Spatial Temporal Stability Research Articles

The Multi-Annual Residency of Juvenile Smooth Hammerhead Shark in an Oceanic Island Nursery

The increased risk of local extinction becomes critical for sharks depending on the narrow and isolated coastal habitats of oceanic islands. This includes large pelagic oceanic sharks that use such habitats as nurseries, as previously hypothesized for the smooth hammerhead Sphyrna zygaena, the least known of cosmopolitan large hammerhead sharks. We used a combination of acoustic and satellite telemetry in a juvenile population of Faial and Pico islands, Azores, mid-north Atlantic, to confirm if this isolated archipelago holds nurseries, and to answer questions related to their function and spatial–temporal stability. Our long-term acoustic tracking data showed a cluster of individual core home ranges in specific areas of north shore Faial, and surface positions from five Argos-linked tagged individuals also showed a clustering overlap in those areas for up to 1 year. These patterns seem to reveal a true habitat preference within the Faial-Pico island (sub) population of juvenile smooth hammerhead shark, and thus constitute strong evidence for this area to be considered a nursery. Some individuals remained in this nursery for up to 4 years, especially during summers. Sharks also showed a strong diel behavior, typically using the inshore nurseries during the day and moving further offshore during the night, during which they increased activity and dove deeper, most possibly to feed. We speculate that a combination of increased feeding opportunities, expanded trophic niche, and reduced predatory pressure may be a key evolutionary driver for the existence, prolonged use, and even preference of coastal nurseries at oceanic islands by juvenile smooth hammerhead shark. Given that these nurseries may constitute essential fish habitat for this species, they should be explicitly included in spatial management measures at the local and regional scales, as they may also play a role of greater importance to the north Atlantic population of this oceanic species.

PO-639-08 IDENTIFICATION OF CONDUCTION PATTERNS DURING ATRIAL FIBRILLATION USING ARTIFICIAL INTELLIGENCE: HOLISTIC FULL CHAMBER VIEW

Atrial fibrillation (AF) is thought to be maintained by reentrant and focal driver regions that may have some spatial-temporal stability. Recently, several cardiac mapping systems have implemented algorithms for automatic detection of these arrhythmogenic conduction patterns (CPs) during AF. Many of these algorithms divide the atrium into overlapping patches, sequentially analyzing each patch with the driver identification algorithms. Patch-based analyses may misrepresent local CPs as the number and trajectory of wavefronts entering and leaving the analyzed patch are uncertain. However, when a holistic view of chamber-wide activation is used, machine learning algorithms can ubiquitously identify arrhythmogenic CPs. Develop and evaluate a machine learning approach that can automatically identify and locate arrhythmogenic CPs. Propagation maps of clinical AF from nine patients were transformed into a 2D image space using conformal mapping, and these images were used to train and evaluate a UNet architecture model. Rotational and focal CPs were identified by the AcQTrack algorithm (Acutus Medical) and manually confirmed. The clinical dataset was supplemented with eikonal simulations of focally (n=400) and rotationally driven (n=200) AF, where the time and location of the rotational and focal drivers were randomized and known. The UNet architecture was trained using five of the clinical AF cases (n=7,880 frames) and simulated AF (200 focal and 100 rotational simulations, n=14,380 frames). A test set, consisting of five clinical AF cases (n=6,172 frames) and simulated AF (200 focal and 100 rotational simulations, n=14382 frames), were independently used to evaluate the model performance. The UNet model accurately detected the time and location of arrhythmogenic CPs in the atrium - Clinical AF DICE 0.91 and Simulated AF DICE 0.98. The presented machine learning approach can accurately identify and locate arrhythmogenic targets. It has potential to overcome limited view problem in detecting arrhythmogenic targets that is inherent problem of patch-based heuristic algorithms.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Inverted microbial community stratification and spatial–temporal stability in hypersaline anaerobic sediments from the S’Avall solar salterns

