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The objective of this study was to determine the chemical profile and to evaluate the antibacterial activity of the essential oils of

Spin-orbit coupling (SOC) links spin space and real space and leads to solids with intriguing spin topologies and transport properties, such as anisotropic magnetoresistance (AMR). The orientation of a real-space symmetry axis with respect to the spin direction determines the size of SOC-induced changes of the electronic structure. To show this effect at the single-molecule level, the authors arrange Pb dimers on a ferromagnetic Fe layer and observe that the AMR resulting from their molecular orbitals depends strongly on the dimer orientation.

We study the magnetic interactions in atomic layers of Fe and $5d$ transition metals such as Os, Ir, and Pt on the (001) surface of Rh using first-principles calculations based on density functional theory. For both stackings of the $5d$/Fe bilayer on Rh(001) we observe a transition from an antiferromagnetic to a ferromagnetic nearest-neighbor exchange interaction upon $5d$ band filling. In the sandwich structure $5d$/Fe/Rh(001) the nearest-neighbor exchange is significantly reduced. For Fe/Ir bilayers on Rh(001) we consider spin spiral states in order to determine exchange constants beyond nearest neighbors. By including spin-orbit coupling we obtain the Dzyaloshinskii-Moriya interaction (DMI). The magnetic interactions in Fe/Ir/Rh(001) are similar to those of Fe/Ir(001) for which an atomic scale spin lattice has been predicted. However, small deviations between both systems remain due to the different lattice constants and the Rh vs Ir surface layers. This leads to slightly different exchange constants and DMI and the easy magnetization direction switches from out-of-plane for Fe/Ir(001) to in-plane for Fe/Ir/Rh(001). Therefore a fine tuning of magnetic interactions is possible by using single $5d$ transition-metal layers which may allow to tailor antiferromagnetic skyrmions in this type of ultrathin films. In the sandwich structure Ir/Fe/Rh(001) we find a strong exchange frustration due to strong hybridization of the Fe layer with both Ir and Rh which drastically reduces the nearest-neighbor exchange. The energy contribution from the DMI becomes extremely large and DMI beyond nearest neighbors cannot be neglected. We attribute the large DMI to the low coordination of the Ir layer at the surface. We demonstrate that higher-order exchange interactions are significant in both systems which may be crucial for the magnetic ground state.

The field of molecular spintronics exploits the properties of organic molecules possessing a magnetic moment, either native in the form of radicals or induced by the insertion of transition metal magnetic ions. To realize logic or storage molecular spin-tronics devices, molecules with stable different magnetic states should be deposited on a substrate, and switching between the states controllably achieved. By means of a first-principles calculations, we have devised a functional molecule exhibiting different magnetic states upon structural changes induced by current injection. We investigate the prototypical case of non-planar M-Phthalocyanine (MPc), where M is a transition-metal ion belonging to the 4d and 5d series. We find that for ZrPc and HfPc deposited on a graphene decorated Ni(111) substrate, two different structural conformations could be stabilized, for which the molecules attain different magnetic states depending on the position of the M ion – whether above the Pc or between the Pc and the substrate –, acting therefore as molecular magnetic button. Our work indicates an intuitive way to engineer a magnetic molecular switch with tailored properties, starting from the knowledge of the basic atomic properties of elements and surfaces.

The induced spin polarization of Ir atoms on a ferromagnetic Fe double layer on W(110) has been investigated with spin-polarized scanning tunneling microscopy. An unoccupied state is observed with a spin polarization exceeding 60% that is inverted with respect to the Fe layer. This inversion is due to the tunneling gap acting as an orbital and spin filter. Distance dependent measurements show that the spin polarization remains approximately constant over the entire experimentally accessible range, from far in the tunneling regime to 1 angstrom from the point of contact formation. This is corroborated by density functional theory calculations which show that the inversion of spin polarization occurs within 0.5 angstrom of the adatom. Funding Agencies|Deutsche Forschungsgemeinschaft [SFB 677]; [SFB 668]

We report on the magnetic coupling between isolated Co atoms as well as small Co islands and Ni(111) mediated by an epitaxial graphene layer. X-ray magnetic circular dichroism and scanning tunneling microscopy combined with density functional theory calculations reveal that Co atoms occupy two distinct adsorption sites, with different magnetic coupling to the underlying Ni(111) surface. We further report a transition from an antiferromagnetic to a ferromagnetic coupling with increasing Co cluster size. Our results highlight the extreme, sensitivity of the exchange interaction mediated by graphene to the adsorption site and to the in-plane coordination of the magnetic atoms.

