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AimThe short-term and long-term efficacy of different thermal percutaneous ablation techniques remains a topical issue. Our group implemented percutaneous laser ablation (LA), a moving-shot technique to increase efficiency and reduce costs and variability of LA by applying multiple lower-intensity energy illuminations (MLIEI) covering the nodular volume (V) through changes in position of a single laser fiber within the thyroid nodule. The aim of the present study was to evaluate the efficacy of the single-fiber LA-MLIEI during a 5-year follow-up and to identify possible predictors of the final outcome.MethodsProspective study: Thirty outpatients (23 women and seven men) with benign symptomatic thyroid nodules were assigned to single-fiber LA-MLIEI, between 2012 and 2015. A single LA session was performed under real-time ultrasound (US) guidance using a 1,064-nm continuous-wave laser at 3 W. A 400-µm optical fiber was inserted through a 21-gauge needle, and 3–10 illuminations were performed per nodule, administering between 400 and 850 J/illumination. The total administered energy was calculated on the initial V of the nodule and the estimated ablation area. US evaluation was performed after LA-MLIEI at 1 week and 1, 3, 6, and 12 months and after that annually up to 5 years. Clinical symptoms, laboratory thyroid function during follow-up, and acute and chronic complications of treatment were registered.ResultsOn follow-up, 67% (n: 20) were responders to single-fiber LA-MLIEI, while 33% (n: 10) were non-responders. The responder group initiated V reduction (ΔV) at 1 month, with remission of symptoms, and presented a 50% ΔV at 3 months of treatment; the maximum response was achieved at 24 months and remained stable until the end of the study. The non-responder group presented a ΔV of less than 50% at 12 months; though a tendency to >50% ΔV was observed at 24–36 months, there was subsequent regrowth, and 40% of this group required surgery. ΔV was positively correlated with the total administered energy/V (J/V) and inversely with nodule V. No severe adverse effects were observed. Thyroid function remained normal in all patients. Remission of symptoms occurred rapidly after 1 month.ConclusionsLA with multiple fractional discharges employing a single fiber in a unique session is a safe and inexpensive technique that allows rapid reduction of thyroid nodules, with a stable response up to 5 years, similarly to what has been reported with the conventional LA. Total nodule volume appears as a predictive factor of the reduction.

In the past few years, it has been established that Laser Ablation Surface Engineering (LASE) is a very effective way of producing surfaces which have Secondary Electron Yields (SEY)¿

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2021, Tutor: Jordi Soriano Fradera, The aim of this thesis is to investigate the impact of localized laser ablation on the activity in neuronal cultures. We analyzed neuronal network’s behaviour before and after the ablation, centering the study in a time window of about 10 minutes after damage. The results show that the global activity and functional connectivity decrease after the applied damage, together with the emergence of functional communities that indicate a fragmentation of the network. In addition, it seems that new functional links appear in the neighborhood of the targeted area, suggesting the strengthening of the surviving connections and hints at the fight of the culture against damage. The results could be interesting to model damage in the brain

The proximity of the &ldquo, post-antibiotic era&rdquo, where infections and minor injuries could be a cause of death, there are urges to seek an alternative for the cure of infectious diseases. Copper nanoparticles and their huge potential as a bactericidal agent could be a solution. In this work, Cu and Cu oxide nanoparticles were synthesized by laser ablation in open air and in argon atmosphere using 532 and 1064 nm radiation generated by nanosecond and picosecond Nd:YVO4 lasers, respectively, to be directly deposited onto Ti substrates. Size, morphology, composition and the crystalline structure of the produced nanoparticles have been studied by the means of field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), the energy dispersive spectroscopy of X-rays (EDS), selected area electron diffraction (SAED) and X-ray diffraction (XRD). The UV-VIS absorbance of the thin layer of nanoparticles was also measured, and the antibacterial capacity of the obtained deposits tested against Staphylococcus aureus. The obtained deposits consisted of porous coatings composed of copper and copper oxide nanoparticles interconnected to form chain-like aggregates. The use of the argon atmosphere contributed to reduce significantly the formation of Cu oxide species. The synthesized and deposited nanoparticles exhibited an inhibitory effect upon S. aureus.

Attribution of the panel The Virgin with the Child and an Angel today in the Art Museum of Girona is under study due to the existence of two hypotheses, both of them not thoroughly documented, pointing Jan Massys and Bernardo Luini as potential authors. Attribution process is an important issue in many museums and collections. In this article, the question is addressed by combining material and iconographic information, paying special attention to the information yielded by minor components, and by following the material characteristics of the existing restoration interventions. In addition to imaging and classical analytical techniques (SEM and FTIR), the capability of a new developed Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry system for minor elements and thin layers detection is also discussed. Results confirmed a 16th century palette and revealed the use of specific pigments such as Verditer and Smalt. Analytical results combined with iconographic characteristics, permitted the contextualization of the painting in North Europe in the circle of production of Antwerp between 1500–1550. This conclusion does not allow the direct attribution to Jan Massys but minimize the probabilities of Bernadino Luini as author.

