Distances In Excess Research Articles

Timing and route of migration of mature female blue crabs in a large, wind‐driven estuary

AbstractObjectiveQuantify the timing of mature female blue crab Callinectes sapidus migration and the routes they take in the Croatan, Albemarle, and Pamlico Estuarine System (CAPES) in North Carolina, USA.MethodsMark–recapture data collected by commercial crabbers in northeastern North Carolina during 2008 and 2009 identified the timing, rate, and route of movement for 1049 postcopulatory female blue crabs out of 8400 tagged (17.5% recapture).ResultMature female blue crabs consistently moved from their original, up‐estuary release sites towards the Oregon Inlet spawning sanctuary in early summer. Although crabs averaged 2 km/d and covered distances in excess of 50 km during the tagging season, no recaptures were reported from inside or within 10 km of inlet spawning sanctuaries connecting the CAPES to the Atlantic Ocean. The vast majority of recaptures were concentrated within the area where Albemarle, Currituck, and Croatan sounds merge, which is likely due to a combination of high fishing effort and the narrowing of the waterways that concentrate mature females as they migrate south towards spawning sanctuaries.ConclusionThe high concentration of blue crab recaptures in this region suggests that extending no‐take, inlet sanctuary boundaries into these waters may protect mature females as they migrate to the inlet spawning grounds.

Probabilistic shaped 128-APSK CV-QKD transmission system over optical fibres.

In this Letter we present a discrete modulated, continuous variables quantum key distribution implementation using two probabilistically shaped, 128-symbol, amplitude and phase shift keying constellations. At Bob's detection side, a polarization diverse, true heterodyne receiver architecture is implemented for symbol recovery. We demonstrate experimentally that our system is capable of achieving security against collective attacks, while using accessible, telecom-grade material, and of functioning for an indefinitely long period of time at distances in excess of 185 km, in the asymptotic regime.

Long-range quasi-non-diffracting Gauss-Bessel beams in a few-cycle laser field.

Many applications ranging from nonlinear optics to material processing would benefit from pulsed ultrashort (quasi-)non-diffracting Gauss-Bessel beams (GBBs). Here we demonstrate a straightforward yet efficient method for generating such zeroth- and first-order GBBs using a single reflective spatial light modulator. Even in the sub-8-fs range there are no noticeable consequences for the measured pulse duration. The only effect is a weak "coloring" of the outer-lying satellite rings of the beams due to the spectrum spanning over more than 300 nm. The obtained beams have diffraction half-angles below 40 μrad and reach propagation distances in excess of 1.5 m.

The use of aerosol data in Auger Fluorescence Detector analysis

The Pierre Auger Observatory’s Fluorescence Detector (FD) consists of 27 telescopes arranged in four sites around the perimeter of the 3000 square kilometre Surface Detector (SD). Cosmic ray extensive air showers are viewed via the nitrogen fluorescence light they induce in the atmosphere. Careful treatment of light attenuation processes must be made, especially given that some showers are viewed at distances in excess of 30 km. Of particular importance is the attenuation due to scattering by aerosol particles, a challenging topic given that aerosol concentrations can vary on time-scales of hours. At the Auger Observatory, the vertical distribution of aerosols is measured hourly with a series of bi-static lidar systems (consisting of central laser facilities and each of the FD sites), and three times per night with a Raman lidar system. In this contribution we describe the use of aerosol profiles in the analysis of air shower data, in particular in the estimation of the cosmic ray primary energy, and the depth of shower maximum, Xmax. We also demonstrate how statistical and systematic uncertainties in the aerosol concentrations propagate through to a contribution to energy and Xmax uncertainties.

Experimental Generation of ELF Radio Signals Using a Rotating Magnet

This paper presents a simple, compact, and low-power method for generating extremely low-frequency radio signals below ~500 Hz. This paper is motivated by the prohibitively large size and low efficiency of conventional antennas operating in this frequency range. The successful generation of time-varying magnetic fields produced by the physical rotation of a 3 cm3 permanent magnet is demonstrated. Ground plane and receiver orientation effects are analyzed both theoretically and experimentally. Observations as a function of distance from the source indicate that the fields are dominated by the static component, rather than by the radiation component, of the generated field. Based on these observations, the electromagnetic radiation emitted by a spinning magnet source is predicted to be weak. Nevertheless, static magnetic signaling using this technique is proven to be both possible and practical at frequencies below ~500 Hz and at distances in excess of 100 m.

