Influencia de la refusion en las propiedades mecanicas y composicion quimica de aleaciones odontologicas

The objective of the study presented in this article was to analyze the influence of remelting of two odontological alloys: Dentorium and Steeldent, on the mechanical properties and on the chemical composition. For the two alloys, samples, containing 10% and 50% new alloy, were subjected to tensile test, micrography and chemical analysis. The alloys presented similar mechanical properties, except for the elongation, which presented higher values for the Dentorium 50% new alloy. This is due to the smaller carbides formed in this sample. The remelting itself seems not to be responsible for these differences, but they are probably due to the lack of a good control of the casting process. The micrography showed a dendritic column matrix, with carbides in the interdentric region and inside dendritic grain. In the chemical composition was observed few elements percentage change.

Silent period in carpal tunnel syndrome

The silent period is a misunderstood electrophysiological phenomenon leading to several different hypotheses explaining its electrogenesis. It has been studied by different authors and different methodologies giving a wide variability of results, therefore an exact pattern of its normal values does not exist. This work was undertaken to define the normal morphology and duration of the silent period obtained by supramaximal stimulus of the median nerve, during maximum isometric effort of the abductor pollicis brevis muscle against resistance, using 20 adult volunteers without neurological alterations. The normal median duration was 104.6 milliseconds. The same methodology was applied to 20 hands from 20 patients with carpal tunnel syndrome. The silent period showed many types of morphological alterations, but the major alteration observed was a tendency to temporal elongation. No correlation between the severity of the carpal tunnel syndrome and the silent period alterations were observed.

Unsaturated polyester based composites reinforced with curauá fiber - Preliminary studies

Curauá fiber processing characterization has been performed throughout the different processing steps. Unsaturated polyester has been used as matrix in the production of curauá reinforced composite samples. Compression molding process has been used to prepare the samples. Tensile strength, impact resistance, flexural strength, Young's modulus and elongation at break have been accessed for curauá composites in comparison with fiberglass composites. Mechanical properties were found not to attend the company's internal standards specification. However, the work has shown some alternatives to solve these problems such as the modification of equipment characteristics and resin formulation, the necessity of incorporation of a higher content of fiber and the possibility of using a new type of filler. Copyright © 2000 Society of Automotive Engineers, Inc.

Morphology and histochemistry of the hyolingual apparatus in chameleons

We reexamined the morphological and functional properties of the hyoid, the tongue pad, and hyolingual musculature in chameleons. Dissections and histological sections indicated the presence of five distinctly individualized pairs of intrinsic tongue muscles. An analysis of the histochemical properties of the system revealed only two fiber types in the hyolingual muscles: fast glycolytic and fast oxidative glycolytic fibers. In accordance with this observation, motor-endplate staining showed that all endplates are of the en-plaque type. All muscles show relatively short fibers and large numbers of motor endplates, indicating a large potential for fine muscular control. The connective tissue sheet surrounding the entoglossal process contains elastin fibers at its periphery, allowing for elastic recoil of the hyolingual system after prey capture. The connective tissue sheets surrounding the m. accelerator and m. hyoglossus were examined under polarized light. The collagen fibers in the accelerator epimysium are configured in a crossed helical array that will facilitate limited muscle elongation. The microstructure of the tongue pad as revealed by SEM showed decreased adhesive properties, indicating a change in the prey prehension mechanics in chameleons compared to agamid or iguanid lizards. These findings provide the basis for further experimental analysis of the hyolingual system. © 2001 Wiley-Liss, Inc.

Activity of benomyl for control of postbloom fruit drop of citrus caused by Colletotrichum acutatum

Postbloom fruit drop (PFD) of citrus caused by Colletotrichum acutatum produces orange-brown lesions on petals and induces the abscission of young fruitlets and the retention of the calyces. Despite the fact that C. acutatum is not highly sensitive to benomyl in culture, this fungicide provides good control of the disease under field conditions. This study was undertaken to determine the effect of benomyl on various stages of disease development to understand the basis for its effectiveness in the field. We found that benomyl at 1.0 μg/ml reduced colony area of C. acutatum by about 75% and completely inhibited growth of C. gloeosporioides. Benomyl did not prevent conidial germination even at 100 μg/ml, but reduced germ tube elongation at 10 and 100 μg/ml. When benomyl was applied to flower clusters on screen-house-grown plants before inoculation, disease severity was greatly reduced. Applications at 24 and 48 h, but not at 72 h, after inoculation reduced PFD severity. Application of benomyl to symptomatic petals not bearing conidia did not prevent or reduce production of inoculum. Application to petals bearing conidia reduced viability of these fungal propagules by only about 50%. The viability of appressoria on mature leaves was not affected by benomyl application. Even when appressoria on mature leaves were stimulated to germinate by treatment with flower extracts, subsequent application of benomyl did not reduce propagule numbers below original levels. Benomyl appears to act by preventing infection and early development of the fungus in petals. However, once symptoms have developed, this fungicide has only minimal effects on further disease development and spread.

