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Model selection in linear mixed-effect models
Full text linkLinear mixed-effects models are a class of models widely used for analyzing different types of data: longitudinal, clustered and panel data. Many fields, in which a statistical methodology is required, involve the employment of linear mixed models, such as biology, chemistry, medicine, finance and so forth. One of the most important processes, in a statistical analysis, is given by model selection. Hence, since there are a large number of linear mixed model selection procedures available in the literature, a pressing issue is how to identify the best approach to adopt in a specific case. We outline mainly all approaches focusing on the part of the model subject to selection (fixed and/or random), the dimensionality of models and the structure of variance and covariance matrices, and also, wherever possible, the existence of an implemented application of the methodologies set out
Item weighted Kemeny distance for preference data
Full text linkPreference data represent a particular type of ranking data where a group of people gives their preferences over a set of alternatives. The traditional metrics between rankings don’t take into account that the importance of elements can be not uniform. In this paper the item weighted Kemeny distance is introduced and its properties demonstrated
Resting energy expenditure and body composition in morbidly obese, obese and control subjects
No full textResting energy expenditure (REE) was investigated by indirect calorimetry in relation to body composition and to different degrees of obesity in order to assess if a defective energy expenditure contributes to extra body fat accumulation. Differences were found between control subjects (group C; BMI 23±0.5 kg/m2, REE 5890±218 kJ/day; mean±SEM) and obese subjects (group O; BMI 34.2±0.9 kg/m2, REE 7447±360 kJ/day;P<0.0001) and between group C and morbidly obese subjects (group MO; BMI 49.9±1.6 kg/m2, REE 8330±360 kJ/day;P<0.0001); REE was not significantly different between groups O and MO. Body composition data were obtained by means of body impedance analysis. Even though group MO had a fat mass higher than group O, body cell mass, the metabolically active body compartment, was similar in groups O and MO, and this fact may have contributed to the similar REE in the two groups. Multiple regression analysis gave the following equation as the best predictor of REE: REE (kJ/day)+1591±49BW+74BCM-737G (R2=0.88), where BW is body weight, BCM is body cell mass and G is a dummy variable coding group membership (group C=1; group O=2; group MO=3). Thus the analysis showed a negative impact of obesity on REE beyond body composition variables. © 1994 Springer-Verlag
Resting metabolic rate and postabsorptive substrate oxidation in morbidly obese subjects before and after massive weight loss
No full textOBJECTIVE: To investigate the changes of resting metabolic rate (RMR) and postabsorptive oxidation of carbohydrates (CHO), lipids (LIP) and proteins (PT) in morbidly obese subjects after long-term stable massive weight reduction. DESIGN: Longitudinal, intervention study of a bilio-pancreatic by-pass. SUBJECTS: Ten (Four men, six women) obese subjects (BMI: 53.7 ± 2.1 kg/m2, men, nine women) control subjects (BMI: 21.4 ± 1.0 kg/m2). MEASUREMENTS: RMR and substrates oxidation (indirect calorimetry), body composition (bioelectrical impedance), plasma concentrations of glucose, FFA, insulin and thyroid hormones before (T0, prior to surgery), during (T1: 1-3 months, and T2: 9-16 months following surgery) and after (T3: 36-42 months following surgery) massive weight loss. RESULTS: At T3 BMI proved to be stably reduced to 32.9 ± 1.3 (P < 0.0001). The RMR progressively reduced both in absolute value (T3: -2566 kJ/24 h; P < 0.0001 vs T0) and normalized for fat-free mass (FFM; T0: 123 ± 3.8, T1: 109 ± 3.3, T2: 112 ± 7.1, T3: 105 ± 4.6 kJ/kg-FFM·24 h; P < 0.05). At T3 the normalized RMR became significantly lower than the corresponding value of a control group (118 ± 2.5 kJ/kg-FFM.24 h; P < 0.01). The long term trend in substrates oxidation showed that CHO oxidation increased while LIP oxidation decreased; PT oxidation did not significantly change for the whole of the study. CONCLUSION: Previously morbid obese subjects have an energy sparing metabolism and a normal postabsorptive oxidation of LIP and CHO
Reply from Buscemi S et al. Glycaemic variability using continuous glucose monitoring and endothelial function in the metabolic syndrome and in Type 2 diabetes. Authors' reply
No full textA NEW WATER-SOLUBLE FLUORINATED POLYMER BASED ON A POLYASPARTAMIDE AND OXADIAZOLE UNITS AS A POTENTIAL ARTIFICIAL OXYGEN (O2) CARRIER
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