Spark Plasma Sintering Bulk Sm2 Fe17NxMagnets

High performance Sm2Fe17Nx magnetic powders were fabricated by ball-milling method and were compacted using spark plasma sintering(SPS) technique.Effects of processing conditions on the magnetic properties and decomposition dynamic of the magnets were investigated.It is found that higher sintering temperature improves the densification of the magnets, while deteriorates their magnetic properties simultaneously due to the decomposition of the Sm2Fe17Nx.Sintering at lower temperature can preserve the crystal structure of Sm2Fe17Nx compound, while the powders cannot be consolidated into a fully dense compact.An increased compressive pressure leads to better magnetic properties and higher density for the magnet at the same sintering temperature.     

Facile Synthesis and Proposed Mechanism of α,ω‐Oxetanyl-Telechelic Poly(3-nitratomethyl-3-methyl oxetane) by an SN2(i) Nitrato Displacement Method in Basic Media

The synthesis of a novel heterocyclic–telechelic polymer, α,ω-oxetanyl-telechelic poly(3-nitratomethyl-3-methyl oxetane), is described. Infrared spectroscopy (IR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) spectroscopy have been used to confirm the successful synthesis, demonstrating the presence of the telechelic-oxetanyl moieties. Synthesis of the terminal functionalities has been achieved via displacement of nitrato groups, in a manner similar to that employed with other leaving groups such as azido, bromo, and nitro, initiated by nucleophiles. In the present case, displacement occurs on the ends of a nitrato-functionalized polymer driven by the formation of sodium nitrate, which is supported by the polar aprotic solvent N,N-dimethyl formamide. The formation of an alkoxide at the polymer chain ends is favored and allows internal back-biting to the nearest carbon bearing the nitrato group, intrinsically in an S_N2(i) reaction, leading to α,ω-oxetanyl functionalization. The telechelic-oxetanyl moieties have the potential to be cross-linked by chemical (e.g., acidic) or radiative (e.g., ultraviolet) curing methods without the use of high temperatures, usually below 100°C. This type of material was designed for future use as a contraband simulant, whereby it would form the predominant constituent of elastomeric composites comprising rubbery polymer with small quantities of solids, typically crystals of contraband substances, such as explosives or narcotics. This method also provides an alternative approach to ring closure and synthesis of heterocycles.     

α-溴化芳香酮合成方法的改进

在氧化铜存在的条件下,以单质溴为溴源,芳香酮可有效地转化成相应的α-溴代酮,所有产物结构都通过了核磁共振氢谱的表征。     

Identification of Natural Products as Potential Pharmacological Chaperones for Protein Misfolding Diseases

Defective protein folding and accumulation of misfolded proteins is associated with neurodegenerative, cardiovascular, secretory, and metabolic disorders. Efforts are being made to identify small-molecule modulators or structural-correctors for conformationally destabilized proteins implicated in various protein aggregation diseases. Using a metastable-reporter-based primary screen, we evaluated pharmacological chaperone activity of a diverse class of natural products. We found that a flavonoid glycoside ( C-10 , chrysoeriol-7-O-β-D-glucopyranoside) stabilizes metastable proteins, prevents its aggregation, and remodels the oligomers into protease-sensitive species. Data was corroborated with additional secondary screen with disease-specific pathogenic protein. In vitro and cell-based experiments showed that C-10 inhibits α-synuclein aggregation which is implicated in synucleinopathies-related neurodegeneration. C-10 interferes in its structural transition into β-sheeted fibrils and mitigates α-synuclein aggregation-associated cytotoxic effects. Computational modeling suggests that C-10 binds to unique sites in α-synuclein which may interfere in its aggregation amplification. These findings open an avenue for comprehensive SAR development for flavonoid glycosides as pharmacological chaperones for metastable and aggregation-prone proteins implicated in protein conformational diseases.     

The dependence of fatigue crack growth on hydrogen in warm-rolled 316 austenitic stainless steel

The fatigue crack growth rate of warm-rolled AISI 316 austenitic stainless steel was investigated by controlling rolling strain and temperature in argon and hydrogen gas atmospheres. The fatigue crack growth rates of warm-rolled 316 specimens tested in hydrogen decreased with increasing rolling temperature, especially 400 °C. By controlling the deformation temperature and strain, the influences of microstructure (including dislocation structure, deformation twins and α′ martensite) and its evolution on hydrogen-induced degradation of mechanical properties were separately discussed. Deformation twins deceased and dislocations became more uniform with the increase in rolling temperature, inhibiting the formation of dynamic α′ martensite during the crack propagation. In the cold-rolled 316 specimens, deformation twins accelerated hydrogen-induced crack growth due to the α′ martensitic transformation at the crack tip. In the warm-rolled specimens, the formation of α′ martensite around the crack tip was completely inhibited, which greatly reduced the fatigue crack growth rate in hydrogen atmosphere.     

Collagen network as the scaffold for spontaneously distributed optical resonators

The idea behind this work was to acquire one dimensional lasing in the Rhodamine 6G dye doped collagen fibers with the control of random lasing phenomenon properties by changing the dye molecular arrangement. We show that a simple manipulation of the dye concentration in biopolymeric fibril matrix bulk and an additional use of α-cyclodextrin (α-CD) molecules determine formation of specific dye aggregates and as a consequence the shift of the random lasing emission wavelength in the desired direction. The analysis of the light transport mean free path in function of the dye and (α-CD) concentration was done with the use of coherent back scattering technique.     

Influence of Composition on Self-toughening and Oxidation Properties of Y-α-Sialons

Y-α-sialon ceramics with different compositions were hot-press sintered. Varying the m or n value in theα-Sialon general formula, both the α-sialon grain morphology and phase assemblages present diversification, therefore, affecting the toughness and hardness. Meanwhile, varying the compositional parameters also influenced the composition and structure of the intergranular glass phase, as well as its oxidation behavior at 1100-1200 ℃. The oxidation of the intergranular phase Mt in the Y-α-sialon ceramics was significantly enhanced with further rising the oxidation temperature to 1300 ℃.     

Response surface optimization of supercritical CO2 extraction of α-tocopherol from gel and skin of Aloe vera and almond leaves

Supercritical fluid extraction (SFE) was studied as an alternative technology in the pharmaceutical industry for the separation of α-tocopherol from gel and skin of Aloe vera and almond leaves. The influence of operating conditions was investigated on the recovery of supercritical carbon dioxide (SC-CO₂) extraction of α-tocopherol from three-year old Aloe vera (Aloe barbadensis Miller) leaf gel. The obtained results were compared with the conventional Soxhlet extraction. Response surface methodology (RSM) was applied to optimize effective variables on the extracted recovery of α-tocopherol. The maximum α-tocopherol recovery of 53.41% from Aloe vera gel was obtained with employing RSM predicted optimal operating conditions of 32 MPa, 45.91 °C, 0.84 ml SC-CO₂/min and 140 min for extraction. The α-tocopherol extraction yield for gel and skin of Aloe vera and almond leaves at these optimal operating conditions were obtained 1.53, 16.29 and 2.61 mg/100 g dry sample, respectively.     

Friction and wear properties of high-velocity oxygen fuel sprayed WC-17Co coating under rotational fretting conditions

Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed(HVOF) technique WC-17 Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope(SEM), energy dispersive X-ray spectroscopy(EDX), and X-ray diffractrometry(XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy(OM), and surface topography. The experimental results reveal that the WC-17 Co coating adjusted the boundary between the partial slip regime(PSR) and the slip regime(SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17 Co coating in prevention of rotational fretting wear.