Structural basis for inhibition of cyclin-dependent kinase 9 by flavopiridol

Flavopiridol has been shown to potently inhibit CDK1 and 2 (cyclin-dependent kinases 1 and 2) and most recently it has been found that it also inhibits CDK9. The complex CDK9-cyclin T1 controls the elongation phase of transcription by RNA polymerase II. The present work describes a molecular model for the binary complex CDK9-flavopiridol. This structural model indicates that the inhibitor strongly binds to the ATP-binding pocket of CDK9 and the structural comparison of the complex CDK2-flavopiridol correlates the structural differences with differences in inhibition of these CDKs by flavopiridol. This structure opens the possibility of testing new inhibitor families, in addition to new substituents for the already known leading structures such as flavones and adenine derivatives. © 2002 Elsevier Science (USA). All rights reserved.

RNA reallocation during initial spermatic meiosis of Pseudonannolene tocaiensis Fontanetti, 1996

Toluidine Blue dye containing increasing concentrations of Mg2+ or Ca2+ can show loss of metachromacy at a certain concentration of the inorganic cation when staining DNA-protein complexes in vitro and in vivo. This process has been named Critical Electrolyte Concentration (CEC) and is applied to the study of protein-nucleic acid complexes at different stages of chromatin supra-organization. Male gametocytes of the species Pseudonannolene tocaiensis were studied, observing a large amount of ribonucleoproteins in the gametocytes cytoplasm throughout prophase I. The nucleolus is maintained during most of the prophase. The highly condensed region showing the bouquet formation appeared stained with the typical tonality for chromatin; this region corresponds to the constitutive heterochromatin. We also observed the presence of RNA all through the chromosomes in prophase I. The permanence of this material surrounding the chromosomes during male meiosis is difficult to explain, since a great reduction of the products of spermatogenesis occurs due to the fact that most of the material of the spermatozoids is not used during fecundation. However, in P. tocaiensis this material is remains even at the spermatids. It is known that during the spermiogenesis of certain insects, RNA synthesis continues at the spermatid, being subsequently eliminated from the nucleus and then from the cell due to the elongation of the nucleus. Therefore, we could suggest that permanence of this material (RNA) during meiosis has a function in the process of cell division.

Effect of diclofenac sodium on the healing process of end-to-end anastomosis in carotid arteries of rabbits. Histopathological and biomechanical studies

Aim. Diclofenac sodium is a non-steroidal anti-inflammatory drug commonly used to attenuate painful inflammatory reactions in surgery. However, it may delay healing in the skin and gastrointestinal tract. The aim of this study was to evaluate the influence of Diclofenac in vascular healing. Methods. Ninety rabbits had their carotid arteries sectioned and reconstructed by end-to-end anastomosis with interrupted sutures. The animals were randomly allocated into 3 groups of 30 each and treated by intramuscular route with saline (control), 5 mg/kg/day of diclofenac sodium (DS-5), and 10 mg/kg/day of diclofenac sodium (DS-10). Treatment began on the day of surgery and lasted 4 days. Angiography, biomechanical properties (failure load, failure elongation, yield point, yield point elongation, and stiffness were obtained from the load/elongation curve), macroscopic and histological examinations (hematoxylin-eosin, Masson, Calleja, Picrossirius-red), and scanning electron microscopy were studied in both arteries on the 3rd and 15th postoperative days. Results. No significant differences in biomechanical properties were observed either in the 3 groups or the experimental times. The carotid artery healing process was similar in the 3 groups. Conclusion. Diclofenac sodium did not cause alterations nor delayed carotid artery healing.

Ultrastructural characteristics of spermiogenesis in the domestic duck (Anas platyrhynchos)

In this present study was observed that the spermatids underwent morphological differentiation and modifications, which primarily comprised nuclear elongation, during the process of spermiogenesis in the domestic duck. The acrosome was formed and the flagellum developed concomitantly with nuclear modifications. Thus, various modifications could be observed during this process, especially changes in the distribution of cytoplasmic organelles. Long cisternae of the rough endoplasmic reticulum present in the spermatid cytoplasm dissociated into vesicles and the distal centriole initiated the development of the flagellum in the cellular portion opposite to the acrosome. The ultrastructure of the spermatids of the domestic duck did not show the characteristic development of pre-acrosomal granules, but the acrosomal granule could be directly visualized in this species. © 2005 Blackwell Verlag.

Micropropagação de Calendula officinalis L

Micropropagation of Calendula officinalis L. is usually propagated through seeds and therefore shows high diversity in flower size and colour, what causes quantitative and qualitative chemical variability. A micropropagation protocol was established for clonal propagation of this species to achieve homogeneous biomass, more appropriate for the production of phytotherapics. Explants harvested from capitula were the most appropriate for the micropropagation process. MS culture medium supplemented with 1.0 mgL-1 BAP and 6.0 gL-1 Phytagel™ enhanced shoot proliferation, while MS medium supplemented with 0.5 mgL-1 Kinetin and 6.0 gL-1 Phytagel™, increased shoot elongation. Plantlets (80%) cultured in MS/2 medium supplemented with 1.0 mgL-1 de IBA rooted.

