On uniformly rotating fluid drops trapped between two parallel plates

This contribution is about the dynamics of a liquid bridge between two fixed parallel plates. We consider a mathematical model and present some results from the doctoral thesis [10] of the first author. He showed that there is a Poisson bracket and a corresponding Hamiltonian, so that the model equations are in Hamiltonian form. The result generalizes previous results of Lewis et al. on the dynamics of free boundary problems for "free" liquid drops to the case of a drop between two parallel plates, including, especially the effect of capillarity and the angle of contact between the plates and the free fluid surface. Also, we prove the existence of special solutions which represent uniformly rotating fluid ridges, and we present specific stability conditions for these solutions. These results extend work of Concus and Finn [2] and Vogel [18],[19] on static capillarity problems (see also Finn [5]). Using the Hamiltonian structure of the model equations and symmetries of the solutions, the stability conditions can be derived in a systematic way. The ideas that are described will be useful for other situations involving capillarity and free boundary problems as well

Persistent quantum interfering electron trajectories

The emission of above-ionization-threshold harmonics results from the recombination of two electron wavepackets moving along a "short" and a "long" trajectory in the atomic continuum. Attosecond pulse train generation has so far been attributed to the short trajectory, attempted to be isolated through targeted trajectory-selective phase matching conditions. Here, we provide experimental evidence for the contribution of both trajectories to the harmonic emission, even under phase matching conditions unfavorable for the long trajectory. This is finger printed in the interference modulation of the harmonic yield as a function of the driving laser intensity. The effect is also observable in the sidebands yield resulting from the frequency mixing of the harmonics and the driving laser field, an effect with consequences in cross-correlation pulse metrology approaches.Comment: 13 pages, 3 figure

Special studies of AROD system concepts and designs

Signal to noise ratios in airborne range and orbit determination system, and carrier and range loop performance analyse

On the particle paths and the stagnation points in small-amplitude deep-water waves

In order to obtain quite precise information about the shape of the particle paths below small-amplitude gravity waves travelling on irrotational deep water, analytic solutions of the nonlinear differential equation system describing the particle motion are provided. All these solutions are not closed curves. Some particle trajectories are peakon-like, others can be expressed with the aid of the Jacobi elliptic functions or with the aid of the hyperelliptic functions. Remarks on the stagnation points of the small-amplitude irrotational deep-water waves are also made.Comment: to appear in J. Math. Fluid Mech. arXiv admin note: text overlap with arXiv:1106.382

Effective operators from exact many-body renormalization

We construct effective two-body Hamiltonians and E2 operators for the p-shell by performing $16\hbar\Omega$ ab initio no-core shell model (NCSM) calculations for A=5 and A=6 nuclei and explicitly projecting the many-body Hamiltonians and E2 operator onto the $0\hbar\Omega$ space. We then separate the effective E2 operator into one-body and two-body contributions employing the two-body valence cluster approximation. We analyze the convergence of proton and neutron valence one-body contributions with increasing model space size and explore the role of valence two-body contributions. We show that the constructed effective E2 operator can be parametrized in terms of one-body effective charges giving a good estimate of the NCSM result for heavier p-shell nuclei.Comment: 9 pages, 8 figure

Ab-initio shell model with a core

We construct effective 2- and 3-body Hamiltonians for the p-shell by performing 12\hbar\Omega ab initio no-core shell model (NCSM) calculations for A=6 and 7 nuclei and explicitly projecting the many-body Hamiltonians onto the 0\hbar\Omega space. We then separate these effective Hamiltonians into 0-, 1- and 2-body contributions (also 3-body for A=7) and analyze the systematic behavior of these different parts as a function of the mass number A and size of the NCSM basis space. The role of effective 3- and higher-body interactions for A>6 is investigated and discussed

Chromospheric Variability in SDSS M Dwarfs. II. Short-Timescale H-alpha Variability

