In situ preparation and properties of polyvinyl alcohol/synthetic ribbon-like nanocellulose composites.

This study presents a novel approach in which a dual network (DN) composite, comprising polyvinyl alcohol (PVA) and ribbon-like nanocellulose (RC), was synthesized in one step using the volume exclusion effect involved in enzyme-catalyzed cellulose synthesis. Additionally, the impact of PVA as a crowding reagent during enzymatic catalysis on the in situ formation of nanocellulose and its resulting aspect ratio was explored. In contrast, the other two composites were created by incorporating enzyme-catalyzed synthetic block cellulose (BC) and its acid-hydrolyzed regenerated disc-shaped cellulose (DC) into the PVA. Subsequently, the mechanism by which three distinct types of nanocellulose, varying in morphology and size, was explored to elucidate their contributions to enhancing the properties of PVA. The results demonstrated that PVA/RC outperformed PVA/BC and PVA/DC. The elevated aspect ratio and intricate network structure of RCs not only significantly bolster the mechanical robustness of PVA/RC, leading in an 86.40 % surge in tensile strength and a remarkable 277.03 % rise in tensile modulus in comparison to pure PVA, but also induce a slight enhancement in elongation at break. Moreover, the thermal stability and biodegradability of PVA/RC was enhanced. Collectively, this study introduces an innovative strategy for the efficient fabrication of biodegradable composites with enhanced properties.

High mechanical property and antibacterial poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/functional enzymatically-synthesized cellulose biodegradable composite.

Biodegradable materials with antibacterial properties are highly promising. A novel antimicrobial nanocellulose (ECP) was synthesized in one-step by enzyme-catalyzed method to improve the mechanical and antimicrobial properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(HB-co-HV)]. The biodegradable nanocomposites were prepared by melt blending and the performance analysis results show that the nanocomposites display enhanced mechanical performances and antibacterial activities. Compared with the neat P(HB-co-HV), the P(HB-co-HV) doped with 0.5 wt%-ECP shows the highest mechanical properties with yield strength/elongation at break of 29.3 MPa, 7.63 %, respectively, an increase of 38 %/59 %, and a clear inhibition zone against Staphylococcus aureus (S. aureus) of approximately 3.0 mm. As a heterogeneous nucleation agent, ECP optimizes nucleation, and the interfacial interaction between phenol group and matrix promotes the compatibility and dispersion of ECP, resulting in superior mechanical properties of ECP-based composites. The P(HB-co-HV)/ECP nanocomposites have great potential in biomedical materials especially for the bone defect filling material.

Epitaxial Crystallization of Poly(ε-caprolactone) on Reduced Graphene Oxide at a Low Shear Rate by In Situ SAXS/WAXD Methods.

The interfacial interaction between polymers and reinforcements has a positive effect on the properties of polymer nanocomposites, and a further study on the evolution of this interfacial interaction under a shear field is conducive to reasonable regulation of the properties of polymer nanocomposites. For this purpose, epitaxial crystallization of poly(ε-caprolactone) (PCL) on reduced graphene oxide (RGO) is investigated by shearing at the shear rate of 3 s-1 by in situ synchrotron radiation. In situ two-dimensional small-angle X-ray scattering (2D SAXS) results suggest that the imposed shear field promotes the orientation of the polymer chains, resulting in the formation of a large periodic structure of PCL on the RGO surface. In addition, higher shear temperatures facilitate the conformational adjustment of the PCL molecular chain on RGO at the shear rate of 3 s-1, resulting in the formation of thicker lamellae. In situ two-dimensional wide-angle X-ray diffraction (2D WAXD) results show that shear enhances the crystallinity of the PCL/RGO nanocomposite and promotes the oriented growth of epitaxial and bulk crystals. The current findings can improve the understanding of the structural evolution behavior of PCL/RGO nanocomposites after shear and especially enhance dramatically our understanding of the underlying mechanism of influence of shear on interfacial epitaxial crystallization in polymer/graphene nanocomposite systems.

High-density polyethylene crystals with double melting peaks induced by ultra-high-molecular-weight polyethylene fibre.

