31 research outputs found
Characterisation of the potential of frequency modulation and optical feedback locking for cavity-enhanced absorption spectroscopy
A combination of optical feedback self-locking of a continuous-wave
distributed feedback diode laser to a V-shaped high finesse cavity, laser phase
modulation at a frequency equal to the free spectral range of the V-cavity and
detection of the transmitted laser beam at this high modulation frequency is
described for possible application in cavity-enhanced absorption
spectroscopy.In order to estimate an absorbance baseline noise of laser
intensity and frequency modulated light triplet passed through the V-cavity in
open air, a 1.5-cm long optical cell filled by C2H2 at low pressure was placed
behind the cavity output mirror. The performance of the setup was evaluated
from the experimental bandwidth normalised relative intensity noise on the
cavity output and the frequency modulation absorption signals induced by C2H2
absorption in the 1.5-cm cell. From these data we estimate that the
noise-equivalent absorption sensitivity of 2.1*10^-11 cm^-1 Hz^-1/2 by a factor
of 11.7 above a shot-noise limit can be achieved for C2H2 absorption spectra
extracted from the heterodyne beat signals recorded at the transmission maxima
intensity peaks of the successive TEM00 resonances.Comment: 18 pages, 8 figures, submitted to Appl. Phys. B 28.07.201
Gas emission during laparoscopic colorectal surgery using a bipolar vessel sealing device: A pilot study on four patients
ABSTRACT: BACKGROUND: Dissection during laparoscopic surgery produces smoke containing potentially toxic substances. The aim of the present study was to analyze smoke samples produced during laparoscopic colon surgery using a bipolar vessel sealing device (LigaSuretrade mark). METHODS: Four consecutive patients undergoing left-sided colectomy were enrolled in this pilot study. Smoke was produced by the use of LigaSuretrade mark. Samples (5,5l) were evacuated from the pneumoperitoneum in a closed system into a reservoir. Analysis was performed with CO2-laser-based photoacoustic spectroscopy and confirmed by a Fourier-transform infrared spectrum. The detected spectra were compared to the available spectra of known toxins. RESULTS: Samples from four laparoscopic sigmoid resections were analyzed. No relevant differences were noted regarding patient and operation characteristics. The gas samples were stable over time proven by congruent control measurements as late as 24 h after sampling. The absorption spectra differed considerably between the patients. One broad absorption line at 100 ppm indicating H2O and several unknown molecules were detected. With a sensitivity of alpha min ca 10-5 cm-1 no known toxic substances like phenol or indole were identified. CONCLUSION: The use of a vessel sealing device during laparoscopic surgery does not produce known toxic substances in relevant quantity. Further studies are needed to identify unknown molecules and to analyze gas emission under various conditions
Infrared Spectroscopy on Smoke Produced by Cauterization of Animal Tissue
In view of in vivo surgical smoke studies a difference-frequency-generation (DFG) laser spectrometer (spectral range 2900â3144 cmâ1) and a Fourier-transform infrared (FTIR) spectrometer were employed for infrared absorption spectroscopy. The chemical composition of smoke produced in vitro with an electroknife by cauterization of different animal tissues in different atmospheres was investigated. Average concentrations derived are: water vapor (0.87%), methane (20 ppm), ethane (4.8 ppm), ethene (17 ppm), carbon monoxide (190 ppm), nitric oxide (25 ppm), nitrous oxide (40 ppm), ethyne (50 ppm) and hydrogen cyanide (25 ppm). No correlation between smoke composition and the atmosphere or the kind of cauterized tissue was found
A high affinity RIM-binding protein/Aplip1 interaction prevents the formation of ectopic axonal active zones
Synaptic vesicles (SVs) fuse at active zones (AZs) covered by a protein
scaffold, at Drosophila synapses comprised of ELKS family member Bruchpilot
(BRP) and RIM-binding protein (RBP). We here demonstrate axonal co-transport
of BRP and RBP using intravital live imaging, with both proteins co-
accumulating in axonal aggregates of several transport mutants. RBP, via its
C-terminal Src-homology 3 (SH3) domains, binds Aplip1/JIP1, a transport
adaptor involved in kinesin-dependent SV transport. We show in atomic detail
that RBP C-terminal SH3 domains bind a proline-rich (PxxP) motif of
Aplip1/JIP1 with submicromolar affinity. Pointmutating this PxxP motif
provoked formation of ectopic AZ-like structures at axonal membranes. Direct
interactions between AZ proteins and transport adaptors seem to provide
complex avidity and shield synaptic interaction surfaces of pre-assembled
scaffold protein transport complexes, thus, favouring physiological synaptic
AZ assembly over premature assembly at axonal membranes. - See more at:
http://elifesciences.org/content/4/e06935#sthash.oVGZ8cdi.dpu
Enhancement of Antiferromagnetic Correlations Induced by Nonmagnetic Impurities: Origin and Predictions for NMR Experiments
Spin models that have been proposed to describe dimerized chains, ladders,
two dimensional antiferromagnets, and other compounds are here studied when
some spins are replaced by spinless vacancies, such as it occurs by
doping. A small percentage of vacancies rapidly destroys the spin gap, and
their presence induces enhanced antiferromagnetic correlations near those
vacancies. The study is performed with computational techniques which includes
Lanczos, world-line Monte Carlo, and the Density Matrix Renormalization Group
methods. Since the phenomenon of enhanced antiferromagnetism is found to occur
in several models and cluster geometries, a common simple explanation for its
presence may exist. It is argued that the resonating-valence-bond character of
the spin correlations at short distances of a large variety of models is
responsible for the presence of robust staggered spin correlations near
vacancies and lattice edges. The phenomenon takes place regardless of the long
distance properties of the ground state, and it is caused by a ``pruning'' of
the available spin singlets in the vicinity of the vacancies. The effect
produces a broadening of the low temperature NMR signal for the compounds
analyzed here. This broadening should be experimentally observable in the
structurally dimerized chain systems
, , , and
, in ladder materials such as , in the
spin-Peierls systems and , and in several others since it
is a universal effect common to a wide variety of models and compounds.Comment: 18 pages revtex with 26 figures include
Mid-infrared laser-spectroscopic sensing of che
This letter reports on mid-infrared laser-based detection and analysis of chemical species. Emphasis is put on broadly tunable laser sources and sensitive detection schemes. Selected examples from our lab illustrate the performance and potential of such systems in various areas including environmental and medical sensing