Crack Patterns of Environmental Plastic Fragments.

Secondary microplastics usually come from the breakdown of larger plastics due to weathering and environmental stress cracking of plastic wastes. In the present study, 5013 plastic fragments were collected from coastal beaches, estuary dikes, and lake banks in China. The fragment sizes ranged from 0.2 to 17.1 cm, and the dominant polymers were polypropylene and polyethylene. Cracks were observed on the surfaces of 49-56% of the fragments. Based on the extracted crack images, we proposed a general crack pattern system including four crack types with specific definitions, abbreviations, and symbols. The two-dimensional spectral analysis of the cracks suggests that the first three patterns showed good regularity and supported the rationality of the pattern system. Some crack metrics (e.g., line density) were closely correlated with the carbonyl index and additives (e.g., phthalate esters) of fragments. For crack investigation in field, we proposed a succinct protocol, in which five crack ranks were established to directly characterize the degree of cracking based on the line density values. The system was successfully applied to distinguish the differences in crack features at two representative sites, which indicates that crack pattern is a useful tool to describe the morphological changes of plastic surfaces in the environment.

Recent Progress on the Confinement, Assembly, and Relaxation of Inorganic Functional Fillers in Polymer Matrix during Processing.

Functional polymer composites have gained extensive interest due to their wide range of applications. Various functionalities are mainly provided by functional fillers and their networks in polymer matrix. Therefore, morphology control on filler network has important influence on the final functionalities. The confinement, assembly, and relaxation of inorganic functional fillers in polymers are thought as the basic issues related to such control. Processing as the means to achieve the desired shape and properties for materials often involves strong temperature and shear field, among other factors-not to mention the complex interaction between polymer and filler. These processing fields and interactions during processing are reported to have profound influence on the confinement, assembly, and relaxation of inorganic fillers in polymer matrix. Therefore, various functionalities could be significantly affected by processing. This paper is a review of recent developments in this area.

Significantly improving oxygen barrier properties of polylactide via constructing parallel-aligned shish-kebab-like crystals with well-interlocked boundaries.

Recently, some attempts have been made to enhance the gas barrier properties of semicrystalline polymers by precisely controlling the arrangement of their impermeable crystalline lamellae. However, it is still a great challenge to achieve regular arrangement of the lamellae along the direction perpendicular to the gas diffusion path, especially using conventional polymer processing technologies. This work presents a novel and simple strategy to dramatically improve oxygen barrier performance of biobased and biodegradable polylactide (PLA) through constructing parallel-aligned shish-kebab-like crystals with well-interlocked boundaries with the aid of a highly active nucleating agent. The nucleating agent was introduced into PLA by melting compounding and the sheet-like specimens were fabricated by compression molding. We demonstrate that the fibrillar nucleating agent dispersed in PLA melt can serve as shish to induce the change of crystallization habit of PLA from isotopic spherulitic crystals to unique shish-kebab-like crystals and the shear flow in the compression molding can induce the highly ordered alignment of the nucleating agent fibrils as well as the subsequent shish-kebab-like crystals along the direction parallel to the sheet surface. More importantly, the growing lamellae are found to interpenetrate and tightly interlock with each other at the boundary regions of the shish-kebab-like crystals in the later stage of the crystallization, forming a densely packed nanobrick wall structure to prevent gas molecules from permeating through the crystals and thus imparting the PLA sheets with unprecedentedly low oxygen permeability. This work provides not only a successful example of preparing semicrystalline polymer with super gas barrier properties by tailoring crystal superstructure but also a promising route to rapidly fabricate high-performance food packaging materials via industrially meaningful melt processing.

Advances in the oral microbiota and rapid detection of oral infectious diseases.

