Search for: All records

ABSTRACT Caenorhabditis elegans gut and cuticle produce a disruptive amount of autofluorescence during imaging. Although C. elegans autofluorescence has been characterized, it has not been characterized at high resolution using both spectral and fluorescence lifetime-based approaches. We performed high resolution spectral scans of whole, living animals to characterize autofluorescence of adult C. elegans. By scanning animals at 405 nm, 473 nm, 561 nm, and 647 nm excitations, we produced spectral profiles that confirm the brightest autofluorescence has a clear spectral overlap with the emission of green fluorescent protein (GFP). We then used fluorescence lifetime imaging microscopy (FLIM) to further characterize autofluorescence in the cuticle and the gut. Using FLIM, we were able to isolate and quantify dim GFP signal within the sensory cilia of a single pair of neurons that is often obscured by cuticle autofluorescence. In the gut, we found distinct spectral populations of autofluorescence that could be excited by 405 nm and 473 nm lasers. Further, we found lifetime differences between subregions of this autofluorescence when stimulated at 473 nm. Our results suggest that FLIM can be used to differentiate biochemically unique populations of gut autofluorescence without labeling. Further studies involving C. elegans may benefit from combining high resolution spectral and lifetime imaging to isolate fluorescent protein signal that is mixed with background autofluorescence and to perform useful characterization of subcellular structures in a label-free manner. 

In this inter-continental study of stream diatoms, we asked three important but still unresolved ecological questions: 1) What factors drive the biogeography of species richness and species abundance distribution (SAD); 2) Are climate-related hypotheses, which have dominated the research on the latitudinal and altitudinal diversity gradients, adequate in explaining spatial biotic variability; and 3) Is the SAD response to the environment independent of richness? We tested a number of climatic theories and hypotheses (i.e., the species-energy theory, the metabolic theory, the energy variability hypothesis, and the climatic tolerance hypothesis) but found no support for any of these concepts as the relationships of richness with explanatory variables were non-existent, weak or unexpected. Instead, we demonstrated that diatom richness and SAD evenness generally increased with temperature seasonality and at mid- to high total phosphorus concentrations. The spatial patterns of diatom richness and the SAD—mainly longitudinal in the US, but latitudinal in Finland—were defined primarily by the covariance of climate and water chemistry with space. The SAD was not entirely controlled by richness, emphasizing its utility for ecological research. Thus, we found support for the operation of both climate and water chemistry mechanisms in structuring diatom communities, which underscores their complex response to the environment and the necessity for novel predictive frameworks. 

Abstract A Large Ion Collider Experiment (ALICE) has been conceived and constructed as a heavy-ion experiment at the LHC. During LHC Runs 1 and 2, it has produced a wide range of physics results using all collision systems available at the LHC. In order to best exploit new physics opportunities opening up with the upgraded LHC and new detector technologies, the experiment has undergone a major upgrade during the LHC Long Shutdown 2 (2019–2022). This comprises the move to continuous readout, the complete overhaul of core detectors, as well as a new online event processing farm with a redesigned online-offline software framework. These improvements will allow to record Pb-Pb collisions at rates up to 50 kHz, while ensuring sensitivity for signals without a triggerable signature.