguishes between the two binding mechanisms: minor groove binding induces an asymptotic decrease of the D fluorescence lifetime, while intercalation gives a monotonically increasing lifetime and the appearance of an additional short lifetime. We assayed Quinacrine, Hoechst and 4′-6′diamidine-2-phenyl indole, which in control experiments performed on oligodeoxyribonucleotides (oligos) lacking the A are demonstrated not to interfere with the D fluorescence. The changes in fluorescence lifetimes measured in the case of dual-labeled oligos are thus caused by structural changes in the DNA that modify the D-A distance. The appearance of the short-lived transient in the fluorescence decay of Ds attached to dual-labeled oligos upon binding of an intercalator can be interpreted as denaturation. © 2007 The Authors
La riduzione dei tempi di risposta: indagine nel settore mobile-arredo della provincia di Pordenone
No full textLa ricerca empirica oggetto del lavoro è stata svolta nell'ambito di un progetto di ricerca e formazione riguardante i temi della competitività delle aziende del Friuli Venezia Giulia e del Veneto orientale alla luce dei modelli e dei paradigmi produttivi più recenti quali la produzione snella e la competitività basata sul tempo di risposta
Time-resolved homo-FRET studies of biotin-streptavidin complexes
No full textFörster resonance energy transfer is a mechanism of fluorescence quenching that is notably useful for characterizing properties of biomolecules and/or their interactions. Here we study water-solutions of Biotin-Streptavidin complexes, in which Biotin is labeled with a rigidly-bound fluorophore that can interact by Förster resonance energy transfer with the fluorophores labeling the other, up to three, Biotins of the same complex. The fluorophore, Atto550, is a Rhodamine analogue. We detect the time-resolved fluorescence decay of the fluorophores with an apparatus endowed with single-photon sensitivity and temporal resolution of ~ 30 ps. The decay profiles we observe for samples containing constant Biotin-Atto550 conjugates and varying Streptavidin concentrations are multi-exponential. Each decay component can be associated with the rate of quenching exerted on each donor by each of the acceptors that label the other Biotin molecules, depending on the binding site they occupy. The main features that lead to this result are that (i) the transition dipole moments of the up-to-four Atto550 fluorophores that label the complexes are fixed as to both relative positions and mutual orientations; (ii) the fluorophores are identical and the role of donor in each Biotin-Streptavidin complex is randomly attributed to the one that has absorbed the excitation light (homo-FRET). Obviously the high-temporal resolution of the excitation-detection apparatus is necessary to discriminate among the fluorescence decay components
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The Subgraph Similarity Problem
Full text linkSimilarity is a well known weakening of bisimilarity where one system is required to simulate the other and vice versa. It has been shown that the subgraph bisimilarity problem, a variation of the subgraph isomorphism problem where isomorphism is weakened to bisimilarity, is NP-complete. We show that the subgraph similarity problem and some related variations thereof still remain NP-complete
Observer-based, discrete-time, sliding mode throttle control for drive-by-wire operation of a racing motorcycle engine
No full textAbstract—In this brief, the problem of designing a drive-by-wire
throttle control system for a high-performance motorcycle engine
is considered. Given the characteristics of the electromechanical
system to be controlled, an observer-based, discrete-time sliding
mode (DTSM) servo controller with integral action is adopted.
The controller is designed on the basis of an identified model of the
system, whose states are estimated by means of a state observer.
Different state observer structures are analyzed, and it is shown
that the main characteristics of standard state-feedback-based
sliding mode control systems are preserved. A theoretical analysis
is also presented showing that a separation principle holds, so
that the state observer and the DTSM controller can be designed
independently. The performances of the designed controller are
illustrated by reporting the results of tests performed on track
with a racing motorcycle
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