bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructural investigation of iron nitride layers formed by low-temperature gaseous nitriding
Authors: Inia D. K. , Vredenberg A. M. , Boerma D. O. , Tichelaar F. D. , Schut H. , van Veen A.
Published: March 2008

Iron nitride layers were formed by a novel low-temperature gaseous nitriding process. Nitriding occurs at a temperature of 325 °C through NH3decomposition at the surface of Ni (25 nm) coated Fe, followed by N transport through the Ni film into the underlying Fe, where nitride precipitation takes place. The role of Ni is to protect Fe from oxidation by gas impurities and to serve as a catalyst for NH3decomposition. The precipitation behavior and the development of microstructure were studied by means of elastic recoil detection, cross-sectional transmission electron diffraction (XTEM), and positron annihilation (PA). From PA and XTEM no evidence was found for the occurrence of porosity during nitriding (an effect found at higher temperatures due to the decomposition of the nitrides into Fe and N2). XTEM showed that the original columnar α–Fe grains transform into smaller ′–Fe4N grains which subsequently transform into larger ε–Fe3−xN grains. This microstructural evolution of smaller ′ grains forming in the original columnar α–Fe structure occurs in one of two growth modes of the nitride in the Fe layer, i.e., throughout the entire depth range of the Fe layer, or preferentially at the Ni/Fe interface when an iron oxide layer is present at this interface.
Hydraulic activity and microstructural characterization of new fly ash–belite cements synthesized at different temperatures
Authors: Guerrero A. , Goñi S. , Macías A. , Luxán M. P.
Published: March 2008

The influence of the synthesis temperature of a new fly ash–belite cement (FABC) on its hydraulic activity and microstructural characteristics is discussed in this work. Three types of FABC were synthesized at 700, 800, and 900 °C after a previous hydrothermal treatment at 200 °C of the fly ash, CaO, and water mixture. The hydraulic activity of the pastes was evaluated during a period of 200 days from mixing through the combined water content, previously determined from thermogravimetric analyses, and the hydration advance degree by x-ray diffraction (XRD). The microstructure characterization of the pastes was studied by scanning electron microscopy (SEM).
Intrinsic microcrystalline silicon by postgrowth anneals
Authors: Yoon Jong-Hwan
Published: March 2008

Hydrogenated microcrystalline silicon (μc-Si:H) grown by a conventional plasma-enhanced chemical vapor deposition from high hydrogen-diluted silane was annealed by increasing the temperature from 25 to 450 °C at a constant rate of 12 °C/min (one annealing cycle). Dark-conductivity activation energy gradually increases with increasing the number of annealing cycle to a saturation value of about 0.6 eV, observed in truly intrinsic μc-Si:H films. For the saturated state, the dark conductivity of the order of 10−8 S/cm was obtained. Little or no change in the oxygen content was observed after the annealing.
Relationship between the microstructure and nanoindentation hardness of thermally evaporated and magnetron-sputtered electrochromic tungsten oxide films
Authors: Ong C. W. , Wong H. Y. , Pang G. K. H. , Baba-Kishi K. Z. , Choy C. L.
Published: March 2008

Tungsten oxide (WOx) films were fabricated by (i) reactive thermal evaporation (RTE) at room temperature with oxygen ambient pressurePO2as a parameter, and (ii) reactive magnetron sputtering (RMS) with substrate temperatureTsas a parameter. The film structure revealed by x-ray photoelectron spectroscopy, x-ray diffraction, density measurements, infrared absorption, and atomic force microscopy was correlated with the nanoindentation hardnessH. The RTE WOxfilms deposited at highPo2were amorphous and porous, whileHdepended appreciably on normalized penetration depthhD(indentation depth/film thickness) due to the closing of the pores at the point of indentation. Decrease inPo2from 10 to 2 × 10−3mtorr led to smaller porosity, weakerhDdependence ofH, and higher averageH(measured athD≈ 0.2 to 0.3, for example). The RMS WOxfilm deposited at room temperature was amorphous and denser than all RTE films. The rise in substrate temperatureTsfirst densified the film structure (up to 110 °C) and then induced crystallization with larger grain size forTs≥ 300 °C. Correspondingly, thehDdependence ofHbecame weaker. In particular,Hof the RMS sample deposited at 110 °C showed a peak athDslightly above 1 owing to pileup at the contact point of indentation. For higherTs, pileup occurred at shallowerhDand the averageH(measured athD≈ 0.2 to 0.3, for example) rose, accompanied by the increase of grain size.
Corrosive wear of the Co–Cr–W alloy in liquid zinc
Authors: Wang Xibao , Liang Yong
Published: March 2008

The corrosive wearing behavior of the Co–Cr–W alloy in liquid zinc was investigated using a specially designed wearing test machine. Its corrosion rate and wear rate during corrosive wearing process with different conditions were analyzed. The corrosive wearing mechanism of the Co–Cr–W alloy was investigated by analysis on its sliding surface using scanning electron microscopy, energy dispersive spectrometry, and microhardness sclerometer. The experimental results led to the following conclusions: (i) The corrosion of the Co–Cr–W alloy is accelerated by wearing process in the liquid zinc. (ii) The liquid zinc provides obvious lubrication to the sliding surfaces of this alloy and then reduces its wearing rate during the corrosive wearing process. (iii) Its corrosive wearing rate is increasing sharply with increasing temperature of the liquid zinc. (iv) The corrosive wearing of the Co–Cr–W alloy is caused by preferential corrosion of the eutectic phases in this alloy and fatigue cracking of the worn surface. The fatigue wearing of this alloy is directly due to the synthetic effect of strain hardening of the layer on and under sliding surface and serious stress corrosion in the crack tips during the corrosive wearing period.
Ordered structure formation in the flux-grown Ba(Mg1/3Ta2/3)O3 single crystals
Authors: Lee Yu-Chang , Chou Chen-Chia , Tsai Dah-Shyang
Published: March 2008

