87 research outputs found
Hartle-Hawking boundary conditions as Nucleation by de Sitter Vacuum
It is shown that, for a de Sitter Universe, the Hartle-Hawking (HH) wave
function can be obtained in a simple way starting from the
Friedmann-Lemaitre-Robertson-Walker (FLRW) line element of cosmological
equations. An oscillator having imaginary time is indeed derived starting from
the Hamiltonian obtaining the HH condition. This proposes again some crucial
matter on the meaning of complex time in cosmology. In order to overcome such
difficulties, we propose an interpretation of the HH framework based on de
Sitter Projective Holography.Comment: 23 pages, 2 figures, accepted for publication in Physics of the Dark
Univers
On the quantization of the extremal Reissner-Nordstrom black hole
Following Rosen's quantization rules, two of the Authors (CC and FF) recently
described the Schwarzschild black hole (BH) formed after the gravitational
collapse of a pressureless "star of dust" in terms of a "gravitational hydrogen
atom". Here we generalize this approach to the gravitational collapse of a
charged object, namely, to the geometry of a Reissner-Nordstrom BH (RNBH) and
calculate the gravitational potential, the Schr\"odinger equation and the exact
solutions of the energy levels of the gravitational collapse. By using the
concept of BH effective state, previously introduced by one of us (CC), we
describe the quantum gravitational potential, the mass spectrum and the energy
spectrum for the extremal RNBH. The area spectrum derived from the mass
spectrum finds agreement with a previous result by Bekenstein. The stability of
these solutions, described with the Majorana approach to the Archaic Universe
scenario, show the existence of oscillatory regimes or exponential damping for
the evolution of a small perturbation from a stable state.Comment: 7 pages, to appear in Europhysics Letter
Chemotherapy-Response Monitoring of Breast Cancer Patients Using Quantitative Ultrasound-Based Intra-Tumour Heterogeneities
© 2017 The Author(s). Anti-cancer therapies including chemotherapy aim to induce tumour cell death. Cell death introduces alterations in cell morphology and tissue micro-structures that cause measurable changes in tissue echogenicity. This study investigated the effectiveness of quantitative ultrasound (QUS) parametric imaging to characterize intra-tumour heterogeneity and monitor the pathological response of breast cancer to chemotherapy in a large cohort of patients (n = 100). Results demonstrated that QUS imaging can non-invasively monitor pathological response and outcome of breast cancer patients to chemotherapy early following treatment initiation. Specifically, QUS biomarkers quantifying spatial heterogeneities in size, concentration and spacing of acoustic scatterers could predict treatment responses of patients with cross-validated accuracies of 82 ± 0.7%, 86 ± 0.7% and 85 ± 0.9% and areas under the receiver operating characteristic (ROC) curve of 0.75 ± 0.1, 0.80 ± 0.1 and 0.89 ± 0.1 at 1, 4 and 8 weeks after the start of treatment, respectively. The patients classified as responders and non-responders using QUS biomarkers demonstrated significantly different survivals, in good agreement with clinical and pathological endpoints. The results form a basis for using early predictive information on survival-linked patient response to facilitate adapting standard anti-cancer treatments on an individual patient basis
Quantum oscillations in the black hole horizon
By applying Rosen's quantization approach to the historical Oppenheimer and
Snyder gravitational collapse and by setting the constraints for the formation
of the Schwarzschild black hole (SBH), in a previous paper [1] two of the
Authors (CC and FF) found the gravitational potential, the Schrodinger
equation, the solution for the energy levels, the area quantum and the quantum
representation of the ground state at the Planck scale of the SBH. Such results
are consistent with previous ones in the literature. It was also shown that the
traditional classical singularity in the core of the SBH is replaced by a
quantum oscillator describing a non-singular two-particle system where the two
components, named the "nucleus" and the "electron", strongly interact with each
other through a quantum gravitational interaction. In agreement with the de
Broglie hypothesis, the "electron" is interpreted in terms of the quantum
oscillations of the BH horizon. In other words, the SBH should be the
gravitational analogous of the hydrogen atom. In this paper, it is shown that
these results allow us to compute the SBH entropy as a function of the BH
principal quantum number in terms of Bekenstein-Hawking entropy and three
sub-leading corrections. In addition, the coefficient of the formula of
Bekenstein-Hawking entropy is reduced to a quarter of the traditional value.
