Simulació numèrica de fenòmens de transferència de calor i dinàmics de fluids transitoris

The work carried out during the 4 year research activity can be barely classified in two main lines. On the one hand, a considerable effort is taken to address issues related with the verification of multi-dimensional and transient solutions that are obtained by numerical simulations. Within the studied cases, we can consider cases of piston-cylinder ows within geometries similar to those of hermetic reciprocating compressors.This issue is mentioned in Part I. On the other hand, numerical simulations of different phenomena have been performed. More emphasis has been given to the natural convection ow within enclosures. This is explained in Part II. The case extensively studied has been the natural convection ow. The natural convection ow within enclosures has attracted the attention of many researchers due to its potential to model numerous applications of engineering interest, such as cooling of electronic devices, air ow in buildings, heat transfer in solar collectors, among others. The natural convection studies corresponding to the parallelepipedic enclosures can be classified into two elementary classes: i) heating from a horizontal wall (heating from below); ii) heating from a vertical wall. The characteristic example of the former case is the Rayleigh-B_enard ow, however this research is on the cavities heated from the side. This configuration is referred commonly as the differentially heated cavity.

Desenvolupament de codis numèrics per a la resolució de fluxos turbulents en ordinadors paral·lels emprant discretitzacions tipus symmetry-preserving

Projecte de recerca elaborat a partir d’una estada a la University of Groningen, Holanda, entre 2007 i 2009. La simulació directa de la turbulència (DNS) és una eina clau dins de la mecànica de fluids computacional. Per una banda permet conèixer millor la física de la turbulència i per l'altra els resultats obtinguts són claus per el desenvolupament dels models de turbulència. No obstant, el DNS no és una tècnica vàlida per a la gran majoria d'aplicacions industrials degut al elevats costos computacionals. Per tant, és necessari cert grau de modelització de la turbulència. En aquest context, s'han introduïts importants millores basades en la modelització del terme convectiu (no lineal) emprant symmetry-preserving regularizations. En tracta de modificar adequadament el terme convectiu a fi de reduir la producció d'escales més i més petites (vortex-stretching) tot mantenint tots els invariants de les equacions originals. Fins ara, aquest models s'han emprat amb èxit per nombres de Rayleigh (Ra) relativament elevats. En aquest punt, disposar de resultats DNS per a configuracions més complexes i nombres de Ra més elevats és clau. En aquest contexte, s'han dut a terme simulacions DNS en el supercomputador MareNostrum d'una Differentially Heated Cavity amb Ra=1e11 i Pr=0.71 durant el primer any dels dos que consta el projecte. A més a més, s'ha adaptat el codi a fi de poder simular el fluxe al voltant d'un cub sobre una pared amb Re=10000. Aquestes simulacions DNS són les més grans fetes fins ara per aquestes configuracions i la seva correcta modelització és un gran repte degut la complexitat dels fluxes. Aquestes noves simulacions DNS estan aportant nous coneixements a la física de la turbulència i aportant resultats indispensables per al progrés de les modelitzacións tipus symmetry-preserving regularization.

Quantum dynamics of crystals of molecular nanomagnets inside a resonant cavity

It is found that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. A strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing indirect evidence of the coherent microwave radiation by the crystals. A similar dependence has been found for a crystal placed between the Fabry-Perot superconducting mirrors.

Domicola lithodesi n.gen n.sp. (Amphipoda: Calliopiidae), inhabitant of thepleonal cavity of a South African lithodid crab

Domicola lithodesi, a new genus and species of gammaridean amphipod is described. It is placed in the family Calliopiidae. Two specimens, a male and a preparatory female, were collected in August 1990 from the pleonal cavity of the lithodid crab Lithodes ferox (Filhol, 1885), an anomuran crab caught at 300 m depth from off Namibia. The more relevant characters are: anophtalmous; body smooth, gammarid-like, male smaller than female, urosomite 1 with a prepeduncular spine; telson broad, entire, unlobed and unarmed; short rostrum; accessory flagellum scale-like, calceoli absent; lower lip without inner lobes; coxa 4 posteriorly excavated; gnathopods basic, subequal, with numerous palmar spines; dactyls on P3-7 with specialized adhesive organs; coxal gill 7 present; uropods eusirid type.

