A. Campos

Oral glutamine and the healing of colonic anastomoses in rats.

BACKGROUND Recent evidence has suggested that glutamine is one of the primary energy sources of the colon. The aim of this study was to evaluate the effects of oral glutamine supplementation on the healing of colonic anastomoses in rats. METHODS Forty-eight adult male Wistar rats, weighing 174.41 +/- 37.39 g, were housed in individual cages. All rats had free access to water and standard rat chow. The rats were randomized to receive daily, for 7 days before the operation and during the postoperative period, 10% L-glutamine (GLN group) or 10% glycine (GLY group) in isonitrogenous and isovolumetric solutions (1.5 g/kg per day), through an orogastric tube. On the eighth day, rats were anesthetized and subjected to 2 colonic transections, one 6 cm distal from the ileocecal valve and another 5 cm distal from the first transection. Bowel continuity was restored by 2 end-to-end, single layer, everted, anastomoses with 8 interrupted sutures (6-0 nylon). After the operation, the rats were kept in individual cages and had free access to water and rat chow. One-half of the rats in each group were killed either on postoperative day 3 or 8, and the 2 colonic anastomoses of each animal were resected and stored in 0.9% saline and 10% formalin for tensile strength and histologic (hematoxylineosin and collagen densitometry) studies, respectively. Students t-test and Kruskal Wallis tests were used for statistical analysis. RESULTS Total rupture strength was significantly higher in the GLN group (GLN: 0.068 +/- 0.045 kgf versus GLY: 0.042 +/- 0.027 kgf, p = .04). The mean monocytes infiltrate was significantly smaller in the GLN group (p = .04). The collagen densitometry analysis demonstrated greater percent area of type I (mature) in the GLN group compared with GLY (58.65 +/- 11.70% versus 41.79 +/- 10.54%, p = .0000), respectively. Subgroup analyses according to the day of rat death were still significant: GLN 3: 54.22 +/- 10.02% versus GLY 3: 41.92 +/- 13.31% (p = .04) and GLN 8: 62.63 +/- 12.13% versus GLY 8: 41.67 +/- 7.69% (p = .0004). Type III collagen (immature) percent area was significantly smaller in the GLN groups colonic anastomoses (GLN: p = .0000; GLN 3: p = .04 and GLN 8: p = .0003, respectively). CONCLUSIONS Perioperative oral glutamine supplementation increases total rupture strength and improves the percent area of mature collagen at the anastomoses sites on postoperative days 3 and 8.

A semiconductor lighting system controlled through a LIN network to automotive application

This paper proposes an intelligent lighting system for bus interior environment using LEDs (light emitting diodes) controlled through an automotive communication network. The system consists on a master central control and slaves lighting modules, using a LIN (local interconnect network) network to perform communication. This network is a low cost alternative to the proposed system requirements, due to its low bit rate and physical needs. The slaves are independent lighting modules that supply a group of LEDs and measure the environment lighting level. The master sets LEDs module parameters (slaves), such as the state (on/off), and desired lighting level The master makes the user interface, sets the lighting parameters, as timer and lighting level and, more over, it establishes communication with other bus systems through a CAN (controller area network) gateway. This paper presents a complete logical description, including block and state diagrams, a physical description and some relevant experimental results.

An analysis about valley fill filters applied to electronic ballasts

This paper presents a detailed analysis about valley fill filters applied to power factor (PF) correction of electronic ballasts. Comparative results about input current THD are done in this study, verifying if it meets the IEC 61000-3-2 standard requirements, that determines the maximum amplitude of each harmonic component from 2/sup nd/ up to 39/sup th/. Power factor (PF), total harmonic distortion (THD), crest factor (CF), auxiliary circuit losses, and operation principles are also presented.

Off-line LED driver for street lighting with an optimized cascade structure

This paper presents a converter structure applied to supply high-power light-emitting diodes (LEDs) from the ac line in a street lighting system, based on the reduced redundant power processing principle. To guarantee high power factor and low harmonic distortion for the input ac current, a buck-boost operating in discontinuous conduction mode is employed as a power factor corrector. The second converter of the structure controls the current on the LED string, but it does not process all the power. This is done by summing the voltages of the first with the second converters. Avoiding the double processing of the power, the efficiency is improved. In addition to that, the capacitance value of the first converter is dramatically reduced by increasing the ripple limits, making possible the use of film capacitors to increase the life span of the system. The power and control designs are shown in detail. A laboratory prototype, with a rated power of 75 W for a rated input voltage of 220 Vrms, was built to show the feasibility of the idea.

Compact Lamp Using High-Brightness LEDs

This paper proposes a circuit for a compact lamp based on high-brightness LEDs. It aims energy savings, high luminous efficacy and high useful life when substituting incandescent or compact fluorescent bulbs for LEDs without any change in the electric system installation. In order to supply the LEDs by mains with a forward current, the Buck converter has been chosen. The load can be composed by 36 to 52 LEDs of 5 mm connected in series, resulting in a converter output voltage between 90 V and 187 V. The advantage of series connection is that all LEDs produce the same brightness since its luminous intensity is proportional to the supplied current. The disadvantage is that the damage of one LED could results in an open-circuit, turning off the entire group. To fix this problem, the proposed idea on this work is the introduction of Diacs connected in parallel with groups of LEDs. So, if one LED burns the breakdown voltage is reached, and the Diac in parallel with this group become a short- circuit guaranteeing the operating of the others groups. To verify the proposed idea, the compact lamp has been implemented and tested.

