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Neuromorphic object tracking architecture, based on compound eyes, and implementation on FPGA
No full textRecent findings in neuroscience, show that rapid changes in flight direction of a housefly/blowfly (mainly to track objects) are attributable to neural circuits distributed behind its photo-receptors. While tracking objects, using its compound eye structure, a fly is able to detect changes in the motion of the object quickly and changes its own motion accordingly. The working of these neural circuits may be modelled as a set of leaky integrate and fire neurons connected in a special manner to form a competitive feedback control. Based on this knowledge, we present a neuromorphic competitive control circuit utilizing an inference neuron model to control N actuators and analyze their outputs for tracking an object. This model was simulated in software first and then implemented on a Xilinx Artix-7 XC7A35T- ICPG236C FPGA board using Verilog. The results show an observable decoherence phenomenon between the neurons and support the working principle of the model. © 2018 IEE
Role of functionalities in structural analogues urocanic acid and l -histidine, toward the formation of anhydrous and hydrated molecular salts
No full textCocrystallization of structural analogues urocanic acid and l-histidine with mono-, di-, and trisubstituted hydroxy benzoic acids has been carried out to gain insights into the formation of anhydrous and hydrated molecular salts. Urocanic acid generated anhydrous molecular salts with 2-hydroxy, 3,5-dihydroxy, and 2,4,6-trihydroxybenzoic acids, whereas 2,3-dihydroxy, 3,4-dihydroxy, and 3,4,5-trihydroxybenzoic acids resulted in hydrated salts. Cocrystallization experiments of anhydrous l-histidine with 2,3-dihydroxy, 3,4-dihydroxy, 3,5-dihydroxy, 3,4,5-trihydroxy, and 2,4,6-trihydroxybenzoic acids resulted in hydrated molecular salts. However, l-histidine 2-hydroxybenzoic acid formed an anhydrous molecular salt. In this context, the hitherto elusive structure of native urocanic acid (anhydrous form) has been determined. The rationale for the formation of hydrated and anhydrous salts is evaluated in terms of the hydroxyl substituents on benzoic acids and the presence of additional amino group in l-histidine. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) proved the presence or absence of hydration, whereas Fourier-transform infrared (FT-IR) experiments confirmed proton transfer suggesting the formation of molecular salts for those combinations that did not produce good quality single crystals for diffraction. © 2019 American Chemical Society
Blue-shifted hydrogen bonding in the gas phase CH/D 3 CN···HCCl 3 complexes
No full textBlue-shifting H-bonded complexes between CHCl 3 and CH/D 3 CN have been identified by Fourier transform infrared spectroscopy in the gas phase at room temperature. The change in FTIR peak intensity of the mixture of the two components as a function of temperature and composition provides the basis for identification of the H-bonded band in the infrared spectrum. On complex formation with CH 3 CN and CD 3 CN, the Câ'H stretching frequency of CHCl 3 shifts to the blue by +8.7 and +8.6 cm â'1 , respectively. The molecular electrostatic potential calculation at the MP2/6-311++G� level has been used to arrive at the geometry of the complex. It has been reported in the literature that CHCl 3 and CH/D 3 CN form red-shifting H-bonded complex in Ar matrix. The red shifting has been verified by doing ab initio calculations in the presence of Ar atoms, which has been attributed to the matrix effect at low temperature. The interaction of Ar with CH 3 CN makes the CH 3 CN more basic and as a result it becomes better hydrogen bond acceptor and causes red shift. The potential energy scans and NBO analysis of the Cl 3 CH···NCCH 3 complex have been compared with those of F 3 CH···NCCH 3 and Cl 3 CH···NH 3 complexes. The change in electron density of the CHCl 3 as a function of Câ'H···N distance shows that the approach of CH 3 CN to CHCl 3 induces a shift in electron density from the H atom to the Cl atoms of CHCl 3 which leads to Câ'H bond contraction and blue shifting of Câ'H stretching frequency. However, in the complex Cl 3 CH···NH 3 , where frequency shift to the red is reported, charge transfer and electrostatic interaction dominate. © 2019 American Chemical Society
Accurate and precise microscale measurements of boron isotope ratios in calcium carbonates using laser ablation multicollector-ICPMS
