Generation of ultra-short light pulses by a rapidly ionizing thin foil

A thin and dense plasma layer is created when a sufficiently strong laser pulse impinges on a solid target. The nonlinearity introduced by the time-dependent electron density leads to the generation of harmonics. The pulse duration of the harmonic radiation is related to the risetime of the electron density and thus can be affected by the shape of the incident pulse and its peak field strength. Results are presented from numerical particle-in-cell-simulations of an intense laser pulse interacting with a thin foil target. An analytical model which shows how the harmonics are created is introduced. The proposed scheme might be a promising way towards the generation of attosecond pulses. PACS number(s): 52.40.Nk, 52.50.Jm, 52.65.RrComment: Second Revised Version, 13 pages (REVTeX), 3 figures in ps-format, submitted for publication to Physical Review E, WWW: http://www.physik.tu-darmstadt.de/tqe

Ikan Pelangi Iriatherina Werneri (Meiken, 1974) dengan Hormon Estradiol-17β

Pembetinaan ikan pelangi (Iriatherina werneri) adalah langkah awal untuk mendapatkan individu betina fungsional (XY). Jika individu betina fungsional ini dikawinkan dengan jantan normal (XY) akan menghasilkan individu ikan jantan super (YY). Penelitian ini bertujuan untuk mengevaluasi kondisi optimum dosis dan lama perendaman yang berbeda untuk pembetinaan ikan pelangi dengan menggunakan hormon estradiol-17β yang dirancang menggunakan rancangan acak lengkap pola faktorial yang terdiri atas faktor dosis dan lama perendaman masing-masing diulang tiga kali kemudian data dianalisis secara statistik (ANOVA). Telur ikan pelangi stadia embrio bintik mata direndam dalam larutan estradiol-17β dosis 0, 200, 400 dan 600 μg L-1 selama 6, 12, dan 18 jam, kemudian larva dipelihara selama 70 hari. Hasil penelitian menunjukkan bahwa perlakuan estradiol-17β dapat meningkatkan persentase betina; dosis 400 dan 600 μg L-1 selama 6 dan 12 jam meningkatkan persentase betina secara nyata (p0,05)

Keragaman Genotipe dan Morfometrik Ikan Tengadak Barbonymus Schwanenfeldii (Bleeker 1854) Asal Sumatera, Jawa, dan Kalimantan

Studi keragaman genotipe dan fenotipe populasi awal ikan tengadak (Barbonymus schwanenfeldii) asal Sumatera, Jawa, dan Kalimantan merupakan upaya pemanfaatan sumber daya genetik ikan tengadak untuk kegiatan budi daya secara berkelanjutan. Tujuan penelitian ini adalah melakukan evaluasi keragaman genotipe dan fenotipe ikan tengadak asal Sumatera, Jawa, dan Kalimantan. Analisis keragaman genotipe dilakukan secara molekuler dengan metode Random Amplified Polymorphism DNA (RAPD) menggunakan primer OPA 08, OPA 09 dan OPC 02 sedangkan keragaman fenotipe dilakukan berdasarkan pengukuran truss morphometric. Hasil penelitian menunjukkan polimorfisme genetik tertinggi (40%) ditemukan pada ikan jantan populasi asal Jawa dan ikan betina asal Kalimantan dengan nilai heterozi- gositas tertinggi 0,18 sedangkan polimorfisme terendah (18%) ditemukan pada ikan betina populasi asal Jawa dengan tingkat heterozigositas 0,08. Jarak genetik ketiga populasi berkisar 0,48-0,55 sedangkan antara ikan jantan dan betina berki-sar 0,19-0,24. Hasil analisis fungsi kanonikal truss morfometrik ikan tengadak pada 21 karakter terukur menun- jukkan sebaran pengukuran ketiga populasi berada pada kuadran yang berbeda. Persentase indeks keseragaman intra- populasi menunjukkan indeks keseragaman genetik tertinggi pada populasi Jawa (66,7-86,7 %) dengan indeks kesera- gaman interpopulasi (0-6%) pada populasi Kalimantan dan (0%) pada populasi Sumatera. Berdasarkan data keragaman genotipe dan fenotipe ikan jantan asal Jawa dan ikan betina asal Kalimantan berpotensi sebagai sumber genetik donor untuk pengembangan budidaya ikan tengadak

The wall shear rate distribution for flow in random sphere packings

The wall shear rate distribution P(gamma) is investigated for pressure-driven Stokes flow through random arrangements of spheres at packing fractions 0.1 <= phi <= 0.64. For dense packings, P(gamma) is monotonic and approximately exponential. As phi --> 0.1, P(gamma) picks up additional structure which corresponds to the flow around isolated spheres, for which an exact result can be obtained. A simple expression for the mean wall shear rate is presented, based on a force-balance argument.Comment: 4 pages, 3 figures, 1 table, RevTeX 4; significantly revised with significantly extended scop

Coherent control using adaptive learning algorithms

We have constructed an automated learning apparatus to control quantum systems. By directing intense shaped ultrafast laser pulses into a variety of samples and using a measurement of the system as a feedback signal, we are able to reshape the laser pulses to direct the system into a desired state. The feedback signal is the input to an adaptive learning algorithm. This algorithm programs a computer-controlled, acousto-optic modulator pulse shaper. The learning algorithm generates new shaped laser pulses based on the success of previous pulses in achieving a predetermined goal.Comment: 19 pages (including 14 figures), REVTeX 3.1, updated conten

Theory of Pump Depletion and Spike Formation in Stimulated Raman Scattering

By using the inverse spectral transform, the SRS equations are solved and the explicit output data is given for arbitrary laser pump and Stokes seed profiles injected on a vacuum of optical phonons. For long duration laser pulses, this solution is modified such as to take into account the damping rate of the optical phonon wave. This model is used to interprete the experiments of Druhl, Wenzel and Carlsten (Phys. Rev. Lett., (1983) vol. 51, p. 1171), in particular the creation of a spike of (anomalous) pump radiation. The related nonlinear Fourier spectrum does not contain discrete eigenvalue, hence this Raman spike is not a soliton.Comment: LaTex file, includes two figures in LaTex format, 9 page

PENGARUH SALINITAS TERHADAP KELULUSAN HIDUP DAN PERTUMBUHAN BENIH IKAN BAWAL AIR TAWAR, Colossoma macropomum

The aim of this study was to know the optimal salinity level on survival and growth rates of Colossoma macropomum on larvae rearing in different salinity media. The treatment tested with six different salinities were 0; 2; 4; 6; and 10 ‰. This study was conducted from May 15 to June 12, 2006. The experiment design was arranged in completely randoumizes design with six treatments and three replications. Stock density was 1 fish/l with mean initial body weight 0.48 ± 0.03 g and initial total body length 3.04 ± 0.18 cm. The result showed that the optimal salinities between 5.74 – 6.35 ‰, which was giving growth rates 9.31 % and survival rates 100 %. On minimum salinitiy media (0 ‰) showed growth rate 5.45 % and survival rate 19.17 %