Aeronautical Engineering: A special bibliography with indexes, supplement 72, July 1976

This bibliography lists 184 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1976

Classical and quantum mechanics with chaos

This thesis is concerned with the study, classically and quantum mechanically, of the square billiard with particular attention to chaos in both cases. Classically, we show that the rotating square billiard has two regular limits with a mixture of order and chaos between, depending on an energy parameter, E. This parameter ranges from -2w(^2) to oo, where w is the angular rotation, corresponding to the two integrable limits. The rotating square billiard has simple enough geometry to permit us to elucidate that the mechanism for chaos with rotation or curved trajectories is not flyaway, as previously suggested, but rather the accumulation of angular dispersion from a rotating line. Furthermore, we find periodic cycles which have asymmetric trajectories, below the value of E at which phase space becomes disjointed. These trajectories exhibit both left and right hand curvatures due to the fine balance between Centrifugal and Coriolis forces. Quantum mechanically, we compare the spectral analysis results for the square billiard with three different theoretical distribution functions. A new feature in the study is the correspondence we find, by utilising the Berry-Robnik parameter q, between classical E and a quantum rotation parameter w. The parameter q gives the ratio of chaotic quantum phase volume which we can link to the ratio of chaotic phase volume found classically for varying values of E. We find good correspondence, in particular, the different values of q as w is varied reflect the births and subsequent destructions of the different periodic cycles. We also study wave packet dynamics, necessitating the adaptation of a one dimensional unitary integration method to the two dimensional square billiard. In concluding we suggest how this work may be used, with the aid of the chaotic phase volumes calculated, in future directions for research work

Unsupervised maritime target detection

The unsupervised detection of maritime targets in grey scale video is a difficult problem in maritime video surveillance. Most approaches assume that the camera is static and employ pixel-wise background modelling techniques for foreground detection; other methods rely on colour or thermal information to detect targets. These methods fail in real-world situations when the static camera assumption is violated, and colour or thermal data is unavailable. In defence and security applications, prior information and training samples of targets may be unavailable for training a classifier; the learning of a one class classifier for the background may be impossible as well. Thus, an unsupervised online approach that attempts to learn from the scene data is highly desirable. In this thesis, the characteristics of the maritime scene and the ocean texture are exploited for foreground detection. Two fast and effective methods are investigated for target detection. Firstly, online regionbased background texture models are explored for describing the appearance of the ocean. This approach avoids the need for frame registration because the model is built spatially rather than temporally. The texture appearance of the ocean is described using Local Binary Pattern (LBP) descriptors. Two models are proposed: one model is a Gaussian Mixture (GMM) and the other, referred to as a Sparse Texture Model (STM), is a set of histogram texture distributions. The foreground detections are optimized using a Graph Cut (GC) that enforces spatial coherence. Secondly, feature tracking is investigated as a means of detecting stable features in an image frame that typically correspond to maritime targets; unstable features are background regions. This approach is a Track-Before-Detect (TBD) concept and it is implemented using a hierarchical scheme for motion estimation, and matching of Scale- Invariant Feature Transform (SIFT) appearance features. The experimental results show that these approaches are feasible for foreground detection in maritime video when the camera is either static or moving. Receiver Operating Characteristic (ROC) curves were generated for five test sequences and the Area Under the ROC Curve (AUC) was analyzed for the performance of the proposed methods. The texture models, without GC optimization, achieved an AUC of 0.85 or greater on four out of the five test videos. At 50% True Positive Rate (TPR), these four test scenarios had a False Positive Rate (FPR) of less than 2%. With the GC optimization, an AUC of greater than 0.8 was achieved for all the test cases and the FPR was reduced in all cases when compared to the results without the GC. In comparison to the state of the art in background modelling for maritime scenes, our texture model methods achieved the best performance or comparable performance. The two texture models executed at a reasonable processing frame rate. The experimental results for TBD show that one may detect target features using a simple track score based on the track length. At 50% TPR a FPR of less than 4% is achieved for four out of the five test scenarios. These results are very promising for maritime target detection