Formation of ordered structure in flux-grown Ba(Mg1/3Ta2/3)O3(BMT) single crystals was studied using x-ray diffraction, electron diffraction, and high-resolution electron microscopy. The low-temperature-grown crystals exhibited no sign of B-site ordering. Annealing at 1500 °C induced the 1:2 ordered phase, and its content increased with the annealing time. The superlattice diffraction peaks were broad initially; they sharpened rapidly with the annealing time. Diffuse superlattice reflections were found in electron diffraction patterns of 1500 °C annealed BMT; they turned into sharp reflections under long annealing time or higher temperature, 1600 °C. The intensity of diffuse reflections was sparsely distributed, but the maximum intensity location was determined in the digitized recording of image plate. The maximum intensity sites of two diffuse reflections in the 〈111〉 direction deviated from the presumed 1/3 and 2/3 positions and shifted towards the center. The diffuse reflection and the deviation from regular positions were interpreted as the composition modulation during B-site cation diffusion.
Synthesis of Al2O3–SiC from kyanite precursor
Authors: Amroune A. , Fantozzi G.
Published: March 2008

Carbothermal reduction of kyanite, a natural aluminosilicate with high alumina content (Al2O3 · SiO2), was used as a way to synthesize SiC–Al2O3 powder. Carbon black was mixed with the mineral precursor in a molar ratio of (C/SiO2) = 5.5. The Carbothermal reaction sequence was studied in the temperature range 1260–1550 °C. Completion of the reaction at 1550 °C gave β–SiC-whiskers and α–Al2O3 particles as final products. From observations, the impurities contained in the mineral precursor behave as catalysts for the vapor–liquid–solid whisker growth mechanism. When the specific surface area of the starting carbon was increased from 330 to 996 m2/g, the carbothermal reaction rate increased but the morphology of the SiC-whiskers became very irregular. This study aimed to identify the main reaction conditions for obtaining a favorable morphology of the synthesized powder for elaborating Al2O3–SiC-whisker composite materials by using low cost starting materials and a relatively simple in situ synthesis route in comparison to the conventional way of separately preparing the phases SiC (whiskers) and Al2O3 before elaborating composites.
Mechanistic studies in combustion synthesis of NiAl–TiB2 composites: Effects of gravity
Authors: Lau Cheryl , Mukasyan Alexander , Pelekh Aleksey , Varma Arvind
Published: March 2008

Combustion synthesis (CS) of NiAl-based materials reinforced by TiB2 particles was investigated under both terrestrial and microgravity conditions. The synthesized metal matrix composites (MMC) are characterized by very fine (<1 μm) reinforced particulates, which have strong bonding along their entire surface with matrix (NiAl) and are distributed uniformly in it. It was found that microgravity leads to a decrease in the average TiB2 particle size, while higher volume fraction of NiAl component in the material leads to the formation of coarser reinforced particulates. The mechanism of structure formation of different MMCs during CS was identified by using the quenching technique. For example, it was shown that TiB2 grains appear due to crystallization from the complex (Ni–Al–Ti–B) liquid solution formed in the combustion front. An overall decrease of microstructural transformation rates was observed under microgravity.
High fracture resistance of carbon fiber treated by electron beam irradiation
Authors: Nishi Yoshitake , Toriyama Takashi , Oguri Kazuya , Tonegawa Akira , Takayama Kazuo
Published: March 2008

A crack reduction by electron beam (EB) irradiation treatment for carbon fiber, used without the traditional method of accompanying heat, was developed to modify the mechanical properties at lower temperature. The EB treatment improved the resistance to fracture. Namely, the maximum ratio of fractured samples (maxRf) and the minimum bending strain on fracture (minεf) were defined as simple indicators of fracture resistance and became smaller by the EB treatment. Furthermore, a critical density of dangling bonds for a fracture was suggested and determined for carbon fiber treated by EB irradiation. The EB irradiation to reduce cracking and the determination of the critical density of dangling bonds are new concepts that can be broadly applied in the fields of aerospace and rapid-transit production engineering.
Pb(ZrxTi1−x)O3 ceramics via reactive sintering of partially reacted mixture produced by a high-energy ball milling process
Authors: Kong L. B. , Ma J. , Zhang T. S. , Zhu W. , Tan O. K.
Published: March 2008

Partially reacted mixtures of Pb(ZrxTi1−x)O3 and its corresponding starting oxide components were obtained by a high-energy ball milling process. The partially reacted powders were characterized by x-ray diffraction and scanning electron microscopy techniques. The sintering behavior of the milled mixtures has demonstrated a distinct volumetric expansion before the densification of the samples, which clearly shows the occurrence of a reactive sintering process of the partially reacted powders. Such process requires a lower densification temperature as compared with the PZT powders produced by the conventional solid-state reaction process. PZT ceramics were found to form directly from the partially reacted powders sintered at 900–1200 °C. The dielectric and ferroelectric properties of the PZT ceramics as a function of sintering temperature and milling time were also studied and discussed.
Third-order nonlinear optical response in PbS-coated CdS nanocomposites
Authors: Liu Bing , Chew Chwee Har , Gan Leong Ming , Xu Guo Qin , Li Heping , Lam Yee Loy , Kam Chan Hin , Que Wen Xiu
Published: March 2008

