Gene expression and fatty acid profiling in longissimus thoracis muscle, subcutaneous fat, and liver of light lambs in response to concentrate or alfalfa grazing

A better understanding of gene expression and metabolic pathways in response to a feeding system is critical for identifying key physiological processes and genes associated with polyunsaturated fatty acid (PUFA) content in lamb meat. The main objective of this study was to investigate transcriptional changes in L. thoracis (LT) muscle, liver, and subcutaneous fat (SF) of lambs that grazed alfalfa (ALF) and concentrate-fed (CON) slaughtered at 23 kg and using the Affymetrix Ovine Gene 1.1 ST whole-genome array. The study also evaluated the relationship between meat traits in LT muscle, including color, pigments and lipid oxidation during 7 days of display, a-tocopherol content, intramuscular fat (IMF) content and the fatty acid (FA) profile. Lambs that grazed on alfalfa had a greater a-tocopherol concentration in plasma than CON lambs (P 0.05). Grazing increased the a-tocopherol content (P < 0.001) and decreased lipid oxidation on day 7 of display (P < 0.05) in LT muscle. The ALF group contained a greater amount of conjugated linoleic acid (CLA), C18:3 n-3, C20:5 n-3, C22:5 n-3, and C22:6 n-3 than did the CON group (P < 0.05). We identified 41, 96 and four genes differentially expressed in LT muscle, liver, and subcutaneous fat, respectively. The most enriched biological processes in LT muscle were skeletal muscle tissue development, being the genes related to catabolic and lipid processes downregulated, except for CPT1B, which was upregulated in the ALF lambs. Animals grazing alfalfa had lower expression of desaturase enzymes in the liver (FADS1 and FADS2), which regulate unsaturation of fatty acids and are directly involved in the metabolism of n-3 PUFA series. The results found in the current study showed that ingesting diets richer in n-3 PUFA might have negative effects on the de novo synthesis of n-3 PUFA by downregulating the FADS1 and FADS2 expression. However, feeding diets poorer in n-3 PUFA can promote fatty acid desaturation, which makes these two genes attractive candidates for altering the content of PUFAs in meat

Sb and N Incorporation Interplay in GaAsSbN/GaAs Epilayers near Lattice-Matching Condition for 1.0–1.16-eV Photonic Applications

As promising candidates for solar cell and photodetection applications in the range 1.0–1.16 eV, the growth of dilute nitride GaAsSbN alloys lattice matched to GaAs is studied. With this aim, we have taken advantage of the temperature gradient in the molecular beam epitaxy reactor to analyse the impact of temperature on the incorporation of Sb and N species according to the wafer radial composition gradients. The results from the combination of X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopies (EDS) show an opposite rate of incorporation between N and Sb as we move away from the centre of the wafer. A competitive behaviour between Sb and N in order to occupy the group-V position is observed that depends on the growth rate and the substrate temperature. The optical properties obtained by photoluminescence are discussed in the frame of the double-band anticrossing model. The growth conditions define two sets of different parameters for the energy level and the coupling interaction potential of N, which must be taken into account in the search for the optimum compositions 1–1.15-eV photonic applications

Effect of the AlAs capping layer thickness on the structure of InAs/GaAs QD

Recently, very thin AlAs capping layers (CLs) have been proposed as a useful tool to increase the performance of InAs/GaAs quantum dot (QDs) devices. However, the structure of QDs after AlAs deposition remains poorly understood and the mechanisms to explain it are often contradictory. In this work, the structural and compositional changes of InAs QDs using different AlAs CL thicknesses have been studied by state-of-the-art STEM-related techniques. First, the heights and In contents of InAs QDs progressively increase with the CL thickness, demonstrating that the AlAs capping produces a strong shielding effect against the decomposition of QDs. However, QD populations for CL thicknesses above 5 ML split into a bimodal distribution in which smaller lenticular QDs cohabit with bigger truncated pyramids. Second, the actual Al contents around the QDs are well below the nominal design, but increasing for thicker CLs. Its distribution is initially non-uniform, tending to accumulate on the flanks of the QDs to the detriment of the apex. Only for thicknesses above 2 ML the Al contents around the QDs start to be similar to those in the regions between the QDs, behaving as a continuous film without irregularities from 5 ML onwards. © 2021 The Author(s)The work has been co-financed by the Spanish National Research Agency (AEI projects MAT2016-77491-C2-2-R and PID2019-106088RB-C33), Regional Government of Andalusia (project FEDER-UCA18-108319) and the European Regional Development Fund (ERDF)

