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De-oiling contaminated bleaching clay by high-pressure extraction

The disposal and re-use of spent bleaching clay from the vegetable oil processing industry is a problem of growing importance. Although today the only practical way of removal of the spent material is disposal, extraction with organic solvents is a well-known method of de-oiling contaminated bleaching clay. In our investigations we compare the extractibility of two different types of bleaching clays with CO₂ as a solvent. All experiments were carried out with a high-pressure extraction plant. The extraction and separation conditions, temperature and pressure, as well as the CO₂ mass flow, were varied during experiments. The aim of our investigations was a complete separation of the oil from the adsorbent. The latter should then be re-used as bleaching clay. The oil and the bleaching clay were analyzed and tested, respectively. The results show that oil of good quality can be recovered and the bleaching clay still has an activity approximately 50% of fresh clay.     

Matrix Interpretations for Proving Termination of Term Rewriting

We present a new method for automatically proving termination of term rewriting. It is based on the well-known idea of interpretation of terms where every rewrite step causes a decrease, but instead of the usual natural numbers we use vectors of natural numbers, ordered by a particular nontotal well-founded ordering. Function symbols are interpreted by linear mappings represented by matrices. This method allows us to prove termination and relative termination. A modification of the latter, in which strict steps are only allowed at the top, turns out to be helpful in combination with the dependency pair transformation. By bounding the dimension and the matrix coefficients, the search problem becomes finite. Our implementation transforms it to a Boolean satisfiability problem (SAT), to be solved by a state-of-the-art SAT solver.     

Competition among causes but not effects in predictive and diagnostic learning.

Causal asymmetry is one of the most fundamental features of the physical world: Causes produce effects, but not vice versa. This article is part of a debate between the view that, in principle, people are sensitive to causal directionality during learning (causal-model theory) and the view that learning primarily involves acquiring associations between cues and outcomes irrespective of their causal role (associative theories). Four experiments are presented that use asymmetries of cue competition to discriminate between these views. These experiments show that, contrary to associative accounts, cue competition interacts with causal status and that people are capable of differentiating between predictive and diagnostic inferences. Additional implications of causal-model theory are elaborated and empirically tested against alternative accounts. The results uniformly favor causal-model theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What's new in ras genes? Physiological role of ras genes in signal transduction and significance of ras gene activation in tumorigenesis

Ras gene mutations have been found with variable prevalence in different tumor types. While during the past decade a lot of information has been accumulated on the frequency of ras oncogene activation in tumors, the last two years brought considerable progress in elucidating molecular mechanisms of signal transduction for which cellular ras proteins are key elements. They transmit signals from upstream tyrosine kinases to downstream serine/threonine kinases ultimately leading to changes of gene expression cytoskeletal architecture, cell-to-cell interactions and metabolism. These signalling pathways are of interest for the physiological regulation of proliferation and differentiation in normal, as well as in cancer tissue. Mutational activation of cellular ras genes to transforming oncogenes is thought to promote cell growth even in the absence of extracellular stimuli, and may thereby contribute to the initiation and/or progression of tumors.     

The metabolism of IgE. Studies in normal individuals and in a patient with IgE myeloma

IgE metabolic turnover studies with purified radioiodinated IgE were performed in normal individuals and in a patient with IgE myeloma. The validity of the turnover studies was established in several ways, including comparisons of radioiodinated IgE turnover with the turnover of endogenously labeled 14C-IgE and with the turnover of infused unlabeled IgE in a patient with hypogammaglobulinemia. The geometric mean serum IgE concentration in 73 normal adults was 96 ng/ml with a 68% confidence interval of 24 to 386 ng/ml. Metabolic turnover studies in 10 control individuals disclosed a geometric mean total circulating IgE of 4.1 mug/kg, a mean percentage of the total exchangeable IgE in the intravascular space of 41%, a mean half-time of survival of IgE of 2.7 days, a mean fractional catabolic rate of 94% of intravascular pool per day, and a geometric mean synthetic rate of 3.8 mug/kg/day. IgE has the lowest synthetic rate and highest fractional catabolic rate of the five major classes of immunoglobulin molecules. In contrast to these normal values, a patient with IgE myeloma had a serum IgE comcentration of 42 mg/ml, a total circulating IgE of 1.7 g/kg, and a synthetic rate of 270 mg/kg/day. Furthermore, although the synthetic rate was vastly increased, the survival time was prolonged and the fractional catabolic rate was decreased to 5.1 days and 16 to 22% of the intravascular pool per day, respectively. These data are compatible with the concept that IgE is catabolized in part by a mechanism common to all immunoglobulin classes and in part by a unique mechanism not available to other immunoglobulins. At very high IgE serum concentrations, such as those encountered in patients with IgE myeloma, the unique mechanism would be saturated and only the catabolic pathways available to all immunoglobulins would be available to IgE.