PbS-coated CdS nanocomposite particles were synthesized by an ion displacement method in an inverse microemulsion. Their growth kinetics were studied with UV–vis spectroscopy. Transmission electron microscopic characterization shows that PbS-coated CdS particles are uniform in size with a mean diameter of 6 nm. The electron diffraction patterns demonstrate their crystalline nature. Third-order nonlinear optical properties in the samples were investigated using the Z-scan technique with femtosecond laser pulses at 780-nm wavelength. The nonlinear refractive index of PbS-coated CdS nanocomposite particles in microemulsion varied with the molar ratio of Cd/Pb ions and reached a maximum of 5.3 × 10−12 cm2/GW for the sample with a Cd/Pb ion ratio of 1 to 2. The observed large refractive nonlinearity in these nanocomposite particles may be attributed to the optical Stark effect and strong interfacial and inter-nanoparticle interactions.
Analysis of depth-sensing indentation tests with a Knoop indenter
Authors: Riester L. , Bell T. J. , Fischer-Cripps A. C.
Published: March 2008

The present work shows how data obtained in a depth-sensing indentation test using a Knoop indenter may be analyzed to provide elastic modulus and hardness of the specimen material. The method takes into account the elastic recovery along the direction of the short axis of the residual impression as the indenter is removed. If elastic recovery is not accounted for, the elastic modulus and hardness are overestimated by an amount that depends on the ratio of E/H of the specimen material. The new method of analysis expresses the elastic recovery of the short diagonal of the residual impression into an equivalent face angle for one side of the Knoop indenter. Conventional methods of analysis using this corrected angle provide results for modulus and hardness that are consistent with those obtained with other types of indenters.
Phase transformation effects on the wear properties of alumina gel–polymer matrix nanocomposites
Authors: Luo Jiazhong , Lannutti John , Seghi Robert
Published: March 2008

A phase transformation in an alumina gel provided an elegant means of isolating the effect of filler properties on the wear resistance of particle-reinforced thermosetting polymer–matrix composites. This transformation was useful because it takes place without significantly altering filler porosity. This produced a wear surface apparently reflecting the vermicular growth patterns in the γ-alumina in the δ-aluminum monohydrate matrix. Nucleation of γ-alumina in the gel matrix produced wear rates comparable to commercial composites.
Correlation of the Raman spectra with the thermal conductivity of a set of diamond wafers prepared by chemical vapor deposition
Authors: Etz Edgar S. , Hurst Wilbur S. , Feldman Albert
Published: March 2008

Raman spectroscopy, at laser excitation wavelengths of 514.5, 785, and 1064 nm, is used to study a set of chemical-vapor-deposited (CVD) diamond wafers of known thermal conductivity κ. The in-plane thermal conductivity (at 25 °C) of the diamond wafers ranges from 4 to 22 W cm−1 K−1 and represents a wide range of diamond quality. The spectra were obtained from both macro/micro- sampling measurements, examining the top and bottom wafer surface, as well as wafer cross-sections. Discussed are the peak positions and linewidths of the Raman bands and their relation to sp3-bonded diamond and sp2-bonded carbon in the context of diamond quality and perfection, and the effects of wafer heterogeneities. The detailed analysis of the Raman spectra provides a robust correlation with the room-temperature bulk (or macroscopic) thermal conductivity of these samples. The correlation is made through the determination of the band area ratios of the diamond Raman line at 1333 cm−1 to that of the 1550 cm−1 band characteristic of nondiamond carbon impurities. This dependence is most pronounced for the Fourier-transform Raman data obtained with infrared excitation at 1064 nm, due to resonance enhancement, and therefore allows the detection of carbon impurities, especially for high-quality CVD diamond.
Influence of ligand groups in Ti precursors on phase transformation and microstructural evolution of TiO2 thin films prepared by the wet chemical process
Authors: Ting Chu-Chi , Chen San-Yuan
Published: March 2008

TiO2 thin films prepared by metalorganic decomposition (MOD-TiO2) and sol-gel processes (SG-TiO2) were investigated in terms of the anatase-to-rutile phase transformation and microstructural evolution. It was found that the chemical reactivity of the ligand groups initially coordinated on the titanium precursor plays a decisive role in the structure development of as-deposited SG- and MOD-TiO2 films. MOD-TiO2 films consist of small aggregated particles and therefore, tend to coalesce together to form an inhomogeneous microstructure during the anatase-to-rutile phase transformation. On the other hand, SG-TiO2 films consist of uniform large particles that tend to grow homogeneously. MOD-TiO2 films showed a higher crystallization temperature than the SG-TiO2 films but the temperature of the anatase-to-rutile phase transformation is much lower in MOD- (approximately 775 °C) as compared to SG-TiO2 films (approximately 930 °C). The activation energy (Q) was estimated as 524 and 882 kJ/mol for the MOD- and SG-TiO2 films, respectively. The lower transformation temperature and activation energy in MOD-TiO2 films were due to smaller grain size and more potential nucleation sites existing in the un-transformed MOD-TiO2 film structure, which can accelerate the rate of anatase-to-rutile transformation.
Dielectric properties of oxide structures by a laser-based direct-writing method
Authors: Young D. , Wu H. D. , Auyeung R. C. Y. , Modi R. , Fitz-Gerald J. , Pique A. , Chrisey D. B. , Atanassova P. , Kodas T.
Published: March 2008

