Fabio Ricci - Academia.edu (original) (raw)

Papers by Fabio Ricci

2013 7th International Workshop on Traceability in Emerging Forms of Software Engineering (TEFSE), 2013

Latent Semantic Indexing (LSI) is an advanced method widely and successfully employed in Informat... more Latent Semantic Indexing (LSI) is an advanced method widely and successfully employed in Information Retrieval (IR). It is an extension of Vector Space Model (VSM) and it is able to overcome VSM in canonical IR scenarios where it is used on very large document repositories. LSI has also been used to semi-automatically generate traceability links between software artefacts. However, in such a scenario LSI is not able to overcome VSM. This contradicting result is probably due to the different characteristics of software artefact repositories as compared to document repositories. In this paper we present a preliminary empirical study to analyze how the size and the vocabulary of the repository-in terms of number of documents and terms (i.e., the vocabulary)-affects the retrieval accuracy. Even if replications are needed to generalize our findings, the study presented in this paper provides some insights that might be used as guidelines for selecting the more adequate methods to be used for traceability recovery depending on the particular application context.

Carbohydrate research

The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause se... more The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause serious damage to the tourism and fishing industries along the Adriatic coast. Mucilage is presently thought to be the result of the aggregation of dissolved organic matter (DOM) into particulate organic matter (POM). Three principal classes of compounds have been identified in organic matter by spectrometric determination: carbohydrates, proteins and lipids. Carbohydrates are suspected to play a role in the first steps of DOM aggregation. Despite its importance in understanding the processes leading to mucilage formation, our present knowledge of the composition of the mucilage carbohydrate fraction is incomplete. Due to its high sensitivity and specificity, liquid chromatography coupled with electrospray-ionization tandem mass spectrometry (LC-ESIMS/MS) is gaining an increasing importance as a powerful technique for carbohydrate purification and characterization in complex samples. In th...

In this study monthly cruises were carried out from November 2001 to November 2004 in four transe... more In this study monthly cruises were carried out from November 2001 to November 2004 in four transects along the coast of Pesaro (NW Adriatic Sea). Phytoplanktonic populations (Bacillariophyceae and Dinophyceae), chemical-physical parameters and eutrophic factors were analysed to localize eutrophic and bloom events. Phytoplankton community was often dominated by diatoms. Bacillariophyceae blooms occurred in February 2002 and 2004 (Skeletonema costatum) and May 2002 (Chaetoceros spp.); Dinophyceae blooms occurred in autumn periods.

This study reports the concentrations of important tracers of the marine environment, 210 Po and ... more This study reports the concentrations of important tracers of the marine environment, 210 Po and 210 Pb, in different matrices from field samples collected at Central Adriatic Sea (Italy), a non-contaminated marine ecosystem. 210 Po concentration appears to decrease with increasing distance from the coast and a significant difference in 210 Po concentrations in seawater samples at two different depths is not appreciable. 210 Po and 210 Pb present the same trend in the different periods of the year. 210 Po and 210 Pb present high concentration factors and high Kd values: in particular 210 Po shows values of 2.4 10 4 in plankton, 3.2 10 5 in the particulate fraction and 1.1 10 5 in sediment; 210 Pb shows values of 1.3 10 4 in plankton, 1.8 10 4 in the particulate fraction and 4.9 10 4 in sediment. The 210 Po/ 210 Pb ratio results < 1 in sea water and >1 in the particulate fraction, sediment and plankton due to a significant fractionation occurring between the two radionuclides during their removal from solution to particle and due to their different biogeochemical cycling pathways in the marine environment. The noticeable accumulation of 210 Po in the food chain is not accompanied by an identical accumulation of 210 Pb. Due to its biomagnification in the marine food chain, 210 Po provides the larges radiation dose to any marine organism under natural conditions. The data reported provide reference values for the Central Adriatic (Mediterranean Sea) coastal environment.

