Gait switches in deep-diving beaked whales : biomechanical strategies for long-duration dives

Work in the Canary Islands was funded by the Office of Naval Research and the National Oceanographic Partnership Program (NOPP), by a consortium consisting of the Canary Islands Government, the Spanish Ministry of Environment and the Spanish Ministry of Defense and by the European environmental funding LIFE-INDEMARES program for the inventory and designation of the Natura 2000 network in marine areas of the Spanish territory, headed by Fundacion Biodiversidad, with additional support from the Cabildo Insular of El Hierro. Fieldwork in the Ligurian Sea was funded by NOPP. Research in the Gully was funded by the Strategic Environmental Research and Development Program (SERDP) programs RC-2113 and RC-2337. L.M.M.L. was funded by a ‘la Caixa’ Fellowship within the 2010 UK Framework Programme. N.A.d.S. was funded for this study by ONR and by the EU FP7 Marie Curie project SOUNDMAR. M.J. was funded by a Marie Curie Career Integration Grant, and from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions.Diving animals modulate their swimming gaits to promote locomotor efficiency and so enable longer, more productive dives. Beaked whales perform extremely long and deep foraging dives that probably exceed aerobic capacities for some species. Here, we use biomechanical data from suction-cup tags attached to three species of beaked whales (Mesoplodon densirostris, N = 10; Ziphius cavirostris, N = 9; and Hyperoodon ampullatus, N = 2) to characterize their swimming gaits. In addition to continuous stroking and stroke and-glide gaits described for other diving mammals, all whales produced occasional fluke-strokes with distinctly larger dorsoventral acceleration, which we termed 'type-B' strokes. These high-power strokes occurred almost exclusively during deep dive ascents as part of a novel mixed gait. To quantify body rotations and specific acceleration generated during strokes we adapted a kinematic method combining data from two sensors in the tag. Body rotations estimated with high-rate magnetometer data were subtracted from accelerometer data to estimate the resulting surge and heave accelerations. Using this method, we show that stroke duration, rotation angle and acceleration were bi-modal for these species, with B-strokes having 76% of the duration, 52% larger body rotation and four times more surge than normal strokes. The additional acceleration of B-strokes did not lead to faster ascents, but rather enabled brief glides, which may improve the overall efficiency of this gait. Their occurrence towards the end of long dives leads us to propose that B-strokes may recruit fast-twitch fibres that comprise similar to 80% of swimming muscles in Blainville's beaked whales, thus prolonging foraging time at depth.PostprintPeer reviewe

A blind test of photometric redshift prediction

Results of a blind test of photometric redshift predictions against spectroscopic galaxy redshifts obtained in the Hubble Deep Field with the Keck Telescope are presented. The best photometric redshift schemes predict spectroscopic redshifts with a redshift accuracy of |Delta-z|<0.1 for more than 68 percent of sources and with |Delta-z|<0.3 for 100 percent, when single-feature spectroscopic redshifts are removed from consideration. This test shows that photometric redshift schemes work well at least when the photometric data are of high quality and when the sources are at moderate redshifts.Comment: 14 pp., accepted for publication in A

The Genetics of Self-Compatibility and Associated Floral Characters in Tolpis (Asteraceae) in the Canary Islands

This is the publisher's version, also available electronically from http://www.jstor.org/stable/10.1086/668788.Members of the genus Tolpis (Asteraceae) endemic to the Canary Islands comprise a monophyletic group with the dispersal of one species to the Cape Verde Islands. Most species are self-incompatible or pseudo-self-compatible perennials. However, one species, Tolpis coronopifolia, consists of self-compatible annual plants with several floral features typical of the selfing syndrome. The evolution of self-compatibility and the selfing syndrome was studied by producing synthetic hybrids between self-incompatible/pseudo-self-compatible and self-compatible plants to determine the genetic architecture of breeding system and floral trait differences. There was a correlation between self-compatibility and selfing floral traits in the F2 generation. Self-incompatibility in Tolpis appears to be controlled by a locus of major effect but with modifier loci affecting seed set. Segregation of floral traits indicates that they are controlled by multiple loci. The high molecular similarity between plants with the two breeding systems suggests that divergence of the self-compatible T. coronopifolia from self-incompatible/pseudo-self-compatible ancestors has been recent. The association between breeding system and floral features likely results from pleiotropy or close linkage and may have facilitated the rapid evolution of the morphologically distinct self-compatible T. coronopifolia

Brain Model State Space Reconstruction Using an LSTM Neural Network

Objective Kalman filtering has previously been applied to track neural model states and parameters, particularly at the scale relevant to EEG. However, this approach lacks a reliable method to determine the initial filter conditions and assumes that the distribution of states remains Gaussian. This study presents an alternative, data-driven method to track the states and parameters of neural mass models (NMMs) from EEG recordings using deep learning techniques, specifically an LSTM neural network. Approach An LSTM filter was trained on simulated EEG data generated by a neural mass model using a wide range of parameters. With an appropriately customised loss function, the LSTM filter can learn the behaviour of NMMs. As a result, it can output the state vector and parameters of NMMs given observation data as the input. Main Results Test results using simulated data yielded correlations with R squared of around 0.99 and verified that the method is robust to noise and can be more accurate than a nonlinear Kalman filter when the initial conditions of the Kalman filter are not accurate. As an example of real-world application, the LSTM filter was also applied to real EEG data that included epileptic seizures, and revealed changes in connectivity strength parameters at the beginnings of seizures. Significance Tracking the state vector and parameters of mathematical brain models is of great importance in the area of brain modelling, monitoring, imaging and control. This approach has no need to specify the initial state vector and parameters, which is very difficult to do in practice because many of the variables being estimated cannot be measured directly in physiological experiments. This method may be applied using any neural mass model and, therefore, provides a general, novel, efficient approach to estimate brain model variables that are often difficult to measure

