Exact Phase Research Articles

Quantum effect of inductance on geometric Cooper-pair transport

We introduce a model for a flux-assisted Cooper-pair pump, the sluice, which is used to study geometric charge transport. Our model allows for a nonvanishing loop inductance going beyond the usual treatment with an exact phase bias. We derive the device Hamiltonian and current operators for different elements of the system and calculate the pumped charge carried by the ground state in the adiabatic limit. We show that extending the model beyond the exact phase bias has a weak but potentially non-negligible effect on the charge transport. This effect is observed to depend on the external flux bias. The adiabatic energy level and eigenstate structures are studied and the unusual features are explained. Finally, we discuss the requirements of adiabaticity.

Exact phase space localized projectors from energy eigenstates

In investigations of the emergence of classicality from quantum theory, a useful step is the construction of quantum operators corresponding to the classical notion that the system resides in a region of phase space. The simplest such constructions, using coherent states, yield operators which are approximate projection operators -- their eigenvalues are approximately equal to 1 or 0. Such projections may be shown to have close to classical behaviour under time evolution and these results have been used to prove some useful results about emergent classicality in the decoherent histories approach to quantum theory. Here, we show how to use the eigenstates of a suitably chosen Hamiltonian to construct exact projection operators which are localized on regions of phase. We elucidate the properties of such operators and explore their time evolution. For the special case of the harmonic oscillator, the time evolution is particularly simple, and we find sets of phase space localized histories which are exactly decoherent for any initial state and have probability 1 for classical evolution. These results show how approximate decoherence of histories and classical predictability for phase space histories may be made exact in certain cases.

How Can Cytoreduction Surgery Improve the Prospects for Cancer Patients Receiving Immunotherapy?

Cancer, the leading cause of death for people under the age of 85 years in the USA, claims over 1500 lives per day [1,2]. The four most common cancers (lung, colorectal, prostate and breast cancer) account for more than half of total cancer incidences in the USA [2]. The most common cancer therapies are surgery, chemotherapy and radiation [2]. Except for a few chemotherapeutic regimens, surgery is the only definitive treatment available. Unfortunately, surgery has a 40–60% recurrence rate depending on the type of cancer [2]. This high recurrence rate has led to the combination of surgery with traditional therapies such as chemotherapy, immunotherapy and radiation. Immunotherapy utilizes the body’s own immune system to target cancer cells. Almost a century ago, it was hypothesized that a tumor can be recognized as foreign by the host and thus the immune system can be effective in eliminating these foreign cells [3]. Since then, the cancer immune response has been confirmed in knockout mice [4] and the exact phases of this mechanism, termed immunoediting, are still being rigorously studied [5]. Immunotherapy is advantageous because of its low toxicity, tumor specificity and ability to potentially produce long-term immunity. Immunotherapy seeks to eliminate cancer through both active and passive approaches [6]. Active immunotherapy utilizes our knowledge of tumor antigen expression and exploits endogenous, immunological processes of T-cell induction to eliminate the tumor [7]. Regardless of the modality, the primary goal of active immunotherapy is to prime and induce antigen-specific T-cell responses in order to eradicate residual disease and prevent postoperative recurrences. On the other hand, passive immunotherapy involves the use of immunologically active agents that are capable of exerting anti-tumor effects independently from the host’s immune system [7]. Such passive approaches include adoptive T-cell transfer techniques, which involve ex vivo amplification and reintroduction of autologous cytokine-induced killer or lymphokine-activated killer cells [7]. Various mechanisms by which immunotherapy reduces tumor burden have been elucidated, including increased intratumoral neutrophils, enhanced CD8 T-cell trafficking and decreased vasculature of the tumor [8,9].

Investigation of frustrated and dimerized classical Heisenberg chains

We have considered the 1D dimerized frustrated antiferromagnetic (ferromagnetic) Heisenberg model with arbitrary spin S. The exact classical magnetic phase diagram at zero temperature is determined using the LK cluster method. The cluster method results show that the classical ground-state phase diagram of the model is very rich, including first-order and second-order phase transitions. In the absence of dimerization, a second-order phase transition occurs between antiferromagnetic (ferromagnetic) and spiral phases at the critical frustration αc=±0.25, a well-known result. In the vicinity of the critical points αc, the exact classical critical exponent of the spiral order parameter is found to be 1/2. In the case of a dimerized chain (δ≠0), the spiral order shows stability and exists in some part of the ground-state phase diagram. We have found two first-order phase boundaries separating antiferromagnetic (uud and duu) phases from the spiral phase.

