Spin liquid phase in a spatially anisotropic frustrated antiferromagnet

We explore the effect of the third nearest-neighbors on the magnetic properties of the Heisenberg model on an anisotropic triangular lattice. We obtain the phase diagram of the model using Schwinger-boson mean-field theory. Competition between N\'eel, spiral and collinear magnetically ordered phases is found as we vary the on the ratios of the nearest, J1, next-nearest, J2, and third-nearest, J_3, neighbor exchange couplings. A spin liquid phase is stabilized between the spiral and collinear ordered states when J2/J1 < 1.8 for rather small J3/J1 < 0.1. The lowest energy two-spinon dispersions relevant to neutron scattering experiments are analyzed and compared to semiclassical magnon dispersions finding significant differences in the spiral and collinear phases between the two approaches. The results are discussed in the context of the anisotropic triangular materials: Cs2CuCl4 and Cs2CuBr4 and layered organic materials, kappa-(BEDT-TTF)2X and Y[Pd(dmit)2]2.Comment: 11 pages, 9 figure

Spin liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

Linear spin wave theory shows that ring exchange induces a quantum disordered region in the phase diagram of the title model. Spin wave spectra show that this is a direct manifestation of competing classical orders. A spin liquid is found in the `Goldilocks zone' of frustration, where the quantum fluctuations are large enough to cause strong competition between different classical orderings but not strong enough to stabilize spiral order. We note that the spin liquid phases of $\kappa$-(BEDT-TTF)${_2}X$ and $Y$[Pd(dmit)$_2$]$_2$ are found in this Goldilocks zone.Comment: 5 pages, 3 figure

Constructive Delivery of Deeds Dependent upon Death of Grantor

Constructive Delivery of Deeds Dependent Upon Death of Granto

Advancing loneliness and social isolation as global health challenges: taking three priority actions

Loneliness and social isolation have been identified as critical global health issues in the aftermath of the coronavirus disease 2019 (COVID-19) crisis. While there is robust scientific evidence demonstrating the impact of loneliness and social isolation on health outcomes and mortality, there are fundamental issues to resolve so that health authorities, decision makers, and practitioners worldwide are informed and aligned with the latest evidence. Three priority actions are posited to achieve a wider and more substantial impact on loneliness and social isolation. They are 1) strengthening the evidence base; 2) adopting a whole-of-systems approach; 3) developing policy support for governments worldwide. These priority actions are essential to reduce the pervasive impact of loneliness and social isolation as social determinants of health

Hyperspectral Cubesat Constellation for Natural Hazard Response (Follow-on)

The authors on this paper are team members of the Earth Observing 1 (E0-1) mission which has flown an imaging spectrometer (hyperspectral) instrument called Hyperion for the past 15+ years. The satellite is able to image any spot on Earth in the nadir looking direction every 16 days and with slewing, of the satellite for up to a 23 degree view angle, any spot on the Earth can be imaged approximately every 2 to 3 days. EO-1 has been used to track many natural hazards such as wildfires, volcanoes and floods. An enhanced capability that has been sought is the ability to image natural hazards in a daily time series for space-based imaging spectrometers. The Hyperion cannot provide this capability on EO-1 with the present polar orbit. However, a constellation of cubesats, each with the same imaging spectrometer, positioned strategically can be used to provide daily coverage or even diurnal coverage, cost-effectively. This paper sought to design a cubesat constellation mission that would accomplish this goal and then to articulate the key tradeoffs

An Ultra-Wideband, Microwave Radar for Measuring Snow Thickness on Sea Ice and Mapping Near-Surface Internal Layers in Polar Firn

Sea ice is generally covered with snow, which can vary in thickness from a few centimeters to >1 m. Snow cover acts as a thermal insulator modulating the heat exchange between the ocean and the atmosphere, and it impacts sea-ice growth rates and overall thickness, a key indicator of climate change in polar regions. Snow depth is required to estimate sea-ice thickness using freeboard measurements made with satellite altimeters. The snow cover also acts as a mechanical load that depresses ice freeboard (snow and ice above sea level). Freeboard depression can result in flooding of the snow/ice interface and the formation of a thick slush layer, particularly in the Antarctic sea-ice cover. The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an ultra-wideband, microwave radar capable of operation on long-endurance aircraft to characterize the thickness of snow over sea ice. The low-power, 100mW signal is swept from 2 to 8GHz allowing the air/snow and snow/ ice interfaces to be mapped with 5 c range resolution in snow; this is an improvement over the original system that worked from 2 to 6.5 GHz. From 2009 to 2012, CReSIS successfully operated the radar on the NASA P-3B and DC-8 aircraft to collect data on snow-covered sea ice in the Arctic and Antarctic for NASA Operation IceBridge. The radar was found capable of snow depth retrievals ranging from 10cm to >1 m. We also demonstrated that this radar can be used to map near-surface internal layers in polar firn with fine range resolution. Here we describe the instrument design, characteristics and performance of the radar

Adjusting Behavioural Surveillance and Assessing Disparities in the Impact of COVID-19 on Gay and Bisexual Men’s HIV-Related Behaviour in Australia

COVID-19 has disrupted sexual behaviour and access to health systems. We adapted regular HIV behavioural surveillance of gay and bisexual men (GBM) in Australia in response to COVID-19, assessed the impact on the profile of the sample, the participants’ HIV-related behaviour, and whether COVID-19 may have accentuated existing disparities in the Australian HIV epidemic. Data collected from five states during July 2017–June 2021 were included (N = 31,460). The emphasis on online recruitment after COVID-19 led to smaller sample sizes, greater geographic reach, and a higher proportion of bisexual-identifying participants. Most participants (88.1%) reported physical distancing and 52.1% had fewer sex partners due to COVID-19. In the COVID-19-affected rounds (July 2020–June 2021), the number of male partners, recent HIV testing and pre-exposure prophylaxis (PrEP) use all fell, and HIV risk among the smaller group of participants who reported casual sex increased. COVID-related changes were generally more pronounced among GBM aged under 25 years, participants from suburbs with fewer gay residents, and bisexual men. These groups should be prioritised when encouraging GBM to reengage with HIV testing services and effective prevention methods, like condoms and PrEP

RIN4 Interacts with Pseudomonas syringae Type III Effector Molecules and Is Required for RPM1-Mediated Resistance in Arabidopsis

In Arabidopsis, RPM1 confers resistance against Pseudomonas syringae expressing either of two sequence unrelated type III effectors, AvrRpm1 or AvrB. An RPM1-interacting protein (RIN4) coimmunoprecipitates from plant cell extracts with AvrB, AvrRpm1, or RPM1. Reduction of RIN4 protein levels inhibits both the hypersensitive response and the restriction of pathogen growth controlled by RPM1. RIN4 reduction causes diminution of RPM1. RIN4 reduction results in heightened resistance to virulent Peronospora parasitica and P. syringae, and ectopic defense gene expression. Thus, RIN4 positively regulates RPM1-mediated resistance yet is, formally, a negative regulator of basal defense responses. AvrRpm1 and AvrB induce RIN4 phosphorylation. This may enhance RIN4 activity as a negative regulator of plant defense, facilitating pathogen growth. RPM1 may "guard" against pathogens that use AvrRpm1 and AvrB to manipulate RIN4 activity