Study of isobaric analogue resonances in65Cu by proton scattering from64Ni

Zeitschrift für Physik A Hadrons and nuclei - Excitation functions of the elastic proton scattering by64Ni were measured in the energy rangeE p =5.0–6.2 MeV at 90°, 125° and...     

Toxicity of zinc oxide nanoparticles to the annelid <Emphasis Type="Italic">Enchytraeus crypticus</Emphasis> in agar-based exposure media

Toxicity of zinc oxide nanoparticle (ZnO-NPs) powder and water soluble salt of Zn (ZnCl₂) to the annelid Enchytraeus crypticus was tested in agarose gel. Influence of the spiking method on the resulting size of nanoparticles and on E. crypticus mortality was studied. Two methods of ZnO-NPs powder (mean particle size diameter of 10 nm) introduction into the exposure media were used. In the first method, the nano-powder was initially cryogenically ground with dry agar followed by an addition of water. The second procedure began with re-suspension of nanoparticles in demineralized water containing a dispersant (sodium pyrophosphate decahydrate). The obtained colloid was subsequently mixed with hot agar gel. Relative mortality in worms observed after 96 h of their exposure to the ZnO-NPs concentrations (all in mg of ZnO-NPs per kg of agar) of 50, 100, 200, 500 and 1000 in the cryogenically ground medium ranged between 28.9 % and 34.4 % and it did not exhibit any concentration dependence. When the second method of exposure media preparation was applied, the relative mortality ranged from 0 % to 66.6 % in the same concentration region depending on the concentration. Scanning electron microscopy (SEM) revealed the presence of large agglomerates (1–10 µm in diameter) in the media prepared by cryogenic grinding with the highest concentration of ZnO-NPs. Neither the cryogenically ground media with lower ZnO-NPs concentrations nor any media prepared from colloidal solutions contained agglomerates exceeding 100 nm, detectable by SEM. Hydrodynamic diameters of particles in the colloids used in the second method of agar preparation were measured using dynamic light scattering (DLS) and ranged between 164 nm and 240 nm. The observed toxicity was thus clearly dependent on the size of ZnO-NPs agglomerates and the technique of exposure media preparation. Experimentally detected LC₅₀ value for dissolved Zn²⁺ was 37.2 mg kg^?1 in agar. The same concentration of Zn induced an approximately 30 % mortality of E. crypticus when administered in form of cryogenically ground ZnO-NPs with agar. No observable effects were found at this ZnO-NPs concentration when the exposure medium was prepared from the colloid solution.     

From realistic to simple models of associating fluids. II. Primitive models of ammonia,ethanol and models of water revisited

Recently developed methodology to construct primitive models of associating fluids directly from realistic intermolecular potential functions is applied to ammonia, ethanol and several models of water. Hard cores of the molecules are pictured as fused hard-sphere bodies defined by composite short-range repulsions, and the Coulombic repulsions and attractions are approximated by hard-sphere and square-well potentials, respectively. Hard-sphere diameters are determined directly from the parent potential using a theoretical route and the range of the square-well attraction is adjusted using constraints imposed on hydrogen bonding. It is shown that the developed primitive models, despite their simplicity and lack of any long-range interactions, are able to reproduce the structural properties (the set of the site–site correlation functions) of the parent realistic models and may thus serve well as a reference in the perturbation theory.     

The melting phenomenon in random-walk model of DNA

The melting phenomenon in a double-stranded homopolypeptide is considered. The relative distance between the corresponding monomers of two polymer chains is modeled by the two-dimensional random walk on the square lattice. Returns of the random walk to the origin describe the formation of hydrogen bonds between complementary units. To take into account the two competing interactions of monomers inside the chains, we obtain a completely denatured state at finite temperature T _c .     

Mode locking and efficient generation of pulsed difference-frequency radiation in two-color heterolasers

Efficient schemes are proposed for generation of picosecond pulses in the mid/far-IR and THz ranges through intracavity nonlinear mixing of fields generated in two-color injection heterolasers, operating in the mode-locking regime at room temperature. It is shown that these schemes make it possible to increase the peak lasing power by a factor of about 100.     

Nonclassical Solutions of Fully Nonlinear Elliptic Equations

We prove the existence of non-smooth solutions to fully non-linear elliptic equations. Received: June 2006, Accepted: January 2007     

V2-dependence of centrifugal constants of H2O molecules in the Morse oscillator model

It is shown in this paper that the centrifugal constantsC ^l (t) calculated in the Morse, oscillator model for the sequence from the operator H _red ^(t) , which is used in processing the rotational levels of the H₂O molecule, are linked by recurrence relations, which enables H _z ^(t) –H _z ^(O) to be given in closed form.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 56–58, October, 1982.