BASIC ECONOMIC OPTIMIZATION MODEL FOR A CONTINUOUS EXTRACTION PROCESS*

A basic mathematical model, mainly focused on economic assessment is directly applied to a counter-current, stage-wise, solvent-selective extraction system. A standard extraction model, based on the modeling of a mixer-settler process, is used as point of departure. This system is used to extract a dissolved compound in a process stream. Thereafter sensible operating and economic parameters are integrated into it. An adequate handling of these parameters allows a practical preliminary optimization process modeling. The economic assessment model can be applied from one to "ri" stages in any industrial stage-wise process unit. An optimum number of stages are determined based on solvent extraction and economic assessment.     

CuFe2O4 Nanoparticles: A Magnetically Recoverable Catalyst for Selective Deacetylation of Carbohydrate Derivatives

An efficient protocol for the rapid room temperature deacetylation of carbohydrate derivatives using CuFe₂O₄ nanoparticles as an inexpensive and reusable catalyst is presented. After separation of the catalyst with an external magnet, the reaction products are easily obtained in good purity and excellent yields.     

Hepatitis C: Part I. Routine serologic testing and diagnosis

Hepatitis C, which is caused by the hepatitis C virus (HCV), is a major public health problem in the United States. HCV is most efficiently transmitted through large or repeated percutaneous exposures to blood. Most patients with acute HCV infection develop persistent infection, and 70 percent of patients develop chronic hepatitis. HCV-associated chronic liver disease results in 8,000 to 10,000 deaths per year, and the annual costs of acute and chronic hepatitis C exceed $600 million. An estimated 3.9 million Americans are currently infected with HCV, but most of these persons are asymptomatic and do not know they are infected. To identify them, primary health care professionals should obtain a history of high-risk practices associated with the transmission of HCV and other bloodborne pathogens from all patients. Routine testing is currently recommended only in patients who are most likely to be infected with HCV.     

Adult psychological functioning of individuals born with craniofacial anomalies

This study represents an initial investigation into the adult psychological functioning of individuals born with craniofacial disfigurement. A total of 24 men and women born with a craniofacial anomaly completed paper and pencil measures of body image dissatisfaction, self-esteem, quality of life, and experiences of discrimination. An age- and gender-matched control group of 24 non-facially disfigured adults also completed the measures. As expected, craniofacially disfigured adults reported greater dissatisfaction with their facial appearance than did the control group. Craniofacially disfigured adults also reported significantly lower levels of self-esteem and quality of life. Dissatisfaction with facial appearance, self-esteem, and quality of life were related to self-ratings of physical attractiveness. More than one-third of craniofacially disfigured adults (38 percent) reported experiences of discrimination in employment or social settings. Among disfigured adults, psychological functioning was not related to number of surgeries, although the degree of residual facial deformity was related to increased dissatisfaction with facial appearance and greater experiences of discrimination. Results suggest that adults who were born with craniofacial disfigurement, as compared with non-facially disfigured adults, experience greater dissatisfaction with facial appearance and lower self-esteem and quality of life; however, these experiences do not seem to be universal.     

New alkaloids from the indopacific sponge Stylissa carteri

Two samples of the marine sponge Stylissa carteri collected in Indonesia yielded two new bromopyrrole alkaloids: debromostevensine (1) and debromohymenin (2), as well as nine other known congeners (3-11). The structures of the new compounds were unambiguously established on the basis of their NMR and mass spectra.     

The complexity and approximation of fixing numerical attributes in databases under integrity constraints

Consistent query answering is the problem of characterizing and computing the semantically correct answers to queries from a database that may not satisfy certain integrity constraints. Consistent answers are characterized as those answers that are invariant under all minimally repaired versions of the original database. We study the problem of repairing databases with respect to denial constraints by fixing integer numerical values taken by attributes. We introduce a quantitative definition of database repair, and investigate the complexity of several decision and optimization problems. Among them, Database Repair Problem (DRP): deciding the existence of repairs within a given distance to the original instance, and CQA: deciding consistency of answers to simple and aggregate conjunctive queries under different semantics. We provide sharp complexity bounds, identifying relevant tractable and intractable cases. We also develop approximation algorithms for the latter. Among other results, we establish: (a) The -hardness of CQA. (b) That DRP is MAXSNP-hard, but has a good approximation. (c) The intractability of CQA for aggregate queries for one database atom denials (plus built-ins), and also that it has a good approximation.     

Influence of individual aggressiveness on the dynamics of competitive populations

Two populations are subdivided into two categories of individuals (hawks and lows). Individuals fight to have access to a resource which is necessary for their survival. Conflicts occur between individuals belonging to the same population and to different populations. We investigate the long term effects of the conflicts on the stability of the community. The model is a set of ODE's with four variables corresponding to hawk and dove individuals of the two populations. Two time scales are considered. A fast time scale is used to describe frequent encounters and fightings between individuals trying to monopolize the resource. A slow time scale is used for the demography and the long term effects of encounters. We use aggregation methods in order to reduce this model into a system of two ODE's only for the total densities of the two populations which is found to be a classical Lotka-Volterra competition model. We study different cases of proportions of hawks and doves in both populations on the global coexistence and the mutual exclusion of the two populations. Pure dove tactics in both populations are unstable. In cases of mixed hawk and dove in both populations, there is coexistence. Pure dove or mixed hawk-dove tactics in one population can coexist with pure hawks in the other one when the costs of fightings between hawks are large enough.     

Idiopathic thrombocytopenic purpura in a liver transplant recipient with previous primary biliary cirrhosis

The loss of immunotolerance has been implicated in the pathogenesis of both primary biliary cirrhosis (PBC) and idiopathic, immune-mediated thrombocytopenic purpura (ITP). An association between these two autoimmune diseases has been well described. We describe a 41-year-old woman in whom ITP developed 457 days after liver transplantation for PBC while receiving immunosuppressive medications sufficient to maintain allograft function. Our case report, the first to describe post-transplant ITP in association with PBC, demonstrates the persistence of the underlying immune dysregulation of PBC after transplantation. The practice of decreasing the dosage of immunosuppressive medication to maintenance levels after transplantation may unmask the effects of this defect in immunotolerance.