Matrix-assisted pulsed laser evaporation direct-write (MAPLE-DW) is a laser-based method of directly writing mesoscopic patterns of electronic materials. Patterns of composite BaTiO3/SiO2/TiO2 dielectric material were written onto Pt/Au interdigitated-electrode test structures, with precise control over final dielectric properties. Scanning electron microscopy indicates random close-packed structures of BaTiO3 and SiO3 particles, with interstitial spaces partially filled with titania. Depending on the BaTiO3:silica ratio, the dielectric constant ranged from 5 to 55 and followed a 4-component logarithmic rule of mixing. This work demonstrates that the transfer process and the final material properties of MAPLE-DW oxide materials are largely decoupled.
Ferroelectric SrBi2Ta2O9 single-crystal growth and characterization
Authors: Sih B. , Tang J. , Dong M. , Ye Z-G.
Published: March 2008

Using a new composite flux and an improved growth process, large and high-quality ferroelectric SrBi2Ta2O9 (SBT) single crystals (up to 25 × 20 mm2 area) were successfully grown from high-temperature solutions. The effects of chemical, thermodynamic, and kinetic parameters on the growth results were systematically studied. The optimum system for the growth of SBT crystals has been identified. B2O3 additive was shown to play an important role in improving the effectiveness of the Bi2O3 solvent. The grown SBT single crystals exhibit a dominant (001)-orientation and large single-domain areas. The dielectric and ferroelectric properties measured in relation to crystal orientations have confirmed the absence of any polarization component normal to the (Bi2O2)2+ sheets of the structure, indicating a high anisotropy in the properties.
Kinetic analysis of solid-state processes
Authors: Málek Jiří , Mitsuhashi Takefumi , Criado José Manuel
Published: March 2008

A simple method for kinetic analysis of solid-state processes has been developed. A criteria capable of classifying different processes is explored here with a view toward visualizing the complexity of solid-state kinetics. They provide a useful tool for the determination of the most suitable kinetic model. The method has been applied to the analysis of crystallization processes in amorphous ZrO2 and RuO2. It is found that the crystallization kinetics of as-prepared sample exhibits a complex behavior under nonisothermal conditions. This is probably due to an overlapping of the nucleation- and crystal-growth processes at the beginning of crystallization. As a consequence, the Johnson–Mehl–Avrami nucleation-growth model cannot be applied. A two-parameter autocatalytic model provides a good description of the crystallization process under isothermal and nonisothermal conditions.
Temporal Trends in Largemouth Bass Mortality, with Fishery Implications
Authors: Allen Micheal S. , Walters Carl J. , Myers Randall
Published: March 2008

We reviewed estimates of annual exploitation (u) and total mortality (Z) for populations of largemouth bass Micropterus salmoides and used a simulation model to explore how temporal changes in u have influenced those populations. The review produced 32 estimates of u and 30 of Z spanning 51 years. Fishing mortality was roughly parabolic through time, with a mean of 0.35 for 1976–1989 and a mean of 0.18 for 1990–2003. Thus, average fishing mortality rates have declined by about one-half since about 1990. Total mortality declined with the decline in u, suggesting that changes in u caused lower overall total mortality rates. The evidence further suggests that the decline in u was caused by the voluntary release of fish by anglers rather than by changes in overall fishing effort. The simulation model showed that the decline in exploitation increased adult largemouth bass abundance but reduced the ability of size and bag regulations to improve population metrics owing to low rates of directed harvest. Discard mortality (i.e., the mortality of fish caught and released) would not negate the benefits of lower exploitation unless the mortality of fish caught and released was 0.3 or higher. Changes in angler behavior have substantially reduced fishing mortality for largemouth bass fisheries, which should be considered when developing management plans for this species and others with high rates of voluntary release.
Temporal Trends in Voluntary Release of Largemouth Bass
Authors: Myers Randall , Taylor John , Allen Micheal , Bonvechio Timothy F.
Published: March 2008

We used creel survey data collected from 1975 to 2006 to evaluate temporal changes in the voluntary release of legally harvestable largemouth bass Micropterus salmoides at four Texas reservoirs and two Florida lakes noted for providing high-quality largemouth bass fisheries. The voluntary release rate increased substantially over time at all six water bodies and reached asymptotic levels exceeding 0.90 in two Texas reservoirs in the early 2000s. Year explained from 68% to 96% of the variability in voluntary release rates. The level of voluntary release ranged from 0.53 to 0.99 among Texas reservoirs in the early 2000s. The increase in voluntary release over time was similar at the two Florida lakes, which had identical largemouth bass harvest regulations, but the levels differed. Catch and release of legally harvestable largemouth bass was more prevalent than harvest at five of the six water bodies included in this study but also varied across small spatial scales. Fishery managers should measure the level of voluntary release and be mindful of the potential effects of high voluntary release when considering the use of harvest restrictions to restructure largemouth bass populations.
Validation of Daily Growth Increment Formation in the Otoliths of Juvenile Cyprinid Fishes from the Brazos River, Texas
Authors: Durham Bart W. , Wilde Gene R.
Published: March 2008

Age data are commonly used by fisheries biologists to assess a number of important population characteristics. For cyprinid fishes, there have been few attempts to assess the validity of age estimates, particularly those based on otolith microstructure. We assessed the periodicity of growth increment formation in the otoliths of three species of cyprinid from the Brazos River, Texas, two of which are of conservation concern. We immersed juvenile sharpnose shiners Notropis oxyrhynchus, smalleye shiners N. buccula, and plains minnow Hybognathus placitus in a 100-mg/L solution of alizarin complexone for 24 h and sampled fish at 5-d intervals for 30 d. Regression models indicated high correspondence between number of days posttreatment and number of growth increments between the alizarin mark and the edge of the otolith for all three species (sharpnose shiner: r2 = 0.99; smalleye shiner: r2 = 0.98; plains minnow: r2 = 0.97). Slopes of regression lines did not differ from 1.0 (t-test: P < 0.05), indicating that growth increments are deposited daily in these three species. Our results provide evidence that daily growth increments are reliable sources of age information for cyprinids.
New Species Richness Predictors First Tested on Fish in a Small Tropical Stream
Authors: Głowacki Łukasz , Penczak Tadeusz
Published: March 2008

