U Pb and Sm Nd geochronologic studies of the eastern Borborema Province, Northeastern Brazil: initial conclusions

The Borborema Province of NE Brasil comprises the central part of a wide Pan-African-Brasiliano orogenetic belt that formed as a consequence of late Neoproterozoic convergence and collision of the São Luis-West Africa craton and the São Francisco-Congo-Kasai cratons. New Sm Nd and U Pb results from the eastern part of this province help to define the basic internal architecture and pre-collisional history of this province, with particular emphasis on delineating older cratonic terranes, their fragmentation during the Mesoproterozoic, and their assembly into West Gondwana during the Pan African-Brasiliano orogeny at ca. 600 Ma. The region can be divided into three major geotectonic domains: a) Rio Piranhas-Caldas Brandão massif, with overlying Paleoproterozoic to Neoproterozoic supracrustal rocks, north of the Patos Lineament; b) the Archean to Paleoproterozoic São Francisco craton (SFC) to the south; and c) a complex domain of Paleoproterozoic to Archean basement blocks with several intervening Mesoproterozoic to Neoproterozoic fold belts in the center (south of Patos Lineament and north of SFC). The northern and central domains comprise the Borborema Province. Archean basement gneiss and Transamazonian granulite of northern SFC are exposed in the southern part of the central domain, underlying southern parts of the Sergipano fold belt. Basement in the Rio Piranhas massif appears to consist mostly of Transamazonian (2.1 to 2.2 Ga) gneissic rocks; Nd model ages (TDM) of ca. 2.6 Ga for 2.15 Ga gneisses indicate a substantial Archean component in the protoliths to these gneisses. The Caldas Brandão massif to the east yields both Transamazonian and Archean U Pb zircon and Nd (TDM) ages, indicating a complex architecture. Metasedimentary rocks of the Jucurutu Formation yield detrital zircons with original crystallization ages as young as 1.8 Ga, indicating that these rocks may be late Paleoproterozoic and correlate with other ca. 1.8 Ga cratonic supracrustal rocks in Brazil such as the Roraima Group and Espinhaço Group. Most metavolcanic and pre-Brasiliano granitic units of the Sergipano (SDS), Pajeú-Paraíba (SPP), Riacho Pontal (SRP), and Piancó-Alto Brígida (SPAB) fold belts in the central domain formed ~ 1.0 ± 0.1 Ga, based on U Pb ages of zircons. Nd model ages (TDM) for these same rocks, as well as Brasiliano granites intruded into them and large parts of the Pernambuco-Alagoas massif, are commonly 1.3-1.7 Ga, indicating that rocks of the fold belts were not wholly derived from either older (> 2.1 Ga) or juvenile (ca. 1.0 Ga) crust, but include mixtures of both components. A simple interpretation of Brasiliano granite genesis and the Nd data implies that there is no Transamazonian or Archean basement underlying large parts of these fold belts or of the Pernambuco-Alagoas massif. An exception is a belt of syenitic Brasiliano plutons (Syenitoid Line) and host gneisses between SPAB and SPP that clearly has a Transamazonian (or older) source. In addition, there are several smaller blocks of Archean to Transamazonian gneiss that can be defined within and among these fold belts. These blocks do not appear to constitute a continuous basement complex, but appear to be isolated older crustal fragments. Our data support a model in which ca. 1.0 Ga rifting was an important tectonic and crust-forming event along the northern edge of the São Francisco craton. Our data also show that significant parts of the Borborema Province are not remobilized Transamazonian to Archean crust, but that Mesoproterozoic crust is a major feature of the Province. There are several small remnants of older crust within the area dominated by Mesoproterozoic crust, suggesting that the rifting event created several small continental fragments that were later incorporated into the Brasiliano collisional orogen. We cannot at present determine if the Rio Piranhas-Caldas Brandão massifs and the older crustal blocks of the central domain were originally part of the São Francisco craton or whether some (or all) of them came from more exotic parts of the Proterozoic Earth. Finally, our data have not yet revealed any juvenile terranes of either Transamazonian or Brasiliano age. © 1995.