No full textThe boron isotope compositions (δ 11 B) of biogenic carbonates have proven to be an invaluable tool for investigating changes in ocean carbonate chemistry, especially the impacts of declining seawater pH due to rising levels of atmospheric CO 2 . Accurate, high precision boron isotopic measurements, however, remain analytically challenging with conventional approaches being extremely time consuming and labour intensive. Here we present a new analytical approach for high precision accurate measurements of boron isotope compositions in biogenic carbonates. We show that a laser ablation MC-ICPMS system equipped with 10 13 Ω amplifiers provides a powerful tool for determining micro-scale δ 11 B values with an internal precision of �0.15� (2SD) and a total long-term accuracy of better than 0.22�, which is equivalent to or better than those of conventional solution-based methods. This accuracy is achieved by careful subtraction of baseline interference around the masses of 10 B and 11 B, which arises from matrix-specific scattered Ca, C, and O ions. We also report detailed protocols for time-response corrections of transient signals in biogenic carbonates, essential for high precision boron isotopic measurements when using 10 13 Ω amplifiers. The overall veracity of our laser ablation MC-ICPMS method is further demonstrated by the isotopic variability observed at macro-(mm) and micro-scales (μm) in both calcite and aragonite biogenic minerals. An aragonite deep-sea coral, Desmophyllum dianthus, is shown to preserve large (up to 6�) variations in δ 11 B accompanied by near synchronous changes in B/Ca. This variability is excessive compared to that expected for the relatively stable carbonate ion system of deep-ocean water and is therefore attributed to isotopic and elemental fractionation of B during coral biomineralisation. In contrast, cyclic 2.5� variability is found in the sclerosponge Ceratoporella nicholsoni, which can be directly linked to seasonal changes in seawater pH. These examples highlight the power of laser ablation MC-ICPMS and its ability to accurately and precisely recover small environmental signals in boron isotopes. We thus show that these significant improvements in both the internal precision and now long-term accuracy and reproducibility of laser ablation MC-ICPMS, together with its microscale analytical capabilities and relatively rapid ease of operation, have the potential to revolutionise the study of boron isotope systematics in biogenic carbonates. © 2019 The Royal Society of Chemistry
Erratum: Author Correction: Structural insights into the activation of metabotropic glutamate receptors (Nature (2019) 566 7742 (79-84))
No full textThe surname of author Toon Laeremans was misspelled 'Laermans'. This error has been corrected online
Lizards from suburban areas learn faster to stay safe
No full textEnhanced cognitive ability is beneficial in unpredictable and harsh environments, as it enables animals to respond with flexibility. For animals living in urbanized areas, local environments not only are altered but can rapidly change during their lifetime. Urban residents are therefore challenged with identifying novel dangers and safe refuges in dynamic environments. We demonstrate that the tropical agamid lizard Psammophilus dorsalis experiences dramatically different habitats not only across the rural to urban spatial scale but also over the short temporal scale of a few years in suburban areas. Differences in environmental stability are expected to affect rates of learning and reversal learning in resident lizards. In testing arenas, lizards from these populations were required to choose a designated 'safe' refuge instead of an 'unsafe' one after simulated predator attacks. The contingency for safety was switched during the reversal learning task. In general, P. dorsalis showed high rates of learning and reversal learning, but lizards from suburban areas were quicker to learn and unlearn the location of the safe refuge than those from rural areas. This demonstrates for the first time to our knowledge that suburban lizards have faster learning and reversal learning skills for a key survival-related behaviour, finding safety in unpredictable environments. © 2019 The Author(s) Published by the Royal Society. All rights reserved
An Automated Gradient Enhanced Bat Algorithm
