Search results for "BAND"
showing 10 items of 2610 documents
Electronic properties of poly(pyrrylene vinylenes): a theoretical approach
1993
Abstract We present a theoretical investigation of the electronic properties of poly(pyrrylene vinylene) and its methyl and methoxy derivatives by using the valence effective Hamiltonian (VEH) method. Theoretical calculations predict that the electronic properties of poly(pyrrylene vinylene) remain almost unaffected upon methyl substitution, while a noticeable lowering of ∼0.4 eV is obtained for the ionization potential and energy gap upon methoxy substitution. The VEH trends are in quantitative agreement with experimental data reported for poly(thienylene vinylene) derivatives.
Ground state properties of SmB6
2002
Abstract We have studied the ground state properties of the intermediate valence narrow-gap semiconductor SmB 6 by means of point-contact (PC) spectroscopy and specific heat measurements. The density of states derived from PC tunneling spectra could be decomposed into two energy-dependent parts with E g =21 meV and E d =4.5 meV wide gaps, and a finite residual density of states at the Fermi level. The specific heat of SmB 6 is enhanced below about 2 K, more pronounced for the sample with less impurities. This behavior can be attributed to the formation of a coherent state within the residual density of states in the energy gap.
Theoretical characterization of the electronic properties of unsymmetrical phthalocyanine analogues
1993
Abstract The electronic structure of unsymmetrical phthalocyanine-based compounds is investigated using the nonempirical valence effective Hamiltonian (VEH) method. The VEH results predict a slight but continuous destabilization of the HOMO level and a monotonous narrowing of the HOMO-LUMO energy gap as the size of the system increases. The theoretical trends are found to agree with optical absorption experimental data and show that the optical properties of phthalocyanine can be monitored by adjusting the size of the π-conjugated macrocycle.
Elaboración un instrumento para conocer las características de la banda sonora de la programación infantil de televisión
2014
Television is one of the most important elements in the construction of the musical and audible reality of children and teenagers. It offers a selected and edited version of a musical environment, with an indisputable level of communicative and patrimonial influence. This paper is part of a research project that sets out to know what children are listening to in children’s television programming, in a sample of Latin American television coverage. The general objective has been to establish the parameters of everyday listening experiences and to create an instrument which is able to determine the objective elements of listening environments through their most notable medium: the soundtrack o…
Paesi abbandonati e il ritorno della vita con l'arte
2020
In Italia, nella seconda metà del Novecento, numerosi furono i centri urbani abbandonati, a causa, ad esempio, dell’emigrazione, dei dissesti idrogeologici e degli eventi sismici. In Sicilia, i paesi di Gibellina, Salaparuta, Poggioreale, nella provincia di Trapani e Montevago, nella provincia di Agrigento, dopo il terremoto, del gennaio 1968, che colpì la parte occidentale dell’Isola, furono abbandonati e, negli anni successivi, ricostruiti, anche in siti distanti. Certamente l’attenzione iniziale fu rivolta alla costruzione delle nuove città, mentre dopo i danni dovuti alle scosse sismiche i resti degli antichi paesi furono lasciati al loro lento ed inesorabile degrado. Più recentemente, …
Rethinking Deinstitutionalization: Exploring the Boundary Conditions for Abandoning and Decoupling Highly Diffused and Institutionalized Practices
2020
Deinstitutionalization of taken-for-granted practices as a natural consequence of ever increasing entropy seems to directly contradict the major institutional thesis, namely, that over time isomorphic forces increase and, as a result, possibilities for deinstitutionalization decrease culminating in the impossibility of abandoning in highly institutionalized fields. We argue that the possibilities for deinstitutionalization have been overestimated in organizational literature and offer a revisited account of deinstitutionalization vs. institutional isomorphism and institutionalized vs. highly diffusing-but-not-institutionalized practices. A freedom for choice between alternative practices ex…
A comparative study of mobile messaging services acceptance to participate in television programmes
2010
PurposeThe purpose of this paper is to analyse key drivers of consumer acceptance of short messaging services (SMS) to participate in TV programmes.Design/methodology/approachThe technology acceptance model (TAM) and the theory of planned behaviour (TPB) have been integrated for the determinants of the acceptance of mobile data services incorporating variables regarding consumer‐media interaction (perceived value and affinity). The model has been tested using structural equation modelling.FindingsPerceived value, attitude and affinity towards television (TV) programmes determine SMS acceptance to participate in TV programmes in Spain. In contrast, subjective norm, perceived value and attitu…
Natural optical anisotropy of h-BN: Highest giant birefringence in a bulk crystal through the mid-infrared to ultraviolet range
2018
The giant birefringence of layered h-BN was demonstrated by analyzing the interference patterns in reflectance and transmittance measurements in the mid-infrared to the deep ultraviolet energy range. The refractive index for polarization perpendicular to the c axis is much higher than the refractive index for polarization parallel to the c axis, and it displays a strong increase in the ultraviolet range that is attributed to the huge excitonic effects arising from the unique electronic structure of h-BN. Thus, h-BN is shown to exhibit a giant negative birefringence that ranges from -0.7 in the visible to -2 in the deep ultraviolet close to the band gap. The electronic dielectric constants f…
First Retrievals of ASCAT-IB VOD (Vegetation Optical Depth) at Global Scale
2021
Global and long-term vegetation optical depth (VOD) dataset are very useful to monitor the dynamics of the vegetation features, climate and environmental changes. In this study, the radar-based global ASCAT (Advanced SCATterometer) IB (INRAE-BORDEAUX) VOD was retrieved using a model which was recently calibrated over Africa. In order to assess the performance of IB VOD, the Saatchi biomass and three other VOD datasets (ASCAT V16, AMSR2 LPRM V5 and VODCA LPRM V6) derived from C-band observations were used in the comparison. The preliminary results show that IB VOD has a promising ability to predict biomass $(\mathrm{R}=0.74,\ \text{RMSE} =44.82\ \text{Mg}\ \text{ha}^{-1})$ , which is better …
A combined optical-microwave method to retrieve soil moisture over vegetated areas
2011
A simple approach for correcting for the effect of vegetation in the estimation of the surface soil moisture (wS) from L-band passive microwave observations is presented in this study. The approach is based on semi-empirical relationships between soil moisture and the polarized reflectivity including the effect of the vegetation optical depth which is parameterized as a function of the normalized vegetation difference index (NDVI). The method was tested against in situ measurements collected over a grass site from 2004 to 2007 (SMOSREX experiment). Two polarizations (horizontal/vertical) and five incidence angles (20◦, 30◦, 40◦, 50◦, and 60◦) were considered in the analysis. The best wS est…