Marine Drugs, 2014

The dinoflagellate Alexandrium minutum is known for the production of potent neurotoxins affectin... more The dinoflagellate Alexandrium minutum is known for the production of potent neurotoxins affecting the health of human seafood consumers via paralytic shellfish poisoning (PSP). The aim of this study was to investigate the relationship between the toxin content and the expression level of the genes involved in paralytic shellfish toxin (PST) production. The algal cultures were grown both in standard f/2 medium and in phosphorus/nitrogen limitation. In our study, LC-HRMS analyses of PST profile and content in different Mediterranean A. minutum strains confirmed that this species was able to synthesize mainly the saxitoxin analogues Gonyautoxin-1 (GTX1) and Gonyautoxin-4 (GTX4). The average cellular toxin content varied among different strains, and between growth phases, highlighting a decreasing trend from exponential to stationary phase in all culture conditions tested. The absolute quantities of intracellular sxtA1 and sxtG mRNA were not correlated with the amount of intracellular toxins in the analysed A. minutum suggesting that the production of toxins may be regulated by post-transcriptional mechanisms and/or by the concerted actions of alternative genes belonging to the PST biosynthesis gene cluster. Therefore, it is likely that the sxtA1 and sxtG gene expression OPEN ACCESS Mar. Drugs 2014, 12 5259 could not reflect the PST accumulation in the Mediterranean A. minutum populations under the examined standard and nutrient limiting conditions.

Physical Review B, 2011

We present a theoretical and experimental study of the magneto-optical (MO) Kerr effect (MOKE) on... more We present a theoretical and experimental study of the magneto-optical (MO) Kerr effect (MOKE) on inhomogeneous systems. Starting from ab initio calculated band structures and using the effective medium approximation or the recently proposed alternating composition layers approximation [Phys. Rev. B 78, 134411 (2008)], we show that the complex Kerr angle can be reproduced also when a nonuniform distribution of the inhomogeneities is present. Applying our formalism to Mn-Ge-based systems, we find that a realistic account of the inhomogeneous concentration of Mn-rich precipitates in a Ge matrix is a necessary condition in order to describe, within the theoretical approach, the experimental Kerr spectra. The agreement between theoretical and measured MOKE spectra shows the validity of the model considered and establishes its predictive power also for a continuously varying concentration distribution of magnetic species in the system.

Water Research, 2007

The massive accumulation of organic matter, which periodically occurs in the northern Adriatic Se... more The massive accumulation of organic matter, which periodically occurs in the northern Adriatic Sea, and in other locations worldwide, is presently thought to be the results of the aggregation of dissolved organic matter (DOM) into particulate organic matter (POM). This phenomenon is the result of human activities and propitious weather conditions. Although many aspects of the phenomenon are well understood, the trigger mechanisms leading to mucilage formation have not been clarified yet, probably as a consequence of inadequate analytical approaches. In this context, the recent advancements in LC-MS interfacing might contribute in clarifying the mechanism of mucilage formation. In the present paper, hydrophilic interaction liquid chromatography coupled with electrospray tandem mass spectrometry (HILC-ESI-MS/MS) is proposed as an innovative method for the investigation of underivatized oligosaccharides in mucilage samples. Recent findings suggest that the significant presence of these compounds in seawater can play an important role in the initial steps of the agglomeration processes forming gelatinous material. Our results reveal the presence of several maltodextrines in the water-soluble fraction of mucilage macroaggregates, collected in various locations of the northern Adriatic Sea. In our knowledge, the proposed method is the first application of LC-MS in the investigation of marine mucilage.

Physical Review B, 2008

We develop an ab initio computational approach to calculate the magneto-optical Kerr effect spect... more We develop an ab initio computational approach to calculate the magneto-optical Kerr effect spectra of layered and nanogranular compounds as a function of several structural and geometrical parameters:(i) composition,(ii) film thickness, and (iii) position, thickness, and ...

Physical Review B, 2013

We demonstrate that the inclusion of van der Waals dispersive interaction sensibly improves the p... more We demonstrate that the inclusion of van der Waals dispersive interaction sensibly improves the prediction of lattice constants by density functional theory in iron-chalcogenides (FeCh) superconductor compounds, namely FeSe and FeTe. We show how generalized gradient approximation (GGA) for the exchange correlation potential overestimates the out-of-plane lattice constants in both compounds when compared with experiments. In addition, GGA predicts a too weak bonding between the neutral FeCh layers, with a sensible underestimation of the bulk modulus. van der Waals corrected simulations completely solve both problems, reconciling theoretical results with experiments. These findings must be considered when dealing with theoretical predictions in FeCh compounds.

Journal of Superconductivity and Novel Magnetism, 2013

The influence of inhomogeneity on magnetic materials is considered; in particular, we examine how... more The influence of inhomogeneity on magnetic materials is considered; in particular, we examine how it affects the magneto-optical (MO) response of films and multilayers.

