Comment on “Characterization of Interfacial Properties in Fiber-Reinforced Cementitious Composites”

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65561/1/j.1151-2916.1993.tb03959.x.pd

Dendrochronological approach to the radial growth of okoume (Congo)

La croissance radiale de 4 sections d'okoumé du Congo provenant de 4 arbres différents est analysée. La présence dans la région d'au moins une saison sèche marquée permet de définir des cernes de croissance annuels. Ils sont mesurés et les courbes des largeurs de cernes sont confrontées de manière graphique afin de vérifier que l'année de formation attribuée à chaque cerne est exacte (interdatation). Le synchronisme est mauvais lorsque les courbes appartiennent à des arbres différents. Pour lever le doute quant à la validité de la délimitation des cernes annuels, une confrontation avec les enregistrements pluviométriques de Pointe Noire est tentée. Le résultat du test est positif et les limites de cernes établies au début de l'étude sont maintenues. L'approche dendrochronologique sur une espèce telle que l'okoumé est donc possible mais une vérification de l'interdatation par confrontation avec des données climatologiuqes est indispensable. Ce type d'approche conduisant à une datation absolue des cernes peut être d'un grand intérêt en écologie tropicale : elle permet en particulier de replacer les analyses biogéochimiques des cernes dans un cadre chronologique exact, ou encore d'apprécier la vitesse de progression des lisières forestières. (Résumé d'auteur

Robust Estimation for Linear Panel Data Models

In different fields of applications including, but not limited to, behavioral, environmental, medical sciences and econometrics, the use of panel data regression models has become increasingly popular as a general framework for making meaningful statistical inferences. However, when the ordinary least squares (OLS) method is used to estimate the model parameters, presence of outliers may significantly alter the adequacy of such models by producing biased and inefficient estimates. In this work we propose a new, weighted likelihood based robust estimation procedure for linear panel data models with fixed and random effects. The finite sample performances of the proposed estimators have been illustrated through an extensive simulation study as well as with an application to blood pressure data set. Our thorough study demonstrates that the proposed estimators show significantly better performances over the traditional methods in the presence of outliers and produce competitive results to the OLS based estimates when no outliers are present in the data set

Vegetation trend after roller chopping and native grass seeding in La Rioja

In La Rioja plains, roller chopping and buffelgrass seeding is a widespread strategy for forage rec uperation of deg raded rangelands. Native grass species seeding arises a s apossible alternative strategy. The purpose of this study was to evaluate the medium time impacts of roller chopping and roller chopping + native species seeding on grass forage yield, cover and density and woody cover in degraded sites of critic environments of the mentioned region. Four treatments were evaluated, T0=control, T1=Roller chopping, T2= Roller chopping+Trichloris crinite (Lag.) Parodi seeding and T3= Roller chopping+Trichloris crinite (Lag.) Parodi and Pappophorum vaginatum Phil. seeding on three degraded environments. T1, T2 y T3 produced important increments (p<0.05) on grass forage grass, total perennial grass cover and density respect to T0. Initial impacts of roller chopping with and without seeding produced 68±13% diminution of woody cover with an annual recuperation rate of 7±2%. Results of this study suggest that, especially roller chopping + native grass seeding would be a promising alternative strategy for rapid recuperation of grass forage capacity of degraded areas at La Rioja plains.En Los Llanos de La Rioja, el rolado y siembra de buffel (Cenchrus ciliaris L.) es una estrategia difundida para recuperar la p roductividad de aéreas altamente degradadas. La siembra de especies nativas surge como una posible estrategia alternativa. El objetivo de este estudio fue evaluar el impacto a mediano plazo del rolado y rolado + siembra de especies nativas sobre la producción de forraje, eficiencia de uso de las precipitaciones, densidad y cobertura de gramíneas y cobertura de leñosas en sitios degradados de ambientes críticos de la región. Se evaluaron 4 tratamientos T0=testigo, T1=Rolado, T2= Rolado+ siembra de Trichloris crinita (Lag.) Parodi y T3=Rolado+siembra de Tricholris crinita y Pappophorum vaginatum Phil. en tres ambientes degradados. T1, T2 y T3 produjeron importantes incrementos (p<0,05) en la producción de forraje, la densidad y cobertura de gramíneas perennes respecto a T0. El impacto del rolado con o sin siembra produjo una disminución inicial del 68±13% de la cobertura de leñosas, y una posterior tasa de recuperación anual del 7±2%. Los resultados de este estudio sugieren que especialmente el rolado+siembra de especies nativas sería una estrategia alternativa promisoria para recuperar rápidamente la capacidad forrajera del estrato herbáceo en áreas degradas de ambientes críticos de Los Llanos de La Rioja

