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The theory of oscillations can be studied from a mathematical point of view in terms of differential equations. The differential equation is written and then the solution or solutions worked out and mathematically analysed. Provided physical, economic, social, or other phenomena can be modelled in terms of equivalent differential equations, the solutions and results are applicable to all phenomena all the same. On the other hand, it is sometimes easier to learn a topic by having an experimental topic in mind. It is otherwise maybe surprising that a large body of phenomena in many fields of application will be easily understood if the equations are understood for a given case. The experimental analysis that forms the basis of this book is cantilever dynamics in dynamic atomic force microscopy (AFM). In a nutshell, the motion of the cantilever in dynamic AFM can be approximated to a perturbed driven oscillator. The generality of the analysis presented here can be confirmed by noting that much of what is covered in this book, particularly when dealing with the linear equation in section 1, is similar to what is covered in generic expositions such as that by Tipler and Mosca1 or the Feynman’s lectures on physics2 . Maybe the main advantage of this exposition is that the linear and nonlinear theories of oscillators, particularly phenomena that can be reduced to the analysis of a point-mass on a spring, are discussed in detail and differences in terminology that could lead to doubt, clarified. This means that this book can be used as a textbook to teach oscillation theory with a focus on applications. This is possible because oscillations are present generally in physics, engineering, biology, economics, sociology and so on. In summary, all phenomena dealing with oscillations can be reduced, to a first approximation, to a restoring parameter, i.e., force in mechanics, following Hooke’s law. Since the AFM field is a niche in science, the general theory of oscillation does not cover the particularities of the field. This book covers such particularities. Thus, the book can be used as an introduction to dynamic AFM and oscillation theory that covers the terminology required to understand dynamic AFM. On the other hand, the ubiquity and generality of oscillation theory ensures that the book can also be used as a general introduction to oscillation theory at an undergraduate level. There is also advanced material, particularly in the second section of the book where nonlinearities are covered. For the sake of transnationality, standard terminology is employed throughout when possible, especially in the first section (Book 1). The first section is based on the standard linear differential equations. The second section is based on non-linear theory and covers advancements in dynamic FM over the past three decades (1990s – 2022). Both sections are complimentary and exploit standard terminology in oscillation theory when possible. The first section can be supplemented with the chapter on oscillations by Tipler and Mosca1 and with Feynman’s lectures on physics, volume 1, chapters 21 to 23. These two textbooks use standard terminology, even if not necessarily the same. Examples are drawn here from both texts and analogies also exploited. The second section is mathematically more advanced since it discusses nonlinear theory. The second section is highly geared towards applications in AFM, but this does not mean that the discussion lacks generality. Rather, the nonlinear theory presented here is highly general and translational. The second section can be supplemented by following Raman’s course on dynamic AFM. His course is available online3 . There are another two important resources to supplement the second section. First, the thesis of Carlos Álvarez Amo, also available online4 . Second, a varied set of papers that are referenced throughout the text., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Resumen del póster presentado al 16th European Microscopy Congress, celebrado en Lyon (Francia) del 28 de agosto al 2 de septiembre de 2016.-- et al., Honeycomb-like hematite nanoflakes/branched polypyrrole nanoleaves heterostructures with a 3D complex structure have been synthesized and employed as high-performance negative electrodes for asymmetric supercapacitors application. The detailed TEM-STEM characterization and deep EELS chemical analysis at the nanoscale has been combined to elucidate the mechanisms underlying the formation and morphology evolution of core-branch Fe2O3@PPy heterostructures.[1] In addition, we have studied the mechanism of converting MoO2 nanoflakes into 2D free-standing MoS2 electrode by sulfurization process for water splitting. In this way, the atomic resolution aberration corrected HAADF STEM reveals the sulfurization mechanism in an unprecedented detail, together with EELS chemical maps. Furthermore, in-situ electrical measurements have been performed by means of c-AFM on the MoO2/MoS2 nanoflakes surfaces in order to detect their electronic active sites., We acknowledge the funding from Generalitat de Catalunya 2014 SGR 1638, 2014 SGR 797 and MINECO coordinated projects between IREC and ICN2 TNT-FUELS and e-TNT (MAT2014-59961-C2-2-R). Xuan Zhang is grateful for financial support from China Scholarship Council. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program.

