A micromachined thermal emitter for fast transient temperature operation with a novel hot-plate concept is presented. This concept is based on a nonaxis-symmetric design with excellent mechanical properties during temperature modulation combined with high thermal decoupling. Especially, the mechanical stress induced by the thermal expansion of the hot-plate and their suspension was improved. This results in a reduced sensitivity for buckling of the hot-plate. The thermal emitter is fabricated using silicon on insulator (SOI) technology and KOH-etching. Different suspension structures were realized and mechanical and thermal characterizations were performed. Besides the realization of the new hot-plate suspension design, a high thermal emission at wavelengths 5 m has been achieved using ceramic coatings for emissivity enhancement. This kind of emission tuning owns-in contrast to the typical surface and bulk structuring methods-the possibility to act simultaneously as a heater passivation.
An optical sensor system based on evanescent field excitation of fluorophore-labeled DNA-targets specifically binding to immobilized DNA probes has been developed, thus enabling for real-time analysis of hybridization events. Oligonucleotide probes are directly immobilized on the surface of the disposable sensor chip via biotin/neutravidin linkage and hybridize to complementary Cy5-labeled target DNA in the sample; this is recorded as an increase in the fluorescence signal. Under optimized conditions the hybridization rate was constant and directly proportional to the target concentration. When an 18mer oligonucleotide was used as a probe a linear calibration curve was obtained for a 56mer single-stranded DNA target derived from the neomycin phosphotransferase gene, a selection marker in a variety of genetically modified plants, with an estimated lower limit of detection of 0.21 nmol L(-1). No cross-hybridization to a 51mer actin DNA target was observed and even a single-nucleotide mismatch led to a negligible signal. A shutter in the readout device enabled separate detection of targets hybridizing to probes immobilized at the inlet and outlet sides, respectively, of the flow channel. This opens a route toward a real-time DNA array format with analysis times as short as 1-2 min. As a realistic sample a Cy5-labeled 56 bp PCR product was measured after separation of the double-stranded DNA by simple heat denaturation with a detection limit clearly lower than that of traditional gel electrophoresis.
Background and PurposeCollateral status is an important factor determining outcome in acute ischemic stroke (AIS). Hence, different collateral scoring systems have been introduced. We applied different scoring systems on single- and multi-phase computed tomography (CT) angiography (spCTA and mpCTA) and compared them to CT perfusion (CTP) parameters to identify the best method for collateral evaluation in patients with AIS.
MethodsA total of 102 patients with AIS due to large vessel occlusion in the anterior circulation who underwent multimodal CT imaging and who were treated endovascularly were included. Collateral status was assessed on spCTA and mpCTA using four different scoring systems and compared to CTP parameters. Logistic regression was performed for predicting favorable outcome.
ResultsAll collateral scores correlated well with each other and with CTP parameters. Comparison of collateral scores stratified by extent of perfusion deficit showed relevant differences between groups (P<0.01 for each). An spCTA collateral score discriminated best between favorable and unfavorable outcome as determined using the modified Rankin Scale 3 months after stroke.
ConclusionsCollateral status evaluated on spCTA may suffice for outcome prediction and decision making in AIS patients, potentially obviating further imaging modalities like mpCTA or CTP.
A novel micromachined thermal emitter for fast transient temperature operation is presented. Compared to most commercial available thermal emitters, the one here presented is able to operate in a pulsed mode. This allows the use of lock-in techniques or pyrodetectors in the data acquisition without the use of an optical chopper for light modulation. Therefore, these types of thermal emitters are very important for small filter photometers. Several hotplate suspension concepts were studied in order to find a design with excellent mechanical stability and high thermal decoupling. In contrary to the classical spider suspension design, a novel approach based on a non-axis-symmetric design is presented. The thermal emitters are fabricated using silicon on insulator technology and KOH-etching. The emitters are heated with Pt-meanders. For temperature determination an additional Pt-structure is deposited onto the hot-plates. The emitters are mounted in TO-5 housings using a ceramic adhesive and gold wire bonding. The used operation temperature is 750°C. In pulsed operation it's important to have a large modulation depth in terms of thermal radiation intensity in the needed spectral range. The maximal reachable modulation depth ranges from ambient temperature to steady state temperature. A modulation frequency of 5 Hz still allows using nearly the maximum modulation depth. A parameterized finite element model was realized and adapted to the measured data. This was the basis for the numerical optimization procedure for a new improved design.
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