Showing papers by "University of Oregon published in 1995"

Stages of embryonic development of the zebrafish.

Abstract: We describe a series of stages for development of the embryo of the zebrafish, Danio (Brachydanio) rerio. We define seven broad periods of embryogenesis--the zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and hatching periods. These divisions highlight the changing spectrum of major developmental processes that occur during the first 3 days after fertilization, and we review some of what is known about morphogenesis and other significant events that occur during each of the periods. Stages subdivide the periods. Stages are named, not numbered as in most other series, providing for flexibility and continued evolution of the staging series as we learn more about development in this species. The stages, and their names, are based on morphological features, generally readily identified by examination of the live embryo with the dissecting stereomicroscope. The descriptions also fully utilize the optical transparancy of the live embryo, which provides for visibility of even very deep structures when the embryo is examined with the compound microscope and Nomarski interference contrast illumination. Photomicrographs and composite camera lucida line drawings characterize the stages pictorially. Other figures chart the development of distinctive characters used as staging aid signposts.

Invariance theory, the heat equation, and the Atiyah-Singer index theorem

Abstract: Pseudo-Differential Operators Introduction Fourier Transform and Sobolev Spaces Pseudo-Differential Operators on Rm Pseudo-Differential Operators on Manifolds Index of Fredholm Operators Elliptic Complexes Spectral Theory The Heat Equation Local Index Formula Variational Formulas Lefschetz Fixed Point Theorems The Zeta Function The Eta Function Characteristic Classes Introduction Characteristic Classes of Complex Bundles Characteristic Classes of Real Bundles Complex Projective Space Invariance Theory The Gauss-Bonnet Theorem Invariance Theory and Pontrjagin Classes Gauss-Bonnet for Manifolds with Boundary Boundary Characteristic Classes Singer's Question The Index Theorem Introduction Clifford Modules Hirzebruch Signature Formula Spinors The Spin Complex The Riemann-Roch Theorem K-Theory The Atiyah-Singer Index Theorem The Regularity at s = 0 of the Eta Function Lefschetz Fixed Point Formulas Index Theorem for Manifolds with Boundary The Eta Invariant of Locally Flat Bundles Spectral Geometry Introduction Operators of Laplace Type Isospectral Manifolds Non-Minimal Operators Operators of Dirac Type Manifolds with Boundary Other Asymptotic Formulas The Eta Invariant of Spherical Space Forms A Guide to the Literature Acknowledgment Introduction Bibliography Notation

Long-Range Order in a Two-Dimensional Dynamical XY Model: How Birds Fly Together.

Abstract: We propose a nonequilibrium continuum dynamical model for the collective motion of large groups of biological organisms (e.g., flocks of birds, slime molds, etc.) Our model becomes highly nontrivial, and different from the equilibrium model, for $dl{d}_{c}=4$; nonetheless, we are able to determine its scaling exponents exactly in $d=2$ and show that, unlike equilibrium systems, our model exhibits a broken continuous symmetry even in $d=2$. Our model describes a large universality class of microscopic rules, including those recently simulated by Vicsek et al.

Mutation accumulation and the extinction of small populations

Abstract: Although extensive work has been done on the relationship between population size and the risk of extinction due to demographic and environmental stochasticity, the role of genetic deterioration in the extinction process is poorly understood. We develop a general theoretical approach for evaluating the risk of small populations to extinction via the accumulation of mildly deleterious mutations, and we support this with extensive computer simulations. Unlike previous attempts to model the genetic consequences of small population size, our approach is genetically explicit and fully accounts for the mutations inherited by a founder population as well as those introduced by subsequent mutation. Application of empirical estimates of the properties of spontaneous deleterious mutations leads to the conclusion that populations with effective sizes smaller than 100 (and actual sizes smaller than 1,000) are highly vulnerable to extinction via a mutational meltdown on timescales of approximately 100 generations. We ...

