Planar Waveguide from PPV Derivatives

Abstract. We report in this paper the result of thin film fabrication of MEH-PPV and MEH-PPB having good optical transparency and low surface roughness suitable for planar waveguide application. The linear optical properties of the polymers were characterized using reflectometry and prism coupling, while the non-linear optical property was measured by means of optical third harmonic generation (THG). The waveguide attenuation of the polymer films was determined by employing prism coupling set-up equipped with a photodiode array detector. The MEH-PPV waveguide film was shown to have a very low attenuation of 0.5 dB cm-1 at 1064 nm yielding an unprecedentedly high figure of merits of 11 at 1 GW/cm2. Pandu Gelombang Planar dari Turunan PPVSari. Dalam tulisan ini dilaporkan fabrikasi film tipis polimer MEH-PPV dan MEH-PPB yang mempunyai transparansi optik tinggi dan permukaan yang halus sehingga cocok untuk aplikasi pandu gelombang planar. Sifat optic linier dari polimer yang bersangkutan diukur dengan teknik reflektometri dan kopling prisma dan sifat optic nonlinier diukur dengan metoda third harmonic generation (THG). Selanjutnya, atenuasi pandu gelombang dari film polimer yang bersangkutan diukur dengan konfigurasi kopling prisma dan detector diode arrat. Film pandu gelombang yang dihasilkan dalam eksperimen ini memiliki atenuasi rendah sebesar 0.5 dB cm-1 pada panjang gelombang 1064 nm dan menghasilkan "figure of merits" (FOM) sebesar 11 pada intensitas 1 GW/cm2 yang merupakan nilai tertinggi sejauh ini

Neural mechanisms underlying sensitivity to reverse-phi motion in the fly

Optical illusions provide powerful tools for mapping the algorithms and circuits that underlie visual processing, revealing structure through atypical function. Of particular note in the study of motion detection has been the reverse-phi illusion. When contrast reversals accompany discrete movement, detected direction tends to invert. This occurs across a wide range of organisms, spanning humans and invertebrates. Here, we map an algorithmic account of the phenomenon onto neural circuitry in the fruit fly Drosophila melanogaster. Through targeted silencing experiments in tethered walking flies as well as electrophysiology and calcium imaging, we demonstrate that ON-or OFF-selective local motion detector cells T4 and T5 are sensitive to certain interactions between ON and OFF. A biologically plausible detector model accounts for subtle features of this particular form of illusory motion reversal, like the re-inversion of turning responses occurring at extreme stimulus velocities. In light of comparable circuit architecture in the mammalian retina, we suggest that similar mechanisms may apply even to human psychophysics

De-noising of diffusion-weighted MRI data by averaging of inconsistent input data in wavelet space

Diffusion Weighted Images datasets with high spatial resolution and strong diffusion weighting are often deteriorated with low SNR. Here, we demonstrate the feasibility of a recently presented repetition-free averaging based de-noising (AWESOME). That technique reduces noise by averaging over a series of N images with varying contrast in wavelet space and regains intensities and object features initially covered by noise. We show that high resolution DWIs are achievable in a quality that almost equals to that obtained from 6fold complex averaging

Actividad antioxidante de extractos de torta de aceite de semilla de Sclerocarya birrea

The antioxidant activity of methanolic extracts from Sclerocarya birrea kernel oil meal, extracted using two different methods was evaluated. The extraction was carried out using magnetic stirring of the material in methanol/water (80:20 v/v) overnight followed by two ultra-sonic treatments for 45 min. (Overnight extract, ONEXT) and three ultra-sonic treatments for 45 min. only (Ultra-sonic extract, USEXT), respectively. Three fractions were obtained from each extract and the contents of total phenolic compounds were determined in each fraction according to the Folin-Ciocalteau method as 34.6, 54.8, and 58.6 mg/g of dry product in ONEXT and 29.6, 84.8, 143.9 mg/g in USEXT, respectively. The antioxidant activity of the extracts was evaluated according to the β-carotene-linoleic acid assay, where the extracts and their fractions showed significant effect (pSe ha evaluado la actividad antioxidante de extractos metanólicos de torta de aceite de semilla de Sclerocarya birrea extraídos usando dos métodos diferentes. La extracción se llevó a cabo mediante agitación magnética del material en metanol/agua (80:20 v/v) durante toda la noche seguida de dos tratamientos con ultrasonidos durante 45 min. (extracto ONEXT) y solo tres tratamientos con ultrasonidos durante 45 min. (extracto USEXT), respectivamente. Se obtuvieron tres fracciones de cada extracto y el contenido total de compuestos fenólicos se determinó en cada fracción según el método de Folin-Ciocalteau como 34.6, 54.8 y 58.6 mg/g de producto seco en ONEXT y 29.6, 84.8 y 143.9 mg/g en USEXT, respectivamente. La actividad antioxidante de los extractos fue evaluada mediante el ensayo del β-carotenoácido linoleico donde los extractos y sus fracciones mostraron efectos significativos (

Test of the Conserved Vector Current Hypothesis by beta-ray Angular Distribution Measurement in the Mass-8 System

The beta-ray angular correlations for the spin alignments of 8Li and 8B have been observed in order to test the conserved vector current (CVC) hypothesis. The alignment correlation terms were combined with the known beta-alpha-angular correlation terms to determine all the matrix elements contributing to the correlation terms. The weak magnetism term, 7.5\pm0.2, deduced from the beta-ray correlation terms was consistent with the CVC prediction 7.3\pm0.2, deduced from the analog-gamma-decay measurement based on the CVC hypothesis. However, there was no consistent CVC prediction for the second-forbidden term associated with the weak vector current. The experimental value for the second-forbidden term was 1.0 \pm 0.3, while the CVC prediction was 0.1 \pm 0.4 or 2.1 \pm 0.5.Comment: 31 pages, 12 figures, Accepted for publication in Phys. Rev.