1,159 research outputs found
Some pH measurements in the Arabian Sea along the West coast of India
pH measurements of the waters of an oceanic environment are important both for the Physical Oceanographer and the Marine Biologist. Whereas variations in the pH values in a vertical plane give an idea of the vertical mixing produced, and thus an idea of the stratification, they also provide a clue as to the extent of the photosynthetic zone (euphotic zone) where phytoplankton can thrive and conduct
photosynthesis. Again close relationship exists between the pattern of distribution of pH and that of dissolved oxygen content, and the thermal discontinuity in the vertical is also related to the pH distribution in the vertical. Hence an attempt has been made to study the variation of pH with the available data collected on board R. V. Varuna
Duplicate entry=================================On some ph measurements in the Arabian Sea along the west coast of India
pH measurements of the waters of an oceanic environment are important both for the Physical Oceanographer and the Marine Biologist. Whereas variations in the pH values in a vertical plane give an idea of the vertical mixing produced, and thus an idea of the stratification, they also provide a clue as to the extent of the photosynthetic zone (euphotic zone) where phytoplankton can thrive and conduct photosynthesis. Again close relationship exists between the pattern of distribution of pH and that of dissolved oxygen content, and the thermal discontinuity in the vertical is also related to the pH distribution in the vertical. Hence an attempt has been made to study the variation of pH with the available data collected on board R. V. Varun
Functional evolution of quantum cylindrical waves
Kucha{\v{r}} showed that the quantum dynamics of (1 polarization) cylindrical
wave solutions to vacuum general relativity is determined by that of a free
axially-symmetric scalar field along arbitrary axially-symmetric foliations of
a fixed flat 2+1 dimensional spacetime. We investigate if such a dynamics can
be defined {\em unitarily} within the standard Fock space quantization of the
scalar field.
Evolution between two arbitrary slices of an arbitrary foliation of the flat
spacetime can be built out of a restricted class of evolutions (and their
inverses). The restricted evolution is from an initial flat slice to an
arbitrary (in general, curved) slice of the flat spacetime and can be
decomposed into (i) `time' evolution in which the spatial Minkowskian
coordinates serve as spatial coordinates on the initial and the final slice,
followed by (ii) the action of a spatial diffeomorphism of the final slice on
the data obtained from (i). We show that although the functional evolution of
(i) is unitarily implemented in the quantum theory, generic spatial
diffeomorphisms of (ii) are not. Our results imply that a Tomanaga-Schwinger
type functional evolution of quantum cylindrical waves is not a viable concept
even though, remarkably, the more limited notion of functional evolution in
Kucha{\v{r}}'s `half parametrized formalism' is well-defined.Comment: Replaced with published versio
Some observations on the continental shelf waters along the east coast of India
The hydrographic investigations of the shelf waters along the East coast of
India (in the Bay of Bengal) were conducted during the month of March 1963 from
Vishakhapatnam coast to Point Calimere coast on board the Researdi Vessel
VARUNA. Due to the hmited period available it was not possible to work out
any planned linear sections for dynamic studies and hence the ship had to resort
to a zig-zag track covering the shelf as far as possible within a duration of one week.
Observations of temperature and saUnity at all the 164 stations were done at 0, 5,
10, 20, 30 and 50 metres. Since the data collected do not permit to have a detailed
study of water masses along the East coast, the temperature and salinity characteristics
were subjected to a frequency jiistribution study and discussed in the
following text. Moreover, the whole area has been arbitrarily divided into four
regions, viz., Vishakhapatnam to Kakinada, Kakinada to Kottapatam, Kottapatam
to Madras and Madras to Point Calimere ; and the average temperature and
salinity conditions at selected isobaric levels have been discussed
Critical Crossover Between Yosida-Kondo Dominant Regime and Magnetic Frustration Dominant Regime in the System of a Magnetic Trimer on a Metal Surface
Quantum Monte Carlo simulations were carried out for the system of a magnetic
trimer on a metal surface. The magnetic trimer is arranged in two geometric
configurations, viz., isosceles and equilateral triangles. The calculated
spectral density and magnetic susceptibility show the existence of two phases:
Yosida-Kondo dominant phase and magnetic frustration dominant phase.