Limited discrepancy search

Abstract: Many problems of practical interest can be solved using tree search methods because carefully tuned successor ordering heuristics guide the search toward regions of the space that are likely to contain solutions. For some problems, the heuristics often lead directly to a solution— but not always. Limited discrepancy search addresses the problem of what to do when the heuristics fail. Our intuition is that a failing heuristic might well have succeeded if it were not for a small number of "wrong turns" along the way. For a binary tree of height d, there are only d ways the heuristic could make a single wrong turn, and only d(d-i)/2 ways it could make two. A small number of wrong turns can be overcome by systematically searching all paths that differ from the heuristic path in at most a small number of decision points, or "discrepancies." Limited discrepancy search is a backtracking algorithm that searches the nodes of the tree in increasing order of such discrepancies. We show formally and experimentally that limited discrepancy search can be expected to outper-form existing approaches. 1 Introduction In practice, many search problems have spaces that are too large to search exhaustively. One can often find solutions while searching only a small fraction of the space by relying on carefully tuned heuristics to guide the search toward regions of the space that are likely to contain solutions. For many problems, heuristics can lead directly to a solution—most of the time. In this paper, we consider what to do when the heuristics fail. We will focus our attention on procedures for tree search. Our objective is simple: For search problems with heuristically ordered successors, we will develop a search procedure that is more likely to find a solution in any given time limit than existing methods such as chronological backtracking and iterative sampling [Lan-gley, 1992]. The outline of this paper is as follows: In the next section, we discuss existing algorithms. Limited discrepancy search (LDS) is introduced in Section 3 and compared to existing techniques in Section 4. We discuss variations of LDS that we believe will be useful for solving realistic problems in Section 5. We conclude by presenting our experimental results in Section 6. 2 Existing Strategies Consider a tree search problem for which the successor ordering heuristic is so good that it almost always leads directly to a solution. Such problems are common both …

Mutation and Conservation

Abstract: Mutation can critically affect the viability of small populations by causing inbreeding depression, by maintaining potentially adaptive genetic variation in quantitative characters, and through the erosion of fitness by accumulation of mildly detrimental mutations. I review and integrate recent empirical and theoretical work on spontaneous mutation and its role in population viability and conservation planning. I analyze both the maintenance of potentially adaptive genetic variation in quantitative characters and the role of detrimental mutations in increasing the extinction risk of small populations. Recent experiments indicate that the rate of production of quasineutral, potentially adaptive genetic variance in quantitative characters is an order of magnitude smaller than the total mutational variance because mutations with large phenotypic effects tend to be strongly detrimental. This implies that, to maintain normal adaptive potential in quantitative characters under a balance between mutation and random genetic drift (or among mutation, drift, and stabilizing natural selection), the effective population size should be about 5000 rather than 500 (the Franklin-Soule number). Recent theoretical results suggest that the risk of extinction due to the fixation of mildly detrimental mutations may be comparable in importance to environmental stochasticity and could substantially decrease the long-term viability of populations with effective sizes as large as a few thousand. These findings suggest that current recovery goals for many threatened and endangered species are inadequate to ensure long-term population viability. La mutacion puede afectar criticamente la viabilidad de poblaciones pequenas al causar la depresion de endocria, mantener la variacion genetica potencialmente adaptativa en caracteres cuantitativos, y por medio de la erosion de la condicin por acumulacion de mutaciones levemente perjudiciales. En el presente estudio revise e integre trabajos empiricos y teoricos recientes sobre mutaciones espontaneas y su papel en la viabilidad de las poblaciones y la planificacion para la conservacion. Se analizo tanto el mantenimiento de la variabilidad genetica potencialmente adaptativa en los caracteres cuantitativos como el papel de las mutaciones perjudiciales en el incremento de riesgo de extincion de las poblaciones pequenas. Experimentos recientes indican que la tasa de produccion de varianza genetica cuasineutral y potencialmente adaptativa en los caracteres cuantitativos es de un orden de magnitud menor que la varianza mutacional total debido a que las mutaciones con efectos fenotipicos pronunciados tienden a ser fuertemente perjudiciales. Esto implica que a efecto de mantener el potencial adaptativo normal en los caracteres cuantitativos bajo un balance entre mutacion y deriva genica al azar (o entre mutacion, deriva genica y seleccion natural estabilizadora), el tamano poblacional efectivo debe ser de aproximadamente 5000 y no 500 (numero de Franklin-Soule). Resultados teoricos recientes sugieren que el riesgo de extincion debido a la fijacion de mutaciones levemente perjudiciales podria ser comparable en importancia a la estocasticidad ambiental y podria reducir substancialmente la viabilidad a largo plazo de las poblaciones con un tamano poblacional efectivo de solo unos pocos miles. Estos descubrimientos sugieren que las metas de recuperacion para muchas especies en peligro y amenazadas son inadecuadas para asegurar la viabilidad poblacional a largo plazo.

