Crystal structure and magnetic properties of CuSb2O4

The crystal structure of a copper antimonite (CuSb₂O₄) was determined from X-ray powder diffraction data. The structure was solved by simulated annealing in direct space using the Rietveld method. The compound crystallizes in tetragonal symmetry and space group P4 ₂ bc (106); unit cell parameters a = b = 8.76033(5) Å, c = 5.79786(4) Å, Z = 4, V = 444.947(5) Å³ and density (calc.) = 5.539 g cm^?3. The CuO₆ polyhedra are strongly elongated due to Jahn–Teller distortion in a [2+2+2] coordination arrangement, i.e. there are two long axial Cu–O1 bonds of 2.447(13) Å and in the equatorial plane there are two intermediate Cu–O2 bonds of 2.07(3) Å and two short Cu–O2 bonds of 1.88(2) Å. The SbO₃ pyramidal arrangement is almost regular with Sb–O1 bonds of 1.97(2) Å (2×) and Sb–O2 of 1.959(5) Å. The experimentally obtained Raman spectrum is consistent with values obtained from theoretical modelling studies. The magnetic behaviour of this new compound suggests that it belongs to the class of S = 1/2 Heisenberg chain systems.     

l-Carnitine and Long-Chain Acylcarnitines are Positively Correlated with Ambulatory Blood Pressure in Humans: The SABPA Study

The prevalence of hypertension in sub-Saharan Africa is increasing rapidly, and treatment remains challenging. Although the use of l-carnitine in treatment has received much attention, studies reporting on physiological l-carnitine levels in hypertensives are limited. Our aim was to determine physiological levels of l-carnitine and acylcarnitines in African and Caucasian men, and to investigate associations between ambulatory blood pressure (BP) and carnitine levels. Participants included 101 African and 101 Caucasian teachers. Ambulatory BP measurements were conducted, and l-carnitine and acylcarnitine levels determined. African men showed significantly higher systolic BP (p < 0.001), diastolic BP (p < 0.001) and l-carnitine levels (p = 0.01). In both ethnic groups, partial regression analyses revealed a positive association between BP and l-carnitine, although in Caucasians it was with systolic (r = 0.20, p = 0.045), and in Africans with diastolic BP (r = 0.23, p = 0.023). After adjusting for confounders, an independent positive association between systolic (R ² = 0.37, β = 0.12, p = 0.041) and diastolic BP (R ² = 0.39, β = 0.14, p = 0.018) and l-carnitine and long-chain acylcarnitines (R ² = 0.38, β = 0.17, p = 0.005 and R ² = 0.39, β = 0.15, p = 0.011) were found, independent of ethnicity. Physiological l-carnitine levels were not only higher in Africans than in Caucasians but also above the expected reference range. Despite promising results on l-carnitine (and its short-chain derivatives) in hypertension treatment regimens, our findings paradoxically show that elevated BP is significantly associated with higher physiological l-carnitine and long-chain acylcarnitine levels.     

Equations of motion for general constrained systems in Lagrangian mechanics

This paper develops a new, simple, explicit equation of motion for general constrained mechanical systems that may have positive semi-definite mass matrices. This is done through the creation of an auxiliary mechanical system (derived from the actual system) that has a positive definite mass matrix and is subjected to the same set of constraints as the actual system. The acceleration of the actual system and the constraint force acting on it are then directly provided in closed form by the acceleration and the constraint force acting on the auxiliary system, which thus gives the equation of motion of the actual system. The results provide deeper insights into the fundamental character of constrained motion in general mechanical systems. The use of this new equation is illustrated through its application to the important and practical problem of finding the equation of motion for the rotational dynamics of a rigid body in terms of quaternions. This leads to a form for the equation describing rotational dynamics that has hereto been unavailable.     

A tale of two methods: Comparing regression and instrumental variables estimates of the effects of preschool child care type on the subsequent externalizing behavior of children in low-income families.

We apply instrumental variables (IV) techniques to a pooled data set of employment-focused experiments to examine the relation between type of preschool childcare and subsequent externalizing problem behavior for a large sample of low-income children. To assess the potential usefulness of this approach for addressing biases that can confound causal inferences in child care research, we compare instrumental variables results with those obtained using ordinary least squares (OLS) regression. We find that our OLS estimates concur with prior studies showing small positive associations between center-based care and later externalizing behavior. By contrast, our IV estimates indicate that preschool-aged children with center care experience are rated by mothers and teachers as having fewer externalizing problems on entering elementary school than their peers who were not in child care as preschoolers. Findings are discussed in relation to the literature on associations between different types of community-based child care and children's social behavior, particularly within low-income populations. Moreover, we use this study to highlight the relative strengths and weaknesses of each analytic method for addressing causal questions in developmental research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparing domestic water heating technologies

Solar water heaters (SWH) and drain water heat recovery (DWHR) systems are two household technologies currently available in the marketplace that can lower usage of utility-supplied energy. While there is considerable interest in utilizing these technologies to reduce energy costs and environmental impact, actual implementation of these systems in houses remains low. This study examines possible reasons for this low adoption rate using Guelph (Ontario) as a case study representative of medium-sized Canadian cities. A model was created to determine the implementation rate required for each technology to meet the goals of Guelph's Community Energy Plan and the level of financial incentive required to achieve the desired implementation rate. Water conservation and the need to address both new development and the existing housing stock emerge as critical factors. Solar water heating was found to require significantly higher subsidies than drain pipe heat recovery, corresponding to a higher cost per unit of energy saved. Non-economic factors that reduce the adoption rate of new technology are discussed, and it is observed that a need for community education related to the new technologies and inertia associated with current water heating technology are the primary factors for adoption rates below levels predicted based on economics alone.     

Development and validation of a measure of irrational belief.

Describes the development of a 20-item measure of irrational belief, using 73 undergraduates, that asks only about irrational belief and not about anxiety. Two studies of the scale produced evidence that it has good internal consistency and good test–retest reliability. Three additional studies of the scale found evidence of validity. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)