SPATIAL DISTRIBUTION OF BASALTIC ROOTLESS CONES AS A FUNCTION OF WATER AVAILABILITY: ICELANDIC AND EXPERIMENTAL STUDIES

2016 ◽  
Author(s):  
Nell C. Davis ◽  
◽  
Reinhard A. Wobus ◽  
Richard W. Hazlett ◽  
Jeffrey Karson
Keyword(s):  
Spatial Distribution ◽  
Water Availability ◽  
Experimental Studies ◽  
Rootless Cones

scholarly journals Multiple Objects Interacting with a Solidification Front

2020 ◽  
Author(s):  
Sidhanth Tyagi ◽  
Cécile Monteux ◽  
Sylvain Deville
Keyword(s):  
Spatial Distribution ◽  
Solidification Front ◽  
Volume Fraction ◽  
Experimental Studies ◽  
Solute Concentration ◽  
Multiple Objects ◽  
Material Microstructure ◽  
Foreign Objects ◽  
Engineering Sciences ◽  
Structural And Functional Properties

The interaction of foreign objects suspended in a liquid melt with an advancing solidification front is of special interest in nature (e.g. frost heave) and engineering sciences (e.g. crystal growth). The front can engulf the object, trapping it into the growing crystal, or the front can repel the object, pushing it ahead of itself. Therefore, the object-front confrontation can have a strong influence on the properties of the solidified material. In particular, the spatial distribution of the objects in the resulting microstructure determines the material's structural and functional properties. The past theoretical models and experimental studies have mostly investigated the interaction of isolated, spherical, and hard objects in pure melts. However, the outcome of object-front interactions in complex (more realistic) systems, where multiple objects and solutes are present, is still poorly understood. Here we show the interaction of multiple oil droplets with an ice-water front in the absence and presence of solute effects using in situ cryo-confocal microscopy. We observe the formation of a compact agglomerated layer resulting in a force equilibrium different from the isolated object approach. We elucidate the role of solute during the evolution of a material microstructure in the presence of foreign objects. We report on how the object size, number of objects, and bulk solute concentration influence the front morphology and the subsequent object spatial distribution. Our results depict how the presence of multiple objects with varying solute concentration can modify the object-front interactions and hence, can lead to the formation of complex microstructures, difficult to predict theoretically. We suggest that the volume fraction of objects suspended in a liquid melt in conjunction with the amount of bulk solute concentration are two important criteria to be incorporated in the development of object-front interaction models. Furthermore, our simplified approach of using oil-in-water emulsions can serve as a good analogue for studying the development of material microstructure in presence of foreign objects. <br>

scholarly journals ANALYSIS OF THE ELECTROPHYSICAL AND PHOTOELECTRIC PROPERTIES OF NANOCOMPOSITE POLYMERS BY THE MODIFIED KELVIN PROBE

2017 ◽  
Vol 8 (4) ◽  
pp. 386-397 ◽  
Author(s):  
K. U. Pantsialeyeu ◽  
A. U. Krautsevich ◽  
I. A. Rovba ◽  
V. I. Lysenko ◽  
R. I. Vorobey ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Polymer Nanocomposites ◽  
Electrostatic Potential ◽  
Carbon Nanomaterials ◽  
Experimental Studies ◽  
Scanning Probe ◽  
Physical Parameters ◽  
Kelvin Probe ◽  
Photoelectric Properties ◽  
Optical Probing

At present for analysis of the homogeneity of materials properties are becoming widely used various modifications of a scanning Kelvin probe. These methods allow mapping the spatial distribution of the electrostatic potential. Analysis of the electropotential profile is not sufficient to describe any specific physical parameters of the polymer nanocomposites. Therefore, we use an external energy impact, such as light. Purpose of paper is the modification of the Kelvin scanning probe and the conduct of experimental studies of the spatial distribution and response of the electrostatic potential of the actual polymer nanocomposites to the optical probing.Carried out the investigations on experimental Low density polyethylene composites. Carbon nanomaterials and nanoparticles of silicon dioxide or aluminum as fillers are used. As a result, maps of the spatial distribution of the electrostatic potential relative values and the surface photovoltage. Statistical analysis of the electrophysical and photoelectric properties homogeneity, depending on the component composition of the composites carried out. In addition, with reference to matrix polymers, the Kelvin scanning probe, in combination with the optical probing, made it possible to detect a piezoelectric effect. The latter, can used as a basis for the development of new methods for studying the mechanical properties of matrix polymers.

scholarly journals Assessment of the Spatial Distribution of Moisture Content in Granular Material Using Electrical Impedance Tomography

Sensors ◽  
2019 ◽  
Vol 19 (12) ◽  
pp. 2807 ◽  
Author(s):  
Jan Porzuczek
Keyword(s):  
Spatial Distribution ◽  
Moisture Content ◽  
Granular Material ◽  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Optical Tomography ◽  
Experimental Studies ◽  
Impedance Tomography ◽  
Wide Range ◽  
Voltage Signal