The effects of transformational leadership on teacher attitudes and student performance in Singapore

Abstract: Summary Transformational leadership theory was examined in 89 schools in Singapore using a split sample technique (N = 846 teachers). The study sought to examine the influence of transformational leader behavior by school principals as it related to organizational commitment, organizational citizenship behavior, teacher satisfaction with leader, and student academic performance. Attitudinal and behavioral data were collected from both teachers and principals; student academic performance was collected from school records. School level analyses showed that transformational leadership had significant add-on effects to transactional leadership in the prediction of organizational commitment, organizational citizenship behavior, and teacher satisfaction. Moreover, transformational leadership was found to have indirect effects on student academic achievement. Finally, it was found that transactional leadership had little add-on effect on transformational leadership in predicting outcomes. Implications and directions for future research are discussed.

Evolution and extinction in a changing environment: a quantitative-genetic analysis.

Abstract: Because of the ubiquity of genetic variation for quantitative traits, virtually all populations have some capacity to respond evolutionarily to selective challenges. However, natural selection imposes demographic costs on a population, and if these costs are sufficiently large, the likelihood of extinction will be high. We consider how the mean time to extinction depends on selective pressures (rate and stochasticity of environmental change, and strength of selection), population parameters (carrying capacity, and reproductive capacity), and genetics (rate of polygenic mutation). We assume that in a randomly mating, finite population subject to density-dependent population growth, individual fitness is determined by a single quantitative-genetic character under Gaussian stabilizing selection with the optimum phenotype exhibiting directional change, 'or random fluctuations, or both. The quantitative trait is de- termined by a finite number of freely recombining, mutationally equivalent, additive loci. The dynamics of evolution and extinction are investigated, assuming that the population is initially under mutation-selection-drift balance. Under this model, in a directionally changing environment, the mean phenotype lags behind the optimum, but on the average evolves parallel to it. The magnitude of the lag determines the vulnerability to extinction. In finite populations, stochastic variation in the genetic variance can be quite pronounced, and bottlenecks in the genetic variance temporarily can impair the population's adaptive capacity enough to cause extinction when it would otherwise be unlikely in an effectively infinite population. We find that maximum sustainable rates of evolution or, equivalently, critical rates of environmental change, may be considerably less than 10% of a phenotypic standard deviation per generation.

