seit 2020 | Hauptamtlicher Professor für IT-Security und Künstliche Intelligenz an der Leibniz-FH |
2020 | IT Security Projektleiter, Continental Reifen Deutschland GmbH, Hannover |
2019-2020 | Postdoc. Forscher, Medizinische Hochschule Hannover |
2019 | Leiter Forschung und Entwicklung, Identass GmbH&Ko. KG, Gießen |
2018-2019 | Lehrbeauftragter, Universität Bayreuth |
2018 | Habilitation in Informatik an der Universität Bayreuth |
2012-2018 | Akademischer Rat a. Z., Universität Bayreuth |
2012 | Postdoc. Forscher, Scuola Superiore Sant’Anna, Pisa, Italien |
2011 | Promotion in Informatik an der Philipps-Universität Marburg |
2009-2012 | Wissenschaftlicher Mitarbeiter, Philipps-Universität Marburg |
2007-2009 | Softwareentwickler |
2001-2007 | Studium der Diplom-Mathematik an der Justus-Liebig-Universität Gießen |
Prof. Dr. Oleg Lobachev
Studiengangsverantwortung IT-Security
- Planung und Durchführung von Lehrveranstaltungen
- Studierendenbetreuung
- Mitwirkung in den Studiengremien der Leibniz FH
Leibniz-FH
- Komplexität in Software
- Machine Learning
- Projekt mit Industriepartnern
- Grundlagen IT-Security
Universität Bayreuth
- Künstliche Intelligenz II
- Funktionale Programmierung
- Computergraphik I
- Multimediale Systeme
- Java
Philipps-Universität Marburg
- Funktionale Programmierung
Publikationen
GIT Labor-Fachzeitschrift, 10: 3234.
Scientific Reports, 1:16487
The human spleen is equipped with an organ-specific microcirculation. The initial part of the venous circulation is formed by spleen-specific large microvessels, the sinuses. Sinuses eventually fuse to form venules and veins. For more than 170 years there have been debates, whether splenic red pulp capillaries join sinuses, i.e., whether the microcirculation is closed or openor even simultaneously closed and open. We have now solved this question by three-dimensional reconstruction of a limited number of immunostained serial sections of red and white pulp areas, which were visualized in virtual reality. Splenic capillaries have special end structures exhibiting multiple small diverging endothelial cell processes, which always keep a certain distance to the walls of sinuses. Only very few capillary ends were difficult to diagnose. Positive identification of these end structures permits to conclude that the human splenic microcirculation is entirely open. This is also true for the perifollicular capillary network and for capillaries close to red pulp venules. Follicles are supplied by a relatively dense open perifollicular capillary net, which is primarily, but not exclusively, fed by sheathed and few non-sheathed capillaries from the surrounding red pulp network.
LINK ÖFFNENHistochemistry and Cell Biology, 155(2):227239, ISSN 1432-119X.
Various lung diseases, including pulmonary hypertension, chronic obstructive pulmonary disease or bronchopulmonary dysplasia, are associated with structural and architectural alterations of the pulmonary vasculature. The light microscopic (LM) analysis of the blood vessels is limited by the fact that it is impossible to identify which generation of the arterial tree an arterial profile within a LM microscopic section belongs to. Therefore, we established a workflow that allows for the generation-specific quantitative (stereological) analysis of pulmonary blood vessels. A whole left rabbit lung was fixed by vascular perfusion, embedded in glycol methacrylate and imaged by micro-computed tomography (µCT). The lung was then exhaustively sectioned and 20 consecutive sections were collected every 100 µm to obtain a systematic uniform random sample of the whole lung. The digital processing involved segmentation of the arterial tree, generation analysis, registration of LM sections with the µCT data as well as registration of the segmentation and the LM images. The present study demonstrates that it is feasible to identify arterial profiles according to their generation based on a generation-specific color code. Stereological analysis for the first three arterial generations of the monopodial branching of the vasculature included volume fraction, total volume, lumen-to-wall ratio and wall thickness for each arterial generation. In conclusion, the correlative image analysis of µCT and LM-based datasets is an innovative method to assess the pulmonary vasculature quantitatively.
LINK ÖFFNENIEEE Access, 9: 152514152535, ISSN 2169-3536.
Registration of histological serial sections is a challenging task. Serial sections exhibit distortions and damage from sectioning. Missing information on how the tissue looked before cutting makes a realistic validation of 2D registrations extremely difficult. This work proposes methods for ground-truth-based evaluation of registrations. Firstly, we present a methodology to generate test data for registrations. We distort an innately registered image stack in the manner similar to the cutting distortion of serial sections. Test cases are generated from existing 3D data sets, thus the ground truth is known. Secondly, our test case generation premises evaluation of the registrations with known ground truths. Our methodology for such an evaluation technique distinguishes this work from other approaches. Both under- and over-registration become evident in our evaluations. We also survey existing validation efforts. We present a full-series evaluation across six different registration methods applied to our distorted 3D data sets of animal lungs. Our distorted and ground truth data sets are made publicly available.
LINK ÖFFNENHistochemistry and Cell Biology, 155(3):341354, ISSN 1432-119X.
We reconstructed serial sections of a representative adult human spleen to clarify the unknown arrangement of the splenic microvasculature, such as terminal arterioles, sheathed capillaries, the red pulp capillary network and venules. The resulting 3D model was evaluated in virtual reality ({VR}). Capillary sheaths often occurred after the second or third branching of a terminal arteriole and covered its capillary side or end branches. The sheaths started directly after the final smooth muscle cells of the arteriole and consisted of cuboidal {CD}271++ stromal sheath cells surrounded and infiltrated by B lymphocytes and macrophages. Some sheaths covered up to four sequential capillary bifurcations thus forming bizarre elongated structures. Each sheath had a unique form. Apart from symmetric dichotomous branchings inside the sheath, sheathed capillaries also gave off side branches, which crossed the sheath and freely ended at its surface. These side branches are likely to distribute materials from the incoming blood to sheath-associated B lymphocytes and macrophages and thus represent the first location for recognition of blood-borne antigens in the spleen. A few non-sheathed bypasses from terminal arterioles to the red pulp capillary network also exist. Red pulp venules are primarily supplied by sinuses, but they also exhibit a few connections to the capillary network. Thus, the human splenic red pulp harbors a primarily open microcirculation with a very minor closed part.
LINK ÖFFNENFrontiers in Virtual Reality, 2, ISSN 2673-419.
3D reconstruction is a challenging current topic in medical research. We perform 3D reconstructions from serial sections stained by immunohistological methods. This paper presents an immersive visualization solution to quality control (QC), inspect, and analyze such reconstructions. QC is essential to establish correct digital processing methodologies. Visual analytics, such as annotation placement, mesh painting, and classification utility, facilitates medical research insights. We propose a visualization in virtual reality (VR) for these purposes. In this manner, we advance the microanatomical research of human bone marrow and spleen. Both 3D reconstructions and original data are available in VR. Data inspection is streamlined by subtle implementation details and general immersion in VR.
LINK ÖFFNENIEEE Access, 8:1348913506, ISSN 2169-3536.
This work presents two methods that facilitate a 3D reconstruction of microscopic blood vessels in the volume slightly larger than 1 mm3 . The source of the data are histological serial sections, i.e., microscopic images of probes, stained with immunohistochemistry. Odd and even sections have different stainings in our primary data set. Thus, firstly, an approach to register an alternately-stained series is presented. With image filtering and a feature-detection-based registration we obtain a registered stack of 148 serial sections. The series has missing sections, locally damaged sections, artifacts from acquisition. All these hinder correct connectivity of blood vessels. With our second approach we interpolate the missing information while maintaining the connectivity. We achieve this with deformations based on dense optical flow. The presented methodology is applicable to further histological series. A combination of both approaches allows us to reconstruct more than 76% larger volumes. An important detail was the composition mode of images. Summarizing, we use methods from image processing and computer vision to create large-scale 3D models from immunostained histological serial sections.
LINK ÖFFNENPLOS ONE, 13(2): 121.
