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Spatial modulation : a spatial multiplexing technique for efficient wireless data transmission
No full textThe need for high peak data rates with the corresponding need for significantly increased spectral efficiencies and the support for service specific QoS requirements are the key elements that drive the research in the area of wireless communication access technologies. Among the set of existing technologies, MIMO-OFDM with adaptive coding and modulation is promising candidate for future wireless systems. A few basic algorithms for multiple antenna systems and many refinements thereof have been intensively studied in the past few years. Mainly, there are three categories of MIMO techniques. First, multiple antennas can be used to improve the power efficiency by maximizing spatial diversity. The second multiple antenna algorithm exploits channel knowledge at the transmitter. In this thesis, channel information is assumed to be known only at the receiver side and no channel information exists at the transmitter side. The third type uses layered space-time approach to transmit multiple independent data streams over the antennas to increase capacity. A well-known technique is the proposed BLAST architecture. Such technique is called spatial multiplexing. There still exist several problems for a practical deployment of spatial multiplexing multiple antenna systems. One of them is the complexity of the algorithms due to seemingly unavoidable ICI. Of course, the performance of the system can be traded off against the receiver complexity, but this is not desirable. Furthermore, multiple antenna systems are known to achieve relatively good performance in idealistic channel conditions. However, the performance of these systems degrades severely under non-ideal channel conditions. A key to solving these issues is seen in the avoidance of ICI whilst maintaining the spatial multiplexing gain. The goals seem contradictory, but the feasibility is demonstrated in this thesis. The basic idea is named SM
Lateralization of spatial attention in the human brain : a 'virtual lesion' approach
No full textThe ability to direct attention to different locations in space appears to require the involvement of cortical networks located in the parietal lobe in the human brain. The cognitive deficits of neglect and extinction suggest that the right parietal cortex supports to a greater degree the ability to attend to contralateral space than the left parietal cortex. Using the technique of Transcranial Magnetic Stimulation II conducted a series of experiments aimed at establishing the effectiveness of different experimental paradigms for biasing the attentional function. In another series of experiments, using only behavioral methods without TMS, I studied the nature of the interhemispheric connections and the interactions between the two brain hemispheres by testing the effects of symmetry perception (symmetrical arrangement of the stimuli as well as symmetry of the perceived objects) on performance. Based on the findings from the experiments I was able to delineate a contiguous region in right parietal cortex whose deactivation results in a significant bias of spatial attention towards the ipsilateral side of space, thus confirming the hypothesis that spatial attention is functionally lateralized. The findings also support the idea of the competitive nature of the interactions between the two hemisphere resulting in a dynamic balance in the intact state. This balance can be perturbed by unilateral deactivation, with the right hemisphere being more susceptible to modulation than the left hemisphere, and it can be paradoxically restored by bilateral deactivation. The interhemispheric connections mediate the competitive balance between the two hemispheres by exchanging predominantly excitatory signals, but the facilitation and inhibition effects on performance seem to involve higher-order representations of distributed neural activity, which do not necessarily result in a low-level point-to-point activation exchange between homologous regions in the two hemispheres
Web Coverage Processing Service (WCPS) Implementation Specification
No full textThe Open GeoSpatial Consortium (OGC) is the main driving force for open, interoperable service interfaces for geospatial information. To serve this mission, OGC develops and maintains a family of modular standards. The historically main standard for multi-dimensional raster data is the Web Coverage Service (WCS) Implementation Specification which defines basic access functionality on server-stored raster data (aka "coverages").
During the development of WCS several requests have came up to add this or that processing functionality. It was decided, however, to keep WCS basic in its function- ality and rather have a separate, WCS-relate d standard which allows users to compose their own functions without complexity restrictions – in short: to develop a standard offering a raster processing language.
The pertaining specification is the Web Coverage Processing Service (WCPS) Implementation Specification which is currently under development within OGC, by a working group initiated and led by Jacobs University Bremen. WCPS provides access to original or derived sets of geospatial coverage information, in forms that are useful for client-side rendering, input into scientific models, and other client applications. As such, WCPS includes WCS functionality and extends it with an expression language to form requests of arbitrary complexity allowing, e.g., multi-valued coverage results.
