Search results for "MONUC"

High-frequency EPR study on Cu4Cu- and Co4Co-metallacrown complexes

2019

Abstract High-frequency/high-field electron paramagnetic resonance studies on two homonuclear 12-MC-4 metallacrown complexes Cu4Cu and Co4Co are presented. For Cu4Cu, our data imply axial-type g-anisotropy with g x = 2.03 ± 0.01 , g y = 2.04 ± 0.01 , and g z = 2.23 ± 0.01 , yielding g = 2.10 ± 0.02 . No significant zero field splitting (ZFS) of the ground state mode is observed. In Co4Co, we find a m S = ± 3 / 2 ground state with g = 2.66 . The data suggest large anisotropy D of negative sign.

Gasdynamic ECR ion source for negative ion production

2018

H− ion sources are needed in various areas of accelerator technology, such as beam injection into cyclotrons and storage rings and as a part of neutral beam injectors for plasma heating in experimental facilities studying thermonuclear fusion. It was recently demonstrated that gasdynamic ion source based on ECR discharge in a simple mirror trap is very efficient for proton beam production [1]. Here we use the gasdynamic plasma source as the first stage driver of volumetric negative ion production through dissociative electron attachment (DEA) [2]. Experiments were performed with a pulsed 37 GHz / up to 100 kW gyrotron radiation in a dual-trap magnetic system, which consists of two identical…

Reorientations and translations in a fragile glass-former: magnetic resonance studies of meta-fluoroaniline

1999

Abstract The rotational dynamics in supercooled liquid and glassy meta-fluoroaniline was studied using proton and fluorine spin-lattice relaxation times. It is shown that while proton relaxation is dominated by homonuclear relaxation, for fluorine heteronuclear relaxation prevails. The results could be well described using a distribution of correlation times. The mean correlation times show pronounced deviations from the simple Arrhenius law. In addition translational self-diffusion coefficients were measured for T>200 K using a static magnetic field gradient technique.

Magnetic exchange interaction in clusters of orbitally degenerate ions. I. Effective Hamiltonian

2001

Abstract A new effective Hamiltonian is reported for the kinetic exchange between two arbitrary terms 2S A +1 Λ A and 2S B +1 Λ B that can be ground or excited in octahedrally coordinated transition metal ions. This Hamiltonian is applicable to both homo- and heterometallic clusters. For the homonuclear cluster the resonance part of the effective Hamiltonian is also presented for the case when one of the ions is excited. The operator part of the exchange Hamiltonian contains symmetry adapted products of the cubic irreducible tensors acting in orbital spaces ΛA and ΛB and scalar product of site spin operators. The parameters of the Hamiltonian are defined by the relevant intercenter transfer…

Study of electrostatic potential surface distribution of wild-type plastocyaninSynechocystissolution structure determined by homonuclear NMR

2003

Plastocyanin is a small (∼10 kDa), type I blue copper protein that works as an electron donor to photosystem I from cytochrome f in both chloroplast systems and in some strains of cyanobacteria. Comparative studies of the kinetic mechanisms of plastocyanins in different organisms show that the electron transfer from photosystem I happens by simple collision in cyanobacteria but through a intermediate transition complex in green algae and superior plants. Previous work has proved that this effect cannot be explained by structural variations across the different plastocyanins but it can be explained by differences in the electrostatic potential distribution at the protein surface. In that cas…

Rescattering and vibrations in homonuclear diatomic molecules in a strong electromagnetic field

2009

Abstract The electron of a H 2 + driven by a strong electromagnetic field induces molecular vibrations. Numerical and analytical results show that the molecule behaves as a parametric oscillator and can be treated as a kicked oscillator. The results are discussed from the point of view of the electron's periodic dressing and undressing processes.

Lumbosacral disc herniation: spinal interventional chemonucleolysis with CT-intradiscal oxygen-ozone (O2-O3) mixture with periradicular and perigangl…

2007

Kongo Demokrātiskās Republikas loma starptautiskajās attiecībās. 2005-2013

2016

Maģistra darba tēma ir “Kongo Demokrātiskās Republikas loma starptautiskajās attiecībās 2005-2013” Kongo Demokrātiskās Republikas iekšpolitiskie un ārpolitiskie procesi Latvijā ir nepietiekami pētīti. Darbā skatīts kā procesi lielākajā valstī Subsahāras reģionā skar starptautisko organizāciju-ANO un ES, kā arī atsevišķu lielvalstu-Lielbritānijas,Francijas, ASV,Ķīnas politiku. Pētijumā svarīga loma ir iekšpolitiskajiem procesiem-paramilitāru grupu aktivitātēm,korupcijai,jo tie ir saistīti ar ārvalstu-gan reģionālu,gan pasaules mēroga darbībām. Kongo Demokrātiskās Republikas problemātika skaidri parāda ģeopolitisko interešu sadursmi gan starp Eiropas, gan pasaules lielvalstīm,kuras atbalsta d…

Jenisseensosides C and D, biologically active acylated triterpene saponins from Silene jenisseensis

1997

Abstract We previously reported the isolation and structure elucidation of a new trans - p -methoxycinnamoyl triterpene-saponin along with its cis - p -methoxycinnamoyl isomer as an inseparable mixture from the roots of Silene jenisseensis . In a continuing study on this plant, two additional new acylated triterpene-saponins were obtained as an inseparable mixture. Their structures have been established by chemical means and spectroscopic methods including 1D and 2D homonuclear and heteronuclear correlation NMR spectroscopy as 3- O -[β- d -galactopyranosyl-(1 → 2)-β- d -glucuronopyranosyl]-28- O -[{α- l -rhamnopyranosyl-(1 → 2)}- {4- O - trans - p -methoxycinnamoyl}-β- d -fucopyranosyl] qui…

Plasmon Excitations in Mixed Metallic Nanoarrays

2019

Features of the surface plasmon from macroscopic materials emerge in molecular systems, but differentiating collective excitations from single-particle excitations in molecular systems remains elusive. The rich interactions between single-particle electron-hole and collective electron excitations produce phenomena related to the chemical physics aspects within the atomic array. We study the plasmonic properties of atomic arrays of noble (Au, Ag, and Cu) and transition-metal (Pd, Pt) homonuclear chains using time-dependent density functional theory and their Kohn-Sham transition contributions. The response to the electromagnetic radiation is related to both the geometry-dependent confinement…