Showing papers by "University of Arizona published in 1999"
TL;DR: In this article, a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators were developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive readout, and the fabrication of threedimensional micro-optical and micromechanical structures, including photonic bandgap-type structures.
Abstract: Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging1, optical data storage2,3 and lithographic microfabrication4,5,6. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures7.
1,975 citations
TL;DR: In this article, the authors attempt hemispheric temperature reconstructions with proxy data networks for the past millennium, focusing not just on the reconstructions, but the uncertainties therein, and important caveats.
Abstract: Building on recent studies, we attempt hemispheric temperature reconstructions with proxy data networks for the past millennium. We focus not just on the reconstructions, but the uncertainties therein, and important caveats. Though expanded uncertainties prevent decisive conclusions for the period prior to AD 1400, our results suggest that the latter 20th century is anomalous in the context of at least the past millennium. The 1990s was the warmest decade, and 1998 the warmest year, at moderately high levels of confidence. The 20th century warming counters a millennial-scale cooling trend which is consistent with long-term astronomical forcing.
1,742 citations
TL;DR: The capability of the shuffled complex evolution automatic procedure is compared with the interactive multilevel calibration multistage semiautomated method developed for calibration of the Sacramento soil moisture accounting streamflow forecasting model of the U.S. National Weather Service and suggests that the state of the art in automatic calibration now can be expounded.
Abstract: The usefulness of a hydrologic model depends on how well the model is calibrated. Therefore, the calibration procedure must be conducted carefully to maximize the reliability of the model. In general, manual procedures for calibration can be extremely time-consuming and frustrating, and this has been a major factor inhibiting the widespread use of the more sophisticated and complex hydrologic models. A global optimization algorithm entitled shuffled complex evolution recently was developed that has proved to be consistent, effective, and efficient in locating the globally optimal model parameters of a hydrologic model. In this paper, the capability of the shuffled complex evolution automatic procedure is compared with the interactive multilevel calibration multistage semiautomated method developed for calibration of the Sacramento soil moisture accounting streamflow forecasting model of the U.S. National Weather Service. The results suggest that the state of the art in automatic calibration now can be exp...
1,680 citations
TL;DR: Treatment with sustained-release bupropion alone or in combination with a nicotine patch resulted in significantly higher long-term rates of smoking cessation than use of either the nicotine patch alone or placebo.
Abstract: Background and Methods Use of nicotine-replacement therapies and the antidepressant bupropion helps people stop smoking. We conducted a double-blind, placebo-controlled comparison of sustained-release bupropion (244 subjects), a nicotine patch (244 subjects), bupropion and a nicotine patch (245 subjects), and placebo (160 subjects) for smoking cessation. Smokers with clinical depression were excluded. Treatment consisted of nine weeks of bupropion (150 mg a day for the first three days, and then 150 mg twice daily) or placebo, as well as eight weeks of nicotine-patch therapy (21 mg per day during weeks 2 through 7, 14 mg per day during week 8, and 7 mg per day during week 9) or placebo. The target day for quitting smoking was usually day 8. Results The abstinence rates at 12 months were 15.6 percent in the placebo group, as compared with 16.4 percent in the nicotine-patch group, 30.3 percent in the bupropion group (P<0.001), and 35.5 percent in the group given bupropion and the nicotine patch (P<0.001). B...
1,589 citations
TL;DR: RSV lower respiratory tract illnesses in early childhood are an independent risk factor for the subsequent development of wheezing up to age 11 years but not at age 13, and this association is not caused by an increased risk of allergic sensitisation.
1,552 citations
TL;DR: In this article, the authors examined the potential benefits and risks associated with participation in five types of activities: prosocial (church and volunteer activities), team sports, school involvement, performing arts, and academic clubs.
