Molecular mobility in bulk and in near-surface nano-layers of ultra-high-molecular-weight polyethylene

A comparative study of molecular dynamics in near-surface nanolayers and in a bulk of polyethylene is presented. Molecular mobility in near-surface nanolayers of polyethylene reactor powders and melt-crystallized films of various molecular weights prepared in different crystallization conditions were studied with the help of thermoluminescence technique using high frequency glow dicharge Ar plasma for surface activation. Molecular mobility in a bulk of the same samples was investigated by the method of radio thermoluminescence, in which a deeply penetrating γ-quanta from 60Co radiation was used for activation of the bulk. A marked difference in a temperature position of the peaks on the glow curves of plasma-induced thermoluminescence and those of radiothermoluminescence correspoding to γ- and ß-transitions was found to depend on crystallisation conditions and molecular weight. Quasi-independent segmental mobility (ß-relaxation) in the near-surface nano-layers of UHMWPE reactor powder particles synthesized at low temperatures appeared to be unexpectedly unfreezed at the temperature higher than that in the bulk. It was supposed that this happend because of crystallization under the confinement conditions during low-temperature polymerization leads to formation of a specific surface structure.

Petrology of Granitoids of the Selennyakh Ridge (Verkhoyansk-Kolyma Orogenic Belt)

The Verkhoyansk-Kolyma orogenic belt is characterized by intense Late Mesozoic granitoid magmatism. Numerous granitoids plutons form longitudinal belts, elongated parallel to the boundaries of major tectonic structures (Main and Northern), and transverse belts, oriented across or at an angle to them. The Main belt is dominated by massifs of granodiorite-granite composition, accompanied by tin-tungsten, boron-tin, and gold mineralization of various scale. Therefore, understanding their petrological and genetic characteristics and crystallization conditions leading to the generation of mineralization is of not only theoretical but also practical interest. The aim of the research was a detailed study of petrography, geochemical features and crystallization conditions of granodiorite-granite massifs of the Selennyakh block of the Omulevka terrane of the Kolyma-Omolon microcontinent that forms part of the Verkhoyansk-Kolyma orogenic belt. It was found that the formation of granitoids took place in an active continental margin setting and was long-term and complex. During the evolution of magmatism, the homodrome character of development (granodiorites → granites → leucogranites and aplites) was replaced by the antidrome one (granite-porphyries and granodiorite-porphyries). The Rb-Sr isotopic age of the rocks varies from 136 to 122 Ma. The generation of the parent melts for the granitoid massifs occurred within the lower crust at the boundary between amphibolite and dacite-tonalite substrates at temperatures of 1070–990° C and a pressure of 1.1–0.9 GPa. These parameters are comparable to those of the melt that formed the granodiorite-porphyry dikes: 990° C and 0.94 GPa. Maintaining high temperatures of the melt formation from initial to final derivatives at deeper levels of the magma chamber with a simultaneous increase in their fluid saturation requires the supply of juvenile heat and fluids. The main mineral in the territory is tin. The formation of mineralization is associated with late fluid-saturated derivatives of the granitoid melt. During the crystallization of leucogranites and pegmatites, fluorine was the main Sn-extracting agent. With depth, in the course of crystallization of granite and granodiorite porphyries, boron and then sulfur became the major extractants of tin.

Novel Device and Strategy for Growing Large, High-Quality Protein Crystals by Controlling Crystallization Conditions

Neutron diffraction experiments are informative for determining the locations of hydrogen atoms in protein molecules; however, much larger crystals are needed than those required for X-ray diffraction. Thus, additional techniques are required to grow larger crystals. Here, a unique crystallization device and strategy for growing large protein crystals are introduced. The device uses two micropumps to control crystal growth by altering the precipitant concentration and regulating the pinpoint injection of dry air flow to the crystallization cell. Furthermore, the crystal growth can be observed in real time. Preliminary microbatch crystallization experiments at various concentration ranges of polyethylene glycol (PEG) 4000 and sodium chloride were first performed to elucidate optimized crystallization conditions. Based on these results, a device to precisely control the sodium chloride and PEG concentrations and the supply of dry air to the crystallization cell was used, and 1.8 mm lysozyme and 1.5 mm alpha-amylase crystals with good reproducibility were obtained. X-ray data sets of both crystals were collected at room temperature at BL2S1 of the Aichi Synchrotron Radiation Center and confirmed that these crystals were of high quality. Therefore, this crystallization device and strategy were effective for growing large, high-quality protein crystals.