This paper presents a method for the online determination of the spatial distribution of the moisture content in granular material. It might be essential for the monitoring and optimal control of, for example, drying processes. The proposed method utilizes Electrical Impedance Tomography (EIT). As an exemplary material for experimental research, the black chokeberry (Aronia melanocarpa) was used. The relationship between the electrical impedance of the chokeberry and its moisture content was determined for a wide range of frequencies (20 Hz–200 kHz). The EIT research consisted of both simulation and experimental investigation. Experimental studies of the spatial distribution of the moisture content were performed in a cylindrical vessel equipped with 8 electrodes circumferentially arranged. The voltage signal from the electrodes was acquired simultaneously using the data acquisition module. Due to the high impedance of the chokeberries, exceeding 109 Ω for the dried matter, extraordinary instrumentation was necessary to be applied. On the other hand, raw chokeberry was characterized by a several orders of magnitude lower impedance (103–104 Ω), especially for high frequencies. The wide range of the observed impedance was able to be measured owing to its use of the voltage stimulation instead of the current stimulation (which is most common for EIT). The image reconstruction problem was solved using an iterative Gauss–Newton algorithm and the EIDORS (Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software) package. The obtained results showed a satisfactory ability to localize an insufficiently dried part of the material. Prospective ways to improve the imaging quality are also discussed.

scholarly journals Myco- and photobiont associations in crustose lichens in the McMurdo Dry Valleys (Antarctica) reveal high differentiation along an elevational gradient

2019 ◽  
Author(s):  
Monika Wagner ◽  
Arne C. Bathke ◽  
Craig Cary ◽  
Robert R. Junker ◽  
Wolfgang Trutschnig ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Water Availability ◽  
Abiotic Factors ◽  
Distribution Patterns ◽  
Elevational Gradient ◽  
Mcmurdo Dry Valleys ◽  
Bipartite Network ◽  
Dry Valleys ◽  
Climate Conditions ◽  
Crustose Lichens

AbstractThe climate conditions of the McMurdo Dry Valleys (78° S) are characterized by low temperatures and low precipitation. The annual temperatures at the valley bottoms have a mean range from −30 °C to −15 °C and decrease with elevation. Precipitation occurs mostly in form of snow (3-50 mm a−1 water equivalent) and, liquid water is rare across much of the landscape for most of the year and represents the primary limitation to biological activity. Snow delivered off the polar plateau by drainage winds, dew and humidity provided by clouds and fog are important water sources for rock inhibiting crustose lichens. In addition, the combination of the extremely low humidity and drying caused by foehn winds, confined to lower areas of the valleys, with colder and moister air at higher altitudes creates a strongly improving water availability gradient with elevation.We investigated the diversity and interaction specificity of myco-/photobiont associations of a total of 232 crustose lichen specimens, collected along an elevational gradient (171-959 m a.s.l.) within the McMurdo Dry Valleys with regard to the spatial distribution caused by climatological and geographical factors. For the identification of the mycobiont and photobiont species three markers each were amplified (nrITS, mtSSU, RPB1 and nrITS, psbJ-L, COX2, respectivley). Elevation, associated with a water availability gradient, turned out to be the key factor explaining most of the distribution patterns of the mycobionts. Pairwise comparisons showed Lecidea cancriformis and Rhizoplaca macleanii to be significantly more common at higher, and Carbonea vorticosa and Lecidea polypycnidophora at lower, elevations. Lichen photobionts were dominated by the globally distributed Trebouxia OTU, Tr_A02 which occurred at all habitats. Network specialization resulting from mycobiont-photobiont bipartite network structure varied with elevation and associated abiotic factors.Along an elevational gradient, the spatial distribution, diversity and genetic variability of the lichen symbionts appear to be mainly influenced by improved water relations at higher altitudes.

scholarly journals Spatial Distribution of Cholesterol in Lipid Bilayers

2019 ◽  
Author(s):  
M. Aghaaminiha ◽  
S. Sharma
Keyword(s):  
Spatial Distribution ◽  
Phase Behavior ◽  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Structural Integrity ◽  
Hydrophobic Interactions ◽  
Experimental Studies ◽  
Molecular Simulations ◽  
Cholesterol Concentration ◽  
Strongly Correlated

