Is a wind turbine a point source? (L)

Measurements show that practically all noise of wind turbine noise is produced by turbine blades, sometimes a few tens of meters long, despite that the model of a point source located at the hub height is commonly used. The plane of rotating blades is the critical location of the receiver because the distances to the blades are the shortest. It is shown that such location requires certain condition to be met. The model is valid far away from the wind turbine as well.     

Study of scalar meson a0(980) from B→a0(980)π decays

In this paper, we calculate the branching ratios and the direct CP-violating asymmetries for decays B0 →a00(980)π0, a0+(980)π-, a0-(980)π and B- →a00(980)π-, a0-(980)π0 by employing the perturbative QCD (pQCD) factorization approach at the leading order. We found that (a) the pQCD predictions for the branching ratios are around (0.4 - 2.8) × 10-6, consistent with currently available experimental upper limits; (b) the CP asymmetries of B0→ao(980)π0 and B-→a0-(980)π0 decays can be large, about (70-80)% for α = 100°.     

Realization of a SU(2)×SU(6) system of fermions in a cold atomic gas

We report the realization of a novel degenerate Fermi mixture with an SU(2)×SU(6) symmetry in a cold atomic gas. We successfully cool the mixture of the two fermionic isotopes of ytterbium 171Yb with the nuclear spin I=1/2 and 173Yb with I=5/2 below the Fermi temperature T_{F} as 0.46TF for 171Yb and 0.54TF for 173Yb. The same scattering lengths for different spin components make this mixture featured with the novel SU(2)×SU(6) symmetry. The nuclear spin components are separately imaged by exploiting an optical Stern-Gerlach effect. In addition, the mixture is loaded into a 3D optical lattice to implement the SU(2)×SU(6) Hubbard model. This mixture will open the door to the study of novel quantum phases such as a spinor Bardeen-Cooper-Schrieffer-like fermionic superfluid.     

Evidence of a canted magnetic state in self-doped LaMnO(3+δ) (δ?=?0.04): a magnetocaloric study

We report a detailed investigation of the magnetocaloric properties of self-doped polycrystalline LaMnO(3+δ) with δ?=?0.04. Due to the self-doping effect, the system exhibits a magnetic transition from a paramagnetic to ferromagnetic-like canted magnetic state (CMS) at ～120?K, which is associated with an appreciably large magnetocaloric effect (MCE). The CMS is an inhomogeneous magnetic phase developing due to a steady growth of antiferromagnetic correlation in its predominant ferromagnetic state below ～120?K. The stabilization of CMS in this material is concluded from a comprehensive analysis of magnetocaloric data using Landau theory, which is in excellent agreement with our neutron diffraction study. The magnetic entropy change versus temperature curves for different applied fields collapse into a single curve, revealing a universal behavior of MCE. Our studies suggest that investigation of MCE is an effective technique to acquire fundamental understanding about the basic magnetic structure of a system with complex competing interactions.     

Geometric magnetic frustration in Ba(2)Sn(2)Ga(3)ZnCr(7)O(22): a two-dimensional spinel based Kagomé lattice

The properties of a two-dimensional geometrically frustrated magnetic material based on the Kagomé net, Ba(2)Sn(2)ZnGa(3)Cr(7)O(22), are reported. The Kagomé net is fully filled with magnetic ions. A Curie-Weiss theta theta(W) = -312 K is found with a spin glass transition at approximately 1.5 K, indicating strong geometrical magnetic frustration. This compound is the most two dimensional of a structural series with the geometrically frustrated materials ZnCr(2)O(4) and SrCr(8)Ga(4)O(19). The comparison of their properties tests the influence of different degrees of coupling between Kagomé layers on magnetic frustration within a single chemical and structural family.     

Can X(5568) be a tetraquark state?

Very recently, the D0 collaboration has reported the observation of a narrow structure, X(5568), in the decay process X(5568)→ B_s~0π±using the 10.4fb~(-1) data of pp collision at 8~(1/2) = 1.96 TeV. This structure is of great interest since it is the first hadronic state with four different valence quark flavors, b, s, u, d. In this work,we investigate tetraquarks with four different quark flavors. Based on the diquark-antidiquark scheme, we study the spectroscopy of the tetraquarks with one heavy bottom/charm quark and three light quarks. We find that the lowest-lying S-wave state, a tetraquark with the flavor [su][bd] and the spin-parity JP= 0~+, is about 150 MeV higher than the X(5568). Further detailed experimental and theoretical studies of the spectrum, production and decays of tetraquark states with four different flavors are vital to gain a better understanding of the nature and classification of hadron exotic states.     

Dangling-bond logic gates on a Si(100)-(2 × 1)-H surface

Atomic-scale Boolean logic gates (LGs) with two inputs and one output (i.e. OR, NOR, AND, NAND) were designed on a Si(100)-(2 × 1)-H surface and connected to the macroscopic scale by metallic nano-pads physisorbed on the Si(100)-(2 × 1)-H surface. The logic inputs are provided by saturating and unsaturating two surface Si dangling bonds, which can, for example, be achieved by adding and extracting two hydrogen atoms per input. Quantum circuit design rules together with semi-empirical elastic-scattering quantum chemistry transport calculations were used to determine the output current intensity of the proposed switches and LGs when they are interconnected to the metallic nano-pads by surface atomic-scale wires. Our calculations demonstrate that the proposed devices can reach ON/OFF ratios of up to 2000 for a running current in the 10 μA range.     

