The effect of acoustic mode on time-resolved temperature measurements in a Rijke-tube pulse combustor

Radial profiles are reported of average and rms temperature in a propane flame for the first, second, and third acoustic modes at four different axial positions above the burner in a Rijke-tube combustor. Selected plots of the power spectral density (PSD) of temperature fluctuations are also reported. These radial profiles are then compared to similar ones made in the same flame, but in the absence of the acoustic field. Visual observations and photographs of the flame showed a remarkable change in flame height and structure with the onset of acoustic oscillations. This reduction in flame length, caused by the enhanced mixing due to the acoustic velocity fluctuations, gave rise to higher and lower average and rms temperatures near or well above the burner, respectively. In general, the PSD plots had a broad frequency content. The general trend was a decrease in magnitude with an increase in frequency. All cases presented broad-band peaks at around 5 Hz related to the flame flickering phenomenon. Preferred frequencies were observed in the oscillating PSD plots related to the fundamental frequency as well as subharmonics in the tube. (C) 2000 Elsevier B.V. Ltd. All rights reserved.

Levenberg-Marquardt application to two-phase nonlinear parameter estimation for finned-tube coil evaporators

A procedure for calculation of refrigerant mass flow rate is implemented in the distributed numerical model to simulate the flow in finned-tube coil dry-expansion evaporators, usually found in refrigeration and air-conditioning systems. Two-phase refrigerant flow inside the tubes is assumed to be one-dimensional, unsteady, and homogeneous. In themodel the effects of refrigerant pressure drop and the moisture condensation from the air flowing over the external surface of the tubes are considered. The results obtained are the distributions of refrigerant velocity, temperature and void fraction, tube-wall temperature, air temperature, and absolute humidity. The finite volume method is used to discretize the governing equations. Additionally, given the operation conditions and the geometric parameters, the model allows the calculation of the refrigerant mass flow rate. The value of mass flow rate is computed using the process of parameter estimation with the minimization method of Levenberg-Marquardt minimization. In order to validate the developed model, the obtained results using HFC-134a as a refrigerant are compared with available data from the literature.

Mathematical modeling of the ester oil-refrigerant R134A mixture two-phase flow with foam formation through a small diameter tube

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Pressure drop correlation for oil-refrigerant R134a mixture flashing flow in a small diameter tube

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Variability of physicochemical properties of an epoxy resin sealer taken from different parts of the same tube

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Does sealing endotracheal tube cuff pressure diminish the frequency of postoperative laryngotracheal complaints after nitrous oxide anesthesia?

Study Objectives: To study endotracheal tube (ETT) cuff pressures during nitrous oxide (N2O) anesthesia when the cuffs are inflated with air to achieve sealing pressure, and to evaluate the frequency of postoperative laryngotracheal complaints.Design: Prospective, randomized, blind study.Setting: Metropolitan teaching hospital.Patients: 50 ASA physical status I and II patients scheduled for elective abdominal surgery.Interventions: Patients received standard general anesthesia with 66% N2O in oxygen. In 25 patients, the ETT cuff was inflated with air to achieve a sealing pressure (P-seal group). In 25 patients, the ETT cuff was inflated with air to achieve a pressure of 25 cm H2O (P-25 group).Measurements and Main Results: ETT intracuff pressures were recorded before (control) and at 30, 60, 90, 120, and 150 minutes during N2O administration. We investigated the frequency and intensity of sore throat, hoarseness, and dysphagia in patients in the Post-Anesthesia Care Unit (PACU) and 24 hours following tracheal extubation. The cuff pressures in the P-seal group were significantly lower than in the P-25 group at all time points studied (p < 0.001), with a significant increase with time in both groups (p < 0.001). The cuff pressures exceeded the critical pressure of 30 cm H2O only after 90 minutes in the P-seal group and already by 30 minutes in the P-25 group. The frequency and intensity of sore throat, hoarseness, and dysphagia were similar in both groups in the PACU and 24 hours after tracheal extubation (p > 0.05).Conclusions: Minimum ETT sealing cuff pressure during N2O anesthesia did not prevent, but instead attenuated, the increase in cuff pressure and did not decrease postoperative laryngotracheal complaints. (C) 2004 by Elsevier B.V.

Effectiveness and safety of endotracheal tube cuffs filled with air versus filled with alkalinized lidocaine: a randomized clinical trial

CONTEXTO E OBJETIVO: Os tubos traqueais são dispositivos utilizados para manutenção da ventilação. A hiperinsuflação do balonete do tubo traqueal, causada pela difusão do óxido nitroso (N2O), pode determinar lesões traqueais, que se manifestam clinicamente como odinofagia, rouquidão e tosse. A lidocaína, quando injetada no balonete do tubo traqueal, difunde-se através de sua parede, determinando ação anestésica local na traquéia. O objetivo foi avaliar a efetividade e a segurança do balonete do tubo traqueal preenchido com ar comparado com o balonete preenchido com lidocaína, considerando os desfechos: sintomas cardiovasculatórios (HAS, taquicardia); odinofagia, tosse, rouquidão e tolerância ao tubo traqueal. TIPO DE ESTUDO E LOCAL: Estudo clínico prospectivo, realizado no Departamento de Anestesiologia da Faculdade de Medicina da Unesp, campus de Botucatu. MÉTODOS: A pressão do balonete do tubo traqueal foi medida, entre 50 pacientes, antes, 30, 60, 90 e 120 minutos após o início da inalação de N2O anestésico. As pacientes foram distribuídas aleatoriamente em dois grupos: Air, em que o balonete foi inflado com ar para obtenção de pressão de 20 cm H2O, e Lido, em que o balonete foi preenchido com lidocaína a 2% mais bicarbonato de sódio a 8,4% para obtenção da mesma pressão. O desconforto antes da extubação, e manifestações clínicas como dor de garganta, rouquidão e tosse foram registrados no momento da alta da unidade de cuidados pós-anestésicos, e dor de garganta e rouquidão foram avaliadas também 24 horas após a anestesia. RESULTADOS: Os valores da pressão no balonete em G2 foram significativamente menores do que os de Air em todos os tempos de estudo, a partir de 30 minutos (p < 0,001). A proporção de pacientes que reagiu ao tubo traqueal no momento da desintubação foi significantemente menor em Lido (p < 0,005). A incidência de odinofagia foi significantemente menor em Lido no primeiro dia de pós-operatório (p < 0,05). A incidência de tosse e rouquidão não diferiu entre os grupos. CONCLUSÕES: Durante ventilação artificial, empregando-se a mistura de oxigênio e N2O, a insuflação do balonete com lidocaína 2% alcalinizada impede que ocorra aumento significante da pressão no balonete e determina maior tolerância ao tubo traqueal e menor incidência de odinofagia no pós-operatório, podendo então ser considerada mais segura e com maior efetividade.

Biliary tract reconstruction using jejunal tube: an experimental study in dogs

BACKGROUND: To physiologically reconstruct the biliary tract, Crema et al suggested the application of the Monti principle to the biliary tract, already used in humans for the urinary tract. With this technique, a jejunal segment is transversely retubularized. This study aimed to evaluate the efficacy of jejunal tube interposition between the common bile duct and duodenum in dogs.METHODS: Thirteen dogs underwent a laparoscopic common bile duct ligature, followed by a biliodigestive connection by jejunal tube interposition after one week. The levels of glutamic-pyruvic and glutamic-oxalacetic transaminases, total bilirubins, alkaline phosphatase and gamma-glutamyltransferase were assessed before surgery and thereafter weekly until euthanasia, which was performed 6 weeks after biliodigestive connection.RESULTS: Data on 9 dogs were analyzed statistically. The dogs presented with obstructive jaundice after common bile duct ligature, as confirmed by biochemical examination. They showed a statistically significant reduction in cholestasis after biliodigestive connection by jejunal tube interposition and were healthy until the end of the experiment.CONCLUSION: A statistically significant reduction was seen in total bilirubin and canalicular enzymes (alkaline phosphatase and gamma-glutamyltransferase) in the 9 dogs 6 weeks after biliodigestive conviction by jejunal tube interposition.

Can sieve-element plastids in Panicum maximum (Poaceae) leaves act in the blockage of injured sieve-tube elements?