Determining and mapping species sensitivity to trawling impacts: the BEnthos Sensitivity Index to Trawling Operations (BESITO)

Applying an ecosystem approach requires a deep and holistic understanding of interactions between human activities and ecosystems. Bottom trawling is the most widespread physical human disturbance in the seabed and produces a wide range of direct and indirect impacts on benthic ecosystems. In this work, we develop a new index, the BEnthos Sensitivity Index to Trawling Operations (BESITO), using biological traits to classify species according to their sensitivity to bottom trawling. Seventy-nine different benthic taxa were classified according to their BESITO scores in three groups. The effect of trawling on the relative abundance of each group (measured as biomass proportion) was analysed using General Additive Models (GAMs) in a distribution model framework. The distribution of the relative biomass of each group was mapped and the impact of trawling was computed. Species with the lowest BESITO score (group I) showed a positive response to trawling disturbance (opportunistic response) whereas species with values higher than 2 (group III) showed a negative response (sensitive response). Species with a BESITO score of 2 did not show a significant response to the pressure (tolerant response). Trawling disturbance reduced relative biomass of sensitive species by 31% across the study area. This value increased to 46% when shelf-break was considered in isolation and reached values of 59.6% in the most impacted habitat (deep-sea muddy sands). The new index classified successfully the analysed species according to their sensitivity to trawling allowing modeling the impact of trawling disturbance on sensitive species, without the masking effect of opposed responses

Analysis of Learning Records to Detect Student Cheating on Online Exams: Case Study during COVID-19 Pandemic

In March 2020, due to the Covid19 pandemic, higher education had to switch from face-to-face to exclusively virtual mode overnight. In this unexpected scenario, supervisors also had to adapt the assessment procedures, including the exams. This caused a significant controversy, as, according to many students, supervisors were more concerned about how to prevent students from cheating, than actually measuring their learning. This paper introduces an experience that implemented several of the students' requests in an online exam and conducts a comprehensive analysis of students’ behavior according to the virtual learning environment records. Different existing software tools are used for the analysis, complemented with a Python application ad-hoc developed. The objective indicators gathered provide evidence that some students cheated and invite focusing on evidence-based assessment

Spatial assessment of benthic habitats vulnerability to bottom fishing in a Mediterranean seamount

Physical damage caused by the mechanical impact of bottom fishing gears on epibenthic community can reduce the biomass and coverage of habitat-forming species as well as the richness and diversity of the rest of the associated community. A practical development of a methodology for spatially assessing the potential degree of disturbance that benthic habitats suffered as a consequence of trawling and long-lining was carried out using a seamount located within a marine Natura 2000 site in the western Mediterranean as a case of study. By jointly assessing the extent of the impact and mapping the sensitivity of all the habitats to these fishing activities, vulnerability and disturbance per benthic habitat and pressure type was evaluated. Habitat sensitivity and fishing effort were combined using a disturbance matrix which categorize grid cells in 9 different levels of disturbance. Additionally, different thresholds of probability of presence of the different habitats obtained from distribution models were used to identify priority conservation and potential recovery. Around 50% of the area was disturbed by fishing and all habitats, both biogenic and non-biogenic, were subjected to fishing. Most of the trawling effort was carried out on soft bathyal substrates while the percentage of longlining effort carried out on hard bottoms was relatively higher than for trawling. Biogenic habitats showed significantly greater sensitivity to both trawling and longlining than non-biogenic habitats. Disturbed, priority conservation and potential recovery areas were identified and mapped in order to inform marine spatial planning.En prensa1,86

