Mathematics

Coenzyme Q is an essential component of the respiratory chain, where it represents a mobile pool between dehydrogenases and cytochromes. The fact that Q is a free component, and its concentration is not in great excess over the Km of the respiratory complexes, renders this compound potentially rate-limiting in the respiratory chain. On the other hand, the rate of lateral diffusion of Q in the mitochondrial membrane is not a limiting step under physiological conditions. Quinoid compounds, which act as inhibitors of the respiratory chain at the level of Q, besides being useful tools for investigations of electron transfer, could be important in pathology as inhibitors of respiration.

Two studies were conducted to examine gender differences in trait (habitual) versus state (momentary) mathematics anxiety in a sample of students (Study 1: N = 584; Study 2: N = 111). For trait math anxiety, the findings of both studies replicated previous research showing that female students report higher levels of anxiety than do male students. However, no gender differences were observed for state anxiety, as assessed using experience-sampling methods while students took a math test (Study 1) and attended math classes (Study 2). The discrepant findings for trait versus state math anxiety were partly accounted for by students' beliefs about their competence in mathematics, with female students reporting lower perceived competence than male students despite having the same average grades in math. Implications for educational practices and the assessment of anxiety are discussed.

Two studies were conducted to examine gender differences in trait (habitual) versus state (momentary) mathematics anxiety in a sample of students (Study 1: N = 584; Study 2: N = 111). For trait math anxiety, the findings of both studies replicated previous research showing that female students report higher levels of anxiety than do male students. However, no gender differences were observed for state anxiety, as assessed using experience-sampling methods while students took a math test (Study 1) and attended math classes (Study 2). The discrepant findings for trait versus state math anxiety were partly accounted for by students' beliefs about their competence in mathematics, with female students reporting lower perceived competence than male students despite having the same average grades in math. Implications for educational practices and the assessment of anxiety are discussed.

Serum cholinesterase activity decreases 30% during pregnancy and remains depressed during the postpartum period. However, succinylcholine recovery is not prolonged in term-pregnant patients. This contrasts with results obtained in other patients with decreased serum cholinesterase activity. To better understand this paradox, the authors compared serum cholinesterase activity and recovery from succinylcholine, 1 mg/kg, in nonpregnant (with and without oral contraceptive use), in term-pregnant, and in postpartum patients. Serum cholinesterase activity was lower in both term-pregnant (3.66 +/- 0.39 U/ml, means +/- SE) and postpartum (2.84 +/- 0.35 U/ml) patients than in nonpregnant patients not taking oral contraceptives (5.01 +/- 0.33 U/ml, P less than 0.05). Cholinesterase activity in postpartum patients also was significantly lower than in nonpregnant patients taking oral contraceptives (4.81 +/- 0.63, P less than 0.05). In contrast, the time to 25% twitch-height recovery did not differ between term-pregnant (470 +/- 56 s) and nonpregnant patients taking (499 +/- 29 s) or not taking (501 +/- 21 s) oral contraceptives, but was significantly increased in postpartum patients (685 +/- 22 s, P less than 0.001). The similar duration of action of succinylcholine in term-pregnant patients (with decreased serum cholinesterase activities) and nonpregnant patients may be related to the increased volume of distribution of succinylcholine at term.

The effectiveness of increased air motion and dust removal in reducing radon decay product concentration in residences subject to radon intrusion was evaluated in a 78-m3 room under steady-state conditions for air infiltration rates between 0.2 and 0.9 air changes per hour. Room-size, portable electrostatic precipitators and high-efficiency fibrous filters were tested as typical residential air cleaning devices; a portable box fan and a ceiling fan were employed as typical residential air movers. Reductions in working levels of 40-90% were found. The fate of radon decay products, with and without mixing fans, was determined by direct measurement. When mixing fans were used, most of the nonairborne potential alpha-energy was plated out on the room surfaces; less than 10% was deposited on the fan blades or housing. Results were compared to a mathematical model based on well-mixed room air, and good agreement was obtained.

By the use of non-linear constitutive equations suitable for the characterization of anisotropic viscoelastic incompressible materials under finite deformations, the paper is devoted to analytical study on the dynamic stress field in arterial walls under the combined action of the pressure of blood on the inner surface and the pressure from the neighbouring components of the body on the outer surface. By using short time range approximations, the magnitudes of the radial and circumferential stresses are examined at various locations of the vascular wall and for different time intervals. It is observed that consideration of the mechanical influence of the external tissues and the inertial forces makes the derived stress field quite close to the experimental results reported recently by Fung et al. (1979), in comparison to the results of Cheung et al. (1972), who did not consider the aforementioned factors. It can thus be concluded that these factors need be considered for the studies of the stress field in arteries in vivo.

The problem of free-vibration of the cranial vault is studied in the paper by taking into account the dissipative material behaviour of both the skull and the brain. Two mathematical models are considered for this purpose. In one model, the layered structure (inner table, diploë and outer table) of the skull is considered, the outer surface of the skull being assumed to be traction-free while the second model assumes the homogeneity of the skull but takes into account the mechanical influence of the scalp. Results of numerical computation show that the dissipative material behaviour of the skull as well as the brain and also the mechanical influence of the scalp have a significant effect on the frequency spectrum of the freely vibrating cranial system.

... Since I4.P/ is moduli-independent, it can be expressed either in terms of the quantized charges P or in terms of the (dressed) central and matter charges ZAB . ; P/; ZI . ; P/ (see Sect. ... S1 Á 1 2ZAB Z AB ZI Z NJ ıI NJ; S2 Á 1 4 ABCD ZAB ZCD ZI ZJ ıIJ; Page 8. 24 ...

... Since I4.P/ is moduli-independent, it can be expressed either in terms of the quantized charges P or in terms of the (dressed) central and matter charges ZAB . ; P/; ZI . ; P/ (see Sect. ... S1 Á 1 2ZAB Z AB ZI Z NJ ıI NJ; S2 Á 1 4 ABCD ZAB ZCD ZI ZJ ıIJ; Page 8. 24 ...