Furthermore, a critical transition between these two phases can be induced by
changing the configuration of the magnetic trimers from isosceles to
equilateral triangle.Comment: 8 pages, 4 figures; accepted for publication in J. Phys. Soc. Jp
Theory of Scanning Tunneling Spectroscopy of a Magnetic Adatom on a Metallic Surface
A comprehensive theory is presented for the voltage, temperature, and spatial
dependence of the tunneling current between a scanning tunneling microscope
(STM) tip and a metallic surface with an individual magnetic adatom. Modeling
the adatom by a nondegenerate Anderson impurity, a general expression is
derived for a weak tunneling current in terms of the dressed impurity Green
function, the impurity-free surface Green function, and the tunneling matrix
elements. This generalizes Fano's analysis to the interacting case. The
differential-conductance lineshapes seen in recent STM experiments with the tip
directly over the magnetic adatom are reproduced within our model, as is the
rapid decay, \sim 10\AA, of the low-bias structure as one moves the tip away
from the adatom. With our simple model for the electronic structure of the
surface, there is no dip in the differential conductance at approximately one
lattice spacing from the magnetic adatom, but rather we see a resonant
enhancement. The formalism for tunneling into small clusters of magnetic
adatoms is developed.Comment: 12 pages, 9 figures; to appear in Phys. Rev.
Programmable Quantum Processors based on Spin Qubits with Mechanically-Mediated Interactions and Transport
Solid state spin qubits are promising candidates for quantum information
processing, but controlled interactions and entanglement in large, multi-qubit
systems are currently difficult to achieve. We describe a method for
programmable control of multi-qubit spin systems, in which individual
nitrogen-vacancy (NV) centers in diamond nanopillars are coupled to
magnetically functionalized silicon nitride mechanical resonators in a scanning
probe configuration. Qubits can be entangled via interactions with
nanomechanical resonators while programmable connectivity is realized via
mechanical transport of qubits in nanopillars. To demonstrate the feasibility
of this approach, we characterize both the mechanical properties and the
magnetic field gradients around the micromagnet placed on the nanobeam
resonator. Furthermore, we show coherent manipulation and mechanical transport
of a proximal spin qubit by utilizing nuclear spin memory, and use the NV
center to detect the time-varying magnetic field from the oscillating
micromagnet, extracting a spin-mechanical coupling of 7.7(9) Hz. With realistic
improvements the high-cooperativity regime can be reached, offering a new
avenue towards scalable quantum information processing with spin qubits.Comment: 7 pages, 4 figure
Astrophysical S_{17}(0) factor from a measurement of d(7Be,8B)n reaction at E_{c.m.} = 4.5 MeV
Angular distribution measurements of H(Be,Be)H and
H(Be,B) reactions at ~4.5 MeV were performed to
extract the astrophysical factor using the asymptotic normalization
coefficient (ANC) method. For this purpose a pure, low emittance Be beam
was separated from the primary Li beam by a recoil mass spectrometer
operated in a novel mode. A beam stopper at 0 allowed the use of a
higher Be beam intensity. Measurement of the elastic scattering in the
entrance channel using kinematic coincidence, facilitated the determination of
the optical model parameters needed for the analysis of the transfer data. The
present measurement significantly reduces errors in the extracted
Be(p,) cross section using the ANC method. We get
~(0)~=~20.7~~2.4 eV~b.Comment: 15 pages including 3 eps figures, one figure removed and discussions
updated. Version to appear in Physical Review
Long-range Kondo signature of a single magnetic impurity
The Kondo effect, one of the oldest correlation phenomena known in condensed
matter physics, has regained attention due to scanning tunneling spectroscopy
(STS) experiments performed on single magnetic impurities. Despite the
sub-nanometer resolution capability of local probe techniques one of the
fundamental aspects of Kondo physics, its spatial extension, is still subject
to discussion. Up to now all STS studies on single adsorbed atoms have shown
that observable Kondo features rapidly vanish with increasing distance from the
impurity. Here we report on a hitherto unobserved long range Kondo signature
for single magnetic atoms of Fe and Co buried under a Cu(100) surface. We
present a theoretical interpretation of the measured signatures using a
combined approach of band structure and many-body numerical renormalization
group (NRG) calculations. These are in excellent agreement with the rich
spatially and spectroscopically resolved experimental data.Comment: 7 pages, 3 figures + 8 pages supplementary material; Nature Physics
(Jan 2011 - advanced online publication
The Kondo Box: A Magnetic Impurity in an Ultrasmall Metallic Grain
We study the Kondo effect generated by a single magnetic impurity embedded in
an ultrasmall metallic grain, to be called a ``Kondo box''. We find that the
Kondo resonance is strongly affected when the mean level spacing in the grain
becomes larger than the Kondo temperature, in a way that depends on the parity
of the number of electrons on the grain. We show that the single-electron
tunneling conductance through such a grain features Kondo-induced Fano-type
resonances of measurable size, with an anomalous dependence on temperature and
level spacing.Comment: 4 Latex pages, 4 figures, submitted to Phys. Rev. Let
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