662 research outputs found
Effect of equal channel angular pressing on the microstructure and mechanical properties of Al-10Zn-2Mg alloy
No full textExperimental Demonstration of the Concept of Endothermic Fuels for Providing Efficient Cooling to Scramjet Combustors
Get PDFThe development of endothermic fuels is important for providing efficient cooling to scramjet combustors operating at high Mach numbers. Generally the fuel itself can be used as coolant for the engine elements. Since preheating the fuel is desirable before combustion, it can be circulated in heat transfer passages em-bedded inside the hot engine parts so that the excess heat of the engine is removed by the fuel and in the process the fuel is also regeneratively preheated to the desired temperature. Endo-thermic fuels pertain to a class of fuels, which make use of certain endothermic reactions to provide an additional heat sink for cooling the engine hot end parts through embedded heat ex-change devices. While traditional fuels use only the sensible heat of the fuels for cooling, endothermic fuels provide cooling through two routes, namely, the absorption of the sensible heat and through the use of endothermic reactions. At the Propulsion Division, NAL, the concept of endothermic cooling has been ex-perimentally demonstrated using kerosene as the fuel and molec-ular sieves as the cracking catalyst. A laboratory scale catalytic reactor was used for carrying out the catalytic reaction. A differ-ence of 114 K was observed for endothermic cooling whereas the conventional method of cooling gave only 18 K. The details of this important experiment are described in this pape
Insertion and deletion tolerance of point processes
Get PDFWe develop a theory of insertion and deletion tolerance for point processes. A process is insertion-tolerant if adding a suitably chosen random point results in a point process that is absolutely continuous in law with respect to the original process. This condition and the related notion of deletion-tolerance are extensions of the so-called finite energy condition for discrete random processes. We prove several equivalent formulations of each condition, including versions involving Palm processes. Certain other seemingly natural variants of the conditions turn out not to be equivalent. We illustrate the concepts in the context of a number of examples, including Gaussian zero processes and randomly perturbed lattices, and we provide applications to continuum percolation and stable matching
ESR Study of a Cr5+ Centre in Ferroelectric Ammonium Sulphate
No full textX-band electron spin resonance (ESR) studies of (CrO4)2- doped, X-irradiated single crystals of ferroelectric ammonium sulphate ((NH4)2SO4, TC = 223 K) at 300 and 208 K are reported. The paramagnetic centre responsible for the ESR spectrum is identified to be Cr5+. Superhyperfine interaction of the unpaired electron with two equivalent protons is observed. The spin-Hamiltonian parameters which are nearly axial at 300 K, with g < g indicating a dx2-y2 orbital ground state, acquired rhombic character below TC indicating a distortion of the sulphate tetrahedron. An increase in the value of the proton superhyperfine constant in the ferroelectric phase is indicative of stronger hydrogen bonding
Mycobacterium Smegmatis RecA And SSB : Structure-Function Relationships, Interaction With Cofactors And Accessory Proteins
No full textHomologous genetic recombination, because of its fundamental roles in the maintenance of genome stability and evolution, is an essential cellular function common to all organisms. This process also plays important roles in the repair of damaged DNA molecules, generation of genetic diversity and proper segregation of chromosomes. The genetic exchange is a highly orchestrated process that entails a plethora of control mechanisms and a large number of proteins, of which RecA and SSB are two proteins that have been chosen for further investigation(s) in the present study. In addition, we have also investigated the interaction between SSB and UvrD1, which plays an important role in DNA repair pathways, especially nucleotide excision repair (NER) and mismatch repair as well as DNA replication and recombination. Chapter 1 reviews the literature regarding various aspects of homologous recombination, with an emphasis on the biochemical and the biophysical aspects of RecA and SSB proteins. In addition, it provides an overview of the study of DNA repair and recombination in mycobacteria.
