A Survey of Spatial Deformation from a User-Centered Perspective

The spatial deformation methods are a family of modeling and animation techniques for indirectly reshaping an object by warping the surrounding space, with results that are similar to molding a highly malleable substance. They have the virtue of being computationally efficient (and hence interactive) and applicable to a variety of object representations. In this paper we survey the state of the art in spatial deformation. Since manipulating ambient space directly is infeasible, deformations are controlled by tools of varying dimension - points, curves, surfaces and volumes - and it is on this basis that we classify them. Unlike previous surveys that concentrate on providing a single underlying mathematical formalism, we use the user-centered criteria of versatility, ease of use, efficiency and correctness to compare techniques

Interactive form creation: exploring the creation and manipulation of free form through the use of interactive multiple input interface

Most current CAD systems support only the two most common input devices: a mouse and a keyboard that impose a limit to the degree of interaction that a user can have with the system. However, it is not uncommon for users to work together on the same computer during a collaborative task. Beside that, people tend to use both hands to manipulate 3D objects; one hand is used to orient the object while the other hand is used to perform some operation on the object. The same things could be applied to computer modelling in the conceptual phase of the design process. A designer can rotate and position an object with one hand, and manipulate the shape [deform it] with the other hand. Accordingly, the 3D object can be easily and intuitively changed through interactive manipulation of both hands.The research investigates the manipulation and creation of free form geometries through the use of interactive interfaces with multiple input devices. First the creation of the 3D model will be discussed; several different types of models will be illustrated. Furthermore, different tools that allow the user to control the 3D model interactively will be presented. Three experiments were conducted using different interactive interfaces; two bi-manual techniques were compared with the conventional one-handed approach. Finally it will be demonstrated that the use of new and multiple input devices can offer many opportunities for form creation. The problem is that few, if any, systems make it easy for the user or the programmer to use new input devices

Physical non-viral gene delivery methods for tissue engineering

The integration of gene therapy into tissue engineering to control differentiation and direct tissue formation is not a new concept; however, successful delivery of nucleic acids into primary cells, progenitor cells, and stem cells has proven exceptionally challenging. Viral vectors are generally highly effective at delivering nucleic acids to a variety of cell populations, both dividing and non-dividing, yet these viral vectors are marred by significant safety concerns. Non-viral vectors are preferred for gene therapy, despite lower transfection efficiencies, and possess many customizable attributes that are desirable for tissue engineering applications. However, there is no single non-viral gene delivery strategy that “fits-all” cell types and tissues. Thus, there is a compelling opportunity to examine different non-viral vectors, especially physical vectors, and compare their relative degrees of success. This review examines the advantages and disadvantages of physical non-viral methods (i.e., microinjection, ballistic gene delivery, electroporation, sonoporation, laser irradiation, magnetofection, and electric field-induced molecular vibration), with particular attention given to electroporation because of its versatility, with further special emphasis on Nucleofection™. In addition, attributes of cellular character that can be used to improve differentiation strategies are examined for tissue engineering applications. Ultimately, electroporation exhibits a high transfection efficiency in many cell types, which is highly desirable for tissue engineering applications, but electroporation and other physical non-viral gene delivery methods are still limited by poor cell viability. Overcoming the challenge of poor cell viability in highly efficient physical non-viral techniques is the key to using gene delivery to enhance tissue engineering applications

Innovative robot hand designs of reduced complexity for dexterous manipulation

This thesis investigates the mechanical design of robot hands to sensibly reduce the system complexity in terms of the number of actuators and sensors, and control needs for performing grasping and in-hand manipulations of unknown objects. Human hands are known to be the most complex, versatile, dexterous manipulators in nature, from being able to operate sophisticated surgery to carry out a wide variety of daily activity tasks (e.g. preparing food, changing cloths, playing instruments, to name some). However, the understanding of why human hands can perform such fascinating tasks still eludes complete comprehension. Since at least the end of the sixteenth century, scientists and engineers have tried to match the sensory and motor functions of the human hand. As a result, many contemporary humanoid and anthropomorphic robot hands have been developed to closely replicate the appearance and dexterity of human hands, in many cases using sophisticated designs that integrate multiple sensors and actuators---which make them prone to error and difficult to operate and control, particularly under uncertainty. In recent years, several simplification approaches and solutions have been proposed to develop more effective and reliable dexterous robot hands. These techniques, which have been based on using underactuated mechanical designs, kinematic synergies, or compliant materials, to name some, have opened up new ways to integrate hardware enhancements to facilitate grasping and dexterous manipulation control and improve reliability and robustness. Following this line of thought, this thesis studies four robot hand hardware aspects for enhancing grasping and manipulation, with a particular focus on dexterous in-hand manipulation. Namely: i) the use of passive soft fingertips; ii) the use of rigid and soft active surfaces in robot fingers; iii) the use of robot hand topologies to create particular in-hand manipulation trajectories; and iv) the decoupling of grasping and in-hand manipulation by introducing a reconfigurable palm. In summary, the findings from this thesis provide important notions for understanding the significance of mechanical and hardware elements in the performance and control of human manipulation. These findings show great potential in developing robust, easily programmable, and economically viable robot hands capable of performing dexterous manipulations under uncertainty, while exhibiting a valuable subset of functions of the human hand.Open Acces