Towards a constructive approach of a gauge invariant,massiveP(φ)2 theory

As part of a possible constructive approach to a gauge invariantP()₂ theory, we consider massive, scalar, polynomially selfcoupled fields in a fixed external Yang-Mills potentialA in two-dimensional euclidean space. For a large class ofA's we show that the corresponding euclidean Green's functions for the fields have a lower mass gap for weak coupling which is uniform inA. The result is obtained by adapting the Glimm-Jaffe-Spencer cluster expansion to the present situation through Kato's inequality, which reflects the diamagnetic effect of the Yang-Mills potential. A discussion of the corresponding gauge covariance is included.     

~(13)C(α, n)~(16)O background in a liquid scintillator based neutrino experiment

α from natural radioactivity may interact with a nucleus and emit a neutron. The reaction introduces the background to the liquid scintillator(LS) based neutrino experiments. In the LS detector, α comes from 238 U,232Th,and 210 Po decay chains. For Gadolinium-doped LS(Gd-LS) detector, α also comes from 227 Ac. The nucleus 13 C is a natural component of Carbon which is rich in the LS. The background rate and spectrum should be subtracted carefully from the neutrino candidates. This paper describes the calculation of neutron yield and spectrum with uncertainty estimated. The results are relevant for many existing neutrino experiments and future LS or Gd-LS based experiments.     

A Batch Chemiluminescence Determination of Enoxacin Using a Tris-(1,10-phenanthroline)ruthenium(II)–Cerium(IV) System

A batch type chemiluminescence (CL) determination of enoxacin is described. In this work, it was observed that enoxacin could enhance the chemiluminescence (CL) emission Ru(phen)₃ ²⁺–Ce(IV) system and this enhancement effect was dependent on the concentration of enoxacin, based on which, CL system was established for the determination of enoxacin. Under the optimum experimental conditions, the linear range and detection limit are 0.6406–64.06 μg/ml and 0.0210 μg/ml, respectively. The R.S.D. is 1.75%. (n=10). The proposed method has been applied to detect the content of enoxacin in pharmaceutical formulation and human serum with satisfactory results. The possible mechanism of the CL reaction was discussed.     

Estimation of vector static magnetic field by a nitrogen-vacancy center with a single first-shell ~(13)C nuclear(NV–~(13)C)spin in diamond

We suggest an experimental scheme that a single nitrogen-vacancy(NV) center coupled to a nearest neighbor~(13) C nucleus as a sensor in diamond can be used to detect a static vector magnetic field. By means of optical detection magnetic resonance(ODMR) technique, both the strength and the direction of the vector field could be determined by relevant resonance frequencies of continuous wave(CW) and Ramsey spectrums. In addition, we give a method that determines the unique one of eight possible hyperfine tensors for an(NV–~(13) C) system. Finally, we propose an unambiguous method to exclude the symmetrical solution from eight possible vector fields, which correspond to nearly identical resonance frequencies due to their mirror symmetry about~(14)N–Vacancy–~(13) C(~(14)N–V–~(13) C) plane.     

The dipole moment function of CO(a 3Π)

The dipole moment function of the a ³Π state of CO is calculated using the multi-configuration self-consistent-field method of Wahl and Das. Only the dominant valence charge-transfer correlation configurations are mixed with the Hartree-Fock configuration since only the region between the classical turning points of the v = 1 vibrational level is considered. The calculated function does not agree with the shape of the fitted dipole moment function of Wicke et al. Configurations chosen on the basis of the model of optimized valence configurations do not determine an accurate dipole moment function for an open shell system.     

Is X(3872) a bound state?

All existing experimental evidence for the bound state nature of X(3872) relies on observing its decay products,which are measured with a finite experimental mass resolution that is typically △m≥2 MeV,and much larger than its alleged binding energy,B_X=0.00(18) MeV.On the other hand,we have found recently that there is a clear cancellation in the 1~(++) channel of the invariant DD~*mass around the threshold between continuum and the bound state.This is very much like a similar cancellation in the proton-neutron continuum with the deuteron in the1~(++) channel.Based on comparative fits with a common Tsallis distribution of the experimental cross-sections for prompt production of deuterons and X(3872) in pp collisions with a finite p_T,we find a strong argument for questioning the bound state nature of this state,which also suggests that the large observed production rate could be consistent with a half-bound state.     

The Λ c (2940)+ as a D*N Molecule in a Constituent Quark Model and a Possible Λ b (6248)

The Λ _c (2940)⁺ is studied in a constituent quark model. The model describes the deuteron as an NN bound state and the X(3872) as a DD* molecule. We studied the meson baryon sector and found a D*N bound state consistent with the data available for the Λ _c (2940)⁺. The existence of this bound state in this picture implies the existence of a ${\bar B^* N}$ partner that we predict as a Λ _b (6248). Different decay channels for this state are also studied.