Non equilibrium optical properties in semiconductors from first--principles: a combined theoretical and experimental study of bulk silicon

The calculation of the equilibrium optical properties of bulk silicon by using the Bethe--Salpeter equation solved in the Kohn--Sham basis represents a cornerstone in the development of an ab--initio approach to the optical and electronic properties of materials. Nevertheless calculations of the {\em transient} optical spectrum using the same efficient and successful scheme are scarce. We report, here, a joint theoretical and experimental study of the transient reflectivity spectrum of bulk silicon. Femtosecond transient reflectivity is compared to a parameter--free calculation based on the non--equilibrium Bethe--Salpeter equation. By providing an accurate description of the experimental results we disclose the different phenomena that determine the transient optical response of a semiconductor. We give a parameter--free interpretation of concepts like bleaching, photo--induced absorption and stimulated emission, beyond the Fermi golden rule. We also introduce the concept of optical gap renormalization, as a generalization of the known mechanism of band gap renormalization. The present scheme successfully describes the case of bulk silicon, showing its universality and accuracy.Comment: 14 pages, 13 figure

Comprehensive evaluation of phenolic profile in dark chocolate and dark chocolate enriched with Sakura green tea leaves or turmeric powder

Recently, a huge number of studies have confirmed the important role of chocolate polyphenols in human health, underlining its beneficial effects especially in the treatment of cardiovascular diseases. However, a thorough evaluation of chocolate phenolic profile is still lacking. This study aimed at a comprehensive characterization of dark chocolate phenolic profile, using non-targeted mass spectrometry identification. This approach allowed a tentative identification of 158 individual phenolic compounds: 67 were newly detected in dark chocolate, among these 38 were observed for the first time in chocolate as well as in cocoa beans or products. Ellagitannins, which have never been reported in cocoa or chocolate, represented about the 10% of the phenolic profile of dark chocolate. The enrichment of dark chocolate with Sakura green tea leaves or turmeric powder influenced and modified the phenolic profile, resulting in a phenolic concentration increase. In this way, this functional chocolate might maximize the beneficial effect of chocolate consumption, combining the positive health effects of chocolate, turmeric and green tea and, at the same time, reducing the amount of sugars and calories introduced with chocolate

Effect of ripening and in vitro digestion on the evolution and fate of bioactive peptides in Parmigiano-Reggiano cheese

The influence of ripening and in vitro digestion on the peptidomic profile of Parmigiano-Reggiano (PR) cheeses was investigated. Ripening and in vitro digestion thoroughly modified the peptidomic profile of the three cheeses. Twenty-six bioactive peptides were identified in undigested PR. Some peptides were degraded and others released during ripening. After digestion, 52 bioactive peptides were identified. Semi-quantitative data suggested that bioactive peptides released after digestion can be clustered in 5 groups according to the ripening time. VPP and IPP peptide levels in undigested samples were in the range of 4.52–11.34 and 0.66–4.24 mg kg−1, with the highest amounts found in 18-month ripened PR. YPFPGPI peptide was absent in undigested PRs but was released after digestion, especially in the 12-month-old sample (20.18 mg kg−1). The present study suggests possible differences in bioactive peptide levels after digestion as a function of the duration of ripening of PR cheese

Protocatechuic and 3,4-Dihydroxyphenylacetic Acids Inhibit Protein Glycation by Binding Lysine through a Metal-Catalyzed Oxidative Mechanism

The mechanism of inhibition of advanced glycation end product (AGE) formation by protocatechuic acid and 3,4-dihydroxyphenylacetic acid (DHPA) has been studied using a widespread applied in vitro model system composed of bovine serum albumin (BSA) and supraphysiological glucose concentrations. Protocatechuic acid and DHPA inhibited the formation of Amadori compounds, fluorescent AGEs (IC50 = 62.1 \ub1 1.4 and 155.4 \ub1 1.1 \u3bcmol/L, respectively), and N\u3b5-(carboxymethyl)lysine (IC50 = 535.3 \ub1 1.1 and 751.2 \ub1 1.0 \u3bcmol/L, respectively). BSA was pretreated with the two phenolic acids, and the formation of BSA\u2013phenolic acid adducts was estimated by nanoflow liquid chromatography\u2013electrospray ionization\u2013quadrupole time-of-flight mass spectrometry. Results showed that the tested phenolic acids bound key sites of glycation in BSA through a metal-catalyzed oxidative mechanism. The antiglycative activity mechanism involved the formation of BSA\u2013phenolic acid adducts, and it is unlikely that this occurs in vivo. These results raise the problem to design in vitro models closer to physiological conditions to reach biologically sound conclusions

