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Due to their characteristics, colloidal particles are able to control the dispersion of many organic and inorganic pollutants in soils and streams. Colloidal precipitates generated by acid mine drainage (AMD) process are usually amorphous or nanocrystalline materials, and their stability plays a crucial role in controlling the fate of metals released by sulphide oxydation. This paper describes a study of elements release (Fe, Al, Mn, Cd, Co, Cr, Cu, Ni, S, Zn) due to desorption or destabilization of three different colloidal precipitates, two ochreous and a greenish-blue precipitate, sampled at the Libiola mine site (northwest Italy). The samples were heated at high temperature in order to verify this treatment as inertization process. At room temperature, the most easily extracted element was S (with released percentages from 8.39 to 29.17 %), but considerable amounts of Cu, Zn and Mn (up to 16.6, 610.6 and 595.6 mg/kg, respectively) were also observed in the leachates for greenish-blue precipitates. The highest release of elements (S > Cu, Zn, Mn, Cd > Co, Ni > Al, Fe, Cr), with minor differences depending on the mineralogical composition of the samples, was observed for heat-treated samples obtained through moderate heating and mainly formed by anhydrous phases. Samples treated at high temperature had the lowest release, with only Cu showing a significant concentration in the leachate of greenish-blue precipitates. The results showed that dissolution/desorption is limited from ochreous natural colloidal precipitates occurring at the Libiola mine site but also that high amounts of some metals can be remobilized from greenish-blue precipitates. The destabilization of all percipitates through dehydratation–dehydroxylation can further remobilize important amounts of ecotoxic elements. Heat treatment at high temperature could be a definitive, although expensive, way to fix heavy metals in the solid fraction, preventing their dispersion in the surrounding environment.

The N-doped TiO2 has been synthesized by sol–gel method, using titanium isopropoxide, isopropanol and an aqueous solution of ammonia with ratio 2:1:10. The concentrations used for the NH3 aqueous solution were 3, 7, 10 and 15 %. The samples have been analysed by X-ray diffraction, electron microscopy (SEM and TEM) thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), micro-Raman spectroscopy and diffuse reflectivity. TEM, SEM, DSC and TGA showed that the morphology is influenced by the presence of N3− ions but not by the concentration of the solution. Instead reflectance gave us a relation between values of the energy gap and the concentration of N3− ions: the gap between valence and conduction band lowers as the concentration of NH3 in the starting solution increases. From these results we can say that the properties of the material have been tuned by doping with nitrogen ions because the particles absorb more light in the visible range, and this is important for photovoltaic and photocatalytic applications.

Adenylate kinase activity in rod outer segment membranes of bovine retina decreased of about 55% when exposed to an extremely low frequency electromagnetic field of 75 Hz and 250 μT. The effect was independent of the time of permanence in the field. Negligible effects of the field were found on the enzymatic activity of a soluble isoform of adenylate kinase or of rod outer segment membranes solubilized with Triton, suggesting the importance of the membrane in determining the conditions of the enzyme inactivation.

This paper illustrates a new thermodynamic and kinetic model that describes the relationship between the water self-diffusion coefficient, D w/g ∗ , in hydrogel contact lenses, in terms of water matric potential (ΨM) and equilibrium water content (EWC). Experimental measurements on commercial contact lenses yield water thermodynamic activity values ranging between 0.996 and 0.999. The corresponding ΨM matric potential is, respectively, between −8 and −2 J/mol at temperature 35°C. Comparison between water self-diffusion coefficients derived in this paper and those suggested by other authors shows that our values are greater (25%–50%) than the previous ones. The impact of this model on the nature of the oxygen permeability, Π, in the lenses has been evaluated and the changes of Π with ΨM and EWC are predicted and compared with direct experimental measurements. For the contact lenses investigated, the oxygen permeability turns out to be only a quadratic function of equilibrium water content, despite the fact that the fraction of the “free” water molecules can be as high as 50%.