Functionalism and Grammar

Abstract: This book is Prof. Givon's long-awaited critical examination of the fundamental theoretical and methodological underpinnings of the functionalist approach to grammar. It challenges functionalists to take their own medicine and establish non-circular empirical definitions of both 'function' and 'structure'. Ideological hand-waving, however fervent and right-thinking, is seldom an adequate substitute for analytic rigor and empirical responsibility. If the reductionist extremism of the various structuralist schools is to be challenged on solid intellectual grounds, the challenge cannot itself be equally extreme in its reductionism. The book is divided into nine chapters: 1. Prospectus, somewhat jaundiced (overview) 2. Markedness as meta-iconicity: Distributional and cognitive correlates of syntactic structure 3. The functional basis of grammatical typology 4. Modal prototypes of truth and action 5. Taking structure seriously: Constituency and the VP node 6. Taking structure seriously II: Grammatical relations and clause union 7. The distribution of grammar in text: On interpreting conditional associations 8. Coming to terms with cognition: Coherence in text vs. coherence in mind 9. On the co-evolution of language, mind and brain.

A homeobox gene essential for zebrafish notochord development

Abstract: The notochord is a midline mesodermal structure with an essential patterning function in all vertebrate embryos. Zebrafish floating head (flh) mutants lack a notochord, but develop with prechordal plate and other mesodermal derivatives, indicating that flh functions specifically in notochord development. We show that floating head is the zebrafish homologue of Xnot, a homeobox gene expressed in the amphibian organizer and notochord. We propose that flh regulates notochord precursor cell fate.

Cognitive and affective determinants of fan satisfaction with sporting event attendance.

Abstract: The current study proposes and tests a structural model of fan satisfaction with attending a sporting event. Specifically, three cognitive antecedents (expectancy disconfirmation, team identificati...

Handbook of perturbative QCD

Abstract: The elements, theoretical basis, and experimental status of perturbative quantum chromodynamics are presented. Relevant field-theoretic methods are introduced at a nonspecialist level, along with a review of the basic ideas and methods of the parton model. This is followed by an account of the fundamental theorems of quantum chromodynamics, which generalize the parton model. Summaries of the theoretical and experimental status of the most important hard-scattering processes are then given, including electron-positron annihilation, deeply inelastic scattering, and hard hadron-hadron scattering, as induced both by electoweak interactions and by quantum chromodynamics directly. In addition, a discussion is presented of the global fitting approach to the determination of parton distributions in nucleons.

Collapse and repair of replication forks in Escherichia coli

Abstract: Single-strand interruptions in a template DNA are likely to cause collapse of replication forks. We propose a model for the repair of collapsed replication forks in Escherichia coli by the RecBCD recombinational pathway. The model gives reasons for the preferential orientation of Chi sites in the E. coli chromosome and accounts for the hyper-rec phenotype of the strains with increased numbers of single-strand interruptions in their DNA. On the basis of the model we offer schemes for various repeat-mediated recombinational events and discuss a mechanism for quasi-conservative DNA replication explaining the recombinational repair-associated mutagenesis.

Mutational meltdowns in sexual populations

Abstract: Although it is widely acknowledged that the gradual accumulation of mildly deleterious mutations is an important source of extinction for asexual populations, it is generally assumed that this process is of little relevance to sexual species. Here we present results, based on computer simulations and supported by analytical approximations, that indicate that mutation accumulation in small, random-mating monoecious populations can lead to mean extinction times less than a few hundred to a few thousand generations. Unlike the situation in obligate asexuals in which the mean time to extinction (te ) increases more slowly than linearly with the population carrying capacity (K), te increases approximately exponentially with K in outcrossing sexual populations. The mean time to extinction for obligately selfing populations is shown to be equivalent to that for asexual populations of the same size, but with half the mutation rate and twice the mutational effect; this suggests that obligate selfing, like obligate asexuality, is inviable as a long-term reproductive strategy. Under all mating systems, the mean time to extinction increases relatively slowly with the logarithm of fecundity, and mutations with intermediate effects (similar to those observed empirically) cause the greatest risk of extinction. Because our analyses ignore sources of demographic and environmental stochasticity, which have synergistic effects that exacerbate the accumulation of deleterious mutations, our results should yield liberal upper bounds to the mean time to extinction caused by mutational degradation. Thus, deleterious mutation accumulation cannot be ruled out generally as a significant source of extinction vulnerability in small sexual populations or as a selective force influencing mating-system evolution.

