Infrared detectors allow the remote and contactless measurement of the temperature of an object through radiometry. By using an array of multiple IR sensors assembled into a camera, a thermal image of a scene can be collected without the need for illumination. The applications for early infrared photon detectors were limited, because their requirement for cryogenic cooling resulted in bulky systems. The evolution of micromachining technology enabled the development of uncooled bolometric detectors, which found more widespread use in both military and civilian settings. Typical use cases include vision enhancement, navigation and collision avoidance, process control, search and rescue operations, surveillance, building inspection, process control and medical diagnostics. However, the relatively high costs of infrared cameras have prevented a more widespread use in consumer-oriented applications. Part of the challenge is the complex set of requirements for materials used in resistive bolometers, which measure the incident IR radiation through the absorption-induced temperature change of a free-standing and thermally-isolated thermistor. The desired properties include a high IR absorption, a large magnitude and an excellent linearity of the temperature coefficient of resistance (TCR), a high electrical and thermal resistance as well as a low amount of intrinsic noise sources. Typically, a stack of layers is required to fulfill all the mentioned requirements, which results in a complex fabrication process. In this work, we instead developed a bolometer based on a single functional layer of sub-10 nm thin platinum. Reducing the thickness and number of layers has the immediate advantage of allowing for a better thermal isolation and a smaller thermal capacitance. Both measures help to improve the sensitivity, the temperature resolution and the thermal time constant, which represent the most important figures-of-merit of IR detectors. An additional benefit of this approach is a simple and cost-effective fabrication process, the complexity of which commonly scales with the number of mask layers and required lithography steps. Platinum has attractive properties and a long history of use as a thermistor material for temperature sensors. However, to achieve an effective absorption of IR radiation, a thickness in the nanometer-range is required to match the metal film's impedance to that of free space. A surface micromachining process was developed at the Stanford Nanofabrication Facility that enables the reliable fabrication of the resulting delicate detector structures with aspect ratios in excess of 8000:1. The process is compatible with post-CMOS integration and wafer level packaging. Plasma enhanced atomic layer deposition (PE-ALD) was selected for a repeatable and homogeneous deposition of the functional layers. A careful investigation of the thickness dependence of the relevant material properties was performed in order to establish the required knowledge for the design and modeling of the detectors structures. A steep increase in both the electrical and thermal resistivity was measured for a reduction of the Pt film thickness below 10 nm. The TCR of thin-film Pt was found to decrease simultaneously. The characterization of the optical properties of Pt showed an increase in both the real and imaginary part of the complex refractive index for smaller layer thicknesses. The risk of damage from high current densities in the Pt thin film due to electromigration was also evaluated and found to be unproblematic. Through the characterization of the mechanical properties of nanometer-thin PE-ALD layers, a reduction of the Young's modulus of Al₂O₃ of up to 50% compared to bulk values was determined, whereas only a slight degradation was found for Pt. All layers exhibited tensile residual stresses with an average value around 131 MPa. A detailed performance model was compiled based on these measured material properties and allowed the accurate prediction of the detector's characteristics as well as an understanding of trade-offs involved in its design. In order to fully exploit the unique features of a bolometer with a single functional layer, an improved geometry based on a self-supporting serpentine structure was subsequently developed, which provides an increase in the sensitivity by a factor of four. The properties of fabricated demonstrator structures were characterized using a vacuum chamber setup. Depending on the employed layer thicknesses, the thermal time constant of the detectors was found to be in the range of 0.7 ms to 4.5 ms. These values are up to an order of magnitude faster compared to state-of-the-art bolometric detectors thanks to the comparatively low thermal mass of the free-standing structure. The sensitivity to IR radiation improved drastically with a reduction in Pt thickness and responsivities of 4×10⁸ V/WA could be achieved for 6 nm thin Pt layers. This value corresponds to a temperature resolution (NETD) of 70 mK, which is based on the measured 1/f noise characteristics of Pt and the assumption of infrared optics with an F-number equal to one. While this new detector technology still leaves room for improvement, the achieved temperature resolution is only about a factor of two away from the performance of commercially available bolometers, which exhibit a significantly slower reaction time and have to rely on a more complicated fabrication process. In summary, we demonstrated an uncooled IR detector based on a single free- standing, sub-10 nm thin Pt layer for the first time. Its performance profits significantly from the reduction in film thickness enabled by the use of PE-ALD. The presented results and the lessons learned from this work can assist in the use of released, nanometer-thin layers for MEMS devices in other domains that can profit equally from such a development. ; Infrarotdetektoren ermöglichen das kontaktlose Messen der Temperatur eines entfernten Objekts durch Radiometrie. Durch die Verwendung einer Kamera, die aus einer Matrix aus mehreren Detektoren besteht, kann außerdem ein Wärmebild einer Szene aufgenommen werden, ohne dass hierfür eine Lichtquelle notwendig ist. Die Einsatzgebiete für die ersten auf halbleitenden Materialien basierenden Infrarot- Photodetektoren waren eingeschränkt, da die Notwendigkeit einer kryogenischen Kühlung zu aufwändigen und unhandlichen Systemen führte. Die Entwicklung der Herstellungsmethoden aus der Mikrosystemtechnik ermöglichte die Fertigung von ungekühlten bolometrischen Detektoren, die vielfältige Anwendungen in militärischen und zivilen Bereichen fanden. Typische Anwendungsgebiete umfassen z.B. die Verbesserung der Sicht (ähnlich zu Nachtsichtgeräten), die Unterstützung bei der Navigation und der Vermeidung von Kollisionen, die Überwachung von Objekten, die Suche nach vermissten Personen, die Diagnose und Überwachung von technischen Prozessen, die zerstörungsfreie Werkstoffprüfung, die Gebäudediagnostik oder den Einsatz bei medizinische Untersuchungen. Die hohen Kosten von Infrarot-Kameramodulen haben jedoch bisher eine weitere Verbreitung im privaten Bereich weitgehend verhindert. Ein Teil der Herausforderung bei der Entwicklung von IR-Detektoren ist in den komplexen Anforderungen begründet, die Materialien für den erfolgreichen Einsatz in Bolometern erfüllen müssen. Das Messprinzip dieser Art von Detektoren basiert typischerweise auf der Auswertung des elektrischen Widerstands eines freistehenden, thermisch-isolierten Thermistors, der sich aufgrund von absorbierter Infrarotstrahlung mit der Temperatur ändert. Zu den für diesen Einsatz gewünschten Eigenschaften zählen ein hoher Absorptionskoeffizient für Infrarotstrahlung, ein hoher elektrischer und thermischer Widerstand, eine hohe und möglichst lineare Änderung des Widerstands mit der Temperatur und ein geringes intrinsisches Rauschen. Häufig muss eine Kombination von verschiedenen Materialien verwendet werden, um alle Bedingungen zu erfüllen, was zu einem komplexen