Lateral Trapping Research Articles

Acutely Trapped Ventricle: Clinical Significance and Benefit from Surgical Decompression.

Focal ventricular obstruction--trapped ventricle--results in cerebrospinal fluid accumulation, mass effect and possible clinical deterioration. There are no systematic studies on the benefit of surgical decompression in adults. We reviewed patients admitted with acutely trapped ventricle on brain imaging to assess their prognosis and the effect of surgical intervention on 30-day mortality. Of the 392 patients with trapped ventricle, the most common causes were brain tumor (45%), intracerebral hemorrhage (ICH) (20%), and subdural hematoma (SDH) (14%). Lateral ventricle trapping accounted for 97% of cases. Two hundred and twenty-one patients (56%) received a surgical intervention for trapped ventricle or its causes; 126 (83%) were treated with craniotomy, 26 (17%) with craniectomy, 30 (14%) with external ventricular drain (EVD) alone, 23 (10%) with ventriculoperitoneal shunt alone, and 16 (7%) with endoscopic fenestration of the septum pellucidum. Surgical intervention was associated with mortality reduction from 95% (n = 54) to 48% (n = 11) in the ICH group, from 47% (n = 27) to 12% (n = 15) in the tumor group and from 90% (n = 18) to 20% (n = 7) in the SDH group (p < 0.001 for all comparisons). Univariate logistic analysis showed that surgical intervention and tumor etiology were associated with decreased mortality while age, ICH etiology, intraventricular hemorrhage, midline shift, and anticoagulation were associated with increased mortality. On multivariate logistic regression, surgical intervention remained associated with decreased mortality (p < 0.0001; OR 0.20, 95% CI 0.09-0.42). On subgroup analysis of the ICH cohort, surgical intervention was also associated with decreased mortality (p = 0.028). Neurosurgical intervention for decompression in patients with trapped ventricle can have a measurable beneficial effect on early mortality.

Two-dimensional high efficiency thin-film silicon solar cells with a lateral light trapping architecture.

Introducing light trapping structures into thin-film solar cells has the potential to enhance their solar energy harvesting as well as the performance of the cells; however, current strategies have been focused mainly on harvesting photons without considering the light re-escaping from cells in two-dimensional scales. The lateral out-coupled solar energy loss from the marginal areas of cells has reduced the electrical yield indeed. We therefore herein propose a lateral light trapping structure (LLTS) as a means of improving the light-harvesting capacity and performance of cells, achieving a 13.07% initial efficiency and greatly improved current output of a-Si:H single-junction solar cell based on this architecture. Given the unique transparency characteristics of thin-film solar cells, this proposed architecture has great potential for integration into the windows of buildings, microelectronics and other applications requiring transparent components.

Quantitative analysis of temperature dependent acoustic trapping characteristics by using concentric annular type dual element ultrasonic transducer

This paper presents the temperature dependence of lateral acoustic trapping capability by probing the speed of sound in individual lipid droplets at a given temperature of water and measuring its corresponding displacement, a value for quantitatively evaluating a spring-like behavior of the acoustic trap with certain strength. A 20/40MHz dual element LiNbO3 ultrasonic transducer is fabricated to simultaneously perform both transverse trapping and sound speed measurement for each droplet over a discrete temperature range from 20°C to 30°C. Time of flight method is employed for pulse tracking that determines the arrival time of an echo reflected back from either a trapped droplet or a mylar film.The estimated speeds of sound in water and droplets are 1484.8m/s and 1431.6m/s at 20°C, while 1506.0m/s and 1400.6m/s at 30°C, respectively. As the temperature rises, the sound speed in droplets decreases at an average rate of 3.1m/s/°C, and the speed in water increases at 2.1m/s/°C. The average displacement varies from 150.0μm to 179.0μm with an increasing rate of 2.9μm/°C, and its standard deviation is obtained between 1.0μm and 2.0μm over the same temperature range. Reduced sound speed as a function of rising temperature results in increased displacement, indicating that the trapping strength is adjustable by regulating ambient temperature in water as well as by changing transducer excitation parameters. Therefore, the results suggest that the temperature dependence of this trapping technique can be exploited for developing a remote manipulation tool of micron-sized particles in a thermally fluctuating environment. It is also shown that any deviated trapping strength caused by thermal disturbance near the trap can be restored to its desired level by compensating either temperature difference or trapping system condition.

