Automatic lumen segmentation in IVOCT images using binary morphological reconstruction

Abstract Background Atherosclerosis causes millions of deaths, annually yielding billions in expenses round the world. Intravascular Optical Coherence Tomography (IVOCT) is a medical imaging modality, which displays high resolution images of coronary cross-section. Nonetheless, quantitative information can only be obtained with segmentation; consequently, more adequate diagnostics, therapies and interventions can be provided. Since it is a relatively new modality, many different segmentation methods, available in the literature for other modalities, could be successfully applied to IVOCT images, improving accuracies and uses. Method An automatic lumen segmentation approach, based on Wavelet Transform and Mathematical Morphology, is presented. The methodology is divided into three main parts. First, the preprocessing stage attenuates and enhances undesirable and important information, respectively. Second, in the feature extraction block, wavelet is associated with an adapted version of Otsu threshold; hence, tissue information is discriminated and binarized. Finally, binary morphological reconstruction improves the binary information and constructs the binary lumen object. Results The evaluation was carried out by segmenting 290 challenging images from human and pig coronaries, and rabbit iliac arteries; the outcomes were compared with the gold standards made by experts. The resultant accuracy was obtained: True Positive (%) = 99.29 ± 2.96, False Positive (%) = 3.69 ± 2.88, False Negative (%) = 0.71 ± 2.96, Max False Positive Distance (mm) = 0.1 ± 0.07, Max False Negative Distance (mm) = 0.06 ± 0.1. Conclusions In conclusion, by segmenting a number of IVOCT images with various features, the proposed technique showed to be robust and more accurate than published studies; in addition, the method is completely automatic, providing a new tool for IVOCT segmentation.

Influence of the substitutional solute on the mechanical properties of Ti-Nb binary alloys for biomedical use

Titanium alloys are widely used in the manufacture of biomedical implants because they possess an excellent combination of physical properties and outstanding biocompatibility. Today, the most widely used alloy is Ti-6Al-4V, but some studies have reported adverse effects with the long-term presence of Al and V in the body, without mentioning that the elasticity modulus value of this alloy is far superior to the bone. Thus, there is a need to develop new Ti-based alloys without Al and V that have a lower modulus, greater biocompatibility, and similar mechanical strength. In this paper, we investigated the effect of Nb as a substitutional solute on the mechanical properties of Ti-Nb alloys, prepared in an arc-melting furnace and characterized by density, X-ray diffraction, optical microscopy, hardness and elasticity modulus measurements. The X-ray and microscopy measurements show a predominance of the α phase. The microhardness values showed a tendency to increase with the concentration of niobium in the alloy. Regarding the elasticity modulus, it was observed a nonlinear behavior with respect to the concentration of niobium. This behavior is associated with the presence of the α phase.

Stability and dynamics of terrestrial planets in binary star systems: application on Alpha Centauri

Binary stars are frequent in the universe, with about 50% of the known main sequence stars being located at a multiple star system (Abt, 1979). Even though, they are universally thought as second rate sites for the location of exo-planets and the habitable zone, due to the difficulties of detection and high perturbation that could prevent planet formation and long term stability. In this work we show that planets in binary star systems can have regular orbits and remain on the habitable zone. We introduce a stability criterium based on the solution of the restricted three body problem and apply it to describe the short period planar and three-dimentional stability zones of S-type orbits around each star of the Alpha Centauri system. We develop as well a semi-analytical secular model to study the long term dynamics of fictional planets in the habitable zone of those stars and we verify that planets on the habitable zone would be in regular orbits with any eccentricity and with inclination to the binary orbital plane up until 35 degrees. We show as well that the short period oscillations on the semi-major axis is 100 times greater than the Earth's, but at all the time the planet would still be found inside the Habitable zone.