VPS27 controls vacuolar and endocytic traffic through a prevacuolar compartment in Saccharomyces cerevisiae.

Abstract: Newly synthesized vacuolar hydrolases such as carboxypeptidase Y (CPY) are sorted from the secretory pathway in the late-Golgi compartment and reach the vacuole after a distinct set of membrane-trafficking steps. Endocytosed proteins are also delivered to the vacuole. It has been proposed that these pathways converge at a "prevacuolar" step before delivery to the vacuole. One group of genes has been described that appears to control both of these pathways. Cells carrying mutations in any one of the class E VPS (vacuolar protein sorting) genes accumulate vacuolar, Golgi, and endocytosed proteins in a novel compartment adjacent to the vacuole termed the "class E" compartment, which may represent an exaggerated version of the physiological prevacuolar compartment. We have characterized one of the class E VPS genes, VPS27, in detail to address this question. Using a temperature-sensitive allele of VPS27, we find that upon rapid inactivation of Vps27p function, the Golgi protein Vps10p (the CPY-sorting receptor) and endocytosed Ste3p rapidly accumulate in a class E compartment. Upon restoration of Vps27p function, the Vps10p that had accumulated in the class E compartment could return to the Golgi apparatus and restore correct sorting of CPY. Likewise, Ste3p that had accumulated in the class E compartment en route to the vacuole could progress to the vacuole upon restoration of Vps27p function indicating that the class E compartment can act as a functional intermediate. Because both recycling Golgi proteins and endocytosed proteins rapidly accumulate in a class E compartment upon inactivation of Vps27p, we propose that Vps27p controls membrane traffic through the prevacuolar/endosomal compartment in wild-type cells.

Lung Cancer in Radon-Exposed Miners and Estimation of Risk From Indoor Exposure

Abstract: Background : Radioactive radon is an inert gas that can migrate from soils and rocks and accumulate in enclosed areas, such as homes and underground mines. Studies of miners show that exposure to radon decay products causes lung cancer. Consequently, it is of public health interest to estimate accurately the consequences of daily, low-level exposure in homes to this known carcinogen. Epidemiologic studies of residential radon exposure are burdened by an inability to estimate exposure accurately, low total exposure, and subsequent small excess risks. As a result, the studies have been inconclusive to date. Estimates of the hazard posed by residential radon have been based on analyses of data on miners, with recent estimates based on a pooling of four occupational cohort studies of miners, including 360 lung cancer deaths. Purpose : To more fully describe the lung cancer risk in radon-exposed miners, we pooled original data from 11 studies of radon-exposed underground miners, conducted a comprehensive analysis, and developed models for estimating radon-associated lung cancer risk. Methods : We pooled original data from 11 cohort studies of radon-exposed underground miners, including 65 000 men and more than 2700 lung cancer deaths, and fit various relative risk (RR) regression models. Results : The RR relationship for cumulative radon progeny exposure was consistently linear in the range of miner exposures, suggesting that exposures at lower levels, such as in homes, would carry some risk. The exposure-response trend for never-smokers was threefold the trend for smokers, indicating a greater RR for exposure in never-smokers. The RR from exposure diminished with time since the exposure occurred. For equal total exposure, exposures of long duration (and low rate) were more harmful than exposures of short duration (and high rate). Conclusions: In the miners, about 40% of all lung cancer deaths may be due to radon progeny exposure, 70% of lung cancer deaths in never-smokers, and 39% of lung cancer deaths in smokers. In the United States, 10% of all lung cancer deaths might be due to indoor radon exposure, 11% of lung cancer deaths in smokers, and 30% of lung cancer deaths in never-smokers. This risk model estimates that reducing radon in all homes exceeding the U. S. Environmental Protection Agency's recommended action level may reduce lung cancer deaths about 2%-4%. These estimates should be interpreted with caution, because concomitant exposures of miners to agents such as arsenic or diesel exhaust may modify the radon effect and, when considered together with other differences between homes and mines, might reduce the generalizability of findings in miners. [J Natl Cancer Inst 87 :817-827, 1995]

