Nutritional composition, heavy metal contents and lipid quality of five marine fish species from Cameroon coast

The nutritional value, heavy metal content and lipid quality of five marine fishes from, Cameroon coast were be investigated. Fish samples from Ilisha africana, Sardinella, maderensis, Cyprinus carpio, Arius parkii and Ethmalosa fimbriata were collected at, the Douala sea port, carried to the laboratory, washed with distilled water and, processed. Proximal composition, minerals, lipid quality and heavy metal analyses, were performed using AOAC standard methods. Results show that proteins (18.43%), and lipids (3.69%) contents were higher in Ilisha africana. Cyprinus carpio had the, highest ash content (4.59%). Contents of minerals and heavy metals were found as, follows: P > Mg > K > Ca > Na > Fe > Zn > Cu > Mn and Hg > Pb > Cd > As. Oils extracted from C. carpio, A. parkii and E. fimbriata were semi-siccative while those of I. africana and S. maderensis were siccative. Thus, these fish species are good sources of proteins and, minerals that can be used for managing mineral deficiencies in humans and animals.

Na2 Vibrating in the Double-Well Potential of State 2 1Σu+ (JM = 00): A Pulsating "Quantum Bubble" with Antagonistic Electronic Flux

The theory of concerted electronic and nuclear flux densities associated with the vibration and dissociation of a multielectron nonrotating homonuclear diatomic molecule (or ion) in an electronic state ^2S+1Σ_g,u⁺ (JM = 00) is presented. The electronic population density, nuclear probability density, and nuclear flux density are isotropic. A theorem of Barth , presented in this issue, shows that the electronic flux density (EFD) is also isotropic. Hence, the evolving system appears as a pulsating, or exploding, "quantum bubble". Application of the theory to Na₂ vibrating in the double-minimum potential of the 2  ¹Σ_u⁺ (JM = 00) excited state reveals that the EFD consists of two antagonistic components. One arises from electrons that flow essentially coherently with the nuclei. The other, which is oppositely directed (i.e., antagonistic) and more intense, is due to the transition in electronic structure from "Rydberg" to "ionic" type as the nuclei traverse the potential barrier between inner and outer potential wells. This "transition" component of the EFD rises and falls sharply as the nuclei cross the barrier.

Isotope effects of reactions in quantum solids initiated by IR + UV lasers: quantum model simulations for Cl((2)P(3/2)) + X(2)(ν) → XCl + X in X(2) matrices (X = H, D)

Six isotope effects (i)-(vi) are discovered for the reactions Cl + H(2)(ν) → HCl + H in solid para-H(2) ( 1 ) versus Cl + D(2)(ν) → DCl + D in ortho-D(2) ( 2 ), by means of quantum reaction dynamics simulations, within the frame of our simple model ( J. Phys. Chem. A 2009 , 113 , 7630 . ). Experimentally, the reactions may be initiated for ν = 0 and ν ≥ 1, by means of "UV only" photodissociation of the matrix-isolated precursor, Cl(2), or by "IR + UV" coirradiation ( Kettwich , S. C. , Raston , P. L. , and Anderson , D. T. J. Phys. Chem. A 2009 , 113 , 7621 . ), respectively. Specifically, (i) various shape and Feshbach reaction resonances correlate with vibrational thresholds of reactants and products, due to the near-thermoneutrality and low barrier of the system. The energetic density of resonances increases as the square root of mass, from M(X) = M(H) to M(D). (ii) The state selective reaction ( 1 ), ν = 1, is supported by a shape resonance, whereas this type of resonance is absent in ( 2 ), ν = 1. As a consequence, time-resolved measurements should monitor different three-step versus direct error-function type evolutions of the formation of the products. (iii) The effective barrier is lower for reaction 1 , ν = 0, enhancing the tunneling rate, as compared to that for reaction 2 , ν = 0. (iv) For reference, the reaction probabilities P versus total energy E(tot) in the gas exhibit sharp resonance peaks or zigzag behaviors of the reaction probability P versus total energy, near the levels of resonances ( Persky , A. and Baer , M. J. Chem. Phys . 1974 , 60 , 133 . ). These features tend to be washed out and broadened for reaction 1 , and even more so for reaction 2 . For comparison, they disappear for reactions in classical solids. (v) The slopes of P versus E(tot) below the potential barrier increase more steeply for reaction 1 , ν = 0, than for reaction 2 , ν = 0. This enhances the tunneling rate of the heavier isotopomer, reaction 2 , ν = 0, compared to that for reaction 1 . (vi) For a given value of the UV frequency, the translational energy E(trans) increases with mass M(X). Again, this effect supports tunneling of the heavier isotopomer. The isotope effects (i)-(iii), (iv)-(v), and (vi) may be classified as energetic, translational amplitude, and kinematic, respectively. Specifically, the effects (iv)-(v) are due to a systematic decrease of the amplitudes of translational motions of the reactant molecules, from quasi infinite in the gas via still rather large values of para-H(2)(ν) and smaller values for ortho-D(2)(ν) to very small values in classical solids. These isotope effects are special phenomena in quantum solids, which do not occur, neither in the gas phase nor in classical solids. Quantitative predictions, e.g., for the effects of increasing UV frequency on the ratio of reactions probabilities for the UV only versus IR + UV experiments, must account for the interplay of various isotope effects, e.g., (vi) combined with the antagonistic effects (iii) versus (iv) and (v).

