Spin-Crossover beyond the traditional Fe(II) complexes: ab initio study of spin-state stability in complexes with Mn, Ni and Ru

Tradicionalment el fenomen de spin-crossover s’ha estudiat en complexos hexacoordinats de Fe2+. L’objectiu d’aquesta tesi és aprofundir en aquest fenomen en complexos amb metalls de transició menys convencionals i altres nombres de coordinació mitjançant un estudi computacional. El capítol 3 presenta l’estudi d’un compost de ruteni amb capacitat de transferir electrons a molècules acceptores i per tant amb potencials aplicacions en cel•les solars. En els capítols 4 i 5 s’analitzen complexos de Ni porfirina amb biestabilitat i spin-crossover per irradiació amb llum. El capítol 6 tracta dels estats magnètics i d’oxidació de complexos de manganès. El treball estudia les diferències en la fotoquímica d’aquests metalls amb la dels complexos de ferro. L’exemple de la porfirina de Ni funcionalitzada amb un braç fenilazopiridínic dóna informació sobre el mecanisme de spin-crossover dirigit pel lligand amb canvi de coordinació. En els complexos de Mn, l’estabilitat relativa dels estats singlet i triplet depèn del caràcter sigma-donador del lligand axial.Tradicionalmente el fenómeno de spin-crossover se ha estudiado en complejos hexacoordinados de Fe2+. El objetivo de esta tesis es profundizar en este fenómeno en complejos con metales de transición menos convencionales i otros números de coordinación mediante un estudio computacional. El capítulo 3 presenta el estudio de un compuesto de rutenio con capacidad de transferir electrones a moléculas aceptoras y por lo tanto con potenciales aplicaciones en celdas solares. En los capítulos 4 y 5 se analizan complejos de Ni porfirina con spin-crossover después de ser irradiados por luz. El capítulo 6 trata de los estados magnéticos y de oxidación de complejos de manganeso. El trabajo estudia las diferencias en la fotoquímica de estos metales con la de los complejos de hierro. El ejemplo de la porfirina de Ni funcionalizada con un brazo fenilazopiridínico aporta información sobre el mecanismo de spin-crossover dirigido por el ligando con cambio de coordinación. En los complejos de Mn, la estabilidad relativa de los estados singlete y triplete depende del carácter sigma-dador del ligando axial.Spin-crossover phenomenon has traditionally been studied for hexacoordinated Fe2+ complexes. The aim of this thesis is to get insight on this phenomenon in less conventional transition metals and other coordination numbers by means of a computational study. Chapter 3 presents the study of a ruthenium compound with ability to transfer electrons to acceptor molecules and, hence, with potential applications in solar cells. Chapters 4 and 5 analyze Ni porphyrin complexes exhibiting spin-crossover after irradiation with light. Chapter 6 treats the magnetic and oxidation states of manganese complexes. The work studies the differences in the photochemistry of these metals with respect to the iron complexes. The example of Ni porphyrin functionalized with a phenilazopyridine arm helps to understand the mechanism of coordination-induced spin-crossover. In Mn complexes, the relative stability of the singlet and triplet states depends on the sigma-donor character of the axial ligand

