J.W.O. van den Berg

Assessment of the contribution of sustainability indicators to sustainable development: a novel approach using fuzzy set theory

As a consequence of the impact of sustainability on agricultural production systems, a standardized framework to monitor sustainable development would have great practical utility. The objective of this paper is to introduce fuzzy set theory and develop fuzzy mathematical models to assess sustainable development based on context-dependent economic, ecological, and societal sustainability indicators. Membership functions are at the core of fuzzy models, and define the degree to which indicators contribute to development. Although a decision-making process regarding sustainable development is subjective, fuzzy set theory links human expectations about development, expressed in linguistic propositions, to numerical data, expressed in measurements of sustainability indicators. In the future, practical implementation of such models will be based on elicitation of expert knowledge to construct a membership function. The fuzzy models developed in this paper provide a novel approach to support decisions regarding sustainable development.

Minimum protein requirements in liver cirrhosis determined by nitrogen balance measurements at three levels of protein intake.

Nitrogen balance at three levels of protein intake was measured in eight patients with cirrhosis of the liver; moreover, at each level of protein intake, the effects on nitrogen balance of branched-chain amino-acid enriched protein and natural protein were compared. From these nitrogen balance data, minimum protein requirements were calculated by linear regression analysis. The patients were in a negative nitrogen balance on a 40 g protein diet (-0.75 +/- 0.15 gN.), and in positive nitrogen balance on 60 g (+1.23 +/- 0.22 gN.) or 80 g of protein per day (+2.77 +/- 0.20 g N.). Their mean minimum protein requirement (48 +/- 5 g of protein/day or 0.75 g/kg/day) is higher than expected in healthy people; the safe level of protein intake (mean + 2 sd) is 58 g per day or 1.2 g/kg/day. Nitrogen balances and protein requirements were not different on branched-chain amino-acid enriched diets. The physical condition of the patients improved when they came into positive nitrogen balance; the higher rates of protein intake were well tolerated without onset of encephalopathy. We conclude that protein requirements are elevated in cirrhosis of the liver; diets supplying less than 60 g of protein per day should not be prescribed in long term treatment of cirrhotic patients.

Fuzzy classification using probability-based rule weighting

Design of fuzzy classifiers based on probabilistic fuzzy systems is considered. It is shown that the statistical properties of the training data can be used for the design of fuzzy rule based classification systems. Takagi-Sugeno type fuzzy systems are designed for estimating the underlying conditional probability density function for the data. Probabilistic rule weighting is introduced, and classifiers based on the discriminant function approach are formulated. It is shown that some of the fuzzy classifiers that have been proposed in the literature can be formulated in terms of probabilistic rule weighting. Furthermore, the relation to certainty factor approach to fuzzy classifiers is considered.

Body Composition in Patients With Acquired Immunodeficiency Syndrome: A Validation Study of Bioelectric Impedance Analysis

The objective of this validation study was to explore bioelectric impedance analysis (BIA) as a way to assess nutritional status and body composition. The study was done in the outpatient department of the AIDS unit at University Hospital Dijkzigt, Rotterdam, The Netherlands. Eleven clinically stable patients with AIDS were studied. Total body water, body fat, lean body mass, and body cell mass were measured and calculated with multiple dilution techniques and BIA. With linear regression analysis, a strong correlation was found between total body water and lean body mass derived from BIA and multiple dilution techniques (r2 = .96 and .98, respectively), and slightly weaker correlation was found for body cell mass and body fat (r2 = .88 and .76, respectively). These results suggest that BIA is a suitable method for the assessment of body cell mass in HIV-infected patients without opportunistic infections. The technique is safe, noninvasive, fast, and inexpensive.

Primary bile acid diarrhoea without an ileal carrier defect: quantification of active bile acid transport across the ileal brush border membrane.

Unexplained bile acid malabsorption associated with diarrhoea that responds to cholestyramine was first described in 1973 but convincing evidence of the proposed mechanism--a defective active ileal bile acid transport--has never been substantiated. Active bile acid transport was quantified in vitro using brush border membrane vesicles prepared from terminal ileal biopsy specimens from 10 patients who fulfilled the criteria of idiopathic bile acid diarrhoea. They were recruited from 181 patients with bile acid malabsorption of various causes. Transport was quantified as in vitro Na+ dependent bile acid transport (INBAT), expressed as pmol taurocholate/mg brush border membrane protein/15 seconds, and in vitro Na+ dependent bile acid local transport capacity (INBALTC), expressed as pmol taurocholate/g ileal biopsy tissue/15 seconds. The lowest INBAT and INBALTC values in the 10 patients with idiopathic bile acid diarrhoea were well above the 10th centile values of a control group of 132 patients. Both INBAT (mean (range) 88 (30-136)) and INBALTC (158 (85-268)) values were significantly higher in the 10 patients than in the control group (INBAT: mean (range) 63 (1-244), INBALTC: mean (range) 98 (1-408)). Quantification of active ileal bile acid transport in these 10 patients with idiopathic bile acid malabsorption suggests that a genetic (carrier) defect is rare in adults.

Na+-dependent bile acid transport in the ileum: the balance between diarrhea and constipation.

