2,949 research outputs found
Fast, Sample-Efficient, Affine-Invariant Private Mean and Covariance Estimation for Subgaussian Distributions
We present a fast, differentially private algorithm for high-dimensional
covariance-aware mean estimation with nearly optimal sample complexity. Only
exponential-time estimators were previously known to achieve this guarantee.
Given samples from a (sub-)Gaussian distribution with unknown mean
and covariance , our -differentially private
estimator produces such that as long as . The
Mahalanobis error metric measures the distance
between and relative to ; it characterizes the error
of the sample mean. Our algorithm runs in time , where is the matrix multiplication exponent.
We adapt an exponential-time approach of Brown, Gaboardi, Smith, Ullman, and
Zakynthinou (2021), giving efficient variants of stable mean and covariance
estimation subroutines that also improve the sample complexity to the nearly
optimal bound above.
Our stable covariance estimator can be turned to private covariance
estimation for unrestricted subgaussian distributions. With
samples, our estimate is accurate in spectral norm. This is the first such
algorithm using samples, answering an open question posed by Alabi
et al. (2022). With samples, our estimate is accurate in
Frobenius norm. This leads to a fast, nearly optimal algorithm for private
learning of unrestricted Gaussian distributions in TV distance.
Duchi, Haque, and Kuditipudi (2023) obtained similar results independently
and concurrently.Comment: 44 pages. New version fixes typos and includes additional exposition
and discussion of related wor
The BTC40 Survey for Quasars at 4.8 < z < 6
The BTC40 Survey for high-redshift quasars is a multicolor search using
images obtained with the Big Throughput Camera (BTC) on the CTIO 4-m telescope
in V, I, and z filters to search for quasars at redshifts of 4.8 < z < 6. The
survey covers 40 sq. deg. in B, V, & I and 36 sq. deg. in z. Limiting
magnitudes (3 sigma) reach to V = 24.6, I = 22.9 and z = 22.9. We used the
(V-I) vs. (I-z) two-color diagram to select high-redshift quasar candidates
from the objects classified as point sources in the imaging data. Follow-up
spectroscopy with the AAT and CTIO 4-m telescopes of candidates having I < 21.5
has yielded two quasars with redshifts of z = 4.6 and z = 4.8 as well as four
emission line galaxies with z = 0.6. Fainter candidates have been identified
down to I = 22 for future spectroscopy on 8-m class telescopes.Comment: 27 pages, 8 figures; Accepted for publication in the Astronomical
Journa
The Effects of Fire Fighting and On-Scene Rehabilitation on Hemostatis
Fire fighting is a dangerous occupation â in part because firefighters are called upon to perform strenuous physical activity in hot, hostile environments. Each year, approximately 100 firefighters lose their lives in the line of duty and tens of thousands are injured. Over the past 15 years, approximately 45% of line of duty deaths have been attributed to heart attacks and another 650-1,000 firefighters suffer non-fatal heart attacks in the line of duty each year. From 1990 to 2004, the total number of fireground injuries has declined, yet during this same period, the number of cases related to the leading cause of injury - overexertion/strain â remained relatively constant.
It is well recognized that fire fighting leads to increased cardiovascular and thermal strain. However, the time course of recovery from fire fighting is not well documented, despite the fact that a large percentage of fire fighting fatalities occur after fire fighting activity. Furthermore, on scene rehabilitation (OSR) has been broadly recommended to mitigate the cardiovascular and thermal strain associated with performing strenuous
fire fighting activity, yet the efficacy of different rehabilitation interventions has not been
documented.
Twenty-five firefighters were recruited to participate in a âwithin-subjects, repeated measuresâ study designed to describe the acute effects of fire fighting on a broad array of physiological and psychological measures and several key cardiovascular
variables. This study provided the first detailed documentation of the time course of recovery during 2œ hours post-fire fighting. Additionally, we compared two OSR strategies (standard and enhanced) to determine their effectiveness.published or submitted for publicationnot peer reviewe
Grazing Behaviour of Dorper Sheep and Farmed Goats and Their Implications for Natural Resource Management in Western NSW
The introduction of exotic herbivores into the semi-arid and arid zones of Australia resulted in dramatic change in the native vegetation (e.g. Noble and Tongway 1986; Friedel et al. 1990). Overgrazing and trampling reduced ground cover and changed species composition from dominance by perennial grasses and shrubs to dominance by annual species over extensive areas (e.g. Gunn 1986), or assisted the encroachment of woody species (Wilcox and Cunningham 1994).