The anaerobic hypersaline sediments of an ephemeral pond from the S’Avall solar salterns constituted an excellent study system because of their easy accessibility, as well as the analogy of their microbial assemblages with some known deep-sea hypersaline anaerobic brines. By means of shotgun metagenomics and 16S rRNA gene amplicon sequencing, the microbial composition of the sediment was shown to be stable in time and space. The communities were formed by prokaryote representatives with a clear inferred anaerobic metabolism, mainly related to the methane, sulfur and nitrate cycles. The most conspicuous finding was the inverted nature of the vertical stratification. Contrarily to what could be expected, a methanogenic archaeal metabolism was found to dominate in the upper layers, whereas Bacteria with fermentative and anaerobic respiration metabolisms increased with depth. We could demonstrate the methanogenic nature of the members of candidate lineages DHVE2 and MSBL1, which were present in high abundance in this system, and described, for the first time, viruses infecting these lineages. Members of the putatively active aerobic genera Salinibacter and Halorubrum were detected especially in the deepest layers for which we hypothesize that either oxygen could be sporadically available, or they could perform anaerobic metabolisms. We also report a novel repertoire of virus species thriving in these sediments, which had special relevance because of their lysogenic lifestyles.

Breakup of ultra-thin liquid films on vertical fiber enhanced by Marangoni effect

An ultra-thin liquid film flowing down a vertical uniformly heated cylinder under the influence of gravity is investigated. A thin liquid film model is derived, assuming that the film thickness h is much smaller than the fiber radius a. To predict the breakup of film, the van der Waals attraction, proportional to h-3, is taken into account. Linear stability analysis shows that the Rayleigh-Plateau instability is enhanced by the long-range attractions and Marangoni effect. The spatial-temporal stability analysis shows that the instability is absolute when A+M>0.17 (A is a composite Hamaker number accounting for the strength of van der Waals attractions and M is the Marangoni number). A self-similarity analysis shows that the film thins as h∼(tr-t)1/5 (tr is the breakup time), which is supported by the numerical simulations of the thin film model. Although the scaling is independent on the Marangoni effect, nonlinear simulations demonstrate that the breakup time tr decreases as the Marangoni effect becomes stronger, demonstrating that the breakup process is accelerated by the Marangoni effect. Nonlinear simulation also shows that the thin heated or non-heated film mainly breaks up in the absolutely unstable regime.

Influences of trailing boundary layer velocity profiles on wake vortex formation in a high-subsonic-turbine cascade

In this paper, delayed detached eddy simulations are performed to study wake flows of a turbine blade at a high subsonic exit Mach number, [Formula: see text], and high Reynolds number, [Formula: see text], based on the chord length and outlet velocity. It is found that a slight change in the trailing suction profile would have a big influence on the formation of wake vortex street, which is believed to be caused by the change in the boundary layer state near the trailing edge, and suction boundary layer with a fuller velocity profile tends to destabilize the wake flow, promoting the generation of wake vortex and enhancing the unsteady effect. Local spatial-temporal stability analyses of the wake velocity profiles suggest that wake flows with asymmetric velocity profiles might have a stabilizing effect. It is suggested that the vortex formation and its strength can be controlled by making some slight modifications on the rear blade suction surface, and the mixing loss in the wake can be reduced due to a weaker unsteady effect.

Spatial–temporal stability analysis of faceted growth with application to horizontal ribbon growth

Spatial–temporal stability analysis has been applied to a solidification model that includes both isotropic and non-isotropic kinetics. In agreement with previous temporal stability analyses, it was shown that the kinetics associated with the propagation of steps across a facet can stabilize solidification processes that would normally be thermally unstable. In cases where the solidification is unstable, it was also shown that pulling the solid with a tangential velocity can cause a transition from “absolute” instability where perturbations cause growth at all locations to “convective” instability where a perturbation grows as it propagates, but at any fixed location disturbances decay away after the perturbation passes. These results were applied to understand instabilities in the floating silicon method (FSM), which is a particular type of horizontal ribbon growth. It was shown that increasing pull-speeds in FSM leads to increasingly unstable thermal growth conditions, but the combination of the kinetics of faceted growth and the tangential pull velocity can stabilize the process. As the pull speed increases, however, the process becomes increasingly sensitive to perturbation.