Several studies have shown that the dysregulation of the oral microbiota plays a crucial role in human health conditions, such as dental caries, periodontal disease, oral cancer, other oral infectious diseases, cardiovascular diseases, diabetes, bacteremia, and low birth weight. The use of traditional detection methods in conjunction with rapidly advancing molecular techniques in the diagnosis of harmful oral microorganisms has expanded our understanding of the diversity, location, and function of the microbiota associated with health and disease. This review aimed to highlight the latest knowledge in this field, including microbial colonization; the most modern detection methods; and interactions in disease progression. The next decade may achieve the rapid diagnosis and precise treatment of harmful oral microorganisms.

Accumulation and re-distribution of microplastics via aquatic plants and macroalgae - A review of field studies.

The aquatic plants and macroalgae are primary producers with major roles regarding the maintenance of ecosystems but their interaction with microplastics (MPs) has received less attention than animals. We summarize the methodologies used, the MPs abundances and their characteristics across the literature on MPs pollution in aquatic plants and macroalgae. The sampling and quantification of MPs still lacks consistency between studies, which increased the uncertainty in cross-comparisons. The abundance of MPs varied by orders of magnitude between species and were mostly fibers and polymers with large degrees of production and applications. Filamentous species contained more MPs than others. The average ratio of MPs between vegetated and unvegetated sites reached 3:1. The average ratio of MPs between the biotic and abiotic fractions reached 2193:1, suggesting a high level of retention in fields. Our findings supported that aquatic plants and macroalgae are critical in the plastic flux within the marine environments.

Holes on surfaces of the weathered plastic fragments from coastal beaches.

The surface morphology of weathered plastics undergoes a variety of changes. In this study, 3950 plastic fragments from 26 beaches around the world, were assessed to identify holes. Holes were identified on 123 fragments on 20 beaches, with the highest frequency (10.3 %) being identified at Qesm AL Gomrok Beach in Egypt. The distribution of holes could be divided into even, single-sided, and random types. The external and internal holes were similar in size (37 ± 15 µm) of even type fragments. The external holes were larger than the internal holes in single-sided (516 ± 259 µm and 383 ± 161 µm) and random (588 ± 262 µm and 454 ± 210 µm) fragment types. The external hole sizes were positively correlated with the internal hole sizes for each type. This study reports a novel deformation phenomenon on the surface of weathered plastics and highlights their potential effects on plastics.

Effect of film thickness on morphological evolution in dewetting and crystallization of polystyrene/poly(ε-caprolactone) blend films.

In this Article, the morphological evolution in the blend thin film of polystyrene (PS)/poly(ε-caprolactone) (PCL) was investigated via mainly AFM. It was found that an enriched two-layer structure with PS at the upper layer and PCL at the bottom layer was formed during spinning coating. By changing the solution concentration, different kinds of crystal morphologies, such as finger-like, dendritic, and spherulitic-like, could be obtained at the bottom PCL layer. These different initial states led to the morphological evolution processes to be quite different from each other, so the phase separation, dewetting, and crystalline morphology of PS/PCL blend films as a function of time were studied. It was interesting to find that the morphological evolution of PS at the upper layer was largely dependent on the film thickness. For the ultrathin (15 nm) blend film, a liquid-solid/liquid-liquid dewetting-wetting process was observed, forming ribbons that rupture into discrete circular PS islands on voronoi finger-like PCL crystal. For the thick (30 nm) blend film, the liquid-liquid dewetting of the upper PS layer from the underlying adsorbed PCL layer was found, forming interconnected rim structures that rupture into discrete circular PS islands embedded in the single lamellar PCL dendritic crystal due to Rayleigh instability. For the thicker (60 nm) blend film, a two-step liquid-liquid dewetting process with regular holes decorated with dendritic PCL crystal at early annealing stage and small holes decorated with spherulite-like PCL crystal among the early dewetting holes at later annealing stage was observed. The mechanism of this unusual morphological evolution process was discussed on the basis of the entropy effect and annealing-induced phase separation.

Microplastics in fishes and their living environments surrounding a plastic production area.

