Showing papers by "Williams College published in 1998"

Entanglement of Formation of an Arbitrary State of Two Qubits

Abstract: The entanglement of a pure state of a pair of quantum systems is defined as the entropy of either member of the pair. The entanglement of formation of a mixed state $\ensuremath{\rho}$ is the minimum average entanglement of an ensemble of pure states that represents \ensuremath{\rho}. An earlier paper conjectured an explicit formula for the entanglement of formation of a pair of binary quantum objects (qubits) as a function of their density matrix, and proved the formula for special states. The present paper extends the proof to arbitrary states of this system and shows how to construct entanglement-minimizing decompositions.

Accelerating invasion rate in a highly invaded estuary

Abstract: Biological invasions are a major global environmental and economic problem. Analysis of the San Francisco Bay and Delta ecosystem revealed a large number of exotic species that dominate many habitats in terms of number of species, number of individuals and biomass, and a high and accelerating rate of invasion. These factors suggest that this may be the most invaded estuary in the world. Possible causes include a large number and variety of transport vectors, a depauperate native biota, and extensive natural and anthropogenic disturbance.

The illusion of transparency: Biased assessments of others' ability to read one's emotional states.

Abstract: Three sets of studies provide evidence for an illusion of transparency, or a tendency for people to overestimate the extent to which others can discern their internal states. People often mistakenly believe that their internal states "leak out" more than they really do. The authors attribute this bias to a tendency for people to adjust insufficiently from the "anchor" of their own phenomenological experience when attempting to take another's perspective. Evidence for this illusion is provided by showing that liars overestimate the detectability of their lies (Studies la, lb, and lc) and that people believe their feelings of disgust are more apparent than they actually are (Studies 2a and 2b). A final pair of experiments ( Studies 3a and 3b) explores the implications of the illusion of transparency for people's reluctance to intervene in emergencies. All 3 sets of studies also provide evidence consistent with the proposed anchoring and adjustment interpretation. Fans of Edgar Allan Poe will recall that the key passage in The Tell-Tale Heart is one in which the protagonist does his best to play it cool during a conversation with three police officers. It is a performance made more difficult by the fact that the officers happen to be standing directly above the hidden body of the protagonist's murder victim. As he becomes increasingly anxious that the officers suspect his guilt, he begins to hear what he takes to be his victim's heart beating underneath the floorboards. He becomes convinced that the sound, which in reality is the beating of his own heart, can be heard by the officers as well. Eventually, his emotions get the best of him and he gives himself away:

A 7 Minute Neurocognitive Screening Battery Highly Sensitive to Alzheimer's Disease

Abstract: Objective To determine the validity and reliability of a rapidly administered neurocognitive screening battery consisting of 4 brief tests (Enhanced Cued Recall, Temporal Orientation, Verbal Fluency, and Clock Drawing) to distinguish between patients with probable Alzheimer's disease (AD) and healthy control subjects. Subjects Sixty successive referrals to the Memory Disorders Clinic at Southwestern Vermont Medical Center, Bennington, who were diagnosed as having probable AD and 60 community-dwelling volunteers of comparable age, sex distribution, and education. Design Interrater and test-retest reliability, intergroup comparisons between patients with AD and control subjects on the 4 individual tests, and determination of probability of dementia for patients with AD and control subjects using the entire battery of tests. Setting Outpatient care. Main Outcome Measure Comparison of the probability of dementia on the 7 Minute Screen with the criterion standard of clinical diagnosis established by examination and laboratory studies. Secondary Outcome Measures Test-retest and interrater reliability (correlation coefficients), time for administration. Results Mean time of administration was 7 minutes 42 seconds. Mean scores for patients with AD and control subjects on all 4 individual tests were significantly different (for each,P Conclusions The 7 Minute Screen appears highly sensitive to AD and may be useful in helping to make initial distinctions between patients experiencing cognitive changes related to the normal aging process and those experiencing cognitive deficits related to dementing disorders such as AD. It has reasonable interrater and test-retest reliability, can be administered in a brief period, and requires no clinical judgment and minimal training.