Abstract: We examined the potential benefits and risks associated with participation in five types of activities: prosocial (church and volunteer activities), team sports, school involvement, performing arts, and academic clubs. Our sample included 1,259 mostly European American adolescents (approximately equal numbers of males and females). First, we explore the link between involvement in these activities and our indicators of positive and negative development. Involvement in prosocial activities was linked to positive educational trajectories and low rates of involvement in risky behaviors. In contrast, participation in team sports was linked to positive educational trajectories and to high rates of involvement in one risky behavior, drinking alcohol. Then, we explore two possible mediators of these associations: peer associations and activity-based identity formation. The evidence supported our hypothesis that group differences in peer associations and activity-based identities help explain activity group diffe...
1,551 citations
TL;DR: In this article, a general review of the effects of fire on belowground systems with emphasis placed on the changes in physical, biogeochemical and biological properties of soils and the resulting consequences these changes have for ecosystem sustainability.
1,485 citations
TL;DR: A montane grassland restoration project in northern New Mexico is described that was justified and guided by an historical sequence of aerial photographs showing progressive tree invasion during the 20th century, and a south- western network of fire histories illustrates the power of aggregating historical time series across spatial scales.
Abstract: Applied historical ecology is the use of historical knowledge in the man- agement of ecosystems. Historical perspectives increase our understanding of the dynamic nature of landscapes and provide a frame of reference for assessing modern patterns and processes. Historical records, however, are often too brief or fragmentary to be useful, or they are not obtainable for the process or structure of interest. Even where long historical time series can be assembled, selection of appropriate reference conditions may be com- plicated by the past influence of humans and the many potential reference conditions encompassed by nonequilibrium dynamics. These complications, however, do not lessen the value of history; rather they underscore the need for multiple, comparative histories from many locations for evaluating both cultural and natural causes of variability, as well as for characterizing the overall dynamical properties of ecosystems. Historical knowledge may not simplify the task of setting management goals and making decisions, but 20th century trends, such as increasingly severe wildfires, suggest that disregarding history can be perilous. We describe examples from our research in the southwestern United States to illustrate some of the values and limitations of applied historical ecology. Paleoecological data from packrat middens and other natural archives have been useful for defining baseline conditions of vegetation communities, determining histories and rates of species range expansions and contractions, and discriminating between natural and cultural causes of environmental change. We describe a montane grassland restoration project in northern New Mexico that was justified and guided by an historical sequence of aerial photographs showing progressive tree invasion during the 20th century. Likewise, fire scar chronologies have been widely used to justify and guide fuel reduction and natural fire reintroduction in forests. A south- western network of fire histories illustrates the power of aggregating historical time series across spatial scales. Regional fire patterns evident in these aggregations point to the key role of interannual lags in responses of fuels and fire regimes to the El Nino-Southern Oscillation (wet/dry cycles), with important implications for long-range fire hazard fore- casting. These examples of applied historical ecology emphasize that detection and expla- nation of historical trends and variability are essential to informed management.
1,372 citations
TL;DR: In this article, the covariant behavior of Lu-Hf and Sm-Nd isotopes during most magmatic processes has been recognized, but the details of this behavior in the depleted mantle reservoir have not been adequately examined.
1,250 citations
TL;DR: In this paper, a 2° lat × 3° long grid of summer drought reconstructions for the continental United States estimated from a dense network of annual tree-ring chronologies is described.
Abstract: The development of a 2° lat × 3° long grid of summer drought reconstructions for the continental United States estimated from a dense network of annual tree-ring chronologies is described. The drought metric used is the Palmer Drought Severity Index (PDSI). The number of grid points is 154 and the reconstructions cover the common period 1700–1978. In producing this grid, an automated gridpoint regression method called “point-by-point regression” was developed and tested. In so doing, a near-optimal global solution was found for its implementation. The reconstructions have been thoroughly tested for validity using PDSI data not used in regression modeling. In general, most of the gridpoint estimates of drought pass the verification tests used. In addition, the spatial features of drought in the United States have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design. The drought reconstructions show that the 1930s “Dust Bow...
