Atomically thin layers of MoS2 via a two step thermal evaporation-exfoliation method

Two dimensional molybdenum disulfide (MoS(2)) has recently become of interest to semiconductor and optic industries. However, the current methods for its synthesis require harsh environments that are not compatible with standard fabrication processes. We report on a facile synthesis method of layered MoS(2) using a thermal evaporation technique, which requires modest conditions. In this process, a mixture of MoS(2) and molybdenum dioxide (MoO(2)) is produced by evaporating sulfur powder and molybdenum trioxide (MoO(3)) nano-particles simultaneously. Further annealing in a sulfur-rich environment transforms majority of the excess MoO(2) into layered MoS(2). The deposited MoS(2) is then mechanically exfoliated into minimum resolvable atomically thin layers, which are characterized using micro-Raman spectroscopy and atomic force microscopy. Furthermore Raman spectroscopy is employed to determine the effect of electrochemical lithium ion exposure on atomically thin layers of MoS(2).     

Calculation of Achievable Information Rates of Long-Haul Optical Transmission Systems Using Instanton Approach

A method for estimation of achievable information rates of high-speed optical transmission systems is proposed. This method consists of two steps: 1) approximating probability density functions for energy of pulses, which is done by the instanton approach, and 2) estimating achievable information rates by applying a method originally proposed by Arnold and Pfitser. Numerical results for a specific optical transmission system (submarine system at transmission rate 40 Gb/s) are reported     

Contact-crack problem with friction in spruce

This analysis presents of how friction in wood-to-metal interfaces can affect data from wedge-splitting tests on Double Cantilever Beam (DCB) spruce specimens. Cases evaluated were short cracks, and cracks emanating from a long notch. A numerical analysis is performed to clarify the influence of frictional characteristics at the wood-aluminium wedge interface on stress intensity factors. This demonstrates a correlation between fracture toughness (KIc) and contact friction (μ) in fracture mode I for short cracks. However, the effect of friction diminishes, when the crack tip moves away from the contact area. Analysis and conclusions are relevant to other situations where components develop cracks in close proximity to contact regions, for example, in predicting the strength with dowel fasteners.     

Survival of Listeria innocua in rainbow trout protein recovered by isoelectric solubilization and precipitation with acetic and citric acids

During mechanical fish processing, a substantial amount of protein is discarded as by-products. Isoelectric solubilization and precipitation (ISP) is a process that uses extreme pH shifts to solubilize and precipitate protein from by-products to recover previously discarded protein. Typically, strong acids are used for pH reduction, but these acids do not have a pasteurization effect (6 log reduction) on bacterial load; therefore, organic acids were used during ISP processing to test the impact on Listeria innocua concentrations. Headed and gutted rainbow trout (Oncorhynchus mykiss) were inoculated with L. innocua, homogenized, and brought to the target pH with granular citric acid (pH 2.0 and 2.5) or glacial acetic acid (pH 3.0 and 3.5). Proteins were solubilized for 10 min at 4°C, and insoluble components (e.g., skin and insoluble protein) were removed by centrifugation. The remaining solution was pH shifted to the protein isoelectric point (pH 5.5) with sodium hydroxide, and precipitated protein was separated from the water. Microbial cells for each component (proteins, insolubles, and water) were enumerated on modified Oxford agar (MOX) and tryptic soy agar with 6% yeast extract (TSAYE). The sums of the surviving cells from each component were compared with the initial inoculum levels. No significant differences were observed between results obtained from TSAYE and from MOX (P > 0.05). Significant reductions in microbial populations were detected, regardless of pH or acid type (P < 0.05). The greatest reduction was at pH 3.0 with glacial acetic acid, resulting in a mean reduction of 6.41 log CFU/g in the recovered protein and 5.88 log CFU/g in the combined components. These results demonstrate the antimicrobial potential of organic acids in ISP processing.     

The attitude polarization phenomenon: Role of response measure, attitude extremity, and behavioral consequences of reported attitude change.

