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All-optical approaches to particle acceleration are currently attracting a significant research effort internationally. Key to the interest in a laser based particle accelerator lies in its cost effective and compactness. However, the ion beams accelerated by the laser-driven mechanisms have shortcomings such as a broad energy spectrum and large beam divergence. A recently developed concept of a versatile, miniature linear accelerating module harnesses the extremely high electromagnetic pulses produced by the interaction of intense lasers, and achieves simultaneous focusing, energy selection and post-acceleration of the proton beams. The process boosts the energy of the ions accelerated from the foil, through the application of a large amplitude field within a helical coil, which travels synchronously with the ions. This process lends itself to multi-staging, i.e. the sequential application of laser-driven accelerating fields, which is highly promising for significant increase of the accelerated proton energies. The project aims to develop this multi-stage approach which is totally new in the context of laser-driven protons, and can pave the way towards miniature, modular ion accelerators providing beams suitable for medical, scientific and industrial applications.

The suspension system in vehicles supports the vehicle's road stability and ride quality by scaling down the vibration responses resulting from road surface's roughness. This research focuses on fatigue life analysis of coil spring component. Static linear analysis is conducted on the 3D model of helical coil spring to investigate deformation and stress responses. Modal analysis evaluates the characteristics of vibration, i.e. natural resonance frequencies and corresponding mode shapes. The stress frequency response is generated after performing the harmonic analysis on the spring. Dynamics and performance of spring are analyzed over practical frequency range of 0 Hz to 200 Hz. Fatigue life estimation of vehicle suspension spring is performed using the stress data obtained from frequency response analysis. The stress-life (S-N) approach is utilized for fatigue life assessment of suspension spring. This durability analysis technique can be utilized in the automotive industry to improve reliability of vehicles. The outcome of this research can contribute in analysis and design of modern smart vehicles.

Regulation of brain temperature is critical for managing heat stress-related adverse events. It can be achieved by external cooling of the head. Head cooling systems that are lightweight, portable, and suitable for active work scenarios, such as firefighting, mining, and construction work, are currently unavailable on the market. This study proposes a novel active head cooling system that a) uses phase change material for thermal storage and b) can be designed for portability. The closed-loop bench-top system consists of two heat exchangers: a water-cooled heat exchanger with an attached heater, mimicking heat generated from the head, and a helical tube heat exchanger surrounded with ice as a heat sink. These heat exchanges are interconnected by tubing for water circulation. The system performance is assessed by the cooling duration that depends on the mass of ice used and the heat transfer rate. The system was evaluated for different heat loads varying from rest to exercise condition (20 W – 40 W) and flowrates (0.25 l/min – 0.65 l/min). The results show that the system can handle a heat generation rate of 40 W from the head for 100 min (for the flowrate of 0.25 l/min), which is about 3 times the safe duration of firefighting drills. The cooling time increases linearly with decreasing heat load: 138 min for 30 W and 190 min for 20 W, an increase of 38%, and 90%, respectively. It also increases with a decreasing flow rate. The range of Nusselt number for helical coil flow is about 4.4 – 6.8 times higher when compared to that of a straight pipe flow. The helical design of the heat exchanger leads to enhanced heat transfer owing to the formation of Dean’s vortical flow. The results suggest that the head cooling system, having possible features of being portable, cost-effective, lightweight, and easy to use, can assist in the thermoregulation of brain temperature for workers during elevated thermal stress conditions.

