Ovarian follicular dynamics in Nelore breed (Bos indicus) cattle

The most common beef cattle raised in Brazil is the Nelore breed (Bos indicus). Information obtained by ultrasonography on follicular growth in Bos taurus cattle has been accumulating rapidly. However, there are few publications to date on follicular development in Bos indicus breeds. The follicular dynamics in Nelore heifers and cows during natural or prostaglandin (PG)-induced estrous cycle were studied. From the detection of estrus onward, all animals were examined daily by ultrasonography for one (n=35) or two (n=10) consecutive estrous cycles. The follicular dynamic in Nelore cattle was characterized by the predominance of 2 follicular waves in the cows (83.3%, n=18, P<0.05) and 3 waves in the heifers (64.7%, n=16, P<0.05). Most of the cattle observed over 2 consecutive estrous cycles presented the same pattern of follicular waves in the first and second cycle, and only 30% showed variation in the number of waves from one cycle to the other. Most of the follicular parameters analyzed were not affected by PG treatment or age but were altered by follicular waves. Consequently, data on cows and heifers were combined according to the number of follicular waves. The ovulatory follicle was larger than the other dominant follicles (P<0.05), and the ovulatory wave was shorter than the preceding waves (P<0.05). The interovulatory interval was longer in animals showing 3 waves than those exhibiting 2 waves (P<0.05). Maximum diameter of the dominant follicle (around 11 mm) and of the corpus luteum (CL, approximately 17 mm) were smatter than those reported for European breeds. In conclusion, the results demonstrate that although the dominant follicle and corpus luteum are smaller than in European breeds, the follicular dynamics in Nelore cattle were similar to those observed in European breeds and were characterized by 2 or 3 follicular waves for cows and heifers, respectively, during the natural or prostaglandin-induced estrous cycle. (C) 1997 by Elsevier B.V.

Feeding habit of the Amazon river prawn Macrobrachium amazonicum larvae

To investigate the feeding habit of Macrobrachium amazonicum, three experiments were carried out assessing the stage at which larvae start exogenous feeding, the acceptance of inert food by different larval stages and the ratio between live and inert diet ingested by larvae at each larval stage. In the first experiment, newly hatched larvae were kept in 500-mL beakers and fed from stages I, II or III onward. Larval survival was not affected by the larval stage at which exogenous feeding started, but mean weight gain was lower when food was offered from stage III onward. In the second experiment, 60 larvae from each stage (I to IX) were fasted for 2 h and then fed on inert diet in excess. Only larvae from stage IV onward accepted this inert diet. In the last experiment, newly hatched larvae were stocked in a larviculture tank and fed daily on both Artemia nauplii and inert diet. After 15 min, food content in the digestive tract of individual larvae was analyzed under stereomicroscopy. Larvae in stage I did not feed, while live food was accepted from stage II onward and inert food from stage III onward. Larvae in stages IV, V and VI accepted both foods with no preference, while inert food was predominant in stages VII to IX In conclusion, to feed M amazonicum larvae on Artemia before stage II or on inert diet before stage IV is unnecessary. It increases production costs and may impair water quality. From stages IV to VI, feeding on Artemia and inert diet is probably necessary, while inert diet should be the main food item from stage VII onward. This schedule may optimize feeding management and production costs. (c) 2007 Elsevier B.V. All lights reserved.

Exact boundary control for the wave equation in a polyhedral time-dependent domain

We establish exact boundary controllability for the wave equation in a polyhedral domain where a part of the boundary moves slowly with constant speed in a small interval of time. The control on the moving part of the boundary is given by the conormal derivative associated with the wave operator while in the fixed part the control is of Neuman type. For initial state H-1 x L-2 we obtain controls in L-2. (C) 1999 Elsevier B.V. Ltd. All rights reserved.

