Showing papers by "University of Alicante published in 2007"

The Sonogashira Reaction: A Booming Methodology in Synthetic Organic Chemistry†

Abstract: 3.7. Palladium Nanoparticles as Catalysts 888 3.8. Other Transition-Metal Complexes 888 3.9. Transition-Metal-Free Reactions 889 4. Applications 889 4.1. Alkynylation of Arenes 889 4.2. Alkynylation of Heterocycles 891 4.3. Synthesis of Enynes and Enediynes 894 4.4. Synthesis of Ynones 896 4.5. Synthesis of Carbocyclic Systems 897 4.6. Synthesis of Heterocyclic Systems 898 4.7. Synthesis of Natural Products 903 4.8. Synthesis of Electronic and Electrooptical Molecules 906

TREC: Experiment and evaluation in information retrieval

Abstract: Any books that you read, no matter how you got the sentences that have been read from the books, surely they will give you goodness. But, we will show you one of recommendation of the book that you need to read. This trec experiment and evaluation in information retrieval is what we surely mean. We will show you the reasonable reasons why you need to read this book. This book is a kind of precious book written by an experienced author.

Organocatalytic asymmetric conjugate additions

Abstract: The asymmetric organocatalytic conjugate addition of nucleophiles to Michael acceptors is reviewed. Herein an overview of the most important developments and concepts of this flourishing area of catalysis organized by the type of nucleophile involved in the process is reported.

Magnetism in Graphene Nanoislands

Abstract: We study the magnetic properties of nanometer-sized graphene structures with triangular and hexagonal shapes terminated by zigzag edges. We discuss how the shape of the island, the imbalance in the number of atoms belonging to the two graphene sublattices, the existence of zero-energy states, and the total and local magnetic moment are intimately related. We consider electronic interactions both in a mean-field approximation of the one-orbital Hubbard model and with density functional calculations. Both descriptions yield values for the ground state total spin S consistent with Lieb’s theorem for bipartite lattices. Triangles have a finite S for all sizes whereas hexagons have S � 0 and develop local moments above a critical size of � 1: 5n m.

Complex Social Networks

Abstract: 1. Introduction 2. Complex networks: basic theory 3. Epidemic diffusion 4. Neighborhood effects in diffusion and play 5. Searching in social networks 6. Search, diffusion, and play in coevolving networks Afterword Appendix A. Generating functions Appendix B. The Ising model Appendix C. Mean-field theory.

Alcohols as electrophiles in C--C bond-forming reactions: the hydrogen autotransfer process.

Abstract: The hydrogen autotransfer process involves an initial oxidative hydrogen elimination, followed by different types of reactions, and is completed with a reductive hydrogen addition to give the final product. The sequence allows the alkylation of different nucleophilic agents using environmentally benign alcohols as electrophiles, mild conditions, and soft bases, with water produced as the only waste material. Recent examples of modulating the organometallic catalyst have also lent themselves to expansion of the range of available substrates, as described in this Minireview.

UV filters : From sunscreens to human body and the environment

Abstract: Recognition of the harmful effects of ultraviolet (UV) radiation on the skin has triggered development of organic chemicals (commonly referred as UV filters) that can absorb UV radiation and attenuate the negative effects of sunlight exposure. Depending on the properties and the intended degree of protection, a wide array of combinations is being marketed as delivering protection against most kinds of UV-induced skin damage. However, some UV filters have dermatological implications, so maximum applicable concentrations have been established. To monitor to what extent commercial products comply with the mandatory limits, several analytical methods have been used for their determination in cosmetics and related products. Further research on the efficacy of UV filters applied on the skin surface has brought to light a gradual attenuation of their UV-protective capacity that cannot solely be attributed to photo-induced decomposition. Investigations carried out to elucidate the reasons underlying this behaviour concluded that UV filters may be systematically absorbed through the skin surface or even released during bathing and washing activities. These observations gave rise to numerous studies aiming to investigate the magnitude and effects of skin penetration as well as accumulation in the water environment. Because of the need for more in-depth investigation into the behavior of UV filters, the initial demand for product certification has been extended to include reliable analytical methods to determine these substances at low concentration levels and in complex matrices (e.g., biological and environmental samples). Until now, most of the available methods, although designed to cover a large variety of substances, quantify them at only high-mg/L levels; however, recently, researchers have paid special attention to developing more sensitive procedures able to determine these substances in biological tissues and fluids or environmental samples at ng/L levels without matrix interferences. This article gives a comprehensive outline of the accumulated knowledge on UV-filter determination in biological and environmental samples and encourages further research in this new, challenging field of analytical, health and environmental science.