[eng] The use of femtosecond lasers has recently gained attention as a result of the recognition to Gérard Mourou and Donna Strickland with the award of the Nobel Prize in Physics 2018 "for their method of generating high-intensity, ultra-short optical pulses". The innumerable areas of application of ultrashort laser pulses have not yet been completely explored, but their possibilities for accessing the microworld are considered highly valuable. Following this spirit, the objective of this thesis consisted in proposing and implementing feasible solutions to the challenges involved in the microfabrication of materials with ultrashort laser pulses for diverse advanced applications. To that end, attention was put in laser ablation of transparent polymers with spatial resolutions that transcend sharpness limitations due to light diffraction. The results presented here were obtained during the development of the doctorate studies of the PhD program in Nanosciences at the Departament de Física Aplicada of the Universitat de Barcelona. It is structured as follows: INTRODUCTION AND OBJECTIVES: This introductory chapter contains a description of the most significant microfabrication techniques, centered on laser-based methods. Having a key role in this thesis, the interaction between laser radiation and matter is shortly reviewed. The physical phenomena motivate the use of femtosecond lasers for the precise processing of transparent materials, where focus is put on their superficial laser ablation, the entailing challenges and its applications. The objectives pursued in this work close this first chapter. EXPERIMENTAL: A description of the experimental setups implementing femtosecond laser systems, methods and materials applied during the trials constituting the developed research is presented in this chapter. The features of the laser sources together with the corresponding laser direct-write setups form the sections of this chapter, followed by some comments on Gaussian beams and their focusing. These found the presentation of the z-scan focusing technique. To close this chapter, some remarks and background about the employed materials are delivered. Z-SCAN FOCUSING METHOD: The results obtained by putting to work the z-scan focusing technique introduced in the previous chapter are presented here. The theme is the development and characterization of the z-scan focusing technique as a method to address the issue of securing surface ablation of transparent material with femtosecond laser pulses. Its successful implementation in surface ablation of the transparent polymer polymethyl methacrylate (PMMA) with high spatial resolution is given as proof of the viability of the proposed strategy for a precise focusing of laser beams onto transparent materials. The contents of this chapter include studies on transmittance and reflectance measurements at different focusing distances between the laser beam waist and the processed material surface through single laser pulse surface ablation and laser surface scanning for channel microfabrication (comparing their results), the beam waist position determination thanks to the transmittance measurements and analysis of the produced surface ablation. APPLICATIONS IN LASER MICROFABRICATION OF MATERIALS: the implementation of the developed z- scan focusing technique was put to use in laser microfabrication of materials with diverse applications. The applications include the irradiation with femtosecond laser pulses of biodegradable polymers for profound hole ablation in polylactic acid (PLA) and study of the its influence in biodegradability of polylactic-co-glycolic acid, the laser perforation for leakage studies on medical use polypropylene bags, and the laser fabrication of microfluidic guides for conductive line printing. Owing to their diversity the chapter is divided in four sections, one for each topic. The various processed materials are briefly introduced, with some background supporting their study. CONCLUSIONS: The last chapter sums up the most relevant results and main achievements that have been obtained during the development of this thesis in the form of closing remarks., [cat] L’ús de làsers d’impulsos ultracurts ha rebut atenció recentment degut al reconeixement amb el Premi Nobel de Física de l’any 2018 a la tècnica que en permet la seva generació. Les seves àrees d’aplicació encara no han estat completament explorades, però les seves possibilitats per accedir al món microscòpic són considerades prometedores. Seguint aquest esperit, l’objectiu d’aquesta tesi és proposar i implementar solucions viables als reptes relacionats amb la microfabricació de materials amb impulsos làser ultracurts, específicament l’ablació làser de polímers transparents amb resolucions espacials que transcendeixin les limitacions de definició associades a la difracció de la llum. INTRODUCCIÓ I OBJECTIUS: Aquest capítol descriu les tècniques de microfabricació més significatives, centrant-se en els mètodes làser. Degut al paper clau del làser en aquesta tesi, es fa una descripció breu de la interacció entre la radiació làser i la matèria. Els objectius plantejats completen aquest primer capítol. EXPERIMENTAL: En aquest apartat es presenta una descripció dels muntatges experimentals amb sistemes làser de duració ultracurta, els mètodes i els materials emprats durant les proves que constitueixen la recerca i que serveixen de base per a la presentació del mètode d’enfocament z-scan. MÈTODE D’ENFOCAMENT Z-SCAN: Els resultats obtinguts amb la tècnica proposada d’enfocament per z-scan són presentats aquí. El tema central és el desenvolupament i caracterització d’aquesta tècnica com a mètode per l’ablació superficial de materials transparents amb impulsos làser ultracurts. La implementació exitosa de l’ablació superficial del polimetilmetacrilat (PMMA) amb elevada resolució espacial demostra la viabilitat de l’estratègia proposada per enfocar amb precisió un feix làser a la superfície de materials transparents. APLICACIONS PER AL MICROPROCESSAMENT LÀSER DE MATERIALS: La implementació de la tècnica desenvolupada d’enfocament per z-scan s’ha pogut traslladar al microprocessament de materials amb làser en diverses aplicacions com la irradiació de polímers biodegradables per a la producció de forats profunds en àcid polílàctic (PLA), la seva influència en la biodegradabilitat de l’àcid polílàctic-co-glicòlic (PLGA), la perforació de fuites en bosses de polipropilè d’ús mèdic, i la fabricació de guies microfluídiques per la impressió de línies conductores. Conclusions: L’últim capítol resumeix els resultats més rellevants i els principals assoliments.

