102,694 research outputs found
Recombinant DNA Molecules of Bacteriophage phi X174
phi X174 DNA structures containing two different parental genomes were detected genetically and examined by electron microscopy. These structures consisted of two monomeric double-stranded DNA molecules linked in a figure 8 configuration. Such DNA structures were observed to be formed preferentially in host recA+ cells or recA+ cell-free systems. Since the host recA+ allele is required for most phi X174 recombinant formation, we conclude that the observed figure 8 molecules are intermediates in, or end products of, a phi X174 recombination event. We propose that recombinant figure 8 DNA molecules arise as a result of "single-strand aggression," are stabilized by double-strand "branch migration," and represent a specific example of a common intermediate in genetic recombination
Deletion mutants of bacteriophage phiX174
Mutants of bacteriophage phiX174 have been isolated that are less dense than wild-type phiX particles in CsCl. When mutant viral (+) strand DNA and wild-type complementary (-) strand DNA are hybridized, the resulting duplex molecules have single-stranded loops characteristic of wild-type-deletion heteroduplexes. The mutant bacteriophages fail to complement phiX amber mutants in cistron E. We conclude that the mutant viruses have deleted approximately 7% of the phiX genome in the region of cistron E
Direction of Translation and Size of Bacteriophage [var phi]X174 Cistrons
Translation of the bacteriophage [var phi]X174 genome follows cistron order D-E-F-G-H-A-B-C. To establish this, the position of a nonsense mutation on the genetic map was compared with the physical size (molecular weight) of the appropriate protein fragment generated in nonpermissive cells. Distances on the [var phi]X174 genetic map and distances on a physical map constructed from the molecular weights of [var phi]X174 proteins and protein fragments are proportional over most of the genome with the exception of the high recombination region within cistron A
Overlap and activity glass transitions in plaquette spin models with hierarchical dynamics
We consider thermodynamic and dynamic phase transitions in plaquette spin
models of glasses. The thermodynamic transitions involve coupled (annealed)
replicas of the model. We map these coupled-replica systems to a single replica
in a magnetic field, which allows us to analyse the resulting phase transitions
in detail. For the triangular plaquette model (TPM), we find for the
coupled-replica system a phase transition between high- and low-overlap phases,
occuring at a coupling eps*(T), which vanishes in the low-temperature limit.
Using computational path sampling techniques, we show that a single TPM also
displays space-time transitions between active and inactive dynamical phases.
These first-order dynamical transitions occur at a critical counting field
s_c(T)>=0 that appears to vanish at zero temperature, in a manner reminiscent
of the thermodynamic overlap transition. In order to extend the ideas to three
dimensions we introduce the square pyramid model which also displays both
overlap and activity transitions. We discuss a possible common origin of these
various phase transitions, based on long-lived (metastable) glassy states.Comment: 12 pages, 9 fig
Comment: Struggles with Survey Weighting and Regression Modeling
Comment: Struggles with Survey Weighting and Regression Modeling
[arXiv:0710.5005]Comment: Published in at http://dx.doi.org/10.1214/088342307000000177 the
Statistical Science (http://www.imstat.org/sts/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Herding Cats: Improving Law School Teaching
What makes a good law teacher? Is excellence in teaching largely a matter of intellectual brilliance, of superior organization and delivery of material, of friendliness and fairness to one\u27s students? Or does it have more to do with style, with stage presence, with the ability to engage an audience in the act of reflective and spontaneous thinking?
While the question of how to define and evaluate teaching necessarily bedevils deans and tenure committees who must make personnel decisions, the focus on defining the competent teacher has obscured from faculty attention the more fundamental question: how can we implement a system to improve faculty performance across the board? It is this question that law schools around the country have not adequately addressed.
Three years ago, the faculty of Franklin Pierce Law Center adopted a program to improve our classroom teaching. This article describes and evaluates that program, in which all three authors played a role
Applications of Massive Integrable Quantum Field Theories to Problems in Condensed Matter Physics
We review applications of the sine-Gordon model, the O(3) non-linear sigma
model, the U(1) Thirring model, and the O(N) Gross--Neveu model to quasi
one-dimensional quantum magnets, Mott insulators, and carbon nanotubes. We
focus upon the determination of dynamical response functions for these
problems. These quantities are computed by means of form factor expansions of
quantum correlation functions in integrable quantum field theories. This
approach is reviewed here in some detail.Comment: 150 pages, 35 figures, published in the I. Kogan Memorial Volume by
World Scientifi
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Genetic Recombination in Bacteriophage {varphi}X174
Genetic recombination in bacteriophage {varphi}X174 usually takes place early in the infection process and involves two parental replicative form (double-stranded) DNA molecules. The host recA protein is required; none of the nine known {varphi}X174 cistron products is essential. The products of a single recombination event are nonreciprocal and asymmetric. Typically, only one of the parental genotypes and one recombinant genotype are recovered from a single cell. An alternative, less efficient recombination mechanism which requires an active {varphi}X174 cistron A protein is observed in the absence of the host recA gene product
PERFORMANCE MEASURES: BANDWIDTH VERSUS FIDELITY IN PERFORMANCE MANAGEMENT
Performance is of focal and critical interest in organizations. Despite its criticality, when it comes to human performance there are many questions as to how to best measure and manage performance. One such issue is the breadth of the performance that should be considered. In this paper, we examine the issue of the breadth of performance in terms of measuring and managing performance. Overall, a contingency approach is taken in which the expected benefits and preference for broad or narrow performance measures depend on the type of job (fixed or changeable).bandwidth, fidelity in performance management, performance measures
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