3,656 research outputs found
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
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
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
Interactive approaches to second/foreign language reading and their implications
Reading is an important activity in both first language (L1) and second/foreign language (SL/ FL) classrooms. Yet, conscious research into the process of reading is a recent activity. This research has brought about a significant change in our knowledge of what reading is. It tells us that there are three kinds of reading processes: (1) reading as decoding what the writer has coded, a bottom-up language-driven process; (2) reading as a top-down, concept-driven process; and (3) reading as an interactive compensatory process
Rapidity distribution as a probe for elliptical flow at intermediate energies
Interplay between the spectator and participant matter in heavy-ion
collisions is investigated within isospin dependent quantum molecular dynamics
(IQMD) model in term of rapidity distribution of light charged particles. The
effect of different types and size rapidity distributions is studied in
elliptical flow. The elliptical flow patterns show important role of the nearby
spectator matter on the participant zone. This role is further explained on the
basis of passing time of the spectator and expansion time of the participant
zone. The transition from the in-plane to out-of-plane is observed only when
the mid-rapidity region is included in the rapidity bin, otherwise no
transition occurs. The transition energy is found to be highly sensitive
towards the size of the rapidity bin, while weakly on the type of the rapidity
distribution. The theoretical results are also compared with the experimental
findings and are found in good agreement.Comment: 8 figure
Designing Second Language Curriculum
Through this article, I have attempted to study
the designing of a second language (L2)
curriculum. The aim is not to suggest a new
theory of L2 curriculum, but to describe in simple
non-technical language the existing theory and
its essential components. I will also explore how
the various components of the theory have been
used to design an L2 syllabus. The overall aim
is to describe the theory and its practice over
the years for the benefit of non-specialist
teachers assigned the role of teaching L2
Is the `IR Coincidence' Just That?
(Abridged) Motch (1985) suggested that in the hard state of GX 339-4 the soft
X-ray power-law extrapolated backward in energy agrees with the IR flux. Corbel
& Fender (2002) showed that the hard state radio power-law extrapolated forward
in energy meets the extrapolated X-ray power-law at an IR break, which was
explicitly observed twice in GX 339-4. This `IR coincidence' has been cited as
further evidence that a jet might make a significant contribution to the X-rays
in hard state systems. We explore this hypothesis with a series of simultaneous
radio/X-ray observations of GX 339-4, taken during its 1997, 1999, and 2002
hard states. We fit these spectra, in detector space, with a simple, but
remarkably successful, doubly broken power-law that requires an IR spectral
break. For these observations, the break position and the integrated radio/IR
flux have stronger dependences upon the X-rays than the simplest jet
predictions. If one allows for a softening of the X-ray power law with
increasing flux, then the jet model agrees with the correlation. We also find
evidence that the radio/X-ray fcorrelation previously observed in GX 339-4
shows a `parallel track' for the 2002 hard state. The slope of the 2002
correlation is consistent with prior observations; however, the radio amplitude
is reduced. We then examine the correlation in Cyg X-1 through the use of radio
data, obtained with the Ryle radio telescope, and RXTE data, from the ASM and
pointed observations. We again find evidence of `parallel tracks', and here
they are associated with `failed transitions' to the soft state. We also find
that for Cyg X-1 the radio flux is more fundamentally correlated with the hard
X-ray flux.Comment: To Appear in the July 2005 Astrophysical Journal; 9 Pages, uses
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Manifestation of geometric frustration on magnetic and thermodynamic properties of pyrochlores (X=Ti, Zr)
We present here magnetization, specific heat and Raman studies on
single-crystalline specimens of the first pyrochlore member of
the rare-earth titanate series. Its analogous compound in the
rare-earth zirconate series is also investigated in the polycrystalline form.
The Sm spins in remain unordered down to at least T = 0.5 K. The
absence of magnetic ordering is attributed to very small values of exchange
() and dipolar interaction ()
between the spins in this pyrochlore. In contrast, the pyrochlore
is characterized by a relatively large value of Sm-Sm spin
exchange (); however, long-range ordering of the
spins is not established at least down to T = 0.67 K, due to
frustration of the spins on the pyrochlore lattice. The ground state
of ions in both pyrochlores is a well-isolated Kramer's doublet. The
higher-lying crystal field excitations are observed in the low-frequency region
of the Raman spectra of the two compounds recorded at T = 10 K. At higher
temperatures, the magnetic susceptibility of shows a broad
maximum at T = 140 K while that of changes monotonically. Whereas
is a promising candidate for investigating spin-fluctuations on a
frustrated lattice as indicated by our data, the properties of
seem to conform to a conventional scenario where geometrical frustration of the
spin exclude their long-range ordering.Comment: 24 pages, 6 figures, Accepted for publication in Phys. Rev.
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