RecA protein is ubiquitous and well conserved among bacterial species. Many archaeal species possess two RecA homologues (RadA and RadB) and eukarya possess multiple homologues of RecA including, Rad51, Rad51B, Rad51C, Rad51D, DMC1, XRCC2, or XRCC3. RecA or its homologues function as polymers, consisting of hundreds of monomers that cooperatively polymerize on single-stranded DNA to form a nucleoprotein filament. E. coli RecA protein participates in Trans Lesion Synthesis (TLS) of DNA and forms the minimal mutasome in association with DNA polymerase V (UmuD’2C). The fundamental mechanism underlying HR, i.e. DNA strand exchange, is one of the most fascinating examples of molecular recognition and exchange between biological macromolecules.
Since the isolation of E. coli recA gene and the subsequent purification of its gene product and also from other organisms, RecA protein has been studied extensively for more than three decades. E. coli RecA protein has pivotal roles in DNA recombination and repair, and binding to DNA in the presence of ATP, is a fundamental property of RecA protein resulting in the formation of a nucleoprotein filament. This is the slow step of the HR process, and is considerably faster on ssDNA than on duplex DNA. Binding of RecA to dsDNA is slower at physiological pH, is accelerated at acidic pH, and the lag in binding at the higher pH values is due to slow nucleation. The ATP and the DNA binding functions of RecA display allosteric interaction such that ATP- binding leads to an increase in affinity to ssDNA-binding and vice-versa. X-ray structures of E. coli RecA complexed with nucleotide cofactors have implicated a highly conserved Gln196 in Mycobacterium smegmatis RecA in the coupling of ATP and the DNA binding domains. The carboxyamide group of Gln196 makes an H-bond with the γ-phosphate group of ATP and the side chain of this residue is observed to move by approximately 2Å towards the ATP, relative to the other residues involved in ATP binding. In addition, a highly conserved Arg198 has also been postulated to interact with the γ-phosphate group of bound ATP and position it for a nucleophilic attack by a conserved residue-Glu96 leading to ATP hydrolyses.
To elucidate the role of Gln196 and Arg198 in the allosteric modulation of RecA functions, we generated MsRecA variant proteins, where in Gln196 was substituted with alanine, asparagine or glutamate; Arg198 was mutated to a lysine. The biochemical characterization of MsRecA and its variant proteins with the objective of defining the allosteric interaction between the ATP- and the DNA-binding sites has been described with in Chapter 2. We observed that while the mutant MsRecA proteins were proficient in ATP-binding they were deficient in ATP hydrolyses. We assayed for the ability of these proteins to bind ssDNA using either nitrocellulose filter binding or Surface Plasmon Resonance (SPR). While we did not detect any ssDNA-binding by the mutant MsRecA proteins in the filter binding assay, we observed only ten-fold reduction in the affinity for ssDNA as compared to wild type MsRecA protein in MsRecAQ196A, Q196N and R198K in the SPR assay. MsRecA Q196E did not show any binding to ssDNA, in both nitrocellulose filter-binding as well as SPR assays. We assayed for the ability of the mutant RecA proteins for their ability to promote DNA-pairing as well as DNA strand exchange. While we observed limited pairing promoted by the mutant proteins relative to the wild-type MsRecA, we observed a complete abrogation of strand exchange in the case of mutant proteins. In addition, we assayed for the co-protease function of MsRecA, by monitoring the cleavage of MtLexA. We observed that only the wild-type MsRecA protein was able to cleave MtLexA, while none of the mutant RecA proteins were able to do so. In order to understand the differences observed between the wild -type and the mutant MsRecA proteins, we analyzed the conformational state of MsRecA and its variant proteins by circular dichroism spectroscopy upon ATP-binding. We observed that while MsRecA and MsRecAQ196N displayed a reduction in the absorbance at 220 nm upon ATP binding, we did not observe any such structural transitions in the other mutant MsRecA proteins that we tested.
Based on our observations and the crystal structure of E. coli RecA bound to ssDNA, in Chapter 2, we propose a dual role for the Gln196 and Arg198 in modulating RecA activities. In the presynaptic filament Gln196 and Arg198 sense the presence of the nucleotide in the nucleotide binding pocket and initiate a series of conformation changes that culminate in the transition to an active RecA nucleoprotein filament. In the active RecA nucleoprotein filament these residues are repositioned such that they now form a part of the protomer-protomer interface. As such they perform two vital functions; they stabilize the protomer-protomer interface by participating in the formation of hydrogen bonds that span the interface as well transmit the wave of ATP hydrolysis across the interface leading to a coordinated hydrolyses of ATP essential for the heteroduplex extension phase of strand exchange reaction.
