Revisiting hotspots and continental breakup—Updating the classical three-arm model

ABSTRACT Classic models proposed that continental rifting begins at hotspots—domal uplifts with associated magmatism—from which three rift arms extend. Rift arms from different hotspots link up to form new plate boundaries, along which the continent breaks up, generating a new ocean basin and leaving failed arms, termed aulacogens, within the continent. In subsequent studies, hotspots became increasingly viewed as manifestations of deeper upwellings or plumes, which were the primary cause of continental rifting. We revisited this conceptual model and found that it remains useful, though some aspects require updates based on subsequent results. First, the rift arms are often parts of boundaries of transient microplates accommodating motion between the major plates. The microplates form as continents break up, and they are ultimately incorporated into one of the major plates, leaving identifiable fossil features on land and/or offshore. Second, much of the magmatism associated with rifting is preserved either at depth, in underplated layers, or offshore. Third, many structures formed during rifting survive at the resulting passive continental margins, so study of one can yield insight into the other. Fourth, hotspots play at most a secondary role in continental breakup, because most of the associated volcanism reflects plate divergence, so three-arm junction points may not reflect localized upwelling of a deep mantle plume.

Devising a method to parametrize the jacket style varieties through the modification of tіpological series structures

The study reported here has revealed the issue related to the inefficient scaling of the uniformity of jacket model designs in the processes involving a typical representative as a result of modification parameters uncertainty. A variant has been proposed to synchronize the critical points of silhouetted allowances by grouping the numeric series in the vector of choosing the value for an increase in the allowance according to the characteristics of style varieties. The influence of shape-forming segmentation on the formation of a classifier of the structural and technological solutions for a jacket has been determined. The built model to support modification vectors has made it possible to describe the sequence of procedures execution by the method of typical representation. The presence of one design category, the same structural parts, the uniformity of style simplifies the processes of choosing and selecting the most characteristic models of the jacket. It was found that the morphological combination of attributes of the physical appearance affects the adjustment of style preferences in a manufacturer’s products. The parameters for typical segmentation relative to the junction points of the structural zones of the optimized five-seam prototype design have been defined as the most influential vectors of jacket modification. A method for scaling the allowance for free fitting has been devised on the basis of data from empirical research. An adequate regression model has been derived for normalizing the silhouette allowance parameters. The constructed model makes it possible to scale silhouette structures by changing the increments at the corner points of the contour according to the prototype of gradation under an automated mode. Practical recommendations have been compiled on the parameters of zonal-modular modification of silhouette designs of jacket varieties: a linear character of the state silhouetted transformation relative to ASi1=5 cm. The normalized parameters for constructing functional and decorative parts have been proposed

Oxidation or dehydrogenation of alpha-hydroxy acids in bioenergetic metabolism: A murburn perspective

Glycolate, lactate, malate, hydroxyglutarate and isocitrate are key alpha-hydroxyacyl metabolic intermediates found in the tissues/cells/organelles of diverse life forms. They are respectively oxidized to glyoxylate, pyruvate, oxaloacetate, ketoglutarate and oxalosuccinate in cell bioenergetic metabolism. These molecules form key junction points for divergent pathways of two to six carbon-backboned molecules (of various classes of biomolecules like carbohydrates, amino acids, etc.). The oxido-reduction of the alpha-hydroxyacyl species is traditionally believed to be carried out by reversible (de)hydrogenases, employing nicotinamide cofactors. Herein, I propose that while the reductive pathway can be mediated in a facile manner by the (de)hydrogenases, the oxidative reaction could more efficiently be coupled with murzyme activities, which employ diffusible reactive (oxygen) species (DRS/DROS/ROS). Such a murburn strategy would enable the system to tide over the highly unfavorable energy barriers of the sequential dehydrogenase reaction (~450 kJ/mol, or more!), to give kinetically viable bimolecular reactions catering to cellular needs. Further, such a scheme does not necessitate any ‘intelligent governance’ or ‘smart decision-making’ of/by the pertinent redox enzymes.

Revisiting Hotspots and Continental Breakup – Updating the Classical Three-arm Model

