Electron transfer by singlet excited state of porphyn and electron acceptor affinity in rigid medium: photoacoustic phase angle analysis

Photoacoustic spectroscopy provides information about both amplitude and phase of the response of a system to an optical excitation process. This paper presents the studies of the phase in the electron transfer process between octaethylporphyn (OEP) and quinone molecules dispersed in a polymeric matrix. It was observed a tendency in the phase behavior to small values only in the spectral region near to 620 nm, while for shorter wavelength did not show any tendency. These measurements suggested that the electron transfer to acceptor occurred with the participation of octaethylporphyn singlet excited state.

Model for subchannel friction factors and flow redistribution in wire-wrapped rod bundles

The fuel element of LMFBR consists of a bundle of rods wrapped with an helical wire as spacer, surrounded by an hexagonal duct. In the present work, a semi-empirical model is developed to calculate bundle average and subchannel based friction factors and flow redistribution. The obtained results were compared to experimental data and they were considered satisfactory for wide range of geometrical parameters.

Static pressure and wall shear stress distributions in air flow in a seven wire-wrapped rod bundle

An experimental investigation is performed in a turbulent flow in a seven wire-wrapped rod bundle, mounted in an open air facility. Static pressure distributions are measured on central and peripheral rods. By using a Preston tube, the wall shear stress profiles are experimentally obtained along the perimeter of the rods. The geometric parameters of the test section are P/D=1.20 and H/D=15. The measuring section is located at L/D=40 from the air inlet. It is observed that the dimensionless static pressure and wall shear stress profiles are nearly independent of the Reynolds number and strongly dependent of the wire-spacer position, with abrupt variations of the parameters in the neighborhood of the wires.

Experimental analysis of pressure drop and flow redistribution in axial flows in rod bundles

Fuel elements of PWR type nuclear reactors consist of rod bundles, arranged in a square array, and held by spacer grids. The coolant flows, mainly, axially along the rods. Although such elements are laterally open, experiments are performed in closed type test sections, originating the appearance of subchannels with different geometries. In the present work, utilizing a test section of two bundles of 4x4 pins each, experiments were performed to determine the friction and the grid drag coefficients for the different subchannels and to observe the effect of the grids in the crossflow, in cases of inlet flow maldistribution.

Thermalhydraulic behavior of electrically heated rod during a critical heat flux transient

In nuclear reactors, the occurrence of critical heat flux leads to fuel rod overheating with clad fusion and radioactive products leakage. To predict the effects of such phenomenon, experiments are performed using electrically heated rods to simulate operational and accidental conditions of nuclear fuel rods. In the present work, it is performed a theoretical analysis of the drying and rewetting front propagation during a critical heat flux experiment, starting with the application of an electrical power step from steady state condition. After the occurrence of critical heat flux, the drying front propagation is predicted. After a few seconds, a power cut is considered and the rewetting front behavior is analytically observed. Studies performed with various values of coolant mass flow rate show that this variable has more influence on the drying front velocity than on the rewetting one.

On the numerical integration of rigid body nonlinear dynamics in presence of parameters singularities

One of the main complexities in the simulation of the nonlinear dynamics of rigid bodies consists in describing properly the finite rotations that they may undergo. It is well known that, to avoid singularities in the representation of the SO(3) rotation group, at least four parameters must be used. However, it is computationally expensive to use a four-parameters representation since, as only three of the parameters are independent, one needs to introduce constraint equations in the model, leading to differential-algebraic equations instead of ordinary differential ones. Three-parameter representations are numerically more efficient. Therefore, the objective of this paper is to evaluate numerically the influence of the parametrization and its singularities on the simulation of the dynamics of a rigid body. This is done through the analysis of a heavy top with a fixed point, using two three-parameter systems, Euler's angles and rotation vector. Theoretical results were used to guide the numerical simulation and to assure that all possible cases were analyzed. The two parametrizations were compared using several integrators. The results show that Euler's angles lead to faster integration compared to the rotation vector. An Euler's angles singular case, where representation approaches a theoretical singular point, was analyzed in detail. It is shown that on the contrary of what may be expected, 1) the numerical integration is very efficient, even more than for any other case, and 2) in spite of the uncertainty on the Euler's angles themselves, the body motion is well represented.