1,113 citations
TL;DR: In the first 371 sq. deg. of actual 2MASS survey data, they identified another twenty objects spectroscopically confirmed using the Low Resolution Imaging Spectrograph (LRIS) at the W.M. Keck Observatory.
Abstract: Before the 2-Micron All-Sky Survey (2MASS) began, only six objects were known with spectral types later than M9.5 V. In the first 371 sq. deg. of actual 2MASS survey data, we have identified another twenty such objects spectroscopically confirmed using the Low Resolution Imaging Spectrograph (LRIS) at the W.M. Keck Observatory.
TL;DR: Following sequential exposure of rats to two different environments or to the same environment twice, the proportion of CA1 neurons with cytoplasmic, nuclear or overlapping Arc expression profiles matched predictions derived from ensemble neurophysiological recordings of hippocampal neuronal ensembles.
Abstract: We used fluorescent in-situ hybridization and confocal microscopy to monitor the subcellular distribution of the immediate-early gene Arc. Arc RNA appeared in discrete intranuclear foci within minutes of neuronal activation and subsequently disappeared from the nucleus and accumulated in the cytoplasm by 30 minutes. The time course of nuclear versus cytoplasmic Arc RNA accumulation was distinct, and could therefore be used to infer the activity history of individual neurons at two times. Following sequential exposure of rats to two different environments or to the same environment twice, the proportion of CA1 neurons with cytoplasmic, nuclear or overlapping Arc expression profiles matched predictions derived from ensemble neurophysiological recordings of hippocampal neuronal ensembles. Arc gene induction is thus specifically linked to neural encoding processes.
TL;DR: In this article, asymptotics for orthogonal polynomials with respect to varying exponential weights wn(x)dx = e−nV(x)-dx on the line as n ∞ were considered.
Abstract: We consider asymptotics for orthogonal polynomials with respect to varying exponential weights wn(x)dx = e−nV(x)dx on the line as n ∞. The potentials V are assumed to be real analytic, with sufficient growth at infinity. The principle results concern Plancherel-Rotach-type asymptotics for the orthogonal polynomials down to the axis. Using these asymptotics, we then prove universality for a variety of statistical quantities arising in the theory of random matrix models, some of which have been considered recently in [31] and also in [4]. An additional application concerns the asymptotics of the recurrence coefficients and leading coefficients for the orthonormal polynomials (see also [4]).
The orthogonal polynomial problem is formulated as a Riemann-Hilbert problem following [19, 20]. The Riemann-Hilbert problem is analyzed in turn using the steepest-descent method introduced in [12] and further developed in [11, 13]. A critical role in our method is played by the equilibrium measure dμV for V as analyzed in [8]. © 1999 John Wiley & Sons, Inc.
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25 Mar 1999TL;DR: In this article, the authors discuss the role of technology in the emergence of the Internet and its role in post-moderation resistance, and discuss the importance of technology and technology in education.
Abstract: PART I: FOUNDATIONS 1. EPISTEMOLOGY AND POSTMODERN RESISTANCE 2. TRUTH 3. THE FRAMEWORK PART II: GENERIC SOCIAL PRACTICES 4. TESTIMONY 5. ARGUMENTATION 6. THE TECHNOLOGY AND ECONOMICS OF COMMUNICATION 7. SPEECH REGULATION AND THE MARKETPLACE OF IDEAS PART III: SPECIAL DOMAINS 8. SCIENCE 9. LAW 10. DEMOCRACY 11. EDUCATION BIBLIOGRAPHY INDEX.
TL;DR: In this paper, the authors report new Hf (and Nd) data for more than 100 sedimentary samples, recent to Archean in age, from a wide range of depositional environments.
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TL;DR: Polymorphisms in induction or constitutive expression allow insects to scan their P450 gene repertoire for the appropriate response to chemical insults, and these evolutionary pressures in turn maintain P450 diversity.
