Horizon effects with surface waves on moving water

Surface waves on a stationary flow of water are considered, in a linear model that includes the surface tension of the fluid. The resulting gravity-capillary waves experience a rich array of horizon effects when propagating against the flow. In some cases three horizons (points where the group velocity of the wave reverses) exist for waves with a single laboratory frequency. Some of these effects are familiar in fluid mechanics under the name of wave blocking, but other aspects, in particular waves with negative co-moving frequency and the Hawking effect, were overlooked until surface waves were investigated as examples of analogue gravity [Sch\"utzhold R and Unruh W G 2002 Phys. Rev. D 66 044019]. A comprehensive presentation of the various horizon effects for gravity-capillary waves is given, with emphasis on the deep water/short wavelength case kh>>1 where many analytical results can be derived. A similarity of the state space of the waves to that of a thermodynamic system is pointed out.Comment: 30 pages, 15 figures. Minor change

Wave modelling - the state of the art

This paper is the product of the wave modelling community and it tries to make a picture of the present situation in this branch of science, exploring the previous and the most recent results and looking ahead towards the solution of the problems we presently face. Both theory and applications are considered. The many faces of the subject imply separate discussions. This is reflected into the single sections, seven of them, each dealing with a specific topic, the whole providing a broad and solid overview of the present state of the art. After an introduction framing the problem and the approach we followed, we deal in sequence with the following subjects: (Section) 2, generation by wind; 3, nonlinear interactions in deep water; 4, white-capping dissipation; 5, nonlinear interactions in shallow water; 6, dissipation at the sea bottom; 7, wave propagation; 8, numerics. The two final sections, 9 and 10, summarize the present situation from a general point of view and try to look at the future developments

Роль тромболизиса в комплексном лечении осложненных аневризм подколенных артерий

RELEVANCE Thrombosis of a popliteal artery aneurysm is an intractable problem. For decades, the number of amputations in this disease has remained at the level of 20% and does not have a significant downward trend due to the fact that during thrombosis of an aneurysm, the infragenicular arteries, the only “outflow paths” for bypass surgery, are also thrombosed. Currently, in order to increase the capacity of the peripheral bloodstream, thrombolytic therapy has been proposed.AIM To evaluate the effectiveness of preoperative and intraoperative thrombolytic therapy in the surgical treatment of thrombosed popliteal aneurysms.MATERIAL AND METHODS In the period from 1997 to 2020, 94 patients with acute ischemia of the lower extremities caused by thrombosed popliteal aneurysms underwent 98 reconstructive surgeries at the N.V. Sklifosovsky Research Institute for Emergency Medicine. The age of the patients was 62.5±10.1 years. Group I (n=66/98 patients, 67.3%) consisted of patients after primary reconstructive surgery; Group II (n=32/98, 32.7%) consisted of patients who, in order to improve the patency of the infragenicular arteries, underwent thrombolytic therapy in addition to surgery (12 preoperative catheter-directed, 20 intraoperative). A retrospective analysis was carried out.RESULTS Limb preservation was achieved in 86.7% of patients. In Group I, early postoperative thrombosis occurred in 22.7% of cases (n=13/98), in Group II — in 6.3% (n=2/32), p<0.05; amputations were performed in Group I in 18.1% of patients (n=12/66), in Group II — in 3.1% of patients (n=1/32), p<0.04.АКТУАЛЬНОСТЬ Тромбоз аневризмы подколенной артерии представляет собой труднорешаемую проблему. На протяжении десятилетий число ампутаций при данном заболевании сохраняется на уровне 20% и не имеет значительной тенденции к снижению в связи с тем, что при тромбозе аневризмы тромбируются также артерии голени, являющиеся единственными «путями оттока» при шунтирующей операции. В настоящее время с целью увеличения емкости периферического русла предложено проведение тромболитической терапии.ЦЕЛЬ Оценка эффективности проведения дооперационной и интраоперационной тромболитической терапии в хирургическом лечении тромбированных аневризм подколенных артерий.МАТЕРИАЛ И МЕТОДЫ В период с 1997 по 2020 год в ГБУЗ «НИИ СП им. Н.В. Склифосовского ДЗМ» выполнено 98 реконструктивных операций у 94 пациентов с острой ишемией нижних конечностей, обусловленной тромбозом аневризм подколенных артерий. Возраст пациентов составил 62,5±10,1 года. I группу (n=66/98 больных, 67,3%) составили пациенты, которым выполнены первичные реконструктивные операции; II группу (n=32/98, 32,7%) составили пациенты, которым с целью улучшения проходимости артерий голени в дополнение к операции проведена тромболитическая терапия (12 — дооперационная катетернаправленная, 20 — интраоперационная). Проведен ретроспективный анализ.РЕЗУЛЬТАТЫ Сохранность конечностей достигнута у 86,7% пациентов. В I группе ранние послеоперационные тромбозы произошли в 22,7% случаев (n=13/98), во II-й группе — в 6,3% (n=2/32), p<0,05; ампутации выполнены в I группе у 18,1% больных (n=12/66), во II-й группе — у 3,1% больных (n=1/32), p<0,04

