Multiple scattering of gamma rays in water,concrete and sand

The transmitted photon spectra of¹³³Ba,²²Na,¹³⁷Cs,⁵⁴Mn and⁶⁰Co point sources are measured through different thicknesses of water, concrete and sand. The multiple-scatter peaks observed in these materials at 60, 90 and 100 keV energies respectively are found to be independent of incident photon energy and thickness of the medium.     

Bounds on the effective thermal conductivity of two-phase systems

The weighted geometric mean of resistors considered for determining the effective thermal conductivityK _E of two-phase systems has been optimised. Solutions of the equations lead to a useful set of bounds. When compared with other bounds the present bounds give the better results in estimating the upper and lower values of the effective thermal conductivity of a two-phase system.     

An Incremental Algorithm for the Maximum Flow Problem

An incremental algorithm may yield an enormous computational time saving to solve a network flow problem. It updates the solution to an instance of a problem for a unit change in the input. In this paper we have proposed an efficient incremental implementation of maximum flow problem after inserting an edge in the network G. The algorithm has the time complexity of O((n)² m), where n is the number of affected vertices and m is the number of edges in the network. We have also discussed the incremental algorithm for deletion of an edge in the network G.     

Laser induced air breakdown using 0.355, 0.532, and 1.06 µm radiation

Studies of breakdown threshold intensity for air at various pressures in the range of 24–760 torr using 0.355, 0.532 and 1.06 μm radiation are reported. We observep ^−0.8 scaling ofI _th at 1.06 μm and a weak scaling ofp ^−0.4 at 0.532 and 0.355 μm radiation. Strong dependence of breakdown spot size on laser power but weak dependence on air pressure is observed.     

Use of non-adiabatic geometric phase for quantum computing by NMR

Geometric phases have stimulated researchers for its potential applications in many areas of science. One of them is fault-tolerant quantum computation. A preliminary requisite of quantum computation is the implementation of controlled dynamics of qubits. In controlled dynamics, one qubit undergoes coherent evolution and acquires appropriate phase, depending on the state of other qubits. If the evolution is geometric, then the phase acquired depend only on the geometry of the path executed, and is robust against certain types of error. This phenomenon leads to an inherently fault-tolerant quantum computation. Here we suggest a technique of using non-adiabatic geometric phase for quantum computation, using selective excitation. In a two-qubit system, we selectively evolve a suitable subsystem where the control qubit is in state |1, through a closed circuit. By this evolution, the target qubit gains a phase controlled by the state of the control qubit. Using the non-adiabatic geometric phase we demonstrate implementation of Deutsch-Jozsa algorithm and Grover's search algorithm in a two-qubit system.     

Magnetism of Fe in SrFe2As2: Local investigation by time differential perturbed angular distribution (TDPAD) spectroscopy

Employing the γ-ray perturbed angular distribution technique, we have measured the magnetic hyperfine field of ⁵⁴Fe in tetragonal and orthorhombic structural phases of SrFe₂As₂. In the tetragonal phase, the magnetic response of ⁵⁴Fe shows Curie-Weiss type local susceptibility, indicating the presence of localized moment on Fe. The temperature dependence of the hyperfine field of ⁵⁴Fe reflects quasi-two dimensional first order magnetic transition at 200 K. Our data indicate that Fe moments in the magnetically ordered phase of SrFe₂As₂ may be canted out of the ab-plane.