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The Global ETD Search service is a free service for researchers
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Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 171 to 174 of 174 (0.069 seconds)| 171 |
Development of a Sensor System for Rapid Detection of Volatile Organic Compounds in Biomedical ApplicationsPaula Andrea Angarita (11806427) 20 December 2021 (has links)
<p>Volatile organic compounds (VOCs) are endogenous byproducts
of metabolic pathways that can be altered by a disease or condition, leading to
an associated and unique VOC profile or signature. Current methodologies for
VOC detection include canines, gas chromatography-mass spectrometry (GC-MS),
and electronic nose (eNose). Some of the challenges for canines and GC-MS are
cost-effectiveness, extensive training, expensive instrumentation. On the other
hand, a significant downfall of the eNose is low selectivity. This thesis
proposes to design a breathalyzer using chemiresistive gas sensors that detects
VOCs from human breath, and subsequently create an interface to process and
deliver the results via Bluetooth Low Energy (BLE). Breath samples were
collected from patients with hypoglycemia, COVID-19, and healthy controls for
both. Samples were processed, analyzed using GC-MS and probed through
statistical analysis. A panel of 6 VOC biomarkers distinguished between
hypoglycemia (HYPO) and Normal samples with a training AUC of 0.98 and a
testing AUC of 0.93. For COVID-19, a panel of 3 VOC biomarkers distinguished
between COVID-19 positive symptomatic (COVID-19) and healthy Control samples
with a training area under the curve (AUC) of receiver operating characteristic
(ROC) of 1.0 and cross-validation (CV) AUC of 0.99. The model was validated
with COVID-19 Recovery samples. The discovery of these biomarkers enables the
development of selective gas sensors to detect the VOCs. </p><p><br></p><p>Polyethylenimine-ether functionalized gold nanoparticle
(PEI-EGNP) gas sensors were designed and fabricated in the lab and metal oxide
(MOX) semiconductor gas sensors were obtained from Nanoz (Chip 1: SnO<sub>2</sub> and Chip
2: WO<sub>3</sub>). These sensors were tested at different relative humidity (RH) levels,
and VOC concentrations. Contact angle which measures hydrophobicity, was 84°
and the thickness of the PEI-EGNP coating was 11 µ m. The PEI-EGNP sensor
response at RH 85% had a signal 10x higher than at RH 0%. Optimization of the
MOX sensor was performed by changing the heater voltage and concentration of
VOCs. At RH 85% and heater voltage of 2500 mV, the performance of the sensors
increased. Chip 2 had higher sensitivity towards VOCs especially for one of the
VOC biomarkers identified for COVID-19. PCA distinguished VOC biomarkers of
HYPO, COVID-19, and healthy human breath using the Nanoz. A sensor interface
was created to integrate the PEI-EGNP sensors with the printed circuit board
(PCB) and Bluno Nano to perform machine learning. The sensor interface can currently
process and make decisions from the data whether the breath is HYPO (-) or
Normal (+). This data is then sent via BLE to the Hypo Alert app to display the
decision.</p>
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High-Frequency Operation of Vertical Organic Field-Effect TransistorsHöppner, Marco, Kheradmand-Boroujeni, Bahman, Vahland, Jörn, Sawatzki, Michael Franz, Kneppe, David, Ellinger, Frank, Kleemann, Hans 21 May 2024 (has links)
The high-frequency and low-voltage operation of organic thin-film transistors (OTFTs) is a key requirement for the commercial success of flexible electronics. Significant progress has been achieved in this regard by several research groups highlighting the potential of OTFTs to operate at several tens or even above 100 MHz. However, technology maturity, including scalability, integrability, and device reliability, is another crucial point for the semiconductor industry to bring OTFT-based flexible electronics into mass production. These requirements are often not met by high-frequency OTFTs reported in the literature as unconventional processes, such as shadow-mask patterning or alignment with unrealistic tolerances for production, are used. Here, ultra-short channel vertical organic field-effect transistors (VOFETs) with a unity current gain cut-off frequency (fT) up to 43.2 MHz (or 4.4 MHz V−1) operating below 10 V are shown. Using state-of-the-art manufacturing techniques such as photolithography with reliable fabrication procedures, the integration of such devices down to the size of only 12 × 6 μm2 is shown, which is important for the adaption of this technology in high-density circuits (e.g., display driving). The intrinsic channel transconductance is analyzed and demonstrates that the frequencies up to 430 MHz can be reached if the parasitic electrode overlap is minimized.