und kostenintensiven Herstellungsprozess führt. In dieser Arbeit wurde eine neue Bolometer-Technologie entwickelt, die als einziges funktionales Material auf einer sub-10 nm dicken Platinschicht basiert. Durch die Reduzierung der Anzahl der Schichten und deren Dicke entsteht der Vorteil einer hervorragenden thermischen Isolation und einer geringeren thermischen Masse der Detektorstruktur. Zusammen ergeben sich hieraus eine Verbesserung der Sensitivität, der Temperaturauflösung und der thermischen Zeitkonstante, den drei wichtigsten Kenngrößen für Bolometer. Ein weiterer Vorteil dieses Ansatzes ergibt sich durch einen einfacheren und damit preiswerteren Herstellungsprozess, dessen Komplexität üblicherweise mit der Anzahl der Ebenen und den benötigten Lithographie-Schritten skaliert. Platin besitzt attraktive Eigenschaften für die Verwendung als Thermistor-Material, was durch die weite Verbreitung von Platin-Widerstandsthermometern belegt ist. Für eine effektive Absorption von Infrarotstrahlung muss die Dicke der Platinschicht für die hier beschriebene Anwendung allerdings im Bereich von wenigen Nanometern liegen, damit eine Impedanz-Anpassung an den Freiraumwellenwiderstand erreichen werden kann. Um die wiederholbare und homogene Abscheidung von Schichten in dieser Größenordnung zu ermöglichen, wurde die Methode der plasmagestützten Atomlagenabscheidung (PE-ALD) gewählt. Hierauf basierend wurde an der Stanford Nanofabrication Facility ein Oberflächenmikromechanik-Fertigungsprozess entwickelt, der die zuverlässige Herstellung von nanometer-dünnen Bolometerstrukuren mit Aspektverhältnissen von über 8000:1 erlaubt. Die prinzipielle Kompatibilität des entwickelten Prozesses konnte sowohl für eine post-CMOS Integration als auch für eine Vakuum-Verkapselung der Sensoren durch Waferbonden gezeigt werden. Zunächst wurden die relevanten Materialeigenschaften der mit PE-ALD abgeschiedenen Schichten und deren Schichtdickenabhängigkeit evaluiert, damit ein ausreichendes Verständnis für den Entwurf und die Modellierung der Bolometerstrukturen erzielt werden konnte. Ein signifikanter Anstieg der spezifischen elektrischen und thermischen Widerstände wurde hierbei für Platin ab einer Schichtdicke kleiner als 10 nm festgestellt. Dieser Anstieg ging mit einer deutlichen Verringerung der Temperaturabhängigkeit des Widerstandes einher. Bei der Charakterisierung der optischen Eigenschaften der Platinschichten im Infrarotbereich wurde eine Erhöhung der realen und imaginären Anteile des Brechungsindexes bei einer Verringerung der Schichtdicke gemessen. Das durch den kleinen stromtragenden Querschnitt entstehende Risiko einer Beschädigung der Pt-Schicht durch Elektromigration wurde ebenfalls evaluiert und konnte als unbedenklich eingestuft werden. Des Weiteren wurden die mechanischen Eigenschaften der verwendeten Schichten bestimmt. Eine Verringerung des Elastizitätskoeffizienten um bis zu 50% wurde für Al₂O₃-Schichten mit einer Dicke von 9 nm festgestellt, während keine signifikante Veränderung der Steifigkeit von Pt beobachtete wurde. Alle charakterisierten Schichten wiesen Zugspannungen mit durchschnittlichen Werten um 131 MPa auf. Auf der Grundlage der gemessenen Materialeigenschaften wurde ein detailliertes analytisches Modell erstellt, mit dessen Hilfe die Eigenschaften der hergestellten Detektoren präzise vorhergesagt und die Abhängigkeit dieser Eigenschaften von den Designparametern verdeutlicht werden konnte. Mit der Entwicklung einer verbesserten Geometrie auf Basis einer freitragenden Serpentinenstruktur ließen sich die besonderen Merkmale des Detektoransatzes mit nur einer funktionalen Schicht ausnutzen, was zu einer Erhöhung der Sensitivität um eine Vierfaches führte. Die Eigenschaften der hergestellten Sensor-Prototypen wurden mit Hilfe eines Vakuumkammer-Aufbaus und eines Schwarzkörperstrahlers bestimmt. Die thermische Zeitkonstante der Detektoren lag – abhängig von der verwendeten Schichtdicke – im Bereich zwischen 0.7 ms und 4.5 ms. Dank der geringen thermischen Masse der nanometer-dicken, freitragenden Schicht sind diese Werte bis zu einer Größenordnung schneller im Vergleich zum Stand der Technik. Die Sensitivität der Sensoren gegenüber Infrarotstrahlung verbesserte sich drastisch für geringere Platin-Schichtdicken. So konnte eine Sensitivität von 4×10⁸ V/WA für Platin mit eine Dicke von 6 nm erreicht werden. Dieser Wert entspricht einer Temperaturauflösung (NETD) von 70 mK unter Berücksichtigung des gemessenen 1/f-Rauschens von Platin und unter der Annahme einer Infrarot-Optik mit einer Blendenzahl F#=1. Obwohl die neuentwickelte Technologie noch Verbesserungspotential besitzt, liegt die erreichte Temperaturauflösung nur um etwa Faktor zwei über der von kommerziell erhältlichen Bolometern, die eine langsamere Zeitkonstante besitzen und auf einen deutlich komplexeren Herstellungsprozess angewiesen sind. Zusammenfassend wurden in dieser Arbeit ungekühlte, bolometrische Infrarotdetektoren, die aus einer einzigen Platinschicht bestehen, entwickelt. Die Leistungsfähigkeit dieser Sensoren konnte durch die Reduktion der Schichtdicke auf wenige Nanometer signifikant verbessert werden, was mit der Verwendung von Atomlagenabscheidung ermöglicht wurde. Die in dieser Arbeit vorgestellten Ergebnisse schaffen eine hilfreiche Voraussetzung für die Verwendung von nanometer-dicken, freitragenden Strukturen bei Bauteilen aus anderen Bereichen der Mikrosytemtechnik, die auf ähnliche Weise von dieser Entwicklung profitieren können.
[EN] Gamma-ray bursts (GRBs) are the most violent explosions in the Universe. Although they were first discovered over half a century ago, yet many problems remain unsolved. Since the successful launch of GRB dedicated missions such as Swift and Fermi, multi-wavelength ground-based observations have provided a new approach to better characterize these events, their host galaxies and understand the underlying physics around the newly born compact objects following the GRB itself. GRB 140629A was a long burst that triggered the Swift satellite and many facilities at different wavelengths followed up this event, including the optical (Swift/UVOT and various facilities worldwide), infrared (Spitzer) and X-rays (Swift/XRT). These data were taken between 40 seconds and 3 yr after the burst trigger, which made this burst a good case to investigate the properties of the dominant jet and its host galaxy. The absorption features displayed in the optical spectrum, taken with the 6.0m BTA telescope, confirmed the redshift of this GRB (z = 2.276 0.001). We found no strong spectral evolution when fitting the spectral energy distribution of the afterglow from the X-rays to optical wavelengths. The hydrogen column density NH was constrained to be 7.2×1021cm−2 along the line of sight. The afterglow in this burst could be explained by a blast wave jet with a long-lasting central engine expanding into a uniform medium in the slow cooling regime. At the end of energy injection, a normal decay phase was observed in both the optical and X-ray bands. An achromatic jet break was also found in the afterglow light curves 0.4 d after the trigger. We fitted the multi-wavelength data simultaneously with a model (based on numerical simulations) and found that the observations could be explained by a narrow uniform jet in a dense environment with a half-opening angle of 6:7 viewed 3:8 off-axis, implying a total released energy of 1:4 1054 erg. Using the redshift and opening angle, we found that GRB 140629A followed both the Ghirlanda and Amati relations. The peak time of the light curve was identified as the onset of the forward shock (181 s after trigger) and we could constrain the initial Lorentz factor (Γ0) in the range 82-118. After fitting the host galaxy spectral energy distribution, we found the host to be a low mass, star-forming galaxy with a star formation rate (SFR) of log(SFR) = 1.1+0.9−0.4 M yr−1. We also obtained a value for the neutral hydrogen density NHI by fitting the optical spectrum, from