Evolution of CaCu3Ti4O12 varistor properties during heat treatment in vacuum

Calcium copper titanate (CaCu3Ti4O12) ceramic varistors were prepared by solid-state method. The samples were several times heat treated in vacuum and the evolution of electrical characteristics were monitored by current density versus electric field measurements and impedance spectroscopy. Repeated heat treatments in vacuum (900 degrees C for 1 h, 0.01 Torr) lead to a desorption of oxygen adsorbed at the grain boundaries and consequently to a degradation of the varistor properties. During further successive heat treatments some oxygen from the grain interior moves to the grain boundary thereby partially restoring the varistor properties. (c) 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Endectocide activity of a new long-action formulation containing 2.25% ivermectin+1.25% abamectin in cattle

The present work aimed to evaluate the endectocide activity of a new injectable long-action formulation, containing ivermectin (IVM) and abamectin (ABA). In each one of the four experiments performed, the following groups were formed: group I: 2.25% IVM (450 mu g/kg) + 1.25% ABA (250 mu g/kg), group II: 3.15% IVM (630 mu g/kg) and group III: control. Eighteen bovine naturally infected by gastrointestinal nematoda were selected for anthelmintic evaluation and necropsied on posttreatment day (PTD) 14 to estimate the total parasitic burden. For the Rhipicephalus (Boophilus) microplus field trial, 30 bovine were selected by means of counts of semi-engorged R. (B.) microplus and the therapeutic and residual efficacy evaluated by tick counts on PTDs 1, 3, 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84 and 91. In the stall test, 15 calves were artificially infested with 5000 R. (B.) microplus (Mozzo strain) larvae three times a week and daily collections of all the engorged female ticks detached from each calf were performed until the PTD 80. Forty bovine naturally infected with Dermatobia hominis larvae were selected and the number of larvae was counted by visual and tactile inspection on PTDs 3, 7, 14, 28, 35, 49, 63, 77, 91 and 105. In this trial, a formulation containing 1% doramectin (200 mu g/kg) was also used. IVM + ABA formulation and 3.15% IVM eliminated four of the eight species of nematode identified. The anthelmintic efficacy of the avermectins association against Haemonchus placei, Cooperia spatulata and C. punctata was 89.64%, 98.84% and 97.69%, while 3.15% IVM achieved 30.98%, 84.79% and 75.56%, respectively. The two formulations evaluated showed reduced acaricide action on the PTD I and 3, reaching high efficacy percentages from PTD 14 onward. The IVM + ABA showed efficacy above 95% in the period between PTDs 21 and 49. In the stall test, it observed no difference (P > 0.05) between the two formulations regarding the R. (B.) microplus counts during the entire evaluation period. IVM + ABA reduced the number of ticks from the PTD 1 to 77 (P < 0.05) and 3.15% IVM reduced (P < 0.05) the tick number from PTD 4 up to PTD 80. The three endectocides showed no difference (P > 0.05) regarding the number of D. hominis larvae and prevented this parasite reestablishment until PTD 105. These results indicate that the IVM + ABA association showed higher anthelmintic activity and similar efficacy against arthropods to the formulation containing 3.15% IVM. (C) 2008 Elsevier B.V. All rights reserved.

Fish Migration, Dams, and Loss of Ecosystem Services in the Mekong Basin

The past decade has seen increased international recognition of the importance of the services provided by natural ecosystems. It is unclear however whether such international awareness will lead to improved environmental management in many regions. We explore this issue by examining the specific case of fish migration and dams on the Mekong river. We determine that dams on the Mekong mainstem and major tributaries will have a major impact on the basin's fisheries and the people who depend upon them for food and income. We find no evidence that current moves towards dam construction will stop, and consider two scenarios for the future of the fisheries and other ecosystems of the basin. We conclude that major investment is required in innovative technology to reduce the loss of ecosystem services, and alternative livelihood strategies to cope with the losses that do occur.

