Faddeev-Merkuriev equations for resonances in three-body Coulombic systems

We reconsider the homogeneous Faddeev-Merkuriev integral equations for three-body Coulombic systems with attractive Coulomb interactions and point out that the resonant solutions are contaminated with spurious resonances. The spurious solutions are related to the splitting of the attractive Coulomb potential into short- and long-range parts, which is inherent in the approach, but arbitrary to some extent. By varying the parameters of the splitting the spurious solutions can easily be ruled out. We solve the integral equations by using the Coulomb-Sturmian separable expansion approach. This solution method provides an exact description of the threshold phenomena. We have found several new S-wave resonances in the e- e+ e- system in the vicinity of thresholds.Comment: LaTeX with elsart.sty 13 pages, 5 figure

Effect of an inhomogeneous external magnetic field on a quantum dot quantum computer

We calculate the effect of an inhomogeneous magnetic field, which is invariably present in an experimental environment, on the exchange energy of a double quantum dot artificial molecule, projected to be used as a 2-qubit quantum gate in the proposed quantum dot quantum computer. We use two different theoretical methods to calculate the Hilbert space structure in the presence of the inhomogeneous field: the Heitler-London method which is carried out analytically and the molecular orbital method which is done computationally. Within these approximations we show that the exchange energy J changes slowly when the coupled dots are subject to a magnetic field with a wide range of inhomogeneity, suggesting swap operations can be performed in such an environment as long as quantum error correction is applied to account for the Zeeman term. We also point out the quantum interference nature of this slow variation in exchange.Comment: 12 pages, 4 figures embedded in tex

A new method to evaluate the dynamic air gap thickness and garment sliding of virtual clothes during walking

With the development of e-shopping, there is a significant growth in clothing purchases online. However, the virtual clothing fit evaluation is still under-researched. In the literature, the thickness of the air layer between the human body and clothes is a dominant geometric indicator to evaluate the clothing fit. However, such an approach has only been applied to the stationary positions of the manikin/human body. Physical indicators such as the pressure/tension of a virtual garment fitted on the virtual body in a continuous motion are also proposed for clothing fit evaluation. Both geometric and physical evaluations do not consider the interaction of the garment with body e.g. sliding of the garment along the human body. In this study, a new framework is proposed to automatically determine the dynamic air gap thickness. First, the dynamic dressed character sequence is simulated in a 3D clothing software via importing the body parameters, cloth parameters and a walking motion. Second, a cost function is defined to convert the garment in the previous frame to the local coordinate of the next frame. The dynamic air gap thickness between clothes and the human body is determined. Third, a new metric called 3D garment vector field (3DGVF) is proposed to represent the movement flow of the dynamic virtual garment, whose directional changes are calculated by cosine similarity. Experimental results show that our method is more sensitive to the small air gap thickness changes compared with start-of-the-arts, allowing it to more effectively evaluate clothing fit in a virtual environment

Alignbodynet: deep learning-based alignment of non-overlapping partial body point clouds from a single depth camera

This paper proposes a novel deep learning framework to generate omnidirectional 3D point clouds of human bodies by registering the front- and back-facing partial scans captured by a single depth camera. Our approach does not require calibration-assisting devices, canonical postures, nor does it make assumptions concerning an initial alignment or correspondences between the partial scans. This is achieved by factoring this challenging problem into ( i ) building virtual correspondences for partial scans, and ( ii ) implicitly predicting the rigid transformation between the two partial scans via the predicted virtual correspondences. In this study, we regress the SMPL vertices from the two partial scans for building the virtual correspondences. The main challenges are ( i ) estimating the body shape and pose under clothing from single partial dressed body point clouds, and ( ii ) the predicted bodies from front- and back-facing inputs required to be the same. We, thus, propose a novel deep neural network dubbed AlignBodyNet that introduces shape-interrelated features and a shape-constraint loss for resolving this problem.We also provide a simple yet efficient method for generating real-world partial scans from complete models, which fills the gap in the lack of quantitative comparisons based on the real-world data for various studies including partial registration, shape completion, and view synthesis. Experiments based on synthetic and real-world data show that our method achieves state-of-the-art performance in both objective and subjective terms

Quantum phase transition in the Frenkel-Kontorova chain: from pinned instanton glass to sliding phonon gas

We study analytically and numerically the one-dimensional quantum Frenkel-Kontorova chain in the regime when the classical model is located in the pinned phase characterized by the gaped phonon excitations and devil's staircase. By extensive quantum Monte Carlo simulations we show that for the effective Planck constant $\hbar$ smaller than the critical value $\hbar_c$ the quantum chain is in the pinned instanton glass phase. In this phase the elementary excitations have two branches: phonons, separated from zero energy by a finite gap, and instantons which have an exponentially small excitation energy. At $\hbar=\hbar_c$ the quantum phase transition takes place and for $\hbar>\hbar_c$ the pinned instanton glass is transformed into the sliding phonon gas with gapless phonon excitations. This transition is accompanied by the divergence of the spatial correlation length and appearence of sliding modes at $\hbar>\hbar_c$.Comment: revtex 16 pages, 18 figure