It is particularly in this context that the recent introduction of new sheep breeds, reputedly hardier than traditional Merinos, and the increasing trend to farming or re-domestication of feral goats, poses serious questions for the ecological sustainability of the region. This ongoing project aims to combine information from laboratory experiments, field studies and producer experience to develop practical management strategies that are supportive of regional and national ground cover targets aimed at reducing wind erosion and maintaining biodiversity values. We report the preliminary results and recommend management strategies
âTeam GBâ and London 2012: The Paradox of National and Global Identities
This article explores the problems associated with ânational identityâ in the UK and examines the tensions arising between the international and local dimensions of the games through examples of domestic (UK) and international (Brazil, Chicago) media coverage of the key debates relating to Londonâs period of preparation. The chapter proposes a conception of London 2012 as exemplar of an event poised to generate insights and experiences connected to a new politics of âcosmopolitanâ identity; insights central to grasping the cultural politics of contemporary urban development-and the paradoxes of national identity in current discourses of Olympism. Properly speaking, cosmopolitanism suits those people who have no country, while internationalism should be the state of mind of those who love their country above all, who seek to draw to it the friendship of foreigners by professing for the countries of those foreigners an intelligent and enlightened sympathy. © 2010 Taylor & Francis
Secondary cities as catalysts for nutritious diets in low- and middle-income countries
The world is facing a malnutrition crisis in the midst of rising rates of urbanization; more than half of the world's population lives in urban areas, a number that is expected to reach two-thirds by 2050, consuming 80% of the world's food. Instead of the development of existing cities into 'mega-cities, ' urbanization is creating a patchwork of smaller urban areas. In 2018, close to half of the world's urban residents lived in settlements or towns with less than 500, 000 inhabitants. These settlements are classified as secondary cities and are, in terms of population, the fastest growing urban areas. Poor diets among city inhabitants are the consequence of a combination of forces. These include changes in types of occupation, particularly for women; food-environment factors; shifts in norms and attitudes regarding food; globalization of food supply chains; lack of infrastructure; post-harvest food loss and waste, etc. Secondary cities offer entry points for food system transformation. Secondary cities are characterized by strong urban-rural linkages and the opportunity for localized food production and consumption. These cities could also play a key role in enhancing resilience to food security shocks. This chapter discusses the challenge of the growing triple burden of malnutrition in urban contexts and argues for the important role of secondary cities in transforming urban food systems. Through three case studies of secondary cities in LMICs, these cities are shown as emerging players in nutrition-centered food system interventions. © The Author(s) 2023
Ring size effect on the solid state assembly of propargyl substituted hexa- and octacyclic peptoids
The investigation of the solid state assembly of propargyl substituted hexa- and octacyclic peptoids highlights the effect of ring size in determining the packing arrangement of the macrocycles. A layered arrangement is obtained in the case of the hexacyclic peptoid 1 and a tubular arrangement in the case of the octacyclic peptoid 2. Guest molecules either intercalate between the layers as in 1 or are located within the peptoid nanotube as in 2
Dynamic gill and mucus microbiomes during a gill disease episode in farmed Atlantic salmon
Amoebic gill disease (AGD) and complex gill disease (CGD) are recurrent gill disorders in Atlantic salmon, resulting in significant aquaculture losses. The role of gill microbiomes in gill disease development is unclear. We undertook a longitudinal study to characterise the gill tissue and gill mucus microbiomes of farmed Atlantic salmon before, and during, a gill disease episode. Using a newly optimised DNA extraction protocol, we sequenced rRNA genes from microbiomes of gill samples taken from 105 individual salmon on a farm, over a summer season. The AGD aetiological agent, Neoparamoeba perurans, was PCR-quantified targeting 18S rRNA genes. Similar analyses were carried out on mucus samples. Mucus scrapings were suitable, non-lethal substitutes for characterisation of the gill prokaryotic community in this study. Gill tissue and gill mucus microbiomes changed during the campaign, correlating with N. perurans concentrations. Time explained 35% of the gill tissue and gill mucus microbiome variance, while N. perurans concentrations explained 5%. Genera including Dyadobacter, Shewanella and Pedobacter were maximally abundant in gill and mucus samples at the timepoint prior to the the detection of gill disorder signs, at T3. Shewanella was significantly more abundant before than during the gill disease episode, and we suggest this genus could be considered in future studies addressing relationships between gill disease and the gill microbiome
Madness decolonized?: Madness as transnational identity in Gail Hornsteinâs Agnesâs Jacket
The US psychologist Gail Hornsteinâs monograph Agnesâs Jacket: A Psychologistâs Search for the Meanings of Madness (2009) is an important intervention in the identity politics of the mad movement. Hornstein offers a resignified vision of mad identity that embroiders the central trope of an âanti-colonialâ struggle to reclaim the experiential world âcolonizedâ by psychiatry. A series of literal and figurative appeals make recourse to the inner world and (corresponding) cultural world of the mad, as well as to the ethno-symbolic cultural materials of dormant nationhood. This rhetoric is augmented by a model in which the mad comprise a diaspora without an origin, coalescing into a single transnational community. The mad are also depicted as persons displaced from their metaphorical homeland, the âinnerâ world âcolonizedâ by the psychiatric regime. There are a number of difficulties with Hornsteinâs rhetoric, however. Her âethnicity-and-rightsâ response to the oppression of the mad is symptomatic of Western parochialism, while her proposed transmutation of putative psychopathology from limit upon identity to parameter of successful identity is open to contestation. Moreover, unless one accepts Hornsteinâs porous vision of mad identity, her self-ascribed insider status in relation to the mad community may present a problematic âre-colonizationâ of mad experience
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