Automatic Activation of Stereotypes: The Role of Self-Image Threat

Abstract: Does self-image threatening feedback make perceivers more likely to activate stereotypes when confronted by members of a minority group? Participants in Study 1 saw an Asian American or European American woman for several minutes, and participants in Studies 2 and 3 were exposed to drawings of an African American or European American male face for fractions of a second. These experiments found no evidence of automatic stereotype activation when perceivers were cognitively busy and when they had not received negative feedback. When perceivers had received negative feedback, however, evidence of stereotype activation emerged even when perceivers were cognitively busy. The theoretical implications of these results for stereotype activation and the relationship of motivation, affect, and cognition are discussed.

Coping and Defense Mechanisms: What's the Difference?

Abstract: Defense mechanisms and coping strategies are discussed as two different types of adaptational processes. They may be clearly differentiated on the basis of the psychological processes involved, but not on the basis of their relation to outcome measures. Criteria that critically differentiate between defense and coping processes include the conscious/unconscious status and the intentional/nonintentional nature of the processes. Criteria based on the dispositional or situational status of the process, and on the conceptualization of the processes as hierarchical, are found to be more a matter of emphasis than of critical difference. A criterion that attempts to differentiate between defense and coping processes on the basis of their relation to psychological or physical health is found to be without support once the bias in self-report outcome measures is recognized.

Prediction intervals for neural networks via nonlinear regression

Abstract: Standard methods for computing prediction intervals in nonlinear regression can be effectively applied to neural networks when the number of training points is large Simulations show, however, that these methods can generate unreliable prediction intervals on smaller datasets when the network is trained to convergence Stopping the training algorithm prior to convergence, to avoid overfitting, reduces the effective number of parameters but can lead to prediction intervals that are too wide We present an alternative approach to estimating prediction intervals using weight decay to fit the network and show via a simulation study that this method may be effective in overcoming some of the shortcomings of the other approaches

Taconian orogeny in the New England Appalachians: Collision between Laurentia and the Shelburne Falls arc

Abstract: Tectonic models of the Ordovician Taconian orogeny in western New England usually invoke a collision between the Laurentian margin and a magmatic arc identified as the Bronson Hill arc. However, in central Massachusetts and southern New Hampshire, rocks in the Bronson Hill arc are 454 to 442 Ma and therefore younger than much of the Taconian deformation and metamorphism in western New England and eastern New York, which began by 470 Ma. U-Pb and single-grain evaporation zircon ages combined with geochemical analyses reveal the presence of an older magmatic arc, the Shelburne Falls arc, that formed west of the Bronson Hill arc at 485 to 470 Ma. The Shelburne Falls arc formed above an east-dipping subduction zone by the Early Ordovician. The Taconian orogeny was the result of the collision between Laurentia and the Shelburne Falls arc beginning ca. 475 to 470 Ma. The younger Bronson Hill arc formed above a west-dipping subduction zone that developed along the eastern edge of the newly accreted terrane during the final stages of and subsequent to the Taconian orogeny. The Taconian orogeny ended when plate convergence between Laurentia and Iapetus was accommodated by the newly developed west-dipping subduction zone instead of by crustal shortening in the Taconian thrust belt. The tectonic history of the New England Appalachians is inconsistent with a Middle Ordovician collision between Laurentia and the proto-Andean margin of Gondwana.

"What, Me Worry?": Arousal, Misattribution, and the Effect of Temporal Distance on Confidence

Abstract: Confidence has been found to vary with temporal proximity to an upcoming task: People's confidence that they will do well tends to diminish as the "moment of truth" draws near. We propose that this phenomenon stems in part from individuals using their pretask arousal as a cue to their level of confidence. Arousal that is part and parcel of "gearing up" to perform a task may be misattributed to diminished confidence. Consistent with this reasoning, participants in two experiments who were encouraged to misattribute their arousal to a neutral source ("subliminal noise") expressed greater confidence in their ability than did participants not able to do so-a result that would not be obtained if arousal was simply a reflection, and not a cause, of diminished confidence.

A Statically Safe Alternative to Virtual Types

Abstract: Parametric types and virtual types have recently been proposed as extensions to Java to support genericity. In this paper we investigate the strengths and weaknesses of each. We suggest a variant of virtual types which has similar expressiveness, but supports safe static type checking. This results in a language in which both parametric types and virtual types are well-integrated, and which is statically type-safe.