Microplastic-associated risks in freshwater ecosystems have triggered significant concerns in recent years. However, the contribution of plastic production processing to microplastic pollution is largely unknown. The present study investigated microplastic pollution in biotic and abiotic compartments in three sites which are in surrounding area of a plastic industrial colony and a site from a reservoir for drinking water as reference. The abundances of microplastics were 0.4-20.5 items/L in surface water, 44.4-124.7 items/kg (ww) in sediment and 1.9-6.1 items/individual in guts of Hemiculter leucisculus from the industrial area. In contrast, the abundances were much lower levels of 0.1 ± 0.1 items/L in surface water, 0.5 ± 0.2 items/kg (ww) in sediment and 0.2 ± 0.01 items/individual in H. leucisculus in the reference site, respectively. A large quantity of raw pellets were found on the grounds surrounding the plastic factories. The dominant shapes of microplastics found in sediment were fragments (67%), followed by pellets (18%). Unexpectedly, neither fragments nor pellets (> 1 mm) were found in any fish. The organ index of liver in Hemiculter leucisculus, including four types of histopathological changes, was up to 5.5-9.9 in the plastic production area and only 1.6 in the reference site. Our results strongly suggest that microplastic pollution was in high level, and the histopathological damage in fish tissues strongly confirmed the microplastic pollution and ecological response of the plastic production area. Our results also indicate that the feeding types of local fish species might be the reasons leading to the absence of raw pellets or fragments in fish, despite high abundances of microplastics existed in their living environments. CAPSULE ABSTRACT: The plastic production area is a special point source of microplastic in the environments.

Microplastic pollution in water and sediment in a textile industrial area.

Microplastics pollution in the environment is closely determined by the surrounding industrial and human activities. In present study, we investigated microplastics in water and sediment samples collected from a textile industrial area in Shaoxing city, China. The abundance of microplastics varied from 2.1 to 71.0 items/L in surface water samples, and from 16.7 to 1323.3 items/kg (dw) in sediment samples. The polymer type was dominated by polyester both in water (95%) and sediment (79%) samples. The majority of the detected microplastics was predominantly colored fibers smaller than 1 mm in diameter. The high level of microplastic pollution detected in local freshwater and sediment environments was attributed to the production and trading activities of textile industries, for which severe regulations should be envisaged in the future to effectively reduce the local microplastic pollution.

The occurrence of microplastic in specific organs in commercially caught fishes from coast and estuary area of east China.

It is important to understand where microplastics go in the body of organisms. They can readily affect target organs and transport microplastic-associated chemicals to humans via consumption. The plastics (>20 µm) in guts and gills of 13 species of fishes from coast estuary areas of China were examined for the presence of microplastics. Muscle and liver were analyzed from a commercial species, the Asian seabass (Lateolabrax maculatus), of which 73% of the suspected items were verified by micro-Fourier Transform Infrared Spectroscopy. We targeted the organ specific distribution of microplastics. Microplastics were detected in gut and gills in 22%-100% and 22%-89% of total individuals, respectively. Microplastics in gut varied from 0.3 to 5.3 items/ind. and varied from 0.3 to 2.6 items/ind in gill, respectively. The size of microplastics in gills were smaller than those found in the guts. No microplastics were detected in the liver or muscle tissue of L. maculatus, and several non-plastic items detected in muscles can be attributed to background contamination. Further research is required using a larger number of specimens and better quality control and quality assurance are required to assess the presence of small microplastics or nanoplastics in fishes internal organs and muscle.

A straightforward method for measuring the range of apparent density of microplastics.