High-density polyethylene (HDPE)/ultra-high-molecular-weight polyethylene (UHMWPE) fibre composites were prepared via solution crystallization to investigate the components of epitaxial crystal growth on a highly oriented substrate. Scanning electron microscopy morphologies of HDPE crystals on UHMWPE fibres revealed that the edge-on ribbon pattern crystals that were formed initially on UHMWPE fibres converted afterwards to a sheet shape as crystallization progressed. Wide-angle X-ray diffraction confirmed that the polymer chain oriented along the fibre axis and the orthorhombic crystal form of HDPE remained unchanged in HDPE/UHMWPE fibre composite systems. The thermal behaviour of the fibre composites measured by differential scanning calorimetry showed double melting peaks, the nature of which, as disclosed by partial melting experiments, is ascribed to bilayer components existing in the induced crystals: the inner layer is composed of more regularly folded chain crystals induced by UHMWPE fibres, and the outer layer formed on the inner one with a thinner and lower ordered crystal structure.

Effects of shear on epitaxial crystallization of poly(ε-caprolactone) on reduced graphene oxide.

Epitaxial crystallization of poly(ε-caprolactone) (PCL) on reduced graphene oxide (RGO) was investigated by shearing at different shear rates of 3 s-1 and 75 s-1 and different shear temperatures of 65 °C, 70 °C and 75 °C, respectively. Two dimensional wide angle X-ray diffraction (2D WAXD) results show that the crystallinity and the orientation degrees of the (110) plane of PCL/RGO nanocomposites with shear are higher than those without shear, but the imposed shear field has no obvious effect on the crystal structure of the PCL matrix. Two dimensional small angle X-ray scattering (2D SAXS) results suggest that the imposed shear field makes PCL chains epitaxially crystallize on RGO surfaces to form thicker lamellae. Thereby the melt points of PCL/RGO nanocomposites with shear are higher than that without shear from the differential scanning calorimetry (DSC) results. These results indicate that the imposed shear field can enhance the orientation of the PCL matrix, and promote epitaxial crystallization of PCL chains on RGO surfaces. Higher shear temperature is the requirement for PCL chains to epitaxially crystallize well on RGO at low shear rate, although it is not required for the samples at high shear rate.

Impact of adjustment measures on reducing outpatient waiting time in a community hospital: application of a computer simulation.

BACKGROUND: As an important determinant of patient satisfaction, waiting time, has gained increasing attention in the field of health care services. The present study aimed to illustrate the distribution characteristics of waiting time in a community hospital and explore the impact of potential measures to reduce outpatient waiting time based on a computer simulation approach. METHODS: During a one-month study period in 2006, a cross-sectional study was conducted in a community hospital located in Shanghai, China. Baseline data of outpatient waiting time were calculated according to the records of registration time and payment time. A simulation technique was adopted to investigate the impact of perspective reform methods on reducing waiting time. RESULTS: Data from a total of 10,092 patients and 26,816 medical consultations were collected in the study and 19,947 medical consultations were included. The average of the total visit time for outpatients in this hospital was 43.6 minutes in the morning, 19.1 minutes in the afternoon, and 34.3 minutes for the whole day studied period. The simulation results suggested that waiting time for outpatients could be greatly reduced through the introduction of appointment system and flexible demand-orientated doctor scheduling according to the numbers of patients waiting at different time of the workday. CONCLUSION: Adoption of an appointment system and flexible management of doctor scheduling may be effective way to achieve decreased waiting time.

[The incidence discriminant model for close contacts of active tuberculosis patients].

OBJECTIVE: To establish a discriminant model and to provide a relatively accurate scientific basis for the early diagnosis of tuberculosis (TB) and detection of the close contacts. METHODS: Through logistic regression analysis, key factors were selected according to Bayes theory and key factors of TB incidence of the close contacts were screened as well as a discriminant model was established. RESULTS: The non-TB incidence discriminant function of the close contacts was described as: Y1= -39.831 (constant) + 1.927 X1 (sputum-frequency) + 3.528 X2 (education) + 0.309 X3 (contact time) + 5.893 X4 (evade) +2.140 X5 (ventilation) + 8.706 X6 (cough) + 30.970 X7 (fever). The discriminant function of non-TB incidence of the close contacts was as: Y2 =-57.875 (constant) + 2.343 X1 (sputum-frequency) + 3.965 X2 (education) + 0.361 X3 (contact time) + 6.296 X4 (evade) + 1.348 X5 (ventilation) + 12.984 X6 (cough) + 36.555 X7 (fever). CONCLUSION: The discriminant model night be used to contribute to the early diagnosis, early intervention and timely treatment on those close contacts of tuberculosis cases.