Prestige drives epistemic inequality in the diffusion of scientific ideas

The spread of ideas in the scientific community is often viewed as a competition, in which good ideas spread further because of greater intrinsic fitness, and publication venue and citation counts correlate with importance and impact. However, relatively little is known about how structural factors influence the spread of ideas, and specifically how where an idea originates might influence how it spreads. Here, we investigate the role of faculty hiring networks, which embody the set of researcher transitions from doctoral to faculty institutions, in shaping the spread of ideas in computer science, and the importance of where in the network an idea originates. We consider comprehensive data on the hiring events of 5032 faculty at all 205 Ph.D.-granting departments of computer science in the U.S. and Canada, and on the timing and titles of 200,476 associated publications. Analyzing five popular research topics, we show empirically that faculty hiring can and does facilitate the spread of ideas in science. Having established such a mechanism, we then analyze its potential consequences using epidemic models to simulate the generic spread of research ideas and quantify the impact of where an idea originates on its longterm diffusion across the network. We find that research from prestigious institutions spreads more quickly and completely than work of similar quality originating from less prestigious institutions. Our analyses establish the theoretical trade-offs between university prestige and the quality of ideas necessary for efficient circulation. Our results establish faculty hiring as an underlying mechanism that drives the persistent epistemic advantage observed for elite institutions, and provide a theoretical lower bound for the impact of structural inequality in shaping the spread of ideas in science.Comment: 10 pages, 8 figures, 1 tabl

Supercurrent flow through an effective double barrier structure

Supercurrent flow is studied in a structure that in the Ginzburg-Landau regime can be described in terms of an effective double barrier potential. In the limit of strongly reflecting barriers, the passage of Cooper pairs through such a structure may be viewed as a realization of resonant tunneling with a rigid wave function. For interbarrier distances smaller than $d_0=\pi\xi(T)$ no current-carrying solutions exist. For distances between $d_0$ and $2d_0$, four solutions exist. The two symmetric solutions obey a current-phase relation of $\sin(\Delta\varphi/2)$, while the two asymmetric solutions satisfy $\Delta\varphi=\pi$ for all allowed values of the current. As the distance exceeds $nd_0$, a new group of four solutions appears, each contaning $(n-1)$ soliton-type oscillations between the barriers. We prove the inexistence of a continuous crossover between the physical solutions of the nonlinear Ginzburg-Landau equation and those of the corresponding linearized Schr\"odinger equation. We also show that under certain conditions a repulsive delta function barrier may quantitatively describe a SNS structure. We are thus able to predict that the critical current of a SNSNS structure vanishes as $\sqrt{T'_c-T}$, where $T'_c$ is lower than the bulk critical temperature.Comment: 20 pages, RevTex, to appear in Phys. Rev. B, 6 figures on request at [email protected]

Mg-induced increase of band gap in Zn1-xMgxO nanorods revealed by x-ray absorption and emission spectroscopy

[[abstract]]X-rayabsorption near-edge structure (XANES) and x-ray emission spectroscopy (XES) measurements were used to investigate the effect of Mgdoping in ZnOnanorods. The intensities of the features in the O K-edge XANES spectra of Zn1−xMgxOnanorods are lower than those of pure ZnOnanorods, suggesting that Mgdoping increases the negative effective charge of O ions. XES and XANES spectra of O 2p states indicate that Mgdoping raises (lowers) the conduction-band-minimum (valence-band-maximum) and increases the band gap. The band gap is found to increase linearly with the Mg content, as revealed by photoluminescence and combined XANES and XES measurements.[[booktype]]紙本[[booktype]]電子版[[countrycodes]]US

Coastal mixing and optics experiment : mooring deployment cruise report R/V Oceanus cruise number 284 31 July-11 August 1996

An array of moorings at four sites at a mid-shelf location in the mid-Atlantic Bight was deployed for a period of 10 months beginning in August 1996 as part of the Coastal Mixing and Optics Experiment (CMO), funded by the Office of Naval Research (ONR). The purpose of this array is to gather information to help identify and understand the vertical mixing processes influencing the evolution of the stratification over the shelf. The observations from this moored array will be used to investigate changes in the stratification in response to atmospheric forcing, surface gravity wave variabilty, surface and bottom boundary layer mixing, current shear, internal waves, and advection. This report describes the primary mooring deployments carried out by the Upper Ocean Processes (UOP) Group on the R/V Oceanus, sailing out of Woods Hole during July, August, and September of 1996.Funding was provided by the Office of Naval Research through Grant No. N00014-95-1-0339

