Lateral Separation Research Articles

The effect of tone-vocoding on spatial release from masking for old, hearing-impaired listeners

Old, hearing-impaired listeners generally benefit little from lateral separation of multiple talkers when listening to one of them. This study aimed to determine how spatial release from masking (SRM) in such listeners is affected when the interaural time differences (ITDs) in the temporal fine structure (TFS) are manipulated by tone-vocoding (TVC) at the ears by a master hearing aid system. Word recall was compared, with and without TVC, when target and masker sentences from a closed set were played simultaneously from the front loudspeaker (co-located) and when the maskers were played 45° to the left and right of the listener (separated). For 20 hearing-impaired listeners aged 64 to 86, SRM was 3.7 dB smaller with TVC than without TVC. This difference in SRM correlated with mean audiometric thresholds below 1.5 kHz, even when monaural TFS sensitivity (discrimination of frequency-shifts in identically filtered complexes) was partialed out, suggesting that low-frequency audiometric thresholds may be a good indicator of candidacy for hearing aids that preserve ITDs. The TVC difference in SRM was not correlated with age, pure-tone ITD thresholds, nor fundamental frequency difference limens, and only with monaural TFS sensitivity before control for low-frequency audiometric thresholds.

Vertical vs Lateral Macrophase Separation in Thin Films of Block Copolymer Mixtures: Computer Simulations and GISAXS Experiments.

Mixtures of two diblock copolymers of very different lengths may feature both macro- and microphase separation; however, not much is known about the mechanisms of separation in diblock copolymer thin films. In the present work, we study thin films of mixtures of two compositionally symmetric block copolymers, both in the one-phase and in the two-phase state, combining coarse-grained molecular simulations (dissipative particle dynamics, DPD) with scattering experiments (grazing-incidence small-angle X-ray scattering, GISAXS). We reveal that the film thickness and selective adsorption of different blocks to the substrate control the distribution of macrophases within the film as well as the orientation of the lamellae therein. In thick films, the mixtures separate in the vertical direction into three layers: Two layers being rich in short copolymers are formed near the film interfaces, whereas a layer being rich in long copolymers is located in the film core. The lamellar orientation in the layers rich in short copolymers is dictated by the surface selectivity, and this orientation only weakly affects the vertical orientation of lamellae in the film core. This provides the opportunity to control the domain orientation in the copolymer films by mixing block copolymers with low-molecular additives instead of relying on a more complicated chemical modification of the substrate. In thinner films, a lateral phase separation appears.

Effect of instantaneous stirring process on mixing between initially distant scalars in turbulent obstacle wakes

A two-channel planar laser-induced fluorescence technique is used to study mixing and reactions between two initially distant scalars in the turbulent wake of a cylindrical obstacle. The scalars are released continuously and isokinetically upstream of the cylinder, with a lateral separation that initially impedes mixing between them. The effect of the turbulent wake on mixing and reaction enhancement is determined by measuring the segregation parameter for cases with and without the cylinder obstruction. Results indicate that scalar mixing and reaction rates (in the low-Damkohler limit) increase significantly in the presence of the cylinder wake. The study also shows that the dominant contribution of total reaction derives from the scalar covariance associated with instantaneous flow processes, and depends strongly on streamwise location within the wake. The results have broad implications for mixing processes in engineering and ecology.

Generation of phase edge singularities by coplanar three-beam interference and their detection.

In recent years singular optics has gained considerable attention in science and technology. Up to now optical vortices (phase point dislocations) have been of main interest. This paper presents the first general analysis of formation of phase edge singularities by coplanar three-beam interference. They can be generated, for example, by three-slit interference or self-imaging in the Fresnel diffraction field of a sinusoidal grating. We derive a general condition for the ratio of amplitudes of interfering beams resulting in phase edge dislocations, lateral separation of dislocations depends on this ratio as well. Analytically derived properties are corroborated by numerical and experimental studies. We develop a simple, robust, common path optical self-imaging configuration aided by a coherent tilted reference wave and spatial filtering. Finally, we propose an automatic fringe pattern analysis technique for detecting phase edge dislocations, based on the continuous wavelet transform. Presented studies open new possibilities for developing grating based sensing techniques for precision metrology of very small phase differences.

Lipid nanodomains change ion channel function.

Signaling proteins and neurotransmitter receptors often associate with saturated chain and cholesterol-rich domains of cell membranes, also known as lipid rafts. The saturated chains and high cholesterol environment in lipid rafts can modulate protein function, but evidence for such modulation of ion channel function in lipid rafts is lacking. Here, using raft-forming model membrane systems containing cholesterol, we show that lipid lateral phase separation at the nanoscale level directly affects the dissociation kinetics of the gramicidin dimer, a model ion channel.