Adverse side effects of statins in the oral cavity

Increased plasma levels of cholesterol are high risk factors of cardiovascular disease. Statins are drugs that inhibit cholesterol synthesis at both pancreatic and extrahepathic levels, being the treatment of choice for hypercholesterolemia. Objective: To analyze the side effects of statins in the mouth cavity, and to analyze the symptoms after interruption of the treatment. Design: Observational study, preliminary. Material and methods: Patients aged 50-70, diagnosed with hypercholesterolemia and undergoing treatment with statins, referred from their primary care physician to the dentist"s office. Anamnesis over oral symptoms was performed in the first visit. Statin treatment was discontinued, followed by lab tests and control visits seven and fifteen days later. We monitored the improvement and/or remission of oral symptoms. Statin treatment was resumed, sending out a report of the patient evolution to the PCP. Symptoms were registered in sheet specially designed for the study. Exclusion criteria: patient refusal, use of drugs for dry mouth treatment, Sjögren"s syndrome. Results: n=26 patients. Dry mouth patients: improvement in 17 out of 23 patients (88.5%). Itchiness: 6 out of 15 cases improved (57.7%). Bitterness: improvement in 13 out of 14 patients (53.8%). Cough: improvement in 11 out of 12 patients (46.1%). Discussion: A high percentage of oral symptoms are associated to treatment with statins. There is a marked improvement after temporary interruption of the treatment. Little is known regarding the side effects of oral treatment with statins. This preliminary study includes a relatively small number of patients. The design of experimental treatments will be required to establish a true correlation between statin treatment and oral symptoms

The reappearance of a forgotten disease in the oral cavity: syphilis

Syphilis is a sexually transmitted disease (STD) produced by Treponema pallidum, which mainly affects humans and is able to invade practically any organ in the body. Its infection facilitates the transmission of other STDs. Since the end of the last decade, successive outbreaks of syphilis have been reported in most western European countries. Like other STDs, syphilis is a notifiable disease in the European Union. In Spain, epidemiological information is obtained nationwide via the country"s system for recording notifiable diseases (Spanish acronym EDO) and the national microbiological information system (Spanish acronym SIM), which compiles information from a network of 46 sentinel laboratories in twelve Spanish regions. The STDs that are epidemiologically controlled are gonococcal infection, syphilis, and congenital syphilis. The incidence of each of these diseases is recorded weekly. The information compiled indicates an increase in the cases of syphilis and gonococcal infection in Spain in recent years. According to the EDO, in 1999, the number of cases of syphilis per 100,000 inhabitants was recorded to be 1.69, which has risen to 4.38 in 2007. In this article, we review the reappearance and the evolution of this infectious disease in eight European countries, and alert dentists to the importance of a) diagnosing sexuallytransmitted diseases and b) notifying the centres that control them

Effect of feed fat by-products with trans fatty acids and heated oil on cholesterol and oxycholesterols in chicken

Chicken is the most widely consumed meat all over the world due to chickens being easy to rear, their fast growth rate and the meat having good nutritional characteristics. The main objective of this paper was to study the effects of dietary fatty by-products in low, medium and high levels of oxidized lipids and trans fatty acids (TFAs) on the contents of cholesterol and oxycholesterols in meat, liver, and plasma of chickens. A palm fatty acid distillate, before and after hydrogenation, and a sunflower-olive oil blend (70/30, v/v) before and after use in a commercial frying process were used in feeding trials after adding 6% of the fats to the feeds. Highly oxidized lipid and TFA feeds significantly increased the contents of cholesterol and oxycholesterols in all tissues of chicken (0.01 < p <= 0.05). The contents of oxycholesterols in chicken meat, liver and plasma obtained from TFA feeding trials varied between 17 and 48 μg/100 g in meat, 19-42 μg/100 g in liver and 105-126 μg/dL in plasma. In contrast, in the oxidized lipid feeding trials, oxycholesterols varied between 13 and 75 μg/100 g in meat, 30-58 μg/100 g in liver and 66-209 μg/dL in plasma. Meat from chickens fed with feeds containing high levels of TFAs or oxidized lipids may contribute to higher ingestion of cholesterol and oxycholesterols by humans.

Stafne bone cavity: a retrospective study of 11 cases

Objective: to describe the clinical and radiological characteristics of patients with Stafne bone cavity. Study design: a retrospective, observational study of 11 cases of Stafne bone cavity. After finding an imagine compatible with Stafne bone cavity in the Orthopantomograph® of 11 patients, a sialography of the mandibular gland was made in 3 cases, computerized tomography (CT) in 6 cases, and in 4 cases surgical intervention to confirm the diagnosis. Results: the average age was 51.5 years, predominantly males. The entity was diagnosed incidentally during a routine radiology in all cases. The sialography revealed glandular tissue within the defect, and the CT demonstrated the conservation of the lingual cortical and the peripheral origin of the lesion. Glandular tissue was found within the lesions of two of the patients who underwent surgery, and in the other two the cavity was empty. No progressive changes were found in any of the 11 cases. Conclusions: Stafne bone cavity was an incidental finding, presenting no evolutionary changes, and as such conservatory therapy based on periodic controls was indicated. Currently, complementary techniques such as CT are sufficient to establish a certain diagnosis.

