Dynamic evolution of COVID-19 vaccine hesitancy over 2021-2023 among Chinese population: Repeated nationwide cross-sectional study.

Globally, the rollout of COVID-19 vaccine had been faced with a significant barrier in the form of vaccine hesitancy. This study adopts a multi-stage perspective to explore the prevalence and determinants of COVID-19 vaccine hesitancy, focusing on their dynamic evolutionary features. Guided by the integrated framework of the 3Cs model (complacency, confidence, and convenience) and the EAH model (environmental, agent, and host), this study conducted three repeated national cross-sectional surveys. These surveys carried out from July 2021 to February 2023 across mainland China, targeted individuals aged 18 and older. They were strategically timed to coincide with three critical vaccination phases: universal coverage (stage 1), partial coverage (stage 2), and key population coverage (stage 3). From 2021 to 2023, the surveys examined sample sizes of 29 925, 6659, and 5407, respectively. The COVID-19 vaccine hesitation rates increased from 8.39% in 2021 to 29.72% in 2023. Urban residency, chronic condition, and low trust in vaccine developer contributed to significant COVID-19 vaccine hesitancy across the pandemic. Negative correlations between the intensity of vaccination policies and vaccine hesitancy, and positive correlations between vaccine hesitancy and long COVID, were confirmed. This study provides insights for designing future effective vaccination programs for emerging vaccine-preventable infectious X diseases.

Assessing public health service capability of primary healthcare personnel: a large-scale survey in Henan Province, China.

BACKGROUND: The public health service capability of primary healthcare personnel directly affects the utilization and delivery of health services, and is influenced by various factors. This study aimed to examine the status, factors, and urban-rural differences of public health service capability among primary healthcare personnel, and provided suggestions for improvement. METHODS: We used cluster sampling to survey 11,925 primary healthcare personnel in 18 regions of Henan Province from 20th to March 31, 2023. Data encompassing demographics and public health service capabilities, including health lifestyle guidance, chronic disease management, health management of special populations, and vaccination services. Multivariable regression analysis was employed to investigate influencing factors. Propensity Score Matching (PSM) quantified urban-rural differences. RESULTS: The total score of public health service capability was 80.17 points. Chronic disease management capability scored the lowest, only 19.60. Gender, education level, average monthly salary, professional title, health status, employment form, work unit type, category of practicing (assistant) physician significantly influenced the public health service capability (all P < 0.05). PSM analysis revealed rural primary healthcare personnel had higher public health service capability scores than urban ones. CONCLUSIONS: The public health service capability of primary healthcare personnel in Henan Province was relatively high, but chronic disease management required improvement. Additionally, implementing effective training methods for different subgroups, and improving the service capability of primary medical and health institutions were positive measures.

Quantifying the benefits of healthy lifestyle behaviors and emotional expressivity in lowering the risk of COVID-19 infection: a national survey of Chinese population.

BACKGROUND: COVID-19 is still prevalent in most countries around the world at the low level. Residents' lifestyle behaviors and emotions are critical to prevent COVID-19 and keep healthy, but there is lacking of confirmative evidence on how residents' lifestyle behaviors and emotional expressivity affected COVID-19 infection. METHODS: Baseline study was conducted in August 2022 and follow-up study was conducted in February 2023. Baseline survey collected information on residents' basic information, as well as their lifestyle behaviors and emotions. Follow-up study was carried out to gather data on COVID-19 infection condition. Binary logistic regression was utilized to identify factors that may influence COVID-19 infection. Attributable risk (AR) was computed to determine the proportion of unhealthy lifestyle behaviors and emotional factors that could be attributed to COVID-19 infection. Sensitivity analysis was performed to test the robustness of the results. RESULTS: A total of 5776 participants (46.57% males) were included in this study, yielding an overall COVID-19 infection rate of 54.8% (95%CI: 53.5 - 56.0%). The findings revealed that higher stress levels [aOR = 1.027 (95%CI; 1.005-1.050)] and lower frequency in wearing masks, washing hands, and keeping distance [aOR = 1.615 (95%CI; 1.087-2.401)], were positively associated with an increased likelihood of COVID-19 infection (all P < 0.05). If these associations were causal, 8.1% of COVID-19 infection would have been prevented if all participants had normal stress levels [Attributable Risk Percentage: 8.1% (95%CI: 5.9-10.3%)]. A significant interaction effect between stress and the frequency in wearing masks, washing hands, and keeping distance on COVID-19 infection was observed (ß = 0.006, P < 0.001), which also was independent factor of COVID-19 infection. CONCLUSIONS: The overall COVID-19 infection rate among residents is at a medium level. Residents' increasing stress and decreasing frequency in wearing masks and washing hands and keeping distance contribute to increasing risk of infection, residents should increase the frequency of mask-wearing, practice hand hygiene, keep safe distance from others, ensure stable emotional state, minimize psychological stress, providing evidence support for future responses to emerging infectious diseases.

