Spherical Vesicles Distorted by a Grafted Latex Bead: An Exact Solution

We present an exact solution to the problem of the global shape description of a spherical vesicle distorted by a grafted latex bead. This solution is derived by treating the nonlinearity in bending elasticity through the (topological) Bogomol'nyi decomposition technique and elastic compatibility. We recover the ``hat-model'' approximation in the limit of a small latex bead and find that the region antipodal to the grafted latex bead flattens. We also derive the appropriate shape equation using the variational principle and relevant constraints.Comment: 12 pages, 2 figures, LaTeX2e+REVTeX+AmSLaTe

Advanced Filter Solutions for High-performance Millimetre and Submillimetre-wave Systems

This thesis is devoted to the investigation of advanced filter design solutions for high-performance millimetre and submillimetre-wave systems. Each of the proposed design solutions are enabled using waveguide-based technologies with the aim of advancing future generations of satellite communications, radar, and remote sensing. As trends for frequency allocations move to higher and higher frequency bands, engineers are faced with increasingly complex challenges such as the degradation of component performance, the inability to correctively tune the performance, or scenarios that all together make circuits infeasible. In light of these challenges, this work seeks to advance the current literature on filter design and proposes many unique design solutions for overcoming manufacturing and accuracy limitations, reducing the transmission losses, and reducing the overall design complexity. Each of the proposed filter solutions that are presented in this thesis are based on either a novel structural design or a novel technology. Each of the proposed designs are presented with functional prototypes as a means of verifying the theory. In the majority of cases, prototypes have been manufactured using high-precision computer numerical control (CNC) milling, and in several articles, exploratory activities with the use of alternative technologies such as stereolithography (SLA) 3D-printing and deep-reactive ion etching (DRIE) are presented. Prior to the presentation of the filter designs, an overview on the design and synthesis of millimetre-wave filters and diplexers is provided and serves as a foundation for the coupling matrix descriptions of symmetric and asymmetric resonator designs throughout this work

Development of an anatomically correct mouse phantom for dosimetry measurement in small animal radiotherapy research

Significant improvements in radiotherapy are likely to come from biological rather than technical optimization, for example increasing tumour radiosensitivity via combination with targeted therapies. Such paradigms must first be evaluated in preclinical models for efficacy, and recent advances in small animal radiotherapy research platforms allow advanced irradiation protocols, similar to those used clinically, to be carried out in orthotopic models. Dose assessment in such systems is complex however, and a lack of established tools and methodologies for traceable and accurate dosimetry is currently limiting the capabilities of such platforms and slowing the clinical uptake of new approaches. Here we report the creation of an anatomically correct phantom, fabricated from materials with tissue-equivalent electron density, into which dosimetry detectors can be incorporated for measurement as part of quality control (QC). The phantom also allows training in preclinical radiotherapy planning and cross-institution validation of dose delivery protocols for small animal radiotherapy platforms without the need to sacrifice animals, with high reproducibility.Mouse CT data was acquired and segmented into soft tissue, bone and lung. The skeleton was fabricated using 3D printing, whilst lung was created using computer numerical control (CNC) milling. Skeleton and lung were then set into a surface-rendered mould and soft tissue material added to create a whole-body phantom. Materials for fabrication were characterized for atomic composition and attenuation for x-ray energies typically found in small animal irradiators. Finally cores were CNC milled to allow intracranial incorporation of bespoke detectors (alanine pellets) for dosimetry measurement

