Trap Position Research Articles

Propagation properties and radiation forces of the chirped Pearcey Gaussian vortex beam in a medium with a parabolic refractive index

In our study, an analytical expression of the second order chirped Pearcey Gaussian vortex beam (CPGVB) in a medium with a parabolic refractive index is derived. We demonstrate its propagation behaviors as well as the effects of the parameters on the propagation properties. Expectedly, the CPGVB performs periodically automatic Fourier transform in the specific positions, but unexpectedly the off-axis autofocusing position can be generated and controlled without changing the laser incident angle. Furthermore, we investigate the radiation forces of the CPGVB, and thus notice that trapping positions form in the beam-propagation direction.

Nonparaxial propagation and the radiation forces of the chirped annular Bessel Gaussian beams

We propose a new class of abruptly autofocusing beams, the chirped annular Bessel Gaussian beams (CABGBs), which are based on the radial Bessel profile. By using the Rayleigh–Sommerfeld diffraction formula, the nonparaxial propagation of the CABGBs is investigated. We find that the initial chirp with negative value tends to intensify the abruptly autofocusing property by shortening the focal length, shrinking the focal spot size, and increasing the peak intensity contrast. The optical trapping effect of the CABGBs acting on a Rayleigh particle is analyzed, and we find that the particle can be stably trapped in three dimensions if the parameters of the CABGBs are appropriate. If the absolute value of the negative chirp increases, the trapping position is shifted toward the input plane, and both the longitudinal and transverse trapping forces rise. A higher magnitude of the radiation forces can be reached if the incident power increases.

Nanoparticle trapping and manipulation using a silicon nanotrimer with polarized light.

Optical tweezers based on plasmonics experience a tremendous development on manipulating nanoparticles but are unable to avoid the problem of Joule heating. In this Letter, we report a silicon nanotrimer to optically trap and manipulate nanoparticles with negligible local heating. The optical forces and trapping potential of the nanotrimer are investigated using the finite-difference time-domain method. The results indicate that the trapping position can be shifted by tuning the polarization of the incident light. Furthermore, the silicon nanotrimer enables simultaneous trapping of multiple nanoparticles using circularly polarized illumination. Our work provides a promising building block for an integrated all-dielectric platform to realize optically driven nanomanipulation, which offers new possibilities for on-chip optical applications.

Propagation properties and radiation forces of the Hermite-Gaussian vortex beam in a medium with a parabolic refractive index.

In this paper, an analytical expression with a triple sum of the Hermite-Gaussian vortex beam (HGVB) propagating in a medium with a parabolic transverse spatial distribution of the refractive index is carried out. The intensity, phase, Poynting vector, and angular momentum of the HGVB are demonstrated analytically. The parabolic parameter, orders of the HGVB, and vortex topological charge affect the propagation properties, respectively. Also, the Poynting vector and angular momentum of the HGVB are shown so that we can further discover the properties. Furthermore, radiation forces are used to demonstrate the optical trapping ability of the HGVB, and several trapping positions are formed by the beam during propagation.

Attraction characteristics of insect pests and natural enemies according to the vertical position of yellow sticky traps in a strawberry farm with high-raised bed cultivation

Abstract The objectives of study was to evaluate the vertical space of flying insects using YST (yellow sticky traps) trapping in a strawberry farm with a high-raised bed system; with assuming the presence of species-specific flying zone. The experimental farm used styrofoam beds (width 30 cm, depth 20 cm) placed on a supporting frame 70 cm high. Small YSTs (12.5 × 7.5 cm, single sticky side) were installed vertically around the high-raised bed system in a 3 × 7 configuration (column × row) vertically at 30-cm intervals, reaching 270 cm high, and spaced 50 cm apart horizontally. The trap positions within the second-ranking (here referred to as ‘zone’) to attract thrips were 60 cm traps above the top of the bed center (TBC), 30 cm traps above the side of the bed (SOB), and 70 cm traps from the ground on the SOB. The attraction zone of whiteflies was the same as that of the thrips except of the 60 cm traps above the SOB. The zones for leafhoppers were formed in all 60 cm traps above the top of the bed (TOB), the 90 cm side traps above the TOB, and 30 cm traps above the TBC. Aphids were frequently attracted at all 90 cm traps above the TBC and 60 cm above the TBC. Sciarid pests were mostly attracted to the traps placed just below the bed center. The zones of natural enemies (total) were formed in 30 cm above the TBC and 70 cm from the ground at the SOB. Thus, the zone 60 cm above the TBC was common position where various pests were frequently attracted with reducing a harmful effect on natural enemies. Consequently, our results could be used as a guideline for the use of YSTs in strawberry farms with high-raised bed systems until new directions are developed.