Initial-condition problem for a chiral Gross-Neveu system

A time-dependent projection technique is used to treat the initial-value problem for self-interacting fermionic fields. On the basis of the general dynamics of the fields, we derive formal equations of kinetic-type for the set of one-body dynamical variables. A nonperturbative mean-field expansion can be written for these equations. We treat this expansion in lowest order, which corresponds to the Gaussian mean-field approximation, for a uniform system described by the chiral Gross-Neveu Hamiltonian. Standard stationary features of the model, such as dynamical mass generation due to chiral symmetry breaking and a phenomenon analogous to dimensional transmutation, are reobtained in this context. The mean-field time evolution of nonequilibrium initial states is discussed.

Fluctuation effects in initial conditions for hydrodynamics

We have studied the fluctuation effects in proton-proton collisions through the analysis of their observables. To investigate the role of fluctuation 5 in the initial conditions, we have used the interacting gluon model, modified by the inclusion of the impact parameter, and have applied the one-dimensional Landau's Hydrodynamical Model to the fireballs thus generated. The rapidity and pseudorapidity distributions were calculated using two distinct procedures, one taking the fluctuations into account and the other the usual method considering only one fireball with the average initial conditions. The results show indeed the importance of fluctuations.

The diagnostic value of Gram stain for initial identification of the etiologic agent of peritonitis in CAPD patients

Objective: To evaluate the effectiveness of the Gram stain in the initial diagnosis of the etiologic agent of peritonitis in continuous ambulatory peritoneal dialysis (CAPD). Design: Retrospective study analyzing the sensitivity (S), specificity (SS), positive predictive value (+PV), and negative predictive value (-PV) of the Gram stain relating to the results of cultures in 149 episodes of peritonitis in CAPD. The data were analyzed in two studies. In the first, only the cases with detection of a single agent by Gram stain were taken (Study 1). In the second, only the cases with two agents in Gram stain were evaluated (Study 2). Setting: Dialysis Unit and Laboratory of Microbiology of a tertiary medical center. Patients: Sixty-three patients on regular CAPD who presented one or more episodes of peritonitis from May 1992 to May 1995. Results: The positivity of Gram stain was 93.2% and the sensitivity was 95.7%. The values of S, SS, +PV, and -PV were respectively: 94.9%, 53.5%, 68.3%, and 90.9% for gram-positive cocci and 83.3%, 98.8%, 95.2%, and 95.6% for gram-negative bacilli. The association of gram-positive cocci plus gram-negative bacilli were predictive of growth of both in 6.8%, growth of gram-positive cocci in 13.7%, and growth of gram-negative bacilli in 72.5%. Conclusions: The Gram stain is a method of great value in the initial diagnosis of the etiologic agent of peritonitis in CAPD, especially for gram-negative bacilli.

Densification and residual stresses induced in glass surfaces by Vickers indentations

Images and profiles of Vickers impressions produced on as-received float-glass were obtained using atomic force microscopy (AFM). The images show that the impression edges undergo elastic recovery parallel to surface. The profiles made it possible to measure vertical elastic recovery, ev(r). For a 40 g nominal load, maximum penetration depth of indenter was (2.20 ± 0.03) μm, and recovery at the impression center was ev(0) = (0.98 ± 0.03) μm. Vertical elastic recovery was non-uniform along profiles. Permanent impressions produced resulted from glass mass displacement downward, producing an increase in glass density in impression vicinity, which is discussed in terms of changes in O-Si-O and Si-O-Si bond angles and Si-O bond length. Near impression edges, pileup was observed for which a simplified model is proposed taking into account the compaction and stresses near the impressions. © 2000 Elsevier Science B.V. All rights reserved.

