Transient Patches Research Articles

Collimated synchrotron threads in wide-angle-tail radio galaxies: cosmic thunderbolts?

ABSTRACT The WAT (wide-angle-tail) radio galaxies ESO 137-006 and 3C338 show radio filaments including some extending between the two radio tails. If, in analogy to the Parker solar wind model, jets carry a powerful relativistic electric current, the continuity equation shows that slow return current responding to a temporal variation in jet power would inevitably lead to a localized short-lived charging-up, i.e. a temporary patch of electric field. Progenitors of the observed radio filaments are the relic jets left by repeated episodes of nuclear activity and pushed sideways by the ram pressure, though remaining connected to the broad radio lobes. The Debye shielding distance, for energetic particles with a p−2-distribution of momentum p, allows a very large Debye scale at the highest energies, approaching the radio galaxy scale, with a huge total energy content. Here, we propose that discharges dissipating the transient patches of electric fields through the filaments illuminate them. Our proposal is based on gradient drift currents within the bipolar jets, allowing for drift speeds approaching the speed of light. We sketch a scenario how a discharge current sometimes gets manifested as a radio filament connecting opposite lobes/tails of a WAT radio galaxy.

Sunflecks in the upper canopy: dynamics of light‐use efficiency in sun and shade leaves of Fagus sylvatica

Summary Sunflecks are transient patches of direct radiation that provide a substantial proportion of the daily irradiance to leaves in the lower canopy. In this position, faster photosynthetic induction would allow for higher sunfleck‐use efficiency, as is commonly reported in the literature. Yet, when sunflecks are too few and far between, it may be more beneficial for shade leaves to prioritize efficient photosynthesis under shade.We investigated the temporal dynamics of photosynthetic induction, recovery under shade, and stomatal movement during a sunfleck, in sun and shade leaves of Fagus sylvatica from three provenances of contrasting origin.We found that shade leaves complete full induction in a shorter time than sun leaves, but that sun leaves respond faster than shade leaves due to their much larger amplitude of induction. The core‐range provenance achieved faster stomatal opening in shade leaves, which may allow for better sunfleck‐use efficiency in denser canopies and lower canopy positions.Our findings represent a paradigm shift for future research into light fluctuations in canopies, drawing attention to the ubiquitous importance of sunflecks for photosynthesis, not only in lower‐canopy leaves where shade is prevalent, but particularly in the upper canopy where longer sunflecks are more common due to canopy openness.

Arthropod traits and assemblages differ between core patches, transient stepping-stones and landscape corridors

ContextRestoring landscape connectivity can mitigate fragmentation and improve population resilience, but functional equivalence of contrasting elements is poorly understood. Evaluating biodiversity outcomes requires examining assemblage-responses across contrasting taxa.ObjectivesWe compared arthropod species and trait composition between contrasting open-habitat network elements: core patches, corridors (allowing individual dispersal and population percolation), and transient stepping-stones (potentially enhancing meta-population dynamics).MethodsCarabids and spiders were sampled from core patches of grass-heath habitat (n = 24 locations across eight sites), corridors (trackways, n = 15) and recently-replanted clear-fells (transient patches, n = 19) set in a forest matrix impermeable to open-habitat arthropods. Species and trait (habitat association, diet, body size, dispersal ability) composition were compared by ordination and fourth corner analyses.ResultsEach network element supported distinct arthropod assemblages with differing functional trait composition. Core patches were dominated by specialist dry-open habitat species while generalist and woodland species contributed to assemblages in connectivity elements. Nevertheless, transient patches (and to a lesser degree, corridors) supported dry-open species characteristic of the focal grass-heath sites. Trait associations differed markedly among the three elements. Dispersal mechanisms and their correlates differed between taxa, but dry-open species in transient patches were characterised by traits favouring dispersal (large running hunter spiders and large, winged, herbivorous carabids), in contrast to wingless carabids in corridors.ConclusionsCore patches, dispersal corridors and transient stepping-stones are not functionally interchangeable within this system. Semi-natural core patches supported a filtered subset of the regional fauna. Evidence for enhanced connectivity through percolation (corridors) or meta-population dynamics (stepping stones) differed between the two taxa.

