Yb-doped strictly all-fiber laser actively Q-switched by intermodal acousto-optic modulation

We show an actively Q-switched ytterbium-doped strictly all-fiber laser. Cavity loss modulation is achieved in a tapered optical fiber by core-to-cladding mode-coupling induced by travelling flexural acoustic waves. When the acoustical signal is switched-off, the optical power losses within the cavity are reduced, and then a laser pulse is emitted. Trains of Q-switched pulses were successfully obtained at repetition rates in the range 1–10 kHz, with pump powers between 59 and 88 mW, at the optical wavelength of 1064.1 nm. Best results were for laser pulses of 118 mW peak power, 1.8 μs of time width, with a pump power of 79 mW, at 7 kHz repetition rate.     

Zinc-phosphate nanoparticles with reversibly attached TNF-α analogs: an interesting concept for potential use in active immunotherapy

The authors’ intention was to prepare nanometer-sized zinc-phosphate nanoparticles that would be capable of binding histidine-rich TNF-α analogs onto their surface via a coordinative bond. Zinc-phosphate nanoparticles with a size of around 60 nm were prepared by a wet precipitation method and characterized using SEM, EDX, XRD, and DLS. First, BSA was bound as a testing protein, afterward two TNF-α analogs with decreased activity were bound to the described nanoparticles. The efficiency of binding and the existence of coordinative bond were confirmed with SDS-PAGE analysis. During binding, particle storage, and release experiments, the prepared TNF-α analogs retained their biological activity—hence the epitopes necessary for formation of antibodies stayed intact. The particle size did not change within a period of 2 weeks. No significant agglomeration was observed, the particles could be quickly dispersed in ultrasound. The present nanoparticles and the general approach of coordinative binding are widely applicable for natural and engineered histidine-rich proteins. The nanoparticles bearing appropriate TNF-α analogs could also be potentially used for active immunotherapy to tackle the chronic inflammatory diseases associated with pathogenically elevated levels of TNF-α.     

Nonlinear dust-ion-acoustic waves in a multi-ion plasma with trapped electrons

A dusty multi-ion plasma system consisting of non-isothermal (trapped) electrons, Maxwellian (isothermal) light positive ions, warm heavy negative ions and extremely massive charge fluctuating stationary dust have been considered. The dust-ion-acoustic solitary and shock waves associated with negative ion dynamics, Maxwellian (isothermal) positive ions, trapped electrons and charge fluctuating stationary dust have been investigated by employing the reductive perturbation method. The basic features of such dust-ion-acoustic solitary and shock waves have been identified. The implications of our findings in space and laboratory dusty multi-ion plasmas are discussed.     

Constant curvature coefficients and exact solutions in fractional gravity and geometric mechanics

We present a study of fractional configurations in gravity theories and Lagrange mechanics. The approach is based on a Caputo fractional derivative which gives zero for actions on constants. We elaborate fractional geometric models of physical interactions and we formulate a method of nonholonomic deformations to other types of fractional derivatives. The main result of this paper consists of a proof that, for corresponding classes of nonholonomic distributions, a large class of physical theories are modelled as nonholonomic manifolds with constant matrix curvature. This allows us to encode the fractional dynamics of interactions and constraints into the geometry of curve flows and solitonic hierarchies.     

Comparison between decoherence time for a two-state spin ½ system with its corresponding quantum retrieval period

The evolution of a two-state quantum system (a spin ½ particle) in both the framework of standard quantum mechanics and under the decoherence regime is considered. The former approach on this issue is the well-known quantum flipping process of a dichotomic system subjected to a time-dependent magnetic field. In the latter approach, the Spin-Boson model is utilized to describe the interaction of system with its environment and the Born-Markov master equation is derived to obtain the decoherence time. It is possible to show that under certain conditions, one may find a potential conflict between the predictions of decoherence theory and the result observed in a typical quantum flipping experiment.     

VEGFR-2 targeted cellular delivery of doxorubicin by gold nanoparticles for potential antiangiogenic therapy

We report a novel gold nanobioconjugate system that achieves targeted delivery of the small molecule drug doxorubicin to endothelial cells using anti-VEGFR-2 antibody conjugated gold nanoparticles (GNPs). The reported nanobioconjugate system combines the inherent ability of GNPs to undergo high levels of derivatization with the precision of antibody recognition of a cell surface antigen. Transmission electron microscopy (TEM) and surface-enhanced Raman spectroscopy (SERS) confirmed intracellular presence of the GNPs. Using a VEGFR-2 expressing cell line and a cell line that is negative for the receptor, in combination with competition assay we established the cell specific targeted delivery of the nanobioconjugate. The nanobioconjugate system described here may have potential drug delivery applications for antiangiogenic cancer therapy.     

Quantum-confined electronic states in atomically well-defined graphene nanostructures

Despite the enormous interest in the properties of graphene and the potential of graphene nanostructures in electronic applications, the study of quantum-confined states in atomically well-defined graphene nanostructures remains an experimental challenge. Here, we study graphene quantum dots (GQDs) with well-defined edges in the zigzag direction, grown by chemical vapor deposition on an Ir(111) substrate by low-temperature scanning tunneling microscopy and spectroscopy. We measure the atomic structure and local density of states of individual GQDs as a function of their size and shape in the range from a couple of nanometers up to ca. 20 nm. The results can be quantitatively modeled by a relativistic wave equation and atomistic tight-binding calculations. The observed states are analogous to the solutions of the textbook "particle-in-a-box" problem applied to relativistic massless fermions.     

Upper Bound on the Density of Ruelle Resonances for Anosov Flows

Using a semiclassical approach we show that the spectrum of a smooth Anosov vector field V on a compact manifold is discrete (in suitable anisotropic Sobolev spaces) and then we provide an upper bound for the density of eigenvalues of the operator (−i)V, called Ruelle resonances, close to the real axis and for large real parts.     

A New Derivation of the Quantum Navier–Stokes Equations in the Wigner–Fokker–Planck Approach

A quantum Navier–Stokes system for the particle, momentum, and energy densities is formally derived from the Wigner–Fokker–Planck equation using a moment method. The viscosity term depends on the particle density with a shear viscosity coefficient which equals the quantum diffusion coefficient of the Fokker–Planck collision operator. The main idea of the derivation is the use of a so-called osmotic momentum operator, which is the sum of the phase-space momentum and the gradient operator. In this way, a Chapman–Enskog expansion of the Wigner function, which typically leads to viscous approximations, is avoided. Moreover, we show that the osmotic momentum emerges from local gauge theory.     

Role of different Skyrme forces and surface corrections in exotic cluster decay

We present cluster-decay studies of ⁵⁶Ni^* formed in heavy-ion collisions using different Skyrme forces. Our study reveals that different Skyrme forces do not alter the transfer structure of fractional yields significantly. The cluster decay half-lives of different clusters lie within ±10% for preformed cluster models (PCM) and ±15% for unified fission models (UFM).