Teaching smoking refusal skills to adolescents

This study examined the effects of a smoking prevention program on the acquisition of refusal skills in junior high school students. Sixty-three seventh graders were randomly assigned to a refusal skill training group (N=29) or a no treatment control group (N=34). Students\u27 refusal skill performance was assessed pre and post training. Assessment consisted of a peer trainer offering the student a cigarette while being videotaped. The smoking refusal skill was broken down into 5 component parts: (1) eye contact; (2) upright posture; (3) voice intonation; (4) response to approach; (5) reason for refusal. Results showed significant improvement for both the training and control groups. However, a significant training by pre-post assessment interaction was also found, F (1,61) = 10.37, p \u3c .01, which indicates that students who received training demonstrated more proficiency in refusal performance after training than those who did not. A generalization probe in the natural environment conducted seven weeks after training showed no differences between the two groups

Quantitative electron phase imaging with high sensitivity and an unlimited field of view

As it passes through a sample, an electron beam scatters, producing an exit wavefront rich in information. A range of material properties, from electric and magnetic field strengths to specimen thickness, strain maps and mean inner potentials, can be extrapolated from its phase and mapped at the nanoscale. Unfortunately, the phase signal is not straightforward to obtain. It is most commonly measured using off-axis electron holography, but this is experimentally challenging, places constraints on the sample and has a limited field of view. Here we report an alternative method that avoids these limitations and is easily implemented on an unmodified transmission electron microscope (TEM) operating in the familiar selected area diffraction mode. We use ptychography, an imaging technique popular amongst the X-ray microscopy community; recent advances in reconstruction algorithms now reveal its potential as a tool for highly sensitive, quantitative electron phase imaging

Teaching smoking refusal skills to adolescents

This study examined the effects of a smoking prevention program on the acquisition of refusal skills in junior high school students. Sixty-three seventh graders were randomly assigned to a refusal skill training group (N=29) or a no treatment control group (N=34). Students\u27 refusal skill performance was assessed pre and post training. Assessment consisted of a peer trainer offering the student a cigarette while being videotaped. The smoking refusal skill was broken down into 5 component parts: (1) eye contact; (2) upright posture; (3) voice intonation; (4) response to approach; (5) reason for refusal. Results showed significant improvement for both the training and control groups. However, a significant training by pre-post assessment interaction was also found, F (1,61) = 10.37, p \u3c .01, which indicates that students who received training demonstrated more proficiency in refusal performance after training than those who did not. A generalization probe in the natural environment conducted seven weeks after training showed no differences between the two groups

Sheet-like chiro-optical material designs based C(Y) surfaces

A spatial structure for which mirror reflection cannot be represented by rotations and translations is chiral. For photonic crystals and metamaterials, chirality implies the possibility of circular dichroism, that is, that the propagation of left-circularly polarized light may differ from that of right-circularly polarized light. Here we draw attention to chiral sheet-or surface-like geometries based on chiral triply-periodic minimal surfaces. Specifically we analyse two photonic crystal designs based on the C(Y) minimal surface, by band structure analysis and by scattering matrix calculations of the reflection coefficient, for high-dielectric contrasts

A phase-retrieval toolbox for X-ray holography and tomography

Propagation-based phase-contrast X-ray imaging is by now a well established imaging technique, which – as a full-field technique – is particularly useful for tomography applications. Since it can be implemented with synchrotron radiation and at laboratory micro-focus sources, it covers a wide range of applications. A limiting factor in its development has been the phase-retrieval step, which was often performed using methods with a limited regime of applicability, typically based on linearization. In this work, a much larger set of algorithms, which covers a wide range of cases (experimental parameters, objects and constraints), is compiled into a single toolbox – the HoloTomoToolbox – which is made publicly available. Importantly, the unified structure of the implemented phase-retrieval functions facilitates their use and performance test on different experimental data

X-ray nanotomography uncovers morphological heterogeneity in a polymerization catalyst at multiple reaction stages

During olefin polymerization on supported catalysts, the controlledmorphological evolution of the catalyst particle is vital for ensuringoptimal product properties and high catalyst activity. We employednon-destructive hard X-ray holotomography to quantitatively assessthe 3D morphology of multiple silica-supported hafnocene-basedcatalyst particles during the early stages of gas-phase ethylene polymerization.Image processing and pore network modeling revealedclear variations in the dimensions and interconnectivity of pristineparticles’ macropore networks. This, together with apparent differencesin the fragmentation behavior of pre-polymerized particles,suggests that the reactivity and morphological evolution of individualparticles are largely dictated by their unique support and porespace architectures. By minimizing the structural heterogeneityamong pristine catalyst particles, more uniform particle morphologiesmay be obtained. Significant polymerization activity,observed in the particles’ interiors, further implies that appropriatepolymerization conditions and catalyst kinetics can guarantee sufficientlyhigh particle accessibilities and thus more homogeneoussupport fragmentation

Sheet-like chiro-optical material designs based C(Y) surfaces

A spatial structure for which mirror reflection cannot be represented by rotations and translations is chiral. For photonic crystals and metamaterials, chirality implies the possibility of circular dichroism, that is, that the propagation of left-circularly polarized light may differ from that of right-circularly polarized light. Here we draw attention to chiral sheet-or surface-like geometries based on chiral triply-periodic minimal surfaces. Specifically we analyse two photonic crystal designs based on the C(Y) minimal surface, by band structure analysis and by scattering matrix calculations of the reflection coefficient, for high-dielectric contrasts