496 research outputs found
Detection and imaging of the oxygen deficiency in single crystalline YBaCuO thin films using a positron beam
Single crystalline YBaCuO
(YBCO) thin films were grown by pulsed laser deposition (PLD) in order to probe
the oxygen deficiency using a mono-energetic positron beam. The sample
set covered a large range of (0.191<<0.791) yielding a
variation of the critical temperature between 25 and 90\,K. We
found a linear correlation between the Doppler broadening of the positron
electron annihilation line and determined by X-ray diffraction (XRD).
Both, the origin of the found correlation and the influence of metallic
vacancies, were examined with the aid of ab-initio calculations that allowed us
(i) to exclude the presence of Y vacancies and (ii) to ensure that positrons
still probe despite the potential presence of Ba or Cu vacancies. In
addition, by scanning with the positron beam the spatial variation of
could be analyzed. It was found to fluctuate with a standard deviation of up to
within a single YBCO film
Demonstration of a heterogeneously integrated III-V/SOI single wavelength tunable laser
A heterogeneously integrated III-V-on-silicon laser is reported, integrating a III-V gain section, a silicon ring resonator for wavelength selection and two silicon Bragg grating reflectors as back and front mirrors. Single wavelength operation with a side mode suppression ratio higher than 45 dB is obtained. An output power up to 10 mW at 20 °C and a thermo-optic wavelength tuning range of 8 nm are achieved. The laser linewidth is found to be 1.7 MHz
Low-threshold heterogeneously integrated InP/SOI lasers with a double adiabatic taper coupler
We report on a heterogeneously integrated InP/silicon-on-insulator (SOI) laser source realized through divinylsiloxane-bis-benzocyclobutene (DVS-BCB) wafer bonding. The hybrid lasers present several new features. The III-V waveguide has a width of only 1.7 mu m, reducing the power consumption of the device. The silicon waveguide thickness is 400 nm, compatible with high-performance modulator designs and allowing efficient coupling to a standard 220-nm high index contrast silicon waveguide layer. In order to make the mode coupling efficient, both the III-V waveguide and silicon waveguide are tapered, with a tip width for the III-V waveguide of around 800 nm. These new features lead to good laser performance: a lasing threshold as low as 30 mA and an output power of more than 4 mW at room temperature in continuous-wave operation regime. Continuous wave lasing up to 70 degrees C is obtained
Diodes with Breakdown Voltages Enhanced by the Metal-Insulator Transition of LaAlO-SrTiO Interfaces
Using the metal-insulator transition that takes place as a function of
carrier density at the LaAlO-SrTiO interface, oxide diodes have been
fabricated with room-temperature breakdown voltages of up to 200 V. With
applied voltage, the capacitance of the diodes changes by a factor of 150. The
diodes are robust and operate at temperatures up to 270 C
Electric-field-induced pyroelectric order and localization of the confined electrons in LaAlO3/SrTiO3 heterostructures
With infrared ellipsometry, x-ray diffraction, and electric transport
measurements we investigated the electric-field-effect on the confined
electrons at the LaAlO3/SrTiO3 interface. We obtained evidence that the
localization of the electrons at low temperature and negative gate voltage is
induced, or at least strongly enhanced, by a pyroelectric phase transition in
SrTiO3 which strongly reduces the lattice polarizability and the subsequent
Coulomb screening. In particular, we show that the charge localisation and the
polar order of SrTiO3 both develop below about 50 K and exhibit similar,
unipolar hysteresis loops as a function of the gate voltage. Our findings
suggest that the pyroelectric order also plays an important role in the quantum
phase transition at very low temperatures where superconductivity is suppressed
by an electric field.Comment: 5 pages, 4 figures, supplementary materia
Probing the electronic transport on the reconstructed Au/Ge(001) surface
By using scanning tunnelling potentiometry we characterized the lateral variation of the electrochemical potential on the gold-induced Ge(001)-c(8 × 2)-Au surface reconstruction while a lateral current flows through the sample. On the reconstruction and across domain boundaries we find that shows a constant gradient as a function of the position between the contacts. In addition, nanoscale Au clusters on the surface do not show an electronic coupling to the gold-induced surface reconstruction. In combination with high resolution scanning electron microscopy and transmission electron microscopy, we conclude that an additional transport channel buried about 2 nm underneath the surface represents a major transport channel for electrons
