Gaussian ellipsoid model for confined polymer systems

Polymer systems in slab geometries are studied on the basis of the recently presented Gaussian Ellipsoid Model [J. Chem. Phys. 114, 7655 (2001)].The potential of the confining walls has an exponential shape. For homogeneous systems in thermodynamic equilibrium we discuss density, orientation and deformation profiles of the polymers close to the walls. For strongly segregated mixtures of polymer components A and B equilibrium profiles are studied near a planar interface separating A and B rich regions. Spinodal decomposition processes of the mixtures in the presence of neutral walls show upon strong confinement an increase of the lateral size of A and B rich domains and a slowing down of the demixing kinetics. These findings are in agreement with predictions from time dependent Ginzburg--Landau theory. In the case, where one wall periodically favors one of the two mixture components over the other, different equilibrium structures emerge and lead to different kinetic pathways of spinodal decomposition processes in such systems.Comment: 18 pages, 16 figures, submitted to J. Chem. Phy

Phonons in a Nanoparticle Mechanically Coupled to a Substrate

The discrete nature of the vibrational modes of an isolated nanometer-scale solid dramatically modifies its low-energy electron and phonon dynamics from that of a bulk crystal. However, nanocrystals are usually coupled--even if only weakly--to an environment consisting of other nanocrystals, a support matrix, or a solid substrate, and this environmental interaction will modify the vibrational properties at low frequencies. In this paper we investigate the modification of the vibrational modes of an insulating spherical nanoparticle caused by a weak {\it mechanical} coupling to a semi-infinite substrate. The phonons of the bulk substrate act as a bath of harmonic oscillators, and the coupling to this reservoir shifts and broadens the nanoparticle's modes. The vibrational density of states in the nanoparticle is obtained by solving the Dyson equation for the phonon propagator, and we show that environmental interaction is especially important at low frequencies. As a probe of the modified phonon spectrum, we consider nonradiative energy relaxation of a localized electronic impurity state in the nanoparticle, for which good agreement with experiment is found.Comment: 10 pages, Revte

Shear Flows of Rapidly Flowing Granular Materials

Shear flows of granular materials are studied in an open channel. The wall shear is calculated from an open channel momentum equation which includes the density variations in the flow. An experimental technique was developed that allowed the measurement of the average density of the flow at different longitudinal locations in the channel. Two sizes of glass beads are examined and results show the variations in the wall shear as a function of various dimensionless parameters

Writing readiness and children with Down Syndrome in an Irish context

There is a dearth of studies investigating writing readiness in children with Down Syndrome (DS) and limited information on appropriate interventions. This article reports on a study conducted in the Republic of Ireland. An uncontrolled pretest-posttest design was implemented using writing readiness measures specifically adapted/developed from the literature to collect data on the writing readiness skills of 28 school-aged children with DS attending mainstream schools in the Republic of Ireland. Teacher/parent perspectives were also gathered during focus groups. The children presented with complex needs in relation to posture, pencil grasp, copying basic shapes, name/letter copying. Teacher and parent reports highlighted the need for collaborative intervention with occupational therapy. Findings from the study supports the need for targeted early collaborative syndrome-specific intervention to support the development of writing readiness in children with DS as an important part of school readiness. Intervention should include adopting a broader emergent literacy approach, teacher education regarding writing readiness and parental involvement in intervention

Exploring the participation of children with Down Syndrome in Handwriting Without Tears®

Background Children with Down Syndrome typically experience difficulties with attention to task and lack motivation when learning to write. This article provides an evaluation of the HWT® method applied as an intervention to promote handwriting amongst children with Down Syndrome attending mainstream school in The Republic of Ireland. Methods In the absence of standardised measures, a purpose-designed group task participation scale and pre- and post-intervention teacher/parent questionnaire were developed by the first author and used to investigate the participation of 40 children with Down Syndrome in HWT® activities. Results Positive changes in participation in HWT® activities were recorded in group data and in teacher/parent report. Conclusions Hands-on multisensory learning approaches such as HWT® may encourage children with Down Syndrome to participate in activities that promote handwriting skills. Further research and the development of robust measures to evaluate handwriting intervention for this population of children is require

Ocean services user needs assessment. Volume 1: Survey results, conclusions and recommendations

An interpretation of environmental information needs of marine users, derived from a direct contact survey of eight important sectors of the marine user community is presented. Findings of the survey and results and recommendations are reported. The findings consist of specific and quantized measurement and derived product needs for each sector and comparisons of these needs with current and planned NOAA data and services. The following supportive and reference material are examined: direct contact interviews with industry members, analyses of current NOAA data gathering and derived product capabilities, evaluations of new and emerging domestic and foreign satellite data gathering capabilities, and a special commercial fishing survey conducted by the Jet Propulsion Laboratory (JPL)