Long-term oscillations in the sleep/wake cycle of infants

The development of circadian sleep-wakefulness rhythm was investigated by a longitudinal study of six normal infants. We propose an entropy based measure for the sleep/wake cycle fragmentation. Our results confirm that the sleep/wake cycle fragmentation and the sleep/wake ratio decrease, while the circadian power increases during the maturation process of infants. In addition to these expected linear trends in the variables devised to quantify sleep consolidation, circadian power and sleep/wake ratio, we found that they present infradian rhythms in the monthly range.     

On the synthesis and structures of the complexes [RuCl(L)(dppb)(N–N)]PF6 (L = CO,py or 4-NH2py; dppb = 1,4-bis(diphenylphosphino)butane; N–N = 2,2′-bipyridine or 1,10-phenanthroline) and [(dppb)(CO)Cl2-Ru-pz-RuCl2(CO)(dppb)] (pz = pyrazine)

The “Ru(P–P)” unit (P–P = diphosphine) is recognized to be an important core in catalytic species for hydrogenation of unsaturated organic substrates. Thus, in this study we synthesized six new complexes containing this core, including the binuclear complex [(dppb)(CO)Cl₂Ru-pz-RuCl₂(CO)(dppb)] (pz = pyrazine) which can be used as a precursor for the synthesis of cationic carbonyl species of general formula [RuCl(CO)(dppb)(N–N)]PF₆ (N–N = diimine). Complexes with the formula [RuCl(py)(dppb)(N–N)]PF₆ were synthesized by exhaustive electrolysis of these carbonyl compounds or from the precursors [RuCl₂(dppb)(N–N)]. The new complexes were characterized by microanalysis, conductivity measurements, IR and ³¹P{¹H} NMR spectroscopy, cyclic voltammetry and X-ray crystallography.     

Photoluminescence of europium(III) dithiocarbamate complexes: electronic structure, charge transfer and energy transfer

For the first time, we observed photoluminescence in Eu(III) dithiocarbamate complexes at room temperature -- more specifically in [Eu(Et(2)NCS(2))(3)phen], [Eu(Et(2)NCS(2))(3)bpy] and the novel [Eu(Ph(2)NCS(2))(3)phen], where phen stands for 1,10-phenanthroline and bpy for 2,2'-bipyridine. Correlations between the electronic structure of the dithiocarbamate ligands on one hand, and covalency, intensity, and ligand field spectroscopic parameters on the other, could be established. Moreover, the relative values of the emission quantum efficiencies obtained for these complexes, as well as their dependence with temperature, could be satisfactorily described by a theoretical methodology recently developed.     

Kristallstruktur der Form III von isotaktischem Poly-l-buten

Ohne Zusammenfassung     

Action-angle variables for the harmonic oscillator: Ambiguity spin × duplication spin

The difficulties of obtaining for the harmonic oscillator a well-defined unitary transformation to action-angle variables were overcome by M. Moshinsky and T. H. Seligman (Ann. Phys. (N.Y.)114 (1978), 243) through the introduction of a spinlike variable (ambiguity spin) from a classical point of view. The difficulty of defining a unitary phase operator for the harmonic oscillator was overcome by Roger G. Newton (Ann. Phys. (N.Y.)124 (1980), 324) also through the introduction of a spinlike variable (named duplication spin by us) but within a quantum framework. Here the relation between the ambiguity spin and the duplication spin is investigated by introducing these two types of spins in the canonical transformation to action-angle variables. In this way both well-defined unitary transformation and phase operators were obtained.     

Comment on the average energy denominator method in perturbation theory

Second-order perturbation expansions are rearranged in a convenient form that justifies taking the smallest energy difference, for non-vanishing matrix elements, as the first approximation in the average energy denominator method.     

Fluorescence enhancement induced by the presence of small silver particles in Eu3+ doped materials

We study the effect of small silver particles on the emission spectrum of Eu³⁺ doped materials. Depending on the excitation frequency and the concentration of silver particles embedded in the host material, a significant enhancement of the fluorescence from the Eu³⁺ ions is observed. This experimental observation corroborates the importance of the long-range electromagnetic interaction between the plasmons on the silver particles and the host medium. A theoretical analysis based on the electromagnetic model is made and satisfactory agreement with experiment is obtained.     

Analyses of radionuclides in soil,water, and agriculture products near the Urgeiriça uranium mine in Portugal

Analyses of soils, irrigation waters, agriculture products (lettuce), green pasture, and cheese were performed in samples collected in the area of the old Urgeiriça uranium mine and milling facilities, Centre-North of Portugal, in order to assess the transfer of uranium series radionuclides in the environment and to man. Soils close to milling tailings display an enhancement of radioactivity. In the drainage basin of the stream Ribeira da Pantanha, receiving drainage from the tailings piles and discharges from the acid mine water treatment plant, there was enhancement of uranium series radionuclide concentrations in water and suspended matter. Agriculture products from kitchen gardens irrigated with water from the Ribeira da Pantanha show an increase of radioactivity, mainly due to uranium isotopes. Agriculture products from other kitchen gardens in this area, irrigated with groundwater, as well pasture and cheese produced locally from sheep milk did not show enhanced radionuclide concentrations. In the Urgeiriça area, some soils display radionuclide concentrations higher than soils in reference areas and, in agriculture products grown there, ²²⁶Ra was the radionuclide more concentrated by vegetables. Through ingestion of these products ²²⁶Ra may be the main contributor to the increment of radiation dose received by local population.     

A X-ray line profile study on as-polymerized isotactic polypropylene

The line profile analysis of high-resolution wide angle X-ray diffraction spectra (WAXS) has been employed to characterize two polypropylenes polymerized by: a) “conventional” Ziegler-Natta catalyst (PP-A) and b) “high-yield” new supported catalyst (PP-B). The observed differences in line-width are most reasonably due to a marked crystallite size anisotropy, more pronounced for PP-A. The smallest size is along the crystallographic a-axis, which is the preferred direction of growth of crystallites. Paracrystalline fluctuations, on the whole larger in the high-yield polymer than in the conventional one, are present. The diffuse background resulting from line profile analysis is preliminarily investigated here in terms of scattering from a microcrystalline array.     

Spectroscopic study of a UV-photostable organic-inorganic hybrids incorporating an Eu3+ beta-diketonate complex.

New europium and gadolinium tris-beta-diketonate complexes have been prepared and incorporated in sol-gel-derived organic-inorganic hybrids, named di-ureasils. The general formula [Ln(btfa)3(4,4'-bpy)(EtOH)] (Ln=Eu, Gd; 4,4'-bpy=4,4'-bipyridine; btfa=4,4,4-trifluoro-1-phenyl-1,3-butanedione) for the complexes was confirmed by X-ray crystallography and elemental analysis. The ground-state geometry of the Eu3+ complex was calculated from the Sparkle/AM1 model. The calculated quantum yield obtained from the Sparkle model and from the crystal structure (both 46%) are in satisfactory agreement with the experimental value (38+/-4%). In the isolated complex the most efficient luminescence channel is S0-->S1-->T-->(5D1, 5D0)-->7F0-6, where the exchange mechanism dominates in the energy-transfer channel T-->(5D1, 5D0). For the Eu3+-based di-ureasils a 50% quantum yield enhancement compared to the Eu3+ complex is observed, which suggests an effective hybrid host-metal ion interaction and an active energy-transfer channel between the hybrid host and the Eu3+ complex. The Eu3+-based di-ureasils are photostable under UVA (360 nm) excitation, whereas under UVB (320 nm) and UVC (290 nm) photodegradation occurs.