Chirality is a fascinating phenomenon that can manifest itself in subtle ways, for example in biochemistry (in the observed single-handedness of biomolecules) and in particle physics (in the charge-parity violation of electroweak interactions). In condensed matter, magnetic materials can also display single-handed, or homochiral, spin structures. This may be caused by the Dzyaloshinskii-Moriya interaction, which arises from spin-orbit scattering of electrons in an inversion-asymmetric crystal field. This effect is typically irrelevant in bulk metals as their crystals are inversion symmetric. However, low-dimensional systems lack structural inversion symmetry, so that homochiral spin structures may occur. Here we report the observation of magnetic order of a specific chirality in a single atomic layer of manganese on a tungsten (110) substrate. Spin-polarized scanning tunnelling microscopy reveals that adjacent spins are not perfectly antiferromagnetic but slightly canted, resulting in a spin spiral structure with a period of about 12 nm. We show by quantitative theory that this chiral order is caused by the Dzyaloshinskii-Moriya interaction and leads to a left-rotating spin cycloid. Our findings confirm the significance of this interaction for magnets in reduced dimensions. Chirality in nanoscale magnets may play a crucial role in spintronic devices, where the spin rather than the charge of an electron is used for data transmission and manipulation. For instance, a spin-polarized current flowing through chiral magnetic structures will exert a spin-torque on the magnetic structure, causing a variety of excitations or manipulations of the magnetization and giving rise to microwave emission, magnetization switching, or magnetic motors.

Sn-phthalocyanine adsorbs on Ag(111) in a physisorbed or a chemisorbed configuration. Both structures are contacted with the tip of a combined scanning tunneling and atomic force microscope. The tunneling conductances of both configurations exhibit similar exponential variations with the tip–molecule distance. The short-range forces, however, display nontrivial distance dependencies. First-principles calculations reproduce the experimental results. Both attractive and repulsive interactions occur between the tip and different parts of the molecule due to a combination of bond formation and electrostatic interactions with the tip electric dipole. Consequently, deformations occur and the force varies in the resulting unexpected fashion.

We predict the occurrence of a novel type of atomic-scale spin lattice in an Fe monolayer on the Ir(001) surface. Based on density functional theory calculations we parametrize a spin Hamiltonian and solve it numerically using Monte Carlo simulations. We find the stabilization of a three-dimensional spin structure arranged on a $(3\ifmmode\times\else\texttimes\fi{}3)$ lattice. Despite an almost vanishing total spin magnetization we predict the emergence of orbital magnetization and large anomalous Hall effect, to which there is a significant topological contribution purely due to the real space spin texture at the surface.

We present a numerical study of the applicability of the sum rule analysis used, in X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS), to evaluate the atomic spin moment of 3d transition metals. Magnetic circular dichroism (MCD) is present both in XAS and RIXS at the L2,3 absorption edges, although the two sum rules presented here assume different experimental setups: in XAS-MCD the magnetic field is parallel to the circularly polarised incident photons, in RIXS-MCD the two are orthogonal (perpendicular geometry). For Mn2+ we explore XAS- and RIXS-MCD by performing atomic model calculation in the single ion limit with inclusion of the appropriate crystal and magnetic fields. The comparison of the XAS-MCD spectra with those measured from a MnFe2O4 sample is used to fix the calculation parameters. The applicability of the XAS- and RIXS-MCD sum rules to Mn2+ is numerically checked within the chosen calculation model.