ACCUMULATIVE FORMS AND DIFFERENTIATION OF SEDIMENTS IN THE COASTAL ZONE OF THE KAMA RESERVOIR

Accumulative forms may be divided into two groups by their morphology, spatial-temporal stability, and the trend of development. The first group is represented by relatively steady forms: beaches, coastal terraces, inset underwater terraces, mouth bars, spits. The second group is represented by the storm swells, tails, and cones forming on the shallows in early spring after the active slumping of the coastal benches or due to discharge of sediment at the mouths of ravines and gullies. The volume of the largest steady forms (bars, spits, coastal terraces) can reach 12 000 m3. The surveyed coastal site is represented by two mineralogical zones. In northern zone a sector of coastal slope – part of the third terrace – serves as a source of sand-gravel and sandy sediments containing resistant minerals (tourmaline, staurolite, leucoxene). The southern mineralogical zone is characterized by clearly expressed prevalence of silicon and hydroxides of iron. The leading process of coastal morpholithogenesis here is longshore drift.

Atomization mechanism of a charged viscoelastic liquid sheet

In order to study atomization mechanism of a viscoelastic liquid sheet in an electric field, the spatial–temporal stability analysis of a viscoelastic liquid sheet injected into a dielectric stationary ambient gas in the presence of a vertical electric field is conducted. The dispersion relations of both sinuous and varicose disturbance modes are solved to explore the spatial–temporal instability of a charged viscoelastic sheet, by setting both the wave number and frequency complex. A parametric study is performed to test the influence of the dimensionless parameters on the absolute instability of the sheet. The results show that the increase of liquid Weber number and time constant ratio, or decrease of gas to liquid density ratio and Reynolds number, can damp the absolute instability. The effect of the liquid elasticity depends on the value of time constant ratio: when time constant ratio is small, the increase of liquid elasticity could amplify absolute growth rate, but the effect is weak when the elasticity number is relatively large; when time constant ratio is large, the increase of liquid elasticity cannot affect the absolute growth rate. Moreover, the variation of electrical Euler number can hardly influence the absolute instability of a charged viscoelastic sheet.

Abstract B144: Hypoxia imaging with [18F]HX4 PET compared with [18F]FMISO and [18F]FAZA: From preclinical to clinical studies.