Real-time data of power infrastructures collected by wireless sensors are the foundation of many smart grid applications. However, the finite life span of the batteries which power the wireless sensor becomes a bottleneck problem as it is expensive to periodically replace these batteries. Energy harvesting can be an effective solution for autonomous, self-powered wireless sensors. In the vicinity of high voltage/current equipment, a strong magnetic field is generated, which could be a consistent energy source. The purpose of this thesis is to present a comprehensive study into a magnetic field energy harvesting system which mainly consists of coil and rectifying circuit with the ultimate goal to obtain the maximum energy as efficiently as possible for a given condition. The main contribution of this thesis is in two research areas: The first area is about the design of an energy harvesting coil. The ferromagnetic core is the most important part to determine the output power from the whole energy harvesting system. Thus, the precise knowledge of ferromagnetism is critical. As the harvesting coil may not fully enclosure the current conductor, the demagnetization factor which is closely related to the core geometry is carefully studied and minimized. Two new core shapes have been proposed and optimized to have much lower demagnetization factors (hence more power) than that of a conventional rod. 1. A bow-tie-shaped core is introduced and designed to have two large end surfaces. By making its two ends broader, more magnetic flux can be guided from the air into the ferromagnetic core. This intensifies the magnetization at the middle of the core where the wire is wound on. 2. A new helical core is introduced as a further improved version of the bow-tie core. It utilizes two big circular plates fitted at the both ends for the flux collection. In the middle, a helical-shaped core is introduced to increase the path of the magnetic flux. Therefore, the separation between the north pole and south pole is lengthened dramatically, which leads to a reduction in the demagnetization factor and an increase in the magnetic flux density. In addition to the core shape, the selection of the core material is studied and found that high permeability ferrite is the most suitable core material due to its high relative permeability and ultra-low conductivity. Thus, the eddy current losses in the ferromagnetic core can be significantly reduced. Experimental results show that the proposed helical coil with only 400 turns of wire can have a power density of 2.1 μW/cm3 when placed in a magnetic flux density of 7 μTrms. This value is 17 times greater than a previously reported design with 40,000 turns of wire (0.12 μW/cm3 ) placed in the same magnetic field. If a longer helical coil with 8,000 turns of wire is placed in a magnetic flux density of 11 μTrms, the produced power density is around 131.4 μW/cm 3 which is comparable to a solar panel working during a cloudy day. The second area is about the rectifying circuit design which utilizes the energy harvested from the coil to power a commercial wireless sensor. A voltage doubler is applied to provide full-wave rectification and simultaneously boost the output voltage. A transient analysis is carried out to calculate the input resistance of a charging capacitor as a function of time. The theoretical analysis indicates that the input resistance is highly related to the input and output voltages. Therefore, a conventional matching network which consists of linear components cannot work well. A switch mode power converter is introduced as a matching network so that the charging capacitor can be isolated from the harvesting coil. The emulated input resistance looking into the power converter is a constant and determined by the frequency and the duty cycle of the power width modulation applied on the switch. The system is designed and made. The experimental results demonstrate that the energy conversion efficiency from the harvesting coil to the storage capacitor is around 74.6% which is twice as large as a previously reported design. Finally, an energy management unit is developed and it effectively utilizes the energy stored in the capacitor to power a commercial wireless sensor. It is shown in this thesis that a highly efficient magnetic field energy harvesting system has been successfully demonstrated. A wireless sensor can be properly powered up by using a small coil (15 cm long) placed in a small magnetic flux density (7 μTrms). The proposed solution is a very efficient and attractive method for harvesting the magnetic field energy for a wide range of smart grid applications.

