AN ARTIFICIAL NEURAL NETWORK FOR SONAR TARGET DETECTION

Neural Network has emerged as the topic of the day. The spectrum of its application is as wide as from ECG noise filtering to seismic data analysis and from elementary particle detection to electronic music composition. The focal point of the proposed work is an application of a massively parallel connectionist model network for detection of a sonar target. This task is segmented into: (i) generation of training patterns from sea noise that contains radiated noise of a target, for teaching the network;(ii) selection of suitable network topology and learning algorithm and (iii) training of the network and its subsequent testing where the network detects, in unknown patterns applied to it, the presence of the features it has already learned in. A three-layer perceptron using backpropagation learning is initially subjected to a recursive training with example patterns (derived from sea ambient noise with and without the radiated noise of a target). On every presentation, the error in the output of the network is propagated back and the weights and the bias associated with each neuron in the network are modified in proportion to this error measure. During this iterative process, the network converges and extracts the target features which get encoded into its generalized weights and biases.In every unknown pattern that the converged network subsequently confronts with, it searches for the features already learned and outputs an indication for their presence or absence. This capability for target detection is exhibited by the response of the network to various test patterns presented to it.Three network topologies are tried with two variants of backpropagation learning and a grading of the performance of each combination is subsequently made.

Collective behavior of laser-produced plasma from a multicomponent YBa2Cu3O7 target in air

The dynamics of diffusion of electrons and ions from the laser-produced plasma from a multielement superconducting material, namely YBa2Cu3O7, using a Q-switched Nd:YAG laser is investigated by time-resolved emission-spectroscopic techniques at various laser irradiances. It is observed that beyond a laser irradiance of 2.6 \xC3\x97 1011 W cm-2, the ejected plume collectively drifts away from the target with a sharp increase in velocity to 1.25 \xC3\x97 106 cm s-1, which is twice its velocity observed at lower laser irradiances. This sudden drift apparently occurs as a result of the formation of a charged double layer at the external plume boundary. This diffusion is collective, that is, the electrons and ions inside the plume diffuse together simultaneously and hence it is similar to the ambipolar diffusion of charged particles in a discharge plasma

Twin peak distribution of electron emission profile and impact ionization of ambient molecules during laser ablation of silver target

Laser-induced plasma generated from a silver target under partial vacuum conditions using the fundamental output of nanosecond duration from a pulsed Nd:yttrium aluminum garnet laser is studied using a Langmuir probe. The time of flight measurements show a clear twin peak distribution in the temporal profile of electron emission. The first peak has almost the same duration as the laser pulse while the second lasts for several microseconds. The prompt electrons are energetic enough ('60 eV) to ionize the ambient gas molecules or atoms. The use of prompt electron pulses as sources for electron impact excitation is demonstrated by taking nitrogen, carbon dioxide, and argon as ambient gases.

Photoemission optogalvanic studies with copper as target electrode

Photoemission optogalvanaic (POG) effect has been observed by irradiating copper target electrode, in a nitrogen discharge cell using 1.06 μm and frequency doubled 532 nm Nd:YAG laser pulse. Measurement of the nature of the variation of POG signal strength with 532 nm laser fluence confirms the two photon induced photoelectric emission from copper. However, using 1.06 μm laser pulses thermally assisted photoemission is observed.

Temporal and spatial evolution of C2 in laser induced plasma from graphite target

Laser ablation of graphite has been carried out using 1.06mm radiation from a Q-switched Nd:YAG laser and the time of flight distribution of molecular C2 present in the resultant plasma is investigated in terms of distance from the target as well as laser fluences employing time resolved spectroscopic technique. At low laser fluences the intensities of the emission lines from C2 exhibit only single peak structure while beyond a threshold laser fluence, emission from C2 shows a twin peak distribution in time. The occurrence of the faster velocity component at higher laser fluences is explained as due to species generated from recombination processes while the delayed peak is attributed to dissociation of higher carbon clusters resulting in the generation of C2 molecule. Analysis of measured data provides a fairly complete picture of the evolution and dynamics of C2 species in the laser induced plasma from graphite.