Impact of Horizontal Edge-Interior and Vertical Canopy-Understory Gradients on the Abundance and Diversity of Bark and Woodboring Beetles in Survey Traps.

Simple SummaryTraps baited with sex attractants and plant odors are used by regulatory agencies to survey for alien invasive forest insects that may arrive via importation of goods from overseas. The performance of these surveys is affected not only by the type of traps and attractants used, but also by where the traps are placed at survey sites. We tested the effect of trap position along horizontal (relative to the forest edge) and vertical (canopy-understory) forest gradients on the diversity and abundance of species of bark and wood boring beetles detected. Both horizontal and vertical trap position affected trap performance, but trends differed among taxa and were context-dependent. For example, jewel beetles were detected mainly in canopy traps regardless of horizontal position, whereas bark and ambrosia beetles were detected mainly in understory traps placed along the forest edge. For optimal early detection of potentially invasive bark and wood boring beetles, surveys should place traps at multiple locations along horizontal and vertical gradients.Semiochemical-baited intercept traps are important tools used to collect information about the presence/absence and population dynamics of forest insects. The performance of these tools is influenced by trap location along both horizontal edge–interior and vertical understory–canopy gradients. Consequently, the development of survey and detection programs requires both the development of effective traps and semiochemical lures but also deployment protocols to guide their use. We used field trapping experiments to examine the impact of both horizontal edge–interior and vertical understory–canopy gradients and their interactions with the species richness and abundance of Buprestidae, Cerambycidae and Curculionidae. Both gradients had significant effects on the diversity and abundance of all three families collected in traps and the pattern of gradient effects differed between the two experiments. In the first experiment, traps were deployed along transects involving large (>100 m) forest gaps and in the second experiment traps transected small (ca. 15 m) forest gaps. These results were consistent with the idea that gradient effects on the abundance and diversity of these three families of forest Coleoptera are context dependent. The results of this study suggest that monitoring programs for bark and woodboring beetles should deploy traps at multiple locations along both vertical understory–canopy and horizontal edge–interior gradients.

Spheroidal trap shell beyond diffraction limit induced by nonlinear effects in femtosecond laser trapping

Abstract Beyond diffraction limit, multitrapping of nanoparticles is important in numerous scientific fields, including biophysics, materials science and quantum optics. Here, we demonstrate the 3-dimensional (3D) shell-like structure of optical trapping well induced by nonlinear optical effects in the femtosecond Gaussian beam trapping for the first time. Under the joint action of gradient force, scattering force and nonlinear trapping force, the gold nanoparticles can be stably trapped in some special positions, or hop between the trap positions along a route within the 3D shell. The separation between the trap positions can be adjusted by laser power and numerical aperture (NA) of the trapping objective lens. With a high NA lens, we achieved dual traps with less than 100 nm separation without utilizing complicated optical systems or any on-chip nanostructures. These curious findings will greatly extend and deepen our understanding of optical trapping based on nonlinear interaction and generate novel applications in various fields, such as microfabrication/nanofabrication, sensing and novel micromanipulations.

Band Gap Variation and Trap Distribution in Transparent Garnet Scintillator Ceramics

This article outlines the main results of a research and development cooperation between Philips Research Eindhoven; Peter the Great St. Petersburg Polytechnic University; Ioffe Institute, St. Petersburg; Utrecht University; and Philips Healthcare. It reviews the properties of garnet ceramics in the (Lu,Gd)3(Ga,Al)5O12:Ce system for medical imaging, especially time-of-flight positron emission tomography (PET). Thermally stimulated luminescence (TSL) peaks are attributed to impurities, verified by intentional codoping of samples. A lately developed method allows extraction of carrier lifetimes, thermal trap depths, and frequency factors from TSL and afterglow measurements. A detailed analysis reveals the presence of a distribution of trap depths, allowing a more accurate afterglow modeling. Activation energies of thermal ionization and trap depths obtained from TSL show the influence of Ga/Al substitution on thermal quenching and on trap position. The resulting nonmonotonic dependence of the conduction band edge with Ga content in (Lu,Gd) garnets is consistent with earlier predictions. Shallow traps determine both signal decay and short-term afterglow. The impact of signal height, rise, and decay times on coincidence resolving time and further on PET image quality is described by analytical models.

