768 research outputs found
Approximating electronically excited states with equation-of-motion linear coupled-cluster theory
A new perturbative approach to canonical equation-of-motion coupled-cluster
theory is presented using coupled-cluster perturbation theory. A second-order
M{\o}ller-Plesset partitioning of the Hamiltonian is used to obtain the well
known equation-of-motion many-body perturbation theory (EOM-MBPT(2)) equations
and two new equation-of-motion methods based on the linear coupled-cluster
doubles (EOM-LCCD) and linear coupled-cluster singles and doubles (EOM-LCCSD)
wavefunctions. This is achieved by performing a short-circuiting procedure on
the MBPT(2) similarity transformed Hamiltonian. These new methods are
benchmarked against very accurate theoretical and experimental spectra from 25
small organic molecules. It is found that the proposed methods have excellent
agreement with canonical EOM-CCSD state for state orderings and relative
excited state energies as well as acceptable quantitative agreement for
absolute excitation energies compared with the best estimate theory and
experimental spectra.Comment: 9 pages 3 figure
STUDY AND MECHANICAL TESTING OF FIBER REINFORCED PLASTIC LAMINATE AND CARBON FIBER LAMINATE COMPOSITE
The use of composite materials at industrial and domestic levels is increasing day by day, due to which the work in the direction of enhancing its mechanical property is being on a fast pace. In this study, the mechanical properties of Polyester resin and Carbon Fibre Composite were analyzed experimentally. Tensile and Compressive strength of the specimen were determined and compared. It was found both laminates together provides a positive impact in the enhancement of mechanical properties of the composite
Efficient Photon Coupling from a Diamond Nitrogen Vacancy Centre by Integration with Silica Fibre
A central goal in quantum information science is to efficiently interface
photons with single optical modes for quantum networking and distributed
quantum computing. Here, we introduce and experimentally demonstrate a compact
and efficient method for the low-loss coupling of a solid-state qubit, the
nitrogen vacancy (NV) centre in diamond, with a single-mode optical fibre. In
this approach, single-mode tapered diamond waveguides containing exactly one
high quality NV memory are selected and integrated on tapered silica fibres.
Numerical optimization of an adiabatic coupler indicates that
near-unity-efficiency photon transfer is possible between the two modes.
Experimentally, we find an overall collection efficiency between 18-40 % and
observe a raw single photon count rate above 700 kHz. This integrated system
enables robust, alignment-free, and efficient interfacing of single-mode
optical fibres with single photon emitters and quantum memories in solids
The Eye in the Neck: Removal of a Sewing Needle from the Posterior Pharyngeal Wall
Foreign body ingestion is a frequent presenting complaint to most emergency departments but the finding of a sewing needle in the posterior pharynx particularly is a rare finding. We report a case of a male patient with a sewing needle lodged in the posterior pharynx despite a history suggestive of chicken bone ingestion, absent clinical features, and negative flexible endoscopic examination. The needle was only identified through cervical spine radiographs. Even subsequent pharyngoscopy, laryngoscopy, and upper oesophagoscopy all proved to be unremarkable with the patient eventually requiring a left neck exploration to remove the needle. The case outlines the importance of simple radiography in suspected foreign body ingestion, even though clinical and endoscopic findings may be unremarkable
Cosmic (super)string constraints from 21 cm radiation
We calculate the contribution of cosmic strings arising from a phase
transition in the early universe, or cosmic superstrings arising from brane
inflation, to the cosmic 21 cm power spectrum at redshifts z > 30. Future
experiments can exploit this effect to constrain the cosmic string tension Gu
and probe virtually the entire brane inflation model space allowed by current
observations. Although current experiments with a collecting area of ~ 1 km^2
will not provide any useful constraints, future experiments with a collecting
area of 10^4-10^6 km^2 covering the cleanest 10% of the sky can in principle
constrain cosmic strings with tension Gu > 10^(-10) to 10^(-12)
(superstring/phase transition mass scale >10^13 GeV).Comment: Accepted for publication in PR
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