Phonon-Dressed Third-Harmonic Generation in Diamond

We demonstrate a strong, elastic, frequency-upshifting optical polarizability that accompanies sum-frequency driving of Raman phonons and two-photon absorption, extending the duality of structural and optical property modification recently observed in light-driven phononics. The effect, phonon-dressed third-harmonic generation (THG), is a degenerate low-frequency analog of coherent anti-Stokes Raman scattering. In diamond, it has a cubic electric susceptibility at least 58 times larger than purely electronic THG, with polarization and frequency dependence reflecting strong coupling to Raman phonon degrees of freedom.Comment: 6 pages, 5 figure

Ultrafast control of material optical properties via the infrared resonant Raman effect

The Raman effect -- inelastic scattering of light by lattice vibrations (phonons) -- produces an optical response closely tied to a material's crystal structure. Here we show that resonant optical excitation of IR and Raman phonons gives rise to a Raman scattering effect that can induce giant shifts to the refractive index and induce new optical constants that are forbidden in the equilibrium crystal structure. We complete the description of light-matter interactions mediated by coupled IR and Raman phonons in crystalline insulators -- currently the focus of numerous experiments aiming to dynamically control material properties -- by including a forgotten pathway through the nonlinear lattice polarizability. Our work expands the toolset for control and development of new optical technologies by revealing that the absorption of light within the terahertz gap can enable control of optical properties of materials over a broad frequency range.Comment: 15 pages, 6 figure

Selection of coronary stents

AbstractIn clinical practice, the operator must decide which stent is most appropriate for the patient. This article focuses on the features of stent design that make a specific stent more or less suitable for a particular type of lesion or anatomy: the “average” coronary lesion, the lesion situated on a curve, the ostial lesion, the bifurcational lesion, the lesion located at the left main stem, the calcified lesion, the chronic total occlusion, the small vessel, the saphenous vein graft, acute or threatened vessel closure, and special situations such as coronary aneurysms and perforations

Soliton compression to few-cycle pulses by cascaded quadratic nonlinearities

Theoretical and numerical investigation of pulse-compression in a nonlinear crystal is presented. SHG soliton number is introduced and show that compression only takes place when it is larger than the "usual" Kerr soliton number. Pulse compression with cascaded quadratic nonlinearities requires that the ratio of the SHG and Kerr soliton numbers N>1

Effect of Nitrosamine (NNAT) on Embryogenesis: Evidence from a Study Using Avian Embryos Exposed to NNAT

Background Birth defects are a known cause of infant death in the United States with higher rates in the Midwest perhaps due to higher use of agrichemicals for farm activities. Nitrate and atrazine are two of the most prevalent agrichemicals contaminating drinking water supplies. When ingested together, in the acidic environment of the human stomach, they can react to form a nitrosamine, NNAT. Many nitrosamines are known to be mutagenic, carcinogenic and teratogenic. Significance Preliminary studies have suggested that NNAT is a teratogen and mutagen. Several other agrichemical compounds have been detected in Nebraska groundwater wells that have the potential to nitrosate and studies are underway to evaluate the risk of adverse birth outcomes associated with exposure to these compounds. In this study, we evaluated growth in chick embryos after exposure to NNAT. Hypothesis We hypothesize that the embryo exposed to NNAT would have delayed development compared to unexposed embryos. Experimental design Three groups of eggs were observed in the study: the treatment group was treated with different doses of NNAT dissolved in Dimethyl sulfoxide (DMSO), the vehicle control group were treated with only DMSO and the untreated group (control). The air sac of the treatment groups was injected with varying concentrations of NNAT at one time to stimulate an acute response and at different times for a chronic response. Result/Data: All analysis was done on SAS 9.4. The effect of treatments on the weight and survival of the embryos were determined using analysis of covariance (ANCOVA) and multiple logistic regression respectively. The effect of treatment was found to be significant on the embryo treated with NNAT after adjusting for the effect of the positions of the eggs during incubation (p\u3c0.0001). Embryos that were untreated (controls) had the highest weight (weight=0.34g), and as the dose of NNAT was increased during treatment the weight of the embryo decreased significantly after incubation for 5 days : 0.245 µmol/l of NNAT (weight=0.15g, p=0.0009), 1.11 µmol/l of NNAT (weight=0.13g, p=0.004), 2.22 µmol/l of NNAT (weight=0.11g, p=0.01) and 3.33 µmol/l of NNAT (weight=0.12g, p=0.01). Also, it was found that the odds of survival among the embryo decreased linearly with increased dose when treated with NNAT as compared to the untreated embryos: 1.11 µmol/l of NNAT vs untreated (OR=0.250 95% C.I. 0.078-0.799), 2.22 µmol/l of NNAT vs. untreated (OR=0.120 95% C.I. 0.042-0.347) and 3.33 µmol/l of NNAT vs untreated (OR=0.106 95% C.I. 0.036-0.311) Conclusion: This study has revealed that weight and odds of survival of embryo exposed to NNAT decreased after 5 days of incubation. Dose-effect of the treatment was also observed during the development of embryos exposed to NNAT. Additional studies, however, is needed to evaluate the toxic effects of DMSO on the chick’s embryo before a conclusion can be reached.https://digitalcommons.unmc.edu/coph_pres/1008/thumbnail.jp

Compression limits in cascaded quadratic soliton compression

Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency