Resource Allocations for Ultra-Reliable Low-Latency Communications

Ultra-reliable low-latency communications (URLLC) is a new feature to be considered for the fifth generation (5G) cellular systems. This feature is essential for the support of envisioned mission-critical applications, particularly in the realm of machine-type communications. These applications require that the messages, which are generally short-length packets, to be exchanged between a source and a destination with the high level of reliability and within a short period of time. The characteristics of URLLC do not fit directly in the conventional communication models. For instance, most of the existing communication models are developed considering moderate levels of reliability, neglecting the small effects of the feedback errors. However, even such small errors cannot be ignored for URLLC. This paper proposes a communication model for URLLC considering the reliabilities of both data and control channels. Then, the optimal and sub-optimal resource allocations are derived. We show that the proposed sub-optimal resource allocations have lower computational complexities with a negligible performance degradations compared to that of the optimal solutions. The results reveal that the possibility of performing only one retransmission can significantly reduce the required radio resources needed for data delivery compared to the case of performing a single transmission round.     

Characterization of sulfhydryl oxidase from <Emphasis Type="Italic">Aspergillus tubingensis</Emphasis>

Background

Despite of the presence of sulfhydryl oxidases (SOXs) in the secretomes of industrially relevant organisms and their many potential applications, only few of these enzymes have been biochemically characterized. In addition, basic functions of most of the SOX enzymes reported so far are not fully understood. In particular, the physiological role of secreted fungal SOXs is unclear.

Results

The recently identified SOX from Aspergillus tubingensis (AtSOX) was produced, purified and characterized in the present work. AtSOX had a pH optimum of 6.5, and showed a good pH stability retaining more than 80% of the initial activity in a pH range 4-8.5 within 20 h. More than 70% of the initial activity was retained after incubation at 50 °C for 20 h. AtSOX contains a non-covalently bound flavin cofactor. The enzyme oxidised a sulfhydryl group of glutathione to form a disulfide bond, as verified by nuclear magnetic resonance spectroscopy. AtSOX preferred glutathione as a substrate over cysteine and dithiothreitol. The activity of the enzyme was totally inhibited by 10 mM zinc sulphate. Peptide- and protein-bound sulfhydryl groups in bikunin, gliotoxin, holomycin, insulin B chain, and ribonuclease A, were not oxidised by the enzyme. Based on the analysis of 33 fungal genomes, SOX enzyme encoding genes were found close to nonribosomal peptide synthetases (NRPS) but not with polyketide synthases (PKS). In the phylogenetic tree, constructed from 25 SOX and thioredoxin reductase sequences from IPR000103 InterPro family, AtSOX was evolutionary closely related to other Aspergillus SOXs. Oxidoreductases involved in the maturation of nonribosomal peptides of fungal and bacterial origin, namely GliT, HlmI and DepH, were also evolutionary closely related to AtSOX whereas fungal thioreductases were more distant.

Conclusions

AtSOX (55 kDa) is a fungal secreted flavin-dependent enzyme with good stability to both pH and temperature. A Michaelis-Menten behaviour was observed with reduced glutathione as a substrate. Based on the location of SOX enzyme encoding genes close to NRPSs, SOXs could be involved in the secondary metabolism and act as an accessory enzyme in the production of nonribosomal peptides.

     

Molecular Engineering of Fracture Energy Dissipating Sacrificial Bonds Into Cellulose Nanocrystal Nanocomposites

Even though nanocomposites have provided a plethora of routes to increase stiffness and strength, achieving increased toughness with suppressed catastrophic crack growth has remained more challenging. Inspired by the concepts of mechanically excellent natural nanomaterials, one‐component nanocomposites were fabricated involving reinforcing colloidal nanorod cores with polymeric grafts containing supramolecular binding units. The concept is based on mechanically strong native cellulose nanocrystals (CNC) grafted with glassy polymethacrylate polymers, with side chains that contain 2‐ureido‐4[1H]‐pyrimidone (UPy) pendant groups. The interdigitation of the grafts and the ensuing UPy hydrogen bonds bind the nanocomposite network together. Under stress, UPy groups act as sacrificial bonds: simultaneously providing adhesion between the CNCs while allowing them to first orient and then gradually slide past each other, thus dissipating fracture energy. We propose that this architecture involving supramolecular binding units within side chains of polymer grafts attached to colloidal reinforcements opens generic approaches for tough nanocomposites.     

Handling mobility in future publish-subscribe information-centric networks

Future information-oriented Internet architectures are expected to effectively support mobility. PSIRP, an EU FP7 research project, designed, prototyped, and investigated a clean-slate architecture for the future Internet based on the publish-subscribe paradigm. PURSUIT, another EU FP7 research project, is further developing this architecture, which we refer to as Ψ, the Publish Subscribe Internet (PSI) architecture, extending it in various directions, including a deeper investigation of higher (transport and application) and lower layers (e.g., various link technologies, such as wireless and optical). In this paper we present the basics of the Ψ architecture, including the built-in multicast and caching mechanisms, with particular focus on mobility support. We discuss how the native, clean-slate, Ψ instantiation of the information-centric model can support mobility and also present an overlay variant of Ψ we have developed in order to provide an evolutionary path to adoption. Based on analysis and simulation we demonstrate the advantages of the proposed architecture compared to well established solutions such as Mobile IPv6.     

Statistical models of fracture

Disorder and long-range interactions are two of the key components that make material failure an interesting playfield for the application of statistical mechanics. The cornerstone in this respect has been lattice models of the fracture in which a network of elastic beams, bonds, or electrical fuses with random failure thresholds are subject to an increasing external load. These models describe on a qualitative level the failure processes of real, brittle, or quasi-brittle materials. This has been particularly important in solving the classical engineering problems of material strength: the size dependence of maximum stress and its sample-to-sample statistical fluctuations. At the same time, lattice models pose many new fundamental questions in statistical physics, such as the relation between fracture and phase transitions. Experimental results point out to the existence of an intriguing crackling noise in the acoustic emission and of self-affine fractals in the crack surface morphology. Recent advances in computer power have enabled considerable progress in the understanding of such models. Among these partly still controversial issues, are the scaling and size-effects in material strength and accumulated damage, the statistics of avalanches or bursts of microfailures, and the morphology of the crack surface. Here we present an overview of the results obtained with lattice models for fracture, highlighting the relations with statistical physics theories and more conventional fracture mechanics approaches.

Statistical models of fracture

All authors

Mikko J. Alava, Phani K. V. V. Nukala &; Stefano Zapperi

https://doi.org/10.1080/00018730300741518

Published online:

28 November 2010

Table     

Dispersing Billiards with Moving Scatterers

We propose a model of Sinai billiards with moving scatterers, in which the locations and shapes of the scatterers may change by small amounts between collisions. Our main result is the exponential loss of memory of initial data at uniform rates, and our proof consists of a coupling argument for non-stationary compositions of maps similar to classical billiard maps. This can be seen as a prototypical result on the statistical properties of time-dependent dynamical systems.     

Phosphopeptide enrichment with stable spatial coordination on a titanium dioxide coated glass slide

Recent advances in phosphoproteomics have established powerful tools to analyze phosphorylation events. However, their spatial localization is lost due to sample homogenization procedures prior to the analysis. Imaging mass spectrometry (IMS) has emerged as a method to visualize the spatial distribution of molecules in tissue samples, but its application is still limited to relatively abundant molecules. Due to low phosphorylation stoichiometry, direct detection and imaging of protein phosphorylation by MS has not been achieved yet. Therefore we have developed a novel phosphopeptide enrichment strategy as a potential tool for in situ affinity imaging MS (AIMS). A specific type of titanium dioxide (TiO₂)‐coated glass slides was designed and validated with casein tryptic digests for their ability to selectively retain phosphopeptides while maintaining their spatial coordination. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermal response of a PVCL–HA conjugate

The synthesis and self‐assembling of a thermoresponsive conjugate of hyaluronic acid (HA) and poly(N‐vinylcaprolactam) (PVCL) is reported. Both polymers were end functionalized: HA via reductive amination, thereby introducing an azide endgroup to the chain end, and PVCL via thioetherification to introduce a propargyl group. The two were coupled with a copper assisted “click” reaction into a bioconjugate composed of HA blocks with the molar mass 3,600 g mol^?1 (1618 saccharide units) and PVCL blocks of 3,500 g mol^?1 (～25 repeating units). The cloud point temperature measured by transmittance was 50–51 °C in water. The calorimetrically observed phase transition temperature of PVCL in the conjugate increased by 2 °C to 47.7 °C, whereas the enthalpy of the phase transition was unaffected by the conjugation. HA‐PVCL conjugate self‐assembles in water upon heating into monodisperse, colloidally stable, hollow spherical particles whose size may be tuned with the heating rate of the solution. Slow and fast heating resulted in vesicles with the hydrodynamic radii of 443 or 275 nm, respectively. The heating rate did not, however, affect the cloud point. Salt did not noticeably affect the size of the polymer particles, presumably because of interactions between the HA and PVCL blocks. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 425–436     

Ab initio calculations of optical properties of silver clusters: cross-over from molecular to nanoscale behavior

Electronic and optical properties of silver clusters were calculated using two different ab initio approaches: (1) based on all-electron full-potential linearized-augmented plane-wave method and (2) local basis function pseudopotential approach. Agreement is found between the two methods for small and intermediate sized clusters for which the former method is limited due to its all-electron formulation. The latter, due to non-periodic boundary conditions, is the more natural approach to simulate small clusters. The effect of cluster size is then explored using the local basis function approach. We find that as the cluster size increases, the electronic structure undergoes a transition from molecular behavior to nanoparticle behavior at a cluster size of 140 atoms (diameter ~1.7 nm). Above this cluster size the step-like electronic structure, evident as several features in the imaginary part of the polarizability of all clusters smaller than Ag₁₄₇, gives way to a dominant plasmon peak localized at wavelengths 350 nm ≤ λ ≤ 600 nm. It is, thus, at this length-scale that the conduction electrons’ collective oscillations that are responsible for plasmonic resonances begin to dominate the opto-electronic properties of silver nanoclusters.     

An Almost Sure Ergodic Theorem for Quasistatic Dynamical Systems

We prove an almost sure ergodic theorem for abstract quasistatic dynamical systems, as an attempt of taking steps toward an ergodic theory of such systems. The result at issue is meant to serve as a working counterpart of Birkhoff’s ergodic theorem which fails in the quasistatic setup. It is formulated so that the conditions, which essentially require sufficiently good memory-loss properties, could be verified in a straightforward way in physical applications. We also introduce the concept of a physical family of measures for a quasistatic dynamical system. These objects manifest themselves, for instance, in numerical experiments. We then illustrate the use of the theorem by examples.