37 research outputs found
On closed rotating worlds
A new solution for the stationary closed world with rigid rotation is
obtained for the spinning fluid source. It is found that the spin and vorticity
are locally balanced. This model qualitatively shows that the local rotation of
the cosmological matter can be indeed related to the global cosmic vorticity,
provided the total angular momentum of the closed world is vanishing.Comment: 10 pages, Revtex, to appear in Phys. Rev. D6
Entropy Identity and Material-Independent Equilibrium Conditions in Relativistic Thermodynamics
On the basis of the balance equations for energy-momentum, spin, particle and
entropy density, an approach is considered which represents a comparatively
general framework for special- and general-relativistic continuum
thermodynamics. In the first part of the paper, a general entropy density
4-vector, containing particle, energy-momentum, and spin density contributions,
is introduced which makes it possible, firstly, to judge special assumptions
for the entropy density 4-vector made by other authors with respect to their
generality and validity and, secondly, to determine entropy supply and entropy
production. Using this entropy density 4-vector, in the second part,
material-independent equilibrium conditions are discussed. While in literature,
at least if one works in the theory of irreversible thermodynamics assuming a
Riemann space-time structure, generally thermodynamic equilibrium is determined
by introducing a variety of conditions by hand, the present approach proceeds
as follows: For a comparatively wide class of space-time geometries the
necessary equilibrium conditions of vanishing entropy supply and entropy
production are exploited and, afterwards, supplementary conditions are assumed
which are motivated by the requirement that thermodynamic equilibrium
quantities have to be determined uniquely.Comment: Research Paper, 30 page
New Classes of Off-Diagonal Cosmological Solutions in Einstein Gravity
In this work, we apply the anholonomic deformation method for constructing
new classes of anisotropic cosmological solutions in Einstein gravity and/or
generalizations with nonholonomic variables. There are analyzed four types of,
in general, inhomogeneous metrics, defined with respect to anholonomic frames
and their main geometric properties. Such spacetimes contain as particular
cases certain conformal and/or frame transforms of the well known
Friedman-Robertson-Walker, Bianchi, Kasner and Godel universes and define a
great variety of cosmological models with generic off-diagonal metrics, local
anisotropy and inhomogeneity. It is shown that certain nonholonomic
gravitational configurations may mimic de Sitter like inflation scenaria and
different anisotropic modifications without satisfying any classical
false-vacuum equation of state. Finally, we speculate on perspectives when such
off-diagonal solutions can be related to dark energy and dark matter problems
in modern cosmology.Comment: latex2e, 11pt, 33 pages with table of content, a variant accepted to
IJT
Dysphagia in Intensive Care Evaluation (DICE): An International Cross-Sectional Survey.
Dysphagia occurs commonly in the intensive care unit (ICU). Despite the clinical relevance, there is little worldwide research on prevention, assessment, evaluation, and/or treatment of dysphagia for ICU patients. We aimed to gain insight into this international knowledge gap. We conducted a multi-center, international online cross-sectional survey of adult ICUs. Local survey distribution champions were recruited through professional and personal networks. The survey was administered from November 2017 to June 2019 with three emails and a final telephone reminder. Responses were received from 746 ICUs (26 countries). In patients intubated > 48 h, 17% expected a > 50% chance that dysphagia would develop. This proportion increased to 43% in patients intubated > 7 days, and to 52% in tracheotomized patients. Speech-language pathologist (SLP) consultation was available in 66% of ICUs, only 4% reported a dedicated SLP. Although 66% considered a routine post-extubation dysphagia protocol important, most (67%) did not have a protocol. Few ICUs routinely assessed for dysphagia after 48 h of intubation (30%) or tracheostomy (41%). A large proportion (46%) used water swallow screening tests to determine aspiration, few (8%) used instrumental assessments (i.e., flexible endoscopic evaluation of swallowing). Swallowing exercises were used for dysphagia management by 30% of ICUs. There seems to be limited awareness among ICU practitioners that patients are at risk of dysphagia, particularly as ventilation persists, protocols, routine assessment, and instrumental assessments are generally not used. We recommend the development of a research agenda to increase the quality of evidence and ameliorate the implementation of evidence-based dysphagia protocols by dedicated SLPs
Registration of image medical data
The paper deals with registration algorithms. Suitable procedures for the registration of image medical data are presented. During our work we used manual
registration and point-based registration methods to register digitized slices of the
temporal bone. To create referential points we included a different type of biological
material to the sample of the explored object and the preparation was embedded in
paraffinn wax. The manual registration was found to be more precise than the point-based registration. Three dimensional reconstructions of the inner ear, ossicles of
the middle ear and the facial nerve were made from the set of registered data
Evaluation of an Electro-Pneumatic Device for Artificial Capillary Pulse Generation used in a Prospective Study in Animals for Surgical Neck Wound Healing
The paper examines the development and testing of an electro-pneumatic device for wound healing therapy after surgery in the neck area. The device generates air pressure values in a miniaturized cuff using electronic circuitry to drive an electro-valve and air compressor. The device works in two distinct modes: continuous pressure mode and pulsating pressure mode. The pressure value setting can vary from 3 to 11 mmHg, and the pulsating pressure mode’s operating frequency range is approximately 0.1 to 0.3 Hz. Laboratory measurements were conducted to evaluate the device’s correct functioning in both continuous and pulsating pressure modes. A four-day prospective study with animals (n = 10) was also conducted to evaluate neck wound healing therapy using the electro-pneumatic device. Out of the twelve histological parameters analysed to reveal the differences between the experimental and control wounds, only one demonstrated a significant difference. Out of the ten animals treated with the device, three showed a significant difference in terms of benefit after therapy. We can therefore conclude that the device potentially improves the wound healing process in the neck area if the pre-set air pressure value does not exceed 8 mmHg