High-field cyclotron resonance and electron-phonon interaction in modulation-doped multiple quantum well structures

A systematic study of electron cyclotron resonance (CR) in two sets of GaAs/Al0.3Ga0.7As modulation-doped quantum-well samples (well widths between 12 and 24 nm) has been carried out in magnetic fields up to 30 T. Polaron CR is the dominant transition in the region of GaAs optical phonons for the set of lightly doped samples, and the results are in good agreement with calculations that include the interaction with interface optical phonons. The results from the heavily doped set are markedly different. At low magnetic fields (below the GaAs reststrahlen region), all three samples exhibit almost identical CR which shows little effect of the polaron interaction due to screening and Pauli-principle effects. Above the GaAs LO-phonon region (B > similar to 23 T), the three samples behave very differently. For the most lightly doped sample (3 x 10(11) cm(-2)) only one transition minimum is observed, which can be explained as screened polaron CR. A sample of intermediate density (6 x 10(11) cm(-2)) shows two lines above 23 T; the higher frequency branch is indistinguishable from the positions of the single line of the low density sample. For the most heavily, doped sample (1.2 x 10(12) cm(-2)) there is no evidence of high frequency resonance, and the strong, single line observed is indistinguishable from the lower branch observed from sample with intermediate doping density. We suggest that the low frequency branch in our experiment is a magnetoplasmon resonance red-shifted by disorder, and the upper branch is single-particle-like screened polaron CR. (C) 1998 Elsevier Science B.V. All rights reserved.

Fermionic zero modes in gauge and gravity backgrounds on T-2

Here we study fermionic zero modes in gauge and gravity backgrounds taking a two-dimensional compact manifold T-2 as extra dimensions. The result is that there exist massless Dirac fermions which have normalizable zero modes under quite general assumptions about these backgrounds on the bulk. Several special cases of gauge background on the torus are discussed and some simple fermionic zero modes axe obtained.

Constructing porous frameworks from one-dimensional cobalt-oxygen clusters and pyridinedicarboxylate ligands adopting two rare coordination modes

A porous material with cobalt-oxygen cluster framework has been synthesized hydrothermally, which possesses large and rigid channels and manifests strong antiferromagnetic interactions, and the pyridinedicarboxylate ligand exhibits two types of rare coordination modes.

Multiplex binding modes of toluidine blue with calf thymus DNA and conformational transition of DNA revealed by spectroscopic studies

It is noteworthy to understand the details of interactions between antitumor drugs and DNA because the binding modes and affinities affect their antitumor activities. Here, The interaction of toluidine blue (TB), a potential antitumor drug for photodynamic therapy of tumor, with calf thymus DNA (ctDNA) was explored by UV-vis, fluorescence, circular dichroism (CD) spectroscopy, UV-rnelting method and surface-enhance Raman spectroscopy (SERS). The experimental results suggest that TB could bind to ctDNA via both electrostatic interaction and partial intercalation.

Two modes of dipole events in tropical Indian Ocean

By analyzing the distributions of subsurface temperature and the surface wind stress anomalies in the tropical Pacific and Indian Oceans during the Indian Ocean Dipole (IOD) events, two major modes of the IOD and their formation mechanisms are revealed. (1) The subsurface temperature anomaly (STA) in the tropical Indian Ocean during the IOD events can be described as a "<" -shaped and west-east-oriented dipole pattern; in the east side of the "<" pattern, a notable tongue-like STA extends westward along the equator in the tropical eastern Indian Ocean; while in the west side of the "<" pattern, the STA has opposite sign with two centers (the southern one is stronger than the northern one in intensity) being of rough symmetry about the equator in the tropical mid-western Indian Ocean. (2) The IOD events are composed of two modes, which have similar spatial pattern but different temporal variabilities due to the large scale air-sea interactions within two independent systems. The first mode of the IOD event originates from the air-sea interaction on a scale of the tropical Pacific-Indian Ocean and coexists with ENSO. The second mode originates from the air-sea interaction on a scale of the tropical Indian Ocean and is closely associated with changes in the position and intensity of the Mascarene high pressure. The strong IOD event occurs when the two modes are in phase, and the IOD event weakens or disappears when the two modes are out of phase. Besides, the IOD events are normally strong when either of the two modes is strong. (3) The IOD event is caused by the abnormal wind stress forcing over the tropical Indian Ocean, which results in vertical transports, leading to the upwelling and pileup of seawater. This is the main dynamic processes resulting in the STA. When the anomalous easterly exists over the equatorial Indian Ocean, the cold waters upwell in the tropical eastern Indian Ocean while the warm waters pileup in the tropical western Indian Ocean, hence the thermocline in the tropical Indian Ocean is shallowed in the east and deepened in the west. The off-equator component due to the Coriolis force in the equatorial area causes the upwelling of cold waters and the shallowing of the equatorial India Ocean thermocline. On the other hand, the anomalous anticyclonic circulations and their curl fields located on both sides of the equator, cause the pileup of warm waters in the central area of their curl fields and the deepening of the equatorial Indian Ocean thermocline off the equator. The above three factors lead to the occurrence of positive phase IOD events. When anomalous westerly dominates over the tropical Indian Ocean, the dynamic processes are reversed, and the negative-phase IOD event occurs.