Crystallization is an essential unit operation for separating and purifying Active Pharmaceutical Ingredients (APIs) in pharmaceutical industry. Conventionally, crystallizers with moving parts such as stirred vessels are always used for crystallization operation. However, their applications are limited by relatively low heat and mass transfer efficiency as well as difficulty of scale-up. In recent years, there has been a growing interest in using fluidic devices without moving parts for crystallization since they can offer better mixing performance, scale-up capability, and small equipment footprint. Meanwhile, continuous operation is preferred for its unique features such as better control of crystal attributes, higher productivity, and lower operating costs. However, one of the main challenges for the fluidic devices applied in continuous crystallization domains is the limited residence time. The residence time cannot be augmented due to adverse influence of mixing intensity. In the experimental work of present research, a recently optimized design of fluidic oscillator along with two other fluidic devices namely helical coil and coiled flow inverter was used for continuous antisolvent crystallization of paracetamol from methanol-water solution. A loop configuration was designed to realize a higher residence time up to ~13.5 min without jeopardizing mixing in the fluidic devices. An offline imaging method using microscope, digital camera, and ImageJ software was employed to measure particle size distribution (PSD) of manufactured crystals. The lognormal distribution was then used to characterize the experimentally observed PSD. The impact of key operating conditions such as operational mode, configuration of the fluidic devices and residence time on PSD of produced paracetamol crystals was evaluated. Population balance equation (PBE) based model as an effective tool is always used for better insight of crystallization process. In the modelling work of present research, a population balance model coupling with conservation equations and crystallization kinetics was established to computationally interpret mixed semi-batch and batch as well as continuous antisolvent crystallization experiments under consideration. Standard method of moment and lognormal distribution with moments-related parameters σ and µ was utilized to simulate PSD. A lumped parameter, namely mixing coefficient C_mix was proposed to characterize the influence of non-ideal mixing on effective supersaturation and consequently PSD of produced crystals. The effectiveness of C_mix was examined in mixed semi-batch and batch operation under a short residence time of the loop (~200 s) as well as continuous operation under relatively large residence times of the loop (~6.5 and ~13.5 min). An effort was made to develop a relation between mixing coefficient C_mix with other process parameters such as residence time, degree of supersaturation, configurations of devices as well as seeds attributes. This thesis performed experimental and computational investigations of antisolvent crystallization of paracetamol in methanol-water solution using fluidic devices without moving parts. Two key points were observed from this research. Firstly, it was found that designed loop setup with the fluidic oscillator exhibited good mixing performance in continuous antisolvent crystallization. In addition, it was observed that established PBE-based models coupling with mixing coefficient C_mix can simulate PSD of manufactured paracetamol crystals in mixed semi-batch and batch as well as continuous crystallization experiments under different operating conditions. The presented experimental setup, approach, results, and computational models will be useful for expanding applications of fluidic devices without moving parts in antisolvent crystallization domains.

Our planet's ice masses play an important role in regulating numerous natural phenomena vital to keep our planet habitable by humans as well as other living species. Since few decades, global climate changes are probably responsible for an increased melt rate of the ice masses causing catastrophes. It is therefore desirable to monitor our planet's ice masses for predicting catastrophes and timely initiating disaster management measures. This monitoring can also provide scientific evidence for supporting anti-climate change efforts. This research contributes to a joint UCL (University College London) - BAS (British Antarctic Survey) project that aims to develop and deploy an Environmental Sensor Network (ESN) at the Thwaites glacier, Antarctica. Glacial ESNs reported in the last two decades are reviewed, focusing on the antenna types used. A link budget framework for designing such antenna systems is presented. As an example, the framework has been used to design an antenna system for deployment at the Thwaites glacier, Antarctica. Design details of six circularly polarized (CP) antennas, one for the englacial sensor probes and five for supraglacial surface receivers are presented. The probe antenna is a 3D bent cross dipole that fits within a borehole of 8 cm diameter while providing a 1 dBic gain at 433 MHz in ice. The other five antennas are printed ones made for use with glacier surface receivers to receive information transmitted by the englacial sensor probes. Out of five, three are cross dipole antennas, while the remaining two are of Archimedean spiral type. All these six antennas provide 3 dB beamwidths of at least 50º in the xz and yz vertical planes catering for transmitter-receiver antenna misalignments caused by extended deployments. The printed cross dipole versions 1 and 2, and the half ring shaped cross dipole antennas for surface receivers provide realized gains of 6.1 dBic, 5.9 dBic, and 5.9 dBic respectively with a quarter wave reflector. The version 2 antenna provides size reduction at the cost of minor gain loss compared to the version 1 antenna. The half ring cross dipole antenna provides improvements in terms of a lower profile, wider 3 dB beamwidth, smaller axial ratio, and purer polarization over all the other antennas developed for use with surface receivers. The axial ratios of all four cross dipole antennas remained below 1.1 dB within the 330-580 MHz band while the co-polarizations remained adequately stronger than the cross polarizations within a 40º beamwidth in both the vertical planes. The spiral antenna version 1 provides a gain of 7.4 dBic at 433 MHz and a -10 dB fractional bandwidth of 47% in snow. Through some design modifications, the version 2 spiral antenna provides significant improvements in the antenna's reflection coefficient, gain, total efficiency, and axial ratio over the version 1 spiral antenna. None of the previous works used these antenna types for the said applications. The previous works used helical, coil ferrite, and Dielectric Resonator antennas for the sensor probe. Types of antennas previously used with surface receivers included Yagi, helical, non-printed cross dipole, and log periodic dipole array. Lastly, the feasibility of 433 MHz band has been investigated for communication ranges up to 2300 metres through ice. Previous works used lower frequencies like 30 MHz, and 151 MHz to achieve such ranges.

