5,500 research outputs found
Low loss Ge-on-Si waveguides operating in the 8–14 µm atmospheric transmission window
Germanium-on-silicon waveguides were modeled, fabricated and characterized at wavelengths ranging from 7.5 to 11 µm. Measured waveguide losses are below 5 dB/cm for both TE and TM polarization and reach values of ∼ 1 dB/cm for ≥ 10 µm wavelengths for the TE polarization. This work demonstrates experimentally for the first time that Ge-on-Si is a viable waveguide platform for sensing in the molecular fingerprint spectral region. Detailed modeling and analysis is presented to identify the various loss contributions, showing that with practical techniques losses below 1 dB/cm could be achieved across the full measurement range
Regulation of vascular endothelial growth factor bioactivity in patients with acute lung injury
Background: Reduced bioactive vascular endothelial growth factor (VEGF) has been demonstrated in
several inflammatory lung conditions including the acute respiratory distress syndrome (ARDS). sVEGFR-1,
a soluble form of VEGF-1 receptor, is a potent natural inhibitor of VEGF. We hypothesised that sVEGFR-1
plays an important role in the regulation of the bioactivity of VEGF within the lung in patients with ARDS.
Methods: Forty one patients with ARDS, 12 at risk of developing ARDS, and 16 normal controls were
studied. Bioactive VEGF, total VEGF, and sVEGFR-1 were measured by ELISA in plasma and
bronchoalveolar lavage (BAL) fluid. Reverse transcriptase polymerase chain reaction for sVEGFR-1 was
performed on BAL cells.
Results: sVEGFR-1 was detectable in the BAL fluid of 48% (20/41) of patients with early ARDS (1.4–
54.8 ng/ml epithelial lining fluid (ELF)) compared with 8% (1/12) at risk patients (p = 0.017) and none of
the normal controls (p = 0.002). By day 4 sVEGFR-1 was detectable in only 2/18 ARDS patients
(p = 0.008). Patients with detectable sVEGFR-1 had lower ELF median (IQR) levels of bioactive VEGF than
those without detectable sVEGFR-1 (1415.2 (474.9–3192) pg/ml v 4761 (1349–7596.6) pg/ml, median
difference 3346 pg/ml (95% CI 305.1 to 14711.9), p = 0.016), but there was no difference in total VEGF
levels. BAL cells expressed mRNA for sVEGFR-1 and produced sVEGFR-1 protein which increased
following incubation with tumour necrosis factor a.
Conclusion: This study shows for the first time the presence of sVEGFR-1 in the BAL fluid of patients with
ARDS. This may explain the presence of reduced bioactive VEGF in patients early in the course of ARDS
Optical properties of highly n-doped germanium obtained by in situ doping and laser annealing
High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8 × 1019 cm−3 has been achieved starting from an incorporated phosphorous concentration of 1.1 × 1020 cm−3. Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved
Radio-Continuum study of the Nearby Sculptor Group Galaxies. Part 1: NGC 300 at lambda = 20 cm
A series of new radio-continuum (lambda=20 cm) mosaic images focused on the
NGC 300 galactic system were produced using archived observational data from
the VLA and/or ATCA. These new images are both very sensitive (rms=60 microJy)
and feature high angular resolution (<10"). The most prominent new feature is
the galaxy's extended radio-continuum emission, which does not match its
optical appearance. Using these newly created images a number of previously
unidentified discrete sources have been discovered. Furthermore, we demonstrate
that a joint deconvolution approach to imaging this complete data-set is
inferior when compared to an immerge approach.Comment: 13 pages, 12 figures, accepted to APSS, new version to correct the
missing reference
The Use of Open Communal Grazing Designs to Screen Options for Grazing Management
An open communal grazing design is described that enables a large number of grazing tactics to be concurrently evaluated in small plots under common grazing conditions. Pasture data indicated that the same level of utilisation occurred inside the experimental plots as in the surrounding field. However, differential grazing may occur where plots have divergent composition. The open communal design was economical using \u3c 5% of the land, livestock and fencing resources of alternative designs. The limitations of the open communal design as a research tool are also discussed
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