No full textStochastic optimization algorithms such as genetic algorithm (GA), particle swarm optimization (PSO) and bat algorithm (BA) carry out global optimization but typically consume substantial computational effort. On the other hand, deterministic algorithms like gradient descent converge rapidly but may get stuck in the local minima of multimodal functions. Thus, a way that couples the strengths of stochastic and deterministic optimization algorithm schemes is needed for better accuracy of final solution without getting trapped in the local minima. Bat algorithm is a recently developed swarm optimization technique which has been found to be a powerful method for multimodal optimization problems. The standard BA shows premature convergence and reduced convergence speeds under some conditions. So, a recently proposed enhanced bat algorithm (EBA) is augmented with gradient search to create a gradient enhanced bat algorithm (GEBA). This paper presents GEBA for optimization which involves post-hybridization of EBA with a gradient based local search algorithm to ensure accurate local exploration at final stages of GEBA. GEBA is tested with several test functions and found to perform very well. An automated gradient enhanced bat algorithm (AGEBA) is developed to addresses the problem of selecting good initial guess for gradient based algorithm. AGEBA is found to be an efficient algorithm requiring only one tuning error parameter thereby saving considerable manual effort. © 2018 IEEE
LipidII interaction with specific residues of Mycobacterium tuberculosis PknB extracytoplasmic domain governs its optimal activation
No full textThe Mycobacterium tuberculosis kinase PknB is essential for growth and survival of the pathogen in vitro and in vivo. Here we report the results of our efforts to elucidate the mechanism of regulation of PknB activity. The specific residues in the PknB extracytoplasmic domain that are essential for ligand interaction and survival of the bacterium are identified. The extracytoplasmic domain interacts with mDAP-containing LipidII, and this is abolished upon mutation of the ligand-interacting residues. Abrogation of ligand-binding or sequestration of the ligand leads to aberrant localization of PknB. Contrary to the prevailing hypothesis, abrogation of ligand-binding is linked to activation loop hyperphosphorylation, and indiscriminate hyperphosphorylation of PknB substrates as well as other proteins, ultimately causing loss of homeostasis and cell death. We propose that the ligand-kinase interaction directs the appropriate localization of the kinase, coupled to stringently controlled activation of PknB, and consequently the downstream processes thereof. © 2019, The Author(s)
Regulating drones in restricted spaces
No full textCommercial and end-user drones come equipped with a wide array of sensors. Unregulated use of such drones in public airspaces poses a serious threat to the privacy of citizens. We make the case for restricted spaces for drones, which are geographic areas for which a host can specify its privacy policies. Guest drones must prove to the host that they are in compliance with the host's policies before entering the restricted space. We then make the case for an information-flow control-based policy enforcement framework on drones, and sketch the design of a prototype framework atop the Robot Operating System (ROS). © 2019 ACM
Modification in the microstructural and electrochromic properties of spray-pyrolysed WO 3 thin films upon Mo doping
No full textAbstract: WO 3 thin films were grown onto the glass and fluorine-doped tin oxide-coated glass substrates using chemical spray pyrolysis technique. X-ray diffraction analyses reveal that all the films possess orthorhombic phase of WO 3 . Morphologies of the films have been found to vary with Mo-doping concentrations. Three-dimensional atomic force micrographs reveal that the 5 at Mo-doped film has the maximum image surface area and is optimal for improved electrochromic performance. Cyclic voltammetry studies show that the cathodic and anodic peak current densities have the highest values for the 5 at Mo-doped WO 3 film. Relative to the undoped film, the change from coloured to bleached state is faster for the 5 at Mo-doped WO 3 film. Considering the reversibility and the switching response from chronoamperometry and the coloration efficiency from cyclic voltammetry, it has been concluded that the 5 at Mo-doped WO 3 film has an optimal electrochromic response. Figure not available: see fulltext.. © 2019, Springer Science+Business Media, LLC, part of Springer Nature