412 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
Sensors and packages based on LTCC and thick-film technology for severe conditions
Reliable operation in harsh environments such as high temperatures, high pressures, aggressive media and space, poses special requirements for sensors and packages, which usually cannot be met using polymer-based technologies. Ceramic technologies, especially LTCC (Low-Temperature Cofired Ceramic), offer a reliable platform to build hermetic, highly stable and reliable sensors and packages. This is illustrated in the present work through several such devices. The examples are discussed in terms of performance, reliability, manufacturability and cost issue
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
Deubiquitylating Enzymes and DNA Damage Response Pathways
Covalent post-translational modification of proteins by ubiquitin and ubiquitin-like factors has emerged as a general mechanism to regulate myriad intra-cellular processes. The addition and removal of ubiquitin or ubiquitin-like proteins from factors has recently been demonstrated as a key mechanism to modulate DNA damage response (DDR) pathways. It is thus, timely to evaluate the potential for ubiquitin pathway enzymes as DDR drug targets for therapeutic intervention. The synthetic lethal approach provides exciting opportunities for the development of targeted therapies to treat cancer: most tumours have lost critical DDR pathways, and thus rely more heavily on the remaining pathways, while normal tissues are still equipped with all DDR pathways. Here, we review key deubiquitylating enzymes (DUBs) involved in DDR pathways, and describe how targeting DUBs may lead to selective therapies to treat cancer patients
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
A Neutral Hydrogen Self-Absorption Cloud in the SGPS
Using data from the Southern Galactic Plane Survey (SGPS) we analyze an HI
self-absorption cloud centered on l = 318.0 deg, b = -0.5 deg, and velocity, v
= -1.1 km/s. The cloud was observed with the Australia Telescope Compact Array
(ATCA) and the Parkes Radio Telescope, and is at a near kinematic distance of
less than 400 pc with derived dimensions of less than 5 x 11 pc. We apply two
different methods to find the optical depth and spin temperature. In both
methods we find upper limit spin temperatures ranging from 20 K to 25 K and
lower limit optical depths ~ 1. We look into the nature of the HI emission and
find that 60-70% originates behind the cloud. We analyze a second cloud at the
same velocity centered on l = 319 deg and b = 0.4 deg with an upper limit spin
temperature of 20 K and a lower limit optical depth of 1.6. The similarities in
spin temperature, optical depth, velocity, and spatial location are evidence
the clouds are associated, possibly as one large cloud consisting of smaller
clumps of gas. We compare HI emission data with 12CO emission and find a
physical association of the HI self-absorption cloud with molecular gas.Comment: 33 pages, 17 figures, 5 tables; Accepted for publication in ApJ. A
version with higher quality images availabe at
http://www.astro.umn.edu/~dkavars/ms.p
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
Ultra-low pressure sensor for neonatal resuscitator
In this work, we study in detail the sensing characteristics of piezoresistive force sensors based on structured LTCC (Low Temperature Co-fired Ceramic) cantilevers carrying a thick-film piezoresistive bridge. These devices show much improved sensitivity compared to classical alumina-based devices, but may exhibit abnormally large signal and drift, which indicates the presence of structural defects originating from fabrication issues or deleterious interactions between materials. To eliminate these effects, the fabrication parameters of the LTCC cantilevers have been studied in detail. By varying materials, layer thicknesses, stacking order and lamination parameters, the respective roles of resistor-termination-tape interactions, plastic deformation of conductor tracks and lamination quality of the LTCC sheets may be elucidated
Search for Interstellar Water in the Translucent Molecular Cloud toward HD 154368
We report an upper limit of 9 x 10^{12} cm-2 on the column density of water
in the translucent cloud along the line of sight toward HD 154368. This result
is based upon a search for the C-X band of water near 1240 \AA carried out
using the Goddard High Resolution Spectrograph of the Hubble Space Telescope.
Our observational limit on the water abundance together with detailed chemical
models of translucent clouds and previous measurements of OH along the line of
sight constrain the branching ratio in the dissociative recombination of H_3O+
to form water. We find at the level that no more than 30% of
dissociative recombinations of H_3O+ can lead to H_2O. The observed spectrum
also yielded high-resolution observations of the Mg II doublet at 1239.9 \AA
and 1240.4 \AA, allowing the velocity structure of the dominant ionization
state of magnesium to be studied along the line of sight. The Mg II spectrum is
consistent with GHRS observations at lower spectral resolution that were
obtained previously but allow an additional velocity component to be
identified.Comment: Accepted by ApJ, uses aasp
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