Showing papers by "Williams College published in 2000"

A threatening intellectual environment: why females are susceptible to experiencing problem-solving deficits in the presence of males.

Abstract: Does placing females in environments in which they have contact with males cause deficits in their problem-solving perfor- mance? Is a situational cue, such as gender composition, sufficient for creating a threatening intellectual environment for females—an en- vironment that elicits performance-impinging stereotypes? Two stud- ies explored these questions. Participants completed a difficult math or verbal test in 3-person groups, each of which included 2 additional people of the same sex as the participant (same-sex condition) or of the opposite sex (minority condition). Female participants in the mi- nority condition experienced performance deficits in the math test only, whereas males performed equally well on the math test in the two conditions. Further investigation showed that females' deficits were proportional to the number of males in their group. Even females who were placed in a mixed-sex majority condition (2 females and 1 male) experienced moderate but significant deficits. Findings are dis- cussed in relation to theories of distinctiveness, stereotype threat, and tokenism. Females currently are a small minority of students and researchers in the natural and physical sciences. A recent National Science Foun- dation (1996) report showed that females constitute 35% of under- graduate students enrolled in physics, math, and computer science classes; 16% of undergraduate students enrolled in engineering classes; and less than 10% of graduate students in physics and engi- neering. Moreover, this report showed that females suffer from higher attrition rates in their academic careers than do males, so that by the time women reach the workplace, they occupy only 22% of jobs in mathematical and scientific domains. Does females' problem-solving performance diminish when they are placed in an environment in which males outnumber them? If so, are such performance deficits specifically linked to domains that are associated with negative ste- reotypes about females' intellectual capacity? Examining these ques- tions can inform theories of how social stereotypes affect the intellectual processing of individuals who are the targets of these stereotypes, as well as educational practice.

The spotlight effect in social judgment: An egocentric bias in estimates of the salience of one's own actions and appearance.

Abstract: This research provides evidence that people overestimate the extent to which their actions and appearance are noted by others, a phenomenon dubbed the spotlight effect. In Studies 1 and 2, participants who were asked to don a T-shirt depicting either a flattering or potentially embarrassing image overestimated the number of observers who would be able to recall what was pictured on the shirt. In Study 3, participants in a group discussion overestimated how prominent their positive and negative utterances were to their fellow discussants. Studies 4 and 5 provide evidence supporting an anchoring-and-adjustment interpretation of the spotlight effect. In particular, people appear to anchor on their own rich phenomenological experience and then adjust--insufficiently--to take into account the perspective of others. The discussion focuses on the manifestations and implications of the spotlight effect across a host of everyday social phenomena.

Emotions in Politics

Abstract: The study of emotion in politics has been active, especially as it relates to the personality of political leaders and as an explanation for how people evaluate significant features around them. Researchers have been divided into two groups—those who study leaders and those who study publics. The research programs have also been divided between those who use emotion to explain reliance on early experience that dominates contemporary judgment and those who use emotion to explain why people respond to the immediate contemporary circumstances around them. More recently, theory and research have attempted to reconcile these two seemingly contradictory roles by integrating them. Emotion's role in politics is pervasive both because emotion enables past experience to be encoded with its evaluative history and because emotion enables contemporary circumstances to be quickly evaluated. More recently still, theoretical models and supporting evidence suggest that there are multiple channels of emotional evaluations.

Monetary Policy Surprises and Interest Rates: Evidence from the Fed Funds Futures Markets

Abstract: This paper estimates the impact of monetary policy actions on bill, note, and bond yields, using data from the futures market for Federal funds to separate changes in the target funds rate into anticipated and unanticipated components. Bond rates' response to anticipated changes is essentially zero, while their response to unanticipated movements is large and highly significant. Surprise policy actions have little effect on near-term expectations of future actions, which helps explain the failure of the expectations hypothesis on the short end of the yield curve.

Defense mechanisms in psychology today. Further processes for adaptation.

