Search

Effective utilization of wild relatives is key to overcoming challenges in genetic improvement of cultivated tomato, which has a narrow genetic basis; however, current efforts to decipher high-quality genomes for tomato wild species are insufficient. Here, we report chromosome-scale tomato genomes from nine wild species and two cultivated accessions, representative of Solanum section Lycopersicon, the tomato clade. Together with two previously released genomes, we elucidate the phylogeny of Lycopersicon and construct a section-wide gene repertoire. We reveal the landscape of structural variants and provide entry to the genomic diversity among tomato wild relatives, enabling the discovery of a wild tomato gene with the potential to increase yields of modern cultivated tomatoes. Construction of a graph-based genome enables structural-variant-based genome-wide association studies, identifying numerous signals associated with tomato flavor-related traits and fruit metabolites. The tomato super-pangenome resources will expedite biological studies and breeding of this globally important crop.

Shear-induced crystallization was examined for poly(1-butene) (PB) and its random copolymer with 1.5 mol % ethylene (PBE) upon shearing at a temperature slightly above the nominal melting temperatu...

Processability of vitrimers strongly relies on the temperature dependence of viscosity. In this study, we analyzed temperature-dependent viscoelasticity of vitrimers based on the dioxaborolane meta...

Pressure effect is of great importance in injection and compression of poly(L-lactide) (PLLA). However, pressure induced crystallization (PIC) and structural change of PLLA have not been thoroughly studied. In this study, we investigated PIC and structure transitions of PLLA using in situ WAXS and SAXS. A mixture of α′ and α crystals were observed at temperatures above 170 °C at high pressures. A frustrated structure was induced at Pc ≥ 100 MPa owing to sliding of chains and crystal blocks upon volume shrinkage. A mesomorphic phase was observed at Pc ≥ 100 MPa or at 190 °C ≥ Tc ≥ 165 °C by SAXS and WAXS. Upon heating the samples prepared at high Pc, doubling lamellar thickening occurred via mutual chain rearrangement between the adjacent lamellae. Based on the results, a phase diagram was revealed for the crystal structures formed and under different crystallization conditions.

As one of the most important vegetable crops in the world, the production of tomatoes was restricted by salt stress. Therefore, it is of great interest to analyze the salt stress tolerance genes. As the non-coding RNAs (ncRNAs) with a length of more than 200 nucleotides, long non-coding RNAs (lncRNAs) lack the ability of protein-coding, but they can play crucial roles in plant development and response to abiotic stresses by regulating gene expression. Nevertheless, there are few studies on the roles of salt-induced lncRNAs in tomatoes. Therefore, we selected wild tomato Solanum pennellii (S. pennellii) and cultivated tomato M82 to be materials. By high-throughput sequencing, 1,044 putative lncRNAs were identified here. Among them, 154 and 137 lncRNAs were differentially expressed in M82 and S. pennellii, respectively. Through functional analysis of target genes of differentially expressed lncRNAs (DE-lncRNAs), some genes were found to respond positively to salt stress by participating in abscisic acid (ABA) signaling pathway, brassinosteroid (BR) signaling pathway, ethylene (ETH) signaling pathway, and anti-oxidation process. We also construct a salt-induced lncRNA-mRNA co-expression network to dissect the putative mechanisms of high salt tolerance in S. pennellii. We analyze the function of salt-induced lncRNAs in tomato roots at the genome-wide levels for the first time. These results will contribute to understanding the molecular mechanisms of salt tolerance in tomatoes from the perspective of lncRNAs.

As one of the most important vegetable crops in the world, the production of tomatoes was restricted by salt stress. Therefore, it is of great interest to analyze the salt stress tolerance genes. As the non-coding RNAs (ncRNAs) with a length of more than 200 nucleotides, long non-coding RNAs (lncRNAs) lack the ability of protein-coding, but they can play crucial roles in plant development and response to abiotic stresses by regulating gene expression. Nevertheless, there are few studies on the roles of salt-induced lncRNAs in tomatoes. Therefore, we selected wild tomato Solanum pennellii (S. pennellii) and cultivated tomato M82 to be materials. By high-throughput sequencing, 1044 putative lncRNAs were identified here. Among them, 154 and 137 lncRNAs were differentially expressed in M82 and S. pennellii, respectively. Through functional analysis of target genes of differentially expressed lncRNAs (DE-lncRNAs), some genes were found to respond positively to salt stress by participating in Abscisic Acid (ABA) signaling pathway, brassinosteroid (BR) signaling pathway, ethylene (ETH) signaling pathway and anti-oxidation process. We also construct a salt-induced lncRNA-mRNA co-expression network to dissect the putative mechanisms of high salt tolerance in S. pennellii. We analyze the function of salt-induced lncRNAs in tomato roots at the genome-wide levels for the first time. These results will contribute to understanding the molecular mechanisms of salt tolerance in tomatoes from the perspective of lncRNAs.

