Introduction and objectives: this study compared the accuracy of ultrasonography in the diagnosis of gastrointestinal tumors in patients with several degrees of clinical suspicion. Material and methods: we recruited patients that were suspect for gastrointestinal neoplasia but with no evidence of localizing symptoms (group A), and patients that were suspect for colon cancer (group B) or for gastric cancer (group C). Accuracy in the diagnosis was compared for: gastric cancer in groups A and C, and for colon cancer in groups A and B. The comparison was made by using the contingency coefficient, which quantifies coincidence of endoscopic and ultrasonographic diagnoses. Results: seventy-nine patients were included in group A (48 males), wherein 12 colon and 5 gastric neoplasms were detected. Group B was comprised of 153 patients (78 males) and included 66 patients with colorectal cancer (CCR). Group C contained 58 patients (35 males), 31 of whom were diagnosed with gastric cancer. The accuracy of sonography for diagnosing colon cancer was 95.5% for group A and 87.5% for group B. The contingency coefficient for endoscopy vs. ultrasonography was greater for group A: 0.658 than for group B: 0.549. The diagnostic accuracy for gastric cancer was 97.4% for group A and 86.2% for group C. The contingency coefficient between endoscopic and ultrasonographic diagnoses was also greater in group A (0.618) than in group C (0.588). Conclusions: the accuracy of ultrasonography in diagnosing colon and gastric cancer is not lower in patients without localizing symptoms.

Introducción y objetivos: en todos los estudios publicados hasta la fecha se ha evaluado la precisión de la ecografía en el diagnóstico del cáncer de colon y del cáncer gástrico en pacientes en los que esta era la sospecha diagnóstica o ya con un diagnóstico establecido de esta patología. Nosotros, en este estudio, comparamos la sensibilidad de la ecografía en pacientes con diferentes grados de sospecha clínica. Material y método: reclutamos pacientes con sospecha de neoplasia digestiva, sin evidencia de síntomas localizadores (grupo A), pacientes con sospecha de cáncer de colon (grupo B) y pacientes con sospecha de cáncer gástrico (grupo C). Comparamos la precisión de la ecografía en el diagnóstico del cáncer gástrico en los grupos A y C, y la precisión en el diagnóstico del cáncer de colon en los grupos A y B. El parámetro usado en la comparación es el coeficiente de contigencia que cuantifica la coincidencia de diagnóstico endoscópico y ecográfico. Resultados: se han incluido 79 pacientes en el grupo A (48 varones y 31 mujeres, con una edad media de 69,3 años), en los que se han diagnosticado 12 neoplasias colónicas y 5 gástricas. El grupo B se compone de 153 pacientes (78 varones y 75 mujeres, con una edad media de 66,5 años) e incluye 66 pacientes con CCR. Finalmente, el grupo C está formado por 58 pacientes (35 varones y 23 mujeres, con una edad media de 67,4 años), siendo diagnosticados de cáncer gástrico 31 pacientes. La precisión de la ecografía en el diagnóstico del cáncer de colon fue del 95,5% en el grupo A y del 87,5% en el grupo B. El coeficiente de contingencia entre los diagnósticos endoscópico y ecográfico también fue superior en el grupo A: 0,658 frente a 0,549. La precisión de la ecografía en el diagnóstico del cáncer gástrico fue del 97,4% en el grupo A y del 86,2% en el grupo C. El coeficiente de contingencia entre los diagnósticos endoscópico y ecográfico también fue mayor en el grupo A (0,618) que en el grupo C (0,588). Conclusiones: la precisión de la ecografía digestiva en el diagnóstico del cáncer de colon y del cáncer gástrico no es inferior en los pacientes en los que no hay una sospecha específica de estas patologías.