Realisation of a Target Classifier For Noise Sources in the Ocean

This thesis addresses one of the emerging topics in Sonar Signal Processing.,viz.the implementation of a target classifier for the noise sources in the ocean, as the operator assisted classification turns out to be tedious,laborious and time consuming.In the work reported in this thesis,various judiciously chosen components of the feature vector are used for realizing the newly proposed Hierarchical Target Trimming Model.The performance of the proposed classifier has been compared with the Euclidean distance and Fuzzy K-Nearest Neighbour Model classifiers and is found to have better success rates.The procedures for generating the Target Feature Record or the Feature vector from the spectral,cepstral and bispectral features have also been suggested.The Feature vector ,so generated from the noise data waveform is compared with the feature vectors available in the knowledge base and the most matching pattern is identified,for the purpose of target classification.In an attempt to improve the success rate of the Feature Vector based classifier,the proposed system has been augmented with the HMM based Classifier.Institutions where both the classifier decisions disagree,a contention resolving mechanism built around the DUET algorithm has been suggested.

Biochemical effects of the pesticide Chlorpyrifos on the fish Oreochromis mossambicus (Peters)

Man uses a variety of synthetic material for his comfortable materialistic life. Thus human interactions may become harmful for various terrestrial and aquatic lives. This is by contaminating their habitat and by becoming a threat to organisms itself. Thus the application and dispersal of several organic pollutants can lead to the development of several mutated forms of the species when exposed to sublethal concentrations of the pollutants. Otherwise, a decrease in number or extinction of these exposed species from earth's face may happen. Pesticides, we use for the benefit of crop yield, but its persistence may become havoc to non-target organism. Pesticides reaching a reservoir can subsequently enter the higher trophic levels. Organophosphorus compounds have replaced all other pesticides, due to its acute toxicity and non-persistent nature.Hence the present study has concentrated on the toxicity of the largest market-selling and multipurpose pesticide, chlorpyrifos on the commonly edible aquatic organism, fish. The euryhaline cichlid Oreochromis mossambicus was selected as animal model. The study has concentrated on investigating biochemical parameters like tissue-specific enzymes, antioxidant and lipid-peroxidation parameters, haematological and histological observations and pesticide residue analysis.Major findings of this work have indicated the possibility of aquatic toxicity to the fish on exposure to the insecticide chlorpyrifos. The insecticide was found as effective to induce structural alteration, depletion in protein content, decrease in different metabolic enzyme levels and to progress lipid peroxidation on a prolonged exposure of 21 days. The ion-transport mechanism was found to be adversely affected. Electrophoretic analysis revealed the disappearance of several protein bands after 21days of exposure to chlorpyrifos. Residue, analysis by gas chromatography explored the levels of chlorpyrifos retaining on the edible tissue portions during exposure period of 21days and also on a recovery period of 10 days.

“Seaweed exudates and settlement behaviour of sedentary organisms"

The present investigation has looked exclusively into the aspect of the biological phenomenon of settling behaviour by two serious fouling offenders encountered in the tropical seas mainly on the hulls of ships and stationary structures in the harbours. The cue to study the behaviour was adopted from the observations so far made by scientists on the epizoic growth of these organisms on the surfaces of algal fronds of variegated shape, texture, size etc. The results do indicate that there are sufficient qualities of bioactive substances produced by plants occupying the lowest categories in organic evolution and curiously enough these substances have withstood the test of time.

Underwater Target Localization, Tracking and Classification

Underwater target localization and tracking attracts tremendous research interest due to various impediments to the estimation task caused by the noisy ocean environment. This thesis envisages the implementation of a prototype automated system for underwater target localization, tracking and classification using passive listening buoy systems and target identification techniques. An autonomous three buoy system has been developed and field trials have been conducted successfully. Inaccuracies in the localization results, due to changes in the environmental parameters, measurement errors and theoretical approximations are refined using the Kalman filter approach. Simulation studies have been conducted for the tracking of targets with different scenarios even under maneuvering situations. This system can as well be used for classifying the unknown targets by extracting the features of the noise emanations from the targets.