We have reconstructed small parts of capillary networks in the human splenic white pulp using serial sections immunostained for CD34 alone or for CD34 and CD271. The three-dimensional (3D) models show three types of interconnected networks: a network with very few long capillaries inside the white pulp originating from central arteries, a denser network surrounding follicles plus periarterial T-cell regions and a network in the red pulp. Capillaries of the perifollicular network and the red pulp network have open ends. Perifollicular capillaries form an arrangement similar to a basketball net located in the outer marginal zone. The marginal zone is defined by MAdCAM-1+ marginal reticular stromal cells. Perifollicular capillaries are connected to red pulp capillaries surrounded by CD271+ stromal capillary sheath cells. The scarcity of capillaries inside the splenic white pulp is astonishing, as non-polarised germinal centres with proliferating B-cells occur in adult human spleens. We suggest that specialized stromal marginal reticular cells form a barrier inside the splenic marginal zone, which together with the scarcity of capillaries guarantees the maintenance of gradients necessary for positioning of migratory B- and T-lymphocytes in the human splenic white pulp.
LINK ÖFFNENThe Visual Computer, 34: 17491759.
PGP public keys are relatively small binary data. Their hashes are used and also visualized for comparison and validation purposes. We pursue a direct, but previously unused approach. We produce colorful images of public keys and other binary data by generating drawing primitives from binary input. Optionally, we also include the hashes in the visualization. The visualization of raw data together with its hash provides a further security benefit. With it we can visually detect hash collisions. The primary focus of this paper is a direct visualization of public keys. We tune the transparency heuristics for better results. Our method visually detects key spoofing on real SHA1 collision data.
LINK ÖFFNENScientific Reports, 8(1), Article number: 15720, ISSN 2045-2322.
Stromal capillary sheath cells in human spleens strongly express CD271, the low affinity nerve growth factor receptor p75. Serial sections of a representative adult human spleen were double-stained for CD271 versus smooth muscle alpha actin (SMA) plus CD34 to visualise capillary sheaths, the arterial tree and endothelial cells by transmitted light. Preliminary three-dimensional (3D) reconstructions of single regions were inspected in virtual reality (VR). This method showed that a large number of CD271+ sheaths occur in a post-arteriolar position often surrounding capillaries located close to divisions of arterioles. The length and diameter of capillary sheaths are rather heterogeneous. Long sheaths were observed to accompany one or two generations of capillary branches. We hypothesise that human splenic capillary sheaths may attract recirculating B-lymphocytes from the open circulation of the red pulp to start their migration into white pulp follicles along branches of the arterial tree. In addition, they may provide sites of interaction among sheath macrophages and B-lymphocytes. Our innovative approach allows stringent quality control by inserting the original immunostained serial sections into the 3D model for viewing and annotation in VR. Longer series of sections will allow to unequivocally localise most of the capillary sheaths in a given volume.
LINK ÖFFNENProcedia CIRP, 67: 6974.
Non-intrusive load monitoring is currently used to analyze changes in the energy consumption of households. Due to the number of electrical consumers, the associated superpositions and the variety of harmonic waves on the shop floor, current proceedings are not applicable in industrial environment. In this paper, patterns in harmonic waves of four manufacturing plants are analyzed in the time and frequency domain. For machine allocation, features were extracted and classified by k-means and support vector machines with an accuracy of 97.3 and 97.9%. For comparison, convolutional neural networks were trained with the harmonic profiles in the time domain with an accuracy of 98.7%.
LINK ÖFFNENMedical Image Analysis, 35: 288302.
The form and exact function of the blood vessel network in some human organs, like spleen and bone marrow, are still open research questions in medicine. In this paper, we propose a method to register the immunohistological stainings of serial sections of spleen and bone marrow specimens to enable the visualization and visual inspection of blood vessels. As these vary much in caliber, from mesoscopic (millimeter-range) to microscopic (few micrometers, comparable to a single erythrocyte), we need to utilize a multi-resolution approach.
Our method is fully automatic; it is based on feature detection and sparse matching. We utilize a rigid alignment and then a non-rigid deformation, iteratively dealing with increasingly smaller features. Our tool pipeline can already deal with series of complete scans at extremely high resolution, up to 620 megapixels. The improvement presented increases the range of represented details up to smallest capillaries. This paper provides details on the multi-resolution non-rigid registration approach we use. Our application is novel in the way the alignment and subsequent deformations are computed (using features, i.e. sparse). The deformations are based on all images in the stack (global).
We also present volume renderings and a 3D reconstruction of the vascular network in human spleen and bone marrow on a level not possible before. Our registration makes easy tracking of even smallest blood vessels possible, thus granting experts a better comprehension.
A quantitative evaluation of our method and related state of the art approaches with seven different quality measures shows the efficiency of our method. We also provide z-profiles and enlarged volume renderings from three different registrations for visual inspection.
