198 research outputs found
Stability of Oscillating Gaseous Masses in Massive Brans-Dicke Gravity
This paper explores the instability of gaseous masses for the radial
oscillations in post-Newtonian correction of massive Brans-Dicke gravity. For
this purpose, we derive linearized perturbed equation of motion through
Lagrangian radial perturbation which leads to the condition of marginal
stability. We discuss radius of instability of different polytropic structures
in terms of the Schwarzschild radius. It is concluded that our results provide
a wide range of difference with those in general relativity and Brans-Dicke
gravity.Comment: 31 pages, 11 figures, to appear in IJMP
Rare Earth Doped Ceria: The Complex Connection Between Structure and Properties
The need for high efficiency energy production, conversion, storage and transport is serving as a robust guide for the development of new materials. Materials with physical-chemical properties matching specific functions in devices are produced by suitably tuning the crystallographic- defect- and micro-structure of the involved phases. In this review, we discuss the case of Rare Earth doped Ceria. Due to their high oxygen diffusion coefficient at temperatures higher than ~500°C, they are very promising materials for several applications such as electrolytes for Solid Oxide Fuel and Electrolytic Cells (SOFC and SOEC, respectively). Defects are integral part of the conduction process, hence of the final application. As the fluorite structure of ceria is capable of accommodating a high concentration of lattice defects, the characterization and comprehension of such complex and highly defective materials involve expertise spanning from computational chemistry, physical chemistry, catalysis, electrochemistry, microscopy, spectroscopy, and crystallography. Results coming from different experimental and computational techniques will be reviewed, showing that structure determination (at different scale length) plays a pivotal role bridging theoretical calculation and physical properties of these complex materials
Advanced modeling of materials with PAOFLOW 2.0:New features and software design
Recent research in materials science opens exciting perspectives to design novel quantum materials and devices, but it calls for quantitative predictions of properties which are not accessible in standard first principles packages. PAOFLOW, is a software tool that constructs tight-binding Hamiltonians from self consistent electronic wavefunctions by projecting onto a set of atomic orbitals. The electronic structure provides numerous materials properties that otherwise would have to be calculated via phenomenological models. In this paper, we describe recent re-design of the code as well as the new features and improvements in performance. In particular, we have implemented symmetry operations for unfolding equivalent k-points, which drastically reduces the runtime requirements of first principles calculations, and we have provided internal routines of projections onto atomic orbitals enabling generation of real space atomic orbitals. Moreover, we have included models for non-constant relaxation time in electronic transport calculations, doubling the real space dimensions of the Hamiltonian as well as the construction of Hamiltonians directly from analytical models. Importantly, PAOFLOW has been now converted into a Python package, and is streamlined for use directly within other Python codes. The new object oriented design treats PAOFLOW's computational routines as class methods, providing an API for explicit control of each calculation.</p
WSES classification and guidelines for liver trauma
The severity of liver injuries has been universally classified according to the American Association for the Surgery of Trauma (AAST) grading scale. In determining the optimal treatment strategy, however, the haemodynamic status and associated injuries should be considered. Thus the management of liver trauma is ultimately based on the anatomy of the injury and the physiology of the patient. This paper presents the World Society of Emergency Surgery (WSES) classification of liver trauma and the management Guidelines
Timing of Early Cholecystectomy for Acute Calculous Cholecystitis: A Multicentric Prospective Observational Study
The definition of Early Cholecystectomy (EC) is still debatable. This paper aims to find whether the timing of EC affects outcomes. The article reports a multicentric prospective observational study including patients with acute calculous cholecystitis (ACC) who had cholecystectomy within ten days from the onset of symptoms. Kruskall-Wallis test, Fisher’s Exact test, and Spearman rank correlation were used for statistical analysis. The patients were divided into three groups depending on the timing of the operation: 0–3 days, 4–7 days, or 8–10 days from the onset of symptoms. 1117 patients were studied over a year. The time from the onset of symptoms to EC did not affect the post-operative complications and mortality, the conversion, and the reintervention rate. The time represented a significant risk factor for intraoperative complications (0–3 days, 2.8%; 4–7 days, 5.6%; 8–10 days, 7.9%; p = 0.01) and subtotal cholecystectomies (0–3 days, 2.7%; 4–7 days, 5.6%; 8–10 days, 10.9%; p < 0.001). ACC is an evolutive inflammatory process and, as the days go by, the local and systemic inflammation increases, making surgery more complex and difficult with a higher risk of intraoperative complications. We recommend performing EC for ACC as soon as possible, within the first ten days of the onset of symptoms
