386 research outputs found
Load sensing surgical instruments
Force and pressure sensing technology applied to smart surgical instruments as well as implants allow to give a direct feedback of loads to the surgeon lead to better reliability and success of surgical operations. A common technology used for sensors is low-cost piezoresistive thick-film technology. However, the standard thick-film firing conditions degrade the properties of medical alloys. In order to avoid this problem, the solution is to decrease the firing temperature of thick films. This work presents the development and characterisation of low-firing thick-film systems (dielectrics, resistors and conductors), formulated to achieve chemical and thermal expansion compatibility with an austenitic stainless steel medical alloy. Adherence tests and results on electrical properties of these systems: resistance, temperature coefficient of resistance (TCR) are presented. It was found that the main issue in these systems lies in mastering the materials interactions during firing, especially at the silver-based resistor terminations. The interaction of silver, resistor and dielectric tends to give rise to highly resistive zones at the terminations, affecting reliability. This can be circumvented by post-firing the resistor terminations at a moderate temperatur
Tracing early evolutionary stages of high-mass star formation with molecular lines
Despite its major role in the evolution of the interstellar medium, the
formation of high-mass stars (M > 10 Msol) is still poorly understood. Two
types of massive star cluster precursors, the so-called Massive Dense Cores
(MDCs), have been observed, which differ in their mid-infrared brightness. The
origin of this difference is not established and could be the result of
evolution, density, geometry differences, or a combination of these. We compare
several molecular tracers of physical conditions (hot cores, shocks) observed
in a sample of mid-IR weak emitting MDCs with previous results obtained in a
sample of exclusively mid-IR bright MDCs. The aim is to understand the
differences between these two types of object. We present single-dish
observations of HDO, H2O-18, SO2 and CH3OH lines at lambda = 1.3 - 3.5 mm. We
study line profiles and estimate abundances of these molecules, and use a
partial correlation method to search for trends in the results. The detection
rates of thermal emission lines are found to be very similar between mid-IR
quiet and bright objects. The abundances of H2O, HDO (1E-13 to 1E-9 in the cold
outer envelopes), SO2 and CH3OH differ from source to source but independently
of their mid-IR flux. In contrast, the methanol class I maser emission, a
tracer of outflow shocks, is found to be strongly anti-correlated with the 12
micron source brightnesses. The enhancement of the methanol maser emission in
mid-IR quiet MDCs may indicate a more embedded nature. Since total masses are
similar between the two samples, we suggest that the matter distribution is
spherical around mid-IR quiet sources but flattened around mid-IR bright ones.
In contrast, water emission is associated with objects containing a hot
molecular core, irrespective of their mid-IR brightness. These results indicate
that the mid-IR brightness of MDCs is an indicator of their evolutionary stage.Comment: 15 pages, 6 figures, 11 tables, accepted for publication in A&A the
11/06/201
The Bell Laboratories (13)CO Survey: Longitude-Velocity Maps
A survey is presented of the Galactic plane in the J=1-0 transition of
(13)CO. About 73,000 spectra were obtained with the 7 m telescope at Bell
Laboratories over a ten-year period. The coverage of survey is (l, b) = (-5 to
117, -1 to +1), or 244 square degrees, with a grid spacing of 3' for |b| < 0.5,
and a grid spacing of 6' for |b| > 0.5. The data presented here have been
resampled onto a 3' grid. For 0.68 km/s channels, the rms noise level of the
survey is 0.1 K on the scale. The raw data have been transformed into
FITS format, and all the reduction processes, such as correcting for emission
in the reference positions, baseline removal and interpolation were conducted
within IRAF using the FCRAO task package and additional programs. The reduced
data are presented here in the form of longitude-velocity color maps at each
latitude. These data allow identification and classification of molecular
clouds with masses in excess of ~ 1,000 solar masses throughout the first
quadrant of the Galaxy. Spiral structure is manifested by the locations of the
largest and brightest molecular clouds.Comment: 23 pages, 7 figures, ApJS submitted (out of 41 frames of Figure4,
only one is included becaue of size limit
Ultra-low pressure sensor for neonatal resuscitator
AbstractA Venturi-type flow sensor has been designed and fabricated for neonatal respiratory assistance to control airway pressure and tidal volume. As the low flow range and sensing principle require the measurement of correspondingly very low pressures, a very responsive sensor, based on a polymer membrane acting onto a piezoresistive cantilever force sensor based on low-temperature co-fired ceramic (LTCC), was developed. This paper details the 3D modelling, manufacture, assembly and characterisation of the sensor. Compared to expensive and fragile MEMS-based devices, this sensor, based on LTCC, thick-film technology and polymer parts, provides an accurate and robust, yet low-cost alternative
Detection of water at z = 0.685 towards B0218+357
We report the detection of the H_2O molecule in absorption at a redshift z =
0.68466 in front of the gravitationally lensed quasar B0218+357. We detect the
fundamental transition of ortho-water at 556.93 GHz (redshifted to 330.59 GHz).
