4,753 research outputs found
Flat Dielectric Grating Reflectors with High Focusing Power
Sub-wavelength dielectric gratings (SWG) have emerged recently as a promising
alternative to distributed-Bragg-reflection (DBR) dielectric stacks for
broadband, high-reflectivity filtering applications. A SWG structure composed
of a single dielectric layer with the appropriate patterning can sometimes
perform as well as thirty or forty dielectric DBR layers, while providing new
functionalities such as polarization control and near-field amplification. In
this paper, we introduce a remarkable property of grating mirrors that cannot
be realized by their DBR counterpart: we show that a non-periodic patterning of
the grating surface can give full control over the phase front of reflected
light while maintaining a high reflectivity. This new feature of dielectric
gratings could have a substantial impact on a number of applications that
depend on low-cost, compact optical components, from laser cavities to CD/DVD
read/write heads.Comment: submitted to Nature Photonic
Predicted Causality in Decision Making: The Role of Culture
In the wider sense, decision making is embedded in the problem-solving process and its many stages (Davidson and Sternberg, 2003; Güss et al., 2010). In the narrow sense, decision making is understood as the ability to select one of several alternatives and to act accordingly (Güss 2004). Previous research has often focused on decision making in relatively predictable environments with clear goals (e.g., expected utility theory of von Neumann and Morgenstern, 1944). In recent decades the focus has been on decision making heuristics, i.e., strategies or rules of thumb, applied in uncertain situations (e.g., Tversky and Kahneman, 1974; Simon, 1979; Gigerenzer and Gaissmaier, 2011).
Causality plays an important role in many cognitive processes – and causal cognition is itself influenced by culture (e.g., Norenzayan and Nisbett, 2000; Medin and Atran, 2004; Beller et al., 2009; Bender and Beller, 2011; for a controversial discussion of causal cognition, see Sperber et al., 1995). Causality is especially important during the decision-making process, because the decision maker has to predict what consequences specific decisions bring about before making a decision
Exergy intensity and environmental consequences of the medical face masks curtailing the COVID-19 pandemic: Malign bodyguard?
On January 30, 2020, the World Health Organization identified SARS-CoV-2 as a public health emergency of global concern. Accordingly, the demand for personal protective equipment (PPE), including medical face masks, has sharply risen compared with 2019. The new situation has led to a sharp increase in energy demand and the environmental impacts associated with these product systems. Hence, the pandemic's effects on the environmental consequences of various PPE types, such as medical face masks, should be assessed. In light of that, the current study aimed to identify the environmental hot-spots of medical face mask production and consumption by using life cycle assessment (LCA) and tried to provide solutions to mitigate the adverse impacts. Based on the results obtained, in 2020, medical face masks production using fossil-based plastics causes the loss of 2.03 × 103 disability-adjusted life years (DALYs); 1.63 × 108 PDF*m2*yr damage to ecosystem quality; the climate-damaging release of 2.13 × 109 kg CO2eq; and 5.65 × 1010 MJ damage to resources. Besides, annual medical face mask production results in 5.88 × 104 TJ demand for exergy. On the other hand, if used makes are not appropriately handled, they can lead to 4.99 × 105 Pt/yr additional damage to the environment in 2020 as determined by the EDIP 2003. Replacement of fossil-based plastics with bio-based plastics, at rates ranging from 10 to 100%, could mitigate the product's total yearly environmental damage by 4–43%, respectively. Our study calls attention to the environmental sustainability of PPE used to prevent virus transmission in the current and future pandemics
Classical and Quantum Equations of Motion for a BTZ Black String in AdS Space
We investigate gravitational collapse of a -dimensional BTZ black
string in AdS space in the context of both classical and quantum mechanics.
This is done by first deriving the conserved mass per unit length of the
cylindrically symmetric domain wall, which is taken as the classical
Hamiltonian of the black string. In the quantum mechanical context, we take
primary interest in the behavior of the collapse near the horizon and near the
origin (classical singularity) from the point of view of an infalling observer.
In the absence of radiation, quantum effects near the horizon do not change the
classical conclusions for an infalling observer, meaning that the horizon is
not an obstacle for him/her. The most interesting quantum mechanical effect
comes in when investigating near the origin. First, quantum effects are able to
remove the classical singularity at the origin, since the wave function is
non-singular at the origin. Second, the Schr\"odinger equation describing the
behavior near the origin displays non-local effects, which depend on the energy
density of the domain wall. This is manifest in that derivatives of the
wavefunction at one point are related to the value of the wavefunction at some
other distant point.Comment: 9 pages, 1 figure. Minor Clarification and corrections. Accepted for
Publication in JHE
Scattering of Giant Holes
We study scalar excitations of high spin operators in N=4 super Yang-Mills
theory, which are dual to solitons propagating on a long folded string in AdS_3
x S^1. In the spin chain description of the gauge theory, these are associated
to holes in the magnon distribution in the sl(2,R) sector. We compute the
all-loop hole S-matrix from the asymptotic Bethe ansatz, and expand in leading
orders at weak and strong coupling. The worldsheet S-matrix of solitonic
excitations on the GKP string is calculated using semiclassical quantization.
