34,151 research outputs found

    Evidence of Program Quality and Youth Outcomes in the DYCD Out-of-School Time Initiative: Report on the Initiative's First Three Years

    Get PDF
    Examines New York City's progress in improving out-of-school-time program quality and serving more children and youth, participants' and parents' overall satisfaction with quality and accessibility, and links between programming, quality, and benefits

    Inside the Bondi radius of M87

    Get PDF
    Chandra X-ray observations of the nearby brightest cluster galaxy M87 resolve the hot gas structure across the Bondi accretion radius of the central supermassive black hole, a measurement possible in only a handful of systems but complicated by the bright nucleus and jet emission. By stacking only short frame-time observations to limit pileup, and after subtracting the nuclear PSF, we analysed the X-ray gas properties within the Bondi radius at 0.12-0.22 kpc (1.5-2.8 arcsec), depending on the black hole mass. Within 2 kpc radius, we detect two significant temperature components, which are consistent with constant values of 2 keV and 0.9 keV down to 0.15 kpc radius. No evidence was found for the expected temperature increase within ~0.25 kpc due to the influence of the SMBH. Within the Bondi radius, the density profile is consistent with ρr1\rho\propto r^{-1}. The lack of a temperature increase inside the Bondi radius suggests that the hot gas structure is not dictated by the SMBH's potential and, together with the shallow density profile, shows that the classical Bondi rate may not reflect the accretion rate onto the SMBH. If this density profile extends in towards the SMBH, the mass accretion rate onto the SMBH could be at least two orders of magnitude less than the Bondi rate, which agrees with Faraday rotation measurements for M87. We discuss the evidence for outflow from the hot gas and the cold gas disk and for cold feedback, where gas cooling rapidly from the hot atmosphere could feed the cirumnuclear disk and fuel the SMBH. At 0.2 kpc radius, the cooler X-ray temperature component represents ~20% of the total X-ray gas mass and, by losing angular momentum to the hot gas component, could provide a fuel source of cold clouds within the Bondi radius.Comment: 14 pages, 8 figures, accepted by MNRA

    Lidar measurements of stratospheric aerosols over Menlo Park, California, October 1972 - March 1974

    Get PDF
    During an 18-month period, 30 nighttime observations of stratospheric aerosols were made using a ground based ruby lidar located near the Pacific coast of central California (37.5 deg. N, 122.2 deg. W). Vertical profiles of the lidar scattering ratio and the particulate backscattering coefficient were obtained by reference to a layer of assumed negligible particulate content. An aerosol layer centered near 21 km was clearly evident in all observations, but its magnitude and vertical distribution varied considerably throughout the observation period. A reduction of particulate backscattering in the 23- to 30-km layer during late January 1973 appears to have been associated with the sudden stratospheric warming which occurred at that time

    On modeling pollution-generating technologies

    Get PDF
    Distinguishing between intended ("good") production and unintended or residual ("bad") generation, we introduce the concept of by-production. In by-production technologies, pollution is an output that satises a "costly disposability" assumption and violates standard free disposability with respect to pollution-causing inputs. Our approach therefore differs substantially from standard approaches to modeling pollution-generating technologies. We show how by-production can be modeled using data envelopment analysis (DEA) methods. With an electric power plant database, we illustrate shortcomings under by-production of two popular eciency indexes: the hyperbolic index and the directional distance function. We propose and implement an alternative eciency index with superior properties.pollution-generating technologies, free disposability, weak disposability, data envelopment analysis, environmental and technical eciency measurement

    Transparency and the Marketplace for Student Data

    Get PDF
    Student lists are commercially available for purchase on the basis of ethnicity, affluence, religion, lifestyle, awkwardness, and even a perceived or predicted need for family planning services. This study seeks to provide an understanding of the commercial marketplace for student data and the interaction with privacy law. Over several years, Fordham CLIP reviewed publicly-available sources, made public records requests to educational institutions, and collected marketing materials received by high school students. The study uncovered and documents an overall lack of transparency in the student information commercial marketplace and an absence of law to protect student information.https://ir.lawnet.fordham.edu/clip/1003/thumbnail.jp

    Comment on "Control landscapes are almost always trap free: a geometric assessment"

    Full text link
    We analyze a recent claim that almost all closed, finite dimensional quantum systems have trap-free (i.e., free from local optima) landscapes (B. Russell et.al. J. Phys. A: Math. Theor. 50, 205302 (2017)). We point out several errors in the proof which compromise the authors' conclusion. Interested readers are highly encouraged to take a look at the "rebuttal" (see Ref. [1]) of this comment published by the authors of the criticized work. This "rebuttal" is a showcase of the way the erroneous and misleading statements under discussion will be wrapped up and injected in their future works, such as R. L. Kosut et.al, arXiv:1810.04362 [quant-ph] (2018).Comment: 6 pages, 1 figur

    Crew appliance concepts. Volume 2, appendix B: Shuttle orbiter appliances supporting engineering data

    Get PDF
    Technical data collected for the food management and personal hygiene appliances considered for the shuttle orbiter are presented as well as plotted and tabulated trade study results for each appliance. Food storage, food operation, galley cleanup, waste collection/transfer, body cleansing, and personal grooming were analyzed

    Lidar measurements of the post-fuego stratospheric aerosol

    Get PDF
    Fifteen lidar observations of the stratospheric aerosol were made between February and November 1975. All observations revealed the greatly increased particulate backscattering that followed the eruption of the volcano Fuego in October 1974. Vertical structure consisted initially of multiple layers, which later merged to form a single, broader peak. Essentially all of the increased scattering was confined to altitudes below 20 km. Hence, aerosol layer centroids in 1975 were typically several km below their altitude prior to the eruption. Radiative and thermal consequences of the measured post-Fuego layer were computed using several recently published models. The models predict a temperature increase of several K at the altitude of the layer, caused by the infrared absorption bands of the sulfuric acid particles. The surface temperature decrease predicted by the models is considerably smaller than 1 K, partly because of the small optical thickness of the volcanic layer, and partly because of its short residence time relative to the earth-ocean thermal response time
    corecore