484 research outputs found
On Amplify-and-Forward Relaying Over Hyper-Rayleigh Fading Channels
Relayed transmission holds promise for the next generation of wireless communication systems due to the performance gains it can provide over non-cooperative systems. Recently hyper-Rayleigh fading, which represents fading conditions more severe than Rayleigh fading, has received attention in the context of many practical communication scenarios. Though power allocation for Amplify-and-Forward (AF) relaying networks has been studied in the literature, a theoretical analysis of the power allocation problem for hyper-Rayleigh fading channels is a novel contribution of this work. We develop an optimal power allocation (OPA) strategy for a dual-hop AF relaying network in which the relay-destination link experiences hyper-Rayleigh fading. A new closed-form expression for the average signal-to-noise ratio (SNR) at destination is derived and it is shown to provide a new upper-bound on the average SNR at destination, which outperforms a previously proposed upper-bound based on the well-known harmonic-geometric mean inequality. An OPA across the source and relay nodes, subject to a sum-power constraint, is proposed and it is shown to provide measurable performance gains in average SNR and SNR outage at the destination relative to the case of equal power allocation
Error Analysis of Fixed-Gain AF Relaying with MRC Over Nakagami-m Fading Channels
This article investigates the error performance of wireless communication systems that employ binary modulations and Amplify-and-Forward (AF) relaying over flat Nakagami-m faded links with maximum ratio combining (MRC) at destination. Specifically, we derive a simple yet accurate closed-form approximation for the average bit error probability (ABEP) and closed-form expressions for its tight upper and lower bounds. The effect of power imbalance between the relayed links is also studied. Numerical investigations show good agreement between proposed theoretical results and simulations whereas our performance bounds are shown to be tighter than previously proposed bounds for the case of unbalanced relayed links
Radiation reaction and the self-force for a point mass in general relativity
A point particle of mass m moving on a geodesic creates a perturbation h, of
the spacetime metric g, that diverges at the particle. Simple expressions are
given for the singular m/r part of h and its quadrupole distortion caused by
the spacetime. Subtracting these from h leaves a remainder h^R that is C^1. The
self-force on the particle from its own gravitational field corrects the
worldline at O(m) to be a geodesic of g+h^R. For the case that the particle is
a small non-rotating black hole, an approximate solution to the Einstein
equations is given with error of O(m^2) as m approaches 0.Comment: 4 pages, RevTe
Dynamical Gauge Conditions for the Einstein Evolution Equations
The Einstein evolution equations have been written in a number of symmetric
hyperbolic forms when the gauge fields--the densitized lapse and the shift--are
taken to be fixed functions of the coordinates. Extended systems of evolution
equations are constructed here by adding the gauge degrees of freedom to the
set of dynamical fields, thus forming symmetric hyperbolic systems for the
combined evolution of the gravitational and the gauge fields. The associated
characteristic speeds can be made causal (i.e. less than or equal to the speed
of light) by adjusting 14 free parameters in these new systems. And 21
additional free parameters are available, for example to optimize the stability
of numerical evolutions. The gauge evolution equations in these systems are
generalizations of the ``K-driver'' and ``Gamma-driver'' conditions that have
been used with some success in numerical black hole evolutions.Comment: New appendix on constraint evolution adde
Gender-sensitive Risks and Options Assessment for Decision making (ROAD) to support WiF2
The Gender-Sensitive Risks and Options Assessment for Decision Making (ROAD) to Support WiF-2 (ROAD migration project), a partnership coordinated by the International Food Policy Research Institute (IFPRI), Australian National University, American University Beirut, Lincoln University, and University of Dhaka, evaluated the ILO-DFID Partnership Programme on Fair Recruitment and Decent Work for Women Migrant Workers in South Asia and the Middle East (Work in Freedom, Phase 2 project [WiF-2]), which operated from 2018 to 2023. The WiF-2 project specifically aimed âto reduce vulnerability to trafficking and forced labour of women and girls across migration pathways leading to the care sector and textiles, clothing, leather and footwear industries (TCLFI) of South Asia and Arab Statesâ (ToC WiF-2)
Reconciling social norms with personal interests: indigenous styles of identity formation among Pakistani youth
