Problemas atuais da juticultura amazônica.

No presente trabalho, os autores procuraram expor os problemas atuais que entravam o desenvolvimento da juticultura amazônica, ressaltando a importância marcante da produção das fibras desta tiliácea como fonte da manutenção do mercado interno brasileiro de matéria prima necessária ao abastecimento do parque nacional de aniagem. Os problemas considerados, no trabalho em questão, foram: 1) problemas de ordem agrícola, 2) problemas de ordem sócio-econômica. Procurou-se, também, de forma sintética, expor a situação do mercado nacional e as possibilidades de exportação. Como conclusão, os autores admitem a necessidade urgente e prioritária de se estimular econômicamente o juticultor a fim de que se possa posteriormente mostrar que a quantidade e qualidade do produto depende em grande parte dos problemas culturais e tecnológicos.Separata da Pesquisa Agropecuária Brasileira, v. 1, p. 1-6, 1966

Design and characterization of a biomimetic composite inspired to human bone

Many biological materials are generally considered composites, made of relatively weak constituents and with a hierarchical arrangement, resulting in outstanding mechanical properties, difficult to be reached in man-made materials. An example is human bone, whose hierarchical structure strongly affects its mechanical performance, toughness in particular, by activating different toughening mechanisms occurring at different length scales. At microscale, the principal toughening mechanism occurring in bone is crack deflection. Here, we study the structure of bone and we focus on the role of the microstructure on its fracture behaviour, with the goal of mimicking it in a new composite. We select the main structural features, the osteons, which play a crucial role in leading to crack deflection, and we reproduce them in a synthetic composite. The paper describes the design, manufacturing and characterization of a newly designed composite, whose structure is inspired to the Haversian structure of cortical bone, and that of a classic laminate developed for comparative reasons. We conclude with a critical discussion on the results of the mechanical tests carried out on the new composite and on the comparative laminate, highlighting strengths and shortcomings of the new biomimetic material

Mechanics of collagen-hydroxyapatite model nanocomposites

Bone is a hierarchical biological composite made of a mineral component (hydroxyapatite crystals) and anorganic part (collagen molecules). Small-scale deformation phenomena that occur in bone are thought tohave a significant influence on the large scale behavior of this material. However, the nanoscale behaviorof collagen–hydroxyapatite composites is still relatively poorly understood. Here we present a molec-ular dynamics study of a bone model nanocomposite that consist of a simple sandwich structure ofcollagen and hydroxyapatite, exposed to shear-dominated loading. We assess how the geometry of thecomposite enhances the strength, stiffness and capacity to dissipate mechanical energy. We find that H-bonds between collagen and hydroxyapatite play an important role in increasing the resistance againstcatastrophic failure by increasing the fracture energy through a stick-slip mechanism

Effect of delamination on the fatigue life of GFRP: A thermographic and numerical study

Delamination is the major failure mechanism in composite laminates and eventually leads to material failure. An early-detection and a better understanding of this phenomenon, through non-destructive assessment, can provide a proper in situ repair and allow a better evaluation of its effects on residual strength of lightweight structural components. Here we adopt a joint numerical-experimental approach to study the effect of delamination on the fatigue life of glass/epoxy composites. To identify and monitor the evolution of the delamination during loading, we carried out stepwise cyclic tests coupled with IR-thermography on both undamaged and artificially-damaged samples. The outcome of the tests shows that IR-thermography is able to identify a threshold stress, named damage stress ?D, which is correlated to the damage initiation and the fatigue performance of the composite. Additionally, we performed FE-simulations, implementing the delamination by cohesive elements. Such models, calibrated on the basis of the experimental fatigue results, can provide a tool to assess the effect of parameters, such as the delamination size and location and composite stacking sequence, on the residual strength and fatigue life of the composite material

SEM Evaluation of the Hybrid Layer of Two Universal Adhesives on Sound and DI Type II Affected Dentin

Universal nanofilled adhesives were recently introduced in restorative dentistry to simplify clinical procedures and improve adhesion in different clinical situation. This study investigated the effectiveness of two universal adhesives on both sound and dentinogenesis imperfecta type II (DI-II)-affected teeth. To evaluate the effectiveness of adhesion on both sound and DI-II-affected teeth, four samples, two sound extracted molars and two extracted molars affected by DI-II were selected. Coronal enamel and dentin were exposed, and the samples were used for testing two different universal adhesives, Universal Bond (Tokuyama) and All-Bond Universal (Bisco). After the adhesive procedures, the samples were stored in saline at room temperature for one week prior to SEM investigation for the interfacial bonding layer. The samples were longitudinally sectioned into two parts, obtaining two sections for the evaluation of the adhesive interface to the SEM. The SEM-morphology of the hybrid layer on the enamel was similar for the two universal adhesives tested. The study of the hybrid layer on sound dentin confirmed the great versatility of All-Bond Universal and Universal Bond adhesives in managing adhesion even on pathological dental substrates. Both universal adhesives tested showed encouraging results on DI-II-affected dentin, creating an effective hybrid layer even on the atubular and less mineralized altered dentin

