Energetics and Possible Formation and Decay Mechanisms of Vortices in Helium Nanodroplets

The energy and angular momentum of both straight and curved vortex states of a helium nanodroplet are examined as a function of droplet size. For droplets in the size range of many experiments, it is found that during the pickup of heavy solutes, a significant fraction of events deposit sufficient energy and angular momentum to form a straight vortex line. Curved vortex lines exist down to nearly zero angular momentum and energy, and thus could in principle form in almost any collision. Further, the coalescence of smaller droplets during the cooling by expansion could also deposit sufficient angular momentum to form vortex lines. Despite their high energy, most vortices are predicted to be stable at the final temperature (0.38 K) of helium nanodroplets due to lack of decay channels that conserve both energy and angular momentum.Comment: 10 pages, 8 figures, RevTex 4, submitted to Phys. Rev.

Quantum Rotation of HCN and DCN in Helium-4

We present calculations of rotational absorption spectra of the molecules HCN and DCN in superfluid helium-4, using a combination of the Diffusion Monte Carlo method for ground state properties and an analytic many-body method (Correlated Basis Function theory) for the excited states. Our results agree with the experimentally determined effective moment of inertia which has been obtained from the $J=0\to 1$ spectral transition. The correlated basis function analysis shows that, unlike heavy rotors such as OCS, the J=2 and higher rotational excitations of HCN and DCN have high enough energy to strongly couple to rotons, leading to large shifts of the lines and accordingly to anomalous large spectroscopic distortion constants, to the emergence of roton-maxon bands, and to secondary peaks in the absorption spectra for J=2 and J=3.Comment: accepted by Phys. Rev. B; changes: included referee suggestions, removed typos, added 10 ref

Communication between health care providers and return-to-work

Sixth International Scientific Conference on Prevention of Work-Related Musculosketal Disorders (PREMUS) Boston, USA, 27-30 august 2007

Echocardiography in chronic aortic insufficiency. Is valve replacement too late when left ventricular end-systolic dimension reaches 55 mm?

To determine whether a ventricular (LV) end-systolic dimension (ESD) greater than or equal to 55 mm and LV left fractional shortening less than 25% are risk factors for aortic valve replacement (AVR) in patients with aortic insufficiency, we analyzed the clinical course and M-mode echocardiograms in 47 consecutive patients who underwent AVR for isolated symptomatic AI. Group 1 patients (n = 27) had a preoperative ESD less than 55 mm (mean 44 mm, range 30-52 mm) and group 2 patients (n = 20) had a preoperative ESD greater than or equal to 55 mm (mean 62 mm, range 55-85 mm). One patient in group 1 and 10 patients in group 2 had left ventricular fractional shortening less than 25%. There were no perioperative or postoperative deaths during an average follow-up of 41 months (range 6-76 months). Five patients had perioperative myocardial infarctions (MIs), three in group 1 and two in group 2. Since myocardial protection with cold potassium cardioplegia was instituted, no patient has suffered a perioperative MI. The average preoperative New York Heart Association functional classification was 2.3 (group 1) and 2.6 (group 2). Postoperatively, it was 1.2 in group 1 and 1.1 in group 2. Thirty-three patients (20 in group 1 and 13 in group 2) had echoc

IgG antibodies in food allergy influence allergen-antibody complex formation and binding to B cells: a role for complement receptors

Allergen-IgE complexes are more efficiently internalized and presented by B cells than allergens alone. It has been suggested that IgG Abs induced by immunotherapy inhibit these processes. Food-allergic patients have high allergen-specific IgG levels. However, the role of these Abs in complex formation and binding to B cells is unknown. To investigate this, we incubated sera of peanut- or cow's milk-allergic patients with their major allergens to form complexes and added them to EBV-transformed or peripheral blood B cells (PBBCs). Samples of birch pollen-allergic patients were used as control. Complex binding to B cells in presence or absence of blocking Abs to CD23, CD32, complement receptor 1 (CR1, CD35), and/or CR2 (CD21) was determined by flow cytometry. Furthermore, intact and IgG-depleted sera were compared. These experiments showed that allergen-Ab complexes formed in birch pollen, as well as food allergy, contained IgE, IgG1, and IgG4 Abs and bound to B cells. Binding of these complexes to EBV-transformed B cells was completely mediated by CD23, whereas binding to PBBCs was dependent on both CD23 and CR2. This reflected differential receptor expression. Upon IgG depletion, allergen-Ab complexes bound to PBBCs exclusively via CD23. These data indicated that IgG Abs are involved in complex formation. The presence of IgG in allergen-IgE complexes results in binding to B cells via CR2 in addition to CD23. The binding to both CR2 and CD23 may affect Ag processing and presentation, and (may) thereby influence the allergic response