Inverted ductal papilloma of the oral cavity secondary to lower lip trauma. A case report and literature review

Inverted ductal papilloma of the oral cavity is an infrequent benign neoplasm of papillary appearance that originates in the secretory duct of a salivary gland. The etiology is unknown, though some authors have related it to human papillomavirus (HPV) infection. We present the case of a 40-year-old woman with a tumor of the lower lip mucosa. Histopathological study of the lesion diagnosed inverted ductal papilloma of the oral cavity. Human papillomavirus DNA detection and typing based on tumor lesion DNA amplification and posterior hybridization, revealed no presence of viral DNA. The antecedents of trauma reported by the patient could have played an important role in the development of this tumor

Contact melting of a three-dimensional phase change material on a flat substrate

In this paper a model is developed to describe the three dimensional contact melting process of a cuboid on a heated surface. The mathematical description involves two heat equations (one in the solid and one in the melt), the Navier-Stokes equations for the flow in the melt, a Stefan condition at the phase change interface and a force balance between the weight of the solid and the countering pressure in the melt. In the solid an optimised heat balance integral method is used to approximate the temperature. In the liquid the small aspect ratio allows the Navier-Stokes and heat equations to be simplified considerably so that the liquid pressure may be determined using an igenfunction expansion and finally the problem is reduced to solving three first order ordinary differential equations. Results are presented showing the evolution of the melting process. Further reductions to the system are made to provide simple guidelines concerning the process. Comparison of the solutions with experimental data on the melting of n-octadecane shows excellent agreement.

Evaluación de un nuevo método de sutura para la cirugía endoscopica transluminal a través de orificios naturales en un modelo animal

Natural Orifice Transluminal Endoscopic Surgery (NOTES) is a novel, potentially less invasive alternative to laparoscopic surgery. However, the problems of transluminal access and closure represent significant obstacles to its successful introduction in humans. Objective: to evaluate the feasibility and safety of a novel device designed for transluminal access and closure in a survival porcine model. Subjects: Four adult female Yorkshire pigs were used in the study. Interventions: While under general anesthesia, the animals were prepared with multiple tap water enemas followed by instillation of an antibiotic suspension and povidone-iodine lavage. At a distance of 15 to 20 cm from the anus, the prototype device (LSI Solutions, Victor, NY, USA) deployed a circumscribing purse-string suture around the planned incision site and subsequently used a blade mechanism to create a 2.5-cm linear incision. The transcolonic incision was then closed by cinching and securing the purse-string suture with a titanium knot by use of a separate hand-activated suture-locking device. Main Outcome Measurements: The animals were monitored daily for signs of peritonitis and sepsis and were survived for 14 days. The peritoneal cavity was examined for peritonitis, and the colonic incision site was examined for wound dehiscence, pericolic abscess formation, and gross adhesions. Tissue samples from both incisional and random peritoneal sites were obtained for histologic examination. Results: Transcolonic incision and closure were successful in all 4 animals. The device performed in a rapid and reproducible fashion. All animals recovered without septic complications. At necropsy, there was no evidence of peritonitis, abscesses, or wound dehiscence. Salpingocolonic and colovesicular adhesions were noted in 3 of 4 animals. Histologic examination revealed microabscesses at the incision site in all animals. Conclusions: The prototype incision and closure device represents a promising solution to the problems of transluminal access for NOTES. The presence of incision-related adhesions and microabscesses signal the need for further refinement in aseptic technique. 

Engineering the thermal emission of macroporous silicon

Todos los cuerpos emiten luz espontaneamente al ser calentados. El espectro de radiacion es una funcion de la temperatura y el material. Sin embargo, la mayoria de los materiales irradia, en general, en una banda espectral amplia. Algunas matereiales, por el contrario, son capaces de concentrar la radiacion termica en una banda espectral mucho mas estrecha. Estos materiales se conocen como emisores selectivos y su uso tiene un profundo impacto en la eficiencia de sistemas sistemas tales como iluminacion y conversion de energia termofotovoltaica. De los emisores selectivos se espera que sean capaces de operar a altas temperaturas y que emitan en una banda espectral muy concisa. Uno de los metodos mas prometedores para controlar y disenar el espectro de emision termico es la utilizacion de cristales fotonicos. Los cristales fotonicos son estructuras periodicas artificiales capaces de controlar y confinar la luz de formas sin precedentes. Sin embargo, la produccion de dichas estructuras con grandes superficies y capaces de soportar altas temperaturas sigue siendo una dificil tarea. Este trabajo esta dedicada al estudio de las propiedades de emision termica de estructuras 3D de silicio macroporoso en el rango espectral mid-IR (2-30 m). En particular, este trabajo se enfoca en reducir la elevada emisividad del silicio cristalino. Las muestras estudiadas en este trabajo tienen una periodicidad de 4 m, lo que limitan los resultados obtenidos a la banda del infrarrojo medio, aunque estructuras mucho mas pequenas son tecnologicamente realizables con el metodo de fabricacion utilizado. Hemos demostrado que el silicio macroporoso 3D puede inhibir completamente la emision termica en su superficie. Mas aun, esta banda se puede ajustar en un amplio margen mediante pequenos cambios durante la formacion de los macroporos. Tambien hemos demostrado que tanto el ancho como la frecuencia de la banda de inhibicion se puede doblar mediante la aplicacion de tecnicas de postprocesado adecuadas. Finalmente hemos mostrado que es posible crear bandas de baja emisividad arbitrariamente anchas mediante estructuras macroporosas aperiodicas.