Species richness predictors serve to provide information related to how many new species would be captured in an additional sampling survey at a site on the basis of what actually was captured in an initial sample survey. Two new species richness predictors, one based on sampling effort units and the other on numbers of specimens obtained in the initial survey, were tested on fish in a small tropical stream sampled with a seine fixed to two sticks, electrofishing, and rotenone, the last of which was considered as the control. The first predictor provided better predictions with electrofishing samples than earlier developed predictors of this type. The latter predictor provided no improvement over previous estimators of its type.
Bayesian Spatial Modeling of Data from Unit‐Count Surveys of Fish in Streams
Authors: Webster Raymond A. , Pollock Kenneth H. , Ghosh Sujit K. , Hankin David G.
Published: March 2008

We describe a framework for spatial modeling of data from surveys of stream‐dwelling fish species in which repeated counts are made of animals within a sample of habitat units. Using Bayesian modeling with Markov chain‐Monte Carlo (MCMC) algorithms, it is possible to estimate fish population size from repeated‐count survey data while allowing fish detection probabilities to vary across the stream. We propose the use of conditional autoregressive models for modeling the spatial dependence of density across the habitat units of the stream. The spatial dependence model can be used along with covariate models for density and detection to predict density at unsampled units and thereby estimate total abundance across the stream. We apply these models to data sampled from an intensive repeated‐count survey of juvenile coho salmonOncorhynchus kisutchin McGarvey Creek, Northern California. Spatial dependence in fish density was detected, and models that account for spatial dependence produced more precise predictions at unsurveyed units, and thus more precise estimates of total stream abundance, than models that assumed spatial independence. Through a small simulation study, we show that ignoring heterogeneity in detection probabilities can lead to significant underestimation of total abundance. Inclusion of heterogeneity by means of a random effect in the detection component of the model can lead to numerical instability of the MCMC method, and we stress the importance of accounting for heterogeneity by incorporating covariates in modeling detection probability.
Response of Larval Lost River and Shortnose Suckers to Wetland Restoration at the Williamson River Delta, Oregon
Authors: Crandall John D. , Bach Leslie B. , Rudd Nathan , Stern Mark , Barry Matt
Published: March 2008

Population declines of the federally endangered Lost River sucker Deltistes luxatus and shortnose sucker Chasmistes brevirostris have been linked to several factors, including the loss of larval nursery habitat associated with lake fringe and riparian wetlands. Restoration of deltaic wetlands in the Williamson River delta, Oregon, is regarded as one strategy that may increase larval nursery habitat and survival. This study examined larval sucker presence, growth, development, and feeding in pilot restoration wetlands at the Williamson River delta to determine whether wetland restoration provides habitat that is conducive to larval rearing. We compared results from the restoration wetlands to those in riparian and lacustrine wetland reference sites during 2003 and 2004. The seasonal timing of larval Lost River and shortnose suckers captured in the restoration wetlands was similar to that in reference sites during the April‐July study period. The frequency of occurrence in the restoration wetlands was comparable to that in reference sites; larvae were collected in 90‐100% of transects during periods of peak abundance. These data are an indication that restored wetlands provide critical habitat for larval suckers. Larval sucker length, developmental phase, and gut fullness in the restoration wetlands indicated that larvae were feeding, growing, and hence, rearing, in those areas. Water temperatures in the restoration wetlands were 3‐4°C higher than those in reference sites, especially early in the season, which may have increased the restoration sites' suitability for larval rearing compared with reference sites. Our results indicate that initial wetland restoration efforts at the Williamson River delta have successfully created suitable rearing habitat for larval Lost River and shortnose suckers and suggest that further large‐scale wetland restoration in the delta will increase larval rearing opportunities and contribute to the recovery of these two endangered species.
Amazon Forest maintenance as a source of environmental services
Authors: Fearnside Philip M.
Published: March 2008

Amazonian forest produces environmental services such as maintenance of biodiversity, water cycling and carbon stocks. These services have a much greater value to human society than do the timber, beef and other products that are obtained by destroying the forest. Yet institutional mechanisms are still lacking to transform the value of the standing forest into the foundation of an economy based on maintaining rather than destroying this ecosystem. Forest management for commodities such as timber and non-timber forest products faces severe limitations and inherent contradictions unless income is supplemented based on environmenta lservices. Amazon forest is threatened by deforestation, logging, forest fires and climate change. Measures to avoid deforestation include repression through command and control, creation of protected areas, and reformulation of infrastructure decisions and development policies. An economy primarily based on the value of environmental services is essential for long-term maintenance of the forest. Much progress has been made in the decades since I first proposed such a transition, but many issues also remain unresolved. These include theoretical issues regarding accounting procedures, improved quantification of the services and of the benefits of different policy options, and effective uses of the funds generated in ways that maintain both the forest and the human population.
The evidence for hippocampal long-term potentiation as a basis of memory for simple tasks
Authors: Izquierdo Iván , Cammarota Martín , Silva Weber C. Da , Bevilaqua Lia R.M. , Rossato Janine I. , Bonini Juliana S. , Mello Pamela , Benetti Fernando , Costa Jaderson C. , Medina Jorge H.
Published: March 2008