Novel variant for application as a prolonged release drug delivery system

A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science in Medicine 2015The dissertation aims to discuss the disulphide and thiol chemistry for use in drug delivery. In particular it focuses on the use of the modified native ovalbumin polymer as a vehicle for the thiol containing captopril. The binding capabilities of thiols expand the area in which peptides and proteins can be used as potential therapeutic drug carriers. It is important that drug delivery systems enhance drug storage stability and in vivo particle stability while delivering the drug efficiently. As part of the developing novel drug delivery systems, thiol-based chemical reactions are distinctive role players in stabilizing disulphide bioconjugated nanostructures for use as efficient drug carrier vehicles in vivo. A review of the current approaches for designing, optimizing and functionalizing nanostructures and conjugates by thiol chemistry modifications was explored. Captopril (Cp) is an Angiotensin-Converting Enzyme (ACE) inhibitor, which acts as an anti-hypertensive, structurally contains a free reactive thiol that binds variably via the thiol/disulphide reaction. A single dose of captopril can regulate hypertension for up to eight hours and the duration of the antihypertensive action of a single dose of 35-75 mg would be taken at 8 hour intervals for 24 hours. Hence the necessities in developing a sustained controlled release ovalbumin carrier system to maintain relatively constant blood pressure levels for 24 hours. The research focused on the construction, characterization and optimization of the thiol conjugated complex for sustained oral drug delivery. The thiol/disulphide-functionalized captopril-ovalbumin conjugate complex was assessed in terms of the structural characteristics and the thiol-disulphide covalent substitution reaction. For analysis of the conjugation complex, the Fourier Transmission IR-spectroscopy (FTIR), H+ NMR and Differential Scanning Calorimetry (DSC) was performed and used to confirm conjugation. Preliminary studies focused on a comparative study of sodium alginate, polyvinyl alcohol and hydroxypropylmethylcellulose hydrogel formulations for the release testing and drug entrapment of the ovalbumin-captopril conjugate complex. Utilizing this data, a series of process variables were used to achieve an optimized formulation through a Box- Behnken statistical design. Furthermore the drug release profiles of the optimised formulation were then analyzed in vitro and in vivo. The captopril released from the formulation was high with a cumulative release of 82%. In vivo analysis was the final testing to verify the validity of the ovalbumin-captopril conjugate complex encapsulated in sodium alginate and utilized a pig model. Ultra Performance Liquid Chromatography (UPLC) blood analysis revealed increased blood levels of captopril (Cmax Cp=33.2ng/mL) in relation to conventional dosage forms validating prolonged (24 hour) site-specific release and increased bioavailability. In conclusion, our validated method was successfully applied to the pharmacokinetic studies of captopril in the blood plasma samples

Enhancing the Thermoelectric Performance of Calcium Cobaltite through Cation Substitution and Non-Stoichiometric Addition

Thermoelectric (TE) materials have the unique ability to convert temperature differences directly into electricity due to the Seebeck effect. Thermoelectric generators have a variety of applications including waste heat recovery for power plants and automotives. For high-temperature waste-heat recovery, misfit layered calcium cobaltite, Ca3Co4O9, is one of the most promising p-type TE oxides offering good durability in air with low cost and minimized environmental impact. A challenge for developing polycrystalline calcium cobaltite TE materials is to improve its energy conversion efficiency for large scale applications. The energy conversion efficiency of TE materials is characterized using the figure-of-merit ZT, which is defined as ZT = S2rho -1K-1T, where S, rho, S 2rho-1, K-1, and T are Seebeck coefficient, electrical resistivity, power factor, thermal conductivity, and temperature respectively. State of the art commercial conventional TE materials, such as bismuth telluride (Bi2Te3) and lead telluride (PbTe), possess values of ZT ≈ 1, which corresponds to an energy conversion efficiency of 10%. Calcium cobaltite single crystals show extraordinary TE performance with an extrapolated ZT value of 0.87 at 973 K.4 By contrast, the TE performance of polycrystals is reported to be only ~20% of that from the single crystal and with the commonly measured ZT of ~0.2 at ~900 K. This dissertation focuses on improving the performance of polycrystalline Ca3Co4O9 ceramics for large scale applications. The present work demonstrates the feasibility of increasing the values of Seebeck coefficient, S and power factor of calcium cobaltite Ca3Co4O9 ceramics through dopant grain boundary (GB) segregation. For the first time in the field of thermoelectrics, various dopants which include Bi, Ba, and co-dopants Bi-Ba were proved to segregate to the GBs and dramatically increased the ZT of Ca3Co4O9, and a high ZT of 0.52 was achieved for Ca3Co4O9 ceramics through dopants grain boundary segregation. The method of introducing the dopants to the grain boundaries, and their origin of the performance enhancement of thermoelectric oxide ceramics were thoroughly investigated and presented in this dissertation