Aprendizagem de línguas e léxico: a negociação de significado em práticas telecolaborativas

This paper is a qualitative ethnographic study that aims to present reflections on negotiation events in teletandem interactions, a synchronous telecollaborative context of language learning, within the scope of the interaction strategies adopted by participants to achieve comprehensibility. The project Teletandem Brasil: foreign languages for all (Telles, 2006) matches up native or proficient speakers of a foreign language with Brazilian undergraduate students to learn each other's language, by communicating synchronically with application softwares like Skype, Oovoo or MSN. on this paper, based on the interpretive perspective of Hermeneutics, we analyze excerpts of teletandem interactions of partnerships established between students of a Brazilian university and American universities. The excerpts presented here have been taken from different moments of the research studies conducted at the teletandem laboratories of UNESP Assis and Sao Jose do Rio Preto and are part of the database of the works of Santos (2008) and Garcia (2010). In this article, in the data analysis, we highlight the focus on form and on lexicon as characteristics of the interactions and analyze how the negotiations happen in this learning context mediated by technology. Among results we may highlight the prevailing of external feedback as a trigger to negotiation moves, the occurrence of adjustment processes between participants to get adapted to each other's interaction behavior, as well as the evolution of this behavior as interactants get familiarized with the computer-mediated communication context, under the shape of changes in the participants choices regarding negotiation of meaning along their interaction experience.

Gap junctions between mast cells and fibroblasts in the developing avian eye

Mast cells are present in the eye of chick embryos from the 14th day onward, displaying metachromatic granules, mainly in the iris anterior surface and pectinate ligament. Ultrastructurally these cells show electron-dense granules and a few thin and short cytoplasmic projections in close contact with fibroblasts. Sometimes these contacts are extensive, with long fibroblast projections partially involving the mast cells. Gap junctions between mast cells and fibroblasts are observed only in the eyes of 16- and 20-day-old embryos. These intercellular specializations are represented by a close apposition of cytoplasmic membranes with an extension up to 300 nm. Gap junctions between mast cells and fibroblasts were not observed previously in vivo or in vitro, although in vitro studies have shown that a number of functionally critical interactions may occur between these cells. Our morphological findings suggest that, in vivo, fibroblasts interact with mast cells and may influence their maturation.

Cytoplasmic bridges, intercellular junctions, and individualization of germ cells during spermatogenesis in Dermatobia hominis (Diptera: Cuterebridae)

During mitotic and meiotic divisions in Dermatobia hominis spermatogenesis, the germ cells stay interlinked by cytoplasm, bridges as a result of incomplete cytokinesis. By the end of each division, cytoplasmic bridges flow to the center of the cyst, forming a complex, called the fusoma. During meiotic prophase I, spermatocytes I present desmosome-like junctions and meiotic cytoplasmic bridges. At the beginning of spermiogenesis, the fusoma moves to the future caudal end of the cyst, and at this time the early spermatids are linked by desmosome-like junctions. Throughout spermiogensis, new and sometimes broad cytoplasmic bridges are formed among spermatids at times making them share cytoplasm. In this case the individualization of cells is assured by the presence of smooth cisternae that outline then structures The more differentiated spermatids have in addition to narrow cytoplasmic bridges, plasmic membranes junctions. By the end of spermiogenesis the excess cytoplasmic mass is eliminated leading to spermatid individualization. Desmosome-like junctions of spermatocytes I and early spermatids appear during the fusoma readjustment and segregations; on the other hand, plasmic membrane junctions appear in differentiating spermatids and are eliminated along with the cytoplasmic excess. These circumstances suggest that belt desmosome-like and plasmic membrane junctions are involved in the maintenance of the relative positions of male germ cells in D. hominis while they are inside the cysts. © 1996 Wiley-Liss, Inc.

Structure of tick anticoagulant peptide at 1.6 Å resolution complexed with bovine pancreatic trypsin inhibitor

The structure of tick anticoagulant peptide (TAP) has been determined by X-ray crystallography at t.6 Å resolution complexed with bovine pancreatic trypsin inhibitor (BPTI). The TAP-BPTI crystals are tetragonal, a = b = 46.87, c = 50.35 Å, space group P41, four complexes per unit cell. The TAP molecules are highly dipolar and form an intermolecular helical array along the c-axis with a diameter of about 45 Å. Individual TAP units interact in a head-to-tail fashion, the positive end of one molecule associating with the distal negative end of another, and vice versa. The BPTI molecules have a uniformly distributed positively charged surface that interacts extensively through 14 hydrogen bonds and two hydrogen bonded salt bridges with the helical groove around the helical TAP chains. Comparing the structure of TAP in TAP-BPTI with TAP bound to factor Xa(Xa) suggests a massive reorganization in the N-terminal tetrapeptide and the first disulfide loop of TAP (CyS5(T)- Cys 15(T)) upon binding to Xa. The Tyr1(T)OH atom of TAP moves 14.2 Å to interact with Asp189 of the S1 specificity site, Arg3(T)CZ moves 5.0 Å with the guanidinium group forming a cation-π-electron complex in the S4 subsite of Xa, while Lys7(T)NZ differs in position by 10.6 Å in TAP-BPTI and TAP-Xa, all of which indicates a different pre-Xa-bound conformation for the N- terminal of TAP in its native state. In contrast to TAP, the BPTI structure of TAP-BPTI is practically the same as all those of previously determined structures of BPTI, only arginine and lysine side-chain conformations showing significant differences.