Transformaciones basadas en el algoritmo Local Binary Pattern de imágenes capturadas con la Kinect para clasificación facial

Máster Universitario en Sistemas Inteligentes y Aplicaciones Numéricas en Ingeniería (SIANI)

Liquid-liquid equilibria in binary solutions formed by [Pyridinium-Derived][F4B] ionic liquids and alkanols:new experimental data and validation of a multiparametric model for correlating LLE data

[EN]Experimental solubility data are presented for a set of binary systems composed of ionic liquids (IL) derived from pyridium, with the tetrafluoroborate anion, and normal alcohols ranging from ethanol to decanol, in the temperature interval of 275 420 K, at atmospheric pressure. For each case, the miscibility curve and the upper critical solubility temperature (UCST) values are presented. The effects of the ILs on the behavior of solutions with alkanols are analyzed, paying special attention to the pyridine derivatives, and considering a series of structural characteristics of the compounds involved.

Correlation and prediction of mixing thermodynamic properties of ester-containing systems Ester+alkane and ester+ester binary systems and the ternary dodecane+ethyl pentonoate+ethyl ethanoate

[EN]Excess thermodynamic properties VE m and HE m, have been measured for the ternary mixture dodecane + ethyl pentanoate + ethyl ethanoate and for the corresponding binaries dodecane + ethyl pentanoate, dodecane + ethyl ethanoate, ethyl pentanoate + ethyl ethanoate at 298.15 K. All mixtures show endothermic and expansive effects. Experimental results are correlated with a suitable equation whose final form for the excess ternary quantity ME contains the particular contributions of the three binaries (i–j) and a last term corresponding to the ternary, all of them obtained considering fourth-order interactions.

Measurements and correlations of the isobaric vapor-liquid equilibria of binary mixtures and excess properties for mixtures containing and alkyl (Methyl, Ethyl) butanoate with an alkane (Heptane, Nonane) at 101.32 kPa.

[EN]In this work, the measurements of the isobaric vapor−liquid equilibrium (VLE) data at 101.32 kPa and the excess molar volumes (vE), obtained at 10 K intervals of temperature in the range (288.15 to 328.15) K, for four binary systems comprised of methyl or ethyl butanoate with two alkanes (heptane and nonane) are presented.

Multiproperty modeling for a set of binary systems. Evaluation of a model to correlate simultaneously several mixing properties of methyl ethanoate+alkanes and new experimental data

[EN] This work makes a theoretical–experimental contribution to the study of ester and alkane solutions. Experimental data of isobaric vapor–liquid equilibria (VLE) are presented at 101.3 kPa for binary systems of methyl ethanoate with six alkanes (from C5 to C10), and of volumes and mixing enthalpies, vE and hE.

Binary liquid-liquid equilibria for systems of mono or disubstituted haloakanes (Cl,Br) and pyiridinium based ionic liquids. Advances in the experimentation and interpretation of results

[EN]This work presents the measurements made to define the temperature−composition curves for a set of binary systems composed of several pyridinium-based ionic liquids (ILs) [bpy][BF4] and [bYmpy][BF4] (Y = 2,3,4) with mono- and dihaloalkanes (Cl and Br) in the temperature interval [280−473] K and at atmospheric pressure. With the exception of the short chain dichloroalkanes (1,1- and 1,2-), all the compounds present some degree of immiscibility with the ionic liquids selected.

Exploring the use of local binary patterns as focus measure

[EN]In this work local binary patterns based focus measures are presented. Local binary patterns (LBP) have been introduced in computer vision tasks like texture classification or face recognition. In applications where recognition is based on LBP, a computational saving can be achieved with the use of LBP in the focus measures. The behavior of the proposed measures is studied to test if they fulfill the properties of the focus measures and then a comparison with some well know focus measures is carried out in different scenarios.

