573 research outputs found
Local Spectral Weight of a Luttinger Liquid: Effects from Edges and Impurities
We calculate the finite-temperature local spectral weight (LSW) of a
Luttinger liquid with an "open" (hard wall) boundary. Close to the boundary the
LSW exhibits characteristic oscillations indicative of spin-charge separation.
The line shape of the LSW is also found to have a Fano-like asymmetry, a
feature originating from the interplay between electron-electron interaction
and scattering off the boundary. Our results can be used to predict how edges
and impurities influence scanning tunneling microscopy (STM) of one-dimensional
electron systems at low temperatures and voltage bias. Applications to STM on
single-walled carbon nanotubes are discussed.Comment: 15 pages, 10 figues, The latest version in pdf format is available at
http://www.physik.uni-kl.de/eggert/papers/LSW-LL.pd
Modal Ω-Logic: Automata, Neo-Logicism, and Set-Theoretic Realism
This essay examines the philosophical significance of -logic in Zermelo-Fraenkel set theory with choice (ZFC). The duality between coalgebra and algebra permits Boolean-valued algebraic models of ZFC to be interpreted as coalgebras. The modal profile of -logical validity can then be countenanced within a coalgebraic logic, and -logical validity can be defined via deterministic automata. I argue that the philosophical significance of the foregoing is two-fold. First, because the epistemic and modal profiles of -logical validity correspond to those of second-order logical consequence, -logical validity is genuinely logical, and thus vindicates a neo-logicist conception of mathematical truth in the set-theoretic multiverse. Second, the foregoing provides a modal-computational account of the interpretation of mathematical vocabulary, adducing in favor of a realist conception of the cumulative hierarchy of sets
Effects of Oxygen During Long-term Hypothermic Machine Perfusion in a Porcine Model of Kidney Donation After Circulatory Death
International audienceBackground:Hypothermic machine perfusion (HMP) has become standard care in many center’s to preserve kidneys donated after circulatory death (DCD). Despite a significant reduction in metabolism at low temperatures, remaining cellular activity requires oxygen. Since the role and safety of oxygen during HMP has not been fully clarified, its supply during HMP is not standard yet. This study investigates the effect of administering oxygen during HMP on renal function in a porcine DCD model.Methods: After 30 minutes of warm ischemia, porcine slaughterhouse kidneys were preserved for 24 hours by means of cold storage (CS), or HMP with Belzer Machine Perfusion Solution (UW- MPS) supplemented with no oxygen, 21% or 100% oxygen. Next, kidneys were reperfused for 4 hours in a normothermic machine perfusion (NMP) setup.Results:HMP resulted in significantly better kidney function during NMP. Thiobarbituric acid-reactive substances (TBARS), markers of oxidative stress, were significantly lower in HMP preserved kidneys. HMP preserved kidneys showed significantly lower ASAT and LDH levels compared to kidneys preserved by CS. No differences were found between the HMP groups subjected to different oxygen concentrations. ATP levels significantly improved during HMP when active oxygenation was applied.Conclusion:This study showed that preservation of DCD kidneys with HMP is superior to CS. Although the addition of oxygen to HMP did not result in significantly improved renal function, beneficial effects were found in terms of reduced oxidative stress and energy status. Oxygen addition proofed to be safe and did not show detrimental effects
Quantum Interference Effects in Electronic Transport through Nanotube Contacts
Quantum interference has dramatic effects on electronic transport through
nanotube contacts. In optimal configuration the intertube conductance can
approach that of a perfect nanotube (). The maximum conductance
increases rapidly with the contact length up to 10 nm, beyond which it exhibits
long wavelength oscillations. This is attributed to the resonant cavity-like
interference phenomena in the contact region. For two concentric nanotubes
symmetry breaking reduces the maximum intertube conductance from to
. The phenomena discussed here can serve as a foundation for building
nanotube electronic circuits and high speed nanoscale electromechanical
devices
An in-vacuum diffractometer for resonant elastic soft x-ray scattering
We describe the design, construction and performance of a 4-circle in-vacuum
diffractometer for resonant elastic soft x-ray scattering and reflectivity. The
diffractometer, installed on the REIXS beamline at the Canadian Light Source,
includes 9 in-vacuum motions driven by in-vacuum stepper motors and operates in
ultra-high vacuum at base pressure of 2 x10^-10 Torr. Cooling to a base
temperature of 18 K is provided with a closed-cycle cryostat. The
diffractometer includes a choice of 3 photon detectors: a photodiode, a
channeltron and a 2D sensitive channelplate detector. Along with variable slit
and filter options, these detectors are suitable for studying a wide range of
phenomena having both weak and strong diffraction signals. Example measurements
of diffraction and reflectivity in Nd-doped (La,Sr)_2CuO_4 and thin film
(Ga,Mn)As are shown.Comment: 9 pages, 8 figure
Bandgap Change of Carbon Nanotubes: Effect of Small Tensile and Torsional Strain
We use a simple picture based on the electron approximation to study
the bandgap variation of carbon nanotubes with uniaxial and torsional strain.