The rapid evolution of resistant bacteria is a huge problem in medicine because makes the treatment of infections more and more difficult. The bactericidal properties of noble metal nanoparticles could be a solution. In this work silver nanoparticles were produced by using two nanosecond Nd:YVO4 lasers operating at 1064 and 532 nm respectively to ablate a silver target submerged in pure de-ionized water. Part of the resulting colloidal solution was injected as a fine stream by a compressed air system and re-irradiated one and three times with the same laser to resize and get uniform nanoparticles. The obtained nanoparticles by ablation and re-irradiation consisted of crystalline Ag nanoparticles with a bimodal size distribution. The particle size has been reduced by subsequent laser re-irradiation with both laser sources, reaching a 40% of mean size reduction. Inhibitory effects on the proliferation of Staphylococcus aureus was demonstrated on silver nanoparticles obtained after re-irradiation with the infrared laser. info:eu-repo/semantics/acceptedVersion

[eng] Exposure to nanoparticles has been associated with adverse effects on human health. When the exposure route is inhalation, nanoparticles can cause pulmonary inflammation which may be more severe than from fine particles, while significant associations between nanoparticles and cardiovascular morbidity have also been also observed. Consequently, industrial processes which release airborne nanoparticles into workplace air have become an issue of growing concern with regard to occupational exposure and potential health hazards for workers. Nanoparticles emitted by industrial activities may be engineered and used as input/output in a process, or formed unintentionally as a result of a given industrial activity and are referred to as process-generated nanoparticles. The latter have high probability to be released from high energy processes (e.g. thermal) and to impact exposure in various scenarios at diverse industrial settings. The present PhD Thesis has three main objectives: to identify nanoparticle sources in industrial settings and characterize their release mechanisms, to characterize the different exposure scenarios, and to assess the effectiveness of mitigation strategies for exposure reduction. These objectives were addressed by applying an integrated assessment of nanoparticle exposures in real-world scenarios. All of the industrial scenarios studied were related to the ceramic industry (e.g. laser ablation of ceramic tiles, thermal spraying of ceramic coatings). The results obtained are presented in the form of four scientific papers. The first scientific publication (1) identified pulsed laser ablation of ceramic tiles as a source of process-generated nanoparticles. This work studied the mechanisms controlling nanoparticle formation and release during ablation of different types of ceramic tiles. High particle number concentrations were detected (3.5×104 to 2.5×106 cm-3) for all of the tiles and with both lasers assessed (near- and mid-infrared). Different particle release mechanisms were identified: during ablation with the near-IR laser particles were emitted through melting and nucleation, while emissions from the mid-IR laser were attributed to melting and mechanical shockwaves. Particle number and mass emissions were dependent on the tile surface characteristics as well as the laser parameters. The second publication (2) characterized nanoparticle emissions and their impact on exposure during thermal spraying of ceramic coatings in a real-world industrial scenario. High particle number (>106 cm−3; 30–40 nm) and mass (60–600 μgPM1 m−3) concentrations were recorded inside the spraying booths, which impacted exposure in the worker area (104–105 cm−3, 40–65 nm; 44–87 μgPM1 m−3). Irregularly-shaped, metal-containing particles (Ni, Cr, W) were sampled from the worker area and a direct link between the spraying activity and exposure was established. In terms of particle number count, 90% of the particles were nanoparticles with sizes 26–90 nm. The third publication (3) discussed the hygroscopic properties of these nanoparticles, which were monitored online with an HTDMA. The nanoparticles emitted were found to take up moderate amounts of water when exposed to elevated relative humidity (87% RH), with their hygroscopicity being distinguishably lower compared to that of the atmospheric background aerosol particles present in the workplace air. Thus, particle hygroscopicity was identified as a useful metric to discriminate process-generated from background particles in workplace air. Finally, the fourth scientific publication (4) quantified the effectiveness of mitigation strategies implemented during four different exposure scenarios under real-world settings. The nanoparticle removal efficiency of source enclosure combined with local exhaust ventilation was quantified to range between 65-99%, The highest efficiency was achieved by the combined use of a strong local exhaust ventilation with full enclosure (99.8%), tested