Survey Talk Research Articles

Stem cell: Therapeutic approach and potential future

The numerous medical breakthroughs stem cell therapy can provide have led to stem cell research experiencing a surge in popularity. Thus, as modern technology develops, stem cell research may become a turning point for the medical field. Stem cell therapy provides several advantages over traditional treatments like surgical procedures, including lower risks, the absence of surgical wounds, and a non-invasive approach. Besides, undifferentiated organism treatment holds more potential to treat a more extensive assortment of illnesses compared with conventional medicines. This writing survey talks about late discoveries on numerous kinds of immature microorganisms, examining their sources, current clinical relevance, and expected potential outcomes. In particular, this audit looks at the accompanying areas of undeveloped cell research: undifferentiated cell treatment in regenerative medication; instigated pluripotent undifferentiated cells (iPSCs) and sickness demonstration; undeveloped cells and neurodegenerative infection; undeveloped cells and immunotherapy; undeveloped cells in regenerative medication; and, whats more, immature microorganisms and maturing. Through our examination, the paper has found that immature microorganisms have extraordinary potential for relieving infections that are impervious to conventional medicines. In any case, moral contemplations remain a worry, and there are as yet many difficulties to beat in the field. This audit means to sum up and look at the momentum of immature microorganism research while likewise featuring the far-reaching capability of undifferentiated cell movement in medication.

Low-dimensional Topology

The workshop brought together experts from across all areas of low-dimensional topology, including knot theory, computational topology, three-manifolds and four-manifolds. In addition to the standard research talks we had two survey talks by Marc Lackenby and Joel Hass, leading to discussions of open problems. Furthermore we had three sessions of fiveminute talks by a total of roughly thirty participants.

A survey on security and policy aspects of blockchain technology

This survey talks about the problem of security and privacy in the blockchain ecosystem which is currently a hot issue in the blockchain community. The survey intended to study this problem by considering different types of attacks in the blockchain network with respect to algorithms presented. After a preliminary literature review it seems that some focus has been given to study the first use case while, to the best of my knowledge, the second use case requires more attention when blockchain is applied to study it. The research is also interested in exploring the link between these two use cases to study the overall data ownership preserving accountable system which will be a novel contribution of this work. However, due to the subsequent government mandated secrecy around the implementation of d ata encryption standard ( DES), and the distrust of the academic community because of this, a movement was spawned that put a premium on individual privacy and decentralized control. This movement brought together the top minds in encryption and spawned the technology we know of as blockchain today. This survey explores the genesis of encryption, its early adoption, and the government meddling which eventually spawned a movement which gave birth to the ideas behind blockchain.

Virtual Reality for Modern Society

Treatment and recovery of the intellectual, mental, and engine sequela of focal sensory system brokenness regularly depends on appraisal instruments to illuminate conclusion and to follow changes in clinical status. Regularly, these evaluations utilize paper-and-pencil psychometrics, involved simple/PC tests, and rating of conduct inside the setting of true useful conditions. The current survey talks about the utilization of virtual reality (VR) innovation in clinical medication, particularly in careful preparing, torment the board and restorative treatment of psychological maladjustment. We present the regular kinds of VR test systems and their operational standards in previously mentioned fields. The clinical impacts are additionally talked about. In pretty much every examination that managed VR test systems, scientists have come to a similar end result that the two specialists and patients could profit by this novel innovation. In addition, favourable circumstances and burdens of the use of VR innovation in each field were talked about, and the future exploration headings were proposed

Online surveys as discourse context: Response practices and recipient design

While a growing body of work has focused on the interactional organization of telephone survey interviews, little if any research in conversation and discourse analysis has examined written online surveys as a form of talk-in-interaction. While survey researchers routinely examine such responses using content analysis or thematic analysis methods, this shifts the focus away from the precise language and turn constructional practices used by respondents. By contrast, in this study we examine open-ended text responses to online survey questions using a conversation analytic and discourse analytic approach. Focusing on the precise turn constructional practices used by survey respondents—specifically, how they formulate multi-unit responses and make use of turn-initial discourse markers—we demonstrate how online survey respondents treat open-ended survey questions much as they would any similar sequence of interaction in face-to-face or telephone survey talk, making online surveys a tenable source of data for further conversation analytic inquiry.

Quantum knot invariants

This is a survey talk on one of the best known quantum knot invariants, the colored Jones polynomial of a knot, and its relation to the algebraic/geometric topology and hyperbolic geometry of the knot complement. We review several aspects of the colored Jones polynomial, emphasizing modularity, stability and effective computations. The talk was given in the Mathematische Arbeitstagung June 24–July 1, 2011.

