Directly Compressible Acetaminophen Compositions Prepared by Fluidized-Bed Granulation

Polyvinylpyrrolidone (PVP) in aqueous solution was used as a binding agent in a fluidized-bed system to agglomerate acetaminophen powder into directly compressible granules. It was found that a minimal amount of 5% w/w PVP in a concentration of 7.5% w/v or less was needed to produce granules with an acceptable flow and the corresponding tablets having enough hardness without capping. There was a strong correlation between the time for 80% dissolved (T₈₀) and the logarithm of granule volume-surface mean diameter. A directly compressible acetaminophen composition to manufacture tablets having a T₈₀ value less than 30 min can be prepared simply by adding an appropriate amount of disintegrant (crospovidone, sodium starch glycolate, or pregelatinized starch) to the agglomerated granules.     

An in vitro model of traumatic neuronal injury: loading rate-dependent changes in acute cytosolic calcium and lactate dehydrogenase release

We developed a new in vitro model of neuronal injury using NT2-N cells to examine the effects of hydrodynamic loading rate on intraneuronal calcium dynamics and lactate dehydrogenase (LDH) release. Our apparatus consisted of a parallel disk viscometer which induced fluid shear stress with well-defined magnitudes and loading rates to cultured cells. We found that the deformation response of the cells was dependent on the severity of the insult, with increased cellular strains generated for higher shear stresses at a constant loading rate. Peak intracellular free calcium concentration correlated with strain, suggesting that mechanical deformation may regulate calcium response. Slowly applied fluid shear stress elicited no response, whereas high loading rates resulted in peak calcium increases 2.9 to 3.6 times baseline values as injury severity was increased. LDH release measured within 5 min after the insult correlated with loading rate. In addition, LDH release continued to increase out to 24 h following high loading rate conditions, demonstrating that the application of fluid shear stress led to prolonged cell damage. The acute response in NT2-N cells subjected to an insult with the CSID is dependent on the loading rate, and these results suggest that initial membrane deformation may trigger subsequent events.     

Interfacial reactions in the squeeze-cast (SAFFIL+C)/SAE 329 Al composite

Interfacial reactions in the squeeze-cast SAE 329 Al alloy reinforced with SAFFIL and carbon fibers were investigated using scanning and transmission electron microscopy and secondary ion mass spectroscopy. The SiO₂ layer added as a binder for the preform of SAFFIL fiber appeared to prevent excessive reaction between the fiber and the molten Al alloy during casting. In the as-cast composite, the reaction between the SiO₂ layer and the Al alloy is considered to produce MgO crystals in the vicinity of SAFFIL fiber. With subsequent heat treatment of the composite to the T6 condition, small crystals of MgO and MgAl₂O₄ were found to form at the surface of SAFFIL fiber as a result of interfacial reaction between the SiO₂ layer and the Al alloy. Even at the T6 condition, significant reactions between the Al alloy and SAFFIL fiber itself were not observed, indicating the effective role of the binder layer in suppressing the degradation of SAFFIL fiber by reaction with the Al alloy.     

A novel method for elimination of line-current harmonics insingle-stage PFC switching regulators

This paper studies a particular single-stage power-factor-correction (PFC) switching regulator employing a discontinuous-conduction-mode (DCM) boost-input cell and a continuous-current-mode (CCM) forward output cell. Although this single-stage PFC regulator can provide a reasonably high power factor when its PFC stage is operating in discontinuous mode, substantial reduction in line-current harmonics is possible by applying a suitable frequency-modulation scheme. This paper derives a frequency-modulation scheme and proposes a practical implementation using a simple translinear analog circuit. A quantitative analysis on the total harmonic distortion (THD) of the line current when the circuit is subject to a limited range of frequency variations is presented along with some considerations for practical design. Experimental data obtained from a prototype confirms the effectiveness of the proposed frequency-modulation scheme. The proposed analog translinear circuit allows custom integrated circuit implementation, making it a viable low-cost solution to the elimination of line-current harmonics in switching regulators     

Optimal solutions for a dynamic bandwidth allocation scheme in high-speed networks

In this paper, we investigate the problem of determining the optimal bandwidth allocation for a Dynamic Bandwidth Allocation Scheme (DBAS). The objective is to minimize the total amount of bandwidth required to satisfy the Quality of Service (QoS) requirements of all traffic streams. It is shown that when the performance functions satisfy a certain number of conditions, there exists a unique optimal bandwidth allocation such that, for each traffic stream, either its QoS is just satisfied or its QoS is over-satisfied and it is allocated zero bandwidth. Such an allocation is said to be efficient. It is also shown that there exists a unique efficient allocation in the entire feasible region. An iterative algorithm is developed to compute the efficient allocation employing its special properties. Numerical examples are presented to demonstrate how the algorithm works. Future extensions of this work are also discussed.Partially supported by NSERC of Canada through grants OGP14020 and STRIN-200.     

Micromachined piezoelectric force sensors based on PZT thin films

A micromachined lead zirconate titanate (PZT) force sensor for scanning force microscope (SFM) is conceptualized by its piezoelectricity. The fabrication procedure is interpreted, and mechanical characteristics of the micromachined PZT force sensors with various lengths are studied in this paper. A compact SFM is constructed by using the piezoelectric PZT sensor. A very clear image is taken by this SFM. The current study of the micromachined PZT force sensor can be considered as a breakthrough of design of SFM as well as a good example of integrated piezoelectric microdevices     

Oxygen absorption kinetics in YBa2Cu3Ox

The oxygen absorption process in highly aligned YBa₂Cu₃O_x samples in air and in pure oxygen was studied at several constant temperatures. The process can be expressed in two steps, a chemical reaction controlled step and a diffusion controlled step. The kinetic equations are as follows respectively:

(1 − a_t) ln(1 − a_t) + a_t = k_Dt

The activation energy was calculated using an Arrhenius equation. The technical conditions of heat treatment for oxygen absorption of highly aligned YBa₂Cu₃O_x crystals are discussed.     

Novel technique for SiO2 formed by liquid-phasedeposition for low-temperature processed polysilicon TFT

A technique for SiO₂ formation by liquid-phase deposition (LPD) at nearly room temperature for low-temperature processed (LTP) polysilicon thin-film transistor (poly-Si TFT) was developed. LPD SiO₂ film with a lower P-etch rate shows a dense structure. LPD SiO₂ also exhibits good electrical characteristics. LTP poly-Si thin-film transistors (TFTs) with LPD SiO ₂ as the gate insulator have been fabricated and investigated. Their characteristics indicate performance adequate for their use as pixel transistors in liquid crystal displays (LCDs)     

An alternative approach to weight function evaluation for an orthotropic crack

The use of the analytically decoupled near-tip displacement solutions as an alternative approach, is presented in this paper for the efficient finite element evaluation of the decoupled weight functions for an orthotropic 2-D crack. This alternative approach has been validated by directly comparing the prior weight function results with a symmetric mesh approach in the crack-tip neighborhood, and indirectly by comparing the calculated stress intensity factors (K_I(II)) values using the computed weight functions with available K_I(II) solutions of the 2-D mixed mode orthotropic cracks. In addition, this approach with analytically decoupled near-tip displacement solutions for calculating weight functions at all locations, can facilitate further extension of weight function evaluations to a more general 2-D anisotropic crack.