Chondrogenic potential of macroporous biodegradable cryogels based on synthetic poly(α-amino acids).

In this study, the potential of highly porous hydrogels based on biodegradable synthetic poly(α-amino acids) to support proliferation and chondrogenesis of human dental pulp stem cells (hDPSCs) was investigated. Covalently crosslinked gels with permanent pores were formed under cryogenic conditions by free-radical copolymerization of poly[N5-(2-hydroxyethyl)-l-glutamine-stat-N5-(2-methacryloyl-oxy-ethyl)-l-glutamine] (PHEG-MA) with 2-hydroxyethyl methacrylate (HEMA) and N-propargyl methacrylamide (PrMAAm) as minor co-monomers. PrMAAm provided alkyne groups for modifying the gels with cell-supporting moieties (RGDS peptides) by the azide-alkyne "click"-reaction. Two types of gels with different compressive moduli were prepared. Each type was modified with two different concentrations of RGDS peptide. X-ray computed nanotomography (nanoCT) was used to visualize and analyze the 3D-structure of the cryogels. It was shown that modifying the PHEG-MA cryogels within the range of RGDS concentrations examined here had a positive effect on the proliferation of hDPSCs. Immunofluorescence staining for collagen type 2 and aggrecan proved that there was differentiation of hDPSCs into chondrocytes.

Excitation of ship waves by a submerged object: New solution to the classical problem.

We have proposed a new method for solving the problem of ship waves excited on the surface of a nonviscous liquid by a submerged object that moves at a variable speed. As a first application of this method, we have obtained a new solution to the classic problem of ship waves generated by a submerged ball that moves rectilinearly with constant velocity parallel to the equilibrium surface of the liquid. For this example, we have derived asymptotic expressions describing the vertical displacement of the liquid surface in the limit of small and large values of the Froude number. The exact solution is presented in the form of two terms, each of which is reduced to one-dimensional integrals. One term describes the "Bernoulli hump" and another term the "Kelvin wedge." As a second example, we considered vertical oscillation of the submerged ball. In this case, the solution leads to the calculation of one-dimensional integral and describes surface waves propagating from the epicenter above the ball.

N-(2-hydroxypropyl) methacrylamide based cryogels--synthesis and biomimetic modification for stem cell applications.

The design of favorable mechanical properties and suitable surface modifications of hydrogels in order to stimulate specific cell response is a great challenge. N-(2-Hydroxypropyl) methacryl-amide (HPMA) was utilized to form macroporous cryogel scaffolds for stem cell applications. Furthermore, one group of scaffolds was enhanced by copolymerization of HPMA with methacryloyl-GGGRGDS-OH peptide in an effort to integrate biomimetic adhesion sites. The cryogels were characterized by stiffness and equilibrium swelling measurements as well as by scanning electron microscopy. Cell culture experiments were performed with human adipose-derived stem cells and substrates were found completely non-toxic. Moreover, RGDS-enriched cryogels supported cell attachment, spreading and proliferation, so they can be considered suitable for designed aims.

[Hybrid revascularization: a combined approach to multivessel coronary artery lesions].

Analysis of effectiveness and feasibility of hybrid approach to multivessel coronary artery disease and problems of interaction between cardiac surgeons and interventional cardiologists in deciding on the choice of revascularization method is performed in the article. Hybrid approach to multivessel disease defined as sternal sparing, off-pump, minimally invasive, hand sewn left internal mammary - left anterior descending (LAD) arteries by-pass graft with percutaneous coronary revascularization of non-LAD lesions to achieve functionally complete revascularization is described in detail. Data of multicenter studies and clinical recommendations for myocardial revascularization is discussed.

Photon neutralizer as an example of an open billiard.

A simple photon cavity consisting of three flat mirrors is considered, which provides a model for a photon neutralizer of negative ion beams to be used in a neutral beam injector for plasma heating in fusion devices. Treating the system as an open mathematical billiard, the mechanism of photon scattering on the sharp boundary between two mirrors is described. Assuming a balance between the continuous injection of the photons into the device and their loss through its open ends, the stationary angular distribution of the photons in the trap is computed in closed form and an estimate for the confinement time of the photons in the neutralizer is provided.

Formation of a magnetic hole above the mirror-instability threshold in a plasma with sloshing ions.

Within the framework of paraxial approximation it is shown that in an anisotropic plasma with sloshing ions confined an open-ended system a magnetic hole is formed near the turning point of the sloshing ions above the threshold of the mirror instability. The magnetic field experiences a jump at the hole boundary from the side of the magnetic mirror. For a small excess over the mirror instability threshold, the surface of the discontinuity has the shape of a truncated paraboloid, and the magnitude of the magnetic field jump at the system axis is proportional to the radius of the hole and gradually decreases to zero away of the axis. It is argued that disappearance of the magnetic hole because of the widening of the sloshing ions angular spread in the course of the neutral beam injection results in abrupt anticorrelated changes of the diamagnetic signals measured near the turning point of the sloshing ions and near the midplane of the gas-dynamic trap.

Formation of an ion beam in an elementary cell with inhomogeneous emission current density.

A well-known Pierce solution that allows focusing a beam of charged particles using properly shaped electrodes outside the beam aperture is generalized to the case of an accelerating system with inhomogeneous emission current density. It is shown that the defocusing effect of the space charge can, in principle, be evenly compensated over the entire cross section of the beam. In contrast to the beam with a uniform emission current density, both the electric potential and the transverse electric field must be controlled along the beam boundary in order to eliminate the angular divergence. However, eliminating the angular spread evenly across the beam constitutes a mathematically ill-posed problem which needs to be solved with the use of one or another method of regularization. An alternative way of diminishing beam emittance is proposed for the beam where the emission current is uniform across the entire aperture except for a narrow beam edge layer and a simple formula for the Pierce electrodes is derived. Numerical simulation has proved the reasonable accuracy of our analytical theory.

Left-side approach to the mitral valve.

BACKGROUND AND AIM OF THE STUDY: The standard, minimally invasive surgical approach to the mitral valve is usually accomplished from the right side, through a longitudinal incision posterior and parallel to the interatrial groove. The left-side approach should perhaps be reconsidered for its suitable exposure of the mitral valve. METHODS: Eleven consecutive patients underwent mitral valve surgery via a left lateral minithoracotomy, with cardiopulmonary bypass performed through the left femoral artery and vein. The left internal mammary artery was used as a coronary graft in one patient. Cardioplegic solution was delivered through the ascending aorta. After direct aorta cross-clamping, mitral surgeries were performed, including mechanical and bioprosthetic implants, redo operations, annuloplasties and repairs. RESULTS: An excellent view of the mitral valve was obtained in all cases, with optimal vision of the whole annulus, chordae tendineae, papillary muscles and aortic valve possible. Exposure of the mitral valve was superior to that achieved with the standard approach from the right, notably with a wider angle of vision and greater flexibility of movement available. Moreover, mitral valve structures were closer to the operator, making the procedure easier to perform. CONCLUSION: The left-side approach to the mitral valve offers excellent vision and exposure of the valve. Although awaiting additional cases to validate results, in the absence of major complications we recommend this technique.