New decoding scheme for LDPC codes based on simple product code structure

In this paper, a new decoding scheme for low-density parity-check (LDPC) codes using the concept of simple product code structure is proposed based on combining two independently received soft-decision data for the same codeword. LDPC codes act as horizontal codes of the product codes and simple algebraic codes are used as vertical codes to help decoding of the LDPC codes. The decoding capability of the proposed decoding scheme is defined and analyzed using the paritycheck matrices of vertical codes and especially the combined-decodability is derived for the case of single parity-check (SPC) and Hamming codes being used as vertical codes. It is also shown that the proposed decoding scheme achieves much better error-correcting capability in high signal to noise ratio (SNR) region with low additional decoding complexity, compared with a conventional decoding scheme.Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Comportamiento y modelación de geo-materiales sometidos a cargas repetitivas

Muchos sistemas geotécnicos están sometidos a solicitaciones repetitivas de pequeña magnitud que producen acumulación de deformaciones en el largo plazo. Este artículo propone un esquema de solución de problemas de borde mecánicos con elementos finitos utilizando un modelo basado en plasticidad para la carga estática y el primer ciclo de carga, complementado por un modelo híbrido con acumulación empírica para la carga repetitiva. El modelo híbrido considera el umbral de deformación elástico, la densidad terminal y "ratcheting". Los resultados del análisis de una fundación superficial sometida a una carga vertical repetitiva muestran la acumulación gradual de deformaciones y el cambio del estado de esfuerzos durante la carga repetitiva. Finalmente, se reconoce la necesidad de un esquema de modelación del comportamiento a largo plazo de suelos sometidos a ciclos térmicos, de congelamiento-deshielo, de humedecimiento-secado y de cambios químicos

Displacement field in contraction-driven faults

We investigate the distribution of strain and deformation in the host sediment that arises once a contraction-driven shear fault has localized and propagated under a zero-lateral strain condition. Numerical modeling of displacement distributions compares well with those measured using 3D seismic data. The parameters that determine the displacement field for a single normal fault embedded in sediments are fault height, overburden effective stress, stiffness, and residual friction angle (or post-peak strength). Proximity to the free boundary biases the displacement pattern, which becomes asymmetric. Although the measured displacements and numerical predictions are similar, the measured magnitude requires pronounced low stiffness of the sediment as well as low post peak shear strength. This requirement suggests that sediments hosting contraction-driven shear faults most likely have high porosity and high clay fraction and have undergone diagenetic reactions involving significant mineral dissolution. The diagenetic evolution of the sediment and its current composition may explain the global scaling relationship between the measured displacement and fault height for polygonal fault systems

Determinants of gastric cancer screening attendance in Korea: a multi-level analysis

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.Abstract Background We aimed to assess individual and area-level determinants of gastric cancer screening participation. Method Data on gastric cancer screening and individual-level characteristics were obtained from the 2007–2009 Fourth Korea National Health and Nutrition Examination Survey. The area-level variables were collected from the 2005 National Population Census, 2008 Korea Medical Association, and 2010 National Health Insurance Corporation. The data were analyzed using multilevel logistic regression models. Results The estimated participation rate in gastric cancer screening adhered to the Korea National Cancer Screening Program guidelines was 44.0% among 10,658 individuals aged over 40 years who were included in the analysis. Among the individual-level variables, the highest income quartile, a college or higher education level, living with spouse, having a private health insurance, limited general activity, previous history of gastric or duodenal ulcer, and not currently smoking were associated with a higher participation rate in gastric cancer screening. Urbanization showed a significant negative association with gastric cancer screening attendance among the area-level factors (odds ratio (OR) = 0.73; 95% confidence interval (CI) = 0.57-0.93 for the most urbanized quartile vs. least urbanized quartile). Conclusion There are differences in gastric cancer screening attendance according to both individual and regional area characteristics

The catalytic core of DEMETER guides active DNA demethylation in Arabidopsis.

The Arabidopsis DEMETER (DME) DNA glycosylase demethylates the maternal genome in the central cell prior to fertilization and is essential for seed viability. DME preferentially targets small transposons that flank coding genes, influencing their expression and initiating plant gene imprinting. DME also targets intergenic and heterochromatic regions, but how it is recruited to these differing chromatin landscapes is unknown. The C-terminal half of DME consists of 3 conserved regions required for catalysis in vitro. We show that this catalytic core guides active demethylation at endogenous targets, rescuing dme developmental and genomic hypermethylation phenotypes. However, without the N terminus, heterochromatin demethylation is significantly impeded, and abundant CG-methylated genic sequences are ectopically demethylated. Comparative analysis revealed that the conserved DME N-terminal domains are present only in flowering plants, whereas the domain architecture of DME-like proteins in nonvascular plants mainly resembles the catalytic core, suggesting that it might represent the ancestral form of the 5mC DNA glycosylase found in plant lineages. We propose a bipartite model for DME protein action and suggest that the DME N terminus was acquired late during land plant evolution to improve specificity and facilitate demethylation at heterochromatin targets

Direct Observation of Cooperative Protein Structural Dynamics of Homodimeric Hemoglobin from 100 ps to 10 ms with Pump–Probe X-ray Solution Scattering