Unsupervised domain adaptive segmentation algorithm based on two-level category alignment.

To enhance the model's generalization ability in unsupervised domain adaptive segmentation tasks, most approaches have primarily focused on pixel-level local features, but neglected the clue in category information. This limitation results in the segmentation network only learning global inter-domain invariant features but ignoring the category-specific inter-domain invariant features, which degenerates the segmentation performance. To address this issue, we present an Unsupervised Domain Adaptive algorithm based on two-level Category Alignment in two different spaces for semantic segmentation tasks, denoted as UDAca+. The first level is image-level category alignment based on class activation map (CAM), and the second one is pixel-level category alignment based on pseudo label. By utilizing category information, UDAca+ can effectively capture domain-invariant yet category-discriminative feature representations to improve segmentation accuracy. In addition, an adversarial learning-based strategy in mixed domain is designed to train the proposed network. Moreover, a confidence calculation method is introduced to mitigate the misleading issues of negative transfer and over-alignment caused by the noise in image-level pseudo labels. UDAca+ achieves the state-of-the-art (SOTA) performance on two synthetic-to-real adaptative tasks, and verifies its effectiveness for image segmentation.

Enhancing adversarial attacks with resize-invariant and logical ensemble.

In black-box scenarios, most transfer-based attacks usually improve the transferability of adversarial examples by optimizing the gradient calculation of the input image. Unfortunately, since the gradient information is only calculated and optimized for each pixel point in the image individually, the generated adversarial examples tend to overfit the local model and have poor transferability to the target model. To tackle the issue, we propose a resize-invariant method (RIM) and a logical ensemble transformation method (LETM) to enhance the transferability of adversarial examples. Specifically, RIM is inspired by the resize-invariant property of Deep Neural Networks (DNNs). The range of resizable pixel is first divided into multiple intervals, and then the input image is randomly resized and padded within each interval. Finally, LETM performs logical ensemble of multiple images after RIM transformation to calculate the final gradient update direction. The proposed method adequately considers the information of each pixel in the image and the surrounding pixels. The probability of duplication of image transformations is minimized and the overfitting effect of adversarial examples is effectively mitigated. Numerous experiments on the ImageNet dataset show that our approach outperforms other advanced methods and is capable of generating more transferable adversarial examples.

TP-Transfiner: high-quality segmentation network for tea pest.

Detecting and controlling tea pests promptly are crucial for safeguarding tea production quality. Due to the insufficient feature extraction ability of traditional CNN-based methods, they face challenges such as inaccuracy and inefficiency of detecting pests in dense and mimicry scenarios. This study proposes an end-to-end tea pest detection and segmentation framework, TeaPest-Transfiner (TP-Transfiner), based on Mask Transfiner to address the challenge of detecting and segmenting pests in mimicry and dense scenarios. In order to improve the feature extraction inability and weak accuracy of traditional convolution modules, this study proposes three strategies. Firstly, a deformable attention block is integrated into the model, which consists of deformable convolution and self-attention using the key content only term. Secondly, the FPN architecture in the backbone network is improved with a more effective feature-aligned pyramid network (FaPN). Lastly, focal loss is employed to balance positive and negative samples during the training period, and parameters are adapted to the dataset distribution. Furthermore, to address the lack of tea pest images, a dataset called TeaPestDataset is constructed, which contains 1,752 images and 29 species of tea pests. Experimental results on the TeaPestDataset show that the proposed TP-Transfiner model achieves state-of-the-art performance compared with other models, attaining a detection precision (AP50) of 87.211% and segmentation performance of 87.381%. Notably, the model shows a significant improvement in segmentation average precision (mAP) by 9.4% and a reduction in model size by 30% compared to the state-of-the-art CNN-based model Mask R-CNN. Simultaneously, TP-Transfiner's lightweight module fusion maintains fast inference speeds and a compact model size, demonstrating practical potential for pest control in tea gardens, especially in dense and mimicry scenarios.

