End-to-End Algebraic Network Coding for Wireless TCP/IP Networks

The Transmission Control Protocol (TCP) was designed to provide reliable transport services in wired networks. In such networks, packet losses mainly occur due to congestion. Hence, TCP was designed to apply congestion avoidance techniques to cope with packet losses. Nowadays, TCP is also utilized in wireless networks where, besides congestion, numerous other reasons for packet losses exist. This results in reduced throughput and increased transmission round-trip time when the state of the wireless channel is bad. We propose a new network layer, that transparently sits below the transport layer and hides non congestion-imposed packet losses from TCP. The network coding in this new layer is based on the well-known class of Maximum Distance Separable (MDS) codes.Comment: Accepted for the 17th International Conference on Telecommunications 2010 (ICT2010), Doha, Qatar, April 4 - 7, 2010. 6 pages, 7 figure

A level playing field for comparing air and rail travel times

The research project was funded by the International Union of Railways (UIC).Background: Shifting travellers from air to rail can reduce environmental impacts and is an important European Union goal. Online travel planning applications allow travellers to easily compare air and rail transport choices, however, they may not accurately consider time travellers spend at the airport or railway station since these depend on buffer times travellers use to protect against delays. Methods: This research investigated the actual time spent at airports and railway stations to analyse the accuracy of travel planning applications and help improve the quality of travel time estimates. The research used a travel time recording application to determine the time spent by passengers at airports and railway stations. Data was collected for 312 trips. The research was supplemented by an extensive literature review of dwell times and multimodal travel planning applications. Results: The research found that travellers spent an average of 157 minutes at airports and 32 minutes at railway stations. Comparing these results to travel planning application, the information shows that the applications significantly underestimate time spent at airports and slightly underestimate time spent at railway stations. The use of unrealistic airport waiting times in travel planning applications distorts traveller perception in favour of air travel. Conclusion: Therefore, railway operators should support the development of improved travel planning applications that better consider waiting times. Improving these applications would be much more cost effective than infrastructure improvements designed to save a few minutes of travel time

Advanced Raman Spectroscopy of Ultrathin RNiO3 films

The present work aims at investigating the structural properties of ultrathin rare-earth nickelate films by Raman Spectroscopy. Two remarkable cases are studied: LaNiO3 deposited epitaxially on LaAlO3, which shows a metal-to-insulator (MIT) transition but only in the ultrathin film regime, and NdNiO3 deposited epitaxially on NdGaO3 showing an upward shift of its MIT temperature by 130 K but only when deposited along the [111]pc direction of the substrate. The extremely small size of the films and overlap of the film and substrate signatures represent an experimental challenge and require the development of ingenious measurement and analysis strategies. To overcome these limitations, we propose the creation of a multidimensional dataset through depth profile acquisitions, in combination with multivariate analysis tools that were employed to extract the signature of the films. Different analysis strategies were used in both cases to adapt to the specificities of the respective samples. For the LNO films deposited along the [001]pc orientation of LAO, Raman depth profile measurements in combination with a Principal Component Analysis (PCA) allowed us to dissociate the signals from the film and the substrate. The evolution of the LNO peaks does not suggest any phase transition, thus, suggesting that a mechanism unrelated to the MIT of other nickelates is triggering the insulating state. This was further validated by ab initio calculations and TEM imaging. All acquired data point towards the following: as LNO becomes very thin, the surface layer (≈ 2pc u.c.), which is the most rigid part of the structure, imposes its structural and insulating characteristic. In the ultrathin regime this continues to a point where the surface of the film alters the interfacial unit cells of the substrate. For the NNO films deposited along the [111]pc orientation of NGO, depth profile measurements in combination with a Non-negative Matrix Factorisation (NMF) allowed us to dissociate the signals from the film and the substrate. The dissociation was performed at room temperature and the acquired knowledge was then utilised to fit an entire temperature series from 5 to 390 K. Comparing the tendency of the Raman signatures with other rare-earth nickelate allowed to support the proposed position of the film in the phase diagram of nickelates by a structural measurement. More generally, the methodology developed in this work is applicable to other systems and opens new perspectives for application of Raman spectroscopy on ultra-thin films