Proteins serve as molecular machines in performing their biological functions, but the detailed structural transitions are difficult to observe in their native aqueous environments in real time. For example, despite extensive studies, the solution-phase structures of the intermediates along the allosteric pathways for the transitions between the relaxed (R) and tense (T) forms have been elusive. In this work, we employed picosecond X-ray solution scattering and novel structural analysis to track the details of the structural dynamics of wild-type homodimeric hemoglobin (HbI) from the clam Scapharca inaequivalvis and its F97Y mutant over a wide time range from 100 ps to 56.2 ms. From kinetic analysis of the measured time-resolved X-ray solution scattering data, we identified three structurally distinct intermediates (I-1, I-2, and I-3) and their kinetic pathways common for both the wild type and the mutant. The data revealed that the singly liganded and unliganded forms of each intermediate share the same structure, providing direct evidence that the ligand photolysis of only a single subunit induces the same structural change as the complete photolysis of both subunits does. In addition, by applying novel structural analysis to the scattering data, we elucidated the detailed structural changes in the protein, including changes in the heme heme distance, the quaternary rotation angle of subunits, and interfacial water gain/loss. The earliest, R-like I-1 intermediate is generated within 100 ps and transforms to the R-like I-2 intermediate with a time constant of 3.2 +/- 0.2 ns. Subsequently, the late, T-like I-3 intermediate is formed via subunit rotation, a decrease in the heme-heme distance, and substantial gain of interfacial water and exhibits ligation-dependent formation kinetics with time constants of 730 +/- 120 ns for the fully photolyzed form and 5.6 +/- 0.8 mu s for the partially photolyzed form. For the mutant, the overall kinetics are accelerated, and the formation of the T-like I-3 intermediate involves interfacial water loss (instead of water entry) and lacks the contraction of the heme-heme distance, thus underscoring the dramatic effect of the F97Y mutation. The ability to keep track of the detailed movements of the protein in aqueous solution in real time provides new insights into the protein structural dynamics.1149sciescopu

Development of discontinuities in granular media

Discontinuous planes often develop in soils; examples include shear bands, desiccation cracks, polygonal faults, and hydraulic fractures. These discontinuities affect the mechanical behavior (stiffness and strength) and transport properties of sediments (fluid migration and diffusion). Contrary to discontinuities in solid materials, granular materials such as soils are already separated at the particle scale. Therefore, the fundamental understanding of the development of discontinuities in soils must recognize their inherent granular nature and effective-stress dependent behavior. This research focuses on particle-scale mechanisms involved in contraction-driven shear failure due to mineral dissolution, desiccation cracks, and hydraulic fractures. Complementary experimental, analytical and numerical methods are used to study three cases. Contraction-driven polygonal fault formation under the seabed. Shear failure planes are often found in sediments that formed under near horizontal burial conditions. Particle-scale volume contraction due to mineral dissolution causes a decrease in the state of stress from the insitu K0-condition to the active failure Ka stress field. Shear strain localization follows in sediment with post-peak strain softening response. Desiccation cracks in saturated fine soils. The formation of desiccation cracks in soils is often interpreted in terms of tensile strength, which contradicts the cohesionless, effective stress dependent frictional behavior of fine grained soils. Experimental results monitored using high resolution time lapse photography point to a proper effective stress-dependent mechanism centered on the invasion of the air-water interface membrane. Miscible and immiscible fluid-driven fracture formation. Hydraulic fracture in granular materials cause grain separation and the development of conduits for preferential fluid flow leading to fracture formation due to the forced invasion of either immiscible or miscible fluids. Capillary, seepage, and skeletal interparticle forces define particle scale mechanisms at the fracture tip. Numerical simulations confirm that the effective stress remains in compression everywhere throughout the granular medium in the three localization mechanisms.Ph.D.Committee Chair: Santamarina, J. Carlos; Committee Member: Bachus, Robert C.; Committee Member: Burns, Susan E.; Committee Member: Cartwright, Joseph A.; Committee Member: Goldsztein, Guillermo; Committee Member: Mayne, Paul W

Does the regional deprivation impact the spatial accessibility to dental care services?

The aim of the present study was to assess the regional deprivation and individual factors that influence how far a person will travel to access dental care. Using data from the Korea Health Panel (2008 to 2011), we selected a group of 4,256 subjects and geocoded their homes and dental hospitals/clinics. Using the road network analysis, we calculated the distance traveled by the subjects for dental care. We used the generalized estimating equation (GEE) for repeated data analysis and included an interaction term between regional deprivation and individual income to determine the effects of the two factors on the choice of a dental hospital/clinic. When the regional deprivation index was divided into three quarters (high, middle, and low), urban areas had higher"high" and "low" levels of deprivation, and rural areas had relatively higher middle level of deprivation. GEE regression showed that the level of education, regional deprivation level, and income all affected the distance traveled to dental clinics. The regional deprivation level had a higher association than income with the travel distance. At the same income level, subjects who lived in the least deprived areas were more likely to travel longer distances than subjects living in the most deprived areas. Regarding the distribution of dental hospitals/clinics, incentive based dental polices for either dental providers or patients are needed that will assure the delivery of dental care despite spatial inequality