Unraveling the degradation mechanism in FIrpic based Blue OLEDs: II. Trap and detect molecules at the interfaces
The impact of organic light emitting diodes (OLEDs) in modern life is
witnessed by their wide employment in full-color, energy-saving, flat panel
displays and smart-screens; a bright future is likewise expected in the field
of solid state lighting. Cyclometalated iridium complexes are the most used
phosphorescent emitters in OLEDs due to their widely tunable photophysical
properties and their versatile synthesis. Blue-emitting OLEDs, suffer from
intrinsic instability issues hampering their long term stability. Backed by
computational studies, in this work we studied the sky-blue emitter FIrpic in
both ex-situ and in-situ degradation experiments combining complementary,
mutually independent, experiments including chemical metathesis reactions, in
liquid phase and solid state, thermal and spectroscopic studies and LC-MS
investigations. We developed a straightforward protocol to evaluate the
degradation pathways in iridium complexes, finding that FIrpic degrades through
the loss of the picolinate ancillary ligand. The resulting iridium fragment was
than efficiently trapped "in-situ" as BPhen derivative 1. This process is found
to be well mirrored when a suitably engineered, FIrpic-based, OLED is operated
and aged. In this paper we (i) describe how it is possible to effectively study
OLED materials with a small set of readily accessible experiments and (ii)
evidence the central role of host matrix in trapping experiments.Comment: 13 pages, 6 figure
Distributing load flow computations across system operators boundaries using the Newton–Krylov–Schwarz algorithm implemented in PETSC
The upward trends in renewable energy penetration, cross-border flow volatility and electricity actors’ proliferation pose new challenges in the power system management. Electricity and market operators need to increase collaboration, also in terms of more frequent and detailed system analyses, so as to ensure adequate levels of quality and security of supply. This work proposes a novel distributed load flow solver enabling for better cross border flow analysis and fulfilling possible data ownership and confidentiality arrangements in place among the actors. The model exploits an Inexact Newton Method, the Newton–Krylov–Schwarz method, available in the portable, extensible toolkit for scientific computation (PETSc) libraries. A case-study illustrates a real application of the model for the TSO–TSO (transmission system operator) cross-border operation, analyzing the specific policy context and proposing a test case for a coordinated power flow simulation. The results show the feasibility of performing the distributed calculation remotely, keeping the overall simulation times only a few times slower than locally
IROA: the International Register of Open Abdomen.
Actually the most common indications for Open Abdomen (OA) are trauma, abdominal sepsis, severe acute pancreatitis and more in general all those situations in which an intra-abdominal hypertension condition is present, in order to prevent the development of an abdominal compartment syndrome. The mortality and morbidity rate in patients undergone to OA procedures is still high. At present many studies have been published about the OA management and the progresses in survival rate of critically ill trauma and septic surgical patients. However several issues are still unclear and need more extensive studies. The definitions of indications, applications and methods to close the OA are still matter of debate. To overcome this lack of high level of evidence data about the OA indications, management, definitive closure and follow-up, the World Society of Emergency Surgery (WSES) promoted the International Register of Open Abdomen (IROA). The register will be held on a web platform (Clinical Registers®) through a dedicated web site: www.clinicalregisters.org. This will allow to all surgeons and physicians to participate from all around the world only by having a computer and a web connection. The IROA protocol has been approved by the coordinating center Ethical Committee (Papa Giovanni XXIII hospital, Bergamo, Italy). IROA has also been registered to ClinicalTrials.gov (ClinicalTrials.gov Identifier: NCT02382770)
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