Fully Biodegradable Poly(hexamethylene succinate)/Cellulose Nanocrystals Composites with Enhanced Crystallization Rate and Mechanical Property

Through a common solution and casting method, low contents of cellulose nanocrystals (CNC) reinforced biodegradable poly(hexamethylene succinate) based composites were successfully prepared for the first time. CNC homogeneously dispersed in PHS matrix at low loadings, showing no obvious aggregation. PHS/CNC composites showed high thermal stability as PHS. As a heterogeneous nucleating agent, CNC promoted the crystallization of PHS under both nonisothermal and isothermal crystallization conditions. In addition, the higher the CNC content, the faster the crystallization of PHS/CNC composites. The heterogeneous nucleating agent role of CNC was directly confirmed by the crystalline morphology study; moreover, the crystal structure of PHS remained unmodified despite the presence of CNC. As a reinforcing nanofiller, CNC also improved the mechanical property of PHS, especially the Young’s modulus and yield strength. In brief, low contents of CNC may improve both the crystallization and mechanical property of PHS, providing an easy method to tune the physical property and promote the wider application of biodegradable polymers.

A new clinopyroxene thermobarometer for mafic to intermediate magmatic systems

Clinopyroxene-only thermobarometry is one of the most practical tools to reconstruct crystallization pressures and temperatures of clinopyroxenes. Because it does not require any information of coexisting silicate melt or other co-crystallized mineral phases, it has been widely used to elucidate the physiochemical conditions of crystallizing magmas. However, previously calibrated clinopyroxene-only thermobarometers display low accuracy when being applied to mafic and intermediate magmatic systems. Hence, in this study, we present new empirical nonlinear barometric and thermometric models, which were formulated to improve the performance of clinopyroxene-only thermobarometry. Particularly, a total of 559 experimental runs conducted in the pressure range of 1 bar to 12 kbar have been used for calibration and validation of the new barometric and thermometric formulation. The superiority of our new models with respect to previous ones was confirmed by comparing their performance on 100 replications of calibration and validation, and the standard error of estimate (SEE) of the new barometer and thermometer are 1.66 kbar and 36.6 ∘C, respectively. Although our new barometer and thermometer fail to reproduce the entire test dataset, which has not been used for calibration and validation, they still perform well on clinopyroxenes crystallized from subalkaline basic to intermediate magmas (i.e., basaltic, basalt-andesitic, dacitic magma systems). Thus, their applicability should be limited to basaltic, basalt-andesitic and dacitic magma systems. In a last step, we applied our new thermobarometer to several tholeiitic Icelandic eruptions and established magma storage conditions exhibiting a general consistency with phase equilibria experiments. Therefore, we propose that our new thermobarometer represents a powerful tool to reveal the crystallization conditions of clinopyroxene in mafic to intermediate magmas.

Thermo-barometric constraints on the Mt. Etna 2015 eruptive event

The petrological study of volcanic products emitted during the paroxysmal events of December 2015 from the summit craters of Mount Etna allow us to constrain T-P-XH2O phase stability, crystallization conditions, and mixing processes along the main open-conduit feeding system. In this study, we discuss new geochemical, thermo-barometric data and related Rhyolite-MELTS modelling of the eruptive activity that involved the concomitant activation of all summit craters. The results, in comparison with the previous paroxysmal events of the 2011–2012, reinforce the model of a vertically extended feeding system and highlight that the activity at the New South-East Crater was fed by magma residing at a significantly shallower depth with respect to the Central Craters (CC) and North-East Crater (NEC), even if all conduits were fed by a common deep (P = 530–440 MPa) basic magmatic input. Plagioclase dissolution, resorption textures, and the Rhyolite-MELTS stability model corroborate its dependence on H2O content; thus, suggesting that further studies on the effect that flushing from fluids with different H2O/CO2 ratio are needed to understand the eruption-triggering mechanisms for high energetic strombolian paroxysmal episodes.

Ionic Liquids as Protein Crystallization Additives

Among its attributes, the mythical philosopher’s stone is supposedly capable of turning base metals to gold or silver. In an analogous fashion, we are finding that protein crystallization optimization using ionic liquids (ILs) often results in the conversion of base protein precipitate to crystals. Recombinant inorganic pyrophosphatases (8 of the 11 proteins) from pathogenic bacteria as well as several other proteins were tested for optimization by 23 ILs, plus a dH2O control, at IL concentrations of 0.1, 0.2, and 0.4 M. The ILs were used as additives, and all proteins were crystallized in the presence of at least one IL. For 9 of the 11 proteins, precipitation conditions were converted to crystals with at least one IL. The ILs could be ranked in order of effectiveness, and it was found that ~83% of the precipitation-derived crystallization conditions could be obtained with a suite of just eight ILs, with the top two ILs accounting for ~50% of the hits. Structural trends were found in the effectiveness of the ILs, with shorter-alkyl-chain ILs being more effective. The two top ILs, accounting for ~50% of the unique crystallization results, were choline dihydrogen phosphate and 1-butyl-3-methylimidazolium tetrafluoroborate. Curiously, however, a butyl group was present on the cation of four of the top eight ILs.