Low Dispersive Compact ID-FDTD Algorithm for Electrically Large Waveguides

A novel compact finite difference time domain (FDTD) scheme is proposed to remedy the anisotropic dispersion characteristic and inaccurate transverse cutoff frequency observed in conventional compact FDTD schemes. The proposed scheme is formulated based on the two-dimensional (2D) isotropic-dispersion finite difference (ID-FD) equation (I. Koh, et al, “Novel explicit 2-D FDTD scheme with isotropic dispersion finite-difference time-domain algorithm” IEEE Trans. Antennas Propag., vol. 54, no. 11, pp. 3505-3510, Nov. 2006), which is a novel low dispersion finite difference (FD) scheme. The formulation is derived for the scaling factors constrained with both the exact phase constant and cutoff frequency in the transverse domain, and for an optimal weighting factor using the least mean square (LMS) algorithm for the ID-FD equation.

Towards a rigorous proof of magnetism on the edges of graphene nanoribbons

A zigzag edge of a graphene nanoribbon supports localized zero modes, ignoring interactions. Based mainly on mean field arguments and numerical approaches, it has been suggested that interactions can produce a large magnetic moment on the edges. By considering the Hubbard model in the weak coupling limit, $U\ensuremath{\ll}t$, for bearded as well as zigzag edges, we argue for such a magnetic state, based on Lieb's theorem. Projecting the Hubbard interactions onto the flat edge band, we then prove that the resulting one-dimensional model has a fully polarized ferromagnetic ground state. We also study excitons and the effects of second neighbor hopping as well as a potential energy term acting on the edge only, proposing a simple and possibly exact phase diagram with the magnetic moment varying smoothly to zero. Finally, we consider corrections of second order in $U$, arising from integrating out the gapless bulk Dirac excitations.

Application ofP-wave hybrid theory to the scattering of electrons from He+and resonances in He and H−

The $P$-wave hybrid theory of electron-hydrogen elastic scattering [Bhatia, Phys. Rev. A 85, 052708 (2012)] is applied to the $P$-wave scattering from He ion. In this method, both short-range and long-range correlations are included in the Schr\"odinger equation at the same time, by using a combination of a modified method of polarized orbitals and the optical potential formalism. The short-range-correlation functions are of Hylleraas type. It is found that the phase shifts are not significantly affected by the modification of the target function by a method similar to the method of polarized orbitals and they are close to the phase shifts calculated earlier by Bhatia [Phys. Rev. A 69, 032714 (2004)]. This indicates that the correlation function is general enough to include the target distortion (polarization) in the presence of the incident electron. The important fact is that in the present calculation, to obtain similar results only a 20-term correlation function is needed in the wave function compared to the 220-term wave function required in the above-mentioned calculation. Results for the phase shifts, obtained in the present hybrid formalism, are rigorous lower bounds to the exact phase shifts. The lowest $P$-wave resonances in He atom and hydrogen ion have also been calculated and compared with the results obtained using the Feshbach projection operator formalism [Bhatia and Temkin, Phys. Rev. A 11, 2018 (1975)] and also with the results of other calculations. It is concluded that accurate resonance parameters can be obtained by the present method, which has the advantage of including corrections due to neighboring resonances, bound states, and the continuum in which these resonances are embedded.

一种基于变量熵求解约束满足问题的置信传播算法

Belief propagation (BP) is a powerful technique that has been applied to solve constraint satisfaction problems (CSPs). In this paper, for solving random CSPs with growing domains, we propose a new strategy based on the variable entropy to fix variables in the procedure of BP decimation. It has been proved that model RB, a representative random CSP with growing domains, exhibits an exact satisfiability phase transition phenomenon, and all instances of model RB are hard at the threshold. We perform the algorithm on the instances of model RB with two different groups of parameters. Numerical results show that the algorithm guided by BP can find solutions efficiently for instances in the regime that is close to the threshold. The running time of the algorithm grows exponentially with the problem size. Besides, the average freedom of the variables decreases as the control parameter (constraint tightness) increases.

Bremsstrahlung simulation in K→πl ± ν l (γ) decays

In physics simulation chains, the PHOTOS Monte Carlo program is often used to simulate QED effects in decays of intermediate particles and resonances. The program is based on an exact multiphoton phase space. In general, the matrix element is obtained from iterations of a universal kernel and approximations are involved. To evaluate the program precision, it is necessary to formulate and implement within the generator the exact matrix element, which depends on the decay channel. Then, all terms necessary for non-leading logarithms are taken into account. In the present letter we focus on the decay K to pi l^pm nu_l and tests of the PHOTOS Monte Carlo program. We conclude a 0.2% relative precision in the implementation of the hard photon matrix element into the emission kernel, including the case where approximations are used.