Post-Laramide removal of the Farallon slab, western United States

Abstract: I propose that post-Laramide removal of the subhorizontally subducting Farallon slab occurred by buckling downward along an approximately east-northeast–trending axis. This process was accomplished by a tearing or necking separation of the subducted slab near the northern and southern boundaries of the United States and propagation of the separated edges toward the central axis of downwelling, accompanied by aesthenosphic upwelling behind the trailing edges. Initial buckling probably began near 50 Ma, and slab removal was complete by 20 Ma. This model is based primarily on the space-time evolution of the “ignimbrite flare-up” (a major mid-Tertiary igneous event of mantle origin), which involved two propagating fronts of initiation of volcanism that followed the proposed motions of the separated slab edges as they converged on central Nevada from the north and southeast. Post-Laramide uplift, extension, establishment of the Cascadia subduction zone, and active magmatism may be consequences of lithosphere-scale modifications caused by the Laramide removal of the slab and the resulting asthenospheric upwelling.

Requirements monitoring in dynamic environments

Abstract: We propose requirements monitoring to aid in the maintenance of systems that reside in dynamic environments. By requirements monitoring we mean the insertion of code into a running system to gather information from which it can he determined whether, and to what degree, that running system is meeting its requirements. Monitoring is a commonly applied technique in support of performance tuning, but the focus therein is primarily on computational performance requirements in short runs of systems. We wish to address systems that operate in a long lived, ongoing fashion in nonscientific enterprise applications. We argue that the results of requirements monitoring can be of benefit to the designers, maintainers and users of a system-alerting them when the system is being used in an environment for which it was not designed, and giving them the information they need to direct their redesign of the system. Studies of two commercial systems are used to illustrate and justify our claims.

Permian-triassic life crisis on land.

Abstract: Recent advances in radiometric dating and isotopic stratigraphy have resulted in a different placement of the Permian-Triassic boundary within the sedimentary sequence of the Sydney Basin of southeastern Australia. This boundary at 251 million years ago was a time of abrupt decline in both diversity and provincialism of floras in southeastern Australia and extinction of the Glossopteris flora. Early Triassic vegetation was low in diversity and dominated by lycopods and voltzialean conifers. The seed fern Dicroidium appeared in the wake of Permian-Triassic boundary floral reorganization, but floras dominated by Dicroidium did not attain Permian levels of diversity and provinciality until the Middle Triassic (244 million years ago).

A call-by-need lambda calculus

Abstract: The mismatch between the operational semantics of the lambda calculus and the actual behavior of implementations is a major obstacle for compiler writers. They cannot explain the behavior of their evaluator in terms of source level syntax, and they cannot easily compare distinct implementations of different lazy strategies. In this paper we derive an equational characterization of call-by-need and prove it correct with respect to the original lambda calculus. The theory is a strictly smaller theory than the lambda calculus. Immediate applications of the theory concern the correctness proofs of a number of implementation strategies, e.g., the call-by-need continuation passing transformation and the realization of sharing via assignments.

Soluble and cell-bound forms of steel factor activity play distinct roles in melanocyte precursor dispersal and survival on the lateral neural crest migration pathway

