705 research outputs found
Semiclassical approach to black hole absorption of electromagnetic radiation emitted by a rotating charge
We consider an electric charge, minimally coupled to the Maxwell field,
rotating around a Schwarzschild black hole. We investigate how much of the
radiation emitted from the swirling charge is absorbed by the black hole and
show that most of the photons escape to infinity. For this purpose we use the
Gupta-Bleuler quantization of the electromagnetic field in the modified Feynman
gauge developed in the context of quantum field theory in Schwarzschild
spacetime. We obtain that the two photon polarizations contribute quite
differently to the emitted power. In addition, we discuss the accurateness of
the results obtained in a full general relativistic approach in comparison with
the ones obtained when the electric charge is assumed to be orbiting a massive
object due to a Newtonian force.Comment: 8 pages (revtex), 8 figure
Aging effect on the integrity of the traditional portuguese timber roof structures
Traditional buildings basically include natural and autochthonous construction materials and are built
with sustainable construction techniques. The knowledge of these materials’s state and construction
techniques is required for a proper conservation/renovation work. It is well known that the lack of
maintenance is one of the main causes that contribute to the high degree of degradation that the
Portuguese traditional buildings unfortunately have. That degradation may even compromise the
overall structural integrity of the building thus reducing its lifetime`s expectation. Meanwhile, a
partial or even full demolition of a building is still an often occurrence in the Portuguese context.
From a sustainable and building heritage perspectives that practise may be inadequate. Taking into
account that generally the degradation problems are linked with roof`s leaking anomalies and that the
structural components of the roof tend to be the first ones to be affected, this timber structural roof
components of Portuguese dwellings were the object of the research work here presented
A COMPARATIVE MULTI-TECHNIQUE INVESTIGATION ON MATERIAL IDENTIFICATION OF GILDING LAYERS AND THE CONSERVATION STATE OF 7 PORTUGUESE MANNERIST ALTARPIECES
This paper deals with the multi-analytical comparative characterization of 59 samples of
gilded and polychrome layers from 7 altarpieces studied during the Gilt-Teller project
(www.gilt-teller.pt). The altarpieces studied here belong to seven churches in the areas of
Lisbon, Santarém, Portalegre and Guarda and display stylistic and constructive features
characteristic to the Mannerism carved wood decoration in Portugal. The applied protocol of
investigation characterized the structure and manufacture technique of gilding; identified the
chemical composition of the layers constituting the gilded polychrome decoration; compared
the materials and gilding techniques encountered in the 7 altarpieces and assessed the
conservation state of each altarpiece. The analytical techniques applied to these purposes
were: stereomicroscopy (SM), optical microscopy (OM), scanning electron microscopy
coupled with energy dispersive X-ray spectrometry (SEM-EDX), X-ray diffraction (XRD),
MALDI-TOF mass spectrometry, μRaman and μFTIR/imaging μFTIR spectroscopies. This
interdisciplinary multi-scale approach was used to elucidate the aspects related to the material
and technical aspects of “talha dourada” decoration, answering to these questions: which are
the original materials and layers in the making of the polychromy and which are the ones
added with posterior interventions; which are the relationships between gilding materials and
techniques, regarding the degree of erudition of each case study; which were the main causes
of degradation and influence to their conservation condition
Relationship between time from symptom''s onset to diagnosis and prognosis in patients with symptomatic colorectal cancer
BACKGROUND: Controversy exists regarding the relationship of the outcome of patients with colorectal cancer (CRC) with the time from symptom onset to diagnosis. The aim of this study is to investigate this association, with the assumption that this relationship was nonlinear and with adjustment for multiple confounders, such as tumor grade, symptoms, or admission to an emergency department. METHODS: This multicenter study with prospective follow-up was performed in five regions of Spain from 2010 to 2012. Symptomatic cases of incident CRC from a previous study were examined. At the time of diagnosis, each patient was interviewed, and the associated hospital and clinical records were reviewed. During follow-up, the clinical records were reviewed again to assess survival. Cox survival analysis with a restricted cubic spline was used to model overall and CRC-specific survival, with adjustment for variables related to the patient, health service, and tumor. RESULTS: A total of 795 patients had symptomatic CRC and 769 of them had complete data on diagnostic delay and survival. Univariate analysis indicated a lower HR for death in patients who had diagnostic intervals less than 4.2 months. However, after adjustment for variables related to the patient, tumor, and utilized health service, there was no relationship of the diagnostic delay with survival of patients with colon and rectal cancer, colon cancer alone, or rectal cancer alone. Cubic spline analysis indicated an inverse association of the diagnostic delay with 5-year survival. However, this association was not statistically significant. CONCLUSIONS: Our results indicated that the duration of diagnostic delay had no significant effect on the outcome of patients with CRC. We suggest that the most important determinant of the duration of diagnostic delay is the biological profile of the tumor. However, it remains the responsibility of community health centers and authorities to minimize diagnostic delays in patients with CRC and to implement initiatives that improve early diagnosis and provide better outcomes. © 2022. The Author(s)
Characterising the Performance of XOR Games and the Shannon Capacity of Graphs
In this paper we give a set of necessary and sufficient conditions such that
quantum players of a two-party {\sc xor} game cannot perform any better than
classical players. With any such game, we associate a graph and examine its
zero-error communication capacity. This allows us to specify a broad new class
of graphs for which the Shannon capacity can be calculated. The conditions also
enable the parametrisation of new families of games which have no quantum
advantage, for arbitrary input probability distributions up to certain
symmetries. In the future, these might be used in information-theoretic studies
on reproducing the set of quantum non-local correlations.Comment: 5 pages. Clarified proof of theorem 1, typos correcte
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