Chiral surface spin textures in Cu2OSeO3 unveiled by soft X-ray scattering in specular reflection geometry.

Resonant elastic soft X-ray magnetic scattering (XRMS) is a powerful tool to explore long-periodic spin textures in single crystals. However, due to the limited momentum transfer range imposed by long wavelengths of photons in the soft x-ray region, Bragg diffraction is restricted to crystals with the large lattice parameters. Alternatively, small-angle X-ray scattering has been involved in the soft energy X-ray range which, however, brings in difficulties with the sample preparation that involves focused ion beam milling to thin down the crystal to below a few hundred nm thickness. We show how to circumvent these restrictions using XRMS in specular reflection from a sub-nanometer smooth crystal surface. The method allows observing diffraction peaks from the helical and conical spin modulations at the surface of a Cu   2 OSeO   3 single crystal and probing their corresponding chirality as contributions to the dichroic scattered intensity. The results suggest a promising way to carry out XRMS studies on a plethora of noncentrosymmetric systems hitherto unexplored with soft X-rays due to the absence of the commensurate Bragg peaks in the available momentum transfer range.

Ferromagnetic Resonance with Magnetic Phase Selectivity by Means of Resonant Elastic X-Ray Scattering on a Chiral Magnet.

Cubic chiral magnets, such as Cu_{2}OSeO_{3}, exhibit a variety of noncollinear spin textures, including a trigonal lattice of spin whirls, the so-called skyrmions. Using magnetic resonant elastic x-ray scattering (REXS) on a crystalline Bragg peak and its magnetic satellites while exciting the sample with magnetic fields at gigahertz frequencies, we probe the ferromagnetic resonance (FMR) modes of these spin textures by means of the scattered intensity. Most notably, the three eigenmodes of the skyrmion lattice are detected with large sensitivity. As this novel technique, which we label REXS FMR, is carried out at distinct positions in reciprocal space, it allows us to distinguish contributions originating from different magnetic states, providing information on the precise character, weight, and mode mixing as a prerequisite of tailored excitations for applications.

Ferroelectric Control of Interface Spin Filtering in Multiferroic Tunnel Junctions.

The electronic reconstruction occurring at oxide interfaces may be the source of interesting device concepts for future oxide electronics. Among oxide devices, multiferroic tunnel junctions are being actively investigated as they offer the possibility to modulate the junction current by independently controlling the switching of the magnetization of the electrodes and of the ferroelectric polarization of the barrier. In this Letter, we show that the spin reconstruction at the interfaces of a La_{0.7}Sr_{0.3}MnO_{3}/BaTiO_{3}/La_{0.7}Sr_{0.3}MnO_{3} multiferroic tunnel junction is the origin of a spin filtering functionality that can be turned on and off by reversing the ferroelectric polarization. The ferroelectrically controlled interface spin filter enables a giant electrical modulation of the tunneling magnetoresistance between values of 10% and 1000%, which could inspire device concepts in oxides-based low dissipation spintronics.

Dual-mode-locking mechanism for an akinetic dispersive ring cavity swept source.

A fast dual-mode-locked akinetic optical swept source in the 1550-nm wavelength band is presented that is tested up to a sweep rate of 797 KHz. It comprises a voltage-controlled oscillator-driven wideband semiconductor optical amplifier (SOA) along with a dispersion compensation fiber, in a ring laser configuration. A Faraday rotating mirror is employed in the cavity as a reflective element in order to achieve better polarization control. By driving the SOA at a high-MHz-frequency value multiple of the resonant frequency f(R), equal to the inverse round trip time, a first-mode locking mechanism is imposed. A second locking mechanism consists in sweeping the radio frequency of the locking signal at a rate slightly detuned from f(R). A dynamic linewidth of 0.8 nm is assessed by measuring the decay of interference signal strength versus optical path difference in a Mach-Zehnder interferometer.

MKK3 regulates mitochondrial biogenesis and mitophagy in sepsis-induced lung injury.