during thermal spraying. Source substitution achieved a 91.5% reduction of exposure concentrations in the worker breathing zone, lower than the expected 100% due to interference from simultaneous sources. Mask respirators managed to reduce worker exposure by 86.7%, whereas source isolation reached maximum efficiency of 84.4%. The results highlight the interdependence of different mitigation strategies (e.g., LEV and source enclosure), which are frequently implemented simultaneously in real-world industrial scenarios. The mitigation measures for exposure reduction have proven to be more efficient when tailored to each specific industrial scenario. The combination of key information and analyses deriving from the experimental scenarios assessed allowed to extract conclusions and recommendations with direct application to the industrial sector under study, [spa] La exposición a nanopartículas se asocia con efectos adversos en la salud humana. En consecuencia, las actividades industriales que liberan nanopartículas al aire en entornos laborales se han convertido en un problema de creciente relevancia desde el punto de vista de salud ocupacional y de los riesgos potenciales para la salud de los trabajadores. Las nanopartículas emitidas por actividades industriales pueden diseñarse y utilizarse como materia prima en procesos industriales, o formarse involuntariamente como resultado de una actividad industrial dada (estas últimas, denominadas con frecuencia nanopartículas de proceso). Las nanopartículas de proceso tienen una alta probabilidad de liberarse durante actividades altamente energéticas (por ejemplo, procesos térmicos) y de generar situaciones de exposición laboral en diversos escenarios y entornos industriales. La presente tesis doctoral tiene tres objetivos principales: identificar fuentes de emisión de nanopartículas en entornos industriales y caracterizar sus mecanismos de liberación, caracterizar los diferentes escenarios de exposición, y evaluar la efectividad de las estrategias de mitigación para la reducción de la exposición. Estos objetivos se abordaron mediante la aplicación de una evaluación integrada de la exposición a nanopartículas en escenarios industriales reales (no en laboratorio). Todos los escenarios industriales estudiados estaban relacionados con procesos térmicos asociados a la industria cerámica (por ejemplo, ablación por láser de baldosas cerámicas, proyección térmica de recubrimientos cerámicos). Los resultados obtenidos se presentan en forma de cuatro publicaciones científicas. La primera publicación científica (1) identificó la ablación por láser pulsado de baldosas cerámicas como una fuente de nanopartículas de proceso. La segunda publicación (2) describió las emisiones de nanopartículas y su impacto en la exposición durante la proyección térmica de recubrimientos cerámicos en un escenario industrial. La tercera publicación (3) analizó las propiedades higroscópicas de estas nanopartículas, que se monitorearon en línea con un HTDMA. Finalmente, la cuarta publicación científica (4) cuantificó la efectividad de las estrategias de mitigación implementadas en cuatro escenarios de exposición diferentes, en entornos industriales bajo condiciones reales de operación. La combinación de información clave y de los análisis derivados de los escenarios experimentales evaluados permitió extraer conclusiones y recomendaciones con aplicación directa al sector industrial cerámico.

Purpose The objective of this study was to characterize the evolution of ocular pain after advanced surface ablation (ASA) to improve strategies in postoperative pain management. Methods This was a multicenter, prospective, descriptive, cohort study. The inclusion criteria were healthy individuals ≥18 years old receiving bilateral alcohol-assisted surface ablation with epithelial removal. Pain intensity was evaluated with the visual analog scale (VAS) and the numeric pain rating scale before and after surgery. Comorbidities (photophobia, burning, tearing, and foreign body sensation) and Hospital Anxiety and Depression (HAD) questionnaire were evaluated before and at 6 hours after surgery. Postoperative treatments included cold patch, topical cold antibiotics, topical steroids, and benzodiazepines. Results Thirty-two consecutive patients having similar profiles of postoperative pain evolution were included. At 0.5 hour after ASA, the pain score by VAS was 37±20 mm, and the maximum pain, 61±31 mm, occurred at 24 hours. Afterward, it decreased progressively until 72 hours after surgery (19±20 mm). Most patients (81%) scored >60 mm, and 44% required rescue medication. Among the comorbidities, all patients had photophobia and 84% had burning sensation. At 6 hours, the HAD score was 5.4±3.9, within the range of values considered as normal. Conclusion Postoperative acute ocular pain after ASA showed a characteristic evolution over time. Recognition of the pattern could be important for improving the acceptance of ASA and for improving strategies in pain management in the postoperative period.

