490 research outputs found
Experimental installation to study the influence of acoustic oscillations on the characteristics of a glow discharge
© Published under licence by IOP Publishing Ltd. It is proposed a sketchy scheme of experimental installation to study the influence of acoustic oscillations having longitudinal, tangential, radial and combined forms on the parameters of a glow discharge
Settlements of Neighboring Buildings During Piling Works
Two case histories of heavy damaging the neighbouring buildings in Sankt-Petersburg during construction the bored piles are presented. The analysis of causes of the damages has shown that ground inflow into the housing tubes due to low strength properties of water saturated liquid-plastic loams is the main cause of additional settlements of existing houses during construction the bored piles of large diameter close to them
Weakly Interacting, Dilute Bose Gases in 2D
This article surveys a number of theoretical problems and open questions in
the field of two-dimensional dilute Bose gases with weak repulsive
interactions. In contrast to three dimensions, in two dimensions the formation
of long-range order is prohibited by the Bogoliubov-Hohenberg theorem, and
Bose-Einstein condensation is not expected to be realized. Nevertheless, first
experimental indications supporting the formation of the condensate in low
dimensional systems have been recently obtained. This unexpected behaviour
appears to be due to the non-uniformity, introduced into a system by the
external trapping potential. Theoretical predictions, made for homogeneous
systems, require therefore careful reexamination.
We survey a number of popular theoretical treatments of the dilute weakly
interacting Bose gas and discuss their regions of applicability. The
possibility of Bose-Einstein condensation in a two-dimensional gas, the
validity of perturbative t-matrix approximation and diluteness condition are
issues that we discuss in detail.Comment: Survey, 25 pages RMP style, revised version, refs added, some changes
made, accepted for publication in Rev. Mod. Phy
Technical constraints on interstellar interferometry and spatially resolving the pulsar magnetosphere
Scintillation of pulsar radio signals caused by the interstellar medium can
in principle be used for interstellar interferometry. Changes of the dynamic
spectra as a function of pulsar longitude were in the past interpreted as
having spatially resolved the pulsar magnetosphere. Guided by this prospect we
used VLBI observations of PSR B1237+25 with the Arecibo and Green Bank radio
telescopes at 324 MHz and analyzed such scintillation at separate longitudes of
the pulse profile. We found that the fringe phase characteristics of the
visibility function changed quasi-sinusoidally as a function of longitude.
Also, the dynamic spectra from each of the telescopes shifted in frequency as a
function of longitude. Similar effects were found for PSR B1133+16. However, we
show that these effects are not signatures of having resolved the pulsar
magnetosphere. Instead the changes can be related to the effect of low-level
digitizing of the pulsar signal. After correcting for these effects the
frequency shifts largely disappeared. Residual effects may be partly due to
feed polarization impurities. Upper limits for the pulse emission altitudes of
PSR B1237+25 would likely be well below the pulsar light cylinder radius. In
view of our analysis we think that observations with the intent of spatially
resolving the pulsar magnetosphere need to be critically evaluated in terms of
these constraints on interstellar interferometry.Comment: 19 pages, 11 figures, published in The Astrophysical Journa
The twisted XXZ chain at roots of unity revisited
The symmetries of the twisted XXZ spin-chain (alias the twisted six-vertex
model) at roots of unity are investigated. It is shown that when the twist
parameter is chosen to depend on the total spin an infinite-dimensional
non-abelian symmetry algebra can be explicitly constructed for all spin
sectors. This symmetry algebra is identified to be the upper or lower Borel
subalgebra of the sl_2 loop algebra. The proof uses only the intertwining
property of the six-vertex monodromy matrix and the familiar relations of the
six-vertex Yang-Baxter algebra.Comment: 10 pages, 2 figures. One footnote and some comments in the
conclusions adde
Auxiliary matrices for the six-vertex model at roots of 1 and a geometric interpretation of its symmetries
The construction of auxiliary matrices for the six-vertex model at a root of
unity is investigated from a quantum group theoretic point of view. Employing
the concept of intertwiners associated with the quantum loop algebra
at a three parameter family of auxiliary matrices
is constructed. The elements of this family satisfy a functional relation with
the transfer matrix allowing one to solve the eigenvalue problem of the model
and to derive the Bethe ansatz equations. This functional relation is obtained
from the decomposition of a tensor product of evaluation representations and
involves auxiliary matrices with different parameters. Because of this
dependence on additional parameters the auxiliary matrices break in general the
finite symmetries of the six-vertex model, such as spin-reversal or spin
conservation. More importantly, they also lift the extra degeneracies of the
transfer matrix due to the loop symmetry present at rational coupling values.
The extra parameters in the auxiliary matrices are shown to be directly related
to the elements in the enlarged center of the quantum loop algebra
at . This connection provides a geometric
interpretation of the enhanced symmetry of the six-vertex model at rational
coupling. The parameters labelling the auxiliary matrices can be interpreted as
coordinates on a three-dimensional complex hypersurface which remains invariant
under the action of an infinite-dimensional group of analytic transformations,
called the quantum coadjoint action.Comment: 52 pages, TCI LaTex, v2: equation (167) corrected, two references
adde
Multitemporal generalization of the Tangherlini solution
The n-time generalization of the Tangherlini solution [1] is considered. The
equations of geodesics for the metric are integrated. For it is shown
that the naked singularity is absent only for two sets of parameters,
corresponding to the trivial extensions of the Tangherlini solution. The motion
of a relativistic particle in the multitemporal background is considered. This
motion is governed by the gravitational mass tensor. Some generalizations of
the solution, including the multitemporal analogue of the Myers-Perry charged
black hole solution, are obtained.Comment: 14 pages. RGA-CSVR-005/9
The combination of type 1 diabetes and eating disorder during pregnancy
The problem of eating disorders currently holds a special place in clinical practice. Bulimia nervosa is one of the main forms of eating disorders, characterized by the difficulty in its treatment and a long, recurrent course. Eating disorders are common in patients with type 1 diabetes mellitus (T1D), especially in adolescent girls.In this article, we present a clinical case of a patient with T1D and bulimia nervosa, which developed before the manifestation of T1D and progressed against its background. The patient is overly concerned with controlling body weight, specifically restricted the intake of carbohydrates, forcibly caused vomiting. During pregnancy fasting ketonuria («low-carb ketone») was repeatedly detected. The minimum weight was 37 kg (BMI 15.2 kg/m2). Particular interest of this case is the course of pregnancy, which ended in the antenatal death. The possible cause could be the restriction on carbohydrate food and prolonged stay in ketosis, that might lead to the development of pregnancy pathology. Additional examination also revealed multiple complications of diabetes and recurrent depressive disorder, which requires conjoint monitoring by an endocrinologist and a psychiatrist.Combination of T1D and eating disorder in a pregnant patient should be considered as an atypical course of the disease
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