Dynamical Analysis of Lower Abdominal Wall in the Human Inguinal Hernia

En aquesta tesi es construeix un simulador numèric de la paret abdominal inferior, per tal de determinar la gènesis i les causes de les hernies inguinal humanes. Així, un model amb dades reals d'aquesta regió del cos humà (correctament discretitzades) ens permetrà reproduir les propietats dinàmiques de diferents elements de la regió permetent la simulació de la hernia en el moment que te lloc.La simulació muscular en general, ha tingut un paper secundari en la simulació numèrica, ja que en ocasions sols han interessat les propietats genèriques del múscul (per això es considera el múscul com un sol element) i no en un estudi detallat de les parts del múscul. El camp on la simulació ha estat més productiva ha estat la simulació cardíaca, a causa del constant interès en la creació de models del múscul cardíac i es per aquest motiu que sols es troben models detallats en aquest cas.La contracció de la fibra muscular va ser simulada fen servir el model reològic de Hill-Maxwell presentat per en J.Bestel en el que es regula la contracció muscular amb una funció de potencial d'activació u(t). Aquest model és el primer model dinàmic en dimensió u a nivell microscòpic de la contracció muscular.Actualment, existeixen moltes conjectures sobre les causes de les hèrnies, malgrat tot, no ha estat possible un estudi detallat sobre l'origen de les hèrnies. Per altra banda, és impossible captar el moment en que es genera una hèrnia, i per altra banda hi ha una carència de model prou detallats de la contracció muscular.En aquesta tesi es presenta un estudi dinàmic de la paret abdominal inferior amb els elements actius (els músculs) i els elements passius (fàscies, lligaments i altres teixits), és per això que es pot dur a terme un estudi amb varis aspectes físics i químics que intervenen a la gènesis de les hernies. El model reprodueix la dinàmica real del àrea tal i com A. Keith i W.J. Lytle varen conjecturar als inicis del segle passat i que són usualment acceptats per la comunitat de cirurgians.Aquest és el primer model que reprodueix la dinàmica real de la regió inguinal, prova la existència de dos mecanismes de defensa (el mecanisme de persiana i el mecanisme de esfínter a l'anell inguinal). Amb aquest model de contracció muscular podem estudiar diversos paràmetres que tenen un paper important a la gènesis de les hernies inguinals i podem dur a terme un estudi més detallat sobre els elements de risc. Aquests paràmetres ( el mòdul de Young, el coeficient de Poison o la pressió intraabdominal, per exemple) tenen un efecte hipotètic no provat en la gènesis de les hèrnies. Aquest treball, avalua l'efecte real de diversos paràmetres al model lineal i proposa una simulació no lineals per la simulació muscular.ABSTRACTThis PhD thesis aims to build a numerical simulator of the inferior abdominal wall, in order to determine the genesis and causes of the inguinal hernia. Thus, a model with real data on the region of human body (properly discretized) has been built that reproduces the dynamic properties of the various elements of the region allowing the simulation of the moment at which the hernia occurs. Muscular simulation in general, has became a secondary subjec regarding numerical simulation, because on many occasions the interest has been concentrated in the general properties of the muscle (so that the muscle is considered a single element) and not in a detailed study of each of the parts of the muscle. The field where simulation has possibly been more productive is the cardiac simulation because of the constant interest in creating models of the cardiac muscle and it is for this reason that the only detailed models that exist are those related to the cardiac muscle. The muscular fibre contraction was simulated using the Hill-Maxwell rehologic model presented by J. Bestel which it regulates the contraction and recovery by means of potential activation function u(t). This model is the first dynamic model in dimension one of a microscopic muscle level. Currently, there is much varying conjecture regarding the causes of hernias, despite this however, a detailed study of their genesis, has not been possible. This is because on the one hand, it is impossible to catch the moment in which a hernia is generated, and, on the other, there is a lack of sufficiently detailed models of the muscles involved. We present a dynamic model of the inferior abdominal wall with the active elements (the muscles) and the passive elements (fascias, ligaments and other tissues), so that a study can be made of the various physical and chemical aspects that generate hernias. The model reproduces the real dynamic of the area, as A. Keith and W.J. Lytle conjectured at the beginning of the past century and commonly accepted by surgery community. This is the first model which reproduces the real dynamic in the inguinal area, so that we can prove the existence of the two defence mechanisms (the shutter mechanism and the sphincter mechanism in the inguinal ring). With this muscular contraction model we can study several parameters that it have an important role in the inguinal hernia genesis and we can do an accurate study about risk elements in the hernia inguinal. This parameters (Young's modulus, Poison's coefficient or intraabdominal pressure, for instance) have an hypothetical and no proved effect in the genesis of inguinal hernias. This work, evaluate the real effect of several parameters in the lineal model and propose a non linear model for the muscular simulation

Virtual simulation of the biomechanics of the abdominal wall with different stoma locations

An ostomy is a surgical procedure by which an artificial opening in the abdominal wall, known as a stoma, is created. We assess the effects of stoma location on the abdominal wall mechanics. We perform three-dimensional finite element simulations on an anatomy model which was generated on the basis of medical images. Our simulation methodology is entirely based on open source software. We consider seventeen different locations for the stoma incision (trephine) and we simulate the mechanical response of the abdominal wall when an intraabdominal pressure as high as 20 kPa is applied. We focus on factors related to the risk of parastomal hernia development such as the deformation experienced by the abdominal wall, the stress levels supported by its tissues and the corresponding level of trephine enlargement. No significant dependence was found between stoma location and the levels of abdominal wall deformations or stress supported by tissues, except for the case with a stoma located on the linea alba. Trephine perimeter and area respectively increased by as much as 44% and 85%. The level of trephine deformation depends on stoma location with considerably higher trephine enlargements found in stomas laterally located with respect to the rectus abdominis muscle.Peer ReviewedPostprint (published version

Biomechanical modelling of the pelvic system: improving the accuracy of the location of neoplasms in MRI-TRUS fusion prostate biopsy

