Random nonlinear layered structures as sources of photon pairs for quantum-information processing

Random nonlinear layered structures have been found to be a useful source of photon pairs with perfectly indistinguishable un-entangled photons emitted into a very narrow spectral range. Localization of the interacting optical fields typical for random structures gives relatively high photon-pair fluxes. Superposing photon-pair emission quantum paths at different emission angles, several kinds of two-photon states (including states with coincident frequencies) useful in quantum-information processing can easily be generated.Comment: 4 pages, 5 figure

Chiral near-field manipulation in Au-GaAs hybrid hexagonal nanowires

We demonstrate the control of enhanced chiral field distribution at the surface of hybrid metallo-dielectric nanostructures composed of self-assembled vertical hexagonal GaAs-based nanowires having three of the six sidewalls covered with Au. We show that weakly-guided modes of vertical GaAs nanowires can generate regions of high optical chirality that are further enhanced by the break of the symmetry introduced by the gold layer. Changing the angle of incidence of a linearly polarized plane wave it is possible to tailor and optimize the maps of the optical chirality in proximity of the gold plated walls. The low cost feasibility of the sample combined to the simple control by using linearly polarized light and the easy positioning of chiral molecules by functionalization of the gold plates make our proposed scheme very promising for enhanced enantioselective spectroscopy applications

"Our God Loves Justice": Study Questions

This document provides a set of study or discussion questions for each chapter and appendix in my book, "Our God Loves Justice: An Introduction to Helmut Gollwitzer" (Fortress 2017). It is provided to facilitate classroom adoption and use in diverse study groups

Second harmonic generation from ZnO films and nanostructures.

Zinc oxide ZnO is a n-type semiconductor having a wide direct band gap (3.37 eV) as well as a non-centrosymmetric crystal structure resulting from hexagonal wurtzite phase. Its wide transparency range along with its second order nonlinear optical properties make it a promising material for efficient second harmonic generation processes and nonlinear optical applications in general. In this review, we present an extensive analysis of second harmonic generation from ZnO films and nanostructures. The literature survey on ZnO films will include some significant features affecting second harmonic generation efficiency, as crystalline structure, film thickness, surface contributes, and doping. In a different section, the most prominent challenges in harmonic generation from ZnO nanostructures are discussed, including ZnO nanowires, nanorods, and nanocrystals, to name a few. Similarly, the most relevant works regarding third harmonic generation from ZnO films and nanostructures are separately addressed. Finally, the conclusion part summarizes the current standing of published values for the nonlinear optical coefficients and for ZnO films and nanostructures, respectively

Antimicrobial Activity and Chemical Composition of Albanian Oregano

Antimicrobial activity of methanolic and aqueous methanolic extracts of oregano was tested against: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, Pseudomonas spp, Candida albicans ATCC 10231, Listeria monocytogenes ATCC 19111 and Salmonella typhimurium ATCC 14028. Antimicrobial activity of oregano essential oil was also tested against: E.coli, P.aeruginosa, S.aureus and C. albicans. Only oregano essential oil was active against microorganisms selected. Essential oil of oregano was analysed by GC-MS. Eighteen components were identified representing 99.48% of the oil. Monoterpenes phenols and derivatives (borneol, 4-terpineol, carvacrol methyl ether, thymoquinone, thymol, carvacrol) represented 74.66 % of essential oil. Carvacrol, p-cymene, thymol and γ-terpinene were the main components. Sesquiterpenes such as trans-caryophyllene, α-humulene, β-bisabolene, δ-Cadinene, caryophyllene oxide were also found

Self-Phase-Matched Second-Harmonic and White-Light Generation in a Biaxial Zinc Tungstate Single Crystal

Second-order nonlinear optical materials are used to generate new frequencies by exploiting second-harmonic generation (SHG), a phenomenon where a nonlinear material generates light at double the optical frequency of the input beam. Maximum SHG is achieved when the pump and the generated waves are in phase, for example through birefringence in uniaxial crystals. However, applying these materials usually requires a complicated cutting procedure to yield a crystal with a particular orientation. Here we demonstrate the first example of phase matching under the normal incidence of SHG in a biaxial monoclinic single crystal of zinc tungstate. The crystal was grown by the micro-pulling-down method with the (102) plane perpendicular to the growth direction. Additionally, at the same time white light was generated as a result of stimulated Raman scattering and multiphoton luminescence induced by higher-order effects such as three-photon luminescence enhanced by cascaded third-harmonic generation. The annealed crystal offers SHG intensities approximately four times larger than the as grown one; optimized growth and annealing conditions may lead to much higher SHG intensities

Second harmonic generation on self-assembled GaAs/Au nanowires with thickness gradient