Abstract: The P450 enzymes (mixed function oxidases, cytochrome P450 monooxygenases), a diverse class of enzymes found in virtually all insect tissues, fulfill many important tasks, from the synthesis and degradation of ecdysteroids and juvenile hormones to the metabolism of foreign chemicals of natural or synthetic origin. This diversity in function is achieved by a diversity in structure, as insect genomes probably carry about 100 P450 genes, sometimes arranged in clusters, and each coding for a different P450 enzyme. Both microsomal and mitochondrial P450s are present in insects and are best studied by heterologous expression of their cDNA and reconstitution of purified enzymes. P450 genes are under complex regulation, with induction playing a central role in the adaptation to plant chemicals and regulatory mutations playing a central role in insecticide resistance. Polymorphisms in induction or constitutive expression allow insects to scan their P450 gene repertoire for the appropriate response to chemical insults, and these evolutionary pressures in turn maintain P450 diversity.
TL;DR: Some benefits of simulation technology include improvements in certain surgical technical skills, in cardiovascular examination skills, and in acquisition and retention of knowledge compared with traditional lectures.
Abstract: Changes in medical practice that limit instruction time and patient availability, the expanding options for diagnosis and management, and advances in technology are contributing to greater use of simulation technology in medical education. Four areas of high-technology simulations currently being used are laparoscopic techniques, which provide surgeons with an opportunity to enhance their motor skills without risk to patients; a cardiovascular disease simulator, which can be used to simulate cardiac conditions; multimedia computer systems, which includes patient-centered, casebased programs that constitute a generalist curriculum in cardiology; and anesthesia simulators, which have controlled responses that vary according to numerous possible scenarios. Some benefits of simulation technology include improvements in certain surgical technical skills, in cardiovascular examination skills, and in acquisition and retention of knowledge compared with traditional lectures. These systems help to address the problem of poor skills training and proficiency and may provide a method for physicians to become self-directed lifelong learners.
TL;DR: It is demonstrated that FN-mediated adhesion confers a survival advantage for myeloma cells acutely exposed to cytotoxic drugs by inhibiting drug-induced apoptosis, which may explain how some cells survive initial drug exposure and eventually express classical mechanisms of drug resistance such as MDR1 overexpression.
TL;DR: It is concluded that CD14/-159 plays a significant role in regulating serum sCD14 levels and total serum IgE levels.
Abstract: Total serum immunoglobulin (Ig)E levels are genetically regulated, but the mechanism of inheritance is not well understood. Cytokines produced by T-helper (Th)1 and Th2 lymphocytes control IgE synthesis. Bacterial antigens may favor the development of Th1 cells from naive CD4-positive T cells through a CD14-dependent pathway. CD14 is constitutively expressed on the surface of monocytes and macrophages, and is also present in serum in a soluble form (sCD14). The CD14 gene maps to chromosome 5q31.1, a candidate region for loci regulating total serum IgE. We hypothesized that genetic variants in the CD14 gene could influence Th-cell differentiation and thus total serum IgE. We identified a C-to-T transition at base pair −159 from the major transcription start site (CD14/−159). Among 481 children recruited from a general population sample, frequency of allele C was 51.4%. TT homozygotes had significantly higher sCD14 levels than did carriers of both the CC and CT genotypes (P = 0.01). TT homozygotes also had ...
TL;DR: In this article, the authors developed a method for estimating the host galaxy dust extinction for type Ia supernovae based on an observational coincidence first noted by Lira, who found that the B-V evolution during the period from 30 to 90 days after V maximum is remarkably similar for all events, regardless of light-curve shape.