Ectrópio palpebral em portador da síndrome de Down e conjuntivite alérgica: Relato de caso

This is a case report of a patient with Down's syndrome with an important mechanical ectropion and elongation of the lower lid related to chronic allergic conjunctivitis, besides cataract and keratoconus. The tarsal strip technique and ressection of redundant and thick conjunctiva was the surgical approach chosen for this case. Functional and cosmetic outcomes were considered satisfactory.

Estudo da perda da tensao do enxerto de tendão calcâneo bovino

Lesion of the anterior cruciate ligament (ACL) in the knee is a problem that affects animals as well as humans and may evolve with joint instability that is often symptomatic and incapacitating. The main option for ligament substitution is the autologous tendon graft. The graft undergoes tensioning during ACL reconstructive surgery to reestablish the normal laxity of the ACL- deficient knee. Although graft tensioning plays a fundamental role in postoperative clinical evolution, ideal tensioning levels have not been established in the literature. Therefore, graft elongation that may occur over time is still one of the main reasons for ligament reconstruction failure. In this study, ten bovine calcaneus tendons underwent two successive assays of physiological tensioning for a maximum deformation of 2.5% of the initial tendon length, maintained for 600s with force (N) values recorded at zero time (initial), 300s and 600s. At the end of the first assay, the tendon returned to its initial length and was maintained at rest for 300s and then the next tensioning assay was initiated, repeating the previous procedure. Statistical analysis revealed that tendon elongation is more pronounced during the initial 300s, reflecting a more accentuated decline in the tension values of the graft. Therefore, 300s after tensioning and fixing the graft, the surgeon can assess with more precision if the tensioning level was adequate.

Propriedades tensiométricas comparadas entre fragmentos do centro tendíneo do diafragma, pericárdio fibroso e peritônio parietal de bovinos não conservados e conservados em glicerina

The behaviour of the non conserved and 98% glycerin conserved specimens for periods of 30, 60 and 90 days of bovine diaphragma's tendinous center, fibrous pericardium and parietal peritoneum submitted to mechanical tests of traction, was observed in ten bovines between 30 months and 36 months of age, crossbreeds, males and females, collecting fragments of these aforesaid membranes in each animal. The diaphragma's tendinous center and parietal peritoneum did not suffered significant modification (p>0.05) in the values of tension when compared to the resistance tests of traction of non conserved and 98% glycerin conserved membranes. However, all the evaluated tissues showed significant increase (p£0.05) of the elongation values when conserved in 98% glycerin for until 90 days. It was also observed that fibrous pericardium is the one which supports greaters tensions. So, it to was concluded, that glycerin is efficient to the conservation of biological membranes besides modifying its mechanical properties.

Correlações entre características morfogênicas e estruturais em pastos de capim-braquiária

The analysis of both morphogenetic and structural characteristics of pasture allows us to understand the response patterns of the plant to the environment. Thus, this study was conducted to evaluate the associations between the morphogenetic and structural characteristics of Brachiaria decumbens under continuous grazing by cattle. The development of individual tillers in pastures was evaluated under two grazing management strategies during three seasons (winter, spring and summer). Pearson correlations between variables were estimated. The lengths of leaf and stem, number of tillers and leaves per tiller, rates of leaf appearance and elongation of leaf and stem of B. decumbens were positively correlated. There was a negative relationship between appearance and lifespan of leaves (r = -0.89). However, positive correlations between leaf appearance rate and number of tillers (r = 0.64) and between length of stem and leaf senescence rate (r = 0.63) were determined. The B. decumbens modifies its morphogenesis to better adapt to climate and grazing management.

Características morfogênicas e estruturais de híbridos de sorgo submetidos a adubação nitrogenada

The effect of two topdressing nitrogen doses was evaluated on the morphogenetic and structural characteristics of sorghum hybrids (Sorghum bicolor (L.) Moench) BRS 801 and 0734006, cultivated in vases in open-air conditions. A completely randomized design was used with four treatments arranged in factorial outline 2x2 (two sorghum hybrids and two nitrogen doses, 50 and 100 kg ha-1), with eight replications per treatment. There was a significant effect of interaction hybrid x fertilization on the leaf appearance rate, the hybrid BRS 801 being more responsive to the increased nitrogen dose. The phyllochron, the total number of leaves and leaf elongation rate, were influenced both by nitrogen doses and by hybrids. The leaf senescence rate was not influenced by factors fertilization and hybrids. These variations in morphogenetic and structural characteristics between the hybrids and/or nitrogen doses, probably indicate that hybrids respond in a different way to topdressing.