Spin-isospin surface responses

The excitation of spin-isospin modes at the surface of a nucleus is investigated in an RPA framework, utilizing a harmonic oscillator basis. The effect of the mixing between the spin-longitudinal and spin-transverse couplings is found to play an important role in explaining the absence of contrast in the ratio between the longitudinal and transverse responses measured in (p, p′) experiments.     

Beyond mean field approach to the beta decay of medium mass nuclei relevant for nuclear astrophysics

The Gamow-Teller strength distributions for the β decay of the ground state as well as the lowest excited states of the rp-process waiting point nuclei ⁶⁸Se and ⁷²Kr are obtained within the complex Excited Vampir variational approach using realistic effective interactions and a rather large model space. The shape mixing is consistently described for both the states in the even-even parent and the states in the odd-odd daugther nucleus. The influence of the shape mixing accounted by the different effective interactions used and comparison with the available data are presented. The possible influence of the decay of the lowest excited states of the parent nuclei in the astrophysical environment of X-ray bursts is discussed.Gamow-Teller strength distributions, β-decay half-lives, and β-delayed neutron emission probabilities for neutron-rich Zr nuclei are investigated for the first time within the complex Excited Vampir approach using a large model space. Comparison with available data and predictions relevant for the astrophysical r process are presented.     

Beta-transition properties for neutron-rich Sn and Te isotopes by Pyatov method

Based on Pyatov’s method, the low-lying Gamow-Teller (GT) 1⁺ state energies and log(ft) values for ^128,130,132Sb and ^132,134,136I isotopes have been calculated. In this method, the strength parameter of the effective spin-isospin interaction is found by providing the commutativity of the GT operator with the central part of the nuclear Hamiltonian. The problem has been solved within the framework of RPA. The calculation results have been compared with the corresponding experimental data.      

A short history of nuclear magnetic moments and GT transitions

We summarize the history and our present understanding of nuclear magnetic moments and Gamow-Teller transitions.The roles of configuration mixing,meson exchange currents and relativistic effects are examined.Experimental evidence for the importance of tensor correlations is also discussed.     

Beta decay rates for nuclei with 115<A<140 for r-process nucleosynthesis

For r-process nucleosynthesis the β-decay rates for a number of neutron-rich intermediate heavy nuclei are calculated. The model for the β-strength function is able to reproduce the observed half-lives quite well.     

Spectral distribution theory—Some recent applications

The application of spectral distribution theory for binding energy, spectra and occupancies using universal-sd interaction in (sd) shell and for Gamow-Teller and M1 strength sums in both (fp) and (sd)-shell is described.     

EC/β+ decay of six medium-heavy nuclei

Previous experimental results of (EC+β+) decay for the medium-heavy nuclei reported by our group since 1996, including 153Er, 157Yb, 209Fr, 128Ce, 130Ce, and 128Pr have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion.     

超重核合成时的驱动势与热熔合反应截面

在双核模型框架下,双核系统生成超重复合核的机理是由双核中的弹核的核子全部转移到靶核产生的,而核子转移是由双核系统驱动势确定的.对有的反应道,核子转移与中质比变化路径之间有比较复杂的关系.原则上动力学方程与驱动势都应该是中子和质子的二维显函数.为处理方便,采用与中质比相关的核子转移路径的选择来取驱动势,得到了接近实验值的超重核合成蒸发剩余截面. 关键词： 超重核 熔合反应 驱动势 激发函数     

Antiparticle Excitation Effect in the Relativistic Spin-Isospin-Dependent Response Function of Nucleus

The spin-isospin-dependent response function of nucleus is studied in the relativistic formalism. Besides the well-known relativistic particlehole and A-hole excitations, the antiparticle excitations such as nucleon-antinucleon, nucleon-antidelta, antinucleon-delta excitations are also taken into account in the calculation of the response function, and the effect of the antiparticle excitation is emphasized. The antiparticle excitation enhances the response function and its effect to the response function is largely determined by the cutoff parameter which is introduced by the need of the renormalization. The position of the peak of the A-hole resonance is mainly dominated by short range correlation Landau-Migdal parameter g', and we find g' is about 0.6. The effect of two-nucleon absorption and projectiletarget form factor are also studied.     

Relativistic chiral mean field model for finite nuclei

We present a method for proper treatment of pion-exchange interaction in the nuclear many-body problem in a relativistic chiral mean field (RCMF) model. The pionic correlation is expressed in 2-particle 2-hole (2p–2h) states in addition to the standard mean field state, to describe the full strength of pionic correlations. The effect of the short-range repulsion is included by way of the unitary correlation operator method (UCOM) for the central part of the pion-exchange interaction. We apply the RCMF model to ¹²C and ¹⁶O. The convergence of pionic energy contributions is realized with pionic quantum number Jπ$J^{\pi }$ up to 10⁻ for ¹²C and 11⁺ for ¹⁶O. The pion-exchange interaction gives the dominant contribution to the binding energy. The pion plays an important role in the formation of the jj  -magic shell effect by way of the Pauli-blocking mechanism of the pion-exchange interaction. The lower pionic quantum numbers Jπ?³⁺$J^{\pi }?3^{+}$ are the dominant components of the nuclear surface structure.     

Therapeutic opportunities in biological responses of ultrasound

The therapeutic benefits of several existing ultrasound-based therapies such as facilitated drug delivery, tumor ablation and thrombolysis derive largely from physical or mechanical effects. In contrast, ultrasound can also trigger various time-dependent biochemical responses in the exposed biological milieu. Several biological responses to ultrasound exposure have been previously described in the literature but only a handful of these provide therapeutic opportunities. These include the use of ultrasound for healing of soft tissues and bones, the use of ultrasound for inducing non-necrotic tumor atrophy as well as for potentiation of chemotherapeutic drugs, activation of the immune system, angiogenesis and suppression of phagocytosis. A review of these therapeutic opportunities is presented with particular emphasis on their mechanisms. Overall, this review presents the increasing importance of ultrasound’s role as a biological sensitizer enabling novel therapeutic strategies.     

