Low-molecular weight aliphatic amides as nucleating agents for poly (L-lactic acid): Conformation variation induced crystallization enhancement

a b s t r a c t Two kinds of low molecular weight aliphatic amides, N, N 0 -ethylenebis (12-hydroxystearamide) (EBH) and N, N 0 -ethylenebisstearamide (EBSA), have been selected in present study to mediate the crystallization behavior of poly (L-lactic acid) (PLLA). The results showed that the crystallization rate of PLLA was significantly improved with the addition of EBH and EBSA, and EBH presented a stronger nucleating efficiency. The correlation between the variation of chain conformation during the early stages of isothermal crystallization and the enhancement of crystallization rate for pure PLLA and its mixtures was investigated by time-resolved FTIR. The formation of interchain conformational-ordered structure and intrachain 10 3 helix structure for amide-doped PLLA preceded that for pure PLLA, suggesting a stimulatory nucleating effect of EBH and EBSA. In the case of PLLA/EBH, the interchain interactions of e(COC þ CH 3 ) and eCH 3 groups were faster than the e(CH 3 þCC) intrachain interactions, while the interchain interactions and the intrachain 10 3 helix formation were nearly synchronous for PLLA/EBSA. The hydrogen bond interaction between hydroxyl groups in EBH and the carbonyl groups in PLLA was proposed to be an important factor influencing the conformation variation during isothermal crystallization of PLLA

Interfacial nucleation in iPP/PB-1 blends promotes the formation of polybutene-1 trigonal crystals

The formation of trigonal Form I\ub4 crystals of polybutene-1 (PB-1) directly from melt has drawn much attention in past decades. In this study, we investigate the fractionated crystallization behavior of PB-1 within droplets formed by blending PB-1 with an excess of isotactic polypropylene (iPP) employing DSC, SEM, in situ synchrotron WAXD and FT-IR. When PB-1 is dispersed into a large number of small size droplets, the heterogeneous nucleation of Form II crystals can be inhibited because the number of droplets is larger than that of active nucleation sites for Form II (i.e., active heterogeneities originally present in bulk PB-1). The nucleation of the finely dispersed PB-1 droplets does not occur homogenously, but at the interface with the iPP matrix, which induces the crystallization of the droplets into Form I\ub4. The crystallization rate of Form I\ub4 at different temperatures was determined by Fourier transform infrared spectroscopy. It was found that trigonal Form I\ub4 crystallizes faster when the content of PB-1 in the blend is lower, and the specific interfacial surface area is larger. The opposite effect has been observed for the kinetics of the metastable Form II formation. It is therefore suggested that Form I\ub4 crystallization is driven by the nucleation of PB-1 at the crystalline iPP surface, which competes with the crystallization of Form II induced by nucleating heterogeneities present in PB-1 droplets

Composition dependent miscibility in the crystalline state of polyamide 6 /polyamide 4,10 blends: From single to double crystalline blends

Unformatted preprint version of the submitted articleIn this work, we studied the composition-dependent miscibility of polyamide 6 and biobased polyamide 4,10 (PA6/PA410) blends, as triggered by crystallization driven phase segregation. The blends were prepared by extrusion melt blending in a wide composition range and studied by Differential Scanning Calorimetry (DSC), X-ray diffraction (both in-situ and ex-situ SAXS/WAXS), and Polarized Light Optical Microscopy (PLOM) during non-isothermal crystallization. The blends were found to be miscible in the amorphous state, as demonstrated by a single Tg that follows the Fox equation as a function of composition. The blends were also considered to be miscible in the melt, as no evidence of phase segregation was found by SAXS or phase contrast microscopy in the melt. The miscibility of the blends in the crystalline state is a strong function of composition. When only 10 or 20% PA6 is present in the blends, co-crystallization was evidenced by DSC and WAXS and the blends exhibited a single PA410 rich crystalline phase. On the other hand, as 30% or more PA6 is added to PA410, crystallization driven phase segregation occurs and progressively increased with PA6 content in the blends. Hence double crystalline blends are formed with both PA6 rich and PA410 rich crystalline phases. Clear evidence of either one or two crystalline phases was demonstrated by temperature-dependent measurements employing DSC, PLOM, WAXS and SAXS. Both the single and double crystalline PA6/PA410 blends exhibited good mechanical properties in view of the excellent compatibility displayed by the blends. The mechanical properties are in line with those exhibited by miscible blends following a simple rule of mixtures.We would like to thank the financial support provided by the BIODEST project; this project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 778092. We also thank finantial support from the Basque Government through project IT309-19. G.L., D.W. and A. J. M thank the support from the National Key R&D Program of China (2017YFE0117800) and the National Natural Science Foundation of China (51820105005). I. Otaegi acknowledges the grant awarded by the Basque Government. G.L. is grateful to the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Y201908). The POLYMAT/UPV/EHU team acknowledge funding from ALBA synchrotron facility through granted proposal number: 2018093081 (March 2019)