Density of microplastics has been regarded as the primary property that affect the distribution and bioavailability of microplastics in the water column. For measuring the density of microplastis, we developed a simple and rapid method based on density gradient solutions. In this study, we tested four solvents to make the density gradient solutions, i.e., ethanol (0.8 g/cm3), ultrapure water (1.0 g/cm3), saturated NaI (1.8 g/cm3) and ZnCl2 (1.8 g/cm3). Density of microplastics was measured via observing the float or sink status in the density gradient solutions. We found that density gradient solutions made from ZnCl2 had a larger uncertainty in measuring density than that from NaI, most likely due to a higher surface tension of ZnCl2 solution. Solutions made from ethanol, ultrapure water, and NaI showed consistent density results with listed densities of commercial products, indicating that these density gradient solutions were suitable for measuring microplastics with a density range of 0.8-1.8 g/cm3.

[X-ray fluorescence spectrometric determination of high rhenium content in rhenium-tungsten alloys used in traveling wave tube].

The matrix effect, spectral overlap and background were investigated for X-ray fluorescence (XRF) spectrometric determination of rhenium content according to the analysis requirement of rhenium-tungsten alloys, a key material used in traveling wave tube. The reason for causing the calibration curve nonlinear was explained theoretically when binary ratio technique of XRF was used. Both theoretical and experimental results show that linear calibration curve can be obtained if the curve is plotted by Re% vs. Re Lalpha X-ray intensity instead of binary ratio technique. The method is rapid and accurate and the results obtained in this work are in good agreement with those of chemical analysis. The method has been successfully applied to product quality control.

An environmentally friendly and fast approach to prepare reduced graphite oxide with water and organic solvents solubility.

In this paper, reduced graphite oxide (RGO) was prepared using thiourea dioxide as reductant and polyvinylpyrrolidone (PVP) as stabilizer. Thiourea dioxide, a cheap and nontoxic industrialized material, was demonstrated to be an efficient reducing agent for graphite oxide (GO) in this paper. Ultraviolet and visible (UV-vis) spectroscopy results revealed that the reduction of GO could be readily achieved in 10 min, a reaction time which is much shorter than those required in common reduction reactions. The procedures of reduction including the by-products are all nontoxic, thus it is absolutely environmentally friendly. To the best of our knowledge, this is the first time that thiourea dioxide was successfully used to prepare RGO. Moreover, the stabilizer, PVP, which could be easily absorbed onto the surface of RGO, provided RGO with good water and organic solvents solubility, with low conductivity though. However, by controlling the content of PVP, RGO with balanced solubility and conductivity can be obtained. The resultant RGO could be used as nanofillers to prepare conductive materials and biomaterials with potential applications as electrical devices or biosensors.

Molecular engineered super-nanodevices: smart and safe delivery of potent drugs into tumors.

A super-nanodevice engineered at molecular level integrates various desired properties in a smart and coordinated way, and can "switch on" or "turn off" certain functionalities as required. Importantly, it can break through complex physiological barriers, and then precisely ferry potent toxic triptolide into tumor cells in vivo, thus significantly maximizing the therapeutic efficacy and reducing the drug toxicity.

Surface phase separation, dewetting feature size, and crystal morphology in thin films of polystyrene/poly(ε-caprolactone) blend.

Thin films of polystyrene (PS)/poly(ε-caprolactone) (PCL) blends were prepared by spin-coating and characterized by tapping mode force microscopy (AFM). Effects of the relative concentration of PS in polymer solution on the surface phase separation and dewetting feature size of the blend films were systematically studied. Due to the coupling of phase separation, dewetting, and crystallization of the blend films with the evaporation of solvent during spin-coating, different size of PS islands decorated with various PCL crystal structures including spherulite-like, flat-on individual lamellae, and flat-on dendritic crystal were obtained in the blend films by changing the film composition. The average distance of PS islands was shown to increase with the relative concentration of PS in casting solution. For a given ratio of PS/PCL, the feature size of PS appeared to increase linearly with the square of PS concentration while the PCL concentration only determined the crystal morphology of the blend films with no influence on the upper PS domain features. This is explained in terms of vertical phase separation and spinodal dewetting of the PS rich layer from the underlying PCL rich layer, leading to the upper PS dewetting process and the underlying PCL crystalline process to be mutually independent.