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Supraleitung in Gallium-implantiertem Silizium / Superconductivity in gallium-implanted siliconSkrotzki, Richard 21 July 2016 (has links) (PDF)
Die vorliegende Arbeit beschäftigt sich mit der elektrischen Charakterisierung 10 nm dünner Schichten bestehend aus amorphen Ga-Nanoclustern eingebettet in Ga-dotiertes polykristallines Si. Die Herstellung der Schichten geschieht via Ionen-Implantation in Si-Wafer samt anschließender thermischer Ausheilung. Elektrische Transportmessungen in Magnetfeldern von bis zu 50 T zeigen, dass die Schichten durch Variation der Ausheilparameter zwei strukturelle Supraleiter-Isolator-Übergänge durchlaufen. TEM-gestützte Strukturanalysen decken auf, dass den Übergängen eine Gefügetransformation zugrunde liegt, die das Wechselspiel zwischen supraleitender Cluster-Kopplung und kapazitiver Ladungsenergie sowie dem Ausmaß von thermischen und Quantenfluktuationen beeinflusst. Im supraleitenden Regime (Tc = 7 K) wird ein doppelt reentrantes Phänomen beobachtet, bei dem Magnetfelder von mehreren Tesla in anisotroper Form die Supraleitung begünstigen. Eine qualitative Erklärung gelingt via selbstentwickeltem theoretischen Modell basierend auf Phaseslip-Ereignissen für Josephson-Kontakt-Netzwerke. Für Anwendungen im Bereich der Sensor-Technologie und Quanten-Logik werden die Schichten erfolgreich via Fotolithographie und FIB (focused ion beam) mikro- und nanostrukturiert. Dadurch gelingt die erstmalige Beobachtung des Little-Parks-Effektes in einer Nanostruktur aus amorphem Ga. / The following thesis is devoted to the electrical characterization of 10 nm thin layers consisting of amorphous Ga nanoclusters embedded in Ga-doped polycrystalline Si. The preparation of the layers is realized via ion implantation in Si wafers plus subsequent thermal annealing. Electrical-transport measurements in magnetic fields of up to 50 T show that the layers undergo two structural superconductor-insulator transitions upon variation of the annealing parameters. Structural analyzes based on TEM investigations reveal an underlying transformation of the size and distance of the clusters. This influences the interplay of the superconducting cluster coupling and capacitive charging energy as well as the extent of thermal and quantum fluctuations. In the superconducting regime (Tc = 7 K) a double-reentrant phenomenon is observed. Here, magnetic fields of several Tesla facilitate superconductivity in an anisotropic way. A qualitative explanation is given via a self-developed theoretical model based on phase-slip events for Josephson-junction arrays. With respect to applications regarding sensor technology and quantum logic circuits the layers are successfully micro- and nanostructured via photolithography and FIB. This allows for the first observation of the Little-Parks effect in a nanostructure of amorphous Ga.
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Supraleitung in Gallium-implantiertem SiliziumSkrotzki, Richard 12 July 2016 (has links)
Die vorliegende Arbeit beschäftigt sich mit der elektrischen Charakterisierung 10 nm dünner Schichten bestehend aus amorphen Ga-Nanoclustern eingebettet in Ga-dotiertes polykristallines Si. Die Herstellung der Schichten geschieht via Ionen-Implantation in Si-Wafer samt anschließender thermischer Ausheilung. Elektrische Transportmessungen in Magnetfeldern von bis zu 50 T zeigen, dass die Schichten durch Variation der Ausheilparameter zwei strukturelle Supraleiter-Isolator-Übergänge durchlaufen. TEM-gestützte Strukturanalysen decken auf, dass den Übergängen eine Gefügetransformation zugrunde liegt, die das Wechselspiel zwischen supraleitender Cluster-Kopplung und kapazitiver Ladungsenergie sowie dem Ausmaß von thermischen und Quantenfluktuationen beeinflusst. Im supraleitenden Regime (Tc = 7 K) wird ein doppelt reentrantes Phänomen beobachtet, bei dem Magnetfelder von mehreren Tesla in anisotroper Form die Supraleitung begünstigen. Eine qualitative Erklärung gelingt via selbstentwickeltem theoretischen Modell basierend auf Phaseslip-Ereignissen für Josephson-Kontakt-Netzwerke. Für Anwendungen im Bereich der Sensor-Technologie und Quanten-Logik werden die Schichten erfolgreich via Fotolithographie und FIB (focused ion beam) mikro- und nanostrukturiert. Dadurch gelingt die erstmalige Beobachtung des Little-Parks-Effektes in einer Nanostruktur aus amorphem Ga. / The following thesis is devoted to the electrical characterization of 10 nm thin layers consisting of amorphous Ga nanoclusters embedded in Ga-doped polycrystalline Si. The preparation of the layers is realized via ion implantation in Si wafers plus subsequent thermal annealing. Electrical-transport measurements in magnetic fields of up to 50 T show that the layers undergo two structural superconductor-insulator transitions upon variation of the annealing parameters. Structural analyzes based on TEM investigations reveal an underlying transformation of the size and distance of the clusters. This influences the interplay of the superconducting cluster coupling and capacitive charging energy as well as the extent of thermal and quantum fluctuations. In the superconducting regime (Tc = 7 K) a double-reentrant phenomenon is observed. Here, magnetic fields of several Tesla facilitate superconductivity in an anisotropic way. A qualitative explanation is given via a self-developed theoretical model based on phase-slip events for Josephson-junction arrays. With respect to applications regarding sensor technology and quantum logic circuits the layers are successfully micro- and nanostructured via photolithography and FIB. This allows for the first observation of the Little-Parks effect in a nanostructure of amorphous Ga.
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