Two-dimensional Localization Research Articles

Measuring image resolution in optical nanoscopy

Resolution in optical nanoscopy (or super-resolution microscopy) depends on the localization uncertainty and density of single fluorescent labels and on the sample's spatial structure. Currently there is no integral, practical resolution measure that accounts for all factors. We introduce a measure based on Fourier ring correlation (FRC) that can be computed directly from an image. We demonstrate its validity and benefits on two-dimensional (2D) and 3D localization microscopy images of tubulin and actin filaments. Our FRC resolution method makes it possible to compare achieved resolutions in images taken with different nanoscopy methods, to optimize and rank different emitter localization and labeling strategies, to define a stopping criterion for data acquisition, to describe image anisotropy and heterogeneity, and even to estimate the average number of localizations per emitter. Our findings challenge the current focus on obtaining the best localization precision, showing instead how the best image resolution can be achieved as fast as possible.

Two-dimensional sub-half-wavelength atom localization via phase control of absorption and gain

We propose a scheme for two-dimensional atom localization based on the coherent controlled absorption and gain of a weak probe field in a four-level double-\ensuremath{\Lambda} system, in which the atom interacts with two orthogonal standing-wave fields. Owing to the space-dependent atom-field interaction, the position probability distribution of the atom passing through the standing waves can be directly determined by measuring the resulting absorption and gain spectra. The phase-sensitive property of the atomic system significantly reduces the uncertainty in the position measurement of the atom. It is found that, by properly varying the parameters of the system, we can achieve sub-half-wavelength atom localization with high precision. Especially the probability of finding the atom at a particular position can be 100$%$ when a photon with certain frequency is absorbed or amplified. Numerical calculations and qualitative analyses show that the enhancement of precision in the position measurement of the atom is attributed to the interference between the one-photon excitation and the phase-dependent three-photon excitation from the closed interacting contour in the laser-driven atomic system.

Atomic layer doping of strained Ge-on-insulator thin films with high electron densities

We demonstrate that phosphorous atomic layer doping in ultra-high vacuum is a viable method to obtain n-type doping of strained germanium-on-insulator thin films. By engineering single and multiple, closely-spaced P δ-layers, we obtain high active electron concentrations (∼1 × 1020 cm−3) and low electrical resistivity (∼120 Ω/square) whilst keeping control over doping profile, structural integrity, and tensile strain levels (e = 0.35%). Investigation of magnetotransport over a large temperature range (1.7-290 K) allows observation of two-dimensional electrons' weak localization up to 30 K.

High-precision two-dimensional atom localization via probe absorption in an M-scheme atomic system

In the present paper, we investigate the behavior of two-dimensional atom localization in a five-level M-scheme atomic system driven by two orthogonal standing-wave fields. We find that the precision and resolution of the atom localization depends on the probe field detuning significantly. And because of the effect of the microwave field, an atom can be located at a particular position via adjusting the system parameters.

On Hokusai's Great wave off Kanagawa : localization, linearity and a rogue wave in sub-Antarctic waters

The Hokusai woodcut entitled The great wave off Kanagawa has been interpreted as an unusually large storm wave, likely to be classed as a rogue wave, and possibly generated from nonlinear wave dynamics (J. H. E. Cartwright and H. Nakamura, Notes Rec. R. Soc. 63, 119–135 (2009)). In this paper, we present a complementary discussion of this hypothesis, discussing in particular how linear and nonlinear mechanisms can both contribute to the emergence of rogue wave events. By making reference to the Great wave's simultaneous transverse and longitudinal localization, we show that the purely linear mechanism of directional focusing also predicts characteristics consistent with those of the Great wave. In addition, we discuss the properties of a particular rogue wave photographed on the open ocean in sub-Antarctic waters, which shows two-dimensional localization and breaking dynamics remarkably similar to Hokusai's depiction in the woodcut.

