9752024
Invadable self-assembly: combining robustness with efficiency
DNA self-assembly is emerging as a key paradigm for nano-technology, nano-computation, and several related disciplines. In nature, DNA self-assembly is often equipped with explicit mechanisms for both error prevention and error correction. For artificial self-assembly, these problems are even more important since we are interested in assembling large systems with great precision. So far, theoretical studies of DNA self-assembly have primarily focused on the efficiency of the assembly process in terms of the program size and the running time. In this paper, we perform a preliminary study of algorithms for DNA self-assembly that are both robust and efficient.Strand invasion is an important error-correction mechanism observed in several natural self-assembling systems. We first define invadable self-assemblies as self-assembling systems which can effectively use the strand invasion mechanism for error-correction. We then show that O(log2 n/ log log n) tiles are sufficient to assemble an n × n square in this model. The running time of our system is Õ (n). We obtain our result by growing a counter which simulates Chinese remaindering. The running time and the program size of our invadable system are within polylogarithmic factors of known lower bounds for general systems, i.e. the efficiency penalty for obtaining robustness is small in our model. We also show how to simulate an arbitrary Turing machine using an invadable self-assembly system.
13538048
Error Free Self-assembly Using Error Prone Tiles
DNA self-assembly is emerging as a key paradigm for nano-technology, nano-computation, and several related disciplines. In nature, DNA self-assembly is often equipped with explicit mechanisms for both error prevention and error correction. For artificial self-assembly, these problems are even more important since we are interested in assembling large systems with great precision. 
 
We present an error-correction scheme, called snaked proof-reading, which can correct both growth and nucleation errors in a self-assembling system. This builds upon an earlier construction of Winfree and Bekbolatov [11], which could correct a limited class of growth errors. Like their construction, our system also replaces each tile in the system by a k × k block of tiles, and does not require changing the basic tile assembly model proposed by Rothemund and Winfree [8]. 
 
We perform a theoretical analysis of our system under fairly general assumptions: tiles can both attach and fall off depending on the thermodynamic rate parameters which also govern the error rate. We prove that with appropriate values of the block size, a seed row of n tiles can be extended into an n × n square of tiles without errors in expected time $\widetilde{O}(n)$, and further, this square remains stable for an expected time of $\widetilde{\Omega}(n)$. This is the first error-correction system for DNA self-assembly that has provably good assembly time (close to linear) and provable error-correction. The assembly time is thesame, up to logarithmic factors, as the time for an irreversible, error-free assembly. 
 
We also did a preliminary simulation study of our scheme. In simulations, our scheme performs much better (in terms of error-correction) than the earlier scheme of Winfree and Bekbolatov, and also much better than the unaltered tile system. 
 
Our basic construction (and analysis) applies to all rectilinear tile systems (where growth happens from south to north and west to east). These systems include the Sierpinski tile system, the square-completion tile system, and the block cellular automata for simulating Turing machines. It also applies to counters, a basic primitive in many self-assembly constructions and computations.
20735579
Kinetically stable task assignment for networks of microservers
• Job titles for all employees • Most recent payroll data (wages, hours, job codes, and dates of hire) • Union contracts • Employee handbooks or benefit descriptions • Summary plan descriptions for health and retirement plans • Benefit costs summaries or insurance bills For a detailed listing of information that BLS economists typically request, please visit the National Compensation Survey Web site at http://www.bls.gov/ncs/collection.htm. What is the National Compensation Survey (NCS)?
8049932
On the variable capacity property of CC/DS-CDMA systems
A complete complementary code based direct sequence code division multiple access (CC/DS-CDMA) system has been proposed recently as a potential candidate for beyond third generation (B3G) wireless communications. This paper addresses the issues that design of efficient code assignment schemes should be based on a flexible physical layer support, which is extremely important for emerging cross-layer designs in future wireless applications. The study in this paper considers a CC/DS-CDMA system with multiple time slots, three traffic classes and two dynamic code-flock assignment schemes, namely random assignment (RA) and compact assignment (CA). Simulation results show that the CC/DS-CDMA system has variable capacity property (VCP), which is sensitively affected by different code-flock assignment schemes. In general, CA can offer lower blocking probability, whereas RA can offer a larger mean system capacity and higher throughput when offered traffic is heavy
32790214
Federating Diverse Collections of Scientific Literature
The Digital Library Initiative (DLI) project at the University of Illinois at Urbana-Champaign is developing the information infrastructure to effectively search technical documents on the Internet. The authors are constructing a large testbed of scientific literature, evaluating its effectiveness under significant use, and researching enhanced search technology. They are building repositories (organized collections) of indexed multiple-source collections and federating (merging and mapping) them by searching the material via multiple views of a single virtual collection. Developing widely usable Web technology is also a key goal. Improving Web search beyond full-text retrieval will require using document structure in the short term and document semantics in the long term. Their testbed efforts concentrate on journal articles from the scientific literature, with structure specified by the Standard Generalized Markup Language (SGML). Research efforts extract semantics from documents using the scalable technology of concept spaces based on context frequency. They then merge these efforts with traditional library indexing to provide a single Internet interface to indexes of multiple repositories.
6781537
Formal Models of Heavy-Tailed Behavior in Combinatorial Search
Recently, it has been found that the cost distributions of randomized backtrack search in combinatorial domains are often heavytailed. Such heavy-tailed distributions explain the high variability observed when using backtrack-style procedures. A good understanding of this phenomenon can lead to better search techniques. For example, restart strategies provide a good mechanism for eliminating the heavy-tailed behavior and boosting the overall search performance. Several state-of-the-art SAT solvers now incorporate such restart mechanisms. The study of heavy-tailed phenomena in combinatorial search has so far been been largely based on empirical data. We introduce several abstract tree search models, and show formally how heavy-tailed cost distribution can arise in backtrack search. We also discuss how these insights may facilitate the development of better combinatorial search methods.
2228993
Visualization in law enforcement
Visualization techniques have proven to be critical in helping crime analysis. By interviewing and observing Criminal Intelligence Officers (CIO) and civilian crime analysts at the Tucson Police Department (TPD), we found that two types of tasks are important for crime analysis: crime pattern recognition and criminal association discovery. We developed two separate systems that provide automatic visual assistance on these tasks. To help identify crime patterns, a Spatial Temporal Visualization (STV) system was designed to integrate a synchronized view of three types of visualization techniques: a GIS view, a timeline view and a periodic pattern view. The Criminal Activities Network (CAN) system extracts, visualizes and analyzes criminal relationships using spring-embedded and blockmodeling algorithms. This paper discusses the design and functionality of these two systems and the lessons learned from the development process and interaction with law enforcement officers.
26701472
Interface descriptions for enterprise architecture
This paper describes our experiences in implementing a repository-based system that records and manages architectural information for an organization-wide set of enterprise information systems. The system is called Interface Descriptions for Enterprise Architecture (IDEA). The IDEA system business case and system creation are discussed, and the use of the system is exemplified by applying it to a set of information systems within a large corporation. We show how the existence of a managed enterprise architecture description enables an important set of analyses: risk analyses, architecture analyses, and change management analyses. Finally, we discuss how the IDEA system has the potential to catalyze even more profound change by changing how the various systems' stakeholders interact.