The tunnelling anisotropic magnetoresistance (TAMR) effect describes the sensitivity of spin-polarized electron transport to the orientation of the magnetization with respect to the crystallographic axes. As the TAMR effect requires only a single magnetic electrode, in contrast to the tunnelling magnetoresistance effect, it offers an attractive route towards alternative spintronics applications. In this work we consider the TAMR effect at the single-atom limit by investigating the anisotropy of the local density of states in the vacuum above transition-metal adatoms adsorbed on a noncollinear magnetic surface, the monolayer of Mn on W(110). This surface presents a cycloidal spin spiral ground state with an angle of 173$^\circ$ between neighbouring spins and thus allows a quasi-continuous exploration of the angular dependence of the TAMR of adsorbed adatoms using scanning tunnelling microscopy. Using first-principles calculations, we investigate the TAMR of Co, Rh and Ir adatoms on Mn/W(110) and relate our results to magnetization direction dependent changes in the local density of states. The anisotropic effect is found to be enhanced dramatically on the adsorption of heavy transition-metal atoms, with values of up to 50% predicted from our calculations. This effect will be measurable even with a non-magnetic STM tip., Comment: 17 pages, 8 figures

We demonstrate the occurrence of compensated spin configurations in Fe clusters and monolayers on Ru(0001) and Rh(111) by a combination of x-ray magnetic circular dichroism experiments, first-principles calculations, and Monte Carlo simulations. Our results reveal complex intracluster exchange interactions which depend strongly on the substrate 4d-band filling, the cluster geometry, as well as lateral and vertical structural relaxations. The importance of substrate 4d-band filling manifests itself also in small nearest-neighbor exchange interactions in Fe dimers and in a nearly inverted trend of the Ruderman-Kittel-Kasuya-Yosida coupling constants for Fe adatoms on the Ru and Rh surface.

We discuss the application of resonant inelastic X-ray scattering to the study of magnetic systems in the soft X-ray range. To this end we distinguish two broad areas. In the first the layout of the experiment is such that the absorption magnetic circular dichroism (MCD) is not zero. In the second the magnetisation is perpendicular to the incident helical beam so that the absorption MCD is zero. In the first area we summarise published results on Fe-Co alloys and we present new data on Mn impurities in Ni together with calculations. In the second area we summarise published results on Ni in Ni-ferrite with final 3s shell excitation and we present new results on Co-metal and Co in Co-ferrite measured with a new approach. This is based on the incident energy dependence of the integral of the Raman spectrum in inner shell excitation (integrated resonant Raman scattering). The potentialities and the limitations of the above methods are critically presented.

To evaluate and compare demographic, clinical, laboratory and angiographic data of Brazilian children and adolescents with Takayasu's arteritis.In this Brazilian multicentre, retrospective study which included 10 paediatric rheumatology centres, we identified 71 children and adolescents with Takayasu's arteritis which were diagnosed before their 19th birthday. The patients' demographic, clinical, laboratorial and angiographic data were recorded. The participants were divided into two groups: children, defined by the WHO as younger than 10 years old (group 1: 36 patients) and adolescents, defined as individuals aged 10 to 19 years old (group 2: 35 patients). Features of both groups concerning disease manifestations were compared.A total of 21 (58.3%) patients in group 1 and 30 (85.7%) patients in group 2 were girls (p=0.01). The mean age at disease onset, the mean time to diagnosis, and the mean follow-up time were 5.7 and 12.7, 1.8 and 0.7, 7.2 and 3.6 years, respectively, in groups 1 and 2 (p0.001, 0.001 and0.001). At initial evaluation, constitutional symptoms (77.5%) were the most predominant symptoms and decreased peripheral pulses (85.9%) was the most predominant clinical sign without differences between groups. The main laboratory findings were increased erythrocyte sedimentation rate followed by leukocytosis. Anaemia, thrombocytosis and higher platelet levels were significantly more frequent in group 1 (p=0.031, 0.001 and 0.018). Angiographic data were similar in both groups.Children presented more laboratory abnormalities but clinical and angiographic characteristics were similar to those presented by the adolescents. Diagnosis delay is longer in younger patients.

The tunneling anisotropic magnetoresistance (TAMR) of single Co atoms adsorbed on a double-layer Fe film on W(110) is observed by scanning tunneling spectroscopy. Without applying an external magnetic field the TAMR is found by comparing spectra of atoms that are adsorbed on the domains and domain walls of the Fe film. The TAMR can be as large as 12% and repeatedly changes sign as a function of bias voltage. First-principles calculations show that the hybridization between Co $d$ states of different orbital symmetries depends on the magnetization direction via spin-orbit coupling. This leads to an anisotropy of the density of states and thus induces a TAMR.

Using first-principles calculations, we show that the magnetic properties of a two-dimensional antiferromagnetic transition-metal surface are modified on the atomic scale by the adsorption of small organic molecules. We consider benzene (C6H6), cyclooctatetraene (C8H8) and a small transition metal - benzene complex (BzV) adsorbed on a single atomic layer of Mn deposited on the W(110) surface -- a surface which exhibits a nearly antiferromagnetic alignment of the magnetic moments in adjacent Mn rows. Due to the spin-dependent hybridization of the molecular pz orbitals with the d states of the Mn monolayer there is a significant reduction of the magnetic moments in the Mn film. Furthermore, the spin-polarization at this organic-antiferromagnetic interface is found to be modulated on the atomic scale, both enhanced and inverted, as a result of the molecular adsorption. We show that this effect can be resolved by spin-polarized scanning tunneling microscopy (SP-STM). Our simulated SP-STM images display a spatially-dependent spin-resolved vacuum charge density above an adsorbed molecule -- i.e., different regions above the molecule sustain different signs of spin polarization. While states with s and p symmetry dominate the vacuum charge density in the vicinity of the Fermi energy for the clean magnetic surface, we demonstrate that after a molecule is adsorbed those d-states, which are normally suppressed due to their symmetry, can play a crucial role in the vacuum due to their interaction with the molecular orbitals. We also model the effect of small deviations from perfect antiferromagnetic ordering, induced by the slight canting of magnetic moments due to the spin spiral ground state of Mn/W(110)., Comment: 11 pages, 11 figures

We demonstrate the occurrence of tunneling anisotropic magnetoresistance on the atomic scale using scanning tunneling microscopy (STM). Our experiments show that noncollinear atomic-scale magnetic structures can be revealed in STM using nonmagnetic tips. These observations can be explained by a variation of the local density of states of an atom depending on its magnetization direction due to spin-orbit interaction. STM simulations based on this effect are in excellent agreement with the experimental images and can explain the bias-voltage-dependent contrast found for two-dimensionally modulated spin textures.

Co and Cr atoms adsorbed to Fe islands on W(110) are investigated with spin-resolved scanning tunneling spectroscopy and first-principles calculations. The spin polarization of the current to Cr adatoms exhibits the same sign as above Fe islands over a wide range of energies. In contrast, it exhibits sign reversals at Co adatoms. These data do not suggest a simple relation between the spin polarization of the current and the orientation of the magnetic moment of the adatom. First-principles calculations reveal that the different spatial decay into the vacuum of majority $s$ and minority $d$ states of the Co adatom is at the origin of the sign reversals of the spin polarization of the current. The different behavior of Cr adatoms is due to their larger exchange splitting and antiferromagnetic coupling to the Fe islands.

Using first-principles calculations, we study the occurrence of non-collinear magnetic order in monatomic Mn chains. First, we focus on freestanding Mn chains and demonstrate that they exhibit a pronounced non-collinear ground state in a large range of interatomic distances between atoms in the chain. By artificially varying the atomic number of Mn we investigate how the magnetic ground state is influenced by alloying the Mn chains with Fe and Cr. With increasing number of 3d-electrons we find a smooth transition in the magnetic phase space starting from an antiferromagnetic state for pure Cr chains through a regime of non-collinear ground states for Mn-rich chains to a ferromagnetic solution approaching the limit of pure Fe chains. Second, we investigate the magnetism in supported Mn chains on the (110)-surfaces of Cu, Pd, and Ag. We show that even a weak chain-surface hybridization is sufficient to dramatically change the magnetic coupling in the chain. Nevertheless, while we observe that Mn chains are antiferromagnetic on Pd(110), a weak non-collinear magnetic order survives for Mn chains on Cu(110) and Ag(110) a few meV in energy below the antiferromagnetic solution. We explain the sensitive dependence of the exchange interaction in Mn chains on the interatomic distance, chemical composition, and their environment based on the competition between the ferromagnetic double exchange and the antiferromagnetic kinetic exchange mechanism. Finally, we perform simulations which predict that the non-collinear magnetic order of Mn chains on Cu(110) and Ag(110) could be experimentally verified by spin-polarized scanning tunneling microscopy., accepted for publication by Phys. Rev. B

Using first-principles calculations, we demonstrate that the vacuum spin polarization of commonly used Fe-coated scanning tunneling microscopy (STM) tips is positive at the Fermi energy---opposite to that of Fe surfaces---and is often lower than expected from magnetic thin films. We consider single Fe atoms and pyramids of five Fe atoms on Fe (001) and (110) surfaces as models of STM tips. While the spin polarization of the local density of states (LDOS) at the apex atom of all considered tips is negative close to the Fermi energy and dominated by minority $d$ electrons, the spin polarization of the vacuum LDOS, crucial for the tunneling current, is positive and controlled by majority states of $sp$ character. These states derive from the atomic $4s$ and $4p$ orbitals and provide a large spillout of charge density into the vacuum. If we replace the Fe apex atom by a Cr, Mn, or Co atom, the vacuum spin polarization remains positive at the Fermi energy, and it is much enhanced for Cr or Mn in the favorable antiferromagnetic spin alignment with respect to the Fe tip body. At energies above the Fermi level, the spin polarization can change sign due to the contribution from antibonding minority $d$ states. Single Mn and Fe atoms on a nonmagnetic tip provided, for example, by a Cu(001) surface display a similar vacuum LDOS with a small positive spin polarization in good agreement with recent experimental findings. For Cr-coated tips, we observe that the spin polarization can display a change in sign very close to the Fermi energy which can complicate the interpretation of the measured asymmetry in spin-polarized tunneling spectroscopy.

Using spin-polarized scanning tunneling microscopy (SP-STM), we observe spin frustration in one monolayer Cr on the triangular lattice of the Pd(111) surface. Our STM measurements demonstrate pseudomorphic growth of the first Cr layer on Pd(111) without intermixing. Using SP-STM in the constant current mode, we observe three different types of images depending on the tip magnetization indicative of a noncollinear $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})$ magnetic superstructure with an angle of $120\ifmmode^\circ\else\textdegree\fi{}$ between moments of nearest-neighbor Cr atoms. The $120\ifmmode^\circ\else\textdegree\fi{}$ N\'eel ground state of Cr/Pd(111) and the SP-STM images are explained based on our first-principles calculations.

Single magnetic atoms on surfaces are the smallest conceivable units for two-dimensional magnetic data storage. Previous experiments on such systems have investigated magnetization curves, the many-body Kondo effect and magnetic excitations in quantum spin systems, but a stable magnetization has not yet been detected for an atom on a non-magnetic surface in the absence of a magnetic field. The spin direction of a single magnetic atom can be fixed by coupling it to an underlying magnetic substrate via the exchange interaction, but it is then difficult to differentiate between the magnetism of the atom and the surface. Here, we take advantage of the orbital symmetry of the spin-polarized density of states of single cobalt atoms to unambiguously determine their spin direction in real space using a combination of spin-resolved scanning tunnelling microscopy experiments and ab initio calculations. By laterally moving atoms on our non-collinear magnetic template, the spin direction can also be controlled while maintaining magnetic sensitivity, thereby providing an approach for constructing and characterizing artificial atomic-scale magnetic structures.

Using first-principles calculations, we demonstrate that an Fe monolayer can assume very different magnetic phases on hcp (0001) and fcc (111) surfaces of $4d$- and $5d$-transition metals. Due to the substrates' $d$-band filling, the nearest-neighbor exchange coupling of Fe changes gradually from antiferromagnetic (AFM) for Fe films on Tc, Re, Ru, and Os to ferromagnetic on Rh, Ir, Pd, and Pt. In combination with the topological frustration on the triangular lattice of these surfaces the AFM coupling results in a $120\ifmmode^\circ\else\textdegree\fi{}$ N\'eel structure for Fe on Re and Ru and an unexpected double-row-wise AFM structure on Rh, which is a superposition of left- and right-rotating $90\ifmmode^\circ\else\textdegree\fi{}$ spin spirals.