Functionalized surfaces and surface functionalization of nanomaterials

Nature leads, we follow. But nanotechnologists are in hot pursuit, in designing controllable structures that can mimic naturally occurring and artificially synthesized materials on a common platform. The supramolecular chemistry concerns the investigation of nature principles to produce fascinating complexed and functional molecular assemblies, as well as the utilization of these principles to generate novel devices and materials, potentially useful for sensing, catalysis, transport and other applications in medical or engineering science. The work presented in this thesis is a compilation of different synthetic methods to achieve inorganic-organic hybrid nanomaterials. Silicatein, a protein enzyme, which acts both as a catalyst and template for the formation of silica needles in marine sponges, has been used for the biosynthesis of semiconductor metal oxides on surfaces. Silicatein was immobilized on gold (111) surfaces using alkane thiol, as well as on a novel self-assembly of NTA on top of a “cushion” of reactive ester polymer has been successfully employed to make functionalised surfaces. The immobilization of silicatein on surfaces was monitored by surface plasmon spectroscopy, atomic force microscopy and confocal laser scanning microscopy. Surface bound silicatein retains its biocatalytic activity, which was demonstrated by monitoring its hydrocatalytic activity to catalyse the synthesis of biosilica, biotitania, and biozirconia. The synthesis of semiconductor metal oxides was characterized using scanning electron microscopy. This hydrolytic biocatalyst is used to synthesize the gold nanoparticles. The gold nanoparticles are formed by reduction of tetrachloroaurate, AuCl4-, by the action of sulfhydryl groups hidden below the surface groups of the protein. The resulting gold nanoparticles which are stabilized by surface bound silicatein further aggregate to form Au nanocrystals. The shape of the nanocrystals obtained by using recombinant silicatein is controlled through chiral induction by the protein during the nucleation of the nanocrystals. As an extension of this work, TiO2 nanowires were functionalized using polymeric ligand which incorporates the nitrilotriacetic acid (NTA) linker in the back bone to immobilize His-tagged silicatein onto the TiO2 nanowires. The surface bound protein not only retains its original hydrolytic properties, but also acts as a reductant for AuCl4- in the synthesis of hybrid TiO2/silicatein/Au nanocomposites. Functionalized, monocrystalline rutile TiO2 nanorods were prepared from TiCl4 in aqueous solution in the presence of dopamine. The surface bound organic ligand controls the morphology as well as the crystallinity and the phase selection of TiO2. The surface amine groups can be tailored further with functional molecules such as dyes. As an example, this surface functionality is used for the covalent binding of a fluorescent dye,4-chloro-7- nitrobenzylurazene (NBD) to the TiO2 nanorods. The polymeric ligands have been used successfully for the in-situ and post-functionalization of TiO2 nanoparticles. Besides to chelating dopamine anchor group the multifunctional ligand system presented here incorporates a modifier molecule which allows the binding of functional molecules (here the dyes pyrene, NBD, and Texas Red) as well as additional entities which allow tailoring the solubility of inorganic nanocrystals in different solvents. A novel method for the surface functionalization of fullerene-type MoS2 nanoparticles and subsequently binding these nanoparticles onto TiO2 nanowires has been reported using polymeric ligands. The procedure involves the complexation of IF-MoS2 with a combination of Ni2+ via an umbrella-type nitrilotriacetic acid (NTA) and anchoring them to the sidewalls of TiO2 nanowires utilizing the hydroxyl groups of dopamine present in the main contents of polymeric ligand. A convenient method for the synthesis of Au/CdS nanocomposites has been presented, which were achieved through the novel method of thiol functionalization of gold colloids. The thermodynamically most stable phase of ZrO2 (cubic) has been obtained at much lower temperature (180°C). These nanoparticles are highly blue fluorescent, with a high surface area.

