Long-range Movement Research Articles

Defect chemistry and colossal dielectric behavior of Nd-modified SrTiO3 lead-free ceramic materials

Colossal permittivity (CP) ceramics have a great potential in the development of miniaturization, integration and lightweight of electronic components. In this work, NdxSr1-xTiO3 (0.000 ≤ x ≤ 0.014) (NST) ceramics are successfully prepared via sintering in N2. Simultaneously microstructure and dielectric properties of NST ceramics are characterized. It can be found that 0.010 ≤ x ≤ 0.014 ceramics show CP (>20000, 20–1 × 106 Hz) and low dielectric loss (<0.04, 20–1 × 106 Hz). In particular, x = 0.010 ceramics exhibit CP (33475, 1 kHz), high insulation resistivity (5.37×108 Ω cm, DC 100 V), low dielectric loss (0.01, 1 kHz) and excellent frequency (20–1 × 106 Hz) and temperature (25–420 °C) stability. In addition, the origin of CP behavior is discussed in NST ceramics based on the characterizations of EPR, XPS, XRD, SEM and complex impedance. The main reason is that the coupling of point defects (TiTi', NdSr⋅, VO⋅⋅) forms the defect dipoles (TiTi'−NdSr⋅, TiTi'−VO⋅⋅−TiTi') and the defect clusters (VO⋅⋅−3TiTi'−NdSr⋅), which produces the electron pinning effect and restricts the long-range movement of the carriers. Additionally, the grain boundary with high insulation resistivity plays a major role in the resistance of ceramics, and it also acts as a high barrier layer to limit the movement of several delocalized carriers.

Dielectric properties of calcium-substituted lanthanum ferrite

ABSTRACTAmong La1-xCaxFeO3-δ (0 ≤ x ≤ 0.5) compounds, the optimal value of the direct current conductivity was registered for a 20% substituted amount. We therefore attempted to study the impedance and dielectric properties of 20% calcium-substituted lanthanum ferrite. We investigated the electric properties in depth between 5 Hz and 13 MHz from 350 to 800°C. The results reveal interesting properties. Indeed, the perovskite shows a huge dielectric constant which promotes its utilization in high-performance dielectric material applications. At a given temperature, ε’ and tan(δ) decrease with increases in frequency. This trend was explained based on the Maxwell Wagner polarization model. The variations in dielectric loss (ε”) with frequency obey the Giuntini theory based on the hopping model. As the temperature increases from 350 to 800°C, the binding energy increases from 0.22 to 0.34 eV, while the minimum hopping distance decreases from 2.16 to 0.12 pm. Consideration of the electric modulus analyzes showed that the relaxation mechanism is dominated at below 400°C by a short-range movement of charge carriers, whereas at above that temperature, a long-range movement of charge carriers is dominant. This study presents a solid foundation for the polarization and dielectric properties of lanthanum ferrite, which is a lead-free, environmentally friendly material and a promising candidate for use in nonlinear optical applications and microwave devices.

Evidence for dielectric suppression in non-magnetic modified multiferroic bismuth ferrite

Structural, magnetic, and electrical properties of polycrystalline Y-Sc codoped BiFeO3 (BFO) ceramics are investigated. Rietveld refinement and Raman spectroscopy analysis provide strong evidence of structural distortion without changing the structure of parent compound (rhombohedral: R3c) after codoping. Distortion due to nonmagnetic codoping marks an abrupt change in magnetic and electrical properties of BiFeO3. Ferromagnetic property is enhanced with a maximum remanent magnetization of 0.0045 emu/g at higher Sc-concentrations. Codoping improves the ferroelectric properties [Pr=13μC/cm2 at (Y,Sc)=(0.03,0.05)] due to the suppression of oxygen vacancies. The frequency-dependent dielectric properties at various temperatures are investigated. The relaxation peak shifts toward room temperature for Bi1−xYxFe1−yScyO3 ceramics, which eventually appeared above 100°C for parent BFO. The suppression of relaxation peak indicates the change in conduction mechanism for codoped ceramics. The conduction process and the relaxation mechanism in parent and Y-Sc codoped BiFeO3 are investigated with electrical modulus and impedance spectroscopy. Frequency-dependent ac conductivity at various temperatures indicates that the conduction mechanism follows the correlated barrier hopping model and is thermally activated. Temperature dependent conductivity studies at different frequencies reveal that the relaxation process in codoped ceramics is due to the long-range oxygen vacancy movement and the low loss values.