Comparative peptidomic profile and bioactivities of cooked beef, pork, chicken and turkey meat after in vitro gastro-intestinal digestion

This study was designed to investigate the potential contribution of bioactive peptides to the biological activities related to the consumption of pork, beef, chicken and turkey meat following in vitro gastro-intestinal digestion. After extraction of the peptidic fractions from digested samples, the bioactivities were evaluated by in vitro antioxidant activity as well as angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) inhibition assays. Pork and turkey meat appeared to be the best sources of antioxidant peptides. Pork was found to be the best source of DPP-IV-inhibitory peptides whereas chicken meat supplied peptides with the highest ACE-inhibitory activity. The comprehensive analysis of the peptidomic profile of digested samples was performed by nano-LC-ESI-QTOF MS/MS analysis. A total of 217, 214, 257 and 248 peptides were identified in digested pork, beef, chicken and turkey meat, respectively. Chicken and turkey meat showed the highest similarity in peptide sequences with 202 common peptides. Sixty-two peptides matched with sequences with previously demonstrated biological activity. In particular, 35 peptides showed ACE-inhibitory activity and 23 DPP-IV inhibitory activity. Twenty-two bioactive peptides were commonly released from the different types of meat. The relative amount of identified bioactive peptides were positively correlated to the biological activities of the different digested meats. Biological significance: The present study describes for the first time a comprehensive peptide profile of four types of meat after in vitro gastro-intestinal digestion. The peptide inventory was used to identify 62 bioactive peptides with ACE- and DPPIV-inhibitory and antioxidant activities. The bioactivity analysis revealed interesting and significant differences between the studied meats. The originality of this work lay in the description of intrinsic differences in physiological functions after the ingestion of meat proteins from different species. In a context in which the current research scene relates meat consumption to the onset of chronic pathologies, this peptide profiling and bioactivity analysis shed light on the possible health benefits of peptides released from meat proteins. In fact, this paper represents a sort of detailed peptide list that may help to predict which peptides could be generated after meat intake and detectable at gastro-intestinal level. It also provides a thorough investigation of novel biological activities associated to meat protein hydrolysates, giving a new positive aspect to meat consumption

Antiproliferative Activity and Cell Metabolism of Hydroxycinnamic Acids in Human Colon Adenocarcinoma Cell Lines

In this study, we investigated the antiproliferative activity and the stability and metabolic fate of the main dietary hydroxycinnamates, using two colonic adenocarcinoma cell models (Caco-2 and SW480). Dihydrocaffeic and dihydroferulic acids were the most effective against cell proliferation in both cell lines with IC50 values of 71.7 \ub1 1.1 and 83.1 \ub1 1.1 \u3bcmol/L, respectively (P < 0.05) in Caco-2. At 200 \u3bcmol/L, caffeic and ferulic acids inhibited SW480 proliferation by 40.8 \ub1 1.6 and 59.9 \ub1 1.3%, respectively. Hydroxycinnamic acids with a catechol-type structure were degraded in Caco-2 cell medium, resulting in the production of H2O2. Intracellular Caco-2 UDP-glucuronosyltransferases and catechol-O-methyltransferases were able to form glucuronide and methyl conjugates. However, only the sulfate conjugates were detected after incubation with SW480. In addition, simple hydroxycinnamates were released from quinic and aspartic conjugates. The remarkable effect of dihydrocaffeic and dihydroferulic acids against cell proliferation is of paramount importance, since these compounds are the main metabolites detectable at the colonic level

Bioaccessibility, bioactivity and cell metabolism of dark chocolate phenolic compounds after in vitro gastro-intestinal digestion