Using spin-polarized scanning tunneling microscopy we show that the magnetic order of 1 monolayer Mn on W(001) is a spin spiral propagating along $⟨110⟩$ crystallographic directions. The spiral arises on the atomic scale with a period of about 2.2 nm, equivalent to only 10 atomic rows. Ab initio calculations identify the spin spiral as a left-handed cycloid stabilized by the Dzyaloshinskii-Moriya interaction, imposed by spin-orbit coupling, in the presence of softened ferromagnetic exchange coupling. Monte Carlo simulations explain the formation of a nanoscale labyrinth pattern, originating from the coexistence of the two possible rotational domains, that is intrinsic to the system.

We propose to tailor exchange interactions in magnetic monolayer films by tuning the adjacent non-magnetic substrate. As an example, we demonstrate a ferromagnetic-antiferromagnetic phase transition for one monolayer Fe on a Ta(x)W(1-x)(001) surface as a function of the Ta concentration. At the critical Ta concentration, the nearest-neighbor exchange interaction is small and the magnetic phase space is dramatically broadened. Complex magnetic order such as spin-spirals, multiple-Q, or even disordered local moment states can occur, offering the possibility to store information in terms of ferromagnetic dots in an otherwise zero-magnetization state matrix., after minor changes, 5 pages, 5 figures, revtex4

We present a comparison of the x-ray elastic scattering at the 2p threshold of Ni calculated both in a single-ion picture with a full description of the multiplet manifolds of the electron configurations and in a one-electron model using a multiple scattering approach for the excited intermediate state. We study the case of perpendicular geometry of the circularly polarized incoming light and analyze the variation of the intensity of the emitted light along a conical scan. We discuss the results obtained in the two approaches for the total and dichroic signals, that confirm the presence of a significant anisotropy as previously predicted in the inelastic case. © 2006 The American Physical Society.

The search for uncompensated magnetic moments on antiferromagnetic surfaces is of great technological importance as they are responsible for the exchange-bias effect that is widely used in state-of-the-art magnetic storage devices. We have studied the atomic spin structure of phase domain walls in the antiferromagnetic Fe monolayer on W(001) by means of spin-polarized scanning tunnelling microscopy and Monte Carlo simulations. The domain wall width only amounts to 6–8 atomic rows. Although walls oriented along 〈100〉 directions are found to be fully compensated, detailed analysis of 〈110〉-oriented walls reveals an uncompensated perpendicular magnetic moment. Our result represents a major advance in the field of antiferromagnetism, and may lead to a better understanding of the magnetic interaction between ferromagnetic and antiferromagnetic materials.

We measured the dispersion of an unoccupied surface state on Pt(111) by imaging scattering states at point defects and step edges using scanning tunneling spectroscopy. By comparison to first-principles electronic structure calculations the state is assigned to an $sp$-derived surface band at the lower edge of the projected bulk band gap. In $dI∕dV(V)$ curves, the onset of the surface-state band appears as a rather broad feature. Its shape results from two spin-orbit split branches with nearly linear dispersion, one of them merging into bulk states at higher energies.

We report systematic first-principles calculations based on the full-potential linearized augmented plane wave method for $3d$ transition-metal (V, Cr, Mn, Fe, Co, Ni) monolayers on the W(001) surface. We predict that V, Cr, and Mn monolayers exhibit a ferromagnetic ground state, while Fe and Co favor the $c(2\ifmmode\times\else\texttimes\fi{}2)$ antiferromagnetic state. This trend is surprising as it is opposite to what was expected from the knowledge of magnetism in ultrathin films and results from strong hybridization at the W interface. In particular, this system is the first case showing antiferromagnetic Co.

