Showing papers by "University of Seville published in 2004"

Biocontrol mechanisms of Trichoderma strains

Abstract: The genus Trichoderma comprises a great number of fungal strains that act as biological control agents, the antagonistic properties of which are based on the activation of multiple mechanisms. Trichoderma strains exert biocontrol against fungal phytopathogens either indirectly, by competing for nutrients and space, modifying the environmental conditions, or promoting plant growth and plant defensive mechanisms and antibiosis, or directly, by mechanisms such as mycoparasitism. These indirect and direct mechanisms may act coordinately and their importance in the biocontrol process depends on the Trichoderma strain, the antagonized fungus, the crop plant, and the environmental conditions, including nutrient availability, pH, temperature, and iron concentration. Activation of each mechanism implies the production of specific compounds and metabolites, such as plant growth factors, hydrolytic enzymes, siderophores, antibiotics, and carbon and nitrogen permeases. These metabolites can be either overproduced or combined with appropriate biocontrol strains in order to obtain new formulations for use in more efficient control of plant diseases and postharvest applications.

Babinet principle applied to the design of metasurfaces and metamaterials.

Abstract: The electromagnetic theory of diffraction and the Babinet principle are applied to the design of artificial metasurfaces and metamaterials. A new particle, the complementary split rings resonator, is proposed for the design of metasurfaces with high frequency selectivity and planar metamaterials with a negative dielectric permittivity. Applications in the fields of frequency selective surfaces and polarizers, as well as in microwave antennas and filter design, can be envisaged. The tunability of all these devices by an applied dc voltage is also achievable if these particles are etched on the appropriate substrate.

Effective negative-/spl epsiv/ stopband microstrip lines based on complementary split ring resonators

Abstract: In this letter a super-compact stopband microstrip structure is proposed. The frequency gap is produced by an array of complementary split ring resonators (CSRRs)-a concept proposed here for the first time-etched on the ground plane. This behavior is interpreted as due to the presence of a negative effective dielectric permittivity in the vicinity of resonance. The resulting device produces a deep rejection frequency band with sharp cutoff, and a pass band that exhibits very low losses and good matching. Due to the sub-lambda operation of CSRRs, the electrical size of the device is very small.

Decamethyldizincocene, a stable compound of Zn(I) with a Zn-Zn bond.

Abstract: Unlike mercury, which has an extensive +1 oxidation state chemistry, zinc usually adopts the +2 oxidation state. Decamethyldizincocene, Zn2(eta5-C5Me5)2, an organometallic compound of Zn(I) formally derived from the dimetallic [Zn-Zn]2+ unit, has been isolated from the low-temperature (-10 degrees C) reaction of Zn(C5Me5)2 and Zn(C2H5)2 in diethyl ether. X-ray studies show that it contains two eclipsed Zn(eta5-C5Me5) fragments with a Zn-Zn distance (+/- standard deviation) of 2.305(+/-3) angstroms, indicative of a metal-metal bonding interaction.

Artificial magnetic metamaterial design by using spiral resonators

Abstract: A metallic planar particle, that will be called spiral resonator (SR), is introduced as a useful artificial atom for artificial magnetic media design and fabrication. A simple theoretical model which provides the most relevant properties and parameters of the SR is presented. The model is validated by both electromagnetic simulation and experiments. The applications of SR's include artificial negative magnetic permeability media (NMPM) and left-handed-media (LHM) design. The main advantages of SR's for such purpose are small electrical size at resonance, absence of magnetoelectric coupling (thus avoiding bianisotropic effects in the continuous medium made of these particles), and easy fabrication. Experimental confirmation of NMPM and LHM behavior using SR's is also reported.

Evidence of melatonin synthesis by human lymphocytes and its physiological significance: possible role as intracrine, autocrine, and/or paracrine substance

