Hyla multifasciata

Number of Pages: 4Integrative BiologyGeological Science

Leptodactylus cunicularius

Number of Pages: 5Integrative BiologyGeological Science

Leptodactylus syphax

Number of Pages: 9Integrative BiologyGeological Science

The hidden history of humming frogs

In the depths of Brazil’s Atlantic Forest, researchers are battling to identify species before they are lost for good. Dr Rafael O de Sá, Professor of Biology at the University of Richmond, Virginia, USA, specialises in a group known as the ‘narrow-mouthed frogs’ and has already found four species new to science

Leptodactylus pentadactylus

Number of Pages: 48Integrative BiologyGeological Science

Leptodactylus savagei

Number of Pages: 19Integrative BiologyGeological Science

Tourism and real estate markets

The short-term renting market has expanded substantially in the recent years due the appearance of digital platforms which link the demand and the supply sides. As a result, many cities have allocated a high share of their lodgings to holiday homes, pressuring long-term housing markets. This work tackles this unexplored issue, presenting the case of Portugal with data from Airbnb and finds that a higher concentration of holiday homes in a location leads to higher housing prices. This effect is particularly localized to the historical centers of Lisbon and Porto

The Biology of Xenopus by R. C. Tinsley and H. C. Kobel

The Biology of Xenopus presents a summary of current knowledge about a single genus resulting from a symposium held at the Zoological Society of London in September 1992. This approach to summarizing available information has also been taken for other taxa, such as Atelopus (Lotters, 1996). However, the task of compiling data for Xenopus is enormous relative to any other amphibian group, because Xenopus laevis has become a model system for molecular and development research (Cannatella and de Sa, 1993). Unfortunately, most of our knowledge of Xenopus is biased toward this single species. There are about 20 recognized species of Xenopus, most of which have been described in the last two decades. Tinsley and Kobel have assembled contributions from 26 authors into 22 chapters covering a wide range of information. The chapters vary in focus, extent, and depth of the material covered

Laser powder bed fusion of INCONEL® 718: optimization of process parameters and residual stress analysis before and after heat treatment

Metals Additive Manufacturing (AM) is a “flourishing” technology, developing fast and successfully. Laser Powder Bed Fusion (LPBF) is among the most used metals AM processes in industry. Inconel® 718 (IN718) is a nickel-based superalloy that maintains its exceptional properties at high and low temperatures, thereby, it is a material commonly used to fabricate high performance components. The purpose of this work is to study the residual stress (RS) evolution of IN718 parts fabricated by LPBF, before and after heat treatment. Firstly, specimens with different combinations of parameters were fabricated to select the optimal LPBF process parameters. With the results from that part of the work, the influence of the individual process parameters on the porosity was studied. Then, new specimens were fabricated with the selected parameters and the RS analyzed by the hole-drilling strain-gage method, in as-built, solution annealed (SA) and SA plus double-aged (DA) conditions. It was concluded that increasing the scanning speed contributes to the reduction of the porosity. Also, for lower scanning speeds, 400 mm/s and lower, a hatching distance of 0.13 mm was defined as optimal. For higher scanning speeds, 600 and 800 mm/s, no relevant influence of the hatching distance, from 0.05 to 0.11 mm, on the porosity was observed. Laser power and layer thickness were not studied. Larger pores were found in specimens with higher porosity. Also, the specimens with higher porosity presented irregular pores and with lower porosity presented spherical-like pores. Regarding the RS evolution, as-built top surface presented uniform RS distribution of approximately 400 MPa. Lateral surface presented anisotropic distribution, with RS magnitudes of 600 to 800 MPa in build direction and 200 to 300 MPa horizontally. After the SA heat treatment, the RS decrease greatly to values between 50 – 200 MPa. Series of carbides were found at the grain boundaries, which were attributed as the cause for oscillations in the RS profile. SA plus DA condition presented RS between 10 to 50 MPa. Heat-treated specimens revealed compressive RS at immediately near the surface.A fabricação aditiva (FA) de metais é uma tecnologia “florescente”, em rápido desenvolvimento e com sucesso. Fusão a laser em leito de pó (LPBF) está entre os processos de FA de metais mais usados na indústria. Inconel® 718 é uma superliga à base de Nickel, que mantém as suas propriedades excecionais a altas e baixas temperaturas, desse modo, é comummente usada para produzir componentes de alto desempenho. O objetivo deste trabalho é estudar a evolução das tensões residuais (TR) de partes produzidas por LPBF, antes e pós tratamento térmico. Primeiramente, produziram-se amostras com diferentes combinações de parâmetros do processo LPBF para selecionar os melhores parâmetros. Com os resultados obtidos dessa parte do trabalho, foi estudada a influência na porosidade dos diferentes parâmetros. Então, produziram-se novas amostras com os parâmetros selecionados e foram analisadas as TR pelo método do furo cego incremental, nas condições: “as-built”, recozido (SA) e SA mais envelhecimento duplo (DA). Concluiu-se que o aumento da velocidade de varredura contribuí para a redução da porosidade. Também, para velocidades mais baixas, 400 mm/s e abaixo, a distância entre passagens de 0.13 mm foi definida como ótima. Para velocidades mais altas, 600 mm/s e 800 mm/s, a influência da distância entre passagens, de 0.05 a 0.11 mm, na porosidade é desprezível. A potência do laser e a espessura das camadas não foram estudados. Poros maiores foram observados nas amostras com maior porosidade. Também, as amostras com maior porosidade exibiram poros irregulares, e com menor porosidade poros esféricos. Em relação à evolução das TR, a face superior “as-built” apresentou uma distribuição das TR uniforme de aproximadamente 400 MPa. A face lateral apresentou distribuição anisotrópica, com TR entre 600 e 800 MPa na direção de deposição, e entre 200 e 300 MPa horizontalmente. Nas amostras SA, as TR reduziram substancialmente para valores entre 50 e 200 MPa. Foram detetados conjuntos de carbonetos, aos quais se atribuiu a ocorrência de oscilações no perfil das TR. A condição SA mais DA apresentou TR entre 10 e 50 MPa. As amostras tratadas termicamente revelaram TR à compressão bem próximo da superfície

Los anfibios del Monumento Natural Barro Colorado, Parque Nacional Soberania y areas adyacentes

This book focuses on the batrachofauna of Barro Colorado Nature Monument. Soberania National Park and adjacent areas. It complements other recent publications on Neotropical amphibians such as those by Rodriguez and Duellman ( 1994) on Peru, Achaval and Olmos (1995) on Uruguay, and Meyer and Foster (1996) on Belize. The goal of these books is to reach a wider audience than the more technical batrachofaunal summaries-e.g., Frogs of Boracéia (Heyer 1990). Amphibians of Argentina (Cei 1985), and Frogs of the Genus Eleutherodactylus in Western Ecuador (Lynch and Duellman 1997). These geographically focused guides are especially useful to students, amateur biologists, and to the increasingly omnipresent ecotourists roaming the Neotropics. However, they are also valuable tools for beginning biology graduate students who are looking for an “organism” to work on, as well as to the trained herpetologist visiting an area for the first time