104,367 research outputs found
SERS active gold nanostructures for selective and ultrabright biolabelling: synthesis and quantitative study
No full textSurface enhanced Raman scattering (SERS) probes based on gold nanoparticles (AuNPs) – organic dyes nanocomposites disclosed new opportunities for multiplexed ultrasensitive biolabelling in vitro or in vivo. SERS labels also have excellent biocompatibility and can be excited with near infrared laser sources, that match the transparency window of biological tissues. Here we report about the preparation of AuNPs obtained by laser ablation synthesis in solution (LASiS)[1,2] and their functionalization with a series of Raman reporter with different spectral fingerprints. The effective differential Raman scattering cross section of these labels were evaluated using liquid Raman standards and the analysis of the surface plasmon band of AuNPs with the Mie – Gans models.[3] We estimated that few (<10) SERS labels are enough to collect a clear Raman spectrum with a common Raman spectrometer. SERS labels were used for the study of nanoparticles uptake in macrophages[4] in order to quantify the number of nanoparticles phagocytized after different times. The conjugation of SERS labels with antibodies that selectively binds antigens over-expressed by specific types of cancerous cells is under investigation for the antibody – directed selective ultrasensitive detection and imaging of cancer.
[1] V. Amendola, M. Meneghetti, Phys. Chem. Chem. Phys. 2009,
[2] V. Amendola, M. Meneghetti; J. Mater. Chem. 2007, 17, 4705–4710.
[3] V. Amendola, M. Meneghetti, J. Phys. Chem. C 2009, 113, 4277–4285.
[4] V. Amendola, M. Meneghetti, S. Fiameni, G. Fracasso, A. Boscaini, M. Colombatti; Submitte
Engineering estimation of the fatigue limit of wrought and defective additively manufactured metals for different load ratios
No full textAn empirical bi-parametric model based on the Vickers hardness HV and a proper microstructural length parameter, l, was proposed to estimate the fully reversed threshold-Stress Intensity Factor for long cracks of wrought and additively manufactured (AM) alloys. In this paper, the model has been extended to positive load ratios (R ≅ 0 and ≅ 0.5). Afterwards, experimental results generated from testing AM specimens containing natural defects were taken from the literature and were compared successfully with the estimation based on the El Haddad Smith Topper and the Atzori Lazzarin Meneghetti models defined solely on the basis of the HV and l
Preparation and quantitative study of gold nanoparticles forSERS biolabelling
No full textSERS probes based on gold nanoparticles – organic dyes nanocomposites are intensively investigated for in vitro and in vivo labelling or for bio-analytical applications. Their main advantages are: biocompatibility, enormous Raman scattering cross section, analysis at wavelengths in the transparency window of biological tissues, multiplex analysis based on the distinctive fingerprint of each label. Here we report about the preparation of AuNP obtained by laser ablation synthesis in solution (LASiS)1-5 and their functionalization with a series of Raman labels with different properties. The Raman scattering cross section and the minimum number of AuNP observable by Raman spectroscopy in different conditions were measured and used for quantitative comparison of the different labels. Optical microscopy and transmission electron microscopy were coupled to Raman analysis for this purpose. Calibration studies were applied to the quantification of cell uptake studies of nanoparticles. The results suggests that, in the best cases, about ten AuNP in the analysis volume are enough for practical application with common Raman spectrometers.
1 V. Amendola, M. Meneghetti, “Laser ablation synthesis in solution and size manipulation of noble metal nanoparticles”, invited Perspective Article, Phys. Chem. Chem. Phys. 2009, Accepted.
2 V. Amendola, M. Meneghetti, J. Phys. Chem. C 2009, 113, 4277–4285.
3 S. Salmaso, P. Caliceti, V. Amendola, M. Meneghetti, J. P. Magnusson, G. Pasparakis, C. Alexander; J. Mater. Chem. 2009, 19, 1608 – 1615.
4 V. Amendola, M. Meneghetti; J. Mater. Chem. 2007, 17, 4705–4710.
5 V. Amendola, S. Polizzi, M. Meneghetti; J. Phys. Chem. B 2006, 110, 7232 – 7237
Bioconjugation and photonic applications of metal nanoparticles obtained by laser ablation in liquid solution
No full textMetal nanoparticles (MNP) have a notable role in nanotechnology, due to their surface plasmon absorption (SPA) and to their surface chemistry. Functionalization and/or bioconjugation are key points for MNP applications, and they depend on surface accessibility and on solvents compatibility with the functional molecules. Often, synthesis methods based on chemical reduction require long and expensive processes to obtain the desired MNP functionalization.
