772 research outputs found

### Effectiveness of management strategies for uninvestigated dyspepsia: systematic review and network meta-analysis

Objective To determine the effectiveness of management strategies for uninvestigated dyspepsia.
Design Systematic review and network meta-analysis.
Data sources Medline, Embase, Embase Classic, the Cochrane Central Register of Controlled Trials, and clinicaltrials.gov from inception to September 2019, with no language restrictions. Conference proceedings between 2001 and 2019.
Eligibility criteria for selecting studies Randomised controlled trials that assessed the effectiveness of management strategies for uninvestigated dyspepsia in adult participants (age ≥18 years). Strategies of interest were prompt endoscopy; test for Helicobacter pylori and perform endoscopy in participants who test positive; test for H pylori and eradication treatment in those who test positive (“test and treat”); empirical acid suppression; or symptom based management. Trials reported dichotomous assessment of symptom status at final follow-up (≥12 months).
Results The review identified 15 eligible randomised controlled trials that comprised 6162 adult participants. Data were pooled using a random effects model. Strategies were ranked according to P score, which is the mean extent of certainty that one management strategy is better than another, averaged over all competing strategies. “Test and treat” ranked first (relative risk of remaining symptomatic 0.89, 95% confidence interval 0.78 to 1.02, P score 0.79) and prompt endoscopy ranked second, but performed similarly (0.90, 0.80 to 1.02, P score 0.71). However, no strategy was significantly less effective than “test and treat.” Participants assigned to “test and treat” were significantly less likely to receive endoscopy (relative risk v prompt endoscopy 0.23, 95% confidence interval 0.17 to 0.31, P score 0.98) than all other strategies, except symptom based management (relative risk v symptom based management 0.60, 0.30 to 1.18). Dissatisfaction with management was significantly lower with prompt endoscopy (P score 0.95) than with “test and treat” (relative risk v “test and treat” 0.67, 0.46 to 0.98), and empirical acid suppression (relative risk v empirical acid suppression 0.58, 0.37 to 0.91). Upper gastrointestinal cancer rates were low in all trials. Results remained stable in sensitivity analyses, with minimal inconsistencies between direct and indirect results. Risk of bias of individual trials was high; blinding was not possible because of the pragmatic trial design.
Conclusions “Test and treat” was ranked first, although it performed similarly to prompt endoscopy and was not superior to any of the other strategies. “Test and treat” led to fewer endoscopies than all other approaches, except symptom based management. However, participants showed a preference for prompt endoscopy as a management strategy for their symptoms.
Systematic review registration PROSPERO registration number CRD42019132528

### Hamilton-Jacobi Method and Gravitation

Studying the behaviour of a quantum field in a classical, curved, spacetime
is an extraordinary task which nobody is able to take on at present time.
Independently by the fact that such problem is not likely to be solved soon,
still we possess the instruments to perform exact predictions in special,
highly symmetric, conditions. Aim of the present contribution is to show how it
is possible to extract quantitative information about a variety of physical
phenomena in very general situations by virtue of the so-called Hamilton-Jacobi
method. In particular, we shall prove the agreement of such semi-classical
method with exact results of quantum field theoretic calculations.Comment: To appear in the proceedings of "Cosmology, the Quantum Vacuum, and
Zeta Functions": A workshop with a celebration of Emilio Elizalde's Sixtieth
birthday, Bellaterra, Barcelona, Spain, 8-10 Mar 201

### Safety and efficacy of antenatal milk expressing for women with diabetes in pregnancy: protocol for a randomised controlled trial

Many maternity providers recommend that women with diabetes in pregnancy express and store breast milk in late pregnancy so breast milk is available after birth, given (1) infants of these women are at increased risk of hypoglycaemia in the first 24 h of life; and (2) the delay in lactogenesis II compared with women without diabetes that increases their infant\u27s risk of receiving infant formula. The Diabetes and Antenatal Milk Expressing (DAME) trial will establish whether advising women with diabetes in pregnancy (pre-existing or gestational) to express breast milk from 36 weeks gestation increases the proportion of infants who require admission to special or neonatal intensive care units (SCN/NICU) compared with infants of women receiving standard care. Secondary outcomes include birth gestation, breastfeeding outcomes and economic impact

### Open Problems on Central Simple Algebras

We provide a survey of past research and a list of open problems regarding
central simple algebras and the Brauer group over a field, intended both for
experts and for beginners.Comment: v2 has some small revisions to the text. Some items are re-numbered,
compared to v