Resumen del póster presentado a la 10th Conferencia Fuerzas y Túnel, celebrada en Girona (España) del 5 al 7 de septiembre de 2016., Under ambient conditions, all surfaces are covered by a thin film of water, ranging in thickness from a fraction of a monolayer to a macroscopic film. Even the thinnest water layer can affect the physical and chemical properties of the substrate. Ferroelectric materials show strong electric fields at the surface. These electric fields can be screened by different mechanisms, namely intrinsic (charge carriers or defects) or extrinsic (chemical environment or adsorbates), that play a crucial role in the stabilization of bulk polarization. In this sense, when considering a ferroelectric material, the electrostatic interactions between the surface and the water molecules electric dipole emerge as new critical aspect for both, the behavior of adsorbed water layers and the polarization dynamics. LiNbO3 (LN) is a ferroelectric oxide perovskite widely used in nonlinear optics and acoustic applications, mainly due to the bulk properties of the material. We applied Near-ambient Xray photoelectron spectroscopy (XPS) to study water adsorption and desorption on ferroelectric oxide crystals such as LiNbO3 at the line CIRCE in ALBA and demonstrated polarization dependent water adsorption and desorption processes and surface discharge dynamics, and probed the existence of a water monolayer even after high vacuum conditions, which stayed on polarized surfaces for temperatures above 250 ºC. But the strong interaction between water molecules electric dipole and ferroelectric surfaces also plays an important role on the formation of ice structures on polarized surfaces. When water layers on ferroelectric polarized surfaces go through a face transition into solid state, the ice layers formed on theses surfaces are also strongly affected by the polarization state. At cryogenic temperatures almost fully polarized ice layers can be formed, with polarization direction depending on the substrate. In this work, we have studied polarization structure of ice layers at 3.5 K on periodically poled LN (PPLN) surfaces by KPFM in a LowT Attocube AFM system, and probed the parallel alignment of the water molecules in agreement with the polarization direction of PPLN as probed by low T PFM characterization.

Trabajo presentado a la Conferencia "BNC-b Research Meeting" celebrada en Barcelona el 14 de julio de 2011., This work was supported by the Ministerio de Ciencia e Innovación (MICINN), Spain, through Project No. FIS2009-08355. J. J. S. thanks the CSIC for a JAE DOC PhD grant.

Trabajo presentado a la Conferencia "BNC-b Research Meeting" celebrada en Barcelona el 14 de julio de 2011.

La manera com es mulla una superfície quan se l'exposa a l'aigua determina fenòmens crucials en biologia, en química i en ciència de materials. Les microscòpies locals de rastreig han obert recentment nous camins per a estudiar capes i gotes d'aigua sobre superfícies que han permès l'estudi de les propietats d'allò mullat a nivell molecular. S'han desenvolupat diverses vies d'aproximació utilitzant aquestes tècniques que proporcionen diferents informacions sobre el fenomen del que és mullat. Per exemple, la microscòpia de rastreig d'efecte túnel s'utilitza per estudiar l'estructura de petits clústers i monocapes de molècules d'aigua absorbides en superfícies. Malauradament, aquests estudis estan limitats a temperatures criogèniques i per substrats conductors. Per investigar fenòmens relacionats amb allò mullat en condicions ambientals, el microscopi de forces atòmiques en modes electrostàtics de no-contacte ha esdevingut una eina molt poderosa. Mitjançant aquesta tècnica s'estudia l'estructura de les capes d'aigua més enllà de la primera monocapa, es poden obtenir imatges de gotes a escala nanomètrica per investigar la hidrofobicitat i la hidrofilicitat a escala molecular, s'investiguen processos químics dins de capes d'aigua o s'intenta millorar la impermeabilitat de recobriments moleculars utilitzats en nanotecnologia. En aquest article es presenta una selecció d'estudis il·lustratius, realitzats mitjançant microscòpies locals de rastreig, sobre diferents aspectes rellevants en ciència i tecnologia relacionats amb l'aigua i les superfícies., The wetting properties of a surface exposed to water determine crucial phenomena in biology, chemistry and material sciences. Scanning Probe Microscopies have recently opened new ways to study water films and droplets on surfaces allowing the study of the wetting properties of surfaces at molecular level. Several approaches providing different information on the phenomena have been developed. Scanning Tunneling Microscopy is being used to study the structure of water clusters and water monolayers, but unfortunately these studies are limited to low temperatures and conductive substrates. Atomic Force Microscopy working in non-contact electrostatic modes has become a powerful tool to investigate wetting in ambient conditions. This technique is being used to study the structure of water films beyond the first monolayer, imaging droplets at the nanometer range to study hydrophobicity and hydrophillicity at molecular level, studying chemical processes within adsorbed water films or probing the impermeability of molecular coatings used in nanotechnology. A selection of illustrative Scanning Probe Microscopy studies covering different scientific and technologically relevant aspects related to water and surfaces on water is presented in this review.