Enantioselective direct aldol reaction: the blossoming of modern organocatalysis

Abstract: We are grateful to the Spanish Ministerio de Educacion y Ciencia, as well as to Generalitat Valenciana and University of Alicante, for their continuous financial support.

Bistable Spin-Crossover Nanoparticles Showing Magnetic Thermal Hysteresis near Room Temperature

Abstract: Spanish Ministry of Education and Science (MEC) (Projects CTQ2005-09385-C03-01 and MAT2004-3849)

Organocatalytic enantioselective multicomponent reactions (OEMCRs)

Abstract: The achieved level of expertise in organocatalytic processes has allowed synthetic chemists to apply this useful synthetic strategy to enantioselective multicomponent reactions. Although, this new methodology is still in its infancy, the reported results show the possibilities and versatility of this type of reaction, with an extraordinary level of atom efficiency being reached. All examples, from classical Mannich, Biginelli, Michael, and Diels–Alder reactions to new amination–reduction and Tietze reactions, allow the synthesis of complex chiral molecules with several stereogenic elements created in just one process. In fact, the organocatalyst acts in this type of process as a clear enzyme mimic, but with an ample substrate scope.

Environmental Strategies and Their Impact on Hotel Performance

Abstract: This study examines the relevance of environmental management as a source of competitive advantage for hotels. The relationship between the environmental proactivity of hotels located in the province of Alicante (Spain) and their economic performance levels was studied, and three strategic groups, based on environmental proactivity, were identified: Proactive, Intermediate and Reactive. The findings show that the degree of proactivity achieved by these hotels does not strongly impact on their organisational performance. Nevertheless, performance levels increase as environmental proactivity grows.

On the Nature of Photogenerated Radical Species Active in the Oxidative Degradation of Dissolved Pollutants with TiO2 Aqueous Suspensions: A Revision in the Light of the Electronic Structure of Adsorbed Water

Abstract: ◦OH radicals photogenerated via hole trapping by water species adsorbed on terminal Ti atoms are widely considered as active species in primary, oxidizing photocatalytic reactions with TiO2 aqueous suspensions. On the basis of the electronic structure of surface-bound water obtained from electron photoemission spectroscopy techniques data reported in the literature, evidence is found that water species specifically adsorbed on terminal (surface) Ti atoms cannot be photooxidized under supra-band gap UV illumination (hν ≥ 3.0 eV). The existing controversy on whether photogenerated valence band free holes are trapped either at adsorbed water species to produce adsorbed ◦OH radicals or at terminal oxygen ions ( ) of the TiO2 surface to generate terminal radicals is therefore solved in favor of the second hypothesis. The frequently proposed photocatalytic oxidation mechanism involving the desorption of photogenerated ◦OH radicals should be refused because adsorbed water cannot be photooxidized. It is concluded...