Aerospace Engineering

It is known that different point mutations in α-tropomyosin (Tm) can cause either hypertrophic (HCM) or dilated (DCM) cardiomyopathy. Both of these serious pathologies have a distinct phenotype with unknown mechanisms of development. Biochemical in vitro studies provide valuable information for exploring downstream consequences of cardiomyopathy mutations in sarcomeric proteins leading to cardiac remodelling and consequent heart failure. Tm is a linear a-helical coil-coiled dimer involved in calcium dependent regulation of muscle contraction. Prior to this work, the effects of mutations in Tm on regulation of muscle contraction have been made exclusively with Tm mutant homodimers. However, individuals with a heterozygous background may express mutant and WT proteins in a 1 : 1 ratio which can assembly into a mixture of αα, αα* and α*α* Tm dimers. We found that presence of mutation has little effect on dimer formation between the mutant and the WT monomers, therefore theoretical ratio of the Tm dimers in vivo may be 1 : 2 : 1, respectively. This assumption would make the heterodimer predominant. The properties of in vitro assembled Tm heterodimers carrying HCM (WT-D175N and WT-E180G) and DCM (WT-E40K, WT-E54K, and WT-D230N) causing mutations were examined including thermal stability, flexibility, actin affinity, calcium regulation of 51 biding, and calcium regulation of myofibril force. We showed that various properties of the heterodimers can be similar to those of the wild-type (thermal stability of reduced WTD175N; actin affinity of WT-E40K, and WT-D175N; ΔpCa of WT-E40K, WT-E54K, WT-E180G, WT-D230N), similar of those to the mutant homodimer (ΔpCa of WT-D175N, flexibility of WT-D175N and WT-E180G), intermediate between the two (actin affinity of WT-E180G), or different from both (thermal stability of reduced WT-E40K, WT-E54K, WT-E180G, and WTD230N; actin affinity ofWT-E40, WT-E54K, and WT-D230N; ΔpCa of D175N). The results demonstrate that the properties of Tm heterodimers cannot be predicted from the interpolation of the WT and mutant homodimer data. The distinct properties of heterodimers establish that it will be important to define if the pathogenic agent is a homodimer, a heterodimer or both for each known cardiomyopathy mutation in Tm.

The objective of this research is to determine the three-dimensional stiffness matrix of a rectangular cross-section helical coil compression spring. The stiffnesses of the spring are derived using strain energy methods and Castigliano's second theorem. A theoretical model is developed and presented in order to describe the various steps undertaken to calculate the spring's stiffnesses. The resulting stiffnesses take into account the bending moments, the twisting moments, and the transverse shear forces. In addition, the spring's geometric form which includes the effects of pitch, curvature of wire and distortion due to normal and transverse forces are taken into consideration. Similar methods utilizing Castigliano's second theorem and strain energy expressions were also used to derive equations for a circular cross-section spring. Their results are compared to the existing solutions and used to validate the equations derived for the rectangular cross-section helical coil compression spring. A finite element model was generated using IDEAS (Integrated Design Engineering Analysis Software) and the stiffness matrix evaluated by applying a unit load along the spring's axis, then calculating the corresponding changes in deformation. The linear stiffness matrix is then obtained by solving the linear system of equations in changes of load and deformation. This stiffness matrix is a six by six matrix relating the load (three forces and three moments) to the deformations (three translations and three rotations). The natural frequencies and mode shapes of a mechanical system consisting of an Additional mass and the spring are also determined. Finally, a comparison of the stiffnesses derived using the analytical methods and those obtained from the finite element analysis was made and the results presented.