In the present work a macroporous brushite bone cement for use either as an injected or mouldable paste, or in the shape of preformed grafts, has been investigated. Macropores have been introduced by adding to the powder single crystals of mannitol which worked as a porogen. The size of the crystals was in the range of 250-500microm in diameter, suitable for cell infiltration, with a shape ratio between 3 and 6. From compression tests on cylindrical samples an elastic modulus in the range 2.5-4.2GPa and a compressive strength in the range 17.5-32.6MPa were obtained for a volume fraction of macropores varying between 15 and 0%. Thus the compressive strength exceeded in all tests the maximum value currently attributed to cancellous bone.

Extremely low frequency electromagnetic fields (ELF-EMFs) of 75 Hz with amplitudes above a threshold of about 125 μT have a dramatic effect on the adenylate kinase (AK) activity of the rod outer segment (ROS) membranes. In fact, the ATP production by ROS membranes or by purified disk membranes placed in the field decreased by approximately 54%. The decrease in enzymatic activity was independent of the time of exposure to the field and was completely reversible. When disk membranes were solubilized with Triton or a soluble isoform of AK was used, negligible effects of the field were obtained on the enzymatic activity, suggesting that the membrane has an important role in determining the conditions for the enzyme inactivation. Bioelectromagnetics 25:545–551, 2004. © 2004 Wiley-Liss, Inc.

Spontaneous processes in an aqueous solution of body simulated fluid (SBF) were monitored in closed vessel for a period of 1 month at 310 K, at atm pressure, and initial pH of 7.2, both with and without exposure to a square pulsed extremely low frequency electromagnetic fields (EM-ELF) of 250 μT, repeated at 75 Hz. The most important findings are that the SBF surface tension (γ), evaluated under the EM-ELF field, is lower than the corresponding value measured without EM-ELF at any time. Furthermore, the pH of the exposed SBF is always more basic than that of the unexposed solution. As a consequence, when the EM-ELF is applied, calcium phosphate salts do not precipitate from the SBF solution for a period as long as 30 days. Behind all these experimental evidences there is only one mechanism: the vaporisation from the SBF-air interface of the CO2(aq) dissolved into the aqueous electrolyte solution. Thermodynamic analysis of these results establish that, at any given time, the difference, Δ, between the measured surface tensions with and without EM-ELF applied, gives the work of the electromagnetic forces to change the extent at which the CO2(aq) adsorbs at the liquid-air interface. It has been demonstrated that the work supply per second and per unit of area by the electromagnetic forces, 3.73 × 10−10 mJ/s cm2, is very near to the experimental slope in the plot Δ vs. t 1.7 × 10−10 mJ/s cm2. This leads to the conclusion that the EM-ELF fields have an interfacial effect on the concentration value of the CO2 (aq) at the SBF-air interface. Because of that, the EM-ELF field is enhancing the CO2 vaporisation rate; thus any other steps, which are a consequence of this mechanism, are changing. These results allow explanation of previous experiments concerning the precipitation of calcium carbonate from flowing hydrogen carbonate aqueous solution in the temperature range 353–373 K at a pressure of 0.1 MPa under the effect of static magnetic fields. Bioelectromagnetics 24:251-261, 2003. © 2003 Wiley-Liss, Inc.

Addition of tricalcium phosphate (alpha-TCP) powders as an aqueous dispersion to a polymethylmethacrylate (PMMA) bone cement is shown to produce a class of composites that due to their microstructure and mechanical properties may be suitable for application as bone substitutes. The PMMA forms a solid cellular matrix with open cells about 100 micrometer in size and incorporating TCP clusters. The TCP aggregates inside the cells form a porous network, with average mesopore diameters of about 0.1 micrometer, that is accessible from the outer surface. If TCP is added to PMMA in the form of dried powders, the composites are not applicable as bone substitutes. The dynamic elastic modulus (DEM) and compressive and tensile strengths were measured and discussed for both classes of composites. The mechanical properties of the bone-substitute composites, although lower than the other class of composites, are still competitive with those properties of a porous ceramic matrix of hydroxyapatite and with those of natural bones.

