Stability of Liquid Bridges between Equal Disks in an Axial Gravity Field

The stability of axisymmetric liquid bridges spanning two equal-diameter solid disks subjected to an axial gravity field of arbitrary intensity is analyzed for all possible liquid volumes. The boundary of the stability region for axisymmetric shapes (considering both axisymmetric and nonaxisymmetric perturbations) have been calculated. It is found that, for sufficiently small Bond numbers, three different unstable modes can appear. If the volume of liquid is decreased from that of an initially stable axisymmetric configuration the bridge either develops an axisymmetric instability (breaking in two drops as already known) or detaches its interface from the disk edges (if the length is smaller than a critical value depending on contact angle), whereas if the volume is increased the unstable mode consists of a nonaxisymmetric deformation. This kind of nonaxisymmetric deformation can also appear by decreasing the volume if the Bond number is large enough. A comparison with other previous partial theoretical analyses is presented, as well as with available experimental results

An experimental analysis of the instability of non-axisymmetric liquid bridges in a gravitational field

he stability limits of nonaxisymmetric liquid bridges between equal in diameter, coaxial disks have been determined experimentally. Experiments have been performed by working with very small size liquid bridges. The experimental setup allows any orientation of the liquid bridge axis with respect to the local gravity vector acceleration. By appropriately orienting the liquid bridge axis, the influence on the stability limits of both the lateral and the axial component of the acceleration acting on the liquid bridge has been investigated

Возможность использования электростимуляции скелетных мышц в реабилитации больных после кардиохирургических операций

Aim. To evaluate the effectiveness of electrical muscle stimulation (EMS) in patients with the complicated early postoperative period after cardiac surgery.Methods. 61 patients (44 men and 17 women) aged 52-70 years with the complicated early postoperative period after cardiac surgery were included in the study. The complications included prolonged length of stay in the intensive care unit and prolonged mechanical ventilation. The initial muscle performance of the lower extremities was measured with the carpal and isokinetic dynamometer in all patients. The six-minute walk test was performed in all patients after they had been transferred to the department of cardiac surgery.Results. Patients in the study group had reduced lower extremity muscle strength at baseline, compared with the control group. After the EMS sessions, the study group patients demonstrated pronounced improvements in muscle performance as compared to the control group. Both knee-joint extension values increased during the isometric contraction as compared to those in the control group (38.8% and 40.0% versus 8.1% and 8.4%, p <0.001), similarly to right knee-joint flexion (23.7% versus 10.1%, p = 0.008), left ankle joint (18.6 versus 4.3%, p = 0.010), right-hand grip strength (18.3 versus 11.1%, p = 0.042). In addition, the six-minute walk test results improved in the EMS group (119.72% (293 meters) and 87.13% (315 meters)) as compared to the control group (p = 0.079).Conclusion. The EMS sessions did not affect the clinical status of cardiac surgical patients with the complicated postoperative period. Moreover, it appeared to be beneficial in terms of the improved lower extremity muscle strength that was more pronounced in the study group than in the control group. Therefore, the effects of EMS on the clinical status of these patients require the further investigation.Цель. Оценить эффективность применения электромиостимуляции (ЭМС) у пациентов с осложненным ранним послеоперационным периодом кардиохирургических операций.Материалы и методы. В исследование включен 61 пациент (44 мужчин, 17 женщин), от 52 до 70 лет, перенесших оперативное кардиохирургическое вмешательство, с осложненным течением раннего послеоперационного периода, приведшего к увеличению срока нахождения в отделении интенсивной терапии, продления искусственной вентиляции легких. Пациентам выполнялась кистевая и изокинетическая динамометрия нижних конечностей, для оценки исходного состояния мышечного статуса обследуемых пациентов. Тест шестиминутной ходьбы проводился после перевода в отделение кардиохирургии.Результаты. Исходно пациенты основной группы имели низкий функциональный статус скелетной мускулатуры нижних конечностей, по сравнению с группой контроля практически во всех группах мышц нижних конечностей. После курса ЭМС отмечено более выраженное улучшение мышечного статуса по сравнению с группой контроля: выше была степень прироста силы изометрического сокращения для правого и левого разгибателей колена (38,8% и 40,0% против 8,1% и 8,4%, р<0,001), сгибателей правого коленного сустава (23,7% против 10,1%, р = 0,008), левого голеностопного сустава (18,6 против 4,3%, р = 0,010), силы сжатия кисти справа (18,3 против 11,1%, р = 0,042). Помимо прочего, отмечается близкий к достоверному процент прироста пройденной дистанции, по данным теста шестиминутной ходьбы и составляет 119,72% (293 метра), и 87,13% (315 метров) для основной, и контрольной группы соответственно (р = 0,079).Заключение. У больных с осложненным послеоперационным периодом кардиохиуругических операций курс ЭМС не вызывал ухудшения клинического состояния. После курса ЭМС отмечено улучшение силы мышц нижних конечностей, более выраженное по сравнению с группой контроля. Оценка влияния курса ЭМС на клиническое состояние данной категории больных требует последующих исследований. Оценка влияния курса ЭМС на клиническое состояние данной категории больных требует последующих исследований

Simulation of non-axisymmetric floating zone crystal growth under microgravity

The possibility of growing crystals of non-circular cross-section by using the floating zone technique is considered, basing the analysis on the isothermal liquid bridge model, and restricting the study to a linear asymptotic analysis. An almost square initial seed is considered in more detail, although the analysis is general and can be applied to other initial shapes, not only of the seed but also of the supply rod, that can be of any cross-section. The influence of non-circular seed and/or feed cross-section shape, and of a possible axial acceleration typical of microgravity platforms (sounding rockets and space labs), on both the liquid interface shape and the solid grown shape, are analysed, including the stability limits by breaking of the molten bridge

A THEORETICAL APPROACH TO IMPULSIVE MOTION OF VISCOUS LIQUID BRIDGES*

Abstract-This paper deals with the dynamics of isothermal, axisymmetric, viscous liquid columns held by capillary forces between two circular, concentric, solid disks. The transient response of the bridge to an excitation consisting of a small change in the value of the acceleration acting along its axis has been solved by using a linearised one-dimensional Cosserat model, which includes viscosity effects. The main hypothesis of this model is that the axial velocity is considered constant in each section of the liquid bridge. The analysis has been performed by using the Laplace transform