1,203 research outputs found
Design of a horizontal neutron reflectometer for the European Spallation Source
A design study of a horizontal neutron reflectometer adapted to the general
baseline of the long pulse European Spallation Source (ESS) is presented. The
instrument layout comprises solutions for the neutron guide, high-resolution
pulse shaping and beam bending onto a sample surface being so far unique in the
field of reflectometry. The length of this instrument is roughly 55 m, enabling
resolutions from 0.5% to 10%. The incident beam is
focussed in horizontal plane to boost measurements of sample sizes of 1*1
cm{^2} and smaller with potential beam deflection in both downward and upward
direction. The range of neutron wavelengths untilized by the instrument is 2 to
7.1 (12.2, ...) {\AA}, if every (second, ...) neutron source ulse is used.
Angles of incidence can be set between 0{\deg} and 9{\deg} with a total
accessible q-range from 4*10^{-3} {\AA}^{-1} up to 1 {\AA}^{-1}. The instrument
operates both in {\theta}/{\theta} (free liquid surfaces) and
{\theta}/2{\theta} (solid/liquid, air/solid interfaces) geometry. The
experimental setup will in particular enable direct studies on ultrathin films
(d ~ 10 {\AA}) and buried monolayers to multilayered structures of up to 3000
{\AA} total thickness. The horizontal reflectometer will further foster
investigations of hierarchical systems from nanometer to micrometer length
scale, as well as their kinetics and dynamical properties, in particular under
load (shear, pressure, external fields). Polarization and polarization analysis
as well as the GISANS option are designed as potential modules to be
implemented separately in the generic instrument layout. The instrument is
highly flexible and offers a variety of different measurement modes. With
respect to its mechanical components the instrument is exclusively based on
current technology. Risks of failure for the chosen setup are minimum.Comment: Matched to the version submitted to Nuclear Instruments and Methods
Comparative adsorption of saturated and unsaturated fatty acids at the iron oxide/oil interface
A detailed comparison of the adsorption behavior of long straight chain saturated and unsaturated fatty acids at the iron oxide/oil interface has been considered using a combination of surface study techniques. Both depletion isotherms and polarized neutron reflectometry (PNR) show that the extent of adsorption decreases as the number of double bonds in the alkyl chains increases. Sum frequency generation spectroscopic measurements demonstrate that there is also an increase in chain disorder within the adsorbed layer as the unsaturation increases. However, for the unsaturated analogues, a decrease in peak intensity is seen for the double bond peak upon heating, which is thought to arise from isomerization in the surface-bound layer. The PNR study of oleic acid adsorption indicates chemisorbed monolayer adsorption, with a further diffuse reversible adsorbed layer formed at higher concentrations.Mary Wood is grateful for funding from the Oppenheimer Trust. The PNR data were collected using the V6 instrument at the Helmholtz-Zentrum Berlin (experiment number MAT-04-2131).This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/acs.langmuir.5b0443
On the Explanation of the Paramagnetic Meissner Effect in Superconductor/Ferromagnet Heterostructures
An increase of the magnetic moment in superconductor/ferromagnet (S/F)
bilayers V(40nm)/F [FFe(1,3nm), Co(3nm), Ni(3nm)] was observed using SQUID
magnetometry upon cooling below the superconducting transition temperature Tc
in magnetic fields of 10 Oe to 50 Oe applied parallel to the sample surface. A
similar increase, often called the paramagnetic Meissner effect (PME), was
observed before in various superconductors and superconductor/ferromagnet
systems. To explain the PME effect in the presented S/F bilayers a model based
on a row of vortices located at the S/F interface is proposed. According to the
model the magnetic moment induced below Tc consists of the paramagnetic
contribution of the vortex cores and the diamagnetic contribution of the
vortex-free region of the S layer. Since the thickness of the S layer is found
to be 3-4 times less than the magnetic field penetration depth, this latter
diamagnetic contribution is negligible. The model correctly accounts for the
sign, the approximate magnitude and the field dependence of the paramagnetic
and the Meissner contributions of the induced magnetic moment upon passing the
superconducting transition of a ferromagnet/superconductor bilayer
Comparative Adsorption of Saturated and Unsaturated Fatty Acids at the Iron Oxide/Oil Interface.
