1,191 research outputs found
Numerical Analysis of Reinforced Concrete Piles under Blast Loads
Pile foundations are commonly used as foundation systems for high-rise buildings and bridges. This paper uses a fully coupled three dimensional numerical modelling procedure to study the performance of pile foundations subjected to ground shocks induced by surface explosions. The comprehensive numerical model includes the pile, surrounding soil, air and the explosive. Appropriate material models are incorporated and dynamic non-linear analysis is carried out using finite element techniques. The soil in which the pile is buried could influence the blast performance of the pile. A parametric study is hence carried out to evaluate the effects of soil properties of density, friction angle, cohesion and Poisson’s ratio on the blast performance of the pile. It is found that density and cohesion of soil have significant effects on the deflection of the pile under blast loading. Poisson’s ratio has some effect, but effect of the soil friction angle is not very significant. The findings of this study will serve as a benchmark reference for future analysis and design of pile foundations to blast loading
Demonstrating various quantum effects with two entangled laser beams
We report on the preparation of entangled two mode squeezed states of yet
unseen quality. Based on a measurement of the covariance matrix we found a
violation of the Reid and Drummond EPR-criterion at a value of only 0.36\pm0.03
compared to the threshold of 1. Furthermore, quantum state tomography was used
to extract a single photon Fock state solely based on homodyne detection,
demonstrating the strong quantum features of this pair of laser-beams. The
probability for a single photon in this ensemble measurement exceeded 2/3
Demonstration of Feed-Forward Control for Linear Optics Quantum Computation
One of the main requirements in linear optics quantum computing is the
ability to perform single-qubit operations that are controlled by classical
information fed forward from the output of single photon detectors. These
operations correspond to pre-determined combinations of phase corrections and
bit-flips that are applied to the post-selected output modes of
non-deterministic quantum logic devices. Corrections of this kind are required
in order to obtain the correct logical output for certain detection events, and
their use can increase the overall success probability of the devices. In this
paper, we report on the experimental demonstration of the use of this type of
feed-forward system to increase the probability of success of a simple
non-deterministic quantum logic operation from approximately 1/4 to 1/2. This
logic operation involves the use of one target qubit and one ancilla qubit
which, in this experiment, are derived from a parametric down-conversion photon
pair. Classical information describing the detection of the ancilla photon is
fed-forward in real-time and used to alter the quantum state of the output
photon. A fiber optic delay line is used to store the output photon until a
polarization-dependent phase shift can be applied using a high speed Pockels
cell
Spatio-temporal dynamics of quantum-well excitons
We investigate the lateral transport of excitons in ZnSe quantum wells by
using time-resolved micro-photoluminescence enhanced by the introduction of a
solid immersion lens. The spatial and temporal resolutions are 200 nm and 5 ps,
respectively. Strong deviation from classical diffusion is observed up to 400
ps. This feature is attributed to the hot-exciton effects, consistent with
previous experiments under cw excitation. The coupled transport-relaxation
process of hot excitons is modelled by Monte Carlo simulation. We prove that
two basic assumptions typically accepted in photoluminescence investigations on
excitonic transport, namely (i) the classical diffusion model as well as (ii)
the equivalence between the temporal and spatial evolution of the exciton
population and of the measured photoluminescence, are not valid for
low-temperature experiments.Comment: 8 pages, 6 figure
The treatment of polycythaemia vera: an update in the JAK2 era
The clinical course of polycythaemia vera is marked by a high incidence of thrombotic complications, which represent the main cause of morbidity and mortality. Major predictors of vascular events are increasing age and previous thrombosis. Myelosuppressive drugs can reduce the rate of thrombosis, but there is concern that their use raises the risk of transformation into acute leukaemia. To tackle this dilemma, a risk-oriented management strategy is recommended. Low-risk patients should be treated with phlebotomy and low-dose aspirin. Cytotoxic therapy is indicated in high-risk patients, with the drug of choice being hydroxyurea because its leukaemogenicity is low. The recent discovery of JAK2 V617F mutation in the vast majority of polycythaemia vera patients opens new avenues for the treatment of this disease. Novel therapeutic options theoretically devoid of leukaemic risk, such as alpha-interferon and imatinib, affect JAK2 expression in some patients. Nevertheless, these drugs require further clinical experience and, for the time being, should be reserved for selected cases
Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions
Data taken with the ALEPH detector at LEP1 have been used to search for gamma
gamma production of the glueball candidates f0(1500) and fJ(1710) via their
decay to pi+pi-. No signal is observed and upper limits to the product of gamma
gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have
been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) <
0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV
at 95% confidence level.Comment: 10 pages, 3 figure
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