Physical Aspects of Local Solid Tumor Growth

Krebszellen haben gemeinsame Eigenschaften, wie unbegrenztes Wachstumspotential und die Vermeidung von Apoptose. Krebs kann als systemische Erkrankung angesehen werden und es reicht daher nicht aus, molekulare Details von Krebs zu verstehen, sondern auch emergente physikalische Eigenschaften von Krebs auf mehreren Größenskalen von Genen über Zellen bis hin zu Geweben. Diese Arbeit konzentriert sich auf physikalische Eigenschaften die an der Krebsprogression, der Migration von Krebszellen und dem Krebswachstum beteiligt sind. Die Migration von Krebszellen führt zur Fähigkeit zur Metastasierung, der häufigsten Ursache für krebsbedingten Tod. Der Schlüssel zu diesem Prozess ist die Verformbarkeit von Krebszellen beim Durchqueren der dichten Mikroumgebung aus extrazellulärer Matrix und anderen Zellen. Der genaue Beitrag des Aktin- und Mikrotubuli-Netzwerks zur zellulären elastischen Verformung und Entspannung ist wichtig und wurde untersucht. Ein wichtiges Ergebnis ist, dass bei kleinen Verformungen (5%) Aktin-Filamente und Mikrotubuli gleichermaßen zur Zellverformung und -relaxation beitragen. So sind die Mikrotubuli für die Migration in Mikroumgebungen von größerer Bedeutung, als es die aktuelle Literatur vermuten lässt. Ein initial gebildeter bösartiger Tumor tritt typischerweise in eine Wachstumsphase ein, in der das umgebende Gewebe verdrängt und eingedrungen wird. Für ein optimales klinisches Behandlungsergebnis sollte der Primärtumor so gut wie möglich entfernt werden, was die genaue Erkennung der Tumorfront und die Identifizierung der Gewebe mit dem Risiko einer Krebsinfiltration beinhaltet. In dieser Arbeit werden natürliche Hindernisse und Grenzen für das Krebswachstum, wie z.B. Fasziengewebsgrenzen oder Gewebekompartimentgrenzen, basierend auf klinischen Daten von Gebärmutterhalskrebs analysiert, die aus der pathologischen Untersuchung von chirurgisch resezierten Tumoren von 518 Patienten gewonnen wurden. Die Wachstumsgrenzen wurden als embryonale Gewebeentwicklungsgrenzen identifiziert und betonen, dass Krebs Entwicklungsmerkmale aufweist, die häufig in der Embryogenese vorkommen. Das gefundene Tumorwachstumsmuster und die -form widersprechen dem das das vorherrschende Dogma der isotropen Tumorwachstum, welches der chirurgischen Tumorresektion und Strahlentherapie zugrunde liegt. Die Tumorform-Distribution weist starke Abweichungen von sphärischer Symmetrie auf, was darauf hindeutet, dass Tumore durch entwicklungsbiologische Kompartimente und deren Kompartimentsgrenzen begrenzt und geformt werden. Computersimulationen liefern auch den Nachweis, dass die klinisch gefundene Tumorinfiltrationswahrscheinlichkeit von Geweben nicht auf der metrischen Entfernung des gefährdeten Gewebes zum Gewebe der Tumorherkunft basiert, sondern auf der ontogenetischen Verwandtschaft der Gewebe

Characterisation and correction of respiratory-motion artefacts in cardiac PET-CT

Respiratory motion during cardiac Positron Emission Tomography (PET) Computed Tomography (CT) imaging results in blurring of the PET data and can induce mismatches between the PET and CT datasets, leading to attenuation-correction artefacts. The aim of this project was to develop a method of motion-correction to overcome both of these problems. The approach implemented was to transform a single CT to match the frames of a gated PET study, to facilitate respiratory-matched attenuation-correction, without the need for a gated CT. This is benecial for lowering the radiation dose to the patient and in reducing PETCT mismatches, which can arise even in gated studies. The heart and diaphragm were identied through phantom studies as the structures responsible for generating attenuation-correction artefacts in the heart and their motions therefore needed to be considered in transforming the CT. Estimating heart motion was straight-forward, due to its high contrast in PET, however the poor diaphragm contrast meant that additional information was required to track its position. Therefore a diaphragm shape model was constructed using segmented diaphragm surfaces, enabling complete diaphragm surfaces to be produced from incomplete and noisy initial estimates. These complete surfaces, in combination with the estimated heart motions were used to transform the CT. The PET frames were then attenuation-corrected with the transformed CT, reconstructed, aligned and summed, to produce motion-free images. It was found that motion-blurring was reduced through alignment, although benets were marginal in the presence of small respiratory motions. Quantitative accuracy was improved from use of the transformed CT for attenuation-correction (compared with no CT transformation), which was attributed to both the heart and the diaphragm transformations. In comparison to a gated CT, a substantial dose saving and a reduced dependence on gating techniques were achieved, indicating the potential value of the technique in routine clinical procedures

A microscopic model of signal transduction mechanisms: olfaction

This thesis recognizes that: in many systems the initial small molecule - receptor recognition processes, and thus signal transduction, is not fully understood to the highest level of scientifc explanation and prediction. One such example of this is olfaction. Molecules cannot necessarily be predicted from a smell, and similarly a smell from molecules. Better understanding of these initial steps, would have important repercussions, especially in the field of rational drug design. So in general the thesis proves the physical feasibility and potential of a novel and generic signaling model, and in particular looks at those processes in olfaction. The conjecture 'Could humans recognize odours through phonon assisted tunneling?' is tested. This is based on the idea (Turin, 1996) that the nose recognizes an odorant's vibrations (phonons) via inelastic electron tunneling (IETS). The nose thus acts as a 'meat spectroscope'. First the background biology of the olfactory system is evaluated, then the conjecture is posed as a soluble problem. Traditional physics ideas are reconciled with the biological environment. It is proven that no physics based objections hold against the working of this new mechanism, thus a predictive and explanatory theory is now introduced to the field. The parameters of odorant discrimination are explored. In particular the 'Huang-Rhys factor' is modeled as a measure of the electron-phonon coupling integral to signal transduction. Several approaches are considered, 'odorant spectra' is created. Objections to the conjecture are considered, in particular the apparent paradox of enantiomer discrimination. The apparent paradox is shown to be obsolete. A correlation between a certain type of flexibility and whether enantiomer pairs smell the same is found. A rule is established: The members of an enantiomer pair will smell alike (type 1) when the molecules are rigid, and will smell different (type 2) when they are flexible. This flexibility refers to a particular property of six-membered rings. A consequence of this finding leads to the investigation of certain steroids in correlation to their bio-effects, and it is found that similar features are apparent, thus the mechanism of biological IETS is applied to other systems