406 research outputs found
Genome-wide association analysis of secondary imaging phenotypes from the Alzheimer's disease neuroimaging initiative study
The aim of this paper is to systematically evaluate a biased sampling issue associated with genome-wide association analysis (GWAS) of imaging phenotypes for most imaging genetic studies, including the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Specifically, the original sampling scheme of these imaging genetic studies is primarily the retrospective case-control design, whereas most existing statistical analyses of these studies ignore such sampling scheme by directly correlating imaging phenotypes (called the secondary traits) with genotype. Although it has been well documented in genetic epidemiology that ignoring the case-control sampling scheme can produce highly biased estimates, and subsequently lead to misleading results and suspicious associations, such findings are not well documented in imaging genetics. We use extensive simulations and a large-scale imaging genetic data analysis of the Alzheimer’s Disease Neuroimag-ing Initiative (ADNI) data to evaluate the effects of the case-control sampling scheme on GWAS results based on some standard statistical methods, such as linear regression methods, while comparing it with several advanced statistical methods that appropriately adjust for the case-control sampling scheme
SemantIC: Semantic Interference Cancellation Towards 6G Wireless Communications
This letter proposes a novel anti-interference technique, semantic
interference cancellation (SemantIC), for enhancing information quality towards
the sixth-generation (6G) wireless networks. SemantIC only requires the
receiver to concatenate the channel decoder with a semantic auto-encoder. This
constructs a turbo loop which iteratively and alternately eliminates noise in
the signal domain and the semantic domain. From the viewpoint of network
information theory, the neural network of the semantic auto-encoder stores side
information by training, and provides side information in iterative decoding,
as an implementation of the Wyner-Ziv theorem. Simulation results verify the
performance improvement by SemantIC without extra channel resource cost
Evolution of cold streams in hot gaseous halos
In the prevailing model of galaxy formation and evolution, the process of gas
accretion onto central galaxies undergoes a transition from cold-dominated to
hot-dominated modes. This shift occurs when the mass of the parent dark matter
halos exceeds a critical threshold known as . Moreover, cold gas
usually flows onto central galaxies through filamentary structures, currently
referred to as cold streams. However, the evolution of cold streams in halos
with masses around , particularly how they are disrupted, remains
unclear. To address this issue, we conduct a set of idealised hydrodynamic
simulations. Our simulations show that (1) for a gas metallicity
, cold stream with an inflow rate per each can persist and effectively transport cold and cool
gas to the central region ( virial radius) in halos with mass , but is disrupted at a radius around virial radius due to
compression heating for halos with mass .
(2) At , the maximum halo mass that capable of hosting and sustaining
cold streams is between and
for gas metallicity , while
for a higher gas metallicity , this value increases to . (3) The evolution and ultimate fate of cold
streams are determined primarily by the rivalry between radiative cooling and
compression. Stronger heating due to compression in halos more massive than
can surpass cooling and heat the gas in cold streams to the hot
( K) phase.Comment: 26 pages, 18 figures, accepted for publication in MNRA
A Non-Stationary VVLC MIMO Channel Model for Street Corner Scenarios
In recent years, the application potential of visible light communication
(VLC) technology as an alternative and supplement to radio frequency (RF)
technology has attracted people's attention. The study of the underlying VLC
channel is the basis for designing the VLC communication system. In this paper,
a new non-stationary geometric street corner model is proposed for vehicular
VLC (VVLC) multiple-input multiple-output (MIMO) channel. The proposed model
takes into account changes in vehicle speed and direction. The category of
scatterers includes fixed scatterers and mobile scatterers (MS). Based on the
proposed model, we derive the channel impulse response (CIR) and explore the
statistical characteristics of the VVLC channel. The channel gain and root mean
square (RMS) delay spread of the VVLC channel are studied. In addition, the
influence of velocity change on the statistical characteristics of the model is
also investigated. The proposed channel model can guide future
vehicle-to-infrastructure (V2I) and vehicle-to-vehicle (V2V) optical
communication system design
Memory management in genome-wide association studies
Genome-wide association is a powerful tool for the identification of genes that underlie common diseases. Genome-wide association studies generate billions of genotypes and pose significant computational challenges for most users including limited computer memory. We applied a recently developed memory management tool to two analyses of North American Rheumatoid Arthritis Consortium studies and measured the performance in terms of central processing unit and memory usage. We conclude that our memory management approach is simple, efficient, and effective for genome-wide association studies
A genome-wide association analysis of Framingham Heart Study longitudinal data using multivariate adaptive splines
The Framingham Heart Study is a well known longitudinal cohort study. In recent years, the community-based Framingham Heart Study has embarked on genome-wide association studies. In this paper, we present a Framingham Heart Study genome-wide analysis for fasting triglycerides trait in the Genetic Analysis Workshop16 Problem 2 using multivariate adaptive splines for the analysis of longitudinal data (MASAL). With MASAL, we are able to perform analysis of genome-wide data with longitudinal phenotypes and covariates, making it possible to identify genes, gene-gene, and gene-environment (including time) interactions associated with the trait of interest. We conducted a permutation test to assess the associations between MASAL selected markers and triglycerides trait and report significant gene-gene and gene-environment interaction effects on the trait of interest
- …