Journal of Physics: Condensed Matter, 2010

We report a joint theoretical and experimental study focused on understanding the optical and mag... more We report a joint theoretical and experimental study focused on understanding the optical and magneto-optical properties of Co-based full-Heusler compounds. We show that magneto-optical spectra calculated within ab-initio density functional theory are able to uniquely identify the features of the experimental spectra in terms of spin resolved electronic transitions. As expected for 3d-based magnets, we find that the largest Kerr rotation for these alloys is of the order of 0.3 o in polar geometry. In addition, we demonstrate that (i) multilayered structures have to be carefully handled in the theoretical calculations in order to improve the agreement with experiments, and (ii) combined theoretical and experimental investigations constitute a powerful approach to designing new materials for magneto-optical and spin-related applications.

Journal of Physics: Conference Series, 2010

Experimental magneto-optical Kerr effect spectra of Mn-implanted Ge samples are interpreted using... more Experimental magneto-optical Kerr effect spectra of Mn-implanted Ge samples are interpreted using an ab-initio theoretical model based on density functional theory. The presence of Mn in the Ge matrix is accounted for considering either Mn precipitation as Mn5Ge3 nanoparticles or as perfect dilution. The Mn concentration profile in the sample is also considered in the theoretical model. The computational results

Chemistry and Ecology, 2014

In the northern Adriatic Sea, Mediterranean Sea, the mucilage phenomenon is usually related to th... more In the northern Adriatic Sea, Mediterranean Sea, the mucilage phenomenon is usually related to the aggregation of extracellular organic matter of phytoplanktonic origin under special seasonal and trophic conditions. Environmental factors, such as temperature, salinity, nitrogen, phosphorus and N/P ratio as well as polysaccharide and monosaccharide levels in the presence and absence of mucilage were investigated in the northern Adriatic Sea. Variations in temperature and salinity during spring in years characterised by mucilage events have been recognised having an important role in preparing a favourable physical environment where mucilage formation could take place. Since the DIN/TP ratio increased markedly during the spring months (March-April) in 2002, 2003 and 2004, preceding the early summer mucilage outbreaks, it appeared that the DIN/TP ratio may be a more robust predictor than the DIN/DIP ratio, which, although more commonly used, exhibited a discontinuous trend. The contents of total carbohydrates, including monosaccharides and polysaccharides, in seawater also varied according to the presence or absence of mucilage, with an increase of polysaccharide levels during the late spring or early summer in the period of the mucilage appearance. The role of carbohydrates in the macro-aggregate formation was also investigated.

Carbohydrate Research, 2009

The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause se... more The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause serious damage to the tourism and fishing industries along the Adriatic coast. Mucilage is presently thought to be the result of the aggregation of dissolved organic matter (DOM) into particulate organic matter (POM). Three principal classes of compounds have been identified in organic matter by spectrometric determination: carbohydrates, proteins and lipids. Carbohydrates are suspected to play a role in the first steps of DOM aggregation. Despite its importance in understanding the processes leading to mucilage formation, our present knowledge of the composition of the mucilage carbohydrate fraction is incomplete. Due to its high sensitivity and specificity, liquid chromatography coupled with electrospray-ionization tandem mass spectrometry (LC-ESIMS/MS) is gaining an increasing importance as a powerful technique for carbohydrate purification and characterization in complex samples. In this work, LC-ESIMS/MS is proposed as a useful method for the investigation of the oligosaccharide content in mucilage samples. The approach was applied using 3-7 unit maltooligosaccharides as reference compounds. The composition of the investigated mucilage sample was further investigated combining LC-ESIMS/MS with classic approaches, such as spectroscopic techniques and liquid chromatography coupled with the refractory index LC-RI.