Objetivo: Evaluar el impacto de la introducción de una trayectoria clínica sobre la atención a los pacientes con un ictus isquémico. Métodos: Se diseñó un estudio de intervención, controlado, sin asignación aleatoria, de seguimiento de 2 cohortes de pacientes, no coincidentes en el tiempo, correspondiente a los períodos inmediatamente anterior (grupo PRE o control) y posterior (grupo POST o intervención) a la introducción de la trayectoria clínica. Las principales medidas del resultado fueron: a) indicadores de calidad asistencial; b) mejora en la capacidad funcional (índice de Barthel) y la función neurológica (escala Canadiense); c) complicaciones intrahospitalarias; d) satisfacción, y e) estancia media. Resultados: Se reclutó a 139 pacientes, 69 correspondientes al período PRE y 70 al período POST, sin que se observaran diferencias significativas al ingreso entre ambos grupos. Se constató una reducción del 36,5% en el tiempo transcurrido desde el ingreso hasta el inicio de la movilización, aunque no se observaron diferencias significativas en los otros indicadores de calidad ni en el incremento de la función neurológica o la capacidad funcional. El porcentaje de individuos con alguna complicación durante el ingreso fue del 44,6% en el período PRE y del 28,6% en el período POST (p = 0,039). No se observaron diferencias significativas en la valoración global del cuestionario de satisfacción, pero los pacientes del período POST presentaron una mayor satisfacción en las dimensiones «información recibida» y «profesionalidad y confianza». La estancia media se redujo de 11 a 10 días. Conclusiones: La introducción de la trayectoria clínica del ictus isquémico puede contribuir a reducir el número de complicaciones y los días de estancia, así como mejorar la calidad de la atención y la satisfacción de los pacientes. Objective: To assess the impact of the implementation of a clinical pathway for stroke patients. Methods: We performed a controlled intervention study without random allocation that compared two non-concomitant cohorts of stroke patients corresponding to the periods immediately before (control group) and after (intervention group) the implementation of a clinical pathway. The main outcome measures were: a) quality of care indicators; b) improvements in functional capacity (Barthel score) and neurological function (Canadian scale); c) nosocomial complications; d) satisfaction, and e) mean length of hospital stay. Results: One hundred and thirty-nine patients were recruited. Sixty-nine corresponded to the period before implementation of the pathway and 70 corresponded to the period after implementation. There were no significant differences between the two groups on admission. A 36.5% reduction in the time from admission to mobilization was observed. No significant differences were observed between the groups for the other quality of care indicators, or in improvements in functional and neurological capacity. Nosocomial complications occurred in 44.5% of patients in the control group compared with 28.6% in the intervention group (p = .039). No significant differences were observed in the overall satisfaction assessment, but patients in the intervention group showed greater satisfaction in the dimensions of «information» and «trust and professionalism». The mean length of hospital stay was reduced from 11 to 10 days. Conclusions: The implementation of the stroke clinical pathway contributed to reducing the length of hospital stay and the number of inpatient complications, as well as to improving some quality of care indicators.

La tesi que es presenta es veu emmarcada dins l’àrea de ciència de superfícies. Dos dels grans temes desenvolupats en aquesta tesi estan relacionats amb l’estudi de superfícies amb constants de xarxa (distàncies atòmiques que componen la molècula) properes a la del pla basal de la fase hexagonal del gel (Ih) (el gel més comú a l’escorça terrestre). L’objectiu d’aquesta premissa és veure com superfícies que tenen la constant de xarxa propera a la del gel (Ih) provoquen que l’aigua d’origen atmosfèric s’adsorbeixi a sobre en forma d’aigua en estat sòlid (gel) i no en forma d’aigua líquida a temperatures relativament altes. Aquest tipus de superfícies tindrien grans utilitats en processos meteorològics tals com la inducció de pluja, comercialització de productes propulsors de neu artificial o simplement per a conèixer els límits de congelació de l’aigua en sistemes biològics. En el capítol 3, es presenta el BaF2 com a possible nucleador de gel sobre la seva superfície, ja que la seva constant de xarxa difereix només un 4% de la del gel (Ih). Amb l’ajuda d’un microscopi de forces atòmiques (AFM) s’ha pogut observar com les molècules d’aigua difonen fàcilment sobre la seva superfície, i a més a més aquestes tenen preferència en la seva acomodació. S’ha observat que els esglaons de BaF2 i les zones que tenen un excés de càrrega degut al clivatge, són els defectes ideals per l’aigua, ja que s’hi sent molt més còmode. Aquests esglaons generats durant el clivatge tenen unes direccions cristal·logràfiques concretes i ben definides, i l’aigua no té una preferència aleatòria per ells sinó que, contràriament del que pensàvem, les molècules d’aigua tenen en general més afinitat per aquells esglaons menys energètics, amb menys densitat d’àtoms al descobert. El BaF2 no és un bon nucleador pel que fa al creixement de gel tridimensional, ja que la conformació que adopten les molècules d’aigua paral·lela al pla no afavoreix la