Algebraic Model for scattering in three-s-cluster systems. I. Theoretical Background

A framework to calculate two-particle matrix elements for fully antisymmetrized three-cluster configurations is presented. The theory is developed for a scattering situation described in terms of the Algebraic Model. This means that the nuclear many-particle state and its asymptotic behaviour are expanded in terms of oscillator states of the intra-cluster coordinates. The Generating Function technique is used to optimize the calculation of matrix elements. In order to derive the dynamical equations, a multichannel version of the Algebraic Model is presented.Comment: 20 pages, 1 postscript figure, submitted to Phys. Rev.

Stability of the liquid particles separation in the apparatus of oil and gas systems

The article considers the methods of associated gas purification from liquid particles. The sintering of liquid particles occurs during the separation process and the trapped droplets can be removed as a liquid stream, i.e. there is no need for unloading units. The droplet size depends on the energy input during their fragmentation. The efficiency of drops separation depends on the flow rate and the intensification of droplets coalescence, film formation and liquid flow to the receiver. The dispersion of the liquid particles is the main drawback of the existing purification methods, i.e. lack of sustainability of particle separation. The comparison of the separation system methods and the devices with flow control elements is carried out. The estimation of gas purification efficiency is conducted. It is concluded that the efficiency of associated gas purification gives the possibility to use it in turbine generators, heating furnaces, etc. It significantly reduces the proportion of gas being flared

Observation of double radiative capture on pionic hydrogen

We report the first observation of double radiative capture on pionic hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC spectrometer, and detected $\gamma$--ray coincidences following $\pi^-$ stops in liquid hydrogen. We found the branching ratio for double radiative capture to be $(3.05 \pm 0.27(stat.) \pm 0.31(syst.)) \times 10^{-5}$. The measured branching ratio and angle-energy distributions support the theoretical prediction of a dominant contribution from the $\pi \pi \to \gamma \gamma$ annihilation mechanism.Comment: 4 Pages, 4 Figures. accepted for publication in Phys. Rev. Let

Синдром компрессии чревного ствола: современные представления о проблеме (обзор литературы)

Celiac trunk compression syndrome is a symptom complex arising from compression of the celiac trunk by the median arcuate ligament, crura of diaphragm or ganglion tissue of the celiac plexus. The main clinical manifestations of this pathological condition are abdominal pain syndrome, indigestion and weight loss. The disease is detected in 0.4–1 % of people in the population, more often in young people. The pathophysiological mechanisms of the development of celiac trunk compression syndrome remain not fully understood, but the key reason for its development is ischemia of the digestive system. The main instrumental methods for diagnosing compression of the celiac trunk are ultrasound duplex scanning of the abdominal aorta and visceral arteries and spiral computed angiography. The only effective treatment for celiac trunk compression syndrome is surgery. Currently, both classical techniques and various minimally invasive technologies are used to decompress the celiac trunk. The advantages of open access include good visual and manual control of anatomical structures, the possibility of eliminating complications, changing the tactics of surgical intervention, if necessary, performing vascular reconstruction. The advantage of minimally invasive surgical technologies is minimal trauma to the abdominal wall tissues, minor postoperative pain syndrome, early rehabilitation, a low risk of developing cusp, wound infection and hernial defects. Regardless of the methodology, surgical treatment can achieve a positive effect in 75–90 % of patients with celiac trunk compression syndrome. These are the modern concepts of epidemiology, pathogenesis, clinical manifestations, diagnosis and methods of treatment of this pathological condition.Синдром компрессии чревного ствола – симптомокомплекс, возникающий вследствие сдавления чревного ствола срединной дугообразной связкой, ножками диафрагмы или нейроганглионарной тканью чревного сплетения. Основными клиническими проявлениями данного патологического состояния являются абдоминальный болевой синдром, диспепсия и снижение массы тела. Заболевание выявляется у 0,4–1 % людей в популяции, чаще – у лиц молодого возраста. Патофизиологические механизмы развития синдрома компрессии чревного ствола остаются не до конца понятными, однако ключевой причиной его развития является ишемия органов пищеварения.Основными инструментальными методами диагностики синдрома компрессии чревного ствола являются ультразвуковое дуплексное сканирование брюшной части аорты и висцеральных артерий и спиральная компьютерная ангиография. Единственным эффективным методом лечения синдрома компрессии чревного ствола является хирургический. В настоящее время для декомпрессии чревного ствола применяются как классические методики, так и различные малоинвазивные технологии. К достоинствам открытого доступа относятся хороший визуальный и мануальный контроль анатомических структур, возможность устранения осложнений, изменения тактики оперативного вмешательства, при необходимости – выполнение сосудистой реконструкции. Преимущество малоинвазивных хирургических технологий заключается в минимальной травме тканей брюшной стенки, незначительном послеоперационном болевом синдроме, ранней реабилитации, низком риске развития спаек, раневой инфекции и грыжевых дефектов. Независимо от методик, хирургическое лечение позволяет добиться положительного эффекта у 75–90 %  пациентов с синдромом компрессии чревного ствола. Таковы современные представления об эпидемиологии, патогенезе, клинических проявлениях, диагностике и методах лечения данного патологического состояния

