Investigating Causal Relations by Econometric Models and Cross-Spectral Methods
There occurs on some occasions a difficulty in deciding the direction of causality between two related variables and also whether or not feedback is occurring. Testable definitions of causality and feedback are proposed and illustrated by use of simple two-variable models. The important problem of apparent instantaneous causality is discussed and it is suggested that the problem often arises due to slowness in recording information or because a sufficiently wide class of possible causal variables has not been used. It can be shown that the cross spectrum between two variables can be decomposed into two parts, each relating to a single causal arm of a feedback situation. Measures of causal lag and causal strength can then be constructed. A generalisation of this result with the partial cross spectrum is suggested.
Introduction to Statistical Quality Control
Quality Improvement in the Modern Business Environment.STAISTICAL METHODS USEFUL IN QUALITY IMPROVEMENT.Modeling Process Quality.Inferences About Process Quality.BASIC METHODS OF STATISTICAL PROCESS CONTROL AND CAPABILITY ANALYSIS.Methods and Philosophy of Statistical Process Control.Control Charts for Variables.Control Charts for Attributes.Process and Measurement Systems System Capability Analysis.OTHER STATISTICAL PROCESS MONITORING AND CONTROL TECHNIQUES.Cumulative Sum and Exponentially Weighted Moving Average Control Charts.Other Univariate SPC Techniques.Multivariate Process Monitoring and Control.Engineering Process Control and SPC.PROCESS DESIGN AND IMPROVEMENT WITH DESIGNED EXPERIMENTS.Factorial and Fractional Factorial Designs for Process Design and Improvement.Process Optimization with Designed Experiments.ACCEPTANCE SAMPLING.Lot--by--Lot Acceptance Sampling for Attributes.Other Acceptance Sampling Techniques.Appendix.Bibliography.Answers to Selected Exercises.Index.
Survey of Wireless Indoor Positioning Techniques and Systems
Wireless indoor positioning systems have become very popular in recent years. These systems have been successfully used in many applications such as asset tracking and inventory management. This paper provides an overview of the existing wireless indoor positioning solutions and attempts to classify different techniques and systems. Three typical location estimation schemes of triangulation, scene analysis, and proximity are analyzed. We also discuss location fingerprinting in detail since it is used in most current system or solutions. We then examine a set of properties by which location systems are evaluated, and apply this evaluation method to survey a number of existing systems. Comprehensive performance comparisons including accuracy, precision, complexity, scalability, robustness, and cost are presented.
Statistics for experimenters : an introduction to design, data analysis, and model building
Science and Statistics. COMPARING TWO TREATMENTS. Use of External Reference Distribution to Compare Two Means. Random Sampling and the Declaration of Independence. Randomization and Blocking with Paired Comparisons. Significance Tests and Confidence Intervals for Means, Variances, Proportions and Frequences. COMPARING MORE THAN TWO TREATMENTS. Experiments to Compare k Treatment Means. Randomized Block and Two--Way Factorial Designs. Designs with More Than One Blocking Variable. MEASURING THE EFFECTS OF VARIABLES. Empirical Modeling. Factorial Designs at Two Levels. More Applications of Factorial Designs. Fractional Factorial Designs at Two Levels. More Applications of Fractional Factorial Designs. BUILDING MODELS AND USING THEM. Simple Modeling with Least Squares (Regression Analysis). Response Surface Methods. Mechanistic Model Building. Study of Variation. Modeling Dependence: Times Series. Appendix Tables. Index.
RAG-1-deficient mice have no mature B and T lymphocytes
The V(D)J recombination activation gene RAG-1 was isolated on the basis of its ability to activate V(D)J recombination on an artificial substrate in fibroblasts. This property and the expression pattern in tissues and cell lines indicate that RAG-1 either activates or catalyzes the V(D)J recombination reaction of immunoglobulin and T cell receptor genes. We here describe the introduction of a mutation in RAG-1 into the germline of mice via gene targeting in embryonic stem cells. RAG-1-deficient mice have small lymphoid organs that do not contain mature B and T lymphocytes. The arrest of B and T cell differentiation occurs at an early stage and correlates with the inability to perform V(D)J recombination. The immune system of the RAG-1 mutant mice can be described as that of nonleaky scid mice. Although RAG-1 expression has been reported in the central nervous system of the mouse, no obvious neuroanatomical or behavioral abnormalities have been found in the RAG-1-deficient mice.