Applied Biochemistry and Biotechnology, 2013

Microalgae are one of the most promising biodiesel feedstocks due to their efficiency in CO 2 fix... more Microalgae are one of the most promising biodiesel feedstocks due to their efficiency in CO 2 fixation and high neutral lipid productivity. Nutrient-stress conditions, including nitrogen starvation, enhance neutral lipid content, but at the same time lead to a reduction of biomass. To maximize lipid production in the diatom Skeletonema marinoi, we investigated two different nitrogen starvation approaches. In the first experimental approach, inocula were effectuated in modified f/2 media with decreasing nitrogen concentration, while in the second experiment, nitrate concentration was gradually reduced through a collection/resuspension system in which the culture was periodically collected and resuspended in culture medium with a lower nitrate concentration. In the first approach, the neutral lipid accumulation was accompanied by a strong biomass reduction, as was expected, whereas the second experiment generated cultures with significantly higher neutral lipid content without affecting biomass production. The total proteins and total carbohydrates, which were also quantified in both experiments, suggest that in S. marinoi, neutral lipid accumulation during nutrient starvation did not derive from a new carbon partition of accumulated carbohydrates.

ASSOCIAZIONE ITALIANA DI …

ABSTRACT The research is based on the study of mucilaginous phenomena and the monitoring activity... more ABSTRACT The research is based on the study of mucilaginous phenomena and the monitoring activity along the coastal area influenced by run off river inputs. Physical and chemical parameters, trophic factors and algal blooms processes were studied. Samples were collected monthly along the coast of Pesaro at 500m and 3000m from the mouth of the Foglia, Metauro, Tavollo and Cesano rivers during the period of November 2003- August 2005; further, net samples along the water column in an aquaculture area nearby Fiorenzuola (PU) were collected. During the appearance of mucilaginous masses, the research consisted in carrying out the mucilages on surface and filming the mucus along the entire water column using a wire drawn camera. The mucilage samples were subsequently analysed by HPLC/RI in order to study the presence of the oligosaccharides.

Acta Chim. …, 2009

... The Role of Dissolved Carbohydrates in the Northern Adriatic Macroaggregate Formation Nunzio ... more ... The Role of Dissolved Carbohydrates in the Northern Adriatic Macroaggregate Formation Nunzio Penna,1 Nives Kova~,2 Fabio Ricci,3 Antonella Penna,4 Samuela Capellacci3 and Jadran Faganeli2 1 Chair of Chemical Oceanography, University of Urbino, Loc. ...

Analytical and Bioanalytical Chemistry, 2003

Carbohydrate contents in seawater, mucilage, and mucilage interstitial waters were analyzed durin... more Carbohydrate contents in seawater, mucilage, and mucilage interstitial waters were analyzed during episodes of mucilage formation in the summers of 2000 and 2001 in the northern Adriatic Sea off Pesaro and in the Gulf of Trieste using 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) and 2,4,6-tripyridyl-s-triazine (TPTZ) assays. The significant presence of polysaccharides in seawater in the presence of mucilage has an important impact on the agglomeration processes forming gelatinous material (macrogels). Characterization of oligosaccharides in the water-soluble fraction of mucilage using HPLC/RI revealed maltose and pentaose as the main components.

Optical amplification issues in packet-switched networks are often underestimated. In fact, EDFAs... more Optical amplification issues in packet-switched networks are often underestimated. In fact, EDFAs have been shown to be seriously impaired by burst-mode packet traffic, due to their internal time-dependent gain dynamics. In this scenario, Linear Optical Amplifiers (LOA) may find an interesting and cost-effective application. LOAs are novel gain-stabilized low-cost SOAs, which already received much attention for cross-gain modulation (XGM) suppression in WDM transmission. In this paper, we present a detailed experimental and theoretical investigation on LOAs used as key amplification blocks for burst-mode packet applications and, in particular, in the MAN WDM packet network demonstrator "WONDER".

2013 7th International Workshop on Traceability in Emerging Forms of Software Engineering (TEFSE), 2013

ABSTRACT Latent Semantic Indexing (LSI) is an advanced method widely and successfully employed in... more ABSTRACT Latent Semantic Indexing (LSI) is an advanced method widely and successfully employed in Information Retrieval (IR). It is an extension of Vector Space Model (VSM) and it is able to overcome VSM in canonical IR scenarios where it is used on very large document repositories. LSI has also been used to semi-automatically generate traceability links between software artefacts. However, in such a scenario LSI is not able to overcome VSM. This contradicting result is probably due to the different characteristics of software artefact repositories as compared to document repositories. In this paper we present a preliminary empirical study to analyze how the size and the vocabulary of the repository-in terms of number of documents and terms (i.e., the vocabulary)-affects the retrieval accuracy. Even if replications are needed to generalize our findings, the study presented in this paper provides some insights that might be used as guidelines for selecting the more adequate methods to be used for traceability recovery depending on the particular application context.