Two-Dimensional Atom Localization via Spontaneous Emission in an Inverted-Y System

We investigate the behavior of two-dimensional atom localization in an inverted-Y system driven by one coherent field and two standing-wave fields. The position probability distribution of the atom passing through the spatial-position-dependent standing-wave fields can be determined by measuring the spontaneously emitted photon. It is found that high-precision two-dimensional atom localization can be obtained by choosing appropriate system parameters.

Dimension expansion and customized spring potentials for sensor localization

The spring model algorithm is an important distributed algorithm for solving wireless sensor network (WSN) localization problems. This article proposes several improvements on the spring model algorithm for solving WSN localization problems with anchors. First, the two-dimensional (2D) localization problem is solved in a three-dimensional (3D) space. This “dimension expansion” technique can effectively prevent the spring model algorithm from falling into local minima, which is verified both theoretically and empirically. Second, the Hooke spring force, or quadratic potential function, is generalized into L p potential functions. The optimality of different values of p is considered under different noise environments. Third, a customized spring force function, which has larger strength when the estimated distance between two sensors is close to the true length of the spring, is proposed to increase the speed of convergence. These techniques can significantly improve the robustness and efficiency of the spring model algorithm, as demonstrated by multiple simulations. They are particularly effective in a scenario with anchor points of longer broadcasting radius than other sensors.

Proton Ion-Microbeam Elemental Analysis for Inhaled Particle-Induced Pulmonary Diseases: Application for Diagnosis and Assessment of Progression

Elemental analysis can be applied in the medical field to investigate the causes of disease. In patients with some pulmonary diseases, elements can be found in the exogenous dust deposited in the lungs and are also accumulated through the loss of cell homeostasis. Diseases induced by inhalation of dust typically affect the lungs. Although there are many pulmonary diseases induced by dust inhalation, it is often difficult to clarify the exact cause. In-air microparticle induced X-ray emission (in-air micro-PIXE) analysis is a method of elemental analysis that employs a proton ion-beam to directly measure the content of elements and their distribution in frozen sections or paraffin sections of tissue. We constantly inhale particles while breathing, but most of us do not develop pulmonary disease. Because in-air micro-PIXE analysis can determine the two-dimensional localization and content of particles in tissue, we can clarify the relationship between inhaled particles and diseases based on such analysis and the immunohistochemical expression of disease-related proteins. Elemental analysis methods like in-air micro-PIXE analysis may be useful for making precise diagnosis amd assesing disease progression to overcome threat such as occupational or environmental exposure.

Optical surface edge Bloch modes: low-loss subwavelength-scale two-dimensional light localization

An optical surface edge Bloch mode is an optical state evanescently bound at an edge on a finite-size three-dimensional photonic crystal; the edge is the intersection of two termination planes on the crystal. Low-loss subwavelength-scale edge modes can appear on an <010> edge of a dielectric woodpile within a complete photonic bandgap. The mode area is as small as 0.066 squared half-in-vacuum-wavelengths. The edge mode has field maxima in vacuum near the termination surface, like surface plasmon modes. This edge mode would provide new opportunities of low-loss light localization in a sub-diffraction-limit space without the use of metal.

Atmospheric pressure-aware seamless 3-D localization and navigation for mobile Internet devices

This paper describes a seamless three-dimensional (3-D) localization and navigation system for smartphones. The smartphone includes an atmospheric pressure sensor to measure the user's altitude that is combined with the outdoor Global Positioning System (GPS) and indoor WiFi-APs localization systems in a seamless 3-D localization system. The smartphone software also provides seamless navigation services by updating map information for both indoor and outdoor locations through the mobile Internet. The indoor floor information calculated from the altitude information is used to project localization anchor nodes, e.g., WiFi-AP, on different floors onto the user's floor with an indoor 3-D localization algorithm using projection distances based on a Received Signal Strength (RSS) algorithm. Tests show that the 3-D method reduces systematic errors and achieves much higher accuracy than the traditional two-dimensional localization method.