Reversal of cardiac and renal damage in a teenager with hypertension: A case report.

The authors describe the case of a 16-year-old male who was incidentally found to have a blood pressure of 200/? mmHg 6 months previously due to blurred vision and was diagnosed with "high risk of hypertension grade 3, renal insufficiency, hypertensive encephalopathy, hypertensive heart disease, and fundus hemorrhage" after relevant examinations were performed. His blood pressure fluctuated around 120/90 mmHg after beginning antihypertensive treatment. While the diagnostic work-up of his hypertension was inconclusive, he had severe hypertension with brachydactyly type E and short stature on physical examination. The patient's cardiac damage and renal insufficiency ultimately returned to normal after strict blood pressure control, suggesting that hypertension and brachydactyly syndrome alone do not cause cardiac and renal damage.

Quantifying Disparities in COVID-19 Vaccination Rates by Rural and Urban Areas: Cross-Sectional Observational Study.

BACKGROUND: Vaccination plays an important role in preventing COVID-19 infection and reducing the severity of the disease. There are usually differences in vaccination rates between urban and rural areas. Measuring these differences can aid in developing more coordinated and sustainable solutions. This information also serves as a reference for the prevention and control of emerging infectious diseases in the future. OBJECTIVE: This study aims to assess the current coverage rate and influencing factors of COVID-19 (second booster) vaccination among Chinese residents, as well as the disparities between urban and rural areas in China. METHODS: This cross-sectional study used a stratified random sampling approach to select representative samples from 11 communities and 10 villages in eastern (Changzhou), central (Zhengzhou), western (Xining), and northeast (Mudanjiang) Mainland China from February 1 to February 18, 2023. The questionnaires were developed by experienced epidemiologists and contained the following: sociodemographic information, health conditions, vaccine-related information, information related to the Protective Motivation Theory (PMT), and the level of trust in the health care system. Vaccination rates among the participants were evaluated based on self-reported information provided. Binary logistic regression models were performed to explore influencing factors of vaccination among urban and rural participants. Urban-rural disparities in the vaccination rate were assessed using propensity score matching (PSM). RESULTS: A total of 5780 participants were included, with 53.04% (3066/5780) being female. The vaccination rate was 12.18% (704/5780; 95% CI 11.34-13.02) in the total sample, 13.76% (341/2478; 95% CI 12.40-15.12) among the rural participants, and 10.99% (363/3302; 95% CI 9.93-12.06) among the urban participants. For rural participants, self-reported health condition, self-efficacy, educational level, vaccine knowledge, susceptibility, benefits, and trust in the health care system were independent factors associated with vaccination (all P＜.05). For urban participants, chronic conditions, COVID-19 infection, subjective community level, vaccine knowledge, self-efficacy, and trust in the health care system were independent factors associated with vaccination (all P＜.05). PSM analysis uncovered a 3.42% difference in vaccination rates between urban and rural participants. CONCLUSIONS: The fourth COVID-19 vaccination coverage rate (second booster) among the Chinese population was extremely low, significantly lower than the previous vaccine coverage rate. Given that COVID-19 infection is still prevalent at low levels, efforts should focus on enhancing self-efficacy to expand the vaccine coverage rate among the Chinese population. For rural residents, building awareness of the vaccine's benefits and improving their overall health status should be prioritized. In urban areas, a larger proportion of people with COVID-19 and patients with chronic illness should be vaccinated.

Quantifying the Adverse Effects of Long COVID on Individuals' Health After Infection: A Propensity Score Matching Design Study.