LINK ÖFFNENPLOS ONE, 11(12):125
The arrangement of microvessels in human bone marrow is so far unknown. We combined monoclonal antibodies against CD34 and against CD141 to visualise all microvessel endothelia in 21 serial sections of about 1 cm2 size derived from a human iliac crest. The specimen was not decalcified and embedded in Technovit® 9100. In different regions of interest, the microvasculature was reconstructed in three dimensions using automatic methods. The three-dimensional models were subject to a rigid semiautomatic and manual quality control. In iliac crest bone marrow, the adipose tissue harbours irregularly distributed haematopoietic areas. These are fed by networks of large sinuses, which are loosely connected to networks of small capillaries prevailing in areas of pure adipose tissue. Our findings are compatible with the hypothesis that capillaries and sinuses in human iliac crest bone marrow are partially arranged in parallel.
LINK ÖFFNENJournal of WSCG, 24(1):18, ISSN 1213-6964
The Metropolis Light Transport algorithm generates physically based images with superior image quality than classical ray tracing. Although it is trivially parallelizable on GPUs by running N MLTs, the performance on current graphics hardware is below par. One of the main problems is the set of incoherent paths due to the independent Markov chains. Since each MLT generates full paths and mutates them sequentially, we construct totally incoherent rays which in negatively affects the performance on the GPU. By using a novel speculative variant of the Metropolis algorithm we increase the similarity of paths and achieve higher coherence. This decreases the computation time significantly. Further, we improve memory access by optimizing the data layout to better utilize coalesced access.
LINK ÖFFNENJournal of Parallel and Distributed Computing, 73(6): 876887.
In this paper we introduce our estimation method for parallel execution times, based on identifying separate parts of the work done by parallel programs. Our run time analysis works without any source code inspection. The time of parallel program execution is expressed in terms of the sequential work and the parallel penalty. We measure these values for different problem sizes and numbers of processors and estimate them for unknown values in both dimensions using statistical methods. This allows us to predict parallel execution time for unknown inputs and non-available processor numbers with high precision. Our prediction methods require orders of magnitude less data points than existing approaches. We verified our approach on parallel machines ranging from a multicore computer to a peta-scale supercomputer.
Another useful application of our formalism is a new measure of parallel program quality. We analyse the values for parallel penalty for both growing input size and for increasing numbers of processing elements. From these data, conclusions on parallel performance and scalability are drawn.
LINK ÖFFNENJournal of WSCG, 21(2):145152, ISSN 1213-6964
We present a device for detection of hail dents in passenger cars. For this purpose we have constructed a new multi-camera deflectometric setup for large specular objects. Deflectometric measurements have strict constraints how cameras can be placed for instance: angular restrictions and distance limitations. An important trait of our system is the static setup we use a single setup for camera configuration for all objects to be scanned. We render the camera images and analyze them for the deflectometric needs to optimize the camera placement w.r.t. multiple parameters. Important ones are the positions of the cameras reflections of the patterns should be clearly visible. Camera parameters are computed using a global optimization procedure for which we efficiently generate a good starting configuration. We introduce an empiric quality measure of a particular camera configuration and present both visual and quantitative results for the generated camera placement. This configuration was then used to build the actual device.
LINK ÖFFNENHabilitation thesis, Universität Bayreuth
PhD thesis, Philipps-Universität Marburg
Logos, Berlin, ISBN 978-3-8325-2881-2
Leibniz-FH Research Paper No. 14
arXiv:1801.02216 [cs.PL]
Arrows are a general interface for computation and an alternative to Monads for API design. In contrast to Monad-based parallelism, we explore the use of Arrows for specifying generalised parallelism. Specifically, we define an Arrow-based language and implement it using multiple parallel Haskells.
As each parallel computation is an Arrow, such parallel Arrows (PArrows) can be readily composed and transformed as such. To allow for more sophisticated communication schemes between computation nodes in distributed systems, we utilise the concept of Futures to wrap direct communication.
To show that PArrows have similar expressive power as existing parallel languages, we implement several algorithmic skeletons and four benchmarks. Benchmarks show that our framework does not induce any notable performance overhead. We conclude that Arrows have considerable potential for composing parallel programs and for producing programs that can execute on multiple parallel language implementations.