Biologische Funktionsanalyse und Identifizierung neuer Substrate der Methyltransferase Dnmt2

Obwohl die DNA Methyltransferase 2 (Dnmt2) hoch konserviert ist und zu der am weitesten verbreiteten eukaryotischen MTase-Familie gehört, ist ihre biologische Funktion nach wie vor unklar. Nachdem lange Zeit keine DNA Methylierungsaktivität nachgewiesen werden konnte, wurde vor einigen Jahren über geringe Mengen an 5-Methylcytosin (5mC) in Retroelementen der “Dnmt2-only”-Organismen D. melanogaster, D. discoideum und E. histolytica berichtet (Kunert et al. 2003; Fisher et al. 2004; Kuhlmann et al. 2005; Phalke et al. 2009). Als kurze Zeit später robuste Methylierung der tRNAAsp durch humane Dnmt2 gezeigt wurde (Goll et al. 2006), wurde zunächst eine Dualspezifität des Enzyms vorgeschlagen (Jeltsch et al. 2006). Neuere Daten zum 5mC-Status verschiedener „Dnmt2-only“-Organismen bilden Anlass für kontroverse Diskussionen über Ausmaß und Bedeutung der DNA Methyltransferaseaktivität von Dnmt2 (Schaefer et al. 2010a; Krauss et al. 2011). Die vorliegende Arbeit konzentriert sich auf die Identifizierung neuer RNA Substrate des Dnmt2-Homologs DnmA aus D. discoideum sowie die biologische Bedeutung der tRNA-Methylierung durch Dnmt2. Wie in anderen Organismen beschrieben, fungiert auch DnmA als tRNAAsp(GUC) MTase in vitro und in vivo. Zusätzlich konnte in vitro tRNAGlu(UUC) als neues Substrat der Dnmt2-Homologe aus D. discoideum und dem Menschen identifiziert werden. In einem Kooperationsprojekt wurde außerdem auch tRNAAsp-Methylierungsaktivität für das Dnmt2-Homolog aus S. pombe (Pmt1) nachgewiesen. Crosslink-RNA-Immunopräzipitationen (RNA-CLIP) mit anschließender Next-Generation-Sequenzierung der mit DnmA assoziierten RNAs zeigen, dass DnmA mit tRNA Fragmenten interagiert, die sich vom Anticodonloop bis in den T-loop erstrecken. Neben der tRNAAsp(GUC) und tRNAGlu(UUC/CUC) sind Fragmente der tRNAGly(GCC) verstärkt angereichert. Inwiefern diese Fragmente eine biologische Funktion haben oder spezifische Degradationsprodukte darstellen, ist noch ungeklärt. Interessanterweise sind von einigen tRNAs wenige Sequenzen von antisense-Fragmenten in den RNA-CLIP Daten zu finden, die etwas kürzer, jedoch exakt komplementär zu den genannten sense-Fragmenten sind. Besonders stark sind diese Fragmente der tRNAGlu(UUC) vertreten. In einem weiteren RNA-CLIP Experiment wurden U-snRNAs, snoRNA und intergenische Sequenzen mit DnmA angereichert. Bei nachfolgenden in vitro Methylierungsstudien konnte ausschließlich die