Objective: To evaluate the prevalence and influencing factors of long COVID, and measure the difference in health status between long COVID and non-long COVID cases. Methods: A cross-sectional survey was conducted from February 1 to 8, 2023, using a stratified random sampling method in four regions (eastern [Changzhou], central [Zhengzhou], western [Xining] and northeastern [Mudanjiang]) of China. The survey collected COVID-19 patients' socio-demographic characteristics and lifestyles information. The scores of lifestyles and health status range from 5 to 21 and 0 to 100 points, respectively. The criteria of "persistent health problems after 4 weeks of COVID-19 infection" issued by the US Centers for Disease Control and Prevention was used to assess long COVID. Multiple linear regression was used to analyze the influencing factors of the health. The bootstrap method was used to analyze the lifestyles' mediating effect. Propensity score matching (PSM) was used to evaluate the net difference in health scores between long COVID and non-long COVID cases. Results: The study included 3165 COVID-19 patients, with 308 (9.73%) long COVID cases. The health score of the long COVID cases (74.79) was lower than that of the non-long COVID cases (81.06). After adjusting for potential confounding variables, we found that never focused on mental decompression was a common risk factor for the health of both groups. Lifestyles was the mediating factor on individuals' health. After PSM, the non-long COVID cases' health scores remained higher than that of long COVID cases. Conclusion: The proportion of long COVID cases was low, but they were worse off in health. Given the positive moderating effect of healthy lifestyles on improving the health of long COVID cases, healthy lifestyles including mental decompression should be considered as the core strategy of primary prevention when the epidemic of COVID-19 is still at a low level.

How urban versus rural population relates to COVID-19 booster vaccine hesitancy: A propensity score matching design study.

During the COVID-19 pandemic, the vaccine hesitancy has significantly affected the vaccination. To evaluate the booster vaccine hesitancy and its influencing factors among urban and rural residents, as well as to estimate the net difference of booster vaccine hesitancy between urban and rural residents. We conducted a nationwide, cross-sectional Internet survey on 1-8 February 2023, and employed stratified random sampling technique to select participants (≥18 years old) from urban and rural areas. Multivariate logistic regression was used to determine the factors impacting booster vaccine hesitancy. Propensity Score Matching was used to estimate the net difference of COVID-19 booster vaccine hesitancy between urban and rural residents. The overall COVID-19 booster vaccine hesitancy rate of residents was 28.43%. The COVID-19 booster vaccine hesitancy rate among urban residents was found to be 34.70%, among rural residents was 20.25%. Chronic diseases, infection status, vaccination benefits, and trust in vaccine developers were associated with booster vaccine hesitancy among urban residents. Barriers of vaccination were associated with booster vaccine hesitancy among rural residents. PSM analysis showed that the urban residents have a higher booster vaccine hesitancy rate than rural residents, with a net difference of 6.20%. The vaccine hesitancy rate increased significantly, and the urban residents have a higher COVID-19 booster vaccine hesitancy than rural residents. It becomes crucial to enhance the dissemination of information regarding the advantages of vaccination and foster greater trust among urban residents toward the healthcare system.

Impacts of travel duration on urban-rural resident free vaccination behavior: Chinese COVID-19 vaccine booster dose evidence.

This study aimed to evaluate how the duration of travel affects the behavior of urban and rural residents regarding free COVID-19 vaccination, and provide scientific evidence for promoting free vaccination and building an immune barrier to cope with future epidemics. From August 3, 2022 to February,18,2023, A follow-up survey was conducted in urban and rural adults in four cities in China to collect information on socio-demographic factors, vaccination status and travel time for vaccination. Propensity score matching (PSM) analysis was deployed to measure the net difference of the enhanced vaccination rate between urban and rural residents in different traffic time distribution. A total of 5780 samples were included in the study. The vaccination rate of the booster dose of COVID-19 vaccine among rural residents was higher than that of urban residents with a significant P-value (69.36% VS 64.49%,p < .001). The traffic time had a significant negative impact on the COVID-19 booster vaccination behavior of urban and rural residents. There was a significant interaction between the travel time to the vaccination point and the level of trust in doctors. Travel time had a negative impact on the free vaccination behavior of both urban and rural residents. The government should optimize and expand the number of vaccination sites and enhance residents' trust in the medical system. This is crucial for promoting free vaccination and effective epidemic management in the future.

