Physical and chemical characterization of thermosoftened bases for molten filled hard gelatin capsule formulations

Dynafill, Dynasan-114, Lutrol-F68, PEG-10000 and PEG-20000 have been examined as potential bases for the preparation of fusion formed solid dispersions for molten filling into hard gelatin capsules. Investigations included, an examination of thermal effects on crystal structure by DSC and XRD, a theological study to evaluate capsule filling characteristics, dissolution studies on drug/base formulations, chemical analysis for free fatty acid impurities in Dynafill and Dynasan-114, and detailed studies on selected drug/base formulations. PEG-20000 and Dynasan-114 were not examined in detail, after preliminary investigations had shown high viscosity and poor filling characteristics for PEG-20000 and poor dissolution characteristics for Dynasan-114. Dynafill provided good release profiles when formulated with a variety of model drugs (Acetohexamide, Ibuprofen, Indomethacin, Quinidine sulphate and Theophylline). Results from hot stage photomicrography supported by DSC and XRD were used to construct a phase diagram of the Ibuprofen/Lutrol-F68 system. The evidence from the phase diagram indicated the formulation of a simple eutectic system with no solid solubility and a eutectic composition at approximately 35% w/w Ibuprofen.     

Vibrational control of linear time lag systems with arbitrarilylarge but bounded delays

It is shown that vibrational stabilization can be effective for linear systems with large bounded delays. Theorems are given that define the procedures for the search of the stabilizing vibrations. Robust oscillatory stabilization insensitive to the delay size is also shown to take place for some classes of systems     

Use of electric power in glass melting

The advantages and disadvantages of electric furnaces for melting frits and enamels and glasses for special applications were examined. It was shown that low-efficiency electric furnaces are more economical than furnaces heated by organic fuel. The main advantage of electric furnaces is the reduction in harmful emissions.Translated from Steklo i Keramika, Nos. 3–4, pp. 8–10, March–April, 1994.     

The accumulation channel driven bipolar transistor (ACBT)

A new three-terminal power switch called the Accumulation Channel driven Bipolar Transistor (ACBT) is proposed and experimentally demonstrated. In the on-state, the characteristics of the ACBT have been found to approach those of a P-I-N rectifier with a MOSFET in series for regulating its current, an equivalent circuit considered to be an ideal for MOS/Bipolar power devices. Unlike previous devices, the high off-state voltage is supported by the formation of a potential barrier to the flow of electrons from the N⁺ emitter into the N-drift region within a depletion region. The absence of the P-base region within the ACBT cells eliminates the parasitic four layer PNPN thyristor which had limited the performance of previous MOS/Bipolar transistor structures. Consequently, the ACBT structure has large maximum controllable and surge current densities in addition to low on-state voltage drop and high-voltage current saturation capability     

Duality transformations for general bi-isotropic (nonreciprocalchiral) media

The transformation is defined to leave a given bi-isotropic medium invariant, whence it is self-dual in this transformation. It is shown that duality transformations always exist in pairs, labeled as left-hand and right-hand transformations. Self-dual fields are seen to be generalizations of the wave fields E± applied in the analysis of reciprocal chiral media. It is demonstrated that plane wave propagation and reflection problems in bi-isotropic media can be solved easily in terms of self-dual field decompositions. Nonreciprocity is seen to give rise to effects like polarization rotation in reflection, which cannot be interpreted in terms of reciprocal chiral media     

Depth resolution calculations for heavy-ion microbeam RBS analysis

A detailed study has been made on the use of MeV heavy ions (Z₁ = 6–8) for microbeam Rutherford backscattering (RBS) analysis, to improve the depth resolution of this technique. The algorithm for determination of the depth resolution was created and applied to the Zagreb microbeam facility. Theoretical estimates of depth resolution for C and O ion RBS analysis of thin oxide films and semiconductors, using annular silicon surface barrier detector (SSBD), are compared to those for proton backscattering analysis. Depth resolution in certain cases may be improved by increasing the heavy-ion energy. Therefore, by the proper choice of the heavy ion and the heavy-ion energy, the depth resolution may be improved, maintaining the efficiency of the RBS method.     

Constrained feed technique for subarrays of large phased arrays

A technique is presented which combines the subarraying qualities of constrained dual transform beamforming sections and partial overlapping networks to produce arrays of contiguous subarrays. This approach is shown to facilitate wideband scanning or limited field of view coverage with a minimum number of controls and low sidelobes