U2-snRNA als potentielles Nicht-tRNA-Substrat der hDnmt2 und DnmA identifiziert werden. Da tRNA Modifikationen im Anticodonloop die Codonerkennung beeinflussen können, wurde ein System etabliert um die Translationseffizienz eines GFP-Reportergens in Wildtyp- und dnmAKO-Zellen zu messen. In D. discoideum wird das Aspartat-Codon GAU ca. zehnmal häufiger genutzt als das GAC Codon, allerdings ist nur eine tRNAAsp(GUC) im Genom der Amöbe kodiert. Aus diesem Grund wurde zusätzlich die Frage adressiert, inwiefern die DnmA-abhängige Methylierung dieser tRNA das „Wobbling“ beeinflusst. Dazu wurde dem Reportergen jeweils eine (GAU)5- und (GAC)5-Leadersequenz vorgeschaltet. Entgegen der Annahme wurde der (GAC)5-Leader in beiden Stämmen etwas effizienter translatiert. Insgesamt zeigte der dnmAKO-Stamm eine leicht erhöhte Translationseffizienz der Reportergene. Vergleichende Analysen zur Aufnahme von Fremd-DNA zeigten signifikant reduzierte Transformationseffizienzen mit einem integrierenden Plasmid in dnmAKO-Zellen. Ein weiterer dnmAKO-Stamm zeigte diesen Effekt jedoch nicht, wobei bei derselben Mutante eine deutlich reduzierte Aufnahme eines extrachromosomalen Plasmids zu verzeichnen war. Untersuchungen zum Einfluss von DnmA auf die Regulation des Retroelements skipper ergaben keinen Zusammenhang zwischen der Generierung kleiner RNAs und der erhöhten Transkription des Retrotransposons in dnmAKO-Zellen (Kuhlmann et al. 2005). Durch Kompensationsversuche sowie Experimente mit einer weiteren dnmAKO-Mutante konnte die Mobilisierung des Retrotransposons nicht eindeutig als DnmA-Funktion eingeordnet werden. In einem weiteren Projekt wurden die Bindung des m5C-bindenden Proteins EhMLBP aus E. histolytica an DNA mittels Rasterkraftmikroskopie abgebildet (Lavi et al. 2006). Neben vermutlich unspezifischen Endbindungsereignissen konnte eine bevorzugte Bindungsstelle des Proteins an LINE DNA (long intersperesed nuclear element) identifiziert werden. Möglicherweise fällt diese mit einem von zwei A/T-reichen Bereichen der LINE DNA zusammen, von denen vermutet wird, dass diese für die Bindung von EhMLBP an DNA von Bedeutung sind. Insgesamt bestätigen die Ergebnisse dieser Arbeit die tRNAAsp Methylierungsaktivität als konservierte Dnmt2-Funktion. Darüber hinaus erweitern sie das Substratspektrum der Dnmt2-Methyltransferasen im Bereich der tRNA. Außerdem wird erstmals ein potentielles Nicht-tRNA Substrat vorgeschlagen. Zusätzlich geben neu entdeckte Phänotypen Hinweise auf vielfältige zelluläre Dnmt2-Funktionen.

