Precision die-punch for trimming the conductors of flat conductor cable

Operation trims conductor to width of 0.004 in. and consistently leaves 0.035 in. spaces between adjacent conductors, adapting cable for termination with standard plug

Absorption spectrum of iron in the vacuum ultraviolet 2950 - 1588 angstrom

Absorption spectrum of iron in vacuum ultraviole

Invariance of Structure in an Aging Colloidal Glass

We study concentrated colloidal suspensions, a model system which has a glass transition. The non-equilibrium nature of the glassy state is most clearly highlighted by aging -- the dependence of the system's properties on the time elapsed since vitrification. Fast laser scanning confocal microscopy allows us to image a colloidal glass and track the particles in three dimensions. We analyze the static structure in terms of tetrahedral packing. We find that while the aging of the suspension clearly affects its dynamics, none of the geometrical quantities associated with tetrahedra change with age.Comment: Submitted to the proceedings of "The 3rd International Workshop on Complex Systems" in Sendai, Japa

Density fluctuations and the structure of a nonuniform hard sphere fluid

We derive an exact equation for density changes induced by a general external field that corrects the hydrostatic approximation where the local value of the field is adsorbed into a modified chemical potential. Using linear response theory to relate density changes self-consistently in different regions of space, we arrive at an integral equation for a hard sphere fluid that is exact in the limit of a slowly varying field or at low density and reduces to the accurate Percus-Yevick equation for a hard core field. This and related equations give accurate results for a wide variety of fields

Multiedge slitter for FCC

Tool cuts multiple slits up to 3 in. long between conductors of flat conductor cables up to 3 in. wide to prepare them for termination on terminal boards or in multipin connectors

Expectations of Field Supervisors in Kenya: Implications for Community-based Human Service Practicums

Community-based learning (CBL), which provides opportunities for undergraduate students to develop disciplinary and work-related knowledge and skills, is increasingly becoming an integral component of higher education. Similar to other countries, there is a widespread belief among employers in Kenya that there is a mismatch between university programs and labour market demands. In order to enhance the employability of graduates, many departments at a Kenyan university have incorporated work-integrated experiential learning opportunities such as practicums in the educational experience for undergraduate students. The aim of this article is to describe the expectations of field supervisors in host organisations participitating in a community-based human services program at a Kenyan University. Fifteen purposively sampled field supervisors participated in individual face-to-face interviews that included questions about their understanding of the department’s expectations of student learning activities during practicums, knowledge of the academic preparation of students in the program and challenges associated with the supervisory role. Six field supervisors exhibited some level of understanding of the expectations of their role in working with practicum students, while nine field supervisors indicated unclear expectations of the students’ practicum experience. Thematic analysis revealed key themes related to: (1) student abilities, learning goals and their contributions to the host organisations, and (2) the academic program of study and academic support available from the university faculty or staff to field supervisors. The results of our study revealed a lack of clarity around practicum expectations for most of the field supervisors interviewed and insufficient preparation of the community-based organisations to host a practicum student. Several recommendations are identified to clarify the expectations of community partner organisations and the staff providing student supervision to ensure benefits for both students and the host organisation. Results from this study can be used to inform the development or improvement of practicum opportunities focused on producing a skilled workforce

The equilibrium intrinsic crystal-liquid interface of colloids

We use confocal microscopy to study an equilibrated crystal-liquid interface in a colloidal suspension. Capillary waves roughen the surface, but locally the intrinsic interface is sharply defined. We use local measurements of the structure and dynamics to characterize the intrinsic interface, and different measurements find slightly different widths of this interface. In terms of the particle diameter $d$, this width is either $1.5d$ (based on structural information) or $2.4d$ (based on dynamics), both not much larger than the particle size. This work is the first direct experimental visualization of an equilibrated crystal-liquid interface.Comment: 6 pages; revised version, submitted to PNA

Local elastic response measured near the colloidal glass transition

We examine the response of a dense colloidal suspension to a local force applied by a small magnetic bead. For small forces, we find a linear relationship between the force and the displacement, suggesting the medium is elastic, even though our colloidal samples macroscopically behave as fluids. We interpret this as a measure of the strength of colloidal caging, reflecting the proximity of the samples' volume fractions to the colloidal glass transition. The strain field of the colloidal particles surrounding the magnetic probe appears similar to that of an isotropic homogeneous elastic medium. When the applied force is removed, the strain relaxes as a stretched exponential in time. We introduce a model that suggests this behavior is due to the diffusive relaxation of strain in the colloidal sample.Comment: long-delayed followup paper to Habdas et al., EPL 67, 477-483 (2004

The pair annihilation reaction D + D --> 0 in disordered media and conformal invariance

The raise and peel model describes the stochastic model of a fluctuating interface separating a substrate covered with clusters of matter of different sizes, and a rarefied gas of tiles. The stationary state is obtained when adsorption compensates the desorption of tiles. This model is generalized to an interface with defects (D). The defects are either adjacent or separated by a cluster. If a tile hits the end of a cluster with a defect nearby, the defect hops at the other end of the cluster changing its shape. If a tile hits two adjacent defects, the defect annihilate and are replaced by a small cluster. There are no defects in the stationary state. This model can be seen as describing the reaction D + D -->0, in which the particles (defects) D hop at long distances changing the medium and annihilate. Between the hops the medium also changes (tiles hit clusters changing their shapes). Several properties of this model are presented and some exact results are obtained using the connection of our model with a conformal invariant quantum chain.Comment: 8 pages, 12figure

Properties of cage rearrangements observed near the colloidal glass transition

We use confocal microscopy to study the motions of particles in concentrated colloidal systems. Near the glass transition, diffusive motion is inhibited, as particles spend time trapped in transient ``cages'' formed by neighboring particles. We measure the cage sizes and lifetimes, which respectively shrink and grow as the glass transition approaches. Cage rearrangements are more prevalent in regions with lower local concentrations and higher disorder. Neighboring rearranging particles typically move in parallel directions, although a nontrivial fraction move in anti-parallel directions, usually from pairs of particles with initial separations corresponding to the local maxima and minima of the pair correlation function $g(r)$, respectively.Comment: 5 pages, 4 figures; text & figures revised in v