Long-term potentiation (LTP) is the enhancement of postsynaptic responses for hours, days or weeks following the brief repetitive afferent stimulation of presynaptic afferents. It has been proposed many times over the last 30 years to be the basis of long-term memory. Several recent findings finally supported this hypothesis: a) memory formation of one-trial avoidance learning depends on a series of molecular steps in the CA1 region of the hippocampus almost identical to those of LTP in the same region; b)hippocampal LTP in this region accompanies memory formation of that task and of another similar task. However, CA1 LTP and the accompanying memory processes can be dissociated, and in addition plastic events in several other brain regions(amygdala, entorhinal cortex, parietal cortex) are also necessary for memory formation of the one-trial task, and perhaps of many others.
Inhibition of caspase-8 activity reduces IFN-gamma expression by T cells from Leishmania major infection
Authors: Pereira Wânia F. , Guillermo Landi V.C. , Ribeiro-Gomes Flávia L. , Lopes Marcela F.
Published: March 2008

Following infection with Leishmania major, T cell activation and apoptosis can be detected in draining lymph nodes of C57BL/6-infected mice. We investigated the mechanisms involved in apoptosis and cytokine expression following Tcellactivation. After two weeks of infection, apoptotic T cells were not detected in draining lymph nodes but activation with anti-CD3 induced apoptosis in both CD4 and CD8 T cells. Treatment with anti-FasLigand, caspase-8 or caspase- 9 inhibitors did not block activation-induced T-cell death. We also investigated whether the blockade of caspase-8 activity would affect the expression of type-1 or type-2 cytokines. At early stages of infection, both CD4 and CD8 T cells expressed IFN-gamma upon activation. Treatment with the caspase-8 inhibitor zIETD-fmk (benzyl-oxycarbonyl-Ile- Glu(OMe)-Thr-Asp(OMe)-fluoromethyl ketone) reduced the proportion of CD8 T cells and IFN-gamma expression in both CD4 and CD8T cells. We conclude that a non apoptotic role of caspase-8 activity may be required for T cell-mediated type-1 responses during L. major infection.
High susceptibility of activated lymphocytes to oxidative stress-induced cell death
Authors: Degasperi Giovanna R. , Castilho Roger F. , Vercesi Anibal E.
Published: March 2008

The present study provides evidence that activated spleen lymphocytes from Walker 256 tumor bearing rats are more susceptible than controls to tert-butyl hydroperoxide (t-BOOH)-induced necrotic cell death in vitro. The iron chelator and antioxidant deferoxamine, the intracellular Ca2+ chelator BAPTA, the L-type Ca2+ channel antagonist nifedipine or the mitochondrial permeability transition inhibitor cyclosporin A, but not the calcineurin inhibitor FK-506, render control and activated lymphocytes equally resistant to the toxic effects of t-BOOH. Incubation of activated lymphocytes in the presence of t-BOOH resulted in a cyclosporin A-sensitive decrease in mitochondrial membrane potential. These results indicate that the higher cytosolic Ca2+ level in activated lymphocytes increases their susceptibility to oxidative stress-induced cell death in a mechanism involving the participation of mitochondrial permeability transition.
Active transcription and ultrastructural changes during Trypanosoma cruzi metacyclogenesis
Authors: Ferreira Ludmila R.P. , Dossin Fernando de M. , Ramos Thiago C. , Freymüller Edna , Schenkman Sergio
Published: March 2008

The differentiation of proliferating epimastigote forms of Trypanosoma cruzi , the protozoan parasite that causes Chagas’ disease, into the infective and non-proliferating metacyclic forms can be reproduced in the laboratory by incubating the cells in a chemically-defined medium that mimics the urine of the insect vector. Epimastigotes have a spherical nucleus, a flagellum protruding from the middle of the protozoan cell, and a disk-shaped kinetoplast - an organelle that corresponds to the mitochondrial DNA. Metacyclic trypomastigotes have an elongated shape with the flagellum protruding from the posterior portion of the cell and associated with a spherical kinetoplast. Here we describe the morphological events of this transformation and characterize a novel intermediate stage by three-dimensional reconstruction of electron microscope serial sections. This new intermediate stage is characterized by a kinetoplast compressing an already elongated nucleus, indicating that metacyclogenesis involves active movements of the flagellar structure relative to the cell body. As transcription occurs more intensely in proliferating epimastigotes than in metacyclics, we also examined the presence of RNA polymerase II and measured transcriptional activity during the differentiation process. Both the presence of the enzyme and transcriptional activity remain unchanged during all steps of metacyclogenesis. RNA polymerase II levels and transcriptional activity only decrease after metacyclics are formed. We suggest that transcription is required during the epimastigote-to-metacyclic trypomastigote differentiation process, until the kinetoplast and flagellum reach the posterior position of the parasites in the infective form.
COL18A1 is highly expressed during human adipocyte differentiation and the SNP c.1136C > T in its "frizzled" motif is associated with obesity in diabetes type 2 patients
Authors: Errera Flavia I.V. , Canani Luís H. , Yeh Erika , Kague Érika , Armelin-Corrêa Lucia M. , Suzuki Oscar T. , Tschiedel Balduíno , Silva Maria Elizabeth R. , Sertié Andréa L. , Passos-Bueno Maria Rita
Published: March 2008