BUBBLE Rap: Social-Based Forwarding in Delay-Tolerant Networks
The increasing penetration of smart devices with networking capability form novel networks. Such networks, also referred as pocket switched networks (PSNs), are intermittently connected and represent a paradigm shift of forwarding data in an ad hoc manner. The social structure and interaction of users of such devices dictate the performance of routing protocols in PSNs. To that end, social information is an essential metric for designing forwarding algorithms for such types of networks. Previous methods relied on building and updating routing tables to cope with dynamic network conditions. On the downside, it has been shown that such approaches end up being cost ineffective due to the partial capture of the transient network behavior. A more promising approach would be to capture the intrinsic characteristics of such networks and utilize them in the design of routing algorithms. In this paper, we exploit two social and structural metrics, namely centrality and community, using real human mobility traces. The contributions of this paper are two-fold. First, we design and evaluate BUBBLE, a novel social-based forwarding algorithm, that utilizes the aforementioned metrics to enhance delivery performance. Second, we empirically show that BUBBLE can substantially improve forwarding performance compared to a number of previously proposed algorithms including the benchmarking history-based PROPHET algorithm, and social-based forwarding SimBet algorithm.
Econometric models based on count data. Comparisons and applications of some estimators and tests
This paper deals with specification, estimation and tests of single equation reduced form type equations in which the dependent variable takes only non-negative integer values. Beginning with Poisson and compound Poisson models, which involve strong assumptions, a variety of possible stochastic models and their implications are discussed. A number of estimators and their properties are considered in the light of uncertainty about the data generation process. The paper also considers the role of tests in sequential revision of the model specification beginr ing with the Poisson case and provides a detailed application of the estimators and tests to a model of the number of doctor consultations.
An efficient recombination system for chromosome engineering in Escherichia coli.
A recombination system has been developed for efficient chromosome engineering in Escherichia coli by using electroporated linear DNA. A defective lambda prophage supplies functions that protect and recombine an electroporated linear DNA substrate in the bacterial cell. The use of recombination eliminates the requirement for standard cloning as all novel joints are engineered by chemical synthesis in vitro and the linear DNA is efficiently recombined into place in vivo. The technology and manipulations required are simple and straightforward. A temperature-dependent repressor tightly controls prophage expression, and, thus, recombination functions can be transiently supplied by shifting cultures to 42 degrees C for 15 min. The efficient prophage recombination system does not require host RecA function and depends primarily on Exo, Beta, and Gam functions expressed from the defective lambda prophage. The defective prophage can be moved to other strains and can be easily removed from any strain. Gene disruptions and modifications of both the bacterial chromosome and bacterial plasmids are possible. This system will be especially useful for the engineering of large bacterial plasmids such as those from bacterial artificial chromosome libraries.
Elevated recombination rates in transcriptionally active DNA
We have examined the effect of RNA polymerase II-dependent transcription on recombination between directly repeated sequences of the GAL10 gene in S. cerevisiae. Direct repeat recombination leading either to plasmid loss or conversion was examined in isogenic strains containing null mutations in the positive activator, GAL4, or the repressor, GAL80. A 15-fold increase in the rate of plasmid loss is observed in cells constitutively expressing the construct compared with cells that are not. Conversion events that retain the integrated plasmid are not stimulated by expression of the repeats. Northern analysis of strains containing plasmid inserts with various promoter mutations suggests that the stimulation in recombination is mediated by events initiating within the integrated plasmid sequences.