Magnetic tweezers optimized to exert high forces over extended distances from the magnet in multicellular systems.

Magnetic tweezers are mainly divided into two classes depending on the ability of applying torque or forces to the magnetic probe. We focused on the second category and designed a device composed by a single electromagnet equipped with a core having a special asymmetric profile to exert forces as large as 230 pN-2.8 μm Dynabeads at distances in excess of 100 μm from the magnetic tip. Compared to existing solutions our magnetic tweezers overcome important limitations, opening new experimental paths for the study of a wide range of materials in a variety of biophysical research settings. We discuss the benefits and drawbacks of different magnet core characteristics, which led us to design the current core profile. To demonstrate the usefulness of our magnetic tweezers, we determined the microrheological properties inside embryos of Drosophila melanogaster during the syncytial stage. Measurements in different locations along the dorsal-ventral axis of the embryos showed little variation, with a slight increase in cytoplasm viscosity at the periphery of the embryos. The mean cytoplasm viscosity we obtain by active force exertion inside the embryos is comparable to that determined passively using high-speed video microrheology.

Modeling sound fields generated by multi-nodal communications networks found in underwater industrial settings

Increasingly as the sea becomes host to marine industrial operations, mid-to-high frequency multi-nodal communication systems are being employed to monitor equipment states and to control remotely controlled and autonomous underwater vessels used to service and tend underwater equipment. From a regulatory standpoint most of this equipment is modeled as single point noise sources and propagation concerns are ameliorated by high-frequency attenuation due to sound absorption through frequency-dependent chemical “relaxation” or “elasticity” characteristics of boric acid (BH3O3) and magnesium sulphate (MgSO4) components in seawater, and assumptions of the directionality of high-frequency signals. But due to the multi-nodal aspect of their operations, these networks actually set up a broad sound field that can be operationally detected at distances in excess of 10km. In this paper we approximate the characteristics of these sound fields by propagation modeling under realistic, but hypothetical scenarios that would be found in offshore and subsea fossil fuel extraction and renewable energy harvesting operations.

The Effect of Ignoring Earth Curvature on Near-Regional Traveltime Tomography and Earthquake Hypocentral Determination

Earthquake hypocenter determination and traveltime tomography with local earthquake data are normally conducted using a Cartesian coordinate system and assuming a flat Earth model, but for regional and teleseismic data Earth curvature is incorporated and a spherical coordinate system employed. However, when the study region is from the local to near-regional scale (1°–4°), it is unclear what coordinate system to use and what kind of incorrect anomalies or location errors might arise when using the Cartesian coordinate frame. In this paper we investigate in a quantitative sense through two near-regional crustal models and five different inversion methods, the hypocenter errors, reflector perturbation and incorrect velocity anomalies that can arise due to the selection of the wrong coordinate system and inversion method. The simulated inversion results show that the computed traveltime errors are larger than 0.1 s when the epicentral distance exceeds 150 km, and increases linearly with increasing epicentral distance. Such predicted traveltime errors will result in different patterns of incorrect velocity anomalous structures, a perturbed Moho interface for traveltime tomography and source position which deviate for earthquake locations. The maximum magnitude of a velocity image artifact is larger than 1.0% for an epicentral distance of less than 500 km and is up to 0.9% for epicentral distances of less than 300 km. The earthquake source location error is more than 2.0 km for epicentral distances less than 500 km and is up to 1.5 km for epicentral distances less than 300 km. The Moho depth can be in error by up 1.0 km for epicentral distances of less than 500 km but is less than 0.5 km at distances below 300 km. We suggest that spherical coordinate geometry (or time correction) be used whenever there are ray paths at epicentral distances in excess of 150 km.

