Precise control of flexible manipulators

The design and experimental testing of end point position controllers for a very flexible one link lightweight manipulator are summarized. The latest upgraded version of the experimental set up, and the basic differences between conventional joint angle feedback and end point position feedback are described. A general procedure for application of modern control methods to the problem is outlined. The relationship between weighting parameters and the bandwidth and control stiffness of the resulting end point position closed loop system is shown. It is found that joint rate angle feedback in addition to the primary end point position sensor is essential for adequate disturbance rejection capability of the closed loop system. The use of a low order multivariable compensator design computer code; called Sandy is documented. A solution to the problem of control mode switching between position sensor sets is outlined. The proof of concept for endpoint position feedback for a one link flexible manipulator was demonstrated. The bandwidth obtained with the experimental end point position controller is about twice as fast as the beam's first natural cantilevered frequency, and comes within a factor of four of the absolute physical speed limit imposed by the wave propagation time of the beam

Retrotransposition-Competent Human LINE-1 Induces Apoptosis in Cancer Cells With Intact p53

Retrotransposition of human LINE-1 (L1) element, a major representative non-LTR retrotransposon in the human genome, is known to be a source of insertional mutagenesis. However, nothing is known about effects of L1 retrotransposition on cell growth and differentiation. To investigate the potential for such biological effects and the impact that human L1 retrotransposition has upon cancer cell growth, we examined a panel of human L1 transformed cell lines following a complete retrotransposition process. The results demonstrated that transposition of L1 leads to the activation of the p53-mediated apoptotic pathway in human cancer cells that possess a wild-type p53. In addition, we found that inactivation of p53 in cells, where L1 was undergoing retrotransposition, inhibited the induction of apoptosis. This suggests an association between active retrotransposition and a competent p53 response in which induction of apoptosis is a major outcome. These data are consistent with a model in which human retrotransposition is sensed by the cell as a “genetic damaging event” and that massive retrotransposition triggers signaling pathways resulting in apoptosis

Comparative effects of verapamil and nitroprusside on left ventricular function in patients with hypertension

AbstractThe effects of verapamil were compared with those of nitroprusside at matched mean arterial pressures and heart rates in 10 symptomatic hypertensive patients during cardiac catheterization. Simultaneous radionuclide angiography and micromanometer pressure measurements were obtained to assess left ventricular pressure-volume relations. Compared with control conditions, verapamil increased left ventricular end-diastolic volume index from 57 ± 16 to 70 ± 28 ml/m2 (p = 0.05) without a significant increase in left ventricular end-diastolic pressure (from 10 ± 4 to 13 ± 6 mm Hg). Despite a downward and rightward shift in the end-systolic pressure-volume relation indicating negative inotropic effects, ejection fraction did not decrease significantly (from 52 ± 9% to 46 ± 9%); cardiac index and stroke volume index remained unchanged. The change in stroke volume index with verapamil was directly related to the magnitude of change in end-diastolic volume index (r = 0.82, p < 0.005), suggesting that the increase in enddiastolic volume did not arise purely from negative inotropic effects. Systemic vascular resistance index decreased from 42 ± 8 to 34 ± 7 mm Hg-min-m2/liter (p < 0.05).In contrast, nitroprusside decreased left ventricular end-diastolic volume index from 57 ± 16 to 41 ± 10 ml/m2 (p < 0.05), cardiac index from 3.2 ± 0.7 to 2.8 ± 0.6 liters/min per m2 (p < 0.05) and stroke volume index from 28 ± 6 to 24 ± 5 ml/m2 (p < 0.01), with no change in systemic vascular resistance index (40 ± 10 mm Hg·min·m2). The end-systolic pressure-volume relation shifted downward and leftward in all patients, stemming from altered left ventricular loading.Thus, in equihypotensive doses, verapamil and nitroprusside have markedly different effects on left ventricular function. The peripheral vasodilation and apparent improvement in left ventricular filling during verapamil balanced the negative inotropic effects, resulting in maintenance of stroke volume and cardiac index. The primary hypotensive effect of verapamil was a decrease in systemic vascular resistance, whereas that of nitroprusside was a decrease in cardiac index stemming from reduced left ventricular preload

Effects of empagliflozin on blood pressure and markers of arterial stiffness and vascular resistance in patients with type 2 diabetes