Learning Object-Independent Modes of Variation with Feature Flow Fields

We present a unifying framework in which "object-independent" modes of variation are learned from continuous-time data such as video sequences. These modes of variation can be used as "generators" to produce a manifold of images of a new object from a single example of that object. We develop the framework in the context of a well-known example: analyzing the modes of spatial deformations of a scene under camera movement. Our method learns a close approximation to the standard affine deformations that are expected from the geometry of the situation, and does so in a completely unsupervised (i.e. ignorant of the geometry of the situation) fashion. We stress that it is learning a "parameterization", not just the parameter values, of the data. We then demonstrate how we have used the same framework to derive a novel data-driven model of joint color change in images due to common lighting variations. The model is superior to previous models of color change in describing non-linear color changes due to lighting.

Il Sistema di Revenue Management strumento per lo sviluppo turistico sostenibile delle destinazioni

Businesses interact constantly with the environment, realizing several and heterogeneous exchanges. Organizations can be considered a system of different interests, frequently conflicting and the satisfaction of different stakeholders is a condition of success and survival. National and international literature attempts to explain the complex connection between companies and environment. In particular, the Stakeholder Theory considers crucial for businesses the identification of different stakeholders and their involvement in decision-making process. In this context, profit can not be considered the only purpose of companies existence and business aims become more numerous and different. The Stakeholder Theory is often utilized as framework for tourism studies, in particular in Sustainable Tourism Development research. In fact, authors consider sustainable the tourism development able to satisfy interests of different stakeholders, traditionally identified as local community and government, businesses, tourists and natural environment. Tourism businesses have to guarantee the optimal use of natural resources, the respect of socio-cultural tradition of local community and the creation of socio-economic benefits for all stakeholders in destinations. An obstacle to sustainable tourism development that characterizes a number of destinations worldwide is tourism demand seasonality. In fact, its negative impact on the environment, economy and communities may be highly significant. Pollution, difficulties in the use of public services, stress for residents, seasonal incomes, are all examples of the negative effects of seasonality. According to the World Tourism Organization (2004) the limitation of seasonality can favour the sustainability of tourism. Literature suggests private and public strategies to minimize the negative effects of tourism seasonality, as diversification of tourism products, identification of new market segments, launching events, application of public instruments like eco-taxes and use of differential pricing policies. Revenue Management is a managerial system based on differential pricing and able to affect price sensitive tourists. This research attempts to verify if Revenue Management, created to maximize profits in tourism companies, can also mitigate the seasonality of tourism demand, producing benefits for different stakeholders of destinations and contributing to Sustainable Tourism Development. In particular, the study attempts to answer the following research questions: 1) Can Revenue Management control the flow of tourist demand? 2) Can Revenue Management limit seasonality, producing benefits for different stakeholders of a destination? 3) Can Revenue Management favor the development of Sustainable Tourism? The literature review on Stakeholder Theory, Sustainable Tourism Development, tourism seasonality and Revenue Management forms the foundation of the research, based on a case study approach looking at a significant destination located in the Southern coast of Sardinia, Italy. A deductive methodology was applied and qualitative and quantitative methods were utilized. This study shows that Revenue Management has the potential to limit tourism seasonality, to mitigate negative impacts occurring from tourism activities, producing benefits for local community and to contribute to Sustainable Tourism Development.