Co-cliques and star complements in extremal strongly regular graphs

Suppose that the positive integer μ is the eigenvalue of largest multiplicity in an extremal strongly regular graph G. By interlacing, the independence number of G is at most 4μ2 + 4μ - 2. Star complements are used to show that if this bound is attained then either (a) μ = 1 and G is the Schläfli graph or (b) μ = 2 and G is the McLaughlin graph

“There isn't anybody else like me around here”: the insider-outsider status of LGBT residents in housing with care schemes for older people

The intersections between aging, social minority status and housing needs in later life is a neglected area of sociological exploration, even more so for older people who identify as lesbian, gay, bisexual and trans (LGBT). Recent sociological findings indicate that older LGBT people in housing schemes stress the importance of bonding social capital and look to other people in their social networks who reflect their identities and experiences as sources of support. In this paper, we examine the insider-outsider status occupied by older LGBT residents living in housing schemes that provide some form of care and support, for example extra care and independent living schemes. We present qualitative findings generated from a mixed-methods study of social inclusion practices in housing with care in England and Wales (UK) (2019-22). In this study 15 LGBT residents participated in semi-structured interviews (55–79 years of age) across a total of 31 interviews. Through a queer gerontological lens we examine how older LGBT people are socially situated within mainstream housing schemes in which they experience partial visibility while also encountering exclusionary pressures that locate them as “the other.” This insider-outsider status undermines the premise of housing with care schemes to provide safe, secure spaces to grow old. We discuss three core themes: (1) how LGBT residents navigate their outsider status in scheme life and how the intersection of disability and minority status amplifies this social location; (2) the exclusionary practices exercised by other residents that reinforce boundaries of sexual and gender normalcy; and, (3) the heightened importance of maintaining external social connections among LGBT residents. We conclude by introducing an alternative notion of marginal aging and expanding on the implications for housing providers, reflecting on their responsibilities for promoting and maintaining queer-friendly environments

Kerosene subsidies for household lighting in India: what are the impacts?

Kerosene subsidy reform is a key policy concern in India and other developing countries. As kerosene is widely used for lighting in India, any price change will likely have considerable public welfare impacts on the large fraction of the poor who do not have access to reliable electricity supply for lighting. In this study, we assess historic kerosene use for residential lighting across population groups separated by urban/rural, expenditure, and electricity service levels using data from India. Consumption trends are used to inform a service demand model and evaluate how changes in fuel price, electricity connection, and supply reliability influence environmental, health and economic outcomes. We find that users relying on kerosene for supplemental lighting—in combination ('stacked') with electricity—accounted for 64% of residential kerosene consumed for lighting in 2005. Tested scenarios that addressed service needs of supplemental users had the greatest welfare benefits, especially in the future. Scenarios reducing PM2.5 emissions from kerosene lighting can avert between 50 and 300 thousand disability adjusted life years relative to a baseline scenario in 2030. Lighting kerosene is highly price sensitive, resulting in a drop in demand of 97% in a scenario in which current subsidies are phased out by 2030. Deadweight loss of the subsidy in 2005 is estimated at $200–950 million, with three quarters attributable to supplemental kerosene lighting. Support for cleaner lighting technologies not reliant on fossil fuel subsidies would appear to be 'no regrets' or 'co-benefits' options for India, and could be implemented in parallel with subsidy removal

The Luminosity Function of X-ray Selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift

We present a measure of the hard (2-8 keV) X-ray luminosity function (XLF) of Active Galactic Nuclei up to z~5. At high redshifts, the wide area coverage of the Chandra Multiwavength Project is crucial to detect rare and luminous (Lx > 10^44 erg s^-1) AGN. The inclusion of samples from deeper published surveys, such as the Chandra Deep Fields, allows us to span the lower Lx range of the XLF. Our sample is selected from both the hard (z 6.3x10^-16 erg cm^-2 s^-1) and soft (z > 3; f(0.5-2.0 keV) > 1.0x10^-16 erg cm^-2 s^-1) energy band detections. Within our optical magnitude limits (r',i' < 24), we achieve an adequate level of completeness (>50%) regarding X-ray source identification (i.e., redshift). We find that the luminosity function is similar to that found in previous X-ray surveys up to z~3 with an evolution dependent upon both luminosity and redshift. At z > 3, there is a significant decline in the numbers of AGN with an evolution rate similar to that found by studies of optically-selected QSOs. Based on our XLF, we assess the resolved fraction of the Cosmic X-ray Background, the cumulative mass density of Supermassive Black Holes (SMBHs), and the comparison of the mean accretion rate onto SMBHs and the star formation history of galaxies as a function of redshift. A coevolution scenario up to z~2 is plausible though at higher redshifts the accretion rate onto SMBHs drops more rapidly. Finally, we highlight the need for better statistics of high redshift AGN at z > 3, which is achievable with the upcoming Chandra surveys.Comment: Accepted for publication in ApJ; 25 pages, 18 figure

Deriving Multiple Benefits from Carbon Market-Based Savanna Fire Management: An Australian Example

