Experimental evidence on the origin of Ca-rich carbonated melts formed by interaction between sedimentary limestones and mantle-derived ultrabasic magmas

In this experimental study, we documented the formation of strongly ultrabasic and ultracalcic melts through the interaction of melilititic and basanitic melts with calcite. Three strongly to moderately SiO2-undersaturated volcanic rocks from the Bohemian Massif (central Europe) were mixed with 10, 30, and 50 wt% CaCO3 and melted at 1100, 1200, and 1300 °C at 2 kbar to evaluate the maximum amount of carbonate that can be assimilated by natural ultrabasic melts at shallow depths. Experiments revealed a surprisingly complete dissolution of the CaCO3, only rarely reaching carbonate saturation, with typical liquidus phases represented by olivine, spinel, melilite, and clinopyroxene. Only in the runs with the most SiO2-undersaturated compositions did abundant monticellite form instead of clinopyroxene. For all starting mixtures, strongly ultrabasic (SiO2 down to 15.6 wt%), lime-rich (CaO up to 43.6 wt%), ultracalcic (CaO/Al2O3 up to ~27) melt compositions were produced at 1200 and 1300 °C, with up to ~25 wt% dissolved CO2. When present, quenched olivine showed much higher forsterite content (Fo95–97) than olivine in the natural samples (Fo79–85). The two major results of this study are (1) silicate-carbonatite melt compositions do not necessarily imply the existence of carbonatitic components in the mantle, because they are also produced during limestone assimilation, and (2) Fo-rich olivines cannot be used to infer any primitive character of the melt nor high potential temperature (Tp).

Influence of the Small Sc and Zr Additions on the As-Cast Microstructure of Al–Mg–Si Alloys with Excess Silicon

This research is devoted to the study effects of complex alloying of Al-0.3 wt.% Mg-1 wt.% Si and Al-0.5 wt.% Mg-1.3 wt.% Si alloys by small additions of Sc and Zr on the microstructure in the as-cast condition. The effect of small additions of these elements on the microhardness, electrical conductivity, grain size and phase composition of the indicated alloy systems was studied. The methods of optical and electron microscopy were used for the study. Moreover, the phase composition was calculated using the Thermo-Calc software package. The study showed a strong effect of the chemical composition of investigated alloys on the size of the grains, which, with a certain combination of additives, can decrease several times. Grain refinement occurs both due to supercooling and formation of primary Al3Sc particles in the liquid phase. Alloys based on Al-0.5 wt.% Mg-1.3 wt.% Si are more prone to the formation of this phase since a lower concentration of Sc is required for it to occur. In addition, more silicon interacts with other elements. At the same time, Al-0.3 wt.% Mg-1 wt.% Si requires lower temperature for complete dissolution of Mg2Si, which can contribute to more efficient heat treatment, which includes reducing the number of steps. TEM data show that during ingot cooling (AlSi)3ScZr dispersoid precipitates. This dispersoid could precipitate as coherent and semi-coherent particles with L12 structure as well as needle-shaped particles. The precipitation of coherent and semi-coherent particles during cooling of the ingot indicates that they can be obtained during subsequent multistage heat treatment. In addition, in the Al0,5Mg1,3Si0,3Sc alloy, metastable β’’ (Mg5Si6) are precipitated.

Multiple motors cooperate to establish and maintain acentrosomal spindle bipolarity in C. elegans oocyte meiosis

ABSTRACTWhile centrosomes organize spindle poles during mitosis, oocyte meiosis can occur in their absence. Spindles in human oocytes frequently fail to maintain bipolarity and consequently undergo chromosome segregation errors, making it important to understand mechanisms that promote acentrosomal spindle stability. To this end, we have optimized the auxin-inducible degron system in C. elegans to remove factors from pre-formed oocyte spindles within minutes and assess effects on spindle structure. This approach revealed that dynein is required to maintain the integrity of acentrosomal poles; removal of dynein from bipolar spindles caused pole splaying, and when coupled with a monopolar spindle induced by depletion of kinesin-12 motor KLP-18, dynein depletion led to a complete dissolution of the monopole. Surprisingly, we went on to discover that following monopole disruption, individual chromosomes were able to reorganize local microtubules and re-establish a miniature bipolar spindle that mediated chromosome segregation. This revealed the existence of redundant microtubule sorting forces that are undetectable when KLP-18 and dynein are active. We found that the kinesin-5 family motor BMK-1 provides this force, uncovering the first evidence that kinesin-5 contributes to C. elegans meiotic spindle organization. Altogether, our studies have revealed how multiple motors are working synchronously to establish and maintain bipolarity in the absence of centrosomes.