The official status of WCPS within OGC is that of a Best Practice document (document no. 06-035r1), ie., an official re commendation by OGC. The report on hand presents an advanced WCPS specification version, which is considered complete and consistent enough to present it for public discussion and, finally, decision on becoming an accepted OGC standard
Discovering multiscale dynamical features with hierarchical Echo State Networks
No full textMany time series of practical relevance data have multi-scale characteristics. Prime examples are speech, texts, writing, or gestures. If one wishes to learn models of such systems, the models must be capable to represent dynamical features on different temporal and/or spatial scales. One natural approach to this end is hierarchical models, where higher processing layers are responsible for processing longer-range (slower, coarser) dynamical features of the input signal. This report introduces a hierarchical architecture where the core ingredient of each layer is an echo state network. In a bottom-up flow of information, throughout the architecture increasingly coarse features are extracted from the input signal. In a top-down flow of information, feature expectations are passed down. The architecture as a whole is trained on a one-step input prediction task by stochastic error gradient descent. The report presents a formal specification of these hierarchical systems and illustrates important aspects of its functioning in a case study with synthetic data
Functionalized polymer vesicles and interactions with Polymyxin B and derivatives
No full textThe goal of this work was to study functionalized polymer vesicles and their interactions with Polymyxin B and its derivatives. The first part of the work investigates the interactions between polymer vesicles made of MPEG-PVL and Polymyxin B and its derivatives using fluorescence and calorimetric studies. It is shown that Polymyxin B binds and penetrates the polymer bilayer only in the presence of THF. This indicates that the hydrophobic part of Polymyxin B alone is not sufficient to penetrate the polymer bilayer. In the second part of the work, we analyzed a nanocompartment system for biotechnological applications. The nanocompartment system consists of a polymer vesicle and membrane proteins acting as selective gates. We have constructed FhuA variants by deleting fragments of varying lengths in the cork domain in the barrel of FhuA in order to study the stability and the transport properties of these variants. We attempted to quantify the number of membrane proteins reconstituted in the polymer vesicle wall introducing an extra cysteine in the periplasmic side of the barrel to be labeled with gold and detected by Cryo-TEM. For the he first time FhuA[Delta]1-129 variant was reconstituted in polymer vesicles made of diblock copolymer loaded with HRP. Industrially important enzymes such as dehydrogenases were encapsulated in nanocompartments using the ethanol method and ink jet method. Furthermore, a nanocompartment system loaded with polycations was studied for selective recovery and controlled release. A reduction uction triggered release from the nanocompartments loaded with calcein is further reported. The release system represents to our knowledge the first trigger system of a chemically modified transmembrane channel which releases an entrapped compound upon the addition of a reducing agent. Two amino labels differing in size were further investigated by recording and analyzing calcein release kinetics
Siderophore production of Pseudomonas syringae and its implications on the biological control of bacterial blight of soybean
No full textSuppression of a plant pathogen's growth in planta by naturally occurring antagonists offers a favorable alternative to classical methods of plant protection. The soybean epiphyte, Pseudomonas syringae pv. syringae strain 22d/93 (Pss22d), exhibits a strong potential to control P. syringae pv. glycinea 1a/96 (Psg1a), the causal agent of bacterial blight of soybean. While suppression of growth of P. syringae pv. glycinea by Pss22d has been shown in greenhouse system as well as under field conditions, underlying mechanism(s) remained unknown. In frame of this work the influence of siderophore production on the biological control system was investigated. Although antagonist and pathogen produce the typical pyoverdin-type siderophore of P. syringae pathovars, they showed clearly distinct iron-chelating phenotypes. Mutational analysis of siderophore production in Pss22d led to the identification of an additional siderophore system with high sequence similarities towards achromobactin biosynthesis genes of Dickeya chrysanthemi. In vitro production of both siderophores by Pss22d was analyzed in detail. The distribution of this second siderophore among different pathovars of P. syringae was investigated. It could be demonstrated that many but not all P. syringae strains produce it. Interestingly, Psg1a belongs to the strains tested positive for the achromobactin-like siderophore. In consequence, pathogen Psg and antagonist Pss22d produced the same set of siderophores and a direct role of competition for iron in the examined biocontrol system could be excluded. Finally, the impact of the two siderophores of Pss22d on in planta performance of respective siderophore mutants was investigated. This study presents novel information on siderophore production of plant-associated bacteria as well as on the role of iron supply for epiphytic fitness and biological control in the phyllosphere
A smart locomotion support component
No full textThe concepts of Urban Search and Rescue robots have been developed since the great Hanshin-Awaji Earthquake in Japan in 1995. A tracked locomotion is the most suitable platform to surmount obstacles and be able to adapt to terrain variations in these environments. Nevertheless, the tracked locomotion that has only one pair of tracks will suffer from coping with rough terrain. The common solution is to use additional tracks that can change their posture relative to the main robot body, a so-called flipper. The typical mechanism is to directly drive the flipper joint with a spur or worm gear, a belt, or a chain drive. The great risk is a broken-joint of the flipper due to the unpredicted high force from shocks or impacts on the flipper when the flipper is moved under load or the robot drives over bumps, stairs, etc. To overcome the flaws,a novel flipper has been developed. The mechanism uses the passive link and the ball screw as the shock absorber. Moreover, the flipper also has modular feature. The control system is designed based on the fuzzy logic control. The promising performance has been verified by series of simulation results that the flipper can be employed as a main tool to support the robot for coping with any kind of obstacles autonomously
SWiM - A Semantic Wiki for Mathematical Knowledge Management
No full textThe aim of the research presented in this technical report was, and still is, to develop a wiki (Leuf and Cunningham, 2001) technology for collaboratively building, editing and browsing mathematical knowledge. This technology is being prototyped in the SWiM system (S-emantic Wi-ki for M-athematical Knowledge Management). Its hyperlinked pages, containing mathematical theories and statements, are stored in OMDoc (Kohlhase, 2006), a markup format for mathematical knowledge representation with numerous applications: creation of customized modules for e-learning, data exchange between different theorem provers, web services and more. SWiM has been intended to be based on an already existing wiki software, preferably a semantic one.
