Range Spanning Research Articles

Wastewater Discharge Transports Riverine Microplastics over Long Distances.

Wastewater discharge from wastewater treatment plants continuously pumps microplastics into rivers, yet their transport distances within these waterways remain unknown. Herein, we developed a conceptual framework by synthesizing the microplastic data from the Yangtze River Basin to evaluate its transport distances, quantifying a significant spatial dependence between large-scale wastewater discharge and riverine microplastics (p < 0.05). The presence of microplastics at a specific sampling site could be attributed to wastewater discharge within a large-scale range spanning >1000 km upstream, encompassing a substantial portion equivalent to one-third of the Yangtze River Basin. The dominance analysis indicated that the contribution of wastewater discharge in rivers with higher discharge (>100 m3/s) to riverine microplastic pollution exceeded 65% within the Yangtze River Basin. The spatial dependence framework of riverine microplastics on wastewater discharge advances our prior understanding of the prevention and control of riverine microplastics by demonstrating that such pollution is not limited to nearby environmental factors.

The effect of the integral length scale of turbulence on a wind turbine aerofoil

The effect of free stream turbulence on a DU96w180 wind turbine aerofoil is investigated through wind tunnel experiments. Wind turbine blades experience large scale, high intensity turbulent inflow during their service life. However, the effect of turbulence is normally neglected in the assessment of their aerodynamic performance. This is normally justified based on common assumptions on the effect of the integral length scale of turbulence, which supposedly only acts in the low-frequency range of the energy spectrum, hence affecting the angle of attack instead of the aerodynamic behaviour. In this study, an experimental setup implementing passive grids is developed to vary independently turbulence intensity and integral length scale in wind tunnel testing, with a range spanning I~5–15% and L~8−33cm respectively. Results show that turbulence effects are not negligible even at the largest integral length scales, provided that a critical value for the turbulence intensity is achieved. Turbulence is found to increase mean and fluctuating Lift and delay separation in stalled conditions.

Reconfigurable FET Biosensor for a Wide Detection Range and Electrostatically Tunable Sensing Response

The nanoscale field effect transistors have emerged as promising candidates for highly sensitive bio/chemical detection. Despite the massive progress, current FET biosensing technologies have limitations in terms of adaptability, versatility and throughput. Herein, we present an approach to dynamically tune the sensing performance of a FET biosensor by local electrostatic gating of the metal-semiconductor junctions. Depending upon the bias applied at the local gates, the device switches its operation configurations to deliver functionalities with markedly different sensing characteristics. Such reconfigurability at the runtime allows application suitability on the go, a feature non-existent in the state-of-art FET biosensors. The results of numerical simulations, based on framework validated against the experimental results, reveal promising sensing performance in terms of a high detection sensitivity (~105) with 104-fold tunable sensitivity window and a wide overall dynamic range spanning >4 orders of magnitude using a single device (a ~100-fold improvement over a conventional FET biosensor). The wide dynamic range is also established through a simple analytical approach based on 1:1 binding kinetics for antibody-antigen system. Taken together, the results strongly suggest that the proposed sensor design, representing the first approach of purely electrostatic phenomenon based tuning of sensing performance, has a considerable potential to enable the future development of more compact, multifunctional and adaptive biosensing platforms.

Inverse Analysis of Radiative Flux Maps for the Characterization of High Flux Sources