Exploring the mechanical character of molybdenum grain boundaries via nanoindentation and three-point-bending

The interactions of interfaces with dislocations have been extensively studied in the past. Still, there is a lack of high throughput methods, which can potentially be used for systematic studies to cover a wide range of grain boundary types. Nanoindentation offers the opportunity to combine a high spatial resolution with high effectiveness, thus enabling to obtain comprehensive mechanical data in the vicinity of grain boundaries. The present study on coarse-grained molybdenum will show results of mechanical property mapping near grain boundaries. Here, for the first time also the indenter tip rotation angle with respect to the loading axis as well as the grain orientation are considered. Results will show that neglecting these parameters can bias interpretations of the interface/dislocation interactions, as the localized deformation paths around the indentation are thereby significantly changed. Systematic experiments on commercially pure, recrystallized molybdenum have been performed to investigate the dependence of the hardness increase near grain boundaries with respect to the boundary misorientation angle. As a complementary method, three-point-bending is applied on mm-sized specimens until individual grain boundaries delaminate, which in turn will be identified and cross-checked with findings of the nanoindentation tests. Doping molybdenum with elements like carbon and/or boron is known to suppress intercrystalline failure. For this reason, the presented grain boundary characterization methods will be applied to extract mechanical changes caused by these doping elements

Recombinant Adeno-Associated Virus Serotype 6 (rAAV6) Potently and Preferentially Transduces Rat Astrocytes In vitro and In vivo

Recombinant adeno-associated virus vectors are an increasingly popular tool for gene delivery to the CNS because of their non-pathological nature, low immunogenicity, and ability to stably transduce dividing and non-dividing cells. One of the limitations of rAAVs is their preferential tropism for neuronal cells. Glial cells, specifically astrocytes, appear to be infected at low rates. To overcome this limitation, previous studies utilized rAAVs with astrocyte-specific promoters or assorted rAAV serotypes and pseudotypes with purported selectivity for astrocytes. Yet, the reported glial infection rates are not consistent from study to study. In the present work, we tested seven commercially available recombinant serotypes- rAAV1, 2, and 5 through 9, for their ability to transduce primary rat astrocytes [visualized via viral expression of green fluorescent protein (GFP)]. In cell cultures, rAAV6 consistently demonstrated the highest infection rates, while rAAV2 showed astrocytic transduction in some, but not all, of the tested viral batches. To verify that all rAAV constructs utilized by us were viable and effective, we confirmed high infectivity rates in retinal pigmented epithelial cells (ARPE-19), which are known to be transduced by numerous rAAV serotypes. Based on the in vitro results, we next tested the cell type tropism of rAAV6 and rAAV2 in vivo, which were both injected in the barrel cortex at approximately equal doses. Three weeks later, the brains were sectioned and immunostained for viral GFP and the neuronal marker NeuN or the astrocytic marker GFAP. We found that rAAV6 strongly and preferentially transduced astrocytes (\u3e90% of cells in the virus-infected areas), but not neurons ( approximately 10% infection rate). On the contrary, rAAV2 preferentially infected neurons ( approximately 65%), but not astrocytes ( approximately 20%). Overall, our results suggest that rAAV6 can be used as a tool for manipulating gene expression (either delivery or knockdown) in rat astrocytes in vivo