Abstract: Although the concept of the defense mechanism was rejected from academic psychology for a number of years, recent empirical studies show renewed interest in defenses. Cognitive psychologists have confirmed the existence of unconscious psychological processes, a requisite for defenses. Developmental, personality, and social psychologists have all found evidence for defense mechanisms that explicate psychological functioning. The relevance of this new information for clinical practice is discussed.

Fish and ships: relating dispersal frequency to success in biological invasions

Abstract: Most studies characterizing successful biological invaders emphasize those traits that help a species establish a new population. Invasions are, however, multi-phase processes with at least two phases, dispersal and introduction, that occur before establishment. Characteristics that enhance survival at any of these three phases will contribute to invasion success. Here, we synthesize information on the dispersal, introduction, and establishment of fishes mediated by ship ballast-water transport. We synthesize 54 reports of at least 31 fish species collected from ballast tanks (Phase 1), including 28 new reports from our recent studies (1986 to 1996). Our literature survey revealed 40 reports of 32 fish species whose introductions have been attributed to ballast transport (Phase 2), of which at least 24 survived to establish persistent populations (Phase 3). We detected little overlap at the species level between these two data sets (Phase 1 vs Phases 2 and 3), but patterns emerged at the family level. The Gobiidae (6 species), Clupeidae (4 species), and Gasterosteidae (1 species) were the most commonly found fish families in ballast tanks (Phase 1). The Gobiidae (13 species), Blenniidae (6 species) and Pleuronectidae (2 species) dominated the list of ballast-mediated introductions (Phase 2); gobies and blennies were the families most frequently established (Phase 3). The invasive success of gobies and blennies may be explained in part by their crevicolous nature: both groups seek refuge and lay eggs in small holes, and may take advantage of the ballast-intake holes on ship hulls. This behavior, not typically associated with invasive ability, may contribute to successful introduction and establishment by facilitating the dispersal phase of invasion. The failure of the pleuronectids to invade may reflect poor salinity match between donor and recipient regions. To develop a predictive framework of invasion success, organisms must be sampled at all three phases of the invasion process. Our comparison of two ballast sampling methods suggests that fishes have been undersampled in ballast-water studies, including our own, and that the role of ballast transport in promoting fish invasions has been underestimated.

Observation of optically induced feshbach resonances in collisions of cold atoms

Abstract: We have observed optically induced Feshbach resonances in a cold ( $l1\mathrm{mK}$) sodium vapor. The optical coupling of the ground and excited-state potentials changes the scattering properties of an ultracold gas in much the same way as recently observed magnetically induced Feshbach resonances, but allows for some experimental conveniences associated with using lasers. The scattering properties can be varied by changing either the intensity or the detuning of a laser tuned near a photoassociation transition to a molecular state in the dimer. In principle this method allows the scattering length of any atomic species to be altered. A simple model is used to fit the dispersive resonance line shapes.

The Hubble Space Telescope key project on the extragalactic distance scale XXV: a recalibration of Cepheid distances to type Ia supernovae and the value of the Hubble constant

Abstract: Cepheid-based distances to seven Type Ia supernovae (SNe) host galaxies have been derived using the standard Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale pipeline. For the first time, this allows for a transparent comparison of data accumulated as part of three different HST projects: the Key Project, the Sandage et al. Type Ia supernovae (SNe) program, and the Tanvir et al. Leo I Group study. Reanalyzing the Tanvir et al. galaxy and six Sandage et al. galaxies, we find a mean (weighted) offset in true distance moduli of 0.12 ± 0.07 mag; i.e., 6% in linear distance, in the sense of reducing the distance scale or increasing H0. Adopting the reddening-corrected Hubble relations of Suntzeff et al. tied to a zero point based on SNe 1990N, 1981B, 1998bu, 1989B, 1972E, and 1960F and the photometric calibration of Hill et al. leads to a Hubble constant of H0 = 68 ± 2(random) ± 5(systematic) km s-1 Mpc-1. Adopting the Kennicutt et al. Cepheid period-luminosity-metallicity dependency decreases the inferred H0 by 4%. The H0 result from Type Ia SNe is now in good agreement, to within their respective uncertainties, with that from the Tully-Fisher and surface brightness fluctuation relations.

