Search results for " generation."
showing 10 items of 1108 documents
Antoni de Martí i Franquès i la generació espontània: Els conflictes entre ciència i religió en el treball del naturalista
2014
Antoni de Marti i Franques, el naturalista tarragoni que va viure en la segona part del segle XVIII i primers decennis del XIX, conegut especialment pels seus notables experiments dedicats a l’estudi de la composicio de l’aire atmosferic, dedica bona part del seu treball experimental a estudiar la generacio espontania. A traves dels manuscrits de Marti i Franques que es conserven i pel testimoni dels seus contemporanis, sabem que estava convencut d’haver comprovat experimentalment l’existencia d’aquest fenomen. Pero, com que era un fervent catolic, no va voler publicar res sobre aquest tema en vida per temor de ser acusat d’heretge. Tampoc el seus descendents van publicar res de la seva obr…
Experimental and theoretical evidence for bilayer-by-bilayer surface melting of crystalline ice
2017
On the surface of water ice, a quasi-liquid layer (QLL) has been extensively reported at temperatures below its bulk melting point at 273 K. Approaching the bulk melting temperature from below, the thickness of the QLL is known to increase. To elucidate the precise temperature variation of the QLL, and its nature, we investigate the surface melting of hexagonal ice by combining noncontact, surface-specific vibrational sum frequency generation (SFG) spectroscopy and spectra calculated from molecular dynamics simulations. Using SFG, we probe the outermost water layers of distinct single crystalline ice faces at different temperatures. For the basal face, a stepwise, sudden weakening of the hy…
Low-temperature exciton absorption in InSe under pressure.
1992
We have investigated the effect of pressure on the lowest direct band-edge exciton of the layered semiconductor InSe by optical-absorption measurements at 10 K and for pressures up to 4 GPa. The Elliott-Toyozawa formalism is used to analyze the line shape of the exciton absorption spectra. In this way we determine the pressure dependence of the lowest direct band gap, the exciton binding energy, and the exciton linewidth. The band gap exhibits a pronounced nonlinear shift with pressure, which is a consequence of the strong anisotropy of intralayer and interlayer bonding. The exciton binding energy decreases with pressure, mainly due to the large increase of the low-frequency dielectric cons…
Dynamics of exciton creation and decay processes in composition – disordered InGaN thin films
2011
In the GaN-based ternary alloys, InGaN crystals have been recognized as key materials for e-h plasmas-exciton dynamics, because of large exciton binding energies (24.8 meV in GaN). We report investigations of creating and recombination dynamics of excitons in commercially important InxGa1-xN composition range from x = 0.1 to 0.18 in which nanoscale indium composition fluctuation occurs and formation of indium rich clusters acting as quantum dots (QD) can be expected. Three MOCVD grown samples having x = 0.1; 0.14 and 0.18 have been investigated using 3D picosecond transient PL spectroscopy. It has been found that the band to band photo excitation at 15 K in whole composition range results i…
Archetypal analysis: contributions for estimating boundary cases in multivariate accommodation problem
2013
[EN] The use of archetypal analysis is proposed in order to determine a set of representative cases that entail a certain percentage of the population, in the accommodation problem. A well-known anthropometric database has been used in order to compare our methodology with the common used PCA-approach, showing the advantages of our methodology: the level of accommodation is reached unlike the PCA approach, no more adjustments are necessary, the user can decide the number of archetypes to consider or leave the selection by a criterion. Unlike PCA, the objective of the archetypal analysis is obtaining extreme individuals, so it is the appropriate statistical technique for solving this type of…
Second- and third-harmonic generation as a local probe for nanocrystal-doped polymer materials with a suppressed optical breakdown threshold
2003
Abstract Second- and third-harmonic generation processes are shown to allow the detection of absorptive agglomerates of nanocrystals in transparent materials and the visualization of optical breakdown in nanocomposite materials. Correlations between laser-induced breakdown and the behavior of the second- and third-harmonic signals produced in SiC/PMMA nanocomposite films are studied. The potential of second- and third-harmonic generation for the on-line visualization of laser breakdown in nanocomposite polymer materials is revealed, with the ablative material removal being monitored by the decay of the second- and third-harmonic signals. The second and third harmonics generated around the o…
Nanorings driven by strong laser fields: dynamics and applications
Fourth‐generation glucose sensors composed of copper nanostructures for diabetes management: A critical review
2022
Abstract More than five decades have been invested in understanding glucose biosensors. Yet, this immensely versatile field has continued to gain attention from the scientific world to better understand and diagnose diabetes. However, such extensive work done to improve glucose sensing devices has still not yielded desirable results. Drawbacks like the necessity of the invasive finger‐pricking step and the lack of optimization of diagnostic interventions still need to be considered to improve the testing process of diabetic patients. To upgrade the glucose‐sensing devices and reduce the number of intermediary steps during glucose measurement, fourth‐generation glucose sensors (FGGS) have be…
Cooperation and cultural transmission in a coordination game
2009
Abstract The aim of this paper is to analyze if cooperation can be the product of cultural evolution in a two-stage coordination game, consisting of a production stage followed by a negotiation phase. We present an overlapping generations model with cultural transmission of preferences where the distribution of preferences in the population and the strategies are determined endogenously and simultaneously. There are several groups in the society; some of them play cooperatively and others do not. Socialization takes place inside the group, but there is a positive rate of migration among groups which parents anticipate. Our main result shows that all groups converge to the cooperative equili…