Behavioural Analysis of a Nonlinear Mechanical System Using Transient Trajectories

This work aims at a better comprehension of the features of the solution surface of a dynamical system presenting a numerical procedure based on transient trajectories. For a given set of initial conditions an analysis is made, similar to that of a return map, looking for the new configuration of this set in the first Poincaré sections. The mentioned set of I.C. will result in a curve that can be fitted by a polynomial, i.e. an analytical expression that will be called initial function in the undamped case and transient function in the damped situation. Thus, it is possible to identify using analytical methods the main stable regions of the phase portrait without a long computational time, making easier a global comprehension of the nonlinear dynamics and the corresponding stability analysis of its solutions. This strategy allows foreseeing the dynamic behavior of the system close to the region of fundamental resonance, providing a better visualization of the structure of its phase portrait. The application chosen to present this methodology is a mechanical pendulum driven through a crankshaft that moves horizontally its suspension point.

Production and heat treatment of cast graphitic steels with additions of niobium

The optimal combination of the mechanical characteristics of austempered spheroidal graphitic cast steel together with modern casting techniques yielded an economically promising product. The maximum potential of the usage of these steels is related to fabrication and characterization techniques, among which, one of the most important is the cooling diagram (TTT curve). In this work, 3 heats of graphitic steels with the following nominal compositions were cast: 1.0 % C, 2.3 % Si, 0.4 % Mn, and with niobium contents of. 0.0 %, 0.5 % and 1.0 %. TTT curves were determined by dilatometric testing and test specimens of these steels were austempered. The samples were then characterized by hardness testing and optical and SEM microscopy. Tensile, impact (no notch) and wear testing were also performed. The addition of niobium produced significant alterations in the TTT diagrams. Increasing niobium content moves the pearlite transformation nose to the right and the bainitic transformation nose to the left. Tensile strength of these alloys was high, in the range of 1700 MPa and impact values were around of 45 Joules for alloy with 1 % Nb, 49 Joules for alloy with 0.5 % Nb and fracture did not occur for the alloy without the addition of Nb.

Production and heat treatment of cast graphitic steels with additions of niobium

The optimal combination of the mechanical characteristics of austempered spheroidal graphitic cast steel together with modern casting techniques yielded an economically promising product. The maximum potentiality of the usage of these steels is related to fabrication and characterization techniques, among which, one of the most important is the cooling diagram (TTT curve). In this work, 3 heats of graphitic steels with the following nominal compositions were cast: 1.0%C, 2.3%Si, 0.4% Mn, and with niobium contents of 0.0%, 0.5% and 1.0%. TTT curves were determined by dilatometric testing and test specimens of these steels were austempered. The samples were then characterized by hardness testing and optical and SEM microscopy. Tensile, impact (no notch) and wear testing were also performed. The addition of niobium produced significant alterations in the TTT diagrams. Increasing niobium content moves the pearlite transformation nose to the right and the bainitic transformation nose to the left. Tensile strength of these alloys was high, in the range of 1700 MPa and impact values were around of 45 Joules for alloy with 1% Nb, 49 Joules for alloy with 0.5% Nb and fracture did not occur for the alloy without the addition of Nb.

Economic Survey of Latin America and the Caribbean 2004-2005

Includes bibliography

Latin America and the Caribbean in the World Economy 2011-2012: Continuing crisis in the centre and new opportunities for developing economies

Includes bibliography