Synthesis and characterization of NH2-porphyrins covalently immobilized on modified-SBA-15

The immobilization of two different succinic-modified carboxy-imide-porphyrins on the surface of amino-modified SBA-15 is reported. The SBA-15 was synthesized and modified by reacting its hydroxyls groups with the OH and/or OR groups of 3-amino propyl triethoxy silane, anchoring the amino group on its surface. Separately, two different derivatives amino-porphyrins (NH₂-5-m-Etio-III-Ni²⁺ and NH₂-2βpyrrolic-m-5,10,15,20-TPP-Ni²⁺) were modified using succinic anhydride to provides these with the carboxyl group appropriate to react covalently with the amino groups previously anchored on the SBA-15; these new hybrid materials have the appropriated textural and chemical characteristics to be used in heterogeneous catalysis. The samples were characterized by XRD, N₂ adsorption isotherms, HR-TEM, TGA/DTA, FTIR, UV/VIS, ¹³C and ²⁹Si NMR-CP/MAS.     

~(10)BE AND THE ACCUMULATIONEVOLUTION OF LOESS

We report here a first series of ~(10)Be measurements on loess samples covering the last 750,000 years. The close correlation of the ~(10)Be data with δ~(18)O variations from deep sea cores allows for establishing a preliminary time scale. Based on this time scale accumulation rates and ~(10)Be fluxes can be calculated. The accumulation-evolution of loess is also discussed in terms of a simple qualitative model of ~(10)Be.     

Inelastic scattering of fast electrons from simple closed shell atoms. I. He,Be

The inelastic collision of fast electrons with ground state closed shell atoms is investigated within the context of First Born Approximation and Random Phase Approximation. Generalized oscillator strengths and total cross sections for 1¹ S n ¹ D transitions in He and 1¹ S n ¹ S in Be are evaluated and discussed.Work supported by Consiglio Nazionale delle Richerche (C.N.R.) through its Istituto di Chimica Quantistica ed Energetica Molecolare in Pisa.     

Carbon-beryllium binding in CH2Be

Ab initio molecular orbital theory is used to study carbon-beryllium binding in the lowest singlet and triplet states of CH₂Be. When electron correlation is included, both singlet and triplet states are significantly bound relative to the ground states of CH₂ and Be fragments.     

Transport of a quantum degenerate heteronuclear Bose-Fermi mixture in a harmonic trap

We report on the simultaneous transport of mixed quantum degenerate gases of bosonic ⁸⁷Rb and fermionic ⁴⁰ K in a harmonic potential. The samples are transported over a distance of to the geometric center of a Ioffe-Pritchard type magnetic trap. This transport mechanism was implemented by modification of the QUIC trap and is free of losses and heating. It significantly extends the capabilities of this trap design. We demonstrate a launching mechanism for quantum degenerate samples and show that highly homogeneous magnetic fields can be created in the center of the QUIC trap. The transport mechanism may also be cascaded to cover even larger distances for interferometric experiments with quantum degenerate samples.     

Friedel phase discontinuity and bound states in the continuum in quantum dot systems

In this Letter we study the Friedel phase of the electron transport in two different systems of quantum dots which exhibit bound states in the continuum (BIC). The Friedel phase jumps abruptly in the energies of the BICs, which is associated to the vanishing width of these states, as shown by Friedrich and Wintgen in [H. Friedrich, D. Wintgen, Phys. Rev. A 31 (1985) 3964]. This odd behavior of the Friedel phase has consequences in the charge through the Friedel sum rule. Namely, if the energy of the BIC drops under the Fermi energy the charge changes abruptly in a unity. We show that this behavior closely relates to discontinuities in the conductance predicted for interacting quantum dot systems.     

A quantum pseudodot system with a two-dimensional pseudoharmonic potential

We investigate the energy spectrum and the corresponding wave functions of an electron confined by a pseudoharmonic potential both including harmonic dot and antidot potentials in the presence of a strong magnetic field together with an Aharonov-Bohm flux field. Exact solutions for the energy levels and wave functions are found for this exactly soluble system. These are all tested under various conditions and also are compared with other works found in the literature. Further, we discuss the related energy spectrum in terms of special values of the proposed pseudoharmonic potential, AB field and magnetic field as a function of magnetic quantum number and magnetic field.     

Ab-initio investigation of electronic properties and magnetism of half-Heusler alloys XCrAl (X=Fe, Co, Ni) and NiCrZ (Z=Al, Ga, In)

The electronic structures and magnetism of the half-Heusler alloys XCrAl (X=Fe, Co, Ni) and NiCrZ (Z=Al, Ga, In) have been investigated to search for new candidate half-metallic materials. Here, we predict that NiCrAl, and NiCrGa and NiCrIn are possible half-metals with an energy gap in the minority spin and a completely spin polarization at the Fermi level. The energy gap can be attributed to the covalent hybridization between the d states of the Ni and Cr atoms, which leads to the formation of bonding and antibonding peaks with a gap in between them. Their total magnetic moments are 1μ_B per unit cell; agree with the Slater-Pauling rule. The partial moment of Cr is largest in NiCrZ alloys and moments of Ni and Al are in antiferromagnetic alignment with Cr. Meanwhile, it is also found that FeCrAl is a normal ferromagnetic metal with a magnetic moment of 0.25μ_B per unit cell and CoCrAl is a semi-metal and non-magnetic.     

High spin polarization in ordered Cr3Co with the DO3 structure: A first-principles study

The electronic structure of the highly ordered alloy Cr₃Co with the DO₃ structure has been studied by FLAPW calculations. It is found that the ferrimagnetic state is stable and that the equilibrium lattice constant of Cr₃Co equals 5.77 Å. A large peak in majority spin density of states (DOS) and an energy gap in minority spin DOS are observed at the Fermi level, which results in a high spin polarization of 90% in the ordered alloy Cr₃Co. The total magnetic moment of Cr₃Co is 3.12μ_B, which is close to the ideal value of 3μ_B derived from the Slater-Pauling curve. An antiparallel alignment between the moments on the Cr (A, C) sites and the Cr (B) sites is observed. Finally, the effect of lattice distortion on the electronic structure and on magnetic properties of Cr₃Co compound is studied. A spin polarization higher than 80% can be obtained between 5.55 and 5.90 Å. With increasing lattice constant, the magnetic moments on the (A, C) sites increase and the moments on the (B, D) sites decrease. They compensate each other and make the total magnetic moment change only slightly.     

Laser energy dependence on femtosecond laser-induced nucleation of protein

We have investigated femtosecond laser-induced nucleation of hen egg-white lysozyme (HEWL) as a function of the laser pulse energy and pulse time width. This is the first recorded study to confirm that the femtosecond laser-induced nucleation of HEWL can be induced at a specific threshold laser energy. The threshold energy is comparable to that of cavitation bubble generation. The results strongly suggest that morphological changes in the solution are key factors for protein nucleation.