The reconstruction of the angular and spatial intensity distribution from radiative flux maps measured in high flux solar simulators (HFSS) or optical concentrators is an ill-posed inverse problem requiring special solution strategies. We aimed at providing a solution strategy for the determination of intensity distributions of arbitrarily complicated concentrating facilities. The approach consists of the inverse reconstruction of the intensities from multiple radiative flux maps recorded at various positions around the focal plane. The approach was validated by three test cases including uniform spatial, Gaussian spatial, and uniform angular distributions for which we successfully predicted the intensity for a square-shaped target with edge length of 0.5 m and for a displacement range spanning ±1.5 m at a resolution of 3.2 × 106 elements, yielding relative errors between 19.8–26.4% and 15.7–25.6% when using Tikhonov regularization and the conjugate gradient least square (CGLS) method, respectively. The latter method showed superior performance and was used at a resolution of 2.35 × 107 elements to analyze EPFL's HFSS comprising 18 lamps. The inverse solution for a single lamp retrieved from experimentally measured and simulated radiative flux maps showed peak intensities of 13.7 MW/m2/sr and 16.0 MW/m2/sr, respectively, with a relative error of 81.1%. The inverse reconstruction of the entire simulator by superimposing the single lamp intensities retrieved from simulated flux maps resulted in a maximum intensity of 18.8 MW/m2/sr with a relative error of 80%. The inverse method proved to provide reasonable intensity predictions with limited resolution of details imposed by the high gradients in the radiative flux maps.

Wide Field-of-view and Broadband Terahertz Beam Steering Based on Gap Plasmon Geodesic Antennas

Despite a plethora of applications ranging from wireless communications to sensing and spectroscopy, the current terahertz beam steering technologies suffer from tremendous insert loss, stringent control of electric bias, limited scanning angle, relatively complicated configuration and narrow operation bandwidth, preventing further practical application. We propose and demonstrate a conceptually new approach for terahertz beam steering by virtue of gap plasmon geodesic antennas. By adjusting the geometric dimension of the gap plasmon geodesic antennas, all gap plasmon modes add coherently along a peculiar direction that depends on the geodesic mean surface. Consequently, high directive beams are generated through the antenna, whose direction could be changed within a wide-angle range spanning ±45° by lateral motion of the feed. Furthermore, an assembled antenna structure consisting of four-element geodesic antennas array is proposed for full 360° beam steering, which can operate in a broadband range from 0.8 THz to 1.2 THz.

Tailoring Material Stiffness by Filler Particle Organization.

In the context of emerging methods to control particle organization in particle-matrix composite materials, we explore, using finite element analysis, how to modulate the material bulk mechanical stiffness. Compared to a composite containing randomly distributed particles, material stiffness is enhanced 100-fold when filler particles are aligned into linear chains lying parallel to the loading direction. In contrast, chains aligned perpendicular to that direction produce negligible stiffness change. These outcomes reveal how zigzag chains, which provide intermediate results, can modulate stiffness. The stiffness decreases gradually with increasing zigzag angle θ over a range spanning 2 orders of magnitude.

Corrections of dual-wire CTA data in turbulent swirling and non-swirling jets

Constant Temperature Anemometers provide opportunities for high data rate in relation to velocity and turbulence measurements in gaseous jets. The application of dual-wire probes in turbulent non-swirling and swirling jets is, however, challenging due to the need to correct for directional responses, velocity gradients and probe misalignments with the mean flow direction. Although swirl flow measurements have been conducted in the past using dual-wire probes, the literature does not include clear methodologies to compensate for both gradient effects and changes to the mean flow direction, particularly in flow regions with high shear and strong swirl over a range spanning (S=0–1.05). As a result, this paper presents an overview of the methodology needed to apply dual-wire probes and accommodate changes to the resultant velocity (mean flow) angle (α) through orienting the probe (ψ). Results show that both velocity gradient effects as well as probe misalignments are strongly affected by radial location, Reynolds number and swirl intensity. This study demonstrates a setup methodology that orients CTA X-wire probes for improved data yield and accuracy for turbulent swirling jets.

Geoelectrohydraulic parameters of shallow sandy aquifer in Itu, Akwa Ibom State (Nigeria) using geoelectric and hydrogeological measurements