The bioaccessibility of phenolic compounds after in vitro gastro-intestinal digestion of dark chocolate, dark chocolate enriched with Sakura green tea and dark chocolate enriched with turmeric powder was studied. The phenolic profile, assessed by accurate mass spectrometry analysis, was modified during in vitro gastro-intestinal digestion, with a considerable decrease of total and individual phenolic compounds. Phenolic acids showed the highest bioaccessibility with hydroxycinnamic acids displaying higher bioaccessibility (from 41.2% to 45.1%) respect to hydroxybenzoic acids (from 28.1% to 43.5%). Isomerisation of caffeoyl-quinic acids and galloyl-quinic acids as well as dimerization of (epi)gallocatechin were also observed after in vitro gastro-intestinal digestion. Antioxidant activity increased after the gastric step and rose further at the end of the digestion. Furthermore, in vitro digested phenolic-rich fractions showed anti-proliferative activity against two models of human colon adenocarcinoma cell lines. Cell metabolism of digested phenolic compounds resulted in the accumulation of coumaric and ferulic acids in the cell media

Muscle mechanical work in walker-assisted locomotion: Instrumentationand modelling for an integrated gait analysis in cerebral palsy

La stima del lavoro meccanico muscolare \ue8 un utile strumento per valutare l'efficienza di un movimento, ma il processo di calcolo presenta ancora molte criticit\ue0 dal punto di vista biomeccanico. Diversi metodi per stimare il lavoro meccanico muscolare durante il cammino sono stati presentati in letteratura, ma nonostante i tentativi fatti per confrontarli, tutti i metodi sono tuttora utilizzati in ambito di ricerca e in ambito clinico. Una pi\uf9 profonda comprensione delle differenze, sia dal punto di vista teorico, che pratico, potrebbe permettere di capire cosa venga effettivamente calcolato da ciascun metodo ed aiutare a fare un uso pi\uf9 appropriato di questa informazione. A questo scopo \ue8 stato validato un modello tridimensionale a corpo completo, consistente in 16 segmenti, utilizzato per raccogliere informazioni cinematiche e dinamiche durante il cammino in ragazzi e bambini sani e in ragazzi e bambini affetti da paralisi cerebrale infantile (CP), camminati a velocit\ue0 spontanea. Lo sviluppo di due maniglie strumentate fissabili sulla struttura di deambulatori pediatrici posteriori ha permesso di misurare cinematica e dinamica dell'arto superiore anche in soggetti con maggiori difficolt\ue0 di deambulazione. Curve di potenza e valori di lavoro meccanico muscolare totale, positivo, negativo o netto, durante cammino normale e durante cammino con deambulatore, sono stati stimati dimostrando che tutti i metodi sono equivalenti quando vengono permessi trasferimenti di energia tra segmenti. Senza possibilit\ue0 di trasferimento di energia, i metodi differiscono tra loro, con differenze dipendenti dal metodo utilizzato e dal movimento studiato. Eccetto alcune criticit\ue0 evidenziate e discusse, l'analisi delle curve di potenza muscolare e dei valori di lavoro meccanico muscolare stimati pu\uf2 fornire utili informazioni sulla funzione locomotoria nel suo complesso, mettendo in luce deficit di propulsione, asimmetrie del cammino, inefficienze di movimento associate ad una ridotta capacit\ue0 di recupero di energia.The estimation of muscle mechanical work can be useful to assess movement efficiency, but it is still a challenging task in biomechanics. Different methods to estimate muscle work during walking have been presented in the literature and, although attempts have been made to investigate differences among them, all methods are still used in research and clinical applications. A deeper understanding of theoretical differences and analogies would allow to know what is exactly computed by each method and help to make a more appropriate use of this information. To this purpose, a 16 segments full-body 3D model was validated and used to collect kinematic and kinetic data from healthy children and cerebral palsy (CP) children walking at self-selected speed. Two instrumented handles fixable on the frame of posterior paediatric walkers were also developed, to measure upper limb kinetics in subjects with more severe walking impairements. Whole-body muscle mechanical power curves and work values, either positive, negative or net, during normal gait and during walker locomotion were obtained, demonstrating that all methods are equivalent when energy transfers between segments are allowed. With no transfers allowed, methods differ among each other, with differences depending on the movements and the methods considered. Apart from some critical issues evidenced and discussed, the analysis of whole-body muscle mechanical power curves and work estimates can provide valuable information on the overall locomotion function, highlighting propulsive deficits, gait asymmetries, movement inefficiencies associated to reduced energy recuperation