In memoriam: James Earl Baumgartner (1943–2011)

James Earl Baumgartner (March 23, 1943–December 28, 2011) came of age mathematically during the emergence of forcing as a fundamental technique of set theory, and his seminal research changed the way set theory is done. He made fundamental contributions to the development of forcing, to our understanding of uncountable orders, to the partition calculus, and to large cardinals and their ideals. He promulgated the use of logic such as absoluteness and elementary submodels to solve problems in set theory, he applied his knowledge of set theory to a variety of areas in collaboration with other mathematicians, and he encouraged a community of mathematicians with engaging survey talks, enthusiastic discussions of open problems, and friendly mathematical conversations.

(Invited) Limiting Current As a Tool to Study Oxygen Transport in PEM Fuel Cells

This talk will be based largely on a survey talk and paper1 presented at the ECS in 2012. At the end, some brief discussion of modeling applications of these methods to a public collection of experimental data2will also be given. The study of oxygen transport in PEM fuel cells requires consideration of water transport as well. Because water can appear in both vapor and liquid form, heat transport must also be considered. The flow-field channels, the diffusion medium, the micro-porous layer, and the electrode all influence transport in different ways, and it is desirable to be able to understand transport limitations in each of these components separately. We will explain how oxygen transport limiting current can be used to study transport in all of these components and briefly outline a model of oxygen, water, and heat transport that arose from the study of limiting current. Fig. 1 shows polarization curves taken with a 5cm2differential cell, using different dilute concentrations of oxygen in nitrogen for the cathode gas feed. At each concentration of oxygen, the polarization curve reaches a limiting current at which the curve becomes vertical. (The current increases occurring below 0.1 V are due to hydrogen evolution and can be ignored in the determination of limiting currents.) Fig. 2 shows a plot of oxygen transport resistance versus limiting current for the polarization curves shown in Fig. 1. Three different regions are apparent. The dry region occurs at low current densities when water production is small enough so that all water can diffuse through the DM/MPL in vapor form. In the transition region, water production becomes large enough so that condensation starts to take place; the liquid water obstructs oxygen transport and increases transport resistance. At large enough current densities, in the wet region, oxygen transport resistance has stabilized at a higher value, indicating that beyond this point the cell is able to manage increasing water production without further impeding oxygen transport towards the cathode. It will be shown that different DM/MPL combinations exhibit different plots of the type shown in Fig. 2. Modeling shows that oxygen transport resistance is determined by a combination of the materials’ ability to transport both heat and water away from the electrode, and a procedure will be described for extracting oxygen transport parameters from limiting current data. A model of water transport in both vapor and liquid form in hydrophobic gas diffusion layers is also formulated, and the physical motivation for the model will be discussed.

Geometric Aspects of Spectral Theory

The workshop “Geometric Aspects of Spectral Theory” brought together leading researchers working in various areas of this vast field of mathematics. The meeting featured presentations on some of the most fascinating recent developments in the subject, including five survey talks given by top experts, as well as reports on the progress made by graduate students and postdocs. A number of new stimulating questions were formulated during the open problem session.

Hilbert’s Sixteenth Problem for Polynomial Liénard Equations

This article reports on the survey talk ‘Hilbert’s Sixteenth Problem for Lienard equations,’ given by the author at the Oberwolfach Mini-Workshop ‘Algebraic and Analytic Techniques for Polynomial Vector Fields.’ It is written in a way that it is accessible to a public with heterogeneous mathematical background. The article reviews recent developments and techniques used in the study of Hilbert’s 16th problem where the main focus is put on the subclass of polynomial vector fields derived from the Lierd equations.

Analysis and Geometric Singularities

The Conference on “Analysis and Geometric Singularities” took place from June 27 to July 3, 2010 and had 53 participants. The organization of the meeting followed the well-established scheme, providing plenty of discussion time which was intensely used, especially by the young participants. The four survey talks were given by Gilles Carron, Jean-Michel Bismut, Ulrich Bunke and Xiaonan Ma.