Editorial: Advances on natural language processing

Abstract: The Information Society needs of a daily progress in order to provide techniques and applications to manage huge amounts of information. NLDB Conferences have been held for the last ten years showing the advances and new techniques developed in the Information Society Technologies (IST) area and Database subject. NDLB Conferences have obtained a maturity in the last few years increasing the number of submissions: 32 submissions in 2003, 65 submissions in 2004 and 95 papers submitted in 2005. But, not only the number of submissions have been increased, the quality of submission has also been increased. For this reason, some papers with positive reviews have been rejected because we could not accept more than a fixed number of papers. Papers were reviewed by three reviewers from the Program Committee. This clearly contributed to the significant number of papers submitted (95). Twenty-nine were accepted as regular papers, while 18 were accepted as short papers. Six of the highest rated papers were selected for extension and publication in this special issue of the Data and Knowledge Engineering Journal. NLDB 2005, the 10th International Conference on Applications of Natural Language to Information Systems was held on June 15–17, 2005, at the University of Alicante, Spain. Since the first NLDB conference in 1995 the main goal has been to provide a forum to discuss and disseminate research on the integration of natural language resources in Information System Engineering. The development and convergence of computing, telecommunications and information systems has already led to a revolution in the way that we work, communicate with each other, buy goods and use services, and even in the way we entertain and educate ourselves. The revolution continues and one of its results is that large volumes of information will increasingly be held in a form which is more natural for users than the data presentation formats typical of computer systems of the past. Natural Language Processing (NLP) is crucial in solving these problems and language technologies will make an indispensable contribution to the success of the information systems. We would like to express here our thanks to all the reviewers for their quick and excellent work. We are also indebted to a number of individuals for taking care of specific parts of the conference program like Reind van de Riet, Elisabeth Mëtais and Farid Mezaine. And finally, thanks to the authors for the excellent quality of their work. The accepted papers are summarised in the following:

Fire persistence traits of plants along a productivity and disturbance gradient in mediterranean shrublands of south‐east Australia

Abstract: Aim To understand changes in fire persistence traits of plants along a latitudinal gradient, considering the interactions between productivity, community (fuel) structure and fire regime. Location A gradient in the south of Australia (latitude 33‐37 ° S; longitude 140‐ 143 ° E), including: Little Desert National Park (VIC), Big Desert Wilderness Park (VIC), Murray-Sunset National Park (VIC), Danggali Conservation Park (SA) and Ta rawi Nature Reserve (NSW). Methods We selected four areas along a latitudinal gradient for which information on fire history and vegetation was available. Then, we tested to what extent the four selected areas have different climate and different fire regimes. Plant cover values of different life forms provided an indication of the plant community structure and flammability, and the proportion of species with different fire persistence traits (resprouting, seedbank persistence) informed us on the trait selection. Results Precipitation decreases and temperature increases from south to north. Thus the selected sites represent a gradient from high productivity (low aridity) in the south to low productivity (high aridity) in the north. Fire statistics suggest that fire frequency parallels productivity. There is a tendency for life form dominance and community structure to shift in such a way that fuel connectivity is reduced towards the north. Resprouting species increase and obligate seeders decrease along the fire‐productivity gradient. Main conclusions Changes in plant traits are difficult to understand without simultaneous consideration of both the disturbance and the productivity gradients. In our study area, fire regime and productivity interact in such a way that decreases in productivity imply changes in fuel structure that produce a reduction in fire frequency. Resprouting species are better represented at the high fire‐productivity part of the gradient, while obligate seeders are better represented at the opposite end of the gradient. The results also emphasize the importance of considering not only climate changes but also changes in fuel structure to predict future fire regimes.

Theories of ageing

Abstract: Ageing is a universal, intrinsic, progressive and deleterious process. Understanding it is of major interest to scientist, physicians as well as to the general population. Critical to this understanding is to formulate comprehensive theories of aging with high predictive and explanatory power. More than 300 theories have been postulated and are reviewed here. The free radical theory of ageing is one of the most prominent and well studied. It was further developed by one of us (JM) in what has become known as the mitochondrial theory of ageing. These theories provide new experimental approaches to further develop our understanding of the phenomenon of ageing.

Plant Spatial Pattern Predicts Hillslope Runoff and Erosion in a Semiarid Mediterranean Landscape

Abstract: The importance of the spatial pattern of vegetation for hydrological behavior in semiarid environments is widely acknowledged. However, there is little empirical work testing the hypothetical covariation between vegetation spatial structure and hillslope water and sediment fluxes. We evaluated the relationships between vegetation structural attributes (spatial pattern, functional diversity), soil surface properties (crust, stone, plant, and ground cover, and particle size distribution) and hillslope hydrologic functioning in a semiarid Mediterranean landscape; in particular, we tested whether decreasing patch density or coarsening plant spatial pattern would increase runoff and sediment yield at the hillslope scale. Runoff and sediment yield were measured over a 45-month period on nine 8 × 2-m plots that varied in vegetation type and spatial pattern. We grouped vegetation into functional types and derived plant spatial pattern attributes from field plot maps processed through a GIS system. We found that there was an inverse relationship between patch density and runoff, and that both runoff and sediment yields increased as the spatial pattern of vegetation coarsened. Vegetation pattern attributes and plant functional diversity were better related to runoff and sediment yield than soil surface properties. However, a significant relationship was found between physical crust cover and plant spatial pattern. Our results present empirical evidence for the direct relationship between the hydrologic functioning of semiarid lands and both the spatial pattern and the functional diversity of perennial vegetation, and suggest that plant spatial pattern, physical crust cover, and functional diversity may be linked through feedback mechanisms.