Abstract: It has been historically assumed that the pineal gland is the major source of melatonin (N-acetyl-5-methoxytryptamine) in vertebrates. Melatonin plays a central role in fine-tuning circadian rhythms in vertebrate physiology. In addition, melatonin shows a remarkable functional versatility exhibiting antioxidant, oncostatic, antiaging, and immunomodulatory properties. Melatonin has been identified in a wide range of organisms from bacteria to human beings. Its biosynthesis from tryptophan involves four well-defined intracellular steps catalyzed by tryptophan hydroxylase, aromatic amino acid decarboxylase, serotonin-N-acetyltransferase, and hydroxyindole-O-methyltransferase. Here, for the first time, we document that both resting and phytohemagglutinin-stimulated human lymphocytes synthesize and release large amounts of melatonin, with the melatonin concentration in the medium increasing up to five times the nocturnal physiological levels in human serum. Moreover, we show that the necessary machinery to synthesize melatonin is present in human lymphocytes. Furthermore, melatonin released to the culture medium is synthesized in the cells, because blocking the enzymes required for its biosynthesis or inhibiting protein synthesis in general produced a significant reduction in melatonin release. Moreover, this inhibition caused a decrease in IL-2 production, which was restored by adding exogenous melatonin. These findings indicate that in addition to pineal gland, human lymphoid cells are an important physiological source of melatonin and that this melatonin could be involved in the regulation of the human immune system, possibly by acting as an intracrine, autocrine, and/or paracrine substance.

Bioclimate envelope models: what they detect and what they hide: Correspondence

Abstract: INTRODUCTION In a recent issue of Global Ecology and Biogeo-graphy , Pearson & Dawson (2003) provided an informative review of the use of bioclimate envelope models (BEM) for predicting future distributional ranges of temperate plant species under expected global climate change. The authors discuss several criticisms of the BEM approach and they conclude that these need not be a major drawback when applied as a starting point for predicting the impacts of potential climate change on species ranges. Here, I argue that the strongly deterministic and reductionist BEM rely on biological assumptions that are much more commonly violated in nature than Pearson & Dawson (2003) assume. Moreover, the statistical methods currently used for model validation overestimate model fits as a result of pseudoreplication. Both features make BEM prone to produce artificially optimistic scenarios of future climate change impacts on plant distributions. Little doubt exists that climate determines the large-scale distributions of many temperate plant species (Woodward, 1987). However , ongoing range shifts are affected by a multitude of other constraints and processes acting on population performance (e.g. These differ greatly across species' ranges from their expanding to their eroding margins, and so also does the character of the respective populations (Lesica & Allendorf, 1995; Davis & Shaw, 2001). This will most probably result in geographically differential responses to changing environmental conditions , a point largely ignored by BEM approaches. In the following, I will comment on three major biological critiques of BEM that have been reviewed and downplayed by Pearson & Dawson (2003). BIOTIC INTERACTIONS BEM treat species as if they were acting independently of their biotic environment, thus neglecting potential effects of predation, competition or mutualisms on range dynamics. Pearson & Dawson (2003) argue accordingly that interactions between species may shape their spatial distributions on fine geographical scales, but are of minor importance at coarse scales, which are the main focus of BEM. However biotic interactions, not climate, are commonly considered the principal determinants of low-latitude range limits (Brown et al ., 1996). Moreover, ecological research on biological invasions (unintended 'large-scale experiments') has broadly documented that biotic interactions affect species' performance throughout their established ranges. The release of invaders from their specialist antagonists in invaded areas underpins improved performances as compared with populations within the original range, and thus constitutes a key factor promoting the invasion process (Keane & Crawley, 2002). Range dynamics themselves are likewise affected by biotic …

Accounting for Intangibles: A Literature Review

Abstract: The purpose of Financial Accounting is to provide users of financial statements with information that is useful for efficient decision making. According to the FASB [1978, par. 34], financial reporting should provide information that is useful to present and potential investors and creditors and other users in making rational investment, credit, and similar decisions. Consequently, any event that is likely to affect a firm's current financial position or its future performance should be reported in its annual accounts. In order to provide the users of financial statements with relevant information for investment and credit decision making, standard setting bodies should develop guidelines for the identification of intangible elements, a set of criteria for their valuation and adequate standards for financial reporting. This paper intends to provide a starting point for that endeavor by reviewing the literature published to date in three areas: (i) the economic nature, definition and classification of intangibles, (ii) the relevance of intangibles for investment and lending decisions, and (iii) the ways in which the current accounting model may be modified in order to provide useful information on the determinants of the firms' financial position in their financial statements.

Electrically forced coaxial nanojets for one-step hollow nanofiber design.

Abstract: The outer liquid of a two-liquid coaxial electrified jet is gelled before the onset of natural instabilities to yield hollow nanofibers. By using sol−gel chemistry, innocuous solvents such as glycerol and olive oil, and electrohydrodynamics, it is possible to make such structures in a rather straightforward manner.