Long-distance spin transport in a disordered magnetic insulator

Spin transport through magnetic insulators via magnons has recently been explored for a growing variety of magnetic systems with long-range order and well-understood spin excitation spectra. Here we show dramatic effects of spin transport through an amorphous magnetic insulator, which is both magnetically and structurally disordered. We generate and detect spin flow though amorphous yttrium-iron-garnet ($a$-YIG) thin films in a non-local geometry by use of the spin Hall and inverse spin Hall effects in platinum strips separated by 10 or more microns. By comparing non-local spin transport in $a$-YIG on suspended micromachined thermal isolation platforms to the same experiment performed on a bulk substrate, we show strong effects of in-plane thermal gradients on spin transport in the disordered magnetic insulator. The resulting non-local voltage signals are orders of magnitude larger than those seen in crystalline magnetic insulators, with easily measurable spin signals seen even at distances in excess of $100$ microns. In analogy to heat transport, where disordered materials support a range of vibrational excitations that can allow large thermal conductivities, we suggest that efficient spin transport in disordered magnetic systems can occur via a similar spectrum of excitations that relies on strong local exchange interactions and does not require long-range order. This work not only opens a new area for fundamental experimental and theoretical studies of spin transport, but also sets a new direction in materials science for magnonic and spintronic devices.

Does the underground sidewall station survey method meet MHSA standards?

The accuracy of all underground surveying is regulated by the standards described in the South African Mine Health and Safety Act. Four categories of accuracy is described. This pa-per describes the evaluation of accuracy standards of a typically configured sidewall station survey network in a narrow mine tunnel environment. The sidewall system lends itself to re-duced risk exposure and greater efficiency coupled with added redundancy normally not found in standard underground networks. The question is asked whether or not this method of sur-veying will meet the MHSA standards of accuracy that was developed for typical hangingwall traverse type networks. Results obtained from a survey closure using a network of clusters of four sidewall stations demonstrates that under the described circumstances it will provide ac-curacies that are within the minimum standards of accuracy of a Class “A” survey as pre-scribed by the Mine Health and Safety Act. It was found that a survey of the same network using clusters of only two sidewall stations method could not provide the same closure results over longer distances, but that this system lends itself well to Class “C” type surveys for re-connaissance and measuring purposes. Results indicated that the second method of surveying appears to have a greater probability of severe bearing error propagation over distances in excess of 180m and would require regular check surveys in order to strengthen the network. Some of the advantages and disadvantages of the sidewall survey system are discussed to pro-vide a better understanding of the application of this method of surveying on South African mines.

Very long distance connection of gigawatt‐size offshore wind farms: extra high‐voltage AC versus high‐voltage DC cost comparison

This study presents a cost comparison between commercially available high-voltage DC (HVDC) and extra high-voltage AC shore connection (±320 kV voltage source converter and 420 kV–50 Hz single-core and three-core cables), for a 1 GW offshore wind farm cluster, considering transmission distances up to 400 km. The HVDC system is a point-to-point connection whereas multiple AC intermediate compensating stations are envisaged for AC when needed. Capital costs are evaluated from recently awarded contracts, operating costs include energy losses and missed revenues due to transmission system unavailability, both estimated using North Sea wind production curves. Optimal AC intermediate compensation, if any, and reactive profiles are also taken into account. Resultsshow that HVDC has lower transmission losses at distances in excess of 130 km; however, due to the combined effect of lower AC capital cost and unavailability, using three-core aluminium cables can be more convenient up to 360 km distance.

Seismic geomorphology of cretaceous megaslides offshore Namibia (Orange Basin): Insights into segmentation and degradation of gravity-driven linked systems