The calcineurin-NFAT pathway and muscle fiber-type gene expression.

Abstract: To test for a role of the calcineurin-NFAT (nuclear factor of activated T cells) pathway in the regulation of fiber type-specific gene expression, slow and fast muscle-specific promoters were exami...

Structure determination of soybean and wheat glucosylceramides by tandem mass spectrometry.

Abstract: Glucosylceramide (GluCer) is a major sphingolipid of plant tissue and, thus, abundant in nature and in dietary food sources. The lipid backbones of mammalian GluCer (sphingosine, d18:1(delta4), and ceramide) induce cell death (apoptosis) and inhibit colon carcinogenesis, it is critical to know the structures of GluCer present in plants as a first step toward understanding this potential link between diet and cancer. This study characterized the molecular species of GluCer from soybean and wheat by low-resolution, high-resolution and tandem mass spectrometry. Soybean GluCer was comprised primarily (>95%) of ceramide with 4,8-sphingadiene (d18:2(delta4,delta8)) and alpha-hydroxypalmitic acid (h16:0); the remainder had the same backbone with h18:0, h20:0, h22:0 and h24:0 fatty acids. Wheat GluCer had three major ceramide, d18:2(delta4,delta8) with h16:0, d18:1(delta8) with h16:0 and d18: 2(delta4,delta8) with h20:0, and smaller amounts of other homologs. These backbones differ from those of mammalian sphingolipids, which often have a delta4-double bond (but rarely a delta8-double bond), and have alpha-hydroxy fatty acids in only some cases. Previously unexplained fragmentations that were diagnostic for the type of sphingoid base backbone (i.e. by homolytic cleavage of the doubly allylic C-6-C-7 bond to yield a stable distonic allylic radical cation and an allylic radical neutral) were also identified. Hence this method should be useful in the identification of double bonds in sphingolipids, and structure-function relationships between sphingolipids and colon carcinogenesis.

Deuterium in the Galactic Centre as a result of recent infall of low-metallicity gas

Abstract: The Galactic Centre is the most active and heavily processed region of the Milky Way, so it can be used as a stringent test for the abundance of deuterium (a sensitive indicator of conditions in the first 1,000 seconds in the life of the Universe). As deuterium is destroyed in stellar interiors, chemical evolution models predict that its Galactic Centre abundance relative to hydrogen is D/H = 5 x 10(-12), unless there is a continuous source of deuterium from relatively primordial (low-metallicity) gas. Here we report the detection of deuterium (in the molecule DCN) in a molecular cloud only 10 parsecs from the Galactic Centre. Our data, when combined with a model of molecular abundances, indicate that D/H = (1.7 +/- 0.3) x 10(-6), five orders of magnitude larger than the predictions of evolutionary models with no continuous source of deuterium. The most probable explanation is recent infall of relatively unprocessed metal-poor gas into the Galactic Centre (at the rate inferred by Wakker). Our measured D/H is nine times less than the local interstellar value, and the lowest D/H observed in the Galaxy. We conclude that the observed Galactic Centre deuterium is cosmological, with an abundance reduced by stellar processing and mixing, and that there is no significant Galactic source of deuterium.

The isoperimetric problem on surfaces of revolution of decreasing Gauss curvature

Abstract: We prove that the least-perimeter way to enclose prescribed area in the plane with smooth, rotationally symmetric, complete metric of nonincreasing Gauss curvature consists of one or two circles, bounding a disc, the complement of a disc, or an annulus. We also provide a new isoperimetric inequality in general surfaces with boundary.