Collagen XVIII can generate two fragments, NC11-728 containing a frizzled motif which possibly acts in Wnt signaling and Endostatin, which is cleaved from the NC1 and is a potent inhibitor of angiogenesis. Collagen XVIII and Wnt signaling have recently been associated with adipogenic differentiation and obesity in some animal models, but not in humans. In the present report, we have shown that COL18A1 expression increases during human adipogenic differentiation. We also tested if polymorphisms in the Frizzled (c.1136C>T; Thr379Met) and Endostatin (c.4349G>A; Asp1437Asn) regions contribute towards susceptibility to obesity in patients with type 2 diabetes (113 obese, BMI =30; 232 non-obese, BMI < 30) of European ancestry. No evidence of association was observed between the allele c.4349G>A and obesity, but we observed a significantly higher frequency of homozygotes c.1136TT in obese (19.5%) than in non-obese individuals (10.9%) [P = 0.02; OR = 2.0 (95%CI: 1.07-3.73)], suggesting that the allele c.1136T is associated to obesity in a recessive model. This genotype, after controlling for cholesterol, LDL cholesterol, and triglycerides, was independently associated with obesity (P = 0.048), and increases the chance of obesity in 2.8 times. Therefore, our data suggest the involvement of collagen XVIII in human adipogenesis and susceptibility to obesity.
Update on the etiology, diagnosis and therapeutic management of sexual precocity
Authors: Brito Vinicius Nahime , Latronico Ana Claudia , Arnhold Ivo J. P. , Mendonça Berenice Bilharinho
Published: March 2008

Precocious puberty is defined as the development of secondary sexual characteristics before the age of 8 years in girls and 9 years in boys. Gonadotropin-dependent precocious puberty (GDPP) results from the premature activation of the hypothalamic-pituitary-gonadal axis and mimics the physiological pubertal development, although at an inadequate chronological age. Hormonal evaluation, mainly through basal and GnRH-stimulated LH levels shows activation of the gonadotropic axis. Gonadotropin-independent precocious puberty (GIPP) is the result of the secretion of sex steroids, independently from the activation of the gonadotropic axis. Several genetic causes, including constitutive activating mutations in the human LH-receptor gene and activating mutations in the Gs protein a-subunit gene are described as the etiology of testotoxicosis and McCune-Albright syndrome, respectively. The differential diagnosis between GDPP and GIPP has direct implications on the therapeutic option. Long-acting gonadotropin-releasing hormone (GnRH) analogs are the treatment of choice in GDPP. The treatment monitoring is carried out by clinical examination, hormonal evaluation measurements and image studies. For treatment of GIPP, drugs that act by blocking the action of sex steroids on their specific receptors (cyproterone, tamoxifen) or through their synthesis (ketoconazole, medroxyprogesterone, aromatase inhibitors) are used. In addition, variants of the normal pubertal development include isolated forms of precocious thelarche, precocious pubarche and precocious menarche. Here, we provide an update on the etiology, diagnosis and management of sexual precocity.
Análise crítica do uso dos índices do Homeostasis Model Assessment (HOMA) na avaliação da resistência à insulina e capacidade funcional das células-beta pancreáticas
Authors: Vasques Ana Carolina J. , Rosado Lina Enriqueta F. P. L. , Alfenas Rita de Cássia G. , Geloneze Bruno
Published: March 2008

A disfunção das células-beta e a resistência insulínica são anormalidades metabólicas inter-relacionadas na etiologia do diabetes tipo 2. Em diversos países, tem sido observado o aumento da prevalência de obesidade e diabetes em associação com a presença da resistência insulínica. Nesse contexto, é útil a mensuração da resistência insulínica e da capacidade funcional das células-beta nos indivíduos. Os índices Homeostasis Model Assessment (HOMA) têm sido amplamente utilizados, representando uma das alternativas para avaliação desses parâmetros, principalmente por figurarem um método rápido, de fácil aplicação e de menor custo. Esta revisão discute sobre a origem e a evolução dos índices HOMA, bem como as particularidades do método, abordando aspectos relacionados à sua validação e aos pontos de corte existentes para sua interpretação.
Avaliação do metabolismo da glicose em pacientes acromegálicos antes e após tratamento com octreotide LAR
Authors: Correa Lívia L. , Taboada Giselle F. , Van Haute Flávia R. , Casini Alessandra F. , Balarini Giovanna A. , Vieira Neto Leonardo , Machado Evelyn de O. , Fontes Rosita , Andrade Cláudia C. de , Schrank Yolanda , Gadelha Mônica R.
Published: March 2008