We prove that the magnetic ground state of a single monolayer Fe on W(001) is $c(2\ifmmode\times\else\texttimes\fi{}2)$ antiferromagnetic, i.e., a checkerboard arrangement of antiparallel magnetic moments. Real space images of this magnetic structure have been obtained with spin-polarized scanning tunneling microscopy. An out-of-plane easy magnetization axis is concluded from measurements in an external magnetic field. The magnetic ground state and anisotropy axis are explained based on first-principles calculations.

Resonant inelastic x-ray scattering (RIXS) and resonant photoemission spectroscopy (RPES) can be used to selectively measure the ground-state properties of atoms in solid materials. For the two types of experiment we compare the sum rules developed in the past years to extract quantitative information from the measured spectra. We show that if the measurements are not sensitive to the emitted photon polarization state (in RIXS) or to the photoelectron spin orientation (in RPES), the two experiments exhibit the same angular dependence of the spectral intensities but differ in some numerical coefficients in the sum rules. In particular we give explicit expressions for the RIXS sum rules in the so-called perpendicular geometry for all the cases of practical interest. These rules can serve, in combination with the well-known x-ray magnetic circular dichroism sum rules in absorption, to evaluate the quadrupole and octupole moments of the scattering atoms.

We report the cross-cultural adaptation and validation into Brazilian-Portuguese of the parent's version of two health related quality of life instruments. The Childhood Health Assessment Questionnaire (CHAQ) is a disease specific health instrument that measures functional ability in daily living activities in children with juvenile idiopathic arthritis (JIA). The Child Health Questionnaire (CHQ) is a generic health instrument designed to capture the physical and psychosocial well-being of children regardless the underlying disease. The Brazilian CHAQ was revalidated, while the CHQ has been derived from the Portuguese version. A total of 471 subjects were enrolled: 157 patients with JIA (27% systemic onset, 38% polyarticular onset, 9% extended oligoarticular subtype, and 26% persistent oligoarticular subtype) and 314 healthy children. The CHAQ discriminated clinically healthy subjects from JIA patients, with the systemic, polyarticular and extended oligoarticular subtypes having a higher degree of disability, pain, and lower overall well-being scores when compared to their healthy peers. Also the CHQ discriminated clinically healthy subjects from JIA patients, with the systemic onset, polyarticular onset and extended oligoarticular subtypes having a lower physical and psychosocial well-being score when compared to their healthy peers. In conclusion the Brazilian versions of the CHAQ-CHQ are reliable and valid tools for the combined physical and psychosocial assessment of children with JIA.

Values of complement lytic activity of classical and alternative pathways, assessed by measuring the time required to lyse 50% of target red blood cells, and the concentration of complement components C3, C4 and factor B were estimated in the sera of 103 healthy children aged 3 to 14 y. Age-dependent variations were seen in the C3 and factor B concentrations, but not in C4, with the highest values found among 5-6-y-old children. Variations in classical and alternative lytic activity were not detected in this group of children, although the values are significantly different from our previously published data on adults, using the same kinetic assay (1). We also evaluated the relationship between the lytic activity of the classical (CPT) and alternative pathways (APT) and the levels of complement components. There were significant correlations between: APT and factor B, APT and C3, C3 and C4, C3 and factor B, and C4 and factor B concentrations. The normal ranges measured here can be used in the initial screening of Brazilian children presenting diseases involving the complement system. This study also contributes to a better understanding of the complement system ontogeny.

The angular dependence of the resonant inelastic X-ray scattering cross section is studied within the ion-model for 3d metals. A geometrical setup with the incidence direction perpendicular to the magnetic axis and a conical scan of the outgoing radiation is chosen. The total and dichroic intensities have angular asymmetries related to the interference between intermediate states in the process. We show the results of the full calculation of the cross section comparing them with the commonly used fast collision approximation.

Magnetic single-atom contacts have been controllably fabricated with a scanning tunnelling microscope. A voltage-dependent spin valve effect with conductance variations of ≈40% is reproducibly observed from contacts comprising a Cr-covered tip and Co and Cr atoms on ferromagnetic nanoscale islands on W(110) with opposite magnetization. The spin-dependent conductances are interpreted from first-principles calculations in terms of the orbital character of the relevant electronic states of the junction.