Here we investigated the SH generation at the wavelength of 400 nm (pump laser at 800 nm, 120 fs pulses) of a "metasurface" composed by an alternation of GaAs nano-grooves and Au nanowires capping portions of flat GaAs. The nano-grooves depth and the Au nanowires thickness gradually vary across the sample. The samples are obtained by ion bombardment at glancing angle on a 150 nm Au mask evaporated on a GaAs plane wafer. The irradiation process erodes anisotropically the surface, creating Au nanowires and, at high ion dose, grooves in the underlying GaAs substrate (pattern transfer). The SHG measurements are performed for different pump linear polarization angle at different positions on the "metasurface" in order to explore the regions with optimal conditions for SHG efficiency. The pump polarization angle is scanned by rotating a half-wave retarder plate. While the output SH signal in reflection is analyzed by setting the polarizer in s or p configuration in front of the detector. The best polarization condition for SHG is obtained in the configuration where the pump and second harmonic fields are both p polarized, and the experiments show a SH polarization dependence of the same symmetry of bulk GaAs. Thus, the presence of gold contributes only as field localization effect, but do not contributes directly as SH generator

Resonant Absorption in GaAs-Based Nanowires by Means of Photo-Acoustic Spectroscopy

Semiconductor nanowires made of high refractive index materials can couple the incoming light to specific waveguide modes that offer resonant absorption enhancement under the bandgap wavelength, essential for light harvesting, lasing and detection applications. Moreover, the non-trivial ellipticity of such modes can offer near field interactions with chiral molecules, governed by near chiral field. These modes are therefore very important to detect. Here, we present the photo-acoustic spectroscopy as a low-cost, reliable, sensitive and scattering-free tool to measure the spectral position and absorption efficiency of these modes. The investigated samples are hexagonal nanowires with GaAs core; the fabrication by means of lithography-free molecular beam epitaxy provides controllable and uniform dimensions that allow for the excitation of the fundamental resonant mode around 800 nm. We show that the modulation frequency increase leads to the discrimination of the resonant mode absorption from the overall absorption of the substrate. As the experimental data are in great agreement with numerical simulations, the design can be optimized and followed by photo-acoustic characterization for a specific application

Ulipristal acetate before in vitro fertilization: Efficacy in infertile women with submucous fibroids

Background: The presence of submucous fibroids strongly impacts on IVF results, therefore, these patients should be considered for surgical or medical treatment. The aim of this study was to assess the role of Ulipristal acetate (UPA), a selective progesterone receptor modulator, in restoring uterine cavity deformation due to submucous fibroids, in infertile patients attempting an IVF treatment. The secondary study outcome was to evaluate the impact of preconception UPA treatment on rate of biochemical pregnancy, ongoing pregnancy, and live birth compared to a control group without fibroids. Methods: Infertile patients with submucosal fibroid (Type 1 and Type 2 according to FIGO classification) were enrolled in the study as fibroids group and received 1 to 3 treatment cycles of UPA, according to their response, as reflected by fibroid volume reduction and restoration of normal uterine cavity. Patients in control group were randomly selected from a general IVF cohort by a ratio of 2:1 with fibroids group, matched by age, BMI, type and cause of infertility and antral follicle count. The impact of UPA on fibroids volume reduction was evaluated. IVF outcome was compared between groups. Results: Twenty-six patients underwent UPA treatment revealed a mean volume reduction of their fibroids of 41%. A total of 15 (57.6%) biochemical pregnancy were obtained, resulting in 13 (50%) ongoing pregnancy and 9 (34.6%) healthy babies were already delivered. Similar results were obtained in control group. Conclusion: Restoration of normal uterine cavity by UPA treatment prior to IVF treatment avoids surgery and establishes a pregnancy rate comparable to a control group without fibroids

Microbiologically Contaminated and Over-Preserved Cosmetic Products According Rapex 2008-2014

We investigated the Rapid Alert System (RAPEX) database from January 2008 until week 26 of 2014 to give information to consumers about microbiologically contaminated cosmetics and over-preserved cosmetic products. Chemical risk was the leading cause of the recalls (87.47%). Sixty-two cosmetic products (11.76%) were recalled because they were contaminated with pathogenic or potentially pathogenic microorganisms. Pseudomonas aeruginosa was the most frequently found microorganism. Other microorganisms found were: Mesophilic aerobic microorganisms, Staphylococcus aureus, Candida albicans, Enterococcus spp., Enterobacter cloacae, Enterococcus faecium, Enterobacter gergoviae, Rhizobium radiobacter, Burkholderia cepacia, Serratia marcescens, Achromabacter xylosoxidans, Klebsiella oxytoca, Bacillus firmus, Pantoea agglomerans, Pseudomonas putida, Klebsiella pneumoniae and Citrobacter freundii. Nine cosmetic products were recalled because they contained methylisothiazolinone (0.025%–0.36%), benzalkonium chloride (1%), triclosan (0.4%) in concentrations higher than the limits allowed by European Regulation 1223/2009. Fifteen products were recalled for the presence of methyldibromo glutaronitrile, a preservative banned for use in cosmetics. Thirty-two hair treatment products were recalled because they contained high concentrations of formaldehyde (0.3%–25%)