Dynamics of liquids with high viscosity contrast in unevenly rotating Hele-Shaw cell

The paper is devoted to the experimental study of the dynamics of an interface between two liquids with high viscosity contrast filling a vertical, circular narrow gap rotating about a horizontal axis at a speed modulated by librations. The equilibrium shape and stability of the interphase boundary are considered. In the absence of librations, under the action of the centrifugal force the boundary has an axisymmetric shape. At librations, at certain frequency ratios, the interface loses its axisymmetric position: in the cavity reference frame, it is displaced in the radial direction. It is theoretically shown that the discovered phenomenon is explained by the average action of gravity; the results of experiments and theory are consistent. The experiments reveal that with an increase in the modulation amplitude the circular interface loses stability in a threshold manner: an azimuthally periodic relief, quasi-stationary in the cavity frame, emerges. This is associated with the Kelvin-Helmholtz instability due to tangential oscillations of the less viscous liquid near the interface. A dimensionless parameter that determines the stability of the interface is obtained in the limit of high dimensionless libration frequency. The stability threshold increases with the decrease in the dimensionless frequency. This article is part of the theme issue 'New trends in pattern formation and nonlinear dynamics of extended systems'.

Investigation of chemoconvection in vibration fields

This study is devoted to the investigation of the chemoconvection in a two-layer miscible system caused by the neutralisation reaction proceeding in the convective-controlled (CC) regime under the influence of vertical vibrations. The CC regime without vibrational influence is characterized by the development of a density wave and vigorous convection in the upper layer, ensuring a high reaction rate and forcing the reaction front to move downwards more rapidly than in the well-known diffusive-controlled (DC) regime. It is shown that vibrations lead to some deceleration of the convection that depends both on the magnitude of the vibrational acceleration and on the initial concentrations of the reagents. Analysis of the system behaviour depending on the dimensionless parameters is carried out. It is demonstrated that the theory of thermal vibrational convection may be applied for reacting systems on quasi-steady time intervals.

Influence of the static field on a heavy body in a rotating drum with liquid

The behaviour of a heavy cylindrical body in a rotating horizontal cylindrical cavity filled with viscous liquid is investigated experimentally. Several modes of the body behaviour depending on the rate of the cavity rotation, i.e., the ratio of the centrifugal force of inertia and the gravity, are detected. At a fast rotation rate, the body makes the solid-body rotation, remaining immobile relative to the cavity due to the action of the centrifugal force. In the absence of rotation, under the influence of gravity, the body occupies a position in the lower part of the cavity. At slow uniform rotation rate, the body is dragged by the cavity boundary and shifts to some angle relative to the initial position. With an increase in the rotation rate, the body is repulsed from the cavity boundary and occupies a suspended position, stationary in the laboratory frame, at a certain distance from it. In the suspension regime and the partial repulsion regime, which precedes it, the body performs auto-oscillations that resemble the precession. The flow structures near the suspended cylinder are studied using the PIV method.

Epidural steroid injections: update on efficacy, safety, and newer medications for injection

The best evidence for epidural injection appears to be in the setting of radicular pain with epidural steroid and non-steroid injections more efficacious than non-epidural injections. Studies showed the efficacy of non-particulate steroid to approach the efficacy of particulate steroid and very limited comparisons demonstrated no significant difference between epidural steroid and epidural non-steroid (local anesthetic) injection. Preliminary studies evaluating epidural injection of disease modifying anti-rheumatic drugs such etanercept and tocilizumab showed conflicting results and had significant limitations. Randomized studies support better efficacy of transforaminal injection due to greater incidence of ventral epidural spread of injectate when compared to interlaminar injection. Thus, the transforaminal approach is recommended when unilateral radicular pain is limited to one nerve root. However, the transforaminal approach is associated with greater incidence of central nervous system injury, including paraplegia, attributed to embolization of the particulate steroid. Recent studies showed that non-particulate steroids potentially last as long as particulate steroids. Therefore non-particulate steroid should be used in initial transforaminal epidural injection. Future studies should look into the role of adjunct diagnostic aids, including digital subtraction angiography, in detecting intravascular injection and the ideal site of needle placement, whether it is the safe triangle or the triangle of Kambin. Finally, the role of epidural disease -modifying antirheumatic drugs in the management of back pain needs to be better elucidated.

(-)-Sclareol Conversion in Ritter's Reaction Conditions

The main products of sclareol (1) Ritter’s reaction in mild conditions are (8R,13R)-Labd-14(15)-en-8,13-diacetamide (2) (8R,13S)-Labd-14(15)-en-8,13-diacetamide (3) stereoisomeric on C13 atom and having unrearranged native diol skeleton. We present in the current communication the results of sclareol converting (1) into nitrogen-containing labdanes in the Ritter’s reaction conditions.

Gallstone dissolution using mono-octanoin infusion through an endoscopically placed nasobiliary catheter

Endoscopic sphincterotomy is widely being used for the treatment of common bile duct stones. In a small group of patients the gallstones are large in size and, hence, difficult to be extracted after a successful endoscopic sphincterotomy. We used a constant infusion of mono-octanoin through a nasobiliary catheter in nine such patients. This method was successful in partial or complete dissolution of the stones in 74% of the patients. In the remaining 36% of the patients, the stones were noted to be soft allowing easy extraction by crushing.

Renal hydrogen ion secretion after release of unilateral ureteral obstruction

The effect of 24 h of unilateral ureteral obstruction on HCO3 reabsroption and urinary acidification was studied in dogs. The postobstructed kidney (EK) had a significantly lower glomerular filtration rate and renal plasma flow than the contralateral kidney (CK). Urinary pH prior to HCO3 loading was significantly higher in the EK as was maximal HCO3 reabsorption. Saline loading depressed HCO3 reabsorption to the same degree in both kidneys. Urinary PCO2, during HCO3 loading, and during phosphate infusion, was significantly lower in the EK than the CK. Fractional Na excretion was significantly higher in the EK than the CK after deoxycorticosterone acetate administration. Na2SO4 administration enhanced acid excretion only in the CK. K excretion was significantly lower in the EK than the CK both during HCO3 loading and Na2SO4 administration. There was redistribution of cortical blood flow from the outer cortex toward the inner cortex in the EK as compared to the CK. There was no difference in plasma renin activity from both renal veins. These data demonstrate enhanced proximal H+ secretion (which is abolished by volume expansion) and impaired distal H+ secretion by the postobstructed kidney. The distal defect is likely an effect of a generalized disorder of distal transport in that both K secretion and steroid-responsive Na reabsorption were impaired in the postobstructed kidney.