1.AbstractWe have performed molecular simulations to study spatial distribution and orientation of cholesterol molecules within three symmetric lipid bilayer systems: two binary lipid mixtures, namely, DOPC/CHOL (1, 2-dioleoyl-sn-glycero-3-phosphocholine/cholesterol) and SM/CHOL (d20:1/20:0 sphingomyelin /Cholesterol), and a tertiary mixture of DOPC/SM/CHOL. We have studied the behavior of these bilayers at temperatures varying from 400 K to 210 K and cholesterol molar concentration from 0% to 60%.We observe that the spatial distribution of cholesterol is strongly correlated with the phase of the bilayer. In the disordered phase, cholesterol molecules are predominantly present near the center of the bilayer. In the ordered phase, cholesterol molecules are mainly present in the leaflets. At the order - disorder transition temperature, the fraction of cholesterol molecules is equal in the two leaflets and the center. In the leaflets, cholesterol molecules are oriented parallel to the bilayer normal, while near the center, cholesterol molecules are randomly oriented. In agreement with previous experimental studies, we find that increasing the cholesterol concentration favors ordered phase of the bilayers. The preference of cholesterol molecules to be present in the leaflets in the ordered phase is attributed to their favorable hydrophobic interactions with the lipid tails.2.Statement of SignificanceCholesterol has an important role in governing the physical properties of lipid bilayers, including their structural integrity, phase behavior and permeability. The spatial distribution of cholesterol in lipid bilayers is not well-understood because of the challenges associated with performing experiments for such a measurement. We show, via molecular simulations, that the spatial distribution of cholesterol molecules is strongly correlated with the phase behavior of the lipid bilayers. In the ordered phase, cholesterol molecules are predominantly present in the leaflets, whereas in the disordered phase, cholesterol molecules are in the center region of the bilayer. These results are important for understanding the relationship between lipid bilayer composition and their biological function and response.

scholarly journals Sensitivity of the Spatial Distribution of Fixations to Variations in the Type of Task Demand and Its Relation to Visual Entropy

2021 ◽  
Vol 15 ◽  
Author(s):  
Piero Maggi ◽  
Francesco Di Nocera
Keyword(s):  
Spatial Distribution ◽  
Adaptive Systems ◽  
Mental Workload ◽  
Experimental Studies ◽  
Transportation Systems ◽  
Task Demands ◽  
Entropy Rate ◽  
Mental Demand ◽  
Visual Spatial ◽  
Different Types

Ocular activity is known to be sensitive to variations in mental workload, and recent studies have successfully related the distribution of eye fixations to the mental load. This study aimed to verify the effectiveness of the spatial distribution of fixations as a measure of mental workload and its sensitivity to different types of demands imposed by the task: mental, temporal, and physical. To test the research hypothesis, two experimental studies were run: Experiment 1 evaluated the sensitivity of an index of spatial distribution (Nearest Neighbor Index; NNI) to changes in workload. A sample of 30 participants participated in a within-subject design with different types of task demands (mental, temporal, physical) applied to Tetris game; Experiment 2 investigated the accuracy of the index through the analysis of 1-min epochs during the execution of a visual-spatial task (the “spot the differences” puzzle game). Additionally, NNI was compared to a better-known ocular mental workload index, the entropy rate. The data analysis showed a relation between the NNI and the different workload levels imposed by the tasks. In particular: Experiment 1 demonstrated that increased difficulty, due to higher temporal demand, led to a more dispersed pattern with respect to the baseline, whereas the mental demand led to a more grouped pattern of fixations with respect to the baseline; Experiment 2 indicated that the entropy rate and the NNI show a similar pattern over time, indicating high mental workload after the first minute of activity. That suggests that NNI highlights the greater presence of fixation groups and, accordingly, the entropy indicates a more regular and orderly scanpath. Both indices are sensitive to changes in workload and they seem to anticipate the drop in performance. However, the entropy rate is limited by the use of the areas of interest, making it impossible to apply it in dynamic contexts. Conversely, NNI works with the entire scanpath and it shows sensitivity to different types of task demands. These results confirm the NNI as a measure applicable to different contexts and its potential use as a trigger in adaptive systems implemented in high-risk settings, such as control rooms and transportation systems.

scholarly journals Modeling of magnetic fields and signals of a ferromagnetic pipe flaw detector induced by a through hole defect

2020 ◽  
Vol 100 (4) ◽  
pp. 49-56
Author(s):  
A.E. Goldshtein ◽  
◽  
V.Yu. Belyankov ◽  
Keyword(s):  
Spatial Distribution ◽  
Numerical Model ◽  
Magnetic Fields ◽  
Magnetic Induction ◽  
Experimental Studies ◽  
Electrical Signal ◽  
Flaw Detector ◽  
Pipe Surface ◽  
Induction Transducer ◽  
Through Hole

A numerical model has been developed for interaction of the magnetizing field of a short solenoid with a ferromagnetic pipe exhibiting a through hole in the wall, which takes into account nonlinear magnetic properties of the test object. This model was used to calculate spatial distribution of magnetic induction in the pipe wall and spatial distribution of the components of the magnetic induction vector near the pipe surface with a through hole. The validity of the numerical model was confirmed by physical modeling results. The results of theoretical and experimental studies were used to develop a simplified analytical model that describes behavior of the magnetic field of the defect and the electrical signal of the induction transducer of a magnetic flaw detector that implements the method of magnetic flux leakage. It is shown that the dependence of the signal of the induction transducer induced by the through hole on the gap is close to a linear one, and its dependence on the hole diameter is close to a quadratic one. The results obtained in the study can be used for creation, numerical modeling and measurement of magnetic fields.

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