Abstract: Trunk neural crest cells segregate from the neuroepithelium and enter a 'migration staging area' lateral to the embryonic neural tube. After some crest cells in the migration staging area have begun to migrate on a medial pathway, a subpopulation of crest-derived cells remaining in the migration staging area expresses mRNAs for the receptor tyrosine kinase, c-kit, and tyrosinase-related protein-2, both of which are characteristic of melanocyte precursors. These putative melanocyte precursors are subsequently observed on the lateral crest migration pathway between the dermatome and overlying epithelium, and then dispersed in nascent dermal mesenchyme. Melanocyte precursors transiently require the c-kit ligand, Steel factor for survival. Although Steel factor mRNA is transiently expressed in the dorsal dermatome before the onset of trunk neural crest cell dispersal on the lateral pathway, it is no longer produced by dermatomal cells when melanocyte precursors have dispersed in the dermal mesenchyme. To assess the role of Steel factor in migration of melanocyte precursors on the lateral pathway, we analyzed melanocyte precursor dispersal and fate on the lateral pathway of two different Sl mutants, Sl, a null allele, and Sld, which lacks cell surface-associated Steel factor but produces a soluble form. No melanocyte precursors were detected in the dermatome of embryos homozygous for the Sl allele or in W mutants that lack functional c-kit. In contrast, in embryos homozygous for the Sld allele, melanocyte precursors appeared on the lateral pathway, but subsequently disappear from the dermis. These results suggest that soluble Steel factor is required for melanocyte precursor dispersal on the lateral pathway, or for their initial survival in the migration staging area. In contrast, membrane-bound Steel factor appears to promote melanocyte precursor survival in the dermis.

Motoneuron fate specification revealed by patterned LIM homeobox gene expression in embryonic zebrafish

Abstract: In zebrafish, individual primary motoneurons can be uniquely identified by their characteristic cell body positions and axonal projection patterns. The fate of individual primary motoneurons remains plastic until just prior to axogenesis when they become committed to particular identities. We find that distinct primary motoneurons express particular combinations of LIM homeobox genes. Expression precedes axogenesis as well as commitment, suggesting that LIM homeobox genes may contribute to the specification of motoneuronal fates. By transplanting them to new spinal cord positions, we demonstrate that primary motoneurons can initiate a new program of LIM homeobox gene expression, as well as the morphological features appropriate for the new position. We conclude that the patterned distribution of different primary motoneuronal types within the zebrafish spinal cord follows the patterned expression of LIM homeobox genes, and that this reflects a highly resolved system of positional information controlling gene transcription.

Attachment Patterns in the Psychotherapy Relationship: Development of the Client Attachment to Therapist Scale.

Abstract: A panel of 9 therapists generated items for an instrument designed to measure the psychotherapy relationship from the perspective of attachment theory. The initial version of the Client Attachment to Therapist Scale (CATS) contained 100 items that were administered at 4 counseling agencies in survey packets to 138 clients who had completed at least 5 sessions with their therapists. Factor analysis suggested that 36 items loaded on 3 subscales, which we labeled Secure, kvoidant-Fearful, and Preoccupied-Merger. CATS factors correlated in expected directions with survey measures of object relations, client-rated working alliance, social self-efficacy, and adult attachment. Cluster analysis identified 4 types of client attachment. Significant differences in social competencies (object relations, etc.) were evident across types of attachment. Implications of attachment patterns for the understanding of client transference are discussed. Attachment theory was originally developed to explain the behavioral and emotional responses that keep young children and their caregivers in close physical proximity (Bowlby, 1969). From this foundation, attachment theory offers an explanation for responses to separation and loss (Bowlby, 1973) and the development of emotional attachments after infancy (Ainsworth, 1989; Bowlby, 1977). In an optimal attachment bond, the caregiver provides a comforting presence for the child that reduces anxiety and promotes feelings of security. From this secure base, the child is able to explore the physical and social environment (Bowlby, 1969, 1988). In Ainsworth's pioneering studies of attachment (Ainsworth, Blehar, Waters, & Wall, 1978), in sequential phases of a laboratory observation, children explored a novel play environment in the presence of their mother and were then observed during a brief separation from their mother, exposure to a stranger, and reunion with their mother. Three patterns of attachment were identified. Infants who displayed the secure pattern freely explored in their mother's

Summary of Coastal Geologic Evidence for past Great Earthquakes at the Cascadia Subduction Zone

Abstract: Earthquakes in the past few thousand years have left signs of land-level change, tsunamis, and shaking along the Pacific coast at the Cascadia subduction zone. Sudden lowering of land accounts for ...