Then, it is shown that, by performing a correct rescaling of the energy levels,
the semi-classical Bohr-like approach to BH quantum physics, previously
developed by one of the Authors (CC), is consistent with the obtained results
for large values of the BH principal quantum number. After this, Hawking
radiation will be analysed by discussing its connection with the BH quantum
structure. Finally, it is shown that the time evolution of the above mentioned
system solves the BH information paradox.Comment: 29 pages.Comments are welcome. arXiv admin note: text overlap with
arXiv:1912.0647
Self-medication of migraine and tension-type headache: summary of the evidence-based recommendations of the Deutsche Migräne und Kopfschmerzgesellschaft (DMKG), the Deutsche Gesellschaft für Neurologie (DGN), the Österreichische Kopfschmerzgesellschaft (ÖKSG) and the Schweizerische Kopfwehgesellschaft (SKG)
The current evidence-based guideline on self-medication in migraine and tension-type headache of the German, Austrian and Swiss headache societies and the German Society of Neurology is addressed to physicians engaged in primary care as well as pharmacists and patients. The guideline is especially concerned with the description of the methodology used, the selection process of the literature used and which evidence the recommendations are based upon. The following recommendations about self-medication in migraine attacks can be made: The efficacy of the fixed-dose combination of acetaminophen, acetylsalicylic acid and caffeine and the monotherapies with ibuprofen or naratriptan or acetaminophen or phenazone are scientifically proven and recommended as first-line therapy. None of the substances used in self-medication in migraine prophylaxis can be seen as effective. Concerning the self-medication in tension-type headache, the following therapies can be recommended as first-line therapy: the fixed-dose combination of acetaminophen, acetylsalicylic acid and caffeine as well as the fixed combination of acetaminophen and caffeine as well as the monotherapies with ibuprofen or acetylsalicylic acid or diclofenac. The four scientific societies hope that this guideline will help to improve the treatment of headaches which largely is initiated by the patients themselves without any consultation with their physicians
Evaluation of appendicitis risk prediction models in adults with suspected appendicitis
Background
Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis.
Methods
A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis).
Results
Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent).
Conclusion
Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified
The PICTURE study -- prostate imaging (multi-parametric MRI and Prostate HistoScanning™) compared to transperineal ultrasound guided biopsy for significant prostate cancer risk evaluation.
OBJECTIVE: The primary objective of the PICTURE study is to assess the negative predictive value of multi-parametric MRI (mp-MRI) and Prostate HistoScanning™ (PHS) in ruling-out clinically significant prostate cancer. PATIENTS AND METHODS: PICTURE is a prospective diagnostic validating cohort study conforming to level 1 evidence. PICTURE will assess the diagnostic performance of multi-parametric Magnetic Resonance Imaging (mp-MRI) and Prostate HistoScanning™ (PHS) ultrasound. PICTURE will involve validating both index tests against a reference test, transperineal Template Prostate Mapping (TPM) biopsies, which can be applied in all men under evaluation. Men will be blinded to the index test results and both index tests will be reported prospectively prior to the biopsies being taken to ensure reporter blinding. Paired analysis of each of the index tests to the reference test will be done at patient level. Those men with an imaging lesion will undergo targeted biopsies to assess the clinical utility of sampling only suspicious areas. The study is powered to assess the negative predictive value of these imaging modalities in ruling-out clinically significant prostate cancer. DISCUSSION: The PICTURE study aims to assess the performance characteristics of two imaging modalities (mp-MRI and Prostate HistoScanning) for their utility in the prostate cancer pathway. PICTURE aims to identify if either imaging test may be useful for ruling out clinically significant disease in men under investigation, and also to examine if either imaging modality is useful for the detection of disease. Recruitment is underway and expected to complete in 2014
Constraining the generalized uncertainty principle with neutron interferometry
The non-zero minimal length arises in various theories of gravity, leading to the so-called generalized uncertainty principle (GUP). In this short paper we analyze the GUP effects on neutron interferometry, showing that the obtained phase shifts depend on the mass and velocity of the particle. New upper bounds on the dimensionless GUP parameter have been found that are in agreement with the literature
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