Overload-resistant pressure sensors in the nominal range of 10 mbar (1 kPa)

AbstractDifferential pressure sensors with silicon diaphragms provide a nominal measuring range of 10 mbar (1 kPa) at a measurement uncertainty of ≤2⋅10−3. An additional external overload protection mechanism is required to achieve an overload reserve up to 160 bar (16 MPa). To integrate the overload protection at the wafer level, a micromechanical overload protection is needed. Such a micromechanical overload protection for differential pressure sensors can be produced from heat-treated glass. The functional principle limits the diaphragm deflection. Here, we demonstrate an overload capability reaching 50 bar (5 MPa) for a silicon diaphragm with a nominal measuring range of 10 mbar and a diaphragm thickness of 30 μm

First Order Calculation of the Inclusive Cross Section pp to ZZ by Graviton Exchange in Large Extra Dimensions

We calculate the inclusive cross section of double Z-boson production within large extra dimensions at the Large Hadron Collider (LHC). Using perturbatively quantized gravity in the ADD model we perform a first order calculation of the graviton mediated contribution to the pp to ZZ cross section. At low energies (e.g. Tevatron) this additional contribution is very small, making it virtually unobservable, for a fundamental mass scale above 2500 GeV. At LHC energies however, the calculation indicates that the ZZ-production rate within the ADD model should differ significantly from the Standard Model if the new fundamental mass scale would be below 15000 GeV. A comparison with the observed production rate at the LHC might therefore provide direct hints on the number and structure of the extra dimensions.Comment: 7 pages, 7 figures, accepted for publication in Phys. Rev.

Thermal decomposition of RDX from reactive molecular dynamics

We use the recently developed reactive force field ReaxFF with molecular dynamics to study thermal induced chemistry in RDX [cyclic-[CH2N(NO2)]3] at various temperatures and densities. We find that the time evolution of the potential energy can be described reasonably well with a single exponential function from which we obtain an overall characteristic time of decomposition that increases with decreasing density and shows an Arrhenius temperature dependence. These characteristic timescales are in reasonable quantitative agreement with experimental measurements in a similar energetic material, HMX [cyclic-[CH2N(NO2)]4]. Our simulations show that the equilibrium population of CO and CO2 (as well as their time evolution) depend strongly of density: at low density almost all carbon atoms form CO molecules; as the density increases larger aggregates of carbon appear leading to a C deficient gas phase and the appearance of CO2 molecules. The equilibrium populations of N2 and H2O are more insensitive with respect to density and form in the early stages of the decomposition process with similar timescales

Eta Carinae across the 2003.5 Minimum: Analysis in the visible and near infrared spectral region

We present an analysis of the visible through near infrared spectrum of Eta Carinae and its ejecta obtained during the "Eta Carinae Campaign with the UVES at the ESO VLT". This is a part of larger effort to present a complete Eta Carinae spectrum, and extends the previously presented analyses with the HST/STIS in the UV (1240-3159 A) to 10,430 A. The spectrum in the mid and near UV is characterized by the ejecta absorption. At longer wavelengths, stellar wind features from the central source and narrow emission lines from the Weigelt condensations dominate the spectrum. However, narrow absorption lines from the circumstellar shells are present. This paper provides a description of the spectrum between 3060 and 10,430 A, including line identifications of the ejecta absorption spectrum, the emission spectrum from the Weigelt condensations and the P-Cygni stellar wind features. The high spectral resolving power of VLT/UVES enables equivalent width measurements of atomic and molecular absorption lines for elements with no transitions at the shorter wavelengths. However, the ground based seeing and contributions of nebular scattered radiation prevent direct comparison of measured equivalent widths in the VLT/UVES and HST/STIS spectra. Fortunately, HST/STIS and VLT/UVES have a small overlap in wavelength coverage which allows us to compare and adjust for the difference in scattered radiation entering the instruments' apertures. This paper provides a complete online VLT/UVES spectrum with line identifications and a spectral comparison between HST/STIS and VLT/UVES between 3060 and 3160 A.Comment: 13 pages, 11 figures + atlas. The paper accepted for the ApJS and is accompanied with an atlas in the online edition pape

Simultaneous Quantitative MRI Mapping of T1, T2* and Magnetic Susceptibility with Multi-Echo MP2RAGE.

The knowledge of relaxation times is essential for understanding the biophysical mechanisms underlying contrast in magnetic resonance imaging. Quantitative experiments, while offering major advantages in terms of reproducibility, may benefit from simultaneous acquisitions. In this work, we demonstrate the possibility of simultaneously recording relaxation-time and susceptibility maps with a prototype Multi-Echo (ME) Magnetization-Prepared 2 RApid Gradient Echoes (MP2RAGE) sequence. T1 maps can be obtained using the MP2RAGE sequence, which is relatively insensitive to inhomogeneities of the radio-frequency transmit field, [Formula: see text]. As an extension, multiple gradient echoes can be acquired in each of the MP2RAGE readout blocks, which permits the calculation of [Formula: see text] and susceptibility maps. We used computer simulations to explore the effects of the parameters on the precision and accuracy of the mapping. In vivo parameter maps up to 0.6 mm nominal resolution were acquired at 7 T in 19 healthy volunteers. Voxel-by-voxel correlations and the test-retest reproducibility were used to assess the reliability of the results. When using optimized paramenters, T1 maps obtained with ME-MP2RAGE and standard MP2RAGE showed excellent agreement for the whole range of values found in brain tissues. Simultaneously obtained [Formula: see text] and susceptibility maps were of comparable quality as Fast Low-Angle SHot (FLASH) results. The acquisition times were more favorable for the ME-MP2RAGE (≈ 19 min) sequence as opposed to the sum of MP2RAGE (≈ 12 min) and FLASH (≈ 10 min) acquisitions. Without relevant sacrifice in accuracy, precision or flexibility, the multi-echo version may yield advantages in terms of reduced acquisition time and intrinsic co-registration, provided that an appropriate optimization of the acquisition parameters is performed

Terug naar kleine bijen? : ervaringen met 'terugverkleinde' bijen

Tweede van een serie van drie artikelen over de relatie tussen de celgrootte bij bijenvolken en de gevoeligheid van honingbijen voor ziekten en parasieten. Uit ervaringen van imkers in o.a. de VS blijkt dat het overzetten van bijenvolken op raten met een kleinere celdiameter kan leiden tot een grotere vitaliteit van de bijen en resistentie tegen de varroamijt (Varroa destructor) en tracheeënmijt (Acarapis woodii). Ook is een sterkere volksontwikkeling en honingopbrengst te zien bij kleine bijen op kleine celle