Sepsis is a systemic inflammatory response to infection and a major cause of death worldwide. Because specific therapies to treat sepsis are limited, and underlying pathogenesis is unclear, current medical care remains purely supportive. Therefore targeted therapies to treat sepsis need to be developed. Although an important mediator of sepsis is thought to be mitochondrial dysfunction, the underlying molecular mechanism is unclear. Modulation of mitochondrial processes may be an effective therapeutic strategy in sepsis. Here, we investigated the role of the kinase MKK3 in regulation of mitochondrial function in sepsis. Using clinically relevant animal models, we examined mitochondrial function in primary mouse lung endothelial cells exposed to LPS. MKK3 deficiency reduces lethality of sepsis in mice and by lowering levels of lung and mitochondrial injury as well as reactive oxygen species. Furthermore, MKK3 deficiency appeared to simultaneously increase mitochondrial biogenesis and mitophagy through the actions of Sirt1, Pink1, and Parkin. This led to a more robust mitochondrial network, which we propose provides protection against sepsis. We also detected higher MKK3 activation in isolated peripheral blood mononuclear cells from septic patients compared with nonseptic controls. Our findings demonstrate a critical role for mitochondria in the pathogenesis of sepsis that involves a previously unrecognized function of MKK3 in mitochondrial quality control. This mitochondrial pathway may help reveal new diagnostic markers and therapeutic targets against sepsis.

Fluid management in acute respiratory distress syndrome.

PURPOSE OF REVIEW: Fluid management is one of the most important measures shown to impact acute respiratory distress syndrome (ARDS) outcomes. This review summarizes the current strategies aimed at evaluating and modulating lung fluid balance. RECENT FINDINGS: Multiple recent studies have shown that a conservative fluid management in ARDS patients had beneficial effects on morbidity and mortality. These findings were replicated also in different patient populations assumed to have potential deleterious effects from this approach. So far, only one retrospective study raised the possibility of impaired cognitive function in ARDS patients managed with a conservative fluid strategy. Thermodilution methods and serum biomarkers can be used to monitor lung fluid balance and guide therapy. Recent evidence has indicated significant detrimental effects associated with beta-2 agonists use in ARDS, despite a putative beneficial role in the resolution of alveolar edema seen in preliminary studies. SUMMARY: Dynamic monitoring of lung fluid balance needs to be implemented to guide fluid therapy in ARDS patients. A conservative fluid strategy seems safe and yields overall good clinical outcomes, but its impact on cognitive function needs to be evaluated in further studies. The role of colloids and other pharmacological agents deserves further investigation.

Tris(pyrazolyl)methane and 1,8-naphthalimide-functionalized dialkynylgold(I) anionic complexes.

The reaction of tetrapropylammonium bis(acetylacetonato)gold(I) with alkyne derivatives of the tris(pyrazolyl)methane and 1,8-naphthalimide functional groups yielded two new compounds, both bridged by the linear C[triple-bond]C-Au-C[triple-bond]C spacer, namely tetrapropylammonium bis{3-[2,2,2-tris(1H-pyrazol-1-yl)ethoxy]prop-1-yn-1-yl}aurate(I), (C16H28N)[Au(C14H13N6O)2], and tetrapropylammonium {η(2)-µ-3-[2,4-dioxo-3-azatricyclo[7.3.1.0(5,13)]trideca-1(12),5,7,9(13),10-pentaen-3-yl]prop-1-yn-yl}bis{3-[2,4-dioxo-3-azatricyclo[7.3.1.0(5,13)]trideca-1(12),5,7,9(13),10-pentaen-3-yl]prop-1-yn-1-yl}digold(I) deuterochloroform disolvate, (C16H28N)[Au2(C15H8NO2)3]·2CDCl3. The alkyne-functionalized scorpionate ligand [Au{C[triple-bond]CCH2OCH2C(pz)3}2](-) features two potentially tridentate tris(pyrazolyl)methane donor groups oriented in a `trans' position relative to the C[triple-bond]C-Au-C[triple-bond]C spacer. The naphthalimide-containing compound comprises a σ-bonded NI-CH2-C[triple-bond]C-Au-C[triple-bond]C-CH2-NI unit (NI is the naphthalimide group) π-coordinated to an NI-CH2-C[triple-bond]C-Au neutral fragment. The crystal packing of this compound is supported by π-π stacking interactions of the NI unit, generating a three-dimensional network containing channels accommodating the tetrapropylammonium cations and deuterated chloroform solvent molecules.