From microtiter plates to droplets - there and back again

Droplet-based microfluidic screening techniques can benefit from interfacing established microtiter plate-based screening and sample management workflows. Interfacing tools are required both for loading preconfigured microtiter-plate (MTP)-based sample collections into droplets and for dispensing the used droplets samples back into MTPs for subsequent storage or further processing. Here, we present a collection of Digital Microfluidic Pipetting Tips (DMPTs) with integrated facilities for droplet generation and manipulation together with a robotic system for its operation. This combination serves as a bidirectional sampling interface for sample transfer from wells into droplets (w2d) and vice versa droplets into wells (d2w). The DMPT were designed to fit into 96-deep-well MTPs and prepared from glass by means of microsystems technology. The aspirated samples are converted into the channel-confined droplets’ sequences separated by an immiscible carrier medium. To comply with the demands of dose-response assays, up to three additional assay compound solutions can be added to the sample droplets. To enable different procedural assay protocols, four different DMPT variants were made. In this way, droplet series with gradually changing composition can be generated for, e.g., 2D screening purposes. The developed DMPT and their common fluidic connector are described here. To handle the opposite transfer d2w, a robotic transfer system was set up and is described briefly

A network model of interpersonal alignment in dialog

In dyadic communication, both interlocutors adapt to each other linguistically, that is, they align interpersonally. In this article, we develop a framework for modeling interpersonal alignment in terms of the structural similarity of the interlocutors’ dialog lexica. This is done by means of so-called two-layer time-aligned network series, that is, a time-adjusted graph model. The graph model is partitioned into two layers, so that the interlocutors’ lexica are captured as subgraphs of an encompassing dialog graph. Each constituent network of the series is updated utterance-wise. Thus, both the inherent bipartition of dyadic conversations and their gradual development are modeled. The notion of alignment is then operationalized within a quantitative model of structure formation based on the mutual information of the subgraphs that represent the interlocutor’s dialog lexica. By adapting and further developing several models of complex network theory, we show that dialog lexica evolve as a novel class of graphs that have not been considered before in the area of complex (linguistic) networks. Additionally, we show that our framework allows for classifying dialogs according to their alignment status. To the best of our knowledge, this is the first approach to measuring alignment in communication that explores the similarities of graph-like cognitive representations. Keywords: alignment in communication; structural coupling; linguistic networks; graph distance measures; mutual information of graphs; quantitative network analysi

Continuum limit of amorphous elastic bodies: A finite-size study of low frequency harmonic vibrations

The approach of the elastic continuum limit in small amorphous bodies formed by weakly polydisperse Lennard-Jones beads is investigated in a systematic finite-size study. We show that classical continuum elasticity breaks down when the wavelength of the sollicitation is smaller than a characteristic length of approximately 30 molecular sizes. Due to this surprisingly large effect ensembles containing up to N=40,000 particles have been required in two dimensions to yield a convincing match with the classical continuum predictions for the eigenfrequency spectrum of disk-shaped aggregates and periodic bulk systems. The existence of an effective length scale \xi is confirmed by the analysis of the (non-gaussian) noisy part of the low frequency vibrational eigenmodes. Moreover, we relate it to the {\em non-affine} part of the displacement fields under imposed elongation and shear. Similar correlations (vortices) are indeed observed on distances up to \xi~30 particle sizes.Comment: 28 pages, 13 figures, 3 table

Structure, Stresses and Local Dynamics in Glasses

The interrelations between short range structural and elastic aspects in glasses and glass forming liquids pose important and yet unresolved questions. In this paper these relations are analyzed for mono-atomic glasses and stressed liquids with a short range repulsive-attractive pair potentials. Strong variations of the local pressure are found even in a zero temperature glass, whereas the largest values of pressure are the same in both glasses and liquids. The coordination number z(J) and the effective first peak radius depend on the local pressures J's. A linear relation was found between components of site stress tensor and the local elastic constants. A linear relation was also found between the trace of the squares of the local frequencies and the local pressures. Those relations hold for glasses at zero temperature and for liquids. We explain this by a relation between the structure and the potential terms. A structural similarity between liquids and solids is manifested by similar dependencies of the coordination number on the pressures.Comment: 7 pages, 11 figure