2,369 research outputs found
Earthquakes and tsunamis caused by low-angle normal faulting in the Banda Sea, Indonesia
As the world's largest archipelagic country in Earth's most active tectonic region, Indonesia faces a substantial earthquake and tsunami threat. Understanding this threat is a challenge because of the complex tectonic environment, the paucity of observed data and the limited historical record. Here we combine information from recent studies of the geology of Indonesia's Banda Sea with Global Positioning System observations of crustal motion and an analysis of historical large earthquakes and tsunamis there. We show that past destructive earthquakes were not caused by the supposed megathrust of the Banda outer arc as previously thought but are due to a vast submarine normal fault system recently discovered along the Banda inner arc. Instead of being generated by coseismic seafloor displacement, we find the tsunamis were more likely caused by earthquake-triggered submarine slumping along the fault's massive scarp, the Weber Deep. This would make the Banda detachment representative not only as a modern analogue for terranes hyper-extended by slab rollback but also for the generation of earthquakes and tsunamis by a submarine extensional fault system. Our findings suggest that low-angle normal faults in the Banda Sea generate large earthquakes, which in turn can generate tsunamis due to earthquake-triggered slumping. Low-angle normal faults in the Banda Sea have caused large earthquakes that indirectly generated tsunamis due to earthquake-triggered submarine slumping, according to an analysis of historical earthquake and tsunami events and GPS observations.Peer reviewe
A randomised clinical trial on the efficacy of 5% fluorocalcium phosphosilicate-containing novel bioactive glass toothpaste.
Dentine hypersensitivity (DH) is a common and harrowing dental condition. A novel BioMin-F technology that contains 5% fluorocalcium phosphosilicate bioactive glass has been introduced. It forms fluorapatite, which is more stable towards acid erosion. There is a lack of literature with the utility of this toothpaste in treating DH. Therefore, the authors of this randomised clinical trial have aimed to compare and evaluate the efficacy of 5% fluorocalcium phosphosilicate with an 8% arginine and calcium carbonate and placebo toothpaste. A total of 75 patients clinically diagnosed with DH were randomly divided into three groups: Group A, 5% fluorocalcium phosphosilicate; Group B, 8% arginine and calcium carbonate; and Group C, placebo. The DH was evaluated by tactile and evaporative stimuli, and a visual analogue scale (VAS) was used for evaporative stimuli at pre-baseline, baseline (15 days) and post-baseline (1 month). The results showed symptoms of DH were reduced in all three groups. However, Group A showed a better reduction of DH than the other two groups. The toothpaste containing 5% fluorocalcium phosphosilicate was reported to be more efficacious than the other two toothpastes in managing DH. This novel development opens up a unique opportunity in the prevention and management of DH and may also be beneficial in preventing acid erosion of the tooth surface and in the maintenance of oral hygiene by reducing the effects of plaque accumulation and gingival inflammation
ROM-based quantum computation: Experimental explorations using Nuclear Magnetic Resonance, and future prospects
ROM-based quantum computation (QC) is an alternative to oracle-based QC. It
has the advantages of being less ``magical'', and being more suited to
implementing space-efficient computation (i.e. computation using the minimum
number of writable qubits). Here we consider a number of small (one and
two-qubit) quantum algorithms illustrating different aspects of ROM-based QC.
They are: (a) a one-qubit algorithm to solve the Deutsch problem; (b) a
one-qubit binary multiplication algorithm; (c) a two-qubit controlled binary
multiplication algorithm; and (d) a two-qubit ROM-based version of the
Deutsch-Jozsa algorithm. For each algorithm we present experimental
verification using NMR ensemble QC. The average fidelities for the
implementation were in the ranges 0.9 - 0.97 for the one-qubit algorithms, and
0.84 - 0.94 for the two-qubit algorithms. We conclude with a discussion of
future prospects for ROM-based quantum computation. We propose a four-qubit
algorithm, using Grover's iterate, for solving a miniature ``real-world''
problem relating to the lengths of paths in a network.Comment: 11 pages, 5 figure
Two-Stage Rotational Disordering of a Molecular Crystal Surface: C60
We propose a two-stage mechanism for the rotational surface disordering phase
transition of a molecular crystal, as realized in C fullerite. Our
study, based on Monte Carlo simulations, uncovers the existence of a new
intermediate regime, between a low temperature ordered state,
and a high temperature disordered phase. In the intermediate
regime there is partial disorder, strongest for a subset of particularly
frustrated surface molecules. These concepts and calculations provide a
coherent understanding of experimental observations, with possible extension to
other molecular crystal surfaces.Comment: 4 pages, 2 figure
NMR Techniques for Quantum Control and Computation
Fifty years of developments in nuclear magnetic resonance (NMR) have resulted
in an unrivaled degree of control of the dynamics of coupled two-level quantum
systems. This coherent control of nuclear spin dynamics has recently been taken
to a new level, motivated by the interest in quantum information processing.
