Surfactant-aided exfoliation of molydenum disulphide for ultrafast pulse generation through edge-state saturable absorption

We use liquid phase exfoliation to produce dispersions of molybdenum disulphide (MoS2) nanoflakes in aqueous surfactant solutions. The chemical structures of the bile salt surfactants play a crucial role in the exfoliation and stabilization of MoS2. The resultant MoS2 dispersions are heavily enriched in single and few (<6) layer flakes with large edge to surface area ratio. We use the dispersions to fabricate free-standing polymer composite wide-band saturable absorbers to develop mode-locked and Q- switched fibre lasers, tunable from 1535-1565 and 1030-1070 nm, respectively. We attribute this sub-bandgap optical absorption and its nonlinear saturation behaviour to edge-mediated states introduced within the material band-gap of the exfoliated MoS2 nanoflakes.Comment: 6 pages, 5 figure

Nucleate pool boiling in the long duration low gravity environment of the Space Shuttle

The results are presented of an experimental study of nucleate pool boiling performed in the low gravity environment of the space shuttle. Photographic observations of pool boiling in Freon 113 were obtained during the 'Tank Pressure Control Experiment,' flown on the Space Transportation System, STS-43 in August 1991. Nucleate boiling data from large (relative to bubble size) flat heating surfaces (0.1046 by 0.0742 m) was obtained at very low heat fluxes (0.22 to 1.19 kW/sq m). The system pressure and the bulk liquid subcooling varied in the range of 40 to 60 kPa and 3 to 5 C respectively. Thirty-eight boiling tests, each of 10-min duration for a given heat flux, were conducted. Measurements included the heater power, heater surface temperature, the liquid temperature and the system pressure as functions of heating time. Video data of the first 2 min of heating was recorded for each test. In some tests the video clearly shows the inception of boiling and the growth and departure of bubbles from the surface during the first 2 min of heating. In the absence of video data, the heater temperature variation during heating shows the inception of boiling and stable nucleate boiling. During the stable nucleate boiling, the wall superheat varied between 2.8 to 3.8 C for heat fluxes in the range of 0.95 to 1.19 kW/sq m. The wall superheat at the inception of boiling varied between 2 to 13 C

Dynamics of the Solar Magnetic Network. II. Heating the Magnetized Chromosphere

We consider recent observations of the chromospheric network, and argue that the bright network grains observed in the Ca II H & K lines are heated by an as yet unidentified quasi-steady process. We propose that the heating is caused by dissipation of short-period magnetoacoustic waves in magnetic flux tubes (periods less than 100 s). Magnetohydrodynamic (MHD) models of such waves are presented. We consider wave generation in the network due to two separate processes: (a) by transverse motions at the base of the flux tube; and (b) by the absorption of acoustic waves generated in the ambient medium. We find that the former mechanism leads to an efficient heating of the chromosphere by slow magnetoacoustic waves propagating along magnetic field lines. This heating is produced by shock waves with a horizontal size of a few hundred kilometers. In contrast, acoustic waves excited in the ambient medium are converted into transverse fast modes that travel rapidly through the flux tube and do not form shocks, unless the acoustic sources are located within 100 km from the tube axis. We conclude that the magnetic network may be heated by magnetoacoustic waves that are generated in or near the flux tubes.Comment: 30 pages, 8 figures, Accepted in Astrophysical Journa

Ultrafast Raman laser mode-locked by nanotubes

We demonstrate passive mode-locking of a Raman fiber laser using a nanotube-based saturable absorber coupled to a net normal dispersion cavity. This generates highly chirped 500 ps pulses. These are then compressed down to 2 ps , with 1.4 kW peak power, making it a simple wavelength-versatile source for various applications

Effect of Integrated Nutrient Management on Vegetative Growth and Yield in Mango Cv. Himsagar

An experiment was conducted to study the effect of various combinations of integrated nutrient management schedules on vegetative growth and yield in mango cv. Himsagar at Regional Research Station, Gayeshpur, B.C.K.V., Nadia, West Bengal, during the years 2009-2011. Maximum total increment in plant height (108.00 cm), plant spread in E-W direction (123.00 cm) and N-S direction (105.00 cm), and tree volume (85.95 m3) was recorded in 500:250:250g NPK/tree/year + 50kg FYM + 250g&nbsp;Azospirillium&nbsp;(T6) compared to that in other treatments. This treatment (T6) also significantly increased total number of fruits (234.12 fruits / tree), average fruit weight (263.10g) and yield (58.56kg /tree)

The Effect Of Using Pre-questioning On Students' Reading Comprehension Achievement

Membaca merupakan keterampilan yang rumit untuk dicapai karena siswa menunjukkan kesulitannya dalam pelajaran ini. Tujuan penelitian ini untuk mengetahui adakah perbedaan yang signifikan pada prestasi pemahaman membaca siswa sebelum dan setelah pemberian pre-questioning dan mengetahui masalah-masalah yang dihadapi siswa dalam pemahaman membaca dan pre-questioning. Populasinya adalah siswa kelas dua SMPN 1 Seputih Banyak. VIII A diplih sebagai kelas penelitian. Penelitian ini menggunakan pre-test dan post-test satu kelompok. T-test pengukuran berulang digunakan untuk menganalisa data. Nilai rata-rata pre-tes 53.52 dan post test 69.15. Jadi, ada peningkatan sebesar 15.64. Hasil t-test menunjukkan t-ratio lebih tinggi daripada t-table (18.485 > 2.042) dengan signifikan level p 2.042) with the level of significant is p < 0.05 and significant two tail is p=0.000. It can be said that pre-questioning technique has effect on students’ reading comprehension achievement