Effect of chitosan on hyphal growth and spore germination of plant pathogenic and biocontrol fungi

Abstract: Aims: To investigate the toxic effect of chitosan on important root pathogenic and biocontrol fungi (nematophagous, entomopathogenic and mycoparasitic). Methods and Results: We have used standard bioassays to investigate the effect of chitosan on colony growth and developed bioassays to test spore germination. The results showed that the root pathogenic and mycoparasitic fungi tested were more sensitive to chitosan than nematophagous and entomopathogenic fungi. Chitosanases (and perhaps related enzymes) are involved in the resistance to chitosan. Two fungi, one sensitive to chitosan, Fusarium oxysporum f. sp. radicis-lycopersici, and one less sensitive, Pochonia chlamydosporia, were selected for ultrastructural investigations. Transmission electron microscopy revealed differences in the ultrastructural alterations caused by chitosan in the spores of the plant pathogenic fungus and in those of the nematophagous fungus. Confocal laser microscopy showed that Rhodamine-labelled chitosan enters rapidly into conidia of both fungi, in an energy-dependent process. Conclusions: Nematophagous and entomopathogenic fungi are rather resistant to the toxic effect of chitosan. Resistance of nematophagous and entomopathogenic fungi to chitosan could be associated with their high extracellular chitosanolytic activity. Furthermore, ultrastructural damage is much more severe in the chitosan sensitive fungus. Significance and impact of the study: The results of this paper suggest that biocontrol fungi tested could be combined with chitosan for biological control of plant pathogens and pests.

Post-fire hydrological and erosional responses of a Mediterranean landscpe: Seven years of catchment-scale dynamics

Abstract: We studied medium-term dynamics of fire effects on catchment runoff and sediment yield in a dry-Mediterranean area in Alicante, E Spain. The study area was a mixed forest and agricultural terraced landscape that was affected by a wildfire in August 1998. We measured runoff and sediment yield in two catchments – burned and unburned – during the first seven years after the wildfire. Post-fire vegetation cover dynamics were also monitored. Total runoff and sediment yield in the burned catchment (35 mm and 4563 kg ha − 1 , respectively) were considerably greater than in the unburned catchment (0.03 mm, and 0.12 kg ha − 1 ). Annual runoff and sediment yield increased with time after fire until the third post-fire year, and then decreased progressively. However, even five years after the wildfire, differences in annual runoff and sediment yield between the burned and the unburned catchments were still about two orders of magnitude. Post-fire vegetation cover increased very slowly during the initial post-fire years, and differences between burned and unburned areas persisted six years after the wildfire. Most studies on post-fire hydrology and erosion have identified the first one or two post-fire years as the critical period for high runoff and erosion risk, indicating short-term ecosystem resilience to wildfire. However, we found that wildfire impact on catchment runoff and sediment yield in Mediterranean drylands may be amplified by drought periods that delay plant recovery, and thus wildfire impacts may be still of great importance several years after the fire.

Question Answering in Restricted Domains: An Overview

Abstract: Automated question answering has been a topic of research and development since the earliest AI applications. Computing power has increased since the first such systems were developed, and the general methodology has changed from the use of hand-encoded knowledge bases about simple domains to the use of text collections as the main knowledge source over more complex domains. Still, many research issues remain. The focus of this article is on the use of restricted domains for automated question answering. The article contains a historical perspective on question answering over restricted domains and an overview of the current methods and applications used in restricted domains. A main characteristic of question answering in restricted domains is the integration of domain-specific information that is either developed for question answering or that has been developed for other purposes. We explore the main methods developed to leverage this domain-specific information.