Numerical tools for computational design of acoustic metamaterials

The notion of metamaterials as artificially engineered structures designed to obtain specific material properties, typically unachievable in naturally occurring materials, has captured the attention of the scientific and industrial communities. Among the broad range of applications for such kind of materials, in the field of acoustics, the possibility of creating materials capable of efficiently attenuating noise in target frequency ranges is of utmost importance for a lot of industrial areas. In this context, the so-called locally resonant acoustic metamaterials (LRAMs) can play an important role, as their internal topology can be designed to exhibit huge levels of attenuation in specific frequency regions by taking advantage of internal resonance modes. With a proper, optimized topological design, LRAMs can be used, for instance, to build lightweight and thin noise insulation panels that operate in a low-frequency regime, where standard solutions for effectively attenuating the noise sources require dense and thick materials. Given the importance of the topological structure in obtaining the desired properties in acoustic metamaterials, the use of novel numerical techniques can be exploited to cre-ate a set of computational tools aimed at the analysis and design of optimized solutions. These are based on three fundamental pillars: (1) the multiscale homogenization of complex material structures in the microscale to get a set of effective properties capa-ble of describing the material behavior in the macroscale, (2) the model-order reduc-tion techniques, which are used to decrease the computational cost of heavy computa-tions while still maintaining a sufficient degree of accuracy, and (3) the topology optimi-zation methods that can be employed to obtain optimal configurations with a given set of constraints and a target material behavior. This set of computational tools can be applied to design acoustic metamaterials that are both efficient and practical, i.e. they behave according to their design specifications and can be produced easily, for in-stance, making use of novel additive manufacturing techniques.La concepció dels metamaterials com a estructures dissenyades artificialment amb l’objectiu d’obtenir un conjunt de propietats que no són assolibles en materials de manera natural, ha captat l’atenció de les comunitats científiques i industrials. Dins de l’ampli ventall d’aplicacions que se’ls pot donar als metamaterials, si ens centrem en el camp de l’acústica, la possibilitat de crear un material capaç d’atenuar de manera efectiva sorolls en rangs de freqüència concrets és de gran interès en multitud d’indústries. En aquest context, els anomenats “locally resonant acoustic metamaterials” (LRAMs) destaquen per la possibilitat de dissenyar la seva topologia interna per tal que produeixin elevats nivells d’atenuació en regions concretes de l’espectre de freqüències. Amb un disseny topològic òptim, els LRAMs poden servir, per exemple, per a la construcció de panells lleugers aïllants de soroll, que operin en rangs de freqüències baixos, en els quals la solució clàssica requereix de materials d’elevada densitat i espessor. Donada la importància de l’estructura topològica dels metamaterials acústics en l’obtenció de les propietats desitjades, resulta convenient l’ús de mètodes numèrics punters per al desenvolupament d’un conjunt d’eines computacionals que tinguin per objectiu l’anàlisi i el disseny de solucions òptimes. Tals eines es fonamenten en tres pilars: (1) la homogeneïtzació multiescala d’estructures de material complexes a una escala micro que derivi en l’obtenció de propietats efectives que permetin descriure el comportament del material a una escala macro, (2) tècniques de reducció per minimitzar l’esforç computacional mantenint nivells de precisió suficients i (3) mètodes d’optimització topològica emprats per a l’obtenció de configuracions òptimes donat un conjunt de restriccions i unes propietats de material objectiu. Aquestes eines computacionals es poden aplicar al disseny de metamaterials acústics que resultin eficients i pràctics a la vegada, és a dir, que es comportin segons les especificacions de disseny i siguin fàcilment fabricables, per exemple, mitjançant tècniques punteres d’impressió 3D

Numerical tools for computational design of acoustic metamaterials

Tesi en modalitat de compendi de publicacionsThe notion of metamaterials as artificially engineered structures designed to obtain specific material properties, typically unachievable in naturally occurring materials, has captured the attention of the scientific and industrial communities. Among the broad range of applications for such kind of materials, in the field of acoustics, the possibility of creating materials capable of efficiently attenuating noise in target frequency ranges is of utmost importance for a lot of industrial areas. In this context, the so-called locally resonant acoustic metamaterials (LRAMs) can play an important role, as their internal topology can be designed to exhibit huge levels of attenuation in specific frequency regions by taking advantage of internal resonance modes. With a proper, optimized topological design, LRAMs can be used, for instance, to build lightweight and thin noise insulation panels that operate in a low-frequency regime, where standard solutions for effectively attenuating the noise sources require dense and thick materials. Given the importance of the topological structure in obtaining the desired properties in acoustic metamaterials, the use of novel numerical techniques can be exploited to cre-ate a set of computational tools aimed at the analysis and design of optimized solutions. These are based on three fundamental pillars: (1) the multiscale homogenization of complex material structures in the microscale to get a set of effective properties capa-ble of describing the material behavior in the macroscale, (2) the model-order reduc-tion techniques, which are used to decrease the computational cost of heavy computa-tions while still maintaining a sufficient degree of accuracy, and (3) the topology optimi-zation methods that can be employed to obtain optimal configurations with a given set of constraints and a target material behavior. This set of computational tools can be applied to design acoustic metamaterials that are both efficient and practical, i.e. they behave according to their design specifications and can be produced easily, for in-stance, making use of novel additive manufacturing techniques.La concepció dels metamaterials com a estructures dissenyades artificialment amb l’objectiu d’obtenir un conjunt de propietats que no són assolibles en materials de manera natural, ha captat l’atenció de les comunitats científiques i industrials. Dins de l’ampli ventall d’aplicacions que se’ls pot donar als metamaterials, si ens centrem en el camp de l’acústica, la possibilitat de crear un material capaç d’atenuar de manera efectiva sorolls en rangs de freqüència concrets és de gran interès en multitud d’indústries. En aquest context, els anomenats “locally resonant acoustic metamaterials” (LRAMs) destaquen per la possibilitat de dissenyar la seva topologia interna per tal que produeixin elevats nivells d’atenuació en regions concretes de l’espectre de freqüències. Amb un disseny topològic òptim, els LRAMs poden servir, per exemple, per a la construcció de panells lleugers aïllants de soroll, que operin en rangs de freqüències baixos, en els quals la solució clàssica requereix de materials d’elevada densitat i espessor. Donada la importància de l’estructura topològica dels metamaterials acústics en l’obtenció de les propietats desitjades, resulta convenient l’ús de mètodes numèrics punters per al desenvolupament d’un conjunt d’eines computacionals que tinguin per objectiu l’anàlisi i el disseny de solucions òptimes. Tals eines es fonamenten en tres pilars: (1) la homogeneïtzació multiescala d’estructures de material complexes a una escala micro que derivi en l’obtenció de propietats efectives que permetin descriure el comportament del material a una escala macro, (2) tècniques de reducció per minimitzar l’esforç computacional mantenint nivells de precisió suficients i (3) mètodes d’optimització topològica emprats per a l’obtenció de configuracions òptimes donat un conjunt de restriccions i unes propietats de material objectiu. Aquestes eines computacionals es poden aplicar al disseny de metamaterials acústics que resultin eficients i pràctics a la vegada, és a dir, que es comportin segons les especificacions de disseny i siguin fàcilment fabricables, per exemple, mitjançant tècniques punteres d’impressió 3D.Postprint (published version