Crystal structure and lamellar thickening of poly( l -lactide) (PLLA) prepared with and without high pressure were investigated via DSC and in situ synchrotron WAXS/SAXS. α and α′ and some β crystals were found in the PLLA specimens isothermally crystallized at 165 °C under pressure higher than 500 bar. Lamellar thickening via melt-recrystallization and crystal transformations of α′-to-α and β-to-α crystals were observed upon heating. The SAXS peak first showed up at q∼0.29 nm−1, corresponding to the long period (L) of ∼22 nm. When the annealing temperature was raised to ∼170 °C, an unusual scattering peak corresponding to long period ∼43 nm showed up. This latter scattering peak is absent in PLLA prepared at atmospheric pressure. The results suggest a precursor with more extended chain conformation is probably produced during the crystallization under high pressure and the melting processes, which facilitated fast thickening by the fusion of adjacent lamellae via chain-sliding into lamellae of doubled thickness.

Stereocomplex (SC) crystals usually act as nucleating agents in polylactide (PLA). However, we previously found that PLA homo-crystallization can occur prior to SC crystal formation. In this work, to introduce a small amount of SC crystals into poly(D-lactide) (PDLA) and investigate further their effect on PDLA crystallization behaviours, random poly(L,D-lactide) (PLDLA) copolymers with L-lactyl contents of 89%, 83% and 50% as well as poly(L-lactide) (PLLA) were synthesized and then blended into PDLA. The crystallization behaviours and crystal structures of the blends were characterized by polarized optical microscopy, differential scanning calorimetry (DSC), X-ray diffraction, and in situ wide angle X-ray scattering. Interestingly, the spherulite growth rate G of PDLA is much smaller in the blends in the presence of previously formed SC crystals than in neat PDLA, whereas the nucleation density is higher and the crystallization half-time determined by DSC is shorter, revealing a higher overall crystallization rate due to the nucleating effect of the introduced SC crystals. The zero growth temperatures Tzg of PDLA in the blends were determined as 165 °C, about 20 °C below the equilibrium melting point of PDLA and not affected by SC crystals, revealing the same supercooling degrees. It is proposed that prior formation of SC crystals in the blends enhanced the constraints of the added high molecular weight PLDLA copolymers and PLLA on PDLA chain diffusion, resulting in slow chain conformation adjustments for the following observed slow spherulite growth of PDLA.

Male sterile mutants can be used in breeding or commercial cultivation in tomato, but there are few research reports on their proteomics. In this study, we analyzed the metabolic pathways and biological functions of differentially abundant proteins (DAPs) involved in two stages of stamen development of the tomato flowers by using a high through-put iTRAQ labeled proteomic approach. There was a total of 1476 DAPs which should associated with the occurrence of pollen abortion in tomato. Moreover, there were more DAPs in the four membrane systems. It shows that membrane systems are very important for tomato pollen development. According to KEGG analysis, these signaling pathways including starch and sucrose metabolism (map00500), tropane, piperidine and pyridine alkaloids biosynthesis (map00960), amino sugar and nucleotide sugar metabolism (map00520) have important effects on pollen development. These results were verified by using mass spectrometry PRM. Finally, two candidate genes (Solyc11g065770 and Solyc11g065530) were found that may be related to pollen development and cause pollen abortion by comparison of protein-protein interaction networks and on the basis of previous studies on ms-7 gene. This data and model will provide a new insight into tomato genetic male sterility 7 and contribute to the improvement of tomato hybrid breeding. Biological significance: Artificial emasculation is still the main method of tomato hybrid breeding at present. Adopting male sterility in tomato cross breeding could greatly improve the production efficiency and seed purity; reduce the cost. Although numerous researches have been conducted to select the genes related to male sterility, the molecular mechanism remains unclear in tomato. In this study, we used the high-through-put iTRAQ labeled proteomic approach, to perform a novel comparison of expression profiles in GMS tomato line and its wildtype line. Based on these results, we proposed the potential regulated protein network involved in pollen development mechanism of tomato GMS and two candidate genes. SIGNIFICANCE: Artificial emasculation is still the main method of tomato hybrid breeding at present. Adopting male sterility in tomato cross breeding could greatly improve the production efficiency and seed purity; reduce the cost. Although numerous researches have been conducted to select the genes related to male sterility, the molecular mechanism remains unclear in tomato. In this study, we used the high-through-put iTRAQ labeled proteomic approach, to perform a novel comparison of expression profiles in GMS tomato line and its wildtype line. Based on these results, we proposed the potential regulated protein network involved in pollen development mechanism of tomato GMS and two candidate genes.

Tremendous progress has been achieved in the field of gene editing in plants, such as with the use of zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR). Because of the potential advantages associated with mutant creation and crop germplasm innovation, genome editing technology has been rapidly developed and widely used in crop improvement in recent years. In this review, we aim to document some of the important recent developments and applications of genome-editing tools, especially with respect to gene knock-ins. We introduce the mechanism underlying knock-ins and different outcomes of insertion. We also discuss genome editing tools and methods developed to improve insertion efficiencies. Additionally, we review the recent trends in genetic editing biotechnologies; several strategies are being developed to further improve the efficiency of plant gene knock-ins. Undoubtedly, CRISPR/Cas technology will boost the development of new plant breeding techniques tremendously.