Deep-diving beaked whales dive together but forage apart

Funding: Data collection and analysis were performed with funds from the U.S. Office of Naval Research (ONR), the US National Oceanographic Partnership Program (NOPP), the US Strategic Environmental Research Development Program (SERDP) and the Spanish Government National Projects CETOBAPH (CGL2009-13112) and DEEPCOM (CTM2017-88686-P). J.A.T. is currently the recipient of a FPU Doctoral Scholarship (FPU16/00490) from the Spanish Ministry of Universities. M.J. is supported by the Aarhus University Research Foundation and the EU H2020 research and innovation programme under Marie Skłodowska-Curie grant 754513. P.A. is funded by an Agustín de Bethencourt fellowship from the Cabildo Insular de Tenerife and NAS by a Ramón y Cajal fellowship from the Spanish Government. V.E.W. is funded by a University of Auckland Doctoral Scholarship. C.J.P.G. is partially funded by the Ministry of Science and Innovation (MICINN) of Spain under Grant PID2019-110442GB-I00. T.A.M. thanks partial support from CEAUL (funded by FCT - Fundação para a Ciência e a Tecnologia, Portugal, through the project UIDB/00006/2020).Echolocating animals that forage in social groups can potentially benefit from eavesdropping on other group members, cooperative foraging or social defence, but may also face problems of acoustic interference and intra-group competition for prey. Here, we investigate these potential trade-offs of sociality for extreme deep-diving Blainville′s and Cuvier's beaked whales. These species perform highly synchronous group dives as a presumed predator-avoidance behaviour, but the benefits and costs of this on foraging have not been investigated. We show that group members could hear their companions for a median of at least 91% of the vocal foraging phase of their dives. This enables whales to coordinate their mean travel direction despite differing individual headings as they pursue prey on a minute-by-minute basis. While beaked whales coordinate their echolocation-based foraging periods tightly, individual click and buzz rates are both independent of the number of whales in the group. Thus, their foraging performance is not affected by intra-group competition or interference from group members, and they do not seem to capitalize directly on eavesdropping on the echoes produced by the echolocation clicks of their companions. We conclude that the close diving and vocal synchronization of beaked whale groups that quantitatively reduces predation risk has little impact on foraging performance.PostprintPeer reviewe

S-Nitrosothiol-modified nitric oxide-releasing chitosan oligosaccharides as antibacterial agents

S-nitrosothiol-modified chitosan oligosaccharides were synthesized by reaction with 2-iminothiolane hydrochloride and 3-acetamido-4,4-dimethylthietan-2-one, followed by the thiol nitrosation. The resulting nitric oxide (NO)-releasing chitosan oligosaccharides stored ~0.3 μmol NO/mg chitosan. Both the chemical structure of the nitrosothiol (i.e., primary and tertiary) and the use of ascorbic acid as a trigger for NO donor decomposition were used to control the NO-release kinetics. With ascorbic acid, the S-nitrosothiol-modified chitosan oligosaccharides elicited a 4-log reduction in Pseudomonas aeruginosa (P. aeruginosa) viability. Confocal microscopy indicated that the primary S-nitrosothiol-modified chitosan oligosaccharides associated more with the bacteria relative to the tertiary S-nitrosothiol system. The primary S-nitrosothiol-modified chitosan oligosaccharides elicited minimal toxicity towards L929 mouse fibroblast cells at the concentration necessary for a 4-log reduction in bacterial viability, further demonstrating the potential of S-nitrosothiol-modified chitosan oligosaccharides as NO-release therapeutics

Functionalized Mesoporous Silica via an Aminosilane Surfactant Ion Exchange Reaction: Controlled Scaffold Design and Nitric Oxide Release

Nitric oxide-releasing mesoporous silica nanoparticles (MSNs) were prepared using an aminosilane-template surfactant ion exchange reaction. Initially, bare silica particles were synthesized under basic conditions in the presence of cetyltrimethylammonium bromide (CTAB). These particles were functionalized with nitric oxide (NO) donor precursors (i.e., secondary amines) via the addition of aminosilane directly to the particle sol and a commensurate ion exchange reaction between the cationic aminosilanes and CTAB. N-Diazeniumdiolate NO donors were formed at the secondary amines to yield NO-releasing MSNs. Tuning of the ion exchange-based MSN modification approach allowed for the preparation of monodisperse particles ranging from 30 to 1100 nm. Regardless of size, the MSNs stored appreciable levels of NO (0.4–1.5 μmol mg–1) with tunable NO release durations (1–33 h) dependent on the aminosilane modification. Independent control of NO release properties and particle size was achieved, demonstrating the flexibility of this novel MSN synthesis over conventional co-condensation and surface grafting strategies

Dark solitons in mode-locked lasers

Dark soliton formation in mode-locked lasers is investigated by means of a power-energy saturation model which incorporates gain and filtering saturated with energy, and loss saturated with power. It is found that general initial conditions evolve into dark solitons under appropriate requirements also met in the experimental observations. The resulting pulses are well approximated by dark solitons of the unperturbed nonlinear Schr\"{o}dinger equation. Notably, the same framework also describes bright pulses in anomalous and normally dispersive lasers

Seasonal and inter-annual variability in nutrient supply in relation to mixing in the Bay of Biscay

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