Four studies examined the generality of attitude polarization (C. G. Lord et al, 1979). Biased assimilation of essays on 2 controversial issues was substantial and correlated with reported attitude change. Polarization was observed for reported attitude change on capital punishment and generally stronger in Ss with extreme than moderate attitudes. Polarization was not indicated in a pre–post measurement design. For affirmative action, reported polarization was not observed. The hypothesis that Ss reporting polarization would subsequently write particularly strong essays was not supported, although those reporting depolarization wrote relatively weak essays. The results suggest the relevance of individual differences in reported attitude change but do not confirm the powerful inferences frequently drawn regarding the pervasive, undesirable consequences of self-reported attitude polarization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A digital tachometer for high-temperature telemetry utilizing thermally uprated commercial electronic components

The high-temperature environment of an oil well requires reliable downhole instrumentation, typically based on simple and robust circuits, low power consumption, and smart measurement algorithms. In this paper, we present an electronic design and measurement methodology for a simple microcontroller-based digital tachometer, optimized for downhole spinner-flowmeter applications and multichannel telemetry. We have developed and experimentally evaluated an effective algorithm for direction-sensitive rotational speed measurement, which combines quadrature pulse decoding with the method of dependent count. The algorithm employs a temperature compensation technique, making it suitable for the high-temperature application of commercial-grade electronic parts. Our results confirm the functionality and reliable operation of the tachometer, targeted at high-temperature short-term oil-well logging applications.     

Combinatorial constructions of low-density parity-check codes for iterative decoding

This paper introduces several new combinatorial constructions of low-density parity-check (LDPC) codes, in contrast to the prevalent practice of using long, random-like codes. The proposed codes are well structured, and unlike random codes can lend themselves to a very low-complexity implementation. Constructions of regular Gallager codes based on cyclic difference families, cycle-invariant difference sets, and affine 1-configurations are introduced. Several constructions of difference families used for code design are presented, as well as bounds on the minimal distance of the codes based on the concept of a generalized Pasch configuration.     

MacNeish-Mann theorem based iteratively decodable codes for optical communication systems

A novel family of low-density parity-check codes is proposed based on MacNeish-Mann theorem for construction of mutually orthogonal Latin squares. Codes from this family have high code rate, girth at least six, large minimum distance, and significantly outperform conventional forward error correction schemes based on Reed-Solomon (RS) and turbo codes.     

Instanton-based techniques for analysis and reduction of error floors of LDPC codes

We describe a family of instanton-based optimization methods developed recently for the analysis of the error floors of low-density parity-check (LDPC) codes. Instantons are the most probable configurations of the channel noise which result in decoding failures. We show that the general idea and the respective optimization technique are applicable broadly to a variety of channels, discrete or continuous, and variety of sub-optimal decoders. Specifically, we consider: iterative belief propagation (BP) decoders, Gallager type decoders, and linear programming (LP) decoders performing over the additive white Gaussian noise channel (AWGNC) and the binary symmetric channel (BSC). The instanton analysis suggests that the underlying topological structures of the most probable instanton of the same code but different channels and decoders are related to each other. Armed with this understanding of the graphical structure of the instanton and its relation to the decoding failures, we suggest a method to construct codes whose Tanner graphs are free of these structures, and thus have less significant error floors.     

LDPC-Coded MIMO Optical Communication Over the Atmospheric Turbulence Channel

In this paper, coded multiple-input-multiple-output (MIMO) communication schemes for data transmission over the optical atmospheric turbulence channels are studied. Two strategies are proposed and compared. The first is based on repetition coding, and the second on space-time (ST) coding. Both approaches employ low-density parity-check (LDPC) codes. The LDPC codes are designed using the concept of pairwise balanced design (PBD), balanced incomplete block design (BIBBD), and block-circulant (array) codes. To improve the spectral efficiency, we employ a bit-interleaved (BI) LDPC-coded modulation based on the pulse amplitude modulation (PAM). A better bit error rate (BER) performance is achieved by the iteration of extrinsic information between a demapper and LDPC decoder. The simulations show that the LDPC-coded MIMO schemes can operate under a strong atmospheric turbulence and at the same time provide excellent coding gains compared with the transmission of uncoded data. To verify the efficiency of the proposed coding schemes, achievable information rates are computed when the turbulence is modeled by a gamma-gamma distribution.