Discrete Geometry

Discrete Geometry deals with the structure and complexity of discrete geometric objects ranging from finite point sets in the plane to more complex structures like arrangements of n -dimensional convex bodies. Classical problems such as Kepler's conjecture and Hilbert's third problem on decomposing polyhedra, as well as classical works by mathematicians such as Minkowski, Steinitz, Hadwiger and Erdös are part of the heritage of this area. By its nature, this area is interdisciplinary and has relations to many other vital mathematical fields, such as algebraic geometry, topology, combinatorics, computational geometry, convexity, and probability theory. At the same time it is on the cutting edge of applications such as geographic information systems, mathematical programming, coding theory, solid modelling, computational structural biology and crystallography. The workshop was attended by 40 participants. There was a series of 12 survey talks giving an overview of developments in Discrete Geometry and related fields: In addition, there were 18 shorter talks and an open problem session chaired by János Pach on Wednesday evening — a collection of open problems resulting from this session can be found in this report. The program left ample time for research and discussions in the stimulating atmosphere of the Oberwolfach Institute.

Computational Algebraic Topology

The workshop was conducted jointly with a workshop in statistical learning theory. There was substantial interaction between the two groups, both formally in terms of talks attended by members of both groups, as well as via informal discussions. The intellectual themes which were presented during the workshop are described below. Sensor nets and engineering applications: In the opening talk R. Ghrist spoke about the topology necessary to develop methods for determining intruders have entered a net of sensors, and for counting their number. Ghrist, jointly with V. de Silva and Y. Baryshnikov, has developed techniques based directly on homological calculations as well as on integrals over Euler characteristics which hold promise for implementable algorithms. In order for such algorithms to be maximally useful, one must develop error insensitive methods, which will require more probabilistic methods to be included within the algebraic topological framework. Combinatorial applications: Several presentations at the workshop elaborated on the subject of combinatorial algebraic topology. D. Kozlov has given a survey talk, which has set the accents on the subject, tying together structures, methods, and applications, as these are present at the current state of the development. Talks by R. Jardine and M. Raussen concerned the combinatorial and computational aspects of homotopy theory, finding applications of such abstract notions as Quillen's closed model category. K. Knudson gave an interesting account of connections between persistent homology and discrete morse theory. Finally, the talk of E. Babson dealt with more probabilistic aspects and served as a bridge to the presentations of M. Kahle and P. Bubenik. Dynamical systems: K. Mischaikow and S. Day spoke about the use of algebraic topology to understand the qualitative structure of dynamical systems. Mischaikow introduced his paradigm of building databases of dynamical systems based on choices of parameter values. His methods permit the construction of partitions of parameter space within which the qualitative structure remains the same. In addition, Conley index methods, or rather their computational versions, are used to prove the existence of fixed points, recurrent points, and invariant subsets within a given region in a spatial domain. Data analysis: G. Carlsson and V. de Silva spoke about applications of various kinds of diagrams to understand the qualitative geometric nature of data sets. For example, persistence diagrams allow one to recover Betti numbers of sublevel sets of a probability distribution, multidimensional persistence allows one to study sublevel sets of various functions as well, and the analysis of structure theorems for certain kinds of quivers permits one to extend the bootstrap methods to clustering, Betti numbers, as well as to perform dynamic clustering (i.e. clustering over time). There are now viable computational methods for all of these applications. Probabilistic methods: M. Kahle and P. Bubenik spoke about the beginnings of stochastic algebraic topology. Work at the level of zeroth Betti numbers has already been carried out by M. Penrose, under the heading of “geometric random graphs”. What is now needed is an extension of this work to higher dimensional homology groups, as well as to the barcodes which arise in persistent homology. Ultimately, precise results along these lines will open up the possibility of direct evaluation of significance of various qualitative observations given a null hypothesis. There were also several talks more centered at applications, such as vision recognition (J. Giesen) and material science (R. MacPherson). All things considered, the workshop was a great success in terms of scientific interaction, both within this group, as well as with the researchers in statistical learning theory, as was witnessed by many involved discussions, which often lasted well into the late evenings.

Mini-Workshop: Arithmetik von Gruppenringen

The mini workshop "Arithmetic of group rings" was attended by 16 participants from Belgium, Brazil, Canada, Germany, Hungary, Israel, Italy, Romania and Spain. The expertise was a good mixture between senior and young researchers. It was a very stimulating experience and thesize of the group allowed excellent discussions amongst all participants. Very fruitful were the problem sessions, resulting in the problems listed at the end of this report. The main highlights of the conference were: The complete calculation of the projective Schur subgroup of the Brauer group by Aljadeff and del Rio. Hertweck's solution of the first Zassenhaus conjecture for finite metacyclic groups. the description of special subgroups of the unit group of integral group rings, such as the hypercentre and the finite conjugacy centre, and the relation with respect to the normalizer of the trivial units. discussion of the present state of art via several survey talks presented and the problem sessions The group G determines its integral group ring \mathbb Z G and its group V(\mathbb Z G) of normalized units. Several talks addressed the interplay of the cohomological properties of these three objects. Further topics included twisted group rings, group rings over local rings, polynomial growth and identities, orders and semigroup rings, Lie structure, representation-theoretic and algorithmic methods.