An alternative is represented by laser ablation synthesis of metal nanoparticles in liquid solution (LASiS).[1-3] LASiS provides stable colloidal solutions in water or in organic solvents, without any ligand or stabilizing molecule. Therefore MNP surface is usually free and functionalization occurs directly in the same solvent where MNP are obtained. These methods proved to be suitable for the conjugation in one step of MNP with a wide range of organic- and bio-molecules, also allowing the real time monitoring of the surface coverage process by UV-Vis spectroscopy. By fitting the UV-Vis spectra with a model based on the Mie theory, also the average size of MNP can be obtained with good accuracy.[1-3]
The size of MNP obtained by LASiS can be further manipulated by a chemical free laser techniques inspired by top down and bottom up approaches. Gold nanoparticles (AuNP) with average radii of 4.5 nm were obtained in this way, which allowed the sensing of AuNP bioconjugation with bovine serum albumin (BSA) down to a ratio of 10:1 for AuNP:BSA.[4]
The conjugation of AuNP with the thermo-responsive polymer poly-N-isopropylacrylamide was exploited for the temperature controlled cellular uptake of AuNP and the photothermal therapy of AuNP loaded human breast adenocarcinoma MCF7 cells.[5]
Non functionalized AuNP have been studied for nonlinear optical applications. AuNP synthesized by LASiS in water solution of sodium dodecylsuphate have been used for the optical doping of polystirene opals, which allowed the controlled red shift of the photonic pseudogap. The strong SPA of AuNP also allowed the switching of the photonic bandgap upon irradiation with 9 ns laser pulses at 532 nm.[6]
A blend of zinc phthalocyanines (ZnPc) and gold nanoparticles obtained by LASiS in tetrahydrofuran showed enhanced optical limiting properties at 532 nm (9 ns) due to a photoinduced redox mechanism between AuNP and ZnPc. This mechanism allowed the self healing of gold nanoparticles during the optical limiting measurements, though the laser induced photo-fragmentation of AuNP at the base of the limiting process.[7]
1. V. Amendola, S. Polizzi, M. Meneghetti; J. Phys. Chem. B 2006, 110, 7232 – 7237.
2. V. Amendola, S. Polizzi, M. Meneghetti; Langmuir 2007, 23, 6766 – 6770.
3. V. Amendola, G. A. Rizzi, S. Polizzi, M. Meneghetti; J. Phys. Chem. B 2005, 109, 23125 – 23128.
4. V. Amendola, M. Meneghetti; J. Mater. Chem. 2007, 17, 4705-4710.
5. S. Salmaso, P. Caliceti, V. Amendola, M. Meneghetti, G. Pasparakis, A. Cameron; Submitted.
6. V. Morandi, F. Marabelli, V. Amendola, M. Meneghetti, D. Comoretto; Adv. Func. Mater. 2007, 17, 2779–2786.
7. V. Amendola, S. Polizzi, K. Kadish, D. Dini, M. Hanack, M. Meneghetti; In preparation
Notch and Fracture Mechanics-Based Assessment of Multiaxial Fatigue Thresholds of Defects and Sharp Notches in Metallic Materials
Full text linkThis investigation focuses on the constant amplitude (CA) multiaxial fatigue limit of components made of metallic materials weakened by defects, cracks, and sharp U- and/or V-notches. To estimate the multiaxial fatigue thresholds of plain, sharply notched, and cracked materials and defects, a novel theoretical framework based on the well-known averaged strain energy density (SED) criterion is proposed, which extends the Atzori–Lazzarin–Meneghetti (ALM) diagram to multiaxial loading. The proposed design equations are validated against 128 experimental multiaxial fatigue limits, taken from the literature
Tra ecdotica e comparatistica: le riviste e la fondazione della filologia romanza : atti del Convegno annuale della Scuola di dottorato europea in filologia romanza, Siena, 3-4 ottobre 2006
No full textIl volume pubblica gli atti del Convegno Annuale della Scuola di dottorato Europea in Filologia romanza tenutosi a Siena, 3-4 ottobre 2006.
Indice: M. L. Meneghetti, Presentazione. PARTE PRIMA: SAGGI. M. Zink, «Romania»: la naissance de la philologie romane en France - R. Antonelli, Dalla «Rivista di Filologia romanza» agli «Studj romanzi»: la tradizione italiana - G. Lucchini, Ascoli e l'«Archivio glottologico italiano» - G. Holtus, Gli indirizzi e l'attività principale della «Zeitschrift für romanische Philologie» nei suoi primi decenni - L. Formisano, Le riviste degli anni '70-'90 del XIX secolo e il dibattito sull'epica romanza - M. Arbor Aldea - P. L. Gradín, La dimensión europea de la lírica gallego-portuguesa en los inicios de la Filología Románica - A. Varvaro, La linguistica nelle riviste di Filologia Romanza tra 1870 e 1880. PARTE SECONDA: DOCUMENTI. S. Morgana, Il Proemio all'«Archivio Glottologico Italiano» - Prospectus di "Romania" - Prospect della «Zeitschrift für romanische Philologie» - Dall'epistolario Monaci-De Lollis. Indici.The volume contains Proceedings of the Annual Conference of the Scuola di dottorato Europea in Filologia romanza (Siena, 3-4 October 2006).
