Does Shadowing Relate to Nuclear Radius?

The A-dependence of nuclear shadowing in the partonic shadowing model is analysed. We point out that the nuclear shadowing is related to the average number of shadowed nucleons rather than the nuclear radius.     

Muon transfer from ground state deuterium to helium nuclei and its temperature dependence

The energy and time distributions of the decay X-rays of excited, metastable, molecular (dμHe)*-resonances were measured. The comparison of the observed energy spectra with calculated ones suggests that decay from the rotational state J = 1 dominates at the investigated conditions. The muon transfer rates from ground state deuterium to the helium isotopes ³He and ⁴He at low temperatures were determined from the time distributions of these spectra. Additionally, the temperature dependence of the muon transfer rate was clearly established in deuterium / ⁴He mixtures. This revised version was published online in August 2006 with corrections to the Cover Date.     

Directed triple systems

Directed triple systems are an example of block designs on directed graphs. A block design on a directed graph can be defined as follows. Let G be a directed graph of k vertices which contain no loops. Let S be a set of υ elements. A collection of k-subsets of S with an assignment of the elements of each k-subset to the vertices of G is called a block design on G of order υ if the following is satisfied. Any ordered pair of elements of S is assigned λ times to an edge of G.For example, if S = {a, b, c, d, e} and

and bae; cad; abc; dbe; acd; bce; adb; cde; aed; bec; is a collection of 3-subsets so written that in each subset the first element is assigned to the vertex 1, the second to 2, and the third to 3, then the collection is a block design on G with λ = 1.In this paper, it is shown that for the graph

if λ = 1, then the graph exists for all υ such that ν ? 2 mod 3.     

Fatigue Crack Nucleation at Σ3(1 1 2) Boundary in a Ferritic Stainless Steel

The effect of a geometrical relationship between a grain boundary (GB) plane and a tensile axis on intergranular fatigue cracking along 3(1 1 2) twin boundaries has been investigated in Fe-30%Cr alloy crystals. Fatigue experiments were carried out on the three kinds of the specimens containing the 3(1 1 2) twin boundary. It was found that the fatigue cracking behavior was sensitive to the geometry of the GB plane. In a specimen where both the GB plane and a slip vector lying in the GB plane in adjacent grains are inclined to the tensile axis at 45°, the fatigue cracks were nucleated preferentially along the twin boundary at a stress amplitude of 170 MPa. The specimen with the GB plane normal to the tensile axis showed that the fatigue crack was initiated from a slip band formed within a constituent grain at a stress amplitude of 300 MPa. When the GB plane was inclined to the tensile axis but the slip vector lying in the GB plane was normal to the tensile axis, development of additional slips formed perpendicular to the GB plane were observed at a specific site of the GB. Initiation of intergranular fatigue cracks at the site was recognized at a stress amplitude of 250 MPa. It can be suggested that the GB plane normal to the tensile axis provides the highest fatigue performance among them. The difference in the cracking property among these specimens could be understood in terms of the effective Schmid factor derived from elastically incompatible stress.     

Physical and theoretical aspects of a new vacuum arc controltechnology-self arc diffusion by electrode: SADE

Our new vacuum arc control technology SADE doubles the high current interruption capability of our conventional axial magnetic field technology. First, we describe the vacuum arc motion behavior recorded by a high speed charge-coupled device video camera. This arc behavior is closely related to axial magnetic field intensity. In particular, it depends on the profile of the externally generated axial magnetic field. The anode spot is likely to move to the highest magnetic field intensity. Second, we describe analytical results for concentration of vacuum arc at the anode side contact surface. This analysis implies the possibility of an ideal magnetic field profile and intensity for vacuum arc control. Finally, we describe experimental results for vacuum arc control compared with the physical and theoretical results mentioned above, and we show a practical electrode configuration for vacuum interrupters and its application in a high current interruption experiment     

Timing restoration dynamics in an actively mode-locked fiber ring laser

Using electronic phase detection, we study the dynamics that govern pulse retiming in an actively mode-locked fiber laser. We compare the dynamics for amplitude and for phase modulation and identify the characteristic time constants for each case. The retiming dynamics for amplitude modulation are revealed as a first-order exponential decay, whereas for phase modulation the dynamics are those of a damped harmonic oscillator. We show that the measured time constants agree with predictions given by the soliton perturbation theory.     

Desynchronization of chaos in coupled logistic maps

When identical chaotic oscillators interact, a state of complete or partial synchronization may be attained in which the motion is restricted to an invariant manifold of lower dimension than the full phase space. Riddling of the basin of attraction arises when particular orbits embedded in the synchronized chaotic state become transversely unstable while the state remains attracting on the average. Considering a system of two coupled logistic maps, we show that the transition to riddling will be soft or hard, depending on whether the first orbit to lose its transverse stability undergoes a supercritical or subcritical bifurcation. A subcritical bifurcation can lead directly to global riddling of the basin of attraction for the synchronized chaotic state. A supercritical bifurcation, on the other hand, is associated with the formation of a so-called mixed absorbing area that stretches along the synchronized chaotic state, and from which trajectories cannot escape. This gives rise to locally riddled basins of attraction. We present three different scenarios for the onset of riddling and for the subsequent transformations of the basins of attraction. Each scenario is described by following the type and location of the relevant asynchronous cycles, and determining their stable and unstable invariant manifolds. One scenario involves a contact bifurcation between the boundary of the basin of attraction and the absorbing area. Another scenario involves a long and interesting series of bifurcations starting with the stabilization of the asynchronous cycle produced in the riddling bifurcation and ending in a boundary crisis where the stability of an asynchronous chaotic state is destroyed. Finally, a phase diagram is presented to illustrate the parameter values at which the various transitions occur.     

4f-electric quadrupolar effects on the lattice constants and magnetism of RCu2Ge2 (R=rare-earths)

The temperature dependence of the lattice constants of the alloys, RCu₂Ge₂ (R=Nd, Tb, Dy, Ho and Tm) shows the existence of a lattice strain due to the alignment of the 4f-electric quadrupole at low temperatures. This strain could be related to the deviation of the Néel temperatures (T _N ) from that predicted by de Gennes scaling, thereby indicating the role of the quadrupole on the magnetism. On the other hand, in PrCu₂Ge₂, for which the enhancement ofT _N is the largest in thisR series, the lattice constants interestingly behave as if the 4f-quadrupole moment is almost quenched and the anomalous magnetism in this case is attributed to some degree of 4f-delocalisation.     

R-matrix methods for studying nuclear effects in μCF

Properties ofR-matrix theory that are useful for studying muon-catalyzed fusion reactions are reviewed, and applications to the dt system are discussed, using both improved adiabatic and non-adiabatic (variational) wave functions. We give complex eigenvalues and - sticking fractions for the (L, v)=(0,0) and (0, 1) states of dt using variational Hamiltonian matrix elements that have been properly symmetrized by means of the Block operator. Expressions for the fusion rate and - sticking fraction are developed from a time-dependent theory that uses the complex-energy states corresponding to the poles of the systemS-matrix. These are shown to reduce with the appropriate approximations to the expressions and values commonly used. Additional nuclear effects on these quantities can easily be studied within the framework developed, but they are not expected to be large.