RDP3: a flexible and fast computer program for analyzing recombination
Summary: RDP3 is a new version of the RDP program for characterizing recombination events in DNA-sequence alignments. Among other novelties, this version includes four new recombination analysis methods (3SEQ, VISRD, PHYLRO and LDHAT), new tests for recombination hot-spots, a range of matrix methods for visualizing over-all patterns of recombination within datasets and recombination-aware ancestral sequence reconstruction. Complementary to a high degree of analysis flow automation, RDP3 also has a highly interactive and detailed graphical user interface that enables more focused hands-on cross-checking of results with a wide variety of newly implemented phylogenetic tree construction and matrix-based recombination signal visualization methods. The new RDP3 can accommodate large datasets and is capable of analyzing alignments ranging in size from 1000×10 kilobase sequences to 20×2 megabase sequences within 48 h on a desktop PC. Availability: RDP3 is available for free from its web site http://darwin.uvigo.es/rdp/rdp.html Contact: darrenpatrickmartin@gmail.com Supplementary information: The RDP3 program manual contains detailed descriptions of the various methods it implements and a step-by-step guide describing how best to use these.
Estimation and Inference in Two-Step Econometric Models
A commonly used procedure in a wide class of impirical applications is to impute unobserved regressors, such as expectations, from an auxiliary econometric model. This two-step (T-S) procedure fails to account for he fact that imputed regessors are measured with sampling error, so hypothesis tests based on the estimated covariance matrix of the second-step estimator are biased, even in large samples. We present a simple yet general method of calculating asymptotically correct standard errors in T-S models. The proceedure may be applied even when joint estimation methods, such as full information maximum likelihood, are inappropriate or computationally infeasible. We present two examples from recent empirical literature in which these corrections have a major impact on hypothesis testing.
Introduction to Statistical Quality Control
Quality Improvement in the Modern Business Environment.STAISTICAL METHODS USEFUL IN QUALITY IMPROVEMENT.Modeling Process Quality.Inferences About Process Quality.BASIC METHODS OF STATISTICAL PROCESS CONTROL AND CAPABILITY ANALYSIS.Methods and Philosophy of Statistical Process Control.Control Charts for Variables.Control Charts for Attributes.Process and Measurement Systems System Capability Analysis.OTHER STATISTICAL PROCESS MONITORING AND CONTROL TECHNIQUES.Cumulative Sum and Exponentially Weighted Moving Average Control Charts.Other Univariate SPC Techniques.Multivariate Process Monitoring and Control.Engineering Process Control and SPC.PROCESS DESIGN AND IMPROVEMENT WITH DESIGNED EXPERIMENTS.Factorial and Fractional Factorial Designs for Process Design and Improvement.Process Optimization with Designed Experiments.ACCEPTANCE SAMPLING.Lot--by--Lot Acceptance Sampling for Attributes.Other Acceptance Sampling Techniques.Appendix.Bibliography.Answers to Selected Exercises.Index.
A survey of indoor positioning systems for wireless personal networks
Recently, indoor positioning systems (IPSs) have been designed to provide location information of persons and devices. The position information enables location-based protocols for user applications. Personal networks (PNs) are designed to meet the users' needs and interconnect users' devices equipped with different communications technologies in various places to form one network. Location-aware services need to be developed in PNs to offer flexible and adaptive personal services and improve the quality of lives. This paper gives a comprehensive survey of numerous IPSs, which include both commercial products and research-oriented solutions. Evaluation criteria are proposed for assessing these systems, namely security and privacy, cost, performance, robustness, complexity, user preferences, commercial availability, and limitations.We compare the existing IPSs and outline the trade-offs among these systems from the viewpoint of a user in a PN.
Resource recombinations in the firm: knowledge structures and the potential for schumpeterian innovation
Building on the resource-based view of the firm, this paper explores the notion of ‘resource recombinations’ within the firm. We suggest such recombinations can occur when competencies within the firm (which are interpreted as organized clusters of firm resources) either combine to synthesize novel competencies (synthesis-based recombinations) or experience a reconfiguration or relinking with other competencies (reconfiguration-based recombinations). Central to this paper is an examination of the antecedents necessary for such innovation to occur, and in particular the nature of knowledge in the firm. We argue that several characteristics of knowledge (tacitness, context specificity, dispersion) and its social organization (the way competencies come to be formed and institutionalized) will have important consequences on the likelihoods of resource recombinations. Our paper develops a model of resource recombination likelihoods and propositions. © 1998 John Wiley & Sons, Ltd.