Evidence of the Anomalous Fluctuating Magnetic State by Pressure-Driven 4f Valence Change in EuNiGe3.

In rare-earth compounds with valence fluctuation, the proximity of the 4f level to the Fermi energy leads to instabilities of the charge configuration and the magnetic moment. Here, we provide direct experimental evidence for an induced magnetic polarization of the Eu3+ atomic shell with J = 0, due to intra-atomic exchange and spin-orbital coupling interactions with the Eu2+ atomic shell. By applying external pressure, a transition from antiferromagnetic to a fluctuating behavior in EuNiGe3 single crystals is probed. Magnetic polarization is observed for both valence states of Eu2+ and Eu3+ across the entire pressure range. The anomalous magnetism is discussed in terms of a homogeneous intermediate valence state where frustrated Dzyaloshinskii-Moriya couplings are enhanced by the onset of spin-orbital interaction and engender a chiral spin-liquid-like precursor.

Simulation of Dielectric Properties of Nanocomposites with Non-Uniform Filler Distribution.

Dielectric properties for nanocomposites with metallic fillers inside a polymer matrix were determined using CST STUDIO SUITE-Electromagnetic field simulation software followed by the free-space Nicolson-Ross-Weir procedure. The structure is randomly generated to simulate the intrinsic non-uniformity of real nanomaterials. Cubic insertions were equated to corresponding spherical particles in order to provide either the same volume index or the same exterior surface index. The energy concentration around the inserts and within the entire material was determined as useful information in practice in order to design materials tailored to avoid exceeding the field/temperature limit values. The paper successfully associated the dialectic measurements with the results from the computer simulations, which are mainly based on energetic effects in electromagnetic applications. The experimental results are comparable with the software simulation in terms of precision. The conclusions outline the practical applications of the method for both electromagnetic shielding and microwave domain/telecommunications applications.

Interface-induced room-temperature multiferroicity in BaTiO3.

Multiferroic materials possess two or more ferroic orders but have not been exploited in devices owing to the scarcity of room-temperature examples. Those that are ferromagnetic and ferroelectric have potential applications in multi-state data storage if the ferroic orders switch independently, or in electric-field controlled spintronics if the magnetoelectric coupling is strong. Future applications could also exploit toroidal moments and optical effects that arise from the simultaneous breaking of time-reversal and space-inversion symmetries. Here, we use soft X-ray resonant magnetic scattering and piezoresponse force microscopy to reveal that, at the interface with Fe or Co, ultrathin films of the archetypal ferroelectric BaTiO3 simultaneously possess a magnetization and a polarization that are both spontaneous and hysteretic at room temperature. Ab initio calculations of realistic interface structures provide insight into the origin of the induced moments and bring support to this new approach for creating room-temperature multiferroics.

Vasodilator-stimulated phosphoprotein deficiency potentiates PAR-1-induced increase in endothelial permeability in mouse lungs.

Vasodilator-stimulated phosphoprotein (VASP) is implicated in the protection of the endothelial barrier in vitro and in vivo. The function of VASP in thrombin signaling in the endothelial cells (ECs) is not known. For the first time we studied the effects of VASP deficiency on EC permeability and pulmonary vascular permeability in response to thrombin receptor stimulation. We provided the evidence that VASP deficiency potentiates the increase in endothelial permeability induced by activation of thrombin receptor in cultured human umbilical vein endothelial cells (HUVECs) and isolated mouse lungs. Using transendothelial resistance measurement, we showed that siRNA-mediated VASP downregulation in HUVECs leads to a potentiation of thrombin- and protease-activated receptor 1 (PAR-1) agonist-induced increase in endothelial permeability. Compared to control cells, VASP-deficient HUVECs had delayed endothelial junctional reassembly and abrogated VE-cadherin cytoskeletal anchoring in the recovery phase after thrombin stimulation, as demonstrated by immunofluorescence studies and cell fractionation analysis, respectively. Measurement of the capillary filtration coefficient in isolated mouse lungs demonstrated that VASP(-/-) mice have increased microvascular permeability in response to infusion with PAR-1 agonist compared to wild type mice. Lack of VASP led to decreased Rac1 activation both in VASP-deficient HUVECs after thrombin stimulation and VASP(-/-) mouse lungs after PAR-1 agonist infusion, indicating that VASP effects on thrombin signaling may be correlated with changes in Rac1 activity. This study demonstrates that VASP may play critical and complex role in the regulation of thrombin-dependent disruption of the endothelial barrier function.

