120 research outputs found
Multi-trophic Interactions and Long-term Volunteer Collected Data: Networks of plant-caterpillar-parasitoid interactions across time, space, and a changing climate
The preservation of ecological complexity is an important goal for ecologists as communities respond to global change. Inherent to these efforts is the quantification and evaluation of the multiple dimensions of biodiversity, including well studied metrics of taxonomic, phylogenetic, and functional diversity. Studies on multi-trophic systems have primarily focused on taxonomic diversity, yet recent efforts have highlighted the importance of examining an underutilized biodiversity metric: interaction diversity, or the richness and abundance of the unique links connecting species. My dissertation research contributes to understanding spatial and temporal variation in the diversity of plant-caterpillar-parasitoid interactions. A central theme of my dissertation research is the use of long-term citizen science data from sites across the Americas to understand how interaction diversity changes across latitudinal, climate, disturbance, and seasonal gradients. My research in tropical forests documented the impacts of climate change. I found increases in extreme precipitation events caused reductions in interaction and species diversity with associated losses in an important ecosystem function: Biological control of herbivores by their natural enemies. In a temperate fire-adapted forest, I provided evidence for the scale-dependent nature of interaction diversity and its implications for how diversity is maintained in frequently disturbed systems. To understand spatial and temporal variation in interactions, I evaluated patterns in the beta-diversity of interactions and its components. Using this methodology, I found evidence of latitudinal patterns in the turnover of interactions, providing support that interactions are more variable in tropical than temperate regions. In the Brazilian Cerrado and Yucatan Peninsula, Mexico, I found seasonal variation in interaction diversity is primarily a consequence of seasonally constant species rewiring their interactions rather than seasonal differences in species composition. Finally, an important goal for ecology is to develop effective methods that increase the public's awareness and action toward biodiversity conservation. I fielded over 300 citizen scientists on research expeditions that contribute to the collection and rearing of these long-term data and administered surveys to understand the impact of different team models. Based on these surveys, multiple team models are effective for achieving diverse objectives and corporate teams are particularly valuable for sustainability partnerships. Together, this body of research provides evidence that interaction diversity uniquely contributes to broad patterns of biodiversity and ecosystem structure. Further, novel partnerships with various citizen science team models are an effective and efficient method to engage a diverse public audience interested in the preservation of biodiversity
EVOLUTION OF THE SUBCONTINENTAL LITHOSPHERE DURING MESOZOIC TETHYAN RIFTING: CONSTRAINTS FROM THE EXTERNAL LIGURIAN MANTLE SECTION (NORTHERN APENNINE, ITALY)
Our study is focussed on mantle bodies from the External Ligurian ophiolites, within the Monte Gavi and Monte Sant'Agostino areas. Here, two distinct pyroxenite-bearing mantle sections were recognized, mainly based on their plagioclase-facies evolution. The Monte Gavi mantle section is nearly undeformed and records reactive melt infiltration under plagioclase-facies conditions. This process involved both peridotites (clinopyroxene-poor lherzolites) and enclosed spinel pyroxenite layers, and occurred at 0.7–0.8 GPa. In the Monte Gavi peridotites and pyroxenites, the spinel-facies clinopyroxene was replaced by Ca-rich plagioclase and new orthopyroxene, typically associated with secondary clinopyroxene. The reactive melt migration caused increase of TiO2 contents in relict clinopyroxene and spinel, with the latter also recording a Cr2O3 increase. In the Monte Gavi peridotites and pyroxenites, geothermometers based on slowly diffusing elements (REE and Y) record high temperature conditions (1200-1250 °C) related to the melt infiltration event, followed by subsolidus cooling until ca. 900°C. The Monte Sant'Agostino mantle section is characterized by widespread ductile shearing with no evidence of melt infiltration. The deformation recorded by the Monte Sant'Agostino peridotites (clinopyroxene-rich lherzolites) occurred at 750–800 °C and 0.3–0.6 GPa, leading to protomylonitic to ultramylonitic textures with extreme grain size reduction (10–50 μm). Compared to the peridotites, the enclosed pyroxenite layers gave higher temperature-pressure estimates for the plagioclase-facies re-equilibration (870–930 °C and 0.8–0.9 GPa). We propose that the earlier plagioclase crystallization in the pyroxenites enhanced strain localization and formation of mylonite shear zones in the entire mantle section. We subdivide the subcontinental mantle section from the External Ligurian ophiolites into three distinct domains, developed in response to the rifting evolution that ultimately formed a Middle Jurassic ocean-continent transition: (1) a spinel tectonite domain, characterized by subsolidus static formation of plagioclase, i.e. the Suvero mantle section (Hidas et al., 2020), (2) a plagioclase mylonite domain experiencing melt-absent deformation and (3) a nearly undeformed domain that underwent reactive melt infiltration under plagioclase-facies conditions, exemplified by the the Monte Sant'Agostino and the Monte Gavi mantle sections, respectively. We relate mantle domains (1) and (2) to a rifting-driven uplift in the late Triassic accommodated by large-scale shear zones consisting of anhydrous plagioclase mylonites.