SWiM will encourage users to collaborate: non-mathematicians can collaborate in creating a "Wikipedia (Wikipedia, 2006) of mathematics" by compiling the knowledge available so far, while scientists can collaboratively develop new theories. However, to encourage users to contribute, wiki-like openness to anybody probably will not suffice. Unlike the text formats used by common semantic wikis, the OMDoc format makes the fine-grained semantic structure that is implicit in the text explicit in the markup, making it tedious to author by hand. Moreover, only after a substantial initial investment (writing, annotating and linking) on the author's part, the community can benefit from the added-value services supported by the format - e.g. the creation of customized textbooks (Melis and Siekmann, 2004). If author and beneficiary of such services were different persons, though, only few persons would be willing to contribute to a knowledge base. This "MKM 2 author’s dilemma" (Kohlhase and Kohlhase, 2004) can be overcome when the authors themselves are rewarded for their contributions by being offered added-value services, which improve as soon as users contribute annotations and cross-references, - for example a facility for navigation through the knowledge base along paths of semantic relations between the theories, which are computed from the OMDoc document collection.
The contribution of this research is threefold:
1. The architecture of SWiM has been specified.
2. A partial implementation has been done, and it has been evaluated.
3. Parts of the OMDoc 1.2 standard have been improved (mainly those parts used in the SWiM implementation, i.e. the example documents, the presen- tation XSLT style sheets and the system ontology).
Further information about the project is available from its homepage http://kwarc.eecs.iu-bremen.de/projects/swim/ . A ready-to-install package will be available for download there from March 2007, and an online demo is available.
The research presented here has been conducted from February to August 2006 in the context of my diploma thesis, which has been supervised by Prof. Bernd Walter (University of Trier) and Prof. Michael Kohlhase (Jacobs University Bremen) (Lange, 2006a). For this report, the thesis has been revised. Outdated facts have been brought up-to-date, and certain aspects of the evaluation have been concretized with further research on this topic for my Ph.D. thesis in mind, but the requirements analysis (section 2), the specification (section 3) and the implementation described in section 4 remained unchanged
The Error Controlling Algorithm for Learning OOMs
No full textObservable operator models (OOMs) are matrix models for describing stochastic processes. In this report we proposed a novel algorithm for learning OOMs from empirical data. Like other learning algorithms of OOMs, the presented algorithm is based upon the learning equation, a linear equation on observable operators involving two adjustable matrices P and Q. The algorithm designs P, Q so that an upper bound of the error between the estimated model and the "real" model is minimized. So we call it the error controlling (EC) algorithm.
One important feature of the EC algorithm is that it can be used online, where it updates the estimation of observable operators on each new observation via a set of RLS-like formulas. By the linearity of the learning equation, we are able to prove the asymptotic correctness of the online learning procedure.
The main numerical problem of the EC algorithm is to control t he condition of the learning equation online (or minimize it offline), leading to an optimization problem of special form. For this special problem we propose d an efficient method that searches for the global optimum alternatively on two orthogonal directions and call it the orthogonal searching (OS) algorithm. The performance of EC, in which the OS algorithm is used as the inner optimizer, is studied through some (offline and online) leaning examples
Investigation of structural, conformational, and dynamic properties of polypeptides by fluorescence-based techniques
No full textStructural, conformational, and dynamic changes in polypeptides play an important role in protein folding. In order to study these structural and dynamic changes in polypeptides in different environments, several fluorescence-based techniques are described in this thesis. The structural and conformational changes in polypeptides were probed by fluorescence resonance energy transfer (FRET), where tryptophan (Trp) and 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) were employed initially as the donor and acceptor, respectively. The unique photophysical character of the acceptor, in particular its low extinction coefficient, allows measurements of average distances in short peptides with high accuracy. An aspargine derivative, Fmoc-DBO (Dbo), was synthesized in order to introduce the fluorophore into the peptide chain at either the C- or N-terminal position through solid-phase synthesis. For the first time, we applied a donor/acceptor pair with such a short Förster distance (10 Å) in biological molecules. Initially, this FRET pair was established for application in very simple and flexible peptides, namely Gly-Ser peptides with varying lengths. This FRET pair was extended to polyproline (Trp-(Pro)n-Dbo) as the backbone between Trp and Dbo. In this case, the length of the peptide chain was also varied (n = 1-6) . In addition, the Trp/DBO FRET pair was applied to study the conformational changes upon phosphorylation in polypeptides. The effect of phosphorylation on energy transfer was studied in two synthetic peptides, which were derived from two popular protein kinases