Improved Thermoluminescence Properties of Natural NaCl Salt Extracted From Mediterranean Sea Water Relevant to Radiation Dosimetry

Thermoluminescence (TL) technique has been used to characterize and determine the dosimetric properties of natural sodium chloride (NaCl) salt extracted from the Seawater of the Mediterranean Sea. The TLD grade material was prepared by evaporation and annealing the powder obtained from the aqueous solution. The TL properties include the response to theb-irradiation dose and the effects resulting from annealing up to 700oC, heating rate and fading. The analysis involve using total Glow Curve Deconvolution (GCD) to separate the inherent overlapping TL-peaks and determine the TL characteristics and the trapping parameters using general order (GO)kinetics (activation energy, kinetic order, peak position of trap and the frequency factor). The GL-curves exhibit well defined TL-peaks around 140oC, 225oC and 380oC and response depending on the annealing temperature due to variations due to formation of the structural defects. A linear response was noticed over the delivered range of absorbed doses up to 4Gy. The fading results gave evidence that TL emission is due to a redistribution of trapping levels and indicate that the prominent TL-peak near 225oCis useful for TL-dosimetric applications.

Optical trapping and orientation-resolved spectroscopy of europium-doped nanorods

Europium-doped NaYF4 nanorods with a high aspect ratio are optically trapped using a single fibre tip optical tweezers. Three distinct trapping positions of the nanorods are observed: in contact with the fibre tip, close to the tip and 5 µm from the tip end. The direction and polarisation-dependent Eu3 + photoluminescence is investigated by recording the emission parallel and perpendicular to the nanorod long axis through the trapping fibre and the microscope objective, respectively. These spectroscopic measurements permit an unambiguous determination of the nanorod orientation.

All-Fiber Active Tractor Beam Generator and its Application

We propose and demonstrate an all-fiber probe to generate an active tractor beam by changing the gradients of optical intensity distributions. We grind the tip of a seven-core fiber (SCF) into a truncated hexagonal pyramid shape to integrate three equivalent two-core fiber optical tweezers in an SCF. Three optical tweezers produce three trapping locations along the fiber main axis. By adjusting and controlling the incident laser power in each core, we may perform multiple functions, including microparticles optical trapping, long-distance attraction, bidirectional transportation, and axial-direction position controllable adjustment. The proposed all-fiber active tractor beam generator is convenient to integrate and low cost. The all-fiber probe has the compatibility of optical tweezers and optical tractor beams. The increased effective range of optical pull broadens the scope of feasible optical trapping and will pave the way towards more efficient light-powered miniature machines, tools, and applications.

Decay microscope for trapped neon isotopes

We review the design, simulation, and tests, of a detection system for measuring the energy distribution of daughter nuclei recoiling from the beta-decay of laser trapped neon isotopes. This distribution is sensitive to several new physics effects in the weak sector. Our `decay microscope' relies on imaging the velocity distribution of high energy recoil ions in coincidence with electrons shaken-off in the decay. We demonstrate by way of Monte-Carlo simulation, that the nuclear microscope increases the statistical sensitivity of kinematic measurements to the underlying energy distribution, and limits the main systematic bias caused by discrepancy in the trap position along the detection axis.

Statistical analysis of the impact of charge traps in p-type MOSFETs via particle-based Monte Carlo device simulations

In this paper, statistical analysis of the static impact of charge traps on the drain current of p-type metal–oxide–semiconductor field-effect transistors is presented. The study was carried out by employing a 3-D particle-based Monte Carlo device simulator, which is capable of accounting for the interplay between charge traps and the random dopant fluctuation effect. It was observed that the impact of a single charged trap on the transistor’s on-current is strongly dependent on the trap position along the channel length, on trap depth into the gate oxide, and on the trap position along the channel width. The current deviation estimated from statistical simulations is shown to be exponentially distributed, in agreement with experimental data from the literature. Results are also compared with uniform channel theory predictions.