Принципы хирургического лечения рецидивных грыж пищеводного отверстия диафрагмы (обзор литературы)

Recurrent hiatal hernia is the re-displacement of the abdominal organs into the chest after surgical treatment. Indications for repeated surgical interventions for this pathology are resistant to medical correction gastroesophageal reflux or anatomical disorders, bearing the risk of developing life-threatening conditions. The key task of revision interventions is to identify and address the causes of the failure of the primary operation. The main factors of the recurrence of hernias of this localization are the large size of the hiatal opening, the mechanical weakness of the legs of the diaphragm and the shortening of the esophagus. To increase the reliability of the esophageal aperture plasty in the surgical treatment of recurrent hiatal hernias, prosthetic materials are widely used. When the esophagus is shortened, it is possible to increase its length by creating a gastric stalk (gastroplasty) or fixing the stomach to the anterior abdominal wall (gastropexy). The disadvantage of both methods is the occurring functional impairment. An alternative approach is the formation of a fundoplication wrap in the chest with the closure of the esophageal opening only with its own tissues. To eliminate or prevent the development of gastroesophageal reflux, antireflux reconstruction is an essential component of operations for recurrent hiatal hernias. The option of fundoplication is selected in accordance with the contractility of the esophagus. With normokinesia, circular fundoplication was preferred, with impaired motor skills – free reconstructions.Под рецидивными грыжами пищеводного отверстия диафрагмы понимают любые варианты повторного смещения органов брюшной полости в грудную клетку после хирургического лечения. Показаниями к повторным оперативным вмешательствам при данной патологии являются не поддающийся медикаментозной коррекции гастроэзофагеальный рефлюкс или анатомические нарушения, несущие риск развития угрожающих жизни состояний. Ключевая задача ревизионных вмешательств заключается в выявлении и устранении причин неудачного исхода первичной операции. Основными факторами повторного возникновения грыж данной локализации являются большие размеры хиатального отверстия, механическая слабость ножек диафрагмы и укорочение пищевода. Для повышения надежности пластики пищеводного отверстия диафрагмы при хирургическом лечении рецидивных хиатальных грыж широко используются протезирующие материалы. При укорочении пищевода возможно увеличение его длины созданием желудочного стебля (гастропластика), фиксация желудка к передней брюшной стенке (гастропексия). Недостатком обеих методик являются возникающие функциональные нарушения. Альтернативный подход – формирование фундопликационной манжеты в грудной клетке с закрытием пищеводного отверстия только собственными тканями. Для устранения или профилактики развития желудочно-пищеводного заброса обязательным компонентом операций при рецидивных хиатальных грыжах является антирефлюксная реконструкция. Вариант фундопликации выбирается в соответствии с сократительной способностью пищевода. При нормокинезии предпочтительны циркулярные фундопликации, при нарушениях моторики – свободные реконструкции

