Axial crystals – macroscopic symmetry and tensor properties

ABSTRACT

Axial crystals have axial symmetry which keeps invariant straight line with a fixed point. Axial symmetry groups include 27 non-cubic crystallographic point groups and 5 limit groups describing symmetry of textures and liquid crystals. We show that, except for four cases, each axial symmetry belongs to one of five axial types: polar, chiral, pseudopolar (three basic axial types), directional (possessing none of characteristic properties of basic types) or rotational (exhibiting characteristic properties of all basic types). Each basic type can appear in two structurally different variants with the same symmetry. These variants can coexist and form a mesoscopic structure (antiparallel ferroelectric or chiral domain structure, mixture of enantiomers). We examine macroscopic properties of axial types and variants, and experimental accessivity of their characteristic features.     

Progress in studying entanglement and steering from the macroscopic view

Magnons,the collective excitation of magnetically ordered materials,have attracted considerable interest for their low energy consumption,long coherence time and useful working frequency from gigahertz to terahertz.Besides,magnons can coherently interact with phonons,microwave and optical photons,as well as superconducting qubits,as schematically depicted in Figure 1,providing a novel platform to achieve hybrid quantum systems[1].Hybridizing distinct quantum systems with multitasking capabilities is critical in quantum information processing,because a single quantum system cannot keep pace with the fast development of quantum information and satisfy the requirement of building perfect quantum information networks[2].The emergying field cavity spintronics has inspired many interesting physics like nonreciprocal microwave propagation and energy level attraction,together with quite a few applications such as magnon sensors and magnon-photon transducers.     

Electron–positron pairs production in a macroscopic charged core

Classical and semi-classical energy states of relativistic electrons bounded by a massive and charged core with the charge-mass radio Q/M$Q/M$ and macroscopic radius Rc$R_c$ are discussed. We show that the energies of semi-classical (bound) states can be much smaller than the negative electron mass-energy (−mc²$-m{c}^2$), and energy-level crossing to negative energy continuum occurs. Electron–positron pair production takes place by quantum tunneling, if these bound states are not occupied. Electrons fill into these bound states and positrons go to infinity. We explicitly calculate the rate of pair-production, and compare it with the rates of electron–positron production by the Sauter–Euler–Heisenberg–Schwinger in a constant electric field. In addition, the pair-production rate for the electro-gravitational balance ratio Q/M=¹⁰⁻¹⁹$Q/M={10}^{-19}$ is much larger than the pair-production rate due to the Hawking processes.     

Relaxation and ordering processes in “macroscopic Wigner crystals”

The equilibrium configurations of a macroscopic Wigner crystal (2D system of interacting charged balls, mechanically excited) and their evolution towards these equilibrium configurations are presented. In particular, the variations of the number of remaining dislocations at equilibrium according to the number of particles, confinement shape and temperature have been extensively explored. One important result is the exhibition of the rapid creation of an unique grain boundary and its shrinkage during the annealing.Received: 25 February 2004, Published online: 18 June 2004PACS: 68.65.-k Low-dimensional, mesoscopic, and nanoscale systems: structure and nonelectronic properties - 73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems     

Back-action in the measurement of “macroscopic quantum superpositions” in microwave cavities

We analyze the back-action of nonlinear atomic homodyning measurements on steady-state macroscopic superpositions that can be generated in high-Q microwave cavities. We show that a full characterization of the state requires measurements such that the macroscopic superposition is irreversibly destroyed, that is, it cannot be reconstructed by using the scheme that was used to generate it in the first place.     

Influences of decoherence on the generation of a macroscopic superposition state using weak cross-Kerr effect

Considering a system in which a single photon and a coherent field propagate through a Kerr medium, when the weak cross-Kerr interaction between the coherent state and the single photon under decoherence is involved, this paper derives analytically a macroscopic superposition state by the superoperator method and investigates the influences of decoherence on the coherence properties of the obtained state. It finds that the macroscopic superposition state will experience evolution from a pure superposltion state to a mixed state in a dissipative environment and the Kerr effect makes the field display a periodic revival from decoherence for a short time.     

Local canted spin behaviour in Co1.4−x Zn x Ge0.4Fe1.2O4 spinels: A macroscopic, mesoscopic and microscopic study

DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements have been reported for the Co_1.1−x Zn _x Ge_0.1Fe_1.2O₁ spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important role of magnetic anisotropy (due to the presence of Co²⁺ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed.     

Can strong electric dipole transitions in deformed rare earth nuclei be explained by the macroscopic behavior of the octupole phonon?

