Manipulation of Light with Magneto-optic Stripe Domain Films

Magnetic diffraction grating materials, being developed to provide a simple means of deflecting light in a two dimensional, solid state fashion are discussed. The most promising material, for several applications, appears to be bismuth substituted iron garnet films in epitaxial form. Calculations indicate that deflection efficiency greater than 60% is possible in the near infrared region of the spectrum. Within the field of view of the deflector, measurements predict that 105 resolvable spots can be expected. Applications include: (1) general purpose deflection of free laser light, (2) image processing of extended sources such as transparencies, (3) programmable lensing, and (4) fiber optic matrix switching

Dispersal Dynamics in a Wind-Driven Benthic System

Bedload and water column traps were used with simultaneous wind and water velocity measurements to study postlarval macrofaunal dispersal dynamics in Manukau Harbour, New Zealand. A 12-fold range in mean wind condition resulted in large differences in water flow (12-fold), sediment flux (285-fold), and trap collection of total number of individuals (95-fold), number of the dominant infaunal organism (84-fold for the bivalve Macomona liliana), and number of species (4-fold). There were very strong, positive relationships among wind condition, water velocity, sediment flux, and postlarval dispersal, especially in the bedload. Local density in the ambient sediment was not a good predictor of dispersal. Results indicate that postlarval dispersal may influence benthic abundance pat- terns over a range of spatial scales

Seabed drag coefficient over natural beds of horse mussels (Atrina zelandica)

Measurements of seabed drag coefficient, C100, were made under tidal currents at four sites in Mahurangi Harbour, New Zealand. At the first three sites the dominant roughness element was the pinnid bivalve, Atrina zelandica (horse mussel). At the fourth site, which was devoid of horse mussels but covered in cockle shells, patches of seaweed and crab burrows, C100 was smallest (0.0055), but still twice as large as the value typically applied to abiotic, flat, cohesionless seabeds (0.0025). The mean drag coefficient plus-or-minus standard error at the three sites with horse mussels was: 0.0082 ± 0.0010 (site 1); 0.0096 ± 0.0009 (site 2); 0.0115 ± 0.0016 (site 3). There were no clear differences amongst sites 1, 2 and 3 in terms of the attributes of individual horse mussels (e.g. shell height, width or orientation), which could have been used to explain the ranking of the drag coefficients. There were, however, differences amongst the three sites in terms of spatial distribution of individual bivalves. The site with the highest density of horse mussels, site 1, had the lowest drag coefficient and an areal concentration (λ) of horse mussels higher than typical values cited for the critical concentration (λc) for the onset of skimming flow over various idealized, three-dimensional roughness elements. At sites 2 and 3, the drag coefficient was given by: C100=[κ/1n (300/mkλ)]2 which was valid for λ \u3c λ c, where κ is von Karman\u27s constant, k is the horse mussel height (i.e., protrusion above the seabed), m ≈ 100 and λc ≈ 0.2. The stable eddies that are hypothesized to lodge between roughness elements at concentrations greater than λc may influence benthic community dynamics

Caustics of Compensated Spherical Lens Models

We consider compensated spherical lens models and the caustic surfaces they create in the past light cone. Examination of cusp and crossover angles associated with particular source and lens redshifts gives explicit lensing models that confirm previous claims that area distances can differ by substantial factors from angular diameter distances even when averaged over large angular scales. `Shrinking' in apparent sizes occurs, typically by a factor of 3 for a single spherical lens, on the scale of the cusp caused by the lens; summing over many lenses will still leave a residual effect.Comment: 21 pages, 5 ps figures, eps

ANALISIS PEMAHAMAN KONSEP MATEMATIKA SISWA DENGAN MODEL PEMBELAJARAN PROBLEM BASED LEARNING PADA POKOK BAHASAN SEGITIGA (Study deskriptif di Kelas VII SMP Negeri 2 Plered Kab. Cirebon)