which we derived logNHI = 21:0 0:3, classifying this host as a damped Lyman-alpha system. High ionisation lines (N V,Si IV) were also detected in the optical spectrum. Furthermore, polarisation observations by the MASTER network indicated that this burst was weakly polarised. GRB 190829A was detected by both Fermi and Swift but what made a unique event out of it was the detection of very high energy (VHE) gamma-rays by the High-Energy Stereoscopic System telescopes (HESS). The prompt gamma-ray emission displayed two emission episodes separated by a quiescent gap of 40 s. We followed it up with the 10.4 m Gran Telescopio CANARIAS (GTC) and gathered observations of the afterglow of GRB 190829A and its underlying supernova during the following days. We determined the redshift of this event (z = 0.0785 0.005) and compared GRB 190829A to GRB 180728A, another GRB with similar prompt behaviour at VHE energies, and discussed the implications regarding the underlying physical mechanisms producing these two GRBs. Together with the prompt emission data, the 10.4 m GTC data was used to better understand the emission mechanisms and possible progenitors. In the detailed analysis of the multi-band observations of the afterglow, we found the observational properties of the multi-wavelength afterglow could be explained by the cooling frequency passing between the optical and X-ray bands at the early epoch. A few days after, we saw the transition from the afterglow spectrum to the underlying supernova (dubbed SN 2019oyw) spectrum, which dominated the light curve at later times. Although the prompt emission temporal properties of GRB 190829A and GRB 180728A were similar, the two gamma-ray pulses were different in the spectral domain. We also found that the SN 2019oyw associated with GRB 190829A is powered by Ni decay and could be classified as a Type Ic-BL (broad line) supernova. The spectroscopic and photometric properties of this supernova were consistent with those observed for SN 1998bw (also related to another burst, GRB 980425) but SN 2019oyw evolved much faster than SN 1998 bw. Besides these above mentioned two long-duration GRBs, we also investigated the prompt emission and the afterglow properties of a sample of shortduration gamma-ray bursts (sGRBs) including GRB 130603B and another eight sGRB events during 2012-2015. They were observed by several multi-wavelength facilities, including the 10.4m GTC telescope. Prompt emission high energy data of those events were obtained by INTEGRAL-SPI-ACS, Swift-BAT and Fermi- GBM satellites. The prompt emission data by INTEGRAL in the 0.1–10 MeV energy range for sGRB 130603B, sGRB 140606A, sGRB 140930B, sGRB 141212A, and sGRB 151228A did not show signs of the extended emission or the precursor activity and their spectral and temporal properties were found to be similar to those seen in case of other short-duration bursts. For sGRB 130603B, our new afterglow photometric data constrained the pre-jet-break temporal decay due to denser temporal coverage. Its afterglow light curve, containing both our new data as well as previously published photometric data, was broadly consistent with the interstellar medium (ISM) afterglow model. Modelling the host galaxies of sGRB 130603B and sGRB 141212A using the LePHARE software supported a scenario where the burst environment was undergoing moderate star formation activity. From the inclusion of our late-time data for the additional eight sGRBs, we were able to place tight constraints on the non-detection of the afterglow, host galaxy or any underlying 'kilonova' emission. Finally, our late-time afterglow observations of the short-duration GRB 170817A (related to the gravitational wave GW 170817) are also discussed and compared with the sub-set of short-duration GRBs. ; [ES] Los estallidos de rayos gamma (GRBs) son los fenómenos más energéticos del Universo que, descubiertos hace más de medio siglo, presentan en la actualidad muchos incógnitas que aún están por resolver. Tras el lanzamiento exitoso de Swift y Fermi, la observación de los GRBs en múltiples longitudes de onda está proporcionando un nuevo enfoque para poder comprender mejor este fenómeno. Uno de los GRBs estudiados en este trabajo ha sido GRB 140629A, un estallido de larga duración que detectó el satélite Swift y que se pudo observar en diferentes longitudes de onda, obteniéndose un conjunto de datos abundantes que incluye el óptico (por medio de Swift/UVOT y de otras instalaciones astronómicas en todo el mundo), infrarrojo (Spitzer) y rayos X (Swift/XRT). Los datos analizados se tomaron entre 40 segundos y 3 años después del GRB, haciendo de este un caso propicio para poder investigar las propiedades tanto de la emisión colimada como de la de la galaxia anfitriona. A través de las líneas de absorción características presentes en el espectro óptico se derivó el corrimiento al rojo de este GRB (z = 2.276 0.001). Por otro lado, la evolución de la distribución espectral de energía en el rango del óptico a los rayos X no es significativa. La densidad de columna de hidrógeno NH se midió en 7.2 ×1021cm−2 a lo largo de la línea de visión. La postluminiscencia observada se puede explicar por medio de la existencia de un chorro colimado resultante de la onda expansiva procedente de un motor central de larga duración, produciéndose la expansión en un medio uniforme y en el régimen de enfriamiento lento. También al final de la fase de inyección de energía, se observa una fase de declive tanto en la banda óptica como en la de rayos X. Igualmente se encuentra una desviación (rotura) de la caída del flujo observado de la postluminiscencia, de manera acromática, en las curvas de luz de la posluminiscencia 0.4 d después del GRB. Ajustamos los datos de las múltiples longitudes de onda de manera simultáneamente con un modelo basado en una simulación numérica y encontramos que las observaciones pueden explicarse por un chorro uniforme estrecho en un ambiente denso con un ángulo de abertura de 6:7 visto 3:8 fuera de su eje, lo que implica que se liberó una energía total de 1:4 1054 erg. Usando el valor del corrimiento al rojo y el ángulo de abertura, encontramos que GRB 140629A obedece las relaciones de Ghirlanda y Amati. Desde el momento del máximo de la curva de luz, identificado como el inicio de la onda de choque que se propaga en el tiempo (181 s después del disparo), el factor de Lorentz inicial (Γ0) debe situarse en el rango 82-118. Haciendo un ajuste de los valores fotométricos de la galaxia anfitriona, encontramos se trata de una galaxia de baja masa con formación estelar y una tasa de formación estelar de log(SFR)=1.1+0.9−0.4 M yr−1 . Obtenemos un valor de la densidad del hidrógeno neutro NHI ajustando el espectro óptico, logNHI = 21:0 0:3, clasificando este sistema como un sistema de Lyman-alfa amortiguado. Las líneas de alta ionización (N V, Si IV) también se detectan en el referido espectro. Y las observaciones de polarización realizadas por el telescopio MASTER indican que este estallido es un evento débilmente polarizado. El segundo evento de los estudiados ha sido GRB 190829A, que fue detectado por Fermi y Swift y también a rayos-gamma de muy alta energía (VHE) por HESS (Sistema estereoscópico de alta energía). La emisión temprana mostró dos episodios de emisión separados por un intervalo sin actividad alguna con una duración de 40 s. Presentamos las observaciones del 10.4 m Gran Telescopio CANARIAS (GTC) en relación a la post-luminiscencia de GRB 190829A y su supernova subyacente. El corrimiento al rojo de este evento se detectó con z=0.0785 0.005. También comparamos GRB 190829A con GRB 180728A, un estallido con un comportamiento similar, y discutimos las implicaciones en los mecanismos físicos subyacentes que producen estos dos GRBs. Los datos fotométricos multi-banda junto con la observación espectroscópica de este evento se tomaron con el telescopio GTC de 10.4m. Junto con los datos de la emisión inicial, los datos del GTC se utilizan para comprender los mecanismos de emisión y el posible progenitor. En el análisis detallado de las observaciones multibanda del resplandor, encontramos que este evento es consistente con el paso de la frecuencia de enfriamiento entre las bandas ópticas y de rayos X en épocas tempranas. Luego estudiamos la supernova subyacente 2019oyw, que domina las fases más tardías. Aunque las propiedades temporales de emisión rápida de GRB 190829A y GRB 180728A son similares, los dos pulsos de rayos-gamma son diferentes en el dominio espectral. Encontramos que SN 2019oyw, asociada con GRB 190829A se puede explicar por la desintegración de Ni y ha sido clasificada como una supernova de Tipo Ic-BL. Las propiedades espectroscópicas y fotométricas de esta supernova son consistentes con las observadas para SN 1998bw (asociada a GRB 980425), pero mostrando una evolución más rápida. Además de los dos GRBs de larga duración reseñados anteriormente, también investigamos la emisión rápida y las propiedades de la postluminiscencia del estallido de rayos gamma de corta duración GRB 130603B así como de otros 8 eventos GRB de corta duración, detectados durante el periodo 2012-2015, y observados por varias instalaciones en diferentes longitudes de onda, incluyendo el telescopio GTC de 10.4 m de diámetro. Los satélites INTEGRAL (SPI-ACS), Swift (BAT) and Fermi (GBM) obtuvieron datos de alta energía de dichos GRBs. Los datos de emisión temprana por INTEGRAL en el rango de energía de 0,1 a 10 MeV para sGRB 130603B, sGRB 140606A, sGRB 140930B, sGRB 141212A y sGRB 151228A no muestran ningún indicio de la emisión extendida o la actividad precursora y sus propiedades espectrales y temporales son similares a los que se ven en el caso de otros GRBs de corta duración. Para sGRB 130603B, nuestros nuevos datos fotométricos en relación a la posluminiscencia restringen el decaimiento temporal previo al desvío en la curva de luz producida por la expasión del chorro, gracias a haber dispuesto de una cobertura temporal más completa. La curva de luz de la postluminiscencia, que contiene tanto nuestros datos fotométricos nuevos como los publicados anteriormente, es consistente con el modelo de post-luminiscencia atravesando un medio de tipo interestelar (ISM). El modelado de las galaxias anfitrionas de sGRB 130603B y sGRB 141212A, utilizando el software LePHARE, respalda un escenario en el que el entorno de la explosión en la galaxia huésped está experimentando una actividad de formación estelar moderada. A partir de la inclusión de nuestros datos para los otros 8 GRBs de corta duración anteriormente referidos, podemos imponer restricciones estrictas a la no detección de la postluminiscencia, la galaxia anfitriona o cualquier emisión de kilonova subyacente. Nuestras observaciones tardías en el tiempo, de la post-luminiscencia de sGRB 170817A / GW170817 también se discuten y comparan con el subconjunto de GRBs de corta duración. ; With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709. ; Peer reviewed
Organic and Macromolecular Chemistry -- Survey of Multiple Mechanical Transitions in Polymers in Relation to Thermal Transitions -- La Préparation et Quelques Propriétés Thermiques des Mono- et Dihalogénures de L'Hydrazine -- Thermal Analysis of Aminobenzimidazoles -- Thermal Behaviour of Some Organic Compounds with Ionic Character -- Radiothermogravimetry a Technique for Determining Pyrolysis Mechanisms -- The Selection of Catalysts by Thermogravimetry -- Investigation of the Melting Behaviour of Organic Substances by Differential Scanning Calorimetry -- Identification par Analyse Thermique Differentielle et par Thermogravimetrie D'Une Serie D'Amino-Acides Aliphatiques Satures -- Characterization of Unusual Lipids by Novel Thermoanalytical Techniques -- Pressure Dependence of Phase Transitions in Bis (4'-n-Alkoxybenzal) -1,4-Phenylenediamines -- Acid-Soap Formation in Various Anhydrous Sodium Soaps -- The Evaluation of Thermosetting Polymers by Thermal Analytical Methods -- Torsional Braid Analysis of the Cure of a Cycloaliphatic Epoxy Resin -- Analysis of the Curing Reactions of Thermosetting Polymers by DSC -- Application of Thermal Analysis to Evaluation of Semiconductor Encapsulation -- Studies of the Thermal Breakdown of Polybenzimidazoles -- Investigations of Thermal Properties of Some Polyesterimides with Polynaphthalene Rings in the Side Chain -- Oxidative Thermal Degradation of Selected Polymeric Spacecraft Materials -- The Identification of High Polymers by Thermal Degradation in the Mass Spectrometer -- Investigations of the Stability of Polymers by Thermal Volatilization Analysis -- Evolved Gas Analysis Using an Ion Selective Electrode -- Quantitative Determination of the Combined Styrene in the Butadiene-Styrene Copolymers -- Differential-Thermo-, Thermo-Gravimetrische- und Infrarot-Spektralanalyse von Inden-Cumaron-Harzen -- Application of Simultaneous DTA/TG and DTA/MS Analysis for Predicting in Advance of Processing the Flammability and Toxicity of Gases of Composite Textile Fabrics and Polymers -- Low Temperature Isothermal Pyrolysis of Cellulose -- Thermogravimetry of Cellulose by Gamma-Ray Absorption -- The Kinetics of the Reaction of CO2 with Cellulose Triacetate Carbons in the Range 1160–1240K -- A Study of Reaction Mechanisms by DSC and TG -- Thermal Nalysis of Lignin -- Etude de la Vitesse de Cristallisation de Divers PP -- Thermal Analyses of Polymers. IX. First order Phenomena in Polystyrene -- Multiple Transitional Regions Observed in Several Free-Radical Polymerized Polymethacrylates by Thermal, Ultrasonic and Optical Techniques -- Melting of some Aromatic and Heterocyclic Oligomers -- Transition and Relaxations in Polyquinoxalines -- The Characterisation of Textile Fibre Blends Containing Polyamide by Differential Thermal Analysis -- The Sol-Gel Transition in Polysaccharide Gels -- The Thermal Behaviour of Modified Keratins -- Ceramics -- Calculation of Phase Boundaries by Thermochemical Methods in Contrast to Thermal Analysis -- Appl?cat?on of Mathemat?cal Stat?st?cs and Pattern Recogn?t?on Methods to the Evaluat?on of DTA Results -- Dilatometric Study of Consolidated Powdered Materials -- Interest of Thermal Analysis in Gypsum and Plaster Industry -- Investigation of the Solid Solutions of Calcium Hydrogermanosilicates by Thermal Analysis and Other Physico-Chemical Methods -- DTA and X-Ray Analysis on Phase Transitions and Compatibility Relationships in the Pseudobinary System Barium Metasilicate-Barium Metagermanate -- The Use Differential-Thermal, Thermogravimetric and Gas-Volumetric Analyses to Study Peculiar Crystalline Structure of Calcium Hydrosilicate Monocrystals -- Study of the Hydration of Vitreous Blastfurnace Slag with a High Magnesia Content and of Related Materials -- Differential Thermal Analysis as Applied for the Study of the Peculiar Phase Composition and Structure of the Cement Stone Hardened Under Long Effects of High Temperatures//Pressures and Corrosion Factors -- Kinetics of the Oxidation of TiC-Coated Cemented Carbide -- Untersuchungen der Oxidation von Titankarbid -- Reactions between Vanadium Pentoxide and Aluminates -- Kinetics and Mechanism of the Reaction Between Lead Orthosilicate and Potassium Carbonate -- Examination of the System: "Clinker + Gypsum + Water" through the Method of Differential Thermal Analysis -- Earth Sciences -- Thermal Analysis in Earth Science: Experience and Expectations -- Petrologische Anwendung der Inversionstemperatur-Bestimmung von Quarzen -- DTA in the Characterization of Adsorbent Clays -- Examination of Hydrothermal Rock Alterations with Derivatograph -- DTA of Various Cyclohexylammonium Smectites -- The Dissociation of Strontianite and Its Quantitative Estimation by Thermogravimetry -- DTA, TG, IR and Isotopic Analyses and Properties of Phlogopite, Biotite Muscovite and Lepidolite in Temperature Range of Metamorphic Reactions -- A DTA Study of the Effect of pH on the Adsorption of N-Dodecylamine from Aqueous Solution Onto Oxide Mineral Surfaces.