New methods for the functionalization of metathesis polymers

Two general strategies for the functionalization of metathesis polymers are presented in this dissertation. Introducing Sacrificial Synthesis, many of the limitations of ruthenium-catalyzed ROMP have been overcome. Here, the living ROMP polymer to be functionalized was turned into a diblock copolymer by polymerizing dioxepine monomers onto the desired first polymer block. The second block was then later removed to leave “half-a-dioxepin”, i.e. exactly one hydroxyl group, at the chain-end. The efficiency of Sacrificial Synthesis is also studied. Thiol groups were also placed by a sacrificial strategy based on cyclic thioacetals. 2-Phenyl-1,3-dithiepin could be polymerized and subsequently cleaved by hydrogenation with Raney-Nickel. The presence of thiol groups on the chain end has been proven by chemical means (derivatization) and by coating gold-nanoparticles. The second strategy, vinyl lactone quenchingv is a termination reaction based on vinyl esters. After a metathesis step, an inactive Fischer-type carbene is formed. Such acyl carbenes are unstable and self-decompose to set an inactive ruthenium complex and the functional group free without changing the reaction conditions. The two compounds vinylene carbonate and 3H-furanone gave rise to the placement of aldehydes and carboxylic acids at the polymer chain ends without the necessity to perform any deprotection steps after the functionalization. The development of those two functionalization methods led to several applications. By reacting hydroxyl-functionalized ROMP-polymers with norbornene acid, macromonomers were formed which were subsequently polymerized to the respective graft-copolymers. Also, the derivatization of the same functionalized polymers with propargylic acid gave rise to alkyne-functionalized polymers which were conjugated with azides. Furthermore, “ugly stars”, i.e. long-chain branched structures were synthesized by polycondensation of ABn-type macromonomers and telechelic polymers were accessed combining the described functionalization techniques.

Inorganic-organic hybrid polymers: Solution-processible coating materials for defined surface functionalization

A new class of inorganic-organic hybrid polymers could successfully been prepared by the combination of different polymerization techniques. The access to a broad range of organic polymers incorporated into the hybrid polymer was realized using two independent approaches.rnIn the first approach a functional poly(silsesquioxane) (PSSQ) network was pre-formed, which was capable to initiate a controlled radical polymerization to graft organic vinyl-type monomers from the PSSQ precursor. As controlled radical polymerization techniques atom transfer radical polymerization (ATRP), as well as reversible addition fragmentation chain transfer (RAFT) polymerization could be used after defined tuning of the PSSQ precursor either toward a PSSQ macro-initiator or to a PSSQ macro-chain-transfer-agent. The polymerization pathway, consisting of polycondensation of trialkoxy-silanes followed by grafting-from polymerization of different monomers, allowed synthesis of various functional hybrid polymers. A controlled synthesis of the PSSQ precursors could successfully be performed using a microreactor setup; the molecular weight could be adjusted easily while the polydispersity index could be decreased well below 2.rnThe second approach aimed to incorporate differently derived organic polymers. As examples, polycarbonate and poly(ethylene glycol) were end-group-modified using trialkoxysilanes. After end-group-functionalization these organic polymers could be incorporated into a PSSQ network.rnThese different hybrid polymers showed extraordinary coating abilities. All polymers could be processed from solution by spin-coating or dip-coating. The high amount of reactive silanol moieties in the PSSQ part could be cross-linked after application by annealing at 130° for 1h. Not only cross-linking of the whole film was achieved, which resulted in mechanical interlocking with the substrate, also chemical bonds to metal or metal oxide surfaces were formed. All coating materials showed high stability and adhesion onto various underlying materials, reaching from metals (like steel or gold) and metal oxides (like glass) to plastics (like polycarbonate or polytetrafluoroethylene).rnAs the material and the synthetic pathway were very tolerant toward different functionalities, various functional monomers could be incorporated in the final coating material. The incorporation of N-isopropylacrylamide yielded in temperature-responsive surface coatings, whereas the incorporation of redox-active monomers allowed the preparation of semi-conductive coatings, capable to produce smooth hole-injection layers on transparent conductive electrodes used in optoelectronic devices.rnThe range of possible applications could be increased tremendously by incorporation of reactive monomers, capable to undergo fast and quantitative conversions by polymer-analogous reactions. For example, grafting active esters from a PSSQ precursor yielded a reactive surface coating after application onto numerous substrates. Just by dipping the coated substrate into a solution of a functionalized amine, the desired function could be immobilized at the interface as well as throughout the whole film. The obtained reactive surface coatings could be used as basis for different functional coatings for various applications. The conversion with specifically tuned amines yielded in surfaces with adjustable wetting behaviors, switchable wetting behaviors or as recognition element for surface-oriented bio-analytical devices. The combination of hybrid materials with orthogonal reactivities allowed for the first time the preparation of multi-reactive surfaces which could be functionalized sequentially with defined fractions of different groups at the interface. rnThe introduced concept to synthesis functional hybrid polymers unifies the main requirements on an ideal coating material. Strong adhesion on a wide range of underlying materials was achieved by secondary condensation of the PSSQ part, whereas the organic part allowed incorporation of various functionalities. Thus, a flexible platform to create functional and reactive surface coatings was achieved, which could be applied to different substrates. rn

