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Completing our reports concerning the reaction products from calcium halides and the amino acid proline, two different solids were found for the reaction of l- and dl-proline with CaI2. The enanti-opure amino acid yields the one-dimensional coordination polymer catena-poly[[aqua-μ3-l-proline-tetra-μ2-l-proline-dicalcium] tetra-iodide 1.7-hydrate], {[Ca2(C5H9NO2)5(H2O)]I4·1.7H2O} n , (1), with two independent Ca(2+) cations in characteristic seven- and eightfold coordination. Five symmetry-independent zwitterionic l-proline mol-ecules bridge the metal sites into a cationic polymer. Racemic proline forms with Ca(2+) cations heterochiral chains of the one-dimensional polymer catena-poly[[di-aquadi-μ2-dl-proline-calcium] diiodide], {[Ca(C5H9NO2)2(H2O)2]I2} n , (2). The centrosymmetric structure is built by one Ca(2+) cation that is bridged towards its symmetry equivalents by two zwitterionic proline mol-ecules. In both structures, the iodide ions remain non-coordinating and hydrogen bonds are formed between these counter-anions, the amino groups, coordinating and co-crystallized water mol-ecules. While the overall composition of (1) and (2) is in line with other structures from calcium halides and amino acids, the diversity of the carboxyl-ate coordination geometry is quite surprising.

In catena-poly[copper(II)-di-μ-chlorido-μ-proline-κ(2)O:O'], [CuCl2(C5H9NO2)]n, two symmetry-independent metal cations adopt distorted octahedral coordination, typical for d(9) Jahn-Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a Cu(II) centre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter (i.e. a). The O:O'-bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for Cu(II); the vast majority of amino acid derivatives of this cation are characterized by N,O-chelation.

Reactions of calcium bromide with enantiopure and racemic proline in aqueous solution lead to two solids in which the zwitterionic amino acid acts as a bridging ligand between neighbouring cations. Depending on the chirality of the amino acid, topologically very different products are obtained. With racemic proline, bromide acts as a simple uncoordinated counter-anion for the cationic heterochiral chains in catena-poly[[aquacalcium(II)]-μ-aqua-μ3-DL-proline-μ2-DL-proline], {[Ca(C5H9NO2)2(H2O)2]Br2}n. In agreement with chemical intuition, only carboxylate and aqua O atoms coordinate the alkaline earth cation in a low-symmetry arrangement. In contrast, L-proline affords the two-dimensional network poly[dibromidobis(μ2-L-proline)calcium(II)], [CaBr2(C5H9NO2)2]n, with an unexpected CaBr2 unit in a more regular coordination sphere.

Under accelerated and controlled evaporation, chain polymers crystallize from aqueous solutions of Ca(II) and Mn(II) halides with enantiopure L-alanine or racemic DL-alanine. In all ten solids thus obtained zwitterionic amino acid ligands bridge neighbouring cations. The exclusively O-donor-based coordination sphere around the metal cations is completed by aqua ligands; the halides remain uncoordinated and act as counter-anions for the cationic strands. Despite the differences in ionic radii and electronic structure between the main group and the transition metal cation, their derivatives with L-alanine share a common structure type. In contrast, the solids derived from DL-alanine differ and adopt structures depending on the metal cation and the halide. Homochiral chains of either chirality or heterochiral chains with different arrangements of crystallographic inversion centres along the polymer strands are encountered. On average, the six-coordinated Ca(II) cations, devoid of any ligand field effect, show more pronounced deviation from idealized octahedral geometry than the d-block cation Mn(II).

It is now well established that the time course of perceptual processing influences the first second or so of performance in a wide variety of cognitive tasks. Over the last 20 years, there has been a shift from modeling the speed at which a display is processed, to modeling the speed at which different features of the display are perceived and formalizing how this perceptual information is used in decision making. The first of these models (Lamberts, 1995) was implemented to fit the time course of performance in a speeded perceptual categorization task and assumed a simple stochastic accumulation of feature information. Subsequently, similar approaches have been used to model performance in a range of cognitive tasks including identification, absolute identification, perceptual matching, recognition, visual search, and word processing, again assuming a simple stochastic accumulation of feature information from both the stimulus and representations held in memory. These models are typically fit to data from signal-to-respond experiments whereby the effects of stimulus exposure duration on performance are examined, but response times (RTs) and RT distributions have also been modeled. In this article, we review this approach and explore the insights it has provided about the interplay between perceptual processing, memory retrieval, and decision making in a variety of tasks. In so doing, we highlight how such approaches can continue to usefully contribute to our understanding of cognition.