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La necesidad de buscar alternativas energéticas limpias para suplir las necesidades de la humanidad en el futuro, ha llevado a la ciencia a considerar fuentes como el viento y el sol, por las innumerables ventajas que tienen al ser renovables y permanentes. Para aprovecharlas es importante el desarrollo de aplicaciones prácticas que permitan su masificación, razón por la cual se propone la síntesis de materiales semiconductores orgánicos que puedan utilizarse en dispositivos fotovoltaicos que sean más accesibles y eficientes a los que se usan hoy en día. El presente trabajo tiene como objetivo la síntesis de materiales semiconductores con aplicaciones fotovoltaicas, dirigidos a dispositivos que sean de menor costo al del actual. En este se muestran los resultados de la síntesis del poli-3,4-diisobutoxitiofeno mediante la polimerización oxidativa de su monómero, y cuya estructura fue corroborada mediante RMN, MALDI-TOF y FT-IR. Se obtuvieron como resultados de su caracterización óptica un ancho de banda de bajo valor (Eg=1.98-2.06 eV) y baja eficiencia de fluorescencia (Φ= 0.0056). Se hizo la polimerización electroquímica del monómero sobre tres electrodos diferentes obteniéndose que el sustrato sobre el cual se electropolimeriza más favorablemente es sobre FTO. Estas excelentes propiedades encontradas abren la posibilidad de que este material pueda ser utilizado en celdas solares orgánicas como material tipo p dentro de la capa activa. Adicionalmente, el bajo costo de su síntesis (aproximadamente $650.000.oo por 0.20g) lo hace un material con potencial en la fabricación de dispositivos de menor costo. El estudio de las películas depositadas por spin coating de mezcla poli-3,4-diisobutoxitiofeno y PCBM, los cuales actúan como material tipo p y n, respectivamente, dentro de la capa activa, muestra que estas deben formarse a bajas velocidades y se les debe hacer un tratamiento térmico a 80°C para lograr la reorganización de los sustituyentes alcoxi del polímero, lo cual mejora la absorción de luz visible y se disminuye la eficiencia de fluorescencia de la mezcla, probando así una buena interacción entre los dos materiales. ; Abstract: The need to find clean energy alternatives meeting the needs of humanity in the future has led the scientists take into consideration sources such as wind and sun due to their advantages being clean, renewable and over all permanent. In order to take advantage of them the development of practical applications for its massification plays an important role in the research. For this reason we propose that the synthesis of organic semiconductor materials which can be used in photovoltaic devices can be more accessible and efficient than those used nowadays. The present work aims the synthesis of semiconducting materials with photovoltaic applications targeted at devices cheaper than the current costs. It shows the results of the synthesis of poly-3,4-diisobutoxythiophene by oxidative polymerization of the monomer, whose structure was confirmed by NMR, MOLDI-TOF and FT-IR. With optical characterization methods results for low bandwidth (Eg = 1.98-2.06 eV) and low fluorescence (Φ = 0.0056) were obtained. The monomer electropolymerization was made under three electrodes, was founded that the best substrate for these was the FTO electrode. These excellent properties founded, open the possibility that this material can be used in organic solar cells as p-type material in the active layer and on top of that the low synthesis costs (approximately $ 650.000.oo COP per 0.20 g) makes it a potential material in the manufacture of low cost devices. The study of depositing the films by spin coating of mixture of poly-3,4-diisobutoxythiophene and PCBM acting as p and n-type material within the active layer, respectively, shows that they have to be formed at low speeds as well as being annealed at 80°C for remodeling the alkoxy chains of the polymer, in order to on the one hand enhance the absorption in the visible light spectrum and on the other hand to decrease the fluorescence of the mixture, which in that way proves a good interaction between both materials. ; Maestría
Background/Aim. Due to their low tolerance to pollutants and hand-to-mouth pathways the health risk is very high in children's population. The aim of this study was to evaluate risk to children's health based on the content of heavy metals in urban soil samples from Podgorica, Montenegro. This study included the investigation of several toxic metals such as Pb, Cd, Cu and Zn in soil samples from public parks and playgrounds. Methods. Sampling was conducted in a period October-November, 2012. Based on cluster analysis, soil samples were divided into two groups related to similarity of metal content at examinated locations: the group I - near by recreational or residential areas of the city, and the group II - near traffic roads. Concentration of toxic metals, in urban soil samples were determined by a graphite furnace atomic absorption spectrometry (Pb and Cd) and by inductively coupled plasma optical emission spectrometry technique after microwave digestion. Due to exposure to urban soil, non-cancerogenic index hazardous index (HI) for children was estimated using 95th percentile values of total metal concentration. The value of the total (ingestion, dermal and inhalation) HI is calculated for maximum, minimum and the average concentration of metals for children. Results. Mean concentrations of Pb, Cd, Cu and Zn in the surface layer of the studied urban soils were 85.91 mg/kg, 2.8 mg/kg and 52.9 mg/kg and 112.5 mg/kg, respectively. Samples from group II showed higher metal content compared to group I. Urbanization and traffic are the main sources of pollution of the urban soils of Podgorica. Most of the samples (93.5%) had a high Pb content, 12.9% of the samples had a higher content of Cd, while Cu and Zn were within the limits prescribed by national legislation. At one location the level of security for lead is HI = 0.8 and very closed to maximum acceptable value of 1. It is probably the result of intensive traffic near by. Conclusion. All metals investigated showed relatively higher concentrations at sites that were close to industrial places and high ways. The mean concentrations of Pb and Zn and maximum concentrations of Pb, Cd, and Zn were higher than presented values in the National Regulation. ; Uvod/Cilj. Zbog niske tolerancije na zagađivače i puta prenošenja ruke-usta, rizik od narušenja zdravlja je veoma visok u dečjoj populaciji. Cilj ovog rada bio je da se izvrši procena rizika po zdravlje dece na osnovu sadržaja teških metala u uzorcima gradskog zemljišta u Podgorici, Crna Gora. Ovo istraživanje je obuhvatilo određivanje koncentracija nekoliko toksičnih metala kao što su Pb, Cd, Cu i Zn u uzorcima zemljišta javnih parkova i dečijih igrališta. Metode. Uzorkovanje je sprovedeno tokom oktobra i novembra 2012. godine. Klaster analizom uzorci zemljišta podeljeni su u dve grupe na osnovu sličnosti sadržaja metala na ispitivanim lokacijama: grupa I - uzorci sa mesta u rekreativnim ili stambenim delovima grada i grupa II - uzorci iz parkova i igralište blizu saobraćajnice. Koncentracija metala u uzorcima urbanog zemljišta određena je primenom atomske apsorpcione spektrometrije pomoću grafitne kivete (Pb i Cd) i tehnike optičke emisione spektroskopije sa induktivno kuplovanom plazmom (Cu i Zn) nakon mikrotalasne digestije. Na osnovu stepena izloženosti uticaju gradskog zemljišta, nekancerogeni indeks opasnosti (hazard index - HI) za decu izračunat je na 95. procentu vrednosti ukupne koncentracije metala. Vrednost za ukupni (ingestioni, dermalni i inhalacioni) HI izračunata je za maksimalne, minimalne i srednje koncentracije ispitivanih metala za decu. Rezultati. Srednja koncentracija toksičnih metala u uzorcima površinskog sloja zemljišta iznosila je 85,91 mg Pb/kg tla, 2,8 mg Cd/kg tla, 52,9 mg Cu/kg tla i 112,5 mg Zn/kg tla. Sadržaj metala bio je značajno veći u uzorcima zemljišta iz grupe II nego u uzorcima grupe I. Ovo jasno ukazuje na izražen i uočljiv uticaj urbanizacije, a naročito saobraćaja, na zagađenje zemljišta. Većina uzoraka (93,5%) imala je povećan sadržaj Pb, 12,9% uzoraka imalo je povećan sadržaj Cd, dok je sadržaj Cu i Zn bio u granicama propisanim nacionalnom regulativom. Na jednoj lokaciji vrednost za nivo bezbednosti za olovo bio je HI = 0,8, vrlo blizu maksimalne prihvatljive vrednosti koja iznosi 1, što je verovatno posledica intenzivnog saobraćaja u neposrednoj blizini ispitivane lokacije. Zaključak. Ispitivani metali imali su više koncentracije na mestima u blizini industrijske zone i autoputa. Prosečne koncentracije Pb i Zn, kao i maksimalne koncentracije Pb, Cd i Zn bile su više od vrednosti propisanih nacionalnom regulativom.