This study applies modern seismic geomorphology techniques to deep-water collapse features in the Orange Basin (Namibian margin, Southwest Africa) in order to provide unprecedented insights into the segmentation and degradation processes of gravity-driven linked systems. The seismic analysis was carried out using a high-quality, depth-migrated 3D volume that images the Upper Cretaceous post-rift succession of the basin, where two buried collapse features with strongly contrasting seismic expression are observed. The lower Megaslide Complex is a typical margin-scale, extensional-contractional gravity-driven linked system that deformed at least 2 km of post-rift section. The complex is laterally segmented into scoop-shaped megaslides up to 20 km wide that extend downdip for distances in excess of 30 km. The megaslides comprise extensional headwall fault systems with associated 3D rollover structures and thrust imbricates at their toes. Lateral segmentation occurs along sidewall fault systems which, in the proximal part of the megaslides, exhibit oblique extensional motion and define horst structures up to 6 km wide between individual megaslides. In the toe areas, reverse slip along these same sidewall faults, creates lateral ramps with hanging wall thrust-related folds up to 2 km wide. Headwall rollover anticlines, sidewall horsts and ramp anticlines may represent novel traps for hydrocarbon exploration on the Namibian margin.The Megaslide Complex is unconformably overlain by few hundreds of metres of highly contorted strata which define an upper Slump Complex. Combined seismic attributes and detailed seismic facies analysis allowed mapping of headscarps, thrust imbrications and longitudinal shear zones within the Slump Complex that indicate a dominantly downslope movement of a number of coalesced collapse systems. Spatial and stratal relationships between these shallow failures and the underlying megaslides suggest that the Slump Complex was likely triggered by the development of topography created by the activation of the main structural elements of the lower Megaslide Complex.This study reveals that gravity-driven linked systems undergo lateral segmentation during their evolution, and that their upper section can become unstable, favouring the initiation of a number of shallow failures that produce widespread degradation of the underlying megaslide structures. Gravity-driven linked systems along other margins are likely to share similar processes of segmentation and degradation, implying that the megaslide-related, hydrocarbon trapping structures discovered in the Namibian margin may be common elsewhere, making megaslides an attractive element of deep-water exploration along other gravitationally unstable margins.

12CO emission from EP Aquarii: Another example of an axi-symmetric AGB wind?

The CO(1-0) and (2-1) emission of the circumstellar envelope of the AGB star EP Aqr has been observed using the IRAM PdBI and the IRAM 30-m telescope. The line profiles reveal the presence of two distinct components centered on the star velocity, a broad component extending up to ~10 km/s and a narrow component indicating an expansion velocity of ~2 km/s. An early analysis of these data was performed under the assumption of isotropic winds. The present study revisits this interpretation by assuming instead a bipolar outflow nearly aligned with the line of sight. A satisfactory description of the observed flux densities is obtained with a radial expansion velocity increasing from ~2 km/s at the equator to ~10 km/s near the poles. The angular aperture of the bipolar outflow is ~45 deg with respect to the star axis, which makes an angle of ~13 deg with the line of sight. A detailed study of the CO(1-0) to CO(2-1) flux ratio reveals a significant dependence of the temperature on the star latitude, smaller and steeper at the poles than at the equator at large distances from the star. Under the hypothesis of radial expansion and of rotation invariance about the star axis, the effective density has been evaluated in space as a function of star coordinates. Evidence is found for an enhancement of the effective density in the northern hemisphere of the star at angular distances in excess of ~3" and covering the whole longitudinal range. The peak velocity of the narrow component is observed to vary slightly with position on the sky, a variation consistent with the model and understood as the effect of the inclination of the star axis with respect to the line of sight. While the phenomenological model presented here reproduces well the general features of the observations, significant differences are also revealed, which would require a better spatial resolution to be properly described.

The 17 May 2013 M 4.6 Ladysmith, Quebec, Earthquake

Although moderate in size ( M N 5.2, M 4.6), the earthquake that occurred near Ladysmith, Quebec, on 17 May 2013 was one of the best‐recorded earthquakes to have occurred in eastern Canada in recent years due to the fortuitous deployment of U.S. Transportable Array stations in a region that was already well covered by the Canadian National Seismograph Network. This data set allowed us to study the earthquake and its aftershocks in better detail than we could have done in the past. Moment tensor and first‐motion focal mechanisms suggest that it was a typical western Quebec earthquake resulting from thrust faulting on a northwest‐striking plane. Several methods were used to determine the depth, all indicating a depth of 12–15 km. The aftershock sequence, which included a magnitude 4.1 ( M N) earthquake occurring 10 min after the mainshock, was relatively rich in M N>3.0 events and contrasts sharply with that of the 2010 Val‐des‐Bois earthquake (also in western Quebec). Strong‐motion data from the Ladysmith earthquake contributed to an ongoing study to model soft soil amplification and basin effects. The earthquake was felt to distances in excess of 500 km, and more than 4300 people filled out an online “Did You Feel It?” survey, providing a detailed picture of macroseismic effects. Visits to Ladysmith and nearby communities found evidence for minor damage confined to the epicentral area. It is difficult to correlate the Ladysmith sequence with any known faults in the region, but it is noted that some local‐scale lineaments in the epicentral area trend subparallel to the nodal planes of the focal mechanism.