Proceedings of the 33rd Spring Conference on Computer Graphics, SCCG 2017, Mikulov, Czech Republic, May 15-17, 2017, pages 14:114:11
Histological serial sections allow for 3D representation of anatomical structures in microscopic to mesoscopic range. However, due to the nature of the acquisition, they suffer from severe anisotropy: 14-to-1 in a single average microscopic paraffin section. We present an interpolation method based on optical flow and show that standard interpolation methods are less suited for serial sections.
With our non-linear interpolation approach we are able to represent the „movement“ of image parts that are of interest. This allows for better 3D reconstructions and further insights in microanatomy.
LINK ÖFFNENWSCG '2016: short communications proceedings: The 24th International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision 2016 in co-operation with EUROGRAPHICS: University of West Bohemia, Plzen, Czech Republic, May 30 - June 3 2016, p. 17-23.
WSCG 2014: Poster Papers Proceedings: 22nd International Conference in Central Europeon Computer Graphics, Visualization and Computer Vision in co-operation with EUROGRAPHICS Association, p. 45-48.
Eurographics Workshop on Visual Computing for Biology and Medicine, VCBM 2014, Vienna, Austria, Proceedings, pages 6978
The spleen is one of the organs, where the micro-structure and the function on that level are not completely understood. It was for example only recently found that is has an open circulation, which distinguishes it from all other organs. Imaging the complete vascular network from the arteries to open-ended capillaries would greatly facilitate research in this area. The structure of such tissue is best uncovered using immunehistological staining. This can however only be applied to thin tissue sections and larger structures span several slices. Due to the deformation induced when cutting the specimen, standard registration algorithms cannot be used to merge the images into a volume. We propose a specialized matching algorithm to robustly determine corresponding regions in the images. After a rigid alignment of the scans, we use a cubic B-spline to deform and align the images. During this process we minimize the total deformation to produce as accurate results as possible.
LINK ÖFFNENWSCG 2014: communication papers proceedings: 22nd International Conference in Central Europeon Computer Graphics, Visualization and Computer Visionin co-operation with EUROGRAPHICS Association, p. 361-368.
Functional and Logic Programming 11th International Symposium, FLOPS 2012, Kobe, Japan, May 23-25, 2012. Proceedings, pages 197212
A parallel computation with early termination property is a special form of a parallel for loop. This paper devises a generic highlevel approach for such computation which is expressed as a scheme for algorithmic skeletons. We call this scheme map+reduce, in similarity with the map-reduce paradigm. The implementation is concise and relies heavily on laziness. Two case studies from computational number theory support our presentation.
LINK ÖFFNENProceedings of the Fourth International Workshop on High-level Parallel Programming and Applica- tions, HLPP 10, pages 2534
Computer Algebra in Scientific Computing 12th International Workshop, CASC 2010, Tsakhkadzor, Armenia, September 6-12, 2010. Proceedings, pages 178193
Workshop on Many-Cores at 22nd International Conference on Architecture of Computing Systems: 4755.
Parallel Computing Technologies 10th International Conference, PaCT 2009, Novosibirsk, Russia, August 31 September 4, 2009. Proceedings, pages 7383
The paper investigates and compares skeleton-based Eden implementations of different FFT-algorithms on workstation clusters with distributed memory. Our experiments show that the basic divide-and-conquer versions suffer from an inherent input distribution and result collection problem. Advanced approaches like calculating FFT using a parallel map-and-transpose skeleton provide more flexibility to overcome these problems. Assuming a distributed access to input data and re-organising computation to return results in a distributed way improves the parallel runtime behaviour.
LINK ÖFFNENIntelligent Computer Mathematics 9th International Conference, AISC 2008, 15th Symposium, Calculemus 2008, 7th International Conference, MKM 2008, Birmingham, UK, July 28 August 1, 2008. Proceedings, pages 141154
This paper discusses the pros and cons of using a functional language for implementing a computer algebra system. The contributions of the paper are twofold. Firstly, we discuss some languagecentered design aspects of a computer algebra system the language unity concept. Secondly, we provide an implementation of a fast polynomial multiplication algorithm, which is one of the core elements of a computer algebra system. The goal of the paper is to test the feasibility of an implementation of (some elements of) a computer algebra system in a modern functional language.
LINK ÖFFNEN