International audience ; We demonstrate a deep-UV laser at 236.5 nm based on extracavity fourth-harmonic generation of a Q-switched Nd: YAG single-crystal fiber laser at 946 nm. We first compare two nonlinear crystals available for second-harmonic generation: LBO and BiBO. The best results at 473 nm are obtained with a BiBO crystal, with an average output power of 3.4 W at 20 kHz, corresponding to a second-harmonic generation efficiency of 38%. This blue laser is frequency-converted to 236.5 nm in a BBO crystal with an overall fourth-harmonic generation yield of 6.5%, corresponding to an average output power of 600 mW at 20 kHz. This represents an order of magnitude increase in average power and energy compared to previously reported pulsed lasers at 236.5 nm. This work opens the possibility of LIDAR detection of dangerous compounds for military or civilian applications. The development of deep-UV solid-state lasers based on nonlinear frequency conversion has opened applications previously based on excimer lasers, such as material processing or spectroscopy applications. The most common approach is fourth-harmonic generation of the 1064 nm laser line of Nd:YAG, which has been a commercial product for many years. Unfortunately, important applications, such as manufacturing of Bragg gratings or waveguides, would be more efficient using wavelengths below 250 nm. Moreover, some particular spectroscopic applications, such as detection of dangerous compounds, require specific wavelengths in the deep-UV. One possible solution is to use a fundamental laser operating at a lower wavelength, such as the 946 nm laser line of Nd:YAG. Subsequent fourth-harmonic generation leads to a wavelength of 236.5 nm, which lies in the absorption band of molecules related to improvised explosive devices or nuclear, radiological, biological, and chemical components [1,2]. The challenge is to obtain enough pulse energy to increase the detection range and accuracy. Unfortunately, previous works at 236.5 nm only demonstrated a maximum energy of 500 nJ [3,4], with an average power of 20 mW. This energy limitation comes from the difficulty to obtain significant laser output in Nd:YAG at 946 nm, because the quasi-three-level transition induces strong thermal effects. Recently, we demonstrated that single-crystal fiber technology could significantly improve the available laser output at 946 nm in Nd:YAG, owing to an optimized thermal management allowed by the crystal geometry and packaging [5,6]. In this Letter, we propose to use a Nd:YAG single-crystal fiber Q-switched oscillator at 946 nm as a source for efficient fourth-harmonic generation. We show that this leads to an order of magnitude increase over previously reported results both in pulse energy and average power at 236.5 nm. The experimental setup is displayed in Fig. 1. The laser is a Q-switched oscillator at 946 nm based on a Nd:YAG single-crystal fiber [6]. It emits an average power of 9.2 W in a linearly polarized beam at a repetition rate of 20 kHz, with a pulse width of 45 ns. The beam profile is Gaussian with a measured beam quality of M 2 x ˆ 1.11 and M 2 y ˆ 1.13 (Fig. 3). The pulse energy is 460 μJ, corresponding to a peak power of 10.2 kW. Several crystals are commercially available to perform second-harmonic generation (SHG) to the visible range. We consider three crystals: lithium tetraborate LiB 3 O 5 (LBO), bismuth borate BiB 3 O 5 (BiBO), and periodically poled titanium phosphate (PPKTP). Their material and nonlinear properties are displayed in Table 1. LBO is the most commonly used nonlinear crystal for visible SHG. While its nonlinearity is low compared to the other two crystals (d eff ˆ 0.81 pm∕V), it has low walk-off, large angular acceptance, a very high damage threshold , and can be manufactured in large dimensions with very good optical quality. In contrast, BiBO has a large nonlinear coefficient (d eff ˆ 3.34 pm∕V), but suffers from a large walk-off and low angular acceptance, often resulting in elliptical output beam. This also lowers the conversion efficiency for tight focusing when compared to crystals with a lower walk-off value. Furthermore, BiBO is a hygroscopic crystal that cannot be exposed to ambient air for a very long period of time.
Die seit 2004 in Deutschland bekannt gewordenen Fälle der illegalen Rückführung und irrtümlichen Fehlverbringung von gemäß der Verordnung (EG) Nr. 1774/2002 nicht für den Genuss durch den Menschen bestimmten tierischen Nebenprodukten (TNP) der Kategorie 3 in die Lebensmittelkette haben zu der politischen Diskussion beigetragen, ob die Pflicht der Materialidentifizierbarkeit durch das Getrennthalten TNP am Ort des Anfalls sowie die ausschließliche Kennzeichnung ihrer Transportbehälter bei der Beförderung einen ausreichenden Schutz der Verbraucher garantieren können. Um eine ordnungsgemäße Verwendung TNP der Kategorie 3 sicherzustellen, hat der Bundesrat ihre unmittelbare und eindeutige Kennzeichnung, z.B. durch Farbstoffe, gefordert. Ziel dieser Arbeit war es, einen geeigneten, futtermittelrechtlich zugelassenen Marker für Schlachtnebenprodukte der Kategorie 3 zu erörtern, der eine technisch praktikable, vom Ort des Anfalls bis zum Verarbeitungsbetrieb optisch eindeutige, dauerhafte und nach der Verarbeitung nachweisbare sowie umwelt- und wirtschaftsverträgliche Markierung von Schlachtnebenprodukten zur sicheren Verfolgbarkeit ihrer bestimmungsgemäßen Verwendung als TNP der Kategorie 3 ermöglicht, um ihren Eintrag in die Lebensmittelkette zu unterbinden, ohne die Neutralität der Endprodukte bei der Verwendung markierter TNP als Rohstoffe für Futtermittel zu beeinträchtigen. Für die Markierung von Schlachtnebenprodukten mittels Sprühsystemen wurden für Futtermittel zugelassene, färbende Zusatzstoffe (Verordnung (EG) Nr. 1831/2003) sowie in der medizinischen Diagnostik etablierte Fluoreszenz-Farbstoffe ausgewählt und hinsichtlich der Eindeutigkeit ihrer Markierung, ihrer Farbhaltung nach Bearbeitung sowie ihrer optischen Neutralität in Lebens- und Futtermitteln, die aus markierten TNP hergestellt worden sind, von fünf ungeschulten Prüfpersonen im Rahmen einer einfach beschreibenden, sensorischen und unabhängigen Prüfung gemäß §35 LMBG (L 00.90-6, ASU) beurteilt. Die Ergebnisse der sensorischen Prüfung wurden mit den RGB-Farbprofilen der markierten und nicht markierten TNP vergleichend analysiert. Zum Nachweis des irrtümlichen oder vorsätzlichen Eintrags von mit den ausgewählten Markerfarbstoffen markierten TNP in Lebensmitteln konnten die Analyseverfahren Dünnschichtchromatographie (DC), optische Emissionsspektrometrie mit induktiv gekoppeltem Hochfrequenzplasma (ICP-OES), Photometrie sowie die Fluoreszenzspektrometrie hinsichtlich ihrer Anwendbarkeit untersucht werden. Die Untersuchung der sensorischen Neutralität der Markerfarbstoffe im Endprodukt Futtermittel erfolgte unter anderem durch einen Futtermittelpräferenzversuch an neun Hunden der Rasse Beagle. Brillantsäuregrün E142 (1,3 mg E142/kg TNP) konnte auf Grund der Eindeutigkeit der Markierung von Schlachtnebenprodukten durch die gegenüber den nativen TNP signifikant unterschiedlichen Rot-Farbintensitäten bei gleichzeitiger Neutralität in den Endprodukten (Lebens- oder Futtermittel) und einer guten bis sehr guten Farbhaltung nach dem Waschen der Nebenprodukte, der Kühl- (8°C über zwei Tage) sowie Gefrierlagerung (-25°C über 14 Tage) und dem Verwenden einer 14, 90 als auch 150 Tage gelagerten Farbstofflösung in Kombination mit dem chemisch nachweisbaren Titandioxid (90 mg