Perpendicular and in-plane hole asymmetry in a strained NiFe2O4film.

Strained materials can exhibit drastically modified physical properties in comparison to their fully relaxed analogues. We report on the x-ray absorption spectra (XAS) and magnetic circular dichroism (XMCD) of a strained NiFe2O4inverse spinel film grown on a symmetry matched single crystal MgGa2O4substrate. The Ni XAS spectra exhibit a sizable difference in the white line intensity for measurements with the x-ray electric field parallel to the film plane (normal incidence) vs when the electric field is at an angle (off-normal). A considerable difference is also observed in the FeL2,3XMCD spectrum. Modeling of the XAS and XMCD spectra indicate that the modified energy ordering of the cation 3dstates in the strained film leads to a preferential filling of 3dstates with out-of-plane character. In addition, the results point to the utility of x-ray spectroscopy in identifying orbital populations even with elliptically polarized x-rays.

Functionalized O-alkyldithiocarbonates: a new class of ligands designed for luminescent heterometallic materials.

The new ligand 4-PyCH(2)OCS(2)Na, that combines two different donor groups in one molecule (a soft -CS(2)(-) group and a hard pyridine moiety), has been synthesized. The ligand coordinates to a [(bipy)Re(CO)(3)](+) center in a monodentate fashion through one of its soft sulfur atoms, leaving the hard pyridine terminus free for further coordination chemistry. Using a Ni(II) dithiophosphonate linker, the heterometallic {[CH(3)OCH(2)CH(2)OP(An)S(2)](2)Ni}[4-PyCH(2)OCS(2)Re(bipy)(CO)(3)](2) complex is obtained, through the coordination of two pyridine groups to the Ni(II) center. This simple, high-yield stepwise strategy toward heterometallic complexes could be easily transferable to other 1,1-dithiolate ligands and used in combination with a large variety of luminescent metallic systems.

Observation of compact ferrimagnetic skyrmions in DyCo3 film.

Owing to the experimental discovery of magnetic skyrmions stabilized by the Dzyaloshinskii-Moriya and/or dipolar interactions in thin films, there is a recent upsurge of interest in magnetic skyrmions with antiferromagnetic spins in order to overcome the fundamental limitations inherent with skyrmions in ferromagnetic materials. Here, we report on the observation of compact ferrimagnetic skyrmions for the class of amorphous alloys consisting of 4f rare-earth and 3d transition-metal elements with perpendicular magnetic anisotropy, using a DyCo3 film, that are identified by combining X-ray magnetic scattering, scanning transmission X-ray microscopy, and Hall transport technique. These skyrmions, with antiparallel aligned Dy and Co magnetic moments and a characteristic core radius of about 40 nm, are formed during the nucleation and annihilation of the magnetic maze-like domain pattern exhibiting a topological Hall effect contribution. Our findings provide a promising route for fundamental research in the field of ferrimagnetic/antiferromagnetic spintronics towards practical applications.

Highly organized structures and unusual magnetic properties of paddlewheel copper(II) carboxylate dimers containing the pi-pi stacking, 1,8-naphthalimide synthon.