### Classical and semi-classical energy conditions

The standard energy conditions of classical general relativity are (mostly)
linear in the stress-energy tensor, and have clear physical interpretations in
terms of geodesic focussing, but suffer the significant drawback that they are
often violated by semi-classical quantum effects. In contrast, it is possible
to develop non-standard energy conditions that are intrinsically non-linear in
the stress-energy tensor, and which exhibit much better well-controlled
behaviour when semi-classical quantum effects are introduced, at the cost of a
less direct applicability to geodesic focussing. In this article we will first
review the standard energy conditions and their various limitations. (Including
the connection to the Hawking--Ellis type I, II, III, and IV classification of
stress-energy tensors). We shall then turn to the averaged, nonlinear, and
semi-classical energy conditions, and see how much can be done once
semi-classical quantum effects are included.Comment: V1: 25 pages. Draft chapter, on which the related chapter of the book
"Wormholes, Warp Drives and Energy Conditions" (to be published by Springer),
will be based. V2: typos fixed. V3: small typo fixe

### Electronic health records to facilitate clinical research

Electronic health records (EHRs) provide opportunities to enhance patient care, embed performance measures in clinical practice, and facilitate clinical research. Concerns have been raised about the increasing recruitment challenges in trials, burdensome and obtrusive data collection, and uncertain generalizability of the results. Leveraging electronic health records to counterbalance these trends is an area of intense interest. The initial applications of electronic health records, as the primary data source is envisioned for observational studies, embedded pragmatic or post-marketing registry-based randomized studies, or comparative effectiveness studies. Advancing this approach to randomized clinical trials, electronic health records may potentially be used to assess study feasibility, to facilitate patient recruitment, and streamline data collection at baseline and follow-up. Ensuring data security and privacy, overcoming the challenges associated with linking diverse systems and maintaining infrastructure for repeat use of high quality data, are some of the challenges associated with using electronic health records in clinical research. Collaboration between academia, industry, regulatory bodies, policy makers, patients, and electronic health record vendors is critical for the greater use of electronic health records in clinical research. This manuscript identifies the key steps required to advance the role of electronic health records in cardiovascular clinical research

### The holographic principle

There is strong evidence that the area of any surface limits the information
content of adjacent spacetime regions, at 10^(69) bits per square meter. We
review the developments that have led to the recognition of this entropy bound,
placing special emphasis on the quantum properties of black holes. The
construction of light-sheets, which associate relevant spacetime regions to any
given surface, is discussed in detail. We explain how the bound is tested and
demonstrate its validity in a wide range of examples.
A universal relation between geometry and information is thus uncovered. It
has yet to be explained. The holographic principle asserts that its origin must
lie in the number of fundamental degrees of freedom involved in a unified
description of spacetime and matter. It must be manifest in an underlying
quantum theory of gravity. We survey some successes and challenges in
implementing the holographic principle.Comment: 52 pages, 10 figures, invited review for Rev. Mod. Phys; v2:
reference adde

### Notes on Black Hole Fluctuations and Backreaction

In these notes we prepare the ground for a systematic investigation into the issues of black hole fluctuations and backreaction by discussing the formulation of the problem, commenting on possible advantages and shortcomings of existing works, and introducing our own approach via a stochastic semiclassical theory of gravity based on the Einstein-Langevin equation and the fluctuation-dissipation relation for a self-consistent description of metric fluctuations and dissipative dynamics of the black hole with backreaction of its Hawking radiance

### Energy inequalities in interacting quantum field theories

The classical energy conditions, originally motivated by the Penrose-Hawking
singularity theorems of general relativity, are violated by quantum fields. A
reminiscent notion of such conditions are the so called quantum energy
inequalities (QEIs), which are however not known to hold generally in quantum
field theory. Here we present first steps towards investigating QEIs in quantum
field theories with self-interaction.Comment: to appear in the proceedings of the conference "Progress and Visions
in Quantum Theory in View of Gravity - Bridging Foundations of Physics and
Mathematics", Leipzig 2018; 8 page

### On the Perturbative Stability of Quantum Field Theories in de Sitter Space

We use a field theoretic generalization of the Wigner-Weisskopf method to
study the stability of the Bunch-Davies vacuum state for a massless,
conformally coupled interacting test field in de Sitter space. We find that in
$\lambda \phi^4$ theory the vacuum does {\em not} decay, while in
non-conformally invariant models, the vacuum decays as a consequence of a
vacuum wave function renormalization that depends \emph{singularly} on
(conformal) time and is proportional to the spatial volume. In a particular
regularization scheme the vacuum wave function renormalization is the same as
in Minkowski spacetime, but in terms of the \emph{physical volume}, which leads
to an interpretation of the decay. A simple example of the impact of vacuum
decay upon a non-gaussian correlation is discussed. Single particle excitations
also decay into two particle states, leading to particle production that
hastens the exiting of modes from the de Sitter horizon resulting in the
production of \emph{entangled superhorizon pairs} with a population consistent
with unitary evolution. We find a non-perturbative, self-consistent "screening"
mechanism that shuts off vacuum decay asymptotically, leading to a stationary
vacuum state in a manner not unlike the approach to a fixed point in the space
of states.Comment: 36 pages, 4 figures. Version to appear in JHEP, more explanation

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