Friendship and loneliness among bullies and victims: Data from seven countries

Abstract: Research suggests that the relationship between school bullying and its various risk factors should be clearer among girls than boys, and should become stronger with age, as roles within the peer group stabilise. This paper tests this theory by comparing sex, school type, and bully/victim status differences in friendships and playground social interactions, using data from nine surveys in seven countries: China, England, Ireland, Italy, Japan, Portugal, and Spain. A total of approximately 48,000 children completed various translations of the Olweus Bullying Questionnaire. Small but generally consistent main effects were found for sex and school type (boys and primary pupils enjoyed playtimes more and had more friends, but were also more likely to spend playtimes alone). Larger effects were consistently found for bully/victim status (victims were significantly worse off on all the measures in all the samples where a difference was found, while bullies and neutrals did not differ consistently), but the interactions between these factors varied widely between samples and there were few consistent patterns. It is concluded that bullying is a universal phenomenon with many negative correlates for victims and few (if any) for bullies, but that there are cultural variations in the way that bullying is related to sex, age, and social support.

Fauna of the Mediterranean Hydrozoa

Abstract: This study provides a systematic account of the hydrozoan species collected up to now in the Mediterranean Sea. All species are described, illustrated and information on morphology and distribution is given for all of them. This work is the most complete fauna of hydrozoans made in the Mediterranean. The fauna includes planktonic hydromedusae, benthic polyps stages and the siphonophores. The Hydrozoa are taken as an example of inconspicuous taxa whose knowledge has greatly progressed in the last decades due to the scientific research of some specialists in the Mediterranean area. The number of species recorded in the Mediterranean almost doubled in the last thirty years and the number of new records is still increasing. The 457 species recorded in this study represents the 12% of the world known species. The fauna is completed with classification keys and a glossary of terms with the main purpose of facilitating the identification of all Meditrranean hydrozoan species

The influence of employee organizational citizenship behavior on customer loyalty

Abstract: This work analyzes the effect that service company employee behavior has on customer perceptions of the quality of services received, and the consequent company performance. Organizational citizenship behavior has been recognized as relevant behavior of some employees, but its role regarding customer perceptions and company profitability remains unexplored. Beginning with a brief review of the conceptual background of organizational citizenship behavior, service quality, and its consequences, this paper proposes a model to test these relationships empirically. Some helpful recommendations for managing service companies are presented.

Accumulation of astaxanthin and lutein in Chlorella zofingiensis (Chlorophyta).

Abstract: When grown photoautotrophically, Chlorella zofingiensis strain CCAP 211/14 accumulates a significant amount of valuable carotenoids, namely astaxanthin and lutein, of increasing demand for use as feed additives in fish and poultry farming, as colorants in food, and in health care products. Under standard batch-culture conditions, this microalgal strain exhibits high values of both growth rate (about 0.04 h−1) and standing cell population (over 1011 cells l−1, or 7 g dry weight l−1). Lutein, in a free (unesterified) form, was the prevalent carotenoid during early stages of cultivation (over 0.3 pg cell−1, equal to 4 mg g−1 dry weight, or 20 mg l−1 culture), whereas esterified astaxanthin accumulated progressively, to reach a maximum (over 0.1 pg cell−1, equal to 1.5 mg g−1 dry weight, or 15 mg l−1 culture) in the late stationary phase. A differential response of lutein and astaxanthin accumulation was also recorded with regard to the action of some environmental and nutritional factors. C. zofingiensis CCAP 211/14 represents a unique model system for analyzing the differential regulation of the levels of primary (lutein) and secondary (astaxanthin) carotenoids. Relevant also from the biotechnological viewpoint, this photosynthetic organism, with outstanding attributes for fast photosynthetic growth and carotenoid accumulation, might prove most valuable for its application to the mass production of either or both lutein and astaxanthin.

Centralized Resource Allocation Using Data Envelopment Analysis

Abstract: While conventional DEA models set targets separately for each DMU, in this paper we consider that there is a centralized decision maker (DM) who “owns” or supervises all the operating units. In such intraorganizational scenario the DM has an interest in maximizing the efficiency of individual units at the same time that total input consumption is minimized or total output production is maximized. Two new DEA models are presented for such resource allocation. One type of model seeks radial reductions of the total consumption of every input while the other type seeks separate reductions for each input according to a preference structure. In both cases, total output production is guaranteed not to decrease. The two key features of the proposed models are their simplicity and the fact that both of them project all DMUs onto the efficient frontier. The dual formulation shows that optimizing total input consumption and output production is equivalent to finding weights that maximize the relative efficiency of a virtual DMU with average inputs and outputs. A graphical interpretation as well as numerical results of the proposed models are presented.