StrongE1 transitions of greater than 10^–3 Weisskopf units occur in many octupole states in the deformed rare earth region. It is shown using the droplet model that the electric dipole moment resulting from the macroscopic behaviour of the octupole phonon cannot by itself account for the observedE1 strengths, and it is observed that this result is consistent with the proposal of Donner and Greiner and of Zilges von Brentano and Richter that admixtures of the giant dipole resonance into the low energy octupole states are responsible for the fastE1 transitions. It is also suggested that calculations similar to those performed by Egido and Robledo forN 92 nuclei may be able to reproduceE1 transitions inN=94–104 nuclei.Supported by the National Science Foundation and the State of Florida     

发射光谱法测定高纯银中微量金,铂,钯,铑,铱,锑,铅,铋,铁,铜,…

本文研究了贵金属标准溶液除氯离子的有关问题，解决了高纯硝酸银中贵金属等杂质元素的样配制，以硝酸银直接压样于普通电极中直流电弧激发，可测定９９．０－９９．９９％的高纯银，该方法简便、快速、准确。     

锰结核中硅,铝,铁,镁,磷,钾,锰,钛的XRFA

本文叙述了用XRF分析锰结核中Si、Al、Fe、Mg、P、K、Mn和Ti的方法。按照通常锰结核的主次成分制备6个人工合成标准,根据Sherman方程计算了已知成分(二元系统)的相对强度。用L-T方求得了互致元素校正的理论α系数(基本的、混合的、修正的),用DATAFLEX151B计算机以BASIC语言汇了“PRA,APU”计算机程序。然后进行非线性回归分析了锰结核样品得到了满意的结果。     

ICP-AES同时测定铝合金中Fe,Si,Cu,Mg,Mn,Ni,Zn,Ti,Cr,Sr等杂质元素

本文通过基体干扰和操作条件的试验研究，分别用基体匹配法和干扰系数法校正基体干扰和待测元素间的干扰，建立了以氢氧化钠溶样，ICP－AES同时测定铝合金中铁、锰、铜、锌、镁、钛、硅、镍、铬、锶等杂质元素的方法。方法快速、简便、可靠，回收率93％－102％，适用于进出口铝合金的快速检验。     

发射光谱法测定二氧化锆中钙,镁,铝,铁,钛,铪,硅

本文介绍了用碳酸钡作缓冲剂测定二氧化锆中Ｍｇ，Ｆｅ，Ａｌ，Ｃａ，Ｔｉ，Ｈｆ，Ｓｉ杂质元素的发射光谱方法。该方法直接压样于普通电极中，简便，快速。取得了满意的结果。     

FAAS法测定营养素中K,Na,Ca,Mg,Mn,Cu,Zn,Fe等微量元素

本文应用火焰原子吸收法测定了营养素（含美国加营素Ｅｎｓｕｒｅ、中国“茶汤”、豆奶晶和速溶奶粉）中钾、钠等８种微量元素的含量、对于产品质量控制和医用保健食品开发有着重要意义。方法简便快速、灵敏准确，８种微量元素的平均回收率为９８．３８～１０２．６９％；变异系数为１．３８～４．１６％。     

ICP—AES法直接测定锡锭中的As,A1,Bi,Cd,Cu,Fe,Pb,Se,Sb,Zn

以电荷耦合器件为检测器的全谱直读等离子体光谱仪直接测定锡锭中Ａｓ、Ａ１、Ｂｉ、Ｃｄ、Ｃｕ、Ｆｅｄ、Ｐｂ、Ｓｅ、Ｓｂ、Ｚｎ十种杂质元素的含量。该方法简便、快速且具有比化学法更低的检出限,加标回收试验结果不明,回收率为９２％－１０５％,ＲＳＤ均小于１．５％。     

光电直读光谱法测定稀土铝合金中La,Ce,Pr,Nd,Sm ,Si,Fe,Cu

本文报道了稀土铝合金中La,Ce,Pr,Nd,Sm,Si,Fe,Cu的光电直读光谱测定，对光源的激发方式及最佳工作条件进行了选择，应用KH－5高能预火花光源，采用单向全功率放电，先冲洗3秒，然后预燃5秒，曝光10秒。各元素谱线间无干扰，。使用固体试样，样品处理简单。经试验验证该法简便快速，精密度准确度高，含量在0．001％－0．002％之间RSD＜6％，0．02％－0．3％之间RSD＜3％，标准样品的测定值与准确值吻合较好，结果令人满意。