Digital manufacturing constitutes a real industrial revolution that is transforming the production processes from the early stages of research and development to mass production and marketing. The biggest difference in comparison with old fabrication methods is the possibility to perform changes in the pattern design just by using mouse clicks instead of modifying an already fabricated prototype, which results in faster, cheaper and more efficient fabrication processes. For example, new technologies enabling the production of printed electronic devices on flexible substrates and compatible with roll-to-roll processing methods would result in cheaper fabrication costs than the traditional batch processing of silicon wafers. Such fabrication methods comprise a series of processing steps which are applied to the substrates while they are moving on rolls in the fabrication line. Therefore, it is desired that the new technologies can work at high speeds allowing at the same time the production of miniaturized features. Lasers are a versatile tool that can meet the demands of flexibility, speed, resolution and compatibility with roll-to-roll processing of digital manufacturing. The main advantages of laser radiation rely in its unique properties: high directionality, coherence and monochromaticity. The combination of such properties allows generating high intensities that can be focused into extremely small volumes, which makes lasers an ideal tool for the processing of materials at the micro- and nano-scale, not only as a subtractive but also as an additive technique. Laser ablation is the best known subtractive technique and it consists in the irradiation of a material with a focused laser beam. In the case of working with transparent materials, surface ablation constitutes a serious challenge since it is necessary to develop new strategies that allow controlling the position where the energy is delivered to ensure that ablation really occurs in the surface without modifying the bulk material. On the other hand, lasers can also be used as additive tools. For example, laser-induced forward transfer (LIFT) allows the transfer of materials in both solid and liquid state with high spatial resolution. In spite of the extensive amount of research on LIFT, some challenges still remain. For instance, the understanding of the particular printing dynamics encountered during the high speed printing of liquids, or the problem of printing uniform, continuous and stable lines with high spatial resolution. The objective of this thesis is to propose and implement feasible solutions to some of the challenges that are associated with both the subtractive and additive laser based techniques presented above. On one side, we study the laser ablation of transparent polymers using femtosecond laser pulses with the aim of achieving spatial resolutions that overcome the diffraction limit, and at the same time solving the problem of the required precise focusing of the laser beam on the materials surface. On the other side, we study the LIFT transfer dynamics during the high speed printing of liquids, and we propose alternative printing strategies to solve the inherent quality defects usually encountered during the formation of printed lines. Finally, two different approaches that are a combination of both subtractive and additive techniques are presented; we implement LIFT for the fabrication of liquid microlenses used for the surface nanopatterning of materials, and on the other side, we create fluidic guides by laser ablation for the printing of high quality continuous lines., La fabricació digital de dispositius tecnològics requereix el desenvolupament de noves i millors tècniques per al microprocessament de materials que al mateix temps siguin compatibles amb mètodes de producció en sèrie a gran escala com el roll-to-roll processing. Aquestes tècniques han de complir certs requisits relacionats amb la possibilitat de realitzar canvis de disseny ràpids durant el procés de fabricació, alta velocitat de processament, i al mateix temps permetre la producció de motius de forma controlada amb altes resolucions espacials. En la present tesi es proposen i implementen solucions viables a alguns dels reptes presents a la microfabricació amb làser tant substractiva com additiva. D'una banda, es presenta un nou mètode d'enfocament del feix làser sobre la mostra per l'ablació superficial de materials transparents que permet obtenir resolucions espacials que superen el límit de difracció del dispositiu òptic. D'altra banda, es duu a terme un estudi de la dinàmica de la impressió de líquids mitjançant làser a alta velocitat, de gran interès de cara a la implementació industrial de la tècnica. A més, es presenten estratègies d'impressió de tintes conductores amb l'objectiu de produir línies contínues amb alta qualitat d'impressió. Finalment s'inclouen dues propostes que són producte de la combinació d’ambues tècniques, la impressió de líquids i l'ablació amb làser.

