Polymorphism and phase transformation in the dimethyl sulfoxide solvate of 2,3,5,6-tetrafluoro-1,4-diiodobenzene.

A new polymorph (form II) is reported for the 1:1 dimethyl sulfoxide solvate of 2,3,5,6-tetrafluoro-1,4-diiodobenzene (TFDIB·DMSO or C6F4I2·C2H6SO). The structure is similar to that of a previously reported polymorph (form I) [Britton (2003). Acta Cryst. E59, o1332-o1333], containing layers of TFDIB molecules with DMSO molecules between, accepting I...O halogen bonds from two TFDIB molecules. Re-examination of form I over the temperature range 300-120 K shows that it undergoes a phase transformation around 220 K, where the DMSO molecules undergo re-orientation and become ordered. The unit cell expands by ca 0.5 Å along the c axis and contracts by ca 1.0 Å along the a axis, and the space-group symmetry is reduced from Pnma to P212121. Refinement of form I against data collected at 220 K captures the (average) structure of the crystal prior to the phase transformation, with the DMSO molecules showing four distinct disorder components, corresponding to an overlay of the 297 and 120 K structures. Assessment of the intermolecular interaction energies using the PIXEL method indicates that the various orientations of the DMSO molecules have very similar total interaction energies with the molecules of the TFDIB framework. The phase transformation is driven by interactions between DMSO molecules, whereby re-orientation at lower temperature yields significantly closer and more stabilizing interactions between neighbouring DMSO molecules, which lock in an ordered arrangement along the shortened a axis

Shallow angle water entry of ballistic projectiles

The water-entry of ballistic projectiles is investigated using high-speed digital imaging to capture the subsurface cavity dynamics. Specially designed 0.22 caliber projectiles are fired into water at shallow angles to the free surface (5º to 15º) at Mach numbers between 0.3 and 1.0. Redesigned projectile tip geometries allowed projectiles to successfully enter the water and travel large distances underwater, due to the subsurface vapor-cavity that forms after impact, dramatically decreasing drag on the projectile. Projectile dynamics, critical entry angle and cavity formation are discussed for various bullet geometries, and results show that successful water-entry is a function of tip shape and length-to-diameter ratio. The data conclusively show that bullets with lower length-to-diameter ratios tumble inside the vapor cavity, while higher length-to-diameter ratios can lean against the cavity walls inducing a planing force pushing them back inside the cavity and mitigating the tumbling behavior. Experimental cavity observations of vapor-cavity formation is compared to a modified version of Logvinovich's [1] theoretical model, which includes an updated formulation of the model and an angle of attack correction. Despite the unsteady nature of this problem, this improved steady state model fits well with experimental data and serves as an accurate design tool for naval engineers.http://deepblue.lib.umich.edu/bitstream/2027.42/84284/1/CAV2009-final100.pd

Developing Interventions for Children's Exercise (DICE): a pilot evaluation of school-based exercise interventions for primary school children aged 7 to 8 years.

BACKGROUND: Developing Interventions for Children's Exercise (DICE) is an initiative aimed at determining effective school-based exercise programs. To assess feasibility, we conducted a pilot study of exercise sessions which varied in duration and frequency. METHODS: Exercise interventions were delivered to Year 3 pupils (age 7-8 years; n = 73) in primary schools within Yorkshire, UK. Evaluations were conducted using focus group sessions, questionnaires and observations. RESULTS: The study revealed positive aspects of all interventions, including favorable effects on children's concentration during lessons and identified the value of incorporation of the DICE concept into curriculum lessons. Children appeared enthused and reported well-being and enjoyment. Areas requiring attention were the need for appropriate timetabling of sessions and ensuring the availability of space. CONCLUSION: The concept and sessions were well-accepted by teachers who confirmed their full support of any future implementation There appears to be potential for the encouragement and empowerment of teachers to support physical activity and healthy school environments, and to take an interest in the health of their pupils. Ultimately, these findings should assist in the design of successful exercise interventions in the school setting

Implicit Theories of Learning as Reflected in One Upper Elementary Teacher\u27s Talk

Strong empirical evidence exists indicating language can influence students’ beliefs about ability. Professional literature for teachers offers practical advice on how to adjust their classroom-based talk to support student achievement by orienting students toward an incremental theory of ability. Yet, little empirical work has been done to investigate how teacher talk plays out moment-to-moment within the classroom context. This study reports on a qualitative analysis of one upper elementary teacher\u27s talk with regard to implicit theories of learning. Findings suggest teacher talk is dynamic and overlapping, operating along a continuum from entity-oriented talk to incremental-oriented talk across varied classroom situations. Additionally, a relationship was identified between teacher autonomy and the implicit theories of learning used in the teacher’s talk. Examples of varied teacher talk during classroom activities are presented, and scholarly and practical implications for language use, learning, and instruction are included

Paired atom laser beams created via four-wave mixing

A method to create paired atom laser beams from a metastable helium atom laser via four-wave mixing is demonstrated. Radio frequency outcoupling is used to extract atoms from a Bose Einstein condensate near the center of the condensate and initiate scattering between trapped and untrapped atoms. The unequal strengths of the interactions for different internal states allows an energy-momentum resonance which leads to the creation of pairs of atoms scattered from the zero-velocity condensate. The resulting scattered beams are well separated from the main atom laser in the 2-dimensional transverse atom laser profile. Numerical simulations of the system are in good agreement with the observed atom laser spatial profiles, and indicate that the scattered beams are generated by a four-wave mixing process, suggesting that the beams are correlated.Comment: 5 pages, 3 figure

Customised patient implants : future lifeline of the medical industry

Published ArticleLong-term growth in the additive fabrication industry will come from designs that are difficult, time-consuming, costly, or impossible to produce using standard techniques. Growth will occur with advances in the current additive processes, coupled with breakthroughs in new materials, which are expected to emerge over the next five to 10 years. These advanced materials will better satisfy the design requirements of many new products. The paper considers currently available technologies and discusses recent advancements in direct metal freeform fabrication and its potential of revolutionising the medical industry