Experimental evidence of localized oscillations in the photosensitive chlorine dioxide-iodine-malonic acid reaction

The interaction between Hopf and Turing modes has been the subject of active research in recent years. We present here experimental evidence of the existence of mixed Turing-Hopf modes in a two-dimensional system. Using the photosensitive chlorine dioxide-iodine-malonic acid reaction (CDIMA) and external constant background illumination as a control parameter, standing spots oscillating in amplitude and with hexagonal ordering were observed. Numerical simulations in the Lengyel-Epstein model for the CDIMA reaction confirmed the results.

Pd-catalysed amidation of 2,6-dihalopurine nucleosides. Replacement of iodine at 0 ºC

Pd-catalysed reactions of 2-Cl, 2-Br and 2-I derivatives of a 6-chloropurine nucleoside with benzamide have been compared, using Pd2dba3, Xantphos and Cs2CO3 in toluene, between 20 and 80 °C. The reactivity order was 2-I > 2-Br > 6-Cl ≫ 2-Cl. The 2-I substituent could be replaced even at 0 °C, under conditions disclosed here for the first time. On the other hand, the replacement of the chlorine atom at position 2 (2-Cl) required 110 °C.

Pd-catalysed amidation of 2,6-dihalopurine nucleosides. Replacement of iodine at 0 ºC

Pd-catalysed reactions of 2-Cl, 2-Br and 2-I derivatives of a 6-chloropurine nucleoside with benzamide have been compared, using Pd2dba3, Xantphos and Cs2CO3 in toluene, between 20 and 80 °C. The reactivity order was 2-I > 2-Br > 6-Cl ≫ 2-Cl. The 2-I substituent could be replaced even at 0 °C, under conditions disclosed here for the first time. On the other hand, the replacement of the chlorine atom at position 2 (2-Cl) required 110 °C.

Muntatge i caracterització d'una placa DSSC: Buscant potència

Treball de recerca realitzat per alumnes d'ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit científic del Jovent l'any 2009. Els objectius inicials foren la construcció d una 'Cèl•lula Solar Sensibilitzada mitjançant un Colorant’ (DSSC) amb el tint d una col llombarda i posterior caracterització segons el dossier 'Nanocrystalline Solar Cell Kit: Recreating Photosynthesis’. Les DSSC (Dye Sensitized Solar Cell) són un tipus de cèl•lules que imiten els principis que la fotosíntesis ha fet servir exitosament durant més de 3,5 bilions d anys. S’han construït algunes DSSC i se n’ha provat la seva eficiència. El seu funcionament es basa en l’energia d’un fotó que excita un electró i el fa saltar de nivell energètic fins que es desprèn de l’àtom de colorant, deixant un forat en la molècula. Aquest electró lliure passa a través de la capa de TiO2 fins arribar a la càrrega on es genera el corrent elèctric. Tot seguit, l’electró arriba al contra-elèctrode i és aquí on entra en contacte amb l’electròlit, el mediador iode/triiode. Aquest regenera l’electró, que anteriorment ha saltat del colorant, oxidant-se ell mateix.

Estudi per la selecció de CAG pel procés de potabilització de l'ETAP Ter

El present document representa l’estudi per la selecció de CAG pel procés de potabilització de l’ETAP Ter a partir d’un disseny experimental de planta pilot de menor escala. Es determina l'adequació de carbó en base a les característiques físiques (superfície BET, índex de iode...) i la capacitat d’eliminació de COT i UV respecte la mostra a tractar.

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. 

Dynamics of turing patterns under spatiotemporal forcing

We study, both theoretically and experimentally, the dynamical response of Turing patterns to a spatiotemporal forcing in the form of a traveling-wave modulation of a control parameter. We show that from strictly spatial resonance, it is possible to induce new, generic dynamical behaviors, including temporally modulated traveling waves and localized traveling solitonlike solutions. The latter make contact with the soliton solutions of Coullet [Phys. Rev. Lett. 56, 724 (1986)] and generalize them. The stability diagram for the different propagating modes in the Lengyel-Epstein model is determined numerically. Direct observations of the predicted solutions in experiments carried out with light modulations in the photosensitive chlorine dioxide-iodine-malonic acid reaction are also reported.