Hidas K., Borghini G., Tommasi A., Zanetti A. & Rampone E. 2021. Interplay between melt infiltration and deformation in the deep lithospheric mantle (External Liguride ophiolite, North Italy). Lithos 380-381, 105855
Evaluation of PD-L1 expression in various formalin-fixed paraffin embedded tumour tissue samples using SP263, SP142 and QR1 antibody clones
Background & objectives: Cancer cells can avoid immune destruction through the inhibitory ligand PD-L1. PD-1 is a surface cell receptor, part of the immunoglobulin family. Its ligand PD-L1 is expressed by tumour cells and stromal tumour infltrating lymphocytes (TIL).
Methods: Forty-four cancer cases were included in this study (24 triple-negative breast cancers (TNBC), 10 non-small cell lung cancer (NSCLC) and 10 malignant melanoma cases). Three clones of monoclonal primary antibodies were compared: QR1 (Quartett), SP 142 and SP263 (Ventana). For visualization, ultraView Universal DAB Detection Kit from Ventana was used on an automated platform for immunohistochemical staining Ventana BenchMark GX.
Results: Comparing the sensitivity of two different clones on same tissue samples from TNBC, we found that the QR1 clone gave higher percentage of positive cells than clone SP142, but there was no statistically significant difference. Comparing the sensitivity of two different clones on same tissue samples from malignant melanoma, the SP263 clone gave higher percentage of positive cells than the QR1 clone, but again the difference was not statistically significant. Comparing the sensitivity of two different clones on same tissue samples from NSCLC, we found higher percentage of positive cells using the QR1 clone in comparison with the SP142 clone, but once again, the difference was not statistically significant.
Conclusion: The three different antibody clones from two manufacturers Ventana and Quartett, gave comparable results with no statistically significant difference in staining intensity/ percentage of positive tumour and/or immune cells. Therefore, different PD-L1 clones from different manufacturers can potentially be used to evaluate the PD- L1 status in different tumour tissues. Due to the serious implications of the PD-L1 analysis in further treatment decisions for cancer patients, every antibody clone, staining protocol and evaluation process should be carefully and meticulously validated
GENETIC RESCUE OF ISOLATED CUTTHROAT TROUT
Anthropogenic habitat destruction has isolated innumerable populations that now face increased extinction risk due to demographic and genetic factors. Although often the best strategy, restoring connectivity can be challenging or even harmful. Such is the case for westslope cutthroat trout (Oncorhynchus clarkii lewisi; WCT) in the Missouri River basin, which are limited to completely isolated populations. Nonnative species threaten WCT in connected watersheds and barrier removal could be detrimental. My dissertation examines trade-offs and strategies for the management of isolated WCT. I first examined how nonnative trout species and climate change influence the distribution of WCT using a multispecies, dynamic occupancy model parameterized with 21,917 surveys collected over 30 years. I predicted that the future distribution of WCT will decline by 16%, primarily due to warming water increasing the distributions of harmful nonnative species. I next asked whether genetic metrics indicated that isolated WCT populations are at risk of inbreeding depression. I found very low effective population sizes (Ne \u3c 25) in two of five WCT populations, suggesting risks of inbreeding depression could be high. A promising conservation strategy is to restore gene flow into small populations, which can increase vital rates and, ultimately, persistence probability (i.e., genetic rescue). To examine genetic rescue as a conservation strategy for WCT, we first conducted a literature review to examine what aspects of genetic rescue remain uncertain, including the duration and magnitude of genetic rescue and when gene flow may reduce fitness. Finally, we conducted an experimental test of genetic rescue in four isolated WCT populations. In the two smallest populations, we found that F1 hybrids had a 71% and 379% increase in fitness relative to residents, suggesting genetic rescue occurred. However, in the two larger populations, we found minimal evidence for genetic rescue. Overall, this research demonstrates that isolation likely poses risk to WCT, but removing barriers could pose a far greater risk owing to increased interactions with nonnative trout species. These results provide further evidence that when restoring connectivity is not an option genetic rescue is a powerful conservation strategy for at-risk populations of diverse taxa