Perception of Sunflecks by the UV-B Photoreceptor UV RESISTANCE LOCUS8.

Sunflecks, transient patches of light that penetrate through gaps in the canopy and transiently interrupt shade, are eco-physiologically and agriculturally important sources of energy for carbon gain, but our molecular understanding of how plant organs perceive and respond to sunflecks through photoreceptors remains limited. The UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8) is a recent addition to the list of plant photosensory receptors, and we have made considerable advances in our understanding of the physiology and molecular mechanisms of action of UVR8 and its signaling pathway. However, the function of UVR8 in the natural environment is poorly understood. Here, we show that the UVR8 dimer/monomer ratio responds quantitatively and reversibly to the intensity of sunflecks that interrupt shade in the field. Sunflecks reduced hypocotyl growth and increased CHALCONE SYNTHASE (CHS) and ELONGATED HYPOCOTYL5 gene expression and CHS protein abundance in wild-type Arabidopsis (Arabidopsis thaliana) seedlings, but the uvr8 mutant was impaired in these responses. UVR8 was also required for normal nuclear dynamics of CONSTITUTIVELY PHOTOMORPHOGENIC1. We propose that UVR8 plays an important role in the plant perception of and response to sunflecks.

Ways to patch a broken heart

Biomaterials Minimizing how invasive a surgical procedure is can benefit the patient, and the same could be true for the delivery of transient patches to help repair damaged tissues. Montgomery et al. designed optimal scaffolds from biodegradable poly[octamethylene maleate (anhydride) citrate] that were confined in bioreactors in their extended shape while seeded with cells. Patches as large as a square centimeter could then be compressed and delivered through an orifice a millimeter wide to repair rat hearts, where the residual stress from the injection process causes the scaffold to return to its original shape, but without damaging the cells. Further tests showed the successful delivery of patches to porcine epicardium, aorta, and liver. Nat. Mat. 10.1038/nmat4956 (2017).

Copepod Aggregations: Influences of Physics and Collective Behavior

Dense copepod aggregations form in Massachusetts Bay and provide an important resource for right whales. We re-examine the processes which might account for the high concentrations, investigating both horizontally convergent flow, which can increase the density of depth-keeping organisms, and social behavior. We argue that the two act in concert: social behavior creates small dense patches (on the scale of a few sensing radii); physical stirring brings them together so that they merge into aggregations with larger scales; it also moves them into areas of physical convergence which retain the increasingly large patch. But the turbulence can also break this apart, suggesting that the overall high density in the convergence zone will not be uniform but will instead be composed of multiple transient patches (which are still much larger than the sensing scale).

Effects of bulk aggregation on PEI–SDS monolayers at the dynamic air–liquid interface: depletion due to precipitation versus enrichment by a convection/spreading mechanism

The dynamic interfacial adsorption from mixtures of high molecular weight poly(ethylene imine) (PEI) and sodium dodecyl sulfate (SDS) has been studied by neutron reflectometry and ellipsometry at the expanding air–water interface created by an overflowing cylinder. Aggregation of PEI and SDS in the bulk solution has very different consequences on the dynamic interfacial properties depending on the polyelectrolyte charge density. At high pH, where PEI has low charge density, bulk aggregation depletes the solution of surface-active monomers and small complexes; the aggregates do not adsorb to the dynamic liquid interface as a result of their slow diffusion, and the surface excess is depleted. At low pH, where PEI has a high charge density, bulk aggregates reach the surface and reorganise to spread thin transient patches of material across the interface, enriching rather than depleting the surface excess. This study highlights that in order to optimise the performance of polymer–surfactant mixtures under conditions relevant to processing and applications, further work is required to understand their behaviour under non-equilibrium conditions.