We find an exact agreement between the gauge theory and string theory results.Comment: 13 pages. v2: minor corrections, references adde
Holographic Entanglement Entropy in P-wave Superconductor Phase Transition
We investigate the behavior of entanglement entropy across the holographic
p-wave superconductor phase transition in an Einstein-Yang-Mills theory with a
negative cosmological constant. The holographic entanglement entropy is
calculated for a strip geometry at AdS boundary. It is found that the
entanglement entropy undergoes a dramatic change as we tune the ratio of the
gravitational constant to the Yang-Mills coupling, and that the entanglement
entropy does behave as the thermal entropy of the background black holes. That
is, the entanglement entropy will show the feature of the second order or first
order phase transition when the ratio is changed. It indicates that the
entanglement entropy is a good probe to investigate the properties of the
holographic phase transition.Comment: 19 pages,15 figures, extended discussion in Sec.5, references adde
Hydrodynamics of a 5D Einstein-dilaton black hole solution and the corresponding BPS state
We apply the potential reconstruction approach to generate a series of
asymptotically AdS (aAdS) black hole solutions, with a self-interacting bulk
scalar field. Based on the method, we reproduce the pure AdS solution as a
consistency check and we also generate a simple analytic 5D black hole
solution. We then study various aspects of this solution, such as temperature,
entropy density and conserved charges. Furthermore, we study the hydrodynamics
of this black hole solution in the framework of fluid/gravity duality, e.g. the
ratio of the shear viscosity to the entropy density. In a degenerate case of
the 5D black hole solution, we find that the c function decreases monotonically
from UV to IR as expected. Finally, we investigate the stability of the
degenerate solution by studying the bosonic functional energy of the gravity
and the Witten-Nester energy . We confirm that the degenerate solution
is a BPS domain wall solution. The corresponding superpotential and the
solution of the killing spinor equation are found explicitly.Comment: V2: 23 pages, no figure, minor changes, typos corrected, new
references and comments added, version accepted by JHE
Influence of COVID-19 on the preventive health behaviours of indigenous peoples of Australia residing in New South Wales: a mixed-method study protocol.
Introduction Chronic conditions impact Indigenous Peoples of Australia at a much higher rate than non-Indigenous Australians. Attendance at the Medicare Benefits Scheme (MBS) supported Indigenous health checks are crucial to improve prevention and management of chronic health conditions. However, in conjunction with lifestyle and environmental factors, attendance rates at primary healthcare services for screening and treatment have fallen in Australia during the COVID-19 pandemic. This study aims to explore the influence of the COVID-19 pandemic on preventive health behaviours of Indigenous Australians and the associated barriers to, and enablers of, engagement with health services to formulate a targeted intervention strategy.
Methods and analysis A concurrent mixed-methods study (comprising quantitative and qualitative data collection methods) will be employed. Descriptive analysis of MBS data about the characteristics of Indigenous Peoples of Australia claiming health assessment services will be performed. Generalised estimating equation regression models will be used to examine the use of health assessment services over time. Qualitative interviews informed by Indigenous research methods will be conducted. Interviews will investigate barriers to, and enablers of, engagement with health services. Thematic approach guided by the principles of indigenist praxis, storytelling and collaborative research will be used to analyse the interview data. The project commenced in July 2020 and will be completed by July 2022.
Ethics and dissemination The project received ethics approval from the Aboriginal Health and Medical Research Council of New South Wales and the University of New England Human Research Ethics Committee. Findings will be disseminated via peer-reviewed journal articles, conferences, government and relevant stakeholder reports, and infographics
High-throughput molecular technologies for unraveling the mystery of soil microbial community: challenges and future prospects
Soil microbial communities play a crucial role in soil fertility, sustainability, and plant health. However, intensive
agriculture with increasing chemical inputs and changing environments have influenced native soil microbial
communities. Approaches have been developed to study the structure, diversity, and activity of soil microbes to
better understand the biology and plant-microbe interactions in soils. Unfortunately, a good understanding of soil
microbial community remains a challenge due to the complexity of community composition, interactions of the
soil environment, and limitations of technologies, especially related to the functionality of some taxa rarely
detected using conventional techniques. Culture-based methods have been shown unable and sometimes are
biased for assessing soil microbial communities. To gain further knowledge, culture-independent methods relying
on direct analysis of nucleic acids, proteins, and lipids are worth exploring. In recent years, metagenomics,
metaproteomics, metatranscriptomics, and proteogenomics have been increasingly used in studying microbial
ecology. In this review, we examined the importance of microbial community to soil quality, the mystery of
rhizosphere and plant-microbe interactions, and the biodiversity and multi-trophic interactions that influence the
soil structure and functionality. The impact of the cropping system and climate change on the soil microbial
community was also explored. Importantly, progresses in molecular biology, especially in the development of
high-throughput biotechnological tools, were extensively assessed for potential uses to decipher the diversity and
dynamics of soil microbial communities, with the highlighted advantages/limitations
- …