Residual stress measurements and analysis by destructive and non-destructive techniques

This investigation is focused on the evaluation of residual stresses resulting from cold deformation and welding in candidate target structural materials such as martensitic Alloys EP-823 and HT-9, and austenitic Type 304L stainless steel (SS). Measurements of residual stresses were performed by both destructive and nondestructive techniques including ring-core (RC), neutron diffraction (ND) and positron annihilation spectroscopy (PAS). The results obtained by the PAS method indicate that the residual stresses in the cold-worked specimens were significantly enhanced with increased level of cold reduction. Residual stress measurements by the RC method on welded specimens consisting of similar materials revealed tensile stresses on both sides. The welded specimens consisting of similar and dissimilar materials showed compressive residual stresses on one side (Alloy EP-823) and tensile stresses on the other side (Type 304L SS). In general, a good agreement in the measured residual stresses was observed based on their comparisons on different configurations of testing specimens using state-of-the art experimental techniques

On the concentration of the capacity for a code division multiple access system

We prove the concentration of the capacity, in the large system limit, for a code division multiple access system over an additive white Gaussian noise channel, with Gaussian signature sequences and {\it binary input} symbols. The probabilistic tools that are used are quite powerful and could have applications in many other similar situations

A Class of Transformations that Polarize Symmetric Binary-Input Memoryless Channels

A generalization of Ar\i kan's polar code construction using transformations of the form $G^{\otimes n}$ where $G$ is an $\ell \times \ell$ matrix is considered. Necessary and sufficient conditions are given for these transformations to ensure channel polarization. It is shown that a large class of such transformations polarize symmetric binary-input memoryless channels.Comment: 7 pages, 1 figur

Exchange of Limits: Why Iterative Decoding Works

We consider communication over binary-input memoryless output-symmetric channels using low-density parity-check codes and message-passing decoding. The asymptotic (in the length) performance of such a combination for a fixed number of iterations is given by density evolution. Letting the number of iterations tend to infinity we get the density evolution threshold, the largest channel parameter so that the bit error probability tends to zero as a function of the iterations. In practice we often work with short codes and perform a large number of iterations. It is therefore interesting to consider what happens if in the standard analysis we exchange the order in which the blocklength and the number of iterations diverge to infinity. In particular, we can ask whether both limits give the same threshold. Although empirical observations strongly suggest that the exchange of limits is valid for all channel parameters, we limit our discussion to channel parameters below the density evolution threshold. Specifically, we show that under some suitable technical conditions the bit error probability vanishes below the density evolution threshold regardless of how the limit is taken.Comment: 16 page

Polar Codes are Optimal for Lossy Source Coding

We consider lossy source compression of a binary symmetric source using polar codes and the low-complexity successive encoding algorithm. It was recently shown by Arikan that polar codes achieve the capacity of arbitrary symmetric binary-input discrete memoryless channels under a successive decoding strategy. We show the equivalent result for lossy source compression, i.e., we show that this combination achieves the rate-distortion bound for a binary symmetric source. We further show the optimality of polar codes for various problems including the binary Wyner-Ziv and the binary Gelfand-Pinsker problemComment: 15 pages, submitted to Transactions on Information Theor

Reconstruction of destruction – in vitro reconstitution methods in autophagy research

International audienceAutophagy is one of the most elaborative membrane remodeling systems in eukaryotic cells. Its major function is to recycle cytoplasmic material by delivering it to lysosomes for degradation. To achieve this, a membrane cisterna is formed that gradually captures cargo such as organelles or protein aggregates. The diversity of cargo requires autophagy to be highly versatile to adapt the shape of the phagophore to its substrate. Upon closure of the phagophore, a double-membrane-surrounded autophagosome is formed that eventually fuses with lysosomes. In response to environmental cues such as cytotoxicity or starvation, bulk cytoplasm can be captured and delivered to lysosomes. Autophagy thus supports cellular survival under adverse conditions. During the past decades, groundbreaking genetic and cell biological studies have identified the core machinery involved in the process. In this Review, we are focusing on in vitro reconstitution approaches to decipher the details and spatiotemporal control of autophagy, and how such studies contributed to our current understanding of the pathways in yeast and mammals. We highlight studies that revealed the function of the autophagy machinery at a molecular level with respect to its capacity to remodel membranes

Fluorescence energy transfer enhancement in aluminum nanoapertures

Zero-mode waveguides (ZMWs) are confining light into attoliter volumes, enabling single molecule fluorescence experiments at physiological micromolar concentrations. Among the fluorescence spectroscopy techniques that can be enhanced by ZMWs, F\"{o}rster resonance energy transfer (FRET) is one of the most widely used in life sciences. Combining zero-mode waveguides with FRET provides new opportunities to investigate biochemical structures or follow interaction dynamics at micromolar concentration with single molecule resolution. However, prior to any quantitative FRET analysis on biological samples, it is crucial to establish first the influence of the ZMW on the FRET process. Here, we quantify the FRET rates and efficiencies between individual donor-acceptor fluorophore pairs diffusing in aluminum zero-mode waveguides. Aluminum ZMWs are important structures thanks to their commercial availability and the large literature describing their use for single molecule fluorescence spectroscopy. We also compare the results between ZMWs milled in gold and aluminum, and find that while gold has a stronger influence on the decay rates, the lower losses of aluminum in the green spectral region provide larger fluorescence brightness enhancement factors. For both aluminum and gold ZMWs, we observe that the FRET rate scales linearly with the isolated donor decay rate and the local density of optical states (LDOS). Detailed information about FRET in ZMWs unlocks their application as new devices for enhanced single molecule FRET at physiological concentrations

Nanophotonic enhancement of the F\"orster resonance energy transfer rate on single DNA molecules

Nanophotonics achieves accurate control over the luminescence properties of a single quantum emitter by tailoring the light-matter interaction at the nanoscale and modifying the local density of optical states (LDOS). This paradigm could also benefit to F\"orster resonance energy transfer (FRET) by enhancing the near-field electromagnetic interaction between two fluorescent emitters. Despite the wide applications of FRET in nanosciences, using nanophotonics to enhance FRET remains a debated and complex challenge. Here, we demonstrate enhanced energy transfer within single donor-acceptor fluorophore pairs confined in gold nanoapertures. Experiments monitoring both the donor and the acceptor emission photodynamics at the single molecule level clearly establish a linear dependence of the FRET rate on the LDOS in nanoapertures. These findings are applied to enhance the FRET rate in nanoapertures up to six times, demonstrating that nanophotonics can be used to intensify the near-field energy transfer and improve the biophotonic applications of FRET

Environmental orientation and ecotourism awareness among pilgrims, adventure tourists, and leisure tourists

For the sustainable development of tourism in destination areas, it is important to have responsible visitors with high pro-environmental orientation and a critical minimum knowledge of ecotourism. Most of the pilgrimage, adventurous, and leisure destinations of India are in ecologically sensitive locations with bountiful environmental resources. Thus, understanding tourists’ environmental orientation is critical for destination management. In this context, the present study investigates the environmental orientation and ecotourism awareness of tourists visiting some of the key environmental hotspots of northern India. A comparative analysis of the environmental orientations of pilgrims, adventurists, and leisure tourists is also carried out. The findings generally reveal that there exist significant differences among these categories in terms of environmental orientation and awareness about ecotourism. Pilgrims and adventurists exhibit superior environmental orientation compared to leisure tourists. Yet, when it comes to the awareness of ecotourism, none of the groups under study show great awareness, except that adventurists stand better compared to the other two groups