Eva M Sobas,1 Sebastián Videla,2,3 Miguel J Maldonado,1 Jose C Pastor1,4 1Instituto Universitario de Oftalmobiologia Aplicada (IOBA), Universidad de Valladolid, Valladolid, Spain; 2Laboratorios Dr Esteve S.A., Barcelona, Spain; 3Department of Experimental and Health Sciences, Faculty of Health and Life Sciences, Universitat Pompeu Fabra, Barcelona, Spain; 4Department of Ophthalmology, Hospital Clinico Universitario, Valladolid, Spain Purpose: Laser vision correction is one of the most commonly performed elective surgical procedures in ophthalmology. Generally, discomfort besides pain (photophobia, burning sensation, tearing, and foreign body sensation) after these procedures is not taken into consideration in the clinical practice. The objective is to provide data on these symptoms and their relevance after advanced surface ablation (ASA). Methods: Single-center survey study based on a structured questionnaire relative to the patients’ perceived symptoms after ASA. Inclusion criteria were: ≥18 years old, no ocular disease, with myopia (0.75 to 9 D) or hyperopia (0.25 to 5 D) with or without astigmatism, receiving ASA on at least one eye. All procedures were performed by the same surgeon. Adescriptive analysis was performed. Results: Seventy-three consecutive patients (34 men and 39 women) were included in the study. The median (range) of age was 33 (19–64) years. Sixty-nine patients had surgery done on both eyes. Postoperative pain was the most frequent comorbidity (97% [95% confidence interval {CI}: 90–100]) with a median (range) of intensity (verbal numerical rating scale) score of 7(2–10). Photophobia: 85% (95% CI: 75–92); burning sensation: 62% (95% CI: 50–73); tearing: 59% (95% CI: 47–70); and foreign body sensation: 48% (95% CI: 36–60) were also prevalent postoperative symptoms. Pain during ASA was reported for 44% (95% CI: 32–56) of patients.Conclusion: Comorbidities such as pain, photophobia, burning sensation, tearing, and foreign body sensation are prevalent after ASA procedure. Postoperative pain should be taken into consideration due to its prevalence and intensity. A new and more efficient postoperative analgesic protocol should be established. Keywords: pain, photophobia, refractive surgery, survey

La tècnica de LA-ICP/MS presenta certs avantatges respecte altres tècniques d'anàlisi molt interessants per l'aplicació en el Camp de l'estudi del Patrimoni Cultural. Per una banda l'Ablació Laser aporta la possibilitat de la presa de mostra no manual, metodologia en moltes ocasions, més adequada en termes de destructivitat que els mètodes tradicionals. D'altra banda l'ús d'un ICP/MS com a detector aporta un nivell de sensibilitat per a la detecció de majoritaris i minoritaris però també de components en molt baixes concentracions que permet l'obtenció de resultats amb molt poca quantitat de mostra. Malgrat això, el seu ús per la caracterització materials d'objectes del Patrimoni Cultural està molt restringit i fins a dia d'avui només es troben estudis aplicats a objectes ceràmics, metàl·lics i algunes aproximacions a materials d'arxiu, però no en l'aplicació específica a obra pictòrica. Una de les restriccions més importants ve relacionada amb les dimensions dels objectes, en general massa grans per ser analitzats en equips comercials. Des d'un punt de vista analític existeixen dos aspectes importants a tenir present per la caracterització material d'aquest tipus d'objectes. Per una banda la heterogeneïtat intrínseca que presenten, fet que implica una complexitat important per la gran varietat de materials i estructures que es poden trobar. Per l'altre, la necessitat de conservar la integritat física, el que limita en molts casos la metodologia i procediments que es poden aplicar. En aquest context, l'objectiu d'aquesta tesi doctoral ha estat el desenvolupament d'un sistema de LA-ICP/MS per a la caracterització material no destructiva d'objectes del Patrimoni Cultural i la seva aplicació a diferents tipologies d'objectes, especialment a Pintura de Cavallet i Materials d'Arxiu. Dues de les aportacions més importants en el marc d'aquest treball han estat el desenvolupament d'un sistema òptic i la construcció d'una cel·la d'ablació. El sistema òptic permet dirigir el laser sobre un punt concret de l'objecte. A més permet també controlar tant el diàmetre del feix làser incident (diàmetre dels cràters d'ablació 100 µm) com la zona irradiada mitjançant una microcàmera de control. D'altra banda la cel·la d'ablació dissenyada és de fons obert i pot ser posicionada en qualsevol punt de l'objecte permetent l'anàlisi in situ sense restriccions en les seves mides, sense la necessitat d'extreure una mostra prèviament. Finalment l'aplicació de polsos successius sobre un mateix punt permet obtenir la informació estratigràfica, amb bona resolució espaial, tant en superfície com en profunditat. En l'aplicació a Pintura de Cavallet els objectius responen a l'avaluació del senyal obtingut, la capacitat d'identificar la composició tant de majoritaris com de minoritaris, així com la resolució en profunditat, per l'adquisició de la informació estratigràfica de capes pictòriques i de preparació, fent especial èmfasi en la capacitat de detectar capes primes com veladures. Aquesta fase es va dur a terme mitjançant l'anàlisi de pintures simulacre realitzades al laboratori i també amb obra real. En el cas d'obra real s'han analitzat dues pintures sobre taula, una amb tècnica al tremp Verge amb el nen i un àngel atribuïda a Jan Massys, i una a l'oli titulada Retrato de Piero de Medici 'il Gotoso', de Jacomo Pontormo. En ambdós casos s'ha determinat la composició tant de superfície com de capes subjacents i s'ha contribuït a la contextualització i atribució de les obres. En el cas de Material d'Arxiu, l'estudi s'ha centrat també en la caracterització material de manuscrits antics, fabricats a mà de draps i escrits amb tinta ferrogàl·lica. En aquest cas s'han estudiat les capacitats en termes de caracterització i distribució espaial en superfície, tant dels materials constitutius com dels efectes induïts per tractaments de conservació, en especial de desacidificació i laminació, avaluant els efectes de factors de corrosió i la seva influència en la conservació dels manuscrits. Per les dues aplicacions la tècnica ha aporta informació útil i es constitueix com una alternativa complementària a altres tècniques utilitzades en el camp com el SEM-EDX o FTIR., Laser Ablation -ICP/MS is a technique which presents certain advantages regarding analysis of objects from Cultural Heritage field. In one hand the Laser Ablation device provides and alternative sampling procedure that may be more suitable for the analysis in this context. On the other hand the use of the ICP/MS as a detector, allows for the determination of the elemental composition in a wide range of concentrations with a minimum amount of material required. Nevertheless, its use for the material characterization of Cultural Heritage objects is highly restricted and only some experiences are published on the field of ceramic objects, metallic and some few cases study in manuscript analysis, but not on the analysis of paintings. One of the main drawbacks is the dimensions of the objects. As a consequence there are no commercially available instruments for LA-ICP/MS, including ablation cell, that permit the analysis of large objects like artworks neither Laser Ablation systems for “in situ” sampling had not been described until recently. From an analytical point of view, there are two primary concerns when characterizing works of art composition: the heterogeneity in the distribution of the components, at the macro and micro levels, and the need to preserve the physical integrity of each object In order to accomplish the analysis of objects regardless their size and material heterogenic composition, a specific optical system and ablation cell have been designed and coupled to the ICP/MS. The whole system has been applied on two different type of objects, easel Painting and Manuscripts, and some capabilities for each application evaluated. The capability of the developed LA-ICP/MS system for the analysis of paintings was evaluated in terms of damage produced on the artwork and its potential for stratigraphic composition determination by analyzing real painting such as the portrait of a member of the Medici Family attributed to Jacopo Pontormo, and a mannerist painting attributed to Jan Massys. Regarding the application to Manuscripts the main objective was the characterization of the original material composition and the effects of some restoration interventions in the pH, corrosion and degradation, evaluating the superficial resolution and the possibility to perform maps of the distribution. Results were compared with those obtained by SEM/EDX and FTIR.