The members of the super family of single stranded DNA binding proteins (SSB) play an important role in all aspects of DNA metabolism including DNA replication, repair, transcription and recombination. Prokaryotic SSBs bind ssDNA with high affinity and generally with positive cooperativity. Several lines of evidence suggest that prokaryotic SSBs are modularly organized into three distinct domains: the N-terminal DNA binding domain and acidic C-terminal domain are linked by a flexible spacer. Studies from our laboratory have revealed that M. smegmatis SSB plays a concerted role in recombination-like activities promoted by the cognate RecA.
The C- terminal of SSB is known to be involved in its ability to interact with other proteins. We have previously reported that the C-terminal domain of M. smegmatis SSB, which is not essential for interaction with DNA, is the site for the binding of cognate RecA. The data in Chapter 3 describes the characterization of the SSB C-terminus with the objective of delineating the elements responsible for mediating protein-protein interaction, as well as to define the mechanism by which SSB is able to modulate the activities of RecA. To map the RecA interaction domain of SSB we created deletion mutants in MsSSB lacking 5, 10, 15 or 20 residues from the C-terminal. The truncated SSB proteins were expressed with a His- tag at the N- terminus and purified to homogeneity using a Ni-NTA affinity matrix. We observed unlike MsSSB, MsSSB∆C5 and MsSSB∆C10, MsSSB∆C15 and MsSSB∆C20 were unable to support three-strand exchange catalyzed by MsRecA. Based on the observation that interaction with SSB is essential for MsRecA to catalyze the strand Exchange reaction, we postulate that the RecA interacting domain of SSB is situated between the 15th and the 20th residue from the C-terminal. Further, the C-terminal of MsSSB modulates the transitions between DNA binding modes. Unlike the case with EcSSB where deletion of the last 8 residues from the C-terminal stabilizes the (SSB)35 mode of ssDNA binding, we observe that in case of MsSSB the deletion of C-terminal seems to destabilize the (SSB)35. In addition, the transition from the low density binding mode to a high density mode involves the formation of several intermediates when the C-terminal residues are deleted.
With the objective of understanding the functions to the C-terminal of SSB independent of its DNA-binding domain in modulating RecA functions, we employed a peptide corresponding to the 35 residues from the C-terminal of the MsSSB. We observed that the C-terminal region alone is capable of interacting with RecA. In addition we also observed that the C-terminal domain of SSB stimulates RecA functions independent of its DNA binding domain.
To address the question, whether the stimulatory effect of the C-terminal domain of SSB in the absence of its DNA-binding domain is restricted to RecA or is a generalized phenomenon associated with all SSB interacting proteins; we tested the effect of C-terminal domain of SSB on UvrD which is known to interact with SSB. UvrD participates in several pathways of DNA metabolism, which include the nucleotide excision repair (NER) and mismatch repair pathway, replication and recombination. Genetic evidence suggests that UvrD and SSB interact in vivo. We tested the effect of mycobacterial SSB on M. tuberculosis UvrD1 (MtUvrD1) functions in vitro. We observe that MtUvrd1 physically interacts with SSB. Further, presence of SSB has an inhibitory effect on the helicase activity of MtUvrD1 and that this effect is dependent on the C-terminal region as the deletion of residues from the C-terminal of SSB abrogates the inhibitory effect of SSB. However, unlike RecA, the C-terminal region of SSB alone had no effect on the helicase activity of UvrD1. We also observed that MsSSB has opposing effects on the ATPase activity of MtUvrD1. In the presence of low concentrations of SSB the ATPase activity is enhanced, while we observed an inhibition when the concentration of MsSSB is high.