The morphologies and structures of crystalline polymers depend on the crystallization condition, such as the quenching rate, crystallization temperature, pressure, and molecular weight, tacticity, branching, topology and so on. The morphologies and growth of poly ( d -lactic acid) (PDLA) spherulites were observed by POM when the samples isothermally crystallized at various temperatures after cooling from 200 °C to 250 °C. The crystallization behavior of PDLA was characterized by DSC measurements at various temperatures and it is not consistent with the kinetics of spherulite growth, which is due to the difference between the characterized partial and total crystallization behavior. It was found that the formation of the banded spherulites of PDLA is not only dependent on the crystallization temperatures, but also on the melting temperatures. Light fluctuation of the POM images was investigated during heating and it was found that the dark bands or black bands disappeared earlier than the bright ones during heating of the banded spherulites. The observed melting phenomenon implies mutiple lamellar stacking model inside the spherulites. The formation condition of the banded spherulites morphology was discussed based on the crystallization rate and diffusion rate. The proposed mechanism would be helpful to understand the structure and formation of PDLA ring-banded spherulites.

Structures of polymers depend on the degree of polymerization and chain conformation, and the chain conformation plays a key role on the structure formation and structure transition of an existing ...

Polymorphic transformation from the form II to form I crystal was investigated for isotactic polybutene-1 (PB) and butene-1/ethylene copolymers (PBE) with differential scanning calorimetry (DSC) and dielectric response spectroscopy (DRS). DRS detected the so-called α relaxation of segments within the amorphous phase, and DSC traced a degree of form II to I transformation with time. It turned out that incorporation of the ethylene comonomers in PBE suppressed the crystallization and plasticized the amorphous phase, and the II to I transformation was greatly accelerated in particular at low T close to Tg. To normalize Tg enabled normalization of the α relaxation frequency (detected in DRS), but not the II to I transformation rate (detected in DSC): extra acceleration was noted for samples with a number fraction of ethylene monomers of 4.3% or higher. The extra acceleration is attributed to (1) heterogeneity of segmental mobility that facilitates the crystal growth and (2) crystal defects accumulating at the fold surface that cause internal stress to accelerate the nucleation.

Soluble sugar is known to improve the sweetness and increase tomato sauce yield. Studies have focused on improving the content of soluble sugar in tomato fruits, usually by promoting functional genes. We studied two genes (SlINVINH1 and SlVPE5) that inhibited the accumulation of soluble sugar in tomato fruits and obtained two genes’ knocked-out lines (CRISPR-invinh1 or CRISPR-vpe5) using CRISPR/Cas9. Aggregated lines with CRISPR-invinh1 and CRISPR-vpe5 were gained by hybridization and self-pollination. Compared to wild-type lines, the glucose, fructose, and total soluble solid (TSS) contents of CRISPR-invinh1 and CRISPR-vpe5 increased significantly. Glucose, fructose, and TSS levels further improved simultaneously with CRISPR-invinh1 and CRISPR-vpe5 than with single gene knock-out lines. This indicates that these genes have a synergistic effect and will increase the soluble sugar content. Thus, the knock-out SlINVINH1 and SlVPE5 may provide a practical basis for improving the sweetness of tomato fruits and their processing quality.

The crystallization behaviors and microstructures of poly(l-2-hydroxyl-3-methylbutanoic acid)/poly(l-lactide) blends [P(L-2H3MB)/PLLA] were investigated by OM, DSC, SAXS, in situ temperature-dependent WAXD, and in situ synchrotron WAXS. The blends exhibited a homogeneous state at 250 °C. In the cooling process, P(L-2H3MB), with higher melting temperature, crystallized first at 166.7 °C and drove the formation of the phase separation and microstructure. And the amorphous P(L-2H3MB) and PLLA were excluded into the interlamellar and interfibrillar regions of the former P(L-2H3MB) crystallites. For P(L-2H3MB)/PLLA (5/5), the amorphous P(L-2H3MB) in the interfibrillar regions continued to form crystallites sequentially at 134.6 °C, which clearly confirmed the fractional crystallization of P(L-2H3MB). In our knowledge, this unique fractional crystallization has not been reported yet, of the component in miscible blend, which crystallized first under little confinement. This work provided a new viewpoint and und...

Polymer crystallization is crucial to the properties of polymers, which are determined by thermal dynamics and kinetics. The formation of polymorphism has turned out to be very important for applic...