Investigation of Hydrodynamic Characteristics of High Speed Multihull Vessels including Shallow Water Effect

The objective of this paper is to investigate the hydrodynamic characteristics of high speed catamaran and trimaran ships at different speeds and finite depths using Computational Fluid Dynamics (CFD) techniques. Three dimensional Rankine Source Panel Method with non-linear free-surface boundary condition is used to capture free-surface potential flow around ship hull. Wave pattern, wave resistance, sinkage and trim for varying lateral and longitudinal separation of hull with varying water depths are determined and compared with each other to investigate spacing and depth effects on multihull ship. Computed results show a significant increase in total resistance for water of finite depth compared to deep water. A significant increase in sinkage and trim has also been found in the case of shallow water for both vessels.

Liquid-based stationary phase for deterministic lateral displacement separation in microfluidics.

Deterministic lateral displacement (DLD) is a promising separation scheme in microfluidic systems. In traditional DLD, a periodic array of solid posts induces the separative migration of suspended particles moving through the system. Here, we present a radical departure from traditional DLD systems and use an array of anchored liquid-bridges as the stationary phase in the DLD device. The liquid-bridges are created between two parallel plates and anchored to the bottom one by cylindrical wells. We show that the non-linear particle dynamics observed in traditional DLD systems is also present in the anchored-liquid case, enabling analogous size-based separation of suspended particles. The use of liquid-bridges as the stationary phase presents additional possibilities in separation technologies, potentially eliminating or significantly reducing clogging, enabling renewable and/or reconfigurable systems, allowing a different set of fabrication methods and providing alternative ways to separate particles based on their interaction with liquid-liquid interfaces. Some of these advantages could also extend to filtration methods based on similar liquid-based stationary phases.

Terminal chop: New technique for full thickness nuclear segmentation in mature hard cataract.

We describe an efficient technique, “Terminal Chop,” for full thickness nuclear segmentation in mature hard cataracts. Terminal chop utilizes the principle of secondary rock breakage system with stress concentration to break these hard nuclei. In this technique consonant to drag picks, a specially designed chopper “Terminator” is used to initiate a unique dispersive mechanical force to create a full thickness nuclear crack (crack formation) at the weakest soft and thin equator, which automatically traverses through the center and to the equator on the other side. Lateral separation of both the instruments placed at the equator, propagates the initial full thickness nuclear crack (crack propagation), breaking the entire nucleus into two complete pieces including the posterior plate. The direction of splitting follows the cleavage plane in a more direct manner, thus requiring least fracture force, least manipulation and stress, much lower than compressive stress, causing minimal trauma, and highly satisfactory postoperative results.

Design and Construction of Cervix Phantom for Brachytherapy Dose Assessment Procedure for Clinical Application

An important point to consider in a brachytherapy dosimetry study is the design of an appropriate phantom size in calculations or experimental measurements. Perspex sheets of various size and thickness are used to design the cervix phantom. The aim of the study is to design and construct cervix phantom to mimic the pelvic segment of a standard adult human patients undergoing Brachytherapy. This is to allow assessment of dose to cervix and the surrounding tissues during cervix Brachytherapy. The methodology include; first phantom design where physical dimensions of the phantom were determined from a sampling of 30 patients’ cases to simulate an average patient size. Secondly, construction of phantom with fabricated cylindrical shape, composed of 6 mm Perspex sheets, and the assembly enclosed with the 4 mm Perspex sheet. The result of the constructed phantom had lateral separation of 34 cm, an anterior and posterior separation of 27 cm; with length of 33 cm. The Perspex pieces were glued to each other with Trichloromethane (chloroform) at room temperature. Chloroform dissolves the Perspex (PMMA), and when applied to the surfaces of the Perspex sheets, the surfaces stick together after the chloroform dries up. In forming the surface of the phantom, the 4 mm Perspex sheet was oven heated to a temperature of 140?C to make the sheet malleable. One end of the phantom was made thicker than the other end by gluing another 6 mm Perspex sheet such that the thickness of that particular end of the phantom was 12 mm. A hole of diameter 6.5 cm, which was a little bit posterior to the phantom, was created central to the 12 mm end of the phantom. The opening created was covered by 11 x 11 cm2 and 12 mm Perspex slab which was formed by gluing two 6 mm sheets together. A hole of diameter 5 cm was also made central to the cover created, such that the centre of this hole matches that of the hole on the end of the phantom. A 2.4 cm thick ring with internal diameter of 5 cm and external diameter of 6 cm was fabricated from 2.4 cm Perspex slab, which was formed from gluing four pieces of 6 mm Perspex sheets together. The fabricated ring was mounted on the 11 x 11 cm2 cover created such that the internal walls of the ring and that of the hole in the cover matches. The ring was then glued to the cover using the chloroform. The built phantom simulate actual patient anatomy and produce an excellent result to be use for clinical application.