Estudo experimental da ação dos anti-inflamatórios não hormonais inibidores seletivos da ciclooxigenase 2 (COX-2) e anti-inflamatórios tradicionais na regeneração óssea

OBJECTIVE: The aim of this study is to compare the effects of traditional nonsteroidal anti-inflammatory drugs with nonsteroidal anti-inflammatory drugs that are selective cyclooxygenase-2 (COX-2) inhibitors in the process of bone regeneration in a rat model. MATERIALS AND METHODS: Forty-four Wistar strain rats were subjected to osteotomy of the right femur and randomly divided into 3 groups according to the drug to be given (diclofenac, rofecoxib, or placebo). Each group was divided into 2 subgroups according to the time to euthanasia after the surgery. The animals of Subgroup 1 were submitted to euthanasia 2 weeks after surgery, and those of Subgroup 2, underwent euthanasia 4 weeks after surgery. Radiographic examinations and bone callus histomorphometry were analyzed. RESULTS: No intergroup statistical difference was found in the bone callus area or in bone formation area 2 and 4 weeks after surgery. Intra-group analysis concerning the bone neoformation area inside the callus showed a significant difference within the diclofenac group, which presented less tissue. CONCLUSIONS: Fracture consolidation in Wistar rats occurs within less than 2 weeks, and the use of nonsteroidal anti-inflammatory drugs does not significantly influence this process.OBJETIVO: Comparar os efeitos do uso de antiinflamatórios não-esteróides tradicionais (AINES) e AINES que são inibidores seletivos da ciclooxigenase-2 (COX-2), no processo de regeneração óssea em ratos. MATERIAL E MÉTODO: Quarenta e quatro ratos da linhagem Wistar submetidos a osteotomia do femur direito e divididos em três grupos, conforme o medicamento que receberam (diclofenaco, rofecoxib e placebo). Cada grupo foi dividido em dois subgrupos, conforme o tempo até o sacrifício, após a cirurgia. Os animais do subgrupo 1 foram sacrificados duas semanas após a cirurgia e os do subgrupo 2, quatro semanas após a cirurgia. Foram analisados exames radiográficos e a histomorfometria do calo ósseo. RESULTADOS: Não foram encontradas diferenças estatísticas na área do calo ósseo 2 e 4 semanas após a cirurgia. No que se refere à área de neoformação óssea dentro do calo, observou-se diferença estatisticamente significante apenas dentro do grupo do diclofenaco, que apresentou menos tecido. CONCLUSÕES: A consolidação da fratura em ratos Wistar ocorre dentro de 2 semanas e o uso de antiinflamatórios não-esteróides não influi de forma significante neste processo

Compositional boundary layers trigger liquid unmixing in a basaltic crystal mush

Abstract: The separation of immiscible liquids has significant implications for magma evolution and the formation of magmatic ore deposits. We combine high-resolution imaging and electron probe microanalysis with the first use of atom probe tomography on tholeiitic basaltic glass from Hawaii, the Snake River Plain, and Iceland, to investigate the onset of unmixing of basaltic liquids into Fe-rich and Si-rich conjugates. We examine the relationships between unmixing and crystal growth, and the evolution of a nanoemulsion in a crystal mush. We identify the previously unrecognised role played by compositional boundary layers in promoting unmixing around growing crystals at melt-crystal interfaces. Our findings have important implications for the formation of immiscible liquid in a crystal mush, the interpretations of compositional zoning in crystals, and the role of liquid immiscibility in controlling magma physical properties

Efecto del rolado y siembra de buffel sobre la evolución del estrato graminoso en un arbustal degradado del Chaco árido