Glycoform-resolved pharmacokinetic studies in a rat model employing glycoengineered variants of a therapeutic monoclonal antibody
Good pharmacokinetic (PK) behavior is a key prerequisite for sufficient efficacy of therapeutic monoclonal antibodies (mAbs). Fc glycosylation is a critical quality attribute (CQA) of mAbs, due to its impact on stability and effector functions. However, the effects of various IgG Fc glycoforms on antibody PK remain unclear. We used a combination of glycoengineering and glycoform-resolved PK measurements by mass spectrometry (MS) to assess glycoform effects on PK. Four differently glycoengineered mAbs, each still containing multiple glycoforms, were separately injected into rats. Rat models have been shown to be predictive of human PK. At different time points, blood was taken, from which the mAbs were purified and analyzed with a liquid chromatography-MS-based bottom-up glycoproteomics approach. This allowed us to follow changes in the glycosylation profiles of each glycoengineered mAb over time. Enzyme-linked immunosorbent assay measurements provided an absolute concentration in the form of a sum value for all glycoforms. Information from both readouts was then combined to calculate PK parameters per glycoform. Thereby, multiple glycoform kinetics were resolved within one mAb preparation. We confirmed increased clearance of high-mannose (Man5) and hybrid-type (Man5G0) glycoforms. Specifically, Man5 showed a 1.8 to 2.6-fold higher clearance than agalactosylated, complex glycans (G0F). Unexpectedly, clearance was even higher (4.7-fold) for the hybrid-type glycan Man5G0. In contrast, clearance of agalactosylated, monoantennary glycoforms (G0F-N) was only slightly increased over G0F (1.2 to 1.4-fold). Thus, monoantennary, hybrid-type and high-mannose glycoforms should be distinguished in CQA assessments. Strikingly, alpha 2,3-linked sialylation did not affect clearance, contradicting the involvement of the asialoglycoprotein receptor in mAb clearance.Proteomic
Cross section ratio and angular distributions of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8 MeV excess energy
We present new data for angular distributions and on the cross section ratio
of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q =
59.8 MeV. The data have been obtained at the WASA-at-COSY experiment
(Forschungszentrum J\"ulich) using a proton beam and a deuterium pellet target.
While the shape of obtained angular distributions show only a slow variation
with the energy, the new results indicate a distinct and unexpected total cross
section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the
variation of the production mechanism within this energy interval.Comment: 9 pages, 9 figure
Measurement of the Reaction in Search for the Recently Observed Resonance Structure in and systems
Exclusive measurements of the quasi-free reaction have
been performed by means of collisions at = 1.2 GeV using the WASA
detector setup at COSY. Total and differential cross sections have been
obtained covering the energy region = (2.35 - 2.46) GeV, which
includes the region of the ABC effect and its associated resonance structure.
No ABC effect, {\it i.e.} low-mass enhancement is found in the
-invariant mass spectrum -- in agreement with the constraint from
Bose statistics that the isovector pion pair can not be in relative s-wave. At
the upper end of the covered energy region -channel processes for Roper,
and excitations provide a reasonable description
of the data, but at low energies the measured cross sections are much larger
than predicted by such processes. Adding a resonance amplitude for the
resonance at =~2.37 GeV with =~70 MeV and observed
recently in and reactions leads to an
agreement with the data also at low energies
Neutron-Proton Scattering in the Context of the (2380) Resonance
New data on quasifree polarized neutron-proton scattering, in the region of
the recently observed resonance structure, have been obtained by
exclusive and kinematically complete high-statistics measurements with WASA at
COSY. This paper details the determination of the beam polarization, checks of
the quasifree character of the scattering process, on all obtained
angular distributions and on the new partial-wave analysis, which includes the
new data producing a resonance pole in the - coupled partial
waves at () MeV -- in accordance with the dibaryon
resonance hypothesis. The effect of the new partial-wave solution on the
description of total and differential cross section data as well as specific
combinations of spin-correlation and spin-transfer observables available from
COSY-ANKE measurements at = 2.27 GeV is discussed
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