Pseudo analytical solution to time periodic stiffness systems

An analytical form of state transition matrix for a system of equations with time periodic stiffness is derived in order to solve the free response and also allow for the determination of system stability and bifurcation. A pseudoclosed form complete solution for parametrically excited systems subjected to inhomogeneous generalized forcing is developed,based on the Fourier expansion of periodic matrices and the substitution of matrix exponential terms via Lagrange-Sylvester theorem. A Mathieu type of equation with large amplitude is presented to demonstrate the method of formulating state transition matrix and Floquet multipliers. A two-degree-of-freedom system with irregular time periodic stiffness characterized by spiral bevel gear mesh vibration is presented to find forced response in stability and instability. The obtained results are presented and discussed.     

光通信用雪崩光电二极管(APD)频率响应特性研究

吸收层、电荷层和倍增层分离结构雪崩光电二极管(SACM-APD),包括InP/InGaAs、InAlAs/InGaAs和Si/Ge APD是光通信领域近年来研究的热点. 本文基于电路模型,系统比较了不同外延层厚度、不同材料以及不同结构APD的频率响应特性,重点探讨Si/Ge APD吸收层厚度、光敏面大小、寄生参数等各项参数对带宽的影响,仿真结果与实际器件实验数据相符合. 本文的研究成果对SACM-APD的优化设计具有指导意义. 关键词： SACM-APD 电路模型 频率响应     

Parallelization of the polarizable embedding scheme for higher-order response functions

We present a parallel implementation of the Polarizable Embedding (PE) method, an advanced quantum mechanics/molecular mechanics (QM/MM) approach, for Hartree–Fock (PE-HF) and density functional theory (PE-DFT). The parallelization includes calculations of energies and linear, quadratic, and cubic response functions. The couplings to the QM system due to the polarizable embedding potential have been implemented using a master/slave approach. The implementation shows good scaling behaviour, demonstrated through calculations on a small (a water molecule in a bulk of water molecules) and a larger system (Green Fluorescent Protein (GFP)).     

Analysis of transient responses in a laminated piezoelectric cylindrical shell

A hybrid numerical method is proposed for analysis of transient responses in a multilayered piezoelectric cylindrical shell.In the present method,the associated equations of the displacement field and the electro-potential field are developed using an analytical-numerical method.The piezoelectric cylindrical shell is discretized into layered annular elements along the wall thickness direction.The governing equations are determined by Hamilton's Principle considering the coupling between the elastic and elec...     

Electron-related optical responses in triple δ-doped quantum wells

A detailed theoretical study on the electron-related optical responses in triple δ-doped GaAs quantum wells in the presence of non-resonant, monochromatic intense laser field is presented. For this purpose, we first obtained the bound subband energy levels and their corresponding envelope wave functions of the structure for different central doping concentrations within the effective-mass approximation. Then, we calculate the effect of the non-resonant intense laser field on the optical properties of this structure using the compact-density-matrix approach via the iterative method. We found that the optical absorption coefficients and refractive index changes in the triple δ-doped GaAs quantum well can be modulated by changing the central doping concentration and the intensity of the non-resonant, monochromatic laser field. In addition, it is shown that a sufficiently intense laser field suppresses the multiple quantum well configuration towards a single potential well one and the optical response becomes practically independent of the δ-doping concentration.     

Enhanced suppression of residual water in a "270" WET sequence

In certain water suppression experiments, the residual water, which comes from a region away from the center of the RF coil and experiences a much smaller flip angle than the designed one, may appear. The residual water in the WET sequence can be reduced significantly by using a composite 90(x)( degrees )90(y)( degrees )90(-x)( degrees )90(-y)( degrees ) pulse, which de-excites molecules experiencing a small flip angle. The composite pulse, however, has two null excitation points near on resonance, causing a severe loss of spectrum intensity and baseline distortion toward the null points. Since the residual water experiences a very small flip angle, it can be treated as a linear spin system; i.e., the intensity of the residual water is proportional to the pulse strength and width. Based on this principle, the residual water can be reduced dramatically by replacing the 90 degrees pulse in the "270" WET sequence with a 270 degrees pulse for one out of every four scans, without noticeable loss of intensity and baseline distortion.     

Dielectric responses of graded composites having generalized gradation profiles

Under an external uniform electric field, the dielectric response of graded cylindrical composites having generalized dielectric profile inclusions is investigated. The generalized dielectric profile of graded cylindrical inclusion is expressed in the form, $\varepsilon _i (r)=c(b+ r)^k\e^{\beta r}$ where $r$ is the radial variable of the cylindrical inclusions and $c$, $b$, $k$ and $\beta $ are parameters. The local potential solution of generalized dielectric profile graded composites is derived by means of the power series method and the effective dielectric response is predicted in the dilute limit. Moreover, from the result of generalized profile, the analytical solutions of local potentials and the effective responses of graded composites having three cases of dielectric profiles, i.e., the exponential profile $\varepsilon_\i (r)=c\e^{\beta r}$, the general power law profile $\varepsilon_\i (r)=c(b+r)^k$ and the profile $\varepsilon_\i (r)=cr^k\e^{\beta r}$, are sorted out, respectively. In the dilute limit, our exact results are used to test the validity of differential effective dipole approximation (DEDA) for estimating the effective response of graded cylindrical composites, and it is shown that the DEDA is in excellent agreement with the exact result.