A netron halo in 8He

The structure of $^8$He is investigated within a three-cluster microscopic model. The three-cluster configuration $\alpha+^2n+^2n$ was used to describe the properties of the ground state of the nucleus. The obtained results evidently indicate the existence of a neutron halo in $^8$He.Comment: 14 pages, 6 postscript figures, submitted to Phys. Atom. Nuc

Nuclear charge radius of 8^8He

The root-mean-square (rms) nuclear charge radius of ^8He, the most neutron-rich of all particle-stable nuclei, has been determined for the first time to be 1.93(3) fm. In addition, the rms charge radius of ^6He was measured to be 2.068(11) fm, in excellent agreement with a previous result. The significant reduction in charge radius from ^6He to ^8He is an indication of the change in the correlations of the excess neutrons and is consistent with the ^8He neutron halo structure. The experiment was based on laser spectroscopy of individual helium atoms cooled and confined in a magneto-optical trap. Charge radii were extracted from the measured isotope shifts with the help of precision atomic theory calculations

Breakup reaction models for two- and three-cluster projectiles

Breakup reactions are one of the main tools for the study of exotic nuclei, and in particular of their continuum. In order to get valuable information from measurements, a precise reaction model coupled to a fair description of the projectile is needed. We assume that the projectile initially possesses a cluster structure, which is revealed by the dissociation process. This structure is described by a few-body Hamiltonian involving effective forces between the clusters. Within this assumption, we review various reaction models. In semiclassical models, the projectile-target relative motion is described by a classical trajectory and the reaction properties are deduced by solving a time-dependent Schroedinger equation. We then describe the principle and variants of the eikonal approximation: the dynamical eikonal approximation, the standard eikonal approximation, and a corrected version avoiding Coulomb divergence. Finally, we present the continuum-discretized coupled-channel method (CDCC), in which the Schroedinger equation is solved with the projectile continuum approximated by square-integrable states. These models are first illustrated by applications to two-cluster projectiles for studies of nuclei far from stability and of reactions useful in astrophysics. Recent extensions to three-cluster projectiles, like two-neutron halo nuclei, are then presented and discussed. We end this review with some views of the future in breakup-reaction theory.Comment: Will constitute a chapter of "Clusters in Nuclei - Vol.2." to be published as a volume of "Lecture Notes in Physics" (Springer

Torsion and accelerating expansion of the universe in quadratic gravitation

Several exact cosmological solutions of a metric-affine theory of gravity with two torsion functions are presented. These solutions give a essentially different explanation from the one in most of previous works to the cause of the accelerating cosmological expansion and the origin of the torsion of the spacetime. These solutions can be divided into two classes. The solutions in the first class define the critical points of a dynamical system representing an asymptotically stable de Sitter spacetime. The solutions in the second class have exact analytic expressions which have never been found in the literature. The acceleration equation of the universe in general relativity is only a special case of them. These solutions indicate that even in vacuum the spacetime can be endowed with torsion, which means that the torsion of the spacetime has an intrinsic nature and a geometric origin. In these solutions the acceleration of the cosmological expansion is due to either the scalar torsion or the pseudoscalar torsion function. Neither a cosmological constant nor dark energy is needed. It is the torsion of the spacetime that causes the accelerating expansion of the universe in vacuum. All the effects of the inflation, the acceleration and the phase transformation from deceleration to acceleration can be explained by these solutions. Furthermore, the energy and pressure of the matter without spin can produce the torsion of the spacetime and make the expansion of the universe decelerate as well as accelerate.Comment: 20 pages. arXiv admin note: text overlap with gr-qc/0604006, arXiv:1110.344