A multistep photoionization with three resonant polarized photons has been used to separate the odd and even isotopes of gadolinium. Due to their hyperfine structure (I= 3 2 ), the 155,157Gd isotopes can be photoionized via a J=2→2→1→0 scheme with three п photons whereas the even isotopes cannot. If a time delay is introduced between the three laser pulses we show that the presence of a low intensity dc magnetic field affects the selectivity. The effect of this weak field on the 156Gd photoionization rate has been calculated independently of the optical pumping and the result is in good agreement with the experiment.

Proton transfers occurring between fragments (ion and neutral) derived from the same parent ion result from a compromise between the cross section of the reaction and the velocity of separation of the fragments. Moreover, the independent rotation of the latter may be responsible for the apparent “long distance” of these transfers. The loss of an olefin from alkyl-phenyl-ethers and the loss of ketene from phenyl-acetates derive from such a mechanism.

The ionization potentials assigned to non-bonding electrons of chlorine, bromine and oxygen in 96 molecules and 108 different structures are discussed. The Silberstein-Siegbahn model used with Smith—Ree—Magee-Eyring net charges appears to be a good approach for the calculation of the chemical shifts on complicated molecules. The easily computable Coulombic contribution to the ionization potential IP , seems to be the main one to account for the observed chemical shifts.

Two-color, two-photon resonance-enhanced ionization spectra have been obtained for aniline, phenol and phenotole near and above the ionization threshold in an effusive and supersonic beam. Precise adiabatic ionization energies have been measured. The electric field dependence of these energies is found to be consistent with a field-ionization red shift of the thresholds. The two-color photoionization technique has been successfully applied to determine a set of vibrational frequencies of the excited neutral and ground ionic states of these molecules.

The ionization and fragmentation of dimethyl and diethyl ether have been studied by means of photoionization at room temperature and low temperature. The parent ion thresholds show evidence of hot band effects, and the adiabatic ionization potentials have been determined to be 10.01 ± 0.01 eV for dimethyl ether and 9.60 ± 0.01 eV for diethyl ether. The temperature dependence of thresholds for the primary fragmentation processes in both molecules can be accounted for by rotational and vibrational hot band effects. Heats of formation at absolute zero have been obtained for the species CH3O CH2+, CH3CH2O = CHCH3+ and CH2 = OCH2CH3+. Evidence is obtained for important contributions of autoionization to ionization and fragmentation at higher energies.

Les effets isotopiques observes sur les spectres de masses de tous les derives deuteries de l'ethylene ont ete determines. Ces effets sont en accord avec les resultats donnes par la theorie du quasi-equilibre. La perte ďun atome H est favorisee par rapport a celle d'un atome D dans les ions partiellement substitues. La fragmentation avec perte ďune molecule HD est la plus probable, comme le laisse prevoir la theorie.Les spectres de masse calcules sont en bon accord avec les resultats experimentaux, si on admet que, par impact electronique, une fraction importante ďions dans l'etat fondamental est produite par auto ionisation ; le spectre de photoelectron doit etre corrige de cette contribution pour donner la courbe de distribution ďenergie interne des ions.

On etudie les processus du frittage pour des agregats de MgO contenant des pores ouverts et fermes. Le processus dominant a partir du debut du frittage est l'elimination des pores fermes associee au grossissement des pores ouverts. Il apparait que le frittage est gouverne principalement non par la diffusion, mais par les modifications d'energie libre differentielle resultant du mouvement desordonne des ions entre les plans des surfaces

L’etude des effets isotopiques observes au cours de la dissociation d’ions metastables de l'ethylene et de ses 6 homologues deuteries a ete reprise pour la reaction correspondant a la perte de H2 , HD ou D2 . Les effets intermoleculaires observes sur C2 H4 et C2 D4 sont peu importants. Par contre, les effets intramoleculaires mettent en evidence des rapports entre perte de H2 /HD et/ou perte de HD/D2 qui varient entre 10 et 50 selon l’homologue deuterie.Le calcul de ces effets isotopiques a l'aide de la theorie du quasi-equilibre a permis de mettre en evidence l'influence de la difference d’energie de zero des fragments, entre les differentes reactions isotopiques et egalement l'influence moins connue des frequences de vibration qui agit sur le facteur de frequence et sur la variation de la constante de vitesse en fonction de l'energie au voisinage du seuil. Un bon accord entre valeurs calculees et experimentales a ete trouve sans l’intervention d’effet tunnel.