Efficient two-dimensional atom localization via spontaneous emission in a single decay channel

We investigate the two-dimensional atom localization behaviors in a four-level atomic system via controlled spontaneous emission in a single decay channel. It is found that the detecting probability and precision of atom localization behaviors can be significantly improved via adjusting the system parameters. More importantly, the two-dimensional atom localization patterns reveal that the maximal probability of finding an atom within the sub-half-wavelength domain of the standing waves can reach unity when the corresponding conditions are satisfied. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.

High-precision atom localization via controllable spontaneous emission in a cycle-configuration atomic system

A scheme for realizing two-dimensional (2D) atom localization is proposed based on controllable spontaneous emission in a coherently driven cycle-configuration atomic system. As the spatial-position-dependent atom-field interaction, the frequency of the spontaneously emitted photon carries the information about the position of the atom. Therefore, by detecting the emitted photon one could obtain the position information available, and then we demonstrate high-precision and high-resolution 2D atom localization induced by the quantum interference between the multiple spontaneous decay channels. Moreover, we can achieve 100% probability of finding the atom at an expected position by choosing appropriate system parameters under certain conditions.

Observation of the gradual transition from one-dimensional to two-dimensional Anderson localization

We study the gradual transition from one-dimensional (1D) to two-dimensional (2D) Anderson localization upon transformation of the dimensionality of disordered waveguide arrays. An effective transition from a 1D to a 2D system is achieved by increasing the number of rows forming the arrays. We observe that, for a given disorder level, Anderson localization becomes weaker with increasing numbers of rows-hence the effective dimension.

An anti-collision algorithm for localization of multiple chirp-spread-spectrum nodes

This paper develops an anti-collision algorithm for localization of multiple chirp-spread-spectrum (CSS) tag nodes. The CSS is a physical layer defined in IEEE 802.15.4a, and can be used for ranging between two CSS nodes. This ranging operation involves measuring the time-of-flight of the chirp-modulated signal. If anchor CSS nodes are installed at the known positions, a tag CSS node can calculate its coordinate based on the distances between these nodes. When there are multiple tag nodes, however, the tag nodes can fail to calculate their locations because their ranging signals collide with each other. Although the CSMA/CA is adopted for the medium access control protocol of IEEE 802.15.4a, it is not suitable for localization because a tag node must measure at least three successive distances for two-dimensional localization. The proposed algorithm uses a back-off time to prevent collisions, and all tag nodes compete to acquire the authority to use a channel. The proposed algorithm uses two special packets to synchronize the tag nodes for localization. For a theoretical evaluation of the proposed algorithm, the probability of the channel occupation of each tag node is analyzed. Through experiments, the performance of the anti-collision algorithm is verified.

Two-dimensional Localization of an RFID Tag by Using a Weighted Integral Sensor on a Square Boundary

This paper presents a novel method for the localization of an RFID tag in two-dimensional (2D) space, which can be used in location-aware systems. First, in a 2D square domain inside which an RFID tag is freely placed and moved, we show that a line on which the RFID tag exists can be estimated from the weighted integrals of the magnetic field created by the tag along the boundary of the domain. Then, for measuring them, we develop a square-shaped magnetic sensor composed of three coils only: two pairs of oppositely-wound rectangle coils connected in series on the parallel sides of the squared domain, and four bow-tie-shaped coils connected in series on all sides. The average localization error is 5.9 mm in the 160 mm × 160 mm domain.