Resource recombinations in the firm: knowledge structures and the potential for schumpeterian innovation
Building on the resource-based view of the firm, this paper explores the notion of ‘resource recombinations’ within the firm. We suggest such recombinations can occur when competencies within the firm (which are interpreted as organized clusters of firm resources) either combine to synthesize novel competencies (synthesis-based recombinations) or experience a reconfiguration or relinking with other competencies (reconfiguration-based recombinations). Central to this paper is an examination of the antecedents necessary for such innovation to occur, and in particular the nature of knowledge in the firm. We argue that several characteristics of knowledge (tacitness, context specificity, dispersion) and its social organization (the way competencies come to be formed and institutionalized) will have important consequences on the likelihoods of resource recombinations. Our paper develops a model of resource recombination likelihoods and propositions. © 1998 John Wiley & Sons, Ltd.
RAG-1 and RAG-2, adjacent genes that synergistically activate V(D)J recombination.
The vast repertoire of immunoglobulins and T cell receptors is generated, in part, by V(D)J recombination, a series of genomic rearrangements that occur specifically in developing lymphocytes. The recombination activating gene, RAG-1, which is a gene expressed exclusively in maturing lymphoid cells, was previously isolated. RAG-1 inefficiently induced V(D)J recombinase activity when transfected into fibroblasts, but cotransfection with an adjacent gene, RAG-2, has resulted in at least a 1000-fold increase in the frequency of recombination. The 2.1-kilobase RAG-2 complementary DNA encodes a putative protein of 527 amino acids whose sequence is unrelated to that of RAG-1. Like RAG-1, RAG-2 is conserved between species that carry out V(D)J recombination, and its expression pattern correlates precisely with that of V(D)J recombinase activity. In addition to being located just 8 kilobases apart, these convergently transcribed genes are unusual in that most, if not all, of their coding and 3' untranslated sequences are contained in single exons. RAG-1 and RAG-2 might activate the expression of the V(D)J recombinase but, more likely, they directly participate in the recombination reaction.
Possible emergence of new geminiviruses by frequent recombination.
Although exchange of genetic information by recombination plays a role in the evolution of viruses, the extent to which it generates diversity is not clear. We analyzed genomes of geminiviruses for recombination using a new statistical procedure developed to detect gene conversions. Geminiviruses (family, Geminiviridae) are a group of plant viruses characterized by a genome of circular single-stranded DNA (approximately 2700 nucleotides in length) encapsidated in twinned quasi-isometric particles. Complete nucleotide sequences of geminiviruses were aligned, and recombination events were detected by searching pairs of viruses for sequences that are significantly more similar than expected based on random distribution of polymorphic sites. The analyses revealed that recombination is very frequent and occurs between species and within and across genera. Tests identified 420 statistically significant recombinant fragments distributed across the genome. The results suggest that recombination is a significant contributor to geminivirus evolution. The high rate of recombination may be contributing to the recent emergence of new geminivirus diseases.
THE RELATION OF RECOMBINATION TO MUTATIONAL ADVANCE
The method of calculation is shown whereby a formula has been derived that states approximately the ratio of the rate of accumulation of advantageous mutant genes in a population that undergoes recombination to the rate in an otherwise nonrecombining one. A table is given showing the ratios thus found for different frequencies of advantageous mutations and different degrees of their advantage. I t is shown that this calculation does not apply for mutant genes that act advantageously only when in some special combinations with one or more other mutant ,genes, and that as far as these cases of special synergism are concerned recombining lines have no evolutionary advantage over non-recombining ones. Other limitations of the formula are pointed out and assessed. I t is explained that most factors that retard the rate of recombination--for example, linkage, rari ty of outbreeding, intercalation of sexual reproduction between more frequent cycles of asexual propagation, and partial isolation between subpopulat ions--must usually cause little long-term retardation of the speed of advance that is fostered by recombination. Moreover, even where long-term evolution has virtually ceased, recombination of mutant genes still confers upon a population the means of adopting short-term genetic "dodges", that adjust it to ecological and "physical" changes in its circumstances, much more rapidly than would be possible for a comparable asexual population. Under conditions where only stability of type is needed, a non-recombining population does not actually degenerate as a result of an excess of mutation over selection, after the usual equilibrium between these pressures is reached. However, a kind of irreversible ratchet mechanism exists in the non-recombining species (unlike the recombining ones) that prevents selection, even if intensified, from reducing the mutational loads below the lightest that were in existence when the intensified selection started, whereas, contrariwise, "drif t" and what might be called "selective noise" must allow occasional slips of the lightest loads in the direction of increased weight.
