Thermal neutron polarisation

The basic principle for the production of polarised thermal neutrons is discussed and the choice of various crystal monochromators surveyed. Brief mention of broad-spectrum polarisers is made. The application of polarised neutrons to the study of magnetisation density distributions in magnetic crystals, the dynamic concept of polarisation, principle and use of polarisation analysis, the neutron spin-echo technique are discussed.     

Spin-orbit splitting in theN-Δ spectra and the deformed baryon model

The absence of appreciable spin-orbit splitting in the low-lying even and odd parity states of the nucleon and delta is puzzling in conventional quark models. A constitutent quark model, in which the quarks interact through gluon as well as pion exchange, and the baryon is allowed to deform in the excited states, may provide a solution to the problem.     

Sample size determination for comparing two therapies taking both the α (type I or false positive) error and the β (type II or false negative) error into consideration

The sample size required for determination of a given degree of difference between two therapies or modalities A and B being compared with each other, supposing that the sample sizes are equal, is given by Here C_α/2 is the upper α/2 percentile point of the standard normal distribution, C_1?β is the abscissa cutting off the proportion 1?β in its upper tail and β in its lower tail; p_A and p_B are the probabilities of favorable response to A and B; if p?_A and p?_B are the corresponding measured proportions, then $\text{p}$ = $\text{1}\text{2}$(p?_A + p?_B); and the Q's are 1 minus the p's. When it is desirable to use unequal size groups, the sample sizes n₁     

The influence of geostrophic force on the stability of an heterogeneous conducting fluid with a radial gravitional force

The linear and nonlinear stability of a heterogeneous incompressible inviscid perfectly conducting fluid between two cylinders is investigated in the presence of a radial gravitational force and geostrophic force. The stability for linear disturbances is investigated using the normal mode method, while the nonlinear stability is investigated by applying the energy method. In the case of linear theory, it is found that a necessary condition for in stability is that the algebraic sum of hydrodynamic, hydromagnetic and rotation Richardson number is less than one quarter somewhere in the fluid. A semi-circle theorem similar to that of Howard is also obtained. In the case of nonlinear disturbances a universal stability estimate namely a stability limit for motions subject to arbitrary nonlinear disturbances is obtained in the form $$E \leqslant E_0 \exp ( - 2M\tau ).$$ The motion is asymptotically stable if $$\delta \leqslant 1 + J_m + J_H $$ somewhere in the fluid. This asymptotic stability limit is improved using the calculus of variation technique. We also find that whenδ=1/4, andJ _R=1, both the linear and nonlinear stability criteria coincide and in that particular case, we have a necessary and sufficient condition for stability.     

Time structure of the hadronic component of extensive air showers

Proceedings - Mathematical Sciences - A detailed study of the time structure of hadrons of energy > 5 GeV in extensive air showers has been carried out at Ootacamund (8·00 gm/cm2) using...     

Doubly ortho-linked quinoxaline/triarylamine hybrid as a bifunctional, dipolar electroluminescent template for optoelectronic applications

The titled hybrid (Q-H) works as a clippable optoelectronic unit. Q-spacer-Q systems function as efficient orange emitters reaching EL intensities (L) of up to 6840 cd m-2 with etaext of 0.77% and operation efficiencies of 1.60 cd A-1 and 0.8 lm W-1. Notably, Q-An acts as a (bluish) green emitter, reaching L of 12347 cd m-2 with similar operational efficiency.     

Steady flow generated by the differential rotation of a porous disk of finite thickness

When a body of fluid bounded by a porous disk of finite thickness is disturbed from a state of rigid rotation by an enhanced (or reduced) angular velocity of the disk, a few authors followed Darcys model and observed that the centrifugal pumping occurs through the entire porous layer regarded as a convection zone. The shear stress can develop only at the edge of the porous layer. We use a porous disk of high permeability that allows the fluid in the porous disk to deform in response to the changing angular velocity. Based on the Birkmans model, we solve for the steady non-linear flow and observe that there arises (i) a convection zone of nearly uniform angular velocity at the boundary (within the porous layer) and (ii) a transition zone adjacent to the convection zone which provides a smooth transition to the interior. This makes the model relevant to some astrophysical situations as described by some authors [1, 3]. The two point boundary value problem is solved subject to the boundary conditions, the far field conditions, and the matching conditions at the fluid-porous medium interface. The solution is obtained using a numerical procedure known as the method of Adjoints.Received: June 13, 2002; revised: July 7, 2003