Peer reviewe

The inner circumstellar dust of the red supergiant Antares as seen with VLT/SPHERE/ZIMPOL

The processes by which red supergiants lose mass are not fully understood thus-far and their mass-loss rates lack theoretical constraints. The ambient surroundings of the nearby M0.5 Iab star Antares offers an ideal environment to obtain detailed empirical information on the outflow properties at its onset, and hence indirectly, on the mode(s) of mass loss. We present and analyse optical VLT/SPHERE/ZIMPOL polarimetric imaging with angular resolution down to 23 milli-arcsec, sufficient to spatially resolve both the stellar disk and its direct surroundings. We detect a conspicuous feature in polarised intensity that we identify as a clump containing dust, which we characterise through 3D radiative transfer modelling. The clump is positioned behind the plane of the sky, therefore has been released from the backside of the star, and its inner edge is only 0.3 stellar radii above the surface. The current dust mass in the clump is $1.3^{+0.2}_{-1.0} \times 10^{-8}$ M$_{\odot}$, though its proximity to the star implies that dust nucleation is probably still ongoing. The ejection of clumps of gas and dust makes a non-negligible contribution to the total mass lost from the star which could possibly be linked to localised surface activity such as convective motions or non-radial pulsations.Comment: 15 pages, accepted for publication in MNRA

Proof of Bose-Einstein Condensation for Interacting Gases with a One-Particle Spectral Gap

Using a specially tuned mean-field Bose gas as a reference system, we establish a positive lower bound on the condensate density for continuous Bose systems with superstable two-body interactions and a finite gap in the one-particle excitations spectrum, i.e. we prove for the first time standard homogeneous Bose-Einstein condensation for such interacting systems

Blue Straggler Stars: Early Observations that Failed to Solve the Problem

In this chapter, I describe early ideas on blue stragglers, and various observations (some published, some not) that promised but failed to resolve the question of their origin. I review the data and ideas that were circulating from Allan Sandage's original discovery in 1953 of "anomalous blue stars" in the globular cluster M3, up until about 1992, when what seems to have been the only previous meeting devoted to Blue Straggler Stars (BSSs) was held at the Space Telescope Science Institute.Comment: Chapter 2, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G. Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe

Differences in coronary flow and myocardial metabolism at rest and during pacing between patients with obstructive and patients with nonobstructive hypertrophic cardiomyopathy

Fifty patients with hypertrophic cardiomyopathy underwent invasive study of coronary and myocardial hemodynamics in the basal state and during the stress of pacing. The 23 patients with basal obstruction (average left ventricular outflow gradient, 77 ± 33 mm Hg; left ventricular systolic pressure, 196 ± 33 mm Hg, mean ± 1 SD) had significantly lower coronary resistance (0.85 ± 0.18 versus 1.32 ± 0.44 mm Hg min/ml, p < 0.001) and higher basal coronary flow (106 ± 20 versus 80 ± 25 ml/min, p < 0.001) in the anterior left ventricle, associated with higher regional myocardial oxygen consumption (12.4 ± 3.6 versus 8.9 ± 3.3 ml oxygen/min, p < 0.001) compared with the 27 patients without obstruction (mean left ventricular systolic pressure 134 ± 18 mm Hg, p < 0.001).Myocardial oxygen consumption and coronary blood flow were also significantly higher at paced heart rates of 100 and 130 beats/min (the anginal threshold for 41 of the 50 patients) in patients with obstruction compared with those without. In patients with obstruction, transmural coronary flow reserve was exhausted at a heart rate of 130 beats/min; higher heart rates resulted in more severe metabolic evidence of ischemia with all patients experiencing chest pain, associated with an actual increase in coronary resistance. Patients without obstruction also demonstrated evidence of ischemia at heart rates of 130 and 150 beats/min, with 25 of 27 patients experiencing chest pain. In this group, myocardial ischemia occurred at significantly lower coronary flow, higher coronary resistance and lower myocardial oxygen consumption, suggesting more severely impaired flow delivery in this group compared with those with obstruction. Abnormalities in myocardial oxygen extraction and marked elevation in filling pressures during stress were noted in both groups.Thus, obstruction to left ventricular outflow is associated with high left ventricular systolic pressure and oxygen consumption and therefore has important pathogenetic importance to the precipitation of ischemia in patients with hypertrophic cardiomyopathy. Patients without obstruction may have greater impairment in coronary flow delivery during stress