Synthesis and hygrothermal aging of polycarbonates containing a bisphenol fluorene moiety.

This study aims to synthesize a specific type of polycarbonate with high refractive index, low birefringence, and resistance to hygrothermal aging by copolymerizing 2,2'-bis(2-hydroxyethoxy)-1,1'-binaphthyl (BNE) with 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (BPEF). Comparative analysis revealed that the copolymer synthesized from BNE and BPEF demonstrated superior hydrolytic stability relative to the bisphenol A-based polycarbonate. This augmented stability can be attributed to the monomers' higher pKa values, rendering acidic substances less capable of dissociating and thereby mitigating ester hydrolysis under hygrothermal conditions. Furthermore, the investigation probed into the phenomenon of physical aging in copolymerized polycarbonate when exposed to hygrothermal environments. It was discerned that the enthalpy loss, observable under both dry and hygrothermal conditions, could be linearly correlated with the difference between the aging temperature and the glass transition temperature (Tg), signifying a close correlation between the magnitude of physical aging and Tg. A lower Tg in the copolymerized polycarbonate led to more pronounced physical aging within the same timeframe, resulting in an augmentation of tensile strength and modulus, while higher Tg effectively mitigated the physical aging phenomenon.

Synthesis and Properties of Bio-Based Polycarbonates Containing Silicone Blocks.

This study aims to investigate the effects of different hydroxy-terminated silicones on the properties of polycarbonate-silicone copolymers (ICS-PC) by introducing flexible and hydrophobic silicone into isosorbide-based polycarbonate through melt transesterification- polycondensation method. Through compatibility and transesterification experiments, it is confirmed that the alcohol-hydroxyl polydimethylsiloxane (a-PDMS) has higher reactivity and silicone conversion than the phenol-hydroxyl polydimethylsiloxane (p-PDMS), but the conversion does not exceed 81%. Polyether-modified silicone (PEMS) exhibits better compatibility and higher reactivity, thus resulting in higher conversion that can reach 86%. Effects of the type and content of silicone on the glass transition temperature (Tg), optical transparency, saturated water absorption, and mechanical strength of ICS-PCs were also discussed. It is found that p-PDMS has higher Tg, hydrophobicity, and mechanical strength with similar silicone content, but the total transmittance does not exceed 60%. In contrast, the PEMS system exhibits better optical transparency due to its improved compatibility with the PC matrix, with a total transmittance of up to 73%, Tg exceeding 150 °C while maintaining excellent flexibility and hydrophobicity. These results are helpful to further improve the comprehensive properties of bio-based polycarbonates.

From CNN to Transformer: A Review of Medical Image Segmentation Models.

Medical image segmentation is an important step in medical image analysis, especially as a crucial prerequisite for efficient disease diagnosis and treatment. The use of deep learning for image segmentation has become a prevalent trend. The widely adopted approach currently is U-Net and its variants. Moreover, with the remarkable success of pre-trained models in natural language processing tasks, transformer-based models like TransUNet have achieved desirable performance on multiple medical image segmentation datasets. Recently, the Segment Anything Model (SAM) and its variants have also been attempted for medical image segmentation. In this paper, we conduct a survey of the most representative seven medical image segmentation models in recent years. We theoretically analyze the characteristics of these models and quantitatively evaluate their performance on Tuberculosis Chest X-rays, Ovarian Tumors, and Liver Segmentation datasets. Finally, we discuss the main challenges and future trends in medical image segmentation. Our work can assist researchers in the related field to quickly establish medical segmentation models tailored to specific regions.

Response of soybean and maize roots and soil enzyme activities to biodegradable microplastics contaminated soil.

Although biodegradable plastic film is a promising alternative product for reducing polyethylene plastic pollution in agricultural soils, the effects of its residues on plant growth and soil properties remain unclear. In this study, we conducted an experiment to investigate root properties and soil enzyme activities in Poly (butylene adipate-co-terephthalate) microplastics (PBAT-MPs) contaminated soil (0 % (CK), 0.1 %, 0.2 %, 0.5 % and 1 % of dry soil weight) with soybean (Glycine max (Linn.) Merr.) and maize (Zea mays L.). The results show that PBAT-MP accumulation in soil negatively affects root growth, and alter soil enzyme activities, which may then constrain C/N cycling and potential yields. For soybean, the total root length, total root surface area and root biomass decreased by 34 %- 58 %, 34 %- 54 % and 25 %- 40 % at the harvesting stage compared to CK, respectively. The negative effects of PBAT-MPs on maize roots were greater than on soybean roots. The total root length, root surface area and root biomass of maize decreased by 37 %- 71 %, 33 %- 71 % and 24 %- 64 % at the tasseling and harvesting stage, respectively (p < 0.05). Furthermore, a statistical analysis of the data indicates that the inhibition of soybean and maize root growth by PBAT-MP accumulation was mediated by the significantly different impacts of PBAT-MP addition on C-enzyme (ß-xylosidase, cellobiohydrolase, ß-glucosidase) and N-enzyme activities (leucine-aminopeptidase, N-acetyl-ß-glucosaminidase, alanine aminotransferase) in rhizosphere and non-rhizosphere soil, possibly due to interactions with plant-specific root exudates and microbial communities. These findings show the potential risks posed by biodegradable microplastics on the plant-soil system, and suggest that biodegradable plastic film should be applied with caution.