Analysis and Geometric Singularities

The conference on “Analysis and Geometric Singularities” took place from August 19 to August 25, 2007. The meeting was a popular one, with all spots taken, and its atmosphere was lively and full of activity. Participants ranged from many experts and old hands in the field to many young postdocs and graduate students, and the interaction between researchers at all levels was clearly productive for everyone. The talks were notably very well attended throughout the week, and many were accompanied by lively discussions. Each day was structured thematically: every day except Wednesday began with a longer (70 minute) survey talk on some general theme in the subject; the other talks each day were shorter (55 minutes) and focused on that theme. Wednesday morning, however, was devoted to five half-hour lectures by some of the younger participants. The first day's theme was spectral geometry; the lecture by Iosif Polterovich surveyed many recent results connecting spectral asymptotics and dynamics; later talks that day were given by Mueller, Kordyukov, Paycha and Grieser. Tuesday's survey talk by Mihalis Dafermos on the mathematics of black holes was followed by the lectures of Rodnianski, Vasy, Baer and Perry; the first two of these especially focusing on mathematical relativity. Thursday's survey by Jared Wunsch on propagation of singularities for the Schroedinger equation was followed by talks by Lesch, Ammann, Moscovici and Dai. Friday's theme was index theory, with a survey by Richard Melrose and other lectures by Carron, Albin, Bunke and Richardson. The young researchers who spoke on Wednesday were Azzali, Degeratu, Mazzieri, J. Mueller and Rochon. The scientific level of the talks was uniformly high, as will be seen from the abstracts which follow; many interesting results were announced, and the survey talks helped provide a focus which in turn facilitated communication between researchers in the various different fields represented. Overall, the conference gave clear evidence that the field of analysis on singular spaces is very active, and indeed is extending in many new directions. The many strong young researchers here indicate that the field has a bright future!

Algorithm Engineering

The workshop Algorithm Engineering , organized by Giuseppe Italiano (Roma), Petra Mutzel (Dortmund), Peter Sanders (Karlsruhe), and Martin Skutella (Dortmund) was held May 6th – May 12th, 2007. The goal of the workshop was to bring together researchers with different background, e.g., from combinatorial optimization, algorithmic theory, and algorithm engineering, in order to strengthen and foster collaborations in the area of algorithm engineering and to identify key research directions for the future. There were 47 international participants out of which 23 mainly work in the area of algorithm engineering, 11 in algorithm theory, and 13 in combinatorial optimization. A considerable number of participants visited the Oberwolfach Institute (MFO) for the first time. In five survey talks given by renowned specialists in the field, the state of the art in selected areas of high interest was demonstrated. The introductory talk was presented by Giuseppe Italiano (Roma) who gave “a personal and historical perspective” of algorithm engineering. Bill Cook (Atlanta) presented the newest results as well as engineering efforts for solving huge TSP instances. Friedhelm Meyer auf der Heide (Paderborn) suggested new algorithmic challenges in the area of Computer Graphics. Ian Munro (Waterloo) introduced the audience into the area of succinct data structures which is getting increasingly important with huge data sets. In this context, also external memory and cache-oblivious algorithms are getting growing interest. The survey talk by Gerth Brodal (Aarhus) presented theory and practice for these type of algorithms. In addition, we organized a series of sessions containing shorter contributions of roughly 30 minutes. Here, we particularly encouraged young researchers to present their recent results. The focus of the program lay on recent developments in various areas that are relevant for the broad topic of algorithm engineering. Examples are mathematical programming, external memory algorithms, succinct data structures, resilient data structures, dynamic data structures, online algorithms, graph algorithms, geometric computation, analysis of local search algorithms, and algorithmic game-theory. In total, we had 32 talks of which 15 can be assigned to the area of algorithm engineering, 8 to the area of algorithmic theory, and 7 to the area of combinatorial optimization, which we think was an ideal mixture for the purpose of this workshop. We found it encouraging that after the talks a lot of discussion took place between the participants. We also like to mention that Peter Sanders (Karlsruhe) introduced the new DFG Priority Program 1307 Algorithm Engineering , which will start in fall 2007. As the coordinator of this program he pointed out the specific goals of the program and the chances for the area of algorithm engineering. All of the participants had the chance to discuss different aspects of algorithm engineering in the open problem session on Thursday evening. In our view, and as expressed by many of the participants, the workshop was a great success. We (including many participants) have learned a lot during this week, also from the three different research communities present at the workshop, and got many new ideas for exciting research projects. The program of the workshop was well-received by the participants as the good quality of presentations and the enthusiasm of the speakers and the audience gave raise to joint research among the participants. In particular exchange between young researchers and experienced scientists was promoted. We wish to thank Oberwolfach for this unique opportunity to bring together the three different research groups at this great place in order to strengthen the area of algorithm engineering. The following collection of abstracts in chronological order gives a more detailed overview of the program.