2013 7th International Workshop on Traceability in Emerging Forms of Software Engineering (TEFSE), 2013

Latent Semantic Indexing (LSI) is an advanced method widely and successfully employed in Informat... more Latent Semantic Indexing (LSI) is an advanced method widely and successfully employed in Information Retrieval (IR). It is an extension of Vector Space Model (VSM) and it is able to overcome VSM in canonical IR scenarios where it is used on very large document repositories. LSI has also been used to semi-automatically generate traceability links between software artefacts. However, in such a scenario LSI is not able to overcome VSM. This contradicting result is probably due to the different characteristics of software artefact repositories as compared to document repositories. In this paper we present a preliminary empirical study to analyze how the size and the vocabulary of the repository-in terms of number of documents and terms (i.e., the vocabulary)-affects the retrieval accuracy. Even if replications are needed to generalize our findings, the study presented in this paper provides some insights that might be used as guidelines for selecting the more adequate methods to be used for traceability recovery depending on the particular application context.

Carbohydrate research

The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause se... more The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause serious damage to the tourism and fishing industries along the Adriatic coast. Mucilage is presently thought to be the result of the aggregation of dissolved organic matter (DOM) into particulate organic matter (POM). Three principal classes of compounds have been identified in organic matter by spectrometric determination: carbohydrates, proteins and lipids. Carbohydrates are suspected to play a role in the first steps of DOM aggregation. Despite its importance in understanding the processes leading to mucilage formation, our present knowledge of the composition of the mucilage carbohydrate fraction is incomplete. Due to its high sensitivity and specificity, liquid chromatography coupled with electrospray-ionization tandem mass spectrometry (LC-ESIMS/MS) is gaining an increasing importance as a powerful technique for carbohydrate purification and characterization in complex samples. In th...

In this study monthly cruises were carried out from November 2001 to November 2004 in four transe... more In this study monthly cruises were carried out from November 2001 to November 2004 in four transects along the coast of Pesaro (NW Adriatic Sea). Phytoplanktonic populations (Bacillariophyceae and Dinophyceae), chemical-physical parameters and eutrophic factors were analysed to localize eutrophic and bloom events. Phytoplankton community was often dominated by diatoms. Bacillariophyceae blooms occurred in February 2002 and 2004 (Skeletonema costatum) and May 2002 (Chaetoceros spp.); Dinophyceae blooms occurred in autumn periods.

This study reports the concentrations of important tracers of the marine environment, 210 Po and ... more This study reports the concentrations of important tracers of the marine environment, 210 Po and 210 Pb, in different matrices from field samples collected at Central Adriatic Sea (Italy), a non-contaminated marine ecosystem. 210 Po concentration appears to decrease with increasing distance from the coast and a significant difference in 210 Po concentrations in seawater samples at two different depths is not appreciable. 210 Po and 210 Pb present the same trend in the different periods of the year. 210 Po and 210 Pb present high concentration factors and high Kd values: in particular 210 Po shows values of 2.4 10 4 in plankton, 3.2 10 5 in the particulate fraction and 1.1 10 5 in sediment; 210 Pb shows values of 1.3 10 4 in plankton, 1.8 10 4 in the particulate fraction and 4.9 10 4 in sediment. The 210 Po/ 210 Pb ratio results < 1 in sea water and >1 in the particulate fraction, sediment and plankton due to a significant fractionation occurring between the two radionuclides during their removal from solution to particle and due to their different biogeochemical cycling pathways in the marine environment. The noticeable accumulation of 210 Po in the food chain is not accompanied by an identical accumulation of 210 Pb. Due to its biomagnification in the marine food chain, 210 Po provides the larges radiation dose to any marine organism under natural conditions. The data reported provide reference values for the Central Adriatic (Mediterranean Sea) coastal environment.