RDP: detection of recombination amongst aligned sequences
SUMMARY Recombination Detection Program (RDP) is a program that applies a pairwise scanning approach to the detection of recombination amongst a group of aligned DNA sequences. The software runs under Windows95 and combines highly automated screening of large numbers of sequences with a highly interactive interface for examining the results of the analyses.
Promotion of atrial fibrillation by heart failure in dogs: atrial remodeling of a different sort.
BACKGROUND Studies of atrial fibrillation (AF) due to atrial tachycardia have provided insights into the remodeling mechanisms by which "AF begets AF" but have not elucidated the substrate that initially supports AF before remodeling occurs. We studied the effects of congestive heart failure (CHF), an entity strongly associated with clinical AF, on atrial electrophysiology in the dog and compared the results with those in dogs subjected to rapid atrial pacing (RAP; 400 bpm) with a controlled ventricular rate (AV block plus ventricular pacemaker at 80 bpm). METHODS AND RESULTS CHF induced by 5 weeks of rapid ventricular pacing (220 to 240 bpm) increased the duration of AF induced by burst pacing (from 8+/-4 seconds in control dogs to 535+/-82 seconds; P<0.01), similar to the effect of 1 week of RAP (713+/-300 seconds). In contrast to RAP, CHF did not alter atrial refractory period, refractoriness heterogeneity, or conduction velocity at a cycle length of 360 ms; however, CHF dogs had a substantial increase in the heterogeneity of conduction during atrial pacing (heterogeneity index in CHF dogs, 2. 76+/-0.16 versus 1.46+/-0.10 for control and 1.51+/-0.06 for RAP dogs; P<0.01) owing to discrete regions of slow conduction. Histological examination revealed extensive interstitial fibrosis (connective tissue occupying 12.8+/-1.9% of the cross-sectional area) in CHF dogs compared with control (0.8+/-0.3%) and RAP (0. 9+/-0.2%) dogs. CONCLUSIONS Experimental CHF strongly promotes the induction of sustained AF by causing interstitial fibrosis that interferes with local conduction. The substrates of AF in CHF are very different from those of atrial tachycardia-related AF, with important potential implications for understanding, treating, and preventing AF related to CHF.
genetic algorithm positioning system process control sample size solar cell visible light dna sequence learning object indoor positioning received signal strength statistical process control indoor localization quantum dot statistical proces indoor positioning system count datum hecke algebra factorial design ieee standard binding site escherichia coli weighted moving average knowledge structure statistical quality control poisson structure cell cycle choice behavior econometric model quality level exponentially weighted moving fractional factorial design saccharomyces cerevisiae selection bia affine weyl group statistical process monitoring power conversion efficiency dye-sensitized solar cell charge transport uniform resource identifier learning object metadatum embryonic stem cell moving average control object class dye-sensitized solar reusable learning object linkage disequilibrium quantity discount spatial process spatial econometric population parameter embryonic stem reusable learning object metadatum heterojunction solar cell dna repair location fingerprinting cell development indoor positioning technique spatial econometric model radiation tolerance heterojunction solar genetic linkage signal peptide bulk heterojunction dna segment recombination rate bulk heterojunction solar dna recombination wifi-based indoor localization surface recombination escherichia coli. low-density lipoprotein indoor positioning solution proposed positioning system surface recombination velocity solar cells. neisseria meningitidi genetic heterogeneity learning object review dna break xrcc5 wt allele xrcc5 gene t cell receptor v(d)j recombination v(d)j recombination-activating protein 1 excretory function neuritis, autoimmune, experimental leukemia, b-cell dna sequence rearrangement immunoglobulin class switch recombination immunoglobulin class switching lipoprotein receptor dna breaks, double-stranded telomere maintenance v(d)j recombination genome encoded entity vdj recombinase recombination, genetic crossover (genetic algorithm) meiotic recombination homologous recombination