A New Look at Carbon Abundances in Planetary Nebulae. IV. Implications for Stellar Nucleosynthesis

Abstract: This paper is the fourth and final report on a project designed to study carbon abundances in a sample of planetary nebulae representing a broad range in progenitor mass and metallicity. We present newly acquired optical spectrophotometric data for three Galactic planetary nebulae, IC 418, NGC 2392, and NGC 3242, and combine them with UV data from the IUE Final Archive for identical positions in each nebula to determine accurate abundances of He, C, N, O, and Ne at one or more locations in each object. We then collect abundances of these elements for the entire sample and compare them with theoretical predictions of planetary nebula abundances from a grid of intermediate-mass star models. We find some consistency between observations and theory, lending modest support to our current understanding of nucleosynthesis in stars below 8 M☉ in birth mass. Overall, we believe that observed abundances agree with theoretical predictions to well within an order of magnitude but probably not better than to within a factor of 2 or 3. However, even this level of consistency between observation and theory enhances the validity of published intermediate-mass stellar yields of carbon and nitrogen in the study of the abundance evolution of these elements.

Conflicting Equalities? Cultural Group Rights and Sex Equality

Abstract: This article explores the tensions within multiculturalist theory between the aspiration to promote cultural recognition and the need to promote and protect women's concern with issues of sex and gender inequality. The article asseses the three main approaches to the reconciliation of sexual equality and group rights; according priority to the traditional values and practices of cultural groups; accepting collective and cultural rights but within a framework international human rights; and finally, the acceptance of group rights subject to respect for individual rights and freedoms. By focusing on the experience of aboriginal women activists in Canadian politics and their struggle to preserve constitutional sex equality, this article argues that only the third approach provides adequate safeguards for women in their public and private roles.

Inflation, monetary transparency, and g3 exchange rate volatility

Abstract: There is a tension between pre-float instincts that a more disciplined monetary policy should diminish exchange rate volatility with the apparent reality that macroeconomic fundamentals do not drive G3 exchange rates in the short-run. The recent movement towards greater transparency in monetary policymaking may partially reconcile this conflict. This possibility depends on the extent to which domestic inflation and interest rate surprises contribute to short-run volatility in G3 exchange rates. These are precisely the type of shocks which should diminish in frequency and effect as monetary transparency increases. If monetary transparency is effective, variations over time in American, German, and Japanese central bank institutions and behavior should match up with the timing of these shocks and the magnitude of their impact on bilateral exchange rates. We set out a simple model of the implications of different monetary regimes for the response of inflation, interest rates, and exchange rates to inflation surprises. We then develop an operational measure of central bank transparency, and apply it to the history of the Bank of Japan, the Bundesbank, and the Federal Reserve in the period 1975-1998, finding significant shifts in institutional transparency for the Federal Reserve and for the Bank of Japan in the late 1980s. To test for a relationship between transparency and volatility, we estimate and analyze structural VAR models of relative interest rates, inflation rates, and exchange rates for the DMB- and DM-$. An assessment of the importance of domestic inflation and interest rate shocks to G3 exchange rate volatility indicates that increases in central bank transparency could meaningfully but not totally diminish that volatility.

Searching an Ex Situ Collection of Wheat Genetic Resources

Abstract: A theoretical model is developed and applied to the search for disease and pest resistance in ex situ collections of wheat genetic resources, employing actual data on frequency distributions, disease losses, and search costs. Experiments developed from case studies clarify several misperceptions about the value of gene banks and their utilization by breeders. The observation that wheat breeders “use” gene banks rarely does not imply that marginal accessions have low value. High costs of transferring genes with conventional breeding techniques mean that it may be efficient to store certain categories of genetic resources (such as landraces) “unused” for many years. Copyright 2000, Oxford University Press.

Identifying dementia in the primary care practice.