The first band of the photoelectron spectrum of HDO has been recorded. In agreement with the selection rules of the group theory, the fundamental terms of the three symmetric vibrations of HDO ( C s symmetry) have been observed. Taking the geometry of the ion as parameters, the Franck-Condon factors for the ionization of H 2 O, D 2 O and HDO have been calculated. The geometry of the H 2 O + , D 2 O + , HDO + ions (ground state) have been determined accurately by comparison of the calculated results with the corresponding photoelectron spectra. This geometry is approximately the same for the three ions: r OH  1,00 A and

The photoelectron spectra of C 2 H 4 and of six deuterated molecules of ethylene — C 2 D 4 , C 2 D 3 H, C 2 H 3 D, cis -C 2 H 2 D 2 , trans -C 2 H 2 D 2 and gem -C 2 H 2 D 2 — have been recorded with the 584-A resonance line of He. The adiabatic ionization potentials of the X 2 B 3u and the 2 B 3g states of the seven isotopic components have been determined with an accuracy of about 7 meV. The ionization potentials of the other excited electronic states have been measured with a lower accuracy owing to a less well defined onset. The measured ionization potentials of C 2 H 4 are 10.514 eV, 12.431 eV, 14.4 3 eV, 15.7 4 eV and 18.7 eV. The vibrational structure of the first electronic band shows that the two normal modes ν 2 (symmetric CC stretching) and ν 3 (symmetric HCH bending) are excited simultaneously. The measured vibrational frequencies show no abnormal isotopic effect if the assignment given in the literature for the ν 2 and ν 3 modes in C 2 H 4 + are reversed and if a stronger excitation of the ν 3 symmetric bending mode in the least deuterated compounds is assumed. The vibrational modes most strongly excited in the second and third electronic bands are ν 1 (symmetric CH stretching) and ν 3 , and in the fourth band ν 3 .

Laser-induced dissociation of phenetole ions has been carried out. The ions have been prepared in a well-defined excited state by resonance-enhanced two-photon, two-color ionization (R2PI/2C). Appearance energies of 2.431 and 2.82 eV have been determined for the first dissociation pathways leading to C 6 H 6 O + and C 5 H 6+ ionic fragment. The dissociation spectrum as well as detailed dissociation rate constants versus internal energy have been obtained. The dissociation rates are compared with those expected from RRKM theory. A complex reaction scheme has been assumed in order to explain the observed discrepancy.

The photoelectron spectra of halogeno-3-propynes and halogenomethylcyanides (F, Cl, Br) have been determined. The ionization potentials (IP) of various

Ionisation of argon atoms in high Rydberg states (HR) by collisions with CCl4 and CCl3 F has been investigated. Absolute cross sections for the dissociative electron attachment are reported, together with the identities of the negatively and positively charged species produced in coincidence in the collision. The dependence of the cross sections on the principal quantum number n and the HR argon velocity alows us to determine the limits of the theoretical "free electron" model and the role of the core Ar+ in the outcome of the reaction.

Measurements of absolute ionizing reaction cross sections in collisions between argon atoms in high Rydberg states (HR) and CCl4, CCl3F, CH3I, SF6, C6F6, CF4, and CO are reported together with their dependence on the HR argon velocity (570–2100 m/sec). The identity of the positively and negatively charged reaction products has been investigated with a coincidence TOF mass spectrometer. A comparison of the present data with results of other bound and free electron experiments and theoretical predictions is given.