Introduction. Older African American women are particularly vulnerable to unhealthy lifestyle behaviors such as physical inactivity and the resultant chronic diseases and conditions. This study explored older African American women's perception of physical activity as well as facilitators of and barriers to being physically active in their local environment. Methods. Using a participatory research approach, a total of 7 women aged 65 years and over had their PA level assessed objectively through accelerometry. In addition, physical activity was discussed through the photo-elicitation procedure, which was supplemented by semistructured interviews. Qualitative thematic analysis was used to identify patterns and themes emerging from participants' interview. Results. Participants exhibited low levels of physical activity and viewed "physical activity" to be a broadly defined, nonspecific construct. Interviews revealed that many participants lack important knowledge about physical activity. A variety of personal, social, and environmental facilitators and barriers were reported by the participants. Conclusion. Efforts should be made towards clarifying information on physical activity in this population in order to help them incorporate physical activity into their routines, overcome barriers, and make use of opportunities to be active.

Reactions of manganese(II) chloride, bromide and iodide with proline as an enantiopure and racemic ligand result in six crystalline solids for which diffraction experiments have been performed at 100 K. For two of these compounds, crystal structures at ambient temperature had been reported previously. The most surprising outcome of our systematic comparison lies in the role of chirality: with enantiopure proline three different coordination polymers have been obtained, whereas racemic proline yields isomorphous mononuclear complexes under the same reaction conditions.

The crystal structure of dl-alanine hydro-iodide (1-carb-oxy-ethanaminium iodide), C(3)H(8)NO(2) (+)·I(-), is that of an organic salt consisting of N-protonated cations and iodide anions. The compound features homochiral helices of N-H⋯O hydrogen-bonded cations in the [010] direction; neighbouring chains are related by crystallographic inversion centers and hence show opposite chirality. The iodide counter-anions act as hydrogen-bond acceptors towards H atoms of the ammonium and carb-oxy groups, and cross-link the chains along [100]. Thus, an overall two-dimensional network is formed in the ab plane. No short contacts occur between iodide anions.

Aim: The aim of this study was to investigate the prevalence of eating problems and their association with neurological and behavioural disabilities and growth among children born extremely preterm (EPC) at age 6 years., Method: A standard questionnaire about eating was completed by parents of 223 children (125 males [56.1%], 98 females [43.9%]) aged 6 years who were born at 25 weeks' gestation or earlier (mean 24.5 wks, SD 0.7 wks; mean birthweight 749.1 g, SD 116.8 g), and parents of 148 classmates born at term (66 males [44.6%], 82 females [55.4%]). All children underwent neurological, cognitive, and anthropometric assessment, and parents and teachers completed a behaviour scale., Results: Eating problems were more common among the EPC than the comparison group (odds ratio [OR] 3.6, 95% confidence interval [CI] 2.1-6.3), including oral motor (OR 5.2, 95% CI 2.8-9.9), hypersensitivity (OR 3.0, 95% CI 1.6-5.6), and behavioural (OR 3.8, 95% CI 1.9-7.6) problems. Group differences were reduced after adjustment for cognitive impairment, neuromotor disability, and other behaviour problems. EPC with eating problems were shorter, lighter, and had lower mid-arm circumference and lower body mass index (BMI) even after adjusting for disabilities, gestational age, birthweight, and feeding problems at 30 months., Interpretation: Eating problems are still frequent in EPC at school age. They are only partly related to other disabilities but make an additional contribution to continued growth failure and may require early recognition and intervention.

Background: Participant drop-out occurs in all longitudinal studies, and if systematic, may lead to selection biases and erroneous conclusions being drawn from a study., Aims: We investigated whether drop out in the Avon Longitudinal Study of Parents And Children (ALSPAC) was systematic or random, and if systematic, whether it had an impact on the prediction of disruptive behaviour disorders., Method: Teacher reports of disruptive behaviour among currently participating, previously participating and never participating children aged 8 years in the ALSPAC longitudinal study were collected. Data on family factors were obtained in pregnancy. Simulations were conducted to explain the impact of selective drop-out on the strength of prediction., Results: Drop out from the ALSPAC cohort was systematic and children who dropped out were more likely to suffer from disruptive behaviour disorder. Systematic participant drop-out according to the family variables, however, did not alter the association between family factors obtained in pregnancy and disruptive behaviour disorder at 8 years of age., Conclusions: Cohort studies are prone to selective drop-out and are likely to underestimate the prevalence of psychiatric disorder. This empirical study and the simulations confirm that the validity of regression models is only marginally affected despite range restrictions after selective drop-out.