Chemoafferent degeneration and carotid body hypoplasia following chronic hyperoxia in newborn rats

Abstract: 1To define the role of environmental oxygen in regulating postnatal maturation of the carotid body afferent pathway, light and electron microscopic methods were used to compare chemoafferent neurone survival and carotid body development in newborn rats reared from birth in normoxia (21 % O2) or chronic hyperoxia (60 % O2). 2Four weeks of chronic hyperoxia resulted in a significant 41 % decrease in the number of unmyelinated axons in the carotid sinus nerve, compared with age-matched normoxic controls. In contrast, the number of myelinated axons was unaffected by hyperoxic exposure. 3Chemoafferent neurones, located in the glossopharyngeal petrosal ganglion, already exhibited degenerative changes following 1 week of hyperoxia from birth, indicating that even a relatively short hyperoxic exposure was sufficient to derange normal chemoafferent development. In contrast, no such changes were observed in the vagal nodose ganglion, demonstrating that the effect of high oxygen levels was specific to sensory neurones in the carotid body afferent pathway. Moreover, petrosal ganglion neurones were sensitive to hyperoxic exposure only during the early postnatal period. 4Chemoafferent degeneration in chronically hyperoxic animals was accompanied by marked hypoplasia of the carotid body. In view of previous findings from our laboratory that chemoafferent neurones require trophic support from the carotid body for survival after birth, we propose that chemoafferent degeneration following chronic hyperoxia is due specifically to the loss of target tissue in the carotid body.

Sedimentology, geochronology and provenance of the Proterozoic Itremo Group, central Madagascar, and implications for pre-Gondwana palaeogeography

Abstract: Proterozoic metasediments of the Itremo Group in central Madagascar probably represent a passive margin sequence predating Gondwana assembly. The quartzites are well-sorted quartz arenites that contain flat lamination, wave ripples, current ripple cross-lamination, and dune cross bedding. The carbonate rocks preserve abundant stromatolites and algal laminates. A continental source is indicated by mudrock major and trace element chemistry. The combination of lithologic association, sediment architecture and mudrock chemistry indicates that the sequence was deposited on a continental shelf or platform. SHRIMP data from detrital zircons indicate that the source area included early Proterozoic and late Archean rocks with ages between 1.85 and 2.69 Ga, and that the depositional age of the Itremo Group must be less than 1855 ± 11 Ma. The sequence has been deformed into a series of large-scale folds separated by ductile shear zones. SHRIMP data indicate both massive lead loss from detrital zircons and new zircon growth in the metasediments at 833 ± 112 Ma, which we interpret as the age of metamorphism of the sequence. Comparison of detrital grain ages with basement ages in East Africa and in India indicates that the source area for the Itremo Group probably lay on the present African mainland.

Recognition of Alzheimer's disease: the 7 Minute Screen.

Abstract: Background and objectives Because Alzheimer's disease (AD) tends to be underdiagnosed, we developed a brief neurocognitive screening battery to identify AD patients. The 7 Minute Screen consists of four individual tests (orientation, memory, clock drawing, verbal fluency). The screen can be rapidly administered and scored and therefore may be appropriate for use in the primary care setting. This study determined the validity and reliability of the 7 Minute Screen in distinguishing patients with AD from healthy controls. Methods The 7 Minute Screen was administered to 60 consecutive referrals to a memory disorders clinic who were subsequently diagnosed with probable AD and to 60 community-dwelling individuals. Analysis of the combined scores on the four individual tests was used to determine the probability of dementia in each subject. We also evaluated test-retest and inter-rater reliability, as well as the time required to administer the battery. Results When compared with the normal subjects, the patients with AD were significantly more impaired on each of the four tests included in the 7 Minute Screen. When the four tests were combined into a logistic regression model, the battery correctly diagnosed 92% of the patients with AD and 96% of the normal subjects. The battery performed equally well when only patients with mild and very mild AD were included. Mean time for administration and scoring was 7 minutes 42 seconds. Conclusions The 7 Minute Screen is a reliable and valid instrument for identifying patients with AD. It appears to be a potentially useful tool for identifying patients with AD in a primary care setting.

