Growing degree-day measurement of cyst germination rates in the toxic dinoflagellate Alexandrium catenella

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fischer, A., & Brosnahan, M. Growing degree-day measurement of cyst germination rates in the toxic dinoflagellate Alexandrium catenella. Applied and Environmental Microbiology, 88(12), (2022): e02518-21, https://doi.org/10.1128/aem.02518-21.Blooms of many dinoflagellates, including several harmful algal bloom (HAB) species, are seeded and revived through the germination of benthic resting cysts. Temperature is a key determinant of cysts’ germination rate, and temperature–germination rate relationships are therefore fundamental to understanding species’ germling cell production, cyst bed persistence, and resilience to climate warming. This study measured germination by cysts of the HAB dinoflagellate Alexandrium catenella using a growing degree-day (DD) approach that accounts for the time and intensity of warming above a critical temperature. Time courses of germination at different temperatures were fit to lognormal cumulative distribution functions for the estimation of the median days to germination. As temperature increased, germination times decreased hyperbolically. DD scaling collapsed variability in germination times between temperatures after cysts were oxygenated. A parallel experiment demonstrated stable temperature–rate relationships in cysts collected during different phases of seasonal temperature cycles in situ over three years. DD scaling of the results from prior A. catenella germination studies showed consistent differences between populations across a wide range of temperatures and suggests selective pressure for different germination rates. The DD model provides an elegant approach to quantify and compare the temperature dependency of germination among populations, between species, and in response to changing environmental conditions.We gratefully acknowledge support to A.D.F. and M.L.B. through the Woods Hole Center for Oceans and Human Health (National Science Foundation grants OCE‐0430724, OCE‐0911031, OCE‐1314642, and OCE-1840381 and National Institutes of Health grants NIEHS‐1P50‐ES02192301 and P01ES028938)

White Organic Light-Emitting Diodes with fine chromaticity tuning via ultrathin layer position shifting

Non-doped white organic light-emitting diodes using an ultrathin yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on either side of the interface between a hole-transporting NPB (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl) layer and a blue-emitting DPVBi (4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl) layer are described. Both the thickness and the position of the rubrene layer allow fine chromaticity tuning from deep-blue to pure-yellow via bright-white with CIE coordinates (x= 0.33, y= 0.32), a external quantum efficiency of 1.9%, and a color rendering index of 70. Such a structure also provides an accurate sensing tool to measure the exciton diffusion length in both DPVBi and NPB (8.7 and 4.9 nm respectively)

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Quantitative response of Alexandrium catenella cyst dormancy to cold exposure

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Protist 169 (2018): 645-661, doi:10.1016/j.protis.2018.06.001.Many dinoflagellate cysts experience dormancy, a reversible state that prevents germination during unfavorable periods. Several of these species also cause harmful algal blooms (HABs), so a quantitative understanding of dormancy cycling is desired for better prediction and mitigation of bloom impacts. This study examines the effect of cold exposure on the duration of dormancy in Alexandrium catenella, a HAB dinoflagellate that causes paralytic shellfish poisoning (PSP). Mature, dormant cysts from Nauset Marsh (Cape Cod, MA USA) were stored at low but above freezing temperatures for up to six months. Dormancy status was then determined at regular intervals using a germination assay. Dormancy timing was variable among temperatures and was shorter in colder treatments, but the differences collapse when temperature and duration of storage are scaled by chilling-units (CU), a common horticultural predictor of plant and insect development in response to weather. Cysts within Nauset meet a well-defined chilling requirement by late January, after which they are poised to germinate with the onset of favorable conditions in spring. Cysts thus modulate their dormancy cycles in response to their temperature history, enhancing the potential for new blooms and improving this species’ adaptability to both unseasonable weather and new habitats/climate regimes.This work was supported by the National Science Foundation [OCE-0430724, OCE-0911031]; the National Institute of Environmental Health Sciences [1P50-ES01274201, 1P01ES021923]; the National Park Service Cooperative Agreement [H238015504]; and the Friends of Cape Cod National Seashore

Rate Equation Theory for Organic Diode Laser and Experimental Validation with Microcavity OLED