A Novel, Non-Invasive Microwave-Based Device for the Treatment of Axillary Hyperhidrosis

INTRODUCTION: A new non-invasive microwave device was developed to treat axillary hyperhidrosis. This study reports a large, multicenter, randomized, sham-controlled clinical trial investigating efficacy and safety. METHODS: 120 adult subjects were randomized to treatment group (n=81) or sham group (n=39) and were treated in two sessions spaced two weeks apart. Each axilla was marked using a template, anesthetized using local anesthesia, and treated using a device handpiece that delivers microwave energy through the skin. Follow-up was 6 months for the sham group and 12 months for the treatment group. RESULTS: The mean age of subjects was 32.8 years; 58% of the subjects were female. The primary efficacy measure was the percentage that had HDSS scores reduced to 1 or 2 (from 3 or 4 at baseline), implying sweat that was not noticeable or was tolerable. Results for the treatment group were 89% at 30-days post-treatment, 67% at 6-months, and 69% at 12-months. Sham group results were 54% at 30-days and 44% at 6-months (p<0.001 at 30 days and p=0.019 at 6 months). Additionally, 91% of treated subjects showed at least a one point decrease in HDSS score at 30 days, and 81% at 12-months. Treatment-related adverse events were generally mild and all but one completely resolved. The most common adverse events were transient patches of altered sensation in the skin of the treated arm (n=9, 9.9%). Most subjects experienced transient post-treatment local sequelae in the axilla including edema, tenderness, and bruising. CONCLUSION: A new microwave-based device and procedure has been developed with a very high efficacy for treating axillary hyperhidrosis, with results that show promising stability for long-term relief. DISCLOSURES: Research was supported by Miramar Labs. Larry K. Fan, MD is a consultant and has received research funding from Miramar Labs. William P. Coleman, MD is a consultant and shareholder and has received research funding from Miramar Labs. Dee Anna Glaser, MD is a consultant and shareholder and has received research funding from Miramar Labs. Michael S. Kaminer, MD is a consultant and shareholder and has received research funding from Miramar Labs. Suzanne L. Kilmer, MD is a consultant and has received research funding from Miramar Labs. Robert Nossa, MD has received research funding from Miramar Labs. Stacy R. Smith, MD is a consultant and has received research funding from Miramar Labs.

Seasonal ice cycle at the Mars Phoenix landing site: 2. Postlanding CRISM and ground observations

The combination of ground observations from the Mars Phoenix Lander and orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provided a detailed view of the formation of late summer surface water ice at the landing site and surrounding regions. CRISM observations of the landing site during and immediately after Phoenix operations were analyzed to track the seasonal and diurnal ice cycles during the late spring to late summer, and a nonlinear mixing model was used to estimate grain sizes and relative abundances of water ice and dust. The surface around the Phoenix landing site was ice‐free from late spring through midsummer, although transient patches of mobile ices were observed in an 85 m diameter crater to the northeast of the landing site. At the ∼10 km diameter Heimdal Crater, located ∼10 km east of the landing site, permanent patches of water ice were observed to brighten during the late spring and darken during the summer, possibly as fine‐grained water ice that was cold trapped onto the ice during late spring sintered into larger grains or finally sublimated, exposing larger‐grained ice. CRISM spectra first show evidence of widespread ice during the night at solar longitude (Ls) ∼ 109°, ∼9 sols before Phoenix's Surface Stereo Imager detected it. CRISM spectra first show evidence of afternoon surface ice and water ice clouds after Ls ∼ 155°, after Phoenix operations ended.

Microhabitat selection by sea turtles in a dynamic thermal marine environment

1. Reproductive fitness is often compromised at the margins of a species' range due to sub-optimal conditions. 2. Set against this backdrop, the Mediterranean's largest loggerhead sea turtle (Caretta caretta) rookery at Zakynthos (Greece) presents a conundrum, being at a very high latitude for this species, yet hosting a high concentration of nesting. 3. We used visual surveys combined with global positioning system (GPS) tracking to show that at the start of the breeding season, individuals showed microhabitat selection, with females residing in transient patches of warm water. As the sea warmed in the summer, this selection was no longer evident. 4. As loggerhead turtles are ectothermic, this early season warm-water selection presumably speeds up egg maturation rates before oviposition, thereby allowing more clutches to be incubated when sand conditions are optimal during the summer. 5. Active selection of warm waters may allow turtles to initiate nesting at an earlier date.

