Robust nanopatterning by laser-induced dewetting of metal nanofilms

We have observed nanopattern formation with robust and controllable spatial ordering by laser-induced dewetting in nanoscopic metal films. Pattern evolution in Co film of thickness 1\leq h\leq8 nm on SiO_{2} was achieved under multiple pulse irradiation using a 9 ns pulse laser. Dewetting leads to the formation of cellular patterns which evolve into polygons that eventually break up into nanoparticles with monomodal size distribution and short range ordering in nearest-neighbour spacing R. Spatial ordering was attributed to a hydrodynamic thin film instability and resulted in a predictable variation of R and particle diameter D with h. The length scales R and D were found to be independent of the laser energy. These results suggest that spatially ordered metal nanoparticles can be robustly assembled by laser-induced dewetting

Thickness-dependent spontaneous dewetting morphology of ultrathin Ag films

We show here that the morphological pathway of spontaneous dewetting of ultrathin Ag films on SiO2 under nanosecond laser melting is found to be film thickness dependent. For films with thickness h between 2 <= h <= 9.5 nm, the morphology during the intermediate stages of dewetting consisted of bicontinuous structures. For films 11.5 <= h <= 20 nm, the intermediate stages consisted of regularly-sized holes. Measurement of the characteristic length scales for different stages of dewetting as a function of film thickness showed a systematic increase, which is consistent with the spinodal dewetting instability over the entire thickness range investigated. This change in morphology with thickness is consistent with observations made previously for polymer films [A. Sharma et al, Phys. Rev. Lett., v81, pp3463 (1998); R. Seemann et al, J. Phys. Cond. Matt., v13, pp4925, (2001)]. Based on the behavior of free energy curvature that incorporates intermolecular forces, we have estimated the morphological transition thickness for the intermolecular forces for Ag on SiO2 . The theory predictions agree well with observations for Ag. These results show that it is possible to form a variety of complex Ag nanomorphologies in a consistent manner, which could be useful in optical applications of Ag surfaces, such as in surface enhanced Raman sensing.Comment: 20 pages, 5 figure

Self-organized metal nanostructures through laser driven thermocapillary convection

When ultrathin metal films are subjected to multiple cycles of rapid melting and resolidification by a ns pulsed laser, spatially correlated interfacial nanostructures can result from a competition among several possible thin film self-organizing processes. Here we investigate self-organization and the ensuing length scales when Co films (1-8 nm thick) on SiO_{\text{2}} surfaces are repeatedly and rapidly melted by non-uniform (interference) laser irradiation. Pattern evolution produces nanowires, which eventually break-up into nanoparticles exhibiting spatial order in the nearest neighbor spacing, \lambda_{NN2}.The scaling behavior is consistent with pattern formation by thermocapillary flow and a Rayleigh-like instability. For h_{0}\leq2 nm, a hydrodynamic instability of a spinodally unstable film leads to the formation of nanoparticles.Comment: 10 pages, 3 figure

Investigation of pulsed laser induced dewetting in nanoscopic metal films

Hydrodynamic pattern formation (PF) and dewetting resulting from pulsed laser induced melting of nanoscopic metal films have been used to create spatially ordered metal nanoparticle arrays with monomodal size distribution on SiO_{\text{2}}/Si substrates. PF was investigated for film thickness h\leq7 nm < laser absorption depth \sim11 nm and different sets of laser parameters, including energy density E and the irradiation time, as measured by the number of pulses n. PF was only observed to occur for E\geq E_{m}, where E_{m} denotes the h-dependent threshold energy required to melt the film. Even at such small length scales, theoretical predictions for E_{m} obtained from a continuum-level lumped parameter heat transfer model for the film temperature, coupled with the 1-D transient heat equation for the substrate phase, were consistent with experimental observations provided that the thickness dependence of the reflectivity of the metal-substrate bilayer was incorporated into the analysis. The spacing between the nanoparticles and the particle diameter were found to increase as h^{2} and h^{5/3} respectively, which is consistent with the predictions of the thin film hydrodynamic (TFH) dewetting theory. These results suggest that fast thermal processing can lead to novel pattern formation, including quenching of a wide range of length scales and morphologies.Comment: 36 pages, 11 figures, 1 tabl

Teacher Perceptions of Two Multi-Component Interventions: Disability Awareness and Science

