Kovalenko's Full-Rank Limit and Overhead as Lower Bounds for Error-Performances of LDPC and LT Codes over Binary Erasure Channels

We present Kovalenko's full-rank limit as a tight lower bound for decoding error probability of LDPC codes and LT codes over BEC. From the limit, we derive a full-rank overhead as a lower bound for stable overheads for successful maximum-likelihood decoding of the codes.Comment: A short version of this paper was presented at ISITA 2008, Auckland NZ. The first draft was submitted to IEEE Transactions on Information Theory, 2008/0

Subinhibitory concentrations of trimethoprim and sulfamethoxazole prevent biofilm formation by Acinetobacter baumannii through inhibition of Csu pilus expression

ABSTRACT Acinetobacter baumannii is emerging as a multidrug-resistant nosocomial pathogen of increasing threat to human health worldwide. Pili are important bacterial virulence factors, playing a role in attachment to host cells and biofilm formation. The Csu pilus, which is assembled via the chaperone-usher secretion system, has been studied in A. baumannii ATCC 19606. Here we show that, in opposition to previous reports, the common laboratory strain ATCC 17978 produces Csu pili. We found that, although ATCC 17978 was resistant to sulfamethoxazole (Smx) and trimethoprim (Tmp), subinhibitory concentrations of these antibiotics abolished the expression of Csu and consequently produced a dramatic reduction in biofilm formation by ATCC 17978. Smx and Tmp acted synergistically to inhibit the enzymatic systems involved in the bacterial synthesis of tetrahydrofolate (THF), which is required for the synthesis of nucleotides. The effects of these antibiotics were partially relieved by exogenous THF addition, indicating that Smx and Tmp turn off Csu assembly by inducing folate stress. We propose that, for Acinetobacter , nanomolar concentrations of Smx and Tmp represent a “danger signal.” In response to this signal, Csu expression is repressed, allowing biofilm dispersal and escape from potentially inhibitory concentrations of antibiotics. The roles of antibiotics as signaling molecules are being increasingly acknowledged, with clear implications for both the treatment of bacterial diseases and the understanding of complex microbial interactions in the environment. </jats:p

Thermal stress analysis of double-ceramic-layered thermal barrier coatings based on rare earth element

So far, many studies have been conducted to increase the operating temperature of gas turbine engine because it enables to achieve the high efficiency with lower emission. As a part of continuous studies, various thermal barrier coatings (TBCs) have been applied onto hot-components as an efficient thermal insulating system. A typical TBC system consists of four layers: a metallic substrate, bond-coats, top-coats and thermally grown oxide between bond-coats and top-coats. Conventionally, top-coats are made of ceramic material such as 8% mol yttria stabilized zirconia (8YSZ) because of its low conductivity. However, 8YSZ based TBC suffers from considerable damage during the operating above 1200° due to the phase transformation and sintering, resulting in volume change and a decrease of strain tolerance.1 Therefore, several oxide groups having the pyrochlore or fluorite structure are recommended to replace 8YSZ. To date, La2Zr2O7 (LZ), La2Ce2O7 (LC), LaTi2Al9O19 (LTA) and Sr(Zr0.9Yb0.1)O2.95(SZYb) are of high interest.1-3 Besides, double ceramic layer (DCL) is also applied on the bond-coats to improve the durability of TBC. Generally, the first top-coat (TC1) is made of the conventional 8YSZ as stress buffer on the bond-coats. Then, an alternative material is deposited as the second top-coat (TC2). In this study, using finite element (FE) analysis, we investigate thermal stress of the DCL typed TBC based on candidate materials when they have the same thermal insulating capacity above 1200°. As shown in fig. 1, a periodic FE model is constructed by taking both thermo-mechanical behavior and topological characteristics into account. Assuming that the turbine inlet temperature is 1500°, the surface of TC2 is heated by impinging gas of 1300° and the substrate is cooled by the internal cooling air equivalent to 700° for 3 cycles. As a result, the system having the lowest thermal stress is LC, followed by LTA, SZYb, and LZ. For all materials, the maximum stress always occurs during the heating period. Remarkably, the position and the moment where the maximum stress occurs are all different. The maximum stress is observed at the vicinity of the wavy oxide layer or TC2. But its moment is irregular such that it may occur at either the highest temperature or the room temperature. Consequently, it can be assumed that the service life is affected by not only the highest temperature but also the temperature difference during the operating cycle. Although LC is determined as the most suitable system to the given specific operation condition, there would exist the other optimal systems for different operation conditions, which can be further investigated by the proposed FE analysis in this study. Please click Additional Files below to see the full abstract

The Role of Government to Bridge Digital Gap between Urban and Rural Area in Korea

The Ministry of Food, Agriculture, Forestry and Fisheries (MIFAFF) in Korea has made an abundant effort to develop agricultural/rural informatization since the 1990’s. Initially, it focused on the development of three different types of infrastructure to bridge the gap between rural and urban areas: household personal computer (PC) penetration, Internet use, and broadband Internet connection accessibility. The 81% of broadband accessibility in 2002 increased to 100% in rural areas in 2007. In addition, from 1998 to 2002, a total of 241,356 farmers took diverse education programs provided by MIFAFF. As a big effort from MIFAFF, Food and Agro-product e-commerce of Farmers has also increased continuously; as of 2009, its transaction is estimated as 1.89 billion USD. Many projects on u-Farm have been launched for future intelligent farming. However, MIFAFF are now facing new challenges

Understanding public support for carbon capture and storage policy: The roles of social capital, stakeholder perceptions, and perceived risk/ benefit of technology

Bureau of Economic Geolog