Physiological analysis of central and peripheral insect circadian pacemaker neurons

Alle bisher untersuchten Lebewesen besitzen (circadiane) innere Uhren, die eine endogene Perioden-länge von ungefähr 24 Stunden generieren. Eine innere Uhr kann über Zeitgeber mit der Umwelt synchronisiert werden und ermöglicht dem Organismus, rhythmische Umweltveränderungen vorweg zu nehmen. Neben einem zentralen Schrittmacher, der Physiologie und Verhalten des Organismus steuert, gibt es in unterschiedlichen Organen auch periphere Uhren, die die zeitlichen Abläufe in der spezifischen Funktion dieser Organe steuern. In dieser Arbeit sollten zentrale und periphere Schrittmacherneurone von Insekten physiologisch untersucht und verglichen werden. Die Neurone der akzessorischen Medulla (AME) von Rhyparobia maderae dienten als Modellsystem für zentrale Schrittmacher, während olfaktorische Rezeptorneurone (ORNs) von Manduca sexta als Modellsystem für periphere Schrittmacher dienten. Die zentralen Schrittmacherneurone wurden in extrazellulären Ableitungen an der isolierten AME (Netzwerkebene) und in Patch-Clamp Experimenten an primären AME Zellkulturen (Einzelzellebene) untersucht. Auf Netzwerkebene zeigten sich zwei charakteristische Aktivitätsmuster: regelmäßige Aktivität und Wechsel zwischen hoher und niedriger Aktivität (Oszillationen). Es wurde gezeigt, dass Glutamat ein Neurotransmitter der weitverbreiteten inhibitorischen Synapsen der AME ist, und dass in geringem Maße auch exzitatorische Synapsen vorkommen. Das Neuropeptid pigment-dispersing factor (PDF), das von nur wenigen AME Neuronen exprimiert wird und ein wichtiger Kopplungsfaktor im circadianen System ist, führte zu Hemmungen, Aktivierungen oder Oszillationen. Die Effekte waren transient oder langanhaltend und wurden wahrscheinlich durch den sekundären Botenstoff cAMP vermittelt. Ein Zielmolekül von cAMP war vermutlich exchange protein directly activated by cAMP (EPAC). Auf Einzelzellebene wurde gezeigt, dass die meisten AME Neurone depolarisiert waren und deshalb nicht feuerten. Die Analyse von Strom-Spannungs-Kennlinien und pharmakologische Experimente ergaben, dass unterschiedliche Ionenkanäle vorhanden waren (Ca2+, Cl-, K+, Na+ Kanäle sowie nicht-spezifische Kationenkanäle). Starke, bei hohen Spannungen aktivierende Ca2+ Ströme (ICa) könnten eine wichtige Rolle bei Ca2+-abhängiger Neurotransmitter-Ausschüttung, Oszillationen, und Aktionspotentialen spielen. PDF hemmte unterschiedliche Ströme (ICa, IK und INa) und aktivierte nicht-spezifische Kationenströme (Ih). Es wurde angenommen, dass simultane PDF-abhängige Hyper- und Depolarisationen rhythmische Membranpotential-Oszillationen verursachen. Dieser Mechanismus könnte eine Rolle bei PDF-abhängigen Synchronisationen spielen. Die Analyse peripherer Schrittmacherneurone konzentrierte sich auf die Charakterisierung des olfaktorischen Corezeptors von M. sexta (MsexORCO). In anderen Insekten ist ORCO für die Membran-Insertion von olfaktorischen Rezeptoren (ORs) erforderlich. ORCO bildet Komplexe mit den ORs, die in heterologen Expressionssystemen als Ionenkanäle fungieren und Duft-Antworten vermitteln. Es wurde die Hypothese aufgestellt, dass MsexORCO in pheromonsensitiven ORNs in vivo nicht als Teil eines ionotropen Rezeptors sondern als Schrittmacherkanal fungiert, der unterschwellige Membranpotential-Oszillationen generiert. MsexORCO wurde mit vermeintlichen Pheromonrezeptoren in human embryonic kidney (HEK 293) Zellen coexprimiert. Immuncytochemie und Ca2+ Imaging Experimente zeigten sehr schwache Expressionsraten. Trotzdem war es möglich zu zeigen, dass MsexORCO wahrscheinlich ein spontan-aktiver, Ca2+-permeabler Ionenkanal ist, der durch den ORCO-Agonisten VUAA1 und cyclische Nucleotide aktiviert wird. Außerdem wiesen die Experimente darauf hin, dass MsexOR-1 offensichtlich der Bombykal-Rezeptor ist. Eine weitere Charakterisierung von MsexORCO in primären M. sexta ORN Zellkulturen konnte nicht vollendet werden, weil die ORNs nicht signifikant auf ORCO-Agonisten oder -Antagonisten reagierten.