Abstract: Background The purpose of this study was to evaluate the utility (i.e., positive and negative predictive value) of the 7 Minute Screen in identifying patients with probable Alzheimer's disease (AD) in a primary care practice. A second objective was to estimate the number of undiagnosed AD patients in a typical primary care practice. Methods One hundred thirty-seven successive admissions (96%) of patients over the age of 60 to a primary care practice over a 53-day period who completed informed consent documents were administered the 7 Minute Screen. All patients who screened positive (n = 13) and a random sample of those who screened negative (n = 26) returned for full diagnostic evaluation. Positive predictive value (PPV) and negative predictive value (NPV) of the 7 Minute Screen were determined using the criterion standard of clinical diagnosis established by examination, history, and laboratory studies. Test-retest reliability and time for administration were also determined. Results Of the 137 patients evaluated, 13 screened positive and 124 screened negative. Eleven of the 13 patients who screened positive were willing to return to the primary care practice for follow-up evaluation. A random sample of 26 patients who screened negative all agreed to return for follow-up evaluation. Of the 11 patients who screened positive and who returned for evaluation, 10 were subsequently diagnosed with probable AD. The remaining patient was diagnosed with mixed dementia. The caregivers of the two patients who refused to return were contacted and both indicated that the patients were having significant cognitive problems as verified by an activities of daily living scale. Of the 26 patients who screened negative, 25 were judged to be cognitively normal and the 26th was judged to have mild cognitive impairment. Discussion In successive admissions of patients over the age of 60 in a primary care practice, the 7 Minute Screen showed a PPV of 91% and an NPV of 96% in identifying patients who were subsequently identified with AD or other dementing disorder. These data suggest that this may be a useful instrument in identifying patients who should undergo diagnostic evaluation for AD and other dementing disorders. Additionally, extrapolation from the data in this practice suggests that there may be between 75 and 100 AD patients in the typical primary care practice, many of whom may not be diagnosed.

Using Statistics to Determine Causal Relationships

Abstract: (2000). Using Statistics to Determine Causal Relationships. The American Mathematical Monthly: Vol. 107, No. 1, pp. 24-32.

Interpreting and Inventing Social Reality

Abstract: Clearly, Leon Festinger hit upon an important subject when he formulated social comparison theory nearly 50 years ago. The ways that people view their opinions, their abilities, and their life situations vary according to the standing of other people. Recently, during the National Basketball Association lockout, star New York Knicks center Patrick Ewing said that current NBA salaries were “about survival, about being able to feed our families” (Newsweek, January 4, 1999, p. 108). Ewing’s salary was $18.5 million per year. That is probably enough to eat on. However, the amount of money made by owners is Ewing’s standard of comparison. Similarly, in resigning Bernie Williams, the New York Yankees baseball team paid the star outfielder $87.5 million for 7 years, so that Williams would not feel underpaid in comparison to first baseman Mo Vaughn, who signed with the California Angels for $80 million for 6 years. Why would Williams only feel happy if his salary compared well to Vaughn’s?

Children's Welfare Exposure and Subsequent Development

Abstract: We examine the extent to which children are exposed to the welfare system through their mother's receipt of benefits and its impact on several developmental outcomes. Using data from the matched mother-child file from the National Longitudinal Survey of Youth (NLSY), we find that children's welfare exposure is substantial. By age 10 over one-third of all children will have lived in a welfare household; black, non-Hispanic children face a much higher rate of exposure. Simple correlations suggest a strong negative relationship between maternal welfare receipt and children's outcomes. In this paper we implement three alternative strategies (instrumental variables, sibling difference, and child fixed effects models) designed to identify whether this correlation can be attributed to the mother's welfare receipt directly or to other characteristics of mothers who receive welfare, regardless of whether or not those characteristics are observable to the researcher. Based on the results of all three estimation strategies, we find little evidence of any causal link between maternal welfare receipt and children's developmental outcomes.

