Reflections on an Experiment, Evaluating the Impact of Spatialisation on Exploration

This paper reports on an experiment designed to evaluate whether visualising a digital library (using a spatialisation technique) can influence exploratory search behaviour. In the experiment we asked participants to complete a set of novel tasks using one of two interfaces - a visualisation interface, ExploViz, and its search-based equivalent, LibSearch. A set of measures were used to capture sensemaking and exploratory behaviour and to analyse cognitive load. As results were non-significant, we reflect upon the design of the experiment, consider possible issues and suggest how these could be addressed in future iterations

Interest Rate Reforms and Economic Growth in SADC Countries: The Savings and Investment Channel

The 2008/2009 global financial crisis has re-ignited the debate around financial reforms with contrasting views with regards to the impact of financial reforms on economic growth. This study examines the impact of interest rate reforms on economic growth through savings and investments in SADC countries for the period 1990-2015. Three specifications are used for the analysis; the first one determines the influence of interest rate reforms on savings, the second one analyses the effect of savings on investments while the third one examines whether investments have a positive impact on economic growth. The Pooled Mean Group (PMG) estimation technique is employed for analysis. The results show that interest rate reforms have a positive impact on economic growth through savings and investments. The study therefore recommends that market forces should be allowed to determine real interest rates and furthermore, real interest rates maintained at artificially low levels may harm economic growth.JEL Codes - C50; E20; E6

Trajectory-based differential expression analysis for single-cell sequencing data

Trajectory inference has radically enhanced single-cell RNA-seq research by enabling the study of dynamic changes in gene expression. Downstream of trajectory inference, it is vital to discover genes that are (i) associated with the lineages in the trajectory, or (ii) differentially expressed between lineages, to illuminate the underlying biological processes. Current data analysis procedures, however, either fail to exploit the continuous resolution provided by trajectory inference, or fail to pinpoint the exact types of differential expression. We introduce tradeSeq, a powerful generalized additive model framework based on the negative binomial distribution that allows flexible inference of both within-lineage and between-lineage differential expression. By incorporating observation-level weights, the model additionally allows to account for zero inflation. We evaluate the method on simulated datasets and on real datasets from droplet-based and full-length protocols, and show that it yields biological insights through a clear interpretation of the data. Downstream of trajectory inference for cell lineages based on scRNA-seq data, differential expression analysis yields insight into biological processes. Here, Van den Berge et al. develop tradeSeq, a framework for the inference of within and between-lineage differential expression, based on negative binomial generalized additive models

Interest rate reforms and economic growth: the savings and investment channel

The 2008/2009 global financial crisis has re-ignited the debate around financial reforms with contrasting views with regards to the impact of financial reforms on economic growth. This study examines the impact of interest rate reforms on economic growth through savings and investments in SADC countries for the period 1990-2015. Three specifications are used for the analysis; the first one determines the influence of interest rate reforms on savings, the second one analyses the effect of savings on investments while the third one examines whether investments have a positive impact on economic growth. The Pooled Mean Group (PMG) estimation technique is employed for analysis. Furthermore, the ARDL bounds tests are conducted for the individual countries to test for cointegration. The results show that cointegration is detected in most countries for each one of the three specifications. Also, interest rate reforms have a positive impact on economic growth through savings and investments. The study therefore recommends that market forces should be allowed to determine real interest rates and furthermore, real interest rates maintained at artificially low levels may harm economic growth

Interest rate reforms and economic growth: the savings and investment channel

The 2008/2009 global financial crisis has re-ignited the debate around financial reforms with contrasting views with regards to the impact of financial reforms on economic growth. This study examines the impact of interest rate reforms on economic growth through savings and investments in SADC countries for the period 1990-2015. Three specifications are used for the analysis; the first one determines the influence of interest rate reforms on savings, the second one analyses the effect of savings on investments while the third one examines whether investments have a positive impact on economic growth. The Pooled Mean Group (PMG) estimation technique is employed for analysis. Furthermore, the ARDL bounds tests are conducted for the individual countries to test for cointegration. The results show that cointegration is detected in most countries for each one of the three specifications. Also, interest rate reforms have a positive impact on economic growth through savings and investments. The study therefore recommends that market forces should be allowed to determine real interest rates and furthermore, real interest rates maintained at artificially low levels may harm economic growth

Small-scale mobility fostering the interaction networks of Patagonia (Argentina) hunter-gatherers during the Late Holocene: Perspectives from strontium isotopes and exotic items

During the Late Holocene, hunter-gatherer interaction networks significantly grew in intensity and extension across Patagonia. Although this growth is evidenced by the increased flow of exotic items across the region, the mechanisms behind these strengthening social networks remain unclear. Since evidence suggests that some individuals might have performed long-distance trips, this article aims to address the potential relationship between these individuals and the flows of exotic items in North Patagonia. We analyzed 54 enamel teeth for strontium isotopes and reconstructed their probable mobility using mixed-effect models and isotope-based geographic assignments. We inferred population and individual mobility trends and compared them against the flow of exotic items built from a standardized compilation. Our results indicate that most individuals have isotopic composition compatible with residence within their burial and surrounding areas. However, a few individuals show isotopic composition incompatible with their burial areas, which suggests axes -from the burial location to the most likely isotope integration area- of extraordinary mobility. At the same time, the flows of exotic items overlap with these axes around the eastern sector of the study area suggesting that this location could have been a central point of convergence for people and items. We argue that small-scale socially driven mobility could have played a relevant role as a general mechanism of interaction that fostered and materialized Patagonian interaction networks during the Late Holocene