Influence of Seed Processing by Frugivorous Birds on Germination Success of Three North American Shrubs

Abstract: Coevolutionary models of the interactions between fruiting plants and avian seed dispersers have been influenced by the assumption that regurgitation and defecation of seeds have diffferent effects on seed coats, and consequently seed germination. We evaluated how the manner of seed processing affects seed germination by feeding fruits of three bird-dispersed shrubs, spicebush (Lindera benzoin), chokecherry (Prunus virginiana), and arrowwood (Viburnum dentatum), to captive cedar waxwings (Bombycilla cedrorum) and thrushes (Turdus migratorius, Hylocichla mustelina, Catharus guttatus and C. minimus). Cedar waxwings defecate all seeds, whereas thrushes regurgitate most seeds. For all three shrub species and all five bird species, there were no differences in germination success between seeds manually cleaned of pulp, and cleaned, bird-passed seeds, regardless of whether seeds were regurgitated or defecated. However, seeds of Lindera and Prunus that were defecated by cedar waxwings and planted with f...

Quantum entanglement as a quantifiable resource

Abstract: Quantum mechanical objects can exhibit correlations with one another that are fundamentally at odds with the paradigm of classical physics; one says that the objects are entangled. In the last few ...

Pattern of defoliation and its effect on photosynthesis and growth of Goldenrod

Abstract: 1. Leaf area was removed from Solidago altissima in either a dispersed pattern (half of every leaf removed) or a concentrated pattern (every other leaf removed) and effects on leaf gas exchange, vegetative growth and flowering were examined relative to undefoliated controls. Gas exchange was measured for leaves remaining after defoliation and for regrowth leaves that developed post-damage (at 7, 16 and 26 days post-defoliation). 2. Area-based photosynthetic rates of leaves remaining after defoliation were not affected by either dispersed or concentrated damage, but damage of both types enhanced area-based photosynthesis of regrowth leaves at 16 days post-defoliation and to a lesser extent at 26 days post-defoliation. 3. Dispersed damage, but not concentrated damage, stimulated mass-based photosynthesis of undamaged leaves remaining after defoliation. Undamaged leaves remaining after defoliation and regrowth leaves on damaged plants had higher specific leaf area (leaf area/leaf mass) than comparable leaves on control plants. Mass-based photosynthesis was more strongly elevated by defoliation than area-based photosynthesis because of this increase in specific leaf area. 4. Plants with dispersed damage recovered more quickly from defoliation; they had higher relative growth rates in the first week post-defoliation than plants with concentrated damage. Both types of defoliation caused similar reductions in flower production. 5. These results add to accumulating evidence that dispersed damage is generally less detrimental to plants than concentrated damage and suggest that physiological changes in leaves may be part of the reason.

Global warming on Triton

Abstract: Triton, Neptune's largest moon, has been predicted to undergo significant seasonal changes that would reveal themselves as changes in its mean frost temperature. But whether this temperature should at the present time be increasing, decreasing or constant depends on a number of parameters (such as the thermal properties of the surface, and frost migration patterns) that are unknown. Here we report observations of a recent stellar occultation by Triton which, when combined with earlier results, show that Triton has undergone a period of global warming since 1989. Our most conservative estimates of the rate of temperature and surface-pressure increase during this period imply that the atmosphere is doubling in bulk every 10 years, significantly faster than predicted by any published frost model for Triton. Our result suggests that permanent polar caps on Triton play a c dominant role in regulating seasonal atmospheric changes. Similar processes should also be active on Pluto.

In vivo analysis of the myosin heavy chain IIB promoter region

Abstract: The myosin heavy chain (MHC) IIB gene is preferentially expressed in fast-twitch muscles of the hindlimb, such as the tibialis anterior (TA). The molecular mechanism(s) for this preferential expres...

Defensiveness and Defense Mechanisms

Abstract: This introduction to the Journal of Personality's special issue on the topic of defense mechanisms raises the question of why defenses have been largely overlooked in personality research. Although defenses were originally discussed in the context of psychopathology, for the past 60 years psychodynamically oriented psychologists have understood that defenses play an important part in normal psychological development. Recently, psychologists outside the field of personality have incorporated the ideas of unconscious mental processes and of defenses into their research programs. In this issue, personality researchers discuss their ideas about defense mechanisms, organized around three topical areas: current conceptualizations of defense, the measurement of defense mechanisms, and the integration of defense mechanisms into personality research. The issue concludes with a commentary on these articles and provides suggestions for future work.

