TEM investigation of YBa2Cu3O7 thin films on SrTiO3 bicrystals

YBa2Cu3O7 films in c-axis orientation on bicrystalline SrTiO3 substrates are investigated by TEM. The films and the substrates are examined in cross-section and in plane view. The grain boundary of the bicrystal substrate contains (110) faceted voids, but is otherwise straight on a nanometer scale. Contrary to this, the film grain boundary is not straight grain boundary can be up to 100 nm for a 100 nm thick film. The deviation from the intended position of the YBCO grain boundary can already occur at the film/substrate interface where it can be as much as ±50 nm

A HREM study of the atomic structure and the growth mechanism of the YBa2Cu3O7/YSZ interface

The interface between yttria-stabilized zirconia (YSZ) substrate and YBa2Cu3O7 (YBCO) film was studied by high-resolution electron microscopy. In all specimens we have observed an intermediate layer of BaZrO3 located between the substrate YSZ and YBCO. The BaZrO3 layer is composed of almost equally aligned domains being 4¿8 nm in the lateral directions. Reaction products such as Y and Cu oxides were never observed in or close to the BaZrO3 reaction layer but they do occur in the YBCO film. The stacking sequence of BaZrO3/YBCO is predominantly (BaZrO3)-ZrO2-BaO/CuO-BaO-(YBCO) with CuO layer as the beginning YBCO layer. Sometimes a stacking sequence (BaZrO3)-ZrO2-BaO/BaO-CuO2-(YBCO) with a BaO layer as the beginning YBCO layer was observed. This stacking is related to a dislocation with Burgers vector a'/2 [111], where a' = 0.42 nm is the lattice constant of the cubic BaZrO3. Three main epitaxial relations (0°, 45°, 9°) between YSZ and YBCO were observed. These can be explained by near-coincidence site lattices ¿ = 25, ¿ = 49 and ¿ = 13 (for a YSZ substrate). Usually the (001) plane of the YBCO film is parallel to the (001) plane of the BaZrO3 layer and parallel to the substrate surface. In case YBCO is grown on an inclined YSZ substrate, the (001) plane of the YBCO film is parallel to the substrate surface and thus not parallel to the (001) plane of the YSZ substrate

Microstructures of ramp-edge YBa2Cu3Ox/PrBa2Cu3Ox/YBa2Cu3Ox Josephson junctions on different substrates

Ramp-edge YBa2Cu3/PrBa2Cu3Ox/YBa2Cu3Ox Josephson junctions with PrBa2Cu3Ox (PrBCO) or SrTiO3 as a separating layer on different kinds of substrate have been studied by high-resolution electron microscopy. The bottom YBa2Cu3Ox (YBCO) layer and the separating layer (PrBCO or SrTiO3) were epitaxially c oriented, irrespective of the substrate (yttria stabilized zirconia (YSZ), SrTiO3 or NdGaO3, all in (001) orientation). The use of ion milling in the manufacturing of Josephson junctions was found to yield smooth slopes with an angle of about 20°. The Josephson junction was facing away from the beam direction was found to have a dimple in the substrate near the base of the junction. The barrier layers were observed to have a homogeneous thickness. These layers were as the top YBCO layers were oriented with their c-axis perpendicular to (001) plane of the substrate for perovskite substrates and perpendicular to the surface for YSZ substrates. In the case of a YSZ substrate, the dimple in the substrate as well as the slope of the substrate close to the base of the junction were found to lead to small angle grain boundaries in the YBCO film as well as randomly oriented YBCO grains, which results in a poor ramp-edge junction. In the case of SrTiO3 or NdGaO3 substrate, all components of the device were fully epitaxial, thus resulting in good ramp-edge junctions

The atomic structure of large-angle grain boundaries Σ5\Sigma 5 and Σ13\Sigma 13 in YBa2Cu3O7−δ{\rm YBa_2Cu_3O_{7-\delta}} and their transport properties

