7,920 research outputs found
A stellar census of the nearby, young 32 Orionis group
The 32 Orionis group was discovered almost a decade ago and despite the fact
that it represents the first northern, young (age ~ 25 Myr) stellar aggregate
within 100 pc of the Sun ( pc), a comprehensive survey for members
and detailed characterisation of the group has yet to be performed. We present
the first large-scale spectroscopic survey for new (predominantly M-type)
members of the group after combining kinematic and photometric data to select
candidates with Galactic space motion and positions in colour-magnitude space
consistent with membership. We identify 30 new members, increasing the number
of known 32 Ori group members by a factor of three and bringing the total
number of identified members to 46, spanning spectral types B5 to L1. We also
identify the lithium depletion boundary (LDB) of the group, i.e. the luminosity
at which lithium remains unburnt in a coeval population. We estimate the age of
the 32 Ori group independently using both isochronal fitting and LDB analyses
and find it is essentially coeval with the {\beta} Pictoris moving group, with
an age of Myr. Finally, we have also searched for circumstellar disc
hosts utilising the AllWISE catalogue. Although we find no evidence for warm,
dusty discs, we identify several stars with excess emission in the WISE W4-band
at 22 {\mu}m. Based on the limited number of W4 detections we estimate a debris
disc fraction of per cent for the 32 Ori group.Comment: Accepted for publication in MNRAS; 24 pages, 17 figures and 10 table
Proposal to demonstrate the non-locality of Bohmian mechanics with entangled photons
Bohmian mechanics reproduces all statistical predictions of quantum
mechanics, which ensures that entanglement cannot be used for superluminal
signaling. However, individual Bohmian particles can experience superluminal
influences. We propose to illustrate this point using a double double-slit
setup with path-entangled photons. The Bohmian velocity field for one of the
photons can be measured using a recently demonstrated weak-measurement
technique. The found velocities strongly depend on the value of a phase shift
that is applied to the other photon, potentially at spacelike separation.Comment: 6 pages, 4 figure
Control of polymorphism in coronene by the application of magnetic fields
Coronene, a polyaromatic hydrocarbon, has been crystallized for the first
time in a different polymorph using a crystal growth method that utilizes
magnetic fields to access a unit cell configuration that was hitherto unknown.
Crystals grown in magnetic field of 1 T are larger, have a different appearance
to those grown in zero field and retain their structure in ambient conditions.
We identify the new form, beta-coronene, as the most stable at low
temperatures. As a result of the new supramolecular configuration we report
significantly altered electronic, optical and mechanical properties.Comment: 32 pages, 17 figure
Realisation of Hardy's Thought Experiment
We present an experimental realisation of Hardy's thought experiment [Phys.
Rev. Lett. {\bf 68}, 2981 (1992)], using photons. The experiment consists of a
pair of Mach-Zehnder interferometers that interact through photon bunching at a
beam splitter. A striking contradiction is created between the predictions of
quantum mechanics and local hidden variable based theories. The contradiction
relies on non-maximally entangled position states of two particles.Comment: 5 page
Toroidal Perturbations of Friedmann-Robertson-Walker Universes
Explicit expressions are found for the axisymmetric metric perturbations of
the closed, flat and open FRW universes caused by toroidal motions of the
cosmic fluid. The perturbations are decomposed in vector spherical harmonics on
2-spheres, but the radial dependence is left general. Solutions for general
odd-parity -pole perturbations are given for either angular velocities or
angular momenta prescribed. In particular, in case of closed universes the
solutions require a special treatment of the Legendre equation.Comment: 13 page
Polymorphism in cyclohexanol
The crystal structures and phase behaviour of phase II and the metastable phases III0 and III of cyclohexanol, C6H11OH,
have been determined using high-resolution neutron powder,
synchrotron X-ray powder and single-crystal X-ray diffraction techniques. Cyclohexanol-II is formed by a transition from the plastic phase I cubic structure at 265 K and crystallizes in a tetragonal structure, space group P�4421c (Z0 = 1), in which the molecules are arranged in a hydrogen-bonded tetrameric ring motif. The structures of phases III0 and III are monoclinic, space groups P21/c (Z0 = 3) and Pc (Z0 = 2), respectively, and are characterized by the formation of hydrogen-bonded molecular chains with a threefold-helical and wave-like nature, respectively. Phase III crystallizes at 195 K from a sample of phase I that is supercooled to ca 100 K. Alternatively, phase III may be grown via phase III0, the latter transforming from supercooled phase I at ca 200 K. Phase III0 is particularly unstable and is metastable with respect to both I and II. Its growth is realised only under very restricted conditions, thus making its characterization especially
challenging. The cyclohexanol molecules adopt a chair
conformation in all three phases with the hydroxyl groups in
an equatorial orientation. No evidence was found indicating
hydroxyl groups adopting an axial orientation, contrary to the majority of spectroscopic literature on solid-state cyclohexanol; however, the H atom of the equatorial OH groups is found to adopt both in-plane and out-of-plane orientations
CNS tuberculosis and stroke, burden, management challenges and future needs for care and research
An estimated 10 million cases of Tuberculosis (TB) and 1.6 million deaths due to this disease occurred worldwide in 2017 (1). About 1.7 billion people, 23% of the world’s population are estimated to have latent TB infection and are thus at risk of developing active TB disease during their life time. TB is mostly common in developing countries and Pakistan ranks 5th among 30 high-burden countries and 5th for Drug Resistant TB (DRTB). The incidence of TB in Pakistan is 267 per 100,000 (1) with an estimated 525,000 cases in 2017 including 57,000 cases among those who were less than 15 years of age
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