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Any: 2014, Tutor: Juan Marcos Fernandez Pradas, Solutions of silver nanoparticles are obtained by laser ablation in order to analyze the effectivity of this method. The laser used was a Nd:YAG with 1064 nm of wavelength. Characterization of these particles was done using a tranmission electron microscope and a spectrophotometer of double beam, in order to measure both the size and the absorption spectrum of these nanoparticles. The average diameter of the produced nanoparticles increases, from 9 to 22 nm, as the laser pulse energy increases from 9 to 13 mJ. These particles obtained in solution present a strong absorption due to plasmon resonance around 400 nm. It is observed that the peak absorbance of each sample is directly related with the concentration and the size of silver nanoparticles. The position and the maximum value of the peak absorbance variates when ablation time, energy density or laser energy are changed. Ablation efficiency is reduced as time progresses during the process due to the absorption and dispersion of laser light by the nanoparticle solution.

The plume generated by ablation of hydroxyapatite targets under ArF excimer laser irradiation has been investigated by means of fast intensified charge coupled device (CCD) imaging and optical emission spectroscopy. Results have shown that the plume splits into two plasma clouds as it expands. Time and spatial resolved spectra have revealed that under the experiment conditions emission is mostly due to calcium neutral atoms and calcium oxide molecular radicals. Imaging of the plume with the aid of bandpass filters has demonstrated that the emissive species in the larger and faster plasma cloud are calcium neutral atoms whereas in the smaller and slower one are calcium oxide molecular radicals. Pulsed laser deposition (PLD) is a good technique to deposit thin films of complex compounds, and many authors 1‐6 have used it to obtain hydroxyapatite (HA) coatings for medical prostheses. This motivated us to study the HA laser ablation process through the characterization of the plume by fast intensified CCD imaging. 7,8 The resultant pictures of the plasma generated by ArF excimer laser irradiation of HA targets revealed the presence of two different emissive regions. Thus, in this paper we develop a more comprehensive analysis of the HA laser ablation plume by means of time and space resolved optical emission spectroscopy