So far, over 50 spontaneous male sterile mutants of tomato have been described and most of them are categorized as genetic male sterility. To date, the mechanism of tomato genetic male sterility remained unclear. In this study, differential proteomic analysis is performed between genetic male sterile line (2-517), which carries the male sterility (ms10

Memory effects play an important role in understanding polymer crystallization, especially for self-seeding or self-nucleation of polymer crystallization. Amorphous poly(l-lactic acid) (PLLA) was prepared via quenching after holding at various temperatures. Melt structure and cold crystallization behaviour of PLLA were explored by WAXD, DSC, and FTIR. Both isothermal and non-isothermal cold crystallization behaviours of PLLA show obvious melting memory effects. WAXD profiles and FTIR spectrums indicate that various conformations of the prepared amorphous samples can be distinguished. Fewer entanglements of polymer melt may promote molecular chain motions when holding at lower temperatures and facilitate the subsequent crystallization. The melt memory effect plays a role as “self-plasticization” rather than “self-nucleation”. Real-time FTIR implies the amorphous conformational differences originate from the fresh formed melt structure more than the possibly retained crystal structure. The melt memory effect is a memory of temperature-related dynamic competition of the chain conformations developed in the melting process and the self-nucleated melt is in the metastable heterogeneous state, which may be the origin of the unerased melt memory effect above the equilibrium melting point.

Intra- and inter-molecular interactions play an important role in polymer chain dynamics. Polymer crystallization behavior and crystalline structure are affected by the chain dynamics. The enantiomer containing PLLA and PDLA is considered as an important nucleation for PLA crystallization since it was found. The mixtures containing PDLA and stereocomplex (SC) crystal were prepared via different solvents or without any solvent. The effect of the stereocomplex promoted homopolymer crystallization and the non-isothermal crystallization behaviors of the prepared mixtures were characterized by DSC. The DSC results showed that the crystallization temperature of the homopolymer in the PDLA/SC mixtures increases with the stereocomplex contents as cooling from 200 °C at 10 °C/min. The increased crystallization temperature reduces with decreasing of cooling rate, and the increasing is even negligible when the cooling rate is 1 °C/min or lower. The promoted crystallization behavior could be influenced by melting temperature and melting time. FTIR results indicated the CH3⋯O interactions between the enantiomers of polylactide is related to the solvents with different solubility parameters for sample preparations. The stereocomplex effect on the PDLA crystallization in the mixtures was discussed based on the molecular interactions between enantiomers and chain dynamics in presence of obstacles.

Dynamics of polymer chains not only is a fundamental bridge between the structures and properties of polymers but also plays a crucial role in the formation of polymer structures. The slow crystallization caused low crystallinity of Poly (lactic acid) (PLA) is the bottleneck for its applications. The chain dynamics affected memory for recrystallization morphology and behavior of poly ( d -lactic acid) (PDLA) were observed by POM and characterized by DSC. The POM images showed that the PDLA could outline the morphology of original banded spherulites after recrystallization from melting of the original spherulites. The re-formed crystal inherited the crystalline location from the original crystalline morphology, forming a circle ring morphology that is following up the initial banded spherulites, even though the circle ring was constructed of smaller spherulites. DSC results showed various crystallization behaviors of PLA recrystallization with different thermal history. The influence of heating temperature, keeping time, and cooling rate on the recrystallization morphology were investigated and discussed. It was proposed that the adjustment and change of PDLA chain conformation is more difficult in various states between the crystalline and melt than that of other polymers, which relates to the strength of melt and entropy.

The crystallization and melting behaviors of weakly segregated diblock copolymer (MPEG-b-PLLA) have been investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). The microphase separation of MPEG-b-PLLA significantly influenced the crystallization behavior of PEG and the melting behavior of PLLA block, which formed during the two-step crystallization process. PLLA block crystallized from melt under various cooling rates (Rc, PLLAs) in the first step, and PEG sequentially crystallized in the second process as the temperature cooled from 60 °C to −70 °C at 10 °C/min. With Rc, PLLA decreasing, PEG was more excluded out of the interlamellar regions of PLLA crystals, and concentrated into the interfibrillar regions, and formed the different microphase separation formed, which may attribute to the fractional crystallization and homogeneous nucleation. Then the melting peak of PLLA at lower temperature enhanced with the micro-domains of PEG growing, which could be ascribed to that PEG block could accelerate the melting of PLLA near these micro-domains.

So far, over 50 spontaneous male sterile mutants of tomato have been described and most of them are categorized as genetic male sterility. To date, the mechanism of tomato genetic male sterility remained unclear. In this study, differential proteomic analysis is performed between genetic male sterile line (2-517), which carries the male sterility (ms1035 ) gene, and its wild-type (VF-11) using isobaric tags for relative and absolute quantification-based strategy. A total of 8272 proteins are quantified in the 2-517 and VF-11 lines at the floral bud and florescence stages. These proteins are involved in different cellular and metabolic processes, which express obvious functional tendencies toward the hydroxylation of the ω-carbon in fatty acids, the tricarboxylic acid cycle, the glycolytic, and pentose phosphate pathways. Based on the results, a protein network explaining the mechanisms of tomato genetic male sterility is proposed, finding the compromising fat acid metabolism may cause the male sterility. These results are confirmed by parallel reaction monitoring, quantitative Real-time PCR (qRT-PCR), and physiological assays. Taken together, these results provide new insights into the metabolic pathway of anther abortion induced by ms1035 and offer useful clues to identify the crucial proteins involved in genetic male sterility in tomato.