Juvenile Osprey Navigation during Trans-Oceanic Migration.

To compensate for drift, an animal migrating through air or sea must be able to navigate. Although some species of bird, fish, insect, mammal, and reptile are capable of drift compensation, our understanding of the spatial reference frame, and associated coordinate space, in which these navigational behaviors occur remains limited. Using high resolution satellite-monitored GPS track data, we show that juvenile ospreys (Pandion haliaetus) are capable of non-stop constant course movements over open ocean spanning distances in excess of 1500 km despite the perturbing effects of winds and the lack of obvious landmarks. These results are best explained by extreme navigational precision in an exogenous spatio-temporal reference frame, such as positional orientation relative to Earth's magnetic field and pacing relative to an exogenous mechanism of keeping time. Given the age (<1 year-old) of these birds and knowledge of their hatching site locations, we were able to transform Enhanced Magnetic Model coordinate locations such that the origin of the magnetic coordinate space corresponded with each bird's nest. Our analyses show that trans-oceanic juvenile osprey movements are consistent with bicoordinate positional orientation in transformed magnetic coordinate or geographic space. Through integration of movement and meteorological data, we propose a new theoretical framework, chord and clock navigation, capable of explaining the precise spatial orientation and temporal pacing performed by juvenile ospreys during their long-distance migrations over open ocean.

Wind Conditions in a Fjordlike Bay and Predictions of Wind Speed Using Neighboring Stations Employing Neural Network Models

AbstractThis paper evaluates the applicability of neural networks for estimating wind speeds at various target locations using neighboring reference locations along the south coast of Newfoundland, Canada. The stations were chosen to cover a variety of topographic features and span distances in excess of 100 km. The goal of the study is to provide a general description of the summer wind conditions along the south coast of Newfoundland and to assess the potential application of neural networks for wind speed predictions. Analysis of wind data from July to October showed the wind going dominantly toward the northeast with speeds ranging from 0 to 45 m s−1. The efficacy of neural networks to predict wind speeds varied among stations and was largely influenced by the presence/absence of wind barriers. Sensitivity analysis on neural network performance concluded that an absolute minimum of 3000 h of continuous monitoring is needed to effectively train neural networks to predict wind speeds. The conclusions of this study have implications for future work utilizing wind speed data where a generalization of uniform wind speeds is assumed.

Weakening of the π*–π* dimerisation in 1,2,3,5-dithiadiazolyl radicals: structural, EPR, magnetic and computational studies of dichlorophenyl dithiadiazolyls, Cl2C6H3CNSSN

A series of dichlorophenyl dithiadiazolyls (DCP-DTDA) have been prepared and structurally characterized by X-ray diffraction (1 = 2,3-DCP-DTDA; 2 = 2,4-DCP-DTDA; 3 = 2,5-DCP-DTDA, 4 = 3,4-DCP-DTDA and 5 = 3,5-DCP-DTDA). All the radicals adopt cis-cofacial π*–π* dimers with intra-dimer S⋯S contacts in the range 3.119(8)–3.300(5) A. The propensity for chloro-aromatics to adopt a β-sheet structure assists formation of lamellar structures in 1–5 with intra-stack Cl⋯Cl contacts in the range 3.44(1)–3.82(1) A. Perpendicular to the stacking direction, the packing is dominated by formation of intermolecular S⋯Cl contacts. Variable-temperature magnetic susceptibility measurements on 1–5 in the range 5–300 K reveal the onset of paramagnetism around ca. 200 K. Solid-state EPR studies reveal that this paramagnetism is associated with thermal population of a triplet excited state. A good fit to the Bleaney–Bowers model determined the exchange interactions (2J) between the radicals in the dimers to be in the range −904 to −1529 cm−1. Computational studies of the dimerisation process indicate that at intra-dimer S⋯S distances in excess of 3.2 A the closed-shell singlet becomes destabilized with respect to both the open-shell singlet and triplet state configurations.

