258 research outputs found

### The evaluation of the safety of medical hemostatic foam based on aluminum and iron chlorides

The aim of this work was to determine the effect of the concentrations of aluminum chloride and iron (III) chloride in the medical foam of hemostatic action, prepared according to a previously developed technology, on the process of postoperative complications formation during the stopping of bleeding from parenchymal organs. On the third day after the simulation of parenchymal bleeding the following safety criteria for the use of the developed drug were studied on the liver of rats: the degree of inflammation, the number of adhesions formed, the thickness and prevalence of fibrin plaque, the presence of blood clots. In addition, the postoperative activity of the operated animals was monitored. In total, 9 compositions of medical foam were studied in the range of metal chloride concentrations from 0% to 15%. Each group included 4 outbred rats of both sexes. While studying postoperative complications after the use of a composition containing 5% aluminum chloride and 10% iron (III) chloride, it was found that this combination of substances produced a strong cauterizing effect on the liver wound. When using it, multiple adhesions, a thick spreading fibrin coating, and severe inflammation of the wound were observed. Medical foam containing aluminum chloride and iron (III) chloride at concentrations of 10% and 0% as active ingredients, on the contrary, was effective and didn’t cause any significant complications. Animals in this group had no adhesive, inflammatory processes and signs of bleeding recurrence, there was a thin layer of fibrin in the area of the liver wound. Based on the data obtained and previously conducted studies, the concentrations of the active ingredients of aluminum chloride 10% and iron (III) chloride 0% were selected for inclusion in the composition of the medicine being developed

### Vacuum polarization of a scalar field in wormhole spacetimes

An analitical approximation of $$ for a scalar field in a static
spherically symmetric wormhole spacetime is obtained. The scalar field is
assumed to be both massive and massless, with an arbitrary coupling $\xi$ to
the scalar curvature, and in a zero temperature vacuum state.Comment: 10 pages, RevTeX, two eps figure

### A Star Harbouring a Wormhole at its Core

We consider a configuration consisting of a wormhole filled by a perfect
fluid. Such a model can be applied to describe stars as well as neutron stars
with a nontrivial topology. The presence of a tunnel allows for motion of the
fluid, including oscillations near the core of the system. Choosing the
polytropic equation of state for the perfect fluid, we obtain static regular
solutions. Based on these solutions, we consider small radial oscillations of
the configuration and show that the solutions are stable with respect to linear
perturbations in the external region.Comment: abstract was change

### Analytical approximation of the stress-energy tensor of a quantized scalar field in static spherically symmetric spacetimes

Analytical approximations for ${}$ and ${}$ of a
quantized scalar field in static spherically symmetric spacetimes are obtained.
The field is assumed to be both massive and massless, with an arbitrary
coupling $\xi$ to the scalar curvature, and in a zero temperature vacuum state.
The expressions for ${}$ and ${}$ are divided into
low- and high-frequency parts. The contributions of the high-frequency modes to
these quantities are calculated for an arbitrary quantum state. As an example,
the low-frequency contributions to ${}$ and ${}$ are
calculated in asymptotically flat spacetimes in a quantum state corresponding
to the Minkowski vacuum (Boulware quantum state). The limits of the
applicability of these approximations are discussed.Comment: revtex4, 17 pages; v2: three references adde

### A single model of traversable wormholes supported by generalized phantom energy or Chaplygin gas

This paper discusses a new variable equation of state parameter leading to
exact solutions of the Einstein field equations describing traversable
wormholes. In addition to generalizing the notion of phantom energy, the
equation of state generates a mathematical model that combines the generalized
phantom energy and the generalized Chaplygin gas models.Comment: 6 pages, no figure

### Static wormholes on the brane inspired by Kaluza-Klein gravity

We use static solutions of 5-dimensional Kaluza-Klein gravity to generate
several classes of static, spherically symmetric spacetimes which are analytic
solutions to the equation $^{(4)}R = 0$, where $^{(4)}R$ is the
four-dimensional Ricci scalar. In the Randall & Sundrum scenario they can be
interpreted as vacuum solutions on the brane. The solutions contain the
Schwarzschild black hole, and generate new families of traversable Lorenzian
wormholes as well as nakedly singular spacetimes. They generalize a number of
previously known solutions in the literature, e.g., the temporal and spatial
Schwarzschild solutions of braneworld theory as well as the class of self-dual
Lorenzian wormholes. A major departure of our solutions from Lorenzian
wormholes {\it a la} Morris and Thorne is that, for certain values of the
parameters of the solutions, they contain three spherical surfaces (instead of
one) which are extremal and have finite area. Two of them have the same size,
meet the "flare-out" requirements, and show the typical violation of the energy
conditions that characterizes a wormhole throat. The other extremal sphere is
"flaring-in" in the sense that its sectional area is a local maximum and the
weak, null and dominant energy conditions are satisfied in its neighborhood.
After bouncing back at this second surface a traveler crosses into another
space which is the double of the one she/he started in. Another interesting
feature is that the size of the throat can be less than the Schwarzschild
radius $2 M$, which no longer defines the horizon, i.e., to a distant observer
a particle or light falling down crosses the Schwarzschild radius in a finite
time

### Double giant resonances in deformed nuclei

We report on the first microscopic study of the properties of two-phonon
giant resonances in deformed nuclei. The cross sections of the excitation of
the giant dipole and the double giant dipole resonances in relativistic heavy
ion collisions are calculated. We predict that the double giant dipole
resonance has a one-bump structure with a centroid 0.8 MeV higher than twice
energy for the single giant dipole resonance in the reaction under
consideration. The width of the double resonance equals to 1.33 of that for the
single resonance.Comment: 5 pages, 2 postscript figure

### Galactic rotation curves inspired by a noncommutative-geometry background

This paper discusses the observed at rotation curves of galaxies in the
context of noncommutative geometry. The energy density of such a geometry is
diffused throughout a region due to the uncertainty encoded in the coordinate
commutator. This intrinsic property appears to be sufficient for producing
stable circular orbits, as well as attractive gravity, without the need for
dark matter.Comment: 12 pages, 3 figures. Published in Gen.Rel.Grav. 44 (2012) 905-91

### Possible wormholes in a brane world

The condition R=0, where R is the four-dimensional scalar curvature, is used
for obtaining a large class (with an arbitrary function of r) of static,
spherically symmetric Lorentzian wormhole metrics. The wormholes are globally
regular and traversable, can have throats of arbitrary size and can be both
symmetric and asymmetric. These metrics may be treated as possible wormhole
solutions in a brane world since they satisfy the vacuum Einstein equations on
the brane where effective stress-energy is induced by interaction with the bulk
gravitational field. Some particular examples are discussed.Comment: 7 pages, revtex4. Submitted to Phys. Rev.

### Wormhole Geometries In $f(R,T)$ Gravity

We study wormhole solutions in the framework of f (R,T) gravity where R is
the scalar curvature, and T is the trace of the stress-energy tensor of the
matter. We have obtained the shape function of the wormhole by specifying an
equation of state for the matter field and imposing the flaring out condition
at the throat. We show that in this modified gravity scenario, the matter
threading the wormhole may satisfy the energy conditions, so it is the
effective stress-energy that is responsible for violation of the null energy
condition.Comment: 9 pages, 4 figures, published version, references adde

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