Research on identity formation has been conducted mostly in Western contexts. We extend and complement such research by exploring qualitatively the strategies and styles of identity formation employed by emerging adults in Pakistan. Whereas Western theories of identity formation often provide a negative view of normative orientation as âblind obedienceâ without exploring alternatives, our thematic analysis of semi-structured interviews with 12 Pakistani emerging adults suggests a much more complex interplay between personal interests and normative influences on identity formation. Participants described various ways of reconciling normative expectations (parental, religious, and cultural) with their personal interests, preferences, and explorations, when deciding about their careers, relationships, and values. In Pakistani culture, normative influences seem to play a more positive and flexible role in identity formation than is suggested by previous Western research
Molecular profiling of signet ring cell colorectal cancer provides a strong rationale for genomic targeted and immune checkpoint inhibitor therapies
We would like to thank all patients whose samples were used in this study. We are also thankful to the Northern Ireland Biobank and Grampian Biorepository for providing us with tissue blocks and patient data; and Dr HG Coleman (Queenâs University Belfast) for her advice on statistical analyses. This work has been carried out with financial support from Cancer Research UK (grant: C11512/A18067), Experimental Cancer Medicine Centre Network (grant: C36697/A15590 from Cancer Research UK and the NI Health and Social Care Research and Development Division), the Sean Crummey Memorial Fund and the Tom Simms Memorial Fund. The Northern Ireland Biobank is funded by HSC Research and Development Division of the Public Health Agency in Northern Ireland and Cancer Research UK through the Belfast CRUK Centre and the Northern Ireland Experimental Cancer Medicine Centre; additional support was received from Friends of the Cancer Centre. The Northern Ireland Molecular Pathology Laboratory which is responsible for creating resources for the Northern Ireland Biobank has received funding from Cancer Research UK, Friends of the Cancer Centre and Sean Crummey Foundation.Peer reviewedPublisher PD
Epigenetic silencing of CREB3L1 by DNA methylation is associated with high-grade metastatic breast cancers with poor prognosis and is prevalent in triple negative breast cancers
Methylation within specific CpG regions of the CREB3L1 gene in different breast tumor subtypes. The relative methylation was plotted for each tumor subtype. Methylation in regions 2 and 3 show an inverse correlation with CREB3L1 mRNA expression (found in Fig. 6b), whereas methylation in regions 16, 19 and 20 show a direct correlation with CREB3L1 mRNA expression. For all panels: normal (nâ=â97), luminal (nâ=â357), human epidermal growth factor receptor 2 (HER2) amplified (nâ=â19), triple negative breast cancer (TNBC) (nâ=â113). Statistical differences were analyzed using post-hoc pairwise comparison: *p <0.05; **p <0.01; ***p <0.001. (PDF 97 kb
Corotating and irrotational binary black holes in quasi-circular orbits
A complete formalism for constructing initial data representing black-hole
binaries in quasi-equilibrium is developed. Radiation reaction prohibits, in
general, true equilibrium binary configurations. However, when the timescale
for orbital decay is much longer than the orbital period, a binary can be
considered to be in quasi-equilibrium. If each black hole is assumed to be in
quasi-equilibrium, then a complete set of boundary conditions for all initial
data variables can be developed. These boundary conditions are applied on the
apparent horizon of each black hole, and in fact force a specified surface to
be an apparent horizon. A global assumption of quasi-equilibrium is also used
to fix some of the freely specifiable pieces of the initial data and to
uniquely fix the asymptotic boundary conditions. This formalism should allow
for the construction of completely general quasi-equilibrium black hole binary
initial data.Comment: 13 pages, no figures, revtex4; Content changed slightly to reflect
fact that regularized shift solutions do satisfy the isometry boundary
condition
Covered in stigma? The impact of differing levels of Islamic headâcovering on explicit and implicit biases toward Muslim women
Given the prominence of Muslim veilsâin particular the hijab and fullâface veilâin public discourse concerning the place of Muslims in Western society, we examined their impact on nonâMuslimsâ responses at both explicit and implicit levels. Results revealed that responses were more negative toward any veil compared with no veil, and more negative toward the fullâface veil relative to the hijab: for emotions felt toward veiled women (Study 1), for nonâaffective attitudinal responses (Study 2), and for implicit negative attitudes revealed through response latency measures (Studies 3a and 3b). Finally, we manipulated the perceived reasons for wearing a veil, finding that exposure to positive reasons for wearing a veil led to better predicted and imagined contact (Study 4). Practical and theoretical implications are discussed
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