Driven fragmentation of granular gases

The dynamics of homogeneously heated granular gases which fragment due to particle collisions is analyzed. We introduce a kinetic model which accounts for correlations induced at the grain collisions and analyze both the kinetics and relevant distribution functions these systems develop. The work combines analytical and numerical studies based on direct simulation Monte Carlo calculations. A broad family of fragmentation probabilities is considered, and its implications for the system kinetics are discussed. We show that generically these driven materials evolve asymptotically into a dynamical scaling regime. If the fragmentation probability tends to a constant, the grain number diverges at a finite time, leading to a shattering singularity. If the fragmentation probability vanishes, then the number of grains grows monotonously as a power law. We consider different homogeneous thermostats and show that the kinetics of these systems depends weakly on both the grain inelasticity and driving. We observe that fragmentation plays a relevant role in the shape of the velocity distribution of the particles. When the fragmentation is driven by local stochastic events, the longvelocity tail is essentially exponential independently of the heating frequency and the breaking rule. However, for a Lowe-Andersen thermostat, numerical evidence strongly supports the conjecture that the scaled velocity distribution follows a generalized exponential behavior f (c)~exp (−cⁿ), with n ≈1.2, regarding less the fragmentation mechanisms

Projecte executiu d'una instal·lació de climatització i control d'un habitatge unifamiliar

Moltes vegades l’usuari d’una instal•lació de climatització o calefacció, no dóna la suficient importància al sistema que l’hi ha de proporcionar un millor confort amb el màxim rendiment. Aquest confort és un factor determinant, entre molts d’altres, de la “qualitat de vida”. Mentre que el rendiment és un factor important a nivell econòmic i ecològic. Tot i tenir prevalença els aspectes d’estalvi energètic, aquests no impliquen haver de renunciar a un confort tèrmic i a un estalvi econòmic. Un dels aspectes que es centra el projecte és promoure l’ús racional de les fonts energètiques (solar, biomassa) per a la correcta climatització dels habitatges. El projecte es desenvolupa en l’àmbit domèstic, concretament correspon a un habitatge unifamiliar. Aquest està situat a la població de Roda de Ter, província de Barcelona. L’objectiu principal del projecte és l’elecció del sistema de climatització i el seu dimensionament, per tal de donar el màxim confort als usuaris que habitin a la vivenda. Criteris ambientals i eficients han estat objecte a considerar pel disseny constructiu de l’habitatge. Una de les mesures importants presses en el projecte, ha estat l’elecció de les diferents parts que formen la instal•lació de climatització. Es fa referència als aïllaments dels tancaments, el sistema solar de recolzament, equips de producció de fred i calor, entre d’altres. En el projecte, s’ha dut a terme un estudi dels diferents tancaments de l’habitatge, tot determinat per a cada un d’ells, el seu coeficient de transmissió tèrmica. Per seleccionar l’equipament més adequat s’ha partit de les condicions climatològiques del municipi de Roda de Ter i s’ha realitzat el càlcul de les necessitats tèrmiques de l’edifici. L’habitatge incorpora una instal•lació de captació solar tèrmica. Aquesta aportarà un suport energètic a tot el sistema de producció de calor, ja sigui per la producció d’aigua calenta sanitària com per el calefactat de la vivenda. La col•locació dels panells a la façana sud tindrà una doble funció: a més de proporcionar energia solar tèrmica, serviran d’elements de protecció solar en la temporada d’estiu. La caldera usada per donar recolzament tèrmic utilitzarà com a combustible el “pellet”. El “pellet” és un tipus de biomassa llenyosa que consta d’un derivat de la fusta en format granulat. Es defineix i es detalla el consum energètic en biomassa, electricitat i cost econòmic anual que ocasionarà la instal.lació dissenyada. El sistema de terra radiant adoptat permetrà el refrescament en èpoques estivals i el calefactat en èpoques hivernals. Aquest donarà el confort tèrmic necessari a cada estança de l’habitatge. En el projecte també es marquen les pautes bàsiques pel control de la instal•lació solar així com el control dels grups de bombament i la mescla d’aigua del terra radiant.