We present a new model for an organic laser diode based on rate equations for polarons, singlet and triplet excitons, both in host and dopant molecules, and photon densities. The model is validated by comparing calculated optical responses with measurements on high-speed low-Q OLEDS under pulsed nanosecond electrical excitation. The model confirms the threshold-current density of ~500A/cm2 observed in the recent first experiment with indication of lasing in an OLED with DFB-grating in the group of Adachi [1], if the Q-factor ~20K and no residual absorption occurs

Scenario building and runout modelling for debris flow hazards in pro-/periglacial catchments with scarce past event data: application of a multi-methods approach for the Dar catchment (western Swiss Alps)

In high mountain areas, the disposition (susceptibility of occurrence) for debris flows is increasing in steep terrain, as – due to climate change – rapid glacier retreat and permafrost degradation is favouring higher availability of loose sediments. The probability of occurrence and magnitude of pro- and periglacial debris flows is increasing, too, as triggering events such as heavy thunderstorms, long-lasting rainfalls, intense snow melt or rain-on-snow events are likely to occur more often and more intensely in future decades. Hazard assessment for debris flows originating from pro- and periglacial areas is thus crucial but remains challenging, as records of past events on which local magnitude-frequency relationships and debris flow scenarios can be based on are often scarce or inexistent. In this study, we present a multi-methods approach for debris flow hazard scenario building and runout modelling in pro- and periglacial catchments with scarce past event data. Scenario building for the debris flow initiation zone reposes on (i) the definition of meteorological and hydrological triggering scenarios using data on extreme point rainfall and precipitation-runoff modelling, and (ii) the definition of bed load scenarios from empirical approaches and field surveys. Numerical runout modelling and hazard assessment for the resulting debris flow scenarios is carried out using RAMMS-DF, which was calibrated to the studied catchment (Le Dar, western Swiss Alps) based on the area of debris flow deposits from the single major event recorded there in summer 2005. The developed approach is among the first to propose systematic scenario building for pro- and periglacial debris flows triggered by precipitation dependent events

Observation of rogue waves in a 980nm-laser diode subject to filtered optical feedback

International audienceIn this work, rogue waves are observed in a 980 nm laser diode subject to filtered optical feedback via an fibre Bragg grating. A rogue-wave map is established for the first time experimentally as functions of optical feedback ratio and laser current. Rogue waves in our laser system are identified as a part of low frequency fluctuation jump-ups

Sixty years of Sverdrup : a retrospective of progress in the study of phytoplankton blooms

Author Posting. © The Oceanography Society, 2014. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 27, no. 1 (2014): 222–235, doi:10.5670/oceanog.2014.26.One of the most dramatic large-scale features in the ocean is the seasonal greening of the North Atlantic in spring and summer due to the accumulation of phytoplankton biomass in the surface layer. In 1953, Harald Ulrik Sverdrup hypothesized a now canonical mechanism for the development and timing of phytoplankton blooms in the North Atlantic. Over the next 60 years, Sverdrup's Critical Depth Hypothesis spurred progress in understanding of bloom dynamics and offered a valuable theoretical framework on which to build. In reviewing 60 years of literature, the authors trace the development of modern bloom initiation hypotheses, highlighting three case studies that illuminate the complexity, including both catalysts and impediments, of scientific progress in the wake of Sverdrup's hypothesis. Most notably, these cases demonstrate that the evolution of our understanding of phytoplankton blooms was paced by access not only to technology but also to concurrent insights from several disciplines. This exploration of the trajectories and successes in bloom studies highlights the need for expanding interdisciplinary collaborations to address the complexity of phytoplankton bloom dynamics

Nanotoxicology: characterizing the scientific literature, 2000–2007

Understanding the toxicity of nanomaterials and nano-enabled products is important for human and environmental health and safety as well as public acceptance. Assessing the state of knowledge about nanotoxicology is an important step in promoting comprehensive understanding of the health and environmental implications of these new materials. To this end, we employed bibliometric techniques to characterize the prevalence and distribution of the current scientific literature. We found that the nano-toxicological literature is dispersed across a range of disciplines and sub-fields; focused on in vitro testing; often does not specify an exposure pathway; and tends to emphasize acute toxicity and mortality rather than chronic exposure and morbidity. Finally, there is very little research on consumer products, particularly on their environmental fate, and most research is on the toxicity of basic nanomaterials. The implications for toxicologists, regulators and social scientists studying nanotechnology and society are discussed