OBJETIVO: Avaliar o metabolismo da glicose em pacientes acromegálicos antes e após o tratamento com octreotide LAR. PACIENTES E MÉTODOS: Este foi um estudo longitudinal e prospectivo com 30 pacientes do ambulatório de pesquisa em acromegalia do Serviço de Endocrinologia do Hospital Universitário Clementino Fraga Filho da Universidade Federal do Rio de Janeiro (HUCFF/UFRJ). Eles foram submetidos à avaliação clínica e laboratorial com dosagens de hormônio do crescimento (GH), fator de crescimento semelhante à insulina tipo I (IGF-I), insulina, pró-insulina, peptídeo C, hemoglobina glicosilada (HbA1c), proteína de ligação do IGF tipo 1 (IGFBP-1) e a um teste oral de tolerância à glicose (TOTG), antes e após seis meses de tratamento com octreotide LAR. Foi aplicado o teste dos postos sinalizados de Wilcoxon e o critério de determinação de significância adotado foi o nível de 5%. RESULTADOS: Encontraram-se 16 pacientes (54%) com tolerância normal à glicose, sete (23%) com intolerância à glicose e sete (23%) com diabetes melito (DM). Doze pacientes completaram os seis meses de tratamento, sendo que houve piora da tolerância à glicose em três e piora do controle glicêmico dos dois pacientes diabéticos. Houve aumento da circunferência abdominal (p = 0,03) e queda do GH (p = 0,04), % IGF-I acima do limite superior do valor de referência (%LSVR) (p = 0,001), insulina (p = 0,019), peptídeo C (p = 0,002) e do modelo de avaliação homeostática (HOMA-IR) (p = 0,039). CONCLUSÕES: Nesta série, o tratamento com octreotide LAR acarretou piora da tolerância à glicose em três pacientes não-diabéticos e piora do controle glicêmico em dois diabéticos, apesar da diminuição da resistência insulínica (RI).
Sobrepeso na adolescência de filhos de mães que tiveram distúrbios glicêmicos na gestação
Authors: Buzinaro Elizabeth Fernandes , Berchieri Carolina Bragiola , Haddad Adriana Lúcia Mendes , Padovani Carlos Roberto , Pimenta Walkyria de Paula
Published: March 2008

OBJETIVO: Observar se diferentes graus de hiperglicemia durante a gestação determinam diferentes freqüências de obesidade e suas comorbidades na adolescência dos filhos. MÉTODOS: Participaram 73 filhos distribuídos em três grupos, segundo a tolerância à glicose materna: G1 (n = 27) teste oral de tolerância à glicose (TOTG) e glicemia diária (GD) normais; G2 (n = 23) TOTG normal e GD elevada; G3 (n = 23) TOTG e GD alterados (diabetes melito ges tacional - DMG). Todos foram submetidos à avaliação clínica (antropometria), a um questionário (dados neonatais, hábitos alimentares) e a dosagem basal de glicose e perfil lipídico sérico. A comparação entre os grupos foi feita por análise de variância e teste de Goodman. RESULTADOS: As mães G3 apresentaram glicemia de jejum (GJ) e GD mais elevadas que as G2 e G1 (GJ: 98 ± 10 versus 83 ± 5 versus 78 ± 10 mg/dL; GD: 104 ± 12 versus 93 ± 7 versus 85 ± 9 mg/dL, respectivamente; p < 0,001). As mães G2 apresentaram GD mais elevada que as G1 (93 ± 7 versus 85 ± 9 mg/dL; p < 0,001). O peso de nascimento (PN) dos filhos G3 foi mais elevado que o dos G2 e G1 (3.667 ± 527 versus 3.167 ± 565 e 3.282 ± 401 g, respectivamente; p < 0,05). Os filhos G3 apresentaram maior freqüência de sobrepeso que os G1 (52,2 versus 14,8%; p < 0,05). CONCLUSÕES: Mães com DMG, apresentando GJ e GD elevadas, têm filhos com maior PN e maior freqüência de sobrepeso na adolescência. Esses filhos precisam ser acompanhados desde a infância.
Subclinical encephalopathy in chronic obstructive pulmonary disease
Authors: Lima Olga Maria Pinto de , Oliveira-Souza Ricardo de , Santos Omar da Rosa , Moraes Pedro Araújo de , Sá Leonardo Fontenelle de , Nascimento Osvaldo J.M.
Published: March 2008

BACKGROUND: Clinical and experimental evidence suggests that chronic obstructive pulmonary disease (COPD) is associated with a variety of mental symptoms that range from cognitive slowing to mental confusion and dementia. PURPOSE: To test the hypothesis that COPD leads to cognitive impairment in the absence of acute confusion or dementia. METHOD: The global cognitive status of 30 patients with COPD without dementia or acute confusion and 34 controls was assessed with a Brazilian version of the Mini-Mental State Exam (MMSE). RESULTS: The MMSE scores were significantly lower in the patient group and inversely related to the severity of COPD. This finding could not be attributed to age, education, gender, daytime sleepiness, hypoxemia, chronic tobacco use, or associated diseases such as diabetes, depression, high blood pressure or alcoholism. CONCLUSION: These results suggest the existence of a subclinical encephalopathy of COPD characterized by a subtle impairment of global cognitive ability.
Vasopressin serum levels and disorders of sodium and water balance in patients with severe brain injury
Authors: Cintra Eliane de Araújo , Araújo Sebastião , Quagliato Elizabeth M.A.B. , Castro Margaret de , Falcão Antônio Luiz Eiras , Dragosavac Desanka , Terzi Renato G.G.
Published: March 2008

BACKGROUND: Disorders of water and sodium balance are frequently seen in patients with severe brain injury (SBI), and may worsen their prognosis. PURPOSE: To evaluate vasopressin (AVP) serum levels and sodium and water balance disorders during the first week post-injury in patients with SBI. METHOD: Thirty-six adult patients with SBI (admission Glasgow Coma Scale score < 8) and an estimated time of injury < 72 hours were prospectively studied. Clinical and laboratory data were recorded and AVP was measured in venous blood samples collected on the 1st, 2nd, 3rd and 5th days following inclusion. RESULTS: AVP serum levels remained within the normal range in SBI patients (either traumatic or non-traumatic), although tended to be greater in non-survivor than in survivor patients (p=0.025 at 3rd day). In-hospital mortality was 43% (15/36), and serum sodium and plasma osmolality variabilities were greater in non-survivor than in survivor patients during the observation period (p<0.001). CONCLUSION: AVP serum levels remained within the normal range values in these SBI patients, but those who died have shown higher incidence of abnormal sodium and water balance during the first week post-injury.