Design and Implementation of an Integrated Biosensor Platform for Lab-on-a-Chip Diabetic Care Systems

Recent advances in semiconductor processing and microfabrication techniques allow the implementation of complex microstructures in a single platform or lab on chip. These devices require fewer samples, allow lightweight implementation, and offer high sensitivities. However, the use of these microstructures place stringent performance constraints on sensor readout architecture. In glucose sensing for diabetic patients, portable handheld devices are common, and have demonstrated significant performance improvement over the last decade. Fluctuations in glucose levels with patient physiological conditions are highly unpredictable and glucose monitors often require complex control algorithms along with dynamic physiological data. Recent research has focused on long term implantation of the sensor system. Glucose sensors combined with sensor readout, insulin bolus control algorithm, and insulin infusion devices can function as an artificial pancreas. However, challenges remain in integrated glucose sensing which include degradation of electrode sensitivity at the microscale, integration of the electrodes with low power low noise readout electronics, and correlation of fluctuations in glucose levels with other physiological data. This work develops 1) a low power and compact glucose monitoring system and 2) a low power single chip solution for real time physiological feedback in an artificial pancreas system. First, glucose sensor sensitivity and robustness is improved using robust vertically aligned carbon nanofiber (VACNF) microelectrodes. Electrode architectures have been optimized, modeled and verified with physiologically relevant glucose levels. Second, novel potentiostat topologies based on a difference-differential common gate input pair transimpedance amplifier and low-power voltage controlled oscillators have been proposed, mathematically modeled and implemented in a 0.18μm [micrometer] complementary metal oxide semiconductor (CMOS) process. Potentiostat circuits are widely used as the readout electronics in enzymatic electrochemical sensors. The integrated potentiostat with VACNF microelectrodes achieves competitive performance at low power and requires reduced chip space. Third, a low power instrumentation solution consisting of a programmable charge amplifier, an analog feature extractor and a control algorithm has been proposed and implemented to enable continuous physiological data extraction of bowel sounds using a single chip. Abdominal sounds can aid correlation of meal events to glucose levels. The developed integrated sensing systems represent a significant advancement in artificial pancreas systems

Mechanisms of deterioration of nutrients

The retention of flavor during freeze drying was studied with model systems. Mechanisms by which flavor retention phenomena is explained were developed and process conditions specified so that flavor retention is optimized. The literature is reviewed and results of studies of the flavor retention behavior of a number of real food products, including both liquid and solid foods are evaluated. Process parameters predicted by the mechanisms to be of greatest significance are freezing rate, initial solids content, and conditions which result in maintenance of sample structure. Flavor quality for the real food showed the same behavior relative to process conditions as predicted by the mechanisms based on model system studies

Metal-Organic Frameworks in Germany: from Synthesis to Function

Metal-organic frameworks (MOFs) are constructed from a combination of inorganic and organic units to produce materials which display high porosity, among other unique and exciting properties. MOFs have shown promise in many wide-ranging applications, such as catalysis and gas separations. In this review, we highlight MOF research conducted by Germany-based research groups. Specifically, we feature approaches for the synthesis of new MOFs, high-throughput MOF production, advanced characterization methods and examples of advanced functions and properties