Quantum effects of translational motions in solid para-hydrogen and ortho-deuterium: anharmonic extension of the Einstein model

An anharmonic extension of the Einstein model is developed in order to describe the effect of translational zero point motion on structural and thermodynamic properties of para-H(2) and ortho-D(2) crystals in the zero temperature limit. Accordingly, the molecules carry out large amplitude translational motions in their matrix cage, which are formed by the frozen environment of all other molecules. These translations lead from the molecular equilibrium positions via the harmonic to the anharmonic domain of the potential energy surface. The resulting translational distributions are roughly isotropic, and they have approximately Gaussian shapes, with rather broad full widths at half-maximum, FWHM(para-H(2)/ortho-D(2)) = 1.36/1.02 Å. The translational zero point energies induce expansions of the crystals, in nearly quantitative agreement with experimental results. Furthermore, they make significant contributions to the sublimation energies and zero pressure bulk moduli. These quantum effects decrease with heavier molecular masses. The corresponding isotope effects for ortho-D(2) compared to para-H(2) are confirmed by application of the model to Ar crystals. The results imply consequences for laser induced reaction dynamics of dopants with their host crystals.

Initial Processes of Laser Induced Diatomic Molecular Photodissociation in Matrices: Quantum Simulations for F2 in Ar in Reduced Dimensionality

Quantum dynamical simulations of ultrafast processes of F2 in an Ar matrix induced by a pump laser pulse show that photoexcitation (i) is followed by (ii) a stretch of the dissociative bond, (iii) collision with, vibrational excitations of, and possible exit through the nearest neighbour atoms of the surrounding cage, and (iv) finally, subsequent rescattering of the dissociated atoms causing vibrations of additional matrix atoms. If the laser pulse ended before the onset of process (iii), the initial steps (i) and (ii) are similar to photodissociations in the gas phase and are, therefore, well described in terms of the wavepacket dynamics of the diatomic molecule in reduced dimensionality. For specific symmetry constraints, the initial processes (i), (ii), and (iii) may be described in terms of just 1- and 2- or 3-dimensional wavepacket dynamics, respectively. At the end of the laser pulse, this low-dimensional wavepacket may serve to prepare the high-dimensional one for the subsequent laser-free dynamics of the total system.

The Cl + H2 --> HCl + H reaction induced by IR + UV irradiation of Cl2 in solid para-H2: quantum model simulation

Recent experimental investigations by the group of D. T. Anderson (Kettwich, S. C.; Raston, P. L.; Anderson, D. T. J. Phys. Chem. A 2009, 113, DOI 10.1021/jp811206a) show that the reaction Cl + H(2) --> HCl + H in the para-H(2) crystal can be induced by infrared (IR) + ultraviolet (UV) coirradiations causing vibrational pre-excitation of the molecular reactant, H(2)(v=1), and generation of the atomic reactant, Cl((2)P(3/2)), by near-resonant photodissociation of a matrix-isolated Cl(2) molecule in the C (1)Pi(u) state, respectively. The corresponding reaction probability P(v=1) for the reactants Cl + H(2)(v=1) is approximately 0.15; this is approximately 25 times larger than P(v=0) for Cl + H(2)(v=0) (as initiated by pure UV irradiation). We present a simple three-step quantum model which accounts for some important parts of the experimental results and allows predictions for other scenarios, for example, UV photodissociation of the Cl(2) molecule by a laser pulse. The first step, vibrational pre-excitation of H(2), yields the molecular initial state which is described using the Einstein model of the para-H(2) crystal. The second step, photodissociation of Cl(2), generates the Cl((2)P(3/2)) atom approaching H(2)(v=1). In the third step, Cl reacts with H(2)(v=1) much more efficiently than with H(2)(v=0) close to threshold. The ultrashort time domains (approximately 100 fs) of steps 2 plus 3 support one- and then two-dimensional models of photodissociation of Cl(2) by short laser pulses and of the subsequent reaction of the system Cl-H-H embedded in frozen environments. The widths of the corresponding wave function describing the translational motion of the reactants is revealed as a significant parameter which is determined not only by the duration of the laser pulse but, even more importantly, by the width of the Gaussian-type distribution of the center of mass of the H(2) molecule in its Einstein cell. As a consequence, the resulting P(v) are quite robust versus variations of the UV pulse durations, allowing extrapolations to continuous wave irradiation. Quantum dynamics simulations of the reaction reveal that the experimental results are due to energetic and dynamical effects.

