Precision manipulation of organic and inorganic nanoentities for enhanced optical biodetection at deterministic positions

In the last decade, considerable research interests are focused on applying semiconductor quantum dots (QDs) for bioimaging, sensing, and therapeutic delivery. Compared to traditional organic dyes, semiconductor QDs exhibit higher fluorescent brightness, better resistance to photo-bleaching, tunable sizes/colors, wider absorption peak and larger stokes shifts. However, the applications of QDs as biosensors are still largely conducted in bulk colloidal suspensions, which present considerable difficulties in sensing a minute amount of bioanalyte. It is highly desirable if the QDs can be registered at designated locations for position-predicable optical analysis and sensing. Raman scattering spectroscopy has been utilized to unambiguously identify molecules based on their intrinsic vibrational "fingerprint" states. However, due to the relatively small Raman scattering cross-section, the intensity of Raman signal is usually 1/10⁶ of that of Rayleigh scattering. The recent discovery of Surface enhanced Raman scattering (SERS) dramatically improves the Raman signal and rejuvenates this field. An enhancement factor (EF) as high as 10¹² have been reported, which can readily detect various single molecules, essential for early-stage disease detection, warfare agent detection, environmental pollutant detection, and biomolecule detection. However, SERS substrates with such high EF usually suffer from reproducibility and uniformity issues. Moreover, SERS detection is still largely conducted in a seek-and-find manner which substantially limits the detection efficiency. Most SERS detections are carried out by drying analyte solutions on SERS substrates to force molecules to attach to hotspots before the detection. The employed drying methods can be different among individual research groups. Quantitative comparison of these results should be conducted carefully. It is highly desirable to directly detect molecules in suspension to accurately evaluate the performances of different SERS substrates. However, when directly measuring SERS signals of molecules in suspension, due to the inefficient diffusion based binding process, much less molecules can closely interact with hot spots compared to those on dried SERS samples. As a result, direct SERS detection from suspension can often be less sensitive by a few orders of magnitudes compares to those in dried condition. It is of great interest to investigate new mechanisms to detect analyte molecules directly from analyte solutions with high sensitivity. In this research, I rationally designed and synthesized various types of nanostructures, including ZnO, Si, and Au nanowires, ZnO nanosuperstructures, and hybrid nanocapsules. Such materials have unique optical/plasmonic properties and could be used in various applications, particularly in biochemical sensing. Two types of optical nanobiosensors have been designed, fabricated, characterized, and investigated. They are fluorescence-based QD-on-nanowire assemblies and SERS-photonic-crystal hybrid nanosensors. The QD-on-nanowire florescent nanosensors operated uniquely by focusing analyte molecules to the assembled QDs on tips of nanowires before detection via specific biochemical conjugation. Molecules, such as biotin, can be revealed unambiguously in a location deterministic manner with substantially enhanced sensitivity. In the development of SERS-photonic-crystal hybrid nanosensors, two enhancement mechanisms, including guided-mode resonance (GMR) and electrokinetic effect, were studied and applied in improving the sensitivity and efficiency of molecule detection, respectively. Such a hybrid device has been proposed and studied for the first time, which can readily improve the detection sensitivity by a robust 4-5 times in addition to the 10⁹-10¹⁰ SERS enhancement. This dissertation work, exploring innovative materials design, synthesis, and manipulation, has made an important forward step in the next-generation biochemical detection platform.Materials Science and Engineerin

Interferometric gravitational wave detectors vibrational isolation

Interferometric Gravitational Wave Detectors, coming online lin late 2000, look for small space strains, leading to apparent motions of test masses of 10-19 m or less; isolation from other forces is crucial. They require a formidable vibration isolation level in a frequency range between few Hz and few kHz. The off-band residual motion must be kept below 10-12 m not to saturate the phase sensors. These exceptional requirements are met, in all degrees of freedom, with a chain of active and passive filters. The key isolation mechanism is the use of mechanical oscillators above their resonant frequencies, pendula horizontally, springs vertically. Very high quality pendular suspensions are needed at the mirror level to limit the thermal noise from fluctuations in the dissipation mechanisms. Off-band electromagnetic actuators on or near the mirror keep its magnitude of attenuation in the longitudinal direction. To provide the bulk of the attenuation, virtually all in the vertical direction, they are suspended from Seismic Noise Attenuation Systems. Attenuation filters, either active or passive, are chained, each providing 2 or 3 orders of magnitude of attenuation. Passive attenuation is obtained with springs and pendula. The vertical is the toughest direction to deal with because the oscillators also fight against gravity. The vertical attenuation requirements, although orthogonal to the beam direction, are only slightly less stringent than the vertical ones due to cross-couplings (Earth curvature is the source of one of them). High internal damping springs organized in hierarchical stacks are used in most early designs. More advanced designs increasingly rely on chains of filters equipped with high quality cantilever springs driven to low resonant frequencies by different mechanisms. The Quality Factors of each resonance are actively and/or passively spoiled at the chain suspension point. IN the latest designs, Ultra Low Frequency Oscillators filter out the microseismic and other low frequency perturbations. This paper addresses one approach to achieving the required seismic isolation level