The precise mechanistic details of how SSB is able to act as an accessory protein to RecA, in context of homologous recombination and stimulates its biochemical activities have been a subject of debate. Whereas research from some groups has shown that the stimulatory effect SSB is mediated through its ability to melt DNA secondary structure, thereby allowing RecA to overcome the kinetic barrier imposed by the presence of secondary structure in ssDNA, others postulate that SSB plays a direct role in the stabilization of RecA nucleoprotein filament and prevents its dissociation. Chapter 3 discusses the experimental evidence in favor of the aforesaid models and based on the results of our experiments; we propose that the accessory functions of SSB may be mediated by a mechanism that involves elements of both models. While interaction with SSB can bring about a conformational change in RecA that is reflected in the enhanced levels of strand exchange and co-protease activity, the helix destabilizing function of SSB is essential during heteroduplex extension and to sequester the displaced strand such that it does not participate in any further pairing reactions. The novel finding that we present in Chapter 3 is that the interaction of SSB C-terminal alone has a stimulatory effect upon RecA activities. Furthermore, we observed that M. tuberculosis UvrD1 is a weak interaction partner of SSB. The physical and functional interactions between MsSSB with RecA on the one hand, and MsSSB and UvrD1 on the other highlight different types of cross-talk between the components of HR and DNA repair pathways. In contrast to the results of earlier studies, our results indicate that protein-protein interactions alone between SSB and RecA may modulate the RecA mediated processes of presynapsis, homologous pairing and strand exchange between homologous DNA molecules as well as modulate its co-protease activity. In addition, our studies indicate that a direct protein-protein interaction is responsible for the modulation of UvrD1 activities by SSB
Determinants of postpartum anemia among women from a rural population in southern India
No full textPS Rakesh,1 Vijayaprasad Gopichandran,2 Dimple Jamkhandi,1 Krishna Manjunath,1 Kuryan George,1 Jasmin Prasad11Department of Community Health, Christian Medical College, Vellore, 2School of Public Health, SRM University, Kanchipuram District, Tamil Nadu, IndiaBackground: Even though the problem of anemia during pregnancy has been adequately emphasized, very little attention has been paid to postpartum anemia. The objective of the current study was to estimate the mean change in maternal hemoglobin from 36 weeks' gestation to 6 weeks postpartum and to identify the factors associated with anemia during the postpartum period among women in a rural development block in Tamil Nadu, India.Methods: Ninety-three pregnant women were interviewed using a structured questionnaire at 36 weeks' gestation and then at 2 and 6 weeks postpartum. Blood samples were collected from the participants at 36 weeks' gestation and at 6 weeks postpartum. Paired t-tests assessing the difference in mean hemoglobin prepartum and postpartum, univariate analysis, and multiple logistic regression to identify factors associated with postpartum anemia were done using Statistical Package for the Social Sciences version 12 for Microsoft Windows software.Results: The proportion of study subjects who were anemic (hemoglobin <11 g/dL) at 36 weeks' gestation was 26.8% and at 6 weeks postpartum was 47.3% (hemoglobin <12 g/dL). The mean hemoglobin at 36–38 weeks' gestation was 11.70±1.43 g/dL and at 6 weeks postpartum was 12.10±1.27 g/dL. Anemia at 36 weeks' gestation (odds ratio [OR] 10.47, 95% confidence interval [CI] 2.37–42.34), heavy blood loss perceived by the mother during delivery (OR 12.91, 95% CI 2.01–61.25), younger maternal age (<21 years, OR 2.45, 95% CI 1.28–23.86), and inadequate iron supplementation during the postpartum period (OR 3.53, 95% CI 1.18–11.37) were identified as significant factors associated with anemia at 6 weeks postpartum.Conclusion: Anemia during the third trimester of pregnancy, heavy bleeding perceived by the mother during delivery, younger maternal age, and inadequate iron supplementation during the postpartum period were associated with postpartum anemia.Keywords: anemia, hemoglobin, iron deficiency, postpartu
Generalized Vertex Induced Connected Subsets of a Graph
No full textLet k be a positive integer. A graph G = (V,E) is said to be a k - connected graph if for any given subset S of V (G) with |S| = k, the subgraph induced by S is connected. In this paper, we explore some properties of k - connectedness and its minimality conditions with respect to other graph theoretic parameter
Die Brille mit Gedächtnis : Interaktives Lernen mit einem mobilen Augmented-Reality-System
Get PDFBekel H. Die Brille mit Gedächtnis : Interaktives Lernen mit einem mobilen Augmented-Reality-System. Bielefeld (Germany): Bielefeld University; 2010.Informatische Forschung beschäftigt sich zumeist mit der Spezialisierung auf einen bestimmten Bereich und der Entwicklung optimierter Verfahren für eine bestimmte Aufgabe. Innerhalb des Projektes VAMPIRE wurde das ehrgeizige Ziel verfolgt, ein umfassendes Gesamtsystem in Form eines computergestützten Assistentensystems zu entwickeln, welches eine Vielzahl an Funktionalitäten bieten soll. Bei dieser Entwicklung wurden ebenfalls die zu lösenden Aufgaben auf verschiedene Arbeitsgruppen aufgeteilt und von den jeweiligen Experten bearbeitet.