<p>In two classic papers, Burke and Dewey (1973) and Dewey and Burke (1974) proposed that continental rifting begins at hotspots - domal uplifts with associated magmatism - from which three rift arms extend. Rift arms from different hotspots link up to form new plate boundaries along which the continent breaks up, generating a new ocean basin and leaving failed arms termed aulacogens within the continent.  In subsequent studies, hotspots became increasingly viewed as manifestations of deeper upwellings or plumes, which were the primary cause of continental rifting. We revisit this conceptual model and find that it remains useful, though some aspects require updates based on subsequent results.  Many three-arm systems identified by Burke and Dewey (1973) are now recognized to be or have been boundaries of transient microplates accommodating motion between diverging major plates. Present-day examples include the East African Rift system and the Sinai microplate.  Older examples include rifts associated with the opening of the South Atlantic in the Mesozoic and the North Atlantic Ocean over the last 200 Ma,  rifts in the southern U.S associated with the breakup of Rodinia, and intracontinental rifts formed within India during the breakup of Gondwanaland. The microplates form as continents break up, and are kinematically distinct from the neighboring plates, in that they move separately. Ultimately, the microplates are incorporated into one of the major plates, leaving identifiable fossil features on land and/or offshore. In many cases the boundaries of microplates during continental breakup are located on preexisting zones of weakness and influenced by pre-existing fabric, including older collisional zones. Hotspots play at most a secondary role in continental breakup, in that most of the associated volcanism reflects plate divergence, so three-arm junction points may not reflect localized upwelling of a deep  mantle plume.</p>

A Novel Composite with Structural Health Monitoring Functionality via 2D and 3D Impedance Mapping Topography

We report the transformation of a conventional composite material into a multifunctional structure able to provide information about its structural integrity. A purposely positioned grid of carbon fabric strips located within a glass fibre laminate in alternating 0/90 configuration combined with a ternary nanomodified epoxy matrix imparted structural health monitoring (SHM) topographic capabilities to the composite using the impedance spectroscopy (IS) technique. The matrix was reinforced with homogenously dispersed multi-walled carbon nanotubes (MWCNTs) and carbon black (CB). A sinusoidal electric field was applied locally over a frequency range from 1 Hz to 100 kHz between the junction points of the grid of carbon fabric strips. The proposed design enabled topographic damage assessment after a high-velocity impact via the local monitoring of the impedance. The data obtained from the IS measurements were depicted by magnitude and phase delay Bode plots and Nyquist plots. The impedance values were used to create a 2D and a multi-layer (3D) contour topographical image of the damaged area, which revealed crucial information about the structural integrity of the composite.

Visual-Motor Perception and Handwriting Performance of Students with Mixed Subtype Dyslexia

This studyaimed to characterize and compare the visual-motor perception and handwriting performance of students with mixed dyslexia and students with good academic performance. Twenty-six schoolchildren of both sexes participated in this study, aged 9 to 11 years and 11 months old, from fourth and fifth grades of an elementary school in municipal public schools, from an average socioeconomic level, divided into two groups: Group I (GI) composed of 13 students with a multidisciplinary diagnosis of mixed developmental dyslexia and Group II (GII) composed of 13 students with good academic performance from a municipal school and matched according to gender, education, and age to GI. All students in this study were subjected to the application of the following procedures: Developmental Test of Visual Perception III—DTVP-III, Dysgraphia Scale and writing analysis by NeuroScript MovAlyzeR 6.1 software. The results were analyzed statistically using the following tests: Mann-Whitney test, Wilcoxon signed-rank test, and Friedman test, aiming to verify intragroup and intergroup differences for the variables of interest in the DTVP-III, the Dysgraphia Scale, and the measures of handwriting speed and pressure by the MovAlyzeR software. The results were analyzed statistically at a significance level of 5% (0.050). The results showed that there were statistically significant differences between GI and GII in the parameters of the Dysgraphia Scale, floating lines, irregular spaces between words, junction points, sudden movements, and dimension irregularities. GII showed a superior performance in relation to GI in the variables analyzed with the DTVP-III in visual-motor integration, reduced motricity perception, and general visual perception. There was no statistically significant difference between GI and GII in the variables analyzed by the MovAlyzeR software. The results of this study allowed us to conclude that students with mixed dyslexia present a lower performance profile than the students with good academic performance in general visual perception, reduced motricity visual perception, and visual-motor perception skills, which may be the cause of the quality of dysgraphic writing characterized by floating lines, irregular spaces, junction points, sudden movements, and dimension irregularities.

The enhancement of cutting capacity of a grinding wheel when processing ductile steel blank parts by ultrasonic activation

