585 research outputs found
Muscle action potential scans and ultrasound imaging in neurofibromatosis type 2
INTRODUCTION: The neuropathy in patients with neurofibromatosis type 2 (NF2) is difficult to quantify and follow up. In this study we compared 3 methods that may help assess motor axon pathology in NF2 patients. METHODS: Nerve conduction studies in median nerves were supplemented by deriving motor unit number estimates (MUNEs) from compound muscle action potential (CMAP) scans and by high-resolution ultrasound (US) peripheral nerve imaging. RESULTS: CMAP amplitudes and nerve conduction velocity were normal in the vast majority of affected individuals, but CMAP scan MUNE revealed denervation and reinnervation in many peripheral nerves. In addition, nerve US imaging enabled monitoring of the size and number of schwannoma-like fascicular enlargements in median nerve trunks. CONCLUSION: In contrast to conventional nerve conduction studies, CMAP scan MUNE in combination with US nerve imaging can quantify the NF2-associated neuropathy and may help to monitor disease progression and drug treatments
Luminescence tuning of MOFs via ligand to metal and metal to metal energy transfer by co-doping of 2∞[Gd2Cl6(bipy)3]*2bipy with europium and terbium
The series of anhydrous lanthanide chlorides LnCl3, Ln=Pr–Tb, and 4,4'-bipyridine (bipy) constitute isotypic MOFs of the formula 2∞[Ln2Cl6(bipy)3]*2bipy. The europium and terbium containing compounds both exhibit luminescence of the referring trivalent lanthanide ions, giving a red luminescence for Eu3+ and a green luminescence for Tb3+ triggered by an efficient antenna effect of the 4,4'-bipyridine linkers. Mixing of different lanthanides in one MOF structure was undertaken to investigate the potential of this MOF system for colour tuning of the luminescence. Based on the gadolinium containing compound, co-doping with different amounts of europium and terbium proves successful and yields solid solutions of the formula 2∞[Gd2-x-yEuxTbyCl6(bipy)3]*2bipy (1–8), 0≤x, y≤0.5. The series of MOFs exhibits the opportunity of tuning the emission colour in-between green and red. Depending on the atomic ratio Gd:Eu:Tb, the yellow region was covered for the first time for an oxygen/carboxylate-free MOF system. In addition to a ligand to metal energy transfer (LMET) from the lowest ligand-centered triplet state of 4,4'-bipyridine, a metal to metal energy transfer (MMET) between 4f-levels from Tb3+ to Eu3+ is as well vital for the emission colour. However, no involvement of Gd3+ in energy transfers is observed rendering it a suitable host lattice ion and connectivity centre for diluting the other two rare earth ions in the solid state. The materials retain their luminescence during activation of the MOFs for microporosity
The de Haas-van Alphen effect across the metamagnetic transition in SrRuO
We report a study of the de Haas-van Alphen (dHvA) effect on the itinerant
metamagnet SrRuO. Extremely high sample purity allows the
observation of dHvA oscillations both above and below the metamagnetic
transition field of 7.9 T. The quasiparticle masses are fairly large away from
the transition, and are enhanced by up to an extra factor of three as the
transition is approached, but the Fermi surface topography change is quite
small. The results are qualitatively consistent with a field-induced Stoner
transition in which the mass enhancement is the result of critical
fluctuations.Comment: 4 pages, 3 figure
Molecularly imprinted conductive polymers for controlled trafficking of neurotransmitters at solid–liquid interfaces
We realize a molecularly imprinted polymer (MIP) which is imprinted with the
retinal neurotransmitter glutamate. The films prepared by electrochemical
deposition have a smooth surface with a granular morphology as observed using
an atomic force microscope. Multiple reflection attenuated total reflection
infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS)
are used to chemically confirm the imprint of a neurotransmitter in the MIP at
the solid–liquid and the solid–air interface, respectively. Fluorescence
spectroscopy using the dye fluorescamine is used to monitor the changes in
neurotransmitter concentration in various solvents induced by application of
voltage to the MIP. By controlling neurotransmitter trafficking across a
solid–liquid interface with voltage, we suggest the possibility of using such
a neurotransmitter imprinted MIP for chemical stimulation of retinal neurons.