Takayasu arteritis and hyperthyroidism: A secondary hypertension case report.

INTRODUCTION: Renovascular disease and hyperthyroidism are secondary hypertension. Takayasu arteritis (TAK) is a chronic, progressive, nonspecific great vasculitis involving the aorta and its major branches. It is one of the causes of renal artery stenosis. Hyperthyroidism is an endocrine disease caused by improper continuous synthesis and secretion of excessive thyroid hormone by the thyroid gland. Both diseases can raise blood pressure (BP). CASE PRESENTATION: we present a case of 18-year-old. Female, after exercise, fatigue palpitations. The maximum BP was 190/87 mm Hg, ankle-brachial index was <0.9. C-reactive protein and erythrocyte sedimentation rate were elevated. Imaging revealed multiple vascular stenosis. Triiodothyronine, tetraiodothyroxine, serum-free triiodothyronine, serum-free thyroxine, thyroid peroxidase antibody and thyroid stimulating receptor antibody were elevated. TSH reduced. She was diagnosed with TAK and hyperthyroidism. After treatment, the BP was normal, the thyroid function gradually returned to normal, and the symptoms improved. CONCLUSION: It is suggested that the BP of both upper limbs should be measured in newly diagnostic hypertension. If BP is not measured in both upper limbs, it is likely to be missed diagnosis. The cause of vascular stenosis needs to be identified, otherwise interventional treatment may lead to aggravation of the condition. Few cases of TAK complicated with hyperthyroidism have been reported. Both diseases are related to the immune system, whether there is any correlation between the 2 diseases, further research is needed. Early diagnosis, early treatment, the earlier intervention, the better prognosis.

Comprehensive effects of lifestyle reform, adherence, and related factors on hypertension control: A review.

Despite the effectiveness of currently available antihypertensive medications, there is still a need for new treatment strategies that are more effective in certain groups of hypertensive and for additional resources to combat hypertension. However, medication non-adherence was previously recognized as a major problem in the treatment of hypertension. The mechanisms behind the positive impacts of lifestyle changes might occur in different ways. In comparison with other studies, the efficacy and effectiveness of lifestyle modifications and antihypertensive pharmaceutical treatment for the prevention and control of hypertension and concomitant cardiovascular disease have been demonstrated in randomized controlled trials. However, in this review, the attitudinal lifestyle modifications and barriers to blood pressure control were elaborated on. An effective method for reducing blood pressure (BP) and preventing cardiovascular events with antihypertensive medications has been outlined. Maintaining healthy lifestyle factors (body mass index, diet, smoking, alcohol consumption, sodium excretion, and sedentary behavior) could lower systolic blood pressure BP by 3.5 mm Hg and reduce the risk of cardiovascular disease (CVD) by about 30%, regardless of genetic susceptibility to hypertension. Conducting a lifestyle intervention using health education could improve lifestyle factors, such as reducing salt, sodium, and fat intake, changing eating habits to include more fruits and vegetables, not smoking, consuming less alcohol, exercising regularly, maintaining healthy body weight, and minimizing stressful conditions. Each behavior could affect BP by modulating visceral fat accumulation, insulin resistance, the renin-angiotensin-aldosterone system, vascular endothelial function, oxidative stress, inflammation, and autonomic function. Evidence of the joint effect of antihypertensive medications and lifestyle reforms suggests a pathway to reduce hypertension.

Multifunctional role of an ionic liquid in melt-blended poly(methyl methacrylate)/ multi-walled carbon nanotube nanocomposites.

Poly(methyl methacrylate) (PMMA)/multi-walled carbon nanotube (MWNT) nanocomposites with a homogeneous dispersion of MWNTs have been fabricated by a simple melt-mixing method in the presence of a room-temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6]. It has been found that the ionic liquid provided multiple functions in the preparation of the nanocomposites: (1) the ionic liquid acts as an effective compatibilizer to significantly improve the dispersion of MWNTs in the PMMA matrix; (2) the ionic liquid is an efficient plasticizer for the prepared nanocomposites, inducing a drastically reduced glass transition temperature in the PMMA matrix; (3) the ionic liquid acts as a processing aid for the melt processing of PMMA/MWNT nanocomposites; (4) the ionic liquid increases the electrical conductivity as a dopant. This strategy is free of solvents and compatible with industrial applications, which opens new avenues for the larger-scale fabrication of polymer/carbon nanotube nanocomposites.