In dieser Arbeit lag der Hauptfokus darauf, ein hochgradig integriertes und vor allem lernfähiges Gesamtsystem in Form eines Demonstrators zu konstruieren, welcher bereits eine Vielzahl von Funktionen des späteren Assistentensystems integrieren sollte. Der Schwerpunkt lag hier nicht auf der Spezialisierung in einem bestimmten Bereich, sondern vielmehr darauf, eine Vielzahl von benötigten Verfahren zu finden, für die Aufgabe zu modifizieren und gemeinsam in ein System zu integrieren, um eine Brille mit Gedächtnis überhaupt realisieren zu können.
Technische Basis für die Realisierung einer Brille mit Gedächtnis ist eine Augmented-Reality-Apparatur, deren Kernstück aus zwei Kameras und einem 3-D-Display besteht und welche für die akustische Kommunikation über ein Mikrophon und über Kopfhörer verfügt. Dies ermöglicht, dass die visuelle Perzeption von Mensch und Maschine identisch ist und Systeminformationen sowohl visuell als auch akustisch mitgeteilt werden können.
Auf dieser Hardwareplattform wurde ein System entwickelt, das eine Vielzahl von Funktionen so integriert, dass es auf natürliche Weise mit dem Benutzer interagieren und Gedächtnislücken des Benutzers in Bezug auf verlegte Gegenstände schließen kann. Das System kann einerseits Objekte erlernen und andererseits dem Benutzer sein erlangtes Wissen mitteilen.
Bei der Entwicklung eines solchen Systems ist die große Herausforderung in der Kombination von Echtzeitfähigkeit und der komplexen Funktionsweise in einem mobilen System zu sehen. Um ein System zu entwickeln, welches zur Laufzeit Wissen durch möglichst natürliche Mensch-Maschine-Kommunikation erlangen und wiedergeben kann, mussten Wege gefunden werden, mit denen bei der Verarbeitung Rechenzeit gespart werden kann. Eine der Kernideen für die Lösung dieses Problems bestand darin, den Benutzer als Experten für die Korrektur bzw. die Steuerung des Systems zu verwenden. In dieser Arbeit wird aufgezeigt, dass erst die Integration des menschlichen Experten in die Verarbeitungsprozesse des künstlichen Systems die Verwendung von Verfahren ermöglicht, welche zwar eine geringere Leistungsfähigkeit bieten als vergleichbare komplexere Algorithmen, dafür aber einen sehr geringen Rechenaufwand benötigen und somit überhaupt erst für ein mobiles System in Frage kommen. Die fehlende Robustheit und Fehlerfreiheit der informatischen Verfahren wird durch die enge Interaktion mit dem menschlichen Experten kompensiert.
Um den Benutzer eines solchen Systems als Experten für die Korrektur von Systemungenauigkeiten oder gar -fehlern mit einbeziehen zu können, wurde in dieser Arbeit ein System entwickelt, mit dem über die natürliche Kommunikation durch Sprache und Gestik ein gemeinsames Verständnis von Mensch und Maschine im gegebenen Kontext erlangt werden konnte. Dabei kann der Benutzer sowohl durch Zeigegesten die Aufmerksamkeit des Systems lenken als auch durch natürliche Bewegungen mit dem Finger die Systemfunktionen über ein virtuelles Menü steuern. Alternativ kann die Steuerung des Systems verbal erfolgen.