A 3D model simulation using computational fluid dynamics (ANSYS) was used to assess the heat transfer from the molten glass to incoming air at ambient temperature. A system model was developed to simulate an experimental helical coil counter-flow test heat exchanger. The molten glass is also implemented as a falling thin film (< 3mm) to absorb thermal energy in a concentrating solar power plant. The phosphorous pentoxide glass flow is treated as a laminar, Newtonian and gravity-driven flow over a slightly inclined flat plate using an explicit finite difference scheme to evaluate important heat transfer performance. In the cold regime (~30 oC), a transient unit that uses solid-liquid phase change for thermal cold storage was analyzed. Computational fluid dynamics (Fluent-ANSYS) was used to model the phase change behavior of lithium nitrate trihydrate (LiNO3H2O) by modeling a unit cell of a thermal energy storage heat exchanger. In this analysis, the time required to input thermal energy (melt) the phase change material is calculated to assess its heat transfer performance. By modeling different unit cell domains, the overall heat transfer coefficient and mean conductance are calculated for two different heat exchanger designs.

This thesis investigates the use of Computational Aeroacoustics (CAA) in predicting sound generation and attenuation within a rectangular duct containing a swept helical coil. CAA is a field that has seen significant growth in recent years respective of the increase in computer resources and the advancement of commercially available computational fluid dynamic (CFD) solvers. CAA research is focused on the development of numerical simulations of acoustic sources and radiation from timedependent flow phenomena. Generally, these numerical simulations are achieved by solving the full transient compressible Navier-Stokes equations. In this investigation, the commercially available CFD software Star-CCM+ from CD-Adapco is used for predicting fluid mechanical effects and sound generation. A duct and coil geometry are created in CAD software and then imported to the CFD solver. The computational mesh is generated through a series of refinements aided with use of broadband noise source models which implement acoustic analogies. These models predict locations and strengths of acoustic sources by solving for surface and volume sound values regarding fluid-surface interaction and turbulent flow. Mesh refinement is performed using steady-state Reynolds averaged Navier-Stokes (RANS) equations with a two-equation turbulence closure model to reduce computational costs. Following completion of a refined mesh, a transient simulation is implemented using a hybrid method of RANS and spatially filtered Navier-Stokes equations. Point sources are defined within the fluid domain to perform Fast Fourier transforms (FFT) to acquire Sound Pressure Level (SPL) versus frequency data for comparison with experimental microphone data at a future time.

Among the various combinations of metals used to form alloys, certain combinations, such as Ni and Ti, are known to exhibit unique properties, like the ability to remember a shape after deformation. Because of these novel and unique properties, they are known as `Shape Memory Alloys (SMAs)’ and are desirable for use in various fields of engineering application; eg., in sensors, actuators, biomedical stents and devices, energy absorption, vibration damping, etc, as they can absorb and dissipate mechanical/thermal energies by undergoing a reversible hysteretic shape change under the applied mechanical/thermal cyclic loadings. This reflects the effects of microstructural changes occurring during phase transformation between Austenite (A) and Martensite(M) phases, as well as the martensite-variants orientations at high stress levels ( Mi to Mj, where i and j are different variants). As typically utilized in applications, a particular shape memory alloy (SMA) device or component also need to operate under a large number of thermo-mechanical cycles, hence, the importance of accounting for the cyclic behavior characteristics in modeling and characterization of these systems. This dissertation work focus on: (1) a detailed study of a recently-formulated, multi-mechanism-based, comprehensive, thus complex modeling framework formulated by Saleeb et al, in particular the physical significance of the multiple, inelastic mechanisms that are used to regulate the partitioning of energy dissipation and storage governing the evolutionary thermo-mechanical response of shape memory behavior; (2) a comprehensive characterization of the cyclic response of the specific complex real shape memory alloy like Ni49.9Ti50.1, also commonly known as 55NiTi, for isobaric tests under the entire relevant bias stress range from 10 to 300MPa, and for sufficient number of thermal cycles (100 cycles here); (3) implementation of the calibrated SMA model in the study of its effectiveness in the large-scale simulations of SMA actuators of coil-spring and tube configurations; and (4) experimental validation for the calibrated SMA model for the large-scale simulation for helical-coil spring actuation. This study proved that the SMA model is capable to characterize the thermo-mechanical behavior of the complex alloy system and can be implemented to analyze large scale applications which involve inhomogeneous, multi-axial stress states and large deformation.