Ileal Na+-dependent bile acid transport was quantified in vitro as the uptake of 3H-taurocholate into brush-border membrane vesicles. Vesicles were prepared from ileal biopsies of 158 patients placed in 10 diagnostic categories. Active bile acid transport (expressed as picomoles taurocholate uptake per milligram brush-border membrane protein per 15 s, median and interquartile ranges indicated) did not differ significantly in 6 categories: irritable bowel syndrome (71, 35-97; n = 21), colon polyps (42, 30-89; n = 29), colitis (62, 33-91; n = 31), postvagotomy or postcholecystectomy (69, 37-97; n = 11), diarrhea without increased bile acid loss (58, 48-85; n = 12), and lack of gastrointestinal pathology (74, 45-103; n = 22). A decreased active bile acid transport was found in 3 categories: ileal disease (4, 1-36; n = 11), partial ileal resection (5, 1-35; n = 5), and constipation (41, 22-50; n = 8). Bile acid transport was increased in patients with bile acid-losing diarrhea with endoscopically and histologically normal ilea (111, 94-135; n = 8). These findings indicate that a low fecal bile acid loss, presumed to be present in constipated patients, is associated with a low Na+-dependent ileal bile acid transport and a high bile acid loss is associated with a high active bile acid transport. Ileal bile acid transport might be regulated by the availability of bile acids to the ileal enterocytes.

Primary Bile Acid Malabsorption: A Pathophysiologic and Clinical Entity?

Primary bile acid malabsorption is defined as chronic diarrhoea with bile acid malabsorption of unknown cause and a symptomatic response to cholestyramine. Convincing evidence of the proposed pathophysiology-a defect of the active bile acid absorption in the distal ileum-has never been substantiated. We found no evidence of a bile acid transport defect across the ileal brush border membrane in 10 patients with primary bile acid malabsorption; moreover, transport was significantly higher than in a control group. In the patients with primary bile acid malabsorption the estimated bile acid pool was significantly larger than in a control group and in a group of patients with ileal disease. In addition, the oroanal transit time of radiopaque markers was shorter in the primary bile acid malabsorption group than in both other groups. This suggests that the bile acid pool size as well as intestinal motility could play a role in the pathophysiology of primary bile acid malabsorption.

Evaluation Studies of the 13C-Mixed Triglyceride Breath Test in Healthy Controls and Adult Cystic Fibrosis Patients with Exocrine Pancreatic Insufficiency

The 13C-mixed triglyceride (13C-MTG) breath test (BT) is a safe and noninvasive method to measure exocrine pancreatic function. We examined the reproducibility of the 13C-MTG BT in a group of 17 healthy controls and 8 adult patients with cystic fibrosis (CF). In controls no statistically significant difference in percentage dose recovered (PDR) was found between the first and the second result of repeated tests: the mean values were 35.5 +/- 5.5 vs. 32.3 +/- 7.4 PDR (n = 17). Also in the group of CF patients (n = 8) no significant difference between duplicate tests was found: mean values 17.5 +/- 7.5 and 17.5 +/- 7.8 PDR, respectively. The coefficient of repeatability is 8 PDR for the controls and CF patients together. Two factors might influence the outcome of the test. First, individually measured CO2 excretion instead of the usually assumed 9 mmol/h/kg CO2 production might alter the result of the 13CO2-MTG BT. Therefore CO2 production was measured by indirect calorimetry in 12 healthy controls and 13 CF patients. Measured CO2 excretion was not significantly different between healthy controls and CF patients. Secondly, exercise might influence BT results due to its separate effects on both CO2 production and excretion. The influence of physical exercise at a level of 25 or 50 W was studied on a bicycle ergometer in 4 healthy controls during the last 5 min of each 30-min sampling period. Exercise gave lower test results, on average 85% of the PDR value at rest. Incidently, it was observed in 1 patient that use of 13C-enriched food during the day preceding the test caused inappropriately low test results in the 13C-MTG BT. The 13C-MTG BT is a test with a fair but less than desirable reproducibility. Test conditions should be standardized to eliminate confounding influences. Exercise should be limited or strictly defined. Diet on the day preceding the test should not contain naturally 13C-enriched food. There is no need to measure individual CO2 production.

New method for the determination of bile acid turnover using 75Se-homocholic acid taurine

The introduction of 75Se-homocholic acid taurine (75SeHCAT) greatly facilitates the investigation of diarrhoea of unknown origin. By using gamma-labelled bile acids, daily faecal bile acid loss can be measured in total collected stools, thus circumventing laborious mixing and sampling. The 75SeHCAT method proved to be reliable for the determination of bile acid turnover, giving results identical to the established turnover method using 14C-taurocholic acid. The new method however, is simpler and faster.

A Novel Algorithm for Visualizing Concept Associations

An associative concept space is a map that visualizes the associations between concepts in a scientific field. In this paper, we propose a novel algorithm for constructing an associative concept space. This algorithm can be seen as an alternative to multidimensional scaling, which is typically used in the literature on knowledge domain visualization. We describe experiments in which the proposed algorithm and multidimensional scaling are both used for constructing an associative concept space of the computational intelligence field. It turns out that the associations between concepts in this field are better reflected in the concept space constructed using the proposed algorithm than in the concept space constructed using multidimensional scaling