Dynamics of Electronic States and Spin−Flip for Photodissociation of Dihalogens in Matrices: Experiment and Semiclassical Surface-Hopping and Quantum Model Simulations for F2 and ClF in Solid Ar

Three approaches are combined to study the electronic states' dynamics in the photodissociation of F(2) and ClF in solid argon. These include (a) semiclassical surface-hopping simulations of the nonadiabatic processes involved. These simulations are carried out for the F(2) molecule in a slab of 255 argon atoms with periodic boundary conditions at the ends. The full manifold of 36 electronic states relevant to the process is included. (b) The second approach involves quantum mechanical reduced-dimensionality models for the initial processes induced by a pump laser pulse, which involve wavepacket propagation for the preoriented ClF in the frozen argon lattice and incorporate the important electronic states. The focus is on the study of quantum coherence effects. (c) The final approach is femtosecond laser pump-probe experiments for ClF in Ar. The combined results for the different systems shed light on general properties of the nonadiabatic processes involved, including the singlet to triplet and intertriplet transition dynamics. The main findings are (1) that the system remains in the initially excited-state only for a very brief, subpicosecond, time period. Thereafter, most of the population is transferred by nonadiabatic transitions to other states, with different time constants depending on the systems. (2) Another finding is that the dynamics is selective with regard to the electronic quantum numbers, including the Lambda and Omega quantum numbers, and the spin of the states. (3) The semiclassical simulations show that prior to the first "collision" of the photodissociated F atom with an Ar atom, the argon atoms can be held frozen, without affecting the process. This justifies the rigid-lattice reduced-dimensionality quantum model for a brief initial time interval. (4) Finally, degeneracies between triplets and singlets are fairly localized, but intertriplet degeneracies and near degeneracies can span an extensive range. The importance of quantum effects in photochemistry of matrix-isolated molecules is discussed in light of the results.

Design of UV laser pulses for the preparation of matrix isolated homonuclear diatomic molecules in selective vibrational superposition states

The preparation of matrix isolated homonuclear diatomic molecules in a vibrational superposition state c0Phie=1,v=0+cjPhie=1,v=j, with large (|c0|2 approximately 1) plus small contributions (|cj|2<<1) of the ground v=0 and specific v=j low excited vibrational eigenstates, respectively, in the electronic ground (e=1) state, and without any net population transfer to electronic excited (e>1) states, is an important challenge; it serves as a prerequisite for coherent spin control. For this purpose, the authors investigate two scenarios of laser pulse control, involving sequential or intrapulse pump- and dump-type transitions via excited vibronic states Phiex,k with a dominant singlet or triplet character. The mechanisms are demonstrated by means of quantum simulations for representative nuclear wave packets on coupled potential energy surfaces, using as an example a one-dimensional model for Cl2 in an Ar matrix. A simple three-state model (including Phi1,0, Phi1,j and Phiex,k) allows illuminating analyses and efficient determinations of the parameters of the laser pulses based on the values of the transition energies and dipole couplings of the transient state which are derived from the absorption spectra.

Coherent spin control of matrix isolated molecules by IR+UV laser pulses: quantum simulations for ClF in Ar

Two coherent sequential IR+UV laser pulses may be used to generate two time-dependent nuclear wave functions in electronic excited triplet and singlet states via single (UV) and two photon (IR+UV) excitation pathways, exploiting spin-orbit coupling and vibrational pre-excitation, respectively. These wave functions evolve from different Franck-Condon domains until they overlap in a domain of bond stretching with efficient intersystem crossing. Here, the coherence of the laser pulses is turned into optimal interferences of the wave packets, yielding the total wave packet at the target place, time, and with dominant target spin. The time resolution of spin control is few femtoseconds. The mechanism is demonstrated by means of quantum model simulations for ClF in an Ar matrix.