131,188 research outputs found
Experimental local realism tests without fair sampling assumption
No full textFollowing the theoretical suggestion of [E. Santos, Phys. Lett. A 327, 33 (2004);
E. Santos, Eur. Phys. J. D 42, 501 (2007)], we present experimental results addressed to
test restricted families of local realistic models, but without
relying on the fair sampling assumption
On the measurement of photon flux in parametric down-conversion
No full textWe report the measurement of the photons flux produced in parametric down-conversion, performed
in photon counting regime with actively quenched silicon avalanche photodiodes as single photon
detectors. Measurements are done with the detector in a well defined geometrical and spectral situation.
By comparison of the experimental data with the theory, a value for the second order
susceptibilities of the non linear crystal can be inferred
Fragmented Ownership and Second Homes in Tourism Resorts
No full textIn spite of the generally accepted view that second homes induce a higher seasonality and a lower occupancy rate than hotels, they persistently prevail
in many tourism destinations. This paper introduces a mechanism to illustrate and analyze the decision problem of constructing second homes or hotels. We introduce a two period game with two players representing a developer of buildings in a tourism destination D and a tourist T. D owns a piece of land and faces two alternatives: to construct a hotel or to build a second
home. T has to choose between buying a second home or renting a hotel room. Another ingredient of the model is an externality mechanism representing
the value placed by tourists on the probability of finding an available place at the destination. The paper shows the persistence of sub-optimal equilibria in the game, in which the land is allocated to a socially inefficient use (second homes rather than hotels). We show that a necessary condition for such inefficiency to emerge is that the related externality cannot be internalized.
This occurs under a regime of dispersed ownership
Exploring the dynamics of the efficiency in the Italian hospitality sector. A regional case study
No full textThis paper introduces a methodology to describe and compare the economic relative performance of the
hospitality sector of the Italian regions during the period 2000–2004. Dynamics of the hospitality sector
of each region is represented by the evolution of its economic efficiency. The investigation involves the
following steps: a static Data Envelopment Analysis (DEA) to estimate the pure economic efficiency;
two different notions of distances between time series and hierarchical clustering techniques are used
to classify the economies in the sample. By using a correlation-based distance, three main clusters are
detected, while two clusters are identified when the average distance is used. The trend patterns, identified by employing the correlation distance, can be interpreted in terms of exogenous factors that influence the economic efficiency of the group of regions, causing shocks picked up by the high volatility as
well as structural breaks. By employing the average distance, one infers information on the cluster that
have had similar efficiency values over the period under analysis. This efficiency can be also interpreted
in terms of a particular type of hospitality management as well as the firm structure. Following the analysis, some policy and management implications are presented
MeSH term explosion and author rank improve expert recommendations
Get PDFInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Ultrabroadband pulse shaping with a push-pull deformable mirror
No full textWe report the programmable pulse shaping of ultrabroadband pulses by the use of a novel design of electrostatic deformable mirror based on push pull technology. We shape few-optical pulses from near-IR and visible optical parametric amplifiers, and demonstrate strong-field control of excited state population transfer in a dye molecule
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Ultrafast internal conversion in a low band gap polymer for photovoltaics: experimental and theoretical study
No full textUltrafast dynamics upon photoexcitation in a low band gap polymer for photovoltaics is investigated both experimentally and theoretically. Our work sheds light on the excess energy relaxation processes occurring immediately after photon absorption and responsible for dissipation in the photovoltaic process of light harvesting and energy storage. A peculiar non-adiabatic decay path through a conical intersection (CI) between the higher excited state S-2 and the first singlet state S-1 is identified by ultrafast spectroscopy and theoretical calculations. Ultrafast twisting of the initially flat conformation in S-2 drives the system to the CI connecting the two potential energy surfaces, actually eliciting an internal conversion within 60 femtoseconds, followed by planarization along the adiabatic surface in S-1. Relaxed potential energy profiles (PEPs) of ground and lowest excited states along a dihedral coordinate, calculated within the time dependent density functional theory (TDDFT) approach, support the S-2/S-1 CI mechanism. Furthermore a screening of the widely used hybrid and range separated exchange-correlation (XC) DFT functionals has been carried out finding different descriptions of S-2/S-1 PEPs and good agreement between experimental data and long-range corrected DFT
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
Get PDFBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Ultrafast carrier recombination in highly n-doped Ge-on-Si films
Get PDFWe study the femtosecond carrier dynamics of n-type doped and biaxially strained Ge-on-Si films which occurs upon impulsive photoexcitation by means of broadband near-IR transient absorption spectroscopy. The modeling of the experimental data takes into account the static donor density in a modified rate equation for the description of the temporal recombination dynamics. The measurements confirm the negligible contribution at a high n-type doping concentration, in the 1019 cm−3 range, of Auger processes as compared to defect-related Shockley-Read-Hall recombination. Energy resolved dynamics reveal further insights into the doping-related band structure changes and suggest a reshaping of direct and indirect conduction band valleys to a single effective valley along with a significant spectral broadening of the optical transitions
- …