Stresses analysis in semi-elliptic leaf spring and comparison with the SAE J788 (1982) norm

In this work are presented the values found with the experimental testing, in the semi-elliptic leaf spring, utilizing 24 strain gages, distributed in five leaves of springs; these values have been compared to the calculated values found with the application of Norm SAE J788 (1982). The results showed discrepancy between the values measured and calculated and that the Norm is not indicated to determine the actuating stress in any point of any leaf of the leaf spring, but due to its simplicity and quickness of the process it presents good precision for the pre-development of the product. Copyright © 2002 Society of Automotive Engineers, Inc.

The natural history of carpal tunnel syndrome: A study of 20 hands evaluated 4 to 9 years after initial diagnosis

Carpal tunnel syndrome (CTS) is the most frequent entrapment neuropathy. In the last decade several papers have been published on epidemiology, clinical aspects, diagnosis, and treatment, but little is known about its natural history. The objective of this work was to study the natural history of CTS syndrome. From 358 patients with clinical and conduction study diagnosis of CTS, 12 cases were identified that had refused surgical treatment, had not used anti-inflammatory medications, and had not undergone orthopaedic procedures, such as immobilization or anaesthetic infiltration. These 12 patients have 20 compromised hands which have been followed up for between 4 and 9 years. In all cases sensory and motor conduction studies were performed on the median nerve, at the beginning and end of follow-up period. Electrical improvement was marked in 5 hands and slight in 3; there was no significant change in 10, and deterioration in 2. As 8 hands (7 patients) showed improved clinical symptoms and conduction studies over several years, this brings the universally accepted procedure of surgical treatment into doubt.

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.

Kinetic study of the plastoquinone pool availability correlated with H2O2 release in seawater and antioxidant responses in the red alga Kappaphycus alvarezii exposed to single or combined high light, chilling and chemical stresses

Under biotic/abiotic stresses, the red alga Kappaphycus alvarezii reportedly releases massive amounts of H2O2 into the surrounding seawater. As an essential redox signal, the role of chloroplast-originated H2O2 in the orchestration of overall antioxidant responses in algal species has thus been questioned. This work purported to study the kinetic decay profiles of the redox-sensitive plastoquinone pool correlated to H2O2 release in seawater, parameters of oxidative lesions and antioxidant enzyme activities in the red alga Kappaphycus alvarezii under the single or combined effects of high light, low temperature, and sub-lethal doses of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), which are inhibitors of the thylakoid electron transport system. Within 24 h, high light and chilling stresses distinctly affected the availability of the PQ pool for photosynthesis, following Gaussian and exponential kinetic profiles, respectively, whereas combined stimuli were mostly reflected in exponential decays. No significant correlation was found in a comparison of the PQ pool levels after 24 h with either catalase (CAT) or ascorbate peroxidase (APX) activities, although the H2O2 concentration in seawater (R = 0.673), total superoxide dismutase activity (R = 0.689), and particularly indexes of protein (R = 0.869) and lipid oxidation (R = 0.864), were moderately correlated. These data suggest that the release of H2O2 from plastids into seawater possibly impaired efficient and immediate responses of pivotal H2O2-scavenging activities of CAT and APX in the red alga K. alvarezii, culminating in short-term exacerbated levels of protein and lipid oxidation. These facts provided a molecular basis for the recognized limited resistance of the red alga K. alvarezii under unfavorable conditions, especially under chilling stress. © 2006 Elsevier B.V. All rights reserved.

Initial concentration profile influence on migration measurements from plastic packaging: A simulation study

Migration of components from plastic packaging into foodstuffs or into medicines is a very important issue, concerning public health. Using experimental techniques, like gas chromatography-mass spectrometry, these essays measure total migration and specific migration of components from plastic packaging. This work presents an explanation and applications of a numerical technique tool for this measurement, allowing the comprehension of the diffusion process and the estimate of component migration in difficult or impractical measurements. As an application example, the non-uniform influence of initial concentration profile on the migration is presented, demonstrating the necessity of this profile determination for high quality considerations on involved metrology.