Für den Fall, dass die visuelle Erkennung der Gestik durch geänderte Lichtverhältnisse oder die akustische Erkennung der Sprache durch Störgeräusche fehlerhaft sind, gewährleistet die Kombination dieser beiden Kommunikationsmöglichkeiten, dass der Benutzer das System über den alternativen Kommunikationsweg an die veränderten Bedingungen anpassen kann, so dass in beiden Fällen die Funktionalität erhalten bleibt. Das System kann dem Benutzer sowohl durch akustische Signale als auch über das Display Informationen, wie beispielsweise über die Systemzustände oder Verarbeitungsergebnisse, mitteilen; auf diese kann der Benutzer bei Bedarf reagieren und damit das System steuern.
Neben der Funktion zur Systemsteuerung ist die natürliche Kommunikation eine weitere wesentliche Voraussetzung für die Entwicklung eines online trainierbaren und somit lernfähigen Objekterkenners. Dem Objekterkenner des entwickelten Demonstrators kann neues Objektwissen einerseits durch Präsentation von Objekten vermittelt werden. Andererseits kann das System selbstständig, von einem Aufmerksamkeitssystem gesteuert,Bilddaten aufnehmen und diese interaktiv durch Kommunikation mit dem Benutzer für den Objekterkenner verfügbar machen.
Die erste Möglichkeit interaktiven Objektlernens besteht darin, dass dem System durch den Benutzer neue Objekte in natürlicher Art und Weise aus mehreren Ansichten präsentiert werden. Das System nimmt dabei die Bilddaten auf und erlernt die Objekte nach Nennung des Namens. Diese Variante eignet sich insbesondere für das Erlernen von solchen Objekten, mit denen der Benutzer hantiert.
Dagegen ermöglicht die zweite Variante, dass auch Objekte aus der Umgebung des Benutzers komfortabel gelernt werden. Dazu werden, von einem Aufmerksamkeitssystem gesteuert, Bilddaten aufgenommen, während sich der Benutzer ganz natürlich in seiner Umgebung bewegt. Diese Bilddaten können anschließend unter Zuhilfenahme Selbstorganisierender Karten strukturiert, im Display visualisiert und anschließend komfortabel gelabelt werden. Die so nach Objekten getrennten Bilddaten werden dem Klassifikator zum Erlernen übertragen. Für die Strukturierung der Daten wurden Bildmerkmale nach dem MPEG-7 Standard in der originalen oder in einer für die Aufgabe optimierten Version verwendet. Diese entsprechen dabei grob zwei unterschiedlichen Kategorien, einerseits Farbmerkmalen und andererseits kanten- oder strukturbasierten Merkmalen. Die Gewichtung der Merkmale kann der Benutzer je nach Charakteristik der Bilddaten variieren. In der Arbeit wird an zwei unterschiedlichen Datensätzen aufgezeigt, dass es die Clusterung der Bilddaten durch die SOM ermöglicht, dass eine große Anzahl an Bildausschnitten in wenigen Schritten nach Objekten getrennt werden und interaktiv vom Benutzer gelabelt werden kann. Dabei erhöht die Möglichkeit, die Gewichtung der Merkmale zu variieren, die Trennungseffizienz der Bilddaten.
Für beide Arten des online-Lernens von Objekten wurde ein kognitiv motiviertes Lernverfahren entwickelt, bei dem einerseits, wie beim menschlichen Kurzzeitgedächtnis,Wissen über eine kleine Menge von Objekten nahezu unmittelbar zur Verfügung stehen kann und andererseits nach längerer Zeit eine Vielzahl von Objekten in einer Art Langzeitgedächtnis gespeichert werden kann.
Diese zwei Lerngeschwindigkeiten werden dabei von der in drei Verarbeitungsebenen unterteilten Architektur des verwendeten VPL-Klassifikators ermöglicht. Dazu wird beim schnellen Erlernen von Objektwissen nur die letzte Schicht neu trainiert, was zu einer geringeren Robustheit führt und wodurch die Erkennungperformanz nur bei einer geringen Anzahl von Objekten zufriedenstellend ist. Zu einem Zeitpunkt, an dem das System nicht ausgelastet ist und somit Ressourcen frei sind, findet das robustere und zeitaufwändigere Erlernen über alle Schichten statt. Wie sich die Performanz der beiden Verfahren bei variierender Objektanzahl im Hinblick auf die Rechenzeit verhält, wurde an Standarddatensätzen ermittelt.