Irrigation-facilitated low-density polyethylene microplastic vertical transport along soil profile: An empirical model developed by column experiment.

The emerging issue of microplastic pollution of agricultural soils derives from the intensive utilization of plastic mulching film. Although surface runoff may transport microplastic off-site, infiltration may also facilitate microplastic transport from surface soil to deeper depths. Microplastic comprises a relatively new category of soil contaminants, whose transport in the soil has not yet been widely studied. In this study, we investigated microplastic transport from contaminated surface soil (50 g kg-1) driven by irrigation, from permanent wilting point to saturation, and developed an empirical model to characterize the resulting accumulation of microplastic along soil profile. A soil column experiment was conducted under various treatments: the control, 1, 2 and 4 runs of irrigation. Soil samples were collected from inside and outside of soil cracks (if present) in each soil layer (0-2 cm (source layer), 2-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-50 cm). The results showed that with increasing irrigation runs, microplastic in the source soil layer decreased, while microplastic contents in deeper soil depths increased significantly (p < 0.05), varying from 7.03 g kg-1 in 2-5 cm to 0.29 g kg-1 in 40-50 cm soil. The microplastic content detected in soil cracks was 1.3-17.8 times higher than that detected in the soil matrix at similar depths, indicating that the transported microplastic is prone to be enriched in soil cracks. In addition, the total amount of transported microplastic increased 1.5 times after four irrigation runs, and the variations were significantly observed especially at deeper soil depths. Based on correlation analyses, data-fitted empirical models that relate cumulative microplastic to the depth of soil layer and irrigation runs indicate that irrigation-facilitated microplastic transport could be well-characterized (R2 >0.92). Further research is needed to develop an physical-based model in order to assess microplastic migration risks driven by irrigation and other agricultural management practices.

Effects of plastic particles on germination and growth of soybean (Glycine max): A pot experiment under field condition.

Plastic residues have become a serious environmental problem in areas where agricultural plastic film are used intensively. Although numerous of studies have been done to assess its impacts on soil quality and crop yields, the understanding of meso-plastic particles effects on plant is still limited. In this study, low density polyethylene (PE) and biodegradable plastic (Bio) mulch film were selected to study the effects of meso-plastic debris on soybean germination and plant growth with the accumulation levels of 0%, 0.1%, 0.5% and 1% in soil (w: w, size ranging 0.5-2 cm) by a pot experiment under field condition. Results showed that the germination viability of soybean seeds was reduced to 82.39%, 39.44% and 26.06% in the treatments with 0.1%, 0.5% and 1% added plastic debris compared to the control (CK), respectively, suggesting that plastic residues in soil inhibit the viability of soybean seed germination. The plastic debris had a significant negative effect on plant height and culm diameter during the entire growth stage of soybean. Similarly, the leaf area at harvest was reduced by 1.97%, 6.86% and 11.53% compared to the CK in the treatments with 0.1%, 0.5% and 1% plastic debris addition, respectively. In addition, the total plant biomass under plastic addition was reduced in both the flowering and harvesting stages, compared to the CK. For the different type of plastic residues, plant height, leaf area and root/shoot ratio at group PE were significantly lower than those of groups treated by Bio. In conclusion, PE debris had a greater negative effects on plant height, culm diameter, leaf area and root/shoot ratio while Bio debris mainly showed the adverse effects on germination viability and root biomass especially at the flowering stage. Therefore, further research is required to elaborate plastic particles' effects on different stages of crops and soil quality.

Optimized Association of Short Alkyl Side Chains Enables Stiff, Self-Recoverable, and Durable Shape-Memory Hydrogel.