In this dissertation an integrated framework of process performance monitoring and fault diagnosis was developed for nuclear power systems using robust data driven model based methods, which comprises thermal hydraulic simulation, data driven modeling, identification of model uncertainty, and robust residual generator design for fault detection and isolation. In the applications to nuclear power systems, on the one hand, historical data are often not able to characterize the relationships among process variables because operating setpoints may change and thermal fluid components such as steam generators and heat exchangers may experience degradation. On the other hand, first-principle models always have uncertainty and are often too complicated in terms of model structure to design residual generators for fault diagnosis. Therefore, a realistic fault diagnosis method needs to combine the strength of first principle models in modeling a wide range of anticipated operation conditions and the strength of data driven modeling in feature extraction. In the developed robust data driven model-based approach, the changes in operation conditions are simulated using the first principle models and the model uncertainty is extracted from plant operation data such that the fault effects on process variables can be decoupled from model uncertainty and normal operation changes. It was found that the developed robust fault diagnosis method was able to eliminate false alarms due to model uncertainty and deal with changes in operating conditions throughout the lifetime of nuclear power systems. Multiple methods of robust data driven model based fault diagnosis were developed in this dissertation. A complete procedure based on causal graph theory and data reconciliation method was developed to investigate the causal relationships and the quantitative sensitivities among variables so that sensor placement could be optimized for fault diagnosis in the design phase. Reconstruction based Principal Component Analysis (PCA) approach was applied to deal with both simple faults and complex faults for steady state diagnosis in the context of operation scheduling and maintenance management. A robust PCA model-based method was developed to distinguish the differences between fault effects and model uncertainties. In order to improve the sensitivity of fault detection, a hybrid PCA model based approach was developed to incorporate system knowledge into data driven modeling. Subspace identification was proposed to extract state space models from thermal hydraulic simulations and a robust dynamic residual generator design algorithm was developed for fault diagnosis for the purpose of fault tolerant control and extension to reactor startup and load following operation conditions. The developed robust dynamic residual generator design algorithm is unique in that explicit identification of model uncertainty is not necessary. Finally, it was demonstrated that the developed new methods for the IRIS Helical Coil Steam Generator (HCSG) system. A simulation model was first developed for this system. It was revealed through steady state simulation that the primary coolant temperature profile could be used to indicate the water inventory inside the HCSG tubes. The performance monitoring and fault diagnosis module was then developed to monitor sensor faults, flow distribution abnormality, and heat performance degradation for both steady state and dynamic operation conditions. This dissertation bridges the gap between the theoretical research on computational intelligence and the engineering design in performance monitoring and fault diagnosis for nuclear power systems. The new algorithms have the potential of being integrated into the Generation III and Generation IV nuclear reactor I&C design after they are tested on current nuclear power plants or Generation IV prototype reactors.

A family of Coil Pumps has been developed at Loughborough University over the last 10 years by the author. The coil pump, sometimes known as the 'hydrostatic pump', was known and used in the 18th and 19th centuries, since then it appears to have been forgotten. Laboratory investigations lead to a theory for predicting the behaviour of this little known pump The theory is based on an assessment of the boundary levels of the liquid plugs within the loops. From this work, two types of suction pump were derived and the lift pump theory was developed and adapted to predict their behaviour. One suction pump was based on one helical coil and it required a regulated air supply. The second pump used two helical coils 'back to back' one taking water into the pump and the other (of larger capacity) withdrawing it. Laboratory tests were carried out on a number of versions of both suction pumps and the experimental results agreed well with those produced by the theory. Practical applications of this family of pumps included a low cost stream powered lift pump, a dosing pump, a sewage suction pump and a sewage treatment process.

