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Time-series characteristics of UK commercial property returns: testing for multiple changes in persistence
The random-walk hypothesis, vis-Ă -vis asset prices , suggests that prices traded in a market cannot be predicted based on historical information. Employing unsecuritised UK commercial property returns, we analyze this hypothesis, investigating multiple changes in persistence in the series . Our results uncover multiple changes in persistence in both the aggregate and sector-specific data. We highlight some implications for academics, practitioners and regulators
Multiple changes in persistence vs. explosive behaviour: the Dotcom bubble
Based on a method developed by Leybourne, Kim and Taylor (2007) for detecting multiple changes in persistence, we test for changes in persistence in the dividend-price ratio of the NASDAQ stocks. The results confirm the existence of the so-called Dotcom bubble around the last turn of the century and its start and end dates. Furthermore, we compare the results with a test for detecting and date-stamping explosive unit-root behaviour developed by Phillips, Wu and Yu's (2011) also applied to the NASDAQ price and dividend indices. We find that Leybourne, Kim and Taylor's test is capable of detecting the Dotcom bubble as much as Phillips, Wu and Yu's test is, but there are significant differences between the bubble start and end dates suggested by both methods and between these and the dates reported by the financial media. We also find an unexpected negative bubble extending from the beginning of the 1970s to the beginning of the 1990s where the NASDAQ stock prices were below their fundamental values as indicated by their dividend yields, which has not been reported in the literature so far
Bell inequality violation by entangled single photon states generated from a laser, a LED or a Halogen lamp
In single-particle or intraparticle entanglement, two degrees of freedom of a
single particle, e.g., momentum and polarization of a single photon, are
entangled. Single-particle entanglement (SPE) provides a source of non
classical correlations which can be exploited both in quantum communication
protocols and in experimental tests of noncontextuality based on the
Kochen-Specker theorem. Furthermore, SPE is robust under decoherence phenomena.
Here, we show that single-particle entangled states of single photons can be
produced from attenuated sources of light, even classical ones. To
experimentally certify the entanglement, we perform a Bell test, observing a
violation of the Clauser, Horne, Shimony and Holt (CHSH) inequality. On the one
hand, we show that this entanglement can be achieved even in a classical light
beam, provided that first-order coherence is maintained between the degrees of
freedom involved in the entanglement. On the other hand, we prove that filtered
and attenuated light sources provide a flux of independent SPE photons that,
from a statistical point of view, are indistinguishable from those generated by
a single photon source. This has important consequences, since it demonstrates
that cheap, compact, and low power entangled photon sources can be used for a
range of quantum technology applications
Blood and sputum biomarkers in COPD and asthma: a review
Chronic obstructive pulmonary disease (COPD) and asthma are lung inflammatory diseases that represent major public health problems. The primary, and often unique, method to evaluate lung function is spirometry, which reflects disease severity rather than disease activity. Moreover, its measurements strictly depend on patient's compliance, physician's expertise and data interpretation. The limitations of clinical history and pulmonary function tests have encouraged focusing on new possible tracers of diseases. The increase of the inflammatory response in the lungs represents an early pathological event, so biological markers related to inflammation may play key roles in earlier diagnosis, evaluation of functional impairment and prognosis. Biomarkers are measurable indicators associated with the presence and/or severity of a biological or pathogenic process, which may predict functional impairment, prognosis and response to therapy. The traditional approach based on invasive techniques (bronchoalveolar lavage and biopsies) may be replaced, at least in part, by using less invasive methods to collect specimens (sputum and blood), in which biomarkers could be measured. Proteomics, by the association between different protein profiles and pathogenic processes, is gaining an important role in pulmonary medicine allowing a more precise discrimination between patients with different outcomes and response to therapy. The aim of this review was to evaluate the use of biomarkers of airway inflammation in the context of both research and clinical practice
Detection of Contact Binaries Using Sparse High Phase Angle Lightcurves
We show that candidate contact binary asteroids can be efficiently identified
from sparsely sampled photometry taken at phase angles >60deg. At high phase
angle, close/contact binary systems produce distinctive lightcurves that spend
most of the time at maximum or minimum (typically >1mag apart) brightness with
relatively fast transitions between the two. This means that a few (~5) sparse
observations will suffice to measure the large range of variation and identify
candidate contact binary systems. This finding can be used in the context of
all-sky surveys to constrain the fraction of contact binary near-Earth objects.