Neuropathologic features in the hippocampus and cerebellum of three older men with fragile X syndrome

<p>Abstract</p> <p>Background</p> <p>Fragile X syndrome (FXS) is the most common inherited form of intellectual disability, and is the most common single-gene disorder known to be associated with autism. Despite recent advances in functional neuroimaging and our understanding of the molecular pathogenesis, only limited neuropathologic information on FXS is available.</p> <p>Methods</p> <p>Neuropathologic examinations were performed on post-mortem brain tissue from three older men (aged 57, 64 and 78 years) who had received a clinical or genetic diagnosis of FXS. In each case, physical and cognitive features were typical of FXS, and one man was also diagnosed with autism. Guided by reports of clinical and neuroimaging abnormalities of the limbic system and cerebellum of individuals with FXS, the current analysis focused on neuropathologic features present in the hippocampus and the cerebellar vermis.</p> <p>Results</p> <p>Histologic and immunologic staining revealed abnormalities in both the hippocampus and cerebellar vermis. Focal thickening of hippocampal CA1 and irregularities in the appearance of the dentate gyrus were identified. All lobules of the cerebellar vermis and the lateral cortex of the posterior lobe of the cerebellum had decreased numbers of Purkinje cells, which were occasionally misplaced, and often lacked proper orientation. There were mild, albeit excessive, undulations of the internal granular cell layer, with patchy foliar white matter axonal and astrocytic abnormalities. Quantitative analysis documented panfoliar atrophy of both the anterior and posterior lobes of the vermis, with preferential atrophy of the posterior lobule (VI to VII) compared with age-matched normal controls.</p> <p>Conclusions</p> <p>Significant morphologic changes in the hippocampus and cerebellum in three adult men with FXS were identified. This pattern of pathologic features supports the idea that primary defects in neuronal migration, neurogenesis and aging may underlie the neuropathology reported in FXS.</p

Whole-system analysis reveals high greenhouse gas emissions from citywide sanitation in Kampala, Uganda

Global estimates of emissions of greenhouse gasses do not take into account the complex service chain in rapidly growing cities in low- and middle-income countries. This paper presents an end-to-end analysis to estimate emissions from all stages of the sanitation-service chain, using Kampala in Uganda as an example. We show that emissions associated with long periods of storage of faecal waste in sealed anaerobic tanks (49%), discharge from tanks and pits direct to open drains (4%), illegal dumping of faecal waste (2%), leakage from sewers (6%), wastewater bypassing treatment (7%) and uncollected methane emissions at treatment plants (31%), are contributing to high levels of greenhouse-gas emissions. Sanitation in Kampala produces 189 kt CO2 e per year, which may represent more than half of the total city-level emissions. Significant further empirical and modelling work is required to update estimates of greenhouse-gas emissions from sanitation systems globally

Hot Streaks in Artistic, Cultural, and Scientific Careers

The hot streak, loosely defined as winning begets more winnings, highlights a specific period during which an individual's performance is substantially higher than her typical performance. While widely debated in sports, gambling, and financial markets over the past several decades, little is known if hot streaks apply to individual careers. Here, building on rich literature on lifecycle of creativity, we collected large-scale career histories of individual artists, movie directors and scientists, tracing the artworks, movies, and scientific publications they produced. We find that, across all three domains, hit works within a career show a high degree of temporal regularity, each career being characterized by bursts of high-impact works occurring in sequence. We demonstrate that these observations can be explained by a simple hot-streak model we developed, allowing us to probe quantitatively the hot streak phenomenon governing individual careers, which we find to be remarkably universal across diverse domains we analyzed: The hot streaks are ubiquitous yet unique across different careers. While the vast majority of individuals have at least one hot streak, hot streaks are most likely to occur only once. The hot streak emerges randomly within an individual's sequence of works, is temporally localized, and is unassociated with any detectable change in productivity. We show that, since works produced during hot streaks garner significantly more impact, the uncovered hot streaks fundamentally drives the collective impact of an individual, ignoring which leads us to systematically over- or under-estimate the future impact of a career. These results not only deepen our quantitative understanding of patterns governing individual ingenuity and success, they may also have implications for decisions and policies involving predicting and nurturing individuals with lasting impact