Knowledge of geoelectrohydraulic parameters is paramount in the management of groundwater resource and the design and construction of safe engineering structures. Results obtained from integrated borehole-constrained geophysical analyses and interpretations, in situ measurements on water samples and laboratory analyses of aquifer units were employed in estimating the basic geoelectrohydraulic parameters such as formation factor, porosity, tortuosity, coefficient of permeability, bulk and interface conductivities. Other parameters estimated are Dar-Zarrouk parameters and transmissivities. The application of empirical and semi-empirical models in the analyses of sixteen evenly spread resistivity and hydrogeological data of sixteen nearby aquifer repositories measured in laboratory were combined with the results of in situ measurements of water samples to obtain the geoelectrohydraulic properties. The ranges of results obtained and their variations established through computations and graphical illustrations show goodness of fit when compared with other ranges and variations documented in literatures. From the results, the upper hydrogeological units have bulk resistivity range of 804–6001Ωm with mean value of 4118Ωm. The range of water resistivity and the mean are respectively 21.9–612.0Ωm and 237.7Ωm. Formation resistivity factor ranges from 9.8 to 36.7 with an average value of 21.6. The estimated range and mean values of porosity were 16.7–29.69% and 21.8%. The tortuosity values range from 1.79 to 2.48 with a mean value of 2.11. The hydraulic conductivity values of the aquifer units gave a range spanning between 3.03×10−5 (2.6) and 2.38×10−4m/s (20.60m/day) with an average value of 7.46×10−5m/s (6.45m/day). The economic aquifers have thicknesses ranging from 27.9 to 103.0m and a mean value of 63.1m. The range and the mean values of Dar-Zarrouk parameters are 9.0×10−3–3.5×10−2Ω−1 and 1.8×10−2Ω−1 for longitudinal conductance and 22,432–565,882Ωm2 and 28,6393Ωm2 for transverse resistance respectively. The transmissivity also lies between 73 and 1186m2/day with a mean value of 672.0m2/day. The deduced parameters can be used as the physical basis for predicting groundwater flow and a guide to designing geofluid flow modelling programmes in the saturated subsurface of the study area. The estimated models and spatial spread of parameters from data processing are promising and suitable for use in contaminant migration modelling. They can also be used to improve the quality of existing models in the study area.

A passively mode-locked, self-starting femtosecond Yb:KYW laser with a single highly dispersive semiconductor double-chirped mirror for dispersion compensation

We demonstrate a semiconductor double-chirped mirror consisting of an AlAs/GaAs multilayer stack grown by molecular beam epitaxy. The mirror has a high negative group velocity dispersion of −2450 ± 100 fs2 and a reflectivity exceeding 98.9% over the spectral range spanning ±4 nm around 1035 nm. When used to compensate the cavity dispersion in a diode-pumped femtosecond Yb:KY(WO4)2 oscillator, at 490 mW of the absorbed pump power, the laser delivered 110 mW in pulses of 240 fs duration.

Pincer-like claws in centipedes (Chilopoda): multiple evolutionary origin of similar form and serial pattern

In most Chilopoda, the walking legs end in a single-tip claw usually accompanied by short accessory spines. Instead, in all species of three small and only distantly related geophilomorph taxa (Diphyonyx, Neogeophilidae, Eucratonyx), the claws of an anterior set of leg pairs are unusually pincer-like. By integrating different microscopic techniques, including confocal laser scanning microscopy, we found that these modified claws are very similar in form, internal structure, and pattern of variation in shape along the trunk in all three taxa: the claws are distinctly swollen and bent, provided with peculiar bulges, and flanked by a conspicuous additional branch, either cylindrical or flattened, which overreaches the tip of the claw; instead, the internal cuticular features are not modified with respect to the condition in the other centipedes, claiming against the possibility of controlled abduction/adduction between claw and branch. Irrespective of the total number of leg pairs (63–129), the claws change gradually from pincer-like to usual shape invariantly in the range spanning between the 34 and the 45% of the total number of leg pairs. Despite these similarities, pincer-like claws originated independently in the three taxa, and by way of fundamentally different changes, either by the dramatic modification of the already existent anterior accessory spine (Diphyonyx, Neogeophilidae) or by the production of a novel cuticular projection (Eucratonyx). Moreover, their shared pattern of variation along the body was most probably constrained by already operating developmental processes controlling the longitudinal patterning of the trunk.