Exploring the Number Jungle: A Journey into Diophantine Analysis

Abstract: Opening thoughts: Welcome to the jungle A bit of foreshadowing and some rational rationale Building the rationals via Farey sequences Discoveries of Dirichlet and Hurwitz The theory of continued fractions Enforcing the law of best approximates Markoff's spectrum and numbers Badly approximable numbers and quadratics Solving the alleged ""Pell"" equation Liouville's work on numbers algebraic and not Roth's stunning result and its consequences Pythagorean triples through diophantine geometry A quick tour through elliptic curves The geometry of numbers Simultaneous diophantine approximation Using geometry to sum some squares Spinning around irrationally and uniformly A whole new world of $p$-adic numbers A glimpse into $p$-adic analysis A new twist on Newton's method The power of acting locally while thinking globally Selected big picture question commentaries Hints and remarks Further reading Acknowledgments Index

Absolute CH radical concentrations in rich low-pressure methane-oxygen-argon flames via cavity ringdown spectroscopy of the A transition

Abstract: The authors measure absolute methylidyne (CH) radical concentrations in a series of rich 31.0 Torr (4.13 kPa) methane-oxygen-argon flames using cavity ringdown spectroscopy. Probing via the CH A{sup 2}{Delta}-X{sup 2}II transition near 430 nm gives a sensitivity of 3 x 10{sup 9 cm{sup {minus}3}} for experimental conditions, yielding a signal-to-noise ratio greater than 1,000 for the strongest transitions observed. The authors measure profiles of CH mole fraction as a function of height above a flat-flame burner for rich flames with equivalence ratios of 1.0, 1.2, 1.4, and 1.6. These flames are modeled using the following mechanisms: (1) the GRI Mech 2.11, (2) a mechanism by Prada and miller, (3) a modified GRI 2.11 mechanism, which employs a more realistic increased CH + O{sub 2} rate coefficient, and (4) the new GRI Mech 3.0. Generally good agreement between the models and the data is found, with the GRI 3.0 and modified 2.11 mechanisms best reproducing the data. The greatest discrepancies are observed at the richest stoichiometry, where all of the models predict a wider CH profile shifted further from the burner than experimentally observed.

Enzymes of sphingolipid metabolism in plants.

Abstract: Publisher Summary The predominant sphingolipids in plant tissues are glucosylceramides and complex glycophosphosphingolipids, the inositolphosphorylceramides (InsPCers). The latter are demonstrated in only a few plant tissues but comprise a structurally diverse group of molecules, exhibiting variability in the number and arrangement of monosaccharides linked to the inositol head group. Ceramides and free long chain bases are also present at low concentrations in plant tissues. Considerable structural diversity exists among the glucosylceramides from various plant tissues with respect to long chain base and fatty acid composition: these results have been summarized previously. The most abundant long chain bases in plant glucosylceramides (and ceramides) are isomers of 4,8-sphingadienine, 4-hydroxy-8-sphingenine, and 8-sphingenine, α-Hydroxy fatty acids account for >90% of the total fatty acids of glucosylceramide. Saturated C 16 to C 24 acyl chains are most abundant, although monounsaturated hydroxy fatty acids are common in some cereals. 4-Hydroxysphinganine and 4-hydroxysphingenine, together with saturated C 24 hydroxy fatty acid, are prevalent in InsPCers. Sphingolipid metabolism in plants was investigated only recently and focused on demonstrating and characterizing the in vitro activities of the major enzymatic steps. Assay procedures for these reactions, optimized for plant preparations, are discussed in this chapter. Methods of preparing membrane fractions appropriate for these assays are described.

The Acquisition of Japanese Numeral Classifiers: Linkage between Grammatical Forms and Conceptual Categories.

Abstract: This study examines the acquisition of Japanese numeral classifiers in Japanese preschool children, ages 3 to 6, with a primary emphasis on developing comprehension ability Numeral classifiers, widely distributed in languages of East and Southeast Asia and the New World, are a group of morphemes that usually occur adjacent to quantity expressions The selection of numeral classifiers is determined by the inherent semantic properties of the noun whose quantity is being specified, suggesting that developing patterns of comprehension should be linked to underlying patterns of semantic and conceptual development Previous research claims that children acquire certain distributional patterns very early but that the acquisition of the semantic system is a very slow process We argue instead that different techniques and stimulus contrast sets reveal a much greater sensitivity to semantic relations in young children than was previously considered possible Reasons for the apparent slowness in classifier acquisition are also discussed