10,181 research outputs found
A geochemical and petrological study of the tertiary minor intrusions of Rhum, northwest Scotland
The Rhum minor intrusion suite is petrographically and compositionally variable, the majority of the basic rocks are aphyric dolerites but olivine phyric (picritic) and plagioclase phyric (big feldspar) dolerites are also present. In addition, several medium to coarse grained gabbro and peridotite plugs occur. Intermediate rocks are not abundant and acid dykes are rare. The basic and intermediate intrusions occur in a variety of structural environments all over the island, the gabbros and peridotites are generally emplaced as plugs in the northern and southern Torridonian tracts, while the few acid dykes are usually closely associated with the plutonic acid rocks. Twelve classes of dolerite (Groups 1-12) and five classes of gabbro have been distinguished on geochemical and petrographic grounds. The suite as a whole is characterised by high MgO levels when compared with rocks of analogous differentiation in other Tertiary suites of North-West Britain, Several of the group 1 picrites are believed to have existed as mafic liquids with 15-20 wt% MgO at high crustal levels. In addition the basic members (dolerite groups 2 to 4) and several of the gabbros are characterised by higher Ni and Cr and lower Al(_2)O(_3) than comparable British Tertiary rocks. Discriminant Function analysis of the compositional variation within the basic members of the Rhum minor intrusion suite has shown that the majority of these rocks are completely transitional between alkali olivine basalt and tholeiite basalt and contrast with the mildly alkaline Skye Main Lava Series and the mildly tholeiitic Ardnamurchan cone sheets. In contrast, the dolerite groups 5 and 6 are very similar to some of the Skye magma types and consequently are believed to be outlying members of the Skye regional dyke swarm. Of the intermediate rocks, the dolerite groups 8 and 9 and the gabbroic differentiates are tholeiitic in affinity and the dolerite groups 10 to 12 are alkalic in affinity. Detailed field and geochemical investigation has shown there is a progression from tholeiitic basic magmas to high MgO more alkalic composition with time. Despite the known presence of a large upper crustal magma chamber on Rhum, the geochemical variation of the majority of the basic rocks is cottatible with processes operating below 15 km within the lower crust, or in the upper mantle at depths up to 80 km. In contrast the big feldspar (group 7) dolerites and the magmas which gave rise to the peridotite plugs are believed to have been tapped from a high level crustal magma chamber. In addition the divergence towards more extreme alkalic and tholeiitic compositions in the intermediate rocks coupled with their general porphyritic nature and their major oxide and trace element variation suggests that they are the product of low pressure fractionation processes
Unbounded-error One-way Classical and Quantum Communication Complexity
This paper studies the gap between quantum one-way communication complexity
and its classical counterpart , under the {\em unbounded-error}
setting, i.e., it is enough that the success probability is strictly greater
than 1/2. It is proved that for {\em any} (total or partial) Boolean function
, , i.e., the former is always exactly one half
as large as the latter. The result has an application to obtaining (again an
exact) bound for the existence of -QRAC which is the -qubit random
access coding that can recover any one of original bits with success
probability . We can prove that -QRAC exists if and only if
. Previously, only the construction of QRAC using one qubit,
the existence of -RAC, and the non-existence of
-QRAC were known.Comment: 9 pages. To appear in Proc. ICALP 200
Participatory cotton breeding for organic and low input farming in Central India
Up to 80% of world’s organic cotton is produced in India. However, involved producers are facing increased difficulties to find suitable cultivars. Few hybrids selected for high input farming and genetically-modified (GM) cotton, which is explicitly excluded in organic farming, are presently dominating the Indian seed market. In addition farmers have lost their traditional knowledge on seed production and hybrid seed needs to be purchased each season
Transport in Almost Integrable Models: Perturbed Heisenberg Chains
The heat conductivity kappa(T) of integrable models, like the one-dimensional
spin-1/2 nearest-neighbor Heisenberg model, is infinite even at finite
temperatures as a consequence of the conservation laws associated with
integrability. Small perturbations lead to finite but large transport
coefficients which we calculate perturbatively using exact diagonalization and
moment expansions. We show that there are two different classes of
perturbations. While an interchain coupling of strength J_perp leads to
kappa(T) propto 1/J_perp^2 as expected from simple golden-rule arguments, we
obtain a much larger kappa(T) propto 1/J'^4 for a weak next-nearest neighbor
interaction J'. This can be explained by a new approximate conservation law of
the J-J' Heisenberg chain.Comment: 4 pages, several minor modifications, title change
Fractional Operators, Dirichlet Averages, and Splines
Fractional differential and integral operators, Dirichlet averages, and
splines of complex order are three seemingly distinct mathematical subject
areas addressing different questions and employing different methodologies. It
is the purpose of this paper to show that there are deep and interesting
relationships between these three areas. First a brief introduction to
fractional differential and integral operators defined on Lizorkin spaces is
presented and some of their main properties exhibited. This particular approach
has the advantage that several definitions of fractional derivatives and
integrals coincide. We then introduce Dirichlet averages and extend their
definition to an infinite-dimensional setting that is needed to exhibit the
relationships to splines of complex order. Finally, we focus on splines of
complex order and, in particular, on cardinal B-splines of complex order. The
fundamental connections to fractional derivatives and integrals as well as
Dirichlet averages are presented
1/f spectrum and memory function analysis of solvation dynamics in a room-temperature ionic liquid
To understand the non-exponential relaxation associated with solvation
dynamics in the ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate,
we study power spectra of the fluctuating Franck-Condon energy gap of a
diatomic probe solute via molecular dynamics simulations. Results show 1/f
dependence in a wide frequency range over 2 to 3 decades, indicating
distributed relaxation times. We analyze the memory function and solvation time
in the framework of the generalized Langevin equation using a simple model
description for the power spectrum. It is found that the crossover frequency
toward the white noise plateau is directly related to the time scale for the
memory function and thus the solvation time. Specifically, the low crossover
frequency observed in the ionic liquid leads to a slowly-decaying tail in its
memory function and long solvation time. By contrast, acetonitrile
characterized by a high crossover frequency and (near) absence of 1/f behavior
in its power spectra shows fast relaxation of the memory function and
single-exponential decay of solvation dynamics in the long-time regime.Comment: 10 pages, 4 figure
The Sizes of 1720 MHz OH Masers: VLBA and MERLIN Observations of the Supernova Remnants W44 and W28
We have used the NRAO Very Long Baseline Array (VLBA) to image OH(1720 MHz)
masers in the supernova remnants W28 and W44 at a resolution of 40 mas. We also
used MERLIN to observe the same OH(1720 MHz) masers in W44 at a resolution of
290 x 165 mas. All the masers are resolved by these VLBA and MERLIN
observations. The measured sizes range from 50 to 180 mas and yield brightness
temperature estimates from 0.3--20 x 10**8 K. We investigate whether these
measured angular sizes are intrinsic and hence originate as a result of the
physical conditions in the supernova remnant shock, or whether they are scatter
broadened sizes produced by the turbulent ionized gas along the line of sight.