This work reports a self-healing and shape-memory hydrogel integrating multiple mechanical properties. The network configuration is featured as entangled networks cross-linked by distributed association of very short alkyl chains (hexyl, six carbons). These cross-linking knots are interconnected by the long hydrophilic polyvinyl alcohol backbone. The optimal aggregation of hexyl side chains leads to the broadened distribution in bonding strength as verified by static and dynamic mechanical characterization. These structural features contribute to high strength, toughness, stiffness, and yet fast recoverability. Furthermore, the hydrophobic and supramolecular nature of aggregated alkyl chains offers high durability and solvent-assistant healing function. Finally, distributed association of hexyl side chains confers a broadened temperature-dependent modulus, allowing for encoding stepwise shape recovery from a temporary shape at different temperatures and/or times.

Cell culture medium supplemented with taurine decreases basic charge variant levels of a monoclonal antibody.

OBJECTIVE: To explore the impact of taurine on monoclonal antibody (mAb) basic charge variants in Chinese hamster ovary (CHO) cell culture. RESULTS: In fed-batch culture, adding taurine in the feed medium slightly increased the maximum viable cell density and mAb titers in CHO cells. What's more, taurine significantly decreased the lysine variant and oxidized variant levels, which further decreased basic variant contents from 32 to 27%. The lysine variant content in the taurine culture was approximately 4% lower than that in control condition, which was the main reason for the decrease in basic variants. Real-time PCR and cell-free assay revealed that taurine played a critical role in the upregulation of relative basic carboxypeptidase and stimulating extracellular basic carboxypeptidase activities. CONCLUSION: Taurine exhibits noticeable impact on lower basic charge variants, which are mainly due to the decrease of lysine variant and oxidized protein variants.

Molecular epidemiology of pneumococcal isolates from children in China.

OBJECTIVES: To investigate the molecular epidemiology of pneumococcal isolates in Chongqing, China. METHODS: In this cross-sectional study, 51 invasive Streptococcus pneumoniae (S. pneumoniae) strains were from children with invasive pneumococcal disease (IPD) and 32 carriage strains from healthy children from January 2010 to December 2013 at the Children's Hospital of Chongqing Medical University, Chongqing, China. Multilocus sequence typing was used to identify the sequence types (STs). Capsular serotypes were determined by multiplex polymerase chain reaction. Drug susceptibility and resistance was determined by minimum inhibitory concentrations. RESULTS: In this study, 11 serotypes were identified among the 83 S. pneumoniae clinical isolates tested. Prevalent serotypes were 19A (20.4%), 6A/B (20.4%), 19F (15.7%), 14 (14.5%), and 23F (10.8%). Serotype 19F was the most frequent carriage strain, and serotype 19A was the most frequent invasive strain. The ST983 was the most prevalent ST for carriage strains, and ST320 was the most prevalent ST for invasive strains. For gene analysis, psaA (99.5%) and piaA (98.6%) were present and much conserved in all pneumococci tested. The cps2A and pcsB genes were more frequent in invasive isolates than carriage strains. Antimicrobial resistance rates of invasive pneumococcal isolates to erythromycin, penicillin, meropenem, cefotaxime, and clindamycin were higher than the carriage isolates from children. CONCLUSION: Our epidemiological evidence shows that 19A, 6A/B, 19F, 14, and 23F remain the most prevalent serotypes, which can be targeted by PCV13. Genotypes and drug resistance varied between carriage and invasive strains. The PsaA and PiaA may be good protein vaccine candidates.

[Effects of water stress and nitrogen fertilization on peanut root morphological development and leaf physiological activities].

Taking 'Huayu 22' peanut as test material, effect of soil water content and nitrogen fertilization on the leaf physiological activities and root morphological characteristics of peanut plants were analyzed. Two levels of soil water condition were: (1) well-watered condition and (2) moderate water stress, and three levels of nitrogen were: (1) none nitrogen (N0), (2) moderate nitrogen (N1, 90 kg · hm(-2)) and (3) high nitrogen (N2, 180 kg · hm(-2)). The results showed that N1 significantly increased the peanut yield under two water conditions, but showed no significant effect on harvest index compared with N0. Under water stress condition, N1 had no significant effects on total root biomass and total root length, but the total root surface area was remarkably increased. The nitrogen fertilization significantly increased the root length and root surface area in 20-40 cm soil layer, and N2 significantly increased the root biomass and root surface area in the soil layer below 40 cm. The application of nitrogen remarkably increased CAT and POD activities in leaf, while MDA content was decreased with the increase of nitrogen level. Under well-watered condition, the root biomass, root length and root surface area in the soil layer below 40 cm and total root surface area were significantly reduced by nitrogen application, however, only N1 could increase leaf protective enzyme activities. Correlation analysis showed that the root length in 20-40 cm soil layer and SOD, CAT, POD activities in leaf were highly significantly related with peanut yield.