A brain-inspired compact cognitive mapping system

In many simultaneous localization and mapping (SLAM) systems, the map of the environment grows over time as the robot explores the environment. The ever-growing map prevents long-term mapping, especially in large-scale environments. In this paper, we develop a compact cognitive mapping approach inspired by neurobiological experiments. Mimicking the firing activities of neighborhood cells, neighborhood fields determined by movement information, i.e. translation and rotation, are modeled to describe one of the distinct segments of the explored environment. The vertices with low neighborhood field activities are avoided to be added into the cognitive map. The optimization of the cognitive map is formulated as a robust non-linear least squares problem constrained by the transitions between vertices, and is numerically solved efficiently. According to the cognitive decision-making of place familiarity, loop closure edges are clustered depending on time intervals, and then batch global optimization of the cognitive map is performed to satisfy the combined constraint of the whole cluster. After the loop closure process, scene integration is performed, in which revisited vertices are removed subsequently to further reduce the size of the cognitive map. The compact cognitive mapping approach is tested on a monocular visual SLAM system in a naturalistic maze for a biomimetic animated robot. Our results demonstrate that the proposed method largely restricts the growth of the size of the cognitive map over time, and meanwhile, the compact cognitive map correctly represents the overall layout of the environment. The compact cognitive mapping method is well suitable for the representation of large-scale environments to achieve long-term robot navigation. Electronic supplementary materialThe online version of this article (10.1007/s11571-020-09621-6) contains supplementary material, which is available to authorized users.     

Pretreatment of outer membrane vesicle and subsequent infection with influenza virus induces a long-lasting adaptive immune response against broad subtypes of influenza virus

Influenza is an acute respiratory disease and a global health problem. Although influenza vaccines are commercially available, frequent antigenic changes in hemagglutinin might render them less effective or unavailable. We previously reported that modified outer membrane vesicle (fmOMV) provided immediate and robust protective immunity against various subtypes of influenza virus. However, the effect was transient because it was innate immunity-dependent. In this study, we investigated the effects of consecutive administration of fmOMV and influenza virus on the adaptive immune response and long-term protective immunity against influenza virus. When the mice were pretreated with fmOMV and subsequently infected with influenza virus, strong influenza-specific antibody and T cell responses were induced in both systemic and lung mucosal compartments without pathogenic symptoms. Upon the secondary viral challenge at week 4, the mice given fmOMV and influenza virus exhibited almost complete protection against homologous and heterologous viral challenge. More importantly, this strong protective immunity lasted up to 18 weeks after the first infection. These results show that pretreatment with fmOMV and subsequent infection with influenza virus efficiently induces broad and long-lasting protective immunity against various virus subtypes, suggesting a novel antiviral strategy against newly-emerging viral diseases without suitable vaccines or therapeutics.     

Using long-term monitoring of fen hydrology and vegetation to underpin wetland restoration strategies

Question: How can long-term monitoring of hydrological and ecological parameters support management strategies aimed towards wetland restoration and re-creation in a complex hydrological system? Location: Newham Bog National Nature Reserve, Northumberland, UK, a site with a long history of active management, and recorded as drought-sensitive over the last 100 years. Methods: Water level readings are correlated with longer-term hydrological databases, and these data related to vegetation data collected intermittently over a 12 year period. Two analyses are undertaken: (1) a composite DCA analysis of 1993 and 2002 survey data to assess plant community transitions within the wetland and over time, and (2) analysis of recent vegetation data to explore wider vegetation gradients. This allows (3) communities to be classified using NVC classes and (4) integrated with revised Ellenberg F-values. Results: Drought impact and subsequent hydrological recovery over a 22-year period are quantified. Vegetation data display strong moisture and successional gradients. Analysis shows a shift from grassland communities toward mire communities across much of the site. Conclusion: The site is regionally unique in that it has a detailed long-term monitoring record. Hydrological data and vegetation survey have allowed the impact of the most recent ‘groundwater’drought (1989–1997) to be quantified. This information on system resilience, combined with eco-hydrological analyses of plant community-water regime/quality relationships, provide a basis for recommendations concerning conservation and restoration.     

Development of a freeze-drying protocol for the long-term storage of S9-fraction at ambient temperatures

The purpose of this study was to investigate the long-term stabilization of the liver S9-fraction that is widely used in genotoxicity assays in order to mimic bio-activating processes of xenobiotics in vitro. A successful long-term stabilization of the S9-fraction meets the growing demand for the construction of a lab independent device for the detection of genotoxic compounds in field studies with an integrated module for the metabolic activation of pre-genotoxic compounds.The carbohydrates sucrose, trehalose and raffinose were tested in different concentrations or mixtures in order to increase the product stability of the S9-fraction during and after freeze-drying. The activity of the freeze-dried S9-samples was evaluated by means of their potential to activate pre-genotoxic compounds. The successful long-term stabilization of enzymes of the rodent liver S9-fraction for 6 weeks at room temperature by freeze-drying in the presence of 250 mM trehalose is presented.     