While the current data on the temporal and angular broadening of pulsars,
masers and extragalactic soures toward W44 and W28 can be understood in terms
of scattering, we cannot rule out that these large sizes are intrinsic. Recent
theoretical modeling by Lockett et al. suggests that the physical parameters in
the shocked region are indicative of densities and OH abundances which lead to
estimates of sizes as large as what we measure. If the sizes and structure are
intrinsic, then the OH(1720 MHz) masrs may be more like the OH(1612 MHz) masers
in circumstellar shells than OH masers associated with HII regions. At two
locations in W28 we observe the classical S-shapes in the Stokes V profiles
caused by Zeeman splitting and use it to infer magnetic fields of order 2
milliGauss.Comment: 24 pages, 6 figures, accepted by Ap
The Formaldehyde Masers in Sgr B2: Very Long Baseline Array and Very Large Array Observations
Observations of two of the formaldehyde (H2CO) masers (A and D) in Sgr B2
using the VLBA+Y27 (resolution ~0.01") and the VLA (resolution ~9") are
presented. The VLBA observations show compact sources (<10 milliarcseconds, <80
AU) with brightness temperatures >10^8 K. The maser sources are partially
resolved in the VLBA observations. The flux densities in the VLBA observations
are about 1/2 those of the VLA; and, the linewidths are about 2/3 of the VLA
values. The applicability of a core-halo model for the emission distribution is
demonstrated. Comparison with earlier H2CO absorption observations and with
ammonia (NH3) observations suggests that H2CO masers form in shocked gas.
Comparison of the integrated flux densities in current VLA observations with
those in previous observations indicates that (1) most of the masers have
varied in the past 20 years, and (2) intensity variations are typically less
than a factor of two compared to the 20-year mean. No significant linear or
circular polarization is detected with either instrument.Comment: 20 pages, 3 figures, 5 tables, accepted to Ap
The Detection of Outflows in the IR-Quiet Molecular Core NGC 6334 I(North)
We find strong evidence for outflows originating in the dense molecular core
NGC 6334 I(North): a 1000 Msol molecular core distinguished by its lack of HII
regions and mid-IR emission. New observations were obtained of the SiO 2-1 and
5-4 lines with the SEST 15-m telescope and the H2 (1-0) S(1) line with the ESO
2.2-m telescope. The line profiles of the SiO transitions show broad wings
extending from -50 to 40 km/s, and spatial maps of the line wing emission
exhibit a bipolar morphology with the peaks of the red and blue wing separated
by 30". The estimated mass loss rate of the outflow is comparable to those for
young intermediate to high-mass stars. The near-IR images show eight knots of
H2 emission. Five of the knots form a linear chain which is displaced from the
axis of the SiO outflow; these knots may trace shock excited gas along the path
of a second, highly collimated outflow. We propose that I(N) is a rare example
of a molecular core in an early stage of cluster formation.Comment: 4 pages, LaTeX, 3 ps figures, accepted by ApJ
The Remarkable Mid-Infrared Jet of Massive Young Stellar Object G35.20-0.74
The young massive stellar object G35.20-0.74 was observed in the mid-infrared
using T-ReCS on Gemini South. Previous observations have shown that the near
infrared emission has a fan-like morphology that is consistent with emission
from the northern lobe of a bipolar radio jet known to be associated with this
source. Mid-infrared observations presented in this paper show a monopolar
jet-like morphology as well, and it is argued that the mid-infrared emission
observed is dominated by thermal continuum emission from dust. The mid-infrared
emission nearest the central stellar source is believed to be directly heated
dust on the walls of the outflow cavity. The hydroxyl, water, and methanol
masers associated with G35.20-0.74 are spatially located along these
mid-infrared cavity walls. Narrow jet or outflow cavities such as this may also
be the locations of the linear distribution of methanol masers that are found
associated with massive young stellar objects. The fact that G35.20-0.74 has
mid-infrared emission that is dominated by the outflow, rather than disk
emission, is a caution to those that consider mid-infrared emission from young
stellar objects as only coming from circumstellar disks.Comment: Accepted for publication in ApJ Letters; 4 pages; 2 figures; a
version with full resolution images is available here:
http://www.ctio.noao.edu/~debuizer
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