Invisibility in billiards

The question of invisibility for bodies with mirror surface is studied in the framework of geometrical optics. We construct bodies that are invisible/have zero resistance in two mutually orthogonal directions, and prove that there do not exist bodies which are invisible/have zero resistance in all possible directions of incidence

Towards FIB-SEM Based Simulation of Pore-Scale Diffusion in SCR Catalyst Layers

The diffusivity in the upper Cu-Chabazite layer of a dual layer ammonia oxidation catalyst with a lower Pt layer was investigated. In a first step, the pore structure of the upper Cu-Chabazite catalyst layer was determined by Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) slice&view tomography. From the FIB-SEM data the 3D pore structure of the catalyst was reconstructed and diffusion simulations were performed on the reconstructed pore geometry, resulting in an estimated effective diffusivity of D$_{eff}$/D$_{gas}$ = 0.31. To validate the FIB-SEM derived estimates of the diffusivity, measurements of CO oxidation on the dual layer catalyst were performed, where the CO was oxidized in the lower Pt-layer while the upper SCR layer served as an inactive diffusion barrier. In this way, the effective diffusivity can be determined from the measured CO conversion. An effective diffusion coefficient of D$_{eff}$/D$_{gas}$ = 0.11 was obtained from the CO oxidation measurements, three times lower than the value obtained from the FIB-SEM data, but in line with previous literature data for the effective diffusivity in monolith washcoat layers. Additional NH$_{3}$ oxidation experiments were performed on the dual layer catalyst. The results were well reproduced by a reactor model applying the effective diffusion coefficient obtained by the CO oxidation experiments. The origin of this apparent inconsistency is currently not understood and requires further investigation

Pengendalian Persediaan Bahan Baku Menggunakan Metode Min-max Stock di PT. Panca USAha Palopo Plywood

Penelitian ini bertujuan untuk menghindari kelebihan dan kekurangan bahan baku dengan menghitung besarnya persediaan bahan baku di PT. Panca Usaha Palopo Plywood. Penelitian ini menggunakan metode studi kasus yang bersifat kualitatif yang berguna menerapkan solusi pada masalah terkini. Data penelitian ini diperoleh dari dari data pertahun Perusahaan dengan pihak terkait. Temuan penelitian ini menunjukkan bahwa standar pelaksanaan dan pengelolaan persediaan bahan baku telah sesuai dengan standar yang telah ditentukan Perusahaan. Peneliti menyimpulkan bahwa PT. Panca Usaha Palopo Plywood cukup efisien, efektif, dan ekonomis namun masih terdapat kelemahan-kelemahan dalam kegiatan dalam pengelolaan persediaan bahan baku Perusahaan seperti kurangnya pemahaman karyawan akan peraturan mengenai tindakan disiplin yang ada, kurangnya kepuasan karyawan, terhadap sikap Perusahaan dalam pemberian kompensasi, serta pemesanan bahan baku yang tidak teratur sehingga mengakibatkan penumpukan di gudang.dan sebaliknya kekurangan stock digudang, pengelolaan persediaan bahan baku

Interplay between s-d exchange interaction and Rashba effect: spin-polarized transport

We investigate the spin-polarized transport properties of a two-dimensional electron gas in a n-type diluted magnetic narrow gap semiconductor quantum well subjected to a perpendicular magnetic and electric field. Interesting beating patterns in the magneto resistance are found which can be tuned significantly by varying the electric field. A resonant enhancement of spin-polarized current is found which is induced by the competition between the s-d exchange interaction and the Rashba effect [Y. A. Bychkov and E. I. Rashba, J. Phys. C 17, 6039 (1984)].Comment: 4 pages, 3 figures, Appl. Phys. Lett. (in press

Achieving Steady and Stable Energy from AlGaAsGaAs Solar Cells

The hetero junction operating as a solar cell is based on n GaAs p GaAs p Al0.75Ga0.25As. This paper investigates the influence of radiation electron ray on layers of hetero-junction AlGaAsGaAs. Long term operation in the radiation zone degrades solar cell power operating parameters and reduces overall cell’s life. The impact of radiation electron ray has been analyzed with various doses on layers of the AlGaAsGaAs hetero junction. V-A characteristics and parameters such as the photocurrent density (Jsc), voltage at open circuit (Voc) and energy conversion efficiency ( (η), are evaluated for different doses of electron radiations. It is shown that current and voltage decrease when irradiation doses increase. Further, Jsc and η parameters decrease proportionally to the increase of the electron radiation doses whereas Voc is only slightly decreased

Bringing out the gimp: fashioning the SM imaginary

The intention of this article is to investigate the cultural power associated with the gimp and the gimp mask. The gimp is a clothed or costumed SM body, frequently a submissive that often wears a leather or rubber costume that covers and effectuates the entire body including the face. The gimp is also a representation of SM that circulates throughout fashion and film and other forms of popular culture. Since the gimp’s first outing and naming in the film Pulp Fiction it has become the byword for the head-to-toe leather SM look that has been appropriated by a number of designers as way of exploring and exploiting the relationship between fashion, fetishism, and transgression. As a counterpoint to the popular image of SM in fashion and film, this article also explores how the artists Catherine Opie and Robert Mapplethorpe have represented the gimp, not as an index of horror or transgressive style rather as an affirmative image of their own SM communities that, while still intended to shock, is an defiant attempt to rescue or reclaim the gimp from its negative associations

Genetic modification of Bluetongue virus by uptake of "synthetic" genome segments

Since 1998, several serotypes of Bluetongue virus (BTV) have invaded several southern European countries. In 2006, the unknown BTV serotype 8 (BTV8/net06) unexpectedly invaded North-West Europe and has resulted in the largest BT-outbreak ever recorded. More recently, in 2008 BTV serotype 6 was reported in the Netherlands and Germany. This virus, BTV6/net08, is closely related to modified-live vaccine virus serotype 6, except for genome segment S10. This genome segment is closer related to that of vaccine virus serotype 2, and therefore BTV6/net08 is considered as a result of reassortment. Research on orbiviruses has been hampered by the lack of a genetic modification method. Recently, reverse genetics has been developed for BTV based on ten in vitro synthesized genomic RNAs. Here, we describe a targeted single-gene modification system for BTV based on the uptake of a single in vitro synthesized viral positive-stranded RNA. cDNAs corresponding to BTV8/net06 genome segments S7 and S10 were obtained by gene synthesis and cloned downstream of the T7 RNA-polymerase promoter and upstream of a unique site for a restriction enzyme at the 3'-terminus for run-off transcription. Monolayers of BSR cells were infected by BTV6/net08, and subsequently transfected with purified in vitro synthesized, capped positive-stranded S7 or S10 RNA from BTV8/net06 origin. "Synthetic" reassortants were rescued by endpoint dilutions, and identified by serotype-specific PCR-assays for segment 2, and serogroup-specific PCRs followed by restriction enzyme analysis or sequencing for S7 and S10 segments. The targeted single-gene modification system can also be used to study functions of viral proteins by uptake of mutated genome segments. This method is also useful to generate mutant orbiviruses for other serogroups of the genus Orbivirus for which reverse genetics has not been developed yet