Recent increasing frequency of compound summer drought and heatwaves in Southeast Brazil

An increase in the frequency of extremely hot and dry events has been experienced over the past few decades in South America, and particularly in Brazil. Regional climate change projections indicate a future aggravation of this trend. However, a comprehensive characterization of drought and heatwave compound events, as well as of the main land-atmosphere mechanisms involved, is still lacking for most of South America. This study aims to fill this gap, assessing for the first time the historical evolution of compound summer drought and heatwave events for the heavily populated region of Southeast Brazil and for the period of 1980-2018. The main goal is to undertake a detailed analysis of the surface and synoptic conditions, as well as of the land-atmosphere coupling processes that led to the occurrence of individual and compound dry and hot extremes. Our results confirm that the Sao Paulo, Rio de Janeiro and Minas Gerais states have recorded pronounced and statistically significant increases in the number of compound summer drought and heatwave episodes. In particular, the last decade was characterized by two austral summer seasons (2013/14 and 2014/15) with outstanding concurrent drought and heatwave conditions stemmed by severe precipitation deficits and a higher-than-average occurrence of blocking patterns. As result of these land and atmosphere conditions, a high coupling (water-limited) regime was imposed, promoting the re-amplification of hot spells that resulted in mega heatwave episodes. Our findings reveal a substantial contribution of persistent dry conditions to heatwave episodes, highlighting the vulnerability of the region to climate change

Optimization of organotypic cultures of mouse spleen for staining and functional assays

By preserving cell viability and three-dimensional localization, organotypic culture stands out among the newest frontiers of cell culture. It has been successfully employed for the study of diseases among which neoplasias, where tumoral cells take advantage of the surrounding stroma to promote their own proliferation and survival. Organotypic culture acquires major importance in the context of the immune system, whose cells cross-talk in a complex and dynamic fashion to elicit productive responses. However, organotypic culture has been as yet poorly developed for and applied to primary and secondary lymphoid organs. Here we describe in detail the development of a protocol suitable for the efficient cutting of mouse spleen, which overcomes technical difficulties related to the peculiar organ texture, and for optimized organotypic culture of spleen slices. Moreover, we used microscopy, immunofluorescence, flow cytometry and qRT-PCR to demonstrate that the majority of cells residing in spleen slices remain alive and maintain their original location in the organ architecture for several days after cutting. The development of this protocol represents a significant technical improvement in the study of the lymphoid microenvironment in both physiological and pathological conditions involving the immune system

Effects of Drought on Mortality in Macro Urban Areas of Brazil Between 2000 and 2019.

A significant fraction of Brazil's population has been exposed to drought in recent years, a situation that is expected to worsen in frequency and intensity due to climate change. This constitutes a current key environmental health concern, especially in densely urban areas such as several big cities and suburbs. For the first time, a comprehensive assessment of the short-term drought effects on weekly non-external, circulatory, and respiratory mortality was conducted in 13 major Brazilian macro-urban areas across 2000-2019. We applied quasi-Poisson regression models adjusted by temperature to explore the association between drought (defined by the Standardized Precipitation-Evapotranspiration Index) and the different mortality causes by location, sex, and age groups. We next conducted multivariate meta-analytical models separated by cause and population groups to pool individual estimates. Impact measures were expressed as the attributable fractions among the exposed population, from the relative risks (RRs). Overall, a positive association between drought exposure and mortality was evidenced in the total population, with RRs varying from 1.003 [95% CI: 0.999-1.007] to 1.010 [0.996-1.025] for non-external mortality related to moderate and extreme drought conditions, from 1.002 [0.997-1.007] to 1.008 [0.991-1.026] for circulatory mortality, and from 1.004 [0.995-1.013] to 1.013 [0.983-1.044] for respiratory mortality. Females, children, and the elderly population were the most affected groups, for whom a robust positive association was found. The study also revealed high heterogeneity between locations. We suggest that policies and action plans should pay special attention to vulnerable populations to promote efficient measures to reduce vulnerability and risks associated with droughts

Repetition of estrus is the most frequent reproductive problem after breeding in dairy cattle from Rio de Janeiro, Brazil.

Reproductive efficiency is one of the key elements for any milk production system to be successful. In this regard, reproductive management must be planned properly and the identification of the main reproductive disorders that affect the herd is primordial for decisionmaking. The aim of the present study was to identify the main reproductive problems that affect dairy herds on Rio de Janeiro (RJ), Brazil. Data regarding breed, age, reproductive disorder occurrence, and breeding system were individually collected from dairy cows raised at 25 farms located at RJ. The occurrence of reproductive disorders was reported in 37% of the studied animals. Estrous repetition (76.2%) and abortion (15.6%) were the most frequent reproductive problems reported. Estrous repetition was more common in older animals (>6 years old). However, an association between abortion and age of animal was not observed, nor an association between breeding system and occurrence of abortion. The present results demonstrated that estrous repetition is the main obstacle to the reproductive efficiency in dairy herds at RJ, and that the replace of older cows by heifers is an important point within reproductive management of a dairy herd