The Marine light - mixed layer experiment cruise and data report, R/V Endeavor : cruise EN-224, mooring deployment, 27 April-1 May 1991, cruise EN-227, mooring recovery, 5-23 September 1991

The Marine Light - Mixed Layer experiment took place in the sub-Arctic North Atlantic ocean, approximately 275 miles south of Reykjavik, Iceland. The field program included a central surface mooring to document the temporal evolution of physical, biological and optical properties. The surface mooring was deployed at approximately 59°N, 21°W on 29 April 1991 and recovered on 6 September 1991. The Upper Ocean Processes Group of the Woods Hole Oceanographic Institution was responsible for design, preparation, deployment, and recovery of the mooring. The Group's contrbution to the field measurements included four different types of sensors: a meteorological observation package on the surface buoy, a string of 15 temperature sensors along the mooring line, an acoustic Doppler current profiler, and four instruments for measuring mooring tension and accelerations. The observations obtained from the mooring are sufficient to describe the air-sea fluxes and the local physical response to surface forcing. The objective in the analysis phase will be to determine the factors controlling this physical response and to work towards an understanding of the links among physical, biological, and optical processes. This report describes the deployment and recovery of the mooring, the meteorological data, and the subsurface temperature and current data.Funding was provided by the Office of Naval Research under Contract N00014-89-J-1683

A genome-wide view of Caenorhabditis elegans base-substitution mutation processes

Knowledge of mutation processes is central to understanding virtually all evolutionary phenomena and the underlying nature of genetic disorders and cancers. However, the limitations of standard molecular mutation detection methods have historically precluded a genome-wide understanding of mutation rates and spectra in the nuclear genomes of multicellular organisms. We applied two high-throughput DNA sequencing technologies to identify and characterize hundreds of spontaneously arising base-substitution mutations in 10 Caenorhabditis elegans mutation-accumulation (MA)-line nuclear genomes. C. elegans mutation rate estimates were similar to previous calculations based on smaller numbers of mutations. Mutations were distributed uniformly within and among chromosomes and were not associated with recombination rate variation in the MA lines, suggesting that intragenomic variation in genetic hitchhiking and/or background selection are primarily responsible for the chromosomal distribution patterns of polymorphic nucleotides in C. elegans natural populations. A strong mutational bias from G/C to A/T nucleotides was detected in the MA lines, implicating oxidative DNA damage as a major endogenous mutagenic force in C. elegans. The observed mutational bias also suggests that the C. elegans nuclear genome cannot be at equilibrium because of mutation alone. Transversions dominate the spectrum of spontaneous mutations observed here, whereas transitions dominate patterns of allegedly neutral polymorphism in natural populations of C. elegans and many other animal species; this observation challenges the assumption that natural patterns of molecular variation in noncoding regions of the nuclear genome accurately reflect underlying mutation processes

The unequal impact of parenthood in academia

Across academia, men and women tend to publish at unequal rates. Existing explanations include the potentially unequal impact of parenthood on scholarship, but a lack of appropriate data has prevented its clear assessment. Here, we quantify the impact of parenthood on scholarship using an extensive survey of the timing of parenthood events, longitudinal publication data, and perceptions of research expectations among 3064 tenure-track faculty at 450 Ph.D.-granting computer science, history, and business departments across the United States and Canada, along with data on institution-specific parental leave policies. Parenthood explains most of the gender productivity gap by lowering the average short-term productivity of mothers, even as parents tend to be slightly more productive on average than nonparents. However, the size of productivity penalty for mothers appears to have shrunk over time. Women report that paid parental leave and adequate childcare are important factors in their recruitment and retention. These results have broad implications for efforts to improve the inclusiveness of scholarship. &nbsp;</p