OBJECTIVES: To determine whether differences in body fat composition and body fat distribution patterns are associated with a prolongation of the corrected QT interval for heart rate (QTc) on the electrocardiogram (EKG) during rest and exercise. DESIGN: Cross-sectional evaluation of the QTc interval in three groups of premenopausal women during rest and two exercise conditions (50% VO 2 max and VO 2 max). SUBJECTS: Thirty-one healthy women with a mean age of 35 y (27±44 y) were classi®ed as either obese (n 22; percent body fat [%BF] b 30%) or nonobese (NO; n 9; %BF 27%) by hydrostatic weighing. Obese subjects matched for age and %BF were grouped by waist to hip ratio (WHR) into two groups: upper body obesity (UBO; n 11; WHR ! 0.85) and lower body obesity (LBO; n 11; WHR 0.75). MEASUREMENTS: RR and QT intervals were measured in a double-blind design with the aid of calipers and magnifying lens for seven consecutive beats in lead II from a 12-lead EKG at a paper speed of 25 mm/sec. Five consecutive cardiac cycles excluding the longest and shortest RR and QT intervals were averaged and calculated for QTc interval using Bazett's formula. RESULTS: Mean QTc intervals were signi®cantly different (P`0.001) across the groups for each condition. For all conditions, UBO had the longest QTc interval as compared to LBO and NO respectively (i.e., Rest: 0.426; 0.413; 0.399 sec 1/2 ; Mid50%: 0.447; 0.426; 0.409 sec 1/2 ; Max: 0.390; 0.374; 0.357 sec 1/2 ). CONCLUSIONS: The QTc interval is positively associated with UBO even at the same level of body fat in moderately obese women. It is clear that abdominal obesity may be one of the risk factors for a prolonged QTc interval in premenopausal women.

Detailed investigations of spin-on polymethylsilsesquioxane (PMSSQ)-based low-K materials were carried out by means of time-of-flight secondary ion mass spectrometry (ToF-SIMS) to identify the reaction kinetics and mechanisms occurring during the manufacturing of nanoporous dielectrics for ULSI applications. Analysis of the static SIMS fingerprints led to the identification of key species related to the PMSSQ oligomers, as well to the observation of features related to the initial functionality of the precursor materials. The intensity variations of the key species with thermal curing reveal the polymerization kinetics of the dielectric precursors. In addition, thermal decomposition and volatilization of the polymethylmethacrylate-dimethylaminoethylmethacrylate copolymer (PMMA-co-DMAEMA) porogen was established based on the detection of fragments related to the different moieties of the copolymer molecule. Porogen degradation takes place via cleavage of the DMAEMA co-monomer at low temperature, followed by volatilization of the residual PMMA-enriched polymer upon annealing at higher temperature. Several complementary phenomena occurring during the formation of these complex systems can be evaluated by ToF-SIMS, revealing major features crucial to materials development and the manufacturing of novel low-dielectric-constant (K) dielectrics.