Photonic band gaps in materials with triply periodic surfaces and related tubular structures

We calculate the photonic band gap of triply periodic bicontinuous cubic structures and of tubular structures constructed from the skeletal graphs of triply periodic minimal surfaces. The effect of the symmetry and topology of the periodic dielectric structures on the existence and the characteristics of the gaps is discussed. We find that the C(I2-Y**) structure with Ia3d symmetry, a symmetry which is often seen in experimentally realized bicontinuous structures, has a photonic band gap with interesting characteristics. For a dielectric contrast of 11.9 the largest gap is approximately 20% for a volume fraction of the high dielectric material of 25%. The midgap frequency is a factor of 1.5 higher than the one for the (tubular) D and G structures

Search for jet extinction in the inclusive jet-pT spectrum from proton-proton collisions at s=8 TeV

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.The first search at the LHC for the extinction of QCD jet production is presented, using data collected with the CMS detector corresponding to an integrated luminosity of 10.7  fb−1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The extinction model studied in this analysis is motivated by the search for signatures of strong gravity at the TeV scale (terascale gravity) and assumes the existence of string couplings in the strong-coupling limit. In this limit, the string model predicts the suppression of all high-transverse-momentum standard model processes, including jet production, beyond a certain energy scale. To test this prediction, the measured transverse-momentum spectrum is compared to the theoretical prediction of the standard model. No significant deficit of events is found at high transverse momentum. A 95% confidence level lower limit of 3.3 TeV is set on the extinction mass scale

Searches for electroweak neutralino and chargino production in channels with Higgs, Z, and W bosons in pp collisions at 8 TeV

Searches for supersymmetry (SUSY) are presented based on the electroweak pair production of neutralinos and charginos, leading to decay channels with Higgs, Z, and W bosons and undetected lightest SUSY particles (LSPs). The data sample corresponds to an integrated luminosity of about 19.5 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV collected in 2012 with the CMS detector at the LHC. The main emphasis is neutralino pair production in which each neutralino decays either to a Higgs boson (h) and an LSP or to a Z boson and an LSP, leading to hh, hZ, and ZZ states with missing transverse energy (E-T(miss)). A second aspect is chargino-neutralino pair production, leading to hW states with E-T(miss). The decays of a Higgs boson to a bottom-quark pair, to a photon pair, and to final states with leptons are considered in conjunction with hadronic and leptonic decay modes of the Z and W bosons. No evidence is found for supersymmetric particles, and 95% confidence level upper limits are evaluated for the respective pair production cross sections and for neutralino and chargino mass values

Formation of a Cobalt Magnetic Dot Array via Block Copolymer Lithography

Single-domain cobalt dot arrayswith high magnetic particle density, patterned over large areas (e.g., 10 cm diameter wafers) are fabricated by self-assembled block copolymer lithography, using a polystyrene-poly(ferrocenyldimethylsilane) copolymer as a template. By varying the copolymer type and etching conditions the magnetic properties can be tuned. The Figure shows a typical array of Co dots with tungsten caps obtained via this procedure

Room-temperature synthesis of a-SiO2 thin films by UV-assisted ozonolysis of a polymer precursor

A room-temperature synthesis route for thin films of amorphous silica (a-SiO2) based on irradiation of a silicon-containing polymer by UV light in pure O2 atmosphere has been developed. The chemical conversion of spin-coated films of poly(pentamethyldisilylstyrene) (pPMDSS) to silicon oxycarbide and finally to amorphous silica is achieved by UV-assisted ozonolysis. The conversion process has been followed by Fourier transform infrared spectroscopy (FTIR), ellipsometry, and X-ray photoelectron (XPS) and Auger electron spectroscopies (AES). The control of the irradiation time allows for control of the chemical composition of the converted films ranging from that of a silicon oxycarbide for short exposure times to that of a-SiO2 after 18 h of exposure. The surface composition of the fully converted films obtained by XPS is characterized by an atomic ratio O/Si = 2.00 ± 0.07. Auger electron depth profiles reveal a uniform chemical composition of the a-SiO2 films with a residual carbon content in the bulk of the films below 1%. Converted a-SiO2 films of thicknesses up to 150 nm were achieved. Ellipsometry shows that the conversion of the films in a-SiO2 is accompanied by a progressive decrease of the film thickness and evolution of the refractive index to an asymptotic value of 1.44. The film surface of the converted films probed by optical microscopy over large areas and by atomic force microscopy (AFM) does not show any cracks and is atomically flat with a RMS roughness below 0.4 nm

Synthesis and Morphological Behavior of Silicon-Containing Triblock Copolymers for Nanostructure Applications

We report the synthesis of high molecular weight triblock copolymers of the type ABA and BAB, where A is polyisoprene (PI) and B is poly(pentamethyldisilylstyrene) (P(PMDSS)), respectively. The volume fraction of the minority component (PI) for the ABA copolymer was 0.33, while that for the BAB copolymer was 0.23. The synthesis procedure of the P(PMDSS) blocks corresponded to that of polystyrene (PS), and low polydispersity with targeted compositions were achieved. The morphology of the triblock copolymers was characterized by transmission electron microscopy (TEM) and digital Fourier transform patterns. From TEM and diffraction analysis, the ABA polymer exhibited the double gyroid cubic morphology, while the BAB polymer showed a P(PMDSS) spherical domain morphology. The double gyroid morphology is the first to be reported in a silicon-containing block copolymer and consists of two three-dimensionally continuous, interpenetrating but nonintersecting networks of PI in a matrix of P(PMDSS)). Preliminary oxidative studies using ozone or O2-RIE on the tricontinuous phase show that nanoporous structures can be generated

Image Deconvolution Ringing Artifact Detection and Removal via PSF Frequency Analysis

Abstract. We present a new method to detect and remove ringing ar-tifacts produced by the deconvolution process in image deblurring tech-niques. The method takes into account non-invertible frequency com-ponents of the blur kernel used in the deconvolution. Efficient Gabor wavelets are produced for each non-invertible frequency and applied on the deblurred image to generate a set of filter responses that reveal ex-isting ringing artifacts. The set of Gabor filters is then employed in a regularization scheme to remove the corresponding artifacts from the deblurred image. The regularization scheme minimizes the responses of the reconstructed image to these Gabor filters through an alternating algorithm in order to suppress the artifacts. As a result of these steps we are able to significantly enhance the quality of the deblurred images produced by deconvolution algorithms. Our numerical evaluations us-ing a ringing artifact metric indicate the effectiveness of the proposed deringing method