The Influence of Silicon Nanoclusters on the Optical Properties of a-SiNx Samples: A Theoretical Study

By means of ab-initio calculations we investigate the optical properties of pure a-SiN$_x$ samples, with $x \in [0.4, 1.8]$, and samples embedding silicon nanoclusters (NCs) of diameter $0.5 \leq d \leq 1.0$ nm. In the pure samples the optical absorption gap and the radiative recombination rate vary according to the concentration of Si-N bonds. In the presence of NCs the radiative rate of the samples is barely affected, indicating that the intense photoluminescence of experimental samples is mostly due to the matrix itself rather than to the NCs. Besides, we evidence an important role of Si-N-Si bonds at the NC/matrix interface in the observed photoluminescence trend

The Discovery of Initial Fluxes of Metabolic P Systems

A central issue in systems biology is the study of efficient methods to infer fluxes of biological reactions starting from experimental data. Among the different techniques proposed in the last years, in the theory of Metabolic P systems Log-Gain principles have been introduced, which prove to be helpful for deducing biological fluxes from temporal series of observed dynamics. However, crucial tasks remain to be performed for a complete suitable application of these principles. In particular the algebraic systems introduced by the Log-Gain principles require the knowledge of the initial fluxes associated with a set of biochemical reactions. In this paper we propose an algorithm for estimating initial fluxes, which is tested in two case studies

Application of Seismic Tomography and Geotechnical Modeling for the Solution of Two Complex Instability Cases

The geotechnical instability of sites and artificial structures is a widespread problem that particularly affects heavily anthropized areas and historical cities, and often this instability is linked to human activities and to interventions carried out without adequate preliminary geotechnical studies. The most common procedure for assessing unstable sites includes base studies such as drilling boreholes, shallow excavations, and engineering geology studies. However, more and more often, some geophysical techniques are associated to the above intervention, represent the first phase of assessment, and allow optimizing the possible campaign of excavations and boreholes. Compared to direct surveys, the geophysical ones provide extensive and continuous information, are moderately invasive, and have a remarkably advantageous information-to-cost ratio. In this chapter, we illustrate two examples of characterization of unstable sites. The first case concerns the ancient walls of an Italian city, and the second one deals with the instability of a road slope. In both cases, the geotechnical modeling is also based on the results of preliminary geophysical surveys

MP Modeling of Glucose-Insulin Interactions in the Intravenous Glucose Tolerance Test

The Intra Venous Glucose Tolerance Test (IVGTT) is an experimental pro- cedure in which a challenge bolus of glucose is administered intra-venously and plasma glucose and insulin concentrations are then frequently sampled. An open problem is to construct a model representing simultaneously the entire control system. In the last three decades, several models appeared in the literature. One of the mostly used one is known as the minimal model, which has been challenged by the dynamical model. However, both the models have not escape from criticisms and drawbacks. In this paper we apply Metabolic P systems theory for developing new physiologically based models of the glucose-insulin system which can be applied to the Intra Venous Glucose Tolerance Test. We considered ten data-sets obtained from literature and for each of them we found an MP model which ts the data and explains the regulations of the dynamics. Finally, further analysis are planned in order to de ne common patterns which explain, in general, the action of the glucose-insulin control system

Linking Bistable Dynamics to Metabolic P Systems

Bistability, or more generally multistability, is an important recurring theme in biological systems. In particular, the discovery of bistability in signal pathways of genetic networks, prompts strong interest in understanding both the design and function of these networks. Therefore, modelling these systems is crucial to understand their behaviors, and also to analyze and identify characteristics that would otherwise be di cult to realize. Although di erent classes of models have been used to study bistable dynamics, there is a lag in the development of models for bistable systems starting from experimental data. This is due to the lack of detailed knowledge of biochemical reactions and kinetic rates. In this work, we propose a procedure to develop, starting from observed dynamics, Metabolic P models for multistable processes. As a case study, a mathematical model of the Schl ogel's dynamics, which represents an example of a chemical reaction system that exhibits bistability, is inferred starting from observed stochastic bistable dynamics. Since, recent experiments indicate that noise plays an important role in the switching of bistable systems, the success of this work suggests that this approach is a very promising one for studying dynamics and role of noise in biological systems, such as, for example, genetic regulatory networks