Application of Least-Cost Movement Modeling in Planning Wildlife Mitigation Measures along Transport Corridors: Case Study of Forests and Moose in Lithuania

The present work presents the development of a moose movement model to explore the value of wildlife mitigation structures and examine how hypothetical changes in land use patterns could alter wildlife habitats at landscape scales. Collisions between vehicles and animals pose a threat to humans and wildlife populations, the most dangerous collisions being with moose. Migrations of moose are generally predictable and habitat-dependent. Here, we use GIS-based simulations of moose movements to examine road-related habitat fragmentation around the main highways A1 and A2 in Lithuania. From forest data, we develop a moose habitat suitability map. Then, by running multiple simulation iterations, we generate potential moose pathways and statistically describe the most efficient potential long-range movement routes that are based on the principles of habitat utilization. Reflecting the probabilities of cross-highway moose movement, ranks are assigned to all 1 km highway segments, characterizing them in terms of their likelihood of moose movement, and thus identifying discrete migration corridors and highway crossing zones. Bottlenecks are identified through simulation, such as where sections of wildlife fencing end without highway crossing structures, thereby creating a ‘spillover’ effect, i.e., moose moving parallel to the highway, then crossing. The tested model has proven the prognostic capacity of the tool to foresee locations of moose-vehicle collisions with high accuracy, thus allowing it to be a valuable addition to the toolbox of highway planners.

Unsustainable Science

Unsustainable Science

Travel linearity and speed of human foragers and chimpanzees during their daily search for food in tropical rainforests

To understand the evolutionary roots of human spatial cognition, researchers have compared spatial abilities of humans and one of our closest living relatives, the chimpanzee (Pan troglodytes). However, how humans and chimpanzees compare in solving spatial tasks during real-world foraging is unclear to date, as measuring such spatial abilities in natural habitats is challenging. Here we compared spatial movement patterns of the Mbendjele BaYaka people and the Taï chimpanzees during their daily search for food in rainforests. We measured linearity and speed during off-trail travels toward out-of-sight locations as proxies for spatial knowledge. We found similarly high levels of linearity in individuals of Mbendjele foragers and Taï chimpanzees. However, human foragers and chimpanzees clearly differed in their reactions to group size and familiarity with the foraging areas. Mbendjele foragers increased travel linearity with increasing familiarity and group size, without obvious changes in speed. This pattern was reversed in Taï chimpanzees. We suggest that these differences between Mbendjele foragers and Taï chimpanzees reflect their different ranging styles, such as life-time range size and trail use. This result highlights the impact of socio-ecological settings on comparing spatial movement patterns. Our study provides a first step toward comparing long-range spatial movement patterns of two closely-related species in their natural environments.

Relaxation dynamics of Ni/epoxy composites studied by dielectric relaxation spectroscopy

Dynamic dielectric properties of nickel (Ni)/epoxy composites are investigated by broadband dielectric spectroscopy over a wide frequency range (approximately 1–107 Hz) and temperature range (approximately −20 to 200°C). Multiple dielectric relaxation processes in the Ni/epoxy composites are identified, corresponding to conductivity, interfacial polarization (IP), and α-relaxation. With increasing temperature, both dielectric permittivity and loss of composites increase, arising from enhanced dipolar mobility; approaching the glass transition temperature ( T g), a clear α-relaxation appears, which can be attributed to the onset of cooperative chain movement. Further increasing temperature activates the long-range movement of space charges, as manifested by an IP superimposed on the ionic conductivity. A transition from insulator (below T g) to semiconductor (above T g) is also observed for the studied composite system.

Faraday Rotation in Discotic Liquid Crystals by Long-Range Electron Movement

Faraday rotation (FR), a magneto-optic (MO) property of a material, is the rotation of the plane of polarization of light by a magnetic field in the direction of the propagation of the light. Being...