The substituted carboxylate compounds N-(3-propanoic acid)-1,8-naphthalimide (HL(C2)) and N-(4-butanoic acid)-1,8-naphthalimide (HL(C3)) react with Cu(2)(O(2)CCH(3))(4)(H(2)O)(2) in the presence of either pyridine (py) or 4,4'-bipyridine (bipy) to produce the dimeric complexes [Cu(2)(L(C2))(4)(py)(2)].2(CH(2)Cl(2)).(CH(3)OH) (1), [Cu(2)(L(C3))(4)(py)(2)].2(CH(2)Cl(2)) (2), [Cu(2)(L(C2))(4)(bipy)].unknown solvent (3), and [Cu(2)(L(C3))(4)(bipy)].(CH(3)OH)(2).(CH(2)Cl(2))(3.37) (4). The core of these four compounds contains the square Cu(2)(O(2)CR)(4) "paddlewheel" secondary building unit (SBU) structural motif with nonbonding Cu...Cu distances that average 2.66 A, with each copper in a nearly square pyramidal geometry. Strong pi-pi stacking interactions of the 1,8-naphthalimide groups organize the structures of 1 and 2 into sheets and into a three-dimensional structure for 1. The propylene connector in the L(C3) ligand allows an arrangement of the 1,8-naphthalimide groups that is different from the square shape of the SBU core. Use of the 4,4'-bipyridine linking ligand produces a three-dimensional structure for 4 organized by both covalent bonds and noncovalent forces where the 1,8-naphthalimide groups organize into a sheet structure and the 4,4'-bipyridine ligands link the sheets. In contrast, in 3, the 1,8-naphthalimide groups overlap to form only one-dimensional ribbons, with the second dimension formed by the 4,4'-bipyridine ligands and the third dimension linked by mechanical interlocking of these two-dimensional units. Although many of the pi-pi stacking interactions of the 1,8-naphthalimide groups are made with the dipole vectors of this group oriented at 180 degrees (head-to-tail arrangement), skewed arrangements are observed in many cases. Ab initio calculations show that the interaction is relatively insensitive to this angle of rotation, apart from the region of steric repulsion when the rotation angle of the dipoles approaches 0 degrees. Structural results also demonstrate that the rings can slip with respect to each other and maintain substantial interactions. Magnetic measurements show that the compounds are strongly antiferromagnetically coupled with J values ranging from -270 to -341 cm⁻¹, values typical for these types of dimers. [corrected]

Biocompatibility of Polyimides: A Mini-Review.

Polyimides (PIs) represent a benchmark for high-performance polymers on the basis of a remarkable collection of valuable traits and accessible production pathways and therefore have incited serious attention from the ever-demanding medical field. Their characteristics make them suitable for service in hostile environments and purification or sterilization by robust methods, as requested by most biomedical applications. Even if PIs are generally regarded as "biocompatible", proper analysis and understanding of their biocompatibility and safe use in biological systems deeply needed. This mini-review is designed to encompass some of the most robust available research on the biocompatibility of various commercial or noncommercial PIs and to comprehend their potential in the biomedical area. Therefore, it considers (i) the newest concepts in the field, (ii) the chemical, (iii) physical, or (iv) manufacturing elements of PIs that could affect the subsequent biocompatibility, and, last but not least, (v) in vitro and in vivo biocompatibility assessment and (vi) reachable clinical trials involving defined polyimide structures. The main conclusion is that various PIs have the capacity to accommodate in vivo conditions in which they are able to function for a long time and can be judiciously certified as biocompatible.

Benzobis(imidazolium) salts as templates for the self-assembly of starburst [24]pseudorotaxanes and their corresponding carbene-based classic [22]pseudorotaxanes.

Benzobis(imidazolium) salts ([BBI-H2-R4]2+, R = alkyl, aryl) interact with crown ethers through a combination of hydrogen bonds, ion-dipole, and π-π stacking interactions to form starburst [24]pseudo-rotaxanes. This new recognition motif allows the extension of four side-arms directly from the cavity of the crown ether, thus positioning the wheel component in a straddled orientation onto the axle, while their carbene-based derivatives show the classical shape of regular [22]pseudorotaxanes.

Cdc42 regulates adherens junction stability and endothelial permeability by inducing alpha-catenin interaction with the vascular endothelial cadherin complex.