Abstract Introduction: Tumor hypoxia is an important prognostic factor in overall survival for chemotherapy and radiotherapy. Quantifying and localizing hypoxia non-invasively is therefore important. At present, hypoxia PET tracers lack high tumor-to-background (TBR) ratios. The nitroimidazole [18F]HX4, has shown promise in pre-clinical (Dubois et al. PNAS 2011) and phase I human setting (van Loon et al. EJNMMI 2010). However, until now no comparative research has been conducted between the latest promising hypoxia tracers in order to define the best marker. In a pre-clinical study [18F]HX4 was compared to the hypoxia tracers [18F]FMISO and [18F]FAZA on 3 endpoints; optimal imaging time point, spatial reproducibility and oxygen dependency. Clinical studies investigated the optimal time point and spatial-temporal stability for [18F]HX4 imaging. Methods: In pre-clinical experiments, WAG/Rij rats bearing rhabdomyosarcoma R1 tumors were injected with 20 ± 4 MBq of [18F]HX4, [18F]FMISO or [18F]FAZA, followed by PET/CT imaging up to 6h post-injection (h p.i.). For each tracer TBR was calculated and reproducibility was investigated by voxel-to-voxel analysis or a DICE similarity coefficient. Oxygen sensitivity was studied by altering the tumoral hypoxia status either by carbogen/nicotinamide treatment or 7% oxygen breathing. In clinical trials, NSCLC (N=15) [NCT01024829, NCT01210378] and HNSCC (N=10) [NCT01347281] patients were injected with 403 ± 53 MBq [18F]HX4 and PET/CT imaging was performed at several time points up to 4h p.i.. Tumor uptake (TBR>1.4), image contrast changes over time, hypoxic fraction (HF) and spatial-temporal stability were evaluated. Results: In pre-clinical setting, [18F]HX4 uptake reached a stabilized and maximal TBR at 3h p.i. (TBR=7.2) which is significantly higher compared to the plateau phase of [18F]FAZA reached at 2h p.i. (TBR=3.9, P<0.05). [18F]FMISO did not reach a plateau. Voxel-to-voxel comparisons and DICE similarity coefficient calculations showed a high short- and long-term spatial reproducibility except for [18F]FAZA, which performed poor on a 48 hour interval. Increasing the hypoxic fraction by 7% oxygen breathing resulted in enhanced mean standardized uptake values for both [18F]HX4 (P<0.01) and [18F]FAZA (P<0.05). Only [18F]FMISO uptake was found to be reversible upon reoxygenation using nicotinamide and carbogen. In patients, a TBR>1.4 was observed in 72% of NSCLC and in 74% of HNSCC target lesions, with average HF of 14 ± 17% and 25 ± 22%, respectively. In the hypoxic lesions, TBR increased up to 4h p.i., providing a better contrast at the latest time-points. [18F]HX4 uptake was stable in time and space for the heterogeneous pattern in NSCLC lesions (2h vs. 4h p.i.: r = 0.77 ± 0.10). Conclusions: Both pre-clinical and clinical studies support [18F]HX4 as a robust hypoxia tracer, with the highest image contrast from 3h p.i. onwards, sensitivity to hypoxia and high reproducibility. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B144. Citation Format: Sarah Peeters, Catharina Zegers, Natasja Lieuwes, Wouter van Elmpt, Frank Hoebers, Hoda Sharifi, Bart Reymen, Michel Öllers, Felix Mottaghy, Jonas Eriksson, Albert Windhorst, Guus van Dongen, Dirk de Ruysscher, Ludwig Dubois, Philippe Lambin. Hypoxia imaging with [18F]HX4 PET compared with [18F]FMISO and [18F]FAZA: From preclinical to clinical studies. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B144.

Spatial-Temporal Stability of an Electrified Viscoelastic Liquid Jet

This paper presents theoretically the spatial-temporal instability behavior of an electrified viscoelastic liquid jet. Dimensionless parameters have been tested for their influence on the transition of absolute and convective instability for the electrified viscoelastic liquid jet. The results show that larger electrical Euler and Weber numbers can change the flow to convectively unstable. The increase of Reynolds number can decrease the absolute growth rate. Variations of time constant and density ratio rarely change the spatial-temporal instability behavior of the jet. The disturbance wavelength changes very little with these parameters when the flow is absolutely unstable.

Assessing the temporal stability of spatial patterns in crop yields using combine yield monitor data

Using previous years’ yield patterns may be one method of breaking a field into management zones for the purpose of site-specific management. For this method to be useful there must be temporal stability of yield patterns and there must be a sound method of assessing the spatial-temporal stability of yield in a field. To this end, a method was developed to give a non-biased estimate of the within-field spatial-temporal stability of yield. The method determined the probability that the normalized yield for all years available at a given location in the field fit within the accuracy limits of the combine. Combine accuracies of ± 2.5%, 5% and 10% of the field mean yield and gridded data of 3 m, 6 m, and 9 m cell sizes, as well as crop choice were all included in the model to assess its sensitivity to changes in these factors. The resulting spatial-temporal stability maps were well correlated with visual estimations of the spatial yield patterns. The model results were highly influenced by the inputted combine accuracy, but grid size and crop choice had little affect on the proportion of the field or the spatial pattern of temporal stability in the two field sites examined. The sensitivity of the model to changes in the input value for the combine accuracy indicated that a good estimate of this value is required for the determination of the stable patterns in a field. Key words: Spatial-temporal stability, yield