Efficient MOF-Sensitized Solar Cells Featuring Solvothermally Grown [100]-Oriented Pillared Porphyrin Framework-11 Films on ZnO/FTO Surfaces.

Owing to their abilities to assemble and organize a large number of redox and photoactive components in highly ordered periodic fashion, crystalline porous metal-organic frameworks (MOFs) have the potential to execute myriad complex functions, including charge transport and light to electrical energy conversion when the required conditions are fulfilled. Herein, we demonstrate an unprecedented spontaneous solvothermal growth of precisely [100]-oriented pillared porphyrin framework-11 (PPF-11) films featuring vertically aligned Zn-tetrakis(4-carboxyphenyl)porphyrin (ZnTCPP) walls and horizontally aligned 2,2'-dimethyl-4,4'-bipyridine beams attached to annealed ZnO-fluorine-doped tin oxide (FTO) surfaces and their remarkable photovoltaic performance in liquid-junction solar cells. The [100]-oriented PPF-11/ZnO-FTO photoanodes displayed excellent photovoltaic response (short-circuit current ( JSC): 4.65 mA/cm2, open-circuit voltage ( VOC): 470 mV, power conversion efficiency: 0.86%) that easily outperformed all control devices as well as previously reported porphyrin and Ru(bpy)32+-based visible light-harvesting MOFs with 10-1000 times greater photocurrent density and 2-375 times higher efficiency. The superior photovoltaic behavior of [100]-oriented PPF-11/ZnO films compared to epitaxially grown MOF thin films on insulating self-assembled monolayers and drop-cast PPF films with different orientations can be attributed to several factors, including better charge separation, transport, and injection capabilities of the former. The noncatenated PPF-11 was able to host electron-deficient C60 guests, filling in nearly half of its cavities and engage them in ZnTCPP/C60 charge-transfer interaction. However, the C60-doped PPF-11/ZnO films displayed much weaker photovoltaic response than undoped [100]-oriented PPF-11/ZnO films presumably due to exclusion of I-/I3- electrolyte from the C60-occupied cavities and the inability of isolated C60 guests to support long-range charge movement.

Training Population Optimization for Prediction of Cassava Brown Streak Disease Resistance in West African Clones.

Cassava production in the central, southern and eastern parts of Africa is under threat by cassava brown streak virus (CBSV). Yield losses of up to 100% occur in cases of severe infections of edible roots. Easy illegal movement of planting materials across African countries, and long-range movement of the virus vector (Bemisia tabaci) may facilitate spread of CBSV to West Africa. Thus, effort to pre-emptively breed for CBSD resistance in W. Africa is critical. Genomic selection (GS) has become the main approach for cassava breeding, as costs of genotyping per sample have declined. Using phenotypic and genotypic data (genotyping-by-sequencing), followed by imputation to whole genome sequence (WGS) for 922 clones from National Crops Resources Research Institute, Namulonge, Uganda as a training population (TP), we predicted CBSD symptoms for 35 genotyped W. African clones, evaluated in Uganda. The highest prediction accuracy (r = 0.44) was observed for cassava brown streak disease severity scored at three months (CBSD3s) in the W. African clones using WGS-imputed markers. Optimized TPs gave higher prediction accuracies for CBSD3s and CBSD6s than random TPs of the same size. Inclusion of CBSD QTL chromosome markers as kernels, increased prediction accuracies for CBSD3s and CBSD6s. Similarly, WGS imputation of markers increased prediction accuracies for CBSD3s and for cassava brown streak disease root severity (CBSDRs), but not for CBSD6s. Based on these results we recommend TP optimization, inclusion of CBSD QTL markers in genomic prediction models, and the use of high-density (WGS-imputed) markers for CBSD predictions across population.

Movement Ecology of Pest Helicoverpa: Implications for Ongoing Spread.