DARIAH Beyond Europe

International audienceDARIAH, the digital humanities infrastructure with origins and an organisational home in Europe, is nearing the completion of its implementation phase. The significant investment from the European Commission and member countries has yielded a robust set of technical and social infrastructures, ranging from working groups, various registries, pedagogical materials, and software to support diverse approaches to digital humanities scholarship. While the funding and leadership of DARIAH to date has come from countries in, or contiguous with, Europe, the needs that drive its technical and social development are widely shared within the international digital humanities community beyond Europe. Scholars on every continent would benefit from well-supported technical tools and platforms, directories for facilitating access to information and resources, and support for working groups.The DARIAH Beyond Europe workshop series, organised and financed under the umbrella of the DESIR project (“DARIAH ERIC Sustainability Refined,” 2017–2019, funded by the European Union’s Horizon 2020 Research and Innovation Program), convened three meetings between September 2018 and March 2019 in the United States and Australia. These workshops served as fora for cross-cultural exchange, and introduced many non-European DH scholars to DARIAH; each of the workshops included a significant delegation from various DARIAH bodies, together with a larger number of local presenters and participants. The local contexts for these workshops were significantly different in their embodiment of research infrastructures: on the one hand, in the U.S., a private research university (Stanford) and the de facto national library (the Library of Congress), both in a country with a history of unsuccessful national-scale infrastructure efforts; and in Australia, a system which has invested substantially more in coordinated national research infrastructure in science and technology, but very little on a national scale in the humanities and arts. Europe is in many respects ahead of both host countries in terms of its research infrastructure ecosystem both at the national and pan-European levels.The Stanford workshop had four main topics of focus: corpus management; text and image analysis; geohumanities; and music, theatre, and sound studies. As the first of the workshops, the Stanford group also took the lead in proposing next steps toward exploring actionable “DARIAH beyond Europe” initiatives, including the beginnings of a blog shared among participants from all the workshops, extra-European use of DARIAH’s DH Course Registry, and non-European participation in DARIAH Working Groups.The overall theme of the Library of Congress workshop was “Collections as Data,” building on a number of U.S.-based initiatives exploring how to enhance researcher engagement with digital collections through computationally-driven research. In Washington, D.C., the knowledge exchange sessions focussed on digitised newspapers and text analysis, infrastructural challenges for public humanities, and the use of web-archives in DH research. As at Stanford, interconnecting with DARIAH Working Groups was of core interest to participants, and a new Working Group was proposed to explore global access and use of digitised historical newspapers. A further important outcome was the agreement to explore collaboration between the U.S.-based “Collections as Data” initiatives and the Heritage Data Reuse Charter in Europe. The third and final workshop in the series took place in March 2019 in Australia, hosted by the National Library of Australia in Canberra. Convened by the Australian Academy of the Humanities (AAH), together with the Australian Research Data Commons (ARDC) and DARIAH, this event was co-located with the Academy’s second annual Humanities, Arts and Culture Data Summit. The first day of the event, targeted at research leadership and policy makers, was intended to explore new horizons for data-driven humanities and arts research, digital cultural collections and research infrastructure. The two subsequent days focused on engaging with a wide variety of communities, including (digital) humanities researchers and cultural heritage professionals. Organised around a series of Knowledge Exchange Sessions, combined with research-led lightning talks, the participants spoke in detail about how big ideas can be implemented practically on the ground. This poster reflects on the key outcomes and future directions arising from these three workshops, and considers what it might look like for DARIAH to be adopted as a fundamental DH infrastructure in a complex variety of international, national, and regional contexts, with diverse funding models, resources, needs, and expectations. One major outcome of all workshops was the shared recognition that, in spite of extensive funding, planning, and goodwill, these workshops were not nearly global enough in their reach: most importantly they were not inclusive of the Global South. Our new DARIAH beyond Europe community has a strong shared commitment to address this gap