Characterization of an embedded RF-MEMS switch

An RF-MEMS capacitive switch for mm-wave integrated circuits, embedded in the BEOL of 0.25μm BiCMOS process, has been characterized. First, a mechanical model based on Finite-Element-Method (FEM) was developed by taking the residual stress of the thin film membrane into account. The pull-in voltage and the capacitance values obtained with the mechanical model agree very well with the measured values. Moreover, S-parameters were extracted using Electromagnetic (EM) solver. The data observed in this way also agree well with the experimental ones measured up to 110GHz. The developed RF model was applied to a transmit/receive (T/R) antenna switch design. The results proved the feasibility of using the FEM model in circuit simulations for the development of RF-MEMS switch embedded, single-chip multi-band RF ICs

A micro-structured 5kW complete fuel processor for iso-octane as hydrogen supply system for mobile auxiliary power units Part I. Development of autothermal reforming catalyst and reactor

A micro-structured autothermal reformer was developed for a fuel processing/fuel cell system running on iso-octane and designed for an electrical power output of 5kWel. The target application was an automotive auxiliary power unit (APU). The work covered both catalyst and reactor development. In fixed bed screening, nickel and rhodium were identified as the best candidates for autothermal reforming of gasoline. Under higher feed flow rates applied in microchannel testing, a catalyst formulation containing 1 wt.% Rh on alumina prepared by the sol–gel synthesis route proved to be stable at least in the medium term. This catalyst was introduced into the final prototype reactor designed to supply a 5kW fuel cell, which was based upon m cro-structured stainless steel foils. The reactor was optimised for equipartition of flows by numerical simulation. Testing in a pilot scale test rig, which was limited to a specified power equivalent of 3.5kWel, revealed more than 97% conversion of gasoline at 124 Ndm3/min total flow-rate of reformate, which corresponded to a WHSV of 316.5 Ndm3/(h gcat)

Role of sucrose and phloem–xylem interaction in recovery of water status and hydraulic dehydration impacts in tobacco plants (Nicotiana tabacum)

The role of phloem–xylem interaction via sucrose exchanges in recovery of dehydration impacts, specifically xylem embolism, has not been directly investigated thus far. Most previous studies were indirect approaches leading to suggestive conclusions. We hypothesized that a block in phloem loading and so no exchange of sucrose with xylem affect tolerance and recovery of tobacco plants (Nicotiana tabacum) during dehydration and after the rehydration phase. Transgenic N. tabacum (αNtSUT1-antisense) plants, which showed impaired phloem loading and high accumulation of soluble sugars in leaves, were compared to the wild-type (WT) plants. The water status, osmotic adjustments, leaf turgor, stomatal conductance, xylem cavitation, and stem xylem sucrose content were determined during dehydration and after the rehydration phases. Results showed that retention of sucrose outside phloem conduits highly improved water status, osmotic adjustment and turgidity of the source leaves in the transgenics during drought period. However, no impact occurred on stomata function and tolerance to xylem cavitation in αNtSUT1. After the rehydration period, WT plants with free phloem transport and phloem–-xylem exchange of sucrose recovered better their water status, leaf turgidity, stomatal conductance and xylem functioning than αNtSUT1 plants. The accumulation of sucrose in leaves of transformants ameliorated their tolerance to water deficit by reinforcing the osmotic adjustment mechanism at the leaf level. However, lack of sucrose in phloem sieve resulted in impairment of hydraulic recovery of xylem from drought of αNtSUT1 after rehydration. This suggests a crucial role of the phloem–-xylem exchange of sucrose in refilling of embolized xylem vessels.Peer Reviewe

Armenbibel

hrsg. von Rudolf Ehwal