This work presents an experimental and theoretical investigation of anaerobic fluidized bed reactors (AFBRs). The bioreactors are modeled as dynamic three-phase systems. Biochemical transformations are assumed to occur only in the fluidized bed zone. The biofilm process model is coupled to the system hydrodynamic model through the biofilm detachment rate; which is assumed to be a first-order function of the energy dissipation parameter and a second order function of biofilm thickness. Non-active biomass is considered to be particulate material subject to hydrolysis. The model includes the anaerobic conversion for complex substrate degradation and kinetic parameters selected from the literature. The experimental set-up consisted of two mesophilic (36±1ºC) lab-scale AFBRs (R1 and R2) loaded with sand as inert support for biofilm development. The reactor start-up policy was based on gradual increments in the organic loading rate (OLR), over a four month period. Step-type disturbances were applied on the inlet (glucose and acetic acid) substrate concentration (chemical oxygen demand (COD) from 0.85 to 2.66 g L-1) and on the feed flow rate (from 3.2 up to 6.0 L d-1) considering the maximum efficiency as the reactor loading rate switching. The predicted and measured responses of the total and soluble COD, volatile fatty acid (VFA) concentrations, biogas production rate and pH were investigated. Regarding hydrodynamic and fluidization aspects, variations of the bed expansion due to disturbances in the inlet flow rate and the biofilm growth were measured. As rate coefficients for the biofilm detachment model, empirical values of 3.73⋅10(4) and 0.75⋅10(4) s² kg-1 m-1 for R1 and R2, respectively, were estimated.

Background: the Positive Predictive Value (PPV) of signs and symptoms for the diagnosis of colon and gastric cancer is low. Furthermore, many patients are referred to us to discard a digestive tract neoplasm with no symptoms suggestive of its whereabouts, in whom clinical PPV is even lower. This study evaluates the usefulness of ultrasonography as a first approach to diagnosis. Material and methods: seventy-nine patients were recruited into the study (48 males with an average age of 69.3 years). Ultrasonography was performed on all patients prior to endoscopy. Parameters studied included diagnostic accuracy for colon and gastric cancer, ultrasonographic diagnoses, and number of endoscopies that can be avoided. Predictive factors for neoplasm location were also studied. Results: five gastric cancers (6.3%), 12 colon cancers (15,1%), 3 pancreatic cancers (3.8%), 2 uterine neoplasms (2.5%), and 2 hypernephromas (2.5%) were diagnosed. The figures for sensitivity, specificity, PPV, Negative Predictive Value (NPV) and global accuracy of ultrasonography were 80%, 98.6%, 80%, 98.6%, and 97.4%, respectively, for gastric cancer, while these figures were 100%, 94.5%, 80%, 100%, and 95.5%, respectively, for colon cancer. Ultrasonography enabled to avoid 10% of endoscopic explorations. The only parameter that helps locate a neoplasm is the presence of anemia, which is more frequently associated with a diagnosis of colon cancer: 30.4 versus 4.3% (p = 0.033). Conclusions: in patients without specific symptoms who were sent to us for discarding digestive tract neoplasm, "extra-digestive" neoplasms were frequently diagnosed. If we further take into account the high diagnostic accuracy of ultrasonography, then this procedure could be a very good first approach towards such diagnosis.