Background An accurate knowledge of the relocation of prostate neoplasms during biopsy is of great importance to reduce the number of false negative results. Prostate neoplasms are visible in magnetic resonance images (MRI) but it is difficult for the practitioner to locate them at the time of performing a transrectal ultrasound (TRUS) guided biopsy. In this study, we present a new methodology, based on simulation, that predicts both prostate deformation and lesion migration during the biopsy. Methods A three-dimensional (3-D) anatomy model of the pelvic region, based on medical images, is constructed. A finite element (FE) numerical simulation of the organs motion and deformation as a result of the pressure exerted by the TRUS probe is carried out using the Code-Aster open-source computer software. Initial positions of potential prostate lesions prior to biopsy are taken into consideration and the final location of each lesion is targeted in the FE simulation output. Results Our 3-D FE simulations show that the effect of the pressure exerted by the TRUS probe is twofold as the prostate experiences both a motion and a deformation of its original shape. We targeted the relocation of five small prostate lesions when the TRUS probe exerts a force of 30 N on the rectum inner wall. The distance travelled by these lesions ranged between 5.6 and 13.9 mm. Conclusions Our new methodology can help to predict the location of neoplasms during a prostate biopsy but further studies are needed to validate our results. Moreover, the new methodology is completely developed on open-source software, which means that its implementation would be affordable to all healthcare providers

Virtual simulation of the biomechanics of the abdominal wall with different stoma locations

Biomedical engineering; Gastrointestinal diseases; Mathematics and computingIngeniería Biomédica; Enfermedades gastrointestinales; Matemáticas e InformáticaEnginyeria Biomèdica; Malalties gastrointestinals; Matemàtiques i informàticaAn ostomy is a surgical procedure by which an artificial opening in the abdominal wall, known as a stoma, is created. We assess the effects of stoma location on the abdominal wall mechanics. We perform three-dimensional finite element simulations on an anatomy model which was generated on the basis of medical images. Our simulation methodology is entirely based on open source software. We consider seventeen different locations for the stoma incision (trephine) and we simulate the mechanical response of the abdominal wall when an intraabdominal pressure as high as 20 kPa is applied. We focus on factors related to the risk of parastomal hernia development such as the deformation experienced by the abdominal wall, the stress levels supported by its tissues and the corresponding level of trephine enlargement. No significant dependence was found between stoma location and the levels of abdominal wall deformations or stress supported by tissues, except for the case with a stoma located on the linea alba. Trephine perimeter and area respectively increased by as much as 44% and 85%. The level of trephine deformation depends on stoma location with considerably higher trephine enlargements found in stomas laterally located with respect to the rectus abdominis muscle.Financial support for the current research was granted by Universitat Rovira i Virgili, project number 2018PFR-URV-B2-29

Raymond C. Read (2007) Arthur Keith, the anatomist who evisioned herniosis

Carta a l'editor de la revista "Hernia" en referència a l'article publicat amb el títol: "Arthur Keith, the anatomist who evisioned herniosis"We would like to add a comment on another important contribution of Arthur Keith to the Weld of herniology, that is, the original and accurate description of the inguinal “shutter” mechanism, a remarkable anatomic action against development of an inguinal hernia. [...] Today, virtual reality surgical simulation models allowing three-dimensional (3D) visualization of the human inguinal anatomy can be used as a complementary tool to assess dynamics of the inguinal area. In fact, using simulations with the Wnite element method we have recently confirmed the physiological “shutter” mechanism already described almost 100 years ago. These virtual reality Wndings are our present tribute to the outstanding anatomic descriptions of Arthur Keith.Postprint (published version

Computational modeling of electromechanical propagation in the helical ventricular anatomy of the heart

The classical interpretation of myocardial activation assumes that the myocardium is homogeneous and that the electrical propagation is radial. However, anatomical studies have described a layered anatomical structure resulting from a continuous anatomical helical disposition of the myocardial fibers. To further investigate the sequence of electromechanical propagation based on the helical architecture of the heart, a simplified computational model was designed. This model was then used to test four activation patterns, which were generated by propagating the action potential along the myocardial band from different activation sites.Peer ReviewedPostprint (author’s final draft

Phenomenological Vessel Scattering Study Based on Simulated Inverse SAR Imagery

This paper presents a study on the origin of the dominating scattering mechanisms observed in polarimetric synthetic aperture radar (SAR) images of ships. The study has been made by using numerical simulations, which have been carried out with a radar cross section (RCS) prediction tool (GRaphical Electromagnetic COmputing) and a SAR simulator. Extensive series of simulations has been run for realistic 3-D geometrical models of ships with various sizes. Different radar parameters, aspect angles, and sea surface states have been considered in the scenario. Data analysis with coherent target decompositions has indicated characteristic polarimetric signatures for particular ships within a speci¿c range of viewing angles. This happens at highly oblique incidences where the responses appear to be less sensitive to changes in the operating frequency and bearing angles. Under such conditions, ship scattering can be schematized by the distribution of a set of guide scatterers with high RCS. Their positions and polarimetric characteristics are quantitatively summarized in a new feature vector, which has been proposed to be the basis for classi¿cation algorithms. Key ideas about this vector are presented at the end of this paper, jointly with some examples related to three different ships. Recent publications have shown that they can be successfully cast within a new unsupervised vessel classi¿cation scheme.JRC.G.6-Security technology assessmen