Abstract: We develop a method for estimating the host galaxy dust extinction for type Ia supernovae based on an observational coincidence first noted by Lira, who found that the B-V evolution during the period from 30 to 90 days after V maximum is remarkably similar for all events, regardless of light-curve shape. This fact is used to calibrate the dependence of the Bmax-Vmax and Vmax-Imax colors on the light-curve decline rate parameter Δm15(B), which can, in turn, be used to separately estimate the host galaxy extinction. Using these methods to eliminate the effects of reddening, we reexamine the functional form of the decline rate versus luminosity relationship and provide an updated estimate of the Hubble constant of H0 = 63.3 ± 2.2(internal) ± 3.5(external) km s-1 Mpc-1.
TL;DR: The findings indicate that nonpharmacological therapies produce reliable and durable changes in several sleep parameters of chronic insomnia sufferers and there is no clear evidence that improved sleep leads to meaningful changes in daytime well-being or performance.
Abstract: This paper reviews the evidence regarding the efficacy of nonpharmacological treatments for primary chronic insomnia. It is based on a review of 48 clinical trials and two meta-analyses conducted by a task force appointed by the American Academy of Sleep Medicine to develop practice parameters on non-drug therapies for the clinical management of insomnia. The findings indicate that nonpharmacological therapies produce reliable and durable changes in several sleep parameters of chronic insomnia sufferers. The data indicate that between 70% and 80% of patients treated with nonpharmacological interventions benefit from treatment. For the typical patient with persistent primary insomnia, treatment is likely to reduce the main target symptoms of sleep onset latency and/or wake time after sleep onset below or near the 30-min criterion initially used to define insomnia severity. Sleep duration is also increased by a modest 30 minutes and sleep quality and patient's satisfaction with sleep patterns are significantly enhanced. Sleep improvements achieved with these behavioral interventions are sustained for at least 6 months after treatment completion. However, there is no clear evidence that improved sleep leads to meaningful changes in daytime well-being or performance. Three treatments meet the American Psychological Association (APA) criteria for empirically-supported psychological treatments for insomnia: Stimulus control, progressive muscle relaxation, and paradoxical intention; and three additional treatments meet APA criteria for probably efficacious treatments: Sleep restriction, biofeedback, and multifaceted cognitive-behavior therapy. Additional outcome research is needed to examine the effectiveness of treatment when it is implemented in clinical settings (primary care, family practice), by non-sleep specialists, and with insomnia patients presenting medical or psychiatric comorbidity.
TL;DR: In this article, the authors present a new analysis of the transport of cosmic rays in a turbulent magnetic field that varies in all three spatial dimensions using a numerical simulation that integrates the trajectories of an ensemble of test particles from which they obtain diffusion coefficients based on the particle motions.
Abstract: We present a new analysis of the transport of cosmic rays in a turbulent magnetic field that varies in all three spatial dimensions. The analysis utilizes a numerical simulation that integrates the trajectories of an ensemble of test particles from which we obtain diffusion coefficients based on the particle motions. We find that the diffusion coefficient parallel to the mean magnetic field is consistent with values deduced from quasi-linear theory, in agreement with earlier work. The more interesting and less understood transport perpendicular to the average magnetic field is found to be enhanced (above the classical scattering result) by the random walk, or braiding, of the magnetic field. The value of κ⊥ obtained is generally larger than the classical scattering value but smaller than the quasi-linear value. The computed values of κ⊥/κ∥, for a representation of the interplanetary magnetic field, are 0.02-0.04; these values are of the same general magnitude as those assumed in recent numerical simulations of cosmic-ray modulation and transport in the heliosphere, and give reasonable agreement with spacecraft observations of cosmic rays. Some consequences of these results for the interpretation of heliospheric observations are discussed.
TL;DR: In this article, Johnson/Cousins B, V, R, and I photometric observations of 22 recent Type Ia supernovae (SNe Ia): SNe 1993ac, 1993ae, 1994M, 1994S, 1994T, 1994Q, 1994ae, 1995D, 1995E, 1995al, 1995ac, 1995ak, 1995bd, 1996C, 1996X, 1996Z, 1996ab, 1996ai, 1996bk, 1996bl, 1996bo, and 1996bv.