The study aimed to identify the relations between the sticking intensity and ultrasonic vibrations (UV) used for processing and evaluate the wheels’ performance when grinding ductile materials blank parts. The authors carried out the numerical simulation of local temperatures and the 3H3M3F steel workpiece temperature when grinding by ultrasonic activation. The study determined that the application of ultrasonic vibrations with the amplitude of 3 µm causes the decrease in local temperatures by 13…40 %, and in blank part temperature – up to 20 %. The calculation identified that the activation of ultrasonic vibrations with the amplitude of 3 µm causes the decrease in the glazing coefficient by 33 % for cutting grain and by 7 % for deforming grain. When increasing the longitudinal feed rate or the grinding depth, the glazing coefficient increases to a lesser degree when using the ultrasonic vibration than in the case without ultrasonic activation. The authors carried out the numerical simulation of local temperatures when scratching the 3H3M3F steel specimens by single abrasive grains with ultrasonic activation. The sticking deformation and the stresses resulted from this deformation and affecting the junction points of sticking with grains with and without ultrasonic vibrations application are calculated. The experimental research included the micro-cutting of specimens with single abrasive grains. The experiments identified that the abrasive grains wear out and glaze to a lesser degree when micro-cutting a workpiece with ultrasonic vibrations activation. The lowering of the intensity of sticking of the workpiece material particles to the abrasive grains due to the adhesion causes the decrease in the glazing coefficient when using ultrasonic activation. The study considered the possibility to enhance the efficiency of flat grinding through the use of the energy of ultrasonic vibrations applied to a blank part in the direction with the grinding wheel axis. A workpiece fixed in the device between the vibration transducer and the support is one of the components of a vibration system. The authors performed the experiment when grinding 3H3M3F and 12H18N10T steel workpieces with the wheel face. When grinding with ultrasonic vibrations, the grinding coefficient increases up to 70 %, and the redress life increases twice or thrice.

Simulation of heat transfer at the junction of the attic floor to the building envelope

Numerous studies and thermal imaging inspection of multi-storey residential buildings indicate characteristic places with increased heat loss. In houses built in accordance with modern domestic regulatory requirements for the thermal resistance of enclosing structures, the actual thermal resistance of walls and windows coincides with the standard. However, nodes of elements of external enclosing structures with increased values of heat loss were found. Insulation of the junction points allows increasing the thermal resistance of the external enclosing structures. In order to increase the energy efficiency of a building, the design of the insulation of the junction of the ceiling in the technical attic has been proposed, which is protected by a patent for a useful model. The linear heat transfer coefficients of the junction point of the ceiling in the attic are analyzed. It was revealed that such information was not indicated in the regulatory documents. Reducing heat loss is achieved by arranging additional layers of insulation in the form of aerogel slabs at the junction of the ceiling to the external enclosing structures. The analysis of the energy efficiency of the proposed design of the junction unit of the attic floor as a "cold bridge" was carried out according to the results of mathematical modeling in the DAMWERK software package. Based on the simulation results, the temperature distribution in the junction of the ceiling in the technical attic was established. The linear heat transfer coefficient of the recommended junction point of the ceiling in the technical attic has been determined, the value of which should be taken into account when developing the Energy Efficiency section. The results obtained confirm the feasibility of introducing the proposed structural design of the floor abutment unit in the technical attic, which will improve the energy efficiency of the building's thermal insulation envelope.

Dendrons and Dendritic Terpolymers: Synthesis, Characterization and Self-Assembly Comparison

To the best of our knowledge, this is the very first time that a thorough study of the synthetic procedures, molecular and thermal characterization, followed by structure/properties relationship for symmetric and non-symmetric second generation (2-G) dendritic terpolymers is reported. Actually, the synthesis of the non-symmetric materials is reported for the first time in the literature. Anionic polymerization enables the synthesis of well-defined polymers that, despite the architecture complexity, absolute control over the average molecular weight, as well as block composition, is achieved. The dendritic type macromolecular architecture affects the microphase separation, because different morphologies are obtained, which do not exhibit long range order, and various defects or dislocations are evident attributed to the increased number of junction points of the final material despite the satisfactory thermal annealing at temperatures above the highest glass transition temperature of all blocks. For comparison reasons, the initial dendrons (miktoarm star terpolymer precursors) which are connected to each other in order to synthesize the final dendritic terpolymers are characterized in solution and in bulk and their self-assembly is also studied. A major conclusion is that specific structures are adopted which depend on the type of the core connection between the ligand and the active sites of the dendrons.

Selection criteria and a mathematical model for the additional source of reactive power in a backbone network

In a backbone network (𝑈􀯡 ≥ 220 𝑘𝑣), when the high-voltage lines are loaded with power less than natural power, we have excess reactive power. Supplying this power into the lower-voltage networks (𝑈􀯡 ≤ 110 𝑘𝑣) would be technically and economically unfeasible and requires compensation on site. In the article, in accordance with the electricity quality criterion, and taking into account the principle of a systemic approach, and using the self- and mutually reactive impedances of the network junction points, a mathematical model for selecting a compensating device in a backbone network is adopted. The quality criterion of electricity involves enforcement of requirements for the operating voltages in the junction points of a backbone network. According to the obtained mathematical model, in the junction points nodes where the operating voltages exceed their permitted values, there will be installed the compensating devices for receiving excess reactive power. However if any junction point has a high reactive load and the voltage, in this context, is below its permitted value, then, according to a model, there is a need for installing the source of reactive power in this junction point. Herewith, according to economic criterion, the model envisages the optimal redistribution of mentioned source of reactive power between the junction points of a distribution network connected to backbone network junction point.