The endothelial adherens junctions (AJs) consist of trans-oligomers of membrane spanning vascular endothelial (VE)-cadherin proteins, which bind beta-catenin through their cytoplasmic domain. beta-Catenin in turn binds alpha-catenin and connects the AJ complex with the actin cytoskeleton. We addressed the in vivo effects of loss of VE-cadherin interactions on lung vascular endothelial permeability and the role of specific Rho GTPase effectors in regulating the increase in permeability induced by AJ destabilization. We used cationic liposomes encapsulating the mutant of VE-cadherin lacking the extracellular domain (DeltaEXD) to interfere with AJ assembly in mouse lung endothelial cells. We observed that lung vascular permeability (quantified as microvessel filtration coefficient [K(f,c)]) was increased 5-fold in lungs expressing DeltaEXD. This did not occur to the same degree on expression of the VE-cadherin mutant, DeltaEXDDeltabeta, lacking the beta-catenin-binding site. The increased vascular permeability was the result of destabilization of VE-cadherin homotypic interaction induced by a shift in the binding of beta-catenin from wild-type VE-cadherin to the expressed DeltaEXD mutant. Because DeltaEXD expression in endothelial cells activated the Rho GTPase Cdc42, we addressed its role in the mechanism of increased endothelial permeability induced by AJ destabilization. Coexpression of dominant-negative Cdc42 (N17Cdc42) prevented the increase in K(f,c) induced by DeltaEXD. This was attributed to inhibition of the association of alpha-catenin with the DeltaEXD-beta-catenin complex. The results demonstrate that Cdc42 regulates AJ permeability by controlling the binding of alpha-catenin with beta-catenin and the consequent interaction of the VE-cadherin/catenin complex with the actin cytoskeleton.

Multiple coordination modes of a new ditopic bis(pyrazolyl)methane-based ligand.

A new ditopic ligand, N-(2,2-bis(pyrazolyl)ethyl)-2,2-bis(pyrazolyl)acetamide ((pz)2CH-C(O)-NH-CH2-CH(pz)2, L4Pz, pz = pyrazolyl ring), comprising two bis(pyrazolyl)methane donor groups linked via an amide bridge, has been prepared from the reaction of HOOCCH(pz)2 and H2NCH2CH(pz)2. The ligand coordinates to various metallic salts (i.e. AgO3SCF3, PdCl2, Re(CO)5Br, and Fe(BF4)2), in either a κ2-µ-κ2 or a κ3-µ-κ2 fashion, depending on the coordination preferences of the metallic center. These compounds were characterized by NMR, UV-Vis and IR spectroscopy, and in solid state by single crystal X-ray diffraction. In the case of silver(i), a mono-dimensional coordination polymer was obtained, while the others were found to be discrete complexes. The synthesis and characterization of a heterobimetallic complex is also described. In solid state, all compounds are associated into supramolecular architectures via hydrogen bonding and pyrazolyl embrace interactions.

Silver(I) and rhenium(I) metal complexes of a 2,2'-bipyridine-functionalized third-generation tris(pyrazolyl)methane ligand.

Heterotopic ligands offer the possibility of preparing polynuclear bimetallic complexes. Recent studies of heteroditopic ligands and their metal complexes have focused on novel supramolecular systems, biological activity, and the development of MRI contrast agents. The heteroditopic ligand Bipy-CH2-O-CH2-C(pz)3 (Bipy-L; Bipy is 2,2'-bipyridine and pz is pyrazolyl) reacts with AgBF4 to produce the coordination polymer catena-poly[[silver(I)-(µ-5-{[tris(pyrazol-1-yl)methoxy]methyl-κ2N,N'}-2,2'-bipyridine-κ2N,N')] diethyl ether hemisolvate], {[Ag(C22H20N8O)]BF4·0.5C4H10O}n, and with Re(CO)5Br to form the discrete compound bromidotricarbonyl(5-{[tris(pyrazol-1-yl)methoxy]methyl}-2,2'-bipyridine-κ2N,N')rhenium(I), [ReBr(C22H20N8O)(CO)3]. The silver(I) compound is a one-dimensional coordination polymer, built up by a κ2 coordination mode of the bipyridine group and a κ2-κ0 coordination mode of the -C(pz)3 donor set. In [ReBr(Bipy-L)(CO)3], the ligand coordinates only via the bipyridine end, leaving the -C(pz)3 donor set free for further coordination interactions.