In this study, a series of monodispersed poly(L-lactide) (PLLA) were synthesized by the ring-opening polymerization with Schiff base aluminum catalyst, and the effects of the number-average molecular weight (Mn) on the crystallization and melting behaviors of PLLA were investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The total crystallization rate of PLLA was Mn-dependent, which reached the maximum value for PLLA with Mn of 18.6 kg/mol. In addition, when Mn of PLLA was 18.6 kg/mol, the melting enthalpy (ΔHm) showed a maximum value (87.1 J/g), which was the highest reported value till now. The critical temperature for change of crystal formation from δ- to α-form crystals increased in the isothermal crystallization process with Mn increasing. In the reheating procedure, high-Mn PLLA demonstrated a small exothermal peak prior to the dominant melting peak, corresponding to crystal transition from δ- to α-form, but low-Mn PLLA didn’t show the peak of crystal transition. These different crystallization and melting behaviors were attributed to the different chain mobility of PLLA with different Mn.

Poly(L-lactide) (PLLA)/graphene nanosheet (GNS) composites and pure PLLA were prepared by the solution blending method. Crystalline structures and crystallization behaviors of PLLA in the composite were investigated by XRD, POM, SAXS, and DSC. It was found that α′ form PLLA formation seemed to be more preferred than α form PLLA formation in PLLA/GNS composites at crystallization temperatures Tcs within the α′–α crystal formation transition region due to the existence of GNSs, resulting in an obvious shift of the α′–α crystal formation transition of PLLA in PLLA/GNSs towards high Tcs compared with that of pure PLLA. At Tcs below α′–α crystal formation transition, the formed α′ crystal turned to be more imperfect due to GNS addition, while at Tcs above α′–α crystal formation transition, the crystal structure of α form PLLA was not affected by GNSs. Further POM observations at high Tcs with only α crystal formed showed that PLLA spherulites were well formed in both PLLA/GNSs and pure PLLA, however with very different crystallization kinetics while isothermally crystallizing at different Tcs. The PLLA crystallization process of PLLA in PLLA/GNSs was accelerated by GNSs with both the nucleation rate and spherulite growth rate increased mainly because of the increasing segmental mobility of PLLA chains due to GNS addition; whereas, GNSs showed no observable influence on the determined zero growth temperature Tzg of α form PLLA and the Tzg was estimated lower than the equilibrium melting point of PLLA, indicating that the crystal growth of PLLA is mediated by a transient mesophase with the transition temperature of Tzg between the mesophase and melt not influenced by GNSs in PLLA. Synchrotron on-line SAXS results revealed that the long periods of PLLA in PLLA/GNS composites isothermally crystallized at different Tcs are much smaller than those in pure PLLA. The GNSs are helpful in forming more perfect recrystallized α form PLLA after the α′ form PLLA is melted with increasing Tcs. The presence of GNSs resulted in imperfect α form PLLA from melt directly when it is isothermally crystallized at different Tcs within the temperature range of α′–α crystal formation transition.

Intracytoplasmic sperm injection (ICSI) and embryo transfer (ET) in nonhuman primates, e.g. rhesus and cynomolgus monkeys, has been widely used in researches of reproductive and developmental biology, and the success rate has been improved significantly. However, unwanted multiple pregnancy occurs frequently during the ICSI-ET in monkeys, most of which leads to miscarriages. To improve the birth rate of pregnancies and to safeguard health of host and baby monkeys, multifetal pregnancy reduction (MPR) is necessary. In this study, a total of 10 monkeys with multiple pregnancies received MPR through transabdominal ultrasound-guided potassium chloride injection into beating hearts of selective fetuses. To assess MPR efficiency, 31 monkeys with normal singleton pregnancies and 25 monkeys with twin pregnancies without MPR were used as controls. The aim of the reduction is to keep only one fetus, no matter twin or triplet pregnancy originally. Our results show that six cases of MPR were successful and all of them retained single fetus. Moreover, about 1 month (30.2 ± 1.2 days) of gestation is a better timing for MPR than later stage (50.7 ± 1.9 days). We also found that the remaining fetuses developed normally with full-term gestation and normal birth weight. In conclusion, transabdominal ultrasound-guided potassium chloride injection is a safe and effective MPR method for monkeys with multiple pregnancies.

