We have used neutron reflectometry to investigate the behavior of a strong polyelectrolyte brush on a sapphire substrate, grown by atom transfer radical polymerization (ATRP) from a silane-anchored initiator layer. The initiator layer was deposited from vapor, following treatment of the substrate with an Ar/H 2 O plasma to improve surface reactivity. The deposition process was characterized using X-ray reflectometry, indicating the formation of a complete, cross-linked layer. The brush was grown from the monomer [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC), which carries a strong positive charge. The neutron reflectivity profile of the swollen brush in pure water (D 2 O) showed that it adopted a two-region structure, consisting of a dense surface region ∼ 100 Å thick, in combination with a diffuse brush region extending to around 1000 Å from the surface. The existence of the diffuse brush region may be attributed to electrostatic repulsion from the positively-charged surface region, while the surface region itself most probably forms due to polyelectrolyte adsorption to the hydrophobic initiator layer. The importance of electrostatic interactions in maintaining the brush region is confirmed by measurements at high (1 M) added 1:1 electrolyte, which show a substantial transfer of polymer from the brush to the surface region, together with a strong reduction in brush height. On addition of 10 -4 M oppositely-charged surfactant (sodium dodecyl sulfate SDS), the brush undergoes a dramatic collapse, forming a single dense layer about 200 Å in thickness, which may be attributed to the neutralization of the monomers by adsorbed dodecyl sulfate ions in combination with hydrophobic interactions between these dodecyl chains. Subsequent increases in surfactant concentration result in slow increases in brush height, which may be caused by stiffening of the polyelectrolyte chains due to further dodecyl sulfate adsorption.3

Practice-based research networks (PBRNs)—collaborations of practice settings that work together to generate research knowledge—are underused in mental health services research. This article proposes an agenda for mental health services research that uses a variety of PBRN structures and that focuses on what really happens in practice, the effectiveness of practice innovations in real world care, the challenges of implementing evidence supported interventions, modification of clinician behavior, and assessment of the effect of mental health policy changes on practice. The challenges of conducting research within PBRNs are substantial, including difficulties in maintaining positive member relations, securing ongoing funding, sustaining productivity, overcoming IRB entanglements and achieving both scientific excellence in recruitment and measurement validity and utility for practitioner members. However, the awareness of these challenges allows researchers and practitioners to build networks that creatively overcome them and that infuse mental health services research with heavy doses of the realities of everyday clinical practice.

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This study examined the association of homelessness and related factors with child psychiatric and behavior disorders (diagnosed with structured diagnostic interviews) and child cognitive ability (on the Kaufman Brief Intelligence Test) in a randomly selected sample of 157 homeless children and their mothers and a comparison of 61 housed children and their mothers. Homeless children had more disruptive behavior disorders and lower cognitive scores than housed children. In multivariate analyses, maternal verbal scores and child nonverbal scores were associated with child verbal ability; maternal education, homelessness, and child nonverbal scores were related to child behavior disorders.

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