Marine Drugs, 2014

The dinoflagellate Alexandrium minutum is known for the production of potent neurotoxins affectin... more The dinoflagellate Alexandrium minutum is known for the production of potent neurotoxins affecting the health of human seafood consumers via paralytic shellfish poisoning (PSP). The aim of this study was to investigate the relationship between the toxin content and the expression level of the genes involved in paralytic shellfish toxin (PST) production. The algal cultures were grown both in standard f/2 medium and in phosphorus/nitrogen limitation. In our study, LC-HRMS analyses of PST profile and content in different Mediterranean A. minutum strains confirmed that this species was able to synthesize mainly the saxitoxin analogues Gonyautoxin-1 (GTX1) and Gonyautoxin-4 (GTX4). The average cellular toxin content varied among different strains, and between growth phases, highlighting a decreasing trend from exponential to stationary phase in all culture conditions tested. The absolute quantities of intracellular sxtA1 and sxtG mRNA were not correlated with the amount of intracellular toxins in the analysed A. minutum suggesting that the production of toxins may be regulated by post-transcriptional mechanisms and/or by the concerted actions of alternative genes belonging to the PST biosynthesis gene cluster. Therefore, it is likely that the sxtA1 and sxtG gene expression OPEN ACCESS Mar. Drugs 2014, 12 5259 could not reflect the PST accumulation in the Mediterranean A. minutum populations under the examined standard and nutrient limiting conditions.

Physical Review B, 2011

We present a theoretical and experimental study of the magneto-optical (MO) Kerr effect (MOKE) on... more We present a theoretical and experimental study of the magneto-optical (MO) Kerr effect (MOKE) on inhomogeneous systems. Starting from ab initio calculated band structures and using the effective medium approximation or the recently proposed alternating composition layers approximation [Phys. Rev. B 78, 134411 (2008)], we show that the complex Kerr angle can be reproduced also when a nonuniform distribution of the inhomogeneities is present. Applying our formalism to Mn-Ge-based systems, we find that a realistic account of the inhomogeneous concentration of Mn-rich precipitates in a Ge matrix is a necessary condition in order to describe, within the theoretical approach, the experimental Kerr spectra. The agreement between theoretical and measured MOKE spectra shows the validity of the model considered and establishes its predictive power also for a continuously varying concentration distribution of magnetic species in the system.

Water Research, 2007

The massive accumulation of organic matter, which periodically occurs in the northern Adriatic Se... more The massive accumulation of organic matter, which periodically occurs in the northern Adriatic Sea, and in other locations worldwide, is presently thought to be the results of the aggregation of dissolved organic matter (DOM) into particulate organic matter (POM). This phenomenon is the result of human activities and propitious weather conditions. Although many aspects of the phenomenon are well understood, the trigger mechanisms leading to mucilage formation have not been clarified yet, probably as a consequence of inadequate analytical approaches. In this context, the recent advancements in LC-MS interfacing might contribute in clarifying the mechanism of mucilage formation. In the present paper, hydrophilic interaction liquid chromatography coupled with electrospray tandem mass spectrometry (HILC-ESI-MS/MS) is proposed as an innovative method for the investigation of underivatized oligosaccharides in mucilage samples. Recent findings suggest that the significant presence of these compounds in seawater can play an important role in the initial steps of the agglomeration processes forming gelatinous material. Our results reveal the presence of several maltodextrines in the water-soluble fraction of mucilage macroaggregates, collected in various locations of the northern Adriatic Sea. In our knowledge, the proposed method is the first application of LC-MS in the investigation of marine mucilage.

Physical Review B, 2008

We develop an ab initio computational approach to calculate the magneto-optical Kerr effect spect... more We develop an ab initio computational approach to calculate the magneto-optical Kerr effect spectra of layered and nanogranular compounds as a function of several structural and geometrical parameters:(i) composition,(ii) film thickness, and (iii) position, thickness, and ...

Physical Review B, 2013

We demonstrate that the inclusion of van der Waals dispersive interaction sensibly improves the p... more We demonstrate that the inclusion of van der Waals dispersive interaction sensibly improves the prediction of lattice constants by density functional theory in iron-chalcogenides (FeCh) superconductor compounds, namely FeSe and FeTe. We show how generalized gradient approximation (GGA) for the exchange correlation potential overestimates the out-of-plane lattice constants in both compounds when compared with experiments. In addition, GGA predicts a too weak bonding between the neutral FeCh layers, with a sensible underestimation of the bulk modulus. van der Waals corrected simulations completely solve both problems, reconciling theoretical results with experiments. These findings must be considered when dealing with theoretical predictions in FeCh compounds.

Journal of Superconductivity and Novel Magnetism, 2013

The influence of inhomogeneity on magnetic materials is considered; in particular, we examine how... more The influence of inhomogeneity on magnetic materials is considered; in particular, we examine how it affects the magneto-optical (MO) response of films and multilayers.