A general model and thresholds for random constraint satisfaction problems

In this paper, we study the relation among the parameters in their most general setting that define a large class of random CSP models d-k-CSP where d is the domain size and k is the length of the constraint scopes. The model d-k-CSP unifies several related models such as the model RB and the model k-CSP. We prove that the model d-k-CSP exhibits exact phase transitions if klnd increases no slower than the logarithm of the number of variables. A series of experimental studies with interesting observations are carried out to illustrate the solubility phase transition and the hardness of instances around phase transitions.

PT-Symmetric Talbot Effects

We show that complex PT-symmetric photonic lattices can lead to a new class of self-imaging Talbot effects. For this to occur, we find that the input field pattern has to respect specific periodicities dictated by the symmetries of the system. While at the spontaneous PT-symmetry breaking point the image revivals occur at Talbot lengths governed by the characteristics of the passive lattice, at the exact phase it depends on the gain and loss parameter, thus allowing one to control the imaging process.

3상 불평형 정전류 부하 조건에서의 동 위상 판별에 대한 분석 및 한계에 관한 연구

In this paper, the necessity for the identification of the absolute phase value is introduced and analyzed for a particular conductor line of a 3-phase type distribution network and the recent methods are also introduced. For the determination of the exact phase value for a specific point in the line, as compared with the phase reference point, the measured phase value must be within a range of ±60[°]. However, the phase of a particular point can fluctuate depending on the line constant, transformer wiring method, line length, line amperage, etc. A theoretical formulation such as Simulink modeling and analysis for a distribution network are conducted for the identification of phase at a specific point in the line. In particular, through evaluating the effects of unbalanced current loads at the time of determination of the phase value, the limitations of the present method for the determination of phases is described.

Mechanochemical synthesis of alumina nanoparticles: Formation mechanism and phase transformation

Abstract Nanosized alumina powders were synthesized by mechanochemical treatment of stoichiometric mixture of anhydrous AlCl3 and CaO. X-ray powder diffraction (XRD), differential thermal and thermogravimetric analysis (DSC-TG), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to understand the formation mechanism and the exact phase transformation sequence in this system. Milling of the initial raw materials resulted in the formation of crystalline CaO and partially amorphous AlCl3, with no sign of chemical reaction between the constituents. Heating the as-milled powder led to the formation of amorphous aluminum hydroxide (Al(OH)3) and calcium chloride (CaCl2). Based on the results obtained in this study, AlCl3 hydrolyses in the heating stage and CaO adsorbs the produced HCl forming CaClOH and CaCl2 crystalline phases. Heat treatment of the amorphous Al(OH)3 resulted in the formation of amorphous alumina (Al2O3). Amorphous alumina transformed into η-, κ-, and α‐Al2O3 when calcined at higher temperatures. Based on Rietveld refinement, it was concluded that η-Al2O3 and κ-Al2O3 phases are stable up to an average critical crystallite size of around 13 nm and 39 nm respectively.

Hybrid theory ofP-wave electron-hydrogen elastic scattering

We report on a study of electron-hydrogen scattering, using a combination of a modified method of polarized orbitals and the optical potential formalism. The calculation is restricted to $P$ waves in the elastic region, where the correlation functions are of Hylleraas type. It is found that the phase shifts are not significantly affected by the modification of the target function by a method similar to the method of polarized orbitals and, except at the very lowest energies, they are close to the phase shifts calculated earlier by Bhatia [A. K. Bhatia, Phys. Rev. A 69, 032714 (2004)]. This indicates that the correlation function is general enough to include the target distortion (polarization) in the presence of the incident electron. The important fact is that in the present calculation, to obtain similar results only a 35-term correlation function is needed in the wave function compared to the 220-term wave function required in the above-mentioned previous calculation. Results for the phase shifts, obtained in the present hybrid formalism, are rigorous lower bounds to the exact phase shifts. Accurate values for the effective range parameters are also calculated.

Investigation of Shelf Life of Potency and Activity of the Lactobacilli Produced Bacteriocins Through Their Exposure to Various Physicochemical Stress Factors.

Three Lactobacilli strains, Lactobacillus casei NCIMB 11970, Lactobacillus plantarum NCIMB 8014, Lactobacillus lactis NCIMB 8586 have been used for the production of bacteriocins. Though, their production phase, their biochemical nature, their mode of activity even their genetic structure have been widely investigated, there are hardly any studies investigating their potency and activity in depth of time, in other words their shelf life under several physicochemical conditions that may occur during their production in large scale. As such, the effect of several factors influencing the activity and the potency of bacteriocins when produced in large scale was examined as due to bacteriocins peptide nature degradation or denaturation might occur, under extreme physicochemical conditions. During scale-up process, differences between the output data may occur, such as concerning biomass, metabolic by-products and limiting substrate concentrations. These may affect negatively the activity and the potency of the bacteriocins. For investigating these effects and minimizing them, numerous studies were conducted, which were related to the exact phase of the production of these substances, the effect of dilution and temperature changes. These studies could be used in order to minimize the scaling-up effect when decided to produce these peptides in large scale.