Travelling-stripe forcing generates hexagonal patterns

We study the response of Turing stripe patterns to a simple spatiotemporal forcing. This forcing has the form of a traveling wave and is spatially resonant with the characteristic Turing wavelength. Experiments conducted with the photosensitive chlorine dioxide-iodine-malonic acid reaction reveal a striking symmetry-breaking phenomenon of the intrinsic striped patterns giving rise to hexagonal lattices for intermediate values of the forcing velocity. The phenomenon is understood in the framework of the corresponding amplitude equations, which unveils a complex scenario of dynamical behaviors.

CO2 wedged hepatic venography in the evaluation of portal hypertension.

BACKGROUND/AIMS/METHODS During hepatic vein catheterisation, in addition to measurement of hepatic venous pressure gradient (HVPG), iodine wedged retrograde portography can be easily obtained. However, it rarely allows correct visualisation of the portal vein. Recently, CO2 has been suggested to allow better angiographic demonstration of the portal vein than iodine. In this study we investigated the efficacy of CO2 compared with iodinated contrast medium for portal vein imaging and its role in the evaluation of portal hypertension in a series of 100 patients undergoing hepatic vein catheterisation, 71 of whom had liver cirrhosis. RESULTS In the overall series, CO2 venography was markedly superior to iodine, allowing correct visualisation of the different segments of the portal venous system. In addition, CO2, but not iodine, visualised portal-systemic collaterals in 34 patients. In cirrhosis, non-visualisation of the portal vein on CO2 venography occurred in 11 cases; four had portal vein thrombosis and five had communications between different hepatic veins. Among non-cirrhotics, lack of portal vein visualisation had a 90% sensitivity, 88% specificity, 94% negative predictive value, and 83% positive predictive value in the diagnosis of pre-sinusoidal portal hypertension. CONCLUSIONS Visualisation of the venous portal system by CO2 venography is markedly superior to iodine. The use of CO2 wedged portography is a useful and safe complementary procedure during hepatic vein catheterisation which may help to detect portal thrombosis. Also, lack of demonstration of the portal vein in non-cirrhotic patients strongly suggests the presence of pre-sinusoidal portal hypertension.

Plasma leptin turnover rates in lean and obese Zucker rats

Conscious female adult lean and obese Zucker rats were injected through the jugular vein with radioactive iodine-labeled murine leptin; in the ensuing 8 min, four blood samples were sequentially extracted from the carotid artery. The samples were used in a modified RIA for leptin, in which paired tubes received the same amount of either labeled or unlabeled leptin, thus allowing us to estimate both leptin levels and specific radioactivity. The data were used to determine the decay curve parameters from which the half-life of leptin (5.46 ± 0.23 min for lean rats and 6.99 ± 0.75 min for obese rats) as well as the size of its circulating pool (32 pmol/kg for lean rats and 267 pmol/kg for obese rats) and the overall degradation rate (96 fkat/kg for lean rats and 645 fkat/kg for obese rats) were estimated. These values are consistent with the hormonal role of leptin and the need for speedy changes in its levels in response to metabolic challenge.

Dynamics of turing patterns under spatiotemporal forcing

We study, both theoretically and experimentally, the dynamical response of Turing patterns to a spatiotemporal forcing in the form of a traveling-wave modulation of a control parameter. We show that from strictly spatial resonance, it is possible to induce new, generic dynamical behaviors, including temporally modulated traveling waves and localized traveling solitonlike solutions. The latter make contact with the soliton solutions of Coullet [Phys. Rev. Lett. 56, 724 (1986)] and generalize them. The stability diagram for the different propagating modes in the Lengyel-Epstein model is determined numerically. Direct observations of the predicted solutions in experiments carried out with light modulations in the photosensitive chlorine dioxide-iodine-malonic acid reaction are also reported.

Travelling-stripe forcing generates hexagonal patterns

We study the response of Turing stripe patterns to a simple spatiotemporal forcing. This forcing has the form of a traveling wave and is spatially resonant with the characteristic Turing wavelength. Experiments conducted with the photosensitive chlorine dioxide-iodine-malonic acid reaction reveal a striking symmetry-breaking phenomenon of the intrinsic striped patterns giving rise to hexagonal lattices for intermediate values of the forcing velocity. The phenomenon is understood in the framework of the corresponding amplitude equations, which unveils a complex scenario of dynamical behaviors.