Design of An Optical Tweezers System with Fast Digital Feedback for Studying the Mechanochemistry of Cardiac Myosin

Cardiac myosin powers the contraction of the heart and has load dependent kinetics that enable it to adjust its power output in response to load. Dysfunction of cardiac myosin's mechanochemistry can lead to diseases including heart failure, and therefore, there is an outstanding need to probe how mutations and potential therapeutic compounds affect myosin's mechanochemistry under load. Given that cardiac myosin has fast cycling kinetics, we have developed a fast optical trapping system specifically tailored towards probing the mechanochemistry of cardiac myosin. A field programmable gate array (FPGA) board digitizes force signals, applies tunable digital filtering for feedback clamping, controls trap positions through fast interfaces to direct digital synthesizer (DDS) boards, and oscillates the sample stage. Amplified frequencies from each DDS drive acousto-optic deflectors for steering the trapping laser beams. This FPGA-DDS feedback system can respond to changes in bead position due to myosin binding in <33 microseconds. The synchronously acquired data include internal trap position commands, calculated feedback errors, and sample stage position. To demonstrate the system capabilities, we examined the mechanochemical properties of cardiac myosin using the three-bead-assay developed by the Spudich lab. Using our system, it is possible to clearly resolve the kinetics and mechanics of the cardiac myosin working stroke. We use an improved methodology for binding event identification and synchronization, enabling better resolution of the substeps of the myosin working stroke. We also demonstrate the ability of this system to probe the load dependent kinetics of cardiac myosin using both an isometric force feedback clamp and harmonic force spectroscopy. The speed of the system enables measurement of these parameters at physiologically relevant ATP concentrations despite the short lived binding interactions between actin and myosin.

A Quantitative Study of the Secondary Acoustic Radiation Force on Biological Cells during Acoustophoresis

We investigate cell-particle secondary acoustic radiation forces in a plain ultrasonic standing wave field inside a microfluidic channel. The effect of secondary acoustic radiation forces on biological cells is measured in a location between a pressure node and a pressure anti-node and the result is compared with theory by considering both compressibility and density dependent effects. The secondary acoustic force between motile red blood cells (RBCs) and MCF-7 cells and fixed 20 µm silica beads is investigated in a half-wavelength wide microchannel actuated at 2 MHz ultrasonic frequency. Our study shows that the secondary acoustic force between cells in acoustofluidic devices could play an important role for cell separation, sorting, and trapping purposes. Our results also demonstrate the possibility to isolate individual cells at trapping positions provided by silica beads immobilized and adhered to the microchannel bottom. We conclude that during certain experimental conditions, the secondary acoustic force acting on biological cells can dominate over the primary acoustic radiation force, which could open up for new microscale acoustofluidic methods.

Investigation of gate oxide traps effect on NAND flash memory by TCAD simulation**Project supported by the SanDisk Info Tech Shanghai, China and the Institute of Microelectronic Materials & Technology, School of Materials Science and Engineering, Shanghai Jiao Tong University, China.

The effects of gate oxide traps on gate leakage current and device performance of metal–oxide–nitride–oxide–silicon (MONOS)-structured NAND flash memory are investigated through Sentaurus TCAD. The trap-assisted tunneling (TAT) model is implemented to simulate the leakage current of MONOS-structured memory cell. In this study, trap position, trap density, and trap energy are systematically analyzed for ascertaining their influences on gate leakage current, program/erase speed, and data retention properties. The results show that the traps in blocking layer significantly enhance the gate leakage current and also facilitates the cell program/erase. Trap density ∼ 1018 cm−3 and trap energy ∼ 1 eV in blocking layer can considerably improve cell program/erase speed without deteriorating data retention. The result conduces to understanding the role of gate oxide traps in cell degradation of MONOS-structured NAND flash memory.

End-Cretaceous Quartz Arenite Formation in an Estuarian Environment under Brine Influence, N. Germany; Linked to both Deccan Volcanism and Chicxulub Impact Degassing during Climate Change