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

A Sampling-Based Method for Highly Efficient Privacy-Preserving Data Publication

The data publication from multiple contributors has been long considered a fundamental task for data processing in various domains. It has been treated as one prominent prerequisite for enabling AI techniques in wireless networks. With the emergence of diversified smart devices and applications, data held by individuals becomes more pervasive and nontrivial for publication. First, the data are more private and sensitive, as they cover every aspect of daily life, from the incoming data to the fitness data. Second, the publication of such data is also bandwidth-consuming, as they are likely to be stored on mobile devices. The local differential privacy has been considered a novel paradigm for such distributed data publication. However, existing works mostly request the encoding of contents into vector space for publication, which is still costly in network resources. Therefore, this work proposes a novel framework for highly efficient privacy-preserving data publication. Specifically, two sampling-based algorithms are proposed for the histogram publication, which is an important statistic for data analysis. The first algorithm applies a bit-level sampling strategy to both reduce the overall bandwidth and balance the cost among contributors. The second algorithm allows consumers to adjust their focus on different intervals and can properly allocate the sampling ratios to optimize the overall performance. Both the analysis and the validation of real-world data traces have demonstrated the advancement of our work

Nanoscale Assembly of Copper Bearing-Sleeve via Cold-Welding: A Molecular Dynamics Study

A bearing is an important component in contemporary machinery and equipment, whose main function is to support the mechanical rotator, reduce the friction coefficient during its movement, and guarantee the turning accuracy. However, assembly of a nanoscale bearing and sleeve is a challenging process for micro-nano mechanical manufacturers. Hence, we show the cold-welding mechanism of a copper nanobearing-nanosleeve via molecular dynamic simulations. We demonstrate that it is feasible to assemble a bearing and sleeve at the nanoscale to form a stable mechanism. The effect of temperature in the range of 150 to 750 K is investigated. As the temperature rises, the mechanical strength and the weld stress of the welded structures markedly decrease, accompanied by the observation of increasing disorder magnitude. This comparison study is believed to facilitate future mechanical processing and structural nano-assembly of metallic elements for better mechanical performance

CuMoxW(1-x)O4 Solid Solution Display Visible Light Photoreduction of CO2 to CH3OH Coupling with Oxidation of Amine to Imine

The photoreduction of carbon dioxide (CO2) to valuable fuels is a promising strategy for the prevention of rising atmospheric levels of CO2 and the depletion of fossil fuel reserves. However, most reported photocatalysts are only active in the ultraviolet region, which necessitates co-catalysts and sacrificial agents in the reaction systems, leading to an unsatisfied economy of the process in energy and atoms. In this research, a CuMoxW(1-x)O4 solid solution was synthesized, characterized, and tested for the photocatalytic reduction of CO2 in the presence of amines. The results revealed that the yield of CH3OH from CO2 was 1017.7 μmol/g under 24 h visible light irradiation using CuW0.7Mo0.3O4 (x = 0.7) as the catalyst. This was associated with the maximum conversion (82.1%) of benzylamine to N-benzylidene benzylamine with high selectivity (>99%). These results give new insight into the photocatalytic reduction of CO2 for valuable chemical products in an economic way

Cumulative Effects of Climatic Factors on Terrestrial Vegetation Growth

Extensive studies have focused on instantaneous and time-lag impacts of climatic factors on vegetation growth; however, the chronical and accumulative indirect impacts of antecedent climatic factors carrying over for a period of time on vegetation growth, defined as cumulative effects, are less investigated. Here we aimed to disentangle the cumulative effects of climatic factors on vegetation growth by using vegetation indexes and accumulated meteorological data. First, we investigated the explanation and fit of climate changes on vegetation variations by applying stepwise multiple linear regression with Akaike information criterion. Then, we obtained the correlation coefficients and lagged time of climatic factors on vegetation growth whereby partial correlation and time-lag effect analyses. Results showed that (i) consideration of cumulative climate effects increased the explanation and fit of climate changes on vegetation dynamics for more than 77% of vegetated surface with an average global explanation of 68.33%, which was approximately 3.35% higher than the scenario when only time-lag effects were considered; (ii) big differences exhibited in the correlation coefficients and lagged times under the scenarios with cumulative climate effects considered or not; and (iii) positive accumulated temperature (accumulated solar radiation) effects with zero (three-month) time lag dominates most mid-high latitude ecosystems, and negative accumulated temperature effects with three-month delay dominates the temperate arid and semiarid regions and tropical dry ecosystems. By comparison, accumulated precipitation had relatively complex cumulative effects on vegetation growth. We concluded that climatic factors had significant cumulative effects on vegetation growth; consideration of the cumulative effects helps us better understand the climate-vegetation interactions