Cosmic-Lab: Optical companions to binary Millisecond Pulsars

Millisecond Pulsars (MSPs) are fast rotating, highly magnetized neutron stars. According to the "canonical recycling scenario", MSPs form in binary systems containing a neutron star which is spun up through mass accretion from the evolving companion. Therefore, the final stage consists of a binary made of a MSP and the core of the deeply peeled companion. In the last years, however an increasing number of systems deviating from these expectations has been discovered, thus strongly indicating that our understanding of MSPs is far to be complete. The identification of the optical companions to binary MSPs is crucial to constrain the formation and evolution of these objects. In dense environments such as Globular Clusters (GCs), it also allows us to get insights on the cluster internal dynamics. By using deep photometric data, acquired both from space and ground-based telescopes, we identified 5 new companions to MSPs. Three of them being located in GCs and two in the Galactic Field. The three new identifications in GCs increased by 50% the number of such objects known before this Thesis. They all are non-degenerate stars, at odds with the expectations of the "canonical recycling scenario". These results therefore suggest either that transitory phases should also be taken into account, or that dynamical processes, as exchange interactions, play a crucial role in the evolution of MSPs. We also performed a spectroscopic follow-up of the companion to PSRJ1740-5340A in the GC NGC 6397, confirming that it is a deeply peeled star descending from a ~0.8Msun progenitor. This nicely confirms the theoretical expectations about the formation and evolution of MSPs.