The recent introduction and spread of Helicoverpa armigera throughout South America highlight the invasiveness and adaptability of moths in the Helicoverpa genus. Long-range movement in three key members, H. armigera, H. zea, and H. punctigera, occurs by migration and international trade. These movements facilitate high population admixture and genetic diversity, with important economic, biosecurity, and control implications in today's agricultural landscape. This is particularly true for the spread of resistance alleles to transgenic crops expressing Bacillus thuringiensis (Bt) toxins that are planted over vast areas to suppress Helicoverpa spp. The ability to track long-distance movement through radar technology, population genetic markers, and/or long-distance dispersal modeling has advanced in recent years, yet we still know relatively little about the population trajectories or migratory routes in Helicoverpa spp. Here, we consider how experimental and theoretical approaches can be integrated to fill key knowledge gaps and assist management practices.

Kinesin-2 Controls the Motility of RAB5 Endosomes and Their Association with the Spindle in Mitosis.

RAB5 is a small GTPase that belongs to the wide family of Rab proteins and localizes on early endosomes. In its active GTP-bound form, RAB5 recruits downstream effectors that, in turn, are responsible for distinct aspects of early endosome function, including their movement along microtubules. We previously reported that, at the onset of mitosis, RAB5positive vesicles cluster around the spindle poles and, during metaphase, move along spindle microtubules. RNAi-mediated depletion of the three RAB5 isoforms delays nuclear envelope breakdown at prophase and severely affects chromosome alignment and segregation. Here we show that depletion of the Kinesin-2 motor complex impairs long-range movement of RAB5 endosomes in interphase cells and prevents localization of these vesicles at the spindle during metaphase. Similarly to the effect caused by RAB5 depletion, functional ablation of Kinesin-2 delays nuclear envelope breakdown resulting in prolonged prophase. Altogether these findings suggest that endosomal transport at the onset of mitosis is required to control timing of nuclear envelope breakdown.

Effect of oxygen vacancies on dielectric properties of Ba(1-x)Nd(2x/3)TiO3 compounds

In the present work, the effects of temperature and frequency on the electrical transport properties of polycrystalline samples of Ba(1-x)Nd2x/3TiO3 (BNxT) (x = 0.00 and x = 0.04), prepared by molten-salt method, are discussed. X-Ray diffraction reveals that all the samples crystallize in a tetragonal symmetry (space group P4mm) with the formation of nanoparticles. The crystallite size was found to vary around 40 nm. DC-conductivity measurements show and that all samples are characterized by a semiconductor behavior. The frequency dependent behavior of conductivity was well fitted in Jonscher's universal power law and interpreted in terms of Overlapping Large Polaron Tunneling (OLPT) mechanism. The Cole-Cole plot analysis of impedance spectra enabled to distinguish two relaxation behaviors assigned to originate from grains and grain boundaries. Besides, it was found that the electrical behavior of the ceramics is dominated by the grain-boundary response. Furthermore, the frequency dependence of electric modulus was studied and explained using Kohlrausch-Williams-Watts (KWW) model and the normalized M″/Mmax″ spectra of the samples suggest that the distribution of relaxation times is temperature dependent and originates by the same mechanism. In addition, the conductivity and electrical response behavior in all the samples can be attributed to the long-range movement of oxygen vacancies.

High dielectric constant and relaxor behavior in La0.7Sr0.25Na0.05Mn0.8Ti0.2O3 manganite

The dielectric properties of La0.7Sr0.25Na0.05Mn0.8Ti0.2O3 (LSNMTi0.2) were investigated as a function of temperature and frequency. Compared with the dielectric constants of most ferroelectric and relaxor materials, in this compound we have found a colossal dielectric constant phenomenon consisting in a low frequency dielectric constant ε″ over 106 around room temperature. However, Frequency and temperature dependent ac conductivity and complex impedance studies were linked to semiconducting grains and insulating grain boundaries, which support the non-Debye type of relaxation in the polycrystalline sample. Furthermore, decrease in the resistive properties with an increase in temperature, explained in terms of the mobility of the charge carriers, signaled the semi-conductor behavior with negative temperature coefficient of resistance (NTCR). The scaling behavior of the Modulus spectra M″ versus frequency allowed us to understand whether the short-range or the long-range movement of charge carriers is the dominant in relaxation process, confirming the non-Debye type of multiple relaxations in the system. The variation in the dielectric permittivity, explained in terms of the space charge polarization according to the Maxwell–Wagner model and the Koop's phenomenological theory and the large dielectric response, was induced by the barrier layers in the grain boundaries and the mixed-valent structures of Mn3+/Mn4+ and Ti4+/Ti3+.