Funktion und Biogenese kleiner RNAs in Dictyostelium discoideum

RNA mediated gene silencing pathways are highly conserved among eukaryotes and they have been well investigated in animals and in plants. Longer dsRNA molecules trigger the silencing pathways: RNase III proteins and their dsRNA binding protein (dsRBP) partners recognize those molecules as a substrate and process 21 nucleotide long microRNAs (miRNAs) or small interfering RNAs (siRNAs). Some organisms encode RNA dependent RNA polymerases (RdRPs), which are able to expand the pool of existing siRNAs. Argonaute proteins are able to bind small regulatory RNAs and are subsequently recruited to target mRNAs by base complementary. This leads in turn to transcriptional or posttranscriptional silencing of respective genes. The Dictyostelium discoideum genome encodes two Dicer homologues (DrnA and DrnB), five Argonaute proteins (AgnA to AgnE) and three RdRPs (RrpA to RrpC). In addition, the amoeba is known to express miRNAs and siRNAs, while the latter derive mainly from the DIRS-1 retrotransposon. One part of this work focused on the miRNA biogenesis pathway of D. discoideum. It was shown that the dsRNA binding protein RbdB is a necessary component for miRNA processing in the amoeba. There were no mature miRNAs detectable by Northern blot analysis in rbdB- strains, which is also true for drnB mutants. Moreover, primary miRNA-transcripts (pri-miRNAs) accumulated in rbdB- and drnB- strains. Fluorescence microscopy studies showed a nuclear localization of RbdB. RbdB accumulated in distinct perinucleolar foci. These were reminiscent of plant dicing bodies that contain essential protein components for miRNA processing. It is well known that RNase III enzymes and dsRBPs work together during miRNA processing in higher eukaryotes. This work demonstrated that the same is true for members of the amoebozoa supergroup. In Arabidopsis the nuclear zinc finger protein Serrate (SE) is also necessary for miRNA processing. The D. discoideum homologue SrtA, however, is not relevant which has been shown by the analysis of the respective knockdown strain. MiRNAs are known to be differentially expressed in several RNAi knockout strains. The accumulation of miRNAs in agnA- strains and a strong decrease in rbdB- strains were criteria that could thus be successfully used (among others) to identify and validate new miRNAs candidates by Illumina®-RNA sequencing. In another part of this study, the silencing and amplification of the DIRS-1 retrotransposons was analyzed in more detail. It was already known that DIRS-1 transcripts and extrachromosomal DIRS-1 DNA molecules accumulated in agnA- strains. This phenotype was correlated with the loss of endogenous DIRS-1 siRNAs in the knockout strain. By deep sequencing analysis of small RNAs from the AX2 wild type and the agnA- strain, the strong decrease of endogenous DIRS-1 siRNAs in the mutant strain (accounting for 70 %) could be confirmed. Further analysis of the data revealed an unequal distribution of DIRS-1 derived siRNAs along the retroelement in the wild type strain, since only very few of them matched the inverted terminal repeats (ITRs) and the 5’- half of the first open reading frame (ORF). Besides, sense and antisense siRNAs were asymmetrically distributed, as well. By using different reporter constructs it was shown indirectly that AgnA is necessary for the RrpC mediated production of secondary DIRS-1 siRNAs. These analyses also demonstrated an amplification of siRNAs in 5’- and in 3’-direction. Further analysis of the agnA- strain revealed that not only DIRS-1 sense transcripts but also ORF2 and ORF3 encoded proteins were enriched. In contrast, the ORF1 encoded protein GAG was equally expressed in the mutant and the wild type. This might reflect the unequal distribution of endogenous DIRS-1 siRNAs along the retrotransposon. Southern Blot and PCR-analyses showed that extrachromosomal DIRS-1 DNA molecules are present in the cytoplasm of angA- strains and that they are complementary to sense transcripts of intact DIRS-1 elements. Thus, the extrachromosomal DIRS-1 intermediates are likely incomplete cDNA molecules generated by the DIRS-1 encoded reverse transcriptase. One could hypothesize that virus like particles (VLPs) are the places of DIRS-1 cDNA synthesis. At least, DIRS-1 GAG proteins interact and fluorescence microscopy studies showed that they localize in distinct cytoplasmic foci which accumulate in close proximity to the nuclei.

Metabolic disorders in the transition period indicate that the dairy cows' ability to adapt is overstressed

Metabolic disorders are a key problem in the transition period of dairy cows and often appear before the onset of further health problems. They mainly derive from difficulties the animals have in adapting to changes and disturbances occurring both outside and inside the organisms and due to varying gaps between nutrient supply and demand. Adaptation is a functional and target-oriented process involving the whole organism and thus cannot be narrowed down to single factors. Most problems which challenge the organisms can be solved in a number of different ways. To understand the mechanisms of adaptation, the interconnectedness of variables and the nutrient flow within a metabolic network need to be considered. Metabolic disorders indicate an overstressed ability to balance input, partitioning and output variables. Dairy cows will more easily succeed in adapting and in avoiding dysfunctional processes in the transition period when the gap between nutrient and energy demands and their supply is restricted. Dairy farms vary widely in relation to the living conditions of the animals. The complexity of nutritional and metabolic processes Animals 2015, 5 979 and their large variations on various scales contradict any attempts to predict the outcome of animals’ adaptation in a farm specific situation. Any attempts to reduce the prevalence of metabolic disorders and associated production diseases should rely on continuous and comprehensive monitoring with appropriate indicators on the farm level. Furthermore, low levels of disorders and diseases should be seen as a further significant goal which carries weight in addition to productivity goals. In the long run, low disease levels can only be expected when farmers realize that they can gain a competitive advantage over competitors with higher levels of disease.