Ultrafast Optical Modulation of Second- and Third-Harmonic Generation from Cut-Disk-Based Metasurfaces

We design and fabricate a metasurface composed of gold cut-disk resonators that exhibits a strong coherent nonlinear response. We experimentally demonstrate all-optical modulation of both second- and third-harmonic signals on a subpicosecond time scale. Pump−probe experiments and numerical models show that the observed effects are due to the ultrafast response of the electronic excitations in the metal under external illumination. These effects pave the way for the development of novel active nonlinear metasurfaces with controllable and switchable coherent nonlinear response

Plasmon-based photopolymerization: near-field probing, advanced photonic nanostructures and nanophotochemistry

Cataloged from PDF version of article.Hybrid nanomaterials are targeted by a rapidly growing group of nanooptics researchers, due to the promise of optical behavior that is difficult or even impossible to create with nanostructures of homogeneous composition. Examples of important areas of interest include coherent coupling, Fano resonances, optical gain, solar energy conversion, photocatalysis, and nonlinear optical interactions. In addition to the coupling interactions, the strong dependence of optical resonances and damping on the size, shape, and composition of the building blocks provides promise that the coupling interactions of hybrid nanomaterials can be controlled and manipulated for a desired outcome. Great challenges remain in reliably synthesizing and characterizing hybrid nanomaterials for nanooptics. In this review, we describe the synthesis, characterization, and applications of hybrid nanomaterials created through plasmon-induced photopolymerization. The work is placed within the broader context of hybrid nanomaterials involving plasmonic metal nanoparticles and molecular materials placed within the length scale of the evanescent field from the metal surface. We specifically review three important applications of free radical photopolymerization to create hybrid nanoparticles: local field probing, photoinduced synthesis of advanced hybrid nanoparticles, and nanophotochemistry

Optical creation of vibrational intrinsic localized modes in anharmonic lattices with realistic interatomic potentials

Using an efficient optimal control scheme to determine the exciting fields, we theoretically demonstrate the optical creation of vibrational intrinsic localized modes (ILMs) in anharmonic perfect lattices with realistic interatomic potentials. For systems with finite size, we show that ILMs can be excited directly by applying a sequence of femtosecond visible laser pulses at THz repetition rates. For periodic lattices, ILMs can be created indirectly via decay of an unstable extended lattice mode which is excited optically either by a sequence of pulses as described above or by a single picosecond far-infrared laser pulse with linearly chirped frequency. In light of recent advances in experimental laser pulse shaping capabilities, the approach is experimentally promising.Comment: 20 pages, 7 eps figures. Accepted, Phys. Rev.

Hsp90 orchestrates transcriptional regulation by Hsf1 and cell wall remodelling by MAPK signalling during thermal adaptation in a pathogenic yeast

Acknowledgments We thank Rebecca Shapiro for creating CaLC1819, CaLC1855 and CaLC1875, Gillian Milne for help with EM, Aaron Mitchell for generously providing the transposon insertion mutant library, Jesus Pla for generously providing the hog1 hst7 mutant, and Cathy Collins for technical assistance.Peer reviewedPublisher PD

The Identification of Protein Kinase C Iota as a Regulator of the Mammalian Heat Shock Response Using Functional Genomic Screens

BACKGROUND: The heat shock response is widely used as a surrogate of the general protein quality control system within the cell. This system plays a significant role in aging and many protein folding diseases as well as the responses to other physical and chemical stressors. METHODS/PRINCIPAL FINDINGS: In this study, a broad-based functional genomics approach was taken to identify potential regulators of the mammalian heat shock response. In the primary screen, a total of 13724 full-length genes in mammalian expression vectors were individually co-transfected into human embryonic kidney cells together with a human HSP70B promoter driving firefly luciferase. A subset of the full-length genes that showed significant activation in the primary screen were then evaluated for their ability to hyper-activate the HSP70B under heat shock conditions. Based on the results from the secondary assay and gene expression microarray analyses, eight genes were chosen for validation using siRNA knockdown. Of the eight genes, only PRKCI showed a statistically significant reduction in the heat shock response in two independent siRNA duplexes compared to scrambled controls. Knockdown of the PRKCI mRNA was confirmed using quantitative RT-PCR. Additional studies did not show a direct physical interaction between PRKCI and HSF1. CONCLUSIONS/SIGNIFICANCE: The results suggest that PRKCI is an indirect co-regulator of HSF1 activity and the heat shock response. Given the underlying role of HSF1 in many human diseases and the response to environmental stressors, PRKCI represents a potentially new candidate for gene-environment interactions and therapeutic intervention

Cherenkov radiation emitted by ultrafast laser pulses and the generation of coherent polaritons

We report on the generation of coherent phonon polaritons in ZnTe, GaP and LiTaO$_{3}$ using ultrafast optical pulses. These polaritons are coupled modes consisting of mostly far-infrared radiation and a small phonon component, which are excited through nonlinear optical processes involving the Raman and the second-order susceptibilities (difference frequency generation). We probe their associated hybrid vibrational-electric field, in the THz range, by electro-optic sampling methods. The measured field patterns agree very well with calculations for the field due to a distribution of dipoles that follows the shape and moves with the group velocity of the optical pulses. For a tightly focused pulse, the pattern is identical to that of classical Cherenkov radiation by a moving dipole. Results for other shapes and, in particular, for the planar and transient-grating geometries, are accounted for by a convolution of the Cherenkov field due to a point dipole with the function describing the slowly-varying intensity of the pulse. Hence, polariton fields resulting from pulses of arbitrary shape can be described quantitatively in terms of expressions for the Cherenkov radiation emitted by an extended source. Using the Cherenkov approach, we recover the phase-matching conditions that lead to the selection of specific polariton wavevectors in the planar and transient grating geometry as well as the Cherenkov angle itself. The formalism can be easily extended to media exhibiting dispersion in the THz range. Calculations and experimental data for point-like and planar sources reveal significant differences between the so-called superluminal and subluminal cases where the group velocity of the optical pulses is, respectively, above and below the highest phase velocity in the infrared.Comment: 13 pages, 11 figure

mTOR Controls Ovarian Follicle Growth by Regulating Granulosa Cell Proliferation

We have shown that inhibition of mTOR in granulosa cells and ovarian follicles results in compromised granulosa proliferation and reduced follicle growth. Further analysis here using spontaneously immortalized rat granulosa cells has revealed that mTOR pathway activity is enhanced during M-phase of the cell cycle. mTOR specific phosphorylation of p70S6 kinase and 4E-BP, and expression of Raptor are all enhanced during M-phase. The predominant effect of mTOR inhibition by the specific inhibitor Rapamycin (RAP) was a dose-responsive arrest in the G1 cell cycle stage. The fraction of granulosa cells that continued to divide in the presence of RAP exhibited a dose-dependent increase in aberrant mitotic figures known as anaphase bridges. Strikingly, estradiol consistently decreased the incidence of aberrant mitotic figures. In mice treated with RAP, the mitotic index was reduced compared to controls, and a similar increase in aberrant mitotic events was noted. RAP injected during a superovulation regime resulted in a dose-dependent reduction in the numbers of eggs ovulated. Implications for the real-time regulation of follicle growth and dominance, including the consequences of increased numbers of aneuploid granulosa cells, are discussed