A Family of Electronic Ballasts Integrating Power Factor Correction and Power Control Stages to Supply HPS Lamps

This paper presents a family of high power factor electronic ballasts applied to the public lighting system. Flyback, buck-boost, boost or SEPIC converter is employed in the power factor correction stage, integrated to the power control stage through a single active switch. The use of a half-bridge inverter, to supply the lamp, becomes possible through the employment of a flyback converter in the lamp power control stage. The lamp is supplied in a low frequency voltage square waveform in order to guarantee the safe lamp operation, regarding to the acoustic resonance phenomenon. The presented solutions to supply HPS lamps take the advantage of low cost and simplicity. The shared switch characteristics are analyzed and discussed during this work. A comparative analysis among the presented electronic ballasts is performed

In utero malnutrition influences wound healing of newborn rats as measured by tensile strength and collagen deposition.

BACKGROUND Studies have investigated the consequences of intrauterine malnutrition on birth weight and overall survival but not on wound healing. This study aims to assess the influence of in utero malnutrition on wound healing of newborn rats. METHODS Pregnant Wistar rats were divided into 2 groups. Study rats were given 50% of the food intake of controls throughout pregnancy in a pair-fed manner. The body weight and length of the newborns were measured. Newborns were breast-fed until day 21, when a laparotomy was performed. The effect of the laparotomy was assessed by measure of the wound strength and collagen deposition at postoperative day (POD) 7 (n = 15) and POD 21 (n = 15). RESULTS The body weight and length of newborns of malnourished mothers were significantly smaller at birth compared with controls (respectively, 4.5 +/- 0.1 g vs 5.8 +/- 0.1 g, p = .0003 and 4.6 +/- 0.1 cm vs 5.2 +/- 0.1 cm, p = .0003). Maximum, rupture, and tensile strength of malnourished newborns were smaller than controls on POD 7 (0.281 +/- 0.031 vs 0.470 +/- 0.031, p = .0061, 0.112 +/- 0.06 kgf vs 0.173 +/- 0.08 kgf, p = .0495 and 0.019 +/- 0.002 kgf/mm2 vs 0.024 +/- 0.003 kgf/mm2, p = .050, respectively). On POD 21, only tensile strength remained lower (0.044 +/- 0.003 kgf/mm2 vs 0.058 +/- 0.003 kgf/mm2, p = .0477). Type I collagen deposition of malnourished newborns was similar to controls on POD 7 (57.69 +/- 10.06 vs 48.34 +/- 15.65, p = .3187) and on POD 21 (75.6 +/- 7.21 vs 80.0 +/- 9.92, p = .4212). CONCLUSIONS In utero malnutrition decreases the abdominal wound strength of newborn rats but not the collagen deposition, suggesting that breast-feeding nutrition is effective in recovering the collagen deposition but not overall wound strength.

A fully digital control employing a dead beat technique for active power filters

This paper presents a digital control with digital signal processor (DSP) application for active power filters employing a dead beat technique, which can also be extended for any inverter application. The paper focuses in the DSPs contribution to improve the dynamic of the digital control, providing a fast processing of the control law, assuring the required compensation. Moreover, it shows the application for both series and shunt active power filter employing a dead beat control technique.

Design procedure for a compact lamp using high-intensity LEDs

This paper proposes a circuit to a compact lamp based on light emitting diodes (LEDs). It aims energy savings, high luminous efficiency and high useful life with the replacement of incandescent or compact fluorescent lamps by LEDs without any change in the electrical system installation. In order to supply the LEDs by mains with a constant current, the Buck converter has been used because it provides an output voltage lower than the input one. The circuit has been designed to supply 36 to 52 high-brightness LEDs connected in series, resulting in a converter output voltage between 90 V and 187 V. The load can also be composed of power LEDs. The main disadvantage of series connection is that the damage of one LED can results in an open-circuit, disconnecting the entire group. The proposed idea to solve this problem is the introduction of Diacs connected in parallel with groups of LEDs. So, if one LED burns, the Diac in parallel with this group keeps the current path, guaranteeing the operation of the others groups. To verify the proposed idea, prototypes of the lamp have been implemented and tested.

An electronic ballast to supply automotive HID lamps in a low frequency square waveform

This paper presents an electronic ballast to supply a 35 W high intensity discharge (HID) xenon lamp for automotive applications. The ballast consists on a bidirectional flyback operating in discontinuous conduction mode (DCM) and an igniter circuit. The converter supplies the lamp in a 400 Hz square waveform and the igniter is responsible for providing the necessary voltage for lamp start up. The purpose of this work is to supply the xenon lamp from a 12 V battery with a reduced number of components, decreasing the system final costs without penalty the reliability. Some experimental results are presented to validate the proposed ballast behavior.