Bending Moduli of Charged Membranes Immersed in Polyelectrolyte Solutions

We study the contribution of polyelectrolytes in solution to the bending moduli of charged membranes. Using the Helfrich free energy, and within the mean-field theory, we calculate the dependence of the bending moduli on the electrostatics and short-range interactions between the membrane and the polyelectrolyte chains. The most significant effect is seen for strong short-range interactions and low amounts of added salt where a substantial increase in the bending moduli of order $1 k_BT$ is obtained. From short-range repulsive membranes, the polyelectrolyte contribution to the bending moduli is small, of order $0.1 k_BT$ up to at most $1 k_BT$. For weak short-range attraction, the increase in membrane rigidity is smaller and of less significance. It may even become negative for large enough amounts of added salt. Our numerical results are obtained by solving the adsorption problem in spherical and cylindrical geometries. In some cases the bending moduli are shown to follow simple scaling laws.Comment: 16 pages, 6 figure

Elucidating glycosaminoglycan–protein–protein interactions using carbohydrate microarray and computational approaches

Glycosaminoglycan polysaccharides play critical roles in many cellular processes, ranging from viral invasion and angiogenesis to spinal cord injury. Their diverse biological activities are derived from an ability to regulate a remarkable number of proteins. However, few methods exist for the rapid identification of glycosaminoglycan–protein interactions and for studying the potential of glycosaminoglycans to assemble multimeric protein complexes. Here, we report a multidisciplinary approach that combines new carbohydrate microarray and computational modeling methodologies to elucidate glycosaminoglycan–protein interactions. The approach was validated through the study of known protein partners for heparan and chondroitin sulfate, including fibroblast growth factor 2 (FGF2) and its receptor FGFR1, the malarial protein VAR2CSA, and tumor necrosis factor-α (TNF-α). We also applied the approach to identify previously undescribed interactions between a specific sulfated epitope on chondroitin sulfate, CS-E, and the neurotrophins, a critical family of growth factors involved in the development, maintenance, and survival of the vertebrate nervous system. Our studies show for the first time that CS is capable of assembling multimeric signaling complexes and modulating neurotrophin signaling pathways. In addition, we identify a contiguous CS-E-binding site by computational modeling that suggests a potential mechanism to explain how CS may promote neurotrophin-tyrosine receptor kinase (Trk) complex formation and neurotrophin signaling. Together, our combined microarray and computational modeling methodologies provide a general, facile means to identify new glycosaminoglycan–protein–protein interactions, as well as a molecular-level understanding of those complexes

Caterpillars and fungal pathogens: two co-occurring parasites of an ant-plant mutualism

In mutualisms, each interacting species obtains resources from its partner that it would obtain less efficiently if alone, and so derives a net fitness benefit. In exchange for shelter (domatia) and food, mutualistic plant-ants protect their host myrmecophytes from herbivores, encroaching vines and fungal pathogens. Although selective filters enable myrmecophytes to host those ant species most favorable to their fitness, some insects can by-pass these filters, exploiting the rewards supplied whilst providing nothing in return. This is the case in French Guiana for Cecropia obtusa (Cecropiaceae) as Pseudocabima guianalis caterpillars (Lepidoptera, Pyralidae) can colonize saplings before the installation of their mutualistic Azteca ants. The caterpillars shelter in the domatia and feed on food bodies (FBs) whose production increases as a result. They delay colonization by ants by weaving a silk shield above the youngest trichilium, where the FBs are produced, blocking access to them. This probable temporal priority effect also allows female moths to lay new eggs on trees that already shelter caterpillars, and so to occupy the niche longer and exploit Cecropia resources before colonization by ants. However, once incipient ant colonies are able to develop, they prevent further colonization by the caterpillars. Although no higher herbivory rates were noted, these caterpillars are ineffective in protecting their host trees from a pathogenic fungus, Fusarium moniliforme (Deuteromycetes), that develops on the trichilium in the absence of mutualistic ants. Therefore, the Cecropia treelets can be parasitized by two often overlooked species: the caterpillars that shelter in the domatia and feed on FBs, delaying colonization by mutualistic ants, and the fungal pathogen that develops on old trichilia. The cost of greater FB production plus the presence of the pathogenic fungus likely affect tree growth

Towards an international standard on feature structures representation

Colloque avec actes et comité de lecture. internationale.International audienceThis paper describes the preliminary results of a joint initiative of the TEI (Text Encoding Initiative) Consortium and the ISO Committee TC 37SC 4 (language Resource management) to provide a standard for the representation and interchange of feature structures