[Abridged] We present the first comprehensive study of short-timescale chromospheric H-alpha variability in M dwarfs using the individual 15 min spectroscopic exposures for 52,392 objects from the Sloan Digital Sky Survey. Our sample contains about 10^3-10^4 objects per spectral type bin in the range M0-M9, with a total of about 206,000 spectra and a typical number of 3 exposures per object (ranging up to a maximum of 30 exposures). Using this extensive data set we find that about 16% of the sources exhibit H-alpha emission in at least one exposure, and of those about 45% exhibit H-alpha emission in all of the available exposures. Within the sample of objects with H-alpha emission, only 26% are consistent with non-variable emission, independent of spectral type. The H-alpha variability, quantified in terms of the ratio of maximum to minimum H-alpha equivalent width (R_EW), and the ratio of the standard deviation to the mean (sigma_EW/), exhibits a rapid rise from M0 to M5, followed by a plateau and a possible decline in M9 objects. In particular, R_EW increases from a median value of about 1.8 for M0-M3 to about 2.5 for M7-M9, and variability with R_EW>10 is only observed in objects later than M5. For the combined sample we find that the R_EW values follow an exponential distribution with N(R_EW) exp[-(R_EW-1)/2]; for M5-M9 objects the characteristic scale is R_EW-1\approx 2.7, indicative of stronger variability. In addition, we find that objects with persistent H-alpha emission exhibit smaller values of R_EW than those with intermittent H-alpha emission. Based on these results we conclude that H-alpha variability in M dwarfs on timescales of 15 min to 1 hr increases with later spectral type, and that the variability is larger for intermittent sources.Comment: Submitted to ApJ; 20 pages, 15 figure

Effect of cinacalcet cessation in renal transplant recipients with persistent hyperparathyroidism

Background. Persistent hyperparathyroidism after renal transplantation affects bone and allografts. Cinacalcet, a calcimimetic, reduces serum calcium and PTH in renal transplant recipients with persistent hyperparathyroidism. Here, we address the question whether this effect of cinacalcet persists after withdrawal. Methods. Therefore, cinacalcet was stopped after 12 months treatment in 10 stable renal transplant patients. Serum calcium, phosphate, PTH, creatinine and cystatin C were monitored for 3 months. Results. Serum calcium, normalized in nine patients before cessation of cinacalcet (2.32 ± 0.05mmol/l, mean ± SEM), increased after 3 months of discontinuation by 0.17 ± 0.04mmol/l, P < 0.05, but remained within the normal range in eight patients. Compared with the time point of cessation, PTH remained unchanged or decreased further after 3 months without therapy in six patients. Measurements of cystatin C suggested an improvement of the glomerular filtration rate after cessation in 9 out of 10 patients (1.55 ± 0.09 vs 1.33 ± 0.12 mg/l, P < 0.01). Conclusion. First, a beneficial effect of cinacalcet beyond the duration of a 12-month therapy appears to be present in some patients and second, the previously suspected influence of cinacalcet therapy on renal function is reversible. Thus, it is reasonable to consider a trial of cinacalcet cessation to identify these patients. The optimal time point for such a discontinuation is unknown. The present observations are preliminary. They clearly require a prospective randomized trial for definitive confirmatio

The calcimimetic cinacalcet normalizes serum calcium in renal transplant patients with persistent hyperparathyroidism

Background. Treatment of persistent hyperparathyroidism in renal transplant patients resistant to calcium and vitamin D sterols is limited and often requires parathyroidectomy. Given the potential hazards linked to surgery, an alternative approach to manage excess parathyroid hormone (PTH) secretion is needed. Calcimimetics inhibit PTH secretion by modulating the calcium-sensing receptor in the parathyroid. Lowering of the serum calcium concentration with the calcimimetic cinacalcet has previously been demonstrated in patients with primary hyperparathyroidism or with secondary hyperparathyroidism on dialysis. Here we present the first clinical observations of a calcimimetic in patients with persistent hyperparathyroidism. Methods. A 30 mg dose of cinacalcet was prescribed once daily for 3 months to seven female and seven male stable renal transplant patients, aged 23-65 years, 7 months to 14 years after transplantation, with a serum creatinine ranging from 89 to 229 µmol/l and persistent hyperparathyroidism. Concomitant medication included cyclosporin and low-dose prednisone in all patients. Results. On cinacalcet, serum calcium decreased and normalized in all but two patients (baseline 2.72±0.03 mmol/l; 1 month 2.42±0.04 mmol/l, P<0.001), whereas serum PTH and phosphate levels did not change significantly. A slight reduction in renal function, as assessed by serum creatinine concentration, was observed at months 2 and 3 (P<0.05). An immunoglobulin-deficient patient developed colitis after 1 week of treatment and cinacalcet was withdrawn. No patient stopped cinacalcet because of other presumed side effects. Conclusion. Calcimimetics are a promising therapy in renal transplant patients with persistent hyperparathyroidism. Prospective controlled studies must now be designed focusing on functionally relevant musculo-skeletal end-points and allowing the exclusion of negative effects on long-term renal and general outcome of such patient