L'interaction des rayonnements α, β ou γ avec la matiere conduit a l'ionisation et l'excitation des molecules du milieu. La photoionisation a l'aide du rayonnement synchrotron ou de lasers permet l'etude detaillee des mecanismes primaires de production et de dissociation d'ions. Des etudes, a l'aide de lasers, de spectroscopie, d'energie des etats et de cinetique de fragmentation des ions sont decrites pour le phenol et le phenetole. Le rayonnement synchrotron permet d'etudier l'excitation et l'ionisation en couche interne dans le domaine d'energie entre 20 et 1 000 eV. Une predissociation rapide de HBr et CH3 Br excitees en couche 3d a ete observee ainsi qu'une dissociation selective de l'ion doublement charge CH3 Br++ .

The time-resolved fluorescence of hexafluorobiacetyl (CF 3 COCOCF 3 ) was studied at pressures down to 0.05 Torr over the excitation energy range 22000 – 30000 cm −1 . The zero-pressure fluorescence lifetime and the pressure effect as functions of energy were measured. The energy dependence of the fluorescence radiative rate k rad s was determined from the fluorescence quantum yield measurements at low and high pressures. By means of a Rice—Ramsperger—Kassel—Marcus calculation the dissociation process was shown to be important compared with intersystem crossing and internal conversion only for energies greater than 28000 cm −1 . These results are in good agreement with those published by Van der Werf and Kommandeur on biacetyl.

Photoionization of organic molecules with tunable UV laser light is studied by time of flight mass spectrometry (TOF Ms). The possibilities of the apparatus are described. In the present work, the total ion current is used for the study of aniline, benzylamine and benzylchloride ions. Two and three photon ionization have been observed.

The photoelectron spectra of 6 dibromoalkanes and 9 bromofluoroalkanes have been recorded in the region of 10 to 11 eV, corresponding to the ionization of the n electrons of the bromine atom. For most of the compounds four peaks are observed. In the dibromoalkanes these correspond to a spin-orbit coupling of the two bromine atoms. In the bromofluoroalkanes the peaks have been assigned to two different conformations of the molecule, each giving rise to a doublet. This study shows that differences in the ionization potentials may exist between preferential conformations of a molecule.

Relative electron impact ionization cross sections for the metastable 23S and 21S states and for the highly-excited, long-lived states of helium were obtained using a double electron beam technique.

Well-resolved absorption spectra of the B←X forbidden transition of the chlorobenzene cation have been obtained for the first time by two-photon induced dissociation of the ground state ion. The φ + fragment ions are detected with a time-of-flight mass spectrometer. The wavelength dependence of the fragment ion yield reflects the spectroscopy of the φCl + B intermediate state reached by the first photon. Chlorobenzene cations are formed by resonance-enhanced two-photon ionization (R2PI) process. B←X vibronic transitions are observed due to vibronic interactions between the nearby B and C states. A preliminary analysis of the spectra is proposed.

Les methodes de determination de la distribution d'energie interne, ainsi que la preparation d'ions d'energie interne bien definie, sont brievement passees en revue. L'utilisation des lasers permet de realiser de nouvelles etudes dans ce domaine, en particulier la photodissociation d'ions et surtout l'ionisation biphotonique resonnante qui sera davantage detaillee

The absolute electron impact ionization cross sections for lithium in the energy range between 100 and 2000 eV were measured by the nonmodulated crossed beam technique. The neutral lithium beam is produced by a Knudsen cell and crossed at right angles with the electron beam. The ions formed are collected on a plate and their intensity determined with a dc amplifier. The neutral beam is condensed on a cold trap cooled with liquid nitrogen, this temperature being much lower than that required to obtain total condensation. The amount of metal deposited is measured by the isotopic dilution technique and by atomic absorption, and the density of the atoms in the neutral beam is calculated. The total absolute ionization cross sections can then be determined. All possible errors have been carefully analyzed and their magnitudes estimated. The absolute ionization cross section for Li at an energy of 500 eV is QLi=0.358 × 10−16 cm2. This value is half of that obtained by McFarland and Kinney. The partial ionization...