Detector Description and Performance for the First Coincidence Observations between LIGO and GEO

For 17 days in August and September 2002, the LIGO and GEO interferometer gravitational wave detectors were operated in coincidence to produce their first data for scientific analysis. Although the detectors were still far from their design sensitivity levels, the data can be used to place better upper limits on the flux of gravitational waves incident on the earth than previous direct measurements. This paper describes the instruments and the data in some detail, as a companion to analysis papers based on the first data.Comment: 41 pages, 9 figures 17 Sept 03: author list amended, minor editorial change

Development of an anthropomorphic mobile manipulator with human, machine and environment interaction

An anthropomorphic mobile manipulator robot (CHARMIE) is being developed by the University of Minho's Automation and Robotics Laboratory (LAR). The robot gathers sensorial information and processes using neural networks, actuating in real time. The robot's two arms allow object and machine interaction. Its anthropomorphic structure is advantageous since machines are designed and optimized for human interaction. Sound output allows it to relay information to workers and provide feedback. Allying these features with communication with a database or remote operator results in establishment of a bridge between the physical environment and virtual domain. The goal is an increase in information flow and accessibility. This paper presents the current state of the project, intended features and how it can contribute to the development of Industry 4.0. Focus is given to already finished work, detailing the methodology used for two of the robot's subsystems: locomotion system; lower limbs of the robot.- This project has been supported by the ALGORITMI Research Centre of University of Minho's School of Engineering

Microstructure, defects, and mechanical properties of wire + arc additively manufactured AlCu4.3-Mg1.5 alloy

The wire with a composition of AlCu4.3%Mg1.5% was customized and used to deposit the WAAM alloy with the power source of cold metal transfer. The microstructure, defect, and mechanical properties of the as-deposited and heat-treated WAAM alloys were studied. Key findings demonstrated that the microstructure of the as-deposited alloy was characterized by a hierarchical distribution of dendrites, equiaxed grains, and a slight number of columnar grains. The volume fraction of the network-like scattered coarse particles of second phases θ + S reduced by 95% after the T6 heat treatment. With an average microhardness of 161.4 HV, the mean yield strength and ultimate tensile strength of the WAAM alloy increased by 116% and 66% achieving 399 MPa and 485 MPa in the horizontal direction after heat treatment. The precipitation of a high density of needle-shaped metastable S′ precipitates was responsible for the significantly enhanced mechanical properties. However, this WAAM alloy has exhibited an anisotropic tensile property. A considerable number of sharp-angled defects like linear and chain-like micropores, which generally depress the mechanical properties, were formed in the WAAM alloys

Combination of metabolomic and proteomic analysis revealed different features among Lactobacillus delbrueckii subspecies bulgaricus and lactis strains while in vivo testing in the model organism Caenorhabditis elegans highlighted probiotic properties

Lactobacillus delbrueckii represents a technologically relevant member of lactic acid bacteria, since the two subspecies bulgaricus and lactis are widely associated with fermented dairy products. In the present work, we report the characterization of two commercial strains belonging to L. delbrueckii subspecies bulgaricus, lactis and a novel strain previously isolated from a traditional fermented fresh cheese. A phenomic approach was performed by combining metabolomic and proteomic analysis of the three strains, which were subsequently supplemented as food source to the model organism Caenorhabditis elegans, with the final aim to evaluate their possible probiotic effects. Restriction analysis of 16S ribosomal DNA revealed that the novel foodborne strain belonged to L. delbrueckii subspecies lactis. Proteomic and metabolomic approaches showed differences in folate, aminoacid and sugar metabolic pathways among the three strains. Moreover, evaluation of C. elegans lifespan, larval development, brood size, and bacterial colonization capacity demonstrated that L. delbrueckii subsp. bulgaricus diet exerted beneficial effects on nematodes. On the other hand, both L. delbrueckii subsp. lactis strains affected lifespan and larval development. We have characterized three strains belonging to L. delbrueckii subspecies bulgaricus and lactis highlighting their divergent origin. In particular, the two closely related isolates L. delbrueckii subspecies lactis display different galactose metabolic capabilities. Moreover, the L. delbrueckii subspecies bulgaricus strain demonstrated potential probiotic features. Combination of omic platforms coupled with in vivo screening in the simple model organism C. elegans is a powerful tool to characterize industrially relevant bacterial isolates