Abstract: We present 1210 Johnson/Cousins B, V, R, and I photometric observations of 22 recent Type Ia supernovae (SNe Ia): SNe 1993ac, 1993ae, 1994M, 1994S, 1994T, 1994Q, 1994ae, 1995D, 1995E, 1995al, 1995ac, 1995ak, 1995bd, 1996C, 1996X, 1996Z, 1996ab, 1996ai, 1996bk, 1996bl, 1996bo, and 1996bv. Most of the photometry was obtained at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics in a cooperative observing plan aimed at improving the database for SNe Ia. The redshifts of the sample range from cz = 1200 to 37,000 km s-1 with a mean of cz = 7000 km s-1.
TL;DR: Barth and Kallapur as discussed by the authors investigated the role of book value in cross-sectional valuation models and found that including book value of equity in the valuation specification eliminates the negative relation.
Abstract: This study provides an explanation for the anomalous significantly negative price‐earnings relation using the simple earnings capitalization model for firms that report losses. We hypothesize and find that including book value of equity in the valuation specification eliminates the negative relation. This suggests that the simple earnings capitalization model is misspecified and the negative coefficient on earnings for loss firms is a manifestation of that misspecification. Furthermore, we provide evidence on three competing explanations for the role that book value of equity plays in valuing loss firms. Specifically, we investigate whether the importance of book value in cross‐sectional valuation models stems from its role as (1) a control for scale differences (Barth and Kallapur 1996), (2) a proxy for expected future normal earnings (Ohlson 1995; Penman 1992), or (3) a proxy for loss firms' abandonment option (Berger et al. 1996; Barth et al. 1996; Burgstahler and Dichev 1997). Our results do not suppo...
TL;DR: In this paper, asymptotics of orthogonal polynomials with respect to weights w(x)dx = e Q(x)-dx on the real line were considered.
Abstract: We consider asymptotics of orthogonal polynomials with respect to weights w(x)dx= e Q(x) dx on the real line, where Q(x)=∑ 2m k=0 qkx k , q2m> 0, denotes a polynomial of even order with positive leading coefficient. The orthogonal polynomial problem is formulated as a Riemann-Hilbert problem following [22, 23]. We employ the steepest-descent-type method introduced in [18] and further developed in [17, 19] in order to obtain uniform Plancherel-Rotach-type asymptotics in the entire complex plane, as well as asymptotic formulae for the zeros, the leading coefficients, and the recurrence coefficients of the orthogonal polynomials. c 1999 John Wiley & Sons, Inc.
TL;DR: Pattern reinstatement was strongest during sharp wave–ripple oscillations, suggesting that these events may reflect system convergence onto attractor states corresponding to previous experiences, and do not necessarily reflect persistence of an active memory.
Abstract: During slow wave sleep (SWS), traces of neuronal activity patterns from preceding behavior can be observed in rat hippocampus and neocortex. The spontaneous reactivation of these patterns is manifested as the reinstatement of the distribution of pairwise firing-rate correlations within a population of simultaneously recorded neurons. The effects of behavioral state [quiet wakefulness, SWS, and rapid eye movement (REM)], interactions between two successive spatial experiences, and global modulation during 200 Hz electroencephalographic (EEG) "ripples" on pattern reinstatement were studied in CA1 pyramidal cell population recordings. Pairwise firing-rate correlations during often repeated experiences accounted for a significant proportion of the variance in these interactions in subsequent SWS or quiet wakefulness and, to a lesser degree, during SWS before the experience on a given day. The latter effect was absent for novel experiences, suggesting that a persistent memory trace develops with experience. Pattern reinstatement was strongest during sharp wave-ripple oscillations, suggesting that these events may reflect system convergence onto attractor states corresponding to previous experiences. When two different experiences occurred in succession, the statistically independent effects of both were evident in subsequent SWS. Thus, the patterns of neural activity reemerge spontaneously, and in an interleaved manner, and do not necessarily reflect persistence of an active memory (i.e., reverberation). Firing-rate correlations during REM sleep were not related to the preceding familiar experience, possibly as a consequence of trace decay during the intervening SWS. REM episodes also did not detectably influence the correlation structure in subsequent SWS, suggesting a lack of strengthening of memory traces during REM sleep, at least in the case of familiar experiences.