ИСПОЛЬЗОВАНИЕ СИСТЕМНОГО ТРОМБОЛИЗИСА ДЛЯ ЛЕЧЕНИЯ ОСТРОЙ ИШЕМИИ КОНЕЧНОСТЕЙ

ABSTRACT. Treatment of acute limb ischemia remains a serious problem in vascular surgery. There are both surgical and conservative therapies. Systemic thrombolysis is one of supplementing methods, and in some cases, it is the method of choice, especially when surgical therapy is not possible. The paper presents our experience of systemic thrombolytic therapy in the treatment of acute limb ischemia. РЕЗЮМЕ. Лечение острой ишемии конечностей остается серьезной проблемой в ангиохирургии. Существуют как хирургические, так и консервативные методы лечения. Один из методов, дополняющий, а в ряде случаев являющийся и методом выбора — системный тромболизис, особенно когда выполнение оперативного лечения невозможно. В статье представлен наш опыт использования системной тромболитической терапии в лечении острой ишемии конечностей.

Trapping and instability of directional gravity waves in localized water currents

The influence of localized water currents on the nonlinear dynamics and stability of large amplitude, statistically distributed gravity waves is investigated theoretically and numerically by means of an evolution equation for a Wigner function governing the spectrum of waves. It is shown that water waves propagating in the opposite direction of a localized current channel can be trapped in the channel, which can lead to the amplification of the wave intensity. Under certain conditions the wave intensity can be further localized due to a self-focusing (Benjamin-Feir) instability. The localized amplification of the wave intensity may increase the probability of extreme events in the form of freak waves, which have been observed in connection with ocean currents

SYSTEMIC THROMBOLYSIS FOR TREATMENT OF ACUTE LIMB ISCHEMIA

ABSTRACT. Treatment of acute limb ischemia remains a serious problem in vascular surgery. There are both surgical and conservative therapies. Systemic thrombolysis is one of supplementing methods, and in some cases, it is the method of choice, especially when surgical therapy is not possible. The paper presents our experience of systemic thrombolytic therapy in the treatment of acute limb ischemia

THE RESULTS OF SURGICAL TREATMENT OF TRICUSPID VALVE INFECTIVE ENDOCARDITIS USING VALVE REPAIR AND VALVE REPLACEMENT OPERATIONS

Aim. To evaluate in-hospital and long-term results of surgical treatment of patients with infective endocarditis of the tricuspid valve, to compare the effectiveness of valve repair and valve replacement techniques, and to identify risk factors of mortality and reoperations. Materials and methods. 31 surgical patients with tricuspid valve infective endocarditis were evaluated. Patients were divided into 2 groups. In Group 1 (n = 14) repairs of the tricuspid valve were performed, in Group 2 (n = 17) patients had undergone tricuspid valve replacements. Epidemiological, clinical, microbiological and echocardiographic data were studied. Methods of comparative analysis, the Kaplan–Meier method, and Cox risk models were applied. Results. The most common complication of in-hospital stay was atrioventricular block (17.7% of cases in Group 2). In Group 1, this type of complication was not found. Hospital mortality was 7.14% in Group 1, and 0% in Group 2. Long-term results have shown the significant reduction of heart failure in general cohort and in both groups. In Group 1 the severity of heart failure in the long term was less than in Group 2. No significant differences in the severity of tricuspid regurgitation were found between the groups. In 7-year follow up no cases of death were registered in Group 1. Cumulative survival rate in Group 2 within 60 months was 67.3 ± 16.2%. No reoperations were performed in patients from Group 1. In Group 2, the freedom from reoperation within 60 months was 70.9 ± 15.3%. Combined intervention was found as predictor of postoperative mortality. Prosthetic valve endocarditis was identified as risk factor for reoperation. Conclusion. Valve repair and valve replacement techniques of surgical treatment of tricuspid valve endocarditis can provide satisfactory hospital and long-term results. Tricuspid valve repair techniques allowed reducing the incidence of postoperative atrioventricular block. In the long-term, patients after tricuspid valve repair have shown less severity of heart failure as well as better rates of survival and freedom from reoperation. Combined intervention and prosthetic endocarditis were found to be main risk factors for adverse outcome