Algebraic Groups

The workshop continued a series of Oberwolfach meetings on algebraic groups, started in 1971 by Tonny Springer and Jacques Tits who both attended the present conference. This time, the organizers were Michel Brion, Jens Carsten Jantzen, and Raphaël Rouquier. During the last years, the subject of algebraic groups (in a broad sense) has seen important developments in several directions, also related to representation theory and algebraic geometry. The workshop aimed at presenting some of these developments in order to make them accessible to a “general audience” of algebraic group-theorists, and to stimulate contacts between participants. Each of the first four days was dedicated to one area of research that has recently seen decisive progress: The first three days started with survey talks that will help to make the subject accessible to the next generation. The talks on the last day introduced to several recent advances in different areas: arithmetic groups, eigenvalue problems, counting orbits over finite fields, quivers and reflection functors. In order to leave enough time for fruitful discussions, the number of talks (generally of one hour) was limited to four per day. Besides the scientific program, the participants enjoyed a piano recital on Thursday evening, by Harry Tamvakis. The workshop was attended by 53 participants, coming mainly from Europe and North America. This includes 6 PhD students, supported by the Marie Curie program of the European Union. The organizers are grateful to the EU for this support, and to the MFO for providing excellent working conditions.

Diophantische Approximationen

Diophantische Approximationen

Some mathematical questions of theory of information transmission

A survey talk given by M.S. Pinsker at the Summer Seminar on Information Theory and Statistical Methods of Automatic Control, Prague, May 25---June 4, 1965, was published in Kybernetika journal of the Czech Academy of Sciences (1966, vol. 2, no. 2, pp. 117---146). By the courtesy of the editors of Kybernetika, we are allowed to publish an abridged version of the talk, which concisely and clearly exposes final mathematical results that underlie Shannon's information theory. The content of the talk is deeply intertwined with the author's works. The talk is almost unknown to Russian readers, and with this publication we fill this gap, thereby paying tribute to our outstanding scientist and friend.

T-Duality in Type II String Theory via Noncommutative Geometry and Beyond

It is by now well known that there are five (super) string theories, which are related to each other by transformations called dualities. If two such string theories are related by a duality transformation, it means that they are mathematically equivalent descriptions, and the string theories are said to be dual to each other. Here we review global aspects of one such duality, called T-duality in type II string theory, involving compactifications of spacetimeX with H -flux. That is,X is a principal torus bundle over M , with H -flux, and applying T-duality transformation along the fibre in general gives a space which does not admit a global manifold description. We precisely identify the cases in which the T-dual is another principal torus bundle with H-flux. This is always the case when when the torus bundle is of rank one, i.e. in the case of circle bundles. In general, the T-dual spacetime will have different topology to the original spacetime. For the case of torus bundles of rank greater than or equal to 2, we precisely identify the cases when the Tdual is a continuous field of stabilized noncommutative tori fibred over M , which globally corresponds to a certain crossed product C∗-algebra. This is always the case when the torus bundle is of rank two or less. The general case, when the rank or the principal torus bundle X with H-flux is greater than or equal to 3, leads to continuous fields of nonassociative and noncommutative tori in the fibre directions. Even in the general case, the action of T-duality is again globally realized by taking a certain twisted crossed product C∗-algebra (but now in a tensor category), and motivates an axiomatic definition of string T-duality. In this way, we see that both noncommutative and nonassociative geometry appears naturally in the study of Tduality. This article comprises essentially of a transcript of my talks that were delivered at the 21st Nishinomiya-Yukawa Memorial Symposium on Theoretical Physics: “Noncommutative Geometry and Quantum Spacetime in Physics”, Japan, 11–15 Nov 2006. I am grateful to the organizers for the invitation to give a series of survey talks based on the joint work with my collaborators, P. Bouwknegt, J. Evslin, K. Hannabuss and J. Rosenberg. In the title, the phrase “and beyond” refers to nonas-