The line is highly optically thick and relatively wide (15 km/s FWHM), with a
profile that is similar to that of the previously detected CO(2--1) and
HCO^+(2--1) optically thick absorption lines toward this quasar. From the
measured level of the continuum at 330.59 GHz, which corresponds to the level
expected from the power-law spectrum already
observed at lower frequencies, we deduce that the filling factor of the H_2O
absorption is large. It was already known from the high optical thickness of
the CO, ^{13}CO and C^{18}O lines that the molecular clouds entirely cover one
of the two lensed images of the quasar (all its continuum is absorbed); our
present results indicate that the H_2O clouds are covering a comparable
surface. The H_2O molecules are therefore not confined to small cores with a
tiny filling factor, but are extended over parsec scales. The H_2O line has a
very large optical depth, and only isotopic lines could give us the water
abundance. We have also searched for the 183 GHz line in absorption, obtaining
only an upper limit; this yields constraints on the excitation temperature.Comment: 4 pages, 3 figures, accepted in ApJ Letter
The Water Vapor Abundance in Orion KL Outflows
We present the detection and modeling of more than 70 far-IR pure rotational
lines of water vapor, including the 18O and 17O isotopologues, towards Orion
KL. Observations were performed with the Long Wavelength Spectrometer
Fabry-Perot (LWS/FP; R~6800-9700) on board the Infrared Space Observatory (ISO)
between ~43 and ~197 um. The water line profiles evolve from P-Cygni type
profiles (even for the H2O18 lines) to pure emission at wavelengths above ~100
um. We find that most of the water emission/absorption arises from an extended
flow of gas expanding at 25+-5 kms^-1. Non-local radiative transfer models show
that much of the water excitation and line profile formation is driven by the
dust continuum emission. The derived beam averaged water abundance is
2-3x10^-5. The inferred gas temperature Tk=80-100 K suggests that: (i) water
could have been formed in the "plateau" by gas phase neutral-neutral reactions
with activation barriers if the gas was previously heated (e.g. by shocks) to
>500 K and/or (ii) H2O formation in the outflow is dominated by in-situ
evaporation of grain water-ice mantles and/or (iii) H2O was formed in the
innermost and warmer regions (e.g. the hot core) and was swept up in ~1000 yr,
the dynamical timescale of the outflow.Comment: Accepted for publication in ApJ letters [2006 August 7] (5 pages 2,
figures, not edited
Selective Methylation of Arenes: A Radical CâH Functionalization/CrossâCoupling Sequence
A selective, nonchelationâassisted methylation of arenes has been developed. The overall transformation, which combines a CâH functionalization reaction with a nickelâcatalyzed crossâcoupling, offers rapid access to methylated arenes with high para selectivity. The reaction is amenable to lateâstage methylation of smallâmolecule pharmaceuticals
Multi-line Herschel/HIFI observations of water reveal infall motions and chemical segregation around high-mass protostars
(Abridged) We use HIFI maps of the 987 GHz H2O 2(02)-1(11) emission to
measure the sizes and shapes of 19 high-mass protostellar envelopes. To
identify infall, we use HIFI spectra of the optically thin C18O 9-8 and H2O-18
1(11)-0(00) lines. The high-J C18O line traces the warm central material and
redshifted H2O-18 1(11)-0(00) absorption indicates material falling onto the
warm core. We probe small-scale chemical differentiation by comparing H2O 752
and 987 GHz spectra with those of H2O-18.
Our measured radii of the central part of the H2O 2(02)-1(11) emission are
30-40% larger than the predictions from spherical envelope models, and axis
ratios are <2, which we consider good agreement. For 11 of the 19 sources, we
find a significant redshift of the H2O-18 1(11)-0(00) line relative to C18O
9-8. The inferred infall velocities are 0.6-3.2 km/s, and estimated mass inflow
rates range from 7e-5 to 2e-2 M0/yr, with the highest mass inflow rates
occurring toward the sources with the highest masses, and possibly the youngest
ages. The other sources show either expanding motions or H2O-18 lines in
emission. The H2O-18 1(11)-0(00) line profiles are remarkably similar to the
"differences" between the H2O 2(02)-1(11) and 2(11)-2(02) profiles, suggesting
that the H2O-18 line and the H2O 2(02)-1(11) absorption originate just inside
the radius where water evaporates from grains, typically 1000-5000 au from the
center. In some sources, the H2O-18 line is detectable in the outflow, where no
C18O emission is seen.
Together, the H2O-18 absorption and C18O emission profiles show that the
water abundance around high-mass protostars has at least three levels: low in
the cool outer envelope, high within the 100 K radius, and very high in the
outflowing gas. Thus, despite the small regions, the combination of lines
presented here reveals systematic inflows and chemical information about the
outflows.Comment: Accepted for publication in Astronomy & Astrophysics; 10 pages body +
10 pages appendi
Discovery of Interstellar Hydrogen Fluoride
We report the first detection of interstellar hydrogen fluoride. Using the
Long Wavelength Spectrometer (LWS) of the Infrared Space Observatory (ISO), we
have detected the 121.6973 micron J = 2 - 1 line of HF in absorption toward the
far-infrared continuum source Sagittarius B2. The detection is statistically
significant at the 13 sigma level. On the basis of our model for the excitation
of HF in Sgr B2, the observed line equivalent width of 1.0 nm implies a
hydrogen fluoride abundance of 3E-10 relative to H2. If the elemental abundance
of fluorine in Sgr B2 is the same as that in the solar system, then HF accounts
for ~ 2% of the total number of fluorine nuclei. We expect hydrogen fluoride to
be the dominant reservoir of gas-phase fluorine in Sgr B2, because it is formed
rapidly in exothermic reactions of atomic fluorine with either water or
molecular hydrogen; thus the measured HF abundance suggests a substantial
depletion of fluorine onto dust grains. Similar conclusions regarding depletion
have previously been reached for the case of chlorine in dense interstellar
clouds. We also find evidence at a lower level of statistical significance (~ 5
sigma) for an emission feature at the expected position of the 4(3,2)-4(2,3)
121.7219 micron line of water. The emission line equivalent width of 0.5 nm for
the water feature is consistent with the water abundance of 5E-6 relative to H2
that has been inferred previously from observations of the hot core of Sgr B2.Comment: 11 pages (AASTeX using aaspp4.sty) plus 2 figures; to appear in ApJ
Letter
- âŠ