Index: M. L. Meneghetti, Presentazione. PARTE PRIMA: SAGGI. M. Zink, «Romania»: la naissance de la philologie romane en France - R. Antonelli, Dalla «Rivista di Filologia romanza» agli «Studj romanzi»: la tradizione italiana - G. Lucchini, Ascoli e l'«Archivio glottologico italiano» - G. Holtus, Gli indirizzi e l'attività principale della «Zeitschrift für romanische Philologie» nei suoi primi decenni - L. Formisano, Le riviste degli anni '70-'90 del XIX secolo e il dibattito sull'epica romanza - M. Arbor Aldea - P. L. Gradín, La dimensión europea de la lírica gallego-portuguesa en los inicios de la Filología Románica - A. Varvaro, La linguistica nelle riviste di Filologia Romanza tra 1870 e 1880. PARTE SECONDA: DOCUMENTI. S. Morgana, Il Proemio all'«Archivio Glottologico Italiano» - Prospectus di "Romania" - Prospect della «Zeitschrift für romanische Philologie» - Dall'epistolario Monaci-De Lollis. Indici
Prevenzione dell’insuccesso scolastico in studenti di prima classe secondaria di II grado: uso della batteria AMOS 8-15.
No full texto studio è un’attività complessa che coinvolge abilità cognitive e metacognitive. Le difficoltà di studio che possono emergere coinvolgono potenzialmente gli aspetti motivazionali e/o strategici. La presente ricerca ha lo scopo di analizzare i profili motivazionali/strategici di studenti con insuccesso nello studio. Come strumento di valutazione è stata utilizzata la batteria AMOS 8-15 (Cornoldi, De Beni, Zamperlin e Meneghetti, 2005). A una classe di 25 studenti di prima classe di scuola secondaria di secondo grado è stata somministrata l’intera batteria. I risultati hanno evidenziato che il gruppo di studenti in difficoltà presenta delle carenze negli aspetti strategici e motivazionali. Di questo gruppo sono stati analizzati e discussi i casi di due studenti che presentano differenti profili metacognitivi e di prestazione nello studio
A unified treatment of the fatigue limit of components weakened by stress raisers, subject to multiaxial mode I, II, and III loading
Full text linkThis paper discusses the dependency of the fatigue limit ∆σg,th of components on the size of stress raisers, such as cracks, defects, and U- or V-notches, under mode I, II, and III loading conditions in Constant Amplitude (CA) fatigue. As summarized in the Atzori-Lazzarin-Meneghetti (ALM) diagram, depending on the size and acuity of the stress raiser and the material fatigue properties, three different fatigue limit regimes can be identified: (i) for short cracks, ∆σg,th approaches the plain fatigue limit ∆σ0, (ii) for long cracks or sharp notches, ∆σg,th is governed by the long crack fatigue propagation threshold ∆Kth,LC, and (iii) for blunt notches, ∆σg,th is governed by the theoretical stress concentration factor Kt. In this work, the ALM diagram is extended to include mode II and III loading conditions by proposing a single design curve for any stress raiser subjected to any loading condition by employing the averaged Strain Energy Density criterion. The averaged SED is a fatigue m..
High-Cycle Fatigue Crack Paths in Specimens having Different Stress Concentration Features
No full textThis paper summarises an attempt to study the high-cycle fatigue cracking behaviour in specimens of low carbon steel weakened by U-notches. The specimens were tested under uniaxial fatigue loading with a load ratio equal to 0.1, and the considered Kt values, calculated with respect to the gross area, ranged from 3.8 up to about 25. The generated crack paths were quite irregular showing a propagation occurring in alternate trans- and intra-crystalline mode: in many cases, this made difficult to unambiguously measure orientation and length of Stage 1 planes. In spite of these experimental difficulties, the observed material cracking behaviour seemed to suggest that a Stage 1-like process could always be assumed to be representative of the crack initiation phenomenon, and this held true independently of the notch sharpness. In light of the fact that, at a mesoscopic level, crack initiations never occurred on material planes parallel to the notch bisector, we attempted to investigate whether it was possible to use a critical plane approach to estimate high-cycle fatigue damage in notched components under uniaxial fatigue loading. In more detail, the generated results have initially been re-analysed by using the Modified Wöhler Curve Method re-interpreted in terms of the Theory of Critical Distances [Susmel L. A unifying approach to estimate the high-cycle fatigue strength of notched components subjected to both uniaxial and multiaxial cyclic loadings. Fatigue Fract Eng Mater Struct 2004;27:391–411]. The accuracy in predicting the high-cycle fatigue behaviour of the considered multiaxial fatigue method was then compared to the accuracy of two other uniaxial approaches: the classical one by Smith and Miller [Smith RA, Miller KJ. Prediction of fatigue regimes in notched components. Int J Mech Sci 1978;20:201–206] and the one recently proposed by Atzori and co-workers [Atzori B, Lazzarin P, Meneghetti G. A unified treatment of the mode I fatigue limit of components containing notches or defects. Int J Fract 2005;133:61–87] and based on the use of some classic LEFM concepts. In particular, this comparison was performed considering virtual specimens having the same geometries as the ones investigated in the present study, but assuming that they were made of materials having mechanical properties known from the literature. This exercise allowed us to see that the high-cycle fatigue damage in notched specimens under uniaxial fatigue loading can satisfactorily be predicted not only using Mode I-crack based methods, but also using multiaxial fatigue criteria modelling the crack initiation phenomenon
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