Hábitos higiénico-dietéticos respecto al consumo de alimentos ricos en yodo durante el primer trimestre de la gestación

Objetivo: Conocer los hábitos higiénico-dietéticos de las mujeres embarazadas respecto al consumo de alimentos ricos en yodo durante el primer trimestre de la gestación. Material y método: Estudio observacional, descriptivo, transversal y multicéntrico. Se estudiaron las mujeres embarazadas en el primer trimestre de la gestación que acudieron a la consulta de control del embarazo del programa de atención a la salud sexual y reproductiva (ASSIR) de la Región Sanitaria del Ámbito Centro del Instituto Catalán de la Salud durante el año 2006. Para la recogida de datos se utilizó un cuestionario que cumplimentó la matrona en una entrevista individual en la primera visita de control de embarazo. Resultados: Se recogieron 823 cuestionarios cumplimentados. El 6% (50) de las gestantes no consumía pescado y el 83% (683) lo hacía menos de cuatro veces por semana. El 17% (138) no consumía leche y el 39% (324) bebía un vaso al día. El 42% (342) de las gestantes utilizaba sal yodada para la preparación y condimentación de los alimentos, frente al 50% (412) que no la empleaba. El 22% (184) de las gestantes tomaba algún tipo de suplemento de yodo, y el 18% (148) de la muestra manifestó ser fumadora. Conclusiones: Las mujeres embarazadas de nuestro ámbito de estudio tienen un consumo reducido de alimentos ricos en yodo. Además, tanto el consumo de sal yodada como la utilización de suplementos que contengan yodo durante el embarazo resultan también insuficientes.

Hábitos higiénico-dietéticos respecto al consumo de alimentos ricos en yodo durante el primer trimestre de la gestación

Objetivo: Conocer los hábitos higiénico-dietéticos de las mujeres embarazadas respecto al consumo de alimentos ricos en yodo durante el primer trimestre de la gestación. Material y método: Estudio observacional, descriptivo, transversal y multicéntrico. Se estudiaron las mujeres embarazadas en el primer trimestre de la gestación que acudieron a la consulta de control del embarazo del programa de atención a la salud sexual y reproductiva (ASSIR) de la Región Sanitaria del Ámbito Centro del Instituto Catalán de la Salud durante el año 2006. Para la recogida de datos se utilizó un cuestionario que cumplimentó la matrona en una entrevista individual en la primera visita de control de embarazo. Resultados: Se recogieron 823 cuestionarios cumplimentados. El 6% (50) de las gestantes no consumía pescado y el 83% (683) lo hacía menos de cuatro veces por semana. El 17% (138) no consumía leche y el 39% (324) bebía un vaso al día. El 42% (342) de las gestantes utilizaba sal yodada para la preparación y condimentación de los alimentos, frente al 50% (412) que no la empleaba. El 22% (184) de las gestantes tomaba algún tipo de suplemento de yodo, y el 18% (148) de la muestra manifestó ser fumadora. Conclusiones: Las mujeres embarazadas de nuestro ámbito de estudio tienen un consumo reducido de alimentos ricos en yodo. Además, tanto el consumo de sal yodada como la utilización de suplementos que contengan yodo durante el embarazo resultan también insuficientes.

Acylation of chiral alcohols: a simple procedure for chiral GC analysis

The use of iodine as a catalyst and either acetic or trifluoroacetic acid as a derivatizing reagent for determining the enantiomeric composition of acyclic and cyclic aliphatic chiral alcohols was investigated. Optimal conditions were selected according to the molar ratio of alcohol to acid, the reaction time, and the reaction temperature. Afterwards, chiral stability of chiral carbons was studied. Although no isomerization was observed when acetic acid was used, partial isomerization was detected with the trifluoroacetic acid. A series of chiral alcohols of a widely varying structural type were then derivatized with acetic acid using the optimal conditions. The resolution of the enantiomeric esters and the free chiral alcohols was measured using a capillary gas chromatograph equipped with a CP Chirasil-DEX CB column. The best resolutions were obtained with 2-pentyl acetates (α = 3.00) and 2-hexyl acetates (α = 1.95). This method provides a very simple and efficient experimental workup procedure for analyzing chiral alcohols by chiral-phase GC.