Sub-5-pm linewidth, 130-nm-tuning of a coupled-cavity Ti:sapphire oscillator via volume Bragg grating-based feedback

A novel coupled-cavity Ti:sapphire oscillator architecture featuring a volume Bragg grating as a feedback element is presented. The oscillator provides continuous wave lasing within a spectral linewidth as narrow as 5 pm. The output can be wavelength-tuned over an ultrabroad spectral range of 130 nm, extending from 714 to 842 nm. This unique combination of narrow spectral linewidth and wide tuning range makes the laser suitable for applications such as sensing and Raman and absorption spectroscopy. The laser also displays ideal TEM₀₀ mode operation throughout its tuning range with output powers beyond 300 mW. Detailed studies of the cw lasing dynamics across the wide tuning range are described. The general architecture of this design can be implemented for high resolution tuning across the broad spectral emission bands of other solid state lasers with single mode operation.     

Improved high-performance liquid chromatographic determination of pilocarpine and its degradation products in ophthalmic solutions importance of octadecylsilane column choice

An improved high-performance liquid chromatographic (HPLC) method for the determination of pilocarpine, isopilocarpine, pilocarpic acid and isopilocarpic acid in ophthalamic solutions was developed. The new method was adapted from the USP HPLC method for pilocarpine base and has been shown to give superior resolution of pilocarpine related substances compared to any previously reported HPLC technique. However, evaluation of several brands of C₁₈ (octadecylsilane, ODS) columns revealed significant column-to-column variability: only to (YMC Pack ODS-AM and Supelco LC-18-DB) out of eight columns tested were capable of baseline resolution of these analytes. Additionally, optimization of the diluent was needed to prevent any significant interconversion of the carpic acids to their respective carpines. Analyses for pilocarpine and its degradation products in several commercial ophthalmic formulations were performed to demonstrate the precision, accuracy and general applicability of the method. The preparation of a stable resolution test solution is also described.     

MR imaging of experimental and clinical thrombi at 1.5 T

We have previously reported that the T1 and T2 of experimental clots at 0.47 T varies considerably depending upon the method used in their preparation. However, these studies, while relevant to midfield imaging, may not reflect accurately the behavior of such thrombi at higher field strengths. Accordingly, we studied the T1 and T2 at 1.5 T of experimental thrombi prepared by several methods and compared these results with the relaxation times of clinical deep venous thrombi measured in situ in patients. The relationship between the T2 values for the different clot preparation methods was different at 1.5 T than at 0.47 T. The combined use of thrombin and epsilon-amino caproic acid produced thrombi with T1 and T2 indistinguishable from clinical deep venous thrombi.     

Hitting time of a moving boundary for a diffusion

We obtain asymptotic estimates for the quantity r = log P[T_f[rang]t] as t → ∞ where T_f = inf\s{s : |X(s)|[rang]f(s)\s} and X is a real diffusion in natural scale with generator a(x) d²(·)/dx² and the ‘boundary’ f(s) is an increasing function. We impose regular variation on a and f and the result is expressed as r = ∫^t₀ λ₁ (f(s) ds(1 + o(1)) where λ₁(f) is the smallest eigenvalue for the process killed at ±f.     

Magnetic behaviour of some Mn.III2.VI4 compounds and their alloys

Measurement of the magnetic susceptibility χ as a function of temperature were made on polycrystalline samples from the alloy systems Cd_1−zMn_zGa₂Se₄, Zn_1−zMn_zGa₂Se₄ and Cd_1−zMn_zIn₂Te₄ which had been subjected to various heat treatments. The 1/χ versus T curves indicated that for the Zn---Se alloys, for all values of z, samples slowly cooled to room temperature were antiferromagnetic showing ideal Curie-Weiss behaviour, but for samples quenched from 700°C the behaviour was a mixture of antiferromagnetic and spin-glass. For the Cd---Se alloys, samples from the range (0.6 < z < 1.0) showed very similar behaviour, but in the range (0 < z < 0.6) even the very slowly cooled samples showed a mixture of antiferromagnetic and spin-glass behaviour. For the Cd---Te alloys, all samples, however heat-treated, showed spin-glass form. Values of the Curie-Weiss constant Ф were determined from all of the 1/χ versus T curves, and by comparison with the T(z) phase diagrams for the different alloy systems, the values of Ф were correlated with the ordering of the Mn atoms on the cation lattice. It is shown that the experimental values of Ф can give a very convenient way of determining the type of ordering and the degree of order in such alloys.     

Neutron multiplicities in inelastic collisions of132Xe with197Au

The multiplicities of neutrons emitted from the light and heavy fragments, respectively, in the inelastic scattering of 7.5 MeV/amu¹³² Xe ions from¹⁹⁷Au have been studied as a function of total energy loss. The measured multiplicity ratios are close to the Au-Xe mass ratio for all Q-values, consistent with a rapid thermalization of the excitation energy. The absolute multiplicity values are lower than expected and suggest significant pre-equilibrium effects.