Fully-Coupled Electromechanical Simulations of the LV Dog Anatomy Using HPC: Model Testing and Verification

Verification of electro-mechanic models of the heart require a good amount of reliable, high resolution, thorough in-vivo measurements. The detail of the mathematical models used to create simulations of the heart beat vary greatly. Generally, the objective of the simulation determines the modeling approach. However, it is important to exactly quantify the amount of error between the various approaches that can be used to simulate a heart beat by comparing them to ground truth data. The more detailed the model is, the more computing power it requires, we therefore employ a high-performance computing solver throughout this study. We aim to compare models to data measured experimentally to identify the effect of using a mathematical model of fibre orientation versus the measured fibre orientations using DT-MRI. We also use simultaneous endocardial stimuli vs an instantaneous myocardial stimulation to trigger the mechanic contraction. Our results show that synchronisation of the electrical and mechanical events in the heart beat are necessary to create a physiological timing of hemodynamic events. Synchronous activation of all of the myocardium provides an unrealistic timing of hemodynamic events in the cardiac cycle. Results also show the need of establishing a protocol to quantify the zero-pressure configuration of the left ventricular geometry to initiate the simulation protocol; however, the predicted zero-pressure configuration of the same geometry was different, depending on the origin of the fibre field employed.This work has been done with the support of the grant SEV-2011-00067 of Severo Ochoa Program, awarded by the Spanish Government to the Barcelona Supercomputing Center. Part of the research leading to these results has received funding from the Seventh Framework Programme (FP7/2007-2013) under grant agreement n 611823. It has also been partially funded from the by the Spanish Ministry of Economy and Competitiveness (TIN2011-28067).Peer ReviewedPostprint (author's final draft

Data Descriptor : A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment.Peer reviewe

Dissolved oxygen dynamics under ice: Three winters of high-frequency data from Lake Tovel, Italy

Under-ice dissolved oxygen (DO) metabolism and DO depletion are poorly understood, limiting our ability to predict how changing winter conditions will affect lake ecosystems. We analyzed under-ice DO dynamics based on high-frequency (HF) data at two depths (5 and 25 m) for three winters (January– March 2014, 2015, and 2016) in oligotrophic Lake Tovel (1178 m above sea level; maximum depth 39 m). Specifically, we assessed diel metabolic rates based on HF data of DO, temperature, and light for winter 2016 and seasonal DO depletion rates based on HF data of DO for all three winters. For 2016, calculations of metabolic rates were possible only for 34% and 3% of days at 5 and 25 m, respectively; these metabolic rates generally indicated net heterotrophy at both depths. Low success in modeling metabolic rates was attributed to low diel DO variability and anomalous diel DO patterns, probably linked to under-ice physical processes. Seasonal DO patterns for the three winters showed increasing, decreasing, or stable DO trends at 5 m while at 25 m patterns always showed decreasing DO trends but with different rates. Our multiyear study permitted us to hypothesize that the observed intraannual and interannual differences in DO depletion can be attributed to variable snow cover determining the penetration of radiation and thus photosynthesis. This study brings new insights to DO dynamics in ice-covered systems, highlights the challenges linked to under-ice lake metabolism, and advocates for a modeling approach that includes physical processes

Reinterpretation of the dinoflagellate Glenodinium sanguineum in the reddening of Lake Tovel, Italian Alps

Lake Tovel in the Italian Alps is famous for its blood-red water during summer, caused by a dinoflagellate named Glenodinium sanguineum. The red colour has been largely absent since 1964 and a project aimed at understanding the underlying cause of the colour change was begun in 2000. It appears that there are three dinoflagellates in the lake that morphologically somewhat resemble ‘G. sanguineum’. One of these agrees with the ‘red form’ of G. sanguineum studied in the detailed work of Baldi (1941), and is now very scarce in the plankton. The other agrees with Baldi's ‘green form’ and now dominates the plankton. Transmission electron microscopy has demonstrated that the third taxon is identical to what Dodge et al. (1987) identified as G. sanguineum from Lake Tovel. It did not develop a red colour under any of the growth conditions used in our experiments. The red form is very similar to Woloszynskia coronata, but differs in cyst morphology. It is shown that the red and green forms of G. sanguineum sensu Baldi are clearly distinct species. Reduction in nutrient loads entering the lake subsequent to changes in animal husbandry practices in the lake's catchment occurred around 1964. This apparently tipped the balance between the three species of dinoflagellates, resulting in the near disappearance of the red form from the plankton and concomitant disappearance of the red colour from the lake

Monohydroxy-hydrazone-functionalized Thermally Crosslinked Polymers for Nonlinear Optics

The synthesis and properties of six hydrazone-functionalized crosslinked polymers possessing stable nonlinear optics (NLO) properties are presented. First, a series of six hydroxy-functionalized, NLO-active hydrazone chromophores were synthesized. These chromophores were then grafted via its hydroxy functionality on an epoxy polymer to obtain the six NLO-active soluble prepolymers. The grafting reaction yielded multiple secondary hydroxyl sites, which were used for further crosslinking by formulation of the prepolymer with a blocked polyisocyanate crosslinker. This formulation was spin-coated on glass slides to form 2-2.5 thick defect-free transparent films. The films were corona-poled above their glass-transition temperatures to align the chromophores in a noncentrosymmetric fashion and were simultaneously cured. The thermal characteristics of the second-order nonlinearity of the six polymers were compared to illustrate the key structure-property relationships underlying the performance of the films in terms of NLO activity and thermal stability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 770-781, 200