We present the results of a computer simulation of the atomic structures of large-angle symmetrical tilt grain boundaries (GBs) $\Sigma 5$ (misorientation angles \q{36.87}{^{\circ}} and \q{53.13}{^{\circ}}), $\Sigma 13$ (misorientation angles \q{22.62}{^{\circ}} and \q{67.38}{^{\circ}}). The critical strain level $\epsilon_{crit}$ criterion (phenomenological criterion) of Chisholm and Pennycook is applied to the computer simulation data to estimate the thickness of the nonsuperconducting layer ${\rm h_n}$ enveloping the grain boundaries. The ${\rm h_n}$ is estimated also by a bond-valence-sum analysis. We propose that the phenomenological criterion is caused by the change of the bond lengths and valence of atoms in the GB structure on the atomic level. The macro- and micro- approaches become consistent if the $\epsilon_{crit}$ is greater than in earlier papers. It is predicted that the symmetrical tilt GB $\Sigma5$ \theta = \q{53.13}{^{\circ}} should demonstrate a largest critical current across the boundary.Comment: 10 pages, 2 figure

Denial of long-term issues with agriculture on tropical peatlands will have devastating consequences

Letter to the Editor

Assessing habitat requirements of Asian tapir in forestry landscapes: Implications for conservation

The iconic large-bodied Asian tapir (Tapirus indicus) is endemic to Southeast Asia and is currently listed as endangered. To date, little is known about how tapir respond to habitat fragmentation in forestry landscapes. This study aimed to assess tapir occurrence in eight forestry reserves, outside the main protected areas in Peninsular Malaysia, using non-intrusive camera trapping methods. These reserves include logged or unlogged, contiguous or fragmented, peat swamp forest and lowland dipterocarp forest. Out of 345 camera-trapping locations, over six years, we detected tapir at 39 locations, represented by 960 images. An assessment of vegetation structure and landscape variables was conducted to identify the key factors associated with their tapir presence. We found that tapir occurrence significantly increased with the number of trees with a DBH of 5–45 cm, number of saplings, percentage of canopy cover, trees with a DBH of more than 45 cm and distance from the nearest road. While, tapir detection decreased with the number of dead fallen trees and number of palms. Our data highlights the importance of conserving these remaining fragmented forest reserves, particularly peat swamp forests and ways in which suitable habitat conditions may be created to support tapir populations. We conclude by discussing intervention approaches such as relocation, reintroduction and restocking and restoration to improve the structural attributes of vegetation utilised by tapirs

Learning to love the world's most hated crop

The 2019 Inter-governmental Panel (IPCC) Report on Climate Change and Land highlighted the urgency and scale of the environmental impact from human-induced landscape change. Palm oil has historically had a particularly negative reputation for driving deforestation, biodiversity loss, greenhouse gas emissions, social exploitation and damaging health. In the eyes of many in the West, it is regarded as the world’s most hated crop. However, palm is highly productive compared with other crops and produces 40% of the worlds edible oil from only 5% of vegetable oil producing land and 0.4% of agricultural land in total. It has the potential to meet future demand for oil with minimum additional environmental and climate impact compared with other sources of vegetable oil. The related high value density has the potential to move millions of vulnerable smallholder farmers out of poverty. Given the conclusions of the IPCC Climate and Land Report, it is therefore important to re-examine the crop’s reputation in light of the accumulated evidence and to properly understand the full impacts across the environmental, health, social and economic factors. We present a comprehensive review of the benefits and risks of the crop across these dimensions and provide a new synthesis. We conclude that while oil palm has had a significant negative impact on habitat and biodiversity, it plays a minor role compared with poaching, illegal logging and threats from climate change. There are important opportunities for the industry to reverse this damage. Its reputation for negative health impacts are not backed up by the scientific evidence and indeed there may be health benefits from substituting some oils in the diet with oil palm. Positive social and economic impacts are most obvious in areas where proper market-led economies are in place, but there can be significant negative social impacts in less developed areas. We conclude that much of the reputation of palm oil is not based on a balanced interpretation of the scientific evidence. Provided future development is zero deforestation, does not occur on peat, uses methane capture technology at the mills, empowers indigenous smallholders and supports the regeneration of secondary forest, we conclude that oil palm can be the most environmentally, socially and economically sustainable means to meet future demand for vegetable oil. Indeed, with pro-active collaboration with relevant non-government organisations, oil palm can be part of the solution to reversing the degradation of tropical forest biome

Evolusi Projek Konservasi Tapir Malaya

Kertas ini mengupas sejarah penubuhan projek daripada tahun 2002 sehingga kini yang meliputi tim projek, aspek penyelidikan yang dijalankan serta sumbangan penerbitan. Kertas ini menyenaraikan cabaran projek di masa hadapan