Prenatal Stress Effects Are Partially Ameliorated by Prenatal Administration of the Neurosteroid Allopregnanolone

Abstract: This study examined the effects of exposure to prenatal stress on young and adult rats, and whether the concomitant administration of an anxiolytic neurosteroid, allopregnanolone (3-alpha-hydroxy-5 alpha-pregnan-20-one), could ameliorate some of the behavioral dysfunctions associated with prenatal stress. Pregnant dams were assigned to one of five treatment groups on gestational day 14. These groups were exposed to either 1) restraint for 45 min three times daily; 2) a vehicle injection twice daily; 3) 5 mg/kg allopregnanolone twice daily; 4) restraint with allopregnanolone injections; or 5) nonhandled controls. Assays for plasma allopregnanolone concentrations indicated that exogenous allopregnanolone injections significantly raised circulating levels to a comparable degree in gestational day 20 dams and their fetuses. At 7 days of age, however, subjects prenatally exposed to allopregnanolone either alone or with restraint now had lower circulating levels compared to the other groups, suggesting some negative compensatory change. Behavioral results suggested that the effects of prenatal stress on affective behaviors (ultrasonic vocalizations emitted after a brief maternal separation at 7 days of age, and plus-maze behavior at 70 days of age) could be reversed by coadministration of allopregnanolone. When locomotor activity was assessed at 16 and 60 days of age, no comparable reversal effect was observed. In fact, the allopregnanolone groups had results similar to those of the restraint alone group. Thus, for some neuronal systems, allopregnanolone may exert either a direct teratogenic effect or an indirect effect due to neurosteroid-induced behavioral changes in the pregnant dam.

Transforming Narratives: A Change Event in Constructivist Family Therapy†

Abstract: One important clinical task in family therapy involves transforming the client's construction of the presenting problem from an individual, intrapersonal view to an interpersonal, relational, or systemic one (Sluzki, 1992). To study the transformation process in initial sessions, we sampled 8 families in which the referring parent requested help for a child's problem. The 8 therapists, trained and experienced in Sluzki's (1992) narrative approach, attempted to facilitate a transformation in the parents' initial construction of the problem. In 4 sessions, the transformation was independently judged to be successful by the therapist and observers, while in 4 other sessions the transformation was judged to be unsuccessful. Videotapes of the 8 interviews were analyzed qualitatively, and the parents' verbatim descriptions of the problem were coded using the Cognitive Constructions Coding System (Friedlander, 1995). We compared the successful and the unsuccessful sessions and developed a conceptual model of the successful transformation process that included client performances as well as therapist operations (Greenberg, 1986). While many elements in the model were consistent with Sluzki's (1992) "blue-print" transformation, several new elements were added. Practical implications are described, along with limitations and recommendations for future research.

Preschool antecedents of defense mechanism use in young adults: a longitudinal study.

Abstract: Preschool antecedents of the use of defense mechanisms were longitudinally studied using data from 90 nursery school children who were again evaluated at age 23. Defense use was determined by coding Thematic Apperception Test (H.A. Murray, 1943) stories with a method previously shown to be reliable and valid. The findings indicated continuity between preschool personality and subsequent defense use for male participants but little continuity for female participants. Young men's use of the age-inappropriate defense of denial was predicted by indications at ages 3-4 of low ego resiliency and psychological difficulties in the areas of emotion, intellect, impulse control, and social interactions.