Introducción: el valor predictivo positivo de síntomas y signos en el diagnóstico del cáncer de colon y gástrico es bajo. Además, muchos pacientes son remitidos para descartar una neoplasia digestiva, sin síntomas que sugieran su localización, siendo el VPP de la clínica aún menor. En este trabajo evaluamos la utilidad de la ecografía como primera aproximación diagnóstica. Material y método: se han reclutado 79 pacientes (48 varones, edad media 69,3 años). En todos ellos se realiza una ecografía antes de la endoscopia. Se evalúa la precisión en el diagnóstico del cáncer de colon y gástrico, los diagnósticos ecográficos y el número de endoscopias que se evitarían. También se buscan factores predictivos de la localización de la neoplasia. Resultados: se han diagnosticado 5 neoplasias gástricas (6,3%) y 12 de colon (19%), 3 cáncer de páncreas (3,8%), 2 neoplasias uterinas (2,5%) y 2 hipernefromas (2,5%). Las cifras de sensibilidad, especificidad, VPP, VPN y precisión de la ecografía fueron 80%, 98,6%; 80%; 98,6%; y 97,4% respectivamente en el diagnóstico del cáncer gástrico, y del 100%, 94,5%; 80%; 100% y 95,5% respectivamente en el diagnóstico del cáncer de colon. La ecografía permitió evitar el 10% de las endoscopias. El único dato que orienta la localización de la neoplasia es la presencia de anemia, que se asocia con mayor frecuencia al diagnóstico de cáncer de colon: 30,4 versus 4,3% (p = 0,033). Conclusiones: en los pacientes remitidos para descartar una neoplasia digestiva, con síntomas inespecíficos, se diagnostica con frecuencia de patología neoplásica ajena al tubo digestivo. Si consideramos, además, la elevada precisión diagnóstica de la ecografía, esta podría ser una muy buena primera aproximación diagnóstica.

The present work is focused on evaluating the anaerobic digestion of complex substrates (proteins and carbohydrates) in anaerobic fluidized bed reactors (AFBRs). In a previous paper, an AFBR model was adjusted using only the experimental data obtained during the acclimatization stage (glucose and acetate-based feeding) of two mesophilic bioreactors. Here, the sensitivity of that model to represent the digestion processes of proteins such as gelatin and albumin, and sucrose as a carbohydrate, is analyzed. Some kinetic expressions and parameters for the enzymatic hydrolysis processes need to be modified to represent the real behavior of bioreactors. Under the analyzed operating conditions, a hydraulic retention time higher than 1 day is suggested to ensure good system efficiency.

Objective: endoscopic mucosal resection with ligation (EMRL) is considered an efficient, safe method for the treatment of some esophageal, gastric and colorectal tumors. We conducted this study using a porcine model in order to compare the safety of esophageal EMRL with two multiband ligation systems, since many centers only use these ligator models in EMRL (commercialized for varix ligation). Methods: eight pigs were used, which were submitted to 23 esophageal resections without previous injection. Ten resections were conducted using the Six Shooter Saeed model, and 13 resections used the Speedband Superview Super 7 model. The technique was also compared by making random cuts either above or below the band. Results: five perforations occurred, all of them using the Speedband model. This represents 38.5% of total in the Speedband model group. No perforation occurred when using the Six Shooter model (p = 0.046). On the contrary, no significant differences were found regarding frequency of perforation when cutting above or below the band. Conclusions: esophageal EMRL using the Speedband model without previous injection leads to perforation in a high percentage of cases in an experimental animal model. Further studies are required to find out whether a previous injection may increase the safety of this technique with this ligator model

Objetivo: en los últimos años se han publicado varios trabajos que encuentran la mucosectomía con banda (MB) como un método seguro para el tratamiento de algunos tumores esofágicos, gástricos y colorrectales. Hemos realizado este estudio en animales de experimentación (cerdos) para comparar la seguridad de la MB en esófago, con dos modelos de ligadores multibanda, ya que muchos centros sólo disponen de estos modelos de ligadores comercializados para la ligadura de varices esofágicas. Métodos: se utilizaron 8 cerdos en los que se realizaron 23 resecciones esofágicas sin inyección previa. Se hicieron 10 resecciones con el modelo Six Shooter Saeed y 13 resecciones con el modelo Speedband Superview Super 7. También se comparó la técnica realizando el corte aleatoriamente por debajo o por encima de la banda. Resultados: se produjeron 5 perforaciones, todas con el modelo Speedband. Del total de casos en los que se utilizó este modelo se perforaron el 38,5% frente a ninguna de las intervenciones con el modelo Six Shooter, lo que alcanzó significación estadística (p = 0,046). No hubo deferencias estadísticamente significativas en la frecuencia de perforación, entre realizar el corte por debajo o por encima de la banda. Conclusiones: MB esofágica realizada con el modelo Speedband sin inyección previa, da lugar a perforación en un porcentaje elevado de casos en el animal de experimentación. Se precisan más estudios para establecer si la inyección previa incrementa la seguridad de la técnica con este modelo de ligador.