Abordagem initial do paciente com mielopatia aguda não compressiva

Acute myelopathy are characterized by spinal cord dysfunction, developing sensitive, motor and autonomic signs and symptons. Since they are relatively rare, there are some difficulties to early diagnosis and to the beginning of the treatment. So, literature was reviewed to describe the main aetiologies of acute non compressive myelopathy: 1) demyelinating diseases; 2) systemic disease; 3) parainfectious; 4) delayed radiation myelopathy; 5) vascular myelopathy; 6) idiopatic and 7) vitamin B12 deficiency. Besides, we suggest an algorithm to initial approach of these patients and further aethiologic investigation. © Copyright Morelra Jr. Editora.

A 2-D delaunay refinement algorithm using an initial prerefinement from the boundary mesh

An improvement to the quality bidimensional Delaunay mesh generation algorithm, which combines the mesh refinement algorithms strategy of Ruppert and Shewchuk is proposed in this research. The developed technique uses diametral lenses criterion, introduced by L. P. Chew, with the purpose of eliminating the extremely obtuse triangles in the boundary mesh. This method splits the boundary segment and obtains an initial prerefinement, and thus reducing the number of necessary iterations to generate a high quality sequential triangulation. Moreover, it decreases the intensity of the communication and synchronization between subdomains in parallel mesh refinement. © 2008 IEEE.

Influence of grinding on the roundness, residual stresses and microstructure of VC131 steel analysed by varying the type of cutting fluid

This paper by R. E. Catai, E. C. Bianchi, P. R de Águia and M. C. Alves reports on the results of an analysis made of roundness errors, residual stresses, and SEM micrographs of VC131 steel. The analysis involved workpieces ground with two types of cutting fluid: synthetic cutting fluid and emulsive oil. In this study, the cutting parameters were kept constant while the type of cutting fluid was varied. The amount of cutting fluid injected in the process was also varied, aiming to identify the ideal amount required to obtain good results without causing structural damage to the workpiece. The SEM analyses of roundness errors and residual stresses revealed that, of the two cutting fluids, emulsive oil provided better tensions due to its greater lubricating power.

Effect of the density and of the distance of Brachiaria decumbens staff on the initial growth of Coffea arabica L. Seedligns

The aim of this work was to evaluate the interference of three densities (4, 8 and 16 plants/m 2) of Brachiaria decumbens Stapf distributed at three different distances (0, 10 and 20 cm from coffee plants) on the initial growth of Coffea arabica L. seedlings. Dark red Latosoil was used as substrate to fill up 70 liters cement boxes. Coffee seedlings at 15 cm height and 8 leaves stage were planted in each box. B. decumbens seedlings were transplanted when they reached two to four leaves stage. The experimental design was a randomized blocks with ten treatments and three replications. At the end of the experiment were measured, height, leaf number, leaf area, chlorophyll content and dry weight of coffee plants. Dry weight of B. decumbens leaves was also evaluated. The leaf area and leaf dry weight was shown to be more sensitive parameters to the interference of Brachiaria plants. Dry weight of coffee plants were reduced from 60% to 88% when the B. decumbens were transplanted 0 cm from the coffee plant. With distance of 10 cm the reduction of dry weight increased with the increase of the density of the B. decumbens. In the coexistence of the coffee plants with 16 plants/m 2 of B. decumbens, there was a reduction in the dry weight of about 80% at the distances of 0 and 20 cm. Regarding leaf area, the reduction was 47% on the average in the density of 4 plants/m 2 of B. decumbens The reduction in leaf area at other densities was higher at the distance of 0 and 20 cm, and 55% reduction was obtained at the distance of 10 cm.

Stresses and strains: situation analysis of the Caribbean family

Includes bibliography