Gene-editing technologies have made it feasible to create nonhuman primate models for human genetic disorders. Here, we report detailed genotypes and phenotypes of TALEN-edited MECP2 mutant cynomolgus monkeys serving as a model for a neurodevelopmental disorder, Rett syndrome (RTT), which is caused by loss-of-function mutations in the human MECP2 gene. Male mutant monkeys were embryonic lethal, reiterating that RTT is a disease of females. Through a battery of behavioral analyses, including primate-unique eye-tracking tests, in combination with brain imaging via MRI, we found a series of physiological, behavioral, and structural abnormalities resembling clinical manifestations of RTT. Moreover, blood transcriptome profiling revealed that mutant monkeys resembled RTT patients in immune gene dysregulation. Taken together, the stark similarity in phenotype and/or endophenotype between monkeys and patients suggested that gene-edited RTT founder monkeys would be of value for disease mechanistic studies as well as development of potential therapeutic interventions for RTT.

PLLA grafted poly(castor oil) copolymers (PCO-g-PLLA) were successfully synthesized and used to enhance the tensile toughness of PLLA. The tensile toughness and elongation at break of the blends are 10 times greater and 30 times more than those of neat PLLA, respectively, with minimal reduction in the tensile strength of PLLA. Strong interfacial interaction between PLLA and PCO, homogeneous dispersion of the PCO rubbery particles in PLLA matrix, and the formation of cross-linking structure of PCO and PLLA were found to play important roles in the improvement of the toughness. (C) 2014 Elsevier B.V. All rights reserved.

The crystalline morphology and structure of poly(L-lactide) (PLLA) in a PLLA film–chloroform system were investigated by means of wide angle X-ray diffraction (WAXD), polarized optical microscopy (POM) and atomic force microscopy (AFM). Birefringent and nonbirefringent ring banded supra-structures with radial periodic variation of thickness were obtained, which were induced by micro-evaporation of solvents and concentration gradient of PLLA. The ring banded morphologies consisted of multilayer lamellar crystals, which is a manifestation of alternating ridge and valley bands of periodic variation of thicknesses along the radial direction. The formation of the ring banded supra-structures is associated with diffusion and crystal growth induced periodic variation of concentration gradient, which is attributed to diffusion-related rhythmic growth and the competition between diffusion of polymer segments and growth of crystal lamellae. The mechanism of such banded-ring formation was explored on the basis of rhythmic growth resulting from non-linear diffusion.

Biocompatible and biodegradable block copolymers (BBCPs) have become increasingly important in polymer science, and have many potential applications in polymer materials. The structures of BBCPs, which are determined by the competition between crystallization, microphase separation, kinetics and processing, have a tremendous influence on the final properties and applications. In this review, the most recent advances are highlighted in the crystalline structures and morphologies of BBCPs with at least one crystalline block. Particular emphasis is placed on the influences of chemical composition, molecular architecture, crystallization pathway, and film thickness on the structures and morphologies of the block copolymers. The formation and the characteristics of the structures grown in the block copolymers are helpful for understanding the interplay between crystallization and phase segregation, morphologies, structural evolution and their applications.

Strain-induced cold crystallization behavior and structure evolution of amorphous poly(lactic acid) (PLA) stretched within 70-90 degrees C were investigated via in situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements as well as differential scanning calorimetry (DSC) measurements. The data obtained from the stretched samples within 70-90 degrees C showed that all of the formed crystals are disordered alpha' form with more compact chain packing than that of the cold crystallization. Upon stretching at 70 degrees C, the mesocrystal appears first then forms crystal with strain increasing. The stacked structure consisting of less perfect crystalline phase, mesocrystal and oriented amorphous phase emerges at the final stage of stretching. Drawing at 80 degrees C, only the crystal can be induced at lower strain with higher crystallization rate. With strain increasing, the crystallinity and crystal orientation increase, leading to the formation of analogous 'shish-kebab'. The structure evolution at 90 degrees C is similar to that at 80 degrees C, but with much earlier crystallization onset and higher crystallization rate. The difference in strain-induced crystallization behavior of amorphous PLA within 70-90 degrees C can be attributed to the competition between chain orientation caused by stretching and chain relaxation. It was proposed that the strain-induced mesocrystal/crystal and the lamellae are formed from the mesophase originally existing in PLA glass according to the obtained data.

The cold crystallization behaviors and structure evolutions of amorphous PLA stretched within a high-temperature range (100–150 °C) were investigated via in situ synchrotron WAXS and SAXS measurements. The PLA stretched at 120 °C exhibits excellent mechanical properties with the highest modulus, stretching strength and moderate elongation, which is attributed to the coordination effect of thermally-induced initial crystallinity and moderate chain segment mobility. The WAXS results showed that the diffraction peaks of (200/110) and (203) planes shift to higher 2θ values, which indicates the formation of more ordered α′ and α forms during PLA stretching within 100–150 °C. More α forms can be formed from the stretched α′ form and/or from the amorphous phase at 100 °C. The phase diagram of α and α′ forms in stretched PLA with stretching temperature was proposed according to the obtained data of lattice spacing. The crystallinity of stretched PLA increases faster than that which underwent quiescent cold crystallization at the same temperature. The SAXS results indicated that the long period and lamellar thickness along and vertical to the stretching direction of PLA stretched within 100–150 °C exhibit distinct variations, which is attributed to the difference of strain-induced crystallization and lamellar orientation.