The current state of the art approach to restore sight in certain cases of
blindness is the replacement of damaged photoreceptors by a subretinal implant
consisting of light-sensitive photodiodes. Thus a future perspective of our
work would be to chemically stimulate the neurons by replacing the photodiodes
in the subretinal implant by the neurotransmitter imprinted polymer film
The balancing act between high electronic and low ionic transport influenced by perovskite grain boundaries
\ua9 2024 The Royal Society of Chemistry.A better understanding of the materials\u27 fundamental physical processes is necessary to push hybrid perovskite photovoltaic devices towards their theoretical limits. The role of the perovskite grain boundaries is essential to optimise the system thoroughly. The influence of the perovskite grain size and crystal orientation on physical properties and their resulting photovoltaic performance is examined. We develop a novel, straightforward synthesis approach that yields crystals of a similar size but allows the tuning of their orientation to either the (200) or (002) facet alignment parallel to the substrate by manipulating dimethyl sulfoxide (DMSO) and tetrahydrothiophene-1-oxide (THTO) ratios. This decouples crystal orientation from grain size, allowing the study of charge carrier mobility, found to be improved with larger grain sizes, highlighting the importance of minimising crystal disorder to achieve efficient devices. However, devices incorporating crystals with the (200) facet exhibit an s-shape in the current density-voltage curve when standard scan rates are used, which typically signals an energetic interfacial barrier. Using the drift-diffusion simulations, we attribute this to slower-moving ions (mobility of 0.37
7 10-10 cm2 V-1 s-1) in combination with a lower density of mobile ions. This counterintuitive result highlights that reducing ion migration does not necessarily minimise hysteresis
Observation of the complete rupture of a buried polymer layer by off-specular neutron reflectometry
Metamagnetism and critical fluctuations in high quality single crystals of the bilayer ruthenate Sr3Ru2O7
We report the results of low temperature transport, specific heat and
magnetisation measurements on high quality single crystals of the bilayer
perovskite Sr3Ru2O7, which is a close relative of the unconventional
superconductor Sr2RuO4. Metamagnetism is observed, and transport and
thermodynamic evidence for associated critical fluctuations is presented. These
relatively unusual fluctuations might be pictured as variations in the Fermi
surface topography itself. No equivalent behaviour has been observed in the
metallic state of Sr2RuO4.Comment: 4 pages, 4 figures, Revtex 3.
The ground state of Sr3Ru2O7 revisited; Fermi liquid close to a ferromagnetic instability
We show that single-crystalline Sr3Ru2O7 grown by a floating-zone technique
is an isotropic paramagnet and a quasi-two dimensional metal as spin-triplet
superconducting Sr2RuO4 is. The ground state is Fermi liquid with very low
residual resistivity (3 micro ohm cm for in-plane currents) and a nearly
ferromagnetic metal with the largest Wilson ratio Rw>10 among paramagnets so
far. This contrasts with the ferromagnetic order at Tc=104 K reported on single
crystals grown by a flux method [Cao et al., Phys. Rev. B 55, R672 (1997)]. We
have also found a dramatic changeover from paramagnetism to ferromagnetism
under applied pressure. This suggests the existence of a substantial
ferromagnetic instability on the verge of a quantum phase transition in the
Fermi liquid state.Comment: 5 pages, 4 figures, to be published in Phys. Rev. B : Rapid co
Critical adsorption near edges
Symmetry breaking surface fields give rise to nontrivial and long-ranged
order parameter profiles for critical systems such as fluids, alloys or magnets
confined to wedges. We discuss the properties of the corresponding universal
scaling functions of the order parameter profile and the two-point correlation
function and determine the critical exponents eta_parallel and
eta_perpendicular for the so-called normal transition.Comment: 22 pages, 5 figures, accepted for publication in PR
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