Journal of Physics: Condensed Matter, 2010

We report a joint theoretical and experimental study focused on understanding the optical and mag... more We report a joint theoretical and experimental study focused on understanding the optical and magneto-optical properties of Co-based full-Heusler compounds. We show that magneto-optical spectra calculated within ab-initio density functional theory are able to uniquely identify the features of the experimental spectra in terms of spin resolved electronic transitions. As expected for 3d-based magnets, we find that the largest Kerr rotation for these alloys is of the order of 0.3 o in polar geometry. In addition, we demonstrate that (i) multilayered structures have to be carefully handled in the theoretical calculations in order to improve the agreement with experiments, and (ii) combined theoretical and experimental investigations constitute a powerful approach to designing new materials for magneto-optical and spin-related applications.

Journal of Physics: Conference Series, 2010

Experimental magneto-optical Kerr effect spectra of Mn-implanted Ge samples are interpreted using... more Experimental magneto-optical Kerr effect spectra of Mn-implanted Ge samples are interpreted using an ab-initio theoretical model based on density functional theory. The presence of Mn in the Ge matrix is accounted for considering either Mn precipitation as Mn5Ge3 nanoparticles or as perfect dilution. The Mn concentration profile in the sample is also considered in the theoretical model. The computational results

Chemistry and Ecology, 2014

In the northern Adriatic Sea, Mediterranean Sea, the mucilage phenomenon is usually related to th... more In the northern Adriatic Sea, Mediterranean Sea, the mucilage phenomenon is usually related to the aggregation of extracellular organic matter of phytoplanktonic origin under special seasonal and trophic conditions. Environmental factors, such as temperature, salinity, nitrogen, phosphorus and N/P ratio as well as polysaccharide and monosaccharide levels in the presence and absence of mucilage were investigated in the northern Adriatic Sea. Variations in temperature and salinity during spring in years characterised by mucilage events have been recognised having an important role in preparing a favourable physical environment where mucilage formation could take place. Since the DIN/TP ratio increased markedly during the spring months (March-April) in 2002, 2003 and 2004, preceding the early summer mucilage outbreaks, it appeared that the DIN/TP ratio may be a more robust predictor than the DIN/DIP ratio, which, although more commonly used, exhibited a discontinuous trend. The contents of total carbohydrates, including monosaccharides and polysaccharides, in seawater also varied according to the presence or absence of mucilage, with an increase of polysaccharide levels during the late spring or early summer in the period of the mucilage appearance. The role of carbohydrates in the macro-aggregate formation was also investigated.

Carbohydrate Research, 2009

The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause se... more The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause serious damage to the tourism and fishing industries along the Adriatic coast. Mucilage is presently thought to be the result of the aggregation of dissolved organic matter (DOM) into particulate organic matter (POM). Three principal classes of compounds have been identified in organic matter by spectrometric determination: carbohydrates, proteins and lipids. Carbohydrates are suspected to play a role in the first steps of DOM aggregation. Despite its importance in understanding the processes leading to mucilage formation, our present knowledge of the composition of the mucilage carbohydrate fraction is incomplete. Due to its high sensitivity and specificity, liquid chromatography coupled with electrospray-ionization tandem mass spectrometry (LC-ESIMS/MS) is gaining an increasing importance as a powerful technique for carbohydrate purification and characterization in complex samples. In this work, LC-ESIMS/MS is proposed as a useful method for the investigation of the oligosaccharide content in mucilage samples. The approach was applied using 3-7 unit maltooligosaccharides as reference compounds. The composition of the investigated mucilage sample was further investigated combining LC-ESIMS/MS with classic approaches, such as spectroscopic techniques and liquid chromatography coupled with the refractory index LC-RI.

Applied Biochemistry and Biotechnology, 2013

Microalgae are one of the most promising biodiesel feedstocks due to their efficiency in CO 2 fix... more Microalgae are one of the most promising biodiesel feedstocks due to their efficiency in CO 2 fixation and high neutral lipid productivity. Nutrient-stress conditions, including nitrogen starvation, enhance neutral lipid content, but at the same time lead to a reduction of biomass. To maximize lipid production in the diatom Skeletonema marinoi, we investigated two different nitrogen starvation approaches. In the first experimental approach, inocula were effectuated in modified f/2 media with decreasing nitrogen concentration, while in the second experiment, nitrate concentration was gradually reduced through a collection/resuspension system in which the culture was periodically collected and resuspended in culture medium with a lower nitrate concentration. In the first approach, the neutral lipid accumulation was accompanied by a strong biomass reduction, as was expected, whereas the second experiment generated cultures with significantly higher neutral lipid content without affecting biomass production. The total proteins and total carbohydrates, which were also quantified in both experiments, suggest that in S. marinoi, neutral lipid accumulation during nutrient starvation did not derive from a new carbon partition of accumulated carbohydrates.