Patterns in and kinetics of phase separation in binary mixtures

This work focused mainly on two aspects of kinetics of phase separation in binary mixtures. In the first part, we studied the interplay of hydrodynamics and the phase separation of binary mixtures. A considerably flat container (a laterally extended geometry), at an aspect ratio of 14:1 (diameter: height) was chosen, so that any hydrodynamic instabilities, if they arise, could be tracked. Two binary mixtures were studied. One was a mixture of methanol and hexane, doped with 5% ethanol, which phase separated under cooling. The second was a mixture of butoxyethanol and water, doped with 2% decane, which phase separated under heating. The dopants were added to bring down the phase transition temperature around room temperature.rnrnAlthough much work has been done already on classical hydrodynamic instabilities, not much has been done in the understanding of the coupling between phase separation and hydrodynamic instabilities. This work aimed at understanding the influence of phase separation in initiating any hydrodynamic instability, and also vice versa. Another aim was to understand the influence of the applied temperature protocol on the emergence of patterns characteristic to hydrodynamic instabilities. rnrnOn slowly cooling the system continuously, at specific cooling rates, patterns were observed in the first mixture, at the start of phase separation. They resembled the patterns observed in classical Rayleigh-Bénard instability, which arises when a liquid continuously is heated from below. To suppress this classical convection, the cooling setup was tuned such that the lower side of the sample always remained cooler by a few millikelvins, relative to the top. We found that the nature of patterns changed with different cooling rates, with stable patterns appearing for a specific cooling rate (1K/h). On the basis of the cooling protocol, we estimated a modified Rayleigh number for our system. We found that the estimated modified Rayleigh number is near the critical value for instability, for cooling rates between 0.5K/h and 1K/h. This is consistent with our experimental findings. rnrnThe origin of the patterns, in spite of the lower side being relatively colder with respect to the top, points to two possible reasons. 1) During phase separation droplets of either phases are formed, which releases a latent heat. Our microcalorimetry measurements show that the rise in temperature during the first phase separation is in the order of 10-20millikelvins, which in some cases is enough to reverse the applied temperature bias. Thus phase separation in itself initiates a hydrodynamic instability. 2) The second reason comes from the cooling protocol itself. The sample was cooled from above and below. At sufficiently high cooling rates, there are situations where the interior of the sample is relatively hotter than both top and bottom of the sample. This is sufficient to create an instability within the cell. Our experiments at higher cooling rates (5K/h and above) show complex patterns, which hints that there is enough convection even before phase separation occurs. Infact, theoretical work done by Dr.Hayase show that patterns could arise in a system without latent heat, with symmetrical cooling from top and bottom. The simulations also show that the patterns do not span the entire height of the sample cell. This is again consistent with the cell sizes measured in our experiment.rnrnThe second mixture also showed patterns at specific heating rates, when it was continuously heated inducing phase separation. In this case though, the sample was turbid for a long time until patterns appeared. A meniscus was most probably formed before the patterns emerged. We attribute the reason of patterns in this case to Marangoni convection, which is present in systems with an interface, where local differences in surface tension give rise to an instability. Our estimates for the Rayleigh number also show a significantly lower number than that's required for RB-type instability.rnrnIn the first part of the work, therefore, we identify two different kinds of hydrodynamic instabilities in two different mixtures. Both are observed during, or after the first phase separation. Our patterns compare with the classical convection patterns, but here the origins are from phase separation and the cooling protocol.rnrnIn the second part of the work, we focused on the kinetics of phase separation in a polymer solution (polystyrene and methylcyclohexane), which is cooled continuously far down into the two phase region. Oscillations in turbidity, denoting material exchange between the phases are seen. Three processes contribute to the phase separation: Nucleation of droplets, their growth and coalescence, and their subsequent sedimentation. Experiments in low molecular binary mixtures had led to models of oscillation [43] which considered sedimentation time scales much faster than the time scales of nucleation and growth. The size and shape of the sample therefore did not matter in such situations. The oscillations in turbidity were volume-dominated. The present work aimed at understanding the influence of sedimentation time scales for polymer mixtures. Three heights of the sample with same composition were studied side by side. We found that periods increased with the sample height, thus showing that sedimentation time determines the period of oscillations in the polymer solutions. We experimented with different cooling rates and different compositions of the mixture, and we found that periods are still determined by the sample height, and therefore by sedimentation time. rnrnWe also see that turbidity emerges in two ways; either from the interface, or throughout the sample. We suggest that oscillations starting from the interface are due to satellite droplets that are formed on droplet coalescence at the interface. These satellite droplets are then advected to the top of the sample, and they grow, coalesce and sediment. This type of an oscillation wouldn't require the system to pass the energy barrier required for homogenous nucleation throughout the sample. This mechanism would work best in sample where the droplets could be effectively advected throughout the sample. In our experiments, we see more interface dominated oscillations in the smaller cells and lower cooling rates, where droplet advection is favourable. In larger samples and higher cooling rates, we mostly see that the whole sample becomes turbid homogenously, which requires the system to pass the energy barrier for homogenous nucleation.rnrnOscillations, in principle, occur since the system needs to pass an energy barrier for nucleation. The height of the barrier decreases with increasing supersaturation, which in turn is from the temperature ramp applied. This gives rise to a period where the system is clear, in between the turbid periods. At certain specific cooling rates, the system can follow a path such that the start of a turbid period coincides with the vanishing of the last turbid period, thus eliminating the clear periods. This means suppressions of oscillations altogether. In fact we experimentally present a case where, at a certain cooling rate, oscillations indeed vanish. rnrnThus we find through this work that the kinetics of phase separation in polymer solution is different from that of a low molecular system; sedimentation time scales become relevant, and therefore so does the shape and size of the sample. The role of interface in initiating turbid periods also become much more prominent in this system compared to that in low molecular mixtures.rnrnIn summary, some fundamental properties in the kinetics of phase separation in binary mixtures were studied. While the first part of the work described the close interplay of the first phase separation with hydrodynamic instabilities, the second part investigated the nature and determining factors of oscillations, when the system was cooled deep into the two phase region. Both cases show how the geometry of the cell can affect the kinetics of phase separation. This study leads to further fundamental understandings of the factors contributing to the kinetics of phase separation, and to the understandings of what can be controlled and tuned in practical cases. rn