Automatic road detection system for an air–land amphibious car drone

In recent years, unmanned aerial vehicle (UAV) technologies have rapidly developed. Drones, which are one type of UAV, are used in many industrial fields, such as photography, delivery and agriculture. However, a commercial drone can fly for only approximately 20 min on one charge. Furthermore, drones are prohibited from flying in some areas, and cannot be operated in bad weather. Due to the development of drone technologies, we must reduce energy consumption and achieve long-range movement. To overcome these limitations, we develop a new air–land amphibious car drone that can fly and requires less power consumption in land mode; this extends the range of mobility of the drone. Moreover, land mode can be used to pass through restricted areas or bad weather conditions by sliding. Furthermore, we develop a Convolutional Neural Network (CNN)-based algorithm for detecting the road in a captured scene. To more accurately segment the road region based on images from the equipped camera of the drone, we propose atrous spatial pyramid pooling (ASPP) ResNet blocks, instead of Resblocks, which were proposed by DeepLab. The experimental results demonstrate that the proposed method improves the pixel accuracy (PA) to 85.6% and achieves a mean Intersection over Union (mIoU) of 55.8%.

The H-subunit of the restriction endonuclease CglI contains a prototype DEAD-Z1 helicase-like motor.

CglI is a restriction endonuclease from Corynebacterium glutamicum that forms a complex between: two R-subunits that have site specific-recognition and nuclease domains; and two H-subunits, with Superfamily 2 helicase-like DEAD domains, and uncharacterized Z1 and C-terminal domains. ATP hydrolysis by the H-subunits catalyses dsDNA translocation that is necessary for long-range movement along DNA that activates nuclease activity. Here, we provide biochemical and molecular modelling evidence that shows that Z1 has a fold distantly-related to RecA, and that the DEAD-Z1 domains together form an ATP binding interface and are the prototype of a previously undescribed monomeric helicase-like motor. The DEAD-Z1 motor has unusual Walker A and Motif VI sequences those nonetheless have their expected functions. Additionally, it contains DEAD-Z1-specific features: an H/H motif and a loop (aa 163–aa 172), that both play a role in the coupling of ATP hydrolysis to DNA cleavage. We also solved the crystal structure of the C-terminal domain which has a unique fold, and demonstrate that the Z1-C domains are the principal DNA binding interface of the H-subunit. Finally, we use small angle X-ray scattering to provide a model for how the H-subunit domains are arranged in a dimeric complex.

New splicing variants of mitochondrial Rho GTPase-1 (Miro1) transport peroxisomes.

Microtubule-dependent long-distance movement of peroxisomes occurs in mammalian cells. However, its molecular mechanisms remain undefined. In this study, we identified three distinct splicing variants of human mitochondrial Rho GTPase-1 (Miro1), each containing amino acid sequence insertions 1 (named Miro1-var2), 2 (Miro1-var3), and both 1 and 2 (Miro1-var4), respectively, at upstream of the transmembrane domain. Miro1-var4 and Miro1-var2 are localized to peroxisomes in a manner dependent on the insertion 1 that is recognized by the cytosolic receptor Pex19p. Exogenous expression of Miro1-var4 induces accumulation of peroxisomes at the cell periphery and augments long-range movement of peroxisomes along microtubules. Depletion of all Miro1 variants by knocking down MIRO1 suppresses the long-distance movement of peroxisomes. Such abrogated movement is restored by reexpression of peroxisomal Miro1 variants. Collectively, our findings identify for the first time peroxisome-localized Miro1 variants as adapter proteins that link peroxisomes to the microtubule-dependent transport complexes including TRAK2 in the intracellular translocation of peroxisomes in mammalian cells.