E171/ kg TNP) als Markerfarbstofflösung zur eindeutigen Markierung von Nebenprodukten der Schlachtung am Ort ihres Anfalls selektiert werden. Die für die Markierung bestimmten Dosierungen der Markerfarbstoffe gelten für Tiere und Menschen als unbedenklich. Die mit den färbenden Zusatzstoffen E142 und E171 markierten Nebenprodukte der Schlachtung können mittels DC (Nachweisgrenze: ≥7,5 µg E142/kg Probe) beziehungsweise ICP-OES und Photometrie (Nachweisgrenze ICP-OES: 8,3 mg E171/kg Probe) ab einem eingebrachten Anteil von 0,55% (DC: E142) beziehungsweise 9% (ICP-OES: E171) in diversen Produkten (Lebens- oder Futtermittel) nachgewiesen werden. In den chemisch und thermisch extrahierten Fetten aus markierten, fettreichen TNP waren die Farbstoffe E142 und E171 jedoch nicht nachweisbar. Eine Fluoreszenzmarkierung TNP kann hingegen nicht präferiert werden, da nicht markierte Nebenprodukte der Schlachtung eine sichtbare und fluoreszenzspektrometrisch nachweisbare Autofluoreszenz aufweisen und in den thermisch verarbeiteten Produkten keine für die Fluoreszenz-farbstoffe charakteristischen Absorptions- und Emissionsspektren nachweisbar waren. Die Markierung mittels Sprühtechnik erscheint unter den Aspekten Substanzverlust und adaptierter Markerfarbstoff pro Kilogramm TNP praktikabel. Die im Labor bestimmte Markierungszeit für TNP (5 sec./kg) ist unter Einbeziehung der Durchsatzraten am Schlachthof als zu lang zu bewerten. Durch die rückstandsfreie Entfernung der Farbstoffe von Edelstahl- und glatten Kunststoffflächen sowie glasierten Fliesen ergeben sich keine Nachteile der Markierung TNP für die Produktion von Futtermitteln und technischen Erzeugnissen. Die in dem Präferenzversuch untersuchten Futtermittel für Hunde aus markierten TNP zeigten keine Abweichungen von der handelsüblichen sensorischen Produktqualität und hinsichtlich ihrer Haltbarkeit durch Sterilisation (F0-Wert). Mit E142 und E171 markierte TNP (Kat. 3) eignen sich somit als Rohstoffe zur Herstellung von Heimtierfuttermitteln. Bei Anwendung einer Kombinationsfarbstofflösung (E142 und E171) würden die für die Marker anfallenden Kosten pro Tonne TNP bis zu 33 Euro betragen. Bei der ausschließlichen Verwendung von E142, welches der optisch eindeutig markierende Farbstoff ist und das eine hohe Sensitivität im dünnschichtchromatographischen Nachweis zeigt, würden die Kosten 1,70 bis 3,40 Euro/t betragen. Bisher konnte kein EU-einheitlicher Rechtsrahmen zur Markierung TNP der Kategorie 3 gestaltet werden. Die politische Diskussion wird aber vor allem national fortgesetzt. ; Since 2004 several illegal or aberrant transfers of animal by-products (ABP) from category 3 (according to Regulation (EC) No. 1774/2002: not intended for food production) back into food chain, have led to the political discussion, whether duty of material identifiability by separate storing of ABP on site and sole labeling of containers during transport are sufficient to protect consumers from ABP not intended for human consumption. To guarantee adequate utilisation of ABP from category 3, the German Federal Council claimed for an immediate and conclusive marking of ABP by dyeing or similar solutions. This study was implemented to define a convenient, registered feed additive for dyeing of slaughter by-products from category 3, which realize a feasible, from extraction to processing visually conclusive, long-lasting, traceable as well as sustainable and cost-effective marking on site to ensure traceability of intended utilisation as ABP from category 3 and to prevent their influx into food chain, without an impairment of the neutrality of products (e.g. pet food) made from marked ABP. For marking of slaughter by-products by air spraying device, registered colouring feed additives (Regulation (EC) No. 1831/2003) as well as diagnostically established fluorescence pigments were selected and investigated regarding their marking unambiguousness, colour retention after processing and visual neutrality in food and feed made from marked ABP by evaluation of five untrained judging persons in the course of a simply delineative, sensorial and impartial test (official list of analysis methods, ASU §35 LMBG, L 00.90-6), and by comparative RGB-colour measurement of images scanned from stained ABP samples. Detection of aberrant or deliberate discharge of marked ABP into food production was evaluated by investigation of thin layer chromatography (TLC), inductively coupled plasma optical emission spectrometry (ICP-OES), photometry and fluorescence spectrometry. Neutrality of marking feed additives in feedstuff was determined by a feeding preference test with nine dogs of the Beagle breed using pet food made from unmarked und marked ABP. Lissamine Green E142 (1,3 mg E142 per kg ABP) was selected as marker dye for slaughter by-products on site based on its unambiguousness of marking due to the significant different red-colour intensity compared to the non-marked ABP as well as the simultaneous neutrality of the colouring additive E142 in the final products feed and food. Colour retention of E142 marking was conclusive with regard to handling by washing, cold (8°C for two days) respectively fridge storage (-25°C for 14 days) and utilisation of a 14-, 90- and 150-days-stored marker solution. For marking, Lissamine Green was combined with the chemical detectable and registered food colour titanium dioxide (E171: 90 mg/kg ABP). The marker additives are classified as safe for humans and animals within the preferred concentrations for colouring ABP. With E142 und E171 marked ABP were traceable in food and feed using detection methods TLC (limit of detection: ≥7,5 µg E142 per kg sample), photometry and ICP-OES (limit of detection: ≥8,3 mg E171 per kg sample) at a proportion of 0,55% (TLC: E142) respectively 9% (ICP-OES: E171), whereas the named markers were not detectable in chemical and thermal extracted fats produced from marked high-fat ABP. Based on the visible and fluorescence spectrometric detectable autofluorescence of animal tissues as well as the uncharacteristic emission and absorption spectra of fluorescence pigments in processed ABP, fluorescence markers are not preferential for marking of slaughter by-products from category 3. Marking of slaughter by-products by air spraying device appeared practicable in due consideration of marker depletion and tissue-adapted marker per kg ABP. Current time of marking under laboratory conditions (5 sec. per kg ABP) must be graded as too long, regarding high transfer rates in slaughterhouses. Concerning the residue-free cleaning of stainless steel and even plastic surfaces from the marker solution, the utilisation of marked ABP for manufacturing of feed and technical products is unproblematic. Investigated pet food samples produced from marked ABP were from comparable commercial sensory product quality and showed no deviation of normal storability due to sterilisation. In conclusion, with E142 and E171 visible marked ABP from category 3 are suitable as crude materials for pet food production. The application of the combined marker solution (E142 and E171) have to be evaluated as comparative expensive (33 Euro per ton ABP), while the exclusive application of E142 as the optic conclusive and sensitive detectable marker for ABP is associated with sustainable costs from 1,70 to 3,40 Euro per ton ABP. To date, an EU-common regulatory framework for marking of ABP from category 3 could not be specified. Nevertheless the political discussion is still continued, especially in Germany.