ASSOCIAZIONE ITALIANA DI …

ABSTRACT The research is based on the study of mucilaginous phenomena and the monitoring activity... more ABSTRACT The research is based on the study of mucilaginous phenomena and the monitoring activity along the coastal area influenced by run off river inputs. Physical and chemical parameters, trophic factors and algal blooms processes were studied. Samples were collected monthly along the coast of Pesaro at 500m and 3000m from the mouth of the Foglia, Metauro, Tavollo and Cesano rivers during the period of November 2003- August 2005; further, net samples along the water column in an aquaculture area nearby Fiorenzuola (PU) were collected. During the appearance of mucilaginous masses, the research consisted in carrying out the mucilages on surface and filming the mucus along the entire water column using a wire drawn camera. The mucilage samples were subsequently analysed by HPLC/RI in order to study the presence of the oligosaccharides.

Acta Chim. …, 2009

... The Role of Dissolved Carbohydrates in the Northern Adriatic Macroaggregate Formation Nunzio ... more ... The Role of Dissolved Carbohydrates in the Northern Adriatic Macroaggregate Formation Nunzio Penna,1 Nives Kova~,2 Fabio Ricci,3 Antonella Penna,4 Samuela Capellacci3 and Jadran Faganeli2 1 Chair of Chemical Oceanography, University of Urbino, Loc. ...

Analytical and Bioanalytical Chemistry, 2003

Carbohydrate contents in seawater, mucilage, and mucilage interstitial waters were analyzed durin... more Carbohydrate contents in seawater, mucilage, and mucilage interstitial waters were analyzed during episodes of mucilage formation in the summers of 2000 and 2001 in the northern Adriatic Sea off Pesaro and in the Gulf of Trieste using 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) and 2,4,6-tripyridyl-s-triazine (TPTZ) assays. The significant presence of polysaccharides in seawater in the presence of mucilage has an important impact on the agglomeration processes forming gelatinous material (macrogels). Characterization of oligosaccharides in the water-soluble fraction of mucilage using HPLC/RI revealed maltose and pentaose as the main components.

Optical amplification issues in packet-switched networks are often underestimated. In fact, EDFAs... more Optical amplification issues in packet-switched networks are often underestimated. In fact, EDFAs have been shown to be seriously impaired by burst-mode packet traffic, due to their internal time-dependent gain dynamics. In this scenario, Linear Optical Amplifiers (LOA) may find an interesting and cost-effective application. LOAs are novel gain-stabilized low-cost SOAs, which already received much attention for cross-gain modulation (XGM) suppression in WDM transmission. In this paper, we present a detailed experimental and theoretical investigation on LOAs used as key amplification blocks for burst-mode packet applications and, in particular, in the MAN WDM packet network demonstrator "WONDER".

2013 7th International Workshop on Traceability in Emerging Forms of Software Engineering (TEFSE), 2013

ABSTRACT Latent Semantic Indexing (LSI) is an advanced method widely and successfully employed in... more ABSTRACT Latent Semantic Indexing (LSI) is an advanced method widely and successfully employed in Information Retrieval (IR). It is an extension of Vector Space Model (VSM) and it is able to overcome VSM in canonical IR scenarios where it is used on very large document repositories. LSI has also been used to semi-automatically generate traceability links between software artefacts. However, in such a scenario LSI is not able to overcome VSM. This contradicting result is probably due to the different characteristics of software artefact repositories as compared to document repositories. In this paper we present a preliminary empirical study to analyze how the size and the vocabulary of the repository-in terms of number of documents and terms (i.e., the vocabulary)-affects the retrieval accuracy. Even if replications are needed to generalize our findings, the study presented in this paper provides some insights that might be used as guidelines for selecting the more adequate methods to be used for traceability recovery depending on the particular application context.