A detached eddy simulation model for the study of lateral separation zones along a large canyon‐bound river

AbstractLateral flow separation occurs in rivers where banks exhibit strong curvature. In canyon‐bound rivers, lateral recirculation zones are the principal storage of fine‐sediment deposits. A parallelized, three‐dimensional, turbulence‐resolving model was developed to study the flow structures along lateral separation zones located in two pools along the Colorado River in Marble Canyon. The model employs the detached eddy simulation (DES) technique, which resolves turbulence structures larger than the grid spacing in the interior of the flow. The DES‐3D model is validated using Acoustic Doppler Current Profiler flow measurements taken during the 2008 controlled flood release from Glen Canyon Dam. A point‐to‐point validation using a number of skill metrics, often employed in hydrological research, is proposed here for fluvial modeling. The validation results show predictive capabilities of the DES model. The model reproduces the pattern and magnitude of the velocity in the lateral recirculation zone, including the size and position of the primary and secondary eddy cells, and return current. The lateral recirculation zone is open, having continuous import of fluid upstream of the point of reattachment and export by the recirculation return current downstream of the point of separation. Differences in magnitude and direction of near‐bed and near‐surface velocity vectors are found, resulting in an inward vertical spiral. Interaction between the recirculation return current and the main flow is dynamic, with large temporal changes in flow direction and magnitude. Turbulence structures with a predominately vertical axis of vorticity are observed in the shear layer becoming three‐dimensional without preferred orientation downstream.

Analysis and Modeling of Vehicle Following Behavior in Mixed Traffic Conditions

Abstract Car following models replicate the behaviour of a car following another car. In mixed traffic conditions, leader-follower vehicle types are not only car-car cases but also there are different combinations of vehicles (e.g., car-two wheeler and heavy vehicle-auto-rickshaw). Due to weak lane discipline, the follower is unable to strictly follow the lead vehicle. The other types of following behaviour like staggered following, following between vehicles, etc. are also observed under mixed traffic conditions. Depending on speed and position of vehicles in front, the subject vehicle may follow a leading vehicle with varying levels of lateral separation or stagger. The nature, extent and impact of such interactions need to be investigated for characterizing following behaviour under mixed traffic conditions. Hence, the present study focuses on analysis and modelling of vehicle following behaviour under mixed traffic conditions. The current study uses an open access mixed traffic trajectory data collected on an urban arterial road in Chennai city, India. The collected dataset includes 3005 vehicle trajectories with a total of 111,629 observations. To identify the different types of following behaviour, the extent of overlap (%) between leader-follower pair was used. The vehicle following behaviour was classified into three types: 1) Car Following 2) Staggered following and 3) Following between two vehicles. The vehicle following behaviour were analysed for different categories of vehicles and also, for different types of follower-leader pair. When the follower is a smaller size vehicle compared to a leader, it generally follows the leader. It was observed that when the vehicle size increases, staggered following behaviour of vehicle also increases. Subject vehicle chooses a following behaviour based on size of follower and leader, speeds of follower and leader, longitudinal gap between follower and leader, types of follower and leader. Multinomial Logistic Regression model was used to model the choices of vehicle following behaviour. This study has interesting implications in identifying vehicle-specific and vehicle following parameters for car following models to be adopted under mixed traffic and non-lane discipline traffic conditions.

Effect of the transverse magnetic field on spatiotemporal dynamics of quadruple Gaussian laser beam in plasma in weakly relativistic and ponderomotive regime

The spatiotemporal dynamics of a quadruple Gaussian laser beam in plasma is studied in the presence of an external magnetic field by taking into account the relativistic and ponderomotive nonlinearities. Using the paraxial approximation approach, two coupled equations for longitudinal (in time) and transverse (in space) beam width parameters are derived. Their evolution determines the pulse dynamics in time and space. The effects of the initial laser parameters, such as the lateral separation and laser intensity on self-focusing and self-compression mechanisms, are discussed. The results illustrate that the laser beam is focussed and compressed in an enhanced manner in the presence of an external magnetic field. The three dimensional spatiotemporal profile of the normalized intensity of the pulse is studied at different positions where the beam is either focussed or compressed. A three dimensional portrait of the normalized intensity as a function of distance and time is also shown.