Mechanobiological Modulation of Cytoskeleton and Calcium Influx in Osteoblastic Cells by Short-Term Focused Acoustic Radiation Force

Mechanotransduction has demonstrated potential for regulating tissue adaptation in vivo and cellular activities in vitro. It is well documented that ultrasound can produce a wide variety of biological effects in biological systems. For example, pulsed ultrasound can be used to noninvasively accelerate the rate of bone fracture healing. Although a wide range of studies has been performed, mechanism for this therapeutic effect on bone healing is currently unknown. To elucidate the mechanism of cellular response to mechanical stimuli induced by pulsed ultrasound radiation, we developed a method to apply focused acoustic radiation force (ARF) (duration, one minute) on osteoblastic MC3T3-E1 cells and observed cellular responses to ARF using a spinning disk confocal microscope. This study demonstrates that the focused ARF induced F-actin cytoskeletal rearrangement in MC3T3-E1 cells. In addition, these cells showed an increase in intracellular calcium concentration following the application of focused ARF. Furthermore, passive bending movement was noted in primary cilium that were treated with focused ARF. Cell viability was not affected. Application of pulsed ultrasound radiation generated only a minimal temperature rise of 0.1°C, and induced a streaming resulting fluid shear stress of 0.186 dyne/cm2, suggesting that hyperthermia and acoustic streaming might not be the main causes of the observed cell responses. In conclusion, these data provide more insight in the interactions between acoustic mechanical stress and osteoblastic cells. This experimental system could serve as basis for further exploration of the mechanosensing mechanism of osteoblasts triggered by ultrasound

Investigation of Network Architecture Development and Properties in Thermoset Matrices

Matrices employed in composite materials directly influence overall composite properties. In all thermoset materials, molecular level interactions and transformations during cure result in heterogeneous architecture. Variability in connectivity results from the often dramatic spatial and topological changes that occur during the crosslinking process. Compatibility (fillers, pigments, additives), temperature gradients and reactivity differences in the precursors only serve to increase the complexity of network formation. The objective of the research herein is to characterize and understand the relationships between cure conditions, conversion, connectivity, network architecture and properties in glassy thermosetting matrix resins. In this research, epoxy and vinyl ester resins (VERs) were characterized to identify controlling factors in the development of network architecture and understand how they affect the mechanical properties. VERs cure under low temperature conditions (\u3c 50 °C) via redox catalysis resulted in vitrification limiting conversion with resulting glass transition temperatures (Tgs) approximately 15 °C above the cure temperature. Subsequently, in situ ligand exchange altered the activity of the metal catalyst, and the reduced connectivity of the resulting networks translated into a 30% reduction in stiffness above Tg. Network architecture was further manipulated by changing the chemical composition of the backbone. Incorporation of POSS nanoparticles into VERs resulted in changes to initial network development, with higher levels of conversion prior to vitrification. 3,3’-DDS was cured with a variety of epoxies and examined for conversion, connectivity and mechanical properties. Comparison with 4,4’-DDS revealed significant correlations between molecular level structure and properties. The research established relationships between cure conditions, conversion, connectivity and properties in glassy thermosetting matrix resins. Specifically, the importance of early stages of network development was correlated to ultimate properties. Network architecture is sensitive to the mobility, concentration and rate of matrix development. These parameters can be altered through changes in temperature or initiating system. Control of the network architecture and ultimately mechanical properties can be achieved by tailoring reaction rate and mobility appropriately. Rapid conversion with inadequate mobility increases heterogeneity and reduces mechanical viability through poor connectivity. Conversion must occur at rates comparable to mobility to ensure high conversion and excellent connectivity to maximize mechanical properties