Open woodland and savanna decline in a mixed-disturbance landscape (1938 to 1998) in the Northwest Wisconsin (USA) Sand Plain

Our research illustrates how a landscape mosaic changes in association with a mixed natural-anthropogenic disturbance history. Our study area is the Northwest Wisconsin (USA) Sand Plain (NWSP), a region with a rich disturbance history including fire, insects and clearcut forestry. We integrated historic airphotos from 1938, 1960, 1980 and 1998 within a GIS to describe change among four landcover classes describing a canopy-closure gradient: closed forests, woodlands, savannas and “open barrens”. Our work addresses two literature needs: empirical studies of mixed-disturbance landscapes, and nonforest habitats within a forest matrix. Our analysis shows that: the area of open barrens fluctuated, woodlands and savannas declined severely and closed forests increased through time. Falling median patch sizes and other landscape metrics suggest that the woodlands are becoming more fragmented. The landcover transitions driving this change vary according to time and place. The dominant transitions are toward closed forests from all classes, and transitions toward open barrens are also consistently important. The woodlands, savannas and open barrens habitats are mostly comprised of transient patches, persisting for less than 20 years. This contrasts with closed forests that often persist for 40 plus years. These changes are consistent with the disturbance regime that is shifting from fire- to forestry-dominance. Our results show a trend towards landscape simplification, manifest as losses of intermediate-density habitats (woodland and savanna) and shrinking patch sizes. The transient nature of the nonforest habitats shows that disturbance resulting in total or partial canopy removal will be vital for their conservation at a landscape scale.

Tribological Properties and Electrical Signal Transmission of Copper–Graphite Composites

The correlation between tribological properties of resin bonded copper–graphite composites and electrical signal transmission is investigated. Particular attention is given to the loss of electrical signal at the sliding interface and the amount of signal noise as a function of the composition in the composite. A custom designed slip-ring type tribotester with a copper ring has been used for this study. Results show that the tribological properties of the sliding couple, that is closely associated with morphology of sliding surfaces and the presence of transfer films, determine the amount of voltage drop at the interface and electrical signal noise. The change of the applied load during sliding experiment changes the coefficient of friction (COF) and energy loss at the sliding interface, suggesting that the effective contact area at the rubbing surface of the composite strongly affects the amount of voltage drop. It is also found that the electrical signal noise is directly related with the fluctuation of the friction coefficient caused by the variation of contacts at the sliding interface and by the transient patches of transfer films on the surface of the ring.

HOW TRANSIENT PATCHES AFFECT POPULATION DYNAMICS: THE CASE OF HYPOXIA AND BLUE CRABS

Transient low-oxygen patches may have important consequences for the population dynamics of estuarine species. We investigated whether these transient hypoxic patches altered population dynamics of the commercially important blue crab (Callinectes sapidus) and assessed two alternative hypotheses for the causal mechanism. One hypothesis is that temporary reductions in habitat due to hypoxia increase cannibalism. The second hypothesis is that crab population dynamics result from food limitation caused by hypoxia- induced mortality of the benthos. We developed a spatially explicit individual-based model of blue crabs in a hierarchical framework to connect the autoecology of crabs with the spatial and temporal dynamics of their physical and biological environments. Three primary scenarios were run to examine the interactive effects of (1) hypoxic extent vs. static and transient patches, (2) hypoxic extent vs. prey abundance, and (3) hypoxic extent vs. cannibalism potential. Static patches resulted in populations limited by egg production and recruitment whereas transient patches led to populations limited by the effects of cannibalism and patch interactions. Crab survivorship was greatest for simulations with the largest hypoxic patches which also had the lowest prey abundance and lowest crab densities. In these simulations, nearly all crab mortality was accounted for by aggression, not starvation. In addition, increased prey abundance had little influence on crab abundance and dynamics, and massive reductions in prey abundance (.50%) were necessary to decrease crab abundance, survival, and egg production. Our analyses suggest that cannibalism coupled with decreased egg production determined key aspects of crab demography. Specifically, decreased cannibalism potential resulted in a food-limited crab population with long development times and high adult crab densities whereas increased cannibalism potential led to low adult crab densities with higher individual egg production rates. Our analyses identified several key knowledge gaps, including the nature of crab-crab cannibalism and the role of refuges from predation. Several experiments are suggested to test model predictions and to improve understanding of ecosystem-population linkages for this estuarine species.

