Determination of <Superscript>93</Superscript>Zr in nuclear power plant wastes

A radioanalytical method (based on separation using UTEVA columns and ICP-MS measurement) has been used for determination of ⁹³Zr in 37 nuclear power plant samples. As ⁹³Nb might affect the detection of ⁹³Zr, Monte Carlo activation model was used to calculate the expected ⁹³Zr/^natZr mass ratio, which was compared to measured ones. It was found, that a decontamination factor of 10³ is sufficient to get a measurement uncertainty of less than 10%.     

Dissipation of the herbicide active ingredient glyphosate in natural water samples in the presence of biofilms

Dissipation of the herbicide active ingredient glyphosate was investigated in natural waters. To assess combined effects, glyphosate was applied in its pure form (glyphosate isopropylammonium salt) and in preparation Roundup Classic® formulated with polyethoxylated tallowamines (POEA). Standing and running surface water samples originated from Lake Balaton and River Danube between early May and mid-June of 2015. The kinetics of dissipation of glyphosate, measured by high-performance liquid chromatography combined with UV-VIS absorbance detection or tandem mass spectrometry, was investigated under laboratory conditions in aquaria with or without the presence of biofilms. The quantity and the biofilm structure of algal biomass were determined by in vivo fluorimetry and scanning electron microscopy. The presence of POEA affected the dissipation of glyphosate, and dissipation profiles differed in the investigated natural waters. Significantly higher initial concentrations of glyphosate were measured in River Danube for treatment with formulated glyphosate (101.4 ± 6.2 µg L^?1), than with glyphosate alone (79.9 ± 6.6 µg L^?1), and dissipation to a residual level (57.6 ± 1.4 µg L^?1) consequently took longer (approximately by 1 day). Degradation of glyphosate from the initial level (91.24 ± 5.9 µg L^?1) in Lake Balaton was not detected. Phytotoxic effects of glyphosate, particularly if enhanced by a formulant on algal biomass, were observed. Thus, 5–18% and 11–33% of algal biomass reduction was determined in River Danube upon treatments with glyphosate and Roundup Classic®, respectively. Corresponding biomass decreases in Lake Balaton were 1.3–13% and 9–14%, respectively, accompanied by an overall decay in the algal biofilms. In River Danube, treatments resulted in the occurrence of 1.4–5.8% of green algae in the algal biomass in 28 days, while green algae were not detected in the untreated control. The results indicate that glyphosate is capable of modifying the structure of the algal community and to induce increased secretion of extracellular polymeric substances matrix in the biofilms assessed.     

Ordinary differential operators in Hilbert spaces and Fredholm pairs

Let be a path of bounded operators on a real Hilbert space, hyperbolic at . We study the Fredholm theory of the operator . We relate the Fredholm property of to the stable and unstable linear spaces of the associated system . Several examples are included to point out the differences with respect to the finite dimensional case, in particular concerning the role of the spectral flow. We define a general class of paths A for which many properties typical of the finite dimensional framework still hold. Our motivation is to develop the linear theory which is necessary for the set-up of Morse homology on Hilbert manifolds. Received: 9 March 2001; in final form: 1 March 2002 / Published online: 2 December 2002     

Green chemical syntheses and applications within organophosphorus chemistry

Application of the microwave (MW) technique offers many advantages in organophosphorus syntheses. Reluctant reactions may take place on MW irradiation. In most cases, MWs make the reactions more efficient in respect of rate, selectivity and yield. The benefits are shown via representative examples. MW irradiation may replace a catalyst, or simplify catalytic systems. The synthesis of catalysts incorporating heterocyclic P-ligands is also discussed. Where it was relevant, structural chemical details were also provided.     

Low-frequency dilatational wave propagation through unsaturated porous media containing two immiscible fluids

An analytical theory is presented for the low-frequency behavior of dilatational waves propagating through a homogeneous elastic porous medium containing two immiscible fluids. The theory is based on the Berryman–Thigpen–Chin (BTC) model, in which capillary pressure effects are neglected. We show that the BTC model equations in the frequency domain can be transformed, at sufficiently low frequencies, into a dissipative wave equation (telegraph equation) and a propagating wave equation in the time domain. These partial differential equations describe two independent modes of dilatational wave motion that are analogous to the Biot fast and slow compressional waves in a single-fluid system. The equations can be solved analytically under a variety of initial and boundary conditions. The stipulation of “low frequency” underlying the derivation of our equations in the time domain is shown to require that the excitation frequency of wave motions be much smaller than a critical frequency. This frequency is shown to be the inverse of an intrinsic time scale that depends on an effective kinematic shear viscosity of the interstitial fluids and the intrinsic permeability of the porous medium. Numerical calculations indicate that the critical frequency in both unconsolidated and consolidated materials containing water and a nonaqueous phase liquid ranges typically from kHz to MHz. Thus engineering problems involving the dynamic response of an unsaturated porous medium to low excitation frequencies (e.g., seismic wave stimulation) should be accurately modeled by our equations after suitable initial and boundary conditions are imposed.     

Periodic solutions to some problems of n-body type

We prove the existence of at least one T-periodic solution to a dynamical system of the type $$ - m_i \ddot u_i = \sum\limits_{j = 1,j \ne i}^n {\triangledown V_{ij} (u_i - u_j ,{\text{ }}t)}$$ (1) where the potentials V _ij are T-periodic in t and singular at the origin, u _i ε R ^k i=1, ..., n, and k≧3. We also provide estimates on the H ¹ norm of this solution. The proofs are based on a variant of the Ljusternik-Schnirelman method. The results here generalize to the n-body problem some results obtained by Bahri & Rabinowitz on the 3-body problem in [6].     

On q-analogues and stability theorems

In this survey recent results about q-analogues of some classical theorems in extremal set theory are collected. They are related to determining the chromatic number of the q-analogues of Kneser graphs. For the proof one needs results on the number of 0-secant subspaces of point sets, so in the second part of the paper recent results on the structure of point sets having few 0-secant subspaces are discussed. Our attention is focussed on the planar case, where various stability results are given.     

Studies of UV photochemistry and transition moment directions of 4,5′,8-trimethyl-psoralen (TMP) by means of polarized infrared ATR spectroscopy

The UV homodimerization of 4,5′,8-trimethyl-psoralen (TMP) both in a solvent and in crystalline thin layers has been investigated.

In the crystalline phase, TMP was found to dimerize completely to the trans—anti stereoisomer. On the basis of polarized IR ATR spectra of thin layers deposited onto a KRS-5 plate, both the monomer and the dimer of TMP were found to have well-defined orientations. The directions of several transition moments have been calculated.

On irradiating TMP in solution, the photochemical reaction results in the cis—syn stereoisomer.