In this paper, a new procedure for the design and analysis of Heat and Power Plants is presented. In this formulation, thermodynamic solutions obtained by maximizing the plant efficiency are used to find the economic design of the plant. In fact, by applying the Karush-Kuhn-Tucker conditions it is possible to relate thermodynamic and economic solutions. A formal context for the use of thermodynamic models in solving complex optimization problems that arise in the area of synthesis and design of chemical processes is introduced. The proposed methodology has been successfully applied for two plant arrangements. Rigorous models have been used to model the plant equipments. The obtained results are presented in order to illustrate the proposed procedure.

A steady state model of an anaerobic methanogenic biofilm reactor-module that accounts for the biological interactions of four microbial groups, ionic equilibrium in solution, gas-liquid transfer phenomena and biofilm processes is presented. The model consists of a continuous stirred tank reactor type that allocates an inert support material, whose specific surface is taken into account. The biofilm model assumes an homogeneous biofilm of uniform thickness and constant density with no mass transfer resistance. The biofilm detachment process rate is modeled as a second-order function on the biofilm thickness and a first-order function on the mass fraction of the fixed biomass concentration of each microbial group. The balance equations for non-active biomass in liquid and biofilm are included. The model predictions have been satisfactorily compared with steady state experimental data reported in literature from a one-phase methanogenic biofilm system treating an acetic acid-based synthetic effluent, and a two-phase system with combined suspended (acidogenic) and attached (methanogenic) microbial growth treating a food industry wastewater composed by two residual process streams.

Introduction: usually found in the gastrointestinal tract, carcinoids are the most frequent neuroendocrine tumors. Most of these lesions are located in areas that are difficult to access using conventional endoscopy (small intestine and appendix); carcinoid tumors found in the gastroduodenal tract and in the large intestine can be studied endoscopically; in these cases, if localized disease is confirmed, local treatment by endoscopic resection may be the treatment of choice. Since endoscopic ultrasonography has been shown to be the technique of choice for the study of tumors exhibiting submucosal growth, the selection of patients who are candidates for a safe and effective local resection should be based on this technique. Patients and method: we selected patients with gastrointestinal carcinoid tumors who were endoscopically treated between 1997 and 2002. Those patients with tumors measuring less than 10 mm, which had not penetrated the muscularis propria, and those with localized disease were considered candidates for endoscopic resection. The endpoints of this study were to assess the effectiveness (complete resection) and safety (complications) of the technique. Follow-up consisted of eschar biopsies performed one month and twelve months after the resection. Results: during the aforementioned period, we resected endoscopically 24 tumors in 21 patients (mean age: 51.7 years; 71.5% males). Most lesions were incidental discoveries made during examinations indicated for other reasons. Resection was indicated in most cases as a result of the suspected presence of a carcinoid tumor after endoscopic ultrasonography. Endoscopic ultrasonography also enabled us to clearly identify the layer where the lesion had originated, as well as the size of the lesion. The carcinoid tumor was removed in 13 cases (54.2%) by using the conventional snare polypectomy technique, in 9 cases (37.5%) assisted by a submucosal injection of saline solution and/or adrenaline, and in 2 cases (8.3%) after ligating the lesion with elastic bands. In all cases the resection was complete, with no recurrence during the follow-up period, and no major complications, except for a single case in which a post-polypectomy hemorrhage occurred that was endoscopically solved. Conclusions: in properly selected patients, the endoscopic resection of carcinoid tumors is a safe and effective technique that permits a complete resection in all cases with few complications. Endoscopic ultrasonography is the technique of choice for selecting the patients who are candidates for endoscopic resection.