The ultrastructural features and the plastid changes caused by sample preparation were studied in sieve elements of Panicum maximum leaves. Samples of expanded leaves, taken near the ligule region, were fixed and processed by common light and transmission electron microscopy methods. In mature sieve-tube elements, the protoplast is electron-translucent and plastids are the most frequent organelles. Mitochondria and smooth endoplasmic reticulum segments are also visible and occupy a parietal position within the cell. The plastids are globular and show electron-dense proteinaceous inclusions in the stroma. The protein crystals are predominantly cuneate, but thin crystalloids and amorphous and/or filamentous proteins also occur. The presence of intact plastids plus others in different phases of plastid envelope rupture were interpreted as evidence that this rupture is a normal event in response to injury. This plastid envelope rupture is possibly activated by the release of pressure in the sieve-tube element. After plastid membrane vesiculation, the stroma and the protein crystals are dispersed within the sieve-element ground cytoplasm. The vesicles originating from the plastid envelope move to one cell pole, while protein crystalloids move to the opposite pole and agglomerate in the sieve-plate region. Our findings indicate that these protein crystalloids, which deposit in the sieve plate, may act in sieve-plate pores occlusion, preventing the release of phloem sap, similar to the role of P-protein in dicotyledons. (c) 2008 Elsevier GmbH. All rights reserved.

Ontogenetic shifts in the digestive tube and diet of Bryconamericus stramineus Eigenmann, 1908 (Osteichthyes, Characidae)

Aim: Studies on feeding of early life stages are very important to the understanding of the biology and trophic ecology of fish species. Therefore, the aim of this work is to describe the development of the digestive tube, and to characterize the diet of larvae and juveniles of Bryconamericus stramineus Eigenmann, 1908 of the upper Parana River floodplain; Methods: Larvae were obtained from, monthly samples during nychthemeral cycles with four-hour interval between samplings from February/91 to February/92, utilizing a conical-cylindrical plankton net; Results: At the preflexion stage, larvae at approximately 4.00 mm SL, showed a morphologically undifferentiated straight tube, with the anterior region more dilated. At the flexion stage a differentiation in the anterior region of the digestive tube occurs, with the intestine wall getting thicker (8.30 mm SL). The formation of pyloric caeca occurs at 9.00 mm SL. At the postflexion stage the first loop is formed at 9.25 mm SL and the second loop at about 10.00 mm SL. Bryconamericus stramineus consumed mainly cladocerans, also ingesting copepods, rotifers, nematodes, algae, insects and inorganic particles. Along the development, there was an increase in the number of food items and a diversification in the number of consumed taxa; Conclusions: Changes in the diet of B. stramineus larvae were not observed, being them zooplanktivores during all the initial development. However, an increase of large preys, such as insects larvae, was observed at the end of the larval period and in juveniles, suggesting a tendency towards invertivory. Larvae and juveniles preferentially fed during the night.

Effects of bamboo stands on seed rain and seed limitation in a rainforest

Bamboos often negatively affect tree recruitment, survival, and growth, leading to arrested tree regeneration in forested habitats. Studies so far have focused on the effects of bamboos on the performance of seedlings and saplings, but the influence of bamboos on forest dynamics may start very early in the forest regeneration process by altering seed rain patterns. We tested the prediction that the density and composition of the seed rain are altered and seed limitation is higher in stands of Guadua tagoara (B or bamboo stands), a large-sized woody bamboo native from the Brazilian Atlantic Forest, compared to forest patches without bamboos (NB or non-bamboo stands). Forty 1 m(2) seed traps were set in B and NB stands, and the seed rain was monitored monthly for 1 year. The seed rain was not greatly altered by the presence of bamboos: rarefied seed species richness was higher for B stands, patterns of dominance and density of seeds were similar between stands, and differences in overall composition were slight. Seed limitation, however, was greater at B stands, likely as a resulted of reduced tree density. Despite Such reduced density, the presence of trees growing amidst and over the bamboos seems to play a key role in keeping the seeds falling in B stands because they serve as food sources for frugivores or simply as perches for them. The loss of such trees may lead to enhanced seed limitation, contributing ultimately to the self-perpetuating bamboo disturbance cycle. (C) 2008 Elsevier B,V. All rights reserved.

Bamboo overabundance alters forest structure and dynamics in the Atlantic Forest hotspot

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)