Pseudo-gap and possible Spin-Peierls transition in the vanadium oxide VOSb 2 O 4

We report on the magnetic susceptibility and electron spin resonance measurements on polycrystalline samples of the vanadium oxide VOSb₂O₄, a quasi-one-dimensional S = 1/2 Heisenberg system. The susceptibility vanishes at zero temperature, but there is no cusp at the onset of the susceptibility drop, and the ESR linewidth exhibits an increase characteristic of a phase transition at a much lower temperature. We show that this behaviour is consistent with the formation of a pseudo-gap in a spin-Peierls system in the adiabatic limit. Received 7 February 2001 and Received in final form 24 April 2001     

Direct Antifungal Effect of Femtosecond Laser on Trichophyton rubrum Onychomycosis

Onychomycosis is caused by dermatophyte infection of the nail. Though laser energy has been shown to eliminate dermatophytes in vitro, direct laser elimination of onychomycosis is not successful due to difficulties in selectively delivering laser energy to the deeper levels of the nail plate without collateral damage. Femtosecond (fsec) infrared titanium sapphire lasers circumvent this problem by the nonlinear interactions of these lasers with biological media. This quality, combined with the deeply penetrating nature of the near-infrared radiation, allows elimination of deeply seeded nail dermatopytes without associated collateral damage. Nail cuttings obtained from patients with onychomycosis caused by Trichophyton rubrum underwent fsec laser irradiation using increasing laser intensities with the focus scanned throughout the whole thickness of the nail specimen. The efficacy of the laser treatment was evaluated by subculture. Scanning electron microscopy was used to determine fsec laser-induced collateral damage. We found that a fsec laser fluence of 7 × 10³¹ photons m⁻² s⁻¹ or above successfully inhibited the growth of the fungus in all samples examined, whereas laser intensities above 1.7 × 10³² photons m⁻² s⁻¹ affected the structure of the nail plate. Our findings suggest that T. rubrum-mediated onychomycosis may be treated by fsec laser technology.     

Condensate-free superfluid induced by the frustrated proximity effect

Since the discovery of superfluidity in 4He and Landau's phenomenological theory, the relationship between Bose condensation and superfluidity has been intensely debated. 4He is known by now to be both superfluid and condensed at low temperature, and more generally, in dimension D≥2, all superfluid bosonic models realized in experiments are condensed in their ground state, the most recent example being provided by ultracold bosonic atoms trapped in an optical lattice. In this Letter, it is shown that a 2D gas of bosons which is not condensed at T=0 can be achieved by populating a layer through a frustrated proximity effect from a superfluid reservoir. This condensate-free bosonic fluid is further shown to be a superfluid with incommensurate correlations.     

Two degree of freedom gyroscopic systems with linear integrals

In this paper we consider the first integrals, linear in velocities, of conservative gyroscopic systems with two degrees of freedom. A precise criterion which specifies whether a given gyroscopic system possesses a linear integral is derived. When the kinetic energy has the structure of a standard form of the metric of revolution, all the possible systems which admit a linear integral and corresponding integrals are determined explicitly. Two examples are considered to illustrate the usefulness of the derived results.     

Applying stochastic goal programming: A case study on water use planning

A decision support model to help public water agencies allocate surface water among farmers and authorize the use of groundwater for irrigation (especially in Mediterranean dry regions) is developed. This is a stochastic goal programming approach with two goals, the first concerning farm management while the other concerns environmental impact. Targets for both goals are established by the agency. This model yields three reduction factors to decide the different reductions in available surface water, standard groundwater and complementary groundwater that the agency should grant/authorize for irrigation, this depending on if it is a dry or wet year. In drought periods, the model recommends using more groundwater (in percentage) than in wet periods. A case study using year-to-year statistical information on available water over the period 1941–2005 is developed through numerical tables. A step-by-step computational process is presented in detail.     

Field-induced staggered magnetization and magnetic ordering in Cu2(C5H12N2)2Cl4

We present a 2D NMR investigation of the gapped spin-1/2 compound Cu2(C5H10N2D2)2Cl4. Our measurements reveal the presence of a magnetic field-induced transverse staggered magnetization (TSM) which persists well below and above the field-induced 3D long-range magnetically ordered (FIMO) phase. The symmetry of this TSM is different from that of the TSM induced by the order parameter of the FIMO phase. Its origin, field dependence, and symmetry can be explained by an intradimer Dzyaloshinskii-Moriya interaction, as shown by DMRG calculations on a spin-1/2 ladder. This leads us to predict that the transition into the FIMO phase is not in the BEC universality class.     

Heavy metals in petroleum-contaminated surface soils in Serbia

Investigation of heavy metal contamination levels as well as their association types with substrates in petroleum-contaminated surface soil was carried out using modified sequential extraction method. In that way, remobilization capacity of metal cations, both in natural conditions and in accidents, has been studied. Moreover, partitioning of heavy metals, originating from spilt oil derivative, among surface soil substrates was estimated. Extreme contamination with lead was discovered, as well as the increased concentrations of zinc and copper. Oil-derived Pb and Zn were found to be distributed between carbonates and amorphous Fe-oxides, whereas Cu was found to be dominantly associated with amorphous Fe-oxides. Appreciable amounts of these metals were also found to be incorporated into more resistant structures. In petroleum-contaminated surface soil, substrates of cadmium are carbonates, whereas nickel has the great affinity toward hydrous Mn-oxides. Cd is proven to be the most mobile metal in oil-contaminated surface soil.