Revival of Prism-Based TIR Microscopy - Versatile Tracking of Fluorescent and Scattering Probes with NM-Precision

Current single-molecule microscopy experiments mostly rely on the fluorescence signal of fluorescent proteins, organic dyes or quantum dots attached to proteins of interest. However, these probes suffer from certain limitations, namely limited number of photons before photobleaching, photon blinking, and fluorescence saturation. Consequently, the temporal and spatial resolution by which single molecules can be tracked is limited. Promising candidates for replacing fluorescent probes are gold nanoparticles (GNPs). GNPs exhibit a large scattering cross section in the optical spectrum due to plasmon resonance, provide long-term stability and allow for versatile surface chemistry. Furthermore, because generation of photons relies on elastic scattering, their emission rate does not saturate.Here, we present a camera-based wide-field imaging technique for GNP-labeled proteins using a novel parabolic prism-type total-internal reflection (TIR) microscope. We demonstrate the advantages of GNPs over commonly used fluorescent probes and discuss the pros and cons of prism-type versus objective-type TIR microscopy. We demonstrate that prism-based TIR microscopy allows imaging of fluorescent and scattering probes with high signal-to-noise, excellent control over a wide range of incidence angles, and even illumination intensities within a field of view. When tracking surface-immobilized GNPs (40 nm diameter) we obtained two-dimensional localization precisions as good as 5 angstrom within 30 ms exposure time. We demonstrate localization experiments of kinesin-1 motors labeled with GNPs walking on surface-immobilized microtubules. When GNPs where bound to the tail or motor domains of kinesin-1 we found localization precisions of 3.6 nm and 1.9 nm within 30 ms exposure time, respectively. Furthermore GNP-loaded motors showed 8 nm stepping along microtubules at 3 μM MgATP within image acquisition times of 15 ms. Our method allows for precise localization of biomolecules within short acquisition times over long time scales.

Atom localization via controlled spontaneous emission in a five-level atomic system

We investigate the one- and two-dimensional atom localization behaviors via spontaneous emission in a coherently driven five-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of atom localization behaviors can be significantly improved via adjusting the system parameters. More importantly, the two-dimensional atom localization patterns reveal that the maximal probability of finding an atom within the sub-wavelength domain of the standing waves can reach unity when the corresponding conditions are satisfied. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.

Two-dimensional sub-half-wavelength atom localization via controlled spontaneous emission

We propose a scheme for two-dimensional (2D) atom localization based on the controlled spontaneous emission, in which the atom interacts with two orthogonal standing-wave fields. Due to the spatially dependent atom-field interaction, the position probability distribution of the atom can be directly determined by measuring the resulting spontaneously emission spectrum. The phase sensitive property of the atomic system leads to quenching of the spontaneous emission in some regions of the standing-waves, which significantly reduces the uncertainty in the position measurement of the atom. We find that the frequency measurement of the emitted light localizes the atom in half-wavelength domain. Especially the probability of finding the atom at a particular position can reach 100% when a photon with certain frequency is detected. By increasing the Rabi frequencies of the driving fields, such 2D sub-half-wavelength atom localization can acquire high spatial resolution.

Two-dimensional atom localization via two standing-wave fields in a four-level atomic system

We propose a scheme for the two-dimensional (2D) localization of an atom in a four-level Y-type atomic system. By applying two orthogonal standing-wave fields, the atoms can be localized at some special positions, leading to the formation of sub-wavelength 2D periodic spatial distributions. The localization peak position and number as well as the conditional position probability can be controlled by the intensities and detunings of optical fields.

Proposal for efficient two-dimensional atom localization using probe absorption in a microwave-driven four-level atomic system

The behavior of two-dimensional (2D) atom localization is explored by monitoring the probe absorption in a microwave-driven four-level atomic medium under the action of two orthogonal standing-wave fields. Because of the position-dependent atom-field interaction, the information about the position of the atom can be obtained via the absorption measurement of the weak probe field. It is found that the localization behavior is significantly improved due to the joint quantum interference induced by the standing-wave and microwave-driven fields. Most importantly, the atom can be localized at a particular position and the maximal probability of finding the atom in one period of the standing-wave fields reaches unity by properly adjusting the system parameters. The proposed scheme may provide a promising way to achieve high-precision and high-resolution 2D atom localization.