Impact of Etna’s volcanic emission on major ions and trace elements composition of the atmospheric deposition
Mt. Etna, on the eastern coast of Sicily (Italy), is one of the most active volcanoes on the planet and it is widely recognized as a big source of volcanic gases (e.g., CO2 and SO2), halogens, and a lot of trace elements, to the atmosphere in the Mediterranean region. Especially during eruptive periods, Etna’s emissions can be dispersed over long distances and cover wide areas. A group of trace elements has been recently brought to attention for their possible environmental and human health impacts, the Technology-critical elements. The current knowledge about their geochemical cycles is still scarce, nevertheless, recent studies (Brugnone et al., 2020) evidenced a contribution from the volcanic activity for some of them (Te, Tl, and REE). In 2021, in the framework of the research project “Pianeta Dinamico”, by INGV, a network of 10 bulk collectors was implemented to collect, monthly, atmospheric deposition samples. Four of these collectors are located on the flanks of Mt. Etna, other two are in the urban area of Catania and three are in the industrial area of Priolo, all most of the time downwind of the main craters. The last one, close to Cesarò (Nebrodi Regional Park), represents the regional background. The research aims to produce a database on major ions and trace element compositions of the bulk deposition and here we report the values of the main physical-chemical parameters and the deposition fluxes of major ions and trace elements from the first year of research. The pH ranged from 3.1 to 7.7, with a mean value of 5.6, in samples from the Etna area, while it ranged between 5.2 and 7.6, with a mean value of 6.4, in samples from the other study areas. The EC showed values ranging from 5 to 1032 μS cm-1, with a mean value of 65 μS cm-1. The most abundant ions were Cl- and SO42- for anions, Na+ and Ca+ for cations, whose mean deposition fluxes, considering all sampling sites, were 16.6, 6.8, 8.4, and 6.0 mg m-2 d, respectively. The highest deposition fluxes of volcanic refractory elements, such as Al, Fe, and Ti, were measured in the Etna’s sites, with mean values of 948, 464, and 34.3 μg m-2 d-1, respectively, higher than those detected in the other sampling sites, further away from the volcanic source (26.2, 12.4, 0.5 μg m-2 d-1, respectively). The same trend was also observed for volatile elements of prevailing volcanic origin, such as Tl (0.49 μg m-2 d-1), Te (0.07 μg m-2 d-1), As (0.95 μg m-2 d-1), Se (1.92 μg m-2 d-1), and Cd (0.39 μg m-2 d-1). Our preliminary results show that, close to a volcanic area, volcanic emissions must be considered among the major contributors of ions and trace elements to the atmosphere. Their deposition may significantly impact the pedosphere, hydrosphere, and biosphere and directly or indirectly human health
The OCaml system release 5.0: Documentation and user's manual
This manual documents the release 5.0 of the OCaml system. It is organized as follows. Part I, "An introduction to OCaml", gives an overview of the language. Part II, "The OCaml language", is the reference description of the language. Part III, "The OCaml tools", documents the compilers, toplevel system, and programming utilities. Part IV, "The OCaml library", describes the modules provided in the standard library. Part V, “Indexes”, contains an index of all identifiers defined in the standard library, and an index of keywords
Impact of geogenic degassing on C-isotopic composition of dissolved carbon in karst systems of Greece