Photoionization‐efficiency curves for C2H2 and C2D2 have been remeasured in the wavelength region from onset of ionization to 600 A, using a gold‐coated grating and the Hopfield continuum as a photon source. The curve shapes of the molecule ions near threshold are compared with calculations of the Franck—Condon factors. Nearly exact agreement between experiment and calculation is obtained when taking into account hot bands. A general discussion is given for the shape of the molecule‐ion curve and for that of the fragment ions, C2H+ and C2D+. The observed onsets of ionization for the latter ions are 17.22— and 17.34 eV, respectively.

Determinations of the average kinetic energy of dissociation for a series of similar metastable transitions in a variety of hydrocarbon molecules have been carried out. For a given metastable transition, the kinetic energy release is always the same, indicating that it is independent of the prior history of the ion. In the case of C4H9+ where different isomers could exist, this can only be explained by rearrangement processes. The results are discussed in relation to the quasi-equilibrium theory.

Photoionization‐efficiency curves for ions of the molecule and of selected fragments of C2H4 and CHDCHD are reported for the wavelength region from onset of ionization to 600 A. The minimum threshold of ionization is 10.50 eV for both molecules. In addition, certain features of the ion‐yield curves are discussed and identified as resulting from vibrationally excited states or from autoionization from Rydberg levels leading to electronically excited states. Threshold measurements of the acetylene ions permit calculation of heats of dissociation and indicate that the C2H2+ ion is formed without excess activation energy. Of the vinyl ions, the threshold for the C2H3+ ion is the most clearly defined and leads to a C2H3–H bond‐dissociation energy of 100 kcal·mole−1.

The well‐resolved absorption spectrum of a large non‐radiative aromatic ion like chlorobenzene has been obtained by the method of resonance‐enhanced multiphoton dissociation (REMPDI). The cations are prepared in the ground electronic state with well‐defined rovibrational energy excess by resonace‐enhanced two‐photon ionization (R2PI). The light of a second laser excites the ions through a (1+1) process into predissociative states which dynamics has been first studied. The wavelength dependence of the fragment ion yield reflects the spectroscopy of the intermediate ionic state reached by the first photon. In this work, we present the completely vibrationally resolved spectrum of the B←X transition of φC1+. For the first time the rotational contour of the vibronic bands of R2PI‐prepared ions has been calculated. The comparison with the experimental band shapes has brought additional arguments for the assignment of the spectral features.

Two-color, two-photon resonance enhanced ionization (R2PI-2C) is shown to be a powerful tool for the determination of adiabatic ionization potentials and vibrational frequencies of ground ionic states of polyatomic cations. Results on the laser induced dissociation of phenetole cations prepared by R2PI-2C will be presented.

Franck Condon factors (FCF) for polyatomic molecules will be discussed. Elaborate potential functions can only be used in a quasi diatomic approximation. Most of the polyatomic calculations of FCF are made with a harmonic potential. Various methods of calculations using this approximation will be briefly presented. The problem of transformation of normal coordinates from one state to the other will be discussed. Approximations in this transformation may lead to large errors. Three types of applications will be developed for the ionization of polyatimoc molecules.

On etudie les processus du frittage pour des agregats de MgO contenant des pores ouverts et fermes. Le processus dominant a partir du debut du frittage est l'elimination des pores fermes associee au grossissement des pores ouverts. Il apparait que le frittage est gouverne principalement non par la diffusion, mais par les modifications d'energie libre differentielle resultant du mouvement desordonne des ions entre les plans des surfaces

The mass spectrum of C3O2 and the appearance potentials of its fragments were measured. Where comparison is possible, the values found are compatible with the values calculated by means of the existing physicochemical data, and values for other fragments are presented for which no previous data were found.

Franck-Condon factors have been calculated for vertical transitions of H(2)O and D(2)O involving both bond length and angle changes. It is shown that even in the harmonic oscillator approximation different Franek-Condon factors are obtained for positive and negative angle changes. The results are used to obtain the geometry of the ion ground state. Satisfactory agreement is obtained for the isotope effect on the vibrational transition probabilities. The effects of anharmonicity are discussed semi-quantitatively.