The Psychological Experience of COVID-19 Vaccination and Its Impact on the Willingness to Receive Booster Vaccines among the Chinese Population: Evidence from a National Cross-Sectional Study.

The purpose of this study was to assess the psychological experience of COVID-19 basic vaccination, the willingness to receive booster vaccines, and to determine their relationships among Chinese people. Between 6 August 2021 and 9 August 2021, a research firm performed a national cross-sectional online survey among Chinese individuals (aged over 18), using the snowball sampling approach, with 26,755 participants. Factor analysis and binary logistic regression were used to evaluate the existing associations. The overall COVID-19 vaccination psychological experience score of the participants was 25.83 (25.78~25.89; scores ranged from 7-35). A total of 93.83% (95%CI = 93.54~94.12) of respondents indicated a willingness to receive booster vaccines. After classifying psychological experiences associated with COVID-19 vaccination into positive and negative experiences and adjusting for confounding factors, for the former, the willingness to receive booster vaccines for participants with the highest scores of 13-15 was 3.933 times higher (OR = 3.933, 95%CI = 3.176~4.871) than participants who obtained scores of 3-9, and for the latter, the willingness to receive booster vaccines for participants with the highest scores of 19-20 was 8.871 times higher (OR = 8.871, 95%CI = 6.240~12.612) than participants who obtained scores of 4-13. Our study suggests that a good psychological experience with vaccination is positively associated with an increased willingness to receive booster vaccines.

Association between lifestyle and COVID-19 vaccination: A national cross-sectional study.

Objective: To assess lifestyles, COVID-19 vaccination coverage rates, and the relationships between lifestyles and COVID-19 vaccination among Chinese population. Methods: We collected data on sociodemographics, perception of the COVID-19 pandemic, lifestyles, and self-reported COVID-19 vaccination via an online survey in China. The chi-square goodness-of-fit test was used to monitor sample saturation throughout the formal online survey. The binary logistic regression analyses were conducted to examine the association between COVID-19 vaccination rate and lifestyle score. We assigned values to 12 lifestyles ranging from positive to negative, with positive lifestyles receiving a higher score and negative lifestyles receiving a lower score, ranging from 1 to 5. For each participant, the total lifestyle scored from 12 to 56. Restricted cubic spline (RCS) was used to visualize the trends and correlations between lifestyle score and COVID-19 vaccination coverage. Propensity score matching (PSM) was used to explore the association between specific lifestyles and COVID-19 vaccination. Results: A total of 29,925 participants (51.4% females) responded. The lifestyle score of the sample was 44.60 ± 6.13 (scoring range: 12-56). COVID-19 vaccination rate was found to be 89.4% (89.1-89.8%). Female participants reported a higher vaccination rate than male participants (91.5 vs. 87.1%). Compared to Q1, COVID-19 vaccination coverage rates increased with lifestyle total scores [OR Q2 = 1.901 (1.718-2.103), P < 0.001; OR Q3 = 2.373 (2.099-2.684), P < 0.001; and OR Q4 = 3.765 (3.209-4.417), P < 0.001]. After applying PSM, it was determined that all the 12 specific healthy lifestyles analyzed, including maintaining a healthy body weight, a healthy diet, regular physical exercises, adequate sleep, regular physical examination, and others, were found to be positive factors for COVID-19 vaccination. Conclusion: The majority of mainland Chinese lived a healthy lifestyle throughout the COVID-19 pandemic, and the rate of COVID-19 vaccination was high. Specific healthy lifestyles contributed to COVID-19 vaccination coverage rates significantly. According to the study's findings, global efforts to achieve herd immunity should be prioritized by continually promoting healthy lifestyles and improving public perception of COVID-19 vaccines.

Bioinspired synthesis of calcium carbonate hollow spheres with a nacre-type laminated microstructure.