The Earth C-cycle is complex, where endogenic and exogenic sources are interconnected, operating in a multiple spatial and temporal scale (Lee et al., 2019). Non-volcanic CO2 degassing from active tectonic structures is one of the less defined components of this cycle (Frondini et al., 2019). Carbon mass-balance (Chiodini et al., 2000) is a useful tool to quantify the geogenic carbon output from regional karst hydrosystems. This approach has been demonstrated for central Italy and may be valid also for Greece, due to the similar geodynamic settings. Deep degassing in Greece has been ascertained mainly at hydrothermal and volcanic areas, but the impact of geogenic CO2 released by active tectonic areas has not yet been quantified. The main aim of this research is to investigate the possible deep degassing through the big karst aquifers of Greece. Since 2016, 156 karst springs were sampled along most of the Greek territory. To discriminate the sources of carbon, the analysis of the isotopic composition of carbon was carried out. δ13CTDIC values vary from -16.61 to -0.91‰ and can be subdivided into two groups characterized by (a) low δ13CTDIC, and (b) intermediate to high δ13CTDIC with a threshold value of -6.55‰. The composition of the first group can be related to the mixing of organic-derived CO2 and the dissolution of marine carbonates. Springs of the second group, mostly located close to Quaternary volcanic areas, are linked to possible carbon input from deep sources
Structural and Optical Characterization of III-V Nanostructures Monolithically Grown on Si Substrates
Group III-V semiconductor nanostructures have emerged as an important material platform over the past decades for wide-range device implementation in the field of electronics and optoelectronics. Among them, nanowires (NWs) are particularly attractive owing to the elastic strain relaxation through their sidewall facets which allows for the combination of lattice mismatched materials. Hence, optically active III-V materials become compatible with the mature and prevalent Si platform. Moreover, NWs are ideal for hosting quantum dots (QDs) ensuring their deterministic positioning and uniformity. This configuration opens the route for sophisticated applications including single photon emission, a crucial function in quantum information processing. In addition, another type of nanostructures that has attracted attention is the two-dimensional nanosheets, whose principal benefit is the band structure tuning from bulk to 2D by modulation of their thickness. Consequently, they are established as promising blocks for various optoelectronic devices and applications.
In the current thesis, we reported the growth of self-catalysed AlGaAs NWs monolithically on Si (111) substrates via solid-source molecular beam epitaxy (MBE). The self-formation of an Al-rich shell is exhibited, which is thicker at the base and thins down towards the NW tip, while it demonstrates wide alloy fluctuations. The predominantly ZB structure presents twin defects and occasional WZ insertions, further increasing the intricacy of the NWs. The optical probing via photoluminescence reveals fully tuneable emission with the Al content of the alloy.
Among the morphological variations of AlGaAs NWs, the branched NWs are of unique interest. The branching events increase with Al content, while the branches are confirmed to grow on the NW trunks epitaxially. In addition, complex compositional distribution in the branches is presented, as Ga-rich stripes along the growth direction of the branches, attributed to the different nucleation energies on different faces at the liquid/solid interface of the branch, intersect with Ga-rich stripes perpendicular to them, deriving from the rotation of the sample during growth.
Moreover, self-catalysed, single GaAs/AlGaAs dot-in-wire structures have been designed and grown by inserting a short GaAs segment in each AlGaAs NW. The exhaustive optical probing reveals centrally localized peaks, with a decently narrow linewidth of roughly 490 ÎĽeV. The QD emission is comprised of an exciton and a biexciton transition, while a high degree of polarization is noticed when compared to the AlGaAs NW-related emission. The above characteristics are important steps towards achieving single photon emission.
Finally, we optically inspect InAs nanosheets grown via MBE via photoluminescence measurements. Pristine nanosheets exhibit surface charge via carrier trapping mechanisms at the surface states, which is suggestive of the “memory effect”. The impact of sulphur passivation and core/shell configuration on the optical response of the nanosheets is evaluated. In addition, we fabricated an optoelectronic memory unit based on pristine InAs nanosheets, adopting a field-effect transistor configuration, which demonstrates negative photoresponse with good reproducibility and ultra-low power consumption
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