Sensitivity studies on the multi-sensor conductivity probe measurement technique for two-phase flows

The objective of this study is to advance the local multi-sensor conductivity probe measurement technique through systematic investigation into several practical aspects of a conductivity probe measurement system. Firstly, signal “ghosting” among probe sensors is found to cause artificially high bubble velocity measurements and low interfacial area concentration (ai) measurements that depend on sampling frequency and sensor impedance. A revised electrical circuit is suggested to eliminate this artificial variability. Secondly, the sensitivity of the probe measurements to sampling frequency is investigated in 13 two-phase flow conditions with superficial liquid and gas velocities ranging from 1.00–5.00m/s and 0.17–2.0m/s, respectively. With increasing gas flow rate, higher sampling frequencies, greater than 100kHz in some cases, are required to adequately capture the bubble number frequency and ai measurements. This trend is due to the increase in gas velocity and the transition to the slug flow regime. Thirdly, the sensitivity of the probe measurements to the measurement duration as well as the sample number is investigated for the same flow conditions. Measurements of both group-I (spherical/distorted) and group-II (cap/slug/churn-turbulent) bubbles are found to be relatively insensitive to both the measurement duration and the number of bubbles, as long as the measurements are made for a duration long enough to capture a collection of samples characteristic to a given two-phase flow system (or a statistical ensemble). Fourthly, investigation into the orientation of a double-sensor probe in the pipe indicates that the sensors should be oriented parallel to the pipe wall to ensure symmetric bubble velocity measurements. Lastly, Monte Carlo simulations are performed to study the effects of the axial (s) and lateral (d) probe sensor separation distances. In addition to previous criteria on the ratio of s to the bubble diameter, it is found that s/d should be greater than four to minimize errors in the measured bubble velocity.

RANS prediction of FLNG-LNG hydrodynamic interactions in steady current

The hydrodynamic interaction between a floating liquefied natural gas system (FLNG) and a liquefied natural gas carrier (LNG) has been studied in steady current using a Reynolds Averaged Navier-Stokes solver. A double body approximation method is adopted to investigate the hydrodynamics of the two vessels in close proximity neglecting the free surface effects. Initially, five benchmark ship–ship interaction cases combining different flow speeds, drafts and relative positions are replicated. Comparisons with measured test data and with computational results from literature are made, suggesting the flow field, pressure distribution and forces and moments acting on the hulls are well predicted. Using the validated numerical setup, systematic computations on the hydrodynamic interactions of the FLNG-LNG offloading system have been carried out in steady current. The forces and moments on the hulls with varying relative longitudinal and lateral separations are estimated and explained. Furthermore, full scale computations are conducted to quantify scale effects existing in the present study. From the obtained results, scale effects are evident in the surge force but found to be much less influential in the sway force, roll moment and yaw moment predictions for the cases tested.

Rajendra Prasad’s Terminal Chop: New Technique For Full Thickness Nuclear Segmentation in Hard Cataract

‘Direct chop’ has become the procedure of choice in hard cataracts but is still fraught with incomplete cracks and difficult instrument manipulation. We describe a new technique, ‘Terminal Chop’, for full thickness nuclear segmentation in hard cataract. A short, shallow, central trench is sculpted in the central nucleus, the phaco tip is engaged at the distal end of the trench and impaled into the nucleus, keeping the tip directed towards the equator parallel to the pupillary plane within the superficial layers of the nucleus. Equator of the nucleus is then slightly lifted vertically and brought out at the capsulotomy edge. A specially designed blunt tipped chopper is then simply passed around the lens equator and hooked. A small full thickness nick is created adjacent to the phaco tip using a blunt chopper. With a firm grip of the nucleus at the equator, lateral separation of the 2 instruments is initiated to create a vector force of 90 degrees, splitting the entire nucleus from equator to equator through the centre, into two complete clean halves. Direction of splitting follows the cleavage plane through the lens fibres thus causing minimal trauma.

Spatial correlation of atmospheric wind at scales relevant for large scale wind turbines

Wind measurements a short distance upstream of a wind turbine can provide input for a feedforward wind turbine controller. Since the turbulent wind field will be different at the point/plane of measurement and the rotor plane the degree of correlation between wind speed at two points in space both in the longitudinal and lateral direction should be evaluated. This study uses a 2D array of mast mounted anemometers to evaluate cross-correlation of longitudinal wind speed. The degree of correlation is found to increase with height and decrease with atmospheric stability. The correlation is furthermore considerably larger for longitudinal separation than for lateral separation. The integral length scale of turbulence is also considered.