A spin label technique has been developed for the study of intercalation mechanisms in DNA utilizing a modified ethidium bromide as a model ligand, and specifically synthesized spin labels of carcinogenic aromatic amines and a series of nitrobenzene chromophores. The technique takes advantage of the characteristic ESR anisotropy of the corresponding spin labels complexed with DNA. Analysis of the orientation dependent information thus obtained for the spin labels of ethidium bromide, 2-aminofluorene, 2-aminoanthracene and 6-aminochrysene have clearly shown that the ligand moieties in all four respective complexes are accommodated in adjacent base pair layers of the DNA with the nitroxide reporter oriented in one preferential direction. The geometry of the nitroxide rings with respect to their respective constraining ligands in a particular complex appeared to be largely dependent upon the size of the ligand moiety and the position of the reporter attachment on the ligand molecule. A coplanar configuration is most favored for the spin labels in which the ligand moiety per se is a three fused ring with the nitroxide substituted at a position which is on or close to the longitudinal end of the ligand molecule. In the case of nitrobenzene spin labels, the 2,4-dinitrobenzene analogues with amine linkage to the nitroxide reporter demonstrated the strongest binding with DNA by intercalation and the reporter nitroxide is oriented 45 degrees to the plane of the benzene ring and is due primarily to the steric hindrance of the 2-nitrosubstituent. This binding is found to be largely dependent upon the number of nitro-substituents, their relative position on the benzene ring, and the type of linkage between the ligand and the nitroxide reporter, suggesting that polirization bonding is a major driving force in their complex formation with DNA. Temperature studies in which the heat-induced release of the bound label is monitored by ESR gives an accurate measure of the complex dissociation characteristics which parallel exactly the helical-coil cooperative melting transition monitored by optical absorption measurements. The extent of dissociation of the bound spin labels parallels almost exactly the melting, i.e. unzipping of the DNA double helix suggesting that the spin labels are immobilized by intercalation at the site on the DNA which is directly involved in the maintenance of the double helical structure. Analysis of the ESR spectra of the complexes in terms of the extent of immobilization indicates that for aromatic amine spin labels, two different binding species exist, one strongly immobilized presumably at a G-C pair region and the other partially immobilized in a region other than G-C. This is quite different from those complexes formed with ethidium bromide and nitrobenzene in which no more than one species of immobilized spin was observed. Competitive binding of the labels with respect to their parent ligand and binding isotherm results show that nitroxide substitution does not effect the type of binding but does effect the extent of binding, i.e. binding constant with the labeled compound having a much lower affinity.

The purpose of this investigation was to evaluate a conical shaped, steel tine picking reel mounted in an experimental helical vegetable harvester for effectiveness in detaching snap beans. Two double helix picking reels, each of a different pitch, were tested. One reel had a pitch of three inches, and the other had a pitch of four inches. Laboratory tests were conducted to determine the effects of helix speed, reel speed, and reel pitch on picking efficiency and pod damage. The average picking efficiency was 83.2 percent. An average of 31.8 percent of the picked pods were broken and an average of 16.0 percent of the pods were picked in clusters. Statistical analysis of the test results showed that only the interaction between reel speed and reel pitch was significant for the responses percentage of pods broken and percentage of pods picked in clusters. High speed motion picture films of the picking action were studied to determine the mode of pod detachment. Four modes were observed and grouped into two classes depending on condition of the detached pods. The acceptable group consisted of pods that the tines detached at either the pod-pedicel junction or at the pedicel-plant stem junction. The films indicated pods of the unacceptable group were either broken when one tine accelerated a pod into a second tine or when a tine contacted the pedicel and created tensile stresses within the pod thus removing part of the pod with the pedicel. The helical coil was observed to support the plant stalk and act on it to aid in pod detachment through application of a force opposite to the picking tine force.