Photophysics of pentacene-doped picene thin films

Here were report a study of picene nano-cristalline thin films doped with pentacene molecules. The thin films were grown by supersonic molecular beam deposition with a doping concentration that ranges between less than one molecules of pentacene every 104 picene molecules up to about one molecule of pentacene every 102 of picene. Morphology and opto-electronic properties of the films were studied as a function of the concentration of dopants. The optical response of the picene films, characterized by absorption, steady-state and time-resolved photoluminescence measurements, changes dramatically after the doping with pentacene. An efficient energy transfer from the picene host matrix to the pentacene guest molecules was observed giving rise to an intense photoluminescence coming out from pentacene. This efficient mechanism opens the possibility to exploit applications where the excitonic states of the guest component, pentacene, are of major interest such as MASER. The observed mechanism could also serve as prototypical system for the study of the photophysics of host guest systems based on different phenacenes and acenes.Comment: 15 pages, 6 figure

Fatty acid profile of milk fat in goat supplemented with iodized salt

Iodine is an essential nutrient of the human and animal diet which is needed for the synthesis of the thyroid hormones. These hormones play an important role in the regulation of fat metabolism. In fact, increased thyroid hormone levels stimulate fat mobilization, leading to increased concentrations of plasma triglyceride (Nikkila and Kekki, 1972) and enhanced oxidation of fatty acids in many tissues. Recently, Bauman et al. (2006) showed the involvement of a protein called spot 14, highly responsive to thyroid hormones, in the regulation of the mammary synthesis of milk fat. However, the effects of Iodine supplementation on plasma and milk fatty acid profile in dairy animals has not been elucidated yet. The aim of this study was to evaluate if the fatty acid (FA) profile of milk changes in goats supplemented with Iodine. Thirty crossbreed dairy goats were divided into 3 groups were used and supplemented with 0 (group 0), 450 (group 1), or 900 (group 2) μg of KI/day per head. Each dose of KI (76.5% of Iodine) was orally administered in water every day for 8 weeks. Milk yield was recorded and milk samples were collected every two weeks. A total of 120 milk samples were analyzed by gas chromatography (GC). Milk yield was not influences by treatments. Milk fat content was the highest (P<0.01) in group 1 (4.65%) compared to group 0 (4.15%) and group 2 (4.17%). Iodine treatments did not influence milk fatty acid profile except for the content of some short-chain fatty acids. In particular, only the contents of C8:0 FA (2.22, 2.24 and 2.12 in groups 0, 1 and 2, respectively; P<0.01) and C10:0 (9.74, 9.49 and 9.02 in groups 0, 1 and 2, respectively; P<0.01) decreased due to supplementation with the highest dose of KI. In conclusion, in this study Iodine supplementation did not show substantial effects on goat’s milk FA profile, probably due to the low doses of KI used. Nevertheless, the observed decrease of some short-chain fatty acids, which are synthesized ex-novo by the mammary gland, in goats supplemented with the highest KI dose tested is compatible with a potential involvement of Iodine or thyroid hormones in the regulation of fat synthesis in the mammary gland

Effect of dietary oil supplementation on fatty acid profile of backfat and intramuscular fat in finishing pigs

Two groups of finishing gilts were fed, for 4 weeks, a commercial feed enriched (2%) with either rapeseed oil or sunflower oil. Pig growth was monitored bi-weekly and the fatty acid composition of backfat and Longissimus muscle was determined after slaughtering. Type of dietary oil affected significantly the fatty acid profile of pork fat, especially the C18:3n-3 concentration which was higher in pigs fed rapeseed oil than in those fed sunflower oil. The content of monounsaturated fatty acids (MUFA) of Longissimus muscle was significantly higher than that of backfat, due to the its higher concentration of C18:1cis9 and C16:1. Differently, the long-chain n-3 polyunsaturated fatty acids (PUFA) content was higher in backfat than in Longissimus muscle. These results confirm that it is possible to manipulate the fatty acid composition of the diet, in order to improve the health properties of the adipose tissues of pork meat

Charge recombination reduction in dye-sensitized solar cells by means of an electron beam-deposited TiO2 buffer layer between conductive glass and photoelectrode

A thin anatase titanium dioxide compact film was deposited by electron beam evaporation as buffer layer between the conductive transparent electrode and the porous TiO2-based photoelectrode in dye-sensitized solar cells. The effect of such a buffer layer on the back transfer reaction of electrons to tri-iodide ions in liquid electrolyte-based cells has been studied by means of both electrochemical impedance spectroscopy and open circuit photovoltage decay analysis. The influence of the thickness has been also investigated and an increment in overall quantum conversion efficiency eta as high as +31% with respect to the standard cell - fabricated onto an uncoated conductive glass - has been revealed in the case of a 120 nm thick buffer layer. (C) 2010 Elsevier B.V. All rights reserve