Hydrodynamics of passing-over motion during binary droplet collision in shear flow**Project supported by the NSAF (Grants No. U1530260), the National Natural Science Foundation of China (Grant No. 51306158), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20130621), and the Special Program for Applied Research on Super Computation of the NSFC–Guangdong Joint Fund (the second phase).

A combined experimental and numerical study is undertaken to investigate the hydrodynamic characteristics of single-phase droplet collision in a shear flow. The passing-over motion of interactive droplets is observed, and the underlying hydrodynamic mechanisms are elucidated by the analysis of the motion trajectory, transient droplet deformation and detailed hydrodynamic information (e.g., pressure and flow fields). The results indicate that the hydrodynamic interaction process under shear could be divided into three stages: approaching, colliding, and separating. With the increasing confinement, the interaction time for the passing-over process is shorter and the droplet processes one higher curvature tip and more stretched profile. Furthermore, the lateral separation Δy/R1 exhibits larger decrease in the approaching stage and the thickness of the lubrication film is decreased during the interaction. As the initial lateral separation increases, the maximum trajectory shift by the collision interaction is getting smaller. During the collision between two droplets with different sizes, the amplitude of the deformation oscillation of the larger droplet is decreased by reducing the size ratio of the smaller droplet to the bigger one.

Improved pillar shape for deterministic lateral displacement separation method to maintain separation efficiency over a long period of time

Abstract Deterministic lateral displacement (DLD) separation utilizes streamlines produced by an array of pillars, which determine the critical diameter. However, particle clogging often occurs at the gaps between the pillars and alters the streamlines. This leads to a drastic reduction in the separation efficiency. In this study, a topology optimization technique has been applied to design a new pillar shape. This will allow the gap between the pillars to be increased in order to minimize particle clogging without affecting the originally designed critical diameter, thereby maintaining higher separation efficiency over a long period. Experimental investigations revealed that a DLD device with the optimized pillar forms a smaller clogging region over a longer period of time than DLD devices with circular- or triangular-shaped pillars. In the DLD device with the optimized pillars enables to maintain 92.2% separation efficiency in displacement mode over 30 min, whereas in circular pillars the separation efficiency in displacement mode progressively reduces to 77%. This result leads to the conclusion that the microfluidic device with the optimized pillar shape can provide consistent separation efficiency for a long period of time. It is believed that this device could be used for separating rigid particles as alternative way to produce super-monodispersed micro-particles with affordable cost.

A knee brace alters patella position in patellofemoral osteoarthritis: a study using weight bearing magnetic resonance imaging

To assess using weight bearing magnetic resonance imaging (MRIs), whether a patellar brace altered patellar position and alignment in patellofemoral joint (PFJ) osteoarthritis (OA). Subjects age 40-70 years old with symptomatic and a radiographic Kellgren-Lawrence (K-L) evidence of PFJOA. Weight bearing knee MRIs with and without a patellar brace were obtained using an upright open 0.25T scanner (G-Scan, Easote Biomedica, Italy). Five aspects of patellar position were measured: mediolateral alignment by the bisect offset index, angulation by patellar tilt, patellar height by patellar height ratio (patellar length/patellar tendon length), lateral patellofemoral (PF) contact area and finally a measurement of PF bony separation of the lateral patellar facet and the adjacent surface on the femoral trochlea (Fig.1). Thirty participants were recruited (mean age 57 SD 27.8; body mass index (BMI) 27.8 SD 4.2); 17 were females. Four patients had non-usable data. Main analysis used paired t tests comparing within subject patellar position with and without brace. For bisect offset index, patellar tilt and patellar height ratio there were no significant differences between the brace and no brace conditions. However, the brace increased lateral facet contact area (P=.04) and decreased lateral PF separation (P=.03). A patellar brace alters patellar position and increases contact area between the patella and femoral trochlea. These changes would lower contact stress at the PFJ. Such changes in patella position in weight bearing provide a possible biomechanical explanation for the success of the PFJ brace in clinical trials on PFJOA.

A binary phase field crystal study for phase segregation of liquid phase heteroepitaxial growth

The binary phase field crystal (PFC) model is employed to investigate influences of atomic sizes and mobility differences on the liquid phase heteroepitaxial. It was found that large size atoms are driven toward regions of tensile stress which correspond to peaks in a compressively strained film but to valleys in a film with tensile strain. Small size atoms are on the contrary in contrast for large size atoms. Due to the existence of vertical separation and lateral separation resulting from atomic size differences, the epitaxial layer exhibits double-island phenomenon: light and dark islands. In the presence of different mobilities, atoms with greater mobility accumulate at the film surface. And in the process of epitaxial growth, there are misfit dislocations nucleating in valleys where the strain is highest.