Dipolar excitons in a potential trap in a magnetic field

The conditions for observing the Zeeman spin splitting compensation in an exciton Bose gas have been investigated. The magnetoluminescence of spatially indirect, dipolar excitons in a 25-nm-wide GaAs/AlGaAs quantum well upon their accumulation in a lateral electrostatic trap has been studied in the Faraday geometry. The critical magnetic field Bcr below which the spin (paramagnetic) splitting of the luminescence line for a heavy-hole exciton at the trap center is almost completely compensated due to the exchange interaction in a dense Bose gas has been found to increase linearly with exciton concentration in qualitative agreement with the theory. Using a potential trap is fundamentally important. Incomplete compensation is observed in a homogeneous photoexcitation spot for dipolar excitons: the splitting is considerably smaller than that for a spatially direct exciton but differs noticeably from zero. The spin splitting compensation effect is observed only under neutral charge balance conditions—there is no Zeeman splitting suppression in a charged quantum well.

CO2 geological storage: hydro‐chemo‐mechanical analyses and implications

AbstractThe injectivity of CO2 and the integrity of the reservoir‐caprock system are affected by CO2 invasion, water‐CO2‐mineral reactions, and ensuing mineral dissolution and precipitation. We identify different zones around an injection well and investigate the effects of these hydro‐chemo‐mechanical interactions. Geochemical analyses combine a comprehensive mass balance formulation with chemical calculations using published equations and PHREEQC. This analysis framework is used to assess near‐well, pool, and far‐field conditions, and to determine species concentrations, pH, changes in brine density, and changes in mineral and fluid volume in the reservoir. Results show that the brine density may increase by as much as 1.2% and can sustain convective flow of CO2 dissolved brine; the characteristic time scale for convection can be as short as a few years in some permeable formations currently being considered for storage. The precipitation of secondary minerals near the injection well increases the mineral volume by a maximum of 5%, yet, only a minor decrease in CO2 permeability is anticipated. Dissolution may result in unsupported caprock (the span should not exceed 20% of the caprock thickness to prevent failure), and may cause compaction‐driven shear failure of the reservoir. Finally, the analysis of lateral capillary trapping shows that the CO2 pool is only a few meters thick in leveled caprock interfaces and in the absence of geometric traps.

An analytical approach for the determination of the lateral trap position in ultra-scaled MOSFETs

We propose a new method to determine the lateral trap position in ultra-scaled MOSFETs with a precision of less than 1 nm. The method is based on an analytical model which links the surface potential in the presence of a discrete trap to the drain voltage. We demonstrate that the dependence between the surface potential in the damaged region of the channel and the drain voltage is quasi-linear. The unique slope of this dependence corresponds to a particular lateral trap position and can thus be used as a fingerprint to locate the trap. A high accuracy is reached due to a negligibly small impact of the random dopant fluctuations on the slope magnitude. To verify our analytical approach we employ standard technology computer aided design (TCAD) methods, including random discrete dopants for both n- and p-MOSFETs with various channel lengths.

Study of Random Telegraph Noise in UTBOX Silicon-on-Insulator nMOSFETs

This paper reports on the behavior of Random Telegraph Signals (RTSs) in ultra-thin buried oxide (UTBOX) Silicon-on-Insulator (SOI) nMOSFETs. Emphasis is on the amplitude ΔID, which is studied in function of the front-gate, the back-gate and the drain bias. As will be shown, a careful analysis of the drain-to-source bias-dependence in forward and reverse operation enables to determine the lateral trap position in the channel. Combined with the back-gate voltage dependence, it is concluded that the Generation-Recombination (GR) centers responsible for the RTS are in the silicon film rather than in the gate oxide.

Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

Recent experiments have demonstrated a fluctuation-induced lateral trapping of spherical colloidal particles immersed in a binary liquid mixture near its critical demixing point and exposed to chemically patterned substrates. Inspired by these experiments, we study this kind of effective interaction, known as the critical Casimir effect, for elongated colloids of cylindrical shape. This adds orientational degrees of freedom. When the colloidal particles are close to a chemically structured substrate, a critical Casimir torque acting on the colloids emerges. We calculate this torque on the basis of the Derjaguin approximation. The range of validity of the latter is assessed via mean-field theory. This assessment shows that the Derjaguin approximation is reliable in experimentally relevant regimes, so that we extend it to Janus particles endowed with opposing adsorption preferences. Our analysis indicates that critical Casimir interactions are capable of achieving well-defined, reversible alignments both of chemically homogeneous and of Janus cylinders.

Optimal beam diameter for lateral optical forces on microspheres at a water-air interface

Optical tweezers with a low numerical aperture microscope objective is used to manipulate the microspheres at the water-air interface. In this letter, we determine the optimal optical trap for the lateral manipulation of microspheres at a water-air interface. The experimental results show that the trapping force is influenced by the expansion of the trapping beam at the back aperture of the objective. The optimal filling ratio of 0.65 is suggested for lateral optical manipulation at the water-air interface. The lateral trapping forces at the water-air interface are theoretically investigated with the ray-optics model. The numerical results show that the lateral trapping forces can be changed by shrinking the diameter of the trapping laser beam. The numerical results are in accordance with the experimental results.