In Argentinean Chaco Arid region, rolling and buffelgrass seeding is widespread. In this region, information related to its short and medium time effects on vegetation attributes is available. The purpose of this study was to evaluate the long time impacts (10 years) of roller chopping and buffelgrass seeding on grass yield, precipitation use efficiency and cover in a degraded site of the mentioned region. The treatments were: T0 = No roller chopping-seeding (Control) and T1= Roller chopping+buffelgrass seeding. Forage grass yield and precipitation use efficiency tended to be higher in T1 than in T0 during the evaluation period. Forage grass yield increment in T1 was highly associated to increment in total perennial grass cover (R2=91%), mainly due to buffelgrass cover (R2=76%). In T1, native perennial grass cover showed a negative lineal tendency in relation to years. Annual native grass, perennial native grass, total perennial grass and buffelgras covers followed a quadratic tendency related to years. Results of this study suggest that roller chopping and simultaneous buffelgrass seeding is, from a point of view of animal production, an efficient strategy for rapid restoration of grass cover and grazing capacity of degraded areas and that its effects maintains in the long time.En el Chaco Árido, el rolado y siembra de buffel (Cenchrus ciliaris var. Texas 4464) está ampliamente difundido, contándose solo con información de los efectos a corto y mediano plazo de la aplicación de esta técnica sobre atributos de vegetación. El objetivo fue evaluar el impacto a largo plazo (10 años) del rolado y siembra de buffel sobre la producción de materia seca acumulada, eficiencia del uso de la precipitación y cobertura de gramíneas en un ambiente degradado de la región. Los tratamientos fueron: T0 = Sin rolado ni siembra (Testigo) y T1= Rolado + siembra simultanea de buffel. La producción de forraje y la eficiencia de uso de la precipitación tendieron a ser mayores en T1 respecto a T0, en todo el período evaluado. El incremento de la producción en T1 estuvo altamente relacionado al incremento en la cobertura de pastos perennes totales (R2=91%), principalmente a la cobertura de buffel (R2=76%). En T1, la cobertura de pastos nativos perennes tendió a disminuir en el tiempo, mientras que la cobertura de pastos nativos anuales, la de pastos perennes totales y la de buffel, presentaron una tendencia cuadrática. Estos resultados sugieren que el rolado y siembra de buffel, desde un punto de vista de la producción animal, es una eficiente estrategia para recuperar la capacidad de forrajera de sitios degradados del Chaco Árido

Using standardized indicators to analyse dry/wet conditions and their application for monitoring drought/floods: A study in the Logone catchment, Lake Chad basin

The standardized precipitation index (SPI) and standardized streamflow index (SSI) were used to analyse dry/wet conditions in the Logone catchment over a 50-year period (1951–2000). The SPI analysis at different time scales showed several meteorological drought events ranging from moderate to extreme; and SSI analysis showed that wetter conditions prevailed in the catchment from 1950 to 1970 interspersed with a few hydrological drought events. Overall, the results indicate that both the Sudano and Sahelian zones are equally prone to droughts and floods. However, the Sudano zone is more sensitive to drier conditions, while the Sahelian zone is sensitive to wetter conditions. Correlation analysis between SPI and SSI at multiple time scales revealed that the catchment has a low response to rainfall at short time scales, though this progressively changed as the time scale increased, with strong correlations (≥0.70) observed after 12 months. Analysis using individual monthly series showed that the response time reduced to 3 months in October

No FeS layer in Mercury? Evidence from Ti/Al measured by MESSENGER

In this study we investigate the likeliness of the existence of an iron sulfide layer (FeS matte) at the core-mantle boundary (CMB) of Mercury by comparing new chemical surface data obtained by the X-ray Spectrometer onboard the MESSENGER spacecraft with geochemical models supported by high-pressure experiments under reducing conditions. We present a new data set consisting of 233 Ti/Si measurements, which combined with Al/Si data show that Mercury's surface has a slightly subchondritic Ti/Al ratio of 0.035 ± 0.008. Multiphase equilibria experiments show that at the conditions of Mercury's core formation, Ti is chalcophile but not siderophile, making Ti a useful tracer of sulfide melt formation. We parameterize and use our partitioning data in a model to calculate the relative depletion of Ti in the bulk silicate fraction of Mercury as a function of a putative FeS layer thickness. By comparing the model results and surface elemental data we show that Mercury most likely does not have a FeS layer, and in case it would have one, it would only be a few kilometers thick (<13km). We also show that Mercury's metallic Fe(Si) core cannot contain more than ∼1.5 wt.% sulfur and that the formation of this core under reducing conditions is responsible for the slightly subchondritic Ti/Al ratio of Mercury's surface. © 2020 Elsevier B.V