3,306 research outputs found
Universality and Scaling Behaviour of Injected Power in Elastic Turbulence in Worm-like Micellar Gel
We study the statistical properties of spatially averaged global injected
power fluctuations for Taylor-Couette flow of a worm-like micellar gel formed
by surfactant CTAT. At sufficiently high Weissenberg numbers (Wi) the shear
rate and hence the injected power p(t) at a constant applied stress shows large
irregular fluctuations in time. The nature of the probability distribution
function (pdf) of p(t) and the power-law decay of its power spectrum are very
similar to that observed in recent studies of elastic turbulence for polymer
solutions. Remarkably, these non-Gaussian pdfs can be well described by an
universal large deviation functional form given by the Generalized Gumbel (GG)
distribution observed in the context of spatially averaged global measures in
diverse classes of highly correlated systems. We show by in-situ rheology and
polarized light scattering experiments that in the elastic turbulent regime the
flow is spatially smooth but random in time, in agreement with a recent
hypothesis for elastic turbulence.Comment: 8 pages, 3 figure
Femtosecond carrier dynamics and saturable absorption in graphene suspensions
Nonlinear optical properties and carrier relaxation dynamics in graphene,
suspended in three different solvents, are investigated using femtosecond (80
fs pulses) Z-scan and degenerate pumpprobe spectroscopy at 790 nm. The results
demonstrate saturable absorption property of graphene with a nonlinear
absorption coefficient, , of ~2 to 9x10^-8 cm/W. Two distinct time scales
associated with the relaxation of photoexcited carriers, a fast one in the
range of 130-330 fs (related to carrier-carrier scattering) followed by a
slower one in 3.5-4.9 ps range (associated with carrier-phonon scattering) are
observed.Comment: 3 pages, 2 figures, 2 table
Brillouin Scattering Studies of La_{0.77}Ca_{0.23}MnO_3 Across Metal-Insulator Transition
Temperature-dependent Brillouin scattering studies have been carried out on
La_{0.77}Ca_{0.23}MnO_3 across the paramagnetic insulator - ferromagnetic metal
(I-M) transition. The spectra show a surface Rayleigh wave (SRW) and a high
velocity pseudo surface acoustic wave (HVPSAW) besides bulk acoustic waves
(BAW). The Brillouin shifts associated with SRW and HVPSAW show blue-shifts,
where as the frequencies of the BAW decrease below the I-M transition
temperature (T_C) of 230 K. These results can be understood based on the
temperature dependence of the elastic constants. We also observe a central peak
whose width is maximum at T_C.Comment: 7 pages, 8 figure
Detection of Sugar-Lectin Interactions by Multivalent Dendritic Sugar Functionalized Single-Walled Carbon Nanotubes
We show that single walled carbon nanotubes (SWNT) decorated with sugar
functionalized poly (propyl ether imine) (PETIM) dendrimer is a very sensitive
platform to quantitatively detect carbohydrate recognizing proteins, namely,
lectins. The changes in electrical conductivity of SWNT in field effect
transistor device due to carbohydrate - protein interactions form the basis of
present study. The mannose sugar attached PETIM dendrimers undergo charge -
transfer interactions with the SWNT. The changes in the conductance of the
dendritic sugar functionalized SWNT after addition of lectins in varying
concentrations were found to follow the Langmuir type isotherm, giving the
concanavalin A (Con A) - mannose affinity constant to be 8.5 x 106 M-1. The
increase in the device conductance observed after adding 10 nM of Con A is same
as after adding 20 \muM of a non - specific lectin peanut agglutinin, showing
the high specificity of the Con A - mannose interactions. The specificity of
sugar-lectin interactions was characterized further by observing significant
shifts in Raman modes of the SWNT.Comment: 12 pages, 3 figure
Large nonlinear absorption and refraction coefficients of carbon nanotubes estimated from femtosecond Z-scan measurements
Nonlinear transmission of 80 and 140 femtosecond pulsed light with wavelength through single walled carbon nanotubes suspended in water
containing sodium dodecyl sulphate is studied. Pulse-width independent
saturation absorption and negative cubic nonlinearity are observed,
respectively, in open and closed aperture Z-scan experiments. The theoretical
expressions derived to analyze the z-dependent transmission in the saturable
limit require two photon absorption coefficient and a
nonlinear index to fit the data.Comment: 10 pages, 2 figures. Accepted and to appear in Applied Physics
Letter
P02.155. Stress Management and Resilience Training (SMART) program to decrease stress and enhance resilience among breast cancer survivors: a randomized trial
Precise time and frequency intercomparison between NPL, India and PTB, Federal Republic of Germany via satellite symphonie-1
A time and frequency intercomparison experiment conducted using Earth stations in New Delhi, India and Raisting, FRG is described. The NPL clock was placed at New Delhi Earth Station and the Raisting Clock was calibrated with PTB/Primary standard via LORAN-C and travelling clocks. The random uncertainity of time comparisons, represented by two sample Allan Variance sigma (30 seconds), was less than 10 nanoseconds. The relative frequency difference between the NPL and Raisting Clocks, SNPL, RAIS, as measured over the 44 days period was found to be -15.7 x 10 to the -13th power. The relative frequency difference between PTB Primary Standard and Raisting Clock, SPTB, RAIS, during this period, was measured to be -22.8 x 10 to the -13th power. The relative frequency difference between NPL clock and PTB Primary Standard, SNPL, PTB, thus, is +7.1 x 10 to the -13th power. The clock rate (UTC, India) of +7.1 + or - 0.5 x 10 to the -13th power, agrees well with that obtained via VLF phase measurements over one year period and with USNO travelling clock time comparisons made in September, 1980
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