This study investigated teachers’ perspectives about two interventions designed to promote kindergarteners’ attitudes toward peers with disabilities. Interviews with teachers were conducted following the 6-week interventions. Teachers shared views on the best and most difficult aspects of the interventions, perceived benefits for teachers and children, and suggestions for improving the interventions. Teachers’ responses were analyzed using content analysis. One salient teacher reported benefit was notable improvement in social skills made by all students. Moreover, students in the experimental condition displayed increased acceptance of peers with disabilities, whereas teachers reported becoming more confident discussing the topic of disability with students. Teachers also reported that although it was difficult to step back and observe children in cooperative learning groups, it was beneficial to see that when children were given opportunities to handle social situations on their own, many were capable of doing so. Implications for practice and recommendations for future research are discussed

Teacher Perceptions of Two Multi-Component Interventions: Disability Awareness and Science

This study investigated teachers’ perspectives about two interventions designed to promote kindergarteners’ attitudes toward peers with disabilities. Interviews with teachers were conducted following the 6-week interventions. Teachers shared views on the best and most difficult aspects of the interventions, perceived benefits for teachers and children, and suggestions for improving the interventions. Teachers’ responses were analyzed using content analysis. One salient teacher reported benefit was notable improvement in social skills made by all students. Moreover, students in the experimental condition displayed increased acceptance of peers with disabilities, whereas teachers reported becoming more confident discussing the topic of disability with students. Teachers also reported that although it was difficult to step back and observe children in cooperative learning groups, it was beneficial to see that when children were given opportunities to handle social situations on their own, many were capable of doing so. Implications for practice and recommendations for future research are discussed

Helping Developing Countries Implement the Young Athletes Program

The Center for Social Development and Education is implementing Young Athletes (YA), a motor play program, in five developing countries: Kenya, Romania, Malawi, Venezuela, and Tanzania. Young Athletes is a theoretically-based program designed to improve the motor development of children with disabilities (ages 3-7) through various motor activities. Clinical trials conducted by CSDE (Favazza et al., 2013) indicate that the Young Athletes program significantly improves the motor skills of children with disabilities. The program is now being introduced internationally to address the needs of children in developing countries

The Neurovascular Relation in Oxygen-induced Retinopathy

Purpose: Longitudinal studies in rat models of retinopathy of prematurity (ROP) have demonstrated that abnormalities of retinal vasculature and function change hand-in-hand. In the developing retina, vascular and neural structures are under cooperative molecular control. In this study of rats with oxygen-induced retinopathy (OIR) models of ROP, mRNA expression of vascular endothelial growth factor (VEGF), semaphorin (Sema), and their neuropilin receptor (NRP) were examined during the course of retinopathy to evaluate their roles in the observed neurovascular congruency. Methods: Oxygen exposures designed to induce retinopathy were delivered to Sprague-Dawley rat pups (n=36) from postnatal day (P) 0 to P14 or from P7 to P14. Room-air-reared controls (n=18) were also studied. Sensitivities of the rod photoreceptors ($S_{rod}$) and the postreceptor cells (Sm) were derived from electroretinographic (ERG) records. Arteriolar tortuosity, $T_A$, was derived from digital fundus images using Retinal Image multi-Scale Analysis (RISA) image analysis software. mRNA expression of $VEGF_{164}$, semaphorin IIIA (Sema3A), and neuropilin-1 (NRP-1) was evaluated by RT–PCR of retinal extracts. Tests were performed at P15–P16, P18–P19, and P25–P26. Relations among ERG, RISA, and PCR parameters were evaluated using linear regression on log transformed data. Results: Sm was low and $T_A$ was high at young ages, then both resolved by P25–P26. $VEGF_{164}$ and Sema3A mRNA expression were also elevated early and decreased with age. Low Sm was significantly associated with high $VEGF_{164}$ and Sema3A expression. Low Srod was also significantly associated with high VEGF164. $S_{rod}$ and Sm were both correlated with $T_A$. NRP-1 expression was little affected by OIR. Conclusions: The postreceptor retina appears to mediate the vascular abnormalities that characterize OIR. Because of the relationships revealed by these data, early treatment that targets the neural retina may mitigate the effects of ROP

Self-inflicted penetrating eye injuries using a razor blade: Case report

<p>Abstract</p> <p>Background</p> <p>A 23 year old white male with a history of social and behavioural problems attempted to blind himself chemically, with alcohol, and mechanically, with a razor blade.</p> <p>Methods</p> <p>Observational case report of a patient who self-inflicted bilateral scleral lacerations with a razor blade, after losing his job.</p> <p>Results</p> <p>The patient sustained bilateral inferior scleral perforations, with hypotony and a right traumatic cataract. He received urgent surgical repair, and prophylactic antibiotics. There were no retinal breaks or detachments. He later underwent successful cataract surgery to the right eye.</p> <p>Conclusion</p> <p>Self-inflicted ocular injury may be possible in non-psychotic patients, as a situational response to a life event. Urgent repair can completely restore vision in some cases. Referral for psychiatric counseling is mandatory.</p