Sol–gel synthesis and characterization of a new four-layer K0.5Gd0.5Bi4Ti4O15 Aurivillius phase

Monophasic K0.5Gd0.5Bi4Ti4O15 powders were synthesized via a citrate-based sol–gel route. Rietveld analysis of powder X-ray diffraction data confirmed the composition to be a pure four-layer Aurivillius phase with an orthorhombic structure (space group A21 am and unit cell parameters a = 5.42798(52) A, b = 5.41821(41) A, and c = 41.2723(33) A) at room temperature. The chemical composition and the morphology of the sintered pellets were examined by field emission scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). The dielectric properties were investigated as a function of temperature (27–600 °C) at various frequencies (10 Hz–1 MHz), and the phase transition was observed at 560 °C. Ferroelectric nature of K0.5Gd0.5Bi4Ti4O15 was demonstrated by the polarization–electric field (P–E) hysteresis loop. Equivalent circuit modeling of the complex impedance data was employed to determine the conduction behavior. The temperature dependence of dc conductivity was found to follow the Arrhenius law associated with the activation energy of 1.22 ± 0.02 eV and was attributed to the long-range movement of oxygen vacancies.

Trajectory and Concentration PM10 on Forest and Vegetation Peat-Fire HYSPLIT Model Outputs and Observations (Period: September – October 2015)

Forest and vegetation peat-fire is one of the main sources of air pollution in Kalimantan, predominantly during the dry period. In 2015, forest and vegetation fire in Central Kalimantan and South Kalimantan emit large quantities of smoke leading to poor air quality. Haze is a phenomenon characterized by high concentration of particulate matter. This research objective is to analyze trajectory and dispersion of concentration particulate matter, PM10 in Banjarbaru and Palangka Raya. Dynamics of PM10 (Particulate matter less than or 10 µm in size) on vegetation peat-fire is done using GDAS (Global Data Assimilation System) output with a horizontal resolution 1º which corresponds to 100 km × 100 km for input model. Climate conditions in the period September to October 2015 at generally during dry season of El Nino year. The Hybrid-single Langrangian Integrated Trajectory (HYSPLIT) model was used to investigate concentration and long-range movement of this pollutant from the source to the receptor area. We used time-series data on PM10 readings obtained from two stations Banjarbaru (South Kalimantan) and Palangka Raya (Central Kalimantan) belonging to Meteorology Climatology and Geophysics Agency (BMKG). We also used weather parameter such as wind speed and direction. We investigated trajectory run from hotspots information MoF (Sipongi Output Programs) and HYSPLIT. We compared concentration obtained from PM10 observation and its concentrations trend. The dispersion pattern, as simulated by HYSPLIT showed that the distribution of PM10 was greatly influenced by the wind direction and topography. There is a large difference between the concentration of PM10 Palangka Raya and Banjarbaru.

Abstract IA19: Mechanisms of alternative telomere recombination

Abstract Telomere length maintenance is a requisite feature of cellular immortalization and a hallmark of human cancer. While most human cancers express telomerase activity, approximately 10-15% employ a recombination-dependent telomere maintenance pathway known as Alternative Lengthening of Telomeres (ALT), an incompletely understood process that is characterized by multi-telomere clusters. We have recently shown that a DNA double-strand break (DSB) response at ALT telomeres triggers long-range movement and clustering between chromosome termini, resulting in homology-directed telomere synthesis (Cho et. al. Cell 2014). Damaged telomeres initiate increased random surveillance of nuclear volumes before displaying rapid directional movement and association with recipient telomeres over micron-range distances. This phenomenon required Rad51 and the Hop2-Mnd1 heterodimer, implicating a specialized homology searching mechanism that exhibits similarities to meiotic recombination in ALT dependent telomere maintenance. This presentation will describe unpublished data that defines signaling events that are responsible for homology directed telomere synthesis during ALT. Using a novel methodology to purify nascent telomeres, we have identified the basic requirements for break induced telomere synthesis, including the specific DNA polymerases and helicases involved. Data derived from this approach reveals mechanisms of homology directed DNA synthesis that substantially differ from either normal replicative DNA synthesis or from existing models of break induced replication that have been defined in yeast. These data reveal an ordered series of events necessary for ALT telomere synthesis and have implications for homology directed DNA repair at other genomic locations. This work was supported by NIH grants GM101149, CA138835, and CA17494, and funds from the Abramson Family Cancer Research Institute and Basser Research Center for BRCA Citation Format: Roger A. Greenberg. Mechanisms of alternative telomere recombination. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr IA19.