A detailed comparison of the adsorption behavior of long straight chain saturated and unsaturated fatty acids at the iron oxide/oil interface has been considered using a combination of surface study techniques. Both depletion isotherms and polarized neutron reflectometry (PNR) show that the extent of adsorption decreases as the number of double bonds in the alkyl chains increases. Sum frequency generation spectroscopic measurements demonstrate that there is also an increase in chain disorder within the adsorbed layer as the unsaturation increases. However, for the unsaturated analogues, a decrease in peak intensity is seen for the double bond peak upon heating, which is thought to arise from isomerization in the surface-bound layer. The PNR study of oleic acid adsorption indicates chemisorbed monolayer adsorption, with a further diffuse reversible adsorbed layer formed at higher concentrations.Mary Wood is grateful for funding from the Oppenheimer Trust. The PNR data were collected using the V6 instrument at the Helmholtz-Zentrum Berlin (experiment number MAT-04-2131).This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/acs.langmuir.5b0443
Ligand-lipid and ligand-core affinity control the interaction of gold nanoparticles with artificial lipid bilayers and cell membranes
Monoclonal antibodies to nucleic acid-containing cellular constituents: probes for molecular biology and autoimmune disease.
Pennsylvania Folklife Vol. 39, No. 3
• The General Store • Pennsylvania German in Public Life • Building a One-Room School: The Dynamics of School Board Decision-Making at the Turn of the 20th Century • Washington Hood: 500th Graduate of the United States Military Academy • Grandmother Schultz • Aldes un Neies (Old and New)https://digitalcommons.ursinus.edu/pafolklifemag/1127/thumbnail.jp
Magnetic proximity effects in V/Fe superconductor/ferromagnet single bilayer revealed by waveguide-enhanced polarized neutron reflectometry
Polarized neutron reflectometry is used to study the magnetic proximity
effect in a superconductor/ferromagnet (SC/FM) system of composition
Cu(32nm)/V(40nm)/Fe(1nm)/MgO. In contrast to previous studies, here a single
SC/FM bilayer, is studied and multilayer artefacts are excluded. The necessary
signal enhancement is achieved by waveguide resonance, i.e. preparing the
V(40nm)/Fe(1nm) SC/FM bilayer sandwiched by the highly reflective MgO substrate
and Cu top layer, respectively . A new magnetic state of the system was
observed at temperatures below 0.7 TC. manifested in a systematic change in the
height and width of the waveguide resonance peak. Upon increasing the
temperature from 0.7 TC to TC, a gradual decay of this state is observed,
accompanied by a 5% growth of the diffuse scattering. According to theoretical
studies, such behavior is the result of the magnetic proximity effect. Due to
the presence of the thin FM layer the superconducting electrons are polarized
and, as a result, near the SC/FM interface an additional magnetic layer appears
in the SC with thickness comparable to ksi, the coherence length of the
superconductor.Comment: Submitted to the Journal of Superconductivity and Novel Magnetism. 11
pages, 6 figures
Volume-rendered optical coherence tomography angiography during ocular interventions: Advocating for noninvasive intraoperative retinal perfusion monitoring.
We aimed to test for feasibility of volume-rendered optical coherence tomography angiography (OCTA) as a novel method for assessing/quantifying retinal vasculature during ocular procedures and to explore the potential for intraoperative use. Thirty patients undergoing periocular anaesthesia were enrolled, since published evidence suggests a reduction in ocular blood flow. Retinal perfusion was monitored based on planar OCTA image-derived data provided by a standard quantification algorithm and postprocessed/volume-rendered OCTA data using a custom software script. Overall, imaging procedures were successful, yet imaging artifacts occurred frequently. In interventional eyes, perfusion parameters decreased during anaesthesia. Planar image-derived and volume rendering-derived parameters were correlated. No correlation was found between perfusion parameters and a motion artifact score developed for this study, yet all perfusion parameters correlated with signal strength as displayed by the device. Concluding, volume-rendered OCTA allows for noninvasive three-dimensional retinal vasculature assessment/quantification in challenging surgical settings and appears generally feasible for intraoperative use
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