Introducción: los carcinoides son los tumores neuroendocrinos más frecuentes, representado el tracto digestivo una de sus localizaciones más habituales. La mayoría de las lesiones se localizan en áreas poco accesibles para la endoscopia convencional (intestino delgado y apéndice); los carcinoides localizados en el tracto gastroduodenal y en el intestino grueso pueden ser estudiados endoscópicamente; en estos casos, si se confirma una enfermedad localizada, el tratamiento local mediante resección endoscópica puede ser el tratamiento de elección. Dado que la ecoendoscopia se ha mostrado como la técnica de elección en el estudio de los tumores de crecimiento submucoso, la selección de los pacientes candidatos a una resección local segura y efectiva ha de basarse en esta técnica. Pacientes y método: se han seleccionado los pacientes con tumores carcinoides digestivos tratados endoscópicamente entre 1997 y 2002. Se consideraron subsidiarios de resección endoscópica aquellos pacientes con tumores menores de 10 mm, que respetan la muscular propia y con un estudio de extensión negativo. Los objetivos finales del estudio fueron la evaluación de la eficacia (resección completa) y seguridad (complicaciones) de la técnica. El seguimiento consistió en biopsias de la escara al mes y los 12 meses de la resección. Resultados: en el periodo referido hemos resecado endoscópicamente 24 tumores en 21 pacientes (edad media de 51,7 años; 71,5% varones). Las lesiones eran en su mayoría hallazgos incidentales en exploraciones indicadas por otros motivos. La resección se indicó en la mayoría de los casos por sospecha ecoendoscópica de tumor carcinoide. La ecoendoscopia además permitió establecer con claridad la capa de origen de la lesión y el tamaño de la misma. La extirpación se llevó a cabo en 13 casos (54,2%) mediante la técnica convencional de polipectomía con asa, en 9 casos (37,5%) asistida con inyección submucosa de suero salino y/o adrenalina y en 2 casos (8,3%) tras ligar la lesión con bandas elásticas. En todos los casos la resección fue completa, sin recidivas durante el seguimiento. En un único caso se produjo una complicación mayor: una hemorragia postpolipectomía que se controló endoscópicamente. Conclusiones: la resección endoscópica de los tumores carcinoides, en pacientes bien seleccionados, es una técnica segura y eficaz permitiendo una resección completa en todos los casos con escasas complicaciones. La ecoendoscopia es la técnica de elección para seleccionar los pacientes candidatos a resección endoscópica.

A rigorous dynamic model of anaerobic biofilm reactor (Mussati et al., 1998) is used to optimize and evaluate different loading strategies in anaerobic wastewater treatment systems. This work includes variations in the original model so that the results of process simulation also represent the initial events of the start up operation as regards the biofilm growth. The model was implemented in gPROMS (General Process Modeling System). Different dynamic optimization formulations are evaluated. Start up strategies are considered and discussed. A sensitivity analysis regarding kinetic data on optimal start up policies under two different conditions is included. The first condition consists of a fixed maximum load, and the other one is the maximum load supported by the system, which varies according to the kinetic data being used. Changes in maximum specific growth rate, half saturation constant and specific death rate of Monod's model generate different optimal start up periods; whereas optimal start up time did not change when the maximum allowed load for each reactor is considered.

In this paper, a new strategy involving an evolutionary algorithmic procedure for the optimization of Multiple Stage Flash (MSF-M) Systems is presented. A "detailed model" of an MSF-M System is developed according to rigorous material, momentum and energy balances for each stage. The model of the MSF-M System is represented as a complex NLP, which incorporates a high number of nonlinear constraints that difficult the global optimum determination. Here we present a hybrid methodology that uses optimal solutions obtained from a "thermodynamic method" to find the "economic global optimal solution". A pre-processing stage (solving successive NLPs) is used to initialize the final NLP problem. A Case Study and a discussion of the results are presented.