Three-dimensional Optical-resolution Photoacoustic Microscopy

Optical microscopy, providing valuable insights at the cellular and organelle levels, has been widely recognized as an enabling biomedical technology. As the mainstays of in vivo three-dimensional (3-D) optical microscopy, single-/multi-photon fluorescence microscopy and optical coherence tomography (OCT) have demonstrated their extraordinary sensitivities to fluorescence and optical scattering contrasts, respectively. However, the optical absorption contrast of biological tissues, which encodes essential physiological/pathological information, has not yet been assessable. The emergence of biomedical photoacoustics has led to a new branch of optical microscopy optical-resolution photoacoustic microscopy (OR-PAM), where the optical irradiation is focused to the diffraction limit to achieve cellular1 or even subcellular level lateral resolution. As a valuable complement to existing optical microscopy technologies, OR-PAM brings in at least two novelties. First and most importantly, OR-PAM detects optical absorption contrasts with extraordinary sensitivity (i.e., 100%). Combining OR-PAM with fluorescence microscopy or with optical-scattering-based OCT (or with both) provides comprehensive optical properties of biological tissues. Second, OR-PAM encodes optical absorption into acoustic waves, in contrast to the pure optical processes in fluorescence microscopy and OCT, and provides background-free detection. The acoustic detection in OR-PAM mitigates the impacts of optical scattering on signal degradation and naturally eliminates possible interferences (i.e., crosstalks) between excitation and detection, which is a common problem in fluorescence microscopy due to the overlap between the excitation and fluorescence spectra. Unique for optical absorption imaging, OR-PAM has demonstrated broad biomedical applications since its invention, including, but not limited to, neurology, ophthalmology, vascular biology, and dermatology. In this video, we teach the system configuration and alignment of OR-PAM as well as the experimental procedures for in vivo functional microvascular imaging

Noise Kernel and Stress Energy Bi-Tensor of Quantum Fields in Hot Flat Space and Gaussian Approximation in the Optical Schwarzschild Metric

Continuing our investigation of the regularization of the noise kernel in curved spacetimes [N. G. Phillips and B. L. Hu, Phys. Rev. D {\bf 63}, 104001 (2001)] we adopt the modified point separation scheme for the class of optical spacetimes using the Gaussian approximation for the Green functions a la Bekenstein-Parker-Page. In the first example we derive the regularized noise kernel for a thermal field in flat space. It is useful for black hole nucleation considerations. In the second example of an optical Schwarzschild spacetime we obtain a finite expression for the noise kernel at the horizon and recover the hot flat space result at infinity. Knowledge of the noise kernel is essential for studying issues related to black hole horizon fluctuations and Hawking radiation backreaction. We show that the Gaussian approximated Green function which works surprisingly well for the stress tensor at the Schwarzschild horizon produces significant error in the noise kernel there. We identify the failure as occurring at the fourth covariant derivative order.Comment: 21 pages, RevTeX

Impacts of environmental factors and human disturbance on composition of roadside vegetation in Xishuangbanna National Nature Reserve of Southwest China

AbstractVegetation-disturbance-environment relationships in Xishuangbanna Nature Reserve (XNR) was examined using multivariate analysis to understand the impacts of environmental factors and human disturbance on vegetation along the highway corridor. The results show that native forests were the best habitat for protected/endangered species and native species. The exotic plants Eupatorium odoratum and Eupatorium adenophora were found primarily in secondary forests and their presence was positively associated with altitude and soil potassium concentrations. The distribution of two protected plants, Phoebe nanmu and Pometia tomentosa, was negatively associated with road disturbance. Understanding the complex effects of environmental factors and human disturbance is key for developing conservation and restoration strategies for roadside plant ecosystems

Mixing state of atmospheric particles over the North China Plain

In this unique processing study, the mixing state of ambient submicron aerosol particles in terms of hygroscopicity and volatility was investigated with a Hygroscopicity Tandem Differential Mobility Analyzer and a Volatility Tandem Differential Mobility Analyzer. The measurements were conducted at a regional atmospheric observational site in the North China Plain (NCP) from 8 July to 9 August, 2013. Multimodal patterns were observed in the probability density functions of the hygroscopicity parameter κ and the shrink factor, indicating that ambient particles are mostly an external mixture of particles with different hygroscopicity and volatility. Linear relationships were found between the number fraction of hydrophobic and non-volatile populations, reflecting the dominance of soot in hydrophobic and non-volatile particles. The number fraction of non-volatile particles is lower than that of hydrophobic particles in most cases, indicating that a certain fraction of hydrophobic particles is volatile. Distinct diurnal patterns were found for the number fraction of the hydrophobic and non-volatile particles, with a higher level at nighttime and a lower level during the daytime. The result of air mass classification shows that aerosol particles in air masses coming from north with high moving speed have a high number fraction of hydrophobic/non-volatile population, and are more externally mixed. Only minor differences can be found between the measured aerosol properties for the rest of the air masses. With abundant precursor in the NCP, no matter where the air mass originates, as far as it stays in the NCP for a certain time, aerosol particles may get aged and mixed with newly emitted particles in a short time

Thermal Unparticles: A New Form of Energy Density in the Universe

Unparticle \U with scaling dimension d_\U has peculiar thermal properties due to its unique phase space structure. We find that the equation of state parameter \omega_\U, the ratio of pressure to energy density, is given by 1/(2d_\U +1) providing a new form of energy in our universe. In an expanding universe, the unparticle energy density \rho_\U(T) evolves dramatically differently from that for photons. For d_\U >1, even if \rho_\U(T_D) at a high decoupling temperature $T_D$ is very small, it is possible to have a large relic density \rho_\U(T^0_\gamma) at present photon temperature $T^0_\gamma$, large enough to play the role of dark matter. We calculate $T_D$ and \rho_\U(T^0_\gamma) using photon-unparticle interactions for illustration.Comment: 5 pages; v3, journal version