Carbon markets afford potentially useful opportunities for supporting socially and environmentally sustainable land management programs but, to date, have been little applied in globally significant fire-prone savanna settings. While fire is intrinsic to regulating the composition, structure and dynamics of savanna systems, in north Australian savannas frequent and extensive late dry season wildfires incur significant environmental, production and social impacts. Here we assess the potential of market-based savanna burning greenhouse gas emissions abatement and allied carbon biosequestration projects to deliver compatible environmental and broader socio-economic benefits in a highly biodiverse north Australian setting.Drawing on extensive regional ecological knowledge of fire regime effects on fire-vulnerable taxa and communities, we compare three fire regime metrics (seasonal fire frequency, proportion of long-unburnt vegetation, fire patch-size distribution) over a 15-year period for three national parks with an indigenously (Aboriginal) owned and managed market-based emissions abatement enterprise. Our assessment indicates improved fire management outcomes under the emissions abatement program, and mostly little change or declining outcomes on the parks. We attribute improved outcomes and putative biodiversity benefits under the abatement program to enhanced strategic management made possible by the market-based mitigation arrangement.For these same sites we estimate quanta of carbon credits that could be delivered under realistic enhanced fire management practice, using currently available and developing accredited Australian savanna burning accounting methods. We conclude that, in appropriate situations, market-based savanna burning activities can provide transformative climate change mitigation, ecosystem health, and community benefits in northern Australia, and, despite significant challenges, potentially in other fire-prone savanna settings

The impact of COVID-19 lockdown measures on older residents' social connections and everyday wellbeing within housing schemes that provide care and support in England and Wales

The COVID-19 pandemic and the lockdown measures imposed as a result affected the lives of people in all parts of society across the world. In 2020, during the first UK national lockdown, older adults (aged 70 years and over) were told to ‘shield’ within their homes, as they were regarded as being at higher risk of serious COVID-19 infection compared to other age groups. This paper explores older adults' experiences of COVID-19 lockdown measures whilst living in housing with care schemes for older people. The purpose is to examine the impact of the lockdown measures on scheme life including social connections amongst residents and their general everyday wellbeing during this time. We present qualitative findings based on interviews with 72 residents who took part in longitudinal and cross-sectional interviews across 26 housing with care schemes. Data were analysed using a thematic framework approach to examine specifically their experiences of living in housing with care schemes during the 2020 UK lockdown. The paper highlights that COVID-19 restrictions had a detrimental impact on the social connections and interactions of older residents living in housing with care schemes, as well as on their feelings of autonomy and independence. Despite this, residents adapted and coped with self-isolation restrictions and sought out positive ways to maintain social contact with others inside and outside to the scheme. We further highlight the tensions that providers of housing for older adults faced in promoting residents' autonomy and connectedness whilst also trying to provide a safe living environment and protect residents from risk of COVID-19 infection. Our findings apply not only to a pandemic situation but to the broader understanding of how housing with care for older adults must navigate between autonomy and support

Future Arctic temperature change resulting from a range of aerosol emissions scenarios

The Arctic temperature response to emissions of aerosols—specifically black carbon (BC), organic carbon (OC), and sulfate—depends on both the sector and the region where these emissions originate. Thus, the net Arctic temperature response to global aerosol emissions reductions will depend strongly on the blend of emissions sources being targeted. We use recently published equilibrium Arctic temperature response factors for BC, OC, and sulfate to estimate the range of present‐day and future Arctic temperature changes from seven different aerosol emissions scenarios. Globally, Arctic temperature changes calculated from all of these emissions scenarios indicate that present‐day emissions from the domestic and transportation sectors generate the majority of present‐day Arctic warming from BC. However, in all of these scenarios, this warming is more than offset by cooling resulting from SO2 emissions from the energy sector. Thus, long‐term climate mitigation strategies that are focused on reducing carbon dioxide (CO2) emissions from the energy sector could generate short‐term, aerosol‐induced Arctic warming. A properly phased approach that targets BC‐rich emissions from the transportation sector as well as the domestic sectors in key regions—while simultaneously working toward longer‐term goals of CO2 mitigation—could potentially avoid some amount of short‐term Arctic warming.Key PointsReductions in anthropogenic black carbon emissions alone could slow Arctic warming by mid‐centuryArctic cooling from reduced BC is more than offset by warming from reduced SO2 across all of the RCP mitigation scenariosDomestic and transport emissions from Asia hold the greatest potential for reducing Arctic warming from anthropogenic aerosolsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133610/1/eft2124_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133610/2/eft2124.pd

Hard X-ray emitting Active Galactic Nuclei selected by the Chandra Multi-wavelength Project

We present X-ray and optical analysis of 188 AGN identified from 497 hard X-ray (f (2.0-8.0 keV) > 2.7x10^-15 erg cm^-2 s^-1) sources in 20 Chandra fields (1.5 deg^2) forming part of the Chandra Multi-wavelength Project. These medium depth X-ray observations enable us to detect a representative subset of those sources responsible for the bulk of the 2-8 keV Cosmic X-ray Background. Brighter than our optical spectroscopic limit, we achieve a reasonable degree of completeness (77% of X-ray sources with counter-parts r'< 22.5 have been classified): broad emission line AGN (62%), narrow emission line galaxies (24%), absorption line galaxies (7%), stars (5%) or clusters (2%). We find that most X-ray unabsorbed AGN (NH<10^22 cm^-2) have optical properties characterized by broad emission lines and blue colors, similiar to optically-selected quasars from the Sloan Digital Sky Survey but with a slighly broader color distribution. However, we also find a significant population of redder (g'-i'>1.0) AGN with broad optical emission lines. Most of the X-ray absorbed AGN (10^22<NH<10^24 cm^-2) are associated with narrow emission line galaxies, with red optical colors characteristically dominated by luminous, early type galaxy hosts rather than from dust reddening of an AGN. We also find a number of atypical AGN; for instance, several luminous AGN show both strong X-ray absorption (NH>10^22 cm^-2) and broad emission lines. Overall, we find that 81% of X-ray selected AGN can be easily interpreted in the context of current AGN unification models. Most of the deviations seem to be due to an optical contribution from the host galaxies of the low luminosity AGN.Comment: 26 pages; 13 figures (7 color); accepted for publication in the Astrophysical Journa