Investigation of Lateral Trap Position by Random Telegraph Signal Analysis in Moderate Inversion in n-Channel MOSFETs

aDepartment of Electronics Engineering, National Chiao Tung University, Hsin-Chu 300, Taiwan bDepartment of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan cAdvanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan dDepartment of Photonics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan eDepartment of Photonics & Institute of Electro-Optical Engineering, National Chiao Tung University, Hsin-Chu 300, Taiwan

Adaptive optics in an optical trapping system for enhanced lateral trap stiffness at depth

In optical trapping systems the trap stiffness, or spring constant, deteriorates dramatically with trap depth due to optical aberrations and system misalignment. This can severely hamper studies that employ optical tweezers to make accurate quantitative measurements. Here, a deformable membrane mirror is used, in conjunction with a random search algorithm, to correct for these aberrations by optimizing on a merit factor that is directly proportional to the trap stiffness. Previous studies have sought to address this issue but none have used a merit factor that is directly proportional to the trap stiffness. We demonstrate that the lateral trap stiffness, measured with and without aberration correction at increasing depths, improves throughout the trapping range of a conventional trap and allows us to extend the maximum depth at which we can trap from 136 to 166 μm. At a depth of 131 μm, trap stiffness improved by factors of 4.37 and 3.31 for the x- and y-axes respectively. The aberration correction resulted in deformable membrane mirror shapes where a single shape could be applied throughout a wide range of trap depths, showing significant improvement, and had the added benefit of making the lateral trapping forces more uniform in x and y.

Compensation of dipolar-exciton spin splitting in magnetic field

Magnetoluminescence of spatially indirect dipolar excitons in 25nm GaAs/AlGaAs single quantum well collected within a lateral potential trap has been studied in Faraday geometry. The paramagnetic spin splitting of the luminescence line of the heavy-hole excitons in the trap centre is completely compensated at magnetic field below critical value ≈2Т. The effect of spin splitting compensation is caused by the exchange interaction in dense exciton Bose gas which is in qualitative agreement with the existing theoretical concepts.

Bathymetric controls on sediment transport in the Hudson River estuary: Lateral asymmetry and frontal trapping

Analyses of field observations and numerical model results have identified that sediment transport in the Hudson River estuary is laterally segregated between channel and shoals, features frontal trapping at multiple locations along the estuary, and varies significantly over the spring‐neap tidal cycle. Lateral gradients in depth, and therefore baroclinic pressure gradient and stratification, control the lateral distribution of sediment transport. Within the saline estuary, sediment fluxes are strongly landward in the channel and seaward on the shoals. At multiple locations, bottom salinity fronts form at bathymetric transitions in width or depth. Sediment convergences near the fronts create local maxima in suspended‐sediment concentration and deposition, providing a general mechanism for creation of secondary estuarine turbidity maxima at bathymetric transitions. The lateral bathymetry also affects the spring‐neap cycle of sediment suspension and deposition. In regions with broad, shallow shoals, the shoals are erosional and the channel is depositional during neap tides, with the opposite pattern during spring tides. Narrower, deeper shoals are depositional during neaps and erosional during springs. In each case, the lateral transfer is from regions of higher to lower bed stress, and depends on the elevation of the pycnocline relative to the bed. Collectively, the results indicate that lateral and along‐channel gradients in bathymetry and thus stratification, bed stress, and sediment flux lead to an unsteady, heterogeneous distribution of sediment transport and trapping along the estuary rather than trapping solely at a turbidity maximum at the limit of the salinity intrusion.

The impact of interface/border defect on performance and reliability of high-k/metal-gate CMOSFET

The impact of interface/border defect on performance and reliability was investigated for gate-first and gate-last high-k/metal-gate CMOSFET. For high-k/metal-gate CMOSFET, VFB roll-off is critical as effective oxide thickness (EOT) scales below 15 angstrom (Å) especially for metal gate-first device with an extra capping layer to adjust VTH. By proposing a model of metal-gate process induced interface trap releasing oxygen, the vertical and lateral interface trap distribution and the dependence of interfacial layer (IL) on VFB roll-off phenomena can be well interpreted. In this work, we found that VFB roll-off can be improved by reducing oxygen vacancy (VO) at the HfO2/IL interface with suppression of oxygen diffusion from high-k to IL. By the way, a metal gate-last process with lower interface trap was proposed to minimize VO formation by suppress oxygen releasing, thus optimize a 28nm 15Å EOT HfO2/metal-gate CMOSFET with low VFB–EOT roll-off, it can be a reference for sub 22nm CMOSFET with thin EOT (<15Å) design.