Forests are one of the major carbon sinks that significantly contribute towards achieving targets of the Kyoto Protocol, and its successors, in reducing greenhouse (GHG) emissions. In order to contribute to regular National Inventory Reporting, and as part of the on-going development of the Irish national GHG reporting system (CARBWARE), improvements in characterisation of changes in forest carbon stocks have been recommended to provide a comprehensive information flow into CARBWARE. The Irish National Forest Inventory (NFI) is updated once every six years, thus there is a need for an enhanced forest monitoring system to obtain annual forest updates to support government agencies and forest management companies in their strategic decision making and to comply with international GHG reporting standards. Sustainable forest management is imperative to promote net carbon absorption from forests. Based on the NFI data, Irish forests have removed or sequestered an average of 3.8 Mt of atmospheric CO2 per year between 2007 and 2016. However, unmanaged and degraded forests become a net emitter of carbon. Disturbances from human induced activities such as clear felling, thinning and deforestation results in carbon emissions back into the atmosphere. Funded by the Department of Agriculture, Food and the Marine (DAFM, Ireland), this PhD study focuses on exploring the potential of data from L-band Synthetic Aperture Radar (SAR) satellite based sensors for monitoring changes in the small stand forests of Ireland. Historic data from ALOS PALSAR in the late 2000s and more recent data from ALOS-2 PALSAR-2 sensors have been used to map forest areas and characterise the different disturbances observed within three different regions of Ireland. Forest mapping and disturbance characterisation was achieved by combining the machine learning supervised Random Forests (RF) and unsupervised Iterative Self-Organizing Data Analysis (ISODATA) classification techniques. The lack of availability of ground truth data supported use of this unsupervised approach which forms natural clusters based on their multi-temporal signatures, with divergence statistics used to select the optimal number of clusters to represent different forest classes. This approach to forest monitoring using SAR imagery has not been reported in the peer-review literature and is particularly beneficial where there is a dearth of ground-based information. When applied to the forests, mapped with an accuracy of up to 97% by RF, the ISODATA technique successfully identified the unique multi-temporal pattern associated with clear-fells which exhibited a decrease of 4 to 5 decibels (dB) between the images acquired before and after the event. The clustering algorithm effectively highlighted the occurrence of other disturbance events within forests with a decrease of 2±0.5dB between two consecutive years, as well as areas of tree growth and afforestation. A highlight of the work is the successful transferability of the algorithm, developed using ALOS PALSAR, to ALOS-2 PALSAR-2 data thereby demonstrating the potential continuity of annual forest monitoring. The higher spatial and radiometric resolutions of ALOS-2 PALSAR-2 data have shown improvements in forest mapping compared to ALOS PALSAR data. From mapping a minimum forest size of 1.8 ha with ALOS PALSAR, a minimum area of 1.1 ha was achieved with the ALOS-2 PALSAR-2 images. Moreover, even with some different backscatter characteristics of images acquired in different seasons, similar signature patterns between the sensors were retrieved that helped to define the cluster groups, thus demonstrating the robustness of the algorithm and its successful transferability. Having proven the potential to monitor forest disturbances, the results from both the sensors were used to detect deforestation over the time period 2007-2016. Permanent land-use changes pertaining to conversion of forests to agricultural lands and windfarms were identified which are important with respect to forest monitoring and carbon reporting in Ireland. Overall, this work has presented a viable approach to support forest monitoring operations in Ireland. By providing disturbance information from SAR, it can supplement projects working with optical images which are generally limited by cloud cover, particularly in parts of northern, western and upland Ireland. This approach adds value to ground based forest monitoring by mapping distinct forests over large areas on an annual basis. This study has demonstrated the ability to apply the algorithm to three different study areas, with a vision to operationalise the algorithm on a national scale. The main limitations experienced in this study were the lack of L-band SAR data availability and reference datasets. With typically only one image acquired per year, and discrepancies and omissions existing within reference datasets, understanding the behaviour of certain cluster groups representing disturbances was challenging. However, this approach has addressed some issues within the reference datasets, for example locating areas for which a felling licence was granted but where trees were never cut, by providing detailed systematic mapping of forests. Future satellites such as Tandem-L, SAOCOM-2A and 2B, P-band BIOMASS mission and ALOS-4 PALSAR-3 may overcome the issue of limited SAR image acquisitions provided more images per year are available, especially during the summer months.
Robots are mechanical systems that perform tasks through a series of perception, cognition, and manipulation steps. Robots with dimensions between 10-9 -10-4 m are classified as micro/nanobots. These are often called micro/nanoswimmers (or micro/nanomotors) since most micro/nanobots are used in liquid environments. These tiny robots can be precisely guided to locations where human access is restricted. Consequently, micro/nanobots are widely applicable in different fields, including environmental cleaning, medicine, exploration, and military applications. Micro/nanobots (or micro/nanoswimmers) are often designed differently from their macro-sized counterparts for two reasons. First, while macro-sized robots typically use onboard batteries, micro/nanobots generally use external energy sources, such as chemical, magnetic, electric, acoustic, and optical energy, due to the current technological restriction of battery miniaturization. Second, micro/nanobots must create a propulsive force differently than macro-sized robots. Unlike macro-sized robots, micro/nanobots swimming in a Newtonian liquid by reciprocal motion show zero net displacement since the drag force exerted on objects dominates over the inertial force at such small scales. Methods to create propulsive forces in micro/nanobots can be inspired by small-scale living entities. For example, microorganisms create propulsive forces by using non-reciprocal motion, such as spermatozoon and bacterial flagellum that use undulatory and cork-screw locomotion, respectively. The purpose of this dissertation is to design and fabricate micro/nanobots and study their propulsion mechanisms. Four micro/nanobots are newly designed by tuning properties of micro/nanobots, such as geometry, material, physical, and chemical properties. Furthermore, their propulsion mechanisms are understood for efficient and controlled propulsion by fully characterizing their resultant locomotion in Newtonian fluids. In the first chapter, general knowledge of micro/nanobots, including definition and theory of micro/nanobots, is introduced. In the following chapters (chapter 2-4), the state of the art of micro/nanobots actuated by different external energies is thoroughly reviewed, especially focusing on the effect of the design of micro/nanobots on their locomotion and propulsion mechanisms in fluids. Newly developed micro/nanobots are introduced in each chapter, consisting of subsections addressing motivation, experimental methods, results and discussion, and conclusion. Chapter 2 reports catalytically driven core−shell nanowires. The investigated catalytic locomotion in H2O2 solution shows that, unlike conventional bimetallic nanowires that are self-electroosmotically propelled, our core−shell nanowires show both a noticeable decrease in rotational diffusivity and increase in motor speed with increasing nanowire length. Numerical modeling based on self-electroosmosis attributes decreases in rotational diffusivity to the formation of toroidal vortices at the nanowire tail, but fails to explain the speed increase with length. To reconcile this inconsistency, we propose a combined mechanism of self-diffusiophoresis and electroosmosis based on the oxygen gradient produced by catalytic shells. The possible contribution of diffusiophoresis to an otherwise well-established electroosmotic mechanism sheds light on future designs of nanobots, at the same time highlighting the complex nature of nanoscale propulsion. Chapter 3 reports multi-wavelength light-responsive Janus microbots consisting of black TiO2 microspheres asymmetrically coated with a thin Au layer. Conventional photocatalytic micro/nanobots are limited to the use of specific wavelengths of light due to their narrow light absorption spectrum, which limits their effectiveness for applications in biomedicine and environmental remediation. Unlike conventional robots, our microbots are propelled by light, both in H2O2 solutions and in pure H2O over a broad range of wavelengths including UV, blue, cyan, green, and red light. An analysis of the motion of the robots shows that the robot speed decreases with increasing wavelength, which has not been previously realized. A significant increase in robot speed is observed when exploiting the entire visible light spectrum (>400 nm), suggesting a potential use of solar energy, which contains a great portion of visible light. Finally, stop−go motion is also demonstrated by controlling the visible light illumination, a necessary feature for the steerability of micro/ and nanomachines. Chapter 4 reports two types of newly developed nanobots that are magnetically actuated. First, nanowire-based magnetic surface walkers are reported. The nanowires are made of hard-magnetic CoPt alloy synthesized by means of template-assisted galvanostatic electrodeposition. The hard-magnetic behavior of the nanowires allows their alignment to be programmed with an applied magnetic field, as they can retain their magnetization direction after pre-magnetizing them. Their propulsion mechanism can be changed as a function of the applied rotating magnetic field frequency. By engineering the macroscopic magnetization, the locomotion mechanism of the nanowires is set to tumbling, precession, or rolling depending on the frequency of an applied rotating magnetic field. In addition, vortices were found by tracking polystyrene microbeads trapped around the CoPt nanowire when they were propelled by precession or rolling motion. Second, magnetically driven multilink nanowires are reported. The employed manufacturing process enables tuning the geometrical and material properties of nanowires and, therefore, allow resembling the shape and swimming strategies of spermatozoon. The resultant structure comprises an elastic eukaryote-like polypyrrole tail and rigid magnetic nickel links connected by flexible polymer bilayer hinges. Under a planar oscillatory magnetic field, the multilink nanowires display planar undulations. The multilink design exhibits an increase in swimming efficiency with increasing numbers of hinges in the structure. Annex 1 covers important yet overlooked aspects in the fabrication of nanowires observed during the fabrication process of nanobots. We examine the junction quality of electrochemically grown segmented nanowires. We particularly focus on the Au-Co system to illustrate this aspect. Annex 2 provides a strategy to fabricate supported anodic aluminum oxide (AAO) membranes, which served as templates to grow long nanowires with modulated diameters. This approach was also employed to fabricate core-shell nanobot reported in chapter 2.