Inversion of Nitrogen Redistribution in Austenitic Steel by Severe Plastic Deformation

Using the Mössbauer spectroscopy and transmission electron microscopy (TEM) methods, the temperature boundary of a strain-induced transformation with the inversion of the direction of nitrogen redistribution is determined in the structure of the FeMn22Cr18N0.83 austenitic steel. Deformation by high pressure torsion in Bridgman anvils below the temperature limit (298 K) leads to an increase in the amount of nitrogen in the interstitial solid solution and deformation above the limit (373 K) leads to a decrease in this value. An increase in the deformation temperature leads to the complete dissolution of the products of cellular decomposition and the formation of submicrocrystalline austenite with secondary nanocrystalline nitrides. Changes in the direction of nitrogen redistribution are explained by the competition between the mechanisms of relaxation of the structure along the paths of dispersion, dissolution of nitrides by dislocation, and decomposition of a solid solution supersaturated with nitrogen.

How to Master Interfaces in MMCs with Reactive Constituents

It is evident that the interface in MMCs plays a crucial role with respect to thermophysical and mechanical properties of the composites. Inert systems like copper/carbon or silver/carbon will have low performance due to a very weak bonding between the constituents, whereas in reactive systems like Al/carbon, Fe(Ni)/WC and WC-Co/diamond the interfacial reaction has to be clearly controlled to avoid uncontrolled reactions. Such reactions may lead to partial or even complete dissolution of the phases and thus can have very detrimental impact on properties. In this contribution, we will summarize and present different approaches and recent results to overcome any interfacial problems. This can be either technological parameters like time, temperature, rate of consolidation, contact time in infiltration or inherent parameters like nominal composition, coatings, and surface terminations. It is of general interest to adjust optimal interfacial conditions for each application to achieve ideal properties in the composites.

High speed growth of MAPbBr3 single crystals via low-temperature inverting solubility: enhancement of mobility and trap density for photodetector applications

High-quality CH3NH3PbBr3 hybrid perovskite single crystal growth and outstanding optoelectronic application using the complete dissolution at low temperatures based on low temperature solubility, which has been demonstrated for the first time.

The Problem as a Developmental Resource

The paper presents an attempt to treat psychological problems in their positive function, as a resource for personality development. Life at large may be treated as problem-solving. Conscious and satisfying living is not a problem-free one, but rather the living heading toward the 39 infantile problems toward profound existential and insoluble problems of an adult living which direct one’s path of personal maturation. Any problem begins with a contradiction of two oppositions, and besides straightforward or compromise strategies of resolving the contradiction, an ultimate dialectical solution is also possible through ascending to a broader framework, scheme of things in which the initial contradiction dissolves, ceases to exist anymore. This way of solving the problem is the way of increased understanding and advanced personality development. The author has elaborated a specific group practice of working with participants’ life problems based on the facilitation of experience processing. This Life Enhancement Work allows to identify inner barriers hampering the experience processing, and the participants become able to unveil the solution they have within themselves; the result is either transformation of the problem into a more mature one or its complete dissolution.

Features of induction heating during hardening of tools from high-speed steel

The fundamental differences in the kinetics of transformations of high-speed steels during heating by high-frequency induction currents (HFC) and in salt baths are considered. At HFC, the high temperature at the "carbide — matrix" boundaries promotes more complete dissolution of carbides in austenite, which improves the quality of the tool. Keywords: high frequency current, salt bath, hardening, high speed steel, interphase boundary. [email protected]