Transcription termination at intrinsic terminators: the role of the RNA hairpin

Abstract: Intrinsic termination of transcription in Escherichia coli involves the formation of an RNA hairpin in the nascent RNA. This hairpin plays a central role in the release of the transcript and polymerase at intrinsic termination sites on the DNA template. We have created variants of the lambda tR2 terminator hairpin and examined the relationship between the structure and stability of this hairpin and the template positions and efficiencies of termination. The results were used to test the simple nucleic acid destabilization model of Yager and von Hippel and showed that this model must be modified to provide a distinct role for the rU-rich sequence in the nascent RNA, since a perfect palindromic sequence that is sufficiently long to form an RNA hairpin that could destabilize the entire putative 12-bp RNA-DNA hybrid does not trigger termination at the expected positions. Rather, our results show that both a stable terminator hairpin and the run of 6-8 rU residues that immediately follows are required for effective intrinsic termination and that termination occurs at specific and invariant template positions relative to these two components. Possible structural or kinetic modifications of the simple model are proposed in the light of these findings and of recent results implicating "inchworming" and possible conformational heterogeneity of transcription complexes in intrinsic termination. Thus, these findings argue that the structure and dimensions of the hairpin are important determinants of the termination-elongation decision and suggest that a complete mechanism is likely to involve specific interactions of the polymerase, the RNA terminator hairpin, and, perhaps, the dT-rich template sequence that codes for the run of rU residues at the 3' end of the nascent transcript.

Temperature-sensitive mutations that cause stage-specific defects in Zebrafish fin regeneration.

Abstract: When amputated, the fins of adult zebrafish rapidly regenerate the missing tissue. Fin regeneration proceeds through several stages, including wound healing, establishment of the wound epithelium, recruitment of the blastema from mesenchymal cells underlying the wound epithelium, and differentiation and outgrowth of the regenerate. We screened for temperature-sensitive mutations that affect the regeneration of the fin. Seven mutations were identified, including five that fail to regenerate their fins, one that causes slow growth during regeneration, and one that causes dysmorphic bumps or tumors to develop in the regenerating fin. reg5 mutants fail to regenerate their caudal fins, whereas reg6 mutants develop dysmorphic bumps in their regenerates at the restrictive temperature. Temperature-shift experiments indicate that reg5 and reg6 affect different stages of regeneration. The critical period for reg5 occurs during the early stages of regeneration before or during establishment of the blastema, resulting in defects in subsequent growth of the blastema and failure to differentiate bone-forming cells. The critical period for reg6 occurs after the onset of bone differentiation and during early stages of regenerative outgrowth. Both reg5 and reg6 also show temperature-sensitive defects in embryonic development or in ontogenetic outgrowth of the juvenile fin.

Motivational Climate, Psychological Responses, and Motor Skill Development in Children’s Sport: A Field-Based Intervention Study

Abstract: Recent research in educational psychology suggests that provision of a mastery motivational climate will maximize enjoyment, perceived competence, and intrinsic motivation in children (Ames, 1992a, 1992b, 1992c). Minimal research has been conducted to test this proposition in the physical domain. The purpose of this study was to examine the effectiveness of a performance versus mastery oriented teaching program on children’s enjoyment, perceived competence, intrinsic motivation, and motor skill development. Children (N = 119) 8 to 12 years of age were randomly assigned to one of the two programs for 3 weeks during an organized sports program. Results revealed that children in the mastery oriented group reported significantly higher levels of enjoyment and exhibited better motor skills than those in the performance oriented group. In-depth interviews further indicated that children in the mastery program were almost unanimous in reporting high levels of perceived competence and intrinsic motivation, while ...