This paper presents investigations on the effects of nanosecond laser processing parameters on depth and width of microchannels fabricated from polymethylmethacrylate (PMMA) polymer. A neodymium-doped yttrium aluminium garnet pulsed laser with a fundamental wavelength of 1,064 nm and a third harmonic wavelength of 355 nm with pulse duration of 5 ns is utilized. Hence, experiments are conducted at near-infrared (NIR) and ultraviolet (UV) wavelengths. The laser processing parameters of pulse energy (402–415 mJ at NIR and 35–73 mJ at UV wavelengths), pulse frequency (8–11 Hz), focal spot size (140–190 μm at NIR and 75 μm at UV wavelengths) and scanning rate (400–800 pulse/mm at NIR and 101–263 pulse/mm at UV wavelengths) are varied to obtain a wide range of fluence and processing rate. Microchannel width and depth profile are measured, and main effects plots are obtained to identify the effects of process parameters on channel geometry (width and depth) and material removal rate. The relationship between process variables (width and depth of laser-ablated microchannels) and process parameters is investigated. It is observed that channel width (140–430 μm at NIR and 100–150 μm at UV wavelengths) and depth (30–120 μm at NIR and 35–75 μm at UV wavelengths) decreased linearly with increasing fluence and increased non-linearly with increasing scanning rate. It is also observed that laser processing at UV wavelength provided more consistent channel profiles at lower fluences due to higher laser absorption of PMMA at this wavelength. Mathematical modeling for predicting microchannel profile was developed and validated with experimental results obtained with pulsed laser micromachining at NIR and UV wavelengths.

ArF excimer laser pulses (193 nm, 20 ns, 150 mJ) have been focused on a hydroxyapatite (HA) target in similar conditions to those normally used for thin film deposition. Fast intensified CCD images of HA laser ablation plumes have been taken in vacuum and under different water vapor pressures ranging from 0.01 mbar to 1 mbar. Images of HA ablation in vacuum have shown a plume freely expanding at a constant velocity of 2.3 × 106 cm/s. HA ablation under a water vapor pressure of 0.01 mbar has revealed an expansion behavior very similar to that of ablation in vacuum. Images taken under a water vapor pressure of 0.1 mbar have shown the formation of a shock structure in the plume. Finally, HA ablation under a water vapor pressure of 1 mbar has revealed the development of some irregularities in the shape of the plume.

[spa] El estudio del crecimiento y de las propiedades constitutivas de los recubrimientos de fosfato de calcio obtenidos mediante ablación con láser ha permitido buscar las condiciones de depósito óptimas para obtener hidroxiapatita. Se ha demostrado que es posible depositar capas compactas de hidroxiapatita de alta calidad cristalina para ser utilizados como recubrimientos de implantes de Ti6A14V bioactivos, estables y duraderos. Mediante el control de los parámetros tecnológicos involucrados en el depósito por ablación con láser es posible obtener recubrimientos con diferentes características para que puedan ajustarse a los requerimientos de cada aplicación específica. Es necesario utilizar temperaturas de substrato superiores a 400 grados C para poder sintetizar fases cristalinas. Una presión de vapor de agua de 50 Pa favorece la obtención de recubrimientos de hidroxiapatita. Los ritmos de depósito lentos favorecen también la presencia de hidroxiapatita en detrimento de los otros fosfatos de calcio.

The improvement of the reliability of the contact between the osseous tissues and the implant materials has been tested by recovering the metallic implants with ceramic materials, usually calcium phosphates. In our study, the calcium phosphate recovering layers were deposited by means of a pulsed-laser deposition technique. Our aim was to to evaluate the tissue interactions established between cortical bone and titanium implants covered by five different layers, ranging from amorphous calcium phosphate to crystalline hydroxyapatite, obtained by altering the parameters of the laser ablation process. The surgical protocol of the study consisted in the simultaneous implantation of the five types of implants in both the tibial dyaphisis of three Beagle dogs, sacrificed respectively one, two and three months after the last surgical procedures. After the sacrifice, the samples were submitted to a scheduled procedure of embedding in plastic polymers without prior decalcification, in order to perform the ultrastructural studies: scanning microscopy with secondary and backscattered electrons (BS-SEM). Our observations show that both in terms of the calcified tissues appearing as a response to the presence of the different coatings and of time of recovering, the implants coated with crystalline calcium phosphate layers by laser ablation present a better result than the amorphous-calcium-phosphate-coated implants. Moreover, the constant presence of chondroid tissue, related with the mechanical induction by forces applied on the recovering area, strongly suggests that the mechanisms implied in osteointegration are related to endomembranous, rather than endochondral ossification processes

Silver nanoparticles have been synthetized and deposited on cp Ti substrates in one-step process by the use of laser ablation in open air. The nanoparticles are produced by ablating Ag foil using two different lasers and an inert gas jet oriented into the interaction zone to prevent oxidation and to direct the ablated material to the substrate. The HRTEM images and FFT confirmed the crystalline nature of the obtained silver nanoparticles with the presence of oxidized ones, while FE-SEM revealed that the nanoparticles were uniformly distributed on Ti substrates. The Ag-containing Ti substrates showed good antibacterial activity against Lactobacillus salivarius. info:eu-repo/semantics/acceptedVersion