Shear effect on crystal structure, morphology and melting behavior of poly( l -lactide) (PLLA) were investigated by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and in-situ polarized optical microscope (POM). Influences of steady shear on PLLA melt was investigated during annealing. The impacts of crystallization temperature ( T c ) and shear rate (SR) on crystal structure, crystal growth rate, nucleation, and melting behavior were studied. It could be clarified into the low ( −1 ) and high shear rate ranges in terms of the crystal structure, growth rate, nucleation and melting behavior. It was found that phase transition and recrystallization during heating completely changed the stack structure. A new stable structure was established after a temperature jump in the melting range. Cylindric morphology arranged with spherulite was also observed in the polymer films at high T c influenced by shear effect.

Morphologies and structures determined by crystallization of the blocks, microphase separation of the copolymers, and vitrification of PLLA block in poly(l-lactide-b-ethylene oxide) (PLLA-b-PEO) copolymers were investigated using microscopic techniques and synchrotron small angle X-ray scattering. The PLLA-b-PEO copolymer films were crystallized from two different annealing processes: melt crystallization (process A) or crystallized from glass state of PLLA block after quenching from melt state (process B). The relationship between the crystalline morphology and microstructure of the copolymers were explored using SAXS. The morphology and phase structure are predominated by crystallization of PLLA block, and greatly influenced by microphase separation of the copolymers. In process B, lozenge-shape and truncated lozenge-shaped PLLA crystals of nanometer scale can be observed. The crystalline morphology is markedly affected by the microstructure formed during the annealing process. Star-shaped morphologies stacked with PLLA single crystals were observed.

Purpose. To increase the accuracy of coding for infantile diarrhea. Method. Case records of diarrhea, from January 2011 to December 2013, were searched in a hospital through the medical record management system, and the coding on the front page of the records was subjected to retrospective investigation and analysis. Results. During these years, 5.44% of all discharged patients were cases of infantile diarrhea, the majority of which were infants, accounting for 61.27%, followed by children, accounting for 17.27%. In 2011 and 2012, the codes for infantile diarrhea were mistakenly classified as K52.9. Through reviews of medical records, it was found that as a matter of fact, infectious diarrhea accounted for 70.49%, and non-infectious diarrhea accounted for 29.56%. Conclusion. The hospital should reinforce the training given to clinicians in writing the front page of medical records, along with ICD-10 training. The staff involved in the coding work should communicate with clinicians better, thereby ...

The evolution of morphologies of isothermally crystallized thin films with different thicknesses of poly(L-lactide-b-ethylene oxide) diblock copolymer was observed by optical microscopy (OM) and atomic force microscopy (AFM). Dendritic superstructures stacked with lamellae were investigated in thin films with approximately 200 nm to approximately 400 nm thickness. The lamellar structure was a lozenge- or truncated-lozenge-shaped single crystal of PLLA confirmed by AFM observations. The contour of the dendritic superstructures is hexagonal, and two types of sectors, [110] and [100], can be classified in terms of the chain-folding and crystal growth directions. These phenomena are due to the interplay of the crystallization of the PLLA block, the microphase separation of the block copolymer, and the effect of the film thickness. The growth process of the superstructure can be classified into three steps: the growth of the main branches, the growth of the secondary side branches along the main branch, and the tertiary side branches. PLLA growth rates decrease in copolymer films thinner than 1 microm. Layer-layer phase structure of the copolymer driven by the crystallization of PLLA and the microphase separation of the copolymer appears to be a key factor explaining the crystallization and morphological behavior of this system.

The catalytic activities of gamma-Al(2)O(3) supported noble metal (Pd, Pt, Au, Ag, Rh) catalysts were tested and compared for catalytic oxidation of o-xylene. The results show that Pd/Al(2)O(3) is the most active catalyst among these noble metal catalysts. The effects of Pd loading and gas hourly space velocity (GHSV) on the activity of Pd/Al(2)O(3) catalyst for o-xylene oxidation were investigated at low temperature from 60 to 190 degrees C. At 1 wt% Pd loading, 100 ppm o-xylene can be completely oxidized to CO(2) and H(2)O at ca.110 degrees C over the Pd/Al(2)O(3) catalyst at a GHSV of 10,000 h(-1). The 1% Pd/Al(2)O(3) was characterized using BET, XRD methods. The XRD patterns showed that PdO was the dominant species in the fresh Pd/Al(2)O(3) catalyst and metallic I'd was the main phase in both the H(2) pretreated and the used catalysts. The metallic I'd is proposed to be the active species for o-xylene oxidation. The mechanism of o-xylene oxidation was studied with respect to the behavior of adsorbed species on Pd/Al(2)O(3) surface examined by in situ DRIFTS and the gas products detected by the online GC/MS. On the basis of experimental results, a simplified mechanism for the catalytic oxidation of o-xylene over Pd/Al(2)O(3) was proposed. (C) 2008 Elsevier B.V. All rights reserved.