Eyewitness Identification Procedures: The Fifth Rule

Abstract: The National Institute of Justice recently published a report of the first 28 cases in which convicted felons were exonerated by DNA evidence after varying numbers of years in prison. Remarkably, all of these cases contained one or more false eyewitness identifications (Connors, Lundregan, Miller, & McEwan, 1996). To those unfamiliar with the hundreds of published studies on the subject, this disclosure may come as something of a shock. To members of the scientific community, however, it suggests the humbling possibility that our research has underachieved in its impact on the criminal justice system. The time has come for eyewitness researchers and experts to move out of the laboratory and courtroom-and into the police station. The time has come to use all that we know to improve the procedures used to conduct the lineups and photoarrays that too often give rise to mistaken identifications. In this light, the guidelines put forth by Wells, Small, Penrod, Malpass, Fulero, and Brimcombe (1998) represent a most important, insightful, and necessary step. The four recommendations-for double-blind lineup testing, nonbiased instructions, the matching of distractors to the witness's description, and the immediate assessment of confidence-are ideally suited to minimize many potential problems. But what about the potential negative impact of failing to elevate-and hence, relegating-other prescriptions to "rule" status? The rationale for limiting the number of rules is commendable, as is the need to ensure that these rules be relatively independent of one another, feasible, and easy to justify. But there is one recommendation (already being implemented in some precincts) that the authors considered and did not propose that is arguably the most important rule of all: the videotaping of the lineup and witness identification. There are two reasons for this proposed addition. First, we need to acknowledge that the circumstances surrounding lineup identifications are often not accurately preserved or represented in police reports and testimony. As with others who serve as eyewitness experts, I have had more than one occasion to observe that descriptions of the process given by investigators are often inconsistent with statements made by the witnesses themselves or even with videotapes when these are available (in my own experience, for example, I have

Threat to Gender Representation: Identity and Identification

Abstract: To investigate the effect of a threat to gender identity on the use of defense mechanisms, college students were given false feedback regarding their sex-role identity. Male and female students who were given gender-contrary feedback showed a marked increase in the use of the defense of identification, as compared to students who were given gender-consistent feedback. Further, both affect change and the use of identification was a function of the degree of discrepancy between feedback condition and conscious gender identity.

Discrimination in the Small Business Credit Market

Abstract: This paper uses data from the 1993 National Survey of Small Business Finances to determine the extent to which minority-owned small businesses face constraints in the credit market beyond those faced by white-owned small businesses. First, we present qualitative evidence indicating that black- and white-owned firms report similar concerns about the factors that may affect their businesses except that blacks are far more likely to report problems with credit availability. Second, we conduct an econometric analysis of loan denial probabilities by race and find that black-owned small businesses are almost three times more likely to have a loan application denied. Even after controlling for the differences in credit-worthiness and other factors that exist between black- and white-owned firms, blacks are still about twice as likely to be denied credit. A series of specification checks indicates that this gap is unlikely to be largely attributed to omitted variable bias. Third, we conduct a similar analysis regarding interest rates charged to approved loans and find black-owned firms pay higher interest rates as well. Finally, even these results are likely to understate differences in credit access because many potential black-owned firms are not in operation due to the lack of credit and those in business may be too afraid to apply. These results indicate that the racial disparity in credit availability is likely caused by discrimination.

A New Look at Carbon Abundances in Planetary Nebulae. III. DDDM1, IC 3568, IC 4593, NGC 6210, NGC 6720, NGC 6826, and NGC 7009

Abstract: This paper is the third in a series reporting on a study of carbon abundances in a carefully chosen sample of planetary nebulae representing a large range in progenitor mass and metallicity. We make use of the IUE Final Archive database containing consistently reduced spectra to measure line strengths of C III] λ1909 along with numerous other UV lines for the planetary nebulae DDDM1, IC 3568, IC 4593, NGC 6210, NGC 6720, NGC 6826, and NGC 7009. We combine the IUE data with line strengths from optical spectra obtained specifically to match the IUE slit positions as closely as possible, in order to determine values for the abundance ratios He/H, O/H, C/O, N/O, and Ne/O. The ratio of C III] λ1909/C II λ4267 is found to be effective for merging UV and optical spectra when He II λ1640/λ4686 is unavailable. Our abundance determination method includes a five-level program whose results are fine-tuned by corrections derived from detailed photoionization models constrained by the same set of emission lines. All objects appear to have subsolar levels of O/H, and all but one show N/O levels above solar. In addition, the seven planetary nebulae span a broad range in C/O values. We infer that many of our objects are matter-bounded, and thus the standard ionization correction factor for N/O may be inappropriate for these PNs. Finally, we estimate C/O using both collisionally excited and recombination lines associated with C+2 and find the well-established result that abundances from recombination lines usually exceed those from collisionally excited lines by several times.