β4-Subunit increases Slo responsiveness to physiological Ca2+ concentrations and together with β1 reduces surface expression of Slo in hair cells

Changing kinetics of large-conductance potassium (BK) channels in hair cells of nonmammalian vertebrates, including the chick, plays a critical role in electrical tuning, a mechanism used by these cells to discriminate between different frequencies of sound. BK currents are less abundant in low-frequency hair cells and show large openings in response to a rise in intracellular Ca(2+) at a hair cell's operating voltage range (spanning -40 to -60 mV). Although the molecular underpinnings of its function in hair cells are poorly understood, it is established that BK channels consist of a pore-forming α-subunit (Slo) and a number of accessory subunits. Currents from the α (Slo)-subunit alone do not show dramatic increases in response to changes in Ca(2+) concentrations at -50 mV. We have cloned the chick β(4)- and β(1)-subunits and show that these subunits are preferentially expressed in low-frequency hair cells, where they decrease Slo surface expression. The β(4)-subunit in particular is responsible for the BK channel's increased responsiveness to Ca(2+) at a hair cell's operating voltage. In contrast, however, the increases in relaxation times induced by both β-subunits suggest additional mechanisms responsible for BK channel function in hair cells.

STATE TRANSITIONS IN BRIGHT GALACTIC X-RAY BINARIES: LUMINOSITIES SPAN BY TWO ORDERS OF MAGNITUDE

Using X-ray monitoring observations with the ASM on board the RXTE and the BAT on board the Swift, we are able to study the spectral state transitions occurred in about 20 bright persistent and transient black hole and neutron star binaries. We have confirmed that there is a correlation between the X-ray luminosity corresponding to the hard-to-soft transition and the X-ray luminosity of the following soft state. This correlation holds over a luminosity range spanning by two orders of magnitude, with no indication of a flux saturation or cut-off. We have also found that the transition luminosity correlates with the rate of increase in the X-ray luminosity during the rising phase of an outburst or flare, implying that the origin of the variation of the transition luminosity is associated with non-stationary accretion in both transient sources and persistent sources. The correlation between the luminosity corresponding to the end of the soft-to-hard transition and the peak luminosity of the preceding soft state is found insignificant. The results suggest that the hysteresis effect of spectral state transitions is primarily driven by non-stationary accretion when the mass accretion rate increases rather than the mass accretion rate decreases. Our results also imply that Galactic X-ray binaries can reach more luminous hard states during outbursts of higher luminosities and of similar rise time scales as those observed. Based on the correlations, we speculate that bright hard state beyond the Eddington luminosity will be observed in Galactic binaries in the next century. We also suggest that some ultra-luminous X-ray sources in nearby galaxies, which stay in the hard states during bright, short flares, harbor stellar-mass compact stars.

Extreme Tunability of Interactions in aLi7Bose-Einstein Condensate

We use a Feshbach resonance to tune the scattering length a of a Bose-Einstein condensate of 7Li in the |F=1,mF=1> state. Using the spatial extent of the trapped condensate, we extract a over a range spanning 7 decades from small attractive interactions to extremely strong repulsive interactions. The shallow zero crossing in the wing of the Feshbach resonance enables the determination of a as small as 0.01 Bohr radii. Evidence of the weak anisotropic magnetic dipole interaction is obtained by comparison with different trap geometries for small a.

Fluctuations in acoustic transmissions when propagation is at an oblique angle to the direction of oceanic tides

Ocean tides such as the lunar M2 tide in coastal regions cause time variations (also range variations) in water depth as well as sound speed profile. When acoustic transmissions are perpendicular to the direction of the tide the received signal exhibits the fundamental oceanographic frequency of the tide and overtones of the fundamental. When the transmissions are along the direction of the tide or at an oblique angle over a range spanning several tidal wavelengths, some reduction in fluctuations can be expected from general theoretical considerations. This phenomenon is studied using the adiabatic mode/WKB model, and the implications for coastal regions are discussed. For example, in SWAT data, the tidal phase remains constant over a 10 km range span along the tidal wave-front, but undergoes change over a similar range span along the tidal direction. Several illustrative examples are presented to show both the magnitude and complexity (relevant to overtone structure) of the acoustic fluctuations. [Work supported by ONR (PE-62435N), and administered by NRL.]