Avoidance Response in Goldfish: Emotional and Temporal Involvement of Medial and Lateral Telencephalic Pallium

Abstract: The hippocampus and the amygdala are involved in avoidance learning in mammals. The medial and lateral pallia of actinopterygian fish have been proposed as homologous to the mammalian pallial amygdala and hippocampus, respectively, on the basis of neuroanatomical findings. This work was aimed at studying the effects of ablation of the medial telencephalic pallia (MP) and lateral telencephalic pallia (LP) in goldfish on the retention of a conditioned avoidance response previously acquired in two experimental conditions. In the first experiment, fish were trained in nontrace avoidance conditioning. In the second experiment, fish were trained in trace avoidance conditioning in which temporal cues were crucial for the learning process. An MP lesion affected the retention of the avoidance response in both procedures; in contrast, an LP lesion impaired the retention only in the trace-conditioning procedure. These data support the presence of two different systems of memory in fish, based on discrete telencephalic areas: the MP, involved in an emotional memory system; and the LP, involved in a spatial, relational, or temporal memory system. Moreover, these differential effects were similar to those produced by amygdalar and hippocampal lesions in mammals. We conclude that these specialized systems of memory could have appeared early during phylogenesis and could have been conserved throughout vertebrate evolution.

A review and classification of heuristics for permutation flow-shop scheduling with makespan objective

Abstract: Makespan minimization in permutation flow-shop scheduling is an operations research topic that has been intensively addressed during the last 40 years. Since the problem is known to be NP-hard for ...

Lonely in the crowd: Recollections of bullying

Abstract: This study examined the long-term correlates of victimization in school with aspects of functioning in adult life, using a specially designed Retrospective Bullying Questionnaire, which also included questions about short-term effects (e. g. suicidal ideation and intrusive memories) and victimization experiences in adulthood. Current relationship quality was assessed in terms of self-perception, attachment style and friendship quality. In total, 884 adults (35% male) from two occupations (teacher, student) and three countries (Spain, Germany, UK) participated. Victims and especially stable victims (in both primary and secondary school) scored lower on general self-esteem and higher on emotional loneliness, and reported more difficulties in maintaining friendships, than non-victims. Victims in secondary school had a lower self-esteem in relation to the opposite sex and were more often fearfully attached. The data revealed additional differences by gender, occupation and country level, but no further interactions with victim status. This indicates a general association between victimization in school and quality of later life predominately robust to variations in gender, occupation and country. Possible limitations caused by the retrospective nature of victimization reports are acknowledged.

Development of the inhibitory component of the executive functions in children and adolescents.

Abstract: The development of inhibitory control, one component of the executive functions, during childhood and adolescence was the focus of the present study. A group of 99 participants between 6 and 17 years of age were studied using the Stroop test. Results suggest the existence of age-related differences both in response times and errors that follow a nonlinear relationship. Interference increased in the first age groups, declining from around 10 years till 17 years. Data also suggest that word reading plays an important role in the performance of the task. When reading is blocked, linear relationships between age and interference measures emerge, showing an increase in inhibitory functions during childhood and adolescence.

Very low-voltage analog signal processing based on quasi-floating gate transistors

Abstract: A novel design principle for very low-voltage analog signal processing in CMOS technologies is presented. It is based on the use of quasi-floating gate (QFG) MOS transistors. Similar to multiple input floating gate (MIFG) MOS transistors, a weighted averaging of the inputs accurately controlled by capacitance ratios can be obtained, which is the basic operating principle. Nevertheless, issues often encountered in MIFG structures, such as the initial charge trapped in the floating gates or the gain-bandwidth product degradation, are not present in QFG configurations. Several CMOS circuit realizations using open- and closed-loop topologies, have been designed. They include analog switches, mixers, programmable-gain amplifiers, track and hold circuits, and digital-to-analog converters. All these circuits have been experimentally verified, confirming the usefulness of the proposed technique for very low-voltage applications.