The spatial and temporal distribution of grain‐size breaks in turbidites

ABSTRACTGrain‐size breaks are surfaces where abrupt changes in grain size occur vertically within deposits. Grain‐size breaks are common features in turbidites around the world, including ancient and modern systems. Despite their widespread occurrence, grain‐size breaks have been regarded as exceptional, and not included within idealized models of turbidity current deposition. This study uses ca 100 shallow sediment cores, from the Moroccan Turbidite System, to map out five turbidite beds for distances in excess of 2000 km. The vertical and spatial distributions of grain‐size breaks within these beds are examined. Five different types of grain‐size break are found: Type I – in proximal areas between coarse sand and finer grained structureless sand; Type II – in proximal areas between inversely graded sand overlain by finer sand; Type III – in proximal areas between sand overlain by ripple cross‐laminated finer sand; Type IV – throughout the system between clean sand and mud; and Type V – in distal areas between mud‐rich (debrite) sand and mud. This article interprets Types I and V as being generated by sharp vertical concentration boundaries, controlled by sediment and clay concentrations within the flows, whilst Types II and III are interpreted as products of spatial/temporal fluctuations in flow capacity. Type IV are interpreted as the product of fluid mud layers, which hinder the settling of non‐cohesive grains and bypasses them down slope. Decelerating suspensions with sufficient clay will always form cohesive layers near to bed, promoting the generation of Type IV grain‐size breaks. This may explain why Type IV grain‐size breaks are widespread in all five turbidites examined and are commonplace within turbidite sequences studied elsewhere. Therefore, Type IV grain‐size breaks should be understood as the norm, not the exception, and regarded as a typical feature within turbidite beds.

A density functional theory study of paramagnetic cyclopentadienylcobalt(III) derivatives: fluoride versus cyanide

The cobalt(III) complexes Cp₂Co₂F₄ and Cp₂Co₂(CN)₄ have been studied by density functional theory methods as representatives of the experimentally known Cp₂Co₂X₄ species with the weak-field fluoride ligand and the strong-field cyanide ligand. Both complexes were found to have relatively complicated energy surfaces with low-energy triplet and quintet spin state structures as well as the expected singlet-state structures for Co(III) complexes. This existence of singlet-, triplet-, and quintet-state structures of similar energies complicates the study of these complexes by density functional theory. The B3LYP* method of Reiher et al. was chosen in an effort to provide the most reliable estimates of the relative energies of the singlet, triplet, and quintet spin states. The lowest-energy Cp₂Co₂F₄ structure was found to be a doubly bridged quintet spin state structure, with similar triplet and singlet structures lying within ∼4 kcal mol⁻¹ of this quintet structure. The lowest-energy Cp₂Co₂(CN)₄ structure was found to be a triplet spin state structure, with a singlet structure lying within ∼1 kcal mol⁻¹ of this triplet structure. Almost all of the Cp₂Co₂X₄ structures were found to have nonbonding Co···Co distances in excess of 2.9 Å, as expected for Co(III) complexes. In general, structures with trans stereochemistry of the Cp and other terminal ligands were found to be of lower energy than the corresponding structures with cis stereochemistry.

Controlled particle positioning using liquid film squeeze flow

Particles trapped in a fluid layer between a glass slide and coverslip can be moved by depressing the coverslip at one edge. This simple premise is explored as a way of making a system capable of micron accuracy particle manipulation with the fluid retained within these disposable and universally used surfaces. Piezoelectric stacks are used to depress the coverslip and the ensuing particle motion is characterised. In this work we add, to this method, a visual feedback control system to interface with four piezoelectric stacks. Through this method control of location and trajectory of 6.02μm particles is demonstrated over distances in excess of 100μm and with an accuracy of half the particle diameter. Such accuracy has potential for applications in moving functionalised mobile particles to static adherent cells.