Phase equilibria calculations for ill-defined mixtures using the prsv equation of state

A method for the calculation of vapor-liquid equilibria (VLE) for multicomponent systems using continuous thermodynamics is presented. The Extended Spline Fit Technique (ESFT) is used to represent the molar distribution curve of petroleum fluids. A continuous version of the Peng-Robinson-Stryjek-Vera (PRSV) equation of state (EOS) with Generalized Single Carbon Number Properties (GSCNP) is utilized. For continuously distributed components, following the suggestion of Hendriks (1987), the number of equations solved is reduced through integration over the range of the distributing variable using Legendre-Gauss quadrature. Integrated equations are solved using accelerated successive substitution. Flash, dew and bubble point calculations for an imaginary and a real system yield satisfactory results.     

Outcome of plasma exchange therapy in thrombotic microangiopathy after renal transplantation

Thrombotic microangiopathy (TMA) in renal transplant recipients is commonly associated with calcineurin inhibitors (CNIs), though several factors such as vascular rejection, viral infections and other drugs may play a contributory role. We report a series of 29 patients with TMA, all of whom were on CNIs. Though plasma exchange (PEx) is widely used to treat TMA, therapeutic guidelines are not well defined. All our patients were treated with PEx and discontinuation of CNIs. Thrombotic microangiopathy was diagnosed at a median of 7 days post-transplant. The mean decrease in Hgb and platelets during TMA was 66% and 64%, respectively, and peak serum creatinine during TMA was 7.4 +/- 2.9 mg%. Mean duration of PEx therapy was 8.5 (range 5-23) days. Recovery of platelet count to 150K/mcL and Hgb to 8-10 g/dL were used as endpoints for PEx. Twenty-three/29 (80%) patients recovered graft function after PEx. Twenty/23 (87%) patients who recovered were placed back on CNl. Nineteen/20 (95%) patients tolerated reinstitution of CNl without recurrence of TMA. In post-transplant TMA, PEx was associated with a graft salvage rate of 80%, reversal of hematological changes can be used as the endpoint for PEx therapy and CNl can be reintroduced without risk of recurrence in the majority of patients.     

Internal Friction in Lithium Aluminosilicate Glass-Ceramics

This paper describes the results of an investigation of the anelastic behavior of two glass-ceramic materials with similar compositions, one nucleated with TiO₂ and the other with ZrO₂. The influence of the grain size, residual glass fraction, and composition was examined. A low-frequency torsion pendulum was constructed for this purpose. The as-received TiO₂-nucleated. Corning Code 9608 ceramic exhibits an attenuation peak at about 750°C; when heat-treated at 1200°C for 167 h, the attenuation peaks at approximately 850°C. The ZrO nucleated glass-ceramic showed no such peak. Our results indicate that this anelastic behavior is due to grain boundary sliding, but the rates and magnitude of sliding are strongly dependent on boundary chemistry.     

Effect of filtration on virgin olive oil stability during storage

The effect of filtration and dehydration on the stability and quality of virgin olive oil during storage at room temperature (25 °C) and under accelerated conditions (40 °C) was studied. Different types of monovarietal olive oil, namely unfiltered (UF), filtered (F) and filtered‐dehydrated (FD), were obtained from Arbequina, Colombaia, Cornicabra, Picual and Taggiasca cultivars. Results showed that filtration and dehydration decreased the rate of hydrolysis of the triacylglycerol matrix, especially at the higher temperature and in oils with a higher initial free acidity (e.g. free acidity of 0.82% and 0.63% in UF and FD Colombaia samples, respectively, after 8 months of storage), and delayed the appearance of rancid defects (e.g. UF and FD Arbequina samples lost extra‐virgin grade after 10 and 12 months of storage, respectively). The formation of simple phenols due to the hydrolysis rate of their secoiridoid derivatives was also greater in unfiltered olive oils (e.g. 174 μmol/kg and 137 μmol/kg in UF and FD Picual samples, respectively, after 8 months of storage). Thus, filtration and especially dehydration could help to prolong the shelf life of high‐quality and less stable olive oils like those obtained from the Arbequina and Colombaia varieties.     

Impact of Parameter Variations on Circuits and Microarchitecture

Parameter variations, which are increasing along with advances in process technologies, affect both timing and power. Variability must be considered at both the circuit and microarchitectural design levels to keep pace with performance scaling and to keep power consumption within reasonable limits. This article presents an overview of the main sources of variability and surveys variation-tolerant circuit and microarchitectural approaches     

Topology optimization of periodic microstructures with a penalization of highly localized buckling modes

The problem of determining highly localized buckling modes in perfectly periodic cellular microstructures of infinite extent is addressed. A double scale asymptotic technique is applied to the linearized stability problem for a periodic structure built from linearly elastic microstructures. The obtained stability condition for the microscale level is then used to establish a comparative analysis between different material distributions in the base cell subjected to the same strain field at the macroscale level. The idea is illustrated by some two‐dimensional finite element examples and used to design materials with optimal elastic properties that are less prone to localized instability in the form of local buckling modes at the scale of the microstructure. Copyright © 2002 John Wiley & Sons, Ltd.     

Reverse Micellar Extraction of Lysozyme Using Two Dialkyl Sodium Phosphinates

The extraction of lysozyme was studied using di‐(2,4,4‐trimethylpentyl) sodium phosphinate, R₂POONa, and di‐(2,4,4‐trimethylpentyl) sodium dithiophosphinate, R₂PSSNa. For a R₂POONa reverse micellar system, all lysozyme was removed from the aqueous phase when the pH of the aqueous solution was set below the pI of the protein. The extraction of lysozyme into a R₂PSSNa reverse micellar system was independent of the pH of the aqueous phase. A solubilization limit of lysozyme exists in the R₂POONa reverse micellar phase. The lysozyme recovery was 70% from the R₂POONa reverse micellar phase, and less than 10% from the R₂PSSNa reverse micellar phase.     

Generalization of the possibility of eliminating the filtration step in the determination of acid-soluble chloride content in cement and concrete by potentiometric titration

In this work, it is demonstrated that it is possible to eliminate the filtration step in the determination of the acid-soluble chloride content of cement and concrete by potentiometric titration, irrespective of the method used for detecting the end-point of the titration. Extensive analytical results are presented corresponding to several types of cement and to a broad range of chloride concentrations in concrete. Some requirements to avoid errors in such analytical determinations are discussed.     

Performance of curaua fibers in pullout tests

Natural lignocellulosic fibers are successfully replacing synthetic fibers as the reinforcement phase of composite materials in many engineering applications, including automobile parts. In addition to well-known conventional lignocellulosic fibers, others with promising properties, like that obtained from the leaves of the curaua plant (Ananas erectifolius) found in the Amazon region of Brazil, are now being considered. The present work investigated microstructural aspects associated with the performance of curaua fibers in pullout tests carried out to characterize the fibers interfacial strength with a polyester matrix. The results have shown that the naturally bonded filaments that constitute a curaua fiber present interspatial voids between them. These voids play an important role in providing adherence of the fiber surface to a polyester matrix, resulting in an effective reinforcement for a curaua-strengthened composite.