The crystallization behaviors and morphology of asymmetric crystalline-crystalline diblock copolymers poly(ethylene oxide-lactide) (PEO-b-PLLA) were investigated using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and microscopic techniques (polarized optical microscopy (POM) and atomic force microscopy (AFM)). Both blocks of PEO5-b-PLLA(16) can be crystallized, which was confirmed by WAXD, while PEO block in PEO5-b-PLLA(30) is difficult to crystallize because of the confinement induced by the high glass transition temperature and crystallization of PLLA block with the microphase separation of the block copolymer.

Poly(lactic acid) (PLA) is a bio-based and compostable thermoplastic polyester that has rapidly evolved into a competitive commodity material over the last decade. One key bottleneck in expanding the field of application of PLA is the control of its structure and properties. Therefore, in situ investigations under cooling are necessary for understanding the relationship between them. The most intriguing feature of a supercooled liquid is its dramatic rise in viscosity as it is cooled toward the glass transition temperature (T-g) though accompanied by very little change in the structural features observable by typical X-ray experiments. The deformation behaviors and structure evolution of glassy PLA during uniaxially stretching below Tg were investigated in situ by synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) techniques. The stretched samples were measured by differential scanning calorimetry (DSC). The obtained results showed that the deformation and yield stress of glassy PLA are strongly dependent on the stretching temperatures together with the transition from mesophase to mesocrystal and the formation of cavities. With the increase in drawing temperature, the onset of the mesocrystal formation is delayed to a higher strain value, whereas corresponding to the same critical orientation degree of amorphous chains (f(am) approximate to 0.45). The DSC results indicated that the post-T-g endothermic peak corresponding to the melting of mesocrystal appears and shifts to a higher temperature with increasing stretching temperature, followed by the down-shifts (to a lower temperature) of the exothermic peak of cold crystallization of PLA. The appearance of a small exothermic peak just before the melting peak related to the transition of the alpha' to alpha crystal implies the formation of an alpha' crystal during cold crystallization in the drawn PLA samples. The structure evolution of glassy PLA stretched below T-g was discussed in details.

Poly(lactic acid) (PLA) is a bio-based and compostable polymer that has quickly developed into a competitive material, but the control of crystallinity is a bottleneck in extended utilization. The crystallization of PLA has been a rich topic because of the existence of two enantiomeric forms of poly(L-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) can form stereocomplex (SC) crystal with high melting point that can be used to control the crystallization behaviors. The SC crystal was regarded as an effective nucleating agent for promoting the crystallization rate and crystallinity of PLA. We investigated cold crystallization of PLLA/PDLA (1:1) mixture with in situ WAXS measurements and found that the homo-crystal of PLA formed earlier than the SC-crystal in the mixture within the measured temperature range, which is different from the melting crystallization. The final crystalline structures are in correspondence with the melting and cold crystallization temperature, and the transition of homo-PLA (δ to α) is not altered by the crystallization procedure. The SC-crystal can be detected in both cold and melting crystallization of the mixture at the temperatures lower than 150 °C, which is conflict with the reported results. A new crystallization mechanism of the mixture was proposed to understand the crystallization behaviors in PLLA/PDLA mixtures. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45663.

Biocompatible and biodegradable block copolymers (BBCPs) have become increasingly important in polymer science, and have many potential applications in polymer materials. The structures of BBCPs, which are determined by the competition between crystallization, microphase separation, kinetics and processing, have a tremendous influence on the final properties and applications. In this review, the most recent advances are highlighted in the crystalline structures and morphologies of BBCPs with at least one crystalline block. Particular emphasis is placed on the influences of chemical composition, molecular architecture, crystallization pathway, and film thickness on the structures and morphologies of the block copolymers. The formation and the characteristics of the structures grown in the block copolymers are helpful for understanding the interplay between crystallization and phase segregation, morphologies, structural evolution and their applications.

The effect of pretreatment on Pd/Al2O3 catalysts for the catalytic oxidation of o-xylene at low temperature was studied by changing the pretreatment and testing conditions. The fresh and pretreated Pd/Al2O3 catalysts were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results showed that the pretreatment dramatically changed the Pd/PdO ratio and then significantly affected the Pd/Al2O3 activity; while the pretreatment had not much influence on Pd particle size. The Pd/Al2O3 pre-reduced at 300 degrees C/400 degrees C, which has fully reduced Pd species, showed the highest activity; while the fresh Pd/Al2O3, which has fully oxidized Pd species, presented the worst performance, indicating the Pd chemical state plays an important role in the catalytic activity for the o-xylene oxidation. It is concluded that metallic Pd is the active species on the Pd/Al2O3 catalyst for the catalytic oxidation of o-xylene at low temperature.