A brief review and a new treatment for rigid bodies collision models

In general the motion of a body takes place in a confined environment and collision of the body with the containing wall is possible. In order to predict the dynamics of a body in this condition one must know what happens in a collision. Therefore, the problem is: if one knows the pre-collision dynamics of the body and the properties of the body and the wall one wants to predict the post-collision dynamics. This problem is quite old and it appeared in the literature in 1668. Up to 1984 it seemed that Newton's model was enough to solve the problem. But it was found that this was not the case and a renewed interest in the problem appeared. The aim of this paper is to treat the problem of plan collisions of rigid bodies, to classify the different models found in the literature and to present a new model that is a generalization of most of these models.

Determinação do sexo em catfish de canal (Ictalurus punctatus) utilizando endoscopia

A identificação precoce do sexo em peixes é um procedimento importante para o desenvolvimento de estratégias que facilitem o manejo no plantel de reprodutores. A endoscopia pode ser utilizada para essa identificação, embora em peixes seu uso ainda seja restrito. Diante disso, o objetivo deste trabalho foi validar o uso do endoscópio rígido via poro urogenital para determinação do sexo do catfish de canal (Ictalurus punctatus). O equipamento utilizado foi um endoscópio Multipurpose Rigid™ 30º com 2,7 mm de diâmetro e 18 cm de comprimento. Foram examinados 60 peixes com peso variando entre 86 e 1.032 gramas nos quais foi introduzido o endoscópio via poro genital e, logo em seguida, eutanaziados para confirmação do sexo. Amostras de tecido gonadal foram coletadas para avaliação histológica do estádio de maturação e confirmação do sexo. Os resultados mostraram que dos 60 peixes examinados, 57 tiveram confirmação positiva do sexo via endoscopia, o que corresponde a 95% da amostra. A utilização da endoscopia para determinação do sexo em I. punctatus via poro genital é viável.

Intestinal parasites in school food handlers in the city of Uberlândia, Minas Gerais, Brazil

In order to verify the presence of intestinal parasites in food handlers, stool samples were collected from 104 cooks and their helpers that were working in food preparation in 20 public elementary schools, in various areas of the city of Uberlândia, Minas Gerais, Brazil. The samples were collected during the months of November and December, 1988, in plastic flasks containing a 10% formaldehyde solution and processed by the Hoffmann, Pons & Janer method. The sediment was examined using triplicate slides. All individuals were females aged between 24 to 69 years. Intestinal parasites were found in 85.0% of the studied schools and 47.1% of the studied food handlers (cooks and helpers) were found to be positive. Among the 49 infected food handlers, 32 (65.3%) carried a single parasite and 17 (34.7%) carried two parasites. The following intestinal parasites were found: Giardia lamblia (21.1%), Entamoeba coli (21.1%), hookworms (9.6%), Ascaris lumbricoides (5.8%), Entamoeba histolytica (2.9%), Hymenolepis nana (1.9%), Strongyloides stercoralis (1.0%). These data emphasize the need for a rigid semi-annual control in all school food handlers, including diagnosis, specific treatment and orientation about the mechanisms of transmission of the intestinal parasites.

Purification and parcial characterization of a hemagglutinating factor (HAF): a possible adhesive factor of the diffuse adherent of Escherichia coli (DAEC)

The mannose-resistant hemagglutinating factor (HAF) was extracted and purified from a diffuse adherent Escherichia coli (DAEC) strain belonging to the classic enteropathogenic E. coli (EPEC) serotype (0128). The molecular weight of HAF was estimated to be 18 KDa by SDS-PAGE and 66 KDa by Sephadex G100, suggesting that the native form of HAF consists of 3-4 monomeric HAF. Gold immunolabeling with specific HAF antiserum revealed that the HAF is not a rigid structure like fimbriae on the bacterial surface. The immunofluorescence test using purified HAF on HeLa cells, in addition to the fact that the HAF is distributed among serotypes of EPEC, suggests that HAF is a possible adhesive factor of DAEC strains

Airborne fungi in the city of Porto Alegre, Rio Grande do Sul, Brazil

Knowledge of anemophilous fungi in a given city or region is important for the ecological diagnosis and specific treatment of allergic manifestations induced by inhaled allergens. In order to diagnose the presence of anemophilous fungi, several qualitative and quantitative techniques are used depending on the study place. This study of fungal air spores was performed with a Rotorod Sampler®, an equipment which samples the air through a plastic rod attached to an electric engine that makes it spin fast enough to collect the particles in the air. The samples were collected once a week during 24 hours using the standard cycle of the manufacturers. A total of 52 samples were obtained from April 2000 through March 2001. The results revealed prevalence of ascosporos (50.49%), Cladosporium (17.86%), Aspergillus/Penicillium (15.03%), basidiosporos (3.84%), rusts (3.82%), and Helminthosporium (2.49%), and a lesser frequency of Botrytis (1.22%), Alternaria (1.19%), smuts (0.90%), Curvularia (0.87%), Nigrospora (0.61%), and Fusarium (0.08%). Also, 1.59% of the spores detected here could not be identified by the systematic key used. More fungal spores were observed during the summer than during the autumn.

Cutaneous infection caused by Corynebacterium pseudodiphtheriticum: a microbiological report

We report here a rare case of cutaneous infection due to Corynebacterium pseudodiphtheriticum. The patient presented to the clinical laboratory with a skin ulcer on his left leg. Gram-stained preparation of the purulent secretion revealed the presence of numerous rod-shaped Gram-positive organisms in the absence of any other species. The organism was grown in pure culture on sheep blood agar and was further identified as C. pseudodiphtheriticum using a commercial identification system (API-Coryne, BioMérieux, France). The infection was successfully treated with ciprofloxacin. This case emphasizes the importance of the clinical microbiology laboratory in correctly identifying Gram-positive organisms obtained in pure culture from skin ulcers.

SURVIVAL, INDUCTION AND RESUSCITATION OF Vibrio cholerae FROM THE VIABLE BUT NON-CULTURABLE STATE IN THE SOUTHERN CARIBBEAN SEA

The causative agent of cholera, Vibrio cholerae, can enter into a viable but non-culturable (VBNC) state in response to unfavorable conditions. The aim of this study was to evaluate the in situ survival of V. cholerae in an aquatic environment of the Southern Caribbean Sea, and its induction and resuscitation from the VBNC state. V. cholerae non-O1, non-O139 was inoculated into diffusion chambers placed at the Cuare Wildlife Refuge, Venezuela, and monitored for plate, total and viable cells counts. At 119 days of exposure to the environment, the colony count was < 10 CFU/mL and a portion of the bacterial population entered the VBNC state. Additionally, the viability decreased two orders of magnitude and morphological changes occurred from rod to coccoid cells. Among the aquatic environmental variables, the salinity had negative correlation with the colony counts in the dry season. Resuscitation studies showed significant recovery of cell cultivability with spent media addition (p < 0.05). These results suggest that V. cholerae can persist in the VBNC state in this Caribbean environment and revert to a cultivable form under favorable conditions. The VBNC state might represent a critical step in cholera transmission in susceptible areas.

A new and practical viscerotome

An instrument consisting of a sheath-like tube 22 1/2 cm. long with a rod or trocar and attached cutting blade is described. It may be used to obtain fragments of non hollow organs, 7mm wide by five to ten centimeters long, to substitute the classic viscerotome. No failures have occurred in viscerotomies of the liver so far. The greatest advantage of this instrument is its relatively small size. Its more practical use is to overcome the difficulties which may hamper the use of the classical viscerotome. This is very important as the need arose to reorganize the network of viscerotomy service. In some areas or countries where no complete autopsies can be performed, biopsy samples have been reduced to such a small size that no practical Information has been received in the last few years. The difficulties of performing an autopsy prevents the obtention of useful vathological data on several diseases affecting the population, even among putients dying in hospitais. The viscerotomy is also the practical solution for this problem.

Antimicrobial Resistance of Shigella spp. isolated in the State of Pará, Brazil

INTRODUCTION: Shigella spp. are Gram-negative, nonsporulating, rod-shaped bacteria that belong to the family Enterobacteriaceae and are responsible for shigellosis or bacillary dysentery, an important cause of worldwide morbidity and mortality. METHODS: We studied the antibiotic resistance profiles of 122 Shigella spp. strains (81 S. flexneri, 41 S. sonnei, 1 S. boydii) isolated from patients (female and male from 0 to 80 years of age) presenting diarrhea in different districts of the State of Pará, in the North of Brazil. The antibiotic resistance of the strains, isolated from human fecal samples, was determined by the diffusion disk method and by using the VITEK-2 system. RESULTS: The highest resistance rate found was the resistance rate to tetracycline (93.8%), followed by the resistance rate to chloramphenicol (63.9%) and to trimethoprim/sulfamethoxazole (63.1%). Resistance to at least three drugs was more common among S. flexneri than S. sonnei (39.5% vs. 10%). Six (4.9%) strains were susceptible to all the antibiotics tested. All strains were susceptible to cefotaxime, ceftazidime, ciprofloxacin, nalidixic acid and nitrofurantoin. CONCLUSIONS: High rates of multidrug resistance in Shigella spp. are a serious public health concern in Brazil. It is extremely important to continuously monitor the antimicrobial resistances of Shigella spp. for effective therapy and control measures against shigellosis.