TL;DR: Men and women interact extensively within families and households and in other role relations as mentioned in this paper, which raises important questions about how interaction creates experiences that confirm, or potentially could undermine, the beliefs about gender difference and inequality that underlie the gender system.
Abstract: ▪ Abstract The gender system includes processes that both define males and females as different in socially significant ways and justify inequality on the basis of that difference. Gender is different from other forms of social inequality in that men and women interact extensively within families and households and in other role relations. This high rate of contact between men and women raises important questions about how interaction creates experiences that confirm, or potentially could undermine, the beliefs about gender difference and inequality that underlie the gender system. Any theory of gender difference and inequality must accommodate three basic findings from research on interaction. (a). People perceive gender differences to be pervasive in interaction. (b). Studies of interaction among peers with equal power and status show few gender differences in behavior. (c). Most interactions between men and women occur in the structural context of roles or status relationships that are unequal. These s...
TL;DR: Four experiments used the head-turn preference procedure to assess whether infants could extract and remember information from auditory strings produced by a miniature artificial grammar and found infants generalized to new structure by discriminating new grammatical strings from ungrammatical ones after less than 2 min exposure to the grammar.
TL;DR: In this article, the authors show that the estimated separate contributions of sets of dummy variables to the explained portion and the overall decomposition are not dependent upon the choice of left-out reference groups.
Abstract: The standard wage decomposition methodology produces arbitrary results when attempting to estimate the separate contributions of sets of dummy variables to the unexplained portion of the wage decomposition: the estimates are not invariant with respect to the choice of reference groups. However, the estimated separate contributions of sets of dummy variables to the explained portion and the overall decomposition are shown not to be dependent upon the choice of left-out reference groups. A similar identification problem applies to continuous variables, although this may not be as likely to cause problems in practice.
TL;DR: In this paper, a linear instability of nonaxisymmetric Rossby waves in a thin nonmagnetized Keplerian disk was found when there is a local maximum in the radial profile of a key function (r)≡(r)S2/Γ(r), where −1=(∇×v)/Σ is the potential vorticity, S=P/ΣΓ is the entropy, Σ is surface mass density, P is the vertically integrated pressure, and Γ are the adiabatic index.
Abstract: We find a linear instability of nonaxisymmetric Rossby waves in a thin nonmagnetized Keplerian disk when there is a local maximum in the radial profile of a key function (r)≡(r)S2/Γ(r), where −1=(∇×v)/Σ is the potential vorticity, S=P/ΣΓ is the entropy, Σ is the surface mass density, P is the vertically integrated pressure, and Γ is the adiabatic index. We consider in detail the special case where there is a local maximum in the disk entropy profile S(r). This maximum acts to trap the waves in its vicinity if its height-to-width ratio max(S)/Δr is larger than a threshold value. The pressure gradient derived from this entropy variation provides the restoring force for the wave growth. We show that the trapped waves act to transport angular momentum outward. A plausible way to produce an entropy variation is when an accretion disk is starting from negligible mass and temperature, therefore, negligible entropy. As mass accumulates by either tidal torquing, magnetic torquing, or Roche-lobe overflow, confinement of heat will lead to an entropy maximum at the outer boundary of the disk. Possible nonlinear developments from this instability include the formation of Rossby vortices and the formation of spiral shocks. What remains to be determined from hydrodynamic simulations is whether or not Rossby wave packets (or vortices) "hold together" as they propagate radially inward.