Der Objekterkenner ist die Basis für das Wiederfinden von Objekten. Dazu enthält das System eine Vorstufe des VAMs in Form eines Bildergedächtnisses, in welchem die zuletzt wahrgenommenen Aufenthaltsorte jedes Objektes abgelegt werden und auf Nachfrage vom Benutzer visuell präsentiert werden können. Somit können verlegte Objekte vom Benutzer erfragt werden. Das Bild von dem gesuchten Objekt in seiner zuletzt vom System wahrgenommenen Position wird eingeblendet und ermöglicht so ein leichtes Wiederfinden
Modeling of evolving textures using granulometries
No full textThis chapter describes a statistical approach to classification of dynamic texture images, called parallel evolution functions (PEFs). Traditional classification methods predict texture class membership using comparisons with a finite set of predefined texture classes and identify the closest class. However, where texture images arise from a dynamic texture evolving over time, estimation of a time state in a continuous evolutionary process is required instead. The PEF approach does this using regression modeling techniques to predict time state. It is a flexible approach which may be based on any suitable image features. Many textures are well suited to a morphological analysis and the PEF approach uses image texture features derived from a granulometric analysis of the image. The method is illustrated using both simulated images of Boolean processes and real images of corrosion. The PEF approach has particular advantages for training sets containing limited numbers of observations, which is the case in many real world industrial inspection scenarios and for which other methods can fail or perform badly. [41] G.W. Horgan, Mathematical morphology for analysing soil structure from images, European Journal of Soil Science, vol. 49, pp. 161–173, 1998. [42] G.W. Horgan, C.A. Reid and C.A. Glasbey, Biological image processing and enhancement, Image Processing and Analysis, A Practical Approach, R. Baldock and J. Graham, eds., Oxford University Press, Oxford, UK, pp. 37–67, 2000. [43] B.B. Hubbard, The World According to Wavelets: The Story of a Mathematical Technique in the Making, A.K. Peters Ltd., Wellesley, MA, 1995. [44] H. Iversen and T. Lonnestad. An evaluation of stochastic models for analysis and synthesis of gray-scale texture, Pattern Recognition Letters, vol. 15, pp. 575–585, 1994. [45] A.K. Jain and F. Farrokhnia, Unsupervised texture segmentation using Gabor filters, Pattern Recognition, vol. 24(12), pp. 1167–1186, 1991. [46] T. Jossang and F. Feder, The fractal characterization of rough surfaces, Physica Scripta, vol. T44, pp. 9–14, 1992. [47] A.K. Katsaggelos and T. Chun-Jen, Iterative image restoration, Handbook of Image and Video Processing, A. Bovik, ed., Academic Press, London, pp. 208–209, 2000. [48] M. K¨oppen, C.H. Nowack and G. R¨osel, Pareto-morphology for color image processing, Proceedings of SCIA99, 11th Scandinavian Conference on Image Analysis 1, Kangerlussuaq, Greenland, pp. 195–202, 1999. [49] S. Krishnamachari and R. Chellappa, Multiresolution Gauss-Markov random field models for texture segmentation, IEEE Transactions on Image Processing, vol. 6(2), pp. 251–267, 1997. [50] T. Kurita and N. Otsu, Texture classification by higher order local autocorrelation features, Proceedings of ACCV93, Asian Conference on Computer Vision, Osaka, pp. 175–178, 1993. [51] S.T. Kyvelidis, L. Lykouropoulos and N. Kouloumbi, Digital system for detecting, classifying, and fast retrieving corrosion generated defects, Journal of Coatings Technology, vol. 73(915), pp. 67–73, 2001. [52] Y. Liu, T. Zhao and J. Zhang, Learning multispectral texture features for cervical cancer detection, Proceedings of 2002 IEEE International Symposium on Biomedical Imaging: Macro to Nano, pp. 169–172, 2002. [53] G. McGunnigle and M.J. Chantler, Modeling deposition of surface texture, Electronics Letters, vol. 37(12), pp. 749–750, 2001. [54] J. McKenzie, S. Marshall, A.J. Gray and E.R. Dougherty, Morphological texture analysis using the texture evolution function, International Journal of Pattern Recognition and Artificial Intelligence, vol. 17(2), pp. 167–185, 