Variable-Centered Consistency in Model RB

Model RB is a model of random constraint satisfaction problems, which exhibits exact satisfiability phase transition and many hard instances, both experimentally and theoretically. Benchmarks based on Model RB have been successfully used by various international algorithm competitions and many research papers. In a previous work, Xu and Li defined two notions called i-constraint assignment tuple and flawed i-constraint assignment tuple to show an exponential resolution complexity of Model RB. These two notions are similar to some kind of consistency in constraint satisfaction problems, but seem different from all kinds of consistency so far known in literatures. In this paper, we explicitly define this kind of consistency, called variable-centered consistency, and show an upper bound on a parameter in Model RB, such that up to this bound the typical instances of Model RB are variable-centered consistent.

Lithium abundances along the red giant branch: FLAMES-GIRAFFE spectra of a large sample of low-mass bulge stars

Context: A small number of K-type giants on the red giant branch (RGB) is known to be very rich in lithium (Li). This fact is not accounted for by standard stellar evolution theory. The exact phase and mechanism of Li enrichment is still a matter of debate. Aims: Our goal is to probe the abundance of Li along the RGB, from its base to the tip, to confine Li-rich phases that are supposed to occur on the RGB. Methods: For this end, we obtained medium-resolution spectra with the FLAMES spectrograph at the VLT in GIRAFFE mode for a large sample of 401 low-mass RGB stars located in the Galactic bulge. The Li abundance was measured in the stars with a detectable Li 670.8 nm line by means of spectral synthesis with COMARCS model atmospheres. A new 2MASS (J-K) - Teff calibration from COMARCS models is presented in the Appendix. Results: Thirty-one stars with a detectable Li line were identified, three of which are Li-rich according to the usual criterion ($\log\epsilon({\rm Li})>1.5$). The stars are distributed all along the RGB, not concentrated in any particular phase of the red giant evolution (e.g. the luminosity bump or the red clump). The three Li-rich stars are clearly brighter than the luminosity bump and red clump, and do not show any signs of enhanced mass loss. Conclusions: We conclude that the Li enrichment mechanism cannot be restricted to a clearly defined phase of the RGB evolution of low-mass stars ($M\sim1M_{\sun}$), contrary to earlier suggestions from disk field stars.

Smooth and Energy Saving Gait Planning for Humanoid Robot Using Geodesics

A novel gait planning method using geodesics for humanoid robot is given in this paper. Both the linear inverted pendulum model and the exact Single Support Phase (SSP) are studied in our energy optimal gait planning based on geodesics. The kinetic energy of a 2-dimension linear inverted pendulum is obtained at first. We regard the kinetic energy as the Riemannian metric and the geodesic on this metric is studied and this is the shortest line between two points on the Riemannian surface. This geodesic is the optimal kinetic energy gait for the COG because the kinetic energy along geodesic is invariant according to the geometric property of geodesics and the walking is smooth and energy saving. Then the walking in Single Support Phase is studied and the energy optimal gait for the swing leg is obtained using our geodesics method. Finally, experiments using state-of-the-art method and using our geodesics optimization method are carried out respectively and the corresponding currents of the joint motors are recorded. With the currents comparing results, the feasibility of this new gait planning method is verified.

Smooth and energy saving gait planning for humanoid robot using geodesics

A novel gait planning method using geodesics for humanoid robot is given in this paper. Both the linear inverted pendulum model and the exact Single Support Phase SSP are studied in our energy optimal gait planning based on geodesics. The kinetic energy of a 2-dimension linear inverted pendulum is obtained at first. We regard the kinetic energy as the Riemannian metric and the geodesic on this metric is studied and this is the shortest line between two points on the Riemannian surface. This geodesic is the optimal kinetic energy gait for the COG because the kinetic energy along geodesic is invariant according to the geometric property of geodesics and the walking is smooth and energy saving. Then the walking in Single Support Phase is studied and the energy optimal gait for the swing leg is obtained using our geodesics method. Finally, experiments using state-of-the-art method and using our geodesics optimization method are carried out respectively and the corresponding currents of the joint motors are recorded. With the currents comparing results, the feasibility of this new gait planning method is verified.

The phase diagram of the Gauss model on a decorated square lattice

Using equivalent transformation and spin-rescaling methods, the Gauss model on a decorated square lattice is studied. It is found that the square decorated Gauss lattice could be transformed into a regular square Gauss lattice with nearest-neighbor, and next-nearest-neighbor interactions. By calculating the regular square-lattice Gauss model, the critical temperature of the Gauss model is obtained on a decorated square lattice, and the exact phase diagram of this system can also be obtained.