We find (i) that the magnitude of slope of bandgap versus strain has an almost
universal behaviour that depends on the chiral angle, (ii) that the sign of
slope depends on the value of and (iii) a novel change in sign
of the slope of bandgap versus uniaxial strain arising from a change in the
value of the quantum number corresponding to the minimum bandgap. Four orbital
calculations are also presented to show that the orbital results are
valid.Comment: Revised. Method explained in detai
Influence of the in-medium pion dispersion relation in heavy ion collisions
We investigate the influence of medium corrections to the pion dispersion
relation on the pion dynamics in intermediate energy heavy ion collisions. To
do so a pion potential is extracted from the in-medium dispersion relation and
used in QMD calculations and thus we take care of both, real and imaginary part
of the pion optical potential. The potentials are determined from different
sources, i.e. from the --hole model and from phenomenological
approaches. Depending on the strength of the potential a reduction of the
anti-correlation of pion and nucleon flow in non-central collisions is observed
as well as an enhancement of the high energetic yield in transverse pion
spectra. A comparison to experiments, in particular to -spectra for the
reaction Ca+Ca at 1 GeV/nucleon and the pion in-plane flow in Ne+Pb collisions
at 800 MeV/nucleon, generally favours a weak potential.Comment: 25 pages, using REVTeX, 6 postscript figures; replaced by published
versio
van der Waals interaction in nanotube bundles : consequences on vibrational modes
We have developed a pair-potential approach for the evaluation of van der
Waals interaction between carbon nanotubes in bundles.
Starting from a continuum model, we show that the intertube modes range from
to . Using a non-orthogonal tight-binding approximation
for describing the covalent intra-tube bonding in addition, we confirme a
slight chiral dependance of the breathing mode frequency and we found that this
breathing mode frequency increase by 10 % if the nanotube lie inside a
bundle as compared to the isolated tube.Comment: 5 pages, 2 figure
Patient and physician satisfaction in an observational study with methyl aminolevulinate daylight-photodynamic therapy in the treatment of multiple actinic keratoses of the face and scalp in 6 European countries
BACKGROUND
Guidelines recommend treating actinic keratoses (AKs) as they are recognized as precursors of invasive squamous cell carcinoma.
OBJECTIVE
The objective of this study was to collect real-world clinical data on the use of methyl aminolevulinate daylight photodynamic therapy (MAL DL-PDT) for the treatment of face and scalp AK in Europe.
METHODS
A prospective, multicenter, non-interventional study was conducted in six European countries in patients receiving a single treatment of MAL DL-PDT for face and/or scalp AK. Patient-reported outcomes were assessed by patient questionnaires at baseline and at 3 months after treatment, efficacy was assessed at 3 months using a 6-point global improvement scale, and adverse events (AE) were recorded at each visit.
RESULTS
Overall, 325 patients were enrolled from 52 investigational centres, 314 of whom attended the 3-month visit. Most patients had multiple lesions (58.4% had >10 lesions) with lesions mainly located on the scalp (60.0%) and/or forehead (54.2%). AKs were predominantly grade I (39.4%) or grade II (33.2%), and 10.5% of patients had grade III lesions. The proportions of patients and physicians that were overall satisfied to very satisfied with the MAL DL-PDT treatment were 80.4% and 90.3%, respectively. The vast majority of patients (90.0%) would consider using MAL DL-PDT again if needed. Physician-assessed efficacy at 3 months was at least much improved in 83.5% of patients, with 45.9% of patients requiring no retreatment. Related AEs were reported in 15% of patients.
CONCLUSION
Use of MAL DL-PDT for multiple face and/or scalp AKs resulted in high levels of patient and physician satisfaction in clinical practice in Europe, reflecting the good efficacy and high tolerability of this convenient procedure
Measurement of mechanical vibrations excited in aluminium resonators by 0.6 GeV electrons
We present measurements of mechanical vibrations induced by 0.6 GeV electrons
impinging on cylindrical and spherical aluminium resonators. To monitor the
amplitude of the resonator's vibrational modes we used piezoelectric ceramic
sensors, calibrated by standard accelerometers. Calculations using the
thermo-acoustic conversion model, agree well with the experimental data, as
demonstrated by the specific variation of the excitation strengths with the
absorbed energy, and with the traversing particles' track positions. For the
first longitudinal mode of the cylindrical resonator we measured a conversion
factor of 7.4 +- 1.4 nm/J, confirming the model value of 10 nm/J. Also, for the
spherical resonator, we found the model values for the L=2 and L=1 mode
amplitudes to be consistent with our measurement. We thus have confirmed the
applicability of the model, and we note that calculations based on the model
have shown that next generation resonant mass gravitational wave detectors can
only be expected to reach their intended ultra high sensitivity if they will be
shielded by an appreciable amount of rock, where a veto detector can reduce the
background of remaining impinging cosmic rays effectively.Comment: Tex-Article with epsfile, 34 pages including 13 figures and 5 tables.
To be published in Rev. Scient. Instr., May 200
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