NMR has been the workhorse for the experimental implementation of quantum
protocols, allowing exquisite control of systems up to seven qubits in size.
Here, we survey and summarize a broad variety of pulse control and tomographic
techniques which have been developed for and used in NMR quantum computation.
Many of these will be useful in other quantum systems now being considered for
implementation of quantum information processing tasks.Comment: 33 pages, accepted for publication in Rev. Mod. Phys., added
subsection on T_{1,\rho} (V.A.6) and on time-optimal pulse sequences
(III.A.6), redid some figures, made many small changes, expanded reference
Brillouin scattering studies in FeO across the Verwey transition
Brillouin scattering studies have been carried out on high quality single
crystals of FeO with [100] and [110] faces in the temperature range of
300 to 30 K. The room temperature spectrum shows a surface Rayleigh wave (SRW)
mode at 8 GHz and a longitudinal acoustic (LA) mode at 60 GHz. The SRW mode
frequency shows a minimum at the Verwey transition temperature of 123 K.
The softening of the SRW mode frequency from about 250 K to can be
quantitatively understood as a result of a decrease in the shear elastic
constant C, arising from the coupling of shear strain to charge
fluctuations. On the other hand, the LA mode frequency does not show any
significant change around , but shows a large change in its intensity. The
latter shows a maximum at around 120 K in the cooling run and at 165 K in the
heating run, exhibiting a large hysteresis of 45 K. This significant change in
intensity may be related to the presence of stress-induced ordering of
Fe and Fe at the octahedral sites, as well as to stress-induced
domain wall motion.Comment: 14 pages, 3 figures, accepted in Physical Review B 200
Analysis of the Dynamics of Liquid Aluminium: Recurrent Relation Approach
By use of the recurrent relation approach (RRA) we study the microscopic
dynamics of liquid aluminium at T=973 K and develop a theoretical model which
satisfies all the corresponding sum rules. The investigation covers the
inelastic features as well as the crossover of our theory into the
hydrodynamical and the free-particle regimes. A comparison between our
theoretical results with those following from a generalized hydrodynamical
approach is also presented. In addition to this we report the results of our
molecular dynamics simulations for liquid aluminium, which are also discussed
and compared to experimental data. The received results reveal that (i) the
microscopical dynamics of density fluctuations is defined mainly by the first
four even frequency moments of the dynamic structure factor, and (ii) the
inherent relation of the high-frequency collective excitations observed in
experimental spectra of dynamic structure factor with the two-,
three- and four-particle correlations.Comment: 11 pages, 4 figure
Approximate Quantum Cloning with Nuclear Magnetic Resonance
Here we describe a Nuclear Magnetic Resonance (NMR) experiment that uses a
three qubit NMR device to implement the one to two approximate quantum cloning
network of Buzek et al.Comment: 4 pages RevTeX4 including 5 postscript figures. Submitted to PR
Universal mechanism of discontinuity of commensurate-incommensurate transitions in three-dimensional solids: Strain dependence of soliton self-energy
We show that there exists a universal mechanism of long-range soliton
attraction in three-dimensional solids and, therefore, of discontinuity of any
commensurate-incommensurate (C-IC) phase transition. This mechanism is due to
the strain dependence of the soliton self-energy and specific features of the
solid-state elasticity. The role of this mechanism is studied in detail for a
class of C-IC transitions where the IC modulation is one-dimensional, the
anisotropy in the order parameter space is small, and the symmetry of the
systems allows the existence of the Lifshitz invariant. Two other mechanisms of
soliton attraction are operative here but the universal mechanism considered in
this paper is found to be the most important one in some cases. Comparison with
the most extensively studied C-IC transition in shows that the
experimentally observed thermal anomalies can be understood as a result of the
smearing of the theoretically predicted discontinuous transition.Comment: 8 pages (extended version, title changed
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