Living at the top. Connectivity limitations and summit depth drive fish diversity patterns in an isolated seamount

The fish assemblages of the Galicia Bank and the closest continental slope (northwest of Spain) were analysed using otter trawls to improve our understanding of how environmental drivers structure seamount fish communities in the deep sea. The effect of environmental drivers on these assemblages was studied using multivariate techniques together with the variation in α and β diversity across assemblages. Fish fauna in the study area was distributed in 5 different assemblages generated by the action of 3 main drivers: depth, distance to the coast and presence of cold-water corals. The observed differences in species composition among assemblages were mostly explained by species turnover across a depth gradient. The seamount summit and the continental slope showed important differences despite sharing similar depths, mainly because several species requiring shallow juvenile habitats were absent from the summit. These absences were observed in both summit assemblages inside and outside the cold-water coral reef. Our results show that in isolated seamounts with relatively deep summits, the lack of connectivity with shallower areas limits the presence of certain species, probably due to the impossibility for these species to migrate directly from shallow to deeper seabed areas. These species are replaced by species with preferences for deeper habitats, providing the fish assemblages located at the top of the summit with a deeper profile than observed in fish assemblages of the continental slope.En prensa2,48

Growth interruption strategies for interface optimization in GaAsSb/GaAsN type-II superlattices

Recently, GaAsSb/GaAsN type II short-period superlattices (SLs) have been proposed as suitable structures to be implemented in the optimal design of monolithic multi-junction solar cells. However, due to strong surface Sb segregation, experimental Sb composition profiles differ greatly from the nominal square-wave design. In this work, the improvement of the interface quality of these SLs in terms of compositional abruptness and surface roughness has been evaluated by implementing different growth interruption times under Sb4/As4 (soaking) and As4 (desorption) overpressure conditions before and after the growth of GaAsSb layers, respectively. The com-bined effects of both processes enhance Sb distribution, achieving squarer compositional profiles with reduced surface roughness interfaces. It has been found that the improvement in compositional abruptness is quantita-tively much higher at the lower interface, during soaking, than at the upper interface during desorption. Conversely, a larger decrease in surface roughness is achieved at the upper interface than at the lower interface. Fitting of the Sb segregation profiles using the 3-layer kinetic fluid model has shown that the increase in Sb incorporation rate is due to the decrease in segregation energy, presumably to changes in the surface recon-struction of the floating layer at the surface

Strain-balanced type-II superlattices for efficient multi-junction solar cells

Multi-junction solar cells made by assembling semiconductor materials with different bandgap energies have hold the record conversion efficiencies for many years and are currently approaching 50%. Theoretical efficiency limits make use of optimum designs with the right lattice constant-bandgap energy combination, which requires a 1.0–1.15 eV material lattice-matched to GaAs/Ge. Nevertheless, the lack of suitable semiconductor materials is hindering the achievement of the predicted efficiencies, since the only candidates were up to now complex quaternary and quinary alloys with inherent epitaxial growth problems that degrade carrier dynamics. Here we show how the use of strain-balanced GaAsSb/GaAsN superlattices might solve this problem. We demonstrate that the spatial separation of Sb and N atoms avoids the ubiquitous growth problems and improves crystal quality. Moreover, these new structures allow for additional control of the effective bandgap through the period thickness and provide a type-II band alignment with long carrier lifetimes. All this leads to a strong enhancement of the external quantum efficiency under photovoltaic conditions with respect to bulk layers of equivalent thickness. Our results show that GaAsSb/GaAsN superlattices with short periods are the ideal (pseudo)material to be integrated in new GaAs/Ge-based multi-junction solar cells that could approach the theoretical efficiency limit