Maastrichtian off-shore carbonate sediments and transitional estuarian quartz arenite (primarily subarkosic/arkosic) deposited in N Germany, underwent indirect effects by end-Cretaceous plume volcanism (Caribbean Arc/Antilles, Amirante Arc/Seychelles, Deccan Traps) and by the Chicxulub impact during climate change. In addition, brines of local salt structures had increasing influence on pore water chemistry of siliciclastics deposited in rim synclines and sub-rosion bowls during the transition from salt pillow state (Upper Campanian/Maastrichtian) to diapirism since the KPgB (66.043 Ma) until end-Paleocene. As main drivers degassing (CO2, SO2 et al.), temperature rise, acid rain/metal toxicity of both volcanic and impact origin caused kill effects by acidification (pH-drop) of sea water resp. dissolution processes on land initiated by complex acid mixtures onto both marine and continental sediments; all in all, leaving a remarkable reduction of the clastics’ primary mineral content, accompanied by kaolinite in-situ neoformation (quartz, kaolinite). Furthermore, driving effects even controlled lithofacies and sequence-analytical patterns (LST, TST, HST). Around the Lower/Upper Maastrichtian B. (MFS) radiolarian ooze was deposited across flat estuarian mouth channels during an ingression (tsunami), originally as soft pebbles, then diagenetically slightly consolidated. Surprisingly, the radiolarian skeletons normally composed of opal or celestite, were identified as β-quartz and elementary silicon. The latter hitherto unknown in nature, demands extreme reducing conditions (in Industries: by elementary A1, Mg, C) in pore water as possibly given by brines (see Atlantis II-Deep, Red Sea). The top portions of the uppermost Maastrichtian deposits of N Germany were eroded by the KPgB-convulsive events. However, recent publications (i.e. from Seymour Island, Antarctica) make evident that Deccan volcanism played obviously a prime role versus the Chicxulub impact during reversal magnetization (Chron 29 R). Thus, there exists a high probability that plume volcanism had important influence on the quartz arenite in-situ formation by degassing and related acid in combination with brines in trap position of the ascending salt diapirs. Accordingly, Price’s concept (2001) major impacting may cause plate motion, has to be modified towards the version plume mechanism and may have the same or even stronger effect, thereby relating to recent studies on the Arabian Platform, Jordan. A synopsis of Phanerozoic loss of biodiversity-events caused by both plume volcanism and impacting comparatively exposes Homo sapiens since the Industrial Revolution as a geological force in biotic as well as abiotic processes in Earth History.

Ohmic contact formation mechanism of Ge-doped 6H-SiC

Abstract We present a comprehensive investigation of mechanism of ohmic contact characteristic in Ge-doped 6H-SiC single crystals. Raman mapping and Rutherford backscattering spectrometry reveal high crystalline quality of Ge-doped 6H-SiC and the Ge as a substitutional impurity. Deep-level transient spectroscopy (DLTS) spectrum was measured. Its Arrhenius fitting shows two shallow energy levels. They are below the conductive band bottom 0.298 eV and 0.323 eV respectively. The first-principles calculations indicate that the no new levels are in ( Ge ) Si configuration, but ( Ge ) C can induce deep levels in 6H-SiC. Thus, the shallow energy levels are caused by native defects which arise in a process of crystal growth. The two characteristics shallow energy levels, the small trap cross sections and positions near to conductive band bottom, can emit electron under effect of an applied field. In addition, the Ge Si bonds are relatively easily to break for generating electrons to jump into conductive band bottom though the shallow energy levels.

Photothermal forces enhanced by nanoneedle array for nanoparticle manipulation

Plasmonic nanostructures provide strong electromagnetic fields enhancement and confinement for nanoparticle trapping. Here, we study the thermal and optical nanoparticle trapping effects using plasmonic nanoneedles array. Results show that the photo-thermal force outside the nanostructure can affect movements of nanoparticles in the far field as a result of heat transfer. The thermal force is decreased about one order of magnitude for nanoparticle at about 6μm away from the nanostructure where the optical force is no longer effective. Plasmonic nanoneedles with high aspect ratio provides more trapping positions in three dimensions. The thermal force together with the near field optical force make plasmonic nanoneedles array a flexible and wide working range manipulation strategy for nanoparticles.

Effects of the Supercell's Size on Muon Positions Calculations of La&lt;sub&gt;2&lt;/sub&gt;CuO&lt;sub&gt;4&lt;/sub&gt;

The outcome of the density functional theory (DFT) technique within the supercell's framework of La2CuO4 (LCO) are reported. We evaluatedlocal dipolar fields of muon's position inside LCO assuming dipolar interaction is occurred by varying the supercell's size. We found out that the field on proposed muon's trapping positions were known to be not affected so much by supercell's size and still fairly larger than the experimental data. Our results suggest that the inclusion of quantum effects of implanted muon and the electronic spin are required to explain experimental data.