formació de gel tridimensional, però gràcies a la seva constant de xarxa i als defectes ocasionats durant el clivatge resulta que és un nucleador bidimensional. S’ha seguit el mateix patró pel CaF2, un compost isoestructural del BaF2, amb la diferència que té una constant de xarxa més petita, que difereix un 14% respecte la cara basal del gel (Ih). Els experiments realitzats mostren com l’aigua s’hi adsorbeix de manera aleatòria i més caòtica, tot i que té certa preferència pels esglaons com en el cas del BaF2. Podem concloure doncs, que la constant de xarxa és un paràmetre molt important, però no és l’únic. En el capítol 5, es planteja l’opció d’obtenir una superfície de manera artificial, amb les característiques que busquem per tal que l’aigua s’hi adsorbeixi en forma de gel (Ih) fàcilment. La tècnica utilitzada per aquest propòsit és la Langmuir-Blodgett, la qual ens permet fer monocapes en l’interfase líquid-gas, i es poden transferir a una superfície sòlida. Depenent de la superfície, obtindrem monocapes hidrofòbiques o hidrofíliques. Tot i que l’objectiu llunyà és formar una monocapa ideal i observar a través de l’AFM com s’adsorbeix l’aigua a sobre, fins ara s’ha aconseguit formar superfícies hidrofíliques a partir de substrats hidrofòbics (grafit) i també formar superfícies hidrofòbiques a partir de substrats hidrofílics (mica). Les molècules utilitzades per a la formació de les monocapes són alcohols alifàtics de cadena llarga, estudiats a la bibliografia com a possibles bons nucleadores de gel. En el capítol 4, l’atenció es veu desviada per l’investigació de la càrrega residual que es produeix a sobre de les superfícies. Per les propietats electròniques que té el grafè, es va creure convenient fer-lo servir de superfície model. A través de la punta d’AFM s’ha injectat càrrega a una làmina de grafè sobre òxid de silici, i s’ha vist com la càrrega provocada per la punta es va dissipant cap a l’òxid de silici en funció de la humitat relativa. Amb aquest estudi es va poder analitzar l’efecte de càrrega residual en superfícies i el rol que hi juga l’aigua. En aquest treball també es va fer pal·lesa que les dimensions de la punta determinaven fortament les mesures electroestàtiques en AFM., This thesis is framed into the surface science area. Two main chapters developed in the present work are related to the study of surfaces with lattice constant near to the basal plane of the hexagonal ice (Ih) (the most common ice on Earth). The main goal of this topic is observe how these surfaces induce water adsorption on its surfaces as solid water at high temperatures. These surfaces could be used in meteorological processes such as rain induction, snow making industry or the knowledge of the freezing limits of water in biological systems. In chapter 3, BaF2 is presented as a possible ice nucleation because its lattice constant differs only 4% respect to the basal plane of the hexagonal ice (Ih). With the help of an Atomic Force Microscopy (AFM) it can be observed how water molecules easily spread on the surface and showing adsorption preferences. It was observed that steps and charge excess zones on BaF2 surface are perfect defects to water molecules anchoring, where water molecules feel more comfortable. Steps generated during the cleavage have specific and well defined crystallographic directions, and water molecules have preference and more affinity for the less energetic steps (with less atomic density). Finally, it is concluded that BaF2 is not a good three-dimensional nucleator because the conformation of water molecules onto the plane does not promote the ice formation, but the lattice constant and defects caused during the cleavage make it a good two-dimensional ice nucleator. The same studies were performed on CaF2, an isostructural compound of BaF2 but with a different lattice constant, which differs 14% from basal plane of the hexagonal ice (Ih). The experiments show chaotic and random water adsorption on CaF2 but with a certain preference to the steps. It can be concluded that the lattice constant is an important parameter to consider but is not the only parameter to take account. In chapter 5, the construction of an artificial surface with specific characteristics is proposed. The goal is to create a surface capable to induce water freezing. The technique used for this purpose is the Langmuir-Blodgett trough, which allows a monolayer formation in the liquid-gas interface that can be transferred to a solid substrate. Depending on the surface, hydrophilic or hydrophobic monolayers are obtained. Although water adsorption with AFM was studied yet in this thesis, we were able to form hydrophobic surfaces from hydrophilic substrates (mica) and hydrophilic surfaces from hydrophobic substrates (graphite). The molecules used for this purpose are long chain aliphatic alcohols, studied in the bibliography as probably good ice nucleators. In chapter 4 our attention is diverted to the study of residual charge produced on the surfaces. Due to the electronic properties of graphene, it was thought appropriate to use it as a model surface. Using the AFM tip charge was injected onto a graphene sheet deposited on a silicon oxide wafer, and discharging of the graphene sheet was observed. The charge spreading to the silicon oxide depends on the relative humidity. The role of adsorbed water in the discharge of surfaces was analysed. This work also demonstrated that the probe dimensions have critical influence on the electrostatic measures in AFM.