High phase angle lightcurve data can also reveal the absolute sense of the
spin.Comment: 4 pages, 4 figures, 1 table. Accepted for publication in ApJ
Degeneration and regeneration of peripheral nerves: role of thrombin and its receptor PAR-1
The peripheral nervous system has a striking regeneration potential and after damage extensive changes in the differentiation state both of the injured neurons and of the Schwann cells are observed. Schwann cells, in particular, undergo a large scale change in gene expression becoming able to support axonal regeneration. Nerve injury is generally associated to inflammation and activation of the coagulation cascade. Thrombin acts as a polyfunctional signalling molecule exerting its physiological function through soluble target proteins and G-protein-coupled receptors, the protease-activated receptors (PARs) [1]. Recently, we have demonstrated that the activation of the main thrombin receptor, PAR-1, in Schwann cells favours their regenerative potential determining the release of factors which promote axonal regrowth [2]. The pro-regenerative potential of thrombin seems to be exerted in a narrow range of concentrations (pM-nM range). In fact, our preliminary data indicate that high levels of thrombin in the micromolar range slow down Schwann cell proliferation and induce cell death. On the contrary, PAR-1 activating peptides mimic the pro-survival but not the pro-apoptotic effects of thrombin. Controlling thrombin concentration may preserve neuronal health during nerve injury and represent a novel target for pharmacologic therapies
CAOS spectroscopy of Am stars Kepler targets
The {\it Kepler} space mission and its {\it K2} extension provide photometric
time series data with unprecedented accuracy. These data challenge our current
understanding of the metallic-lined A stars (Am stars) for what concerns the
onset of pulsations in their atmospheres. It turns out that the predictions of
current diffusion models do not agree with observations. To understand this
discrepancy, it is of crucial importance to obtain ground-based spectroscopic
observations of Am stars in the {\it Kepler} and {\it K2} fields in order to
determine the best estimates of the stellar parameters.
In this paper, we present a detailed analysis of high-resolution
spectroscopic data for seven stars previously classified as Am stars. We
determine the effective temperatures, surface gravities, projected rotational
velocities, microturbulent velocities and chemical abundances of these stars
using spectral synthesis. These spectra were obtained with {\it CAOS}, a new
instrument recently installed at the observing station of the Catania
Astrophysical Observatory on Mt. Etna. Three stars have already been observed
during quarters Q0-Q17, namely: HD\,180347, HD\,181206, and HD\,185658, while
HD\,43509 was already observed during {\it K2} C0 campaign.
We confirm that HD\,43509 and HD\,180347 are Am stars, while HD 52403,
HD\,50766, HD\,58246, HD\,181206 and HD\,185658 are marginal Am stars. By means
of non-LTE analysis, we derived oxygen abundances from O{\sc
I}7771--5{\AA} triplet and we also discussed the results obtained with
both non-LTE and LTE approaches.Comment: accepted in MNRAS main journal 13 pages, 11 figures, 3 tables. arXiv
admin note: text overlap with arXiv:1404.095
Complexity transitions in global algorithms for sparse linear systems over finite fields
We study the computational complexity of a very basic problem, namely that of
finding solutions to a very large set of random linear equations in a finite
Galois Field modulo q. Using tools from statistical mechanics we are able to
identify phase transitions in the structure of the solution space and to
connect them to changes in performance of a global algorithm, namely Gaussian
elimination. Crossing phase boundaries produces a dramatic increase in memory
and CPU requirements necessary to the algorithms. In turn, this causes the
saturation of the upper bounds for the running time. We illustrate the results
on the specific problem of integer factorization, which is of central interest
for deciphering messages encrypted with the RSA cryptosystem.Comment: 23 pages, 8 figure
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