Optical trapping force reduction and manipulation of nanoporous beads.

We studied the interaction of infrared optical traps with controlled-pore glass (CPG) beads in aqueous medium. The lateral optical trapping force and stiffness were experimentally found considerably smaller than those of their solid counterparts. The simulation using an average refractive index revealed significant losses of effective trapping efficiency, which quantitatively agreed well with experimentally fitted curves. This effect was ascribed to the reduced relative refractive index of medium-filled CPG beads with respect to the medium. Combining optical trapping with mechanical confinements, we demonstrated a microfluidic platform allowing for the synthesis of multiple DNA oligonucleotide sequences on individual beads of interest.

Noise in Submicron Metal–Oxide–Semiconductor Field Effect Transistors: Lateral Electron Density Distribution and Active Trap Position

Experiments were carried out for the n-channel devices, processed in a 0.3 µm spacer less complementary metal–oxide–semiconductor technology. Random-telegraph-signal measurements were performed for the constant gate voltage. It is supposed that electron concentration in the channel decreases from the source to the drain contact. Lateral component of the electric field is inhomogeneous in the channel and it has a minimum value near the source and reaching the maximum value near the drain electrode. Drain current is given by two components – diffusion and drift ones. Diffusion current component is independent on the x-coordinate and it is equal to the drift current component for the low electric field. The model explaining the experimentally observed capture time constant dependence on the lateral electric field and the trap position is given. From the dependence of the capture time constant τc on the drain current could be calculated longitudinal coordinate of the trap position.

Noise in Submicron Metal–Oxide–Semiconductor Field Effect Transistors: Lateral Electron Density Distribution and Active Trap Position

Experiments were carried out for the n-channel devices, processed in a 0.3 µm spacer less complementary metal–oxide–semiconductor technology. Random-telegraph-signal measurements were performed for the constant gate voltage. It is supposed that electron concentration in the channel decreases from the source to the drain contact. Lateral component of the electric field is inhomogeneous in the channel and it has a minimum value near the source and reaching the maximum value near the drain electrode. Drain current is given by two components – diffusion and drift ones. Diffusion current component is independent on the x-coordinate and it is equal to the drift current component for the low electric field. The model explaining the experimentally observed capture time constant dependence on the lateral electric field and the trap position is given. From the dependence of the capture time constant τc on the drain current could be calculated longitudinal coordinate of the trap position.

Single aerosol trapping with an annular beam: improved particle localisation

In this paper we explore the trapping of aerosol droplets using an annular beam, formed by blocking the central portion of a Gaussian beam, and quantify the improvements over conventional Gaussian beam traps. Recent work on the modelling of single aerosol dynamics within an optical tweezer trap [Burnham et al., Journal of the Optical Society of America B, 2011, 28, 2856-2864] has indicated that the use of annular beams can allow smaller droplets to be trapped, which we experimentally verify. We also demonstrate that annular beams allow droplets to be trapped at higher powers, and with reduced axial displacement with increasing power, than Gaussian beams. We confirm these results, due to a reduction in the axial scattering forces, using this theoretical model. Finally back focal plane interferometry is used to determine the axial and lateral trap stiffnesses for a series of droplets, showing a significant increase in the axial : lateral trap stiffness ratio from 0.79 ± 0.04 to 1.15 ± 0.04 when an annular beam is used.

Integrability breakdown in longitudinaly trapped, one-dimensional bosonic gases

A system of identical bosons with short-range (contact) interactions is studied. Their motion is confined to one dimension by a tight lateral trapping potential and, additionally, subject to a weak harmonic confinement in the longitudinal direction. Finite delay time associated with penetration of quantum particles through each other in the course of a pairwise one-dimensional collision in the presence of the longitudinal potential makes the system non-integrable and, hence, provides a mechanism for relaxation to thermal equilibrium. To analyse this effect quantitatively in the limit of a non-degenerate gas, we develop a system of kinetic equations and solve it for small-amplitude monopole oscillations of the gas. The obtained damping rate is long enough to be neglected in a realistic cold-atom experiment, and therefore longitudinal trapping does not hinder integrable dynamics of atomic gases in the 1D regime.

Optical trapping with π-phase cylindrical vector beams

The use of π-phase radially and azimuthally polarized vector beams in optical trapping is investigated. We find that by tuning the relative phase between the eigenmodes comprising the beams, the optical forces applied to a trapped particle are modified. In particular, axial trapping efficiency is enhanced with increasing z polarization and the lateral trapping efficiency of the vector beams is reduced compared to a Gaussian input beam. In addition, this is the first experimental demonstration of low-power optical trapping in an aqueous environment using vector beams, which may have important applications in biological systems.