Cellular uptake of polyurethane nanocarriers mediated by gemini quaternary ammonium.

The effective passage of drug formulations into tumor cells is a key factor in the development of nanoscale delivery systems. However, rapid cellular uptake with reduced toxicity remains a great challenge for efficient and safe delivery. In this study, we first use gemini quaternary ammonium (GQA) as a cell internalization promoter to enhance the cellular uptake of drug nanocarriers. It is found that a twenty times faster cell internalization could be achieved by introducing GQA into biodegradable multiblock polyurethane nanomicelles, as confirmed by flow cytometry and confocal laser scanning microscopy (CLSM) studies. Meanwhile, an added methoxyl-poly(ethylene glycol) (mPEG) outer corona could protect these cationic micelles from cytotoxicity at high concentrations, as verified by methyl tetrazolium (MTT) assay. Moreover, GQA not only acts as an enhancer for rapid cellular entry, but also plays an important role in controlled self-assembly and high drug loading capacity. Our work offers a new understanding on the role of cationic surfactants; and provides a facile and economical approach for the design of versatile drug nanocarriers to achieve efficient delivery and good biocompatibility.

The morphological and biomechanical changes of keratocytes cultured on modified p (HEMA-MMA) hydrogel studied by AFM.

The poor integration with host cornea tissue and the low mechanical properties of pHEMA hydrogel for artificial cornea remains a difficult problem to solve. A modified pHEMA hydrogel, MMA copolymerized and type-I collagen and bFGF immobilized, was previously prepared in an attempt to solve the problems. In this study, the cytotoxicity of Col/bFGF-p (HEMA-MMA) and p (HEMA-MMA) was studied by cell adhesion assay and atomic force microscopy (AFM). The results of cell adhesion assay show that the attachment of keratocytes on the modified membrane is much higher than that of the unmodified membrane. This indicates that the material after modification have better cell-material interaction. The AFM images reveal that the morphology of keratocytes cultured on different substrate is obviously different. The cell cultured on modified membrane presented a completely elongated and spindle-shape morphology. The force-distance indicates that the biomechanical of keratocytes changes significantly after culturing on different substrates. The adhesion force (2328+/-523 pN) and Young's modulus (0.51+/-0.125 kPa) of the cell cultured on modified membrane are much higher, and the stiffness (0.08+/-0.022 mN/m) is lower than those of the cell cultured on unmodified membrane. These results show that the cytotoxicity of Col/bFGF-p (HEMA-MMA) for keratocytes is much improved.

[Investigation on oral lesions in 64 Chinese HIV/AIDS patients in Guangxi province].

OBJECTIVE: To investigate the prevalence, age and gender distribution and clinical features of HIV/AIDS oral lesions in patients in Guangxi province, and to provide the epidemiological information for prevention and treatment of these diseases in the certain population. METHODS: A total of 64 HIV/AIDS patients were included in this study. All patients HIV serum-status was confirmed in Guangxi Center of Disease Control (GXCDC). Oral examination was carried out by standardized specialists. HIV/AIDS orofacial lesions were recorded and diagnosed using the EC Clearing House Criteria on Oral Problems related to HIV Infection (1992). RESULTS: Among the total of 64 HIV/AIDS patients included in this study, there were 53 males and 11 females, with mean age of 36.1 years. Candidiasis was the most common lesion with the pseudomembranous type predominating. High prevalences of xerostomia, 11 oral ulceration and 7 HIV related periodontitis were noted. 6 Herpetic stomatitis and 3 herpes zoster, 2 oral hairy leukoplakia and 1 Kaposi's sarcoma and 1 lymphadentitis also were found. CONCLUSION: This study shows a high prevalence of candidiasis, salivary gland disease. Maybe oral ulceration prevalence is not increased, but lesion severity is increased with more severe heperiform or major RAU. It suggested that HIV/AIDS usually shows oral lesion and partly can appear in early phase.