2003. [55] J. McKenzie, Classification of dynamically evolving textures using evolution functions, Ph.D. Thesis, University of Strathclyde, UK, 2004. [56] S.G. Mallat, Multiresolution approximations and wavelet orthonormal bases of L2(R), Transactions of the American Mathematical Society, vol. 315, pp. 69–87, 1989. [57] S.G. Mallat, A theory for multiresolution signal decomposition: the wavelet representation, IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 11, pp. 674–693, 1989. [58] B.S. Manjunath and W.Y. Ma, Texture features for browsing and retrieval of image data, IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 18, pp. 837–842, 1996. [59] B.S. Manjunath, G.M. Haley and W.Y. Ma, Multiband techniques for texture classification and segmentation, Handbook of Image and Video Processing, A. Bovik, ed., Academic Press, London, pp. 367–381, 2000. [60] G. Matheron, Random Sets and Integral Geometry, Wiley Series in Probability and Mathematical Statistics, John Wiley and Sons, New York, 1975
Scientometric Portrait of Homi Jehangir Bhabha: The Father of Indian Nuclear Research Programme
Get PDFQuantitative and qualitative analysis with graphic representation of the publication productivity of a scientist facilitates easy and clear perception about the work of a scientist. Bhabha’s scientific work spanned over more than three decades (1933-1967) during which he published 104 publications, which could be classified into nine fields: Interaction of Radiation with Matter (4), Quantum Electrodynamics (5), Mathematical Physics (2), Cosmic Ray Physics (18), Elementary Particle Physics (14), Field Theory (15), General Physics (2), Nuclear Physics (4) and General (40). The highest number of publications (6) were published in 1941, 1945 and 1964 respectively. The average number of publications published per year was 3.05. His productivity coefficient was 0.05 which is a clear indicates that his publication productivity was quite consistent throughout his scientific career. He was single author in 79 of his publications and the main author in 24 publications indicates that he always preferred to work himself and lead the team as ‘mentor’. Bhabha had 22 collaborators during the period. Team of research collaborators working with a successful scientist documents the sociological aspect of history of science while generating knowledge by a leader in a domain.
Bhabha became a citable author in 1937. Bhabha received 1211 citations to his 30 publications out of 104 publications. Out of 104, 74 publications did not receive any citations. Out of 74 publications, 40 publications dealt subjects mainly of general interest. Bhabha’s 86.66 percent of cited publications received their first citations within four years of their publication indicates that his publications were noticed immediately and had direct impact among the fellow researchers working all over the world. His overall citation rate was 11.64 per cited publication. The highest citations 389 were received to the domain ‘Cosmic ray physics’. The highest number of citations received were 45 in 1938. His self-citations were only 24 (1.98%) and citations by others were 1187 (98.02%). The highest self citations were six in 1946. Bhabha’s mean diachronous self-citation rate was 1.98. The highest citation rate 28.4 was to the domain ‘Quantum electrodynamics. His single authored publications have received the highest number 863 (71.26%) of citations. Bhabha’s five publications have been cited more than 100 times each. His publications have been cited by the authors working in various diverse fields like nuclear physics, mathematical physics, instrumentation, optics, geophysics and geochemistry, condensed matter physics, applied physics, electrical and electronic engineering, mechanical engineering etc., indicating a very diverse influence and impact of Bhabha’s publications. Bhabha’s publications have also been cited by the Nobel laureates like V. L. Ginzberg, Wolfgang Pauli, H. A. Bethe, M. Born, W. Bothe, E. P. Wigner, H. Yukawa, P. M. S. Blackett and C. N. Yang which is an indication of his originality of ideas and high quality of publications
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