Anggun Maya Sari. NIM 59451058. “Analisis Pemahaman Konsep Matematika Siswa dengan Model Pembelajaran Problem Based Learning pada Pokok Bahasan Segitiga”. (Studi Deskriptif di Kelas VII SMP Negeri 2 Plered). Pembelajaran yang efektif adalah pembelajaran yang menyediakan kesempatan kepada siswa untuk belajar mandiri, sehingga dalam prosesnya siswa dapat memperoleh pemahaman dan pengetahuan dengan lebih mendalam. Akan tetapi proses kegiatan pembelajaran matematika yang berlangsung disekolah, pada umumnya guru hanya sekedar penyampai informasi tanpa mempertimbangkan seberapa jauh pemahaman siswa terhadap konsep matematika dari pokok bahasan segitiga yang disampaikan. Tujuan penelitian ini adalah 1) mengetahui seberapa besar pemahaman konsep yang dimiliki peserta didik; 2) mengetahui factor pendukung dan penghambat peserta didik dalam memahami konsep yang diberikan; 3) mengetahui deskripsi aktivitas siswa dalam memahami konsep matematika melalui model pembelajaran Problem Based Learning; 4) mengetahui respon siswa setelah melaksanakan model pembelajaran Problem Based Learning; 5) mengetahui sejauhmana pemahaman konsep matematika siswa setelah mengikuti proses pembelajaran Problem Based Learning. Penerapan model pembelajaran Problem Based Learning (PBL) merupakan salah satu model pembelajaran yang dapat memberikan kondisi belajar aktif kepada siswa. Dengan diterapkannya pembelajaran matematika dengan model pembelajaran PBL, diharapkan dapat membantu siswa dalam memahami konsep matematika. Penelitian ini menggunakan pendekatan kualitatif dan kuantitatif dengan metode deskriptif. Pengumpulan data menggunakan lembar observasi, pedoman wawancara, angket dan tes. Informan dalam penelitian ini adalah kelas VII yang sudah dibentuk kelompok kelas, yaitu VII A, VII D dan VII F. dengan menggunakan proportionate stratified random sampling, maka dari masingmasing kelompok kelas didapat 18 siswa sebagai informan penelitian. Berdasarkan dari hasil wawancara tentang siswa dalam pemahaman konsep matematika, diperoleh siswa masih kurang dan masih perlu banyak bimbingan. Aktivitas siswa selama pembelajaran melalui model pembelajaran PBL diperoleh dari hasil lembar observasi dengan nilai rata-rata dari semua aspek sebesar 54,39% yang termasuk dalam kategori sedang. Berdasarkan angket respon siswa setelah dilaksanakan model pembelajaran PBL termasuk dalam kategori baik dengan nilai rata-rata 76,44%. Pemahaman konsep matematika siswa setelah mengikuti proses pembelajaran dengan model pembelajaran PBL diperoleh siswa lebih rajin dalam mencari bahan untuk menyelesaikan soal-soal yang diberikan dan menambah pemahaman siswa mengenai konsep matematika, meski masih belum 100% benar, dan hasil tes didapat nilai rata-rata 39% yang termasuk dalam kategori sangat kurang. Kata Kunci: Pemahaman konsep matematika, Problem Based Learning, Segitig

The optimal cloning of quantum coherent states is non-Gaussian

We consider the optimal cloning of quantum coherent states with single-clone and joint fidelity as figures of merit. Both optimal fidelities are attained for phase space translation covariant cloners. Remarkably, the joint fidelity is maximized by a Gaussian cloner, whereas the single-clone fidelity can be enhanced by non-Gaussian operations: a symmetric non-Gaussian 1-to-2 cloner can achieve a single-clone fidelity of approximately 0.6826, perceivably higher than the optimal fidelity of 2/3 in a Gaussian setting. This optimal cloner can be realized by means of an optical parametric amplifier supplemented with a particular source of non-Gaussian bimodal states. Finally, we show that the single-clone fidelity of the optimal 1-to-infinity cloner, corresponding to a measure-and-prepare scheme, cannot exceed 1/2. This value is achieved by a Gaussian scheme and cannot be surpassed even with supplemental bound entangled states.Comment: 4 pages, 2 figures, revtex; changed title, extended list of authors, included optical implementation of optimal clone

The linear Fokker-Planck equation for the Ornstein-Uhlenbeck process as an (almost) nonlinear kinetic equation for an isolated N-particle system

It is long known that the Fokker-Planck equation with prescribed constant coefficients of diffusion and linear friction describes the ensemble average of the stochastic evolutions in velocity space of a Brownian test particle immersed in a heat bath of fixed temperature. Apparently, it is not so well known that the same partial differential equation, but now with constant coefficients which are functionals of the solution itself rather than being prescribed, describes the kinetic evolution (in the infinite particle limit) of an isolated N-particle system with certain stochastic interactions. Here we discuss in detail this recently discovered interpretation.Comment: Minor revisions and corrections (including the title

A Survey of Hydroxyl Toward Supernova Remnants: Evidence for Extended 1720 MHz Maser Emission

We present the results of GBT observations of all four ground-state hydroxyl (OH) transitions toward 15 supernova remnants (SNRs) which show OH(1720 MHz) maser emission. This species of maser is well established as an excellent tracer of an ongoing interaction between the SNR and dense molecular material. For the majority of these objects we detect significantly higher flux densities with a single dish than has been reported with interferometric observations. We infer that spatially extended, low level maser emission is a common phenomenon that traces the large-scale interaction in maser-emitting SNRs. Additionally we use a collisional pumping model to fit the physical conditions under which OH is excited behind the SNR shock front. We find the observed OH gas associated with the SNR interaction having columns less than approximately 10^17 per square cm, temperatures of 20 to 125 K, and densities 10^5 per cubic cm.Comment: 24 pages, 23 figures, Accepted to ApJ, March 26, 2008; v2 - added Figure 6, minor clarifications to text in Sections 3 and