On the reality of upper mesospheric/lower thermospheric turbulent “eddies”

The structure of atmospheric turbulence and its relationship to the refractive index discontinuities responsible for the scattering of radio waves are discussed. Emphasis is placed more on the nature of the intermittent scatterers observed at upper mesospheric/lower thermospheric altitudes than on volume scattering. The preferred model is of transient patches composed of vortex strings. An overview of the methods used to estimate the rate of dissipation of turbulent energy using MF radar data which emphasizes the advantages of imaging Doppler interferometry is presented, together with a review of pertinent laboratory investigations of coherent structures. An attempt is made to remove the contamination by gravity waves from imaging Doppler interferometry fluctuating velocity data. Emphasis is given to the fact that all radar measurements of turbulent intensity to date are upper estimates, not only because of the presence of gravity wave fluctuations contaminating the data, but also because the turbulence itself is not stationary and homogeneous but intermittent in both space and time. The intermittent nature of the turbulence, in which the refractive index discontinuities responsible for the radar backscatter are associated with decaying, homogeneous turbulent coherent structures, is in contrast to the theory of volume scattering, which assumes the radar pulse volume to be partially filled with stationary, homogeneous turbulence.

Growth and survival of white clover (Trifolium repens) transplanted into patches of different grass species

Previous studies on Trifolium repens L. showed differentiation with respect to neighbouring plant species and local environmental conditions. In this study, we conducted a series of reciprocal transplants among and within different pastures and among neighbouring grass species (Lolium perenne L., Dactylis glomerata L., and Holcus lanatus L.). While the presence of a grass neighbour decreased survival and growth of T. repens, no evidence of differentiation by T. repens to either local environmental conditions or to neighbouring grass species was found. We suggest that T. repens, in systems like our study pastures that have small, transient grass patches, may show inconsistent and ephemeral responses to the presence of neighbouring plants, whereas in other systems with larger grass patch size and a longer period of exposure to selection processes, T. repens show fine-scale biotic differentiation to neighbouring grass species. Keywords: population differentiation, white clover, selection, microevolution, transplantation.

Temperature finestructure and microstructure observations in a coastal upwelling region during a period of variable winds (Oregon, summer 1974)

Profiles of temperature and temperature gradient made during two 4-day cruises with a freely-falling probe, in conjunction with conductivity-temperature-depth (CTD) and current meter records, are used to examine a 100-m water column on the Oregon shelf for evidence of finestructure-microstructure correlation, shear-induced mixing, and double-diffusive convecting layers. The rate of dissipation of temperature fluctuations, ε ν , is founnd to be as large as 2 × 10 −5 °C 2 s −1 in a well-stirred surface layer, and as low as 7 × 10 −11 °C 2 s −1 in a region undisturbed by intrusions or boundary stirring. For the surface mixed layer, a decade-long, + 1 slope was observed in the temperature gradient spectrum for vertical wavelengths greater than about 5 mm. If this is assumed to be a viscous-convective subrange, the rate of dissipation of mechanical energy, ε, is calculated to be 0.06 cm 2 s −3 . Transient patches of intense microstructure, 1 to 2 m in extent, can occur in the thermocline. Variations in temperature variance of 10 3 can occur over small vertical separations in several intrusions, but when normalized by the local finestructure gradient (yielding the Cox number) the range is considerably less. A 4-m thick ‘hole’ in the microstructure appears in a shallow, cold intrusion. A warm intrusion has a complicated, time-dependent vertical structure and a low Cox number (less than 10). An interleaving at about 60 m produces a 0.10°C, 10-m thick inversion with many small-scale features indicative of overturning; the Cox number is about 600 in this case. Although all the temperature inversions have T-S gradients favorable for double-diffusive convection, no systems of layers are found. In general, the results are similar to those from other observations of oceanic microstructure associated with the different types of finestructure.