Two forms of long-term depression in a polysynaptic pathway in the leech CNS: one NMDA receptor-dependent and the other cannabinoid-dependent

Although long-term depression (LTD) is a well-studied form of synaptic plasticity, it is clear that multiple cellular mechanisms are involved in its induction. In the leech, LTD is observed in a polysynaptic connection between touch mechanosensory neurons (T cells) and the S interneuron following low frequency stimulation. LTD elicited by 450 s low frequency stimulation was blocked by N-methyl-d-aspartic acid (NMDA) receptor antagonists. However, LTD elicited by 900 s low frequency stimulation was insensitive to NMDA receptor antagonists and was instead dependent on cannabinoid signaling. This LTD was blocked by both a cannabinoid receptor antagonist and by inhibition of diacylglycerol lipase, which is necessary for the synthesis of the cannabinoid transmitter 2-arachidonyl glycerol (2-AG). Bath application of 2-AG or the cannabinoid receptor agonist CP55 940 also induced LTD at this synapse. These results indicate that two forms of LTD coexist at the leech T-to-S polysynaptic pathway: one that is NMDA receptor-dependent and another that is cannabinoid-dependent and that activation of either form of LTD is dependent on the level of activity in this circuit. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Delivering RapidArc®: A comprehensive study on accuracy and long term stability

PurposeTo establish the reliability and accuracy of a UNIQUE Linac in delivering RapidArc treatments and assess its long term stability.Materials and methodsUNIQUE performance was monitored and analyzed for a period of nearly two years. 2280 Dynalog files, related to 179 clinical RapidArc treatments were collected. Different tumor sites and dose scheduling were included, covering the full range of our treatment plans. Statistical distributions of MLC motion error, gantry rotation error and MU delivery error were evaluated. The stochastic and systematic nature of each error was investigated together with their variation in time.ResultsAll the delivery errors are found to be small and more stringent tolerances than those proposed by TG142 are suggested. Unlike MLC positional errors, where a linear relationship with leaf speed holds, other Volumetric Modulated Arc Therapy (VMAT) parameters reveal a random nature and, consequently, a reduced clinical relevance. MLC errors are linearly related only to leaf speed no matter the shape of the MLC apertures. Gantry rotation and MU delivery are as accurate as major competing Linacs. UNIQUE was found to be reliable and accurate throughout the investigation period, regardless of the specific tumor sites and fractionation schemes.ConclusionsThe accuracy of RapidArc treatments delivered with UNIQUE has been established. The stochastic nature of delivery errors is proven. Long term statistics of the delivery parameter errors do not show significant variations, confirming the reliability of the VMAT delivery system.     

Use of multispectral satellite datasets to improve ecological understanding of the distribution of Invasive Alien Plants in a water-limited catchment,South Africa

Invasive Alien Plants (IAPs) pose major threats to biodiversity, ecosystem functioning and services. The availability of moderate resolution satellite data (e.g. Sentinel-2 Multispectral Instrument and Landsat-8 Operational Land Imager) offers an opportunity to map and monitor the occurrence and spatial distribution of IAPs. The use of two multispectral remote sensing data sets to map and monitor IAPs in the Heuningnes Catchment, South Africa, was therefore investigated using the maximum likelihood classification algorithm. It was possible to identify areas infested with IAPs using remote sensing data. Specifically, IAPs were mapped with a higher overall accuracy of 71%, using Sentinel-2 MSI as compared to using Landsat 8 OLI, which produced 63% accuracy. However, both sensors showed similar patterns in the spatial distribution of IAPs within the hillslopes and riparian zones of the catchment. This work demonstrates the utility of the two multispectral data sets in mapping and monitoring the occurrence and distribution of IAPs, which contributes to improved ecological modelling and thus to improved management of invasions and biodiversity in the catchment.     

Calretinin: Modulator of neuronal excitability

Calretinin is a member of the calcium-binding protein EF-hand family first identified in the retina. As with the other 200-plus calcium-binding proteins, calretinin serves a range of cellular functions including intracellular calcium buffering, messenger targeting, and is involved in processes such as cell cycle arrest, and apoptosis. Calcium-binding proteins including calretinin are expressed differentially in neuronal subpopulations throughout the vertebrate and invertebrate nervous system and their expression has been used to selectively target specific cell types and isolate neuronal networks. More recent experiments have revealed that calretinin plays a crucial role in the modulation of intrinsic neuronal excitability and the induction of long-term potentiation (LTP). Furthermore, selective knockout of calretinin in mice produces disturbances of motor coordination and suggests a putative role for calretinin in the maintenance of calcium dynamics underlying motor adaptation.     

Dynamics of a Tasmanian cushion heath community

Abstract. Little is known of the dynamics of the alpine cushion plant communities of Tasmania. The present study investigates the nature of the short (5 yr) and long (850 yr plus) term dynamics within one such community at Newdegate Pass, Tasmania. This involved observations of permanent plots, quadrat sampling of cushion heath in different stages of a secondary succesion and cuticular analysis of a core through the cushion peat. Data from the peat core showed the continued presence of the cushion heath community at this site for at least 850 yr, while the regeneration patterns indicated community composition was largely achieved by species accumulation rather than species replacement. Over a 5–yr period there was little or no change in total percentage cover yet a surprisingly high degree of interspecific competition for space in areas of complete plant cover. These observations best fit non equilibrium models of community succession and stability.