In this Article, we combine the characters of hyperbranched polymers and the concept of double-hydrophilic block copolymer (DHBC) to design a 3D crystal growth modifier, HPG-COOH. The novel modifier can efficiently control the crystallization of CaCO(3) from amorphous nanoparticles to vaterite hollow spheres by a nonclassical crystallization process. The obtained vaterite hollow spheres have a special puffy dandelion-like appearance; that is, the shell of the hollow spheres is constructed by platelet-like vaterite mesocrystals, perpendicular to the globe surface. The cross-section of the wall of a vaterite hollow sphere is similar to that of nacres in microstructure, in which platelet-like calcium carbonate mesocrystals pile up with one another. These results reveal the topology effect of the crystal growth modifier on biomineralization and the essential role of the nonclassical crystallization for constructing hierarchical microstructures.

Deformation Behavior and Precipitation Features in a Stretched Al-Cu Alloy at Intermediate Temperatures.

Deformation behavior and precipitation features of an Al-Cu alloy are investigated using uniaxial tensile tests at intermediate temperatures. It is found that the true stress drops with the decreased strain rate or the increased deformation temperature. The number of substructures and the degree of grain elongation decrease with the raised temperature or the decreased strain rate. At high temperatures or low strain rates, some dynamic recrystallized grains can be found. The type of precipitates is influenced by the heating process before hot tensile deformation. The content and size of precipitates increase during tensile deformation at intermediate temperatures. As the temperature increases over 200 °C, the precipitation process (Guinier Preston zone (G.P. zones)→θ'' phase→θ' phase) is enhanced, resulting in increased contents of θ'' and θ' phases. However, θ'' and θ' phases prefer to precipitate along the {020}Al direction, resulting in an uneven distribution of phases. Considering the flow softening degree and the excessive heterogeneous precipitation of θ'' and θ' phases during hot deformation, the reasonable strain rate and temperature are about 0.0003 s-1 and 150 °C, respectively.

Novel morphology of calcium carbonate controlled by poly(L-lysine).

The novel calcium carbonate (CaCO(3)) morphology, twin-sphere with an equatorial girdle, has been obtained under the control of poly(L-lysine) (PLys) through gas-diffusion method. The effect of the concentration of calcium cation and PLys, the reaction time, and the initial pH value are investigated, and various interesting morphologies, including twin-sphere, discus-like, hexagonal plate, and hallow structure are observed by using scanning electronic microscopy. Laser microscopic Raman spectroscopy studies indicated that all these CaCO(3) are vaterite. A possible mechanism is suggested to explain the formation of the twin-sphere based morphologies according to the results. It is proven that alkaline polypeptides can control the mineralization of CaCO(3) precisely as the reported acidic polypeptides and double hydrophilic block copolymers.

Effects of blending sequences and molecular structures of the compatibilizers on the morphology and properties of PLLA/ABS blends.

The effects of molecular structures of the compatibilizers and blending sequences on the morphology and properties of the immiscible poly(l-lactide)/acrylonitrile-butadiene-styrene (PLLA/ABS) blend are investigated herein. The comb-like polymers (RC), which are constituted by a poly(methyl methacrylate) (PMMA) backbone and side chains and a few epoxy groups distributed randomly along the backbone, are found to be better compatibilizers for improving the morphology and mechanical properties of the PLLA/ABS blend, compared to linear polymers (RL) constituted by a PMMA backbone and epoxy groups along the backbone. In addition, the blending sequence, which dictates the extent of grafting reaction between carboxyl end groups of PLLA and epoxy groups in the RL and RC compatibilizers, is found to influence the diffusion and location of the in situ formed RL-g-PLLA and RC-g-PLLA polymers in the blend system. By blending RL or RC polymers with ABS phase firstly, the epoxy groups are diluted by ABS phase; thus, during the second step, blending with PLLA phase, lightly grafted polymers are formed. This method is found to be the best sequence to compatibilize the PLLA/ABS system. When the PLLA phase is mixed with the compatibilizers firstly, the highly grafted polymers are prone to be trapped in the PLLA phase, because the PMMA segments are shielded by the densely grafted PLLA segments from interacting efficiently with the ABS phase, and thus the morphology and mechanical properties of the blend deteriorate accordingly.